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

The adsorption process of 2,2′: 2′,5″-terthiophene molecules on two different types of silver surfaces was studied by means of surface enhanced Raman scattering (SERS) and UV–Vis absorption spectroscopy. Both techniques support the hypothesis of an adsorption-induced polymerisation process of these molecules. The vibrational pattern of the chemisorbed layer was found to be almost identical with that of bulk polythiophene samples and a red shift from 3.5 to 2.5 eV of the electronic absorption is observed in agreement with the Kuhn–Kuhn model. A concomitant decrease in visible photoluminescence was also observed.