Innovative Dual-Emitting Ratiometric Fluorescence Sensor for Tetracyclines Detection Based on Boron Nitride Quantum Dots and Europium Ions

On account of the excessive residues and serious detriments, it is imminent to develop an efficient method to determine tetracyclines (TCs) for protecting human health. In this work, a novel ratiometric fluorescence sensor was constructed for TCs based on a powerful boron nitride quantum dot and europium ion (BNQD-Eu3+) system. The blue-emitting BNQDs were synthesized via a facile hydrothermal route using boric acid and urea as precursors. When TCs were presented in the hybrid probe of BNQDs and Eu3+, blue fluorescence of BNQDs was quenched and red fluorescence of Eu3+ was enhanced, which can be attributed to the inner filter effect, photo-induced electron transfer, as well as the antenna effect. Besides, it was confirmed that the proposed sensor possessed good detection limits of 0.019, 0.104, and 0.028 μM for tetracycline (TET), oxytetracycline, and doxycycline, respectively. Additionally, the results of BNQD-Eu3+-based sensing of TET in milk and beef samples showed an insignificant difference from those of liquid chromatography–mass spectrometry. Moreover, the BNQD-Eu3+-based test paper was successfully used in the easy and visual detection of TCs by the naked eyes, indicating the practical applicability of the sensor.