Abstracts Category : Other

Size and Shape Control in Metal Nanoparticles and Nanocomposites

by Tomendro Subedi

This thesis describes major findings on the shape transformation of the precursor silver decahedral nanoparticles (AgDeNPs) with pentagonal symmetry and twin defects into silver pentagonal prism nanoparticles (AgPPNPs) using Br as a shape selective reagent. Silica-encapsulation of the gold-plated AgDeNPs was also carried out forming ordered arrays of silica encapsulated gold-plated AgDeNPs ([emailprotected]@AgDeNPs) of different sizes. At first, synthetic procedures for AgDeNPs (pentagonal bipyramids), silver pentagonal rod nanoparticles (AgPRNPs) and gold-plating of AgDeNPs ([emailprotected]) were optimized. Gold plating enhances the chemical stability of AgDeNPs and preserves the superior plasmonic properties of silver. This thesis deals with the transformation of the precursor AgDeNPs into silver pentagonal prism nanoparticles (AgPPNPs) using Br as a shape selective reagent. The degree of truncation was monitored by transverse LSPR plasmon band position shift with varying Ag/Br molar ratio. Length control was addressed from 50 nm to 128 nm by varying the amount of added silver. Colloidal synthesis of the silica encapsulation of the gold-plated AgDeNPs was also done forming [emailprotected]@AgDeNPs of different diameters. Silica coating was developed using the modified Stber process. [emailprotected]@AgDeNP of different size/diameter was prepared and studied. [emailprotected]@AgDeNPs of different diameters were obtained that ranged from 45 nm up to 310 nm. Overall, this thesis work on AgPPNPs should be useful for the applications on localized surface plasmon resonance (LSPR), based on the biological and chemical sensing devices. [emailprotected]@AgDeNPs of different thicknesses provides an opportunity for the size-dependent plasmonic properties that include metallodielectric arrays for photonic applications, LSPR sensing, and SERS.