Structural, Optical and Catalytic Properties of Bimetallic and Metal-Semiconductor Nanorods

Metal and semiconductor nanomaterials exhibit highly tunable electric, magnetic, optical and catalytic properties. To obtain desired properties, structure and composition of the nanomaterials must be fine-tuned, which requires fundamental understanding of the growth mechanism. In the thesis research, we study Au-Cu alloy nanorods (NRs) growth mechanism using single particle scattering spectroscopy. From electrodynamics simulations, it was revealed that the unusual features of the single particle scattering spectra were due to atomic level structural defects made up of few atoms on the surface of NRs, caused by galvanic replacement reaction (GRR). NRs are further explored as templates for GRR using HAuCl4. Interestingly, NRs transformed into hollow rods or break into nanospheres via a hollow junction dumbbell shaped intermediate, at different concentrations of HAuCl4. The hollow rods showed enhanced catalytic activity for p-nitrophenol reduction, while dumbbell shaped intermediates displayed junction dependent optical properties. Later plasmon-exciton interactions in Ag-CdS hybrid nanorods were explored. The absorption studies revealed mixed electronic states at the metal semiconductor interface while the CdS length dependent photoluminescence displayed by hybrid nanorods was trap state emission. Our detailed studies of the structural transformation mechanisms and corresponding optical properties provide guidance to fabricate nanomaterials with tunable structure and compositions for exciting applications