title: Water- and organo-dispersible gold nanoparticles supported by using ammonium salts of hyperbranched polystyrene: preparation and catalysis.
abstract: Gold nanoparticles (1 nm in size) stabilized by ammonium salts of hyperbranched polystyrene are prepared. Selection of the R groups provides access to both water- and organo-dispersible gold nanoparticles. The resulting gold nanoparticles are subjected to studies on catalysis in solution, which include reduction of 4-nitrophenol with sodium borohydride, aerobic oxidation of alcohols, and homocoupling of phenylboronic acid. In the reduction of 4-nitrophenol, the catalytic activity is clearly dependent on the size of the gold nanoparticles. For the aerobic oxidation of alcohols, two types of biphasic oxidation are achieved: one is the catalyst dispersing in the aqueous phase, whereas the other is in the organic phase. The catalysts are reusable more than four times without loss of the catalytic activity. Selective synthesis of biphenyl is achieved by the homocoupling of phenylboronic acid catalyzed by organo-dispersible gold nanoparticles.
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, and CREST, JST, Kasuga, Fukuoka 816-8580 (Japan).
authors.forename: Lei
authors.initials: L
authors.lastname: Gao
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishikata
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kojima
authors.forename: Katsumi
authors.initials: K
authors.lastname: Chikama
authors.forename: Hideo
authors.initials: H
authors.lastname: Nagashima
mesh_terms: D000447:Aldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D006046:Gold / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D015394:Molecular Structure; D009596:Nitrophenols / Q000737:chemistry; D010084:Oxidation-Reduction; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D000447:Aldehydes; D007659:Ketones; D009596:Nitrophenols; D011137:Polystyrenes; D000644:Quaternary Ammonium Compounds; D014867:Water; D006046:Gold; C024836:4-nitrophenol
keywords: biphasic catalysis; gold; homogeneous catalysis; nanoparticles; polymers