One-step synthesis of monodisperse AuNPs@PANI composite nanospheres as recyclable catalysts for 4-nitrophenol reduction

Oxidative polymerization of aniline was carried out in ethanol using chloroauric acid (HAuCl4) as the oxidant. Simultaneous reduction of HAuCl4 and formation of gold nanoparticles (AuNPs) and polyaniline (PANI) composite nanospheres (AuNPs@PANI nanospheres) were achieved without using any templates or structure-directing agents. The composite nanospheres are uniformly distributed with an average diameter of about 400 nm, in which the ultrafine AuNPs with size of about 2-4 nm were evenly embedded in the PANI matrix which acted as the dispersing agent and stabilizer of AuNPs. In addition, the catalytic performance of these composite nanospheres towards the reduction of 4-nitrophenol in the presence of NaBH4 was studied. Furthermore, the possible formation mechanism and catalytic mechanism of the self-assembled AuNPs@PANI nanospheres were also discussed.