VIBRATIONAL SPECTROSCOPIC STUDY OF 4-CYANOBENZOIC ACID ADSORBED ON SILVER

The adsorption behavior of 4-cyanobenzoic acid (4CBA) on a silver film has been investigated by infrared and Raman spectroscopies. The Langm uir adsorption model was applicable not only to the self-assembling bu t also to the spin-coating processes. By taking the infrared reflectio n-absorption and surface-enhanced Raman (SER) spectra simultaneously, the 4CBA molecule was concluded to adsorb onto the film as 4-cyanobenz oate with its two oxygen atoms bound symmetrically to the surface, ass uming a perpendicular orientation with respect to the surface. From th e peak shift and band broadening analysis of the SER spectrum of 4CBA taken in an aqueous silver sol, on the sol surface, however, the molec ule appeared to be bound via both the carboxylate and nitrile groups, assuming a flat orientation on the surface. Although the origin of suc h a different adsorption mechanism could not be clarified, it was tent atively ascribed to the different surface morphology.