| This dissertation involves the construction of a sum frequency generation imaging microscope and the development of the sum frequency generation imaging microscopy (SFGIM) to study heterogeneous samples. This nonlinear microscope shall provide a spatial distribution overview of the surface and chemically identify the molecules at the interface based on the adsorbed molecules inherent vibrational spectrum. Due to the continuous interest in studying the physical and chemical properties of the adsorbed molecules on surfaces, this technique has been developed and designed to have a chemical sensitivity, interface specificity and spatial resolution of ∼2 mum. Then, several experiments were designed for the imaging microscope to test its capability in providing the chemical contrast of the interfacial molecules within its limit of resolution.;These studies included the patterned microcontact printed self-assembled monolayers on gold with variation in different terminal functional groups, chain length of the thiol molecules, the stamping and backfilling times, mixing of two different alkanethiol molecules at the boundary of two defined regions that affected the interpretation of the chemical contrast (two-dimensionally); initial catalysis reaction/chemical reactivity (carbon monoxide on chemisorbed on Pt and cyanide ions reacting on gold forming linearly bound CN- ions and complex compounds); and adsorbed octadecanethiol molecules on the mild steel and zinc surfaces to study the formation and orientation of the alkanethiol molecules on the surface including the interpretation, which resulted to whether the surface was homogenous or heterogeneous.;SFG imaging microscopy provided the chemical contrast on two-dimensional form based on the inherent vibrational spectrum of the adsorbed molecules at the interface whether the molecules on the surface have different terminal functional group, different orientation (odd-even effect), stability, and heterogeneity. The microscope has the capability to locate the molecules on the surface and provide chemical identification based on the changes of the vibrational spectrum.;The significance of all these experiments will soon lead to more complicated systems to learn more about the surface chemistry of the molecules adsorbed on the surface and how their stability is affected by a change in environment with the application of heat, potential, substrate, and chemical environment (exposure of the substrate with adsorbed molecules to different corroding solvents). The ability to locate the molecules spatially has opened an opportunity to study them in a two-dimensional domain and understand their nature (chemical and physical properties) separately.;The heterogeneity of surfaces has always been an issue in surface chemistry, where the surfaces have been assumed to be constantly homogeneous over an entire area due to the averaging of the SFG signal. Therefore, a model system has to be used to provide a controlled modified surface and heterogeneity of the adsorbed molecules. The imaging microscope has been used recently to address some experiments that contributed to the fundamental views of surface chemistry. Thus, microcontact printing process is a unique soft lithography method that uses a patterned polydimethyl siloxane stamp to transfer thiol molecules on gold in a patterned and controlled fashion. |
