The reversible wetting transition between superhydrophilicity and superhydrophobicity of tremella-like CuxO@CuxS nanosheets prepared by one-step anodization and the application of on-demand oil/water separation

A simple one-step anodizing process is developed for the large-scale preparation of the tremella-like CuxO@CuxS nanosheet films on Cu mesh, and the prepared organic-free CuxO@CuxS nanosheet films on Cu mesh exhibit excellent mechanical stability and corrosion resistance. The fresh organic-free tremella-like CuxO@CuxS nanosheets have the superhydrophilicity and underwater superoleophobicity. But after storage in atmosphere for about 6 days under room temperature, the wettability is gradually transformed into superhydrophobicity and superlipophilicity. Importantly, the wettability can turn back again to the superhydrophilicity and underwater superoleophobicity after the annealing process at 200 degrees C in air environment. So the stable reversible wetting transition is realized, then the transition mechanism has been investigated by the detailed X-ray photoelectron spectroscopy (XPS) characterization, and is mainly attributed to the production of hydroxide radicals and adsorption of C-C/C-H species on the CuxO@CuxS nanosheet surface. Lastly, the prepared tremella-like CuxO@CuxS nanosheets on copper mesh have been successfully applied for on-demand oil/water separation with high efficiency. (c) 2021 Elsevier B.V. All rights reserved.