Band-Engineered ZnWOs₄@Ni-BiOCl Z-Scheme Heterojunction for Synergistic Visible Light-Driven Photocatalytic Detoxification, Attenuation of Ecotoxicity, and Ultrasensitive Electrochemical Sensing of Tetracycline

The rational design of Z-scheme heterojunctions presents a robust approach for comprehensive environmental remediation through simultaneous pollutant detection and degradation. In this study, a hierarchical Z-scheme heterostructure ZnWO₄@Ni-BiOCl (ZW@Ni-BOC) was synthesized by in situ anchoring of nickel-doped bismuth oxychloride (Ni-BOC) nanoflakes onto zinc tungstate (ZW) nanorods. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) confirmed tightly connected interfaces, while the optimized 1.5:1 ZW@Ni-BOC exhibited superior charge separation, broadened visible-light absorption, and a high density of surface-active sites. When configured on a glassy carbon electrode, ZW@Ni-BOC served as an ultrasensitive electrochemical sensor for tetracycline (TC), delivering sensitivity of 11.66 μA μM⁻¹ cm⁻², detection limit of 0.66 nM, and broad linear response range. The composite also achieved rapid photocatalytic degradation of TC, Rhodamine B, and chlorpyrifos under visible light. Mechanistic analysis using UV-Vis diffuse reflectance spectroscopy and radical scavenger tests confirmed the Z-scheme charge transfer mode, supported by Liquid chromatography Mass spectrometery-based product identification. Quantitative structure activity relationship toxicity modeling revealed marked toxicity reduction of intermediates, and antibacterial assays showed full inactivation of Staphylococcus aureus and Escherichia coli within 60 min of irradiation. This work highlights ZW@Ni-BOC as a multifunctional, scalable nanoplatform enabling integrated sensing, catalytic detoxification, toxicity mitigation, and microbial disinfection.