Organosilane Surface Functionalization and Interfacial Zinc-Ion-Carbohydrate Interactions Studied by Vibrational Sum Frequency Generation, X-Ray Photoelectron Spectroscopy, and Second Harmonic Generation

This thesis reports attempts to model the fundamental interactions that occur at liquid/solid interfaces by using organosilane chemistry to tailor mineral oxide surfaces with the chemical moieties commonly found in biogeochemical and biological systems. The need for molecular-level understanding of chemical processes in such systems is addressed by utilizing vibrational sum frequency generation (SFG), X-ray photoelectron spectroscopy (XPS), and second harmonic generation (SHG).;The initial studies investigate interfacial zinc ion-carbohydrate interactions at the water/solid interface. The development of glucosamide-functionalized fused silica surfaces is characterized and shown to be quantitative. The thermodynamic binding parameters reveal that zinc ion adsorption may occur through a multivalent mechanism between different surface carbohydrate moieties, and that the adsorption may be hindered due to tightly bound surface groups, or electrostatic repulsion from zinc ions adsorbed to easily accessible surface sites.;Zinc ion adsorption on undecanol-functionalized fused silica surfaces is also investigated as a comparison to the glucosamide-functionalized fused silica studies. The undecanol- functionalized surface is fully characterized and the absolute surface site density of the material is determined with a combination of XPS and SHG. The thermodynamic binding parameters of zinc ions to functionalized fused silica are compared to bare fused silica to better understand the impact of interfacial metal-carbohydrate adsorption in pollutant transport. The additional number of hydroxyl groups in the glucoamide-functionalized fused silica system does not appear to enhance metal ion adsorption when compared to undecanol-functionalized fused silica.;In addition, a new platform for surface functionalization is explored through the mild oxidation of aminophenylsilane-functionalized surfaces to azidophenyl moieties, followed by the copper-catalyzed azide-alkyne cycloaddition (CuAAC) of low-molecular-weight alkynes and alkyne-modified oligonucleotides. Quantitative conversions are determined by analyzing XPS N1s responses, and vibrational SFG spectra are analyzed to determine the platform's viability for molecular orientation analysis.;Finally, adsorption of amino acids on diopside surfaces is investigated to determine if chiral mineral oxide surfaces played an important role in chiral selectivity and bond formation during the prebiotic era. The preliminary results demonstrate the potential use of vibrational SFG in the molecular orientation analysis of adsorbed L- and D-glutamic acid on naturally flat diopside (110) and (1-10) surfaces.