Advanced Materials and Nano Systems: Theory and Experiment (Part 3)

Plasmonic metal-semiconductor heterostructure has become the most prominent content for water splitting by photocatalytic means. It is thought to be an effective, clean, and affordable energy source. Hydrolysis, water splitting, and destruction of organic dyes have all demonstrated the high efficiency of LSPR formation by these materials. A noble metal combined with a low bandgap semiconductor makes for the perfect photocatalyst. In this case, both semiconductors and noble metals can absorb visible light. They are prone to producing positive and negative pairs and inhibit their recombination, causing the resulting electron-hole pairs to interact with the chemicals in the immediate environment, thereby increasing photocatalytic activity. The strong SPR's combined effect with the efficient separation of photogenerated electrons and holes supported by noble metal particles can be credited with the increased photocatalytic activity. It has become a useful method for overcoming the limitations of conventional photocatalysts and promoting photocatalytic mechanisms.

This book chapter has three main goals: briefly describing plasmonic dynamics, explaining the preparation techniques, analyzing the key characteristics of the plasmonic metal nanostructure that influence photocatalysis, summarizing the reported literature, and offering an in-depth explanation of the four fundamental plasmonic energy transfer process.

Ancient human history invites significant learning with unknowing facts and fascinations. Significant development and transitions in the human lifestyle are visualized from the capitalized materials. “Ceramics”, as antique as it sounds, is frequently used for innumerable applications. From pottery to pellets, ammunition to antennas, electrolytes to electronics, all exist under the radar of ceramic materials. The dominant trait of ceramic materials for advanced applications is constantly replenished to extract peerless products for future utilization. Ionic or covalent bonding in ceramic microstructures administers their suitable mechanical, electrical and chemical characteristics. Pristine ceramics display low conductivity and chemical stability, while doped ceramics via implanted impurities empower their characteristics. The nature of dopants and defect substitution differs on the target application. The vastly introspected energy sector is permeated with acceptor-doped perovskite ceramics, while the defense sector inquests over piezoelectric ceramics and ceramic composites. The trivial facet amongst all is the use of Barium Zirconate (BaZrO3 ) based ceramic compositions. It has been substantially contemplated to visualize the role played by BaZrO3 in multiple domains. Either as a parent material or as an additive, BaZrO3 attracts research groups from diverse sectors. Compiled with innumerable advantages, it accompanies a few limitations. The vital thing is the high sintering temperature along with the trade-off between proton conductivity and chemical stability. However, BaZrO3 -based ceramics are keenly monitored and tailored in an attempt to subsidize the maximum possible drawback with a simultaneous improvement in their properties. In the following chapter, we emphasize BaZrO3 -based ceramic and ceramic composites as smart materials for advanced applications. The extended applications in the energy sector, photocatalysts for hydrogen production, smart bullet systems in defense and microwave dielectric resonators for wireless communications are elaborately introspected with key insights. 

In this study, we have proposed an anode material based on Silicon doped graphene (Siligraphene) for developing the Li-ion batteries (LIBs). We have predicted that Siligraphene can be an anode material for lithium batteries. In particular, we have found that the Siligraphene sheet can adsorb lithium atoms in different sites in a hexagonal structure. Also, we have found that Lithium atoms can be diffused along the plane of siligraphene. The energy of diffusion of siligraphene (SiC3 ) is about 0.095eV, and for Li on top of silicon atoms is about 0.223eV, indicating rapid charging/discharging processes. During charging and discharging, the electrode LixSiC3 exhibits small variations in voltage, making them a potential candidate for Li-ion batteries.

Light-emitting diodes, especially white light-emitting diodes are very attractive and fascinating lighting sources at this present time because they have the potential for high energy saving and environmental friendliness as compared to conventional lighting sources such as incandescent and fluorescent lamps and also have wide applications in a variety of fields including in lighting, architectural and medical etc. Among the various applications, the lighting sector is one of the most important fields because it consumes a large amount of electricity. About 15-22% of total electricity production in the world is consumed in the lighting sector. Therefore, understanding how to fabricate a white light-emitting diode is very necessary in order to improve its practical application further. Basically, there are two methods of fabrication for white light emitting diode, mixing of multiple LEDs and phosphor converted white light emitting diode (pc-WLED). The luminous efficiency and rendering index is influenced by the type of fabrication. In this chapter, the general introduction of light emitting diode (LED), its working principle, characteristics of light including CIE, color temperature and rendering index, the different modes of fabrication for white light-emitting diodes, and their advantages and disadvantages have been discussed.

The enhancement of nano-system properties, particularly low dimensional structures, is of great importance for future devices. Using spin-polarized Density Functional Theory (DFT), electronic and piezoelectric properties of II-VI monolayer (ZnO, ZnS, CdO and CdS) are studied. Variations of these properties are further studied under substitutional doping of non-metal atoms (boron and carbon). Doping with a B/C atom transforms all the monolayers into half-metallic ferromagnet, with changes arising mainly from p-orbitals of the dopant (B/C) atom. Reduction of band gap energy from its pristine structure is observed in all the doped cases. Observations predicted that the B-doped ZnO and ZnS monolayer showed negative structural stiffness and negative piezoelectric tensors, while C-doping remains stable with enhanced elastic as well as piezoelectric properties of the monolayer.

The physical properties of the (Zr1-xTix)3AlC2 MAX-phase compounds have been studied using the first-principle plane-wave method in the framework of the DFT theory. The Perdew-Burke-Ernzerhof parametrization was chosen for the exchange correlation (XC) energy. The equilibrium ground-state properties of the named compounds were calculated and compared with the reported experimental and theoretical data. The stability of our compounds has been analyzed. The electronic structures were predicted, indicating all our compounds exhibit a metallic behavior. The mechanical stability and elastic moduli were evaluated from the elastic constants. The effect of temperature and pressure on Bulk modulus, Debye temperature and heat capacity have been investigated and discussed in detail. 

First-principles DFT calculations were used to investigate surface segregation processes in ordered Pt3X (where X=Nb, Ti) alloys. Using pristine Pt (111) surface as a reference, the effect of surface segregation on the adsorption energy of O2 atoms in Pt3X alloys was evaluated. Our results showed that surface segregation due to direct exchange is only feasible for the Pt3Nb alloy (Esegr = - 0.3833 eV) but not for its Ti analogue (Esegr = 0.516 eV). In contrast, for both Pt3X alloys, surface segregation due to antisite migration and leading to the formation of a Pt-skin or overlayer, favouring oxygen atom adsorption, an essential step in ORR, is possible. Interestingly, reverse migration of X atoms from the bulk to replace Pt atoms on the surface is an endothermic process and is thus very unlikely. Analysis of the surface segregation energy for configurations involving a direct exchange of Pt atoms located beyond the third layer in the slab model with Nb atoms at the surface indicates the formation of pristine bulk like Pt (111) surface from Pt3Nb surface is unlikely. The energy of adsorption for the O-atom on pristine Pt (111) surface shows that the presence of minute quantities of dopant Nb atoms in the sub-surface layer could enhance its suitability for ORR. Comparison of O-atom adsorption energy on the various surface segregation models of Pt3X alloys to that of pristine Pt (111) surface shows that the formations of a Pt-skin or overlayer on the Pt3Nb surface due to surface segregation change the O-atom adsorption energy on this surface to 0.34 eV which is just 0.14 eV higher than the optimal value of 0.20 eV. Our results also show that the binding of an oxygen atom to the fcc Pt site in Pt3Ti is lower in energy compared to its binding on a pristine Pt (111) surface. In comparison, the binding of an oxygen atom to the fcc Pt site in Pt3Ti is of the same magnitude as that of the pristine Pt (111) surface.

The size range of nanoparticles between 1-100nm is unique because of their extremely small structure with a very high surface area to volume ratio. Besides naturally produced nanoparticles, there is a huge worldwide demand for synthetic nanoparticles. These synthetic nanoparticles are modified to some extent according to the specific need. These manipulations at the nano-scale paved the way for a popular branch of science called nanotechnology. However, with the massive use of nanoparticle-based industrial products in our day-to-day lives, we knowingly or unknowingly ignore their impact on the environment. The air, water, and soil quality determines environmental health, which is reflected by a healthy ecosystem and its biodiversity. The existing intricate interaction between humans and their surrounding environment is important for maintaining a fine balance in the ecosystem. Any change in this interaction may lead to adverse consequences. The nanoparticles released in the environment cause a varying degree of effects on the ecosystem based on the type, surface coating, and degree of its environmental transformation. Some nanoparticles are harmful to the environment and some are beneficial. Some of the nanoparticles in the environment get bioaccumulated in plants and animals, disturbing their growth and productivity. Remediation by nanoparticles has been effective in removing some toxic compounds from the environment, thereby providing a way to minimize pollution efficiently. Thus, in this review, we have tried to present an overview of the sources, fate, and effects of nanoparticles available in air, water, and soil. We strongly advocate for the long-term assessment of nanoparticles, and the formulation of strict guidelines for their usage by the concerned industries for better environmental health, and in turn a healthy ecosystem.

This investigation holds the search for optimum sites for Lithium on Silicene Monolayer, by studying the adsorption energy on putting the Lithium atom on different possible sites. The center of the hexagonal structure in silicene was found to be the most favourable site. Using transition state search (TSS) the optimized stable state is confirmed. A low Diffusion Energy Barrier (DEB) of 0.348 eV indicates that the adsorption of Li over silicene can occur easily. Multiple adsorptions are considered, up to 4 Li atoms upon silicene substrate. The metallic property of pristine silicene is maintained throughout Li atom adsorption. Large adsorption energy in each of the adsorption suggests that silicene may be promising for Li-based battery material. 

The development of nanoscience and nanotechnology has improved our quality of life. The new class of materials known as nanoparticles (NPs) contributes to the development of nanotechnology. For the NPs, at least one dimension of particles should be 1 to 100 nm. The synthesis approaches can modify NPs structure and size, which is crucial in molecular biology, physics, chemistry, medicine, and material science. The high surface area of NPs can be achieved via synthesis approaches, providing increased value and imperative parameters like surface reactivity. Several approaches to synthesizing NPs can be used, mainly categorized into two parts: bottom-up and top-down. These two categories are classified based on the starting materials used to synthesize the NPs. This review discussed the brief of synthesis approaches and their utilization in the field of nanotechnology and nanoscience. The novel approach to the synthesis of NPs i.e., the electrochemical discharge process, is discussed in detail. The materials synthesis like ZnO, carbon, graphene, and other metal oxide and their composite are discussed in tabular form. Finally, the challenges, advantages, disadvantages, conclusions and NPs synthesis are discussed.

Water is essential for all living things, whether it is human beings, animals or plants. Around 70% of the total earth's surface is covered by water, however only a small fraction of it (2.5%) is found as fresh water. On the other hand, due to anthropogenic activities like industrialization, a huge increase in population, utilization of toxic chemicals in agricultural activities etc., the available freshwater bodies have been contaminated by various kinds of pollutants, including toxic chemicals released mainly from industries like textile, which causes hazardous to both human being and aquatic life. Therefore removal of these toxic chemicals before entering into fresh water bodies is of great importance. Heterogeneous semiconductor photocatalysis is the most effective green method in this regard because it enables to degrade the pollutants into non hazardous products like CO2 and H2O without releasing any harmful residue. Therefore, understanding the knowledge of photocatalysis mechanism is very significant to enable further improvement. Hence, this chapter presents the basic mechanism of photocatalysis, its drawbacks and the advanced strategies to improve the catalytic efficiency. Finally some of the important factors that provide strong influences on the catalytic activity also have been discussed.