SURFACE-ENHANCED RAMAN-SPECTRA FROM THE FILMS FORMED ON NICKEL IN THEPASSIVE AND TRANSPASSIVE REGIONS

Surface enhanced Raman (SER) spectra were obtained from nickel electro des immersed in berate buffer solution (pH 8.4) at +100, +600, and +90 0 mV(SCE) using electrodeposited gold particles to produce the surface enhancement effect. Comparison with earlier experiments performed usi ng silver particles to obtain SERS indicates that the spectra of the n ickel passive films are identical regardless of whether silver or gold is used. At +100 mV, the nickel passive film consists of amorphous Ni (OH)(2);NiO is not observed. At +600 mV, amorphous Ni(OH)(2) persists, and Au-O forms on the gold particles. The SER spectrum of the transpa ssive film formed on nickel at +900 mV consists of peaks located at 48 0 and 560 cm(-1) and it is speculated that the species responsible for the Raman scattering resembles NiOOH. Upon returning the potential to +100 mV from +900 mV, Ni(OH)(2) reforms, accompanied by NiO. This is the first example of the use of gold particles to explore the passive film of nickel and the first time the SER spectrum of the transpassive film on nickel has been measured.