Excited-State Behavior of Luminescent Glutathione-Protected Gold Clusters

The excited-state behavior of luminescent gold clusters provides new insights in understanding their photocatalytic activity in the visible region. The excited state of glutathione-protected gold nanoclusters (AuGSH), which is characterized by the long-lived excited state (τ = 780 ns), arises from the ligand-to-metal type transition. These AuGSH clusters are in a partially oxidized state (Au(I)) and are readily reduced by chemical or electrochemical methods. Interestingly, a metal core transition with short-lived lifetime (τ < 3 ps) appears along with a longer lifetime in reduced AuGSH clusters. The role of the oxidation state of gold clusters in dictating the photocatalytic reduction of methyl viologen is discussed.