Surface Raman scattering studies on the adsorption of p-hydroxybenzoic acid at Au electrodes with ultraviolet excitation

The potential-dependent surface Raman spectrum of adsorbed p-hydroxybenzoic acid (PHBA) on a roughened Au electrode has been obtained with ultraviolet excitation at 325 nm. The surface Raman spectra of PHBA are sensitive to the negative shift of potential and the electrode potential at which the resonance (potential of maximum intensity) occurs varies with the vibrational mode, indicating that the PHBA molecules are chemisorbed on the Au surface. A non-radiative charge transfer mechanism could probably explain the experiment results in the present work. The probable reasons are given.