Thesis(M.S.)--Auburn University, 2006. / Abstract. Includes bibliographic references (p.101-106).

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21590号 / 理博第4497号 / 新制||理||1646(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺西 利治, 教授 島川 祐一, 教授 吉村 一良 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

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Two Systems were designed. The first permits tunable on-demand softening of a hydrogel network. The second permits reversible on demand ligand exchange within a hydrogel network. Both means were shown to be cytocompatible and their uses demonstrated in cell culture of mesenchymal stem cells and 3T3 fibroblast cells.

Monofunctional platinum(II) complexes, such as phenanthriplatin and pyriplatin, have notably different characteristics from the bifunctional anticancer complexes, such as cisplatin and oxaliplatin, which have detrimental toxicities and resistance associated with them. The unique properties of the monofunctional complexes may be exploited to target cancer cells without producing the toxic side effects associated with the current FDA-approved platinum-based anticancer drugs. To advance the understanding of these monofunctional platinum(II) complexes, this study replaced the chloride leaving ligand with an acetate group, which should increase solubility and alter the rate of reactivity with key amino acid and nucleotide targets. Phenanthriplatin and pyriplatin compounds were reacted with silver acetate to form insoluble silver chloride and the desired complex. Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to characterize the new complexes and conduct kinetic assays with guanosine 5'-monophosphate (5’-GMP). A rate constant of 2.9 (± 0.7) x 10-2 M-1s-1 was determined for the reaction between pyriplatin and 5’-GMP, previously. A preliminary rate constant of 1.8 (± 0.1) x 10-2 M-1s-1 was determined for the newly synthesized cis-[Pt(NH3)2(py)OAc]+ complex with 5’-GMP. Ligand exchange kinetics directly influences the anticancer activity and toxicity of platinum drugs. Initial results indicate that the solubility is increased, and the rate of reaction is decreased by the acetate ligand.

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<div><br></div><div><p>Noble metal nanoparticles have been studied extensively as heterogeneous catalysts for electrocatalytic and thermal reactions. In particular, the support material for the catalytic species is known to play a role in influencing the geometric and electronic properties of the active site as well as its catalytic performance. Polycrystalline gold electrodes have been used as a support to modify the electrocatalytic behavior of adsorbed molecular species. Here, we have studied two electrocatalytic processes- the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR), using Au nanoparticle-based catalysts.</p> <p>Transition metal dichalcogenides are well-known HER catalysts that show structure-sensitive catalytic activity. In particular, undercoordinated sulfur sites at the edges of bulk materials as well as amorphous clusters and oligomers tend to show the highest reactivity. The hydrogen adsorption energy of MoS_x nanoclusters can be further tuned through the metallic support. Here, we synthesize colloidal Au@MoS₄^2-, Au@WS₄^2-and Au@MoS₄^2--WS₄^2- using a biphasic ligand-exchange method. The MoS₄^2- and WS₄^2- complexes show higher HER activity when supported on Au nanoparticles than on to a carbon control, illustrating the electronic role played by the support material.</p> <p>In the second project, Au nanoparticle cores are utilized as supports for Pd submonolayer and monolayer surfaces in order to catalyze the two-electron reduction of O₂ to generate hydrogen peroxide. Bulk surfaces of Pt and Pd are excellent catalysts for the four-electron reduction of O₂ to H₂O. In order to achieve high selectivity for H₂O₂, we postulate that the ensemble geometry of the Pd surface must be reduced to small islands or single atoms based on literature studies that have shown that large Pd ensembles are required for O–O bond cleavage. In this study, we synthesize several submonolayers surface coverages of Au@Pd core-shell nanoparticles using a biphasic ligand-exchange method. As the Pd coverage decreases from monolayer to submonolayer, the peroxide selectivity rises but is accompanied by an increase in catalytic overpotential. The highest peroxide selectivity was observed for 0.1 layers of Pd on Au, which likely exhibits the highest fraction of isolated atom and small cluster geometric ensembles of Pd.</p><br></div>