Full conjugated multilayer thin films fabricated by the alternate adsorption of partially doped polyaniline (PANI) as a polycation and water-soluble poly(4-carboxyphenyl)acetylene(PA) as a polyanion were used as nanoreactors to study the in situ preparation of PbS nanoparticles．First

the self-assembled mulfilayers were immersed in a l mol／L NaOH solution to fabricate a controlled content of free carboxylic acid binding groups．Chemical reaction within the polymer film was initiated by absorbing Pb2+ from a 0.4 mol/L aqueous solution of Pb(Ae)2 and followed by exposing the film to H2S gas．UV-Vis absorption studies reveal that the absorption spectral profilesof the films are dependent on the dipping time of the film in the Pb(Ac)2 solution．AFM and TEM microscopic examinations of the films reveal that PbS crystals with rhomboid structures are formed in the films．The particles of narrow size distribution stand vertically on the film plane．Due to being doped by PbS

the photoelectric conversion property of ultra．thin composite films．which can be measured with a conventional three．electrode photoelectroehemieal cell using 0.5 mol/L KCl solution as the supporting electrolyte．is improved obviously．The results show that the valHe of the photocurrent for an 8-layer film is 3 times higher than that of the original film．