Carbon dots as rapid assays for detection of mercury(II) ions based on turn-off mode and breast milk.

In this research, nitrogen co-doped carbon dots were synthesized by solid thermal method with citric acid used as the precursor of carbon, and melamine as nitrogen source. Such carbon dots show high quantum yield of 44%. Furthermore, the native fluorescence of CDs can be reduced by mercury(II), while other metals had no significant influence on fluorescence intensity. During the study, the optimal parameters were selected, such as pH or time for incubation with analyte. Under the optimal conditions, quenching effect caused by mercury ions was evaluated. It was observed that with increasing mercury concentration, the fluorescence of the carbon dots decreased proportionally. The response was characterized by linearity within the range from 2 to 14 μM. Moreover, the limit of detection was 0.44 μM. It was the first time that human milk was used as a real sample to test the applicability of carbon dots. The study results demonstrated good recovery in the 74-111% range (RSD < 6%) As a novel carbon material, CDs show promise for broader applications in analyzing complicated biological samples.