Probing the Catalytic Activity of Reduced Graphene Oxide Decorated with Au Nanoparticles Triggered by Visible Light

Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO-Au NPs) were obtained by the in situ reduction of GO and AuCl4(aq)- by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O-2 through the transfer of SPR-excited hot electrons to O-2 molecules adsorbed from air. The SPR-mediated catalytic oxidation of p-amino-thiophenol (PATP) to p,p'-dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR-mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge-transfer processes from rGO to Au took place and contributed to improved SPR-mediated activity. Since the transfer of electrons from Au to adsorbed O-2 molecules is the crucial step for PATP oxidation, in addition to the SPR-excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au-to-O-2 charge-transfer process.