Surface raman spectroelectrochemistry. Part I. Heterocyclic, aromatic, and aliphatic amines adsorbed on the anodized silver electrode

In this work we have verified the remarkable sensitivity of Raman spectroscopy for the study of adsorbed pyridine on a silver surface, and extended its applicability to other nitrogen heterocycles and amines. New bands in the scattering spectrum of adsorbed pyridine have been characterized, which were not previously reported, as well as the Raman intensity response of all the surface pyridine bands as a function of electrode potential. As a result of these experiments, we have proposed a model of the adsorbed species for pyridine in which the adsorption is anion induced, leading to an axial end-on attachment to the electrode surface. The ability to obtain resonance Raman spectra with good signal-to-noise with laser powers less than 1.0 mW, reported here for the first time, opens up possibilities of surface Raman studies with relatively inexpensive laser systems. As laser power requirements are relaxed, reliability is improved, and greater tuning ranges can be achieved for wavelength dependent studies. We previously demonstrated the potential of resonance Raman spectroscopy for monitoring solution kinetic behavior [2], and now have shown that NR as well as RR spectroscopy has sufficient sensitivity to extend the studies of kinetic processes to include those occurring at electrode surfaces.