A Comparison of Photocatalytic Activities of Gold Nanoparticles Following Plasmonic and Interband Excitation and a Strategy for Harnessing Interband Hot Carriers for Solution Phase Photocatalysis

Light driven excitation of gold nanoparticles (GNPs) has emerged as a potential strategy to generate hot carriers for photocatalysis through excitation of localized surface plasmon resonance (LSPR). In contrast, carrier generation through excitation of interband transitions remains a less explored and underestimated pathway for photocatalytic activity. Photoinduced oxidative etching of GNPs with FeCl₃ was investigated as a model reaction in order to elucidate the effects of both types of transitions. The quantitative results show that interband transitions more efficiently generate hot carriers and that those carriers exhibit higher reactivity as compared to those generated solely by LSPR. Further, leveraging the strong π-acidic character of the resulting photogenerated Au⁺ hole, an interband transition induced cyclization reaction of alkynylphenols was developed. Notably, alkyne coordination to the Au⁺ hole intercepts the classic oxidation event and leads to the formation of the catalytically active gold clusters on subnanometer scale.