Graphene deposited with metal nanostructures can have important applications in various areas. This paper reports the in situ deposition of gold nanostructures with well-defined shapes, including triangular nanoplate and cuboid, on unfunctionalized reduced graphene oxide (rGO) by a two-step process. The first step is to coat a layer of HAuCl4 on an rGO film on glass, which is prepared by the reduction of a graphene oxide film with aluminum in an HCl solution. The second step is to reduce the dry HAuCl4 layer to metallic Au nanostructures with ethylene glycol vapor at 160 degrees C for 15 min, which gives rise to the deposition of Au nanostructures with well-defined shapes on rGO. No solvent or additives are added during the chemical reduction. The shape of the Au nanostructures depends on the Au loading. The majority of the Au nanostructures are triangular nanoplates, when the Au loading is low. The Au nanostructures with hexagonal nanoplate and pentahedron nanoplate shapes become remarkable at high Au loading. Moreover, the shape of the Au nanostructures can be changed to cuboid by introducing acids into the HAuCl4. The different shapes of the Au nanostructures deposited on rGO are interpreted in terms of the generation and diffusion rates of the Au atoms.
