Self-assembled monolayer films of (3-mercaptopropyl)trimethoxysilane (3MPT) and their hydrolysis products on Ag and Au surfaces are characterized using Raman spectroscopy, FTIR spectroscopy, ellipsometry, X-ray photoelectron spectroscopy (XPS), and electrochemistry. 3MPT monolayers are formed through metal-thiolate bonding through the S atom on both metals, similar to other alkanethiol chemisorption chemistries. The orientation of 3MPT molecules in these monolayers is similar on both metals. Prior to hydrolysis, the molecules form an organized monolayer with the methoxy headgroups oriented largely parallel to the surface and the propyl chain in a largely trans conformation. When the methoxy groups are hydrolyzed, the 3MPT molecules cross-link through the formation of siloxane bonds. Although the surface vibrational spectroscopy indicates the presence of a small number of unreacted silanol groups on the siloxane surface, cyclic voltammetry of underpotential deposition of Pb suggests that the Si-O-Si network is highly cross-linked and relatively free from gross defects. The number of these unreacted silanols is estimated using XPS to be fewer than 5% of the original Si-O sites in the 3MPT monolayer.

Results are presented which demonstrate the use of Raman spectroscopy for the characterization of alkylsilane layers covalently bound to silica surfaces. Raman spectra of molecular assemblies of octadecylsilane have been studied by use of a thin silica gel/Ag sandwich structure as the substrate. The Ag surface, used to provide electromagnetic enhancement to the octadecylsilane overlayer, is modified with a monolayer of (3mercaptopropyl)trimethoxysilane, which is used as a molecular

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Approaches for frequency/wavelength calibration of multichannel Raman spectrometers are presented. These approaches are directed towards practical use in laboratories in which multipurpose or specialized applications result in the need for frequent spectrometer calibration. These approaches are also useful when the sample type or configuration does not permit calibration by more routine methods. Guidelines are presented for effective use of polynomials commonly found in spectrometer calibration software for conversion of pixel number to either wavenumber or wavelength. Guidelines for the selection and use of Raman calibration standards are also presented. Standards currently used for calibration of Raman spectrometers are reviewed. Improved frequency data for indent' and the Ar+ plasma lines are presented, along with frequency data for two materials (imidazole and α-cyclodextrin) which are recommended for use as solid Raman standards.

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