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.