Rapid determination of tetracycline utilizing a ratiometric fluorescence with Co-doped carbon quantum dots

This study successfully synthesized high performance blue emissive carbon dots (ZrN-CDs) using citric acid, zirconium chloride, and ethylenediamine as precursors through a hydrothermal method. The resulting ZrN-CDs exhibit excitation-independent emission characteristics, along with good water solubility, salt resistance, and photobleaching resistance. The fluorescence resonance energy transfer (FRET) mechanisms allow for the selective attenuation of ZrN-CD fluorescence by tetracyclines (TCs). Building on this effect, a dual-emission ratiometric fluorescent sensor was developed by integrating europium ions (Eu3 +), featuring an inverse fluorescence signal response to enhance detection accuracy through self-calibration. The fluorescence emission behavior of ZrN-CDs (F440) showed selective quenching in response to TCs, while the characteristic emission of Eu3+ (F615) exhibited fluorescence enhancement due to the antenna effect (AE). Quantification of common TCs antibiotics, including tetracycline (TET) and oxytetracycline (OTC), was achieved by recording the fluorescence intensity ratio (F615/F440). The limits of detection (LOD) for TET and OTC reached 0.029 mu M and 0.016 mu M, respectively. This method was successfully applied to the detection of TET in bovine, goat, and camel milk, with recovery rates ranging from 83.65 % to 106.60 %, thereby confirming the reliability and effectiveness of the sensor in practical applications.