Preparation of Pink Emitting N,S-Co-Doped Carbon Dots and Application for Trace Water Detection and Fluorescent Ink

Nitrogen–sulfur co-doped pink fluorescent carbon dots (N,S-CDs) with uniform structure were successfully synthesized by the one-step solvothermal method using sulfosalicylic acid and [Formula: see text]-phenylenediamine as precursors and ethanol as solvent. Photophysical measurements indicated that N,S-CDs exhibited excitation independence and excellent optical stability, with the fluorescence quantum yield of 12.21% and the fluorescence lifetime of 7.07[Formula: see text]ns. The prepared N,S-CDs solution was estimated to be utilized as fluorescent ink for information encryption, and be used as a fluorescent sensor to detect trace water in organic solvents (anhydrous ethanol, DMF). Furthermore, broad linear detection ranges (0–10%), low limit of detection (e.g., 0.187% for ethanol, 0.179% for DMF) had been achieved with this method. Based on the UV–Vis absorption spectra and fluorescence lifetime evaluation, the proposed mechanism underlying the trace water detection capability of the synthesized carbon dots in organic solvents stems from the interplay between water and fluorophore molecules facilitated by dynamic quenching.