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

摘要

Polymethylthiophene polybutylthiophene and polyoctylthiophene films have been synthesized on electrochemically roughened gold electrodes by anodic oxidation of the corresponding monomers. In situ and ex situ surface-enhanced Raman scattering (SERS) studies of these films lead to high quality spectra the intensity of which is more than one hundred times greater than that obtained, under identical conditions, on platinum electrodes. Marked modifications of the positions, widths and relative intensities of the Raman bands observed during the polymer doping-dedoping process are attributed to structural transformations. During the redox process, the oxidized to reduced intensity ratio of the symmetric v(C=C) mode of polyalkylthiophene ring obeys a Nernst equation when the applied potential to the working electrode is varied. In addition, the solubility of polyalkylthiophenes in organic solvents allows analysis of their SERS spectra in colloidal silver solutions. The very low concentration (10~(-7) - 10~(-10) M) and the mild experimental conditions used in these experiments indicate that a huge amplification of the Raman signal takes place.