The assignment of the XPS peaks of the CQDs/ZnO composite and commercial ZnO.
| Photocatalyst | Element | Peak (eV) | Surface group | Assignment |
|---|---|---|---|---|
| CQDs/ZnO composite | Zn 2p | 1044.42 | Zn | Zn (2p1/2) |
| 1021.30 | Zn | Zn (2p3/2) | ||
| O 1s | 530.34 | Zn–O | Oxygen bonded to zinc | |
| 531.81 | C–O | Oxygen singly bonded to CQDs | ||
| C 1s | 284.21 | C | Graphitic carbon | |
| 285.78 | C–O | Alcoholic or etheric structure in CQDs | ||
| 288.55 | C C | π-Electrons in aromatic ring of CQDs | ||
| Commercial ZnO | Zn 2p | 1044.16 | Zn | Zn (2p1/2) |
| 1021.08 | Zn | Zn (2p3/2) | ||
| O 1s | 529.61 | Zn–O | Oxygen bonded to zinc | |
| 531.31 | Zn–OH | Surface hydroxyl group of ZnO |