Efficient detection of Cu²⁺ in wastewater by carbon quantum dots derived from natural deep eutectic solvents...

Heavy metal pollution has become an urgent environmental problem. However, the traditional heavy metal ions detection methods mostly need large precision instruments, which have disadvantages such as complex sample processing, long detection time and high cost. Carbon quantum dots (CQDs) are efficient to solve the problems of fewer active sites and poor selectivity. Natural deep eutectic solvents (NADESs), a green precursor with adjustable structure design, can purposefully modify the required functional groups on the surface of CQDs and make it possess better performance. In this study, NA-CQDs from NADESs using one-step solvothermal method were successfully synthesized. The results showed that the diameters of NA-CQDs range from 3 to 6 nm. The optical properties indicated that it has excellent optoelectronic properties, excitation-dependent and pH stability. It proved that the fluorescent intensity of Cu²⁺ was strongly quenched by the NA-CQDs compared to other metal ions and was linear in the range of 0.0001-50 μM. The mechanism of NA-CQDs synthesis and Cu²⁺ detection is also speculated. NA-CQDs have great potential in the detection of heavy metals in wastewater.