STUDY OF THE AG+ SURFACE COMPLEXES OF MUREXIDE BY SERS AND SERRS SPECTRA AT AG ELECTRODES

It is shown that the broadening of the surface-enhanced Raman scatteri ng (SERS) band of murexide adsorbed at Ag electrode in comparison with ordinary Raman scattering (ORS) spectrum is connected mainly with the existence of the two types of well-defined species: molecules adsorbe d at active sites and those at 'normal' places at electrode surface. T he molecules adsorbed at active sites are very similar to the complex of the adsorbate with Ag+ cation. Our observations stress the necessit y of the distinguishing of the species present simultaneously at the e lectrode surface. This is extremely important for the quantitative ana lysis of resonance Raman (RR) enhancement factor in surface-enhanced r esonance Raman scattering (SERRS) experiments because the surface comp lexes may often exhibit significantly different visible absorption max ima than the 'free' molecules themselves. The relative active-site fac tor of about 4-5 was evaluated from the electromagnetic maximum in the profile of SERS intensity vs. applied potential. (C) 1998 Elsevier Sc ience B.V. All rights reserved.