SERS SPECTRA OF POLYTHIOPHENE IN DOPED AND UNDOPED STATES

Raman spectra of polythiophene films electrochemically deposited onto silver and platinum electrodes have been investigated using 514.5 nm l aser excitation. Contrary to the case for platinum, the use of roughen ed silver electrodes leads to the observation of surface-enhanced Rama n scattering (SERS), allowing the vibrational characterization of poly thiophene in a doped state. Since these vibrational modes are very dif ferent from those obtained for the undoped species, this provides a me ans of evaluating the amount of defects in both states of polythiophen e films. According to SERS selection rules, the polythiophene appears to be bound to the silver surface with the ring planes perpendicular t o that surface.