Preparation of highly luminescent nitrogen-doped carbon quantum dots and their detection of tetracycline antibiotics

The massive use of tetracyclines poses a risk to human health and their quantitative testing is urgent. This work provides a novel nitrogen-doped carbon quantum dots (N-CQDs) fluorescent probe which was prepared by a facile one-pot hydrothermal method using glucose and ethylenediamine as precursors for the detection of tetracycline antibiotics. The fluorescence intensity of the CQDs was greatly enhanced by the doping of nitrogen. The fabricated N-CQDs exhibited a spherical shape with an average diameter of 2.66 nm. It displayed blue fluorescence, a quantum yield of 10.97 % and an excitation-dependent emission behavior. It also had excellent stability, such as resistance to the effects of varying ionic strength, pH and continuous UV light irradiation. The N-CQDs detect tetracycline antibiotics including tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) based on fluorescence quenching caused by the inner filter effect (IFE) with excellent specificity. The limits of detection (LOD) were 0.344, 0.265, and 0.117 μM, respectively. The proposed method has been successfully applied to the determination of tetracycline antibiotics in rat serum and milk samples with satisfactory recoveries, confirming that the proposed fluorescent probe has practical application prospects.