title: Fabrication of Au/graphene-wrapped ZnO-nanoparticle-assembled hollow spheres with effective photoinduced charge transfer for photocatalysis.
abstract: Heterostructures of gold-nanoparticle-decorated reduced-graphene-oxide (rGO)-wrapped ZnO hollow spheres (Au/rGO/ZnO) are synthesized using tetra-n-butylammonium bromide as a mediating agent. The structure of amorphous ZnO hollow spheres is found to be transformed from nanosheet- to nanoparticle-assembled hollow spheres (nPAHS) upon annealing at 500 °C. The ZnO nPAHS hybrids with Au/rGO are characterized using various techniques, including photoluminescence, steady-state absorbance, time-resolved photoluminescence, and photocatalysis. The charge-transfer time of ZnO nPAHS is found to be 87 ps, which is much shorter than that of a nanorod (128 ps), nanoparticle (150 ps), and nanowall (990 ps) due to its unique structure. The Au/rGO/ZnO hybrid shows a higher charge-transfer efficiency of 68.0% in comparison with rGO/ZnO (40.3%) and previously reported ZnO hybrids. The photocatalytic activities of the samples are evaluated by photodegrading methylene blue under black-light irradiation. The Au/rGO/ZnO exhibits excellent photocatalytic efficiency due to reduced electron-hole recombination, fast electron-transfer rate, and high charge-transfer efficiency.
authors: Department of Physics and Energy Harvest-Storage Research Center and ‡Department of Chemical Engineering, University of Ulsan , Ulsan 680-749, South Korea.
authors: Nguyen Tri
authors: NT
authors: Khoa
authors: Soon Wook
authors: SW
authors: Kim
authors: Dae-Hwang
authors: DH
authors: Yoo
authors: Shinuk
authors: S
authors: Cho
authors: Eui Jung
authors: EJ
authors: Kim
authors: Sung Hong
authors: SH
authors: Hahn
keywords: charge transfer; gold nanoparticle; graphene oxide; hierarchical aggregate; photoinduced reactivity; zinc oxide