Abstract: Using layer-by-layer self-assembly techniques, we successfully constructed nanostructured mul-tilayer films of conjugated polymer (sulfonic acid ring substituted polyaniline, SPAn)/semiconductornanoparticles(Q-CdS).Cyclic voltammograms of single layer film of SPAn in 0.1mol/L Na₂SO₄ solution(pH=3.0) consists of two redox peaks.The electrochemical processes associated with the peaks are twosteps redox doping.The S^2- in the composite films is unstable and easily oxidized to product S, S₂O₃^2- and SO₄^2- as being determined by X-ray photoelectron spectroscopy.The films of the first layer SPAn exhibiteda weak photoinduced cathodic current over the potential range between Oand -600 mV(vs.SCE) in 0.1mol/L LiClO₄ solution in acetonitrile.The self-assembly films of SPAn/Q-CdSexhibited a photocathodicacurrent under cathodic bias and photoanodic current under anodic bias.In contract, the films of poy(sodi-um 4-styrenesolfonate)/Q-CdSonly exhibited a photoinduced anodic current from - 500 to 600 mV.Itimplied that the state(doping or undoping) of the conjugated polymer play an important role in determiningthe photoelectrochemical properties of the films.

Key words: Layer-by-layer self-assembly, Nanocomposite films, Photoelectrochemistry