Charge-pathway regulation via plasmon-mediated upconversion-semiconductor coupling enables all-weather photocatalytic antibiotic degradation and bacterial inactivation in wastewater

Photocatalytic wastewater remediation is often limited by incomplete solar-spectrum utilization and rapid recombination of photogenerated charges, especially when both chemical pollutants and microbial pathogens must be addressed. Here, we report a plasmon-mediated upconversion-semiconductor nanoheterojunction (NaYF 4 :Yb,Tm@TiO 2 /Fe 3 O 4 /Au) that reorganizes interfacial charge-transfer pathways to enable broadband, multifunctional photocatalysis. The coupled architecture promotes directional charge separation and multichannel reactive oxygen species (ROS) generation, with superoxide radicals serving as the dominant functional species in antibiotic degradation. Photoelectrochemical analyses reveal enhanced carrier extraction under visible and near-infrared illumination, while Open-circuit photopotential decay (OCPD) and light-off Electron paramagnetic resonance (EPR) measurements demonstrate that photogenerated electrons can be temporarily stored and released to sustain post-illumination ROS generation, enabling dark-phase ciprofloxacin degradation. Under simulated solar light, NTFA achieves 88.9% ciprofloxacin degradation within 120 min and near-complete inactivation of Escherichia coli and Staphylococcus aureus. The catalyst also retains > 70% activity after five cycles and shows good performance in real wastewater matrices. These results highlight how plasmon-upconversion coupling links spectral excitation to charge utilization and ROS generation, providing a mechanistic blueprint for designing broadband-responsive, all-weather photocatalysts for simultaneous chemical and biological water treatment.