Electrostatic Self-Assembly Multilayer Films Of CdS And Au Nanoparticles

Nano-composite material is an important advancing front study field in material science. The semiconductor and metal nanoparticle composite membrane system has received wide attention and turn to a hot point of material study because of their excellent photoelectric properties. In this paper, we prepared CdS nanoparticle/organic and Au'nanoparticle composite films via electrostatic self-assembly method (ESAM) and studied their structure and properties. We also prepared some photoelectric devices and explore the mechanisms of photovoltaic conversion and electroluminescence.A series of near roundness CdS nanoparticles with a particle diameter of 3~6nm have been prepared by controlling the concentration and proportion of reactants and adopting sodium hexametaphosphate as stabilizing agent. The studies demonstrate that these particles present obvious quantum size effect and an appropriate excess of Cd2+ ion and hexametaphosphoric acid group polysnion are helpful to the dispersion and flame capability's improvement of particles. Another series of near roundness monodisperse Au nanoparticles with a diameter of 12.3nm was prepared via sodium citric acid deoxidizing auric chloride acid. Conductive polymer poly (p-phenylene vinylene) (PPV) and precursor of PPV were prepared via Wessling's method.We have assembled CdS nanoparticles with PDDA, CuPc and precursor of PPV into films by ESAM. All these systems present good assembly capability. CdS/CuPc and CdS/PPV optoelectronic cells have been assembled and CuPc presents best sensitization to CdS. We also assembled a CdS/PPV electroluminescence device. The study indicates that the composite membrane's photoluminescence is due to CdS nanoparticles and the electroluminescence is due to the luminescence of polymer PPV.Au/PDDA , SiO2/PDDA , {[Au/PDDA]/[SiO2/PDDA]m}n composite films were assembled and Au/SiO2 film was prepared via the thermal treatment of {[Au/PDDA]/[SiO2/PDDA]m}n film. The study indicates that self-assembly monolayer membrane of Au nanoparticle distributes as sub-monolayer. After Au nanoparticles are assembled in multilayer, surface plasma resonance absorption peak got a red shift because ofthe polarizing effect of the surrounding media and the coupling effect of surface plasma waves between the next Au nanoparticles. With the increasing of number of films, the pitch of each Au nanoparticles turns larger; the phenomena of red shift turn weak.