Plasmonic Resonances and Their Application to Thin-Film Solar Cell

This chapter furnishes the plasmonic properties of metal nanostructure and its application to thin-film solar cell. Plasmonics is an emerging branch of nanooptics where light metal interaction in subwavelength domain is studied. Metal supports surface plasmon resonance that has tunable signature, which depends on the morphology as well as surrounding media. These plasmonic resonances can be tuned in a broader range of solar spectra by changing several parameters such as size, shape and medium. Moreover, metals show scattering properties that could be utilized to enhance optical path length of photon inside the thin film of solar device. The chapter mainly focusses on the study of plasmonic resonance of smaller- and larger-sized metal nanoparticle using semi-analytical as well as numerical approach. For the estimation of optical properties like extinction spectrum and field profile of larger-sized nanoparticle, finite-difference time-domain (FDTD) method is used. The field distribution in both silver and gold nanoparticle cases has been plotted in ‘on’ resonance condition, which has a broader range of applications

Investigations of surface potentials

The potential energy at the surface of materials, like graphene, might be able to trap atoms and molecules. In order to probe this possibility, the theoretical foundations of Density Functional Theory are studied, and the need for numerical calculations is understood. Iterative methods to solve numerical calculations are presented. Quantum ESPRESSO, a Linux package used for numerical calculations is examined, and its important features are explained. Simple simulations involving Aluminium, and Silicon are carried out. The accuracy of quantum ESPRESSO is verified using the Hydrogen molecule, for which we have the analytical solution. Four different attempts at modeling graphene are then presented. The system of a single hydrogen molecule and a graphene sheet, is then studied. Finally, the notion of accuracy in numerical calculations is analyzed in light of the simulations that have been run.Bachelor of Science in Physic

Precursor-Driven Nucleation and Growth Kinetics of Gold Nanostars

Recently, seed-mediated approach has been widely utilized for synthesizing monodisperse gold nanostars well-known for plasmonic and sensing applications. Herein, we report a single step seedless/templateless organic synthesis procedure for the complex 3D gold nanostars with a high degree of size/shape control, involving the complexation of polyvinylpyrrolidone (PVP) in polar solvent <i>N</i>,<i>N</i>-dimethylformamide (DMF) and their reduction of AuCl₄^– ions along with hydrochloric acid (HCl) as an effective mediator. On the basis of the kinetic optical absorption and Fourier transform infrared (FTIR) spectroscopy measurements, a convenient ligand exchange mechanism has been proposed for the first time to the best of our knowledge to understand the evolution of these complex shaped gold nanostructures. The coordination interaction among PVP and DMF as well as PVP–DMF–AuCl₄ has been identified as the major driving factors influencing the temporal evolution of the size/shape-controlled gold nanostars

Parametric Study of Wire-EDM Process in Al-Mg-MoS2 Composite Using NSGA-II and MOPSO Algorithms

Al-Mg-based composite is used in producing a variety of components. To improve the machinability of the composite, MoS2 is added. For characterizing the machining of the Al-Mg-based composite, different wt.% (2, 4, and 6) of MoS2 are added as reinforcement. Wire Electrical Discharge Machining (WEDM) process is performed to analyze the kerf width and surface roughness. Due to the complex nature of the WEDM process, the necessity for its optimization through the use of innovative methods is well-proven in the process of research. Evolutionary algorithms, specifically genetic algorithm based on NSGA-II and Multiple Objective Particle Swarm Optimization (MOPSO), are used for optimizing kerf width and surface roughness. For assessing the impact of current, pulse on time, and gap voltage on kerf width and surface roughness, an analysis of the selected WEDM process parameters is performed. MOPSO takes lesser iterations as compared to NSGA-II in giving nearly the same optimal fronts for achieving low kerf width and surface roughness. The 10–12 A of current, 50–57 µs of pulse on time, and 30–33 V of gap voltage are used for the WEDM process based on the Pareto-optimal solutions and better performance is achieved on the samples. In addition, the supplementary DOE method is applied to determine the relationship between factors affecting a process and the response. The analysis revealed that current has played a major part in the governance of kerf width and surface roughness over pulse on time and gap voltage for Al-Mg-MoS2 composite

Solvent-Adaptable Poly(vinylpyrrolidone) Binding Induced Anisotropic Shape Control of Gold Nanostructures

Conformational changes in the intrinsic chemical structure of the polymer poly­(<i>N</i>-vinyl-2-pyrrolidone) (PVP) in aqueous as well as (in)­organic solvents essentially dictates the novel room temperature seedless synthetic procedure for the reduction of hydro-chloroauric acid (HAuCl₄.3H₂O) leading to the formation of different anisotropic size/shaped gold nanoparticles. The interaction between gold metal ions and PVP at the given specific monomer to metal ratio leads to sequential metal ligand exchange, thereby simultaneously utilizing the mild reducing property as well as distinct structure-directing/capping ability of PVP in different (in)­organic solvents, the synchronized features of which have been carefully explored through NMR and FTIR measurements identifying the foolproof signatures of the polymer coordination interaction for the first time in designing the systematic nucleation and growth/stabilization procedures of anisotropic metal gold nanostructures. Furthermore, the complementary XPS data evaluates the quantitative role of coupled oxygen and nitrogen components of the pyrrolidone ring in the PVP–solvent complex in asserting seedless surface mediation as well as the morphology driven localized surface plasmon suitable for wide range of plasmonic as well as photonic applications

Density functional theory calculations and Hirshfeld surface analysis of propyl-para-hydroxybenzoate (PHB) for optoelectronic application

The geometries, electrostatic potential, Mulliken charge analysis, Natural Bond Orbital analysis and polarizabilities of propyl-para-hydroxybenzoate were calculated using B3LYP functional with 6-311++G(d,p) basis set. The calculated geometries are well matched with the experimental values. The Mullliken atomic charge analysis shows that the eventual charges are contained in the molecule. The NBO analysis explains the intramolecular charge transfer in the PHB molecule. The bonding features of the molecule were analyzed with the aid of Hirshfeld surface analysis. The frontier molecular orbital analysis showed the charge transfer obtained within the molecule. The calculated hyperpolarizability of the PHB molecule was 6.977E −30 esu and it was 8.9 times that of standard urea molecule