Boron and nitrogen co-doped carbon dots as the dual functional fluorescent probe for Fe3+ and pH detection

Carbon dots doped with boron and nitrogen atoms (B, N-CDs) were designed and prepared by hydrothermal strategy using citric acid, urea and borax as raw materials. The structure and optical properties of B, N-CDs were characterized by various characterization technologies. The results showed that the B, N-CDs exhibited good mono-dispersion, excellent fluorescence stability, and high fluorescence intensity (quantum yield up to 32 %). A dual-functional Fe3+ and pH detection platform based on B, N-CDs was constructed. The Fe3+ sensing method based on B, N-CDs fluorescence quenching showed an excellent linear relationship between 0.044–70 μM (R2 = 0.994), with a detection limit as low as 0.044 μM. Then, this detection method was successfully applied to the high-accuracy detection of Fe3+ in water samples and iron supplement tablets. The study of the quenching mechanism showed that the fluorescence of B, N-CDs was quenched by Fe3+ in two ways: static quenching and dynamic quenching. Moreover, B, N-CDs can also be used as a pH fluorescence sensor in the ranges of pH 2.0–4.8 and 5.2–7.6. The developed sensing system based on B, N-CDs has high selectivity and sensitivity for the detection of Fe3+, and a wide detection range for pH.