Green-emitting carbon quantum dots as efficient fluorescent probes for Cu2+ and EDTA detection by “turn-on-off” strategy

Copper is essential for human body because it plays an important role in various physiological processes, so the sensitive detection of Cu 2+ ions is a vital topic in human health and environment safe. In this work, green-emitting carbon quantum dots (CQDs) facilely synthesized by a microwave-assisted hydrothermal method were used as fluorescent probes for Cu 2+ detection. The CQDs showed a rapid and sensitive response to Cu 2+ with a color change and brightened fluorescence. The fluorescence enhancement of CQDs reaches 4.51-fold by 5 μM Cu 2+ as a typical “turn-on” strategy. A good linear relation of the fluorescence enhancement by Cu 2+ appears in a range of 0.1–1 μM Cu 2+ with a limit of detection (LOD) of 2.46 nM. Then, the enhanced fluorescence of Cu 2+ -CQDs could be rapidly decreased by EDTA via a quenching response (“turn-off”). A linear range of the fluorescence decrease and EDTA concentration is 1–10 μM with a LOD of 0.19 μM. The interference experiments for the detections of both Cu 2+ and EDTA show a high selectivity. The practical detections of both Cu 2+ and EDTA in actual water samples and spiked samples demonstrated good reproducibility and effective recovery rates. In addition, the Cu 2+ -CQDs even had a slow “turn-off” response to histidine over 20 natural amino acids. Overall, the CQDs-based “turn-on-off” detection methods with high sensitivity and selectivity in this work can be considered a promising new choice for the fluorescence analysis of Cu 2+ and EDTA.