▎ 摘　　要

Chemical and physical properties of silver nanoparticles (Ag NPs) are strongly influenced by NP size. The control of NP size is crucial for tuning or enhancing the properties of Ag NPs. In this paper, the size controlled Ag NPs have been achieved and dispersed on graphene (GE) sheets (Ag NPs/GE) using an eco-friendly and environment-friendly approach of thermal annealing method. The formation of size controlled Ag NPs has been restrained and it includes two stages. One is the formation of metallic Ag by reduction of Ag+ at low temperature (below 400 degrees C), wherein the ultrafine and highly dispersed Ag NPs can be obtained; another is growth and aggregation of Ag NPs at high temperature due to increasing surface diffusion coefficient of Ag atoms (above 400 degrees C). The Ag NPs/GE-400 presented an excellent antimicrobial activity due to the ultrafine size (similar to 9.6 nm), while the Ag NPs/ GE-700 exhibited an excellent SERS activity and sensitivity because of the appreciate size (similar to 95.8 nm). The Ag NPs/GE-500 (similar to 25.3 nm) presented the modest antimicrobial and SERS properties. Thus, our work may provide a reference to synthesize size-selected Ag NPs-based materials with a certain application using the thermal annealing method.