Bifunctional Nitrogen and Fluorine Co-doped Carbon Dots as Fluorescence Probe for Silicon and Mercury by pH Switching

New nitrogen and fluorine co-doped carbon dots were synthesized and used as a dual function fluorescent probe for silicon and mercury ions. The size of CDs was 10 nm. At optimum conditions (pH = 13, λ_ex = 360 nm, and λ_em = 518 nm), the detection limit (DL) of silicon was 16.6 nM. Linear calibration was observed in the range of 0.8-35 µM. This fluorescence probe for silicon detection is presented for the first time and had the lowest detection limit in comparison with different previously reported techniques. In addition to the above property, these co-doped carbon dots had the second function as a fluorescence probe for mercury detection at pH = 8. The DL for mercury was 38 nM. The performance of this probe was also compared with other co-doped carbon dots. Excellent sensitivity and selectivity, simple method, low-cost materials, and applicability in real sample analysis are advantages of this dual function fluorescence probe.