Nitrogen/sulfur co-doped blue fluorescent carbon dots as a bifunctional probe for highly sensitive detection of chlortetracycline and lead ions

Abstract

Aiming at the problem of simultaneous monitoring of chlortetracycline (CTC) and lead ions (Pb²⁺) in food and the environment, high-performance nitrogen/sulfur co-doped blue fluorescent carbon dots (NS-CDs) were successfully synthesized by a one-step solvothermal method using oxalic acid and 1-amino-2-naphthol-4-sulfonic acid as precursors. The NS-CDs have a high quantum yield of 39.5% and excellent photostability. Based on the efficient quenching of NS-CD fluorescence by CTC and Pb²⁺, a dual-functional fluorescence sensing platform for simultaneous detection of CTC and Pb²⁺ was constructed for the first time. Under the optimized conditions, the linear detection ranges for CTC and Pb²⁺ were 0–35 µM (R² = 0.9911) and 0–5.4 µM (R² = 0.9948), respectively, and the detection limits were as low as 2.32 µM and 0.22 µM, respectively. The probe was successfully applied to the analysis of real river water samples. The recoveries of CTC and Pb²⁺ were 92.4–101.5% and 92–98.3% (RSD < 4%), respectively. This work provides a novel, simple and low-cost solution for the rapid and integrated on-site detection of multi-class pollutants in complex matrices.