Carrot-Derived Nitrogen-Doped Dual-Emission Carbon Dots for Ratiometric Detection of Tetracycline and Oxytetracycline.

The antibiotic contamination in aquatic environments, particularly in aquaculture systems, poses substantial risks to ecological balance and human health. To address this issue, we engineered a novel ratiometric fluorescent probe utilizing dual-emission carbon dots (D-CDs) synthesized from sustainable biomass carrot and nitrogen-rich precursors (melamine and o-phenylenediamine) through an efficient one-pot hydrothermal approach. The D-CDs exhibited dual emission peaks at 425nm and 540 nm under 370nm excitation. The fluorescence intensity ratio (F₅₄₀/F₄₂₅) demonstrated linear response toward tetracycline (TC) and oxytetracycline (OTC), with wider linear detection ranges of 0.027-133.3 µM for TC and 0.027-233.3 µM for OTC, respectively. Low detection limits (17.7 nM for TC and 22.04 nM for OTC) were also achieved. Mechanistic studies revealed that quenching resulted from static quenching and inner filter effects. The probe showed exceptional stability under high ionic strength and long storage conditions. Real-sample monitoring in lake water and aquaculture samples yielded recovery rates of 90.4-103.5% with RSD < 6.88%, which was validated by high-performance liquid chromatography (HPLC), demonstrating the promising potential of this probe.