Fig. 4 XPS spectra of (a) Co 2p for
Co3O4 QDs/ZCS and CoP/ZCS; (b) Zn 2p for
ZCS, CoP/ZCS, Co3O4 QDs/ZCS and
Co3O4 QDs/ZCS/CoP; (c) Cd 3d for ZCS,
CoP/ZCS, Co3O4 QDs/ZCS and
Co3O4 QDs/ZCS/CoP; (e) S 2p for ZCS,
CoP/ZCS, Co3O4 QDs/ZCS and
Co3O4 QDs/ZCS/CoP.