| Water-in-oil microemulsion can be used as a nanoreactor and a template for synthesizing nanomaterials of interest to chemists. Palladium nanoparticles dispersed by a water-in-oil microemulsion are highly effective catalysts for hydrogenation of olefins in an organic solvent. Pd, Rh, and bimetallic Pd/Rh nanoparticles synthesized in a water-in-hexane microemulsion can be deposited directly on surfaces of functionalized multiwalled carbon nanotubes with high yields. The CNT-supported Pd nanoparticles are active catalysts for hydrogenation of olefins, for carbon-carbon bond formation, and for carbon-oxygen bond cleavage reactions. The CNT-supported Rh nanoparticles are active catalysts for hydrogenation of arenes and the CNT-supported bimetallic Pd/Rh nanoparticles show an unusually high catalytic activity for hydrogenation of anthracene. Nitroaromatics (such as dinitrotoluene, trinitrotoluene and nitrobenzene) found in explosive vapors from buried landmines can be reduced to aminoaromatics by a novel process involving the Pd/CNT metal nanocatalysts. These aminoaromatics are fluorescent and may provide a method for detecting and characterizing nitroexplosives. Carbon nanotube (CNT)-supported Pt nanoparticles (average diameter of 3.8 +/- 0.7 nm) produced by the microemulsion method exhibit high catalytic activities for hydrogenation reactions including conversion of benzene to cyclohexane. The kinetics of the conversion of benzene to cyclohexane catalyzed by the CNT-supported Pt catalyst, was studied by proton NMR and by fluorescence.; The Au/CNT nanoparticles show remarkable performance for oxidation of cyclohexene without peroxide initiators and for homocoupling of phenylboronic acid with a quantitative yield. The possibility of synthesizing unique gold nano-clusters such as Au20 using the microemulsion technique will be discussed. The CNT-supported metallic nanoparticles are all recycled and can be reused at least 10 times without losing catalytic activities. These novel nanoparticle catalysts are opening a new field for chemical catalysis. |
