Candidate: Ke Du

Degree of: Doctor of Philosophy

Department: Chemistry

Title: SynTheses and fundamental characterization of Nanoparticles and their clusters

Committee:
Dr. Subra Muralidharan, Chair
Dr. Michael Barcelona
Dr. Sherine Obare
Dr. Dongil Lee
Dr. Brian Tripp

Date: Tuesday, June 6, 2006 9:00 a.m. 2708 Wood Hall

Abstract: Nanoparticles of gold derivatized with monolayers of thiocarboxylic acid ligands, core/shell nanoparticle composites of gold and silica, gold-glutathione clusters, and titania nanoparticles were synthesized and their surface properties (extent of ligand coverage, net negative charge, and zeta potential) characterized by capillary electrophoresis as a function of pH, ionic strength, and dielectric constant for the first time.  The hydrodynamic radii of the nanoparticles were determined by dynamic laser light scattering and used to calculate the net surface charge, extent of ligand coverage, and zeta potentials of the nanoparticles from electrophoretic mobilities. The ligand derivatized nanoparticles had similar hydrodynamic radius of about 20 nm which was twice the value determined by transmission electron microscopy. This indicated the possibility of the formation of multilayers of carboxylic acid groups on the surface of the nanoparticles.  These nanoparticles had a surface ligand concentration of about 10-12 moles/cm2 based on the net negative charge at a pH value of 10.8 which only accounted for the solvent accessible groups and not all the ligand groups as the light scattering technique. In general the net negative charge and associated zeta potentials increased with pH due to an increasing number of carboxylic acid groups being deprotonated with pH.  The net charge and zeta potential decreased with increasing ionic strength and decreasing dielectric constant due to the association of Na+ ions with the carboxylate ions on the surface of the nanoparticles. The Au/SiO2 and SiO2/Au nanoparticles exhibited quite different behavior from each other as a function of ionic strength and dielectric constant, the former behaving more like a bulk material and the latter like the ligand derivatized gold nanoparticles.  The behavior of gold glutathione nanoparticles was similar to the thiocarboxylic acid derivatized gold nanoparticles at different pH, ionic strength, and dielectric constant.  Aggregates containing gold glutathione nanoparticles were identified by capillary electrophoresis at various ionic strengths and dielectric constants.  New and novel synthetic routes to obtain monodisperse TiO2 nanoparticles of average radii 101 nm (acid hydrolysis) and 63 nm (base hydrolysis) were developed.  These nanoparticles were also characterized by capillary electrophoresis.  

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