Preparation of Nitrogen-Doped Fluorescent Carbon Quantum Dots and Detection Study of Tetracycline

Tetracycline (TC) is a broad-spectrum antibiotic primarily used for the prevention and treatment of bacterial infections in humans and animals. However, excessive use of tetracycline can lead to accumulation in the body, posing risks to human health. In this study, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using sucrose as the carbon source and ethylenediamine as the nitrogen source via a microwave method. N-CQDs were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible spectroscopy (UV-vis). The preparation conditions for N-CQDs were optimized, and the results showed that when glycerol was used as the solvent, the mass ratio of sucrose to ethylenediamine was 1:4, and the microwave power was 800 W, the fluorescence quantum yield of the synthesized N-CQDs reached 43.78%. Optimisation of the TC detection process indicated that at a reaction temperature of 50 °C, a reaction time of 20 min, and a buffer solution pH of 7, within a concentration range of 1.6 to 45 µmol/L, the linear regression equation for TC concentration versus N-CQDs fluorescence quenching degree is (F₀-F)/F₀ = 0.01042 c + 0.42759, with an R² value of 0.99344 and a detection limit of 45 nmol/L. Experiments were conducted to determine the recovery rate and precision of TC in milk samples. The results showed that the recovery rates ranged from 94% to 107%, while the precision (RSD) was within the range of 1% to 4%, indicating that the synthesized N-CQDs can sensitively and efficiently detect TC. In this study, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using sucrose as the carbon source and ethylenediamine as the nitrogen source via a microwave method.