Figure 4

XPS spectra of Cu₂S-mesh (a), core level Cu 2p (b), core level S 2p (c). C 1 s core level XPS spectrum of the freshly prepared superhydrophilic Cu₂S film (d), superhydrophobic Cu₂S film: stored in air for two days (e), superhydrophilic Cu₂S film: soaking in ethanol solution for 4 hours (f).