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 andwere used as label-free probes for Cu²⁺ detection in water. The detection of Cu²⁺ by CQD probesis related to a quenching of fluorescence by a photo induced electron transfer mechanism. The quenched fluorescence of the CQDs by Cu²⁺ can be recovered by adding ethylene diaminetetraacetic acid. The yellow-visual fluorescent CQD probes have a linear detection range from 0.25 to 10 μM, a detection limit of 0.029 5 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 inon-line detection.