THE CHEMICAL EFFECT IN SURFACE-ENHANCED RAMAN-SCATTERING (SERS) FOR PIPERIDINE ADSORBED ON A SILVER ELECTRODE

The relative SERS enhancement factors for piperidine on a silver elect rode were determined as a function of the incident wavelength and appl ied potential. The charge transfer effect (G(CT)) on Raman intensity w as estimated from these data, The total chemical effect, which is defi ned as a product of G(CT) and the so-called ''active sites'' effect, a mounts to at least 15 for piperidine adsorbed on silver (a system for which ''charge transfer'' is from the adsorbed molecule to the metal). This chemical enhancement factor is very close to that for pyridine a dsorbed on silver (''charge transfer'' from the metal to the adsorbed molecule). Thus, the short-range enhancement mechanism can be equally effective for both directions of ''charge transfer''.