Surface-enhanced Raman spectroscopic studies of tricyanovinylthiophene in silver colloid solution

The adsorption behavior of a tricyanovinylthiophene chromophore on a silver metal surface was determined by using the surface-enhanced Raman scattering (SERS) technique. The salt effect was also examined by using silver colloid. It was found that the molecule is adsorbed through the nitrogen atom of the diphenylamine group in the molecule and the molecular axis lies flat or is tilted on the surface of silver metal. The Raman intensity enhancement of tricyanovinylthiophene without salt is very low compared with that when salt (sodium chloride) is present, suggesting that the interaction between the molecule and metal surface without salt is insufficient to induce a Raman signal. However, with the help of sodium chloride, the Raman signal was dramatically enhanced and behaved like the usual SERS phenomenon. The polarization effect was also studied and all peaks measured were found to be polarized; depolarized peaks were weak in the present experiment.