Effect of different excitation wavelength on SERS spectra of pyridine

Abstract

SERS spectra of pyridine has been already recorded on a silver electrode in a potential range from 0.0 to -1.40 V with a saline solution, pyridine / KCl (0.1M / 0.1M), by using the 514.5 nm exciting line. Under these experimental conditions, the maximum intensity of the enhanced 8a and 9a bands is reached at -0.75 V and -1.20 V, respectively, being the 9a band what dominates the spectrum at negative electrode potential. We intend now to record pyridine SERS spectra under the same experimental conditions but varying only the excitation wavelength, 488 nm and 785 nm, in order to check how it affects to the relative intensities and to vibrational wavenumbers of the bands. The analysis of the relative intensities of the bands vs the electrode potential at different excitation wavelength allows to detect the resonance condition. From the analysis of SERS spectra, it can be concluded that no significant wavenumbers shifts have been detected, while the relative intensities of the bands and the electrode potential to which the maximum intensity is reached are slightly different at 785 nm, as expected for an incident radiation at low energy.