Electronic and Optical Properties of Gold and Gold Composite Nanoparticles

Sahu, Aditya Kumar (2022) Electronic and Optical Properties of Gold and Gold Composite Nanoparticles. PhD thesis, Indian Institute of Science Education and Research Kolkata.

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Abstract

The thesis includes experimental, theoretical, and simulation studies of optical and structural orientation behavior of systems consisting of metallic nanoparticles and related composite materials. We developed methods to synthesize shape-controlled gold nanoparticles in various shapes namely nanospheres and nanorods. We studied the detailed growth kinetics of the synthesized samples by employing an experimental approach to analyze growth-relevant information using spectroscopic and microscopic methodologies. UV-visible spectroscopy has been used to evaluate the optical properties of the as-prepared nanoparticles and monitor nanoparticle growth over time. Our blue-shift observation in growth dynamics is an interesting phenomenon that depends on the physicochemical properties of the surrounding medium. The analytical approach of the finite difference time domain (FDTD) simulation method is also used to study the adhesion and proliferation of gold nanoparticle formation to understand the growth kinetics. The near-field interactions between the particles lead to a change in the color of aggregates. Rather than forming uncontrolled aggregations, the particles can self-assemble around other structures that act as frameworks for the assembly. Our theoretical and experimental correlated studies provide an approach to understand the growth kinetics of nanoparticle synthesis. Our studies on two-dimensional gold selenide establish the structural stability and electronic properties using ab-initio density functional theory (DFT). We have carried out the synthesis and characterization of different phases of AuSe, namely α-AuSe and β- AuSe. We establish that α-AuSe is a metallic, whereas β-AuSe is a semiconductor. Our work consists of theoretical and experimental assessment of 2D-layered AuSe for their prospective applications in sensing devices, catalytic supports, energy conversion, and storage systems, encouraging more research on these systems.

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