In-situ study of NAD⁺ adsorbed on a chemically roughened silver surface has been conducted using surface enhanced Raman scattering method combined with a confocal technique. The recorded spectra depict that under polarization conditions from 0.4 to 0.2 V, the adenine moiety of NAD⁺ adopts a perpendicular orientation via the N7 and amino group with respect to the silver surface. In the more negative potential range from 0.1 to -0.2 V, the adenine ring moiety tends to lay on the surface in a flat conjugation. In addition, the adsorption mode of the nicotinamide moiety also shifts with the potential scan. It could be concluded that the adsorption ways of both adenine and nicotinamide moieties are dependent of the applied voltages due to existing a flexible pyrophosphate bridging of them.

Key words: NAD⁺, confocal Raman, in-situ SERS, silver electrode