Surface-Enhanced Resonance Raman Spectroscopy of Flavins on Silver Nitrate-Modified Cu and Fe as Well as Cu-Zn-Pb and Fe-C-Cr-Ni Surfaces

Abstract

Surface-enhanced resonance Raman spectroscopy (SERRS) of riboflavin, flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) on Cu, Cu-Zn-Pb, and Fe as well as Fe-C-Cr-Ni has been performed by means of the modification of these substrates with silver nitrate. It is found that the SERR spectrum of a flavin molecule on the alloy Cu-Zn-Pb is different from that on the pure Cu, and this is also the case for a flavin molecule on the alloy Fe-C-Cr-Ni and on pure Fe. This result indicates possibly that Zn, rather than Cu, and Ni or Cr, rather than Fe, in the alloys also interact with the flavin molecules. In addition, the three flavins on the same supporting metal surfaces also exhibit some differences in the SERR spectra. This result implies an involvement of the side chains of the flavin molecules in the enhancement. The SERR spectra of the three flavins are compared with their resonance Raman (RR) spectra. On the basis of our experimental results, a direct interaction of N–5and possibly also O–4in the flavins with silver is suggested. The general effectiveness of this method for obtaining SERS is demonstrated, and the enhancement mechanism of these substrates is also briefly discussed.