A bright carbon-dot-based fluorescent probe for selective and sensitive detection of mercury ions

In this work, we demonstrated a convenient and green strategy for the synthesis of bright and water-soluble carbon dots (CDs) by carbonizing sodium citrate and glutathione together in a hydrothermal method for the first time. Without post surface modification, the as-synthesized CDs display fluorescence quantum yield (QY) as high as 21.03% and show superior stability not only in concentrated salt solutions but also in neutral and alkaline media. The probe exhibits selective and sensitive recognition capability towards mercury ion (Hg²⁺) in aqueous solution. The fluorescence of CDs can be quenched by Hg²⁺ through an effective electron energy transfer process. It displays a linear quenching effect toward mercury ion in the concentration range of 0-15μM with a correlation coefficient (R²) of 0.99. The limit of detection is determined to be 25nM at the signal to noise ratio of 3. These attractive merits would enable the extensive applications of this probe in environmental science and analytical chemistry in the future.