A plasmonic heterojunction for full-spectrum light harvesting and photoinduced charge storage: NaYF 4 :Yb,Tm@TiO 2 /Fe 3 Jing Zheng, Miao Yuan, Yang Wu, Jiarong Wang, Dan Shan, Chaoran Wang, Yifan Zheng, Yunqi Wang, Huanyu Cui, Baiqi Wang
The practical application of photocatalysts in environmental remediation remains constrained by insufficient solar-spectrum utilization, rapid photogenerated charge recombination, and loss of catalytic activity under dark conditions. Herein, we report a multifunctional NaYF₄:Yb, Tm@TiO₂/Fe₃O₄/Au (NTFA) S-scheme nanoheterojunction designed to address these limitations through integrated full-spectrum light harvesting, plasmon-enhanced charge separation, and charge-storage-assisted catalysis. The NaYF₄:Yb, Tm upconversion nanoparticles extend photoresponse into the near-infrared region, Au nanoparticles introduce localized surface plasmon resonance to enhance light absorption and interfacial charge transfer, and Fe₃O₄ serves as an electron-trapping and storage component. This synergistic architecture provides a measurable photoresponse across UV, visible, and near-infrared photons while suppressing electron–hole recombination and sustaining catalytic reactions after light irradiation ceases. With optimized Au loading, NTFA-4 achieved 94.1% degradation of malachite green, markedly outperforming conventional photocatalysts. Notably, its charge-storage capability enabled continued pollutant degradation under dark conditions, demonstrating potential for overcoming intermittency in solar-driven water treatment. In municipal wastewater, NTFA-4 removed 94.3% of malachite green and 73.6% of ammonia nitrogen, confirming its effectiveness in complex aqueous matrices. This work provides a rational strategy for constructing multifunctional photocatalytic heterojunctions with extended spectral response, enhanced charge dynamics, and persistent catalytic activity for sustainable wastewater remediation.