Sulphur and nitrogen doped carbon dots synthesis by microwave assisted method as quantitative analytical nano-tool for mercury ion sensing

Quantum dots prepared from carbon precursors are a rising star among novel trends in the field of carbon materials. The subject of this paper is the synthesis of carbon dots that can serve as a sensor for determination of heavy metals such as mercury. Carbon dots were obtained in this study with a fast method of microwave synthesis and application of citric acid with glutathione or thiourea. Both versions of carbon dots have optical properties, i.e. fluorescence; however, when thiourea was used as a doping element precursor, the dots made better sensors as - due to quenching by mercury ions - the carbon dots synthesized from citric acid and thiourea have more significant optical effect than those made form citric acid and glutathione. As-synthesized carbon dots had relative quantum yield (QY) as 26% and the limit of quantification when these dots were used was 5.4 mu M. In order to test the sensor efficiency in real samples, river water and wastewater were used.