A smart Zn-MOF-based ratiometric fluorescence sensor for accurate distinguish and optosmart sensing of different types of tetracyclines

Tetracyclines misuse has brought enormous pressure on the environment, and it is significant to develop sensitive and selective methods for detecting tetracyclines. A ratiometric fluorescence-enhanced sensor with Zn-based metal-organic framework (HNU-55) as detection signal and rhodamine B (RhB) as reference signal is constructed for differentiation and optosmart detection of tetracyclines. Sensor specifically recognizes tetracyclines through chelation between Zn2+ of sensor and –OH of tetracyclines and sensitizes tetracyclines to induce fluorescence enhancement. The π–π stacking interactions between sensor and tetracyclines induce aggregation of tetracyclines. Intermolecular hydrogen bonding enhances sensor rigidity and limits its conformational rotation, further strengthening the fluorescence. Different fluorescence emission of sensor achieves discrimination of four tetracyclines. Fluorescent sensing array based on sensor distinguishes four tetracyclines precisely by principal component analysis. Binding energies and bond angles calculated from density functional theory are attributed to distinguish tetracyclines. Detection limits of sensor for doxycycline, tetracycline, oxytetracycline and chlortetracycline are 4.6, 2.6, 4.7 and 7.5 nmol/L, respectively. Applying sensor for tetracyclines detection in lake water obtains satisfactory recoveries. The portable optosmart sensing system is developed for on-site visual quantification of tetracyclines. An effective strategy for accurate identification and optosmart sensing of tetracyclines offers a wide range of applications in environmental monitoring.