Fluorescent Carbon Dots Derived From Soy Sauce for Picric Acid Detection and Cell Imaging

Picric acid (PA) is a powerful nitro-aromatic explosive that harms the environment and human health. Developing non-toxic and low-cost sensors for the rapid detection of PA is essential. An environment-friendly fluorescent probe for PA detection is designed based on carbon dots (CDs) directly separated from edible soy sauce by silica gel column chromatography. Neither organic reagents nor heating process was needed to prepare CDs. The obtained CDs exhibit bright blue fluorescence, good water solubility, and photostability. The fluorescent probe for PA was developed according to the CD's fluorescence can be significantly quenched via the inner filter effect between CDs and PA. The linear range was 0.2–24 µM with a limit of detection of 70 nM. This proposed method was successfully employed to detect PA in the real water samples with satisfactory recoveries between 98.0–104.0%. Moreover, the CDs were suitable for fluorescence imaging of HeLa cells owing to their low toxicity and good biocompatibility. Graphical Abstract