Quantum Dots Reconfigure the Band Energetics to Enable a Reversed Z-Scheme in Fully Encapsulated Heterointerfaces

Photocatalytic Z-scheme systems are fundamentally limited by insufficient interfacial contact and rigid band alignment requirements, which restrict efficient charge transport and material selection. Here, we report a quantum dots (QDs)-induced interface reconstruction strategy that simultaneously reconfigures band energetics and maximizes interfacial coupling, enabling control over charge transfer direction. By employing an ultrasmall-size-driven dissolution–reprecipitation method, a novel core–satellite nanostructure was formed with the BiOBr quantum dots distributed around the AgBr/Ag particles. Oxygen-defective atomic-layered BiOBr quantum dots exhibit shifted band edges arising from quantum confinement and vacancy-mediated surface dipoles, establishing a thermodynamically favorable Z-type alignment with AgBr that cannot be achieved with bulk BiOBr or nanosheets. More critically, the full encapsulation of Ag/AgBr nanoparticles by ultrathin quantum dots transforms discrete point contacts into a continuous coupling network, drastically reducing interfacial resistance. Experiments and calculations collectively reveal ultrafast (<1 ps) electron migration from AgBr to BiOBr QDs via Ag bridges, while vacancies of BiOBr QDs act as electron traps, further suppressing carrier recombination. Therefore, the quantum-dots-engineered composite system forms long-lived charge-separated states exceeding 6000 ps, improving the generation ROS and Ag+, resulting in a significantly higher bacterial inactivation rate of 100% against Escherichia coli under visible light. The study establishes a generalizable semiconductor QD-based design strategy for interface dominated charge flow engineering in functional photocatalytic and optoelectronic systems.