One-step synthesis of size-tunable gold nanoparticles/reduced graphene oxide nanocomposites using argon plasma and their applications in sensing and catalysis

•A one-step dual-reduction strategy of synthesizing AuNPs/rGO nanocomposites by argon plasma.•The AuNPs decorated on rGO are size- and density-tunable.•The underlying mechanism for the reduction of AuNPs was thoroughly discussed.•The AuNPs/rGO nanocomposites show excellent SERS and catalysis performance.