In situ green synthesis of Au nanoparticles onto polydopamine-functionalized graphene for catalytic reduction of nitrophenol

In this paper, a simple, green and environmental-friendly method is developed for depositing gold nanoparticles (Au NPs) on the surface of polydopamine (PDA)-functionalized graphene (graphene/PDA) for highly efficient catalysis. In this approach, graphene/PDA was prepared through the self-polymerization of dopamine in the presence of graphene oxide (GO) in aqueous solution. With the addition of HAuCl4, AuCl4-1 ions were adsorbed on the surface of graphene/PDA and in situ reduced to metallic Au NPs owing to the abundant catechol groups on the PDA chain. In the whole procedure, PDA not only acts as the surface modifier of graphene, but more importantly it also serves as the reducing agent and stabilizer for Au NPs simultaneously, avoiding the usage of any toxic reducing reagent or special stabilizing agent. The graphene/PDA-Au NPs were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-Ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that the size and amount of Au NPs are tunable by changing the experimental conditions. The obtained graphene/PDA-Au NPs nanocomposite, combining the advantages of graphene and Au NPs, exhibits remarkable catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. Considering its green facile preparation procedure and high catalytic activity, the prepared graphene/PDA-Au NPs holds great promise as a highly efficient, cost-effective and environmental-friendly catalyst for industrial applications.