Photonic analysis of colloidal plasmonic nanoparticles

In this thesis we investigate the optical behavior of different plasmonic nanoparticles ranging from solid metallic (Au) spheres to copper sulfide (CuS) nanoplatelets. We use computational electromagnetic analysis to predict light-particle interactions at the nanoscale. The dissertation includes four chapters. Chapter 1 is a brief introduction to the fields of Nano photonics, plasmonics and metamaterials. In Chapter 2, we review the theory used to analyze the photonic materials and phenomena that we investigate. This includes Maxwell's field equations for predicting the propagation of electromagnetic waves, Mie Theory for predicting electromagnetic scattering and absorption by sub wavelength particles and Mie-Gans theory for predicting electromagnetic scattering and absorption by colloidal spheroidal particles. In Chapter 3 we study the plasmonic behavior of colloidal metallic (gold) nanoparticles and discuss the dependency of localized surface plasmon resonance (LSPR) on the particle size and the refractive index of the background medium. We also study the optical properties of magnetite (Fe3O4) nanoparticles and develop a closed-form expression for the dielectric function of such particles at in the optical spectrum by curve fitting experimental data. In the later part of the chapter we analyze the plasmonic properties of magnetite-gold core-shell nanoparticles. In Chapter 4, we discuss the synthesis and characterization of the covellite (CuS) nanoplatelets. We use the Drude model for the dielectric function of CuS nanoparticles and use the Mie-Gans theory to fit the Drude model parameters to measured spectral data. We study the plasmonic behavior of the nanoplatelets, especially the absorption spectra and its dependence on the size and aspect ratio of the particles as well as the orientation of the platelets relative to the polarization of the incident field.