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

• Published in: Chemistry : a European journal 2015-06, Vol.21 (27), p.9889-9894
• Main Authors: Wang, Jiale, Trindade, Fabiane J., de Aquino, Caroline B., Pieretti, Joana C., Domingues, Sergio H., Ando, Romulo A., Camargo, Pedro H. C.
• Format: Article
• Language: English
• Subjects: Catalytic activity; Catalytic oxidation; Chemistry; Decoration; Excitation; Gold; Graphene; Hot electrons; nanoparticles; Oxidation; Oxides; photocatalysis; surface plasmon resonance
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201500677

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 O2 through the transfer of SPR‐excited hot electrons to O2 molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (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 O2 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‐O2 charge‐transfer process. Decorating with gold: Charge transfer between reduced graphene oxide (rGO) and Au nanoparticles (NPs) and its effect on the surface plasmon resonance (SPR)‐mediated catalytic activity on light excitation were investigated in rGO–Au NP hybrids. SPR‐mediated oxidation of p‐aminothiophenol to p,p′‐dimercaptoazobenzene was increased for rGO–Au NPs relative to individual Au NPs. Under light excitation, SPR‐excited hot electrons and electrons transferred from rGO to Au occupy energy levels above the Fermi level EF that can participate in the activation of adsorbed O2 molecules (see figure; VB: valence band, CB: conduction band).