Continuous UV irradiation synthesis of ultra-small Au nanoparticles decorated Cu2O with enhanced photocatalytic activity

Noble metal nanoparticles (NPs) with controlled size and shape can be easily prepared by UV irradiation at room temperature. In this work, ultra-small Au NPs were successfully continuously synthesized via an UV irradiation approach, and the synthesis conditions of Au NPs with the size of 1.8 nm have been optimized to be an exposure time of 1.4 min, a HAuCl4 precursor concentration of 0.8 mM and a pH value of 10.4. The growth dynamics of Au NPs was investigated under different exposing time of the electron beam in transmission electron microscopy (TEM), revealing the formation of NPs via the oriented attachment of individual nanoparticles. In addition, well dispersed ultra-small Au NPs decorated Cu2O composites were obtained from this in-situ strategy and showed an enhanced photocatalytic activity compared with that of Au-free oxides and Au- Cu2O from direct replacement method.