Photomediated Oxidation of Atomically Precise Au25(SC2H4Ph)18(-) Nanoclusters.
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.
†National Energy Technology Laboratory (NETL), United States Department of Energy, Pittsburgh, Pennsylvania 15236, United States.|‡URS, P.O. Box 618, South Park, Pennsylvania 15129, United States.
Douglas R
DR
Kauffman
†National Energy Technology Laboratory (NETL), United States Department of Energy, Pittsburgh, Pennsylvania 15236, United States.
Dominic
D
Alfonso
†National Energy Technology Laboratory (NETL), United States Department of Energy, Pittsburgh, Pennsylvania 15236, United States.
Christopher
C
Matranga
§Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Gao
G
Li
§Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Rongchao
R
Jin
density functional theory; electrochemistry; excited-state charge transfer; gold clusters; photochemistry; spectroscopy