Hybrid Nanostructured Materials Obtained from Ti-Oxo Nanobuilding Blocks
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Fabrication of Polystyrene/CdS Hybrid Nanocomposites Embedded with CdS Nanowires by a Soft Solution-Processing Route Shu-Hong Yu and Masahiro Yoshimura Center for Materials Design, Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226, Japan ABSTRACT A novel one-step soft solution-processing (SSP) route called solvothermal-copolymerization technique was successfully developed for in situ fabrication polystyrene (PS)/CdS nanocomposites embedded with CdS nanowires in ethylenediamine media at lower temperature (80-140oC). In this route, the polymerization of the styrene monomers and the formation of the CdS nanocrystallites occur simultaneously in a certain temperature range. The results show that the quantum-fined CdS nanowires with diameters 4-15 nm and lengths up to several micrometers via the present one-step route were embedded in the PS matrix and had [001] preferential orientation. Both temperature and solvent were found to play a key role in the synthesis of the nanocomposites. The produced novel hybrid nanocomposites display obvious quantum size effects and interesting fluorescence features. INTRODUCTION Inorganic-organic nanocomposites are currently intensively investigated due to their potential applications as high technology materials [1-3]. Especially, nanocomposite structures provide a new method to improve the processability and stability of materials with interesting properties. These hybrid nanocomposites inherit some of the properties of both the polymer and the inorganic materials [1-3], such as the mechanical characteristics performances, catalytic, optical, and electronic features of inorganic colloids or polymers. Among these, semiconductor/polymer nanocomposites have attracted much recent attention due to their many advantages over single phase particle systems. Various kinds of polymer or surfactant modified CdS [4-7] or CdSe [8-13] nanocomposites were reported in recent years. Among them, polymer/inorganic nanocrystals composites are particularly interesting materials in the study of electrical transport [12] and fabrication of nanocrystal-based light-emitting diodes (LEDs) prepared with polymers and CdSe nanocrystals [8-10, 13]. CdS/PVK (N-polyvinylcarbazole) polymer composite was found to be photoconductive material [4]. Greenham et al [12] reported the photoluminescence and photoconductivity of composite materials by mixing of MEH-PPV and CdSe or CdS. They found that rapid charge separation occurred at the polymer/nanocrystals interface, which was confirmed by the strong photoluminescence quenching effect. In this paper, we develop a new strategy for fabricating polystyrene (PS)/CdS nanowires nanocomposites by a soft solution-processing (SSP) route called a solvothermal-copolymerization technique. The organic solvent polyamines such as ethylenediamine (en) was chosen both as a shape controller of CdS nanocrystals and as the reaction media. The electronic and optical properties of the PS/CdS nanowires nanocomposites were investigated.
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