Visible ratiometric fluorescence sensor based on Mg, N-CDs@ZIF-8 for sensitive detection of oxytetracycline and discrimination of tetracycline antibiotics

A novel and visible ratiometric fluorescence sensor based on magnesium and nitrogen co-doped carbon dots (Mg, N-CDs) encapsulated in zeolitic imidazolate framework-8 (Mg, N-CDs@ZIF-8) was designed for effective detection of oxytetracycline (OTC), employing a “turn-off/turn-on” fluorescence sensing strategy. The blue-emission Mg, N-CDs@ZIF-8 was quenched owing to fluorescence resonance energy transfer by OTC, while the green fluorescence of OTC was significantly enhanced through the interaction of Mg 2+ and Zn 2+ with OTC, enhancing the visual tracking of OTC through a distinct blue-to-green color transition. This sensor displayed a wide linearity range (0.02 − 25 μg/mL), a low detection limit (14.2 ng/mL), and a fast response time (6 min). The validity of the sensor was successfully verified by detecting OTC in milk, honey, tap water, and lake water samples. Additionally, an expandable fluorescence sensor array was constructed for the discrimination of four tetracycline antibiotics (TCs) in real samples, indicating significant application in complex environmental samples.