A one-stone-two-birds strategy: cerium-doped carbon dots as a dual probes platform for quantification of tetracycline and carmine in foods

We developed a dual-functional fluorescent probe based on cerium-doped carbon dots (Ce-CDs). The Ce-CDs were synthesized via a facile hydrothermal route using trimesic acid, L-lysine, and cerium nitrate as precursors, serving to quantify both tetracycline (TET) and carmine (CM). The Ce-CDs show excellent excitation-independent fluorescence, with optimal excitation at 340 nm, emission at 410 nm, and quantum yield of 17.4%. Due to the inner filter effect and static quenching, their fluorescence intensity decreased linearly with increasing TET/CM concentration, enabling a new fluorescent probe. The developed sensing platform exhibited a wide linear response (0.125–50.0 µM) and high sensitivity, with limits of detection of 0.037 µM for TET and 0.035 µM for CM. The method’s accuracy and precision were rigorously evaluated in complex food samples. Recoveries for TET in a variety of meats (pork, pork liver, beef, chicken) fell between 94.4% and 113%, and for CM in foodstuffs (dried strawberries, bayberry juice, red bull drink) fell between 92.0% and 115%, with relative standard deviations ≤ 5.8%. Thus, Ce-CDs are excellent probes for food TET and CM detection.