Carbon dots-based fluorescent turn off/on sensor for highly selective and sensitive detection of Hg2+ and biothiols

In this work, sodium salicylate and ethylenediamine (EDA) are used as the precursors to synthesize green fluorescent carbon dots (CDs). The CDs have some attractive properties, including better oxidation resistance, good water solubility, and excellent stability in high ionic strength solutions in a pH range of 6.0–10.0. Compared to other metal ions , only Hg 2+ can quench the fluorescence of CDs, and with the introduction of biothiols, the fluorescence of the CDs/Hg 2+ system can be recovered. Therefore, a turn off/on fluorescent sensor is constructed using CDs as a fluorescent probe , and the sensor is applied to the detection of Hg 2+ and biothiols (glutathione, homocysteine and cysteine). In addition, the fluorescent sensor exhibits excellent selectivity and sensitivity. The linear range of Hg 2+ is 0.05–10 μM with the detection limit of 44 nM. Glutathione, homocysteine, and cysteine have a linear response in the range of 0.5–10 μM with the limit of detection of 80, 76, and 69 nM, respectively. Furthermore, the fluorescence method is successfully used to detect Hg 2+ in actual water samples and biothiols in human plasma.