A “Signal Relay” Mode Triggered by Bimetallic Synergistic Enhancement in an MOF-Based Multiemission Fluorescence Sensing/Adsorption Platform for Broad-Concentration-Range Tetracycline Antibiotics Visual Detection
Han Jiang, Zhongling Xu, Yue Wang, Jie Song, Yiwei Wu, Xiaoxiao Yu, Jing Wang
Abstract
The widespread misuse of tetracycline antibiotics (TCs) and their persistent low-concentration residues in animal-derived foods pose critical threats to human health, while existing analytical methods lack the capability for continuous therapeutic drug monitoring. Herein, a multiemission MOF-on-MOF fluorescence sensing platform codoped with Eu 3+ and Zn 2+ was engineered via epitaxial growth for simultaneous adsorption and detection of tetracycline, oxytetracycline, chlortetracycline, and doxycycline. By leveraging the differential coordination affinities of Eu 3+ and Zn 2+ toward TCs, a “signal relay” response mechanism was innovatively designed: At trace concentrations (0.05–6 μM), TCs preferentially bind to Eu 3+ sites via the antenna effect, generating linearly enhanced fluorescence at 616 nm with an ultralow detection limit of 9 nM (22-fold below EU MRLs). Upon Eu 3+ site saturation (>6 μM), Zn 2+ domains initiate coordination-induced aggregation of TCs, triggering a second-stage fluorescence enhancement at 520 nm that extends the dynamic range to 40 μM. This platform was successfully applied to detect TCs across wide concentration ranges in environmental water, animal-derived foods, and veterinary drugs. A novel dual-metal-doped MOF-on-MOF integrates broad detection range, fast adsorption kinetics, better stability, and multiscenario applicability, while multiemission wavelengths enhance the sensitivity of fluorescence color changes, better meeting practical needs for visual detection.