UV enhanced synthesis of high density Au coated ZnO nanocomposite.

We report the synthesis of high density Au coated ZnO nanocomposites by UV irradiation using a mixed solution of ZnO nanowires, HAuCl4 and Na2CO3. This synthesis process is easier and faster than a hydrothermal process in synthesizing Au/ZnO nanocomposites. The morphology, size distribution and density of the Au nanoparticles on the ZnO nanowires, which affect the photocatalytic efficiency of the synthesized Au/ZnO nanocomposite, were affected by the pH of the mixed solution. In order to obtain damage-free ZnO nanowires and small Au nanoparticles, the pH of the mixed solution should be adjusted to 7-8. UV irradiation promoted the formation of metallic Au nuclei, regardless of the presence of a ZnO photocatalyst. Au/ZnO nanocomposites were fabricated by Au reduction due to UV irradiation, followed by attachment of metallic Au nuclei to the ZnO nanowires, rather than by the photocatalytic reaction of ZnO. We propose this process as the dominent mechanism of the UV enhanced synthesis of Au/ZnO nanocomposites.