Electrochemical and surface-enhanced Raman spectroscopy studies of 4-phenylpyridine adsorption at the gold/solution interface

摘要

The adsorption of 4-phenylpyridine (4-PhPy) on the Au electrode was examined using conventional electrochemical techniques: cyclic voltammetry and impedance measurements and also by surface enhanced Raman spectroscopy (SERS) in a wide range of electrode potentials. Electrochemical results indicate the strong adsorption of 4-Phpy molecules, particularly at the positively charged Au electrode. The wide shoulder of capacity close to the pzc suggests that the composition and/or the structure of 4-Phpy monolayer change with the sign of the surface charge on the electrode. Investigation of integrity of adsorbed layer, however, indicates that adsorbed molecules do not form tight, compact monolayer even in the case of adsorption from saturated solution. SERS spectra provided evidence for gradual, potential-induced reorientation of the molecular plane with respect to the surface, from nearly vertical in the negatively charged electrode, to more flat at the positively charged metal surface.