(594g) Investigation of Solid/Liquid Interfaces by Sum Frequency Spectroscopy: Acetonitrile Adsorption on a Pt Covered Support

Sum-Frequency spectroscopy (SFS) is a relatively new technique that is increasingly being utilized to investigate so-called "buried interfaces". The power of the nonlinear optical approach lies in the ability to selectively probe interfacial molecular vibrational properties, even in the presence of significant bulk phase species with similar (or identical) vibrational signatures. In this study, SFS has been used to probe the interface between a model catalyst (Pt coated Al₂O₃/CaF₂) and liquid consisting of neat acetonitrile and acetonitrile in ethanol. Vibrational features associated with both CN stretching (~2238 and 2270 cm^-1) and CH stretching (~2939 and 2984 cm^-1) are observed for the adsorbed nitrile. Various concentrations of acetonitrile in ethanol have also been studied and a red-shift in the peak position in both the cyano and methyl stretching regions has been observed. Finally, an attempt has been made to study this system during hydrogenation by following the transient behavior of the cyano stretch.