Date of Award

6-2008

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Dr. Dongil Lee

Second Advisor

Dr. Michael Barcelona

Third Advisor

Dr. Nora Berrah

Fourth Advisor

Dr. Yirong Mo

Abstract

Properties of nanometer-sized gold(Au) particles, especially those that are protected by a monolayer coating of thiolate ligands, called 'Monolayer Protected Clusters' (MPCs), are of rigorous multidisciplinary interest for their potential applications in catalysis and electronics due to their variation with size.

In larger core diameter sizes (>1.5nm) AuMPCs show metallic behavior as observed from electrochemical measurements. On the other hand, sub-nanometer ([approximate]1.1nm) AuMPCs exhibit molecule-like electronic behavior which is typical of Au38 nanoparticles. The various alkane chain thiols(C4 S-C12 S) capped Au38 MPCs have been examined with independent analytical tools, producing a remarkably consistent picture of these materials.

The chemical structure and/or surrounding environment contribute to the electron transfer phenomenon. For rationalizing electron transfer phenomenon it is important to understand the 2D arrangements of AuMPC in the solid state. MPC-based Langmuir monolayers offer particular virtues for the investigation of the correlation between interparticle distance and electron transfer dynamics.

To extend charge transfer studies, the charge transfer quenching of photoexcited semiconductor (TiO2 ) by hexanethiolate AuMPCs with core diameters of 1.1-4.9 nm were employed. The quenching efficiency of AuMPCs was compared using Stern-Volmer plots.

The size dependence of the AuMPC plays a vital role on the quenching efficiency. KQ was found to linearly correlate with the MPC capacitance. This suggests that the quenching process is dominantly controlled by the capacitance of the electron acceptor (AuMPC).

In the research presented here, characterization of AuMPCs and charge transfer between semiconductor and AuMPCs have been studied through electrochemistry, spectroscopic analysis, and other techniques. The correlation between electron transfer dynamic and interparticle distances in the AuMPCs monolayer has been estimated using Langmuir trough by horizontal touch voltammetry (HTV) measurements.

Comments

5th Advisor: Dr. Gellert Mezel

Access Setting

Dissertation-Open Access

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