Electrochemical preparation of poly(3-thiopheneacetic acid) and its n-typesemiconductor property

3-Thiopheneacetic acid (3TA) was electrochemically oxidized and polymerized on indium tin oxide (ITO) electrodes in a 0.05 mol dm(-3) tetrabutylammoni um perchlorate (TBAP) acetonitrile solution; also, the photoelectrochemical proper ties of the resulting poly(3-thiopheneacetic acid) (P3TA) were stud ied. The film showed n-type semiconductor properties, although anion-doped conducting polymer prepared by electrochemical oxidation is generally of th e p-type. An anodic photocurrent due to oxygen evolution from water was obs erved under white-light irradiation in a 0.1 mol dm(-3) Na2SO4 aqueous solu tion. The anodic photocurrent density at 1.9 V vs. Ag/AgCl was 1.1 mA cm(-2 ) and the flat-band potential of P3TA, estimated from the onset of an anodi c photocurrent, was -0.1 V vs. Ag/AgCl. The band gap of P3TA was 2.4 eV, ob tained from an hv vs. (hv PC)(1/2) plot.