Use of Deep Ultraviolet Emissive Carbon Dots as a Novel Optical Sensor for the Detection of Tetracyclines in Milk

Stable deep ultraviolet emissive carbon dots (DUV-CDs) were produced as a novel optical sensor to detect the concentration of tetracyclines (TCs) in milk. The 2,4-dihydroxybenzoic acid and lysine were used as the precursor for DUV-CDs synthesis. Experiments show that the optimal excitation wavelength and the fluorescence peak wavelength of the carbon dots are 273 and 298 nm, respectively. With the addition of TCs, the fluorescence intensity of DUV-CDs would be significantly quenched. It is inferred by experiments that the fluorescence of DUV-CDs is quenched by TCs due to the combined effect of inner filter effect (IFE) and hydrogen bonding. The results showed that the method has high sensitivity and a large measurement range. The linear range can be fit in the range of 0.25–30 mg/L in water where ${R}^{{2}}$ is 0.996 and the limit of detection (LOD) is $49.94~\mu \text{g}$ /L. Meanwhile, the linear range is 0.5–40 mg/L in milk, ${R}^{{2}}$ is 0.991, and the LOD is $70.61~\mu \text{g}$ /L. In this article, the DUV-CDs were applied to foodstuffs for the first time. Compared with the traditional detection method, the DUV-CDs method has the advantages of high sensitivity, simple operation, safety, high energy utilization, and low cost. A new method was established for detecting TCs in milk, which may aid in the detection of food safety.