Abstract: Nitrogen doped fluorescence carbon dots (N-CDs) were successfully synthesized by a facile one step solid phase pyrolysis treatment using malic acid as the carbon source and ammonium phosphate as the nitrogen source. The fluorescence quantum yield of the obtained N-CDs reaches 20.7% and the N-CDs have approximately spherical morphology with an average diameter of 3.3 nm. The as prepared N-CDs were used as the fluorescent probe to detect ciprofloxacin (CIP) based on the enhancement of N-CDs fluorescence upon adding CIP. The optimal experimental mass conditions are 7.5 μg/mL of N-CDs, pH=5.91, and 5 min of incubation time for the detection of CIP. The enhancement of N-CDs fluorescence exhibits a good linear relationship with the concentration of CIP ranged from 0.39 μmol/L to 40.0 μmol/L under the optimal conditions. The linear regression equation is ΔF=1.61×10⁷[CIP]-3.28 with a correlation coefficient R²=0.994. The detection limit and relative standard deviation (n=5) are estimated to be 0.12 mol/L and 4.2%, respectively. The interference experiments indicate that potential coexistence substances (except copper ions) have ignorable effects on the detection of CIP, and the interference of copper ions could be masked with 4% ammonium oxalate solution. Finally, the proposed sensor was successfully applied to analyze real samples with satisfactory results.

Key words: nitrogen doped carbon dots, ciprofloxacin, fluorescence probe, fluorescence enhancement