Antibacterial Performance of a Gold-Loaded g-C₃ N₄ Nanocomposite System in Visible Light-Dark Dual Mode

Semiconductor photocatalysis technology, which can kill pathogenic microorganisms in a green and broad-spectrum way, is a new research field with great application potential. Due to the dependence on light, semiconductor materials have the problems of low utilization rate of sunlight and inactivation under dark conditions. A simple Au-loaded g-C₃ N₄ (Au/g-C₃ N₄ ) nanocomposites was studied. Under dark conditions, the antibacterial efficiency of 1.2 % Au/g-C₃ N₄ reached 99.1 % relative to 10⁵  CFU (Colony-FormingUnits)/mL E. coli. Under light conditions, the antibacterial efficiency of 0.9 % Au/g-C₃ N₄ reached 94.1 % relative to 10⁷  CFU/mL E. coli. The influence of contact time, Au loading and bacterial concentration on its antibacterial performance under dark conditions was discussed in detail. Through photoelectrochemistry, SEM, TEM and reactive oxygen species (ROS) detection the microscopic charge behaviour was revealed in the system, and a light-dark dual-mode antibacterial mechanism was proposed.