Gold used to be regarded as catalytically inert until about 20 years ago when it was shown that supported gold clusters < 5 nm in diameter exhibited some unique catalytic properties. Based on this revelation, several studies have demonstrated the feasibility of reactions previously thought of as impossible on gold. The ability of gold to oxidize CO below ambient temperatures at rates higher than conventional CO oxidation catalysts (Pd and Pt) has been shown to hold potentials for technological applications. Extensive past and on-going research are geared towards elucidating the mechanistic details of this reaction. The nature of the active sites, the effect of the supports and the effect of moisture are still debated in literature. I therefore present some experimental results supported with density functional theory calculations to shed additional light on some of the issues concerning gold catalysis in general, and low temperature CO oxidation in particular. Previous studies of the effect of moisture on oxide-supported gold reported that although water promotes CO oxidation on this surface by as much as two orders of magnitude, it is only a spectator molecule on the surface. I present here evidence for strong water-oxygen interactions when water is co-adsorbed with atomic oxygen on Au(111). Impinging a CO beam on the surface co-adsorbed with oxygen and water produces water-enhanced CO oxidation. Based on these results, I propose that CO reacts with hydroxyls formed from water-oxygen interactions to form CO₂, similar to a previous observation on Pt(111). Exposing a Au(111) surface pre-covered with ¹⁶O to isotopically labeled carbon dioxide (C¹⁸O₂) showed that ¹⁶O¹⁸O (m/e = 34) was produced from carbonate formation and decomposition. Estimates of reaction probability and activation energy gave ~ 10⁻⁴ - 10⁻⁵ and -0.15 eV respectively. The effect of annealing on the reactivity of oxygen pre-covered Au(111) was investigated using water, carbon monoxide and carbon dioxide as probe molecules. Precovering Au(111) with atomic oxygen followed by annealing resulted in surfaces that were less reactive towards water, CO and CO₂. Annealing is believed to stabilize the reactive metastable oxygen thereby increasing the barrier to reaction similar to what is reported on other surfaces. / text

Gold nanoshells (GNS) are a new class of nanoparticles that can be optically tuned to scatter or absorb light from the near-ultraviolet to near-infrared (NIR) region by varying the core (dielectric silica) /shell (gold) ratio. In addition to spectral tunability, GNS are inert and bioconjugatable making them potential labels for in vivo imaging and therapy of tumors. We report the use of GNS as exogenous contrast agents for enhanced visualization of tumors using narrow band imaging (NBI). NBI takes advantage of the strong NIR absorption of GNS to distinguish between blood and nanoshells in the tumor by imaging in narrow wavelength bands in the visible and NIR, respectively. Using tissue-simulating phantoms, we determined the optimum wavelengths to enhance contrast between blood and GNS. We then used the optimum wavelengths for ex-vivo imaging of tumors extracted from human colon cancer xenograft bearing mice injected with GNS. Systemically delivered GNS accumulated passively in tumor xenografts by enhanced permeability and retention (EPR) effect. Ex-Vivo NBI of tumor xenografts demonstrated tumor specific heterogeneous distribution of GNS with a clear distinction from the tumor vasculature. The results of the present study demonstrate the feasibility of using GNS as contrast agents to visualize tumor tissues using NBI technique. / text

Murrell-Mottram empirical atomistic many-body and Gupta n-body potentials have been used to study various aspects of the cluster chemistry of copper, silver, gold and nickel. Simulated annealing techniques have been used to search for the global minima of the four metals with up to 55 atoms. Icosahedral, decahedral, octahedral, hexagonal closed packed and hexagonal prismatic structures were found. The gold clusters show some rearrangements and distortions from ideal geometries. Polyhedral cluster calculations up to 1 500 atoms predict that icosahedra and truncated octahedra are particularly stable. Calculations on the structures of copper-gold alloy clusters show that gold atoms prefer to occupy the surface of the cluster. A simple approximation to model the passivation of gold clusters by thiol ligands predicts that for 55 atoms the passivated cuboctahedron is more stable than the icosahedron, the reverse of the order for the bare clusters. Molecular dynamics simulations of gold adatoms on the gold (111) surface and of the impact of a 55 atom gold cluster with the gold (111) surface have been performed.

A large quanti ty of gold'vork was produced in Cyprus during the Late Bronze Age. This thesis is the result of a detailed investiGation of this material. The thesis consists of two parts. Part One comprises general backeround information essential to the study. This begins with a brief summary of the nineteenth century excavations in Cyprus which brought to light so much of the finest &old'fork. This is followed by an outline of the limited contextual evidence from tombs, settlements, sanctuaries and hoards. The rest of Part One considers the possible sources of the gold itself and the techniques which \ .... ere used by the Late Bronze Ace t,'oldsmiths. Part Two comprises a detailed analysis of the eold"ork. This is based for the most part on objects which were physically exal:dned, '\{ith the aid of a microscope. These represent a large proportion of the available material, but the analysis also takes account of as many as possible of the other known and published items. Each class of object is subdivided for convenience according to type or decoration, and relevant technical points are discussed. ".ihere possible, comparisons are made with material :from other areas such as the Aege~ or the Kear Last. The chronology is indicated where it is known. The final conclusions offer a summary of the relationship between Cyprus and other areas with reference to the goldwork. The extent of the ~1ycenaean contribution is discussed, and the material is placed "Ii thin its historical framework. Volume Two comprises the descriptive catalogue of the objects which were examined.It also contains the Plates and Figures.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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No description available.

In the canyon where the Fraser River flows through the Cascade mountains, migrating salmon supported a large, dense native population. By 1850 the Hudson’s Bay Company had several forts on other parts of the Fraser River and its tributaries but found the canyon itself inaccessible. Prior to the gold rush, whites rarely ventured there. Discoveries of gold in Fraser River in 1856 drew the attention of outsiders and a rush of miners, and led eventually to permanent white settlement on mainland British Columbia. Contrary to much historiography, these were not foregone results. Instead, the gold rush was a complex process of negotiation and conflict among competing groups as they sought to profit from gold discoveries. The Hudson’s Bay Company sought to gain and retain control of the resource by incorporating it into its trade and by excluding outsiders. But miners arrived by the thousands, and the Company was forced to try to regulate miners’ access to the resource. However, as a group, miners were cohesive and self-reliant; they had little need for outside intervention. The Hudson’s Bay Company was unable to regulate them while pursuing its own ideas of profit. The British government subsequently revoked the Hudson Bay Company’s trade license, and proclaimed British Columbia a colony. In efforts to impose its own ideals of order on the gold fields, the government introduced a new colonial administration which, following a chain of command extending from London through Victoria to the Fraser, sought to organize the population in the spaces of the Fraser Canyon. Government authority was reinforced by the legal system’s flexible responses to the diverse population’s activities it deemed illegal. By studying the interactions of natives, miners, traders, administrators, and the legal system, I have attempted to untangle the ways in which white men negotiated their particular racist and masculinist ideals and sought to impose them in the spaces of the Fraser Canyon.

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