[Studies of surface-enhanced Raman spectroscopy on bare Ti electrode]

Various roughening methods for the bare Ti electrode such as mechanical roughening, electrochemical oxidation-reduction method and chemical etching were tried to obtain surface-enhanced Raman spectra (SERS) successfully for the first time. The results of the experiments proved that mechanical roughening and electrochemical oxidation-reduction method could be successfully employed in roughening titanium electrode, however, surfaces roughened in such ways showed no SERS-activity in Raman detection. Finally, chemical etching with hydrofluoric acid was proved to be an effective way to get SERS-active titanium surface, and surface-enhanced Raman spectra of pyridine adsorbed on a titanium surface was observed for the first time. In order to get the most effective titanium surface, roughening conditions, including concentration of the acid, the time of etching and the external potential, were investigated. As illustrated, Raman activity varies with conditions changing in roughening processes and the most reasonable condition for roughening was indicated. The result showed that at the concentration of hydrofluoric acid 0.33% (Wt) and 5 min for etching, the most SERS-active rough titanium surface could be obtained. In addition, with an external potential to speed up corrosion, the surface of titanium electrode tended to form a thin film of oxide, which prevented further corrosion and caused SERS-activity decrease. Thus, in this paper, the surface-enhanced Raman spectra of pyridine (pyridine 0.01 mol L(-1), and electrolyte KCl 0.1 mol L(-1)) adsorbed on bare roughed Ti electrode were observed at open circuit potential. Referring to the calculations of enhancement factor of pyridine on electrode, the enhancement factor is about 102 on the roughened titanium electrode.