In situ synthesis of S-doped coal-based carbon quantum dots and its application to Cr⁶⁺ detection

BACKGROUND: Coal-based carbon quantum dots have better stability compared with other carbon quantum dots prepared from small molecules as carbon sources. Elemental doping can effectively improve the fluorescence performance of carbon quantum dots. However, the electronegativity difference between sulfur and carbon is small and the charge transfer between the two is very weak, so it is very difficult to dope sulfur onto carbon quantum dots by chemical methods. High sulfur content coal can achieve in situ synthesis of sulfur-containing carbon quantum dots. RESULTS: The results showed that the prepared quantum dots had good stability and which increased with the increase of coal rank. CQDS is well dispersed, with an average particle size between 2.44 and 2.74 nm. It can emit light blue fluorescence under the UV excitation of 365 nm. It was found that trace amount of Cr6+ had a fluorescence quenching effect on CQDS and a good linear relationship was observed in the range of 0-100 mu mol center dot L-1. CONCLUSION: Quantum dots doped with S atoms have better selectivity, interference resistance, and sensitivity in the detection of metal ions. The stability and the particle size of CQDS are increased with the coal rank. The quantum yield of CQDS prepared from high sulfur content coal is higher than low sulfur content coal which has same rank. The addition of Cr6+ to CQDS produces a dynamic fluorescence quenching. This study provides a new idea for the green preparation of coal-based carbon quantum dots and the ion detection. (c) 2023 Society of Chemical Industry.