Bifunctional carbon dots based on L-aminopropanol and citric acid: For rapid detection of chlortetracycline and ethanol anti-counterfeiting.

Food and environmental safety concerns arising from chlortetracycline (CTC) residues, together with the frequent adulteration of ethanol fuel, have increased the demand for rapid detection and anti-counterfeiting strategies. The development of functional materials capable of both antibiotic recognition and solvent differentiation is therefore of great interest for convenient monitoring in related fields. In this work, blue-emissive carbon dots (B-CDs) were synthesized via a one-step hydrothermal method using L-aminopropanol and citric acid as precursors. The as-prepared B-CDs exhibit stable and linear fluorescence responses as a function of B-CD dosage, enabling their use as reliable fluorescent markers in ethanol systems. In ethanol-methanol mixtures, the fluorescence intensity of B-CDs shows a gradual and linear decrease with increasing methanol volume fraction, enabling effective evaluation of ethanol adulteration levels. In addition, B-CDs display a pronounced fluorescence quenching response toward chlortetracycline, while showing negligible responses to other antibiotics and various metal ions, demonstrating high selectivity for CTC detection with a low detection limit of 0.25 μM.