Optimized preparation of nitrogen-doped carbon dots by response surface methodology and application in Cd2+ detection

The technical parameters of synthesizing N-doped carbon quantum dots (N-CQDs) from citric acid and tris(hydroxymethyl)aminomethane (Tris) were optimized using a Box-Behnken model of response surface methodology. Statistical analysis showed the quantum yield was significantly affected by reaction time and Tris weight. The optimal synthesis conditions were reaction temperature at 170 °C, reaction time of 4.50 h and Tris weight of 0.70 g, with the quantum yield up to 82.4%. The N-CQDs probe was further applied for Cd2+ detection. The fluorescence intensity and Cd2+ concentration were linearly related in the range of 20-300 µg·L−1 with a relation coefficient of 0.9956 and a detection limit of 20.69 µg·L−1.