Sulphur and Nitrogen-Doped Carbon Dot-Based Fluorescence “Turn-Off” Sensor for 2,4,6-Trinitrophenol

In terms of both international public security and environmental protection, nitroaromatic explosive substances like 2,4,6-trinitrophenol (TNP) receive great concern, and its detection has relevance in health sector as well. Herein, we have synthesized a fluorescent sensor for easy and fast detection of TNP. Sulphur and nitrogen-doped carbon dots (S,N-CDs) were synthesized via microwave irradiation method using L-cysteine as the sulphur and nitrogen donor and citric acid as the carbon source. The prepared S,N-CDs were examined by various analytical techniques, such as DLS, photoluminescence (PL) studies, UV–visible absorption studies, lifetime analysis, FT-IR, TEM, and SEM analysis. The developed S,N-CDs can act as a selective fluorescent probe for TNP. S,N-CDs show a detection limit of 0.29 µM and a limit of quantification of 0.95 µM towards TNP with appreciable selectivity and sensitivity. Thus, a fast and easy direct turn-off detection of TNP is developed by this fluorescence sensing platform. Further, TNP detection on a paper-strip based sensing platform was also performed.