A ratiometric fluorescent sensor based on carbon dots encapsulated in ZIF-8 for visual discrimination and detection of tetracycline and chlortetracycline

Tetracyclines (TCs), widely used in livestock farming, accumulate in ecosystems and pose health risks due to their persistence. Existing detection methods suffer from high cost, complex procedures, and insufficient specificity. Herein, a dual-emission fluorescent composite (CDs@ZIF-8) was designed by encapsulating carbon dots (CDs) into a zeolitic imidazolate framework-8 (ZIF-8). The composite material exhibits distinct dual emission peaks at 332 nm (ZIF-8) and 492 nm (CDs), and achieves ratiometric fluorescence sensing and differentiation between two structurally analogous antibiotics tetracycline (TC) and chlortetracycline (CTC) by quenching the ZIF-8 peak and enhancing the CD peak. The sensor achieves low detection limits of 7.13 nM for TC and 7.25 nM for CTC, with excellent selectivity and anti-interference capability over other antibiotics. A colorimetric logic gate and smartphone-based RGB analysis platform were developed for visual discrimination and quantitative detection, demonstrating high accuracy in real-sample analysis. This work provides a robust, low-cost strategy for on-site monitoring of TC antibiotics.