Nitrogen and Sulfur Co‐Doped Carbon Dots as Fluorescence Sensor for Sensitive and Visual Identification and Detection of p‐Nitrophenol and Picric Acid

ABSTRACT Nitrogen and sulfur co‐doped carbon dots (NS‐CDs) were successfully synthesized from L‐cysteine and ethanolamine via a one‐pot hydrothermal method. In mixed ethanol/H 2 O solvent, NS‐CDs exhibit selective and sensitive fluorescence quenching response towards TNP and 4‐NP over other explosives. The low detection limits were as low as 0.272 µmol/L for TNP and 0.339 µmol/L for 4‐NP, demonstrating the high sensitivity of NS‐CDs. A comparison of the fluorescence and absorbance spectra suggests that the fluorescence quenching mechanism involves absorption competitive quenching (ACQ) and fluorescence resonance energy transfer (FRET). NS‐CDs showed satisfactory recoveries in the detection of TNP and 4‐NP in real water samples. Addtionally, NS‐CDs enabled visual identification of TNP and 4‐NP through a color change in a test paper model. This work demonstrates that nitrogen and sulfur co‐doping is an effective strategy for preparing sensitive fluorescent chemosensors based on carbon dots.