Abstract: Polythiophene/titanium dioxide (PTh/TiO₂) composite particles were synthesized via the photoinduced polymerization of thiophene in a TiO₂-chloroform suspension. The resultant composite particles were characterized by BET analysis, scanning electron microscopy, laser particle size analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The XPS spectra indicated that a strong interaction exists between the S sites of the polymer backbone and the TiO₂ particles. The UV-Vis DRS spectra showed that the resultant composite particles are responsive to visible light. The photocatalytic activities of the PTh/TiO₂ composite particles were examined through the degradation processes of a rhodamine B (RhB) solution under UV irradiation and visible light irradiation. The degradation ratios of the RhB solution were found to be 76% and 98% after UV irradiation (180 min) and visible light irradiation (10 h), respectively. The photocatalysis reactive mechanisms under UV irradiation and visible light irradiation were investigated using disodium ethylenediamine tetraacetate (EDTA-2Na, hole scavenger) and furfuryl alcohol (radical scavenger). The oxidant from the holes and the radicals are competitive. Under UV irradiation, photogenerated holes are the main active species while under visible light irradiation the radicals are the main oxidant for the degradation of RhB.

Key words: photoinduced polymerization, polythiophene, titanium dioxide, composite particle, photocatalsis, rhodamine B