Spectroscopic evidence for adsorption-induced polymerisation of terthiophene at silver surfaces

The adsorption process of 2,2':2',5″-terthiophene molecules on two di fferent types of silver surfaces was studied by means of surface enhanced R aman scattering (SERS) and UV-Vis absorption spectroscopy. Both techniques support the hypothesis of an adsorption-induced polymerisation process of t hese molecules. The vibrational pattern of the chemisorbed layer was found to be almost identical with that of bulk polythiophene samples and a red sh ift from 3.5 to 2.5 eV of the electronic absorption is observed in agreemen t with the Kuhn-Kuhn model. A concomitant decrease in visible photoluminesc ence was also observed.