In this paper, we report a microwave-assisted biosynthesis method with Cinnamomum camphora (CC) leaf extract for the green and rapid synthesis of Ag nanoparticles (NPs). The as-produced Ag nanoparticles were immobilized onto CeO2 as supported Ag/CeO2 catalyst, which proved to be efficient for carbon monoxide (CO) oxidation. Active components in the plant extract were identified by FTIR analysis and later on validated through simulated experiments. The results revealed that polyphenols and proteins were the reducing and protecting agents, respectively. The optimum preparation conditions for the catalyst were irradiation time of 140 s, Ag loadings of 5 wt.%, CC extract concentration of 25 g L-1 and sintering temperature of 300 degrees C. Since biomolecules adsorbed over the surface of catalyst was detrimental to its catalytic activity, calcination to remove the biomolecules was critical to the enhanced activity. Considering the trade-off between particle size and biomass removal extent, the optimum calcination temperature was determined to be 300 degrees C. (C) 2015 Elsevier B.V. All rights reserved.