Advances in Glass Research 3031202651, 9783031202650

Citation preview

Advances in Material Research and Technology

Shadia Jamil Ikhmayies   Editor

Advances in Glass Research

Advances in Material Research and Technology Series Editor Shadia Jamil Ikhmayies, Physics Department, Isra University, Amman, Jordan

This Series covers the advances and developments in a wide range of materials such as energy materials, optoelectronic materials, minerals, composites, alloys and compounds, polymers, green materials, semiconductors, polymers, glasses, nanomaterials, magnetic materials, superconducting materials, high temperature materials, environmental materials, Piezoelectric Materials, ceramics, and fibers.

Shadia Jamil Ikhmayies Editor

Advances in Glass Research

Editor Shadia Jamil Ikhmayies Amman, Jordan

ISSN 2662-4761 ISSN 2662-477X (electronic) Advances in Material Research and Technology ISBN 978-3-031-20265-0 ISBN 978-3-031-20266-7 (eBook) https://doi.org/10.1007/978-3-031-20266-7 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed 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 Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Glass is an inorganic solid amorphous material which exhibits glass transition temperature by stopping the kinetics under the supercooled liquid region when crystallization is bypassed. Glass is hard, brittle, and a malleable material with high corrosion resistance, and high compressive strength. It is usually transparent or translucent to visible light, but it nearly absorbs all ultraviolet B light (UVB). This material has many chemical, physical, mechanical, thermal, and optical properties that attracted the attention of researchers in industry and academia. These properties made glass a very important material for several applications such as electronics, optoelectronics, photonics, photovoltaics, construction, medicine, communications, sensing, nuclear waste storage, and many others. Among the important applications is the use of rare-earth ion-doped glasses in optoelectronic devices such as fiber amplifiers, solidstate high-power lasers, light amplifiers, and light-emitting diodes. Improvements in glass properties can come from modifying the composition and technical advances in processing. This book includes nine chapters which cover most of the glass families in the form of reviews and experimental research. The reader of the book will find fundamentals, methods of fabrication, characterization techniques, properties, and applications of glasses. Beginners, undergraduate, and graduate students will find that this book supplies them with sufficient information to build on. The book is suitable to be a textbook for some materials such as “glass science and engineering”, and “glass design”, for the undergraduate and graduate stages. It can be a reference for some graduate and undergraduate materials such as “materials characterization”, and “Ceramics and Glass Technology” for undergraduate students in metallurgical and materials engineering disciplines. It can also be a textbook for special courses such as “Glass Processing Course”, which is directed to researchers and professionals in glass design and industry. Glass designers will need this book as a rich source of knowledge of glass production, processing, and characterization technologies. Architects will get an advantage from this book to be familiar with the different types of glasses that they use in their work. Chapter “Overall Aspects of Glasses for Photonic Devices” by José Luis Clabel Huamán et al. is an introduction to glasses, where the authors review the history v

vi

Preface

and challenges in glass development, traditional and new manufacturing processes, characterization techniques, structural, thermal, and optical properties, and glass types and applications. The authors present recent advances in the science of glass, and its application in photonic devices. They also show that the glass network has significant implications both in terms of optical and mechanical properties. Chapter “Redox Reactions in Glasses” by Hosam Othman discusses redox reactions in glasses and the factors affecting them. The chapter also discusses the techniques that can be used for determining the redox states and speciation of polyvalent ions in glass. The author showed that glasses doped with multivalent elements are of practical importance as radiation shielding materials, optoelectronics materials, optical data storage materials in high-density memory devices, biomedical materials, materials for use in white light-emitting diodes, and in the nuclear waste industry. Chapters “Phosphate Glasses: Synthesis, Properties and Applications” and “Structural and In Vitro Bioactivity of Phosphate-Based Glasses for Bone Regeneration” investigate phosphate glasses, where chapter three is a review, while chapter four is an experimental work. Chapter “Phosphate Glasses: Synthesis, Properties and Applications” by Bhasker Pratap Choudhary and N. B. Singh reviews phosphate glasses, where their preparation methods, characterization techniques, properties, and applications are thoroughly discussed. Their uses in biomedicine, optics, and electrochemistry as low-temperature sealing glasses, and as hosts for nuclear wastes are discussed. In addition, applications of different types of phosphate glasses in electronics and laser technology have been discussed in this chapter. In Chapter “Structural and In Vitro Bioactivity of Phosphate-Based Glasses for Bone Regeneration” by M. Mohan Babu et al., the authors developed three series of phosphate glasses by incorporating various amounts of ZnO, TiO2 , and Al2 O3 . Focusing was on the development of a novel bioglass system 8ZnO–22Na2 O–24CaO–46P2 O5 and on the influence of ZnO, TiO2 , and Al2 O3 incorporation on structural, mechanical strength, degradation, pH variation, formation of hydroxyapatite (Hap) layer on the glass surface, and cell viability for generation of bone resorbable implants. The results obtained by the authors confirmed the suitability of the produced glasses for bone repair, tissue engineering, and regeneration applications. Chapter “Advances in Chalcogenide Glasses (ChGs): Past, Present, and Future Applications” by Neeraj Mehta reviews the advances in chalcogenide glasses (ChGs) from their early developing stage to the present time. The chapter covers the progression of various features of ChGs from scientific principles to significant everyday products, and the past, present, and future outlooks of ChGs-based devices. Chapter “Advances in Luminescent Glass Research Towards High-End Applications” by Erdinç Erol et al. focuses on luminescent glasses, where it reviewed lanthanide and/or QDs-doped glasses to achieve more stable high-performance devices. The chapter summarizes the synthesis methods, and highlights the latest developments in luminescent glasses for a variety of high-tech applications such as solid-state lighting and displays, security (anti-counterfeiting), optical temperature sensing, and solar energy (solar spectrum conversion), along with a comparison of their advantages and disadvantages discussed in detail. This chapter provides

Preface

vii

a brief yet insightful introduction to both new and experienced luminescent glass researchers. Chapter “Synthesis and Characterization of Rare Earth Doped ZnO-Al2 O3 -SiO2 Glasses and Transparent Glass-Ceramics” by Itamar Nunes de Assis Jr. et al. summarizes some of the most recent results on the mechanical, thermal, structural, and optical properties of the promising aluminum-silicate glassy system (ZnO–Al2 O3 – SiO2 ) and its glass-ceramic counterpart. After doping with rare-earth ions, the authors succeeded in improving the transparency and thermometric properties of glassceramics. Moreover, this chapter includes a review of the calorimetry approaches related to rare-earth improvements in the thermal stability of glass, besides modification of the activation energy for crystallization. In addition, the reader will find some discussions about higher sensibility reached in Nd3+ /Ce3+ —co-doped aluminosilicate glass applied in optical thermometry. Chapters “Porphyrin and Phthalocyanine as Materials for Glass Coating– Structure and Properties” and “Phthalocyanine and Porphyrin Films on Glass Substrates—Processing, Properties and Applications” by Barbara Popanda and ´ Marcin Sroda present an experimental work with a review of phthalocyanines and porphyrins as materials for glass coatings. Chapter Porphyrin and Phthalocyanine as Materials for Glass Coating—Structure and Properties is an introduction to the nature of phthalocyanines as materials for glass coatings, where the most widely used synthesis methods of porphyrins and phthalocyanines are discussed. The spectroscopic characteristics of the compounds are provided based on UV-ViS and photoluminescence studies. The nonlinear optical and electric properties of various metal-phthalocyanines are discussed. Current and future applications of phthalocyanines are presented. This chapter is an introduction to chapter Phthalocyanine and Porphyrin Films on Glass Substrates—Processing, Properties and Applications which discussed the methods of coating preparation of phthalocyanines and porphyrins on the glass substrates, with the advantages and disadvantages of these methods. It also discussed the characteristics of the double-layer materials based on metallophthalocyanines or metalloporphyrins, the semiconductor inorganic oxide applied on glass, and the optical and electrical properties of the coatings. Finally, the application of phthalocyanines and porphyrins in organic light-emitting diodes (OLEDs) and solar cells is presented. Amman, Jordan

Shadia Jamil Ikhmayies

Contents

Overall Aspects of Glasses for Photonic Devices . . . . . . . . . . . . . . . . . . . . . . J. L. Clabel H., G. Lozano C., I. C. Pinto, R. F. Falci, V. A. G. Rivera, Y. Messaddeq, and E. Marega Jr.

1

Redox Reactions in Glasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hosam Othman

53

Phosphate Glasses: Synthesis, Properties and Applications . . . . . . . . . . . . Bhasker Pratap Choudhary and N. B. Singh

79

Structural and In Vitro Bioactivity of Phosphate-Based Glasses for Bone Regeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 M. Mohan Babu, P. Venkateswara Rao, Nibu Putenpurayil Govindan, Raghavendra Gujjala, and P. Syam Prasad Advances in Chalcogenide Glasses (ChGs): Past, Present, and Future Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Neeraj Mehta Advances in Luminescent Glass Research Towards High-End Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Erdinç Erol, Miray Çelikbilek Ersundu, and Ali Erçin Ersundu Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 Glasses and Transparent Glass-Ceramics . . . . . . . . . . . 213 Itamar Nunes de Assis Junior, Alisson Torquato, and M. Reza Dousti Porphyrin and Phthalocyanine as Materials for Glass Coating—Structure and Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 ´ Barbara Popanda and Marcin Sroda

ix

x

Contents

Phthalocyanine and Porphyrin Films on Glass Substrates—Processing, Properties, and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 ´ Barbara Popanda and Marcin Sroda Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

Overall Aspects of Glasses for Photonic Devices J. L. Clabel H., G. Lozano C., I. C. Pinto, R. F. Falci, V. A. G. Rivera, Y. Messaddeq, and E. Marega Jr.

Abstract This chapter is a review dedicated to recent advances in the science of glass and its application in photonic devices with a straightforward, easy-to-read style. It is important to mention as a starting point that recent advances in this material indicate that the glass network has significant implications both in terms of the optical and mechanical properties and, therefore, the functionalities of glass as a smart material. In this sense, it is essential for the development of new technologies or innovations to better understand the effects of manufacturing techniques to achieve the desired product. In this context, we provide an overview of the history and challenges in glass development, traditional and new manufacturing processes, characterization techniques (structural, thermal, and optical properties), glasses family, and photonic device applications. Keywords Glasses · Thermal properties · Structural properties · Optical properties

1 Challenges in the Development of Glasses Since their appearance1 the glasses can be considered a crucial step in the history of mankind, because they not only play an active role in everyday life but also due to their promising applications in the development of new devices for the well-being of humanity. Over centuries various companies dedicated to manufacturing glasses, and their applications have emerged due to the diversity of areas in which they are immersed (medicine, construction, transportation, energy conversion, new light

1

2600 B.C., Syrian origin.

J. L. Clabel H. (B) · G. Lozano C. · E. Marega Jr. Physics Institute of São Carlos - University of São Paulo, São Paulo, São Carlos 13560-970, Brazil e-mail: [email protected] I. C. Pinto · R. F. Falci · V. A. G. Rivera · Y. Messaddeq Centre d’optique, photonique et laser, Université Laval, 2375 rue de la Terrasse, Québec, Qc, Canada e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. J. Ikhmayies (ed.), Advances in Glass Research, Advances in Material Research and Technology, https://doi.org/10.1007/978-3-031-20266-7_1

1

2

J. L. Clabel H. et al.

sources, lenses to see from dimensions of a few microns to thousands of kilometers from the earth, telecommunications, security, weapons, hardware development, including nanotechnology, esthetic, entertainment and pleasure [1], and so on just to mention), which it represents today not only a source of the economic world if not also a continuous innovation source to the future. In this context, the National Academy of Engineering (NAE, Washington, DC, USA) recognized glass and glass ceramics as central to many of the great engineering successes of the twentieth century, such as solid-state lasers, glass fiber optics, and glasses for obtaining images technologies, and glass films in microelectronic devices among others [2]. For example, Edwards et. al. [1] reported that in 2013 the glass industry managed to replace, on a large scale, incandescent bulbs with compact fluorescent bulbs, thus removing 4200 tons of CO2 [1]. Such an impressive and overwhelming advance has been only possible because there is a strong community of researchers around the world (both for academics and business community) dedicated to developing, from basic science, new knowledge to increment the complexity of the material (new glassy alloys with various unique properties), obtaining as such new opportunities for the applications of glasses and therefore new technologies and disruptive innovations. Glasses are defined as solids with a randomized three-dimensional structure that does not present a long-range periodic atomic structure (usually with an order of a few nanometers), and exhibits a region of glass transformation that is time dependent. The transformation process of a substance into a glass, i.e., a non-crystalline amorphous solid, is known as vitrification [3]. In 1932, a theory for glass structure was proposed by W. H. Zachariansen [4], where he established the topological conditions necessary for easy formation of glass. Such theory classifies the cations in a glass as: (a) Network-formers: elements which normally have coordination numbers of 3 or 4 (b) Network-modifiers: elements which generally have coordination numbers ≤6. (c) Intermediates: which may either reinforce the network (coordination number of 4) or further loosen the network (coordination numbers of 6–8), but cannot form a glass per-se. For example, in oxide glasses, the relation between the oxygen and the cation of the oxide compound essentially influences the glass-forming ability of the oxide. In this manner, compounds selection of the glass provides certain strategic and competitive advantages in the material and therefore influences the characteristics of the product and its cost. Nowadays, there are numerous new and traditional glass families (silicate[5], borate [6], chalcogenide [7], fluoride [8], germanate [9], halide [10], phosphate[11], tellurite [12] or a mixture of these components, or other inorganic oxide glasses, as so also organic, metallic, and ceramic glasses) that are studied strongly to develop the next level of innovation in glass for addressing the most significant challenges facing the world today. Such families of glasses have challenged the traditional notion of what constitutes a glass, inspiring the research community to think more broadly about the possibilities of entirely new glass chemistries. For example, silicate glasses are the oldest amorphous materials, and therefore the best known and most developed, with wide technological applications, where more than 95% of the existing glass companies in the world work with these silicate glasses and their mixtures.

Overall Aspects of Glasses for Photonic Devices

3

Despite all the scientific knowledge developed and identified techniques for the manufacture of glasses, glass formation requires a more precise comprehension of the fabrication process. Under this scenario and considering the scope of this chapter, we can mention some current challenges: 1. When the components of the glass are molten, employing the melt-quenching technique, the atoms are forming unions and continuously ordering themselves seeking to find their thermodynamic equilibrium, it is at this moment that we have a dynamic structure. Then, after doing the heat treatment of the glass, we have a static structure. In both cases, the computer simulations are of big help to understand the structure forming in the glasses (e.g., diffusion process, local symmetries, transitions states, electrostatic and kinetic energy, among other phenomena). For example, in the simulation of molecular dynamics, we can obtain the compatibility of the time scale with high-speed shock events, thus becoming a very suitable tool to study the effect of shock loading on the structure of a glass. 2. In addition, structural relaxation in glasses is a dynamic phenomenon involving cooperative atomic motions, in which glass structure changes with annealing temperature and time. We can assume that the kinetics of structural relaxation are closely related to the wide distribution of the nanoscale heterogeneous structure state in glasses, which implies structural changes of two types of α-relaxation and β-relaxation [13]. 3. When the glass is employed as the substrate, it requires a good surface for the junction (the interface is as state border controls the changes but does not stop them). For example, when temperature increases, the mobility of ions inside the glass increases (both anionic and cationic), which can generate an ionic exchange process at the interface. Some volatile species can be lost, generating significant structural modifications detrimental to applications such as integrated quantum photonics or plasmonics. 4. Glasses are also employed as photonic devices, hence it is important to decrease the signal optical losses into the glass. For instance, there are many studies carried during the last 40 years, hence, many processing techniques for the purification of glasses, with special attention to the transmission performance of the middle infrared (mid-IR). 5. Photonic and optoelectronic devices based on thin films are of interest from various research fields including but not limited to material science, integrated quantum photonics and quantum engineering. In this frame, 3D glass is a good approximation to obtain those devices, however, process fabrication in 3D via printing is still a challenge for the scientific community. 6. New application of photonic glass has promoted many novel devices and components that go beyond the original use, much of this event was based on the successful preparation of silica glass. Nevertheless, silica glass suffers from some disadvantages (short transmittance range, narrow emission band, high phonon energy, optical amplification, low rare-earth ions (REI) solubility, and low gain coefficient), which limit the further expansion of related materials and devices.

4

J. L. Clabel H. et al.

For instance, among other technologies to solve the explosion of big data, it is necessary to develop a large capacity for transmitting information, and ultrafast real-time processing. In this perspective, soft2 glasses have attracted great attention and interest from researchers. 7. Another challenge in the glass technologies is the development of the lightemitting diodes (LEDs) that, in contrast to conventional light bulbs, are more efficient with low energy dissipation and exhibit longer lifetimes. In this sense, it is necessary to fabricate more transparent glasses with high gain in order for the light to be emitted in the different desired visible colors. For the points mentioned above, we hope that interdisciplinary exchanges between the scientific and enterprise communities will enhance creativity in solving these and other problems. In such a context, we feel that this chapter deals with essential current issues and is exciting in the context of the advancement of science and technology.

2 Glass Manufacturing Process The history of glass manufacturing dates back to 1400 B.C. with the first glass casting evidence in wax molds [14]. Blow casting has also taken place throughout time with the manufacturing of glass bottles and art pieces [15]. Since then, many techniques have been studied and developed such as melt-quenching, sol-gel, hot-pressing of gels, physical vapor deposition, chemical vapor deposition, spark plasma sintering, scaffold fabrication techniques, 3D printing, additive manufacturing, or selective laser melting, among others. To understand the conditions for glass formation, it is essential to consider the glass-forming ability (GFA) of the glass system, which describes the resistance of the melt toward crystallization during the cooling process [16]. Many models have been investigated to understand the ability of the system to form a glass [17]. Glass systems are usually made by network formers, e.g., silica (SiO2 ), phosphorous oxide (P2 O5 ), tellurium oxide (TeO2 ), germanium oxide (GeO2 ), etc. These network formers can form a rigid glass network with a cationcentered polyhedron connected by bridging oxygen (BO) as defined by the W. H. Zachariansen random network theory [4]. However, recent studies show that glasses can be formed without following these principles [18]. Even though glass formers can form a glass on their own, network-modifiers, e.g., alkaline and alkaline earth elements, can be added to the glass to depolymerize the glass structure, improving its GFA and defining the glass properties. Sometimes the added elements to the systems are intermediaries, that is, they can either act as a network former or as a modifier in different regions of the glass structure, e.g., ZnO, Al2 O3 , etc. [3]. 2

The term “soft” mainly refers to the relatively low melting and softening temperature, small viscosity, and low hardness of these glasses in comparison with the silica glasses. Additionally, they can offer unique material properties absent in silica glasses including high linear refractive index, high transparency from the near-infrared (NIR) to the mid-infrared (MIR) region, high RE solubility, low phonon energy, etc.

Overall Aspects of Glasses for Photonic Devices

5

Here we discuss the more traditional methods of fabrication of glasses and in Section 5 we will display advances in glass forming for optical fibers.

2.1 Melt Quenching The most traditional method to fabricate glasses is the conventional melt-quenching technique (see Fig. 1). Melt quenching is very convenient for glassmakers as it has relatively low cost, is simple to perform, and is suitable for most glass systems [3, 19]. The method consists in first mixing the compounds, with high purity, in a recipient, usually an agate mortar, and taking the compounds into a furnace for melting. The components are usually taken into the furnace in a crucible. Such crucible is inert to the compounds of the glassy system to avoid contamination of the glass and/or damage to the recipient. For instance, the typical melting temperature of a multi-component chalcogenide, tellurite, germanate, borate, and silica glass is around 500, 750, 1400, 1650, and 1800 °C, respectively. During the melting process the control of furnace atmosphere can significantly influence glass properties. Many studies have been exploring the effect of different atmospheres on the properties of the glass [20, 21]. One of the main reasons for the use of a controlled atmosphere is to avoid the presence of hydroxyl groups (OH− ) due to its influence on glass structure and properties [22], such as the lasing properties [23–26], transparency in the infrared region, chemical stability [27], and fiber losses [28], among others.

Fig. 1 Comparing conventional melt-quenching and sol-gel techniques, considering the temperature as function of time. Here, T r is room temperature, t 0 and t a are the start and finish times of the process, respectively

6

J. L. Clabel H. et al.

After melting, glasses are quenched into a mold heated at the appropriate temperature. Defining the cooling rate of the quenching process is crucial for the glass properties given the sensibility of the glass mechanical properties, thermal expansion coefficient, and glass-transition temperature (T g ) with its thermal history [29, 30]. Lower cooling rates favor higher crystallization in the glass [31], while high cooling rates increase the formation of structural defects [32]; therefore, it is important to have good control over the cooling rate of the glass. The abrupt cooling in quenching and the consequent “freeze” of the glass structure lead to internal stress in the resulting glass. For this, after quenched, the glass is taken into another furnace for annealing [3]. The furnace must be at the annealing temperature to assure better softening of the glass structure. Melt-quenching technique must usually involve melting temperatures above 1000 °C and rapid cooling to form glass. The glass samples are then cut and polished at the desired shape or also could be ground.

2.2 Sol-Gel The sol-gel technique is an important wet-chemical technique employed to synthesize inorganic materials and organic-inorganic hybrids from liquid sources. In this manner, a low-temperature and chemistry-based alternative to produce glasses is by sol-gel, the technique is explored mainly in the field of bioactive glasses [33], semiconductors [34], and optoelectronics [35]. A suspension of colloids “sol” is obtained by the hydrolysis and polycondensation of alkoxides, usually in the form MOR where M is the metal and R is the alkyl group. Silica glasses are commonly obtained using tetraethyl orthosilicate (Si(OR)4 ), known as “TEOS” [36]. The solution is prepared with an organic solvent (ethanol, 2-propanol, etc.) in water and an acid or basic catalyst to accelerate the hydrolysis process and produce the suspension of solid particles in the sol for the condensation reaction. Usually, the process occurs either with a good stirring at room temperature or at temperatures around 40–80 °C. Polycondensation reactions advance with the cross-linking and polymerization of the suspension to form a wet gel, which is a solid interconnected network of coalesced solid particles [36]. The dry gel is obtained by removing the reactants (water, solvents, catalysts, and reaction products) from the pores of the wet gel with a controlled thermal treatment (50–80 °C). Finally, the glass is obtained by sintering and densifying the dry gel by heat treatment at high temperatures [36, 37]. The sol-gel method allows more control of the purity, homogeneity of the precursors, particles size, and porosity, which is particularly important to increase the bioactivity in biomedical applications [38]. Detailed information about sol-gel method and characterization can be found in [39]. Figure 1 shows comparing conventional meltquenching and sol-gel techniques, considering the temperature as a function of time. In addition, Table 1 shows a qualitative comparison between the glass techniques discussed here.

Overall Aspects of Glasses for Photonic Devices Table 1 Comparison between melt-quenching and sol-gel techniques

7

Technique

Advantages

Disadvantages

Melt quenching

Simplicity Low-cost Versatility of sizes and shapes Easy to produce in large scale

Low homogeneity Lower purity compared to other methods

Sol-gel

High homogeneity Control of particle size and shape High degradability (bioactive glasses) High purity

Complex process Expensive raw materials Difficult to reproduce in large scale

3 Characterization Techniques of Glasses For centuries, humanity has developed the skills and facilities necessary to prepare high-quality glasses from various compositions to cover diverse needs. The primary reason for this progress is the large array of characterization techniques that has been developed and applied to many industrial problems. Nevertheless, depending on the desired end glass, the fabrication processes can involve a variety of techniques. Within this framework, the scientific community has accepted that characterization methods are used in research from a complementary point of view. Several characterization techniques in the same glass allow us to understand the properties of the material and to answer scientific and technical questions to achieve the desired glass. This section will discuss characterization techniques to determine the structural, thermal, mechanical, and optical properties in glasses accepted and employed by the community.

3.1 Structural Properties 3.1.1

XPS

X-ray photoelectron spectroscopy (XPS) is a technique used for qualitative and quantitative elemental identification and is commonly used to determine the surface chemistry stoichiometry of the glasses. XPS technique evaluates the sample local chemical environments and even estimates the ratio of the different chemical state in the samples through exploration of the energy levels of the constituent atoms [40]. The basic principle of the XPS technique is the photoelectric effect which can be explained through the energy level diagram shown in Fig. 2a. Here, the glass is irradiated with an X-ray beam with energy hv (low energy ~ 1.5 KeV, in order to provoke the photoelectric effect) that will be absorbed by the atoms, leading to

8

J. L. Clabel H. et al.

the origin of the excited state, which is relaxed by the emission of a photoelectron (atom ionization) from the inner electronic layers (core) of the atom. The spectrum is dominated by three photoelectron peaks, corresponding to electrons originating in the 1s orbitals of the carbon (C1s), nitrogen (N1s), and oxygen (O1s) atoms in the sample, e.g., the C1s peak can be due to an outermost surface layer of contaminants containing carbon. Further, the kinetic energy of the ejected electron E K leaving the target atom depends on the energy of the incident photon, and is expressed as follows [40]: E B = hv − E K − φ s , where hv is the energy of incoming radiation, E B is the binding energy of the photoelectron with respect to the Fermi level, and φ s is the work function of electrons from the glass. Based on the analysis of the correlation between the binding energy of C1s peak and sample work function (φ s ), the C1s peak was given according to 289.58-φ s [41]. Such a formula makes chemical state determination more accurate and more reliable bonding assignments [42]. The φ s of the glass samples must be considered for each type of glass, from this value the spectra must be referenced to the binding energy of C1s in the study of glass sample. The information obtained from XPS measurements relies on the observation of photoelectrons emitted from core levels of the atoms in the sample surface region. Here, the elements present on the surface of the sample are directly characterized by determining the binding energies of the photoelectric peaks. Thus, it is possible to determine information around the chemical composition, oxidation state and elemental analysis, and interaction between electrons in the electronic structure (electronic correlation) of closed-shell atoms and molecules. From the survey of XPS spectrum, the atomic concentration of constituent elements in the glass can be estimated, see Fig. 2b (up). The peak shift can be used to predict the glass local chemical environments, Fig. 2b (down). The peak around ~530 eV is associated with BO atoms environment, i.e., oxygen atoms covalently bonded to glass networkforming atoms on both sides (Te–O–Te). While the peak around ~529 eV is due to

(a)

(b)

Fig. 2 a Basic principle of an X-ray photoelectron spectroscopy, b origin of XPS core levels with different binding energies for a binary glass sample TeO2 –ZnO

Overall Aspects of Glasses for Photonic Devices

9

non-bridging oxygens (NBO) atoms environment, i.e., oxygen atoms are ionically bonded, at least on one side or double-bonded to a glass network-forming atom. In the glass system (ZnO–TeO2 ), the addition of ZnO gives rise to TeO2 , ZnTeO3 , and Zn2 Te3 O8 , predominantly the latter [43].

3.1.2

Raman Spectroscopy

When a laser beam with energy (frequently at the visible range) hv hits a sample, a photon interacts with the electron cloud and chemical bonds of a molecule and excites it to a virtual energy state [44]. Subsequently, a small fraction of the incident radiation is scattered, either elastically or inelastically, giving rise to emitted photons of energies either higher or lower than that of the incoming radiation, this is called the Raman effect. Therefore, the Raman shift may be useful in distinguishing the structure of different constituents into the network. Molecular groups form glasses with a limited number of vibrational modes associated with the masses of the constituent atoms, the interatomic forces, and the geometry of their arrangement. Raman effect in glass is associated with the shortrange vibration of molecular groups. In glasses, the random network distribution of short-range vibration (up to 3 Å) is based on basic structure determined by the properties of the chemical bonds as coordination number, bond length, and bond angles [45]. However, the distribution of bonding forces and bond angles within the tetrahedral network causes the broadening and overlapping of the Raman bands. In this manner, structural details can be obtained from the knowledge of the characteristic vibrational frequencies of the short-range molecular species. For instance, silicate glasses have a structure based on a network of SiO4 tetrahedra (network formers) that displays a short-range order due to its amorphous nature. In the pure silica, the oxygen ion connects two tetrahedra (BO), but when cations alkali or alkaline earth metals are incorporated (network-modifiers) they break the Si–O bonding (depolymerization) by creating an ionic bond between the freed oxygen and the cation, i.e., more NBO into the glass network. The presence of modifier species leads to different types of tetrahedral coordination in the glass network and is denoted by Qn , where n is the number of BO, varying between 0 and 4 [46]. Q4 coordination corresponds to silicate without NBOs, Q3 to species with one NBO, and so forth. The spectra of silicate glasses are mainly due to the two most intense vibrational modes of the SiO4 unit, the symmetric stretching ν s (~500 cm−1 ), and a bending mode δ s (~1000 cm−1 ). Such spectral interpretation is based on the vitreous silica, the broad band between 300 and 600 cm−1 is associated with the bending vibrations (δSi–O ) of the polymerized structure, while the band centered at 800 cm−1 is affected by compositional and structural changes [47]. The hydroxyl group in SiO2 glasses is verified in the band centered at 3598 cm−1 . The weak band near 2350 cm−1 arise due to Si–OH groups involved in intra-tetrahedral hydrogen bonding across an edge of the SiO4 tetrahedron [44]. M. Heili et. al. focus on the densification measured by Raman spectroscopy in SiO2 and GeO2 –SiO2 systems [48]. For the SiO2 glass, the bands centered at 800 and 430 cm−1 are assigned to Si–O–Si stretching and

10

J. L. Clabel H. et al.

T2b vibrational mode, respectively. The two sharp bands at 480 and 598 cm−1 are denominated defect bands and are assigned to the breathing vibration, the intensity of these bands increases with the increasing temperature. The addition of GeO2 leads to a narrowing of the main band, indicating a reduction of inter-tetrahedra T–O–T angle distribution (T = Ge or Si). For these two glasses, the defect bands’ intensities increase with increasing temperature, indicating a structural change. Thus, the higher the density is, the higher the Raman defect band intensities are for the pure silica glass, but the opposite behavior is observed in GeO2 –SiO2 glass. Tellurite glasses present three structures, TeO4 trigonal bipyramid, TeO3 trigonal pyramid, and TeO3+1 polyhedral. Based on 670 and 760 cm−1 observed in Raman spectra, it can be said that those wave numbers belong to the stretching vibration of trigonal bipyramid and trigonal pyramid or TeO3+1 units, respectively [12]. Then, the reduced phonon energy increases the efficiency of luminescence and provides the possibility to develop more efficient visible optical lasers.

3.2 Thermal and Mechanical Properties Fabrication of glasses implies the knowledge of their thermal and mechanical properties. Such values of characteristic glass temperatures are essential in the synthesis process for annealing, melting point, thermal shock, and heat treatment. Further, glasses like any other material exhibit a limit on damage resistance under elastic deformation, pressure, and impact, which are fundamental characteristics for the design of new glassy devices such as optical fibers, smart phone screens, windshields, and flexible thin glass, just to mention few examples.

3.2.1

Differential Scanning Calorimetry

The differential scanning calorimetry (DSC) is widely used to characterize the phase transitions of glasses to evaluate, among other properties, their thermal stability. The thermal stability is determined by the difference of the onset crystallization temperature (Tx ) and the glass-transition temperature (Tg ), i.e., ΔT = Tx − Tg . Larger values of ΔT (≥ 100◦ C) indicate good thermal stability, i.e., the thermal stability can be defined as a delay in the nucleation process, which permits, e.g., drawing optical fibers (in general, ΔT > 100 °C is preferable for practical applications). In addition, the chosen compositions are found to have excellent glass-forming ability with high thermal stability. Such value is critical for the fabrication of optical fibers and photonic devices [3, 5]. In order to determine such temperatures, a common technique is the heat-flux DSC, where the system calculates the heat involved (exothermic or endothermic process) in the temperature increments of the sample compared with a reference material [49]. The output data is the heat flow as a function of the temperature, where both Tg and Tx are calculated in the regions where there is an abrupt heat change with the intersection of tangents of the base line and the extrapolation of the

Overall Aspects of Glasses for Photonic Devices

(a)

11

(b)

Fig. 3 a Illustration of a DSC thermogram of a glass showing three regions: glass transition, crystallization, and melting. Tg and Tx can be determined by the intersection of the tangents, denoted as green lines. Tc and Tm are located at the maximum and minimum of the peak, respectively. b Illustration of a typical TMA thermogram of a glass. Similar to DSC, Tg is determined by the intersection of the tangents. Ts is centered at the maximum compression. The slopes of the linear regions (dashed lines) give the linear coefficients of thermal expansion α

linear region during the phase transition as can be seen in Fig. 3a. Other important temperatures are the crystallization temperature Tc and the melting point Tm .

3.2.2

Differential Thermal Analysis

Similar to DSC, differential thermal analysis (DTA) provides the same information of the glass transition, crystallization, and melting process. In contrast to DSC, DTA measures the difference in temperature between the reference material and the sample, see Fig. 3.

3.2.3

Thermal Gravimetric Analysis

Thermogravimetric or thermal gravimetric analysis (TGA) measures the weight changes of a sample as a function of the temperature at a constant heating rate, in general, and under various atmospheres (vacuum, air, oxygen, nitrogen, etc.). The TGA system consists of a furnace with a balance inside and a crucible. For instance, the use of different atmospheres causes different decomposition behaviors such as melting time and weight losses [50, 51]. Both DSC and TGA are used in conjunction to evaluate the thermal stability of the glasses.

3.2.4

Thermomechanical Analysis

Besides calculating the characteristic temperatures in glass material, the thermal expansion coefficient can be obtained as a function of temperature using thermomechanical analysis (TMA). For instance, silica-quartz glass possesses a low thermal

12

J. L. Clabel H. et al.

Fig. 4 Schematics of a Vickers hardness test (left). The sample is indented and the diagonal lengths of the impression give the magnitude of the hardness (right)

expansion coefficient (6.7 × 10−7 /K), typical values of tellurite glasses are around (17 − 15) × 10−6 /K, and lead glasses possess values between (7.5 − 9.0) × 10−6 /K. Such coefficient depends on the host. In this technique, the sample is inserted into a furnace and a force is applied while temperature increases. At the same time, the system measures the length of the sample during the whole process. Figure 3b shows a TMA thermogram, where the value of Tg is calculated in the intersection of the tangents of the linear regions where an abrupt transition from the glassy to liquid occurs, similar to the DSC thermogram. The softening point Ts is the temperature at which the glass begins to deform under its weight [51] and is located at the maximum compression point. The linear coefficients of thermal expansion α can be estimated using the slopes of the linear regions of the thermogram.

3.2.5

Vickers Hardness Test

The Vickers hardness test is a method for determining the hardness3 of a material. It consists of indenting a material with a diamond pyramid indenter by applying a force perpendicular to the sample and the hardness is given by the depth of indentation on, in this case, the glass. This produces an impression in the glass and the magnitude of the hardness, expressed in Vickers hardness (HV), is given by the applied force and the length of the diagonals (see Fig. 4) as HV = 1.85544 F/d2 [52] since d1 ≈ d2. This last means that the smaller the size of the print, the greater the hardness of the glass. For example, silica glasses have 635 kg/mm2 while tellurite glasses have around 430 kg/mm2 , such values are evident when evaluating the fragility of those glasses [52]. In addition, the chemical composition of silicate glasses significantly affects the hardness values. 3

The ability of a material to resist elastoplastic deformation.

Overall Aspects of Glasses for Photonic Devices

13

It is important to mention that the NBO reduces the connectivity of the glass, which in turn alters the short- and medium-range order, i.e., affecting the packing fraction and therefore the glass hardness. The Vickers hardness test is one of the easiest techniques to quantify hardness since the calculations do not depend on the size of the intender.

3.2.6

Impulse Excitation Technique

Mechanical properties such as Young’s modulus and Poisson’s ratio can be measured using the impulse excitation technique (IET). IET is an easy, fast, and non-destructive method for characterizing acoustic and mechanical properties of a material, which are essential for material applications and quality control procedures. Here, a rectangular sample is suspended by two supports, whose positions depend on the length of the sample. Afterward, excitation by mechanical vibrations is applied at the central point between the supports with an impact bar to generate sound waves, which can be recorded by a high-precision microphone. The acoustic signal is treated by Fourier transformation to obtain the natural frequency of the material. Using the mass, dimensions, and natural frequency of the sample, Young’s modulus, shear modulus, and Poisson’s ratio can be obtained according to the American Society for Testing and Materials (ASTM) standard [53]. For instance, typical values of Young’s modulus of tellurite glasses are around 60–70 GPa. For more technical details of this technique, the reader is referred to [53, 54].

3.3 Optical Properties Here the reader will find some physical background and some experimental techniques that can provide information on the glass optical properties. The techniques described here can provide valuable information on the glass optical performance. This section is divided into four subsections, first some theoretical background on the origins of the linear refractive index in glasses and some expected values from different glassy systems will be presented. In the second part, a brief introduction on light absorption and some of its spectroscopic information will be presented. After discussing photoluminescence, static and dynamic processes are presented to understand the glass performance as a good host optical medium. Finally, the last part will be devoted to a thermo-optical technique known as thermal lens spectroscopy, in which the glass thermal diffusivity can be measured.

3.3.1

Refractive Index

When light travels through an isotropic dielectric medium such as glass, the oscillating electric field of the electromagnetic wave displaces the bounded electrons from

14

J. L. Clabel H. et al.

the equilibrium positions. The oscillating electric field makes the electrons move like a damped harmonic oscillator, then the equation of motion can be written as [55] m

→ → r d 2− d− r − → → r = −e E , + mγ + mω02 − 2 dt dt

(1)

where m is the electron mass, r is the position vector, e is the magnitude of the electron charge, t is the time, γ is the damping factor, ω0 is the natural oscillation − → − → ˜ frequency of the system, and the oscillating electric field is E = E 0 ei( K z−ωt) , where i is the square root of −1, K˜ is the complex wave number, z is the coordinate of the direction of propagation, and ω the frequency of the electromagnetic wave. Since − → the oscillating electric field moves the electrons, a time-dependent polarization ( P ) − → is created, so in terms of P the solution of Eq. (1) is − → P =

N e2 − → E, −mω2 − iωmγ + mω02

(2)

where N = number of electrons per unit of volume. Using Eq. (2) together with the wave equation in a dielectric medium [56], one can find the solution as   ω 2  N e2 1 2 ˜ 1 + m 0 × ω2 −ω2 −iγ ω , where 0 is the permittivity of free space, and K = c 0 the complex wave number K˜ is given as K˜ = k + i α.

(3)

In terms of the complex refractive index [57, 58] N˜ =n + i κ ω K˜ = N˜ . c With κ is the extinction coefficient and α =

(4) ω κ, c

where c is the speed of light. − → − → Now the oscillating electric field can be written as E = E o e−αz ei(kz−ωt) . As can be seen, from the term e−αz , the electric field gets attenuated when propagating through  − →2 the medium. In terms of intensity (∝  E  ), it holds a proportionality to e−2zα , with 2α as the absorption coefficient. Substituting the complex wave number K˜ given in Eq. (4) into the formula of K˜ 2 given before, then   1 N e2 . N˜ 2 = 1 + m 0 ω02 − ω2 − iγ ω

(5)

Equation (5) is true, assuming that all electrons are similarly bound. On the contrary, only a fraction of the electrons will be associated with one resonance

Overall Aspects of Glasses for Photonic Devices

15

frequency, another fraction to another frequency, and so on. Now Eq. (5) will be a summation for all resonance frequencies,   fu N e2 2 ˜ N =1+ u ω 2 − ω 2 − i γu ω m 0 u

(6)

and f u is known as the oscillator strength [57], where u is the number of oscillators, while ωu and γu are related to the oscillator u. In the transparent region of glass, the damping constant γu is very small compared to ωu2 − ω2 , then the refractive index can be represented by   fu N e2 . n =1+ u ω2 − ω2 m 0 u 2

(7)

From experimental refractive index data collected at different wavelengths, a fitting procedure can be done. Equation (7) written in terms of the wavelengths is known as Sellmeier’s formula and fits very well with the experimental data, as seen in Fig. 5. There are several techniques and equipments capable of measuring the refractive index with precision, such as Abbe refractometer [57, 58], ellipsometry [59], prism-coupling [60], and interferometry [61] to cite a few. The refractive index is highly dependent on the glass composition, i.e., in tellurite glasses n ~ 1.8–2.3 [62], germanate glasses n ~ 1.7–2 [63], phosphate glasses 1.46– 2.2 [64], silica glasses n ~ 1.43–1.49 [65], and chalcogenide glasses n ~ 2.22-3.51 [66]. Fig. 5 Refractive index dispersion of a germanate-gallate glass—experimental data and fitted Sellmeier equation

16

3.3.2

J. L. Clabel H. et al.

Absorption

The intensity of light passing through glass diminishes, depending on the type of glass, this decrease in intensity comes from different sources—absorption, scattering, and reflection. Absorption comes from allowed optical transitions, and when all other sources that can vary the beam intensity are unconsidered (reflection and scattering), the variation of the light intensity is given by the Lambert-Beer law [67]: I = I0 e−αd , where I 0 is the incident light intensity, α is the absorption coefficient, and d is the sample thickness. In commercial spectrometers, transmission measurements are done by comparing the incident light intensity with that of transmitted light as a function of wavelength (λ), namely, the transmittance: T = II0 . Another quantity that can be measured is the absorbance, and it’s defined as   I0 A = log10 (8) = −log10 (T ). I Generally, in the literature, one can find the absorption measurement on doped glasses shown as the absorption coefficient (α) or absorbance. The absorption coefficient and absorbance are quantities that vary linearly with the absorber concentration, often being used to check the doping quality/quantity of glasses [68], as shown in Fig. 6. Figure 6 shows an absorption coefficient graph for thulium-doped phosphate glasses. In this glass system, the Tm3+ doping quantity varies for each glass, the linear behavior from α with the Tm3+ quantity can be noted in the inset. It’s easy to obtain α from the transmittance measurement, here, we can find that, T = II0 = e−αd , where d is the thickness of the sample, then Fig. 6 Absorption coefficient from Tm3+ -doped phosphate glasses [69]

Overall Aspects of Glasses for Photonic Devices

α(λ) =

A 1 × . log10 e d

17

(9)

In addition, the optical density (OD in dB) is defined as   I . O D = −10 × log I0

(10)

When light reflection cannot be neglected, transmitted and reflected light must satisfy the condition: R + T = 1. For normal incidence, reflection is independent of the polarization [57], and it depends only on the medium-glass interface refractive 2

−n 2 index as R = nn 11 +n . 2 Reflectance measurements are made similarly by commercial spectrometers, generally with an accessory. The measurement is made using an integrating sphere where the light reflected from the sample reflects on its wall until it reaches the detector, both diffuse and specular reflection. For thin films, these measurements need to be carefully made and each contribution can be analyzed. For further details on this the reader can see [70, 71].

3.3.3

Photoluminescence

Glasses are widely used as hosts for optically active ions/materials [72, 73] due to their stable environments and dopant solubility. Steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL) are non-destructible and experimentally feasible techniques that together with other techniques, such as absorption, hold valuable information on the interaction of the active ions/materials with the environment, each other, and other dopants. PL is one of the many luminescence that a material can have (thermoluminescence, bioluminescence, electroluminescence, etc.), and it’s achieved by optically exciting the material. When measuring steady-state emission, the system is always excited by a continuous light source and its PL is collected. On the other hand, for TRPL, the intensity decay is measured by exciting the system with a pulsed light source, where the pulse width is smaller than the systems decay time. When the excited electrons return to the fundamental state, they can decay through various pathways, radiative and non-radiative, as shown in Fig. 7. In addition, the overlap between the absorption and emission cross sections leads to energy transfers between them, known as Forster Resonant Energy Transfer (FRET). One can evaluate the energy transfer quantitatively through the microparameters of energy transfer [74] as CAD

3c = 8π 4 n 2

D A σem (λ) × σabs (λ)dλ,

(11)

18

J. L. Clabel H. et al.

Fig. 7 Three-level degenerated system showing, a excitation by light absorption b non-radiative decay to lower energy, c radiative decay

D where A refers to acceptor, D refers to donor, σem is the donor emission cross A section, and σabs is the acceptor absorption cross section, while c, n, and λ refer to speed of light, refractive index, and wavelength, respectively. Here one of the active ions/materials is the energy donor, and the other is the energy acceptor. When the cross sections do not overlap, this energy transfer can be mediated by one or more lattice phonons, and the non-resonant energy transfer microparameter becomes [75]

CAD

∞ D  + e−(2ρ+1)S0 S0m 3c glower D A λm × σabs = (λ)dλ (ρ + 1) σem D 8π 4 n 2 gupper m m=0

(12)

1 1 with λ+ m = ( 1 −mω0 ) , ρ = (eω0 /kT −1) is the average phonon occupancy at temperature λ T, k is Boltzmann’s constant, and ω0 = highest phonon energy, where  is Planck’s constant divided by 2π, and m in the denominator of Eq. (12) is the electron mass. D D and gupper are the donor lower and upper level degeneracies, S0 is the Also glower Huang-Rhys factor [76]. These energy transfers and the non-radiative decays from the emitting material have a direct impact on the measured lifetime, since [77]:

η=

Aradi, j + Anon−radiative . τrad

(13)

1 With τrad = Aradi, , where Aradi, j is the radiative decay rate, Anon−radiative is the j non-radiative decay rate, and η is the quantum efficiency.

Overall Aspects of Glasses for Photonic Devices 1

Decay 1 Decay 2 Decay 3

PL Intensity (a.u.)

Fig. 8 Experimental data from Er3+ -doped germanate glasses under 980 nm excitation and 1532 nm emission. In the figure the decays are becoming faster from 1 to 3

19

0.0

0.5

1.0

1.5

2.0

Time (ms)

3.3.4

Lifetime

The lifetime measurement gives valuable information on the decay mechanisms and energy migration in the system under study [78, 79]. Depending on the interactions and decay paths that the studied system has, one can measure the TRPL and find the appropriate decay function through fitting procedures. With these phenomena, the measured lifetime can be larger than the radiative lifetime decay, leading to quantum efficiencies bigger than unity [80, 81]. Figure 8 shows PL intensity decays from Er3+ -doped germanate glasses under 980 nm excitation, and 1532 nm emission. If they follow a single exponential form then the with decay time can be found by I (t) = Io e−t/τ . Since a lot of mechanisms interfere

n Ii e−t/τi the measured lifetime, the decay could be a multiexponential I (t) = i=1 or a stretched exponential decay [82–84].

3.3.5

Absorption and Emission Cross Sections

With the absorption coefficient in hand, a very useful and meaningful quantity can be derived, the absorption cross section (σabs (λ)). The absorption cross section describes an effective area in which the absorber interacts with light in its environment (glass composition). In order to evaluate the absorption cross section, the ion’s density (N) must be known without any difficulty, σabs (λ) =

α(λ) . N

(14)

In Table 2, the dependence of the absorption cross section on the absorber and light wavelength was verified.

20

J. L. Clabel H. et al.

Table 2 Absorption cross section for some absorbers-doped glasses Glass

Absorber

Wavelength (nm)

σabs (×10−20 cm2 )

ZBLAN*

Yb3+

~975

~1.1 [85]

Silicate

BACs**

~1240

2.1 [86]

Oxyfluoride

Ag nanoparticles (ϕ = 2.8 nm)

480

0.04 − 0.3 [87]

Silicate

Oxygen-deficient centers

~163

0.08 [88]

Germano-gallate

Tm3+

1650

0.47 [68]

* Fluoride glass, ZrF4–BaF2–LaF3–AlF3–NaF, commonly known as ZBLAN ** Bismuth active centers

Einstein’s A21 and B12 coefficients are related to the emission and absorption radiative transition rates [74]. But, Einstein’s relationship is considered a simple two-level system. For real systems, more suitable approximations for the transition rates are used. For instance, Fuchtbauer-Ladenburg equation [89], Judd-Ofelt theory, or McCumber theory [90–92] can be used. McCumber theory or reciprocity relation is defined as [92]  − hν . σem (ν) = σabs (ν)exp kB T 

(15)

Here is the excitation energy between the two levels, v is frequency of light, k B is Boltzmann’s constant, and T is the absolute temperature. Namely, the emission cross section σem (ν) (defined for transitions between two sharp individual levels 1 2 and 2 is given as σem (ν) = 8πA21n 2cν 2 gem (ν), A21 = 1/(radiative lifetime), gem (ν) is the 0 emission lineshape function of the transition, ν0 is the peak frequency, and n is the 2 refractive index), and the absorption cross section σabs (ν) = gg21 8πA21n 2cν 2 gabs (ν) can 0 be a good approximation as long as the width of the individual Stark level is small compared to k B T (thermal equilibrium with the lattice), where g1 and g2 are the levels 1 and 2 degeneracies, respectively, and gabs (ν) is the absorption lineshape function of the transition. That is, to employ the McCumber theory one must comply with such requirements, but glasses doped with REI do not show a transition between two energy levels; on the contrary, those are broadband due to their network characteristic (different sites), and for such reason that those glasses are known with nonhomogenous broadband emission. In this case, it is more recommended to employ the Fuchtbauer-Ladenburg equation: σem (λ) =

3λ5 Aradi, j I (λ)  , 8π cn 2 λI (λ)dλ

(16)

where I (λ) is the emission intensity at the wavelength λ and Aradi, j is the radiative transition rate between the levels i ↔ j, besides we can write gem (ν) =  λII (λ) . (λ)dλ

Overall Aspects of Glasses for Photonic Devices

21

Fig. 9 Absorption and emission cross sections from the 4 I13/2 →4 I15/2 of Er3+ transition in germano-gallate glass

Here care must be taken when measuring the emission cross section, since some effects, such as reabsorption, can deform the spectra, for that some measuring techniques must be applied to avoid such deformation in the photoluminescence spectra. This reabsorption process occurs when some of the active ions/material in the glass have strong absorption at such emission wavelength. In Fig. 9, this is shown for Er3+ doped germanate glasses, where both the emission and absorption cross sections (McCumber theory) overlap, which means another Er3+ ion could absorb emitted radiation from one Er3+ ion in the vicinity.

3.3.6

The Commission International De L’Eclairage (CIE) Coordinates

Human eyes respond to light in the visible region, and the brain processes that light to our perception of color. Nevertheless, when we are dealing with photoluminescent materials in the visible region, color perception with the naked eye of the emitted light is not an accurate way to characterize the emission spectrum. Therefore, it is crucial to quantify the human perception of color. The Commission Internationale de L’Eclairage (CIE) developed the CIE color space for this purpose and is widely used for measuring colored light. This color space is based on observer sensitivity functions named tristimulus values, and is represented by coordinates in the CIE 1931 chromaticity diagram. Hence, the color of a photoluminescence spectrum can be quantified in (x, y)-coordinates. For instance, the coordinate of the reference white color is (0.33, 0.33). The CIE 1931 chromaticity diagram is illustrated in Fig. 10, where the outer boundary represents the spectrum locus of pure monochromatic lights expressed in single wavelengths, and the black curve with dots is the Planckian locus, where each point corresponds to the correlated color temperature (CCT). The CCT is a calculated temperature (in K) for a type of light emitted by a blackbody radiator.

22

J. L. Clabel H. et al.

Fig. 10 CIE 1931 chromaticity diagram showing the Planckian locus curve, where the CCTs are represented by dots

In Sect. 7.8, the CCT of different kinds of white light in REI-doped glasses shall be discussed. For further information regarding the development of the CIE standards and (x, y)coordinates calculation from the photoluminescence spectrum, the reader can refer to [93].

3.3.7

Thermal Lens

The thermal lens is a photothermal phenomenon in which a beam heats the sample through non-radiative channels. In this technique, a Gaussian beam generates heat in the sample and due to the Gaussian nature of the beam, a temperature gradient is formed. With the temperature change, the refractive index is changed, thus forming the lensing effect. The technique has been used for measuring the thermal diffusivity of crystals, ceramics, liquids, and glasses [94, 95] with absorption coefficient as low as 10−7 cm−1 [96], it is a very sensitive, non-destructive, simple pump-probe technique and measurements can be done at room temperature [95]. There are two main setups for this technique: single beam method or modematched dual beam and mode-mismatched dual beam. Here we will only discuss the second setup since it is proved to have better signal-to-noise ratio [97]. The mode-mismatched dual-beam setup is shown in Fig. 11. As said before, the pump laser heats the sample creating a temperature gradient, to obtain it, some assumptions need to be done: (i) sample thickness must be smaller than the confocal length of the beams; (ii) sample is larger than pump beam waist (denoted as ωpump ), the sample is absorbing (iii) low power; (iv) refractive index

Overall Aspects of Glasses for Photonic Devices

23

Fig. 11 Diagram of the mode-mismatched dual-beam setup dn change dT is constant inside the sample during the excitation; and (v) probe beam power must be low to avoid additional thermal lens effect formation. The heat generated by the pump beam per unit length and per unit time between r, which is the radial length, and r + dr in the sample is written as Q(r ) = 2π AI (r )dr, where A is the absorption coefficient at the pump wavelength (λpump ), I(r) is the pump intensity, given by 

2Ppump − I (r ) = e π ωpump

2r 2 2 ωpump



.

(17)

With Ppump being the pump beam power. Solving the heat transfer equation with the appropriate time-dependent boundary conditions [98], the solution for the temperature variation is defined as 2Ppump A ΔT (r, t) = 2 π cρωpump

t 0

  2 2r 2 /ωpump 1 × exp − dt ' ' 1 + 2t ' /tc 1 + 2ttc

(18)

ω2

pump and tc = 4D , and D is the sample thermal diffusivity, tc is the characteristic thermal ˇ time, t is the time, and here ρ is sample density. To help visualize a schematic diagram of the thermal lens effect is shown in Fig. 12.

Fig. 12 A variation on the refractive index due to the temperature gradient—forming a diverging lens or converging lens

24

J. L. Clabel H. et al.

Fig. 13 Sample geometric position in relation to pump beam and probe beam waists

The refractive index variation with the temperature can be written as n(r, T ) = dn dn dn ΔT . If dT < 0 a divergent lens is formed, if dT > 0 a converging lens n 0 + dT is formed. This refractive index variation makes the sample behave like an optical element causing a phase change [99]: θ = tc

t 0

−P

   2 2r 2 /ωpump 1 1 − exp − dt ' , ' 1 + 2t ' /tc 1 + 2t

(19)

tc

Al

dn where θ = kλpump , with A as defined before, l as the sample thickness, and k the dT pump thermal conductivity. All that is described above is an effect from the pump beam, since this is a pumpprobe technique, we need to focus now on the probe beam. In the mode-mismatch setup, the sample position relative to the beam waists is shown in Fig. 13. As the probe beam passes through the sample, its intensity can be written as

⎡ I (t) = I0 ⎣1 −

⎞⎤2

⎛

2mV θ ⎠⎦ . × tan−1 ⎝   t  2 2 2 + 1 + 2m + V 2 (1 + 2m) + V

(20)

tc

In which Z 2  Z C soV = ZZ 1c , and Z c is the confocal length of the beam probe, 2  ω and m = ω1probe . pump Equation (20) together can be fitted with the experimental data to obtain thermal dn < 0, and the fit is shown in Fig. 14. diffusivity. A thermal lens signal for dT Table 3 shows some thermal diffusivity values measured by this technique.

Overall Aspects of Glasses for Photonic Devices

25

Fig. 14 Experimental data and fitting curve of Eq. (20) dn for a dT < 0 for a phosphate glass

Intensity

Experimental data Theoretical Fitting

Time

Table 3 Diffusivity for different materials obtained by the thermal lens technique

Material

D (×10−3 cm2 /s)

Soda-lime glass [100]

4.9 ± 0.3

Nd:YAG4 [101]

47.5 ± 0.9

Y2 O3 [102]

26

Tellurite [62]

2.6 ± 0.2

4 Glass Families Depending on the application, the glass must meet certain specifications. The chemical and physical properties frequently change with the type of glass families. In the following subsections, we will describe some of these glass families that are best known in the literature, it is worth mentioning that we have not discussed here silica or ZBLAN glasses because more in-depth studies on the subject can be found in the literature [3, 54, 55, 103].

4.1 Tellurite Glasses Tellurite glasses based on tellurium oxide are promising by their high non-linear refractive index, high dielectric constant, absence of hygroscopic properties, and low melting temperature, as well as good chemical stability and broad IR spectral region [12, 104]. These advantages in their physical properties play a key role in 4

Neodymium Yttrium Aluminum Garnet (NdYAG, NdY3 Al5 O12 ) is a synthetic crystalline material of the garnet group.

26

J. L. Clabel H. et al.

multiple applications as reported recently. Their physical properties depend on the type of tellurite glass formed and composition, i.e., binary, ternary, and quaternary tellurite glasses [12]. The structure of tellurite glass is generally based on binary systems, while those ternary and quaternary glass systems are used as glass-matrix to REI trivalent. For instance, a diversification of the tellurite glass systems can be found in [12]. Most of the structural studies on tellurite glasses have focused on systems containing modifier cations such as alkalis and alkaline-earths [105]. Tellurite glass has three basic structural units: TeO4 (trigonal bipyramid), TeO3 (trigonal pyramidal), and an intermediate with TeO3+δ polyhedron [12]. The addition of a modifier cation to TeO2 can convert TeO4 trigonal bipyramids with BO to TeO3+1 polyhedral with two terminal oxygens, and break up the Te–O–Te network via the creation of NBO atoms on the three- and four-coordinated Te–O units. Among their remarkable properties, tellurite glasses must have wide transparency, mainly mid-IR spectra and high linear and non-linear refractive indices, enabling photonic applications (e.g., supercontinuum generation, optical switches, mid-IR laser, and solid-state light generation). These characteristics are associated with composition. For example, in a transparent glass, the long-wavelength transmission is limited by absorption related to chemical bond vibrations, also called phonon energy. To the control of the absorption in long wavelength, network-modifiers (e.g., Li, Na, K, Rb, and Cs) and intermediates (e.g., Zn, Mg, Ba, and Pb) with specific absorption and greater than that of tellurium is a strategy used to maximize their properties. Networkmodifiers such as alkali metals, which promote the formation of NBO, give rise to trigonal pyramidal TeO3 units that absorb at 740 cm−1 compared to 650 cm−1 for trigonal bipyramid TeO4 units; this shift induces a decrease in the mid-IR transmission window [106]. Desirema et. al. [107] found that alkali metals with small ionic radii decrease the thermal expansion coefficient, the glass-transition temperature, and the chemical durability. However, an increase in the linear refractive index and the third-order susceptibility was observed. Clabel et. al. [108] investigated the influence of REI on the polarization and oxygen packing density (OPD) on the glass structure and analyzed the coordination environment of REI on the glass composition. They showed a linear behavior of the polarizability as a function of NBO/(BO+NBO) ratio in a binary tellurite glass system. Furthermore, the increase of REI concentration produces different environments for REI with bonds through single-paired electrons, which favors the formation of NBO. The presence of REI becomes much more significant with decreasing phonon energy of the TeO2 (with TeO3 and TeO4 units) hosts. Such combination affects to different degrees the electronic distortion and therefore creates asymmetric sites for REI. Likewise, few experimental and simulation approaches have been provided to explain phase transition behavior and tellurite glasses’ short-range and long-range structural analysis [109].

Overall Aspects of Glasses for Photonic Devices

27

4.2 Aluminosilicate Glasses Aluminosilicate glasses are oxide glasses that exist as binary or ternary systems [110]. The importance is mainly due to their chemical durability, scratch resistance, good mechanical, and thermal properties [111]. The aluminosilicate can be modified by different cations, e.g., alkali, alkaline earth, or rare-earth metal. The aluminosilicate structure depends on the addition of the modifier’s type and modifier’s concentration to the glass network. The change in the concentration leads to the formation of subtypes of glasses: (i) alkaline earth aluminosilicate glasses contain 52–60% SiO2 , 15–25% Al2 O3 , and about 15% alkaline earth; (ii) alkali aluminosilicate glasses are formed from 10 to 25% Al2 O3 [111]. The properties of these glasses, such as density ρ, refractive index n, thermal expansion, and infrared spectra, depend on glass formation. The Al2 O3 (Al) ratio to modifier (M) in these aluminosilicates leads to a structural change of aluminum, due to their size, as Al tetrahedral coordination, five-coordinated Al, and octahedral coordination Al. Indeed, when there are high concentrations of Al2 O3 , the ratio Al/M is >1, Al ions take higher coordination states (Al3+ does not exist in tetrahedral coordination) and act as network-modifiers. Likewise, when the concentration of modifiers is found in excess or equal to the Al2 O3 content, i.e., Al/M is 80%, respectively. Among the most important characteristics are its high chemical durability, high light transmission, and low thermal expansion (3.3 × 10−6 K−1 at 20 °C). (ii) Alkaline earth containing borosilicate glass (also known as low-borate borosilicate glass) when containing 75% SiO2 and 8–12% B2 O3 , and incorporated with alumina (Al2 O3 ) and alkaline earth up to 5%. Such composition improves glass physical properties, high chemical durability, and the thermal expansion in the range of (4.0–5.0) × 10−6 K−1 . It is mainly used to produce lamps and tube envelopes. (iii) High-borate borosilicate glasses are denominated when containing 15–25% B2 O3 . These systems can be incorporated with small amounts of alkalis and alumina (Al2 O3 ), resulting in low softening points and low thermal expansion, their later is suitable for glass-to-metal seals. In high-borate glasses, Elmer et al. [118] found an optimum composition more stable against devitrification and deformation than alumina-free glass to quaternary system (62.7SiO2 , 26.9B2 O3 , 6.6Na2 O, 3.5Al2 O3 in wt%) and ternary system (65SiO2 , 26B2 O3 , 9.0Na2 O in wt%). Introducing alkali and alkaline earth elements into the structure, the cations act as modifiers and reduce the connectivity in the tetrahedral network. Alkali ions convert BO4 to BO3 states and create NBO when the ratio of concentration (alkali/B2 O3 ) < 0.5 and (alkali/B2 O3 ) > 0.5, respectively. When modifiers are added to borosilicate glasses the formation of BO4 over BO3 occurs up to about 40% alkali, depending upon modifier and silica content, with the formation of more NBO [119]. Y. Yue et al. [120] reported that increasing CaO/Na2 O dramatically lowers the contents BO4 and BO3 and increases NBO. However, these trends are dependent on boron content because of energetic constraints of mixing of various network cations. Also they suggested that Ca2+ more strongly promotes the formation of NBO than K+ because of the higher field strength of its cation modifier. Reiser et. al. [121] reported the effect of Al: Si and (Al + Na):Si ratio on the physical properties, revealing that the melting temperatures increased as Al:Si increased and decreased as (Al + Na):Si ratios increased. The formation of BO4 decreases across both to Al: Si and (Al + Na):Si ratio, likewise, glass-transition temperatures (T g ) and enthalpies of formation (ΔHf,ox ) were strongly negatively correlated with Na2 O concentration. Chemical durability in borosilicate is shown to be dependent on the varying (MgO)/(MgO+ CaO) ratio, due to that borosilicate glass undergoes both leaching of modifier ions through an ion exchange process, and etching of the glass network, leading to the dissolution of the glass surface [122]. The leaching of Ca2+ (~50 nm) is greater than Mg2+ ( T g (GN3) > T g (GN4). This is evident mainly at higher heating rates, where there is a decrease of about 20 °C in T g . We suggest that this is due to the presence of Ce3+ ions. However, more calorimetric characterizations with different concentrations of Ce3+ are needed to verify this fact. The crystallization temperature, T cr , increases for the GN3 and GN4 samples, probably due to the greater molar mass of the Eu3+ and Nd3+ ions than the Ce3+ ion, interfering in the diffusion process, which also increases the initial crystallization temperatures Tx , as mentioned in other studies [27, 28]. The details of these results are listed in Table 3.

4.2.2

Determination of Activation Energy of Crystallization Using the Ozawa and Kissinger Approaches

As explained in item 2.1, we will obtain the activation energies of crystallization using the approaches of Ozawa and Kissinger first. For this purpose, we show the curves for the Ozawa and Kissinger graphics in the Fig. 6a, b for GN1, GN2 and GN3 and in the Fig. 7a, b for GN4. Based on the Ozawa method, the activation energies of the crystallization processes are 214, 116, 186, and 202 kJ/mol, while in the Kissinger method, these values are 226, 169, 194, and 183 kJ/mol for the GN1, GN2, GN3, and GN4 samples respectively. These results indicate that rare earth doping can decrease the activation energy of crystallization of silicate glass, which may depend, among other factors, on the ionic

228

I. N. de Assis Junior et al.

Fig. 5 Typical DSC curves of a GN1, b GN2, c GN3 and d GN4 glass samples at different heating rates

radius and the mass of each ion. The ionic radius of the Ce4+ is 87 pm, for Eu3+ ion is 94.7 pm and for the Nd3+ ion is about 98 pm. In this scenario, the activation energy after the co-doping is greater than the single doping due to the smaller ionic radius of Eu3+ ions. Compared with other compositions containing silica, which acts as a glass former, and titanium, which acts as a nucleating agent, the activation energies of crystallization of the GNx series of glasses are noticeably lower. Therefore, the glassceramic formation of the GN2, GN3, and GN4 samples is relatively more viable than the GN1.

4.2.3

Determination of the Activation Energy of Crystallization, Avrami Index, and Crystal Growth Dimensionality Using Modified Kissinger

The values of n, Avrami Index, are the same for the four vitreous systems and vary from 1.80 to 4.23 for the GN1, GN2, GN3, and GN4 systems. It should be noted that m = n, as discussed in item 2.1 of this chapter, is used mainly for the dimensionality of crystal growth [21, 38]. This could be justified as all the glasses went through

GN4

GN3

GN2

719.25

726.25

20

714.39

5

724.45

730.31

20

10

727.31

15

15

720.51

721.17

5

735.50

20

10

720.12

731.53

10

15

705.00

740.16

751.27

15

20

5

732.59

735.21

5

GN1

T g (°C)

10

ϕ(°C/min)

Sample

904.23

894.99

880.66

859.32

907.51

899.31

887.13

864.51

882.08

875.25

858.3

833.73

895.17

885.33

871.90

859.32

T cr (°C)

864.53

852.71

838.68

824.33

870.75

859.37

854.09

837.95

849.66

846.02

827.52

805.71

862.56

853.74

839.24

825.11

T x (°C)

177.97

170.54

161.41

144.93

177.20

172.00

165.96

144.00

146.60

143.72

138.3

128.73

143.9

145.00

136.70

126.7

Thermal stability(Δ°C)

202.0518

166.63

145.40

177.80

ΔE Ozawa (kJ/mol)

183.48

201.55

146.50

194.46

ΔE Kissiger (kJ/mol)

4,23

1.8

3.8

3.4

n

4,23

1.8

3.8

3.4

m

0.0838

0.2388

0.6072

0.8506

0.0503

0.0792

0.5440

0.8705

0.0325

0.0712

0.6794

0.9992

0.0163

0.0301

0.2889

0.7676

α

194.66

207.00

170.40

236.30

ΔE Avrami (kJ/mol)

Table 3 Physical and thermal data of GN1, GN2, GN3, and GN4 glasses: glass transition temperature (T g ), initial crystallization temperature (T x ), crystallization temperature (T cr ), thermal stability (ΔT = T cr − T g ), activation energy of crystallization in the Kissinger method (ΔE Kissinger ), in the Ozawa method (ΔE Ozawa ) and modified Kissinger method (ΔE Avrami ), Avrami Index (n), dimensionality of crystal growth (m), and volume fraction of crystals (α)

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 … 229

230 Table 4 Measured lifetimes of excited states of Ce3+ and Eu3+ in the series of glass and glass-ceramics [28]

I. N. de Assis Junior et al. Sample

τ (Eu3+ ) (ms) λexc = 393 nm λemi = 612 nm

τ (Ce3+ ) (ns) λexc = 290 nm λemi = 360 nm

GN2

–

3.12

GN22h

–

1.84

GN225h

–

1.62

GN250h

–

1.61

GN2100h

–

1.61

GN3

1.77

6.77

GN32h

1.57

5.98

GN325h

1.45

4.48

GN350h

1.44

3.64

GN3100h

1.44

3.60

Fig. 6 a Ozawa plots using Eq. (2), and b Kissinger plots using Eq. (3) for GN1, GN2, and GN3 silicate glass samples [41]

Fig. 7 a Ozawa plots using Eq. (2), and b Kissinger plots using Eq. (3) for GN4 silicate glass samples

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 …

231

an initial heat treatment stage for nucleation for 3 h, so, there is fixed number of nuclei at the beginning of the crystallization process. As discussed in Sect. 2.1, the onset crystallization and ending crystallization temperatures were used to calculate the volumetric crystallization fraction. T f is about 860, 875, 885, and 870 °C for the GN1, GN2, GN3, and GN4 samples, respectively. Figure 8a–d show the graphics of log [−ln (1 − α)] versus log ϕ for the GN1, GN2, GN3, and GN4 samples. On obtaining the values for n and m, we can calculate the activation energies of crystallization for each glassy system using the graph of ln(ϕ n /Tcr2 ) versus 1000/Tcr , and we can calculate ΔE considering a linear slope as shown in Fig. 9a–d for GN1, GN2, GN3. and GN4 samples, respectively. The Avrami index of n ∼ = 2 for the GN3 sample indicates a unidimensional crystallization growth with a constant volumetric nucleation rate, while n ∼ = 3 para for the GN1 samples indicates a volumetric nucleation and a bidimensional crystal growth. For the GN2 and GN4 samples we achieved n ∼ = 4, which is related to volume nucleation and two-dimensional growth mechanisms. According to these results, we can suggest that the crystallization mechanism depends on the existence of rare earth ions, and their ionic mass that interferes in the diffusive process of chemical species, since the samples GN2, GN3, and GN4 with rare earth ions such as Ce3+ , Ce3+ + Eu3+ , and Ce3+ +Nd3+ respectively, show different mechanics, indicating that these

Fig. 8 Plot of log [−ln (1 − α)] versus log ϕ for GN1, (a) GN2, (b), GN3 (c), and GN4, d samples; n is the slope of the plot as 3.4, 3.8, and 1.8. The related data of the samples are presented in Table 3

232

I. N. de Assis Junior et al.

Fig. 9 Plot of ln (ϕn /T cr 2 ) versus 1000/T cr for GN1 (a), GN2 (b), GN3 (c), GN4 (d) with n equal to 3.4, 3.8, 1.8 and 4.23, respectively, using Eq. (6)

Fig. 10 Absorption spectra for as-prepared and heat-treated samples for GN1 and GN2 glasses [27]

ions participate in the crystallization process. In order to confirm how these ions could modify the crystallization process we need a more detailed study [41]. We found that the linear correlation coefficients found in Figs. 6a, b, 7a, b and 9a–d by using Ozawa, Kissinger, and modified Kissinger approaches are very close

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 …

233

Fig. 11 Normalized emission spectra for GN2 and GN1 samples under a 314 nm and b 394 nm [27]

to 1 or −1, especially for GN2 and GN4 glasses using the Kissinger method and for GN3 glass using the Ozawa method. Therefore, these methods are more suitable for the study of the activation energy in the crystallization process of these vitreous systems, since they do not take into account the crystallization mechanisms quantified in the Avrami Index, so it is necessary that a more detailed study of the possible crystallization mechanisms must be performed. The numerical results for the crystallization activation energies in the approaches of Ozawa and Kissinger represent the general estimation of this energy, without taking into account the contribution of nucleation and growth. We suggest that there may be more than one type of crystallization mechanism that control the process, as the values of the linear correlation coefficient for the modified Kissinger approach are subtly less than −1, unlike other approaches, but this does not disqualify the method, being more effective to know the crystallization mechanisms clearly (Figs. 10 and 11). The activation energy of crystallization values are close in the approaches of Ozawa and Kissinger, since it reaches 145.40–146.50 kJ/mol for samples of GN2 glass. This shows that Ce3+ ions participate in the crystallization process and reduce the activation energy from 177.80–194.46 to 145.40–146.50 kJ/mol in GN2. The activation energy of GN3 and GN4 glasses is above these values at 201.55 kJ/mol for GN3 using Kissinger and 202.05 for GN4 using Ozawa, showing in terms of magnitude the participation of rare earth ions in these processes. The differences between the values in the applied approaches can also be related to the precision of the values obtained for T x and T cr , since different DSC equipments were used in these analysis. However, the three methods applied are physically equivalent and resulted in relatively close values.

234

I. N. de Assis Junior et al.

4.3 Thermal Stability The thermal stability of the glass is generally defined as ΔT = T cr − T g [16], which is related to thermal shocks and resistance to crystallization or resistance to devitrification. Therefore, glasses with low thermal stability are generally not recommended for the construction of optical fibers, where small crystals can form at temperatures above T g , resulting in a likely opaque optical system. In the work presented here, the thermal stability of the glasses is around 126– 177 °C, with emphasis on the GN3 and GN4 glasses, which is generally high when compared to other glasses, such as tellurite glasses (~50 °C) [42, 43], although they are inferior to phosphorus silicate glasses (~250 °C) [44]. The GN3 and GN4 samples containing Eu3+ and Nd3+ ions, respectively, show even better thermal stability than the glass samples GN1 and GN2, with an ΔT of around ~177 °C.

4.4 Optical Properties One of the challenging topics on glass-ceramics is improving their luminescence efficiency by incorporating the optically active ions in the crystalline phases, where the phonon energy is low. However, the transparency of the glass-ceramic system is still a matter of challenge. A significant difference in the refractive index between the crystalline phase and the vitreous phase, or large crystals with a size comparable to the incident wavelength, can generate a high luminous scattering and reduce the transparency in the glassceramic [45]. The type of nucleating agent also affects the transparency of the glasses. The use of TiO2 as a nucleating agent in glass-ceramics affects transparency depending on its oxidative state. When presented as Ti3+ , this ion provides strong absorption in UV-Vis and emits considerably in the green-red region. Meanwhile, the ion in the Ti4+ state has UV absorption, with emission in the blue region. These emissions have been exploited in calcium aluminosilicates with a low concentration of OH− to manufacture LEDs with tunable white emissions. Such emissions depend on the excitation power, in addition to tunable emissions between the green-blue region, varying the concentration of Ti3+ /Ti4+ and Eu2+ /Eu3+ [46]. In our studies on the ZnO–Al2 O3 –SiO2 system, the presence of Ti3+ significantly increases absorptions at 400–500 nm, which significantly compromises transparency [27]. This problem is partially solved with the addition of CeO2 , leading to the reduction of Ti3+ to the Ti4+ form as follows: Ti3+ + Ce4+ → Ti4+ + Ce3+

(12)

During oxidation, the formation of Ti4+ moves the absorption to the UV region, increasing the transparency in the visible region. Additionally, we note that the

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 …

235

increase in heat treatment keeps the absorption low to λ > 480 nm for samples containing CeO2 . However, the UV absorption edge undergoes a 30 nm red-shift [27], as shown in Fig. 12. Concomitantly, varying the size of the crystals in the range 5– 10 nm does not affect the transparency of the sample. Therefore, the addition of CeO2 changes the color of the zinc aluminosilicate ceramics to yellow, but it is still more transparent than the free-Ce3+ sample. Knowing the increased transparency, we explored how the interaction of two optically active ions in this matrix would be, in this case Ce3+ with Eu3+ . We confirm that the crystallization kinetics is not altered by insertion of Eu3+ ions and no secondary crystalline phase appear [27]. The emission spectra under excitation at 393 and 314 nm demonstrate that the increase in heat treatment for single Ce3+ -doped samples favor the incorporation of Ce3+ in the crystalline phase, with concomitant oxidation of the Ti3+ form to Ti4+ as evidenced by the shift of emission from the green region to the blue region, as shown in Fig. 13a [27]. In addition, an anomalous band was detected at 700 nm for these samples, which appears only after heat treatment, as could be seen in Fig. 13b. Interestingly, the increase in crystallinity in our samples co-doped with Eu3+ /Ce3+ was accompanied by an increase in the asymmetry of the Eu3+ ion sites, indicated both by the parameters of Judd-Ofelt and by the increase in the ratio between the intensities of the transitions 5 D0 → 7 F2 and 5 D0 → 7 F1 [28]. Current studies with Eu3+ -doped gahnite crystals demonstrate that the degree of asymmetry may be related to Eu3+ ions being able to replace both Zn2+ ions in the ZnAl2 O4 structure, as well as being associated with Al3+ when having a preference for octahedral sites [45]. In this case, it is corroborated that the gahnite crystals in glassceramics maintain the asymmetric sites and favor the hypersensitive transitions of Eu3+ , leading to higher branching rates for the transition 5 D0 → 7 F2 and expanding its use as a solid state laser [27]. Fig. 12 Excitation and emission spectra for GN3 heat treated samples (after nucleation during 3 h at 670 °C) [28]. The numbers 2, 25, 50, and 100 in the legend represent the heat treatment time in hours

236

I. N. de Assis Junior et al.

Fig. 13 Emission bands as functions of temperature for a glass and b glass-ceramics of Nd/Ceco-doped aluminosilicate under laser excitation at 800 nm

It is known that f–d transitions are more sensitive to the ligand field than f–f transitions. In our case, Eu3+ emissions reduced slightly, as well as their lifetime, with the increase in heat treatment in Ce3+ /Eu3+ -doped samples, as could be seen in Fig. 14. On the other hand, the Ce3+ emission rises up with the enlarged heat-treatment. This enlargement in 450 nm emission of Ce3+ could be associated with possible energy transfer Eu3+ –Ce3+ . Additionally, the values of the lifetime of the emission at 360 nm are almost twice that of the single Ce3+ -doped samples, demonstrating the major luminescence efficiency of Ce3+ when inserted into the gahnite crystals. The interaction of Eu3+ –Ce3+ ions in glass-ceramics is not always supported by the presence of both in the crystalline phase. Zhou et al. report that in Y3 Al5 O12 embedded transparent glass-ceramics, Ce3+ ions are located in the crystals, while Eu3+ ions are distributed only in the vitreous phase [47]. The yellow emission of Ce3+ and the red of Eu3+ could be adjusted only by varying the concentration of both. Zhou et al. also noticed that the increase in sintering temperature leads to a progressive reduction in the formation of Y3 Al5 O12 crystals, which significantly reduces the yellow emission of Ce3+ [47]. Our results also did not show the existence of Eu2+ during the formation of the crystals. This leads to a considerable difference compared to how the crystallization process affected emissions in calcium aluminosilicate doped with Eu3+ . Guo et al. [4] attest that the insertion of Eu3+ ions into the crystalline structure BaAl2 Si2 O8 replaces Ba 2+ ions with the increase of heat treatment. As they are different valences, two Eu3+ ions are needed to replace three Ba2+ ions. According to the author, this stimulates the reduction of the Eu3+ to the Eu 2+ form, whereas vacancies during these substitutions have electrons available. Then, the emergence of the ionic species Eu 2+ generates a broadband of intense emission between 400 and 560 nm. This makes it possible that, together with the red emissions of the Eu3+ species, a significant generation of white light occurs with the increase of the heat treatment. Bouchouicha et al. [48] reported that this charge compensation also occurs in the formation of melilite (Ca2 Mg0.25 Al1.5 Si1.25 O7 ) with progressive replacement of Ca2+

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 …

237

by Eu3+ in the crystalline structure and subsequent reduction to the Eu2+ form. The authors observed a considerable reduction in the full width at half maximum (FWHM) of the emission band at 545 nm (4f6 5d → 4f7 ) of Eu2+ with the increase in heat treatment, as well as an increase in the intensity of this emission. Concomitantly, there is a reduction in red Eu3+ emissions, indicating that the increase in heat treatment time leads to a considerable reduction of Eu3+ → Eu2+ due to the incorporation of Eu2+ in the anorthite and melilite phase. Bouchouicha et al. [48] demonstrated that the increase in heat treatment causes a blue shift of the transition 4f6 5d → 4f7 from Eu2+ , as well as progressively reducing Eu3+ emissions and favoring Eu2+ emissions. In general, after the heat treatment, the emissions are moved from the orange-red region to the yellow-green region. Additionally, the reduction in the lifetime of the 4f6 5d → 4f7 transition strongly indicates that transfer processes are operative from Eu2+ to Eu3+ in glass-ceramics, owing to reducing the distance between ionic species in crystalline environments. In addition to the charge compensation mechanism, other means have been explored to increase the Eu2+ ionic species in Al2 O3 –SiO2 systems. In aluminosilicate oxyfluoride glass ceramics, the efficiency of the Eu3+ → Eu2+ reduction in the amorphous phase is associated with increased electronegativity around the europium. Antuzevics et al. [49] showed by electron paramagnetic resonance (EPR) spectroscopy that increasing fluoride concentration increases the Eu3+ → Eu2+ conversion in the amorphous phase. This provides an intense emission in the blue region in the precursor glass rich in fluorine, while for a sample low in fluorine, this emission only occurs after heat treatment. The dependence of the blue emission in relation to the heat treatment is explained due to the charge compensation incorporating Eu2+ in the SrF2 crystalline phase after sintering for samples low in fluorine.

4.5 Optical Thermometry The optical temperature sensors based on Nd3+ stand out due to the difference in energy between the levels 4 F7/2 , 4 F5/2 and 4 F3/2 of this ion being around 1000 cm−1 , causing the three levels to be thermally coupled with the rise in temperature. In general, the intensity of the 4 F7/2 → 4 I9/2 (750 nm) and 4 F5/2 → 4 I9/2 (810 nm) transitions tend to become progressively the same, or even greater, than that of the 4 F3/2 → 4 I9/2 (890 nm) with increasing temperature [50]. Note that these emissions are located in the first biological window, making the materials doped with Nd3+ ions promising in the biomedical area when using the LIR technique. Many works focused mainly on crystalline materials co-doped with Nd3+ /Yb3+ [51]. In this context, few studies have studied how glass and vitroceramics from aluminosilicates can be used as optical sensors when they are doped with Nd3+ . As far as we know, the interest in investigating optical thermometry in silicate glasses using Nd3+ has recently appeared in the studies by Back et al. [52] in bismuth silicate glass-ceramic.

238

I. N. de Assis Junior et al.

In our study, under excitation at 584 nm, the ratio between the transitions F7/2 → 4 I9/2 (750 nm) and 4 F5/2 → 4 I9/2 (810 nm) generated SR = 1331/T2 for the vitreous sample. This value is higher than those reported for the same thermal coupling in Bi4 Ti3 O12 : Yb3+ /Nd3+ [53], CaWO4 : Yb3+ /Nd3+ /Li3+ [54] and Y2 SiO5 : Yb3+ /Nd3+ [55]. In addition, the ratio of these emissions from the glass sample obtained repeatability of 98.5%, considering three heating cycles. On the other hand, we explored how the 4 F3/2 → 4 IJ emissions (J = 13/2, 11/2, 9/2) would vary with increasing temperature under 800 nm laser excitation. Although not very affected, we detected a growth of a band at 1200 nm, as can be seen in Fig. 13. This band is related to 4 F5/2 → 4 I13/2 , which may have had its transition probability increased due to the thermal coupling between levels 4 F5/2 and 4 F3/2 . When making the ratio of the transition 4 F3/2 → 4 I13/2 with the transition 4 F3/2 → 4 I11/2 , we obtained S R = 1496.3/T2 for glass-ceramic, while for glass, S R = 1398.42/T2 , showing that the use of aluminosilicates as temperature sensors in this region is very promising. In addition, we noted that by reducing the incident laser power, there were no significant changes in the calibration curves, corroborating that the reason for these intensities has good reproducibility. Therefore, our matrix shows promising results as a thermal sensor using emissions in the infrared region, either under excitation at 584 or 800 nm. This makes Nd3+ doped aluminum glasses, and glass-ceramics good alternatives to conventional pyrometers, since CCD detectors are inexpensive and allow applications on an industrial scale. 4

5 Summary Silicate glasses were prepared by a melt-quenching technique and transformed to glass-ceramics using two-stage heating treatments for the nucleation and crystal growth. The crystal growth and crystallization dynamics were studied applying various theoretical methods to the DSC profiles of silicate glasses with and without rare earth ions. We showed that rare earth ions could favor the crystallization process by lowering the crystallization activation energy, while glass transition temperatures and glass thermal stability were also improved. After the ceramization, the crystalline phases were detected using XRD technique and confirmed by microscopic techniques. These nanocrystalline phases are in nanoscale as could probably decrease the transparency of the glasses, however, the partial crystallizations in glass-ceramics increases the mechanical resistance of the glassy system. We have examined the luminescence spectra of the glasses doped with Nd3+ ions which showed a relatively good optical sensibility to the temperature. These glasses and glass-ceramics samples are promising for various applications in optoelectronics and photonics in general and for optical thermometry in particular, as they show good mechanical stability, high thermal stability, and good sensibility to the variation of temperature when doped with rare earth ions.

Synthesis and Characterization of Rare Earth Doped ZnO–Al2 O3 –SiO2 …

239

Acknowledgements The results given in this chapter were gathered by summing up the outputs of various projects ran by the contributions of our colleagues from Universidade Federal de São Carlos (Prof. Edgar Zanotto and Prof. Ana Candida Rodrigues), Universidade de São Paulo (Prof. Andrea de Camargo), Universidade Federal de Alagoas (Prof. Carlos Jacinto), and our collaborator from India (Dr. Atiar Molla). The authors are thankful to CNPq for the scholarships and project grants (no. 310941/2018-0, 421900/2018-0 and 308145/2021-6) and to FACEPE for the master degree scholarship granted to F.A. Torquato through the project no. IBPG-0898-3.03/19 and the research grant to I. Nunes through the project no. BIC-1127-3.03/19.

References 1. Shelby, J. E. (2020). Introduction to glass science and technology. The Royal Society of Chemistry. 2. Li, C., Dong, B., Li, S., & Song, C. (2007). Chemical Physics Letters, 443, 426. 3. Le Bourhis, E. (2008). Glass mechanics and technology. Wiley-VCH. 4. Guo, Y., Lu, Y., Liu, C., Wang, J., Han, J., & Ruan, J. (2021). Journal of Alloys and Compounds, 851. 5. Yang, B., Liu, X., Wang, X., Zhang, J., Hu, L., & Zhang, L. (2014). Optics Letters, 39, 1772. 6. Sun, Y., Yu, F., Liao, M., Wang, X., Li, Y., Hu, L., & Knight, J. (2020). Journal of Luminescence, 220. 7. Piasecki, P. (2010). Journal of Nanophotonics, 4, 043522. 8. Khan, S. K. I., Kuzmann, E., Nomura, K., Ali, A. S., Akiyama, K., Homonnay, Z., Sinkó, K., & Pavi´c, L. (2021). Journal of Non-Crystalline Solids, 561. 9. Li, J. Q. L., Yang, Y., Zhou, D., Yang, Z., Xu, X. (2013). Journal of Applied Physics, 113. 10. Yang, Q., Zhao, L., Yu, H., Min, Q., Chen, C., Zhou, D., Yu, X., Qiu, J., Li, B., & Xu, X. (2019). Journal of Alloys and Compounds, 784, 535. 11. Zekri, M., Herrmann, A., Turki, R., Rüssel, C., Maâlej, R., & Damak, K. (2019). Journal of Luminescence, 212, 354. 12. Chiappini, A., Zur, L., Enrichi, F., Boulard, B., Lukowiak, A., Righini, G. C., & Ferrari, M. (2019). Glass ceramics for frequency conversion. Elsevier Ltd. 13. Holand, W., & Beall, G. (2002). Glass-ceramic technology, 1st ed. The American Ceramic Society. 14. Araújo, E. B., & Idalgo, E. (2009). Journal of Thermal Analysis and Calorimetry, 95, 37. 15. Lesz, S., & Dercz, G. (2016). Journal of Thermal Analysis and Calorimetry, 126, 19. 16. Kumar, M. P., Sankarappa, T., & Awasthi, A. M. (2008). Physica B: Condensed Matter, 403, 4088. 17. Fokin, V. M., Cabral, A. A., Reis, R. M. C. V., Nascimento, M. L. F., & Zanotto, E. D. (2010). Journal of Non-Crystalline Solids, 356, 358. 18. Zheng, Q., Zhang, Y., Montazerian, M., Gulbiten, O., Mauro, J. C., Zanotto, E. D., & Yue, Y. (2019). Chemical Reviews, 119, 7848. 19. Ozawa, T. (1970). Journal of Thermal Analysis, 2, 301. 20. Kissinger, H. E. (1956). Journal of Research of the National Bureau of Standards, 57, 217. 21. Matusita, K., Komatsu, T., & Yokota, R. (1984). Journal of Materials Science, 19, 291. 22. Matusita, K., & Sakka, S. (1980). Journal of Non-Crystalline Solids, 39, 741. 23. Suta, M., & Meijerink, A. (2020). Advanced Theory and Simulations, 3, 1. 24. Bednarkiewicz, A., Marciniak, L., Carlos, L. D., & Jaque, D. (2020). Nanoscale, 12, 14405. 25. L. D. C. C. D. Brites, S., & Millán, A. (n.d.). Handbook on the physics and chemistry of rare earths (Vol. 48, p. 339). 26. Liu, X., Lei, R., Huang, F., Deng, D., Wang, H., Zhao, S., & Xu, S. (2019). Journal of Luminescence, 210, 119.

240

I. N. de Assis Junior et al.

27. Molla, A. R., Rodrigues, A. M., Singh, S. P., Lancelotti, R. F., Zanotto, E. D., Rodrigues, A. C. M., Dousti, M. R., de Camargo, A. S. S., Magon, C. J., & Silva, I. D. A. (2017). Journal of the American Ceramic Society, 100, 1963. 28. Dousti, M. R., Molla, A. R., Rodrigues, A. C. M., & de Camargo, A. S. S. (2017). Optical Materials, 69, 372. 29. Kurajica, S., Šipuši´c, J., Zupancic, M., Brautovi´c, I., & Albrecht, M. (2021). Journal of NonCrystalline Solids, 553. 30. Alekseeva, I. P., Dymshits, O. S., Ermakov, V. A., Zhilin, A. A., & Tsenter, M. Y. (2013). Glass Physics and Chemistry, 39, 113. 31. Escardino, A., Amoros, J. L., Gozalbo, A., & Orts, M. J. (1999). British Ceramic Transactions, 98, 196. 32. Atkinson, I., Anghel, E. M., Munteanu, C., Voicescu, M., & Zaharescu, M. (2014). Ceramics International, 40, 7337. 33. Yekta, B. E., Alizadeh, P., & Rezazadeh, L. (2007). Journal of the European Ceramic Society, 27, 2311. 34. Mirhadi, B., Mehdikhani, B., & Askari, N. (2012). Solid State Sciences, 14, 430. 35. Hu, M. L. B., Yuan, B., Wang, P., Wang, J., Han, J. (2018). ECS Journal of Solid State Science and Technology, 7. 36. Al-Harbi, O. A. (2009). Ceramics International, 35, 1121. 37. Al-Harbi, O. A. (2007). Advances in Applied Ceramics, 106, 235. 38. Aly, K. A., Othman, A. A., & Abousehly, A. M. (2009). Journal of Alloys and Compounds, 467, 417. 39. Aly, K. A., Saddeek, Y. B., & Dahshan, A. (2010). Philosophical Magazine, 90, 4429. 40. Vijayan, C., Soundararajan, N., Chandramohan, R., Ramaswamy, S., & Gnanadurai, P. (2015). Journal of Thermal Analysis and Calorimetry, 119, 91. 41. de Assis, I. N., Peña-Garcia, R., & Dousti, M. R. (2020). Solid State Sciences, 107. 42. Souri, D., & Shahmoradi, Y. (2017). Journal of Thermal Analysis and Calorimetry, 129, 601. 43. Dousti, M. R., Amjad, R. J., Sahar, M. R., Zabidi, Z. M., Alias, A. N., & De Camargo, A. S. S. (2015). Journal of Non-Crystalline Solids, 429, 70. 44. Souza, M. T., Crovace, M. C., Schröder, C., Eckert, H., Peitl, O., & Zanotto, E. D. (2013). Journal of Non-Crystalline Solids, 382, 57. 45. Priya, R., Negi, A., Singla, S., & Pandey, O. P. (2020). Optik, 204, 164173. 46. Morassuti, C. Y., Finoto, S., Silva, J. R., Nunes, L. A. O., Guyot, Y., Boulon, G., Baesso, M. L., Bento, A. C., Rohling, J. H., Lima, S. M., & Andrade, L. H. C. (2021). Journal of Alloys and Compounds, 853, 155898. 47. Zhou, Y., Chen, D., Tian, W., & Ji, Z. (2015). Journal of the American Ceramic Society, 98, 2445. 48. Bouchouicha, H., Panczer, G., De Ligny, D., Guyot, Y., Baesso, M. L., Andrade, L. H. C., Lima, S. M., & Ternane, R. (2016). Journal of Luminescence, 169, 528. 49. Antuzevics, A., Kemere, M., Krieke, G., & Ignatans, R. (2017). Optical Materials, 72, 749. 50. Zhao, Y., Wang, X., Zhang, Y., Li, Y., & Yao, X. (2020). Journal of Alloys and Compounds, 817, 152691. 51. Wang, X., Liu, Q., Bu, Y., Liu, C. S., Liu, T., & Yan, X. (2015). RSC Advances, 5, 86219. 52. Back, M., Casagrande, E., Trave, E., Cristofori, D., Ambrosi, E., Dallo, F., Roman, M., Ueda, J., Xu, J., Tanabe, S., Benedetti, A., & Riello, P. (2020). ACS Applied Materials and Interfaces, 12, 55195. 53. Chen, H., Bai, G., Yang, Q., Hua, Y., Xu, S., & Chen, L. (2020). Journal of Luminescence, 221, 117095. 54. Xu, W., Hu, Y., Zheng, L., Zhang, Z., Cao, W., Liu, H., & Wu, X. (2019). Journal of Luminescence, 208, 415. 55. Maciel, G. S., & Rakov, N. (2020). Ceramics International, 46, 12165.

Porphyrin and Phthalocyanine as Materials for Glass Coating—Structure and Properties ´ Barbara Popanda and Marcin Sroda

Abstract The chapter is an introduction to the nature of phthalocyanines as materials for glass coatings. Data of the close analogues porphyrins is reported. The most widely used synthesis methods of porphyrins and phthalocyanines are discussed. The spectroscopic characteristic of the compounds is provided based on UV-ViS and photoluminescence studies. The nonlinear optical and electric properties of various metal-phthalocyanines are discussed. Current and future applications of the phthalocyanines are presented. This chapter is an introduction to the second one entitled “Phthalocyanine and porphyrin films on glass substrate—processing, properties, and applications” where characterizations of hybrid materials are described in detail. Keywords Phthalocyanine · Porphyrin · Structure · Synthesis methods · Absorption · Luminescence · Electrical properties · Applications

1 History of Investigations of Phthalocyanine The first mention of phthalocyanines appears at the beginning of the twentieth century. German chemists, Braun and Tcherniac [1], carried out synthesis of ocyanobenzamide by using substituted benzene derivates in 1907. They heated phthalimide with acetic anhydrous. As a by-product of heated o-cyanobenzamide, they received insoluble, dark blue compound, which was later identified as a metalfree phthalocyanine. Twenty years later, Swiss researchers, Henri de Diesbach and Edmond von der Weid from the University of Fribourg [2], worked on the synthesis of substituted benzene derivates by nitriles groups. They conducted a reaction of 1,2dibromobenzene with copper cyanide, in quinoline. They obtained a blue product, which was very stable in sulfuric acid, alkaline, and in the heat. It was probably ´ B. Popanda (B) · M. Sroda Faculty of Materials Science and Ceramics, AGH University of Science and Technology, A. Mickiewicza 30, 30-059 Kraków, Poland e-mail: [email protected] ´ M. Sroda e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 S. J. Ikhmayies (ed.), Advances in Glass Research, Advances in Material Research and Technology, https://doi.org/10.1007/978-3-031-20266-7_8

241

242

´ B. Popanda and M. Sroda

copper phthalocyanine. In 1928, in the Scottish dyes factory Scottish Dyes Ltd. were synthetized phthalamide from phthalic anhydride and ammonia. As a result of glassy enamel failures/cracks of the iron reactor, blue-green impurity in the final product was observed. Dandrige together with Drescher and Thomas carried out primary analysis of this compound, which was iron complex. It was probably iron phthalocyanine. Further experiments gave another metallophthalocyanines (FePc, CuPc, NiPc). The results of these experiments have been patented in 1929 [3]. It is the first patent of phthalocyanine compounds. Imperial Chemical Industries (ICI) bought Scottish Dyes Ltd. in 1928. ICI was interested in the structure of the newly synthetized colored substance. A sample of this substance was transferred to Reginald P. Linstead at the Imperial College in London. He identified the correct structure of phthalocyanines by using a combination of elemental analysis, such as oxidative degradation, and ebullioscopic molecular mass determination. He noticed that the structure of dyes is similar to naturally occurring porphyrins. Additionally, Linstead gave the name to the newly synthetized dyes—phthalocyanine. The name phthalocyanine is a combination of two words: naphtha and cyanine (blue). Prefix phthal originated from naphtha (rock oil). Results of Linstead and ICI researchers have been published in a series of six articles in the Journal of the Chemical Society [4– 9]. Linstead and Robertson studied metal-free phthalocyanine and nickel, copper, and platinum phthalocyanines on the basis of X-ray diffraction. The results of their works confirmed the structure of phthalocyanines and gave the information that these phthalocyanines crystallize in the monoclinic arrangement [10–14]. The potential of phthalocyanines as a pigment in industry was increased in the 1930s. Max Wyler from the ICI research center in Manchester developed a methodology of industrial manufacturing phthalocyanines. Phthalic anhydride was melted with metal salt, in the present of a catalyst, for example ammonium molybdate. In 1935, ICI began producing copper phthalocyanine under the name Monastral Blue [15]. The development of research on phthalocyanine occurred in the next decades. Polymorphism of metal-free and other phthalocyanine, absorption spectra, magnetic, electrical (photoand dark conductivity), and catalytic properties, red-ox (reduction and oxidation), and physical properties (e.g. solubility) were recognized [16]. Water-soluble phthalocyanines (e.g. sulfonated, chloride phthalocyanines) for the textile industry were developed and patented in the 1950s and 1960s [17]. It needs to be highlighted that, the first patented phthalocyanine was sulfonated-phthalocyanine [3]. The research on the synthesis of phthalocyanine has been conducted in various academic research centers around the world since the ‘60s of the previous century. Since the year 1997, a new magazine entitled Journal of Porphyrins and Phthalocyanines has been devoted to the phthalocyanine compounds.

Porphyrin and Phthalocyanine as Materials for Glass …

243

2 Structure of Phthalocyanine and Porphyrins The phthalocyanine macrocycle is composed of four benzopyrrole rings connected by azomethine bonds. They form a characteristic system of the conjugated double bonds containing 18 delocalized π electrons, fulfilling the Hückel rule of aromaticity [18, 19]. This internal chromophore system is a core of the macrocycle. The structure of phthalocyanines is very similar to naturally occurring porphyrins. Therefore, phthalocyanines belong to the porphyrinoid family. Phthalocyanines are also called tetraazabenzoporphyrins. Metal-free phthalocyanine has two hydrogen atoms inside the macrocycle core, whereas metal complexes coordinate one or two metal cations inside the macrocycles core. The macrocycle ligand is marked as Pc (C32 H16 N8 2− ). Metalfree and metallophthalocyanines are marked as H2 Pc and MPc, respectively [18, 19]. The primary oxidation state of the macrocycle ligand is −2. The name phthalocyanine refers to both substituted and unsubstituted metal-free phthalocyanine and phthalocyanine complexes with various metals [19]. The phthalocyanine macrocycle can be substituted non-peripherally at the position α4 (22–25), α8 (15–18) and peripherally at β4 (8–11), β8 (1–4) (Fig. 1) [19, 20]. A metal cation inside the macrocycle core can be bonded axially, for example with the fluoride atom (anion) or the molecule (Fig. 2) [21]. Phthalocyanine can form different metal complexes (Figs. 3 and 4), which are related to types of the coordinated metal (location of the metal in the periodic table and its atomic radius). Metals of block s (e.g. Li, Mg, and Be) form PcM type of the complex, also called the flat complex. Lithium has oxidation state +1 and a small atomic radius which allows it to place two atoms inside the macrocycle core. Alkaline earth metals also form the complex, type PcM. Metals with the large radius and oxidation state +2 can form a complex of the type named the concave. In these complexes, metal cation (e.g. Pb2+ ) is larger than space in the macrocycle core which induces its location above a plane of the macrocycle ligands. The examples of binuclear, PcM2 complex are Tl2 Pc and [L-Sm-μ-(Pc)-Sm-L] [17, 22]. Metals from block f (lanthanide and actinide) with oxidation state +3 are able to form a Fig. 1 Structure of phthalocyanine with labeled peripheral positions

244

´ B. Popanda and M. Sroda

Fig. 2 Structure of phthalocyanine with labeled non-peripheral and axial positions

sandwich-type metal complex of phthalocyanine (Pc2 M). They are located between two macrocycle ligands due to larger radius than space in the macrocycle core. Moreover, lanthanides can also form triple-decker complexes [23]. Specific types of the sandwich complex are bicyclic and stapled complexes, which contain three or six isoindoline (benzopyrrole) units. Phthalocyanine has also macrocycle analogues such as subphthalocyanine and superphthalocyanine (Fig. 4). The first one has three isoindoline units that are linked with the boron cation inside the subphthalocyanine core, whereas the latter consists of five conjugated benzopyrrole units that form the complex with UO2+ 2 cation [17, 22]. Phthalocyanines belong to colorful substances that strongly absorb light in the range UV-ViS. Phthalocyanines generally are blue or green in color but can vary from yellow/orange to brown/red. Blue-color and green-color phthalocyanines absorb light in the red and violet regions, respectively [24]. Color of phthalocyanines strongly depends on types of the metal cation, axial and peripheral substituents, solvent polarity, pH (acid-base environment), and reaction in solution (redox) [24, 25]. Phthalocyanines are very thermally stable compounds. They do not melt, but sublimate at temperature higher than 200 °C [26]. Seoudi et al. [27] conducted thermogravimetric analysis (TGA), in nitrogen atmosphere, of H2 Pc, MgPc, MnPc, FePc, CoPc, ZnPc, and PbPc. They observed some mass loss in the range from 220 to 510 °C. PbPc was the most stable phthalocyanine in the test group. Phthalocyanines and their metal complexes are stable in air at a temperature below 350 °C, however, in vacuum some of phthalocyanines degrade above 900 °C. Phthalocyanines are more stable in nitrogen than in oxygen condition. Thermal stability can be correlated with the polymorphism forms of specific phthalocyanine complex, for example, CuPc has five polymorph forms, but the most thermally stable is β-CuPc [26, 28]. Unsubstituted metal-free phthalocyanine and metallophthalocyanine are insoluble in water and are most commonly used in chemistry solvents. They have low solubility, c.a. 1 mg/dm3 in acidic mediums, such as trichloroacetic acid (TCA), sulfuric acid (SA), and in some high-boiling solvents [26, 29]. However, only H2 Pc, CuPc, CoPc, and NiPc are stable and easily dissolved in sulfuric acid. The stability in the acidic medium is increased with increasing mass of the coordinated metal [30]. In the most popular solvents, such as alcohols (e.g. MeOH and EtOH), ketones (e.g. acetone), and other popular ones, dimethyl formamide (DMF), dimethyl sulfoxide (DMSO),

Porphyrin and Phthalocyanine as Materials for Glass …

245

Fig. 3 The metal complex types of phthalocyanine without the ligands

tetrahydrofuran (THF), phthalocyanines, can achieve concentration between 10–4 and 10–7 M [26, 29]. The structure of phthalocyanine can be damaged to phthalic acid or phthalimide in solutions of the strong oxidizers [28].

246

´ B. Popanda and M. Sroda

Fig. 4 The metal complex types of phthalocyanine (PcM) with the extra ligands (L)

In addition, thermally and chemically stable phthalocyanines show also catalytical, electrical (photoconductivity, semiconduction), magnetic, and red-ox properties [31, 32].

2.1 Subphthalocyanine Subphthalocyanines are close analogues of phthalocyanines. The structure of subphthalocyanine consists of three conjugated benzopyrrole units, containing boron as a central atom (Fig. 5). This macrocycle system has 14 delocalized electrons. The subphthalocyanine macrocycle complies with Huckel’s rule of aromaticity with C3v

Porphyrin and Phthalocyanine as Materials for Glass …

247

Fig. 5 Structure of subphthalocyanine

symmetry. Thermal stability is related to the presence of substituent. GonzálezRodríguez et al. [33] have carried out thermal analysis of various subphthalocyanines with different peripheral and axial substituents in non-oxidized conditions. These compounds (with axial substituents) are very stable; the first loss of the mass is observed at temperature above 300 °C. Thermal stability is increasing in order of axial ligands: Br < OH ≤ OPh ~ Cl. The most stable chloroboronsubphthalocyanine has no substituents. Subphthalocyanines can be sublimed at the pressure of 0.013 Pa. They can be substituted axially and peripherally. The macrocycle system of subphthalocyanine with the axial substituent is not flat but shows cone-shaped geometry [34]. Subphthalocyanine was discovered in 1972. Meller and Ossoko have carried out synthesis of boron derivates of phthalocyanine by condensation of the dicyanobenzene and boron halides [35]. A structure of the newly synthetized compound was investigated and characterized in 1974 [36]. The first synthetized subphthalocyanine was chloroboronsubphthalocyanine, which has purple color in a solid state. Crystal structure redetermination of boron subphthalocyanine chloride was carried out by Virdo and co-workers [37]. Subphthalocyanines, such as boron subphthalocyanine chloride and boron subphthalocyanine bromide, are soluble in chloroform, dichloroethane, dimethylformamide, and acetone. However, they are insoluble in non-polar solvents (e.g. hexane) and some of the polar solvents (methanol) [34]. Subphthalocyanines, like phthalocyanines, undergo reversible protonation, depending on the pH of the solution. Bernhard et al. examined changes in the structure of various subphthalocyanines in acidic mediums [38]. They used three different acids, with different pH values, such as trifluoroacetic acid, methanesulfonic acid, and trifluoromethanesulfonic acid. Protonation is shown by a color change of the subphthalocyanines solutions from pink, through blue to green. Additionally, protonation of subphthalocyanines can be confirmed by FTIR and 1 H-NMR.

248

´ B. Popanda and M. Sroda

Fig. 6 Structure of superphthalocyanine

2.2 Superphthalocyanine Superphthalocyanine also belongs to the phthalocyanine analogues. Only one superphthalocyanine is probably known by now. It is a complex of five conjugated benzopyrrole units (isoindoline units), and the uranyl cation (UO2+ 2 ) (Fig. 6). It is a dark-blue microcrystalline solid, insoluble in most common solvents. It is slightly soluble in benzene, chloronaphthalene, and toluene. The solution of superphthalocyanine is bright-green in color [39]. Superphthalocyanine was first synthetized in 1975 by Day et al. [40]. In an acidic medium, superphthalocyanine decomposes into metal-free phthalocyanine, the uranyl cation, and dicyanobenzene [41].

2.3 Porphyrins and Subporphyrins Porphyrins are naturally occurring analogues of phthalocyanines. Characteristic structure of porphyrins consists of four conjugated pyrrole rings linked by the methine bridges (Fig. 7) [42]. All porphyrins contain the characteristic macrocyclic system of porphine. Porphines are not found in nature [43]. Various porphyrin analogues are known, like chlorins, bacteriochlorins, etc. [44]. Porphyrins analogues coordinated with metal cation are called metalloporphyrins. Porphyrin macrocycle can be substituted at β (2, 3, 7, 8, 12, 13, 17, 18) positions and meso (5, 10, 15, 20) positions [42]. Porphyrin has four acidic-basic centers. During metalation porphyrins loss two protons and metal cation are coordinated by four nitrogen atoms inside of macrocycle core. When the porphyrin ligand is protonated, then it forms a dication. When the porphyrin macrocycle loses protons, then the macrocycle core forms a

Porphyrin and Phthalocyanine as Materials for Glass …

249

Fig. 7 Structure of porphyrin with labeled positions

dianion. The dianion can be formed by the metallation process [19]. Metalloporphyrins play a key role in biological processes. The most popular complexes of porphyrins are chlorophyll, cobalamine (vitamin B12), and heme. Porphyrins are colored compounds. The name porphyrin is derived from the Greek porphyra, which means purple [44]. Porphyrins are also named “pigments of life”. The color of these compounds is related to the coordinated metal in the porphyrin core. Generally, metalloporphyrins are more stable than metal-free porphyrins. They are soluble in alkali media, pyridine, and less in alcohols. They are insoluble in acidic media [45]. The first subporphyrin, tribenzosubporphyrine, was synthetized in 2006. The structure of subporphyrin consists of three pyrrole rings, linked by the methine bridges and coordinated by boron. Subporphyrin has 14 delocalized electrons compared with porphyrin [46]. Phthalocyanines and porphyrins exhibit semiconducting, magnetic, luminescent, and spectroscopic properties. They are very reactive and undergo various types of reactions, like catalytic, coordination, photochemical, polymerization, and redox [19].

3 Synthesis Methods 3.1 Phthalocyanines Synthesis 3.1.1

Metal-Free Phthalocyanine

Metal-free phthalocyanine can be synthetized in various reactions. Four main types are as follows: I.

Phthalonitrile reactions with bases:

´ B. Popanda and M. Sroda

250

(a) Reaction of phthalonitrile with DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or DBN (1,5-diazabicyclo[4.3.0]non-5-ene]. This reaction is carried out in refluxing atmosphere of pentanol or another primary alcohol. (b) Reaction of phthalonitrile in basic solvents, like DMAE (N,N-dimethyl-2aminoethanol). (c) Reaction of phthalonitrile with ammonia in the alcohol solution. II. Phthalonitrile and reducing agent: (a) Cyclotetramerization of phthalonitrile in the presence of reduction agents, e.g. hydroquinone. III. Demetallation reactions: (b) Demetallation by acids of the labile metallophthalocyanine complexes, like Li2 Pc and Na2 Pc. IV. Reaction of 1,3-diiminoisoindoline as a precursor: (c) 1,3-diiminoisoindoline reacts in the refluxing solution of DMAE. The electrochemical reduction of diiminoisoindoline in DMF is more efficient than the reaction in the polar aprotic solvents, e.g. DMF and DMSO [17]. 3.1.2

Metallophthalocyanine

Metal-containing phthalocyanines can be synthetized as follows: (a) Sintering of phthalonitrile and the specific metal salt or metal. (b) Phthalonitrile reaction with the metal salt, in the high-boiling solvents, e.g. DMF and chloronaphthalene. (c) Reaction of phthalonitrile with the metal salt. The reaction runs in the solution. Additional base, like DBU, is presented in the reaction solution. (d) Reaction of phthalonitrile derivates (e.g. phthalic acid or phthalimide) and the metal salt with urea. This reaction can be carried out in the solvent or by the melting method. (e) Similar to metal-free phthalocyanine, to synthetized metallophthalocyanine, 1,3-diiminoisoindoline as a precursor can be used. A metal salt and a base (DBAE) are added. (f) Reaction of metal-free phthalocyanine with the appropriate metal salt. (g) Reaction of metallophthalocyanine with the metal salt. Phthalocyanine with the labile cation or cations are required for this method. The reaction runs in the solution [17].

Porphyrin and Phthalocyanine as Materials for Glass …

3.1.3

251

Bisphthalocyanine Synthesis

Bisphthalocyanine was first synthetized in the 1960s by Kirin et al. [47, 48]. Rareearth bisphthalocyanines are synthetized from o-dicyanobenzene and the appropriate metal salt, at a temperature above 300 °C, for approximately 3 h. Sintering of the substrates is carried out in the glass ampoule. Today, for the synthesis, the triacetate salt is commonly used. The main disadvantages of this method are that metal-free phthalocyanine and the labile monophthalocyanine complex, with the rare-earth cation and the axial ligand derived from the metal salt presented as a co-product. That’s why the reaction mixture is purified by column chromatography filled with alumina. Some examples of substituted homoleptic (two same phthalocyaninato ligands) and heteroleptic (two different ligand complexes, e.g. phthalocyaninato ligand and porphyrinato ligand) lanthanide complexes of phthalocyanine are summarized in [49]. It must be highlighted that lanthanide complexes of phthalocyanine occur under various names: sandwich phthalocyanine, double-decker phthalocyanine, bis(phthalocyaninato) metal complexes in the literature. Substituted metal-phthalocyanine As mentioned in chapter ten, phthalocyanines macrocycle can be substituted nonperipherally and peripherally. Suitable substituted o-dicyanobenzene as a precursor is generally used for the peripheral substitution, in the reaction with appropriate metal salts. For synthesis of unsymmetrical substituted phthalocyanines, we can use, e.g. o-dicyanobenzenes or 1,3-diiminoisoindolines. (See references [17, 50, 51] for more details.)

3.1.4

Water-Soluble Metallophthalocyanine

Phthalocyanines are soluble in some common organic solvents, but insoluble in water. That’s why synthesis pathways of water-soluble phthalocyanine has been developed. This fact contributed to the growing importance of phthalocyanines in the textile industry as a dye. These phthalocyanines are substituted by anionic or cationic groups. Non-ionic water-soluble phthalocyanines are also investigated. Generally, substituted o-dicyanobenzene derivates are used for the synthesis. Water-soluble phthalocyanines contain, e.g. amines, carboxyls, and sulfonyl groups. Non-ionic water-soluble phthalocyanines contain carbohydrate, polyethyleneglycol, and polyhydroxylated groups [52, 53]. Purification of phthalocyanines Unsubstituted phthalocyanines are purified by sublimation. Another possibility is the dissolution of phthalocyanine in the concentrated sulfuric acid and fast precipitation on the ice or cold water. However, this method is suitable for copper phthalocyanine, which is soluble in acid. Other phthalocyanines, except CoPc and NiPc, can be demetallized or hydrolyzed in the acid medium. Moreover, dissolution of phthalocyanine in sulfuric acid is one of the methods to provide water-soluble phthalocyanines.

252

´ B. Popanda and M. Sroda

Metal-free phthalocyanine can be purified by recrystallization in high-boiling aromaticity solvents. For metal-phthalocyanine recrystallization, another organic solvent, like pyridine, can be used. The second most popular method is chromatography. Column chromatography with alumina, thin film chromatography (TLC), high-performance liquid-chromatography (HPLC) or gel-permeation methods are widely used [17, 54].

3.2 Subphthalocyanines Synthesis In 1972, Meller and Ossoko have synthetized the first subphthalocyanine (SubPc) by a reaction of phthalonitrile and boron halide in the high-boiling solvent (1chloronaphthalene) at 200 °C [35]. Claessens et al. [55] proposed the mechanism of chloroboronsubphthalocyanine formation as follows: 1. 2. 3. 4.

Formation of intermediate in the reaction of phthalonitrile with boron chloride. Oligomerization of phthalonitrile-BCl3 system that provides adduct formation. Hydrolysis of the adduct. Formation of a precursor of SubPc by successive addition of three molecules of (1Z)-3-chloro-N-(dichloroboryl)-1H-isoindol-1-imine. 5. Ring closure of SubPc precursor and reduction of formed complex to SubPc. Subphthalocyanine without axial-bonded halogen atom can be synthetized in a reaction of phthalonitrile with triphenylboron and DBU base and in the naphthalene solvent [56]. For synthesis substituted boron, subphthalocyanines are substituted with desired group o-dicyanobenzene as a precursor and boron halides. Mono-substituted phthalonitriles (e.g. 4-nitrophthalonitrile) are used to produce trisubstituted subphthalocyanine, while disubstituted phthalonitriles (e.g. diiodophthalonitrile) were used to obtain hexasubstituted subphthalocyanines [34, 57]. Subphthalocyanine can be also synthetized by using isoindolinediimines and their derivatives to obtain subphthalocyanine and the substituted subphthalocyanines derivates. These reactions are carried out in solutions (naphthalene, DMSO, or (N,N-dimethylamino) ethanol) and at a temperature of about 100 °C [58, 59]. The third type method of SubPc synthesis is based on exchanging the substituent at the central atom (axial substituent) [58, 59]. Subphthalocyanine can be used to synthetize unsymmetrically substituted phthalocyanine in the reaction of subphthalocyanine with diiminoisoindoline in solvent condition [60]. Synthesis of water-soluble SubPc’s can be found in the reference [61]. The method of SubPc synthesis can be applied to produce subnaphthalocyanine, which is a synthetic analogue of subphthalocyanine, but in place of phthalonitrile, other precursors, like 2,3-naphthalenedicarbonitrille and boron halides, should be used [62].

Porphyrin and Phthalocyanine as Materials for Glass …

253

3.3 Superphthalocyanine Synthesis As mentioned in Sect. 2 of chapter ten, so far, only one superphthalocyanine has been synthetized successfully as follows: − Phthalonitrile reacts with anhydrous UO2 Cl2 in dry DMF [40] or quinoline under nitrogen gas condition [39]. Very small amounts of metal-free phthalocyanine were identified in the reaction mixture. That’s why the product was washed with various solvents (methanol, acetone) and extracted twice by the Soxhlet extractor using ethanol and benzene [39]. Superphtalocyanine is unstable. The reaction of superphthalocyanine and metal salt leads to the formation of metallophthalocyanine, phthalonitrile, and UO2 Cl2 [63, 64].

3.4 Porphyrins Synthesis (a) Rothemund synthesis In 1935, Rothemund described a method of porphyrin synthesis, based on condensation of aldehydes and pyrrole in pyridine. The reaction was carried out in the sealed vessel at temperatures of 140–240 °C [65]. The synthesis is very easy, but yields very poorly [66, 67]. (b) Adler–Longo synthesis This method is based on pyrrole and aldehyde heated at boiling point of the acidic solvent (e.g. propionic acid) under atmospheric conditions. It is a suitable method to obtain meso-arylporphyrins [68–70]. (c) Lindsey synthesis It is a two-step method of the porphyrin synthesis. The first step is dissolution and mixing of aldehyde, pyrrole, and a catalyst in dimethylformamide or chloroform under inert gas conditions. The second step is oxidation of porphyrinogen to porphyrin [71–74]. (d) Microwave activation To obtain porphyrin bases and metalloporphyrins, the reaction of pyrrole and aldehyde in solvents (propionic acid and nitrobenzene) is needed. This reaction is assisted by microwave radiation. Synthetized free-base porphyrin metal salt and solvent (DMF) are added to a vial with substituted porphyrin and then the reaction mixture is treated by radiation [75]. Other methods of porphyrins production are given in the reference [76]. 3.4.1

Metal-Porphyrin Synthesis

As mentioned in Sect. 3 of chapter ten, metalloporphyrins can be synthetized by metalation of free-base porphyrin. It is a two-step reaction:

´ B. Popanda and M. Sroda

254

(1) First, free-base porphyrins are obtained in a reaction between pyrrole and aldehyde in the propionic acid. (2) Further reaction is between synthetized free-base porphyrin and the metal salt in refluxing DMF. Additionally, metalloporphyrin can be synthetized by the one-pot method. It is a reaction of pyrrole, aldehyde, and the metal salt in mixed solvents [77, 78].

3.4.2

Water-Soluble Porphyrins

Similar to water-soluble phthalocyanines, methods of water-soluble porphyrin production are developed. These porphyrins have been substituted by cationic and anionic groups. Some details about synthesis of these groups of the compounds are reviewed in [79]. Purification of porphyrins Porphyrins, mainly metalloporphyrins, are purified by using chromatography methods (column and adsorption) or by crystallization and sublimation methods [79]. Tribenzosubporphyrin, the first subporphyrin, was synthetized in 2006 [46]. (3-oxo-2,3-dihydro-1H-isoindol-1-yl)acetic acid with boric acid is heated up to 350 °C. To synthetize meso-substituted subporphyrin (meso-arylsubporphyrin), pyridine-tri-N-pyrrolylborane and arylaldehydes undergo reaction in solution (odichlorobenzene) in the presence of acid under air-open conditions. Other methods involve synthetic pathways with a precursor, like tripyrromethene borane precursor or meso-thienylsubporphyrins [80].

4 Spectroscopic Properties of Phthalocyanines, Bisphthalocyanine, Porphyrins, and Their Homologues 4.1 Phthalocyanines and Bisphthalocyanines Phthalocyanines exhibit intensive absorption in the visible region (620–700 nm) and in the ultraviolet region (340–400 nm) corresponding to Q band and B band, respectively. B band is also called the Soret band. Metal-free phthalocyanine shows low symmetry, therefore the highest occupied molecular orbital (HOMO) does not degenerate. That’s why metal-free phthalocyanine shows two Q bands. Incorporation of metal/metals to macrocycle causes the formation of thermodynamically stable phthalocyanine dianion characterized by higher symmetry that exhibits only single Q band. Splitting of Q-like bands is also observed in spectra of unsymmetrically substituted phthalocyanines [81]. Derived metal complexes (MPc) with closed-shell configuration show additional bands in the region below 300 nm. These bands are called N, L, C. Metalphthalocyanines from d- and f -block of the periodical table show extra bands induced

Porphyrin and Phthalocyanine as Materials for Glass …

255

by charge-transfer transition (CT). There are two types of transfer: the metal-ligand charge transfer (MLCT) or the ligand-metal charge transfer (LMCT). Charge transfer transition can appear when the energy of d-orbital of the metal cation is located between HOMO–LUMO orbitals of the phthalocyanine macrocycle ligand [82]. Sandwich-type phthalocyanine (also called double-decker phthalocyanine or bisphthalocyanine) shows intensive absorption of Q and B bands. Q bands are hypsochromically shifted (c.a. 35–50 nm) and split into two Q-like bands. These effects are due to interactions of two macrocycle ligands [83]. Position of the Q band depends on two main factors. The first one is correlated with a type of the metal cation and its carrier and an atomic radius of the metal cation/s. The second factor is the configuration affecting the shift of the Q band. For example, cations with closed-shell configuration (e.g. Li, Mg, and Zn) exhibit the Q band at ~670 nm. Metal-phthalocyanines with open-shell configuration show the Q band in the region of 630–650 nm. A few metal-phthalocyanines exhibit very redshift of the Q band, e.g. manganese phthalocyanines (808, 828 nm). At this moment, an effect of the oxidation state is not clearly correlated with a change of the Q-like bands on the absorption spectrum [24]. Axial ligands induce minor changes of the Q band position. For example, chromium phthalocyanine with various fluoride axial ligands shows only a 5–6 nm shift in the position of the Q bands. Peripheral substituents cause greater shift of the Q band. For example, unsubstituted CoPc and CoPc with CN− at β position show absorption band at 668 nm and at 686 nm, respectively. When macrocycle ligand of CoPc is substituted at α position by dimethylamino substituents ((CH3 )2 N), the Q band is located at 778 nm [24]. Another factor inducing, generally, a slight shift of the Q band position is a type of the solvent. However, the solvent can interact with the macrocycle or/and metal cation and results in the formation of agglomerates or adducts. Moreover, the presence of additional substances in the solution, e.g. electron acceptors, changes the envelope of spectra [24, 83]. Luminescence Generally, phthalocyanines exhibit luminescence in the range from 600 to 850 nm. However, the localization of maximum of emission band and quantum yield of luminescence strongly depends on the following factors: − metal cations, − their electron configuration and their oxidations states, and − number and character of peripheral substituents. Higher efficiency of luminescence is observed for metal-phthalocyanines, coordinated by closed-shell metal cations. Phthalocyanines with open-shell electron configuration of the metals may or may not exhibit luminescence, e.g. FePc, CoPc, and NiPc. It depends on the character of metal cations with open-shell electron configuration. When metal cations are diamagnetic (Pd2+ , Pt2+ ), complexes usually exhibit fluorescence, while complexes with paramagnetic cations usually do not show emissions. The highest quantum yield is observed for metal-free phthalocyanines and

256

´ B. Popanda and M. Sroda

their derivates. It must be highlighted that luminescence of phthalocyanines solution depends on factors connected with the environment of the solution, such as pH, presence of heavy atoms, polarity of solvents, presence of additional compounds (e.g. Lewis acids or basics), formation of aggregates or protonation of analyzed compounds, and interaction between fluorophores [84]. Luminescence data of recently developed phthalocyanines and their derivates are shown in Table 1.

4.2 Porphyrin Free-base porphyrins and their metal derivates are close analogues of synthetic dyes—phthalocyanines. These groups show similar changes of the photophysical properties as phthalocyanines. Goutermann has studied the electronic spectra of porphyrins [100]. Metalloporphyrins show three regions of absorption. The first range is from 500 to 600 nm, where two Q bands are observed. The second region is from 380 to 420 nm, where B band (Soret band) appears. Similar to phthalocyanines, weak absorption bands, called N, L, and M in the third region below 350 nm (200– 350 nm), are visible. Free-base porphyrins have two pairs of Q bands: Qx and Qy between 450 and 700 nm. Reduction of number of Q bands from free-base porphyrin to metalloporphyrins can be correlated with the change of the symmetry from D2h to D4h . Substituted free-base porphyrins and metalloporphyrins exhibit luminescence with the quantum yields values from 10–3 to 0.2 or 10–4 to 0.2, for fluorescence and phosphorescence, respectively [100, 101]. The absorption and emission bands can be hypsochromic and bathochromic shifted. The localization of the maximum bands is strongly correlated with − type of coordinated metal cations and their electron configuration, − numbers and characters of substituents, − form of preparation (thin film or solution), − environmental conditions: pH, − aggregation of the molecule, and − interaction between fluorophores, presence of other compounds (e.g. Lewis acids and bases), etc. [100–110]. Photophysical parameters of porphyrins are summarized in Table 2.

4.3 Subphthalocyanines and Superphthalocyanine Subphthalocyanines (SubPc’s), similar to phthalocyanines, show two main ranges of absorption, the absorption band in blue region is assigned to the Soret band (B band) and electron transition S0 → S2 , while a band in the red region corresponds to the Q band and electron transition S0 → S1 . Soret bands show less intensive absorbance

Phthalocyanine

DMF

DMSO

2(3),9(10),16(17),23(24)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyanine

1(4),8(11),15(18),22(25)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyanine

1,8(11),15(18),22(25)-tetra-(3,5-di-tertbutylphenoxy) phthalocyanine

Tetrakis [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl)phenoxy phthalocyanine

2(3), 9(10), 16(17), 23 (24)-Tetra-(4-(4-methoxyphenylethyl)-5-propyl-2,4dihydro-3H-1,2,4-triazol-3-one) phthalocyanine

2(3), 9(10), 16(17), 23 (24)-tetra-(5-chloro-2-(2,4-dichlorophenoxy) phenoxy)phthalocyanine

Peripherally tetra-2-methylbenzothiazole substituted metal-free phthalocyanine

Non-peripherally tetra-2-methylbenzothiazole substituted metal-free phthalocyanine

2(3),9(10),16(17),23(24)-tetrakis(4-isopropylbenzyloxy) phthalocyanine

2

3

4

5

6

7

8

9

10

toluene

DMF

DMF

DMSO

THF

CHCl3

CHCl3

1,8,15,22-tetra-(2,3-dihydro-1,4-benxodioxin-2-ylmethoxy)-metal-free phthalocyanine

DMSO

Solvent

1

Metal-free phthalocyanine

No

Table 1 Luminescence properties of metal-free and metal-phthalocyanines

342

343

343

339

344,414

318

328

344

384

318

Soret band(nm)

667,704

671,715

671,700

672, 702, 612sh , 640sh

684, 711, 627sh , 652sh

672, 702, 613sh , 643sh

690, 721, 619sh , 651sh

692, 722, 632sh , 662sh

669,704, 613sh , 642sh

700,726

Q band(nm)

705

689,717

670,700

701,669

651

700

724

–

–

731

Excitation(nm)

709

723

705

707

718

710

730

–

–

739

Emission(nm)

0.17

0.10

0.16

0.09

0.094

0.018

0.13

–

–

0.15

Quantum Yield

(continued)

Yalçın et al. [92]

Demirba¸s et al. [91]

Demirba¸s et al. [91]

Demirba¸s et al. [90]

Demirba¸s et al. [89]

Sen et al. [88]

Canlıca [87]

Kantekin et al. [86]

Kantekin et al. [86]

Gorduk [85]

References

Porphyrin and Phthalocyanine as Materials for Glass … 257

Phthalocyanine

2(3),9(10),16(17),23(24)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyaninato magnesium(II)

1(4),8(11),15(18),22(25)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyaninato magnesium(II)

(magnesium1,8(11),15(18),22(25)-tetra-(3,5-di-tertbutylphenoxy)phthalocyanine,

12

13

14

2(3),9(10),16(17),23(24)-tetrakis(4-isopropylbenzyloxy) phthalocyaninato oxotitanium(IV)

1,8,15,22-tetra (2,3-dihydro-1,4-benxodioxin-2-ylmethoxy)- zinc phthalocyanine

2(3),9(10),16(17),23(24)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyaninato zinc(II)

1(4),8(11),15(18),22(25)-Tetrakis-(3-(3-(3,4-dimethoxyphenyl)-3oxoprop-1-en-1-yl)phenoxy)phthalocyaninato zinc(II)

(zinc 1,8(11),15(18),22(25)-tetra-(3,5-di-tert-butylphenoxy)phthalocyanine,

Tetrakis [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl)phenoxy phthalocyaninato] zinc(II)

15

16

17

18

19

20

D-block metal phthalocyanine

1,8,15,22-tetra-(2,3-dihydro-1,4-benxodioxin-2-ylmethoxy)-magnesium phthalocyanine

11

S-block metal phthalocyanine

No

Table 1 (continued)

DMSO

DMSO

DMF

DMF

DMSO

toluene

DMSO

DMF

DMF

DMSO

Solvent

316

327

318

350

321

345,396

324

305

339

322

Soret band(nm)

702

697

694, 626sh

696, 625sh

703 680

694

700 681

703 679, 612sh

693, 625sh

699, 629sh 681, 614sh

705

689

680, 614sh

702

702

Excitation(nm)

702

Q band(nm)

692

710

705

688

712

710

706

696

681

712

Emission(nm)

0.17

0.10

0.13

0.14

0.18

0.23

0.17

0.25

0.29

0.28

Quantum Yield

(continued)

Sen et al. [88]

Canlıca [87]

Kantekin et al. [86]

Kantekin et al. [86]

Gorduk [85]

Yalçın et al. [92]

Canlıca [87]

Kantekin et al. [86]

Kantekin et al. [86]

Gorduk [85]

References

258 ´ B. Popanda and M. Sroda

Tetra-(5-chloro-2-(2,4-dichlorophenoxy) phenoxy) zinc phthalocyanine

Peripherally tetra-2-methylbenzothiazole substituted zinc(II) phthalocyanine

Non-peripherally tetra-2-methylbenzothiazole substituted zinc(II) phthalocyanine

2(3),9(10),16(17),23(24)-tetrakis(4-isopropylbenzyloxy) phthalocyaninato zinc(II)

9(10),16(17),23(24)-tri-tert-butyl-2-(pent- 4-yloxy)phthalocyaninato zinc(II)

2,9,16,23-tetra-tert-butyl-phthalocyaninato zinc(II)

1(4),8(11),15(18),22(25)-Tetra-(2-phenylphenoxy)phthalocyaninato zinc(II)

2(3),9(10),16(17),23(24)-Tetra-(2-phenylphenoxy)phthalocyaninato zinc(II)

1,8(11),15(18),22(25)-tetra-(3,5-di-tert-butylphenoxy) cobalt phthalocyanine

2(3), 9(10), 16(17), 23(24)-tetra-(4-(4-methoxyphenylethyl)-5-propyl-2,4- DMF dihydro-3H-1,2,4-triazol-3-one) lead phthalocyanine

Tetra-(5-chloro-2-(2,4-dichlorophenoxy) phenoxy) lead phthalocyanine

Peripherally tetra-2-methylbenzothiazole substituted lead(II) phthalocyanine

22

23

24

25

26

27

28

29

30

31

32

33

DMF

DMSO

DMSO

DMSO

DMSO

CHCl3

CHCl3

toluene

DMF

DMF

DMSO

2(3),9(10), 16(17), 23(24)-tetra-(4-(4-methoxyphenylethyl)-5-propyl-2,4- DMF dihydro-3H-1,2,4-triazol-3-one) zinc phthalocyanine

21

Solvent

Phthalocyanine

No

Table 1 (continued)

361

347

375, 400

327

357

333,381

350

350

356

329

357

358

360

Soret band(nm)

320 670 650 –

679, 612sh 699, 632sh 682, 616sh 684, 615sh

709

704

–

692

702

684

684

691

702

689

689

697

Emission(nm)

Not fluorescence

Not fluorescence

Not fluorescence

320

679, 612sh

720

683

693

678

681

656

Excitation(nm)

682

693

678

682

689

Q band(nm)

–

0.218

0.148

0.16

0.15

0.15

0.13

0.14

0.19

0.12

Quantum Yield

(continued)

Demirba¸s et al. [91]

Demirba¸s et al. [90]

Demirba¸s et al. [89]

Canlıca [87]

Ali et al. [94]

Ali et al. [94]

K˛edzierski et al. [93]

K˛edzierski et al. [93]

Yalçın et al. [92]

Demirba¸s et al. [91]

Demirba¸s et al. [91]

Demirba¸s et al. [90]

Demirba¸s et al. [89]

References

Porphyrin and Phthalocyanine as Materials for Glass … 259

Non-peripherally tetra-2-methylbenzothiazole substituted lead(II) phthalocyanine

34

CHCl3 CH2 Cl2 DMSO

Axially bis-[3-(furan-2-yl)-1-(4-[(2-hydroxyphenyl) methylidene]aminophenyl) prop-2-en-1-one] substituted silicon(IV) phthalocyanine

Axially bis-{[(2-hydroxyphenyl)methylidene]aminophenyl)-3-(5phenylthiophen-2-yl)prop-2-en-1-one} substituted silicon(IV) phthalocyanine

Tetrakis [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl)phenoxy phthalocyaninato] gallium(III)Cl

Octakis-2,3,9,10,16,17,23,24-(p-fluorophenoxy) phthalocyaninato gallium chloride

1,8,15,22-tetra-(2,3-dihydro-1,4-benxodioxin-2-ylmethoxy)-indium phthalocyanine chloride

Tetrakis [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl)phenoxy phthalocyaninato] indium(III)Cl (5)

1(4),8(11),15(18),22(25)-Tetra-(2-phenylphenoxy)phthalocyaninato indium (III)acetate

2(3),9(10),16(17),23(24)-Tetra-(2-phenylphenoxy)phthalocyaninato indium (III)acetate

Octakis-2,3,9,10,16,17,23,24-(p-fluorophenoxy) phthalocyaninato indium CHCl3 CH2 Cl2 chloride

36

37

38

39

40

41

42

43

44

DMSO

DMSO

DMSO

DMSO

DMF

DMF

Axially bis(4-isopropylbenzyloxy)phthalocyaninato silicon(IV)

toluene

DMF

Solvent

35

P-block phthalocyanines

Phthalocyanine

No

Table 1 (continued)

350–370

360

329,378

317

326

350–370

316

357

356

355

334

Soret band(nm)

Emission(nm)

−715

676 665 −690

713, 643sh 695, 625sh – 698

703

683

691, 624sh

718

695

719

719

712

−705

−700

696

701

691

686, 619sh

680

676

680

675

672

675

Not fluorescence

Excitation(nm)

677

671

675

726

Q band(nm)

−0.086

0.019

0.014

0.041

0.023

−0.32

0.15

0.21

0.15

0.26

Quantum Yield

(continued)

Burtsev et al. [96]

Ali et al. [94]

Ali et al. [94]

Sen et al. [88]

Gorduk [85]

Burtsev et al. [96]

Sen et al. [88]

Kahriman et al. [95]

Kahriman et al. [95]

Yalçın et al. [92]

Demirba¸s et al. [91]

References

260 ´ B. Popanda and M. Sroda

Phthalocyanine

bis-{2(3), 9(10), 16(17), 23(24)-(tetrapyridin-4-yloxy phthalocyaninato)} lanthanum(III)

bis-{2,3,9,10,16,10,16,17,23,24-octa(4-tertbutylphenoxy) phthalocyaninato} cerium(III)

tris-{2,3,9,10,16,10,16,17,23,24-octa(4-tertbutylphenoxy) phthalocyaninato} cerium(III)

tris-{1(4),8(11),15(18),22(25)-tetra(4-tertbutylphenoxy) phthalocyaninato} dineodymium(III)

bis-{2,3,9,10,16,10,16,17,23,24-octa(4-tertbutylphenoxy) phthalocyaninato} gadolinium(III)

bis-{1(4), 8(11), 15(18), 22(25)-(tetraphenoxy phthalocyaninato)} dysprosium(III) complex

1(4), 8(11), 15(18), 22(25)-(tetraphenoxy phthalocyaninato) erbium(III) chloride

1(4), 8(11), 15(18), 22(25)-(tetraphenoxy phthalocyaninato) lutetium(III) acetate

bis-{2(3), 9(10), 16(17), 23(24)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium(III)

bis-{1(4), 8(11), 15(18), 22(25)-(tetrapyridin-4-yloxy phthalocyaninato)} ytterbium(III)

45

46

47

48

49

50

51

52

53

54

F-block metal phthalocyanines

No

Table 1 (continued)

DMSO

DMSO

DMSO

DMSO

DMSO

CHCl3

DMSO

CHCl3

CHCl3

DMSO

Solvent

340–380

340–380

~321, 430

~322

~430

333, 356, 483

300–400

352

352

340–380

Soret band(nm)

694

687

~627, 695

~623, 696

~625, 694

681, 615

662, 665

653, 698

652, 663, 702

685

Q band(nm)

670

670

695

695

695

615

707

595

595

670

Excitation(nm)

703

711

699

710

719

–

710

709

709

700

Emission(nm)

0.005

0.016