Preparation of zno supported gold nanocrystals: Briefly, The Zno mesocrystals (MCs) were prepared by calcination at 300°C for 6 h for further applications. Then, Au was deposited on the ZnO MCs from an HAucl4 solution mixed with Zno MCs at a pH value of about 9.5 for 48 h with stirring. The sample was washed with deionized water by centrifugation multiple times. Finally, the Au-loaded Zno MCs were treated with 10% O2 in He flow at 200°C for 1.5 h