To further confirm valence state of copper from the ZnO/Cu2O
CSNCs, XPS analysis was used. Fig. 1b presents the photoelectron
spectrum of Cu. Corrected with reference to C1s (284.9 eV), the
peak at 931.8 eV is corresponding to the binding energy of Cu 2p3/
2, the other peak at 951.5 eV is corresponding to Cu 2p1/2 signal.
There was no peak between the Cu 2p3/2 peak and Cu 2p1/2 peak.
These results indicate that Cu species in composites is the copper(I)
species [14].