Synthesis and assembly of gold nanoparticle-doped polymer solid foam films at the liquid/liquid interface and their catalytic properties

Gold nanoparticle-doped poly(2-vinylpyridine) (P2VP) microcapsules and foam films were synthesized and assembled at the P2VP chloroform solution/HAuCl4 aqueous solution interface at 25 degrees C. It was found that Au nanoparticles with the average diameter of 2.1 nm were homogeneously embedded in and adsorbed on the walls of the capsules and foams, the nanoparticles were composed of Au(0) and Au(III) with the molar ratio of about 75/25, and the mass percent of Au elements was measured to be 19.65%. The formation of the nanostructures was attributed to the self-assembly of P2VP at the liquid/liquid interface, the simultaneous reduction of AuCl4- ions by a small amount of ethanol in the chloroform and adsorption of AuCl4- ions. After irradiated by UV-light for 1 h, the average diameter of the nanoparticles was found to be 2.2 nm, and the AuCl4- ions were transformed to Au(0) completely. The catalytic performance of these composite nanostructures were evaluated by using the reduction of 4-nitrophenol (4-NP) by potassium borohydride in aqueous solutions. The catalytic activity was very high in the first cycle, decreased rapidly and slightly in the second and third cycles, respectively, due to the aggregation of some nanoparticles, and stabilized after the third cycle. (C) 2011 Elsevier Inc. All rights reserved.