title: Unexpected Size Effect Observed in ZnO-Au Composite Photocatalysts.
abstract: Semiconductor-metal nanocomposites prepared with well-defined gold nanoclusters, such as Au25, Au144, and Au807, showed size-dependent photocatalytic activities for the reduction of nile blue and azobenzene. Whereas the photoreduction of nile blue was directly related with the charge separation and transfer rate from the photoexcited ZnO to gold nanoclusters, the photoreaction of azobenzene showed unexpected size effect with a clear threshold. Mechanistic investigations revealed that the photoreduction of azobenzene proceeded via a proton-coupled electron transfer process. The photocatalytic activity of the ZnO-Au nanocomposites was also dependent on the excitation intensity, demonstrating that the multielectron/multiproton process was controlled by the charge separation and transfer in the nanocomposites.
authors.affiliation: Department of Chemistry, Kyung Hee University , Seoul 130-701, Korea.
authors.forename: Noh Soo
authors.initials: NS
authors.lastname: Han
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Dukhan
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Kyung Hee University , Seoul 130-701, Korea.
authors.forename: Jong Woon
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Jaehyun
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Kyung Hee University , Seoul 130-701, Korea.
authors.forename: Hyeong Seop
authors.initials: HS
authors.lastname: Shim
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Dongil
authors.initials: D
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Kyung Hee University , Seoul 130-701, Korea.
authors.forename: Jae Kyu
authors.initials: JK
authors.lastname: Song
keywords: Au nanocluster; azobenzene; multielectron; nanocomposite; photocatalysis