Synthesis, Application and Future Perspectives of Smart Nano-materials - Part 1

Cumulative demand for energy needs enormous growth in more secure and diversified energy sources with high energy generation capacity and successful strategies to reduce greenhouse gas emissions. Amongst various energy approaches, they are constructing a system using hydrogen (H2 ) as the primary carrier that can facilitate a secure and clean energy future. The development of technologies that meet desired performance and cost requirements for the safe and reliable storage and transportation of hydrogen produced from various sources and intended for diverse uses is crucial for establishing a future hydrogen economy. Hydrogen is one of the effective, renewable, and environmentally benign sources of alternative energy. Electrocatalytic and photocatalytic water splitting, along with the Chemocatalytic process from chemical sources using suitable nanomaterial based catalysts, have shown great proficiency for hydrogen evolution and are believed to be a promising avenue to reach the goal of future hydrogen economy. Smart nanomaterials, including metal nanoparticles (NPs) and nanoclusters (NCs), have been extensively investigated for the catalytic hydrogen evolution reaction (HER). Moreover, the crucial properties of nanomaterials, such as porosity, active sites, morphology, shape and size of NPs, chemical compositions, metal-support interactions, and metal-reactant/solvent interaction in nanomaterials, are the major factors affecting the performance of catalytic HER. In the current chapter, we discuss the state-of-art design of various carbon and MOF based/derived nanocatalysts along with their performance for hydrogen evolution from Electrocatalytic, Photocatalytic and Chemocatalytic reactions.

This chapter focuses on core-shell type carbon-coated metal nanoparticles, which possess distinct properties that can be manipulated to enhance their interactions with electromagnetic radiation. The synergism at the magnetic metallic core and carbon shell interface plays a vital role in augmenting the optical response of these nanoparticles. Consequently, it becomes crucial to develop synthesis strategies that optimize the defects at this interface. In this chapter, we provide a detailed description of a cost-effective pyrolytic synthesis approach and present mechanistic studies on the microwave absorption (at GHz frequencies) and optical limiting behavior of the synthesized core-shell nanostructures. The pyrolysis synthesis strategy offers a lowcost method for producing the core-shell nanoparticles. By carefully controlling synthesis parameters, we achieve precise control over the structure and composition of the nanoparticles. Moreover, we investigate the defects and their distribution at the interface, as these defects significantly influence the optical properties of the nanostructures. Furthermore, we explore the microwave absorption capabilities of the synthesized core-shell nanostructures at GHz frequencies. By characterizing their absorption behavior, we gain insights into their potential applications in microwave technologies, such as EMI shielding and stealth technology. Additionally, we examine the optical limiting behavior of the core-shell nanostructures, which refers to their ability to attenuate intense light and protect optical devices from damage. Through comprehensive optical characterization and analysis, the mechanistic insights on the optical limiting behavior of the synthesized nanostructures are elucidated. The findings evolve the understanding of light-matter interactions in these nanostructures and pave the way for their potential applications in various technological fields.

The outstanding optical characteristics, including photoluminescence, photobleaching resistance and light stability of carbon quantum dots, have been increasingly being used in more and more fields, including ideal crudesubstantial for creating sensing materials during the last few years. Carbon quantum dots, which are, in general, tiny carbon nanoparticles (<10 nm in size), have been developed either by “Top-down” or “Bottom-up” approaches, with further modification during the preparation or post-treatment. Majorly, the synthesized carbon quantum dots show high potential towards biomedicine, optronics, catalysis and sensors and are rather dissimilar from those of the bulk material’s characteristics. This chapter highlights the techniques involved in design and preparation of high-quality carbon quantum dots. The summary of the reported strategies and techniques for their preparation will hopefully provide a valuable insight for relevant work.

In the present review, the concept of nanochemistry and its applications has been lucidly dealt. The idea of miniaturization of materials for harnessing the benefits of size-dependent properties started in the middle of the last century. Due to their tunable physical and chemical properties along with versatile potential applications nanomaterials are technically more advanced than their bulk counterparts. On the basis of size, shape, composition and origin, nanomaterials can be classified. Technological operations throughout the world are mainly controlled by science and engineering. Nanomaterials have opened a new beginning and contributed to various fields of modern science and technology. Nanotechnology fields are evolving that could generate a global market for mineral, non-fuel commodities and agricultural products. Presently, Nanotechnology is characterized as a revolutionary discipline in terms of its influence on industrial applications. Nanotechnology offers probable solutions to several problems using emanating nano techniques. The review covers from definition to classification, various available ways for the synthesis of nanomaterials. It also deals with a wide variety of applications for nanomaterials.

 Supercapacitors are recognized as a potent device for posterity. It is crucial to take into account the energy and power densities of the supercapacitor. Modern fabrication techniques and the development of better electrode materials will be enabling the supercapacitor to operate at high power and energy densities. Supercapacitors have much attention devoted because of their distinctive traits like high power, long cycle life and environmentally benign nature. They bridge the highpowered conventional capacitors and high energy batteries. There is an enormous scope to improve the energy densities of electrochemical supercapacitors without sacrificing their high-power densities. In this view, a research community has been working extensively to improve the advancement of supercapacitors with various nanostructured materials. A lot of effort has been made recently to enhance the quality and performance of supercapacitors. Activated carbon products with high surface area and porous nature are commercialized. Research communities are looking for an alternative and superior material to replace the commercially available activated carbon material. To match the energy storage quality and performance of commercialized carbon, a variety of alternative materials are available. Various materials, including metal oxide, polymers, and other carbon allotropes, are competing to replace commercially available carbon, but they fall short in terms of performance or cost of manufacture. Nanostructured metal oxides rank among the best materials.

In this chapter, the various nanostructured metal oxides and their electrochemical behaviors as, the positive electrode is critically analyzed from both research and applications perspectives. Here, concise descriptions of various nanostructured metal oxides and their behaviors as positive electrode for supercapacitor applications are explored.

TiO2 nanomaterials can be synthesized in various types of structures, such as nano-powder, nano-films, nano-rods, nano-crystals, etc., by various methods such as biological, precipitation, hydrothermal, electrochemical, solvothermal, spray pyrolysis, co-precipitation, micro-emulsion, solution-combustion, and sol-gel, etc. Each method has unique importance, merits, and demerits. Such as biological method is an ecofriendly method and avoids toxic chemicals in the preparation of TiO2 -based nanomaterials. The co-precipitation technique is very convenient and easy, but its control over size distribution is not good, which results in coarser particles instead of nanoparticles. The micro-emulsion method facilitates good control over the particle size by the ratio of surfactant to water, low reaction temperature, and short processing time. The sol-gel method has high homogeneity in crystals, better tuning over the shape and size of the crystals with reasonable preparation cost. The hydrothermal and solvothermal processes have good chemical uniformity and a higher probability of synthesizing unique metastable structures at minimum reaction temperatures but nanomaterials synthesized via these methods are not stable for application at the higher temperature. The electrochemical technique facilitates a multifaceted and minimum temperature method to synthesize TiO2 nanoparticles with good control over crystallite size, better yield, and negligible environmental effect. To synthesize the nanostructures of TiO2 , liquid phase processing is the most convenient method since it gives better homogeneity in the product with good control over shape and size. In this chapter, short literature regarding the synthesis of TiO2 nanostructure by various methods and its applications are discussed. Moreover, the regeneration of used TiO2 -based nanoparticles is also reported.