Matchstick-Like Cu₂S@Cu_<i>x</i>O Nanowire Film: Transition of Superhydrophilicity to Superhydrophobicity

We fabricated a matchstick-like Cu₂S@Cu_<i>x</i>O nanowire film on copper mesh by applying a Cu­(OH)₂ nanowires template-sacrificial method, which can transformed from superhydrophilic to superhydrophobic just after storage in air for a certain period without any further organic modification. The surface morphology, chemical composition and the wettability were investigated by Scanning Electron Microscopy (SEM), X-ray diffractometer (XRD), Raman, X-ray Photoelectron Microscopy (XPS), and contact angle measurement. Results showed that the change of surface chemical composition and the trapped air among the matchstick-like structures were the decisive factors for the wettability transition. Therefore, on-demand oil/water separation was achieved, which was performed by using the superhydrophilic–underwater superoleophobic mesh for separating light oil/water mixtures and the superhydrophobic one for separating heavy oil/water mixtures