Green Nanomaterials: Processing, Properties, and Applications (Advanced Structured Materials, 126) 9811535590, 9789811535598

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Advanced Structured Materials

Shakeel Ahmed Wazed Ali   Editors

Green Nanomaterials Processing, Properties, and Applications

Advanced Structured Materials Volume 126

Series Editors Andreas Öchsner, Faculty of Mechanical Engineering, Esslingen University of Applied Sciences, Esslingen, Germany Lucas F. M. da Silva, Department of Mechanical Engineering, Faculty of Engineering, University of Porto, Porto, Portugal Holm Altenbach, Faculty of Mechanical Engineering, Otto von Guericke University Magdeburg, Magdeburg, Sachsen-Anhalt, Germany

Common engineering materials reach in many applications their limits and new developments are required to fulfil increasing demands on engineering materials. The performance of materials can be increased by combining different materials to achieve better properties than a single constituent or by shaping the material or constituents in a specific structure. The interaction between material and structure may arise on different length scales, such as micro-, meso- or macroscale, and offers possible applications in quite diverse fields. This book series addresses the fundamental relationship between materials and their structure on the overall properties (e.g. mechanical, thermal, chemical or magnetic etc) and applications. The topics of Advanced Structured Materials include but are not limited to • classical fibre-reinforced composites (e.g. glass, carbon or Aramid reinforced plastics) • metal matrix composites (MMCs) • micro porous composites • micro channel materials • multilayered materials • cellular materials (e.g., metallic or polymer foams, sponges, hollow sphere structures) • porous materials • truss structures • nanocomposite materials • biomaterials • nanoporous metals • concrete • coated materials • smart materials Advanced Structured Materials is indexed in Google Scholar and Scopus.

More information about this series at http://www.springer.com/series/8611

Shakeel Ahmed Wazed Ali •

Editors

Green Nanomaterials Processing, Properties, and Applications

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Editors Shakeel Ahmed Department of Chemistry Government Degree College Mendhar Jammu, India

Wazed Ali Indian Institute of Technology Delhi New Delhi, India

ISSN 1869-8433 ISSN 1869-8441 (electronic) Advanced Structured Materials ISBN 978-981-15-3559-8 ISBN 978-981-15-3560-4 (eBook) https://doi.org/10.1007/978-981-15-3560-4 © Springer Nature Singapore Pte Ltd. 2020 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

Preface

Use of nanomaterials as a multifunctional agent is a revolutionary paradigm shift in all areas of advancements including transdisciplinary segments. In this direction, the research community is engaged in exploring various innovative routes to synthesize various nanomaterials for a range of value-added products. Most recently, it has been proven that either the ways of synthesis or the nanomaterials themselves are not meeting the expectation of green movement in terms of exclusion of toxicity parameters in new innovation to achieve holistic development to protect sustainability in our ecosystem. Nevertheless, significant efforts have been put together to discover and open up the wonder properties of nanomaterials where researchers have very wisely adopted eco-friendly greener approaches to provide a green solution in totality. The current edited book is the most recent glimpse of the same approach, whereas the context of various chapters is designed to record and analyze the recent green inventions in the world of green nanomaterials. The chapters are composed of eminent researchers and academicians in their own expertise. We are very sure that this book entitled ‘Green Nanomaterials’ will serve as a reference handy for the readers and followers aspired in the exploration of the potential of nanomaterials in sustainable ways. We are very much thankful to all the contributors for their positive consents and efforts to compose this book with the most recent findings in this area. Sincere thanks go to ‘Springer Nature’ for publishing this book in one of the most demanded fields at the right time. Jammu, India New Delhi, India

Shakeel Ahmed Wazed Ali

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Contents

Introduction to Green Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . Pintu Pandit and T. Nadathur Gayatri

1

Green Nanomaterials: A Sustainable Perspective . . . . . . . . . . . . . . . . . . Sukanchan Palit and Chaudhery Mustansar Hussain

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Characterisation of Green Nanomaterials . . . . . . . . . . . . . . . . . . . . . . . T. Anukiruthika, S. Priyanka, J. A. Moses and C. Anandharamakrishnan

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Green Synthesis of Metal Nanoparticles for Electronic Textiles . . . . . . . Ashish Kapoor, Pramod Shankar and Wazed Ali

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Green Nanofillers for Polymeric Materials . . . . . . . . . . . . . . . . . . . . . . . T. P. Mohan and K. Kanny

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Biosynthesis and Applications of Metal Nanomaterials . . . . . . . . . . . . . 139 Shweta Kishen, Akshita Mehta and Reena Gupta Carbon Dots from Renewable Resources: A Review on Precursor Choices and Potential Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Perumalsamy Vishnukumar, Sivashunmugam Sankaranarayanan, Muruganandham Hariram, Singaravelu Vivekanandhan and Rodrigo Navia Advances with Synthesis and Applications of Green Bionanomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Aswathy Jayakumar, K. V. Heera, Thoniparambil Sunil Sumi, Meritta Joseph and E. K. Radhakrishnan Green Nanomaterials for Wastewater Treatment . . . . . . . . . . . . . . . . . . 227 Poonam Singh, Sanjay Kumar Yadav and Mohammed Kuddus Bionanomaterials from Agricultural Wastes . . . . . . . . . . . . . . . . . . . . . . 243 Manpreet Kaur, Akshita Mehta, Kamal Kumar Bhardwaj and Reena Gupta

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Surface Modification of Bio-polymeric Nanoparticles and Its Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 K. S. Yoha, S. R. Priyadarshini, J. A. Moses and C. Anandharamakrishnan Biopolymer Nanocomposites and Its Application in Food Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 R. Preethi, M. Maria Leena, J. A. Moses and C. Anandharamakrishnan Tissue Engineering Applications of Bacterial Cellulose Based Nanofibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 Semra Unal, Oguzhan Gunduz and Muhammet Uzun

About the Editors

Dr. Shakeel Ahmed is Assistant Professor at Higher Education Department, Govt. of Jammu and Kashmir, Jammu, India. He obtained his PhD in the area of biopolymers and bio-nanocomposites. He has published several research articles in the area of green nanomaterials and biopolymers for various applications including biomedical, packaging, sensors, and water treatment. He has also contributed several book chapters, and written review articles on green synthesis of metal/metal oxides and nanomaterials. He is member of Royal Society of Chemistry (UK) and American Chemical Society. He has published several books in the area of green materials with publishers of international repute. Dr. Wazed Ali is Assistant Professor at the Department of Textile Technology, Indian Institute of Technology (IIT) Delhi. After obtaining his Master’s and PhD from IIT Delhi in 2006 and 2011, respectively, he joined GE India Technology Centre Pvt. Ltd. (JFWTC), Bangalore as a research scientist. He was a recipient of the Bolton Fellowship from the University of Bolton, UK for three year’s PhD program at IIT Delhi. He was awarded the prestigious Commonwealth Split-Site Doctoral Fellowship 2008 from the Commonwealth Fellowship Commission, London to pursue one-year research work in the UK during his PhD. He has published several research articles in international journals and has also filed for a US patent. He is a life member of the Indian Natural Fibre Society.

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Introduction to Green Nanomaterials Pintu Pandit and T. Nadathur Gayatri

Abstract This chapter presents an introduction to nanomaterials, which can be synthesized by green chemistry, or nano-sized functionally advanced materials which have high-performance applications in energy generation and storage, carbon dioxide fixation, electronic devices and are sustainable in terms of production and application with respect to the environment. Methods in brief of preparation of nanoparticles and nanofibres, advantages of green synthesis, and limitations of nanomaterials are discussed. This chapter also provides information related to recent research work on green nanomaterials and the available methods for their synthesis. It also gives a comprehensive overview of the recent status and suggests future directions for employing green nanomaterials for possible various application mainly in the biotechnology, agriculture and biomedical areas. The sustainability of major natural resources utilized in green nanomaterials’ synthesis is considered. Keywords Green nanomaterial · Nanotechnology · Sustainability · Raw materials

1 Introduction 1.1 Nanotechnology and Nanomaterials The word ‘nano’ refers to the dimension of length of the order of 10−9 m (Tolle 2007). Nanotechnology considers the knowledge area of engineering and understanding of nanoscaled materials and devices, wherein materials exhibit unusual phenomena leading to special applications. Comparison of the dimensions of objects occurring in the living world can be done by considering the red blood cell—7000 nm wide P. Pandit (B) Department of Textile Design, National Institute of Fashion Technology, Ministry of Textiles, Government of India, NIFT Campus, Mithapur Farms, Patna 800001, India e-mail: [email protected]; [email protected] T. N. Gayatri Department of Fibres and Textile Processing Technology, Institute of Chemical Technology, Matunga, Mumbai 400019, India © Springer Nature Singapore Pte Ltd. 2020 S. Ahmed and W. Ali (eds.), Green Nanomaterials, Advanced Structured Materials 126, https://doi.org/10.1007/978-981-15-3560-4_1

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and 2000 nm long, rhinovirus which causes the common cold, being 25 nm wide, DNA molecule being 2 nm thick and silicon atom with a diameter of 0.2 nm.

1.2 Properties of Nanomaterials The chemical reactivity of a material is highly dependent on the ratio of its surface area to volume. The surface area of a nanoparticle is exponentially larger than its unit volume. When a material block is dismantled and cut down to nano-size, the combined surface area of the particles is vastly greater than the surface area of the starting block. This finds immediate application in the surface area sensitive processes like catalysis, adsorptive removal of pollutants and sustained drug release and wound healing in medicine where chemical reactivity and coverage are linked. Products can be coated with thin films of nanomaterials to exhibit specific properties, like hydrophobicity for water repellency or resistance to microbial or fungal growth while leaving the product appearance unchanged. Newtonian physics is not applicable to the behaviour of nanomaterial as such rules apply to bulk matter while at nano-level physical properties like electric conductivity, colour, strength, weight and chemical properties are drastically different. One illustration is bulk silver which is non-toxic, but silver nanoparticles can kill viruses on contact. Normally, brittle ceramics can become more elastic when the size of their component grains is reduced to minuscule nanometre diameter. A gold particle of 1 nm diameter appears red in colour. Both graphite and diamond are constitutionally of only the carbon element, but the sheet-like arrangement of atoms in graphite makes it flaky while the tetrahedral arrangement of atoms internally makes diamond hard.

1.3 Classification of Nanomaterials Nanomaterials are classified on the basis of the order of dimensions to which their electron is restricted, ranging from one, two or three dimensions (Suresh 2013). • Zero-dimensional (0-D) nanomaterial Zero-dimensional shapes are the most basic and symmetric, including spheres, cubes and polygon, with nano-dimensions along all the axes of x, y and z. Metallic nanoparticles of gold and silver and semiconductor like quantum dots are examples of this class, being spherical in shape and with diameters ranging from 1–50 nm.

Introduction to Green Nanomaterials

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• One-dimensional (Quasi 1D) nanomaterial In these nanostructures, one dimension of the nanostructure will lie beyond the nanometre range, such as observed in nanowires, nanorods and nanotubes from metals and metal oxides. These materials are several micrometres long but are just a few nanometres across the diameter (Xia et al. 2003). • Two dimensional (2-D) nanomaterial In nanomaterials, like nano films and thin-film multilayers, nanosheets or nanowalls two dimensions lie beyond the nanometre range. The surface area of nano films could be in the range of several square micrometres, but the thickness remains at the nanoscale. There exist fewer types and of inorganic nano-objects in the 2D class. • Three-dimensional (3-D) nanomaterial Objects having a cumulative size in the non-nanometre range of the order of micrometres or millimetres but exhibiting nanometric features like nano-sized confinement spaces or those formed by the periodic arrangement and assembly of nano-sized units can be considered ‘3D nanosystems.’ With all dimensions beyond the nano range, they still exhibit unusual molecular and bulk properties, reflecting their component units which are in the nanoscale (1–100 nm). Three-dimensional nanocrystals are formed from the organization of 0D spheres, and 1D rods or 2D plates give rise to unusual superstructures, such as in box-shaped graphene or mesostructured platinum films.

1.4 Nanoparticles 1.4.1

Carbon-Based Nanoparticles

Carbon-based polymers such as fullerenes, carbon dots, nano-diamonds and nanofoams are a class of nanomaterial, which are much researched. Carbon nanotubes are just layers of graphite rolled into a tube form, which could be single- or multi-walled, depending on the number of layers. Fullerenes consisting of C60 (Pal et al. 2011), single-walled nanotubes and multi-walled nanotubes have been suggested for use in composites as structural reinforcements to conventional materials and even as drug carriers (Prasek et al. 2011). Graphene is also a carbon-based nanomaterial made of a one carbon atom thick, single layer sheet structure similar to natural graphite (Naahidi et al. 2013).

1.4.2

Dendrimers

Dendrimers are highly branched polymers whose shape, size, branching length, generation number and surface functionality can be controlled at the synthesis stage.

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Fig. 1 TEM image of a Carbon nanotube, b PAMAM dendrimer and c Silver nanoparticles

From a nano-sized centre, polymeric branches of defined length and structure grow outward, generating porous enclosures, in the whole molecule, which allows for the trapping or encapsulating drug molecules, fragrance molecules or even biological cells. TEM image of PAMAM dendrimer is given in Fig. 1b (Anandalakshmi and Venugobal 2017).

1.4.3

Metal Nanoparticles

Nanogold, nanosilver and metal oxides, like titanium dioxide and closely packed semiconductor like quantum dots, derived from metal atoms, are metal-based nanoparticles. Metallic nanoparticles are often formed as solid colloidal solutions. Further, they are amenable to surface modification to achieve target functionality as they possess the large surface area to volume ratio. They can be synthesized in different forms like a rod, dot or cubes and often exhibit special optical properties like fluorescence or surface enhanced resonance, allowing for easy detection at low concentrations, and hence, their imaging applications. TEM image of the silver nanoparticle is given in Fig. 1c

1.5 Approach for Synthesis of Nanoparticles Synthetic approaches to nanoparticles could be configured to be either top-down or bottom-up methods as shown in Fig. 2 (Ahmed 2015). When thin films or bulk materials are scaled down by various lithographic and mechanical techniques like grinding, milling and thermal/laser ablation, it is a top-down method. Bottom-up methods use basic building blocks (atoms, molecules, nanoparticles, etc.) to self-organize from nuclei to grow into superstructures, of greater complexity. Most chemical or biological synthetic procedures which make complex 3D structures at low cost and in bulk fall into the bottom-up class of methods (Colson et al. 2013).

Introduction to Green Nanomaterials

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Fig. 2 Approach for nanomaterial synthesis

1.6 Global Market Scenarios of Nanoparticles The analysis of the global market for nanoparticles showed that its value is projected to rise to USD 91.1 million by 2020, at CAGR of 5.4% from 2015 to 2020. Increasing investments in nanotechnology research and development with applications in pharmaceuticals, textiles and agriculture in the high growth rate developing nations are expanding the market (Rai et al. 2009; Chaudhry et al. 2010). Production of nanoscale silver, (AgNPs), has allowed their potential use in electronic and transparent conductor applications, in antimicrobial consumer goods and medical products causing the nanosilver market to rise in value from US$290 million in 2011 to around US$1.2 billion by 2016 (Murphy et al. 2015). The use of AgNPs to make bactericidal cotton fibres and hence antimicrobial fabric has been commercialized, along with nanosilver-based wall paint, for mould-resistant constructions, which is another high volume consumer product. There is much interest in nanofinished textiles for medical use, which need to be antimicrobial, along with odour control inner garments and bedding fabrics, where AgNPs can be easily used. The composition of nanoparticles mostly utilized in the medical industry in devices and products is of metals such as gold and silver, metal oxides of zinc and titanium and salts such as calcium phosphate. These particles make up a market share of over 30%.

2 Synthesis of Metal Nanoparticles Metal nanoparticles can be prepared by three different methods—physical, chemical and green process—which are described below.

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2.1 Physical Synthesis One common physical process, through which nanoparticles are synthesized, is evaporation–condensation that is performed in a tube furnace at atmospheric pressure. The precursor metallic or metal oxide material, placed in a boat at the furnace centre, is vaporized into an inert carrier gas medium like argon, nitrogen or even air and is subsequently condensed to nanoparticles (El-Nour et al. 2010). Mechanical milling performed using ball milling machinery initiates a solid-state displacement reaction. Milling/grinding reduces the particle size, and blends of particles into new phases mechanochemical processes modify the chemical composition of precursors, by pressure-induced reactions on stressed solid phase (Ghorbani 2014). Pulsed laser ablation (PLA) has the advantage of giving nanoparticle product with a uniform size distribution, i.e. low dispersity. Initially, a laser pulse vaporizes a target to form a plasma plume, which then expands adiabatically in the closed volume; as the expansion ends, condensation to nanoparticles begins (Hassan and Wagner 2017). Process parameters like energy, wavelength and duration of pulse of laser along with the substrate phase (liquid or gas) and duration of ablation can modify the product properties (Amendola and Meneghetti 2009).

2.2 Chemical Synthesis Chemical approach involves reduction of a solution of metal ions, at specific temperature, with a reagent of defined concentration and with an ultrasonic vibration or stirring, or under microwave irradiation, to finally form microscopic metal clusters or aggregates (El-Nour et al. 2010). The wet chemical process of nanoparticle synthesis is a bottom-up strategy for synthesizing nanoparticles from the atoms of elements of the starting material. Sol–gel process is another physico-chemical process in which a network is formed from a colloidal suspension (sol) of metal oxide or other metal derivatives that then condenses through gelation of the sol solution to form a gel in liquid phase (Zhang et al. 2014). Solvothermal synthesis starts from precursor molecules in a solvent medium, heat treated to generate nanoparticles bottom-up. The reaction vessel is closed to promote decomposition or further chemical reaction of the precursors, under conditions of high temperature and/or high pressure. When the solvent is water, the process is ‘hydrothermal synthesis.’

2.3 Green Synthesis Reducing agents from natural sources like polysaccharides or plants extract or biological micro-organism like bacteria and fungus can be used to synthesize nanoparticles.

Introduction to Green Nanomaterials

2.3.1

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Biological Synthesis

Biosynthesis metallic nanoparticles from microorganisms such as bacteria, actinomycetes, fungi and algae which is green and eco-friendly process. The synthesis of nanoparticles may be internal to the cell or an external reaction, depending on the location of the nanoparticle product (Hasan 2015).

2.3.2

Plant Extract Mediated Synthesis

The mode of usage of plant extracts to produce nanoparticles is simple, in that, the extract is mixed with a solution of the metal salt at different temperature and kept under constant stirring, sometimes under ultrasonic or microwave irradiation for a specific time duration. The single-step biogenic reduction of metal ion to base metal is fast, may be carried out at room temperature and atmospheric pressure, such that scale-up is easily possible. The reducing agents identified are plant secondary metabolites, chemically classified as alkaloids, tannins, terpenoids and co-enzymes (Makarov 2014). Extracts of varied plant species have been employed in synthesizing metallic nanoparticles; alternately, live plants have also been used (Mittal et al. 2013). Some of them are presented in Table 1.

2.4 Advantage of Green Synthesis Over Conventional Process Green synthesis of metal nanoparticles is a cheaper, simpler and environmental benign alternative to conventional chemical and physical methods, with good yields that do not require complex reagents, or high-end apparatus (Malik 2014). Some of the herbs used in green synthesis of metallic nanoparticles are considered briefly.

3 Herbs Used for Green Synthesis of Metallic Nanoparticles Exploratory research indicates that the following herbs (leaf and fruit) are rich in biomolecules which can be utilized for synthesis of nanoparticle.

3.1 Jackfruit Leaf Artocarpus heterophyllus, commonly known as jackfruit, common in India and Southeast Asia, consists of dark green, alternate, fairly large and oval-shaped leaves which are deeply lobed on young shoots. The leaf is shown in Fig. 3.

8 Table 1 Plant extract used in the synthesis of nanoparticles

P. Pandit and T. N. Gayatri Plant species

Nanoparticle size

Shape

Acalypha indica

20–30 nm

Spherical

Allium sativum (garlic clove)

4–22 nm

Spherical

Aloe vera

50–350 nm

Triangular

Apiin extracted (henna leaves)

7.5–65 nm

Triangular

Boswellia ovalifoliolata

30–40 nm

Calotropis procera

150–1000 nm

Camelia sinensis

30–40 nm

Carica papaya

25–50 nm

Catharanthus roseus

48–67 nm

Citrus sinensis peel

10–35 nm

Spherical

Datura metel

16–40 nm

Quasilinear

Emblica officinalis

10–20 nm

Euphorbiaceae latex

10–20 nm

Nelumbo nucifera (lotus)

25–80 nm

Spherical, triangular

Mentha piperita (peppermint)

5–150 nm

Spherical

Moringa oleifera

57 nm

Tanacetum vulgare

16 nm

Syzygium cumini

29–92

Spherical

Aloe vera

50–350 nm

Spherical

Apiin extracted (henna leaves)

7.5–65 nm

Spherical

Cinnamomum camphora

3.2–20 nm

Cubic

Camelia sinensis

30–40 nm

Cymbopogon sp. (lemon grass)

200–500 nm

Emblica officinalis

15–25 nm

Mentha piperita (peppermint)

5–150 nm

Spherical

Psidium guajava

25–30 nm

Spherical

Ag nanoparticle

Au nanoparticle

Spherical

(continued)

Introduction to Green Nanomaterials Table 1 (continued)

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Plant species

Nanoparticle size

Shape

Tanacetum vulgare

11 nm

Pyrus sp. (pear fruit extract)

200–500 nm

Triangular

Parthenium leaf

50 nm

Face-centred cubic

Ag/Au bimetallic nanoparticle Anacardium occidentale

~6 nm at 27 °C; 17 nm at 100 °C

Azadirachta indica (neem)

50–100 nm

Swietenia mahogani

50 nm

Pb nanoparticle Jatropha curcas L. latex

10–12.5 nm

Cu nanoparticle Euphorbiaceae latex

10.5 nm

Indium oxide nanoparticle Aloe vera

5–50 nm

Spherical

3.2–20 nm

Hexagonal

Pd nanoparticle Cinnamomum camphora Pt nanoparticle Diopyros kaki

15–19 nm

Hybrid Ag nanoparticle Eucalyptus Fig. 3 Panasa (Artocarpus heterophyllus) leaves

50–150 nm

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Fig. 4 Narikela (Cocos nucifera) leaves

All parts of the leaf contain sticky white latex (Crane et al. 2005). Phytochemical screening has revealed that the hot water extract of leaf contains flavonoids, leucoanthocyanins, anthocyanins and tannins as components (Chandrika et al. 2006).

3.2 Coconut Leaf Cocos nucifera plant, commonly known as coconut, has pinnate leaves of 4–6 m (13–20 ft) long with pinnae 60–90 cm long as shown in Fig. 4. Its potential for antioxidant, antibiotics and free radical scavenging activity is much investigated. Total phenol content (TPC) of coconut leaf extract is 0.59–2.22 mg/g. Phenolic compounds function as a green reducing agent.

3.3 Night Flowering Jasmine Leaf Nyctanthes arbortristis commonly known as a night flowering jasmine tree and the leaf is shown in Fig. 5, growing in India and other tropical and subtropical region is a medicinal plants with a wide spectrum of biological activity. An alkaloid named nactanthine is also found in leaves. Leaves also contain mannitol, astringent, resinous substances, ascorbic acid, sugar, tannic acid, methyl salicylate and trace of volatile oils.

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Fig. 5 Parijata (Nyctanthes arbortristis) leaves

3.4 Indian Gooseberry Fruit Phyllanthus emblica, commonly known as Indian gooseberry (amla), originated in India, and the fruit is shown in Fig. 6. The fruit extract of amla and its individual constituents has shown to impart antioxidant effect. Amla is a rich source of Vitamin C, a water-soluble antioxidant that acts as a scavenger of free radicals. Amla also contains a variety of active constituents like polyphenols, flavones, tannins, anthocyanins, flavonols, ellagic acid and derivatives (Singh et al. 2012).

4 Silver Nanoparticles Silver nanoparticles, of the class of noble metal nanoparticles, have been of interest since they exhibit a range of bactericidal and fungicidal activities making them Fig. 6 Amalaki (Phyllanthus emblica) fruits

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popular for common use in a wide variety of consumer products, including plastics, soaps, pastes, food and textiles (Rauwel 2015). Conventionally, silver nanoparticles are synthesized using synthetic chemicals as reducing agents which later, during the use of the product, cause various biological risks due to their general toxicity, even at residual levels. Feasible, alternate and superior reagents have been found in biological molecules derived from plant sources in the form of extracts and used in green synthesis. An example is the synthesis of silver nanoparticles using aqueous leaf extract of Azadirachta indica, as reducing agent and capping agent. Well dispersed, spherically shaped silver nanoparticles with a diameter of 34 nm were formed from silver ions, at the end of 15 min of reduction, without using toxic chemicals. The silver nanoparticles were active against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria (Ahmed et al. 2016). Khalil et al. (2014) prepared quasi-spherical silver nanoparticles of 20–25 nm size by means of using hot water olive leaf extract as reductant and stabilizer on silver nitrate solution. The silver nanoparticles were mostly spherical with an average size of 20–25 nm. Silver nanoparticles showed better antibacterial efficacy, against multi-drug-resistant S. aureus, Pseudomonas aeruginosa and E. coli compared to OLE extract alone (Fig. 7). The synthesis of silver nanoparticles using silver nitrate as precursor and leaf extracts of three plants, Musa balbisiana (banana), A. indica (neem) and Ocimum tenuiflorum (black tulsi), as reducing and stabilizing agent has been achieved. Silver nanoparticles showed much stronger antimicrobial activity against E. coli and Bacillus sp. relative to both silver nitrate and raw plant extracts. Moong bean (Vigna radiata) and chickpea (Cicer arietinum) seeds treated with silver nanoparticles showed faster and more successful germination pointing to the low toxicity of silver nanoparticles (Banerjee et al. 2014). Fig. 7 Action mode of inorganic UV filters

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5 Copper Nanoparticles Copper nanoparticles have garnered attention for their special optical and electrical properties, along with good thermal conductivity and corrosion resistance. Copper is cheaper compared to noble metals like gold and silver and also has effective antimicrobial action. Well dispersed, spherical and monodisperse copper nanoparticles have found application in lubricants and also as nano-fluids, etc. (Khodashenas and Ghorbani 2014). Copper nanoparticles are susceptible to aggregation and oxidation, which could be by adding a suitable stabilizer for capping of copper nanoparticles. Copper nanoparticles are widely used in wound dressings for their biocidal properties, as well as in the manufacturing industry as gas sensors, in catalytic process, high-temperature superconductors and solar cells. Environmentally safe copper nanoparticles/perlite composites are prepared without the use of any toxic reductants or capping agents. Leaves of Euphorbia esula L. functioned as both reductant and stabilizer for the formation of copper nanoparticles with a size lower than 32 nm. The Cu NPs/perlite composites showed good response in the catalytic reduction of 4-nitrophenol and were reusable without loss of the catalytic function. Nanostructured copper particles are prepared using Garcinia mangostana leaf extract (Prabhu et al. 2017) as a reducing agent with precursor metal ions from copper nitrate. Spherical copper nanoparticles agglomerated to a particle size of 20– 25 nm were obtained. These Cu nanoparticles had good antibacterial action against E. coli and S. aureus. In another study, authors presented a novel biological approach for the formation of copper nanoparticles using precursor ions from copper sulphate with clove as the reducing agent. The particles size of obtained copper nanoparticles was in the range of 5–40 nm (Subhankari and Nayak 2013). Khan et al. (2016) developed zero-valent copper (Cu) nanoparticles, protected with starch, by chemical reduction of copper salt solution using reducing agent, ascorbic acid at low temperature. Copper nanocrystals were found to have average crystallite size of 28.73 nm. Fabrication of copper nanoparticle using catharanthus roseus by green synthesis and act as dual purpose ‘reducing and capping’ agent. The size of nanoparticle ranges between 40 and 47 nm and appears like coral reef. Copper nanoparticles also exhibited excellent antibacterial activity (Birla et al. 2009).

6 Zinc-Based Nanoparticles Zinc nanoparticles have an unusual combination of physical and chemical properties, such as high chemical stability, high electrochemical coupling coefficient, wide range of radiation absorption and strong photostability, leading to its multifunctional

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usage. Zinc oxide behaves as a semiconductor, whose covalence is on the boundary separating ionic and covalent semiconductors. It possesses a broad energy band gap (3.37 eV), large free exciton binding energy (60 meV) and high thermal and mechanical stability at room temperature, which allows to its potential use in optoelectronics, as a piezoelectric ceramic switch and in laser technology. The piezoand pyroelectric properties of ZnO allow for its use as a sensor, transducer, energy generator and photocatalyst for hydrogen production. The low toxicity, biocompatibility and biodegradability of zinc oxide favour its application in biomedicine and in agriculture (Kołodziejczak-Radzimska and Jesionowski 2014). Zinc oxide nanoparticles show exciting photoluminescence properties and resistance to oxidation. The ZnO particles also were found to emit light in the UV to blue range by suggesting that it can be used for UV protection. In a typical process, zinc chloride was dissolved in a phenylether and complexed with oleylamine to form Zn2+ , after which it nucleates into the final structure. Hexagonal zinc nanoparticles having a diameter of 250–350 nm were formed. Pavani et al. (2011) studied the synthesis of zinc nanoparticles by extracellular synthesis method using Aspergillus species. The synthesized zinc nanoparticles showed absorption maxima at 230 nm. Zinc nanoparticles have a size in the range of 50–120 nm. Sangeetha et al. (2011) prepared stable and spherical nanostructured zinc oxide by green chemical method using zinc nitrate and aloe vera leaf extract. The yield from precursor was greater than 95% having polydispersed zinc oxide nanoparticles with an average particle size between 25 and 40 nm. The particle size could be modified by changing the concentrations of leaf extract.

7 Green Synthesis of Nanofibres Nanofibers prepared by using ecological solvents or naturally occurring biodegradable polymers have found a niche use in medical devices for wound healing and controlled drug release, especially because of their high surface area and membrane-like structure. Electrospun nanofibers mats have been green synthesized using hydroxypropyl cellulose (HPC) separately or by addition of fibre forming polymer like poly(vinyl alcohol) (PVA) or polyvinylpyrrolidone (PVP) to enhance the mechanical properties of the nanofibers mats. Favourable properties like thermal stability and visual appearance and mechanical properties of PVA or PVP were dramatically enhanced with the addition of HPC. Drug loading on such nanofibres allowed for sustained release of drug, when tested in vitro (El-Newehy et al. 2018). A green nanofiber prepared by using H2 O2 -assisted water-soluble chitosan/polyvinyl alcohol (WSCHT/PVA) dissolved in water, an eco-friendly solvent, was done. This is necessary to replace organic solvents used to solubilize waterinsoluble polymers, with aqueous spinnable solutions. It is essential for end applications of nanofibres in environmental solutions or in biological systems that no

Introduction to Green Nanomaterials

15

toxic chemicals be used in their processing. The method developed produces uniform nanofibers, with PVA, polyvinyl alcohol as a supporting polymer and chitosan made water soluble by a heterogeneous reaction (Pervez and Stylios 2018). Carbon nanofibers (CNF) have been commonly prepared from synthetic carbon polymer precursors, and organic solvents like methylene dichloride and dimethylsulphoxide used to dissolve these are toxic and hazardous. But their preparation from naturally available precursors with benign solvents is less common. Porous carbon nanofibers (CNF) having high surface area were electrospun from a solution of polymerized sucrose and poly (vinyl alcohol) (PVA) in water. Thermal treatment for stabilization, at 350 °C, followed by carbonization of the electrospun polymer at 950 °C in reducing environment formed semigraphitic CNF. In situ doping of Ag nanoparticles in CNF increased electrical conductivity tenfold with just 0.1 wt% Ag doping (Chakravarty et al. 2017).

8 Application of Nanoparticles in Textile Finishing Conventional textile finishes that impart advantages such as water repellency and stain repellency, to the fabric are rarely durable to frequent laundering. Nanoparticles with their characteristic large surface area and high surface energy bind to fabrics, with greater strength conferring better durability of the desired textile property (Kathirvelu et al. 2009). Nanoparticles provide functional application like chromic behaviour, antibacterial properties, self-cleaning and UV protective, etc., but most significant to textile use are antibacterial, UV protective and colouration properties.

8.1 Antibacterial Finishing Odour control, stain control and restricting spread of infection in densely populated areas (clean human environment being a civilizational need), all of these require antibacterial coatings on medical devices, hygienic products, water purification systems, medical surgery equipment, textiles, food packaging and storage material. Hygiene finishes protect the textile user from pathogenic or odour causing microorganisms in common textile garments like socks, sportswear and working clothes as well as mattresses, floor coverings and shoe linings. Protection of the textile itself from damage caused by fungi or rot producing microorganisms is another goal. Quaternary ammonium compounds, like Triclosan (2, 4, 4-hydrophenyl trichloro (II) ether), having action against Gram-negative and Gram-positive bacteria are often used as additives in laundering formula (Fouda 2012). Natural antibacterial compounds exist, and like chitosan [poly-(1-4)-d-glucosamine], a cationic polysaccharide, is obtained by alkaline deacetylation of chitin, the major component in crustacean shells (Ye et al. 2006). Natural antimicrobial compounds like sericin, neem extract, natural dyes, aloe vera, tea extract, coconut shell extract, Sterculia foetida

16 Table 2 Grades and classification of UPF

P. Pandit and T. N. Gayatri UPF

Transmittance (%)

Protection level

Grade

>40