Reduced graphene oxide-stabilized copper nanocrystals with enhanced catalytic activity and SERS propertiesElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra05186c

Well-defined Cu/reduced graphene oxide (rGO) hybrid materials are successfully synthesized by controlling the amount of ascorbic acid and maintaining an appropriate pH value. We found that graphene oxide (GO) served not only as the precursor for graphene, but also as an effective surfactant to hamper the aggregation of copper nanoparticles, resulting in a small size of the copper nanoparticles. Furthermore, the as-prepared copper composites can serve as an effective catalyst for 4-nitrophenol in aqueous conditions and exhibit surface enhanced Raman scattering in the detection of crystal violet (CV). Notably, the obtained copper nanoparticle hybrids with rGO have extremely high air stability after exposure to air. Density functional theory calculations firstly reveal that rGO can effectively prevent Cu nanoparticles from spontaneous oxidation due to its slightly lower ionization potential than that of Cu nanoparticles. We expect the as-prepared rGO-stabilized copper nanocrystals with small size to meet the increasing demands of industrial applications at reduced costs. The as-obtained Cu/rGO hybrids possess excellent air stability, a higher catalytic efficiency to the reduction of p -nitrophenol and exhibit surface-enhanced Raman scattering activity.