Bi/Bi4O5Br2 Ohmic-like heterojunction drives enhanced photocatalytic antibacterial action via electron transfer and ROS

Abstract

Electron transfer plays a pivotal role in catalytic reactions and physiological processes, with its modulation capable of altering catalytic efficiency and interfering with microbial metabolic pathways to enhance antibacterial outcomes. In this study, we designed a Bi/Bi₄O₅Br₂ nanosheet Ohmic-like heterojunction as a photodynamic therapy (PDT)-compatible semiconductor nano-agent. Under visible light irradiation, this heterojunction engineer's electron transfer pathways at both abiotic (material) and abiotic–biotic (material–bacteria) interfaces. The tightly contacted atom-sharing Bi heterostructure within the heterointerface generates an intrinsic electric field, which promotes the transfer of photogenerated electrons from Bi₄O₅Br₂ to Bi nanoparticles at the Bi–Bi₄O₅Br₂ interface, significantly boosting reactive oxygen species (ROS) production. Notably, the high conductivity of metallic Bi further activates direct electron transfer from the Bi₄O₅Br₂ interface to the bacterial surface. This dual electron-transfer mechanism—coupled with ROS generation—induces synergistic damage: ROS downregulate genes associated with ribosome, DNA, and ATP synthesis in Escherichia coli, while electron interference disrupts the bacterial electron transport chain, upregulating genes linked to membrane and ion transport. The resulting photoresponsive dual-interface system demonstrates excellent safety and potent antibacterial efficacy against both Escherichia coli and Staphylococcus aureus. Our findings highlight the critical role of targeted electron transfer (beyond ROS alone) in PDT for combating pathogenic bacterial infections and antibiotic resistance, offering a design strategy for next-generation multifunctional antimicrobial photocatalysts.