Table 3.
Recent advances in the preparation of CDs, their corresponding properties, and Cu2+ ion sensing performance
| Precursors | Synthesis route | QY (%) | Linear range | LOD | References |
|---|---|---|---|---|---|
| Chemical precursor | |||||
| Citric acid, urea | Solvothermal | 39–43 | 1–10 µM | 40 nM | [139] |
| Ionic liquids | Microwave-assisted pyrolysis | 10.23–25.8 | – | 5 nM | [148] |
| Glucose and PEG-200 | Microwave-assisted pyrolysis | – | 2.0x10−12–1.5x10−9 mol mL−1 | 5.8x10−13 mol | [149] |
| o-phenylenediamine | Hydrothermal | 2 | 2–80 nM | 1.8 nM | [145] |
| Uric acid, phenylboronic acid | Hydrothermal | – | 0.0033–80 µM | 1.5 nM | [150] |
| Chitosan hydrogel | Microwave-assisted pyrolysis | – | – | 0.5 μM | [151] |
| Aminophenylboronic acid | Thermal combustion | 1.6 | 1–25 µM | 0.3 µM | [152] |
| Ethylenediaminetetraacetic acid | Hydrothermal | – | 0–0.4 µM | 3.47 nM | [144] |
| Citric acid, l-cysteine, dextrin | Microwave-assisted pyrolysis | 22 | 0–30 µM | 20 nM | [138] |
| Green precursors | |||||
| Petroleum coke | Ultrasonic-assisted chemical oxidation | 9.8 | 0.25–10 µM | 0.0295 µM | [153] |
| Prawn shells | Hydrothermal | 9 | - 5 µM | 5 nM | [140] |
| Vegetables | Hydrothermal | 37.5 | 0–100 nM | 9.98 nM | [154] |
| Pear juice | Hydrothermal | – | 0.1 to 50.0 mg L−1 | 0.1 mg L−1 | [141] |
| Waste polyolefins residue | Hydrothermal | 4.84 | 1–8 µM | 6.33 nM | [142] |
| Bamboo leaves | Hydrothermal | 7.1 | 0.333 to 66.6 µM | 115 nM | [143] |