Characterization and applications of surface enhanced vibrational spectroscopy

Surface-enhanced vibrational spectroscopy (SEVS), the general term that is applied to both surface-enhanced Raman scattering (SERS) and surface-enhanced infrared adsorption (SEIRA), is now being used for a wide variety of applications. This dissertation describes an investigation into two applications of SEVS and an investigation into some of the properties that create the enhancement of the infrared and Raman spectra of species on certain types of surfaces.; The first application discussed in the dissertation (Chapter 2) is the characterization of a direct deposition (DD) interface between a gas chromatograph (GC) and a Fourier transform infrared (FT-IR) spectrometer in which the absorbance of the deposits is increased by SEIRA. The zinc selenide (ZnSe) substrate used in a commercial DD-GC/FT-IR interface was coated with 5 nm film of nanoparticulate silver by physical vapor deposition. The resulting SEIRA spectra were successfully identified using a database of condensed-phase reference spectra. DD GC/SEIRA could distinguish between constitutional isomers when GC/mass spectrometry (MS) was not able to distinguish the authentic molecule.; In the ensuing two chapters, the effect of metal island percolation on SEIRA spectra is described. When metallic nanoparticles start to coalesce, the shape of absorption bands of organic adsorbates becomes dispersive. That the dispersive line shape is not caused by a chemical effect, as some authors had postulated, was shown by measuring the spectrum of liquid n-heptane that was in contact with the percolated metal film. Band symmetry can be optimized by reducing the size of the metal islands to avoid percolation.; In Chapter 5, an analogous application the GC/SEIRA interface described in Chapter 2 is reported, but where SERS spectra were measured instead of SEIRA spectra. After the chromatographic run was finished, the silver-coated ZnSe substrate was warmed from liquid nitrogen temperature to room temperature under vacuum. The vacuum chamber was then opened to the atmosphere. The substrate with each component separated by the GC was moved to a Raman microscope where the SERS spectrum was measured. A significant decrease in the limit of detection was noticed in comparison to the case where a silver coating was not present.; To determinate of the optimum parameters for the vapor-deposition of silver for SERS measurements, substrates were prepared on which silver films with a wide range of thicknesses had been deposited at different rates. The results of this project are described in Chapter 6. (Abstract shortened by UMI.)...