Yellow-visual fluorescent carbon quantum dots from petroleum coke for the efficient detection of Cu2+ ions

Yellow-visual fluorescent carbon quantum dots (CQDs) were prepared from petroleum coke by ultrasonic-assisted chemical oxidation and were used as label-free probes for Cu2+ detection in water. The detection of Cu2+ by CQD probes is related to a quenching of fluorescence by a photoinduced electron transfer mechanism. The quenched fluorescence of the CQDs by Cu2+ can be recovered by adding ethylene diamine tetraacetic acid. The yellow-visual fluorescent CQD probes have a linear detection range from 0.25 to 10 μM, a detection limit of 0.0295 μM, a response time of 3 s, and a superior sensitivity and selectivity for Cu2+ detection compared to other fluorescent probes. The CQDs are easy to prepare, economical, reusable, fast to respond and can be used in on-line detection.