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.