Optimizing the Au Particle Doping Size for Enhanced Photocatalytic Disinfection under Low-Intensity Visible Light

Here, we present the effect of 1.2-9.9 nm Au particles on crystal violet-treated polymer under a low intensity of visible light. The use of Au particles ≤ 6.3 nm promoted charge carrier transfer from crystal violet to Au particles. Photospectroscopy analyses and DFT computations revealed that a change in the electronic band structure caused by the size reduction of the particle altered the charge carrier transfer pathway in crystal violet. Especially for crystal violet─1.2 nm Au particles, charge carrier transfer predominantly occurs at the S₁ of crystal violet because the T₁ state lacks sufficient potential energy for transfer. 1.2 nm Au particles on crystal violet not only most significantly enhanced the generation of O₂•^-, H₂O₂, and ^•OH by minimizing unnecessary side reactions or energy loss but also showed the most potent disinfection activity against Staphylococcus aureus, even at low visible light flux levels (0.037-0.054 mW cm^-2), which resulted in a 5.3 log reduction in viable bacteria after 6 h exposure to visible light. This finding provides fundamental insights into the Au effect as a cocatalyst in photocatalysts and the development of light-activated self-sterilizing surfaces that can be applied to various hospital surfaces to prevent the spread of pathogens, which remains a global challenge.