Fundamental Studies of Reactions between NO3 Radicals and Organic Surfaces
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Ultrahigh vacuum (UHV) surface science experiments were designed to study reaction kinetics and mechanisms of gas-phase NO3 radicals with well-organized, highly characterized, organic thin films. The surface reactions were monitored in situ with reflection-absorption infrared spectroscopy (RAIRS). The oxidation states of surface-bound molecules were identified with X-ray photoelectron spectroscopy (XPS). Consumption of vinyl groups was observed concurrently with formation of organic nitrates in RAIRS. XPS spectra showed little oxidation of sulfur head groups. The observed rate constant was determined based on the consumption of carbon-carbon double bonds and the formation of organic nitrates. Using this rate constant, the initial reaction probability was determined to be (3 Â± 1) X 10-3. This reaction probability is approximately two orders of magnitude higher than that for the reactions between the same surface and pure O3, which is due to the higher electron affinity of NO3 relative to O3. These results led to the development of a proposed mechanism that involves electrophilic addition of NO3 to the double bonds. Reactions between NO3 and a methyl-terminated SAM were also monitored in situ with RAIRS. In the CH3-SAM studies, hydrogen abstraction was observed during NO3 exposure. The results presented in this thesis should help develop an understanding of the fundamental interfacial reaction dynamics of NO3 radicals with organic surfaces.
- Masters Theses