Defense Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Indika U. Arachchige

Abstract

The advent of nanoscience and nanotechnology has sparked many research forefronts in the creation of materials with control over size, shape, composition, and surface properties.1,2 However, for most of the applications, nanoscale materials need to be assembled into functional nanostructures that exhibit useful and controllable physical properties. Therefore, numerous efforts on the assembly of nanoparticles (NPs) using organic ligands, polymers and polyelectrolytes have been reported.3,4 However, the interactions between NPs are mediated by intervening ligands, which are detrimental to charge transport and limit the thermal stability. Hence, developing a new method to produce solid state nanostructures with direct NP linkage has become a significant challenge. To avoid the bridging ligands and improve the conductivity of NP based solid state structures, a novel strategy has been developed in which colloidal NPs undergo condensation to wet “jello-like” hydrogel with direct interfacial linkage. Then hydrogels can be dried supercritically to produce aerogels.5 Resultant nanostructures exhibit low densities, large open interconnected pores, and high internal surface areas and are containing entirely of colloidal metal NPs.6 Since noble metal NPs have been widely used in applications such as catalysts, sensors, and novel electrochemical device components, we herein expanded the sol-gel method to noble metal NPs to produce a new class of metal aerogels.

In the dissertation, the synthesis of hollow Ag hollow NPs, Au/Ag alloy NPs, and Au/Pt/Ag alloy hollow NPs with tunable sizes and physical properties, and their oxidative-assembly into high-surface-area, mesoporous, self-supported gel framework has been achieved. The gelation kinetics have been controlled by tuning the oxidant/thiolate molar ratio that governs the rate of NP condensation, which in turn determines the morphology, optical transparency, surface area, and porosity of the gel frameworks. These low-density mesoporous nano-architectures displaying optical transparency or opacity, enormously surface area, and interconnected meso-to-macro pore structure are promising candidates for catalytic, electrocatalytic, and SERS-based sensing applications. The SERS activity of Au/Ag alloy aerogels has been studied and significant signal enhancement was achieved. The performance of the Au/Pt/Ag aerogel towards methanol oxidation reaction has been studied via cyclic voltammetry and significant electro-catalytic activity was observed.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-13-2016

Available for download on Wednesday, May 12, 2021

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