Preparation of nitrogen-doped carbon quantum dots from chelating agent and used as fluorescent probes for accurate detection of ClO− and Cr(Ⅵ)

In this study, a novel ionic sensor based on nitrogen-doped carbon quantum dots (N-CQDs) was developed for sensitive detection of hypochlorite ions (ClO−) and dichromate ions (Cr(Ⅵ)) by fluorescence spectrometry. The N-CQDs was synthesized by hydrothermal method using Methyl Glycine Diacetic acid Trisodium Salt (MGDA) and Ethylenediamine (EDA) with bright blue fluorescence, high fluorescence quantum yield, abundant surface groups and good dispersion. The N-CQDs had a remarkable emission characteristic at 450 nm under the ultraviolet light of 350 nm, and the ClO− and Cr(Ⅵ) ions could quantificationally quench the fluorescence of this emission band. The results showed that N-CQDs had broad linear detection range and the detection limits of trace ClO− and Cr(Ⅵ) ions are 5.0 μM and 2.1 μM, respectively. Subsequently, further verify the reliability of this study and the N-CQDs played an excellent role in the ion detection of actual water samples. The quenching mechanism of ClO− is proved to be dominated by static quenching, while the quenching mechanism of Cr(Ⅵ) is mainly due to inner filter effect. This study is envisioned to efficiently prepare N-CQDs with novel raw materials, provide enlightening insights for enriching the detection of various trace ions by CQDs, and open up a new way to use fluorescence characteristics for water detection.