Green controllable synthesis of Au-Ag alloy nanoparticles using Chinese wolfberry fruit extract and their tunable photocatalytic activity

Abstract

The controllable synthesis of Au-Ag alloy nanoparticles (NPs) without any hazardous or expensive chemical agent has been a challenge. This paper reports on the Chinese wolfberry fruit extract-assisted synthesis of Au-Ag alloy NPs with homogeneous composition, uniform alloy microstructure and a small average size less than 15 nm. The composition and the surface plasmon resonance (SPR) wavelength of Au-Ag alloy NPs could be linearly adjusted by the synthesis time in one-pot. Au-Ag alloy NPs were characterized by means of various techniques, and then their synthesis mechanism was discussed. The obtained Au-Ag alloy NPs were used as photocatalysts for the reduction reactions of 2-, 3-, and 4-nitrophenol and exhibited superior photocatalytic activity and stability. The rate constants of the above photocatalytic reactions could be linearly tuned by the composition of the Au-Ag alloy NPs and also by their addition amount, displaying a new method to control the rate constant. Furthermore, based on the controllable synthesis, the rate constant could even be predetermined just through setting the synthesis parameters of the Au-Ag alloy NPs.