Integrated smartphone-sensing and remediation platform empowered by hole-confinement-triggered Fe-Cu diatomic nanozymes for precise management of tetracyclines.

Mimicking the sophisticated oxidative machinery of natural monooxygenases for high-performance biosensing remains a grand challenge, primarily due to the elusive control over positive charge carriers (holes) required for efficient signal amplification. Here, we report an atomically precise Fe-Cu heteronuclear diatomic catalyst (Fe-Cu-HDC) that unlocks unprecedented analytical sensitivity through a novel asymmetric hole-confinement mechanism. Unlike traditional single-atom catalysts where charge carriers are delocalized, the Fe-Cu interface acts as a decisive "hole trap" spatially concentrating reactive charge carriers at the active center. This localized accumulation triggers the formation of potent high-valent iron species and facilitates barrierless oxygen activation, providing the rapid mineralization of >80% tetracycline within 80 min with a superior reaction rate (Vmax = 0.27 mM min-1). Leveraging this hole-driven enzymatic proficiency, we engineered an integrated 3D-printed platform comprising a continuous-flow filtration reactor and a smartphone-based colorimetric sensor array. This portable device enables the simultaneous rapid mineralization and fingerprint-like discrimination of tetracycline antibiotics in complex real-world matrices (raw milk and livestock wastewater) with a detection limit as low as 30 nM. The platform maintains >90% activity after 18 d of storage and demonstrates laboratory-grade accuracy in raw milk and livestock wastewater. Our findings not only demystify the electronic origin of bio-inspired oxidation but also establish hole-carrier engineering as a transformative dimension for designing the next generation of intelligent, cofactor-free biosensors for on-site diagnostics and environmental surveillance.