posted on 2015-12-16, 22:16authored byDouglas 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.