Preparation Of Au/ZnO Nanocomposites And Their Gas Sensing Performance

ZnO is an important n-type semiconductor material. It is stable in physics and chemical, and superiority in price, which is widely used in the field of gas sensors. Recently, the scientists have studied the crystal effect of ZnO. But there is few reports for interaction between Au nanoparticles and ZnO nanomaterials. In this essay, Au nanoparticles loaded ZnO were prepared, and the ZnO facets effects on Au/ZnO ethanol-sensing were studied. Controlling the expossed facets will be a good way to improve the gas sensing performangce. The works of this thesis were as follows:1. ZnO nanocones, nanoflakes and nanorods were prepared by different methods, the exposed facets were {1011},{0001} and{1010}, respectively. Au nanoparticles were loaded by stirring the mixture of Au colloids and ZnO aqueous solution. The Au/ZnO nanocomposites were characterized by HRTEM, XPS, and XRD. High surface energy of{1011} facet led to the strong interaction between the Au NPs and the ZnO nanocones and small Au NPs, which improved the activity and promoted the generation of active oxygen species. TPSR results indicated higher amounts of active oxygen species led that most of ethanol is oxidated at relative low temperature, which may result in the remarkable change of electron depletion layer and high ethanol-sensing response of the Au/ZnO nanocones.2. Au nanoparticles with different size were loaded on ZnO nanocone surface. The diameters of the Au nanoparticles were 4.5 and 14.0 nm. The size effect of Au on Au/ZnO ethanol-sensing performance was studied. The Au/ZnO nanocomposites were characterized by XRD, SEM, and TEM. Because there are more donor defects on the surface of ZnO with small Au loaded, which promote the production of active oxygen species and ethanol gas sensing reaction.