Directionally Designed Double Z-Scheme Heterojunction: BiOBr and Carbon Dots-Reduced TiO2-x for Targeted Photocarriers Separation in Photocatalytic Sterilization.

TiO2 photocatalysis holds promise for sterilization but faces limitations in rapid charge recombination, UV-restricted activity, and pathogen electrostatic repulsion. Herein, a directionally designed double direct Z-scheme BiOBr@CDs-TiO2- x heterojunction is constructed, in which defective BiOBr microspheres core with dominant (110) facets exhibiting photochromism via hole trapping is synergistically integrated with carbon dots (CDs)-modified TiO2- x shell. Amine-functionalized CDs simultaneously reduce and dope TiO2- x, thereby generating oxygen vacancies and enhancing positive surface charges. By leveraging BiOBr's hole-trapping affinity and CDs' electron-transmitting capability, BiOBr@CDs-TiO2- x achieves spatial charge separation via a double Z-scheme mechanism. This system eradicates 99.9% of Escherichia coli (5 × 108 CFU mL-1), Staphylococcus aureus (2 × 108 CFU mL-1), and Candida albicans (1 × 108 CFU mL-1) in 1 h, concomitantly achieving biofilm clearance and pollutant degradation under visible light. The work pioneers CDs' novel application in constructing oxygen vacancies of TiO2- x and establishes a carrier-affinity-driven paradigm for directional heterojunction design.