Master of Science (MSc)
Faculty of Science
This thesis reports key findings in the synthesis and transformation of silver nanoparticles (AgNPs) with pentagonal symmetries. The main focus of the thesis work is on the synthesis of silver decahedral nanoparticles (AgDeNPs) and their transformation into larger AgDeNPs and silver pentagonal rod nanoparticles (AgPRNPs). In another direction, produced AgNPs were stabilized by gold plating. In a one-stage photochemical synthesis of AgDeNPs (pentagonal bipyramid, J13 solid), oxidative etching by hydrogen peroxide was implemented to achieve complete conversion of the small silver platelet precursor NPs. For convenient laboratory synthesis of high-purity size-selected AgDeNPs, we have also adapted LEDs as a light source and documented optimal exposure time, LED power, and wavelength range. In the absence of platelet impurities, AgDeNPs produced by the new-generation procedure could be conveniently re-grown into larger sizes using silver ions as a precursor. Thermal one-dimensional regrowth of new-generation AgDeNPs into AgPRNPs has been reliably accomplished with the precise variation in rod length (by varying amounts of added silver) and width (by using different seed AgDeNPs). Chemical stability of prepared AgNPs was improved by deposition of a uniform thin layer of gold at the surface with the controlled slow rate. The produced gold-plated silver nanoparticles (Au@AgNPs, shell@core) were found to be stable in such aggressive chemical environment as: 1.5 M NH3, 0.5 M H2O2, and 150 mM NaCl solutions, where AgNPs were degraded in several minutes. Furthermore, strong SPR and surface uniformity of AgNPs have been advantageously preserved after gold plating. With the reported reproducible synthetic protocols that can be readily implemented in any chemistry laboratory, AgDeNPs and AgPRNPs will serve as a versatile plasmonic platform with a precisely tunable surface plasmon resonance (SPR) from ca. 430 nm (rounded AgDeNPs) to 1100+ nm (longitudinal SPR of longer AgPRNPs). This plasmonic platform should be useful and advantageous for diverse range of applications, especially plasmonic sensing and surface-enhanced Raman spectroscopy (SERS).
Murshid, Nimer, "Controlled Transformation of Nanoparticles with Tunable Surface Plasmon Resonance" (2013). Theses and Dissertations (Comprehensive). 1623.