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Photomediated Oxidation of Atomically Precise Au25(SC2H4Ph)18 Nanoclusters

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journal contribution
posted on 2015-12-16, 22:16 authored by Douglas R. Kauffman, Dominic Alfonso, Christopher Matranga, Gao Li, Rongchao Jin
The anionic charge of atomically precise Au25(SC2H4Ph)18 nanoclusters (abbreviated as Au25) is thought to facilitate the adsorption and activation of molecular species. We used optical spectroscopy, nonaqueous electrochemistry, and density functional theory to study the interaction between Au25 and O2. Surprisingly, the oxidation of Au25 by O2 was not a spontaneous process. Rather, Au25–O2 charge transfer was found to be a photomediated process dependent on the relative energies of the Au25 LUMO and the O2 electron-accepting level. Photomediated charge transfer was not restricted to one particular electron accepting molecule or solvent system, and this phenomenon likely extends to other Au25–adsorbate systems with appropriate electron donor–acceptor energy levels. These findings underscore the significant and sometimes overlooked way that photophysical processes can influence the chemistry of ligand-protected clusters. In a broader sense, the identification of photochemical pathways may help develop new cluster-adsorbate models and expand the range of catalytic reactions available to these materials.

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