Effectively detect doxycycline in variable sample fields through simple fluorescence strategy using nitrogen doped carbon dots as probe.

The convenient and widespread implementation of doxycycline (DOXY) detection still requires the development of new methods to enable rapid detection across various environments. In this study, blue-emitting nitrogen-doped carbon dots (N-CDs) were successfully prepared using glutamine and anhydrous citric acid as primary materials. Correspondingly, a simple and sensitive fluorescence method for detecting DOXY was developed using N-CDs as probe. The fluorescence intensities of N-CDs were significantly quenched by variable concentrations of DOXY based on the internal filtration effect, which was verified through quantum efficiency correction experiment. Under the optimized testing conditions, the concentrations of DOXY showed a good linear relationship with fluorescence quenching efficiencies in the range of 0.1-35 μg/mL, with a detection limit (LOD) of 0.018 μg/mL, suggesting the good analytical performance. This method was successfully applied for the determination of DOXY in human plasma, dairy products and tap water samples, demonstrating satisfactory recoveries and reproducibility. The results highlight the promising potential of this approach for clinical monitoring of blood drug concentrations, detection of drug residues, and environmental sample analysis.