Spatiotemporal antibacterial strategy via intra-particle charge transfer-enhanced self-photooxidation of Cu₂O nanoparticles

Due to its photocatalytic instability, Cu₂O can function as a potent source of Cu²⁺ ions. Upon exposure to light irradiation, Cu₂O nanoparticles (NPs) undergo self-photooxidation, wherein facet-dependent charge separation facilitates the leaching of Cu²⁺ ions. This process generates a microenvironment with a high ion concentration, thereby ensuring effective bacterial eradication. Cu-based antimicrobial agents eliminate bacteria by releasing Cu²⁺ ions and generating reactive oxygen species (ROS). However, their limited ion release and diffusion constraints impede bactericidal efficiency. This study introduces a self-photooxidation strategy that employs Cu₂O NPs for the spatiotemporal eradication of bacteria. Under light exposure, Cu₂O NPs undergo photodecomposition, rapidly releasing Cu²⁺ ions at a rate that surpasses bacterial motility. Additionally, the exothermic reaction induces thermal convection, directing motile Escherichia coli toward the NP surfaces, thereby enhancing antibacterial efficacy. The processes of self-photooxidation, bacterial motility, and cell viability were quantified at the level of individual particles and cells using optical microscopy. These findings demonstrate that the facet-dependent electronic properties of shape-controlled Cu₂O NPs optimize charge transfer, thereby enhancing self-photooxidation and antibacterial performance. This strategy addresses the limitations of conventional Cu-based antimicrobials and enables precise optical control of bactericidal activity.