| When liquids and solids are considered, attention is usually focused on the bulk properties of the phase. Interfaces have been shown to exhibit properties which are very different from the bulk phase. Because many important chemical processes occur at interfaces including corrosion, catalysis, chemical reactions, and self assembly, the ability to characterize and describe interfaces is crucial for a well developed description of a chemical system. The advent of new experimental techniques that are able to provide a microscopic picture of buried interfaces have greatly increased the understanding of these systems. The development of surface sensitive nonlinear photon based techniques which can be used at ambient temperatures and pressures has grown dramatically over the last few decades. Of these techniques SFG has proven to be very beneficial because of its molecular specificity. This manuscript details the setup and use of a homemade sum frequency generation vibrational spectroscopy system and studies performed on the interfacial chemistry of corrosion inhibitors and ionic liquids. Solving the existing corrosion problems and preventing future problems requires a detailed understanding of the mechanisms of corrosion. The interfacial properties of 5-methylbenzotriazole on copper and octadecanethiol on mild steel has been examined in this study. Room-temperature ionic liquids have become a widely studied class of compounds within the last decade because of their unique properties. Recent studies have shown that imidazolium based ionic liquids can be used as lubricants, a conductive media for fuel cells and solar cells, and heterogeneous catalysis. Because most of these applications involve interfacial chemistry it is important to develop a molecular level description of how ionic liquids behave at an interface. The ionic liquids on hydrophilic and hydrophobic quartz have been examined in this dissertation. Sum frequency generation spectroscopy provides the ability to probe these systems in situ. Electrochemical methods, contact angle measurements, and x-ray photoelectron spectroscopy were also used to support the sum frequency spectroscopy. |
