Handbook of Consumer Nanoproducts [1st ed. 2022] 9811686971, 9789811686979, 9789811686986, 9789811686993

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Shadpour Mallakpour Chaudhery Mustansar Hussain

Handbook of Consumer Nanoproducts

Handbook of Consumer Nanoproducts

Shadpour Mallakpour • Chaudhery Mustansar Hussain

Handbook of Consumer Nanoproducts With 359 Figures and 92 Tables

Shadpour Mallakpour Chemistry Isfahan University of Technology Isfahan, Iran

Chaudhery Mustansar Hussain Chemistry and Environmental Science New Jersey Institute of Technology Newark, NJ, USA

ISBN 978-981-16-8697-9 ISBN 978-981-16-8698-6 (eBook) ISBN 978-981-16-8699-3 (print and electronic bundle) https://doi.org/10.1007/978-981-16-8698-6 © Springer Nature Singapore Pte Ltd. 2022 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Dedication by C. M. Hussain I would like to dedicate this handbook to My beloved GOD “Meray Pyarey Allah (SWT)” Dedication by S. Mallakpour I would like to dedicate this handbook to My wife MINA My son IMAN My Daughters Adeleh and Fereshteh My Granddaughter TERMEH

Preface

Recently, nanotechnology-based consumer products have generated a fast-growing buyer market. The majority of nanoproducts are usually used in healthcare and fitness, home and garden, appliances, coatings, electronics, foods and beverages, sporting goods, clothing, bikes, touch screens, and automobiles. Additionally, apart from their antimicrobial and antibacterial properties, nanoparticles have been heavily used in a wide range of medical supplies and household products, such as food packing and storage utensils, cleaning agents, textiles, water filters, humidifiers, and sprays. The production, transportation, daily use, and disposal of nanoproducts have already influenced the environment and human health, although these effects are still not well understood quantitatively. In the natural environment, nanoparticles undergo further transformations: being released as ions, aggregated and agglomerated, surface modified, or embedded into natural matrices. This handbook offers a comprehensive understanding about nanoproducts manufacturing, utilization, and impact on the environment. In general, this handbook summarizes recent progresses and developments in nanotechnology-based consumer products at both experimental and theoretical models scales. To capture the comprehensive impression of consumer nanoproducts and to offer reader a logical and eloquent design of the topic and concentrated up-to-date reference, the handbook is divided into several parts, where each part comprises several chapters. It starts with an introduction where modern research perspective of consumer nanoproducts is explored. Part 2 discusses design and engineering technology for consumer nanoproducts. Part 3 defines various consumer nanoproducts based on polymer films and bio-hybrid polymer nanofiber. Part 4 talks about consumer nanoproducts based on polymer nanocomposites matrices. Part 5 details consumer nanoproducts based on composites based on shape-memory alloys. Part 6 is dedicated to consumer nanoproducts based on bio-nanoceramics and bio-nanocomposites, and Part 7 debates consumer nanoproducts based on biocompatible nanopolymers. Part 8 describes consumer nanoproducts based on graphene and graphene nanocomposite. Then Part 9 to 14 are devoted to consumer nanoproducts for biomedical, food, textile and packaging, cosmetics & environment, advanced consumer nanoproducts (waterborne paints, adhesives, coatings, and dispersible lattices) applications. In Part 15, safety risk, ELSI & economics of consumer nanoproducts are detailed. Part 16, clarified role of consumer vii

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nanoproducts for green and sustainable future. Then Last part 17 of conclusion having discussion on consumer nanoproducts in antimicrobial application. The aim of this handbook is to deliver the recent advancements in nanotechnology-based consumer products arena. This handbook is intended for a very wide-ranging audience working in the fields of advanced materials science, chemistry, chemical engineering and technology, physics, and sustainability. This handbook will be an invaluable reference source for the libraries in universities and industrial institutions, government and independent institutes, individual research groups, and scientists working in the field of nanoproducts. Overall, this handbook is planned to be a useful handbook for advanced undergraduate, graduate students, researchers, and scientists who are searching for new advanced nanoproducts for modern research demands. The editors and contributors of all chapters are famous researchers, scientists, and experts from academia and industry. On behalf of Springer, we thank contributors of all chapters for their exceptional and wholehearted efforts in making of this handbook. Special thanks to Swati Meherishi (Editorial Director, Springer Nature), Niraja Deshmukh (Project Coordinator, Springer Nature), and the entire Major Reference Works team at Springer Nature for their wholehearted support and help during this project. In the end, all appreciation to Springer for publishing this handbook. Isfahan, Iran Newark, USA March 2022

Shadpour Mallakpour Chaudhery Mustansar Hussain

Acknowledgments

We would like to acknowledge Chaudhery Ghazanfar Hussain for his dedicated support during compilation of this handbook. We also would like to thank Dr. Vajiha Behranvand, Dr. Farbod Tabesh, Miss Fariba Sirous, and Elham Azadi for their special support during the making this handbook.

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Contents

Volume 1 Part I

Introduction: Consumer Nanoproducts

.................

1

1

Consumer Nanoproducts: A Brief Introduction . . . . . . . . . . . . . . . Gaurav Yadav and Md. Ahmaruzzaman

3

2

Green Nanoproducts: A Far-Reaching Review . . . . . . . . . . . . . . . Sukanchan Palit and Chaudhery Mustansar Hussain

17

3

New Consumer Nanoproducts: Modern Perspective . . . . . . . . . . . Deepankara V. Shastri and Kantha D. Arunachalam

35

4

Consumer Nanoproducts: A New Viewpoint . . . . . . . . . . . . . . . . . Sherly Antony, Prasanth Rathinam, R. Reshmy, Raveendran Sindhu, Parameswaran Binod, and Ashok Pandey

59

Part II Design and Engineering Technology for Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6

Effect of Mechanical Alloying in Polymer/Ceramic Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. V. Khumalo and M. C. Khoathane

79

Identification and Quantification of Nanomaterials in Consumer Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pratap Kumar Deheri and Biswabandita Kar

101

Part III Consumer Nanoproducts Based on Polymer Films and Bio-hybrid Polymer Nanofiber . . . . . . . . . . . . . . . . . . . . . . . . . . 7

77

Polymer-Hybrid Nanocomposites Films and Fiber-Based Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kamlesh Kumar and Sunita Mishra

141

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Part IV Consumer Nanoproducts Based on Polymer Nanocomposites Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

9

10

159

Consumer Nanoproducts Based on Polymer Nanocomposites Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . María Paula Guarás and Vera A. Alvarez

161

Polymer Nanocomposites for Futuristic Energy Storage Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. K. Nath and J. M. Kalita

189

Metal Organic Framework Nanoparticles-Based Polymeric Membrane for Industrial Mixture Separation . . . . . . . . . . . . . . . . Dipeshkumar D. Kachhadiya and Z. V. P. Murthy

227

Part V Consumer Nanoproducts Based on Composites Based on Shape Memory Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

241

11

Polymer Nanocomposite Matrix-Based Nanoproducts . . . . . . . . . . Ihsan Flayyih Hasan AI-Jawhari

243

12

Polycarbonate Nanocomposites for High Impact Applications Vishwanath Dagaji Jadhav, Akhil Jayawant Patil, and Balasubramanian Kandasubramanian

...

257

Part VI Consumer Nanoproducts Based on Bionanoceramics and Bionanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Nanoproducts Based on Shape Memory Materials Ali Nabipourchakoli and Baode Zhang

............

Part VII Consumer Nanoproducts Based on Biocompatible Nanopolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Bionanoceramic and Bionanocomposite-Based Nanoproducts: Concepts, Processing, and Applications . . . . . . . . . . . . . . . . . . . . . Tanvir Arfin

Part VIII Consumer Nanoproducts Based on Graphene and Graphene Nanocomposite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Graphene Nanocomposite-Based Nanoproducts for Renewable Energy Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seyyed Mojtaba Mousavi, Seyyed Alireza Hashemi, Chin Wei Lai, and Gity Behbudi

283 285

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Graphene Nanocomposite-Based Nanoproducts . . . . . . . . . . . . . . . Susanta Bera, Atanu Naskar, Hasmat Khan, and Sunirmal Jana

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17

Novel Graphene-Based Nanocomposites-Based Nanoproducts Srinivasarao Yaragalla, Bhavitha K. B., and Sabu Thomas

...

401

18

Graphene-Based Nanoproducts: Applications and the Vast Vision for the Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sukanchan Palit and Chaudhery Mustansar Hussain

419

Consumer Nanoproducts Based on Graphene and Graphene Nanocomposite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tanvir Arfin

437

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20

Performance of Graphene: A Brief Literature Review on Technologies for Composite Manufacturing . . . . . . . . . . . . . . . . . . R. Sundarakannan, V. Arumugaprabu, S. Vigneshwaran, P. Sivaranjana, and R. Deepak Joel Johnson

21

Consumer Applications of Graphene and Its Composites . . . . . . . Ramesh K. Guduru and Anurag Ateet Gupta

22

Applications of Graphene and Graphene-Based Nanocomposite for Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jnyanashree Darabdhara and Md. Ahmaruzzaman

Part IX 23

Consumer Nanoproducts for Biomedical Applications . . .

Nanotechnology Applied to Personalized 3D Dressings for Diabetic Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Guillermo Tejada Jacob, Guillermo R. Castro, and Vera A. Alvarez

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501

523

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Consumer Nanoproducts for Biomedical Applications . . . . . . . . . Deepa Thomas, R. Reshmy, Eapen Philip, Aravind Madhavan, Raveendran Sindhu, Parameswaran Binod, and Ashok Pandey

25

“Nanosilver”: A Versatile and New-Generation Nanoproduct in Biomedical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Anchita Diwan, Parinita Singh, and Ayush Mongia

575

Synthesis of Biocompatible Chitosan Nanoparticles by Some Greener Methods for Drug Encapsulations . . . . . . . . . . . . . Srijita Basumallick

595

26

27

Application of Nanoparticles in Medicine . . . . . . . . . . . . . . . . . . . . May M. Eid

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29

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Contents

Characterization of Nanoparticles by FTIR and FTIR-Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . May M. Eid Biomedical Applications of Nanozymes: Disease Diagnosis and Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Venkata Krishna Bayineni, Venkateswara R. Naira, and Ravi-Kumar Kadeppagari Plant-Based Consumer Health Gold Nanoproducts: Benign Nanoformulations for Wound Healing and Treatment of Infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Nandini Sharma, Prishita Sharma, and Kanchan Batra

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Volume 2 Part X

Consumer Nanoproducts for Food . . . . . . . . . . . . . . . . . . . .

715

31

Consumer Nanoproducts for Food . . . . . . . . . . . . . . . . . . . . . . . . . Prasanth Rathinam, Sherly Antony, R. Reshmy, Raveendran Sindhu, Parameswaran Binod, and Ashok Pandey

717

32

Zein-Based Nanoproducts in Nutrition and Food Sectors . . . . . . . Soumitra Banerjee, Patel Chandra Prakash, and Ravi-Kumar Kadeppagari

735

33

Nanotechnology: A Revolutionary Approach Toward Food Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mansi Rastogi, C. V. Bhavana, and Ravi-Kumar Kadeppagari

34

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Application of Nanotechnology for Encapsulation of Micronutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chandan Kumar Sahu, Shelke Dhanashri Sanjay, and Ravi-Kumar Kadeppagari Nanosensors: Consumer Nanoproducts for the Detection of Adulterants and Toxicants in Food . . . . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Anantpreet Kaur Sood, and Vaidehi Sharma Plant-Based Nanomaterials: Novel and Highly Effectual Preservatives for Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Kartika Goyal, and Ambika Singh

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Contents

Part XI 37

38

39

40

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Consumer Nanoproducts for Textile and Packaging . . . . .

825

The Design, Synthesis, and Characterization of Iron Oxide-Based Coating-Based Nanoproducts . . . . . . . . . . . . . . . . . . Fatma Kubra Ata, Seda Yalçınkaya, and Serap Yalcin

827

Skin Substitute: An Eco-friendly and Nano-Based Transdermal Wound Dressing Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sneha Paul and Changam Sheela Sasikumar

847

Starch Based Bio-nanocomposites : Modern and Benign Materials in Food Packaging Industry . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Parul Chandra, Atishay Jain, Lavanya Ahuja, Kanchan Batra, and Nandini Sharma Wrinkle-Resistant Fabrics: Nanotechnology in Modern Textiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shikha Gulati, Sanjay Kumar, Sanah Kumar, Vidhi Wadhawan, and Kanchan Batra

Part XII

Consumer Nanoproducts for Cosmetics

..............

881

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929

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Consumer Nanoproducts for Cosmetics . . . . . . . . . . . . . . . . . . . . . Reshu Virmani and Kamla Pathak

931

42

Nanocosmetics: Opportunities and Risks . . . . . . . . . . . . . . . . . . . . Ambika and Pradeep Pratap Singh

963

43

Role of Nanotechnology in Cosmeceuticals . . . . . . . . . . . . . . . . . . . Mahtabin Rodela Rozbu, Samiha Nuzhat, and Paulraj Mosae Selvakumar

985

44

Nanobiotechnology-Based Anti-aging Products . . . . . . . . . . . . . . . 1005 Rex Jeya Rajkumar Samdavid Thanapaul, Mosae Selvakumar Paulraj, and Daniel S. Roh

45

Nanocosmeceuticals: Novel and Advanced Self-Care Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1031 Shikha Gulati, Sanjay Kumar, Rachit Wadhwa, Shweta Lamba, and Kanchan Batra

46

Advancing of Zinc Oxide Nanoparticles for Cosmetic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1057 Ravi Chauhan, Amit Kumar, Ramna Tripathi, and Akhilesh Kumar

47

Utilization of Consumer Nanoproducts for Cosmetics and Their Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1073 Shashi Chawla, Divyanshi Thakkar, and Prateek Rai

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Part XIII

Consumer Nanoproducts for Environment

...........

1095

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Nanoproducts: Biomedical, Environmental, and Energy Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1097 Shikha Kaushik

49

Composite Nanocoatings for Environmental Remediation . . . . . . . 1123 A. Joseph Nathanael and Palaniswamy Suresh Kumar

50

Biomass-Based Carbon Materials for Heavy Metal Removal Sathya Moorthy Ponnuraj and Palaniswamy Suresh Kumar

51

Environmental and Occupational Health Hazards of Nanomaterials in Construction Sites . . . . . . . . . . . . . . . . . . . . . . . . 1157 S. Ajith and V. Arumugaprabu

52

Consumer Nanoproducts for Environment . . . . . . . . . . . . . . . . . . 1169 Anika Tasnim Chowdhury, Nazifa Rafa, Ahmedul Kabir, and Paulraj Mosae Selvakumar

53

Bio-nanocomposites for Modern Agricultural Applications . . . . . . 1201 Matias Menossi, Claudia Casalongué, and Vera A. Alvarez

54

Consumer Nanoproducts and Environmental Engineering Science: Critical Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1239 Sukanchan Palit and Chaudhery Mustansar Hussain

55

Toxicological Perspectives and Environmental Risks of Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1253 Shikha Gulati, Sanjay Kumar, Shradha Jain, Radhika, Nandini Sharma, and Kanchan Batra

56

Consumer Nanoproducts Based on Polymer Nanocomposites for Food Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1277 Caren Rosales, Magdalena L. Iglesias-Montes, and Vera A. Alvarez

57

Consumer Nanocomposites for Environmental Pollution Control: A Far-Reaching Review . . . . . . . . . . . . . . . . . . . . . . . . . . 1301 Sukanchan Palit and Chaudhery Mustansar Hussain

58

Environmental Aspect on Nanoproducts Saptarshi Roy and Md. Ahmaruzzaman

. . . . 1139

. . . . . . . . . . . . . . . . . . . . 1321

Part XIV Advanced Consumer Nanoproducts (Waterborne Paints, Adhesives, Coatings, and Dispersible Lattices) . . . . . . . . . . . 59

1343

Silver-Nanoparticle-Embedded Antimicrobial Paints . . . . . . . . . . . 1345 Murodjon Abdukhakimov, Renat Khaydarov, Praveen Thaggikuppe Krishnamurthy, and Svetlana Evgrafova

Contents

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Eco-friendly Nanostructured Materials for Arsenic Removal from Aqueous Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355 Estefanía Baigorria, Romina P. Ollier Primiano, and Vera A. Alvarez

Part XV Safety Risk, ELSI, and Economics of Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

1379

Nanoproducts and Legal Aspects of Consumer Protections: An Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1381 Mohammad Ershadul Karim

Part XVI Green and Sustainable Future with Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1407

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Sustainable Future with Nanoproducts . . . . . . . . . . . . . . . . . . . . . 1409 Sukanchan Palit, Chaudhery Mustansar Hussain, and Shadpour Mallakpour

63

Green and Sustainable Approaches of Nanoparticles A. Ravikumar and K. S. Prakash

64

Green and Sustainable Future with Consumer Nanoproducts . . . . 1455 Saruchi, Vaneet Kumar, Harsh Kumar, and Diksha Bhatt

65

Nanocarriers for Antioxidant Cosmetic Products . . . . . . . . . . . . . 1473 Jimena S. Gonzalez, Romina P. Ollier Primiano, and Vera A. Alvarez

Part XVII 66

. . . . . . . . . . 1433

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1497

Consumer Nanoproducts in Antimicrobial Application . . . . . . . . . 1499 Sujith Ravi and Ishwarya R. Kishore

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1515

About the Authors

Professor Shadpour Mallakpour, organic polymer chemist, graduated from the Department of Chemistry, University of Florida (UF), Gainesville, Florida, USA, in 1984. He spent 2 years as postdoc at UF. He joined the Department of Chemistry, Isfahan University of Technology (IUT), Iran, in 1986. Professor Mallakpour held several positions such as chairman of the Department of Chemistry and deputy of research of the Department of Chemistry at IUT. From 1994 to 1995, he worked as visiting professor, University of Mainz, Germany, and from 2003 to 2004 as visiting professor, Virginia Tech, Blacksburg, USA. Now he has published more than 890 journal papers and book chapters and more than 440 conference papers and has received more than 40 awards. The most important award to him was given for the selection of first laureate on fundamental research, at 21st Khwarizmi International award in 2008. He has been listed as the Top 1% Scientists in Chemistry in ISI Essential Science Indicators since 2003. He was selected as academic guest of the 59th Meeting of Nobel Prize Winners in Chemistry, 2009, at Lindau, Germany. He has presented many lectures as invited or keynote speaker in different national and international conferences and universities. He was member of organizing and scientific committees for several national and international conferences. He was also the chairperson of many national and international meetings. In recent years, he has focused on the preparation and characterization of polymers containing chiral amino acid moieties under green conditions using ionic liquids and microwave irradiation as new technology,

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and on introducing these aspects in nanotechnology for the preparation of novel chiral bionanocomposite polymers as well as polymer nanocomposities for hazardousmaterials-removal technologies. Chaudhery Mustansar Hussain, PhD, is an adjunct professor and director of laboratories in the Department of Chemistry and Environmental Science at the New Jersey Institute of Technology (NJIT), Newark, New Jersey, USA. His research is focused on the applications of nanotechnology and advanced materials, environmental management, analytical chemistry, smart materials and technologies, and other various industries. Dr. Hussain is the author of numerous papers in peerreviewed journals as well as a prolific author and editor of approximately hundred books, including scientific monographs and handbooks in his research areas. He has published with Elsevier, American Chemical Society, Royal Society of Chemistry, Springer, John Wiley & Sons, and CRC Press.

Contributors

Murodjon Abdukhakimov Institute of Nuclear Physics, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan Md. Ahmaruzzaman Department of Chemistry, National Institute of Technology, Silchar, Assam, India Lavanya Ahuja Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Ihsan Flayyih Hasan AI-Jawhari Department of Biology, Faculty of Education for Pure Sciences, University of Thiqar, AL-Nasiriya, Iraq S. Ajith Department of Civil Engineering, Kalasalingam Academy of Research and Education, Krishnankoil, Tamil Nadu, India Vera A. Alvarez Thermoplastic Composite Materials, Institute of Research in Materials Science and Technology (INTEMA), CONICET –Mar del Plata National University, Mar del Plata, Argentina Ambika Department of Chemistry, Hansraj College, University of Delhi, Delhi, India Sherly Antony Department of Microbiology, Pushpagiri Institute of Medical Sciences and In-charge of Microbial Technology and Infectious Diseases Laboratory, Pushpagiri Research Centre, Thiruvalla, Kerala, India Tanvir Arfin Environmental Materials Division, CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nagpur, India Hyderabad Zonal Centre, CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Hyderabad, Telangana, India V. Arumugaprabu Department of Mechanical Engineering, School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India Kantha D. Arunachalam Centre for Environmental Nuclear Research, SRM Institute of Science and Technology, Chennai, India xxi

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Contributors

Fatma Kubra Ata Department of Genetics and Bioengineering, Kirsehir Ahi Evran University, Kirsehir, Turkey Estefanía Baigorria Thermoplastic Composite Materials, Institute of Research in Materials Science and Technology (INTEMA), CONICET –Mar del Plata National University, Mar del Plata, Argentina Institute of Science and Technology, São Paulo State University (UNESP), Sorocaba, Brazil Soumitra Banerjee Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India Srijita Basumallick Department of Chemistry, Asutosh College under Calcutta University, Kolkata, India Kanchan Batra Department of Zoology, Kalindi College, University of Delhi, New Delhi, Delhi, India Gity Behbudi Department of Chemical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran Susanta Bera Specialty Glass Technology Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, West Bengal, India Diksha Bhatt Department of Biotechnology, CT Group of Institutions Jalandhar, Jalandhar, Punjab, India C. V. Bhavana Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India Parameswaran Binod Microbial Processes and Technology Division, CSIRNational Institute for Interdisciplinary, Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, India Claudia Casalongué Grupo de Fisiología del Estrés en Plantas, Instituto de Investigaciones Biológicas (IIB), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina Guillermo R. Castro Laboratorio de Nanobiomateriales, CINDEFI, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP) -CONICET (CCT La Plata), Buenos Aires, Argentina Parul Chandra Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Ravi Chauhan THDC Institute of Hydropower Engineering and Technology, Tehri, India

Contributors

xxiii

Shashi Chawla Department of Chemistry, Amity Institute of Applied Sciences, Amity University Uttar Pradesh, Noida, India Anika Tasnim Chowdhury Science and Math Program, Asian University for Women, Chittagong, Bangladesh Jnyanashree Darabdhara Department of Chemistry, National Institute of Technology, Silchar, Assam, India Pratap Kumar Deheri Kalinga Institute of Industrial Technology (KIIT), Bhubaneswar, Odisha, India Shelke Dhanashri Sanjay Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India Anchita Diwan Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India May M. Eid Spectroscopy Department, National Research Center (NRC), ElDokki, Cairo, Egypt Svetlana Evgrafova Sukachev institute of forest of the Siberian Division of the Russian Academy of Sciences, Krasnoyarsk, Russian Federation Institute of Fundamental Biology and Biotechnology, Siberian Federal University, Krasnoyarsk, Russian Federation Jimena S. Gonzalez Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Universidad Nacional de Mar del Plata (UNMdP) – Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina Kartika Goyal Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India María Paula Guarás Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina Ramesh K. Guduru Pandit Deendayal Petroleum University, Gandhinagar, Gujarat, India Shikha Gulati Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Anurag Ateet Gupta Pandit Deendayal Petroleum University, Gandhinagar, Gujarat, India

xxiv

Contributors

Seyyed Alireza Hashemi Nanomaterials and Polymer Nanocomposites Laboratory, School of Engineering, University of British Columbia, Kelowna, Canada Chaudhery Mustansar Hussain Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ, USA Magdalena L. Iglesias-Montes Grupo de Ecomateriales, Instituto de Investigaciones de Ciencia y Tecnología de Materiales (INTEMA), CONICETUNMdP, Mar del Plata, Argentina Vishwanath Dagaji Jadhav Plastic and Polymer Engineering Department, Maharashtra Institute of Technology, Aurangabad, Maharashtra, India Atishay Jain Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Shradha Jain Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Sunirmal Jana Specialty Glass Technology Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, West Bengal, India R. Deepak Joel Johnson Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha School of Medical and Technical Sciences, Thandalam, Chennai, Tamil Nadu, India Bhavitha K. B. International and Inter-University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India Department of Physics, St Teresas’s College, Ernakulam, Kerala, India Ahmedul Kabir Science and Math Program, Asian University for Women, Chittagong, Bangladesh Dipeshkumar D. Kachhadiya Department of Chemical Engineering, Sardar Vallabhbhai National Institute of Technology, Surat, Gujarat, India Ravi-Kumar Kadeppagari Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India J. M. Kalita Department of Physics, Cotton University, Guwahati, India Balasubramanian Kandasubramanian Polymer Processing Laboratory, Department of Metallurgical and Materials Engineering, Defence Institute of Advanced Technology (DU), Ministry of Defence, Pune, Maharashtra, India Biswabandita Kar Kalinga Institute of Industrial Technology (KIIT), Bhubaneswar, Odisha, India Mohammad Ershadul Karim Faculty of Law, University of Malaya, Kuala Lumpur, Malaysia Bangladesh Supreme Court, Dhaka, Bangladesh

Contributors

xxv

Shikha Kaushik Department of Chemistry, Rajdhani College, University of Delhi, New Delhi, India Hasmat Khan Specialty Glass Technology Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, West Bengal, India Renat Khaydarov Institute of Nuclear Physics, Academy of Sciences of Uzbekistan, Tashkent, Uzbekistan M. C. Khoathane Department of Chemical, Metallurgical and Materials Engineering, Polymer Technology Division, Tshwane University of Technology, Pretoria, South Africa M. V. Khumalo Department of Chemical, Metallurgical and Materials Engineering, Polymer Technology Division, Tshwane University of Technology, Pretoria, South Africa Ishwarya R. Kishore Faculty of Medicine and Health Sciences, Department of Microbiology, SRM Medical College Hospital and Research Centre, SRM Institute of Science and Technology, Chengalpet, Tamilnadu, India Venkata Krishna Bayineni Department of Biology, Prayoga Institute of Education Research, Bengaluru, Karnataka, India Praveen Thaggikuppe Krishnamurthy JSS College of Pharmacy, Ootacamund, Tamil Nadu, India Akhilesh Kumar Department of Physics, Govt. Girls P. G. College, Rajajipuram, Lucknow, India Amit Kumar THDC Institute of Hydropower Engineering and Technology, Tehri, India Harsh Kumar Department of Chemistry, Dr B R Ambedkar National Institute of Technology Jalandhar, Jalandhar, Punjab, India Kamlesh Kumar CSIR-Central Scientific Instruments Organisation, Sector-30, Chandigarh, India Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India Sanah Kumar Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Sanjay Kumar Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Palaniswamy Suresh Kumar Environmental and Water Technology, Centre of Innovation (EWTCOI), Ngee Ann Polytechnic, Singapore, Singapore Vaneet Kumar Department of Applied Sciences, CT Group of Institutions Jalandhar, Jalandhar, Punjab, India

xxvi

Contributors

Chandan Kumar Sahu Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India Chin Wei Lai Nanotechnology and Catalysis Research Center, University of Malaya, Kuala Lumpur, Malaysia Shweta Lamba Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Aravind Madhavan Rajiv Gandhi Center for Biotechnology, Thiruvananthapuram, India Shadpour Mallakpour Chemistry, Isfahan University of Technology, Isfahan, Iran Matias Menossi Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina Sunita Mishra CSIR-Central Scientific Instruments Organisation, Sector-30, Chandigarh, India Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India Ayush Mongia Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Seyyed Mojtaba Mousavi Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan Z. V. P. Murthy Department of Chemical Engineering, Sardar Vallabhbhai National Institute of Technology, Surat, Gujarat, India Ali Nabipourchakoli Nuclear Science and Technology Research Institute, Tehran, Iran Venkateswara R. Naira Department of Biology, Prayoga Institute of Education Research, Bengaluru, Karnataka, India Atanu Naskar Specialty Glass Technology Division, CSIR-Central Glass and Ceramic Research Institute, Kolkata, West Bengal, India A. K. Nath Department of Physics, Cotton University, Guwahati, India A. Joseph Nathanael Centre for Biomaterials, Cellular and Molecular Theranostics (CBCMT), Vellore Institute of Technology (VIT), Vellore, TN, India Samiha Nuzhat Science and Math Program, Asian University for Women, Chittagong, Bangladesh

Contributors

xxvii

Romina P. Ollier Primiano Thermoplastic Composite Materials, Institute of Research in Materials Science and Technology (INTEMA), CONICET –Mar del Plata National University, Mar del Plata, Argentina Sukanchan Palit Department of Chemical Engineering, University of Petroleum and Energy Studies, Energy Acres, Post-Office-Bidholi via Premnagar, Dehradun, Uttarakhand, India Ashok Pandey Centre for Innovation and Translational Research, CSIR- Indian Institute for Toxicology Research (CSIR-IITR), Lucknow, India Kamla Pathak Faculty of Pharmacy, Uttar Pradesh University of Medical Sciences, Etawah, Uttar Pradesh, India Akhil Jayawant Patil Department of Mechanical Engineering, Birla Institute of Technology and Science, Pilani, Goa, India Sneha Paul Medical division, Scope eknowledge, A Straive company, Chennai, India Mosae Selvakumar Paulraj Science and Math Program, Asian University for Women, Chittagong, Bangladesh Panaiyaanmai - Centre for Self reliance and Sustainable Development, Munnetram Green Industry, Kadayam, Tenkasi, Tamil Nadu, India Eapen Philip Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara, Kerala, India Sathya Moorthy Ponnuraj Department of Nano Science and Technology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India K. S. Prakash Department of Chemistry, Bharathidasan Government College for Women (Autonomous) (Affiliated to Pondicherry University, Pondicherry), Puducherry, India Patel Chandra Prakash Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India Pradeep Pratap Singh Department of Chemistry, Swami Shraddhanand College, University of Delhi, Delhi, India Radhika Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Nazifa Rafa Science and Math Program, Asian University for Women, Chittagong, Bangladesh Prateek Rai Department of Chemistry, Amity Institute of Applied Sciences, Amity University Uttar Pradesh, Noida, India

xxviii

Contributors

Mansi Rastogi Department of Environment Sciences, Maharshi Dayanand University, Rohtak, Haryana, India Prasanth Rathinam Department of Biochemistry, Pushpagiri Institute of Medical Sciences and In-charge of Biochemistry Laboratory and Medical Biotechnology Laboratory, Pushpagiri Research Centre, Thriuvalla, Kerala, India Sujith Ravi Faculty of Medicine and Health Sciences, Department of Microbiology, SRM Medical College Hospital and Research Centre, SRM Institute of Science and Technology, Chengalpet, Tamilnadu, India A. Ravikumar Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, India R. Reshmy Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara, Kerala, India Daniel S. Roh Division of Plastic and Reconstructive Surgery, Department of Surgery, Boston University School of Medicine, Boston, Massachusetts, USA Caren Rosales Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones de Ciencia y Tecnología de Materiales (INTEMA), CONICETUNMdP, Mar del Plata, Argentina Saptarshi Roy Department of Chemistry, National Institute of Technology, Silchar, Assam, India Mahtabin Rodela Rozbu Science and Math Program, Asian University for Women, Chittagong, Bangladesh Rex Jeya Rajkumar Samdavid Thanapaul Division of Plastic and Reconstructive Surgery, Department of Surgery, Boston University School of Medicine, Boston, Massachusetts, USA Saruchi Department of Biotechnology, CT Group of Institutions Jalandhar, Jalandhar, Punjab, India Changam Sheela Sasikumar Clinical research, S.S healthcare; Clinical Research, Hycare Super specialty, Seed Fund Technical sub committee; Golden Jubilee Women Biotech Park; Department of Biochemistry, Saveetha Dental College, Chennai, India Paulraj Mosae Selvakumar Science and Math Program, Asian University for Women, Chittagong, Bangladesh Nandini Sharma Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Prishita Sharma Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India

Contributors

xxix

Vaidehi Sharma Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Raveendran Sindhu Microbial Processes and Technology Division, CSIRNational Institute for Interdisciplinary, Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, India Ambika Singh Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Parinita Singh Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India P. Sivaranjana School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India Anantpreet Kaur Sood Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India R. Sundarakannan School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India Guillermo Tejada Jacob Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina Divyanshi Thakkar Department of Chemistry, Amity Institute of Applied Sciences, Amity University Uttar Pradesh, Noida, India Deepa Thomas Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara, Kerala, India Sabu Thomas International and Inter-University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala, India Ramna Tripathi THDC Institute of Hydropower Engineering and Technology, Tehri, India Deepankara V. Shastri Centre for Environmental Nuclear Research, SRM Institute of Science and Technology, Chennai, India S. Vigneshwaran Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha School of Medical and Technical Sciences, Thandalam, Chennai, Tamil Nadu, India Reshu Virmani School of Pharmaceutical Sciences, MVN University, Palwal, Haryana, India

xxx

Contributors

Vidhi Wadhawan Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Rachit Wadhwa Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India Gaurav Yadav Department of Chemistry, National Institute of Technology, Silchar, Assam, India Serap Yalcin Department of Molecular Biology and Genetics, Kirsehir Ahi Evran University, Kirsehir, Turkey Seda Yalçınkaya Department of Food Engineering, Süleyman Demirel University, Isparta, Turkey Srinivasarao Yaragalla Istituto Italiano di Tecnologia, Smart Materials Group, Genova, Italy Baode Zhang Liaoning Shihua University, Fushun, Liaoning, China

Part I Introduction: Consumer Nanoproducts

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Consumer Nanoproducts: A Brief Introduction Gaurav Yadav and Md. Ahmaruzzaman

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Composition of Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterial Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPI Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Natural Source of Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inorganic Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metallic Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer-Based Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lipid-Based Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 6 8 8 10 10 10 12 12 13 14 14 15

Abstract

Nanotechnology is an advanced technology widely used for the manufacture of scratchless eyeglasses, ceramic coating in the solar cells, transparent sunscreens, crack-resistant paints, and many more. Nanotechnology provides the lighter, stronger, smarter, and cleaner surfaces. Properties of a particle in nanoscale change in uncertain ways. Nanotechnology can increase performance and new functionalities as well as decrease the use of chemical hazardous substance. Nanomaterials have a wide range of novel applications creating a new revolution for industries, e.g., nanoparticles of TiO2 used in sunscreens. In our daily life, a lot of products that we use have a significant role of nanotechnology, from tennis rackets to clothing. Most of these products are made with the help of nanotechnology and also contain nanomaterials. With the help of nanotechnology, more than 380 products are available for the consumers. G. Yadav · M. Ahmaruzzaman (*) Department of Chemistry, National Institute of Technology, Silchar, Assam, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_85

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G. Yadav and M. Ahmaruzzaman

In the automobile sector, there are many safety factors related to nanotechnology. In tires, nanomaterials improve the adhesive property so that in the wet condition, a vehicle can stop. The rigidity of a car can be increased with the help of nanoparticles. Nanotechnology can also be applied for the processing, safety, packaging, and production of food. A nanocoating process should enhance food packaging by taking antimicrobial agents right on the coated film surface. Nanomaterials are widely being used in medicine and biology in various ways and encompass the direct application of products into patients. Aerogel that acts as an excellent insulator is a nanomaterial. The consumption of nanoparticles in developed countries is found to be more than 1012 particles/day consisting of mixed silicates and TiO2. In nanofood products, engineered nanomaterials fall into three categories: surface functionalized materials, inorganic, and organic. In this chapter, we read the various uses of nanotechnology in various fields. In this context, we will discuss the most representative use of the nanoproducts and their activities as well as advantages of nanotechnology with a brief overview. Keywords

Nanotechnology · Consumer nanoproducts · Consumer product inventory (CPI) · Applications · Natural sources

Introduction Nanotechnology has various potentials for the development of new applications and products in many consumer and industry sectors. This is because nanotechnology can offer better functionalities and performance as well as decrease the use of unsafe chemical substances, generate less waste, and consume materials and energy, thus increasing effectiveness. A wide range of novel applications leads to nanotechnology as a hotbed of the industrial revolution [1]. Many nanotechnology products belong to fitness, and the health sector includes cosmetic products on the Woodrow Wilson Database [2]. This is followed by other applications like electronics, paints, food, and much more. The database leads to suffering from insufficient information. CPI (consumer product inventory) in 2010 listed 1012 products from 24 countries. After CPI, nanotechnology-related inventory has expanded over the globe. A German company launches a nanotechnology-related product database in 2006 [3]. In May 2014, nearly 586 products are listed in this database. In 2009, two European organizations BEUC (European consumer organization) and ANEC (European consumer voice in standardization) made a joint effort to develop “consumer nanoproducts with nano-claims” available in Europe for consumers [4]. In 2011 and 2012, a new version focused on products containing silver nanoparticles, and it contains 141 silver nanoproducts. Ecological council, Danish consumer council, and the Technical University of Denmark launched “The Nanodatabase” in 2012 that

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Consumer Nanoproducts: A Brief Introduction

5

contains nanoproducts available for purchase and available in the European market [5]. This inventory currently contains 1423 products and is continually updated. CPI database provides relevant and useful information to stakeholders who are involved in (a) developing tools and strategies that ensure safe and responsible use of the nanoproducts and (b) understanding which products include nanotechnology. In the USA, nanotechnology is regulated without any provisions as hazardous chemical substances and pesticides. When nanomaterials are used as drugs, cosmetics, and food additives, these are regulated under the FFDCA (Federal Food, Drug, and Cosmetic Act). In European Union, nanoproducts are regulated under registration, evaluation, and authorization regulations and the CLP (classification, labeling, and packaging) regulation when classified as hazardous chemical substances [6]. European Commission also regulated the nanoproducts that contain cosmetics and titanium dioxide but not zinc oxide [7]. European Union brings many advantages like a lower cost for industries, and thus an inventory would benefit for companies, consumers, and government [8] (Fig. 1).

Fig. 1 Nanotechnology from lab to consumer products

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Table 1 Various uses of nanoproducts and nanomaterials Science or industry Medicine

Cosmetology

Construction industry

Textile industry Food industry

Electronic Motor industry

Application Bandages, plasters, dressing on wound with disinfecting layer of Ag NPs Curtains, clothing, screens Nanotubes covering implants Ag nanoparticles-enriched soap Facial cream enriched with copper, silver, platinum, and gold Ag NPs containing antibacterial paint Self-cleansing or fog-free property of glass Antistatic membrane formed by nanoparticles Socks made of fibers Nanosilver deposition into AC working in nonvegetarian plants Packaging of food products

Graphene battery is used in electrical resistant coating Durable and lightweight materials Car care products

Additional feature of nanoproducts Due to continue release of Ag nanoparticles, antibacterial effect may last for a week Helps to limit the infections in hospital; having biocidal property Increases surface for consistency Bacteria elimination Greater efficiency due to active substances Protect the wall to retard the growth of microorganisms For fireplaces Waterproof that allows only steam Prevent from unpleasant odors Air purification to prevent contaminations Extends the storage life and assure the safety of the product. Ag nanoparticles prevent it from mold, fungi, and bacterial flora Consider the natural conductor of electricity which is most effective Modern construction solutions Shine and dirt resistant for a long time

The innovation in nanoproducts gives much more benefit and opportunity in many branches of the market. One of the necessary features is to make certain the safety of life and protect the environment. This results in the safe use of the nanoproducts. With the help of innovation, nanoscale began to form products with new applications and properties given in the Table 1 (Source: Own research by: Pulit et al., 2012; Nowacka & Niemczuk, 2012; Szymański, 2012; Sokół 2012; Szewczyk, 2011; Schlecht & Schroeder, 2010).

Composition of Nanoproducts In recent years, nanotechnology-based products are growing fast for consumer. Of the 1817 materials listed in CPI, approximately 39 various types of nanomaterials are found in these products that are formed from metal like Ti, Zn, Au, and Ag; metal oxide like ZnO, TiO2, and Fe2O3; and carbonaceous (CNTs, graphene, fullerenes, carbon) and silica. Metals and metal oxides comprise one of the largest nanoproduct compositions that is almost 37% of the product. Metal oxides like TiO2, SiO2, and

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Consumer Nanoproducts: A Brief Introduction

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ZnO are the most used nanomaterial in products worldwide. Ag nanoparticle is the most important for the production of various nanoproducts; it is used in 207 products (14.5%) [5]. Due to its antimicrobial property [9], it is present in 438 (24%) products listed in CPI. Of carbonaceous materials (89), the majority of them contain single- or multiwalled CNTs (38 products) and carbon nanoparticles (39) or carbon black. Nanomaterial components listed in CPI are given below: Aluminum oxide, boron, calcium, carbon, carbon nanotube, ceramics, carnauba wax, cerium oxide, chromium, cobalt, clay, copper, fullerene, gold, graphite, graphene, iodine, iridium, iron, lead, liposome, lithium, manganese, magnesium, nanomicelles, nanocellulose, nickel, organics, palladium, polymer, platinum, retinol, silver, silicon, titanium, tungsten disulfide, zinc oxide, zeolite, and zirconia

Some of the nanoproducts contain more than one component, like TiO2 and Ag that are combined with each other in ten products (electronics and cosmetics). Zinc oxide and titanium dioxide are paired in 10 products (cosmetics, paints, and sunscreens). Silver and nano-ceramics are used in combination for cosmetics, water filtration products, and humidifiers. These result in the use of nanohybrids [10] in consumer products (Fig. 2).

Fig. 2 Nanoproduct growth during the period from 2005 to 2010

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Nanomaterial Function Nanoproducts give unexpected benefits by adding nanomaterials into products. Nanomaterials like silicon dioxide and titanium dioxide are used for protective coatings and environmental treatment (treat air and water in the home to protect products). Silver, gold, titanium dioxide, and others are used for cosmetic products. A wide variety of nanoproducts related to health (dietary supplements) contains silver, gold, calcium, magnesium, ceramics, silicon dioxide, etc. Silver has a wide range of applications. It is mostly used in household products, medical supplies, food packaging, textiles, cleansing agents, water filters, and sprays. Apart from Ag, ZnO and TiO2 are also used in food packaging to maintain colors and prevent them from spoiling. CNTs are widely used in industries and products like clothing, bike, touch screens, and sporting goods for their excellent strength and superior thermal and electrical conductivity. Gold NPs are good for biological and chemical imaging. Gold NPs are also important for diagnosis of cancer and cancer therapy, catalysis, and sensing. Silver NPs are mostly used for their anti-inflammatory and antimicrobial properties. They are most extensively used for catalytic, optical, and sensing for detecting various monitoring biotransformation [11] and biomolecules. CNTs have cytoprotective effect [12] and antioxidant potential. This helps in detection of chronic skin diseases, infections, and early-stage skin cancer. It is also applied in cosmetic products such as makeup, moisturizers, and sunscreens [12] (Fig. 3).

CPI Growth In 2011, CPI mentioned 1314 products: from then, 489 products are not available containing nanoparticles, and 500 products are added. In 2015, the total number of products available is 1814. CPI is the most extensive inventory of nanotechnology consumer products available based on the review. Among 62 countries, products come from 622 companies. The products listed in CPI have the following criteria: (1) they are happily acquired by consumers, (2) they contain nanoparticles by manufacturer, and (3) their claim appears in CPI staff for containing nanoparticles. There is continuous growth of products containing nanotechnology; not all products are available in the market. In 2011, the nanoproduct market value was about 4.18 billion dollars, and by the end of 2014, the total cost of manufacture of nanoproduct crosses should be 2.6 trillion dollars by lux research. And it was estimated that in 2025 its value would be 100 billion dollars. Various numbers of nanoproducts from various countries are listed in the table (source: file:///C:/Users/ DELL/Downloads/Beilstein_J_Nanotechnol-06-1769-s001.pdf). Serial number 1 2 3 4 5

Country USA Korea Germany UK Japan

Companies 290 64 63 35 32

Products 773 132 338 104 56 (continued)

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Consumer Nanoproducts: A Brief Introduction

Serial number 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

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Country China Denmark France Taiwan Australia Canada Switzerland Italy Israel Poland Austria Thailand Singapore Malaysia Finland Others Total

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Products 57 47 34 28 21 17 44 14 10 17 11 4 24 4 3 86 1814

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clothing cosmetics sporting goods

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Fig. 3 Various benefits of nanomaterial additives into consumer product

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Some Key Concepts Nanoparticle term is simply referred as a nanomaterial in general. Nanoparticles are solid, and three-dimensional sizes range from 1 to 1000 nm with many functionalities. They can interact with many cells in the human body. Nanoparticles can improve the stability and solubility of the active compound. Drug’s efficiency can be enhanced with the help of nanotechnology and also protect the drug for degradation. Food packaging is done with nanomaterials to enhance its aging process and increase its life or avoid spoilage. Food supplement such as dietary plays an influential role in the medical field. Food supplements can be used in cardiovascular disease, neurological, diabetes, and cancer. Nanoparticle possesses various characteristics, some of which are used in cosmetic and dermatological. Engineered NPs are used for better skin permeation. CNTs are used in chronic skin disease diagnosis and infections. It is also used in moisturizers, sunscreens, makeup, and rejuvenating products.

Natural Source of Nanoproducts In recent years, plants and their part play an exciting role in the cosmetic, pharmaceutical, and food industries. Plant-based products provide a significant role in the treatment of some diseases and are of low cost. Nanotechnology used for medical purposes is termed nanomedicine. With the help of nanoscale, we can control and manipulate matter by new systems [13, 14]. Nanotechnology helps to integrate molecules, due to this show less toxicity, greater efficiency, and multiple mechanisms of action. Much biological activity in humans occurs at the nanoscale, making nanomedicine cross barriers and interact with the tissues [15]. Numerous reactive nanomaterials are able to absorb the biomolecules. Nanomedicine could provide cost-effective and improved healthcare; for example, silver nanoparticle obtained from Ananas comosus is an antioxidant. Fullerene is used as an antiaging obtained from plant extract name Camellia sinensis [16]. Lipid nanoparticles are used as an antioxidant [17], UV protector, and hydratation [18]. Polymeric NPs obtained from aloe vera should be used to treat burn wounds [19]. Plant extract Aloe vera Iresine herbstii Pistacia integerrima Plectranthus amboinicus

Name of NPs Polymeric NPs Silver NPs Gold NPs ZnO NPs

Applications Burn wound treatment Antimicrobial and eczema Psoriasis and anti-inflammatory Antifungal

References [19] [20] [21] [22]

Types of Nanoparticles Nanoparticles are of different types. Nanoparticles are categorized into two parts: inorganic and organic. Inorganic NPs contain metallic NPs, silica NPs, and ceramic NPs, and organic NPs contain lipid NPs and polymeric NPs (Fig. 4).

Consumer Nanoproducts: A Brief Introduction

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Fig. 4 Nanotechnology in health products

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Inorganic Nanoparticles Inorganic nanoparticle size ranges from 2 to 100 nm. Inorganic nanoparticles contain Ag, Au, SiO2, TiO2, etc. Inorganic nanoparticles are biocompatible, nontoxic, hydrophilic, and stable as compared to organic nanoparticles. Inorganic nanoparticles are made up of inorganic elements like Ag, Au, Si, Ti, etc., and organic nanoparticles are formed from polymers. In sunscreens, TiO2 is the most widely used nanoparticle because it has a high sun protection factor. It acts as a UV filter in sunscreens [23]. Inorganic nanoparticles gained intense attention in oncology due to a wide range of applications like tumor drug delivery, imaging, and enhancement of radiotherapy. Iron oxide is widely used in MRI for hyperthermia. Metallic nanoparticles are heavily used in engineering and biomedical science. Gold nanoparticles are used to enhance the capacity of drugs so they can easily reach the targeted site. Silver NPs are widely used in medical field due to antifungal, antibacterial, antiviral, anti-inflammatory, and osteoinductive effect [24–26]. Because of this, it is used for the treatment of cancer including breast cancer cells [27]. Silica nanoparticles are used in various fields such as photodynamic therapy, gene delivery, drug delivery, protein delivery, and for diagnosis of DNA. Carbon nanotubes have various properties like ultralightweight, high thermal conductivity, electronic property, and high aspect ratio. Single-walled CNTs have additional property called photoluminescence which is applied in diagnosis. CNTs have various advantages over others like nonbiodegradable, non-immunogenic nature, biocompatible, elastic nature, and having minimum cytotoxicity.

Metallic Nanoparticles Many metals form the nanostructure. These nanoparticles have a sizeable areavolume ratio and surface area and have unique physical and optical properties that are easy to prepare [14, 28, 29]. The particle’s surface can be functionalized and modified due to the surface chemistry [14, 28]. These characteristics of metallic NPs are essential for cancer treatment. These are also helpful in analytical processes, sensing, and imaging. Silver and gold nanoparticles have various types of catalytic and optical properties. With the help of gold NPs, the drug delivery system can be studied [29]. Gold NPs are also used for immune labeling of samples. Iron oxide is the most widely used nanoparticle. They have paramagnetic properties; along with that, they show chemical stability, highly magnetic, and low toxicity under physiological condition [26], so they can be used for tracking of stem cells [29]. It is also used in electronics and functional coatings of the material to protect. Besides these, they are easy to recycle. Metallic nanoparticles have gained intense attention in the market in various products like clothing, footwear, creams, and plastic containers. Some other applications of metallic nanoparticle are given below [30].

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Consumer Nanoproducts: A Brief Introduction

Metals Aluminum Iron Gold Silver Silica Copper Manganese Cerium Nickel Titanium dioxide Zinc

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Applications Explosive, fuel additives, coating additive Environment remediation, magnetic imaging Photodynamic therapy, cellular imaging Batteries, photography, electrical, antimicrobial Drugs carrier, adsorbent, gene delivery, thermal and electric insulator, filter materials Antibiotic treatment, antimicrobial (antibacterial, antiviral, antifouling, etc.), catalyst, lubricants, nanocomposite coating, inks, filters Catalyst, batteries Computer chip, fuel additive Conduction, magnetic property, printing ink, catalyst Sterilization, antibacterial coating, cosmetics, photocatalyst, sunscreens Sunscreen, skin protection

Polymer-Based Nanoparticles Polymer NPs are submicron-sized reliable drug carriers that may or may not be degradable. Polymeric NPs have a large surface-to-volume ratio, so they have the ability to change the bioactivity of drugs [31]. They can be easily synthesized and has wide applications in all fields [32]. They allow specific targeting, controlled release of drugs, and stability. Natural polymers like dextran, proteins like albumin and gelatin, alginate, chitosan, and a synthetic polymer such as PLA (polylactic acid), copolymers of glycolic and lactic acid, and PCL (poly-Ɛ-caprolactone) are used to prepare polymeric NPs [14, 28, 33–35]. Sometimes synthetic polymers are also used. For NP production, natural hydrophilic polymers are efficient due to better biocompatibility, drug-loading capacity, and less opsonization [36]. Polymeric NPs contain protein nanoparticles having many advantages. Proteins like gelatin and albumin show properties like biocompatibility and are easy to prepare. Protein NPs have the ability to bind the drugs in a nonspecific manner. They can interact with the solvent [37] also. Albumin is a highly effective drug carrier [38]. It is refer for albumin effective found in blood plasma and act as a protein carrier for drugs. Type of polymer PLGA/PLA/ PCL PLGA AcDex Biopolymer of PCL PCL/PGLA

Bioactive/type of drug Coumarin-6 (C-6) Rapamycin Hyperforin Amphotericin B Amp-B Ciprofloxacin

Application purpose Bioimaging, theranostics, and drug delivery

References [39]

Anti-glioma activity Anti-inflammatory activity Antifungal

[40] [41] [42]

Accelerated healing, tissue regeneration, anti-inflammatory

[43] (continued)

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Type of polymer PEG

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PGLA

Bioactive/type of drug Pegademase bovine Paclitaxel (PTX) Curcumin

PLGA

Fenofibrate

PLGA-PEG

Application purpose Immunodeficiency disease

References [44, 45]

Brain cancer, pancreatic andovarian

[46]

Pancreatic cancer, antibacterial Activity Diabetic retinopathy

[44, 47] [48]

Lipid-Based Nanoparticles Lipid NPs contain phytosomes, ethosomes, liposomes, and matrix-based nanostructures like NLCs (nanostructured lipid carriers), LDCs (lipid-drug conjugates), SLNs (solid-lipid nanoparticles), etc. [28]. Lipid NPs allow drug targeting and poorly water-soluble molecule [49]. Liposome having sizes that range from 50 to 1000 nm is an ideal drug delivery due to their morphology. Their structure entrapped the drugs having high molecular weight. Gene therapy and anticancer delivery are the prime focus of liposome formulations [14]. Liposome protects, stores, and transfers a considerable amount of drugs. The lipid protects the drugs from chemical inactivation and enzymatic degradation. It is also possible to form cationic and anionic liposomes with enhanced efficiency. SNLs composed of lipid solids are colloidal particles at both body and room temperature. SNLs are biodegradable and biocompatible, lack organic solvent, provide drug stability, and are easy to scale up [38, 50]. Many classes of SNLs are used for drug delivery, such as antioxidant, antibacterial, genetic material, and therapeutic use [28, 51]. Drug targeting, gene delivery, and vaccine delivery are also successfully used [28]. NLCs provide stability during storage, better drug loading, and drug release modulation [28, 52].

Conclusion The use of nanotechnology-based products is increasing continuously and gains attention. Nanotechnology is used to overcome issue like low water solubility, low permeability, and low in vivo stability. This chapter tells us about the capability of nanoparticles and the use of nanomaterials in daily lives. In the future, there will be a need of more products, and we need to increase the knowledge of consumers about nanoproducts. The positive attitude of the respondents helps in growing the use of nanoproducts. The financial condition of consumers like adjusting the price helps a lot to grow the use of nanoproducts.

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Links https://www.sciencedirect.com/science/article/pii/B9780128167878000193 https://pubs.rsc.org/en/content/articlehtml/2016/en/c5en00182j https://ec.europa.eu/health/scientific_committees/opinions_layman/en/nanotechnologies/l-3/5nanoparticles-consumer-products.htm https://backend.orbit.dtu.dk/ws/portalfiles/portal/118574286/AbstractBook_2015_SNO_SUN.pdf https://www.beilstein-journals.org/bjnano/articles/6/181 https://www.mdpi.com/2079-4991/10/5/979/pdf http://www.marketresearch.com/Future-Markets-Inc-v3760/

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Green Nanoproducts: A Far-Reaching Review Sukanchan Palit and Chaudhery Mustansar Hussain

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Aim and Objective of This Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Vast Scientific Doctrine of Nanomaterials and Engineered Nanomaterials . . . . . . . . . . . . . . . . Green Nanoproducts and the Vast World of Science and Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . Desalination, Membrane Science, and the Future of Global Water Shortage . . . . . . . . . . . . . . . . . . . Application of Nanotechnology in Groundwater Remediation and Drinking Water Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Environmental and Energy Sustainability and the Vast Vision for the Future . . . . . . . . . . . . . . . . . . Green Nanotechnology, Green Sustainability, and the Visionary Future . . . . . . . . . . . . . . . . . . . . . . . . Recent Scientific Advancements in the Field of Green Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . Recent Scientific Advances in the Field of Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recent Scientific Advancements in the Field of Green Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . The Vast Scientific Sagacity and Scientific Profundity in the Field of Application of Green Nanomaterials in Environmental Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arsenic and Heavy Metal Groundwater Remediation and the Application of Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Future Scientific Directions and Futuristic Recommendations of This Study . . . . . . . . . . . . . . . . . . Conclusion, Summary, and Vast Scientific Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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S. Palit Department of Chemical Engineering, University of Petroleum and Energy Studies, Energy Acres, Post-Office-Bidholi via Premnagar, Dehradun, Uttarakhand, India e-mail: [email protected] C. M. Hussain (*) Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ, USA e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_1

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Abstract

The world of science of nanotechnology, nanomaterials, and engineered nanomaterials today stands in the middle deep scientific introspection and vision. Green nanoproducts in the similar vein has immense applications in environmental protection and are in the path of newer rejuvenation. Nanotechnology has been defined as research and development at the atomic, molecular, or macromolecular scales. Rapid industrialization, burgeoning human population, loss of natural resources, and degradation of ecological biodiversity have urged scientists and engineers globally to delve deep into the area of nanotechnology and nanomaterials. Nanoproducts and nanomaterials have today tremendous applications in diverse areas of science and engineering. Green nanotechnology and its immense scientific prowess will veritably one day open new doors of scientific innovation and scientific instinct in the field of nanomaterials and engineered nanomaterials. In this treatise, the authors deeply elucidate on the vast application areas of nanomaterials and nanoproducts in environmental protection and vast and varied areas of science and technology. The areas of green chemistry, green engineering, and green sustainability are dealt with immense scientific vision and scientific profundity in this chapter. Green nanotechnology is a marvel of science and technology today. Environmental degradation and destruction of biodiversity are challenges of science and civilization today. This chapter will surely unfold newer futuristic thoughts and newer futuristic recommendations in the field of green nanoproducts applications in environmental remediation and the vast world of environmental engineering science. A new dawn in the field of global science and engineering will surely evolve if scientists and engineers move towards positive research directions in green nanotechnology, green chemistry, and green engineering. Keywords

Green · Nanoproducts · Nanotechnology · Nanomaterials · Water · Environment · Pollution · Arsenic

Introduction Mankind and science today are in the middle of deep scientific vision and scientific far-sightedness. The challenges and scientific intricacies of human civilization and environmental protection are today vast and versatile. Environmental engineering, chemical engineering, and nanotechnology are vast areas of scientific endeavor. Immense challenges, immense vision, and the targets of scientific research pursuit are the veritable forerunners towards a new scientific world of nanotechnology and nanomaterials/nanoparticles. Vast industrialization, loss of natural resources, and the needs of science and technology in human advancements are the true pallbearers towards a new domain of nanomaterials and green nanoproducts. Conventional and nonconventional environmental engineering tools are the true research areas of

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environmental protection science today. There are lot of limitations and challenges in the path towards scientific triumph in application of environmental engineering tools. Nanotechnology, nanoparticles, and nanomaterials are the boons of human civilization today and thus the need of a detailed scientific investigation. Engineered nanomaterials and green chemistry are the other areas of deep scientific investigation today. The world today is moving from one crisis over another. Technology and engineering science has practically no answers to the burgeoning crisis of heavy metal and arsenic groundwater and drinking water contamination. Thus the need of a concerted effort in research pursuit in green nanotechnology, nanomaterials, and green nanoproducts. The upshot of this treatise is vast and replete with scientific imagination and scientific ingenuity. Nanomaterials and engineered nanomaterials applications in science and human society will all be the forerunners towards a new era in green nanotechnology, green chemistry, and green engineering. Thus a new world order in nanotechnology and material science will gear forward towards a newer scientific landscape in diverse areas of science and engineering which includes applied sciences. Biological sciences and the world of biotechnology and bioremediation are the needs and marvels of science and technology. Human scientific perseverance and deep futuristic scientific thoughts will veritable open a new door of scientific knowledge and scientific discernment.

The Aim and Objective of This Study The aim and objective of this study is to elucidate on the scientific success and the scientific excellence in the areas of nanotechnology applications in environmental protection and green sustainability. Environmental or green sustainability will on the long run be the upshot of civilization’s scientific prowess. Energy and environmental sustainability and its application areas in human society are the requirements of civilization’s progress. Sustainable development whether it is energy, environmental, social, or economic are the immediate needs of the hour. The authors tread upon the field of green or environmental sustainability. Green nanotechnology and nanobiotechnology are the marvels of scientific research pursuit globally today. In the similar vein, green chemistry and green engineering are moving from one visionary phase to another. The primary aim and objective of this treatise is to elucidate upon the success and vision in green nanotechnology and nanoproducts applications in human society. The main advantages and disadvantages in the application of green nanotechnology in human society are the other main pillars of this chapter. Health effects and public health engineering issues are the major concerns of application of nanomaterials in environmental remediation. These are the other focal points of this chapter. A deep investigation in environmental and green sustainability also is one of the pivots of this chapter. In engineering and technological sense, global stance in environmental or green sustainability is not that developed. The visionary words of Mrs. Gro Harlem Brundtland, former Prime Minister of Norway, on the “science of sustainability” needs to be reenvisioned and revitalized with the progress of scientific rigor and civilization. This treatise vastly redefines the needs of environmental

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sustainability in the march of human civilization. The other areas of deep scientific introspection are the domains of green engineering, conventional and nonconventional environmental engineering techniques. United Nations Sustainable Development Goals will surely embolden the challenges, the needs of human society, and the scientific marvels and ingenuity in the fields of sustainability, environmental protection, nanotechnology, and chemical engineering. Today, chemical engineering is aligned with diverse areas of scientific vision. A newer beginning and a newer futuristic thought in the field of integrated water resource management, wastewater management, and urban water quality management will veritably open new windows of scientific innovation and scientific instinct in decades to come. These scientific and engineering issues are deeply delved with scientific conscience in this chapter. The major research thrust area today are the fields of sustainable resource management, waste minimization, zero-waste concepts, and circular economy. A deep scientific introspection and a vastly scientific reinventing in the field of circular economy and waste reduction will surely open new windows of scientific imagination, scientific prowess, and deep scientific provenance. Zero-waste tools and its vast fundamental concepts are the scientific imperatives and scientific adjudication of human scientific progress. In this treatise, the authors deeply pronounce and reiterate the immediate needs of circular economy and blue economy in the true emancipation of environmental protection and its scientific integrity.

The Vast Scientific Doctrine of Nanomaterials and Engineered Nanomaterials The vast and varied scientific doctrine of nanomaterials and engineered nanomaterials are veritably changing the face of human civilization today. Engineered nanomaterials and its applications in diverse areas of science and engineering are the wonders of science, civilization, and mankind today. The application of green nanotechnology and green nanoproducts will surely widen the scientific thoughts and scientific ingenuity globally today. The scientific doctrine and the scientific imagination in the field of nanomaterials, nanoproducts, and nanocrystals needs to be advanced and reenvisioned with the progress of science, technology, and civilization. Green nanotechnology and application of green chemistry and green engineering in human advancements and scientific rigor will surely go a long and visionary way in true realization of the science of environmental protection. The scientific world and humankind are today in a state of disaster as sustainability whether it is energy, environmental, or social are in the process of new rejuvenation. In this entire treatise, the authors stress on the scientific success, the scientific needs, and the profundity of engineering science in the avenues of determination and scientific grit. Integrated water resource management and wastewater management are in a state of disaster in many developing nations around the world. Drinking water is scarce in many nations around the globe. Thus the need of Sustainable Development Goals in the true realization of water remediation and environmental protection.

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Green Nanoproducts and the Vast World of Science and Engineering Green nanoproducts and green nanotechnology are today visionary areas of scientific research pursuit. Humankind’s immense scientific and engineering vision, and the global challenges of water science and technology are the torchbearers towards a new genre and a deep scientific and engineering ingenuity. Arsenic and heavy metal groundwater poisoning are the disasters and catastrophes in many developing and developed nations around the world. South Asia particularly Bangladesh and India are in the throes of world’s largest environmental disasters that is arsenic groundwater and drinking water poisoning and thus the immediate need of the science of green nanoproducts, green nanotechnology, and green nanoproducts. Human mankind’s research and development areas in green nanoproducts will surely one day unveil the scientific intricacies, and the scientific challenges and barriers in the field of both green nanotechnology, green engineering, and environmental pollution control. In this treatise, the authors deeply elucidate the applications of green nanoproducts and green nanotechnology in the true realization and the true upbraiding of the science of environmental protection and global industrial pollution control. A newer remarkable area in the field of environmental engineering science is slowly emerging as science, technology, and human scientific progress moves forward. The vast world of science and engineering of environmental integrity and security will surely ensue in the wide path towards scientific forbearance and deep scientific articulation. In the near future, green nanotechnology will revolutionize the vistas of learning outcomes, deep scientific intellect, and the redemption of science and engineering.

Desalination, Membrane Science, and the Future of Global Water Shortage Desalination and membrane science are the veritable inventions and scientific vision of tomorrow. Water stressed countries around the world today stands in the midst of deep scientific difficulties, provenance, and barriers. The frontiers of the science of desalination and membrane science are today surpassing vast and varied visionary boundaries. Desalination and membrane science are today opposite sides of the visionary coin. The future of global water shortage and lack of clean drinking water are the true burdens of human civilization today. In many South Asian countries around the world, arsenic groundwater poisoning is challenging the human progress and the scientific determination. Mankind’s immense scientific grit and alacrity will surely open new vistas of learning outcomes and environmental engineering curriculum in developing and developed nations around the world. Membrane separation processes are today linked with integrated water resource management and integrated urban water quality management. Water resource engineering, public health engineering, and environmental engineering science are today linked with each other. Management of people, planet, and human habitat are the

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utmost needs of the hour. The United Nations Sustainable Development clearly states the need of energy, environmental, social, and economic sustainability as moments of scientific truth and scientific vision. Today, sustainable resource management and circular economy are the scientific truth and the scientific judgement of global environmental engineering crisis. Human successive generations in arsenic infected regions around the globe particularly India and Bangladesh are in an unusual health-related burden and technologies should be readdressed and reinvented in the global mitigation of this monstrous crisis. Thus the future of global water shortage will surely enhance the needs of scientific understanding and scientific divination in human civilization in days to come.

Application of Nanotechnology in Groundwater Remediation and Drinking Water Treatment Groundwater and drinking water contamination in developing and developed nations around the world are today veritably challenging the global scientific fabric. The scientific redeeming, deep scientific ardor, and the world of scientific challenges in the field of groundwater remediation will eventually usher in a new age in the field of nanotechnology and green nanotechnology. Application of nanotechnology in groundwater remediation is a novel area of engineering science. Technologies and innovations in the field of water and wastewater treatment will truly unravel the scientific travails and scientific barriers of chemical engineering separation processes. The true concepts of chemical process engineering such as unit operations of chemical engineering, mass transfer operations, heat transfer, chemical reaction engineering, and process integration will today unveil the vast domains of environmental protection and water remediation integrity. Graphenes, fullerenes, and carbon nanotubes are today intensely used in diverse areas of engineering research endeavor. Due to their remarkable physicochemical properties, nanomaterials applications are changing the vast scientific frontiers. Also conventional and nonconventional environmental engineering tools in water and wastewater treatment are the other areas of deep scientific comprehension. Soon a new age of desalination and membrane separation processes will lead to a visionary as well as an effective are of engineering and science.

Environmental and Energy Sustainability and the Vast Vision for the Future The global scientific stance and ingenuity in environmental and energy sustainability are bright and groundbreaking. Today, frequent environmental disasters, loss of ecological biodiversity, and environmental degradation are challenging and deeply confronting the vast scientific firmament. The vast vision for the future in the field of environmental sustainability, water purification science, and industrial wastewater treatment needs to be reorganized as science and engineering moves forward towards one paradigm over another. The visionary words on the science of “sustainability” by Dr. Gro Harlem Brundtland, former Prime Minister of Norward, need to

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be rethought and revisited with the progress of civilization and science. United Nations Sustainable Development Goals also need to be strictly addressed across all developing and developed nations around the world. Lack of clean drinking water, improper sanitation, education, human habitat, and housing are the pillars of United Nations Sustainable Development Goals. Circular economy and sustainable resource management are the needs of today’s human progress and human scientific rigor. Sustainability can never be ignored if civilization is in the process of mitigation of climate change, global warming, and scarcity of pure drinking water. In water stressed countries around the globe, desalination techniques and membrane science assume immense importance. The authors in this treatise deeply and profoundly address these scientific and engineering issues.

Green Nanotechnology, Green Sustainability, and the Visionary Future Green nanotechnology and environmental or green sustainability will surely unfold newer visionary areas in the vast domains of environmental protection, water and wastewater treatment. The science of sustainability today stands in the middle of vision, transcendence, and immense scientific determination. The visionary future in environmental engineering, chemical process engineering, and membrane science are the absolute needs of the hour. The world today is moving towards rapid industrialization and immense economic growth. Nanotechnology with green chemistry and green engineering are thus the utmost imperatives of science and civilization. Green sustainability or environmental sustainability are today the visionary areas of scientific research pursuit. Environmental sustainability and water and wastewater treatment are two opposite sides of the visionary coin. Human civilization’s immense scientific stance and scientific forbearance needs to be readdressed and restructured with the march of science and engineering. Nanotechnology and nanoengineering are today integrated with diverse areas of science and engineering such as environmental engineering, chemical engineering, biological sciences, biotechnology, biomedical engineering, and applied sciences. Today, humankind’s immense scientific prowess and engineering vision in the field of environmental protection lies in the hands of the domain of green nanotechnology and nanobiotechnology. Nanobiotechnology is a novel area of science and engineering today. A deep introspection in the domain of green nanotechnology, nanobiotechnology, and water resource management are the needs of human advancements today. The authors deeply investigate these issues along with the interfaces of environmental protection with nanotechnology.

Recent Scientific Advancements in the Field of Green Nanoproducts Technology and engineering science of nanoproducts and green nanotechnology are today in the avenues of deep scientific revelation and scientific fortitude. Human race is in the midst of immense scientific and engineering turmoil. Global environmental

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disasters are veritably in the process of human civilization’s catastrophe. Here comes the scientific and engineering applications of green nanotechnology and green nanoproducts. In this section, the authors deeply delve into the scientific difficulties and scientific barriers in nanotechnology applications and the issues of public health engineering. Verma et al. (2019) [1] deeply discussed with cogent insight green nanotechnology and advancements in phytoformulation research. The ultimate goal of any scientific development is to increase human well-being and human health. A newer dawn in the field of green nanotechnology is ushering in immense scientific might and determination [1]. Novel strategies are highly required for the achievement of safe and therapeutic treatments beyond the conventional ones. Green nanotechnology is a branch of technology that utilizes the fundamental concepts of green chemistry and green engineering. Green nanotechnology is a branch of nanotechnology which can be applied in phytoformulations, and it significantly contributes to environmental sustainability through the production of nanomaterials and nanoproducts [1]. The vast scientific rationale behind the use of plants in nanoparticle formulations is that they are easily available and vastly possesses a wide variety of metabolites, such as vitamins, antioxidants, and nucleotides. International laws and regulations, domestic laws, government and private party programs and regulations, and the vast gamut of policies are being carefully reviewed and readdressed to increase their utility and nurture and enhance these nanomaterials applications in human society [1]. The authors deeply discussed in details the herbal approach for developing nanoparticles, nanoparticles synthesized from plant extracts, and the green synthesis of metal nanoparticles [1]. Risk aspect and risk assessment of green nanotechnology will surely lead a long and visionary towards a sustainable global order. Risk management and risk communication are the other areas of scientific introspection. Today, green nanoproducts have immense scientific potential and are moving towards commercialization. Thus a new world of scientific regeneration is evolving in the vast scientific landscape [1]. Dhingra et al. (2010) [2] deeply discussed in minute details the sustainable nanotechnology through green methods and life cycle thinking. Life cycle thinking is a major area of human scientific and engineering rigor. Deeply citing the myriad applications of nanotechnology, this paper vastly emphasizes the need to conduct “life cycle” based assessments as early in the product development process [2]. This is for better understanding of the potential environmental and the health consequences of nanomaterials over the entire life cycle of a nano-enabled product [2]. Incorporating life cycle thinking for making largely informed decisions at the product design stage, combining life cycle and risk analysis, using sustainable manufacturing practices and implementing green chemistry solutions and alternatives are seen as plausible solutions. The scientific vision of sustainability nanotechnology solutions are the coinwords of today’s endeavor of science and engineering. The authors deeply discussed nanomanufacturing methods and environmental concerns, industrial ecology and life cycle analysis, and energy intensity of carbon nanofibers and nanoparticles. Combination of life cycle analysis and risk assessment are the other pillars of this research pursuit [2].

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OECD Science, Technology and Industry Policy Papers, No.5 (2013) [3] deeply discussed with scientific insight and scientific forbearance nanotechnology for green innovation. This paper brings together information collected through discussions and projects undertaken by OECD working party on nanotechnology (WPN). Sustainable and diverse scientific solutions are the needs of the hour in global scientific landscape [3]. This report discusses (1) introduction to green nanotechnology, (2) strategies for green innovation, and (3) the impact of green nanotechnology. The need for development of affordable ways of addressing global challenges in areas such as energy, environment, and health has never been so intriguing. Human habitat and scientific ardor are today in the process of newer regeneration. Nanotechnology for green innovation or green nanotechnology aims for products and processes that are highly safe, energy efficient, reduce wastes, and lessen greenhouse gas emissions [3]. This report deeply elucidates the policy environment for green nanotechnology, the potential impact of nanotechnology for green innovation, and green innovation through nanotechnology. Nanotechnology for sustainable development of tires and nanotechnology for efficiency of electronic and optical components are the other cornerstones of this research pursuit. Human sufferings are immense today due to global water shortage and global warming. In less developed countries around the world, it is a terrible and gruesome condition [3]. Thus strategies for green innovation through technology are the utmost needs of the hour. Fostering nanotechnology research from laboratory to commercialization will go a long and visionary way in the proper implementation of nanotechnology to human society. This report widely discusses these scientific and engineering issues behind green nanotechnology applications [3]. A new beginning in the field of green nanotechnology and green nanoproducts will surely usher in futuristic vision and futuristic recommendations. Environmental engineering curriculum and its learning outcomes globally needs to be revamped. In this entire treatise, the authors deeply reiterate these scientific and engineering issues.

Recent Scientific Advances in the Field of Nanomaterials Nanocrystals and nanomaterials are the veritable coinwords of scientific emancipation globally. Scientific humanism and the world of engineering and science are today in the crossroads of an immense environmental disaster and thus the need of the truth and revelation of science and technology. In this section, the authors deeply discuss with scientific and engineering insight the recent advances in the field of nanocrystals and nanomaterials with special importance on green nanotechnology. Werkneh et al. (2019) [4] discussed with immense scientific insight applications of nanotechnology and biotechnology for sustainable water and wastewater treatment. Water pollution and freshwater scarcity have become a serious problem and a burning issue throughout the world. It has concerns to both public health, environmental engineering, and human health [4]. To reduce these challenges, various treatment techniques have been adopted. Civilization’s scientific and engineering

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prowess are in a state of immense disaster as civilization confronts climate change and global warming. Among the various technologies, nanotechnology and sustainable biotechnology-based treatment tools are usually applied separately for water and wastewater treatment [4]. Green sustainability stands in the middle of introspection and scientific and engineering ardor [4]. The ardor and the difficulties in nanotechnology applications in environmental remediation are discussed with lucid insight in this paper. Heavy metal groundwater and drinking water contamination are veritable burden to science and civilization. The authors pointedly focus on the various tools of environmental remediation and nanotechnology applications [4]. A new direction in the field of nanomaterials and engineered nanomaterials will surely evolve as science, technology, and mankind moves ahead. Improved water supply and proper sanitation are the areas of high concern in many developing and developed nations around the world. Environmental biotechnology and nanotechnology will surely usher in a new era in human mankind. From the industrial sectors and due to lack of improved water supply and sanitation systems, high quantities of pollutants are discharged and thrown into the surrounding environment every day. Increasing concentrations of toxic pollutants including heavy metals, organic and inorganic pollutants, and other complex compounds are being discharged in huge volumes in domestic and industrial wastewaters [4]. Therefore, there is an urgent need to remove these pollutants from wastewater before the final discharge of the treated water into the natural environment and the surrounding ecosystem. Mankind’s immense scientific prowess and ardor in the field of water purification, water and wastewater treatment thus needs to be reenvisioned as science and engineering surges ahead [4]. Firstly, there is an immediate need of deliberations in conventional and nonconventional environmental engineering techniques. The conventional water treatment technologies used for remediation of water pollutants are the activated carbon-based adsorption, membrane filtration, ion exchange, coagulation and flocculation, reverse osmosis, flotation and extraction, electrochemical treatment, advanced oxidation processes and biosorption that are being used in several industrial and commercial scenarios. Nanomaterials are very small in size, i.e., approximately 1–100 nm and shows unique characteristics that enables them to be used in water and wastewater applications [4]. They exhibit high surface area to volume ratio, which is very significant to produce high surface area than the bulk counterparts. Nano-oxides (silver, gold, iron, and titanium) are common nanomaterials which have been employed for the remediation of pollutants in contaminated water and soil environment scenarios. The vast and ever-growing field of environmental biotechnology offers to solve complex environmental remediation problems. The International Society of Environmental Biotechnology defines environmental biotechnology as an “environment that helps to promote the development, use, and regulation of biological systems for the remediation of contaminated land, air and water environments that works in an efficient manner to sustain a vastly environment friendly society” [4]. Nanotechnology offers immense advantages such as unique physicochemical characteristics such as the large specific surface area, higher reactivity, and small size. Nanotechnology offers several advantages

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because of their unique physicochemical characteristics such as large surface area, higher reactivity, and small size. Environmental biotechnology addresses veritably sustainability issues such as environmental friendliness and low cost for largescale industrial operations [4]. Today in the scientific arena, vision and ingenuity are the needs of civilization’s progress. Sustainability whether it is environmental or energy are the utmost needs of civilization’s progress. In this treatise, the technological advancements of nano and biotechnologies for the sustainable and effective treatment of water and wastewater treatment are veritably addressed [1]. The applications of various nanomaterials for disinfection and microbial control, adsorption and catalytic oxidation, and sensing and environmental monitoring issues have also been elucidated in details in this treatise [1]. With vast respect to microbial technology, their advantages and disadvantages in bioremediation and biotransformation of contaminants as well as toxicological aspects are deeply explained [4]. Biswas et al. (2005) [5] deeply discussed with vision and scientific far-sightedness nanoparticles and the environment. Nanoparticles are a class of materials with properties distinctively different from their bulk and large scale. A critical review of the very broad topic of environmental nanoparticles is deeply presented in this paper [5]. Engineering vision, technological transcendence, and the truth of science are the needs of human mankind and its progress. Nanocrystals and nanoparticles applications are the next generation science and engineering. Because of the vast nature of the topic, this review endeavor is focused on gas-borne nanoparticles. Nanoparticle sources, anthropogenic emissions from industrial and occupational settings, and conversion and formation in the atmosphere are discussed in minute details in this paper [5]. Nanotechnology has been deeply defined as research and development initiative at the atomic, molecular, or macromolecular scales. Today, nanoparticles are highly considered to be the building blocks for the science of nanotechnology and are referred to particles with at least one dimension of less than 100 nm [2]. Nanoscale materials find extensive use in a variety of different areas such as electronic, magnetic, and optoelectronic, biomedical, pharmaceutical, cosmetic, energy, environmental, catalytic, and material science applications. Today, there is a growing concern that nanoparticles could be highly detrimental to the environment and the human health. Thus a newer area of scientific introspection in the field of environmental health is slowly emerging. Environmental and sustainable energy technology are the other areas of scientific research pursuit in this chapter. The field of nanoscience and nanotechnology today has tremendous promise and vast applicability in a variety of different sectors. Human civilization’s scientific advancements in the field of nanotechnology today are in the midst of scientific forbearance and deep scientific thoughts and ingenuity [5]. Today, detailed understanding of process parameters, process design, and mechanistic pathways of nanoparticle formation needs to be addressed and developed. These are the areas of future recommendations of this study [5]. Nanomaterials and the areas of applied sciences such as physics, chemistry, biological sciences, and biotechnology are today integrated with each other. In the similar vein, environmental engineering science and chemical process engineering

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are also integrated with the science of nanotechnology. In this entire treatise, the authors deeply stress on the scientific needs and the vast scientific profundity in the application of nanomaterials in human scientific advancements.

Recent Scientific Advancements in the Field of Green Nanotechnology Green nanotechnology, green chemistry, and green engineering are today in the avenues of newer regeneration. Environmental degradation and disasters are urging scientists, engineers, and governments globally to delve deep into green technology and green engineering research. In this section, the authors deeply elucidate the success of engineering and science in proper implementation of green nanotechnology in the global scenario. In today’s scientific world, one needs to be aware of the limitations and possible threats of application of nanomaterials and nanotechnology in environmental remediation. These areas need to be covered with lucidity and insight as science and civilization moves forward. Nath et al. (2013) [6] deeply discussed with scientific vision and scientific determination green nanotechnology as a new hope for medical biology. The development of eco-friendly technologies in material synthesis is of considerable importance in order to expand their biological applications. The science of nanotechnology and green nanotechnology are today opposite sides of the visionary coin. This review highlights the classification of nanoparticles giving special emphasis on biosynthesis of metal nanoparticle by viable and important organisms [6]. This treatise also focuses on the applications of these biosynthesized nanoparticles in a wide area such as catalysis, targeted drug delivery, cancer treatment, antibacterial agent, and the important domain of biosensors. Humankind today stands in the middle of deep scientific vision and scientific redeeming. The proliferation of science and engineering in the global scenario needs to be reenvisioned as civilization treads forward [6]. Nanomaterials, with its characteristic dimension at the range of 1–100 nm, are at the leading edge and promising area of science and engineering today. In recent decades, nanomaterials, specifically metal nanoparticles, have received immense interest in diverse areas of applied science ranging from nanotechnology to biological sciences. Although widespread interest and vision in nanomaterials is recent, the concept was actually introduced over 40 years back [6]. Due to extremely small size and high surface volume ratio of nanoparticles, the physicochemical properties of nanoparticles-containing materials are quite different from bulk materials. The authors discussed in details classification of nanoparticles, superparamagnetic particles, liposomes, fullerenes, buckyballs, and carbon nanotubes [6]. The areas of dendrimer, quantum dots, and liquid crystals are the other areas of scientific introspection in this treatise [6]. Nanomaterials and engineered nanomaterials are today in the path of newer scientific and engineering rejuvenation and vision. A new dawn in the field of green nanotechnology is slowly emerging today. Metal nanoparticles and characterization methods and synthesis of metal nanoparticles by traditional chemical and physical methods are the other

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cornerstones of this article [6]. Laser ablation, inert gas condensation, sol-gel method, and hydrothermal and solvothermal synthesis are also discussed in minute details. Bioinspired green material synthesis and its scientific and engineering vision are also dealt in minute details in this paper. Applications of metal nanoparticles in medical biology are also dealt with lucid and cogent insight in this paper [6]. In this review, the authors provided an account of the biological methods for metal nanoparticles(green nano) synthesis, as well as its applications in biomedical devices and environmental remediation. Metal nanoparticle biosynthesis is discussed in minute details in this paper. Today, very less research and development forays are found in the science of sustainability and nanotechnology. Thus, this is the immediate need of the hour. The transformation towards sustainable development is veritably an important economic opportunity. What is needed today is the areas of redevelopment – a groundbreaking shift in the field of medical sciences and human advancements. Today, an important area of human progress is the field of medical science. The authors deeply discuss these scientific, engineering, and sustainability issues [6]. Goel et al. (2014) [7] discussed with scientific and engineering vision green nanotechnology. Green nanotechnology is application of nanotechnology in the vast domain of sustainable development. This domain targets and envisions sustainability whether environmental or energy [7]. Green nanotechnology is the result of the world’s vast and large fascination with tiny molecules and the scientific potential involved in it [7]. Green nanotechnology is highly supporting the development of sustainable solutions to address various global issues. The greatness and the scientific ingenuity in the field of green technology and nanotechnology are today ushering in a new epoch in the field of global science and engineering initiatives. Green nanotechnology uses green chemistry, green engineering, and industrial ecology to discover the magical world of nanomaterials and nano-products [7]. Thus green nanotechnology and green chemistry needs to be revamped as science, engineering, and humankind moves forward. The authors discussed in details the goals and aspects of nanotechnology, innovations in green nanotechnology, and concerns relating to innovations of green nanotechnology. The main goals and the vision of green nanotechnology is to produce nanomaterials and engineered nanomaterials that do not harm the environment and ecology and are eco-friendly also to derive specific nanoproducts from these nanomaterials and using them in welfare of human society [7]. Today, green nanotechnology and green nanomaterials are in the path of newer vision and newer scientific imagination [7]. Green nanotechnology works on the principle of green chemistry and green engineering. This area of research pursuit targets conservation of natural resources without harming the environment and ecological biodiversity. Civilization, humankind, science, and engineering today stands in the midst of scientific vision and vast scientific understanding. The authors discussed in minute details the green nanotechnology applications such as (1) nanotechnology for greener cars, (2) micro- and nanofibrillar cellulose, (3) efficiency in electronic components, and (4) carbon nanotubes for green innovation [7]. The authors also discussed in minute details the environmental sustainability issues behind green nanotechnology applications in human society. The main concern of green nanotechnology applications are the upstream processing

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of these green nanoproducts. Surely, the world of science and engineering will witness a new beginning if research and development initiatives in nanomaterials and engineered nanomaterials moves towards right directions of scientific ingenuity [7]. Nanoscience and nanoengineering today stands in the middle of deep scientific introspection and vision. This entire treatise targets the interface of green chemistry and green engineering with nanotechnology. A new dawn in the field of green nanotechnology will surely evolve if humankind pursues science and engineering in the right directions.

The Vast Scientific Sagacity and Scientific Profundity in the Field of Application of Green Nanomaterials in Environmental Protection Green nanomaterials and green nanocrystals are today in the wide path of scientific divination. Technological and engineering challenges are immense in the application of nanocrystals and green nanotechnology in human society. Application of nanomaterials and engineered nanomaterials in environmental remediation are the new avenues of science and engineering today. The authors in this treatise deeply trudges into the field of nanocrystals applications, green nanomaterials applications, and green nanotechnology applications. A new day in the field of engineering science will evolve as mankind and science confronts the numerous environmental issues, loss of natural resources, and environmental degradation. In today’s global scientific scenario, green nanomaterials and green nanotechnology are at the forefront of research and development initiatives. The sagacity and profundity of science of green nanotechnology needs to be reenvisioned and restructured with the march of science and civilization. Rapid industrial growth, mass manufacturing, and rampant industrialization are at the forefront of a global disaster that is loss of ecological biodiversity and environmental degradation. In this entire treatise, the authors deeply target the need of green nanotechnology and green engineering in the research pursuit of humankind. The status of global environment is extremely grave and thought-provoking due to rapid degradation of environment and global ecology. The immediate need of global research and development initiative in the field of green nanomaterials is to target areas of applications of nanotechnology in environmental engineering, chemical process engineering, petroleum engineering, and applied sciences. Provision of clean drinking water, proper sanitation, housing, shelter, and the success of the science of environmental and energy sustainability are all the utmost needs of human civilization today. In this treatise, the authors deeply discussed the need of nanocrystals in the pursuit of the science of environmental protection and water remediation. A new era in the field of environmental engineering science will surely emerge if science and civilization move in the right direction with immense scientific might, forbearance, and scientific grit.

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Arsenic and Heavy Metal Groundwater Remediation and the Application of Nanotechnology Arsenic and heavy metal groundwater remediation are veritable disasters of human civilization today. In South Asia such as Bangladesh and India, this is an evergrowing disaster. Application of innovative technologies such as nanomaterials and nanotechnology are visionary areas of scientific research pursuit. The world of challenges, the immense difficulties and barriers in scientific pursuit in groundwater remediation will truly be the forerunners of futuristic thoughts and futuristic vision. Groundwater remediation and the vast world of environmental engineering are today aligned with the science and engineering of nanotechnology. In many countries of South Asia, arsenic groundwater contamination has taken monstrous proportions. Technology development and technology management are today the needs of global science and engineering in every fields. In water and wastewater treatment, technology development is the need of the hour. Nanomaterials and nanocrystals research areas are surging ahead as mankind and science confronts with the devastating challenges of water and wastewater contamination. The crux of this treatise is multifaceted with a deep and sound vision towards green nanotechnology. Scientific and technological advancements and engineering vision are the need of human civilization today and its progress. Water and industrial wastewater treatment are the primordial issues of science and technology today. South Asia is in the middle of a greater devastation that is arsenic and heavy metal groundwater contamination. This is the largest engineering and scientific disaster in the global scenario. Application of nanotechnology and nanomaterials in water treatment and environmental remediation are new avenues of science and engineering. A deep introspection in the application of nanotechnology in arsenic groundwater remediation and its scientific truth and scientific greatness will surely open new domains of research pursuit in years to come [8–21].

Future Scientific Directions and Futuristic Recommendations of This Study Science, technology, and mankind are today in the path of newer scientific divination. Future scientific directions and future recommendations of this study needs to be envisioned as regards application of green nanotechnology in human progress and scientific advancements. The world of science and engineering today stands befallen and transfixed as human scientific endeavor surges forward. Nanotechnology, nanomaterials, and green engineering are today’s targeted areas of scientific vision and profundity. The world of science and technology stands immensely shocked today as degradation of environment, loss of ecological biodiversity, and depletion of natural resources devastates the scientific fabric globally [20], [21]. The futuristic targets of environmental protection and nanotechnology can be summarized as:

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• A greater scientific emancipation in the field of nanoscience and nanoengineering. • Sustainable water resources need to be reorganized and revitalized as civilization moves forward. • Environmental, energy, social, and economic sustainability need to be envisioned as global environment needs to be protected. • Sustainable development as regards environmental remediation needs to be burgeoned with the progress of science [17–19]. In this chapter, the author deeply targets the need of nanotechnology and nanoengineering in green chemistry and green engineering. A newer visionary era in nanocrystals, nanoparticles, and green nanotechnology will surely evolve if a larger vision in the field of scientific validation is replete with scientific ingenuity and scientific truth. Governments around the world should be able to stand forward with immense vision if futuristic targets in environmental remediation are met. The overarching goal of this treatise is to target the futuristic needs of nanotechnology in environmental protection and a greater emancipation of green nanotechnology. Nanoscience and nanoengineering are the wonders of global science and engineering and the scientific truth of present-day human civilization. Future directions in research pursuit should be targeted towards a greater scientific and engineering emancipation of green chemistry, green engineering, and green nanotechnology. Today, human scientific and engineering vision in the field of green nanotechnology and environmental nanotechnology are in a state of immense introspection and vision. A deep scientific understanding and knowledge prowess are the utmost needs of the hour. A new visionary epoch will surely emerge if scientists, engineers, researchers, governments, and the human society takes a rigid step towards successful implementation of green engineering, green chemistry, and green nanotechnology. The future of environmental protection and nanotechnology lies in the hands of these scientific and engineering issues [17–19].

Conclusion, Summary, and Vast Scientific Perspectives Science, technology, and engineering are moving fast in this present-day human civilization. Green nanoproducts and nanomaterials are the marvels and the need of human civilization today. Technological and scientific prowess and validation are needed as there are health issues in the application of nanotechnology in human society. Nanocrystals applications in diverse areas of science and engineering are the immediate needs of the hour as civilization and science stands in the middle of environmental degradation. Ever-growing population, rapid industrialization, and the new vision of science and engineering are the veritable forerunners towards a newer visionary era in the field of environmental protection, chemical process engineering, and the vast world of nanoscience and nanoengineering. Successive human generations need to be envisioned as regards protection of environment. Green nanoproducts or nanomaterials are today latent areas of engineering science yet highly developed. The ingenuity and the profundity of heavy metal groundwater

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remediation needs to be envisioned in the crucial juncture of introspection and vision. The vision of mankind needs to be reorganized as regards application of green nanotechnology. In this chapter, the authors deeply target the need of both nanoscience and green nanotechnology in the advancement of science and human society. Green nanotechnology is the alignment of green chemistry, green engineering, and nanotechnology. Scientific truth, the vast scientific knowledge and understanding, and the world of challenges in the field of nanotechnology and nanoengineering will surely open up new areas of scientific research pursuit in environmental protection and green chemistry. The scientific perspectives in environmental protection and application of nanomaterials will widen knowledge and prowess in human scientific pursuit in decades to come. Mankind will one day truly usher in a new era and a newer thought process in environmental and water and wastewater remediation if concerted efforts from scientists, engineers, and governments move in the right direction. Climate change is another area of research pursuit today. This area is aligned with nanotechnology and nano-remediation. Scientific perspectives and deep scientific prowess will immensely be a boon of human civilization if environmental protection and environmental engineering are deeply envisioned.

References 1. Verma A, Gautam SP, Bansal KK, Prabhakar N, Rosenholm JM (2019) Green nanotechnology: advancement in phytoformulation research, medicines. MDPI J 6(39):1–10. https://doi.org/10. 3390/medicines6010039 2. Dhingra R, Naidu S, Upretim G, Sawhney (2010) Sustainable nanotechnology: through green methods and life-cycle thinking. Sustainability 2010(2):3323–3338. https://doi.org/10.3390/ su2103323 3. OECD (2013, June 14) Nanotechnology for green innovation. OECD science, technology and industry policy papers, no. 5, OECD Publishing, Paris 4. Werknek AA, Rene ER (2019) Chapter-19: applications of nanotechnology and biotechnology for sustainable water and wastewater treatment. In: Bui XT et al (eds) Water and wastewater treatment technologies: energy, environment and sustainability. Springer Nature, Singapore, pp 405–430 5. Biswas P, Wu C-Y (2005) Nanoparticles and the environment. J Air Waste Manag Assoc 55: 708–746 6. Nath D, Banerjee P (2013) Green nanotechnology-a new hope for medical biology. Environ Toxicol Pharmacol 36:997–1014 7. Goel A, Bhatnagar S (2014) Green nanotechnology. Bio Evolution 2014:3–4. www. giapjournals.com/bioevolution 8. Palit S (2017) Chapter-17: application of nanotechnology, nanofiltration and drinking and wastewater treatment- a vision for the future. In: Grumezescu AM (ed) Water purification. Academic Press, London, pp 587–620 9. Palit S (2016) Nanofiltration and ultrafiltration- the next generation environmental engineering tool and a vision for the future. Int J Chem Tech Res 9(5):848–856 10. Palit S (2016) Filtration: frontiers of the engineering and science of nanofiltration-a far-reaching review. In: Ortiz-Mendez U (ed) CRC concise encyclopedia of nanotechnology(Taylor and Francis). Kharissova. O.V., Kharisov. B.I, pp 205–214

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11. Palit S (2017) Chapter-14: advanced environmental engineering separation processes, environmental analysis and application of nanotechnology- a far-reaching review. In: Hussain CM, Kharisov B (eds) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge, pp 377–416 12. Hussain CM, Kharisov B (2017) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge 13. Hussain CM (2017) Chapter-19: magnetic nanomaterials for environmental analysis. In: Hussain CM, Kharisov B (eds) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge, pp 3–13 14. Hussain CM (2018) Handbook of nanomaterials for industrial applications. Elsevier, Amsterdam 15. Hussain CM (2019) Handbook of environmental materials management. Elsevier, Amsterdam 16. Hussain CM (2020) Handbook of functionalized nanomaterials for industrial applications. Elsevier, Amsterdam 17. Hussain CM (2020) Handbook of manufacturing applications of nanomaterials. Elsevier, Amsterdam 18. Hussain CM (2020) Handbook of industrial applications of polymer nanocomposites. Elsevier, Amsterdam 19. Hussain CM (2020) Handbook of nanomaterials for sensing applications. Elsevier, Amsterdam 20. www.wikipedia.com. Accessed on 7 Jan 2021 21. www.google.com. Accessed on 13 May 2021

Important Websites http://www.insituarsenic.org https://www.epa.gov›report-environment https://www.epa.gov

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New Consumer Nanoproducts: Modern Perspective Deepankara V. Shastri and Kantha D. Arunachalam

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innovations and Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology: Materials Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Nanoindustry from Molecular Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Nanoproducts (Nps) in the Consumer Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Food Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silica (SiO2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silver (Ag) Nanoparticles in the Food Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Titanium Dioxide (TiO2) in the Food Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zinc Oxide (ZnO) in the Food Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Textile Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Electronics Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology and Its Implications to Electronics Innovation . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Nanoelectronics R&D stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoproducts in Cosmeceutical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Moisturizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sunscreens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anti-Aging Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hair Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Skin Cleaning Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lip and Nail Care . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exposure and Penetration of Nanoparticles to Skin and Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Innovations in Nanoconsumer Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Easy-to-Clean Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anti-Graffiti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antimicrobial Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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D. V. Shastri · K. D. Arunachalam (*) Centre for Environmental Nuclear Research, SRM Institute of Science and Technology, Chennai, India e-mail: [email protected]; [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_2

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Anti-Fingerprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antifog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corrosion Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wear and Tear Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scratch Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tensile Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Photocatalytic Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antireflective Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanophotonics and Consumer Industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages and Disadvantages of Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potential Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potential Drawbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Nanotechnology is invariably becoming a modern science of the promising future because of its key aspects in various aspects in various aspects like electronics, medicine, and many engineering features. Due to its interdisciplinary nature ranging from modern medicine, food, microelectronics, pharmaceuticals, and cosmetics. During initial days, it was limited to elite engineering perspectives, but at present it is booming into consumer product industries at a brisker pace. Even though the production of nanoparticles remains quite a complex and costly process, the distinct advantages are far more than its drawbacks. A considerable majority of consumer products that use nanotechnology exploit interface effects. By clever manipulation of one interface just by making it rougher, smoother, or increasing the density of particles we can change many properties like surface area, volume, etc. Another major effect used in consumer nanoproducts is a quantum mechanical effect where we can make products unique by manipulating optical, electronic, and magnetic properties. But what bothers is the application of nanotechnology in fields like pharmaceuticals; cosmetics needs to be studied further for its complications for health. Perhaps familiar consumer products like mobile phones and modern computers have mostly used nanotechnology for production to date, economic drive, and rise of technology, making way to fit more and more components in small areas of electronic products, which is possible only by nanotechnology. As device sizes shrink it’s becoming more portable, economical, and energy efficient. In this chapter, there is various innovation to nanotechnology and modern perspectives of effects on the consumer market are explored. Keywords

Nanoconsumer products · Interface effects · Consumer market · Innovations in nanoproducts · Nanoelectronics · Nanophotonics consumer market · Cosmeceutical

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Introduction The most punctual precise statement of nanotechnology is given in a discourse delivered by Richard Feynman (American physicist, 1918–1988) in 1959, famously known as “there’s plenty of room at the bottom.” In this intellectual discourse, Feynman examined the significance of manipulating things from a more minor and deep perspective and it could reveal to us quite a bit of incredible effects regarding bizarre wonders that happen in complex circumstances. He portrayed how material wonders alter their appearance relying upon the size and presented two difficulties: formation of a nanomotor and the downsizing of letters to the magnitude that would allow the entire encyclopedia Britannica to fit on the header of a pin. There’s an extraordinary interdisciplinary combination of researchers committed to the extensive investigation of a world so little, researchers could not perceive it – even with a microscope that we can call it as nanotechnology, the area of atoms and nanostructures. Nanotechnology is so new, nobody is certain what will happen to it. So as to instantly comprehend the uncommon universe of nanotechnology, we undoubtedly have to get a thought of the units of measurements included. A nanometer (nm) is one-billionth of a meter, more shorter compared to visible light. As little as a nanometer may be, it’s still extensively contrasted with the nuclear range. A particle has a distance across of about 0.1 nm. A molecule’s core is a lot smaller – about less than 1 nm. You and everything around you is made of molecules. Nature has idealized the study of assembling everything around us according to molecular designs. For example, our bodies are amassed in a particular way from many living cells. Cells can be correlated with natural nanomachines. At the nuclear range, components are at their most essential level. On the nanoscale, we can possibly manipulate these particles to make nearly any structures as per our needs. A famous talk named “little wonders: the world of nanoscience,” nobel prize winner Dr. Horst störmer explained nanoscale is extra appealing than the nuclear scale on the grounds that the nanoscale remains the primary thing where we can collect things – it’s not until we begin assembling particles that we can make anything valuable. Specialists at times typically differ about what sufficiently establishes the nanoscale, yet as a standard rule, you can typically consider nanotechnology managing anything estimating somewhere in the effective range of 1 and 100 nm greater than microscale, and less than that is the nuclear range. Nanotechnology is swiftly turning into a multidisciplinary domain. Scholars, scientific experts, physicists, and specialists are completely engaged with the investigation of material properties at the nanoscale. Many scientists trust that the various controls build up a typical language and speak with each other. At exactly that key point, Dr. Horst störmer says, “can we instruct nanoscience since you can’t comprehend the universe of nanotechnology without a firm base in various modern sciences?”

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As of now, researchers discover two nano-sized structures specifically noteworthy: nanowires and carbon nanotubes. Nanowires can be remarkably small in the size of 1–100 nm, once in a while as little as 1 nanometer. Researchers would like to utilize them to fabricate small transistors for PC chips and other electronic gadgets. Over the most recent few years, carbon nanotubes have eclipsed nanowires. We’re despite everything finding out regarding these structures however, what we’ve discovered this far is intriguing. Carbon nanotube is a chamber of carbon molecules in the nanolevel. Envision a layer of carbon particles which would resemble a layer of hexagons. In the event that you fold that layer into a cylinder, you’d have a carbon nanotube. Carbon nanotube characteristics rely upon techniques of rolling the layer. As such, despite the accomplished fact that all carbon nanotubes are typically made of carbon, they can be altogether various from each other typically depending on how you adjust the specific molecules. With the precise organization of atoms, you can make a carbon nanotube that is many times greater strength than steel, yet multiple times lightweight. Leading specialists undoubtedly intend to make construction materials out of carbon nanotubes, especially for possible things like modern vehicles and planes. More lightweight means of transport would mean better eco-friendliness, and the additional quality means expanded traveler security. Carbon nanotubes can likewise be potent semiconductors with the appropriate strategy of particles. Researchers are as yet taking a shot at discovering approaches to produce carbon nanotubes, a sensible choice for transistors in microchips, and different hardware.

Innovations and Impacts By far most nanotech everyday consumer items available currently take utilize of interface impacts. The interface is a 2D surface that denotes the link between two materials. At the point when an interface is made smoother or rougher, we can manipulate surface area. To increase the surface to volume ratio we can downsize the particle size. A material comprising nanoscopic building squares displays a very huge surface region to volume proportion. This impacts for instance the reactant movement of nanoparticles. The reverse, a nanoporous framework, can be utilized as a layer infiltration form or as a protective material. This impact can likewise be abused when property of a provided substance is applied to a surface. In numerous cases, a little, practically undetectable covering of the material will at present give the wanted physical property. Additional sorts of impacts that are starting to be fused on nanotech items are quantum mechanical impacts, yet to a much smaller degree than interface impacts. Quantum mechanics can bring about exceptional optical, electrical, as well as attractive engineering properties of nanomaterials. This impact was taken advantage of as right on time as medieval occasions when gold nanoparticles were utilized to enrich church windows with a ruddy shading. A cuttingedge audio player or smartphone stores information instantly in memory utilizing the

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quantum mechanical tunnel impact. At long last, despite the fact that it’s anything but a normal physical impact as on account of interface and quantum impacts, multifaceted nature is another significant factor promoting inclusion in nanotech consumer items. The customer profits by the accession of smaller and compact gadgets have been most obviously outlined by the microelectronics industry. There gives off an impression of being no end as far as anyone can tell to the consistent advancement of processor speed and memory size by utilizing scaling down to make progressively complex hardware. A few item developments depend either on the utilization of nanoparticles or alleged nanotubes. Numerous different items manage improved water repellency. Thus these three issues are quickly presented underneath. This is followed by a far-reaching rundown of impacts and advancements. Many book chapters are available regarding nanomaterials [1–3].

Nanotechnology: Materials Perspective The absolute most encouraging nanomaterials are formations where carbon molecules led by basically in hexagons, comprising football similar structures familiar as fullerenes, chambers familiar as carbon nanotubes, and sheets known as graphene. In 1990, scientists at the Max Planck Institute for Atomic Physics and at the University of Arizona found a technique for synthesizing fullerenes in bigger amounts. This development prompted extensive fullerene-related protecting movement by substances that presently observed financially feasible chances, including scholarly professionals furthermore, organizations. Fullerenes have been utilized commercially to upgrade items, for example, badminton rackets furthermore, cosmetic agents; however, their majority encouraging applications are in natural hardware and biological sciences. The development of mono-walled carbon nanotubes – chambers with dividers produced using a solitary walled layer of carbon – was at the same time detailed in 1993 by analysts of NEC Corporation in Japan and by scientists at IBM in California [4]. Considering at that point, the investigation into carbon nanotubes has withdrawn; for instance, at the US National Science Foundation, nanotubes were the second most intensely subsidized nanotechnology point in the range of 2001 and 2010. Likewise with fullerenes, a range of business items as of now utilize carbon nanotubes, including thin films. Nonetheless, the considerable guarantee applications – those that take favorable positions of the electrical properties of carbon nanotubes – remain apparent to be numerous from the business stage [5]. Graphene, the most up-to-date carbon-based nanomaterial of intrigue, was at that point depicted hypothetically in 1947, in any case, its physical segregation didn’t happen till 2004, when Andre Geim, Konstantin Novoselov, and partners at the University of Manchester indicated that they could utilize adhesive tape to split separate graphene sheets from graphite sources. In 2010, Geim and Novoselov won the Nobel Prize for their graphene work. Their rational advancement incited impressive graphene-related protection, however with barely any business items up until this point. Graphene has applications extending gadgets to biosensing, yet huge

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obstacles to execute remains. With regard to incorporating graphene into solar cells applications and batteries maintain a guarantee for enhanced energy change and capacity, yet similar advancement requires enhancements in large-scale assembling and transportation operation. A few wonders become articulated as the magnitude of the framework size diminishes. These comprise measurable mechanical impacts, just as quantum mechanical impacts, for instance, the “quantum size impact” where the electronic characteristics of solids are changed with an incredible decrease in molecule size. This impact doesn’t become an integral factor by going from full-scale to small-scale measurements. Nonetheless, quantum impacts can become huge when the nanometer size extent is achieved, normally at separations of below 100 nm, the alleged quantum domain. Furthermore, various physical properties change when contrasted with perceptible frameworks. One model is the expansion in the surface area to volume proportion adjusting mechanical, thermal, and reactant characteristics of materials. Dissemination and responses at the nanoscale, nanostructures materials, and nanodevices from quick particle transport are for the most part said to be nanoionics. Mechanical characteristics of nanosystems are of enthusiasm for the nanomechanics study. The reactant action of nanomaterials likewise starts possible dangers in their communication with biological materials. Many books cover nanomaterials and the techniques that can play vital roles in many industrial procedures, such as increasing sensitivity, magnifying precision, and improving production limits and also environmental effects of nanomaterials [6–8]. Materials diminished to the nano-measure can show various characteristics contrasted with what they display on a macroscale, empowering special uses. A material, for example, gold, which is artificially idle at ordinary scales, can fill in as an intense substance impetus at nanoscales. A great part of the interest with nanotechnology originates upon these quantum and surface marvels that issue displays in the nanorange [9].

Consumer Nanoindustry from Molecular Perspective Current engineered science has arrived at where we can manipulate smaller molecules to whatsoever desired shape. These techniques are utilized currently to fabricate a broad range of valuable synthetic compounds in the field of pharmaceuticals or consumer polymers. This capacity brings up the issue of stretching out this sort of control to the following bigger level, looking for techniques to gather these single particles into supramolecular assembly consisting of numerous atoms organized in an all-around characterized way. These methodologies use the ideas of self-assembly additional supramolecular science to consequently organize themselves into several valuable compliances through a bottom-up approach. The idea of molecular recognition is particularly significant: Particles can be structured with the goal that a particular setup or course of action is supported due to noncovalent intermolecular forces. The Watson–Crick base-pairing requirements are a straightforward consequence of this, as is the

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particularity of an enzyme being specific to a single substrate, or the precise folding of the protein itself. In this manner, at least two segments can be intended to be reciprocal and commonly appealing with the goal that they make an increasingly unpredictable and helpful aggregate. Such bottom-up approaches ought to be equipped for creating gadgets to resemble and be a lot less expensive than top-down strategies, however might be overpowered as the scale and unpredictability of the ideal assembly increments. Majority helpful structures demand complex and thermodynamically improbable game plans of particles. Incidentally, there are numerous instances of self-assembly dependent on molecular recognition in science, most prominently Watson–Crick base pairing and chemical substrate communications. The test for nanotechnology is whether these standards can be utilized to design the latest builds notwithstanding characteristic ones.

Applications of Nanoproducts (Nps) in the Consumer Industry The recognition, the estimation, and the evaluation of NPs contained in shopper items, for example, food, food bundling, beauty care products, and individual consideration items are especially in research and development stages. Matrix, where the NPs are scattered, addresses the exploratory plan important to quantify the arrangement of physicochemical boundaries needed, a decision distinctive one case at a time case. A total nanoproducts portrayal probably won’t be attainable in all circumstances, however the consolidated utilization of various strategies.

Food Industry The innovative work of nanotechnologies in the food area is dynamic and extraordinary in all means, from food handling to the packing and transportation. Some food items presently advanced by NPs enhance the supplement and bioactive transportation frameworks, surface and flavor illustration, and microbiological control. In the domain of food handling and bundling, NPs are utilized either as antimicrobial and to construct profoundly touchy biosensors for identifying pathogens, allergens, and contaminants that can influence food quality and security [10]. The consequence of these uses is that numerous food items, expended now and again from hundreds of years and containing normally happening NPs, are currently enhanced by purposefully included or defiling NPs, and the defilement could have its underlying foundations additionally in the farming, where nanoformulations are utilized to support the agriculture [11]. In the food industry, the portrayal of nanoparticles ought to incorporate five phases: as fabricated, as conveyed for use in food/feed items, as present in the food/feed grid, as utilized in contamination testing, and as present in biological fluids and tissues, this in light of the fact that the equivalent physicochemical boundary may change in the various situations. The assurance of the

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physicochemical qualities of nanoparticles is significant in all phases since, for instance, as fabricated include the laborers’ introduction, in situ (in the food/feed lattice) is pertinent for the poisonousness testing and in natural liquids and tissues are significant for the “absorption, distribution, metabolism, and excretion.” Upon the record of representative produced nanomaterial detailed in [12], the most explored NPs in the food area are SiO2, TiO2, ZnO, and Ag since they are those straightforwardly included or in a roundabout way consolidated in food by means of ecological pollution or movement from food connection materials [13, 14].

Silica (SiO2) There are different types of synthetic silica (SiO2) for food uses. Silica colloidal are settled scatterings of nonagglomerated, for the most part round SiO2, particles utilized in the food business as a guide for explaining wine, lager, organic product juices, and so on. Precipitated silica is comprised of essential particles in the extended scope of between 5 and 100 nm, collected and clustered in the last item; it is utilized as anti-caking substance in food powders, in medicinal services items, for example, toothpaste, cleansers, and beautifiers. Pyrogenic silica comprises of agglomerated and totaled essential particles of the size normally from 5–100 nm; it is utilized in beautifiers and toothpaste as an antistatic operator in creature feed and hygroscopic powders, as a bearer for dynamic fixings, and as an antifoaming specialist in the production of decaffeinated espresso and tea, broiler, and fish handling working paper [15]. Powdery items like dry milk, instant soups, ketchup preparing blends, cake blends, espresso flavors, and nutrients are without a doubt the items where the presence of SiO2 as E551 is increasingly plausible as a result of its anti-caking properties.

Silver (Ag) Nanoparticles in the Food Industry Silver is an additive (E174) confirmed by the European Commission approved to be utilized quantum satis as a silver-dyed crush or as a minuscule sheet to shading the outside covering of ice cream parlor, for the beautification of chocolates, and in alcohols. Due to its antibacterial activity, silver is additionally permitted in the handling, the preservation, and the utilization of food, e.g., as an antibacterial covering of food readiness equipment, stockpiling compartments, bundling materials, and internal surfaces of ice chests and dishwashers, just as being consolidated into plastic food holders [16]. Nanosilver isn’t in this way thought to be a food additive, regardless of whether it may be ingested as dietary enhancements; however, it may be found in food items as a contaminant, as lingering of pesticide medicines in farming or relocating from compartments, realizing that bundling materials including AgNPs have been industrially accessible outside the European Union (EU) since numerous time [17]. Silver

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is typically looked as AgNPs, i.e., in its particulate structure considering it must remain unblemished as molecule after processing using the gastrointestinal tract [18]. In any case, silver nanoparticles are hard to be identified considering they will in general break down in particles or potentially total/agglomerate.

Titanium Dioxide (TiO2) in the Food Industry Food-class TiO2 is in the EU as E171 and its determination for food utilizes is in Commission Directive, which updates the Commission Directive 95/45/EC. In Europe, its utilization in nourishments is allowed by and large, with some predetermined exemptions, at quantum satis levels (i.e., as a great part of the substance that is required for the ideal impact, yet not more), whereas in the USA, the utilization of TiO2 as a human food–added substance should not surpass 1% by weight. TiO2 is utilized as an additive for color (splendid white, shading record CI 77891, pigment white 6) in human food items in view of its brilliance, refractive index 2.4, and as a surface changer in a wide assortment of sweet nourishments, toothpaste, and another eatable items. TiO2 is every now and again announced as a “natural color agent” and is thus all around acknowledged by customers. TiO2 is likewise utilized in oral pharmaceutical details, and the Pharmaceutical Excipients Handbook [19] considers nano-sized TiO2 a nonaggravation and nontoxic binding material. Data about the physicochemical characteristics of nanosized TiO2 for food applications is constrained despite the fact that the quantity of items containing it is extensive and expanding; no data is generally provided regarding the amount, molecule size, and molecule structure in any event, when the item is marked as including E171.

Zinc Oxide (ZnO) in the Food Industry ZnO is recorded as “usually accepted as harmless” (GRAS) by the US FDA (21CFR182.8991). As a food added substance, it is the most regularly utilized zinc supplement in the stronghold of oat-based nourishments. ZnO has been additionally joined into the linings of food jars in bundles for meat, fish, corn, and peas to save colors and to forestall decay. The flow look function for finding successful biocidal specialists, option in contrast to the highly expensive gold and silver, is concentrating on metal oxides and ZnO, in its nanoparticulate structure, and is a decent possibility for the advancement of different food bundling items as a result of its antimicrobic and ultraviolet-permeable properties [20–22]. The physicochemical portrayal of ZnO NPs for food applications is still scant, just scarcely any investigations have concentrated on the movement of ZnO nanoparticles to food and the toxicant effect of ZnO NPs should, in any case, be assessed to decide the positive or negative impacts on sanitation [23].

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Textile Industry The major drawback of fabrics is getting simply soiled. Fabrics created of cotton are lean to absorb fluids. This disadvantage can be defeated by expanding the water repellency with fluorinated carbon chains making the material more hydrophobic. A notable hydrophobic material is polytetrafluoroethylene (PTFE) or teflon. This material has been utilized to create waterproof garments, for example, Gore-Tex, which comprises a few covered layers encompassing a slender teflon film (Fig. 1). Nanoparticles, for example, SiO2, increase the washing perpetual quality of the fabric finish. Dendrimers have been accounted for to upgrade the water repellency by expanding the fluorine content in the outermost layer of texture. A few material items from connections to whole outfits have been associated with the “nano” term up until now. Anyway, the innovation is for the most part dependent on the old-style fluorinated carbon. The space of “functional materials” has developed altogether. What’s more, one potential new usefulness is the chambering of electronic gadgets into clothes, familiar as “wearable gadgets”; these may discover applications in athletic sports, medication, and well-being. Silver-containing textures have been effectively researched for rewarding neurodermatitis. Silver-containing socks have been accounted for in the forestalling foot bad odor. The notable UV-defensive property of titanium dioxide has likewise been added to material filaments. Addition of TiO2 particles to the polymer soften brings about a manufactured fiber with inserted UV assurance. This item has been effectively used to produce material with a light assurance constituent of up to 80.

Fig. 1 Schematic representation of layers corresponding to teflon/Gore-Tex. (Source-Wikimedia Commons, the free media repository)

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Consumer Electronics Industry The term nanoelectronics alludes to the utilization of nanotechnology in electronic segments. These segments are frequently just a couple of nanometers in size. Be that as it may, the smaller electronic segments become, the harder they are to produce. Nanoelectronics covers a differing set of gadgets and materials, with the basic trademark that they are little to such an extent that physical impacts modify the properties of the materials on a nanoscale – between atomic collaborations and quantum mechanical properties assume a critical job in the activities of these gadgets. At the nanoscale, new marvels overshadow those that hold influence in the full-scale world. The principal transistors worked in 1947 were more than 1 centimeter in size; the littlest working transistor today is 7 nanometers in length – over 1.4 multiple times littler (1 cm rises to ten million nanometers). The consequence of these endeavors are billion-transistor processors where, when industry grasps 7 nm assembling methods, 20 billion transistor-based circuits are incorporated into a solitary chip. Nanoscale junctions are in still research stage for various applications in consumer electronic industry[47, 48]. In modern electronics, the trendy expression “nano” has gotten focus recently because of nano-sized transistors and nano-displays with exceptional color contrast. Be that as it may, there are various areas where nanotechnology could have played a job, for example, display screens, memory, and battery. Late advancements have offered to ascend to a mammoth jump in the size of memory and processors.

Nanotechnology and Its Implications to Electronics Innovation • By lessening the size of transistors utilized in incorporated circuits. • Specialists are building up to memory chips with an expected thickness of 1 TB (terabytes) of memory for every square inch and this expands the thickness of memory chips. • By improving showcase screens/display on hardware gadgets, this lessens power utilization and furthermore the weight and thickness of the screens. • By customary scaling limits in standard complementary metal oxide semiconductor (CMOS) innovation. This improvement of nanoelectronic parts are called as “Past CMOS” area of advancement.

Applications of Nanoelectronics R&D stage • Cadmium selenide nanocrystals stored on plastic sheets are to shape adaptable electronic circuits. The point of researchers is for low-force prerequisites, basic manufacture procedure, and mix of adaptability. • Incorporating silicon nanophotonics parts into complementary metal-oxide-semiconductor (CMOS) coordinated circuits. This optical strategy is planned to give

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faster information communication between incorporated circuits than is conceivable with signs. Building up a lead-free bind solid sufficient for space missions and other highpressure situations utilizing copper nanoparticles. Working with incorporated circuits utilizing carbon nanotubes has been created by researchers at Stanford University. They had likewise evolved techniques to expel metallic nanotubes, a calculation to manage skewed nanotubes. A laser that utilizes a nano-designed silicon surface helps generate the light with a lot more tight recurrence control created by researchers at Caltech. Nanowires that would empower level board showcases to be adaptably produced using anodes. Transistors worked in single-atom-thick graphene film to empower exceptionally rapid transistors. Analysts have built up an intriguing strategy for framing PN intersections, a key segment of transistors, in graphene. Combination gold nanoparticles with natural atoms to make a transistor familiar as a NOMFET (nanoparticle organic memory field-effect transistor). Causing coordinated circuits with highlights that can be estimated in nanometers (nm). Utilizing carbon nanotubes to guide electrons to enlighten pixels, bringing about a lightweight, millimeter-thick “nano-emissive” show board. Utilizing nanosized attractive rings to make magnetoresistive random access memory (MRAM). Scientists have created less power, higher thickness techniques utilizing nanoscale magnets called magnetoelectric irregular access memory (MeRAM), and furthermore created atomic-estimated transistors which increment transistor thickness in coordinated circuits. Utilizing self-adjusting nanostructures to fabricate nanoscale coordinated circuits.

Nanoproducts in Cosmeceutical The word “cosmeceutical” is used to define a product that fits the niche between a drug and cosmetics. Cosmeceuticals are the quickest developing section of the consumer industry, and various skin cosmeceutical medicines for conditions, for example, photoaging, melanin-related Suntan, wrinkles, and hair harm have come into far-reaching use. In the cosmeceutical field, nanotechnology has assumed a significant job. Utilizing new strategies to control subjects at a nanolevel, they have been at the base of various advancements, start up new viewpoints for the eventual fate of the cosmeceutical sector. Nanotechnology-supported cosmeceuticals provide the upside of assorted variety in items, and expanded bioavailability of dynamic fixings and increment the tasteful intrigue of cosmeceutical items with delayed impacts. Anyway, expanded utilization of nanotechnology in cosmeceuticals has elevated worry regarding the conceivable infiltration of nanoparticles through the skin and expected dangers to people’s well-being. Among the innovations utilized to

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create exquisite and powerful cosmeceuticals, nanotechnology discovers uncommon spots. In the restorative field, it is accepted that the smaller particles are promptly assimilated into the skin and fix harm effectively and all the more productively [24]. Integration of nanotechnology and cosmeceuticals is planned for making infuriate scents last more, sunscreens to protect the skin, antiaging creams to retaliate the years, and lotions to keep up the hydration of the skin. A portion of the nanotechnologysupported developments are nanoemulsions, nanocapsules, nanopigments, liposome plans, nanocrystals, strong lipid nanoparticles, carbon nanotubes, fullerenes, and dendrimers. The essential favorable circumstances of utilizing nanoparticles in cosmeceuticals remember progress for the dependability of corrective fixings by epitomizing inside the nanoparticles; proficient security of the skin from destructive bright (UV) beams; tastefully satisfying items focusing of dynamic fixing to the ideal site; and controlled arrival of dynamic elements for delayed impact [25, 26].

Moisturizers Stratum corneum is the essential barrier between the body and the external environment. Water from the layer corneum gets dissipated rapidly prompting parchedness. This lack of hydration of skin can be deflected by utilizing lotions that give adaptability to the skin. At the point when lotions are applied to the skin, a thin film of humectant is shaped which holds dampness and provides a superior look to the skin. Liposomes, nanoemulsions, and solid lipid nanoparticles are broadly utilized saturating plans on account of their drawn-out impacts. These are viewed as the most helpful item for the administration of different skin conditions.

Sunscreens Sunscreens are applied to protect the skin from harmful sunlight. Zinc oxide (ZnO) and titanium dioxide (TiO2) are the best affirmed mineral-based fixing that shields the skin from sun harm. This mineral structures a materialistic boundary on the skin that reflects UVA and UVB beams from infiltrating bottom to the more deeper layers of skin and is less bothering [27]. The principal disadvantage of sunscreens is it leaves white powdery substance on the skin [28]. This is the place nanoparticles take into play. Enhanced sunscreens are only one of the numerous imaginative employments of nanotechnology. Sunscreen items utilizing nanoparticles of ZnO or TiO2 are straightforward, less oily, and less rank and have expanded stylish intrigue.

Anti-Aging Products Chemical items, contamination, stress, harmful sun rays, and scraped areas are engaged with skin maturing. Collagen assumes a significant job in skin restoration and wrinkles inversion impact. The amount of collagen in the skin diminishes

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alongside age. The maturing of the skin shows itself from multiple points of view: drying out, loss of versatility and surface, diminishing, harmed obstruction work, the appearance of spots, alteration of surface line isotropy, and, at long last, wrinkles. The greater part of the cosmeceuticals have been created with cases of anti-wrinkle and firming, saturating and lifting, and skin conditioning and brightening action. Anti-aging items are the fundamental cosmeceuticals in marketing as of now being made utilizing nanotechnology. L’Oreal has utilized nanotechnology in items, for example, Revitalift anti-wrinkle cream which contains nanosomes of Pro-Retinol An, and claims that it immediately retains the skin and decreases the presence of wrinkles. The use of retinol can increment epidermic water content, epidermal hyperplasia, and cell restoration while improving the collagen union [29]. Retinol additionally meddles with melanogenesis and represses lattice metalloproteinases, which are engaged with collagen breakdown. The medical advantages remember a decrease in the presence of barely recognizable differences and wrinkles and helping of lentigines [30]. Lancôme acquaints Hydra Zen Cream with recharge the skin’s solid look which comprises nano-encapsulated tri-ceramide [31].

Hair Care Hair care is one more encouraging domain for nanotechnology. Industries are utilizing nanotechnology in hair care items and exploration is continuous to find the methods of how nanoparticles can be utilized to forestall going bald and preserve glow, and well-being of hairs. Not at all like normal hair fixing items, nanoemulsion in hair makeup doesn’t obliterate the external structure of the hair filaments, called fingernail skin, to infiltrate into the hair strands. Sericin made out of cationic sericin nanoparticles is a functioning territory of hair cosmeceuticals. Research has demonstrated that sericin nanoparticles in hair cosmeceuticals effectively cling to the outside of the hair seal and handle the harmed fingernail skin [32].

Skin Cleaning Application The skin is secured with a hydrolipid layer that, contingent upon the territory of the bodies, contains emissions from sebaceous organs and from apocrine and eccrine perspiration organs. Decay items from corneocytes and cornification during the time spent being spilled are additionally present. This film gives a characteristic safeguard counter pathogenic life forms yet in addition draws in soil and toxins from the earth. In some cases, the microbes there on the skin exterior follow up on segments of the surface film and make unwanted side effects, for example, those subsequent from the digestion of mixes found in apocrine perspiration that make stench [33]. Therefore, occasional purifying to evacuate the useless, dirt, and smell is basic to keep up skin well-being. Purifying is additionally important to evacuate the dirt (which may incorporate microscopic organisms) from the skin exterior that is procured by accidental touch or by deliberate application (prescriptions or cosmetics and other

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restorative items). Silver nanoparticles are utilized as skin disinfectants and sterilization. Nano Cyclic Inc. makes nanocyclic a chemical pink cleanser which is a deductively adjusted mix of nanosilver and characteristic fixings and cases that it executes destructive microscopic organisms and parasites, battle skin breaks out, and decreases age spots and sun-harmed skin [34].

Lip and Nail Care Lip care is one more hopeful category of cosmeceuticals. Distinctive nanoparticles can be fused into lipstick and lip sparkle which will relax or relieve the lips by forestalling transepidermal water loss. Korea Research Institute of Bioscience and Biotechnology possess a patent that depicted that it is conceivable to get ready shades showing the wide scope of colors utilizing gold or silver nanoparticles by blending in different make-up proportions and whose shading can be kept up for an extensive stretch of time [35]. Nanoparticles of silica are utilized in lipsticks to enhance the homogenous circulation of shades. When applied, they keep the shades from relocating or seeping into the scarcely discernible difference of lips [36]. Nanotechnology-supported nail cosmeceuticals have different preferences over traditional items. An examination uncovered that nail polishes having nanosized particles increase strength, deface obstruction, and effective opposition of the human nails. Nano Labs Corp. (a nanotechnology innovative work organization) was granted a temporary patent for its unique nano-nail clean and polish having favorable circumstances that it dries to a hard state, opposes stun, splitting, scratching, and chipping and its flexibility offers prevalent simplicity of utilization without breaking. One of the new procedures which may have the extraordinary possibility in the cosmeceuticals is the consolidation of nanoparticles having antifungal action in nail clean to treat parasitic toenail diseases.

Exposure and Penetration of Nanoparticles to Skin and Body Utilization of nanoparticles has made new changes; however, it additionally presents a few dangers and vulnerabilities. Expanding the creation and utilization of nanomaterials brings about an expanding number of laborers and buyers presented to nanomaterials. This shows there is a more noteworthy requirement for data on their risk paths. Human beings’ paths of vulnerability to nanoparticles are breath ingestion, and dermal courses [37]. Breath intake is the most widely recognized route of presentation to airborne nanoparticles [38]. Laborers may breathe in nanoparticles while manufacturing or end customers may breathe in on the utilization of aerosolized cosmeceuticals. The statement of nanoparticles in the respiratory framework relies upon their associations with respiratory epithelium film. Nanoparticles may move by means of the nasal nerves to the cerebrum and access the sensory system [39]. In light of their size, these nanoparticles can without much of a stretch access the circulation system inhalation or skin and from that point, they are shipped to the different organs. Ingestion may happen from

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unexpected hand to mouth movement of nanoparticles or from those cosmeceuticals that are application close to the mouth or lips. Huge divisions of nanoparticles quickly drop off the body after ingestion, yet a little part might be captured up by the body which moves into the various organs [40]. Another path of introduction of nanoparticles into the circulation is dermal ingestion. Dominant parts of cosmeceuticals are applied to the skin. Three pathways of entrance over the skin have been recognized: intercellular, transfollicular, and transcellular [41]. Development of the cosmeceutical sector is expanding step by step as the cosmeceuticals advertise is exceptionally differentiated, with items originating from major and little makers and neighborhood organizations around the globe. Nanotechnology speaks to the key advances of the twenty-first century, offering fantastic open doors for both exploration and enterprise. The fast spread and marketing of nanotechnology in cosmeceuticals have offered an ascend to extraordinary specialized and financial yearnings, yet additionally question about the rising dangers to well-being and security of customers. Subsequently, cosmeceutical items dependent on nanotechnology ought to be structured and sold in a manner that completely regards the strength of customers and nature [42].

Innovations in Nanoconsumer Industry Easy-to-Clean Products The issue of exterior floor or any product surface contamination is huge, particularly while taking into account more energy surfaces, for example, glass or metal, which have a solid inclination to absorb different particles. Regular techniques depend on the decrease in surface free energy without losing the material characteristics, for example, transparent materials. By and large the water and oil repellency is expanded when the contact edge of the water is above 100
. This wonder is used in nonstick surfaces, for example, fricasseeing skillet (Teflon). New methodologies depend on natural/inorganic nanocomposites which give characteristics like perfluorinated polymers such as teflon.

Anti-Graffiti The significant disadvantage of regular plaster, blocks, or cement is its solid sponginess which gives an amazing substrate to extensive spray painting. A normal way to deal with this depends on a polyurethane (PUR) covering that gives perpetual insurance and prevents the paint from penetrating into the divider. This can comprise a two-segment framework, which responds after applying straightforwardly on the divider. Any spray painting on the ensured exterior can be expelled without any problem. In any case, there is little in this covering that is true “nano,” in spite of the fact that this term is now and again referenced in this field.

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Antimicrobial Coating Battling microorganisms is regularly accomplished by specific chemical agents. Two inorganic methodologies can be utilized for cleaning surfaces. The first is in light of the photocatalytic action of titanium dioxide as depicted underneath. The second endeavors the toxicity of specific metallic cations, for example, silver. Silver has since quite a while ago been familiar with its amazing antimicrobial impact because of the arrival of silver particles which are taken up by organisms and apply a harmful impact. Present day draws near increment its movement by scattering silver in ultrafine particles. The outrageous increment in surface region upgrades silvers’ normal disinfecting capacity.

Anti-Fingerprint Metallic surfaces, for example, hardened steel obtain effortlessly recolored when contacted with exposed hands. The optical reflectivity of the material modifies because of the exchange of oil from the skin despite the fact that the deposit of finger grease cannot be avoided completely, an anti-fingerprint coating diminishes the sight by cloaking their traces (refractive index) of the protecting covering matches that of the oil. In this manner, enemies of fingerprints covered metal surfaces show up darker contrasted with their unprotected partners.

Antifog Bringing a cold surface into a hotter encompassing will prompt fogging. This impact is unavoidable except if the surface is warmed. It results from the arrangement of small beads on the reflection surface dispersing the light and nebulizing reflections. A super hydrophilic covering can forestall drop formation partly. The droplets just converge into a slim water layer on the mirror without modifying the reflectivity to an extreme. Photocatalytic TiO2 coverings are super-hydrophilic when presented to adequate UV light.

Corrosion Protection Metallic portions in car fabricate are usually heat treatment to accomplish the wanted form. Throughout this warming procedure the steel will erode. It very well may be ensured against high-temperature consumption by applying a nanoparticulate covering.

Wear and Tear Protection A decrease of abrasion on surfaces in mechanical contacts can be accomplished likewise by diminishing grating or by hardening surfaces through coverings. The grating coefficient can be diminished by diamond-like carbon coatings (DLC). These

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amorphous coverings provide a hardness of around 20 GPa. One more methodology is in view of surfaces which decrease erosion productively.

Scratch Resistance Tough nanoparticles, for example, SiO2, can be utilized to develop scratch-safe coverings. For instance, they can be joined in a natural framework to enhance the scratch opposition of polishes.

Tensile Strength Addition of nanoscale parts into composites will improve their tensile and impact strength quality. Carbon nanotubes provide the most elevated elasticity ever watched. Regarding this, carbon nanotubes are relied upon to be of incredible significance in the future.

Insulation The standard of insulating material depends on large porosity which encases as much air as could be expected under the circumstances. The material uses the low thermal conductivity of air, also, free wind current is repressed. In this manner, the density of material is a significant measure. The lower the density the more air is encased and the improved the protection will be. The protecting capacity of a provided material, for example, glass wool, can be expanded by thickening the protecting layer. In such a manner, nanoporous materials provide prevalent properties. Silica aerogels have the most minimal thermal conductivity and density, everything being equal. They are some of the time called frozen smoke. Their warm conductivity can be as low as 0.016 W/(m·K)4, with a thickness of 0.005–0.2 g/cm3. They are made by a sol-gel process. In any case, silica aerogel is extremely fragile and costly to deliver. In this manner, adaptable and less expensive choices have been created, which offer predominant protection and can be a lot more slender than customary protecting material.

Photocatalytic Surfaces Very hydrophobic areas are tainted to a far lower degree than surfaces with a higher interfacial pressure. Furthermore, freely reinforced dirt particles are evacuated effectively by wetting. Other than this technique to build the characteristic stain repellency of a surface by decreasing its free energy, we can straightforwardly assault adsorbents by deteriorating them through photocatalysis. Consequently even a profoundly sticky surface, for example, glass, could be outfitted with a self-cleaning finish which is enacted with ultraviolet light.

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In any case, this methodology is just appropriate for exterior applications. A typical material for photocatalytic coatings is titanium dioxide (TiO2). TiO2 is a light scatter and a UV safeguard. The main property makes it an ideal element for white paint (white color), the last gives the self-cleaning and UV-secure capacity. TiO2 is a compound semiconductor which exists in three distinctive substance structures: anatase, rutile, and brookite type, and just the initial two are broadly utilized for various applications. The photocatalytic action can be improved by bringing down the recombination rate of electrons and holes in anatase TiO2 particles. This can be accomplished by doping the particles with silver. The presence of silver gives an extra antibacterial quality as recently portrayed.

Antireflective Coating In numerous applications, a solid reflection from a flat surface is bothersome, for example, for spectacles or displays. The reflectivity of a surface can be diminished by two various ideas: the first presents a nanoscale and nano-roughness, which diminishes uniform reflection through light dissipating. This idea is once in a while alluded to as a nano-moth-eye structure in light of the fact that a similar rule is found in insects which helps in camouflage. It can likewise be utilized to build the affectability of solar-based cells because of the upgraded transmission. In any case, the magnitude of a productive moth-eye structure must be in the range of 150–200 nm. The least demanding approach to acquire such a structure is decorating, which is constrained to nearly little regions. The subsequent idea depends on the covering of alternating layers of silicon dioxide and titanium dioxide. These two materials give a solid difference in refractive index bringing about an altogether higher transmission and diminished reflection. Despite the fact that being increasingly costly, the subsequent idea offers superior control. Be that as it may, the thickness of the layers is in the scope of a few hundred nanometers and in this way not really a topic of nanotechnology.

Nanophotonics and Consumer Industry Nanophotonics is classified under nanophysics and is the unification of nanotechnology with photonics. On a very basic level, it is a blend of photonics and optoelectronics at nanoscale measurements. Nanophotonics innovation is empowering a wide scope of photonics items going from high-productivity solar cells to ultrasecure communication followed by health care. Despite the fact that numerous nanophotonics items are as yet under examination, numerous items, for example, nanophotonics PV cells, nanophotonics LEDs, and nanophotonics OLEDs are impressively driving the market development. The interest for cutting-edge gadgets, for example, longer battery life, compacted size, more noteworthy information transmission speed, and high usefulness can be accomplished by executing nanophotonics innovation.

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In the gadgets business, scaling down of segments and their integration has been drifting for longer than 10 years. With the appearance and radical universality of cell phones, the drive to accomplish more prominent productivity from the smallest gadgets has additionally picked up boost and given energy to the nanophotonic gadget to advertise the world over. As indicated by the United Nations Industrial Development Organization (UNIDO), worldwide creation has been developing fundamentally throughout the previous, not many years, in this way prompting an expansion in the worldwide portion of manufacturing value added (MVA) in GDP (gross domestic product) from 15.1% to 16.5% during 2009–2018. The MVA development rate which shows the advancement of manufacturing enterprises powers development of the nanophotonic gear showcase. Nanophotonic gadgets are generally utilized in ventures, for example, telecommunication, health care, semiconductors, aviation and defense, consumer electronics, and also in the automobile industry. Because of the higher switching speeds of the photonic incorporated circuits, nanophotonic products include a more appeal inside signal processing applications. Nanophotonics gets new possibilities in the instrumentation for nanoscale, data and communication management, chemical and biomedical sensor application, advanced solar cell and lighting, environmental remediation, and medical treatment. The widespread development of cybercrime exercises across numerous divisions is the key factor in increasing the development of the nanophotonic equipment industry. Nanophotonic chips are picking up noticeable quality in fiber optics links of huge server farms to forestall digital attacks. The information helped through optical fibers is encoded, empowering a solid forward leap in cybersecurity. The nanophotonic equipment showcase esteem is foreseen to reach $1.5 billion by 2023, developing a compound annual growth rate (CAGR) of 21.23% over the figure time of 2018–2023 [43]. Optical filters are finding more applications in UV resistance, antireflection and protection against scratches and abrasion etc. Many recent researchs are promising in innovation and take consumer market in the next decade[44–46].

Advantages and Disadvantages of Nanotechnology Since any technology comes with both pros and cons, nanotechnology also has few, but when compared to the impact it is giving in the consumer industry or many sectors, drawbacks are negligible.

Potential Advantages • Nanotechnology is now producing new materials accessible that could transform numerous zones of production. For instance, nanotubes and nanoparticles, which are cylinders and particles just a couple of atoms over, and aerogels, materials made out of light and solid materials with insulating properties, could make ready for new methods and predominant items. Also, robots that are just a couple of

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nanometers long, called nanobots, and nanofactories could help build original materials and items. • Nanotechnology may change the manners by which we get and use energy. Specifically, solar power may become cheaper. Energy-storing gadgets will turn out to be increasingly productive thus. Nanotechnology will likewise start new techniques for creating and storing energy. • The area of gadgets is set to be reformed by nanotechnology. Quantum dots, for instance, are minuscule light-producing cells that could be utilized for brightness or for cause, for example, display screens. Silicon chips would earlier be able to include a large number of parts, however, the innovation is arriving at its limit; at one point, circuits become so little that if a molecule is out of place circuit won’t work properly. Nanotechnology will permit circuits to be developed precisely on an atomic level. • Nanotechnology can possibly get significant progress in medication. Nanobots could be sent into a patient’s arteries to gather up blocks. Medical procedures could turn out to be a lot quicker and progressively exact. Wounds could be fixed cell by cell. It may be possible to even repair genetic disorders. Nanotechnology could likewise be utilized to improve drug production, fitting medications at a molecular level to produce them progressively compelling and diminish adverse effects.

Potential Drawbacks • Since these particles are little, issues can really emerge from the inhaling of these nanoparticles, much like the issues an individual gets from breathing in minute asbestos particles. • By and by, nanotechnology is pricey, and creating it can cost you a ton of cash. It is likewise entirely hard to make, which is presumably why items made with nanotechnology are increasingly costly. • Because of very compact-sized recording devices and cameras, the possibility of misuse of them raises privacy and security concerns. • Due to very small particle sizes, there’s a possibility of lotions and skincare products can get into the bloodstream; it may be a toxin. • All things considered, nanotechnology, as different advances before it, will cause significant changes in numerous economic zones. In spite of the fact that items made conceivable by nanotechnology will at first be a costly extravagance when accessibility expands, an ever-increasing number of business sectors will feel the effect. A few innovations and materials may get out of date, prompting organizations to spend significant time in those regions leaving the enterprise. Modifications in production forms realized by nanotechnology may bring about occupation misfortunes like reduction of employment. • Nanotechnology increases the chance of little recording gadgets, which would be practically imperceptible. All the more genuinely, it is conceivable that nanotechnology could be weaponized. Atomic weapons would be simpler to make and

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further arms may likewise be created. One chance is the purported “intelligent bullet,” an automated projectile that could be monitored and pointed precisely. These improvements may demonstrate an aid for the defense; yet in the event that they fell into inappropriate hands, the outcomes would be critical.

Conclusions The consumer products effectively accessible have just started to misuse the capability of nanotechnology. As has appeared in this chapter, most customer items right now accessible depend on interface impacts. In any case, the significant possibility that can be normal from the enormous research interest in nanoscience has not yet reached the buyer. For instance, customer items that misuse quantum impacts or the one of a kind electronic properties of carbon nanotubes have just started to scratch the surface. Moreover, there are different impacts that show guarantee. The genuine guarantee of nanotechnology may show up when items start to make utilization of more than one of these impacts. For example, the fuse of carbon nanotubes into sports items utilizes their mechanical quality and high surface region to volume proportion, yet future items could likewise use their electronic properties and little size, for instance interfacing various levels in coordinated circuits or for working up novel nanotube transistors. Such an approach may prompt progressive items that can extraordinarily improve the personal satisfaction of the normal purchaser.

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and dyed hair. US Patent. 8709455. Available: https://patentimages.storage.googleapis.com/ad/ 1c/92/67b401b7504d9b/US8709455.pdf 33. Ertel K. Personal cleansing products: properties and use. Cosmetic formulation of skin care products. CRC Press; 2005. p. 59–90 34. Cyclic Cleansing Bar 40g PINK. In: www.lunese.com [Internet]. [cited 17 Jul 2020]. Available: http://www.lunese.com/ProductDetails.asp?ProductCode¼CY-40P 35. Chung BH, Lim YT, Kim JK, Jeong JY, Ha TH (2009) Cosmetic pigment composition containing gold or silver nano-particles. US Patent 20090022765:A1. Available: https:// patentimages.storage.googleapis.com/a1/39/10/e7fbc227336fba/US20090022765A1.pdf 36. Petit JLV, Gonzalez RD, Botello AF (2013) Lipid nanoparticle capsules. US Patent 20130017239:A1. Available: https://patentimages.storage.googleapis.com/16/2a/ad/ ffd5ea23feba98/US20130017239A1.pdf 37. Oberdörster G, Oberdörster E, Oberdörster J (2005) Nanotoxicology: an emerging discipline evolving from studies of ultrafine particles. Environ Health Perspect 113:823–839 38. Yah CS, Iyuke SE, Simate GS (2012) A review of nanoparticles toxicity and their routes of exposures. Iran J Pharm Sci 8:299–314 39. Gupta RB, Kompella UB (2006) Nanoparticle technology for drug delivery. Available: http:// www.gimitec.com/file/49.pdf 40. Raj S, Sumod US, Jose S, Sabitha M (2012) Nanotechnology in cosmetics: opportunities and challenges. J Pharm Bioallied Sci:186. https://doi.org/10.4103/0975-7406.99016 41. Buzea C, Pacheco II, Robbie K (2007) Nanomaterials and nanoparticles: sources and toxicity. Biointerphases 2:MR17–MR71 42. Lohani A, Verma A, Joshi H, Yadav N, Karki N (2014) Nanotechnology-based cosmeceuticals. ISRN Dermatol 2014:843687 43. Zion Market Research. Global nanophotonics market expected to reach USD 66.03 Billion by 2022. [cited 19 Jul 2020]. Available: https://www.zionmarketresearch.com/news/nano photonics-market 44. Pirvaram A, Talebzadeh N, Rostami M, Leung SN, O’Brien PG (2021) Evaluation of a ZrO2/ ZrO2-aerogel one-dimensional photonic crystal as an optical filter for thermophotovoltaic applications. Thermal Science and Engineering Progress, Elsevier 45. Yang D, Kumar S, Wang H (2009) Temporal filtering technique using time lenses for optical transmission systems. Advances in Imaging and Electron Physics, Elsevier 46. Shilpa R, Mudachathi R (2021) Increasing the free spectral range of Fabry-Perot cavities using dissimilar 1D photonic crystals. Materials Letters, Elsevier 47. Roy TR, J.D.R. J, Sen A (2021) Inelastic tunnel transport and nanoscale junction thermoelectricity with varying electrode topology. Adv Theory Simul 4:2100054. https://doi.org/10.1002/ adts.202100054 48. Niu, L-L, Fu H-Y, Suo Y-Q, Liu R, Sun F, Wang S-S, Zhang G-P, Wang C-K, Li Z-L (2021) Physica E: Low-dimensional Systems and Nanostructures, Elsevier

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Consumer Nanoproducts: A New Viewpoint Sherly Antony, Prasanth Rathinam, R. Reshmy, Raveendran Sindhu, Parameswaran Binod, and Ashok Pandey

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Definition of Consumer Nanoproduct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . History and Characteristics of Consumer Nanoproduct . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effects on Health and Environment Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Database or Inventories on Consumer Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Products Inventory (CPI) of Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Nanodatabase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Others . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Marketing of Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulations and ISO Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GHS and Labeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . International Organizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Various Expert Committees in USA and European Continent Include . . . . . . . . . . . . . . . . .

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S. Antony Department of Microbiology, Pushpagiri Institute of Medical Sciences and In-charge of Microbial Technology and Infectious Diseases Laboratory, Pushpagiri Research Centre, Thiruvalla, Kerala, India P. Rathinam Department of Biochemistry, Pushpagiri Institute of Medical Sciences and In-charge of Biochemistry Laboratory and Medical Biotechnology Laboratory, Pushpagiri Research Centre, Thriuvalla, Kerala, India R. Reshmy Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara, Kerala, India R. Sindhu (*) · P. Binod Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary, Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, India A. Pandey Centre for Innovation and Translational Research, CSIR- Indian Institute for Toxicology Research (CSIR-IITR), Lucknow, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_106

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Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

Abstract

The last two decades has witnessed several consumer nanoproducts based on nanotechnology and nanomaterials being increasingly developed and marketed at a fast rate. With more and more products being added each year, one needs to understand the complexities behind the development of these products, their scope of use, and their marketing strategies. Regulations are now put in place for the manufacture, transportation, routine use, and disposal of these nanoproducts as they have been noted to have a tremendous impact both on environment and human health. Hence, newer and greener nanotechnology is the need of the hour! History of development of these products, their ever-evolving use in daily life, and the various inventory databases are lined out in detail in this chapter. Keywords

Consumer nanoproduct · Nanotechnology · Nanomaterials · Nanostructured materials · Nanoproduct database · Inventory nanoproducts

Introduction Nanoscaling and its various scientific applications have brought forth the advent of a new era of nanotechnology and nanoscience. This revolutionary technology comes with a futuristic vision of societal change, economic growth, and a sustainable environment. The myriad of possibilities for its applications as consumer products being with nanomaterials (NMs) has been incorporated in varying order of quantity and miscellany (Table 1). There is evident large-scale commercialization and delivery of nanoproducts thus translating bench side research into marketed consumer products. A big multibillion dollar industry now exists with NMs in various aspects of biomedical engineering and healthcare, automotive manufacturing, appliance manufacturing, cosmetics, food and beverages, energy applications, information technology, and construction. Yet, regulatory issues do exist with regards to toxicity, disposal, and accumulation in environment and possible health hazards in humans and animals [11, 48].

Consumer Nanoproducts Definition of Consumer Nanoproduct A plethora of products available in the market contain or are derivatives of nanomaterials. Many products have used the term nano to indicate the small size without actually having any nanomaterials [25]. Therefore, a “consumer nanoproduct” or

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Table 1 Important terminologies and their definitions used in this book [7, 19, 28, 42] Term One nanometer Nanoscale/Nanosize Nanoscience

Nanotechnology

Nanomaterial

Nano-object Nanoparticle Nanofiber Nanocomposite Nanostructure Nanostructured materials

Definition One millionth of a millimeter (1 nm {metric} ¼ 109 m{SI}) “nano” derived from the Greek word meaning dwarf Approximately diameter in the range of 1–100 nm (ISO/TS 12805:2011) or EC Definition (2011/696/EU) The study of phenomena and manipulation of materials at atomic, molecular, and macromolecular scales, where properties differ significantly from those at a larger scale The design, characterization, production, and application of structures, devices, and systems by controlling shape and size at nanometer scale [42]. Richard Feynman, a physicist in 1959 who is considered as the father of nanotechnology, introduced this concept. But, the term was first used in 1974, by a researcher at the University of Tokyo named Norio Taniguchi EC Definition (2011/696/EU) states that NM is a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm – 100 nm [18] Material that possesses one or more peripheral nanoscale dimensions Nano-object with three external nanoscale dimensions A nanomaterial with two analogous exterior nanoscale dimensions and a third larger dimension A multiphase structure with no less than one phase on the nanoscale dimension Composed of interconnected constituent parts in the nanoscale region Materials containing internal or surface nanostructure

“nanotech product” is defined as mixtures and articles containing or derived nanomaterials available in market for use by consumers [11]. This represents any product with (or claiming to contain) manufactured nanomaterials, even small quantities nanomaterials [10]. The product has to go through different stages of R and D, manufacturing, and regulations before it reaches the consumer (Fig. 1). The purpose of the products is used to define the different product categories, e.g., health and fitness products, food and beverages, cross-cutting, automotive, and goods for children. When the product category is subdivided, it is known as the product type, e.g., health and fitness group includes subcategories like sporting goods, personal care, cosmetics, filtration, clothing, and sunscreen [10]. There is definitely a gray zone in the knowledge in various databases which all products are actually available in the market and the source and exact quantity of nanomaterial in them [21]

Nanomaterials (NMs) There are many loopholes for labeling nanoproducts as a well-harmonized definition for nanomaterials still does not exist. Details are depicted in Table 1. There may be

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Fig. 1 Development of an ideal consumer nanoproduct through different stages of research and development and marketing regulations

appreciable differences in many of its properties when compared to the macromolecular counterpart [25, 31, 45].

Nanostructured Materials (NSM) For definition, refer to Table 1.

History and Characteristics of Consumer Nanoproduct The evolution of nanotechnology and nanoscience has resulted in development of various products. The two major phases of discovery and development in nanotechnology were [41]: (i) Nano-I (first foundational phase): This science centric phase occurred in the first decade of nanotechnological advancements, i.e., 2001 to 2010, where the focus was on research mainly inter-disciplinary research at the nanoscale. It resulted in identification and elaboration at nanoscale of new phenomena, characteristics, properties, and functions; creation of a library of modules which would be the corner stone for future services; and gradual improvement of already existing products. (ii) Nano-II (second foundational phase): This R and D phase driven by socioeconomic considerations occurred during 2011 to 2020 where the focus was on more complex nanosystems where the base is an amalgamation of science and engineering. This has helped in a smooth transition toward measuring directly in a good time resolution, designing of new products, and bulk use of nanotechnology.

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Composition and Classification of Nanomaterials The major four material-based categories [31] include the following: (i) Carbon-based: From the name itself, NMs, those containing carbon atoms, e.g., fullerenes (C60& C70), carbon nanotubes (CNTs), carbon nanofibers (CNFs), vapor-grown carbon fibers (VGCFs)/vapor-grown carbon nanofibers (VGCNFs), carbon black, graphene (Gr), and carbon onions. They can be produced by laser ablation, arc discharge method, chemical vapor deposition (CVD), and by catalytic chemical vapor deposition (CCVD). (ii) Inorganic-based: They comprise metal and metal oxides, e.g., gold or silver, titanium dioxide (TiO2) and zinc oxide (ZnO), and silicon dioxide (SiO2). They can be synthesized by precipitation of salts in aqueous medium, hydrothermal synthesis, micro-emulsions, polyol process, etc. (iii) Organic-based: NMs made from organic matter by help of weak interactions. (iv) Composite-based: They are multiphase, i.e., they are made by combining NPs with other NPs or with larger bulk-type materials.

Sources of Nanomaterials The lines of demarcation between the three sources are often blurred resulting in overlapping of the origins. The three sources of NPs are: (i) Incidental nanomaterials: They are by-products of industrial processes and rarely natural events thus produced incidentally. (ii) Engineered nanomaterials (ENMs): They are synthetic, e.g., carbon NPs, TiO NPs, and hydroxyapatites. They are seen in NPs in varied biomedical and healthcare products, part of diesel, engine exhaust, cigarette smoke, building demolition, etc. (iii) Naturally produced nanomaterials: They are found occurring naturally in the environment. Nanobacteria like Pseudomonas stutzeri were found to produce metal NPs by binding to heavy metals and acts by precipitating [26]. Nanobes are novel nano-organisms, discovered on sandstones in Western Australia [47]. Magnetotactic bacteria produce magnetic oxide NPs which continue to be harnessed in biomedical application [2].

Five Nanomaterial Properties The size, agglomeration, impurity, contaminant dissociation, recycling, and disposal are the five properties of NPs based on which there is a risk description. This is associated with risk of corrosion, instability, degradation properties, and accumulation in flora and fauna including human beings [10, 11, 27, 35]. Range of Products and Applications First NMs to be incorporated were nanoclays into polymer resins, i.e., nylon 6-clay hybrids in Toyota car manufacturing in 1989 which improved its overall sturdiness, durability, and stability [39]. Following this, many metallic nano-oxides like TiO2, ZnO,

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SiO2 were also used widely in products with cleaning properties, in UV light protection, or in other products with special viscoelastic behavior. The ENPs that were first commercialized in medical field were in pharmaceuticals, for example, addition of metallic oxide (ZnO and TiO2) in sun block creams. Following this nanoparticulate silver was incorporated into chronic wound-care dressings owing to its antimicrobial properties. Lately CNTs and graphene owing to their properties and unique structures are being incorporated into various consumer products. Hence now the clearly identifiable five major categories of nanoproduct composition are there. They are: (i) (ii) (iii) (iv) (v)

Those products which have not expressed or not advertised the content Metal and their oxides Carbonaceous NMs Silicon-based NMs Others like polymers, organics, ceramics, etc.

The different nanomaterials in consumer products where the majority of nanoproducts have a nanomaterial composition is suspended in liquids like water, oil, lubricants, creams, followed by solid products like mixtures of CNTs plus plastic and surface bound like textiles, a laptop keyboard coated with AgNPs others include bulk, nanostructured bulk (nanoscale computer processor), nanostructured surface (nanofilm-coated products) [10, 11, 48]. The timeline for the development of various consumer nanoproducts and processes began in the early twenty-first century. Presently there are four generations of development of consumer nanoproducts [41]. (i) First-generation nanoproducts: During the 2000s, various passive nanostructures were incorporated into products. The nanoscale element like NPs or nanoclay platelet or NTs were integrated into a matrix material fit for coatings, films, and composites or they were used as a part of a bulk NSM. (ii) Second-generation nanoproducts, i.e., active nanostructures were used extensively during 2005 to 2010. The nanoscale element is the functional structure nanospheres and NSMs for drug delivery which would respond to external stimuli such as pH or temperature giving a controlled release. In addition, nanowires with amplifying mechanistic action were used as sensors and actuators, transistors, and other electronics. (iii) Third-generation nanoproducts were having mainly 3D nanosystems (2010 onwards). They were being used in bio-assembly systems (e.g., template DNA and viruses), electrical and chemical template-guided assembly. (iv) Fourth-generation nanoproducts (2015 until 2020): represented by an assorted molecular nanosystems with targeted molecular level functions.

Effects on Health and Environment Safety With the promise of benefits, nanoproducts have stormed the markets and have found their way to our daily life. Various nanotech or nanoproducts having NMs

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or ENMs in them are integrated or laced on to our day to day usage. The critical gaps in knowledge and the lack of uniformity in its regulations both in industry and research globally have spelt out an impending problem. The possibility of it being a double-edged sword need to be kept in mind, and serious consideration of its deleterious effects on our health as well as environment need to be undertaken before its release into the global or local markets. The process of the large-scale manufacturing of nanoproducts, its proposed use, the exposure levels in humans, problems faced in its discarding, and handling either in the original or modified forms ultimately translates to no restriction for its movement, through the environment and this foist blatant and latent health risks both in humans and in the environment (Fig. 2) The major challenge in this is that the NMs need to be detected and quantified to evaluate their state, the translocation phenomena, and bio-persistence. In humans, foreign substances or organisms normally have to face certain barriers. The largest barrier is the skin unless and until a breach is there in the epithelium, while some organs like the lung and GIT are easily susceptible. The origin of NPs and the various routes by which they access humans includes inhalation, ingestion, and direct skin contact. NPs which are inhaled or ingested can readily spread through the circulation and reach the other sites or organs in the human body [8, 14, 15, 48], while for the environment, exposure is related to material aging, waste production, and disposal [35]. The probable chance of exposure to the NMs in nanoproducts depends mainly on the site of exposure (Table 2).

Toxicology Data of Nanomaterials A screening-based strategy is needed in real time within a bigger testing background for environmental health and safety (EHS). This is to serve as the first impediment that a nanoproduct and ENM-enabled product must pass before they are being exposed to more laborious testing. Many suggestions have elaborated on a five-tier screening process where the first tier is a routine screen based on material amount, technology categories, size, properties, and use. This is followed by a tier 2 where categorically a 100% release is assumed and the actual release evaluated. In tier 3, define the free particle persistence and dissolved fractions’ fate, while in tier 4, toxicity testing is both acute and chronic. Finally with tier 5, material-specific and site-specific investigations are undertaken. All this provides the essential information on taking a decision on a nanoproduct [12, 36]. In fact, a risk communication system targeted directly at the consumers to make out the nanoproducts multiple values and combine them into the decision-making process especially in marketing phase [34]. The toxicity of nanoproducts is multifaceted and based on various aspects of the NPs incorporated in them [29]. It depends on dose and exposure time effect, i.e., molar concentration of NPs in the contiguous medium multiplied by the contact time, while a pre-exposure effect does exist too, whereby a short contact time or the exposure of low NP concentrations beforehand will stimulate the cellular phagocytic activity. Another factor is the NP’s capability of aggregation and concentration effect, where increasing the concentration results in promotion of aggregation. Another effect is the particle size, where there is size-dependent

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toxicity, i.e., NPs with smaller diameter penetrate more and disrupt the cellular systems than NPs of larger diameters. The next factor affecting toxicity is the particle shape effect where there is a shape-dependent toxicity at different aspect ratios. The rising hazardous effects of NPs are inversely proportional to the particles size and directly proportional to surface area. There is also a surface functionalization effect with definite impact on translocation and subsequent oxidation processes at the cellular and subcellular level. In addition there exists a crystal structure effect with minor difference in the crystal’s structure; there are characteristic changes in the cellular uptake, oxidative mechanisms, and subcellular localization [16, 23, 37].

Environmental and Human Health Hazard Profile Judging Tools Nano-safety is a cause for concern for mainly three groups, the researcher, industrial workers, and finally the end users the consumers. There are a host of tools to evaluate ENM’s potential risks and help in making informed decisions. There are many tools being developed for the same. Few of the important tools are elaborated below.

Fig. 2 Impact of consumer-based nanoproducts linked to ultimate fate of NMs in ecological system

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Table 2 Possible cumulative risk assessment at the various sources or route of entry of Nanoproducts in humans [9–11, 33] I. 1.

2.

3.

II. 1.

2.

3.

III.

IV.

a

Nanoproducts Details if any Inhalation route:a Spraying/spray products: Spray guns Generate small aerosol particle sizes Propellant Disinfectant sprays with nano-Ag, sprays impregnation sprays with nano-silica and sunscreen sprays with nano-TiO2 and nano-ZnO generate small aerosol particle Pump sprays Nano- Ag Larger droplets/aerosols are generated Less volatile solvents are used Powders Cement with nano-TiO2 products Face powder with nano-silica Plaster/gypsum, powder paints with nano-TiO2 Nanomaterials Sports equipment, electronics, and for in solid surface treatment of equipment and matrices and buildings on surfaces

Oral route: a Food additives CaCO3 used as food additive (E170) ➔ contains a nano-fraction TiO2 (E171) and silica (E551) in children specially Sunscreens Intake of Nano-TiO2 and nano-ZnO incorporated sunscreen lipstick and possibly from hand-to-mouth behavior of children Medicines Lipid, polymer, and protein-based particles Drug delivery systems/nanocarriers of drugs Dermal: Small wound Nano-Ag➔risks may be acceptable dressings at considering the risk associated with nonhome treatment Hospital treatment of burns Eye: Current information does not appear that eye exposure to NMs would lead to any significant risks. Further information on eye toxicity might be warranted

Exposure levels

Very high exposure levels Significant exposure levels

Low exposure level

Need to measure actual exposure levels associated with specific products As long as the nanomaterial stays embedded in the solid matrix no exposure But if in production, repair, and disposal of such products, there is possible release of NMs high exposure High oral exposure

High oral exposure if exposed, more studies

High oral exposure can lead to systemic toxicity [40]

Systemic toxicity such as argyria and elevated liver enzyme levels

Following exposure, NPs gains accesses to other organs like the liver, brain, heart, and spleen

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NanoRiskCat NanoRiskCat was the first screening tool for categorization of risk profiles to human health and ecology. This was developed by Hansen et al. which aims to provide a guideline for first-tier assessment companies and regulators regarding the hazard and exposure potential of consumer products containing various ENPs. They used five colored dots where the first three dots indicates the exposure level for the specialized final users, major clients, and of course for the surrounding milieus, while the latter dual dots specifically addresses the nanoproducts humans and the environment hazard potential (Fig. 3). A framework is used to determine various information of relevance to NPs, while the assessments with regard to hazards pertaining to health and ecology was centered on a tree with nodes dealing with the various aspects of the regulatory classifications, raw toxicity information, and other endpoints. Life Cycle Assessment and Risk Assessment of Nanoproducts (LICARA) nanoSCAN This Internet-based tool was developed by European Framework 7 project to assess the advantages and disadvantages plus threats of ENM-enabled products throughout its stages of development, i.e., from cradle to grave. The Nano Guidance for Risk Informed Deployment (NanoGRID) This is an Excel app which is based on a tiered methodology to determine the varying impacts of ENM-enabled products on environment, health, and safety. It details if any additional tests need be done for sorting out aforementioned concerns [24].

Fig. 3 NanoRisk categorization of a nanoproduct

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Database or Inventories on Consumer Nanoproducts There is no clarity on what NanoTech products are really available on the market, i.e., details regarding the nanotech product and the number and types available and altered over time. In addition, there is hardly much data available on how much, when, and what exactly the consumers are exposed to. This overall lack of statistics hinders both the quality and computation aspects of consumer exposure assessment of nanoproducts. With the purpose of addressing these shortcomings, different databases or inventories are available globally. Though the major ones include Consumer Products Inventory (CPI) and Nanodatabase, there are many other databases available. The product categories are uniform in CPI and Nanodatabases ranging from food and beverages, home and garden, electronics and computers, machines, health and fitness, cross-cutting, automotive, and goods for children. Nonetheless, there is clear lack of uniformity in all the nanodatabases regarding the data displayed, exposure–risk parameters evaluated and private and public information access! [6, 22, 48].

Consumer Products Inventory (CPI) of Nanotechnology It was established in the USA in 2005 as off shoot of the Project on Emerging Nanotechnologies (PEN) and was supported by its charitable trusts and Woodrow Wilson International Center for Scholars. It details 1600 plus products currently involving NPs mainly. Its frequency of updating is annually and was the first of its kind, with focus only on the North American market [6, 43].

The Nanodatabase The Nanodatabase was established in Europe in 2012 by DTU Environment, the Danish Ecological Council, and Danish Consumer Council. It is an inventory comprising of nanomaterials (NMs)-based nanoproducts. It is updated daily with detailed information of the product, with roughly 4200 plus products with its exposure as well as the hazard information using NanoRiskCat. It allows the user to sort and extract data as it is equipped with different analytical tools. When the products were analyzed, majority fell into the category which were having unsupported claims [22, 48].

Others Another inventory providing public information includes the Nanoproduktdatenbank, but the major disadvantage is it being in German language, with a focus on German markets. Another inventory is The European Consumer

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Organisation (BEUC) which contains only nanosilver particle-based items. Few other registries are available on a country basis like the Danish, Belgian, and France nanoregistries in the respective countries, all of which are updated annually but limited data available publically [22].

Marketing of Nanoproducts Daily, new nanoproducts are being introduced in the market by following a good nanotechnology commercialization model. The global capacity of the nanoproduct market is estimated to a whopping $400 billion [1]. The present status and predicted growth of the nano-industry is detailed in Table 3. There is major investment in sales of nanoproducts, in medical, manufacturing, and energy industries. Generally, the nanoproduct sales are anticipated to grow over the upcoming years. The leading spots among nanocatalysts, hydrocarbonprocessing nanoproducts, are increasingly being utilized in nanoproducts pharmaceutical preparations and medical equipment. The market size, market potential, and the general economic picture must be kept looked into before marketing a nanoproduct. There are many barriers existing to a successful commercialization of nanotechnology, the inability to produce a practical prototype, perform safety testing, large-scale manufacturing, lack of funds, adverse public perception of nanoproducts, etc. [27].

Regulations and ISO Technical Specifications Just like two sides of a coin, though there is lot of benefits of incorporating NMs into products, risks exist too! Just a few years back, there was a scare in Germany, with hundred people becoming ill after using a nano-designed aerosol. This resulted into local authorities performing a nano-recall the first of its kind. However, later, it was found that fault lied elsewhere and not with the nano component [49]. Hence governments and international agencies need to cooperate and bring

Table 3 The present market scope for nanotechnology, nanofiber products, and in textiles

Heads Nanotechnology Nanofiber products Nanotextiles

Present market value in dollars (year data taken) $2.0 billion (2018) $927 million (2018)

Projected market value in dollars for the (year) $2.1 billion (2023) $4.3 billion (2023)

Compound annual growth rate (CAGR) 19.4% 36.2%

Reference [4] [5]

$5.1 billion (2019)

$14.8 billion (2024)

23.6%

[3]

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forth legislation, laws, and rules to be followed and enforced globally. Certain governments and organizations have implemented this to reduce and avoid risks associated with these products. There is no consensus internationally for the defining the research of NPs, production, handling, labeling, toxicity testing, and evaluation of the impact.

GHS and Labeling The United Nations Economic Commission for Europe [44] proposed The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) which states the chemicals cataloguing by hazard types and suggests the inclusion of labels and data sheets pertaining to safety. [44] Two kinds of labeling exist: mandatory and voluntary labeling. In the EU, plain product labeling of products containing nanomaterials aims to create awareness in consumers whether they want to buy such product or not. Few other countries do encourage voluntary labeling [25, 32].

International Organizations (i) Basel Convention (BC): Has taken steps to advance research to generate data for enhanced understanding of the likely threats of discarded NMs, nano-waste, plus best practices relating to its safe disposal. (ii) World Health Organization (WHO) and International Labour Organization (ILO): Main focus is to protect employees from possible hazards of massproduced NMs. (iii) Food and Agriculture Organisation (FAO): Food safety assessment in food and additives containing NMs (United Nations). (iv) ECOSOC’s Sub-Committee of Experts: Review the GHS labeling to nanomaterials [44] (v) Strategic Approach to International Chemicals Management (SAICM): A global action plan was crafted by recognized thirteen activities in relation to NP-related products and identified them as an emerging policy issue (EPI). (vi) International Organization for Standardization (ISO): ISO/TS80004-1:2015 (en) and ISO/TS 80004-2:2015 both replaced the previous 2010 standard and now elaborate two parted document details out the various terms used in nanotechnology generally and nano-objects, respectively. But one can note that though this is a global issue recognized by many international bodies and governments, a uniform legal enforcement is lacking. Risk assessment of NMs is one of the important regulatory aspects in marketing of nanoproducts [13, 30–32].

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The Various Expert Committees in USA and European Continent Include • EPA facilitates innovation and ensures safety of the substances effective from 2017 entails a must reportage of the associated exposure levels and safety information on the nanoscale substances as part of chemicals under Toxic Substances Control Act (TSCA) section 8[a] [45]. • US Food & Drug administration (FDA) created the Nanotechnology Task Force to monitor and advice regarding the regulatory steps needed for NM-based products [20]. Similarly, this role in Europe, are played by The European Food Safety Authority (EFSA) and The European Medicines Agency (EMA) [20] • The Organisation for Economic Co-operation and Development (OECD) Environment Directorate from 2006 have a Working Party on Manufactured Nanomaterials (WPMN) which inspects the safety of manufactured nanomaterials [38]. • The United States Occupational Safety and Health Administration [46] and The European Agency for Safety and Health at Work (EU-OSHA) both detail out the rights of the workers which need be complied to by the employers [17, 46]. • Others include the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) and The Scientific Committee on Consumer Safety (SCCS)

Conclusion It is well documented and proven that this wonder technology has immense potential. Nonetheless, it is vital that we harness the full benefit of it by not only developing nanoproducts in general but also taking full responsibility by establishing uniform guidelines and regulations globally in their production, manufacture, processing, waste disposal, and other parts of its life cycle. Thus, every aspect is given its due importance and not make it a rat race for mindless developments. The target is the attainment of the betterment of mankind as a whole, increasing shelf life of otherwise short-lived consumables and services, improving drug delivery, and much more!

Important Websites 1. 2. 3. 4.

The nanodatabase. https://www.nanodb.dk/ National Nanotechnology Initiative (NNI) https://www.nano.gov/ Nanonature. https://nano.nature.com/ Nanotechnology Products Database (NPD). https://product.statnano.com/

Acknowledgment Reshmy P and Raveendran Sindhu acknowledge the Department of Science and Technology for sanctioning projects under DST WOS-B Scheme.

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Part II Design and Engineering Technology for Consumer Nanoproducts

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Effect of Mechanical Alloying in Polymer/ Ceramic Composites M. V. Khumalo and M. C. Khoathane

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Natural Raw Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of Ceramic Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High-Energy Ball Milling (HEBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Techniques and Methods of HEBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEBM in Polymer-Ceramics Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEBM in Thermoplastic Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEBM in Thermoset Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEBM in Polymer Metal Matrix Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

The chapter presents ceramics-polymers composites using mechanical alloying (MA). Ceramics are classified as inorganic and nonmetallic materials that are essential to our daily lifestyle. Many ceramics, both oxides and non-oxides, are currently produced from polymer precursors. Ceramics generally have an amorphous or a nanocrystalline structure and consist of excellent structural such as stability, oxidation resistance, creep resistance, high-temperature mechanical, and good dielectric properties. Nevertheless, they have a fundamental weakness in that they are easily fractured and require high-temperature processes for the fabrication of integrated substrates. Composites are now one of the most M. V. Khumalo (*) · M. C. Khoathane Department of Chemical, Metallurgical and Materials Engineering, Polymer Technology Division, Tshwane University of Technology, Pretoria, South Africa e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_4

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important classes of engineered materials, because they offer several outstanding properties as compared to conventional materials. Composites are fast-developing segment in the polymer industry; composites filled with materials having at least one dimension in the micro- and nanometer-size range such as nanofillers, nanoclays, or nanotubes and ceramics represent a step change in technology in the composite area. MA is a solid-state powder processing technique involving repeated welding, fracturing, and re-welding of powder particles in a high-energy ball mill. This technique was originally developed to produce oxide dispersion strengthened (ODS) nickel and iron-base super alloys for aerospace applications. MA has been substantiated to be capable of synthesizing a variety of equilibrium and nonequilibrium phases, including nanocrystalline and amorphous materials. Recently MA has been demonstrated to be a most versatile and economical process for synthesis of nanocrystalline materials, due to its simplicity, low cost, and ability to produce large amount of material. The chapter focuses on the preparation processes; general microstructures; mechanical, chemical, electrical, and optical properties; and potential applications. Keywords

Ceramics · Alumina · Polymers composites · Polymer nanocomposites · Mechanical alloying · Composites · Nanocomposites · Clays · High-energy ball milling

Introduction High-performance plastics and composites, which developed in the twentieth century, have penetrated to the international economy and people’s lives in different fields with an exceptional rate of development in the history. They have become the substitutes for traditional materials, showing improved performance. Now, with the speedy development of science and technology, materials play an important role in the international economy. New materials are still the beginning of new technologies, and materials science, energy technology, and information science have become the three pillars of modern science and technology [1]. Two main kinds of polymers are thermoplastics and thermosets. According to global worldwide researchers, production of thermoplastics is approximately 200 billion pounds per year, or approximately 25 pounds for every person on the planet. Only a small fraction of this amount is filled and used as a composite, but a small fraction of this large number is still a significant amount of material [2]. By far the most important thermoplastic composites are made from flexible thermoplastics, i.e., semicrystalline materials with a glass transition temperature below room temperature. Thermoplastics’ applications are in flexible and rigid packaging, motor industry, engineering sector and agriculture, etc. Thermosets are simply melt resins that chemically react from low viscosity liquids to form solid materials during a processing called curing. Thermosets are commonly used for high-temperature applications; some of the

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common products are electrical equipments, motor brush holders, printed circuit boards, circuit breakers, etc. Commercial plastic resins may contain two or more polymers in addition to various additives and fillers. These are added to improve some properties such as the processability; thermal, chemical, or environmental stability; and mechanical properties of the final products [3]. The term composite materials was firstly used in abroad in the 1950s, and it has been used domestically from about the 1970s. Composite material is a kind of complex multicomponent multiphase system, and it is difficult to be defined accurately. A composites materials is made by combining two or more materials into unique one with superior properties that cannot be met by conventional monolithic materials, such as metal and its alloys, ceramics, and polymers [4, 5]. The purpose of composites allows the new materials to have strengths from both materials, frequent times covering the original materials’ weaknesses. Composites are different from alloys because they are combined in such a way that it is difficult to tell one particle, element, or substance from the other. They usually classified by the type of reinforcements they use. The reinforcements are embedded into a matrix that holds it together and used to strengthen the composites [6]. Composite materials have several advantages over traditional engineering materials, which made them more attractive in many industrial applications. Composite materials have superior mechanical properties and commonly classified at following distinct two levels: The first level of classification is usually made with respect to the matrix constituent. The major composite classes include organic matrix composites (OMCs), metal matrix composites (MMCs), and ceramic matrix composites (CMCs). The term organic matrix composite is generally assumed to include two classes of composites, namely, polymer matrix composites (PMCs) and carbon matrix composites commonly referred to as carbon-carbon composites. The most important inorganic nonmetallic matrix composite materials are ceramic matrix composites (CMCs) and carbon-based composite materials such as C/C composite materials (Fig. 1). These four types of matrices produce common types of composites. Majority of the composites used commercially are polymer-based matrices. In a composite,

Matrices

Polymer Matrix Composites (PMC)

Thermosets

Metal Matrix Composites (MMC)

Thermoplastics

Fig. 1 Classification of matrix materials [7]

Ceramic Matrix Composites (PMC)

Carbon and Graphic matrix composites (CGMC)

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matrix is an important phase, which is defined as a continuous one. The important function of a matrix hold the reinforcement phase in its embedded place, which acts as stress transfer point between the reinforcement and matrix and protects the reinforcement from adverse conditions [7].

Polymer Matrix Composites Polymer matrix composites (PMCs), because of their inherent characteristics, have become the fastest-growing and most widely used composite materials. Compared with traditional materials such as metals, PMCs have the following characteristics: • • • • • • • • • • •

High specific strength and modulus Excellent fatigue and fracture resistance Good damping characteristics Multifunctional performance Good processing technics Anisotropic and properties designability High fracture toughness Good puncture resistance Good corrosion and abrasion resistance Low cost Lower thermal expansion properties

PMCs consist of thermoset or thermoplastic matrix resins reinforced by ceramic, metal, fibers, carbon, and graphic that are much stronger and stiffer than the matrix. They are attractive because of lightweight, stronger, and stiffer than the unreinforced polymers or conventional metals. PMCs have additional advantages of their properties and forms could be tailored to meet the needs of a specific application. Highperformance reinforcement materials are of the highest interest in various industries like military and aerospace [8]. Basically all commercially important polymers have applications where the polymer is filled, although definitely some materials are more commonly filled than others. Typically, the reason that a specific polymer is a good or bad candidate for use as the continuous phase of a composite is its ability to form strong interactions with particular filler. Polymers are ideal materials as they could be processed easily, as they are lightweight, and have desirable mechanical properties. Both thermosetting and thermoplastic resins could be used as the polymer phase; the former had the advantage of low viscosity while the latter had the advantage of the possibility of recycling and reuse [9]. The use of polymer composites in various engineering applications had become state of the art. The multiauthor volume provides a useful summary of updated knowledge on polymer composites in general, practically integrating experimental studies, theoretical analyses, and computational modelling at different scales, i.e., from nano- to macroscale. Comprehensive consideration was given to four major areas: structure and properties of polymer nanocomposites, characterization and modelling, processing and application of

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macrocomposites, and mechanical performance of macrocomposites. It influences the mechanical properties, shear modulus, and shear strength and its processing characteristics. Reinforcement phase is the principal load-carrying member in a composite. Therefore, the orientation of the reinforcement phase decides the properties of the composite [10].

Ceramics Overview Ceramics has been the focus of increased interest during the last century since it exhibits better hardness, stiffness, and chemical stability compared to many other materials. The word ceramics originated from “Keramos” meaning burnt stuff and is derived from the Greek word keramikos. Ceramics cover a vast area of inorganic, nonmetallic materials including white wares, structural clay products, refractories, glass and glass-ceramics, cement, concrete, lime, foundry sand, oxide ceramics, and non-oxide ceramics such as boride, carbide, and nitride. Developments in the twentieth century that stimulated progress in ceramics include advances in science and technology in general, the rise of new industries, advances in military technology, and also the overwhelming concern for health, safety, and environment [11– 13]. Ceramics are generally categorized as conventional or traditional ceramics, which contain clay and clay-based materials, and high-tech or advance ceramics which are from synthetic raw materials and having specific structural and functional properties. The highest attraction of structural ceramics has constantly been the capability of operating at temperatures far above those of metals. Structural applications include engine components, cutting tools, and chemical process equipment. Electronic applications for ceramics with low coefficient of thermal expansion and high thermal conductivity include superconductors, substrates magnets, and capacitors [14] (Table 1). Many compounds in ceramics contained both ionic and covalent bonding. The general properties of those materials depend on the dominant bonding mechanism. Compounds that were either mostly ionic or mostly covalent had higher melting points than compounds in which neither kind of bonding predominates. In polymers, the bonding within the chains are covalent bonds (strong and directional), while the hydrogen bonding and Van der Waals’ forces between the chains are relatively weak, which resulted in lower melting points, higher thermal expansion coefficients, lower Table 1 Ceramics variety of chemical bonding [14]

Compound MgO Al2O3 SiO2 Si3N4 SiC

Melting point 0C 2798 2050 1715 1900 2830

Covalent %% 27 37 49 70 89

Ionic %% 73 63 51 30 11

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stiffness, etc. In ceramics, different types of bonding mechanism could occur: ionic, e.g., in oxides and silicates (Al2O3, MgO, SiO2, etc.); covalent, e.g., in nonmetallic carbides and nitrides (SiC, B4C, BN, Si3N4, AlN, Si2N2O, SiO2, etc.); and metallic, e.g., in transition-metal carbides and nitrides, etc., and they often coexist in the same physicochemical phases.

Natural Raw Materials It has been understood that clay mineral is an excellent raw material for various hightemperature ceramic requirements. The ceramic properties of clays are largely governed by the crystal structure and the crystal composition of their essential constituents and the nature and amount of accessory minerals present. Since silicates and alumina silicates are easily available, they are also inexpensive and thus provide the backbone of high tonnage products in ceramic industry [15]. The principal clay mineral groups are kaolinite, smectite, and palygorskite. Clay minerals can be divided into chain and layer structures. The layer structures are branched into 1:1 and 2: 1 (dimorphic and trimorphic). Classification of clay minerals is indicated below (Fig. 2).

Layer Structure

Two layer type (1:1)

Three layer type (2:1)

(Sheet structure composed of one silica layer and one alumina layer)

(Sheet structure composed of two silica layers and one alumina layer)

Equi dimensional (Kaoline group)

e.g. Kaolinite, Dickite Nacrite etc

Elongate (Halloysite group)

e.g. Halloysite

Regular mixed layer type

(Ordered stacking of alternate layers of different types e.g. Chlorite group)

Equi dimensional (montmorillonite group)

e.g. Montmorillonite vermiculite, sauconite

Fig. 2 The category of layer structure steps for natural raw materials

Chain structure type

(Hornblende like chains) e.g. Attapulgite, sepiolite palygorskite

Elongate (montmorillonite group)

e.g. Montmorillonite, Nontronite saponite, hectorite

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Classification of Ceramic Matrix Composites CMP are a family of new materials which are attracting considerable industrial interest and investment worldwide. They are defined as materials whose microstructures compromise a continuous metallic phase (the matrix) into which a second phase, or phases, has been artificially introduced [16]. CMP can be divided into two types: microcomposites and nanocomposites; in the microcomposites, micro-size second phases such as particulate, platelet, whisker, and fiber were dispersed at the grain boundaries of the matrix. Some of the more common discontinuous reinforcements include whiskers, platelets, and particulates having compositions of Si3N4, silicon carbide (SiC), aluminum nitride (AlN), titanium diboride, boron carbide, and boron nitride. Of these, silicon carbide has been the most widely used because of its stability with a broad range of ceramic oxide and non-oxide matrices [17]. The main purpose of these composites is to improve the fracture toughness. On the other hand, the nanocomposites can be grouped into three types: intragranular and intergranular composites and nano/nanocomposite as shown in (Fig. 3). As schematically drawn in below figure, in the intra- and intergranular nanocomposites, the nano-size particles are disperse mainly within the matrix grains or at the grain boundaries of the matrix, respectively. Their aim improved not only the mechanical properties such as hardness, fracture strength, toughness, and reliability at room temperature but also high-temperature mechanical properties such as hardness strength and creep and fatigue fracture resistances [18]. CMPs are promising materials; by combining different ceramic matrix materials with special suitable fibers, new properties could be created and tailored for interesting technical fields [20, 21]. CMPs were established to overcome the intrinsic

Fig. 3 The classification of ceramics nanocomposites [19]

Inter-type

Inter-type

Intra/inter-type

Nano/nano-type

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brittleness and lack of reliability of monolithic ceramic, with a view to introduce ceramics in structural parts used in severe environments, such as rocket and jet engines, gas turbines for power plants, heat shields for space vehicles, fusion reactor first wall, and heat treatment furnaces. Ceramic matrices could be characterized as either oxides or non-oxides and in some cases might contain residual metal after processing [22]. Some of the more common oxide matrix includes alumina, silica, and mullite. Among alumina and mullite had been most widely used because of their in-service thermal and chemical stability and their compatibility with common reinforcements.

Nanomaterials Nano-structured (NS) materials are defined as solids having microstructural features in the range of 1–100 nm (¼ (1–100)  10–9 m) in at least one dimension [23]. These materials have outstanding mechanical and physical properties due to their extremely fine grain size and high grain boundary volume fraction. When the size of material is in range of the nano-size, the main components of the material concentrate on the surface. For example, when the particle is 2 nm in diameter, the surface atoms will occupy 80% overall. The enormous surface could produce surface energy, and then nanometer-sized objects generate the strong aggregation, which enlarges the particle size. Ceramic-based nanocomposites and metal-based nanocomposites can be made by the method of nano-phase in situ growth; their performances were improved significantly, but there are still difficulties to accurately control the content of reinforcements and the chemical composition of generated products by in situ reaction. Organic-inorganic molecular interactions have covalent bond type, coordination bond type, and ionic bond type; each type of nanocomposite material has its corresponding preparation methods. For example, the preparation of nanocomposites with covalent bond type adopts the sol-gel method basically. The materials can achieve the level of the dispersion of molecular grade, so they get the superior performance. High-energy mechanical milling can be used to produce nanopowder. There are two routes for producing nanopowders using mechanical milling: (a) milling a single-phase powder and controlling the balance point between fracturing and cold welding, so that particles larger than 100 nm will not be excessively cold welded, and (b) producing nanopowders using mechanochemical processes [24].

High-Energy Ball Milling (HEBM) A new process called “mechanical alloying” (MA) had been developed, which produces homogeneous composite particles with an intimately dispersed, uniform internal structure. Materials formed by hot consolidation of the powders achieved the long sought-after combination of dispersion strengthening and age-hardening in a high-temperature alloy. Mechanical milling (involving one material) and mechanical

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alloying (involving two or more materials) generally refer to high-energy ball milling techniques, employed to process materials in the solid state. Those non-equilibrium processing routes, responsible for the early successes in oxide dispersionstrengthening of metallic superalloys, involve a variety of metastable inorganic materials. The morphologies (both single component and alloys) are used to form extended solid solutions, novel intermediate phases, alloys from immiscible metals and oxides, metal-ceramic composites, and nanocrystalline materials [25, 26]. Since its inception by Benjamin around 1966, HEBM has been used to produce oxygen dispersionstrengthened (ODS) iron- and nickel-based alloys for aerospace engineering. Mechanical alloying (attrition, also generally known as HEBM) was a multipurpose tool to produce nanostructured materials with a wide variety of chemical compositions and atomic structures [27]. The material/particle dimension did not matter significantly, as long as it was smaller than the size of the balls, because material got grinded within a very short period of time and becomes powder with the high-energy impact of the balls [28]. Ball milling can enable the purposeful execution of physical and chemical transformations in powdered materials. That method confirmed that the physical and chemical behaviors of molecules and ordered and disordered solids could be affected by non-hydrostatic mechanical stresses and the associated strains [29]. Ball milling was performed at room temperature on dry mixtures of powders, which had the undisputable advantages of avoiding the need for high temperatures, hazardous solvents, and complex in situ polymerization processes. In addition, ball milling not only represented an interesting alternative for the mass production of hybrid organic-inorganic materials; it is also an environmentally and economically sustainable method for fabricating nanocomposites with temperature-sensitive molecules. For the past two decades, HEBM has broadly been used as a versatile process to produce a variability of progressive compound powders. The core difference between high-energy milling by planetary ball mill, Spex mill, attritor mill, and the conventional milling was previously methods applied considerably on larger doses of energy to the particles over time. Significant improvement in the mechanical, chemical, and physical properties has been achieved, through chemistry modifications and conventional thermal, mechanical, and thermomechanical processing methods [30, 31]. The large amount of energy consumed by high-energy mills was possibly a burden in its industrial application of the method. That was because the electrical energy consumed for the production of the powders by high-energy mills was added to the final price of the products [32]. Scientific investigations by material scientists have been directed continuously towards improving the properties and performance of materials (Table 2).

Techniques and Methods of HEBM Ball milling has been applied in numerous solvent-free carbon-carbon bond formations. Various types of ball mills are known, and they include ball mills (drum), jet mills, bead mills, vibration ball mills, planetary ball mills, and horizontal rotary ball

88 Table 2 Typical capacities of the different types of mills [30]

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Mill type Mixer mills Planetary mills Attritors Uni-ball mill

Sample weight Up to 2  20 g Up to 4  250 g 0.5 to 100 kg Up to 4  2000 g

mills [33]. All of these devices are based on the principle that a starting material is placed between two surfaces and crushed because of the impact and/or frictional forces that are caused by collisions between these surfaces. The various mills differ in the method of how the motion causes the collisions created. Besides the intensive grinding effect, the collisions often lead to an energy transfer, which results in an increase of internal temperature and pressure. For the achievement of better control of these factors, some ball mills have cooling/heating devices attached. In general, ball mills are able to produce materials with a particle size of 100 nm. Rodriguez et al. described a planetary ball mill that contained a main disk that can rotate at a high rotational speed and can accommodate one to eight grinding bowls. These bowls hold a number of balls as grinding medium and rotate around their own axes in opposite directions, relative to the main disc. The rotational speeds are between 100 and 1000 rpm. Vibration ball mills contain only one or two grinding chambers, which accommodate one or more grinding balls and can be shaken at a frequency of between 10 and 60 Hz, in three orthogonal directions. Some vibration ball mills have cooling/heating systems, which allow a temperature control while grinding [34]. Other terms found in the literature to describe the same milling technique are high-speed ball milling (HSM), high-speed vibrational ball milling (HSVM), shaker milling, or HEBM. Horizontal rotary ball mills have the advantage that they could be operated at a high relative velocity of the grinding medium (up to 14 ms1) that cannot be reached by other types (up to 5 ms1) [35]. The HEBM media comprise the milling balls, grinding vessel, vial, jar, or bowl. The HEBM media are a major source of contamination via diffusion as well as abrasion. Stainless steel, hardened steel, tungsten carbide (WC), and zirconia (ZrO2) are the most commonly used HEBM media. Often, process-controlling agents (PCA) are used to decrease the sticking of the powder to balls and walls of the milling jar. PCA can be in solid, liquid, or gaseous form and can get adsorbed on the surface of the metal, thereby causing a reduction in surface energy. The milling temperature is an important variable [36]. For high-temperature requirements, electrical heating is employed to heat the milling vial in order to increase the temperature of milling, and this is expected to promote alloying process through diffusion. This can lead to an increase in the minimum achievable grain size. Milling speed was varied depending on the type of ball mill, ball-to-powder ratio, and purpose of HEBM. Usually, higher milling speed lead to higher-impact energy caused by faster grain refinement [37]. Aluminum (A‘) was a reactive element; therefore, milling was performed in an inert atmosphere or in vacuum. Argon (Ar) was the most commonly used milling atmosphere. Use of nitrogen, hydrogen, and helium was also reported. Other gases, like NH3, could be introduced to induce chemical reactions, which lead to reactive

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Fig. 4 Schematic representation of formation of nanocrystalline grains during HEBM [30]

HEBM. Ball-to-powder weight ratio (BPR) had significant effect on the kinetics of alloying and/or grain refinement. BPR largely depended on the purpose and type of HEBM. A small BPR might not induce any significant grain refinement. Milling time is very important factor, which should be long enough to achieve steady-state grain reduction and completed alloying. However, longer ball milling time increased chances of contamination, costs time and money, and might lead to the formation of unwanted phases (Fig. 4).

HEBM in Polymer-Ceramics Composites HEBM is one of the effective processes for fabricating polymer-ceramic composite powders as it allows incorporation of the ceramic phases into the polymer particles. The technique polymer nanocomposites with nano-sized ceramic particulate reinforcement can be produced through numerous deformations, fracturing, and cold welding events. After a certain period of milling, powder microstructure homogeneity can be achieved. In addition, simplicity, high efficiency, and low cost of ball milling method have drawn scientist to attention [38]. Alumina is a ceramic metal oxide of great importance. The material was used as building material, refractory material, and electrical and heat insulator, due to its high strength, corrosion resistance, chemical stability, low thermal conductivity, and good electrical insulation.

HEBM in Thermoplastic Matrix Composites The medium-density polyethylene (MDPE) powder is reinforced with nano-sized alumina (Al2O3) particles. SEM micrographs of pure MDPE regular shape powder converted to flake shapes as milling time increased. Also the outcomes demonstrated that an increase in milling time causes to decrease the agglomeration of alumina. The DSC profiles of samples explained that ball milling has little effect on crystalline temperature and melting point of all materials including MDPE and its nanocomposites. The nanocomposite shows more thermal stability than pure polyethylene proved by TGA tests [39]. During the HEBM process, the outcomes showed that the consistent shape of PBT powders was converted into flakes and the nano

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antimony oxide (Sb2O3) particles were well deagglomerated and better dispersed in the poly(butylene terephthalate) (PBT) matrix. Mechanochemical stimulation provided by the HEBM process produced a reduction in the molecular weight of PBT, which favors the first step of thermal degradation. Furthermore, two Tg’s were attained in the case of the nanocomposite powders when the milling time was over 3 hours, one of them being slightly higher than that of the pure PBT, which showed that there was a special interaction between PBT and nano-Sb2O3 particles. However, the HEBM process led to a decreasing of the PBT crystallinity [40]. The authors further explained PBT nanocomposites contained modified nano-Sb2O3 particles were dispersed by two different dispersing techniques, which includes high-speed rotating to disperse HSR and high-energy ball milling to disperse HEBM. The dispersion, interfacial interaction, and mechanical properties of nanocomposites were investigated. The results showed that the dispersion and compatibility of nanocomposites dispersed by HEBM were better than that of HSR. From the analysis of interfacial interactions between nano-Sb2O3 particles and PBT matrix, the interfacial adhesion (B) and tensile strength of interfacial (σ i) were decreased with the increase of nano-Sb2O3 particle content. Polymer-clay nanocomposites were fabricated from medium-density polyethylene and organically modified Na-montmorillonite (MMT) using the planetary ball milling as a new method. The milling time and the addition of clay have not affected on the crystal structure of MDPE matrix. The addition of clay reduces the crystalline size of MDPE. Ball milling was also effective in reducing the crystallite size of MDPE. The ball milling has influence on the crystallinity of MDPE, especially during the early stage of milling. The crystallinity of MDPE decreases as the clay contents increased. It could reduce the intensity of XRD peaks by only 5 wt% clay [60]. The effects of HEBM under different conditions on the structure of Na+montmorillonite (Na-MMT) and the organo-montmorillonite (Cloisite 30B) were investigated. Ball milling increased the structural disorder: peeling off of layers from the particles was observed, followed by the exfoliation of the particles, indicated by the disappearance of the (001) reflection [41]. Shao and his co-workers reported a novel technology, solid state shear milling (S3M), to prepare poly(ethylene terephthalate)/Na+-montmorillonite nanocomposites used the pristine Na+-MMT without organic modification to avoid the problem that the organic modifiers [42]. The intercalated PET/Na+-MMT co-powders could be produced under the strong shear forces of pan-milling, increased interlayer spacing of pristine Na+-MMT from 1.17 nm to 1.48 nm, which could be further delaminated during subsequent twinscrew extrusion. The Na+-MMT had a heterogeneous nucleation effected on the crystallization of PET, which was strengthened by milling. Na+-MMT was incorporated into a poly(ε-caprolactone)-starch blend by means of a ball mill. The milling time strongly influenced the mechanical and barrier properties. In particular, the best results in terms of elastic modulus and permeability coefficient were achieved with a complete delamination of the pristine clay structure. In summary, the milling process not only had demonstrated to be a promising compatibilization method for immiscible PCL-starch blends, but it could be also used to improve the dispersion of nanoparticles into the polymer blends [43]. Planetary ball mill was employed to

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produce MDPE matrix nanocomposites reinforced with different clay contents. The results showed the effects of milling time and clay content on the particle size of polyethylene powder. The results showed that during milling, the regular shape of pure polyethylene powder converts into flake shapes and the average particle size of the powder increased upon increased milling time because the welding mechanism was predominant. The potential of ball milling was investigated in the meltprocessing of PP/clay-based compounds to improve the clay dispersion [44]. Depends on milling parameters, the nature of the clay and the presence of other components during milling, different changes in the clay structure such as delamination and breakage has been observed. Nevertheless, the main concern was the particle agglomeration caused by milling. Preliminary milling of clay alone led to large particle agglomeration in case of the organoclay, which results in a poor clay dispersion in the final compounds. Ball milling demonstrated some potential to improve the dispersion of the clay, especially in the case of the inorganic clays, which could be an alternative to the use of organoclays. Based on author’s paper, PP/organophilic montmorillonite (OMMT) nanocomposites were successfully prepared without any compatibilizers by solid-state shear compounding (S3C) using pan-mill equipment. When OMMT and PP were co-milled, exfoliation of the OMMT layers as well as formation of nanocomposites of OMMT with PP could be realized as a result of the weak interlayer structure of OMMT and the fairly strong shear forces offered by pan-milling [42]. Water-soluble PVP/MMT nanocomposites prepared via solution intercalation method were investigated. The nanocomposites prepared by attrition ball milling showed better optical transparency than the ones by simple stirring because the more rigorous mixing could induce the smaller sizes of tactoid or primary particle in the nanocomposites. PVP and MMT were considerably compatible enough to form an exfoliated nanocomposite up to 20 wt% MMT contents [45]. The solid-state shear pan-milling was employed to prepare a series of polymer/layered silicate (PLS) nanocomposites. During the process of pan-milling at ambient temperature, poly(vinyl alcohol)/ organic montmorillonite (PVA/OMMT) was effectively pulverized, resulting in coexistence of intercalated and exfoliated OMMT layers. Microscopy analysis indicated that OMMT dispersed homogeneously in PVA matrix, and diffraction analysis illustrated that pan-milling has an obvious effect on increase in the interlayer spacing of OMMT and resulted in coexistence of intercalated and exfoliated OMMT layers formed [46]. Sorrentino investigated HEBM used to prepare the composites of poly(3-caprolactone), and modified Mg-A‘ layered double hydroxide [47], at different inorganic content, has a number of mechanical and physical properties enhanced in comparison to those of the pure PCL polymer. In particular, modulus and stress at yield point resulted improved for all the composites, in spite of the molecular weight reduction of PCL. Strain at break point and stress at break values improved in the composite sample containing 1.4 wt% of inorganic filler. The usage of solid-state ball milling (SSBM) for dispersed cellulose nanowhiskers (CNWs) in starch-based thermoplastics also improve mechanical properties. Different testing demonstrated strong correlation between mechanical reinforcement and nanowhisker dispersion [48]. The starch-pectin-CNW nanocomposites showed high

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dispersion of the nano-sized filler in the matrix; thus, SSBM showed great potential when compared to sol-gel, casting/evaporation, and other methods to disperse those promised nanoparticles. Nano-sized boron nitride (BN) powder was successfully prepared by pulverizing micro-sized BN powder using a ball mill process without any wetting agents. In order to enhance the dispersivity of nano-BN in the polymer matrix, the surfaces of the nano-particles were treated with LDPE, which dissolved in the cyclohexane solvent. In their investigation, the preparation of nano-sized BN dispersed HDPE was successfully performed by using an organic solvent surface treatment method together with a polymer melt mixing process, and the highly enhanced thermal conductive characteristics for the nano-BN/HDPE composites were observed [49]. The authors explained the effect of silica nanoparticles on structure and morphology of LDPE which was investigated. SiO2 nanoparticles were dispersed in a LDPE with cryogenic HEBM. Although HEBM promoted the formation of metastable monoclinic phase in the LDPE, nanocomposites in the form of films never showed differences in their thermal and morphological characteristics, which suggested that there were no high interactions between the polar nanoparticles. The nonpolar polymer and thermal treatment was enough to eliminate the specific microstructure induced by HEBM [50]. According to the studies, PET/SiO2 nanostructure was induced by cryo-milling for 10 h. PET flakes dispersed with the single SiO2 nanoparticles formed the primary composite particles, and conglomerations of those primary composite particles were the secondary composite particles [51]. The typical sizes of the single SiO2 nanoparticles, PET/SiO2 primary composite particles, and the secondary composite particles were 30, 400, and 7.6 μm, respectively. The dispersion homogeneity of SiO2 nanoparticles in PET matrix was far more beyond the capability of conventional methods, which was ascribed to solid processing, high mechanical energy of ball milling, and cryogenic temperature. It was realized from the studies that ball milling and mixing with strong shear force and strike force were applied to get fine dispersion of nano-SiOx particles in poly(phenylene sulfide) (PPS) powder. Ball milling increased total systematic interface energy. The bonds allowed SiOx to dissipate and transfer energy and thus improve PPS impact strength from the addition of nano-SiOx. Crystallization behavior (Tc, Tm, ΔT, Xc, etc.) of nano-SiOx/PPS was influenced by ball milling. Consequently, crystallinity of nano-SiOx/PPS was reduced by 25%, and its Izod impact strength was increased by 89% [52]. Fumed silica nanoparticles with 14 nm of diameter were blended with PMMA, by means of a HEBM process. It was demonstrated how possible to obtain fumed silicaPMMA nanocomposites with a very homogeneous dispersion of the nanoparticles within the PMMA. It has been observed that the properties of the composite were highly dependent on the active milling time: (i) the size of the silica-PMMA nanocomposite particles decreased and (ii) the Tg also decreased. The later result has been assigned to a reduction in the molecular weight of the PMMA due to chain scission during the high-energy blending process [53, 54]. It was further reported by Gonzalez-Benito and his co-worker the effects of the presence of silica nanoparticles in the structure, dynamics, and thermo degradation of PMMA. HEBM was used to

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uniformly disperse nanoparticles within a polymeric matrix (PMMA). FTIR results indicated no signal of degradation processes or secondary reactions induced by HEBM was observed; there was no existence of specific interaction between the silica nanoparticles and the PMMA polymer [55]. HEBM used co-milling in a solid state by low-temperature MA to prepare nickel-ferrite (NiFe2O4) nanopowders and ultrafine PMMA, dispersing nanoparticles in a polymer matrix, and a uniaxial highvelocity cold compaction processed employed a cylindrical, hardened steel die and a new technique with relaxation assists has been studied. It was found that a longer mixing time gave a higher degree of dispersion of the nanopowder on the PMMA particle surfaces [56, 57]. The results obtained from their work showed that PEEK/ SiO2 nanocomposite powder successfully produced by HEBM under ambient temperature. Mechanical milling led to the deterioration of PEEK crystallites and decreased the degree of crystallinity. Mechanical milling has major effects on thermal behavior of PEEK. Non-equilibrium orders imposed the material by repetitive deformed during milling might be responsible for observed changes [58]. The development of HEBM and the presence of TiO2 nanoparticles on the non-isothermal crystallization and fusion behavior of the HDPE were investigated. It has been demonstrated that HEBM was a good method to prepare nanocomposites of well-dispersed TiO2 nanoparticles within an HDPE matrix. It was observed that although in general there was a reduction of crystallinity of the polymer, when nanoparticles were absent, the HEBM process induced a double crystallization process (appearance of both the orthorhombic and metastable monoclinic phases). The authors further explained HEBM promotes the formation of the metastable monoclinic phase in the LDPE, nanocomposites in the form of films never showed important differences in their thermal and morphological characteristics, suggesting there are no high interactions between the polar nanoparticles and the nonpolar polymer and thermal treatment was enough to eliminate the specific microstructure induced by HEBM. The mechanical properties and morphologies of PP composites filled with four different sizes of calcium carbonate (CC) particles were studied. It was clear that the PP matrix and filler size have key effects on improvement of mechanical properties of PP matrix. For all three PP matrices, the yield strength, the flexural strength, and modulus of composites filled with CC25, CC4, and CC1.8 could be regarded as the same. And the yield strength, the flexural strength, and modulus of composites filled with CC0.07 were obviously lower than those of composites filled with other sizes of particles. For all particles, the flexural strength and modulus of the composites increased with increasing filler content, while the yield strength decreased with increasing filler content [59]. A1/PMMA composites with low coefficients of thermal expansion were prepared by attritor milling of A1 and PMMA powders and then hot pressing the powder mixture. The resistivity drops by about 10 orders of magnitude as AI content was increased from 20 to 40 vol. %. The attritor milling helps in reducing the critical volume fraction of metal particles by increasing the aspect ratio. The dielectric constant and dissipation factor of the A1/PMMA composites increase with increase in aluminum content, which is due to interfacial polarization [60].

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HEBM in Thermoset Matrix Composites According to Huang [61], UV-curable ammonium salt ([2-(methacyloyloxy)ethyl] trimethylammonium methyl sulfate (MAOTMA) MAOTMA)-modified MMT/epoxy nanocomposite samples were prepared with the aid of planetary mechanical milling process. TEM microscopy revealed a uniform dispersion of exfoliated MMT lamella in epoxy matrix, and the thermal analyses indicated a substantial improvement on thermal properties, e.g., thermal stability and CTE, of nanocomposites. Analytical results illustrated that the planetary mechanical milling process adopted was a valuable tool for microstructure refinement and physical property enhancement of nanocomposite samples. The induce MMT further exfoliated and homogeneously dispersed in epoxy matrix (diglycidyl ether of bisphenol A) curing in the presence of diaminodiphenyl sulfone and obtained improved mechanical properties, a promised new method had been developed to prepare highly reinforced epoxy/MMT nanocomposites through exerting shearing force on epoxy/ MMT solution. When the novel-structured MMTII was sheared by ball milling in ketone/epoxy solution during the processing of novel-structured epoxy/MMTII nanocomposites, a desirable exfoliation could be achieved in comparison with no ball milling step. The resultant nanocomposites have a high impact toughness, and the impact strength could be increased up to 48.1 kJm2 from 32.1 kJm2, which was about 50% higher than that of pristine matrix by ball milling. Modifying agents, being combined with dodecylbenzyldimethylammonium chloride and metaxylylenediamine, were used to organically modify the clay (MMTII) [62].

HEBM in Polymer Metal Matrix Composites Acrylonitrile-butadiene-styrene (ABS)/iron nanocomposites have been prepared by cryo-milling (HEBM under cryogenic temperature), and a microstructure of iron network in ABS matrix was obtained. ABS/Fe nanocomposites have been successfully obtained by cryo-milling. The cryogenic temperature and cryo-milling greatly enhances the size reduction by improving fracture and restricting cold welding. Both particles and grains refined much faster speed rate, and the comminution limited was moved to the finer end inaccessible to ambi-milling process. 20 hours cryo-milling pulverizes the single ABS/Fe composite particle smaller than 100 nm and refined Fe grains about 20 nm [63]. The authors further explained PANI/iron nanocomposites with both conducting and magnetic properties had been prepared by cryo-milling (HEBM under cryogenic temperature), in which the average size of iron grains attains 20 nm. After cryo-milling for 20 h, the average size of Fe grains was refined to 20 nm; besides, many of Fe particles were dispersed in PANI matrix. It only needed to take 2 or 5 hours to get them dispersed homogeneously in the PANI matrix [64], but the conductivity decreases gradually with the cryo-milling time after 2 h due to the dedoping of DBSA from PANI matrix. Pan-milling technique was developed to prepare ultrafine PP/Fe composite powders, in which the average grain size of the iron particles attained a nanoscale level. An average grain size of

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iron below 100 nm was obtained and reached 28 nm after 30 milling cycles while co-milling with PP. The experimental results showed that co-milling benefited the size reduction both for PP and iron [65]. Microstructural and phase transformation of magnitute induced by HEBM and influence of conducted polyaniline (PANI) on Fe3O4 particles in system of Fe3O4-polyaniline were investigated. Through diffraction analysis, it was found that after HEBM the crystallite size of Fe3O4 particles was rapidly reduced to about 21 nm. Broken PANI chains reacted with the Fe atoms in the surface of Fe3O4 particles formed some paramagnetic phase and a small number of superparamagnetic α-Fe2O3 particles. The magnetic properties of the composites were also changed [66]. Ethylene vinyl acetate (EVA) copolymer, a thermoplastic semicrystalline polymer, has been blended with barium titanate submicrometric particles (BaTiO3) by means of HEBM to obtain composites in the form of films by hot pressing. Two different milling conditions have been considered: room temperature and cryo-milling [67]. The characterization of the samples as powders and films showed the lack of strong interactions between the matrix and the BaTiO3 and that the cryogenic conditions were the most suitable to achieve a uniform dispersion of the nanofiller without altering the structural and morphological properties of the base materials. Magnetic nanocomposites composed of cobalt ferrite (CoFe2O4) nanoparticles and polyvinyl alcohol (PVA) polymer were obtained using a two-step mechanical milling, and the effects of milling time and polymer content were investigated. It was found that single-phase cobalt ferrite of 20  4 nm particle size was distributed uniformly by increasing PVA amount and milling time up to 80 wt.% and 30 hours, respectively; however, the size and shape of particles were not changed drastically. The interaction of PVA chains and magnetic phase has been confirmed in nanocomposite samples. The obtained results in their work prove that mechanical alloying could be an efficient way to yield such advanced functional magnetic nanocomposites [68]. The structural, morphological, dielectric, magnetic properties of CoFe2O4 and various PS concentrations added to CoFe2O4 nanoparticles prepared by coprecipitation method [69]. Characterization results indicated the addition of PS in CoFe2O4 nanoparticles remarkably modified the size of the prepared nanoparticles. Structural analysis by XRD confirms the formation of single-phase cubic spinel structure, and vibrational spectral analysis confirms the Fe-O symmetrical stretching vibrational mode. Hence, from the obtained overall results, it could be concluded that the addition of PS in CoFe2O4 nanoparticles controlled the size of the particles and thus enhanced the dielectric and magnetic properties of CoFe2O4 nanoparticles which would be useful for high-frequency and data storage applications. A polymer nanocomposite of nanocrystalline nickel ferrite and polyethylene (PE) was successfully synthesized using the ball milling process [70]. The ball milling process did not significantly influence the crystallite size of nanocrystalline nickel ferrite in the composite. Magnetic measurements carried out at room temperature suggested characteristics of superparamagnetism, i.e., absence of hysteresis, remanence, and coercivity and lack of saturation magnetization. The nickel ferrite-polyethylene nanocomposite exhibited a blocking temperature of 20 K. The lack of saturation magnetization at high field occurs in association with high field irreversibility and open loop at 50. Rashidi and Ataie [71] reported

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that magnetic nanocomposites composed of mixed cobalt ferrite nanoparticles and PVA or poly ethylene glycol (PEG) polymer were synthesized using a two-step mechanical alloying method. PEG not undergo the local temperature risen and induced heat during milling process melt in both moderate and slow milling conditions. Although nanocomposites, cobalt ferrite nano-particles embedded entirely in melted polymer matrix and the initial hours of milling, obtained composite changes to bulk in ball mill. PVA was properly mixed with cobalt ferrite particles the dispersion of particles with interaction between polymer chains and cobalt ferrite nano-particles obtained in the moderate milling condition. HEBM using co-milling in a solid state by low-temperature mechanical alloying to prepare nickel-ferrite (NiFe2O4) nanopowders and ultrafine poly-(methyl methacrylate) (PMMA), dispersing nanoparticles in a polymer matrix, and a uniaxial high-velocity cold compaction process using a cylindrical, hardened steel die and a new technique with relaxation assists has been studied. Experimental results for different milling systems were presented showing the effects of milling time and material ratio. It was found that a longer mixing time gives a higher degree of dispersion of the nanopowder on the PMMA particle surfaces. Furthermore, with increasing content of NiFe2O4 nanopowder, the reduction of the particle size was more effective. Different postcompacting profiles, i.e., different energy distributions between the upper and lower parts of the compacted powder bed, led to different movements of the various particles and particle layers. Uniformity, homogeneity, and densification on the surfaces in the compacted powder are influenced by the post-compacting magnitude and direction [72, 73]. Raju and Murthy [74] explained a series of nanocomposites of nickel-zinc ferrite plus paraformaldehyde which was successfully synthesized using the mechanical milling process. The milling process significantly influenced the crystallite size of nanocrystalline nickel-zinc ferrite in the composite. With the increases in the volume of polymer, the permittivity, permeability, and dielectric and magnetic loss of all the composites decreased. The permittivity and permeability of all the composites have shown good frequency stability and low dielectric and magnetic losses within the measurement range.

Conclusion In the past years, the interest in the production of polymer nanocomposites by ball milling has considerably increased as the number of publications with related subject has increased. Mechanical alloying is a simple, sophisticated, and convenient processing technique that continues to attract the serious attention of researchers. MA is a complex process that involves many variables, and many of them are interdependent. Therefore, modelling of the MA process is very difficult. Uniform dispersion can be achieved using various types of mechanical methods, including ultrasonication, shear mixing, calendaring, ball milling, stirring, and extrusion. It has become a major potential process for processing advanced materials which awaits to be used in industry. It is now time for material scientists who are interested in developing high-energy mechanical milling into an industrial process to learn from

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researchers who have mastered the art of low-energy mechanical milling. Selection of a proper method or a combination of several methods as well as their processing conditions has to be based on the desired properties of end products. Undoubtedly HEBM valuable equipments to study polyesters materials with different nanofillers and clays there’s least research on this field. The polymer-nanoparticle systems that have been studied this far provided a basis for refinement, and further work will furnish valuable insight into the mechanisms of reinforcement and new methods of nanocomposite design.

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Identification and Quantification of Nanomaterials in Consumer Product Pratap Kumar Deheri and Biswabandita Kar

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Defining Nanomaterials: What Are Nanomaterials? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials in Consumer Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potential Health Risk of Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Preparations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characterization Techniques for Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dynamic Light Scattering (DLS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surface Charge (Zeta Potential (ζ)) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BET-Surface Area Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FTIR and UV-Visible Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-Ray Diffraction (XRD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

It is the age of nanotechnology. Development in the field of nanotechnology and nanomaterials and its applications in the field of materials science, electronics, optics, energy, medicine, and consumer product are growing rapidly. Nanomaterials are widely being used in agricultural products, food packing materials, cosmetic, medicine or pharmaceutical products, food materials, textiles, automobiles, and household chemicals. Use of nanosized materials or nanoparticles (NPs) opens a broad prospect of new materials with improved properties, increased lifetime, better packing materials, new nano-nutrient forms that have high bioavailability, effective food additive, nano-coating with better abrasion

P. K. Deheri · B. Kar (*) Kalinga Institute of Industrial Technology (KIIT), Bhubaneswar, Odisha, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_6

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resistance, nano-coating with super-hydrophobic properties, and lightweight nanomaterial composite with increased mechanical properties, just to name a few. However, nanomaterials have some risk factor due to skin contact and ingestion that may lead to possible health hazard such as fibrosis, inflammation, carcinogenicity, etc. Keywords

Nanomaterials · Consumer products nanomaterials · Nanomaterials helth risk · Nanomaterials identifications and characterizations It is a fact that nanomaterial developments and uses in various fields including consumer products are increasing and so is the consumer exposure too. If the nanomaterials have any health hazardous properties, the risk related to nanomaterial exposure would also be increasing. Hence, the accurate evaluation of the benefits as well as risks associated with any nanomaterials or the engineered nanomaterials is highly desirable for consumer’s protection. Nanomaterials in any products can be in dispersed form in bulk or on surface, as individual particles (particulates), as intercalated particles, as solid solutions, and as agglomerates. This complex structural inhomogeneity or distribution of nanomaterials in consumer products is key to property control. An in-depth analysis of this complex structure will be helpful in property as well as adverse effect determination of the product. However, nanoparticles or nanomaterials usually make a very low percentage in most of the consumer products. At the same time, proper analysis and characterization of these nanomaterials are complex, due to the complex structures. Furthermore, the in situ analysis of these products is complicated due to incompatibility nature of the characterization equipments that can be used for nanomaterial detection and analysis. Consumer products nanomaterials characterization includes physicals, chemicals and biological properties evaluations. The morphological evaluations such as size, shape, dispersion state, surface area and surface morphology, elemental analysis, it's stability and leachability, interaction with living organism or biological response and quantitative analysis are important for any consumer product applications. Here, some analytical techniques suitable for the detection, characterization, and quantification of nanomaterials in consumer’s products such as food, cosmetic products, packaging materials, medicines, etc. are discussed. It is difficult to get complete information about the nanomaterials used in products by using a single characterization technique. The use of two or more characterization techniques that can complement each other to extract the complete information needs extensive knowledge in equipments and data interpretation. The principal objective of this study is to discuss the principles of operations for different characterization techniques, uses in the analysis of nanomaterials in the consumer products, advantages and weakness of these techniques, and some of the emerging techniques that can be used to nanoparticle characterization and can be used as complementary information.

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Introduction Improved physical and chemical properties of nanomaterials (NMs) as compared to their micro or bulk materials make them attractive to a wide range of applications in different fields. Today over 1000 consumer products are available globally that utilize nanomaterials, and it is finding more and more applications daily. Looking at the broad application areas, the most important questions need to be answered are; (1) the potential benefit of nanomaterials when included in consumer products, (2) what are the characteristic properties should be considered for applications in consumer products and (3) what are the adverse effects on health and environment associated with it. Humans and the environments are constantly exposed to these engineered nanomaterials during the production, during use, and after disposal too. To evaluate the benefits of nanomaterial inclusion in consumer product to that of the adverse health effects is the key in nanomaterial selection in any applications. For this, the detailed characterization of nanomaterials is required. In this section of the book, some appropriate analytical techniques for the detection, characterization, and quantification of nanomaterials in food, cosmetics, paints, packaging materials, and textile products are discussed.

Defining Nanomaterials: What Are Nanomaterials? Nanomaterials are typically materials with at least one dimension in the size range of 1–100 nm (1 nm–109 m). Nanomaterial classification based on dimensionality is more concise and clear by taking into consideration confinement of electrons in a nanostructure system [1, 2]. The classifications based on dimensionality and examples are illustrated in Fig. 1 [2]. 1. Zero-dimensional nanostructure (e.g., quantum dots, nanosphere): electron movement is confined in all three dimensions. 2. One-dimensional nanostructure (e.g., nanofibers, nanowires, nanorods): the electrons are free to travel in one direction and confined in the other two directions. 3. Two-dimensional nanostructure (e.g., nanofilms, nanoplates): the electrons can easily move in two directions and are confined in third direction. 4. Three-dimensional nanostructure (e.g., polycrystalline nanostructure, nanopowders, multilayer films). In 3-D nanostructures, 0-D, 1-D, and 2-D nanostructures are interconnected through interface. In this nanostructure system, the electrons are free to move in all three directions, and there are no confinement and limitations. Even though the nanomaterial’s elemental compositions and crystal structures are same as the bulk materials, nanomaterials often show different chemical, physical, and biological properties. Properties include optical properties, chemical and biological reactivity, permeability through membranes, magnetic properties, thermal and electrical properties, etc. Some of the nanoscale properties can be extrapolated

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Fig. 1 Nanoparticles based on dimensionality and examples [2]

from their bulk properties, whereas some other properties may drastically change below a certain size as compared to the bulk properties. For example, nanoparticles have an increased surface to volume ratio compared to bulk materials. Nanomaterials can be much more reactive as chemical reaction rates often related to surface area. Due to increased surface area, nanomaterials have increased catalytic activity. This large increase in catalytic effect can be considered as “true” nanoscale features. However, all nanomaterials may not necessarily have such size reduction effects. But, these nanomaterials have different properties than their bulk material properties and are due to size reduction. Nanomaterials are also classified based on their elemental compositions and physiochemical properties. The properties of a nanomaterial can be affected by its stability, dispersion or agglomeration state, the stability of a colloidal dispersion, or the surface charge. The properties are also largely determined by the properties of matrix materials in which nanoparticles are embedded. Hence, in order to understand the behavior of a nanomaterial, it is often necessary to consider the matrix in which it is embedded. This has an important impact on stabilities, properties, applications, and even the safety of nanomaterials.

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Nanomaterials come from a broad range of materials of different elementals and chemical composition. Hence, properties are different and they are used in a wide range of applications. Nanotechnology itself is a vast area that uses nanomaterials of wide range and manipulation at the nanoscale that has a potential influence on almost all technological applications. Nanomaterials are utilized in a wide range of products that include medical devices (diagnostics, drug delivery), medicinal products, cosmetic products (antimicrobials, UV absorbers in sunscreens, nano-tag for bio-imaging, targeted drug delivery), food and food packaging (enhanced flavor, texture, encapsulation of micronutrients), electronics (data storage, displays), energy and environmental applications (catalysts, photovoltaics, fuel cells), automotive (coatings, tyres, composite body parts), construction (thermal insulation), and advanced materials in general. With their widespread use and diverse applications, there is a large, developing, and valuable global market for nanotechnology. Some of the nanomaterial characteristics and their commercial applications are listed in Table 1.

Nanomaterials in Consumer Products Nanoparticles and engineered nanomaterials can be resulted in smarter, lighter, stronger, and cleaner systems and material. At the nanoscale, the properties of particles may change that can be modulated depending on the requirements. Nanoparticles are widely used in the manufacture of self-healing polymer, paints that are scratch-resistant, anti-fouling, and high light-reflecting, scratch-proof eyeglasses, transparent sunscreens, water/dust-repellent fabrics, self-cleaning windows and solar cells, UV-blocker fabrics and body lotion, sports materials and equipments with better performance and durability, etc. [55–58]. Automobile tyres with nanoparticle fillers can improve adhesion to the road and can be resulted in reducing the stopping distance even in wet conditions. Nanoparticle-strengthened steels are used in manufacturing car body for lightweight but better strength and stiffness. Nano-SiO2 coating can improve antireflection, and the transmittance can be increased up to 95%. Application on solar cell panel will increase the efficiency by minimizing the solar light reflection and producing a high photovoltage current [59, 60]. Doped tin oxide provides scratch resistance and offers transparent protection from ultraviolet radiation, not observed in micron size particles [61, 62]. TiO2 in consumer product: TiO2 nanomaterials in the form of nanospheres, nanowires, nanotubes, nanorods, and nanoflowers are synthesized and are used in many consumer products [63]. TiO2 is frequently used as a “natural coloring agent” and is well accepted by consumers. TiO2 due to its brilliant white color, high brightness, and high refractive index (>2.4) is used as a colorant in many drugs, food products, paints, and cosmetics. It is also used in wide variety of confectionary foods, toothpastes, cottage, mozzarella cheeses, sauces, lemon curd, and low-fat

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Table 1 Types of nanomaterials and their applications Nanomaterials Metallic nanomaterials

Elements/compounds Silver (Ag), gold (Au), platinum (Pt)

Silicon (Si)

Copper (Cu)

Zinc (Zn)

Nickel (Ni), iron (Fe), cobalt (Co)

Metal oxide nanomaterials and ceramic nanomaterials

TiO2

ZnO2

SiO2

Fe3O4 and Fe2O3

Characteristic properties and applications area Antimicrobial agents Bio-imaging (nano-tag) Catalyst, fuel cell catalyst Biomedicine Luminescent display devices Micro and integrated semiconductors Solar energy cells Catalyst, semiconductor (light energy harvesting) Antimicrobial Antifungal Conductive ink Catalysis Antimicrobial, antibiotic, and antifungal coatings, UV filtering, biomarkers, biodiagnostics, and biosensors Magnetic materials Targeted drug delivery Super-paramagnetic Bio-imaging (MRI) Data storage Efficient catalyst, electrode materials Photocatalyst, semiconductor, cosmetics Antimicrobial coating, UV protection coating, abrasion and scratch resistance TiO2 is mostly used as white pigment in paint, textile, plastics, and paper Photocatalyst, semiconductor, cosmetics, UV filtering, antimicrobial coating, flameretardant coating Photocatalyst, semiconductor, catalyst, sensor, cosmetics Drug delivery Optical imaging coating Flame-retardant coating Abrasion and scratch resistance Imaging (MRI), biosensors, targeted drug delivery, cell labeling Magnetic fluid, hyperthermia as cancer therapeutic treatment

References [3–12]

[13–15]

[16–19]

[20]

[21–24]

[25–28]

[29–33]

[34–36]

[37–42]

(continued)

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Table 1 (continued) Nanomaterials

Elements/compounds Rare earth oxide such as Nd2O3, Dy2O3, CeO2

Nanoclays

Carbon-based nano materials

Polymer-based nanomaterials

Carbon nanotubes, fullerene, graphene, graphene oxide, carbon black

Characteristic properties and applications area Solid electrolyte in solid oxide fuel cells, fluorescent materials, luminescence, and electroluminescent devices, special optical glass and plasma display panels, solid oxide fuel cell, UV detectors Mechanical and rheological property modifier, flame retardant, reinforcement in polymer, decrease in oxygen permeability, as pollutant remover (radioactive and dye pollutant) Excellent mechanical, electrical, thermal, optical, and chemical properties Cell/tissue imaging Biosensor, drug delivery, cancer therapy, water purification (organic and inorganic pollutant removal), in battery and capacitor Antibacterial applications, vaccine carrier/drug delivery system

References [43–45]

[46–49]

[48, 50– 53]

[54]

products such as skimmed milk and ice cream as texture modifier [64, 65]. The bandgap of nanoTiO2 is usually ~3.0 eV. Hence, it absorbs light in the UV-visible regions and shows the most promising applications in photocatalytic and photovoltaic applications. TiO2 is an environmentally friendly and efficient material that is extensively used in the photodegradation of numerous organic pollutants and is used in water purification. Moreover, TiO2 nanomaterials are a good choice for UV protecting applications. It has also been used in light-assisted H2O splitting reaction to produce H2 gas for green energy technology. Nano-TiO2 functions as UV filter protecting the paints’ binder material. At the same time, it degrades organic materials via generation of radicals (photocatalytic), which is used for self-cleaning surfaces and antimicrobial coatings [66, 67]. The number of products containing TiO2 is considerable and increasing with time. However, limited information about the physicochemical properties of nanosized TiO2 such as quantity, particle size, size distribution, and particle structure is made available in the product even when the product is labeled as containing TiO2. SiO2 in consumer product: Highly pure, spherical, and microporous SiO2 particles are the most common support for the stationary phase in column chromatography. SiO2 are permeable to many solvents and have a surface area of several hundred square meters per gram.

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Silicon dioxide (SiO2) nanoparticles are used in coating materials too. It improves scratch and abrasion resistance, barrier properties, and total transparency of the coating without reducing gloss and also improves adhesion on substrates with hydroxyl functions. Silicon dioxide (SiO2) nanoparticles reduce shrinkage during curing of polymer composite. There are various forms of synthetic amorphous silica (SiO2) available on the market suitable for food applications. Silica gels are widely employed in food industry as flavor carriers as it is considered nontoxic and safe and can entrap chemicals in its inner pores which results in pronounced flavor stabilization. Nano-silica as filler in polymer matrix is highly promising in improving oxygen and moisture barrier properties that help in extending shelf-life of food products in food packaging technology. Nano-layer silica coating protects the surface of aluminum from oxidative reaction and reduces its reflectivity. High efficiency of nanosized silica compared to that of micron size as anti-caking, clarifying, and adsorption agents has attracted more and more applications [68]. Stabilized silica colloids (5–100 nm) are used in the food industry as an aid for clarifying wine, beer, fruit juices, etc. Magnesium, calcium, and aluminum silicate have been used as anticaking agents in food industries to prevent caking in food products. They are used in healthcare products such as toothpastes, detergents, and cosmetics. They are also used as antifoaming agent in decaffeinated coffee and tea, as carrier for active ingredient, and as antistatic agent in food packaging plastics. SiO2 nanosized particles have been used to construct nanobiosensors. Pt nanoclusters (~2 nm) mixed with the nanoscale SiO2 particles (~10 nm) are used as a glucose oxidase immobilization carrier and to fabricate the glucose biosensor. The sensitivity and performance of biosensors are improved by using nano-SiO2. SiO2 used in concrete and cement pastes improved the particle packing. It acts as a nanofiller and strong binding agent and increases the cohesion between the cement and the aggregate [69]. The detection and quantification of SiO2 nanomaterials could be done quite easily from simple food matrix such as instant tea and coffee. The quantification of SiO2 nanomaterials in tea and coffee can easily be achieved by acid digestion followed by elemental analysis using ICP-MS or ICP-OES spectroscopy. However, this method fails to differentiate natural SiO2 from the additive one. However, identification, separation, sampling, and quantification is complicated if it is from a complex matrix like coating and paints. The separation of SiO2 nanomaterials from the matrix materials involves complicated steps and is different for different matrix materials. ZnO in consumer product: Zinc oxide (ZnO) is a hexagonal crystal that exists in white dusty powder. It has a very broad and versatile range of applications in the field of cosmetics, pharmaceutical, and many engineering uses. Nanosized zinc oxide is transparent for visible light spectrum but block or reflected back the UV light, which makes it interesting to use UV filter in sunscreens. However, ZnO particles used for sunscreens are in the range of 20–60 nm and can easily penetrate human skin. To overcome this hazardous effect, ZnO nanoparticles are coated with SiO2 or Al2O3 and coalesce into aggregates sized 200–500 nm. Such particles cannot penetrate the body through the healthy skin and hence are not hazardous to the health of consumers. Nano-zinc oxide also possesses antimicrobial actions against some bacteria

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and fungi and is used by the pharmaceutical industry for manufacturing zinc ointments, zinc pastes, adhesive tapes, and bandages for skin and wound treatment [70, 71]. Moreover, zinc oxide-based semiconductors are used as transparent conductive layers in blue light-emitting diodes, liquid-crystal screens, and thin-film solar cells [72, 73]. Zinc oxide is used as catalyst to activate vulcanization process [74]. It promotes the process of vulcanization in rubber that is used for tire manufacturing. In addition, its good thermal conductivity improves the removal of heat generated during the friction of the tires. ZnO nanomaterials in cement increase the water resistivity and prolong the processing time. Clay nanoparticles in consumer product: Nanoclays are nanoparticles of layered silicates. The clay layers could be 2:1 (one octahedral layer sandwiched between two tetrahedral layers) or be 1:1 (one octahedral and one tetrahedral joined together). Depending on chemical composition and morphology, clay minerals are classified as montmorillonite, bentonite, kaolinite, hectorite, and halloysite. Montmorillonite consisted of ~1 nm thick aluminosilicate layers and stacked in ~10 μm size. The clay structure is agglomeration/systematically arranged nanostructure plates. Nanoclays are the most commonly used commercial additive used for preparation of nanocomposites used in automotive, aeronautical, and packaging industries. Nanoclay-polymer composites have been often used as rheological modifiers in paints, inks, greases, and cosmetics. It has been used as carriers and delivery systems for the controlled release of drugs. Nanoclays have also been used in water retention application in agriculture field, drilling mud to maintain viscosity, as solid adsorbent to retain dye and inorganic pollutant for water purification applications, as filler in paper and rubber to improve mechanical strength and fire retardancy, and also as base materials in many medicines and cosmetics [75–77]. Furthermore, the bentonite clay has applications across the pet food products, as it is a mineral-rich naturally occurring compound, which provides added supplements to pet food. The addition of nanoclay to pervious concrete has improved the compressive and flexural strength and durability [78]. Metallic nanoparticles in consumer product: Electronics, optics, fluorescent materials, biosensors, as well as catalysts are main applications of metal nanoparticles. Noble metal nanoparticles (Ag, Au, Pt) have been used for several biomedical applications such as anticancer, radiotherapy enhancement, drug delivery, thermal ablation, antibacterial, diagnostic assays, antifungal, and gene delivery [79]. Various functional group compounds such as peptides, antibodies, RNA, and DNA along with biocompatible polymer can be used for surface functionalization to target different cell. Depending on the shape and symmetry, silver and gold nanoparticles show surface plasmon resonance and are used for sensor device fabrications. Silver nanoparticles are employed as conductive fillers in electronically conductive adhesives [80]. Metal nanoparticles also have very important catalytic properties. Ag, Au, Au/Pd, and Pd/Pt bimetallic nanoparticles work as effective catalysts for hydrogenation of olefins [81]. Carbon nanostructure in consumer product: Carbon atom has the ability to form single, double, and triple covalent bonds with another carbon and with other elements. This variable valency enables carbon to form fullerene, carbon nanotubes

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(CNTs), graphene, carbon nanodiamonds (CNDs), and carbon dots (CDs). Carbon nanomaterial development and industrial uses are currently evolving at a rapid pace. Applications in the field of nanoelectronics, gas storage, production of conductive plastics, composites, paints, textiles, batteries with enhanced lifetimes, biosensors, etc. are growing rapidly [82]. Carbon nanomaterials possess good electrical conductivity, heat conductivity, and mechanical properties. They are highly stable and environmentally friendly too [83]. Carbon nanotubes possess high surface areas, high aspect ratios, and high mechanical strength. CNT’s electrical and thermal conductivity is very high (equivalent to copper). The tensile strength is also almost 100 times greater than that of steel. All these unique properties’ combination makes CNT as very good filler materials in polymers and ceramics to make desirable consumer products. Due to high surface curvature, electron can easily be emitted from CNT by little application of potential and hence can be used in electric devices as field emission sources. With the hollow cylindrical nature, CNTs can be used as efficient gas and metal container/ storage [84]. Large surface area and high charge carrier mobility make it potential candidates for application in various sensors. The mobility of electrons in the layers of graphene is more than that in silicon and is explored to replace silicon in the electronic industry.

Potential Health Risk of Nanomaterials Nanotechnologies bring benefits and promises along with combination of risks and uncertainties. Nanotechnologies have revolutionized many industrial sectors, such as the electronics, agriculture, food, food safety, medicine, pharmacy, cosmetic, and personal care, and have become an indispensible part of our everyday life, hence the potential risk of exposure of workers, consumers, and the environment. Human body part such as the skin, intestinal tract, and lungs are in direct contact with the environment. Passive and/or active transport of various substances like water, nutrients, or oxygen occurs through these three points. These three ways are the most possible points of entry for nanoparticles. Nanoparticle injections and implants made up of engineered nanomaterials are other possible routes of exposure [85– 88]. All nanomaterials on exposure will immediately adsorb onto human body surface and due to the smaller size translocate easily to body tissues and organs. The adsorption process will depend on the surface chemistry, surface energy, and surface functionalization. The adverse effect to human health and the environment depends on possible hazards of nanomaterials. The nanomaterial toxicity is directly linked to the physicochemical differences from the bulk materials, their ability to pass biological barriers, and possibility of bioaccumulation. Inhaled nanoparticle causes asthma, bronchitis, emphysema, lung cancer, and neurodegenerative diseases (Parkinson’s and Alzheimer’s diseases). Nanoparticles in the gastrointestinal tract have been linked to colon cancer. Nanoparticles in the circulatory system cause arteriosclerosis, blood clots, arrhythmia, heart diseases, and ultimately cardiac death. Translocation to other organs such as the liver and spleen may damage these organs

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as well. Exposure to some nanoparticles may lead to autoimmune diseases, such as systemic lupus erythematosus, scleroderma, and rheumatoid arthritis [85]. The inhalation of metallic nanomaterials or other dusts causes lung disease, and the type and severity of lung diseases depend on the nature of the material, exposure duration, and dose. The inhalation of metal fumes like zinc and copper leads to metal fume fever, an influenza-like reaction [85, 87]. Inhaled or ingested lead nanomaterials enter blood circulation system and end up in bone and other tissues as deposition. Lead nanomaterial toxicity includes mental function impairment, impaired visual motor performance, memory loss, as well as anemia, fatigue, lack of appetite, abdominal pain, and kidney disease. Nickel nanomaterial exposure via inhalation as dust and fumes is associated with lung and sinus cancer. Excessive amounts of iron nanoparticles increase risk of adenocarcinomas, colorectal tumors, hepatomas, mammary tumors, mesothelioma, and renal tubular cell carcinomas. Organic nanoparticles could be of animal or plant origin and contain fragments and fibers from wood, bone, fur, skin, leather, brooms, flour, grains, tobacco, carpets, paper, etc. These nanostructures can cause the upper respiratory system, eyes, and skin irritation and may lead to bronchitis, allergic reactions, asthma, and dermatitis. In humans, most inhaled carbon nanoparticles get accumulated in the lung where they induce oxidative stress and inflammation (only less than 1% get translocated). However, nanoparticle inhalation and translocation study is challenging due to the small size of particles and the low deposited mass. It requires extremely sensitive 13C radio labeling [89]. Only at high exposures did the 13C label start to accumulate in the liver, heart, olfactory bulb, brain, and kidney. It is also observed that inhalation of iron oxide-based magnetic nanoparticles (~50 nm) for weeks leads to liver, spleen, lung, testis, and brain deposition. The results indicated that both the blood-brain barrier (BBB) and the blood-testis barrier (BTB) were penetrated by the magnetic nanoparticles.

Sample Preparations When working with pure nanomaterial characterization, sample preparation is straightforward. However, detection, characterization, and quantification of nanomaterials in consumer product is highly challenging due to complex matrix chemistry and very low concentrations of nanomaterials in the matrix materials. Sample preparations that involve removing the matrix or separating the nanomaterials from the matrix for both qualitative and quantitative analysis are tedious tasks [90, 91]. The physical and chemical properties of nanomaterials depend on the surrounding matrix and can change if the matrix is removed. Unlike their bulk counterpart, nanomaterials are highly reactive and quickly change their physical and chemical properties when separated from matrix. Thus, the characterization of nanomaterials in consumer products requires sample treatment techniques that are able to separate nanomaterials from complex matrices which may contain particles of similar composition. At the same time, sample surface chemistry manipulation should be minimized to guarantee analytical accuracy and reduce the risks of

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artifacts. The sample preparation, storage, and measurements conditions are other important parameters to be investigated in order to remove the undesired interaction effect with the matrix extract. Another point of consideration is the sample quantity that should be processed in order to be representative for the whole sample. Although a number of techniques are available, their applications in complex situations and at trace levels of nanomaterials are not feasible in most cases. The necessary steps that may be required in nanomaterial characterization in consumer products are (1) digestion, (2) concentration (centrifugation, filtration), and (3) liquid phase extraction or solid phase extraction [91]. In every step of sample preparation from sampling, particle extraction, or matrix removal till final quantitative analysis, a number of quality check criteria should be in place to assess particle stability and recovery. Digestion: Chemical digestion involves the use of strong mineral acids (HCl, HNO3, HF) or may be in combination with hydrogen peroxide and high temperatures by conventional heating or microwave heating in ambient conditions. However, it can cause the dissolution of nanomaterials, thus losing information about their phase purity, size, and concentration in the sample. As an alternative, alkaline digestions have recently been proposed. Alkaline reagent Tetramethylammonium hydroxide (TMAH) is often employed for degradation of organic matrices. Tetramethylammonium hydroxide (TMAH) is able to efficiently digest organic matrix such as soft tissue and selectively extract nanomaterial without dissolving it to free ions [92]. Enzymatic digestions have been proposed as an effective alternative for the analysis of reactive nonmaterial in biological tissues and meat [93, 94]. Enzymatic digestions by proteases or pectinases have also been used to solubilize biological tissue (mammal/plant tissues) [95, 96]. However, the residue of matrix or partially degraded matrix makes the nanomaterial analysis more complex or some time impossible causing many unresolved peaks. Reactive metallic nanoparticles like Zn, Cu, Fe, and Ag can be digested to their corresponding salt solution by using HCl, HNO3, and H2SO4 acid in concentrated or dilute form. However, inert metal like Au and Pt needs aqua regia for dissolution. Dissolution of metal oxide like TiO2, SiO2, and CeO2 can be achieved by strong HF. These acid-based digestions along with ICP-MS/ICP-OES are required to get information of the total element content from the nanomaterials, except if the nanomaterials are insoluble in acids. Sample concentration: The concentrations of nanoparticles from the matrix materials may not be in the detection limit of characterization requirements. Centrifugation can be considered the simplest approach to concentrate and isolate particulates from a suspension. However, unwanted solids are also isolated along with the nanoparticles. Thus centrifugation is not an efficient technique for the fractionation but is useful for isolation of nanomaterials from a dissolved species when ultrafiltration fails [90]. Performance of centrifugation depends on the size and density of the samples. Ultrafiltration and dialysis are based on the use of nanoporous membranes of different materials for nanomaterial separation. Ultrafiltration is based on isolating dissolved species from nanoparticles; hence, dissolution of nanomaterials in the exposure media is studied using it [97]. However, dialysis works on diffusion

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principle and takes long time to achieve separation [90]. Hence, ultrafiltration is preferred over the dialysis. Depending on composition and surface functionality of engineered nanomaterials and the corresponding dissolved species may interact with the membrane surfaces, affecting their recoveries. The filtration retention and elution of an analyte depend on the size of membrane pores [98]. Isolation of NMs from the matrix: There are very few extraction procedures for the isolation of nanomaterials from the matrix discussed in literature [91]. Cationic surfactant in combination with an ionic liquid is used in a liquid-liquid extraction to isolate gold nanoparticles from water and liver [99]. Ag and TiO2 hydrophobic nanoparticles present in water samples can be quantitatively extracted into organic solvent like hexane by surface functionalization using mercaptocarboxylic acid and alkyl amine [100]. By adding complexing agents such as thiosulfate, EDTA, and thiocyanate, selective extraction of Ag, AU, CuO, and ZnO nanoparticles in presence of respective cations can be performed [90]. This technique can be used to quantify the nanomaterials from the soluble metal ions. Sample separation of organic nanoparticles from matrix materials is very tricky. Procedures to isolate intact organic nanomaterials from organic matrices are lacking. Solvent extraction of organic nanomaterials generally leads to a breakup of the structure [101].

Characterization Techniques for Nanomaterials To understand and for correct evaluation of benefits vs. risks of nanomaterials and engineered nanomaterials, it is necessary to identify, quantify, and evaluate the chemical and physical properties. However, characterization of nanomaterials in food matrices and in cosmetic and personal care products poses significant challenges, due to low concentration levels and complex nature of interaction with matrix materials. Furthermore, the interdisciplinary nature of the field makes nanomaterial characterization more challenging. Analytical techniques suitable for the detection, characterization, and quantification of nanomaterials in consumer products such as food and cosmetics products have been discussed in elaboration. Several techniques have been used to characterize the nanomaterials’ shape, size, size distribution, crystal structure, elemental composition, and other physical properties. Most of the time, a combinatorial characterization approach is required to extract complete information of nanomaterials used. The chemical compositions, phases and phase compositions and crystal structure of the nanomaterials are thoroughly investigated as a first step after synthesis. Size, size distribution, degree of agglomeration, surface chemistry and surface charge are then evaluated. However, till today, there are no standardized procedures for it. The challenge with most of the nanomaterial characterizations in natural environment is difficult because of the unstable physical and chemical characteristics of nonmaterial. In colloidal system or in solvent dispersion, nanomaterials tend to (1) interact with the surrounding solvent molecules and other chemical compounds in natural environment, thereby acquiring surface charge, and (2) agglomerate to substantial size and (3) sediments. Thus, measurement of nanomaterials by one single method is a daunting, irreproducible

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Table 2 List of experimental techniques used for nanomaterial characterization Technique Dynamic light scattering (DLS) (Surface charge) Zeta potential, ζ BET-surface area analysis FTIR and UV-visible analysis X-ray diffraction (XRD) Small angle X-ray scattering (SAXS) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM)

Information that can be derived Size (hydrodynamic size), size distribution, detection of agglomerates Nanoparticle stability in matrix Surface area, can differentiate nanosized materials Functional group, nanomaterial surface interaction with organic compounds Crystal structure, phase composition (crystallinity and amorphous content), crystalline grain size Size, shape, size distribution, core shell structure Secondary electron imaging (shape, size), back scattered imaging (phase), energy dispersive X-ray analysis (elemental analysis, semi-quantitative) Bright-field/dark-field analysis (size, shape, crystallinity), selected area diffraction, SAD (phase composition)

task. Nanomaterial properties can be evaluated by more than one technique that complements each other, and all the characterization techniques have their own strengths and limitations [64, 102]. The physical and chemical parameters of a nanometer and the required characterization techniques are listed in Table 2 [64, 102–104].

Dynamic Light Scattering (DLS) Light scattered when it interacts with matter and carries information related to the physical characteristics of the sample. The scattering can be divided into three different types and is expressed as α, a dimensionless constant that is directly related to size parameter (Eq. 1) [105]: α¼

πDp λ

ð1Þ

where πDp is circumference of a particle and λ is wavelength of incident radiation. Based on the value of α, scatterings have three different types [105]: α, Rayleigh scattering (particles are smaller in size compared to wavelength of light, λ); α ≈ 1, Mie scattering (particles are about same in size of the wavelength of light, λ); and α  1, geometric scattering (particle size is much larger than wavelength of light, λ). Particles in suspension are in constant random motion (Brownian motion) due to interaction with the surrounding molecules of the suspending fluid. The suspended particles are illuminated with a coherent light source (laser light). The laser light scattering (LLS) is assumed to be Mie scattering, and both diffraction and scattering (absorption, refraction, and reflection) of the light around the particle in its medium

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are taken into account. Light scatters in all directions, and scattering intensity is a function of the size and shape of the particles. The intensity fluctuations (caused by Brownian motion of molecules in solution) of scattered light are analyzed. The diffusion coefficient (Dτ) of suspended particles that is related to hydrodynamic size of macromolecules can be obtained. The relation between the speed of the particles (diffusion coefficient, Dτ) and the particle size is given by the StokesEinstein equation (Eq. 2) [106]: Dτ ¼

kB T 6πηRH

ð2Þ

where Dτ is translational diffusion coefficient [m2/s] – “speed of the particles,” kB is Boltzmann constant [m2kg/Ks2], T is temperature (K), η is solvent viscosity, and RH is hydrodynamic radius. A basic requirement for the DLS measurement is constant Brownian motion of molecules/particles. Larger particles settle down very quickly due to gravitational force and loss random movement (Dτ ¼ 0) that would lead to inaccurate results. The onset of sedimentation indicates the upper size limit for DLS measurements. On the other hand, smaller particles do not scatter much light, and hence insufficient measurement signal leads to noise only. Signal-to-noise ratio defines the lower size limit in DLS. In DLS, high particle concentration causes multiple scattering so a relatively low concentration is needed to have better signal [107]. The advantages of this technique are (1) can measure a broad range of particle size (2–3000 nm), (2) highly reproducible and reliable as the size is from average value of a large number of particles, (3) size data can be obtained as intensity and/or volume distribution, and (4) almost all automated process and less labor intensive. Disadvantages are (1) measure hydrodynamic size not actual size, (2) DLS principle is valid for single scattering but in practice light is multiple scattered and the contribution cannot be ignored, and (3) it cannot resolve particle mixtures of different size. Guideline for proper size analysis of nonmaterial using DLS [108]: To obtain a reliable size data that can be comparable with other size analysis techniques, the following points must be taken into consideration during sample preparation: (a) Colored sample: If the test sample is colored, it is always recommended to check the absorption of the laser light by the sample. Recording of transmission spectrum of the test sample is recommended. If it is strongly absorbing, DLS is not a recommended technique for size analysis. (b) Sample concentration: In DLS, laser light scattering intensity will depend on particle size, refractive index of solvent, and concentration of measuring sample. Here, we cannot do much with size and RI of solvent; only concentration can be personalized for analysis. Too high concentration causes multiple scattering and high interparticle interaction, while too low concentration results in high signalto-noise ratio and leads to inconsistent results. It is therefore necessary to work out to find the concentration-independent size by analyzing the size and size distribution with various concentrations.

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(c) Effect of salt concentration: If the test particle surface is charged, electrical double layer is formed in aqueous solution. This electrical double layer increases viscous drag with the surrounding solvent molecules. This decreases the diffusion coefficient and hence increases the hydrodynamic size. Addition of a small amount of monovalent neutral salt (such as NaCl) will diminish this effect by screening the electrical double layer. A high concentration of salt induces aggregate formation in charge particles and hence results in increased particle size and poly-dispersity. DLS measurements with some inert monovalent electrolyte are highly recommended, and pure deionized or distilled water should generally be avoided as dispersion medium. (d) Proper equipment handling and sample preparation: The laser should be switched on 30 min prior to measurements. It allows a stable and consistent laser source. The cuvette, solvent measuring chamber should be dust free. Multiple scan should be averaged out to have a consistent result. (e) Concentration effects: In DLS measurement of an optimum concentration is required to have reliable, error-free size data. Too high concentration causes multiple scattering, while too low concentration does not produce enough scattering and error in size data. Moreover, at high concentration, the particle might not be freely mobile due to the strong interparticle interactions. This is especially true for magnetic nanoparticles due to high dipole-dipole interactions [109]. Analysis of nanomaterials in consumer products by DLS: Nanomaterial analysis present within consumer products and nanocomposites is challenging for detection and analysis. DLS technique is highly suitable for nanomaterial analysis in the liquid phase. So, frequent sampling and treatment of consumer products before their analysis is required. This increases error in quantitative analysis but also prevents in situ analysis of the NPs in the environment resulting in unrealistic analysis of NPs [105]. Furthermore, DLS measurement requires RI and viscosity value as input. It is difficult to find and often not available for environmental samples. The applications of engineered nanoparticles in drinking water treatment to remove heavy metals, microorganisms, and organic pollutants appear as a very dynamic branch of nanotechnology [110]. Hence, accurate detection of nonmaterial in drinking water is vital in assessing the risk to the environment and human health, as well as to control nonmaterial discharge. DLS offered good advantages as a technique to analyze the dispersion of carbon black and carbon nanotubes in the aquatic environment [111]. Zero-valent iron nanoparticle can be used for groundwater remediation [105]. However, being magnetic iron highly tends to agglomerate. Addition of guar gum can improve the stability and is monitored by DLS. The cytotoxicity of copper nanoparticles against Escherichia coli was studied using a designed experiment using DLS so that a correlation was obtained between toxicity and particle size [112]. Particle size change is highly effected by the change of pH and temperature and hence the cytotoxic effect. The changes can be tracked using DLS. DLS was used to establish in vitro toxicology assessment of metal oxides. Metal oxide suspensions in culture medium were studied for cytotoxicity effects.

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Evaluation of particle size and formation of secondary larger nanoparticles due to protein encapsulation was confirmed by DLS [113]. Nanomaterial uses in food supplements and food packaging include [105, 114] (1) nanoclays as diffusion barriers as clay-polymer composite; (2) nano-silver as antimicrobial agents; (3) TiO2 as food whitening and brightening especially for confectionary, white sauces and dressings, and certain powdered foods; and (4) silicates and aluminosilicates used in the food industry as anti-caking agents. Silicates and aluminosilicates are also used in pharmaceuticals or nutraceuticals and toothpaste products. Significantly less information of DLS as analytical method to foods is available in the literature. Almost all food materials need sample preparation for the nanomaterials/engineered nanomaterial detection and characterization. Method development is needed to extract nanoparticles from complex matrices without affecting the nanomaterial surfaces as they exist in the native environment. Oxidation reactions can be used in converting organic carbon to carbon dioxide or other volatile gases. Oxidative degradation of organic matters using H2O2 at 60  C can be helpful in extracting nonmaterial without affecting the physical properties much. Concentrated acid (HNO3, HCl) can also be used to oxidize the organic content. However, it may result in acid leaching of the nanoparticles [115]. Complete digestion of nonmaterial using strong acid or maybe combination of acid could be useful for total elemental analysis. However, size/shape information is lost. NaOH digestion of SiO2-soap dissolves the silicon dioxide. However, acid digestion using HCl separates SiO2 without damaging it [115, 116]. Further development is essential to develop reliable size and size distribution analysis techniques.

Surface Charge (Zeta Potential (ζ)) The surface charge controls the nanoparticles’ interaction with themselves and with the surrounding environment and influences their physical state in solvent, in emulsion, or even in a solid matrix. The ζ-potential value provides indirect information on the net surface charge on nanoparticles. Zeta potential is a physical property exhibited by all solid-liquid and liquid-liquid colloidal systems. For nanoparticle stability, highly positive or highly negative ζ-potential value is desired. Zeta potential of nanoparticles with the value of 25 mV has high stability [117]. High surface charge tends to repel and doesn’t agglomerate. Suspended particles are surrounded by a layer of opposite charge of the particle’s surface called the Stern layer (Fig. 2) [118]. In Stern layers ions are strongly bound. An additional layer of more loosely associated ions of opposite charge to the surface is formed that moves with the particle and is termed as diffused layer. The whole system forms an electrical double layer. The interface between the electrical double layer and surrounding environment is termed as slip plane, and potential on slipping plane is zeta potential (ζ). During measurements, nanoparticles are made to move across an externally applied electric potential. The velocity of particle movement is measured from the intensity of scattered laser light. The velocity at different voltage is measured and is

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Fig. 2 Charge distribution and electrostatic potential around a negatively charged particle [118]

used to calculate zeta potential. Electrophoretic mobility (μe) is then measured and converted to the zeta potential (ζ) using the Henry equation (Eq. 3) [118]: μe ¼

2   ζ  f ðk  αÞ 3η

ð3Þ

where μe is electrophoretic mobility and is ratio between the nanoparticle velocity and the external applied field. ε and η are the dielectric constant and the absolute zero-shear viscosity of the medium respectivly. f(k  α) is known as “the Henry function,” where α is the radius of the particle and k is known as the Debye parameter, which represent the thickness of the electrical double layer. The ζ-potential value is dependent on the concentration of the suspension, type of solvent, and other additives if any. DLS can be combined with ζ-potential measurements for a more complete characterization. Zeta potential measurements are relevant only for sub-micron particles. Sedimentation or aggregation of the nanoparticles leads to error in zeta potential measurement, since electrophoretic mobility is strongly changed. Nanoparticle concentration should be in an optimum range that must result in high signal-to-noise ratio and minimize multiple scattering interferences. There are many consumer products such as cosmetics, paints, inks, paper, drug delivery, personal care, and food products that either exist in emulsion form or their preparation steps may involve emulsion formation. The suspensions or dispersions require stability in emulsion in order to meet expected performance criteria. Zeta potential measurements provide information about the surface/interfacial and can predict dispersion stability. Dispersion stability is important to prevent aggregate

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formation and it controls. It is important for the ease of spreading of a paint on substrate surface to produce a thin even film, limited spreading in the case of inks, lipsticks and sunscreens. Even-film coverage, drug suspensions or food dispersions must maintain stability when are stored on the shelf and prevent settling. Zeta potential of TiO2 nanoparticle can be manipulated with the addition of surfactants and by changing pH [119]. Optimized surfactant amount and pH can result in stable TiO2 nanoparticle aqueous suspensions [120]. Untreated SiO2 nanoparticle surfaces were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. In an aim to make it biocompatible, introduction of aminecontaining molecules as coating agents induces positive charge on the silica surface that leads to agglomeration and gel-like network formation [121]. Study shows that L-arginine coating at pH 5.5–6.5 resulted in a 15 mV zeta potential and hence a stable colloid. Change of pH values has large effects on oxide nanoparticles’ (such as TiO2, Fe2O3, Al2O3, ZnO, and CeO2) zeta potential values and hence their stability in solution and even the nanotoxicity [122, 123].

BET-Surface Area Analysis The Brunauer-Emmett-Teller (BET) technique is also used for the characterization of nanoscale materials. It is based on the principle of physical adsorption of a gas on a solid surface. Nitrogen is usually used because of its availability and purity. The amount of nitrogen adsorbed to the surface of the particles is measured at 196  C (boiling point of N2). The sample is cooled using liquid nitrogen to facilitate the gas adsorption. The sample is then removed from the nitrogen atmosphere and heated to facilitate the adsorbed nitrogen to be released. The amount of released/desorbed nitrogen gas is directly related to the total surface including pores in particles. The calculation is based on the BET theory (Eq. 4) [124]:


P=P

n 1

¼

0

P=P

0

1 C  1
P  þ =P0 nm C nm C

ð4Þ

where n is the amount of gas adsorbed at the relative pressure P/P0, nm is the amount of adsorbed gas needed to form monolayer, P is the pressure, and P0 is the saturation P=

pressure of adsorption. To calculate the BET specific surface area, n 1PP=0 is plotted ð P0 Þ
as a function of P=P0 ). From the value nm, the specific surface area (m2/g) can be calculated [124]. Here, C is the BET constant and is related to the energy of monolayer adsorption. From C value the shape of an isotherm in the BET range can be obtained. The volume-specific surface area (VSSA) can be obtained by multiplying the specific surface (S) by its density [125]. It is conventionally stated in units of m2/cm3. When the VSSA is larger than 60 m2/cm3, the material is considered as nonmaterial according to EC (European Commission) definition [125, 126]. It is based on the hypothesis that nonporous and monodisperse spherical particles of 100 nm constituent particle size have SSA of 60 m2/cm3.

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FTIR and UV-Visible Spectroscopy Fourier transform infrared (FTIR) and UV-visible spectroscopy are one of the most important techniques available for material analysis. The techniques are based on the absorption or scattering of electromagnetic (EM) radiation when passed through materials. In its simplest form, an EM is passed through the analytes and the intensity of a beam of light is measured before and after passing through the sample. The difference of the intensity is plotted as a function of wavelength. The electromagnetic (EM) radiation gets absorbed due to change in electronic transition in materials (UV-visible spectroscopy) or change in dipole moment in matter (Fourier transform infrared spectroscopy). Infrared spectroscopy (FTIR) measures the absorption of electromagnetic radiation in the mid-infrared region (4000– 400 cm1). The qualitative aspects of FTIR spectroscopy are one of the most versatile analytical techniques to identify functional group and bond. It is possible to deduce whether specific functional groups such as CO, NH, NH2, C¼C, aromatic ring, etc. are present or not. However, it is not always possible to fully characterize a compound only by examining its IR spectrum. Chromatography, mass spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and various other spectroscopic techniques in combination with FTIR can be used to get much information needed for nanomaterials or the functional group attached to nanomaterials [127]. The IR spectra of clay nanoparticles show well-defined absorption bands corresponding to OH and Si-O stretching and bending vibrations. The OH group stretching vibrations absorb in the 3700–3500 cm1. Bending vibrations of OH groups absorb in the 950–650 cm1 regions. The Si-O stretching appears in the 1050–1000 cm1, while strong bending vibrations appear in the 550–400 cm1 region [128]. Incorporation of clay (montmorillonite) up to 5% into plastic can reduce the water and oxygen permeability and can preserve food materials for longer time. FTIR spectra can be helpful in identifying Si-O stretching that corresponds to clay. Along with it, asymmetric Si-O-C stretching at 1000 cm1 and Si-CH2-R deformation at 1250 cm1 are useful information in deducing clay-polymer structure [129, 130]. The FTIR spectrum of ZnO nanoparticle band at 1608 cm1 is due to the OH bending of water. This indicates the presence of a small amount of water adsorbed on the ZnO nanocrystal surface. A strong band at 465 cm1 is attributed to the Zn-O stretching band [131], while Mn-O stretching vibration appears at 560– 530 cm1 and Ti-O stretching vibration appears at 800–450 cm1 [132, 133]. For surface functionalization of TiO2 for UV protection applications, FTIR study can provide a clear bonding nature in it [134–136]. The disappearance or peak shifting of functional groups of organic compounds confirms the interactions of nanomaterials with the surface active agent. In general a free carboxylic acid C¼O stretching appears at ~1750 cm1. The broad shoulder peaks at ~1650 cm1 in TiO2-citric acid composite confirm the interaction [137]. This shift in CO stretching is due to the

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M-CO bonding that weakens the C¼O bond strength and results in shifting to low energy band. Incorporation of nanoparticles into fabric materials can be confirmed by FTIR analysis. For example, coating of TiO2 nanoparticles on polyester (PET) fabrics resulted in 415, 484, and 494 cm1 compared to untreated PET. Moreover, ZnO nanoparticle coating on PET shows new IR bands at 419, 441, and 484 cm1 [138]. The most important application of UV-visible spectroscopy is to give the information about the nonmaterial’s interaction with light and to determine the functional group in the material. It confirms the presence or absence of a chromophore in the sample which is responsible for the color of the compound. The ability of a fabric treated with nanoparticles or a sunscreen containing nanomaterials to block UV light can be estimated by the ultraviolet protection factor value (UPF) using Eq. 5. The measurement of UPF value can be performed using a UV/visible spectrophotometer [139, 140]: P400nm

280 nm Eλ Sλ Δλ UPF ¼ P400nm 280 nm Eλ Sλ T λ Δλ

ð5Þ

where Eλ is relative erythemal spectral effectiveness, Sλ is spectral irradiation of the skin in UV region (280–400 nm), Tλ is spectral transmittance of the fabric, Δλ is increment relating to wavelength, and λ is wavelength in nanometer. UV-visible spectroscopy too plays an important role in characterizing polymer matrix nanocomposite. PMC with tunable optical properties such as refractive index, UV absorption, transparency, luminescence, etc. are of great significance to develop materials for potential applications. Applications include light-emitting diodes, solar cells, polarizer, color filters, optical communication, data storage devices, and optical sensors and in the biomedical field [141]. Isotropic metal nanoparticles can be distinguished from the anisotropic one by UV-visible spectrometry. The surface plasmon resonance (SPR) of spherical metal nanoparticles produces a single absorption peak. However, asymmetric particles such as ellipsoid and nanorod produce two absorption peaks and are independent of aspect ratio. Moreover, the FWHM (full width half maxima) of the peak carry the nanoparticle size information [142, 143]. UV-Vis spectroscopy is one of the important techniques to understand the optical properties of semiconductor nanomaterials too. One such most frequently used method is Tauc plot [144, 145]. The absorption coefficient (α) is related to the optical bandgap energy and is expressed as (Eq. 6):
 ðαhνÞ2 ¼ constant  hν  Eg

ð6Þ

where Eg is the bandgap energy, h is the Planck constant, and ν is the electromagnetic radiation frequency. For direct bandgap calculation, (αhν)2 have to be plotted against hν and bandgap can be derived by extrapolating the linear portion of the curve to zero absorption.

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X-Ray Diffraction (XRD) X-ray diffraction is based on constructive interference of monochromatic X-rays when it is reflected from an ordered crystalline solid. The scattering is coherent and intensity is significant only along a few well-defined directions stated as Bragg’s law (Eq. 7): nλ ¼ 2dhkl sin θ

ð7Þ

where n is integer, λ is the X-ray wavelength, dhkl is interplanar distance of (hkl) plane, and θ is the angle between incident beam and the crystallographic plane, which is equal to half of the scattering angle 2θ. This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample. Bragg’s law can be deduced from Fig. 3. If we compare the X-ray line path length, it is cleared that line 2 is travelling 2dsinθ length more than the line 1. So, both the line will be in phase and form a constructive interference if only 2dsinθ is equal to integral multiple of λ. X-ray is generated using an X-ray generator and passes through a monochromator. The monochromatic X-ray is then incident on sample to be analyzed, and the diffracted rays are collected through a range of 2θ angles. A plot of intensity vs. diffraction angle is obtained as diffractogram. The XRD plot can be represented as intensity vs. d spacing too. d-Spacings allow identification of the mineral as each mineral has a set of unique d-spacings. Typically, this is achieved by comparison of d-spacings with standard reference patterns. X-ray diffractometer has three main components: X-ray tube, sample holder, and an X-ray detector. X-ray is produced in a cathode-ray tube; a high-voltage application between hot anode and water-cooled cathode produces electrons and accelerates toward target cathode. In collision with the cathode materials, electrons lose energy and the lost energy radiates out as white X-ray. When electrons have sufficient energy to knock inner shell electrons of the target material, characteristic X-ray spectra are produced. The produced X-rays are characteristic of target metal (Cu, Mo, Fe, Cr).

Fig. 3 Bragg’s law; scattering and diffraction of X-ray

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These spectra consist of several components (Kα, Kβ) and have to be passed through monochromator to obtain the desired monochromatic X-ray. X-ray powder diffraction is most widely used for identification of unknown crystalline materials and measurement of sample purity. In combination with Rietveld refinement techniques, quantitative analysis such as phase percentage and amorphous content and determination of unit cell parameters can be performed. The XRD technique can be used to extract informations of nanomaterial with no significant difference from the microcrystallines. However, it should be noted that there is considerable peak broadening with size reductions and it can be used for crystallite size determination. The crystallite size D is related to FWHM of the XRD peaks (Eq. 8) [146]: D¼

Kλ β cos θ

ð8Þ

where D is average crystallite size, K is Scherrer constant and is 0.9, β is FWHM, and θ is the Bragg angle. However, for accurate crystallite size estimation, the instrumental peak broadening has to be considered. The size obtained from XRD peak broadening is from crystallite size. So, don’t confuse it with particle size unless it is cross verified with electron microscopy imaging or any other direct imaging techniques. The phases in a nonmaterial or in composites present can be confirmed from the comparison of experimental data with the standard XRD pattern. The phase percentage can be obtained by comparing the intensity of the peaks. However, manual comparison can lead to lot of errors as amorphous content is unknown; the intensity also depends on the X-ray absorption coefficient. Rietveld refinement is an effective way of analysis to extract all these information with minimum error. In this method the experimental XRD is compared with a simulated pattern using FullProf/TOPAS software. The experimental data is fitted with the standard pattern using the nonlinear least squares approach. Instrument parameters are kept constant, and sample displacement error, lattice parameters, crystallite size, and intensity (scale factor) can be refined to calculate the simulated patterns. For untreated commercial sunscreens, XRD analysis confirms the presence of TiO2 and ZnO nanoparticle with the size information from the peak width [147]. However, the TEM analysis returns a different size value. The atomic arrangement of a nanoparticle surface is not in order and does not diffract or result in incoherent diffraction. Hence, in XRD, size analysis excludes the surface amorphous-like structure part. Hence it is expected that the XRD size estimation always gives smaller in size value than a direct imaging technique. XRD has the limitation to determine particle size, and even crystallite size larger than 200 nm cannot be calculated. XRD cannot detect materials if the weight percentage is below 0.5–1 wt% depending on XRD equipment power and sensitivity. Such difficulty can be overcome by using any other complementary techniques such as SEM and TEM. Polymer-clay nanocomposites enhance the polymers’ mechanical, gas barrier, flame-retardant, electrical, and biodegradable properties. However, the properties’

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Fig. 4 (a) Clay-polymer composite, tactoid, intercalation, and exfoliation, (b) XRD pattern of clay-polymer composite (clay, intercalation, and exfoliation) [148]

enhancement depends on the clay nanomaterial dispersion in polymer matrix. The composite can be [148] (a) tactoid, (b) intercalation, and (c) exfoliation (Fig. 4). The classification is based on the interaction of polymer with clay nanoparticles and the extent of clay layer separation. In tactoids, polymers are bound to clay nanoparticle surfaces. So, the layer structure is intact and resulted in a well-defined XRD peak along (001) plane (Fig. 4). But as polymer molecules enter the clay layer, the basal plane d001 spacing increases and hence the XRD peak position shifts to a lower value. In the third case (exfoliation), clay layer structure is completely lost and hence the XRD peak disappears [148]. Surface functionalizations/modifications of textile fabrics with metal oxide, clay, and metal nanomaterials are carried out to improve UV-blocking, fire-retardant, and antimicrobial properties. The presence or binding of these nanomaterials on textile surface is confirmed by XRD analysis [149, 150]. Even XRD study is a very handy tool in analyzing the surface oxidation of stabilized metallic nanoparticles [151]. Small angle X-ray scattering (SAXS): In small-angle X-ray scattering (SAXS) techniques, elastic scattering of X-rays by a sample is recorded at 0.1–10 measured from the incident beam axes. This scattered X-ray contains information regarding the structure of scattering particles [152]. SAXS can resolve structural information of nanomaterial size ranges between ~0.5 and ~100 nm. The size resolution limits depend on the X-ray wave length (λ ¼ 1.5406 Å, copper target), sample-to-detector distance (SDD), the pixel size and geometry of the X-ray detector, and size of the beam stopper (SAXS setup is shown in Fig. 5) [152]. The scattering intensity I(q) from a collection of particles can be expressed as [153]: I ðqÞ ¼ NS ðqÞPðqÞ

ð9Þ

where N is number of particles, S(q) is structure factors and carries the spatial arrangement information of particles, and P(q) is form factor and is related to spatial

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SDD

-ray

red X

Scatte

X-ray beam

q

2θ Sample Beam stoper 2D detec

tor

Fig. 5 Schematic of a SAXS setup [152]

electron density. Hence, it carries the influence of particle shape and size distributions in small-angle scattering intensity. q is diffraction vector and is given by: q¼

4π λ sin θ

ð10Þ

A proper data processing obtained from SAXS measurement allows to calculate an overall picture of the nanoparticle sizes, shapes, and/or relative position of nanoparticles [152]. In SAXS data simulation, each nanoparticle is assumed to have simple geometrical shape, such as sphere, ellipse, or rod. Still, the SAXS technique has proven to be a powerful tool to determine the mean size, size distribution, shape, and the surface structure. As nanoparticles are increasingly incorporated into many of consumer products, it is more important to gain a deep understanding of their structure-property relationships in the matrix itself. Modern SAXS techniques are effective in situ characterization. Iron oxide core with PEG shell is well characterized by SAXS [154]. The core size and size distribution information is obtained along with the shell (PEG) swelling behavior using this technique. SAXS analysis of carbon nanotube (CNT) embedded in resin matrix can be able to distinguish the alignment of CNT and can be used to interpret the obtained properties [155]. Conventional nanoparticle characterizations present in aerosol involve separation of nanoparticle from the matrix materials. So, correct measurements are difficult as it may change the physical and chemical properties. This shortcoming can be addressed by usage of synchrotron-based in situ SAXS technique and can be successfully used to differentiate individual particles from the aggregates [156]. The distribution, layer orientation, and degree of intercalation into clay layers in a polymer-clay composite can well be studied using directional SAXS technique [157, 158]. SAXS results are more statistically average than TEM imaging

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as sample size is high in SAXS. Moreover, the estimated size is found to be in good agreement with other imaging techniques such as TEM [153].

Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) Electron microscopy helps to observe materials at a nanometer level with high resolution. It is considered one of the most powerful techniques for its capability to visualize nanoparticles size, shape, or aggregation state. This information can be used as complementary information to interpret results from other techniques. The combination of electron microscopy with complementary techniques such as energy dispersive X-ray spectroscopy (EDXS) and electron diffraction (ED) is even more informative. However, there are some limitations to these techniques: (1) high energy of the electron beam can cause damage to biological specimens, (2) high vacuum may cause biological specimen cell wall disruption, and (3) sample preparation for TEM is complex and multiple steps are involved such as sample thinning, fixation, sectioning, and grinding to make electron transparent. Scanning electron microscopy (SEM): In scanning electron microscopy (SEM), a high energetic electron beam is generated at the top using electron gun (Fig. 6a) [159]. There are two types of electron gun: field emission guns (tungsten tip coated with ZrO2, strong electrostatic field induces electron emission) and thermionic guns (tungsten filament, LaB6 is heated to emit electrons). The emitted electron is accelerated and focused on sample surface using a series of electromagnet. The

a

b

Electron source

First condenser lens Second condenser lens

Anode

Anode

Condenser aperture Electron beam

First condenser lens

Condenser lens

Sample

Sec o ele ndary c det tron ect or

Scan coils Objective lens

Sample

Objective lens Select area aperture First intermediate lens

Second intermediate lens Projector lens

Screen

Fig. 6 (a) Schematic of scanning electron microscopy (SEM) and (b) transmission electron microscopy (TEM) [159]

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sample surface is scanned using the high-energy focused electron beam by the help of a scanning coil. Magnification is the ratio between scanning sample area (Raster) to the image display area. When high energy electrons collide with the sample, four different types of interaction are observed: (1) knockout inner shell electron (secondary electron, low energy electron, 10–50 eV), (2) elastic scattering electron (BSE, high energy equivalent to primary source electron, >50 eV), (3) characteristic X-ray is emitted (EDXS analysis), and (4) Auger electrons. Secondary electrons are generated at the sample surface and carry the morphological information such as size and shape. BSEs are elastically scattered electrons and are directly related to atomic number Z (gives atomic number contrast). Heavier elements resulted in brighter images than the light elements. The ejected secondary electron leaves an empty space in inner (K, L) shell. To fill the empty shell, an outer orbital electron leaps from high energy level and the energy difference is emitted as X-ray. This X-ray is fingerprint to each element and can be used for qualitative and semi-quantitative analysis called EDX/EDS analysis. The size/shape analysis of bare nanoparticles is much easier in terms of sample preparation, characterization, and analysis. The characteristic features are prominent (Fig. 7a, b) [160]. However, it does not confirm the phase present. XRD analysis can be used as complementary information for phase formation and purity. EDX analysis can be also carried out to confirm the elements present. Fabric treated with 2 wt% of ZnO2 and TiO2 shows excellent UV light blocking (UPF greater than 50). The hydroxyl and carboxylic acid groups are anchoring the nanoparticles on fabric. The uniform coating is confirmed by SEM imaging (Fig. 7c, d) [138]. The uniformly distributed brighter spot is presumed to be nano ZnO2 and TiO2 particles. BSE imaging along with EDX analysis could have been used to extract more information in characterizing these nanomaterials bonded to fabrics. In BSE the nanoparticles will be resulted in brighter spot than the fabric due to high atomic number (Z) value. EDX can be used in elemental analysis. XRD analysis of this composite can be a handy technique too to prove the presence of ZnO2 and TiO2 particles. But XRD has its limitation in detection below ~0.5 wt percentage that may vary depending on equipment. Ag nanoparticles-treated fabrics are good as antibacterial and antifungal properties and can be used for wound dressing. From the secondary electron imaging of silver-cellulose composite, it is difficult to infer the presence of silver nanoparticles (Fig. 7e) [161]. However, the EDX analysis confirms the presence of Ag elements (Fig. 7f) [161]. Transmission electron microscopy (TEM): Electron beam is transmitted through the sample, and the interference of the transmitted and the diffracted electron beams forms the basis of bright-field imaging. Bright-field image can be formed by selecting the centered electron beam. The image contrast is originated from the thickness and phase difference. The deflected electrons only can also be used to form an image by blocking the centered beam using select area aperture known as a darkfield image. In this imaging technique, the crystalline phase will form brighter region than the amorphous phase. The objective lens form diffraction pattern at back focal plane with electron scattered from crystal planes of crystallites. Both image and diffraction patterns are formed simultaneously in TEM, but it depends on the

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Fig. 7 SEM imaging of consumer products. Secondary electron imaging of ZnO (a) nano-pencil, (b) nano-flowers, (c) nano-TiO2-coated fabrics, (d) nano-ZnO-coated fabrics. (e) Secondary electron imaging of Ag NPs-cellulose composite and (f) EDX analysis of Ag NPs-cellulose composite [138, 160, 161]

focusing of intermediate lens to form/see image or diffraction pattern on the viewing screen. TEM is widely used as a complementary tool to XRD to help determine the nature of polymer-clay nanocomposites. Figure 8 shows typical images of an intercalated and an exfoliated nanocomposite [148]. As discussed earlier, the XRD peak of (001) plane shifts to a lower two-theta value due to polymer insertion in layer structure. The same can be confirmed from the TEM image (Fig. 8a). The layer spacing of (001) plane is ~1.6 nm and increases to ~2.9 nm due to intercalation. However, in exfoliation stacking of (001) plane is lost and corresponding XRD peak disappears. From Fig. 8b, one can infer that the stacking of (001) plane is lost completely and clay layers are uniformly dispersed in polymer matrix. This exfoliation state resulted in achieving maximum mechanical properties with low clay loading. Even the gas and moisture barrier property is improved for a composite and can preserve food for long time without any deterioration to food quality. Figure 9a shows the brightfield imaging of TiO2 separated from commercial sunscreen [162]. The presence

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Fig. 8 Bright-field imaging of polymer-clay composite: (a) intercalated and (b) exfoliated composite [148]

Fig. 9 (a) Bright-field TEM micrograph of TiO2 separated from commercial sunscreen, (b) EDX analysis, (c) silver nanoparticle in antimicrobial solution, and (d) size distribution calculated using Image J software [162, 163]

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of Ti is further confirmed by EDX analysis (Fig. 9b). Commercially available sunscreen product has very low quantity of nano-TiO2. Sample separation/concentration is required prior to TEM analysis. The observed high aggregation might be as a result of removal of surfactant/stabilizing agent from the sunscreen lotion. Furthermore, antimicrobial liquid products intended for humans contain silver nanoparticles. The TEM analysis shows ~12 nm particles with a narrow size distribution (Fig. 9c, d) [163]. In this case there was no need to separate the nanomaterials from its original dispersion solution. And hence a well-dispersed particle can be observed with a very narrow size distribution. A number of analytical methods have been discussed that are used in nanomaterial characterization. Each technique has its strengths and drawbacks. The information that can be obtained includes elemental compositions, phase/phase purity, size/shape, size distribution, and physical state of it in matrix materials. It is impossible to get all the information regarding the nanomaterials present in any product using just one or two characterization techniques. It can only be characterized fully by a combination of analytical techniques. There are several factors that complicate the development of methods to detect and to measure nanomaterials in consumer products: (i) the complex interaction with matrix and the need of special sample preparation procedure; (ii) the lack of standard characterization procedure; and (iii) the development of new analytical techniques and strategies. Most of the research is focused in the area of detection and characterization of nanomaterials. Separating the nanomaterials from the product matrix alters the physicochemical characteristic of nanomaterials. More development in sample preparation method is needed. The current most widespread technique that is used for size/shape and state of dispersion is electron microscopy. However, in electron microscopy (SEM/TEM), the sample size is too low to be considered as the representative of any product. The observation must be substantiated with other techniques like DLS or XRD technique. However, XRD results give crystallite size, not particle size. Again, DLS measure hydrodynamic size, not the actual particle size. So, the investigator has to be careful in comparing both results. Coupled with other characterization methods, UV-Vis spectroscopy is an essential tool to evaluate optical properties of nanomaterials in consumer products. FTIR spectroscopy is a very strong analyzing tool to identify surface functional group. The same UV-Visible and FTIR equipment can be used to study UV and/or IR blocking capacity of any materials for different applications. However, it may not produce the same result for bare nanoparticles as well as for nanoparticles in matrix materials. SAXS is another effective analytical tool in determining the size and shape of nanomaterials and core-shell structures. However, it involves complex mathematical modeling for data interpretation. So, it is always better to complement the observation with electron microscopic imaging study which is direct evidence to microstructure. Moreover, the microstructural study in combination with SAD pattern and EDX analysis further confirm phases and elements present in the nanomaterials.

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Conclusions The characterization of nanomaterials in consumer products such as food, cosmetic/ personal care products, textiles, and paint is tricky and needs extensive work. Sample preparation often is the most challenging step. Nanomaterials in consumer products are very difficult to characterize due to complex interactions with the matrix materials as well as very low concentration in some product. Separation of nanomaterials for characterization involves basically three steps: (1) digestion, (2) concentration, and (3) separation. However, taking out the nanomaterials and characterization may not give the exact physicochemical properties. DLS in combination with zeta potential can be used for size, size distribution, and stability of nanoparticle analysis. UV-Visible spectra can be utilized to determine UV blocking capacity of nanomaterials present in consumer product. X-ray diffraction (XRD) is helpful in phase identification and crystallite size determination. The information can be used as complementary information to the microstructural image from electron microscopy. Small angle X-ray (SAXS) is also a powerful technique in nanomaterial size and shape determination in the matrix material itself. So, it gives more reliable information that can be correlated to the physicochemical properties of nanomaterials in matrix materials. However, one single characterization technique is not sufficient to extract all information of a nanomaterial that is required for applications in any product. Hence, a combination of analytical technique is usually required. So, the researcher or investigator’s strong understanding in this field is required to choose the correct set of characterizations to get all the necessary and reliable information for any specific application.

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Part III Consumer Nanoproducts Based on Polymer Films and Bio-hybrid Polymer Nanofiber

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Polymer-Hybrid Nanocomposites Films and Fiber-Based Nanoproducts Kamlesh Kumar and Sunita Mishra

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packaging Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor and Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electronic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biomedical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Filters and Separators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy Storage and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Textiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermal Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electromagnetic Interference (EMI) Shield Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Polymer hybrid nanocomposite films and fibres have many industrial applications in packaging, sensors and actuators, electronics, biomedical, energy storage, filters and separators, etc. Different polymers and their hybrid composites with metal, and ceramics are used to produce various products for variety of application in different sectors. In present chapter, we discuss the polymer and polymerhybrid nanocomposite film and fibres-based materials and their products. The chapter start with application of different polymer and hybrid nanocomposites films and fibres in packaging, sensor, biomedical and electronic industries. Keywords

Polymer · Hybrid nanocomposite · Films · Fibres · Nanoproducts K. Kumar · S. Mishra (*) CSIR-Central Scientific Instruments Organisation, Sector-30, Chandigarh, India Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India e-mail: [email protected]; [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_15

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Introduction Polymer hybrid nanocomposite films and fibers have many industrial applications due to their low cost, light weight, and easy production. They are extensively used for packaging, sensors and actuators, electronics, biomedical, energy storage, filters, and separators [1–10]. Polymers such as polyimide, polyethyleneimine, polyvinyl alcohol, poly(4-vinyl pyridine), and polyimide along with nanomaterials such as metal oxide nanoparticles, carbon nanotubes, graphene, and multi-walled carbon nanotube can be used to produce polymer hybrid films and fibers, and their properties such as thermal, electrical, mechanical, and rheological can be tailored according to the application in various sectors [11–16]. In the present chapter, we discuss the polymer and polymer-hybrid nanocomposite film and fiber-based materials and their products. An example of practical application of polymer-hybrid nanocomposite for wireless pressure sensor monitoring system is shown in Fig. 1 [17].

Fig. 1 Wireless blood pressure sensor (a) sensor matrix, (b) optical images of a PVDF-HFP/PEDOT array on an inkjet-printed electrode PEDOT:PSS/PET film, (c) pressure mapping with custom-made Bluetooth board (bottom), (d) spatial pressure mapping of sensor array, (e) blood pressure sensor on wrist band, (f) display using smart phone. (Reprinted with permission from ref. [17])

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Different applications of polymer nanocomposites films and fibers are discussed in details in the subsequent sections.

Packaging Products Petroleum resources are widely used to make traditional polymer packaging materials; however, these materials do not have environmental sustainability. The polymer hybrid nanocomposite thin film has replaced the traditional packaging materials due to their better properties and multifunctionalities. The environmental issue and human health threat can be solved by using biodegradable polymer packaging films. Different biodegradable polymer hybrid materials have been prepared for packaging applications [18].Wang et al. have reviewed the applications of different chitosan biopolymer composite films showing various properties used for food packaging applications [19]. Moreover, polymer hybrid nanocomposite materials can provide new sensing and food packaging solutions. For example, polylactic acid hybrid nanocomposite films are lightweight, have different colors, and are superior thermo-mechanical resistant for food packaging applications [20]. The conductive paper made of natural cellulose fibers and conductive polymers have potential to be used as packaging material for electronic equipments or antibacterial applications [21] (Fig. 2). The polymer matrix with uniformly dispersed nanoparticles in the polymer results in a high matrix-filler interfacial area with enhanced thermo-mechanical properties [22]. A wide range of polymer nanocomposites fibers using nanoparticle and polymer matrix are used for nanofillers. These nanofillers can be utilized in civil structures, automobiles, aerospace packaging, thermal materials, and other consumer products.

Fig. 2 Polymer inorganic hybrid composite film for food packaging applications. (Reprinted with permission from ref. [18, 19])

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Sensor and Actuators Polymer films are useful materials to make rapid and reversible sensors due to low cost, light weight, simple fabrication techniques, and easy tunable physical properties. Polymer film can be deposited or mixed with various substances like inorganic and ceramic materials. Sensing effects by polymer film demonstrate the relationship between physical and chemical phenomena in terms of electrical or optical signal. The sensing mechanism can be generated by ion exchange membrane, conductive, dielectric polymer, and optically sensitive polymers to measure humidity, bioactive molecules, pH, temperature, and presence of specific ions [23]. Conjugated polymers have tremendous potential as a chemosensor for onsite monitoring of the food quality and safety in the food processing industry [24]. Moreover, formaldehyde can be sensed in seafood products by a biodegradable hybrid polymer film [25]. Hydrogen gas sensor can be prepared by polymer palladium nanocomposite materials [26]. Siloxane polymer film containing gold nanoparticle enhanced colorimetric detection of cardiac troponin [27] (Fig. 3). Polymer hybrid nanocomposite film can be used as actuators to give response to external stimuli such as light, magnetic, electrical, temperature, or pH [28]. This actuation effect is useful for the tissue engineering, drug delivery, soft robotics, and micro-mechanical applications. Some polymer thin film-based actuators such as a UV-visible light-driven liquid crystal polymer-based photomechanical motor [29], natural sunlight response actuator [30], and a polymer-based flexible solvent responsive membrane[31]are shown in Fig. 4. Due to the large surface area and enhanced electrical and electrochemical properties, polymer hybrid nanofibers are used as sensing materials for high sensitivity and fast response for determining humidity hydrogen peroxide, glucose, and

Fig. 3 (a) Conjugated polymer film-based chemical sensors. Reprinted with permission from ref. [24], (b) polymer membrane-coated palladium nanoparticle and graphene hybrid sensor for highly sensitive hydrogen gas sensing with gas selectivity. (Reprinted with permission from ref. [26])

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Fig. 4 (a) Electroactive polymer composite artificial muscles. Reprinted with permission from ref. [29]. (b) Sunlight actuating polymer film. Reprinted with permission from ref. [30]. (c) Actuating flexible nanoporous poly(ionic liquid) paper-based hybrid membranes. (Reprinted with permission from ref. [31])

pH. The piezoresistive pressure sensors were used to develop the wearable device using 3D membranes of conductive polymer nanofibers [17]. Nanofiber composites made of conducting polymers, polyelectrolytes, and semiconductors are used for the development of various types of gas sensors, and these sensors have more sensitivity and faster responses, compared to the thin film sensors [32]. The magnetic polymeric composite nanofibers can be used to design sensor and actuators depending on their magneto-optical and magnetoresistive properties [33]. Nanofibers composed of polyaniline, chitosan, and single-walled carbon nanotubes have been used as dualmode actuators based on pH and redox reactions [34]. A self-powered pressuresensitive polymer composite nanofiber-based fabric sensor was developed for the human health monitoring applications [35].

Electronic Applications The polymer hybrid nanocomposite films have attracted significant attention in electronic industries due to their better flexibility, low density, low manufacturing cost and better optical parameters. Conductive polymers composites films are used to fabricate flat, flexible screen for computer and televisions. Flexible electronic circuits are prepared by depositing conductive polymer film on the flexible substrate. These flexible electronic materials can be bent and stretched into any shape at any time. These kinds of devices can be used on curved substrates and easy to roll and pack when not required [36, 37] (Fig. 5).

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Fig. 5 Future flexible, bendable, rollable, and foldable touch panel. (Reprinted with permission from ref. [36–38])

Fig. 6 Different uses of polymer composite for biomedical applications. (Reprinted with permission from ref. [39])

Biomedical Applications Polymers are broadly utilized for biomedical applications such as for tissue engineering, scaffolds, and implants, but its mechanical properties are not comparable to the natural bone and tissues. Polymer hybrid nanofibers and films with optimal mechanical and biological features can be used to overcome the limitations of polymers. Polymer composite films have advantages for biomedical application due to good biocompatibility, biodegradability, highly smooth surface, high corrosion resistance, chemical inertness, and nontoxicity [39]. Control drug delivery and a variety of medical products such as disposable surgical cloths, gloves, medical bags, and dialysis bags are some of examples in this category (Fig. 6).

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Polymer nanocomposites fabricated ceramic/metallic nanoparticles in the polymer matrix are promising material for tissue engineering, bone regeneration, and drug delivery applications [40]. Studies on the lipid-coated nanofibers drug-loaded nanocomposite have shown an improvement in the drug sustained release profile [41]. Polymer nanofibrous scaffolds exhibited excellent mechanical properties for various vascular tissue engineering applications due to their reliable cytocompatibility and hemocompatibility [42]. The combination of CNT with biomolecules such as chitosan or heparin can be used to develop novel scaffolds with the properties of expediting cell growth [43]. Biodegradable polymer nanofibrous scaffolds of poly(D,L-lactide-co-trimethylene carbonate) with impressive shape memory properties have been found to have bone-forming ability [44]. Poly(ε-hydroxybutyrate-co-ε-hydroxyvalerate) PHBV–gelatin fibers can be used as an alternative carrier for ocular surface tissue engineering and as an alternative substrate to amniotic membrane [45]. PLGA–tussah silk–graphene oxide have excellent protein and bacterial antifouling characteristics suitable for bone tissue engineering [46].

Filters and Separators Polymer composite membranes have various applications in water purification, food processing, and gas separation. Depending on the pore size, these membrane can be used for microfiltration, ultrafiltration, nanofiltration, and reverse osmosis [47]. Polymer-inorganic composite hybrid membranes exhibit extraordinary gas separation properties for vapor–gas separation applications [48]. Polymer hybrid nanomembrane can be used for airborne nanoparticle filtration [49] as well as water purification [50] (Fig. 7). A reusable membrane was developed by using polysulfone with NaOH nanoparticles and a thin layer of polyamide polymer for oil–water separation process [51]. The cellulose/polyvinylidene fluoride-co-hexafluoropropylene nanofibers having super oleophobic properties can be used for selective separation of water from oil [52]. Different combinations of polymers, ceramics, metal oxides, and carbonaceous material can be used to fabricate nanofiber membranes for removing wastes from water [53].

Energy Storage and Generation Conductive polymer composite materials are fascinating for high-energy storage applications owing to their light weight, flexibility, low cost, controllable resistance, and excellent electrochemical properties. Composites of conductive polymers with flexible substrates are used to make flexible supercapacitors [54]. Moreover, flexible piezoelectric polymer-based energy-harvesting systems can be used for roadway applications [55]. Polymer hybrid composites nanofibers are widely used in batteries, supercapacitors, water desalination, hydrogen production and energy harvesting [56]. The supercapacitive behavior of polymer composite-based electrodes can be

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Fig. 7 (a) Hybrid monolithic aerogel of syndiotactic polystyrene and polyvinylidene fluoride for airborne nanoparticle filtration. Reprinted with permission from ref. [49]. (b) Polymer inorganic hybrid nanocomposite materials for water purification applications. (Reprinted with permission from ref. [50])

optimized for the energy storage applications due to improved cyclic performance and reversible capacity [57]. Dielectric nanocomposites have shown high ability to store and discharge electrical energy [43] due to their interior hierarchical interfaces that lead to the high energy density without the adverse effect of coupling of electric displacement and breakdown strength [58]. A polymer-based nanocomposite with controlled orientation of one-dimensional nanofibers has demonstrated an impressive energy storage performance [59] (Fig. 8).

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Fig. 8 Conductive polymer-based flexible, thin all-solid-state supercapacitor. (Reprinted with permission from ref. [54])

Textiles The nanofiber materials have created a niche area in textile industry by improving the comfort and thermal properties of the textile materials. The variation of pore size with the density of electrospun web area is the controlling parameters for the level of protection and thermal comfort of any fabric [60]. Self-cleaning coatings of polymer nanofibers can be used to reduce contamination on surgical tools and protective clothes by optimizing the surface chemistry and topography of the nanofiber membrane. The cotton fabric modified by TiO2 and TiO2/Ag/PVP nanocomposites has displayed a better antimicrobial activity for self-cleaning fabric applications [61]. Thermomechanical properties of monofilaments from polymeric nanocomposites of nano-clay in polyamide (PA) and polypropylene (PP) matrices have shown better tensile performances with high elastic response and can be a potential material in upholstery and automobile reinforcement tires [62]. The fibers composed of polybutylene terephthalate (PBT) and TiO2 have shown significant improvements in the self-cleaning properties under UV radiation and can be used in textile products [63]. The nanostructured piezoelectric poly nanofibers exhibited excellent durability

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Fig. 9 All-fiber e-textile with high thermal-moisture stability and comfortability. (a) The e-textile with good wearability. (b) Schematic diagram of air permeability and moisture permeability of the e-textile. (c) Schematic diagram of the moisture wicking function of the e-textile in sweating state. (d) SEM micrographs and contact angles of hydrophilic PAN and PA6 fibers. (e) Pore size distribution of hydrophilic PAN and PA6 fibers. (f) Water evaporation rate of cotton fabric, cotton-PAN fabric, and cotton-PA6-PAN fabric (the moisture-wicking fabric). (Reprinted from Copyright (2018), with permission from The Royal Society of Chemistry [66])

and can be used for mart upholstery for car seats or portable materials [64]. The polymeric piezoelectric nanofibers yarns were woven by twisting it that resulted in an increase in its overall strength and toughness along with an achieved energy up to 98 J/g with high stretchability [65] (Fig. 9).

Thermal Barriers Thermal barrier material made from polymer nanofiber composites can be used as a passive thermal insulator or an active temperature regulator. Composites of nanofibers with other materials may take advantage of the better insulation property of nanofibers while providing greater resilience to the composite material. The polymer composite was formed by infiltration of Sn-Ag-Cu matrix into the polyamide fibrous mesh to exhibit a high heat transfer capability with a through-plane and in-plane thermal conductivity [67]. Polyethylene nanofibers with diameters ranging from 10 to 100 nm with ultra-high strength (11 GPa) can be used as thermal conductor with increased dielectric constant over a broad temperature range (20 K–320 K) [68]. A biocompatible and biodegradable polymer composite nanofibers composed

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Fig. 10 Schematic illustrating the action of thermal interface material, which fills the gaps between two contacting surfaces and conducts the heat produced by electronic drives [70]. (Copyright (2012) the American Chemical Society) [70]

of poly(ε-caprolactone) and Fe3O4 nanoparticles coated multiwalled carbon nanotubes have shown an excellent shape memory effect under heat and magnetic field [44, 69] (Fig. 10).

Electromagnetic Interference (EMI) Shield Materials The day-by-day increase in the electrical equipment has raised a threat to environment and people from electromagnetic interference (EMI). The capability for EMI shielding can be further enhanced by making composites of polymers with different materials making it suitable for shielding material. The composites based on poly (ε-caprolactone) along with multiwalled carbon nanotube have shown excellent EMI shielding properties (exhibiting a reflectivity lower than 10 dB), with a shielding effectiveness >20 dB [71]. The overall shielding efficiency (SE) of the polymer composites can be enhanced by using more than one type of nanofillers. Nanoscale silver flakes and multiwalled carbon nanotubes were used with nitrile butadiene rubber to get higher SE with a broad frequency range and high flexibility [72] and the similar properties have been shown by the MWCNTs/Au/polyaniline nanocomposites [73]. The modified carbon fiber/magnetic graphene/epoxy composites have resulted in higher SE over a broad frequency range of 8.2 to 26.5 GHz [74]. Study has found that high SE is not only due to the addition of high conducting fillers but also by adding different types of fillers and its distribution, and extending the conducting network [21]. Polyacrylonitrile nanofiber/metal nanoparticle hybrid membranes have shown better EMI shielding effect compared to pure metal and other synthesized EMI shielding materials (Fig. 11).

Conclusions There is a huge potential of poly nanocomposites film and fibers for various applications such as for textile, electromagnetic shielding, biomedical, thermal, energy harvesting and storage, filter membranes, sensor and actuators. By optimizing the synthesis process parameters and including different polymers and nanomaterials, it is possible to improve the material properties of these materials as per

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Fig. 11 (a) fabrication process of CPAN NF/MNP hybrid nanofiber membranes for EMI shielding. FE-SEM images (Inset with magnified SEM); (b) PAN NF membranes, (c) CPAN NF membranes, (d) CPAN NF@Ag seed, (e) CPAN NF/Ag NP, (f) CPAN NF/Cu NP, and (g) CPAN NF/Ni NP. (Reprinted with permission from ref. [75])

required applications. It is expected that a wide range of polymer nanocomposite materials will continue to grow in the future that will be driven by the consumer product requirements and the market potential.

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Part IV Consumer Nanoproducts Based on Polymer Nanocomposites Matrices

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Consumer Nanoproducts Based on Polymer Nanocomposites Matrices María Paula Guara´s and Vera A. Alvarez

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanocomposites of Polymer Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer/Clay Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer/BaTiO3 Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer/Hexagonal Boron Nitride Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer/Carbon Nanotubes Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer Matrices from Sustainable Renewable Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starch-Based Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLA-Based Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PCL-Based Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commercial Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

In the last years, the development of polymeric-based nanocomposites has been a relevant area with high scientific and industrial interest. This is related with numerous improvements achieved in these materials, derived from the combination of one or more polymeric matrices and the incorporation of an inorganic or organic nanomaterial. The enhanced performance of those materials generally includes better mechanical strength, toughness, and stiffness, improved electrical and thermal conductivity, superior flame retardancy, and higher barrier properties (to moisture M. P. Guarás (*) Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina V. A. Alvarez Thermoplastic Composite Materials, Institute of Research in Materials Science and Technology (INTEMA), CONICET –Mar del Plata National University, Mar del Plata, Argentina © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_17

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and gases). Polymeric nanocomposites can also display unique design possibilities, offering advantages for the production of functional materials with specific and desired properties for different kinds of applications. In addition, the opportunity to use natural resources together with their environmental friendship has also open new and different opportunities for applications of those materials. This contribution revises the advances in consumer nanoproducts based on polymeric matrix nanocomposites. Nanomaterials have been increasingly inserted into consumer products, although research is still ongoing on their possible effects on the environment and human health. The consumer nanoproducts that are present in the market include cosmetics, clothing, food, electronic equipment, etc. At the same time, this has triggered the development of databases and inventories with information on engineered nanomaterials (ENM) embedded in nanoproducts. The objective of the next chapter is to describe the consumer nanoproducts based on polymer nanocomposites matrix present in the market and to evaluate their advantages and disadvantages and their consumption risks. Keywords

Nanoproducts · Polymer matrices · Filler · Nanocomposites

Introduction To understand the structure and properties of nanocomposites, it is necessary to define some basic concepts in advance. Contrary to popular belief, composite materials are as old as nature itself. A clear example of this is wood, the structure of which consists of tubular-structure cellulose fibers wrapped in a lignin matrix. Another example of man-made composite materials in the early days of civilization is the adobe and straw huts, which laid the foundations for the current constructions. A composite material is defined as any system or combination of materials made up of a union (nonchemical, insoluble with each other) of two or more components, which gives rise to a new material with new, characteristic, and specific properties. The properties of the new material depend, then, on the type of interface and the characteristics of the components [16]. Particles such as CaCO3, silica, clay and carbon black, and glass and carbon fibers have been widely used in recent times to improve the mechanical properties of elastomers and polymers. For example, tires have 10–100 nm diameter carbon black particles as filler, epoxy resins are reinforced with 10–20 μm diameter fiberglass used in boat hulls, and compounds filled with carbon fibers 5–20 μm meet the performance demands for applications such as aircraft bodies and sports equipment. Composite materials reinforced with micronsized particles have a small-volume fraction at the filler/polymer interface, compared to nanocomposites. Consequently, nano- and microscale fillers have very different effects on the final properties of a polymer (C. M. [36]). In general, nanotechnology is one of the most interest fields of research since the last century. The general definition of nanotechnology is that technology in which a

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group of processes, materials, applications, and concepts are defined by size. Nanotechnology, more specifically, is defined as the study, design, creation, synthesis, and manipulation of materials creating functional systems through the control of matter at the nanoscale, generating good mechanical and thermal properties with respect to pure polymers and composite materials [62]. The extraordinary potential of this new technology promotes new development routes for high-performance materials. During recent years, nanocomposites have generated much research interest owing to remarkable enhancements in the composites final properties and its applications, using very low-volume fractions of fillers. The term nano is used as a prefix for any unit and means one billionth (10
9) of that unit. Generally speaking, nanomaterials are materials that have at least one dimension in the range of 1–100 nm. A nanometer is approximately the length equivalent to ten hydrogen or five silicon atoms aligned in a line. When some outstanding property of a material, whose organization, random or well-ordered nanopatterns is evidenced, the resulting material is called a nanostructure or nanostructured material (Rajendra Kumar [25]). Nanomaterials exhibit highly attractive multifunctional properties that are clearly different from those of bulk materials. Nanomaterials are generally classified based on their dimensionality, morphology, composition, uniformity, and agglomeration. Depending on the dimensionality of the nanoparticles, the nanomaterials can be classified into 0D, 1D, 2D, and 3D as seen in Fig. 1. Phase-separated polymer blends naturally reach nanoscale phase dimensions. The morphology of the block copolymer domain is generally at the nanoscale level. Asymmetric membranes often have an empty nanoscale structure, mini-emulsion particles, and interfacial phenomena in mixtures and compounds that involve nanoscale dimensions [81]. Polymer nanotechnology is primarily developed to improve performance in terms of gas barrier properties such as oxygen and carbon dioxide. It has also been shown to improve the performance of UV barrier properties. On the other hand, they also improve resistance, rigidity, dimensional stability, and

Fig. 1 Examples of nanoparticles classified according to their dimensionality

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temperature resistance (thermal stability) [83]. There has also been a growing interest in polymer matrix-based nanocomposites initially due to successful studies involving exfoliated clay and other more recent studies involving carbon nanotubes, carbon nanofibers, exfoliated graphite (graphene), nanocrystalline metals, and a large number of nanoscale inorganic reinforcements [37]. Nanomaterials, due to their improved properties over their matrices (without nanofillers), have been increasingly incorporated into consumer products and have provided solutions in many diverse fields. Nowadays, nanotechnology is an emerging area for research and development, basically in most of the disciplines of science and technology. Fields of application include nanoelectronics, polymer-based nanomaterials, nanoparticle drug delivery, polymer-bonded catalysts for fuel cell electrodes and self-assembled layer-by-layer polymer films, nanofibers, printing lithography, polymer blends, and nanocomposites [34]. A common question is “with all the interest and associated large R&D expenditures in nanotechnology (including polymer matrix nanocomposites), why is there not more commercial impact?” Nowadays there are available in the market a number of polymeric matrix nanocomposites. Some important ones are summarized in the final part of the present chapter.

Nanocomposites of Polymer Matrix Polymers today are the materials of choice over metals and ceramics. This is due to its low-density properties, high specific rigidity, high specific resistance (resistance/ density ratio), and ease of manufacturing complex parts on a large scale using traditional injection molding, at low cost and low energy consumption. However, they have very low electrical conductivity, mechanical properties (resistance and Young’s modulus) and low thermal conductivity, and a relatively high coefficient of thermal expansion (CTE) [25]. These properties can be improved by adding an appropriate reinforcing (or filler) volume fraction (i.e., fibers or particles) in the polymer matrix, giving as the final product what are called polymer matrix compounds or nanocomposites, depending on the size of the constituents in matrix. Numerous studies have shown that compared to conventional polymer composites, polymer nanocomposites show improved mechanical and tensile strength, lower scratch and wear resistance, higher thermal distortion temperature, and noise damping. The problems that composites normally present are associated with high reinforcement content, such as decreased toughness, poor optical clarity, and higher melt viscosity [38]. These aspects are less problematic in the production of nanocomposites since a nano-reinforcement volume fraction of less than 10% by weight is enough to produce high-performance polymer nanocomposites [4]. For example, to improve properties likewise in a polymer matrix, the addition of only 1–5% by volume of nanoparticles is required versus 15–40% by volume of micron-sized particles or fibers. However, dispersing nanoparticles or nanofibers is not always an easy task. Modification of the surface with chemical groups compatible with the polymer matrix is often required to avoid (or minimize) agglomerations. Otherwise,

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Fig. 2 Advantages and disadvantages of polymer nanocomposites

nanoparticles tend to clump together and ultimately become responsible for stress concentration and crack formation in polymeric nanocomposites [29]. Polymeric nanocomposites are a blend of two or more constituents or phases, which exhibit different properties from their individual constituents. It is a necessary condition that the constituents dispersed in the polymer matrix have at least one dimension in the range of 1 to 100 nm. Furthermore, these constituents or phases present in the nanocomposite must be insoluble with each other. The size and distribution of the nanofiller are of great importance. As mentioned above, as the specific contact surface area between nanoparticles and polymer chains increases, the interaction within the nanocomposite is more intense. Depending on the nano-reinforcement used in the polymer matrix, improvements such as high-temperature capability, corrosion resistance, noise damping, low cost/manufacture, ductility, high specific stiffness and strength, high thermal conductivity, and low coefficient of thermal expansion can be obtained, compared to the unreinforced polymer [17] (Fig. 2).

Polymer/Clay Nanocomposites Polymeric nanocomposites reinforced with clay nanoparticles are among the first polymeric nanomaterials to emerge on the market as materials for a wide spectrum of applications. Nanoclays are the most widely investigated nanoparticles as reinforcement of different polymer matrices, since they are a readily available and low-cost alternative compared to other nano-reinforcements [59]. Phyllosilicates (2:1) are layered silicates, widely studied. The nanoclay most frequently used is the montmorillonite (MMT). MMT is a hydrated alumina silicate mineral which consists in platelets of an octahedral sheet of alumina sandwiched

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between two sheets of tetrahedral silicate. When certain aluminum atoms are replaced by magnesium atoms, the valence difference between Al and Mg creates negative charges (called cation exchange capacity (CEC)) which are distributed within the plane of the nanoclay layers, balanced by positive counterions (Na+, Li+, Ca2+), typically sodium ions, located between the galleries. Naturally, clay platelets have a thickness of 1 nm and have the other dimensions (i.e., length and width) in the order of 150 nm, up to a size of 1 or 2 μm. Hydration of the sodium ions causes the galleries (or interlayer spacing) to expand and the clay to swell. MMT can absorb large amounts of water (> 20 times its volume) and polar liquids, causing separation of the silicate layers [62]. One strategy to improve the compatibility of clays with polymeric matrices is the organic treatment (chemical modification). It is carried out by ion exchange between inorganic alkali cations on the clay surface with the desired organic cation. This type of modification increases the interlaminar spacing of natural clays, thus favoring dispersion in the polymer matrix [42]. There are diverse clay surface treatments; among the most prominent are the treatments with quaternary ammonium salts, alkylimidazoles, coupling and anchoring agents, reactive diluents, and functional amino compounds. Particularly, sodium ions can be exchanged with organic cations such as ammonium salt to form an organoclay (o-clay). The ammonium cation is known as a “surfactant” due to its amphiphilic nature. The resulting modified clay has a mostly hydrophobic character. Longer alkyl tails (of surfactant) give a more hydrophobic o-clay. Commercially, a variety of modified clays are available (Cloisite TM Na+, 10A, 15A, 20A, 25A, 93A, and 30B). Longer alkyl tails (of surfactant) give a more hydrophobic o-clay. Commercially, a variety of modified clays are available (Cloisite TM Na+, 10A, 15A, 20A, 25A, 93A, and 30B). In its original state, MMT is only miscible with hydrophilic polymers, such as poly(ethylene oxide), polyamide, polyurethane, and poly(vinyl alcohol). In order to make MMT miscible with other polymers such as polypropylene (PP) or polyethylene (PE), the polymers must be modified by grafting a small amount of a modifier such as maleic anhydride (MA). Typically ~1% of MA by weight is used, which acts as a compatibilizer and is very effective dispersing the modified clay into the original polyolefin. Depending on the physical state of the polymer, the clay can be incorporated into the matrix through different mechanisms [25]: • Polymer Intercalation: it is based on a solvent system in which polymer is soluble and also the clay is capable of swelling. Firstly, swelling of the clay in the solvent (water, chloroform, toluene) is generated, increasing the interlaminar space. When the polymer and swollen clay are mixed in the solvent, the polymer chains are sandwiched within the interlaminar space displacing the solvent. Then evaporation of the solvent occurs under suitable conditions according to the formulation. • In Situ Polymerization: clay swells within the liquid monomer or the monomer in solution so that polymerization occurs between the clay sheets. The

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polymerization can be initiated by heat or radiation, by diffusion of a suitable initiator, or by an initiator or organic catalyst pre-fixed by cation exchange within the clay layers. • Melt Intercalation: in this method, both the polymer and the clay are fed in solid state into a discontinuous (Brabender type) or continuous mixer (twin screw extruder). By applying shear stress and temperature, it is possible to transform to the polymer to the melt state and, on the other hand, to increase the interlaminar spacing of the clay to facilitate the intercalation of the polymer chains in the molten state between the filler galleries. This mechanism has certain advantages with respect to those previously mentioned. First, it is environmentally benign due to the absence of organic solvents. Second, it is compatible with the industrial processes currently in use, such as extrusion and injection molding (Fig. 3). Depending on the interactions between the polymer and the layered silicate (modified or not) and also on the method used for the preparation of the nanocomposites, three types of structures can be differentiated to mix polymers and clays (Fig. 4): • Microcomposite-aggregate morphology: When the polymer chains are not capable of intercalating in the interlaminar space of the clays, a microcomposite

Fig. 3 Processing of polymer/clay nanocomposites

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Fig. 4 Possible morphologies of a polymeric nanocomposite

is obtained, and the final properties of the material will be the same as those expected for traditional composite materials. • Nanocomposite-intercalated morphology: One or more polymer chains are inserted between the sheets of the nanoclay, maintaining the parallel arrangement of the lamellar structure. Intercalation of polymer chains increases the basal spacing of the clay flakes. • Nanocomposite-exfoliated morphology: It occurs when the clay sheets are completely dispersed in the polymer matrix, losing the ordered structure of stacked layers. Epoxy-clay nanocomposites, for example, are generally prepared by in situ polymerization. The first step is to disperse the clay into the epoxy resin before curing. This dispersion will later influence the morphology of the resulting nanocomposite. A homogeneous dispersion of the clay in the epoxy matrix will improve the degree of exfoliation; however, the poorly dispersed clay will generate agglomerations, resulting in a final product with poor mechanical and barrier properties [88]. The most widely used methods for dispersing clay in the epoxy resin are mechanical stirring, ultrasound and high shear mixing, ball milling, high-pressure mixing, and the suspension process. These dispersion methods can be more efficient if solvents are used to facilitate dispersion. Brown et al. studied the efficiency of the use of acetone as a solvent; however it did not result in appreciable changes in the morphology and properties of the resulting nanocomposite; it only served to facilitate the processability of the nanocomposite due to a reduction in the viscosity of the system [10]. Today, the possibility of preparing filaments of clay/PLA nanocomposite raw material for use in 3D printing using the fused deposition modeling (FDM) technique has been demonstrated. 3D-printed nanocomposites showed advantages, mainly related to improved shape stability and mechanical properties, over samples without reinforcement. Furthermore, Cicala et al. have reported that the presence of filler in the PLA matrix modifies the rheology of the polymer matrix and improves the share thinning [14].

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Polymer/BaTiO3 Nanocomposites Integrated capacitors perform a major role in the miniaturization of electronic/electrical devices, as they have substantial advantages over traditional discrete capacitors. The possible materials usable in integrated capacitors should be easily processable at low processing temperature. Furthermore, they must be strong and flexible to be compatible with PCB (printed circuit boards) manufacturing processes. Polymers have a low dielectric constant; therefore, they do not have the requirements for capacitors. On the other hand, ferroelectric ceramics have a high dielectric constant but require high processing temperatures. Polymer/ceramic nanocomposites present a decent alternative for manufacturing integrated capacitors due to the unique combination of properties in terms of good processability, flexibility, high dielectric constant, low processing temperature, and low cost. Ferroelectric ceramics, including barium titanate (BaTiO3), are the materials specifically chosen in capacitors due to their high dielectric constant [75]. BaTiO3 is a ferroelectric ceramic with the perovskite structure with a chemical formula of ABO3 (A ¼ Ba, Sr . . .; B ¼ Ti, Zr . . .). The crystal structure of which consists of AO12 cuboctahedra and BO6 octahedra. Depending on the temperature, it can be shown five different crystal arrangements (hexagonal, cubic, tetragonal, orthorhombic, and rhombohedral). All structures present ferroelectric properties, with the exception of the cubic structure. Also, it has low coefficient of thermal expansion and high thermal and chemical stability. Specifically, the electrical properties of polymer/BaTiO3 nanocomposites are an active field of research in various electronic applications, especially for the manufacture of passive components integrated into electronic devices [57]. Depending on the properties such as grain size, purity, crystallographic direction, measurement temperature range, and preparation method, the BaTiO3 dielectric constant can reach values of up to 5000. Among its properties, low direct current leakage, low loss tangent (0.009), low coefficient of thermal expansion, and high thermal and chemical stability stand out. However, at the same time, it has disadvantages such as brittleness and the requirement of high processing temperatures to compact it. These drawbacks can be overcome by adding a certain amount of ceramic powder to a polymer matrix (R. K. [26]). Several BaTiO3-filled composites with polymers such as epoxy [67], polyimide (PI) [64], polystyrene [21], cyanoethyl ester of poly(vinyl alcohol) (CEPVA) [46], and polyvinylidene fluoride (PVDF) [87, 93] have been studied. This type of compound can be used in applications such as integrated capacitors, electronic packaging, piezoelectric capacitors/transducers, multilayer ceramic capacitors, microwave substrate applications, and pressure-sensitive and chemocapacitive sensors. The dielectric constant of nanocomposites can be adapted according to user requirements. The advantage of this type of polymer/ceramic nanocomposite is its ease of processing and low weight compared to all ceramic materials. These factors are highly attractive for energy storage applications. However, there is an intrinsic difficulty in correctly dispersing ceramic nanofillers within polymeric matrices resulting in an aggregated nanocomposite with high presence of agglomerations, especially when the concentration of ceramic nanofillers is high. The lack of homogeneity and the poor

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dispersion of the particles result in negative influences on the dielectric properties and the electrical decomposition properties of the nanocomposites. As already stated, the dielectric performance of BaTiO3 particles depends on the particle size. Usually, the dielectric permittivity of BaTiO3 nanoparticles decreases when particle size is reduced, because it occurs at the transition of structural phase from tetragonal to cubic. Similar results have been found, regarding the dependence of dielectric properties as a function of the size of the reinforcement, in studies of polyvinylidene fluoride (PVDF)/ BaTiO3nanocomposites (B. H. [23]). Other polymer/BaTiO3 systems have been studied, such as the PI/BaTiO3 nanocomposites, and it has been found that the dielectric properties are also affected by the volume fraction of BaTiO3 (B.-H. [22]). However, large particles with higher dielectric permittivity did not lead to increased dielectric permittivity of the resulting polymeric nanocomposites. This result was not completely unexpected, since a large number of factors are those that affect the dielectric properties of polymer nanocomposites. As explained previously, another difficulty that arises is correct dispersion and interface interactions, which are also critical for dielectric relaxation behaviors. By decreasing the particle size to nanoscale, the surface area of the ceramic particles increases, which in turn produces an increase in surface energy and therefore a tendency to agglomerate. Both factors can influence interfacial polarization in nanocomposites. Intensive work has been done to develop methods to improve the dispersion of ceramic nanofillers in the polymer matrix [15]. An effective route by which good results have been obtained is the modification of the surface of the ceramic nanofillers. This technique is useful to modify the interface areas between ceramic nanofillers and polymer matrix and to improve the homogeneity of the nanocomposites [86]. Surface modification of nanofillers has always been a subject of great importance for the manufacture of high-performance polymer nanocomposites. Not only it fulfils the function of improving the dispersion of nanomaterials and the interfacial bond between the polymer matrix and nanomaterials, but it is also important in the dielectric relaxation of nanocomposites since it has an impact on interfacial polarization [71]. Numerous studies have been carried out to understand the behavior and properties of superficially modified nanoparticles. A comparative study evaluated the dielectric properties of modified and unmodified BaTiO3 nanoparticles (6 nm in size). The modifier used was n-hexylphosphonic acid (HPA) [9]. As a result, it was found that the modification of the surface led to significant changes in the dielectric properties: the modified nanoparticles presented a lower dielectric constant and dielectric loss than the unmodified nanoparticles, as well as weaker temperature sensitivity. Since BaTiO3 particles have surface groups such as hydroxyl, they have a polar character on their surface. This fact facilitates the grafting of different types of surfactants on the surface of the particle and favors the formation of a dielectric layer. In order to increase the reactive sites of the nanoparticles, they are often hydroxylated in a H2O2 solution. In this way, it is possible to increase the grafting rate of surfactants (Y. [91]). In the resulting nanocomposites, it has been found that hydroxylation successfully improved dielectric strength, in turn showing a decrease in dielectric permittivity and dielectric loss. In addition, studies show that both

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pristine BaTiO3 and hydroxylated BaTiO3 could be modified by surfactants, such as silane coupling agents [39]. The popularity of silane coupling agents is due to their high reactivity, and, at the same time, they have various functional groups that interact or react with the polymer matrix. Studies conducted on the effects of different silane coupling agents on the performance of BaTiO3/epoxy nanocomposites have shown that these agents played a critical role in their thermal and dielectric properties [31, 32]. Other efficient surfactants for BaTiO3 modification are phosphonates and phosphonic acids [19]. These surfactants have a strong binding affinity for oxides [9]. Another advantage is that they do not present the problems that occur with silane coupling agents, that is, the self-condensation of silane molecules, nor do they react with water. Finally, carboxylates or carboxylic acids also act as commonly used surfactants [79]. By chemisorption they bind with BaTiO3 and other oxides. Another option lies in polymeric surfactants (Fig. 5). They have proven to be an attractive alternative for modifying the surface of nanoparticles. The advantages of using polymers include: 1. The polymer surfactant is able to form a surface layer with different thicknesses and thus create a nucleus-covered structure together with the nanoparticles. It is possible to control the coating structure (especially thickness) by controlling the polymerization processes. 2. The polymer chains favor the formation of interactions with the polymer matrix, thus resulting in more intense interfacial bonds. A distinction needs to be made between the grafting methods. On the one hand, there is the “grafting to” method, which uses the polymer to modify the surface of the nanoparticle to form a shell around it. On the other hand, the “grafting from” method uses the surface of the nanoparticles as nucleation points for the initiation of polymerization of the monomers. Controlled core-shell structures can be made using atomic transfer radical polymerization (ATRP) and reversible additionfragmentation chain transfer polymerization (AFT) techniques [20]. The application of the “grafting from” method may be limited since both polymerizations are limited to the synthesis of certain polymer structures. For the “grafting to” method, the polymer coating can be done in two ways: (1) by physical absorption, caused by electrostatic and van der Waals interactions, and (2) by chemical reaction between the polymer chains and the surfaces of the nanoparticles [84].

Polymer/Hexagonal Boron Nitride Nanocomposites The continuing trend of miniaturization of electronic devices and the increasing power output of electrical equipment have posed the challenge of creating packaging and insulating materials. The main objectives are to develop materials with high thermal conductivity, low coefficient of thermal expansion (CTE), low dielectric constant, high electrical resistivity, high resistance to rupture, and low cost.

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Fig. 5 Methods to design and build core-shell nanoparticles for high-permittivity polymer nanocomposites

Polymeric materials present an attractive alternative to develop this type of material, due to its excellent processability and low cost. However, most polymers are thermally insulating and have a thermal conductivity between 0.1 and 0.5 W·m
1·K
1. One approach to increasing the thermal conductivity of polymers is to introduce inorganic fillers with high thermal conductivity, such as aluminum oxide, aluminum nitride, boron nitride, silicon nitride, beryllium oxide, or diamond. Thermally conductive nanoparticle-reinforced polymeric compounds can be easily processed. This fact led to the obtaining of nanocomposites with improved thermal conductivity due to the type of reinforcement used, and therefore they have been widely used for the thermal management application. Among the nanoparticles used for the processing of heat-conducting polymeric compounds, boron nitride (BN) dielectric ceramic particles are an increasingly attractive option. This is because the resulting heat-conducting compounds can simultaneously provide electrical insulation (wide bandgap of 6 eV) in electronic devices and equipment [48]. Hexagonal boron nitride (h-BN) is an attractive nanofiller for reinforcing polymers due to its properties. Firstly, it has low density (2.1 g/cm3); it also has high mechanical resistance (Young’s modulus, 0.7–0.9 TPa; elastic limit, 35 GPa), thermal stability (stable up to 1000  C under atmospheric conditions), and chemistry; and finally it is intrinsically an electrical insulator [33]. Moreover, h-BN is structurally analogous to graphite and has equally good thermal transport properties. These characteristics make BN-based composite materials perform their great potential in applications for the thermal management of energy systems, such as solar cells, light-emitting diodes, etc. Numerous studies have been developed on BN

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nanomaterials, for example, nanotubes (BNNT) and nanosheets received much attention due to their great performance in improving the thermal conductivity of polymeric compounds while maintaining the electrical insulation properties of a polymeric matrix [13]. Song et al. have studied the exfoliation of h-BN in an organic medium, with the aim of obtaining sheets of nanometric thickness and, subsequently, dispersing the resulting nanosheets in matrices of poly(vinyl alcohol), PVA, and epoxy [72]. Superior thermal transport performance has been obtained in the thus manufactured polymer/h-BN nanocomposite films. The results demonstrate that nanometric-thick h-BN sheets can hold promise with metallike heat transfer performance, as has already been achieved in graphene sheet-reinforced polymer nanocomposites [78]. Zhi et al. have developed a method of preparing thermally conductive thermoplastic nanocomposites with high-volume filler fractions. A 24% by weight h-BNreinforced poly(methyl methacrylate) (PMMA) nanocomposite was reported to have a thermal conductivity of 3.16 WmK
1 [92]. Although significantly improved thermal conductivities were achieved, there are still challenging problems that limit the practical applications of BN-based polymer nanocomposites. First, they have poor post-processing capacity. This problem originates from two critical points: the thermoset matrices adopted and the strong dominant fill-to-fill interactions, especially in highly charged compounds [49]. On the other hand, the other problem with this type of nanocomposites is related to the weak interactions between matrix/polymer filler and interfaces, which generally dramatically impair the final performance. Often this can result in a nanocomposite with high thermal resistance between the charge and the polymer matrix and/or cause deterioration in mechanical and electrical insulation properties simultaneously. Actually, two techniques for processing polymeric h-BN nanocomposites have been developed. On the one hand, most of the methods used involve adding h-BN nanoparticles to a commercial thermoplastic polymer matrix or to a curable thermorigid prepolymer, which has resulted in the aforementioned problems. On the other hand, after several years of research, controlled in situ polymerization techniques have been developed. In situ polymerization is believed to be a very promising technique for preparing nano-BN/polymer nanocomposites. The use of this processing method has certain advantages: (i) the growing polymer chains covalently bond with the BN nanoparticles, which favors the interaction between the nanoparticles and the polymer matrix; (ii) the polymer chains as they grow act as modifiers and polymer matrix, which significantly suppresses the aggregation of nanoparticles and, therefore, results in an excellent dispersion of nanoparticles and favors the reduction of filler interactions to fill in the nanocomposite.

Polymer/Carbon Nanotubes Nanocomposites Carbon-reinforced nanomaterials have had an unprecedented impact in recent decades in terms of their technological scope and their applications in the field of nanotechnology. Carbon is a molecule whose unique catenation properties allow it to form covalent bonds with other carbons in different states of hybridization (sp, sp2,

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and sp3) and thus form a variety of small molecules with long-chain structures. Carbon is a highly versatile material with good mechanical, chemical, optical, and electrical properties. These properties can be adapted according to the final application by manipulating its structure and surface chemistry. Carbon-based materials include a wide range of structures such as graphite, diamond, amorphous carbons, fullerenes, graphite, nanotubes, nanohorns, nanocones, carbynes (linear carbon chains), and carbon onions. The industrially used structures are activated carbon, carbon black, graphite, glassy carbon, diamond, and carbon fibers. The other structures (nanotubes, nanodiamonds, nanocones, nanofibers, whiskers, nanorings, and nanohorns) are in continuous optimization for use in technological applications [40]. Graphite, carbon black, carbon nanofiber (CNF), and carbon nanotubes (CNTs) are carbonaceous inclusions commonly used to develop polymer matrix nanocomposites. Carbonaceous materials are known for their thermal and electrical conductivity properties. According to their dimensions, they can be classified into three groups: (1) carbon black and round silica particles have three dimensions at the nanoscale; (2) CNT and CNF have two dimensions at the nanoscale; and (3) graphite, known to be a layered material, exhibits one dimension at the nanoscale. Carbon black is basically amorphous carbon and has a high surface/volume ratio, which gives it good adhesion to polymer matrices. However, carbon black grains tend to agglomerate and therefore require preprocessing treatments to obtain a correct dispersion in the matrix. CNTs are carbonaceous nanofillers that have attracted considerable attention in recent years because they have been shown to improve the inherent mechanical and electrical properties of nanocomposites compared to unreinforced polymer. Graphite consists of sheets of graphene bound by covalent bonds in the plane and van der Waals forces outside the plane between each layer. The graphene layers are stacked in AB sequences linked by weak van der Waals interactions, which are produced by a delocalized orbital π (Rajendra Kumar [25]). After the identification of their unique structure in the early 1990s, carbon nanotubes (CNTs) have attracted a lot of attention [2]. The basic structure of CNTs is graphene sheets, which are rolled up, with a length-diameter ratio significantly greater than that of any other material, which gives it its extraordinary properties. CNTs are classified as single-wall CNTs (SWCNTs), double-wall CNTs (DWCNTs), triple-wall CNTs, and multiple-wall CNTs (MWCNTs). In particular, CNTs have an extremely high Young’s modulus ( 1 TPa) and tensile strength of 150 GPa. On the other hand, it reaches intrinsic electrical conductivities of approx. 105–106 S/m for metallic CNTs and 10 S/m for semiconductor CNTs and high thermal conductivities (3000–6000 W/mK). These properties are combined with high flexibility, low density (1.3–1.4 g/cm3), and high aspect ratios (up to 1000 or more). Due to the unique combination of properties, the addition of CNT can greatly improve the thermal, mechanical, and electrical properties of the polymer matrix nanocomposites. However, their applications have been limited by their low solubility in commonly used solvents and their difficulty in dispersing in both solvents and polymeric matrices [43]. One of the most effective methods to improve the dispersion of nanotubes in the polymer matrix is the modification of CNTs by polymers. This modification can be classified according to its chemical union: the

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non-covalent or the covalent bond between the CNT and the polymer. Non-covalent modification of CNT consists of the physical adsorption and/or polymer coating to the surface of the CNT. On the other hand, covalent modification of CNTs is the chemical covalent bonding (grafting) of polymer chains onto the surface of the CNTs. Grafting is a very effective process, which produces a dramatic improvement in the interfacial interactions between the nanotubes and the polymer matrix. Interfacial interaction is one of the most critical fields in polymer/CNT compounds [66]. Polymer/CNT compounds can be processed in solution (thermoset and thermoplastic matrices), mass mixing (thermoplastic matrices), melting (thermoset and thermoplastic matrices), and in situ polymerization (thermoset and thermoplastic matrices). The most commonly used polymer matrices for nanocomposites are epoxy resins, polyamide-6 (PA-6), polyacrylonitrile (PAN), polycarbonate (PC), polyethylene (PE), ultrahigh molecular weight polyethylene (UHMWPE), polyimide (PI), poly(methyl methacrylate) (PMMA), polypropylene (PP), polystyrene (PS), polyurethane (PU), and poly(vinyl alcohol) (PVA), among others. The industrial and technological applications related to epoxy/CNT nanocomposites have led to their being widely researched. These nanocomposites are processed using melt or solution blending methods. The typical processing by melt mixing of epoxy/CNT consists of three steps: firstly the CNTs are added directly to the resin, and the mixture is sonicated in an ultrasonic machine at high temperature; secondly a curing agent is added and the mixture is degassed in a vacuum oven; and finally the mixture is placed in molds and cured in an oven [28]. The method is as follows when processing is by solution: the CNTs are dispersed in the solution using sonication; on the other hand, the epoxy resin and curing agent are dissolved in acetone and mixed with the CNT suspension. The mixture is then mechanically agitated and sonicated in a water bath. Finally, the acetone present in the system is removed by rotary evaporation, and the mixture is cured in an oven [50]. Liu et al. studied MWCNT-reinforced epoxy nanocomposites using polyethylenimine as a dispersing agent (covalent modification). The nanocomposites whose nanoparticles were covalently modified showed higher strength and higher storage modulus, due to improved nanotube/polymer interaction [50]. Similar results were observed by Spitalsky et al. in H2O2/NH4OH-modified nano-reinforcements for the production of MWCNT/epoxy nanocomposites [73]. PA-6/CNT compounds are often processed using the fusion method or by caprolactam polymerization. Generally, the melt method consists of the following steps: PA-6 is extruded together with CNTs, using a twin-screw corotating extruder at a barrel temperature of 260  C and a throughput of 5 kg/h. They are pelletized and processed by injection molding [55]. On the other hand, for processing by polymerization, it is as follows: first the CNTs and caprolactam are blended, and the blend is sonicated at 80  C for 2 h; then 6-aminocaproic acid is added to the suspension. This suspension is heated to 250  C with mechanical agitation under an argon atmosphere. After 6 hours of agitation, the blend is removed and poured into water, causing the precipitation of the polymer. The precipitate is pelletized and washed with hot water for subsequent molding [24]. Meincke et al. developed PA-6/CNT compounds processed on a twin-screw extruder. At low percentages of

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reinforcement, the nanocomposite evidences electrical conductivity. In addition, Young’s modulus showed a 27% increase compared to the unreinforced matrix [55]. Gao et al., on the other hand, studied the chemical processing technology, which allowed them to perform continuous spinning of PA-6/SWCNT fibers by in situ polymerization of caprolactam in the presence of amide-functionalized SWCNTs. It was possible to control the number of PA-6 chains grafted onto the SWCNT nanoparticles by controlling the concentration of the initiator. Fibers with improved mechanical resistance and thermal stability were obtained [24]. Pristine CNTs (P-CNTs) present a difficulty in being dispersed in polymer matrices, as previously mentioned. Therefore, numerous processing techniques have been developed, to effectively reduce the aggregation of nanotubes within matrices. Acid oxidation is a method by which reactive oxygen-containing groups such as carboxyl, carbonyl, and hydroxyl are introduced to the surface of CNTs. For this, the use of strong acids, such as HNO3 and H2SO4, is necessary. The final oxidized polymer/CNT nanocomposites (O-CNT) have exhibited better dispersion and interfacial behavior within multiple polymer matrices. Lateral functionalization of CNTs using organic chains or functional groups is another effective way to improve the dispersion of CNTs. Reactive oxygen-containing fractions produced by acid oxidation can be transformed into other functional groups using acrylic, chloridization, amination, esterification, and a variety of other methods [8]. Among the most important applications of CNT/polymer nanocomposites are electromagnetic interference (EMI) shielding, supercapacitor electrodes, photovoltaics devices, thermoelectrics devices, water purification, and gas and chemical vapor sensors, among others.

Polymer Matrices from Sustainable Renewable Sources Biodegradable polymers or biopolymers are polymers capable of being degraded through the metabolism of natural organisms [63]. This process produces gases (CO2, N2), water, biomass, and inorganic salts [5]. It is possible to classify biodegradable polymers in different ways, according to their chemical composition, synthesis method, processing, economic importance, and application, among others. The classification according to the source they come from is divided into (i) polymers from biomass such as agro-polymers (starches or cellulose and proteins), (ii) polymers obtained from microbial production such as polyhydroxyalkanoates (PHAs) (microbial polyesters are produced by biosynthetic function of a microorganism), (iii) conventional polymers and chemically synthesized from monomers from agroresources (polylactic acid, PLA), and (iv) polymers obtained from fossil resources [70]. To achieve full biodegradability, proper handling of waste products must be carried out; that is, after being used, plastics must be properly disposed of in order to allow for biological decomposition (i.e., composting) (Prof. [12]). Among the most important biodegradable polymers, thermoplastic starch (TPS), polylactide (PLA), polycaprolactone (PCL), and polyhydroxybutyrate and polyhydroxyalkanoate (PHA) are especially found due to their promising properties.

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Starch-Based Nanocomposites Thermoplastic starch (TPS) is a promising material for the development of biodegradable polymers. Currently, due to its abundance, it is one of the biodegradable polymers from the cheapest renewable resources available on the market. Depending on the botanical origin of the plant, the starch granules can have different shapes (spheres, platelets, polygonal) and size (from 0.5 to 175 μm). Its chemical composition consists of two components: amylose, composed of 1,4-α-D-glucose bonds in straight chains, and amylopectin, in which the glucose chains are highly branched [58]. The main disadvantages exhibited by thermoplastic starch are poor mechanical properties, high hydrophilicity (which produces changes in properties with humidity), high viscosity (which limits its processing), and high susceptibility to retrodegradation (the material recrystallizes with time, becomes opaque, and suffers exudation of plasticizer to the environment). The mechanical properties of thermoplastic starch evolve over time due to molecular rearrangement, which depends on the processing method and the conditions of storage. When samples are stored below the Tg, they can suffer physical aging with material densification [76]. When T > Tg, the samples are retrograded by increasing their crystallinity [51]. Aging the physical properties are observed for materials with a plasticizer content of less than 25% by weight [54]. This phenomenon induces an increase in the resistance of the material and a decrease in the deformation at break. It is possible to combine thermoplastic starch with other compounds in order to eliminate the disadvantages associated with their properties. These disadvantages can be overcome by using different strategies through physical or chemical means, including chemical modification [56], copolymerization of grafts [41], mixing with other synthetic polymers [27], and the incorporation of fillers such as clay [1] and nanocrystalline cellulose [77]. The incorporation of nanofillers to the polymer blends produces enhancements in the mechanical and barrier properties, driving to materials with high performance/cost ratio. The addition of a certain amount of nanofillers can significantly improve the physicochemical properties of the starch, and the size of the filler can also influence the biological activities of the starch-based materials. Starch-based nanocomposites can generally be processed using two different techniques, casting and extrusion. Although starch offers advantages in biomedical applications in other ones, as in the packaging and automotive industries, are limited and there are not capable of satisfying most of the necessary requirements. For this reason it is essential to incorporate some ecological filler to improve the properties of the starch. Among the different fillers, clay is the most abundant, biomass-based and low-cost filler that is frequently used in many applications. Kaolin is also used as a backing to prepare nanocomposites using thermoplastic starch (TPS) [53]. Often, it is necessary to modify the clay in order to increase its interlayer spacing and thus allow the polymer to be sandwiched between the clay sheets. Although clay modification is a means of increasing interlaminar spacing (d001) to possibly facilitate molecular intercalation of starch, it is demonstrated that the structure of the resulting compounds is more dependent on the hydrophilicity of MMT. The morphology of TPS-based nanocomposites will be highly dependent on the hydrophilicity of the

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MMT and the chemical modification of the TPS. It has been shown that the incorporation of MMT hydrophobic nano-reinforcements such as Cloisite 15A, 6A, and 10A, Nanomer I.30E, etc. led to the formation of microcomposites, showing unaltered interlaminar spacing (d001), using TPS with 30% glycerol [90]. When Cloisite 30B, a more hydrophilic OMMT, was used, higher values of d001 were obtained, corresponding to a higher dispersion of the nano-reinforcement in the TPS. Exfoliated nanocomposites have also been produced with MMT-Na+ due to the more hydrophilic character that makes it more compatible with thermoplastic starch. Uniform dispersion of MMT in thermoplastic starch can be achieved in this case due to polar interactions, especially the hydrogen bonds formed between the MMT-OH groups and the starch molecules [82]. When starch is chemically modified to decrease its hydrophilicity, apolar interactions with MMT can be achieved and as a result a lower dispersion of the reinforcement in the matrix [3]. Nanocellulose (NC) is a rigid particle that appears in the form of a rod and that has high strength and rigidity. Often, it has been used to improve the mechanical properties of various biocomposite materials, processed in different ways, such as films, gels, and foams, and notably to reinforce biopolymer-based electrospun fibers [44]. As is known, both cellulose and starch are biodegradable and belong to the polysaccharide family. The general chemical formula of cellulose and starch is (C6H10O5) and the structural unit is D-glucose. They are isomers with different glycosidic bond connections. Taking advantage of chemical similarity between both polymers, cellulose nanofibers (CNF) are commonly used to reinforce starch resulting in good interfacial bonds. Recently, starch/CNF-based nanocomposites have become increasingly popular in the paper, food, and adhesive manufacturing area, due to their excellent mechanical properties, low cost, and mainly biodegradability [65]. Chang et al., in their work, have impregnated cellulose nanoparticles in a starch matrix, and the compounds containing 5% by weight of cellulose nanoparticles showed a 248% increase in the elastic limit [11]. Patil and Netravali impregnated microfibrillated cellulose (MFC) with starch resin to take advantage of the chemical similarity between starch and cellulose, and the resulting starch/MFC biocomposites showed markedly improved thermal and tensile properties, comparable to the properties of compounds based on edible starch [60].

PLA-Based Nanocomposites Polylactide or poly(lactic acid) (PLA) is a biodegradable thermoplastic polyester that is manufactured using biotechnological processes from renewable resources. Although it can be manufactured from numerous biomass sources, corn has the advantage of providing the highest purity lactic acid required. In order to resurrect the costs of the manufacturing process, alternative starting materials (e.g., woody biomass) are continually being studied; however, due to the complexity of extraction, it is still expensive. In addition to its biodegradability and renewability, PLA exhibits interesting mechanical properties, its Young’s modulus is about 3 GPa, and the tensile strength

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is between 50 and 70 MPa with an elongation at break of about 4% and an impact strength of about 2.5 kJ/m2 [52]. Compared to conventional polymers such as PE, PP, PS, and PET, the mechanical properties of semicrystalline P(l-LA) are attractive, making it an excellent substitute for short-life packaging applications. However, PLA is a brittle material with low-impact resistance, which is one of its main limitations. In addition, the main issue regarding the use of PLA relates to its low capacity and degree of crystallization, which significantly limits its industrial application in durable applications such as automotive and electronics [61]. One solution widely developed in recent years has been to incorporate nano-reinforcements into the PLA matrix. Several types of nanofillers have been considered as reinforcing agents in order to improve their thermomechanical properties, as well as to provide additional functionalities such as fire resistance. PLA-based nanocomposites have been extensively researched in the presence of layered silicates, in order to obtain highly exfoliated structures. The preparation of PLA-based silicate nanocomposites with improved mechanical and barrier properties, in which highly exfoliated structures were obtained, has been successfully obtained using the solvent interleaving processing technique. Pochan and Krikorian investigated the effect of organic modifiers derived from three commercial organophilic clays (Cloisite 30B, Cloisite 25A, and Cloisite 15A) during the formation of PLA matrix nanocomposites. Given the compatibility between the matrix and the Cloisite 30B clay modifier, the mechanical properties of these compounds were improved, showing a 61% increase in Young’s modulus when 15% of Cloisite 30B was added to the matrix [47]. Although PLA is an interesting candidate for use as food packaging in relation to its biodegradability, the oxygen permeability of PLA must be reduced in order for it to be competitive in the oxygen-sensitive food area. Svagan et al. developed layer-by-layer nanocomposites based on PLA films and chitosan/montmorillonite layers. During this procedure, thin-film multilayer structures of chitosan and montmorillonite were assembled mainly by means of electrostatic forces in the extrusion of PLA films. Compared to pure PLA, montmorillonite/chitosan bilayer-coated PLA films achieved almost two orders of magnitude lower oxygen permeability [74]. Due to its unique structural and electronic characteristics, graphene as nanofiller finds promising applications in the field of polymer nanocomposites. Recently, the use of functionalized graphite nanofillers with tricobalt tetraoxide has been developed to increase the fire resistance of PLA [80]. Co3O4/graphite nanofillers were synthesized by an in situ chemical reduction process and redistributed in the PLA matrix by the melt method. As expected, the incorporation of Co3O4/graphene into PLA increased the initial degradation temperature, while slowing down the thermal decomposition process. Also, the heat release rate of the nanocomposites was reduced by 40% compared to pure PLA. The emissions of gaseous products such as hydrocarbons, carbonyl compounds, and carbon monoxide were in turn reduced with the addition of Co3O4/graphene, which was attributed to the combined properties of the barrier effect and the high catalytic activity for CO oxidation of Co3O4/graphene. Historically, silver compounds (neutral or ionic forms) have been widely used for both hygienic and healing purposes. When silver has a nanometer size, its total surface

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area becomes larger, and in this context the antibacterial efficacy increases accordingly. Furthermore, for various applications (water/air treatment and purification, health industry, electronics, textiles, shoe industry, packaging, etc.), there is a growing demand for polymer materials with antimicrobial properties. Since Ag nanoparticles form large aggregates and agglomerates very easily, the preparation of polymer nanocomposites/silver nanoparticles requires them to be properly pre-dispersed, specific surface treatments or the functionalization of the nanoparticles with organic molecules, and/or their incorporation into suitable polymer matrices [18]. Ag nanoparticles with diameters in the range of 3–5 nm were synthesized by Kamyar et al., by a chemical reduction method using silver nitrate and sodium borohydride (as a reducing agent), in a PLA-based solution composed of two solvents (DMF and CH2Cl2). The PLA films after evaporation of the solvents showed a uniform distribution of Ag-NP nanoparticles in the PLA matrix and strong antibacterial activity against E. coli and Staphylococcus aureus bacteria, respectively [68]. Furthermore, following a similar procedure, biodegradable PLA fibers containing nanosilver particles were prepared by electrospinning. These fibers showed a strong bacterial reduction of 98.5% and 94.2% against S. aureus and E. coli, respectively [85].

PCL-Based Nanocomposites Poly(e-caprolactone) or PCL is a semicrystalline, biodegradable polyester derived from petroleum. PCL has good resistance to water, oil, solvent, and chlorine, a low melting point, and low viscosity and is easily processed using conventional polymer processing techniques. It has low mechanical resistance but high flexibility, and its elongation at break can reach values of up to 700% [27]. The recently developed nanocomposite technology consisting of the addition of nanoparticles derived from biomass such as starch or cellulose is of particular interest. Compared to other types of inorganic nanofillers, this type of polymerbased nanoparticles has been given great attention due to its sustainability, biodegradability, and economic benefits. Several methods have been developed to prepare starch-based nanoparticles (SNPs), including precipitation by organic solvents, highpressure homogenization method, and lyophilization method, among others [69]. SNPs were reported to produce significant improvements in the mechanical and water vapor barrier properties of starch films. Biosource nanocomposites based on PCL/SNP by melt mixing and different SNP contents (2.5 to 10 wt.%) have been prepared, obtaining a very good dispersion of the SNPs in the PCL matrix. Furthermore, great improvements were observed in the mechanical properties of the resulting nanocomposites. Even with the addition of 10% by weight of SNP, the nanocomposite still demonstrated good ductility [45]. Poly(e-caprolactone) (PCL)/carbon nanotubes (CNTs) have potential applications in the biodegradable materials market and in the biomedical field [30]. CNTs can help overcome the disadvantages of PCL with respect to mechanical properties and thermal stability. Further studies address the addition of CNT to the PCL matrix and have found that CNTs could improve biodegradation rate, mechanical performance,

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and thermal stability [7]. An alternative “grafting” approach based on in situ ring opening polymerization of e-caprolactone has been successfully developed to covalently graft biodegradable poly(e-caprolactone) onto CNT surfaces. The content of grafted PCL can be easily controlled by adjusting the ratio of CNT-compatible monomers and macroinitiators. After PCL was injected onto CNT surfaces, the core-shell structures with nanotubes promise good solubility/dispersibility of CNT-PCL adducts in low boiling point organic solvents. CNT-injected PCL retains the biodegradability of conventional PCL and can be completely biodegraded by PS lipase in 4 days [89].

Commercial Nanoproducts Nanoproducts market development does not confine itself to the rippling effect; it’s a much more complicated and country-specific process. It is important to take in mind that the key demand-driving factor is offering radically new value to a consumer. In this sense, nanotechnology and nanoproducts not only develop the existing markets but also create new, high-capacity ones (P. C. M. [35]). The annual global market growth rate is averaging 17%. The growth in question is not gradual. There are tens of promising product niches boasting accelerated growth, for example, solar energy conversion (300% annual growth rate); optical electronics, 53%; medical research, clinical diagnostics, and medical equipment using nanotechnology, 32%; fuel nanocells, 23%; nanocomposites, 20%; etc. In 2015 global market capacity is expected to reach a $500 billion mark and surpass $1 trillion if the full cost of consumer nanoproducts is taken into account [6]. Some important polymeric matrix-based nanocomposites available in the market are summarized in Table 1.

Conclusions In this chapter, we have shown that the addition of nanoparticles to polymer matrices produces nanocomposites, a new generation of composite materials, with enhanced but also novel properties. Polymer-based nanocomposite is still a technology revolutionizing the world of material. Nonetheless, there are still several unresolved issues and new challenges in the field of polymer nanocomposites. One really important is the influence of preparation and processing techniques and methodologies on the generation of morphologies and their dependence on the final properties of the system that make it suitable for a required application. The polymer-based nanocomposites still have a huge potential that can be exemplified by the massive investment from government but also companies throughout the entire world. Finally, although there are several commercially available products based on this kind of materials, it is expected a big growth on the next decades together with the generation of a big impact on world business and economy.

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Table 1 Examples of commercial nanoproducts and its applications, characteristics, and producers Commercial polymer nanocomposites Product Characteristics Vestamid Electrically conductive (Nylon 12/CNTs) Nylon Improved modulus, nanocomposites strength, heat distort temperature, barrier properties Durethan KU2-2601 (nylon 6)

Aegis NC (nylon 6/barrier nylon) Polyolefin nanocomposites

Imperm ® M9

Doubling of stiffness, high gloss and clarity, reduced oxygen transmission rate, improved barrier properties Doubling of stiffness, higher heat distort temperature, improved clarity Stiffer, stronger, less brittle, lighter, more easily recycled, improved flame retardancy

Improve barrier properties High barrier properties

Aegis TM OX

Highly reduced oxygen transmission rate, improved clarity Forte Improved temperature nanocomposite resistance and stiffness, very good impact properties Commercial nanofillers Product Characteristics Carbon High electrical and nanotubes thermal conductivity, low thermal expansion coefficient Nanomers

Microfine powder

Applications Industrial parts

Producer Creanova

Automotive parts (e.g., timing belt cover, engine cover, barrier, fuel line), packaging, barrier film Barrier films, paper coating

Bayer, Honeywell Polymer, RTP Company, Toyota Motors, UBE, Unitika

Medium barrier bottles and films

Honeywell Polymer

Step-assist for GMC Safari and Chevrolet Astro vans, heavy-duty electrical enclosure

Basell, Blackhawk Automotive, Plastics Inc., General Motors, Gitto Global Corporation, Southern Clay Products Nanocor Inc.

Multilayer PET bottle and sheets Juice or beer bottles, multilayer films, containers High barrier beer bottles

Bayer

Mitsubishi Gas Chemical Company Honeywell Polymer

Automotive furniture appliance

Noble Polymer

Applications Additives and reinforcements

Producer Bayer, Hyperion Catalysis International, Nanocyl, Zyvex Corp. Nanocor

Nylon, epoxy, unsaturated polyester, engineering resins

(continued)

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Table 1 (continued) Commercial polymer nanocomposites Product Characteristics Cloisite Hydrophilic Organophilic

Dellite

Hydrophilic Organophilic

Bentone

With a broad range of polarity

Masterbatches

Pellet

NanoFil

Improve the mechanical, thermal, and barrier properties Additive, enhance mechanical barrier properties, thermal stability, and flame resistance Nanopigments, e.g., blue, red, green, yellow, high UV stability

Planomers

PlanoColors

PlanoCoatings

Additive, excellent transparency and improved barrier properties

Applications Additives, enhance flexural and tensile modulus, barrier properties and flame retardance of thermoplastics Cables and wires, packaging Automotive, rubbers, Additives to enhance mechanical, flameretardant, and barrier properties of thermoset and thermoplastics Thermoplastic olefin and urethane, styreneethylene-butylenestyrene, ethylene-vinyl acetate Thermoplastics and thermosets

Producer Southern Clay Products

Electric and electronic, medical and healthcare, adhesive, building and construction materials

TNO

Decorative coloring, UV-stable coloring, heavy metal-free coloring Transparent packaging materials, protective coatings, transparent barrier coatings

TNO

Laviosa

Elementis Specialties

PolyOne Corporation, Clariant Corporation, RTP Company

Sud-Chemie

TNO

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Polymer Nanocomposites for Futuristic Energy Storage Applications A. K. Nath and J. M. Kalita

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Layered Silicates and Polymer-Layered Silicate Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . Ionic Liquids and Ionic Liquid-Based Polymer Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Swift Heavy Ion Irradiation and Effects on Polymer Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . Ionic Transport and Electrochemical Properties of Ionic Liquid-Based P(VdF-HFP)-Layered Silicate Nanocomposite Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Swift Heavy Ion Irradiation Effects on Polymer-Layered Silicate Nanocomposite Electrolytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

190 194 196 198 199 212 222 223 223

Abstract

Electronic devices play a continuously increasing role in today’s modern society and the demands of wireless devices being rapidly growing. To ensure a stable current power supply, on board energy storage is essential, and therefore, energy storage devices are of great importance in today’s world. Traditional devices with liquid electrolytes have several limitations due to their bulky size and carry the inherent risk of leakage and safety. With a view to overcome the difficulties associated with bulky size and leakage, solid electrolytes have been emerged. Out of all kinds of solid electrolytes, polymer electrolytes have got utmost importance as they offer several advantages such as structural and chemical stability, shape versatility, low toxicity, etc. Therefore, burgeoning research is going on in the field of polymer electrolyte to get enhanced ionic conductivity and electrochemical stability which facilitate miniaturization, create more flexibility for the design of stand-alone microelectronic devices, and enhance the applicability in diversified fields. Swift heavy ion (SHI) irradiation is a novel technique to improve A. K. Nath · J. M. Kalita (*) Department of Physics, Cotton University, Guwahati, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_18

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electrical, electrochemical, and optical properties of different polymeric materials. Irradiation by high energy ion beam leads to fluence-dependent chainscission and/or cross-linking of the polymer chains which change the molecular weight distribution and molecular structure of the host polymer, which in turn affect electrical and mechanical properties. Considering all these developments in the field of energy storage materials, different polymer electrolyte nanocomposite systems, effects of SHI irradiation, and their probable applications have been reported in this chapter. Keywords

Polymer electrolyte · Nanocomposite · Energy storage · Layered silicate · Swift heavy ion irradiation

Introduction One of the main challenges of today’s information rich technology world is to provide efficient, portable, low-cost, and ecofriendly electrochemical energy conversion and storage devices such as rechargeable batteries. Rechargeable batteries based on liquid electrolyte have several restrictions on their design and size and carry the inherent risk of leakage. The replacement of liquid electrolytes with polymer electrolyte thin films offers numerous advantages to battery technologies in terms of structural and chemical stabilities, shape versatility, low toxicity, etc. and has potential advantages in the continuing trend toward miniaturization. A polymer electrolyte consists of an inorganic salt dissolved in a polymer matrix. The history of polymer electrolytes leads back to 1973 when P.V. Wright and his group observed ionic conductivity in their trail blazing work on poly(ethylene) oxide (PEO) complexed with sodium and potassium thiocyanates and sodium iodide [1]. The electrical properties of these electrolyte systems were studied later by P.V. Wright which established a correlation between ionic conductivity and amorphous phase of the polymer [2, 3]. In 1979, Armand [4] first proposed the use of these electrolyte systems as solid polymer electrolytes for rechargeable batteries which opened a window to the emerging field of polymer electrolytes. The oxygen atoms in PEO have high electron donor power with suitable interatomic separation enabling them to form multiple intra-polymer coordination bonds with cations. The low bond rotation barriers allow segmental motion of the polymer chain providing a mechanism for ion transport [5]. Since the first proposal by Armand in 1979, polymer electrolytes have been adopted in a wide variety of applications. The largely attracted applications of polymer electrolytes are in rechargeable batteries, sensors, fuel cells, supercapacitors, actuators, electrochromic displays, etc. The role of polymer electrolytes in these applications is to separate the electrodes, allow fast and selective transport of ions, and provide electronic insulation between the electrodes. To be suitable for the above-mentioned applications as given in Fig. 1, a polymer electrolyte must satisfy the following important requirements:

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191

Fig. 1 Polymer electrolyte and applications

(i) Polymer electrolytes should have adequate ionic conductivity (~ 10
3 S cm
1) and should be electronically insulator so that ion transport can be facilitated and self-discharge can be minimized. In general, the electrolyte is the component of

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an electrochemical device that sets the upper limit of output power. Therefore, higher electrolyte conductivity implies that a higher output power can be obtained from the device [6]. (ii) Another important requirement of polymer electrolyte is wide electrochemical stability which is important for energy storage devices such as supercapacitors and rechargeable batteries [7]. Polymer electrolyte should have electrochemical stability extending from 0 V up to as high as 5 V to be compatible with electrode materials. (iii) A polymer electrolyte should possess high thermal stability as during the functioning of the device, it may release heat that may result in degradation of the device. The polymer electrolyte used as a component in a device must be capable of maintaining its rated performance and withstand the device operating conditions, particularly the operating temperature. (iv) Polymer electrolyte should be robust against electrical, mechanical, or thermal abuses. It must possess good mechanical strength as to achieve various favorable electrochemical properties. Polymer electrolyte films should be flexible for miniaturized applications. Polymer electrolytes can be primarily classified into three categories: (i) solid polymer electrolytes, (ii) gel polymer electrolytes, and (iii) composite polymer electrolytes. “Solid polymer electrolytes” are solvent-free systems with an ionic conducting phase formed by dissolved salts in a polar polymer matrix [8]. The ionic conductivity of solid polymer electrolytes is typically low, generally lower than 10
6–10
8 S cm
1 at room temperature. In order to increase the ionic conductivity, “gel polymer electrolytes” have been developed by incorporating liquid plasticizer and/or solvents to a polymer-salt complex that is capable of forming a stable gel with the polymer host structure [9]. Gel polymer electrolytes are characterized by a higher ambient ionic conductivity but poorer mechanical properties compared to solid polymer electrolytes. The “composite polymer electrolytes” are prepared by adding inorganic material to the polymer-salt complex [10]. The combination is expected to improve ionic conductivity and electrochemical stability of the polymer electrolyte. The development of polymer electrolytes with high ionic conductivity and electrochemical properties has been an intensive area of research driven by the need to find new electrolytes for miniaturized applications [11]. Classical polymer electrolytes based on a polymer matrix and a solid salt offered low room temperature ionic conductivity restricting them from practical applications. High crystallinity of polymers is the key factor of low ionic conductivity (~10
7 S cm
1) in traditional polymer electrolytes. In this scenario, nanocomposite polymer electrolytes came as a rescue offering higher ionic conductivity (~10
3 S cm
1). Nanocomposite polymer electrolytes are produced by dispersing nanoscale fillers such as Al2O3, TiO2, SiO2, and clay in the polymer matrix [12, 13]. The nanofillers hinder the recrystallization of the polymer chains promoting localized amorphous regions which facilitates the movement of the ions through the polymer matrix leading to enhancement in ionic conductivity. It has been observed that particle size and the type of polymer-filler

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system play a significant role in enhancing electrochemical, thermal, and mechanical properties of nanocomposite polymer electrolytes [14]. One important advancement in the field of polymer electrolytes is the development of polymer-layered silicate nanocomposites. These nanocomposites are formed by the intercalation of polymers inside the interlayer galleries of layered silicate and are gaining great deal of research interest because of their potential importance in the development of polymer electrolytes with enhanced properties for applications in solid-state batteries [15, 16]. Intercalating polymer in layered silicate can produce polymer electrolyte nanocomposites with huge interfacial area which not only reduces the crystallinity of the polymer resulting in higher ionic conductivity but also sustains the mechanical stability [17]. Among the most commonly used inorganic layered hosts, montmorillonite (MMT) is a favored choice in view of its special features of high aspect ratio and high cation-exchange capacity (CEC 80 mequiv./100 g). The high swelling capacity of MMT is significant for the efficient intercalation of polymer inside the interlayer galleries. Aranda and Ruizhitzky [18] have found that intercalated poly(ethylene oxide) (PEO) molecules between silicate galleries impede polymer crystallization, resulting in higher ion conductivity compared with systems without clays. R.J. Sengawa et al. [19] reported that the dispersion of nanoscale MMT clay in poly(vinyl alcohol) (PVA)-poly (ethylene oxide) (PEO) blend matrix produces a large hindrance to the polymer chain dynamics. In recent times, the use of non-volatile, non-flammable ionic liquids (ILs) in polymer electrolytes has emerged as a very promising approach to replace traditional solid salts to improve the ionic conductivity and the interfacial property of polymer electrolytes as it can act both as ion supplying material (salt) and plasticizer which collectively enhance the ionic conductivity of the polymer electrolyte [20, 21]. Ionic liquids are organic salts that exist in liquid state at temperature lower than 100  C [22]. They have engrossed much attention due to their unique properties such as non-volatility, non-flammability, negligible vapor pressure at room temperature, wide electrochemical stability window (~4.5 V), high ionic conductivity (~10
2 S cm
1), excellent thermal and chemical stability, etc. [23, 24]. The polymer gel electrolytes based on ILs have a unique hybrid structure, which possesses cohesive properties of solids (due to polymer matrix) and diffusive properties of liquids (due to IL) simultaneously. Recent works done by many research groups demonstrated that ionic conductivity and electrochemical stability of polymer electrolytes are enhanced by the addition of ILs [24, 25]. For example, P. Yang et al. [26] reported room temperature ionic conductivity of 2.1  10
4 S cm
1 for the IL-based gel polymer electrolyte with poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-HFP)) as polymer matrix and 1-butyl-4-methylpyridinium bis (trifluoromethanesulfonyl)imide (B4MePyTFSI) as ionic liquid. J. Pitawala et al. [27] have studied the properties of polymer gel electrolytes based on P(VdF-HFP) and ionic liquids of the pyrrolidinium cation and the bis(trifluoromethanesulfonyl)imide anion and obtained maximum room temperature ionic conductivity of 1.6  10
3 S cm
1.

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Swift heavy ion (SHI) irradiation is another novel technique to improve material’s properties. Electrical, electrochemical, and optical properties of different polymeric materials can be selectively modified by ion irradiation [28]. Irradiation by high energy ion beam leads to fluence-dependent chain-scission and/or cross-linking of the polymer chains which change the molecular weight distribution and molecular structure of the host polymer, which in turn affect electrical and mechanical properties. When energetic ions penetrate into a polymer material, they lose energy during their passage through the material mainly by two different processes: (i) elastic collisions with the nuclei known as nuclear energy loss and (ii) inelastic collisions with the atomic electrons of the material known as electronic energy loss [29]. In SHI irradiation, electronic energy loss dominants and the kinetic energy of the ejected electrons is transmitted to the lattice by electron-phonon interactions leading to increase of local lattice temperature above the melting point of the material. The melting of the material is followed by a rapid quenching resulting in amorphous columnar structure when the melt solidifies and the material’s properties get modified. SHI irradiation has been reported to increase hardness, strength and wear resistance, ionic conductivity, and density and change the chain length and crystallinity of polymers [30, 31]. Considering the above-mentioned assessment, the present chapter describes works on electrochemical properties of ionic liquid-based polymer electrolyte nanocomposites and the effect of SHI irradiation.

Layered Silicates and Polymer-Layered Silicate Nanocomposites The layered silicates commonly used in the nanocomposites belong to the structural family known as 2:1 phyllosilicates [32]. Their crystal lattice consists of a two-dimensional, 1 nm thick layers which are made up of two tetrahedral sheets of silica fused to an edge-shaped octahedral sheet of alumina or magnesia. The lateral dimensions of these layers vary from 300 Å to several microns depending on the particular silicate. Stacking of the layers leads to a regular van der Walls gap between them called the interlayer or gallery. Isomorphic substitution within the layer (e.g., Al3+ replaced by Mg2+ or by Fe2+ or Mg2+ replaced by Li+) generates negative charges that are normally counterbalanced by hydrated alkali or alkaline earth cations residing in the interlayer. As the forces that hold the stacks together are relatively weak, the intercalation of small molecules between the layers becomes easier [33]. The commonly used layered silicates of 2:1 phyllosilicates family are montmorillonite, hectorite, and saponite. The chemical formulae for montmorillonite, hectorite, and saponite are Na0.33((Al1.67Mg0.33)(OH)2(Si4O10)), Na0.33((Mg, Li)3(OH, F)2(Si4O10)), and (Ca, Na)0.33((Mg, Li)3(Mg, Fe)3(OH)2(Al0.33Si3.67O10)), respectively. All these clays have layered structures with exchangeable cations in the interlayer galleries. Polymers can also be intercalated into the interlayer galleries of these clays. The naturally occurring layered silicates are hydrophilic in nature and not miscible with most of the polymers. In order to mix these hydrophilic layered silicates

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with polymers, it has to be modified to organophilic (organoclay) by exchanging the cations of the interlayers with organic cationic surfactants such as alkylammonium or alkylphosphonium (onium) salts. Because the modified clay (organoclay) is organophilic, its surface energy is lowered and is more compatible with organic polymers. The modification of layered silicates to organoclay not only matches the clay surface polarity with the polarity of the polymer but also expands the clay galleries. This facilitates the penetration of the gallery space by either the polymer precursors or preformed polymer. The maximum extent to which the cations inside the interlayer galleries can be exchanged is called cation exchange capacity and generally expressed in mequiv/100 g. Montmorillonites, hectorite, and saponite are the most commonly used layered silicates. Layered silicates have layer thickness of the order of 1 nm and very high aspect ratio of ~10–1000. Only a few weight percent of properly dispersed layered silicates create much higher surface area for polymer-layered silicate nanocomposites compared to conventional composites. Depending on the nature of the components used (layered silicate, organic cation, and polymer matrix), the strength of interfacial interactions between the polymer matrix and the layered silicates, as well as their methods of preparation, three different types of polymer-layered silicate nanocomposites can be thermodynamically obtained: (i) Phase separated: When the polymer is unable to intercalate between the silicate layers, a phase-separated composite is obtained whose properties remain in the same range as traditional microcomposites. (ii) Intercalated nanocomposite: In intercalated nanostructure, a single or sometimes more than one extended polymer chain is intercalated between the silicate layers resulting in a well-ordered multilayer morphology with alternating polymeric and inorganic layers. (iii) Exfoliated nanocomposite: These nanocomposites are formed when the silicate monolayers individually dispersed in polymer matrix, the average distance between the segregated layers being dependent on clay loading. The separation between the exfoliated nanolayers may be uniform (regular) or variable (disordered), and the stacks of the original clay structure are lost. The systematic studies on the interaction between a clay mineral and a macromolecule dates back to 1949, when Bower [34] described the absorption of DNA by montmorillonite (MMT). In 1963, Greenland [35] synthesized poly(vinyl alcohol)/ montmorillonite nanocomposite system and demonstrated that a polymer could be directly inserted in a clay in an aqueous solution. However, the field of polymerlayered silicate nanocomposite was widely introduced to the academic and industrial laboratories by a group of Toyota researchers in 1995 [36]. The Toyota research group reported improved methods for producing nylon 6 clay nanocomposites using in-situ polymerization. Their work revealed that polymer-clay nanocomposites exhibit superior strength, modulus, heat distortion temperature, water, and gas barrier properties with comparable impact strength as neat nylon 6. They also reported on various other types of polymer-clay hybrid nanocomposites. The

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pioneering work done by Giannelis and his colleagues [37] revealed that intercalation of polymer chains into the interlayer galleries of an organoclay can occur spontaneously on heating a mixture of polymer and silicate clay powder above the polymer glass transition or melt temperature. They explored the possibility of intercalation on the basis of thermodynamical free energy considerations and simulation studies to investigate the conformational and structural arrangement of polymer chains between successive clay layers [38]. Polymer electrolytes based on MMT clay and polymers such as poly(ethylene oxide) PEO and polyacrylonitrile (PAN) showed enhanced ionic conductivity compared to conventional polymer electrolytes [39]. Fan et al. [19] studied the Li-MMT/Na-MMT and PEO16LiClO4 composites and reported 30 times enhancement in room temperature ionic conductivity for the composite polymer film (3.5  10
6 S cm
1) compared to that of the pure PEO16LiClO4 (1.2  10
7 S cm
1). H.W. Chen et al. [40] showed that modified MMT enhances the ionic conductivity of PEO-based polymer electrolytes by 16 times than plain system. The conductivity increase is due to the well-dispersed clay in the system, which tends to disrupt the association of lithium cations and anions. Raghavan Prasanth et al. [13] prepared PVdF-clay nanocomposite PGEs containing 0–4 wt. % clay loading and studied their electrochemical properties. The intercalation/exfoliation of the clay into the polymer matrix was confirmed by XRD. The highest achieved ionic conductivity was 3.08  10
3 S cm
1 at room temperature for PGE containing 2 wt. % of nanoclay [13].

Ionic Liquids and Ionic Liquid-Based Polymer Electrolytes Ionic liquids are a class of materials which have attracted tremendous research interest as holding a great promise for green chemistry applications. Ionic liquids (ILs) are salts of organic cations and anions with melting temperatures below 100  C [41]. Ionic liquids are characterized by weak interactions due to the combination of a large cation and a charge delocalized anion. This results in a low tendency to crystallize due to flexibility of the anion and dissymmetry of the cation [24]. Ionic liquids are liquid electrolytes composed entirely of ions. In recent years, ionic liquids have been the subject of extensive investigation due to their unique properties such as negligible vapor pressure, non-flammability, high ionic conductivity, wide electrochemical stability window, and good chemical and thermal stability [42]. Unlike inorganic salts, which require solvation by a solvent to dissociate into an ion pair, ionic liquids do not require solvation and exist as completely dissociated ion pairs in the liquid state. Ionic liquids can reduce the use of hazardous and polluting organic solvents due to their unique characteristics as well as taking part in various new syntheses. On the basis of their composition, in general ionic liquids can be classified into three different classes, namely, aprotic, protic, and zwitterionic. Aprotic ionic liquids do not contain any acidic proton, while protic ionic liquids contain an acidic proton on the cationic species. Zwitterionic ionic liquids have a positive and a negative electrical charge at different locations within the molecule. On the basis of

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R1 N + N

197

R2

Suitable for Li batteries and supercapacitors X–

Aprotic

R1 N + N

H

Suitable for fuel cells X–

Protic ( )

R1 N + N n

X–

Suitable for IL based membranes

Zwitterionic Fig. 2 Different types of ionic liquids and their applications

composition and types, different ionic liquids are suitable for different applications as highlighted in Fig. 2 [24]. Ionic liquids possess several advantages over conventional organic solvents that make them environmentally benign solvents. Different kinds of organic, inorganic, and organometallic compounds are soluble in ionic liquids. Ionic liquids are highly polar and consist of loosely coordinating bulky ions and mostly have a liquid range up to 300  C. The wide liquid range of ionic liquids is distinct advantageous over traditional solvents which have narrow liquid range. The ionic liquids have low volatility which makes them easy to contain and transfer and can be used under high vacuum conditions. The unique properties of ionic liquids such as non-flammability, high ionic conductivity, electrochemical, and thermal stability make them ideal electrolytes in electrochemical devices like in batteries, capacitors, fuel cells, actuators, and electrochemical sensors [43, 44]. For applications in rechargeable batteries, ionic liquids should have high ionic conductivity. Ionic liquids have reasonably high ionic conductivity of the order of ~10
2 S cm
1 compared to other organic solvents or electrolyte systems [45]. Ionic liquids have advantages over general solvents as they have intrinsic ionic conductivity and do not require additional electrolyte. Ionic liquids also have higher density of ions, and they are denser than water from 1.0 to 1.6 g cm
3 depending on the structure of the ion. Ionic liquids have high thermal stability up to around 450  C. Ionic liquids generally exhibit a wide potential window of around 4.5–5.0 V [46] and large electrochemical stability window up to 7.0 V for some ionic liquid such as 1-butyl-3-methyl-imidazolium tetrafluoroborate [47]. The unique properties of ionic liquids such as high ionic conductivity, non-flammability, and low volatility are significant assets for applications of ionic liquids in polymer electrolytes. The replacement of the conventional, flammable, and volatile, organic solutions in gel polymer electrolyte (GPE) with ionic liquid-based

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polymer electrolytes can greatly reduce the risk of thermal runaway and enhance the conductivity. Scott et al. [48] have reported that imidazolium-based ionic liquids served as excellent plasticizers for poly(methyl methacrylate) with improved thermal stability and ability to significantly reduce the glass transition temperature. Md. Abu Bin Hasan Susan et al. [23] prepared ionic liquid-based polymer electrolytes by in situ free radical polymerization of compatible vinyl monomers in a room temperature ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI). They obtained ambient temperature ionic conductivity close to 10
2 S cm
1 and thermal stability up to ~400  C. J. Fuller et al. [49] reported P(VdF-HFP)-based polymer electrolytes incorporated with hydrophilic 1-ethyl-3methylimidazolium tetrafluoroborate (EMIBF4) and hydrophobic 1-butyl-3methylimidazolium hexaflorophosphate (BMIPF6) room temperature ionic liquids. They found that ionic liquid-based polymer electrolytes with ionic liquid to P (VdF-HFP) mass ratios of 2:1 exhibited ionic conductivities of >10
3 S cm
1 at room temperature and > 10
2 S cm
1 at 100  C. The pioneering work of A. Noda and M. Watanabe [50] showed that in situ polymerization of suitable vinyl monomers in ionic liquids such as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and 1-butylpyridinium tetrafluoroborate (BPBF4) formed mechanically strong and highly conductive polymer electrolyte films exhibiting an ionic conductivity of 10
3 S cm
1 at room temperature. S.A. Hashmi and co-workers [51] extensively studied ionic liquid-based polymer electrolytes for applications in rechargeable batteries and supercapacitors. They obtained high room temperature ionic conductivity of ~3  10
4 S cm
1 with PEO-based lithium ion-conducting polymer electrolytes complexed with lithium trifluoromethanesulfonate (LiCF3SO or LiTf) plasticized with an ionic liquid 1-ethyl 3-methyl imidazolium trifluoromethanesulfonate (EMITf). Magnesium ion-conducting electrolyte films comprising of PEO complexed with magnesium trifluoromethanesulfonate (or magnesium triflate) added with different amount of ionic liquid, 1-ethyl-3methylimidazolium trifluoromethanesulfonate (EMITf) was prepared by Y. Kumar et al. [52].

Swift Heavy Ion Irradiation and Effects on Polymer Electrolytes Swift heavy ion (SHI) irradiation is a special technique for inducing physical and chemical modification in bulk materials. High energetic ion beams have been exploited by researchers in different ways in the field of materials science to induce the desired properties in a material. SHI irradiation can modify the molecular structure in polymers in a controlled way leading to changes in their chemical, electronic, electrical, tribological, and optical properties [53]. SHI (energy >1 MeV/u) irradiation deposits the energy in the material in the near surface region mainly due to the electronic excitation [54]. Ion irradiation of polymers can induce irreversible changes in their macroscopic properties. Electronic excitation, ionization, chain-scission and cross-links, and mass losses are the events that give rise to the observed macroscopic changes [55]. The SHI has large range typically a few tens

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of μm due to which the impinging ions do not get implanted in the material if the thickness of the material film is smaller than the ion range. Ionization trail produced by SHI causes bond cleavages producing free radicals, which are responsible for most of the chemical transformations in polymers, namely, chain-scission, crosslinking, and double and triple bond formation. When an energetic ion penetrates through a material, it loses energy mainly by two nearly independent processes: (i) elastic collisions with the nuclei known as nuclear energy loss (dE/dx)n, which dominates at an energy of about 1 keV/amu, and (ii) inelastic collisions of the highly charged projectile ion with the atomic electrons of the matter known as electronic energy loss (dE/dx)e which dominates at an energy of about 1 MeV/amu or more. For an SHI, the inelastic collision is the dominant mechanism for transfer of energy to the material for producing tracks when its value crosses a threshold value for track formation. In SHI irradiation, the modification of thin films or the near-surface region of the bulk samples is due to the electronic excitation. In this case, the impinging ions do not get embedded in the film due to their large range (typically a few tens of m or larger). SHI irradiation is an up-to-the-minute technique to improve the ionic conductivity and other properties of polymer electrolytes. The changes induced by SHI irradiation depend on the sample parameters like composition, molecular weight, temperature, and ion beam parameters such as energy, mass, and fluence. SHI irradiation has been reported to increase hardness, strength and wear resistance, ionic conductivity, density, change the chain length, and crystallinity of polymers [56]. These modifications result from the changes of the chemical structure caused by changing the chemical bonding when the incident ion breaks the polymer chains, breaks covalent bonds, promotes cross-linking, and liberates certain volatile species. J. Singh et al. [57] studied the effect of electron beam irradiation on the properties of PEG-LiClO4 polymer electrolyte films and reported that ionic conductivity of the unirradiated electrolyte increases from 7.27  10
7 S cm
1 to 1.31  10
5 S cm
1 after irradiation.

Ionic Transport and Electrochemical Properties of Ionic Liquid-Based P(VdF-HFP)-Layered Silicate Nanocomposite Electrolytes Polymer-layered silicate nanocomposites formed by the intercalation of polymers inside the interlayer galleries of layered silicate have been gaining great deal of research interest because of their potential importance in the development of polymer electrolytes with enhanced properties for applications in solid-state batteries. In this chapter, discussion has been confined to poly(vinylidene fluoride-co-hexafluoropropylene) P(VdF-HFP) polymer matrix only. The copolymer P(VdF-HFP) consists of crystalline vinylidene fluoride (VdF) and amorphous hexafluoropropylene (HFP) units. The VdF unit provides an excellent chemical stability and mechanical strength to P(VdF-HFP). The amorphous HFP unit helps in trapping more liquid electrolyte. Hence, polymer electrolytes with P(VdF-HFP) as polymer

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matrix provide high ionic conductivities together with high mechanical stability. The ionic liquid used is 1-butyl-3-methyl imidazolium bromide (BMIMBr). 25–30 wt. % octadecylamine modified montmorillonite (MMT) has been used as the layered silicate. Out of the commonly used layered silicates, modified MMT has been selected because of its special features such as high aspect ratio (~1000), high cation-exchange capacity (CEC ~ 80 mequiv./100 g), large specific surface area (~ 31.82 m2 g
1), and appropriate interlayer charge (~ 0.55) and length scale (clay channel width ¼ 16 Å). At first calculated amount of P(VdF-HFP) was dissolved in acetone and stirred for 6 h at 50  C. Modified MMT was dispersed in 5 ml of tetrahydrofuran (THF) by ultrasonication, and the dispersed MMT solution was then mixed with P(VdF-HFP) solution by magnetic stirrer at 50  C. After 15 h of stirring, ultrasonication was done for 30 min. The viscous slurry thus obtained was cast on petri dishes, and the samples were dried for 2–4 days at room temperature and then kept in vacuum to get flexible, free standing, and rubber-like films. Different P(VdF-HFP)-MMT nanocomposite films were prepared by varying the concentration of modified MMT w.r.t. P(VdF-HFP) as 1.5, 2.5, 5, 7.5, and 10 wt. %. The P(VdF-HFP)-MMT intercalated nanocomposite films were then immersed in ionic liquid BMIMBr for a period of 5 h. The IL, BMIMBr got soaked in the nanocomposite films leading to the formation of P(VdF-HFP)-BMIMBr-MMT intercalated nanocomposite electrolytes. Figure 3 shows a photograph of P(VdF-HFP)-BMIMBr-MMT intercalated nanocomposite electrolyte. Electrochemical and thermal properties of the layered silicate nanocomposite electrolytes have been studied. First of all, nanocomposite formation has been confirmed from HRTEM image as shown in Fig. 4a. The HRTEM micrograph shows that layered silicate forms ordered intercalated tactoids that consist of many parallel silicate layers. It is evident that platelets are oriented edge on and reveal the existence of small thin bundles with each platelet of 3 nm thickness. Direct Fig. 3 A photograph of P(VdF-HFP)-BMIMBr-MMT intercalated nanocomposite electrolyte

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Fig. 4 (a) HRTEM of P(VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolyte. (b) Shows selected area electron diffraction (SAED) pattern. (Reproduced from Ref. [15] with permission of Springer)

observation of HRTEM image revealed unambiguous evidence of the MMT stacks being intercalated and uniformly distributed. It is noteworthy that a somewhat parallel arrangement of several neighboring platelets is maintained. Similar micrographs showing layered silicate structures have been obtained for all MMT loadings. Selected area electron diffraction pattern (SAED) of the area is shown in Fig. 4b. The SAED shows diffuse rings representative of amorphous phase. SAED confirms the highly amorphous nature of the electrolyte system. XRD studies have been carried out in order to monitor the formation of the polymer-layered silicate intercalated nanocomposites. Figure 5 shows the XRD patterns of modified MMT, pure P(VdF-HFP), and nanocomposite polymer electrolytes. The intercalation of P(VdF-HFP) into the interlayer galleries of modified MMT has been confirmed from the shifting of characteristic (001) basal reflection of modified MMT at 2θ ¼ 4.1 to lower angle side in case of nanocomposite electrolyte system. Modified MMT exhibits (001) peak at an angle 2θ ¼ 4.1 corresponding to the interlayer spacing (d001) of 2.15 nm. In case of P(VdF-HFP)BMIMBr-x% MMT electrolyte system, the peak position of (001) plane shifts toward the lower angle side indicating an increase in d001. The values of d-spacing (d001) have been calculated using Bragg’s law, 2dsinθ ¼ nλ, and the values are given in Table 1. An increase in d-spacing of the (001) plane of MMT with increasing concentration of MMT shows that P(VdF-HFP) intercalates into the interlayer galleries of MMT and the intercalation increases with increasing concentration of MMT. Beyond 7.5 wt. % of MMT, intercalation saturates, and no further shifting in (001) peak has been observed. Moreover, Fig. 5 also shows that with increasing concentration of MMT, crystallinity of the nanocomposite electrolyte system decreases. As P(VdF-HFP) intercalates into the interlayer galleries of MMT, the recrystallization of the P(VdF-HFP) chains decreases resulting in decreased

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Fig. 5 XRD patterns of (a) pure modified MMT, (b) pure P(VdF-HFP) and P (VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (c) x ¼ 1.5, (d ) x ¼ 2.5, (e) x ¼ 5.0, ( f ) x ¼ 7.5, and (g) x ¼ 10.0

Table 1 d-spacing, microstrain, and ionic conductivity of nanocomposite polymer electrolytes at different concentrations of MMT Wt. % of MMT 1.5 2.5 5.0 7.5 10.0

d001 (nm) 2.19 2.29 2.67 2.80 2.80

Microstrain (%) 0.26 0.32 0.35 0.37 0.37

Ionic conductivity (mS cm
1) 1.53 4.34 9.80 6.51 1.51

Reproduced from Ref. [15] with permission of Springer

crystallinity. It is observed that lowest crystallinity has been obtained for the nanocomposite electrolyte containing 5 wt. % of MMT. On further increase in MMT concentration, agglomeration of MMT takes place, and the excess MMT remains as a separate phase in the system which is confirmed from the increased intensity of the (001) peak at 7.5 and 10 wt. % of MMT concentration. Due to phase separation of MMT, the crystallinity of the nanocomposite electrolyte system increases at higher (> 5 wt. %) concentration of MMT. As polymer intercalates into the galleries of MMT, a significant compressive strain is expected in MMT layers. This strain arises due to the dislocation of crystal layers of MMT from their regular crystal lattice upon polymer insertion. The singleline approximation method [58] has been employed to calculate microstrain. This procedure involves the extraction and analysis of Gaussian (βG) and Lorentzian (βL)

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components of integral breadth of a single Bragg peak corrected for instrumental broadening. After correcting the instrumental broadening, the remaining line broadening (β) is believed to be due to crystallite size (βcryst) and retained strain (βstrain) broadening. Therefore, β ¼ βcryst þ βstrain

ð1Þ

e ¼ βstrain =4 tan θ

ð2Þ

The calculated microstrain and d spacing of (001) peak are given in Table 1. As d spacing increases, microstrain increases confirming intercalation. Ionic conductivity is a fundamental important property of a polymer electrolyte, and in a gel electrolyte, conductivity is achieved due to the movement of the ions through the interconnected pores of the polymer matrix. Accordingly, the porous structure is one of the important factors in determining the ion transport properties of an electrolyte. The porous structure of the nanocomposite electrolyte system has been confirmed from scanning electron microscope (SEM) micrographs. Figure 6 shows the SEM micrographs of nanocomposite films containing different amounts of MMT. IL is trapped in the pores making conducting pathways for the ions to

Fig. 6 SEM micrographs of P(VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (a) x ¼ 1.5, (b) x ¼ 2.5, (c) x ¼ 5.0, and (d) x ¼ 7.5. (Reproduced from Ref. [15] with permission of Springer)

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Fig. 7 Elemental analysis of P(VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolyte for C, F, Al, Br, Mg, and Si. (Reproduced from Ref. [15] with permission of Springer)

move. In the sample containing 5 wt. % MMT, the polymer domain seems to be more interconnected and uniform with respect to the other composition which is in agreement with the maximum conductivity at this composition. At 7.5 wt. % of MMT, agglomeration of MMT takes place, and the porosity decreases as observed from Fig. 6d. The electrolyte film containing 5 wt. % of MMT was subjected to elemental analysis as shown in Fig. 7. Figure 7 shows the distribution map of C, F, Si, Al, Mg, and Br which comes from P(VdF-HFP), MMT, and IL. Except Br (anion of the IL), all elements are distributed uniformly indicating homogeneous dispersion of all the moieties. Br is present only in some specific regions suggesting that IL is basically present in the pores and the Br
ion moves through the interconnected pores (as confirmed from SEM). Knowing the hydrophilicity of the polymer electrolyte is important for certain applications. Contact angle measurements have been conducted in order to know whether the nanocomposite polymer electrolyte films are hydrophilic or hydrophobic, and the results are shown in Fig. 8. For the MMT concentration of 1.5 wt. %, the contact angle is 39 suggesting that the nanocomposite electrolyte is hydrophilic at that concentration of MMT. With increasing concentration of MMT, the contact angle increases becoming 50 , 64 , and 70 for the MMT concentrations of 5.0, 7.5, and 10.0 wt. %, respectively. The increase in contact angle with increasing concentration of MMT suggests that the hydrophilicity decreases as the concentration of MMT increases. The MMT used in the present system is octadecylamine modified, and hence it is hydrophobic due to the presence of alkyl ammonium cations [59]. On the other hand, the ionic liquid, BMIMBr, is hydrophilic [60], and due to its presence in the pores of the polymer matrix, the nanocomposite films behave as hydrophilic. As the concentration of hydrophobic MMT increases, the hydrophilicity

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Fig. 8 Contact angle measurements of P(VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (a) x ¼ 1.5, (b) x ¼ 5.0, (c) x ¼ 7.5 and (d) x ¼ 10.0

decreases and the nanocomposite films tend to become hydrophobic. This means that increasing MMT content imparts anti-wetting property to the nanocomposite electrolyte films. Ionic conductivity of a polymer electrolyte is the most crucial parameter for practical applications. The ionic conductivity of the nanocomposite polymer electrolytes has been evaluated using the electrochemical impedance spectroscopy. Figure 9 shows the room temperature Nyquist plots of the nanocomposite polymer electrolytes. The plots show a depressed semicircle in the high-frequency region and a spike in the low-frequency region. It is widely accepted that the high-frequency semicircle is due to the parallel combination of bulk resistance and capacitance of the polymer electrolytes, whereas the low-frequency spike is ascribed to the charge transfer resistance and capacitance of the electric double layer formed at the electrode/electrolyte interface. The migration of the ions is represented by the resistance Rb, and the dielectric polarization of the polymer chains is represented by the capacitor Cg. The response of the electrode/electrolyte/electrode cell can be simulated as an equivalent circuit consisting of bulk resistance Rb in parallel with geometrical capacitance Cg in series with the constant phase element (CPE) as shown in inset of Fig. 9. The total impedance of the equivalent circuit can be expressed as

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Fig. 9 Nyquist plots of P (VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (a) 1.5%, (b) 2.5%, (c) 5.0%, (d ) 7.5%, and (e) 10.0%. Inset shows equivalent circuit representing actual cell assembly

 Z Total ¼

1 þ iωCg Rb


1


ZCPE

ð3Þ

where ZCPE is the impedance of the constant phase element. The CPE is a “leaky capacitor” which is attributed to the capacitive dispersion at the electrode/electrolyte contact and is given by the relation [61] ZCPE ðωÞ ¼ 1=ðiωCdl Þn

ð4Þ

where Cdl is the double layer interfacial capacitor independent of angular frequency (ω) and ½ < n < 1. So, the total impedance of the equivalent circuit corresponding to that of the electrode/electrolyte/electrode cell can be given as  Z Total ¼

1 þ iωCg Rb


1


1=ðiωCdl Þn

ð5Þ

At high frequencies, bulk resistances and the capacitances are of comparable magnitude and 1/ωCg ≈ Rb, both the bulk resistance and capacitance are the contributing factors to the overall impedance of the cell. Therefore, at high frequencies the equivalent circuit reduces to a parallel RbCg combination giving rise to a semicircle. At low frequencies, dielectric polarization is high corresponding to high value of Cg and hence 1/ωCg < Rb; so the contribution of Cg becomes negligible to the overall impedance, and the equivalent circuit behaves as a series combination of Rb and a CPE giving an inclined spike displaced by Rb along the real axis. The bulk resistance (Rb) is determined from the intercept of the semicircular arc with the real axis. It is observed that Rb decreases with increasing MMT concentration attaining minimum value at 5.0 wt. % of MMT concentration. On further increase in MMT

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Fig. 10 Variation of ionic conductivity at ambient temperature and IL uptake of P(VdF-HFP)-BMIMBr-MMT nanocomposite polymer electrolytes with varying MMT concentration. (Reproduced from Ref. [15] with permission of Springer)

concentration, Rb again increases. The room temperature ionic conductivity values have been evaluated from the measured values of Rb, and the variation of room temperature ionic conductivity and IL uptake with different MMT concentration is shown in Fig. 10. Room temperature ionic conductivity of P(VdF-HFP)-BMIMBr electrolyte without addition of MMT is 5.63  10
4 S cm
1. On addition of 1.5 wt. % of MMT, ionic conductivity increases to 1.53  10
3 S cm
1. Room temperature conductivity increases with increasing MMT content and attains a value of 9.8  10
3 S cm
1 for 5.0 wt. % of MMT content. The enhancement of conductivity by adding MMT to the polymer matrix is a combined effect of high aspect ratio of the MMT clay particles and increased uptake of ionic liquid, 1-butyl-3-methylimidazolium bromide by the nanocomposites. The IL uptake of the nanocomposites increases with increasing time as well as MMT concentration. At 5.0 wt. % of MMT, the uptake as well as conductivity is maximum. The IL acts both as salt and plasticizer and hence due to plasticization conductivity increases. The intercalation of P (VdF-HFP) into the MMT galleries suppresses the crystallization of the polymer due to steric hindrance produced by MMT layers to the polymer chains leading to the increased uptake of ionic liquid in the amorphous phase which results in enhanced ionic conductivity. Room temperature ionic conductivity of the order of 10
8 to 10
6 S cm
1 has been obtained for conventional electrolytes with general salts. Room temperature ionic conductivity of 9.8  10
3 S cm
1 is obtained in P(VdF-HFP)-BMIMBr-5 wt. % of MMT electrolyte system which is much higher as compared to conventional polymer electrolytes. The gel formation process is composed of two distinct steps. First, the electrolyte solution would mainly enter into the cavities, which are present in the porous host polymer because this process provides the lowest energy barrier for the solution to flow from the outside. In the next step, the temporarily trapped solution in the cavities penetrates into the polymer chain to produce saturation. Finally, the fully swollen polymer reaches an equilibrium condition which provides the maximum conductivity. The nanocomposite films have highly porous morphology as

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confirmed from SEM micrographs. IL, 1-butyl-3-methylimidazolium bromide fills the pores and makes highly conducting pathways for movement of ions. This is the reason of very high ionic conductivity. In spite of having such highly porous structure, free standing films have been obtained as intercalation of P(VdF-HFP) into MMT increases mechanical strength. Hence by intercalation as well as using ionic liquid, highly conducting gel electrolytes have been obtained with good mechanical strength. Beyond 5 wt. % of MMT, certain amount of MMT remains outside in the P(VdF-HFP) phase. Due to the presence of excess MMT, the porosity of the system decreases as evident from SEM micrographs (see Fig. 6). The excess MMT increases the viscosity of the system and hence conductivity decreases. Moreover, the phase-separated MMT blocks the pores as observed in SEM micrographs and hinders the movement of the ions leading to decrease in conductivity. In order to know that the charge transport in the nanocomposite polymer electrolyte films is predominantly ionic in nature, total transference number has been measured. Total transference number is a fraction of the total current carried by the ions, and it has been estimated using Wagner’s polarization technique. The measured values of transference number of P(VdF-HFP)-BMIMBr-MMT nanocomposite polymer electrolytes are 0.91, 0.94, 0.96, 0.95, and 0.90 for the MMT concentrations of 1.5, 2.5, 5.0, 7.5, and 10.0 wt. %, respectively. The transference number increases with increasing concentration of MMT attaining the highest value at 5.0 wt. % of MMT. This reveals that at 5.0 wt. % of MMT concentration, ionic contribution to the total current is maximum which is due to the easier movement of ions at that concentration of MMT. Beyond 5.0 wt. % of MMT, agglomeration of MMT takes place which hinders movement of ions and therefore ionic contribution to current decreases. The high values of ionic transference number (0.90–0.96) suggest that current in the nanocomposite polymer electrolyte films is predominantly ionic in nature. Figure 11 shows the temperature dependence of ionic conductivity of the nanocomposite films. The variation of ionic conductivity with temperature suggests that Fig. 11 Temperature dependence of P(VdF-HFP)BMIMBr-x% MMT nanocomposite polymer electrolytes where (a) x ¼ 1.5, (b) x ¼ 2.5, (c) x ¼ 5.0, (d ) x ¼ 7.5, (e) x ¼ 10.0

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the ionic conduction in the nanocomposite gel polymer electrolyte system obeys the Vogel-Tammann-Fulcher (VTF) relation [62] given by σ ¼ A T
1=2 exp ½
B=kðT
T o Þ

ð6Þ

where A is the pre-exponential factor, B is pseudo-activation energy for conduction, k is the Boltzmann constant, T is the temperature in K, and To is a quasi-equilibrium glass transition temperature usually 30–50 K lower than glass transition temperature, Tg. The VTF relation describes the transport properties in a viscous matrix, and its applicability suggests that the ion transport in the nanocomposite polymer electrolyte system occurs in the amorphous phase assisted by the segmental motions of the polymer chains. As the temperature increases, the polymer chains flex and expand producing more free volume leading to an increase in segmental motion of the polymer chains which facilitates ion transport. The electrochemical stability of the nanocomposite electrolytes at room temperature has been studied by linear sweep voltammetry, and the results are shown in Fig. 12. The decomposition voltage limit can be defined as the potential at which a rapid rise in current was observed and continued to increase as the potential was swept. It can be observed from Fig. 12 that neat ionic liquid, 1 butyl 3 methyl imidazolium bromide has low decomposition voltage of 3.5 V. The electrochemical stabilities of the nanocomposite gel electrolytes are larger compared to pure ionic liquid. With increasing concentration of MMT, the electrochemical stability increases attaining highest value of 5.5 V at 5.0 wt. % of MMT concentration. Beyond 5 wt. % of MMT concentration, electrochemical stability decreases reaching to the values of 5.2 and 4 V for the MMT concentrations of 7.5 and 10 wt. %, respectively. Generally, the irreversible oxidation of the salt anion limits the anodic oxidation window. The Lewis acid sites on the anionic surface of MMT can interact with Br
(Lewis base) of the IL and retard the decomposition of the anion of the IL enhancing the electrochemical stability. Fig. 12 Linear sweep voltammetry plots of (a) pure ionic liquid and P(VdF-HFP)BMIMBr-x% MMT nanocomposite polymer electrolytes where (b) x ¼ 1.5, (c) x ¼ 2.5, (d ) x ¼ 5.0, (e) x ¼ 7.5 and ( f ) x ¼ 10.0. (Reproduced from Ref. [15] with permission of Springer)

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Fig. 13 Interfacial stability of (a) P(VdF-HFP)-BMIMBr electrolyte without MMT and (b) P(VdF-HFP)-BMIMBr electrolyte containing 5.0 wt. % of MMT

Compatibility of polymer electrolytes with electrode materials remains an acute problem for their application in high power rechargeable batteries. Electrolytes lead to the formation of solid-state interface (SEI) layer, and a dendritic growth of lithium occurs at the electrode-electrolyte interface, which results in the decay of ionic conductivity and internal short circuiting of the cell during charge-discharge cycles of the cell. In order to examine the interfacial stability of nanocomposite gel polymer electrolytes before and after addition of MMT, the evaluation of the interface characteristics has been carried out by monitoring the time evolution of ionic conductivity of symmetrical cells of stainless steel/nanocomposite gel polymer electrolyte/stainless steel, stored at room temperature for 20 days. Polymer electrolytes without MMT and containing 5.0 wt. % of MMT (as it has highest conductivity) have been selected to observe the effect of MMT on interfacial stability, and the results are shown in Fig. 13. It is observed that ionic conductivity of both the electrolytes decreases with time but, the decrease of ionic conductivity in the MMT free polymer electrolyte is much larger as compared to that of the P(VdF-HFP)BMIMBr-MMT nanocomposite electrolyte. Moreover, ionic conductivity of the polymer electrolyte without MMT is continuously decreasing up to the 20th day of observation. However, the ionic conductivity of the nanocomposite electrolyte containing 5.0 wt. % of MMT becomes constant after 15th day, and no further decrease in ionic conductivity has been observed. In case of the electrolyte without MMT, the electrode directly comes in contact with the electrolyte, and corrosion reaction takes place easily and the passivation of electrode may eventually produce thick, high-resistive layers resulting in continuous decrease of ionic conductivity. However, in case of the intercalated nanocomposite electrolyte with MMT, the electrode/electrolyte contact area decreases as the presence of high aspect ratio MMT in the polymer matrix can prevent the electrode material to come in direct contact with the electrolyte and hence protect them from further reaction leading to increase in interfacial stability. Studies on thermal properties have been carried out using thermogravimetric (TG) analysis, and Fig. 14 shows TG curves of pure P(VdF-HFP), ionic liquid (BMIMBr), modified MMT, and P(VdF-HFP)-BMIMBr-MMT nanocomposite

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Fig. 14 TG curves of (a) P(VdF-HFP), (b) ionic liquid, (c) MMT and P (VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (d ) x ¼ 1.5, (e) x ¼ 2.5, ( f ) x ¼ 5.0, (g) x ¼ 7.5 and (h) x ¼ 10.0. (Reproduced from Ref. [15] with permission of Springer)

polymer electrolytes with varying concentration of MMT. There is essentially no weight loss for the polymer electrolytes when they are heated from room temperature up to 238  C indicating that no component is volatile inside the electrolytes. From Fig. 14, it is observed that there are three decomposition ranges for the nanocomposite electrolytes. The first range (235–325  C) corresponds to the decomposition of [BMIM]+ cation of 1-butyl-3-methylimidazolium bromide (BMIMBr), the second range (335–505  C) occurs due to decomposition of P(VdF-HFP), and the third range (515–760  C) corresponds to the decomposition of anion [Br]
. It is observed that addition of IL in polymer reduces the decomposition temperature of the electrolyte system which may be attributed to the complexation of [BMIM]+ cations of IL with the polymer that destabilizes the C-H bonds of the polymer. Moreover, with increasing concentration of MMT, the decomposition temperature decreases attaining lowest value at the 5 wt. % of MMT concentration. This can be attributed to the fact that with increasing MMT concentration, amorphicity increases (confirmed from XRD analysis) resulting in decreased thermal stability. It is known that amorphous materials have lower decomposition temperature compared to crystalline materials. Beyond 5.0 wt. % of MMT, agglomeration of MMT takes place leading to increase in crystallinity of the system as confirmed from XRD and SEM studies. Due to increase in crystallinity, thermal stability increases beyond 5.0 wt. % of MMT concentration. The onset decomposition (Tonset) and rapidest decomposition (Trpd) of P(VdF-HFP), ionic liquid, modified MMT, and P(VdF-HFP)-BMIMBr-MMT polymer electrolytes have been calculated by plotting the derivative thermographs of TGA curves. The derivative TG curves are shown in Fig. 15, and the calculated values of Tonset, Trpd, and wt. loss from Tonset to Trpd are summarized in Table 2. For pure P(VdF-HFP), Tonset ¼ 425  C and Trpd ¼ 489  C and from Tonset to Trpd, 50% wt. loss has been observed. With increasing concentration of MMT, Tonset and Trpd decreases attaining lowest values at 5.0 wt. % of MMT concentration. On the other hand, wt. loss from Tonset to Trpd increases with increasing concentration of MMT attaining highest value at 5.0 wt. % of MMT concentration. This shows that thermal stability of the nanocomposite electrolyte system decreases with increasing concentration of MMT which is due to increase in amorphicity of the system. Beyond

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Fig. 15 Derivative of TG curves of (a) P(VdF-HFP), (b) ionic liquid, (c) MMT and P(VdF-HFP)-BMIMBr-x% MMT nanocomposite polymer electrolytes where (d ) x ¼ 1.5, (e) x ¼ 2.5, ( f ) x ¼ 5.0, (g) x ¼ 7.5 and (h) x ¼ 10.0

Table 2 Tonset, Trpd and wt. loss from Tonset to Trpd of P(VdF-HFP), IL, MMT, and nanocomposite polymer electrolytes containing different concentrations of MMT Sample P(VdF-HFP) Ionic liquid MMT P(VdF-HFP)-BMIMBr-1.5% MMT P(VdF-HFP)-BMIMBr-2.5% MMT P(VdF-HFP)-BMIMBr-5.0% MMT P(VdF-HFP)-BMIMBr-7.5% MMT P(VdF-HFP)-BMIMBr-10.0% MMT

Tonset ( C) 425 238 300 290

Trpd ( C) 489 318 375 351

Weight loss from Tonset to Trpd (%) 50 59 11 24

280

336

25

238

303

30

248

311

27

294

364

19

5.0 wt. % of MMT, agglomeration of MMT takes place increasing crystallinity of the system resulting in increase in thermal stability. The agglomerated 2D MMT layers act as mass and heat transport barriers to the volatile species generated during decomposition giving rise to an overall increase in thermal stability of the nanocomposite electrolytes.

Swift Heavy Ion Irradiation Effects on Polymer-Layered Silicate Nanocomposite Electrolytes The detailed results on P(VdF-HFP)-BMIMBr-MMT nanocomposite electrolyte system with varying concentration of modified MMT as discussed in preceding section reveal that the nanocomposite electrolyte containing 5.0 wt. % of modified

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MMT has the best properties. Therefore, this sample has been chosen to irradiate with 100 MeV Si9+ swift heavy ions with a view to further enhance the properties. The ion irradiation of nanocomposite polymer electrolyte films was performed at the 15 UD Pelletron accelerator available at the Inter-University Accelerator Centre (IUAC), New Delhi, India, using Materials Science beam line facilities. The nanocomposite electrolyte films were irradiated by 100 MeV Si9+ ion beam with four different fluences of 5  1010, 1  1011, 5  1011, and 1  1012 ions cm
2 keeping the ion current constant at 0.6 pna. The energy of the Si9+ ion beam was chosen as 100 MeV so that the ion beam completely penetrated the nanocomposite electrolyte films and the films undergo uniform irradiation effects as the projected ion range of 80 μm, as calculated by using SRIM (stopping and range of ions in matter) software, was larger than the nanocomposite polymer electrolyte films of thickness ~ 30 μm. For ion irradiation, the polymer electrolyte films were cut in 1 cm  1 cm area and fixed on the sample holder (ladder) made up of copper. The ladder in the MS chamber is rectangular, and 24 samples can be loaded with six samples on each side at a time. After sample loading, the ladder is inserted in the MS vacuum chamber. Figure 16 shows the photographs of pristine and irradiated P (VdF-HFP)-BMIMBr-MMT intercalated nanocomposite electrolyte films containing 5.0 wt. % of MMT. Six pieces of each sample were fixed on the ladder and irradiated with different fluences. It is observed that with increasing ion fluence, the irradiated portion gets darker due to heat generation during the irradiation process. To study the effect of SHI irradiation, firstly XRD studies were carried out, and Fig. 17 shows the XRD patterns of pristine and 100 MeV Si9+ ion irradiated P(VdF-HFP)-BMIMBr-MMT nanocomposite electrolytes. It is observed that with increasing Si9+ ion fluence, (001) peak shifts toward lower angle side indicating higher gallery spacing of MMT and larger intercalation of P(VdF-HFP). At the ion fluence of 5  1011 ions cm
2, the characteristic MMT peak completely disappears confirming that exfoliation of MMT layers has taken place at that ion fluence. During irradiation, each ion creates a cylindrical molten zone of a few nanometers, transiently along its path, during which the temperature of the sample is quite high and the low viscous polymer has enough time to diffuse into the gallery to cause higher intercalation. It has to be mentioned here that the higher the fluence, the higher is the time of SHI exposure. So, the polymer gets more time to diffuse inside the gallery at higher fluence. Hence, intercalation of the polymer gradually increases with increasing fluence eventually leading to exfoliation at the ion fluence of 5  1011 ions cm
2. As observed from XRD results, upon ion irradiation with increasing ion fluence, the peak (020) broadens and its intensity decreases, which indicates that upon irradiation the larger size polymer chains change into smaller size due to chain-scission [63] and amorphicity of the system increases. The smaller chains with low molecular weight easily intercalate into the interlayer galleries of modified MMT resulting in increased amorphicity. The surface morphology of the pristine P(VdF-HFP)-MMT-IL nanocomposite electrolyte and that of irradiated with fluence 1  1012 ions cm
2 are shown in SEM micrographs in Fig. 18. Pristine P(VdF-HFP)-BMIMBr-MMT nanocomposite

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Fig. 16 Photographs of P(VdF-HFP)-BMIMBr-MMT intercalated nanocomposite electrolyte fixed on the ladder and irradiated at different fluences of (a) pristine, (b) 5  1010, (c) 1  1011, (d) 5  1011, and (e) 1  1012 ions cm
2

electrolyte has porous structure with uniform pores of diameter around 5 μm as observed from Fig. 18a. On SHI irradiation, the porosity increases significantly and the pores get more interconnected. Figure 18b shows the morphology of the electrolyte film irradiated at the fluence of 1  1012 ions cm
2, and it is observed that the irradiated film has pores of diameter 10 μm. Thus, on irradiation with high fluence, the pore size has become double and the pores get highly interconnected.

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Fig. 17 XRD patterns of P (VdF-HFP)-BMIMBr-5 wt. % MMT nanocomposite polymer electrolytes where (a) pristine and irradiated with different ion fluences of (b) 5  1010, (c) 1  1011, (d ) 5  1011, and (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

Fig. 18 SEM micrographs of P(VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolytes where (a) pristine and (b) irradiated with the fluence of 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

Contact angle measurements have been conducted on pristine and irradiated nanocomposite polymer electrolyte films and are shown in Fig. 19. It is observed that with increasing ion fluence, contact angle increases suggesting that the films tend to become hydrophobic after irradiation. Pristine and the films irradiated up to the fluence of 1  1011 ions cm
2 are hydrophilic in nature since the contact angle is less than 90 . However, the films irradiated at higher fluences of 5  1011 and 1  1012 ions cm
2 are hydrophobic as the contact angles are greater than 90 . The transition from hydrophilic to hydrophobic occurs due to the combined effects of the smoothing of surface due to increased porosity on SHI irradiation and increased abundance of hydrophobic MMT on the surface

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Fig. 19 Contact angle measurements of P(VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolytes irradiated with different ion fluences of (a) pristine (b) 5  1010, (c) 1  1011, (d) 5  1011, (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

due to exfoliation caused by SHI irradiation at and beyond the fluence of 5  1011 ions cm
2. Wenzel [64] predicts that the contact angle depends on surface roughness and the contact angle at a surface is given by cos θ ¼ r cos θ0

ð7Þ

where θ is the contact angle at the surface, θ0 is the contact angle for the perfectly smooth surface, and r is the ratio of the areas of the rough and the corresponding smooth surface. With increasing ion fluence, surface roughness decreases and the contact angle θ increases. At the fluence of 5  1011 ions cm
2 and beyond, exfoliation of MMT layers takes place as confirmed from XRD analysis, and the MMT platelets get dispersed in the polymer matrix. As the modified MMT is hydrophobic, the hydrophobicity increases at higher fluences due to exfoliation of MMT layers. According to Cassie [65], the contact angle at a heterogeneous surface depends on the fractional areas of different components of the surface. If the solid surface is composed of two materials, then the contact angle is a function of the two separate contact angles on the pure substrates such that cos θ ¼ f a cos θa þ f b cos θb

ð8Þ

fa and fb are the fractional areas of the two compounds, and θa and θb are the contact angles on smooth heterogeneous surfaces of pure a and pure b materials, respectively. After exfoliation, hydrophobic MMT becomes more abundant at the surface, and the electrolyte film turns hydrophobic from hydrophilic.

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Fig. 20 Variation of room temperature ionic conductivity of P(VdF-HFP)BMIMBr-5% MMT nanocomposite polymer electrolytes with varying ion fluences. (Reproduced from Ref. [28] with permission of Elsevier)

The SHI irradiation increased the room temperature ionic conductivity of pristine electrolyte from 9.8  10
3 S cm
1 to 2.26  10
2 S cm
1 after irradiation with the fluence of 5  1010 ions cm
2. Further, the conductivity increases with increasing ion fluence as shown in Fig. 20. The highest room temperature ionic conductivity of 4.96  10
2 S cm
1 is obtained at the highest fluence (1  1012 ions cm
2) used in the present study. On further increase in fluence, the nanocomposite electrolyte films get burnt. The increasing trend of ionic conductivity with increasing ion fluence can be attributed to the fact that polymer chains are broken on irradiation due to the heat generated in thermal spike that occurred during ion irradiation. The smaller chains with lower molecular weight easily intercalate into the interlayer galleries of modified MMT resulting in increased amorphicity as confirmed from XRD studies. The ionic motion becomes easier in the amorphous phase and the ionic conductivity increases. It is well known that porosity plays an important role in determining the ionic conductivity in polymer electrolytes [66]. Polymer electrolytes having large and interconnected pores have high ionic conductivity as the ions can easily move through the interconnected pathways. From the morphological studies shown in Fig. 18, it is observed that with increasing ion fluence porosity increases and the pores get more interconnected. Large interconnected pores facilitate easier ionic movements leading to increased ionic conductivity. Generally, ionic conductivity depends on mobility and number of charge carriers, and the relationship is governed by σ ¼ nqμ

ð9Þ

where n, μ, and q are the concentration, mobility, and charge of the ions, respectively [67]. With increasing intercalation, mobility of the ions increases as the ions can migrate through the intercalated polymer chains easily. As fluence increases, intercalation also increases as observed from XRD results leading to increase in ionic

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mobility, and consequently, ionic conductivity also increases. At sufficiently high fluence ( 5  1011 ions cm
2), exfoliation of MMT layers takes place, and the exfoliated MMT layers suppress recrystallization of polymer chains leading to increase in ionic conductivity. Ionic mobility is high in amorphous region, and Eq. (9) corroborates increase in ionic conductivity. Moreover, the activation energy (Ea) required for an ion jump is low in case of IL as the salt is in liquid state. Ea can be written as a sum of two terms which are denoted by binding energy (Eb) and strain energy (Es). Eb is the average energy an ion requires to leave its site, and Es is the average kinetic energy an ion needs to structurally distort its surroundings to create a “doorway” through which it can jump to another site. The IL and SHI irradiation induces expansion of the polymer matrix leading to decrease in Es part of activation energy thereby enhancing the ionic conductivity. The total transference number of the pristine nanocomposite polymer electrolyte containing 5.0 wt. % of MMT is 0.96 indicating that the charge conduction is predominantly ionic. On SHI irradiation, the total transference number increases following an increasing trend with increasing ion fluence. At the highest fluence of 1  1012 ions cm
2, the total transference number is 0.98. The increase in the total transference number for the pristine electrolyte from 0.96 to 0.98 for the SHI irradiated electrolyte films indicates that on irradiation the movement of the ions becomes more facile and the contribution of ionic current to the total current increases. The results for temperature dependence of conductivity are shown in Fig. 21. The conductivity of the electrolytes increases with an increase in temperature suggesting that the ionic transport occurs through the carrier ions assisted by the segmental motions of the polymer chains. With increasing temperature, segmental motion increases indicating increase in free volume, and the temperature dependence of conductivity can be related by VTF equation (Eq. 6). VTF behavior indicates that ionic conduction in highly amorphous system is strongly coupled with polymer segmental motion. SHI irradiation makes the system amorphous, and the

Fig. 21 Temperature dependence of ionic conductivity of P(VdF-HFP)BMIMBr-5% MMT nanocomposite polymer electrolytes irradiated with different ion fluences of (a) pristine (b) 5  1010, (c) 1  1011, (d ) 5  1011, (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

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temperature dependence of conductivity follows VTF behavior for the amorphous electrolyte system. The VTF parameters A, B, and T0 have been estimated for the pristine and the SHI irradiated nanocomposite polymer electrolyte films using curve fitting method and are presented in Table 3. It is observed that the pre-exponential factor A increases from 0.68 S cm
1 K1/2 to 4.0 S cm
1 K1/2 for the pristine electrolyte irradiated with the highest fluence of 1  1012 ions cm
2. As pre-exponential factor A is proportional to the carrier concentration, its increase with increasing ion fluence corroborates the fact that carrier concentration increases on SHI irradiation giving rise to an increase in ionic conductivity. The decreasing trends of B and To with increasing ion irradiation fluence reveal that hopping of ions through the segmental motion of the polymer chains becomes easier and ionic conductivity increases on SHI irradiation. The electrochemical stability window of pristine and SHI irradiated IL-based nanocomposite polymer electrolytes have been determined by linear sweep voltammetry, and the results are shown in Fig. 22. It is observed that for the pristine electrolyte, there is no apparent current through the working electrode from open circuit potential up to 5.5 V, and then the current increases gradually when the electrode potential is higher than 5.5 V. This result reveals that the electrochemical stability window for the pristine electrolyte is up to 5.5 V. On irradiation with 100 MeV Si9+ ions, the electrochemical stability window increases, and a continuous Table 3 VTF parameters of pristine and 100 MeV Si9+ ion irradiated nanocomposite polymer electrolyte films with different fluences

Fluence (ions cm
2) Pristine 5  1010 1  1011 5  1011 1  1012

A (S cm
1 K1/2) 0.66 0.88 1.00 3.00 4.00

B (eV) 0.17 0.14 0.10 0.09 0.08

Reproduced from Ref. [28] with permission of Elsevier

Fig. 22 Interfacial stability of P(VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolytes irradiated with different ion fluences of (a) pristine (b) 5  1010, (c) 1  1011, (d ) 5  1011, (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

To (K) 201 197 192 183 180

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increasing trend has been observed with increasing ion fluence attaining maximum value of 6.5 V at the highest fluence of 1  1012 ions cm
2. With increasing ion fluence, intercalation of P(VdF-HFP) into MMT layers increases, and the Lewis acid sites on the surface of MMT interact more easily with the Lewis base (Br
) of the ionic liquid and retard the decomposition of the anion leading to enhanced electrochemical stability window. After exfoliation at and above the fluence of 5  1011 ions cm
2, the Lewis acid-base interactions become more significant, and very high (6.5 V) electrochemical stability has been achieved. The results show that electrochemical stability up to 6.5 V has been obtained for the polymer electrolyte irradiated with the fluence of 1  1012 ions cm
2. Electrode-electrolyte compatibility is another important area of concern for the applicability of polymer electrolytes in rechargeable batteries. The reactivity of electrode with most electrolytes leads to the formation of solid-state interface layers which result in the decay of ionic conductivity [68]. The interfacial stability of the pristine and irradiated polymer electrolytes has been demonstrated by monitoring ionic conductivity at room temperature for a period of 20 days, and the results are shown in Fig. 23. Comparing the results, it is observed that the decrease of room temperature ionic conductivity with time is much larger in pristine electrolyte than the irradiated electrolytes. Moreover, ionic conductivity of pristine electrolyte continuously decreases for a period of 15 days and then becomes stable. However, for the electrolyte irradiated with the fluence of 1  1012 ions cm
2, stability in ionic conductivity has been obtained after 8 days as observed from Fig. 23b. This confirms that 100 MeV Si9+ ion irradiation enhances the interfacial stability of the electrolytes with electrodes. It is also observed that interfacial stability increases with increasing ion fluence. The reason for this can be attributed to the fact that on irradiation intercalation increases finally leading to exfoliation at higher fluence ( 5  1011 ions cm
2). Due to increased intercalation and exfoliation, MMT clay comes in between electrode and electrolyte and reduces the formation of passivation layers on the electrode leading to better interfacial stability.

Fig. 23 (a) Interfacial stability of pristine nanocomposite polymer electrolyte. (b) Interfacial stability of 100 MeV Si9+ ion irradiated nanocomposite polymer electrolytes irradiated with different ion fluences of (a) 5  1010, (b) 1  1011, (c) 5  1011, (d) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

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Studying the thermal properties of nanocomposites is very important to observe the safety and environmental effect [69, 70]. Thermal properties have been studied by thermogravimetric analysis, and the results are depicted in Fig. 24. In case of pure P(VdF-HFP), only one decomposition range is observed; however, for pristine and irradiated nanocomposite electrolytes, two decomposition ranges are observed. The first range (186–284  C) corresponds to the decomposition of [BMIM]+ cations, and the second range (320–430  C) occurs due to decomposition of P(VdF-HFP). The derivative thermographs of TG graphs as shown in Fig. 25 exhibit one peak in case of pure P(VdF-HFP) corresponding to one decomposition range and two peaks in case of pristine and irradiated nanocomposite electrolytes corresponding to two decomposition ranges. It is observed from TGA plots that decomposition temperature (Td) decreases after irradiation. Td for pure P(VdF-HFP) is 435  C and for pristine P(VdF-HFP)-BMIMBr-MMT nanocomposite electrolyte is 265  C. After irradiation, Td decreases as given in Table 4 and becomes 185  C for the electrolyte Fig. 24 TG plots of P (VdF-HFP)-BMIMBr-5% MMT nanocomposite polymer electrolytes irradiated with different ion fluences of (a) pristine (b) 5  1010, (c) 1  1011, (d ) 5  1011, (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

Fig. 25 Derivative of TG plots of P(VdF-HFP)BMIMBr-5% MMT nanocomposite polymer electrolytes irradiated with different ion fluences of (a) pristine (b) 5  1010, (c) 1  1011, (d ) 5  1011, (e) 1  1012 ions cm
2. (Reproduced from Ref. [28] with permission of Elsevier)

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Table 4 Tonset, Trpd, and wt. loss from Tonset to Trpd of nanocomposite polymer electrolytes irradiated with different ion fluences Fluence (ions cm
2) Pristine 5  1010 1  1011 5  1011 1  1012

Tonset ( C) 238 170 166 160 158

Trpd ( C) 303 243 241 234 230

Weight loss from Tonset to Trpd (%) 30 22 21 20 19

Reproduced from Ref. [28] with permission of Elsevier

irradiated with fluence 1  1012 ions cm
2. Addition of IL in pure P(VdF-HFP) reduces the decomposition temperature (Td) of P(VdF-HFP) which may be attributed to the complexation of [BMIM]+ cations of IL with the polymer that destabilizes the C-H bonds of the polymer. On SHI irradiation, amorphicity of the nanocomposite polymer electrolyte films increases as confirmed from XRD studies. SHI irradiation decreases the decomposition temperature by making the electrolyte films more amorphous as the decomposition temperature for amorphous materials is lower than that of the crystalline materials. The derivative thermographs of TG graphs are shown in Fig. 25 which gives the onset decomposition (Tonset) and rapidest decomposition (Trpd). The values of Tonset and Trpd are summarized in Table 4. For pure P(VdF-HFP), Tonset ¼ 425  C and Trpd ¼ 489  C and from Tonset to Trpd, 50% wt. loss has been observed. For the pristine nanocomposite electrolyte, the values of Tonset and Trpd are 238 and 303  C and 30% wt. loss has been observed. From this result it is observed that the rate of decomposition is low in case of nanocomposite electrolyte compared to pure P (VdF-HFP), which is required for practical applicability over large temperature range. Similarly, for the SHI irradiated electrolyte films, the Tonset, Trpd, and % wt. loss decrease as observed from the data given in Table 4. The increased intercalation and exfoliation upon SHI irradiation lead to decrease in the decomposition rate, which can be attributed to the fact that 2-D MMT layers act as mass and heat transport barriers to the volatile species generated during decomposition giving rise to an overall increase in thermal stability of the nanocomposite electrolytes.

Conclusion The field of polymer electrolyte nanocomposites is an emerging area of research as they find widespread applications in energy storage and conversion devices. In this chapter, the properties of polymer electrolyte nanocomposites for futuristic energy storage applications have been discussed. Ionic liquids have shown promise as vital materials of electrochemistry owing to the prospects of offering efficient ion conduction. Incorporation of ionic liquids into polymer networks furnishes a compatible combination resulting in some polymer electrolytes with relatively higher ionic conductivity and electrochemical stability and thus expanding their applications in

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rechargeable batteries, fuel cells, and solar cells. The chapter describes the effect of modified MMT on electrochemical properties of P(VdF-HFP)-BMIMBr-MMT nanocomposite polymer electrolytes. The electrolyte system containing 5.0 wt. % MMT shows ionic conductivity of 9.8  10
3 S cm
1 and thermal stability up to 238  C confirming that the electrolyte is usable over a wide temperature range. The use of swift heavy ion irradiation technique to enhance the morphological, structural, and electrochemical properties has been discussed. The nanocomposite polymer electrolyte containing 5 wt. % of modified MMT has been irradiated with 100 MeV Si9+ ion with different fluences. The room temperature ionic conductivity increases with increasing ion fluence attaining the highest value of 4.96  10
2 S cm
1 at the highest fluence used (1  1012 ions cm
2). Further, the electrochemical stability window increases with increasing ion fluence attaining the highest value of 6.5 V at 1  1012 ions cm
2 irradiation. Despite numerous studies on polymer electrolyte nanocomposites, a polymer electrolyte with high room temperature ionic conductivity is still outstanding. There is a whopping scope for further development of the polymer electrolyte nanocomposites with higher room temperature ionic conductivity for practical applications in rechargeable batteries. The ion conduction mechanism inside the interlayer galleries of MMT has not been thoroughly understood as yet which can further be investigated to tune the properties of the polymer electrolyte nanocomposites. Extensive research is going on to develop single ion-conducting polymer electrolyte; however, the researchers are far away from achieving the goal. Swift heavy ion irradiation with different ion beams and energies can be a promising tool for enhancement of the electrochemical properties of polymer electrolyte nanocomposites.

Important Websites https://www.sglcarbon.com/en/ https://www.iuac.res.in/ https://www.alliedmarketresearch.com/polymer-nanocomposites-market

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Metal Organic Framework NanoparticlesBased Polymeric Membrane for Industrial Mixture Separation

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Dipeshkumar D. Kachhadiya and Z. V. P. Murthy

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors Affecting the Properties of MOFs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods MOF Incorporating into the Polymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Various Applications of MOFs Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pervaporation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Desalination Via Pervaporative Route . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions and Future Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . For Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Journals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

229 230 231 232 232 235 236 236 236 236 236 237

Abstract

Metal organic frameworks (MOFs) are defined as solid crystalline materials synthesized in situ by the interaction of metal ions with organic linkers. MOF nanoparticles (NPs) have been widely used in various industrial separations, mainly membrane-based separation, because of their distinct properties such as narrow pore size, unique chemical features, and availability in multiple shapes. Both organic-inorganic and polymeric materials can be used as support materials. There is good compatibility between the MOFs and polymers. So MOFs can be used as fillers to prepare mixed matrix membranes. In this chapter, special attention is given to the fabrication of MOF membranes and application in the field of liquid mixture separations, such as water/wastewater treatment, nano-

D. D. Kachhadiya · Z. V. P. Murthy (*) Department of Chemical Engineering, Sardar Vallabhbhai National Institute of Technology, Surat, Gujarat, India e-mail: [email protected]; [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_86

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filtration, desalination, and pervaporative separation. This review gives a summary for the synthesis of MOF membranes and their applications in various fields and the challenges for developing MOFs membranes for liquid mixture separation. Keywords

MOFs · MOF membranes · Liquid mixture separation · Pervaporation · Desalination Abbreviations

2-MeIM BSA CA CNT DI DMF GO GOQD IP LBL MIL-101 MMM MOF NMP NPs PA PAN PBI PDA PDMS PEA PEBA PEI PI PSF PVA PVDF rGO SR-AOP TFC TFM UiO-66 ZIF

2-methylimidazol Bovine serum albumin Cellulose Acetate Carbon Nanotubes Deionized water N, N dimethylformamide Graphene Oxide Graphene Oxide Quantum Dots Interfacial Polymerization Layer-by-Layer Material institute lavoisier-101 Mixed Matrix Membrane Metal Organic Framework N-Methyl-2-pyrrolidone Nanoparticles Polyamide Polyacrylonitrile Polybenzimidazole Polydopamine Polydimethylsiloxane Polyetheramine Polyether-Block-Amide Polyetherimide Poly imide Polysulfone Poly(vinylalcohol) Polyvinylidene Fluoride Reduced Graphene Oxide Sulfate Radical Based Advanced Oxidation Processes Thin Film Composite Membrane Thin Film Membrane Universitetet i Oslo - 66 Zeolitic Imidazolate Framework

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Introduction Metal organic framework (MOF) consists of metal centers and organic binders that have high surface areas and distinct pore structures. As compared to conventional porous materials such as zeolites, carbon-based materials, metal oxides, and graphene, MOFs are extensively favored for various applications because of having unique tunable properties and different pore structures [1]. The control of pore structures is easier for MOFs as compared to other nanoporous materials. Nowadays, MOFs incorporated with polymers have gained remarkable attention to enhance MOF porosity and performance in various applications [2]. Membrane material and its properties have a considerable impact on the performance and separation efficiency of the membrane. Polymers, for example, cellulose acetate (CA), polyamide (PA), polysulfone (PSF), polyimide (PI), polydimethylsiloxane (PDMS), and polyvinylidene fluoride (PVDF), are commonly used to fabricate membranes. Polymer materials have several irreplaceable advantages, especially high processability and low production cost [3]. A disadvantage of polymeric membranes is that it generally suffers between selectivity and permeability [4]. The polymer properties hydrophobicity/hydrophilicity and structure stability are crucial for the separation performance of the MOF membrane. Hydrophilic polymers such as polyacrylonitrile (PAN), poly(vinylalcohol) (PVA), and chitosan are generally used because they selectively allow water molecules to pass through it [5]. Hydrophobic polymers like PDMS, polyether-block-amide (PEBA), and polybenzimidazole (PBI) are used to remove organic compounds from the aqueous stream [5]. To enhance the separation efficiency of the membrane, micro/nanoparticles (NPs) are blended into polymeric material to alter the crystal growth mechanism, composition, and pore structure of the membrane, thereby resulting in high performance mixed-matrix membranes (MMMs) [6]. MOFs incorporated membranes are mostly applied for various membrane separation processes like in gas permeation, H2 purification [7], CO2 separation [8], hydrocarbon separation [9]; in pervaporation, for dehydration of solvent [10], removal of dilute organic compound [11], organic-organic mixture separation [12]; nanofiltration [13]; desalination [14]; membrane distillation [15]; etc. Hydrophilicity and hydrophobicity of the membranes plays an essential role in the separation performance for solvent dehydration. Hydrophilic membranes allow water molecules to diffuse through them. PVA, chitosan, and sodium alginate show excellent attraction toward water molecules. The major issue of hydrophilic membrane is its stability and mechanical strength when water concentration is high in the feed solution. Hydrophobic membranes are generally used for the separation of dilute organic species from an aqueous mixture. PDMS, PEBA, and PBI have been commonly used for the separation of an organic-organic mixture. Hydrophobic polymers possess high thermal stability with better mechanical strength. Membrane swelling is the major issue, which can enhance the flux bot lowering the separation factor. It can be minimized by cross-linking or blending the appropriate NPs with the polymer chain [16]. The polymer characteristics are different at below and above the

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glass transition temperature (Tg). To increase the mechanical properties of the polymer, Tg is being modified by blending some NPs with the polymer chain [17].

Factors Affecting the Properties of MOFs While preparing the MOFs with controlled morphology and structure, the most considerable factors are temperature, additives (types of salts), composition (molar ratio), and solvent. Figure 1 shows some typical structures of MOFs used in the pervaporation membrane. Temperature plays a significant role in preparing MOFs by temperature-sensitive methods such as hydro/solvothermal or microwave-assisted methods. Most of the MOFs are prepared in the temperature range of 60–160  C in a closed system to achieve high-quality crystals. The synthesis temperature can play an important role in controlling the crystals’ growth and size. The optimized temperature of the system can result in nano-size crystals. For example, Koshhal et al. [19] prepared CuBTC MOFs at different temperatures and studied their effect on the final product. As per their Fig. 1 Some typical structures of MOFs. (Reproduced with the permission Elsevier [18])

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results, lower relative crystallinity and reduction in specific surface area were observed [19]. The solvent selection is another crucial factor for MOFs preparation. It directly or indirectly affects the interaction between metal ions and organic linkers. They may act as structure-building mediators for MOFs crystals [20]. The different studies showed that the use of other solvents results in different sizes of crystals. Some solvents such as dimethylformamide (DMF), N-methyl-pyrrolidone (NMP), methanol, ethanol, mixed solvent, and water are used to prepare MOFs [20]. For example, Ghorbani et al. [21] prepared a ZIF-8 with different solvents (DMF, DI water, ammonia, and acetone) and studied their effects on crystal growth. The obtained results showed that the solvent with higher polarity achieved nano-sized crystals [21]. Different studies are available on the impact of solvent for different MOFs (ZIF-8, CuBTC, UiO-66, MIL-53 (Al), and HKUST) [22]. There is an effect of molar ratio and type of metal salt on the size and structure of the MOFs crystals [23]. Zhang et al. [24] explained that with the increase in the linker to the salt ratio (Hmim/Zn+2), size reduction was observed for ZIF-8 crystals. Schejn et al. [25] prepared a ZIF-8 with different Zn salts. They concluded that the more reactive metal source is responsible for faster nucleation; thus, a reduction in the particle size was observed from 211 (ZnSO4) to 45 nm (Zn(NO3)2) [25]. There is also an effect of additives on the crystal growth, uniformity, and shape of crystals. We can control the crystal growth and structure coordination by adjusting the reaction kinetics [26]. Various additives are available with different acidity, polarity, and ion strength, such as trifluoroacetic acid, cetyltrimethylammonium bromide, amines, glycerol, benzoic acid, and pyridine [26].

Methods MOF Incorporating into the Polymer Permeability and selectivity of the MOF membranes depend on the size and pore structure of the MOFs. Two types of MOF membranes available for the application: (1) Pristine MOFs membranes and (2) MOFs composite membranes. Pristine membranes are defined as thin-film membranes (TFM) and are mostly prepared by the in situ route [27]. The in situ route is used to prepare continuous MOFs membranes. This can be categorized into direct crystallization, seeded or secondary crystal growth, and liquid phase epitaxy. In situ growth is termed as substrate directly immersed into the MOFs solution. In this method, nucleation and crystal growth takes place on the modified or unmodified substrate during the preparation time. Many researchers have developed MOF membranes on various inorganic materials and polymeric substrates [28]. Kang et al. [29] prepared a microporous MOF membrane on nickel mesh by seeded growth technique in the autoclave. Some defects and cracks on the membrane’s surface occurred due to weak bonding between the MOF layer and substrate [29]. To overcome this problem, secondary growth or seeded technique is developed to prepare continuous MOFs membranes [30]. Zhu et al. [31] prepared a polydopamine grafted ZIF-8 MOF membrane on the modified ceramic α-Al2O3 support. Modification with PDA promotes directly in situ growth to the surface of the substrate [31]. Pan et al. [32] prepared a ZIF-8 membrane on nano-sized ZIF-8 seeded α-Al2O3 substrate via secondary growth

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Fig. 2 Schematic of the thin-film composite membrane. (Reproduced with the permission Elsevier [23])

by immersing the top layer of the porous substrate into the ZIF-8 solution [32]. The layer-by-layer technique is another technique to prepare MOFs membrane. Shekhah et al. [33] developed the thin film layer of HKUST by liquid phase epitaxy method. Liu et al. [34] have developed novel Fe3O4@HKUST-1/MIL-100(Fe) MOFs via a combination of epitaxial growth and layer-by-layer deposition. Blending is another technique to prepared thin film MOF-based MMM. With this method, we can prepared a 1–30 μm thick MOFs layers on the porous substrate. Three steps involved in this process to prepare a membrane: (1) blending the polymer and MOFs particles into the solvent; (2) casting the dope solution on the substrate by doctor blade; and (3) drying process to remove the excess solvent. Liu et al. [35] prepared 2.5 μm thick organophilic layer of ZIF-8@PMPS on the inside surface of Al2O3 capillary by blending process. We can improve the membrane design by adding a thin layer of MOFs as a top selective layer via interfacial polymerization process (IP) (Fig. 2). This thin layer plays a significant role in the selective separation performance of the membrane. In the IP technique, reaction of nucleophile and electrophile reactant is taking place onto the porous substrate, which results into the formation of uniform polymeric chain [36]. To enhance the membranes properties, some additives of fillers have been added to prepare TFNC such as zeolites [37], CNTs [38], GO [39], rGO [22], GOQD [40], TiO2 [41], halloysite [42, 43], and cellulose and silica materials [43]. Other than these fillers, various MOFs such as the ZIF series, CuBTC series, and MIL series have been used as fillers or used as active skin layers to the porous substrates. Figure 3 represents the schematic of preparation of the membrane via different methods.

Various Applications of MOFs Membranes Pervaporation The applications of PV are mainly in three areas: (1) removal of dilute species from the mixtures, (2) recovery of organic solvents, and (3) separation of an organicorganic mixture. In the pervaporation, separation of the selected component is accomplished by the difference in sorption and diffusion through the membrane

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Fig. 3 Schematic diagram of membrane preparation by various methods. (Reproduced with the permission Elsevier [30])

surface [44]. Recently various MOFs such as ZIF-8, ZIF-71, UiO-66, MAF-6, and MOF-5 are widely used in pervaporative separations. To remove organic contaminants from the water, sulfate radical (SO4* ) based advanced oxidation processes (SR-AOP) have been widely used [45]. Zhang et al. [46] prepared a polyamide composite membrane with an interlayer of poly (4-styrenesulfonic acid) modified ZIF-8 for ethanol/water mixture separation (Fig. 4). Obtained results described that the prepared membrane MZIF-8/PA exhibited good separation performance with flux enhancement of 0.81–4.47 kg/m2h. Also, it was found that by decreasing ethanol concentration in the feed, the separation factor decreased from 318 to 127 [46]. Jin et al. [47] synthesized microwave-assisted a

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Fig. 4 Schematic representation of a modification of ZIF-8 particles. (Reproduced with the permission Elsevier [46])

hydrophilic CAU-10-H MOF membrane on the Al2O3 disc via secondary crystal growth for dehydration of ethanol. Wei et al. [48] prepared MOF membrane embedding the ZIF-90 particles onto the surface of the PVA membrane for ethanol dehydration. The prepared hybrid membrane showed 268 g/m2h of flux with a separation factor of 1379 for 90% ethanol-water solution. Pan et al. [49] synthesized a ZIF-90 and its derivativebased membrane for ethanol separation by incorporating the ZIFs particles with PDMS/ PVDF matrix. The prepared membrane showed almost double the total flux of 846 g/m2h with a 15.8 separation factor for 5% of ethanol/water aqueous mixture. Ibrahim and Lin [50] prepared a MOF-5 seeded α-Al2O3 supported membrane of organic mixture separation. Li et al. [51] prepared a hydrophobic membrane for recovery of butanol by incorporating silane-modified ZIF-8 NPs into the PDMS polymer. The prepared membrane showed 480 g/m2h of flux and a separation factor of 56, which is 23% higher than that of unmodified membrane for 1.5 wt% butanol solution [51]. Dehghankar et al. [52] prepared hydrophilic MMM by incorporating the UiO-66 and MIL-101 as nanofiller with PVDF matrix via phase inversion technique. Pure water flux of 360 LMH with 100% BSA rejection was obtained for 0.1 wt% loadings of MIL-101 [52].

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Desalination Via Pervaporative Route We can obtain highly pure water flux through pervaporation due to the nonvolatility of salts in the feed solution [53]. Highly hydrophilic membranes such as PVA, PEBA, PEA, and cellulose are used in the pervaporative desalination process. Different nanomaterials such as GO [54], CNTs [55], SiO2 [56], Al2O3 [57], nanolaponite clay [53], and cellulose nanocrystals [58] have been used to prepare a nanocomposite membrane for pervaporative desalination [59]. Halakoo et al. [60] prepared TFC Cl-PA membrane for pervaporative desalination via LBL deposition of the PEI as a positive charge and GO as negatively charged on the surface of the membrane. Obtained water flux and salt rejections were 8 kg/m2h and > 99.9% of salt rejection. Nigiz et al. [61] prepared GO incorporated NaAl membrane for the desalination process. Prihatiningtyas et al. [62] prepared a CTA/CNCs nanocomposite membrane for saline water treatment. To improve the water flux without lowering the selectivity, a time-controlled alkaline treatment is given to the membranes. Alkaline-treated membrane showed high water flux of 107.5 kg/m2h than that of the original membrane without losing the selectivity (Fig. 5) [62]. Selim et al. [63] developed a low-cost glutaraldehyde cross-linked laponite/PVA membranes with water flux of 31.2 kg/m2h and 99.98% salt rejection. Zeolitic materials can also be used for saline water treatment [64].

Water flux

Rejection (%) 100

100 98

Rejection (%)

Water flux (Kg.m-2.h-1)

150

50 96

0 Untreated

6

20

30

60

Alkaline time (min)

Fig. 5 Performance data of CTA/CNCs membrane for pervaporative desalination. (Reproduced with the permission Elsevier [62])

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Conclusions and Future Perspectives Different types of MOFs and MOFs membranes have been successfully developed in the last 5 years. Membrane-based separation has been discovered as a promising process without compromising membrane permeability and selectivity [23]. There are n numbers of MOFs available with low hydro-stability and large pores, which is not suitable for monovalent ion separation results in poor quality water. Despite this, the literature reported that MOF membranes exhibited good performance in terms of flux and selectivity compared to the commercial membrane. However, till date, no large-scale production of MOFs membranes is reported. Scientists are working on the development of commercial MOFs membranes with better flux, higher selectivity, and thermal/chemical stability for various applications. Future researchers can work on improving the surface area and size distribution of MOFs that can enhance the interfacial compatibility between polymer matrix and nanofillers. There is much scope in MOFs stability and their integration with polymers, which opens many new applications in various fields [65].

For Further Reading Important Websites 1. https://www.borsig.de/en/products-and-services/membrane-technology-for-liq uid-separation/pervaporation 2. https://pervaporation-membranes.com/products/modules 3. https://permionics.com/membranes

Important Journals 1. 2. 3. 4.

Journal of Membrane Science Separation and Purification Technology Desalination Chemical Engineering Science

Important Books 1. Membrane Processes: Pervaporation, Vapor Permeation and Membrane Distillation for Industrial Scale Separations (URL:https://onlinelibrary.wiley.com/doi/book/10.1002/9781119418399) 2. Polymer Nanocomposite Membranes for Pervaporation (URL: https://www.sciencedirect.com/book/9780128167854/polymer-nano composite-membranes-for-pervaporation)

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3. Pervaporation, Vapour Permeation and Membrane Distillation (URL: https://www.sciencedirect.com/book/9781782422464/pervaporationvapour-permeation-and-membrane-distillation) 4. Current Trends and Future Developments on (Bio-) Membranes (URL: https://www.sciencedirect.com/book/9780128163504/current-trendsand-future-developments-on-bio-membranes)

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50. Ibrahim A, Lin YS (2016) Pervaporation separation of organic mixtures by MOF-5 membranes. Ind Eng Chem Res 55:8652–8658. https://doi.org/10.1021/acs.iecr.6b01965 51. Li S, Chen Z, Yang Y, Si Z, Li P, Qin P, Tan T (2019) Improving the pervaporation performance of PDMS membranes for n-butanol by incorporating silane-modified ZIF-8 particles. Sep Purif Technol 215:163–172. https://doi.org/10.1016/j.seppur.2018.12.078 52. Dehghankar M, Mohammadi T, Moghadam MT, Tofighy MA (2021) Metal-organic framework/ zeolite nanocrystal/polyvinylidene fluoride composite ultrafiltration membranes with flux/antifouling advantages. Mater Chem Phys 260:124128. https://doi.org/10.1016/j.matchemphys. 2020.124128 53. Selim A, Toth AJ, Haaz E, Fozer D, Szanyi A, Hegyesi N, Mizsey P (2019) Preparation and characterization of PVA/GA/Laponite membranes to enhance pervaporation desalination performance. Sep Purif Technol 221:201–210. https://doi.org/10.1016/j.seppur.2019.03.084 54. Liang B, Zhan W, Qi G, Lin S, Nan Q, Liu Y, Cao B, Pan K (2015) High performance graphene oxide/polyacrylonitrile composite pervaporation membranes for desalination applications. J Mater Chem A 3:5140–5147. https://doi.org/10.1039/c4ta06573e 55. Yang G, Xie Z, Cran M, Ng D, Gray S (2019) Enhanced desalination performance of poly (vinyl alcohol)/carbon nanotube composite pervaporation membranes via interfacial engineering. J Membr Sci 579:40–51. https://doi.org/10.1016/j.memsci.2019.02.034 56. Talluri VP, Tleuova A, Hosseini S, Vopicka O (2020) Selective separation of 1-Butanol from aqueous solution through pervaporation using PTSMP-silica nano hybrid membrane. Membranes (Basel) 10:55. https://doi.org/10.3390/membranes10040055 57. Knozowska K, Li G, Kujawski W, Kujawa J (2020) Novel heterogeneous membranes for enhanced separation in organic-organic pervaporation. J Membr Sci 599:117814. https://doi. org/10.1016/j.memsci.2020.117814 58. Prihatiningtyas I, Volodin A, Van der Bruggen B (2019) 110th anniversary: cellulose nanocrystals as organic nanofillers for cellulose triacetate membranes used for desalination by pervaporation. Ind Eng Chem Res 58:14340–14349. https://doi.org/10.1021/acs.iecr.9b02106 59. Prihatiningtyas I, Van der Bruggen B (2020) Nanocomposite pervaporation membrane for desalination. Chem Eng Res Des 164:147–161. https://doi.org/10.1016/j.cherd.2020.10.005 60. Halakoo E, Feng X (2020) Layer-by-layer assembly of polyethyleneimine/graphene oxide membranes for desalination of high-salinity water via pervaporation. Sep Purif Technol 234: 116077. https://doi.org/10.1016/j.seppur.2019.116077 61. Ugur Nigiz F (2020) Graphene oxide-sodium alginate membrane for seawater desalination through pervaporation. Desalination 485:114465. https://doi.org/10.1016/j.desal.2020.114465 62. Prihatiningtyas I, Hartanto Y, Van der Bruggen B (2021) Ultra-high flux alkali-treated cellulose triacetate/cellulose nanocrystal nanocomposite membrane for pervaporation desalination. Chem Eng Sci 231:116276. https://doi.org/10.1016/j.ces.2020.116276 63. Selim A, Toth AJ, Fozer D, Haaz E, Mizsey P (2020) Pervaporative desalination of concentrated brine solution employing crosslinked PVA/silicate nanoclay membranes. Chem Eng Res Des 155:229–238. https://doi.org/10.1016/j.cherd.2020.01.015 64. Wang Y, Rong H, Sun L, Zhang P, Yang Y, Jiang L, Wu S, Zhu G, Zou X (2021) Fabrication and evaluation of effective zeolite membranes for water desalination. Desalination 504:114974. https://doi.org/10.1016/j.desal.2021.114974 65. Yang S, Karve VV, Justin A, Kochetygov I, Espín J, Asgari M, Trukhina O, Sun DT, Peng L, Queen WL (2021) Enhancing MOF performance through the introduction of polymer guests. Coord Chem Rev 427:213525. https://doi.org/10.1016/j.ccr.2020.213525

Part V Consumer Nanoproducts Based on Composites Based on Shape Memory Alloys

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ecofriendly Polymer Nanocomposite (EPN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanocellulose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanocellulose Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Nanocellulose in Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Industrial Effluents and Contaminated Waters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymeric Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Use of Nanomaterials in Environmental Health (Nanoremediation) . . . . . . . . . . . . . . . . . . . . . . . . . . . Wood Polymer Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bio-based Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Wood Polymer Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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In this chapter, a review of several researches is done on the development and characterization of polymer nanocomposites. Polymer nanocomposite is a promising multidisciplinary material research activity that could expand the use of polymers for various industrial applications and also in environment to remove pollutants. Polymer nanocomposites are a radical alternate to conventional polymer composites, where large amount of fillers are added to improve the properties. For polymer composite applications, the use of natural fibers is preferred to efficiently reduce the dependence on petrochemical-based plastics. The utilization of renewable materials has attracted researchers because of its easy availability and low cost. They can potentially remove the harmful effects of petroleum-based materials and thus show a greener path in the fields of application of composites. In recent years were used developing nanotechnological I. F. H. AI-Jawhari (*) Department of Biology, Faculty of Education for Pure Sciences, University of Thiqar, AL-Nasiriya, Iraq © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_21

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methods based on adsorption capabilities of cellulosic nanoparticles for monitoring hazardous substances in the environment. Along the examples are the benefits and implications of sustainable design and the use of nanocellulose in environmental applications. The discussion will be focused on structural, mechanical, as well as degradation of cellulose. Nanocellulose, wood polymer nanocomposites have renewability, availability, light weight, low cost, and most importantly minimum environmental impact (Ecofriendly) and have little effect on animal/ human health. The general properties of cellulose include extensive ability of chemical modification and very high aspect ratio leading to the formation of versatile semi-crystalline fibers which is the unique characteristic of nanomaterials as reinforcing agents. There is the presence of strong and complex network of hydrogen bonds which are stabilized by the ordered regions of chain packages of cellulose that resembles nanocrystalline rods. Keywords

Composite · Degradation · Ecofriendly · Environment · Nanocellulose · Nanocomposite · Polymer · Renewability

Introduction Ecofriendly Polymer Nanocomposite (EPN) A composite is defined as a combination of two or materials with different physical and chemical properties and distinguishable interface. In most composite materials, one phase is usually continuous and called matrix, while the other face called the dispersed phase. Nanocomposites refer to composites having one phase nanoscale morphology such as nanoparticles, nanotubes, or lamellar nanostructure. Polymer nanocomposite (PNC) is a promising multidisciplinary material research activity that could expand the use of polymers for various industrial applications and also in environment to remove pollutants [17, 29, 39]. In general, the desirable properties that are needed for many advanced applications, including low gas permeability, high mechanical strength, light weight, high chemical resistance, etc., are not found in commercial polymers. Polymer service has been extended in various fields as PNS enhances the properties of polymer in order to obtain the product with essentially new set of properties. Cellulose is one of the renewable resources and has been identified as a source of biopolymer that can be used as a substitute for petroleum polymers. EPN has been successfully synthesized from cellulose acetate, triethyl citrate plasticizer, and organically modified clay [35]. The polymer matrix for nanocomposite contains 80 wt% pure cellulose acetate and 20 wt% triethyl citrate plasticizer. Results show that better exfoliated and intercalated structure were obtained from nanocomposites containing 5 and 10 wt% organoclay compared with that of 15 wt% organoclay. Tensile strength of cellulosic plastic reinforced with 10 wt% organoclay improved by 180% and thermal stability of the cellulosic

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plastic also increased. Recently, an active antimicrobial packaging material has been successfully synthesized using methyl cellulose (MC) as the matrix with montomorillionite (MMT) as reinforcement [54]. Carvacrol was then added to the as-prepared MMT/MC composite material to form nanocomposites.

Nanocellulose Nanocelluloses, elemental nano-sized constituents of plant fibers, have acquired an extra reputation relative to conventional cellulose fibers due to their huge surface area, high aspect ratio, and high Young’s modulus of 145 GPa [22] resulting from high crystallinity [1, 18, 25]. Furthermore, considered natural materials, nanocelluloses are biodegradable, biocompatible, and renewable [18]. The lateral size of cellulose molecule chains is about 0.3 nm, and these chains form bundles of elongated fibrils still with nano-scale diameters. The cellulose chains are stabilized laterally by hydrogen bonds between their hydroxyl groups [56]. There are three main categories of nanocelluloses [25]: nanofibrillated celluloses, nanocrystalline celluloses, and bacterial celluloses. Nanofibrillated celluloses are elongated strains of superfine fibrils, while nanocrystalline celluloses are rod-like particulates consisting of crystalline cellulose [1, 49, 56]. Bacterial cellulose is produced by down-to-top synthesis, where specific bacteria synthetize bundles of cellulose nanofibrils from low molecular sugars and alcohols [25]. Nanocelluloses can be produced from cellulose pulp using pure mechanical or combined chemical or enzymatic and mechanical treatments. The chemical and enzymatic pretreatments reduce the energy needed for individualization of the nanofibrils. These treatments typically reduce the hydrogen bonds and/or add a repulsive charge, or else reduce the DP or the amorphous part between the individual nanofibrils [26]. One of the most widely used chemical pretreatment is TEMPO (2,2,6,6 tetramethyl-1-piperidinyloxy)-mediated oxidation; another potential chemical oxidation pretreatment reaction for the production of nanocelluloses is periodate oxidation. In this reaction, the C2 and C3 bonds of cellulose are selectively cleaved, yielding 2,3-dialdehyde cellulose, which can be further derivatized with functional groups such as carboxylic acids [31], sulfonic groups [30, 32, 41], or imines [51]. Only a few previous studies of the use of nanocelluloses as water chemicals exist, and they mainly address adsorption applications. TEMPO-oxidized nanocelluloses have been used for the adsorption of various metals from aqueous solutions, most efficiently with lead, calcium, and silver [43]. Succinic anhydridemodified mercerized nanocellulose [14] and amino-modified nanocelluloses [15] showed high efficiency in the removal of metal ions, with good regeneration ability, while Kardam et al. [23] achieved improved heavy metal adsorption capacity subjecting rice straw cellulosics to acid hydrolysis, which produced rod-like cellulose nanocrystals. Yu et al. [55] used carboxylated cellulose nanocrystals for the adsorption of heavy metals with good results, as adsorption was fast, with high capacity, and the adsorbent was easy to regenerate. In flocculation applications,

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TEMPO-oxidized nanocelluloses with CPAM were used to flocculate kaolin clay suspensions, whereupon relative turbidity decreased greatly and the resulting flocs were stronger than with CPAM alone [18]. Nanocelluse has been the topic of a broad range of research as reinforcing agents in nanocomposites because of their nanoscale dimension, renewability, availability, light weight, and low cost, and most importantly, they have minimum environmental impact and have little effect on animal/human health [27, 28]. They offer significant properties of cellulose including its extensive ability of chemical modification, very high aspect ratio leading to the formation of versatile semicrystalline fibers which is the unique characteristic of nano-materials as reinforcing agents. There is a presence of strong and complex network of hydrogen bonds which are stabilized by the ordered regions of chain packages of cellulose [13] that resembles nanocrystalline rods. Based on their preparative methods and structure, there are two main types of nanocellulose: (i) nanocrystalline and (ii) microfibrillated cellulose. (i) Cellulose: Nanocrystalline cellulose, which is extremely crystalline and rigid nanoparticles, is also called cellulose nanowhiskers or cellulose nanocrystals (Fig. 1). This can be prepared from native fibers through acid hydrolysis. A new class of bio-based products with a broad range of applications including automotive industry, construction material, etc. have been developed by using nanocrystals as reinforcing agents. Addition of small amount of nanocrystal can increase the strength, stiffness, and resistance of the material to stress threefold its original strength. Thus, incorporation of nanocrystal makes the nanocomposites an interesting high-performance material. It is also a promising

Fig. 1 Structure of cellulose nanocrystals

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Fig. 2 Structure of cellulose fibrils

green substitute for carbon nanotubes as reinforcing agents in polymer nanocomposites and concrete. Nanocrystal reinforced nanocomposites are used in a variety of applications such as biodegradable plastic bags, textiles, wound dressings, etc. (ii) Microfibrillated cellulose (MFC): The constituent of MFC is nano-sized cellulose fibril having high aspect ratio (Fig. 2). The fibrils are extracted from wood pulp through high-temperature, high-pressure, and high-velocity impact which can be employed in polymer nanocomposites of high mechanical capacity [36]. The strength properties of these nanocomposites are very high, and the Young’s modulus is found to be approximately 20 GPa. Thus, MFC-based nanocomposites that are derived from wood pulp are promising class of substance with outstandingly high mechanical performance. The Young’s modulus of the cellulose crystal is about 134 GPa; therefore, MFC nanofibers are estimated to provide high stiffness to the resultant nanocomposites [44]. However, another type of nanocellulose is known as bacterial cellulose (Fig. 3). Specific bacteria mainly Gluconacetobacter strains secret these cellulose nanofibers extra- cellularly [4, 24, 50]. These bacterial celluloses have exceptional mechanical and physical properties due to its special fibrillar nanostructure. Its properties include high strength, high porosity, high crystallinity (up to 84–89%, [6]), and high elastic modulus [12]. Currently, bacterial cellulose is the topic of research in several fields of applications, reinforcement in nanocomposites [21, 38], bio-medical applications, and fuel cell membranes [10].

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Fig. 3 Secreted of nanofibrils from bacteria

Nanocellulose Applications Polymer nanocomposites are a radical alternate to conventional polymer composites, where large amount of fillers are added to improve the properties. For polymer composite applications, the use of natural fibers is preferred to efficiently reduce the dependence on petrochemical-based plastics [53]. Natural fibers obtained from various plant sources as such or in the form of extracted cellulose have been frequently used for this application [48]. Cellulose in nanodimensions generated from cellulose fibers has much higher mechanical properties than those of natural fibers. Hence, CNs have attracted a great deal of interest in the polymer nanocomposite field. Due to their nanodimensions, high surface area, low density, ability to functionalize, and sufficient strength, they proved to be a better reinforcing material than conventional fibers. Like any other multiphase material, the properties of nanocomposite depend on the morphological aspects and their interfacial interactions. There are four different factors that can affect the performance of CN-based water-soluble polymer nanocomposites [33]. The first, and most critical, is the compatibility of CNs with polymer matrix. This is essential to allow uniform dispersion of reinforcing element into the matrix. The main challenge in attaining excellent performance lies in attaining homogenous dispersion of nanocrystals within the polymer matrix by avoiding the aggregation of nanocrystals. The second factor is the molecular structure of the matrix, which influences the interaction between matrix and CN and their interfacial properties. This is also important in obtaining a good matrix-filler interaction. Here also since both the polymer matrix and reinforcing components are hydrophilic in nature, their interactions can be reasonably good. The third is the aspect ratio of CN particles, which is determined by the origin of the cellulose source and the manufacturing conditions. Since the reinforcing filler used is possessing nano-dimensions, the reinforcing effect is better. Fourth factor is the method of polymer nanocomposite fabrication. Solvent intercalation is the most widely used preparation method for these types of polymers. It is having both advantages and disadvantages. Ease of preparation, control over the nanocrystal aggregation, better dispersion, less damage to the nanocrystals, cost effectiveness, etc. are the advantages, while their inefficiency for large-scale production is a limitation. Several water-soluble polymer-based nanocomposites have been prepared by solvent intercalation method, and their details are briefly highlighted below.

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Applications of Nanocellulose in Environment This section describes a variety of developing nanotechnological methods based on adsorption capabilities of cellulosic nanoparticles for monitoring hazardous substances in the environment. Along the examples, the benefits and implications of sustainable design and the use of NC in environmental applications are also addressed in order to understand and control their properties. In this regard, biodegradable NC can be used in different formats such as template, solid fibers, membranes, films, and 3D networks with low density and thermal transport but high surface area (aerogels, also referred to as sponges) in separation techniques for pollutant remediation. A wide variety of cellulosic nanoparticles isolated from various resources such as sludge, bio waste, plants, and bacteria with low-cost production are used for bioremediation.

Industrial Effluents and Contaminated Waters Nanotechnology actually has applications in all fields of research. Water purification and the treatment of industrial wastewater are at a crucial juncture of vision, ambition, and technological innovation. Contamination of arsenic and heavy metals to groundwater and drinking water is an enormous challenge which has produced a need for nanotechnology, materials science, and nanomaterial nanomanufacturing [52]. The chemicals currently used for wastewater treatment are mainly based on synthetic inorganic or organic compounds. Oil-derived polyelectrolytes are used for the removal of colloidal solids from wastewater by flocculation and coagulation, for example, while activated carbon adsorbents are typically used to remove soluble impurities such as heavy metals and recalcitrance organic matter. Many of these chemicals have associated negative health impacts, and use of activated carbon has proved to be expensive. Moreover, the present synthetic chemicals are not readily biodegradable or renewable. Thus there is a high demand for “green” water chemicals which could offer a sustainable solution for achieving high-performance, cheap water purification. Water chemicals of a new type based on nanoscale particles (nanofibrils) derived from cellulose, i.e., nanocelluloses, are examined as possible bio-based chemicals for wastewater treatment. Two anionic nanocelluloses (dicarboxylic acid, DCC, and sulfonated ADAC) were tested as flocculants in the coagulation-flocculation treatment of municipal wastewater, while the flocculation performance of cationic nanocellulose (CDAC) was studied with model kaolin clay suspensions, and nanocelluloses produced from sulfonated wheat straw pulp fines (WADAC) were tested for the adsorption of lead (Pb(II)). The anionic nanocelluloses (DCC and ADAC) showed good performance in treating municipal wastewater in a combined coagulation-flocculation process with a ferric coagulant. In the case of both anionic nanocelluloses, the combined treatment resulted in a lower residual turbidity and COD in a settled suspension with highly reduced total chemical consumption relative to coagulation with ferric sulfite alone.

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On the one hand, NC materials were used to fabricate absorbent material to control and avoid eutrophication from occurring. Different requirements for a substrate to be considered as a sorbent material include a high adsorption efficiency with a fast adsorption kinetics for selectively hazardous substances, low chemical reactivity, high stability and regeneration capacity with the lowest loss of adsorption, and, finally, good resistance to different matrices such as wastewaters or other more complex aqueous samples. Different functions of NC for creating sorbent materials are addressed. On the one hand, the wide variety of products containing pigments and dyes are of great concern since their waste is released as water containing ionic species into the environment. This class of contaminant is difficult to degrade and produces acute and chronic toxicities and hinders the purification of water following the conventional methodologies. It is estimated that around 20% of such water-insoluble compounds are discharged into the environment as aqueous effluents. Thus, the government agencies are imposing restrictions on colored waste disposal. For these reasons, biocompatible technologies based on NC have been proposed to economically avoid such contaminations to some extent. In the first place, anionic dyes were removed by NC grafted with positively functional groups. In this regard, welldispersed NC containing amine groups were used as excellent sorbent material, achieving the maximum removal efficiency of three different dyes under acidic conditions [19]. In fact, the highest removal efficiency reported for Congo red 4BS is almost 100%. On the other hand, one of the most promising applications of the biocompatible nanofibers lies in the removal of other hazardous nanoparticles released into the environment. Among engineering nanomaterials, AgNPs are the most largely used in everyday items by virtue of their antimicrobial and optical properties; however, they are also considered to be highly toxic to humans and the environment. Therefore, sulfonate-modified NC has been proposed for adsorption of such metallic nanoparticles in aqueous solutions [42]. Thus, dispersive NC was treated with cetyltetramethylammonium salt to achieve good adsorption efficiency, whereas the regeneration of the sorbent material could be easily reached by simply adding thioctic acid solution. This method was automated by packing the nanofibers into a SPE column and applied to waters. Other membrane application for purification of water consists of the removal of virus such as MS2 virus and bacteria such as Escherichia coli [45], which is of great interest in water scarce and stressed areas. In this case, ultrafine cellulose nanofibers prepared by electrospun and modified with different functionalization (with carboxyl and amine ending groups) were used to fabricate filtration membranes. The membrane composed of positively charged amine-modified nanofibers satisfies the National Sanitation Foundation Standards, as regards the good adsorption of viruses and bacteria (slightly negatively charged) via electrostatic interactions. Furthermore, removal of micotoxins was achieved by using NC grafted with fatty acids by interaction of their hydrophobic tails [16].

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Polymeric Nanomaterials Biopolymer has hydrophilic nature, poor water vapor, oxygen, and other gas barriers and poor mechanical properties [3, 11, 40]. Additionally, the properties and efficiencies of biopolymer films can be changed by making a bend as well as a nanocomposite mixture of polymer and a filler (a non-sized component such as nano-clay or nano-sized silica) [3, 11, 40]. Nanotechnology has been used to produce biocomposite materials to increase the toughness of traditional polymer matrices [47]. The composites can be constructed from opposite changed counterparts through electrostatic interactions.

Use of Nanomaterials in Environmental Health (Nanoremediation) Nanoremediation is the application of nanomaterials for environmental remediation. The nanomaterials are used to treat groundwater, polluted air, sediments, soil, and other contaminated materials. For example, titanium oxide (TiO2) is a good candidate for wastewater treatment. Nanomaterials are widely used in various environmental applications with a good success rate in cleaning up oil spills, water disinfectant, air pollution control, and much more. Thus nanomaterials have given rise to a new technology for the purpose of creating a healthy environment, that is, green nanotechnology [37]. It is defined as the science and technology used to introduce nanoparticles into the environment with safe and premeasured harmful effects. Nanoremediation is the application of nanomaterials for ecological remediation. It is being used to treat wastewater, soil, and various other environmental contaminants.

Wood Polymer Nanocomposites Wood polymer nanocomposites (WPNC) are a novel class of wood products with significantly enhanced physical, biological, mechanical, and chemical properties [7, 34]. Besides this, the wood fibers were also used as polymer reinforcing agents to develop wood polymer composite (WPC). In the polymer matrix, the reinforcing filler is pressed and molded in the presence of high temperature and pressure. Using various additives such as binding agents, plasticizer, and flame retardant along with nanoparticles helps to get the finished product tailor-made according to end use application [2, 8]. For a certain period of time, the wood polymer nanocomposite in powder form is put under pressure and temperature in the compression molding press. The WPNC sheets are then cooled to obtain at room temperature [9]. The chemicals used in WPNC formation have to be selected appropriately. The prepared WPNC should not discharge any hazardous substances in the service period and at the end of service life and can be recyclable or easily discarded at the end of service life.

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Bio-based Polymers Wood polymer nanocomposites are typically prepared with thermoplastics or thermosetting resin. The steady rise in crude oil prices, the problem of rising large-scale waste, and the exhaustion of fossil fuels have caused attention in the use of natural sources. A “greener” approach to these problems depends on the use of renewable energy. Easily available are the biopolymers obtained from renewable agricultural feedstock [20, 46]. Since the biopolymers are extracted from renewable resources, the degree of these polymers bio-degradability depends on their chemical structure. The higher the biodegradability, the lesser the degree of cross-linking. Such green polymers provide perceptible advantages over traditional polymers in terms of toxic gas effluence during their service state, energy consumption when synthesizing, and waste output. Several of the desirable characteristics of the biopolymers are biodegradability, high compatibility with other polymers, and low melting temperatures.

Application of Wood Polymer Nanocomposites WPNC has similar functions to solid wood but requires less maintenance and has a much lower strength to – strength ratio and increased service life. It is an exceptional composite material, experimenting with high rates of expansion worldwide and consisting in various proportions of wood, polymer, and other additives. WPNC may be suitably used for indoor and outdoor applications. WPC are produced commercially using radiation process from the mid-1969s. But very few bio-based polymer wood nanocomposites have been developed, with most of other technologies remaining in the stages of research and development. These ecofriendly composites endow new substitutes with the designers to meet the demanding requirements. WPNC products can be useful in telecommunications, manufacturing, automotive, and other applications. The bio-based WPNC can be used as an alternative to steel and fiberglass and can therefore be used as a replacement for automotive parts, the most important market known for the use of WPCs [5]. These composite materials have been used successfully in many applications including the furniture industry and measurement engineering building industry, construction technologies automotive industry, flooring such as solid plank flooring, laminated flooring, and parquet flooring fillets. The key advantages of parquet floors are their abrasion resistance and toughness, which is useful in commercial traffic installations. Although it has high costs, its ease of maintenance and long service life have justified the high parquet flooring price over conventional flooring. They can successfully make various sports equipment, such as baseball bats, hockey sticks, golf heads, etc., and musical instruments such stringed instrument finger boards, wind instruments, flute and trumpet mouthpieces, etc.

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Conclusion Polymer nanocomposite (PNC) is a promising material that is used in various industrial applications and also in environment to remove pollutants. Cellulose is one of the renewable resources which has been identified as a source of biopolymer that can be used as a substitute for petroleum polymers. EPN have been successfully synthesized from cellulose acetate, triethyl citrate plasticizer, and organically modified clay. Nanocellulose has been the topic of a broad range of research as reinforcing agents in nanocomposites because of their nanoscale dimension, renewability, availability, light weight, and low cost, and most importantly, they have minimum environmental impact and have little effect on animal/human health. Nanoremediation is the application of nanomaterials for environmental remediation. The nanomaterials are used to treat groundwater, polluted air, sediments, soils, and other contaminated materials. Nanomaterials are widely used in various environmental applications with a good success rate in cleaning up oil spills, water disinfectant, air pollution control, and much more. Thus, nanomaterials have given rise to a new technology for the purpose of creating a healthy environment, that is, green nanotechnology.

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Polycarbonate Nanocomposites for High Impact Applications

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Vishwanath Dagaji Jadhav, Akhil Jayawant Patil, and Balasubramanian Kandasubramanian

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vacuum Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Role of Vacuum Pressure in Product Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mold Materials in Vacuum Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silicon Rubber Mold in Vacuum Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Epoxy Resin Mould in Vacuum Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Master Model Manufacturing Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Three-Dimensional Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stereolithography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Casting Materials in Vacuum Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acrylonitrile Butadiene Styrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polyurethane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polycarbonate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Processing Techniques for Manufacturing Polycarbonate Nanocomposites . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

258 260 260 262 262 263 263 263 264 264 264 265 266 273 277 277 277

V. D. Jadhav Plastic and Polymer Engineering Department, Maharashtra Institute of Technology, Aurangabad, Maharashtra, India A. J. Patil Department of Mechanical Engineering, Birla Institute of Technology and Science, Pilani, Goa, India B. Kandasubramanian (*) Polymer Processing Laboratory, Department of Metallurgical and Materials Engineering, Defence Institute of Advanced Technology (DU), Ministry of Defence, Pune, Maharashtra, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_22

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Abstract

Polycarbonate, an engineering thermoplastic polymer, has sought attention in recent times from industries to academia, owing to the presence of carbonate group in its structure which imparts properties like high toughness, transparency, and high impact resistance. The versatility of polycarbonate polymer can be observed from its applicability from products in variegated sectors such as automobile parts like helmets, bulletproof glasses in vehicles, bumpers, and headlamp lenses, and it also finds applications in electronics such as capacitors, etc. Contouring of these products is generally conducted by using conventional methods like injection molding, extrusion molding, blow molding, transfer molding, and compression molding. Products fabricated via conventional methods tend to exhibit process defects such as voids in matrix, sink marks, and burn marks which can be overcome by adapting the alternative methodology – “vacuum casting,” which imparts the ability to manufacture products from a range of materials such as thermoplastics, thermosetting resins, and elastomeric materials. Vacuum casting has been adopted for manufacturing products like engineering micro-gears, micro turbines, and pump impellers in automobile sectors. In this review chapter, we present consolidated state of the art on vacuum casting while simultaneously proposing the application of polycarbonate and its composites for manufacturing products in engineering sectors with the aid of vacuum casting in place of conventional methodologies for avoiding engineering drawbacks. Keywords

Polycarbonate · Nanocomposites

Introduction Over the few decades, polymer products and their processing have sought demand due to their properties such as durability, light in weight, and low cost as compared to metallic materials [1]. The fabrication of the polymeric products can be accomplished by techniques such as injection molding [2], extrusion molding, blow molding, and compression molding [3] which are widely used in variegated sectors for large-scale production in applications such as bumpers and helmets for the automotives, rigid and hose pipes for household and agricultural sector, capacitors and sockets for electrical as well as electronics sectors, etc. However, products fabricated by these techniques can have defects like voids in matrix due to air entrapment, sink marks on product surface due to less cooling time [4], and flow marks on the product. One of the major drawbacks of these methodologies is their selectivity to either thermoplastic or thermosetting resins, which imparts limitation during the processing of polymers. Vacuum casting can be one of the efficient alternatives for overcoming these defects due to primarily utilization of vacuum during processing of polymers, thereby giving high-quality finished products (Fig. 1). In this methodology, silicon mold is produced on the basis of a master model which reflects the prototype

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Fig. 1 Vacuum casting setup

geometry through a replication [5]. Master models are created by rapid prototyping techniques, such as three-dimensional printing and stereolithography [6]. Materials used in this technique could be as polyester, polyurethane, epoxy resin, acrylonitrile butadiene styrene, polycarbonate, as well as composites. Polycarbonate has been extensively examined as an imperative polymer for applied and fundamental research due to its various considerable properties, such as ductility, higher glass transition temperature (~147
C), high impact resistance (~600–820 J/m), optical transparency (n ~ 1.6), and blending ability with other polymers, e.g., polyethylene, polypropylene, and polyethylene terephthalate. These inherent properties of polycarbonate are attributed to the presence of carbonate group (O(C¼O)  O) in its main chain structure. Polycarbonate shows higher thermal stability due to the presence of rigid molecular backbone of bisphenol A [7]. Consequently, polycarbonate has been widely exploited in applications like bulletproof glasses, headlamp lenses for vehicle, electronics, architecture, and aerospace. Trautmann et al. have used vacuum casting for the fabrication of polycarbonate material and demonstrated its use for a microneedle array of the prick test for testing of skin allergic application [8]. Moreover, Tang et al. have used vacuum casting for the fabrication of polyurethane material for micro-gears and studied the dimensional accuracy required in micro-gear cavities as compared to master gear, and they showed that gear manufactured by vacuum casting gives 51.7% more surface finish than its master gear model, thereby implying that vacuum casting could be an alternative for micro parts manufacturing without compromising the quality of product [9]. Zhao et al. have used vacuum casting for the fabrication of microriblets using silicone rubber on shark skin for drag-reduction applications via unsaturated epoxy resin mold. Moreover, their calculations for drag-reduction rate for water flow velocity, i.e., 0.45 m/s to 0.9 m/s, demonstrate the viability of vacuum casting for practical drag-reduction applications in aircrafts and ships [10].

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This review aims to highlight the state-of-the-art progress in vacuum casting for polycarbonate material; its fundamentals; the effects of processing parameters of vacuum casting process such as mold temperature, rate of vacuum, and curing temperature; as well as the benefits of vacuum casted products such as surface finish and dimensional accuracy as compared to conventional methodologies. This review also highlights viability of vacuum casting for the fabrication of polycarbonate material and its composites reinforced with materials such as carbon fibers, pineapple leaf fibers, glass fibers, Kevlar fibers, fly ash, calcium carbonate, montmorillonite, and nano-materials such as carbon nanotubes and graphene and graphene oxide; for the enhancement in properties such as electrical conductivity, impact strength, Young’s modulus, tensile strength, flame retardancy, scratch resistance, etc.; and for various engineering applications and materials for mold manufacturing such as silicon rubber and epoxy resin in vacuum casting along with the case studies.

Vacuum Casting Vacuum casting is a replicating method designated by utilization of a vacuum during the processing of mold and casting of commodities. The molds are fabricated using materials like silicon or epoxy resin. The casting materials used in vacuum casting are engineering thermosetting resins such as epoxy resin, polyester, as well as thermoplastics like acrylonitrile butadiene styrene, polypropylene, and polycarbonate. The casting material and mold are processed in an inert environment under vacuum chamber whose pressure is maintained at ~0.1 Pa [11] that helps in degassing the mold and casting the material. The degassing of the materials helps to enhance the properties and to remove air entrapped into molds which is one of the drawbacks of conventional methodologies. Vacuum casting is included in the indirect tooling methodology because it exhibits the necessity of master model before fabrication of any commodity. This master model is fabricated mostly by using the techniques like three-dimensional printing and stereolithography; these processes are part of the rapid prototyping. Rapid prototyping is a group of systems used to rapidly manufacture a master model of a physical part or assembly using three-dimensional computer-aided design (CAD) [12]. In the view of the aesthetic purpose offered by vacuum casting, it shows high accuracy, dimensional and color stability, and finishing. Applying these strengths of vacuum casting, fabrication of the composites for different applications has been reported and tabulated in Table 1 and Fig. 2.

Role of Vacuum Pressure in Product Casting Vacuum pressure present in chamber plays an important role for processing and quality of the product. The rate and time of vacuum pressure depend on the casting material, thickness of the product, etc. The low vacuum pressure can exhibit defects

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Table 1 Vacuum casted products and application Serial no. 1 2 3 4

Materials Polycarbonate Polyurethane Polyurethane Silicon rubber

5

Polyurethane

6

Acrylonitrile butadiene styrene Polyester

8

Product Microneedle array EEG electrode Micro-gear Riblets on shark skin Turbocharger impeller Connectors, Battery cover Impeller

Application Biomedical Biomedical Automobile Aerospace, marine application Household and electronics sector Electronics and telecommunication Mechanical

References [8] [13] [9] [10] [14] [12] [15]

Fig. 2 Vacuum casted products

like shrink marks and insufficient injection; moreover, air pocket and spilling can occur due to high vacuum pressure [16]. During the casting and filling of mold by casting material, it is controlled by filling speed, time, and speed of pressure; whenever there is a longer pressure time, there is a small pressure speed. Pressure time controls the pressure speed and filling speed, and the flow of filling material which is viscous in nature is calculated by using the following equation [17]: Formula for viscous flow of filling material vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi " #
1=k u
K1 u 2K RT P P K t Q ¼ APa : 1 Pa K1 M Pa Flow formula under vacuum condition

ð1Þ

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Q¼

PV t

ð2Þ

dt ¼

VdP Q

ð3Þ

Differential of Eq. (2)

Both sides integrated for getting formula (4) of airtime during vacuum process sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffisffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
K1
K1 K V 2K M P1 P K 1 1 : t¼ A K  1 RT Pa Pa

ð4Þ

where P1 ¼ initial pressure P ¼ pressure after gas filling into vacuum M ¼ gas molar mass V ¼ vacuum container volume T ¼ gas temperature in formula t ¼ filling time of the vacuum R ¼ gas constant A ¼ cross-sectional area K ¼ adiabatic exponent Pa ¼ atmospheric pressure Zang et al. have fabricated motorcycle headlamp shells by using vacuum casting and observed the quality of product for pressure time of 5 and 10 sec respectively, wherein they observed that the product by 5 sec pressure time in which mold was not filled properly exhibited defects such as short shot, which was overcome by 10 sec of pressure time [17].

Mold Materials in Vacuum Casting Silicon Rubber Mold in Vacuum Casting Silicones, otherwise called as polysiloxanes, are polymers made up of repeating units of siloxane, which is utilized in the variegated sectors such as automotives, waterproof connectors, hoses, gaskets, sportswear, footwear, electronics, and as mold materials. In vacuum casting process, the applications are attributed to the properties of silicon rubber such as excellent resistance to higher temperatures (37
C to 260
C), elongation, tear strength (~25 to 40 N/mm), compression set (60
C to 250
C), and tensile strength (2.6 MPa) [18], as compared to conventional rubbers like natural rubber, styrene butadiene rubber, etc. The drawbacks

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which occur in the organic rubber are low ozone resistance and thermal stability and aging factor. The prevalent properties of silicon rubber have made it feasible to be employed as a material for mold in vacuum casting. Silicon rubber has two classes with a perspective of industries: high-temperature vulcanizing silicon rubber (~70
C), also termed as malleable silicone rubbers because of its high viscosity in uncured state, and room temperature vulcanizing silicon rubber (28–40
C), also named as pourable silicone rubbers because of presence in liquid state owing to its low viscosity. Room temperature vulcanizing silicone rubbers are commonly used in fabrication of molds [19]. Molds manufactured by silicon rubber have the capability for the processing of thermoplastics and thermosetting resins. On the view of the productivity, it can produce up to 20 pieces, which depend on the surface finish of product [20].

Epoxy Resin Mould in Vacuum Casting Epoxy resins are low or high molecular weight polymers which ordinarily contain at least two epoxide groups. The epoxide group is also sometimes called as glycidyl or oxirane group, which is the thermosetting polymer and widely used in the aerospace application, surface coating, as well as for fabrication of the mold in the vacuum casting. Vacuum casting process starts with a master model which is fabricated with the help of the three-dimensional printing and stereolithography [11]. The master model is buried in a clay or plaster up to the parting line in the master model. Alternatively, one can use a prototype model for the first half of the part. After coating the master model with a release agent, epoxy resin is poured into the mold box and then cured. The same procedure is repeated for the second half. Runners and gate are added to the master model prior to casting or machined after casting. Air vents are included in the mold because thermosetting resin releases the gases when they are processed. Epoxy mold can be kept at low injection and packing pressure with low infusion and pressing weights. Contingent upon the unpredictability of the part and the material, the mold life is from 50 to 500 pieces [21].

Master Model Manufacturing Technique Three-Dimensional Printing Three-dimensional printing comes under rapid prototyping methodology, which was patented by Sachs et al. in the year 1994. In three-dimensional printing, the model is sliced into two-dimensional layers via computer controlled program [22]. The parts are built using the powdered material, which is spread in the form of the layer structure, and the hardener is added to the powdered material by drops like in an inkjet printer. Currently used three-dimensional technologies used thermoplastic

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polymer filaments for precision accuracy and dimensional stability. Threedimensional printing has the capability to fabricate products of engineering plastics such as polylactic acid, acrylonitrile butadiene styrene, polycarbonate, metal, metalceramic, and composite. This technique can be applied in areas like designing of complex products, biomedical sector for bio-printing tissue and organ, anatomical model for surgical preparation, drug delivery devices. Along with the master model for vacuum casting, three dimensional printing utilised in various sectors due to its advantages like costly mould is not required, milling is not required, recycle material can be use, automated manufacturing [23].

Stereolithography Stereolithography (SL) is the first rapid prototyping technique invented in the year 1984 by Charle Hull, which is the first commercially available prototyper. Stereolithography is a technique that has the capability to fabricate three-dimensional prototype models by using designing software such as computer-aided design and computer-aided modeling [24]. Materials used in stereolithography technique are polymeric resinous materials which are classified into two categories such as radical reaction type like urethane acrylate and cation reaction type like epoxy resin. They are widely used, because it shows high accuracy and dimensional stability in products. Resins used in stereolithography need low viscosity and hardening agents for better processability. Curing time is important to complete the product in a minimal period of time [25], which are cured using laser beam of ultraviolet rays or LED by which it forms the layers. Stereolithography technique is used in various applications such as master model in vacuum casting, three-dimensional copy for shoe model, prototyping diecast parts, investment casting master models, and biomedical parts [26].

Casting Materials in Vacuum Casting Acrylonitrile Butadiene Styrene Acrylonitrile butadiene styrene (ABS) is an engineering thermoplastic, which is synthesized by the polymerization of styrene, an organic compound derived from benzene, and acrylonitrile, a colorless volatile liquid, in presence of polybutadiene a synthetic rubber. The monomer proportion of styrene (~40–60%), acrylonitrile (~15–35%), and butadiene(~5–30%) in acrylonitrile butadiene styrene can vary from grades to grades. Acrylonitrile butadiene styrene has excellent properties such as higher impact strength [27], toughness, and resistance to chemicals. Owing to the properties, acrylonitrile butadiene styrene is used in various sectors such as pipes, safety helmets, telephone switchboard panels, automobile panels, and submersible pumps. The ABS materials for various applications can be fabricated

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using injection molding, extrusion molding, blow molding, as well as rapid prototyping technique such as vacuum casting (Fig. 3). Howe et al. have fabricated connector used in telecommunication switching systems by using vacuum casting of acrylonitrile butadiene styrene, and the comparative study for the stereolithography and the vacuum casting with the view of the time to fabricate the article was reported. They observed that result time required for the fabrication of the product in stereolithography was comparatively more than vacuum casting. They also concluded that stereolithography cannot be used directly due to its demerits such as short shot and flashes on the surface of the product [28].

Polyurethane Polyurethanes (PU) are polymerized using the isocyanate and diol compounds, which form a linkage of the urethane group ((-NH-C(¼O)-O-) [29]. They are utilized in applications such as footwears, seals and gasket in the automobile sector, foams in water filters, and nonwoven medical covers. PU exhibits these multifunctional applications due to properties such as hardness (20 shore A – 80 shore D), high load-bearing capacity, elongation (640%), impact resistance (1.04 kJ/m2), and tensile strength(~38 MPa) (Fig. 4). Seet et al. have fabricated the micro-spike EEG electrode by using vacuum casting of polyurethane via master model, where they observed an improvement in the sensing performance of the electrode, along with higher efficiency [13].

Fig. 3 Structure of acrylonitrile butadiene styrene

O C

H

O

N

C

N

H

H

H

C

O

H

H

C

C

H

H

O

n Fig. 4 Structure of polyurethane

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Fig. 5 Structure of polycarbonate

Polycarbonate Polycarbonate is polymerized using bisphenol A and phosgene [7], via ester exchange and phosgenation process. Polycarbonate exhibits properties like high melting point (~250
C) and impact strength due to the rigid backbone of bisphenol A [7]; the polar group present in polycarbonate imparts chemical solubility. It also exhibits higher optical transparency, due to internal transmission of light nearly same as glass. Polycarbonate possesses drawback such as low scratch resistance; however, its properties can be enhanced with the aid of inorganic fillers and fibers via fabricating into nanocomposites, which has been studied by various researchers (Fig. 5).

Fillers in Polycarbonates Fly Ash Fly ash is by-product as a result of the combustion of the coal in thermal power plants, which is generated in an enormous amount every year. As per a survey, India produces ~112 million tons of fly ash every year [30]. This fly ash shows some adverse effect on the environment like contamination of the water by the presence of the heavy metals such as copper, arsenic, lead, zinc, mercury and uranium that are hazardous to the health of humans as well as animals. The aim of minimizing as well as disposing enormous fly ash is carried out via utilization in various sectors like road construction (~35–40%), cement manufacturing (~35%), lightweight blocks (~25%), and bricks manufacturing (~40–70%), for polymeric composites, and in electrical and household applications such as fire retardancy. Makoto et al. have studied the flame retardancy of polycarbonate with fly ash as a filler and concluded that the presence of the hydroxyl group in the fly ash enhances flame retardancy, wherein thermal degradability was measured with the help of thermal gravimetric analyzer (TGA) which shows an augmented resistance to degradability; also they attributed the thermal stability to hydrogen bond between the fly ash and carbonate group. They also reported flexural strength and observed that the flexural strength is directly proportional to weight loading of fly ash. Flexural strength of polycarbonate/fly ash composite with respect to 10 wt% and 25 wt% was found to be ~90 MPa and ~ 99 MPa showing an enhancement of 10% compared to pristine polycarbonate [31].

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Fig. 6 Structure of calcium carbonate

267

O +2

Ca

C

O

O

-

-

Calcium Carbonate Biominerals are present in an enormous quantity in the environment, which are observed in the form of hills, caves, and rocks. Calcium carbonate (CaCO3) is one of those biominerals, which endures in the form of calcite rock. Calcium carbonate is exploited in various sectors from the last few decades, and due to its properties as well as its availability in extensive amount, they are employed in various applications such as construction industries for self-compacting concrete, asphalt mixture in road construction, food packaging, as well as polymeric composites [32]. Calcium carbonate has been used as an inorganic filler for polycarbonates for enhancing the properties of the material such as flame retardancy, tensile strength, bending modulus, and impact strength (Fig. 6). Wang et al. have proven that mechanical properties of polycarbonate can be enhanced by incorporation of calcium carbonate (CaCO3). The tensile strength, i.e., ~ 91.29 MPa and ~ 87.20 MPa for pristine polycarbonate, was augmented up to ~4% for polycarbonate/calcium carbonate composite as compared to pristine polycarbonate. They also examined elongation at break for polycarbonate/calcium carbonate composite which was found to be 63.28% and 165.06% for pristine polycarbonate. Considering the presence of calcium carbonate aid leads to increase in the brittleness in the composite, thereby decreasing elongation at break [33]. Charde et al. have fabricated polycarbonate and calcium carbonate composite and examined results for glass transition temperature and observed ~145
C for polycarbonate/calcium carbonate composite and ~ 150
C for the pristine polycarbonate. They attributed the decrease in glass transition of calcium carbonate particles in polycarbonate. They also studied load-bearing capacity for glassy, rubbery, as well as transition region, wherein glassy region augmented ~12% load-bearing capacity than that of pristine polycarbonate. The observed that scratch resistance of polycarbonate can be overcome in polycarbonate/calcium carbonate composite [34]. Montmorillonite Montmorillonite is a naturally occurring mineral, in which phyllosilicate group is present, and is found mostly in rocks, sediments, and soils. Considering the availability, montmorillonite is utilized in various applications such as soil additive in the drought-prone areas, a binder for the mud, and heavy metal remover for water and extensively used for polymeric composites [35]. Montmorillonite shows

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Table 2 Polycarbonate properties with fillers Serial no. 1

Polymeric material Polycarbonate

2

Polycarbonate

Calcium carbonate

3

Polycarbonate

Montmorillonite

Fillers Fly ash

Properties Flame retardancy Flexural strength (99 MPa) Tensile strength Elongation at break Load-bearing capacity (12%) Scratch resistance Young’s modulus Storage modulus (816Mpa) Onset temperature (537
C) Heat stability

Result Improved Improved

References [31]

Improved Improved Improved

[33, 34]

Improved Decrease Decrease

[39] [38]

Improved

improvement in optical and thermal properties as well as mechanical properties for the polymer composite, which is attributed to the strong interaction between the montmorillonite and the polymeric matrix when incorporated [36]. Chow et al. have incorporated polycarbonate with montmorillonite and observed thermal stability for the two-phase transition, via glassy phase with temperature of 50
C100
C and rubbery phase with temperature of 150
C which showed that storage modulus is inversely proportional to weight loading of montmorillonite, leading to decrease in stiffness of the composite. They also tested storage modulus for the composite for 3 wt% of montmorillonite incorporated with polycarbonate and observed an onset temperature of ~533 °C and storage modulus of ~715 MPa at (30
C). Similarly, 10 wt% of montmorillonite resulted in ~537
C of onset temperature and ~ 816 MPa of storage modulus for 30
C [37]. Huang et al. have observed that Young’s modulus value is inversely proportional to the percentage of montmorillonite for polycarbonate/montmorillonite composite [38] (Table 2).

Fibers in Polycarbonate Kevlar Fiber Kevlar (-CO-C6H4-CO-NH-C6H4-NH-) is a synthetic aramid fiber, which was introduced by DuPont in the year 1970, which is polymerized by using 1, 4-phenylene-diamine or para-phenylenediamine and terephthaloyl chloride. These fibers are manufactured by extrusion process with the help of small hole called as spinnerets which forms a filaments. Spinnerets are classified according to wet, dry, melt, and gel spinning. The filament fabricated by these techniques is Kevlar fiber, available in eight grades such as Kevlar 29, Kevlar 49, Kevlar 100, Kevlar 129, Kevlar AP, Kevlar XP, Kevlar KM2, and Kevlar 149 [40]. They exhibit properties like higher tensile strength (~2.7GPa), higher stiffness, higher Young’s modulus (~120GPa),

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269

Fig. 7 Structure of Kevlar fiber

relative density (~1.44 gm/cm3), low electrical conductivity, high dimensional stability [41], and high strength to weight ratio (~5) times in comparison with steel, and due to their versatile properties, they are used in various sector such as defense for armor products like helmets and ballistic vests, gloves and jackets for the protection of user from the cut and abrasion, rope and cables, power transmission belts, cycle tires for resistance against puncture, as well as polymeric composites to enhance properties of matrix materials. The incorporation of the polycarbonate with Kevlar fiber shows the enhancement in the properties like ballistic protection and increase in crystallization (Fig. 7). Raerinne et al. have fabricated polycarbonate/Kevlar fiber composite which resulted in improved ballistic protection of ~5.7% to that of pristine polycarbonate [42]. Blumentritto et al. have concluded that properties of composites show more dependency on the fibers and lesser on the matrix where fibers act as a primary loadbearing element [43]. Takayanagi et al. have fabricated polyethylene/Kevlar composite and contemplated thermodynamic properties such as crystallization which was ~36% compared to pristine polyethylene and also concluded that these properties can be improved by the incorporation of Kevlar fibers into the polyethylene matrix [44].

Carbon Fiber Carbon fibers are the synthetic fibers, which is mostly fabricated by using a colorless, volatile liquid acrylonitrile (CH2CHCN) and polyacrylonitrile precursor which involves oxidative stabilization and carbonization [45]. Stabilization is important for balancing quality of the fiber. The cost of carbon fibers is high due to raw materials used like acrylic fiber as well as processing methodology. To overcome this drawback, cheaper commercial acrylic fibers are utilized for the fabrication of the carbon fibers nowadays. These are fabricated by using three steps such as pretreatment stabilization (300
C), carbonatization at 1700
C, and graphitization at higher temperature (2800
C); fibers fabricated by these techniques exhibit properties such as electrical conductivity, high tensile strength (~600 MPa), chemical stability and corrosion resistance, good processability, and recyclability. Considering their properties, they are used in applications such as lightweight automotive parts, manufacturing of parts in aircrafts, wind turbine blades, conductive plastics for the electrical and electronic applications, as well as for the manufacturing of the

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polymeric composites [46]. Polycarbonate is one of the materials in which carbon fibers can be incorporated for the enhancement in mechanical properties like tensile, impact strength, as well as rheological properties. Haung et al. have fabricated polycarbonate/acrylonitrile butadiene styrene/nickel coated- carbon fiber composite, in which they observed increase in tensile strength with increase in carbon fiber loading and also observed that electromagnetic interference shielding was increased along with electrical conductivity [47]. Carneiro et al. have fabricated polycarbonate with the carbon fiber which exhibited improved storage modulus (39%) and yield strength (17%) as compared to pristine polycarbonate. They also observed a decrease in impact strength due to poor adhesion of carbon fiber with polycarbonate matrix. Viscosity was examined at a typical shear rate of 1–103 s1 where they observed a decrease in viscosity with the incremented loading of carbon fiber [48]. Glass Fiber Glass fiber is one of the synthetic fiber, which is conventionally manufactured by the silica (SiO2) sand, by melting at ~1720
C, followed by fiberization, which is a combination of extrusion and attenuation. Then chemical coating is done followed by drying and packing of the manufactured fibers which are classified according to their compositions like E-glass which is manufactured by alumino-borosilicate glass with less than 1%w/w of alkali oxides resulting in properties like high tensile strength (~3445 MPa) and cheaper cost; it is mostly used in reinforcing plastics. The S-glass fiber contains amino silicate glass with the presence of higher concentration of magnesium oxide which increases the tensile strength of fiber (~4890 MPa) [49]. C-glass fibers are with high concentration of boron oxide which results in properties like corrosion resistance, high tensile strength (~3310 MPa), density (~2.52gm/cm3), and Young’s modulus at ~68.9GPA. The A-glass fiber doesn’t contain boron oxide, which results in properties like density (~2.70gm/cm3), Young’s modulus(~73.1GPa), lower thermal conductivity (~0.05 W/m·K) [50], nonflammability, heat insulation, and good sound insulation. Considering their overall properties, glass fibers are with polymeric materials by forming reinforced laminates which are used in marine applications, tanks, vessels, boat hulls, and surfboards. Georgescu et al. have fabricated polycarbonate and polyamide, reinforced with glass fibers where they observed a tensile strength of 40 N/mm2 and 47 N/mm2 for loading (30 wt%) of glass fibers and 5 wt% compatibilizer. Melt flow index for the composite was also observed where they concluded that decrease in flow occurs with the increase in weight of the polycarbonate [51]. Streib et al. had patented work on polycarbonate and glass fiber composite in which they observed impact strength of 29,000 and 37,000 kp cm/cm2 for 0 and 10% of glass fibers incorporated with polycarbonate matrix, respectively [52]. Pineapple Leaf Fiber Every year enormous amount of pineapple leaf fibers are produced, but the very minimal amount of them is used as feedstock for the generation of the energy.

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Pineapple leaf fiber is a natural fiber which belongs to the Bromeliaceae family, exhibiting a ribbonlike structure and vascular bundle system present in fibrous cells [53]. Pineapple leaf fiber exhibits the properties such as good color stability, high tensile strength (~413–1627 MPa), and elongation at break (3%). Considering their properties, pineapple leaf fiber can be used for various sectors like textile, conveyor belt cord, automotive, building and construction material, as well as the extraction of nano-cellulose which was studied by Cherian et al., who reported a 81.75% of cellulose extraction from pineapple leaf fiber for biomedical applications. Pineapple leaf fiber is also used with a polymeric matrix to fabricate a composite for improved mechanical properties and has also been explored with thermosetting resin, engineering thermoplastic, natural rubber, etc., for various mechanical applications. Threepopnatkul et al. fabricated a composite of pineapple leaf fiber and polycarbonate and observed that Young’s modulus of the composite is directly proportional to that of the weight of pineapple leaf fiber. Young’s modulus was found to be 1120 MPa for pristine polycarbonate which was augmented to 1690 MPa for pineapple leaf fiber/polycarbonate composite, along with improvement in thermal stability with a (20 wt%) loading [54] (Table 3).

Table 3 Effect on properties of polycarbonate by incorporation of fibers Serial no. 1

Polymeric material Polycarbonate

2

Polyethylene Polycarbonate

3

Fibers Kevlar

Carbon fiber

Glass fiber

4

Polycarbonate and polyamide Polycarbonate Polycarbonate

5

Polycarbonate

Jute fiber

6

Polycarbonate

7

Polycarbonate and polylactic acid

Bamboo fiber Flax fiber

Pineapple leaf fiber

Properties Ballistic protection rate (259 m/s velocity) Crystallinity Viscosity reduces tensile strength (modulus, yield) Storage modulus Tensile strength

Enhancement 5.7%

References [42]

1%

[44] [48]

Improved 40 N/mm2

Impact strength Young’s modulus Thermal stability Tensile strength Bending strength Shear strength Tensile strength

Improved 1690 MPa Improved 63.1 MPa 87.15 (MPa) 5.26 MPa 9.6 MPa

[56]

Glass transition temperature Degree of crystallization

60
C

[57]

(39%, 17%)

6.87%

[51] [52] [54] [55]

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Nanocomposites of Polycarbonate Graphene and Graphene Oxide Graphene and graphene oxide are synthesized by methodologies derived by Brodie [58], Staudenmaier, and Hummer in which oxidation reaction and two-dimensional crystallographic nature lead to superior properties. They exhibit properties such as high electrical conductivity (~7200 Sm1), high tensile strength (~130GPa), and high transparency (~97%). In the view of their excellent properties, they are utilized in various applications such as transparent conductive films, sensors, fuel cells, and wastewater filtration [59]. Graphene is also used as magnetic materials for absorbent for wastewater filtration. Considering two-dimensional layer structure, surface area, and pore volume, it is also used in biomedical applications. Chaung et al. reported that graphene can be utilized in a therapeutic modalities for cancer treatment and drug delivery system [60], along with electronic applications such as ultra-capacitors as well as for enhancement in the properties of the polymeric material such as polycarbonate (Fig. 8). Kim et al. have fabricated graphene/polycarbonate composite, in which tensile strength was observed for 10 wt% of graphite resulting in ~80% increase and ~60% stiffness. They also observed an increase of ~150% in the Young’s modulus by incorporation of the 15 wt % of graphite in polycarbonate [61]. Yoonessi et al. studied the graphene/polycarbonate composite which was fabricated by emulsion mixing and solution blending methodology and reported a conductivity of 0.226 S/ cm for 1.1 vol% and 0.526 S/cm for 2.2 vol% loading of graphene [62]. Mahendran et al. have fabricated a sheet of graphene oxide reinforced with polycarbonate in which they observed that sheet exhibited excellent bacteriostatic effect against E. coli and S. aureus; further they concluded that it can be used for the biomedical as well as for the food packing [63]. Carbon Nanotubes Chemistry of fullerene was developed in mid of the 1980s, by Smalley and coworkers. Fullerene is a cage-like structure of the carbon with the hexagonal and pentagonal faces. These are classified into two classes, i.e., single-walled carbon nanotube and multi-walled carbon nanotubes. Single-walled nanotubes have single sheet of graphite wrapped into the tube, which are in metallic or semiconductor

Fig. 8 Structure of graphene

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273

Table 4 Effect on properties of polycarbonate by nano-additives Serial no. 1

2

Polymeric matrix Polycarbonate

Polycarbonate

Nano-additives Graphene/ graphene oxide

Carbon nanotubes

Properties Tensile strength Young’s modulus Stiffness Electrical conductivity Antibacterial properties Viscosity Dielectric strength

Enhancement 80% 150%

References [61–63]

60% 0.512 S/cm Improved Two decades Seven decades

[67]

which depends on their chiral angle between hexagon and tube axis [64]. Multiwalled nanotubes are the compilation of nanotubes nested like tree trunk, which are synthesized by using chemical vapor deposition process which gives high purity at low cost [65]. Carbon nanotubes exhibit the superior properties such as extremely higher elastic modulus (1TPa) [64], higher strength (10–100) times than strongest steel, superconductivity, high stability, and light in weight which makes carbon nanotubes an ideal material for their applications. Carbon nanotubes are widely used in various applications such as emitters for vacuum microelectronic device, cathode ray lighting elements, gas discharge tubes in telecom network, nanosized electronic devices, as well as electromagnetic interference shielding. Arjmand et al. studied polycarbonate/carbon nanotube composite, where they observed an improved shielding with absorption and refraction and also observed higher percolation thresholds, lower critical exponents, and electrical resistivity due to increased alignment in carbon nanotubes [66]. Potschke et al. have studied rheological as well as dielectric properties for the carbon nanotube/polycarbonate composite and contemplated melt rheology for the storage modulus with the incorporation of carbon nanotubes leading to increase in storage modulus as well as the viscosity for about two decades. They observed the DC conductivity for the 1wt % loading of carbon nanotubes at room temperature which was found to be increased for more than seven decades [67] (Table 4).

Processing Techniques for Manufacturing Polycarbonate Nanocomposites The comparison of vacuum casting with existing polymer processing conventional methodologies such as injection molding, extrusion molding, reaction injection molding, compression molding, and resin transfer molding with their defects and advantages is tabulated in Table 5.

Processing technique Injection molding

Extrusion molding

Reaction injection molding

Serial no. 1

2

3

Polyurethane

Polycarbonate

Materials Polycarbonate

Polyhedral oligomeric silsesquioxane Polyester

Graphene, carbon nanotubes

Acrylonitrile butadiene styrene

Additives/ polymer Carbon nanotubes, graphene

Mechanical properties Bending strength Tensile strength (~80%) Young’s modulus (~150%) Tensile yield (25%) Improved Izod impact strength Tensile modulus Tensile strength Yield strength Yield strain Modulus Tensile strength (improved) Impact strength and hardness (improved)

Table 5 Comparison of vacuum casting with conventional methodologies

Slow in cycle time, voids in matrix as well as product

Central bursting, extruder surging, thickness variation, diameter variation

Defects Flow and sink marks, voids in product, warpage, weld lines.

Eliminated shrinkage

Continuous segment products, hollow article

Advantages Short cycle time, good surface finish

[73],

[70, 71] [72]

References [27, 61, 68, 69]

274 V. D. Jadhav et al.

Vacuum casting

Compression molding

4

5

Polyester

Unsaturated polyester resins

Polyurethane

Epoxy resin

Sisal fiber (30 vol%)

Tensile strength (990.66 MPa) Ultimate strain (0.0618) Stiffness (32.05 N/ mm) Ductility Stiffness (~11%) Tensile strength (~36%) Tensile strength (92.4 MPa) Brinell hardness (14.4 kJ/m2) Tensile strength (~ 46 MPa) Young’s modulus (~1283 MPa) Blisters, burn marks, sink marks

Warpage.

Low tooling cost; does not require gate, sprue, and runner

Good dimensional and color stability, low in tooling cost, low shrinkage, voids-free product

(continued)

[75]

[74]

[14]

[21]

12 Polycarbonate Nanocomposites for High Impact Applications 275

Processing technique

Resin transfer molding

Serial no.

6

Table 5 (continued)

Polyester

Materials

Sisal fiber (30 vol%)

Additives/ polymer Elongation at break (9%) Tensile strength (~51 MPa) Young’s modulus (~1317 MPa) Elongation at break (10%)

Mechanical properties

Micro voids, dry spots

Defects

Capability to fabricate complex geometrical shapes, color stability in products

Advantages

[75]

References

276 V. D. Jadhav et al.

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Conclusion In the present chapter, we have reviewed the vacuum casting and polycarbonate as a casting material with its composites. The fundamentals of vacuum casting include mold materials, and the role of vacuum pressure in product casting and casting materials has also been explained. Polycarbonate has been focused due to its versatile properties like high tensile strength, high impact resistance, toughness, etc. Further, we have also reviewed the additives like calcium carbonate, montmorillonite, fly ash, fibers like Kevlar, glass, carbon, pineapple leaf fiber, and nano-additives such as graphene/graphene oxide and carbon nanotubes help in enhancement of properties of polycarbonate like mechanical, rheological, and electrical properties. The application of vacuum casted products in various sectors like automobile, mechanical and electronics, and telecommunication along with comparison of conventional polymer processing techniques such as injection molding, extrusion molding, and reaction injection molding has also been studied.

Important Websites https://www.mcam.com/products/engineering-plastics/ https://www.dupont.com/brands/kevlar.html http://binaniindustries.com/our-business-areas/glass-fibre/ https://www.renishaw.com/en/renishaw-vacuum-casting-technology-acceleratesinnovation-for-automatic-juicer-manufacturer-zumex%2D%2D42466 https://www.nanowerk.com/nanotechnology/introduction/introduction_to_nanotech nology_22.php Acknowledgment The authors would like to thank Dr. Surendra Pal, Vice-Chancellor, DIAT (DU), Pune, and Mrs. Suranjana Mandal, Vice-Principal, MIT, Aurangabad, for constant encouragement and support. Mr. Prakash Gore, Mr. Ramdayal Saran, Mr. Raviprakash Magisetty, and Mr. Jay Korde are also acknowledged for continuous technical discussions and support.

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Part VI Consumer Nanoproducts Based on Bionanoceramics and Bionanocomposites

Nanoproducts Based on Shape Memory Materials

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shape Memory Composites, an Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shape Memory Alloy Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shape Memory Polymer Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Applications of Shape Memory Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some Companies with SMP Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Guangzhou Manborui Material Technology Co. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cornerstone Research Group Co. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MedShape Co. (https://www.medshape.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shape Memory Medical (https://www.shapemem.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shandong Yabin Medical Technology Co. Ltd. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (http://m.en.crossnt.com/company-374.html) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Asahi Kasei Corporation (https://www.asahi-kasei.co.jp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Changchun Foliaplast Bio-Tech Co., Ltd. (http://foliaplast.globalchemmade.com) . . . . . . . Composite Technology Development Co. Ltd. (https://www.ctd-materials.com) . . . . . . . . . . EndoShape Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lubrizol Advanced Materials Co. (https://www.lubrizol.com) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoshel LLC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

To overcome the shortcomings of neat shape memory materials (SMMs) and to expand the scope of its applications, researchers found that fabricating composite materials based on SMMs is an adequate alternative method. The composite materials are made up of two or more materials, which keep as individual components. And composites are preferred to have all excellent physical A. Nabipourchakoli (*) Nuclear Science and Technology Research Institute, Tehran, Iran e-mail: [email protected]; [email protected] B. Zhang Liaoning Shihua University, Fushun, Liaoning, China © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_24

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properties of their components. For the traditional shape memory material composites (SMMCs), the matrix of SMMCs keeps the shape memory effect, and the reinforcement fillers gradually increase the physical and mechanical properties. More interestingly, fillers can also enable SMMCs multifunctionalities in the shape recovery process. The fillers that are made of nanomaterials and fibers can be designed as an energy converter to trigger thermally responsive SMM matrix. The real driver of SMMCs market is developing the utilization of shape memory materials for medical applications. The second use of SMMCs is in the structure of self-fixing solid, froths for structure protection. In this chapter, the research results on SMMCs production and application of SMMCs are presented. In addition, the global market for SMMCs is evaluated. Keywords

Shape memory material · Shape memory effect · Poly(L-lactide) · Thermoplastic polyurethane · Poly(ε-caprolactone) · Polymer blends · Shape memory behavior · Shape memory polymer · Carbon nanotubes · Shape fixity · Shape recovery · Nanocomposites · Nanomaterials · Shape memory material market Abbreviations

CMF: CNC: CNF: CNP: CNT: EVA: EVA: GO: MCC: MTM: MWCNTs: NMs: NPs: NSMs: NPs: PEEK: PTFE: PCL: PMMA: POSS: PEGMA: PLACL: rGO: SMP: SWCNTs:

Cellulose microfiber Cellulose nanocrystal Cellulose nanofiber Cellulose nanoparticle Carbon nanotube Ethylene-vinyl acetate Ether-vinyl acetate Graphene oxide Microcrystalline cellulose Montmorillonite (plate-shaped clay) Multiwalled carbon nanotubes Nanomaterials Nanoparticles Nanostructured materials Nanoparticles Poly(ether ether ketone) Polytetrafluoroethylene Poly(ε-caprolactone) Poly(methyl methacrylate) Polyhedral oligomeric silsesquioxanes Poly(ethylene glycol)mono-methylether-monomethacrylate Poly(L-lactide-co-ε-caprolactone) Reduced graphene oxide Shape memory polymer Single-walled carbon nanotubes

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SME: TPU:

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Shape memory effect Thermoplastic polyurethane

Introduction Shape memory materials are the sort of promising upgrades-responsive materials; they can “remember” a naturally visible (changeless) shape, be controlled and “fixed” to an impermanent and lethargic shape under explicit states of temperature and stress, and after that later unwind to the first, tranquil condition under warm, electrical, or ecological direction. Many types of artificial materials can achieve shape change under environment stimuli, including metal and nonmetal alloys, polymers, and ceramics, although each material has its unique mechanisms and properties. These materials were termed shape memory materials. The multiple shape memory effect (SME) is meant for that between the programmed (temporary) shape and the permanent shape; there are one or more intermediate stable shapes, which can be precisely controlled, during shape recovery. The multiple SME can be achieved in any SMM even based on only one transition, which could be the glass transition or melting/crystallization transition. Thus, at least one intermediate shape, i.e., the triple-SME, can be easily obtained within a normal transition temperature range of polymers by step-by-step programming at different temperatures during cooling. From application point of view, the advantage of a narrow temperature range between the intermediate shape and that of permanent in the triple-SME is apparent in, for example, anti-counterfeit labels, as now it is possible to use the intermediate shape as a kind of watermark, which cannot be seen if overheated. The real driver of the shape memory polymer (SMP) market is developing the utilization of SMP for shrewd medication conveyance in human services, orthopedic props, orthodontic embeds and supports, catheters, cardiovascular stents, and so forth. The second principal use of SMP is in the structure of self-fixing solid, froths for structure protection, window sealants, and so forth. The relatively low estimations of SMP, when contrasted with different assets, are a burden for the polymer, which can be changed by reinforcing SMP with extra materials, like Kevlar and fiberglass. A typical market driver among the contrastingly looked at reports for the market is growing use of shape memory and, generally, low firmness esteems individually. Aside from these, the components like stringent guideline about the use of synthetic concoctions and monomers to make mechanical applications item, for example, savvy sedate conveyance framework and inserts, or automotive and transportation, and so forth, are expected to influence the worldwide SMP market. As of late, these polymers are being utilized particularly for deployable segments and structures in aviation. The real applications incorporate supports, pivots, blasts, optical reflectors, transforming skins, and receiving wires. In addition, there are numerous licenses recorded by driving polymer chameleon makers in connection to SMPs applications, for example, intravascular conveyance framework, gripper,

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tunable automotive sections, and hood/situate get together vehicles. Acrylic-based SMP materials have likewise been a work in progress for quite a long while and are being utilized for a wide scope of uses. This segment represented an offer of near 10% of the general market in 2018. The automotive business uses SMP-based actuators and programmed gags for motors during the assembling and get together of vehicles. The item is additionally utilized as a defensive spread for automotive sequential construction systems and damping material. In the aviation part, SMP is used for the utilization of optical reflectors, receiving wires, brackets, transforming skins, blasts, pivots, and so on. SMPs are significantly utilized in the deployable structures and parts in the aviation segment. Europe market will be a key region in the SMP market. This is because of the rising interest in innovative work in the aeronautic trade. The region spends around 10% of its complete aviation turnover in R&D exercises. A portion of the significant activities bolstered by the European Commission for creating airplane business incorporates.

Shape Memory Composites, an Overview To overcome the shortcomings of pure shape memory materials and to expand the scope of applications, researchers found that fabricating composite materials is a good method. The composite materials are made up of two or more materials, which keep as individual components. And composites are preferred to have all excellent physical properties of their components. For the traditional SMPCs, the matrix of SMPs keeps the shape memory effect, and the reinforcement fillers gradually increase the mechanical properties. More interestingly, fillers can also enable SMPCs multifunctionalities in the shape recovery process. The fillers can be designed as an energy converter to trigger thermally responsive SMP matrix, such as joule heat generators, radiofrequency absorbers, or infrared radiation absorbers. The self-healing fillers can also be used to heal cracks in SMP matrix. In addition to SMPCs with SMP matrix, the elastomer-based composites filled by SMP fibers also show unique properties. For example, SMP fibers in elastomer matrix can be used to induce the strain mismatch and therefore fold the plate sheet to a 3D structure. Both excellent mechanical properties and multifunctionalities can be achieved in SMPCs [1–4].

Shape Memory Alloy Nanocomposites The fine reinforcement of shape memory alloy (SMA) can make the composites strengthened without losing their pseudoplasticity and shape memory property [5, 6]. Thus, CNT-reinforced TiNi composites can be expected with excellent properties. The integration of SMAs into composite structures has resulted in many benefits, which include actuation, vibration control, damping, sensing, and self-healing. This discrepancy between academic research and commercial interest is largely associated with the material complexity that includes strong

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thermomechanical coupling, large inelastic deformations, and variable thermoelastic properties. Nonetheless, as SMAs are becoming increasingly accepted in engineering applications, a similar trend for SMA composites is expected in aerospace, automotive, and energy conversion and storage-related applications. In an effort to aid in this endeavor, a comprehensive overview of advances with regard to SMA composites and devices utilizing them is pursued [7, 8]. Cai et al. synthesized carbon nanotube (CNT)-reinforced TiNi matrix composites by spark plasma sintering (SPS) employing elemental powders [9]. The results show that the thermoelastic martensitic transformation behaviors could be observed from the samples that sintered above 800
C even with a short sintering time (5 min), and the transformation temperatures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation. Although decreasing the sintering temperature and time to 700
C and 5 min could not protect defective MWCNTs from reacting with Ti, still-perfect MWCNTs remained in the specimens sintered at 900
C. This method is expected to supply a basis for preparing CNT-reinforced TiNi composites [10].

Shape Memory Polymer Nanocomposites A SMP is reinforced mainly to increase the driving force of the recovery process and to provide better carrying capacity, which correspond to a high elastic modulus and a general elastic modulus, respectively. In general, the reinforcement filler improves these two indicators at the same time [11, 12, 13, 3, 14]. Nabipour Chakoli et al. have reported the data from comprehensive thermomechanical and shape memory tests of poly(L-lactide-co-ε-caprolactone) (PLACL), a biodegradable SMP, that is reinforced with pristine and functionalized MWCNTs [15], and the main conclusions are as follows: (1) The strain fixity (Rf) of the composites almost keeps a stable value with the increase of the filler content at low initial strain deformation. At high initial strain deformations, the addition of MWCNT-g-PLACLs increases the strain fixity of the composites; however, the addition of pMWCNTs has no significant effect on the strain fixity of the composites. (2) The addition of pMWCNTs decreases the strain recovery of the composites. When the MWCNT-g-PLACLs content is less than 2 wt%, the strain recovery initially decreases and then increases with the increase of the MWCNT-gPLACLs content. With further increasing MWCNT-g-PLACLs content up to 3 wt%, the strain recovery decreases again. (3) The recovery stress of the composites increases gradually with increasing the amount of both kinds of reinforcing fillers. The maximum recovery stress can be obtained at the MWCNTs-g-PLACLs content of 2 wt% and the pMWCNTs content of 1 wt%, respectively. After that, with further increasing the reinforcing filler content, the recovery stress of the composites decreases. The addition of

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MWCNTs is beneficial to store the internal elastic energy during stretching and fixing, which leads to the improvement of recovery stress. (4) The strain fixity, strain recovery, and recovery stress of the PLACL (80% LA + 20% CL) and its composites decrease slightly after degradation in PBS at 37
C. Miaudet et al. [16] achieved the very high recovery stress of CNTs/polyvinyl alcohol SMPCs. The maximal stress generated by a CNTs/polyvinyl alcohol fiber reached 150 MPa which is two orders of magnitude higher than that of neat SMPs. The CNT/polyvinyl alcohol fiber was prepared using a special coagulation spinning technique. Surfactant-stabilized CNTs were injected in the co-flowing stream of the coagulating polyvinyl alcohol solution which enabled an extremely high content of CNTs to be incorporated into the polyvinyl alcohol fiber. Zhang et al. [17], using abundant surface hydroxyl of silica, initiated epsiloncaprolactone on the particles. Uniform SiO2/PCL macroparticles were formed. After cross-linking of SiO2/PCL by 4,40 -methylenediphenyl diisocyanate, the SiO2/SMP was prepared. Compared to traditional silica-based filler-filled SMPs, the SiO2/SMP exhibited excellent mechanical strength, high strain, and good shape memory properties due to the introduction of SiO2 as a cross-linking agent. Xu et al. [18] heat treated a nanofabric-type clay attapulgite at 850
C to reinforce shape memory polyurethane (SMPU). The mechanical properties and SME of the nanocomposites were remarkably improved using the nanofabric-type clay attapulgite [19, 20]. Celite, which is primarily composed of silica and alumina, has surface hydroxyl groups. It can be coupled with SMPU chains. Park et al. [21] prepared celite/SMPU with celite acting as a cross-linking agent. The celite improved the shape memory performance and mechanical properties of SMPUs. Lee et al. [22] functionalized silicas with allyl isocyanate groups and made waterborne silica/polyurethane nanocomposites using UV. It was demonstrated that the functionalized silica particles had the function of both reinforcing fillers and stress relaxation retarders. Heat treatment of CNT/SMP composites can remarkably improve the composites conductivity as reported by Cho et al. [23] and Fei et al. [24]. Fei et al. prepared CNTs/poly(methyl methacrylate-co-butyl acrylate) by ultrasound-assisted in situ polymerization. The composites were subjected to a simple heating and cooling process. The mechanism of the increased electrical conductivity was tentatively ascribed as follows: in the original composite, there may be some internal residual stresses or strains in the interface between polymer and CNTs as a result of thermal expansion mismatch and curing shrinkage; after the post-thermal treatment, the interface contact area between the polymer matrix and CNTs may increase, and the thickness of the interfacial polymer may decrease. The two effects reduce the tunneling resistance and thus significantly enhance the electrical conductivity. To construct physical conductive channels in SMPs, Yu et al. [25] and Leng et al. [26] aligned Ni powders and CNTs, respectively, in CB/SMP composites using magnetic field or electrical field. It was reported that compared with the samples with randomly distributed conductive fillers, the electrical resistivity was reduced by over 100 times. Instead of Ni powders, filamentary nickel nanostrands with high aspect ratios can further improve the electrical conductivity of the composite. Lu

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et al. [27] filled filamentary nickel nanostrands and CNTs into shape memory epoxy. The aligned high aspect ratios fillers further facilitated the actuation of the SMP nanocomposite even though a low filler volume content and low electrical voltage were used. Polyhedral oligomeric silsesquioxane (POSS) is a good filler for biodegrade SMPs [28]. Jeon et al. [29] studied the shape memory properties of norbornylPOSS copolymers having either cyclohexyl corner groups or cyclopentyl corner groups. The POSS composites showed two stages of strain recovery, a fast strainrecovery process related to the polynorbornene relaxation in the norbornyl matrix and a second slow strain-recovery process which was assumed to be related to the POSS-rich domains. This two-stage shape recovery is like the triple SME of SMPs. Berllin et al. [30] developed a triple-SMP by copolymerization of poly(ethylene glycol)mono-methylether-monomethacrylate (PEGMA) with poly(caprolactone) dimethacrylate. The polymer had crystalline poly(caprolactone) domains and crystalline polyethylene glycol domains, which act as the two switching phases. Then Kumar et al. [31] filled the triple-SMP with silica-coated nano-iron(III) oxide particles. With the stepwise increases of the magnetic field strength from H ¼ 14.6 and 29.4 kA/m, triple-shape memory behavior was observed. Paderni et al. [32] prepared a triple-shape memory-grafted polymer network containing crystallizable poly(ethylene glycol) side chains and poly(caprolactone) cross-links network. The polymer has two well-separated melting transitions. Then silica-coated nano-iron (III) oxide particles were filled into the polymer; and the MSME by noncontact activation in a stepwise increasing alternating magnetic field was achieved. Gold nanoparticles between 60 and 200 nm in size have a strong absorption of light especially infrared light. Heating of focused light can be absorbed by the gold nanoparticles to increase the temperature of gold nanoparticles/SMP composites locally to trigger the spatially controlled SME. Zhang et al. [33] demonstrated the spatially controllable shape recovery of the gold nanoparticle-filled SMP using focused laser light. Surface-functionalized gold nanoparticles are loaded in semicrystalline shape memory poly(ε-caprolactone) macromolecules. The branched oligo(ε-caprolactone) was cross-linked with hexamethylene diisocyanate. The shape recovery by the localized photothermal effect of gold particles can be controlled by the intensity of light which determines the amount of heat generated by the gold nanoparticles. Once the light is turned off, the heating caused by the light is off. Therefore, the shape recovery can be stopped at any stage [33]. He et al. [34] fabricated a multi-composite SMP consisting of a Fe3O4/SMP region and a CNT/SMP region separated by a pure SMP region. Upon remote actuation using two different magnetic fields of different radiofrequencies, the triple-region composite was capable of controlled two-step shape recovery. The Fe3O4/SMP and CNT/SMP regions have different radiofrequency absorptions. When the deformed composite sample is in 13.56 MHz RF field, only the CNT/SMP region is heated. This leads to the recovery of only the CNT/SMP region. Upon being subjected to subsequent 296 kHz RF field, the Fe3O4/SMP region is selectively heated leading to the recovery of the Fe3O4/SMP region. Finally, the pure SMP region recovers in an oven.

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In some researches, the thermomechanical properties of PLLA nanocomposites reinforced with functionalized multiwalled carbon nanotubes (MWCNTs-g-PLLAs) were determined. For functionalization, PLLA chains were grafted from the surface of MWCNTs. Then, func. MWCNTs/PLLA composite is prepared by solution casting. The results show that the MWCNT-g-PLLAs were dispersed in PLLA matrix adequately. Increasing the weight percentage of MWCNT-g-PLLAs up to 2 wt% led to gradual enhancement of the mechanical properties of nanocomposite. The thermal analysis also revealed the func. MWCNTs increase the melting point and the glass transition temperature of nanocomposite. Also, the DMA results show that incrementing the concentrations of func. MWCNTs is also accompanied with increasing Young’s modulus and the transition temperature of PLLA. The chain stiffness in amorphous phase of PLLA can also increase due to the van der Walls force and the homogeneous dispersion of func. MWCNTs. In addition, the crystallinity of PLLA could be increased due to func. MWCNTs as heterogeneous nucleation points [35]. There are many researches on reinforcing the PLACL using nanomaterials. As an example PLACLs reinforced with well-dispersed multiwalled carbon nanotubes (MWCNTs) were prepared using functionalized MWCNT by in situ polymerization. The surface functionalization of MWCNTs can effectively improve the dispersion and adhesion of MWCNTs in PLACL, and hence, it will have a significant effect on the physical, thermomechanical, and degradation properties of MWCNT/PLACL nanocomposites [36]. Nabipour Chakoli et al. have reported the data from comprehensive thermomechanical and shape memory tests of poly(L-lactide-co-ε-caprolactone) (PLACL), a biodegradable SMP, that is reinforced with pristine and functionalized MWCNTs [15], and the main conclusions are as follows: (1) The strain fixity (Rf) of the composites almost keeps a stable value with the increase of the filler content at low initial strain deformation. At high initial strain deformations, the addition of MWCNT-g-PLACLs increases the strain fixity of the composites; however, the addition of pMWCNTs has no significant effect on the strain fixity of the composites. (2) The addition of pMWCNTs decreases the strain recovery of the composites. When the MWCNT-g-PLACLs content is less than 2 wt%, the strain recovery initially decreases and then increases with the increase of the MWCNT-gPLACLs content. With further increasing MWCNT-g-PLACLs content up to 3 wt%, the strain recovery decreases again. (3) The recovery stress of the composites increases gradually with increasing the amount of both kinds of reinforcing fillers. The maximum recovery stress can be obtained at the MWCNTs-g-PLACLs content of 2 wt% and the pMWCNTs content of 1 wt%, respectively. After that, with further increasing the reinforcing filler content, the recovery stress of the composites decreases. The addition of MWCNTs is beneficial to store the internal elastic energy during stretching and fixing, which leads to the improvement of recovery stress.

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(4) The strain fixity, strain recovery, and recovery stress of the PLACL (80% LA + 20%CL) and its composites decrease slightly after degradation in PBS at 37
C. Zhou et al. discussed the key issues in optimization of the shape memory performance, temperature memory effect, and multiple SME. It is concluded that most shape memory phenomena are intrinsic features of polymeric materials, and based on these basic working mechanisms, it can be enabled the SME in materials, design a new shape memory material with the required shape memory function, and optimize the shape memory performance (Fig. 1) [37]. Electroactive shape memory is influenced by the electrical conductivity of the material resulting in joule heating, whereas the thermal conductivity of the nanocomposite governs the thermally stimulated SME [38]. Karabudak et al. research group grows TiO2 coatings with nano-Ag-doped and micro-arc oxidation technique on NiTi shape memory alloy. The XRD results showed that there were only TiO2 crystal phases (anatase and rutile) on the coating. The results showed that a clean and dense oxide layer was grown on the surface successfully. The surface of nano-Ag-doped TiO2-coated samples appears to be smoother than the surface of the coatings without Ag. The corrosion tests of the coated and uncoated samples were carried out in three different environments (simulated body fluid, synthetic saliva, and cola) at 37
C which is a human body temperature. The corrosion tests showed that the corrosion resistance of TiO2-coated and nano-Ag-doped TiO2-coated samples was much higher than the corrosion resistance of the NiTi substrate. Seven different bacteria (S. aureus, L. monocytogenes, Bacillus subtilis, Salmonella enteritidis, Yersinia enterocolitica, E. coli, P. aeruginosa) which have the human pathogen feature were used in the antibacterial susceptibility tests. The process was conducted based on the disk diffusion method to test the susceptibility of bacterial strains on the selected coated and uncoated samples, and antimicrobial activity was evaluated in the nano-Agdoped TiO2-coated material; P. aeruginosa, Y. enterocolitica, and E. coli (zone

Fig. 1 The heating responsive SME in 3D-printed poly(lactic acid) (PLA) spring [37]

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diameter of 8–14 mm) were found to be moderately susceptible; S. aureus, L. monocytogenes, B. subtilis, and S. enteritidis (zone diameters of 8–14 mm) were found to be resistant. The antimicrobial activity of the coating material NiTi was found to be sensitive for all antibacterial tests. According to the TiO2-coated material results, S. aureus, P. aeruginosa, L. monocytogenes, and E. coli were found to be moderately sensitive and Y. enterocolitica, S. enteritidis, and B. subtilis were found to be resistant [39, 40]. Wu et al. applied shape memory polymers (SMPs) into digital light processing (DLP) technology to realize four-dimensional (4D) printing. However, there is still a great lack of shape memory-photosensitive resins suitable for DLP. They designed novel acrylate-based photosensitive resins for DLP and prepared to fabricate SMP parts with tert-butyl acrylate/1,6-hexanediol diacrylate (tBA/HDDA) networks. The developed SMP with 10 wt% cross-linker can withstand 16 consecutive cycles and retain extremely high shape recovery ratio of 100% even after 14 cycles, the one with 20 wt% cross-linker possesses the best shape fixity ratio of over 96%, and the storage modulus can reach up to 1.48  10 3 MPa with 50 wt% cross-linker. Furthermore, these 4D-printed SMPs only spend 7–13 s in the 180
shape recovery, indicating a good shape recovery rate as shown in Fig. 2. This work confirms that the designed SMPs have potential applications in many areas due to their excellent shape memory performance and provides valuable guidance for the shape memory properties optimization of other SMPs [41]. Abdullah et al. reinforced shape memory polyurethane (SMPU) with multiwalled carbon nanotubes (MWNTs) which were fabricated with through mixing and injection molding with the purpose to improve the shape memory properties of the polymer at low filler content. Variables such as shape fixity and recovery have been measured to evaluate the effect of nanotube fillers on the shape memory behavior of the prepared composites. Thermomechanical tests were

Fig. 2 Preparation and shape memory effect of acrylate-based photosensitive resins for digital light processing [41]

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performed and the shape fixity and shape recovery rate were analyzed. Additions of nanotube fillers increase the relative shape fixity of the polymer nanocomposites, while the experimental results demonstrate that the presences of nanotube fillers reduce the shape recovery rate. The shape recovery of the polymer nanocomposites was decreased due to the limited movement of polymer chains by the MWCNTs [42]. Zhang et al. prepared the graphene oxide-reinforced poly(L-lactide-co-εcaprolactone) (GO/PLACL) nanocomposites. They used molecular dynamics to study the shape memory effect and mechanical properties of GO/PLACL to understand the microscopic mechanism. Two models containing dispersed graphene oxide were constructed. It is shown that the addition of graphene oxide causes the glass transition temperature of material to rise because of limitation on polymer activity. The uniaxial tensile properties of the composites were studied. The results exhibited that strength of composites depends on the interface state of the polymer and graphene oxide. The strength of the composite with covalent bond is much higher than that of another without the covalent bond between graphene oxide and poly(L-lactide-co-ε-caprolactone) generated. Stress-softening effect was observed in the cross-linked composite in the glass state. Their uniaxial tension thermodynamic cycles were carried out to consider the shape memory effect of the composites. It is shown that graphene oxide-reinforced composites with different interactions exhibit fair shape memory effect in the direction of paralleling graphene oxide surface. In terms of the direction perpendicular to graphene oxide sheet, the fixed ratios of the composites decrease slightly about 1.64%–3.63%, and the recovery ratios of the composites with the covalent bond are higher than others about 3.22%–12.93%[43]. In their research, Tsujimoto et al. deal with the synthesis of plant oil-based shape memory materials from epoxidized soybean oil (ESO) and polycaprolactone (PCL). PolyESO/PCLs were synthesized by an acid-catalyzed curing in the presence of PCL. During the reaction, PCL scarcely reacted with ESO, and the crystallinity of the PCL component decreased to form a semi-interpenetrating network structure. The incorporation of the PCL components improved the maximum stress and strain at break of ESO-based network polymer. The polyESO/PCL was gradually degraded by Pseudomonas cepacia lipase. Furthermore, the polyESO/PCLs exhibited excellent shape memory properties, and the strain fixity depended on the feed ratio of ESO and PCL. Figure 3 shows that the shape memory recovery behaviors were repeatedly practicable. The resulting materials are expected to contribute to the development of biodegradable intelligent materials. These striking results provide a new strategy for designing novel biodegradable smart materials [44]. Shape recovery in a commercial ether-vinyl acetate copolymer (EVA) was systematically characterized by Xu et al. The influences of the programming temperature and maximum uniaxial tension strain on the shape fixity ratio and the shape recovery ratio were investigated quantitatively. In addition to excellent SME, high elasticity and high creep were observed at around room temperature (with the EVA in the glassy state). The underlying mechanisms for the different shape recovery phenomena (i.e., creep and the SME) are discussed. Two potential applications utilizing the shape recovery property and high elasticity of this EVA are presented [45].

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Fig. 3 Molecular structure and shape memory test of poly epoxidized soybean oil/polycaprolactone [44]

Tsujimoto et al. developed a bio-based SMP with dynamically cross-linked network structure from trans-1,4-polyisoprene (TPI) derived from Eucommia ulmoides Oliver. Grafting of maleic anhydride onto TPI was performed in 1,2-dichlorobenzene, and the subsequent hydrolysis gave maleatedtrans-1,4-polyisoprene (MTPI). Increasing trend of the grafted maleic moiety was observed with increasing the concentration of maleic anhydride in the grafting reaction. With increase in maleic content, the glass transition temperature (Tg) of the resulting polymer increased, whereas the crystallinity decreased. The maximum stress of the MTPI with carboxylates was larger than that of the protonated MTPI. Above the melting temperature, Young’s modulus of MTPI with carboxylates was higher than that of neat TPI and the protonated MTPI, due to dynamically cross-linked network structure. Figure 4 presents the scheme of cross-linking and shape memory test of sample composite. Furthermore, the MTPI with 1% carboxylate content exhibited excellent shape memory recovery properties, exploiting the combination of the physical cross-linking and the melting of the crystal. The resulting materials are expected to contribute to the development of bio-based intelligent materials [46]. A novel type of covalently cross-linked semicrystalline polymer with shape memory and biocompatibility properties was prepared from alkoxysilane-terminated poly(ε-caprolactone) (PCL) by sol-gel process that allowed the generation of silicalike cross-linking points. A fine-tuning of the cross-linking density and thermal properties (melting temperature) of the materials was obtained by controlling the molecular weight of the PCL precursor (and thus the molecular structure of the resulting network) and the curing conditions. The shape memory behavior was investigated with bending tests. Recovery times of less than 1 second were observed in water depending on the temperature, and a linear correlation of the recovery time with cross-linking density and molecular weight of PCL network precursor was observed [32].

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Fig. 4 Schematic representation of dynamic cross-linking and shape memory test of sample [46]

In their research, Baldi et al. have explored the shape memory capabilities of a novel type of covalently cross-linked semicrystalline polymers, prepared by exploiting the mild sol-gel chemistry, starting from alkoxysilane-terminated poly(ε-caprolactone) (PCL), and using silica-based domains as cross-link points. By adopting PCL precursors with different molecular weights, semicrystalline networks with well-defined cross-link densities and with different crystallization and melting temperatures were obtained. Besides a satisfying one-way shape memory behavior, the materials have displayed a significant two-way shape memory response, undergoing a reversible elongationcontraction process between two distinguished strain levels when subjected to a constant load and cyclically heated/cooled on a temperature region spanning from below the crystallization temperature to above the melting temperature as shown in Fig. 5. The applied load and the cross-link density are revealed as key parameters to obtain tailored actuations. Concurrent wide-angle X-ray diffraction (WAXD) and DSC analyses allowed to ascribe the effect to a structural evolution process occurring during melting and crystallization [47]. Tsujimoto et al., in their research, deal with the synthesis of plant oil-based shape memory materials from epoxidized soybean oil (ESO) and polycaprolactone (PCL). PolyESO/PCLs were synthesized by an acid-catalyzed curing in the presence of PCL. During the reaction, PCL scarcely reacted with ESO, and the crystallinity of the PCL component decreased to form a semi-interpenetrating network structure as shown in Fig. 6. The incorporation of the PCL components improved the maximum stress and strain at break of ESO-based network polymer. The polyESO/PCL was gradually degraded by Pseudomonas cepacia lipase. Furthermore, the polyESO/ PCLs exhibited excellent shape memory properties, and the strain fixity depended on the feed ratio of ESO and PCL. The shape memory recovery behaviors were repeatedly practicable. The resulting materials are expected to contribute to the development of biodegradable intelligent materials [44]. The influence of extreme conditions such as high pressure and high temperature on shape memory function of polymers has received little attention. In this study, the shape memory properties of poly(ε-caprolactone) (PCL)-based nanocomposites with nanocrystalline cellulose (NCC) as fillers are investigated via recrystallization at a

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Fig. 5 The strain of composite under the fixed stress and the schematic representation for strain of composite under fixed stress [47]

Fig. 6 Schematic representation of composite accompanying with a composite sample shape memory test [37]

high temperature under a high-pressure environment by Wang et al. The results exhibit that when the mass ratio of NCC was maintained constant, both the crystal properties and melting temperatures of the nanocomposites decreased with increasing pressure. Furthermore, the shape memory fixity ratios of the recrystallized nanocomposites remained more than 90% due to the fact that the chemical crosslinking structure and the recovery ratios kept increasing with the increase in pressure. The mechanism of the improvement of the shape memory function was further

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High Pressure 140°C, 1 h Cooling

The state of atmospheric pressure

The state of high pressure

PCL crystalline domain

PCL amorphous domain

NCC

Cross-linking point

Fig. 7 Schematic representation of molecular scale of composite under pressure [48]

analyzed, and the result demonstrates that the pressure has a significant influence on the crystal properties of PCL polymers during their recrystallization; subsequently the shape recovery ratio is improved since more molecular chains participate in the shape recovery process (Fig. 7) [48]. Shape memory surfaces with on-demand, tunable nanopatterns are developed to observe time-dependent changes in cell alignment using temperature-responsive poly(ε-caprolactone) (PCL) films. Temporary grooved nanopatterns are easily programmed on the films and triggered to transition quickly to permanent surface patterns by the application of body heat. Figure 8 elucidates the scheme of crosslinking and shape memory test of sample composite. A time-dependent cytoskeleton remodeling is also observed under biologically relevant conditions [49]. Thermally responsive shape memory polymers have promising applications in many fields, especially in biomedical areas. In the Jing et al. research, a simple method was purposed to prepare thermoplastic polyurethane (TPU)/poly(-caprolactone) (PCL) blends that possess shape memory attributes. TPU and PCL were melt compounded via a twin-screw extruder and injection molded at various ratios. Multiple test methods were used to characterize their shape memory properties and reveal the underlying mechanism. The blends containing 25% TPU and 75% PCL possessed the best shape memory properties as indicated by a 98% shape-fixing ratio and 90% shape recovery ratio. This was attributed to the hybrid crystalline and amorphous regions of PCL and TPU. It was also found that PCL and TPU had good miscibility and that the PCL domain in TPU25% had higher crystallinity than neat PCL. The crystalline region in TPU25% could deform and maintain its temporary shape when stretched, which contributed to its high shape-fixing attribute, while the rubbery TPU region assisted in the recovery of the sample upon heating by releasing the deformation energy stored. Moreover, the TPU25% string prepared could knot itself in a hot water bath, indicating

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O C

=

O

= O

O

n

C CH= CH2

PCL macromonomer

Cross-linking

Programming of temporal pattern

Body heat

Recovery of the permanent pattern

Fig. 8 The schematic representation of cross-linking and shape recovery of film using body heat [49]

a potential for suture applications. Lastly, the 3T3 fibroblast cells cultured on the TPU/PCL blends showed high viability and active substrate-cell interactions [50]. Blending commercial homopolymers represents a low cost and an easy scalable process to extend the use of the pristine homopolymers to an industrial level. Actually, the processing of blends by extrusion is the usual solution followed in the industry. However, commonly polymer blends are immiscible, provoking phase separation, which can be in the macro-, micro-, or nanoscale, depending on the polymers as well as on the processing conditions, affecting the final properties of the blends. Therefore, this chapter aims to study the shape memory behavior in biodegradable blends based on poly(lactic acid) (PLA) and poly(ε-caprolactone) (PCL) in different concentrations. A completely thermal and mechanical characterization of the blends was performed, correlating the results with the observed morphology. In addition, two different biodegradation studies were performed in order to correlate the effect of each homopolymer with the degradation behavior of the biodegradable blends [51]. Kim et al. synthesized a series of electroactive shape memory polyurethane (SMPU) nanocomposites from poly(tetramethylene ether) glycol (PTMG), 4,4-methylenebis(phenyl isocyanate) (MDI), and 1,3-butandiol (1,3-BD) with the

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addition of various amounts of thermally reduced graphenes (TRG) which were chemically modified with allyl isocyanate (iTRG). The effects of iTRG on electroactive shape recovery behaviors as well as the conventional direct heat-actuated SMPU material have been studied in terms of morphological, thermal, mechanical, electrical properties and thermomechanical cyclic behavior. It was found that significant increases in electrical conductivity and temperature were obtained high iTRG contents (>2%) to electrically actuate the nanocomposite, along with large increases in glass transition temperature (Tg) and initial modulus with a dramatic drop in elongation at break [52]. Bio-based polyester (BE) was synthesized through polycondensation using the plant-derived resources as the starting materials. Vapor-grown carbon nanofiber (VGCF) was then incorporated into BE to prepare BE/VGCF composites by simple melting blending. The uniform dispersion of VGCF and fairly strong interfacial adhesion between BE and VGCF led to a significant improvement in the mechanical properties of the composites. Besides, the incorporation of VGCF successfully converted the insulating BE into electrically conductive composites with a percolation threshold of 2.5 vol.%. The composites showed excellent electroactive shape memory properties, which reached a shape recovery ratio of 97% within 90 s with a direct current voltage of 20 V. The combination of the significantly improved mechanical properties and excellent electroactive shape memory performance of BE/VGCF composites opens up the new opportunity for the electroactive actuator materials in a sustainable manner [53]. Plasmonic nanoparticles can confine light in nanoscale and locally heat the surrounding. Here the titanium nitride (TiN) nanoparticles were used as broadband plasmonic light absorbers and synthesized a highly photoresponsive hybrid cross-linked polymer from SMP poly(ε-caprolactone) (PCL). The TiN-PCL hybrid is responsive to sunlight, and the threshold irradiance was among the lowest when compared with other photoresponsive shape memory polymers studied previously. Sunlight heating with TiN NPs can be applied to other heat-responsive smart polymers, thereby contributing to energysaving smart polymers research for a sustainable society [54] (Fig. 9). In the present work, the development of a polycaprolactone-based toughened shape memory polyurethane biocomposite promoted by in situ incorporation of chitosan flakes has been demonstrated. The chitosan flakes were homogeneously present in the polymer matrix in the form of nanoflakes, as confirmed by the electron microscopic analysis, and probably developed a cross-linked node that promoted toughness (a > 500% elongation at break) and led to a ~ 130% increment in ultimate tensile strength, as analyzed using a universal testing machine. During a tensile pull, X-ray analysis revealed the development of crystallites, which resulted from a stressinduced crystallization process that may retain the shape and melting of the crystallites stimulating shape recovery (with a ~ 100% shape recovery ratio), even after permanent deformation. The biodegradable polyurethane biocomposite also demonstrates relatively high thermal stability (Tmax at ~360
C) as shown in Fig. 10. The prepared material possesses a unique shape memory behavior, even after permanent deformation up to a > 500% strain, which may have great potential in several biomedical applications [55].

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Fig. 9 The shape memory test of composite [54]

Fig. 10 Demonstration of the shape memory effect in the PCL-PU-chitosan biocomposite in a dry condition and the shape memory ability of the prepared random shaped chitosan polyurethane composite for grip application (temporary shape at room temperature using tensile force; recovered shape in water (wet condition) at 50
C within 5 s). Shape memory behavior of the polyurethane chitosan biocomposite after tensile tension [55]

In research of Molavi et al., a novel thermally actuated triple-SMP (triple-SMP) based on poly(L-lactide) (PLA)/poly(ε-caprolactone) (PCL)/graphene nanoplatelets (GNPs) nanocomposite was prepared by facile solution mixing method, and the design of which was based on two well-separated melting temperatures. In order to improve the dispersion of GNPs in the matrix, functionalization reactions were carried out on the GNPs surface. Functionalization was confirmed by various techniques including FTIR, Raman, and TGA. TEM micrographs revealed an exfoliated morphology for the functionalized GNPs (FGNPs) and a homogeneous dispersion in the matrix. The crystallinity behavior of nanocomposites was investigated by DSC and variable temperature XRD (VT-XRD) analysis, and an increase in crystallinity was observed. Dynamic mechanical analysis (DMA) showed that the presence of FGNPs improves the fixity and recovery ratios because of increase in

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crystallinity and thermal conductivity. The best shape memory behavior was obtained for PLA50/PCL50/FGNP 1.5 nanocomposite [56]. Rapidly electroactive thermoplastic polyurethane (TPU)/polylactide (PLA) shape memory polymer (SMP) blends via phase morphology control and incorporation of conductive multiwalled carbon nanotubes (MWCNTs) were achieved by simple and efficient melt blending in this work. Binary TPU/PLA blends with various composition ratios were firstly prepared, and the effect of phase morphology on shape memory behavior was studied. The optimum shape memory behavior was observed for TPU50/PLA50 blends with co-continuous phase morphology. Then a small number of MWCNTs were selectively incorporated into TPU phase of TPU50/ PLA50 and TPU60/PLA40 blends to realize electroactive shape memory effect. Figure 11 shows the effect of MWCNTs on electrical conductivity of nanocomposite. The formation of double percolation network imparted TPU/PLA/ MWCNT conductive polymer composites with high electrical conductivities in low percolation thresholds, thus realizing rapidly electroactive shape memory behaviors. Additionally, the mechanical properties of TPU/PLA blends (50/50, 60/40) can be enhanced by the addition of MWCNTs even at high temperature. Therefore, our work provides a simple way to fabricate polymer blends with rapid electroactive shape memory performances, good mechanical properties, as well as good processing capability but low cost [57]. In this work of Iregui et al., poly(ε-caprolactone) (PCL)/diglycidyl ether of bisphenol A (DGEBA) blends were electrospun, and the obtained mats were UV cured to achieve shape memory properties. In the majority of studies, when blends with different compositions are electrospun, the process variables such as voltage or flow rate are fixed independently of the composition, and consequently the quality of the fibers is not optimized in all of the range studied. In the present work, using the design of experiments methodology, flow rate and voltage required to obtain a stable process were evaluated as responses in addition to the fiber diameter and shape memory properties. The results showed that the solution concentration and amount of PCL played an important role in the voltage and flow rate. For the shape memory properties, excellent values were achieved, and no composition dependence was

Fig. 11 The effect of MWCNTs concentration on electrical conductivity of nanocomposites [57]

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Fig. 12 Photographs of the manual shape memory test showing (a) the initial longitude, (b) the programming shape, (c) the fixed shape, and (d) the recovered sample [58]

observed. In the case of fiber diameter, similar results to previous works were observed [58] (Fig. 12). In the case of integration, flexible composite skins can be applied over a shape memory foam core obtaining composite sandwich that can be shaped to change its stiffness or to reduce its volume. After the application of a given stimulus (generally by heating), the initial shape can be recovered. Future applications for this class of materials are self-deployable structures for space systems (such as actuators of solar sails or smart aerodynamic structures). In research of Santo et al., two new SMC selfdeployable structures were prototyped: a composite cross and a composite frame containing a thin aluminum sheet as shown in Figs. 13 and 14. The former structure represents a possible deploying configuration for a structural sheet, whereas the latter is a conceptual study of a solar sail. The experimental results are very promising, showing that such structures can successfully self-deploy following the desired design constraints without noticeable damages. Figure 15 represents the shape memory test of prepared composites during shape recovery [59]. Near-term and future spacecraft and satellites will require large ultralightweight structures and components that must be efficiently packaged for launch and reliably deployed on orbit. A new material technology called elastic memory composite (EMC) materials shows promise in meeting these needs. The EMC polymer matrix

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Fig. 13 Shape memory test for prototypes of composite with a composite fame [59]

Fig. 14 Memory and recovery stage for the SMC cross composite [59]

materials enable a fully cured composite structure or component to be deformed or folded for efficient packaging into a spacecraft or launch vehicle and then regain its original shape with no degradation or loss in mechanical or physical properties. A component using EMC materials is fabricated in its deployed, on-orbit shape using conventional composite manufacturing processes by Tupper et al. Then by heating the material and applying force, this fully cured composite material can be folded or deformed for packaging. When cooled, it will retain the package shape indefinitely. When reheated the structure will regain its original shape with little or no external force. This packaging/deployment cycle is reversible as shown in Fig. 16 [60].

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Fig. 15 Details of the shape memory test of the SMC frame [59]

Fig. 16 Demonstration of fully cured elastic memory composite material [60]

In their recent research, Ferreira et al. studied the effect of reduced graphene oxide (rGO) on the thermally induced shape memory properties of poly(lactic acid) (PLA). The rGO was incorporated within PLA at various contents (0.1–1.0 mass%) by melt extrusion. X-ray diffraction showed that PLA/rGO nanocomposites presented decreased crystallinity compared to PLA alone. Differential scanning calorimetry revealed that rGO particles favored the formation of more imperfect PLA crystals.

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Results from thermogravimetric analyses showed that the PLA/rGO composites presented slightly improved thermal stability. Time-domain nuclear magnetic resonance indicated increased molecular mobility for PLA/rGO nanocomposites in relation to PLA. Dynamic mechanical analysis results showed that Tg ¼ 62.9
C for PLA and that this value was reduced for the composites, reaching 54.2
C when the rGO content was 1.0 mass%. The storage moduli (E0 ) were reduced with the increase in rGO content, with a 44% decrease for the composition with 1.0 mass% of rGO. However, above 65
C the E0 values increased substantially, which suggested the role of graphene to fix the heat-relaxed molecules of PLA. For the composites, the thermally induced shape memory data revealed an increase in the maximum strain (εm), reaching 39% and 51% for the composites with the incorporation of rGO at 0.5 and 1.0 mass% content, respectively. The effect of rGO particles on enhancing the shape memory properties of PLA was confirmed by the increases in the recovery rates (Rr) observed for the composites [61]. The effect of the inclusion of nano-hydroxyapatite (nano-HAp) and the porous structure on the shape memory behavior of poly(D,L-lactide) (PDLLA) composites was investigated by Jia et al. Porous, thermal-responsive shape memory composites, PDLLA/nano-HAp, were prepared by a newly developed polymer coagulation, particulate leaching, and cold compression molding technique. The inclusion of nano-HAp to PDLLA led to a higher shape memory transition temperature, improved mechanical strength, and larger recovery force as compared with the neat PDLLA. The nanocomposite with 10 wt% of nano-HAp exhibited the best shape fixity and recoverability with the shortest recovery time. Further increase in the filler content of nano-HAp would reduce the recovery force and prolong the recovery time due to restriction in the movement of the amorphous PDLLA chain segments. The analysis results provide important information for designing biomedical devices using this novel type of bioabsorbable SMP composite [62]. Du et al. investigated the shape memory properties of hydroxyapatite-graft-poly (D,L-lactide) (HA-g-PDLLA) nanocomposites. Hybrid nanocomposites with various HA proportions (5, 10, 15, and 25 wt%) were prepared via in situ grafting polymerization. It is found that the nanocomposites exhibit various shape memory (SM) performances with different HA loadings. Excellent shape memory properties were found for HA-g-PDLLA nanocomposites with 15 wt% inorganic HA proportions, observed through a well-established four-step SM programming cycle method. However, at low HA loading (including pure PDLLA), the samples experienced a severe relaxation process, which caused a plastic, irreversible deformation of the sample and resulted in a poor SM recovery ratio. In addition, the shape memory behaviors of HA25-g-PDLLA nanocomposites and HA25/PDLLA blends were compared. Due to the serious relaxation process caused by the weak interaction forces of hydrogen bonding between HA and PDLLA, the HA25/PDLLA blends had much worse shape recovery ability than the HA25-g-PDLLA nanocomposites [62, 63]. The schematic representation of nanocomposite and its shape recovery test is presented in Fig. 17. The significance of SMP composites (SMPCs) has been analyzed in terms of four aspects: reinforcement, innovation and improvement of driving methods, the

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Fig. 17 Shape recovery test of prepared nanocomposite [63]

creation of specific deformations, and the creation of multifunctional materials. Mu et al. introduce the constitutive theory of SMPs and the post-buckling analysis of SMPCs. Afterward, they introduce the extensive applications of SMPCs in the fields of aerospace, biomedical equipment, self-finishing, deformable mandrels, and the 4D printing of active origami structures, demonstrating their ability to undergo active driving and deformation, their adaptiveness, their ease of transport, and their rapid production capacity, which fully demonstrate the unique advantages of SMPs in solving application problems. Finally, the advantages and disadvantages of SMPCs in applications are summarized, and the prospects for new SMPCs and new SMPC structures are described. Sung et al. studied the loading of the surface-modified carbon nanotube in the PU/ PLA polymer blends. For this purpose, polymer blend nanocomposites based on thermoplastic polyurethane (PU) elastomer, polylactide (PLA), and surface-modified carbon nanotubes were prepared via simple melt-mixing process and investigated for its mechanical, dynamic mechanical, and electroactive shape memory properties. Loading of the surface-modified carbon nanotube resulted in the significant improvement on the mechanical properties such as tensile strength, when compared to the pure and pristine CNT-loaded polymer blends. Dynamic mechanical analysis showed that the glass transition temperature (Tg) of the PU/PLA blend slightly increases on loading of pristine CNT and this effect is more pronounced on loading surface-modified CNTs. Thermal and electrical properties of the polymer blend composites increase significantly on loading pristine or surface-modified CNTs. Finally, shape memory studies of the PU/PLA/modified CNT composites exhibit a remarkable recoverability of its shape at lower applied dc voltages, when compared to pure or pristine CNT-loaded system as presented in Fig. 18 [64]. In the present research of Urquijo et al., melt-mixed poly(lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) 80/20 and 60/40 blends were modified with different CNT contents. Unfilled compositions were immiscible and combined good stiffness (Young’s modulus>2000 MPa), deformability (elongation at break>150%), and, in the case of the 60/40 composition, notched impact strength

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Fig. 18 The shape recovery of composites with pristine and modified MWCNTs accompanying the schematic representation of molecular structure of composites [64]

higher than 100 J/m. The morphology of the unfilled 80/20 composition showed nano-sized, spherical PBAT particles finely dispersed within the PLA matrix, while the 60/40 composition showed an almost co-continuous morphology. In the case of the nanocomposites (NCs), the CNTs located in the minor PBAT phase because of their greater compatibility, producing larger, elongated PBAT domains more characteristic of co-continuous morphology. In addition, the CNTs created percolated networks, and as a result, the NCs showed increased conductivity at CNT contents equal and higher than ≈1.5 wt% as shown in Fig. 19. Although Young’s modulus did not increase significantly in the NCs and the yield strength decreased upon the addition of CNTs, the high deformability of the unfilled blends maintained up to 150% in all the compositions, and, in the case of the 60/40 blend, the impact strength increased up to 250 J/m, i.e., 20 times higher than that of pure PLA [65]. Highly flexible, conductive, and two-way reversible shape memory polyurethane nanocomposites were prepared with the in situ synthesized method, containing different graphene nanosheet contents ranging from 1.0 to 8.0 wt% by Jiu et al. The dispersion of the nanocomposites in the polymer was monitored by scanning electron microscopy, and thermal properties, mechanical properties, electrical properties, and shape memory properties were comparatively investigated. The results showed that the nanocomposite was more stable when the content of graphene is 2 wt% in the cross-linked network structure. In comparison to pristine polyurethane, the graphene-cross-linked polyurethane composite exhibited better thermostability, breaking stress, and exceptional elongation at break. The resulting composite exhibited 93% shape fixity, 95% shape recovery of 2.0% loading, and fast electroactive shape recovery rate. Moreover, the polymers also showed good reversible two-way shape memory behaviors; thus it could be a promising material for the fabrication of graphene-based actuating devices [66]. To use shape memory materials based on poly(lactic acid) (PLA) for medical applications is essential to tune their transition temperature (Ttrans) near to the human body temperature. In their research, Sonseca et al. studied the combination of lactic acid oligomer (OLA), acting as a plasticizer, together with chitosan-

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Fig. 19 The conductivity of composites vs. the concentration of CNTs in composite [65]

mediated silver nanoparticles (AgCH-NPs) to create PLA matrices to obtain functional shape memory polymers for potential medical applications. PLA/OLA nanocomposites containing different amounts of AgCH-NPs were obtained and profusely characterized relating their structure with their antimicrobial and shape memory performances. Nanocomposites exhibited shape memory responses at the temperature of interest (near physiological one), as well as excellent shape memory responses, shorter recovery times, and higher recovery ratios (over 100%) when compared to neat materials. Moreover, antibacterial activity tests confirmed biocidal activity; therefore, these functional polymer nanocomposites with shape memory, degradability, and biocidal activity show great potential for soft actuation applications in the medical field [67]. Shape memory polymers are required to recover fast (seconds to minutes); many applications, particularly in the medical field, would benefit from a slow recovery (days to weeks). In this work, Bartolo et al. exploit the broad glass transition range of photo-cured poly(D,L-lactide) dimethacrylate networks to obtain recovery times of up to 2 weeks, at 11
C below the peak glass transition temperature of 58
C. Recovery times decreased considerably for higher recovery temperatures, down to 10 min at 55
C. A large spread in glass transition values (53.3–61.0
C) was observed between samples, indicating poor reproducibility in sample preparation and, hence, in predicting shape recovery kinetics for individual samples. Furthermore, a staged recovery was observed with different parts of the samples recovering

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Fig. 20 Results from printing test parts: (a) top view of the printed slab with a cross section of 15  7.5 mm2 and 1.5  1.5 mm2 rectangular straight pores; (b) top plane view under the microscope; (c) side view under the microscope showing the decreased pore size in the overexposed bottom layers; (d) magnification of picture (c) showing the voxel pattern; the black square represents one 50  50 μm2 pixel; (e) top view of the gyroid geometry scaffold print test. The part covers an area of 5  10 mm2 containing 3  6 gyroid unit cells with a period of 1.6 mm [68]

at different times. The ability to prepare complex structures using digital light processing stereolithography 3D printing from these polymers was confirmed as shown in Fig. 20. To the best of our knowledge, this work provides the first experimental evidence of prolonged recovery of shape memory polymers [68]. Nowadays, 4D-printed materials are an emerging field of research because the physical structure of these novel materials responds to environmental changes. 3D printing techniques have been employed to print a base material with shape memory properties. Geometrical deformations can be observed once an external stimulus triggers the shape memory effect (SME) integrated into the material. The plasticizing effect is a well-known phenomenon where the microscopic polymer chain movements have been altered and reflected in different shape memory behavior. It has been suggested that a 4D material with localized actuation behavior can be fabricated by utilizing functionally graded layers made from different degrees of plasticizing. Sun et al. demonstrated that a novel 4D material can be fabricated from material extraction continuous printing technique with different loadings of poly(ethylene glycol) (PEG) plasticizer, achieving localized thermal recovery. The schematic representation of shape memory test of composite is presented in Fig. 21. The results indicate that a plasticized functional layer is an effective technique for creating nextgeneration 4D materials [69]. An arc-shape configuration was printed to demonstrate the 4D thermal recovery ability of the fabricated sample (Fig. 22a). Detailed dimensions of the printed model can be found in the Supplementary Materials. The samples needed to be programmed into a temporary shape before 4D recovery could take place. This was done by compressing the arc-like component at 50
C to prevent any possible brittle failure. The compressed sample was then cooled back to room temperature prior to

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Fig. 21 Schematic of shape memory mechanism of arc-like 4D-printed PLA sample [69]

Fig. 22 4D-printed PLA arc (a) and flattened temporary shape (b) [69]

removal of the applied stress for shape fixing. The temporary shape training outcome is presented (Fig. 22b). No visible cracks or delamination was observed after the training process. After shape fixing, a heat gun was utilized above the component to initiate 4D thermal recovery. Videos were taken to visualize thermal recovery, while IR thermal videos were taken to measure the instantaneous temperature [69].

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Sensor Applications of Shape Memory Materials The SME has added one more dimension to potentially widen the application field of SMPs, since it is possible to utilize this feature to design a smart polymeric system to react automatically to the change of the surrounding environment in a passive manner. However, the number of successfully developed SMP products is still rather limited in the commercial market. A couple of commercial products relevant to sensor applications are listed here. The materials used in these applications do have the potential to be used in sensor applications as well [70, 71, 72]. Figure 23 presents a commercial anti-counterfeit SMP label (from Guangzhou Manborui Material Technology Co., Ltd., Guangzhou, China) before and after heating in 65
C oven for 2 minutes to get the embossed feature recovered. 3D surface scanning using a Taylor scanner reveals that the embossed feature, which indicates authentic in Chinese, is about 0.1 mm in height, which is about the same magnitude as that of the surface feature in standard bank coins and can be clearly identified via tactile sensation by fingers [66]. Shape memory polymeric splints are mostly made of poly(ε-caprolactone) (PCL) type of polymers with/without cross-linking. After heating for softening, they can be programmed at body temperature for fitting. After fitting, they become hard and stiff to provide strong support. Contrary to the memory foam, soft and elastic SMP foam is able to simultaneously achieve comfort fitting and provide enough support without compromising in elasticity. Hence, a piece of insole made of such a type of SMP foam (mostly using either ethylene-vinyl acetate (EVA) or PU) is able to maintain the shape of the foot

Fig. 23 Typical anti-counterfeit shape memory polymer (SMP) label (0.16 mm thick) available in the market (from Guangzhou Manborui Material Technology Co., Ltd.). (a) Top, before heating (as received); bottom, after heating in an oven at 65
C for 2 minutes. (b) 3D surface scanning result (using Taylor scanner), which reveals that the surface feature after heating for shape recovery is about 100 μm in height [66]

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Fig. 24 Shape memory ethylene-vinyl alcohol (EVA) insole. Top, after heating and stepping on, foot shape is captured after cooling back to room temperature; bottom, after heating for shape recovery (I). EVA heat shrink tube. The right end is heated for shape recovery (II). Commercial heat shrink label. (a) Original; (b) after heating (placed between printing transparency and tape during heating); (c) after heating (placed between two steel plates fixed by two clips); (d) after heating (freestanding) (III) [73]

after stepping on it for a while during cooling for personalization (Fig. 24 I, top piece). The foot impression can be fully removed after heating for reuse [73]. Probably the top two most successful commercial SMP products at present are heat shrink tubes for protection of cables/wires and heat shrink films (membranes) for label and packaging. Although different types of polymers are used, mostly they are cross-linked via irradiation. In Fig. 24 II, the right end of a piece of heat shrink tube, which is made of cross-linked EVA, is heated to over 80
C, which is above its Tg, so that this part shrinks remarkably. Fig. 24 III(a) is a piece of commercial heat shrink label (with screen-printed protruding oil on one side of its surface), and Fig. 24 III(b–d) present the shapes of the labels after heating under three different restrained conditions, from freestanding to restrained between two rigid plates clipped together. After heating for shrinkage of the label, strip wrinkles are formed in the area coated with protruding oil due to buckling. Consequently, if the label is heated for free recovery [i.e., without any restraint as in Fig. 24 III(d)], instability in the form of a combination of local buckling (wrinkling) and global buckling resulted.

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According to the previous definition, the SME is meant for nonreversible, one-time activation. Although the SME cycle can be repeated after reprogramming, if the programming process is practically not easy without causing any damage or misalignment, etc., sensors based on SMPs have the combined advantages of having high reliability/security and being non-repeatability/nonreusable. An extremely important issue in any real engineering application is the costeffectiveness of a product. The cost (including both material cost and processing cost) of some abovementioned successful commercial products, such as heat shrink tube, EVA/PU foam, and PCL splint, has been widely accepted by the market, since the functions that those products provide are well worth their values. However, for a new application field, for instance, in anti-counterfeit labels, the competitors are other materials and technologies, which are mostly well-developed/well-established and of low price, new unique functions must be identified to justify the high price in using SMP-based alternatives. From application point of view, film and thin sheet should be more convenient in many sensor applications. A piece of SMP film/sheet may be programmed in the in-plane direction (load applied in the length/width direction) or out-of-plane direction (load applied in the thickness direction) [73, 74]. In order to provide the same feature height of 0.1 mm as in most of coins (refer to Fig. 5), so that it could feel by fingers, the thickness of Manborui’s anti-counterfeit SMP label is 0.16 mm, which is far thicker than most commercial anti-counterfeit labels in the market. The typical thickness of hologram label is 40 μm, while the typical thickness of void paper is 100 μm. In-plane programming may be done for any thickness of film/sheet. However, to reduce the material cost, thinner film is preferred in most of the cases. On the other hand, for out-of-plane programming, it is necessary to consider both the cost of material and processing (mostly programming via impression). In the case of utilizing the structural coloring effect via nano-imprinting, although it is possible to minimize the thickness of SMP to reduce the material cost, the mold is actually the most expensive part. An ordinary mold produced by CNC machining or even 3D printing is much cheaper and well-suitable for tactual sensation by finger touching. Thus, the SMP film must have enough thickness in order to be stiff enough to maintain the surface feature upon finger touching. Heat shrink films and tubes are commercially available with different activation temperatures and mechanical properties. Typical polymers used are polyethylene (PE), multilayer co-extruded polyolefin shrink film (POF), oriented polystyrene (OPS), PET, polyvinyl chloride (PVC) for heat shrink films, and radiation-cross-linked EVA for heat shrink tubes. Biaxially oriented PET (BOPET) is the typical substrate material for hologram stickers. The technique to fabricate heat shrink films/tubes with zero Poisson’s ratio upon heating for shape recovery has been widely applied. To prevent tampering, for instance, heating to remove a piece of hologram label or void paper without causing any damage to the label/paper, the anti-heat transfer function should be integrated into the original label/paper to have, for example, selfdestroy function upon heating. Since the heating-responsive SME is an intrinsic property of most polymers, it should be able to easily integrate this effect into currently used polymers in anti-counterfeit applications to enhance the reliability of security. In Fig. 25, a very sharp blade is used to cut lines atop a piece of

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Fig. 25 Cracking in hologram sticker upon heating. (a) Original label, in which no apparent crack can be observed and the color appears vivid; (b) after heating by hair dryer, cracks are apparent and the color turns dull; (c) removal at high temperatures results in tearing of the label [66]

Fig. 26 Anti-heat transfer quick response (QR) code. Left, modified label; right, without modification which is always readable. (a) Before heating, both are quickly readable by smartphone; (b) after heating, the left is unreadable or takes much longer time to read, while the right is still quickly readable as before [26]

commercial hologram sticker. These lines are not easily visible by naked eyes (Fig. 25a). After heating using a hair dryer, these lines open wider, so that it could easily see and thus the label is damaged and the original vivid color turns dull, most likely due to heating-induced surface recovery (Fig. 25b). These precut lines serve as a way to prevent removal of the label at both low and high temperatures, which is able to effectively prevent heating and then the subsequent removal of the anticounterfeit labels (Fig. 25c). This approach can also be integrated into conventional void paper to prevent tampering at high temperatures. Due to the fast readability and greater storage capacity, quick response (QR) code has become a very popular way right now in product tracking, item identification, time tracking, document management, etc. The same heating-then-cracking concept shown in Fig. 25 can be applied to result in anti-heat transfer QR code for improved security as well. As demonstrated in Fig. 26a, before heating, both QR labels with and without modification can be easily identified by a smartphone with QR code scanning function. After heating, a small line crack appears on the upper left corner of the modified label (Fig. 26b). Depending on the exact software used to read the QR code, some take longer time to read the code, while some just cannot recognize the code anymore. Of course, with further modification (e.g., with more precut cracks and larger programming strain), it could make the QR code completely unreadable after heating.

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Stripe interference between two layers with patterns printed atop (Moiré pattern) is another possible application using SMP to produce the moving effect during heating-induced shape recovery. Three examples are illustrated in Fig. 27. In Fig. 27a, upon step-by-step heating, the top layer, which is transparent, moves up

Fig. 27 Moving Moiré pattern based on the shape memory effect (SME) upon gradual heating. (a) Vertical shifting of the top layer upon gradual heating; (b) rotating of the top layer upon gradual heating; (c) vertical shrinking of the top layer upon gradual heating [66]

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gradually, while in Fig. 27b, upon heating, the top transparent layer rotates slightly. Figure 27c is different from above two cases, as the top layer shrinks upon heating. A closer look reveals that there is a fixed relationship between the number of black bands and the actual strain due to shrinkage. Hence, after calibration, this phenomenon may be used in strip-shaped temperature sensors to monitor the maximum heating temperature. Figure 28 demonstrates two possible ways to integrate the heat shrink function with QR code and barcode, respectively, to add in anti-heat transfer function into the original codes. As shown, after heating, both codes become readable and indicate void when scanned to show that both labels have been tampered by heating. The SME in polymeric materials is able to provide not only visible (to see) but also tactile (to feel) change after shape recovery. The latter function is lacking in most of the current anti-counterfeit labels, except the shape memory label in Fig. 5, in which a special polymer with a Tg around 60
C is used. The unique tactual sensation enhances the competitiveness of SMP products and distinguishes them with the products based on other technologies. By selecting a right commercially available engineering polymer, instead of using a newly developed special SMP, it could not only dramatically lower down the cost but also produce anti-counterfeit shape memory labels with the required activation temperature. To increase the difficulty in replication, it might be designed in such a way that upon heating, the pattern of a special microprotrusion array on one side of a plastic film disappears, so that the underneath printed pattern on the other side loses the 3D effect. In Fig. 29a, the microlens array is produced atop a piece of pre-compressed optical polymer film using laser through a microlens for heating of the required locations only. Such a microlens array effect has been applied to realize 3D with naked eyes. The underneath image is specially designed to have more than one picture integrated together (e.g., in Fig. 29b). Through this microlens array, from different viewing angles, it can be seen different individual images (e.g., elephant or tiger in Fig. 13b). If the surface becomes smooth upon heating, the image appears as a mixture of elephant and tiger. The difficulty to perfectly match the image on one side to the microlens array on the other side is a big technical challenge, if anyone attempts to reproduce the 3D effect in a cost-effective way. Customized feature,

Fig. 28 Anti-heat transfer quick response (QR) code (a) and barcode (b). (a) Left, before heating (unreadable); right, after heating (readable to show void). (b) Left three, before heating (unreadable); right, after heating (readable to show void) [66]

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Fig. 29 Array of protrusive microlens which disappears upon heating (a), and without microlens array, the image is a combination of tiger and elephant (b) [67]

which appears upon heating, may be produced by 3D printing as an additional security measure. A highly interesting feature of PCL is that it is able to crystallize/harden at around body temperature after being heated to over its melting temperature, which is about 60
C. Furthermore, at around body temperature to room temperature (about 20
C), the crystallization process takes a few minutes to finish. This feature provides us with abundant time for programming to achieve comfort fitting in those applications, where direct contact with the human body is required [75], such as commercial shape memory splints to fix fractured bone or to stop snoring (e.g., myTAP™ from Airway Management, USA). After cross-linking or blending with other polymers to result in SMHs (in which PCL works as small inclusions), both high shape fixity ratio and high shape recovery ratio could be achieved and in the meantime maintain the abovementioned special features of PCL that are particularly suitable for directbody-contact-fitting. As demonstrated in Fig. 30, the material can be heated to above its melting temperature, and then our 3D fingerprint can be inscribed on the material at room temperature or around body temperature via a single gentle impressing of the finger on the surface of the material. The fingerprint can be fully removed by reheating. The cross section presented in Fig. 30c reveals that the fluctuation in the depth of our fingerprint (adult) is about 70 μm. The phenomenon for the formation of protrusions upon heating can be utilized as a temperature sensor as well. In Fig. 31, the height of a protrusion increases remarkably when it is heated to over a critical temperature, which might be tailored by programming, so that the silver epoxy adhesive atop of the protrusion fractures. Consequently, the electrical circuit, in which the silver epoxy adhesive is part of the circuit, shuts down. Since the glass transition in most polymers is sensitive to the equivalent time-temperature effect, melting transition could be a better choice in such applications. Furthermore, based on the concept of shape memory hybrid (SMH), other non-polymeric materials, such as metals, could be used as the

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Fig. 30 3D fingerprint (2% cross-linked poly(ε-caprolactone) (PCL)). (a) Top view of 3D scanning result. (a1) After finger impression; (a2) after heating, the fingerprint disappears. (b) 3D fingerprint. (c) A-A section of fingerprint

Fig. 31 3D surface scanning results of ethyl-vinyl alcohol (EVA) after programming and coating with silver epoxy adhesive (a) and after heating for shape recovery (b). The height of the EVA protrusion increases from 0.48 mm to 1.6 mm after heating

transition part to achieve a narrower transition temperature range and less sensitivity to the equivalent time-temperature effect [76, 77]. In uniaxial stretching of many polymers at low temperatures, necking and propagation can be observed. After this process of programming, PCL may change from opaque (for thick piece) or translucent (for thin piece) to transparent due to stress-induced crystallization. After subsequent heating, PCL becomes opaque or translucent again. This phenomenon (transition from opaque/translucent to transparent upon severe straining and upon subsequent heating from transparent back to opaque/translucent) may be utilized for anti-counterfeit applications, so that once heated, the feature behind these polymers becomes invisible (thick piece) [78]. While this transition phenomenon is limited to some specific polymers, the stress whitening effect (even silver streaks) is commonly observed in many polymers. Folding a piece of write-on transparency film, which is PVC based, results in a white line, which can be removed by heating to above its Tg (about 60
C). If examined under a microscope, it can be seen many micro lines within the white line,

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and even the structural coloring effect can also be observed. Most of these lines disappear after heating, and so is the structural coloring effect. The diameter of the fibers produced via electro-spinning can reach submicron scale. Even the bulky polymer itself is transparent; the very thin mat produced by electro-spinning could be fully opaque and even in shiny silver color. Upon heating, such a mat made of, for instance, abovementioned PCL or TPU 265A becomes almost transparent [79]. PET is a popular engineering polymer used in a wide range of applications, such as substrate of RFID, printing transparency film, heat shrink film, optical lens (such as lenticular lens and Fresnel lens), etc. Its Tg is typically around 70
C. The heatingresponsive SME of a commercial 75-line-per-inch (LPI) PET lenticular lens sheet, which is placed atop a piece of paper with printed regular line pattern, is demonstrated in Fig. 32. In Fig. 32a, it can be seen regular parallel lines atop the original sheet. After heating and compression to flatten the lens, the lines observed in Fig. 32 a largely disappear (Fig. 32b). Heating to over 80
C again results in the return of the same parallel lines (Fig. 32c) as in Fig. 16a. The underlying mechanism behind this is the heating-responsive SME in the lenticular sheet and the Moiré effect. A Rockwell Hardness Tester DXT-3 is used to make an indent on a piece of Fresnel lens at room temperature. A spherical head is used for impression with a maximum load of 15 Kg. Figure 33a is 3D scanning result after indentation. In Fig. 33b, the cross sections along the dashed line indicated in Fig. 33a are compared for three occasions, namely, after indentation, upon heating to 60
C, and then 80
C. It can be concluded that unlike the abovementioned lenticular lens, in which the shape of the lens is permanent, the profile of this Fresnel lens is most likely produced by hot embossing at around 80
C. Thus, upon heating, not only the indent but also the original feature of Fresnel lens disappears. Flexibility is highly in demand in many types of nonrigid sensors, such as stick type of labels, in order to avoid the problem of easy fracture, which is indeed a major problem in the SMP label. Rubberlike polymeric SMHs are made of silicone mixed with an EVA-based melting glue at high temperatures and then adding in agent for

Fig. 32 The shape memory effect (SME) in a 75-line-per-inch (LPI) PET lenticular lens sheet placed atop a piece of paper with printed regular line pattern. (a) Original lenticular lens sheet; (b) after compressing of lenticular lens sheet at high temperatures; (c) after heating of lenticular lens sheet for shape recovery

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Fig. 33 The shape memory effect (SME) in a commercial Fresnel lens. (a) Surface profile of Fresnel lens after indentation. Dashed line indicating the cross section to be analyzed in (b); (b) cross sections of Fresnel lens after indentation and upon heating to 60 and 80
C, respectively

Fig. 34 Designed mold (a), ethyl-vinyl alcohol (EVA) plate after impression (b), and (c) heating temperature vs. number of recovered parallel lines relationships in three labels prepared using different processing parameters (different programming temperature and different compressive force)

curing. A perfect combination of super-elasticity, which is tunable, and excellent heating-responsive SME enables labels made of such SMHs not only flexible for bending and twisting but also stretchable for significant elongation. In Fig. 34a, b, a mold with one single protrusion (variable triangle cross section) atop is used to impress on a piece of EVA plate with pre-marked parallel lines atop. Upon gradual heating, shape recovery starts from one end and moves toward the other, and thus, more and more lines become straight again. As such, the shape recovery progress, which is related to the highest heating temperature, can be revealed directly by counting the number of recovered parallel lines within the indented area. Figure 34c presents typical experimental results of three such labels programmed using different processing parameters (different programming temperature and different compression force). It is obvious that by means of increasing the density of the parallel lines, better heating temperature estimation is expected. So far, all abovementioned applications are based on the heating-responsive SME. As water is easily accessible, various reversible water-activated anti-

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counterfeit labels have been in the market for some years. On the other hand, costeffective wetting sensors, such as labels to indicate whether a particular item has been wetted by water and then dried back, are also useful. Different materials are used in dental treatments, such as plaque removal, caries treatment, aesthetic interventions, teeth reconstruction, and implants. Indeed, dental material could be made from diverse sources, from metal alloys to SMPs. The advantage to using polymers in dental materials is their high biocompatibility and durability in implants as well as in restoration procedures, among others. Furthermore, SMPs have been used to avoid the biofilm formation during the caries or root canal treatment as well as in implants. Branched SMPs are replacing the metallic wires in orthodontic treatments. Indeed, the advantage of using SMPs instead of metal alloys is that the SMPs do not release metallic ions, which could cause chronic diseases. Moreover, most parts of the SMP degradation sub-products present high biocompatibility. Additionally, the nanocomposites made with SMPs could be applied as platforms for multi-applications, such as sustained release, roots fillers, and biofilms preventative agents, among others [80].

Some Companies with SMP Products Guangzhou Manborui Material Technology Co. (https://manborui.en.ec21.com) Manborui is the exclusive SMP security label producer, which combines research, design, production, and sales. Manborui has experience in the SMP development field and produces shape memory polymers which activate at low/medium temperature. Manborui has in-depth knowledge about the FDA-approved SMP material for medical grade standard. An exclusive label film made from SMP has been developed and supplied for security label printing, which can store embossed logo/text shape information in the synthetic-paperlike film and release these information when exposed to 65
C heat in just seconds. As the producer and supplier of SMP, Manborui’s SMP products for security label printing include SMP label film, SMP label stock, and also security labels, security seal. A SMP label film, specially developed for security label printing, supplied in rolls or sheets, with covert and embossed pattern message hidden inside the label film, on which any of label designs can be printed-transferred to unique security labels (Fig. 35). The label film is applicable for high-quality security labels, security tags, security seal, security tickets, and security coupon (Fig. 36).

Cornerstone Research Group Co. (http://www.crgrp.com)

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Fig. 35 Manborui’s SMP security label film. Weight of label film, 200gram/m2; thickness of film, 0.18 mm; color and finish, white (also available in transparent); activation temperature, 65
C; activation is irreversible SMP rolls; width, 300 mm; core diameter, 75 mm

Fig. 36 Sample application of SMP label film for security label

Cornerstone Research Group’s new rapid-release, shape memory fastening technology uses the unique properties of Veriflex ®, a SMP material. At a specific temperature, this material changes from a rigid state to an elastic state and then returns to a rigid “memorized” state again. Cornerstone Research Group proposes a novel reusable mandrel system utilizing SMP. This technology leverages CRG’s previous R&D from both commercial and governmental programs. In Phase I, CRG will develop a lab-scale prototype SMP mandrel system. The SMP mandrel will offer the Air Force a solution to the current composite fabrication and repair issues. Our goal is to provide a single mandrel system design that will allow quick transition to multiple desired mandrel shapes, maintain structural rigidity through filamentwinding conditions, and then offer a simple and rapid extraction process. The

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proposed mandrel system would function similarly to a rubber inflatable mandrel during insertion and removal; however it would offer structural rigidity like current melt-out and breakout systems during fabrication. This type of mandrel system can only be offered by using a material capable of sharp, controllable, transitioning properties. CRG’s shape memory materials possess these unique property traits. CRG will begin to develop designs and calculate the forces the tooling will experience during the composite fabrication at a lab scale to demonstrate feasibility for Phase II scale-up. The part will contain design aspects that will demonstrate the SMP mandrel system capabilities.

MedShape Co. (https://www.medshape.com) MedShape’s team of engineers and scientists have a proven track record in understanding and developing SMPs. Though other researchers have developed numerous formulations of SMPs, MedShape was the first company to have FDA-cleared and commercialized medical devices manufactured from shape memory polymers. Their proprietary PEEK Altera ® biomedical polymer allows devices to enter the target surgical site in a compact geometry and then be mechanically triggered to deploy into the optimal geometry for maximum fixation inside bone (Fig. 37). PEEK Altera offers many clinical advantages over regular PEEK such as increased deformability without compromising the material strength and toughness, less invasive insertion approach, and reduced force requirements to deploy. Devices manufactured from PEEK Altera are biocompatible, biostable, radiolucent, and MRI safe.

Shape Memory Medical (https://www.shapemem.com) Shape Memory Medical is a California-based medical device company. The team has extensive experience with the SMP technology and the commercialization of medical devices and continues to develop and innovate new therapeutic solutions using SMP technology. Shape Memory Medical is dedicated to developing innovative therapeutic solutions for peripheral vascular, cardiovascular, and neurovascular markets. Shape Memory Medical is a medical device company to introduce an FDA-cleared medical device utilizing SMP technology to a vascular market. The TrelliX Embolic Coil includes a novel SMP porous embolic scaffold, which offers significant advantages in neurovascular and peripheral vascular embolization. The IMPEDE Embolization Plug is indicated to obstruct or reduce the rate of blood flow in the peripheral vasculature. The IMPEDE Embolization Plug comprises a shape memory polymer plug and an anchor coil. The porous embolic scaffold supports the rapid formation of small interconnected clots throughout its structure. The biocompatible and non-inflammatory polymer promotes rapid conversion to organized thrombus, followed by collagen deposition without chronic active inflammation, which leads to a stable occlusion.‡ The anchor coil offers stability in higher-

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Fig. 37 PEEK Altera the product of MedShape Co.

flow locations, and IMPEDE may be used in combination with IMPEDE-FX to minimize artifact in a single vessel. Vascular plugs predictably and effectively fill space in a short time, generally leading to shorter procedure times and less radiation exposure. Each IMPEDE Embolization Plug offers a high embolic material volume and inherent 100% packing density. Packing density has been shown to be an important factor in avoiding recanalization. The SMP portion of the device has no artifact, which facilitates follow-up imaging (Fig. 38).

Shandong Yabin Medical Technology Co. Ltd. (http://m.en.crossnt.com/company-374.html) Shandong Yabin Medical Technology Co., Ltd., established in 2015, is a high-tech enterprise located in Shandong province. Depending on its patented technology, the

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Fig. 38 IMPEDE indication, a medical device used to treat bleeding abnormalities by deliberately blocking blood flow

company designs, produces, and sells series of products such as functional low-temperature thermoplastic splint sheets, splinting precuts, and radiotherapy fixation masks. With a professional design team, a series of advanced automation equipment, and an innovative marketing team. A sample product of the company is Orthopedic fracture thermoplastic splint for finger/Thermoplastic (Fig. 39). The material is able to be softened and modeled under relatively low temperature. Under normal room temperature, the functional positioning membrane is in solid state and firm texture. Under the temperature of 60–70 degrees, the material is able to be activated in 2–3 minutes which will be soft and plastic. The positioning membrane is light, permeable, strong, and with high plasticity. It also has the advantages of good penetrability of X-ray, nontoxic, odorless, and biodegradable. By adding nano-antibacterial and far-infrared material, with the function of anti-bacteria and improve microcirculation.

Asahi Kasei Corporation (https://www.asahi-kasei.co.jp) The Asahi Kasei Group is a diversified manufacturer centered on chemistry. The history of the Asahi Kasei Group is rooted in Japan’s first ammonia production by chemical synthesis, using hydroelectric power, which formed the basis for our synthetic chemicals and chemical fibers businesses. Asahi Kasei Group now contributes to life and living for people around the world through our operations in the three business sectors of material consisting of fibers, chemicals, and electronics; homes consisting of homes and construction materials; and health care consisting of pharmaceuticals, medical devices, and acute critical care. The products, technologies, and services of the Asahi Kasei Group can create new value that helps society overcome current challenges by contributing to a clean environment, to clean energy, and to longevity with health, comfort, and peace of mind. One of the Asahi Kasei Group products is SMP resin, resin composition and the shape memorizing molded

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Fig. 39 Orthopedic fracture thermoplastic splint for finger/ Thermoplastic, applicable in orthopedics, rehabilitation, surgery, burn

product. The Shape-Retaining Doll Hair was developed for pretend-play dolls. It offers easy hairstyling for enjoyment (Fig. 40).

Changchun Foliaplast Bio-Tech Co., Ltd. (http://foliaplast. globalchemmade.com) Changchun Foliaplast Bio-Tech Co., Ltd., established on 2015, which is a modernized technological company mainly focuses on biomedical materials and high-end medical equipment. The company mainly dedicated in the industrialization implementation of “The Fourth-Generation Biomedical Materials,” polylactic acid, poly (L-lactide-co-glycolide), poly(ε-caprolactone), and so on in the medical field, which includes the following: plastic filling injection “Sculptra,” bioabsorbable intrabony fixers (nail, board, bar, pin, and so on), bioabsorbable cannulae implantation in the surgery, bioabsorbable surgical suture, bioabsorbable hemostatic clip, bioabsorbable ophthalmology filler, bioabsorbable dentistry filler, drug sustained-release packing materials, and new type biological tissue engineering devices. Medical grade biodegradable and bioabsorbable PCL raw material. Poly(ε-caprolactone) has excellent biocompatibility, shape memory, biodegradability, etc. It is widely used in various fields. PCL is soft and easy to process. It can be used as tissue engineering scaffolds. PCL has low degradation rate and high crystallinity. Its degradation can be divided into two stages in the body. The first stage is that the molecular weight of PCL declines, but no deformation and weightlessness. The second stage is the molecular weight of PCLs to a certain value, which is followed by the weight loss, gradually uptake and excreting by the body.

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Fig. 40 Shape-Retaining Doll Hair

Composite Technology Development Co. Ltd. (https://www.ctdmaterials.com) Composite Technology Development, Inc. (CTD) specializes in developing state-ofthe-art materials and products for extreme conditions and demanding applications. CTD Engineered Materials Portfolio has over 20 commercial resin systems. CTD specializes in developing boom deployers, composite booms, solar arrays, and SMP composite hinges. The folded configuration of self-deployable structure after heating and stress-induced deformation is presented in Fig. 41 [76].

EndoShape Inc. EndoShape is a venture-backed company seeking to improve embolization procedures for patients and physicians through the application of advanced polymer technology and unique device design. Neurovascular and peripheral vascular embolic coils were fabricated using a novel, photopolymerized SMP (EndoShape Inc., Boulder, CO)

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Fig. 41 Shape memory recovery process of self-deployable structure. Resin from Composite Technology Development, Inc. [81]

specifically formulated to provide radiographic and MRI visibility while minimizing MRI artifacts. Control SMP coils were prepared using a standard formulation of tertbutyl acrylate and poly(ethylene glycol) dimethacrylate [82].

Lubrizol Advanced Materials Co. (https://www.lubrizol.com) The thermoplastic polyurethane (TPU)-based SMP Estane is the SMP-based product of the company. The ESTANE ® TPU (thermoplastic polyurethane) product line consists of polyester, polyether, and specialty polymer compounds. It is a soft, flexible innovative material for custom and complex 3D-printed designs.

Nanoshel LLC Nanoshel LLC is a Wilmington, Delaware-based nanotechnology company specializing in the commercialization of wide range of nanoparticles and innovative materials. SMP resin (potting), shape memory resin solution (coating), and SMP pellet PMM (injection, extrusion) are the Nanoshel products.

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Part VII Consumer Nanoproducts Based on Biocompatible Nanopolymers

Bionanoceramic and Bionanocomposite-Based Nanoproducts: Concepts, Processing, and Applications

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plant Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alginate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cellulose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Animal Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chitin and Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gelatin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiwalled Carbon Nanotube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polystyrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polyamide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polyaniline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polyvinyl Alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carrageenan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Bionanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ceramic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoceramic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of Nanoceramic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Another Preparation Methods of Nanoceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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T. Arfin (*) Environmental Materials Division, CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nagpur, India Hyderabad Zonal Centre, CSIR-National Environmental Engineering Research Institute (CSIRNEERI), Hyderabad, Telangana, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_27

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Abstract

The application of nanomaterials in various scientific and research field has driven progress and development. It has scientifically proved unique opportunities for future advancement due to distinctive features, namely, chemical inertness and comfortable design. Mechanical alloying is a processing technique that is simple, convenient, and sophisticated, and it has persuaded researchers due to underlying features. The material is nanoscale filler and acquires various attributes, namely, high surface area, strong interaction, and low loadings. As per the recent studies, it is observed that nanocomposite is renewable and eco-friendly and casting is minimum and is applied widely. They also reply to issues like challenging energy, pollution, as well as the environment. The possible combination of engineered nanomaterial with flexible polymers provides a critical opportunity for instantly creating and adequately developing the novel valuable material filled with enhanced properties and is a crucial comparison to the material used in the starting phase. In the current book chapter, the highlight is substantially done on applying the material, new conclusion, and future perspective. Keywords

Biocompatibiliy · Polymer matrix · Nanofiller · Bionanocomposites · Bionanoceramics

Introduction The composites are typically comprised of two or more than two essential components which, after properly joining, naturally possess various unique properties either by physical or chemical means. The biocomposites are the necessary material composed of natural and non-biodegradable polymer [5]. Various academic researchers have given the modern concept and valuable information about biocomposites. The bionanocomposite is the distinct class of nanocomposite, including the naturally attained synthetic biofunctional polymer where the size of nanoscopic species is between 1–100 nm, which is responsible for influencing the continuous activity of the composite system [7]. These composites possess various innovative and multifunctional features, namely, biodegradability, antimicrobial activity, and biocompatibility [40, 73]. The distinct parts of such nanomaterial present an extraordinary combination of the polymer with deep concentration, leading to produce the desired products [26]. The efficient and ubiquitous applications enable the bionanocomposite to yield nanomaterial in the polymer systems [8]. From the initial stage of the nanocomposite, a prominent scientist has been working effortlessly in this field due to the attainment of nanohybrid as the functional and structural materials [17]. Along with various critical aspects, the bionanocomposite also shows biodegradability and biocompatibility [59]. However, the bionanocomposite has been instantly recognized as an exciting field because it

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gets synthesized and fabricated easily and in the same way as conventional polymer composites [43]. To adequately develop pollution-free quality, the critical component of bionanocomposites should be altered, which can aid in cleaning the environment, and it can be even degraded [64]. In conclusion, it is observed that individual nanocomposite constituent contains beneficial features [41]. On the consistent basis of precise nature, the effective method for adequately preparing key components, practical application of various bionanocomposite is different from the standard form of the nanocomposite [55]. During 2004, the academic studies on bionanocomposite showed that they mostly used silica nanoparticles and rubber, but since 1941, such materials were reinforced. The bionanocomposites were adequately prepared by naturally making use of polymer matrices which could instantly naturally degrade as inevitable by-product, namely, H2O, gases, and biomass. The end products are then absorbed and eliminated. The biodegradation process is natural. Elementary derivatives are mineralized and then again distributed by the active system’s predictable cycle. The polymer matrix is a source of the biological carrier, and it breaks down as it satisfactorily completes its key objective through the metabolic process of hydrolysis or chain scission. From 1990 to 1992, the term biodegradable was unknown, and the concept was not clear, which created a raft in cleaning about the deceitful and misleading environment. It finally carefully brought about the procurement of precisely defining it with all the standard test protocol and the suitable methods [44]. The functional features and more enhanced capability were typically observed in the bionanocomposite materials (BMs). It was applied in nanosensing for properly packing materials, nanocoating, and self-cleaning uses. At present, such materials are not up to the mark to compete with or replacing petroleum yield plastics because BM is not vital to be used in water and it wets easily finally and it spoils the food. The BM is not capable enough to be employed in a moist environment. Therefore, there was a need to enhance BM either by selecting a suitable polymer or by practical processing techniques, and they should also be cost-effective. The other most important aspect that should be adequately considered is that the food items should be safe in the respective packaging material and gently free from possible contamination. On the gradual incorporation of recent innovative technology, including antimicrobial activity, research is willingly undertaken to develop nanocomposite with minimum toxic effects, and they should also be eco-friendly as well. Clay represents a suitable option properly as it can improve the polymer biodegradation tremendously by uniquely combining the biopolymer like cellulose [10, 71].

Resources Renewable resources (RRs) are precious in the current scenario. They possess ubiquitous features providing various component of feasibility and enhancing the significance of polymeric materials [56]. RR remains the vegetable species or noble

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animals that get economically exploited without the practical use of endangered species, and some biological activities can renew it. On the specific application of RR, the country’s economic growth increases, familiarly most of the developing countries where the biomass, as well as agricultural resources, are abundant and are generating the critical properties of self-sufficiency.

Plant Resources Plant resources (PRs) such as abundant seeds, fruit, and flower are synthesized from a private collection of distinct species in the localized form, posing inadequate tropic importance for the potential consumers. PR’s unique composition in possible terms of excellent quality is lignin, and cellulose and the species-particular components traditionally include steroids and rubber.

Alginate Alginates comprise structural components in the concerned family of Phaeophyceae, and it is not found in the plant of land [72]. The prominent member of Phaeophyceae, brown seaweeds, is naturally found in marine water where the water content represents 90% along with polysaccharides. They possess various features such as cost-effective, safe, non-toxic, and biocompatible, processed quickly into gel [29]. They can absorb water to a large extent, and they can be used as a slimming material in the paper and textile industry.

Cellulose Cellulose is resistant to strong alkali with 17.5 wt%. It undergoes hydrolysis’s creative process at the acidic condition for water-soluble sugars [27]. Cotton fibre and wood are the primary raw material for synthesizing cellulose bioplastics [32]. There are various distinct classes of cellulose-like cellulose nanocrystal [48], bacterial cellulose [49], nanofibrillated cellulose [51], and ethyl cellulose [12, 18, 19, 60, 62]. The cellulose exhibits safe dispersibility properties once it is appropriately used [63]. At present various potential applications of cellulose are being observed, so large amounts of cellulosic waste material are adequately prepared from industrial and agricultural behaviour [9].

Animal Resources For PR, all the traditional technologies are unused, so animal resources (ARs) are implemented where wool, animal fats, and leather are monographed. These local resources are correctly used to progressively improve the quality aspect as such resources’ profitable employment was not objected.

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Chitin and Chitosan Chitin ranks second in the polysaccharide that is available within a similar organism. The unique structure of chitin and cellulose is the same, but it is instantly found that the producing organism is different for both chitin and cellulose [3]. It has a microfibrillar arrangement where the fibrils are embedded in a protein matrix with a diameter ranging between 2.5 and 2.8 nm [61]. There is precisely some fundamental limitation for chitin being traditionally used as flocculant, and it generally works at a limited pH [20]. Chitin deacetylation is responsible for adequately obtaining chitosan. It naturally occurs in incredible abundance within the marine shellfish as biocompatible [2].

Gelatin Gelatin consists precisely of a distinct type of key protein composed of 19 essential amino acids. It is derived from bodily tissue and is appreciated from an early age, but it was operated for the first time as glue in 600 BC [47]. The primary gelation source is naturally bovine hides, pigskin, and cattle bones. It proves an extraordinary ability to produce a film. The manufacture of gelatin became industrialized, and now the application of this protein is gaining interaction as well.

Starch Indeed in this typical day, the possible use of starch is the same as earlier, where 60% of it is correctly employed for food purposes and 40% as industrial applications [65]. The leading chemist carefully studying carbohydrates has merely invented various valuable items, sufficiently establishing starch use [57]. Starch is fixed as bioplastic directly as it possesses diverse aspects like it is water-soluble and articles developed get swell up. It is deformed when brought in direct contact with the moisture, finally limiting the excessive use it [28].

Protein Responsible proteins are typically the most critical and experiment friendly macromolecules with the specific residue of long-chain amino acid, commonly called polypeptide [42]. The name is understandable about its importance and its suitability as it is fundamentally concerned about the physiological methods [13]. Since all the specific proteins are typically composed of amino acids, they naturally possess varied features and function. The academic studies and extensive research for adequately developing adequate protein composite will open the way of future perspective, enabling to enhance the fundamental properties positively [52, 53].

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Multiwalled Carbon Nanotube Multiwalled carbon nanotubes (MWCNTs) consist of various graphite layers instantly surrounded and gently folded on each other as stable form [50]. The simple carbon nanotubes (CNTs) show insoluble behaviour in the polar solvent because of the continuous availability of the hydrophobic surface. It is not adequate to functionalize the polished surface of CNT, enabling it to be soluble in an aqueous solution. It acts as biocompatible and least toxic in practical application [4]. MWCNTs progressively increase the polymer matrix’s thermal conductivity and are responsible for the economic advancement of considerable strength and dispersibility of the composite.

Polystyrene Polystyrene consists precisely of aromatic polymers made by the styrene monomers, and the creative process of manufacturing is cost-effective and minimum [39]. It possesses various features as it acts as an excellent matrix binder exhibiting crystalline structure [21]. It is cell-dependent on continuous dual staining where apoptosis traditionally dominates cell death [58]. It indeed possesses extraordinary features, namely, dielectric [16], impedance [34], electrical double-layer capacitance [35], DC electrical conductivity [14], ionic transport effect [36], irreversible thermodynamics [25], enthalpy [23], potential [24], charge density [22], entropy [11], antibacterial activity [1], cell viability [66], etc.

Polyamide The main commodity polymer is an aliphatic polyamide called nylons. There are properly various distinct types of nylon like nylon-6, nylon-12, nylon-46, nylon-66, and nylon-612 [15]. At present, the prime focus is adjusted on bio-based polyamide thermoplastics developed either partly or wholly from renewable resources [37]. For efficiently producing the polyamides, monomers synthesized by castor oil get fermented. The particular synthetic pattern for obtaining polyamides is similar to the other synthetic polyamide, and hence a considerable number of commercial products are forwarded in the market.

Polyaniline For the last 10 years, a conducting polymer, polyaniline (PANI), obtains a highly studied substance [33]. It exists in a different form with varied physical as well as chemical features [38]. PANI is tough to be processed when putting in a comparative study with other conventional polymers. The manufacturing process of PANI is unusual because of the rigid skeleton framework since it is referred to as a high

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conjugation level [68]. From the other perspective, it is carefully observed that PANI is correctly applied in essential medicine and modern biotechnology, but yet its biocompatibility data is minimal. The primary reason behind such a situation is proper to the reaction of intermediates and monomer, which obtain aromatic amines, and it is also harmful.

Polyvinyl Alcohol Polyvinyl alcohol (PVA) consists of a synthetic and water-soluble polymer, typically exhibiting various outstanding features, namely, biocompatibility, excellent transparency, and biodegradability [31]. It is recognized as a commercially available product derived as a combined production cycle in the petrochemical industry. It cannot be manufactured through monomer’s direct polymerization process since the vinyl alcohol gets converted rapidly as an enol form of acetaldehyde. This possible mechanism is due to the thermodynamic aspect, naturally limiting the kinetic control [45]. Very few valuable information is there on biodegradation-mediated PVA economically driven by beneficial microorganisms except responsible bacteria. The first report on PVA biodegradability based on Fusarium lini-specific activity is phytopathogenic mycete.

Carrageenan In the year 1837, carrageenans were first extracted from seaweeds. The extraction process was carried correctly from the prominent Rhodophyceae family [6]. The sulphate groups present in carrageenan were anionically delivering the chemical reactivity. The brief explanation of the carrageenan extraction mechanism is under secret by modern manufacture on a trade basis. Figure 1 exhibits various steps occurring at the time of carrageenan extraction in the form of a flow chart.

Fig. 1 Flowchart diagram for the extraction of refined carrageenan from seaweeds

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Fig. 2. Various types of applications of bionanocomposite

Applications of Bionanocomposites The bionanocomposites have undoubtedly gained considerable interest, and it is brought up as important material in the technological era. Such necessary material’s unique performance has positively enhanced in direct comparison to others in possible term of considerable flexibility, cost-effectiveness, and so on. It has shown a large extent of application as well. Figure 2 exhibits the applications of bionanocomposites.

Ceramic Ceramic is the main topic of interest for 100 years because of various features like stiffness, hardness, and chemical stability. Recent innovative development has been generated in the growth of ceramic by a unique application and applying military technology, arising interest for health safety and environmental advancement. Ceramics are divided into two parts, traditional and conventional ceramic comprised of clay and clay-based material assembling the synthetic raw material with functional and structural features. Most of the compound has both covalent and ionic bonding. The salient features of materials are dependent on dominant bonding approaches. Clay is considered ubiquitous raw material for fulfilling a higher-temperature ceramic category. The properties of ceramics are controlled through the crystal structure and composition of

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the significant constituent and by the behaviour and quantity of accessory mineral available. The mineral of clay can comprise a layer or chain structure. The proper ratio of layer structure is 1:1 and 2:1. Figure 3 describes the classification of the clay mineral.

Nanoceramic Nanoceramic has an interest in the past few years because of its properties such as extraordinary processing and bioactivity. It can be easily manufactured as it has ordinarily required porosity, proper size, as well as shape. The nanoceramic is naturally of four particular categories based on unique structure – zero-dimensional, one-dimensional, two-dimensional, and three-dimensional structural. The bioceramic has the macro- and nanomaterial which is not regular for the past few years. It is operated in applications such as teeth and bone. Figure 4 exhibits various progressively extent nanoparticle ceramics.

Fig. 3 Different types of classification of the clay mineral

Fig. 4 Different types of applied ceramic nanoparticles

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Fig. 5 Applications of nanoparticle ceramic

The nanoceramics, namely, titanium oxide (TiO2), alumina (Al2O3), hydroxyapatite (HA), zirconia (ZrO2), and silica (SiO2), are instantly made from synthetic pathways for merely enhancing the physiochemical features to deduct the toxicity. Figure 5 reasonably relates to the applied nanoparticle ceramic and its application.

Preparation of Nanoceramic Figure 6 typically indicates the various methods of manufacturing nanoceramics. Such innovative approaches efficiently generate different types of nanoceramic, showing varied shapes, unique composition, and valuable properties.

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Fig. 6 Various process of development of nanoceramics

Another Preparation Methods of Nanoceramics Figure 7 summarizes another distinct method of extensive preparation for nanoceramics.

Calcium Calcium is the leading element of our considerable body and is vital for the proper functioning of specific muscles, prominent bones, and immune cells in the developing organism. Figure 8 shows the various forms of calcium phosphate present in large amounts in the controlled environment. Hydroxyapatite (HAP), calcium phosphate, is uniquely an inorganic component present in all mammal teeth and bone. Bones are made up of collagen molecules and apatite. The physico-chemical features are carefully formulated as per the synthetic HAP crystals for continuous optimization of the biomedical uses. Calcium phosphate serves as the carrying agents for novel agents, namely, drug and antigens, which are employed for treating cancer. It is claimed as a delivery device for antibiotics. Reports suggest that HAP can be combined with various chemical agents for influencing the therapeutic effect [69]. The calcium carbonate nanoparticle is present in substantial quality within the environment in the various sources as eggshells and bones. There are different merits of CaCO3, such as cheaper, biocompatibility, and so on. It is traditionally employed during functional protein and drug delivery. TiO2 is another distinct class of ceramic profitably employed for drug delivery to consider varied types of specific diseases. It is highly applicable in pharmacology and, at present, for photodynamic therapy due to photo-oxidation. The possible TiO2 toxicity naturally decreases when it is instantly brought in direct contact to the necessary material, namely, HAP. Alumina ceramic represents a highly engaged ceramic material that is advanced and demanding. It has different features, like heat resistance and highly stable. It is claimed in the biomedical application.

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Fig. 7 Different types of preparation methods of nanoceramics

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Fig. 8 Various types of calcium in nature

Glioma is a tumour occurring in the central nervous system (CNS) spinal cord and active brain. Valuable TiO2-PEG material proved to be entirely influenced by the malignant glioma treatment [75]. Zirconia is a typical ceramic demonstrating extraordinarily significant and adequate biomedical aspects like medical tools and implements. It is concerned for orthopaedics in synthesizing hip head prostheses. The studies carried on it clear that there is no severe effect of zirconia insertion to the muscle and bone. But some of the official reports are present on the comparative study of this elaborate system, and it amply confirms future needs in specific term of extensive exploration. Boron nitride nanotubes are used correctly in the proper form of transducers due to their extraordinary feature that is chemical and thermal stability. The studies carried out infer about the exploration in the respective field of CNP and putting forward the medical and biological application. SiO2 remains the signature product in the research field and is profitably employed in drug delivering. Mesoporous silica nanoparticles synthesized through the polymerizing silica in the availability of surfactants have different features. It is readily available; volume and surface area; ligand gets attached to the silica surface. It enhances the targetability and biocompatibility. Such nanoparticle can store and release the drugs to the target site, completely working as a controller.

Conclusion They are naturally going to be the succinctly summarized from different types of bionanoceramics and bionanocomposite are already advanced as well as they are favourably reviewed [46, 54, 74]. All such materials are unique due to the

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availability of new chemical, physical, and biological features and are highly capable of applying [67, 70]. On the addition of nanofillers and nanocoating, the material is altered for modifying the surface features [30]. As per the considerable variation, corresponding physical and functional components also get changed and used in various applications. Varied approaches are present for synthesizing the valuable material, where every effective method possesses its possible advantages and then shows its beneficial effect on unique properties [20, 52, 53]. At present, they have gathered lots of interest as per the scientific and industrial culture. Communities are posing extraordinary applications in terms of eco-friendly, recyclable, cost-effective, and energy approaches. It creates harmony and balance between nature and human invention. The critical point to be instantly noticed is that advancement in the nanostructured composite will finally revolutionize the modern era of nanotechnology. Hence, it could be the main concerning topic for multidimensional research in the future. Acknowledgments Authors acknowledge the Knowledge Resource Centre, CSIR-NEERI (CSIRNEERI/KRC/2020/SEP/EMD/2), for their support.

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10. Arfin T, Athar S (2018) Graphene for advanced organic photovoltaics. In: Kanchi S, Ahmed S, Sabela MI, Hussain CM (eds) Nanomaterials: biomedical, environmental, and engineering applications. Scrivener Publishing LLC, Beverly, pp 93–104 11. Arfin T, Fatima S (2014) Conductometric studies with polystyrene calcium phosphate membrane. Asian J Adv Basic Sci 2(1):1–14 12. Arfin T, Kumar C (2014) Synthesis, characterization, conductivity and antibacterial activity of ethyl cellulose manganese (II) hydrogen phosphate. Anal Bioanal Chem 6(4):403–421 13. Arfin T, Mogarkar PR (2018) Bio-based material protein and its novel applications. In: Ahmed S, Ikram S, Kanchi S, Bisetty K (eds) Biocomposites: biomedical and environmental applications. Pan Stanford Publishing, Singapore, pp 405–432 14. Arfin T, Mohammad F (2013a) DC electrical conductivity of nano-composite polystyrenetitanium-arsenate membrane. J Ind Eng Chem 19(6):2046–2051. https://doi.org/10.1016/j.jiec. 2013.03.019 15. Arfin T, Mohammad F (2013b) Synthesis, characterization and influence of electrolyte solutions towards the electrical properties of nylon-6,6 nickel carbonate membrane: test for the theory of uni-ionic potential based on thermodynamics of irreversible processes. In: Lefebure J (ed) Halides: chemistry, physical properties and structural effects. Nova Science Publishers, New York, pp 39–66 16. Arfin T, Mohammad F (2014) Electrochemical, dielectric behaviour and in vitro antimicrobial activity of polystyrene-calcium phosphate. Adv Ind Eng Manag 3(3):25–38. https://doi.org/ 10.7508/AIEM-V3-N3-25 17. Arfin T, Mohammad F (2015a) Dendrimer and its role for the advancement of nanotechnology and bioengineering. In: Wythers MC (ed) Advances in materials science research, vol 21. Nova Science Publishers, New York, pp157-174. 18. Arfin T, Mohammad F (2015b) Electrical conductivity, mechanical stability, antibacterial and anticancer activities of ethyl cellulose-tin (II) hydrogen phosphate. Adv Mater Lett 6(12):1058– 1065. https://doi.org/10.5185/amlett.2015.5896 19. Arfin T, Mohammad F (2016a) Electrochemical, antimicrobial and anticancer effects of ethyl cellulose-nickel (II) hydrogen phosphate. Innov Corros Mater Sci 6(1):10–18. https://doi.org/ 10.2174/2352094906999160307182012 20. Arfin T, Mohammad F (2016b) Chemistry and structural aspects of chitosan towards biomedical applications. In: Ikram S, Ahmed S (eds) Natural polymers: derivatives, blends and composites, vol 1. Nova Science Publishers, New York, pp 265–280 21. Arfin T, Rafiuddin (2009a) Transport studies of nickel arsenate membrane. J Electroanal Chem 636(1-2):113–122. https://doi.org/10.1016/j.jelechem.2009.09.019 22. Arfin T, Rafiuddin (2009b) Electrochemical properties of titanium arsenate membrane. Electrochim Acta 54(27):6928–6934. https://doi.org/10.1016/j.electacta.2009.06.074 23. Arfin T, Rafiuddin (2010) Thermodynamics of ion conductivity of alkali halide across a polystyrene-based titanium arsenate membrane. Electrochim Acta 55(28):8628–8631. https:// doi.org/10.1016/j.electacta.2010.07.091 24. Arfin T, Rafiuddin (2011) An electrochemical and theoretical comparison of ionic transport through a polystyrene-based cobalt arsenate membrane. Electrochim Acta 56(22):7476–7483. https://doi.org/10.1016/j.electacta.2011.06.109 25. Arfin T, Rafiuddin (2012) Metal ion transport through a polystyrene-based cobalt arsenate membrane: application of irreversible thermodynamics and theory of absolute reaction rates. Desalination 284:100–105. https://doi.org/10.1016/j.desal.2011.08.042 26. Arfin T, Rangari SN (2018) Graphene oxide-ZnO nanocomposite modified electrode for the detection of phenol. Anal Methods 10(3):347–358. https://doi.org/10.1039/C7AY02650A 27. Arfin T, Sonawane K (2018a) Bio-based materials: past to future. In: Bio-based materials for food packaging. Springer International Publishing, Cham, pp 1–32 28. Arfin T, Sonawane K (2018b) An excellence method on starch-based materials: a promising stage for environmental application. In: Hussain (ed) Green and sustainable advance materials: application, vol 2. Scrivener Publishing LLC, Beverly, pp 177–208

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29. Arfin T, Sonawane K (2019a) Alginate: recent progress and technological prospects. In: Ahmed S (ed) Alginates: applications in the biomedical and food industries. Scrivener Publishing LLC, Hoboken, pp 45–58 30. Arfin T, Sonawane K (2019b) Biotechnology: past-to-future. In: Shahid-ul-Islam (ed) Integrated green chemistry and sustainable engineering. Scrivener Publishing LLC, Salem, pp 617–645 31. Arfin T, Tarannum A (2017) Polymer materials: from the past to the future. In: Ahmed S, Ikram A, Ikram S (eds) Green polymeric materials: advances and sustainable development. Nova Science Publishers, New York, pp 35–42 32. Arfin T, Tarannum A (2018) Engineered nanomaterials for industrial application: an overview. In: Hussain CM (ed) Handbook of nanomaterials for industrial applications. Elsevier, Amsterdam, pp 127–134 33. Arfin T, Tarannum A (2019) Rapid determination of lead ions using polyaniline-zirconium (IV) iodate-based ion selective electrode. J Environ Chem Eng 7(1):102811. https://doi.org/10.1016/ j.jece.2018.102811 34. Arfin T, Yadav N (2012) Impedance characteristics and electrical double layer capacitance of polystyrene-based nickel arsenate membrane. Anal Bioanal Electrochem 4(2):135–152 35. Arfin T, Yadav N (2013) Impedance characteristics and electrical double-layer capacitance of composite polystyrene-cobalt-arsenate membrane. J Ind Eng Chem 19(1):256–262. https://doi.org/ 10.1016/j.jiec.2012.08.009 36. Arfin T, Jabeen F, Kriek RJ (2011) An electrochemical and theoretical comparison of ionic transport through a polystyrene based titanium-vanadium (1:2) phosphate membrane. Desalination 274(1-3):206–211. https://doi.org/10.1016/j.desal.2011.02.014 37. Arfin T, Falch A, Kriek RJ (2012) Evaluation of charge density and the theory for calculating membrane potential for a nano-composite nylon-6,6 nickel phosphate membrane. Phys Chem Chem Phys 14(48):16760–16769. https://doi.org/10.1039/C2CP42683H 38. Arfin T, Bushra R, Kriek RJ (2013) Ionic conductivity of alkali halides across a polyanilinezirconium (IV)-arsenate membrane. Anal Bioanal Electrochem 5(2):206–221 39. Arfin T, Mohammad F, Yusof NA (2015) Applications of polystyrene and its role as a base in industrial chemistry. In: Lynwood C (ed) Polystyrene: synthesis, characteristics and applications. Nova Science Publishers, New York, pp 269–280 40. Arfin T, Bushra R, Mohammad F (2016) Electrochemical sensor for the sensitive detection of o-nitrophenol using graphene oxide-poly(ethyleneimine) dendrimer-modified glassy carbon electrode. Graphene Technol 1(1):1–15. https://doi.org/10.1007/s41127-016-0002-1 41. Arfin T, Athar S, Rangari S (2018a) Proteins and their novel applications. In: Ahmed S, Kanchi S, Kumar G (eds) Handbook of biopolymers: advances and multifaceted applications. Pan Stanford Publishing, Singapore, pp 75–93 42. Arfin T, Tarannum A, Sonawane K (2018b) Green and sustainable advanced materials: an overview. In: Ahmed S, Hussain CM (eds) Green and sustainable advanced materials: processing and characterization, vol 1. Scrivener Publishing LLC, Beverly, pp 1–34 43. Arfin T, Sonawane K, Tarannum A (2019a) Review on detection of phenol in water. Adv Mater Lett 10(11):753–785. https://doi.org/10.5185/amlett.2019.0036 44. Arfin T, Singh B, Varshney N (2019b) Biological adhesion behavior of superhydrophobic polymer coating. In: Samal SK, Mohanty S, Nayak SK (eds) Superhydrophobic polymer coatings: fundamentals, design, fabrication, and applications. Elsevier, Amsterdam, pp 161–177 45. Arfin T, Sonawane K, Saidankar P, Sharma S (2019c) Role of microbes in the bioremediation of toxic dyes. In: Shahid-ul-Islam (ed) Integrated green chemistry and sustainable engineering. Scrivener Publishing LLC, Salem, pp 443–472 46. Arfin T, Varshney N, Singh B (2020) Ionic liquid modified activated carbon for the treatment of textile wastewater. In: Naushad M, Lichtfouse E (eds) Green materials for wastewater treatment. Springer International Publishing, Cham, pp 257–275 47. Athar S, Arfin T (2017) Commercial and prospective applications of gelatin. In: Ahmed S, Ikram S (eds) Natural polymers: derivatives, blends and composite, vol 2. Nova Science Publishers, New York, pp 199–216

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48. Athar S, Bushra R, Arfin T (2017) Cellulose nanocrystals and PEO/PET hydrogel material in biotechnology and biomedicine: current status and future prospects. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 139–173 49. Borkar R, Waghmare SS, Arfin T (2017) Bacterial cellulose and polyester hydrogel matrices in biotechnology and biomedicine: current status and future prospects. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 21–46 50. Bushra R, Arfin T, Oves M, Raza W, Mohammad F, Khan MA, Ahmad A, Azam A, Muneer M (2016) Development of PANI/MWCNTs decorated with cobalt oxide nanoparticles towards multiple electrochemical, photocatalytic and biomedical application sites. New J Chem 40(11): 9448–9459. https://doi.org/10.1039/C6NJ02054B 51. Khan AU, Malik N, Arfin T (2017) Nanofibrillated cellulose and copoly (amino acid) hydrogel matrices in biotechnology and biomedicine. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 331–352 52. Malik N, Khan AU, Naqvi S, Arfin T (2016a) Ultrasonic studies of different saccharides in α-amino acids at various temperatures and concentrations. J Mol Liq 221:12–18. https://doi.org/ 10.1016/j.molliq.2016.05.061 53. Malik N, Khan AU, Naqvi S, Arfin T (2016b) Ultrasonic investigation of in α-amino acids with aqueous solution of urea at different temperatures: a physicochemical study. J Appl Solution Chem Model 5(4):168–177 54. Malik N, Arfin T, Khan AU (2019) Graphene nanomaterials: chemistry and pharmaceutical perspectives. In: Grumezescu AM (ed) Nanomaterials for drug delivery and therapy. Elsevier, Amsterdam, pp 373–402 55. Mallakpour S, Azadi E, Hussain CM (2020a) Environmentally benign production of cupric oxide nanoparticles and various utilizations of their polymeric hybrids in different technologies. Coord Chem Rev 419:213378. https://doi.org/10.1016/j.ccr.2020.213378 56. Mallakpour S, Hatami M, Hussain CM (2020b) Recent innovations in functionalized layered double hydroxides: fabrication, characterization, and industrial applications. Adv Colloid Interface 283:102216. https://doi.org/10.1016/j.cis.2020.102216 57. Mogarkar PR, Arfin T (2017) Chemical and structural importance of starch based derivative and its applications. In: Ikram S, Ahmed A (eds) Natural polymers: derivatives, blends and composite, vol 2. Nova Science Publishers, New York, pp 73–87 58. Mohammad F, Arfin T (2013) Cytotoxic effects of polystyrene-titanium-arsenate composite in cultured H9c2 cardiomyoblasts. Bull Environ contam Toxicol 91(6):689–696. https://doi.org/ 10.1007/s00128-013-1131-3 59. Mohammad F, Arfin T, Yusof NA (2015) Chemical processes and reaction by-products involved in the biorefinery concept of biofuel production. In: Hakeem KR, Jawaid M, Alothman OY (eds) Agricultural biomass based potential materials. Springer International Publishing, Cham, pp 471–489 60. Mohammad F, Arfin T, Al-Lohedan HA (2017a) Sustained drug release and electrochemical performance of ethyl cellulose-magnesium hydrogen phosphate composite. Mater Sci Eng C 71:735–743. https://doi.org/10.1016/j.msec.2016.10.062 61. Mohammad F, Arfin T, Al-Lohedan HA (2017b) Enhanced biological activity and biosorption performance of trimethyl chitosan-loaded cerium oxide particles. J Ind Eng Chem 45:33–43. https://doi.org/10.1016/j.jiec.2016.08.029 62. Mohammad F, Arfin T, Al-Lohedan HA (2018a) Synthesis, characterization and applications of ethyl cellulose-based polymeric calcium (II) hydrogen phosphate composite. J Electron Mater 47(5):2954–2963. https://doi.org/10.1007/s11664-018-6118-8 63. Mohammad F, Arfin T, Saba N, Jawaid M, Al-Lohedan HA (2018b) Electrical conductivity and biological efficacy of ethyl cellulose and polyaniline-based composites. In: Khan A, Jawaid M, Khan AAP, Asiri AM (eds) Electrically conductive polymers and polymer composites: from synthesis to biomedical applications. Wiley-VCH, Weinheim, pp 181–197

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64. Mohammad F, Arfin T, Al-Lohedan HA (2019a) Development of graphene-based nanocomposites as potential materials for supercapacitors and electrochemicals cells. In: Jawaid M, Ahmad A, Lokhat D (eds) Graphene-based nanotechnologies for energy and environmental applications: micro and nano technologies. Elsevier, Amsterdam, pp 145–154 65. Mohammad F, Arfin T, Bwatanglang IB, Al-Lohedan HA (2019b) Starch-based nanocomposites: types and industrial applications. In: Sanyang ML, Jawaid M (eds) Bio-based polymers and nanocomposites: preparation, processing, properties & performance. Springer International Publishing, Cham, pp 157–181 66. Mohammad F, Arfin T, Al-Lohedan HA (2019c) Biocompatible polylactic acid-reinforced nickel-arsenate composite: studies of electrochemical conductivity, mechanical stability, and cell viability. Mater Sci Eng C 102:142–149. https://doi.org/10.1016/j.msec.2019.04.046 67. Mohammad F, Arfin T, Al-Lohedan HA (2019d) Enhanced biosorption and electrochemical performance of sugarcane bagasse derived a polylactic acid-graphene oxide-CeO2 composit. Mater Chem Phys 229:117–123. https://doi.org/10.1016/j.matchemphys.2019.02.085 68. Onwudiwe DC, Arfin T, Strydom CA (2014) Synthesis, characterization, and dielectric properties of N-butyl aniline capped CdS nanoparticles. Electrochim Acta 116:217–223. https://doi.org/10. 1016/j.electacta.2013.11.046 69. Sarath Chandra V, Baskar G, Suganthi RV, Elayaraja K, Ahymah Joshy MI, Sofi Beaula W, Mythili R, Venkatraman G, Naratana Kalkura S (2012) Blood compatibility of iron-doped nanosize hydroxyapatite and its drug release. ACS Appl Mater Interfaces 4(3):1200–1210. https://doi.org/10.1021/am300140q 70. Sophia AC, Arfin T, Lima EC (2019) Recent developments in adsorption of dyes using graphene based nanomaterials. In: Naushad M (ed) A new generation materials graphene: applications in water technology. Springer International Publishing, Cham, pp 439–471 71. Waghmare SS, Arfin T (2015a) Defluoridation by adsorption with chitin-chitosan-alginatepolymers-cellulose-resins-algae and fungi-a review. Int Res J Eng Tech 2(6):1179–1197 72. Waghmare SS, Arfin T (2015b) Fluoride removal by clays, geomaterials, minerals, low cost materials and zeolites by adsorption: a review. Int J Eng Res 4(11):3663–3676 73. Waghmare SS, Arfin T, Lataye D, Rayalu S, Manwar N, Labhsetware N (2015a) Adsorption behaviour of eggshell modified polyalthia longifolia leaf based alumina as a novel adsorbents for fluoride removal from drinking water. Int J Adv Res Innov Ideas Educ1 (5):904–926 74. Waghmare S, Arfin T, Manware N, Lataye D, Labhsetwar N, Rayalu S (2015b) Preparation and characterization of polyalthia longifolia based adsorbent for removing fluoride from drinking water. Asian J Adv Basic Sci 4(1):12–24 75. Wu KCW, Yamauchi Y, Hong CY, Yang YH, Liang YH, Funatu T, Tsunoda M (2011) Biocompatible, surface functionalized mesoporous titania nanoparticles for intracellular imaging and anticancer drug delivery. Chem Commun 47(18):5232–5234. https://doi.org/10.1039/ C1CC10659G

Part VIII Consumer Nanoproducts Based on Graphene and Graphene Nanocomposite

Graphene Nanocomposite-Based Nanoproducts for Renewable Energy Application

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Seyyed Mojtaba Mousavi, Seyyed Alireza Hashemi, Chin Wei Lai, and Gity Behbudi

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Battery-Powered Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supercapacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solar Cell Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fuel Cell Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

One of the significant challenges of the world is the solution of renewable energy critical and increasing sources. Therefore, the use of renewable energy materials operates one crucial resolution for this challenge. In recent years, solar cell, battery, fuel cell, and energy storage technology is widely investigated as one of the most considerable processes. Graphene nanocomposites are critically presented as a significant solution to world renewable energy difficulties and challenges. On the other hand, graphene-based materials and their composites because of owning the large specific surface areas, hydrophobic properties, etc. S. M. Mousavi Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan S. A. Hashemi Nanomaterials and Polymer Nanocomposites Laboratory, School of Engineering, University of British Columbia, Kelowna, Canada C. W. Lai (*) Nanotechnology and Catalysis Research Center, University of Malaya, Kuala Lumpur, Malaysia e-mail: [email protected] G. Behbudi Department of Chemical Engineering, University of Mohaghegh Ardabili, Ardabil, Iran © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_31

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have a potential impact in a broad range of fields, including nanoproducts. Hence, in this chapter, after a brief introduction of graphene, renewable energy, more detailed information is followed on new approach processes. Eventually, the graphene-based composite for strategic renewable energy has been described. Keywords

Graphene · Composite · Nanocomposite · Renewable energies

Introduction Renewable energy technology has expanded considerably, and the reason for utilizing renewable energy has mainly been to deplete nonrenewable energy supplies, contributing to climate change and global warming. Nonetheless, as opposed to nonrenewable energy technologies, yields for certain technologies of renewable energy are already commercially unpermanent. To dominate this, graphene nanotechnology seeks applications to increase their efficiencies in some of those technologies. There have been several positive developments and breakthroughs, and this chapter aims to put some of these successes to light. Just four sustainable energy areas will be addressed in this chapter: fuel cell technology, battery technology, energy storage products, and solar panel technology. Nanotechnology has found use in a broad variety of fields like renewables. Carbon-based nanoparticles demonstrate enhanced properties compared with nanomaterials from certain components of the periodic table [1]. In recent decades, fast world economic expansion and increment in the growth of the population have increased energy consumption. Renewable energy is one of the most important current issues that are vital for human expansion that has become an issue of national security [2]. One of the main concerns in the modern world is the issue of environmental problems and decreased fossil fuels it also bounded their reserves that affect the world economy and led to the development of environmentally friendly systems and the creation of clean and sustainable renewable energy sources [3]. For this purpose, energy storage device technology has been developed, and a great of research has been done in the field. Moreover, the ever-increasing demand for electric vehicles and their fast expansions cause and create demand for energy storage technologies with a high amount of power and energy density and renewable energy systems. Amid different energy storage strategies, electrochemical energy storage (EES) devices have made tremendous progress with the best properties, including high efficiency and flexibility [4]. Therefore graphene may be a suitable exceptional candidate for an electron-conducting additive in lithium-ion battery cathodes. Because of the fairly recent developments in graphene science, especially by A. Geim et K. Novoselov [5], who in 2010 won a Nobel Prize in Physics for pioneering work on the two-dimensional substance structure [6], a special concern is the possibility of utilizing graphene in energy processing and storage devices [7]. It is attributed to many special characteristics of the materials, including such strong load carrier mobility (20 m2 V1 s1) [8], the large

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theoretical surface area of about 2630 m2 g1 [9], and a wide electrochemical window [10]. With respect to energy production and storage applications, graphene was primarily researched for use in fuel cells [11], solar cells [12], supercapacitors [13], lithium-ion batteries (as an additive to both anode [14] and cathode [15]), and lithium-air batteries [16].

Graphene Nanoparticles GO is a single sheet form of graphite [17] and defined as a two-dimensional (2D) sheet, extremely slight, consisting of sp2 carbon particles in a honeycomb organization with various appealing features such as remarkable mechanical resistance [18], electrical conductivity [19], nuclear obstacle prospects [20] integrating with high-density materials [21], and other uncommon features. As necessities are, endless specialists place graphene in polymers all together that they may design polymer-related nanocomposites [22]. Anyway, the perfect graphene business has wind up being mentioning considering jumbled base-up association [23], low dissolvability [24], and course of action-related agglomeration in light of van der Waals interchanges [25]. It is indispensable that the blends, which are substantially similar graphite or elective carbon sources, may be mixed with graphite using methods for the top-down approach to obtain various perfect graphene benefits. Additionally, the surface is inundated with functionalized oxygen bundles by these blends. The graphite oxidation in protonated solvents promotes oxide in graphite, which contains a couple of graphene oxide (GO) stacked layers. GO recognizes a graphene-like hexagonal carbon structure and contains a hydroxyl (– Generous), carbonyl (C ¼ O), carboxylic destructive (– COOH), alkoxy (C – O – C), and further utilitarian sets focused on oxygen [26, 27]. Other than their mix ease, these oxygenated segments speak to a vast number of focal points over graphene-like higher dissolvability [28], similarly as the opportunities for surface functionalization, e.g., with octadecylamine, planning for their application in nanocomposite materials. Also, GO may be managed by methods for various procedures for the synthesization of decreased graphene oxide (rGO) in order to constrain oxygen sets and get incorporates closer to those of faultless graphene [29]. Starting late, another graphene subordinate class has been given, which is known as graphene quantum dots (GQDs), being on an essential level graphene sheets of 15 mm and diameter 35 g g
1) and oil (>100 g g
1). Nevertheless, such composite materials absorbed oils and water, which decline the efficiency and separation selectivity. Superoleophilic and superhydrophobic 3DGPNs, such as 3D rGO/ polydimethylsiloxane (PDMS) and 3D rGO/polyvinylidene, have been fabricated [62] to absorb oil from water while repelling water completely. Combined hybrid feature of the polymers’ low surface energy and micro/nanoscale structures of graphene in 3DGPN aerogels exhibited high adsorption capacity of organic solvents, oils, and excellent water repellency. Such materials were regarded as the ideal material for the separation of oil and organic solvents from water. Besides, they can be easily recyclable through squeezing or heating. Nevertheless, the heating process is relatively intricate for the especially adsorbent materials when the associated solvents possess high boiling points. Contrary, those elastic adsorbent materials could be opposed by the squeezing method, while three-dimensional graphene-associated materials are prone to damage irreversibly upon the mechanical stress. Therefore, it is mandatory to fabricate 3D graphene materials with high flexibility with the strength to act as adsorbent materials (elastic) to separate oil from the water. To validate this, a report is revealed based on 3D rGO/polyurethane (PU) foams via self-

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assembly of graphene oxide sheets [63]. This composite showed a unique structure that maintained graphene foams’ physical properties and effectively bears the mechanical load upon mechanical stress. Thus, results in 3D rGO/PU foams showed superior hydrophobicity with significant cycling stability. Moreover, it has been noticed that reinforcing cross-linked polymers into 3D-reduced graphene oxide (rGO) aerogels significantly reduces the fragile nature of those 3D rGO aerogels. For example, incorporation of cross-linkable poly (acrylic acid) (XPAA) with 3D rGO resulted in >99.6% porosity of the system which can reversibly support up to 10,000 times their weight with full recovery of their original quantity (volume) [64]. The average absorption capacities for six different oils such as gasoline, diesel, motor oil, pump oil, olive oil, and sesame oil were estimated to be around 120 g g
1 (See Fig. 4). Smart surface modification of adsorbent materials is appealing because the external stimuli’s simple operation could enable the removal and recovery of oil from the aqueous media. The adsorption and desorption process could be easily

Fig. 4 (a) Morphology of the 3D rGO/XPAA aerogels. (b) SEM images of 3D rGO/XPAA aerogels. (c) Digital images showing the compressibility of the 3D rGO/XPAA aerogels during the 10th compression/release cycle. (d) Demonstration of oil absorption using gasoline as the absorbed solvent from t ¼ 0 to t ¼ 35 s. (e) Absorption capacities for various oils expressed as gram oil per gram aerogel. (Reproduced from Ref. 46. Copyright 2020 American Chemical Society)

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harnessed by external stimuli, including heating, electricity, and pH [65, 66]. Out of which, the pH-responsive method is most fascinating due to it could easily regulate the surface property between hydrophilic and hydrophobic and thus rapidly reverse the adsorption and desorption process in a short period of time. For instance, Zhu et al. had fabricated a composite based on a smart surface of 3D graphene foam (GF) by attaching an amphiphilic block of polyhexadecyl acrylate copolymer (P2VP-b-PHA) and poly(2-vinylpyridine) on the surface of graphene foam [67]. In this process, graphene foam was functionalized with another block copolymer (P2VP-b-PHA) through a quaternization and silanization process. The as-prepared 3D composite foam could significantly absorb oil or organic solvents from the aqueous media due to the superoleophobic and superoleophobic surface at different medium pH levels. Besides, the as-prepared 3D composite foam showed superior absorption capacity (approximately 196 times its weight). Removing various heavy metal ions and industrial dyes from industrial wastewater has become a complex challenge for industrialists and researchers. Graphene oxide offers significant adsorption efficiency concerning various water contaminants. Nevertheless, the centrifugation process of adsorbed GO could suppress its applications in the purification of wastewater. The 3D GO/polymer composites comprise of interconnected 3D porous networks and extensive specific surface area so that such materials can easily pass heavy metal ions/dye molecules. For example, a report is revealed based on 3D graphene aerogel (amine-functionalized) prepared through the interaction between polyethylenimine (PEI) and GO sheets with high amine density [68]. It exhibited a too high adsorption capacity (800 mg g
1), and the 3D GO/PEI showed significant adsorption capacity for formaldehyde and carbon dioxide (11.2 wt % at 1.0 bar and 273 K). Anionic polyacrylamide (APAM) is a widely used polymer that is a low-cost and effective flocculant to treat municipal and industrial and wastewater [69]. The incorporation of GO into APAM could beneficial for practical environmental protection applications as the 3D GO/APAM hybrid material can be successfully utilized to separate fuchsin from aqueous solutions [69]. The synergistic effect of the 3D GO/APAM with the porous structure and the adsorbents’ functional groups led to improve the adsorption capacity. These materials are very competitive to the carbon nanotube-based polymer composites for environmental applications [70–72].

Conclusions, Challenges, and Perspectives In summary, the excellent performance of three-dimensional graphene polymer network (3DGPN)-based nanoproducts exhibited a promising series of applications, including energy storage, conducting polymer composites, sensing, and environment protection concerning wastewater treatment. Several challenges still need to be addressed, although the exciting applications of 3DGPNs as nanoproducts are reported. The development of eco-friendly, reliable, and easy fabrication methods with low cost needs to be investigated for finding efficient applications of such 3DGPNs. Research related to 3DGPNs remains at its starting stage compared to other three-dimensional graphene-based composites, including a 3D metal oxide or

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three-dimensional carbon nanotube (3D-CNT). Ongoing rapid progress regarding this field convinces us that 3DGPNs will be versatile materials that would find efficient applications for various fields. In-depth understanding and investigations regarding graphene (2D macromolecule) self-assembly with different polymers are indispensable for fabricating intelligent 3DGPNs for smart applications (sensing, energy storage, etc.). Besides, the interfaces of polymers and graphene in the 3DGPNs are still unclear. It requires thorough analysis to understand deeply for designing materials that would regulate the structure-property relationship. Furthermore, 3DGNs can be introduced reasonably with multifunctional polymers for exploring the various technological applications of the resulting threedimensional graphene-based polymer networks (3DGPNs). A concurrent exhibition of flexibility, compressibility, stretchability, and self-repairing of the multifunctional 3DGPNs has not been understood clearly but is highly needed for nanowearable smart electronic products. Besides, diverse morphologies of 3DGPNs, including single- and double-phase interpenetrating networks, are beneficial for developing electrochemical devices. Considering the various functionalities of 3DGPNs that are achieved from combining interdisciplinary areas including material science, physics, chemistry, and biology, we assure that 3DGPNs could open up a variety of opportunities toward technological applications in diverse areas in the near future.

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69. Yang X, Li Y, Du Q et al (2015) Highly effective removal of basic fuchsin from aqueous solutions by anionic polyacrylamide/graphene oxide aerogels. J Colloid Interface Sci. https:// doi.org/10.1016/j.jcis.2015.04.042 70. Mallakpour S, Khodadadzadeh L (2018) Chapter 7: biocompatible and biodegradable Chitosan nanocomposites loaded with carbon nanotubes. In: Shimpi NG (ed) Biodegradable and biocompatible polymer composites processing, properties and applications. Elsevier/Woodhead Publishing, Sawston/Cambridge, pp 187–221. https://doi.org/10.1016/B978-0-08-100970-3. 00007-9 71. Mallakpour S, Khadem E (2019) Chapter 8: carbon nanotubes for heavy metals removal. In: Kyzas G, Mitrpoulos AC (eds) Composite nanoadsorbents. Elsevier, Amsterdam, pp 181–210. https://doi.org/10.1016/B978-0-12-814132-8.00009-5. eBook ISBN: 9780128141335 72. Mallakpour S, Rashidimoghadam S (2019) Chapter 9: carbon nanotubes for dyes removal. In: Kyzas G, Mitrpoulos AC (eds) Composite nanoadsorbents. Elsevier, Amsterdam, pp 211–244. https://doi.org/10.1016/B978-0-12-814132-8.00010-1. eBook ISBN: 9780128141335

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Sukanchan Palit and Chaudhery Mustansar Hussain

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Aim and Objective of This Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Do You Mean by Graphene-Based Nanoproducts? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Do You Mean by Nanomaterials and Engineered Nanomaterials? . . . . . . . . . . . . . . . . . . . . . . Climate Change and Sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Vast Doctrine of Environmental Sustainability and the Vision for the Future . . . . . . . . . . . . Recent Scientific Advances in the Field of Application of Graphene-Based Nanoproducts . . . Recent Scientific Advancements in the Field of Environmental Protection and Water and Wastewater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials and the Vast World of Environmental Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drinking Water Crisis, Heavy Metal and Arsenic Groundwater Remediation, and the Visionary Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sustainable Resource Management and the Domain of Nanotechnology . . . . . . . . . . . . . . . . . . . . . Future Research Trends in the Field of Environmental Engineering and Chemical Process Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Futuristic Vision and Futuristic Flow of Scientific Thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion, Summary, and Environmental Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Civilization, science, and engineering are today in the avenues of new scientific vision and regeneration. Rapid industrialization, mass manufacturing, and loss of ecological diversity have urged the scientific research community to gear forward towards newer scientific innovations and scientific instinct. Nanotechnology, S. Palit Department of Chemical Engineering, University of Petroleum and Energy Studies, Energy Acres, Post-Office-Bidholi via Premnagar, Dehradun, Uttarakhand, India C. M. Hussain (*) Chemistry and Environmental Science, New Jersey Institute of Technology, Newark, NJ, USA e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_36

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nanomaterials, and engineered nanomaterials are today the marvels of science and engineering. Today, science and technology are huge colossus with a definite purpose of its own. The authors deeply discussed the application of graphenebased nanoproducts in diverse areas of science such as environmental engineering, chemical engineering, and nanotechnology. Today, environmental engineering disasters are destroying the human habitat. The global status of the environment is absolutely grave. Graphene-based nanoproducts are the challenges of human civilization and human scientific progress. The areas of membrane science and distillation are the other hallmarks of this research expertise. Conventional and nonconventional environmental engineering techniques are also the areas of deep scientific introspection. Today, graphene-based nanoproducts and other nanomaterials are in the path of newer scientific regeneration and scientific and engineering vision. The authors elucidate in deep details the domain of environmental sustainability and environmental protection and the recent advances in these fields. A new world of knowledge prowess and scientific dimension will surely emerge in the field of environmental remediation and nanotechnology if researchers, scientists, engineers, and policymakers take active and positive steps in the mitigation of climate change and environmental degradation. Keywords

Graphene · Nanomaterials · Engineered Nanomaterials · Water · Wastewater · Vision · Arsenic · Heavy metals

Introduction Human mankind today stands in the midst of deep scientific forbearance and scientific ingenuity. Nanotechnology is a revolutionary area of science and engineering. Rapid industrialization, global population growth, and large-scale mass manufacturing are veritably destroying the scientific landscape and the scientific fabric. Loss of ecosystems and loss of biodiversity are terribly a matter of immense scientific and engineering concern. Thus the need of a detailed treatise on conventional and nonconventional environmental engineering techniques such as advanced oxidation processes, membrane separation techniques, and desalination. A wide scientific introspection in the application of graphene-based nanoproducts and other nanomaterials are the other hallmarks of this treatise. Human civilization’s immense scientific stance, the world of scientific ingenuity, and the scientific forbearance will eventually open new doors of innovation and instinct in the field of nanotechnology. Today, human suffering and health effects are immense due to heavy metal and arsenic groundwater and drinking water contamination. Bangladesh and the state of West Bengal, India, are in the throes of world’s largest environmental engineering disaster that is arsenic drinking water contamination

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and thus the need of applications of graphene-based nanoproducts as well as other nanomaterials and engineered nanomaterials in environmental remediation, water and wastewater treatment. The authors deeply discuss these scientific and engineering issues with scientific grit and scientific determination. Graphene-based nanoproducts have immense applications in diverse areas of science and engineering. Global environmental challenges and loss of ecological biodiversity are urging scientists and engineers around the world to gear forward towards new innovations and newer discoveries. Environmental engineering curriculum in universities around the world needs to be revamped and reorganized with the surge in research and development initiatives in the field of drinking water and industrial wastewater treatment. A new epoch in the field of nanotechnology and material science will surely usher in with the immense efforts of scientific girth and scientific provenance.

The Aim and Objective of This Study Global water crisis and global warming are today destroying the global scientific and engineering firmament. Engineering vision and scientific verve and motivation in the field of graphene applications are changing the face of human scientific progress and academic rigor. Graphenes, fullerenes, carbon nanotubes, and other nanomaterials and engineered nanomaterials are today the needs of human civilization and have diverse applications in every branch of scientific endeavor. Scientific alacrity and scientific validation in the field of graphene-based nanoproducts applications will eventually open new windows of futuristic vision and future flow of scientific thoughts. Pure water scarcity and proper sanitation are confronting immensely the vast world of public health engineering and thus the need of applications of nanomaterials in the field of drinking water and industrial wastewater treatment. This areas will be dealt with vision in this treatise. Graphene-based nanoproducts have applications in renewable energy and energy sustainability. This is also one of the cornerstones of this well researched treatise. Scientific discernment and deep scientific revelation in the field of nanomaterials and engineered applications will surely be an eye-opener towards the greater vistas of learning and academic rigor in nanotechnology, chemical engineering, and environmental engineering. The vision of this study is to target the scientific and engineering needs of graphene-based nanoproducts. Sustainability whether it is social, economic, energy, or environmental are the scientific imperatives of humankind today. In the similar vein, circular economy and sustainable resource management will be true visionary towards a newer era in the field of science and technology globally. Blue economy or resources from ocean are the other sides of the visionary coin. A deep scientific and engineering introspection into the unknown world of graphene-based nanoproducts applications in circular economy will surely enhance the world of scientific understanding and scientific intellect in decades to come.

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What Do You Mean by Graphene-Based Nanoproducts? Graphene is an allotrope of carbon consisting of a single layer of atoms arranged in a two-dimensional honeycomb lattice. Each atom in a graphene sheet is connected to its three nearest neighbors by a sigma bond and contributes one electron to a conduction band that extends over the whole sheet. This is the same type of bonding seen in carbon nanotubes and polycyclic aromatic hydrocarbons and partially in fullerenes and glassy carbon. A newer scientific ingenuity, profundity, and engineering vision are the needs of graphene and other nanomaterials science today. Scientists have vastly theorized about graphene for decades. It has been unknowingly produced in small quantities for centuries, through the use of pencils and other similar applications of graphite. It was originally observed in electron microscopes in 1962 but only studied while supported on metal surfaces. This material was later discovered, isolated, and characterized in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, who were awarded the Nobel Prize for Physics in 2010 for their groundbreaking research on the material and thus started a new journey of scientific vision in the field of nanomaterials. The global market for graphene was nine million dollars in 2012 [1, 2]. Most of the demand for research and development forays were in the areas of semiconductor, electronics, electric batteries, and composites. Mankind’s vast scientific prowess and positive intellect in the field of graphenes and other engineered nanomaterials will surely transform the scientific barriers and subsequently scientific frontiers [1, 2].

What Do You Mean by Nanomaterials and Engineered Nanomaterials? Nanotechnology, nanomaterials, and engineered nanomaterials are paving the way towards a newer visionary era. The major applications of nanomaterials are in the areas of water purification science and environmental remediation science. The success of civilization and science lies in the domain of nanotechnology today. Nanomaterials can be defined as materials, possessing, at minimum, one external dimension measuring 1–100 nm [1, 2]. The definition given by the European Commission states that the particle size of at least half of the particles in the number size distribution must measure 100 nm or below. Nanomaterial examples are titanium dioxide, silver, synthetic amorphous silica, iron oxide, azo pigments, and phthalocyanine pigments. Engineered nanomaterials are chemical substances or materials that are engineered with particle sizes between 1 and 100 nm in at least one dimension . It is well established that engineered nanomaterials derive many functional advantages and engineering vision from their unique physical and chemical properties. The vision, redeeming and profundity of the science of nanomaterials today needs to be revitalized with the ever-growing concerns for sustainability such as social, economic, energy, or environmental. Sustainability, sustainable resource management, and nanotechnology are today aligned with each other. Circular economy, waste minimization, and the concept of zero-waste tools are the scientific

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vision of today. The authors in this chapter clearly validates the engineering issues in the field of waste reduction and nanotechnology. Successive scientific generations will surely be emboldened if humankind, science, and engineering move towards a right direction in global research and development initiatives [1, 2].

Climate Change and Sustainability Environmental sustainability and climate change mitigation are in today’s scientific world linked to each other. The world today stands shattered at the ever-growing crisis of heavy metal and arsenic groundwater contamination in many developing and developed nations around the world. Humankind’s scientific progeny and the scientific destiny of environmental or green sustainability will eventually lead science and technology towards newer scientific frontiers. Climate change today is a veritable burden of human scientific progress. The situation in developing nations in South Asia is absolutely gruesome and disastrous and thus a deep need of an introspection in the science of sustainability. Here also comes the importance of United Nations Sustainable Development Goals which reiterates the concepts of water purification, drinking water security, proper sanitation, food security, education, and successful human habitat. If sustainable development is not envisioned or implemented in human society, the nation’s economic growth and progress gets stunted. Today, circular economy and sustainable resource management are aligned to each other. These are the novel areas of sound research and development initiatives in environmental engineering and water purification. Thus in the similar vision, scientific prowess, engineering, and technological vision will surely enhance humankind’s scientific hope, scientific girth and determination.

The Vast Doctrine of Environmental Sustainability and the Vision for the Future The vast and varied doctrine of environmental sustainability and water remediation needs to be effectively reenvisioned and nurtured as civilization moves forward. The status of water, clean energy, and human habitat is highly catastrophic as mankind treads forward. The visionary definition of “sustainability” by Dr. Gro Harlem Brundtland, former Prime Minister of Norway, needs to be rethought and revamped as civilization confronts immense environmental and energy issues. Climate change and sustainability are today in the vistas of new innovation and newer scientific ingenuity. A sound concept of circular economy and zero-waste tools will surely usher in a new field in environmental management, sustainable resource management, and nanotechnology. The vision for the future in the field of graphenes or other nanomaterials and their diverse applications will veritably lead a long, effective, and visionary way towards sustainability. The other areas of scientific endeavor which needs deep scientific and engineering introspection are water resource engineering, integrated water resource management, and integrated urban water management.

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Without water resource engineering and environmental engineering, mankind will plunge into a great disaster. Thus humankind’s vision, revelation, and scientific redemption will be highly enhanced if research and development initiatives in environmental pollution control moves towards a visionary paradigm.

Recent Scientific Advances in the Field of Application of Graphene-Based Nanoproducts Graphene and other nanomaterials are the wonders of science today. Engineering science and technology in the global scientific fabric are reenergizing futuristic vision and future flow of scientific thoughts. In this section, the authors deeply elucidate the application of graphene-based nanoproducts in different areas of science and technology. Kemp et al. (2013) [3] deeply elucidate environmental applications using graphene composites and the wide vision of water remediation and gas adsorption. This review deals with wide-ranging environmental studies of graphene-based materials on the adsorption of hazardous materials and photocatalytic degradation of pollutants for water remediation and water pollution control and the physisorption, chemisorption, reactive adsorption, and separation for gas storage. The vast environmental and biological toxicity of graphene, which is an important issue if graphene composites are to be veritably applied in environmental remediation, are also vastly addressed [3]. Environmental pollution and industrial pollution by both water-soluble toxic pollutants as well as noxious greenhouse gases are an ever-growing concern worldwide. Human suffering and human scientific progress are at a state of disaster as heavy metal contamination of drinking water confronts and challenges the vast scientific firmament. At the recent Rio + 20 conference, these issues have been thrust into spotlight again. Additionally, recent studies have shown that another issue affecting environmental integrity is the unpredicted effects certain pollutants are having on the global environment [3]. A newer visionary era in the field of water remediation and graphene nanocomposites will eventually usher in a newer genre and newer scientific validation. A strong scientific validation in nanomaterials applications is the utmost need of the hour. The authors discussed in minute details the water remediation by adsorption, adsorption by ionic pollutants, water remediation by photocatalysts, gas adsorption and gas phase separation, reactive gas adsorption, and environmental and biological toxicity of graphene. The discovery of graphene is rightly regarded as a milestone in the field of material science and composite science as can be seen from the worldwide attention the material has received in the fields of electronic engineering, organo electronics, photonics, supercapacitors, and biosensing to name a few [3]. A remarkable era in the field of graphene-based nanoproducts is slowly emerging. Research and development show that single layer, multilayer, and functionalized graphene sheets, as well as other graphene-based architectures offer a wide range of benefits, opportunities, and scientific challenges. The high stability, large surface area, and environmentally friendly nature of graphenes make it a remarkable and potential candidate

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for environmental applications such as water remediation, toxic gas sensors, and acidic gas capture, and these areas are demonstrated in this article. Human society needs to be revamped as regards scientific vision of nanotechnology applications. Thus the authors with immense scientific judgment detail these scientific and engineering issues [3]. Perraeault et al. (2015) [4] deeply discussed with scientific and engineering insight environmental applications of graphene-based nanomaterials. Graphenebased nanomaterials and nanoproducts are today transforming the vast global environmental engineering firmament. The vision of environmental engineering science, the scientific needs of human society, and the scientific truth of United Nations Sustainable Development Goals will embolden research acumen and scientific foresight in nanotechnology applications [4]. Nanoscience and nanotechnology are today linked with the vast world of environmental protection. Nano-remediation science is today in the path of newer scientific regeneration. The twenty-first century has been termed with vision and scientific prowess as the century of environment [4]. With ever-growing population, rapid industrialization and urbanization, intensification of agricultural activities, contamination of air, soils and aquatic soils, and global climate change are becoming a definite and purposeful focus of political and scientific attention. A new scientific and engineering generation in nano-remediation is slowly emerging with vision, cogent insight, and purpose. Today, there are technologies to mitigate associated health and environmental impacts of nanomaterial applications. The authors discussed in minute details the concepts and properties of graphenes, graphene materials for contaminant adsorption, and graphene-based photocatalytic materials for water contamination. Graphene in membrane and desalination technologies will be an eye-opener towards a newer scientific and engineering genre and a deep scientific profundity. Antimicrobial applications of graphene-based materials are other pillars of this treatise [4]. Graphene-based electrodes for environmental sensing are the other targets of this well researched treatise. The outlook of this research endeavor is bright and far-reaching. During the past decade, significant progress has been envisioned in understanding how graphene and graphene-based materials can be veritably used to address environmental engineering challenges. The world of science and engineering of graphenes are today the marvels and needs to be revisited and revamped as civilization and humankind moves forward. Graphene remains an unique material with properties that could lead potentially to remarkable and significant scientific understanding and discernment in numerous environmental applications. Due to ultrahigh surface area materials, this two-dimensional material thought to be impossible 80 years ago is now providing global scientific and engineering solutions in the progress and advancements in science and humanity [4]. Gong et al. (2011) [5] deeply discussed with cogent insight graphene and its synthesis, characterization, properties, and applications. The world of nanoscience and nanotechnology are today in the vistas of newer scientific regeneration and vision. In this book, the authors discussed in details the synthesis and characterization of graphenes, nucleation, and vertical growth of nano-graphene sheets, synthesis of aqueous dispersion of graphenes, supercritical fluid processing of graphene and

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graphene oxide, and the vast areas of applications of graphene [5]. Electronic transport properties of few-layer graphene materials and large-scale graphene by chemical vapor deposition are the other hallmarks of this treatise. The global success of nanotechnology and graphene applications in diverse areas of science and engineering will be a veritable eye-opener towards a new visionary domain of environmental engineering science and chemical process engineering. Graphene discovered in 2004 by A.K. Geim and K.S. Novoselov is an excellent electronic material and is a promising candidate for the post-silicon age. It has immense potential in the electronic device community, for example, field effect transistor, transparent electrode, etc. Research on graphenes is a rapidly developing field with vastly new concepts and applications emerging at an incredible rate and thus the need of research pursuit in the positive way in diverse applications of graphene-based nanoproducts [5]. Bharech et al. (2015) [6] elucidated and described in minute details in a review on the properties and applications of graphene. Scientific vision, deep scientific understanding, and engineering prowess and acumen are the ultimate needs of the hour [6]. Since the advent of automobile and aerospace industry, research and development globally of materials with better properties has been the keen interest of researchers, students, scientists, and engineers. This is a decade of “future materials.” One such material is graphene. Graphene is a two-dimensional atomic scale hexagonally packed allotrope of carbon. The authors in this treatise deeply discussed in details the forms of graphene, few later graphene and multilayer graphene, graphene oxide, reduced graphene oxide, and production techniques. Production techniques involve mechanical exfoliation, chemically derived graphene from graphite oxide, and the vast applications of chemical vapor deposition [6]. Application areas involve ultracapacitors with better performance than batteries, low-cost water desalination, integrated circuits, and corrosion-resistant coating. Civilization, science, and technology are moving fast from one visionary paradigm over another. Graphene is a very promising material for new types of systems, circuits, and devices where diverse functionalities can be combined into a single material. In today’s scientific endeavor, highly critical issues with the extensive use of graphene in electronics are integrated with mass manufacturing and industrialization. The authors deeply stress on these fundamental engineering issues and the scientific vision behind it [6]. The state of the art in research areas of graphene-based nanomaterials are today in the path of deep scientific acuity and scientific perseverance. Man’s vision and mankind’s scientific ingenuity are today the needs of the hour. In this treatise, the authors deeply tread on the success of civilization and science in human progress.

Recent Scientific Advancements in the Field of Environmental Protection and Water and Wastewater Treatment Technology management and rapid industrialization are the absolute needs of the hour. Integrated water resource management and integrated urban quality management are moving towards positive directions of scientific girth and divination. Today,

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the world stands devastated and degraded with the growing concerns of loss of ecological biodiversity, environmental disasters, and mass scale environmental degradation. A newer scientific genre and scientific profundity will surely emerge in the distant future. Abdelbasir et al. (2019) [7] discussed with vision, insight, and far-sightedness nanomaterials for industrial wastewater treatment. Industrial and domestic wastewater is an universal environmental issue. Recalcitrant organic pollutants, heavy metals, and non-disintegrating materials are a burden to science and human mankind today [7]. Presently removing these pollutants from industrial wastewater in an effective way has become a challenging and monstrous issue. Thus civilization’s scientific prowess and ingenuity are at the crossroads of scientific barriers and scientific travails. Nations around the world are in the process of serious scientific contemplation [7]. This review highlights the use of nanomaterials for the removal of different recalcitrant pollutants from industrial wastewater with a special importance on metal and metal oxide nanomaterials, carbon-based nanomaterials, and nanofiber/nanocomposite membranes [7]. The redemption of science and engineering of nanoparticles and the vast vision for the future needs to be explored at the earliest. The goal of this article is to offer a recent overview and references in the areas of engineered nanomaterials used for removing toxic materials from real industrial wastewater for researchers, students, and industrialists. Wastewater is produced from numerous sources as in residential areas, commercial areas, industrial properties, agricultural lands, etc. Composition of water differs broadly and is highly dependent on the source it is generated from. Due to application of nanomaterials, health effects of human beings, and environmental toxicity are challenging the vast scientific firmament [7]. Nanotechnology research forays can be vastly utilized to address the many complications of water quality to warrant environmental stability and integrated by industrial wastewater and drinking water systems [7]. Overall, nanomaterials are materials of which the structural elements are sized (at the least one dimension) between 1 and 100 nm. A newer beginning in the field of nanotechnology and nanoengineering are the moments of deep scientific truth and scientific profundity. Sustainable and effective solutions are the utmost needs of the hour. Nanomaterials possess superior adsorption capacities, reactivity, and their remarkable mobility in solution [7]. Numerous types of nanomaterials can successfully remove heavy metal ions, organic pollutants, inorganic ions, and bacteria. The authors in this treatise deeply discuss sources and compositions of industrial wastewater, industrial wastewater treatment processes, nanomaterials for industrial wastewater treatment, carbonbased nanoadsorbents, and the areas of retaining and reuse of nanomaterials [7]. Critical comparisons in the field of treatment of wastewater are the other pivots of this treatise. Nanomaterials possess a number of unique physicochemical properties. These features make them very attractive for wastewater treatment. They are (1) higher surface areas compared with conventional nanoparticles, (2) capability of being functionalized with diverse chemical groups, and (3) use as high selectivity recyclable legions for detrimental elements. Detrimental and recalcitrant chemicals are burden to human scientific progress and scientific path.

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A deep and comprehensive thought and introspection will eventually open up newer future recommendations in the areas of environmental pollution in years to come [7]. Mukherjee et al. (2015) [8] discussed with scientific far-sightedness contemporary environmental issues of landfill leachate and its assessments and remedies. Scientific imagination and deep scientific destiny are today the needs of deep comprehension and contemplation. Landfills are the primary option for waste disposal all over the world of science and engineering [8]. Most of the landfills around the globe are old and not engineered to prevent contamination of the underlying soil and groundwater by the toxic leachate. Management of this toxic leachate presents a deep challenging problem to the regulatory authorities [8]. Technology management and integrated water resource management are today aligned to each other. This article focusses on (1) leachate composition, (2) plume migration, (3) contaminant fate, (4) leachate plume monitoring tools, (5) risk assessment techniques, and (6) recent innovations in leachate treatment techniques. This article deeply discusses the areas of water management and the holistic domain of groundwater management and water resource engineering [8]. Hashim et al. (2011) [9] deeply discussed with vision and scientific conscience remediation technologies for heavy metal-contaminated groundwater. The contamination of groundwater by heavy metal, originating from natural soil sources and anthropogenic sources, is a matter of immense concern to global health, health issues, and public health engineering [9]. Remediation of groundwater and drinking water are matters of highest priority in the path towards human scientific progress. Billions of people around the world are today without clean drinking water. In this treatise, 35 approaches for groundwater treatment are reviewed and classified into three large categories which are chemical, biological/biochemical/biosorption, and physicochemical categories [9]. Keeping the sustainability issues and environmental ethics in mind, the technologies encompassing natural chemistry, bioremediation, and biosorption are highly recommended for future scientific recommendations. Mankind’s visionary prowess and milestones in environmental engineering tools will widely open newer doors of global science and engineering. The authors deeply discussed in minute details the sources, chemical property, and speciation of heavy metals in groundwater, technologies for treatment of heavy metal-contaminated groundwater, chemical treatment technologies, reduction by iron-based technologies, soil washing, in-situ chelate flushing, in-situ chemical fixation, and biological, biochemical, and biosorptive treatment technologies [9]. Biosorption of heavy metals by cellulosic materials and agricultural wastes are the other marvels of this treatise. Biological and agricultural engineering are today in the avenues of deep scientific regeneration and engineering vision and profundity. Environmental engineering and water resource engineering curriculum needs to be revamped and reorganized with the economic growth of a nation. Permeable reactive barriers are wonders of science today. Environmental tools using permeable reactive barriers are also areas of scientific and engineering introspection. Adsorption, filtration, and absorption mechanisms are the needs of science and are the pillars of human

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scientific progress. Membrane science and membrane filtration are also the cornerstones of global water technology research pursuits. These issues are deeply validated in this treatise [9]. Saikia et al. (2019) [10] deeply discussed with scientific vision nanotechnology for water remediation. Scarcity of fresh drinking water has escalated to be one of the major global problem. Traditional and conventional water treatment technologies are not adequate enough to produce safe water. Thus the needs of the science of nanotechnology and its innovations and research directions. On that premise, the advent of nanotechnology has given immense scope and opportunities for the removal of heavy metals, microorganisms, and other recalcitrant pollutants [10]. The scientific divination of environmental protection and industrial pollution control today will pave new avenues in the field of nanotechnology applications in human society. The use of various nanomaterials including carbon-based nanomaterials, metal and metal oxides nanomaterials were deeply focused and their modes of operation and scientific innovation towards wastewater remediation are discussed in details [10]. The authors discussed in minute details the current status, adsorption onto nanomaterials, photocatalytic water treatment using nanoparticles, disinfection of wastewater with nanomaterials, nanomembrane in water and wastewater treatment, and the vast domain of limitations of nanoparticles used in wastewater treatment. Environmental engineering and chemical engineering curriculum are today in the process of newer reinventing. The challenges of health effects and eco-toxicity of nanomaterials in human society today need to be deeply pondered with vision, scientific might, and scientific perseverance. This treatise addresses these intricate issues [10]. Varma (2011) [11] deeply discussed with scientific far-sightedness greener approach of nanomaterials and their vast sustainable applications. Green chemistry and green nanotechnology are in the forefront scientific inventions and scientific ingenuity globally. The integration of green chemistry principles with rapidly evolving area of nanoscience and nanotechnology is a need for risk reduction [11]. Chemical process safety, risk assessment, and process safety management are the coinwords of any chemical engineering processes and environmental engineering systems. Human scientific intellect, deep scientific perceptions, and learning outcomes will eventually lead towards a new era in sustainability and application of nanotechnology. The sustainable use of green synthesized nanoparticles in environmental remediation applications and the utility of recyclable magnetic nanoparticles are the other areas of deep scientific contemplation. Greener synthetic strategies and environmental remediation are the other areas of this scientific endeavor. Research and development forays in nanomaterials can lead to new design rules that are eco-friendly and benign in the context of protecting human health, eco-friendly engineering systems, and public health engineering [11]. Green synthesis of nanomaterials are the marvels of the science of nanotechnology. Nanotechnology will open new doors of innovation and inventions as regards environmental remediation. In this article, the author deeply reiterates these scientific, engineering, sustainable, and ethical issues.

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Nanomaterials and the Vast World of Environmental Remediation Nanotechnology is a revolutionary domain of science and technology in the global landscape. Today is the age of fourth industrial revolution [12–16]. Water and wastewater treatment are vastly needed in the global scenario as public health engineering, civil, and environmental engineering are highly struggling with deep scientific travails and barriers. Nano-remediation and bioremediation of water and industrial wastewater treatment are the needs and marvels of engineering science. Billions of people around the world are without pure drinking water [17–20]. A newer age in the field of water purification science and environmental engineering curriculum are the ultimate needs of the scientific vision. Graphenes, fullerenes, and carbon nanotubes have applications in vast and varied areas of science and engineering. A deep scientific thought in the field of water remediation and water science and technology will revitalize man and mankind’s scientific verve, motivation, and scientific validation. Human mankind is today in a state of immense disaster as arsenic and heavy metal groundwater contamination veritably confronts human society and thus the immediate need of both conventional and nonconventional environmental engineering techniques. Apart from application of nanomaterials, ozonation, Fenton’s treatment, electrochemical treatments, and other advanced oxidation processes will veritably pave the visionary way towards effective water purification science. The challenges, the vision, and the difficulties in environmental engineering techniques are immense, bright, and groundbreaking. The needs of environmental protection and industrial pollution control are today transforming the vast scientific fabric globally. Tertiary treatment of industrial wastewater should be the pillars of environmental engineering research endeavor. The scientific divination and the scientific willpower in global tertiary environmental engineering tools will widely open the doors of research in the field of both nanotechnology and environmental protection in the years to come [17–22].

Drinking Water Crisis, Heavy Metal and Arsenic Groundwater Remediation, and the Visionary Future Drinking water crisis and heavy metal and arsenic groundwater remediation are the bane of human civilization and concerted efforts in its mitigation are the utmost needs of the hour. The future of environmental engineering and chemical engineering are bright and far-reaching. Billions of citizens around the world are in the need of fresh drinking water. Man’s immediate vision and humankind’s deep futuristic vision are today in the path of immense catastrophe as global water crisis confronts the human scientific progress and ingenuity. Bangladesh and the neighboring state of West Bengal, India, are plunged into an unending and unsolvable environmental crisis and thus the need of conventional and nonconventional engineering tools which includes applications of nanomaterials. Graphene-based nanoproducts needs to be applied in nano-remediation. This crisis will be mitigated

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if human scientific genre and efforts will lead a long and visionary way in true realization of science and engineering. The true need and the true scientific ingenuity in the field of nano-remediation, bioremediation, and biological sciences needs to be reenvisioned as regards application of nanomaterials and engineered nanomaterials in water remediation. Soil and sub-surface groundwater remediation are the ultimate needs of the hour if civilization can be saved from climate change, global warming, and loss of ecological biodiversity. Humankind’s vision and man’s relentless efforts will thus lead an effective and visionary way in the true path of science and engineering globally. Drinking water crisis and groundwater remediation are today in the latent stage of research endeavor. In the similar vision, desalination technique and membrane science are today in the path of new regeneration and engineering profundity. A newer challenging era in the field of nanomaterials will veritably open newer dimensions in the field of almost diverse areas of research and development pursuits. Environmental chemistry, green chemistry, green nanotechnology, and green technology will surely advance human scientific and academic rigor in research and development initiatives in water science and technology in decades to come.

Sustainable Resource Management and the Domain of Nanotechnology Sustainable resource management and sustainable development are two opposite sides of the visionary coin. The domain of nanotechnology is today aligned with diverse branches of science and technology. A deep futuristic thought and a deep scientific comprehension will unfold the scientific intricacies and the scientific barriers in nanotechnology applications in sustainable resource management. The divination and redeeming of science and engineering need to be rethought as regards application of sustainable resource management in human society. Circular economy is a marvel of science today. Reduce, reuse, and recycle are part and parcel of circular economy. Nanoscience and nanoengineering are today linked with mass manufacturing and manufacturing engineering. A deep futuristic scientific thought in nanotechnology, nanomaterials, and engineered nanomaterials will surely usher in a newer era in the field of applied sciences and global engineering sciences. The authors in this entire treatise profoundly depicts the immediate needs of nanomaterials such as graphene-based nano-products in environmental pollution control, renewable energy, and health care scenario. Humankind’s global engineering vision will surely be emboldened if nanotechnology is aligned with the world of environmental engineering and environmental process engineering. Environmental chemical engineering will thus open newer windows in global scientific initiatives if the scientific domain takes immediate and visionary steps in the field of environmental pollution control, industrial pollution control, and groundwater remediation. A new age in the field of nanoscience and nanoengineering will surely usher in the vast scientific landscape with grit and determination [21–27].

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Future Research Trends in the Field of Environmental Engineering and Chemical Process Engineering Research trends in the field of environmental engineering and chemical process engineering are highly bright and visionary. Environmental management and sustainable development are two sides of the visionary coin. Water resource engineering and water resource management are today’s research pursuit in environmental pollution control. Human scientific progress in the global scenario is in a state of immense scientific and engineering catastrophe. A deep scientific contemplation and scientific provenance are the ultimate needs of the hour. The entire domain of engineering sciences and applied sciences needs to be refurbished if the world needs to mitigate climate changes and global warming. Thus the future lies in the hands of researchers, scientists, policy-makers, and governments across the world. In this treatise, the authors deeply pronounce the needs of environmental engineering and chemical process engineering in the true advancements of science. The world of graphene and other engineered nanomaterials are the scientific truth, scientific ingenuity, and the truth of engineering science today. Water science and technology is a branch of both environmental engineering as well as the holistic domain of chemical process engineering. In water stressed countries around the world, desalination and membrane science are the needs of the hour and the moments of truth. Proper sanitation, water security, food security, energy and environmental sustainability, education, and human habitat are the pillars of United Nations Sustainable Development Goals. Today is a world of immense scientific stress and vast scientific barriers. Public health engineering in developing countries around the world needs to be restressed and revamped as science, engineering, and civilization tread forward. Governments around the world are in the midst of deep scientific vision as well as in scientific travails and thus the immediate need of an effort on war-footing in water purification, drinking water, and groundwater treatment. The vision of mankind and its knowledge prowess and ingenuity will surely be emboldened if the scientific and engineering order globally moves in the right direction.

Futuristic Vision and Futuristic Flow of Scientific Thoughts Futuristic vision of nanotechnology, environmental engineering, and chemical engineering are today in the path of vast scientific and engineering regeneration. Man’s immense scientific ardor and challenges and humankind’s vast scientific urge to excel will pave the way towards a newer genre in the field of nanoremediation and nanotechnology. Futuristic flow of scientific thoughts should be akin to the scientific intricacies in chemical engineering fundamental concepts such as mass transfer operations and process intensification. Graphene applications in water remediation involves many chemical engineering unit operations.

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These are the areas of immense and vivid scientific introspection. Today, nanoscience, nanotechnology, and chemical engineering are in the process of new rejuvenation. Global research and development initiatives will surely be emboldened if humankind moves faster towards ecological engineering, integrated water resource management, and wastewater treatment management. Technology management and industrial system engineering are the needs of human society today. Thus the needs of nanotechnology industrial processes. Process integration and process intensification in chemical engineering and environmental engineering operations will surely open up newer dimensions of research pursuit in decades to come. Another area of deep scientific comprehension is circular economy and thus the immediate need of the science of sustainable resource management. A remarkable genre and profundity will usher in if science and civilization move towards right directions.

Conclusion, Summary, and Environmental Perspectives Today, there is an immediate need of United Nations Sustainable Development Goals. Integrated water resource management and industrial wastewater management are today integrated with the science of nanotechnology. The areas of water purification, proper sanitation, and success of human habitat are today the major pillars of United Nations Sustainable Development Goals. The visionary definition of “sustainability” given by Dr. Gro Harlem Brundtland, former Prime Minister of Norway, will be eventually reenvisioned and revitalized as science, technology, and humankind moves forward. Graphene-based nanoproducts are the marvels of science and engineering today. It has diverse applications and is an interdisciplinary area of science and technology. In this chapter, the authors dealt deeply the vast needs and the growing challenges in nanomaterials application in water remediation. Groundwater heavy metal contamination is today a burden to human scientific success and academic rigor. Here also comes the importance of nanomaterials and engineered nanomaterials applications. The authors deeply reiterate the scientific and technological issues involved in graphene applications. Energy sustainability and renewable energy are coinwords of global scientific progress today. The authors with deep scientific perspectives pronounce the immense needs of energy and environmental sustainability in unveiling the scientific truth in the field of graphene applications. Man’s vast and varied scientific stance and ardor and humankind’s progress will go a long way in paving the way towards energy and environmental sustainability today. Thus a new epoch in the field of nanotechnology and water science and technology will evolve as civilization crosses one frontier over another. Thus United Nations Sustainable Development Goals will be achieved if man and mankind widely move forward towards circular economy in the future. In this entire treatise, the authors stress these scientific issues and thus a newer epoch is emerging.

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References 1. www.wikipedia.com. Accessed on 12/5/2021 2. www.google.com. Accessed on 12/5/2021 3. Kemp KC, Seema H, Saleh M, Le NH, Mahesh K, Chandra V, Kim KS (2013) Environmental applications using graphene composites: water remediation and gas adsorption. Nanoscale 5: 3149–3171. Royal Society of Chemistry Publishing, Cambridge 4. Perreault P, de Faria AF, Elimelech M (2015) Environmental applications of graphene – based nanomaterials. Chem Soc Rev. https://doi.org/10.1039/c5cs00021a. Royal Society of Chemistry Publishing, Cambridge 5. Gong JR (2011) Graphene-synthesis, characterization, properties and applications. InTech, Croatia, ISBN 978-953-307-292-0 6. Bharech S, Kumar R (2015) A review on the properties and applications of graphene. Journal of Material Science and Mechanical Engineering 2(10):70–73 7. Abdelbasir SM, Shalan AE (2019) An overview of nanomaterials for industrial wastewater treatment. Korean J Chem Eng 36(8):1209–1225 8. Mukherjee S, Mukhopadhyay S, Hashim MA, Sengupta B (2015) Contemporary environmental issues of landfill leachate: assessment and remedies. Crit Rev Environ Sci Technol 45:472–590. https://doi.org/10.1080/10643389.2013.876524. Taylor and Francis Group, LLC 9. Hashim MA, Mukhopadhyay S, Sahu JN, Sengupta B (2011) Remediation technologies for heavy metal contaminated groundwater. J Environ Manag 92(2011):2355–2388 10. Saikia J, Gogoi A, Baruah S (2019) Nanotechnology for water remediation. In: Dasgupta N et al (eds) Environmental nanotechnology, environmental chemistry for a sustainable world. Springer Nature Switzerland AG, pp 195–211 11. Varma RS (2011) Greener approach to nanomaterials and their sustainable applications. Curr Opin Chem Eng 1:123–128 12. Palit S (2018) Recent advances in the application of engineered nanomaterials in the environment industry- a critical overview and a vision for the future. In: Hussain CM (ed) Handbook of nanomaterials for industrial applications. Elsevier, pp 883–893 13. Palit S (2015) Microfiltration, groundwater remediation and environmental engineering science- a scientific perspective and a far-reaching review. Nat Environ Pollut Technol 14(4): 817–825 14. Palit S, Hussain CM (2018) Biopolymers, nanocomposites, and environmental protection: a far-reaching review. In: Ahmed S (ed) Bio-based materials for food packaging. Springer Nature Singapore Pvt Ltd, pp 217–236 15. Palit S, Hussain CM (2018) Nanocomposites in packaging: a groundbreaking review and a vision for the future. In: Ahmed S (ed) Bio-based materials for food packaging. Springer Nature Singapore Pvt Ltd, pp 287–303 16. Palit S (2017) Advanced environmental engineering separation processes, environmental analysis and application of nanotechnology- a far-reaching review. In: Hussain CM, Kharisov B (eds) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge, pp 377–416 17. Hussain CM, Kharisov B (2017) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge 18. Hussain CM (2017) Magnetic nanomaterials for environmental analysis. In: Hussain CM, Kharisov B (eds) Advanced environmental analysis- application of nanomaterials, vol 1. The Royal Society of Chemistry, Cambridge, pp 3–13 19. Hussain CM (2018) Handbook of nanomaterials for industrial applications. Elsevier, Amsterdam 20. Palit S, Hussain CM (2018) Environmental management and sustainable development: a vision for the future. In: Hussain CM (ed) Handbook of environmental materials management. Springer Nature Switzerland AG, pp 1–17

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21. Palit S, Hussain CM (2018) Nanomembranes for environment. In: Hussain CM (ed) Handbook of environmental materials management. Springer Nature Switzerland AG, pp 1–24 22. Palit S, Hussain CM (2018) Remediation of industrial and automobile exhausts for environmental management. In: Hussain CM (ed) Handbook of environmental materials management. Springer Nature Switzerland AG, pp 1–17 23. Palit S, Hussain CM (2018) Sustainable biomedical waste management. In: Hussain CM (ed) Handbook of environmental materials management. Springer Nature Switzerland AG, pp 1–23 24. Palit S (2018) Industrial vs food enzymes: application and future prospects. In: Kuddus M (ed) Enzymes in food technology: improvements and innovations. Springer Nature Singapore Pvt Ltd., Singapore, pp 319–345 25. Palit S, Hussain CM (2018) Green sustainability, nanotechnology and advanced materialsa critical overview and a vision for the future. In: Ahmed S, Hussain CM (eds) Green and sustainable advanced materials, Volume-2, applications. Wiley Scrivener Publishing, Beverly, pp 1–18 26. Palit S (2018) Recent advances in corrosion science: a critical overview and a deep comprehension. In: Kharisov BI (ed) Direct synthesis of metal complexes. Elsevier, Amsterdam, pp 379–410 27. Palit S (2017) Nanomaterials for industrial wastewater treatment and water purification. In: Handbook of Ecomaterials. Springer International Publishing, AG, pp 1–41

Consumer Nanoproducts Based on Graphene and Graphene Nanocomposite

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Nanomaterial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene-Based Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fabrication Techniques for Polymer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene-Nanoparticle Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesis Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Creative Processes to Modify Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Suspension/Substrate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Graphene developed as extraordinary material due to its underlying properties of naturally possessing two-dimensional structure. In the current research, the different chemical features have promoted high-performance devices for generating and storing graphene energy. The specific area of graphene is increasing from electronic, chemical utilization to biomedical application. The promising challenges in this research study are to overcome and adequately appreciate graphene’s unique properties in various proper forms. The valuable information and adequate understanding of graphene nanocomposite ensure the safety uses of helpful material. The scientist has undertaken particular efforts to examine recent material to develop fundamental physics. Chemists based on organic and material are working hard for synthesizing T. Arfin (*) Environmental Materials Division, CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nagpur, India Hyderabad Zonal Centre, CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Hyderabad, Telangana, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_39

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the novel synthetic route toward a single layer of high quality, and engineering is working on framing the unique device for the exploitation of extraordinary characteristics of graphene. The future of graphene is prosperous due to the properties and behavior. The current book chapter’s primary focus is on providing an inspirational source to the consumer nanoproduct mechanism of graphene nanocomposite. Keywords

Graphene oxide · Polymer · Nanomaterial · Nanofiller · Solution mixing

Introduction The possible use of nanotechnology came into 1974 as coined by Prof. N.T. as a semiconductor process in an academic conference. But in the year 1959 only, the fundamental concept of building minute thing was properly assigned by Richard Feynman. He attributed that the giant machine could be responsible for building up the small device and the product governed by the atom and finally called it molecular manufacture. Nanotechnology represents a technological field employing diverse materials ranging between 1 nm and 100 nm known as nanomaterials [31]. The nanoscale working permits for carefully manipulating the valuable material attaining the unique properties that usually vary from that present in molecular level or bulk form [17, 42]. The nanoscale is the basis of a new and beneficial application for increased reactivity and functionality due to the more excellent surface-to-volume ratio for enhancing the dispersion. It allows developing uneven application comprised of diverse aspect, namely, medicine, water purification, and so on.

Graphene Nanomaterial The graphene nanomaterial (GM) is different from each other in various ways like lateral dimension, surface chemistry, defect density, quality of single graphene sheet, composition, and purity [8]. The GM is equivalent toward carbon nanotubes peculiar from each other in a practical matter of wall number, effective diameter, considerable length, surface chemistry, a substantial amount, complex composition, and visible form of metal impurities [43]. Figure 1 properly reflects the essential GM and even various characteristics the same as that of colloidal behavior.

Fig. 1 Members of the graphene nanomaterial

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Fig. 2 Key different aspects of an effective method for graphene synthesis

Fig. 3 Material properties of graphene nanomaterials

Graphene Production The creative process of synthesizing graphene (G) is accurately described by the fabrication method, precisely defining the unique properties and possible application. Hence, in this regard, G fabrication is considered an exceptionally fascinating topic of research. To date, it is observed that not even a sole method for synthesis of G has been noted yielding the G that demonstrates optimum properties for the continuous application. The elaborated array of synthesizing approaches of G comprise categories into two processes, namely, physical and chemical method shown in Fig. 2.

Material Properties It has become mandatory to detect that synthesizing had naturally produced singlesheet graphene accurately. Therefore, the size and functional group attached are necessary factors for the dispersion of polymer. Figure 3 demonstrates the various properties of the valuable material illustrated. The significant nanomaterial employed for the consumer is G and its nanocomposite.

Graphene-Based Nanocomposites Graphene-Polymer Nanocomposites In the current nanotech developed world, the used polymer is naturally found to traditionally play an essential task in the active sensor and energy conversion sector

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[3]. The G properties are likely to improve when submerged homogeneously in the matrix, and the masses are used as a filler and as the interaction of polymer [65]. The pristine graphene (PG) does not possess compatibility for the organic polymer, but despite that, it liberates the homogeneous composite [4]. In the specific case of graphene oxide (GO), it typically exhibits compatibility for the organic polymer [5]. G is used correctly as a nanofiller for the different polymer like polyurethane (PU), polystyrene (PS), polyethylene terephthalate (PET), polyaniline (PANI), polyvinylidene fluoride (PVDF), and so on to enhance the characteristics of the polymer merely.

Polyaniline Conducting polymer is a specialized polymer with π-conjugated electrons stretched on the polymer backbone, and it also has a delocalized electron structure [9, 10]. PANI is a naturally exceptional electric and conducting flexible polymer showing obscure composition [32, 37]. PANI can be processed by in situ electropolymerization method. This process can offer advantages, such as less reaction time and practical simplicity. The PANI attained through a method form a thin film. It also showed irregular structures. Epoxy The epoxy resin has merely low thermal conductivity, and on introducing graphene sheets (GS), it showed highly improved quality. On adding 1 wt% of GO to epoxy resin, there are identical effects as that of thermal conductivity, and it is filled with regret by 1 wt% of SWNT. GO-filled epoxy resin of 5 wt% is critically four proper times more than clear epoxy resin [75]. Polyurethane Liang et al. [53] produced three forms of nanocomposite by the gradual process of solution mixing. They traditionally used isocyanate-modified graphene (ICG), sulfonated graphene (SR), nanofiller, reduced graphene, and thermoplastic polyurethane (TPU) in the possible way of the matrix polymer. Even some functional groups are also attached to prepared SG sheets. Polystyrene Polystyrene is a synthetic, hydrophobic, and thermoplastic substance posing a highly globalized demand that comes after PVC [38]. It possesses various properties like noble mixer binding ability in phosphate metal [21]. It exhibits cytotoxicity [60], antibacterial activity [11], DC conductivity [14], transport phenomena [35], doublelayer capacitance [34], thermodynamic effect [25], dielectric [16], ionic potential [24], charge density [22], impedance [33], enthalpy [23], entropy [9, 10], etc. Eda and Chhowalla [49] synthesized PS/FGS composite by adequately employing the method of solution blending. The composite shows various essential features, such as it is efficiently semiconducting in fundamental nature and possesses precisely an ambipolar field effect. The conductivity of the composite tends to reduce with a decrease in temperature to approximately 50 K. It tends to increase marginally with a reduction in temperature to some extent.

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Nafion The uptake of sufficient water for GO increases with the specific content of GO in the Nafion/GO membrane because of the hydrophilic GO. Nafion/Pt-G membrane is barely in possible comparison to Nafion/GO. Nafion/Pt-G does not reveal enough economic improvement at different RHs [51]. PVA The nanocomposite dependent on the wholly exfoliated graphene nanosheet and PVA were synthesized by establishing the facial solution’s proper use. The composite’s mechanical activity was positively enhanced by instantly adding graphene nanosheet in the active PVA matrix. PVDF The PVDF/GO nanocomposite fiber with dry-jet wet spinning showed that at the specific GO concentration of 2 wt%, the composite included significant enhancement in the proper form of toughness. It simultaneously increased the tensile strength as well as the modulus. The possible variation in the mechanical features is typically in co-relation with trace chain conformation disparity specified on the precise drawing. The valuable material sufficiently shows a PVDF mobile because of the conformation irregularity, and kinks naturally tend to get nucleated PVDF chain and GO functional group instantly. The used PVDF fiber handled naturally possesses a conventional translation of the crystal polymorphs [52]. Poly(3,4-ethyldioxythiophene) The new and innovative graphene hybrid material (GHM), namely, PEDOT exhibiting water and an organic method of processing, was reliably produced. The various aspects were observed, such as conductivity of order 0.2 S/m, the light transmittance of more than 80% ranging between the wavelength of 400 and 1800 nm, and the thickness of films of 10 nm. The material has specific features like vigorous and elastic behavior and retention of excellent electrical conductivity after deformation. Such extraordinary characteristics in a unique combination with the easy preparation and critical capability of innovative solution correctly processing merely enabled the PEDOT graphene to sufficiently show enhanced application, and even the combined form conductivity needed transparency, and considerable flexibility was in demand [74]. Polyethylene The melt compounding method was adequately employed for the dispersion of GNPs on PET, which naturally resulted in the possible formation of PET nanocomposite posing positively enhanced mechanical and thermal features. The PET pellet was grounded into fine powder form to improve the interaction ability between GNP sheet and PET chains. The distribution analysis referred to the mixing of GNP to PET, and it received a uniform distribution of GNP in comparison to PET pellet. GNP’s orientation scheme is incredibly efficient, and it reinforced the PET matrix showing enhanced mechanical features. The confirmation was provided by employing the matrices [70].

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Polycarbonate The polycarbonate-based material was reinforced by GO, and then the thin transparent film made through a facile method. The notable film’s microstructure accurately reflected GO’s homogeneous dispersion between nanoscale and microscale. Agglomeration was observed at higher loaded GO that is 0.7%. The PC-GO and GO film indicated extraordinary bacteriostatic action toward E. coli and S. aureus. The antibacterial nature of PC-GO merely enabled it to obtain suitable material for properly employing in the biomedical device as well as in food packing material [54]. Starch The possible starch application is still the same, where 60% of starch applied as food form and 40% as an industrial application [66]. The prominent chemist scientifically studying complex carbohydrate has properly organized various innovative products typically based on starch and its possible uses [59]. Starch is made into bioplastic, but it is water-soluble. The valuable material developed from starch swells up and gets severely deformed on direct exposure to excessive moisture, limiting its practical use [27, 28]. The GO exfoliated within the TWCS economically exploits the waxy starch retrogradation, and such action results in representing a possible interaction between the distinct phases. The BNCs of starch and GO made through melt properly serve as suitable for application in various fields. Alginate Alginate is the salt of calcium (Ca), magnesium (Mg), and sodium (Na) formed from alginic acid attained by brown algae cell wall employed for the enzyme immobilization [29, 72]. In 1944 alginate fibers were first pronounced by Speakman and Chamberlain, studying wet-spinning technique [30]. GAD hydrogels’ possible use for the potential removal of heavy metal clarifies about double network present in GAD positively enhancing the adsorption capacity of heavy ions. It helps in maintaining reusability after several spontaneous adsorption/desorption cycles. Cellulose Cellulose is naturally a biomaterial present in apparent abundance in the kindly earth’s prepared crust. It is sufficiently prepared by rare plants, reliably producing beneficial bacteria [6]. Nanocelluloses (NC) are synthesized through cellulose degradation from aboveground biomass. Some of the nanocelluloses are cellulose nanocrystals [45], cellulose nanofibrils [50], and bacterial cellulose [46]. Ethyl cellulose (EC) has the same structure as present in cellulose and its continuous derivative, but it is the few hydroxyl groups changed by the ethoxy group [18, 19]. EC is obtained from the reaction between alkali and ethyl chloride [63]. EC’s flexible membrane is unswellable, and it is also compatible with the plasticizers [12, 64]. It can also be employed as a rigid form [61]. The cellulose/GO hydrogel remains a modern platform, and it applied in designing different GO base material. The suitable, environmentally familiar reduction process can be

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implemented to typically obtain highly electrical conductivity and mechanical features within the composite.

Chitosan Chitosan is derived from chitin deamination [1]. In 1906, von Furth and Russo suggested standard features of chitosan [62]. There are various advantages of nanoscale chitosan, like antibacterial behavior and minimum toxicity toward mammalian cells [20]. Glycerol permits food interaction between complex CS matrix and GO nanosheets. Hence, valuable CS/GO/glycerol materials are recognized as appropriate material for numerous uses needing enhanced mechanical features [48]. Gelatin Gelatin is typically a functional protein made from native collagen partial hydrolysis. In the continuous availability of dilute acids, it is present in the visible bone and precious skin of a noble animal [44]. RGO/gel composite includes an excellent mechanical feature, and the testing clarifies that adding RGO increases the gelatin film’s tensile strength in moist and rigid condition. It was observed that on adding RGO, no negative behavior on the growth of the cell was found; hence, RGO/gel can be considered critically as suitable material posing unique mechanical features and better cell compatibility [73]. Protein Functional protein corresponds, respectively, to amino acids positively linked through the amide bone [40]. Most of the body hormones obtain polypeptides [13, 41, 55]. Lectins receive a protein with a feature to recognize the residue of carbohydrate [56]. The possible interaction of GO and protein is generally electrostatic and weak. With an increase in the GO oxidation degree, there is a change in the extent of interacting with a protein [58]. Nanotubes MWCNTs are the modern tubes properly containing multiple shells. The size is significant, and it works efficiently compared to SWCNT [47]. The exciting topic at valuable present represents the notable addition of MWCNT in various useful materials for reinforcing fibers. This is primarily because of the excellent mechanical as well as physical features such as significant tensile strength [2]. GO nanosheets were responsible for positively enhancing and stabilizing the MWCNTs dispersion. When minimum GO dose was added to MWCNT, the considerable gap between carbons nanomaterials was bridged, constituting a conductive network. It could permit for developing of a smooth pathway for the conduction of electron. Polyamide Polyamides categorized into diverse class based on the necessary arrangement and monomer chemical nature like aromatic, cycloaliphatic, and aliphatic polyamides

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Fig. 4 Various types of fabrication technique

[36]. Polyamides consist of crystalline polymers made from the condensation reaction of diamine and diacid [15]. The Cr(IV) ion’s adsorption capacity was properly 47.17 mg/g of N6.6/GO graciously according to the fundamental equations and isotherm curves. The equilibrium data observed that Langmuir isotherm was more capable enough [69].

Fabrication Techniques for Polymer The different fabrication processes were given for the polymer/graphene nanocomposite. The proper selection of adequate procedures was dependent on graphene uniform dispersion and the total intercalation of the organic polymers. Figure 4 reveals a thorough process of modern fabrication.

Graphene-Nanoparticle Composite Graphene is properly the material posing lots of principle attraction due to its platelike extraordinary and structure features. So it is infinitely preferable as an attractive substrate for inorganic nanoparticle deposition. The possible disadvantages of graphene sheet aggregation are prevented partly by intercalating particles in the graphene’s distinct layer. Such composites can impart functionality to the graphene used for different applications through the single components’ synergistic behavior. To date, many metal compounds are composed of graphene and derivatives of graphene, e.g., Au, Cu, ZnO, CdS, Sr2Ta2O7, and so on.

Synthesis Approaches Figure 5 shows the different synthesis strategies used for graphene-nanoparticle composite.

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Fig. 5 Ideal various types of synthetic strategies

Creative Processes to Modify Graphene Graphene is modified by several efficient methods, as listed in Fig. 6.

Suspension/Substrate Figure 7 exhibits various parameters responsible for positively affecting specific cells’ effective response toward graphene-based material within the possible suspension and in the proper form of a suitable substrate. It relates to the fact that graphene as a substrate interaction with the cell differs from the suspension of graphene particles.

Applications The G and G derivatives gained attention in modern science and engineering awareness because of the varied number of potential applications. G’s invention and discovery are considered a milestone in the field of material science and noticed. They are profitably employed in the application, as given in Fig. 8.

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Fig. 6 Creative processes of considerable modification of graphene

Fig. 7 Schematic shows different parameters of graphene in suspension and as a supportive substrate

Conclusion In 2004, the G discovery by Geim and Novoselov had sufficiently illustrated the ubiquitous features, and the G derivatives have also persuaded academic researchers on a worldwide basis [7, 26, 39]. A surface group’s continuous availability has provided a novel process to modern synthesis GO-based material by coordinating

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Fig. 8 Various types of application of graphene-based material

with other material [67]. It concluded in designing new material posing record features [57, 68, 71]. Such technology constrained technical limitations like developing the material of required optimization and adequate efficacy. The economic advancement in this academic field helped out for environmental safety as well as eco-friendly maintenance. The selectivity needs to be enhanced along with acute sensitivity for the various components. By instantly following this essential step, the commercial sector will gain either in the practical term of the sustainable economy or controlled environment. Therefore, the investigation technique typically needs sustainable development and continuous optimization of nanocomposite at necessary minimum costing. The developed world is waiting to look forward to green and sustainable material to use for safety regard. Therefore, in this proper context, modern graphene-based material merely requires lots of principal attraction, and many more investigations are needed to fulfil the basic necessity. Acknowledgments Authors acknowledge the Knowledge Resource Centre, CSIR-NEERI (CSIRNEERI/KRC/2020/SEP/EMD/1), for their support.

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38. Arfin T, Mohammad F, Yusof NA (2015) Applications of polystyrene and its role as a base in industrial chemistry. In: Lynwood C (ed) Polystyrene: synthesis, characteristics and applications. Nova Science Publishers, New York, pp 269–280 39. Arfin T, Bushra R, Mohammad F (2016) Electrochemical sensor for the sensitive detection of o-nitrophenol using graphene oxide-poly(ethyleneimine) dendrimer-modified glassy carbon electrode. Graphene Technol 1(1):1–15. https://doi.org/10.1007/s41127-016-0002-1 40. Arfin T, Athar S, Rangari S (2018a) Proteins and their novel applications. In: Ahmed S, Kanchi S, Kumar G (eds) Handbook of biopolymers: advances and multifaceted applications. Pan Stanford Publishing, Singapore, pp 75–93 41. Arfin T, Tarannum A, Sonawane K (2018b) Green and sustainable advanced materials: an overview. In: Ahmed S, Hussain CM (eds) Green and sustainable advanced materials: processing and characterization, vol 1. Scrivener Publishing LLC, Hoboken, pp 1–34 42. Arfin T, Singh B, Varshney N (2019) Biological adhesion behavior of superhydrophobic polymer coating. In: Samal SK, Mohanty S, Nayak SK (eds) Superhydrophobic polymer coatings: fundamentals, design, fabrication, and applications. Elsevier, Amsterdam, pp 161–177 43. Arfin T, Varshney N, Singh B (2020) Ionic liquid modified activated carbon for the treatment of textile wastewater. In: Naushad M, Lichtfouse E (eds) Green materials for wastewater treatment. Springer, Cham, pp 257–275 44. Athar S, Arfin T (2017) Commercial and prospective applications of gelatin. In: Ahmed S, Ikram S (eds) Natural polymers: derivatives, blends and composite, vol 2. Nova Science Publishers, New York, pp 199–216 45. Athar S, Bushra R, Arfin T (2017) Cellulose nanocrystals and PEO/PET hydrogel material in biotechnology and biomedicine: current status and future prospects. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 139–173 46. Borkar R, Waghmare SS, Arfin T (2017) Bacterial cellulose and polyester hydrogel matrices in biotechnology and biomedicine: current status and future prospects. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 21–46 47. Bushra R, Arfin T, Oves M, Raza W, Mohammad F, Khan MA, Ahmad A, Azam A, Muneer M (2016) Development of PANI/MWCNTs decorated with cobalt oxide nanoparticles towards multiple electrochemical, photocatalytic and biomedical application sites. New J Chem 40(11): 9448–9459. https://doi.org/10.1039/C6NJ02054B 48. Cobos M, Gonzalez B, Fernandez MJ, Fernandez MD (2017) Chitosan-graphene oxide nanocomposites: effect of graphene oxide nanosheets and glycerol plasticizer on thermal and mechanical properties. J Appl Polym Sci 134(30):45092. https://doi.org/10.1002/app.45092 49. Eda G, Chhowalla M (2009) Graphene-based composite thin films for electronics. Nano Lett 9(2):814–818. https://doi.org/10.1021/nl8034367 50. Khan AU, Malik N, Arfin T (2017) Nanofibrillated cellulose and copoly (amino acid) hydrogel matrices in biotechnology and biomedicine. In: Jawaid M, Mohammad F (eds) Nanocellulose and nanohydrogel matrices: biotechnological and biomedical applications. Wiley-VCH, Weinheim, pp 331–352 51. Lee DC, Yang HN, Park SH, Kim WJ (2014) Nafion/graphene oxide composite membranes for low humidifying polymer electrolyte membrane fuel. J Membr Sci 452:20–28. https://doi.org/ 10.1016/j.memsci.2013.10.018 52. Lee JE, Eom Y, Shin YE, Hwang SH, Ko HH, Chae HG (2019) Effect of interfacial interaction on the conformational variation of poly(vinylidene fluoride) (PVDF) chains in PVDF/Graphene oxide (GO) nanocomposite fibers and corresponding mechanical properties. ACS Appl Mater Interfaces 11(14):13665–13675. https://doi.org/10.1021/acsami.8b22586 53. Liang J, Xu Y, Hang Y, Zhang L, Wang Y, Ma Y, Li F, Guo T, Chen Y (2009) Infrared triggered actuators from graphene-based nanocomposites. J Phys Chem C 113(22):9921–9927. https:// doi.org/10.1021/jp901284d

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54. Mahendran R, Sridharan D, Santhakumar K, Selvakumar TA, Rajasekar P, Jang JH (2016) Graphene oxide reinforced polycarbonate nanocomposite films with antibacterial properties. Indian J Mater Sci:4169409. https://doi.org/10.1155/2016/4169409 55. Malik N, Khan AU, Naqvi S, Arfin T (2016a) Ultrasonic studies of different saccharides in α-amino acids at various temperatures and concentrations. J Mol Liq 221:12–18. https://doi.org/ 10.1016/j.molliq.2016.05.061 56. Malik N, Khan AU, Naqvi S, Arfin T (2016b) Ultrasonic investigation of in α-amino acids with aqueous solution of urea at different temperatures: a physicochemical study. J Appl Solut Chem Model 5(4):168–177 57. Malik N, Arfin T, Khan AU (2019) Graphene nanomaterials: chemistry and pharmaceutical perspectives. In: Grumezescu AM (ed) Nanomaterials for drug delivery and therapy. Elsevier, Amsterdam, pp 373–402 58. Malik SA, Mohanta Z, Srivastava C, Atreya HS (2020) Modulation of protein-graphene oxide interactions with varying degree of oxidation. Nanoscale Adv 2:1904–1912. https://doi.org/10. 1039/C9NA00807A 59. Mogarkar PR, Arfin T (2017) Chemical and structural importance of starch based derivative and its applications. In: Ikram S, Ahmed A (eds) Natural polymers: derivatives, blends and composite, vol 2. Nova Science Publishers, New York, pp 73–87 60. Mohammad F, Arfin T (2013) Cytotoxic effects of polystyrene-titanium-arsenate composite in cultured H9c2 cardiomyoblasts. Bull Environ Contam Toxicol 91(6):689–696. https://doi.org/ 10.1007/s00128-013-1131-3 61. Mohammad F, Arfin T, Al-Lohedan HA (2017a) Sustained drug release and electrochemical performance of ethyl cellulose-magnesium hydrogen phosphate composite. Mater Sci Eng C 71:735–743. https://doi.org/10.1016/j.msec.2016.10.062 62. Mohammad F, Arfin T, Al-Lohedan HA (2017b) Enhanced biological activity and biosorption performance of trimethyl chitosan-loaded cerium oxide particles. J Ind Eng Chem 45:33–43. https://doi.org/10.1016/j.jiec.2016.08.029 63. Mohammad F, Arfin T, Al-Lohedan HA (2018a) Synthesis, characterization and applications of ethyl cellulose-based polymeric calcium (II) hydrogen phosphate composite. J Electron Mater 47(5):2954–2963. https://doi.org/10.1007/s11664-018-6118-8 64. Mohammad F, Arfin T, Saba N, Jawaid M, Al-Lohedan HA (2018b) Electrical conductivity and biological efficacy of ethyl cellulose and polyaniline-based composites. In: Khan A, Jawaid M, Khan AAP, Asiri AM (eds) Electrically conductive polymers and polymer composites: from synthesis to biomedical applications. Wiley-VCH, Weinheim, pp 181–197 65. Mohammad F, Arfin T, Al-Lohedan HA (2019a) Biocompatible polylactic acid-reinforced nickel-arsenate composite: studies of electrochemical conductivity, mechanical stability, and cell viability. Mater Sci Eng C 102:142–149. https://doi.org/10.1016/j.msec.2019.04.046 66. Mohammad F, Arfin T, Bwatanglang IB, Al-Lohedan HA (2019b) Starch-based nanocomposites: types and industrial applications. In: Sanyang ML, Jawaid M (eds) Bio-based polymers and nanocomposites: preparation, processing, properties & performance. Springer, Cham, pp 157–181 67. Mohammad F, Arfin T, Al-Lohedan HA (2019c) Development of graphene-based nanocomposites as potential materials for supercapacitors and electrochemicals cells. In: Jawaid M, Ahmad A, Lokhat D (eds) Graphene-based nanotechnologies for energy and environmental applications: micro and nano technologies. Elsevier, Amsterdam, pp 145–154 68. Mohammad F, Arfin T, Al-Lohedan HA (2019d) Enhanced biosorption and electrochemical performance of sugarcane bagasse derived a polylactic acid-graphene oxide-CeO2 composite. Mater Chem Phys 229:117–123. https://doi.org/10.1016/j.matchemphys.2019.02.085 69. Parlayici S, Avci A, Pehlivan E (2019) Electrospinning of polymeric nanofiber (nylon6.6/ graphene oxide) for removal of Cr(VI): synthesis and adsorption studies. J Anal Sci Technol 10(1):13. https://doi.org/10.1186/s40543-019-0173-5

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70. Shabafrooz V, Bandla S, Allahkarami M, Hanan JC (2018) Graphene/polyethylene terephthalate nanocomposites with enhanced mechanical and thermal properties. J Polym Res 25(12):256. https://doi.org/10.1007/s10965-018-1621-4 71. Sophia AC, Arfin T, Lima EC (2019) Recent developments in adsorption of dyes using graphene based nanomaterials. In: Naushad M (ed) A new generation materials graphene: applications in water technology. Springer, Cham, pp 439–471 72. Waghmare SS, Arfin T (2015) Defluoridation by adsorption with chitin-chitosan-alginate-polymers-cellulose-resins-algae and fungi-a review. Int Res J Eng Technol 2(6):1179–1197 73. Wang W, Wang Z, Liu Y, Li N, Wang W, Gao J (2012) Preparation of reduced graphene oxide/ gelatin composite films with reinforced mechanical strength. Mater Res Bull 47(9):2245–2251. https://doi.org/10.1016/j.materresbull.2012.05.060 74. Xu Y, Wang Y, Liang J, Huang Y, Ma Y, Wan X, Chen Y (2009) A hybrid material of graphene and poly(3,4-ethydioxythiophene) with high conductivity, flexibility, and transparency. Nano Res 2(4):343–348. https://doi.org/10.1007/s12274-009-9032-9 75. Yu A, Ramesh P, Sun X, Bekyarova E, Itkis ME, Haddon RC (2008) Enhanced thermal conductivity in a hybrid graphite nanoplatelet-carbon nanotube filler for epoxy composites. Adv Mater 20(24):4740–4744. https://doi.org/10.1002/adma.200800401

Performance of Graphene: A Brief Literature Review on Technologies for Composite Manufacturing

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R. Sundarakannan, V. Arumugaprabu, S. Vigneshwaran, P. Sivaranjana, and R. Deepak Joel Johnson

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of Graphene and Processing for Composite Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Reinforced Metal Matrix Composites and Its Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Reinforced Polymer Matrix Composites and Its Properties . . . . . . . . . . . . . . . . . . . . . . . . . Graphene Reinforced Ceramic Matrix Composites and Its Properties . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Developing new material with improved strength is one of the challenges for the researchers in the field of composite materials. In such a way, graphene is one of the attractive materials recently developed and reinforced in different composites to improve their properties. Graphene has superior properties owing to their honeycomb lattice structure and a single layer of carbon atoms arrangement. The main advantage of graphene is their thin layer structure and lightweight. At present, graphene is utilized as reinforcement in the composite material production and various properties has been discussed. The graphene-based composite materials are suitable for various applications such as medicine, electronics, sensor, energy, solar cell, filtration, and mechanical fields. At present, graphene reinforced materials R. Sundarakannan · P. Sivaranjana School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India V. Arumugaprabu (*) Department of Mechanical Engineering, School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India e-mail: [email protected] S. Vigneshwaran · R. D. J. Johnson Department of Mechanical Engineering, Saveetha School of Engineering, Saveetha School of Medical and Technical Sciences, Thandalam, Chennai, Tamil Nadu, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_40

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have been largely developed and investigated. This chapter reports the recent development in composite with graphene reinforcement, in particularly graphene reinforcement effect in the polymer, metal, and ceramic matrixes. Keywords

Graphene · Graphene oxide · Polymer · Metals · Ceramics

Introduction In recent years, composite materials were developing for various application to replace over their conventional materials owing to their good strength, less weight, the resistance of wear, and low cost [1]. Various filler has been reinforced in ceramic, metal, and polymer matrix such as carbon nanotubes CNT [2], Al2O3 [3], TiO2 [4], SiC [5], and industrial waste red mud [6] to enhance on their mechanical properties. Filler reinforced composite materials showed an increase in material properties. There have been numerous research works that reported the properties of filled composites. Graphene advantages and its utilization have been explored during the last decade. The graphene consists of layer-by-layer arrangement of carbon atoms, and it is mostly prepared from carbon-rich materials like graphite [7]. Some notable applications of graphene materials are in energy storage devices, solar cells, nanoelectromechanical systems, transistor, memory devices, photodetector, coatings, electronic application, polymer composites, ceramic composites, and even in metal matrix composites. The graphene poses excellent mechanical, thermal, electrical properties [8]. The graphene delivers tremendous mechanical properties by their monolayer structure, given the mechanical strength of 130GPa proved it considered as one of the strongest materials [9]. Compared to CNT filler, graphene has a higher specific surface area and are not agglomerate easily; when reinforcing, this makes a uniform dispersion in the matrix. Also, CNT is needed to process for modifying the surface to prepared composite. Compared to other filler materials, graphene has less health hazard [10]. Recently, Graphene has been found as an effective reinforcement in the composite materials [11]. Research on the graphene reinforced composites is a developing area, which is more promising and unexploited. The ultimate intent of this review is to deliver a comprehensive picture of the graphene reinforced composites. This review classified and reported the graphene reinforced polymers, metals matrix, and ceramic matrix.

Preparation of Graphene and Processing for Composite Fabrication Mostly graphene is extracted from carbon-rich material like graphite through modified Hummers method [12]. Graphene is formed through layer-by-layer exfoliation of graphite formed with a single layer honeycomb structure [13]. The graphite material undergoes some chemical reaction for reducing it to graphene by the

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process of modified hummer’s method [14]. Most of the authors reported this method to produce graphene oxide. On the other hand, mechanical exfoliation process used to produce the graphene nano-platelets. In this method, planetary mills play a role to produce graphene from bulk graphite material [15]. Graphene can also be synthesized through chemical vapor deposition method. In this method, graphene film was coated on a particular substrate using gas molecules at high temperature [16]. Out of all these methods, graphene processed through chemical reduction is more popularly used, since these methods produce graphene at large amount and are more suitable for utilizing in the practical applications [17]. But at present for developing composites, graphene oxides reduced through exfoliation and chemical reduction is more preferably used and also through modified Hummers’ method [18]. For fabricating graphene composites, various methods have been followed. Some common methods used in fabricating graphene composites with metal, polymer, and ceramic matrixes are listed in Table 1, 2, and 3 respectively. In composite fabrication, dispersion of graphene in the matrix is more important, since it defines the interfacial attraction between the graphene and the matrix. Unfortunately, graphene has high surface area and strong van der Waals forces, this made them to attract each other and agglomerates [19]. But this can be overcome by processing the graphene through surface modification like noncovalent and covalent bonding.

Graphene Reinforced Metal Matrix Composites and Its Properties Reinforcement of graphene in metal matrix composites is more difficult, and it is challenging for researchers. The preparation of metal matrix composite considers some factors such as powder size, shape, percentage of filler. This process of producing composite material, mainly focused on uniform distribution of matrix, plays an important role on the metal matrix composites. Jingyue Wang et al. [80] reported the tensile strength of graphene nanosheet reinforced aluminium matrix composites. The tensile strength of the composites enhanced by 62% due to graphene reinforcement in the aluminum matrix. Graphene reinforcement develops uniform dispersion throughout the matrix. Fadavi Boostani et al. [81] fabricated graphene encapsulated sic nanoparticles reinforced aluminum matrix composites. The result is evident as the tensile and ductility properties were improved by 45% and 84%, owing to the graphene reinforcement. Chi-Hoon et al. [82] fabricated the graphene oxide reinforced aluminum matrix and analyzed the thermal properties of the composites. Thermogravimetric test results showed that the functional group of graphene oxide improved the thermal conductivity of the graphene aluminum matrix significantly up to 15%. Compared to pure aluminum, the tensile strength of the composite decreased on reinforcement, although the elongation properties are enhanced. Wenzheng Zhai et al. [83] studied tribological properties of multi-layer graphene (MLG) reinforced Ni3Al metal matrix composites. The graphene reinforced at different weight such as 0.5, 1.0, 1.5, and 2.0 wt. %. The results concluded that the optimum wear rate at 1.0% of MLG reinforced metal matrix composites. The hardness and elasticity properties significantly increased up to 1.0% of MLG addition and after that decreased.

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Table 1 Processing techniques of graphene reinforced metal matrix composites S. No 1 2 3 4 5 6 7 8 9 10 11 12

Graphene reinforcement Graphene nano sheets Graphene oxide Single-layer graphene oxide Graphene oxide Graphene nanoplatelets Multilayer grapheme Graphene nanoflakes Graphene oxide Multilayer graphene Graphene nanosheets Graphene

Matrix material Aluminum Copper Iron Aluminum Aluminum TiAl

Fabrication method Powder metallurgy Spark plasma sintering Laser sintering Friction stir processing Hot extrusion Spark plasma sintering Hot isostatic pressing

Aluminum alloy Aluminum Ni3Al

Powder metallurgy Powder metallurgy

Copper

Hot-press sintering

Copper

Microwave sintering processes Hot isostatic pressing

Graphene nanoflakes Graphene nanoplatelets

Titanium

Magnesium

15

Graphene nanoplatelets Graphene oxide

Aluminum

16

Graphene

Nickel

Liquid state ultrasonic processing Hot extrusion processes Electrostatic selfassembly In-situ fabrication;

17

Graphene

Aluminum

Sintering process

18

Graphene oxide

Aluminum

19 20

Graphene oxide Multi-layer graphene

Iron Titanium

Direct electrostatic adsorption Laser sintering Spark plasma sintering

13

14

Magnesium alloy

References Jingyue Wang et al [20], 2012 Jaewon Hwang et al [21] 2013 Dong Lin et al [22], 2014 Chi-Hoon Jeon et al [23], 2014 Muhammad Rashad et al [24], 2014 Zengshi Xu et al [25], 2013 S.J. Yan,[26] 2014 Xin Gao et al [27], 2016 WenzhengZhai et al [28], 2014 Hongyan Yue et al, [29] 2016 C. Ayyappadas et al [30], 2017 Zhen Cao et al [31], 2017 Lian-Yi Chen et al [32], 2012 Xian Du et al [33], 2017 Xin Gao et al [34], 2016 Jinlong Jiang et al [35], 2018 Jong-Min Ju et al [36], 2017 Zan Li et al [37], 2014 Dong Lin et al [38], 2014 Y. Song et al [39], 2016

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Table 2 Processing techniques of graphene reinforced polymer matrix composites S. No 1

2

Graphene reinforcement Few-layered graphene sheets Graphene nanosheets

Matrix material Chitosan

Graphene oxide Graphene

Epoxy

Chitosan Hydrogenated Carboxylated Nitrile–Butadiene Rubber Polybenzimidazole

8

Graphene oxide Graphene oxide Graphene oxide Graphene

Polypropylene

Solution-based processing method Solution casting method Cast resin plaques Solution casting method Solutionblending method Solventexchange method Melt-blending

9

Graphene

Polyethylene terephthalate

Melt blending

10

Graphene oxide Graphene oxide Graphene nanosheets Graphene

Glycerol-plasticized pea starch Poly methyl methacrylate

Solution casting method. Solvent casting

High density polyethylene Polyvinylidene fluoride

Melt Mixing Solvent casting

Graphene platelets Graphene nanoplatelets Few-layer graphene Graphene nanoplatelets Graphene

Polyethylene terephthalate

Melt blending

Epoxy

Hot pressing

Polyvinyl alcohol & poly methyl methacrylate Poly(3-hydroxybutyrate-co4-hydroxybutyrate) Polyurethane

Hot compaction

19

Graphene nanoplatelets

Polyurethane

In situ polymerization.

20

Graphene nanosheets

Polybenzimidazole

In-situ polymerization

3 4 5 6 7

11 12 13 14 15 16 17 18

Poly(butylene succinate)

Fabrication method Solution casting method

Epoxy

Solution casting Sol–gel method

References Hailong Fan et al [40], 2010 Xin Wang et al [41], 2011 MinooNaebe et al [42], 2014 Xin Wang et al [43], 2013 Yongzheng Pan et al [44], 2011 Xin Bai et al [45], 2010 Yan Wang et al [46], 2010 Pingan Song et al [47], 2011 Oana M. Istrate et al [48], 2014 Rui Li et al [49], 2010 Gil Gonc¸alves et al [50], 2010 M. El Achaby et al [51], 2013 VarrlaEswaraiah et al [52], 2011 Oana M. Istrate et al [53], 2014 Ming-Yuan Shen et al [54], 2013 Barun das et al [55], 2009 V. Sridhar et al [56], 2012 Xin Wang et al [57], 2012 Santosh kumaryadav et al [58], 2012 Md. Wasiahmad et al [59], 2018

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Table 3 Processing techniques of graphene reinforced ceramics matrix composites S. No 1 2 3 4

Graphene reinforcement Graphene nanosheets Graphene nanofillers Graphene

Matrix material Alumina Silicon nitride Monolithic zrb2 Zirconia

5

Reduced graphene oxide Graphene

6

Graphene flakes

Calcium silicate Zirconia

7

Graphene oxide

Alumina

8

Graphene

9

Graphene nanosheet Graphene platelets Graphene oxide

Zirconium diboride Zrb2–sic

10 11 12 13

Graphene platelets Graphene oxide

14

Graphene oxide

15

Graphene platelet Graphene platelet Graphene nanosheets Graphene

16 17 18 19 20

Few-layer graphene Graphene platelet

WC-Al2O3 Zirconia Boron carbide Alumina/ zirconia Zirconia Boron carbide Silicon carbide Alumina Si3n4 Alumina Alumina and zirconia

Fabrication method Spark plasma sintering. Spark plasma sintering Hot pressing Spark plasma sintering Selective laser sintering Spark plasma sintering Sintering process Spark plasma sintering Hot pressing Process Hot-pressing sintering Spark plasma Sintering Hot-pressing

References Harshit Porwal et al [60], 2016 Hanuˇs Seiner et al [61], 2015 Mehdi ShahediAsl et al [62], 2014 Jung-Hoo Shin et al [63], 2014 CijunShuai et al [64], 2014 A. Smirnov et al [65], 2019 Lu Wang et al [66], 2019 Govindaraajan et al [67], 2018 Xinghong Zhang, Yumin An et al [68], 2015 Xiaoxiao Zhang et al [69], 2019 N. W. Solís et al [70], 2017

Tape casting

A. Kovalčíková et al [71], 2015 Oxide et al [72], 2014

Spark plasma sintering Hot pressing

Layersacaciorincón et al [73], 2016 Richard sedlák et al [74], 2017

Hot pressing

Richard sedlák et al [75], 2017

Rapid sintering route Spark plasma sintering Spark plasma sintering Spark plasma sintering.

Iftikharahmad et al [76], 2017 Tomasz cygan et al [77], 2016 Yuchi fan et al [78], 2012 By kylejiang et al [79], 2014

Li et al. [84] performed microstructural and tensile test analysis on the graphene reinforced aluminum matrix composites. The graphene was reinforced aluminum matrix at various weight percentage such that (0.5, 1, 1.5, and 2%) by hot extrusion techniques. The tensile test reports that the graphene content beyond 1% forms

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agglomeration in grain boundaries and weak bonding of the matrix. This effect decreased the ductility and tensile strength of the composites. Composite with 0.5% graphene significantly improved mechanical properties. Xin Gao et al. [85] studied the mechanical properties on graphene powder reinforced copper matrix. The mechanical properties of the prepared composites increased significantly on graphene reinforcement. Micro hardness and tensile strength reached the maximum at 0.3% graphene reinforcement. Furthermore, addition decreased the mechanical properties and the elastic modulus. Zengrong et al. [86] investigated the mechanical properties on graphene reinforced titanium matrix composites. Graphene addition improved the hardness up to 50% when compared to unfilled composite. Also, the modulus value significantly increased at 5% graphene reinforcement. More addition of the reinforcement decreased the hardness value due to the formation of aggregation throughout the matrix. Saurabh Dixit et al. [87] analyzed the multilayer graphene reinforced aluminum metal matrix composites. The aluminum matrix ductility was increased by 33% on the graphene addition. The graphene reinforced composites show a 45% increase in hardness value. The ultimate tensile strength of the pure aluminum value is 84MPa, and the graphene reinforced aluminum matrix is 147MPa. This study confirmed that graphene reinforcement enhanced mechanical properties of aluminum composites. Duosheng et al. [88] investigated the mechanical properties of graphene reinforcement aluminum composites, and it compares with pure aluminum metal. Graphene was reinforced at different volume fraction, such as 0.5, 1.0, 1.5, and 2.0%, and it mixed with aluminum powder to fabricate the composite plate through vacuum hot pressing sintering method. The compressive strength increased when increasing the graphene weight percentage. The maximum compressive strength of 527Mpa was noted on the 2% graphene reinforcement. After graphene reinforcement, 330% to 586% increment is noted in compressive strength compared to pure aluminum matrix. X.N. mu et al. [89] analyzed the graphene reinforced Ti carbide matrix composites. Composites were fabricated with 0.2% graphene with Ti carbide matrix through the hot rolling process at varying temperatures of 823, 1023, and 1223K. Graphene composites showed 2.5% to 12.5% times increased tensile strength than the pure matrix. The varying temperature plays a significant role in improving the tensile strength of the Ti graphene composites. Xian Du et al. [90] studied the microstructure, mechanical properties of graphene nanoplates reinforced homogenous magnesium alloy (ZK60). The hardness test shows that the maximum hardness value of 78 on 0.1% Gnp reinforcement. The tensile load on the composites reveals the plenty of tear edges. The pure Mg alloys tensile and compressive was compared with 0.05% and 0.1% graphene nanoplates. The ultimate tensile strength, tensile yield strength, and elongation values increased with reinforcement of graphene, the maximum values for that tensile strength UTS 345, TYS 283, Mpa & elongation 17%. Maximum compressive strength is noted on of 0.1% graphene composite (OCs 463Mpa, UYS 279 & failure strain 12%). Hansang et al. [91] compared the 1.vol% graphene oxide reinforced aluminum matrix composites and the pure AuMg5 alloy. The hardness of 73Gpa is recorded on graphene added matrix and 53 Gpa on pure AuMg5 matrix. The composite

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modulus strength enhanced by 30% and the maximum tensile strength is 556 MPa is noted at 1.0% graphene reinforced composite. Furthermore, graphene composite flexural strength value is 813 Mpa, which is over four times higher than the pure composite. Haiboluo et al. [92] analyzed the graphene oxide modified silver nanoparticles (AG-Rgo) reinforced copper matrix. The tensile strength and yield strength were significantly increased on Ag-RGo reinforced matrix, which is 478 Mpa and 332 Mpa, respectively. The elongation is higher on the pure copper matrix and decreased on the addition of reinforcement. The tensile strength reached at maximum on RGO composites which are 52% and 98% higher than the pure copper material. Ankita Bisht et al. [93] investigated on the graphene nanoplatelets reinforced aluminum matrix composites. The graphene is reinforced at different weight percentage such as 0.05, 1, 3, and 5 wt. % and composites were fabricated by spark plasma sintering method. At 3% and 5%, graphene reinforcement develops agglomeration on the composites due to weak interfacial adhesion between reinforcement and matrix. Compared to other weight percentages, 1% of the grapheneenhanced the tensile strength, yield strength, as well as hardness and which are 84, 54.8, and 24.1% higher than the values of pure Aluminum.

Graphene Reinforced Polymer Matrix Composites and Its Properties In Recent years, polymers are widely used in various applications due to their advantages. The filled polymer composites increase the mechanical behavior depending upon the reinforcement percentages. This filler addition forms the good bonding between the matrix, and it creates in improving the uniform stress distribution of composites. This graphene filler effect is discussed in the polymer composites is witnessed by various researchers. Wenchao pang et al. [94] investigated on tribological properties of graphene oxide (GO) reinforced polyethylene matrix, fabricated different weight percentage of GO by hot pressing techniques. Tribological properties were investigated under the different condition on dry, deionized water and seawater. Water absorption studies indicated that 0.13% GO composites exhibited better water resistance properties compare to neat composites. Abrasion wear studies revealed that the addition of the graphene oxide composites lead to decreased wear resistance. GO content significantly improved the crystallinity of the polymer matrix, which increased the micro hardness properties. Orebotse Joseph Botlhoko et al. [95] explained that thermal and mechanical properties of graphene reinforced polylactide/polycaprolactone composites. Graphene oxide reinforced polymer matrix was fabricated by melt mixing method. Thermally reduced graphene was used in this composite. TGA analysis shows that at 100  C, loss of weight in composites is noted due to loss of water molecules. The carbon content present in the composites undergoes the weight loss of peak found at 500  C. Optimal thermal properties of graphene composites were obtained at 700  C thermally reduced graphene reinforcement at 0.05 wt. %. Rui Sun et al. [96] analyzed the behavior of polymer composites

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reinforced single-layer graphene consists of single and double vacancy structure. Compared with single vacancy graphene, composites double vacancy was exhibited better mechanical properties of graphene filled composites. Nitai Chandra Adak et al. [97] reported mechanical properties of graphene oxide and woven carbon fiber reinforced epoxy polymer matrix. Graphene nanofiller incorporated at different weight percentages such as 0.05, 0.1, 0.2, and 0.4% and the fiber weight percentage is maintained. Nanographene filled composites at 0.2% has a maximum tensile strength of 336 MPa. Flexural properties of the fabricated composite significantly increased by 34, 43, 56, and 51%, respectively, when compared to neat composites. After 0.2% of graphene reinforcement, drastic reduction in mechanical properties is noted. Good interlocking characteristics were observed for 0.2% epoxy graphene carbon composites. Suman Chhetri et al. [98] investigated on mechanical, thermal, and topography properties of graphene included epoxy matrix composites. Tensile properties were increased on the reinforcement of graphene. Tensile strength of 0.2% graphene filled composites reached a maximum value of 51 MPa, thus compared to a neat epoxy matrix, 0.2% filled composites have maximum thermal stability. Lingyun Zhang et al. [99] fabricated polystyrene matrix reinforced graphene oxide by melt mixing method. Graphene oxide was incorporated with various weight percentages such as 0.1, 2, and 4%. Tensile strength of composites was significantly increased by the addition of nano filler graphene oxide. Impact strength of composite plates was increased of the graphene addition. TEM studies revealed the good dispersion of the graphene in polystyrene composites. Han Wang et al. [100] reported that uniform distribution of graphene with the matrix is the key to obtain maximum tensile, impact, and toughness strength. Thermal properties of the composites revealed high stability of graphene at 0.3 wt. % reinforcement. MinooNaebe et al. [101] made a comparison study between graphene reinforced epoxy matrix composites and neat epoxy composites. It is found that 0.1% of functionalized graphene reinforcement showed 22% increase in the tensile strength when compared with neat composites. Topographical studies were examined for interfacial bonding, adhesion, and dispersion of functionalized graphene matrix composites. Cui-Cui Wang et al. [102] observed that various percentage of graphene oxide reinforced polypropylene carbon fiber composite. Graphene was prepared by modified Hummers’ method and mixed polypropylene short carbon fiber by melt mixing method. Mechanical tests were conducted and compared with various percentage of graphene and carbon fiber filled composites. The tensile test reported that including graphene and short carbon fiber significantly improved the tensile, flexural, and impact strength. The maximum properties were observed on 0.5% graphene oxide reinforced short carbon fiber filled composites. Differential scanning calorimeter studies revealed that 0.5% GO/SCF composites improved thermal stability of the polymer composites. Annie Moussemba Nzenguet et al. [103] analyzed mechanical properties of graphene oxide reinforced bio nanocomposites films. Graphene oxide incorporated with matrix at different weight percentage such as 0.3, 0.5, 0.7, and 1.0% composites. Graphene composites at 1% exhibited maximum strength. Barun Das et al. [104] analyzed mechanical properties of graphene reinforced polymer

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matrix composites. Graphene was added at a different weight percentage to polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) matrix. The hardness and elastic strength were significantly increased on the addition of graphene for both fabricated specimens. Compared to PVA composites, PMMA composites showed maximum strength.

Graphene Reinforced Ceramic Matrix Composites and Its Properties The Ceramics materials brittle behavior limits their use in the mechanical application. The ceramic materials found its application in the automobile industry, electronic industry, biomedical industry, etc. In recent years, graphene is used as the reinforcement in the ceramic composites. Lenka Kvetkova et al. [105] compared the 1% graphene platelets reinforced silicon nitride composites fabricated through two processes, hot isostatic pressure method and gas sintering method. Graphene platelets composites fabricated through the gas pressure sintering attained the lower fracture value. Pavol Hvizdo et al. [106] conducted the tribological studies for silicon nitride ceramic matrix reinforced of different types of graphene platelets. The ceramic composites were prepared by hot isostatic process on 1700  C at 20MPa for 3 h sample holding time. The wear resistance property was increased on the graphene addition. Notably, 3% composites showed lower wear value which is 60 wt. % than the pure silicon nitrate. Ya-Fei Chen et al. [107] fabricated the graphene nanosheets reinforced on alumina composites by the addition of graphene nanosheets in different weight percentages such as 0.1, 0.2, 0.5, and 1 through hot isostatic processing method. The prepared composites’ bending strength and fracture strength was examined, the 0.2% graphene nanosheet alumina composites showed the maximum strength. The fracture toughness of the reinforced composite showed a 43.5% increase, when compared with pure alumina matrix. Yu Cheng et al. [108] investigated the hardness properties on graphene platelets reinforced alumina oxide and titanium matrix composites. The graphene platelets reinforced at weight percentages such as 0.1, 0.2, 0.4, 0.6, and 0.8%, respectively. The prepared composites hardness and toughness properties increased at 0.2 wt. % of graphene platelet reinforcement. This work concluded that the maximum values observed at 0.2% graphene composites reached maximum fracture value noted at titanium matrix composites which is 67.3% higher when compared to pure aluminum oxide. Cui et al. [109] studied the graphene nanoplatelets incorporated Al2O3 and Ti composites by using hot pressing sintering technique and investigating the mechanical properties. Initially, addition of graphene nanoplatelets increased the mechanical strength, the maximum value was observed on 0.4 wt. % composites, after that mechanical property was decreased. When compared to the pure ceramic, 0.4 wt. % composites increased the flexural strength and fracture strength by 40.13% and 40.78%, respectively.

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Tomasz Cygan et al. [110] investigated on the graphene oxide reinforced alumina matrix by spark plasma sintering method and reported that graphene is an effective reinforcement material to improve the mechanical properties of ceramic composites. Grigoriev et al. [111] reported on the graphene oxide reinforced alumina-silicon carbide composites. The maximum mechanical properties were found on 0.5 wt. % composites (hardness 22GPa, fracture toughness 10.6GPa, and flexural strength 904 MPa, respectively.) Thereafter, additional GO doesn’t improve the strength. Xingzhong Guo et al. [112] prepared the silicon carbide matrix reinforced multilayer graphene composites. The investigation reports 5% graphene composite has a promising hardness value of 16.74 Gpa, bending strength of 265.44 MPa, and dry co-efficient of friction of 0.22. Peter Kun et al. [113] reported that the multilayer graphene reinforcement provides the maximum bending and elastic modulus in ceramic composites. Jian Liu et al. [114] investigated the toughness behavior of graphene platelets reinforced zirconia alumina composites. The ceramic composites prepared from spark plasma sintering method are at different temperatures such as 1450, 1550, 1650, and 1750  C. Composites with 0.18% graphene platelets fabricated condition at 1550  C exhibited maximum toughness strength. Fu Liu et al. [115] analyzed the graphene oxide reinforced SiC composite fabricated by reaction sintering method at a various weight percentage of GO (0.5, 1.0, 1.5 and 3.0). The bending strength and fracture strength were observed on the prepared composites, and it is found that 1.5 wt. % composites showed higher fracture strength of 3.6 MPa. The bending strength of 10% composites increased by 58% when compared to pure SiC composite. Mehdi Mehrali et al. [116] reported the mechanical properties of calcium silicate ceramic matrix filled with reduced graphene oxide composites. In this work, composites are prepared at a different weight percentage of graphene (0.25, 0.5, 0.75, 1.0, and 1.5) by the hot isostatic process. The mechanical properties were compared with pure and the 0.5 wt. % calcium silicate composites such that elastic modulus 52%, fracture strength 123%, and hardness 40%. Harshit porwal et al. [117] produced the graphene reinforced alumina nanocomposites fabricated by powder processing method at different volume percentages of graphene (0.1, 0.5, 0.8, 2, and 5). The composite with 0.8 wt. % of graphene showed improved mechanical characteristics. A linear increase is noted up to 0.8%, after that the mechanical strength was reduced due to improper bonding and also due to agglomeration of graphene.

Conclusions It can be resolved from the review that the graphene has the efficiency to enhance and vary the composite properties, which can be used in broad applications. This is evident from the literature which shows a significant improvement in mechanical, electrical, and thermal characteristics. Reinforcement percentage of graphene in matrix defines the strength of the composite material. The properties of graphene composite mainly depend on the purity, loading ratio, dispersion with matrix, agglomeration, and interaction of graphene with the matrix. It is identified that

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only limited studies explain the effect of the size distribution of graphene in the composite material. Also, the stability of the graphene at high temperature should be addressed in detail since various fabrication processes of the graphene is exposed to very high temperature. Reinforcement of graphene into a polymer, metal, and ceramic composite is still in developing stage. To optimize the processing techniques and to achieve the utilization in the application, the graphene composite should be studied in more details which could develop a new window to utilize graphene in various composite applications.

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biodegradable polylactide/poly(ε-caprolactone) blend composites, Polymer. https://doi.org/10. 1016/j.polymer.2018.02.005 96. Sun R, Li L, Feng C, Kitipornchai S, Yang J (2018) Tensile behavior of polymer nanocomposite reinforced with graphene containing defects. Eur Polym J 98:475–482 97. Adak NC, Chhetri S, Kim NH, Murmu NC, Samanta P, Kuila T (2018) Static and dynamic mechanical properties of graphene oxide-incorporated woven carbon Fiber/epoxy composite. J Mater Eng Perform 27(3):1138–1147 98. Chhetri S, Adak NC, Samanta P, Murmu NC, Kuila T (2017) Functionalized reduced graphene oxide/epoxy composites with enhanced mechanical properties and thermal stability. Polym Test 63:1–1 99. Zhang L, Tu S, Wang H, Du Q (2018) Preparation of polymer/graphene oxide nanocomposites by a two-step strategy composed of in situ polymerization and melt processing. Compos Sci Technol 154:1–7 100. Wang H, Xie G, Fang M, Ying Z, Tong Y, Zeng Y (2017) Mechanical reinforcement of graphene/poly (vinyl chloride) composites prepared by combining the in-situ suspension polymerization and melt-mixing methods. Compos Part B 113:278–284 101. Naebe M, Wang J, Amini A, Khayyam H, Hameed N, Li LH, Chen Y, Fox B (2014) Mechanical property and structure of covalent functionalised graphene/epoxy nanocomposites. Sci Rep 4:4375 102. Wang CC, Zhao YY, Ge HY, Qian RS (2018) Enhanced mechanical and thermal properties of short carbon fiber reinforced polypropylene composites by graphene oxide. Polym Compos 39 (2):405–413 103. Nzenguet AM, Aqlil M, Essamlali Y, Amadine O, Snik A, Larzek M, Zahouily M (2018) Novel bionanocomposite films based on graphene oxide filled starch/polyacrylamide polymer blend: structural, mechanical and water barrier properties. J Polym Res 25(4):86 104. Das B, Prasad KE, Ramamurty U, Rao CNR (2009) Nano-indentation studies on polymermatrix composites reinforced by few-layergraphene. Nanotechnology 20:125705. (5pp) 105. Kvetková L, Duszová A, Kašiarová M, Dorčáková F, Dusza J, Balázsi C (2013) Influence of processing on fracture toughness of Si3N4+ graphene platelet composites. J Eur Ceram Soc 33 (12):2299–2304 106. Hvizdoš P, Dusza J, Balázsi C (2013) Tribological properties of Si3N4–graphene nanocomposites. J Eur Ceram Soc 33(12):2359–2364 107. Chen YF, Bi JQ, Yin CL, You GL (2014) Microstructure and fracture toughness of graphene nanosheets/alumina composites. Ceram Int 40(9):13883–13889 108. Cheng Y, Zhang Y, Wan T, Yin Z, Wang J (2017) Mechanical properties and toughening mechanisms of graphene platelets reinforced Al2O3/TiC composite ceramic tool materials by microwave sintering. Mater Sci Eng A 680:190–196 109. Cui E, Zhao J, Wang X (2019) Determination of microstructure and mechanical properties of graphene reinforced Al2O3-Ti (C, N) ceramic composites. Ceram Int 45(16):20593– 20599 110. Cygan T, Wozniak J, Kostecki M, Petrus M, Jastrzębska A, Ziemkowska W, Olszyna A (2017) Mechanical properties of graphene oxide reinforced alumina matrix composites. Ceram Int 43 (8):6180–6186 111. Grigoriev S, Peretyagin P, Smirnov A, Solis W, Díaz LA, Fernández A, Torrecillas R (2017) Effect of graphene addition on the mechanical and electrical properties of Al2O3-SiCw ceramics. J Eur Ceram Soc 37(6):2473–2479 112. Guo X, Wang R, Zheng P, Lu Z, Yang H (2019) Pressureless sintering of multilayer graphene reinforced silicon carbide ceramics for mechanical seals. Adv Appl Ceram 118(7):409–417 113. Kun P, Tapasztó O, Wéber F, Balázsi C (2012) Determination of structural and mechanical properties of multilayer graphene added silicon nitride-based composites. Ceram Int 38(1): 211–216

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114. Liu J, Yan H, Reece MJ, Jiang K (2012) Toughening of zirconia/alumina composites by the addition of graphene platelets. J Eur Ceram Soc 32(16):4185–4193 115. Liu F, Wang M, Chen Y, Gao J, Ma T (2019) Mechanical properties and microstructure of reaction sintering SiC ceramics reinforced with graphene-based fillers. Appl Phys A 125(10): 680 116. Mehrali M, Moghaddam E, Shirazi SFS, Baradaran S, Mehrali M, Latibari ST et al (2014) Synthesis, mechanical properties, and in vitro biocompatibility with osteoblasts of calcium silicate–reduced graphene oxide composites. ACS Appl Mater Interfaces 6(6):3947–3962 117. Porwal H, Tatarko P, Grasso S, Khaliq J, Dlouhý I, Reece MJ (2013) Graphene reinforced alumina nano-composites. Carbon 64:359–369

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials and Their Importance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbonaceous Nanomaterials and Their Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Properties of Graphene and Its Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Processing of Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Graphene and Graphene Market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphene-Based Products and Technologies Available in the Market . . . . . . . . . . . . . . . . . . . . . . . . . Electrical/Electronic/Thermal Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sports, Safety, and Outdoor Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Audio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Automobiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Textiles/Outfits and Filtration/Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biotech . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coatings, Adhesives, and Oil and Gas Industries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Future Prospects of Graphene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

This chapter provides a comprehensive review of current trends in graphenebased consumer and industrial products. Initially, the chapter focuses on classification of nanomaterials, including carbon-based nanomaterials and their properties and superiority while highlighting the role of different properties in practical applications. Then processing of graphene is briefly discussed for its mass production to address the growing needs of the technological trends and the R. K. Guduru · A. A. Gupta (*) Pandit Deendayal Petroleum University, Gandhinagar, Gujarat, India e-mail: [email protected]; [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_41

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consumer market. It further describes the worldwide market scenario, various applications of graphene and graphene-based consumer products, and technologies currently available in the global markets. Finally, it concludes with a discussion on future prospects of graphene and its composites and associated challenges in meeting the global industrial demands. Keywords

Graphene · Graphene-based composites · Nanomaterials · Applications · Consumer products · Graphene market · Graphene products · Global market · Future prospects

Introduction The promising superior properties of nanomaterials over the conventional macroand microscale counterparts have opened up plethora of opportunities for their practical applications in the consumer world. Among various such nanomaterials, graphene has garnered a greater attention due to its large surface area, lightweight (0.77 mg/m2), hardest nature (than the diamond), ultrahigh strength (~100–300 times the strength of the steels), superior electron mobility (~100 times more to the electron mobility in Si), and better electrical conductivity (~13 times more than the electrical conductivity of Copper) characteristics [1]. These excellent features of graphene seem to provide great potentials to bridge several gaps in the property constrained arena of conventional materials and their applications. The market for graphene-based materials has been expanding quite rapidly in many segments including electronics, sensors, biotechnology, sports, oil and gas, radiation shielding, and textiles [2]. Thus keeping many upcoming opportunities for graphene in mind, here in this chapter, we initially focus on the properties of graphene and its composites followed by avenues for their practical applications. Then, we will discuss about the existing as well as upcoming consumer products of graphene-based materials in the global markets. Finally, we will provide our insights on future prospects of furthering their applications.

Nanomaterials and Their Importance Nanomaterials are of organic/inorganic nature that could exist either in the form of nanoparticles or nanolayers or nanostructured materials. The nanostructured materials usually have internal features, such as grains whose size range is within 1–100 nm, whereas the nanophase/nanoparticle materials could exist as individual particles within the size of 1–100 nm [3, 4]. On the other hand, nanolayer materials could exist in 2D geometry with thickness hardly in the nanoregime. Thus nanomaterials can be divided into different categories based on their dimensionality, especially the dimension in which the size effect could be apparent on the resultant

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property; thus the nanomaterials are classified as 0D, 1D, 2D, and 3D materials [5]. The zero-dimensional materials basically confine the movement of electrons in all the three dimensions, for example, the quantum dots. In case of 1D, the electrons are free to move only along one dimension, and they are confined in the other two directions. The examples for such nanomaterials are nanowires, nanotubes, and carbon nanotubes (CNTs). In 2D, such as thin layer structures, the electrons are free to move in any two directions and are confined in the third direction. The quantum wells and layer-structured materials, such as graphene, graphene oxide, MoS2, and WO3, are the best examples for this class of materials. In case of 3D nanomaterials, the electrons are free to move in all the three directions, the nanoparticles represent this class of materials [6, 7]. The nanomaterials of 0D, 1D, 2D, and 3D can be fabricated using different chemistries, which include carbon, metals, non-metals and their oxides, and sulfides. Figure 1 shows the classification of nanomaterials as per their dimensions. The nanomaterials exhibit unique and enhanced properties when compared with the bulk materials because of their high surface area to volume ratio. They have gained a huge importance in the science and technology as well as the consumer markets in the twenty-first century, while the technological advances were racing toward miniaturizing the current technologies/devices [8, 9]. At the same time, the nanomaterials have also garnered excellent attention in terms of achieving specific functionality and selectivity. For the past couple of decades, the scientific and technological domains of the nanotechnology focused more on miniaturization of the current instruments/machines/devices and sensors to greatly enhance their performance in terms of speed and sensitivity while minimizing the energy consumption, which are expected to impact the consumer markets to a great extent. For example, the nanotechnology has developed mimics of human brains, biosensors for

Fig. 1 Classification of nanomaterials based on their dimensionality. (Reproduced with permission of [5] Copyright Elsevier, 2018)

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early-stage detection of the diseases at the molecular level, and nanoscale electronics for constant monitoring of the local environment with reduced energy requirement for their functionality [10]. The huge improvement in properties of nanomaterials is achieved through their small feature size with large percentage of atoms on the surface or along the grain boundaries. At the same time, the characteristics of nanomaterials are quite sensitive to their sizes [11], which is partly due to the varying surface to volume ratio; thus a large percentage of surface atoms brings in many size-dependent phenomena. Large surface area of nanomaterials can be exploited for many practical/industrial applications, such as filtration processes and catalytic processing because of their enhanced chemical reactivity [12–19]. In case of optical applications, a wide range of nanomaterial-based optical sources (e.g., high-performance lasers and illumination sources) that consume very less energy can be fabricated. For energy storage, large surface area facilitates in storing huge amounts of charge through double-layer formation, for example, the graphene-based supercapacitors exhibit a large increase in the energy storage capacity. The consumer products with varying functionalities can be made by selecting appropriate fabrication methods while controlling their size, shape, and composition [20]. However, assembling nanomaterials is one of the complex processes. Various research groups and industries are working toward developing different synthetic strategies that are economically affordable for fabrication of consumer products that are not only superior to the current products but also conserve the energy and preserve their superior characteristics for longer lifetimes [21].

Carbonaceous Nanomaterials and Their Classification Among various types of nanomaterials, carbon-based nanomaterials (CNMs) have captured a great interest in the scientific and applied communities for the past couple of decades due to their unique structures and excellent properties. The CNMs exhibit very distinctive and superior physical and chemical properties with the virtue of their unique ability to establish robust covalent bonds with diverse hybridization states (sp, sp2, and sp3) that result in a wide variety of structures, including its allotropes and nanostructures [22]. Figure 2 shows the classification of CNMs based on their dimensionality. However, based on the hybridization of C atoms in the covalent bond linkage, CNMs can be categorized into two. The first group contains sp2 hybridization with graphenic nanostructures with densely packed hexagonal honeycomb crystal lattice (Note: They may have sp3 also, but only at the defects and edges). The CNMs that fall under this category are graphene, CNTs, onion-like carbon nanospheres, and carbon dots. These materials exhibit 2D lattice structure with simple hexagons, and the simplest basic representative of this group is a single atom thick graphene sheet. The graphene sheet is also the building block for other nanostructures, such as fullerene (0D), CNT (1D), multilayer stacked carbon nanosheets, or graphite (2D). The complex carbon

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Fig. 2 Classification of CNMs based on their dimensionality. (Reproduced with permission of [22] Copyright ACS Publications, 2018)

nanohorn structures are also made of the same building block, i.e., the graphene sheet. On the other hand, the second group of CNMs contains both sp3 and sp2 hybridizations at various sites of the bonding. They can also possess amorphous and graphitic regions but predominantly sp3 carbon atoms. Nanodiamond and certain types of carbon-dot structures fall under this paradigm. The distinction of these materials is that they are not built upon the single atom or monolayer of graphene building block. For more details on the CNM classification and their properties, one can refer to the review articles [22, 23]. Depending on the structures and varieties, the CNMs have attracted a great attention in various applications ranging from filtration to catalysis, energy storage, strength enhancement, drug delivery, and improved electrical properties. With several advances in the nanotechnologies, the widespread role of CNMs has seen a rapid growth in the recent past, especially after realizing the capabilities of graphene. Among all the CNMs, the graphene took over the presidency with its unbeatable characteristics.

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Properties of Graphene and Its Derivatives Although graphene was discovered in 1987 [24], its potentials were thoroughly studied only in the early to late 2000s. It is usually a stable material under normal conditions with high quality at microscopic level. Researchers [22, 23] have shown its promising characteristics and potentials from the fundamental science as well as technological and applied research perspectives. It is the strongest materials for its weight [25] and exhibits highest rigidity among all the natural and engineered materials. It also has a negative thermal coefficient of expansion [26]. It exhibits pronounced ambipolar electric field effect with high electron mobility at room temperature [27, 28]. The electronic structure of graphene is quite different from a typical 3D material [29]. Unlike other materials, the Fermi level of graphene can be controlled with the applied electric field and can be turned into n- or p-doped accordingly [30]. One of the major advantages of graphene over other materials is its manipulative conductivity, which can be altered using adsorbent materials like water and other chemicals compounds with which it will get doped and result in superior electrical conductivity, which will be higher than copper’s electrical conductivity. On the other hand, the large surface area of graphene (theoretical surface area ~ 2630 m2) is usually much higher than many materials and can be exploited in sensing and energy storage applications as well. Graphene also exhibits intrinsic corrugations, topological defects, and vacancies, which act as reactive sites for sensing and functional applications [22, 23]. Graphene and its derivatives can be adsorbed onto the surfaces through introduction of active groups. For example, the metal interactive groups could help in adsorption of graphene onto metallic surfaces and help develop thin films that could provide lubrication and reduce the friction in many engineering applications, including in the oil and gas industries [31]. In addition, graphene is a hydrophobic material, which helps in creating hydrophobic surfaces for corrosion resistance as well as in the oil drilling operations where the hydrophobic films could help reduce the interactive forces between the drilling tools and the drilling fluids and prevent sticking of tools and other accidents effectively [32]. Graphene can also be used as a filtration media for selective filtration. In addition to the above, the other desirable properties that graphene has for membrane and filtration applications are as follows: (a) thinner than the existing membranes almost by 20,000 times, (b) its ideal pore size, (c) resistance to oxidation (up to 450
C), and (d) mechanical stability [32]. In addition to pure graphene, in recent years, its derivatives graphene oxide (GO) and the graphene composites have also taken up a pivotal importance from the practical applications point of view. Thanks to GO, for its superior functional characteristics, hydrophilic behavior. The hydroxyl and epoxy groups of GO surface, and carboxylic/carbonyl groups on the edges of the GO layers, make the GOD undergo easy chemical fractioning, which opens up the possibilities for organicmineral hybridization [33]. In case of composites, different types of polymers and metal oxides were added to the graphene-based sheets for developing nanocomposites with great structural and multifunctional characteristics. Interestingly, these composites showed quite contrasting properties when compared with the

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regular engineered composites, which will usually follow the rule of mixtures principle. In contrary, the graphene nanocomposites were showing entirely new properties [34]. On top, the functionalization of graphene at the defects and surface sites has shown to prevent aggregation of graphene flakes or sheets in the liquid media as well as in the composites and facilitated the dispersion in the composite matrix phases while imparting superior chemical and physical attributes.

Processing of Graphene Different approaches have been developed to synthesize graphene nanosheets, and they can be categorized into “top-down” and “bottom up” approaches [35]. In many approaches, the graphite-based precursors are employed, which is basically a stack of several graphene layers held together by weak van der Waals forces. Therefore, preparation of graphene from graphite needs to overcome the van der Waals forces while de-stacking the graphene sheets, and this approach is called “top-down.” However, this approach could result in low yields, surface defects, as well as re-agglomeration of separated graphene sheets and involves tedious procedures [36]. On the other hand, the bottom-up approaches focus on putting the building block units, i.e., carbon molecules together, and these are usually obtained from alternative sources. Although, this approach may not offer the capability to produce large surface area graphene sheets, but facilitates in large quantity production of graphene [37]. Following are the techniques that fall under top-down approaches – mechanical exfoliation, graphite intercalation, nanotube slicing, pyrolysis, reduction of graphite oxide, electrochemical exfoliation, sonication, ball milling, and radiation-based methods. On the other hand, the bottom-up approach is implemented in the following techniques: graphene growth from melt – carbon melts, epitaxial growth on SiC, dry ice method, and deposition-based methods. For more details on each technique, the reader is advised to refer to the review articles [35, 38–40] on graphene synthesis. As this chapter focuses more on graphene-based commercial products, much emphasis has been given to scalable techniques. Among various scalable mechanical exfoliation approaches, micromechanical exfoliation is still the key synthesis technique for yielding high-quality graphene, but not suitable for mass production. However, the scotch tape-assisted peel off or exfoliation method developed by Geim and Novoselov seemed to have opened up the gateway for large size graphene flake production up to 1 mm or so [41]. Thus, the processing techniques developed based on exfoliation of graphite or graphene oxide (the derivative of graphite) made it possible for large-scale production of graphene. Prior to that, free-standing graphene was believed to be unstable, and they were expected to scroll and buckle. The shear exfoliation of graphite reported by Keith et al. [42] using stabilizing liquids, such as N-methyl-2-pyrrolidone, sodium cholate, etc., and applying shear forces beyond 104 s 1 seemed to provide the capability for mass production. This approach eliminated the use of sonication as well while implementing less energy consuming and scalable approach. In fact, shearing rate of 104 s 1 or more is easily achievable even using a kitchen blender. Currently,

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graphene is being synthesized on industrial scale following the mechanical approaches [43], but relying on the batch production. However, the mass production faces lots of challenges in terms of graphene quality (defect freeness), consistency in flake sizes and thickness, etc. On the other hand, the bottom-up approaches, like chemical vapor deposition (CVD), facilitate in a great control of the thickness and quality of graphene but not suitable for mass production on industrial scale, except for producing for high-end applications, such as touch screens, LCDs, OLEDs, and solar panels. In the scientific communities, it is believed that the graphene may not be a material of type that follows “one size fits for all.” Depending on the processing technique implemented, the quality of graphene and accordingly its application arena would change.

Applications of Graphene and Graphene Market In 2008, graphene used to cost exorbitantly high, and it was the most expensive material in the world then. However, with advances in exfoliation techniques along with process scale up, the prices have come down. As per literature [44], with increasing quality the graphene cost would increase. There are some processing techniques, such as exfoliation techniques based on intercalation and liquid turned out to be high yield processes at lower costs. Thus, large-scale production of graphene has dramatically increased with the advent of low-cost exfoliation methods. The initial list of commercial producers (as of 2014) of graphene in the global markets can be found in Ref. [44]; however, this list has grown to a large number, and the reader should be able to find the latest list in the following reference [2, 45, 46]. There are many companies currently selling in large quantities. For example, the price of epitaxial graphene on SiC is around 100 $/cm2, which is mostly dominated by the price of the substrate. The deposition of graphene on metallic substrates by CVD technique by Hong and his team from South Korea pioneered the synthesis of large-scale graphene films. It later triggered lots of research on practical applications [47] with wafer sizes up to 760 millimeters (30 in) [48]. By 2017, production of graphene-incorporated electronics started on a commercial fab line with wafer size of 200 mm by IBM [49]. For industrial applications, lubricants and graphene-based oil additives were developed. In the consumer segment, different sportswear, sports equipment, footwear, cell phone and computer cooling systems, sanitary napkins, and as the latest the masks for COVID-19 have been launched using graphene-based materials. Thus industrial and consumer applications of graphene have been accelerated at a large pace. As of 2019, the global market size for graphene was estimated to be around USD 78.7 million, and it was expected to rise at a CAGR of 38.7% from 2020 to 2027 [2]. The increasing demand for lightweight materials with improved strength and durability, renewable energy, and flexible material systems that offer technological advances is expected to drive the demand for graphene and its derivative products. The market segments targeting electrical and thermal properties, and enhanced mechanical strength and durability, and sensors and biotechnological applications are expected to expand the scope of graphene. Current penetration

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Fig. 3 Growth of graphene and related product market in the USA. (Adapted from Ref. [2]. Source: www. grandviewresearch.com)

into electronics, audio, sensors, sports, coatings, energy, and textiles is anticipated to further broaden the market. Among different markets, the USA and China are the leading markets for graphene-based products. The US market has grown with a large number of collaborations among research institutions and manufacturers, and it is one of the key exporters. Figure 3 shows the growth of market for graphene and related products within the USA.

Graphene-Based Products and Technologies Available in the Market Following is an overview on commercial-based products already existing in the current global markets based on graphene and its derivatives, and these are expected to drastically increase in the upcoming years. All the products are categorized based on the applications of the consumer or final applications in the market. For a detailed overview on the consumer products that are already existing in the market as well as upcoming, the reader is advised to refer to the references [2, 38, 50–54].

Electrical/Electronic/Thermal Applications Due to superior electron mobility, electrical conductivity, and thermal conductivity, graphene is being exploited in consumer segment for electrical conductor, electrodes, and heatsink applications. With modification of graphene through doping, it is being extensively utilized in electronics industry. Graphene is an excellent thermal conductor, and many Chinese companies have commercialized several graphenebased heating elements, embedded in wearable and other devices. Following is the list of several products that have already been available in the consumer markets today.

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• Graphene-based conductive inks are developed by Vorbeck Materials, which are then practically implemented in printing the electrical circuits for Siren anti-theft packaging device by global packaging solutions provider MeadWestvaco (MWV). This is the world’s first graphene-based product. MWV developed fully integrated conductive circuits consisting of graphene with excellent conductivity, and these are damage free even upon flexing and wrinkling. Currently, Vorbeck Materials is also making graphene-based composites, coatings, and graphene-enhanced batteries. • PowerBooster, China, was also able to produce 60-inch graphene transparent conductive films in 2012 and 7.5 m2 graphene films on copper and 3- to 20-in single/multipoint touch panels in 2013. • By 2013 December, Wuxi Graphene Film, China, also used graphene for touch screen production. It completed a production line with an annual output capacity of 5 million graphene touch-screen products by 2013 itself. • In 2017, the Team Group, which provides memory solutions and accessories, introduced graphene-coated copper foil in cooling applications of solid-state drives in order to maximize the benefits of cooling via natural passive and direct fan cooling methods for a rapid heat dissipation. The Team Group utilized this technology in their T-FORCE gaming line products. The graphene utilized by Team Group was produced by Nitronix following a patented technology. Interestingly, this technology was demonstrated to offer excellent cooling effect even in the closed spaces. • Huawei and Honor both are implementing the graphene film-based cooling systems in their advanced cell phone technologies. Honor X10, one of the cheapest 5G phone, is utilizing a graphene-based cooling system. Similarly, Huawei Mate 20 X, P40 flagship phone family with three different devices Huawei P40, Huawei P40 Pro and, Huawei P40 Pro Plus are using a graphene film-based cooling technology for heat management purposes. Huawei claims that its Mate 20 X is the world’s first super cool phone equipped with a liquid multidimensional cooling system that consists of vapor chamber (VC) and graphene film, and it reportedly cools off quickly with fast heat dissipation even under heavy loads while gaming. In another similar application, Cryorig, which is a PC gear company, has introduced graphene film-based CPU cooling system. Similar to other players in the market, Cryorig has used graphene-coated heatsink for cooling. In addition, they went a step ahead and used graphenecoated radiator fins too. These cooling systems were developed for small form factor PCs to dissipate the heat up to 125 W. The Cryorig C7G is the smallest cooler used in high-end processors in today’s market. The high performance cooling systems used graphene-coated heatsinks. • Finland-based Emberion launched a graphene-based photodetector, which can detect the wavelengths from 400 nm to shortwave infrared ~1800 nm. This technology replaced the use of two sensors (Silicon and InGaAs) based photodetector systems for a wide range detection. Furthermore, this graphene detector was expected to reduce the cost by 30% when compared to the two sensors based photodetector system.

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• Graphenest launched two graphene products using proprietary graphene production methods. The first one was HexaShield, radiation shield made of graphenebased coating for RF electromagnetic interference (EMI). This coating was expected to reduce the weight and manufacturing cost when compared with the metals and at the same time provides EMI protection for Gigahertz frequency range. • Graphene Security (GS), which is the subsidiary of BGT Materials that produces graphene technologies, unveiled graphene-based LED light bulbs for the UK market. These lights use graphene for thermal dissipation, and these will be eventually hitting the full range of home, commercial, and street lighting systems also. • Graphene Security (GS), which is the subsidiary of BGT Materials that produces graphene technologies, launched flexible and green wireless antenna solutions for the RFID industry where graphene is used as the antenna inlays.

Sports, Safety, and Outdoor Activities Superior strength to weight ratio and high rigidity have attracted graphene toward mechanical and structural applications with lightweight, enhanced flexibility and strength characteristics. Especially the composite materials of graphene incorporated have found the way to commercialization in various sports gadgets. In another example, graphene-added rubber seems to impart reduced wear and friction characteristics while making the tires harder, which is of a great importance in the automobiles, including Formula 1 race. The Graphene Council of North Carolina, USA, has been suggesting replacing the carbon black filler with smaller amounts of graphene in tires in order to achieve better life and improved frictional characteristics. Below are few example list of commercialized products in the global markets. • In 2013, HEAD introduced their new range tennis rackets (YouTek Graphene Speed series) made of graphene composites. These rackets were made lighter, stiffer, and stronger with incorporation of graphene. HEAD offered five different types of rackets with price ranging from $170 to $286. Again in 2014, they launched “Joy” another lightweight and durable graphene-based product but for ski and especially for women. It was made of a graphene-enhanced composite product. It has several variations in models with reasonable prices when compared with the traditional skis. • Vittoria, which is an international wheel producer, currently manufactures and sells the bicycle wheels “Quarno” (Graphene Plus inside) with three different editions (46, 60, and 84 mm) containing graphene-based composites. Its wheels are made of graphene-enhanced composites. They are utilizing graphene nanoplatelets provided by Directa Plus in composites for wheel production. The advantage of these wheels was found to lie in (a) quick heat dissipation (15–30
C lower), an important factor in the slopes, (b) an increase in lateral stiffness (more than 50%), and (c) reduced punctures in the tires. Thus, these

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products turned out to be quite superior compared to the conventional tubes that they have been making earlier. Similarly, Goodyear also launched grapheneenhanced bicycle tires, Eagle F1 and Eagle F1 Supersport. The weight of these tires was just 180 g for a 23 mm model. The Eagle F1 was an “ultra-highperformance all-round road tire,” and the Eagle F1 Supersport tire was even lighter. These tires were made for upper echelons of competition and better suited for road racing, time trial, and triathlon to achieve high speeds. In 2019, Gratomic also launched graphene-enhanced Graphene Ultra Fuel Efficient Tires (GUET). They used plasma-generated high-quality graphene in their tire composite structures, which not only increased the strength and life span but also reduced the weight of the tires. They have received certification for their tires for fuel efficiency after conducting several terrain tests. The UK-based Dassi Bikes developed the world’s first bike made of graphene composite. This bike frame consisted of 1% graphene in the whole body with six layers underneath the top/surface carbon layer weighing only 750 g, which is super lightweight compared to the conventional bike frames. They are targeting to bring it down even further below 400 g. In 2014, Spain-based Catlike launched cycling helmets with “Mixino” name. These helmets had enhanced strength and impact absorption, lightweight, durability, and improved safety after incorporating with graphene. They also launched lightweight and durable graphene-enhanced cycling shoes with “Whisper” name, which combined variety of cycling shoes for road/mountain/triathlon biking. UK’s Century Composites developed Graphex fishing rods using graphene produced by Applied Graphene Materials. These fishing rods have enhanced strength, lightweight, and excellent durability. NRC, the Italian sports equipment maker, launched a new class sports sunglass using graphene-enhanced frames, which were not only lighter and flexible but also quite durable. Grays Hockey of Cambridge, a world renowned hockey stick maker, launched the hockey sticks with graphene-incorporated composite materials. The grapheneenhanced composite technology strengthened the hockey sticks and helped in player’s better performance while providing lightweight, enhanced strength, improved stiffness, and durable hockey sticks. They used the graphene nanoplatelets produced by XG Sciences in their hockey stick composites. In 2017, the University of Manchester and British sportswear brand Inov-8together launched graphene-enhanced hiking boots. They produced grapheneenhanced G-Series shoes and hiking boots, ROCLITE 335 and ROCLITE 345 GTX, respectively. ROCLITE 335 offers increased warmth on cold days, whereas ROCLITE 345 GTX provides waterproof GORE-TEX protection for hiking under wet conditions. In addition, Inov-8 also launched grapheneenhanced X-Talon G 235 in off-road footwear collection. ECD Lacrosse is the manufacturer of high-quality lacrosse tools/kits, along with Global Graphene Group (G3) developed and launched graphene-enhanced Lacrosse gear. They developed customized composites using G3’s graphene and ECD’s polymer which resulted in reduced and increased impact resistance.

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These graphene-enhanced lacrosse heads showed increased stiffness, impact strength, and without no gain in the weight. Australia’s First Graphene and Blue Steel together developed graphene incorporated safety work boots. They used PureGRAPH, i.e., graphene produced by First Graphene, and incorporated it into the boots of Blue Steel’s safety capped boot TPU soles and polyurethane foam innersoles. These boots exhibited enhanced performance, strength, and safety to the consumers. In 2018, Callaway unveiled a graphene-incorporated TRUVIS Chrome Soft Golf Ball. Graphene was added to strengthen the outer core because of which the soft inner core deforms more upon impact, which would help in suppressing the spin and translate more into the speed and distance traveled by the ball. Thus, the golf world has seen dramatic changes with the arrival of graphene coatings on the golf balls. McLaren, the British racing team/supercar manufacturer, has launched a new graphene incorporated RM 50–03 Tourbillon Split Seconds Chronograph Ultralight McLaren F1 sports watch. It weighs hardly 40 g, and the inner mechanism weighs only 7 g. It was made of graphene, titanium, and carbon fiber composites. McLaren’s Applied Technologies division in collaboration with National Graphene Institute and high-end watchmaker Richard Mille developed this lightweight and efficient watch. In 2019, Billabong, the global maker of surf and snow kits (e.g., clothing and gear), announced to launch “Furnace Graphene,” a graphene incorporated suit. The flexible graphene lining was developed on the front and back panels, which help in thermal retention. In their innovative design and approach, the graphene-wrapped yarns do not allow the heat to go out and efficiently keep the suit warm. Vollebak, a sports gear manufacturer, developed a graphene-enhanced jacket that is capable of absorbing the heat and then warming up over time, while conducting electricity, repelling the bacteria, and dissipating the human body’s excess humidity. The jacket is manufactured with a two-sided material with polyurethane + graphene composite on one side and nylon + graphene on the other side. They used graphene nanoplatelets for the above composites. In this jacket, the characteristics of nylon were changed dramatically with the addition of graphene from non-thermal conductor to a thermal conductor, imparting completely new characteristics to its behavior. In 2018, Oakley and Bioracer launched a cycling G+ Graphene Aero jersey that is enhanced using DirectaPlus’ printed G+ planar thermal circuits. This jersey is designed to leverage the unique thermal properties of graphene to dissipate the heat from the rider’s body. The fabrics treated with G+ planar thermal circuits are also electrostatic and bacteriostatic, which contribute to antibacterial characteristics and moisture management and have an anti-odor effect. Interestingly, the graphene circuits placed on the outside of G+ Aero Jersey reduce the friction with air and water and supports in top sporting performance. Versarien in partnership with Bromley Technologies launched grapheneenhanced sleds, and they reported a strong performance of their products in the

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International Bobsleigh and Skeleton Federation World Cup race 2016. They incorporated graphene-enhanced carbon fiber into the skeleton sleds of Bromley. Utilizing these sleds, the players of world cup set the fastest speed record. Directa Plus and Deewear (an Italy-based company) launched D-ONE, a graphene-enhanced sportswear line that combines the design, technology, and wear ability. It is a new-generation sportswear that offers postural compress fabric of DirectaPlus’ Graphene Plus (G+) with the benefits superior comfort. Many Chinese footwear manufacturers are using graphene to develop lightweight, self-sterilizing, and deodorizing shoes in Jinjiang City, Fujian, which is China’s largest production center for sports shoes and footwear makers. They are adding graphene to soles for enhanced characteristics, and they are expected to weigh less than 100 grams. Cecorelax launched a memory-foam pillow that is enhanced with graphene. It is being sold as “Graphene Memory Foam Pillow,” and it is light in weight, flexible, and highly resistant and helps maintain the body temperatures. IstitutoItaliano di Tecnologia (IIT), Italy, in collaboration with a leading Italian shoe company FADEL unveiled a new line of graphene-enhanced shoe products, and it was patented by FADEL. This product was supposed to be providing better thermoregulation and freshness to the feet. In this shoe product, layers of graphene flakes were added to polyurethane for augmented heat dispersion, resistance to moisture, and enhanced antibacterial properties. Along with these characteristics, ventilation system was also developed for a better user experience. In another collaboration, IIT – Italy with an Italian design company Momodesign launched graphene-enhanced helmet for better distribution of impact force and enhanced safety. These helmets were coated with graphene and made them less susceptible to damage compared to the regular without graphene even under high temperature conditions. The superior thermal conductivity of graphene helps dissipate the heat quickly and thereby preserve the inner materials from degradation due to the heat. In addition, it was reported to improve thermal comfort also. Directa Plus along with Luxottica Group, a company that designs, manufactures, and sells eyewear, launched a new graphene-enhanced eyewear collection of Ray-Ban. They add graphene with a special care to facilitate equal distribution of the material along with a special resin all over the front of the frame. They utilized all the superior characteristics of graphene in these glasses including its light absorption properties.

Sensors Advanced sensors play important role in analytical and biomedical fields. Here also graphene is likely to play pivotal role. Following are the examples of several graphene-based products that show promising applications in the field of sensor technology:

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• In November 2016, ICN2 Nanobioelectronics and Biosensors group together developed a graphene oxide (GO)-based sensor which enabled the detection of various analytes (measured substances) in diagnostics, safety/security, and environmental monitoring. This sensor was offered to the market by Biolin Scientific, a renowned Nordic instrumentation company for analytical devices. • In December 2016, San Diego-based Nanomedical Diagnostics, a diagnostics equipment manufacturer, started selling graphene-based sensors and the AGILE R100 systems which are used for real-time detection of small molecules – with no limit on lower size molecules. These graphene-based sensors were portable, less expensive, faster, and very precise in detection and sample processing. • US-based Graphenea launched graphene-based field effect transistors (GFETs) in order to penetrate into the sensors market. They started with production of GFETS10 and GFET-S20 sensor technologies which can be used for gas sensing, bio-sensing, chemical sensing, photodetection, and bioelectronics. These two technologies consist of 36 individual GFETs on a one square centimeter die, but with different layouts for different sensing applications. • In 2017, the Chinese Wuxi Graphene developed graphene-enhanced GF1 health smart watch. It used the chemical vapor deposition technology for developing graphene film, which acts as the conductive element for the touch screen, which replaced the regularly used transparent conducting oxides.

Audio The rigid as well as flexible characteristics of graphene enabled the audio field boom with different products ranging from headphones to earbuds and contact enhancers. Following are some of the graphene-enhanced audio products launched in the worldwide markets with good success. • China-based FiiO Electronics launched FiiO F3 earphones for in-ear monitoring purposes, and it uses graphene-enhanced diaphragm driver. The thin graphene layer enabled the development of a flexible driver for a clean, rich, and highly reproducing transparent high-fidelity sound. • Zolo audio brand by Anker launched Liberty named graphene-enhanced fully wireless earphones. These wireless earphones are sweat proof and come with AI for smart assistance. They are also capable of producing super clear and immersive sound with impressive treble. • UK-based MediaDevil which manufacturers phone, laptop, and tablet accessories has launched wood earphones with “Artisanphonics CB-01” name, which is capable of isolating the noise. These earphones are enhanced with Versarien’s graphene and quite thinner and more flexible than traditional earphone diaphragm materials. These earphones are found to enhance both the treble and bass of the audio waves. • Mad Scientist Audio, a New Zealand-based audio company developed and started to sell Graphene Contact Enhancers (GCE), which can be used on any metal-to-

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metal contacts, such as RCA plugs, sockets, loudspeaker leads, and fuses etc., where the superior wear resistance, lubrication characteristics, and electrical conductivity of graphene have been thoroughly exploited. Ghostek launched Rapture Wireless Headphones, which are the world’s first headphones with graphene drivers. Rapture uses 40 mm graphene drivers for enhanced high-density (HD) audio experience. The other features of this product include Bluetooth 4.1 + EDR, aptX Audio Technology, soft protein leather ear cups, a 3.5 mm audio jack input, built-in HD microphone, and an LED battery status. Pioneer Corporation, a global leader in optical disc technology, developed a graphene diaphragm-based heart rate sports earphones, called SEC-S801BT. It is initially launched in China. The SEC-S801BT is a Bluetooth-enabled dualmode sports earphones that tracks the user’s heart rate and plays the music simultaneously. The graphene diaphragm was reported to be producing superior and accurate sound reproduction with great clarity in the mid- to high-frequency range. These earphones also provide a wider range of frequency response enabling the users with solid listening experience with a deep bass while still having best-in-class middle and high frequencies. China-based CKCOM, a manufacturer of earbuds, launched affordable “Alien Earbuds,” which are a high-quality alternative to expensive wireless earbuds. These earbuds are incorporated with graphene-enhanced drivers and have a playtime of 4.5 h with a built-in mic for hands-free calling, multi-touch button for important gestures, and more. These graphene drivers are light in weight and yet sturdy enough to conduct clear highs, crisp mids, and resonant bass. Most importantly, graphene in these earbuds prevents unwanted sound distortions that usually come with regular audio drivers. CKCOM’s wireless earbuds are the first of their kind and offer premium features at the lowest price. They have all of the bases covered and perfect for exercise, travel, and workouts. ORA, a Canada-based start-up, developed graphene-enhanced audio equipment. It has unveiled grapheneQ a graphene oxide-based composite material. It reportedly allows for louder drivers with a lower Q resonance, and it has been specially designed for acoustic transducers. The Chinese mobile phone maker, Xiaomi, recently launched a new in-ear headphone with “Piston 3 Pro” name, and it uses a graphene membrane for improved sound quality. According to Xiaomi, the graphene diaphragm helps produce more natural sounds.

Automobiles Automobile is another important area where application of graphene is being researched at a fast pace. Few key examples are listed as follows: • US-based Indian Motorcycle launched graphene-based ClimaCommand Classic Seat technology, which has a new graphene-based technology, and it aims to

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provide both heating and cooling to the riders/passengers. It was developed using thermo-electric technology and provides more effective performance than the conventional HVAC-based convection systems. The interesting benefit of this technology is that it actually provides a surface that is cold to touch rather than cool air that is usually provided in the HVAC systems. HELLA, a German-based lubricants company, launched an engine oil product with a specially formulated graphene additive for enhanced lubrication in the internal combustion engines. The graphene nanoplatelets manufactured by XG Sciences in HELLA’s lubricant seemed to be helping in reducing the wear almost by 50% and friction in the IC engines and extend their life. It was also observed to reduce the engine vibrations and improve the power output, while enhancing the fuel economy and ride comfort. Automotive giant Ford has announced to use graphene-based composites for auto body parts starting with the Mustang and F-150. Ford is working in partnership with Eagle Industries and XG Sciences to develop graphene-reinforced composites to reduce the weight and enhance the strength, as well as to reduce the noise. Since 2014, Ford and its partners started testing the graphene-reinforced foam covers for noisy components, such as fuel rails, pumps, and belt-driven pulleys, and chain-driven gears in the front parts of the engines and observed an improvement of 17% in noise reduction, 20% enhancement in the strength, and 30% more in heat resistance. UK-based Perpetuus Advanced Materials launched graphene-enhanced car tires especially with surface-engineered graphene materials. These tires are not only lighter in weight but also stronger and dissipate the heat quickly and highly durable. They claim to enhance the wear resistance almost by 40% over the regular tires. UK-based Linney Tuning developed graphene-enhanced brake and clutch pads with enhanced wear resistance and resistant to heat generated with quick heat dissipation. They are using bi-layer graphene in the development of brake pads, and these are expected to ensure quiet and clean braking performance. At the same time, they provide high strength, low density with less resin and less fad, and highly reliable braking performance. MIT and Lamborghini joined together to develop graphene-enhanced supercapacitor electric vehicle. This car would be a fully electric, supercapacitorpowered automobile which can be charged in minutes, and there would not be any batteries. The Sixth Element, a leading graphene product manufacturer in China, along with partner Shangdong Hengyu Technology Group, a leading Chinese tire manufacturer, developed graphene-incorporated tire formulations with improved performance. Addition of graphene to the tire tread reduced the wear almost by 25%, while its tear strength was doubled and increased the life. A Chinese tire company, Qingdao Sentury Tire, along with Huagao Graphene Technology, a Chinese graphene producer, develops electrostatic tires with graphene composites, and these are expected to perform quite superior over the regular tires.

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• Briggs Automotive Company (BAC), a Manchester company, developed a car with graphene in its bodywork. Graphene was used in the car panels also with enhanced strength and durability. This was one of the best example for graphene incorporation into the automobile bodies and use of graphene composites for enhanced durability of the car body structures.

Textiles/Outfits and Filtration/Membranes Some of the researchers are working on developing textile fiber combining graphene with polymers which in turn would add antibacterial, anti-static, and heat-preserving properties to textiles made from it. This advanced graphene fiber material will be used to make clothing, sportswear, and underwear around the world. Further, the graphene oxide membranes are capable of forming a perfect barrier when dealing with liquids and gasses. They can effectively separate organic solvent from water and remove water from a gas mixture to an exceptional level. They have even been proved to stop helium, the hardest gas to block. Following is the list of few important example products launched in the global markets: • UK-based Alé Cycling released Velocity G+ jersey, which is a grapheneenhanced suit for cycling people. This shirt uses a graphene-incorporated fabric which helps in an active interaction with the body and thereby effectively equalizes the body temperatures while creating an ideal microclimate and keeps the cyclists comfortable even under unpleasant weather conditions. • UK-based planarTECH is developing a bullet proof vest in a joint venture with a Thailand-based IDEATI. This vest is enhanced with graphene for bulletproof and ballistic plate products for body armor. The high strength properties of graphene are exploited in these armors. Currently, IDEATI is supplying to the Royal Thai Army, which is certified as per National Institute of Justice (NIJ) standards. • Shanghai Kyorene New Material Technology, a Chinese company, developed a graphene fiber that is used to produce clothes, sportswear, and underwear products. Armor Guys, a US-based glove maker, uses these fibers and integrated them with high polymer materials at room temperature to impart antibacterial, ultraviolet-proof, anti-static, and heat preservation effects to the ordinary textile products. • Vorbeck Materials and Bluewater developed advanced wearable antennas for military and defense applications. They are jointly offering robust, high-gain, low-cost, and discrete conformal printed graphene antennas embedded in military apparel and backpacks. These high-performance wearable antennas are of great importance in military for tactical and commercial use featuring multiple communication bands including LTE capabilities. The advantages of these wearables include (a) increasing the existing coverage of cell phones by up to 200%; (b) great improvement in the upload and download speeds; (c) omni-directional coverage suing the deployment of an array of antennas; (d) supports a wide range of frequencies from 800–3000 Mhz; (e) durable, flexible, washable,

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non-corrosive, and environmentally friendly; and (f) increased battery life by reducing operating power. • Oros Apparel is a US-based company, which manufactures thermal outerwear using aerogel technology. They have developed gloves made from graphenecoated aerogels, which will keep the body warmth inside the gloves and insulate from the low outer temperatures. In these gloves, the graphene is paced between the body and the aerogel, and the high thermal conductivity of graphene helps in trapping the heat inside the gloves itself, instead of dissipating it out. This technology supported a better thermal energy containment and better insulation when compared to the aerogels without graphene.

Biotech The versatile chemistry of graphene-based nanomaterials including the capability to conjugate with water-soluble and water-insoluble active compounds, DNA, proteins, cells, targeting agents, polymers, and even nanoparticles makes them a desirable nanoplatform for future biomedical research. Few important examples are summarized as below: • UK-based planarTECH along with IDEATI has recently announced about launching of graphene-enhanced antibacterial face masks. As the COVID-19 pandemic has taken a huge toll on the global population and the economy, there is tremendous global demand for face masks. At the same time, the rising pollution levels at an alarming rate demand the masks that effectively filter the air while breathing. Thus, the planarTECH and IDEATI are planning to serve the global communities with graphene-enhanced masks with antibacterial and pollution filtration capabilities. • The UK-based Haydale has developed a roll-to-roll gravure printing of biosensors with graphene due to its superior electrical conductivity and protein adherence characteristics. Using a proprietary HDPlas™ plasma technology, Haydale developed the surface functionalized graphene inks used for gravure printing of base biosensors on cell culture microplates. • GrapheneCA has announced the launch of graphene-based “Dr. Nano,” which is an anti-bacterial coating. Dr. Nano is formulated to create anti-viral environment that would protect different surfaces for 7–10 years. • South Korea’s iCraft in collaboration with UK’s Haydale has announced graphene nanoplatelet incorporated cosmetic face mask sheet, which is faceshaped and utilizes the thermal and electrical conductivity of graphene to help the skin absorb its contents through bio-electric currents. They also filed three patents on graphene-based cosmetic products. • A US-based Jewel Sanitary Napkins (JSN) launched four varieties of grapheneenhanced sanitary napkins in 2019 with a cost of 6$ per piece. The four variations of the napkins are very light panty liners, moderate flow sanitary napkins, heavy

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flow sanitary napkins, and super heavy flow sanitary napkins. These napkins are said to maintain hygiene with high absorption and antimicrobial in characteristics. • GNM has launched a graphene heating element-based eye mask for physical therapy, for the fatigued eyes. These masks emit far-infrared light which is close to the far-infrared rays emitted by human body. The graphene heating pad can help heat the eyes and improve blood circulation and relieve the body pains also. These masks heat up with low power (12 V/3A) in a very short period, and with auto shut off, they provide good protection.

Coatings, Adhesives, and Oil and Gas Industries Graphene coatings can also serve as protective coatings with superior chemical, moisture, corrosion, UV, and fire-resistance properties. On medical devices, these coatings would provide a biocompatible surface that is resistant to degradation. Adding graphene to the adhesive formulation improves the mechanical performance of the matrix resin. Moreover, graphene nanoplatelets make conductive bridges between the silver particles thereby reducing the load of silver needed to attain conductivity. Application of graphene in the oil and gas industry has only been popularized in the last few years. Due to graphene’s unique chemical, structural, electrical, and mechanical properties, it shows applicability for many areas within the oil and gas industry. Areas of application include drilling, lubrication, desalination, anticorrosion coatings, cementing, oil-water separation, oil spill cleanup, and emulsion stabilization to name a few. Important examples are summarized as follows: • Micro Powders along with Garmor launched GraphShield 730, which is a graphene-enhanced anticorrosion additive for powder coatings. It uses Micro Powders’ wax composite technology and Garmor’s proprietary edge functionalized graphene particles with high loading for corrosion resistance applications. Graphene imparts significant corrosion resistance and reduces the corrosion rates almost by 50%. • Thermene launched a new graphene-based thermal paste, which is easy to use and comes in a syringe, which can be applied using a paint brush. The curing time of this paste is around 10 h. It is developed based on graphene-derivative products and used in CPU and video card cooling. It offers a better performance compared to the conventional processor cooling technologies. In fact, the second-generation Thermene’s thermal paste product is even more efficient than the first generation and cools almost 12
C lower than the first generation and also comes with a lower price tag of 25% price reduction. • Applied Graphene Materials launched graphene-incorporated thermally conductive epoxy paste adhesives for Space and Defense sectors. They are producing two unique and novel graphene-enhanced thermally conductive adhesives AGM TP300 and AGM TP400 with high levels of thermal conductivity (3–6 W/mK) along with excellent mechanical, adhesive, and outgassing performance. Interestingly, their densities are as low as 40% that of the competitive conductive

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adhesives, which makes them even lighter. These AGM TP 300/400 are highly versatile and provide cost savings also. James Briggs along with Applied Graphene Materials launched graphene-based anti-corrosive coatings under their brand Hycote, which demonstrated outstanding and repeatable anti-corrosion performance for their automotive aerosol primer. Sweden-based Applied Nano Surfaces (ANS) launched Tricolit GO, which is the first graphene-enhanced low-friction coatings. ANS used the graphene supplied by Applied Graphene Materials. Tricolit is an easy-to-apply spray coatings from cans or in bulk. It reduces the friction and wear. Interestingly, incorporation of graphene in these coatings enhanced their strength and abrasion resistance almost by tenfold. Manchester University in collaboration with Akzo Nobel, a Netherlands paints company, is developing anti-corrosion coatings with graphene oxide incorporated paints for large metal structures (e.g., oil rigs, tankers and bridges, etc.). SAAB and GE are separately developing graphene-based anti-icing coatings to reduce the adhesion or delay the onset of ice formation on the vehicles and airplanes in the cold seasons. Graphene NanoChem has developed PlatDrill, an environmental friendly graphene-based drilling fluid, which is also biodegradable and less toxic compared to the conventional products being sold by the competitors in the same market segment for the same or similar applications. They also produce oil and water-based graphene-drilling additives. They have also been developing graphene-based products for oil recovery, water treatment, and coatings for pipes and equipment. Directa Plus is manufacturing a graphene-based “Graphene Plus,” an eco-friendly and innovative adsorbent for cleaning of oil spills in the oil and gas industries. US-based Lockeed Martin is producing graphene-based filters for wastewater treatment in the oil and gas industry. Their graphene-based Perforene membrane is currently being tested by oil and gas companies for water separation from the oils. In 2015, the Sixth Element Materials along with its partner Toppen Technology developed graphene-enhanced anti-corrosion coating system, which was later deployed to bridges and the wind mill (steel) towers across China. Their coating is based on graphene-zinc primer, which consists of The Sixth Element’s graphene type SE1132 and Toppens 2k-epoxy primer. They reported that addition of 1% graphene reduced the Zn content almost from 25% to 80%, and the corrosion protection life time was doubled. Reduction of Zn also helps reduce the pollution and results in cost savings with increased life time. India-based Tata Steel developed ready-made graphene-coated stirrups, which are being sold as TisconSuperlinks+. Tata Steel claims that the stirrup Superlink+ enhanced the corrosion resistance and supported in better bonding strength than the regular stirrups. It has filed seven patent applications in this technology. Spain-based Avanzare, a nanomaterials and nanotech specialist, developed graphene-based additives to improve the industrial-scale resins. Avanzare

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introduced a graphene additive in industrial resins used for corrosion-resistant applications in the tanks and pipes that are employed for storage and transport of potentially explosive chemicals. The graphene-enhanced coating can also be used to avoid explosions due to the electrostatic charges. Currently, Avanzare is focusing on manufacturing vessels and equipment using the graphene-enhanced resins instead of the usual metals. These resins are cheaper and lighter and have very good corrosion resistance. This graphene-enhanced resin is already being extensively used in the industries and is being sold by Ashland, an international chemical manufacturing company. • Graphene 3D Lab, a global leader in the development and manufacturing of proprietary composites and coatings based on graphene, has unveiled a new product called G6E-GSTMepoxy. It is a highly electrically conductive (resistivity ~0.0001 Ω cm) adhesive with the combination of graphene and silver additives. It can be cured either at room temperature or at elevated temperatures and bonds very well to a wide variety of substrates including metals, composites, ceramics, and glass. The graphene filler in this adhesive contributes to enhanced electrical conductivity and helps prevent the propagation of cracks and thereby improves the durability and fatigue characteristics. These properties are critical when there is bonding between dissimilar materials which are subjected to rapid fluctuations in the temperature and exposed to thermal fatigue. Enhanced fatigue resistance of these adhesives also augments the impact resistance and mitigates the damages caused by any vibrations.

Energy In the last two decades, significant research has been carried out to develop energyrelated materials to meet worldwide energy demand. Among various organic and inorganic materials, graphene exhibits strong potential to contribute to the energy demand in various ways. Solar cells can be manufactured using graphene to enhance power conversion efficiency. Batteries can use graphene to improve charge–discharge cycling performance and overall capacity. Graphene and its various composites can also be used in super capacitors to enhance power density and rate performance. Broadly, the use of graphene can be classified into two main categories: energy storage devices and energy conversion devices. Graphene-based devices can provide clean energy with theoretically zero waste emission. Some of the important examples are highlighted as follows: • Versarien of UK in collaboration with Warwick Manufacturing is currently developing graphene-incorporated lithium ion batteries and supercapacitors for enhanced storage and charge/discharge rate capabilities, where the graphene was expected to provide enhanced electronic conductivity compared to the commonly used conductive carbon. • US-based Urbix unveiled new graphene-based supercapacitors with high energy density (>75 Wh/L) and low leakage currents (0.1 μm, surrounded by a single lipid layer, heterogeneous in nature, and with high lipid aqueous volume), multilamellar vesicles (size >0.1 μm, composed of more than one lipid layer and possess moderate aqueous lipid volume). Liposomes have nontoxic, non-immunogenic, and biodegradable characteristics and are capable of enhancing the bioavailability and therapeutic efficacy of drugs. Furthermore, their flexibility in composition, easy size handling, high enzyme degradation resistance, increased absorption rates in cell membranes, and alternative surface charges make them suitable for biomedical applications. Liposomes were

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used in large biomedical applications ranging from tissue engineering strategies to clinical diagnostics, immunoassays, array configurations, vaccine formulations, theranostics, etc. Additionally, they have been used as a carrier to help deliver a number of drugs such as imaging agents, genetic materials, antigens, chemotherapy agents, and immune modulators. Liposomes can be formulated with a range of biodegradable and biocompatible lipids and functionalized to allow tissue targeting and intracellular delivery with various types of targeting molecules. Nanoliposomes and liposomes possess same physical, chemical, and structural properties. Nanoliposomes provide more surface area and have the capability to enhance solubility, increase controlled release, enhance bioavailability, and improve precise targeting of the bound material compared with liposomes [26]. Liposomes can be synthesized by using natural components like soy, milk, or egg. So they can be considered as foodgrade products. Phospholipid components of liposomes possess a variety of health benefits for humans, such as liver protection and memory improvement. In addition, several cationic lipids, polymers, or peptides may be integrated in the liposomal bilayers allowing the discharge of the trapped drug molecules into the cytoplasm [27, 28].

Biomedical Applications of Nanomaterials Nanotechnologies can be used with its high surface-to-volume ratio to form scaffolds and deliver drugs and growth factors to promote bone formation at the affected site. In animal models, nanotechnologies were also used to modify the gene expression. In biomedicine, nanotechnology materials have become extremely important and have resulted to the emergence of a hybrid science called nanobiotechnology. Some therapeutic nanoparticles range from 10 to 100 nm, so they can flow throughout the circulatory system and enter into the target tissues via capillaries. The architecture of nanomaterials by regulating their surface characteristics is portrayed as an approach for enhancing improved responses targeting a particular application. The coming section discusses the application of nanomaterials in biomedical field which is depicted in Fig. 2.

Drug Delivery Vehicles Drug delivery systems (DDSs) rely on multidisciplinary approaches that bring together pharmaceutical, polymer, chemical, and nanotechnology sciences. Using nanotechnology in the delivery of drugs helps achieve the drug’s optimum dosage to the target position of action and can reduce the adverse side effects of traditional drug therapy. Nano drug delivery approach primarily focuses on overcoming the diagnostic and therapeutic problems related to various diseases. Carbon-based nanomaterial is exploited drug delivery applications. The configuration adaptability of carbon favors the formation of zero-, one-, two-, and threedimensional structures. It has been shown that fullerene has detrimental or protective

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Fig. 2 Biomedical applications of nanoparticles

effects on biological systems which can be used for medicinal application. The unique structure and suitable properties make it as a pioneer nanomaterial for drug delivery applications. Studies showed that fullerenes’ scavenging ability has been used to arbitrate adverse side effects from other chemotherapeutic agents such as doxorubicin and also as a neuroprotective agent. Fullerene can play a significant role in oncology by scavenging reactive species in a defensive mechanism or by causing cellular damage and death. Recently fullerene-based nanocarrier system was also used for the delivery of anti-inflammatory drugs such as ibuprofen [29]. Nucleic acid delivery based on fullerene is another groundbreaking therapeutic technique that has recently been developed in nanomedicine. In addition, fullerene’s epidermal keratinocyte interactions and antioxidant property permitted this stunning nanomaterial to be used in transdermal delivery with tremendous potential. Some studies reported that the water-soluble fullerene derivatives can effectively cross the bloodbrain barrier and be used to deliver drugs into the central nervous system [30]. CNT is another essential nanocarbonaceous material for use in drug delivery. The simple modification method for combining bioactive compounds and ligands,

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extremely broad surface area, chemical purity, possibility, capacity for in vivo realtime monitoring, and free π electron availability make CNTs the ultimate drug delivery vehicle. Several in vitro and in vivo studies demonstrated the potential of CNT in cancer therapy [31]. Chemotherapeutic agents based on platinum are best candidate for use in combination with CNT drug delivery because they are small, reliable, and easily quantifiable due to the metallic core and moreover create better cancer response when used in combination with hyperthermia. In a study, Badea et al. portrayed the capacity of multi-walled carbon nanotubes as a carrier for cisplatin in breast cancer therapy [32]. Graphene and functionalized graphene were also used as drug delivery carriers. The peculiar chemical and physical properties, exceptionally large surface area, and the availability of delocalized π electrons give graphene ultrahigh efficiency in the loading of drugs. The potential of graphene-based carriers for the delivery of anticancer drugs was demonstrated in vitro and in vivo by several groups [33]. In addition, it found application in gene delivery [34]. Because of its biocompatibility, simple surface functionality, and inherent fluorescence properties, CQD has already established its presence in the field of nanomedicine as a drug/gene delivery vehicle. The efficacy of CQD as a DOX carrier and the cytotoxic effect of DOX-loaded CQD on cancer cells were evaluated in various in vitro and in vivo studies. The findings showed that DOX-conjugated CQD have an enhanced cytotoxic effect against tumor cells as compared to free DOX [35]. However, not much use is being made of the potential of CQDs as a gene carrier. Due to their excellent physicochemical properties and better biocompatibility, NDs have appeared as a promising material for developing drug delivery systems with high efficacy and low toxicity. NDs are primarily used as drug carrier in two ways. In the first method, NDs were mounted onto a chemical substrate in the form of thin film resulting in a 2D interaction between drug and ND. For the second kind, NDs form hydrogels by dispersing into aqueous solution, resulting in a 3D interaction between ND and product [36]. Giufa et al. utilized NDs to enhance delivery of DOX using a convection-enhanced delivery method in a preclinical glioma model [37]. In another study, Rafael et al. developed a ND-insulin system for the successful delivery of insulin [38]. Furthermore, NDs were used to deliver antioxidants as they possess highly versatile surface chemistry and favorable surface-to-mass ratio [39]. MCN and its functionalized derivatives exhibit low toxicity and are suitable for drug delivery applications. Numerous studies were reported in which MCN acts as carriers for antitumor drugs like DOX. Carbon nanomaterials are presumably to be advantageous in medicine, especially in forthcoming oncology uses. There are several prospects for drug delivery using carbon-based nanomaterial to release a drug directly at a specific site or to improve the cellular absorption and efficacy of medication. For a long time, gold NPs have been used to deliver molecules to cells. Due to their specific dimensions, tuneable surface characteristics, and controllable drug release, it constitutes highly attractive and favorable candidates in drug delivery applications. It has been used primarily for providing anticancer drugs to cancer

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tissue. In addition, it is used to deliver selective antibiotics, antibacterial agents, antidiabetics, and antioxidants. The molecules are adsorbed onto the Au NPs’ surfaces, and the conjugate is then delivered into the cells as a whole. Zhou et al. developed functionalized gold NPs for the simultaneous delivery of DOX, anticancer drug which is hydrophobic in nature, and diclofenac sodium, an anionic antiinflammatory drug [40]. Laxmi Devi et al. analyzed the potential of gemcitabine hydrochloride-loaded colloidal gold NPs synthesized using gum acacia for the treatment of breast cancer [41]. Peptide capped gold NPs have been shown to be a potential delivery vehicle for the intracellular delivery of DOX. Surface-modified gold NPs are recognized as beneficial vehicles for gene delivery due to their small size, flexible functionalization, and nontoxicity. AuNPs can potentially help overcome some of the gene delivery barriers, including penetration of the cell membrane, prevention of enzymatic degradation, and successful delivery to the intact gene nucleus. Giesen et al. have prepared fluorescent gold nanoparticles by one pot synthesis and assessed its potential for gene delivery in glioblastoma therapy. The in vitro results show that the NPs show better efficacy as carrier to transport DNA in GBM cells and are able to enter three-dimensional stem cell. Peptide capped gold NP has been developed as a vehicle of small interfering RNA delivery for breast cancer treatment [42]. Silver NP-based drug delivery system was also designed for drug delivery applications. Franco-Molina et al. have been exploring colloidal silver for breast cancer treatment. Patra et al. demonstrated the potential of biosynthesized gold and silver NPs for DOX delivery [43]. Benyettou et al. investigated the use of silver NPs as drug delivery platform to deliver doxorubicin and alendronate efficiently to the cervical cancer cells (HeLa) at the same time [44]. In another study, Qui et al. developed a potential efficient drug delivery system in cancer therapy based on camptothecin-covered silver NPs [45]. Prusty et al. have prepared nano silver ornamented polyacrylamide/dextran nanohydrogel hybrid composites for drug delivery [46]. Yadollahi et al. assessed the potential of one pot synthesized silver NPs/chitosan hybrid particles for drug delivery applications [47]. Owing to their novel properties, bimetallic NPs have been identified as important multifunctional materials for drug delivery applications. Fuchigami et al. investigated the utility of magnetic porous Fe-Pt NPs, which are synthesized by hydrothermal process for the targeted delivery of DOX in lung cancer cells. The results of the in vitro study show that the drug-loaded NPs could kill about 70% of the cancer cells [48]. Studies by Chen et al. included the use of folic acid functionalized Fe-Pt NPs as a powerful tool for phototherapy to treat breast cancer. They demonstrated the ability of ultrafast laser-assisted NPs for photothermal cancer therapy [49]. Scientists have drawn attention to NPs derived from metal oxide because they are flexible platforms for biomedical applications and therapeutic intervention. Diverse experimental, preclinical, and clinical studies revealed the ability of ZnO NPs for drug delivery applications. Preliminary work conducted by Yuan et al. has shown that the use of ZnO quantum dots synthesized by chemical hydrolysis method is an efficient drug carrier for DOX [50]. Sadhukhan et al. assessed the ability of ZnO NPs

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conjugated with phenyl boronic acid for quercetin delivery. The in vitro and in vivo studies revealed the efficacy of the prepared NPs in clinical cancer treatment [51]. Magnetic iron oxide nanoparticles are versatile nano platforms for drug delivery applications because they can achieve high drug loading and targeting capabilities due to their remarkable biological and magnetic characteristics. TiO2 nanoparticles have proven to be effective drug delivery nanocarriers. Salahuddin et al. developed nanocomposite based on titanium dioxide and polylactic acid for the sustained delivery of norfloxacin. The in vitro studies have revealed the antibacterial effectiveness of the formulated nanocomposites. The results demonstrated that the nanocomposites could be efficient vehicles for the targeted delivery of anticancer drug [52]. Cerium oxide NPs have immense potential to act as a carrier for drug delivery applications due to their highly favorable characteristics. Shivani et al. formulated a bio safe, antibacterial, and hemocompatible ceria-based nanocarrier system for benzyl isothiocyanate delivery [53]. The incorporation of polymers into medicinal applications revolutionized the area of drug delivery. The use of polymers in the composition of nanoparticles provides advantages such as biodegradability and biocompatibility in drug delivery systems. In addition, surface modification of polymeric NPs with hydrophilic polymers reduces opsonization and provides extended circulation time. Polymers have a vital role in the drug delivery mechanism for the treatment of different diseases such as cardiovascular disorders, cancer, and neurodegenerative diseases. The functionalized polymer NPs have a broad range of applications such as drug delivery in the brain and vagina, gene therapy, vaccine delivery, cancer treatment, and much more. Polymeric NPs deliver the medication not only to a particular location but also at a particular pace that is beneficial in the treatment of several diseases. Numerous sustained release pharmaceutical devices based on nano-polymers have been reported [54]. Andrade and coworkers utilized chitosan NPs as a carrier for N0 -((5-nitrofuran-2-yl) methylene)-2-benzhydrazide against multidrug-resistant infection [55]. Thomas et al. developed alginate NPs and assessed its potential for the controlled release of rifampicin and theophylline [56, 57]. In another study, Thomas et al. utilized alginate-cellulose nanocrystal hybrid NPs for rifampicin delivery [58]. The use of solid lipid NPs as a carrier platform enables an improvement in the therapeutic effectiveness of drugs from various therapeutic types. Solid lipid NPs include ophthalmic disorders, cancer treatment, bacterial infections, and brain targeting. The use of solid lipid NPs offers better pharmacokinetic properties and a modulated release of drugs. Pandya and coworkers produced olmesartan medoxomil-loaded solid lipid NPs by hot homogenization method. The in vitro and in vivo study showed solid lipid NPs enhancing the bioavailability and therapeutic effectiveness of the drug and could act as substitute to traditional oral preparation in hypertension therapy [59]. Different studies demonstrated the potential of liposome formulations for anticancer drug delivery applications. Liposomes also have been widely used as efficient tool for DNA and siRNA delivery. They became a successful candidate for multiple delivery systems due to the simple route of chemical modifications, the ability to hold different types of drugs/genes, and the ability to be delivered by different

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routes. The delivery of encapsulated drug molecules to treat cancer has been facilitated by the liposomes. It has been found that the combination of liposomes and porous nanoparticles can promote the intracellular delivery of therapeutics for cancer cells. Liposomes embedded in iron oxide nanoparticles were often used for gene delivery.

Tissue Engineering Carbon-based nanomaterial has specific electrical, mechanical, and optical properties and can provide an analogous microenvironment as an extracellular biological matrix that offers new tissue engineering possibilities. There are a number of carbon nanomaterials, such as GO CNTs, CQDs, ND, and their derivatives, which are capable of serving as scaffolds for bone tissue engineering. Numerous studies have shown their stimulating effects on cell development, low cytotoxicity, and efficacy for efficient nutrient delivery in the scaffold microenvironment. Prakash and coworkers developed graphene oxide-based nanocomposite for bone tissue regeneration [60]. In another study, Olad et al. formulated graphene oxide and its functionalized derivative for tissue engineering applications. The in vitro investigation demonstrated their biomineralization ability and cell viability [61]. Biomimetic fibrous scaffolds based on functionalized carbon nanotubes received much attention for tissue engineering applications. Chitosan- and cellulose-modified CNTs were also fabricated for bone regeneration. Martinelli et al. developed elastomeric 3D CNT-based composites for cardiac tissue engineering and demonstrated its potential for enhancing cardiac myocyte proliferation and functional maturation [62]. Due to the unique properties such as their high penetration potential and greater surface area with adaptable surface properties, the use of metal NPs is widely proven as a favored candidate for tissue engineering. Pattanashetti et al. assessed the effect of bio inert TiO2 incorporation into polyvinyl alcohol matrix for bone tissue engineering. Surface porosity of nano TiO2 improves tissue binding. The study found that the addition of TiO2 increased the mechanical strength and hydrophilicity of the scaffold [63]. In another study, as a scaffold for tissue engineering, Augustine and coworkers reported the preparation of electrospun polycaprolactone fabricated with ZnO NPs. They were using the ZnO NP ROS activity to stimulate angiogenesis [64]. A wide variety of synthetic and natural polymers have been widely used as tissue regeneration scaffolds. Biopolymers show greater biocompatibility and minimum immunogenicity because of which they have cell binding capability. A significant number of polymer scaffolds have been used in tissue engineering. Zhang et al. developed a three-dimensional composite membrane of poly (ε-caprolactone), poly (ethylene glycol), and magnetic iron oxide for skin tissue engineering [65]. Extremely porous poly (D, L-lactide-co-glycolide) fibrous electrospun mats with considerable surface area have been used to make scaffolds that facilitate cell development and proliferation. Different natural as well as synthetic polymers were electrospun with hydroxyapatite to generate artificial extracellular matrix that

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mimics the extracellular matrix of the native cartilage and is best suited for tissue engineering applications. Liposomes mimic cell matrix. Bioactive agent-loaded liposomes combined with scaffolds provide various intrinsic benefits including stable and effective concentration, potential to develop spatiotemporal patterning, less toxicity, and multiple deliveries of bioactive agents. Combination of liposomes and scaffolds is widely used for bone, tissue, and cartilage regeneration applications. Liposome-scaffolds have the potential to control the release pattern of incorporated bioactive agents and enhance stem cell differentiation and can bring new developments in regenerative medicine and tissue engineering.

Wound Dressing Wound healing is a process whereby a forced response to different stimuli which influence the skin is created. Hemostasis, inflammation, proliferation, and remodeling are the four phases of wound healing process. Previous work shows the significance of the process of inflammation in healing of wounds. Studies show that the nature of wound dressing material has a massive effect on inflammatory response, which can promote or inhibit regeneration of tissues. Also to reduce the microbial infection and improve the healing process, proper selection of wound dressing material is important. Nano scaffold dressings are a better choice for achieving desirable properties. They provide a prodigious method for facilitating the healing of chronic and acute wounds. They can stimulate the multiple stages of healing process. The small-sized nanomaterials are used in nanotechnology to deliver drugs in the wound area. Carbon-based nanomaterial such as GO, reduced graphene, CNT, and fullerene may provide higher mechanical strength and biocompatibility to scaffolds used in wound healing. Numerous studies evaluated grapheme’s potential as a wound healing scaffold and found it suitable due to its peculiar characteristics such as high water absorption power, antibacterial activity, and the ability to add mechanical strength to the composites. Studies demonstrated the antibacterial efficacy of graphene oxide NPs. Copper- and silver-immobilized carbon-based NPs show excellent antibacterial activity and are used as scaffold for wound dressing applications. Vedhanayagam et al. prepared a composite of CNTdendrimer-collagen and assessed its potential for in vivo wound healing and found that the presence of CNT helps to improve the mechanical strength of collage-based scaffold [66]. Noble metal NPs such as gold and silver also have excellent wound healing ability as they demonstrate controlled release, strong mechanical strength, and antibacterial activity against both fungi and bacteria. These NPs show synergic effect towards wound healing when they fabricated with polymers like cellulose, collagen, gelatin, and chitosan. Goutham Rath and colleagues prepared a blend of collagen and silver nanoparticles and investigated its potential for wound healing. The antibacterial efficacy has been demonstrated by in vitro studies. The in vivo experiments depicted its efficacy in healing wounds. The histopathological findings

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concluded that the incorporation of silver NPs in collagen helps to speed up reepithelialization and collagen development [67]. Metal oxide NPs such as silica, cerium oxide, and zinc oxide are widely used in wound dressing. Numerous studies have shown their ability to facilitate collagen deposition and reepithelialization, thus improving the process of wound healing. In a study, in vitro and in vivo modeling revealed the efficacy of silica-gold core-shell material as a wound dressing scaffold and promotes the process of cell adhesion and wound healing [68]. In dermal wound healing, the cerium oxide NPs showed therapeutic efficiency. In addition, the NPs demonstrated greater penetration into the wound tissue and subsequently decreased oxidative damage to proteins and cellular membranes. Natural and synthetic polymer-derived nanomaterials have been found to be suitable tools to prevent infection and wound healing applications because of their specific biological and physicochemical features. Ferreira et al. developed a biomimetic scaffold for wound healing applications, based on poly (L-lactic acid), collagen, PCL diol, and polyesterurethane. The cellular study showed that the proposed scaffold reinforces the process of tissue regeneration and healing process [69]. In another study, Panea et al. found that the antimicrobial dressing consisting of collagen, dextran, and ZnO NPs resulted in faster wound closure and serves as a promising biomaterial for skin regeneration applications [70]. Fabrication of engineered nanomaterials with synthetic or natural polymers is a safer strategy for achieving sustained therapeutic release that speeds up the healing process. The application of liposomes to the skin offers numerous advantages. Liposomes ensured flexibility, improved hydrophilicity, and adhesion, resulting in relatively higher encapsulation efficiency, improved stability, and increased activity in wound healing. Wound dressing based on liposomal hydrogel creates a barrier that successfully avoids wound contamination and further progression to deeper tissue infection. The drug encapsulated within the liposomes raises the concentration of the drug locally and reduces the concentration of systemic drugs, and hydrogels combine the characteristics of moist wound healing with strong fluid absorption. Liposomes and their functionalized derivatives could potentially be used as wound healing carriers.

Molecular Imaging Molecular imaging (MI) is a technique that tracks molecular-level changes in vivo to detect diseases at an early stage. The development of noninvasive methods for tumor microenvironment visualization is important for tumor detection and treatment. Large studies were devoted to the design of stimulus-responsive and intelligent nanoprobes for imaging purpose. Using imaging techniques, a customized treatment can be created for patients by closely observing the region affected by the disease within the body. Contrast agents play an essential part in visualizing a target. CNTs are being used as a probe to enhance tissue penetration in biomedical imaging. Because of its important optical properties, CNTs are used as a contrast agent in imagery. Functionalized CNTs were also used in various imaging techniques for labeling and tracking of cells. Huth et al. reported the preparation of

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polymer-wrapped carbon nanotube complex with fluorescent property for bioimaging applications. The photo physical measurements and in vitro biological studies show its optical properties, cellular uptake, cytocompatibility, and intracellular staining capacity [71]. Due to their excellent photoluminescence properties, CQDs have become very significant for molecular imaging. Functionalized fluorescent CQDs are special materials for bioimaging applications. Microwave-assisted synthesis of functionalized CQD with fluorescence property has excellent potential in bioimaging applications. Silver NPs have been widely used for biolabeling and biodetection. Silver NP-coated substrates are used for the visualization of intracellular proteins. Gold NPs are a very attractive contrasting agent for in vitro and in vivo molecular imaging techniques. It can be used as X-ray contrast agent and for single-particle tracking. Gold NPs modified with Raman-active molecules have wide application for the detection of DNA or proteins. Magnetic iron oxide NPs have attracted interest in cell labeling, magnetic resonance imaging, and bioimaging applications. They are capable of shortening the relaxation time of surrounding protons due to their super paramagnetic behavior and used for cellular and molecular imaging as contrast agents in MRI. They were commonly used to visualize metastases in the spleen, liver, tumors, and lymph nodes, as a blood pool agent in angiography, and to visualize inflammatory lesions such atherosclerotic plaques. Surface-functionalized derivatives of iron oxide NPs were utilized for in vivo imaging and as nanoprobes for understanding living cell molecular interactions. The intellectual combination of polymer chemistry, nanotechnology, and bioimaging sciences has resulted in the development of polymeric NP-based bioimaging probes with extended plasma half-lives, reduced toxicity, enhanced target specificity, and increased stability. These probes were used for imaging tumors and atherosclerosis. For almost all medical imaging techniques, they provide an excellent contrast enhancement that creates the ability to examine tumor activity by monitoring NP kinetics. They have also been used to deliver fluorescent contrast agents. In addition, in positron emission tomography technique, they were used to deliver radioactive tracer. Cao et al. developed fluorescent polymeric NPs with aggregation-induced emission properties by click reaction and implemented for cell imaging [72]. Liposomes are utilized as a carrier for contrast agents in imaging applications such as brain imaging, cardiovascular imaging, liver imaging, tumor imaging, spleen imaging, infection imaging, and inflammatory imaging.

Theranostics (A Type of Molecular Imaging) Theranostics, a combination of therapy and diagnostics, is an emerging nanomedicine paradigm formulated for molecular detection and targeted treatment. It focuses in administering the correct dosage of the drug in the correct location at the correct time by imaging the extent of the disease, delivering treatment, and monitoring the

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effectiveness of real-time therapies. The diagnostic function of theranostic agents indicates the nature, condition, and response of a disease to a particular treatment, whereas the therapeutic function of the agent can be applied in many ways. Nanoparticle-based theranostics can be promising because of their desired characteristics such as efficacy for site-specific delivery and capacity to achieve better synergistic outcomes with reduced side effects. Rapid nanotechnology advances give rise to numerous nanomaterial including polymer conjugations, magnetic NPs, silica NPs, dendrimers, quantum dots, and micelles. Nanotheranostics is suitable for diagnosis, controlled drug release, and therapeutic response monitoring and is expected to play a key role in the advancement of personalized medicine. They are widely used to treat numerous biomedical complications such as cardiovascular diseases and pulmonary disorder. They have gained greater prominence in oncology, where advanced tumors can be correctly identified and effectively treated with fewer side effects. The potential of iron oxide NPs, CQDs, gold NPs, CNT, and silica NPs as nanotheranostics platforms has been well-established. Iron oxide NPs, due to their potential in hyperthermia, can play a combined role in the imaging and therapeutic applications. Because of their ability to be visualized by MRI while their shell can be physically or chemically loaded with therapeutic agents, they are intrinsically very suited for theranostic purposes. The use of carbon-based QDs for biomedical application stems from their ideal chemical and physical properties, including size-dependent stable and narrow emission spectra, wide absorption spectra, and the potential to act as scaffold for targeting ligands and therapeutic drugs and their photostability. Gold NPs have been extensively used for nanotheranostic application because of their unique characteristics including stability, strong surface plasmon absorption, and ease of modification [73]. Aromatic stacking, special physical and surface characteristics, and the high optical absorption of CNTs in the NIR region have made it a promising resource for theranostics. Silica NPs can also function as a tremendous platform for theranostic applications that enables a wide range of imaging and therapeutic agents to be easily loaded, making them a good candidate for theranostic applications.

Biosensors Biosensors were commonly used in the study of metal ions, small biological molecules, and proteins. Nanostructured materials such as carbon-based nanoparticles, metal nanoparticles, and magnetic nanoparticles have been used in sensing applications. The unique characteristics of carbon-based NPs make them suitable for use in a variety of biosensors. Biomolecule integration with them allows for the use of some rather hybrid systems as electrochemical biosensors. Biosensors based on CQDs were used for the detection of inorganic ions in small molecules and biological samples. Graphene-based biosensors were used to detect many essential biomolecules including DNA, dopamine, glucose, and alcohol. Biosensors based on GO have been used as markers for tumor. CNTs have a broad specific surface area

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that enables numerous functional moieties to be immobilized and can be used to identify a wide variety of biological species including glucose, neurotransmitters, pathogen toxins, proteins, and DNA. CNTs have a large specific surface area which enables the immobilization of a wide variety of functional moieties such as biosensing receptors. It has also been used as biomarkers for cancer and for detecting HIV in complex media. A number of metal-based NPs were researched for potential use in biosensors. Fe3O4/Au core-shell nanocomposite probes were designed to detect DNA point mutation in aqueous DNA solutions. Nanosensors based on the Au/Pd NPs have been developed for glucose detection. Au/Ag core-shell nanoparticles labeled by monoclonal antibodies onto silica/polymer shell are a lucrative option for immunosensor chips. Titana nano-shells with a diameter of 10–30 nm were used for the production of bioactive coatings with adjustable permeability and dopamine and ascorbic acid sieving functions for use in neurochemical tracking. The films were synchronized with the nervous tissue and, in the presence of ascorbic acid, enabled selective detection of dopamine, an essential neurotransmitter. The negative charge of the TiO2 NPs enhanced the permeation of positively changed dopamine while restricting the access of ascorbic acid, a negatively charged compound. TiO2 NPs is used in neurochemical monitoring. The TiO2-polyelectrolyte assembly was harmonious with nerve cells and able to track brain activity in vivo. Cerium oxide NPs have potential uses to track dopamine, glucose, glutamate, and hydrogen peroxide. These systems can be utilized in neuroscience research involving neurotransmitter function studies on diseases such as stroke, autism, Alzheimer, and Parkinson. Biosensing applications are also possible using metal NP-polymer composites. Nagasaki et al. showed that biotin-PEG/polyamine cadmium sulfide quantum dots may be used to detect proteins with high sensitivity. PEGlation improved the dispersion stability of cadmium sulfide quantum dots in this work [74]. In another study, Phillips and coworkers utilized Au NP-poly(para-phenyleneethynylene) construct for the detection of bacterial strains [75]. Liposomes are widely used in the field of biosensors. They are used for signal marker compound encapsulation in a broad range of identifying modalities because they have excellent carrier properties. Liposomes possess a large internal cavity for signal marker encapsulation and a broad surface area for the conjugation of recognition elements. A significant feature of their use in bioanalysis is the ability to adjust the liposome surface structure to perform recognition functions with a large variety of analyte forms. Liposomes are utilized for recognition in biotarget detection. Functionalized liposome detectors provide more precise detection. Sensors based on liposome-enzyme combination have been developed as disease biomarkers.

Global Market of Nanomedicine As a result of massive nanotechnology studies and the realization of their applications in human health and environment, there is a wide variety of nanomaterials and nanoproducts available in the industry. In particular, the nanomedicine industry is

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dominated by nano-delivery methods of drugs, and one of the leading fields is in vitro diagnosis. Manufacturers of biopharmaceutical and medical devices are well aware of the potential opportunities of nanotechnology to the healthcare sector, as evidenced by the growing partnerships between these companies and nanomedicine start-ups. Anticancer drugs constitute one of the growing segments of this industry. Nanotechnology applications continue to evolve rapidly, and the overall market for new nanoproducts continues to grow, along with the degree to which they permeate our daily lives. Governments in different countries, due to the variety of potential industrial and military applications, have made investments in nanotechnology research.

Conclusion and Future Perspectives Nanoparticles and their applications in biomedicine and pharmacology have become an important and distinct area of scientific and technological evolution over the last decade. Nanotechnology has gained tremendous public interest owing to the broad applications of nanomaterials in many fields of society such as medicine manufacturing and public health. Nowadays, nanotechnology application is extensively used in various fields such as molecular imaging, drug delivery, biosensing, and wound dressing. Nanomaterials have displayed tremendous potential in developing multifunctional nanoprobes for in vivo applications including imaging and therapy, bearing the excellent intrinsic physical properties and flexible surface, thus increasing vital particle requirements including biocompatibility, efficacy, and colloidal stability. It is expected that nanomaterials will play an important role in the development of advanced diagnostic and therapeutic techniques emerging in the future. Acknowledgment Reshmy R and Raveendran Sindhu acknowledge the Department of Science and Technology for sanctioning projects under DST WOS-B scheme. Aravind Madhavan acknowledges the Department of Health Research, Ministry of Health and Family Welfare, for sanctioning a project under Young Scientist Scheme.

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“Nanosilver”: A Versatile and New-Generation Nanoproduct in Biomedical Applications

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Shikha Gulati, Sanjay Kumar, Anchita Diwan, Parinita Singh, and Ayush Mongia

Contents About the Chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanosilver (NS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unique Properties of Nanosilver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antibacterial Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antifungal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antiviral Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anti-inflammatory Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesis Methods of Nanosilver (NS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical Method of Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Physical Method of Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biological Method of Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanisms of Biological Interactions of Nanosilver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Toxicology of Nanosilver (NS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of NS in the Biomedical Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cardiovascular Implants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Catheters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bone Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wound Dressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Nanotechnology, being a promising arena for creating innovative applications in medicine, is advancing fast due to the immense growth achieved in other diverse fields including mechanics, electronics, food, cosmetics, etc. To productively bifunctionalize nanoparticles for a particular biomedical application, a broad range of physical, chemical, and biological factors have to be taken into account. In this context, silver in the form of nanoparticles is playing a most important role S. Gulati (*) · S. Kumar · A. Diwan · P. Singh · A. Mongia Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_48

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in the field of nanotechnology and nanomedicine due to their challenging and unique size-dependent properties which formulate them and are advanced and essential in a range of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal healthcare products. Silver nanoparticles (AgNPs), or nanosilver (NS), are clusters of silver atoms that range in diameter from 1 to 100 nm and are primarily attracting interest as antibacterial and antimicrobial agents for applications in medicine. Hence, nanosilver is an emerging field of research and has been highly commercialized with a diversity of commercially available products being used clinically. In particular, nanosilver has already been used in everyday consumer products requiring broadspectrum antibiotic performance due to its massive surface area and reactivity. Consequently, there is a need to recognize a worldwide background of nanosilver and their products, and their manufacturers. During the past few years, various novel synthesis methods for nanosilver production have emerged and are being evaluated, making them superior and versatile for biomedical applications. In this chapter, we first introduce the unique physiochemical properties of nanosilver, such as antibacterial, antifungal, antiviral, and anti-inflammatory activity followed by the synthesis routes of nanosilver, including physical, chemical, and biological or green method. Further, in this chapter, we provide an overview of some recent applications of nanosilver. Even though nanosilver has remarkable biomedical potential, its mechanisms of biological interactions and toxicology are also critically discussed in light of potential concerns before extensive application in prevention, diagnosis, and treatment in the biomedical field. Keywords

Nanosilver · Nanoparticles · Drug delivery · Silver · Biomedical applications · Diagnosis · Treatment

About the Chapter This chapter provides an overview on the developments of nanosilver (NS) as a versatile and new-generation nanoproduct in biomedical applications. NS is an advancing arena of research and has been greatly commercialized. The integration of NS into the medical industry is now gaining momentum to exploit the potential of NS in infection prophylaxis. Potentially, NS also demonstrates anti-inflammatory characteristics and speeds up wound healing. NS has its applications in medical device coating, diagnosis, treatment, wound dressings, drug delivery, contraceptive devices, and medical textiles due to their antibacterial, antiviral, antifungal, and antiinflammatory characteristics. Several diverse strategies for the synthesis of NS have been discussed due to the intrinsic versatility of NS, such as physicochemical, physical, chemical, and biological synthesis approaches. In supplement to the intrinsic antimicrobial-related applications, NS has been extensively evaluated owing to their beneficial size-related physicochemical effects exhibited in novel

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electronic, catalytic, magnetic, and optical devices. Although nanosilver (NS) possesses remarkable advantages for various biomedical applications, it exhibits toxicity at some concentrations and can cause some major health issues if not properly administered. Thus, it is essential to address the biosafety of NS in human health. This chapter discusses the advancements of nanosilver (NS) as a versatile and new-generation nanoproduct in biomedical applications.

Introduction Nanotechnology is among the most promising fields for generating novel biomedical advancements. Nanotechnology has emerged as the central axis of the world’s technological applications [48]. For the past several years, nanomaterials had a prompt evolution, thereby pioneering new horizons in the field of scientific, industrial, and technological researches [70]. However, only few nanoproducts are currently in use for biomedical purposes. Alongside gold, among the rare and precious metals, silver metal has been extensively exploited for thousands of years, applications including ornaments, cooking wares, currency, dental alloy, photography, and even explosives. Unadulterated silver is ideally ductile and malleable and possesses the highest electrical and thermal conductivity as well as the lowest contact resistance [47]. Among the silver’s many applications, those that utilized its disinfectant characteristics for hygienic and medicinal impetus are time honored and noteworthy, though the mechanism of action is not yet fully recognized. Metallic silver is subjected to latest engineering mechanization resulting in extraordinarily novel morphologies and properties. Silver is being engineered into minute particles whose size is in nanometers (nm). Upon reaching nanoscale, like various other nanomaterials and mainly owing to their extremely small size, silver particles display remarkably unique physicochemical characteristics and biological activities. Excellent research efforts have been accomplished owing to this field and have yielded encouraging outcomes. As a result, the administration of engineered nanosilver especially in the field of healthcare has been and is being fiercely explored. Nanosilver is emerging as one of the sprightly growing product categories in the nanotechnology domain, and it is evaluated that out of all the nanomaterials in biomedical and healthcare area, nanosilver application has gained the elevated degree of commercialization. Therefore, the exposure to nanosilver in our human body is becoming highly widespread and intimate. On a nanoscale perspective, nanosilver (NS) exhibits excellently unique physical, chemical, and biological characteristics. Therefore, they are among the most eminent nanomaterials and have been extensively utilized to the expanse of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal health care. Due to their plausible bactericidal activity, nanosilver coatings are used on several textiles and also on certain implants. Furthermore, nanosilver particles are being utilized for treating wounds and burns or as contraceptives and commercialized as water disinfectant and room spray. Thus, nanosilver application is emerging as more and more widespread in biotechnology, and due to increased exposure

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toxicological and environmental subjects need to be raised. In stark contrast to the consideration paid to new applications of nanosilver, few investigations provide only limited insights into the interaction of nanosilver particle with the human morphology after entering via dissimilar portals. With the growing applications of nanosilver in medical environment, it is becoming crucial for a better conception of the mechanisms of biological interactions of nanosilver and their potential toxicity.

Nanosilver (NS) Nanosilver (NS) or nanosilver particles (NSPs) are normally present as clusters of silver atoms at 1–100 nm in size range in diameter at least in one dimension. As the nanoparticle decreases in size, the area-to-volume ratio of the surface of NS particles increases adequately which leads to a prominent change in their physical, chemical, and biological properties. For elucidation, nanosilver as well as silver NPs are comparable and exemplify as general terms for all silver nanocrystals, nanospheres, or colloidal NPs (Fig. 1). NS is an evolving field of investigation and has been tremendously commercialized. They have captivated a lot of interest because of their chemical stability, catalytic activity, localized surface plasma resonance, and high conductivity. Silver in a short time has been known to hold antibacterial activity and has been made to use throughout history, from Hippocrates’ early treatment of ulcers to C.S.F. Crede’s treatment for gonococcal infections in newborns. Silver till now was being used clinically, and NS application is emerging as a valuable instrument in

Fig. 1 Different shapes of nanosilver

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the therapeutic armory [6]. Lately, nanosilver (NS) has become of extreme importance in biomedical applications, due to their antibacterial, antifungal, antiviral, and anti-inflammatory actions. Therefore, they have been widely utilized for diagnosis, treatment, drug delivery, medical device coating, wound dressings, medical textiles, and contraceptive devices.

Unique Properties of Nanosilver Nanosilver particles exhibit remarkable physical, optical, and chemical properties because of their dominance of quantum mechanics. These distinct characteristics are used in biomedical imaging and sensing applications such as surface-enhanced Raman scattering and single-step immunoassays. Hence, they are extensively utilized for their antibacterial, antiviral, antifungal, and anti-inflammatory properties (Fig. 2).

Antibacterial Properties Studies evidently showed that silver and NS in aqueous solution release silver ions, which are biologically active and surprisingly transmit bactericidal reaction. A relative study of NS, silver nitrate, and silver chloride showed that NS has elevated antibacterial potency as compared to the free silver ions [14]. This suggests that NS has inherent antibacterial characteristics that are independent of the elution of Ag+ ion. NS amply associates with the bacterial cell walls and has been suggested that it causes lysis [44, 68]. There has been considerable evidence that NS produces reactive oxygen species (ROS), which might aid in both the antibacterial activity of NS and its potential toxicity toward human beings [10]. NS has a wide-ranging

Fig. 2 Unique properties of nanosilver

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antibacterial effect on a range of Gram-negative and Gram-positive bacteria and antibiotic-resistant bacteria strains. Excluding the size and concentration, shape influences the antimicrobial efficiency of NS as well. Sadeghi et al. studied the antimicrobial activity of distinct nanosilver shapes, which comprise of silver nanoplates, silver nanorods, and silver nanoparticles, on Staphylococcus aureus and E. coli, and they found out that silver nanoplates had a remarkable antimicrobial activity [55]. Even though the antimicrobial activity of nanosilver has been widely investigated, the exact process of NS is still evasive. It has also been studied and found that NS particles can release silver ions and associate with the thiol groups of many essential enzymes and phosphorus-containing bases, therefore hampering some functions in cells, such as blocking cell division and DNA replication.

Antifungal Properties NS has proved to be a successful antifungal agent against a wide range of common fungi. Kim et al. investigated NS antifungal characteristics on 44 strains of 6 fungal breeds and discovered that NS can inhibit the development of Candida albicans, Candida glabrata, Candida parapsilosis, Candida krusei, and Trichophyton mentagrophytes effectively [33]. Jolanta et al. also investigated NS suspension, and the assessment demonstrated the antifungal activity of nanosilver against cladosporioides and Aspergillus niger strains where suspension was an efficient growth inhibition factor against these fungi [50]. Nasrollahi et al. [46] observed that NS possesses the ability to disrupt cellular membrane and inhibit their general budding mechanism; however, the precise mechanisms of fungicidal action of NS are still not clear. The utilization of silver nanoparticles with fungicidal properties in fabrication materials can bring about various potential advantages, such as improving their hygienic properties, inhibiting microbial growth and maintaining their mechanical features.

Antiviral Properties Nanosilver (NS) has recently appeared as a novel antiviral agent against numerous viruses and acts as an antiviral agent against HIV-1, hepatitis B virus respiratory syncytial virus, herpes simplex virus type 1, and monkeypox virus. It has been noticed that NS has greater antiviral activity than silver ions, because of their species variation as they dissolve to liberate Ag0 (atomic) and Ag+ (ionic) clusters, whereas silver salts liberate Ag+ ions only. Lara et al. found out that the anti-HIV mechanism of action of NS is on the basis of inhibition of the initial stages of the HIV-1 cycle. NS can attach to glycoprotein (gp)120, thus inhibiting the cluster of differentiation (CD) 4-dependent binding, fusion, and infectivity. They behave as a powerful antiviral agent to obstruct HIV-1 cell-free and cell-associated infection. Additionally, they also hinder the postentry stages of the life cycle of HIV-1 [36]. Although the

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process behind their viral-inhibitory action is not yet entirely understood, NS could be considered as a broad-spectrum factor against a lot of viral strains and is not susceptible to developing resistance.

Anti-inflammatory Properties Nanosilver (NS) exhibits anti-inflammatory characteristics in both animal models as well as in clinic. For instance, in a swine model with contact dermatitis induced by topically applying 1,2-dinitrochlorobenzene, NS modified the utterance of proinflammatory cytokines mutating growth factor-β and tumor necrosis factor-α. Shin and Ye found out that nanosilver enervated nasal symptoms in allergic rhinitis mice and hampered OVA-specific immunoglobulin E, IL-4, and interleukin-10, and that inflammatory cell infiltration and goblet cell hyperplasia were hampered by the nanosilver particles [59]. In a human clinical trial, wound dressing containing NS was noticed to aid the healing of chronic leg ulcers by not only lowering bacterial growth in the wound, but also by slowing down inflammatory response as well. NS’s potentiality to lower the cytokine release and matrix metalloproteinases reduces lymphocyte and mast cell infiltration, induces apoptosis in inflammatory cells [59], and aids in their anti-inflammatory activity.

Synthesis Methods of Nanosilver (NS) Different routes of synthesis result in varied shapes, sizes, stability, and morphology. Nanosilver (NS) has been synthesized generally via three routes – chemical, physical, and biological (green) which are discussed below.

Chemical Method of Synthesis The most widely used method of nanosilver synthesis is chemical reduction. The three main constituents of this method include a silver salt, capping agents or a stabilizer, and reductants. These are necessary to control the growth of NS (Fig. 3). A silver salt which is widely employed in this method due to its chemical stability and low cost in comparison to other available silver salts is silver nitrate. Citrate, borohydride, ascorbate, and hydrogen gas are the reductants used. A reducing agent that is strong and has a faster reduction rate to result in smaller particles is borohydride, because it can avoid NS aggregation during its decomposition and can also exhibit the role of an NS stabilizer [42]. Due to their aggregation, it is challenging to obtain NS in high concentrations. Using a stabilizer during synthesis is often very common. Functional groups are a component of stabilizers such as polymers or ligands and surfactants like poly(methacrylic acid), polyvinylpyrrolidone, poly(methyl methacrylate), poly(ethylene glycol), and others. Stabilizers can also include temperature-sensitive polymers such as collagen and

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Reductants

Ag+

Capping agent

Nanosilver particle

Fig. 3 Synthesis of NS via chemical route

poly(N-isopropylacrylamide). Novel thermal switching applications can be realized by nanosilver that is capped by those chemicals. A two-phase water-organic system can also be employed for NS synthesis. This method produces uniform and controllable nanoparticles. This system involves two constituents that are separated in two phases – a reducing agent and metal precursor; thus, the intensity of interphase transport between oil and aqueous phases controls the rate of interaction; however, the surface of synthesized NS may get contaminated due to high amounts of organic solvents and surfactants, and their removal is also expensive and consumes a lot of time.

Physical Method of Synthesis The most significant physical techniques employed for synthesizing nanosilver from metal samples are laser ablation and evaporation/condensation. Pure nanosilver colloids are obtained without the use of any chemical reagents via laser ablation of metals in solution. The number of laser shots and laser fluences affects the morphology and concentration of nanosilver. Particle size formed is larger along with high concentration when the time duration and laser fluence are increased. In case of the evaporation/condensation technique, NS is synthesized by employing a furnace tube under atmospheric pressure; however, traditional furnace tubes present several challenges, such as gaining thermal stability requires a long duration of time along with increased consumption of energy. In a study, nanosilver was synthesized in high concentrations by using a small ceramic heater which consisted of a local heating area so that a favorable cooling rate could be established for the evaporated vapor [32]. Recently, silver suspension was generated via a novel arc-discharge method in pure water and without any stabilizers or surfactants. Positive and negative electrodes were made by using silver wires and were etched in pure water. During discharge, well-dispersed and stable NS were synthesized as the surface layer of the silver wires was evaporated and condensed in the water.

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Biological Method of Synthesis The need for environment-friendly synthesis methods is increasing in this modern era, and biosynthesis (green synthesis) has gained significant attention with respect to this approach. These methods employ eco-friendly agents for capping and reduction, such as peptides, protein, carbohydrate, several species of yeast, fungi and bacteria algae, and plants. Large-scale chitosan-nanosilver (400 nm) films have been synthesized using chitosan as a stabilizing and chelating agent via an in situ, economical, and fascicled method; the prepared films exhibited phenomenal antibacterial action against Escherichia coli and Bacillus [64]. The biosynthesis method avoids the use of toxic reagents and organic solvents as bacteria, fungi, plants, algae, yeasts, carbohydrates, and proteins are responsible for the production of stabilizing and reducing agent molecules. Enzymatic and nonenzymatic reduction is involved in the possible mechanism of biosynthesis (Fig. 4). NS can be synthesized via enzymatic reduction by nicotinamide adenine dinucleotide phosphate-dependent reductase. However, the reduction rate exhibited by the enzyme is often slow [3]. On the other hand, nonenzymatic reduction takes just a few minutes to complete and is very rapid along with being a viable technique amid extreme conditions, such as high temperature or pH, that enhance the pace of synthesis [60]. This kind of reduction of silver is similar to chemical reduction, except for the fact that plants or microorganisms are employed here as reducing and stabilizing agents. NS that is synthesized biologically is more stable than that which is synthesized chemically, as this method does not involve the use of organic solvents and toxic reagents. Therefore, NS prepared through this method retains its stability for long

Fig. 4 Biosynthesis of NS

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durations. Moreover, as the multiplication of microbial cells continues, NS biosynthesis under a nontoxic concentration of silver nitrate becomes possible [45]. However, this method of synthesis is also susceptible to drawbacks such as the requirement of practicing caution in medical applications because the purification process may lead to pathogenic bacteria that might result in contamination [61].

Mechanisms of Biological Interactions of Nanosilver As indicated by its current clinical use, the antibacterial activity of silver is well established in treating burns [6]. It is accepted that biologically active silver ions are furnished by silver and NS present in aqueous solution, which can effectively exhibit the bactericidal effect. Complete understanding of this mechanism has not yet been realized, but observations from recent studies can somewhat explain the interactions involved [10]. The bactericidal effect that is mediated by silver ions is via interaction with three main components of the bacterial cell: the peptidoglycan cell wall [68] and the plasma membrane, bacterial (cytoplasmic) DNA, and bacterial proteins [68] (Fig. 5). On comparing silver chloride, silver nitrate, and NS, it was found that free silver ions have lower antibacterial effectiveness than NPs [14]. This indicates that the furnishing of Ag+ ions does not influence the intrinsic antibacterial properties that are possessed by NS. It has been proposed that NS results in lysis upon interaction with bacterial cell walls [68]. The potential cytotoxicity of NS toward

Fig. 5 Mechanism of the antibacterial action exhibited by silver ions

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humans and its antibacterial potency [10] both can be explained with respect to the reactive oxygen species (ROS) that are produced by NS. By employing proteomics via 2D electrophoresis in combination with mass spectroscopy of protein samples from NS-treated Escherichia coli cells, efforts have been made to understand the antibacterial mechanism of NS [38]. Upregulation of outer-membrane protein precursors (OmpF, OmpA, and OmpC) has been observed upon NS treatment [38], and a compensatory effect is caused by these precursors to counteract the cell wall damage mediated by both NS and silver ions. Inhibition of ATP synthesis and disintegration of the proton motive force are caused by the disruption of the bacterial membrane and cell wall [38].

Toxicology of Nanosilver (NS) Although nanosilver (NS) possesses remarkable advantages for various biomedical applications, it exhibits toxicity at some concentrations and can cause some major health issues if not properly administered. Thus, it is essential to address the biosafety of NS in human health. The daily quantity of silver extracted from natural sources in water and food consumed by humans is roughly 0.4–30 μg. Some other research performed per toxic effects of NS in biological systems such as viruses, bacteria, and human cells has demonstrated conflicting results [56, 66]. Usually, NS are highly effective antimicrobial agents with nontoxic effects to healthy mammalian cells [62]. On the other hand, several in vitro studies validated the NS toxic effects in rat hepatocytes and neuronal cells, human lung epithelial cells, and murine stem cells. The toxicology study of nanosilver was also performed in vivo. The research demonstrated that exposure of NS in a rat ear model leads to mitochondrial dysfunction, following a temporary or permanent hearing loss, depending on the inoculation dose. In fact, a low concentration of NS was absorbed by retinal cells resulting in structural disruption, because of the increased number of cells that endured oxidative stress. Various investigations performed proved that the surface functionalization leading to variations in surface charge of NS can influence translocation to various tissues, cellular uptake, and cytotoxicity. The extent of the surface charge, as measured by the zeta potential, can impact the number of nanoparticles and their mechanism of uptake into cells. The evaluation of NS toxicity is a twofold procedure. First, the innate toxicity of NS must be assessed, which arises from having the similar extents as biological molecules (e.g., proteins and DNA, 2 nm) and therefore can directly interact to denature proteins and enzymes, damage DNA, and produce free radicals [27]. This is additionally confined by the toxicity of biologically active silver ions [18] and elemental silver [17]. Investigations have demonstrated that NS is toxic to a number of different cell lines, including C18-4 male mouse germline cells [8], NIH3T3 mouse fibroblasts [27], BRL 3A rat liver cells [29], and THP-1 monocytes [18]. Current evidence strongly advocates that NS is toxic via its interaction with mitochondria [10, 27] and initiation of the apoptosis pathway [27] through the production of ROS, causing cell death. The relationship between NS size and

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inhibitory effects on mitochondria was also demonstrated. It was identified that NS of smaller size ( 15 nm) is more toxic than NS of larger size ( 55 nm) [10]. Investigations on oral toxicity and inhalation of NS in Sprague-Dawley rats have demonstrated that low concentrations induce toxicity only after 28 days of contact [33]. Consequently, long-term exposure of NS in food packaging or aerosols to humans might pose toxicity problems. No investigations have been done on the teratogenicity of NS in human trials. Nevertheless, it has been demonstrated that NS can alter the early premature development of zebrafish embryos in vivo [5]. Hence, it can be concluded that NS displays a substantial level of cytotoxicity by investigations done in vitro and in vivo. Long-term exposure is related to increased argyria, which has been demonstrated by in vivo studies. A restricted number of human trials have been performed [22], but the nontoxic and extensive use of NS in vitro [5] and in vivo [57] for wound dressings in the administration of burns has not reflected the apprehensions. Still, the evaluation of any potential NS toxicity is essential for human trials. Precaution must be taken for the use of NS in everyday purposes (e.g., socks, cooking ware) so that the liability of NS contact does not exceed subtoxic levels. Moreover, the environmental effect of NS, which percolates into the water system, must be considered to avert ecological catastrophe.

Applications of NS in the Biomedical Field Remarkable research has been done on NS for its use in biomedicine, with diverse products being used clinically. Groundbreaking applications are being projected and assessed as more knowledge of NS is disseminated throughout medicine. During a medical intervention, implantable devices pose a threat to the reduction of hospitalacquired infections. There are two categories of implantable intrusive devices: one, where implantable devices are completely rooted within the body, and another, where implantable devices are partly implanted inside the patients and are partially exposed to the external environment. Devices such as heart valves, which are fully implantable devices, are prone to contamination throughout the operation and entail prophylactic antibiotic treatment for the first few days postimplantation to prevent infection [9]. In comparison, partly implantable devices such as venous and urinary catheters are in continuous exposure to the external environment and hence susceptible to bacterial colonization. The use of such catheters is limited in clinical practice owing to its high risk of infection. The characteristics of a novel antibacterial coating comprise of low in vivo toxicity, prolonged activity, the capability to act against a wide spectrum of bacteria, high levels of bactericidal and bacteriostatic activity, and biocompatibility. Additionally, the coating should be reproducible, inexpensive, and environmentally benign. Antibacterial coating for cardiovascular diseases must possess hemocompatibility to prevent thrombosis [63]. Herein, we discuss several biomedical applications of NS, ranging from cardiovascular implants to catheters (Fig. 6) (Table 1).

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Fig. 6 Various medical applications of NS

Cardiovascular Implants In 1998, the first-ever cardiovascular medical device, a prosthetic silicone heart valve coated with elemental silver, was designed (Silzone), encouraged by favorable in vitro and in vivo investigations. It was designed to reduce the incidence of endocarditis, to prevent bacterial infection on the silicone valve, and to reduce inflammation response succeeding valve replacement and was consequently used in a clinical trial [23]. The underlying principle behind the usage of silver was to prevent bacterial colonization on the silicone valve, therefore reducing inflammation of the heart. Extensive toxicological investigations of the Silzone demonstrated encouraging biocompatibility. Nevertheless, 4 years into the trial, silver heart valves were discontinued due to elevated rates of paravalvular leakage in patients, hypersensitivity, and inhibition of normal fibroblast function [30], which led to the failure of the trial. As a result, the usage of silver in cardiovascular device coatings has been withdrawn. Currently, NS is being advertised as a sustainable alternative to metal silver in providing a nontoxic and safe antibacterial coating for medical devices. Hence, a new nanocomposite based on diamond-like carbon as a surface coating with 4 – nm NS implanted on the matrix has been synthesized for cardiovascular medical devices (such as heart valves and stents). It was observed that platelet adhesion investigations have shown reduced platelet attachment to the surface of

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Table 1 NS-applied biomedical products and their effects S. no. 1.

Product Silzone

2.

3.

Diamond-like carbon as a surface coating with 4 nm NS implanted ON-Q SilverSoakerTM

4.

Silverline

5.

ActicoatTM

6.

NS-PMMA bone cement

7.

NS-impregnated neurosurgical catheters NS-impregnated plastic catheter Chitosan-nanocrystalline silver dressing NS-carbon-based nanomaterial as surfacecoating agent

8. 9. 10.

Characteristic Cardiovascular implant – to prevent bacterial colonization and reduce inflammation of the heart Cardiovascular medical devices antithrombogenic characteristics and hemocompatibility properties Delivery of medication (e.g., local anesthetics or analgesics) per-, peri-, or postoperatively for pain management or for antibiotic treatment Neurosurgical drain of CSF for hydrocephalus. Also can be adapted for use as shunts. Antibacterial silver NP coating prevents catheter-associated infections Dressing for a range of wounds including burns and ulcers; prevents bacterial infection and improves wound healing Antibacterial activity and low cytotoxicity Efficient silver ion release

Reference [23]

[2]

[12]

[12]

[41]

[1] [20]

Inhibition of biofilm growth in vitro and nontoxic in vivo Improved healing rates

[53]

Presence of antithrombogenic properties after being coated onto cardiovascular medical devices

[2]

[39, 40]

the nanocomposite, and those that did adhere were haphazardly disseminated, signifying that the material has antithrombogenic characteristics. Besides, the surface of nanocomposites demonstrated antibacterial characteristics and was studied for hemocompatibility properties [2]. Furthermore, Ghanbari et al. [21] and Fu et al. [19] also fabricated antibacterial multilayer films comprising of NS and examined their antibacterial, hemodynamic, and mechanical characteristics in vitro for use in coating of the cardiovascular implant [21].

Catheters An extensive study has been conducted to examine NS as antibacterial materials for coating catheters, including central venous catheters (CVC) and neurosurgical catheters. CVCs are significant therapeutic devices for use in replacement therapy (such as renal disease and cancer) and malnutrition [25]. They are used to provide

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access for hemodynamic monitoring, fluid administration, drug-delivery pathways [65], and nutritional support to critically ill patients. Alterations of one-dimensional and two-dimensional NS surfaces are being investigated extensively for antibacterial effects in clinically relevant tools [54]. Although silver is vulnerable to the rapid oxidation process, the outstanding surface-to-volume ratio characteristically outweighs its oxidation process as coating interface has unrelenting Ag+ supply [63]. The bactericidal effects are estimated to be size-dependent since the binding capacity of NS to bacterial cells is influenced by the surface area available for interaction [49]. ON-Q Silver Soaker™ (I-Flow Corporation, CA, USA) and Silverline (Spiegelberg GmbH and Co. KG, Hamburg, Germany) are two commercially accessible medical catheters consisting of NS to inhibit catheter-associated infections [12]. Medical catheters can lead to serious complications as they are prone to bacterial infection, which can quickly spread to the wound and its nearby areas. Due to lack of toxicity and remarkable antibacterial characteristics, NS can reduce the prevalence of bacterial infection and difficulties after surgery. Several diverse methods have been studied for NS-impregnated polymers as antibacterial materials to delay biofilm growth on catheters [58]. Generally, polyurethanes, already recognized as plastic catheters, have been modulated with NS. Plastic catheter tubes can readily be coated with a layer of NS to form effective antibacterial catheters [53].

Bone Cement Each year, globally, millions of individuals are affected by complex and distinctive bone-related pathologies, such as cancers, degenerative and genetic conditions, infectious diseases, and fractures [16]. Regrettably, as the associated infections are accompanied by high morbidity, the resourceful colonization and contamination of orthopedic grafts signify foremost apprehensions in osseous-tissue replacement approaches [11]. Bone is an active tissue that undergoes restorative and regenerative developments through the complex and intrinsic bone-remodeling mechanism [51]. Bone implants are generally rooted to restore or replace severe flaws that irremediably affect osseous tissue, such as tumors, genetic malformations, or traumas. Bone-destruction occurrences, highly inflammatory progressions, and subsequent implant loss are associated with orthopedic and bone-implant-related infections [7]. Bone cement has its use in safe attachment of joint prostheses in, e.g., knee and hip replacement surgery. Total joint replacement has infection rates as high as 1.0–4.0%. Infection rates of antibiotic-loaded bone cement have significantly reduced to between 0.4% and 1.8%, but relying on antibiotics is adverse as bacterial resistance develops rapidly [31]. NS has been evaluated as an antibacterial additive to poly (methyl methacrylate) (PMMA) bone cement conjugated with different NS ratios in vitro. It has been observed that bone cement-conjugated 1% NS entirely prevented the proliferation of methicillin-resistant S. epidermidis, Staphylococcus epidermidis, and methicillin-resistant S. aureus, with no major variation between the nontoxic control group and nanosilver bone cement in qualitative and quantitative toxicity tests. NS-PMMA has shown a reduction in the occurrence of resistance

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through its complex mechanism of action and also demonstrated outstanding antibacterial activity, retardation of biofilm growth, and low toxicity in vitro. NS bone cement did not display toxicity in vivo, signifying good biocompatibility [1]. NS also acted as an additive to ultrahigh-molecular-weight polyethylene for assembling inserts for total joint replacement mechanisms, and it was observed that NS significantly reduced the deterioration of the polymer [43].

Wound Dressing Wound infections signify an essential clinical challenge, with foremost impact on patient mortality and morbidity causing prominent economic consequences [67]. Preventing wound rupture and surgical-site infection is a crucial and challenging feature in current clinical practice [15]. The structural and functional integrity of skin may be disrupted significantly at different stages induced by chemical or physical wounds, causing permanent damage or even death depending on the severity of the wound. The wound-healing mechanism is a complex pathophysiological process, which includes different phases, such as cellular proliferation, coagulation, inflammation, and matrix and tissue remodeling [26]. Since primeval periods, silver-based compounds and resources were used for the exceptional and effective control of distinctive infections [24]. Due to its biological uniqueness and intrinsic physicochemical features, NS provides an extensive variety of effective biocide activities against a remarkable variety of Gram-negative and Gram-positive and anaerobic and aerobic, bacterial strains. Due to the chemical inactivation of mammalian and bacterial cells, they poorly absorb metallic silver. Hence, the ionization of silver is crucial with the aim to provide particular antibacterial effects under physiological circumstances (including the presence of body fluids or secretions). After their dissemination inside cells, Ag+ ions combine with enzymatic and structural proteins [34]. NS used in penetrable wound dressings can interact with bacteria found in exudate and terminate it [69]. Concisely, current facts reveal the following evidence concerning NS skin absorption: (i) in vitro skin permeation by nanoparticles, and (ii) significant increase in permeation of damaged skin [37]. Naturally available biopolymers such as chitosan and collagen exhibit incredible potential concerning the procurement of novel and functionally enhanced platforms for effective wound-healing approaches, when implied along with nanotechnology applications [35]. Aquacel™(ConvaTec), Acticoat™ and Bactigras ™ (Smith & Nephew), Tegaderm™ (3M), and PolyMem Silver™(Aspen) are commercially available products for wound-dressing applications, biocomposites modified with ionic silver and approved by the United States Food and Drug Administration (FDA). The use of NS as carriers also signifies a valuable approach for delayed diabetic wound-healing procedures, as diabetic wounds may be accompanied by several secondary infections. NS can assist diabetic patients in early wound-healing phases, furthermore providing minor marks [41]. Considering the improved antibacterial effects demonstrated by NS and the remarkable attention focused toward their application in medical-device coatings and wound therapy, their biocompatibility and safety characteristics must be thoroughly illuminated [52]. Huang et al. demonstrated that nanocrystalline silver wound dressings significantly reduced the healing

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time by an average of 3.35 days and enhanced bacterial clearance from infected wounds in comparison to silver sulfadiazine, with no hostile effects [28]. Moreover, Chen et al. evaluated NS wound dressings and demonstrated the advantage of NS wound dressings in reducing the healing time for superficial burn wounds, but no change was observed in deep burn wounds, in comparison to 1% silver sulfadiazine. This proposes that NS quickens re-epithelization, but not other segments of wound healing connected with new tissue formation, such as proliferation and angiogenesis [13].

Conclusion Nanosilver (NS) is an extensively investigated nanostructure for exceptional biomedical applications, owing to its size-related attractive physicochemical characteristics and biological functionality, including its high antimicrobial efficacy and nontoxic nature. The application of NS is well reputed for various biomedical applications such as cardiovascular implants, catheters, bone cement, wound dressing, diagnosis, and pharmacological treatment. The shape, composition, and size of NS can have significant effects on its function and potential risks to human health, hence wide-ranging research is needed to completely understand their synthesis, possible toxicity, and characterization. This chapter started with an overview of NS synthesis, then its outstanding biological properties were discussed, followed by toxicology, and then its biomedical applications were reviewed. NS possesses outstanding biological properties, including antiviral and anti-inflammatory characteristics, along with highly distinguished antibacterial properties. Intrinsic parameters such as shape, size, surface charge, concentration, and colloidal state are associated with antimicrobial properties exhibited by NS. Surface functionalization of NS is possible as the available surface of NS allows the coordination of many ligands. Besides their versatile antimicrobial properties, NS provides supplementary chemical, mechanical, optical, and biological properties that suggest them for the design, evaluation, obtaining, and clinical evaluation of performance-enhanced biomaterials and medical tools. NS dressings are now the benchmark in the conventional treatment of burns and wounds. Implantable medical tools, such as venous and neurosurgical catheters, have greatly reduced patient infection and reliance on antibiotic use and the associated costs. However, significant research on toxicrelated mechanisms is mandatory. The existing shortcoming of healthcare practice and the latest experiments resulting from nanosilver-based technology highlight the extraordinary potential of NS in biomedical applications.

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Synthesis of Biocompatible Chitosan Nanoparticles by Some Greener Methods for Drug Encapsulations

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bottlenecks of Biomedical Uses of Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strategies of Preparation of Water-Soluble Chitosan Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of Water-Soluble Depolymerized Chitosan and Its Derivatives by Some Green Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesis of Chitosan Nanoparticles by Ionic Cross-Linking Using TPP . . . . . . . . . . . . . . . . . . . . . Synthesis of Chitosan Nanoparticles by Ionic Cross-Linking Using Bi-carboxylic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synthesis of Chitosan Nanoparticles by Reverse Micelle Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characterization of Chitosan Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fluorescence Properties of Chitosan Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Various Methods of Drug Loading onto Chitosan Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method of Formation of Ionic Complex Between Drug and CS Nanoparticles . . . . . . . . . . . Method of Spray-Drying Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method of Emulsification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method of Micelle Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Method of Poly-electrolyte Complex Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Chitosan is obtained from chitin, and it is the second most abundant biopolymer after cellulose. Chitosan is biocompatible and biodegradable, hence an ideal biomaterial for drug encapsulation and delivery. But chitosan is not soluble in water which is a major bottleneck of chitosan for its biomedical applications. In this chapter, we have discussed some greener methods of making water-soluble chitosan nanoparticles and their drug-encapsulating behaviors. Basically, this chapter describes depolymerization of water-insoluble larger chitosan polymers followed by formation of compact nanostructure by cross-linking. Discussions on S. Basumallick (*) Department of Chemistry, Asutosh College under Calcutta University, Kolkata, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_49

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different types of cross-linking agent and nature of cross-linked chitosan nanoparticles have been presented. Recent reports on drug encapsulation by chitosan nanoparticles, their stability at different pH, and their biomedical applications have been highlighted. Methods of encapsulation of different types of drugs (hydrophilic or hydrophobic) within the chitosan particles have been cited. Keywords

Depolymerization of chitosan · Hydrothermal method · Ionic cross-linking · Drug loading · Biomedical uses of chitosan

Introduction During the recent past application of potential nanomaterials have been nicely described in a series of handbooks by Hussain et al. [1–6]. In this chapter, we shall present synthesis and biomedical applications of another important (web references i–v) nanomaterial, chitosan. Chitosan is a polysaccharide comprised of D-glucosamine and N-acetyl-D-glucosamine joined through a β(1 ! 4) linkage. It is derived from the naturally occurring biopolymer chitin, the second most abundant biopolymer in nature, the first being cellulose. The main sources of chitin are crustacean shells, but it is also seen as a structural component of some fungal cell walls. The structures of both chitin and chitosan are shown in Fig. 1. Chitosans (CS) are classified by the quantity of amine groups present on the chain referred to as either the degree of acetylation (DA) or the degree of deacetylation (DD). The amine groups along the chitosan chain contribute to the unique and beneficial properties of chitosan. It behaves as a cationic polyelectrolyte under neutral and acidic conditions. Chitosan is a nontoxic biomaterial having biocompatible and biodegradable properties and it can be safely used [7–10] as a drug-encapsulating material. Due to the presence of reactive hydroxyl and amine groups along the chain, chitosan can be chemically modified in order to tailor its functionality. This chapter includes some examples of chitosan derivatives with improved solubility and other properties.

Bottlenecks of Biomedical Uses of Chitosan In spite of presence of almost all the requirements of an ideal biomaterial, chitosan is not widely used as a biomaterial for drug encapsulation and drug delivery. This is owing to insolubility of chitosan at biological pH. Chitosan (CS) is soluble only in acidic solution pH < 6.5. In acidic pH the –NH2 groups of chitosan get protonated making it water soluble. Thus, the major challenge [10] of using chitosan in pharmaceutical industries is to prepare water-soluble chitosan at biological pH. Two different strategies are taken to prepare water-soluble chitosan. In one approach hydrophilic groups are introduced to the chitosan skeleton to make it water soluble.

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CH3

CH3

O

O OH

OH

NH

NH

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O

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CH3

CH3

OH

OH NH2

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O O

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OH

OH

CH3

Fig. 1 Structures of chitin (upper) and chitosan (lower). As shown in this image, the chitosan would have a degree of deacetylation of 75%

The other approach is to prepare water-dispersible chitosan nanoparticles. This chapter will primarily deal with the preparation procedure of chitosan nanoparticles and their characterization.

Strategies of Preparation of Water-Soluble Chitosan Nanoparticles A great variety of methods for the synthesis of chitosan nanoparticles can be found in literature, like ionic gelation [11, 12], synthesis with carboxymethylcellulose [13], formulations using glutaraldehyde [14, 15], synthesis with alginate [16], and reverse micelle method [17, 18].

Preparation of Water-Soluble Depolymerized Chitosan and Its Derivatives by Some Green Methods Chitosan is a natural biopolymer obtained by deacetylation of chitin. Cellulose is the most abundant polysaccharide in nature; chitin is the second most natural polysaccharide. Chitosan is a low-cost biodegradable, nontoxic biopolymer easily obtained from the natural polymer chitin by deacetylation. It has high application potential as

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a carrier of drugs through different routes, but the major bottleneck of using chitosan in biomedical applications is its extremely poor solubility in aqueous medium at biological pH. Therefore, it is challenging to develop an easy and cost-effective method of preparation of water-soluble chitosan nanoparticles at biological pH. Currently, water-soluble chitosan is prepared by forming its water-soluble derivatives. But this conversion needs several steps and sometime uses hazardous chemicals [19]. One of the commonly used derivatives is carboxymethyl derivative of chitosan [20]. Other imortant derivatives are Schiff bases of chitosan. On treatment of monochloroacetic acid with such Schiff bases give purely water-soluble chitosan [21]. N-(2-Hydroxy) propyl-3-trimethylammonium chitosan chloride is another important water-soluble derivative [22] of chitosan. Apart from these, several urea groups are included into the chitosan derivatives with quaternary ammonium salt giving water-soluble chitosan [23]. Another type of modification is graft polymerization of dicyandiamide. Due to decrease in crystallization, the solubility decreases [24]. Enzymatic hydrolysis of chitosan is another possible way of getting water-soluble chitosan. Enzyme-catalyzed hydrolysis of chitosan produces water-soluble chitosan; here enzyme catalyst is isolated from soluble part of jelly fig latex [25]. Apart from preparation of water-soluble derivatives of chitosan, derivatives formed by simple conjugations are also a greener path. Another way of making water soluble chitosan is by anchoring with small molecules/groups like carboxymethyl group [20], N-(2-hydroxypropyl)-3-trimethylammonium [26, 27] group, glycol [28] or with water-soluble polymer conjugation like alginate [29, 30], dextrin [31], polyglutamic acid [32], hyaluronic acid [33], sodium cellulose sulfate [34], etc. [36]. Water soluble chitosan may be made by attaching chitosan with long chain fatty acid like oleic acid [36] and palmatic acid [37]. But all these processes need hazardous chemical or expensive enzyme. Compared to these, greener methods of preparation of water-soluble chitosan include deacetylation or depolymerization. Chitosans of well-defined degree of deacetylation (DA) and molecular weights are commercially available, and they are soluble only in the dilute acid. To convert this water-insoluble biopolymer to water-soluble polymer, both depolymerization and deacetylation techniques are largely used. The common methods of depolymerization are hydrolysis by acetic acid and oxidative depolymerization by H2O2 and sodium nitrite. While degree of depolymerization is often indicated by average molecular mass of the polymer and size of the polymer particles, the degree of deacetylation is determined by CHN analysis or by C13NMR study. Apart from simple depolymerization, attempts have also been made to make water-soluble polymer nanoparticles using techniques of ionic gelation or by covalent crosslinking method to form small nanoparticles which will be discussed later. The degree of deacetylation plays an important role in dictating physicochemical and the crosslinking density of the chitosan. Fully deacetylated chitosans have also been prepared by enzymatic hydrolysis of high molecular weight chitosan. Among depolymerization techniques the first one is use of inorganic acid like HCl [38], H3PO4 [39], H2SO4 [40], etc. The second is depolymerization by organic

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acids like acetic acid [41] or formic acid or by using oxidizing agent like H2O2 [42]or ozone [43] or other radical generators like potassium persulfate [44]. Interestingly, physical methods that are perfectly green in all sense, like use of X-ray [45], γ-ray [46],microwave, or ultrasound, have been examined [47, 48]. Table 1 shows the summary of different depolymerization methods of chitosan. Oxidative depolymerization: In oxidative depolymerization the depolymerization as well as decolorization occurs in a single step. The by-products are often gaseous and easily get out. Demin et al. [49] first mentioned that the initial stage of interactions of ozone with polysaccharide is its electrophilic attack on C(1)-H bond with the formation of labile hydro-trioxides, destruction of which results in depolymerization of polysaccharide. Kabal’nova et al. [50] mentioned the detailed mechanism of ozone-mediated cleavage of 1–4 glycoside bond. The formation of aldehyde and carboxyl group was confirmed from IR data as well as potentiometric titration. NaNO2-mediated depolymerization: Chitosan depolymerization by NaNO2 was done by Liu et al. [51]. NaNO2 depolymerization is hugely affected by the concentration of the reactants rather than the chitosan/NaNO2 ratio. The IR spectra indicated associated significant amount of de acetylation as well as decrease in hydrogen bonding between >C¼O. . ...HN- and -C-OH. . ...HO-C. The drawback of this procedure is that aldehyde formed undergoes imine formation by the interaction with free NH2 group of chitosan. H2O2-mediated depolymerization: H2O2 mediated depolymerization was reported by several scientist [42, 52]. The depolymerization by the hydrogen peroxide produced carboxylic acid and reduction in 15% of NH2 groups. The mechanism of depolymerization is more or less same as ozone mediated depolymerization and as Table 1 Depolymerization of chitosan using different agents Method of making water-soluble chitosan Chemical Conjugation of Small modification water soluble molecules

Depolymerization

Polymer Long chain fatty acid Chemical Inorganic depolymerization acid Organic acid Oxidizing agent Enzymatic depolymerization Radiation-mediated depolymerization Hydrothermal depolymerization

Reagents Carboxymethyl group, [N-(2-hydroxypropyl)-3trimethylammonium], glycol Alginate, polyglutamic acid, dextran Oleic acid and N-palmitoylation

HCl,H2SO4, H3PO4 CH3CO2H, formic acid H2O2, O3 Chitosinase X-ray, γ-ray, microwave None

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in the case of ozone mediated depolymerization FTIR shows formation of carboxylic acid. Comparison of the methods: Enzymatic method is best in the sense DD (degree of depolymerization) is more controllable. But it is costly and difficult to purify enzymes. Chemical method is better in terms of yield, but exact optimization is needed to avoid excess by-products. Physical methods are perfectly green, but yield is poor. NaNO2 oxidative depolymerization gives best yield [53] and fastest reaction rate in comparison to all acid-catalyzed reactions [54]. But it forms aldehyde that undergoes other reactions [55] unless reduced by NaBH4 just after reaction. Acetic acid gives moderately good yield more or less similar to mineral acids and almost 100% completion without much by-product, but here reaction time is relatively longer [56]. Inorganic acid hydrolysis gives comparatively clean depolymerization reaction with overall yield after 6 hr. in the presence of excess of reagent being 50– 60% [57]. For H2O2- and O3-mediated depolymerization, the reaction time is less and yield is moderate and depends on other parameters, for example, 6% H2O2 at 80  C with 30 min reaction time gives 30% yield [58]. In case of hydrothermal depolymerization, amorphous chitosan degrades faster [59]. During target-specific drug loading onto these depolymerized chitosans, care should be taken so that drugs are not flashed out [60] before reaching to the target.

Synthesis of Chitosan Nanoparticles by Ionic Cross-Linking Using TPP In this method the ionic gelation technique is applied, which is based on the principle that at acidic conditions, the (-NH2) groups of chitosan are protonated to –NH3+ and interact with anions, like triphosphate, creating nanoparticles [61]. Chitosan nanoparticles are easily prepared by the ionic gelation method using TPP as a crosslinking agent. This is a simple process based on an ionic interaction between positively charged amino groups on chitosan and the negatively charged tripolyphosphate ion at room temperature. This method presents the following advantages: the nanoparticles are obtained spontaneously under mild control conditions without involving high temperatures, organic solvents, or sonication, and it has a surface charge which can be modulated from high to low positive values. Since there are different kinds of chitosan, with distinct deacetylation degrees and molar weights, it is important to study which are the best conditions in order to obtain the smallest nanoparticles with the appropriate superficial charge. Neves et al. [62] have evaluated the influence of pH, ratio of chitosan/tri-polyphosphate (CS:TPP), and acetic acid concentration in the size and zeta potential of the nanoparticles obtained through ionic gelation. The nanoparticles were characterized concerning their antimicrobial activity and morphology using transmission electron microscopy. It has been reported [62] that a small variation up to 5% in pH does not influence significantly on diameter and zeta potential of chitosan nanoparticles.

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It is reported [62] that the parameter that most influenced the zeta potential of the nanoparticles was ratio of CS:TPP and its optimum condition was that at the lowest level it should be 3:0.8. This is the main parameter because the tri-polyphosphate anions interact with the protonated amino groups of chitosan forming nanoparticles. It is due to the fact that with the highest level of CS:TPP (ratio 3:1), there are more cross linkages between polymer and phosphates forming nanoparticles with smaller hydrodynamic diameter. However, for the ratio of 3:0.8, the nanoparticles exhibited average zeta potential greater than 33 mV, while for ratio of 3:1, the average potential was less than 29 mV. It is known that nanoparticles with surface charge greater than 30 mV are more stable and this value is sufficient to prevent aggregation of the particles; therefore, the ratio of CS:TPP 3:0.8 is acceptable for chitosan nanoparticle production. From statistical analysis these authors have shown that with 0.1 and 0.2 M of acetic acid, the observed zeta potential and particle sizes do not vary much. Based on these results, the parameters were fixed at pH 4.4 and acetic acid concentration of 0.1 M and ratio CS:TPP of 3:0.8 was recommended. Under these conditions, the average size of the chitosan nanoparticles was 69.7 nm.

Synthesis of Chitosan Nanoparticles by Ionic Cross-Linking Using Bi-carboxylic Acids Here, a description of the compact folded nanostructure formation of chitosan polymer by cross-linking with bi-carboxylic acid anions has been presented. Since chitosan is a cationic polyelectrolyte at pH < 6.5, it is best cross-linked with phosphate ion (as discussed above). But phosphate-cross-linked chitosan nanostructures are rigid, and therefore drug-releasing processes are hindered. Basumallick and Santra [10] have proposed a hydrothermal method of preparation of chitosan nanoparticles using tartaric acid as cross linker. In this preparation, these researchers have used equal masses of low molecular weight chitosan and L-(+) tartaric acid in a centrifuge tube followed by dissolving the mixture in DI water under brief vortex. The chitosan particles are not dissolved completely and formed a semifluid gel-like material. The mixture is transferred to a Teflon taped hydrothermal container, and the hydrothermal reaction was continued at 150 C for 90 minutes followed by cooling at room temperature. The final product is a transparent liquid at pH 2.97 (step1). The solution obtained in step 1 is then filtered through a 0.2um filter to obtain a transparent liquid at pH 2.93 (step2). The solution is transparent owing to the fact that chitosan is soluble in acidic pH. After step 2, the solution is dialyzed by dialysis bag with 3.5 KDa Mwt cutoff against DI water for 7 days to remove the excess tartaric acid; the pH of the dialyzed clear solution is found to be 6.0 (step 3). The solution obtained in step 3 was filtered through 0.22 μm nylon syringe filter to obtain a solution of clear chitosan nanoparticles at pH 6.5 (final step). Chitosan nanoparticles prepared under such mild hydrothermal route have been shown to be ionically cross-linked particles. Important difference between covalent

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cross-linking of chitosan with bi-carboxylic acid requires more drastic preparation conditions. It is worth mentioning that covalent cross-linking of chitosan with bi-carboxylic acid may be done by chemical and thermal treatment. But the major differences are seen in FTIR spectra with a new amide peak which is absent in case of ionically bound dibasic acid. For example, in malonic acid [63], ionic cross-linked chitosan shows a broad, strong absorption in the region of 3300–2500 cm1 resulting from superimposed –OH and –NH3 + stretching band. Peaks observed at 2823 and 2768 cm1 were due to C–H stretch, and absorption at 1723 and 1675 cm1 corresponds to the presence of asymmetric N–H (–NH3+) bend and asymmetric –COO- stretching, respectively. Very importantly peaks observed at 1520 and 1381 cm1 were due to symmetric N–H (–NH3+) bend, and symmetric –COO- stretching, respectively, gives indication for ionic bond [63]. Similarly peak position are also found for chitosan ionically cross-linked with acetic acid, lactic acid and citric acid. These peaks at 1597 and 1615 cm1 are diminished, suggesting that – NH groups are protonated. The carboxylate band of –COO at 1556 cm1 appeared in all chitosan acid salts. Consequently, it is reasonable to assume that there is an ionic interaction between chitosan and acids. The intense peaks at 1550–1600 cm1 and the weak peaks near 1400 cm1 (attributed to carboxylate anion stretching, respectively). Chitosan lactate shows a large band for –NH2 at 1630 cm1. The shift of this vibration to higher wave numbers compared with the usual wave numbers of the amine group proves the formation of an ionic bond between the –COO groups of the acid and the –NH3+ groups of chitosan. The FTIR spectra of chitosan citrate show bands at 1630 and 1400 cm1 assigned to –NH3+ and –COO, respectively. In addition, the peaks at 1730 cm1 can be seen suggesting the presence of free – COOH groups [64].

Synthesis of Chitosan Nanoparticles by Reverse Micelle Method Reverse micelle method is another green method of chitosan nanoparticle synthesis and useful for drug loading. The basic principle of reverse micelle formation is to select a suitable solvent (here a green solvent), so that hydrophobic part of the surfactant may dissolve but hydrophilic part may accumulate on a micro water drop so that chitosan nanoparticles grow within this aqueous microcontainer. This method has been applied for the preparation of chitosan nanoparticles by different workers including Santra et al. [10] using ethyl acetate as a green non-solvent. These authors have optimized surfactant concentration, temperature of the solution, and effect of degree of depolymerization of chitosan. This method is safe for drug loading.

Characterization of Chitosan Nanoparticles Like metal and metal oxide nanoparticles, the chitosan nanoparticles are best characterized by TEM images, and a typical TEM image of chitosan nanoparticles is shown in Fig. 2.

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Fig. 2 A typical TEM image of chitosan nanoparticles

Basumallick and Santra studied HRTEM images of their tartaric acid-cross-linked chitosan nanoparticles; the high dark field (DF) contrast of CS-TA nanoparticles shows that the particles are dense in their core with a semicrystalline structure having d spacing values close to literature value of chitosan crystal parameter. The particles are spherical of different sizes varying from 100 to 300 nm. The semicrystalline nature with high DF contrast makes it perfect targeting agent in high-angle annular dark field scanning transmission electron microscopy (HAADF-SEM) used to detect NPs inside cells and elevate background. These authors have also carried out 2D proton NMR study [10] on their nanoparticles to understand the fate of tartaric acid within the chitosan nanoparticles.

Fluorescence Properties of Chitosan Nanoparticles Why is fluorescence of chitosan nanoparticles desirable in drug delivery system? This is because one can tract the movement of drug-loaded chitosan nanoparticles within biological system simply by monitoring its fluorescence images. Inherent fluorescence of chitosan nanoparticles was first reported [65] by Haung et al. and subsequently by Basumallick and Santra et al. [10] and explained in detail the genesis of fluorescence exhibited by chitosan nanoparticles. These authors have argued that main fluorophore in chitosan backbone is >C¼O group of acetylated amine and emission peak of a mixture of chitosan tartaric acid is close to reported value [66] of fluorescence from aliphatic poly-ketone indicating carbonyl group plays a major role in imparting fluorescence of chitosan. It is interesting that fluorescence spectra of chitosan nanoparticles depend on the pH of the solution. There is always a red shift at higher pH. This has been explained

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proposing that at low pH amide will be present in its enol form but at neutral pH > C¼O can act as acceptor and N-H as donor to form intramolecular hydrogen bond as in protein. This will disrupt the presence of enol form of >C¼O group of chitosan at low pH. So at higher pH, amide may undergo J aggregation, and the observed red shift has been explained. In a typical >C¼O molecular orbital, HOMO is nonbonding p electron on “C” and LUMO is a π*. Now, N lone pair interacts with π* of >C¼O resulting in increase in the energy of π* (LUMO). As a result, HOMO-LUMO band gap increases. Thus, at lower pH, there is an overall destabilization of excited state with reduction of fluorescence intensity. Moreover, alpha and gamma hydrogen of ketone help in quenching fluorescence from ketone-containing polymer [66]. Now in the present case, gamma hydrogen is bound to an -OH group. At low pH, the –OH group will be protonated withdrawing gamma C-H bond electron towards it. Overall, when compared with chitosan control, the much enhancement of fluorescence might be either due to structural change of CS polymer with more exposure of >C¼O groups or due to short conjugation of -C¼O with N of acetyl group in nanoparticle. The latter explains red shift as well as fluorescence enhancement with pH. In temperature-sensitive fluorescent polymer, amide linkage plays important role. The observed excited wavelength dependent on emission spectra as seen from Fig. 3 indicates that the purified sample of chitosan nanoparticles is a heterogeneous mixture of nanospheres of chitosan with different sizes as seen in the TEM picture.

Fig. 3 Fluorescence spectra of tartaric acid depolymerized chitosan at different excitation wavelength. λex ¼ 287 nm (black), 320 nm (red), 335 nm (green), 340 nm (blue), 350 nm (cyan), 360 nm (pink), 380 nm (yellow)

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Various Methods of Drug Loading onto Chitosan Nanoparticles Basic principles of drug loading onto chitosan nanoparticles are of much impotence in view of their application potential in pharmaceutical industries. Obviously, this will depend on the nature of the drugs. Drugs may be of small molecular type or they may have larger molecular structures. Again, these drugs may be of hydrophobic, hydrophilic, or amphiphilic types. In general drug loading technique is selected by considering the nature of the drug. Some of the commonly used methods of drug loading onto chitosan nanoparticles are discussed here.

Method of Formation of Ionic Complex Between Drug and CS Nanoparticles Because of the cationic properties of chitosan, ion complexes can be formed by electrostatic interaction between chitosan and anionic drugs. Cheng et al. [67] prepared chitosan nanoparticles linked with antisense oligonucleotide drug simply by mixing the CS nanoparticles and this drug in the ratio of 2:1 M proportion. The size of the nanoparticles was around 102.6 nm; the encapsulation efficiency was found very high. Kim et al. [68] encapsulated retinol into chitosan nanoparticles through the electrostatic interaction between the amine group of chitosan and the hydroxyl group of retinol. Encapsulation into chitosan nanoparticles was shown to increase solubility of retinol by more than 1600-fold.

Method of Spray-Drying Technique Spray-drying method can be used as a one-step preparation of nanoparticles loaded with drug. Grenha et al. [69] prepared mannitol microspheres containing chitosan nanoparticles-loaded protein drug by this method. Huang et al. [70] prepared chitosan-iron oxide nanoparticles with various chitosan/iron oxide ratios by spray-drying. Atomic absorption spectrometry results implied that chitosan had strong chelation with iron. Meanwhile, Fe3O4 was crystallized and distributed in the chitosan matrix. These chitosan-iron oxide nanoparticles were stable in water with strong superparamagnetism. Yamamoto et al. [71] investigated the use of chitosan capsules for colon-specific delivery of 5-aminosalicylic acid (5-ASA) drug. The surface of the chitosan capsules containing 5-ASA was coated with hydroxy-propyl methyl cellulose phthalate as an enteric coating material. The experimental results demonstrated that the capsules were able to reach the large intestine 3.5 h after oral administration.

Method of Emulsification Tacrine, an anti-Alzheimer drug-loaded chitosan nanoparticle, was prepared by spontaneous emulsification [72]. The particle size and zeta potential were

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determined by scanning probe microscopy and Zetasizer, respectively. The prepared particles showed good drug-loading capacity. Varshosaz et al. [73] reported chitosan microspheres coated with cellulose acetate butyrate, prepared by the emulsion-solvent evaporation technique, for delivery of 5-ASA into the colon.

Method of Micelle Formation Doxorubicin-chitosan polymeric micelles had excellent drug-loading properties, were suitable for targeting the liver and spleen, and significantly reduced drug toxicity to the heart and kidney [74].

Method of Poly-electrolyte Complex Formation Chitosan is a cationic polymer and alginate [10] is an anionic polymer; they easily form poly-electrolyte complex. Thus, chitosan-Ca-alginate microparticles can be loaded with 5-amino salicylic acid (-5-ASA). Recently, Jain et al. prepared hydrogel microspheres of chitosan grafted with vinyl polymers for the controlled and targeted drug release.

Summary In this chapter, we have discussed the bottlenecks of biomedical uses of chitosan and need of chitosan nanoparticles for biomedical applications. We have described three important greener methods of obtaining chitosan nanoparticles. These are (i) ionic gelation with TPP, (ii) ionic gelation with tartaric acid, and (iii) reverse micelle method. We have also highlighted the need of fluorescent chitosan nanoparticles for biomedical applications and genesis of fluorescent property of chitosan nanoparticles. Finally, we have discussed different methods of drug loading onto chitosan nanoparticles. Acknowledgment The author is thankful to Professor Swadesh mukul Santra of NanoScience Technology Center of the University of Central Florida for motivating me to this research. She is also thankful to the Principal of Asutosh college, Kolkata for academic support. Important Web References Related to Drug Encapsulation and Delivery by Chitosan Nanoparticles (i) (ii) (iii) (iv) (v)

https://www.mdpi.com/1999-4923/9/4/53 https://www.jstage.jst.go.jp/article/cpb/58/11/58_11_1423/_article/-char/ja/ https://iopscience.iop.org/article/10.1088/0957-4484/18/40/405102/meta https://www.sciencedirect.com/science/article/abs/pii/S016836590100342X https://www.sciencedirect.com/science/article/abs/pii/S0268005X16308700

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Application of Nanoparticles in Medicine

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drug Delivery and Targeting Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neurological Disease Control Using Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanisms of Nanoparticle Therapeutics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials for Immunotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Differences in Treatment Response and Toxicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoparticles as Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoparticles in Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chitosan-Encapsulated Au NPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ICG-Functionalized Au NPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Nanoparticles in Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Photodynamic Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interaction of X-Ray and Gamma Radiations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomedicine in Market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potential Hazards of Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Nanotechnology is the focus of much research in the last 30 years. The unique optical, electrical, magnetic, chemical, and biological properties of materials are approximately 10,000 times smaller than the diameter of a hair strand. Researchers have developed methods to synthesize and characterize nanomaterials, and their preclinical utility was reported. Now the new phase of nanomedicine is to translate these technologies to benefit patients.

M. M. Eid (*) Spectroscopy Department, National Research Center (NRC), ElDokki, Cairo, Egypt © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_88

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Keywords

Nanomedicine · Drug delivery · Immunotherapy · Nanotoxicity · Targeting

Introduction Nanomaterials are of great interest for use in biomedicine as imaging tools, phototherapy agents, and gene delivery carriers. In this chapter, we will try to introduce different applications of nanoparticles in nanomedicine. The chapter includes two main topics of nanoparticle application in therapy and diagnosis; then the chapter will close with some examples of nanoparticles that have been authorized by the FDA and the limitation of using nanoparticles concerning their toxicity. The first part of this chapter is a summation of the recent works of researchers in the field of drug delivery, and immunotherapy, whereas the second one shows nanoparticles’ usage in sensing and imaging.

Drug Delivery and Targeting Therapy Recently, targeting has gained great concentricity in biological research. The vascular biology of the normal tissue has a regular structure compared to the irregular branched and disorganized, high vascular density, increased vascular permeability, and impaired lymphatic drainage attributed of solid tumors and inflamed tissue of tumor. These enhanced permeability and retention (EPR) effects permit NPs to efficiently accumulate in tumor tissue. Active targeting using target ligands improves the delivery of NP systems to a specific site. Typical targeting ligands include small molecules, peptides, antibodies and their fragments, and nucleic acids. [1]. The ability of nanoparticles to adhere to and penetrate cell membranes is governed by nanomaterials with very small dimensional face composition, and surface charge and positive charge have been observed to pass through cell membranes by forming membrane holes, generating noticeable cytotoxic effects in the process. However, membrane disruptions can be reduced or even completely avoided by modulating the surface charge density or surface. Therefore, it appears feasible that synthetic materials with optimally engineered surface properties may pass through membranes without disrupting the cell membrane. Colloidal semiconductor core/shell quantum dots (QDs) hold great promise for applications in biotechnology and biomedicine due to their small size (1–5 nm), brightness, and photostability [2]. Drugs and other therapeutic agents are administered to treat specific diseases and disorders with the goal of achieving desired pharmacological effects with minimal side effects. The use of a controlled drug delivery system is a key strategy to enhance the therapeutic efficacy and safety of therapeutic effect. The primary rationale for using an appropriate drug delivery system is the ability to ensure a higher and longer duration biocompatibility of drug as well as improve therapeutic efficacy. Various

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materials with different structural forms are conjugated with drugs to produce nanodrug delivery systems. Considering recent approaches, the most commonly used drug delivery vehicles include nanoparticles (e.g., polymeric, ceramic, and metallic), liposomes, micelles, and dendrimers, etc. A considerable number of preclinical and clinical studies suggest that the materials are rapidly emerging for use in drug delivery applications for the treatment of various diseases [3].

Neurological Disease Control Using Nanomaterials The most common neurodegenerative diseases worldwide include Alzheimer’s disease (AD) and Parkinson’s disease (PD). The common clinical feature of AD is the extracellular deposition of amyloid beta (Aβ) peptide along with phosphorylated tau protein, leading to irreversible neuronal loss and consequent to loss of memory and decision-making ability. Nano-drug delivery system for Alzheimer’s disease. Serious efforts have been made by the scientific community to develop potent molecules and compounds that could mitigate the progression of neurodegenerative diseases. The inability or limited ability to cross the blood-brain barrier (BBB) is the main reason for the limited therapeutic effect of currently available drug molecules. However, nanomedicines are emerging as a new strategy to overcome the BBB and provide the advantage of targeted and sustained release. Additionally, bioavailability over an extended period of time limits the frequency of dosing and minimizes potential side effects. In preclinical studies, RT-loaded poly(lactide-co-gycolide) (PLGA) and polysorbate-80 (PBCA-80)-coated poly(n-butylcyanoacrylate) nanoparticles have shown potential for targeting in the brain [4]. Cancer nanomedicine, the widely accepted paradigm of nanomedicine enhanced permeability and retention (EPR), assumes that cytotoxic drugs can be selectively delivered to tumors using nanomedicines (defined as drug-loaded nanoparticles of 1–1000 nm in diameter) to increase efficacy and minimize the risk of systemic side effects. However, this approach has so far resulted in only modest improvements in the cancer patient survival rate. In contrast, immune checkpoint inhibition (ICI) has led to unprecedented improvements in the survival outcomes of a subset of patients. However, an estimated 13% of cancer patients currently benefit from ICI, and a substantial proportion of patients receiving these therapies develop immune-related adverse events. Therefore, research interest in nanomedicine is rapidly shifting to the adaptation of delivery platforms to increase the percentage of patients who clinically benefit from ICI and other immunotherapies. Currently, there are two paradigms for the use of nanomedicines to potentiate immunotherapy: systemic delivery of nanomedicines that have a tumor-priming effect and local or extratumoral administration of nanomedicines to induce local and/or systemic antitumor immunity. The first paradigm is supported by data from a successful phase III trial, in which women with metastatic triple-negative breast cancer (TNBC) received the combination of nab-paclitaxel plus the antiprogrammed cell death 1 ligand 1 (PD-L1) antibody atezolizumab6. Various manifestations of the second paradigm,

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such as vaccine delivery using lipid-based nanomedicines to promote antitumor immunity, are the focus of preclinical and clinical investigations (e.g., NCT02410733). They hypothesize that the pathophysiology of the tumor microenvironment (TME) limits the uniform delivery of both systemically administered and locally applied nanomedicines, thus compromising their efficacy even when they accumulate in tumor. Therefore, they proposed that nanomedicines should contain not only anticancer drugs but also agents that “normalize” the various components and physiology of the TME, resulting in improved tumor perfusion and reduced hypoxia. This normalization effect has the potential to facilitate not only drug delivery but also oxygen delivery to slow tumor progression and convert an immunosuppressed TME into an immunostimulatory TME [5].

Mechanisms of Nanoparticle Therapeutics Nanomedicine-based drug formulations were originally developed to alter the pharmacokinetics and toxicity profiles of chemotherapy agents and to promote their accumulation in tumors. The ability to concentrate drugs within tumor cells and/or the tumor microenvironment (TME) is also of relevance for enhancing immunotherapy. However, nanomaterials also allow novel mechanisms of action for immunotherapy agents, including the ability to display ligands to immune cells, regulate intracellular delivery of cell impermeable compounds, and control the timing of drug release and/or activation.

Nanomaterials for Immunotherapy Nanoparticle-based delivery systems have several advantages for cancer immunotherapy applications compared to conventional nanomedicine. Conventional cancer nanomedicine usually aims to deliver cytotoxic agents directly to cancer cells; however, immunotherapy often targets nontumor cells, such as resident immune cells in secondary lymphoid tissue or immune and stromal cells in the tumor microenvironment (BOX 2) cells and tissues that could be easily reached by nanoparticles. In addition, the subsequent interaction between nanoparticles and cells or organs can be regulated by functionalizing nanoparticles and modifying their surface. The physicochemical properties of nanoparticles can also be tuned to promote interaction with and stimulation of innate immune cells such as dendritic cells and macrophages. Nanoparticle-based delivery can further enhance the pharmacological properties of drugs, including their solubility, in vivo stability, and pharmacokinetic profile, and protect biological drugs from premature release and degradation [6, 7]

Promotion of Immunogenic Tumor Cell Death Most antitumor drugs aim to kill cancer cells, but not all pathways of cell death are immunogenically equivalent. Tumor cell death events that promote an antitumor

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immune response are referred to as “immunogenic cell death” (ICD). ICD is associated with the extracellular release of damage-associated molecular patterns such as ATP and high mobility group protein B1 (HMGB1) and surface exposure of calreticulin and heat shock protein 90 (HSP90). These factors promote tumor antigen uptake by antigen-presenting cells and their subsequent activation. Traditional ablative cancer therapies, such as chemotherapy or ionizing radiation, differ in their ability to induce ICD, and their immunopotentiation can be abrogated by toxic effects on responding immune cells. Nanomedicine formulations are an attractive modality for promoting ICD because they can concentrate cytotoxic agents in tumor cells. In addition, nanomaterials can be designed to interact directly with external energy sources, allowing for the enhancement of ICD induced by treatments such as radiotherapy and magnetic hyperthermia. Formulation of chemotherapeutic agents into nanoparticles that promote ICD can improve antitumor immunity by enabling more effective delivery of drugs to tumor cells. For example, Doxil, a clinically approved pegylated liposomal formulation of the anthracycline chemotherapeutic doxorubicin, synergized with checkpoint blockade in the treatment of mouse models of colon adenocarcinoma and fibrosarcoma, resulting in greater antitumor activity compared with treatment with free doxorubicin. A recent strategy to improve doxorubicin delivery and increase ICD was based on synthetic high-density lipoprotein nanodiscs, in which the drug is covalently bound to the nanoparticles via an acid-labile linkage. Delivery via nanodiscs resulted in the upregulation of ICD markers in tumors and synergistic effects with anti-PD1 compared to free drug in two mouse models of colon cancer. Although radiation therapy is capable of inducing ICD, it is rarely effective as a monotherapy in promoting sustained antitumor immunity. However, numerous clinical trials are currently investigating radiation therapy as a component of combination immunotherapies. Radiation kills tumor cells by inducing nonrepairable DNA damage, but it can also trigger activation of the cyclic gMP-aMP synthase stimulator-of-interferon genes pathway (cGAS-STING pathway) and subsequent production of proinflammatory cytokines, promoting innate and adaptive antitumor immunity. The radiotherapy dose must be carefully tailored, as high doses of irradiation lead to attenuated STING activation through DNA exonuclease TREX1-dependent cytosolic DNA degradation. An initial, successful proinflammatory radiotherapy response may also be blunted by the recruitment of immunosuppressive immune cells to the tumor. A long-standing concern is that even localized radiotherapy may impair antitumor immunity. However, recent evidence from preclinical studies suggests that radiotherapy can indeed activate tumor-resident T cells, which are comparatively more radioresistant than circulating T cells [8] Several approaches have used nanoparticles to enhance immunopriming triggered by radiotherapy. For example, biodegradable polymer nanoparticles designed to bind proteins from the surrounding solution have been shown to promote T-cell priming following radiotherapy. Intratumoral injection of the nanoparticles after radiotherapy resulted in the capture of protein antigens released from dying cancer cells by the particles, which subsequently passed through lymphatic vessels and were

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internalized by phagocytic professional antigen-presenting cells in the draining lymph node. Nanomedicines can also be used as radioenhancers that interact directly with ionizing radiation to upregulate ICD25. Materials containing elements with a high atomic number (Z) can both absorb and scatter radiation, and therefore high Z nanoparticles that accumulate in tumors can potentiate radiotherapy. In a recent clinical trial, intratumoral injected hafnium oxide nanoparticles were shown to double the frequency of pathological complete response to radiotherapy in patients with sarcoma, leading to a first clinical approval in Europe [9].

Ligand Presentation to Immune Cells (Fig. 1)

Gene Delivery RNA interference (RNAi) is a powerful biological tool that can be used in both cell culture and living organisms. Since it enables targeted degradation of mRNA after the introduction of sequence-specific double-stranded RNA into cells, it has historically been used to research gene functions. Effective siRNA delivery, on the other hand, can necessitate overcoming a number of biological barriers: (1) High molecular weight and negative charges make it difficult to reach the cell, (2) nuclease

Fig. 1 Pathways for the cellular internalization of different types of nanoparticles [10]

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degradation inside the cell, (3) targeting to the appropriate cell compartment, and (4) rapid clearance and instability in vivo. As a result, effective and biocompatible delivery systems are needed to fully realize the potential of RNAi. NPs can provide a solution to the problems associated with siRNA delivery. Because of their ability to shape a condensed complex with nucleic acids, cationic lipid or polymer NPs have been used to transport anionic nucleic acids into cells [32]. This keeps them stable and prevents enzymatic degradation. Cationic materials can also aid in the escape of NPs from endosomes and lysosomes. Endosomal escape can be facilitated by increasing Cl influx in response to groups such as the nitrogens in the cationic polymer polyethyleneimine (PEI), which become protonated in the pH environment of endosomes/lysosomes. As a result of the increased osmotic pressure and swelling, the organelle bursts and the siRNA NPs are delivered. The “proton sponge effect” is the name given to this phenomenon. However, a recent study found that siRNA distribution in a cationic lipid NP system was significantly reduced, with approximately 70% of internalized siRNA being recycled to the extracellular media due to lipid NPs exiting late endosomes/lysosomes [33]. Designing novel NP vehicles that can resist recycling pathways could thus boost siRNA distribution. Fusogenic peptides and cell penetrating peptides have also been used to investigate active targeting methods of nonendocytic absorption of NP delivery of nucleic acids. SiRNA probes have been used to research intracellular trafficking as well as the assembly and disassembly of siRNA NPs to better understand siRNA NP interactions with biological systems. Since immune cells play critical roles in homeostasis and disease, NPs have recently been used to deliver siRNA to silence genes in these cells [11, 12]. In one study, NPs were used to silence Cyclin D1 (CyD1), a cell cycle-regulatory enzyme, in leukocytes in vivo in order to establish the molecule’s exact function in gut inflammation. CyD1 siRNA was loaded into NPs, which were then functionalized with antibodies to the b7 integrin. The researchers discovered that by suppressing leukocyte proliferation and T helper cell 1 cytokine expression, these targeted NPs silenced CyD1 in leukocytes and reversed experimentally induced colitis in mice. Another recent study identified the use of lipid NPs for in vivo siRNA transmission to immune cells to silence disease genes. The study identified the feasibility of targeting multiple gene targets in rodent myeloid cells and demonstrated siRNA-mediated silencing in nonhuman primates’ myeloid cell types. Using siRNA to target tumor necrosis factor-α, the therapeutic potential was verified (TNF-α). Another research used NPs to investigate the immunological mechanisms that cause nonalcoholic steatohepatitis (NASH) (Fig. 2) [13]. TNF-α developed by Kupffer cells can activate the development of NASH by increasing the output of chemokines IP-10 and MCP-1, according to the researchers. Furthermore, silencing TNF-α in myeloid cells decreased chemokine activity and prevented the development of NASH, implying that TNF-α may be a new therapeutic target in NASH. NPs have also been used to deliver siRNA to plant cells at the single cell level to research cellular pathways. One group used amine-conjugated polymeric NPs as vehicles to deliver siRNA to genes involved in cellulose biosynthesis. They

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Fig. 2 The processes involved in generating I-tsNPs. Multilamellar vesicle (MLV)

discovered that NtCesA-1, a factor involved in whole-plant cell wall synthesis, is also necessary for cell wall regeneration in isolated protoplasts [14].

Delivering Hydrophobic Compounds Many biologically active compounds are hydrophobic molecules, meaning they have a low water solubility. Because of their low solubility in aqueous conditions, using such compounds in biological research can be difficult. Currently, a solvent, such as dimethyl sulfoxide (DMSO), or an excipient, such as Cremophor, is used. However, not all molecules can be dissolved in these solvents, and the solvents themselves are often poisonous to living organisms, making the biological experiment more difficult. For in vitro applications, wortmannin, a PI3 kinase inhibitor and a widely used reagent in biology research, needs DMSO. DMSO has been shown to have its own effects on cells and is thus unsuitable for in vivo use. The use of NPs has been strengthened as a technique to solve the difficulty of delivering these hydrophobic agents. Hydrophobic cores in polymeric NPs make them suitable for delivering hydrophobic agents. The use of NP delivery vehicles overcomes the active agent’s solubility while also protecting it from the environment before it is released from the NP. They developed an NP formulation of wortmannin to show the proof-of-principle of this method. The solubility and stability of NP wortmannin were improved. Furthermore, NP wortmannin has the same cell signaling effects as wortmannin. Furthermore, in a mouse model of cancer, NP wortmannin was found to be an effective and potent therapeutic agent in vivo [15]. Delivering Agents to Subcellular Organelles Delivering different agents to particular organelles is one field of active research. The availability and accessibility of a target at the subcellular level is critical for the successful delivery of therapeutic and imaging agents. Delivering agents to subcellular organelles can also reveal molecular processes in organelles that are currently

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unknown. Because of the ease with which NPs can be modified and functionalized, there has been renewed interest in using these vehicles to deliver agents to subcellular organelles. Endocytosis enables targeted NPs to bind to targets on the cell surface and enter the cell. If the target is intracellular, however, NPs and their cargo can be unable to meet the desired target due to NP intracellular sequestration or a lack of subcellular targeting capabilities. To be successful, NPs carrying oligonucleotides must first escape the endosome and then be targeted. For targeted distribution to the nucleus, cytosol, mitochondria, endosomes, and lysosomes, tools for efficient subcellular targeting are evolving. For the design of NPs for subcellular targeting, two approaches are being investigated: (1) passive targeting of NPs to a specific organelle by varying NP characteristics such as scale, shape, and composition and (2) active targeting of NPs to the organelle of interest by functionalizing NP surfaces with targeting ligands directed toward the organelle. These techniques have been used to varying degrees of effectiveness. Biological barriers unique to the target organelle are obstacles to effective subcellular targeting. NPs destined for the nucleus, for example, must pass through the cell membrane, avoid the endosomal 4q-lysosomal pathway, connect with the nuclear pore complex, and be small enough to cross the nuclear membrane [51]. The active transport mechanism has been used to improve nuclear delivery by using targeting ligands like the nuclear localization signal (NLS). The localization of NLS conjugated gold NPs at the nucleus of a cancer cell caused DNA damage in one study. In a different sample, NLS conjugated gold NPs were unable to target the nucleus of cells from outside the plasma membrane because they could not penetrate the cells or were stuck in endosomes. NPs conjugated with NLS and receptor-mediated endocytosis (RME) peptides, on the other hand, were able to enter the nucleus [16]. Biological obstacles to NPs targeting mitochondria include intracellular transport to mitochondria, outer and inner mitochondrial membranes, and toxicity. Most studies have focused on developing metal oxide or liposomal NPs for transmission to mitochondria so far. Electrostatic interactions between the NP and the organelle have also been used to deliver the NP to the mitochondria. In comparison to other cellular membranes, mitochondria have a negative membrane potential, which can lead to the accumulation of lipophilic cations. The fabrication of stearyl triphenyl phosphonium (STPP) targeted liposomes with anticancer agents ceramide and scarleol to target the mitochondria was based on this definition. Since it has both cationic and lipophilic properties, STPP was selected. A polymeric NP device was used by another community to deliver mitochondriaacting therapeutics to their target. A lipophilic triphenyl phosphonium (TPP) cation was used to make the NPs, which has been shown to cross into the mitochondrial matrix. By screening a library of NPs with varying charge and scale in vitro, the team discovered an optimized targeted NP that increased efficacy and decreased toxicity for cancer, Alzheimer’s disease, and obesity as compared to nontargeted NPs or small molecule therapeutics [17].

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Nanoparticles of Mesoporus Silica (MSN) MSNs (mesoporous silica nanoparticles) are a promising candidate for drug delivery systems because they have the ability to perform all functions at the same time. MSNs used as drug delivery systems typically include an ordered array of 2D hexagonal micro- or mesopore structure, uniform particle sizes (80–500 nm), large surface areas (>1000 m2 g
1), high pore volumes (0.5–2.5 cm3 g
1), tunable pore diameters (1.3–30 nm), controllable particle morphology, and both exterior and interior surfaces that can be independently modified with a variety of techniques. Unlike traditional polymer-based drug delivery systems, which have issues like low drug loading ability and poor drug release control, MSN-based drug delivery systems successfully avoid these problems. Because of the large surface areas and pore sizes, a large payload of drug molecules can be carried. To improve drug loading and releasing ability, functional groups preferred by drug molecules can be added to the pore environment and surface. During drug administration, the highly stable pore channels protect encapsulated drug molecules from degradation in harsh environments. MSN materials have excellent biocompatibility at concentrations suitable for pharmacological applications due to their tunable particle morphology. Vallet-Reg was the first to investigate the use of mesoporous silica materials for drug adsorption/desorption at the turn of the century. She was able to show that in 3 days, 80% of the previously loaded ibuprofen was released. In order to achieve an accurate control of drug-releasing rate, a “stimuli-triggered release” concept was brought forward simultaneously by Tanaka and coworkers and Lin and coworkers 2 years later. In Tanaka’s approach, coumarin ligands were immobilized at the pore entrance and on the external surfaces by a grafting method. The uptake and release of guest molecules from pore voids were photo-regulated. The coumarin molecules underwent a dimerization reaction to completely seal the pore entrances when this sample was exposed to UV light (λ > 310 nm). The cleavage of coumarin dimers with UV light (¼ 250 nm) irradiation caused the release of guest molecules. The Lin research group created the first example of using biocompatible MSNs as carriers and inorganic nanoparticles as caps to efficiently deliver drug molecules into animal cells with zero premature release [18]. They used 12 2-(propyldisulfanyl) ethylamine groups to functionalize spherical mesoporous silica nanoparticles with a uniform particle diameter of 200 nm and pore size of 2.3 nm. This MSNs sample was soaked in a concentrated vancomycin or ATP solution to allow cargo molecules to diffuse through the pores. After that, watersoluble cadmium sulfide (CdS) nanocrystals with mercaptoacetic acid groups were added to react with the MSNs’ terminal amino groups. As a result, the CdS nanocrystals were covalently bound to the MSNs and effectively blocked pore entrances. The physiosorbed molecules were washed out of the vancomycin- or ATP-loaded, CdS-capped MSNs. The loading efficiency of vancomycin and ATP was determined to be 25 and 47 mol g
1, respectively, based on a quantitative study of the amounts of each compound controlled by HPLC. This drug delivery system’s controlled release output was assessed. Over a 12-hour period, the substance

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released less than 1% of the drug in buffer solution, indicating strong pore blockage and limited premature release. A rapid release was caused by the addition of disulfide-reducing reagents such as dithiothreitol (DTT) or mercaptoethanol (ME) to cleave the CdS-MSN linkage, with 85% of entrapped molecules released within 24 hours. By taking advantage of the acidic environment at tumor or inflammatory sites (pH 6.8), endosomal or lysosomal compartments of cells (pH 5–6), and the stomach (pH 1.5–3.5), a series of pH-responsive linkers have been exploited for controlled release applications. These pH-responsive linkers have an inert physiological pH response and a robust release at low pH. Casacus et al. reported a pH- and anion-mediated drug delivery system as an example of a pH-responsive release system. The MSN materials were made by combining mercaptopropyl triethoxysilane and TEOS in a cocondensation reaction. To get a preferential anchoring of amino groups on the external surfaces, a second grafting reaction was carried out with N-(3-triethoxysilylpropyl-2-aminoethyl)ethylenediamine. The amines were deprotonated and tightly packed through hydrogen-bonding interactions at high pH values, resulting in the delivery system being in its “open gate” state. Due to the coulombic repulsion effect between positively charged amine groups, when the amines were protonated at low pH conditions, they repelled each other and covered the pore openings, and the delivery system was monitored to its “near gate” state. In the presence of anions, which could intercalate into the open-chain polyamines and close the pore openings, a strong synergic effect was also observed. The size of the anion and the intensity of the polyamine-anion are clearly linked in this effect [19] (Fig. 3). Kawi and colleagues developed another pH-responsive drug delivery system for protein drugs. MSN materials with pore diameters above 10.5 nm and pore volumes

Fig. 3 Schematic graph of opening and closing of the core-shell-structured nanoparticle triggered by pH. With permission from Dr. Homg

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around 1 cm3 g
1 were synthesized in this study to encapsulate bulky proteins without denaturation. Cocondensation was used to add amine groups to these MSN products, which were then filled with a model protein, bovine serum albumin (BSA). After that, the positively charged BSA-loaded MSNs were combined with a pH 5.35 polyacrylic acid (PAA) solution. PAA’s electrostatic assembly blocked pore entrances and trapped BSA proteins; the final BSA loading number was estimated to be 16.3%. In a pH 1.2 acidic medium, no BSA was released from the PAA-encapsulated sample after 5 h, and only 10% was released after 36 h. In a phosphate buffer solution at pH 7.4, however, the carboxyl groups on the PAA chains dissociated and repelled each other, allowing PAA to swell and dissolve into the buffer solution. As a result, 40% of the entrapped BSA was released from the study, indicating that their material is pH sensitive. PAA has also been discovered to shield proteins from enzymatic degradation. They concluded that the BSA conformation has not been significantly altered by the adsorption process by comparing the UV-CD spectra of native and released BSA, implying that the protein activity has been preserved. They proposed that this material could be used to deliver protein drugs orally to target sites with higher pH, such as the small intestine or colon. The Hong research group used a reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid to study covalently immobilized PAA on MSN materials as a pH-sensitive drug delivery device. In this case, the MSNs were grafted with 5,6-Epoxyhexyltriethoxysilane before the template was removed. Via an esterification reaction with the hydroxyl groups, an RAFT agent, S-1-dodecyl-S(,0 -dimethyl-00 -acetic acid) trithiocarbonate, was bound to the MSNs’ exterior surface. Finally, under vacuum, acrylic acid polymerized to form a covalently bonded PAA nanoshell coating on the MSNs. The pH value of the medium had a major impact on the structure of the PAA nanoshell. The PAA nanoshell is deprotonated and soluble in aqueous solutions at pH 8.0, resulting in an open state with pore entrances that can be accessed. As the pH falls below 4.0, however, the PAA nanoshell becomes insoluble and collapses onto the MSN surface, forming a compact sheet. The pH-regulated drug release efficiency of the PAA-coated MSNs was evaluated using fluorescein. At pH 8.0, they saw fluorescein uptake and release from PAA-coated MSNs, but neither was seen at pH 4.0. Their findings confirmed that by modifying pH values, PAA-coated MSNs can reversibly control the loading and releasing of guest molecules. Release triggered by multiple stimuli from multiresponsive controlled release systems has been designed to achieve complex release behaviors in either an individual or synergistic manner, in addition to the comprehensive research conducted on single stimulus-induced drug delivery. Angelos et al. [67] developed a dual pH and light-controlled release mechanism based on the combination of pH-sensitive pseudorotaxane and photo-sensitive nanoimpeller azobenzene. To generate pore surface-functionalized MSNs, a silylated azobenzene derivative was cocondensed with TEOS, and CB [6]/bisalkylammonium containing pseudorotaxane was anchored on the exterior surface of MSNs. They demonstrated that this material could function as AND logic gates, allowing cargo to be delivered only

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when both stimuli were enabled. They imagined that using this device, they would be able to manually monitor the delivery dose. Aznar et al. demonstrated yet another pH and photo-switch release process. A boronate ester linker was formed between saccharide-functionalized MSNs and boronic acid-anchored gold nanoparticle caps in this study. To sever the boronate ester connection, two opening protocols have been suggested. The first is to reduce the pH to 3; the second is to irradiate the material with a laser beam at 1064 nm, which causes plasmon resonance excitation in Au nanoparticles, resulting in a photothermal impact. By repeatedly administering stimuli, both triggers were shown to be capable of generating a pulsatile release of guest molecules [20–22]. Three independent stimuli were verified to be capable of sufficiently unblocking the pore voids in another pseudorotaxane-based MSN recorded by Kim and coworkers. An o-nitrobenzene ester with stalk and a -CD ring made up the pseudorotaxane unit. UV light irradiation will rupture the stalk, which can then be decomposed by lipase, and the -CD ring digested by -amylase. As a consequence, the release of guest molecules can be activated in a number of ways, including by enzymes, light, or both to achieve a synergistic acceleration effect. Feng and coworkers developed a tri-stimuli-sensitive delivery system that involved the development of pyridyldithio-containing polymer functionalized MSNs that were a disulfide bond linked to thiol-modified -CD [70]. To prevent the release of entrapped molecules, the -CD moieties were further cross-linked with diazolinkers. UV light irradiation, as well as the addition of DTT or -CD, is supposed to affect their assembly. The transconfigured diazo-linkers will turn into a cis-azobenzene under 365 nm UV light, losing their high-affinity for -CD molecules. The disulfide relation between -CD and MSNs would be cleaved if DTT was added. Excess -CD would result in the creation of a more stable -CD-diazo cross-linkage and would displace -CD. The pore-blocking polymeric network was opened in all three cases, resulting in tri-stimuli-triggered release. The Vallet-Reg group [71] used the ability of magnetic nanocrystals to produce heat energy under a high-frequency alternating magnetic field in the design of temperature-responsive delivery systems. MSNs were decorated with a thermosensitive copolymer of poly(ethyleneimine)-b-poly (N-isopropyl-acrylamide) (PEI/NIPAM), and magnetic iron oxide nanocrystals were embedded within the silica matrix. They showed that this system could deliver proteins with preserved activity as temperatures rose, as well as an alternating magnetic field that heated the local environment through encapsulated iron oxide nanocrystals. For site-specific drug delivery, light irradiation is a convenient remote-control process. When exposed to certain wavelengths of light, the uptake and release of guest molecules can be triggered quickly. Photochemically sensitive linkers such as azobenzene, o-nitrobenzyl ester, and thymine bases are integrated onto the surface of MSNs to make them photochemically susceptible for light-mediated release after Tanaka and coworkers first demonstrated a coumarin-functionalized MSN material to manipulate drug release. The pseudorotaxane method was also used to monitor drug release with light by varying the stalk and ring components. A photosensitive pseudorotaxane of azobenzene derivative (AB) and -cyclodextrin (-CD) was created by Zink, Stoddart, and coworkers [185]. The pseudorotaxane stalks

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were grafted onto unfunctionalized MSNs with 4-(3-triethoxylsilypropylureido) azobenzene (TSUA) groups or more water-soluble (E)-4-((4 (benzylcarbamoyl)phenyl)diazenyl)benzoic acid groups. Both azobenzene derivatives isomerized from the more stable trans form to the less stable cis form when exposed to 351 nm light. Then pyrene-cyclodextrin (Py-CD) or fluorescently labeled pyrenecyclodextrin (Py-CD) was added. The -CD rings were locked at the orifice due to the high binding affinity between trans-AB and -CD. The isomerization of trans- to cis-AB stalks, on the other hand, resulted in the dissociation of pseudorotaxanes, allowing cargo molecules to be released due to the poor binding between cis-AB and -CD. The AB stalks and Py-CD assembly were found to be stable in the absence of 351 nm UV radiation, but when the sample was subjected to a 351 nm excitation beam for 400 min, full Py-CD dissociation was observed. Similarly, findings from RhB-loaded samples showed that over a 7-h span, more than 90% of RhB was released from the laser light-exposed sample, while less than 30% was released from the unexposed one. They came to the conclusion that their material could be used in light-activated intracellular drug delivery systems. The Kim group also used cyclodextrin to cover the porous reservoirs. MSN materials were functionalized with aminopropyl groups, which were then treated with succinic anhydride in the presence of triethylamine to produce a carboxylic acid-terminated MSNs sample, according to their research. Via a coupling reaction with 2-nitro-5(2-propyn-1-yloxy)- benzenemethanol, the sample was further functionalized by alkyne end groups, yielding a photosensitive o-nitrobenzyl ester moiety that decomposes when exposed to UV light at 350 nm (Fig. 2). The pores were capped with mono-6-azido-CD using the Huigsen 1,3-dipolar cycloaddition reaction after calcein dye filling. The fluorescence strength of the CD-capped calcein-loaded MSNs sample suspension was tracked over time to see if their method was feasible. In the dark, only a faint signal was observed, suggesting that the calcein molecules had been preserved within the pores. The photolysis of the o-nitrobenzyl ester linkage and the diffusion of CD and calcein molecules caused a significant increase in fluorescence intensity when the sample was exposed to UV light. Furthermore, they observed a periodic release activity of their sample in response to successive UV irradiation over short periods of time. In a study conducted by Lin and coworkers (Fig. 4) [72], gold nanoparticles were used as pore-blocking caps due to their demonstrated excellent biocompatibility. Thioundecyl tetraethyleneglycol esternitrobenzylethyl dimethyl ammonium bromide, a photoresponsive linker, was immobilized onto the surface of Au nanoparticles (PR-AuNPs). Via electrostatic interaction, these positively charged species attached to the negatively charged MSN materials, resulting in a PR-AuNP-capped MSN system. The fact that no cargo release was discovered even after 80 h in the dark confirmed a high capping quality. The o-nitrobenzyl ester-containing linker was cleaved by photoirradiation at 365 nm, resulting in negatively charged thioundecyl tetraethyl eneglycolcarboxylate-functionalized Au nanoparticles. As a result, the charge repulsion between Au nanoparticles and MSNs uncovered the pores, allowing guest molecules to diffuse through. In addition, intracellular experiments were carried out in human liver and fibroblast cells using an anticancer drug as cargo for

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Fig. 4 Schematic illustration of photo-induced controlled drug release of PR-AuNP-capped MSNs. With permission from Dr Juan Vivero-Escoto

controlled release. Both cell lines were exposed to light or held in the dark when incubating with either drug-loaded or drug-free samples. Only cells exposed to UV light with internalized drug-loaded MSNs died in large numbers, indicating that this mechanism could transport and release drug molecules within living human cells under photoirradiation regulation [23].

The Differences in Treatment Response and Toxicity Cancer immunotherapy-related adverse events (irAEs) vary significantly from cytotoxic agent-related adverse events in terms of initiation, length, severity, and form. The incidence of irAEs has been linked to a number of immunological, environmental, and lifestyle factors. The use of nanomaterials in cancer immunotherapies adds yet another layer of uncertainty to the toxicity equation, as nanomaterials can be toxic to the immune system. Simultaneously, cancer immunotherapy can alter the immune system’s interaction with nanomaterials, resulting in possible toxicity profiles that vary from those seen with either treatment alone. As a result, traditional toxicity tests of nanomaterials are unlikely to be adequate to completely identify possible cancer immunotherapy side effects and must be extended. Many preclinical cancer nanomedicine experiments, for example, have used liver and kidney markers, as well as blood cell counts and physiological parameters including animal weight loss, as measures of treatment toxicity. These approaches, however, do not account for variations in organ distribution, cytotoxic therapy kinetics, or immunotherapy adverse events. Finally, nothing is understood on how the addition of nanomaterials to cancer immunotherapy affects the immunotherapy’s toxicity profile. Targeted delivery of therapeutic agents to desired tissues or tumors is the subject of conventional cytotoxic cancer nanomedicine. As a result, its toxicity profile is mostly localized and exists in places where nanomaterials have accumulated in higher concentrations, such as the liver and spleen. However, as a result of the release of

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proinflammatory cytokines or the nonspecific recognition of self-antigens by activated T cells targeting peripheral tissues, cancer immune nanomedicine may cause systemic toxicity. As a result, cancer-immune nanomedicine may have a toxicity profile that blends the worst of both worlds: the nanomaterials themselves cause toxicity in the liver and spleen, while their immunostimulatory effects cause adverse reactions in distant organs such as the colonic epithelium or skin. To accurately assess the possible side effects of nanomedicine cancer immunotherapy, a thorough examination of multiple tissues, organs, and organ systems is needed. Aside from the variations in systemic organ involvement, irAE has a different onset and length than cytotoxic therapy. GGI, hepatic, dermatologic, and pulmonary toxicities often arise first, accompanied by endocrine and renal pathologies, according to clinical findings. Although the majority of irAEs manifest instantly, delayed dermatologic and endocrine toxicities are likely. As a result, in cancer nanomedicine research, extended monitoring may be essential to account for lateonset toxic effects [7].

Nanoparticles as Sensors The Biobarcode This route has been improved by the Mirkin community. This approach is devoted to the use of gold NPs’ marvelous surface chemistry for signal transduction amplification and, as a result, for protein and DNA [76] target detection. Metallic or magnetic NPs are the most widely used biosensors. This method has been used to detect cytokines at 30 aM (attomolar) concentrations, as well as a soluble pathogenic biomarker for Alzheimer’s disease at a concentration of about 100 aM. The PSA target protein is combined with a magnetic microparticle (MMP) that has been functionalized with monoclonal antibodies to PSA. PSA gold NP probes are added to PSA that has been bound to MMP. The PSA-specific DNA barcodes are released into solution after further separation by magnetic field application and wash steps, and analyzed using a scanometric assay that takes advantage of gold NP-catalyzed silver enhancement. The sensitivity of this assay was 330 fg mL
1 of PSA (Fig. 5). The DNA biobarcode approach combines the conjugation of several DNA strands onto gold NP surfaces with the ability to detect these DNA strands using PCR amplification or scanometric assays [24]. The Mechanism of the “Chemical Nose” This method was developed by the Rotello group. They discovered that noncovalent chemical interactions allow anionic fluorescent polymers to reversibly attach and detach from functionalized cationic gold NPs. The fluorescence of the fluorescent polymer is turned off when it is attached to the NP. The fluorescence is turned on when it is detached from the NP. The target protein is detected in this system based on the different fluorescence interactions it has as it binds to different forms of surface-modified gold NPs. A fluorescence response pattern is developed and then statistical methods are used to observe it. This process can distinguish between

Fig. 5 The biobarcode method. (a) Development of the NP probe. (b) Method of detection using prostate-specific antigen-conjugated gold NP probes. With permission from Dr Charudharshini Srinivasan [25]

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various molecular targets by observing, quantifying, and recognizing them. This method was first used to detect and sense proteins, and then improved for bacteria, physicochemical distinction between stable, cancerous, and metastatic human breast cells, and isogenic healthy and transformed cells [80, 81]. Since the identity of the target analyte does not need to be identified in order to detect the analyte, “chemical nose” sensing has the advantage of not needing antibodies for detection [26].

Raman Scattering with a Surface Enhancement (SERS) The SERS method has been used to detect individual analytes based on their unique vibrational spectra. SERS spectra have a small width, allowing for multiple analyte detection in complex mixtures, including detection down to single molecules. SERS methods have thus been used to identify biomolecules such as glucose, hemoglobin, bacteria [82], and viruses [83] with extreme sensitivity. In vitro and in vivo, one group investigated the ability of gold NPs encoded with Raman reporters and conjugated with single-chain variant fragment (ScFv) antibodies to target cancer biomarkers including epidermal growth factor receptors (EGFR) [27]. Recently, researchers demonstrated a SERS method for multiphase trace analyte detection based on a thin-film NP array self-assembled at the liquid-liquid interphase. This team was able to identify single-phase and multiple-phase analytes dissolved in water and organic phases [28]. Supermagnetic Iron Oxide Nanoparticles (SPIONs) SPIONs have been used as magnetic tags for a variety of sensors, including giant magnetoresistive (GMR) biosensors [87, 88], which are based on magnetic particle binding to a sensor surface. The magnetic fields of the particles will influence the magnetic fields of the sensor, resulting in changes in the sensor’s electrical resistance. Wang and colleagues at Stanford University recently demonstrated the effectiveness of this technique for protein detection. An array of GMR sensors is used in this assay to detect the engagement of proteins to arrays of surface-bound antibodies using SPIONs as magnetic tags [89]. The target antigen is sandwiched between two antibodies, one bound to the sensor and the other tagged with an SPION in this assay. The underlying sensor detects the presence or absence of magnetized NP. The researchers demonstrated that the assay is matrix insensitive to a variety of biological fluids while still being capable of detecting proteins at molar concentrations and over a broad concentration spectrum. Using a similar strategy, they have shown that MACS particles (commercialized SPIONs for cell separation) can detect cancer-associated proteins in 50% serum at subpicomolar concentrations [90]. They used streptavidin-functionalized antiferromagnetic NPs to detect DNA with high sensitivity (10 pM) recently. Magnetic relaxation switching is also based on the superparamagnetic property of IONPs. Magnetic relaxation switches made of 3–5 nm SPIONs coated with 10 nm thick dextran and stabilized by crosslinking were studied by the Weissleder group [92]. Functionalizing SPIONs with amino groups allows them to bind to a number of sulfhydryl-bearing molecules, resulting in targeted SPIONs. In the presence of a molecule recognized by the ligands immobilized on the NP, the nanoswitches will

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undergo reversible assembly (clustering and declustering), resulting in a shift in the transverse magnetic relativity (1/T2) of surrounding water protons. At the low femtomole level (0.5–10 fmol), changes in relaxation rates caused by NP assembly can be used to detect a number of biological targets, including DNA and proteins [29].

Diagnostic Magnetic Resonance (DMR) The diagnostic magnetic resonance chip-based (DMR) device was developed by the Weissleder group for rapid and quantitative detection of biological targets. IONPs are also used as sensors in the DMR to amplify molecular interactions caused by SPION assemblies. They proved their theory by detecting, with high sensitivity, bacteria and the existence of proteins in parallel. The mass detection limit of the DMR device was two orders of magnitude higher than that of the benchtop NMR relaxometer (detection limit of 15 fmol) [30]. Magnetic NP Relaxation Sensors The dominant mechanism for these NP biosensors is Brownian relaxation [97]. The theory behind this approach is that when target analytes are recognized, MNP accumulates, triggering slower Brownian relaxation responses than individual NPs due to increased hydrodynamic size. Using this theory, a group recently used an AC susceptometer to detect a bacterial antibody with a sensitivity of 0.3 nM [31]. Surface Plasmon Resonance (SPR) Because of their small scale, the confinement effect favors solitary optical properties of gold nanoparticles. The surface plasmon resonance (SPR) absorption of Au NPs causes their colloidal solution to have a distinct characteristic of a strong vivid color. Mie demonstrated this phenomenon theoretically by solving Maxwell’s equation for the absorption and scattering of electromagnetic radiation by spherical particles. Colloidal Au NPs’ sample is ruby red in color. This effect is known as SPR, and it does not exist in individual atoms or in bulk form. According to the theory, as particle size increases, a red change to longer wavelength occurs. The SPR frequency of Au NPs has been shown to be affected by particle size, shape, dielectric properties, aggregate morphology, surface alteration, and the surrounding medium’s refractive index. The SPR peak of 13 nm spherical gold colloids, for example, is around 520 nm, while the peak of 5–6 nm silver NPs is around 400 nm. By adjusting the scale of the Au NPs, the SPR peak of the Au NPs can be systematically tuned [33]. Many studies have used functionalized Au NPs in an immunoassay to show biosensing amplification. The technique of Au NP-enhanced SPR has also been used to establish cholera cell detection assays. Other researchers developed an Au-amplified SPR sandwich immunoassay that detected human immunoglobulin at picomolar levels. These findings indicate that by fine-tuning the configuration parameters, the detection limit of an Au NP-amplified SPR biosensor device can be increased even further. SPR sensors are now commercially available and are used as a powerful method in biomolecular interaction detection, drug discovery, and life science research. Surface plasmons or electromagnetic waves propagating over a metal/dielectric

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interface are involved in the SPR sensor process. The wave vector of plasmons is determined by the media’s dielectric constants and is highly sensitive to the properties of the dielectric medium in contact with the metal. In the Kretchmann configuration, surface plasmons are excited by directing p-polarized light to a glass prism and reflecting from a gold film. Pumping light energy is passed to surface plasmons when the incident optical wave vector’s tangential x-component matches the wave vector of plasmons. At a particular combination of angle of incidence and wavelength, the plasmon coupling condition is usually followed by a dip in reflectivity. The sensing effect is due to the fact that the refractive index of a thin 200–300 nm layer in contact with the SPR-supporting gold is dependent on this resonance state. As a result, by carefully observing the SPR coupling characteristics, knowledge about biological interaction events on the gold film can be obtained. The knowledge of biomolecular interactions is obtained in most SPR systems by measuring the angular or spectral characteristics of light reflected under SPR. The detection limit in this case is usually 105 in terms of refractive index shift, which corresponds to 1 pg mm2 of biomaterial accumulating on the biosensor surface [34]. A photoelastic modulator was used to produce a weak delay amendment to evaluate the SPR step. In the response of the second and third harmonic signals to the polarization and phase change induced by SPR, the variable retarder plays a critical role. The second harmonic signal has a narrower dynamic range than the third harmonic signal without compensating for the phase introduced by SPR. They track the second and third harmonic signals at the same time, with complete precompensation of the SPR-induced initial step. These two signals are influenced by two different properties of the optical beam, the first of which is the polarization amplitude, and the second of which is the phase. As a result, over a large dynamic range, the established system can detect a very small change in refractive index. Functionalized Au NRs have been used as amplification labels in ultrasensitive SPR biosensing. Longitudinal plasmonic resonance of gold nanorods was used to optimize the sensitivity enhancement induced by the electromagnetic interaction between the Au NRs and the sensing film. The nanorod-conjugated antibody’s detection sensitivity is predicted to be 40 pg/ml, which is 25–100 times more sensitive than currently recorded values in the literature. Matsui et al. recently created an SPR sensor that can detect analytes with low molecular weight. Essentially, the system was developed by molecularly preparing SPR sensor detection using an imprinted polymer gel embedded with Au NPs on a gold substrate of a chip. The analyte binding inside the Plasmonics polymer gel caused the swelling effect of the polymer gel, which was used to detect the analyte. The swelling effect increases the distance between the Au NPs and the substrate, causing a change in an SPR curve’s dip to a higher SPR angle. In response to increased dopamine concentration, the updated sensor chip displayed an increasing SPR angle. More significantly, when compared to a sensor chip that was not immobilized with Au NPs, the Au NPs were found to be successful at increasing signal strength. Our findings corroborate their findings, suggesting that Au NPs are needed to improve the sensitivity of the SPR sensor.

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Thanh et al. also defined the creation of an Au NP-based antibody immunoassay system. The assay relies on the aggregation of Au NPs that have been updated with protein antigens in the presence of antibodies specific to those antigens. The absorption changes caused by the aggregation of Au NPs were controlled using an absorption plate reader. Monodispersed protein A-coated gold particles were used to evaluate the amount of antiprotein A in serum samples to demonstrate the new technique’s analytical capabilities. Antiprotein A had a dynamic range of two orders of magnitude and a maximum detection of 1 g/mL. There is space for progress in terms of increasing the biosensor’s sensitivity when combined with Au NP technology. Many more research groups will concentrate on a systematic study of using different sizes and shapes of Au NPs for SPR biosensing applications in the coming years. For example, Nath et al. demonstrated that Au NPs’ specific optical properties can be used to create a label-free biosensor in a chip format. The author demonstrated that Au NPs have a substantial impact on the biosensor’s sensitivity. Chemisorption of Au NPs on amine-functionalized glass was used to make sensor chips. The sensors made from 39 nm Au NPs were the most sensitive to changes in the bulk-refractive index. A sensor fabricated from 39 nm Au NPs had a 20-fold higher detection limit for streptavidin-biotin binding than a sensor fabricated from 13 nm Au NPs [35–39].

Microfluidic Device Using magnetic NPs coated with antibodies against surface antigens, this is one of the most widely used pathogen detection techniques. The optical and magnetic properties of NP are used in these devices. This immunomagnetic method was used in a novel way by one group to attract molecules bound to magnetic NPs from one laminar flow path to another using a local magnetic field gradient. E. coli bound to streptavidin-coated SPIONs and labeled with a biotinylated anti-E. coli antibody is effectively isolated from solutions containing densities of red blood cells identical to blood. Antibody-coated NPs were also used by the Weissleder community in a microfluidic system to detect bacteria. They also discovered that core-shell NPs with Fe metal cores have higher sensitivity for detecting bacterial cells than IONPs. The team recently created a single-gene mutation detection assay based on a magnetic barcoding technique that did not include antibodies. PCR-amplified mycobacterial genes are sequence-specifically captured on polymeric beads that have been modified with complementary DNA, labeled with SPIONs, and identified using NMR in this process. Within 2.5 h, the platform could detect tuberculosis and drug-resistant strains from sputum samples. A similar method that uses rRNA as a target marker for NP labeling was also developed by the researchers. A universal and unique nucleic acid probe that detects 16S rRNA, which is abundant in and common to many bacterial organisms, was used in the analysis. The system was sensitive enough to detect 1–2 E. coli bacteria in 10 mL of blood and estimate bacterial load accurately. Small molecule functionalized NPs have also been used to mark bacteria by a number of classes. By using the bacterial interaction with carbohydrates on mammalian cell surfaces,

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Fig. 6 Depiction of bacteria detection by magnetic glyco-NPs (MGNPs)

one group created a magnetic glyco-NP based device that could detect E. coli strains in 5 min and allow up to 88% removal from the sample (Fig. 6). In another study, vancomycin-modified SPIONs were used in a magnetic capture assay for Gram-positive and Gram-negative bacteria [135]. They also showed that as NP size and ligand coverage on the surface increase, the time needed for efficient NP labeling of bacteria decreases. Similarly, both metallic NPs and QDs have been used in optical biosensing of bacteria. The biobarcode assay method allows for amplification and the simultaneous detection of multiple targets in a single sample. Bacillus subtilis double-stranded genomic DNA was observed at a concentration of 2.5 fM using this method [136]. Salmonella enteritidis was also found at 0.2 fM. Pathogen sensors have also been developed using QDs. In vivo biotinylation of engineered hostspecific bacteriophage and attachment of the phage to streptavidin-coated QDs were described by Edgar et al. The method can detect as few as ten bacteria per mL of the experimental samples and can detect E. coli among many different bacterial strains [40–43].

Cell Search Device These devices are used to isolate individual cells from complex mixtures, which is necessary for biological research and a variety of biological applications. NPs have been studied as sensitive instruments for detecting particular cell types and low-frequency cells. The identification and capture of circulating tumor cells has been one application of concern (CTCs). CTCs have been identified as a strong prognostic biomarker for overall survival in patients with metastatic breast, colorectal, and prostate cancer [139, 140]. They may help in the understanding of the biology of cancer metastasis. Some of the most widely used methods for identifying and capturing CTCs are NP immunomagnetic techniques. Using a ligand-receptordependent method, these techniques use magnetic NPs to target and isolate CTCs. Currently, the only FDA-approved test for CTC evaluation employs an immunomagnetic technique. For the capture of CTCs in vitro, iron NPs coated with a polymer layer carrying biotin analogues and conjugated with anti-EpCAM

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are coated with a polymer layer carrying biotin analogues and conjugated with antiEpCAM. Using an anti-CD45-APC antibody as the NP-targeting ligand, this mechanism can also be used to mark and identify leukocytes. A group of researchers recently demonstrated that anti-HER2 or anti-HER2/neu functionalized IONPs could be used to isolate 73.6% of HER2/neu over-expressing cancer cells spiked in 1 mL of blood. The cancer cells were preferentially captured as a result of the receptor-ligand interactions. In a separate preclinical analysis, PEGylated magnetic NPs were used to detect CTCs in vivo. The researchers used magnetic NPs conjugated with plasminogen activator (uPA) and folate targeted nanotubes to target CTCs in vivo for subsequent detection using photoacoustic flow cytometry. The incorporation of polymers in other organic and inorganic NPplatforms, which can allow targeted detection and surface capture, could lead to novel NP sensors for CTC detection. A group of researchers recently used SERS and targeted polymer-coated gold NPs to specifically test CTCs in the presence of white blood cells. EGF peptides were conjugated to polymer-coated gold NPs that had QSY reporters embedded in them. With a sensitivity range of 1–720 CTCs per mL of whole blood, the NPs successfully detected CTCs in the peripheral blood of 19 patients with squamous cell carcinoma of the head and neck. Biomimetic nanotechnology, which takes advantage of naturally occurring processes, is another technique for cell identification and separation. Biomimetic methods have been explored by the Hong group in order to improve microfluidic devices for cell identification and separation. These devices take advantage of the natural process of cell rolling, which occurs when selectin molecules expressed on endothelial venules interact with glycoprotein receptors on cancer cells. For improved surface sensitivity and specificity, the cell rolling method using E-selectin was recently extended to CTC detection. G7 poly(amidoamine) (PAMAM) dendrimers were also used to engineer cell capture surfaces that allowed multiple ligands to bind to multiple receptors at the same time (multivalent binding). CTC surface capture was substantially improved using a biomimetic combination of dendrimer-mediated multivalent effect and cell rolling.

Nanoparticles in Imaging In molecular imaging, NPs have been investigated as new labels and contrast agents. Because of their special properties, NPs can be used to track molecular targets as well as cell responses in diseases such as cancer and cardiovascular disease. To image and detect tumor cells, molecular imaging methods are frequently used. Fluorescence microscopy is the preferred method for investigating tissue and cells with high spatial resolution. However, this method has a low sensitivity and requires many time-consuming steps to prepare the samples for imaging. As a result, significant efforts have been made to develop effective biosensors aimed at enhancing detection signals for more accurate disease diagnosis. Because of their utility for sensing cells in small quantities, functionalized Au NP-based sensor systems have gotten a lot of attention in biomedical diagnostics. A primary objective in the creation of high detection limits for sensing cancer cells is to design and construct a reliable biosensor with a high detection limit [45, 46].

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Chitosan-Encapsulated Au NPs This method, which involves neutralizing a designer nanocomposite solution, was developed by Ding et al. The gel was created to immobilize cells and conduct electrochemical studies on them, as well as to detect cell adhesion, proliferation, and apoptosis on electrodes. As a model, K562 leukemia cells were used to create an impedance cell sensor. The nanocomposite gel showed improved cell immobilization ability and good biocompatibility, allowing immobilized living cells to maintain their operation. The voltammetric response of living cells immobilized on glassy carbon electrode was irreversible, and the electron transfer resistance increased. This research demonstrated that nanocomposites gels based on biopolymer and NPs have biosensing potential and will open up new avenues for electrochemical studies of cell adhesion, proliferation, and apoptosis [47].

ICG-Functionalized Au NPs SERS experiments on indocyanine green were recorded by Kneipp et al., who demonstrated that the probe can be used to detect living cells. By tracking the SERS local optical fields of the Au NPs, the ICG Au NPs provide spatially localized chemical information from the cell environment. The functionalized Au NPs have the potential to improve the spectral specificity and selectivity of current vibrationalbased chemical analysis approaches for living cells. Souza et al. defined a method for fabricating biologically active molecular networks by directly assembling bacteriophage with Au NPs. They discovered that when phages are engineered with peptides, the cell surface receptor binding and internalization are preserved. The networks can be used to detect living cells using enhanced fluorescence, dark-field microscopy, and surface-enhanced Raman scattering. The Au NP networks’ physical and biological properties provide multimodality for nanobiomedical imaging applications. Similar to oligonucleotide chains, proteins have complementary countersections. Protein targets and biomolecules can be anchored to the surface of Au NPs for detection using other sensing agents and techniques. Typically, the Au NP-based detection scheme can be used to identify multiple protein targets in a single screening test. For targeted imaging, NPs have a lot of potential. First, because of their wide surface area, NPs can deliver a large number of imaging agents at once, improving sensitivity. Second, NPs may be aimed to accumulate at sites where the molecular target is expressed, raising the local concentration of contrast agents, or they may be passively target tissues in vivo through the EPR effect. Because of their high potential for NP adjustment, they can be used as in vivo imaging amplifiers. Finally, they may conduct multimodality imaging by delivering a variety of imaging agents. For cellular imaging, inorganic NPs like QDs are among the most promising fluorescent labels. QDs can emit light at particular wavelengths and can also be calibrated to emit in the near-infrared (NIR) region of the spectrum, which reduces tissue autofluorescence while increasing excitation light penetration.

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Individual proteins in cells and receptors involved in cell movement during development and metastasis have been tracked using monofunctionalized QDs. QDs have been used to image particular tumor biomarkers, such as the targeting of integrin avb3 with arginine-glycine-aspartic acid (RGD) peptide-conjugated NIR QDs. Targeted QDs have also been investigated for their ability to perform multiplex imaging, which entails imaging multiple molecular targets at the same time using different QDs with different emission wavelengths. QDs have recently been used for multiplex molecular imaging of lymph nodes, embryonic stem cells, tumor cells, and blood vessels. Tiny organic molecules were used as near-infrared (NIR) SERS reporters to study gold NPs as a noninvasive modality for in vivo cancer imaging. For the detection of HER2-positive tumors in xenograft models, antibody-conjugated gold NPs were recently used in conjunction with a responsive and stable cyanine reporter that was generated and screened from a combinatorial library of SERS reporters. Other recent in vivo imaging studies in mouse models have focused on the use of several targeted SERS gold NPs for multiplexed imaging. One of the more well-studied NP systems for targeted molecular imaging is magnetic NPs. Magnetic NP imaging systems have shown potential for real-time visualization of biological events, such as cell migration/ trafficking, enzyme activities, and other biological interactions at the molecular and cellular level. Magnetic NPs have also shown promising use as contrast agents in magnetic resonance imaging (MRI), a biomedical technique based on nuclear magnetic resonance of various interacting nuclei. SPIONs, formed from iron oxide crystals coated with dextran or carboxydextran, are widely used MRI contrast agents for cancer imaging. SPIONs have been shown to stay in patients’ tumors for 24 h after injection, compared to 1 h for gadolinium-based MR agents. This distinction is due to the tumor’s easier absorption of the NP and the NP’s lower diffusivity out of the tumor. The use of SPIONs for the selective identification of tumors and their metastases has been studied extensively. SPIONs have also been used to kill cancer cells without the use of ligands. A recombinant human heavy-chain ferritin protein shell containing IONPs was shown to target tumor cells over expressing transferrin receptor 1 in one study. In the presence of hydrogen peroxide, the iron oxide center catalyzed the oxidation of peroxidase substrates, resulting in a color reaction that can be used to image tumor tissues. SPIONs and targeting peptides were mounted on a modified viral scaffold in another study to increase the amount of SPIONs reaching tumor cells. M13, a bacteria-infecting virus, had glutamic acid residues added to its protein coat. Negatively charged residues assisted in the electrostatic assembly of NPs along the filamentous structure of the M13 coat. A peptide that targets the SPARC glycoprotein, which is overexpressed in various cancers, was also made into the viral coat. When compared to conventional approaches in which NPs are directly functionalized with targeting ligands, this method can increase MR imaging contrast. For visualizing biological activities, novel NPs with advanced magnetic properties have also been pursued. Metal-doped ferrite NPs with a composition of MFe2O4, where M is a +2 cation of Mn, Fe, Co, or Ni, are one such class that can be used to tune unique magnetic properties [180]. In vitro, MnFe2O4 NPs were found to be nontoxic and to have the highest magnetic sensitivity, implying that they could make

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better MRI probes. When these NPs were conjugated with antibodies, they improved MRI sensitivity for cancer marker detection. Dendrimers (magnetodendrimers) and liposomes (magnetoliposomes) are two other NP platforms that have been paired with SPIONs. These SPIONs have been used for applications such as cell migration control and in vivo visualization of bone marrow [48–54].

Application of Nanoparticles in Therapy Photodynamic Therapy Preclinical studies have documented the radiosensitization effect of gold nanoparticles (GNPs) in combination with various photon beams. While Monte Carlo simulations of GNPs showed a physical dose enhancement of about 60% for low-energy photons from 192 Ir brachytherapy sources and even X-rays in the kilovoltage range [188], Jain et al. found a similar sensitization effect at kilovoltage and megavoltage X-ray energies. Physical dose enhancement due to improved X-ray absorption was proposed as a potential mechanism of sensitization. However, it should be noted that the GNP measurements used in these studies were different. In other words, GNPs with a diameter of 100 nm were used in the MC analysis, while GNPs with a diameter of 1.9 nm were used in the biological study. GNP with a diameter of 1.9 nm was injected intravenously into mammary tumorbearing mice in conjunction with 250 kVp X-ray in a groundbreaking study by Heinfeld et al. The new procedure had an 86% 1-year survival rate compared to 20% for X-rays alone. Chang et al. used 13 nm GNP in combination with a single dose of 25 Gy of 6 MeV electron beam on melanoma tumor-bearing mice in another study. When compared to a control group, it resulted in a substantial reduction in tumor volume. Furthermore, the number of apoptotic cells was two times higher in GNP plus irradiation animals than in irradiation alone. Interactions between X-rays and GNP are thought to cause the release of photoelectrons from high-Z gold atoms as well as the generation of auger electrons. These electrons have a very small range compared to photons, so they deposit a lot of energy in cells containing GNP or in close proximity to gold atoms. The discrepancies in GNP radiosensitization results may be due to variations in the investigations conducted in terms of key parameters such as GNP shape, size, cell line concentration and type, and radiation energy and type. Burn et al. evaluated the influencing parameters in GNP X-ray radiosensitization in depth to resolve the problem. Large-sized GNP, high molar concentration, and 50 KeV photons were found to be the most effective factors, with a potential dose enhancement factor of 6.4 [ 56–60].

Interaction of X-Ray and Gamma Radiations Zhang et al. studied the irradiation stability and cytotoxicity of GNPs for radiotherapy purposes. Following gamma radiation of 2000–10,000 Rontgen, they found no apparent instability or size difference in spherical GNPs with a diameter

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of 15 nm. The cytotoxicity results revealed that a very high concentration of GNP could trigger a sharp drop in K562 cell viability, whereas a low concentration had no effect. Different types of interactions between photons and GNPs arise depending on the energies of ionizing photons. For photons with energies ranging from 10 to 500 keV, the photoelectric effect is the most common method. The emission of electrons, such as the characteristic X-ray of gold atoms or auger electrons, is the result of this operation. A vacancy in a K, L, M shell following photoelectric absorption results in de-excitation of the atomic system, either by characteristic X-ray or Auger-electron emission, in photoelectric interaction between photons and GNPs. The fluorescence yield determines the relative likelihood of these de-excitation processes. Fluorescence yield is highly influenced by the atomic number (Z), which is low for light atoms and high for heavy atoms like gold. Compton scattering and excitation are observed for photons with energies greater than 500 keV. The photoelectric effect is caused by Compton scattering, which causes atom re-excitation and the release of Compton electrons. After atom excitation and phonon emission, there are certain selection laws that prevent photon emission entirely. The excitation energy is transferred to the host lattice as low-grade heat in phonon emission. This is known as the quenching method. Since photon-phonon transfer processing is the dominant transition in GNPs, high energy excitation in gold induces many phonons and few photons [193]. Pair output dominates at photon energies greater than 1.02 MeV, resulting in positron and electron pairs. Except for Compton scattering, the cross section of photon interactions is highly dependent on Z for both of these interactions, when the photoelectric and pair output effect probabilities are proportional to Z3 and Z2 of atoms. As a result, it is assumed that the interaction of X-rays with gold atoms will release a significant amount of energy, which will be converted into energetic, free electrons and thermal energy Suzy V. Tort et al. investigated the potential of multiwall carbon nanotubes (MWCNTs) and near-IR (NIR) for photothermal cancer treatment. In addition to direct thermal ablation of cancer cells, the thermal effects produced by MWCNTs may have benefits, according to the researchers. When paired with chemotherapy or radiotherapy, hyperthermia can increase the permeability of tumor vasculature, which can improve drug delivery into tumors and enhance tumor cytotoxicity synergistically. When this advantage is combined with other previously identified MWCNT capabilities, such as the ability to transport chemotherapeutic compounds and MRI contrast agents, MWCNTs have the potential to become multifunctional platforms for cancer care [57].

Nanomedicine in Market The FDA has approved for clinical use a significant number of drug products in the nanometer size range (Table 1) [58].

Nanocrystal plalforms

Liposomal platforms

Sirolimus

Aprepitant

Fenofibrate

Fenofibrate

Megestrol acetate

Emend

TriCor

Triglide

Megace ES

Generic name Doxorubicin HCl Liposome Injection Amphotericin B lipid Complex Injection Daunorubicin citrate liposome injection Amphotericin B Cholesteryl Sulfate Injection Amphotericin B Liposome Injection Cytarabine Liposome Injection Verteporfin for Injection

Rapamune

Visudyne

Depocyt

AmBisome

Amphotec

DaunoXome

Albelcet

Drug name Doxil

Table 1 FDA-approved drugs in nanometer size

Strativa Pharmaceuticals, subsidiary of Par Pharmaceutical, Inc.

Sciele Pharma, Inc.

Abbott Laboratories

Merck & Co., Inc.

Wyeth

Novartis

Enzon Pharmaceuticals

Astellas Pharma US. Inc.

Three Rivers Pharmaceuticals

Diatos

Company Ortho Biotech Products, LP Enzon Pharmaccuticals

Hypercholesterolemia and hypertriglyceridemia Hypercholesterolemia and hypertriglyceridemia Anorexia, cachexia, or an unexplained significant weight loss in AIDS patients

Antiemetic

Photodynamic therapy for agedrelated macular degeneration Immunosuppressant

Lymphomatous meningitis

Antifungal

Antifungal

Antineoplastic

Antifungal

Indication Antineoplastic

Oral

Oral

Oral

Oral

Oral

i.v.

i.t.

i.v.

i.v.

i.v.

i.v.

Route of administration i.v.

5-Jul-05

7-May-05

22-Aug02 26-Mar03 5-Nov-04

12-Apr-00

11-Aug97 1-Apr-99

22-Nov96

Approved date 17-Nov95 20-Nov95 8-Apr-96

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Other platforms

paclitaxel albumin-bound particles for injectable suspension ferumoxides injectable solution (superparamagnetic iron oxide)

Abraxane

Feridex

Estrasorb

pegaspargase: pegylated L-asparaginase estradiol topical emulsion

Oncaspar

Bayer HealthCare Pharmaceuticals

Graceway Pharmaceuticals, LLC Abraxis Oncology

Enzon Pharmaceuticals

MRI Contrast Agent

Vasomotor symptoms associated with the menopause Metastatic breast cancer

acute lymphoblastic leukemia

i.v.

i.v.

Transdermal

IM or IV

7-Jan-05

9-Oct-03

1-Feb-94

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Potential Hazards of Nanoparticles Nanoparticles have the same possible hazards as bulk matter due to their extreme microscopic size. These particles have the ability to cause a variety of diseases in the respiratory, cardiovascular, and digestive systems. Carbon nanotubes have the ability to cause a variety of lung pathologies, including epitheloid granuloma, interstitial inflammation, peribronchial inflammation, and lung necrosis, as shown by intratracheal instillation of carbon nanotube particles in mice. The toxicity of carbon nanotubes was discovered to be higher than that of carbon black and quartz. C60 fullerene can induce oxidative stress and GSH depletion in the brain of fishes by entering through the olfactory bulb. Nanoparticles can penetrate the central nervous system either directly through axons of the olfactory pathway or through systemic circulation. Inhalational exposure may cause the olfactory bulb to become involved in humans. The olfactory pathway has been shown to accumulate carbon and manganese nanoparticles in the olfactory bulb in monkeys and rats. This demonstrates that nanoparticle-mediated delivery can one day provide an alternative route for bypassing the blood-brain barrier. However, this can trigger inflammatory reactions in the brain, which should be assessed. In vitro research, Radomski et al. discovered that nanotubes facilitate platelet aggregation and accelerate vascular thrombosis in rats. It was also discovered that fullerenes had no ability to cause platelet aggregation. As a result, fullerenes may be a safer option than nanotubes for developing nanoparticle-based drug delivery systems. Nanoparticle toxicity may be extrapolated to the gastrointestinal tract, causing inflammatory bowel disease. Nanoparticle toxicity may be linked to their ability to trigger the release of proinflammatory mediators, resulting in an inflammatory response and organ damage. If ingested, nanoparticles may enter the bloodstream and travel to various organs and systems, potentially causing toxicity. These have been tested in vitro and in animal models, but extrapolating the effects to the human system is difficult. Further testing and caution are needed before they can be used in humans [59].

Conclusion Nanoparticle in medicine is not an emerging field anymore, rather it is a very wellestablished application. Although so much work has been done, we still need to know more about the side effects and the limitations of introducing nanoparticles into the body of patients.

References 1. Jain RK, Stylianopoulos T (2010) Delivering nanomedicine to solid tumors. Nat Rev Clin Oncol 7(11):653–664 2. Lin J, Zhang H, Chen Z, Zheng Y (2010) Penetration of lipid membranes by gold nanoparticles: insights into cellular uptake, cytotoxicity, and their relationship. ACS Nano 4(9):5421–5429

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Principal of FTIR Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FTIR for Monitoring Molecular Changes in Microorganisms Exposed to Nanoparticles . . . FTIR Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Toxicity of Effects of Silver Nanoparticles on Terrestrial Isopods . . . . . . . . . . . . . . . . . . . . . . . . . Toxicity Tungsten Oxide (WOx) Nanofibers on Digestive Gland Tissue of Porcellio scaber (Isopoda, Crustacea) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Final Thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subtoxic Exposure to ZnO Nanoparticles on Crustacean Digestive Glands Upon . . . . . . . . Toxicity of Iron Oxide Nanoparticles on Liver and Kidneys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nano-FTIR Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AFM-IR Spectroscopic Imaging Benefits and Drawbacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Close-Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deliberation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nano-FTIR Chemical Mapping of Minerals in Biological Materials . . . . . . . . . . . . . . . . . . . . . . Deliberation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbonate-Forming Organism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Subsurface Chemical Nano-Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Probe Single Bacterium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synchrotron FTIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synchrotron Macro ATR-FTIR Microspectroscopic Analysis of Silica Nanoparticle-Embedded Polyester Coated Steel Surfaces Subjected to Prolonged UV and Humidity Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synchrotron FTIR Light Reveals Signal Changes of Biofunctionalized Magnetic Nanoparticle Attachment on Salmonella sp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

One of the most important analytical techniques available to today’s scientists is infrared spectroscopy. Infrared spectroscopy has the advantage of being able to study virtually every sample in virtually any state. With the right sampling method, liquids, solutions, pastes, powders, films, fibers, gases, and surfaces can all be tested. As a result of the improved instrumentation, a number of new sensitive techniques for examining previously intractable samples have been developed. The Fourier transform infrared (FTIR) method is a type of spectroscopy that can detect changes in the total composition of biomolecules by determining changes in functional groups. The vibration and rotation of molecules influenced by infrared radiation at a particular wavelength is measured using FTIR. This method identifies structural differences in molecular binding between entities, which can reveal details about the existence of their interactions. Transmittance FTIR, attenuated total reflectance (ATR–FTIR), and micro-spectroscopy FTIR are the most popular FTIR-based methods for characterization. Keywords

FTIR · FTIR-microscopy · FTIR-AFM · Nanoparticles characterization · Nanotoxicity

Introduction In the 1950s, infrared (IR) spectroscopy was used to develop broad-spectrum molecular analytical instruments [2]. Researchers invented Fourier transform IR (FTIR) spectroscopy based on a modern computational analysis in the 1970s after making many improvements to IR instruments, which led to Naumann and Helm [8] introducing the FTIR technique for in situ analysis of bacteria. Due to the absorption of energy in the infrared region, FTIR can classify molecular signatures in composites. Stretching [29], bending, scissoring, and twisting [1] are all examples of biochemical bonds that can be detected based on their molecular rotational degree and form of movement [18]. Optical spectroscopy techniques have gained greatly from recent developments in instrumentation design, including detectors, sources, and the coupling of spectrometers with microscopes that provide spatially resolved spectra (spatial resolution is determined by incident light wavelength). Furthermore, data processing is being intensively developed in order to provide rapid spectral resolution methods aimed at evidencing the existence of multiple species and – ideally – at determining the sum of each species present (more and more commercial packages are available for data analysis). Mid-infrared (mid-IR) spectroscopy has recently been demonstrated to be a basic, accurate, relatively fast, and cost-effective technique for analyzing complex media and generating specific molecular fingerprints. From quality management to

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forensic examination, it is used in a number of scientific and industrial environments [19]. In this chapter, we will discuss various FTIR techniques used in the nanotechnology area, such as AFM-FTIR for characterization of nanoparticles or FTIR imaging integrated with microfluidic cells for detection of nanoparticle biotoxicity in vitro and in vivo. The synchrotron FTIR is shown at the end of the chapter to demonstrate the effect of SR on the improvement of the IR beam and its impact on measurements.

Principal of FTIR Spectroscopy Molecules have distinct levels of rotational and vibrational energy. If (i) their energy exactly matches the difference between two vibrational energy levels and (ii) the dipole moment of the molecule changes during the vibration, the transition between vibrational levels may occur following the absorption of photons with wavelengths varying between usually 780 nm and 50 m (12800–200 cm
1) (IR selection rule (Fig. 1)). A linear combination of the so-called natural modes of vibration may be used to express any typical molecular vibration. If a molecule with N atoms has nonlinear or linear geometries, it has 3 N -6 or 3 N -5 normal modes, respectively (Fig. 2). A simple harmonic oscillator model may define these modes. The infrared behavior of normal modes can be measured solely by understanding the symmetry of the molecule in question. The use of group theory to classify a molecule according to its symmetry elements demonstrates the relationship between the molecular structure and its vibrational spectrum. The bands seen on the spectra can be used to distinguish the various types of bonds present in a sample. These bands can be defined by their vibrational wavenumber (typical of the transition energy involved, while shifts in wavenumber can reveal changes in bonding and environment), their strength (related to the extent of the change in the

Fig. 1 Selection rule. http://butane.chem.uiuc.edu/pshapley/GenChem1/L15/2.html

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Fig. 2 Vibrational energy levels. https://www.chem.uci.edu/~unicorn/old/H2A/handouts/PDFs/ LectureB4.pdf

bond dipole moment as well as the sample amount and bond polar character), and their band profile (depending on the interactions of the bonding and environment). The main challenge in a spectroscopy experiment is to obtain a good signal intensity (high signal-to-noise ratio – SNR) when taking into account (i) the properties of the light source and its handling, (ii) the detector, and (iii) the sampling conditions and spectral acquisition modes. The incoming beam in infrared spectroscopy is usually given by black body sources, which are temperature dependent and have a low to average brightness (e.g., a globar). Despite some limitations, these are simple, reliable, and inexpensive light sources that emit a broad spectrum of light. An interferometer made up of a beam splitter, a fixed mirror, and a moving mirror moves the emitted radiation from an infrared source. The interferometer uses interference patterns to calculate the wavelength of emitted light, which helps to improve accuracy. Applying IR radiation to a sample and measuring the strength of the passing radiation at a given wavenumber yields IR spectra. The number of scans can be changed depending on the sample analysis quality requirement; currently, the most common number of scans is two. Certain molecular groups’ IR radiation can be detected at particular wavenumbers. The wavenumber is represented by the x-axis, while the absorbance or transmittance is represented by the y axis. Transmittance FTIR, attenuated total reflectance (ATR–FTIR), and micro-spectroscopy FTIR is the most popular FTIR-based methods of characterization. IN FTIR analysis of transmittance, strong samples should be ground with potassium bromide (approximately 5% of the sample weight) and pressed onto a rough pellet. The sample is then sandwiched between two transparent infrared plates. To test various types of samples, various types of transparent material are used. Pick compatible IR transparent windows, such as zinc selenide or diamond glasses, are more suitable for liquid samples. The IR beam passes through the sample in both cases. Since the pressed sample has a low number of spontaneous fluctuations of the baseline, the transmittance process is beneficial because the pressed sample has a

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low noise-to-signal ratio, resulting in higher sensitivity. The absorption sensitivity varies within a sample containing various thicknesses, and the necessary time for sample preparation are both limitations of this process. In general, the absorption bands along the ATR–FTIR spectrum have a lower intensity than the transmitted FTIR spectrum. The depth of penetration is the main difference between transmittance FTIR and ATR–FTIR. The ability to transmit information ATR–FTIR can only probe through samples up to 300 nm in thickness, whereas FTIR tests a range that is an average of the bulk properties of the sample. The sample preparation criteria for these two approaches are also different. The sample is directly mounted on the crystal surface in ATR–FTIR, but the sample must be placed between two clear glasses in transmittance FTIR [10, 24, 25] (Fig. 3).

Fig. 3 Methods of vibrational energy characterization

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FTIR for Monitoring Molecular Changes in Microorganisms Exposed to Nanoparticles FTIR can classify molecular signatures in bacteria composition. Stretching, bending, scissoring, and twisting are all examples of biochemical bonds that can be detected based on their molecular rotational degree and form of movement. Via the use of spectral libraries for each type of bacteria, FTIR techniques were used to identify and classify bacterial strains. These libraries can be purchased as a kit from some scientific firms. FTIR has also been shown in many studies to be capable of distinguishing between intact and damaged cells in stress conditions. Several possible antimicrobial mechanisms have been detected using FTIR: (1) nanoparticles may change the fluidity of cell wall lipids by binding with –CH groups of the membrane measured at 3100–2800 cm
1; (2) the binding of nanoparticles, or ions released from nanoparticles, with amino acids in proteins and enzymes, which changes the protein structures detectable at 1500–1800 cm
1 nanoparticles bound to phosphate groups of nucleic acids in DNA or RNA altering their structures, which are detected in the 600–1200 cm
1 wavenumber range; and (3) nanoparticle catalyzed oxidation mechanisms and generation of reactive oxygen species (ROS), which can cause alterations in polysaccharide structures measured in the 900–1200 cm
1 wavenumber range. Osmotic stress, temperature shock, pH tolerance, chemical shock, UV light, and ultra-strong static magnetic fields have all been used to track bacterial properties and composition in growth and non-growth environments. Similarly, the FTIR transmittance technique was used to investigate the toxicity of selenium on Escherichia coli (E. coli), as well as the exposure of E. coli and Staphylococcus aureus membranes to a series of photocatalytic degradation accompanied by Ag/TiO2 nanoparticle suspension. For ATR–FTIR, a sample volume of 20 to 200 uL can be directly transferred or dried and put onto a crystal surface, which can be produced from a variety of materials with different refractive indices than the sample. The refractive index of the sample, which should be lower than the crystal sample holder, is the most important factor in ATR analysis. Various crystal surfaces exist depending on the type of sample. The IR beam’s penetration capacity through the sample is approximately 300 nm beyond the sample’s surface. To avoid interference from bulk water, a probe may be used to direct the IR beam directly onto the sample in some cases. Due to higher background noise, the resolution of this technique will decrease at higher wavelengths as compared to transmission mode. This restriction does not extend to bacteria analysis since bacteria signatures are observed in the mid-IR. Bacteria are isolated from the liquid sample by membrane filtration before being analyzed by ATR–FTIR. Metrical TM, polyethylene, Anodic, and aluminum oxide are used for bacterial membranes filtration. The toxicity of different nanoparticles, such as ZnO, quantum dots, and carbon nanomaterial, has also been studied using ATR–FTIR. Wang et al., for example, used ATR–FTIR to characterize nanowire photocatalysis in E. coli. The membrane composition of treated cells changed structurally as a result of ATR–FTIR,

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suggesting increased cell permeability. Fang et al. also looked into the toxicity of different quantum dot nanoparticle sizes on E. coli. The toxicity effect of quantum dots is size-dependent, as shown by changes in membrane structure in treated E. coli. Smaller nanoparticles have a high inhibitory effect. Riding et al. investigated the impact of long and short multiwall carbon nanotubes on gram-negative bacteria. According to the scientists, the bactericidal effect of carbon nanotubes is dependent on their size, with shorter tubes causing more toxicity than longer tubes based on the signatures of lipids, amide II, and DNA components found in treated cells.

Benefits, Drawbacks, and Disadvantages For the study of bacteria exposed to stress conditions, such as nanoparticle exposure, both FTIR techniques have advantages and disadvantages. Since sample preparation is simple, the time taken to achieve a spectral analysis is short, and samples can be analyzed in various states (liquid or solid), FTIR is a time-saving technique. Furthermore, only a small amount of the sample is required for analysis – typically in the order of g (solids) or L (liquid) and the method is usually non-destructive. In comparison to other widely used methods for bacterial detection, FTIR is also less costly. FTIR also has three notable benefits: (1) a higher signal-to-noise ratio, (2) a high energy throughput, and (3) high accuracy and stability. The “Fellgett advantage“allows for a higher signal-to-noise ratio since the wavelengths are calculated simultaneously. The “Jacquinot advantage“refers to the high energy throughput achieved by preventing light dispersion in FTIR. The use of a He–Ne (helium–neon) laser, which serves as an internal reference for each scan and provides accurate and stable wavenumber scales of an interferometer, is referred to as the “Connes benefit” in terms of accuracy and stability. For nanotoxicology assays, these three properties of FTIR are useful. In nanotoxicological research, all three of these FTIR properties are useful in the solid phase rather than the liquid phase. However, there are several drawbacks. To avoid artifacts and variations in the spectra caused by the surrounding environmental conditions in sample heterogeneity, multiple background scans, and sample scans are needed. For example, measuring the sample in culture media at various temperatures may affect the sample’s FTIR spectra. Pretreatment of the samples may be necessary to purify the sample and prevent peaks on the spectra from overlapping. Due to the large absorption of water molecules in the 1637 cm
1 wavenumber, water from bacteria samples in liquids will overlap the band of amide compounds and cause a loss of information. This can be avoided in some cases by preparing a dried solid sample. A library for characterization and identification is needed to identify bacteria strains; however, this can be purchased from a variety of scientific companies. Finally, the raw data may necessitate a considerable amount of post-processing analysis. Additional methods to observe changes in intracellular composition in addition to FTIR research. The drawbacks of FTIR analysis can be overcome by integrating it with other techniques. Raman spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy (NMR), and X-ray photoelectron spectroscopy are the most widely used methods to determine the composition of bacteria [5, 6, 15, 26].

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FTIR Imaging Comparisons of healthy and dysfunctional tissue, which can be done using several physical, biological, and biochemical techniques, can be used to detect biological effects. Methods are chosen based on the predicted change, but when a greater understanding of molecular and functional changes is needed, methods that can track a wide variety of structural or functional changes are required. Among these, the difference in molecular composition between normal and abnormal tissue using Fourier Transform Infrared is very promising. This method is focused on the absorption of infrared light, which causes molecular vibrations. The intensities of these vibrations provide quantitative information, while the frequencies provide qualitative information, such as oxidation, changes in cell membrane fluidity, and protein and DNA alterations. Awareness of the existence of these bonds, their structure, and their environment at the molecular level. FTIR microspectroscopy is a non-destructive, label-free, and objective method for distinguishing between normal and abnormal tissues. The backbone vibrations of proteins, lipids, and nucleic acids are the key spectral features of complex structures like cells. All of these contributions are reflected in the infrared spectrum of cells, which provides information on the activation of pathways that protect against oxidative stress, toxic response, and cell death. The most recent FTIR technique, FTIR microspectroscopy, combines an FTIR spectrometer and a microscope to obtain information through spatial and chemical spectral information at the same time. The “replica stamping method” involves either drying a diluted sample directly on an IR transparent plate or pressing the IR transparent plates to a bacterial colony. Two to three bacterial layers can be imprinted on the plate using this method. The advantage of both methods is that they allow for the concentration of IR radiation on the sample and the collection of an accurate spectrum. It also operates in the transmission and attenuated total reflection modes. Although micro-spectroscopy FTIR has restricted spatial resolution, this does not prevent bacteria from being identified using this accessory since they have different degrees of morphologic heterogeneity. FTIR micro-spectroscopy has previously been used to examine the heterogeneity of Legionella bozemanii, Bacillus megaterium, and Candida albicans colonies, as well as E. coli activities in biofilms, endospore bacteria changes after autoclaving, discrepancies between intact and dead E. coli, and live and heat-treated Salmonella typhimurium. The effect of a fullerene-based nanomaterial on Bacillus subtilis and Pseudomonas putida membranes was also studied using FTIR micro-spectroscopy. The researchers discovered that membrane fluidity and lipid composition are influenced by nanomaterial concentration and cell wall composition. In general, FTIR spectroscopic approaches enable high-throughput analysis. Because the vibrational features of the sample are diagnostic biomarkers in FTIR spectroscopy and microscopy, the technique is extremely promising in this regard, and it was successfully exploited for highlighting the biomolecular mechanisms of multiwalled carbon nanotube toxicity on both prokaryotic and eukaryotic cells, as well as demonstrating the technique’s sensitivity to cellular changes indurated by the

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nanotubes. Some authors studying effects of different substances and stress agents in noninvasively, nondestructively conventional bioassays to study deviations in molecular composition between normal relevant concentrations of contaminants. Microscope infrared detectors have a high sensitivity and use broadband or narrow-band mercury cadmium telluride (MCT). Others, such as focal plane array (FPA) detectors, are made up of an array of infrared detector elements that allow for simultaneous acquisition of spectra at multiple locations in the pixel array. These instruments have been successfully coupled to interferometers, resulting in a substantial increase in the rate at which IR images can be obtained. When FTIR is used in conjunction with microfluidic systems, the ultimate goal is to recover spectra from reactive flows flowing within microfluidic channels. Single point analysis, visualization, and imaging are the three most popular acquisition modes. Single point analysis involves documenting a single FTIR spectrum at a specific position on the dataset, obviating the need for a broad description or the study of dynamic systems. However, high spectral resolution can be achieved, which can be useful in applications such as trace detection. The acquisition of several individual point spectra and subsequent recombination to obtain a spatial image of the interrogated sample is referred to as mapping. This method is time-consuming, but it offers a very high SNR for high-quality spectra. FTIR imaging is not the same; in reality, the use of FPA or other array detectors allows for the simultaneous acquisition of thousands of spectra. Despite the lower SNR, a wide area can be mapped in a short period of time and with reasonable spatial resolution due to the use of IR microscopes. When it comes to flow applications, this choice is usually more convenient.

Toxicity of Effects of Silver Nanoparticles on Terrestrial Isopods According to a review of the current literature on AgNP toxicity, it is still uncertain which of the AgNPs’ properties plays the most important role in assessing their negative effects. The release of Ag ions from AgNPs is widely acknowledged as a key factor in assessing the observed toxic effects. Several authors have noted, however, that the toxic effects are not exclusively due to dissolved ions, and that NP size and shape also influence their biological effects. In a FTIRI study, the intrinsic properties of silver nanoparticles, such as size, shape, concentration, and ion release from dissolved nanoparticles, all play a role in the molecular changes in the digestive gland tissue of isopods (Porcellio scaber, Isopoda, Crustaceae) after oral exposure to subtoxic levels and that Ag accumulation in tissues is just one of several factors. The aim was to see how the intrinsic properties of AgNPs (size, shape, concentration, and dissolution potential) interacted with their effects on a model organism (Porcellio scaber, isopoda, Crustaceae) after subtoxic concentrations were consumed. To accomplish this, the research species were fed AgNPs of various sizes and shapes at various subtoxic concentrations: Ag cubical NPs (NCs) with an average particle size of 60 nm, spherical NPs with an average particle size of

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5–6 nm (NSs 5–6 nm), and spherical particles with an average particle size of 11–12 nm (NSs 11–12 nm). The unfolding or misfolding of alpha-helix proteins, as well as a rise in both nucleic acids and carbohydrates, detected by analyzing the specific spectral features that characterize the spectral groups 2, while the sub-toxic effects of the spectral group 3 interpreted as an accumulation of phospholipids and a downregulation of protein synthesis, identified by analyzing the specific spectral features that characterize the spectral groups 3. Many other authors have used the FTIR method to demonstrate how different chemicals influence major biochemical constituents, but there are few FTIR tissue analyses from in vivo nanoparticle studies. Other nanomaterials elicited a particular pattern of molecular response in the same experimental set-up (a) in our previously published studies. The effects of WOx nanowires (nano-WOx) were studied by Novak et al., and the effects of ZnO NPs and ZnCl2 salt were studied by Romih. In general, after ZnCl2 ingestion, more pronounced spectra alterations were observed, indicating that Zn ions are the primary cause of the observed effects. Novak et al. found no effects on proteins or fullers in cells in their findings. These researchers found a rise in carbohydrates after inducing oxidative stress in cells with fullerols under visible light illumination. Proteins, mainly random domains, and altered alpha-helix folding patterns, according to Romih et al. However, when compared to the molecular pattern of spectroscopic group 3 as shown in the research, they did not find alterations in the strength of both Amide I and Amide II. All three studies registered alterations in the signal at 1740 cm1, annotating more phospholipids. Changes in the number of phospholipids indicate changes in membrane fluidity, which can be caused by a variety of stressors, as calculated by FTIR in other studies. Vileno et al. used FTIR to investigate the effects of fullerols on cells and found that they had a similar effect on lipids. These researchers found a rise in the bands associated with lipid peroxidation and protein phosphorylation in fullerol-induced oxidative stress in cells exposed to visible light. The survey revealed that finding generic sub-toxicity markers that could be applied to any sample and any NP is likely difficult, and that admitting that the response in both animal and NP-specific is more accurate. FTIR imaging, which can also provide spatially-resolved information that can be compared with other microscopy techniques, can clearly illustrate and partially disentangle this specificity. The takeaway from this study added to the growing body of evidence that AgNPs effects at sub-toxic concentrations are caused by a complex interaction between the scale, shape, and dissolution of ions from NPs, as well as their combined interactions with tissue. Moreover, instead of searching for a single NP characteristic that causes biological effects, we should look for methods and approaches that can expose the biological implications of the combinatorial effects of various NP characteristics, allowing us to distinguish low-hazard NPs from highly biologically toxic NPs. In this regard, FTIR imaging appears to be a successful candidate.

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Toxicity Tungsten Oxide (WOx) Nanofibers on Digestive Gland Tissue of Porcellio scaber (Isopoda, Crustacea) Many studies have looked at how nano and microparticles affect lipid and protein concentrations, as well as the organization and structure of the most basic macromolecules. Interactions between cells and nanoparticles cause changes in cell metabolism. However, determining the toxicity of nanomaterials is not always easy. Nanostructures’ distinct chemo-physical properties, as compared to their bulk counterparts, often tune the system response to traditional bio-assays in unexpected ways, raising many questions about the results’ reliability. In this study, authors used digestive gland tissue, from WOx nanofibers (nanoWOx) fed animals to supplement the capabilities of FTIR imaging. The aim of this study was to figure out how nano-WOx affects the digestive gland cells of a model organism, the terrestrial invertebrate Porcellio scaber (Isopoda, Crustacea). Because the exposure dose of each test organism can be estimated, the advantage of using this organism is the ability to create a direct correlation between the real exposure dose to nanofibers and the observed effects at various levels of biological organization. The feeding parameters are an integrated organism-level response, as well as sufficient evidence of the effects of various chemicals on the organism. Cellular and biochemical analyses reveal evidence at the cell level following exposure to chemicals or nanoparticles, as well as their mode of action to some extent. The digestive gland cells (hepotopancreas) of terrestrial isopods, which combine the functions of the pancreas and liver invertebrates, are a preferred tissue for studying the effects of unknown or untargeted substances in the digestive system.

Final Thoughts They were able to demonstrate that ingesting WOx nanofibers activates some cellular mechanisms that may serve as a defense against adverse conditions. Before oxidative stress and toxic responses, changes in protein to lipid ratio, lipid peroxidation, and nucleic acid structural alterations were interpreted as responses indicative of a non-homeostatic state. Both partial structural reorganization of nucleic acids and mild lipid peroxidation is thought to be adaptation strategies of cells exposed to irritating nanofibers, according to the researchers. More research is needed to determine whether this is a nanofiber-specific response or a response to a variety of unfavorable conditions.

Subtoxic Exposure to ZnO Nanoparticles on Crustacean Digestive Glands Upon Fourier-Transform Infrared Microscopy (FTIRM) is one such technique, which provides spatially resolved information about a sample’s biochemical composition, allowing for the investigation of the functional groups that distinguish a specimen.

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Movasaghi et al., 2008 revealed that the concentrations, associations, structures, and (bio)chemical environments of the cellular constituents are reflected in the infrared spectra of cells. Although FTIR-based analytical methods have been widely used to investigate the molecular changes associated with abnormal tissues, they have not been widely used in ecotoxicological studies until recently ([18], Aja et al. 2014; Palaniappan and Pramod 2010). This study aimed to see if subtoxic concentrations of ZnO NPs and ZnCl2 (the source of Zn2+) induced different biomolecular profiles in crustacean digestive glands using the FTIRM. We propose that the effects of ZnO NPs are controlled not only by Zn2+ but also by ZnO particulate matter. Data on Zn bioavailability as measured by Zn assimilation into the digestive glands are included with the biomolecular profile data. In conclusion, their findings indicate that ZnO particulate matter alters the biomolecular profile of P. Scaber’s digestive glands and that the results of ZnO NPs are not exclusively attributable to Zn2+. The animals exposed to ZnO NPs had a significantly altered biomolecular profile, which was followed by a very low assimilated fraction of Zn. Subtoxic ZnO NPs exposure alters the biomolecular profile of the digestive gland, which is partly particulate-matter specific (distinct protein conformation) and partly a nonspecific response to the external stimulus (both ZnO NPs and ZnCl2 exposures) (increased protein and RNA content).

Toxicity of Iron Oxide Nanoparticles on Liver and Kidneys FTIR microspectroscopy, a form of vibrational spectroscopy, is a physico-chemical analytical technique for identifying biomolecules’ characteristic functional groups based on their IR absorption. The process consists of a combination of optical microscopy for identifying microscopic features of the sample under investigation and infrared spectroscopy for determining chemical composition. FTIR microspectroscopy’s high spatial resolution – down to single cells – helps researchers to learn about the cellular content and distribution of major biological molecules including lipids, proteins, and nucleic acids in microscopic areas of the sample. Furthermore, FTIR microspectroscopy is sensitive to biomolecule conformation, which is a unique property among spectroscopic methods. FTIR imaging is a valuable method for biochemical analysis of biological samples because of these features. Nanomaterials (NMs) have been extensively studied as possible biomedical instruments for medical diagnostics, treatment, and tissue engineering. Objects with one or more external dimensions in the range of 1–100 nm are the most common definition. NMs can be categorized based on their core material’s chemical composition (organic, inorganic), structural features (consolidated materials, nanodispersions), form (spheres, cubes, rods), or aggregation state (gaseous, liquid, solid). Engineered NMs for biomedicine is typically studied and focused on carbon, silica, and metals of various sizes and shapes, such as nanocrystals, fullerens, quantum dots, or nanoparticles. Nanoparticles (NPs), described as structures with two or three dimensions between 1 and 100 nm, are the most extensively studied of the various NMs used in biomedical research. The growing use of nanomaterials in

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various fields of science and technology has raised concerns about their protection, biocompatibility (defined as a substance’s ability to present an acceptable host response in a specific application), and toxicity. The evaluation of these characteristics is critical since the negative effects of nanomaterial exposure on living organisms cannot outweigh their expected positive effects. Furthermore, understanding the NM’s biocompatibility, identified as the ability to present an effective host response in a specific application, is critical for determining their true potential in biomedicine. FTIR microspectroscopy was used to assess changes in cellular content and/or structure of major biological macromolecules in the liver and kidneys of rats that had been intravenously injected with a low dose of D-mannitol-coated iron (III) oxide nanoparticles (M-IONPs). Iron oxide nanoparticles (IONPs) have been the focus of extensive research in recent years due to their high potential in biomedical applications. The interest in these specific nanoparticles stems primarily from their relatively simple and low-cost fabrication, superparamagnetic properties, and predicted biocompatibility and biodegradability. Furthermore, the ability to alter the nanoparticle surface, such as by coating with organic shells or adding ligands, allows for improved stability in solution, which improves biocompatibility and extends the range of IONP applications. Nonetheless, the nanoparticles cannot be used as diagnostic or therapeutic instruments until their effects on living organisms have been confirmed. The physical, chemical, and structural characteristics of the tested nanoparticles are highly dependent on their correct biodistribution, pharmacokinetics, and thus potential side effects. As a result, before the particles are approved for clinical use, the relationship between their properties and biological response must be established. Only animal model-based studies may provide valuable information on the systemic action of nanoparticles administered in vivo from a toxicological standpoint. Wistar rats were used in this study to determine biochemical changes that occurred in selected organs, such as the liver and kidney, after exposure to M-IONPs. The liver and kidneys were chosen for analysis because of their critical role in purifying the organism of toxins and foreign bodies, like nanoobjects. When nanoparticles are injected intravenously, they may go through metabolic processes such as detoxification, solubilization, decomposition, and elimination. The liver and kidneys are the organs that are most active in the aforementioned processes while also being the most vulnerable to nanoparticle-induced adverse effects. The M-IONPs under investigation had a hydrodynamic scale of 100 nm and a core diameter of 10 nm. They were coated with water-soluble D-mannitol, a polyhydroxy sugar alcohol compound. Due to its biological indifference, D-mannitol appears to be a promising candidate as a coating material, despite its limited use in particle manufacturing. Furthermore, since the vast majority of existing studies have used doses that are equal to or much higher than those used in medical practice, the current experiment used a relatively low dose of the NP. This method may help to expand our understanding of the side effects of IONPs used in low doses, similar to those used in medical diagnostics. The findings demonstrated the utility of FTIR microspectroscopy in the study of long-term biochemical abnormalities caused by intravenously administered

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M-IONPs in the liver and kidneys. 7 days after being exposed to M-IONPs, researchers discovered improvements in the content and structure of major biomolecules. Abnormalities in biochemical composition were even more pronounced in the kidneys than in the liver. Although experimental animals were given a low dose of M-IONPs, changes in the content and/or structure of lipids, phosphate groups, cholesterol, and cholesterol esters in the renal tissue can indicate the existence of oxidative stress within the organ. Such a disruption in redox homeostasis most likely caused the development of LDs, a defense mechanism designed to counteract oxidative stress [4, 16, 20–23, 27].

Nano-FTIR Spectroscopy Binnig et al. pioneered scanning tunnelling microscope (STM) and atomic force microscope (AFM), in which a sharp tip scans across a surface; the detection of surface morphology relies on tunnelling current in STM and van der Waals forces between atoms on the sample and atoms on the tip in AFM. Orthodox scanning probe microscopy has a material blindness restriction. Recent research adds light to scanning probe techniques to improve their ability to distinguish materials. AFM-IR detects a photo-thermal effect by combining an AFM with tunable IR radiation. AFM-IR is a technique that combines an AFM with tunable IR radiation to detect photothermal effects and access chemical information at nanoscale resolution. The limit and access chemical knowledge down to a nanoscale resolution using AFM-IR. The limit resolution of subdiraction is obtained using AFM-IR. This is accomplished by monitoring the diversion of an AFM probe with a sub-diffraction resolution. This is achieved by tracking the diversion of an AFM probe that is in contact with the sample surface and is deflected by rapid transient thermal expansion of the sample as a result of the absorbance of an infrared pulse. This has previously been observed to connect the sample to the absorbance of an infrared pulse. This has already been shown to fit well with conventional macroscopic FT-IR measurements of infrared absorbance. Near-field spectroscopic methods usually combine vibrational spectroscopy contrast with AFM mapping. Near-field methods are vulnerable to objects, whose understanding is crucial for optimizing analytical measurements but is still lacking. IR scattering scanning near-field optical microscopy (IR s-SNOM) and tip-enhanced Raman spectroscopy (TERS), for example, rely on specially designed probes to enhance the near-field signal and complex, tip-specific models to interpret the reported chemical data. Although tip models provide a much-needed but approximate understanding of the measured contrast, the difficult-to-predict tip-sample interactions complicate quantification of results. Similarly, although improving the near field signal is needed for accurate measurements, it may introduce confounding factors that are difficult to monitor or mitigate experimentally. Small changes in experimental parameters can result in significant changes in reported signals, increased noise, and inconsistent (less repeatable) measurements, putting sample preparation under constraints. This inconsistency stems from a lack of understanding

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of the dominant inputs to the reported signal, which makes optimization difficult. Innovative new techniques like photo-induced force microscopy (PiFM), for example, have a lot of promise, but the documented signal is said to be a combination of optical forces, tip-enhanced and direct thermal expansion, and photoacoustic effects. A detailed fundamental understanding, assessment of relative contributions of nanoscale systems, and systematic optimization of data recording are all used to establish a near-field spectroscopic.

AFM-IR Spectroscopic Imaging Benefits and Drawbacks It has a clear mechanism for detecting molecular absorption-induced thermal expansion of the sample, needs no theoretical model for data interpretation, provides chemical contrast without labels, and produces a signal that is correlated to far-field absorption spectra. Monolayer sensitivity in detection has been demonstrated using current state-ofthe-art resonance-enhanced methods; however, these studies depend on the signal enhancement of gold or polymer-coated substrates. Furthermore, although the observed signal is proportional to far-field IR absorption (to a first approximation), recent studies show that the measured AFM-IR contrast is usually made up of contributions from the chemical composition as well as mechanical features arising from cantilever responsivity variations. The use of a subsample piezo expansion to correct for cantilever responsivity has been shown to increase chemical accuracy of recorded contrast, but it provides little improvement in sensitivity when compared to the previous state-of-the-art. As a result, considering its relative simplicity and ability, AFM-IR suffers from many of the same trade-offs as other near-field methods. The analytical ability and fidelity of current AFM-IR methods to research molecular properties of nanoscale materials on substrates of interest to the nanotechnology community, such as Silicon or gl, are all restricted by enhancement, the need for narrowly defined sample preparation, convolution with confounding factors, and low chemical sensitivity (especially when compared to state-of-the-art IR microscopy).

Close-Loop The theory behind a robust closed-loop (CL) responsivity-corrected AFM-IR measurement capability, as well as its implementation. The design is geared toward minimizing measurement noise in AFM-IR, allowing for precise, high sensitivity compositional mapping at the nanoscale without the use of excessively restrictive sample preparation methods or specialized substrates. The theory of the strategy is to modulate and record a harmonic voltage applied to a subsample mechanical actuator (piezo) to maintain a near-zero amplitude harmonic cantilever deflection voltage by real-time feedback control, in contrast to the current practice of recording signal arising from cantilever deflection. This “closed-loop” method of operation

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significantly reduces the reported chemical signal’s sensitivity to both spatial and time-varying changes in cantilever resonance, increasing chemical precision while minimizing noise. Furthermore, maintaining a null deflection eliminates detector saturation, allowing high laser power and cantilever resonance amplification to be used simultaneously. The CL strategy aims to make AFM-IR a more responsive, precise, and user-friendly technique. To illustrate, we first provide a theoretical description of the AFM-IR signals, followed by a complete design, study, and characterization of the controls for reliable, high-quality measurements. Nanomaterials’ molecular information is being mapped. AFM-IR imaging of nano thin materials such as 2D materials, Self-assembled monolayers (SAM), and isolated proteins has been demonstrated in a variety of studies; however, reliable AFM-IR absorption measurements on arbitrary substrates are often constrained by non-local signals, non-chemical effects (responsivity), and noise. The CL method was developed to deal with these issues. In terms of measurement capacity, this work expands AFM-IR sensitivity to include common organic monolayers such as supported lipid bilayers and self-assembled alkanethiols with thicknesses of 1–5 nm. While this research has looked at some of the more obvious sources of noise and presented a method for reducing them, the high quality data now allows for further analysis into other sources of noise, which may lead to even greater changes in the quality of recorded data. This work showed how the established instrumentation outperforms previous state-of-the-art methods by mapping the IR absorption of nanoscale-thick PMMA films on glass and Silicon, which eliminates the need for time-consuming sample preparation on gold or polymer-coated substrates.

Deliberation Near-field spectroscopy methods often require tip- or sample-induced signal enhancement, which allows for sensitive measurements but makes signal and noise prediction and optimization difficult. As a result, AFM-IR has been limited to tiny, isolated samples on unique substrates, but it has the potential for high sensitivity and fidelity nanoscale chemical imaging. We first show that the output of AFM-IR is limited by the effects of time-varying cantilever resonance, which causes a significant increase in noise at large cantilever deflections, especially for samples that produce a large DC bias signal. We then used this knowledge to develop a CL AFM-IR process. Unlike traditional AFM measurements, which emphasize larger cantilever deflections, the CL method uses feedback control to preserve nearzero cantilever deflection when calculating an applied signal to a subsample piezo. This CL control technique produces a regime with minimal noise and saturation effects, allowing for high sensitivity IR absorption measurements on any substrate. We include a thorough review of the proposed controls to ensure reliable and optimal efficiency. We then put the principle to the test on a commercial AFM-IR instrument to see how far we’d come. References improve data collection and processing to allow nanoscale composition mapping on popular substrates such as Silicon and

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glass, thanks to the CL method’s improved sensitivity and reliable phase signal. This advancement enhances AFM-metrology IR’s capabilities in a variety of fields that require accurate nanoscale composition imaging, including high-frequency nanoelectronics, NEMS and MEMS8, and photonics.

Nano-FTIR Chemical Mapping of Minerals in Biological Materials In chemical analysis, Fourier-transform infrared spectroscopy (FTIR) is a standard instrument. It uses the “fingerprint” of the molecular vibrational absorption spectrum in the 3–30 m wavelength range to distinguish virtually any substance. Nano-FTIR spectroscopic near-field microscopy is an exciting new development. It allows scattering near-field optical microscopes (s-SNOM) to work at ultrahigh spatial resolution through a broad mid-infrared spectrum emitted from either a coherent supercontinuum source or an incoherent thermal source. The s-SNOM probes the sample with a nano focused light field using a metalized AFM tip as a lightconcentrating antenna. The nanofocus is a light spot the same size as the tip radius that distinguishes s-optical SNOM’s and topographic resolutions. Backscattered light detection exposes local optical detail. The probed volume usually extends 20 nm laterally and into the sample (sometimes as little as 10 nm). The wavelength has no impact on the high resolution. This allows for the use of long wavelengths, which lead to infrared fingerprint vibrations. s-SNOM has been successfully used with visible, infrared, and terahertz illumination on organic and inorganic materials in fields as diverse as nanoelectronics, phase transition physics, and material recognition. The near-field interaction that underpins it has been theoretically modeled and experimentally confirmed. The measurable contrasts and spectra can be calculated using the sample material’s complex dielectric function, which includes both the absolute efficiency and the step of scattering. Only flat test samples of metals, semiconductors, and polar crystals have been used to show Nano-FTIR.

Deliberation FTIR has long been used to research biominerals in several environments, and nanoFTIR expands this capability to include spectroscopic mapping at the nanometer scale. Phosphates and carbonates in well-studied examples of M. edulis and human dentin show exquisite detail, which fits what electron microscopy and nanoindentation reveal. The discovery of biomineral chemical and structural mapping opens up new avenues for research into mineral arrangements and heterogeneity in biological systems. A noncontact and nondestructive imaging technique can now map intricate carbonate-based natural skeletons inside and through interfaces, which may include transient and stabilized amorphous phases. The approach is specifically applicable to the investigation of stable and diseased types of vertebrate bones and teeth when it comes to apatite studies. Mineral precipitation, aggregation, and ageing can now be studied and quantified in submicrometer detail, allowing researchers to

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gain a deeper understanding of the biological processes underlying bone formation, abnormal growth, and healing in response to drug treatment. The nano-FTIR method is extremely robust and useful for the study of biological materials due to many technological advantages of surface scanning. The samples don’t have to be thin; they just have to be relatively flat to avoid damaging thinsection preparations. Cutting and polishing procedures create unavoidable topographic barriers, which are of little consequence: The off-resonant infrared amplitude, as well as the resonant response in amplitude and phase, are unaffected by height variations of 100 nm, as shown by the repeatability of the carbonate resonance spectra within the sample area containing biocalcite. The s-SNOM amplitude is known to be reduced over a distance equal to the spatial resolution at steep topographic edges, resulting in “edge darkening.” This effect is thought to be responsible for the dark regions seen between calcite crystals in, but it needs to be studied further. The edges of the biocalcite crystals show a mechanical (AFM) resolution well below 30 nm, demonstrating nano-remarkable FTIR’s spatial resolution. The infrared resolution is greater than 20 nm, as shown by the abrupt edges of the nano-FTIR line segment showing the phosphate resonance.

Carbonate-Forming Organism The “phosphate” particles in Mytilus edulis (M. edulis) are easily identified by their spectral signature. But their topographic presence alone would have been difficult to detect. Notice that one of the carbonate resonances is also visible in the nano-FTIR spectra of the “phosphate” particles, indicating that it originates from the crystals underneath. To grasp this effect, remember that the simple near-field interaction probes the sample to a depth on the order of the tip radius (or slightly deeper if the tapping amplitude or average tip-to-sample distance is greater than the tip radius). Backscattering can be affected by buried artifacts if the covering layer is not thicker than a few times the tip radius. This influence has also led to the suggestion that s-SNOM has tomographic mapping capability. The results are the first to demonstrate that different phonon resonances occur in both the covering layer and the buried material. The thickness of the “phosphate” particles is estimated to be on the order of 10–30 nm based on the observed amplitudes, which is consistent with their topographic appearance. In this proof-of-concept analysis, the origin of the “phosphate” particles is unknown. Their irregular distribution may indicate an unidentified preparation artifact. The substance may be a modification of materials in the organic matrix, but the infrared images don’t show this. Nonetheless, the particles may not be dried polishing material (Struers OP-A), which has a poor FTIR absorption at 1073 cm
1 but no discernible nano-FTIR resonance in the frequency range of interest. The observed high spectral phase effect of about 80 , which exceeds that of bioaragonite (50 ) and biocalcite (70 ), is a clear argument for the particles being labeled as crystalline phosphate. For strong polymer vibrations, the spectral phase effect is usually on the order of 30 , but on the order of 400 for strong crystal phonons. The use of phosphate in shell architecture has not been confirmed in mollusks, but

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calcium phosphate is known to be present in the radula (tooth structure) of chitons. Phosphorylated proteins have been proposed as essential organic matrix components in bones. Despite their ambiguous origins, our discovery of “phosphate” particles shows that nano-FTIR can easily locate and chemically identify nanometer-sized material even at high rarefaction. Finally, the observed particles are crystalline for two more reasons: (i) their near-field scattering amplitude is around 103, similar to calcite, and not much smaller than 3,103, as known for two strongly polar crystals, SiC and SiO2; and (ii) their near-field resonance line shape is asymmetric, with the steep high-frequency edge (Fig. 4) typical of strong polar crystals. As has been shown routinely the disorder in a crystal reduces the amplitude significantly. Amorphous materials have a reduced, broadened resonance, while conventional organic materials have an even weaker response, as demonstrated in this analysis by the PMMA resonance peaking at 1.5 near 1150 cm
1. The biomineral composition and density are revealed by the large phosphate bands calculated by nano-FTIR in dentin. To begin, they estimate the local volume fraction f of mineral particles (assuming f ¼ 1 for enamel) to be 0.54, 0.30, and 0.26 for spectra 1, 2, and 3, respectively, based on their peak and baseline amplitudes. In the frequency range of 1020 to 1120 cm1, there are noticeable, position-dependent variations. These differences indicate that (i) tooth materials are made up of many

Fig. 4 Principle of AFM-IR technique. With permission from Dr. Phuong

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mineral types with different vibrational resonances, also on a 20-nanometer scale, and (ii) the mineral composition varies with location. When spectral components are too far below the surface, they can be detected. In contrast to SEM, where the interaction of electrons with bony materials is known to cause damage, s-SNOM is nondestructive. The edges of the tubule lumen are marked by the extracted BE profiles and the extracted infrared profiles. The amplitude (red) and phase (blue) outside the peritubular rim qualitatively correlate with the BE-defined mineral material (black). The different probing depths of the s-SNOM and BE imaging methods account for an exception in the 7.1–7.5 m segment. As a result, both amplitude and phase tend to be capable of calculating minor density shifts. When it comes to spectral variations within the phosphate band, the ratio r is approximately 0.8 and 0.7 for the peritubular and intertubular regions of the large tubule (x,y), respectively, but only 0.7 and 0.6 for the small tubule (x,y). r ¼ 0.80 for enamel. Since most apatite species of interest have not yet been measured as pure substances by s-SNOM, an assignment of the observed nano-FTIR spectral components of a tooth at around 1020, 1055, and 1100 cm1 is unfortunately not straightforward. From theory and studies, it is well understood that 1020, 1055, and 1100 cm are present in enamel and peritubular dentin but not in intertubular dentin, and may be related to the lack of collagen protein, while 1100 cm1 is present in all dentin but not in enamel. We measured and plotted the distribution of three characteristic quantities extracted from nano-FTIR spectral scans, namely, the peak s-SNOM amplitude (red), the ratio r of amplitudes at 1053 cm1 and 1022 cm1 (green; not significant in the tubule lumen), and the phase at 1080 cm1 (blue), in direct comparison with the BEI profiles, to address potential assignments. In general, the shape of the particles as a result of depolarization effects should be taken into account when interpreting infrared absorption in bone. Based on whether the particles are spherical, needle-like, or platelike, density functional theory has recently been applied to the apatite v3 vibrational infrared absorption, predicting strong spectral distortion and splitting (up to 50 cm1) due to macroscopic electrostatic effects (not to be confused with microscopic distortion of lattice cells). Fluorapatite absorption peaks were found at 1038, 1067, 1097 cm1, and hydroxyapatite absorption peaks were found at 1034, 1053, 1105 cm1, with the last two peaks strongly separated by the nonspherical shape of the particles. Similar findings were seen in other studies. Since the mineral in dentin and bone is made up of isolated, locally arranged apatite platelets, strong depolarization effects are likely to distort the infrared spectra in the v3 phosphate resonance area. A systematic investigation of near-field and far-field infrared apatite bands for various shapes of chemically and structurally well-defined nanocrystals is needed. The weaker v1 phosphate band, which is less affected by electrostatic effects than all Raman lines, should be included in such a study.

Subsurface Chemical Nano-Identification Scattering-type scanning near-field optical microscopy (s- SNOM) is a scanning probe microscopy technique that allows for nanoscale-resolved optical imaging of a variety

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of samples, such as polymer, biological materials, semi-conductors, conductors, and insulators. Monochromatic visible, infrared, or terahertz electromagnetic radiation is focused onto the tip of a standard, metalized atomic force microscope (AFM) probe in s-SNOM. At the very tip apex, the tip acts as an optical antenna, concentrating the radiation into highly confined and enhanced near fields. The close fields communicate with the sample surface, changing the amplitude and phase of the backscattered field depending on the local optical sample properties. Nanoscale-resolved images of the sample’s optical properties are obtained by recording back-scattered light as a function of tip position1. The AFM is run in tapping mode, with the tip oscillating naturally to the sample at a frequency to eliminate unwanted background signals. This operation mode produces higher harmonic modulation of the tip-scattered field, but not of the background scattering since the near-field interaction is strongly nonlinearly dependent on the tip-sample distance. The pure near-field signal is obtained by recording the detector signal at higher harmonic frequencies n (typically n>2). The extension of the near fields, which is in the order of the tip apex radius, which is usually about R ¼ 25 nm determines the spatial resolution. Similar to infrared microscopy18, s-SNOM allows for extremely sensitive compositional mapping at infrared frequencies by probing vibrational excitations such as those of molecules or phonons. Nanoscale-resolved infrared spectra can be recorded using a broadband infrared source and Fourier transform spectroscopy of the light scattered by the s-SNOM tip19. Nano-FTIR spectroscopy produces near-field phase spectra that closely match the absorptive properties of organic samples, allowing for nanoscale chemical detection using standard FTIR. Even though s-SNOM and nano-FTIR are surface scanning techniques, the finite penetration depth of near fields into the sample enables subsurface probing of nanoscale structures and defects up to 100 nm. It has also been demonstrated for s-SNOM that depth-resolved information – with the possibility of three-dimensional sample reconstruction can be obtained by analyzing multiple higher harmonic signals, each with a different probing depth. However, the potential capability of nano-FTIR experiments for chemical identification of subsurface material is largely unexplored territory. An experimental and theoretical nano-FTIR spectroscopy analysis of thin subsurface organic layers is presented here. Authors show that (1) subsurface layer nano-FTIR peaks are lower in frequency than bulk materials or thin surface layers, and (2) surface and subsurface layers can be distinguished by examining the ratio of peak heights obtained at different demodulation orders n, without using theoretical modeling or simulations. They studied the well-defined C¼O vibrational mode of a thin polymethyl-methacrylate (PMMA) layer on silicon covered by a polystyrene (PS) layer of varying thickness, which we compared to variously thick exposed PMMA layers on silicon. We also show how a semi-analytical model can be used to deduce and predict nano-FTIR spectra in multilayered samples. Finally, to summarize and analyze the results of a comprehensive theoretical and experimental analysis of the nano FTIR peak characteristics of various thick subsurface layers exhibiting various molecular vibrational modes, demonstrating the relevance and applicability of our findings for a wide range of materials.

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In conclusion, they discovered that the peaks in nano-FTIR phase spectra of subsurface organic layers are spectrally red-shifted as compared to nano-FTIR spectra of the corresponding bulk content and that the redshift is greater than that observed for surface layers as their thickness is reduced. A semi-analytical model for calculating nano-FTIR spectra of multilayered samples, which well describes the observed patterns, backs up our findings. Our model also shows that peak shifts in multilayer nano-FTIR spectra can be traced back to the sample’s momentumdependent Fresnel reflection coefficient, assuming chemically induced peak shifts are removed. They point out that peak shifts caused by sample and momentum are not exclusive to near-field spectroscopy; they also occur in far-field spectroscopy, where the probing momentum is determined by the angle of incidence. Finally, we showed that surface and subsurface layers can be separated without the use of theoretical modeling or simulations by examining the ratio of peak heights obtained at different demodulation orders n. Their findings will be critical for potential applications of nano-FTIR spectroscopy, such as distinguishing peak shifts induced by sample geometry from peak shifts caused by chemical effects including chemical interaction at material boundaries.

Probe Single Bacterium Infrared spectroscopy (IR) is a promising candidate for phenotypic bacterial probing because it offers a molecular characterization of the sample. Due to the wavelength diffraction spatial resolution limit, there have been a large number of examples of its use since its early applications. Innovative techniques incorporating atomic force microscopy (AFM) and vibrational spectroscopy have opened up a new frontier in materials analysis in recent decades, developing chemical maps with resolutions well beyond the Rayleigh diffraction limit, in the 10–100 nm range. Because of its simplicity and flexibility, this rapidly developing area includes tip-enhanced Raman spectroscopy (TERS), scattering scanning nearfield optical microscopy (s-SNOM), and photothermal infrared techniques. The diffraction-limit associated with traditional microspectroscopy optics is bypassed during AFM-IR by monitoring the thermal expansion of materials caused by infrared radiation absorption, with an AFM probe in contact with the sample surface serving as the detector. Unlike s-SNOM, this method provides a direct measure of infrared absorption, making analysis easier. Furthermore, unlike TERS, AFM-IR does not require precisely specified probe tip geometries and is less susceptible to contamination. As a result, the AFM-IR method has been applied to an ever-growing variety of specimens spanning material science disciplines since its inception. Local degradation processes in organic coatings, fibers, oil paint and solid-state insulators, minerals in bitumen, geological specimens, bone and human dentin, the analysis of corrosion inhibitor films, nanoscale domains found in polymer blends, thermosets and nanocomposites, the chemist. The implementation and commercialization of a top-down illumination setup, which allows a wide range of samples assisted by any underlying substrate to be analyzed, has been a significant factor in the recent widespread application of AFM-IR. The original bottom-up illumination experiment, on the other hand, involved the preparation of thin specimens

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near a ZnSe prism. As a result of the top-down configuration, specimen geometries have become less limited, allowing AFM-IR to become a routine analysis technique. However, understanding and eliminating possible infrared imaging objects is a vital consequence of this. Variation of 2,490 in the tip-sample contact area on rough samples, locally enhanced infrared amplitude signals over regions of increased sample thickness (i.e., increased volume of material underneath the probe), and the reliance of the induced resonance on local mechanical properties are all previously recorded sources of artifact in the infrared signal for AFM-IR (hardness). These effects are currently regularly taken into account by experienced microscopists when analyzing AFM-IR data. Since all of the above phenomena are wavelength-independent, normalized local spectra and ratio maps can also be used to rule them out or exclude them (where infrared maps taken at two different wavenumbers are divided, in a process akin to spectral normalization). We present a previously unknown source of artifact and knowledge in this chapter. AFM-IR infrared spectra and maps may display features that are dependent on the reflection of incident infrared from an underlying substrate. More specifically, since this effect is wavelength-dependent, normalization methods will not be able to compensate for it. Since the majority of bacteria are smaller than that (e.g., Staphylococcus aureus has a diameter of less than 400 nm), traditional IR cannot be used to probe single cells or intracellular structures. Combining IR spectroscopy with Atomic Force Microscopy has recently solved the spatial resolution constraint (AFM-IR). The IR absorption is observed indirectly in this case, due to the material’s thermal expansion. In summary, IR absorption causes the growth of antimicrobial resistance (AMR), which is currently one of the most pressing global health issues and is expected to become the leading cause of death by 2050. The development of resistance, as well as the spread of AMR strains, occurs either directly or indirectly through the measurement of oscillation of the AFM cantilever probe, resulting from force impulse, at an alarming rate that far exceeds the rate of 10 produced by IR absorption technique, which allows for spatial resolution approaching 20 nm (AFM-IR). It is possible to collect single spectra from selected spots as well as map the strength of selected wavenumber values within a defined region. New antibiotics are being discovered. New resistant phenotypes emerge regularly around the world, although research into AMR-related changes is often sluggish and constrained by available approaches. Furthermore, common methods like polymerase chain reaction (PCR) and whole gene sequencing (WGS) concentrate solely on genotypic shifts. These methods are insufficient to expose the mechanisms of resistance, necessitating the urgent development of a research tool that can analyze the chemical composition of bacteria. Phenotypic-based recognition of bacteria at the genus, species, and strain, levels has been demonstrated in the literature. The spatial resolution of traditional IR, on the other hand, is limited to a few microns. Given the spatial resolution of AFM-IR, it is clear that the technique allows for chemical/phenotypic probing of individual bacterium cells as well as their intracellular composition. Several examples of AFM-IR applications for single bacteria have been published previously. In summary, in local infrared spectra obtained with AFM-IR, reflection from the underlying substrate produces distinct wavelength-dependent features. This means that, in addition to chemical analysis of an overlying film, details about the local

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composition of a buried substrate can be obtained in a nondestructive manner using AFM-IR. This opens up the fascinating possibility of broadening the photothermal infrared method to include the identification of metallic substrate discontinuities indirectly. Nonetheless, these findings clearly show that the specular reflectance of an underlying substrate, its thermal reaction, and mild interference effects have an impact on local spectra and infrared maps for AFM-IR analysis of thin films. When analyzing AFM-IR data, the nature of the underlying substrate and local variations in specimen thickness should be taken into account [3, 11, 12, 14, 17].

Synchrotron FTIR In most laboratory-based FTIR instruments, the extremely collimated synchrotron infrared (IR) beam provides 100–1000 times greater brightness than traditional thermal Global FTIR sources. The acquisition of high-quality FTIR spectra at diffraction-limited spatial resolutions is possible with this extremely intense beam. As a result, synchrotron FTIR is an excellent analytical tool for obtaining spatially resolved chemical mapping of materials with a lateral resolution of 3–10um (depending on the wavelength used).

Synchrotron Macro ATR-FTIR Microspectroscopic Analysis of Silica Nanoparticle-Embedded Polyester Coated Steel Surfaces Subjected to Prolonged UV and Humidity Exposure A technique based on macroscopic (macro) attenuated total reflection (ATR)-FTIR microspectroscopy was recently developed at the Australian Synchrotron IR beamline to allow the coupling of the synchrotron IR beam to germanium (Ge) ATR element. Because of Ge’s high refractive index (nGe ¼ 4), and ATR-FTIR mapping measurement can be used to probe surface-specific molecular information about materials with four times greater precision than comparable transmission and reflectance modes. The macro ATR-FTIR method, unlike the conventional microscopic (micro) ATR-FTIR approach, only involves a single contact between the sample and the ATR crystal for the entire mapping measurement, which not only increases scanning speed but also decreases the risk of sample damage and cross-contamination between measurement positions. After 3 years of exposure to the subtropical environment in Queensland (Australia), we observed a decrease in the carbonyl (C¼O) band strength in the pure polyester coating with no SiO2NPs present using the synchrotron ATR-FTIR microspectroscopic technique, performed at low resolution in the early stages of development. The chemical evolution of SiO2NPs-embedded polyester composite coatings on steel substrata as a result of environmental factors was observed over time and analyzed at the molecular level using the previously mentioned synchrotron macro ATR-FTIR technique. For the surfaces of polyester composite coatings containing various amounts of SiO2NPs, high-resolution chemical maps were acquired. For 3 years, these samples were exposed to tropical and subtropical

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conditions. In order to determine precise changes in the molecular structure of the surface, a chemometric approach, specifically principal component analysis (PCA), was applied to the synchrotron macro ATR-FTIR spectral data. The findings were then compared to samples that had not been exposed to the atmosphere. The changes in molecular structure, combined with surface topographical data obtained from optical profilometry and atomic force microscopy (AFM), provided insight into changes in the surface properties of coating materials as a result of environmental exposure. This knowledge is crucial for developing methods for increasing the durability of polymer composite coatings. It should be noted that this work represents the first time that direct molecular evidence, performed using high-resolution synchrotron FTIR mapping technology, has been reported to highlight the chemical evolution of polyester composite coatings on steel surfaces as a result of environmental exposure. Final Thoughts, in this chapter, spatially resolved synchrotron macro ATR-FTIR microspectroscopy was shown to be an effective technique in the molecular characterization of surface coating materials when combined with a multivariate data analysis approach. Via high-resolution chemical mapping technology, the technique not only provided a clearer understanding of changes in the molecular distribution over time, but it also provided useful insights into the molecular changes taking place through PCA. The findings obtained using this combined technique showed that changes in the molecular structure of the polymer occurred as a result of environmental exposure. Pure polyester coatings exposed to a tropical climate underwent different changes in molecular structure than those exposed to a subtropical climate. Although changes in the triazine ring and ether group in the melamine resin were two prominent changes in the samples exposed to a tropical environment, changes in the carbonyl group of the polyester resin, as well as changes in the hydroxyl groups, the triazine ring, and hydrocarbon groups, were observed in the samples exposed to a subtropical climate. After 3 years of exposure to both tropical and subtropical conditions, applying SiO2NPs to the polyester coating resulted in similar improvements in the surface chemistry of the surface coatings. The most influential factor that triggered the separation between the control and exposed samples was found to be the v(C ¼ N) stretching mode of triazine ring vibration in the melamine resins, which is possibly due to the triazine ring being hydrolyzed in humid environments. A large number of chemical bonds associated with the melamine/polyester networking structure were shown to be affected at the higher SiO2NPs loading of 9%, resulting in significant surface degradation after long-term exposure to a high UV/high humidity environment.

Synchrotron FTIR Light Reveals Signal Changes of Biofunctionalized Magnetic Nanoparticle Attachment on Salmonella sp. Via the use of a spectral library for each type of bacteria, FTIR techniques could be used to recognize and classify bacterial strains. FTIR spectroscopy is also being used to distinguish fecal Escherichia coli strains from pigs, poultry, and humans as a bacterial source monitoring tool. The use of distinct peaks that are peculiar to various

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bacteria strains or organisms is promising and warrants further study. For fecal E. coli discrimination, FTIR spectra in the range of 2861 to 3026 cm
1 were suggested as suitable specific peaks. Peaks in C-H stretching of CH2 in fatty acids were found at wavenumbers 2852, 2924, and 2946 for C-H stretching of CH2, and 2960 for C-H stretching of CH3 in fatty acids. F. Faghihzadeh et al. announced the discovery of structural changes in molecular binding between microorganisms and metal atoms in nanoparticles. Due to the interaction of cells with AgNPs, FTIR spectra changes in fatty acids, specifically –CH deformation, were recorded to alter bacterial membrane permeability. Compounds’ infrared spectrum and interactions have a special fingerprint for microbial identification. For the screening of microbial bioprocesses, FTIR spectroscopy could be used as a single tool for the study of several cellular metabolites. Pharmacological drug monitoring has also been recorded. The results show that FTIR tracking can be used to track complex and sequential reactions including pathogen attachment to target cells or supporting materials. Synchrotron radiation-based FTIR (SR-FTIR) spectroscopy has a benefit for these experiments because of its higher signal-to-noise ratio (by 100 to 1000 times), higher collimation, and luminance, which can exceed the diffraction limit with 10 m or better compare to traditional FTIR with 75 m spatial resolution. Final thoughts, the SR-FTIR signal changes of amino-functionalized FMN with GA crosslink, antibodies, and Salmonella cells were monitored individually and after reaction steps in this research. Controls, FMNs, glutaraldehyde, the Salmonella antibody, and Salmonella cells alone had their spectra established. At wave number 1672 of NH bending, FMNs had a one-of-a-kind peak (scissoring). The aldehyde peak at wave number 1722 in the glutaraldehyde range showed C¼O stretching. The following are the signal changes for each connection stage. The aldehyde group (1460 cm
1) of glutaraldehyde reacted with the FMN spectrum at wave number 1673 (N-H). The disappearance of FMN-GA peaks at 1763 and 1460 proved this relation. The availability of the aldehyde group on the FMN-GA complex is indicated by the peak at 1778 cm
1 at this point. In the next step, you’ll be able to connect this aldehyde group to Ab. Peaks at wave number 1244 (C-N stretching) were found in the FMNs-GA-Ab spectrum, suggesting that the aldehyde group (GA) was attached to an amino group (Ab). The absence of a peak at 1788 cm
1 also means that Ab still has an aldehyde group connection. The FMNGA-Ab complex was then attached to Salmonella cells in the final stage. Peaks at 1655 cm
1 C¼O amine I react with the NH2 group of Ab, resulting in a CH2 scissoring peak at 1454 cm
1 as a result of the attachment. This phase produced no 1655 cm peaks. At 1649 cm, amide I have a stretching vibration. The changes in magnetic nanoparticle attachments on the Salmonella cell surface gave unique peaks at 1542 and 1414 cm
1 of the amide II band of protein and C¼O symmetric stretching of the COO- group in amino acids and fatty acids, respectively, according to SR-FTIR results. Ab-FMNs without and with target cell attachment had distinct bands at 1244 cm
1 and 1454 cm
1. The target Salmonella had specific SR-FTIR peaks after rapid capture/- concentration and isolation, which could be used in various applications for rapid detection of target Salmonella and the design of a generic machine for rapid, noncontact, non-destructive, and culture-independent

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detection method/plat- type of pathogens in food products. In the future, the approach may be applied to environmental and medical diagnosis [7, 9, 13, 28, 30].

Conclusion In this sense, FTIR techniques provide diagnostic methods for various types of samples. Complementary techniques such as NMR, Raman, XPS, and mass spectroscopy can help determine the intracellular composition and structures of treated and untreated cells by increasing the information density.

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More References Aja M, Jaya M, Vijayakumaran Nair K, Joe IH (2014) FT-IR spectroscopy as a sentinel technology in earthworm toxicology. Spectrochim Acta A 120:534–541

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Bangaoil R, Santillan A, Angeles LM, Abanilla L, Lim A Jr, Ramos MC, Fellizar A, Guevarra L Jr, Albano PM (2020) ATR-FTIR spectroscopy as adjunct method to the microscopic examination of hematoxylin and eosin-stained tissues in diagnosing lung cancer. PLoS One 15(5):e0233626 Beć KB, Grabska J, Huck CW (2020) Biomolecular and bioanalytical applications of infrared spectroscopy – a review. Anal Chim Acta 1133:150–177 Bellisola G, Sorio C (2012) Infrared spectroscopy and microscopy in cancer research and diagnosis. Am J Cancer Res 2(1):1 Bellisola G, Della Peruta M, Vezzalini M, Moratti E, Vaccari L, Birarda G, Piccinini M, Cinque G, Sorio C (2010) Tracking InfraRed signatures of drugs in cancer cells by Fourier Transform microspectroscopy. Analyst 135(12):3077–3086 Chan KLA, Lekkas I, Frogley MD, Cinque G, Altharawi A, Bello G, Dailey LA (2020) Synchrotron photothermal infrared nanospectroscopy of drug-induced phospholipidosis in macrophages. Anal Chem 92(12):8097–8107 Chrabaszcz K, Jasztal A, Smęda M, Zieliński B, Blat A, Diem M, Chlopicki S, Malek K, Marzec KM (2018) Label-free FTIR spectroscopy detects and visualizes the early stage of pulmonary micrometastasis seeded from breast carcinoma. Biochim Biophys Acta (BBA) Mol Basis Dis 1864(11):3574–3584 Marcelli A, Cricenti A, Kwiatek WM, Petibois C (2012) Biological applications of synchrotron radiation infrared spectromicroscopy. Biotechnol Adv 30(6):1390–1404 Meireles LM, Barcelos ID, Ferrari GA, Neves PAADA, Freitas RO, Lacerda RG (2019) Synchrotron infrared nanospectroscopy on a graphene chip. Lab Chip 19(21):3678–3684 Mohamed HT, Untereiner V, Cinque G, Ibrahim SA, Götte M, Nguyen NQ, Rivet R, Sockalingum GD, Brézillon S (2020) Infrared microspectroscopy and imaging analysis of inflammatory and non-inflammatory breast cancer cells and their GAG secretome. Molecules 25(18):4300 Palaniappan PR, Pramod KS (2010) FTIR study of the effect of nTiO2 on the biochemical constituents of gill tissues of zebrafish (Danio rerio). Food Chem Toxicol 48:2337–2343 Pereira L, Flores-Borges DN, Bittencourt PR, Mayer JL, Kiyota E, Araújo P, Jansen S, Freitas RO, Oliveira RS, Mazzafera P (2018) Infrared nanospectroscopy reveals the chemical nature of pit membranes in water-conducting cells of the plant xylem. Plant Physiol 177(4):1629–1638 Ramesh J, Salman A, Mordechai S, Argov S, Goldstein J, Sinelnikov I, Walfisch S, Guterman H (2001) FTIR microscopic studies on normal, polyp, and malignant human colonic tissues. Subsurf Sens Technol Appl 2(2):99–117 Ruggeri FS, Mannini B, Schmid R, Vendruscolo M, Knowles TP (2020) Single molecule secondary structure determination of proteins through infrared absorption nanospectroscopy. Nat Commun 11(1):1–9 Wang JS, Shi JS, Xu YZ, Duan XY, Zhang L, Wang J, Yang LM, Weng SF, Wu JG (2003) FT-IR spectroscopic analysis of normal and cancerous tissues of esophagus. World J Gastroenterol 9 (9):1897

Websites https://www.beilstein-journals.org/bjnano/articles/2/53 https://www.elettra.trieste.it/elettra-beamlines/nanospectroscopy.html https://link.springer.com/article/10.1007/s00216-015-9033-3

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Venkata Krishna Bayineni, Venkateswara R. Naira, and Ravi-Kumar Kadeppagari

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Nanozymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Nanozymes in Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Immunoassays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tumor Theranostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Myocardial Infarction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glucose and Antioxidant Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detection of Superoxide Anions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H2O2 Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Therapeutic Applications of Nanozymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antioxidation and Anti-inflammation Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stem Cell Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gold Nanoparticles for Therapeutic Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bioorthogonal Chemistry and Living Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuroprotection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Antibacterial Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tumor Theranostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cardiovascular Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors Affecting the Properties of Nanozymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Status and Challenges of Practical Applications of Nanozymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Main Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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V. Krishna Bayineni · V. R. Naira Department of Biology, Prayoga Institute of Education Research, Bengaluru, Karnataka, India e-mail: [email protected] R.-K. Kadeppagari (*) Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_91

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Abstract

Nanozymes are new-generation nanoproducts having enzyme-like catalytic properties and highly efficient than the native enzymes. As the catalytic mechanism of nanozymes is gradually revealed, the application fields of nanozymes have also been extensively explored. Recently, developments on nanozymes have made a remarkable progress and attracted a lot of researchers to explore their biomedical applications. Compared to the native enzymes, the nanozymes are highly beneficial due to their better stability, easy production, surface functionalization, reusability, and lower manufacturing costs. Moreover, the functionality of nanozymes can be remotely controlled by various physical factors including magnetic fields, ultrasound, light, and heat. In general, these factors can be regulated to advance the diagnosis and treatment of different diseases in the biomedical environment. Considering the huge potential of nanozymes in diagnosis and treatment (such as biological detection or biosensing, antibacterial, antioxidant, bioorthogonal chemistry, anti-inflammatory treatment, and cancer therapy), wide biological applications of different nanozymes are summarized in this chapter. Also, the factors that affect the properties of nanozymes (such as pH temperature, surface modification, and doping of other elements) are discussed. This chapter will enable the researchers to understand better the recent status of nanozymes and may help for new breakthroughs. At the end of this chapter, the prospects and challenges of using nanozymes in practical applications are discussed. Keywords

Nanozyme · Diagnosis · Treatment · Antibacterial · Antioxidation · Biosensing · Anti-inflammatory · Tumor theranostics

Introduction Nanozymes are a large collection of laboratory-made nanotechnology products that possess intrinsic enzyme-like activities similar to natural enzymes. The limitations in storage, stability, manufacturing, functionalization, sensitivity, and reusability of natural enzymes have triggered scientists across the globe to explore/design a range of nanoproducts for identification of nanozymes. The nanozymes are manufactured with specific functional molecules and are capable of self-assembly to generate a robust specificity to the native enzyme substrates. Moreover, like natural enzymes, the nanozymes also follow the Michaelis-Menten reaction kinetics. The nanozymes could overcome most of the above challenges involved with the use of natural enzymes. These advantages have revolutionized the manufacturing of nanozymes to facilitate an avalanche of applications in the field of biomedical engineering. Since the advent of the first report on Fe3O4 magnetic nanomaterials exhibiting an intrinsic peroxidase-like activity [8], the nanomaterial technology has been taken a radical shift toward the development of artificial enzymes. Presently, numerous nanomaterials were reported to be capable of mimicking a variety of catalytic activities (Table 1).

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Table 1 Novel nanomaterials with a wide variety of enzyme-like activities [24] Type of bioactivity Peroxidase Oxidase Catalase Superoxide oxidase Superoxide dismutase Haloperoxidase Sulfite oxidase Phosphatase Phosphotriesterase Chymotrypsin CO oxidase Protease Restriction endonuclease Carbonic anhydrase

Nanoparticles Fe3O4, Co3O4, CuO, V2O5, MnFeO3, FeS, graphene quantum dots, CeO2, BiFeO3, CoFe2O4, FeTe, magnetoferritin, and gold@carbon dots Au, Pt, CoFe2O4, MnO2, CuO, and NiCo2O4 CeO2, Pt-ferritin, Ir, MoS2 nanosheets, Prussian blue CeO2, fullerene, FePO4microflowers, Gly-cu (OH)2, N-doped porous C-nanospheres CeO2, Mn3O4, Prussian blue (PB), PCN222-Mn, Pt V2O5 nanowire, CeO2x nanorods MoO3 CeO2, Fe2O3 Co3O4/GO nanocomposites, CeO2 Cr-MIL-101 (MIL-101 is a metal organic framework) Cu2O@CeO2core@shellnanocubes Cu-MOF (metal organic framework) CdTe Co-(2,6-bis(2-benzimidazolyl))@terbium-MOF

Applications of Nanozymes The research advancement of nanozymes has paved the way to explore a wide range of biomedical applications from in vitro diagnosis to in vivo therapy of critical diseases. Based on the mode of application, Jiang and coworkers divided the nanozymes into self-acting, synergistic, and remotely controlled. Many recent developments in the field of nanotechnology have broadened the methods for studying new enzymes. The potential catalytic mechanism of nanozymes has yet to be explained when combined with computer theoretical calculations and simulations. Nanozymes’ catalytic activity has been increased as a result of these studies. Nanozymes have shown advantage in biomedical technology for diagnosing and treating diseases.

Application of Nanozymes in Diagnosis Imaging Apart from the enzyme-like activity, nanozymes have exclusive physicochemical properties like paramagnetism, chemiluminescence, and X-ray absorption. For this reason, nanozymes have been developed as excellent disease imaging probes for pathological staining, live cell/organelle imaging, and in vivo imaging [24]. For

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example, peroxidase nanozymes such as magnetoferritin, antibody-functionalized Co3O4, and silica-gold nanoclusters could stain specifically overexpressed biomolecules in tumor-specific tissues, thereby facilitating the contrast of the tumor cells during disease diagnosis via imaging techniques. Therefore, peroxidase-like activity-exhibiting nanozymes were developed for diagnosing cancers related to breast, colorectal, stomach, pancreas, esophageal, and bladder [24]. During the diagnosis of cancer, the analysis of cytological features of cells through nanozyme-based detection has recently been emerged as a cost-effective and less time-consuming technique over the traditional methods like flow cytometry, smearing, and nucleic acid tests. For screening the cancer cells, nanozymes are used to detect circulating tumor cells that can be found in the blood, cerebrospinal fluids, chest water, and mucous liquids. For example, a report on antibody-conjugated Fe3O4 nanoparticles has suggested that nanozymes could isolate, visualize, and quantify the circulating tumor cells concurrently via oxidation of colorimetric 3,30 ,5,50 -tetramethylbenzidine (TMB) and spectroscopic estimation. Similarly, other nanozymes such as silica-gold nanocluster, graphene oxide-gold nanocluster, folic acid-conjugated Pd@Au nanoparticles, magnetic nanoparticles, and Au/Ag core/double-shell nanoparticles have been used to detect several cancers such as breast cancer, cervical cancer, myelogenous leukemia, melanoma tumor cell, and squamous cancer, respectively. Nanozymes have superior advantages (fast, easy, and low-cost) over known methods like polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), and flow cytometry. Even for cell organelle imaging, heterogeneous palladium nanozyme was reported as specific mitochondrial probe due to its effective mediation via photo-driven biorthogonal reaction. Eventually, the nanozyme-based disease imaging was also explored in identifying other specific diseases like jaundice, acquired immunodeficiency syndrome (AIDS), diabetes, and some infectious and neurodegenerative disease. Moreover, the special physicochemical properties of nanozymes such as fluorescence, electricity, and paramagnetism have encouraged the nanotechnologists to explore the nanozymeassisted MRI (magnetic resonance imaging) for effective in vivo disease monitoring and imaging. For example, human-magnetoferritin nanoparticles conjugated with 125 I radionuclide were used as a robust biosensor for nuclear imaging of tumor tissues that enhanced the imaging sensitivity up to 106-fold, compared to the normal MRI [29]. Similarly, graphene quantum dots (peroxidase-like activity) and iridium oxide (catalase-like activity) nanoparticles were also reported as excellent contrast agents for the tumor imaging and treatment [24].

Immunoassays The ELISA is a widely used immunoassay technique during the diagnosis of human diseases. Traditionally, natural enzymes serve as biosensors in the biochemical reactions that involve in the colorimetric detection of specific analytes related to the disease. With the advent of nanozymes, the catalytic efficiency and sensitivities in ELISA could be improved severalfold compared to natural enzymes. The Fe3O4

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magnetic nanoparticles were first nanozymes that are reported to use in immunochromatographic strip for detection of glycoprotein of Ebola virus, which was so rapid and easier than the conventional ELISA method [5]. In another interesting study [18], a dual-mode detecting immunoassay (colorimetric and radiometric fluorescent) was developed using the nanoceria and graphitic carbon nitride quantum dots to determine the concentration of cardiac troponin I, a key protein involved in the diagnosis of acute myocardial infarction. In a very recent study on detection of novel SARS-CoV-2 coronavirus, Co-Fe@hemin nanoparticles were developed as nanozymes having high peroxidase-like activity along with the integration of chemiluminescence immunoassay activity [15]. This immunoassay is a strip-based paper test that requires 16 min of reaction time with a detection limit up to 0.1 ng/ml. Compared to the nucleic acid and serological antibody tests, this immunoassay-based paper test was proved to be more effective in terms of time and false-negatives.

Tumor Theranostics Nanotheranostics has recently been recognized as personalized cancer treatment by concomitant diagnosis and therapy using novel nanozymes. Among the many nanozymes, magnetic Fe3O4 nanoparticles and their nanocomposites have gained center of attention to explore the theranostic applications due to their intrinsic magnetic and multifunctional properties to use in MRI, magnetic hyperthermia treatment, phototherapy, drug delivery, chemotherapy, and gene therapy. The unique ability of functional and surface modulation of Fe3O4 nanoparticlebased nanozymes has also provided a great benefit to obtain high-contrast imaging and enhanced therapeutic efficiencies. The Fe3O4-based nanozymes have other benefits like extended blood circulation times, fast clearance, and minimum side effects [30]. Moreover, the peroxidase-like activity of Fe3O4based nanozymes made an excellent mimic to the well-known Fenton reactions, where endogenous H2O2 is catalyzed into hydroxyl radicals (•OH) leading to the death of tumor cells. Therefore, food and drug administration (FDA-US) has approved a few types of Fe3O4-based nanoparticles that are being used for clinical applications, e.g., ferumoxide and ferucarbotran SHU-555A for liver/ spleen imaging, ferumoxytol and feruglose for angiography, ferumoxtran and ferucarbotran SHU-555C for lymph node/bone marrow imaging, and ferumoxsil for GI oral imaging [30]. Wang and his team developed a novel biodegradable chemodynamic theranostics using nanomicelles, PAsc/Fe@Cy7QB, that facilitates tumor-specific multimodal imaging and improved generation of •OH radicals for enhancing the therapeutic efficacy [25]. Other than iron oxide-based nanozymes, Zhang and his coworkers have reported that carbon-gold hybrid nanoprobes (OMCAPs@ rBSA-FA@IR780) have shown theranostic properties on MGC-803 tumor-bearing mice by demonstrating simultaneous imaging via near-infrared (NIR) fluorescence and photothermal/photodynamic therapy of tumor cells with effective therapeutic efficacy [28].

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Myocardial Infarction Myocardial infarction (heart attack) is mainly linked with the deposition of excess amount of free cholesterol in the blood. For this reason, the detection of cholesterol has a great significance in the food quality control and early diagnosis of various heart-related diseases. As H2O2 is a by-product during the catalytic reaction of cholesterol oxidase, the amount of cholesterol has been quantified indirectly using a number of nanozymes that exhibit peroxidase-like activity. For example, one of the early studies reported a chemiluminescent biosensor having CuO nanoparticles that estimated the amount of cholesterol in the samples of milk powder and human serum by transducing the oxidation of luminol by H2O2, produced during the oxidation of cholesterol by cholesterol-oxidase [10]. Similarly, other nanozymes like graphene quantum dots, Mo, S co-doped carbon quantum dots, Fe3O4-coated C/Ni nanocomposites, nanosized molybdenum disulfide, and carbon nanotube-assisted Prussian blue were also reported as cholesterol biosensors with high catalytic activity and sensitivities [17]. As a next step of advancement in nanozymes, cerium oxide nanoparticles were reported as self-color-changing nanozyme for the estimation of blood cholesterol without any requirement of chromogenic substrates like 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) or 3,30 ,5,50 -tetramethylbenzidine (TMB) [21]. In the future developments of cholesterol determination, novel nanoparticles with intrinsic cholesterol-oxidase activity have to be explored for making robust and a complete nanozyme-based biosensor.

Glucose and Antioxidant Detection Zn-doped CuO nanoparticles were confirmed to exhibit both glucose (as low as 0.27 ppm) and antioxidant (tannic acid, tartaric acid, and ascorbic acid) detection [19]. Liu and his coworkers developed Pt/CeO2 nanocomposites as mimics of peroxidase to detect ascorbic acid linearly in the range of 0.5–30 μM [14].

Detection of Superoxide Anions The reactive oxygen species (ROS) have significant role in various signaling pathways of cell metabolism. Among ROS, the O2•- (superoxide anion) is an intermediate ROS that leads to the production of H2O2 and •OH (hydroxyl radicals) inside the living cells. Uncontrolled release of ROS in living cells, on the other hand, can result in cancer and aging. As a result, detecting superoxide anions in living cells plays an important role in disease early diagnosis and pathological research. Though there are several methods like spectrophotometry, chromatography, chemiluminescence, electron spin resonance, and bio-enzymatic for determination of O2•-, nanozyme-based detection is more reliable, rapid, reproducible, and cost-effective. As a presumable measure, superoxide dismutase-like activity-exhibiting nanozymes have been tested for detection of O2•-. In several reports, nanozymes such as carbon-based manganese (II) phosphate nanoparticles, SiO2-Mn3(PO4)2 nanoparticles, bacterial cellulose-

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based Mn3(PO4)2 nanoparticles, nano-Mn3(PO4)2-chitosan, MnO-embedded carbon nanofibers, carbon-based Mn2P2O7-formylstyrylpyridine film, Pt nanoparticles, and Co-based nanocomposites were used to detect O2•- in cancer cell lines, e.g., HeLa, human melanoma, 4 T1, etc. [3, 6, 22].

H2O2 Detection The H2O2 molecule is a by-product of partial oxidation in a number of biological pathways that involve extensive redox reactions. As a result, early detection of H2O2 is critical for human disease diagnosis and prognosis. The natural enzyme horseradish peroxidase (HRP) has been used for colorimetric detection of H2O2 in the presence of complex substrates, e.g., 2,20 -azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 3,30 ,5,50 -tetramethylbenzidine (TMB), thanks to recent developments in biosensors. Having an efficient catalytic activity and selectivity, the HRP-based biosensors have some critical drawbacks such as degradation due to long-term storage, harsh temperature, and pH conditions. Therefore, Fe3O4 magnetic nanoparticles which exhibit intrinsic natural peroxidase activity along with high stability at critical pH and temperature conditions can be used [8]. Eventually, other nanozymes like gold nanoparticles [31], graphene quantum dots, and AuPd alloy-modified polydopamine were also found to have peroxidase-mimicking properties that made researchers to explore their applications in the diagnosis of human diseases. For example, Ma and his coworkers reported that Fe3O4 nanoparticles could able to detect reduced glutathione (an important tripeptide which is related to a number of diseases like liver damage, cancer, AIDS, etc.) as low as up to 3.0–30.0 μM in A549 cell lines. The detection of reduced glutathione was possible through the indirect estimation of H2O2 [16]. In another study, graphene quantum dot nanozymes were used to detect H2O2 in vivo from the nasopharyngeal carcinoma cells and therefore served as an excellent contrast agent in deep-tissue tumor-targeted catalytic photoacoustic imaging [4]. In another recent study, the detection of apolipoprotein E4 (APOE4) for the early diagnosis of Alzheimer’s disease (AD) was made possible by using AuPd alloy-modified polydopamine nanotubes (having intrinsic peroxidase-mimicking activity) in combination with the gold nanobipyramid-coated Pt nanostructures.

Therapeutic Applications of Nanozymes As mentioned above, nanozymes have been widely used in detection and diagnostic methods. In addition to these applications, many researchers have also studied their therapeutic applications.

Antioxidation and Anti-inflammation Therapy Reactive oxygen species (ROS) are widely distributed in cells as a by-product of cell metabolism. Excessive production of ROS will be very harmful to cells and cause

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many diseases, such as cancer, atherosclerosis, and arthritis. Nanozyme platform shows good performance in the removal of reactive oxygen species and can protect cell components from oxidative stress in vitro and in vivo. Generally, superoxide dismutase is often used for therapeutic applications because of its protective effect as a scavenger of reactive oxygen intermediates. Seal and coworkers have reported the activity of CeO2 nanoparticles as superoxide dismutase mimic. Various studies have been tried to develop superoxide dismutase that mimics nanozymes [13]. It is also proved that nano-cerium oxide can be used for anti-inflammatory activity for eliminating free radical oxygen in J774A.1 mouse macrophage [9]. The synergistic effect of the combined nanozyme activity has been shown to protect cells from ROS harm due to their antioxidant properties [23]. The observations of Singh and colleagues (2019) showed that Mn3O4 nanoparticles have great potential in the treatment of inflammation and other ROS-related diseases.

Stem Cell Growth Superparamagnetic iron oxide (SPIO) nanoparticles have been used to promote the growth of stem cells. It is reported that the commercial SPIO ferucarbotran can promote the cell growth of human mesenchymal stem cells (hMSCs) by reducing H2O2 in the cells and accelerate the cell cycle process. In this report, the intrinsic peroxidase-like activity of SPIO significantly reduces intracellular H2O2 after internalization into hMSCs and free iron ions released by the lysosomal degradation of SPIO, thereby affecting cell cycle control molecules [11].

Gold Nanoparticles for Therapeutic Applications Colloidal gold nanoparticles (AuNPs) have recently demonstrated excellent enzyme-mimicking activities that mimic catalase, peroxidase, superoxide dismutase, oxidase, and reductase. The catalytic properties of AuNPs are influenced by their surface chemistry, morphology, and external factors including temperature or pH. Various application paths have already been investigated, including the regulation of oxidative stress within cells using peroxidase-like nanozymes through their superoxide dismutase and catalase activities. They have also been shown to play a role in a number of biomedical treatments, including photothermal therapy, which means they can absorb light and turn it to heat. Different loading technologies, such as distribution, surface complexation, attachment with capping agents, layer-by-layer assembly, and even encapsulation of drugs in AuNPs, have been used as drug delivery tools. However, the most promising biomedical application is the use of AuNPs as visible optical indicators in pregnancy tests. In addition, they can also be used as protective agents from reactive oxygen species (ROS) [7].

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Bioorthogonal Chemistry and Living Cells The chemical reactions that can be carried out in living cells or tissues without interacting with the organism’s biochemical reactions are known as orthogonal biological reactions. Professor Sletten and coworkers first suggested this in 2009. So far, biorthogonal reactions have assisted in various researches on cellular processes and biomolecules by selectively modifying biological species in biological systems. The findings show that nanoparticles made of platinum and gold have a lot of potential for monitoring and regulating the state of living cells.

Neuroprotection Fullerenes and their derivatives have long been established as free radical “sponges” due to their excellent ability to scavenge various types of ROS. It has been proven to protect the brain from neuronal damage caused by over-generated superoxide free radicals. This fullerene nanozyme has been tested in the Alzheimer’s disease model of Caenorhabditis elegans and has shown excellent neuroprotection against amyloid-β peptide aggregation. It is found that MoO3 nanozyme can be used as a sulfite oxidase mimic for cell detoxification. The lack of natural or artificial sulfite oxidase is related to nervous system damage and early childhood death. It has also been proven that Mn3O4 nanoparticles show high potential for treating neurological diseases caused by ROS [12]. It is reported that nano-cerium oxide, a mimic of superoxide dismutase, can prevent retinal degeneration by inhibiting the production of reactive oxygen intermediates. In their work, nano-cerium oxide in the presence of H2O2 prevented retinal neuron apoptosis induced by reactive oxygen intermediates and the accumulation of reactive oxygen intermediates in cells. They also demonstrated that injecting nanocerium oxide into rats’ eyes can protect retinal photoreceptor cells from lightinduced degeneration [1].

Antibacterial Effects For a long time, many efforts have been made in the fight against infectious diseases caused by bacteria. Various antimicrobial agents have been discovered. However, disadvantages such as poor antibacterial efficiency and heat resistance of organic or inorganic antibacterial agents still prompt us to develop new materials in the antibacterial field. Recently, nanomaterials with catalytic behavior have shown great potential in this field due to their stable and effective antibacterial properties. Therefore, more and more new antibacterial nanomaterials with inherent peroxidelike properties were synthesized. In particular, platinum-based nanocrystals have been widely used in catalysis due to the good control of shape, size, morphology, and

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structure. For example, Wu and his colleagues [26] successfully fabricated Pt hollow nanodendrites, which showed excellent peroxidase-like activity. In 2017, Ye and his colleagues created an INAzyme based on a hydrogel system that generates •OH in situ and has antibacterial effects. The cell wall structure of the bacterial membrane can be destroyed by OH oxidation of the unsaturated bonds of phospholipids.

Tumor Theranostics Effective methods for tumor diagnosis and cancer treatment have attracted many research interests. Many recent studies have focused on the use of nanozymes in tumor therapy, providing us with new tools in the battle against cancer and other diseases. Due to their inherent catalytic behavior, Guo’s work in 2015 demonstrated that nanozymes can be used for photodynamic therapy to treat hypoxic tumor cells [2]. Zhang and colleagues reported in 2018 that metal-organic frameworks modified with Pt nanoparticles can also enhance the effect of photodynamic therapy [2018].

Cardiovascular Medicine By responding to challenges and advancing the imaging and identification of in vivo and ex vivo biomarkers, as well as enhancing tissue regeneration and drug delivery, cardiovascular nanomedicine aims to improve detection and address existing cardiovascular problems and treatment issues. Nanocarriers are directly injected to deliver the medication. Nanocarriers used to treat cardiovascular disorders, and other diseases have chemical properties that vary from one another [20].

Factors Affecting the Properties of Nanozymes The size and morphology of the nanozymes that determine the active site determine the catalytic efficiency of nanozymes. Luo and colleagues evaluated the sizedependent efficiency of glucose oxidase-like AuNP by preparing 13 nm, 20 nm, 30 nm, and 50 nm AuNPs. The experimental results show that the catalytic activity increases with the decrease of the particle size. It is found from the literature that the octahedral-shaped nanozyme performs better due to lower surface energy. The catalytic activity of natural enzymes is known to be affected by pH and temperature. Acidic conditions can promote peroxidase mimic activity, while neutral and alkaline conditions are conducive to catalase-like properties. Moreover, there are some nanozymes that are stable and perform well in a relatively wide pH and temperature range. By changing the pH value from 2 to 12 and the temperature from 4  C to 60  C, it is found that the ceria porous nanorods have the greatest catalytic efficiency at temperatures of 3–4.5  C and 35  C [27]. Similarly, altering the surface of nanozymes will affect the efficiency of the reaction by reducing the active site’s exposure. Doping elements can increase the catalytic activity of nanozymes. The results show that Fe@Fe3O4 core-shell nanoparticles have

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significantly higher catalytic activity than Fe3O4@heparin nanoparticles. This is because the conversion is accelerated by the release of iron ions from the iron center. As a result, the iron core is critical for improving nanozyme properties [27]. Despite the novel applications of the nanozymes, some critical questions are yet to be solved.

Status and Challenges of Practical Applications of Nanozymes There is a need to explore cost-effective manufacturing of nanozymes for decreasing cost of disease diagnosis and therapies. A recent report on preparation of MoO3 nanorods for glucose detection has already been showing a great promise to use algae for synthesis of nanozymes. In the future, nanozyme technology that focuses on the technical improvements in specificity, catalytic activity, reproducibility, and broad enzyme-mimicking activities needs to be developed. The technical challenges of manipulating the microstructure for improved sensitivity and selectivity still need to be addressed. During the clinical testing level, issues like biofouling and false-positive results must be given more attention. Most importantly, the establishment of an international governing body that maintains standard protocols for synthesis and bioconjugation of biomedically important nanozymes could efficiently tackle the reproducibility issue; therefore, clinical acceptance can be made easy. In addition, there is great demand to develop nanozyme-based biosensors as automated point-of-care testing platforms by integrating pathological target isolation, separation, and detection on a single device. In disease imaging techniques, detection sensitivity of nanozymes and quantification of the staining results are the two major issues that require attention. As sensitivity is directly correlated with the catalytic activity, the appearance of false positives may arise while improving the sensitivity of nanozymes. Authors suggested addition of functional amino acid residues or natural enzyme onto the surface of nanozymes to improve the activity and substrate specificity.

Main Websites https://pubs.rsc.org/en/content/articlelanding/2020/cc/d0cc05427e#!divAbstract https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6696937/ https://link.springer.com/article/10.1007/s40820-020-00532-z https://www.tandfonline.com/doi/full/10.1080/21691401.2017.1313268 https://www.frontiersin.org/articles/10.3389/fchem.2019.00046/full

References 1. Chen J et al (2006) Rare earth nanoparticles prevent retinal degeneration induced by intracellular peroxides. Nat Nanotechnol 1:142–150

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Plant-Based Consumer Health Gold Nanoproducts: Benign Nanoformulations for Wound Healing and Treatment of Infections

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Shikha Gulati, Sanjay Kumar, Nandini Sharma, Prishita Sharma, and Kanchan Batra

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wound and Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Wounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stages of Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventional Strategies for Wound Treatment and Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Need of Nanoformulations in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Are Nanoparticles? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoformulations in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Role of Nanoformulations in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metallic Nanoparticles in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gold Nanoparticles: Prime Choice in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Significant Properties of AuNPs over Other Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Synthetic Approaches of Gold Nanoparticles (AuNPs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventional Methods of Synthesis of Gold Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plant-Mediated or Phytochemically Synthesized Gold Nanoparticles: Green Method of Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages of Green Method of Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors Affecting the Quality of Plant Mediated Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steps Involved in the Plant-Mediated or Phytochemically Synthesized Gold Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biomedical Applications of AuNPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gold Nanoformulations in Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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S. Gulati (*) · S. Kumar Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India N. Sharma · P. Sharma Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India K. Batra Department of Zoology, Kalindi College, University of Delhi, New Delhi, Delhi, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_90

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Applications of Gold Nanoparticles Synthesized by Green Method in Wound Healing . . . . . . Concluding Remarks and Future Prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

In the past decade, there has been a tremendous amount of research and breakthroughs in the field of nanotechnology. From here, a new field of phytonanotechnology or plant-based technology of nanoproducts has emerged, which has widespread applications, especially in the field of health and medicine. Since time immemorial we have known the benefits of plants and their parts (roots, leaves, stem, flowers, and fruits). The advancements in nanotechnology have made it possible to study the hidden treasures within plants from a new perspective. This has given rise to industries like nanoceuticals, cosmeceuticals, and nutraceuticals that focus on consumer health via natural supplements conjugated with nanoparticles. These plant-derived nanoproducts have a relatively high internalization rate, proven stability in the gastrointestinal tract, and low immunogenicity, making them far better than traditional formulations. Apart from this, plant-based nanoproducts in therapeutics for diseases like various types of human cancer, diabetes, and curing wound healing are being studied extensively. This chapter focuses on the synthesis and application of plant based AuNPs in wound healing and treatment of infections, highlighting the biomedical applications of the same. In addition, future prospects of plant-derived gold nanoformulations in biological activities are also discussed. Keywords

Nanotechnology · Wound-healing · Gold-nanoparticles (AUNPs) · Phytochemicals · Green-synthesis · Nano formulations

Introduction In recent years, the advancements in nanotechnology, particularly of metal nanoparticles, have significantly contributed to industries handling biomedical tasks. Researchers are deliberately making use of metallic nanoscale formulations due to their higher biocompatibility, lower toxicity, excellent surface functionalities, etc. Uses of nanoproducts in therapeutics for diseases like various types of human cancer, diabetes, and curing wound healing are being studied extensively. Nanoparticles, because of their small size, show high biocompatibility, low toxicity, excellent antimicrobial and antibacterial properties, and effective target specificity, due to which they can be considered as exemplary agents for wound healing processes. Gold nanoparticles (AuNPs) are known to be the most potent in all metal nanoparticles. Scientists have reportedly found high potential in plant-based AuNPs in wound healing and treatment of infections. While treating a wound, the

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level of complexity of the skin tissue structure also becomes a hurdle in choosing the most appropriate method. Classic treatment methods for wound healing have various drawbacks like low elasticity, durability, higher mechanical attachment to the surface causing pain during replacement, ineffective wound closure, etc., because of which researchers have considered the use of nanostructures, particularly phytochemically assembled gold nanoformulations, as the chief approach in resolving the mentioned problems. They can be easily synthesized and are also environmentally friendly. Many plant products can be used in combination with gold nanostructures as stabilizing agents to enhance the process of wound healing. In this chapter, the synthesis and application of these plant-derived gold nanoformulations in wound healing are discussed in detail. The biomedical applications of the same are also highlighted in this chapter. In addition, future prospects of plant-derived gold nanoformulations in biological activities are also presented.

Wound and Wound Healing A wound is break in the continuity of a bodily tissue in which the cutaneous membrane is damaged with or without the bones, nerves, or muscles getting affected. Such damages can be caused by surgeries, infections or diseases, pressure injuries and are highly problematic [1]. They adversely affect the quality of life for a large number of people globally. The healing process starts as soon as any tissue is harmed and is termed wound healing. Wound healing is a complicated process that takes considerable time to be completed and is set off as a response to any stimuli causing skin injury [2]. A number of internal and external factors contribute to the efficacy of the healing process, the most important being the kind of dressing used and wound management involved, including the clinical measures taken, interventions in wound care, and methods used. Properties like the kind of wound present and its intensity are usually taken into account while deciding the treatment [3].

Types of Wounds Wounds can be classified into two basic types: 1. acute and 2. chronic. In simple words, acute wounds have a shorter duration than chronic ones. But there are many more factors that control the transformation of an acute wound into a chronic wound. 1. Acute wounds can range from small cuts and scabs to larger burns, abrasions, and surgical incisions. These take an average of 2–3 weeks for healing and usually have very low to no microbial presence in the initial stages. Additionally, they follow normal stages of healing, unlike chronic wounds. 2. Chronic wounds can be defined as nonhealing wounds that do not follow the normal course of healing and get stuck in one of the stages in the process. Many scientists consider 6–8 weeks as the time limit for the healing of any normal wound, beyond which it becomes a chronic wound [4]. Various factors that lead

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to a wound getting arrested in a stage of healing are increased inflammation, microbial growth or infections, irritation, presence of foreign particles that retard the healing process, decreased macrophage functioning, low blood supply, diminished angiogenesis, and poor oxygenation. Chronic wound infections are easily colonized by bacteria that form bacterial biofilms. These biofilms are nothing but clusters of bacteria enclosing a surface, by producing an extracellular matrix that can contain polysaccharides, proteins, etc. These biofilms protect the bacterial groups against receiving any action by antibacterial medicines or the host immune system. Comorbidities like diabetes also act as a risk factor in contributing to delayed wound healing. Chronic wounds represent a highly researched field due to their large incident rates. Furthermore, many traditional and novel approaches have failed to provide results in response to chronic infections that is why there is a need for efficient utilization of nanoformulated products to overcome the debilitating effects caused by these wounds [5].

Stages of Wound Healing Typically, wound healing comprises of four overlapping stages, namely: 1. hemostasis, 2. inflammation, 3. proliferation, and 4. remodeling (Fig. 1). These phases are known to overlap due to a number of physiological and anatomical factors, inside the body. Various cells involved in the whole process are platelets, progenitor cells, fibroblasts, and keratinocytes. 1. Haemostasis: The initiation of wound closure takes place in this phase. When an injury takes place, a series of clotting steps called the coagulation cascade begin. Clotting factors of the damaged skin start the extrinsic clotting cascade and attachment of platelets to the subendothelial surface initiates the intrinsic clotting cascade. The thrombocytes accumulate to form a fibrin network, which is supported by a vasoconstriction, caused due to release of histamine that stops further bleeding. Numerous messenger molecules like platelet-derived growth factor (PDGF) vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) are released and these help in the activation of macrophages [6]. 2. Inflammation: In this stage, debris and dead cells are cleared out with phagocytosis. It overlaps with hemostasis and may last for 48 h after the injury. Various leukocytes like neutrophils are released along with monocytes and lymphocytes, which then differentiate into macrophages. These inflammatory cells then release

Haemostasis Stage 1

Inflammation Stage 2

Fig. 1 Stages of wound healing

Proliferation Stage 3

Remodelling Stage 4

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proteinases and reactive oxygen species which help in the protection of the wound against bacterial attack. Usually, this stage is prolonged in chronic wounds. 3. Proliferation: Here the formation of granulation tissue, deposition of collagen, angiogenesis, epithelialization, and wound contraction take place. Elastin, hyaluronic acid, collagen, and proteoglycans constitute the extracellular matrix (ECM), which in turn builds the granulation tissue for substitution of the original clot. Angiogenesis involves neovascularization, which is the formation of new blood vessels and is promoted by the release of cytokines and VEGF. Epithelial cells multiply during epithelialization and cover the wound. Finally, fibroblasts differentiate into myofibroblasts which causes wound contraction [6]. 4. Remodeling: This is the last phase of wound healing. It is also known as the maturation stage. Remodeling is initiated two to three weeks after the injury. A mature scar replaces the granulation tissue along with. Unwanted cells are removed cell by apoptosis and blood vessels are generated in granulation tissue. Remodeling may continue for several years. The reconstructed tissue never regains the features of the original skin.

Conventional Strategies for Wound Treatment and Healing The application of topical medicines on the wound and securing it with a dressing is the standard method of treatment. Currently used dressings can be divided into three main categories: 1. traditional (cotton and wool based), 2. artificial (foams, hydrogels, sprays), and 3. biomaterial-based (tissue and xenografts). Further, based on the method of application, they can be categorized as: 1. Primary dressings – applied directly to the injured tissue and 2. Secondary dressings – applied over primary dressings [7]. Conventionally, cotton gauze bandages have been used as a popular choice of dressing materials. These dressings act as a protective barrier for the wound and prevent contamination by foreign particles. But materials like cotton only provide passive protection, not availing transfer of compounds to the injury, due to which new products have been studied and prepared. Artificial wound dressings like foams, gels, and sprays are interactive in nature and provide several advantages like being impermeable to bacteria yet allowing water vapor and oxygen to pass through, but in some cases, they may cause irritation and contact dermatitis [8]. Tissue and xenograft-based treatments are also highly effective but very costly. Usually, the dressing used should create moist conditions to fasten the healing, maintaining the cleanliness of the wound. Moreover, the dressing should be biocompatible, long-lasting, able to prevent bacterial infections, easy-to-apply, and cost-effective. For treating infections in various wounds, topical treatment with antibacterial and antimicrobials like tetracyclines, cephalosporin, etc., is also provided. They are very efficient, low in toxicity and are easy to apply but their absorption is hampered by the stratum corneum. Numerous oral medicines are also used for wound healing like chemotherapeutic drugs like different antibiotics, nonsteroidal anti-inflammatory drugs, and steroidal glucocorticoids. Most of these medicines are anti-inflammatory in nature also helping in overcoming nausea and

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pain but suppress the immune system of the patient. Moreover, these agents are usually very toxic, costly, and dangerous [9]. Additionally, chronic wounds cannot be treated using oral medications as they have a lower target specificity for injured tissues. Bacteria colonizing the chronic wounds may also acquire resistance to oral or topical applications. Regular methods may not provide a desirable outcome, due to which the use of various nanoproducts is currently being promoted to provide an effective solution [10].

Need of Nanoformulations in Wound Healing Currently, the topical route of drug/pharmaceutical administration is the backbone of therapy in wound treatment worldwide. However, this topical delivery of medications is sometimes hampered by the presence of the stratum corneum, which is the outermost layer of the epidermis containing dead cells that act as a barrier. To combat this problem, nanoparticle-based drug formulations and delivery propose as a promising solution, especially in dermatological diseases. To understand the need of nanoparticles in wound healing, it is vital to firstly understand what they are and how they can be useful in effective treatment of wounds.

What Are Nanoparticles? Discovered more than 50 years ago by Richard Feynman (“The Father of Nanotechnology”), nanoparticles are said to be ultrafine, submicroscopic units that are measured in dimensions of nanometers (nm; 1 nm ¼ 109 m). The definition of a nanoparticle was first given in 2008 by the International Organization for Standardization (ISO) as a discrete nanoobject where all three Cartesian dimensions are less than 100 nm. But in 2011 the Commission of the European Union approved a moretechnical but wider-ranging definition: a natural, incidental, or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where for 50% or more of the particles in the number size distribution, one or more external dimensions are in the size range 1 nm–100 nm [11]. Under this definition, a nanoobject requires only one of its characteristic dimensions to be in the range 1–100 nm to be classed as a nanoparticle, even if its other dimensions are outside the specified range. Nanoparticles can be categorized into numerous types on a variety of basis like shape, size, material properties, etc. Some classifications differentiate between inorganic and organic nanoparticles, the first group comprises quantum dots, metallic nanoparticles (gold, silver, silicon, etc.), metallic oxide nanoparticles, etc., and the second group comprises of nanoparticles made of lipids, chitosan, dendrimers, PLGA (polylactic-co-glycolic acid), etc. Nanoparticles can exhibit a variety of effects in different compositions due to their three main properties:

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1. High mobility in Free State 2. Having enormous specific areas 3. Known to exhibit quantum effects The thermal, mechanical, and catalytic properties can be altered by increasing or decreasing surface area/volume ratio and the new properties generated allow applications of nanomaterials in many biological fields like, drug delivery and novel drug development, diagnostic tests, biosensors, and even in vivo imaging. The nanoparticles of chemically manufactured structures like polysaccharides, polymers, metals, and plant-derived bioactive compounds incorporated with active drugs can effectively fight against human pathogens like bacteria and even viruses and can be efficiently used to treat various pathological conditions, like wound healing.

Nanoformulations in Wound Healing Throughout the advancements of nanotechnology in medicine, a variety of innovative nanoformulations have been created for treating many medical complications, especially wound healing. The nanoproducts used are divided into two categories based on their mode of function, namely: 1. The nanoparticles which exhibit intrinsic attributes that are advantageous for the treatment of wounds. 2. The nanoparticles deployed as delivery agents/vehicles to transport the therapeutic drugs/agents which are beneficial for wound healing. Numerous nanoscale strategies have been tested and applied in the area of wound healing, experimentation with a variety of nanoformulations (metallic and metallic oxides, carbon-based, polymeric, etc.) has paved newer methods of treating as well as preventing wounds of all kinds, be it superficial, internal, or even diabetic, and nanotechnology in wound healing has been breaking barriers rapidly. For example, many studies have been conducted to investigate the controlled release of NO (Nitric oxide) from nanoscale delivery agents as NO is very important in cellular proliferation, matrix remodeling, angiogenesis, and inflammation, which are key aspects of wound healing. Apart from this, antibiotics- and antioxidant-coated nanoparticles have been formulated from a variety of sources to achieve faster and efficient wound treatment. Even, growth hormone (FDA approved) incorporated nanoparticles have been produced to increase the rate of cell regeneration in chronic wound tissues. Scientists have also probed the avenues of the gene, RNA interference (RNAi), and small interfering RNA (SiRNA)-based nanotherapies to combine gene-based therapy with tissue regeneration as an effective wound healing treatment but since this is a highly recent concept, in-depth research and experimentation are needed. There are many mechanisms of action of nanoparticles inside the human body and such aspects and their applications are discussed in the following sections [12].

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Role of Nanoformulations in Wound Healing Normal wound repair mechanism is a forced response to unfavorable stimuli at skin tissues or any other organ. It is a cascade process involving various steps that finally result in tissue restoration. It is normally divided into four phases: the hemostasis phase, the inflammatory phase, the proliferation phase which is followed by the remodeling phase. A variety of cells, enzymes, cytokines, proteins, and hormones are involved in tissue repair processes [13]. The methods of treatment vary from topical medications and dressings to Xenografts, but as observed, they have many setbacks like wound dehydration, etc., thus requiring a better and more efficient method of treatment. Consequently, nanomaterials-based treatments have achieved a new horizon in the arena of wound care due to their ability to deliver a myriad of therapeutics into the target site and to simplify the complexity of the normal woundhealing process. The nanoparticles selected when embedded with biomaterials can be used as a potential nanogenerative material. Apart from this, nanotechnology offers new avenues in regenerative medicine as well. In recent years, nanoresearch has furthered to develop molecular engineering strategies for different self-assembling biocompatible nanoparticles. The inherent properties, mainly physicochemical, of the nanomaterials used are responsible for their application in wound healing, dressing, and carriers for different therapeutic agents resulting in differential wound treatment capacity of each nanomaterial. The various properties involved are biodegradability and biocompatibility, size, colloidal stability, surface functionalization and charge, etc. The additional effect of biocompatibility and biodegradability is seen over particles that are nondigestible and nondegradable. But apart from physicochemical properties, another property plays a very vital and indispensable that is the presence of a payload (active ingredient) on the nanomaterial for the wound healing process. The nanomaterials can portray proliferative, proangiogenesis, antibacterial, as well as anti-inflammatory applications in wound healing due to its unique properties. They can even modulate the level of expression of various proteins involved in the cascade process of wound healing and are able to direct molecules to improve wound healing in target sites. Their application is assessed keeping in mind the fact that the smaller the nanomaterials are on the nanoscale the larger their surface area becomes leading to enhanced properties. The main types of nanomaterials used are: nanoparticles, nanocomposites, and coatings and scaffolds. This chapter focuses on metal nanoparticles with special emphasis on gold nanoparticles.

Metallic Nanoparticles in Wound Healing Among all inorganic nanomaterials, the metallic nanoparticles like silver (Ag), gold (Au), zinc oxide (ZnO), titanium dioxide (TiO2), selenium (Se), copper (Cu), etc., have acquired a special status due to impressive biomedical applications of their metallic content. Metal nanoparticles like gold, silver, and zinc exhibit revolutionary

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properties such as low in vivo toxicity along with bacteriostatic and bactericidal activities. Metallic nanoparticles have a unique property of diminishing the toxicity of metals due to their size and surface area to volume ratio. Therefore, the following section of the chapter summarizes some metallic nanoparticles used till now for wound healing. 1. Silver nanoparticles (AgNPs): Silver has long been used in wound healing in both metallic and ionic forms due to its widely known antimicrobial activity. It was prevalent even in the seventeenth and eighteenth century and was used for disinfecting wounds in World War I. The Ag nanoparticles exhibit a plethora of properties like anti-bacterial, antiviral, antifungal, antiangiogenesis, antiplatelet, and anti-inflammatory. The nanoparticles with their extremely small size and high surface to volume ratio are able to sustain the release of silver, thus minimizing its toxicity and prolonging the impact. Ag nanoparticles are known to actively show antibacterial activity against dermal pathogens like Pseudomonas aeruginosa, Streptococcus pyrogens, as well as oxacillin and methicillin resistant S. aureus. 2. Gold nanoparticles (AuNPs): Gold has widely known therapeutic applications in cancer diagnosis and treatment, but it is also used in wound healing, either alone or in conjugation with other substances. The gold nanoparticles are attributed to their antioxidant ability and their capacity to penetrate the skin via interaction with its outermost layer that is stratum corneum, which conventional wound treatments mostly fail to do. When coupled with antioxidants, Au nanoparticles show migration and proliferation of dermal fibroblasts and keratinocytes. Recently they were used to reduce the oxidative stress produced during wound healing by eliminating the Reactive Oxygen Species (ROS) created. 3. Copper nanoparticles (CuNPs): Copper exhibits power wound healing activity due to its antibacterial, immune boosting, and angiogenesis amplifying properties. It also shows antioxidant activity by acting as a cofactor to enzymes like cytochrome oxidase. In nanoforms, its catalytic activity and biocompatibility are enhanced and stabilization along with a coating of various substances like folic acid magnifies its effect manifold. This also minimizes its cytotoxic nature and also increases its efficacy. 4. Silicon nanoparticles (SiNPs): Silicon is a trace element present in the human body which is quite in abundance. It has mostly been used as wound dressings due to its antimicrobial nature and also comes in use by penetrating the dermis and epidermis to show its angiogenic and anti-inflammatory properties. Silicon loaded nanoparticles are known to be quite efficient as they slowly release the active molecule internally that enhances their potency. They are often coated with bioactive molecules like siRNA that help in wound regression and increase the healing process [14]. 5. Zinc oxide nanoparticles (ZnONPs): Zinc has long durability inside living cells and thus along with its antipathogenic property, it would to be a highly stable and efficient method of wound healing. ZnO nanoparticles loaded with medicinal drugs prove to be very effective on postoperative wounds. Cefazolin-loaded ZnO

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Fig. 2 Metallic nanoparticles in wound healing

nanoparticles show amplified cell adhesion, collagen synthesis, and epithelial migration that results in faster wound healing [15]. Also, it governs the autophagocytosis of cells in the wound that is critical for wound repair (Fig. 2). It is evident that metallic nanoparticles are promising and well advancing tool in the field of wound healing, especially gold nanoparticles that will be discussed in the following section.

Gold Nanoparticles: Prime Choice in Wound Healing Extremely small particles of gold, with a diameter ranging from 1 to 100 nm, are termed as gold nanoparticles (AuNPs). When dissolved in a fluid, like water, it is defined as colloidal gold. Gold nanoparticles are being widely used in disciplines like bio-nanotechnology, physics, and chemistry, due to their distinctive physical and chemical properties [16]. Their properties make them excellent agents for various functions and roles in numerous biomedical applications like in drug delivery, imaging and sensing, cancer treatment, etc. Along with the controlled release of drugs, various surface modifications developed have helped in enhancing their role as delivery vectors [17]. Despite gold nanoparticles being thoroughly researched in the past few years, there are some potent features that need to be further investigated. Scientists are currently working towards increasing biocompatibility and lowering the toxicity of these formulations to improve their functionality in biological systems [18, 19].

Significant Properties of AuNPs over Other Nanoparticles Possession of various useful attributes has made gold nanoparticles the prime choice in bionanotechnological applications. These particularly include higher

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biocompatibility, lower toxicity, larger surface-to-volume ratio, easier synthesis, shape tunability, desirable optoelectronic features, etc. Production of several shapes such as tubes, rods, and spheres makes AuNPs extraordinary candidates for applications in genomics, biolabeling, and immunoassays. Nanogold formulations also exhibit multiple colors when interacting with electromagnetic radiations, which explains their role in bio sensing. Physical qualities present like fluorescence quenching and Surface Plasmon Resonance (SPR-oscillation of free electrons in the presence of a particular frequency of light) are also important. Based on their SPR, spherical AuNPs lie in the visible and gold nanorods lie in the infrared region. For the longest time, catalytic characteristics of AuNPs were thought to be absent or not strong enough. It was in 1987 when Haruta et al. found out that oxidation of CO can be catalyzed by AuNPs at or even below room temperature systematically. Various studies after this revelation have explored the role of gold nanoparticles as catalysts for a diverse range of activities. Due to these unique features, gold nanoparticles not only have a wider field of application, but more extensive research is also being carried out on them as compared to other metallic nanoparticles.

General Synthetic Approaches of Gold Nanoparticles (AuNPs) Gold nanoparticle synthesis is described as being easier as compared to other nanoparticles. Two basic approaches for the synthesis of gold nanoparticles are: 1. Top-down approach: In the top-down process, required nanostructure can be achieved by removing the bulk material. It usually makes use of lithographic patterning methods, with small wavelength sources. It has been used in assembling integrated circuits and has successfully provided microscale production but acquiring nanoscale products is quite challenging using this approach, which is why bottom-up techniques have been considered better than that involved in top-down. 2. Bottom-up approach: The bottom-up approach has been inspired by selfassembly of atoms in various biological systems. Physical or chemical forces are used to accumulate basic units into a large structure. The atoms are aggregated till the desired size is obtained. Numerous techniques based on quantum dots and micelles have been developed and utilized. Nanoparticles of several magnetic and semiconductor materials have been synthesized using the same. DNA-assisted assembly approaches are also being used increasingly due to significant advantages like adhesiveness of complementary DNA strands. Every method used is based on these two approaches [20] (Fig. 3).

Conventional Methods of Synthesis of Gold Nanoparticles Synthesis can be classified as physical and chemical. Physical methods utilize electron beam lithography, laser ablation, γ-irradiation, etc. In chemical preparation, stabilizers, capping agents, etc., are used. Additionally, tween 20, a surfactant, has

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Fig. 3 General synthetic approaches of gold nanoparticles

been widely used to prevent aggregation of AuNPs, when being functionalized using thiolate ligands • Physical methods: These frequently involve irradiation using ionizing or nonionizing radiation, which can lead to electron transfer and further, to the reduction of metallic particles. Ionizing radiations, photochemical synthesis, and microwave radiation are widely used processes. • Turkevich method: This is the most popular method of AuNP synthesis. In 1951, Turkevich et al. had created AuNPs using hydrogen tetrachloroaurate and citric acid. Citric acid was put in boiling water, where the citrate ions formed acted as a stabilizer and a reducing agent simultaneously. Sometimes the citrate stabilized AuNPs can undergo irreversible aggregation to avoid which stabilizers or capping agents are used. To change the gold-to-citrate ratio, Frens had altered this procedure in 1973. By this modification, particles of 10–20 nm diameter could be developed more efficiently. Gold nanoparticles can also be functionalized using organic ligands. Thioctic acid has also been used to carry out a two-step functionalization process. • Brust and Schiffrin method: In 1994, Brust and Schiffrin synthesized AuNPs using organic liquids immiscible in water. Sodium borohydride (NaBH4) was used as the reducing agent, along with a reaction between chloroauric acid solution and tetraoctylammonium bromide (TOAB). TOAB acts as both the stabilizing agent and the phase transfer catalyst yet it is not good at binding to the gold nanoparticles, which is why other binding agents like thiols should be used to prevent precipitation of AuNPs. The gold particles produced are 1.5–5 nm in diameter and the size can be varied by varying the reaction conditions like temperature, reduction rate, etc. The AuNPs procured by this method are alkatheniol-protected, which provides them higher stability than others. • Sonochemical synthesis: Additionally, Okitsu et al. used sonolysis in which ultrasonic energy was used for experimental production of gold nanoparticles under 10 nm. The nanoparticles created were under 10 nm in diameter [21]. • Navarro method: Navarro et al. synthesized gold nanoparticles using sodium acetylacetonate and sodium citrate. This provided better control over the

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nanoparticle size. It further helped in increasing local concentration and cell internalization AuNPs [22]. • Seed-mediated method: This method is used to generate gold nanoparticles of varying shapes. It involves reduction of gold salts using a reductant like sodium borohydride creating seed particles. Perrault et al. had developed a seed-based method of AuNP production, just like photography. Here a solution of hydroquinone and HAuCl4 is used, with hydroquinone as the reducing agent. This modification, like Frens, provides better control of the size of the gold nanoparticles being assembled and is ideal for creating particles of 30–300 nm diameter. Structural properties of the AuNPs synthesized can be monitored by controlling the amount of reducing agents used [23]. Use of hazardous reagents and presence of toxic by-products in the mentioned procedures make it essential for researchers to devise environmentally cleaner ways for gold nanoparticle production. Moreover, toxicity of gold nanoparticles varies due to several factors like particle size, surface modifications, etc. Kalimuthu et al. found in their study that Bacillus licheniformis can also be used for synthesizing gold nanocubes in the range of 10–100 nm. Bacterial-synthesized AuNPs are produced at lower temperatures, unlike other chemical methods [24]. Furthermore, other microorganisms, biomolecules, plants can also be employed for creating AuNPs in ecologically cleaner ways.

Plant-Mediated or Phytochemically Synthesized Gold Nanoparticles: Green Method of Fabrication In recent years, the pattern of engineering nano-sized particles mainly of metals has grown, for various objectives (Fig. 4). There are two ways to characterize nanoparticles according to various need, namely, bottom-up and top-down. The bottomup technique involves increasing the material from the lowermost level: atom by atom, molecule by molecule, or cluster by cluster, whereas the top-down approach deals with slicing or successive fragmentation of a bulk material to get the desired result. It has been observed that the bottom-up technique qualifies to be a superior choice because of its involvement of catalytic substances like enzymes and reducing agents that constitute a homogenous system. It does not have demerits like surface structural defect that affect the physical properties of nanoparticles adversely which can be observed in top-down approach [25]. These approaches can be applied to various methods of nanoparticle production like physical, chemical, biological, etc. The biological method, which comprises of utilizing plant/animal or microorganism sources, has gained a lot of popularity due to its advantages over other methods as it is simple and cost-effective, has low energy consumption, and is also eco-friendly because it does not lead to environmental contamination by releasing hazardous by products [26]. Due to this, a new term called “Green Synthesis” has been coined to define the use of plant-based production of nanoparticles, involving a variety of plant parts and metabolic substances. The plant parts being-stem, roots, shoots, leaves,

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Fig. 4 Synthesis of AuNPs using phytochemicals

Fig. 5 Different phytochemicals used in nanoparticle formulations

flowers, bark, seeds, etc., and metabolic products like flavonoids, tannins, steroids, alkaloids, saponins, etc. (Fig. 5).

Advantages of Green Method of Synthesis It is evident from the conventional methods of synthesis that they possess a lot of drawbacks with respect to energy consumption, cost, hazardous by products, toxicity

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of AuNPs produced, etc. The novel method of phytosynthesis of AuNPs poses as an apt solution to these problems because it simplifies the process, reduces the cost and energy consumption, accelerates the process while making it less hazardous at the same time. All the advantages are discussed below in detail: 1. Plant-mediated approach of synthesis of AuNPs is highly economical as well as fast, making it easy for bulk production of stable AuNPs to be done. 2. With the help of downstream processing, optimization techniques, as well as tissue culture of biocompatible plant source, industrial application of AuNPs is easy and beneficial at the same time. 3. Contrary to conventional procedures, this synthetic approach utilizes aqueous water for extraction of plant metabolite/chemical, which requires a normal/ambient range of temperature and pressure, thus saving a lot of energy. 4. Since the plant extracts act as both capping and stabilizing agents, the procedure of green synthesis becomes simpler and can be completed in a single step as well, making it an extremely viable alternative. 5. The phytoconstituents used are easily available and can be obtained from plant parts almost effortlessly as compared to the traditional methods. 6. Because it is a green approach which cuts down on energy and uses simple aqueous solvent for fabrication, it evidently produces zero or very fewer contaminating substances, making it eco-friendly and nonhazardous. The advantages of Green synthesis of nanoparticles though numerous can be summed up in the following points (Fig. 6).

Fig. 6 Advantages of biosynthesized nanoparticles

Easy availability Industrial scale application

Nonhazardous

MERITS Use of Aqueous solvent

Costeffective Simple method

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Factors Affecting the Quality of Plant Mediated Nanoparticles There are various factors which play a significant role in determining the quality of nanoparticles produced by using plants: • • • • • • •

Protocol used Concentration of plant extract Nature of reducing agents used pH of the Reaction mixture Time of incubation Temperature Light intensity, etc.

So far, green synthesis has mainly been used with respect to metallic nanoparticles, especially gold and silver, because of their widely known properties and applications. The fabrication of such nanoparticles is done by incorporating the desired plant extracts with metal salt solutions like HAuCl4.3H2O [Gold (III) chloride trihydrate] for gold biosynthesis and making them undergo a reduction reaction in optimized conditions. The product obtained is then stabilized/capped to give biosynthesized green nanoparticles. An additional step is done after stabilization which is characterization for determining the size distribution, surface area, wettability, porosity, zeta potential, adsorption potential, orientation, crystallinity, etc. Several techniques of characterization are used, namely, UV-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), etc. [27]. Reaction: HAuCl4.3H2O + plant extracts ! Au NPs + by products

Steps Involved in the Plant-Mediated or Phytochemically Synthesized Gold Nanoparticles The phytochemicals used in the process show dual nature and act as oxidizing and reducing agents at the same time, making it primarily a single-step, energy efficient, cost-effective, safe for clinical research, and environmentally benign process. Following are the steps involved in plant-mediated/phytochemically synthesized AuNPs: 1. Isolation of plant extract/phytochemical is done. They are usually watersoluble and comprise of metabolites like alkaloids, amino acids, flavonoids, terpenoids, etc. The basic operations are prewashing, centrifugation, freeze drying, and then identification mostly by chromatographic techniques. 2. Reduction reaction. The plant extract which is isolated is then made to undergo a reduction reaction with desired metal salt solutions, in this case- HAuCl4.3H2O (Gold (III) chloride trihydrate). This reaction takes place in optimized conditions of temperature, pH, radiation, light intensity, salt concentration, plant extract concentration, etc., while constant stirring [28]. (Optimization).

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Extraction of plant products/parts to obtain pure extract by heat stirring or filtration. Redox reaction of phytochemicals with HAuCl4 to create biosynthesized AuNPs. Optimization of temperature, incubation time, pH, plant extract concentration etc Centrifugation and subsequent sedimentation of gold nanoparticles. Characterization of AuNPs by UV-vis, XRD, TEM, FTIR, AFM, EDX, DLS, Zeta potential etc. Fig. 7 Steps involved in the plant-mediated synthesis of gold nanoparticles

3. Capping and stabilization. When the reaction is complete, a characteristic color change is observed in the apparatus which is indicative of the product formation. Followed by the bioreduction reaction, capping and stabilization of nanoparticles obtained is achieved by the phytochemicals/plant extracts only to stabilize them at their size and prevent their aggregation. That is why phytosynthesis of AuNPs is economical and less hazardous. 4. Characterization. Various characterization techniques are utilized to understand the potential of the formulated nanoparticle and its unique properties for better application. Major techniques used are electron microscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visible spectroscopy (UV-Vis), etc. After all these steps are achieved, the desired nanoparticles with physical, chemical, and biological properties are obtained [29, 30]. The entire steps of plant mediated synthesis of gold nanoparticles are summarized in Fig. 7.

Biomedical Applications of AuNPs Due to their unusual properties and numerous surface functionalities, AuNPs play multiple roles in different procedures. Some of these include their use as: • Biological sensors: Gold nanoparticles show a number of colors, because of which they have been used for visualization purposes. SPR-based, enzymatic, surface-enhanced Raman spectrum (SERS)-based, fluorescence-based, electrochemical, colorimetric gold nanobiosensors have been assembled and used for

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detection of many biological compounds like proteins, enzymes and their activities, oligonucleotides, etc. [31, 32]. Bio-imaging: For color-based imaging, organic fluorophores have been used conventionally. But it has been reported that they have limited application due to narrow excitation. AuNPs proved to be better bio-imaging agents due to their flexible features related to size and surface modifications. They are increasingly being used in techniques like photo acoustic imaging, MRI, such as X-ray computed tomography, etc. [33]. Synthetic skin: Scientists in Israel had created a touch and pressure sensitive ultrathin film, with the help of spherical gold nanoparticles, of 3–6 nm diameter along with polyethyleneterepthalate (PET). The manufacturing process is cost effective, but the challenge lies in connecting the artificial film with the brain. Mostly, the film can be used in prosthetics. Cure for heart diseases: Cardiac cells cannot multiply, because of which selfrepair is nearly impossible. AuNPs contained patches have been found useful for curing heart damage. Heart being myogenic in nature creates a hurdle in matching the rhythm of the patches with its own pace. Cancer treatment: Photo thermal effect of AuNPs can destroy tumor cells [34]. Gold nanorods are incorporated with cancer-specific compounds and exposed to radiation. Only those nanostructures are selected that have SPR frequency in the range of 650–900 nm, known as the near-infrared (NIR) region. This region is where both water and tissue hardly absorb any radiation. After exposure, the cancer tissue is locally heated which terminates the tumor [35]. Higher circulation of AuNPs in the blood and better sensitivity of tumor cells result in easier termination of cancerous tissues. Moreover, bio-imaging using AuNPs is applied frequently for tumor detection. Gold nanoparticles can be further conjugated with beneficial functional groups that improve the specificity in recognition of the cancer cells [36, 37]. Enhanced drug delivery: Due to the presence of attributes like larger biocompatibility and surface-to-volume ratio, AuNPs are extensively used as drug delivery agents. Drug particles can be loaded on to gold nanoparticles and controlled release of these at target site is then possible. Gold nanorods are also being widely used to create vaccines against viruses (Fig. 8).

Gold Nanoformulations in Wound Healing Metal nanoparticles like gold, silver, zinc oxide, etc., have been considered extraordinary instruments for wound healing. Gold nanoparticles are described as prime candidates for utilization due to their easy and cost-effective synthesis, lower toxicity, chemical stability, the capability of absorbing near-infrared radiation, and antibacterial activity. Arafa et al. described antibacterial properties of AuNPs in both in vitro and in vivo studies, wherein they acquire thermo-responsiveness by tuning the SPR. AuNPs show bactericidal properties by hindering the uncoiling of DNA

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Bio-sensing

Bio-imaging

Cancer

Artificial skin

Heart diseases

Drug delivery

Vaccines

Blood clot regulation

Brain implants

Sterlization systems

Fig. 8 Biomedical applications of gold nanoparticles in numerous fields

during replication and transcription. They are also found to kill multidrug-resistant bacteria like Staphylococcus aureus. Furthermore, they aid wound healing by acting as antioxidants and interrupting the formation of reactive oxygen species. Additionally, gold nanoparticles also show significant anti-inflammatory activity due to increased release of angiopoietin-1 and vascular endothelial cell growth factor. Another feature is enhanced skin penetration which enables higher efficiency in wound healing. AuNPs also are known to exhibit a positive effect on the healing of infections photo-bio modulation therapy. Repair of affected collagen fibers is also promoted by antimicrobial effects of AuNPs. Many of the methods involved in synthesis and applications of the mentioned AuNPs are hazardous in nature due to the involvement of toxic chemicals like several inorganic compounds, reducing agents, stabilizers, and the by-products formed. High energy radiations used are also harmful. It is essential to develop eco-friendly ways which are in addition economically feasible for producing as well as using these nanoformulations to reduce their toxicity to a minimum. Principles of green chemistry have been recommended to improve the procedures used in gold nanoparticle formulation and to enhance sustainability. Green synthesized gold nanoparticles should be used more often. Several studies reveal phytochemically created gold nanoparticles to be excellent candidates for this purpose.

Applications of Gold Nanoparticles Synthesized by Green Method in Wound Healing Biosynthesis or green synthesis has created new avenues in nanotechnology and medicine and the usage of gold nanoparticles with plant extracts and metabolic products has proved to be more efficient and efficacious than normally produced gold nanoparticles with respect to their production as well as function. Their roles in all areas of medicine especially wound healing are highly advantageous and

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beneficial. Substances like fenugreek seeds containing metabolites like flavonoids, when used with gold nanoparticles, have proved to act as surfactants for the said nanoparticles and have also stabilized the electrostatic stabilization of the tested gold nanoparticles [38]. Apart from fenugreek seeds, the extracts of gold petals, Mirabilis jalapa, and others have also been used for stabilized, and eco-friendly synthesis of gold nanoparticles. Additionally, the extracts from medicinal plants like Nyctanthes arbortristis are able to confer antipathogenic activity to gold nanoparticles that are highly useful in wound healing [39]. Some wound healing applications of phytochemically synthesized gold nanoparticles are as follows: 1. Anti-inflammatory: Anti-inflammation is a highly essential step in the process of wound healing. Scientists have for a long time searched for natural ways to reduce inflammation while healing wounds and recent studies show that biosynthesized gold nanoparticles are able to induce the healing process by giving a boost to inflammatory mediators like T-lymphocytes, B-lymphocytes, and other enzymes which helped achieve tissue regeneration via anti-inflammatory mechanism [40]. 2. Anti-microbial: Green synthesized gold nanoparticles have paved the way for wound healing to become highly efficient by showing properties like antibacterial, antifungal, etc. They also offer a solution in management of drug resistance problem in pathogens [41]. Recently, it was found that gold nanoparticles when coated with aqueous leaf extracts of Mussaenda glabrata inhibited the growth of harmful microbes like Escherichia coli, Bacillus pumilus, Staphylococcus aureus, Aspergillus niger, Pseudomonas aeruginosa, Penicillium chrysogenum, etc. [42]. Also, it was found that green synthesis of gold nanoparticles with plant extracts of Abelmoschus esculentes confer them antifungal property against fungi like Puccinia graminis, A. niger, Candida albicans, etc. 3. Antioxidant: The process of oxidation in places of wounds can lead to cell damage and degeneration and diminish the rate of wound healing. The normal synthetic antioxidants used cause unfavorable effects on health. That is why, nanoparticles, especially gold, are a comparatively better solution for antioxidant activity in wounds. It has been studied that ability of normal antioxidants when conjugated with biosynthesized gold nanoparticles shows increased activity in healing wounds [43]. Apart from this, gold nanoparticles also reported extraordinarily enhanced antioxidant activity when created with help of fruit extracts of cannonball fruit which is Couroupita guianensis [44]. Some of the remarkable applications of phytochemically synthesized/plantmediated gold nanoparticles are listed in Table 1. It is highly evident that the gold nanoparticles when biosynthesized and mediated with plant-products/extracts show increased and enhanced action as compared to normally produced AuNPs. Not only do the green AuNPs show better activity but their production process is relatively simpler, cost effective, energy efficient, nonhazardous, and eco-friendly than other synthesis. Their stability is increased, toxicity

55–98

90–150

~100 15–25

Stem

Leaves

Flowers

Seed

Cassia fistula

Mentha piperita

Mirabilis jalapa

Trigonella-foenum graecum

20–30

Leaves

Acalypha indica

Size of AuNPs nm)

Part of plant used

Plant

Spherical

Spherical

Spherical

Spherical

Spherical

Shape of AuNPs

Table 1 Some examples of plant-derived AuNPs and their wound healing applications

Flavonoids

Polysaccharides

Menthol

Hydroxyl group

Quercetin, plant pigment

Plant metabolites involved

Catalytic

Antimicrobial

Antibacterial

Antihypoglycaemic

Antibacterial

Applications in wound healing

[49]

[48]

[47]

[46]

[45]

References

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is decreased, and harmful effects and limitations that are shown by conventional AuNPs are not a characteristic of phytochemically produced/mediated gold nanoparticles, thus making them the science of our future [50, 51].

Concluding Remarks and Future Prospects The usage of plant derivatives in biosynthesizing metallic nanoparticles especially gold has peaked in the last two decades and the graph seems to be going upwards as we move forward. The many advantages of green synthesis of nanoparticles render a myriad of opportunities to scientists for testing novel theories based on different combinations of plant extracts/products with numerous shapes/sizes of compatible nanoparticles discovered till now. Due to this diversity, the potential of phytonanotechnology is observed in a number of fields like pharmaceuticals, therapeutics, medicine (cancer, diabetes, neurological disorders, wound healing, etc.), renewable energy production, etc. In wound healing, plant-mediated gold nanoproducts alone have shown huge potential which justifies the fact that nanotechnology is the future and we have to keep striving in the right direction to get the desired solution. Since this is the new advent of nanotechnology, exploration in this field is required to correctly and deeply understand the phytochemicals and their mode of action in wound healing and how they are able to direct crucial processes of tissue regeneration and antioxidation. It is also needed that the number of all plant extracts/products be documented that can be useful in wound healing while putting due emphasis on researching for newer phytochemicals as phytonanotechnology paves the way for a future which is energy efficient, healthier, safer, and eco-friendly; thus, an opportunity of such high degree must not be lost.

Important Websites https://www.britannica.com/science/nanoparticle https://nanotechnology.imedpub.com/synthesis-of-gold-nanoparticles-using-plantextract-an-overview.php?aid¼7649 https://www.mdpi.com/journal/biomolecules/special_issues/green_synthesis_ nanoparticles https://www.understandingnano.com/nanotechnology-wound-healing.html https://onlinelibrary.wiley.com/doi/abs/10.1002/lsm.22614 https://rjptonline.org/AbstractView.aspx?PID¼2021-14-2-102 https://www.x-mol.com/paper/1313952619503521792?recommendPaper¼547743 https://jnanobiotechnology.biomedcentral.com/articles/10.1186/s12951-018-04084#:~:text¼Among%20the%20available%20green%20methods,2). https://www.nanoscience.com/techniques/nanoparticle-synthesis/ https://www.grin.com/document/509334

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44. Sathishkumar G, Jha PK, Jha R et al (2016) Cannonball fruit (Couroupita guianensis, Aubl.) extract mediated synthesis of gold nanoparticles and evaluation of its antioxidant activity. J Mol Liq 215:229–236 45. Krishnaraj C, Jagan EG, Rajasekar S, Selvakumar P, Kalaichelvan PT, Mohan N (2010) Synthesis of silver nanoparticles using Acalypha indica leaf extracts and its antibacterial activity against water borne pathogens. Colloids Surf B Biointerf 76(1):50–56 46. Daisy P, Saipriya K (2012) Biochemical analysis of Cassia fistula aqueous extract and phytochemically synthesized gold nanoparticles as hypoglycemic treatment for diabetes mellitus. Int J Nanomedicine 7:1189–1202 47. MubarakAli D, Thajuddin N, Jeganathan K, Gunasekaran M (2011) Plant extract mediated synthesis of silver and gold nanoparticles and its antibacterial activity against clinically isolated pathogens. Colloids Surf B Biointerf 85(2):360–365 48. Vankar PS, Bajpai D (2010) Preparation of gold nanoparticles from Mirabilis Jalapa flowers. Indian J Biochem Biophys 47(3):157–160 49. Aswathy Aromal S, Philip D (2012) Green synthesis of gold nanoparticles using Trigonella foenum-graecum and its size-dependent catalytic activity. Spectrochim Acta Part A Mol Biomol Spectrosc 97:1–5 50. Noruzi M (2015) Biosynthesis of gold nanoparticles using plant extracts. Bioprocess Biosyst Eng 38(1):1–14 51. Cabuzu D, Cirja A, Puiu R, Grumezescu AM (2015) Biomedical applications of gold nanoparticles. Curr Top Med Chem 15(16):1605–1613

Part X Consumer Nanoproducts for Food

Consumer Nanoproducts for Food

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Prasanth Rathinam, Sherly Antony, R. Reshmy, Raveendran Sindhu, Parameswaran Binod, and Ashok Pandey

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current Status on Food and Agriculture Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current Status on Food Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Current Status in Agriculture Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensors for Environmental Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology on Preservation and Shelf Life of Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology and Food Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulation of Nanotechnology on Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Food and Agriculture Associated Nanoparticles Available in Market . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Acceptability and Nanotechnology on Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Health Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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P. Rathinam Department of Biochemistry, Pushpagiri Institute of Medical Sciences and In-charge of Biochemistry Laboratory and Medical Biotechnology Laboratory, Pushpagiri Research Centre, Thriuvalla, Kerala, India S. Antony Department of Microbiology, Pushpagiri Institute of Medical Sciences and In-charge of Microbial Technology and Infectious Diseases Laboratory, Pushpagiri Research Centre, Thiruvalla, Kerala, India R. Reshmy Post Graduate and Research Department of Chemistry, Bishop Moore College, Mavelikara, Kerala, India R. Sindhu (*) · P. Binod Microbial Processes and Technology Division, CSIR-National Institute for Interdisciplinary, Science and Technology (CSIR-NIIST), Thiruvananthapuram, Kerala, India A. Pandey Centre for Innovation and Translational Research, CSIR- Indian Institute for Toxicology Research (CSIR-IITR), Lucknow, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_50

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Regulatory Aspect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 730

Abstract

The food and agriculture sector, both in developing and developed countries, had witnessed a phenomenal revolution with the help of nanotechnology since 2003. This smart technology has been facilitating transformations in the agriculture sector, specifically through the means of (i) nano-modification of seeds, fertilizers, and pesticides (ii) interactive smart foods like nano-encapsulated flavours, nano-emulsions and anti-caking agents (iii) novel food fortification and modification strategies to elevate neutraceutical values with enhanced bioavailability of nutrients. In addition, nanomaterials were also developed to evaluate cultivation of food, quality and food safety, and checking of ecological circumstances. Presently nanotechnology has a global impact on the food industry with predicted profit over 3 trillion USD, and an abundance of nearly 6 million employment in the surging industries worldwide. These food associated ventures are participated in the growth and advertising of nanotechnology driven foods and related products with improved attributes like performance, aesthetic taste, and security. Amazingly, there is an abundance of such goods that are developed and have now been supplied by these food industries over the past decade. In this chapter, the most recent nanotechnology driven prospects in cuisine and cultivation sections are discussed as emphasizing nano-products that reached the consumer, those under development, associated regulations and challenges from selected recent studies. Keywords

Nano-products · Nanotechnology · Nano-materials · Food processing · Agriculture

Introduction Nanotechnology has begun swaying everyday life since the early guideline issued by the United States Department of Agriculture on 9th September, 2003 [1]. Presently with the increased research enthusiasm on nanotechnology, it practically comprise the whole facets in the food and cultivation trade marching from farming, watering and/or its quality improving, food refining and packaging, veterinary feed, and aquaculture [2–5]. By 2020, nanotechnology is estimated with a recent global economic impact of around $3 trillion and projected to provide 6 million associated labourers [6]. As a matter of fact, many industries are associated in developing and promotion of nanotechnology derived commodities intended for bettering manufacture adeptness, food attributes and security. In fact, a large number of products have reached the market and currently been adopted in the food industry. Indeed main

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stream of them are food containing materials but not for direct consumption by people. Except for metal oxides like (TiO2 and Fe2O3), no other nanomaterial containing products are put for direct human consumption, while these metal oxides are used as food pigments and anti-microbial agents, already [2, 4]. Since nanotechnology derived products are used in various sectors, its public acceptance is of utmost importance [7–9]. It ultimately determines the actual application and/or acceptance by the customers [10]. Regardless of the public acceptance and rejection, disposal of nanomaterial wastes will have a toll on the habitat and bring out definite brunt on the plants, animals, and related ecological communities. In the light of unavailable data about their impact on the environment, the proper disposal methods have not been regularized yet by the scientific community, industry, and the governing bodies [10, 11]. This chapter briefly covers the most recent nanotechnology driven opportunities in food and agriculture sectors are discussed as emphasizing nano-products that reached the consumer, those underdevelopment, associated regulations and challenges from selected recent studies. The chapter may also emphasize the immediate need to bring insights towards estimating the danger and harmfulness for the purpose of legislation and public acceptance.

Current Status on Food and Agriculture Nanotechnology Nanotechnology, being a rapidly developing sector, is having its effect in transforming various fields related to day to day life. Traditional sectors like food and agriculture segments also have faced the nanotechnology guided revolutions. Nanotechnology deals with materials with no less than one aspect in the scope of 1 to 100 nm. As a matter of fact nanomatrials have significantly revolutionized each and every aspect of food and agriculture sectors, from the fields to the plates [12]. Numerous nanomaterials have revealed inspiring capabilities in each feature of the food and agriculture industry. The food industry in all its facets from the ingredients to packaging to methods of food analysis is using nanotech tools [12]. This results in numerous applications which are used for improving food production, processing, packaging, and storage. In addition, nanotechnology is used in targeted nutrient delivery as well. Biosensors for food quality monitoring, smart food packaging systems and nanoencapsulation techniques are some of the emerging applications of nanotechnology. Similarly, the agriculture sector has numerous nanotechnology inspired tools like nano-modification of seeds, herbicides, insecticides, intended genetic engineering, conservation, agrichemical distribution, and sensors to track habitat circumstances [2, 12].

Current Status on Food Nanotechnology There exists a discrepancy among the organic nanosystems and nanotechnology influenced nanomaterials that synthesized for a particular specification. Analyzing

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the managerial necessity and interpretations, unlike the nanotechnology influenced materials; organic nanosystems are not an outcome of nanotechnology [13]. Food comprises many nanostructured elements, including components which reach out to nanoscale sizes (e.g., milk proteins, and micelles/lathers/colloids). While nanotechnology inspired nanomaterials that synthesized for a particular specification has motivated many aspects of food industry. Through, the potential use of nanotechnology has been identified in each sections of the food business, the major focus areas include: (1) food processing (entrapping and enhancing the flavours or odours with the help of encapsulation techniques, quality and/or texture improvement using gelation and viscosifying agents) (2) mineral and vitamin supplements (highly stable nutraceuticals with enhanced bio-accessibility) (3) Packing of foods (contamination and/or spoilage sensors; anti-counterfeiting gadgets, safeguarding from harmful rays like UV, and sturdier, more resistant polymer coatings) (4) agriculture (insecticide, manures, composts or vaccine transfer, animal and plant pathogen identification and/or labelling, and directed genetic manipulations). As a matter of fact, food nanotechnology-based innovations have revolutionized the food quality and safety to the end-users [13, 14].

Food Processing Food processing comprises the course of converting raw elements to produce commercial food harvests that prepared, and delivered with comfort, and ingested safely by the end-user. The food processing sector includes the conversion of prepared elements by physical/chemical methods and/or by other techniques. Besides the primary processing techniques like chopping, slicing, freezing, or desiccating, leading to secondary goods, representative activities in food processing involve shredding and softening, condensation, emulsification, and cooking (using various culinary techniques); diverse preservation and sterilization methods (pickling, and pasteurization); and packaging techniques like canning, bottling and tinning [15]. Such techniques are formulated and designed not only to keep the flavour and quality of the food and its ingredients intact but to protect from various means of food spoilage also. Food processing makes use of methods like irradiation, ohmic heating, and high hydrostatic pressure to prevent microbial infestation and guided food spoilage [15]. With the aid of food processing, the shelf life can be increased and the producer can transfer food over distances without any spoilage. Food processing benefits the customers, by providing the availability of different kinds of foods such as seasonal ones (peas and corns) throughout the year. Producing and consuming fresh food being a concern today, food processing also involves in producing healthier food containing micronutrients as well [16]. Nanotechnology influenced nanomaterials hold a significant part in food handling including the integration of vitamins and minerals, agents for gelling and viscosifying, efficient distribution of nutrients, fortification of nutraceuticals, and enmeshing of flavours through nanoencapsulation [17]. Nanostructured food materials claim to offer improvement in taste, texture, and consistency. By increasing the shelf-life of various food materials nanotechnology reduced the food wastage due to spoilage. Nanosensors are used to identify the incidence of contamination, toxins,

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and other food pollutants [18]. The use of nanocarriers for the distribution structures for food flavours and seasonings without altering the basic morphology of food. In fact, nanotechnology driven formation of encasing systems, simple and complex solution systems, and biocompatible matrices for packaging, offers effectual distribution systems. In addition, nano polymers are used in food packaging substituting conventional materials [15]. Nanoparticles exhibit superior encapsulation properties and release dynamics than the conventional encapsulation systems. Nanoencapsulation can mask odours and/or tastes, control the rate of discharge of active components, guarantee time dependant availability at the target, protect from adverse conditions like moisture and heat, and prevent biological and/or chemical degradation, storage, exploitation and displaying compatibility with additional composites of system. Indeed, nanoencapsulation can penetrate deep into the tissues using their lesser size and mediate target-specific distribution of active principals. Man-made and organic polymercentred nanotechnology driven encapsulation delivery schemes with enhanced bioavailability and preservation, are being developed. As a matter of fact the evaluation of nanotechnology-based improvement in food processing is on the basis of; improvements in food quality, presentation, taste, nutritional value, content, and expiration [2, 12, 15, 16]. Nanotechnology influenced systems have brought about a range of improvements in the quality of food, and its taste. Nanoencapsulation techniques revolutionized the use of phytocompounds with important pharmacological activities in food processing. The majority of these phytocompounds have properties like high reactivity, instability, and have poor solubility which limited their use in the food industry. Nanoscale capsulated form of plant pigment anthocyanin and dietary flavonoid: routin encapsulated in ferritin nanocages are examples of the aforesaid advancement which are currently used for controlling the flavour release and culinary balance in foods [19–21]. In addition, such encapsulations enhance the stability of these compounds towards thermal and UV radiation. Deliveries of lipid-soluble bioactive compounds are now achieved with the use of nanoemulsions which not only enhances the water dispersion property but the bioavailability as well [22]. Metallic nanomaterials like titanium dioxide and silicon dioxide are used as food nanomaterials and utilized as colour and/or flow agents. Whereas SiO2 nanomaterials were used as a flavour and/or fragrance carriers in the food industry [23, 24]. Nanoparticles due to their subcellular size are now used to improve the bioavailability of nutraceuticals for enhanced drug bio-accessibility in comparison to the conventional methods. Components like bio-macromolecules and vitamins are liable to extreme pH conditions and enzymatic degradation at the gastrointestinal system and non-capsulated form of these active components fails to achieve the required bioavailability due to their low water solubility [25]. Bioactive compounds based nanoparticles in the form of tiny capsules attain the aim of improved delivery and bioavailability. In addition, this edible capsule machinery can be further extended for the delivery of fragile micronutrients that required in the daily uptake to meet significant health benefits [16]. Effective and targeted delivery of nutrients like proteins and anti-oxidants shall be achieved using transforming them into miniature

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capsule forms using various techniques like nanocomposite formation, nanoemulsification, and nano structuration. In addition, polymeric nanoparticles are also used for encapsulation for the transport and delivery of various bioactive compounds with potential health benefits to the targeted regions [26].

Food Packaging Nano-based food packagings offer enhanced penetrability to have moisture and gas, improved stability and environment friendly to that of conventional packaging material. In addition they possess several advantages like barrier properties, antimicrobial activity, pathogen detection ability (with the help of nanosensors) and consumer alerting mechanisms about the safety status of food [27]. Nanoparticles with various properties can be used as active packaging and/or coating material. Organic and inorganic compounds with antimicrobial property and their use in polymeric matrices are considered for improving the food packaging. Organic compounds being sensitive to the extreme conditions that prevail in food processing steps do not fit for packaging and coating materials. On the contrary inorganic nanoparticles exhibited strong antimicrobial property in reduced accumulations and exhibited more resistance to unfavourable conditions. Hence inorganic nanomatrials as antimicrobial packaging, when comes in contact with the food or the inside space to exhibit bactericidal and/or bacteriostatic properties [28]. Many substances with potent antimicrobial activity like metals, metal-oxides, and chitosan have been recently developed as packaging material [16]. Nanotechnology derived food packaging is categorized as following: • Nanoparticles for improved packaging: Here the nanoparticles are mixed with the polymer matrices for achieving the improvement in the gas barrier properties, temperature, and humidity resistance. Nanoparticles use as an improved packaging material is approved by various national and international authorities [28]. • Nanoparticles as an active packaging: The nanoparticles in the packaging will be directly interacting with the foodstuff and the microenvironment within for enhanced safety. Majority of these nanoparticles will be utilizing the mechanism of antimicrobial property besides the oxygen or UV scavenging machinery [15, 28]. • Nanoparticles as intelligent / smart packaging: These packagings are designed to sense the physiochemical changes in the food, sensing explicit food-related contaminants and/or detection of specific gases from food spoilage. In addition, the development of ‘smart’ packaging can track food safety and avoid counterfeit. Such devices are currently been used by Nestle, British Airways, and MonoPrix Supermarket [15, 16, 28].

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Nanotechnology driven novel devices are now widely used in food wrapping trades. These devices comprise nano-devices, automatic noses, range biosensors, nanaocantilevers, solution-based nanoparticles, and test strips with nanoparticles. Packing matrix containing Nanosensors could trace the external and/or internal niche of food components, capsules, and filling tins aiding in tracing till reaching the end-user. Nanosensors implanted in plastic packaging matrix can detect gases that produced due to food spoilage and change the colour to alert the consumer. Similarly, oxygen scavenging films made of silicate nanoparticles can keep the freshness of the food for a longer period of time. In addition, these films can prevent the growth of mould and other microbes in refrigerators and packaged foods, respectively. Implementation of nanotechnology driven food packaging will result in cost reduction and attempts should be made from the government to accelerate the development of cost-effective and efficient nano-packaging strategies [15, 28].

Current Status in Agriculture Nanotechnology The farming sector make use of nanotechnology to upsurge food cultivation with improved yet targeted nourishment content, value assurance, and care. Effectual use of manures, insecticides, herbicides, developmental factors, controllers are essential for improving crop production and ethical yet controlled use of aforesaid factors are possible through nanocarriers. In comparison with the commercial atrazine, poly (epsilon-caprolactone) based carrier for herbicide atrazine, exhibited significant herbicidal activity in mustard plants [29]. In addition, these nanocapsules showed less or no side effects to plants in comparison with the commercial atrazine. Other widely used nanocarriers are silica and polymeric NPs with modified-release mechanisms used for the controlled delivery of pesticides [30, 31]. In addition, nanoscale carriers are also used to achieve the controlled and slow release of these factors in agriculture. Nanotechnology driven strategies are now been used to improve the crop yields without damaging the environment (known as ‘precision farming) [32]. Nanoparticle facilitated nucleic acid transmission was utilized to advance pestresistance in plants. In fact, many nanomaterials can serve as insecticides with improved pest sensitivity and less/no toxicity. Metal oxide nanoparticles with their inborn toxicity are studied to protect plants from pathogens. Zinc oxide nanoparticles can effectively inhibit diverse pathogenic microbes like fungi and bacteria [33, 34]. Unlike the conventional mineral fertilizers, the development and use of nano fertilizers bring about the novel solution(s) for the advancement in the agriculture sector. Nano fertilizers help in preventing nutrient loss and aid in nutrient incorporation. Nanoscale forms of micronutrients are been utilized as nano fertilizers (Manganese, Copper, Iron, Zinc, Molybdenum, Nitrogen and Boron) [35, 36]. It is eminent that the use of other nanomaterials like carbon nano-onions and chitosan NPs, could help in increased production and value of yield. Applications and acceptability of nano fertilizers have motivated and will transform the fertilizer manufacture businesses by the subsequent decade [37–39].

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Sensors for Environmental Study Nanotechnology driven Nanosensors (wireless in specific) have been developed to monitor various aspects of agriculture sectors. These sensors can detect chemicals in the environment (pesticides and herbicides), and trace amounts of pathogens in the agriculture systems. Such real-time monitoring systems will help to understand possible harvest damages and help in improving crop manufacture through the appropriate and rational practise of nano fertilizers, nano pesticides, and nanoherbicides. Real time tracking of propineb fungicide in an aquatic niche is possible with the help of copper dopped mont morillonite, which have a lower limit of around 1μM [40]. In addition graphene-based nanomaterials are used to detect contaminants in wastewater and aid in improving the water quality, with a potential application in aquaculture [41, 42]. An array of nanomaterials like Cu, Au, Ag nanoparticles, and carbon nanotubes are in pipeline as Nanosensors for the in situ monitoring of crop health and the surrounding environment [43–45].

Nanotechnology on Preservation and Shelf Life of Foods A major problem that associated with the functional food sector is the degradation of the bioactive components and/or inactivation due to the unreceptive environment until it reaches the target site or to the end-user. Prolonging the service life and/or slowing the degradation process of the bioactive counterparts are achieved though nanotechnology derived techniques like encapsulation and edible nano-coatings [15, 46]. Nanotechnology derived, eatable coatings on the food materials will act as a barricade to humidity and aid in efficient exchange of gas whereas in some cases it delivers food additives, and agents for food quality improvement. Nano-coatings are more advantageous as they boost the servable life of the factory-made foods, though the package is unwrapped. It is well studies that the alterations to interfacial surrounding layer properties will lose the pace of the degradation processes. Curcumin, the least stable component in turmeric, exhibited reduced bioactivity and found to be stable to pasteurization after nanotechnology derived encapsulation [3, 46].

Nanotechnology and Food Safety Nanotechnology and nanomaterial associated food safety is of significant health concern, in fact, food borne diseases that associated with microbial pathogens account for about 20 million cases/ annum, around the world. Food safety concerns with the fact that, the food does not cause any harm to the end user either during the process of food preparation and/or when eaten. With respect to the food safety aspect all the foods should be protected from physio-chemical and organic adulteration by the means of transformation, handling and delivery [28, 47].

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Regulation of Nanotechnology on Food Regulations of nano-foods will help to revolutionize the role of nanomaterials in food segment. The regulatory framework faces threats because of the fundamental and technical complications in nanotechnology which are further enhanced by the lack of a unidirectional yet extensive supervisory structure to safeguard end-user safety [48, 49]. Impairments during the risk evaluation of nano-foods had been associated with factors like limited data, lack of models reflecting real-world scenario of nanotechnology derived materials, and reservations regarding the governing bodies [49, 50]. The relaxed rate of risk analysis investigations is also a reason for making the food-related regulations, a difficult task. Due to the potential migration of nanoparticles the risk and/or safety assessment of food-related nanomaterials are essential. Considering the growing interest in nanotechnology and related food products, the synthesis and improvement of nanotechnology based products have not considered the safety of end-users [49, 51]. In fact, the effective directive in foodnanomaterials depends on the inclusiveness of descriptions, obligations of products, and enlisting of nanoproducts that acceptable in the food sectors [49, 52].

Food and Agriculture Associated Nanoparticles Available in Market Commercialized nanofood and agriculture products and their applications are shown in Table 1.

Consumer Acceptability and Nanotechnology on Food The commercial triumph of food merchandise is estimated based on consumer acceptability. In addition to the quality and nutritional values, in the case of foods that irradiated and with intended nucleic acid modifications, the reception is affected by the concerns over health and environment. The reluctance of end-users towards the purchase of nanotechnology guided food products might be due to health concerns [16]. Customer knowledge regarding food products significantly affects the acceptance. In addition necessary steps should be implemented to enhance the dissemination of information about the role of nanotechnology in food industry, which will improve the trust and perception among the end-users. To improve the end-user acceptance regular and consistent efforts should be made on nano food and related products by administrations, manufactures, and other establishments [49, 61].

Health Implications The various properties of nanomaterials play a major role in their effect on the human body. Cationic hydrophilic nanoparticles shown to have significantly increased circulation time with respect to their counterparts [62, 63]. With the available study data, it

Health drink

Food and beverage Food and beverage Food

Food supplements Korean fermented cabbage dish Health supplement Food supplements Beverage

Nanoceuticals slim shake

NanoSlim beverage Oat nutritional drink Tip top bread

Nano B-12 vitamin spray Kimchi

Food additive Health benefits for toddler Food storage Food storage Food storage Food storage Sustain beverage Nanosized powders

Beverage Health drink

Nanotea Fortified fruit juice

Neosino Aquanova Oat chocolate and oat Vanilla nutritional drink Aquasol preservative Nano silver baby Milk bottle Food storage containers Large kitchen appliances Nano-silver salad bowl Nano storage box Novasol Nanoceuticals™

Type of product Food and beverage

Product name NutraLeaseanola active oil

Table 1 Commercial nanoproducts and their applications

Germany Germany Oat chocolate and oat Vanilla nutritional drink Aquanova Baby dream ® co. ltd. (south BlueMoonGoods, LLC, USA Daewoo ® refrigerator, Korea Changmin chemicals, Korea BlueMoonGoods™, USA Aquanova ®, Germany RBC life sciences ® Inc. (USA)

NanoSlim Toddler health, Los Angeles, USA George Weston foods, Enfield, Australia Nanotech, LLC (USA) Korea

Shenzhen Become industry Co. Guangdong, China High Vive. Com, USA RBC Lifesciences, Irving, USA

Manufacturer Shemen, Haifa, Israel

Nanoscale micelle Nanosilver Silver Nanosilver Silver Silver Nanomicelle Nanocolloidal silicate mineral and Hydracel ®

Conversion of vanilla or chocolate into nanoscale Liquid suspended nanoparticle – Nanosized self-assembled liquid structures Nanodroplets NanometricLactobacillus plantarum Silicon Nanomicelles 300 nm of iron particles

Nanomaterial Nanosized self-assembled liquid structures (NSSL) Nanoselenium Micelles 5–100 nm in diameter

[57] [16] [16] [16] [58] [16] [16] [16]

[55] [57] [25]

[55] [56]

[54] [54] [16]

[54]

[16] [16]

References [53]

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OilFresh™ Bioral

Lypo-Spheric vitamin C Daily vitamin boost SoluE SoluC Megace ® ES

Supplements Fortified Jambu juice Vitamin E Vitamin E Nanocrystal dispersion with micronized particles Nanoceramic product Nanocochleate

LivOn labs, USA Hawaii, USA Aquanova Aquanova Par pharmaceutical, Inc., Bristol- Myers Squibb company, new US-based Oilfresh corporation BioDelivery sciences Interna-

[16] [16] [16] [16] [16] [59] [60].

Liposomal nanospheres Silver nanoparticle – – – – Calcium ions in GRAS phos-

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is confirmed that particles with increased circulation time affect the micro-circulation in the host body. Particles in the micro-circulation may affect the lining of arteries and veins, their function, and/or thrombus may occur [64]. In addition, these ultrafine particles may get inhaled and can cause adverse cardiovascular effects. Brain, being the well-vascularized organ aforesaid adverse effects were observed in studies using immortalized brain microglial cells [65, 66]. As per the various literatures, some of these nanoparticles are capable to cross the blood-brain barrier, interact with cellular metabolism. Though the exact mechanism by which the toxicity due to nanomaterials is not completely understood, it is supposed that the major mechanism is through the oxidative stress mechanism [62]. In addition to the properties of nanoparticles, their concentration, and exposure duration, the possibility of toxicity is also influenced by the biological state of an organism and/or individuals susceptibility [67–69]. Chronic inflammation due to the activation of oxidative stress is potent enough to cause fibrosis, mutations, cancers, and secondary mutation. Carcinogenicity and genotoxicity are considered to be the major adverse effects associated with the nanoparticle. Toxicity studies related to the metallic nanoparticles suggested about particle size dependant ability for genotoxicity in human epidermal cells. Persistent particles of substances like asbestos may bring about developing granulomas and lung associated fibrosis. In addition, inhalation of TiO2 (10 mg/m3) may result in lung tumours as well [67].

Consumer Safety As the influence of nano science in the culinary and cultivation sector increased, human exposure to these particles/materials also augmented, consequently [70]. Knowingly or unknowingly anthropological disclosure to the nanomaterials will upsurge in diverse methods, and it is unavoidable. Meagre knowledge is available regarding the metabolism and bio-distribution levels of nanomaterials. However, diverse studies have conducted aiming towards analyzing the possible harmfulness of the nanomaterials that use in food and agriculture, by analyzing diverse samples from crops, pesticides, food packaging, and additives. Nanomaterials, used in food and agriculture sectors will come in direct contact with the human organs, and the exposure is directly comparative to the factors like (1) levels of the nanomaterial present in the product (nanoscale edible coatings versus nano matrices for packaging, and (2) the amount of the product that been consumed or used (consumption of nanoscale edible coated food versus food from a nano matrix packet) [71, 72]. Sometimes, unintentional exposure due to the leaching of nanopackage material is also possible. Nanoclay was found to be migrating from food contact materials into the food stimulants [16]. Such migration may result in accumulation of substances like aluminum (nano form and dissolved form), with an estimated migration rate of 51.65 ng/cm2 for the Aisaika bags and 24.14 ng/cm2 for the Debbie Meyer bags [73]. Likewise, the analyzed migration rate of nano clay from a thin-film is influenced directly by the contact time and temperature. Workers at nano-material producing industries are also at high risk of particle inhalation, skin penetration due to overexposure. Understanding the basic fact that

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the nanomaterial guided toxicity is dependent on the physiochemical characters and dose, regulatory authorities should consider through characterization and assessment of products at multiple levels (in silico, in vitro and in vivo) before and after it reaches the end-user [4, 74, 75]. Factors like physio-chemical factors, osmotic potentials, acid-base levels, chemical aspects, concentration of biomolecules, and micro flora, their metabolism and eventual toxicity should be considered for assessing the risk [71, 72, 74].

Regulatory Aspect The use of nanotechnology in the culinary and cultivation sector is remarkable; however, their interaction with human and animal health and environment raises a concern. The nanoformulation products exert toxicity to the vegetation and wildlife, but no customary regulations and/or policies in place regarding their use and disposal. Consequently, operative regulations and guidelines are compulsory for the harmless usage of nanoparticles in the food and agriculture sector. In the USA, the regulations involved with nanofoods, food packaging other foodrelated nanotechnology products are done by the United States Food and Drug Administration (USFDA). Whereas in Australia and New Zealand, a regulatory body under the Food Standards Code, known as Food Standards Australia and New Zealand (FSANZ) regulate nanofood related aspects [16, 76]. Risk and safety valuation of nanotechnology in the culinary and cultivation sector in the European Union is achievedthrough the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) [77]. According to the SCENIHR, all nanotechnologybased food and agriculture products must undertake security and risk valuation afore being issued to the end-user and all these food products are enclosed by the European Union Novel Foods Regulation (EC 258–97). On the contrary, major nanomaterial producing countries like Japan and China do not have regulations and policies for nanotechnology specific food and/or agriculture products [78]. As mentioned earlier, the lack of regulations is mainly due to the scarcity of evidence concerning exposure and harmfulness to humans, animals, and the environment. However, several countries are coming up with regulatory systems to handle the dangers related by the nanofood. Comprehensive government rules and legislations, in addition to rigorous toxicological evaluation techniques, are vital for the lawful nanotechnological uses. A generally acknowledged global governing scheme is immediately essential for instructing the application of nanoparticles in the food sector [79, 80].

Conclusion Nanotechnology guided improvements in the food and agriculture sectors through refining the food processing, wrapping, transport, quality, and safety to the end-users. Smart nano-devices provide information regarding the state of the food within the package and also aid in pathogen detection if any. Though nanoparticles

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and driven food substances are produced worldwide, very few countries have regulations and policies for the ethical and efficient use. Incomplete and insufficient scientific explorations on nano-food tools hampered the accuracy of any conclusions regarding the associated safety and/or toxicity. Though it is understood that the packaging matrix posses less harm than utilizing nanoparticles as a food ingredient. With the threat of the access of nanoparticles in the body systems and the environment, appropriate regulations, labelling, policies for marketing are required to guarantee the end-user safety to increase acceptability. Thus, if managed and regulated correctly, nanotechnologies can revolutionize the food and agriculture industry which will benefit human health and well being. Acknowledgment Reshmy P and Raveendran Sindhu acknowledge Department of Science and Technology for sanctioning projects under DST WOS-B Scheme.

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Soumitra Banerjee, Patel Chandra Prakash, and Ravi-Kumar Kadeppagari

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Corn/Maize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zein: The Corn Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zein Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zein in Food and Non-food Sectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zein-Based Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applications of Zein-Based Nanoproducts in Food and Nutritional Sectors . . . . . . . . . . . . . . . . . . Food and Nutritional Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shelf Life Extension of Food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Micronutrient Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biodegradable Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensor Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

The corn protein zein is commonly used in the preparation of edible films and coating of candy, fruits, nuts, etc. Recently, zein nanoparticles were used to reinforce the mechanical properties of edible films and in the manufacturing of functional edible films. Antimicrobial zein coatings with essential oils were used for the inhibition of pathogens on whole fruit surfaces. Colloids were developed with zein-based nanoparticles for postharvest treatments of fruits. Nanomaterials based on zein were used in the development of antimicrobial, bioactive, or biodegradable food packaging films/systems. Zein-based food packaging bioactive coatings were also used here. Zein nanoparticles were also used for the development of stable delivery or co-delivery systems for nutraceuticals by nano-encapsulation or co-encapsulation process. They were further used in the development of controlled S. Banerjee · P. C. Prakash · R.-K. Kadeppagari (*) Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_51

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or targeted delivery systems for nutraceuticals. Nanomaterials based on zein were used for the encapsulation of food components and nutrients, and their bioavailability was also improved with zein nanoparticles. Food-grade pickering emulsions were prepared with zein nanoparticles. Recently, gold-coated zein nanophotonic structures were used for the development of platform for the detection of food analytes. Also, zein networks were evaluated recently to check the possibility of replacing animal meat with plant based meat and finding alternatives to cheese. However, further work needs to be done in order to develop this kind of products. This book chapter focuses on recent developments on zein-based nanoproducts with respect to food and nutrition sectors. Keywords

Zein · Edible films · Nanomaterials · Food packaging · Nutraceuticals · Encapsulation · Analytes · cheese

Introduction Corn/Maize Maize or corn (Zea mays) is one of the globally popular nutritious cereals besides wheat and rice. It contains high amount of starch (72%), protein (10%), and fat (4%), for which it is well utilized in different parts of the world as a food source. Besides human food, in developed countries, maize is also used as major domesticated animal feed source. In present days, maize is cultivated in a number of countries as a popular cereal, which may have originated from Mexico about 7000 years ago. The energy density of maize is 365 kcal/100 g, which is comparable to rice and wheat. However, protein content of maize is lesser than rice and wheat. Maize is cultivated in different countries of the world, out of which major cultivators are the USA, China, and Brazil, which approximately contribute 31%, 24%, and 8%, respectively, of total global maize production [31, 44]. Leading five countries for maize production besides the USA are China, Brazil, Argentina, Ukraine, and India. India ranks 6th position in global maize production and produced 25,000 thousand MT of maize in the year 2019 [2]. Maize is one of the versatile cereal crops, which may be cultivated in varied agro-climatic regions. The maize crop requires adequate moisture in soil and temperature range of 18–23  C for the deposition and 28  C for the growth and development of the plant. Similar in varied climatic condition, maize is found to grow well in different types of soil, from loamy sand to clay loam. The soil should contain high organic matters and sufficient soil bacteria and needs to have good water holding capacity with proper drainage. All these conditions are considered good for maize cultivation. Maize can grow in different soil except saline and alkaline soil, which are believed not suitable for maize cultivation. Maize can be grown as an intercrop cultivation system, i.e., maize with soybean, sesame, etc. In

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India, maize is cultivated in all four agricultural seasons, namely, kharif (monsoon), post monsoon, rabi (winter), and spring. Similar to agricultural practice of India, rabi and spring season cultivation needs additional irrigational support to assure a higher yield of maize productivity. However due to availability of rainwater during the months of kharif season, there is lesser need for irrigation facilities. Sowing operation during monsoon season needs to be completed within 12–15 days before monsoon. Sowing time needs to be adjusted and needs to be coinciding with coming monsoon [3, 38]. Changing climate, economical factors, technological development, and other factors are quite responsible for changing global and Indian farming scenario, but still maize cultivation has been identified as a successful crop which addressed several local and global issues, i.e., food security, water scarcity, farming systems, biodiesel, etc. According to the National Centre for Agricultural Economics and Policy Research (NCAP), besides regular food source, maize has gained importance in non-food industrial sectors like textile, paper, glue, alcohol, pharmaceutical, etc., making maize to gain more popularity with time and human population [38]. Maize after harvest can be utilized for manufacturing of various products of versatile nature, i.e., corn starch, corn oil, corn syrup, alcohol, corn flakes, etc. These products are described briefly below. Corn Starch In maize, the major composition is starch, which accounts almost 3/4 part of the total maize grain composition. Hence, this starch received commendable attention for various applications. Corn starch is a biopolymer made up of amylase and amylopectin. Corn starch in natural and modified form can be used for a number of food applications, i.e., thickener, texturizer, fat replacer, and stabilizer, for gel preparation, and for moisture retention properties [9]. It is also used to make corn syrup, dextrose (crystalline glucose), etc. [11]. Corn Oil Corn or maize is not known as oil seeds, because it contains low lipid content (3–5%) in the kernel. During wet or dry milling operation, germ is produced as by-product which will be used to extract oil by crushing and germ contains 80% lipid. Germ represents 9–11% of total kernel weight. Corn oil is suitable for food processing, which contains a significant amount of antioxidants, namely, tocopherols and tocotrienol, besides the high amount of unsaturated fatty acids, including linoleic and oleic acids. Refined corn oil finds its applications in cooking, frying, as a salad oil, and also as raw material for the lipid modification process [8]. Corn Protein Corn protein varies in different varieties from 6 to 12% (d. b.), the majority of which is found in the endosperm tissue (75%) and remaining 25% in the germ and bran. There are four types of proteins in corn, namely, albumin (water soluble), globulin (salt soluble), glutelin (alkali soluble), and zein (alcohol soluble). Out of the four proteins, zein determines the hardness of the corn endosperm [49].

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Zein: The Corn Protein Zein is a protein found in maize, which comes under the category of prolamine that is found exclusively in cereals. It is similar to hordein protein found in barley and gliadin protein found in wheat. Zein is known for its commercial importance which consists of 45–55% of whole corn protein. Zein is basically an amorphous polymer with plasticizing viscoelastic behavior and thermal stability. In the year 1821, John Gorham identified zein presence in the endosperm, as alcohol-soluble protein. From that time, zein has received interest from the scientific community for its possible industrial applications as polymer. Zein has its characteristic soft and ductile nature after precipitation from solvent. Researchers worked to utilize the characteristics to develop plastic kind of materials, with or without added additives. After many efforts, commercial production of zein began in the year 1939 from corn gluten meal [4, 21, 23, 39, 49].

Zein Processing Zein is water insoluble but is soluble in alcohol or high pH alkali solution (pH 11). The presence of higher amount of nonpolar amino acid residues and less amount of basic and acidic nature amino acids causes the abovementioned solubility characteristics of zein. Zein bodies are located in the cytoplasm of endosperm cells in between the starch granules. SDS-PAGE analysis revealed that zein is composed of two distinct bands of molecular weight 23 and 221 kDA and minor bands of 13 and 9.6 kDA. Zein consists of two different peptides of different molecular size, solubility, and charge, namely, α-zein and -zein. α-Zein is the prolamine of corn soluble protein which is soluble at 95% ethanol. This represents nearly 80% of total prolamine present in the corn, and α-zein is the most abundant protein in commercial zein. β-Zein is not soluble in 95% ethanol, but gets soluble in 60% ethanol solution. This second category of zein is not stable and tends to coagulate, henceforth not used for commercialized production. Besides this, some other researchers categorized zein protein fractions based on other techniques. Hydrophobic characteristics of zein were reported because of larger peptides. Argos et al. [5] suggested high helical content possessing a rod-like structure, wheel model for zein, with nine homologous repeating sequences, all arranged in anti-parallel form, altogether stabilized by hydrogen bonding of slight asymmetric nature. Matsushima et al. [32] presented revised Argos et al.’s [5] model based on small-angle X-ray scattering (SAXS) of α-zein and concluded that α-zein particles existed as asymmetric particles of 13 nm length and the model was proposed as an elongated prism-like shape with axial ratio close to 6:1 [24, 28, 49]. For zein production from corn, it has to be extracted with a suitable solvent. Nonpolar amino acids are abundant; hence, solvent used for the extraction needs to have mixed properties, having ionic and nonionic polar groups and nonpolar groups and may be pure solvents or mixed solvents. Different types of solvents may be used

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for the extraction process, i.e., nonaqueous solvents like alcohol solution, ketones, amide solvents, esters, glycols, etc., under different conditions. The dissolving solvents must contain –OH, –NH2, –CONH2, or –COOH groups. Other researchers have reported several organic solvents for zein extraction [45, 49]. Zein solubility in water may be increased by acidic or alkaline deamidation or enzymatic modification. Besides solvents, enzymatic hydrolysis can also be used to make zein soluble in aqueous medium [49]. Different approaches are used for extraction of zein, and major differences in the operation can be classified under the following heads: • • • •

Nature of raw materials used Types of solvents used Purification protocol Method of recovery

For example, raw, dry milled corn may be used as raw material, where zein exists in native form. However, the content of zein is much less, resulting in a reduction of yield and concentration of zein in the extractant. During dry grind ethanol processing, the protein received at the end is called as distillers’ dried grains (DDG) or DDG containing “soluble” (DDGS), which contains 27–30% total protein content, and it is not considered as desirable raw material for good quality zein production. For solvents, most published literatures have indicated usage of two solvents, i.e., a polar solvent like aqueous ethanol or isopropanol for extraction and another nonpolar solvent like hexane or benzene for defatting and decolorization [49].

Zein in Food and Non-food Sectors Zein finds its wide application in different sectors including food and non-food domain. Zein has the capability to form tough, glossy, hydrophobic, greaseproof, antimicrobial, flexible, compressible, grease, and solvent resistance coatings. Zein protective coating on carton stock was found to be quite advantageous for transport or maintaining stocks of doughnuts, crackers, pies, cookies, etc. Zein was also used for coating fiber boards and papers for its grease resistance and other properties. In pharmaceutical industries, zein finds its application for its film-forming ability and antimicrobial properties for coating tablets. In food industries, zein found various applications as coating materials for fortified rice, edible nuts, gums, confectioneries, and candies. For the last two decades, a number of applications of zein were found in the various fields. However, with the introduction of synthetic and petroleum-based ingredients, zein became comparatively expensive. Recent interest on the development of polymeric biodegradable materials made zein again topic of interest for its various applications in the domain of biodegradable films, coating, and plastic applications. Novel plastic materials made from zein were found to be less flammable and less expensive, which made its applications for fabric stiffeners, artificial leathers, lacquer, filament, and films. As reviewed by Ibrahim et al. [21], the USA

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produces highest quantity of corn globally, of which 50% is used for feed purpose, 25% for ethanol production, and remaining 25% used for export and manufacturing of food, fiber, and industrial purposes. Some specific applications of zein are in adhesives, binders, biodegradable plastics, chewing gums, edible moisture-resistant coating for food products, cosmetic powder, acid-sensitive drug delivery system, textile fiber, microspheres, microencapsulated pesticides, paper surface coating, reverse osmosis membranes, starch-based polymers, etc. [4, 21, 39, 41, 49, 55].

Zein-Based Nanoparticles Nanoparticles have wide industrial and day-to-day life applications, but one major problem associated with some nanomaterials is their toxicity [19, 20, 50]. Nanotechnology finds its various applications in food, bioprocessing, and agriculture sectors [19, 20, 43]. Nutrition and quality wise, nanomaterials may have higher values compared to conventional materials. Zein protein as food, it is considered safe. Various applications of zein have been discussed, and adding nanoparticles with zein would find more applications. Zein comes under the category of “Generally Recognized as Safe” (GRAS) biomaterials [17], and no report or published literature was found on toxic behavior of zein nanomaterials. Osborne [36] reported about solubility of maize kernel proteins in 60–99% alcohol but not soluble in water. Kasaai [24] reviewed about preparation of zein nanoparticles by liquid-liquid dispersion method. In this method, zein extracted from corn was taken and dispersed in aqueous ethanol solution and subjected to shear for getting smaller droplets [58]. Due to inter-diffusion of ethanol and water, there was a reduction in solubility of zein; hence zein precipitates as zein nanoparticles. Zein nanoparticles can also be formed by spray-drying process, where zein was initially dissolved in a solvent and is followed by spray drying. Zein nanoparticles made by this method had 200 nm dimensions approximately. Muller et al. [34] reported their work on development of microsphere-based zein by dissolving zein in aqueous ethanol solution under continuous stirring. The solution was vigorously stirred for 15 minutes, and water was added slowly, which changed the ethanol to water ratio from 1:4 to 2:3 (v/v), causing decrease in zein solubility and creation of zein microsphere droplets. Obtained insoluble microspheres were separated from the solution by vacuum filtration and then freeze-dried for 24 hours. Similarly, zeinchitosan microspheres were also prepared. Similar principle of zein’s solubility in mixed solvent was used for preparing microspheres and nanospheres for various applications like pharmaceutical drug encapsulation, essential oil encapsulation, etc. This method is simple and convenient to be adopted over other methods. The described method is called anti-solvent precipitation method where the precipitation of particles happens due to change in solvent concentration, in which the precipitate remains in soluble condition. This method is simple to understand and adopt for preparation of zein microspheres. In the overall process, concentration of zein and ethanol in the dissolving solution is important, which affects the colloidal particle forming process. Rise in ethanol concentration results in smaller-sized particles,

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whereas high zein concentration leads to increase in particle dimension. Though ethanol is primary solvent, methanol and isopropyl alcohol may also be used for similar colloidal particle formation [40, 58]. Guo et al. [16] reported their study on nanostructure of zein in aqueous ethanol solution, where it exists in small globular form of dimension between 150 and 550 nm. The film formation mechanism was also explained.

Applications of Zein-Based Nanoproducts in Food and Nutritional Sectors Food and Nutritional Applications Zein is found in the endosperm of corn which has negative nitrogen balance and lacks basic and acidic amino acids, i.e., tryptophan and lysine. Zein has poor water solubility and doesn’t contain all essential amino acids, which makes zein not ideal protein source for human consumption. As a food, zein was considered waste protein and didn’t attract much attention, until its novel applications were found in different fields. As a food source, zein may be not suitable, but as odorless and tasteless base material, zein nanoparticles may be used as excellent edible carriers for bioactive substances [58]. Zein-based nanomaterials are hydrophobic in nature, get digested slowly, and have better biocompatibility, for which zein-based nano-delivery systems are considered good option compared to other protein sources for oral intake. Its water insolubility property provides a moisture barrier for the coated materials, which in hand increases the storage life and delayed degradation rate inside the gastrointestinal tract. By varying the particle size, residence time inside the gastrointestinal tract can be varied. Reduction in particle size would increase the residence time of the encapsulated materials inside the gastrointestinal tract, which can be extended where slow digestion rate is required for controlled release of encapsulated active materials [24, 26, 47]. Zein nanomaterials can be utilized for nano-encapsulation of dietary supplements [52]. Zein and chondroitin sulfate composite nanoparticles were prepared by antisolvent precipitation method for curcumin delivery. Degeneration resistance of zein-chondroitin sulfate nanoparticles was improved by addition of chondroitin sulfate, which was also responsible for increase in encapsulation efficiency of curcumin. Developed nanoparticles showed good stability between pH 3 and 8 and thermostability till 80  C. Hydrophobic nutrients like curcumin in functional foods can be delivered using zein nanomaterial base, which was also found to be biocompatible [27]. Yuan et al. [56] reported about lutein as a beneficial bioactive compound but with limited applicability since lutein is poorly soluble in water, is unstable, and has low bioavailability. For overcoming these challenges, Yuan et al. [56] worked on encapsulation of lutein with zein nanoparticles coated with sophorolipid. Encapsulated lutein showed stable behavior with increased water solubility and much better biocompatibility and bio-accessibility. Similarly, zein nanoparticles can be used for encapsulation and stabilization of active biomolecules

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like quercetin, fucoxanthin, resveratrol, etc. [56]. In another study reported by Hu et al. [17], zein-lutein nanoparticles were produced using solution-enhanced dispersion by supercritical fluid method (SEDS). Spasojević et al. [51] reported their work on development of composite zein/rosin nanoparticles by anti-solvent co-precipitation method at different zein/resin mass ratio. The developed nanoparticles were found suitable for carvacrol encapsulation. Encapsulation of nutraceuticals is important to protect them from unfavorable storage and gastrointestinal conditions while developing new therapeutic functional foods. Pickering emulsions can be defined as those emulsions which can be stabilized by solid particles located at the interface between two phases. They are considered much more stable compared to other emulsions stabilized by surfactants or biopolymers. Pickering emulsions have amphiphilic behavior, but still they are able to stabilize the emulsion. They may be used for encapsulation of water-insoluble bioactive compounds, although very few food ingredients possess capability to be used as edible pickering emulsions, out of which zein is one. Babazadeh et al. [6] worked on replacement of ethanol with non-flammable polyethylene glycol (PEG 400) for the manufacturing of zein nanoparticles for making zein-carboxymethyl cellulose complexes. These complexes stabilized water in oil (W/O) emulsions and were used for successful nano-encapsulation of rutin, a hydrophobic nutraceutical. Carboxymethyl cellulose ensured better particle size, encapsulation, and stability and more release time. There is growing demand for plant-based proteins with unique textures. Mattice and Marangoni [33] studied on the rheological properties of self-assembled zein network, in comparison with gluten network, chicken muscle tissues, and cheddar cheese. Zein network showed stronger and elastic structure after 24 hours in comparison with meat analogues. However, more investigations need to be carried out for the improvement of zein network strength and overcoming the brittleness. Melting characteristics of zein and cheddar cheese were found to be similar. These studies raise the hope for plant-based meat. Hence it can be concluded that zein finds its wide application in food and nutrition, especially encapsulation of unstable dietary supplements and bioactive compounds like lutein, curcumin, and rutin. In their pickering emulsion form, zein nanoparticles were successfully adopted for encapsulation of nutraceuticals. Also, studies have shown the ability of zein network for the development of animal meat alternate.

Shelf Life Extension of Food Shelf life and safety are two major requirements of foods, and encapsulation by zein nanomaterial along with active compound will be helpful to extend the shelf life of food without compromising food safety. Efficient food-grade antimicrobial agents having no toxic effects are in demand due to raising awareness about food safety among the consumers and producers. Essential oils like thymol and carvacrol contain phenolic hydroxyl groups, which are known for antimicrobial effects which make these compounds natural antimicrobial agents. However those essential

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oils are insoluble in water limiting their application in foods. Hence, those essential oils were nano-encapsulated using zein nanoparticles by liquid-liquid dispersion method which makes them well dispersed in water. Nano-encapsulated essential oils were found suitable for food preservation [53]. Sanchez-Garcia et al. [46] reported their work on the development of nanobiocomposites prepared from carrageenan blended with zein. Here, mica clay was used as additive and glycerol as plasticizer. Developed biocomposite was concluded to have high potency for its application as packaging films or coating for enhancement of food shelf life. Epigallocatechin gallate is a major tea polyphenol, which has higher antioxidant activity, but is not stable under high temperature, oxygen concentration, and pH and easily gets oxidized. Liang et al. [26] worked on the preparation of zein-coated chitosan nanoparticles for the encapsulation and delivery of epigallocatechin gallate, where it was claimed that zein coating increased the controlled release of epigallocatechin gallate. These encapsulated nanoparticles would be helpful to prevent lipid oxidation and increase the shelf life of fat-rich food products [7]. Considering the poor water resistance properties of zein electrospun nanofibers, Niu et al. [35] fabricated zein/ethyl cellulose nanofibers for the encapsulation of cinnamon essential oil, and they were used for the preservation of Agaricus bisporus. Essential oils encapsulated in nanofibers were found suitable, nontoxic, and biodegradable and to extend the shelf life of Agaricus bisporus. Zein in its nano-form can be utilized for the encapsulation of natural essential oils and is found to be a safe food preservative. Also zein nanomaterials have been credited for stabilization of unstable essential oils and ensuring controlled release. Zein can be used for making biodegradable packaging films, and incorporation of antioxidants and antimicrobial agents ensures the extension of shelf life of food.

Micronutrient Encapsulation Carboxymethyl chitosan (CMCS)-coated zein nanoparticles were developed using low energy liquid-liquid dispersion method. Here, vitamin D3 was initially encapsulated into zein and then coated with CMCS. This complex was successfully used for delivering vitamin D3. Encapsulated hydrophobic nutrients in zein/CMCS complex nanoparticles would have better stability and controlled release property [29, 49]. de Boer et al. [12] reported about lutein, which is a type of water-insoluble carotenoid. Lutein is a permitted food color but is sensitive towards ultraviolet and visible light and hence suffers from instability as a food colorant. de Boer [12] prepared lutein-zein colloidal particles using anti-solvent precipitation method, and ascorbic acid was added as antioxidant. It was found from the study that zein nanoparticles were capable to protect lutein from degradation and antioxidant ascorbic acid helped to further improve the photostability of lutein. Zein nanoparticles are suitable edible carriers of flavor compounds [29]. Bioactive materials, micronutrients, and other food components which are not stable or having poor water solubility can be stabilized by using zein nano-form along with other additives for longer storage life.

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Biodegradable Films Synthetic polymers are widely used for different applications including food packaging, but due to their nondegradable nature, environmental impact, and societal awareness, they are not advisable. Hence, biodegradable films have received growing interest particularly in food packaging sector [15]. Zein films can be formed along with plasticizers to improve their elasticity. However, the film’s mechanical and physical properties were not near to synthetic films. Luecha et al. (2010) reported the fabrication of zein montmorillonite (MMT) nanocomposite films using solvent casting and blown extrusion technique. It was concluded from the study that blown extrusion method resulted in the development of nanocomposite film with better thermal resistance and solvent casting resulted in the formation of films with better tensile strength. Several protein sources have been used for biodegradable film development, out of which zein is considered most advantageous film-forming material after physical/chemical processing, due to its tough, glossy, hydrophobic, greaseproof, and antimicrobial properties. Ultraviolet/ozone treatment on zein films controls the surface hydrophilicity, resulted from the conversion of surface methyl groups to carbonyl groups. As a barrier material, zein is excellent, and with controlled surface characteristics, it has several roles in the packaging applications of food and non-food products [48]. Zein nanoparticles may find their utilization in improving the strength of bioactive food packaging [29]. Xin et al. [54] developed zein and potato starch-based biodegradable films containing chitosan nanoparticles incorporated with curcumin. These films delayed physical/chemical changes in Schizothorax prenati fish fillets and extended the shelf life till 15 days. It was further reported that films had good mechanical properties, barrier properties, and oxidation resistance along with antimicrobial and antioxidant properties. This packaging film was concluded to be a better biodegradable alternative for improving storage quality and extending shelf life of fish fillets. Composite films of hydroxypropyl methylcellulose were fabricated with zein nanoparticles, and they showed decreased vapor permeability. While making cellulose film, addition of zein nanoparticles showed the enhancement of film elasticity at lower concentration [15]. Cheng et al. [10] reported about development of edible packaging film using zein and chitosan as base materials along with phenolic compounds and dicarboxylic acids, which were able to be recovered from the composite film, and the developed film showed antioxidant and antimicrobial activities. In another study, nano-TiO2-modified zein/chitosan films were prepared, where it was found that addition of TiO2 nanoparticles could improve the mechanical characteristics, hydrophobic properties, and thermal stabilities of the composite film. The developed film could be used for medical and food packaging applications [42]. In another study, Oymaci and Altinkaya [37] reported their work on bio-nanocomposite film development by solution casting method, where whey protein isolate was used along with zein nanoparticles coated with sodium caseinate. Addition of zein nanoparticles resulted in better water vapor barrier and mechanical properties to films which could be used as biodegradable food packaging materials. Zhang and Wang [57] successfully developed inexpensive, simple, and

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highly ordered biopolymer nanocomposites for the improvement of tensile and gas barrier properties by using magnetic nanofillers, where zein acted as biopolymer matrix. Kashiri et al. [25] developed active zein films incorporated with essential oil (10%) of Zataria multiflora Boiss for antimicrobial activities, and sodium bentonite clay (2%) was used for the enhancement of the packaging material properties, i.e., water vapor permeability, UV light barrier, tensile strength, Young’s modulus, etc. Antimicrobial activities of the active films resulted in the reduction of microbial load [25]. Zein particles were used as fillers for the production of gelatin-based biodegradable films. Tannic acid was used for the modification of gelatin/zein film by solution casting method. This film showed the enhancement of mechanical properties and hydrophobicity [18]. Zein finds its wide application for film development for food packaging applications. Water barrier properties, high mechanical strength, and good thermal stability are some of those properties which make zein-based film as a good biodegradable packaging film. Addition of essential oils or polyphenolic compounds enables zein films with antimicrobial or antioxidant properties which ensure the extension of shelf life of packaged food.

Sensor Developments Zein, due to its unique properties, makes it ideal material for surface-enhanced Raman spectroscopy (SERS) platform for manufacturing biosensors. Unique surface properties of zein film allow its adhesion with gold and surface nanostructure modification by soft lithography. Besides this, zein is environment-friendly, low cost, and available easily as byproduct of ethanol production. Jia et al. [23] reported their work on development of novel biodegradable SERS biosensor made up of inverted pyramid gold-coated nanostructure formed on zein film. The imprinted film was bettered with deposition and fixing of gold nanoparticles created on the gold film surface. This newly fabricated platform was used for the detection of pyocyanin (a toxin released by Pseudomonas aeruginosa) in the rapid sensitive test. This nanosensor was able to detect pyocyanin accurately in the water and can be used as pointof-care detection method. Aghaei et al. [1] developed halochromic sensor, by integrating alizarin dye in zein electrospun nanofibers for real-time monitoring of the quality of rainbow trout fillets (i.e., freshness). Developed sensor was found to be rapid (with only 0.75 min response time) and highly sensitive. Sensor shows realtime color change which can be used in the intelligent food packaging system. Gezer et al. [13] developed biodegradable sensor platform for the detection of peanut allergen (Ara h1 protein) by using gold-coated zein nanophotonic film with surface-enhanced Raman spectroscopy (SERS). Developed biodegradable platform was capable of detecting and quantifying the peanut allergen by using principle component analysis (PCA). However, more studies are needed to be conducted to increase the sensitivity and to develop real food applications. In another study, Gezer et al. [14] reported about the development of biodegradable zein/gold surface-enhanced Raman spectroscopy-based sensing platform for the detection of acrylamide.

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Acrylamide is known for its carcinogenic properties and possibly harmful for humans. Presence of acrylamide resulted in a unique peak at 1447 cm 1, which was used for the detection and quantification of acrylamide within 10 mg to 10μg/10 mL solution concentration. This novel concept will be helpful for the future application in the detection of acrylamide presence in the food sample. Jhuang et al. [22] reported on the immobilization of laccase (the enzymatic time-temperature indicator) on electrospun zein fiber for increasing the stability. The developed system had good stability and was found suitable for food quality monitoring and as intelligent packaging for food application. Ma et al. [30] worked on the fabrication of nanostructured zein-based SERS platform coated with gold, silver, or silver-shelled gold nanoparticles, and they were studied separately for further enhancement of sensitivity for making it as sensitive as nonbiodegradable-based SERS platform. For checking the sensitivity of developed biodegradable sensor, Rhodamine 6G was chosen as a Raman active molecule. It was found that silver-shelled gold nanoparticles gave highest enhancement factor than silver or gold nanoparticles-deposited surfaces. Zein nanomaterials were found to be capable of acting as a potential alternative to nonbiodegradable materials while developing sensors with high sensitivity, low detection time, and easy detection. In addition, zein films were found to have applications in the development of active packaging materials for easy detection of food spoilages and changes in the properties of stored foods and rapid monitoring of food safety and quality.

Conclusions Zein finds its wonderful applications in different areas, because of its biodegradable nature and other unique functional properties. In nano-form, zein was found to have average dimension varying from 50 to 200 nm and has a number of functions in food and nutrition domain, like carrier of nutrients in the core of encapsulated system, encapsulation of water-insoluble nutrient components (i.e., lipids, essential oil, water-insoluble vitamins, antioxidants, etc.), stabilizing unstable bioactive compounds (i.e., food flavors, colors, etc.), increasing bioavailability of food and nutrients (i.e., vitamin D3, curcumin, etc.), and more. As nano-delivery vehicle, encapsulated zein nanomaterials are also having wide applications for efficient and target delivery. Healthcare and pharmaceutical applications of zein nano-form are other domains which need to be explored more. Zein nanomaterials are found to be biocompatible with humans, although more studies are necessary on the immunogenicity of zein nanoparticles under in vivo condition. Zein nanoparticles find their application as the nano-biosensor of their unique surface characteristics, environment-friendly nature, low cost, and easy availability. Nanoparticles are claimed to be efficient delivery vehicles for many bioactive compounds, which have the penetration capabilities in capillaries and cells due to their smaller size, larger surface area, robustness, intracellular uptake, and controlled release at target site. Odorless and tasteless characteristics of zein offer advantage as carrier material for various bioactive materials. Several studies have already been done on zein-

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based nanostructures although more studies on cytotoxicity, degradation, and chemical properties of these structures need to done. Future work needs to address the role of chemical process modification on the biodegradability of zein and zein-based derivatives. In-depth studies need to be done on the influence of zein dimensional geometry on the biodegradability since area of exposure is proportional to zein degradation rate under enzymatic environment. Acknowledgments Authors thank Sri Sharada Peetham, Sringeri, and Jyothy Charitable Trust, Bengaluru, for their support and facilities.

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Nanotechnology: A Revolutionary Approach Toward Food Packaging

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology and Food Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Efficient Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Active Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Smart/Intelligent Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detection of Spoilage and Pathogenic Microbes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Freshness Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time–Temperature Indicators (TTIs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Consumer Acceptability of Nanotechnology Products in Food Packaging . . . . . . . . . . . . . . . . . . . . Challenges with Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Role Played by Stakeholders and Regulatory Agencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Case Scenario: India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Nanotechnology is upcoming field, essentially for the nano-packaging of foods with greater consumer acceptability. This technology has many potential benefits in various areas like food safety, quality, processing, packaging, and delivery of bioactive ingredients. Although consumer is aware of the hazards and safety issues associated with nanofood packaging due to the migration of nanoparticles into food materials, if adequately harnessed this technology could revolutionize food industry globally. Nanotechnology, when applied to food packaging, could be categorized into three parts. The first one is efficient packaging, where nanomaterials and polymer matrix are mixed for improving the tolerance for M. Rastogi Department of Environment Sciences, Maharshi Dayanand University, Rohtak, Haryana, India C. V. Bhavana · R.-K. Kadeppagari (*) Centre for Incubation, Innovation, Research and Consultancy (CIIRC), Department of Food Technology, Jyothy Institute of Technology, Bengaluru, Karnataka, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_92

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humidity and temperature and gas barrier for the packaging raw material. The second one is active packaging, where a direct interaction is put forward between nanomaterials and the food for increasing the resistance against microbes. The third one is smart packaging, where food is tracked for adulteration and safety through the changes that occur due to the interaction between the nano-packaging and food. Nanofood packaging could be bio-based, promoting biodegradability and making the packaging environmentally friendly. In addition, this packaging generates lesser waste material with enhanced food product quality. Envisaging the several challenges that nanofood packaging has to face due to the knowledge gaps, this chapter will discuss how application of nanotechnology to the area of food packaging could enhance the efficacy of whole packaging process and balance the environmental aspects. The role played by stakeholders and regulatory agencies for improving consumer health will also be discussed briefly. Keywords

Nanotechnology · Food packaging · Active packaging · Adulteration · Smart packaging · Biodegradability

Introduction Nanotechnology is promising intervention with a higher application potency in multidisciplinary areas, i.e., biological sciences, engineering, chemistry, and physics. Sir Richard Feynman conceptualized nanotechnology (in 1959), a study that involves manipulation of matter at atomic or molecular levels. It is an emerging area, where control on matter at atomic or molecular scale is possible when minimum one featured dimension is being measured in nanometer. Nanotechnology includes fabrication, accountancy, and maneuvering of nano-range (2000 psi) and in an aqueous solution where high temperature (>200  C) is maintained. The method is divided into two categories as the Batch hydrothermal or the Continuous hydrothermal process. While the continuous hydrothermal reaction takes place at a higher rate in a short time, the batch hydrothermal takes place in

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Fig. 3 (a) typical reverse micelle system, (b) one microemulsion process

phases at the desired rate. With this technique, dislocation-free single crystal particles are grown so high crystalline iron oxide-based nanoparticles are obtained [60]. Sonochemical synthesis is the process of producing various nanostructured materials using powerful ultrasound radiation [75]. Ultrasound chemically causes cavitation in an aqueous environment where foaming and collapse occurs (Ashokkumar et al. 2007). Flowchart of synthesis: FeCl3 :6H2 O þ NaOH ! Mixing ! Sonication ! Drying ! Sintering ! Fe2 O3

Biological-Based Synthesis Methods Biological-based synthesis method called green synthesis is preferred because it is ecofriendly, low cost, and efficient. Biological organisms such as bacteria, fungi, yeast, and plant extracts are used for the synthesis of nanoparticles with the green synthesis method [21] (Fig. 4). In a study conducted in 2006, it was observed that the pathogenic fungus Fusarium oxysporum and the endophytic fungus Verticillium sp. produced magnetite nanoparticles [12]. In another study, it was found that magnetotactic bacteria (MTB) use the iron source to convert magnetite or greigite (Fe3S4) into magnetic crystals [68]. However, advances in the practical use of MTB-Iron oxide-based nanoparticles have been slow, highly due to production limitations. These properties in living organisms are important in nanotechnology and other application areas (Fig. 5).

The Characterization of Iron Oxide-Based Nanoparticles After synthesis of the iron oxide-based nanoparticles is completed, iron oxide-based nanoparticles properties must be determined. For this purpose, characterization techniques are used to understand some properties such as the morphological

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Fig. 4 Green synthesis of iron oxide-based nanoparticles

Fig. 5 Magnetosome formation in Magnetotactic bacteria (a) Magnetotactic bacteria

structure of the iron oxide-based nanoparticles surface, chemical structure, and determination of functional groups. These techniques are divided into two categories as microscopic techniques and spectroscopic techniques [13]. Microscopic characterization techniques generally include the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM offers the opportunity to examine the surface and subsurface regions of nanoparticles. It also provides a high depth of field, high resolution, and a 3-dimensional image [51]. On the other hand, TEM has a higher and spatial resolution that is effective in atomic analysis of iron oxide-based nanoparticles. Also, TEM readily produces projected 2D images of the nanoparticles between 1 nm and 100 nm.

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Spectroscopic characterization techniques are used to determine the crystal structure properties of iron oxide-based nanoparticles such as width, density and angle and chemical structure. Energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), Infrared (IR) absorption spectroscopy, atomic force microscopy (AFM), dynamic light scattering (DLS), hydrophobic interaction chromatography, vibrating sample magnetometry (VSM) are some of the devices used in this technique [13]. In addition, nanoparticle tracking analysis, thermal gravimetric analysis, and zeta-potential measurements are also performed in the characterization of iron oxide-based nanoparticles [6, 76]. In characterization studies, it is stated that besides spectrophotometric and optical techniques, textural and structural features are also important. In this regard, the Brunauer-Emmett-Teller method is generally preferred to determine the specific surface area of a solid, using nitrogen gas as the adsorbate and nitrogen (77 K) as the coolant [13]. Another method, Barret, Joyner, and Halenda, is used to characterize the shape, size, and pore distribution of iron oxidebased nanoparticles by calculating desorption-absorption isotherm [35]. Magnetic characterization techniques are used to determine the magnetic properties of iron oxide-based nanoparticles. VSM are the most important technique to measure iron-oxide-based nanoparticles, such as saturation magnetization, remnant magnetization, etc. [64] (Table 2).

Functionalization of Iron Oxide-Based Nanoparticles For medical applications, organic/inorganic coatings of iron oxide-based nanoaparticles improve dispersion, surface activity, physicochemical and mechanical properties, and biocompatibility. Therefore, iron oxide-based nanoparticles are Table 2 Analytical techniques for characterization of iron oxide-based nanoparticles [6] Technique Dynamic light scattering (DLS) Zeta-potential Near-field scanning optical microscopy (NSOM) Infrared spectroscopy (IR) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) Atomic force microscope (AFM) Nuclear magnetic resonance spectroscopy (NMR) X-ray diffraction (XRD) Small angle X-ray scattering (SAXS) Vibrating sample magnetometry (VSM)

Properties of technique Size distribution Surface charge Shapes and size in nanomaterials Surface properties Size and shape distribution Shape heterogeneity, size, dispersion and accumulation Shape heterogeneity, size, dispersion, accumulation Indirect analysis of size, structure purity, concentration and conformational variations Crystalline properties, size Shape, structure, size, and size transportation Magnetic properties

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used for specific drug targeting, hyperthermia, biosensor, antibacterial activity, and magnetic separation of cells [22, 42]. Functionalization of iron oxide-based nanoparticles of iron oxide have been made various methods include ligand exchange, ligand addition, silane coating, aminosilane coating, polymer coating. Ligand addition is the addition of a ligand molecule to the external surface of nanoparticles. The hydroxyl, carbohydrate, thyol, and phosphonate, etc., groups can bind to the surface of nanoparticles [14]. Ligand exchange method play important role to control the surface properties of nanoparticles [70]. Silica is the most used compound for surface coating of iron oxide-based nanoparticles to reduce the toxicity. Silica coating is used to reduce the toxicity of nanoparticles and to improve stability in water and it protects them in an acidic environment [41, 73] (Fig. 6). Polymer coating of iron oxide-based nanoparticles has been commonly investigated for their unique physical and chemical properties. Polymer coating prevents aggregation of nanoparticle, a steric/electrostatic repulsion can be produced by coating the particles with polymers, and coating is important for MRI and drug delivery applications [4, 43]) (Fig. 7).

Fig. 6 Functionalization of iron oxide-based nanoparticles

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Fig. 7 The organic and inorganic materials used for the functionalization of iron oxide-based nanoparticles

Applications of Iron Oxide-Based Nanoparticles Iron oxide-based nanoparticles commonly used for medical therapy such as magnetic separation, targeted drug delivery, magnetic resonance imaging (MRI), magnetic fluid hyperthermia and thermoablation, modulation of macrophage polarization, and biosensing (Fig. 8) [22]. Iron oxide-based nanoparticles are linked with drugs, gene (siRNA, miRNA), antibody, aptamer, protein, etc. and then magnetic nanoparticles have been widely studied in biomedical areas(Fig. 9). Table 3 summarizes some biomedical applications of iron oxide nanoparticles.

Conclusion This chapter is focused the synthesis, surface functionalization, and characterization of iron oxide nanoparticles, as well as their preclinical use in medicine as summary. Iron oxide nanoparticles are important tools, especially biomedical applications

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Fig. 8 Biomedical applications of iron oxide-based nanoparticles

Fig. 9 Schematic illustration of iron oxide-based nanoparticle

because of magnetic driving via the external field and their unique properties. Today, iron oxide-based nanoparticles have been developing as multifunctional nanoplatform, which can be binding with antibodies, drugs, aptamer, etc. Up to now,

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Table 3 Application of iron oxide-based nanoparticles Topics Iron oxide nanoparticlelipidic micelles miRNA-loaded iron oxideloaded nanoparticles Fe3O4-aminosilane-coated iron oxide nanoparticles Titanium and iron titanium oxide nanoparticles Polymer-iron oxide composite nanoparticles Multifunctional graphene oxide/iron oxide nanoparticles

Application MRI

References [61]

Cancer

[76]

Hyperthermia

[56]

Biosensor

[69]

EPR-independent drug delivery

[55]

Magnetic targeted drug delivery dual magnetic resonance/fluorescence imaging and cancer sensing

[19]

many papers, reviews, book chapters have been written in the literature on iron oxide-based nanoparticles. In the future as now and before, there seems to be a luminous and extensive use of iron oxide nanoparticles and it will continue to be discussed as in this section.

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Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Common Types of Wounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phases of Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Factors Affecting Wound Healing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Intrinsic Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extrinsic Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bottom- up Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Top-down Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Micro-Nano . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction and History of Silver Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Properties and Application of Silver Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diameter, Surface Area and Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shape and Crystallinity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanoparticle Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Particle Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surface Chemistry and Functionalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Measuring SNP Concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Silver in the Term of Nano . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods of Synthesizing Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characterization and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transdermal Drug Delivery System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Administration of Drug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Advantages and Limitation of Transdermal Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics of Several Drug Permeation through Transdermal . . . . . . . . . . . . . . . . . . . . . . . . .

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S. Paul (*) Medical division, Scope eknowledge, A Straive company, Chennai, India C. S. Sasikumar Clinical research, S.S healthcare; Clinical Research, Hycare Super specialty, Seed Fund Technical sub committee; Golden Jubilee Women Biotech Park; Department of Biochemistry, Saveetha Dental College, Chennai, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_83

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Transdermal Film . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Technologies for Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer Membrane Permeation-Controlled TDDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polymer Matrix Diffusion-Controlled TDDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drug Reservoir Gradient-Controlled TDDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Microreservoir Dissolution-Controlled TDDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Transdermal Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple-Layer Drug Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drug Reservoir in Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drug Matrix in Adhesive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drug Delivery Routes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods of Skin Penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Basic Components Required for Transdermal Dressing Material . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics of Polymer Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics of Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Properties that Need to Be Considered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

It is an inevitable truth that nano-transdermal technology in act of temporary wound healing skin substitute is a complicated and controversial theme indeed. Therefore, a lot of attempts were carried out to formulate bio-nano-transdermal dressing material, effective especially for wounds. The local route of administration of a drug is taken into consideration within that the skin plays an important factor in the targeted and systematic flow of drug delivery system. Wound healing is a complicated and dynamic process. With that dealing with nanomaterials such as transdermal films made of synthetic or natural polymers with antimicrobial properties, silver nanoparticle-embedded patches or dressing materials, bio-nano-scaffolds, etc. is a debatable topic due to their beneficial effect on accelerating wound healing as well as the fear of their toxic nature. Hence, this chapter highlights the nano-dressing materials, process of wound healing, and methods of synthesizing silver nanoparticles which have always showed promising role in wound healing process, about the transdermal drug delivery system, and formulation of the same. Keywords

Transdermal technology · Nanotechnology · Silver nanoparticles · Wound healing · Dressing material

Introduction Nanotechnology is about designing the particles and materials in the nanoscale production. Itinvolves numerous physical and chemical methods for synthesis, in addition to control size and shape of the nanoparticles. These types of

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nanoparticles create pressure and toxicity to environmental factors. Therefore, the research on biodegradable nanoparticles is a fast-growing field which plays a vital role in the field of nanomedicine and nanotechnology [1]. Furthermore, dressing of wounds during home accidents or in the war field has been traditionally followed according to particular regional medications. In our country (India) especially in olden times, the people used to cover the wounds with turmeric paste, neem leaf, honey, Aloe vera pulp, and clay and may wrap it with cotton fabric or cloth as an alternative form of protective barrier to the wounded site. Then, slowly, advancement of the medicine leads to the development of topical creams exclusively impregnated with silver nitrate as it has high antimicrobial potential, tincture, alcohol rub, and fibrous synthetic material to cover the wounds such as nylon, polyethylene, and polypropylene [2, 3]. Steadily, there was improvement in the field of wound dressing. Incorporation of various techniques like grafting and biotechnology has been taken into different era of protective covering using skin from fish, pig, and even humans through cloning procedures. Nowadays, large amount of money is spent in the research and development of wound care, and currently, there are varieties of dressing such as dry dressing, wet to dry dressing, chemical impregnated dressing, foam dressing, alginate dressing, hydrofibre dressing, transparent film, hydrogel, hydrocolloid dressing, or self-adaptive dressing [2, 3]. Hence, the limitation in the conventional dressing material has opened new pathway in the research of eco-friendly dressing material.

Wound Healing Wound healing is a complex process. Apoptosis and necrosis are parts of the normal development of healing. Apoptosis is a complex network of biochemical and molecular pathway that regulates cell death. It is one of the main mechanisms in the process of wound healing. This helps in the removal of inflammatory cells and evolution of granulation tissue in the scarred area [4–6]. In healthy individuals, the repair and wound mechanism are as follows: • Neutrophils are first cells that arise during wound, as they prevent invasion from bacteria. Their activity is implicated in local and distinct tissue damage through free oxygen radicals and protease. • Neutrophils that enter the wound would have eliminated microorganism, under apoptosis, and are later consumed by macrophages. • Thus, further leading to the cycle of inflammation process. • Migration of inflammatory cells to colonize the provisional matrix. • Proliferation of fibroblast and vascular cell apoptosis. • Synthesis of extracellular matrix to reconstruct the dermal architecture.

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Common Types of Wounds The common types of wound are shown in Fig. 1.

Phases of Wound Healing There are four phases of healing, namely, inflammatory phase, migratory phase, proliferative phase, and remodelling phase. It is a continuous and steady process merging with the next phase (Fig. 2) [6, 7]. Haemostasis and Inflammation Bleeding usually occurs during skin injury and serves to flush out bacteria or antigen from injured site. Bleeding activates haemostasis which initiates an exudate component such as clotting factor. Fibrinogen elicits the clotting mechanism resulting in coagulation and together the formation of fibrin network to stop bleeding. Clot further dries up and forms scab which gives protection to the wounded site. This is simultaneously followed by inflammation, lasting for a few minutes to 24 hrs or 3 days. Necrotic tissue releases yellowish colour mass, and platelet liberated from blood vessels becomes activated as they contact with mature collagen and forms aggregates as part of clotting mechanism. Migration It involves the movement of epithelial cells and fibroblast to the wounded site. These cells regenerate from margin towards the centre site of the wound, to form a scab accompanied by epithelial thickening. Proliferation It is the next step after the migratory phase; observe skin tightening and epithelial thickening taking place until collagen bridges the wound. The proliferation of fibrin and collagen synthesis lasts for 2 weeks that results in a decrease in blood vessels and oedema. Maturation It is the final stage of the healing phase. During this phase, the tensile strength of skin gets increased, and re-epithelization of skin takes place up to 12 months, according to the condition of the wound.

Factors Affecting Wound Healing There are various factors that affect or delay the healing of wounds in an individual. Therefore the lists of the factors are given out below in the flow chart (Fig. 3).

Intrinsic Factors Health Status Blood flow and better circulation to wounded sites help in faster healing of wounds, e.g. angiogenesis is an important parameter in wound healing;

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Fig. 1 Common types of wound

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Fig. 2 Phases of wound healing

anaemic condition decreases the haemoglobin content that leads to slow blood circulation in the wounded site [8, 9]. Immune Function If the immune system is weak, then the body loses its ability in pervading the pathogens entering through the wounded site [8, 9]. Diabetes It is one of the cause of chronic wound, delaying capillary response to the injury site. Hyperglycaemia is a prevailing condition in diabetes that results in the delay of wound healing, as it lacks the synthesis of insulin and more prone to infection [8, 9]. Age Factors As we age, the oil content of the body diminishes, thus resulting in tearing of the skin, furthermore losing sensory cells. It is more prone to physical and chemical damage [8, 9]. Body Build Obese individuals may have issue with wound healing because of the inability of the body to deliver oxygen and nutrients to the wounded site. Even underweight individuals also face the same problems with the healing process [8, 9].

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Health status Immune function Diabetes Intrinsic Age factors

Body build

Nutritional status Factors Mechanicalstress

Debris

Temperature Extrinsic Maceration

Infection

Chemical stree

Fig. 3 Flow chart of factors affecting wound healing

Nutritional Status Proteins, carbohydrates, fats, vitamins, and trace elements have played a vital role in wound repair. Amino acid (arginine) as a supplement can improve the rate of wound healing [8, 9].

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Extrinsic Factors Mechanical Stress Immobile and sudden pressure results in tissue damage. Debris The debris released on wound such as scab, eschar, and wound dressing debris will disturb the healing process [8, 9]. Temperature Temperature plays an essential role in wound healing, e.g. moist conditions cause difficulty in wound healing, hence leading to various infections. Increased temperatures may lead to changes at the wound site with risk of cellular breakdown, thereby limiting healing process. Desiccation Exposed wound may significantly cause more pain and itchiness and have scab material during healing [8, 9]. Maceration It will cause destruction of tissue and slows down healing. Infection Bacterial colonization of wound site may cause difficulty in the healing process. Other factors can be alcohol, smoking, and synthetic medicines.

Nanotechnology Nanotechnology can be characterized as designing of particles with a remarkable property at a nanoscale. In 1959, Richard Feynman proposed a thought regarding nanotechnology in the discussion “A lot of room at the base,” and Norio Taniguchi (1974) instituted the term nanotechnology. A nanometre is one billionth size of a metre. Atomic force microscope and scanning tunnelling microscope are the two filtering tests that lead the way into the field of nanotech [10]. Emergences of nanoparticles have prompted its applications in different parts, for example, electronics, biomedical, cosmetics, catalyst, and other materials. Nanotechnology is not a new technology. In Ayurveda or sages era, some medicines are in the form of churunam (fine powder), and size of particles suspended in the powder was in nanosize. Still today it is available in the worldwide market.

Bottom- up Approach The materials and devices are fabricated from atomic segments. Bottom-up, or selfget together, ways to deal with nanofabrication use substance or physical powers working at the nanoscale to mass essential units into bigger structures [11]. As segment size abatements in nanofabrication, bottom-up methodologies give an undeniably vital supplement to best down systems. Motivation for bottom-up

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methodologies originates from organic frameworks, where nature has saddled substance strengths to make basically every one of the structures required by life. Specialists want to reproduce nature’s capacity to deliver little groups of particular molecules, which can then self-assembly into more expanded structures [11].

Top-down Approach Nanoparticles are built without nuclear level. The most widely recognized top-down way to deal with creation includes lithographic designing strategies utilizing shortwavelength optical sources [12]. A key favourable position of the top-down methodology – as created in the manufacture of incorporating circuits – is that the parts are both designed and constructed set up, so that now get together step is required [12].

Micro-Nano Day by day the progress of nanotechnology has been noticed in biomedical field such as drug delivery system, medical imaging, and lots more of military purposes [13–17]. There are different kinds of metallic nanoparticles such as gold, silver, platinum, iron, copper, etc., which have shown their unique application in the biomedical sector, e.g. gold and ceramic oxide nanoparticles are used in tumour and anti-inflammatory, silver nanoparticles are proven as an antimicrobial agent, anti-inflammatory, disinfectant, and less toxic to the human system. Thus, silver nanoparticles are given a lot of significance in the wound healing industries.

Introduction and History of Silver Nanoparticles Novel strategies are being developed to probe and manipulate single atoms and molecules. Among all nanoparticles, the metallic nanoparticle, such as silver has application in different ranges, e.g. gadgets, cosmetics, and biotechnology. The benefits of nanoparticles are to penetrate through the skin and target the specific site. Earlier nanoparticles were synthesized by using different physical and chemical methods. Biosynthesis/biological method was later reported. The present chapter emphasizes on synthesis of silver nanoparticles by using biological sources. Silver nanoparticles have differing properties like catalysis, attractive and optical polarizability, electrical conductivity, antimicrobial action, and surface plasmon reverberation [11]. The overall history of nanoscience and nanotechnologies is summarized in the flow chart (Fig. 4) [18]. Nanosilver is a type of nanomaterial which has been subjected into a lot of investigations. Discussions were carried out with base of silver nanoparticles as new and available in this modern era. But the history of nanosilver goes back more than 120 years, and the impact of it with the medical field and lots of other applications is very strong [19–28]. Metallic silver is the third metal known to ancient Egypt and to Chaldean as early as 4000 BCE. Over a millennium,

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Nanoera (BC) Natural fabric-flux, cotton, wool, silk:network pore 20nm Eypt-dyeing of hair by lime, leadoxide & water, process of dyeing leads ingalentine nanoparticles (lead sulpide) British museum-Lieurgs bowel:silver and gold used are in the size of 50100nm

Back groud 1959-Richard feyman:Plenty of room at bottom 1974-Norio tariguchi co:Coins the term Nanotechnology 1986:Eric Dexler:engines of creation, the coming era of nanotechnology

Founding events 2001-National technology initiative 2002-National technology infrastructure network

Science-Society concern 2003-Michael crichton's prey ispublished 2005-NSF funds two"center for nanotechnology in society 2007-Nanoethics journal launched

Science-Science concerns 2008-EU adopte "code of conduct for responsible nanoscience and nanotechnology research 2010-NSF new ethics education requirement

New discoveries 2010-2015Nanotech meets contact lens & virtual reality Axel scherer-detector of heart attack Dragon fly-ispired black silicon fights of bacteria Jenifer Alewis-Tiny 3 printed batteries Zurich-microrobots for eye surgery Creating biodegradable electrodes

Fig. 4 Flow chart showing the history of nanotechnology

silver has been used in various medical conditions. Hippocrates used it in various treatments such as ulcer and wound healing. Mostly silver nitrate was used medically and in published pharmacopeia in Rome 69 BCE. Silver nitrate was used as a medical agent by Gabor 702–705. In 980 AD, Avicenna used silver fillings for blood purifier. By 1800, a wide range of silver used in the transportation of water, wine, milk, etc. have shown longer period of storage [28]. The 120 years of nanosilver has been given in Table 1.

Properties and Application of Silver Nanoparticles Silver nanoparticles have diverse properties such as catalyst, magnetic and optical polarizability, electrical conductivity, microbial activity, and Raman scattering. The properties of it vary according to different parameters [29, 30].

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Table 1 120 years of nanosilver Year 1889 1902 1897 1907 1953 1970s Last 20 decades in market

Inventor and invention Lea M. C. – Citrate-stabilized colloidal silver Further by protein stabilization Collargol Termed as nano range Moudry – Gelatin-stabilizing silver nanoparticles Silver impregnated water filters Collargol Argyrol Protargol was used in various diseases such as syphilis and bacterial infections

Size 7–9 nm – 10 nm23 10 nm23 2–20 nm >100 nm >100 nm

Reference [19, 21] [22] [23] [24] [25] [26, 27] [28]

Diameter, Surface Area and Volume • It has unique properties depending upon the size. • Solubility and stability also vary according to the nature of nanoparticles. • High surface area, compared to volume ratio, is important for catalyst properties.

Shape and Crystallinity • It can be produced with various shapes and size. • Anisotropic shape formed with stabilizing polymer binds with one crystal face and moves in one direction – faster complex SNPs from highly faceted.

Nanoparticle Surface • Tannic acid, citrate, and PVP gave very good capping agent for SNPs. • Especially PVP binds strongly to SNP surface and provides greater stability than citrate and tannic acid.

Particle Stability • Zeta potential helps to measure particle stability > or < 20 mv and has sufficient electrostatic repulsion for stable nature.

Surface Chemistry and Functionalization • PVP or tannic acid is used as capping agent. In the biological application, SNPs were coated with BSA and PEG for stability and have property to flip the surface with positive and negative charge.

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Measuring SNP Concentration • Depending on concentrations, the properties of silver nanoparticles also vary. ICP-MS is used in measuring the concentration of SNPs.

Types of Silver in the Term of Nano Silver Colloids Silver colloids are available to the market in five types. In that mesosilver is the purest colloidal silver and others are not true or pure. NanoXact They are the aggregated spherical nanoparticles that are suspended into water molecules. BioPure Silver It is highly concentrated and available in pure form. OECD Silver This silver was given an Organization for Economic Co-operation and Development direction. Its definition has been chosen as nano-toxicology principles with PVP and citrate surfaces. Custom Silver It has been customized according to the custom organization, biofunctionalized shells, and suspension media. Silver Nanoparticles They have high optical efficiencies and tend to cooperate between the wavelength 550 and 950 nm [30].

Methods of Synthesizing Nanoparticles Chemical Reduction It is one of the processes used in the reduction of silver nanoparticles with the help of ionic salts in the appropriate medium in the vicinity of surfactants utilizing diminishing specialist, e.g. sodium citrate and sodium borohydride [31–34]. Solvothermal Synthesis This is an adaptable low-temperature mechanism; polar solvents under pressure and at temperature over their building focuses are utilized. Under solvothermal conditions, the dissolvability of reactants increments fundamentally, empowering response to happen at lower temperature [31–34]. Solgel Technique It is one of the wet chemical strategy/method utilized for the manufacturing of metal oxides from the available chemicals which represent an integrated system of discrete patches or polymers. This precursor sol can either be deposited on the substrate to form a film or casted into a suitable compartment with fancied shape or used to synthesize particles or powders [31–34].

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Laser Ablation This is the procedure of irradiating so as to expel materials from a strong surface with a laser shaft. Subsequently, they create nanoparticles [31–34]. Biological Method Biological method follows bottom-up approach with reduction or oxidation process. As the name subjects, the biological sources such as microorganism and plants are used for the reduction, capping and stabilizing nanoparticles. The advantages are eco-friendly, cost-effective, faster production, and non-toxic production with any chemicals [31–34]. The systematic biological pathway has been indicated in Fig. 5.

Characterization and Application There are various techniques followed to validate and confirm the synthesis of silver nanoparticles [35–37]. • Scanning electron microscope, eld emission electron microscope, and transmission electron microscope: Basically used to determine the size and morphology of particles. • X-ray diffraction: To study the crystal structure and size. • Fourier transform infrared spectroscopy: To identify the functional groups of biological sample. • Energy dispersion X-ray spectroscopy: To determine the composition information. • Dynamic light scattering: To determine the particle size and is commonly used in chemicals and pharmaceutical industries. • Atomic force microscopy: To identify the mechanical properties of sample.

Fig. 5 Biological pathway of silver nanoparticles

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Silver nanoparticles have a strong role in the field of antimicrobial and antiinflammatory applications till date. There are other various medical applications such as wound dressing material, silver impregnated catheters, vascular prosthesis, ventricle drainage catheters, orthopaedics, and surgical mesh available in the market. Currently, a lot of research is carried out on nanodrug delivery system; liposomes are used to extend the life of drug, biochips as nanodevice used in synthetic neuron, and nanorobots for the microsurgery.

Transdermal Drug Delivery System The skin is an external barrier that provides us with a complete protection against bacterial infections, thereby maintaining the homeostasis of the body. Skin loss occurs frequently as a consequence of blazes, injury, and clutters as the skin is the main organ in contact with the external factors. Generally, wounds are categorized into three classes, for example, superficial wound, partial-thickness wound, and fullthickness wound [38]. The essential guideline of ideal wound healing is to minimize tissue damage and give satisfactory tissue perfusion, oxygenation, appropriate sustenance, and moist injury recuperating environment to re-establish its natural capacity [39]. Traditionally, there are a lot of therapeutic options available to treat wounds, but it takes prolonged time to heal. Due to recent advancements in the field of drug delivery, a rapid recovery can be observed against infections. The transdermal medication conveyance is a novel medication conveyance framework which has been as of late created. The bioadhesive patches containing distinctive constituents of medications are administrated into the skin. It is a non-obtrusive, advantageous, and effortless technique for medication conveyance; additionally it has significantly toxic properties, for example, gastrointestinal poisonous quality [40, 41].

Administration of Drug Drugs that are dermally administered through the skin are categorized as (1) those applied for local action and (2) for systemic effects. Local action impact incorporates those connected on or at the surface of the skin, which applies the activity on the stratum corneum or regulates the function on the epidermis or dermis. The products that come in these criteria are creams, gels, ointments, pastes, suspensions, lotions, foams, sprays, aerosols, and solutions. Transdermal drug delivery system (TDS) or transdermal patches go under the criteria of systemic impact [42]. Transdermal drug delivery system represents discrete dose type of medication to the general flow through the skin. It overcomes drawbacks of oral drug delivery system by providing an end to gastrointestinal lethality and hepatotoxicity [43]. Transdermal patch gives uniform scattering of medication into target site unlike the oral dosage forms which forms blood hikes and troughs [44]. Therapeutical applications to the skin to ease the ailments have been followed since the time of ages and have shown beneficial outcomes.

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Advantages and Limitation of Transdermal Drug Delivery Advantages • It is a convenient method. • It requires only weekly applications. • It also acts as an alternative route to administrate drug by avoiding oral dosage and reducing the toxicity. • The relatively consistent plasma levels are a good indicator for transdermal drug delivery. Limitation • Local irritation at the site of application may be due to adhesive or other excipients used in the formulation of film/patch. • Its molecular weight should be less than 500 Da.

Characteristics of Several Drug Permeation through Transdermal Transdermal permeation is a slow process of diffusion driven by concentration gradient between high in delivering system and zero in prevailing system of the skin. For continuous delivery of drug towards the site, continuous contact of film with considerable amount of time is required [44]. Transdermal patches are currently marketed in transdermal delivery system. Functional parts of film are as follows: • • • •

An impermeable backing. A reservoir holding active ingredients. An adhesive to hold the patch. A protective cover that is peeled away before applying it.

Patches fall into two categories: reservoir and matrix system. Formulation of patches is a complex process. The rate and amount of absorption depends on many factors such as nature of drugs, concentration in reservoir, or matrix and space covered by patch. The release of drug also depends on the site covered by patch. To keep the favourable absorption concentration, large amount of drug is placed in the film [45–47]. There are various methods to enhance the penetration methods and are given in Fig. 6 [48].

Transdermal Film A transdermal patch is defined as an adhesive patch kept over the dermal layer to release a particular dose of medication released through the skin with fore-ordained rate of discharge to venture into the circulation system. Today the most widely recognized transdermal film present in the market is based on semipermeable membranes that are known as patches [49–51].

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Fig. 6 Various methods used to enhance the skin penetration

Technologies for Development A number of technologies have been developed to provide rate control release and skin permeation of drugs. It was classified into four basic approaches [52].

Polymer Membrane Permeation-Controlled TDDS In this system, drug reservoir has been sandwiched between the drug impermeable support overlay and rate-controlling polymeric film. The drugs are allowed to discharge just through the rate-controlling polymeric film. In the drug supply compartment, the drug solids are scattered homogeneously in a strong polymer network, suspended in an unleached viscous fluid medium (e.g. silicone liquid) to frame a paste like suspension or break down in a releasable dissolvable (e.g. alkyl liquor) compound to form clear drug solution. The rate-controlling layer can be either a microporous or a nonporous polymeric film with particular drug permeability. The rate of medication discharge from this TDD framework can be custom-made by fluctuating the organization of the drug repository plan and the permeability coefficient and/or thickness of the rate-controlling layer [52–55].

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Polymer Matrix Diffusion-Controlled TDDS In this approach, the process of medication supply is framed by homogeneously scattering the medication solids in a hydrophilic or lipophilic polymer lattice, and the sedated polymer shape is then formed into medicated discs with a characterized surface zone and controlled thickness. This drug reservoir-containing polymer disc is then mounted onto an occlusive base plate in a compartment manufactured from a drug impermeable plastic backing. Rather than covering the adhesive polymer straightforwardly on the surface of the mediated discs, as demonstrated prior in the main kind of TDD systems, in this system, the adhesive polymer is connected along the perimeter of the patch to shape a segment of adhesive edge encompassing the sedated plate [52–55].

Drug Reservoir Gradient-Controlled TDDS Drug reservoir slope controlled TDDS to beat the non-zero-order (Q versus t½) drug discharge profiles; polymer matrix drug scattering sort TDD system can be altered to have the medication stacking level differed in an incremental way, shaping a gradient of drug reservoir repository along the diffusional way over the multilaminate adhesive layers [55]. The rate of drug discharge from this sort of drug reservoir gradient can be expressed by: dQ/dt ¼ Ka/rDa/ha(t)  Ld(ha).

Microreservoir Dissolution-Controlled TDDS The drug delivery system can be recognized as a hybrid of the reservoir and matrix dispersion drug delivery system. In this approach the drug reservoir is framed by first suspending the drug solids in an aqueous arrangement of water-miscible medication solubilizer, e.g. polyethylene glycol [55].

Types of Transdermal Films Single-Layer Drug Adhesive Adhesive layer of system contains the drugs that not only adhere to other layers but also are responsible for releasing the drugs [56, 57]. The rate of release follows the diffusion phenomenon (Fig. 7). The rate of release of drug is expressed as: dQ=dT ¼ Cr =1=Pm þ 1=Pa : where Cr is the drug concentration in the reservoir compartment, Pa is the permeability coefficient of the adhesive layer, and Pm is the permeability coefficient of the rate-controlling membrane.

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Fig. 7 Single-layer drug in adhesive film

Multiple-Layer Drug Adhesive It is almost similar to a single-layer adhesive, but in here, there are two layers of adhesive that are sandwiched with a single layer of membrane in between them. Release of drug follows the diffusion phenomenon and results in immediate release of drug along with the adhesive layer (Figs. 8, 56,57]. The rate of release of drug is expressed as: dQ=dT ¼

  Ä K a =r nDa =ha Cr :

where Ka/r is the partition coefficient for the interfacial partitioning of the drug from the reservoir layer to adhesive layer.

Drug Reservoir in Adhesive Drug reservoir is immersed in the backing and membrane layer followed by adhesive layer and release liner (Fig. 9). This drug can be available in many forms such as gels, solutions, suspension, or dispersed in solid matrix. Release of the drug is controlled by controlling the membrane (microporous or nonporous) [56, 57]. The rate of drug release from this drug reservoir system is given by dQ/dT ¼ [Ka/r · Da/ha(t)]A(ha). where ha is the thickness of adhesive layer and A is the thickness of the diffusional path.

Drug Matrix in Adhesive Drug availability nature in this particular system is dispersed homogenously in a hydrophilic or lipophilic polymer matrix and designed by semisolid matrix having drug solution or suspension form which is in direct contact with the release liner

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Fig. 8 Multiple-layer drug in adhesive film

Fig. 9 Drug reservoir in adhesive patch

[56, 57]. The rate of release of drug is calculated by the following equation: dQ/dT ¼ ACpDp1/2/2 t. where A is the initial drug loading dose dispersed in the polymer matrix, Cp is the solubility of the drug, and D is the diffusivity of the drug in the polymer (Fig. 10).

Drug Delivery Routes Skin Permeation Anatomy and Physiology of the Skin The skin is the largest organ and receives about one-third of blood. It is multilayered and is divided into three categories: epidermis, dermis, and hypodermis [58, 59].

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Fig. 10 Drug matrix in adhesive patch

Epidermis It is the outer layer of the skin which gives protection from immediate attacks and also tones the skin. 1. Stratum corneum is otherwise known as horny layer of skin. Eventhough the layer is flexible, it is impermeable, hence proving the principle barrier for penetration. The layer constitutes 75 to 80% proteins, 5–15% lipids, and 5–10% ondansetron material. 2. Viable epidermis is found just beneath the stratum corneum. It consists of various layers such as the stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale beneath stratum corneum. Dermis It is the layer found next to epidermis and contains tough connective tissue, hair follicles, and sweat glands. The continuous function of blood supply is important in regulating the body temperature. It provides nutrients and oxygen to the skin removing toxins and waste products. Dermal concentration permeates very low, and concentration difference across the epidermis provides essential driving force for transdermal permeation. Hypodermis It is a subcutaneous tissue made up of fat and connective tissues. This layer helps to regulate temperature and provide nutrition and mechanical protection. During transdermal drug delivery system, drug needs to pass through all these three layers to reach the circulation, while topical drug delivery penetration through stratum corneum is only necessary, thus retention of drug in skin layer is desired (Fig. 11). Drug has been delivered through different routes or pathways according to the drugs [60]. Drug is administrated and passed through the sweat glands, then followed by sebaceous gland, or is penetrated through the layers of hair follicles. Mostly drug that has passed through it is from ointments such as topical delivery

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Fig. 11 Anatomy of the skin

system. But in case of transdermal drug delivery, the drug has been passed through the stratum corneum (Fig. 12). • • • •

Sweat gland. Sebaceous gland. Hair follicles. Stratum corneum: intercellular route is the major pathway for permeation of most drugs across the stratum corneum.

Methods of Skin Penetration Intracellular Penetration Drugs penetrate through the cells of the stratum corneum. It is mostly used in the hydrophilic medications. As the stratum corneum hydrates, water accumulates the external surface of the protein fibres. Polar atoms seem to go through this immobilized water [61, 62]. Intercellular Penetration A non-polar substance passes through the skin by intercellular penetration route. These particles break down and diffuse through the non-watery lipid matrix between the protein fibres [62, 63]. Transappendageal Penetration It is also called as the shunt pathway. In this course, the drug might transverse through the hair follicles, the sebaceous pathway

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Fig. 12 Routes of drug delivery

of the pilosebaceous contraption or the aqueous pathway of the salty sweat organs. The transappendageal pathway is thought to be of minor significance due to its moderately smaller range (less than 0.1% of aggregate surface). However, this course might be of some significance for vast polar compounds [61, 62]. The transdermal permeation can be visualized by a number of series: • Adsorption of a penetrant molecule onto the surface layers of stratum corneum. • Diffusion through the stratum corneum and through the viable epidermis. • Finally through the papillary dermis into the microcirculation. Properties The quality and potential of a dressing material through transdermal or skin penetration depend on physiochemical and biological properties [63]. Physiochemical Properties • Molecular weight should be below or approximately 1000 daltons. • Drug should have affinity on both lipophilic and hydrophilic phases. • Low melting point. • pH range should be between 4 and 6, thus resulting in significant and uniform distribution off drug. Biological Properties • Slow release rate of drug with few mg per day. • Drugs should have half-life t½. • Drugs need to be non-irritating and non-allergic. • Drugs that degrade in gastrointestinal track is an important parameter noted on transdermal drug delivery system.

Basic Components Required for Transdermal Dressing Material Polymers It is one of the basic components of transdermal system. Selection of polymers and designing are vital. There are two categories of polymers: natural polymer, e.g. zein, gelatin, cellulose, chitosan, etc., and synthetic polymers, e.g. hydrin rubber, polyisobutylene, silicon rubber, nitrile, neoprene, etc. [49, 50, 55, and].

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Characteristics of Polymer Selection • Should be stable and non-responsive with the drug moiety. • Easily accessible, created, and fabricated into desired formulation. • The properties of polymer ought to be in such a way that the drug should be easily penetrated through the skin. • Mechanical properties should be stable, when the high-concentration drug is substituted. Release Liners The film is covered by a protective liner until the storage. Outer covering (release liner) is removed and discarded before the application of films. It is composed of non-occlusive (paper fabric) or occlusive (polyethylene, polyvinylchloride) material and release coating layer made up of silicon or Teflon; other materials used as release liner are polyester foil and metalized laminate [49, 50, 52, 57, 60]. Backing Membrane Backing membrane was designed considering various parameters [49, 50, 52, 57]: • It should be flexible. • Low water vapour transmission so as to promote skin hydration and thus greater skin permeability. • Should be chemical resistant and good tensile strength. • Non-irritant. Drugs Drugs selected should be considered with various physiochemical, pharmacokinetic, and pharmacological properties for transdermal system development [49, 50, 52, 57].

Characteristics of Drugs • • • •

Low molecular weight  1000 Da. Solubility nature. Range of melting point (200  C). Lipophilicity, undergo extensive presystematic metabolism, non-ionic, and non-irritant are considered to be suitable for delivery system.

Penetration Enhancers Incorporation of protein enhancers results in the formulation and improves the diffusivity and solubility of drugs through the skin [49, 50, 52, 57].

Properties that Need to Be Considered • Should be non-irritant, non-sensitizing, non-phototoxic, and non-comedogenic. • Should not have pharmacological activity, as it should not bind to receptors.

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• Should be readily formulated into dermatological preparations. • Should adhere and equally spread to the skin. Plasticizers Plasticizers used can be synthetic and natural. Along with brittleness, ductility, adhesiveness, and strength of the film are also improved. Plasticizers have been used in many formulations ranging from 5 to 20% (w/w, dry basis). Glycerol, sorbitol, phosphate, phthalate esters, fatty acid esters, and glycol derivatives such as PEG 200, and PEG 400 [48, 49, 51, 56, and]. Solvents Various solvents used to prepare drug reservoir are water, methanol, chloroform, acetone, isopropanol, dichloromethane, etc. [64]. Role of Nanoparticles in Transdermal Wound Dressing Material Generally, transdermal drug delivery is one of the stimulating areas because the skin naturally acts as a protective barrier against various external factors. Consequently, to develop transdermal patches requires standard materials such as polymers, penetration enhancers, solvents, and drugs with lower molecular weight, size, solubility, and stability potential [65]. Obviously, in the last few decades, nanotechnology has built a strong foundation in the use of nanoparticles in consumer products. For instance, titanium oxide, zinc oxide, and silica nanoparticles have been used in cosmetics, sunscreen cream, desiccant, and free radical scavengers from almost the 1950s. However, these are not anticipated to penetrate through the skin but act as an external layer. Thus the increase of nanoparticle utilization and usage has led its way to transdermal drug delivery system. There are mainly three nanocarrier categories [66]: (1) solid nanocarriers have the slowest drug division: metal core, solid lipid, and solid polymeric nanoparticle; (2) liquid-phase nanocarriers release drug more steadily compared to solid-phase nanocarriers: micelles and nanoemulsions of lipids; (3) liquid crystalline-phase nanocarriers are more reliable and synthesized by monolein, water, and poloxamer. Overall, these resulted in the controversial examination of toxicity to the environment, skin, eye, and mouth, respectively. Much research was carried out with in vitro cytotoxicity test with cell lines, namely, vero cell line, fibroblast (3 T3-L1) cell line, keratinocyte (HaCaT) cell lines, and in vivo and ex vivo models [67]. Studies showed both upside and downside of nanoparticleembedded transdermal patches or dressing material. To the upside, it can easily penetrate through the skin depending on size, charge, and material. To the downside, the acute or chronic level of toxicity is still a debatable topic. Hence, limitation overcomes with substitution of biological or eco-friendly nanoparticles. Bio-Nano-Based Transdermal Wound Dressing Material The advancement in polymer science has laid path towards the transdermal delivery system with considerable flexibility of using natural polymer compared to synthetic and semi-synthetic polymers to stabilize the release of medicine via the intact skin. In our laboratory, we have developed biological and eco-friendly transdermal wound dressing material embedded with bio-silver nanoparticles to boost up the healing process [68, 69]. To illustrate,

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natural polymers such as chitosan and gelatin were used as it is biocompatible, non-toxic, and biodegradable not only that but also possess various other functions, viz. cell delivery systems, orthopaedics, wound healing, ophthalmology, bone healing, antimicrobial, haemostatic, good film-forming property, etc. Exclusively, drug was prepared with a lot of provisions and silver nanoparticles synthesized with the help of biological sources; mushroom (G. lucidum) shows synergistic beneficial properties such as antimicrobial, anti-diabetic, wound healing, anti-inflammatory, and angiogenesis [67]. Nanosize drug used in transdermal material can be easily transferred and targeted to specific site and thus portrays the speedy wound healing process. Characterization and Evaluation of Transdermal Wound Dressing Material The prepared chitosan-gelatin transdermal patches with bio-silver nanoparticles (Fig. 13) are subject to various physicochemical and biomedical evaluation tests to meet the essential requirements [70]. Consequently, thickness of the patch, weight uniformity, folding endurance, percentage moisture content, content uniformity test, moisture uptake, drug content, shear adhesion test, bioadhesion test (Fig. 14), oxygen penetration test (Fig. 15), tensile study (Fig. 16), quick stick (peel-tack) test, probe tack test, microbial penetration test, in vitro drug release studies, in vitro skin permeation studies, skin irritation study, stability studies, in vivo toxicity, or irritation study is carried out to determine the uniform distribution of drug through the film and stability of the film and indicates the capacity of the film to hold the wound exudate and dispersion of the drug towards the wounded site resulting in the complete protection against the external factors; duration and percentage of drug diffused through the diffusion bag and skin are calculated as well as antimicrobial potentiality Fig. 13 Chitosan-gelatin transdermal dressing material

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Fig. 14 Bioadhesive properties

and tensile strength of the patch or dressing material [70, 71]. It is also subjected to analytical characterization techniques to visualize the drug and to determine the size, percentage, and composition of nanoparticles with scanning electron microscope (SEM) (Fig. 17), EDAX (Fig. 18), inductively coupled plasma or optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR) (Fig. 19), liquid chromatography-mass spectroscopy, differential scanning calorimeter, smallangle X-ray diffraction, etc. [72, 73]. Complication of Bio-nanoparticles in Dressing Material Currently in the market, there are not many nano-embedded transdermal patches especially bio-based transdermal patches are till at the bench side. Furthermore, their aren't enough toxicological assesments available, and it is difficult to develop an analytical method for drug delivery; sometimes the process of making is time-consuming and difficult, and the attainted size is not enough to avoid the immune response [74]. Advantages of Bio-nanoparticles in Dressing Material The benefits of using eco-friendly material and bio-nanoparticles like bio-silver nanoparticles and chitosan nanoparticles result in the biodegradability nature. There are numerous processes to prepare the nanoparticles and sometimes can include antibodies

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Fig. 15 Oxygen penetration studies

Fig. 16 Tensile study

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Fig. 17 Chitosan-gelatin transdermal film

in the surface to reach the targeted site; both hydrophilic and hydrophobic drug can be loaded, and they can avoid the immune response due to their size [73, 74].

Conclusion To recapitulate, transdermal patches embedded with nanoparticle drug such as silver nanoparticles enhance the drug delivery through different skin barriers and reach the targeted site, thus avoiding various oral and gastrointestinal troubles and also meeting the required standards in the wound care management. Alternative usage

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Fig. 18 EDAX report of chitosan-gelatin transdermal film

of natural material and bio-silver nanoparticles boosts up the credibility of the wound dressing material as it is eco-friendly and less to non-toxic to the human system. Website http://www.adhexpharma.com/ https://www.researchandmarkets.com/r/rewslv http://leonardino.eu/index.php/nad/ https://axiobio.com/?cmp_id¼11,266,027,574&adg_id¼105,805,492,930& k w d ¼w o u n d s & d e v i c e ¼c & g c l i d ¼C j 0 K C Q i A h Z T 9 B R D m A R I s A N 2 E J2LnOCY71wEewSlEEUJditCUVOQa9R2OOzk7aHT3pyxZ2G1SmkO3 QYaAqW9EALw_wcB.

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Reference 1. Paul S, Jayan A, Sasikumar CS (2015) Physical, chemical and biological studies of gelatin/ chitosan based transdermal films with embedded silver nanoparticles. Asian Pac J Trop Dis 5 (12):975–986. https://doi.org/10.1016/S2222-1808(15)60968-9 2. Shah JB (2011) The history of wound care. J Am College Certified Wound Specialists 3(3):65– 66. https://doi.org/10.1016/j.jcws.2012.04.002 3. Paul S, Dhinakaran I, Mathiyazhagan K et al (2015) Preparation of Nanogel incorporated with silver nanoparticles synthesized from Pongamia Pinnata. L root. Int J Sci Res Knowl 3(12): 0314–0325. https://doi.org/10.12983/ijsrk-2015-p0314-0325 4. Bellamy CO, Malcomson RD, Harrison DJ, Wyllie AH (1995) Cell death and health disease: the biology and the regulation of apoptosis. Semin Cancer Biol 6:3–16 5. Schwartzman RA, Cidlowski JA (1994) Glucocorticoid-induced apoptosis of lymphoid cells. Int Arch Allergy Immunol 105:347 6. Turner TD (1979) Products and their development in wound management. Plast Surg J:75–84 7. Bharambe SV, Darekar AB, Saudagar RB (2013) International. J Pharm Technol 5(3):2764–2786 8. Diegelmann R, Evans M (2004) Wound healing: an overview of acute, fibrotic and delayed healing. Front Biosci 9:283–289 9. Lazarus G, Cooper D, Knighton D, Margolis D, Pecoraro R, Rodeheaver RG (1994) Definitions and guidelines for assessment of wounds and evaluation of healing. Arch Dermatol 130:489–493 10. Yazdanpanah L, Nasiri M, Adarvishi S (2015) Literature review on the management of diabetic foot ulcer. World J Diabetes 6(1):37–53 11. Hussain CM (2020) Handbook of manufacturing applications of nanomaterials. Elsevier 12. Eric DK (1986) Engines of creation: the coming era of nanotechnology. Doubleday. ISBN 0-385-19973-2 13. Levins Christopher G, Schafmeister, Christian E (2005) The synthesis of curved and linear structures from a minimal set of monomers. J Org Chem 70(22):9002–9008 14. “Applications/Products.” National nanotechnology initiative. Retrieved 2007-10-19 15. Albrecht MA, Evans CW, Raston CL (2006) Green chemistry and the health implications of nanoparticles. Green Chem 8:417–432 16. Aiken JD, Finke RG (1999) J Mol Catal A Chem 145:1–44 17. Babincova M, Babinec P (2009). Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub, 153: 243–250 18. Tolochko NK (2009) History of nanotechnology. Nanoscience and nanotechnologies, encyclopedia of life support systems.(http://www.eolss.net/Eolss-sampleAllchapters.aspx) 19. Nowack B, Krug HF, Height M (2011) 120 years of Nanosilver history: implications for policy makers. Environ Sci Technol 45(4):1177–1183 20. Wesley Alexander J, Liebert MA (2009) Surg Infect 10(3) 21. Lea MC (1889) On allotropic forms of silver. Am J Sci 37:476–491 22. Frens G, Overbeek JT (1969) Carey Leas colloidal silver. Kolloid Z Z Polym 233(1–2):922 23. Henglein, Giersig M (1999) Formation of colloidal silver nanoparticles: capping action of citrate. J Phys Chem B 103(44):9533–9539 24. Paal C (1902) Uber colloidales Silber. Ber Dtsch Chem Ges 35(2):2224–2236 25. Boese K (1921) Uber Collargol, seine Anwendung und seine Erfolge in der Chirurgie und Gynakologie. Dtsch Z Chir 163(1–2):62–84 26. Bogdanchikova NE, Kurbatov AV, Tretyakov VV, Rodionov PP (1992) Activity of colloidal silver preparations towards smallpox virus. Pharm Chem J 26(9–10):778–779 27. Bechhold H (1907) Die Gallert filtration. Z Chem Ind Kolloide 2:3-9–33-41 28. Moudry ZV (1953) Process of producing oligodynamic metal biocides. United States Patent 2 (927):052 29. Kasemo B, Johansson S, Persson H, Thormeahlen P, Zhdanov VP (2000) Catalysis in the nm-regime: manufacturing of supported model catalysts and theoretical studies of the reaction kinetics. Top Catal 13:45–53

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Starch Based Bio-nanocomposites : Modern and Benign Materials in Food Packaging Industry

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Shikha Gulati, Sanjay Kumar, Parul Chandra, Atishay Jain, Lavanya Ahuja, Kanchan Batra, and Nandini Sharma

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventional Food Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metals and Alloys in Food Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shortcomings of Conventional Food Packaging Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Why Starch Is Used as a Packaging Material? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Different Types of Starch-Based Films . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermoplastic Starch (TPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starch Plasticizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modification of Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemically Modified Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Physical Modification of Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Enzymatic Modification of Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Various Properties of Thermoplastics and Composites Needed for Food Packaging (Fig. 12) . .. Biodegradable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Barrier Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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S. Gulati (*) · S. Kumar Department of Chemistry, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India P. Chandra · A. Jain · L. Ahuja · N. Sharma Department of Biological Sciences, Sri Venkateswara College, University of Delhi, New Delhi, Delhi, India K. Batra Department of Zoology, Kalindi College, University of Delhi, New Delhi, Delhi, India © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_96

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Mechanical Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermal Property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion and Future Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

As we know, nowadays there is a drastic shift going on in various industries especially “food packaging industry” to contribute for sustainable development by changing their methods. There are some requirements like recyclability, consumer acceptability, nontoxicity, antimicrobial property, antioxidant property, and flexibility which are important to maintain our environment safe and ensure the safety and better quality of food and are discussed in this chapter. Conventionally, food is packed in petroleum-based plastic, but due to its nonrenewable aspect, it has proved to be hazardous for the ecosystem. So, the food packaging industry is now trying to shift to various methods that are eco-friendly and promote sustainable development. These methods mainly focus on maintaining our environment’s safety and ensuring the quality of the food packaged. As a result, scientists moved on to a new avenue, which is biopolymers for food packaging. Biopolymers play an important role in making our ecosystem safe. Numerous sources can be used in the production of biopolymers such as biodegradable films that include polysaccharides, proteins, and lipids. Among polysaccharides, starch due to its low cost and abundance in nature is of significant importance. Starch has various advantages that are helpful as food packaging material such as low thickness, flexibility, and transparency. But these show some drawbacks too, such as the poor mechanical properties and water vapor permeability. The following chapter focuses on the modification of starch film with various nanocomposites to increase the efficiency of starch film and also highlights the current advances in the applications as well as future perspectives of starch-based bio-nanocomposites for food packaging. Keywords

Nanocomposites · Bionanotechnology · Food packaging · Starch bionanocomposites · Biodegradable polymers · Environment-friendly

Introduction Food packaging is important as it ensures that food is protected and maintained until the end of its shelf life. If the packaging is not given much importance, the quality and safety of food will be compromised; hence food packaging is essential. Environmental issues are becoming increasingly important in different parts of the world as a result of which consumers are demanding bio-based packaging materials as an alternative to materials produced from nonrenewable resources [1]. Petroleum-based plastic is widely used in a various range of applications such as packaging and automobile parts. These conventional methods which include synthetic polymers show various properties such as thermal properties, rheological properties, gas and water barrier properties, lightweight, easy to

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manipulate, and cost-effective. Six to 8% of total world oil production is consumed as raw material, as well as the oil required for energy for plastic production. The amount of petroleum used to make plastic not only contributes to the depletion of fossil fuel, but also the overall price of petroleum is influenced by the rate of consumption, contributing to the current rise in raw material costs. Petroleum-based plastic is not limited to packaging materials but also includes agriculture, aerospace, automobile, constructions, sports, domestic, and many more. The production of plastic has grown continuously, approximately more than 300 million tons per year (Plastics Europe, 2015) [2]. Various synthetic polymers are used for food packaging such as plastic, glass, paper, metals, and alloys. The aforementioned substances are non-biodegradable, non-recyclable, and synthetic polymeric materials that are raising serious concerns in environment-related issues. Bioaccumulation is shown in the organism due to phthalates-based plasticizers and BPA. However, some invertebrate species, especially mollusks and crustaceans, tend to portray a large number of concentration factors, as compared to vertebrates. Angiosarcoma of the liver among factory workers is caused due to exposure of carcinogenic vinyl chloride which is the monomer of PVC plastic. Due to environmental pollution problems of petroleum-based plastic, now the researchers are contemplating the replacement of petroleum-based plastic with environment-friendly biodegradable polymer for food packaging materials; these materials, in comparison to fossil fuel-based, are less harmful to the ecosystem, but the packaging material derived from a natural biodegradable polymer is more expensive than a nonbiodegradable synthetic polymer. The presence of oxygen and nitrogen in natural polymer leads the polymer to biodegrade which is absent in synthetic polymer [3]. In the last few decades of publications, starch-based plastics seem to be the front-runner in bio-based materials because of their low cost, renewability, and availability. Starch resists thermoplastic behavior due to intermolecular force and hydrogen bonding. Plasticizers in addition to water show thermoplastic starch. Starch has some drawbacks, namely, strong hydrophobic properties, poor mechanical properties, and barrier properties. Various modifications with nano-fillers increase the various packaging properties of starch [4]. Amylose (linear with some branched) and amylopectin (branched) are two components of starch. Amylose gives strength to films when it is processed, and amylopectin decreases the tensile strength of films. In this chapter, conventional food packaging materials and their shortcomings are discussed in detail. To avoid such downsides, the starch used as a packaging material and its synthesis method are also highlighted in the chapter. Also, the modification of starch films with various nanocomposites resulting in a myriad of properties is highlighted in the chapter.

Conventional Food Strategies Metals and Alloys in Food Packaging Aluminum Aluminum is widely used for packaging food materials because the metal and its alloys are extremely immune to corrosion. What is more important is that they don’t react or injure the food. Metal packaging protects the food from extreme temperatures, keeps it intact for an extended length, and conjointly protects it from

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Fig. 1 Aluminum containers for food packaging

ultraviolet radiations, oil, vapor, and microorganisms. Once the metal is exposed to air, the metal develops a layer of aluminum oxide. This film is colorless and non-flaking. Metal can bear temperatures from
40  C to 350  C, and it ensures equal distribution of warmth within the food materials (Fig. 1).

Aluminum Foil Thickness of aluminum foils varies from 0.004 and 0.24 millimeter thick. The time period of aluminum foil is somewhat around 12 months. The nontoxic nature and barrier properties of foil create it a helpful material in food packaging. Compared to the other plastic materials used for lamination applications, it prevents the migration of water, oxygen, gases, etc. to a larger extent. Aluminum Cans Aluminum is widely used for beverage cans and other types of food packaging that may include foils, cans, and tubes. The food or beverages stored in containers made of aluminum have the ability to retain their taste for a longer duration of time. Around 90% of beverages all around the world is sold in cans made of aluminum. In addition to the barrier properties, it does not modify the organometallic properties of food and does not react with the components of it. Steel The steel used for food packaging applications are mainly of two types; electrolytic tinplate (ETP) and electrolytic chromium/chromium oxide-coated steel (ECCS) (Fig. 2): A) Electrolytic Tinplate (ETP) ETP is a low-carbon-containing steel sheet or coil which is coated on both surfaces with tin. The use of tinplate ensures that the stored food is free from bacterial and other external contaminations. Its shiny surface and the fact that it is resistant to corrosion make tinplates an ideal choice for the food industry. Tinplate

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Fig. 2 Steel containers to store food

products have excellent corrosion protection properties, appealing appearance, and high strength and provide resistance to attack by organic substances for both food and nonfood packaging products. B) ECCS (Electrolytic Chromium/Chromium Oxide-Coated Steel) ECCS (electrolytic chromium/chromium oxide-coated steel) has equal coating weights on both surfaces of the coil. Electrolytic chromium-coated steel (ECCS), sometimes also called tin-free steel, is finding increasing use for food cans. A layer of metallic chromium may also be applied. The function of a chromium coating is to prevent atmospheric oxidation or sulfur staining of the steel by food materials.

Plastics Plastics are highly diverse and one of the most common materials used for packaging foodstuff. Plastics are relatively safer materials for the packaging of food products especially polyolefin as they do not react with food. Chances of contamination are difficult (Fig. 3). Due to plastics’ good barrier properties against water, carbon dioxide, oxygen, and nitrogen, products retain their flavor, aroma, and nutritional value and are protected from external contamination. Plastic packaging may consist of single polymers, e.g., polyethylene terephthalate (PET), polypropylene (PP), high(HDPE) and low-density polyethylene (LDPE), polystyrene (PS), and polyvinyl chloride (PVC). Plastic materials are made up of large, organic (carbon-containing) molecules that can be molded into a variety of useful products; they are fluid, moldable, and heat sealable. Here are some examples of plastic packaging generally used by the food industry [5]:

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Fig. 3 Plastic used in packing food

A) Polyethylene Terephthalate PET is the most ordinarily used plastic within the world. The plastic material is primarily used for food packaging that needs glass-clear quality, e.g., contemporary salads, fruits, cold meats, snacks, etc. PET could be a terribly powerful and versatile plastic material with high impact strength. B) Polypropylene Polypropylene (PP) is one of the most used thermoplastics globally. It is a robust material with strong resistance to chemicals, solvents, acids, and alkalis. The material is colorless naturally but can be dyed to any other different color. PP is a very versatile material that is suitable for packaging fresh meat. PP can be recycled into new raw material as well. C) Polystyrene Polystyrene plastic is made from petrochemicals. Polystyrene is commonly used in food packaging, where it occurs in two forms, rigid and foam. PS is a thermoplastic film with good transparency and high tensile strength, but the only problem is that it provides a poor barrier to moisture and gases.

Glass Glass is preferred as a potent food packaging material due to its inertness, good barrier properties toward moisture and gases, and high recyclable nature. Glass packaging is a type of packaging commonly used in many foods ranging from heat-treated or pressure-packed solid. Unlike metals, glass does not have free electrons that can absorb light energy. It is a tough, durable, and chemically inert material which is being used as a food packaging material for a while now (Fig. 4).

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Fig. 4 Glass containers used to store food

Another reason for its high exploitation is that the chemical integrity of the glass is quite high. Glass is chemically resistant to all food products, both liquid and solid. Moreover, it has good design potential as a result of which glass can be made into different shapes depending on the food to store, making it a preferable food packaging material. Glass is extensively preferred as a packaging material due to its properties; it can be recycled and reused. For example, beer is stored in glass bottles to avoid spoilage. Besides, since glass is neutral, it does not react with the contents of the food. The production of glass containers involves heating a mixture of silica or glass former, sodium carbonate which will act as the melting agent, and limestone/calcium carbonate and alumina which would act as the stabilizers to high temperatures until the materials melt into a thick liquid that is then poured into molds. The surface of glass containers used in food packaging is sometimes coated to provide lubrication and prevent the effects of scratching. This is done to reduce or prevent any kind of damage to the containers. Glass coatings also increase and preserve the strength of the bottle to limit breakage.

Paper Paper and board are also versatile materials like plastic. Paper packaging can be made of parchment paper that is generally thin or has the shape of bags to package foods. Carton board is commonly used in liquid and dry foods, frozen foods, and fast food. The corrugated board is also used, e.g., in pizza packaging. Paper and board are made of natural fibers. These fibers can be bleached or non-bleached. Chemical substances are however needed as additives to achieve suitable properties that enhance packaging efficiency. They are either added directly to the pulp or applied to the surface later on.

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Fig. 5 Different types of food containers made of paper

Pure cellulose comprises long, ribbonlike molecules of glucose units. These molecules are held together side-by-side by hydrogen bonds to form “sheets,” which in turn are piled together in tight layers forming “microfibrils.” The microfibrils group themselves in bundles and groups of these bundles form the paper fiber [5] (Fig. 5).

Different Types of Paper Employed in Food Industries Parchment/Baking Paper Made from the acid-treated pulp, and it is impervious to water and oil (grease resistant); however it is not a good barrier to air and moisture; it is not heat sealable and is generally used to pack fats (butter) because it is grease resistant. It is non-sticky. Kraft Paper Natural kraft is the strongest of all paper and is commonly used for bags and wrapping. It is having high strength and is eco-friendly. It can also delay the shelf life of food items. It is accustomed to pack flour, sugar, and dried fruits and vegetables. Corrugated Board The corrugated cardboard is formed of two layers of kraft with a flute paper in the center. Various boxes that are made out of this cardboard can be single-walled, double-walled, or triple-walled. Although in appearance it may seem weak and delicate, in reality it is protective in nature. The multiple layers make it quite rigid. Corrugated paper is eco-friendly, affordable, and convenient. (Fig. 6).

Shortcomings of Conventional Food Packaging Materials In standard food packaging ways, metals and their alloys, plastics, wood, glass, etc. are used as packaging materials. Victimization of these materials causes several issues associated with setting, especially on health. The following mentioned materials have several shortcomings or disadvantages in terms of packaging of food.

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Fig. 6 Conventional food packaging materials

Metals Metals like aluminum, tin, steel, etc. are used for packaging. However, the following limitations of metals make them unsuitable for food packaging: 1. 2. 3. 4.

Metal is a corrosive material and will have an effect on the standard of food. Metal is a moderately significant packaging material. The food content is not visible once packaging is done. Due to multistep production method, time taken for creation of packages is increased. 5. Metals will react with the food material and may be hazardous for health.

Plastics Plastics are high mass polymers that may be molded into desired shapes like films, trays, bottles, and jars, through victimization by heat and pressure. They don’t offer a complete barrier to gases, vapor, and aromas. Plastics as a food packaging material aren’t thought of as good strategy due to the following reasons: 1. Plastics are leaky to gases that are generated in setting, water vapors, aroma, monomers, and additives. 2. Food elements can mix with plastics, and it’s proved that food embowered in plastics could cause diseases like cancer. 3. Plastics have low compressive strength. 4. Plastics lack heat resistance. 5. Main disadvantage is that plastics are nonreusable.

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Glass The shortcomings of glass embrace properties like its weight and vulnerability to fracture from thermal shock (rapid temperature change) and physical shock. Here are some additional setbacks of glass as a food packaging material: 1. Glass will cause breakage resulting in loss of merchandise. Also, glass is a breakable material; therefore it will break down, and the purpose of protecting food merchandise is contrary to this property of glass. 2. Hermetic seal that’s additional is simply compromised. 3. The multiplied chance of broken glass contaminating the finished product. 4. Color changes of the merchandise due to exposure of sunshine. 5. Expensive food packaging material.

Wood Wood is an adsorbent material. This suggests that it will adsorb close condensable vapors below the fiber saturation. Wood won’t be able to satisfy as a good packaging material as it includes a downside of shrinkage and swelling. Wood doesn’t deteriorate itself; there are some agents inflicting wood deterioration. There are two categories of agents responsible for deterioration, viz., abiotic agents like sun, wind, water, fire, and chemicals and biotic agents like fungi, microorganisms, and insects like termites, powderpost beetles, etc. Fungi as Agent As wood is organic, therefore humans will not digest polyose and different fiber ingredients of wood; however fungi and insects can digest it and use it as a nutritional food. Decay fungi wood rotters will use polysaccharides, whereas stain fungi plainly need straightforward forms like soluble carbohydrates, proteins, and different substances gift within the parenchyma cell of wood. To boot, the presence of atomic number 7 in wood is important for the expansion of fungi in wood. Insect as Agent Insects drill holes and drive lines into wood. Insects are solely second to decay fungi within the economic loss they cause to lumber and wood in commission. Insects are separated into four categories: termites, powderpost beetles, carpenter ants, and marine borers: • Termites: There are two kinds of termites – subterranean termites injure wood that’s untreated, moist, and in direct contact with standing water, soil, and different sources of wet. Dry wood termites attack and inhabit wood that has been dried to wet contents as low as 5 to 100 percent. The injury by dry wood termites is comparative than subterranean termites.

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Table 1 Shortcomings of conventional food packaging materials Metal Corrosive substance Nontransparent

Highly reactive

Plastics Nonrecyclable Low compression strength Lack heat resistance

Glass Breakable substance Changes color

Wood Shrinkage

Heavy than others

Deteriorate by agents (fungi, insects)

Swelling

Paper Nonwaterproof Easily pieced Very light to carry

• Powderpost beetles: Powderpost beetles attack hardwood and softwood. They are known to attack well-seasoned wood as well as freshly harvested and undried wood. • Carpenter ant: Carpenter ants don’t go after wood. They tunnel through the wood and build shelter. They attack most frequently wood in ground contact or wood that’s intermittently wetted. • Carpenter bees: They cause injury primarily to unpainted wood by making giant tunnel so as to get eggs. • Marine borers: They attack and may apace destroy wood in freshwater and saltwater.

Paper Paper as a food packaging material is a sensible choice. Some properties like waterproof, load bearing, simply pieced, etc. are reasons for paper being a good packaging material. However, the waterproof property is relatively poor. Though the carton created of paper is lined, still it is not adequate as it simply leaks the water. The carton is highly susceptible to many sharp objects in terms of toughness, making it inappropriate for sharp-edged merchandise as the sharp objects may get hooked onto it which will compromise the safety of the food packaged. With the exception of these, in terms of load bearing, the carton is restricted, typically ranging from few kilograms to many tens of kilograms, and if food substances are too large, then the purpose of packaging food things is no longer fulfilled (Table 1).

Starch Environmental awareness is increasing day by day, so many fields are considering materials which are eco-friendly in nature and that can replace petroleum-based synthetic materials in packaging field. One of the biodegradable polymers is “starch” which has now become a very significant polymer. Starch is a biodegradable polymer, available at a low cost, and it is thermoplastic in nature. It is a natural

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polymer having glucose monomers. Starch in the form of granules having the size between 1 and 100 micrometers is extracted from various plant tissues. It is a polysaccharide and contains two types of units in its structure named amylose and amylopectin. Amylose is an unbranched polysaccharide chain which is made up of α-D glucose units bonded to each other through α-(1–4) glycosidic bonds. Amylopectin is a branched polysaccharide chain which is made up of α-(1–4) D glucose units that are branched by α-(1–6) glycosidic bonds. The amount of amylose and amylopectin present in starch is around 20%–30% and 70%–80%, respectively [6]. However, the ratio of these two polysaccharides depends on the starch source as well. Lipids and proteins are also present in starch, but in very small amount. Starch is obtained from many botanical sources. Commercial starch is obtained mainly from potato, maize, wheat, rice, corn, and cassava. Cassava is the cheapest and most abundant agricultural source of starch and is cultivated throughout Brazilian territory. Nonconventional starchy sources are taro, banana, plantain, mango, amaranth, quinoa, etc. that are used for starch isolation. These isolated starches derived from botanical sources are known as native starch. These nonconventional types of starch are used in encapsulation, film or cover materials, stabilizing agents for emulsion, nanocrystals preparation, etc. According to the abovementioned concepts, starch is already well known as green material. As a raw material, starch is used in different applications, for example, food, pharmaceutical products, plastics, paint, paperboard, etc. It has both upsides like low thickness, flexibility, and transparency and downsides like poor mechanical properties and water vapor permeability. However, to improve its functionality, starch can be modified through chemical, physical, and enzymatic methods (Fig. 7).

Why Starch Is Used as a Packaging Material? Foods are packed in different packaging materials, such as metals (aluminum, steel, tin), glass, papers, and other polymers (may be synthetic and biopolymers). There are four significant functions of good food package; it involves protection, communication, containment, and convenience to maintain quality as well as safety of any kind of food products while storing and transporting. Shelf life is a term which always comes in our mind whenever packaged foods are discussed, so as to extend a product’s shelf life by preventing unfavorable conditions like spoilage, microbes, chemical contamination, light, moisture, oxygen, and any external force. These above properties are exhibited by plastics polymers such as low-density polyethylene, high-density polyethylene, polyvinyl chloride, as well as biopolymers such as polysaccharides, lipids, and proteins. But to meet the increasing demand for sustainability and environmental safety, natural or biopolymers are extensively used and studied for food packaging. Among all polysaccharides starch is one of the most significant and extensively used in food packaging because in starch, other polymers like lipids and proteins are also present in small amounts. Starch is a relevant food packaging material due to reasons which are considered below [7]:

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AMYLOSE

AMYLOPECTIN Fig. 7 Chemical structures of amylose and amylopectin

1. Biodegradable Polymer The term “bio-based” is defined in European Standard (EN) as “derived from biomass.” Biodegradable polymers are those polymers which are broken down by microorganisms like fungi and bacteria into water, naturally occurring gases like carbon dioxide (CO2), methane (CH4), and biomass. As mentioned earlier, starch is also a biodegradable polymer, so the issue of environmental contamination is automatically solved. There will be no negative impact of using starch as a packaging material. 2. Derived from Botanical Sources (Renewable Sources) Plants synthesize and store starch in their structure as an energy reserve. Starch is found in seeds and in tubers or roots of plants. Botanical sources like wheat, rice, potato, pea, corn, and cassava give starch which is used in packaging fields. Most of the starch produced is derived from corn and cassava. By wet milling processes, starch can be extracted easily from the abovementioned sources [8] (Fig. 8). 3. Antimicrobial Property Antimicrobial means impermeable to microorganisms like bacteria and fungi. Antimicrobial packaging refers to the packaging system in which antimicrobial agents are used for purpose of preventing microbial growth on food products and

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Fig. 8 Botanical sources of starch

hence extending its shelf life. Starch may acquire antimicrobial properties by incorporating antimicrobial components in a polymer matrix, by gas emissions/ flush through modified atmosphere packaging. Using this packaging has been encouraged because of the increasing global food-borne outbreaks with relation to health and safety concerns [9]. 4. Edible Property Starch is derived from botanical sources. Botanical sources are neither toxic in nature nor hazardous to the environment. By packaging food in starch-based films, there will be no impact on health of human beings. Starch is edible too, which is a bonus factor. 5. Barrier Property Food packaging materials should have barrier property. The earth's atmosphere is constituted by many gases, like CO2, O2, N2, etc., and also contains moisture along with dust particles. While packaging, it is assured that there is no permeability to such particles, otherwise their entry will result in spoilage of food products. Starchbased films as packaging materials have barrier property which is an important criterion for selection of packaging materials.

Different Types of Starch-Based Films Starch is a natural chemical compound made up of monomers of glucose. It contains two polysaccharides (amylose and amylopectin) which may vary in starch supply level. Like in thermoplastic starch (TPS), it is predicated that cassava is one of the

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most important in supply for starch. It indicates that existence of sugar and totally different molecular combination correlates with crystalline properties, water absorption, and mechanical behavior. Several researchers have shown that distinction between triple kinetic values of starch (represents thermal decomposition effect) isn’t important. In the study, the starch has smarted the film-forming property. Starch sources, largely biological science sources, play a decisive role in film options because of the magnitude of relation of amylose to amylopectin and totally different structural properties of macromolecules [10]. Different sources like oat starch are a healthier choice because of their higher performance and better chemical science properties. All starch films obtained are colorless, clear, and versatile and simply applicable. Although their surface is swish and slick which is not preferable for defense, Torres et al. (2011) showed in the study that starch was extracted from 12 varieties from anode region product. To create film, properties like Young’s modulus, final enduringness, and elongation at rupture rate ought to be there. There are three stages concerned in biodegradation method wherever films were determined based mostly on their rate of losing weight. The high proportion of weight loss is found in starch, whereas low proportion of weight loss is found in golden potato films. Among 12 sources, cassava is a highly important and widely used starch supply made in geographic area. Because of low price within the world market as compared to different sources of starch, usage of cassava is increasing. Food packaging material shouldn’t be negatively affected by storage and temperature. Thus, to visualize these properties, associate experiments were done on cassava that resulted in no adverse effects occurring in film throughout 8 weeks of storage at a temperature of 25  C. Starch shows an improved interaction with glycerin indicating more H-bonds with amylose than amylopectin chains. Films with glycerin are preponderantly softer and amorphous. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) increase the temperature that subsequently softens the films. Waxy maize films and cassava films each are the same in behavior, once exposed to wetness with the slight distinction in less porosity of starch films that’s related to presence of amylopectin chains. Quinoa seed is found in extremely little dimensions having diameter 3 mm in high chain region of South America. Quinoa seed is among the simplest sources of starch. Up to 80% starch is obtained from this seed. Amylose and amylopectin are present around 10–21% and 79–90%, respectively, in quinoa seeds. Quinoa starch is economical for production of clear perishable starch films. To supply quinoa clear edible films, molding method is employed. The best conditions are 2/21% of glycerin, base-forming pH of 7/10, and drying temperature of 36  C for 14 h. A wide range of research has been done on starch films supported by cassava and maize (high amylose); however there has been quite less analysis regarding films supported by amylum starch. Distinctive property of amylum starch makes it effective to be introduced within the food packaging films. Amylum starch is softened by sorbitol not glycerin because a number of its chemical science properties are quite like starch and potato starch. The waterproofing ability of sorbitol is higher than glycerin, though amylum films show less waterproofing strength than artificial polymers.

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These starch-based films are mostly perishable and have a few limitations. The most serious limitation of perishable films is their hydrophilic character that ends up reducing their stability after they are exposed to totally different environmental conditions. A different approach is using oat starch films which contain 1–3% fat in its natural structure that is precise with respect to the quantity of starch as compared to different sources. Glycerin is employed to melt the oat starch films and is slick; however it doesn’t have any cracks or bubbles in it. Lipids and amylose are naturally warranted in oat starch, the section separation is prevented, and therefore they contribute to scale back hydrophilic character of a substance. Oat starch lipid isn’t capable of stopping changes in the mechanical properties caused by wetness. As mentioned earlier, plants synthesize starch. Fabaceae family of angiospermic plants is usually selected to extract starch. Rosin dicot genus Ahipa is widely used in alternate supply for films. Organ roots are wealthy in presence of starch in rosin dicot genus Ahipa species. This species grows on a small scale in a chain region of Bolivia and northern Argentina. Ahipa starch has superiority over other kinds of starch because it includes lower amylose content that is adequate within the retrogradation range. In this the time and energy required for gelatinization of suspension is reduced, making it more efficient. Food packaging materials ought to have antimicrobial activity that is found in rosin dicot genus Ahipa. Insecticidal and antifungal character is also found in starch extracted from family Fabaceae of plants. “Rotnon” with the chemical having formula C23H22O6 is one of the most necessary characteristics of rosin dicot genus Ahipa. Hence, several researchers all over the world have found that such starch sources have higher performance. Food packaging method must meet the wants of higher interaction between packaging materials and food for the safety and health of humans [11] (Fig. 9).

Fig. 9 Different types of starch-based films

Pachyrhiz US Ahipa Starch Sago Starch

Cassava Starch Starch Based Films

Quinoa Seed Starch

Maize Starch Oats Starch

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Thermoplastic Starch (TPS) Thermoplastic starch is a material that is synthesized by modifying starch, precisely by mixing native starch with a plasticizer. This process needs to be carried out at a temperature well above starch gelatinization temperature. This weakens the hydrogen bonds present in the native starch leading to a fully amorphous freeflowing material. During different thermoplasticization processes, water and glycerol in the starch act as a lubricant that facilitates the mobility of polymer chains. It also slows down retrogradation of TPS products. It will flow at elevated temperature and pressure conditions and can be molded to give both foams and solid molded articles. However, TPS plasticized with water has poor dimensional stability and becomes brittle on losing water molecules. TPS properties can be improved significantly by blending with other polymers, fillers, and fibers. Due to the environmental problems related to nonbiodegradability of petrochemical-based plastics, modified biopolymers are now being considered as an alternative to synthetic polymers for several applications, including packaging for food [12] (Fig. 10).

Amylopectin

Native Starch

Amylose

Plasticized with water

Plasticized with Glycerol

Amylopectin

Amylopectin

Amylose

Glycerol

Amylose

Fig. 10 Native starch conversion to plasticized starch

Plasticized starch

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Starch Plasticizers Thermoplastic starch plasticizers are generally hydrophilic in nature. These substances not only reduce the hardness, density, viscosity, and electrostatic charge of a polymer but also enhance the flexibility of the polymeric chain. Hence the brittle nature of the native starch can be alleviated or removed by using plasticizers that will minimize the possibilities of fractures. Plasticizer molecules penetrate starch granules and destroy the inner gas bonds of starch in high temperature, pressure, and cutting off. These molecules eliminate starch–starch interactions as a result of which they are replaced by starch–plasticizer interactions. Plasticizer molecules will penetrate starch granules and destroy the inner hydrogen bonds of starch [13]. Water is considered to be one of the most effective starch plasticizers and is needed for gelatinization, but it can however easily migrate from the polymer and evaporate due to high vapor pressure. Glycerol is another suitable alternative to water. It is a small molecule with polar nature that can enter starch water channels. It can reduce intermolecular attractions between the polymers to a great extent and impart the flexibility and stability that is needed for the preparation of biodegradable bio-based films. These days’ glycol, sorbitol, maltose, and xylitol also are getting used as starch film plasticizers. Compression molding is being extensively researched for improving the properties of starch-based plastics, one of the major reasons being an improvement in the properties of foam containers. The process involves gelatinization, expansion, and drying. In this way, thermoplastic starch can be molded in different forms, and the property is exploited by food packaging industries. Thermoplastic starch films generally need to have starch content greater than 70% to have biodegradable nature and can be composted then only. Content of plasticizers must not exceed a certain value. Blends When TPS is mixed with any other thermoplastic, generally in molten form, the mixture can be regarded as a polymer blend. Starch can form stable blends with polar polymers [14]. Only biodegradable polyesters such as poly-e-caprolactone (PCL), polybutylene succinate adipate (PBSA), poly-hydroxybutyrate (PHB), and PLA are generally used; otherwise the biodegradable nature would be lost. Polyethylene and polypropylene starch blends are been given importance as compatible starch blends [15]. Composites The term composite refers to matrix polymers that contain glass, fibers, talc, or clay particles (fillers) in dispersed form. Polymers with fillers that are nanosized (1–100 nm) are named nanocomposites [16]. Avella et al. in 2005 successfully created starch clay nanocomposites using montmorillonite, potato starch, and polyesters for food packaging applications. Thermoplastic starch composites with titanium dioxide nanoparticles have also been prepared successfully [17, 18].

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Modification of Starch Starches are often changed to enhance their thermal stability, resistance against acid and bases, shear, time, cooling, or chilling. The texture of the starch can also be changed, and they can be modified to enhance their performance according to the applications. Starch can be modified by chemical, physical, and enzymatic methods [19] (Fig. 11).

Chemically Modified Starch Chemical modification involves the alteration of the chemical properties of starch by adding some new chemicals. The chemical modification doesn’t alter the physical size or form of the starch molecules. Glucose, the monomeric units of the amylose and amylopectin, has three hydroxyl groups where chemical modification may be performed [20].

Acid hydrolysis Degradation Oxidation

Chemical modification

Esterification Substitution Etherification

Cross-linking

Modification of starch

Thermal

Physical modification Non-thermal

Enzymatic modification Fig. 11 Classification of different methods of starch modification

Esterification

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Methods of Chemical Modification • Oxidation The process involves the oxidation of primary or secondary hydroxyl groups of the glucose monosaccharide that leads to the formation of an aldehyde or carboxyl compound. A suitable oxidizing agent is used for this purpose. The efficacy of oxidation depends on the type of oxidant used, source of starch, and the process conditions. Moreover, the oxidation reaction may cause the weakening of intermolecular bonds. The oxidized starch has better water solubility, lower viscosity, and retrogradation tendency in comparison to the non-modified starch. The oxidation of starch can be carried out by using oxidizing agents such as air or oxygen (in the presence of catalysts), inorganic peroxides (H2O2), organic peroxides (NaClO), nitrogenous compounds (HNO3), organic oxidants as well as metal oxides (CrO3). • Esterification Starch can be modified to improve its hydrophobicity through esterification. This improves starch’s thermoplastic properties. The derivatives of these acids like anhydrides and oxychlorides are also used sometimes. The high tendency of starch to get esterified by esterifying agents allows the synthesis of several starch esters, which are used in both food and nonfood applications. For example, starch acetates have good transparency, low gelatinization temperature, and high wear resistance that find their applications in various industries. Esterification improves the properties of starch such that it can be used as a potential biodegradable thermoplastic material. • Etherification Etherification of starch generally involves the addition of hydroxypropyl group (hydroxypropylation) and hydroxyethyl group to the starch (hydroxyethylation). This process is carried out to modify the chemical properties of the starch. Hydroxyethylation improves the drug binding ability for some anticancer and other drugs, whereas hydroxypropylation increases the peak viscosity, water binding capacity, and enzymatic digestibility of starch. • Cationization Treatment of starch with various cationic molecules improves the solubility, stability, dispersibility, and clarity of the starch. This is done by the introduction of amino, ammonium, imino, phosphonium, or sulfonium groups to give a positive ionic charge to starch. Examples are dry cationization, wet cationization, and semidry cationization. This leads to the introduction of cross-links in the starch that enhances stability.

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Physical Modification of Starch The physical modification involves the changes in morphology and 3D structure of starch under the influence of some physical factors like water, temperature, pressure, pH scale and radiation, supersonic waves, etc. Physical modifications result in changes in properties of starch like surface properties, water absorption, and swelling capability. Some major ways are mentioned below: • Heat Moisture Treatment In this process application of heat is done in the presence of 22–27% of moisture content and high temperature above the glass-transition temperature (100–120  C) for a specified length of time that is 1–24 h. This results in a change in size, shape, and granular and crystalline structure of starch. • Radiation Treatment 1) Microwave Irradiation Application of microwave radiation at different percentages of moisture and ranges of temperature is carried out in this process which changes the dielectric constant of starch. Microwave treatment improves the water and oil holding capacity and solubility. It decreases the peak viscosity and gelatinization and the degree of relative crystallinity as well. 2) Gamma Irradiation Gamma radiation can break the amylopectin chains. It can also decrease the amylopectin-to-amylose ratio. It also causes the radiolysis of starch. This increases the pasting viscosity and enthalpy change of starch and molecular weight. It increases the susceptibility of starch to amylase. It also improves properties such as gelatinization, viscosity, swelling power, and solubility. • Moisture Treatment The moisture acts as a plasticizer and anti-plasticizer for starch films for different properties. It causes a plasticizing effect on linear expansion, tensile modulus, and water vapor permeability, while an anti-plasticizing effect on mechanical properties, i.e., tensile strength and toughness. • Mechanical Treatment • Milling It is a form of mechanical treatment. In milling starch is grinded by physical processes which leads to decrease in the ratio of crystalline structure to amorphous. It

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also leads to a sudden increase in surface parameters which is followed by a subsequent decline. • Ultrasound Treatment • Ultra-sonication Treatment of starch with ultrasonic waves. Results of this treatment showed an initial increase in the solubility of starch and then a subsequent decrease in both solubility and viscosity. There is a rise in gelatinization temperature of starch post ultrasound treatment.

Enzymatic Modification of Starch Enzymatic modification of starch can change molecular mass, branch chain length distribution, and amylose/amylopectin ratio by reactions when the enzymes react with gelatinized starch. Common enzymes used in starch processing include alphaamylase, beta-amylase, glucoamylase, and its amylase. These techniques provide us with starches with altered and required physicochemical properties. The sites that are prone to enzymatic attack are the less well-organized amorphous regions, whereas the crystalline regions are more resistant. Glycoside hydrolases like, α-amylases, pullulanases, glucan-branching enzymes and transglycosylases are the common enzymes used for this purpose [20].

Various Properties of Thermoplastics and Composites Needed for Food Packaging (Fig. 12) Biodegradable The biodegradable polymer is a polymer that is degraded by microorganisms. This is biological activity. Various enzymes such as amylases and glucosidase attack the starch and degrade the polymer. Enzymes attack at a specific site of a polymer for the

PROPERTIES

BIODEGRADABLE

WATER

OXYGEN

BARRIER

MECHANICAL

CARBON DIOXIDE

Fig. 12 Different properties of thermoplastics and composites

LIGHT

THERMAL

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degradation of cellulose. The three diverse classes of enzymes, namely, endocellulases, exocellulases, and cellobiohydrolases, are present which degrade cellulose polymer to glucose unit. These three types of biocatalysts are called cellulases. No individual polymer can degrade the complete polymer. The set of enzymes are essential to degrade a polymer. The polymers are degraded biologically in two ways: first, enzymatically degradable polymer and, second, photo-oxidizable (by UV radiation) or thermosoxidizable (by heat) polymers. When these polymers are disposed to the environment after their utilization, they are completely degraded by the organisms available in soil, sea, and sewage. Microbial growth is influenced by glycerol which promotes swelling, thereby mass transport of water and hence the microbial growth as well. Biodegradable materials have been found to some significant use in the field of medicine and its allied field. The occurrence of biodegradation was evidenced by gel permeation chromatography indicating a reduction in molecular weight of TPS after the exposure of the sample; this confirmed that the rate of biodegradation was improved by the influence of starch [21]. Table 2 shows degradation of various modified membranes with time.

Barrier Property As food packaging material, we require moisture barrier property. TPS causes poor water permeability, but starch has a natural hydrophilic character when it is combined with plasticizer glycerol; the swelling of the network holds a significant amount of water; this swelling breaks the structural integrity of matrices and leads to poor barrier property. The complex relationship between polymer matrix and barrier properties depends on various factors such as the structure of the matrix, molecular weight, polarity, crystallinity, and type of reinforcement present. Moisture transfer between food and the surrounding atmosphere will lead to spoilage of food; hence the resistance against water vapor permeability should be as high as possible.

Table 2 Membrane with respective degradation time S. no. 1. 2. 3. 4. 5. 6. 7. 8. 9.

Membrane Maleic anhydride-compatibilized starch–PLA blends Starch films cross-linked with resorcinol formaldehyde 30% glycerol-plasticized starch TPS reinforced with Ss’ TPS reinforced with 10 wt.% CNFs TPS reinforced with 10 wt.% acetylated CNFs TPS/50% commercial calcium carbonate composite 50 wt.% CaCO3/TPS composite 50 wt.% eggshell/TPS composite

Quantity of degradation 91%

Time 42 days

References [6]

100%

60 days

[6]

70% 100% 100% 100%

22 days 60 days 40 days 60 days

[6] [6] [6] [6]

35.37%

15 days

[6]

61.89% 90%

30 days 30 days

[6] [6]

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ASTM D570-81 standard method of studying water resistance of materials involves drying before placing weighed (Wi) samples indefinite volume of deionized water at room temperature for 24 h. Then the samples will be taken out and moisture is removed before weighing (Wf). The calculation of percentage weight gain is given i by % Weight gain ¼ WfW
W [21]: i As light can pass through packaging material and can catalyze oxidation reaction, thus light barrier properties are also required for packaging material [21].

Water Barrier The nature of starch is like a hydrophilic film. Water vapor permeability depends on the diffusivity and solubility of the water molecule in the film matrix. The incorporation of nanostructures leads to mending the pathway of water molecules to traverse the film matrix. The water vapor permeability coefficient quantifies the water vapor barrier. It indicates the amount of water vapor that permits in packaging per unit area and time [22]. Relative humidity and the type of plasticizers that are used influence the water uptake of TPS film. In Table 3, water uptake of two membranes is given in different relative humidity conditions. Oxygen Barrier At low relative humidity (RH), the oxygen barrier properties of most biopolymerbased packaging materials are moderate to a good level. But when relative humidity (RH) is increased, the oxygen barrier properties deteriorate exponentially. The measurement of the oxygen barrier can be done by the oxygen permeability coefficient (OPC). It is the amount of oxygen that permeates per unit of area and time through the wall of packaging material (Siracusa et al. 2008). Low OPC indicates that pressure inside the packaging material drops in such a way that oxidation is retarded [23].

Table 3 Water uptake of maize starch plasticized with isosorbide and glycerol at different Rh S. no. 1. 2. 3. 4. 5. 6.

Membrane Isosorbide as plasticizers with maize starch Glycerol as plasticizers with maize starch Isosorbide as plasticizers with maize starch Glycerol as plasticizers with maize starch Isosorbide as plasticizers with maize starch Glycerol as plasticizers with maize starch

Water uptake 22.8%

Relative humidity 75%

References [6]

25.7%

75%

[6]

8.8%

50%

[6]

10.4%

50%

[6]

4.5%

25%

[6]

5.5%

25%

[6]

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Carbon Dioxide Barrier Carbon dioxide is also important in food packaging applications; carbon dioxide permeability coefficient quantifies the carbon dioxide barrier; it indicates the amount of carbon dioxide that permeates the packaging material per unit area and time [23]. Light Barrier The light which contains radiation energy affects the photosensitive products because it accelerates the photochemical degradation reactions that may deteriorate such products. Exposure to light causes the polymer to undergo oxidative degradation leading to the weakening of the polymers [23].

Mechanical Property The mechanical property of starch-based film was assessed employing a tensile test. This property of starch depends on its ultimate strength, Young’s modulus and elongation at break. For the mechanical property of starch-based biodegradable packaging film, various improvements are developed; these include, first, the addition of new plasticizers such as urea or form amide that aid in the thermoplastic process and also increase the flexibility of the final product by forming hydrogen bonds with starch that replaced the strong interaction between hydroxyl groups. Second is the addition of synthetic biodegradable polymers like poly(vinyl alcohol) (PVOH) and polylactide (PLA) to produce materials with properties intermediate to the two components; resultant blends can be better processed by extrusion or film blowing and have mechanical properties superior to those of starch alone [24]. Third is the addition of compatibilizers to lower interfacial energy, and increased miscibility of two incompatible faces leads to a stable blend with improved characteristics. Amylose/amylopectin ratios vary with the starch source with high-amylose starches that affects the material in two ways. First is increasing strength and ductility. Secondly, it affects gelatinization processes, which generate the uniform amorphous thermoplastic by the action of heat and mechanical work in the extruder. The addition of plasticizers increases the toughness of the starch but decreases the strength and modulus [24] (Table 4).

Thermal Property The thermal stability of starch ether depends on the degree of substitution (DS). With an increase in the degree of substitution (DS), thermal stability increases [25]. In the case of starch–Ag nanoparticles, thermogravimetric analysis was utilized to investigate the effect of various concentrations of Ag nanoparticles on thermal stability and activation energy of starch [26]. In one study starch granules are divided into three categories: (a) diameter 10–15 μm, (b) diameter 5–9.9 μm,

6. 7. 8. 9. 10.

5.

4.

3.

S. no. 1. 2.

Membrane Methylcellulose–glucomannan–pectin Corn starch and poly(vinyl alcohol) blends with glycerol as plasticizer (without PVA) RH, 50% Corn starch and poly(vinyl alcohol) blends with glycerol as plasticizer (PVA) RH, 30% Starch–glycerol–PVA Ratio, 65:35:9 RH, 30% Corn starch-based films with the incorporation of citric acid and carboxymethyl cellulose (CMC) Addition of 10% (wt./wt.) citric acid into starch film CMC was incorporated along with 10% (wt./wt.) citric acid Bamboo cellulose crystals reinforced thermoplastic starch 30% nanocrystal reinforcement into thermoplastic starch Starch nanocomposite films produced by reinforcing acetylated cassava starch nanoparticles (NPs) –

–

66.18% 59.49% – 7.2% 307%  29%

230% (highest)

–

6.57 MPa 16.11 MPa 2.5 MPa 11.9 MPa 69.50  1.16 MPa

150%

Fracture strain 9.85% 113%

4 MPa

Tensile strength 72.63 MPa 1.8 MPa

Table 4 The tensile strength, fracture strain, and Young’s modulus of respective modified membrane

[6] [6] [6] [6] [6] [6]

– – – 20.4 MPa 498.2 MPa 828.68  5.77 MPa

[6]

[6]

– –

References [6] [6]

Young’s modulus – –

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Table 5 Membrane with respective degradation time S. no. 1. 2. 3. 4. 5. 6.

Membrane Glycerol-plasticized TPS Isosorbide-plasticized TPS 20 wt.% leaf wood fiber-reinforced composites 20 wt.% of paper pulp fibers are added Reinforcement of 0.5 wt.% NPs into cassava starch 20 wt.% chitin nanofibers filled starch

Maximum degradation temperature (Tmax) 309  C 304  C 336  C

References [6] [6] [6]

339  C 334  C

[6] [6]

288  C

[6]

and (c) diameter < 5 μm. The thermal energy of different starch grain used is determined by gelatinization enthalpy (ΔH) of granules decreased in order a > b > c. ΔH has been related to crystallinity [27]. Maximum degradation temperature (TMAX) gives the measure of thermal stability of the membrane given in Table 5.

Conclusion and Future Perspectives Petroleum-based materials are used as a conventional food packaging strategy. These strategies also involve the use of metals like aluminum, tin, glass, plastic, etc. which are hazardous to the environment as well as for our health. Most of these materials are nonbiodegradable too, so researches are shifted toward the search for biodegradable material. Biodegradable starch film and certain modifications in their structural and physicochemical properties can be a suitable alternative for modern-day food packaging, while it follows a green approach. Starch sources are mostly botanical so they may not harm the environment in any condition. Cassava, corn, pea, wheat, rice, potato, oats, etc. are the main source of starch which makes films used in food packaging strategies. The difference in the starch source shows different properties of the film used as food packaging material. Modification can be done by the addition of plasticizers termed as thermoplastic or modified chemically physically or enzymatically to improve the 3D structure and various properties such as mechanical, thermal and barrier, etc. The development and modification of these materials are not cost-friendly. Researchers are now trying to implement various other properties such as antioxidant and antibacterial properties [28]. In the case of developing antioxidant films, two critical concerns are important for researchers in this field. First, reduction in the value of the difference in accessing and reporting antioxidant capacity to get a standardized result. Second, for accessing antioxidant capacity, realistic consideration should be taken into account such as food simulant (solvent) rather than utilizing water or antioxidant species. Focused research is needed in the development of these materials in such a way that they show maximum properties and satisfy the condition of costeffectiveness [29, 30].

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Important Websites https://www.azonano.com/article.aspx?ArticleID¼1832 https://www.understandingnano.com/nanocomposites-applications.html https://www.sciencedirect.com/topics/chemical-engineering/nanocomposites https://www.britannica.com/science/nanoparticle/Nanoparticle-applications-inmaterials https://www.britannica.com/science/nanoparticle https://euon.echa.europa.eu/food-packaging https://www.britannica.com/topic/food-preservation/Packaging https://www.nanowerk.com/spotlight/spotid¼51119.php

References 1. Petersen K, Nielsen PV, Bertelsen G, Lawther M, Olsen MB, Nilsson NH, Mortensen G (1999) Potential of bio-based materials for food packaging. Trends Food Sci Technol 10(2):52–68 2. Engel JB, Ambrosi A, Tessaro IC (2019) Development of biodegradable starch-based foams incorporated with grape stalks for food packaging. Carbohydr Polym 225:0144–8617 3. Gadhave RV, Das A, Mahanwar PA, Gadekar PT (2018) Starch based bio-plastics: the future of sustainable packaging. Open J Polymer Chem 8:21–33 4. Ramos O, Periera R, Cerqueira M, Martins J, Teixeira J, Malcata F, Vicente A (2018) Bio-based nanocomposites for food packaging and their effect in food quality and safety. Food Packag Preserv:271–306 5. Raheem D (2013) Application of plastics and paper as food packaging materials – an overview. Emirates J Food Agric 25(3):177–188 6. Prabhu TN, Prashantha K (2016) A review on present status and future challenges of starch based polymer films and their composites in food packaging applications. Polym Compos 39 (7):2499–2522 7. Jha S, Rohilla P, Singh K (2017) Starch based packaging materials: a review. IJRAR- Int J Res Anal Rev 4(4):2349–5138 8. Jeevahan J, Chandrasekaran M, Durairaj RB, Govindaraj M, Britto G (2017) A brief review on edible food packaging materials. J Glob Eng Probl Solut 1:9–19 9. Luna J, Vilchez A (2017) Polymer nanocomposites for food packaging. In: Emerging nanotechnologies in food science, pp 119–147 10. Ramos O, Periera R, Cerqueira M, Martins J, Teixeira J, Malcata F, Vicente A (2018) Bio-based nanocomposites for food packaging and their effect in food quality and safety. In: Food packaging and preservation, pp 271–306 11. Toro RO, Bonilla J, Talens P, Chiralt A (2017) Chapter 9-future of starch-based materials in food packaging. In: Villar MA, Barbosa SE, García MA, Castillo LA, López OV (eds) Starch based materials in food packaging. Academic Press, pp 257–312 12. Molavi H, Behfar S, Shariati MA, Kaviani M, Atarod S (2015) A review on biodegradable starch based film. J Microbiol Biotechnol Food Sci 4(5):456–461 13. Ibarra VG, Sendón R, Rodríguez-Bernaldo de Quirós A (2016) Chapter 29 – antimicrobial food packaging based on biodegradable materials. In: Antimicrobial food packaging. Academic Press, pp 363–384 14. Tang XZ, Kumar P, Alavi S, Sandeep KP (2012) Recent advances in biopolymers and biopolymer-based nanocomposites for food packaging materials. Crit Rev Food Sci Nutr 52 (5):426–442

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15. Noorbakhsh-Soltani S, Zerafat M, Sabbaghi S (2018) A comparative study of gelatin and starch-based nano-composite films modified by nano-cellulose and chitosan for food packaging applications. Carbohydr Polym 189:48–55 16. Arora A, Padua GW (2010) Review: nanocomposites in food packaging. J Food Sci 75(1):43–49 17. Kumar S, Diwan A, Singh P, Gulati S, Choudhary D, Mongia A, Gupta A (2019) Functionalized gold nanostructures: promising gene delivery vehicles in cancer treatment. RSC Adv 9(41): 23894–23907 18. Gulati S, Kumar S, Singh P, Diwan A, Mongia A (2020) Biocompatible chitosan-coated gold nanoparticles: novel, efficient, and promising Nano systems for Cancer treatment. In: Handbook of polymer and ceramic nanotechnology, pp 1–29 19. Nafchi AM, Moradpour M, Saeidi M, Karim A (2013) Thermoplastic starches: properties, challenges, and prospects. Starch-Wiley 65(1–2):61–72 20. Nawaz H, Waheed R, Nawaz M, Shahwar D (2020) Physical and chemical modifications in starch structure and reactivity. In: Chemical properties of starch, Martins Emeje. IntechOpen 21. Park SH, Na Y, Kim J, Kang SD, Park KH (2017) Properties and applications of starch modifying enzymes for use in the baking industry. Food Sci Biotechnol 27(2):299–312 22. Heydari A, Alemzadeh I, Vossoughi M (2013) Functional properties of biodegradable corn starch nanocomposites for food packaging applications. Mater Des 50:954–961 23. Khan B, Naizi MBK, Samin G, Jahan Z (2016) Thermoplastic starch: a possible biodegradable food packaging material- a review. J Food Process Eng 40(3):e12447 24. Kumar N, Kaur P, Bhatia S (2017) Advances in bio-nanocomposite materials for food packaging: a review. Nutr Food Sci 47(4):591–606 25. Rudnik E, Matuschek G, Milanov N, Kettrup A (2005) Thermal properties of starch succinates. Thermochim Acta 427(1–2):63–166 26. Meena, Sharma A (2018) Study of changes induced in thermal properties of starch by incorporating Ag nanoparticles, AIP Conference Proceedings 1953,(1) 27. Kumar R, Kumar A, Sharma NK, Kaur N, Chunduri V, Chawla M et al (2016) Soft and hard textured wheat differ in starch properties as indicated by Trimodal distribution, morphology, thermal and crystalline properties. PLoS One 11(1):e0147622 28. Rhim J, Park H, Ha C (2013) Bio-nanocomposites for food packaging applications. Prog Polym Sci 38(10–11):1629–1652 29. Gulati S, Singh P, Diwan A, Mongia A, Kumar S (2020) Functionalized gold nanoparticles: promising and efficient diagnostic and therapeutic tools for HIV/AIDS. RSC Med Chem 11(11): 1252–1266 30. Kumar S, Mongia A, Gulati S, Singh P, Diwan A, Shukla S (2020) Emerging theranostic gold nanostructures to combat cancer: novel probes for combinatorial immunotherapy and photo thermal therapy. Cancer Treat Res Commun 25:100258

Wrinkle-Resistant Fabrics: Nanotechnology in Modern Textiles

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Shikha Gulati, Sanjay Kumar, Sanah Kumar, Vidhi Wadhawan, and Kanchan Batra

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conventional Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Formaldehyde-Based Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Non-formaldehyde-Based Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanomaterials in Anti-wrinkling Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Titanium Dioxide (TiO2) Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silver (Ag) Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon Nanotubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Zinc Oxide (ZnO) Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chitosan Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Silica (SiO2) Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multifunctional Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Environmental Impact of Use of Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

912 914 914 916 917 918 920 921 921 922 922 923 925 926 926 927

Abstract

Nanotechnology is a growing interdisciplinary branch of science that deals with the utilization of matter at an atomic/molecular/supramolecular scale for diverse purposes. The reason for its impact in wide areas is due to the high effectiveness of nanomaterials. Owing to the small size ( 50 mm). Varieties of materials such as metals, polymers, ceramics, or combination of these materials in any required quantity can be sprayed in the processes. Powder particles or wires can be used as a feedstock material. Heat source can be of combustion flame, plasma jet, or arc wires. Based on the feedstock and heat source materials, thermal spray process can be classified as (i) plasma spraying, in which inert gas is passed between two electrodes to form a plasma flame, (ii) high-velocity oxygen fuel spraying (HVOF), in which heat energy is produced by the combustion of fuel gas, and (iii) arc spraying, in which, the heat energy is produced by an electric arc among the two electrically conductive wires. Instead of heat source, high kinetic energy is used in cold spraying process. Highpressure (~3.5  106 Nm 2) gas with critical velocity (500–1200 ms 1) propels the powder particles to the substrate and develops a coating [35].

Other Wet chemical Synthesis Comparing to PVD and CVD, other wet chemical processes such as sol-gel and spin and dip coating methods have strong practical advantages due to their simplicity, low cost, low-temperature processing, and suitable to deposit on complex and wide varieties of substrates. Nanocomposite coatings using sol-gel precursor were formed by spin coating or dip coating on a substrate. After that the organic residuals and water are removed by pyrolysis and subsequently by nucleation and growth of the nanocomposite film. Mostly the crystallinity, crystal size, and film porosity depend on the pyrolysis treatment of the deposition. In addition to this, it is possible to control numerous parameters such as precursor type, concentration, viscosity, pH, temperature, addition of co-solvent, presence of doping elements, and thickness control to develop simple but effective and uniform coating to attain the desired properties of the final coatings [32]. Several kinds of nanocomposite coatings have been developed by the sol-gel process for various applications. Polymer nanocomposites are prepared by reinforcing small quantities (< 5 wt%) of nanoparticles with various kinds of polymers (thermosets, thermoplastic, or elastomers). For polymer nanocomposites, not all of the above are practically possible. Vaporizing procedures such as PVD and CVD can easily damage the polymer chains at very high temperatures or energies. Therefore, low deposition temperature is typically a basic prerequisite for appropriate polymer nanocomposite coatings.

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Applications of Nanocomposite Coating in Environmental Cleanup Environmental pollution is a serious hazard to our planet. Pollutants such as pesticides, heavy metals, various gases, and some microorganisms can generate terrible harms to both human and the environment. Hence it is vital to monitor the various pollution sources which affect air, water, and soils. The detection of these pollutions is a demanding task, due to their complex nature, mixture of various compounds with high volatility, and low reactivity. Metal oxide-based sensors generally work at high temperature and are not stable in the long run. Nanocomposites with different classes of materials such as metals, metal oxides, polymers, and ceramics can prevail these issues and provide high performance in the sensing. Some of the main attributes should be possessed by an ideal sensor such as the following: (i) room temperature operation, (ii) high sensitivity and reproducibility, (iii) quick response and recovery time, (iv) eco-friendly, (v) low cost, (vi) should not need external source for response and recovery operation, and (vii) should work in ambient surrounding without the supply of external air or oxygen. Many researches are ongoing to develop new sensors which can satisfy many of the above requirements to satisfy the need of a good sensor for environmental monitoring. Following are the most recent advancement of the nanocomposite coatings in the field of environmental monitoring and pollution detection.

Air Quality Monitoring Hydrogen sulfide (H2S) is extremely harmful to both the human beings and the environment. Even at very low concentration, it can affect the nervous system and can cause death. Its threshold limit is 10 ppm. Therefore, earlier detection even at low or sub-ppm concentrations is crucial for the safety of the environment and the population. H2S is usually released by biological products, natural gas, petroleum, and mining fields. Polypyrrole and tungsten trioxide (PPy/WO3) nanocomposite thin film was prepared by in situ photopolymerization on an alumina substrate using TiO2 nanoparticles as the co-photoinitiator by Su et al. [36]. Comparative studies revealed that the H2S sensing response at room temperature of nanocomposite based on PPy/WO3 film was strong even at low concentration than the sensor based on pure WO3 or PPy film. It is claimed that the stretching of the depletion layers at the interface of the PPy with the WO3 film resulted in the high response when the H2S gases are adsorbed at room temperature [36]. Ammonia (NH3) gas is used in several fields such as petrochemical industries, plastic production, textiles, explosives, and also as a fluid in refrigerator [37]. Nevertheless, high concentration exposure to NH3 can cause serious health issues such as respiratory damage, eyes and skin irritation [38]. The threshold limit for ammonia exposure for 8 h is 25 ppm and for 15-min exposure is 35 ppm [37]. Thus, it is vital to monitor NH3 gas to provide safe environment. Yan et al. [39] reported about polyaniline/reduced graphene oxide (PANI/RGO) nanocomposite material filterer

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coated on 3D porous cellulose papers to produce paper-based flexible roomtemperature electronic sensor. It was prepared by in situ PANI polymerization in RGO solution. Even after 1000 bending/extending cycles, this flexible sensor exposed exceptional sensing ability for NH3 and consistent flexibility without noticeable change in sensing performance at room temperature. Compared to pure PANI and RGO, the nanocomposite film exhibits superior sensing ability. This was reported due to the synergistic effects of RGO and PANI, higher specific surface area, higher carrier mobility, and exposed active surfaces. Another NH3 sensor developed on surface plasmon resonance-based fiber-optic gas sensor using poly(methyl methacrylate) (PMMA)/RGO nanocomposite film has been reported by Mishra et al. [40]. Various gases like NH3, H2S, and N2 were tested and found that the sensor probe was more sensitive to NH3 gas. The result of their studies revealed that this sensor has high sensitivity, wider operating range, reusability, and reproducibility. Additionally, the optical fiber probe provides miniaturization, low cost, online monitoring and remote sensing, and immunity to electromagnetic field interference. Nitrogen dioxide (NO2) together with nitrogen oxide (NO) called NOx are existing in the atmosphere due to various combustion processes from factories, power plants, vehicles, and aircrafts. NO2 is a precursor to ozone by combining with atmosphere and form ground-level ozone (O3). It also produces acid rain and a fundamental element of smog. All of these impose massive threat to environment. Layered surface acoustic wave (SAW) sensor using a ZnO guiding layer on LiTaO3 piezoelectric substrate was fabricated by Penza et al. [41]. The highly sensitive layer was created using SWCNT-based nanocomposite coating prepared by the LangmuirBlodgett (LB) coating technique. To provide high sensitivity, the acoustic energy near the surface was confined by a ZnO guiding layer on the SAW transducer. At room temperature, the change in the SAW phase due to the interfering gases such as H2, NH3, and NO2 was monitored in the range of 0.030–1%, 100–1000 ppm, and 1–10 ppm, respectively. The result revealed that high sensitivity, low detection limit, good repeatability, reversibility, and fast response were achieved by this novel layered SAW structures combined with nanocomposite layers. Constant and on-site observation of sulfur dioxide (SO2) is very important due to its poisonous nature to the living beings, plants, and environment. The major sources of SO2 are vehicle exhaust, thermal power plants, and chemical factories. About 5 ppm of SO2 is enough to develop some serious problems, such as respiratory issues, cardiovascular diseases and lung cancer. Room temperature, ultralow SO2 gas sensing was developed by layer-by-layer self-assembled titania (TiO2)/graphene nanocomposite films (Fig. 4) by Zhang et al. [42]. This TiO2/RGO nanocomposite hybrid gas sensor exhibited ppb-level sensing, quick response and recovery, good reversibility, selectivity and repeatability for SO2 gas sensing at room temperature. The excellent sensing was reported to be due to the synergistic effect of TiO2 and RGO, as well as special interaction at TiO2/rGO interfaces [42]. Volatile organic compounds (VOCs) are liquids or solids under normal temperature and pressure but stay as gases in the atmosphere. High level of VOCs is harmful since it can yield new toxic products by reacting with oxygen-based free radicals and can be potentially hazardous to living beings and environment. They are

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Self-assembled with (PDDA/PSS)2

1) TiO2 microspheres 2) Rinse and dry 3) Graphene Oxide

(PDDA/PSS)2

(PDDA/PSS)2

4) Rinse and dry

Substrate

5) Alternative self-assembly 6) Thermal reduction

TiO2 /rGO PDDA

(PDDA/PSS)2 PSS

(PDDA/PSS)2 TiO2

Graphene

Fig. 4 Schematic illustration of TiO2/RGO multilayer hybrid film fabrication process. (Reproduced with permission from [42]. Coryright 2017, Elsevier)

carcinogenic and can cause membrane irritation, dizziness, allergies and respiratory issues. VOCs are usually highly reactive and have low boiling point. It also plays a main role in the climate change and the destruction of the ozone layer. Zn-W-O nanocomposite coatings were fabricated by the sol-gel method and coated on alumina ceramic tube by dip coating method for the detection of VOCs. The proper quantities of ZnWO4 in ZnO-rich samples and in WO3-rich samples provide improve sensing activity towards VOCS. This sensor can detect VOCs like formaldehyde, benzene, and xylene. Due to the lower electronegativity of Zn, for example, ZnO-rich sample shows higher sensitivity than that of WO3 rich sample for 100 ppm formaldehyde [43]. Hierarchical SnO2/ZnO nanocomposite material for highperformance ethanol sensor was developed by Khoang et. al [44] using combined thermal evaporation and hydrothermal method. The result showed that this hierarchical nanocomposite possesses enhanced gas response and selectivity compared to pristine SnO2 nanostructure and suggested that this method can be useful for various other material for gas sensing application. Swelling evaluation of polymer nanocomposite layers using simple thin film optical interferometry method was reported for gas sensing application [45]. It is based on the nanocomposite film expansion at a fixed wavelength to the various light

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intensities. This method was used for VOCs using poly(2-hydroxyethyl methacrylate) (PHEMA) and carbon black/PHEMA nanocomposite layers. This process is very sensitive and measurement of few nanometer swelling as achieved for measuring ethanol. Compared to pristine polymer, nanocomposite film showed pronounced swelling.

Water Quality Monitoring and Treatment One of the other most serious environmental issue is water pollution. Water is a valuable natural resource, and its quality is crucial for the survival of living beings. Clean water access is one of the most basic humanitarian needs, but studies revealed that safe drinking water is not available for more than 1.2 billion people and staggering 2.6 billion people uses drinking water without or little hygienic condition. Hence, the diseases due to water pollution kill millions of people every year. The main source of water pollution is from the industries which release heavy metals such as lead and mercury; synthetic dyes and pigments from textile industries; organic pollutants from pesticides, pharmaceutical industries, and leather factories; and various microbial infectious pollutants. Nanocomposite materials provide promising candidate for monitoring the water quality and also for removal of some kind of pollutants. Most of the nanocomposite used for water purification and monitoring are in the form of nanopowders. Thin film nanocomposite coatings are mainly used as permeable assisted material for filtering heavy metals, salts, and organic contaminants and for desalination. Thin film nanocomposite membranes use nanoparticles such as silica, TiO2, Ag, zeolites, and CNTs. Membrane preparation has been carried out in various ways such as interfacial polymerization, coatings, crosslinking, etc. [46]. Daraei et al.[47] prepared a novel organoclay/chitosan nanocomposite coating on the commercial polyvinylidene fluoride (PVDF) microfiltration membrane. According to their studies, addition of various organoclays with different fractions into the chitosan made it more effective membranes with impressive dye elimination from effluents together with higher permeate flux related to conventional nanofiltration membrane. Nanofiltration (NF) thin film membranes using electrically conductive polyamide-carbon nanotube nanocomposite shown to deliver biofilm-preventing capabilities under extreme bacteria and organic material loadings [48] . The results showed that this polymer nanocomposite thin film materials claim to have high electrical conductivity (400 S/m), good NaCl rejection (>95%), and high-water permeability. This nanocomposite thin film membrane provides a long-term effect and higher reproducibility to prevent the formation of biofilm. Zwitterion functionalized carbon nanotubes (CNTs)/polyamide nanocomposite was used to construct highly effective desalination membranes by Chan et al. [49] (Fig. 5). The flux of water increased by fourfold and the salt rejection ratio increased from 97.6% to 98.6% with the addition of zwitterion functionalized CNTs in a polyamide membrane. Simulation studies also provide conclusive evidence for the efficiency of this nanocomposite membrane for water purification.

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Fig. 5 Fabrication process for CNT/polyamide nanocomposite membrane. (A) Polyethersulfone (PES) ultrafiltration membrane, sandwiched by two poly(tetrafluoroethylene) (PTFE) holders. (B) Zwitterion functionalized CNTs, coated onto the PES membrane. (C) Interfacial polymerization (trimesoyl chloride, (TMC), m-phenylenediamine, MPD)). (D) Photograph of the nanocomposite membrane. (Reproduced with permission from [49]. Coryright 2013, American Chemical Society)

Aluminosilicate-incorporated single-walled nanotubes (SWNTs) within the poly (vinyl alcohol) (PVA) offer a new type of thin film nanocomposite (TFN) membranes for nanofiltration [50]. The surface hydrophilicity increased and the contact angles decreased from 64.2 to 50.5. Due to the presence of nanotubes, the water flux increased. Higher permeate water flux was attained due to the integration of the aluminosilicate single-walled nanotubes. The divalent ion rejection was 97%, whereas monovalent ion rejection was 59% for this thin film nanocomposite membrane. Polystyrene and carbon black nanocomposite thin films were prepared as an adsorbent material for the removal of heavy metals from industrial wastewater by Alshabanat [51]. Thirty ppm of lead was separated in 120 min at pH 6. Freundlich isotherm was used to describe the adsorption data and it followed the pseudosecond-order kinetics. Considering the microbial infections and pollution, very recently Chen et al. [52] developed polyacrylate/Ag nanocomposite coating for antibacterial application. It showed extreme hydrophilicity and wettability with excellent antibacterial and antifouling properties. Biofouling is the unwanted progress of organisms on submerged surfaces. Any unprotected material, which is submerged, will be colonized by these microorganisms and affect the water body. Hence these types of coatings will be of great interest for maintaining the water quality. Chitosan nanocomposite coatings with various inorganic nanomaterials such as Ag, Au, TiO2, ZnO, CdS, SnO2, etc. are used for waste water treatment and antifouling

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coatings. Detailed review about these nanocomposite coatings was given by Kumar et al. [53]. Chitosan-zinc oxide (chitosan-ZnO) nanocomposite coatings were developed on a glass substrate for antifouling application. These nanocomposite coatings displayed anti-diatom activity as well as antibacterial activity against the marine bacterium [54]. Chitosan and halloysite clay nanotube coatings shown to provide anticorrosive protective coating as well as provide improved passive barrier protection and self-healing from the corrosion [55].

Future Perspective and Conclusion The environmental pollution monitoring of nanocomposite coatings is interesting and endless and provide promising perspectives. The advantages of using nanocomposite coatings for the pollution monitoring and remediation are efficient, costeffective, and multitasking. This chapter shows the effect of nanocomposite coating in air and water quality monitoring. Various researchers in the literature reported about their finding where the nanocomposite coatings have been successfully used in the field of environmental pollution detection and remediation process. Numerous advanced platforms that could be considered and exploited over recent years has established the ability of nanocomposite materials to deliver cost-effective and eco-friendly tactics for the removal, degradation, or the reduction of various pollutants, including microorganisms, organic dyes, insecticides, and heavy metal ions. Even though the nanocomposite coatings for environmental monitoring are very promising, their real-world implementation is still challenging, as confirmed by the limited number of reports. Currently the main challenge of nanocomposite coatings is perhaps to translate these basic research discoveries from the laboratory to the progress of commercially feasible environmental monitoring and remediation technologies. Links for further readings about this topic: https://www.labmanager.com/insights/using-nanomaterials-for-environmental-reme diation-750 https://frtr.gov/pdf/meetings/m%2D%2Dfryxell_1_09jun04.pdf https://clu-in.org/techfocus/default.focus/sec/Nanotechnology%3A_Applications_ for_Environmental_Remediation/cat/Overview/

References 1. Hussain CM, Mishra AK (2018) Nanotechnology in environmental science, vol 1. Wiley 2. Hussain CM (2018) Handbook of functionalized nanomaterials for industrial applications, First Edit. Elsevier 3. Hussain CM (2020) Handbook of nanomaterials for manufacturing applications, First Edit. Elsevier 4. Hussain C (2020) Handbook of polymer nanocomposites for industrial applications, First Edit. Elsevier

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Sathya Moorthy Ponnuraj and Palaniswamy Suresh Kumar

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon and Its Allotropes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activated Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sources of Activated Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activated Carbon Production and Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of Activated Carbon Based on Pore Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Adsorption Mechanism in Activated Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Evaluation of Property of Activated Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heavy Metal Classification, Properties, and Their Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effect of Heavy Metals in the Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Heavy Metal Remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

Globally, in agriculture a part of plant products remains as an inedible portion after harvest; such products are organically carbonaceous in nature. Agriculturist used to combust the undesirable agricultural remains in to an amorphous carbon to accelerate the decay and transform into manure for future farming agriculture crops. After the official discovery of activated carbon in the eighteenth century, it was reported to function as an antidote against poison and intestinal disorders.

S. M. Ponnuraj Department of Nano Science and Technology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India e-mail: [email protected] P. S. Kumar (*) Environmental and Water Technology, Centre of Innovation (EWTCOI), Ngee Ann Polytechnic, Singapore, Singapore © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_65

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The application of activated carbon is numerous in various fields; the search for affordable carbon-rich raw materials for manufacturing activated carbon has picked up the pace. Agricultural byproducts such as shells, cobs, seeds, stones, husks, kernels, barks, and woods are available as a potentials source. In this chapter, we discuss about brief history of carbonaceous materials and allotropes of carbons, activated carbon, and various potential agricultural sources of activated carbon; production, activation, classification, and advantages of activated carbon; adsorption and evaluation properties of activated carbon; and its application as heavy metal remediation. Keywords

Agricultural · Activated carbon · Pore size · Heavy metal ions · Adsorption

Introduction Charcoal was reported to possess a ascertain role to carve in the stone of history due to its adsorptive and medical property. Use of charcoal was first reported by Native American around 8000 B.C. for treating stomach ailment using water along with charcoal. Egyptians reported the use of charcoal for purification of bronze metal from its ore by smelting on 3700 B.C. [12]. Later after 2200 years, in 1500 B.C., they used charcoal (a) for the treatment of stomach ailments, (b) to absorb the unpleasant odors from the infected wounds, and (c) for writing on papyrus. Romans around 27 B.C. used charcoal along with crushed bones, oyster, and bark and as a tooth powder to brush the teeth. Accounting the anti-septic property of the charcoal, Indians and Phoenicians around 400 B.C. used it for the purification of water (University of Kentucky, 2012). Voyager used the technique of preserving the water for month together throughout their journey using charcoal. Around 50 A. D., Hippocrates, a great Greek physician considered to be as a father of medicine, was first to report the use of charcoal for the treatment of neural disorder like epilepsy, chlorosis, and vertigo [9]. Later in 2 A.D., famous and pioneering person in the field of physician named as Claudius Galen has regularly referred the use of charcoal in various treatments. Throughout many centuries, charcoal has been widely used in many countries as an excellent antibacterial and antiseptic material. Later in the seventeenth century, a Russian chemist Johann Lowitz initially discovered the discoloration property of charcoal in liquids particularly used in sugar refineries production of white sugar and made it as a visually exciting material to the customers around the world [12]. This iconic discovery had accelerated the scientist to work on the carbonaceous materials and later led to development of official discovery of activated carbon (AC) in the early 1800. Soon after the discovery AC, it was referred in many medical journals to use as an antidote against poison and intestinal disorders around 1820. Frederick Lipscombe was the first person to use AC in commercial applications to purify potable water in 1862.

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A German physicist, Heinrich Kayser, was the first person to coin the word “adsorption” and explained the mechanism of gas uptake by charcoal in the year 1881. Where as in 1883, a French chemist, Gabriel Bertrand, has proved the antidote potential of charcoal in treatment against poison intake; he himself swallowed arsenic mixed with charcoal and demonstrated that he can save himself against the lethal dose of arsenic along with charcoal. Later many such studies were demonstrated by various scientists with different poison with lethal dose. Industrial production of AC was started in early 1909, and soon after the production, it was used in sugar refineries, chemical industries, and food industry as discoloration agents. During World War I (1914–1918), AC was used in the mask worn as personal protective equipment (PPE) by American soldiers to de-toxify the inhaled poisonous gases, in spite it accelerated the production of granular carbons in large scale. From 1979 onwards, AC was widely applied industrially in water purification, industrial waste, offset of gases, cleaning of bottles and wine tanks, etc., Currently, AC was greatly adopted in pharmaceuticals, cosmetic, and food industries. AC was not only used in removing odor and disease causing germs to make water potable but also used in heavy metal remediation. AC was also used in clinical fields in liver, kidney dialysis machines, markers for breast cancer surgery, and many more.

Carbon and Its Allotropes Carbon has been known from ancient times. It is the sixth most abundant element in the earth. Carbon adopts different allotropic forms, i.e., different structural arrangement of the same carbon. Carbon appears naturally in two different forms: amorphous forms (i.e., the application of high pressure and temperature without oxygen turning wood into coal is known as carbonization, e.g., coal, etc.) and crystalline forms (i.e., regular arrangement of carbon atoms in hexagonal and tetragonal arrangement as graphite and diamond, respectively). Fullerene is an artificial crystalline allotrope of carbon, whereas all other forms of carbon, namely coke, wood charcoal, animal charcoal, plant charcoal, sugar charcoal, lamp black, fullerenes, graphene, and CNT are artificial allotropes of carbons. Schematic representation of classification of carbonaceous material based on its allotropic nature is shown in the Fig. 1.

Activated Carbon Activated carbon may be defined as an amorphous form of carbonaceous materials with rich inherent multidimensional property like high degree of porosity with an extended interparticular surface area [5], long shelf life, low density, great surface reactive, high performance in electrical conductivity, and thermal conductivity and good thermal stability characteristics in nature. Properties of an activated carbon are schematically represented in Fig. 2.

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Carbon Crystalline Diamond

Amorphous

Graphite

Coal Coke

Charcoal

Lamp Black

Gas Carbon Plant Charcoal

Wood Charcoal

Sugar Charcoal

Animal Charcoal

Bone Charcoal

Blood Charcoal

Fig. 1 Different allotropes of carbon

Sources of Activated Carbon Activated carbon can be prepared from wide variety of renewable and non-renewable materials of organic origin. Variety of plant, animal, and fossil fuels can be used as an excellent raw material for activated carbon [30]. Materials used in production of activated carbon must satisfy two critical prerequisite, namely, (a) extremely carbon rich and (b) contains low ash content and trace elements, (c) less expensive, (d) less degradation during storage, (e) potent extent of activation, and (f) uninterrupted supply [7]. Sources of the activated carbon can be broadly classified into two major categories: non-renewable (i.e., the source of energy that eventually runs out, namely, fossil fuels like coal, crude oil, natural gas, etc.) is mainly used as raw material for commercial production activated carbon [6] and renewable energy source is a naturally inexhaustible energy source continuously replenished by nature, namely, various agricultural byproducts like nut shells, stones, seeds, huls, seed kernels, bark wood, corn cob, husks, straws, peels, piths, woods, saw dusts, coir dust, bagasse, etc. [18]. Agricultural byproducts have been documented as excellent sources of activated carbon [13]. Agricultural byproducts are easily available and affordable, reduce great distance of transportation and soil waste management, and improve the value addition of crops by increasing the revenue of farmers. Potential agricultural source of carbon-rich materials is categorized in Fig. 3. Moisture, ash, volatile, carbon, hydrogen, nitrogen, sulfur, oxygen, cellulose, hemicelluloses, and lignin contents of an activated carbon produced from agricultural byproducts like nut shells, stones, seeds, seed kernels, bark wood, corn cobs, husks, straws, peels, piths, woods, saw dusts, coir dust, bagasse, etc., were characterized and shown in Fig. 4 [32].

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Fig. 2 Properties of an activated carbon

Activated Carbon Production and Activation A variety of activated carbon production methods are found elsewhere with appropriate change in raw materials and production process. The AC production involves two important processes, namely, (i) carbonization (i.e., conversion of carbon-rich material into pure carbon material devoid of non-carbon and volatile organic compounds). During the processes of carbonization, the non-carbon materials like nitrogen oxygen and hydrogen are released with increase in temperature of the material. Carbonization was carried out by pyrolysis (i.e., thermal disintegration of material at very high temperature (below 800
C) in inert atmosphere) and (ii) activation (i.e., process of introducing countless pores and capillary like arrangements inside the carbonaceous materials). Carbonized material can be activated either by gas or chemical process (Fig. 5).

Fig. 3 Potential agricultural source of carbon-rich materials

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Fig. 4 Analytical characteristic and composition of agricultural biomasses

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In carbonization of agricultural byproducts such as nut shells, stones, seeds, seed kernels, bark wood, corn cobs, husks, straws, peels, piths, woods, saw dusts, coir dust, bagasse, etc., material takes place at different phases with the removal of non-carbonaceous materials at different temperatures as shown in Fig. 6. The initial process of heating the agro byproducts below 200
C causes loss in weight due to the decrease in moisture content of the material. Further heating of the material at the temperature range of 170–200
C initiates the precarbonization phase which results in production of non-pyroligneous liquids and non-condensable gasses. Rise of temperature of the materials (around 250–300
C) causes elimination of non-pyroligneous liquids and tars and results in production of charcoal. Further continuing the rise in temperature above 300
C enriches the carbon content of the charcoal by the release of residual volatile organic compounds. Activation of charcoal was carried out by any one of two different ways, namely, (i) physical

Fig. 5 Process involved in activated carbon production

Fig. 6 Different phases of charcoal carbonization

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Fig. 7 Schematic diagram of physical and chemical activation of charcoal

activation or (ii) chemical activation [30] as shown in figure (7). Physical activation of charcoal is preceded by the carbonization of material. Physical activation of charcoal was carried at the temperature range of 700–1100
C. The charcoal is oxidized by the stream of gases, namely, steam, oxygen, air, and CO2 or a mixture constituting of all the above. Carbon becomes porous, partially gasified and highly activated skeleton was produced due to physical activation. The chemical reaction occurring during the activation is as follows: C þ H2 O➝CO þ H2 C þ 2 H2 O➝CO2 þ 2 H2 During the chemical activation, the carbonization and activation of charcoal takes place simultaneously. Initially, agricultural waste products were submerged with oxidizing and reducing agents such as KOH, K2CO3, H3PO4, and ZnCl2. Chemical activation of charcoal takes place at the temperature of about 450–900
C. After activation of charcoal, the surplus activating agents are leached out and recovered. The process of chemical reaction was quicker than the physical activation. Trace amount of activating agents absorbed by the activated carbon may affect the performance.

Classification of Activated Carbon Based on Pore Size The formation of countless pores and capillaries inside charcoal is known as activation. Size of the capillaries and pore formation increases the internal surface area of the activated carbon which may be used in variety of application such gas, air,

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and water treatments by the process of adsorption. Based on the pore size, activated carbon can be generally classified into three types, namely, microporous (50 nm). Kinetic property of the activated carbon inherently depends upon the pore size and capillarity. Each activated carbon has different functions such as gas absorption, recovery of solvent with mild and high boiling point, and absorption of liquid phase, respectively. The classification of activated carbon and schematic representation of activated carbon is as shown in Figs. 8 and 9. Pore distribution inside the activated carbon depends on the inherent nature of the chosen material. Quantity of accumulation depends upon the significant degree of increase of internal surface area of the activated carbon. Internal surface area of the activated carbon is evaluated using BET (Brunauer, Emmett, and Teller) and nitrogen isotherm at 196
C (www.donau-carbon.com). Internal surface area of activated carbon evaluated as 800–1500 m2/g and 500–1500 m2/g is well suited for gas and air treatment and water purification, respectively.

Fig. 8 Classification of activated carbon

Fig. 9 Activated carbon representing micro-, meso-, and macropore

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Adsorption Mechanism in Activated Carbon The process of accumulation of atom or molecule or ion of gas, solutes of liquid, and thin layer of dissolved solid on the micro-, meso-, and macroporous surface of activated carbon was referred as adsorption. Adsorption is an exothermic process that occurs with the release of heat to the environment. Adsorbent capacity of the activated carbon depends on the (i) nature of the material, (ii) manufacturing process of activated carbon, and (iii) mode of activation. Van der Waals force is understood as the intermolecular force of attraction or repulsion between atoms or molecules or surfaces. Capillary condensation is defined as confinement of condensed gas into liquid at a chemical potential below the corresponding liquid vapor coexist in bulk state. Van der Waals force and capillary condensation play a major role during the adsorption. Adsorption process may be classified into two types, namely, physisorption and chemisorption. During the process of physisorption, no chemical reactions are activated between the activated carbon surfaces and accumulating substances. Accumulation on the activated carbon surface was stabilized by Van der Waals forces or London dispersion forces. Whereas in the process of chemisorption, a chemical reaction is triggered inbetween activated carbon and accumulating substance causing chemical alteration. Physisorption and chemisorptions are schematically represented in Figs. 10 and 11, respectively.

Evaluation of Property of Activated Carbon Activated carbon possesses three significant properties, namely, surface area, pore radius, and total pore volume. The above said properties of the activated carbon highly depend on the intrinsic nature of the source material, manufacturing process, and mode of activation. During the activation process, innumerable pores are created. The surface area of the activated carbon was enhanced about 500–1500 m2/g or even more than that. A spoonful of activated carbon is equivalent to the surface area of the soccer field. Pore radius refers to the average size of the pore formed during activation of carbon. Pore size is usually measured in angstroms (Å). Each carbon has their unique distribution of pore size. Based on the pore size, activated carbon can be classified in to micro-, meso-, and macroporous materials. Summation of volume of each pore on the activated carbon refers to the total pore volume. Total pore volume is usually measured in milliliter per gram (ml/g). In general, higher pore volume is correlated with effectiveness of the activated carbon. The quality of the activated carbon can be evaluated by following any of the international standard protocols enacted by the American Society for Testing and Materials (ASTM), or American Water Work Association (AWWA), or Council of European Federation for Industrial Chemicals (CEFIC) based on the region and application of the product. All other properties like (i) ash content, (ii) water content, (iii) pH, (iv) bulk and vibration density, (v) iodine absorption, (vi) molasses decoloration behavior, (vii) methylene blue absorption, (viii) tetrachloride carbon and butane absorption, (ix) absorption isotherms of various solvents, (x) particle distribution, (xi) hardness, (xii) BET

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Fig. 10 Classification of adsorption in activated carbon

Fig. 11 Schematic representation of physisorption and chemisorptions process. (Source: Adam Hugmanic berger and Abhoyjit S. Bhown 2001)

analysis, (xiii) pore radius, (xiv) phenol concentration, (xv) chlorine half vale length, (xvi) water- and acid-soluble components, and (xvii) estimation of halogen hydrocarbons and other purity test protocols are followed as referred in ASTM, AWWA, and CEFIC (Source: CEFIC, test method for activated carbon).

Heavy Metal Classification, Properties, and Their Sources Metals are natural components of the earth’s crust. Metals having an atomic weight greater than 63, an atomic number >20, and a specific gravity greater than 5 gm/cm3 such as lead (Pb), cadmium (Cd), zinc (Zn), mercury (Hg), arsenic (As), silver (Ag), chromium (Cr), copper (Cu), iron (Fe), and platinum (Pt) are generally referred as heavy metals. Heavy metals can be classified in (a) macronutrient elements, (b) micronutrient elements, (c) highly toxic elements, and (d) precious elements (Fig. 12).

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Fig. 12 Classification of heavy metals

Fig. 13 Properties of heavy metals

Most common heavy metal contaminants are Cd, Cr, Cu, Hg, Pb, and Zn. Living organisms require an optimum concentration of some metal such as Fe, Co, Cu, Mn, Mo, and Zn for proper functioning and coordination of living system [14]. Any metal at higher concentration causes acute toxicity to the living system. Uncontrolled population explosion, rapid industrialization, unplanned urbanization, unskilled use of natural resources, and negligence over production, usage, and discard of remnant products may lead to the progressive release of a quantum of heavy metals into land, water, and air leading to perturbation in biotic environment. Heavy metals are (i) readily soluble in water to form ions [1], (ii) toxic, carcinogenic, and teratogenic insusceptible to biological degradation to transform into harmless products (iii) owing to their long half-life and soil residence >1000 years. (iv) prolonged exposure of food crops and livestock animals in the polluted land and water resources may lead to bio-accumulation and bio-magnification (i.e.) gradually infiltration of heavy metals inside various parts of crops and animals and finally to humans by food chain causing deleterious health effects [29] (Fig. 13).

Effect of Heavy Metals in the Environment Heavy metals have different route source to the environment; their effect on human health on exposure and their critical concentration are enumerated in Fig. 14 [4, 24]. Metabolism of heavy metal remains complex on exceeding its critical

Fig. 14 Heavy metals and their effect on human health with their permissible limits. (Source: Singh et al. [29])

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concentration. Heavy metal accumulation above the critical limit disturbs the metabolic function by two different ways: (i) they disturb the function of the organ by accumulation and (ii) they replace the essential nutrient minerals from their appropriate binding place and by hampering the biological system. Toxic effects due to heavy metals in humans are exhibited in the form such as gastrointestinal disorders, diarrhea, stomatitis, tremor, hemoglobinuria, ataxia, paralysis, and vomiting, and convulsion, depression, and pneumonia either due to ingestion or inhalation of fumes or vapors. These heavy metals are not biodegradable; as a consequence, their presence in water causes serious health problems in human, plants, and animals. Wastewater commonly contains copper, nickel, and lead [22, 35]. Excessive intake of copper can cause capillary damage, hepatic toxicity, and renal damage [3]. Exposure to nickel results in skin irritation and damage to lungs and mucous membrane [23]. The presence of lead in drinking water causes various health disorders and enzyme inhibition. Importantly, the inorganic form of lead is reported to exert drastic effects as compared with organic isoforms [15, 33]. Some heavy metals cause cancer; therefore, it is necessary to remove toxic heavy metal ions from wastewater in order to protect human. In the current year, persistence of numerous chemicals and their derivatives reported to be above the tolerable limit is the prime reason for causing deleterious effect on environment. Children are highly susceptible to ingestion and inhalation of heavy metals causing hampering of multiple organs like the brain, kidney, lungs, bone marrow, and others. Heavy metals contaminate the natural resources and remains as a socioenvironmental threat [2].

Heavy Metal Remediation The removal of toxic heavy metal ions from industrial effluents in recent years gains much attention [19, 25]. The removal of heavy metals from the environment can be classified into biotic and abiotic methods. Biotic methods mean the removal of heavy metals by plants or microorganisms, while abiotic methods consist of physiochemical processes such as precipitation, co-precipitation, electrochemical treatment, ion exchange, liquid–liquid extraction, resins, cementation, electrodialysis, and sorption [16, 21, 27]. Among these methods, sorption is one of the most effective, economic, and simplest methods for the removal of pollutants from wastewaters [11]. Among the different sorbents that have been conventionally used for the removal of heavy metals from solution are zeolite [36], clay [28], and activated charcoal [8]. Activated carbon is widely applied as sorbent due to its high sorption capacity, the sorption capacity is related to the surface characteristics (surface area, pore size and pore volume) of the activated carbon, while surface characteristics of the activated carbon depend on preparation conditions [10, 17]. Activated carbon prepared from Salvadora persica was applied to the sorption study of divalent cations from diluted aqueous solution of lead copper, and nickel was evaluated using Langmuir model. Studies revealed the Activated Carbon prepared at 30 min heating time showed a greater sorption capacity for Cu2+, Pb2+, and Ni2+, and its order of cation sorption is Cu2+ > Pb2+ > Ni2+. An increase in time for the preparation of activated carbon gives a smaller surface area and hence causes decrease

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in the sorption capacity of cations [34]. Similarly, the activated biochar produced from Pinus taeda and the absorption studies were carried out using an aromatic model compound, phenanthrene. The increasing aromaticity and non-protonated carbon fraction of the activated biochar treated at 300
C amounted to 14.7% and 24.0%, respectively, compared to 7.4% and 4.4% for biochar treated at 700
C. The surface area and pore volume were reduced with the increase in pyrolysis temperature, but increased after activation [26]. Activated carbons obtained from corncobs by corncobs were carbonized at 500
C and steam activated (in one- or two-step schemes), or activated with H3PO4. The products were characterized by N2 adsorption at 77 K, using the BET and DR methods. Adsorption capacity was demonstrated by the iodine and phenol numbers, and the isotherms of methylene blue and Pb_2 ions, from aqueous solutions. These activated carbons proved highly porous and rich in mesopores and showed high adsorption capacity for methylene blue and Pb2_ ions. The adsorption capacity of Pb2_, from an unbuffered solution of Pb(NO3)2, was carried out by mixing 50 mg of the powdered carbon with 100 ml of Pb2_ solution of varying concentrations and shaking for 24 h. The residual lead was estimated in the filtered solution using a Perkin-Elmer model 2380 atomic absorption spectrometer. Analysis of the adsorption isotherms of MB and Pb2_ was carried out by applying the linear Langmuir equation [20]. Palm shell AC has been reported to remove heavy metals such as lead, chromium, and copper ions in wastewater due to presence of some functional groups on Palm shell AC that have chemical attraction toward metal ions, such as hydroxyl, lactone, and carboxylic [31]. Lead is often found in wastewater from printed circuit board factories, electronics assembly plants, battery recycling plants, and landfill leachate. If exposed to human body, they can cause central nervous system damage. Apart from that, lead can also damage the kidney, liver, and reproductive system, basic cellular processes, and brain functions. The toxic symptoms of lead are anemia, insomnia, headache, dizziness, and irritability, weakness of muscles, hallucination, and renal damages. Other than lead, copper is also widely used in electronics industry. The copper in animal body is essential in their metabolism. However, excessive ingestion of copper brings about serious toxicological concerns, such as vomiting, cramps, convulsions, or even death.

Conclusion Agriculture-based byproducts like nutshells, stones, seeds, hulls, seed kernels, bark wood, corn cob, husks, straws, peels, piths, woods, saw dust, coir dust, bagasse, etc. remain as a primary resource of carbonaceous materials. Carbonization of raw materials is achieved using pyrolysis, whereas activation was accomplished either using physical or chemical activation. Based on the pore radius, pore surface area, and total pore volume, activated carbons are classified functionally. Classification, properties, and their intervention in environment and human health are portrayed. Heavy metal remediation from various possible sources using the activated carbon is discussed in this chapter.

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References 1. Abdullahi MS (2015) Soil contamination, remediation and plants: prospects and challenges, Soil remediation and plants. Academic, Amsterdam, pp 525–546 2. Abhishek G, Rakesh S, Prashant S, Rajendra D (2017) Heavy metals in drinking water sources of Dehradun, using water quality indices. Anal Chem Lett 7(4):509–519 3. Ajmal M, Khan AH, Ahmad S, Ahmad A (1998) Role of sawdust in the removal of copper (II) from industrial wastes. Water Res 32(10):3085–3091 4. Al Naggar Y, Khalil MS, Ghorab MA (2018) Environmental pollution by heavy metals in the aquatic ecosystems of Egypt. Open Access J Toxicol 3:555–603 5. Bansal RC, Goyal M (2005) Activated carbon adsorption. CRC Press, New York. ISBN no: 97801279993714 6. Bansode RR (2002) Treatment of organic and inorganic pollutants in municipal wastewater by agricultural by-product based granular activated carbons (GAC). Thesis, Osmania University 7. Bergna D, Varila T, Romar H, Lassi U (2018) Comparison of the properties of activated carbons produced in one-stage and two-stage processes. J Carbon Res 4(3):41 8. Faust AD, Aly OM (1983) Chemistry of water treatment. Butterworth Co., Ltd. Acta hydrochim. et hydrobiol. 13(2):216 9. Hassler JW (1963) Activated carbon. Chemical Publishing Company, New York 10. Hassler JW (1974) Purification with activated carbon, 3rd edn. Chemical Publishing Co, Inc., New York 11. Huang CP, Hao OJ (1989) Removal of some heavy metals by mordenite. Environ Technol Lett 10(10):863–874 12. Inglezakis V, Poulopoulos S (2006) Adsorption, ion exchange and catalysis. Amsterdam 3:498–520 13. Ioannidou O, Zabaniotou A (2007) Agricultural residues as precursors for activated carbon production – a review. Renew Sust Energ Rev 11(9):1966–2005 14. Kulbir S, Abdullahi WS, Chhotu R (2018) Removal of heavy metals by adsorption using agricultural based residue: a review. Res J Chem Environ 22(5):65–74 15. Lo W, Chua H, Lam K-H, Bi S-P (1999) A comparative investigation on the biosorption of lead by filamentous fungal biomass. Chemosphere 39(15):2723–2736 16. Lothenbach B, Furrer G, Schulin R (1997) Immobilization of heavy metals by polynuclear aluminium and montmorillonite compounds. Environ Sci Technol 31(5):1452–1462 17. Mattson JS, Mark JHB (1971) Actiouted carbon: sucfirce chemistry and adsorprioiz, from solution. Marcel Dekker, Inc, New York, pp 25–86 18. Mdoe JE (2014) Agricultural waste as raw materials for the production of activated carbon: can Tanzania venture into this business? Huria: Journal of the Open University of Tanzania 16:89–103 19. Meunier N, Drogui P, Montané C, Hausler R, Mercier G, Blais JF (2006) Comparison between electrocoagulation and chemical precipitation for metals removal from acidic soil leachate. J Hazard Mater 137(1):581–590 20. Naseer A, Jamshaid A, Hamid A, Muhammad N, Ghauri M, Iqbal J, Rafiq S, Khuram S, Shah NS (2019) Lignin and lignin based materials for the removal of heavy metals from waste water – an overview. Z Phys Chem 233(3):315–345 21. Ng C, Losso JN, Marshall WE, Rao RM (2002) Freundlich adsorption isotherms of agricultural by-product-based powdered activated carbons in a geosmin–water system. Bioresour Technol 85(2):131–135 22. Ngah WW, Fatinathan S (2008) Adsorption of Cu (II) ions in aqueous solution using chitosan beads, chitosan–GLA beads and chitosan–alginate beads. Chem Eng J 143(1–3):62–72 23. Oliver MA (1997) Soil and human health: a review. Eur J Soil Sci 48:573–592 24. Onakpa MM, Njan AA, Kalu OC (2018) A review of heavy metal contamination of food crops in Nigeria. Ann Glob Health 84(3):488 25. Ozdemir C, Karatas M, Dursun S, Argun ME, Dogan S (2005) Effect of MnSO4 on the chromium removal from the leather industry wastewater. Environ Technol 26:397–400

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26. Park J, Hung I, Gan Z, Rojas OJ, Lim KH, Park S (2013) Activated carbon from biochar: influence of its physicochemical properties on the sorption characteristics of phenanthrene. Bioresour Technol 149:383–389 27. Qin Y, Cai L, Feng D, Shi B, Liu J, Zhang W, Shen Y (2007) Combined use of chitosan and alginate in the treatment of wastewater. J Appl Polym Sci 104:3581–3587 28. Sikalidis CA, Alexiades C, Misaelides P (1989) Adsorption of uranium and thorium from aqueous solutions by the clay minerals montmorillonite and vermiculite. Toxicol Environ Chem 20(1):175–180 29. Singh R, Gautam N, Mishra A, Gupta R (2011) Heavy metals and living systems: an overview. Indian J Pharm 43(3):246 30. Smisek M, Cerney S (1970) Active carbon: manufacture, properties and applications. Elsevier, Amsterdam, pp 286–290 31. Sulaiman F, Abdullah N, Gerhauser H, Shariff A (2011) An outlook of Malaysian energy, oil palm industry and its utilization of wastes as useful resources. Biomass Bioenergy 35:3775– 3786 32. Ukanwa KS, Patchigolla K, Sakrabani R, Anthony E, Mandavgane S (2019) A review of chemicals to produce activated carbon from agricultural waste biomass. Sustainability 11(22): 6204 33. Volesky B (1990) Removal and recovery of heavy metals by biosorption. In: Volesky B (ed) Biosorption of heavy metals. CRC Press, Boca Ration, pp 7–43 34. Wahid F, Mohammadzai IU, Khan A, Shah Z, Hassan W, Ali N (2014) Removal of toxic metals with activated carbon prepared from Salvadora persica. Arab J Chem 10(02):S2205–S2212 35. Xie JZ, Chang H-L, Kilbane JJ (1996) Removal and recovery of metal ions from wastewater using biosorbents and chemically modified biosorbents. Bioresour Technol 57(2):127–136 36. Zamzow MJ, Eichbaum BR, Sandgren KR, Shanks DE (1990) Removal of heavy metals and other cations from wastewater using zeolites. Sep Sci Technol 25(13–15):1555–1569

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Environmental and Occupational Health Hazards of Nanomaterials in Construction Sites S. Ajith and V. Arumugaprabu

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Human Health Risk Assessment Using Hazard Identification and Risk Assessment Technique (HIRA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Basic Mitigation Measures for the Workers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Control Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Green Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Environmental Hazards of Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assessment of Nanoparticles in Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assessment of Nanoparticles in Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Assessment of Nanoparticles in Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Life Cycle Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Important Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abstract

The use of nanomaterials has become increasing in the field of construction to enhance the structural strength of the building and to conserve energy. Besides the foreseeable advantages of nanoproducts, many of the nanotoxicology studies have revealed that the impacts on both health and environment are severe. As large amount of nanomaterials are used in construction sites, its adverse effects on workers’ health and environment have to be addressed. Risk assessment (RA) and life cycle assessment (LCA) are the effective tools which are used to quantify the S. Ajith Department of Civil Engineering, Kalasalingam Academy of Research and Education, Krishnankoil, Tamil Nadu, India V. Arumugaprabu (*) Department of Mechanical Engineering, School of Automotive and Mechanical Engineering, Kalasalingam Academy of Research and Education, Krishnankovil, Tamil Nadu, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_66

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risk of both workers and environment. The quantified risk value gives a clear picture about the hazards which made the environment to get depleted as well as the occupational risk of workers. The most promising technical recommendations are suggested in order to overcome the risk of nanoproducts which are used in construction sites. Keywords

Nanoproducts · Hazard · Risk assessment · Health

Introduction Nanotechnology is defined as the study of extremely small things whose size ranges between 1 and 100 nm. It has the ability to acquire new materials or improve the existing materials with enriched properties. Nowadays it has application in all fields of science and engineering, as it has the ability to see and control each and every atom in the material. The application of nanotechnology in construction materials has several features such as low-weight and high-strength materials and fire retardant, and maintenance is low in coatings. As size is one of the key factors in construction, nanotechnology plays a major role [1]. The role of construction industries in India is significant due to the development of smart cities, transportation, and industrial expansion. Construction industries hold lots of workers all over the country and fulfill peoples demand such as employment and the country’s growth. The construction industries use materials like coarse aggregate (CA), fine aggregate (FA), sand, steel, cement, glass, insulation materials for buildings, etc., but in order to have sustainable buildings, nanomaterials are more emphasized. The evolution of nanoproducts in concrete with its mix ingredients is as shown in Table 1. Nanotechnology has important role in building materials as it has high performance and durability. The mandatory material for any construction is concrete. The advanced characterization techniques and the superior understanding of the cementitious materials at the micro/nano level have the ability to produce large-scale materials [3]. The usage of nanomaterials in building materials and its improvement with the existing materials are listed in Table 2. A report from the United Nations says that almost 50% of the world’s population lives in urban area and it is predicted to increase by 16% at 2050. This will increase the usage of construction materials and demolition of existing buildings. The waste generation due to urbanization reached three billion till 2012. Hence waste management practices with low technology are essential to save the environment in the future [21, 22]. It is known that nanoparticles have a vital role in the building materials, and the need for such materials still exists, but it is seen that the usage of these particles in building materials seems to be very much low. Nevertheless, the most important material in construction such as concrete and asphalt doesn’t reach large-scale manufacturing due to some drawbacks such as increase in price,

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Table 1 Evolution of nanomaterials in concrete [2] S. No 1. 2. 3.

Type of Concrete Ordinary concrete High-performance concrete Ultrahigh-performance concrete

Ingredients FA, CA, cement, and water FA, CA, cement, micro-silica, and water FA, CA, cement, nano-silica, and water

Size mm μm nm

Table 2 Usage and improvements of nanomaterials in building materials Existing materials/ process Mixed with cement mortar Mixed with hardened cement paste Mixed with high-volume fly ash concrete Added in concrete

S. no 1.

Type of nanomaterials Nano-SiO2

2.

Nano-SiO2

3.

Nano-SiO2

4.

Nano-TiO2

5.

Nano-Al2O3

6.

Nano-ZrO2

7.

Nano-CaCO3

Added in concrete

8.

Nano-silica

9.

Nano-cement

Added in concrete Added in cement

10.

Nanotubes/ nanofibers

Mixed with cement mortar Added in cement

Added in cement

Necessity Increase in flexural and compressive strength Increase in consistency and reduced setting time and permeability

Reference [4, 5]

Increases the compressive strength, reduced porosity

[8]

Increase in flexural and compressive strength, accelerate the early age hydration Increase in modulus of elasticity

[9, 10]

Increase in compressive strength, reduction in permeability and porosity Increase in flexural strength, impact resistance, sound absorption, and low specific weight Improved workability, high performance, and strength Increase in hardening of concrete as well as higher compressive and tensile strength Increase ductility, durability, and tensile strength

[12]

[6, 7]

[11]

[13, 14]

[15, 16] [17, 18]

[19, 20]

uncertain performance, and health issues [23, 24]. In addition to this, the workers in the site should have basic knowledge to handle the nanoproducts, hazards, and its consequences. Only then the usage of nanomaterials in construction sites will become effective in practice. This chapter is organized as follows. The next section discusses about the environmental effects of nanoparticles. This is followed by the human health effects of nanoparticles, and finally conclusions are drawn.

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Human Health Risk Assessment Using Hazard Identification and Risk Assessment Technique (HIRA) HIRA is a general tool for identifying risk in the workplace which can be used both for the workers and for the environment. This has two main steps such as likelihood rating and severity rating. These scores can be given based on frequency of the hazard and its consequences, and it differs based on the nature of the workplace. There are also some other techniques to assess the risk in the workplace such as job safety analysis (JSA), job hazard analysis (JHA), and chemical health risk assessment (CHRA). JSA and JHA determine the risk qualitatively by separating each task into sub-activities, whereas CHRA determines the risk using various factors such as duration of the exposure, degree of chemical release and absorbed, and magnitude rating. The risk value is calculated using hazard rating and exposure rating [25], but HIRA is different from those techniques as this can calculate the risk likelihood and severity of the hazards. The likelihood rating as shown in Table 3 is defined as the number of frequency for the particular risk in which it can occur until the completion of an activity. Severity rating as shown in Table 4 is defined as the consequences of the hazards, and risk value is the product of both the likelihood and the severity ratings. Then the risk range as shown in Table 5 is given according to the risk matrix (i.e., as the likelihood level is 5 and the severity level is 5, then the risk matrix will be 5 x 5), and it is categorized accordingly. Table 3 Likelihood rating [26] S. no 1. 2. 3. 4. 5.

Likelihood Almost certain Frequent Conceivable Remote Inconceivable

Description Repeating occurrence Common occurrence Possible to occur Isn’t expected to happen under normal circumstances Not likely to happen

Level 5 4 3 2 1

Table 4 Severity rating [27] S. No 1. 2. 3. 4. 5.

Severity Serious Major Moderate Minor Negligible

Table 5 Risk category [28]

Description Fatality Multiple injuries, occupational cancer Burns, lacerations, dermatitis Temporary uneasiness, irritation Unlikely to cause harm S. No 1. 2. 3. 4.

Risk Range 1–5 5–10 10–15 15–25

Level 5 4 3 2 1 Risk Category Low (L) Medium (M) High (H) Extreme (E)

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The activities in the construction site are chosen based on the usage of nanomaterials to quantify the risk as mentioned in Table 5. The hazards and its consequences for each activity are then listed correspondingly. As per the likelihood and severity ratings, the risk value is calculated. As per the risk assessment from Table 6, it can be known that there is now low risk of any of the construction activities. It indicates that handling and working with nanoproducts has higher risk both in terms of acute and chronic diseases. The use of nanoproducts in construction site cannot be restricted, but if safe handling procedures are followed, then the exposure of nanoproducts and its severity can be reduced. Some of the other methods which are used to assess the risk of nanomaterials are as follows. The impacts of nanoproducts in construction sites were analyzed with respect to children in Thailand. It is identified that respiratory problem and skin irritation were the two major consequences of the nanoproducts. Multinomial and binary logistic regression is used for data analysis in both the cases [30]. The multicriteria decision analyses (MCDA) which are used in risk assessment are multiattribute utility theory (MAUT), analytical hierarchy process (AHP), and outranking. These are the optimization methods in which the identified risk can be ranked according to the expert score and are also known as the decision-making tools. MCDA techniques incorporate stakeholders and decision-makers in policy decision and superior management [31]. The process involved in environmental risk assessment is problem definition, identifying the criteria to compare the alternatives, relative importance, and determining the performance of the alternatives. Furthermore the cyclic steps involved in management are to develop the management plan, implement the strategy, and periodic monitoring and data analysis [32].

Basic Mitigation Measures for the Workers There are different safety measures that have to be followed by the workers by considering the place and type of nanomaterials they are working with. Ingestion, injection, inhalation, dermal, and ocular are some of the types of exposure of nanomaterials. To mitigate the exposure rate, the following points should be considered. In order to avoid dermal exposure, the workers should wear proper hand gloves and coverall while handling nanoparticles in the site. To avoid ingestion of nanoparticles, the workers should not eat or drink in the workplace or after the sudden completion of work, i.e., they are advised to eat after properly washing their hands and face with suitable solutions. To avoid inhaling the nanoparticles, workers should wear respiratory air filters of size N 100 or N95 to avoid lung diseases. To avoid injection personal protective equipments must be used by the workers. To avoid ocular exposure, safety goggles and respirators are mandatory [33].

Cement sack handling Cement paste mixing Mixing of concrete Concreting

2.

Drilling

Steel cutting

Wood cutting

Polishing Painting

Spraying

6.

7.

8.

9. 10.

11.

5.

4.

3.

Activity Excavation

S. no 1.

Agglomerate particles Fine pure matrix materials, liquid aerosol droplets Liquid aerosol droplets

Fine, ultrafine nanoparticles, airborne nanoparticles Fine, ultrafine nanoparticles, airborne nanoparticles Fine, airborne nanoparticles

Particulate matter such as dust and liquid droplets Nano-TiO2, nano-CaCO3, liquid droplets

Nano-SiO2

Hazards Particulate matter such as dust, smoke, and liquid droplets Crystalline silica

Table 6 Human health risk assessment [29]

Nausea, damages to the liver

First- or second-degree burns Lacerations, respiratory problems Silicosis Neurological problems

Chemical burns, lung cancer Asthma, deafness

3

4 4

3

3

3

4

4

3

Fibrotic lung disease Chemical burns, silicosis

4

Likelihood 4

Rashes, eye irritation

Consequence Respiratory problems

4

3 4

3

3

3

4

4

3

2

Severity 4

12

12 16

9

9

9

16

16

9

8

Risk value 20

H

H E

M

M

M

E

E

M

M

Risk category E

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Control Strategies A plan of controls that is designed to achieve the overall objective is known as strategic controls. The different categories of controls in chronological order are as shown in Fig.1. Engineering controls are those which include how to eliminate the hazard from the nanomaterials or how to use an alternative for the same materials. The hierarchy of control indicates that engineering controls must be given top priority and PPE must be given least priority. Substitution is a tough process which requires a lot of experimentation and research for identifying a new material. For instance, local exhaust ventilation system (LEVS) is a suitable engineering control for the workers working in airborne nanomaterials. Furthermore if the hazards cannot be mitigated with the engineering controls then the engineers/managers will prefer for the second hierarchy of control. Administrative controls are preferred when the suggested engineering controls are not much effective. Housekeeping, personal hygiene, reduction in work period, and job rotation are some of the examples of administrative controls. Personal protective equipments (PPE) are those in which the worker is asked to use it every time

Fig. 1 Control strategies

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while handling the nanomaterials to reduce its penetration or exposure. There are different types of PPE’s that can be used which are goggles, respirators, coverall, and hand gloves. PPEs are made of high-density polyethylene textile which is suggested as the most effective material to resist in nanoparticles in human body. Waste must be disposed away from the work site on daily basis, and while handling the waste, several safety precautions has to be taken as same as handling the raw materials [34].

Green Alternatives There are several alternatives to mitigate the severity of nanomaterials for the workers and environment. Green alternatives are those which focus to control the impacts from the manufacturing, usage, and disposal of nanomaterials. The key concepts which are considered in green alternatives are design, usage, and minimization/maximization. For instance, in designing the overall process, there must be significant contribution for safer chemicals, process involved in chemical synthesis, and type of degradation system after use. The materials which are used must be safer solvents and renewable. Also it should minimize the waste and potential health hazards in the workplace [35].

Environmental Hazards of Nanomaterials Environmental risk assessment (ERA) has become a key role in assessing the environmental hazards due to increase in engineered nanoparticles in construction materials. The increased usage of nanoparticles releases sufficient potential risk to the environment in various forms. Due to scarce data and hazard identification techniques, it is difficult to quantify the risk of nanomaterials in construction sites. ERA consists of assessment of hazard, exposure, and risk characterization in which each of these assessment techniques adopts different tools. In order to assess the exposure of nanomaterials, SimpleBox4nano (SB4N) model, for hazard assessment probabilistic species sensitivity distribution (pSSD) model, is used [36]. Due to the unique properties of nanoparticles such as tiny in size, high surface volume, the severity and the toxicity to the environment is relatively high. The demand of nanoparticles in construction materials is increasing for several purposes along with the impacts to the environment. The toxicity effects of the nanoparticles are high, but it is difficult to access as their reactivity is high along with uniqueness in chemical properties and insolubility [37].

Assessment of Nanoparticles in Air The impact of nanoparticles in air is determined by three major factors such as the time taken by the particles to remain airborne, the contact with other particles in the atmosphere, and distance for which the particles can able to travel. There are five

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different process which helps to identify the aspects of nanoparticles in atmosphere such as gravitational settling, agglomeration, diffusion, and wet and dry deposition. In general, it is known that the particles of less than 100 nm have reduced residence time when compared to particles which are greater than 100 nm [38].

Assessment of Nanoparticles in Water The risk of nanoparticles in water can be determined by several factors such as reactivity, solubility, and interaction of the particles with the biological process. As the particles have low mass, the settling time is too high when compared with other particles. These can be removed when the water sample undergoes biotic and abiotic degradation. In order to remove or change the chemical properties of the nanoparticles, the surface area is exposed to the sunlight. Due to the exposure to sunlight, photoreactions may take place which help in changing the properties of the materials [39].

Assessment of Nanoparticles in Soil The performance of nanomaterials in soil generally varies due to the physical and chemical properties of the materials. Nanomaterials which sorb to the soil become immobile, whereas the other material which doesn’t sorb to the soil has higher mobility. The sorption strength of the nanomaterials is subjective to surface characteristics, composition, and size of the particles. The mobility of the soil depends on the properties of the soil such as grain size and porosity [40].

Life Cycle Risk Assessment Life cycle risk assessment (LCRA) is one of the screening techniques in which the risk of nanomaterials throughout its life cycle can be quantified. The following are the steps which is used for LCRA: (a) The life cycle of the product or material has to be described. It includes how the material has replaced the existing materials and its advantages. The life cycle of any product has four different stages such as introduction, growth, maturity, and decline. Each stage has its own importance about the product. (b) The type of material used for the product and its hazards must be identified in each cycle of the product. (c) Qualitative exposure assessment of the material should be done by estimating the duration and frequency of the particular hazard. (d) The possible stages in which exposure may occur have to be identified. (e) With the exposure assessment, the impacts to human and environment have to be evaluated.

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(f) High-risk zones in each life cycle have to be analyzed. (g) Engineering controls/mitigation measures should be implemented to make the risk zones as low as reasonably practical. (h) Assessing the implemented mitigation measures and its efficiency. These steps are repeated until the risk level in each stage becomes low. If the process becomes new and some additional materials are added for the product, then LCRA has to be done. In some cases, if the control strategies are modified or changed, then its efficiency can be checked with respect to the category of risk [41, 42].

Conclusion (a) This chapter discusses about the environmental and occupational health hazards of nanomaterials in construction sites. (b) As infrastructure development in India is high due to smart cities and extension of highways and airports, the need for nanomaterials in construction is also high, but the workers have to follow certain safety steps to avoid its exposure. (c) Health risk assessment of nanomaterials used in construction site is tabulated with the likelihood and severity ratings of the hazards in the site. (d) Suitable mitigation measures, green alternatives, and control strategies have been suggested to reduce the risk level to as low as reasonably practical. (e) Environmental hazards of nanomaterials and its assessment of various environmental factors are briefed to get insight of impacts of nanomaterials. (f) In addition to this, regular safety meetings and toolbox talk must be conducted to create awareness among the workers.

Important Websites 1. www.ckmnt.com 2. https://theconstructor.org/building/nanomaterials-in-construction-applications/ 5638/ 3. https://www.nano.gov/you/nanotechnology-benefits

References 1. Khandve P (2014) Nanotechnology for building material. Int J Basic Appl Res 4:146–151 2. Khitab A, Tausif Arshad M (2014) Nano construction materials. Rev Adv Mater Sci 38(2) 3. Mukhopadhyay AK (2011) Next-generation nano-based concrete construction products: a review. In: Nanotechnology in civil infrastructure. Springer, Berlin/Heidelberg, pp 207–223 4. Li H, Xiao HG, Ou JP (2004) A study on mechanical and pressure-sensitive properties of cement mortar with nanophase materials. Cem Concr Res 34(3):435–438 5. Li H, Xiao HG, Ou JP (2004) A study on mechanical and pressure-sensitive properties of cement mortar with nanophase materials. Cem Concr Res 34(3):435–438

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6. Qing Y, Zenan Z, Deyu K, Rongshen C (2007) Influence of nano-SiO2 addition on properties of hardened cement paste as compared with silica fume. Constr Build Mater 21(3):539–545 7. Cardenas HE, Struble LJ (2006) Electrokinetic nanoparticle treatment of hardened cement paste for reduction of permeability. J Mater Civ Eng 18(4):554–560 8. Feng Q, Liang CD, Liu GM (2004) Experimental study on cement-based composites with nanoSiO 2. Cailiao Kexue yu Gongcheng. Mater Sci Eng (China) 22:224–227 9. Jayapalan AR, Lee BY, Fredrich SM, Kurtis KE (2010) Influence of additions of anatase TiO2 nanoparticles on early-age properties of cement-based materials. Transp Res Rec 2141(1):41–46 10. Li H, Zhang MH, Ou JP (2007) Flexural fatigue performance of concrete containing nanoparticles for pavement. Int J Fatigue 29(7):1292–1301 11. Li Z, Wang H, He S, Lu Y, Wang M (2006) Investigations on the preparation and mechanical properties of the nano-alumina reinforced cement composite. Mater Lett 60(3):356–359 12. Fan JJ, Tang JY, Cong LQ, Mcolm IJ (2004) Influence of synthetic nano-ZrO2 powder on the strength property of Portland cement. Jianzhu Cailiao Xuebao 7(4):462–467 13. Cervellati G, Rosa R (2006) Use of calcium carbonate particles with high surface area in production of plaster, cement, mortar and concrete. PCT Int Appl WO, 2006134080, 40 14. Sato T, Diallo F (2010) Seeding effect of nano-CaCO3 on the hydration of tricalcium silicate. Transp Res Rec 2141(1):61–67 15. Bigley C, Greenwood P (2003) Using silica to control bleed and segregation in self-compacting concrete. Concrete (London) 37(2):43–45 16. Hussain CM (ed) (2018) Handbook of nanomaterials for industrial applications. Elsevier 17. Dham M, Rushing TS, Helferich R, Marth T, Sengupta S, Revur R et al (2010) Enhancement of reactive powder concrete via nano cement integration. Transp Res Rec 2142(1):18–24 18. Hussain CM, Mishra AK (2018) Nanotechnology in environmental science, 2 vols (vol 1). Wiley 19. Li GY, Wang PM, Zhao X (2005) Mechanical behavior and microstructure of cement composites incorporating surface-treated multi-walled carbon nanotubes. Carbon 43(6):1239–1245 20. Hussain CM (ed) (2020) The ELSI handbook of nanotechnology: risk, safety, ELSI and commercialization. Wiley 21. Oliveira ML, Izquierdo M, Querol X, Lieberman RN, Saikia BK, Silva LF (2019) Nanoparticles from construction wastes: a problem to health and the environment. J Clean Prod 219:236–243 22. Hussain CM (ed) (2020) Handbook of functionalized nanomaterials for industrial applications. Elsevier 23. Palit S, Hussain CM (2020) Modern manufacturing and nanomaterial perspective. In: Handbook of nanomaterials for manufacturing applications. Elsevier, pp 3–20 24. Palit S, Hussain CM (2018) Engineered nanomaterial for industrial use. In: Handbook of nanomaterials for industrial applications. Elsevier, pp 3–12 25. Hincapié I, Caballero-Guzman A, Hiltbrunner D, Nowack B (2015) Use of engineered nanomaterials in the construction industry with specific emphasis on paints and their flows in construction and demolition waste in Switzerland. Waste Manag 43:398–406 26. Husin SNH, Mohamad AB, Abdullah SRS, Anuar N (2012) Chemical health risk assessment at the chemical and biochemical engineering laboratory. Procedia Soc Behav Sci 60:300–307 27. Saedi AM, Thambirajah JJ, Pariatamby A (2014) A HIRARC model for safety and risk evaluation at a hydroelectric power generation plant. Saf Sci 70:308–315 28. Pramoth R, Sudha S, Kalaiselvam S (2020) Resilience-based integrated process system Hazard analysis (RIPSHA) approach: application to a chemical storage area in an edible oil refinery. Process Saf Environ Prot 141:246–258 29. Al-Anbari S, Khalina A, Alnuaimi A, Normariah A, Yahya A (2015) Risk assessment of safety and health (RASH) for building construction. Process Saf Environ Prot 94:149–158 30. Díaz-Soler BM, Martínez-Aires MD, López-Alonso M (2019) Potential risks posed by the use of nano-enabled construction products: a perspective from coordinators for safety and health matters. J Clean Prod 220:33–44 31. Musikaphan W, Kitisriworaphan T (2009) Possible impacts of nanoparticles on children of Thai construction industry. In: Nanotechnology in construction 3. Springer, Berlin, Heidelberg, pp 329–336

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32. Linkov I, Satterstrom FK, Steevens J, Ferguson E, Pleus RC (2007) Multi-criteria decision analysis and environmental risk assessment for nanomaterials. J Nanopart Res 9(4):543–554 33. Linkov I, Satterstrom FK, Kiker G, Batchelor C, Bridges T, Ferguson E (2006) From comparative risk assessment to multi-criteria decision analysis and adaptive management: recent developments and applications. Environ Int 32(8):1072–1093 34. Guidelines and Best Practices for Safe Handling of Nanomaterials in Research Laboratories and Industries (2012). Centre for knowledge management of nanoscience and technology, India 35. Amoabediny GH, Naderi A, Malakootikhah J, Koohi MK, Mortazavi SA, Naderi M, Rashedi H (2009, May) Guidelines for safe handling, use and disposal of nanoparticles. In: Journal of physics: conference series (vol 170, no. 1, pp 1–12). IOP Publishing 36. Dhingra R, Naidu S, Upreti G, Sawhney R (2010) Sustainable nanotechnology: through green methods and life-cycle thinking. Sustainability 2(10):3323–3338 37. Jacobs R, Meesters JA, ter Braak CJ, van de Meent D, van der Voet H (2016) Combining exposure and effect modeling into an integrated probabilistic environmental risk assessment for nanoparticles. Environ Toxicol Chem 35(12):2958–2967 38. Kabir E, Kumar V, Kim KH, Yip AC, Sohn JR (2018) Environmental impacts of nanomaterials. J Environ Manag 225:261–271 39. Aitken RJ, Hankin SM, Ross B, Tran CL, Stone V, Fernandes TF et al (2009) EMERGNANO: a review of completed and near completed environment, health and safety research on nanomaterials and nanotechnology Defra Project CB0409. Institute of Occupational Medicine Report TM/09/01 40. Colvin VL (2003) The potential environmental impact of engineered nanomaterials. Nat Biotechnol 21(10):1166–1170 41. Hristozov D, Malsch I (2009) Hazards and risks of engineered nanoparticles for the environment and human health. Sustainability 1(4):1161–1194 42. Romero-Franco M, Godwin HA, Bilal M, Cohen Y (2017) Needs and challenges for assessing the environmental impacts of engineered nanomaterials (ENMs). Beilstein J Nanotechnol 8(1): 989–1014

Consumer Nanoproducts for Environment

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Anika Tasnim Chowdhury, Nazifa Rafa, Ahmedul Kabir, and Paulraj Mosae Selvakumar

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Environmental Benefits from Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Green Nanotechnology in Energy Generation and Conservation . . . . . . . . . Application of Green Nanotechnology in Water Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Green Nanotechnology in Environmental Remediation: Nano-remediation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Nanotechnology in Sensing and Monitoring: Nanocontact Sensors . . . . . . Application of Green Nanotechnology in Manufacturing, Waste Reduction, and Pollution Prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Green Nanotechnology: An Unexplored Horizon . . . . . . . . . . . . . . . . . . . . . . . . . Environmental Harms Caused by Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotoxicology: The Emerging Challenges and Call for Safer Nanomaterial Design . . . Threats Posed by Nanoproducts to the Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nano Waste Management: Challenges Posed by Nanoparticles and Recommended Waste Disposal Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Useful Websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1170 1173 1174 1178 1179 1181 1182 1184 1184 1185 1187 1190 1193 1195 1196

Abstract

Nanotechnology is the study and application of nanoparticles in all fields of science, engineering, and technology, and is one of the fastest-growing branches of technology that takes advantage of the physicochemical benefits that arise from the manipulation of matter at the atomic scale. Consumer nanoproducts have the potential to revolutionize the lifestyles leading in the contemporary world. However, the relation between nanotechnology and the environment has proved to be interesting, yet controversial. This chapter presents the numerous benefits that nanoproducts offer to the environment, as well as the risks that they pose. Green A. T. Chowdhury · N. Rafa · A. Kabir · P. M. Selvakumar (*) Science and Math Program, Asian University for Women, Chittagong, Bangladesh e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_67

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nanotechnology is a subset of green chemistry that mandates the use of safer solvents and reaction conditions and avoids dependence on processes that may produce pollutants. Through green nanotechnology, several far-reaching applications are possible in the sectors of energy generation and conservation, water treatment, environmental sensing, monitoring, and remediation, and waste management. As the field is currently still in the nascent phase, many applications still remain unexplored and the full potential of nanoproducts remains untapped. However, nanoproducts also have the potential to cause great damages to human health and the environment, if not managed well. Therefore, proper safety measures and disposal procedures after appropriate risk assessments are necessary for handling nano waste and need to be urgently incorporated in nations’ policies and legislations. Moreover, awareness and knowledge sharing regarding the benefits and challenges of nanoproducts need to be encouraged between all relevant stakeholders, including the end-users. Keywords

Consumer nanoproducts · Green nanotechnology · Nano-remediation · Nanotoxicology · Nano waste

Introduction Throughout history, scientific discoveries and technological advancements have significantly changed the world by improving our living standards and making our lives easier. However, most inventions are double-edged swords – several of the negative consequences of such technologies are unprecedented and/or evade the attention of the scientific community. For example, with the creation of steam engines, while the world reached a milestone called the industrial revolution, human activities have contributed to the total atmospheric concentration of the greenhouse gas carbon dioxide. Other such examples include chlorofluorocarbons (CFCs), polychlorinated biphenyls, asbestos, and DDTs. Because of human inventions and interventions, the world has been constantly changing; notably, the environment has been deteriorating due to pollution; depletion of resources like air, water, and soil; extinction of wildlife; and destruction of ecosystems. Therefore, significant adjustments need to bring in the behavior of human production and consumption to ensure environmental sustainability. One promising approach to making changes in our lifestyles can be via the use of nanoproducts. The era of nanotechnology, often dubbed as the second industrial revolution, is a fast-emerging branch of technology that exploits the physicochemical benefits that arise from the manipulation of matter at the atomic scale. Nanotechnology is the study and application of nanoparticles in all fields of science, engineering, and technology. More often, nanotechnology is identified as the field of study where phenomena and materials are manipulated at a scale of under 10 nanometers. The European Commission adopted the definition of a nanomaterial in 2011 to be a

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natural, incidental, or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm–100 nm [1]. The size of nanomaterial is usually smaller than bacterial cells but bigger than most molecules. Elements such as metals, groups of compounds such as metal oxides, form groups to build the nanomaterial that takes various shapes and structures like a soccer ball, branching, and interminable combinations of these structures. Besides, nanoparticles also are known to be in the regular and geometric crystal structures, or sometimes irregular. Nanoparticles can be classified into three major groups: natural, incidental, and engineered. The nanoparticles existing in our environments such as ocean spray, volcanic ash, magnetotactic bacteria, mineral composites, and other naturally occurring nanomaterials fall into the first class of nanoparticles. The second group of nanoparticles is known as incidental nanoparticles or waste particles, which are produced through some industrial processes. Engineered nanoparticles – the third category of nanoparticles – are the ones associated with nanotechnology. This group of nanoparticles is further subclassified by the type of basic material and its use, such as metals, semiconductors, metal oxides, nano clays, nanotubules, and quantum dots. The shapes, sizes, and surface coatings of each category are responsible to determine the structure and function of these molecules, giving rise to a specialized function [2]. Such specialized features of nanoparticles have allowed them to demonstrate industrial applications such as increased sensitivity, magnifying precision and improving production limits [3]. Functionalized nanoparticles, commonly known as a type of engineered nanoparticles, have also been discovered to have useful chemical, physical, and mechanical properties that could possibly outperform their regular counterparts. These particles are more likely to produce cheaper and effective consumer products and are mainly used in the development and innovation of various industrial processes. However, functionalized nanoparticles are still in their early stage in most industrial settings, and their adverse effects on human health and environment are yet to be explored if used inappropriately [4]. Thus, engineered nanoparticles have led nanotechnology to successfully penetrate the various sectors of the world economy due to its structural and functional diversity. This implies that due to the rapid evolution of nanoscience and nanotechnology in the past 20 years, the key to many technological innovations is dominated by this branch of science and technology in the twenty-first century. Currently, nanotechnology’s endeavors range from producing unique or upgraded materials, optimizing the fabrication processes, and removing hindrances from the agenda of sustainable development. Its application in the real world is diverse, ranging from its use in drug delivery, as antimicrobials, carbon-based nanomaterials for technology, electrical and electrical components, nanoparticle-reinforced high-performance composite materials, self-cleaning surfaces, and so on. Nanomaterials and polymer nanocomposites have shown significant potential in enhancing some current manufacturing techniques that give rise to the production of more sustainable products. However, the common challenges such as the lack of information, the probable adverse impacts on the environment, human health, safety and sustainability, and economical and legal aspects need to be addressed accordingly [5, 6]. Besides, the application of nanomaterials is also thought to have a promising aspect in environmental protection,

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especially in environmental sustainability. Global water challenges related to clean drinking water are an issue presenting immense distress in this era of scientific vision. One of them is the scientific challenge associated with groundwater remediation, requiring immediate attention. To address this challenge, nanoparticle with their huge potential is opening the way for a broader vision and newer realm in the field of environmental engineering [7]. There are many other applications and market trends in nanotechnologies than those already mentioned, particularly in addressing environmental and climate protection goals. Consumer nanoproducts have the potential to act as tools to mediate the environment. As movements for the environment become popular, nanoproducts can allow consumers to bypass lifestyles that further pollute the environment. However, the future implications of nanotechnology are controversial among scientists. Some groups highlight the fact that applications of nanotechnology are widespread in areas like nanomedicine, nanoelectronics, biomaterials energy production, and consumer products. Others express their concerns on nanotechnology-related toxicity and environmental impact of the nanomaterials, followed by their potential effects on global economics [8]. These concerns have led to disputes in the scientific community as well as among advocacy groups and governments on whether regulation of nanotechnology should be considered as authorized. The relation between nanotechnology and the environment has proved to be interesting, yet controversial. In the energy sector, nanomaterials intervene at a number of stages of the energy flow starting from the primary energy sources and finishing at the end user [9]. Nanotechnology is visioned to transform the way society develops, uses, and disperses materials by recovering and recycling valuable resources in the process of transportation of people and goods, the supply of food, availability of clean water, etc. For the past 30 years, technology responsible for the sustainability of materials has become of great interest as it is an integral subject that addresses environmental quality. Scientists and engineers have shown significant attention toward the generation of cleaner energy by using catalysts in chemical processes that prevent the production of unwanted by-products or by upgrading the quality of effluent and exhaust fumes from vehicles. But, engineers or designers of such technology do not always consider the material functionality of the product. For example, to design a battery-powered vehicle which is considered as a “greener” vehicle, a large amount of toxic and hazardous materials are required, considering it as a cleaner choice in comparison with other gasoline-powered vehicles. However, the use of all the toxic materials in supporting this technology needs to be considered when the assessment of environmental benefit is done. This calls for a joint collaboration of scientists from different disciplines to communicate and take part in balanced basic research. The basic research supporting the development and sustainability of nanotechnology should include some fundamental conditions such as knowledge development related to structure and function at nanoscale; developing a new material that can be modified to experience multifunctioning; method of optimizing the stability control at all possible scales and conditions during use, synthesis, assembly, and processing at all scale; and finally designing research tools that facilitate its operation across multiple length scales [10].

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This chapter provides insights into how nanoproducts can be used for the benefit of the environment. It primarily looks into eco-friendly and sustainable methods of generating electricity, increasing the efficiency of devices, remediation of the environment, and pollution and waste management through the employment of nanoproducts. It also later presents the rebuttal against the proponents of using nanotechnology for the environment by highlighting the potential risks and harms of nanoparticles to the environment. Attempts have also been made to draw up recommendations from existing sources as a way to ensure that the advantages of nanotechnology can be exploited for the environment by minimizing the potential environmental degradation brought about by nanoproducts.

Environmental Benefits from Nanoproducts As mentioned above, the utilization of nanoproducts for the environment can lead to several unprecedented harms. Many of these will be discussed in the next section. Primarily, concerns may arise in the processes of production of nanoparticles as procedures may involve the use of a large number of toxic chemicals and extreme environments, as well as the emission of a huge amount of toxic by-products. In fact, most nanoproducts are made from chemical processes that may generate pollutants, waste energy, or waste materials that are harmful or toxic and therefore require wellplanned and expensive disposal methods. However, this risk can be avoided through the integration of the principles of green chemistry and green engineering to make nanoparticles using what is known as green nanotechnology [11]. Green chemistry mandates the use of safer solvents and reaction conditions and avoidance of dependence on processes that may produce pollutants. For example, instead of using synthetic inorganic chemicals to synthesize nanoproducts, biological sources such as phytochemicals can be used to create safe and eco-friendly metal nanoparticles [12]. On the other hand, green engineering dictates a more sustainable form of design, commercialization, and the use of products that minimize pollution as much as possible to reduce the potential risks to human health and the environment, in a way that does not entail trade-offs with economic viability and efficiency. As a result, the environmentally detrimental origin of nanoparticles can be avoided if the production of nanoparticles involved an environmental sustainability agenda. Green nanotechnology, therefore, arises from marrying these two disciplines. This recently emerged subdiscipline of green nanotechnology, which refers to the use of nanotechnology to manage the potential environmental, health, and safety costs of human activities that can arise from both the production and consumption of goods or services, can be employed to ensure not only an eco-friendly source for these nanoproducts but also to promote eco-friendly uses and ends for the nanoproducts. Green nanotechnology, particularly focused on phytoformulation methods of creation, significantly contributes to environmental sustainability due to their abundances and possession of a broad variability of metabolites, such as vitamins, antioxidants, and nucleotides. Many commonly used nanoparticles, such as gold, copper, copper oxide, titanium dioxide, and zinc oxide, have already been synthesized from plant extracts [13].

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It is worth noting that most of the nanomaterials are made from abundant elements like carbon in diamond or diamondoid form. Products made of such materials will be strong and will require smaller amounts of materials. Other than plants, many microorganisms have also been reported to biosynthesize gold and silver nanoparticles by reducing metal salts to nanoparticles using their NADPH-dependent reductase enzymes through electron shuttle enzymatic metal reduction processes [14]. These nanoparticles are sensitive to pollutants and are thus often used in environmental monitoring systems. Such biophysical abilities of microbes allow the manufacture of nanoparticles cost-effectively and at larger scales. Green nanotechnology has two goals: (i) The first involves the creation of nanoproducts to address environmental problems through the prevention of harm from known pollutant or through the addition of nanoproducts into environmental technologies to clean up polluted environments, and (ii) the second requires for the production of nanoproducts and materials that can minimize the harms of anthropogenic activities to the human health or the environment [11]. As the subdiscipline of green technology specifically aims for environmental protection and conservation and steers the whole discipline of nanotechnology away from causing, sometimes unanticipated, damages to the environment by completely focusing on benefiting the environment, this chapter henceforth dubs the application of nanotechnology for the improvement of the environment as green nanotechnology. To name some benefits, green nanotechnology can considerably contribute to renewable energy generation, thermal insulation, and energy storage and act as sustainable raw materials for manufacturing processes of inorganic products, building materials, and other industrial production processes. Many of these uses of nanoparticles are important for environmental conservation and are thus explored in detail in the coming subsections.

Application of Green Nanotechnology in Energy Generation and Conservation Climate change is slowly occupying an integral part of the concerns of policymakers. Scientists and leaders alike are looking to curb its perpetrator, anthropogenic greenhouse gas emissions. However, reducing greenhouse gas emissions is much more complex, and it needs to be accompanied by reduced demand for high carbon energy sources and increased efficiency of low carbon ones. Nevertheless, as the energy demand continues to expand in the world with the growing population, particularly in developing nations, so does the need for efficient and sustainable technologies for generating and storing energy. Nanotechnology is the field of science that has been and can be used to meet the growing need for energy. Many scientists and engineers today are exploring the prospects of using nanoparticles to increase energy efficiency and renewable energy generation at competitive costs because of the inherent properties of the nanoparticles such as shape, size, crystallinity, and surface which provides advantages like high surface area, well-defined structure, high dispersibility, and high reactivity. In fact, the employment of nanotechnology in fuel cells, solar cells, thermoelectric devices, and improved batteries has become notable in recent years.

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As an optimistic view expects that nanotechnology will gradually occupy a significant role in energy production, the world’s average carbon footprint would reduce, thereby halting and decelerating climate change and its disastrous impacts. The process of designing and creating devices on the nanoscale, also known as nanofabrication, is creating opportunities for new and greener ways to capture, store, and transfer energy. Development and precision in nanofabrication are crucial in solving the world’s current energy crisis [15]. The kinds of nanomaterials used in regards to innovation in the energy sector are often either one dimensional or two dimensional. One-dimensional nanomaterials increase energy density, safety, charge storage (through double layering), and the cycling life of energy storage systems [16, 17]. The use of one-dimensional nanoparticles can mainly be observed in battery electrodes and supercapacitors. On the other hand, two-dimensional nanomaterials draw their strengths from being able to ensure great precision in control and can be engineered into porous structures by applying facile charge and mass transport, which can be used for energy storage and catalytic applications [18]. However, there is still not much applicability of two-dimensional nanomaterials on the industrial scale, where their large-scale use is still being investigated. The most widely used particle in nanofabrication technology is graphene, an allotrope of carbon. It exists as a thin sheet of carbon atoms organized in a hexagonal lattice, and it is extolled for its advantages like low weight, chemical inertness, and low price. Graphene has caused a great stir due to the improvements it has brought in the efficiency of batteries, apart from its other uses that draw advantages from its structure. For example, it can be used to modify sulfur in sulfur-carbon composites to encourage a better electrochemical performance – better than pure sulfur itself, which is important for battery design. As a result, graphene’s scope in improving the performance of lithium-sulfur (Li-S) batteries has been the subject of a growing research body in recent years [19–21]. A nanostructure-based Li-S battery composed of graphene/sulfur/carbon nanocomposite with a multilayer structure (G/S/C), in which nanosized sulfur is layered on both sides of chemically reduced graphene sheets and covered with amorphous carbon layers, has been developed that achieves high conductivity and surface protection of sulfur simultaneously [22]. This simple alteration to composites gives rise to excellent charge/discharge performance, thereby revealing promising characteristics as a high-performance cathode material for Li-S batteries. Li-S batteries have been attracting worldwide attention in recent years because it addresses the limitation of lithium-ion batteries, particularly their reduced gravimetric energy density [23]. Lithium-ion batteries are seen as a green replacement to the usual batteries because of their rechargeability and as a result of producing less toxic waste. It also has a higher energy density and voltage capacity and lower self-discharge rate than other rechargeable batteries, which makes for better power efficiency as a single cell has longer charge retention than other battery types. However, currently, it is a less attractive option for manufacturers because it is a far more expensive and low-yielding option to fossil fuels. With the development of efficient Li-S batteries, the predicament of prioritizing environment versus economy can thus be resolved. Placing nanoparticles onto electrodes of batteries can significantly improve the performance of batteries. Another rechargeable battery that

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suffers from low efficiency is the vanadium redox flow battery. However, with the deposition of carbon nanoparticles onto the graphite electrodes of vanadium redox flow batteries, the energy efficiency rose to up to 84.8% at a current density of as high as 100 milliamperes per square centimeters, and the peak power density reached a value of 508 milliwatts per square centimeters [24]. However, depositing nanoparticles onto electrodes can be energy-expensive. An eco-friendly and energyefficient way of depositing metal nanoparticles onto graphite electrodes to make supercapacitors, electrocatalytic materials, and electrochemical energy storage devices was recently found [25]. The major principle that dictates this advantage of energy efficiency, in this case, was graphite’s inherent reducing potential. Apart from graphene, the prospects of cellulose-based nanomaterials in photovoltaic (PV) devices, energy-storing systems, mechanical energy harvesters, and catalyst components are also being studied [26]. Cellulose is the most abundant plant polymer, making it easily available and applicable on a large scale and at low costs. It, therefore, also serves as an eco-friendly alternative and addresses several environmental challenges. A comprehensive list of nanoparticles and their uses is being looked into to revolutionize the energy sector. It is beyond the scope of this chapter to delve into discussions for them. Nanomaterials are one of the major components of solar cells. As mentioned, nanotechnology can be used to significantly improve the efficiency of PV technologies, and it can do so by plasmonic enhancement in dye-sensitized solar cells [27], increasing the amount of light trapped in crystalline silicon [28], improving the current collection in amorphous silicon devices [29], increasing the efficiency of light conversion by utilizing the flexible bandgaps of nanomaterials [30], and controlling the directivity and photon escape probability of photovoltaic devices [31]. For example, designing titanium dioxide in the form of core-shell structured nanomaterial greatly improves the performances of PV cells by capturing light rays beyond the ultraviolet range [32, 33], as these initially used to capture only the ultraviolet light from the solar spectrum due to its wide bandgap [34]. In fact, core-shell structured titanium oxide nanoparticles derive additional advantages from their structures, such as beneficial tunable optical and electrical properties [34]. The thin-film copper-indium-gallium diselenide (CIGS) technology is considered as the most promising PV nanotechnology, as the cells made from this technology exhibit very high conversion efficiency at relatively lower costs, compared to the rest of the nano-PV technologies [14]. Research is also underway to produce nanowires and other nanostructured materials so that solar cells can be made more efficient than conventional planar silicon solar cells [29]. Nanotechnology also has the potential to increase the energy efficiency of thermoelectric structures as it enables for the optimization of optical, optoelectrical, and thermal responses and therefore provides refrigerant free cooling [35]. Nanophotonics, or nano-optics, is the branch of nanotechnology that studies the behavior of light on the nanometer scale and of the interaction of nanometer-scale objects with light. This subdiscipline is greatly enhancing the optical devices. Nanoparticles are also increasingly being used in coatings, composites, and polymeric structures used in windows, roof, and wall coatings, energy storage, insulation, and other components in buildings that are cautious about their energy consumption. The advantages

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of energy-efficient buildings span far beyond the energy savings and the environmental benefits of cool roofs. The discovery of fuel cells, particularly hydrogen fuel cells, had been a great eureka moment for environmentalists because the only by-product they release is water vapor, which means they could significantly reduce pollution and man-made greenhouse gases. However, their use is still met with wariness. One of the biggest challenges for hydrogen fuel cells is that they require catalysts made of noble metals, such as platinum, which tend to be sensitive to corrosion by carbon monoxide and are also expensive to acquire. Methods of storing hydrogen fuel at a feasible cost are still actively being researched, and thus, the fuel cells are yet not feasible enough for commercial scale. However, nanotechnology can be used to design catalysts in a way that the incomplete combustion that produces carbon monoxide is reduced, therefore increasing efficiency [36]. Carbon nanotubes (CNTs) can also serve as tiny, lightweight cylinders to provide solutions to the storage problems pertaining to hydrogen fuel cells [14]. In fact, CNTs can be used for constructing safe, efficient, and high-density adsorbents for hydrogen storage applications for other kinds of fuel cells and batteries in electronic and automobile applications. Several green nanoparticles are being looked into to bring down the cost of photo splitting of water [37]. Lower cost, more efficient fuel cells, and lower cost of production, distribution, and storage of hydrogen fuel can also be established via nanotechnology [38]. Furthermore, nanotechnology has the capacity to shift the world’s energy need to be met almost fully by nuclear energy, natural gas, and biomass with the transition to a new class of renewable energy composed of solar, wind, and wave [38]. For example, windmills with blades made of epoxy-containing CNTs generate greater amounts of electricity. Solar cells, as discussed, can be made cheaper and more efficient when an array of silicon nanowires is embedded in a polymer in its components. Energy is also conserved by nanoelectronics, as they consume less power to operate and have longer lifespans. Thus, nanotechnology can be used as a vehicle that helps the world enter the post-fossil energy age. Nanomaterials can also be used to increase the efficiency of the combustion of fuels and thus reduce energy consumption. The inclusion of carbon nanoparticles has considerably increased the burning rate and ignition delay in jet fuel [39]. In a study, the addition of iron nanoparticles to biodiesel and diesel fuels has also shown to reduce fuel consumption and volumetric emissions of nitrogen oxides by 4–11%, carbon monoxide by 6–12%, and hydrocarbons by 3–6% [40], many of which are toxic and can cause physical ailments or contribute to the increase in the world’s average temperature. However, this area still warrants further research as the utilization of nanomaterial additives can also have toxic by-products. Cerium oxide nanoparticles have proven to increase engine efficiency and decrease emissions of oxides of nitrogen but can also be emitted as toxic exhausts, which can cause lung inflammation and increased bronchial alveolar lavage fluid, according to a study done on rats [41]. Because of the great prospects of nanotechnology in energy generation and conservation, nanotechnology can further direct a future with green transportations. For example, cerium oxide integrated diesel can help reduce consumers’ carbon footprint by producing lower amounts of carbon dioxide [42]. Nanoparticles are

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already being used to increase the fuel efficiency of buses in the UK, which could reduce the emission of up to two to three billion tons of carbon dioxide per year [43]. The manufacture of propylene oxide (used to make brake fluid, as well as detergents, paint, and plastics) can produce polluting by-products, which can be reduced by the use of silver nanoclusters as catalysts [42]. In addition, electric cars, a vehicle that has been increasingly occupying the automotive market, are made of lithium-ion batteries that use nanoparticle-based electrodes [42]. To sum up, nanotechnology can make a difference to five specific areas relating to the energy sector: 1. fuel additives to increase the efficiency of diesel engines, 2. PV technology for solar cells, 3. the hydrogen economy and fuel cells, 4. batteries and supercapacitors for energy storage, and 5. improved insulation for houses and offices [44]. They reduce the overall energy consumption, provide a cheaper and environmentally friendly way of energy generation, create independent power sources separate from national grids, and facilitate the transition from nonrenewable to clean, renewable energy sources [14]. The implications of nanotechnology in the energy sector are therefore incredibly large, and scientists are yet to explore its full prospects.

Application of Green Nanotechnology in Water Treatment Water is an important natural resource, and safe drinking water is vital for human existence and good quality of life. The rise in demand for water for food production, industries, and the growing population has led to a growing scarcity of freshwater in many parts of the world, exacerbated by the impacts of climate change. When the Sustainable Development Goals were established by the United Nations General Assembly in 2015, ensuring clean water and sanitation (Goal 6) became an important goal for many nations that are severely lacking in the two. Surface water and groundwater are being depleted at a rate faster than they can be replenished, exhausting aquifers and the base flows of rivers [45]. As of 2017, about 30% of the world’s people still lack access to safe drinking water [46]. Seven hundred eighty-five million people lack even a basic drinking water source, and at least two billion people use a drinking water source contaminated with feces [46]. Contaminated water can give rise to waterborne diseases in the population, such as diarrhea, cholera, dysentery, typhoid, and polio. In fact, contaminated drinking water is estimated to cause 485,000 diarrheal deaths each year [46]. Consequently, governments, corporations, and communities are occupied with ensuring the future availability and sustainability of water supplies [47]. Green nanotechnology offers a solution to meet the need of the thirsty population by availing safe water from previously unusable resources. It can be used to purify water through desalination as well as membrane technologies or nano-based procedures that kill pathogens and remove toxic chemicals [11]. Currently, a form of nanotechnology that utilizes nanomaterials like nanofiber filters, CNTs, and other nanoparticles is already making up water treatment systems such as reverse osmosis (RO) plants, nano-filtration, and ultrafiltration membranes. For water treatment specifically, dendrimers, zeolites, carbonaceous nanomaterials, and metals composed of

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nanoparticles [48, 49] are being used because their small size provides advantages in contact efficiency and better elution properties due to their greater surface area [50]. Such nanoparticles possess special antimicrobial properties displayed via various mechanisms, like photocatalytic production of reactive oxygen species that react with the cell wall and cell components of microorganisms, or like oligodynamic disinfection, thereby killing or inactivating those [50, 51]. For example, titanium oxide induces photocatalysis to completely inactivate fecal coliforms within 15 min, which are employed in some commercial purification systems [50]. For areas in developing countries which are struggling with arsenic contamination, magnetic nanoparticles can successfully remove arsenic from drinking water for point of use treatment. Iron oxide nanoparticles, notably of size 12 nm, can bind strongly and specifically to arsenic, over 99% of which can be pulled out by magnets [14]. Nano-filtration (NF), a recently discovered membrane filtration process which utilizes nanometer-sized pores that pass through thin filtration membranes primarily created from polymers, is being widely used to remove polyvalent cations and disinfection by-product precursors such as natural and synthetic organic matters from the surface and fresh groundwater and waters that have low total dissolved solids [52]. Initially, NF had been used in water treatment for a procedure known as “water softening,” where nanofilters basically retain scale-forming hydrated divalent ions while passing smaller hydrated monovalent ions to “soften” water [53, 54]. However, NF is now increasingly being used in pharmaceuticals, fine chemicals, and flavor and fragrance industries [53]. Some water treatment systems drawing principles of nanotechnology are already in use and being developed to cover large-scale commercial use. Nanotechnology also offers remediation opportunities for surface water, groundwater, and wastewater that have contaminated with toxic metal ions, microorganisms, and organic and inorganic solutes. It is expected to be far more efficient in treating water containing heavy metals, bacteria, and viruses, attributed to the nanoparticles’ high dissolution, reactivity, and sorption capacities due to their high specific surface area. Many nanomaterials are actively being investigated to be developed into water treatment systems or remediation of contaminated sites because of their unique activity toward recalcitrant [55, 56]. Examples include iron nanomaterial, ferritin, and polymer nanoparticles [49]. The application of nanotechnology to remediate the environment is another subdiscipline called nanoremediation, described below. Currently, water treatment plants are incredibly resource and capital-draining. However, the ability of nanoparticles to effectively remove toxic and harmful pathogens, metals, and other pollutants could mean cheaper water treatment facilities.

Application of Green Nanotechnology in Environmental Remediation: Nano-remediation Human activities are constantly degrading the environment, leading to a loss of sensitive ecosystems and a diverse pool of genes. Pollutants released from industries and households to air and water alter the natural habitats of many wildlife species,

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and like a circular pathway, the negative impacts ricochet back to the human population. Natural systems can self-regulate to some extent, but if the pollutants’ concentrations are above nature’s capacities to withstand and decontaminate by itself, remediation strategies need to be undertaken by humans. Nano-remediation, the use of nanoparticles to remediate the environment, is a growing industry that is increasingly being developed and used in the treatment of groundwater and wastewater, soil, and other contaminated environments [55, 57]. During nanoremediation, which is often conducted in situ, the target contaminants are brought in contact with nanomaterials under conditions where the nanoparticles can undertake detoxification or immobilization. At the moment, the most frequent and widespread commercial application of nano-remediation is in the cleaning up of groundwater. This is done primarily by using zerovalent metals (ZVMs) because ZVMs are widely available and are able to degrade or sequester contaminants, where contaminants are typically converted to harmless products via redox reactions [58]. The fact that nano-remediation allows for in situ treatment saves a lot of resources, time, and money that may have been spent on excavation or pumping groundwater up. As mentioned above, nanomaterials like CNTs and titanium oxide can clean surface water by purifying, disinfecting, and desalinating [49, 59]. Heavy metals and organic solvents can be degraded by combining zerovalent nanoparticles of iron and magnesium with emulsion liquid membranes, where the membranes are used to increase the contact between these catalytic nanoparticles and the targeted pollutants [14]. This allows for areas to tap into their groundwater sources to meet their water needs, without fear of the negative implications of using contaminated water. In the oil industries, molybdenum disulfide nanocrystals are being used to remove harmful sulfur compounds from crude oil [60]. Both single-walled and multi-walled CNTs and gold particles have shown to adsorb pollutants onto their surfaces. CNTs can effectively rid both air and water streams of organic and inorganic pollutants, thanks to their pore structures and the broad spectrum of functional groups that CNTs can possess due to the manipulation of heat or chemicals [49]. Significant improvements have been shown in capturing toxic or harmful pollutants like dioxins, oxides of nitrogen, volatile organic compounds (VOCs), isopropyl alcohol, and even the greenhouse gas, carbon dioxide, using nanotechnology [49]. The use of nanomaterials to remove toxic gases is also being further inquired into [49, 61]. Although catalysts have been used before to clean exhaust fumes released from industries, the use of nanotechnology provides a better method of removing air pollutants because nanoparticles are far more likely to react with harmful pollutants in the air because of their relatively higher surface area. The use of nanotechnology to clean air is crucial in the bustling urban and industrialized cities, where air pollution is significant. Cities in every part of the world have dangerously high levels of air pollution, thus exposing their inhabitants to risks related to pollutants in the air. This is why the reduction of air pollution is an indirect focus of SDG 3, “Ensure healthy lives and promote wellbeing for all at all ages” and SDG 11, “Make cities and human settlements inclusive, safe, resilient, and sustainable.”

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Application of Nanotechnology in Sensing and Monitoring: Nanocontact Sensors Continuous and long-term exposure to such particulate matter can lead to the development of physical problems, such as lung cancer and heart conditions. In urban areas especially, risks associated with exposure to particulate matter are high. Different particulate and pollutant monitoring and sensing devices can significantly reduce the risks to human health and restrain the amount of unsustainable economic activities. Nanoproducts make for sophisticated rapid and precise sensing and monitoring devices that can detect hazardous pollutants, plant pathogens, and related toxins [11], allowing for higher protection of human health and environment. Several nanocontact sensors are able to detect some metal ions or radioactive elements without a required preconcentration. These are incredibly cost-effective and energy-efficient as they are made of conventional microelectronics manufacturing equipment using simple electrochemical techniques [49]. They are also easy to use onsite, making assessment and monitoring of the environment convenient, with continuous information generation [49]. Nanowires or nanotubes can serve as adequate chemical and biological sensors, while cantilever sensors, or devices made of silicon cantilever array coated with nano-coating, display sensitivity to specific pollutants like volatile organic compounds, heavy metals, pesticides, and harmful bacteria such as salmonella [49]. Pollution can be monitored for both air and water. For air, for example, nanocrystalline metal oxide thin films, called solid-state gas sensors (SGSs), can provide information regarding pollutants in the air using very simplified operation at a faster rate with real-time analysis capability, at a higher resolution, and at lower running costs compared to conventional methods [62]. There have been many other advances in nano-based monitoring and detecting technologies [49]: • Carcinogenic substances, such as chromium (VI) and argon (V), can be detected at very low concentrations by functionalized tetraphenylsilole nanoparticles. • Peptide nano-electrodes produce electric current unique to different metal ions, making identification easy. • Some nanotube and copper composite electrodes are able to detect substances such as organophosphorus pesticides, carbohydrates, and other wood pathogenic substances in low concentrations. • Polymer nanospheres can measure organic contaminants that are present in the environment at very low concentrations. Rapid sensing and monitoring of the environment make for rapid and relevant initiatives to reduce the extent of pollution by allowing for the decision to either reduce pollutants released in the environment or take steps to remediate the environment.

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Application of Green Nanotechnology in Manufacturing, Waste Reduction, and Pollution Prevention Manufacturing is critical to a sustainable world economy and is the primary driver of innovation and high-value job creation in both developed and developing countries [63]. However, current practices of manufacturing are incredibly resource-draining and environmentally degrading. Nanotechnology can bridge the grab between today’s methods of manufacturing and sustainability by what is known as green manufacturing. Green manufacturing is a method of conducting manufacturing processes in a way that uses fewer natural resources, recycles and reuses raw and other materials, and reduces pollution, waste generation, and emission. By promoting green manufacturing, advancements have already been made by nanotechnology in the semiconductor, chemical, petrochemical, materials processing, pharmaceutical, and many other industries [64]. In fact, products miniaturized via nanotechnology require less material and are easy to transport because of their lightness, thus saving both energy and time, but also possess better mechanical and other properties. Nanotechnology thus increases resilience and reduces system cost and replacement tendencies and the overall environmental impact. For instance, plastic pollution, one of the most notable and detested kinds of pollution ravaging aquatic lives due to its non-biodegradability, is being tackled by nanotechnology. Biodegradable plastics are being made from polymers with a molecular structure that is easy to decompose by using the tools and techniques of nanotechnology. Manufacturing processes of goods are often accompanied by a wide range of waste products as well. Many countries are unable to exercise proper disposal methods of these waste products, most of which are harmful or toxic, due to their lack of resources, capital, or even awareness. Another issue of the progressing world is leaving heaps of waste in its wake. Countries without proper disposal technology or resources like land are grappling with the issues pertaining to waste disposal. With the advancement of technology and the elevations of peoples’ living standards, there has been a rapid creation of electronic waste every minute. Electronic waste or e-waste is the discarded electrical or electronic devices which are destined for refurbishment, reuse, resale, and recycle through metal recovery or direct disposal. Many informal sectors in developing nations undertake processing of e-waste, which can cause adverse health effects and environmental pollution. One way to reduce waste generated per capita is by increasing the useful life of consumer products. Nanotechnology can be used to minimize raw material usage, waste production, and energy consumption. Because nanotechnology involves atom by atom construction, it is a clean form of technology that is able to create substances without the production of harmful or toxic by-products; any by-products produced can be fed back into the manufacturing processes [14]. One great innovation is the liquid crystalline display (LCD) screens, which are quickly replacing the screen cathode ray tubes (CRTs) in people’s houses. CNTs being used in the liquid crystalline display (LCD) decreases the impact of the e-waste created from such screens due to the elimination of toxic heavy metals and by increasing energy efficiency and performance. Toxic waste generation and energy consumption are also being decreased.

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Nanotechnology can be used to increase the sustainability of products by making them more efficient, reducing e-waste. Since the 2D organic semiconductors created from nanotechnology were found, it caused a huge uproar due to its optical, electronic, optoelectronic, and mechatronic properties. Such nanostructures can be used as highly efficient biosensors due to their high sensitivity to bioanalytes [65]. Most importantly, the structures being biodegradable and nontoxic due to their natural origin allow them to be a better alternative to inorganic materials that give rise to electronic waste. However, the structures require further research and development for the long-term and large-scale application. Nanoproducts have also been investigated for their ability to salvage usable materials from e-waste. A mixture of epoxy resin, phenolic resin, silica, and additives was able to recover valuable elements and materials from e-waste after the e-waste had been mesoporous materials [66]. Thus, nanotechnology advances the sustainability of products, as well as the environment. Green nanotechnology also led to the development of aqueous microemulsions as an alternative to VOCs in cleaning industries [49]. This means that nanoparticles are replacing toxic and carcinogenic VOCs and other chemicals like chloroform, hexane, and perchloroethylene, which are commonly used in the cleaning, textile, and oil extraction industry. Nanosized aggregates on microemulsions increase specificity for molecules. A microemulsion has recently been synthesized that acts as a connector between water-attractive and water-repellent substances, inserted between the head and tail of the surfactant molecules [49]. The resultant surfactant was able to clean oil from textiles and was very competitive with the conventional cleaning compounds. Nanoscientists are also currently working intensively to create eco-friendly coatings for products like electronics and medicine to bypass pollution. For example, alternatives to chrome VI coatings are being studied to prevent the use of toxic or carcinogenic by-products [14]. Nanoengineered thermites, or nano thermites, with tailored properties, are also being developed using the principles of green nanotechnology for use as primers, reactive materials, and propellant initiators in micro thrusters, power generators, micro-shock generators for drug delivery, and microinitiators [14]. Indiscriminate and improper waste disposal can enter the environment in several ways. A concerning category of waste that often experiences underfunding in disposal, particularly in developing countries, is hospital waste, which can cause environmental hazards because of unsafe disposal in open landfills, groundwater contamination by leachate, and the direct release of untreated hospital wastewater to common drainage, public sewerage systems, or rivers and lakes. Improper healthcare waste management might lead to the pollution and contamination of soil, air, and surface water and groundwater [67]. Pharmaceutical drugs, such as antibiotics, can easily enter the environment because of a lack of proper disposal of antibiotics and can lead to the proliferation of multidrug-resistant (MDR) microbes that can cause infections that may not be treatable using existing antibiotics, thereby increasing mortality and morbidity. Nanoparticles provide one of the most promising strategies in overcoming microbial drug resistance. While packaging nanoparticles with antimicrobial agents itself prevent the development of drug resistance, nitric oxide-

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releasing nanoparticles (NO NPs), chitosan-containing nanoparticles (chitosan NPs), and metal-containing nanoparticles all use multiple mechanisms simultaneously to combat microbes, thereby making the development of resistance to these nanoparticles unlikely [68]. Nanoparticles inhibit resistance development by decreasing uptake and increasing the efflux of drugs from the microbial cell, biofilm formation, and intracellular bacteria. In addition, nanoparticles themselves have shown effective antimicrobial activity against MDR pathogens, such as Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Mycobacterium tuberculosis, vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, and others [69], which is an important advancement in the medical sector as more and more individuals are developing resistance to antibiotics and are thus may become untreatable using existing medicines. As observed from the discussion above, the scope of nanotechnology in manufacturing and waste and pollution reduction is so wide and diverse that it is beyond the scope of this chapter to note down every innovative solution that nanotechnology has brought to these issues.

Application of Green Nanotechnology: An Unexplored Horizon The application of nanotechnology to protect, conserve, and remediate the environment is vast and mostly unexplored. Despite such an exhaustive discussion, the prospects of nanotechnology in the water and energy generation, two of the most important sectors for the human civilization, and in pollution reduction, monitoring, and attenuation have barely been broached. As scientists discover many more nanoparticles, more applications will come up, some as groundbreaking solutions to many of the world’s alarming issues. However, the area of green nanotechnology is not without debates or controversies. Many still view this area with scrutiny and its advantages over conventional methods with skepticism and caution. The impact of freely released nanoparticles on human health and the environment is an actively researched area, so much so that a whole subdiscipline called nanotoxicology emerged from it. The following sections deal with the kinds of harms inflicted upon the environment by nanotechnology and its creations.

Environmental Harms Caused by Nanoproducts The principles of green nanotechnology are yet to be accepted and applied on a scale that spans the whole area of nanotechnology. This means that unsustainable practices of nanoparticle synthesis are still taking place, and thus the environmental harm pertaining to nanoparticle manufacturing processes is still occurring widely worldwide. The most common and special property of all nanoparticles is their miniature size, giving rise to applications for which they are deliberately designed to be unique. Nanoparticles own unique physical and chemical properties due to their high surface area and nanoscale size. Their optical properties are also accounted to be reliant on

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the size, transmitting different colors due to absorption in the visible spectrum. The unique size, shape, and structure bring about properties such as reactivity, toughness, and some additional properties [70]. It cannot be denied that the area of nanotechnology has come up with significant developments and far-reaching discoveries during the past decade. Years back, it was foreseen by researchers that by 2020, the widespread application of nanotechnology would conventionally be applied in all aspects of our daily lives. Despite all the optimism and useful application portrayed by nanotechnology, recently it has been also understood that there is limited knowledge of the potential negative effect imposed by nanoproducts on human health and the environment. Although the future of nanotechnology is supported by a bright outlook, there is also the existence of an increasing concern that some types of nanoparticles might lead to serious health consequences and environmental pollution, both intentionally and unintentionally. Environmental protection and safety have not been the primary goal for most commercially available consumer nanoproducts. Neither textiles with nanosilver to remove perspiration odor nor stable golf clubs with carbon nanotubes were designed to reserve the environmental safety. It is often promised by manufacturers about the benefits of a product, typically without providing the relevant evidence and its negative impacts. At times, the reason behind this is manufacturers themselves are not aware of what adverse effects the nanoproducts can undergo. To determine this, examining the entire life cycle of the raw material from production to disposal at the end of the life cycle is highly recommended and should be strictly maintained. The life cycle assessment (LCA) is recommended as a suitable approach in analyzing and evaluating the ecological advantages or sustainable benefits and the environmental impact of a nanoproduct. Environmental impacts enclose all the environmentally relevant factors, such as extracting resources from the environment as well as the emission of waste gases like carbon dioxide [71].

Nanotoxicology: The Emerging Challenges and Call for Safer Nanomaterial Design A new field, known as nanotoxicology, has emerged nationally and internationally to deal with the impacts and potential harms of nanoparticles. It is a subfield of toxicology, concerning the study of the adverse effects of nanomaterials on ecosystems and organisms. Nanotoxicology gives an understanding of the toxic and biological effects of the nanomaterials and deals with completing the existing knowledge on how they interact with the biological systems. In comparison with the bulk matters, the toxicity of some nanosized chemicals has generally emerged from the fact that nanoparticles have a high surface-to-volume ratio which makes them increasingly reactive. Thus, the smaller size of the nanoparticles serves them an advantage, and they are assumed to perforate efficiently through the cellular membranes and tissues. However, numerous biokinetic studies have also demonstrated that biodistribution does not have a major influence on particle size [72, 73]. The fact that the application of engineered nanomaterials is very widespread in recent days,

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being increasingly manufactured and utilized by a wide variety of products, with uncertainties regarding their potential adverse health effects, makes the risk assessment process challenging. Some in vitro, in vivo, and epidemiological studies have demonstrated evidence of adverse effects due to nanotoxicology. However, in many cases, the interpretation of available data was perplexed by the use of very high doses of nanoparticles to understand its adverse effects [74]. Nanoparticles of heavy metals such as lead, mercury, and tin are viewed to be very stable with a slow degradation rate, leading to many environmental toxicities. To predict the toxicity of a particular type of nanoparticle, the most necessary step is to understand which of its property is significantly responsible for promoting its toxicity. Therefore, even before their use, it is important to recognize how nanoparticles interact with the environment and the human body, to understand the cost of the resulting damage. The undetermined structure and chemical compositions of some nanomaterials could be the reason for increased environmental toxicological pollution. For instance, the size, type, charge, etc. are some of the properties of nanomaterials which turn on the toxicity of nanoparticles in the aqueous environment. Among the environmental damage caused by various nanoparticles, the threat to aquatic life and the movement of nanoparticles through the food chain are some of the serious issues. There is a strong interaction between nanoparticles and the soil, and this results in toxic products which are due to the matrix conditions and the nanoparticle properties. Environmental factors such as temperature, humidity, rate of airflow, etc. contribute to the way how nanoparticles influence the environment. The dispersion rate of nanoparticles increases with high temperature, whereas wind speed facilitates the invasion of nanoparticles through human and plant tissues [75]. Yet, the nanotoxicology community has been trying for almost a decade now to address more technical questions through their research since all of what is thought regarding the nanotoxicity of the particles is mostly based on some mere assumptions. More than thousands of research have been published to explore the impact of nanomaterials on the biological system, but reaching a mutual conclusion is what they lack [76]. Meanwhile, some studies have also come up with potential predictions and guidelines in developing sustainable nanoparticles with safer applications. They have predicted how properties like particle size, charge, composition, and anisotropic morphology are associated with the toxicity of the nanoparticle. It has been well hypothesized from the beginning that reduction in particle size is correlated with increased toxicity of the particle. Correlation between ionic dissolution and toxicity index has also been marked to be definite. Anisotropic morphology or nanoparticles with the rod-shaped structure are assumed to be taken up less efficiently by the tissues and other cellular barriers [77]. To conclude, it could be stated that the current research in the field of nanotoxicology is still in the process of understanding the complexity of the nanoparticles and is struggling to keep up with the fundamental processes of how these materials come in contact with the biological systems. Due to very subtle differences in the properties such as slight changes in the size, the function of the nanoparticle shows immense variation. As a result, expanding the use of nanoproducts makes nanotoxicology research extremely important for society to develop safer nanomaterials for the future [78].

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Threats Posed by Nanoproducts to the Environment It is rare to find documented proof stating every “nanoproduct” is environmentally friendly or sustainable by definition. It is often emphasized by environmental organizations that in many cases the advantages promoted by industries are often overestimated and untested. To date, often the production of nanomaterials requires large amounts of energy, water, and not very environmentally friendly chemicals or solvents. CNTs are one of the most energy-intensive materials known to mankind because, at present, 1 kilogram of it is capable of holding 0.1–1 terajoule (TJ) of energy. This is almost equivalent to the energy content of nearly 167 barrels, i.e., 26,550 liters of crude oil [79]. The carbon-based high-tech production of fullerenes, carbon nanotubes, and carbon nanofibers negates any potential benefits served to the environment, like saving fuel using lighter car bodies due to its energy intensiveness, as high energy demand contributes to the mass production of such products, utilizing large amounts of a nanomaterial. Contrarily, for instance, if only small amounts of CNTs are used to produce specialized plastic films, then environmental advantages can be considered [80]. Thus, benefits such as any potential energy savings in using a nanoproduct must be determined by comparing with the energy consumed during its production. However, this should be considered to be done on a case by case basis.

Properties of Nanoparticles and Related Issues Particle size and surface area are the key to the interaction of materials with biological systems. Evidently, it has been understood reducing the size of the materials leads to an exponential increase in surface area relative to volume. Therefore, the reduced size of the nanomaterials makes the nanomaterial surface more reactive on itself and to its contiguous surrounding. So, particle size and surface area control how the system counters, distributes, and eliminates the surrounding materials. Research has established that various biological processes like endocytosis, cellular uptakes, and the particle efficiency in these processes depend on the size of the material [81]. Some researchers have also explored in vitro cytotoxicity of nanoparticles of distinctive size and varying the other possible factors such as various cell types, conditions in the culture media, and exposure times. The in vivo evaluation is far more difficult as it requires a more comprehensive understanding of the complex nature of the biological systems with different in vivo models [82]. In summary, the size-dependent toxicity of nanoparticles is thought to be credited for its ability to invade the biological systems, interacting with the chemical structure of the organic compounds in living cells and finally modifying the structure. This is thought to cause potential hazards to the system where it interferes with critical biological functions. Some other studies have also demonstrated that the miniature size of nanoparticles also dominates its pharmacological behaviors. Nanoparticles with a size less than 50 nm were seen to rapidly pass across the tissues and possibly impart toxic manifestations. Conversely, nanoparticles with a size greater than 50 nm are positively charged in nature and are taken up by the reticuloendothelial system (RES), which interrupts its path to enter the biological cells. Toxicological studies have revealed the smaller size of nanoparticles leads to

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some potential hazards such as causing respiratory health effects. As per some study observation, nanoparticles with size less than 10 nm deposit in the tracheobronchial region of the respiratory tract leading to toxic effects. The oral toxicity of nanoparticles is also influenced by its size. Generally, oral toxicity and size are inversely proportional. The toxicity of the nanoparticle is also reliant on its shape, such as spherical-shaped nanoparticles undergo endocytosis in a quicker and easier manner in contrast to fiber or rod-shaped particles. Most importantly, the spherical nanoparticles were observed to be relatively less toxic in comparison with their counterparts. Nonspherical nanomaterials are more prone to flow through capillaries leading to biological consequences. The surface charge of nanoparticles significantly influences their interactions with biological systems. This property of the nanoparticle strongly dictates how a neighboring cell responds when exposed to it. Research has found that surface charge of nanoparticles is responsible to change blood-brain barrier integrity and transmembrane permeability. Since surface charge greatly influences the interactions of nanoparticles with the biological systems, the researchers have applied various amendments to regulate their surface characteristics to cause less toxicity [81].

Interaction of Nanoproducts with Humans and the Environment: Potential Hazards New technological developments do not always benefit a society; usually, it involves hazards as well. A hazardous material imposes a threat when exposed to humans and/or the environment, and the level of risk served can be minimized by controlling its exposure through understanding the mechanism of the harm. So far there is no convincing epidemiological evidence that nanometer-sized component serves as the toxic component of particulate air; however, a recent study reported to the Government’s Committee on Medical Effects of Air Pollution has proposed that particle count, reflecting the sub-100 nm component, was discovered to be finely related to the risk of a heart attack. An additional approach was also been taken to investigate the correlation between particulate pollution and cardiac consequences, and these studies have indicated interconnection, leading to inflammation and occasional reduction in red blood cell counts [83, 84]. Moreover, an association between exposure to combustion-driven nanoparticles from diesel soot and atherothrombosis was also recognized by a series of studies. The most vulnerable situation to come in contact with the health hazards due to nanoparticles is an unsafe occupational setting. It is possible to get exposed to the nanoparticle at all phases of the material’s life cycle. Therefore, an inflated risk remains due to the undesirable changes in the surrounding atmosphere, meaning both to the environment and indoor and outdoor workers. Construction workers, petroleum and gas transmission pipeline workers, traffic police officers, farmers, and other workers in many other jobs spend their entire work time or a significant amount of the time in outdoor environments. Yet, barely studies have been conducted to assess the potential health impact due to the exposure of such workers to nanoparticles. However, the existing limited research indicates that people with such occupations are highly exposed to nanoparticles and are put at a high risk of adverse

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health effects. The nanoparticles are also likely to invade from an indoor environment into the outdoors in some cases; as an example, the nanoparticles moving through a filtration system can get into the outdoor spaces through ventilation ducts, affecting the people working outside. The unique physical and chemical properties of nanoparticles enable them to enter and get distributed into indoor and outdoor workplaces rapidly. This ultimately ends up causing biochemical damage to the human cells by initiating chemical reactions. The effects of nanoparticles in leading to environmental and occupational health-related issues are often neglected and not as much prioritized as they should be. In recent days, this issue seems to have received little more attention, and many researchers have now shed some light on the significance of how to determine the workers’ levels of exposure by measuring concentrations of various nanoparticles at indoor and outdoor workplaces [85]. Still, large-scale research should be designed to understand the reaction mechanism of these nanoparticles with the biological system, their biodistribution, and the excretion pathway from the body. The growth and survival of plants and animals in both terrestrial and aquatic environments are greatly influenced when exposed to nanoparticles. A study has claimed to observe a slight reduction in the growth of plant roots in the presence of uncoated aluminum oxide nanoparticles, although using alumina with a phenanthrene coat demonstrated no reduction in root growth. This implies that the surface properties of aluminum oxide play a crucial role in giving rise to the entire toxicity [86]. For the nanoparticles to interact with plants’ roots, it needs to get absorbed from the surface of the roots first and then end up entering the cell wall and finally being absorbed into the roots’ cells. Absorption by the cellular membrane is also possible when the nanoparticles enter the intercellular space. The negative charge on the surface of plants’ cells facilitates the entry of other negatively charged nanoparticles into the intercellular space of the roots’ bark. These nanoparticles then land onto the woody tissue of the plant by entering this space [87]. Sometimes, the nanoparticles are observed to interact with other toxic materials or compounds surrounding them, and this results in both an increase and a decrease in their toxic functionality. This phenomenon of nanoparticles is sometimes speculated to be beneficial to plants, animals, and the environment because the toxic effect of the contaminants gets neutralized by its own toxicity. In contrast, if the nanoparticle seems to interact with a pollutant that is not necessarily harmful, it does not show any toxic effects. The presence of nanoparticles could possibly interfere and alter some other environmental processes like the formation of dust clouds and the stratospheric temperature. The particulate matter and carbon nanosized components, generally released from the burning of plastics, fossil fuels, and industrial fumes, make up the brown clouds. These brown clouds may end up depositing on glaciers, enhancing the absorption of sunlight and resulting in melted glaciers. The nanoparticles and hydrogen present in the atmosphere have a tendency of moving up the stratosphere, resulting in excessive water vapor. Thus, the accumulation of excess water vapor in the stratosphere cools the stratosphere, reducing the stratospheric temperature and also depleting the ozone layer [88].

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Finally, to study the environmental impacts of nanoparticles, it is important to understand how they are used in the workplace, which means to what extent they were exposed to environmental factors. Their interaction and how they are separated into different media like water and air, their feasibility to move in each of these media, and stability should be extensively studied. Therefore, to evaluate their risk, general information about the behavior and toxicity is essential. Yet, this does not serve the absolute information to conduct a realistic evaluation of the potential harms. Rather more specific data such as the expected concentration of nanoparticles in environmental systems would be necessary, to justify an actual risk assessment, which has not been claimed to date. To start the environmental risk assessment of nanoparticles, factors such as the resources, environmental pathways, daily applications of nanoparticles, and which of these nanoparticles are sensitive to plants and animals must be identified [89].

Nano Waste Management: Challenges Posed by Nanoparticles and Recommended Waste Disposal Practices Nano wastes are collectively referred to as the new forms of waste streams. These are the stream of wastes containing nanomaterials or any manufactured nanoscale by-product synthesized during its production, storage, and distribution. It could be any product contaminated by nanomaterials such as pipes, personal protection equipment, etc. Over the last two decades, the number of nanoparticles and nanoproducts had massive escalation from a few kilograms to thousands of tons, resulting in the uncontrollable release into the environment. This is only expected to dramatically increase, considering the flourishment of nanotechnology as a new era of miniaturization at industrial-scale production. Although this was proposed by numerous research publications, the research contains limited scientific information on the feasibility of dealing with the waste streams generated by the nanotechnology-based products at various stages of their lifecycle. The nanomaterials are introduced into the environmental systems mostly through nano waste. When the release of these wastes is not controlled effectively, the nanomaterials continue to interact with the abiotic factors (air, water, soil) and result in contamination of soils, as well as surface and underground water resources. Eventually, this threatens the security of water resources, and the contaminated areas could also possibly be difficult to remediate due to issues like high cleanup costs and lack of appropriate technology for the remediation procedure [90]. To look at some of the examples, fuel additives, lubricants, and cosmetics are some consumer nanoproducts impacting the environment. The nanotechnologically synthesized fuel additives and lubricants are expected to be discharged into the air, soil, and water system through different waste streams. In the due course, entering the aquatic and terrestrial lives through spillages during use or leakages from vehicles, sewage drainage systems become the ultimate fate of the nanomaterials. Similarly, the increased production and use of cosmetics give rise to the waste streams containing nanomaterials directly to the aquatic environment through bathing and swimming, sometimes indirectly through the

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sewage systems as a result of showering and washing processes [91]. So, dealing with nano waste is not very safe due to its small size. Nanoparticles are not decomposed by the traditional methods of waste treatment processes like filtering or incineration, giving them the direct license to release into the environment. Since this ultimately leads to some adverse outcomes, numerous methods have been recently proposed to eliminate or reuse nanoparticles from waste, before the accumulated amount poses a threat to the environment and becomes a serious issue [92]. To address this issue and prevent potential environmental risks, some research findings have suggested establishing a unique waste management approach for nano wastes. Marking such an approach would not be surprising as each nanoparticle has a distinctive way of functioning in the fabrication method, with varying crystal morphologies, toxicity testing procedures, and interaction with abiotic factors at the point where it enters the environment [93–97].

Disposal Procedures for Nano Wastes Due to the fact that a broad range of nanomaterials exists in the nanoproducts, a single procedure for disposal will not serve all classes of nanomaterials. Hence, understanding the properties of specific nano wastes before developing effective discharging practices would be a suitable approach to implement environmentally friendly disposal. It is recommended that the safety measures and disposal procedures necessary for handling nano waste must be based on current knowledge and existing legislation should be taken into account. It should be well ensured before disposal that the hazardous properties of the waste are inactivated. The industrial nano waste that is thought to be concentrated should undergo dilution and deactivation mechanism before disposal. Most importantly, industries responsible for the production of such waste as a by-product of their company operations must go through the EPA approval to prove that the nano waste produced is non-hazardous to the environment. The latest nanoproducts must not be released to the market without suitable disposal procedures. Also, the nano waste disposal procedures developed recently must be assessed and approved by government agencies grounded on reliable evidence provided by the claim-lodging organization. To back up the authenticity of their waste disposal procedures, industries should provide adequate evidence by self-testing their products if possible, concerning current scientific procedures [98]. Thus, initiating sound waste management practices and protocols to limit the spread of nanomaterials into the environment would be a fundamental approach to minimize the long-term accountability by consumer nanoproducts [90]. Importance of Raising Public Awareness Regarding Nano Waste Management It is highly recommended to bring the consumer’s attention toward the understanding of the risks posed by nanoproducts. The consumers and the broader community should be educated with comprehensive knowledge of the potential fate of these nanoproducts. They must be well acquainted with the current scenario that does not deny the fact that nanotechnology can decode many latest challenges; however, it can also possibly pose a serious threat to the environment if used irresponsibly

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[99]. Hence, awareness-raising campaigns, well communication, and proper education are the keys to strengthening the correct understanding and preventing hazardous situations. To understand more about the consequences led by nano wastes containing nanoparticles, increased government and industry funding should be allocated to research institutes to evaluate the existing protocols and evolve the latest disposal and recycling processes as per the situation. It is often argued that a substantial amount of funding is being granted for developing the contemporary nanoproducts but the least attention is offered in designing nano waste disposal techniques. At present, several organizations have taken the initiatives and are currently investigating this emerging concern in an attempt to begin suitable and efficient regulations and policies. However, this initiative would be a finer approach if a unified collaboration at all levels is being addressed for this rising and potentially very hazardous issue. Collaborative approaches such as knowledge and experience sharing, coordinated research, and developing proper guidelines for the producers, users, and waste disposal procedures are some of the addressed ways to move this agenda forward [98].

Application of Nanoproducts and Related Consumer Awareness The striking improvements of nanotechnology were followed by a wide range of industrial and academic applications. The field has advanced and resulted in innumerable options for consumer product applications, out of which many have succeeded in the initial laboratory procedures and are already available in the market for purchase. Nanoparticles are undoubtedly integrated within consumer products, and to know their potential effects on human health and environment, much research has been carried out, and a good number of them are still ongoing [100]. The products based on nanotechnology and nanomaterials have created a booming consumer market industry over the last 10 years. The supermarkets have gained over 1827 consumer products and millions of customers. A minimum of about 39 different nanomaterials had reached the market, mostly made from silver, titanium, zinc, gold, titanium oxide, iron (III) oxide, zinc oxide, metals, and metal oxides, respectively, alongside some other compounds like carbonaceous (carbon, fullerenes, CNTs, graphene) and silica. Most nanotechnology items are typically utilized in healthcare and wellness services, home and nursery, automotive appliances, electronic gadgets, and food and drink purposes [101]. Biotechnology, drug delivery, cosmetics, and biosensors are some other territories where the application of nanotechnology has branched out, showcasing extraordinary potential in the generation of new market products. There is no doubt that the rapid growth of consumer nanoproducts has facilitated the market industry with a huge profit; however, concern toward human health due to the exposure of the nanoproducts has also increased in recent days. Various organizations including research institutes, universities, and government bodies are trying to address the potential adverse impacts of nanoproducts. However, it is claimed that even though widespread research has been conducted, consumers, one of the significant stakeholders, seem to lack the knowledge and attention on the severe consequences of nanoproducts. When several studies reviewed the public perception of nanotechnology, very few

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respondents demonstrated finite knowledge on nanotechnology, and most of them were likely to think that it offered more benefits than risks [102]. Numerous studies have examined public opinion on nanotechnology in the USA and Europe, to understand what attitudes they demonstrate toward nanotechnology. The majority of them reported that the public perception about nanotechnology was expressed to be less pessimistic and they seemed to have little knowledge about the field [103, 104]. In many European studies, it was found that less than half of Europeans have ever heard about nanotechnology and only one of four of them claimed to have spoken to someone on this topic; not very surprisingly, men and the people with higher education seemed to have increased awareness. Also, Northern Europeans had a better understanding than the Southerns [105]. When the public opinion among them was evaluated, they were more leaned toward the benefits of nanotechnology, having slightly satisfying opinions in comparison with risks, whereas a large proportion of the population was indecisive regarding which one to choose [106]. A study in Cardiff, Wales, investigated public knowledge and perception of unfamiliar technologies and products. The majority of participants responded with a relatively positive yet inconclusive opinion about nanotechnology and nanoproducts. A good number of respondents expressed ignorance or claimed that nanoproducts were mostly related to areas making use of advanced technology like electronics, medicine, research, etc. and hardly with everyday products [107]. Another study conducted in South Korea assessed consumer awareness, concerns, expectations for various nanoproducts, and the need for assessment in educating them regarding nanotechnology and nanomaterials. The research revealed that consumers have manifested an unambiguous image of nanotechnology and nanoproducts but do not comprehensively understand what they are. Therefore, they depict a vague picture of nanotechnology in their understanding. Additionally, they discovered that disseminating information on nanoproducts to consumers is highly needed to provide the actual knowledge to the public [108]. The consumers significantly lack the understanding of the technological principles, which is followed by limited awareness regarding the possible harmful effects of nanoproducts on the environment.

Conclusion The major expansion in medicine, agriculture, industry, and other related science fields has experienced rapid progress due to the introduction of nanotechnology. Nanoparticles are the basis of nanotechnology and the key contributors to the advancement of this branch of technology. Among scientists, engineers, and all other people related to this field, the usefulness and threat of nanotechnology have always been a topic of dispute. The particle size has been the major and unique property of nanoparticles that have put this entire field of science into prolonged controversy. Despite the fact that the major effect of particle size on materials’ toxicities has been specified earlier, it is still not very clear what has been the exact mechanism behind particle size, its behavior, and reactivity giving rise to the

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toxicity of nanoparticles. The current situation demands extensive research with appropriate laboratory methods to keep up with the latest issues and ideas of nanoparticles. Nanotechnology takes part in building an environmentally friendly atmosphere by removing contaminants from the air, water, and sewage, besides all other benefits. From being applied in environmental sensors to creating green nanotechnology through the minimization of greenhouse gases, the list of benefits surrounded by this field of technology continues. However, other research findings claiming nanoparticles posing threats to the environment during the disposal of nano waste product are an irony to the entire situation. Also, confusions arise among scientists as yet it has not been successfully established how nanotechnology could be responsible for risking environmental health. At the same time, the fact that a good number of the research findings have stated the toxicity of nanoparticles and their adverse effects on humans and the environment cannot be abandoned without showing concern. To address this concern, scientists, nanotech experts, and all the other important stakeholders are now making an effort to jointly take steps to resolve this dilemma in the scientific community. The main key ideas of the discussion in section “Environmental Harms Caused by Nanoproducts” have been shown in Fig. 1. Some common approaches and guidelines are also proposed to gain a better understanding of the current issue. The risk assessment approach is one of the significant procedures where risk should be assessed at every stage in the life cycle of the

Impact of Consumer Nanoproducts on the environment

Problems

Benefits

Energy Conservation & Generation

Sensors for pollutants

Waste Reduction

Water Treatment

Pollution Prevention

Threatens Aquatic and Terrestrial Lives

Surface/Ground Water Contamination

Nanoremediation

Green Manufacture

Nanowaste Disposal Issues

MDR prevention

Reduced Stratospheric Temperature

Ozone depletion

Reduced Plant Growth

Brown Cloud Formation

Fig. 1 The effects of consumer nanoproducts on the environment

Disrupts Food Chain

Environmental Toxicological Pollution

Glacier Melting

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nanomaterial. It should be kept into consideration that most “conventional” manufacturing methods also have sources that are very much likely to generate contaminants and the process of determining whether nano-based methods are more or less sustainable is by assessing the life cycle. However, it has also been pointed out that investigating the implications of these technologies should be done at the critical period which is in the early development phase, as new methods come in and previous ones are intervened in favor of nano-based approaches [108]. It is also recommended to create a database gathering the properties of different nanoparticles mainly with their toxicological data containing all relevant information related to the nanoparticles to make it readily available for researchers. Occupational exposure is another concern toward human health, and to keep it minimum, safety measures should be well considered while dealing with plants with engineered nanoparticles. The safe handling and application of nanoparticles for research purposes should also be maintained by forming appropriate guidelines. Also, while promoting the benefits of the use of nanoparticles in various fields, we should ensure that no adverse effects result from their use [85]. Finally, apart from the experts, consumers should also own the right to have basic knowledge regarding nanotechnology as their daily lives are surrounded by nanoproducts. Multiple studies conducted so far did not gain satisfactory results on assessing the knowledge and attitude of consumers toward nanoproducts. The majority of the consumers could hardly believe the severity of the consequences it might lead due to unsafe handling and disposal. The need for consumers to understand that they lack the proper understanding of nanoparticles and it is strongly recommended for them to seek this knowledge for their own benefit is something that is still difficult to establish among customers. However, there were also a good number of them who realized the need for awareness and education. Therefore, a risk communication system targeted to the nanoproduct consumers should get initiated to recognize the multiple values and to get them incorporated into the decision-making process. Simultaneously, mass media or other communications channels should be organized and at the same time be executed to ensure an ongoing process of learning the latest developing nanotechnologies and products. Some studies have recommended education and promotional programs for consumers which should focus on receiving reliable and relevant information and make the consumers familiar with different concepts and definitions of nanotechnologies. Besides, the government should start exercising tighter control over nanomaterials, and conducting further social surveillance should be encouraged to examine the levels of public understanding of both the risks and benefits of nanotechnology and nanoproducts [102].

Useful Websites • https://www.youris.com/nano/toxicology/dr_ndeke_musee_to_protect_our_envi ronment_we_need_to_understand_nanotechnology_risks_because_todays_nano products_will_be_tomorrows_waste_streams.kl • https://www.g20-insights.org/policy_briefs/nanowaste-need-disposal-recyclingstandards/

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• https://www.safenano.org/knowledgebase/resources/faqs/what-happens-to-nano materials-in-the-environment/ • https://natureecoevocommunity.nature.com/posts/16310-nano-and-theenvironment • https://www.mistra.org/en/research/mistra-environmental-nanosafety/ • https://www.nanowerk.com/spotlight/spotid¼25937.php • https://www.understandingnano.com/

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Bio-nanocomposites for Modern Agricultural Applications Matias Menossi

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, Claudia Casalongue´, and Vera A. Alvarez

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bio-nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bio-nanocomposite Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bio-nanocomposites as Controlled-Release Systems for Agrochemicals . . . . . . . . . . . . . . . . . Nanotechnology-Based Agroproducts Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commercial and Emerging Nanoproducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nanotoxicity and Environmental Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulation and Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Public Awareness and Acceptance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Agriculture represents one of the most important human activities in the world. Currently, the agricultural system deals with multiple challenges, including population growth, dietary choices, technological progress, climate change, and sustainability. M. Menossi (*) Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina e-mail: [email protected] C. Casalongué Grupo de Fisiología del Estrés en Plantas, Instituto de Investigaciones Biológicas (IIB), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP) y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina V. A. Alvarez Thermoplastic Composite Materials, Institute of Research in Materials Science and Technology (INTEMA), CONICET –Mar del Plata National University, Mar del Plata, Argentina © Springer Nature Singapore Pte Ltd. 2022 S. Mallakpour, C. M. Hussain, Handbook of Consumer Nanoproducts, https://doi.org/10.1007/978-981-16-8698-6_68

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In order to overcome these challenges, many agricultural applications have emerged to enhance productivity and yield of crops: greenhouses, tunnels, mulch, and silage. All of them consist of polymeric films that are placed to increase moisture and temperature and prevent weed growth, and, consequently, they allow less dependence on agrochemicals. The polymer used for these agricultural practices is polyethylene (PE), a nonbiodegradable and nonrenewable material derived from petroleum. Despite their appropriate mechanical and radiometric properties, PE has several environmental disadvantages. The combination of nanotechnology and biopolymers could represent a potential solution to ensure environmental safety, replacing PE with bio-nanocomposites. When bio-based polymers are combined with nanofillers, the resulting bio-nanocomposites exhibit improvements in mechanical, thermal, and barrier properties. Bio-nanocomposites can provide controlled release (CR) of agrochemicals, while efficiently improving permeability, stability, and solubility. The use of biodegradable nanomaterials in agricultural practices can promote sustainable and eco-friendly cultivation reducing soil, water, and air pollution and the indiscriminate use of agrochemicals. Until now, the commercialization of nanotechnology-based agroformulations has been limited and related to several issues: nanotoxicity, government regulation, public knowledge, and production costs. This work highlights the promising application of bio-nanocomposites from organic origin for sustainable development in agriculture applications, in particular chitosan-based nanocomposites, and analyzes their commercial insertion as CR systems for agrochemicals and the limits of their commercialization. Keywords

Agriculture · Biopolymers · Controlled release · Nanocomposites · Nanotechnology

Introduction Since the 1930s/1940s, the incorporation of plastic films with different applications such as greenhouse coating, tunnel covering, and mulching has been increased in agriculture [1]. All these practices can be employed for a wide variety of purposes to protect plants from atmospheric agents, to increase air temperature, to control soil temperature, to reduce water consumption, to limit soil erosion, and to reduce the growth of weeds, as well as for controlled-release (CR) systems of fertilizers, pesticides, and herbicides, among others [2]. Historically, the polymers conventionally used for all these agricultural applications are from petroleum-based nondegradable/nonrenewable materials, particularly polyethylene (PE). This universal polymer has been well-accepted for its mechanical and thermo-optical properties, resistance to all forms of degradation, easy processing, and low cost [2]. However, at the end of their lifetime, every one or two cultivation periods, these nondegradable/nonrenewable polymers have exerted negative consequences, such as:

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1-. Economical disadvantages. The removal of the plastic wastes is timeconsuming with economic costs for farmers. According to Brodhagen et al. [3], US growers spend between $358 and $584 per hectare for removal and disposal of PE mulch films. These films are covered by a wide variety of agrochemicals, rests of soil, and organic matter. For these reasons, PE films need a correct collection and final disposal or recycling with expensive costs for the growers. 2-. Environmental-social disadvantages. As a consequence of economical disadvantages, plastic materials are usually accumulated, stockpiled, or abandoned in landfills or rivers, incorporated into the soil, or burned causing the continual emission of contaminating gases/substances in the atmosphere, water, and soil. Additionally, when the film wastes are incorporated into the soil, their structure can be damaged which can affect the absorption of water and nutrients by plants impacting in their crop yields [1]. In order to overcome these problems associated with the petroleum-based agricultural plastic products and to increase the sustainability of agricultural applications, the use of biodegradable and renewable raw materials becomes to be highly desirable. Contrary to PE films, biodegradable films can be incorporated directly into the soil and be biodegraded by soil moisture and microorganisms at the end of the crop season. The mulching, for example, is an agricultural practice where the biodegradable material is in direct contact with the soil. In this context, the mulching materials should not affect the performance of agricultural soil, i.e., there should be no accumulation of harmful substances [2]. Bio-based polymers or biopolymers are polymers directly extracted/removed from natural resources or produced by the synthesis of monomers obtained from renewable resources or by microorganisms. A number of naturally occurring proteins, lipids, polysaccharides, polyesters, and synthetic biodegradable polymers are considered as bio-based materials for agricultural applications [1]. Averous and Boquillon [4] categorized bio-based polymers in four families according to the method of production (Fig. 1). In contrast to PE films, biodegradable polyesters contain ester bonds that make them susceptible to chemical degradation, including hydrolysis. The hydrolysis breaks up the chemical structure into smaller molecules causing more susceptibility to enzymatic reactions [1]. To replace petroleum-based agricultural plastic, biopolymers-based materials face multiple challenges to improve: • Mechanical behavior, spectra-radiometric characteristics, and barrier properties. The correct combination of mechanical, radiometric, and barrier properties of bio-based materials to agricultural applications is essential. According to Briassoulis [5], the mechanical properties of biodegradable materials mainly depend on their chemical structure, processing and storage variables, application, and degradation. The development of biodegradable agricultural films must achieve the appropriate mechanical properties to assure an easy handling and installation, i.e., adequate strength and elongation at break. Additionally, the

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Fig. 1 Classification of bio-based polymers according to the method of production [4]

radiometric properties must be adjusted with special additives depending on crop type, the season, and the geographical area, for the purpose of inhibiting the growth of weed or providing an increase in the soil temperature [5]. Agro-films require different optical properties depending on their application:

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lower opacity is necessary for greenhouse materials and low tunnels, and higher opacity for mulching films. Concerning barrier properties, biopolymers-based agro-materials should have low enough water vapor permeability (WVP). Low values of WVP will allow to store the soil moisture, reducing the water consumption and preventing the risk of water stress [5]. • Hydrophilic/hydrophobic nature and biodegradability. Biodegradable agricultural films should meet an optimal point regarding their biopolymer hydrophilic/hydrophobic nature since they should degrade 100% at the end of the crop season. Biomass-based polymers are polymers formed in nature, and their hydrophilic character (tendency for brittle) is associated with problems when they are exposed to moisture [3]. On the other hand, the biodegradability of synthesized biopolymers largely depends on their hydrophilic/hydrophobic character. Biodegradability is higher to those biopolymers with hydrophilic/ hydrophobic chains than those with only hydrophilic/hydrophobic segment. The biodegradation rate of hydrophobic biopolymers (which do not allow enzymes, water, and aqueous solutes into their surface) is lower since enzyme reaction rates depend upon the presence of substrate at the active site of an enzyme [3]. • Availability and cost. Compared with PE materials, the major limitation of the biodegradable plastics for agricultural practices is their high cost. This fact applies to biopolyesters, particularly polylactic acid (PLA) and polyhydroxyalkanoate (PHA) [1]. Instead, natural polymers continue to remain a viable alternative to nonrenewable petroleum-based plastics basically due to its low cost and wide availability. Because of all these issues, the performance of biopolymers could be increased considerably, with respect to petroleum-based materials, to represent a potential alternative to agricultural practices. Hence, nanoscience and nanotechnology have the potential to overcome and to make a beneficial impact on these challenges where unique physic-chemical characteristics make novel applications possible. The nanotechnology term involves the understanding, synthesis or preparation, characterization, and manipulation of material at nanoscale. The mechanical, physical, chemical, and functional properties can be significantly improved by reducing from macro-dimension to nano-dimensions a specific dimension of the material [6]. Until now, in the agricultural sector, unlike other fields like pharmaceutical, cosmetic, electronic, and medical, nanotechnology and its benefits have received little attention, and it has not been possible to achieve its massiveness in the market. But, in the last decade, this trend has reversed, and the number of patents and original science publications about agro-nanotechnology has substantially increased [7]. Increasing the efficiency and the productivity, crop protection, and production, through the optimized management of different resources such as water and nutrients, are some of the benefits of working with nanoscale materials for agricultural applications. Pesticides, fertilizers, herbicides, and other agrochemicals have been traditionally applied by spraying or soaking, and because of this, factors such as rain, wind, or

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sunlight can remove, degrade, or decompose them. Consequently, only a small portion of the added agrochemicals reach their target species and functions [8]. Then, the indiscriminate application of agrochemicals potentially has caused water contamination, increase of pathogen and pest resistance, and loss of soil biodiversity, among others worldwide [9]. In addition to the economic disadvantage, agrochemicals have had a direct negative effect on human health and environment. In addition to the costs related to the environment and health, the economic disadvantage is added. In this sense, nanotechnology can provide nano-solutions mainly due to the possibility of reducing the doses of applied agrochemicals. This fact is mainly due to that nanotools-based agrochemical formulations offer advantages such as larger surface structure, higher surface charge, larger mass transfer, higher solubility, larger durability, and lower toxicity, allowing them to improve their properties interactions with target tissues [9]. Nanomaterials manage to minimize the loss of nutrients and decrease the number of chemical products, reducing environmental impact as compared with conventional approaches [8]. Iavicoli et al. [8] summarized the potential applications of nanotechnology in agriculture. They recognized nanopesticides employed to promote plant protection against pests and weeds and prevention of crop diseases, nanosensors which have been utilized as devices to provide smart monitoring of pollutants, and nanofertilizers used to stimulate plant growth and to supply precise nutrient management and obtain high levels of agricultural yield. All these nanotools try to mitigate crop losses caused by biotic and/or abiotic stress. Figure 2 shows benefits of nanotechnology applied to sustainable agriculture to improve plant productivity, increase food and human health, and avoid environmental impacts. Nanomaterials from inorganic and organic origins have been assayed in plant protection and nutritional applications. Among inorganic nanomaterials, metal nanoparticles (NPs) such as silver (Ag), aluminum (Al), copper (Cu), and zinc (Zn) and metal oxides NPs such as zinc oxide (ZnO), silver oxide (Ag2O), and titanium oxide

Environment • Reduce

soil biodiversity losses and enhance the quality of the soil • Protection and remediation of water • Reduce emission of contaminating gases into the atmosphere

Productivity • Reduce agrochemicals losses and their costs • Slow and sustained release of water • Sensing and monitoring soil conditions

Plants

Food & human health • Reduce farmers exposition to agrochemicals • Improve food quality, decreasing agrochemicals levels

Fig. 2 Benefits of nanotechnology in sustainable agriculture

•Improve agrochemicals availability • Cellular delivery of genes and drugs molecules to specific sites • Stimulate plant growth and fight against diseases

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Compatibility with biologically active molecules

Thermal stability Thermal plasticity Melting point

Environmental impact

Control release behavior

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Biodegradability rate

Fig. 3 Advantages of biopolymers into agro-nanotechnology

(TiO2) are proper due to their particular characteristics. Unfortunately, these metal and metal oxides NPs might cause negative effects on the environment, humans, and plants [7]. Particularly, some examples of adverse effects on plants are inhibition in cell growth and nitrogen fixation, reduced germination, decreased root length, and reduced biomass growth, among others. Alternatively, nanomaterials from organic origin like lipids and polymers represent powerful alternatives. Biopolymers have been investigated as CR systems of insecticides, pesticides, fungicides, germicides, and growth stimulants [7]. The advantages of applying biopolymers into agro-nanotechnological materials are summarized in Fig. 3. Between polymers from organic origin, starch has been one of the most commonly used raw materials because it is widely available and relatively easy to handle to prepare biodegradable nanomaterials. However starch films have often resulted brittle and sensitive to environmental humidity and difficult to process [6]. Thus, to innovate in biodegradable nanomaterials, many other different natural polysaccharides including alginate, hyaluronic acid, cellulose, hemicelluloses, as well as the cationic chitin/chitosan have been considered. Moreover, blends of them have resulted in a superlative bio-based composite with beneficial properties for the desired application [6]. In particular, chitosan is a polycationic polymer composed of N-acetyl-D-glucosamine and D-glucosamine units with one amino (NH2) group and two hydroxyl (OH) groups in each repeating glycosidic unit (Fig. 4). In addition to its biodegradability and biocompatibility, the low insolubility and thermal stability confer on chitosan beneficial properties for its nanocomposites as film or agrochemical delivery. This chapter highlights studies on bio-nanocomposites from organic origin and their potentiality as eco-friendly nanomaterials for modern agricultural applications. Chitosan-based nanocomposites as agricultural films as well as carrier for agrochemical delivery will be revised. Finally, it will summarize commercial and emerging nanoformulations as CR systems for agrochemicals, as well as analyze their multiple challenges for their commercialization.

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Fig. 4 Chemical structure of chitosan

Bio-nanocomposites Bio-based and biodegradable polymers from renewable resources appear as potential alternative to traditional nonrenewable/nonbiodegradable synthetic polymers. Nevertheless, as mentioned above, some properties must be improved to obtain a competitive product and to expand their applicability. In this sense, the common way to overcome these limits is through the formulation of multiphase materials such as blends or composites. Bio-nanocomposites are materials obtained by the incorporation of inorganic or organic reinforcement, with at least one dimension in the range of the nanometer (10 9 m), into a bio-based matrix. The nano-reinforcement can be incorporated into biopolymer matrix by three different methods: in situ polymerization, solution exfoliation, and melt intercalation process [10].

Bio-nanocomposite Properties The main reason for incorporating small amounts of nano-sized reinforcements into the biopolymer matrix is due to the improvement of certain properties with respect to neat bio-based polymers (Fig. 5). The behavior of these novel eco-nanomaterials depends on the type and content of reinforcement, the structure polymer/nanofiller, the conditions of the process, and the final dispersion. In general, drastic enhancements in Young’s modulus of bio-nanocomposites are exhibited with the addition of organic nanofillers. In the case of tensile strength and elongation at break (%), the improvements are occasional. For example, Lu et al. [11] studied chitin whiskers as nano-reinforcements into soy protein isolate (SPI) matrix. They prepared bio-nanocomposite films based on glycerol-plasticized SPI with 0, 5, 10, 15, 20, and 30 wt % of chitin whiskers. These authors concluded that Young’s modulus of the 20 wt% chitin whiskers increased approximately six times with respect to neat glycerol-plasticized SPI. In the same work, the elongation at break was in all cases less than 135% with chitin whisker content. The tensile properties of the bio-nanocomposites containing different amounts of nanofillers are shown in Table 1.

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Properties improved with nano-fillers introduction

1

2

Mechanical properties

Thermal properties

3

4

5

Barrier properties

Optical properties

Biodegradability

Fig. 5 Properties improved with nanofillers introduction

In contrast, Arrieta et al. [12] obtained bio-nanocomposite films based on PLA as bio-based matrix and used yerba mate NPs (mate NPs) as nanofillers in two proportions: 0 and 5 wt%. They concluded that the incorporation of mate NPs considerably increased the Young’s modulus in comparison with neat PLA, from 2 to 2.65 GPa approximately. The tensile strength value is two times higher compared with neat PLA, while no considerable modifications were observed on the elongation at break. Other case of bio-nanocomposite with bio-based nanofillers is the work of Cao et al. [13]. They synthesized green nanocomposites with hemp nanocrystals (HNCs) in thermoplastic starch (PS) by casting method and prepared HCNs-PS nanocomposites with 0, 5, 10, 15, 20, 25, and 30 wt% HNCs. Young’s modulus was significantly improved from 0.032 GPa to 0.824 GPa, when increasing the HNCs content from 0 to 30 wt%, while the elongation at break values decreased from 68% to 7.5% with 0 and 30 wt% HNCs content, respectively. In addition, the tensile strength increased 200% in relation to neat PS. Other studies with similar results are the works of Chang et al. that investigated glycerol-plasticized potato starch (GPPS) using chitosan NPs [16] and chitin NPs [14] as nano-reinforcements. Hosseini et al. [15] evaluated the incorporation of chitosan NPs into fish gelatin (FG) matrix films. Young’s modulus, tensile strength, and elongation at break of each mentioned work are indicated in Table 1. In summary, the improvement on Young’s modulus and tensile strength by adding small amounts of nano-reinforcements can be explained by high interaction between the nanofiller and the bio-based matrix [11]. This interaction is increased when both chemical structures are quite similar and the nanomaterial exhibits a homogeneous dispersion [14]. Meanwhile, the opposite happened with elongation at break: the incorporation of nanofillers reduced the motion of the bio-based matrix due to increased intermolecular attractive forces [13]. The mechanical properties for agricultural materials must meet several requirements and standards that have been summarized in the review of Briassoulis [5]: thickness 30–40μm, tensile strength 27 Mpa, and elongation at break 300%. To obtain these standards mechanical properties, many alternatives can be employed: reactive modification, surface functionalization, blending with other biopolymer, changing the plasticizer, varying nanofiller contents, etc. In this sense, Arrieta et al. [12] demonstrated that higher values of elongation at break are achieved when acetyl (tributyl citrate) is incorporated, as a plasticizer, into PLA-mate NPs bio-nanocomposite films.

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Table 1 Tensile properties of bio-nanocomposites with different nanofiller contents Bionanocomposite SPI-chitin whiskers

PLA-mate NPs HCNs-PS

GPPS-chitosan NPs

FG-chitosan NPs

GPPS-chitin NPs

Nanofiller content (%) 0 5 10 15 20 25 30 0 5 0 5 10 15 20 25 30 0 1 2 4 6 8 0 2 4 6 8 0 1 2 3 4 5

Young’s modulus (GPa) ≈ 0.026 ≈ 0.032 ≈ 0.036 ≈ 0.042 ≈ 0.158 ≈ 0.138 ≈ 0.105 ≈ 2.00 ≈ 2.65 0.032 0.035 0.112 0.169 0.243 0.395 0.824 – – – – – – 0.287 0.371 0.392 0.453 0.467 – – – – – –

Tensile strength (MPa) ≈ 3.3 ≈ 3.8 ≈ 5.0 ≈ 5.7 ≈ 8.4 ≈ 8.3 ≈ 6.3 ≈ 27.11 ≈ 48.60 3.9 4.5 6.1 6.9 7.4 8.7 11.5 ≈ 2.84 ≈ 4.40 ≈ 6.93 ≈ 8.50 ≈ 10.80 ≈ 8.90 7.44 7.99 8.77 10.57 11.28 ≈ 2.80 ≈ 3.45 ≈ 5.15 ≈ 6.29 ≈ 7.52 ≈ 7.80

Elongation at break (%) ≈ 205.0 ≈ 134.2 ≈ 106.7 ≈ 102.6 ≈ 34.8 ≈ 32.3 ≈ 28.6 ≈ 4.00 ≈ 2.65 68.2 57.3 50.4 31.2 20.3 16.4 7.5 ≈ 59.3 ≈ 45.5 ≈ 37.6 ≈ 28.1 ≈ 22.6 ≈ 18.2 102.04 70.09 64.72 44.71 32.73 ≈ 59.3 ≈ 43.5 ≈ 30.7 ≈ 26.3 ≈ 21.7 ≈ 19.4

Ref. [11]

[12] [13]

[14]

[15]

[16]

Several researchers [12, 14, 17, 18] investigated bio-nanocomposites and their thermal stability by thermogravimetric analysis (TGA). In particular, Han et al. [17] synthesized eco-friendly bio-nanocomposites based on glycerol-plasticized PSI with nanocellulose fibers. These films were prepared by the addition of 0, 2, 4, 6, and 8 wt% of nanocellulose, and these bio-nanocomposites presented slightly enhanced thermal stability in comparison with glycerol-plasticized SPI film without nanofiller. Films with

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low values of nanocellulose content registered lower mass loss with respect to SPI film with 0 wt% nanocellulose fibers; nevertheless, the opposite happened with high nanoreinforcement contents. Sahraee et al. [18] prepared gelatin-based nanocomposite films containing chitin NPs with 0, 3, 5, and 10 wt% content. The thermographs showed major thermal stability for 5 wt% chitin NPs than 10 wt%, due to agglomeration of NPs. They concluded that films thermal stability enhanced when the chitin NPs are homogeneously dispersed within gelatin matrix. Arrieta et al. [12] studied the incorporation of mate NPs as nanofillers into PLA matrix, besides measuring tensile properties of mate NPs – PLA films. They also investigated thermal stability of these bio-nanocomposites. Their results led to the conclusion that mate NPs protect PLA from thermal degradation and can be associated with the presence of antioxidant agents. Chang et al. [14] studied the influence of chitosan NPs into GPPS matrix films applying TGA analysis and compared to neat GPPS film. The introduction of chitosan NPs decreased mass loss through temperature range, and the improvement of bio-nanocomposites thermal stability was attributed better interactions between the nanofiller and GPPS matrix. Furthermore, works of Abdulkhani et al. [19], Lu et al. [20], and Siqueira et al. [21] prepared bio-nanocomposites and analyzed thermal properties by differential scanning calorimetry (DSC). Abdulkhani et al. [19] investigated bio-nanocomposites of modified cellulose nanofibers as filler into PLA matrix. Bio-nanocomposite films were developed at low contents of NPs, 0, 1, 3, and 5 wt%, and studied the effects of modified cellulose nanofibers with DSC analysis. Nanocomposite films thermal behavior showed quite similar pattern with respect to neat PLA film, and the glass transition temperature (Tg) showed a slight improvement by the addition of nanofibers. The incorporation of cellulose crystallites as filler into PS matrix was studied by Lu et al. [20]. The contents of cellulose nanocrystallites into PS matrix were 0, 2.5, 5, 10, 15, 20, and 30 wt%. By DSC analysis, they concluded that Tg increased with the content of nano-reinforcement. This behavior may be attributed to stronger interactions between starch and cellulose crystallites, making bio-nanocomposite films less flexible. On the other hand, Siqueira et al. [21] used cellulose nanocrystals as reinforcements for preparing bio-nanocomposites using poly(ε-caprolactone) (PCL) as matrix. Bio-nanocomposite films with different amounts of cellulose nano-crystals, 0, 3, 6, 9, and 12 wt%, were processed. DSC analysis reported that Tg values increased when cellulose nanocrystals content was added but no drastic modification was exhibited when varying the filler content. It can be explained as the nanofillers restrict the motion of PCL polymer chains by making hydrogen bonding forces. These works with their experimental Tg data are condensed in Table 2. In general, polysaccharides like cellulose, chitin, chitosan, and starch as nanoreinforcements of bio-based polymer matrix increase Tg through the restriction of polymer chains mobility or making hydrogen bonding forces and, consequently, enhance thermal stability and crystallinity. Eco-nanomaterials with uniform distribution of NPs showed better thermal properties. As previously mentioned, barrier to vapor water is desirable in agriculture field since it allows storing the soil moisture, decreasing water consumption, and

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Table 2 Thermal properties of bio-nanocomposites with different nanofiller contents Bio-nanocomposite PLA-cellulose nanofibers

PS-cellulose crystallites

PCL-cellulose nanocrystals

Nanofiller contents (%) 0 1 3 5 0 2.5 5 10 15 20 30 0 3 6 9 12

Tg ( C) 57.5 58.3 58.5 58.9 ≈ 22.3 ≈ 22.6 ≈ 26.9 ≈ 30.6 ≈ 36.6 ≈ 38.4 ≈ 48.7 62 59.2 57.7 57.4 58.8

Ref. [19]

[20]

[21]

preventing the risk associated with water stress. Significant reductions in diffusivity were reported in several investigations [15–17] [22]. Hosseini et al. [15] analyzed the effect on WVP when chitosan NPs content increased into FG bio-nanocomposite films. WVP of FG with 0% content of chitosan NPs was around 4 x 10 9 g/m.s.Pa. WVP was reduced, approximately, 38% when 8% of chitosan NPs content was introduced. The development of bio-nanocomposite films based on starch matrix and the use of chitin NPs as reinforcements were studied by Chang et al. [16]. WVP of neat GPPS film was, approximately, 5.60 x 10 10 g/m.s.Pa, which decreased between 19 and 25% when 1–2 wt% of chitin NPs are added, respectively. From 2 wt% to higher chitin NPs contents, WVP values reported were slightly lower. Other case that evaluated WVP and compared it with neat biopolymer matrix is the work of Han et al. [17]. They studied the introduction of nanocellulose into glycerolplasticized PSI and the effect of the nanofiller content on barrier property. They reported 1.91 x 10 10 g/m.s.Pa as WVP value to glycerol-plasticized PSI without nanocellulose, and it immediately decreases when nano-reinforcements are added. In comparison with this value, WVP was reduced to 16% when 8% of nanocellulose content was incorporated into bio-nanocomposite film. Besides varying the nano-reinforcement content, film dispersion, and type of nanofiller, Follain et al. [22] prepared bio-nanocomposites based on PCL matrix with cellulose nanocrystals surface-chemical modification by grafting of long-chain isocyanate as nanofiller. In their work they compared the WVP values of these eco-nanomaterials with and without chemical modification and obtained better barrier properties when reactive modification of cellulose nanocrystals was incorporated into PCL matrix.

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In summary, the barrier properties are enhanced when impermeable nanoreinforcements are added and have a good dispersion in the polymer matrix as well as a high aspect ratio. This dramatic improvement can be explained by the increasing of tortuosity in bio-nanocomposite films, and the diffusion processes are slower and, thus, present lower permeability values. Many studies reported that incorporation of nano-reinforcements into biopolymer matrix generates a decrease in spectra-radiometric characteristics in the visible range and the UV region [15, 18, 23]. This behavior is desirable for agricultural applications, such as mulching films, since one of their purposes is to inhibit the light-dependent growth of weeds [2]. FG-based bio-nanocomposite films with the incorporation of different chitosan NPs contents were prepared and optically evaluated by Hosseini et al. [15]. Light barrier properties of bio-nanocomposite films containing high level of chitosan NPs showed a reduction of transparency with respect to neat FG films. Multiple issues are related to this performance; for instance, researchers explain that the increase of opacity could be attributed to the obstruction of light passage by NPs or to the formation of fewer agglomerates [18]. Specifically, according to Chen and Liu [23] when NPs content level is high, the transmitted light could pass through several interfaces between the nano-reinforcement and the bio-based matrix. In consequence, light loss becomes inevitable and is ascribed to the strong reflections and refractions at those interfaces. Particularly, the work of Nasri-Nasrabadi et al. [24] and Han et al. [17] developed eco-friendly nanomaterials that showed increases in transparency levels or did not produce changes in their opacity. Nasri-Nasrabadi et al. [24] explain that their results may be related to the narrow-diameter dispersity of the nanofibers, homogeneous dispersion into polymer matrix, and a strong interaction between nanofiller and matrix. Bio-nanocomposites that increase the transparency levels could be used as greenhouse or low tunnels in agricultural practices [5]. Agro-nanomaterials should disintegrate completely at the end of the crop season. For this reason, disintegrability in composting and enzymatic, in vitro, and soil degradation of green and eco-friendly nanocomposites have been investigated by several authors [25–28]. For the case of Deepa et al. [25] described that the disintegrability in compost conditions exhibited that the rate of degradation of alginate and cellulose nanofibrils bio-nanocomposite films changes with different amounts of reinforcement added into alginate matrix. Due to homogeneous dispersion and strong interaction between the alginate matrix and cellulose nanofibrils, nanocomposites are harder to degrade when the nanofiller contents increase. Nevertheless, at high contents of nanofillers, nanofibrils agglomeration was observed and, in consequence, disintegration is higher. The in vitro degradation of electrospun bio-nanocomposite mats from PLA and cellulose nanocrystals in phosphate buffer solution tests were investigated by Shi et al. [28]. These authors concluded that cellulose nanocrystals incorporation into PLA matrix degraded easier than neat PLA. The enzymatic degradation, using proteinase K as enzyme, of neat PLA and PLA nanocomposites reinforced with cellulose nanocrystals unmodified and modified using a commercial surfactant was

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studied by Luzi et al. [26]. Approximately, 100% weight loss for neat PLA and PLA reinforced with cellulose nanocrystals unmodified composite was reached in 3 days of enzymatic degradation. However, nanocomposites composed of PLA with the presence of surfactant showed slower degradation than neat PLA and PLA with cellulose nanocrystals unmodified. Similar evidence was demonstrated by Pinheiro et al. [27]. The authors compared soil biodegradation of neat cellulose, neat polybutylene adipate terephthalate (PBAT), and PBAT bio-nanocomposites with cellulose nanocrystals and cellulose-functionalized nanocrystals. The addition of cellulose nanocrystals unmodified into PBAT matrix generated a less hydrophobic system and, therefore, had greater trend of biodegradation than the neat PBAT and nanocomposite films reinforced with cellulose nanocrystals modified. Neat PBAT and bio-nanocomposites of PBAT-based cellulose-functionalized nanocrystals showed similar biodegradation rate. For both, their biodegradation rate was lower than 5% after 120 days. In short, bio-nanocomposites can be adapted to meet the biodegradability requirements imposed by agricultural practice. These traits will depend on the crop type, polymer matrix, and nano-reinforcements including their chemical modifications.

Chitosan-Based Nanocomposites In this section, we will carefully review some representative studies focused on bio-based nanocomposites which offered benefits to be used as mulch films. In particular, chitosan-based nanocomposites incorporating organic nanofillers will be prioritized to interpret the advantages and disadvantages of these innovative and promising materials in agriculture. Chitosan-based nanocomposites refer to the chitosan polymer acting as a matrix or chitosan NPs acting as nanofiller with an average particle size less than 100 nm. This nanocomposite could retain exceptionally improved properties from both polymer and NPs [7]. In agriculture, the potential of chitosan-based nanocomposites has an increasing relevance in enhancing plant protection against stress and improving crop yield and management [29]. In this same field, other essential trait is low water solubility of mulch films due to their intimate contact with the irrigation water. Thus, a chitosan and starch blend used as matrix has been designed to contribute to the solution of this problem [30]. The same authors demonstrated that the addition of a specific amount of chitosan caused a twofold reduction in solubility of starch films. However, the maximum tensile strength at rupture did not vary with the addition of chitosan and citric acid, this latter added as cross-linker. In addition to starch, chitosan can also be modified by blending with cellulose because it has modifiable chemical groups [31]. Thus, the stability of chitosan and cellulose blends improves physical properties of different bio-based composites [31]. Innovative bio-based pesticide mulch obtained by blending chitosan and hydroxypropyl methylcellulose (Me-CS50/HPMC50) with a controlled-release ability of the pesticide metalaxyl (Me) proved to be effective in reducing the incidence of Phytophthora-mediated disease in soybean plants [32]. Other cellulose and chitosan-based composite film with an associated antibacterial activity has been proposed as a biomedical material [33]; however, since

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chitosan antimicrobial properties were also very well demonstrated on a wide range of pathogens, we cannot discard that this bio-based blend could be adaptable for its use in agriculture [34]. Focusing on reducing the hazardous environmental impacts of nonbiodegradable films, several chitosan and cellulose blends were successfully characterized [31]. However, one important problem on chitosan-cellulose blend has been the use of solvents to dissolve them. Most of chemical approaches have resulted inappropriate for the production of that blend at industrial scale. Accordingly, to optimize and contribute with a more environmentally friendly procedure, a novel alternative of preparing pH-responsive cellulose-chitosan nanocomposites has been performed [35]. These pH-responsive cellulose-chitosan nanocomposite films also exert slow release of chitosan besides to be nontoxic, biocompatible, and biodegradable, representing a promissory eco-material in the field. Therefore, although several studies exemplify the wide aspects that must be taken into account for the development of a bio-based composite, it is interpreted that the knowledge about its design and characterization to final application consequences, including biodegradability and life cycle, is very limited.

Bio-nanocomposites as Controlled-Release Systems for Agrochemicals CR is defined as the regulated transfer of biologically active ingredients that are available to a targeted site, with the aim to provide certain content level over a longer period [7]. CR technology presents advantages in agriculture field such as reduction of agrochemical doses, minimized losses for evaporation, decreased phytotoxicity, and reduction of harmful chemicals. In this way, nanotechnology could take an important place into the crop productivity due to its potential for efficient delivery of agrochemicals and genetic material using nanocomposites [36]. In order to apply the use of agrochemical nanoformulations, a promising option results from the combination of nanotechnology and renewable/biodegradable polymers due to their biodegradability, biocompatibility, thermal stability, and nontoxic and simple preparation. In this direction, natural biopolymers, more specifically polysaccharides – alginate, starch, cellulose, cyclodextrin, pectin, chitosan, and others – are used as vehicles to encapsulate or absorb active ingredients to elaborate CR systems for agrochemicals [7]. Some strategies such as incorporating pendant groups, cross-linking, and grafting with other polymers are required to enhance the natural polymer properties as CR nanocarriers [7]. Other natural polymers less used as CR systems for agrochemicals are proteins. Casein, collagen, gelatin, soy protein, zein protein, and others are low-cost and high-availability heteropolymers conformed by different amino acids and can play a fundamental role like N source after its disintegration [10]. Among biopolyesters, PLA and PCL are the most used for CR delivery system. According to Ghormade et al. [9], polymer-based nanomaterials as CR systems for agrochemicals can be classified in relation to their nanostructure, as the following:

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• Nanocapsules. Heterogeneous reservoir-type structures. The active ingredient is located and concentrated in an inner central cavity, lined and surrounded by polymer matrix. • Nanospheres. Uniform monolithic structures. The active molecule is homogeneously distributed throughout the polymer matrix. • Nanogels. Water-swollen polymeric networks. Hydrophilic or amphiphilic polymers, physically or chemically cross-linked, which can swell and absorb high quantity of water. The active ingredient is trapped between the nanomaterial networks. • Nanofibers. Homogeneous spinning structures. The spinning solution contained the active ingredient in various concentrations along with the polymer matrix. • Nanomicelles. Core-shell-type structures. Block copolymers with amphiphilic behavior self-assemble in water to form colloidal particles. The process of selfassembly is developed by the hydrophobic interactions on the formation of the hydrophobic micellar core which is coated by a hydrophilic shell. The active ingredient is concentrated inside hydrophobic micellar core. Briefly, investigations on polysaccharides, proteins, and biopolyesters used as vehicles to encapsulate or absorb active ingredients to elaborate CR fertilizer and pesticide are summarized in Table 3 with their nanostructures and benefits. In relation to nanoencapsulation, Kumar et al. [37] developed and evaluated nanocapsules based on alginate and chitosan for CR of acetamiprid as pesticide. This nanoformulation was prepared by polyelectrolyte complexation, characterized by different studies, and analyzed as carriers for CR in vitro at different pH. The same authors concluded that nanocomposites made of alginate and chitosan were better in terms of CR than the commercial agrochemicals. This novel nanoformulation can be employed in different types of soil due to the stability of pesticide at all the pH ranges. Alginate and chitosan matrix used in nanocapsules loading paraquat dichloride as herbicide were also investigated and characterized by Silvia et al. [38]. Size distribution, polydispersion, zeta potential, pH, and chemical stability measurements were used in order to characterize chitosan and alginate nanocapsules. The authors concluded that the formulation of paraquat with chitosan/alginate NPs showed an improvement of herbicidal action than paraquat-free. Finally, chitosan/alginate NP as a carrier system for gibberellic acid as plant growth hormone was studied by Pereira et al. [39]. These authors developed nanocarriers with high encapsulation efficiency. The release of plant growth hormone was modified depending on changes in temperature and pH. With respect to biological activity assays, alginate-chitosan with gibberellic acid showed stronger effects in comparison to the free hormone. Kumar et al. [40] synthesized imidacloprid-loaded sodium alginate NPs as CR for pesticide. NPs were obtained by emulsion cross-linking technology and varying polysaccharide and emulsifier content in the preparation. Nanoformulation was characterized by different methods to confirm NPs belong to nano-size with high encapsulation efficiency. Imidacloprid encapsulation resulted in lower toxicity than plane pesticide. Neem oil/alginate nanoemulsion coated by starch showed a drastic effect on slowing down the release of Azadirachta indica. Imidacloprid was assayed with the purpose of

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Table 3 Bio-nanocomposites as CR systems Nanostructure Nanocapsule

Biopolymer Alginatechitosan

Active ingredient(s) Acetamiprid

Alginatechitosan

Paraquat dichloride

Alginatechitosan

Gibberellic acid

Alginate

Imidacloprid

ChitosanPLA Alginatechitosan

Imidacloprid

PCL

Rosmarinus officinalis essential oil Geraniol R-citronellal

Zein protein

Imazapic Imazapyr

Nanosphere

PCL

Azadirachta indica

Nanogel

Chitosancashew gum Cellulosestarch

Lippia sidoides essential oil

Nanofiber

Dimethyl phthalate

Advantage(s) Reduction of pesticides application Major stability and CR profile for different pH and types of soil Improve the herbicidal action Herbicide and biopolymers showed good association High encapsulation efficiency Showed high effect on biological activity assays High-efficiency encapsulation Lower toxicity Improve CR for herbicide behavior Encapsulation showed lower toxicity Improve herbicide action Reduce the concentration of the applied doses and number of applications High-efficiency encapsulation Encapsulation showed decrease in their toxicity Enhance photostability and thermostability Improve insecticide performance Prolong insecticide action

Reduce initial release rate and higher overall CR of herbicide

Ref. [37]

[38]

[39]

[40] [41] [42]

[43]

[44]

[45]

[46]

[47]

preparing nanocapsules of chitosan-PLA graft copolymer as CR for pesticide [41]. Imidacloprid-loaded chitosan-PLA nanoformulations were developed by two techniques: nanoprecipitation technique and emulsion/solvent evaporation method at three different copolymer/active ingredient weight ratios. These biodegradable amphiphilic copolymer nanocapsules loaded with imidacloprid could prolong pesticide release behavior and presented great influence on the particle size and their distribution. Alginate-chitosan NPs loaded with two different herbicides, imazapic and imazapyr, were studied by Maruyama et al. [42]. Nanoformulation was manufactured using ionotropic gelification method and tested by material characterization techniques. In this work, alginate-chitosan NPs were able to encapsulate imazapic and imazapyr with efficiencies between 50 and 70% and presented more improvements as CR for herbicide than the free forms. Also, these authors demonstrated that alginate-chitosan nanoformulation led to a reduction in toxicity. Khoobdel et al. [43] investigated PCL

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biopolyester as nanocarrier to encapsulate Rosmarinus officinalis essential oil as CR system for pesticides. Nanoprecipitation technique was applied in the development of pesticide-loaded nanocapsules. Rosmarinus officinalis nanocapsules showed an important reduction in the concentration and number of the applied doses. Oliveira et al. [44] manufactured zein protein NPs loaded with two pesticides, geraniol and R-citronellal, using antisolvent precipitation technique and analyzed by different material characterization methods. The zein NPs containing the botanical repellents showed high encapsulation efficiency (>90%), good physicochemical stability, and protection against UV degradation. The nanoencapsulation of this protein with geraniol and R-citronellal decreased the toxicity of these both active ingredients. Regarding nanosphere as nanostructured formulation, Costa et al. [45] used Azadirachta indica as pesticide against Zabrotes subfasciatus to prepare spherical nanocomposite employing PCL as matrix. Nanospheres were developed by using nanoemulsion/solvent displacement and interfacial deposition nanoencapsulation process. PCL and Azadirachta indica nanospheres presented higher stability than conventional agrochemicals and enhanced biological performance to control of pests. An example of nanogel as nanoformulation was demonstrated by Abreu et al. [46]. These authors elaborated this nanostructure based on chitosan-cashew gum and loaded Lippia sidoides as active ingredient. Nanocomposite hydrogel was produced varying cashew gum/chitosan ratios, cashew gum weight percent, and matrix/oil ratio. The results obtained led to the conclusion that chitosan-cashew gum nanogel using relative ratios matrix/oil 10:2 and gum/chitosan 1:1 and 5% cashew gum concentration showed encapsulation levels over 70%. Nanoformulation with relative ratio gum/chitosan 1:10 presented the lowest percentage of oil released after 30 h, compared with ratios of 1:1 and 10:1. Regarding nanofiber as nanostructure, bio-based matrix composed of nanofibrillated cellulose and starch granules was used to develop and evaluate nanofibers as CR system for dimethyl phthalate as herbicide. Patil et al. [47] investigated and morphologically characterized nanofibers with three cellulose-nanofiller contents (0, 2, and 4 wt%) and morphologically analyzed. The authors concluded that reinforcing starch with 2–4 wt% cellulose nanofibers caused significant influence on morphology and release performance of starch granules, decreasing initial release rate and higher overall release of dimethyl phthalate than starch without nanofibers.

Chitosan-Based Nanocomposites as Controlled-Release Systems for Agrochemicals In addition to the agricultural applications mentioned in the previous section, several nanoparticulated systems are being currently incorporated to the chitosan-based nanocomposite in order to minimize environmental pollution caused by overapplication and nonspecific delivery of agrochemicals. Depending on nanofillers, new properties including physical barriers and smart delivery of active compounds could be obtained in the nanocomposite. Besides, results of research indicated that supplying bulk chitosan promotes plant growth and development including innate defense [48]; chitosan NPs were also reported to improve biophysical characteristics

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and antimicrobial activity on several types of plant pathogens [48]. Bioactivity of chitosan-based NPs in plants is directly influenced by physicochemical properties like particle size, size distribution/polydispersity index, and surface charge [48]. On the other hand, application of chitosan-based NPs and nanocomposites containing essential micro- and macronutrients exerts positive effects on several crop yields including horticultural, nonwoody herbaceous fruits and fruit trees [49]. Nanoparticulated nutrients are often applied to formulations since they improve the incorporation in plant cells and, in consequence, minimize nutrient loss. Although these nanofertilizers were sprayed at very low concentrations on plants, they showed very high efficiency in increasing plant growth and quality of seeds and fruits [48]. Some interesting works were studied on preparation and property characterization of chitosan-coated fertilizer with CR. Hence, to improve the utilization of nitrogen (N), phosphorus (P), and potassium (K) compounds as well as water resource at the same time, a new type of chitosan-coated fertilizer of three-layer structure was prepared [50]. The core of this particle was water-soluble nitrogen, while phosphorus and potassium were granular; the inner and the outer coatings were chitosan and poly(acrylic acid-co-acrylamide) polymers, respectively. Both the controllednutritional release and its high water-retention capacity confer to it significant advantages over the current slow-release fertilizers. Although the same authors described that the chitosan in the first layer of the coating material is a biodegradable material and the copolymer poly(acrylic acid-co-acrylamide) in the outer coating material can also be degraded, no experiments on the degradation properties of this material in the soil were included. In this same sense, chitosan NPs were obtained by polymerizing methacrylic acid (MAA) for the entrapment of NPK [51]. Interestingly, when this chitosan-PMAA-NPK nanofertilizer was applied via roots of garden pea (Pisum sativum var. Master B) plants, a significant reduction in root length was detected in a dose-dependent manner. However, CS-PMAA-NPK nanofertilizer had positive effects on growth and productivity upon foliar applications on wheat plant growth in well-drained sand [52]. These apparently contradictory pieces of evidences could be justified on the bases of multiple facts, but they clearly give insights about the putative effect that nanofertilizer delivery system might have in case of being accumulated in soil and how it could impact on different crops cultivated in the same field.

Nanotechnology-Based Agroproducts Challenges According to recent statistics about growing global population, with the current agricultural production levels and their systems, it would be impossible to achieve food security [7]. Conventional agrochemicals and their indiscriminate and extensive use to maximize crop yield and to protect fields from pests and weeds, among others, caused disadvantages regarding environmental impacts and multiple diseases, including animals and human beings. In addition, drastic loss of biodiversity,

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soil fertility, and erosion are other consequences of modern agriculture and traditional agrochemicals [9]. In the context of green nanotechnology and sustainable agriculture, this innovative technology and their applications as smart agroformulations aim to provide solutions in order to minimize nutrient losses, decrease the amount of agrochemical doses, prolong their action, detect environmental pollutants, optimize cost production, increase agronomic yields through enhanced nutrient management, and protect human security. Moreover, it is also necessary to provide knowledge in relation to nanomaterials and their properties, particularly about toxicity issues [7]. Figure 6 illustrates multiple challenges facing nanotechnology-based products to enter the market.

Commercial and Emerging Nanoproducts As mentioned, in contrast to other industrial fields, applications of nanotechnologybased agroproducts continue to be substantially lower. In the last years, this trend has reversed with the rising number of patents from agrochemical companies and original research publications regarding the development of nano-based agroproducts [7]. Unfortunately, in agriculture field, the commercialization of nanotechnology-based formulations is drastically limited and is related to the existence of multiple issues surrounding their usage. Some nanoproducts-wide challenges are high cost associated with their industrial production/processing as well as the difficulty in the scalability of research, the shortcomings in the necessary

Commercial challenges • Difficulties in the scaling • Lack of infrastructure • High economic costs • Inherent limits on agriculture sector

Nanotechnology-based agroproducts challenges Legislation and regulation

• Divergence on nanomaterials regulatory • Evaluate “case-by-case” • Lack of international collaboration

Nanotixicity and Environmental safety • Studies of nanotoxicity over time are required • Apply controls in all stages of life-cycle Public awareness and acceptance • Deficiency in nanotechnology information and advantages

Fig. 6 Multiple challenges faced by commercialization of nanoproducts in agriculture

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infrastructure, economic feasibility of traditional agrochemicals, and limits associated with agriculture field and the implementation of technology [53]. Additionally, the commercialization of nanoformulations must face social perception of the products; in other words, these products may exhibit risks to agriculture and food supply chain and, consequently, impact/damage on environmental safety and human health [36]. Despite increasing agrochemical company patent trend, only a limited number of nanotechnology-based products have reached the market. From the economic perspective, electronic, cosmetic, medical, and pharmaceutical nanomaterials also present high economic costs, but this financial expense is, generally, compensated by high returns [7]. In this direction, one way to decrease costs and expenses is employing NPs derived from renewable natural resources like biopolymers (proteins, polysaccharides) as delivery systems for agrochemicals with low human health and environment impact [36]. Despite the advancements and significant efforts of biopolymers into agro-nanotechnology, the commercialization of nanoproducts from organic origin is still low. It is necessary to put the bio-based polymers with their wide advantages, challenges, and properties in a fundamental role to the implementation, development, and commercialization of this novel technology in the agriculture field. Therefore, it is also essential to carry out studies that focus on the understanding of the fate, transport, behavior, and degradation of NPs in the environment in order to promote safe nanotechnology applications into agricultural sector [53]. Merino et al. [7] have already summarized some breakthroughs in nanotechnology from huge agrochemical companies and institutions. Some examples of these companies that lead nanoformulation production are as follows: BASF German company developed pesticides encapsulated in NPs as controlled-release system; Syngenta American company manufactured nanoemulsions for greater crop efficiency; Bayer German company produced silicate NPs for food production; and Nestlé American company generated nanosensors for pathogen detection and pollutants into food packaging. On the other hand, the University of Kyoto, Clemson, VIT, and Cornell applied nanotechnology to develop nanofertilizers, nanoproducts from agroindustry wastes, and nanoemulsions as herbicide, among others. Fertilizers and pesticides based on nanotechnology are the most commercialized among agroformulations. These nanoproducts oriented for agriculture field have been developed and put on the market by small companies [7]. Table 4 shows the list of some commercial nanoproducts, from organic and inorganic origin, already available in the market with their application and brief description of the nanomaterials that compose them. Details of some nanoproducts with compositions and their advantages, exposed in Table 4, are explained below. Particularly, about commercial nanofertilizers, an Egyptian company produces fertilizers, fungicides, and growth stimulants through normal methods and introduces nanotechnology to promote improvements into agriculture field. More specifically, Saula ® and Vitro NPK are two nanomaterials aimed to improve the utilization of N, P, and K compound as well as supplemented with other metal NPs, such as iron (Fe), Zn, manganese (Mn), Cu, and boron (B), amino acids, and organic acids. On the other

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Table 4 Commercial nanoproducts available in the market Nanoproduct type Nanofertilizer

Commercial nanoproduct Nano-Ag Answer

®

Nanopro ® NanoRise ® NanoGro ® NanoN+™ NanoPhos ® Nanok ® NanoPack ™ NanoCalSi ™ NanoStress ® NanoZn ™ pH5® Saula Drip Saula Solo Saula Motawazen Vitro NPK

AgriHit ™

NovaLand-Nano

Biozar Nano-Fertilizer

NanoMax NPK NanoMax Cal NanoMax Zinc NanoMax Potash NeuCytokin ® NeuCombi ® Nubiotek Nubiotek Nubiotek Nubiotek Nubiotek Nubiotek Nubiotek

®

Ultra HBK Ultra K ® Ultra Mg ® Ultra N ® Ultra NPK ® Ultra P ® Ultra SN ®

Company* Urth Agriculture, USA Aqua-Yield® Operations, LLC, USA

Composition Unknown nanomaterials

Bio-Nano Technology, Egypt

Unknown nanomaterials NPK formulas supplemented with NPs (Fe, Zn, Mn, Cu, and B) NPK formulas supplemented with nanomaterials (Calcium, Sulfur, Mn, Fe, B, Cu, among other NPs) Unknown nanomaterials

Green Earth Nano Science, Inc., Canada Land Green & Technology Co., Ltd., Taiwan Fanavar NanoPazhoohesh Markazi Company, Iran JU Agri Sciences Pvt. Ltd., India

Neu Farm GmbH, Germany Bioteksa, México

Unknown nanomaterials

Mn, Cu, Fe, Zn, molybdenum (Mo), and N NPs Fe, Zn, and Mn NPs

Unknown nanomaterials

Unknown nanomaterials Zn, Fe, Mn, B, Cu, and Mo NPs Unknown nanomaterials

(continued)

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Table 4 (continued) Nanoproduct type

Commercial nanoproduct Nubiotek ® Hyper Bmo Nubiotek ® Hyper CaB Nubiotek ® Hyper FBK Nubiotek ® Hyper Fe +Mg Nubiotek ® Hyper K Nubiotek ® Hyper OXY Nubiotek ® Hyper RFZ Nubiotek ® Hyper Zn VitaSoil Nano Zinc Nano Organic Compound Nano High Nitrogen Compound Nano Low Nitrogen, High Phosphorus, High Potassium Compound Nano High Phosphorus, High Potassium Compound Nano Organic Tag Nano NPK Tag Nano Cal Tag Nano Phos Tag Nano Potash Tag Nano Zinc Argentum

Nanopesticide

Nano-5 ® N-3 ® Nanocu ®

NanoGreen

®

Company*

Composition

Vitasoil Nano Science, Brazil Alert Biotech, India Lazuriton Nano Biotechnology, Co., Ltd. Taiwan

Unknown nanomaterials

Tropical Agrosystem India Pvt. Ltd., India

Unknown nanomaterials

PlantoSys, Netherlands Uno Fortune Inc., Taiwan

Ag NPs

Bio-Nano Technology, Egypt Nano Silver Manufacturing Sdn. Bhd., Malaysia

Copper NPs

Unknown nanomaterials Unknown nanomaterials

Unknown nanomaterials

Bio-ceramics and mixture of metallic oxides

(continued)

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Table 4 (continued) Nanoproduct type

Commercial nanoproduct NSPW-L30SS HTSi

Agro 2400 Agro 2475 Agro 2490

Company* Nanosilva, LLC., USA Nanjing Haitai Nanomaterials Co., Ltd., China Silvertech Kimya San. Tic. Ltd. Şti., Turkey

Composition Ag NPs and silica Silica oxide NPs

Formula with Ag NPs Formula with Ag and Cu NPs Formula with Ag, Cu, and chitosan NPs

*Information is available through company’s website

hand, pH5 ® is a nano-size material used to increase the permeability and adjust pH number. Conversely, a hi-tech Taiwanese company focuses its work on nanotechnology applicability in organic farming. NovaLand-Nano was manufactured as liquid miscellaneous substances trace element fertilizer and contains Mn, Cu, Fe, Zn, molybdenum (Mo), and N NPs. Some advantages are to accelerate nutrient penetration into the plants and speed up plant growth, to increase plant resistance to soil salinization and drought, to improve crop productivity, to contribute seeds germination, and to enhance plant disease resistance. Biozar Nano-Fertilizer ® is a type of biological fertilizer manufactured in Iran to enhance soil fertility and promote growth plant. Biozar Nano-Fertilizer® decreases the application of chemical fertilizers and improves crop yield. Metal NPs of Fe, Zn, and Mn compose the biological fertilizer. On the other hand, NeuCombi ® was developed by a German company. This nanofertilizer is composed of chelated nano-elements (Zn, Fe, Mn, B, Cu, and Mo NPs) and natural phytohormones with nanotechnology. A Brazilian company has developed and manufactured VitaSoil as nanopesticide. This product is a nutrient complex with organic substances that stimulate and promote microorganism’s growth with multiple soil benefits. Another Latin-American company, with business/scientific approach that used nanotechnology in their products, has elaborated two lines of products to enhance yield vegetable crops and fruit trees: Nubiotek ® Ultra and Nubiotek ® Hyper. The first line of products is oriented to restore soil characteristics, and the second line to improve nutrients and their availability. Argentum is another example of nanopesticide that was elaborated by an innovative Netherlander company. This nanoproduct is a bio-based stimulant containing silver (Ag) NPs. They reported benefits to used Ag NPs as biostimulant, such as increase in crop growth and improvement of the absorption of magnesium (Mg), N, Fe, and other elements. Regarding commercial nanopesticides, Nanocu ® was developed by hi-tech Egyptian company and used as fungicide and bactericide. This nanoproduct manufactured with nanotechnology contains Cu NPs in their formula. A Malaysian company developed NanoGreen ® as bactericide product. This nanopesticide is a mixture of bio-ceramics and metallic oxides and presents advantages such as free from harmful ceramics, also can replace chemical fertilizer, improve soil fertility,

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and decrease content of heavy metal elements. Finally, a high-technology Chinese Company manufactured HTSi line nanoproducts, with pesticidal function. These nanopesticides are based on inorganic, nontoxic, and silica oxide NPs. Although commercial nanoproducts available in the market from inorganic origin are quantitatively greater than eco-friendly, biodegradable, and biocompatibility nanoformulations, this trend seems to be balanced with agro-inventions that emerged recently. With respect to nano-enabled patents and publications in agriculture, plant protection, fertilizer, and UV protection inventions/formulas lead in numbers. In this section, some representative nanotechnology-based agro-inventions and their benefits will be revised. Table 5 summarizes the newest emerging nano-inventions, nanoproduct types, and their nano-ingredients. Among nanofertilizer recent patent trends, novel eco-friendly and organic agrobased invention was developed using nanochitin crystal particles in aqueous suspension and mixed with fertilizer to promote plant growth, reduce the dosage of chemical fertilizer, and protect environmental safety [54]. In addition, this invention is produced by utilizing agricultural waste resources and can improve the utilization rate of the fertilizer by 25–50%. Another novel agro-based patent was developed, as aqueous formulation for plant nutrition and fortification, containing two or more metal NPs [55]. Cu, Ag, and Fe NPs were used to manufacture these nanoformulations that, with small proportions, promoted plant growth, decreased the dosage of fertilizer, and, at the same time, reduced environmental impact. A novel nanocomposite fertilizer was prepared using rice as nano-matrix and metal NPs [56]. Mo dioxide or trioxide, Zn oxide, Mn monoxide, dioxide or sesquioxide, zirconium (Zr) dioxide, lanthanum (Ln) sesquioxide, and Mg metal NPs were used to prepare smart nanomaterial with the following benefits: it promotes root and seed system; it protects crop; and it solves all kinds of nutritional deficiency symptoms of rice shoot. To improve the bioavailability of macro- and micronutrients, NPs comprising a nano-matrix core, a release coating layer, and single or plurality of bioactive agent(s) were manufactured as CR system for pesticide, plant growth, fungicide, and insecticide, among others. This novel invention can improve crop efficiency, decrease plant pathogens, and reduce abiotic stress. In relation to biopolyesters and patents, PCL and polyethylene glycol (PEG) were used as release control coating and coronatine as nano-matrix core comprises at least one polymeric material [57]. Other nanofertilizer-based invention was prepared by adding ZnO, TiO2, and other NPs to the NPK nanocomposite for plant nutrition [58]. This aerosol nanoproduct based on foliar application was manufactured to deliver NPK and oxide metal NPs to the plants and exhibits advantages, such as stability of the nanocomposite over time; the dosage can be optimized based on the composition; nanoformulation can increase light absorption; and improvement of fresh weight biomass, root length, area, and diameter. Lastly, a nanofertilizer invention utilizes polymer-based stabilized NPs for the production of self-sanitizing photocatalyst coating for wide agricultural applications: growth stimulation, pre- and postharvest protection, and reduction in water and pesticide dosage [59]. This invention is based on biopolymer chitosan and their derivates as stabilizer and fixator of metal NPs, derivates and others with stabilizers, surfactants, oils, flavors, and amino acids, among others.

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Table 5 Recent agro-inventions based on nanotechnology Nanoproduct type Nanofertilizer

Patent invention Application of nanochitin in improving fertilizer utilization rate Aqueous fertilizer with metal nanoparticles A kind of rice composite nano-matrix fertilizer and preparation method thereof Nanoformulations for plants

Nanopesticide

Nanosensor

Synthesis of nanocomposites and their use in enhancing plant nutrition Photocatalyst polymeric coatings and their uses in sustainable agriculture Light/pH double responsiveness sodium alginate derivative and the preparation method and application thereof Double-loading nanopesticide sustainedrelease capsule for preventing and treating rice sheath blight disease and preparation method thereof Nano-photolysis-resistant controlled-release pesticide with lignin as coating matrix and preparation method thereof Nano-pesticide composite preparation based on phosphate and metal ions and preparation method thereof Nanoparticles of titanium salts obtained from Trichoderma harzianum for the control of agricultural pests Cationic carbon dot, preparation method thereof, and application thereof in nano-silver detection

Nano-ingredients Chitin nanocrystals

Patent number CN 111116263 A

Ref. [54]

Two or more metal NPs Nanocomposite based on starch as nano-matrix and metal NPs PCL – PEG NPs

ES 2726996 T3

[55]

CN 110511094 A

[56]

US 2018/ 0343854 A1 WO 2018005930 A1 BR 1020170079147 A2 CN 110183549 A

[57]

PLA nanocapsules

CN 110786324 A

[61]

Lignin nanocapsules

CN 110946133 A

[62]

Nanocomposite based on phosphate as matrix and metal NPs TiO-TiO2 NPs

CN 110881462 A

[63]

BR 102018013348 A2

[64]

Cationic carbon quantum dot

CN 110724527 A

[65]

NPK and metal oxides NPs Metal NPs

Sodium alginate nanocapsules

[58]

[59]

[60]

(continued)

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Table 5 (continued) Nanoproduct type

Patent invention A kind of chemiluminescence nanosensor and its application for detecting remains of pesticide thiram Field-effect nanosensor for detecting simple metabolites in living organisms

Nano-ingredients Gold nanograins

Patent number CN 109387503 A

Ref. [66]

Graphene nanoribbons

WO 2020039377 A1

[67]

Inventions have been developed in relation to nanopesticides as CR systems of agrochemicals; among the newest nanopesticides patents, novel pH/light double responsiveness sodium alginate for CR of nanometer 2,4-dichloro benzene ethoxyacetic acid pesticide was manufactured [60]. This novel eco-friendly nanomaterial provided the following advantages: good water solubility, degradability, and biocompatibility. Other bio-based nanoformulation was developed with nanocapsules of PLA containing double-loading pesticide for sustained release for pesticide [61]. Many nanoformulations could be prepared following the steps of this invention, and their benefits are high performance of slow release, good effective utilization rate, crop protection, easy preparation process, and contribution to industrialization. Another eco-friendly nanopesticide, used as CR system, was developed utilizing lignin as coating matrix [62]. In addition to presenting good photolysis and oxidation resistance, this nanotechnology-based invention showed good slowrelease effect and has high and controllable drug loading. Novel nanopesticide composite was manufactured based on phosphate and Zn, Cu, Fe, cobalt (Co), calcium (Ca), Mg, Mn, and Ag ions NPs [63]. This hybrid nanocomposite can be synthesized through one-step, present pH stability, low-cost production and can be loaded with different pesticides. Finally, NPs of titanium oxide and dioxide (TiO, TiO2), obtained from microorganisms, were manufactured to control agricultural fungicide, particularly, control of Sclerotinia sclerotiorum [64]. In recent years, nanosensors in agriculture have gained attention, increasing patent numbers and origin scientific publications. In this sense, nanosensors with the ability to detect metal or pesticide have been developed to ensure environmental safety [68]. A nanosensor was prepared using cationic carbon quantum dot to detect Ag NPs [65]. Through electrostatic action, this cationic carbon quantum dot can monitor and detect Ag NPs quantitatively or semiquantitatively by changing their fluorescence characteristics. Cationic carbon quantum dots can combine with nanoAg colloids and produce a fluorescence response, depending on the concentration and the size of nano-Ag. Gold nanograins were used to develop nanosensors with chemiluminescence property and detect the application of remains of thiram pesticide [66]. By gold chemiluminescence, their nanograins generate optical signaling at thiram pesticide presence. This invention presents advantages such as high sensibility and selectivity to monitor pesticide at real time and cheap and simple device.

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Carbon-based nanostructured materials were used to detect and measure metabolites in living organisms [67]. Due to their electrical properties, graphene is susceptible to donor analytes and electron receptors, allowing different molecules to be absorbed on their surface. Graphene-based nanostructured sensors can change their electronic properties when linked with biomolecules.

Nanotoxicity and Environmental Safety Nanotechnology-based products and their applicability into agriculture as CR systems for agrochemicals may represent a pollution source into environment, food chain, and human health, i.e., produce nanotoxicity [8]. Due to the wide variety of chemicals used into agriculture field, differences in geographic/meteorological characteristics, and dosage quantity of chemicals employed, analyzing nanoproducts impact on human health and the environment is a hard work. As a result, researchers have focused their studies on NPs and their toxicity to protect the environment and human health from the detrimental impacts of nano-sized agro-composites. The ecotoxicology studies of nanomaterials are important to study NPs and their delayed effects of environmental exposure. Unfortunately, most of the work associated with agrochemicals over time was developed as laboratory tests over relatively short periods of time. Current data suggests that the efficacy of agrochemicals in the field may be quite different to that suggested in laboratory trials, and, therefore, studies considering performances across a range of scales are considered very valuable [8]. In general, larger particles are less toxic than NPs with identical chemical composition. A wide variety of physicochemical and surface properties such as size, area, and reactivity give complexity to nanotoxicity [7]. According to several authors [68, 69], toxicity of nanoformulations can be affected by different factors, such as duration of exposure, particle size and aggregation, particle size and shape, surface area, types of plant species, environmental conditions, and coating. • Duration of exposure. Major quantity of NPs can penetrate the cell and produce negative effects depending on the molar concentration and the exposition time. • Particle size, concentration, and aggregation. There are divergent reports about concentration of NPs and their toxicity. Aggregation may occur when high concentrations of NPs are added. For this reason, this cumulative of NPs promotes an increased size, nano-size to micro-size, hindering cell penetration and losing their toxicity. • Particle size and shape. Different NPs aspect ratios can produce dissimilar toxicity levels, i.e., NPs present shape-dependent toxicity. • Surface area. The toxicity level and surface area are totally related. An increase of surface area of NPs causes the same effect on toxicity level. • Types of plant species. Differences in the toxicity of NPs could be attributed to variability in the size of seeds and the single-leaf and xylem structure of doubleleaf plants.

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• Environmental conditions. Environmental factors such as light irradiation, soil organic matter, pH, salinity, temperature, coexisting pollutants, and NPs ionic strength modify nanotoxicity behavior. • Coating. The surface of any material is another factor which contributes to NPs toxicity. In general, coatings have benefits since they reduce toxicity, enhance NPs stabilization, and prevent NPs agglomeration. In order to analyze the toxicity and to develop environmental risk assessment studies, nanoformulations must be compared with conventional agrochemicals in relation to freely dissolved ions [70]. Nanotoxicity can be associated with the electrostatic interactions with active ingredients nanomaterials and their concentration in the cytoplasm [54]. Particularly, nanotoxicity and ecotoxicity can be related to some metal oxides NPs, such as TiO2, ZnO, and SiO2. These molecules are photochemically active, i.e., they produce superoxide radicals when they are exposed to light and oxygen and cause plant oxidative stress. In this direction, several works reported that encapsulation of active ingredients decreases their cyto-, gen-, and ecotoxicity in comparison with conventional agrochemicals [54]. Particularly, in the study of Guan et al. [71], a novel photodegradable nanoformulation was prepared based on encapsulation of nano-imidacloprid, as pesticide, with chitosan and sodium alginate as bio-based coating. They investigated the residues of imidacloprid and nano-imidacloprid in a soybean field and concluded that the use of biopolymercoated nano-imidacloprid formulations reduces deposit in soil during the experience, in comparison with the suspension concentrate of imidacloprid. In the review of Iavicoli et al. [8], they exposed that a potential strategy to address agricultural nanotechnology risk study could be a suitable management plan that includes hierarchy of controls. In this direction, this control plan should promote actions in order to eliminate or substitute exposures and, at the same time, apply administrative controls in all stages of life cycle of nano-based formulations. Understanding and knowing the relationships between nanocomposite properties and biological impacts continues to be a priority to modify some nanomaterial features and, thus, minimize and/or mitigate their nanotoxicity and harmful environmental effects [8]. Summarizing, the development and production of nano-agroformulations is hindered by, in first place, high costs and, secondly, lack of nanotoxicity and environmental safety studies. In relation to the last point, environmental risk assessment study is mandatory before these can be placed in market [36].

Regulation and Legislation It is imperative to balance the growth of social acceptance of nanotechnology with regulatory changes, in order to apply nanomaterials in agriculture field and, at same time, protect the environment and human health from potential risks [8]. In this way, regulation and legislation not only play a key role for the application of nanotechnology

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but also in the marketing of their products, in addition to serve as source of public knowledge and awareness [72]. Currently, the major part of nanomaterial regulatory framework is based on size criteria (50

Phaseolus vulgaris

CeO2NPs

10–30

98% 99% Zn (II) 90% Cu (II) 90.2% – – 84.5% Cu (II) 87.2% Cd (II) >90% >45%

References [18] [19] [20] [21] [22] [23] [24] [25] [26] [27]

Removal of Gaseous Pollutants With industrialization becoming an increasingly demanding aspect of globalization, the problem of air pollution aggravated and became much more extensive. The release of the hazardous air pollutants from industries and emissions from coal-fired power plants or automobiles is suspected of causing serious harms to humans including cancer, birth defects, cardiovascular problems and reduced fertility. The release of the hazardous air pollutants from industries and emissions from coal-fired power plants or automobiles is suspected of causing serious harms to humans including cancer, birth defects, cardiovascular problems and reduced fertility. The reduction of these gaseous pollutants by the application of thermal oxidation requires a large amount of energy which is not cost-effective and against the protocols of “sustainable chemistry.” Taking this into consideration, more efficient techniques involving adsorption can be developed for effective removal of the undesired pollutants from the atmosphere [28]. A number of studies in this discipline have unveiled the efficiency of nanoclay minerals in the adsorption of polar and nonpolar gases, and in this regard special mention can be made to the pillared nanoclays which have gained a wide importance in the pollution abatement at present time. Nanoclays have emerged as a fascinating choice to grasp the attention of the scientists and can be applied to minimize and eliminate the gaseous contaminants due to their hydrophobic and hydrophilic features. Molina-Sabio et al. investigated the potential utilization of sepiolite, activated carbon, and mixed pellets and fabricated a novel mixed activated carbon-clay pellet for its application as adsorbents of polar gas molecules such as NH3 and H2S. The dual role of sepiolite, as a binder for other materials and also as an adsorbent due to its polar character, broadens its application discipline [29]. Nguyen-Thanh et al. carried out alteration of Na-montmorillonite with iron to introduce active centers for selective adsorption of hydrogen sulfide [30]. The iron doped clay samples within the interlayer space of aluminum-pillared clay evolved as the most suitable adsorbents for hydrogen sulfide in spite of the decrease in microporosity than the initial pillared clay. These samples had

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Table 3 Removal of various gaseous contaminants using different clays [8] Pollutant p-Xylene n-Hexane Benzene SO2 SO2 SO2 SO2 H2S H2S H2S H2S

Clay mineral Na-montmorillonite Montmorillonite Palygorskite Zeolite Zeolite clinoptilolite Zeolite clinoptilolite Zeolite clinoptilolite Kaolinite Bentonites Montmorillonite

Removal (%) – – – >95% >24% – – – – –

References [31] [32] [33] [34] [35] [36] [37] [38] [39] [30]

better adsorbent efficiency than the samples modified with iron oxocations. Differences in the chemistry and the degree of dispersion of the iron species and also the accessibility of the small pores for H2S result in the variations in the adsorption capacity of the different clay samples. Table 3 summarizes recent studies of the application of clay minerals for the removal of various gaseous contaminants. Furthermore, nanoclays are promising alternatives for air pollutant removal which originate from diverse sources, but their adsorption efficiency depends on the nature of pollutants, the characteristics of the sorbent, and physicochemical environmental factors. Besides, application of the hybrid sorbents could be a prospective approach to elevate the pollutant removal efficiency.

Large-Scale Application Nanoclays are natural materials with pores in the nanometer dimension that have gained a considerable attention worldwide. They display advantageous properties which make them viable alternatives for its utilization as adsorbents of polluting metals in water, amidst which their affordable cost, easy availability, large surface area, and ability to exchange ions are mentionable. The possibility for interlamellar spaces in clay minerals to swell is the underlying reason why they are efficiently employed in the adsorption of water contaminants. The calcareous shale of the Soyatal Formation in Zimapàn, Mexico, contains kaolinite and illite, which adsorb arsenic. This aspect was utilized by the research community to develop an economical, low-technology remediation system [40]. The utilization of synthetic hydrotalcite (HT) nanoclay for the removal of arsenic was demonstrated by Gilmann in order to develop a simple and convenient technology for the purification of water in domestic or large-scale community levels in underdeveloped regions [41]. HT clay underwent modification with ions of chloride, nitrate, and carbonate. Employment of NO3–HT and Cl–HT in batch experiments

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reduced the As (III) concentrations in water below the recommended permissible limit of 10μg/L. Cl–HT was finally used to fabricate a cost-effective continuous filter system involving porous pots or filter candles inserted into the base of vessels. A novel adsorptive mixed matrix membrane with amino acid modified montmorillonite was fabricated by Shokri and Yegani that removed arsenic up to 96% with the ability to recycle [42]. Evaluations of nanoclays as adsorbents have clearly displayed that clay-based material can be used successfully for remediation of wastewater. They are natural, cheap, eco-friendly, and nontoxic, which can be used to provide pure consumable water in developed as well as developing countries. Large-scale commercial water treatment plants by the employment of natural and modified nanoclays are envisioned to attain great advancement in the future.

Nanotubes One-dimensional carbon nanotubes (CNT) are cylindrically straight tubules with diameters measured in the range of nanometer. The accidental discovery of carbon nanotubes in 1991 while studying the graphite electrode surfaces in an electric arc discharge diversified the carbon chemistry and triggered an explosive advancement of research worldwide. Improvements in the synthesis techniques have resulted in the scaling up of production of pure nanotubes, assisting a whole range of promising applications. These tiny carbon nanotubes, in particular, are willing to surpass fullerenes in its competition to the technological marketplace due to its remarkable structure, properties, and topology compared to the parent, planar carbon fibers. The novelty of the nanotubes arises from their size, structure, and topology which provide them with remarkable mechanical properties of high stability, enhanced strength, and stiffness in addition to their low density, elastic deformability, significant adsorption properties, and selectivity [43]. Carbon nanotubes have an inherent subtlety in their structure which is the helical arrangement of the carbon atoms in hexagonal arrays on the honeycomb lattices present on the surface. The novel electronic properties of the carbon nanotubes along the diameter generate a diverse range of exciting electronic device applications [44]. The surrounding carbon atoms of the cylindrical pores of the CNTs interact with the adsorbent molecules. This interaction between the adsorbent molecules and solid surface relies greatly on the size and geometry of the pores. When a molecule is placed in a slit-shaped pore between two flat surfaces, it interacts with both its surfaces, and the extent of the overlap depends on the pore size. However, for pores that are cylindrical and spherical shaped, the resulting potentials are prominent due to the interaction of more surface atoms with the adsorbed molecule [43]. Carbon nanotubes are highly graphitic than activated carbons. Besides, the surface of CNT is highly aromatic comprising a high density of π electrons. These factors enhance the efficiency of adsorption of the carbon nanotubes. Hence, in comparison to activated carbons possessing pores of either wedge or slit-shaped, they can absorb molecules much more effectively [43].

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Removal of Heavy Metals Heavy metals are naturally occurring elements with high atomic mass and density. With the advancement and exponential increase of the applications of heavy metals in industries and domestic and other various medical sectors, there have been raising concerns over their acute toxicity on the health of living organisms and environment contamination [45]. It is associated with several health risks interfering with the metabolic processes and leads to cancer, disruption of the central nervous system, and accumulative poisoning [46]. Lead, a particularly insidious hazard, is pervasive in our environment and has the potential of causing deleterious health effects interfering and affecting the central nervous system and hepatic and renal systems. It is nonbiodegradable, and hence various strategies of lead removal from wastewater have been developed, amidst which adsorption with activated carbon is frequently used. The discovery of carbon nanotubes with high adsorption capability has attracted the fancy of the research community worldwide. Li et al. reported that CNTs have enhanced lead adsorption efficiency and can be employed as an adsorbent for lead removal from contaminated water [47]. It was demonstrated that the efficiency of Pb2+ adsorption of CNTs elevates after oxidation with nitric acid and greatly depends on the pH of the solution. In another study, the adsorption thermodynamics of Pb2+ on CNTs and the thermodynamic parameters (Ko, ΔGo, ΔHo, and ΔSo) at temperatures of 280 K, 298 K, and 321 K have been obtained [48]. Desorption studies revealed that Pb2+ can be easily eliminated from carbon nanotubes by changing the pH of the solution by treating with HCl and HNO3, thus unveiling the promising predominance of CNTs for wastewater treatment. Lu et al. purified commercially available single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) with sodium hypochlorite and demonstrated the adsorption characteristics of zinc from water. There has been a considerable enhancement in the purity of the nanotubes, structure, and nature of the surface after their purification which compelled them to be a suitable applicant for adsorption of Zn2+. The maximum adsorption capacities of Zn2+ calculated by the Langmuir model are 43.66, 32.68, and 13.04 mg g
1 with SWCNTs, MWCNTs, and PAC (commercial powdered activated carbon), respectively, at an initial Zn2+concentration range of 10–80 mgL
1 [49]. Likewise, amorphous Al2O3 supported on carbon nanotubes (Al2O3/CNTs) has shown enhanced adsorption efficiency for its applications in fluoride removal from water at a pH range of 5.0–9.0 [50]. In another study by Li et al., aligned carbon nanotubes (ACNTs) were demonstrated as promising candidate for the removal of fluoride from water. This unusual carbon material was synthesized by catalytic decomposition of xylene using ferrocene as catalyst [51].

Removal of Organic Water Pollutants Carbon nanotubes have been widely utilized for the removal of organic pollutants like 1, 2-dichlorobenzene, n-nonane, and CCl4 from water. The spontaneity and high affinity for the adsorption process has been predicted from thermodynamic calculations [52]. Unique features of commercial CNTs such as purity, structure, and nature

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of the surface can be greatly intensified after its treatment with acid. This modification can provide CNTs advantage over other adsorbents and can be employed for the effective removal of trihalomethanes from wastewater [53]. Agnihotri et al. employed gravimetric techniques to determine the adsorption efficiencies of commercially available carbon nanotubes for organic compounds such as toluene, methyl-ethyl-ketone, hexane, and cyclo-hexane at relative pressures and isothermal conditions [54].

Large-Scale Applications CNTs have been crowned as encouraging materials to be utilized in various environmental fields. The relatively expensive approach of synthesis is one of the prime drawbacks for the large-scale applications of CNT. Recently, the possibility of low-cost mass production of high-quality CNTs was reported. Nanothinx, a spinoff company of the Institute of Chemical Engineering and High Temperature Chemical Processes (ICE-HT), was able to successfully reduce the cost of CNT production by employing a low-cost novel catalyst developed by them. Studies showed that liquefied petroleum gas as carbon source material and the ceramic substrate sphere could be utilized for the cost-effective synthesis of high-purity CNTs. The mass production of CNTs has led to the commercialization and field application of this technology. Freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimeters, are used as filters. They have potential utility for the removal of heavy hydrocarbon components from petroleum in a single filtration step and the production of bacterial free water for consumption [55]. A crucial advantage of these macro-filters over conventional filters is that they can be reused by simply cleaning after each filtration process through repeated ultrasonication and autoclaving, hence regaining their filtration efficiency. Also these filters are robust and devoid of any cracks or surface defects and gave reproducible results. Because of the exceptional high thermal stability of the nanotubes, they can also be operated at ~400  C, which are multiple times higher than that of conventional polymer membrane filters (~52  C). Enhanced mechanical stability, high surface area, and convenient and cost-friendly fabrication of the nanotube membranes may allow them to compete with commercially available ceramic- and polymer-based separation membranes.

Paper Towel Oil spill is the contamination of seawater due to leakage of petroleum as a result of human negligence or an accident. This causes long-term environmental damage and makes the area unsuitable for aquatic habitat. It damages the delicate underwater ecosystem by killing and contaminating fishes and disturbing the global food chain. Commercially available conventional materials absorb oil from water but do not display selectivity. This results in the reduction of oil-capturing efficiency as

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they absorb some water accompanying the oil. Recently, Stellacci and coworkers of MIT unveiled a mat of nanowire fabric made of potassium manganese oxide that is thermally stable and is capable of absorbing up to 20 times its weight in oil while refusing water with its hydrophobic coating [56]. This could be a crucial invention for its application in the cleanup of oil and also other organic pollutants towards environmental remediation. This hydrophobic membrane material is completely impervious to water and remains dry even when soaked in water medium for over a month. They can also selectively remove lipids like oil from the ocean. Furthermore, the oil-loaded membrane can be subjected to heating above the boiling point of oil so that the adsorbed oil evaporates. Once the oil is removed, the nanowire mesh can be reused and recycled. By condensing the evaporated oil, the recovery of oil is possible. Both the membrane and the oil can be put to repeated use. Moreover, production of this nanowire mesh is economical and can be fabricated in bulk quantities. The interwoven mesh is so thin that the fabric looks and feels like paper. Like a paper towel, Seaswarm uses this thin nanofabric to suck up surface spills perfectly. In addition to its application in environmental remediation, it can also be successively employed in filtering and purification of wastewater. This weightless characteristic helped to come up with the idea to build a vehicle that could smoothly glide over the surface of the water in the days to come.

Self-Cleaning Glass After years of continued research and advancement leading glass manufacturer, Pilkington has made the impossible dream a reality for many households. World’s first self-cleaning glass was fabricated with a thin microscopic dual action coating [57]. Pilkington Activ™ range of products aggregates both the properties of selfcleaning and solar control, making them highly advisable among the modern generation looking for glass cleaning solutions. External window cleaning and maintenance has been simplified by the commercial accessibility of glass cleaning agents but is unable to overpower the potency of the novel “self-cleaning glass.” As the name suggests, they can clean dirt present on its surface and require least maintenance. They are coated with transparent and highly reactive nanocatalyst titanium dioxide using a vacuum coating technique called chemical vapor deposition. TiO2 exhibits both photocatalytic and photo-induced superhydrophilic properties. When ultraviolet light hits the glass coated with TiO2 nanoparticles, electrons are generated which convert water molecules into hydroxyl radicals by chemical reaction. This can be attributed to the photocatalytic nature of the nanocatalyst. These radicals degrade the organic dirt. When rainwater hits the glass covered with dirt, it spreads out evenly, washing away the loosened dirt with it and quickly drying without leaving any dirt marks. This technology can also be utilized for the manufacture of self-cleaning solar panels, exterior of buildings, and ocean exploration vessels. It was demonstrated that a layer of organic contaminants of a thickness of up to 10 nm can be cleaned within 1 h exposure to sunlight.

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Solar Active Cloth Black titania (BT) reaps the benefits of a full-spectrum solar absorption and is much active than the commercially available photocatalyst, white titania (P25) [58]. Synthesis of BT involves treating of P25 with H2 under high pressure at about 200  C for 5 days. So, there emerged the need for another simplified synthetic route which would speed up the reaction time and also simultaneously enhance the efficiency of solar absorption. Treatment of P25 with hydrogen plasma converts it into BT (TiO2xHx) of improved solar absorption (83%) in 4–8 h at 500  C. Its nanoparticle exhibits admirable photocatalytic activity and exceptional stability for the degradation of methyl orange which can be entirely attributed to its crystalline-core disordered-shell microstructure. Substitution of the conventional gaseous/plasma hydrogen with hydride powders (NaBH4, N2H4, CaH2, TiH2, etc.) and later releasing molecular hydrogen under mild calcination conditions oversimplifies the conventional synthetic routes. For example, a gel prepared from TiO2 sol with the use of NaBH4 and successive calcinations at 500  C in argon atmosphere converts it to BT in 1.5 h. This method is efficient for the synthesis of black titania in bulk amount and produces in batches of 100 g. However, the desired product can be achieved after washing the crude product to remove the residual Na. Providing fresh and affordable drinking water is one of the challenging obstacles faced by the global community. The growing population and industrialization has led to the increase of contamination of water bodies. At this crucial time, nanotechnology has come to aid and offered innovative solutions for the practical large-scale wastewater treatment applications. This requires the employment of a bulk amount of inexpensive nanomaterials that are also additionally stable, thermally, chemically, and photochemically. No doubt the commercially available white titania P25 assures all the abovementioned benchmarks, but BT with comparable cost and much advanced photocatalytic performance of 83% claims the opportunity. To make the process of wastewater treatment more cost-effective, the nanomaterials used should persist for a longer duration and be able to be recovered at ease for its repeated use. In this regard, immobilization of BT on a high surface area three-dimensional graphene support (BT/3DG) is highly desirable. It provides preconcentration and simultaneously enhances the photocatalytic activity including easy, effective solidliquid separation and recovery. The use of TiO2-x for BT in BT/3DG revealed extraordinary photocatalytic activity and light harvesting features as compared to BT alone. For example, BT/3DG powders efficiently photodegrade MO completely in only 4 min. To accomplish field applications of BT/3DG, a solar active cloth was developed in which BT/3DG hybrids were bonded by a polymeric binder to a nonwoven cloth. This fabricated cloth was buoyant and easily floated on water. It exhibited interesting results of MO degradation in only 10 min. Water remediation studies using the cloths were studied at multiple locations of contaminated water, and it was observed that there occurred a noticeable decline in the total organic carbon (TOC), nitrogen, and phosphorus contents of the treated water and also a significant visible variation in the appearance of the color. This further reduced primary and secondary treatment and

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eventually minimized the cost. So the solar active cloths, which were usually effective for advanced oxidation process (AOP), can also be employed in water remediation techniques without any primary or secondary processes. So far, 8 tons of black titania and 100 kg of 3DG have been utilized to fabricate solar active cloths for the successful remediation of 600 acres of contaminated water at different locations in China.

Transparent Polyurethane Nanofiber Air Filter Fine particulate matter (PM) is an aggregation of numerous solid fine minute particles and droplets of water-soluble ions and other inorganic and carbon containing compounds. Fine particulate has been accredited as a serious threat and is largely released from the combustion of garbage and fossil fuels. PM can be mainly classified into two categories: PM2.5 and PM10 according to the diameter of the particulate matter. PM10 has a limited travel distance and stays in the air for a short time ranging from a few minutes to few hours. Contrastingly, PM2.5 has a longer residence time in the atmosphere and can persist from a number of days to a few weeks. It can enter the body through inhalation and accumulates in the respiratory system, mainly the trachea and lungs, causing serious health hazards such as inflammations, vasoconstrictions, malignancies, and premature death. PM2.5 also affects the ecological environment, disrupting the rainfall patterns and also leading to hazy weather. It is a destructive factor to climate and ecosystem. In this respect, it becomes very important and essential to take measures and control against this particulate matter. In the present day, professional dust masks are available as an outdoor personal protection against severe haze that can effectively block the particulate matter allowing only clean air to pass through. Indoor personal protection equipment such as ventilation systems and air purifier are expensive, are not easy to install, and require constant maintenance for the filter elements. To cut it short, they are not consumer-friendly. The indoor air filters which are used for air protection in commercial buildings rely on a huge cost for pumping systems in exchange for air. Taking this into account, recently, two transparent air filters for its use in residential buildings by window passive ventilation have been developed for consumer purpose. One is porous membrane filter which suffers a drawback of low porosity of the filter, and as a consequence, high ventilation cannot be achieved. The other consumer product to be mentioned is nanofiber air filter with porosity of about 70% and provides high ventilation. A variety of window screens have also been developed to safeguard the quality of indoor air with the application of nanofiber. However, as of today, almost all of the existing nanofiber-based air filters that have been developed failed to simultaneously meet the obligation of high-performance air PM filtering and removal efficiency, low resistance to airflow, and long service life. Hence, for the first time, Chen et al. reported a method for the fabrication of thermoplastic polyurethane (TPU) nanofiber air filters using electrospinning method. The TPU concentrations in polymeric solutions can be modified for tuning the average diameters

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of TPU nanofibers [59]. Recently, electrospun polymer nanofiber networks have been developed as transparent air filters for selective removal of PM2.5. Nonetheless, it still remains a question of challenge to uniformly coat the nanofibers on the window screens cost-effectively and on a large scale. Khalid et al. demonstrated a fast and efficient blow-spinning technique that is independent of high voltage consumption for the large-scale direct coating of nanofibers onto window screens for indoor PM pollution protection. Air filter of 80% transparency and a standard removal efficiency of more than 99% were successfully achieved for PM2.5. A practical test on a real window (1 m  2 m) in Beijing has showed that the nanofiber transparent air filter acquired exciting PM2.5 removal efficiency of 90.6% over 12 h under extremely hazy air conditions [60]. The technology of electrospinning has received extensive praise on account of its minimal energy consumption, easy operation, and eco-friendly approaches for the fabrication of nanofibers [61, 62]. Fibers prepared have enhanced porosity and high specific surface area. A TPU nanofiber air filter has been developed that can be manufactured on a large scale using a spinning bead spinneret [63]. It exhibited high thermal stability, optical transparency of 60%, high PM2.5 elimination capacity of 99.6%, long lifetime, magnified ventilation rate, and weightlessness.

Nanocontact Sensor Taking into account the difficulties and the obstacles that remain inherent at the contaminated sites polluted with toxic heavy metals, it becomes very essential and a pressing demand for the fabrication of an in situ sensor that is sensitive enough to monitor the heavy metal ion concentration before it extends above the permissible limit. Nanocontact sensor comprises of an array of pairs of nanoelectrodes on a silicon chip [64, 65]. The electrodes in each pair are set apart from each other in an atomic scale gap, which is attained by the technology of quantum tunneling. Any electrochemical deposition of even a trace amount of metal ions into the gap can bridge the gap forming a nanocontact between the electrodes, thus stimulating a quantum jump in the electrical conductance. In addition to its extraordinary sensitivity, it is miniaturized, environmentally benign, and cost-friendly which gives it a best opportunity to claim its position for the initial on-site screening test of polluted samples, consequently leading to early threatening and prevention of heavy metal ion pollution.

MoS2 Sponge Oil spillage and discharge of organic solvents and chemicals by the industries into the water bodies have deteriorated the environment resulting in significant energy losses and ecological problems both to the mankind and other life forms. Superhydrophobic sponges have emerged as a potential material and have attracted the fancy of the scientists by their inherent attractive properties including low density,

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affordable price, and high mechanical flexibility and stability. These characteristics render them suitable for selective adsorption of oils and solvents. Wang et al. first reported a convenient and affordable dip coating technique for the fabrication of superoleophillic and superhydrophobic MoS2 sponges. These sponges absorb a wide variety of oils and organic solvents with enhanced selectivity and absorption efficiencies, good recyclability, and high chemical inertness. In addition to this, these sponges can be employed for the continuous absorption and removal of oil pollutants from aqueous bodies by coupling it with a vacuum. The proposed preparation method for the fabrication of MoS2 nanosheet sponges was simple, convenient for scaling up, and cheap and does not insist the use of expensive complicated treatment. Exfoliation of economically powdered MoS2 crystals by ultrasonification in ethanol was carried out. Then, a commercially available three-dimensional porous melamine formaldehyde sponge (MF sponge) was used as a frame for MoS2 coating that has the potentiality to absorb both oil and organic hazardous solvents. The MF sponge underwent a color change from white MoS2 sponge to black after it was immersed in the MoS2 solution by squeezing and degassing method. Finally, after drying, it yielded the MoS2 nanosheet sponge. This dipping and drying process was repeated a number of times to ensure a homogeneous, consistent, and regular MoS2 nanosheet coating. The adhesion of the physical coating of the MoS2 nanosheets onto the sponge framework can be firmly attributed to the mechanical flexibility of the nanosheets and strong van der Waals interaction between the sponge and the MoS2 nanosheets [66–68]. To test the high porosity and the superhydrophobicity of the MoS2 nanosheets and to validate how they would respond as an effective absorbent to organic pollutants, two organic solvents with varying densities were chosen. Rapeseed oil, which served as the first model absorbate as a layer on the aqueous surface, was entirely absorbed by the MoS2 nanosheet sponge within seconds resulting in clear transparent water. Chloroform which is denser than water and sinks to the bottom was also rapidly sucked in by the fabricated sponge. This high absorption capacity could undoubtedly be attributed to the oleophilic nature, capillary action, and the enhanced porosity of the nanosheets. Their absorption capacities are potentially higher than commercially available fabrics, nanowire membranes, and microporous polymers and are comparable to those of ultraviolet carbon aerogels. Moreover, the sponges could be mechanically squeezed out to gather the absorbed oils and can be recycled. For practical large-scale applications, it became necessary to develop a novel, continuous, and efficient method for harvesting oil in situ from an aqueous surface comprising of pipes and peristaltic pump [69, 70]. It was demonstrated how the absorption of pure oil by the MoS2 nanosheet sponge flowed to the collecting cup through the pipes allowing the sponge to repeatedly gather the oil for more than 10 h without any decrease in the working efficiency [71]. This clearly indicated the working stability of the MoS2 sponges. Disturbing the sponge also did not exert any influence on the oil removal efficiency. This novel procedure makes the segregation of oil-water emulsions much simpler and brings us a step closer for the possible applications of remediation of oil spillage.

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MoS2 Nanopores The engineers of the University of Illinois have developed an energy-efficient material for the desalination of seawater with the employment of a nanometer thick sheet of molybdenum disulfide (MoS2) having tiny nanopores [72]. It was especially fabricated to allow substantial volumes of water through selectively preventing the salt and various other pollutants. The research team unveiled that MoS2 sheets had enhanced efficiency (70%) than conventional graphene membranes. Commercially available membranes have pores small enough to prevent salt or impurities, allowing water slowly through it which is time-consuming. These membranes are moderately thick and so demand a good amount of pressure to be administered for filtering at the molecular level. Moreover, reverse osmosis is not efficient and costly and suffers clogging. In this context, scientists have been continuously trying to develop graphene nanomembranes despite of its underlying drawback as it interacts with water. A MoS2 molecule comprises of a molybdenum atom sandwiched between two sulfur atoms. The possibility of generating a pore in the sheet will allow an exposed ring of molybdenum around the center of the pore to be left behind fabricating a nozzle-like shape that drew water through it. Additionally, the monolayer sheets of MoS2 are thin and energy efficient which in turn dramatically decreases the operational costs. MoS2 is a robust material and withstands the necessary pressures and water volumes. Nanotechnology could play a key part in the designing of desalination plants, thereby reducing the cost and making them energy efficient.

Zeolite Cotton It has become very demanding and utmost necessity to develop an economically viable household water treatment (HWT) for delivering water in an efficient and robust way for the underdeveloped regions. Chen et al. demonstrated a convenient flow through filter made by zeolite cotton packing in a tube (ZCT), an affordable device to filter out heavy metal ions from polluted water [73]. The zeolite cotton is constructed by an on-site template-free growth of mesoporous single crystal chabazite zeolite onto the surface of cotton fibers. The device displayed high ion removal capacity, short flow time, reliable supply, easy operation, and strong stability simultaneously. A 65 mL 1000 ppm Cu2+ solution was purified and reduced to its permissible limit ( 4Agþ ðaqÞ þ 6H2 O

ð1Þ

Another approach is based on the work of Morones et al. [31] who found AgNPs attached to the cell membrane and inside the bacteria by TEM analysis. As Ag possesses high affinity for sulfur and phosphorus compounds, it can be anticipated that AgNPs will react with sulfur-rich protein in the bacteria cell membrane and interior of the cell or with phosphorus-containing compounds such as DNA. Therefore, detected morphological changes in the cell membrane of bacteria and possible damage of DNA initiated by reaction with AgNPs have adverse effect on the respiratory chain or cell division processes, causing a cell death. This chapter gives an overview of latest developments in application of silver nanoparticles as an additive in paint industry.

Ag-Nanoparticle-Embedded Paints The major research on the functionalization of paint with AgNPs is focused on wall waterborne paints. These paints, commonly acrylic-based, are suitable environment for bacteria and fungi to grow, due to the fact that they contain cellulosic compounds as thickeners. These compounds can be used by the microorganisms as carbon source producing degradation of the paint: stains, color changes, chalking, and adhesion loosening can be seen in an attacked paint. Silver is usually added to the paints as nanosilver, silver salts, or silver zeolite. Although today the technology to use engineered nanomaterials in paints is still in its infancy, there are quite a number of articles which report about the antimicrobial effects of nanosilver in paints [8, 11, 13, 26]. It was clearly demonstrated that nanosilver in paints was very effective in killing resistant microorganisms, such as Gram-positive and Gram-negative bacteria, fungi, and yeasts. The antibacterial properties of AgNPs are influenced by morphology, size of NPs, and level of partial oxidation, and it has been demonstrated that materials with larger surface area show higher antibacterial activity [16]. The practical applications of AgNPs are limited to some difficulties with getting NPs free of stabilizing agents. In order to represent typical AgNP-embedded paint, AgNP synthesized via the cellulose fiber-based technique has been used [23]. The obtained nanosilver particles suspended in water solution were spherical with diameter of 13  5 nm. Common household acrylic paint widely used for renovating

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and decorating purposes has been used in further experiments. Silver-nanoparticlecontaining acrylic paint was obtained by diluting the initial paint sample with the Ag colloidal solution in such a way as to get the desired value of nanosilver concentration within the desirable testing range. For the laboratory antibacterial tests, a 22 mm x 22 mm pasteboard was covered with silver-nanoparticle-containing acrylic paint. To evaluate the antibacterial and fungicidal properties of silver particles, Escherichia coli was used as a representative Gram-negative bacterium; Staphylococcus aureus and Bacillus subtilis were used as Gram-positive bacteria; Aspergillus niger, Aureobasidium pullulans, and Penicillium phoeniceum were used to represent cosmopolitan saprotrophic fungi. Within the laboratory tests in order to evaluate the antibacterial and fungicidal properties of Ag nanoparticles added to an acrylic paint, samples with Ag-nanoparticle content as well as control samples were immersed in a thin layer of beef-extract agar. 1 mL of suspension with approximately 105 CFU/mL density of the microorganisms to be tested was distributed uniformly on agar surface and incubated at 28  C (CFU ¼ colony-forming units). Antimicrobial activity was evaluated according to the presence or absence of microbial growth just above the sample after a 24-h incubation for bacteria and a 72-h incubation for fungi. All microbiological tests were performed in triplicate. For conducting field tests, the commercially available acrylic paint was thoroughly mixed with 200 ppm silver nanoparticles solutions in various ratios of 20:1, 50:1, and 100:1 in order to get 10 ppm, 4 ppm, and 2 ppm Ag-nanoparticleembedded paint [24]. In field tests building bricks as the surface of putting paints on have been used. The bricks were painted at the temperature of 20  C by applying two layers consecutively by the brush over the period of 7 days. The antimicrobial effect of Ag-nanoparticle-embedded paint has been estimated after 1, 7, and 30 days of painting. The bactericidal effect of the paint within field tests was studied using Escherichia Coli ATCC 25922, Klebsiella pneumoniae ATTCC 13833, Staphylococcus aureus Wood-45, and Pseudomonas aeruginosa 508. The antimicrobial influence of the paints has been checked as follows. Suspension of strains (0,1 mL), prepared in sterile physiological solution in the concentration of 107 CFU/mL, was coated on the surface of painted bricks. The incubation periods were chosen to be 1, 3, 6, and 24 hours at room temperature. The sowing was performed on plates with nutrient medium. SEM measurements have been used to observe silver nanoparticles on the surface of the modified paint. As one can see from Fig. 1, most of initial silver nanoparticles had agglomerated into clusters up to 300 nm in size because of attractive interaction forces between them. The following photographs in Fig. 2 are typical presentation of microbial analysis of a paint film. They show growth of P. phoeniceum and A. pullulans cultures on pasteboard samples modified by silver nanoparticles. The absence of visible growth of the microbes on the sample #2 confirms the antibacterial/antifungal effect of Agnanoparticle-embedded paints. The analogous experiments conducted [22] with A. niger and S. aureus cultures have also demonstrated a pronounced antifungal/ antibacterial efficacy of the water paint modified by silver nanoparticles of 0.8 μg/ cm2 density. Field tests have been conducted using building bricks as the surface of putting paints on (see Table 1).

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Fig. 1 Sample of Ag-nanoparticle-embedded water paint (note the spherical structures corresponding to nanoparticles)

Fig. 2 Growth of P. phoeniceum (left) and A. pullulans (right) cultures on pasteboard samples modified by silver nanoparticles. (Note the white spots corresponding to microbial colonies.) Sample #1 is a control sample, i.e., it was covered with nonmodified paint; sample #2 was covered with the paint modified by silver nanoparticles of 0.8 μg/cm2 density

As seen from Table 1, all tested Ag-nanoparticle-embedded paint samples revealed a bactericidal effect on the surface of bricks. Increase of the nanosilver concentration from 2 ppm up to 10 ppm leads to more pronounced antimicrobial effect. The revealed antimicrobial efficiency of the paint samples without silver nanoparticles is connected with the bactericidal influence of some components of the paint. It is supposed that with the course of time, paint-volatile components will

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Table 1 The antimicrobial effect of Ag-nanoparticle-embedded paints on different microbial strains

Microbe Escherichia Coli ATCC 25922

Klebsiella pneumoniae ATTCC 13833

Staphylococcus aureus Wood-45

Pseudomonas aeruginosa 508

Paint samples Control sample 2 ppm nanosilver 4 ppm nanosilver 10 pm nanosilver Control sample 2 ppm nanosilver 4 ppm nanosilver 10 pm nanosilver Control sample 2 ppm nanosilver 4 ppm nanosilver 10 pm nanosilver Control sample 2 ppm nanosilver 4 ppm nanosilver 10 pm nanosilver

Amount of bacteria on the surface of the paint, CFU 1 3 6 24 150 10 1 0 120 10 0 0 100 0 0 0 20 0 0 0 300 40 10 1 250 30 5 0 130 30 12 0 50 5 0 0 400 100 50 10 320 90 20 0 200 70 10 0 50 10 1 0 300 120 50 1 270 100 30 0 200 80 30 0 80 30 5 0

be evaporated that will reduce the antimicrobial efficiency of the control samples of the paint without nanosilver. Silver-containing paint was able to retard the initial colonization and growth of L. pneumophila, for up to 14 days (Rogers et al. 1995). Although this paint was unsuitable for controlling biofouling over extended time periods, the data suggest that a reformulated paint or electrochemical method of introducing silver ions may be successful. AgNPs can also enhance some selected physical and mechanical properties of emulsion paint [4]. Extensive characterization indicates that the paint containing equal fraction (0.175 wt%) of AgNPs and benzimidazole carbamate (EPW) gave the optimal mix for all physical and mechanical properties examined. The specific gravity was reduced by 16%, the hiding power/opacity increased by 30%, while the abrasion strength was enhanced by 236%. AgNP can be also used in paint industry in a combination with other nanoparticles. For instance, in the study of Bellotti et al. [5], they evaluated the incorporation of silver (of two different sizes), copper, and zinc oxide nanoparticles in indoor waterborne paints and the bio-resistance imparted by them. This mixture of nanoparticles inhibited the growth of C. globosum and A. alternata in agar plate assays, being 10-nm-size silver nanoparticles the more efficient one. In the interesting study of Tornero et al. [38], hybrid ZnO-AgNPs possessed significant antimicrobial properties against bacteria (Pseudomonas aeruginosa, L. monocytogenes, Salmonella spp., S. aureus, and B. subtilis). This waterborne

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paint accomplishes with the European Ecolabel criteria, with broad-spectrum antimicrobial effect due to the use of ZnO-AgNPs on its matrix, and with VOC content 100 times less than the limit for indoor decorative paint.

Environmental Impact of the AgNPs There is still no evidence that humans are being adversely affected by AgNPs while using paints with AgNPs, but it is very likely that AgNPs will be released into environment where they persist or bioaccumulate [40]. The levels in the environment are difficult to determine as they are present at low concentration and AgNPs undergo complicated reactions which change their speciation including dissolution, aggregation, and chemical complexation [12, 30]. The proliferation in the use of AgNPs in different applications hastens the need for the development of inventories of AgNPcontaining products at national and international levels [37]. For instance, the United States Environmental Protection Agency (US EPA) has developed requirements for companies that manufacture “chemical substances containing primary particles, aggregates, or agglomerates in the size range of 1 to 100 nm in at least one dimension” [1]. As for the US Food and Drug Administration, it has issued a series of guidance documents with respect to the use of nanotechnology in FDA-regulated products [2]. Mueller and Nowack [32] mentioned that paints are among the most important sources for AgNP released in the environment (comparing with nanosilver-modified textiles, cosmetics, cleaning agents, and plastics). Despite leakage of silver from outdoor paints, it is not taken into consideration in many of the existing models of silver fate in the environment [6]. Release of (nano)silver from outdoor paint (containing 1.5 mg Ag/m2 of painted surface; average concentration in wet paint—6.2 mg silver nanoparticles/kg) was investigated by Kaegi et al. [18]. The experiment was conducted over 372 days, during which 65 runoff events occurred. The authors found significant leaching of silver nanoparticles (up to 145 μg Ag/L during the initial runoff events). After 1 year more than 30% (0.5 mg/m2) of the initial mass of silver was released into the environment, of which 80% was released during the first eight runoff events. In contrast, only 1% of titania pigments was released during 1 year. Released silver particles were mostly