Evolution upon doping of theπ*andσ*bands of poly-(3-methylthiophene) grafted on Pt electrodes as studied by near-edge x-ray-absorption fine-structure spectroscopy

With the use of near-edge x-ray-absorption fine structure spectroscopy (NEXAFS), the unoccupied ${\pi }^{*}$ and ${\sigma }^{*}$ bands of poly-(3-methylthiophene) electrochemically grafted on to a Pt surface have been probed. The C $K$-edge NEXAFS characteristics confirm that (i) the polymeric chain unit is composed of the same structural architecture as the monomer and (ii) the doping proceeds via a narrowing of the band gap with the appearance of metalliclike behavior. The same tendencies are observed by varying the structure of the monomer and the nature of the dopant which evidences a similar conduction mechanism for these poly-five-membered-heterocycles.