| As a new class of nanomaterials, nanocomposite materials which are constructed by the incorporation of several components with dieffrent properties by various strategies have emerged with the development of nanoscience and nanotechnology. By combining several pure materials, composite nanomaterials can be fabricated with unique properties to meet particular requirements. Nanocomposite materials have attraced considerable attention due to their special catalytic, optic,electric and magnetic properties. In this paper, we are mainly focus on the catalytic performances of polyaniline derivative-supported noble metal nanoparticles based on the successful synthesis of such nanocomposite materials, The polymer matrix include poly(o-phenylenediamine) (POPD), poly(o-toluidine) (POT) and poly(o-aminothio- phenol) (PATP), Two different synthetic strategies were employed for noble metal (gold, palladium) nanocomposite materials. 1) The use of reactivity of monomer and noble metal salt: One-step preparation of polymer stabilized noble nanoparticles when mixing aniline derivative and noble metal salt together. The redox reaction between monomer and salt will lead to the simultaneous formation of noble metal nanoparticles and polymer. 2) The use of reactivity of polyaniline derivative and noble metal salt: two-step synthetic procedures involving the morphology-controllable synthesis of polymer followed by the mixing polymer and noble metal salt together to afford polymer-supported noble metal nanoparticles. Nanocomposite materials synthesized by the above mentioned strategies include goldnanoparticles/POT core/shell nanocomposites, POPD/gold nanoparticles core/shell nanocomposites and PATP-supported gold and palladium nanoparticles. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) and ultraviolet-visible (U-Vis) spectroscopies were employed to characterize the products. Noble metal nanoparticles with high stability and dispersibility, and low size supported by conducting polymers are expected to be synthesized by altering the synthetic conditions to optimize the composition and structure of composites. Applications of polymer-supported noble metal nanoparticles as catalysts in alcohol oxidation and Suzuki coupling are then investigated. The major contributions of this paper are as follows:(1) Uniform spherical gold/POT core/shell nanocomposite materials were successfully fabricated in gold colloid in the presence of nonionic surfactant F127 by chemical polymerization of o-toluidine monomer. The shell thickness of gold/POT core/shell nanocomposite materials can be easily turned by controlling o-toludine concentration and reaction time. If POPD sub-microspheres are used as template and reductant, while HAuCl4 as oxidant, well-defined gold nanoparticles supported on polymer surfaces can be fabricated through a simple solution route. Addition of PVP can prevent the aggregation of gold nanoparticles, while size of gold nanoparticles can be tuned by controlling the HAuCl4 concentration. Catalytic results indicate that high catalytic activity can be performed when catalysts with gold size of 5 nm are used, especially with high catalytic activity and selectivity in the benzyl alcohol oxidation conducted in water media. This implies that such polymer supported gold nanoparticles will show great potential as catalysts in organic catalytic reactions.(2) PATP-supported gold nanoparticles can be fabricated through redox reaction between monomer and HAuCl4. The monomer acts as reductant during the polymerization processes, while its polymerized polymer PATP acts as stabilizer for gold nanoparticles. By changing the molar ratio of monomer to HAuCl4, size of gold nanoparticles can be tuned in the range of 1-5 nm. PATP-stablized gold nanoparticles can be successfully applied as catalysts in Suzuki-Miyaura cross-coupling reaction, with yield more than 90% using less reactive aryl chlorides. Furthermore, PATP-stablized gold nanoparticles used as catalysts in alcohol oxidation is also investigated. (3) PATP-stablized palladium nanoparticles can be obtained through one-step redox reaction between monomer and Pd(NO3)2 in acid solution. The monomer acts as reductant during the polymerization processes, while its polymerized polymer PATP acts as stabilizer for gold nanoparticles. Palladium nanoparticles can be fabricated smaller than 1 nm. Results revealed that such PATP-stablized palladium nanoparticles were active catalysts for Suzuki cross-coupling reaction. High yields can be obtained with arylboronic acid and aryl halides bearing a variety of substituents. It is believed that such polymer-stablized palladium nanoparticles can be used as effective catalysts in other organic reactions, such as Heck reaction of olefin and aryl halide and Sonogashira reaction of alkyne and aryl halide. |
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