Surface-enhanced Raman scattering study of polyalkylthiophenes on gold electrodes and in silver colloids

lPolymethylthiophene polybutylthiophene and polyoctylthiophene films have b een synthesized on electrochemically roughened gold electrodes by anodic ox idation of the corresponding monomers. In situ and ex situ surface-enhanced Raman scattering (SERS) studies of these films lead to high quality spectr a the intensity of which is more than one hundred times greater than that o btained, under identical conditions, on platinum electrodes. Marked modific ations of the positions, widths and relative intensities of the Raman bands observed during the polymer doping-dedoping process are attributed to stru ctural transformations. During the redox process, the oxidized to reduced i ntensity ratio of the symmetric v (C=C) mode of polyalkylthiophene ring obe ys a Nernst equation when the applied potential to the working electrode is varied. In addition, the solubility of polyalkylthiophenes in organic solv ents allows analysis of their SERS spectra in colloidal silver solutions. T he very low concentration (10(-7)-10(-10) M) and the mild experimental cond itions used in these experiments indicate that a huge amplification of the Raman signal takes place. (C) 2001 Elsevier Science B.V. All rights reserve d.