Two hybrid Au-ZnO aggregates with different hierarchical structures: A comparable study in photocatalysis.

Two hierarchical ZnO micro/nano-materials have been prepared by a short-time (45min) hydrothermal reaction without any surfactants. The different morphologies have been characterized comprehensively by XRD, SEM, TEM and XPS technologies. The hierarchical micro- and nano-structures are respectively consisted by the subordinate nano-pieces and nano-hexagonal-rods. Under the illumination of the simulated solar light, the nano-piece-aggregate spends 40min to degrade the 98% of rhodamine 6G solution (10-5mol/L), whereas the nano-rod-aggregate only degrades the 78% of the solution in the same condition. Moreover, the photocatalytic performances of the two ZnO aggregates are significantly improved by loading with Au nanoparticles (NPs) in the same assembly process. The nano-piece-aggregate decorated with the Au NPs spends 24min to decompose the rhodamine 6G solution completely, while nano-rod-aggregate decorated with the Au NPs needs 28min. The related photocatalytic mechanisms are proposed in this paper.