Lanthanide coordination carbon quantum dots construct a ratiometric fluorescent sensor for the detection of norfloxacin in milk

The residues of norfloxacin in milk and other foods cause serious harm to human health. Compared with the other ratiometric fluorescence sensors formed by lanthanide hybridized carbon quantum dots, the synthesized carbon quantum dot of this sensor used citric acid as the carbon precursor. It could act as an internal standard signal (λem = 460 nm) and form ratiometric fluorescence with a Tb3+ characteristic emission peak (λem = 545 nm). More importantly, this carbon quantum dot could sensitize Tb3+ to promote the f-f transition of Tb3+ and enhance its characteristic fluorescence. In addition, the antenna effect between norfloxacin and Tb3+ could further enhance the fluorescence signal at 545 nm. Under the optimal detection conditions, the limit of detection was down to 3.20 nM, and the recovery rate in milk was 94.60–97.00 %. The sensor platform showed a rapid and sensitive response to norfloxacin, providing a simple and effective strategy for the detection of antibiotics in food.