Handbook on Synthesis Strategies for Advanced Materials

No single material or a class of material meets the diverse set of properties required for different applications. Inherent advantages and disadvantages of metals, ceramics, or polymers have made it necessary to develop combinatorial approaches, wherein their functional advantages are maximized and drawbacks are abridged. Composites are the materials comprising two or more constituent materials with significantly different physical, mechanical, electrical, or thermal attributes. Composites offer material characteristics that are different from the individual components and can be engineered to entail synergistic advantages such as high strength, corrosion resistance, electrical or thermal conductivity, and low cost. Notably, in composites, the individual components may remain separate and distinct within the finished structure. The composite material is generally defined by the matrix such as metal-matrix composite, ceramic-matrix composites, and polymer-matrix composites, or by the type and morphological arrangement of the filler such as particle reinforced, fiber reinforced, unidirectional, random, laminates, or honeycombs. Fabrication of composite materials is accomplished by a wide variety of techniques such as melt compounding, in situ polymerization, tufting, tailored fiber placement and filament winding. Depending on the matrix and the filler, different synthetic strategies are adopted. Further with the advent of nano-sized fillers, new class of composites has emerged which have significant important advantages over the conventional composites. This chapter provides details on the synthesis strategies of different polymer-matrix composite materials. A detailed account of the strategies to tailor interfacial adhesion, dispersion, filler asymmetry, filler orientation, and high loading is made, and specific details on the synthesis of nanocomposites and the morphology-interface-property correlation are presented. Recent advances in the theoretical frameworks and the specific applications of the composites are also discussed.

Advent of advanced analytical techniques for nanoscale characterization complemented by novel synthesis methodologies has led to a plethora of functional nanomaterials. These nanomaterials have opened avenues for application of electrochemical sensors in medical diagnostics, biotechnological, environmental monitoring, wellness monitoring and food markets. This chapter presents an overview of the accomplishments of electrochemical sensor devices based on carbon nanomaterials, noble metals, nanostructured polymers, and metal/metal oxides/composite nanostructures. Also, attempt is made to address several concerns around the selection of appropriate nanomaterials, their characterization and means to utilize the interesting chemistry they offer, especially from the point of view of electrochemical sensing.

Although they were not assigned a place in original Mendeleev periodic table, noble gases found a special place in popular science history. Their discovery, prediction about their reactivity, and preparation of first compound of noble gases are a display of utter determination, innovation, scientific temperament, and conviction. Since discovery, noble gases have been considered as inert or rare gases that are unable to react with other elements. This notion was shattered in 1962 when Bartlett prepared first noble gas compound. Subsequently, a flurry of synthetic and structural work ensued in hundreds of noble gas compounds. This chapter will take the readers on a journey of how the noble gases were discovered from the 0.1% discrepancy in assigning the density of nitrogen. Moving further, the chapter will shine light on how a 60 years long dogma related to the inertness of noble gases was overthrown in one master stroke. In addition to this, the chapter will also provide the discussion on the synthesis of compounds of noble gases and how the compounds which are almost impossible to prepare under ambient conditions become reality under high pressure. Furthermore, an enigma related to missing xenon phenomenon and proposed models to explain this paradox has also been included in this chapter. In the last, the chapter would like to draw the attention of the readers toward a question; was coaxing reactivity from these intractable elements not remarkable?

In this chapter, a brief introduction to fluorine and fluorides with an emphasis on their preparation is presented. The general procedures for preparation of fluorides, in particular inorganic fluorides, are explained. Preparation of F₂ and HF, and their properties are discussed in light of their importance to fluoride chemistry. Since the fluorine and fluorides are hazardous, corrosive and reactive materials, the need for special experimental conditions are explained. In addition to F₂ and HF, other fluorinating reagents are also briefly mentioned. The common experimental procedures used for fluorides and oxyfluorides, like solid-state reactions, solid–liquid and solid–vapor reactions as well as non-conventional fluorides preparation methods like sol–gel, hydrothermal, displacement and precipitation reactions are presented. The specific examples of preparation and properties of fluorides and oxyfluorides are presented at the end. The chapter is concluded with a mention of the scope of innovative needs in preparative fluorine chemistry.

Materials having ions in unusual oxidation states have been of interest for long time due to their relevance in understanding the oxidation–reduction process of various physicochemical phenomena, fundamental ionization process of elements as well as their challenging chemistry to prepare them. The ions in unusual oxidation states are usually unstable, and in turn they transform to stable state under ambient conditions or by feeble alteration of thermodynamic parameters or chemical environments. Since attaining such oxidation states is energetically unfavourable, they are generally achieved by either extreme or non-equilibrium thermodynamic conditions or diagonally opposite mild reactions where alternate paths are adopted. The varieties of unusual oxidation states can be conveniently obtained in solutions, but they are extremely reactive and short-lived, and are often encountered as intermediates in various chemical reactions. Cations with such oxidation states can also be stabilized by a variety of organic ligands. However, this chapter is mainly focussed on solid materials where the ions are stabilized primarily by inorganic counter ions and have significantly higher stability for further studies. In this chapter, a brief overview on preparation of materials having unusual oxidation state is presented. The chapter initially explains about the unusual oxidation state and their interest, and then the modes of their stabilization. There are several case studies explaining the process of stabilization of lower and higher valent states, and the role of judicious chemical and thermodynamic conditions, and crystal structure to stabilize them are presented.

The up-converting nanophosphors are the nano-crystalline materials that produce luminescence by converting low-energy radiation (e.g., infrared or near-infrared) into high energy radiation (ultraviolet and visible) via an anti-Stokes shift process. These can be prepared by incorporating up-converting luminescent centers such as lanthanide ions (Ln³⁺ ions, where Ln = Nd, Ho, Er, and Tm) and/or transition metal ions (e.g., Mn²⁺, Ti²⁺, Ni²⁺, Mo³⁺, Re⁴⁺, and Os⁴⁺) into a suitable nano-crystalline host material. The choice of dopant–host combination is decisive in determining the luminescence characteristics of a nanophosphor. Inorganic fluoride hosts such as ALnF₄ and LnF₃ (where A and Ln refer to alkali metal ions and lanthanide ions, respectively) and BF₂ (B stands for Ca and Sr) are found suitable for up-converting Ln³⁺ ions as they exhibit; (i) low phonon energy, (ii) promising doping conditions, (iii) favorable electronic structure, and (iv) excellent chemical, thermal, and photo-stability. Ln³⁺ ions doped fluoride nanophosphors (where Ln = Ho³⁺, Er³⁺, and Tm³⁺) exhibit unique up-conversion luminescence characteristics such as strong emission in visible window, substantial anti-Stokes shifts (>600 nm), prolonged luminescence lifetimes (up to several milliseconds), and sensitization under infrared (IR) or near-infrared (NIR) irradiation. Due to these fascinating luminescence properties, they find potential applications in bio-imaging, drug delivery, tumor targeting, solid-state lighting, energy harvesting. Interestingly, their luminescence characteristics can be altered by varying the doping concentration, dopant–host combination, morphology, crystal structure, and the functional group present over the surface of the nanoparticles. This has given prime focus toward developing novel synthesis techniques that are promising in preparing the fluoride-based nanophosphors of desired morphological, compositional, structural, and optical characteristics. The solution-based synthesis methods or wet chemical methods are very promising in producing nanophosphors of controlled size–shape, phase, and chemical composition. Several solution-based methods were developed in past for the preparation of fluoride-based nanocrystals, with each of them having some merits and demerits. Therefore, a prior understanding of each method is essential before adapting it for material preparation. In this regard, this chapter provides a brief description about a few of solution-based synthesis methods such as hydrothermal, co-precipitation, and thermolysis, which are most versatile in the controlled preparation of a variety of Ln³⁺-doped fluoride nanophosphors (e.g., ALnF₄, BF₂, and LnF₃, where A, B, and Ln stand for alkali metal, alkaline earth metal, and lanthanide ions, respectively).The critical role of reaction parameters such as pH of the reaction medium, precursor amount, ligands, reaction temperature and time on the controlled preparation of Ln³⁺-doped fluoride nanophosphors will be discussed in light of available literature. Further, the impact of morphological, structural, and compositional characteristics of the nanophosphors on their luminescence behavior will be discussed in regard to their biomedical, energy harvesting, and lighting applications.

The rare earth ions produce photoluminescence in the entire range of the electromagnetic spectrum particularly in the UV, vis and NIR regions. The present chapter describes the synthesis of quantum cutting phosphor materials using different methods, such as solid-state reaction, combustion, sol–gel, hot-injection, hydrothermal, along with a melting-quenching method for the glass materials and studies the photoluminescence of the rare earth doped quantum cutting phosphor materials. Quantum cutting (QC) is a downconversion (DC) process in which the conversion of a high-energy photon into the two or more low-energy photons takes place. This process not only takes place in the singly rare earth doped materials but also in the doubly and/or triply rare earth doped materials. The difference is only in the energy transfer route between activator and sensitizer ions. This occurs due to cooperative energy transfer (CET) process. In energy transfer process, the photoluminescence intensity of sensitizer ion decreases whereas the photoluminescence intensity of activator ion increases accordingly. The change in photoluminescence intensity of these ions is highly concentration dependent. The photoluminescence intensity versus pump power measurements shows that the photoluminescence intensity of the visible region is a linear process while that of the NIR region occurs due to nonlinear process. The change in photoluminescence intensity of the sensitizer ions can be established from the lifetime measurements. The preparation and characterization of different rare earth-based quantum cutting materials and their applications in large numbers of the emerging fields have been also included.

There is a need to understand boron and boron chemistry of metals and non-metals. Boron is an electron-deficient atom in bonding and can react with other elements (except noble gases) to form stable compounds, namely B₂H₆, MgB₂, AlB₂, B₄C, SiB₃, BN, Cr₂B, Fe₃B, ZrB₂, LaB₆, etc. It forms tetrahedral, cage-type, trigonal and layered structures, etc. B–B bond can be of single (B–B), double (B = B) or triple (B≡B) types. In metal-rich borides, metal–metal interaction occurs. They are used as catalysts, imparting materials for mechanical, thermal and chemical stability, magnetic, superconducting and coating materials, etc. In this article, several ways of synthesis of metal borides and characterization techniques have been discussed. Also, the synthesis methods for nanostructured metal borides are elaborated. The properties (magnetism, electronic structure, electrical resistivity, optics) of some selected compounds of metal borides in addition to BN, CN are described. Lastly, the applications of selected borides are provided.

The borides, carbides, phosphides, and nitrides of metals or non-metals can be prepared by various methods. This chapter covers the preparation, properties, and applications of polycrystalline samples (powder, thin film in micron to nanometer sized particles) and single crystals of borides, carbides, phosphides, and nitrides. Nature of chemical bonding of transition metal or rare-earth metal nitrides is similar to that of respective carbides (i.e., metallic and ionic bonding in nature). When a few percentages of N/C are present in transition metals, the metal lattice expansion occurs (i.e., the interstitial sites of the metal lattice are occupied by N/C atoms) and then new phases of compounds are formed by further addition of N/C in metal lattice. The s-block elements form nitrides or carbides and chemical bond is usually ionic in nature. The p-block elements form nitrides or carbides and chemical bond is usually covalent in nature. The borides of transition metal or rare-earth metal can have metal rich to boron rich phases (M₂B, MB, M₃B₄, MB₂ to MB₁₂) with M–M, M–B, B–B bonding (metallic, ionic, and covalent bonding in nature). The phosphides of transition metal or rare-earth metal can have metallic and ionic bonding. When the shape of particle changes from 0D, 1D, 2D to 3D in nanosize range, their properties vary. They exhibit interesting electrical, mechanical, magnetic, and optical properties. They are used in many applications such as catalysts, permanent magnetic materials, sensors, LEDs, lasers, super-hard materials, high temperature materials, cutting tools, permanent coloring materials (i.e., jewelry), absorbing medium for microwave to radio-wave ranges, insulating materials, high thermal conducting materials, etc.

Carbon is a most versatile element and its bonding and special nature have long been noted largely due to the variety and quantity of structures. Carbon can make different allotropes like graphite, diamond and fullerene due to its sp¹, sp² and sp³ possible hybridization nature. The development and understanding of carbon-based materials are topics of major interest in science and technology due to their excellent electrical, thermal, mechanical and optical properties. On the other hand, carbon is hardly considered to be toxic material, which makes it easily biocompatible. Carbon-based materials are synthesized using various top-down and bottom-up synthesis approaches. In this chapter, various conventional and more practical synthesis strategies, as well as their mechanism for diamond, fullerene, carbon nanotubes, carbon nanofibers, graphene and graphene oxide with the extracts from published investigations by numerous researchers, will be discussed.

Carbon dots (CDs) are the newest addition to the family of carbon nanomaterials that have generated enormous excitement because of their unique photoluminescence (PL) property. The superior optical properties, biocompatibility, low toxicity and aqueous solubility of CDs have projected these materials as potent alternatives to conventional fluorophores and semiconductor quantum dots. The promising characteristics of CDs, together with their facile synthesis, have led to a rapid pace of research in these nanomaterials. This chapter outlines the various synthesis procedures that are used to obtain CDs from a variety of carbon sources and precursor molecules, their general properties and characterization techniques and the proposed PL mechanisms of CDs. The applications of CDs in diverse areas, like sensing, photocatalysis, bio-imaging, therapeutics and optoelectronics, are also discussed.

Technological advances based on miniaturization of devices have always been pivoted around the synthesis of high-quality advanced inorganic nanomaterials with respect to size and shape and the understanding of the corresponding exotic properties developed. Among them, colloidal metal phosphide nanomaterials have an edge over other colloidal nanomaterials owing to their exceptional properties due to structural and compositional diversity. Furthermore, the presence of earth abundant and environmentally friendly phosphorus makes them cheaper and benign materials. This chapter will give a brief introduction followed by introductory background of metal phosphides including history and properties of metal phosphides. Subsequently, a discussion on synthesis of colloidal metal phosphide nanomaterials is included which deals with methods for the synthesis of colloidal metal phosphide nanomaterials and common phosphorus sources for the metal phosphide synthesis. In the following sections, literature on synthesis of colloidal main group metal- and transition metal phosphide nanomaterials and their applications are incorporated. In the end, the chapter will be concluded with a brief note on future prospective of colloidal metal phosphide nanomaterials.

This article describes the prime role of selenium (Se) and its compounds in mammalian biochemical systems, performing diverse functions like maintenance of health through various selenoenzymes, diagnostic, therapeutic functions and as targeted drug delivery system. The role of inorganic selenium compounds in food chain and in nourishing human health is also briefed. The deficiency, as well as excess selenium, leads to detrimental effects on health. Hence, the essential dose required and its food sources or supplements have been described. Its role in materials science serving for facilitating human life through various electronic devices, solar cells, H₂ evolution catalysts, etc. has also been described briefly. To harness the full potential of such a useful element, what we need is a real compound, material or its formulation in hand with utmost purity. As the properties of compounds are governed by their structures, the literature knowledge helps us to design the selenium compounds appropriately for desired applications. The present article underlines the importance of design, synthesis, purification and characterization of the selenium compounds. In view of this, various classes of selenium compounds and their classical and newly reported synthesis strategies have been described. In the later part of the chapter, the prominent characterization and estimation methods for selenium species have also been described briefly.

Intermetallic phases constitute a unique class of materials composed of two or more metals, sometimes non-metallic elements also, in definite proportions. They have well-defined stoichiometry, crystal structure and can exhibit metallic, covalent or ionic bonding. High mechanical strength, resistance to corrosion and adequate ductility of intermetallic phases make them widely applicable as structural materials for automobiles, aerospace, telecommunication, electronics, transport and heavy industries. There is a huge demand for alloys having high mechanical strength and corrosion resistance at elevated temperatures for energy applications. The physical properties and mechanical strength of alloys are governed by the presence of intermetallic phases in these alloys. The formation of these phases in a given alloy system on other hands is governed by the nature of synthesis of alloys, level of impurity phases present and the heat treatment process. Experimental conditions, like, level of vacuum, annealing temperature, rate of cooling and thermal shock are among the factors that play vital role in tailoring their properties. In the present chapter, types of intermetallic phases, various experimental procedures for their synthesis, processing and their properties will be discussed. Details of synthesis processes including heat treatment in different types of furnaces, mechanical alloying, electrochemical processes, chemical reduction methods will be discussed. Influence of annealing conditions on material properties will also be presented. The knowledge of phase diagram, structure and thermodynamic parameters in fixing the material properties will be brought out. The chapter will also include some of the technologically important intermetallic phases, their method of synthesis, properties and applications.

Solid-state metal hydrides provide a safe and efficient method for hydrogen storage. In this chapter, fundamental mechanism of metal–hydrogen interaction, the thermodynamic and kinetic aspects of hydride formation and the factors affecting them are provided. Metal hydrides are formed by dissociative chemisorption of hydrogen on metals at definite temperature and pressure. A brief description of volumetric and gravimetric set-up required for gas phase hydrogen absorption measurement is presented. Loading of hydrogen on metal can also be realized electrochemically by splitting of water, which is the main concept of metal hydride battery. Representative preparation techniques of different systems such as intermetallic hydrides, light metal hydrides and complex hydrides are illustrated. The techniques employed for characterization of metal hydrides are discussed. Current researches on various applications of metal hydrides are also discussed.

Silicon compounds are very important owing to their stability, non-toxicity, and high natural abundance of silica in earth crust. These materials have been studied for more than a century, and a vast literature on their synthesis and application is available. These are utilized in various forms in organometallics, polymers, material science, and microelectronics, and have immense potential for their application in organic and hybrid electronic devices. Thus, a comprehensive review on synthesis, processing, and potential applications of silicon-based materials was a need of the time. In this chapter, the synthesis of silane, methods of extracting elemental silicon, and their use in the growth of single crystals are discussed. In addition, synthesis strategies of various silicon compounds which include organosilane, silicone, polysilane, and silicene are described and their applications are discussed.

Fusion energy has undisputable potential to cope with the challenges of increasing global energy demand and to protect the environment from global warming. The construction of a fusion reactor based on the D–T fuel cycle has been at the forefront of fusion energy research. Due to insufficient availability of tritium in nature and limited global inventory, the fusion reactors ought to breed their tritium. Tritium is produced in a blanket containing Li-based compounds called tritium breeding blanket surrounding the fusion reactor. Li-based ceramics are candidate materials for the fabrication of tritium breeding blankets. In order to attain tritium self-sufficiency, the blanket must produce enough tritium so as to maintain the tritium breeding ratio (TBR) greater than 1. The present chapter reviews R&D results of powder synthesis, consolidation to form shapes and sintering of Li-based ceramics. Further, this chapter summarizes the challenges and opportunities concerning the processing of Li-based ceramic tritium breeding materials.