The potential dependence of SERS were studied and correlated with the morphology of surface roughness of the metal electrode surface in the electrochemical SERS systems.
With ORC of various conditions during which the surface roughness on electrode were formed, the transient effects on SERS intensities were studied. First, by laser illumination during the oxidation process, microparticles of Ag metal were formed in the surface AgCl layer, which became cluster of larger size after the reduction process. Surface concentration of these larger size surface roughness are observed to have definite effect on the SERS intensity. Secondly, with variations of oxidation time of the ORC, the surface concentration of adatomic roughness on Ag electrode were controlled, and the effect of the surface concentration of adatomic roughness on SERS intensity are confirmed.
It could be concluded from these results that both the chemical mechanism which is related to the adatomic roughness and the electrodynamic mechanism which is related to larger size surface roughness constitute the SERS enhancement mechanism.
With variations of parameters of the electrochemical cell through systematic changes of solvents, adsorbates, and electrolytic ions, more details of SERS could be examined.
The potential dependence of SERS were interpreted as the change of adsorption state of molecules with variation of electrode potential, and the adsorption states are dependent on polar properties of adsorbates and solvents, not on electrolytic materials. Two different adsorption states of pyridine and three adsorption states of benzene take part in their potential dependences of SERS.
In addition, in SERS of some molecules, chemical changes of adsorbates were observed, which may be explored to use SERS as a very sensitive probe for studies of adsorption states and reactions on metal surfaces.
