Superhydrophilicity to superhydrophobicity transition of CuO nanowire films

Abstract

The surface of CuO is known for its hydrophilicity and exhibits superhydrophilic nature as nanowires are present. When exposed in the air at room temperature or treated by low temperature annealing, however, transition from superhydrophilicity to superhydrophobicity of the CuO nanowire films are observed. Since the chemical structure of the films after treatment remains the same as CuO according to x-ray photoelectron spectroscopy spectra, the superhydrophobicity may be attributed to partial deoxidation of the upmost layer of CuO surfaces into Cu2O-like hydrophobic surfaces. Nonetheless, superhydrophilicity is recovered if the superhydrophobic CuO film is subject to high temperature annealing.

Wettability conversion of ultrafast laser structured copper surface

“…Chang et al 7 have studied the wettability transition of CuO nanowire films and found that when the hydrophobic CuO substrate was annealed in air at 350 C, the hydrophilicity was recovered. Several papers also confirmed that low temperature annealing could remove the surface modified monolayer.…”

“…Kietzig et al 8 proposed the decomposition of carbon dioxide into carbon with active magnetite which was created in the laser nanostructuring process as a potential explanation. However, there seems no well accepted theory to explain this behavior because this conversion existed widely in all kinds of metal oxides, including the oxides of Cu, 7 Fe, 8 Ni, 5 Ti, 9 and Zn. 10 In this paper, we aim to clarify the mechanism underlying the wettability transition of picosecond laser microstructured copper surface.…”

“…5,6 Several mechanisms have been proposed to explain this phenomenon. Chang et al 7 suggested that the wettability change of CuO nanowire films was attributed to the partial deoxidation of the upmost layer of CuO surfaces into Cu 2 O-like hydrophobic surfaces. Kietzig et al 8 proposed the decomposition of carbon dioxide into carbon with active magnetite which was created in the laser nanostructuring process as a potential explanation.…”

Facile approach in fabricating hybrid superhydrophobic fluorinated polymethylhydrosiloxane/TiO2 nanocomposite coatings

“…Recently, efforts have been made to fabricate multifunctional superhydrophobic surfaces based on semiconductor oxide materials such as ZnO [12,13], TiO 2 [14,15], and CuO [16,17]; many researchers have chosen TiO 2 to fabricate superhydrophobic surfaces due to their controllable structure, biocompatibility, and desirable stability. Aytug et al [18] fabricated superhydrophobic ceramic coatings by phaseseparated nanostructured composite TiO 2 -Cu 2 O thin films.…”

Facile fabrication of superhydrophobic surfaces with corrosion resistance by nanocomposite coating of TiO2 and polydimethylsiloxane

“…Recently, efforts have been made to fabricate multifunctional superhydrophobic surfaces based on semi-conductor oxide materials such as ZnO [16], Fe 2 O 3 [17], TiO 2 [18] and CuO [19]. TiO 2 nanostructures have become a focus of tremendous interest due to their unique physicochemical properties and good chemical stability related to applications including photocatalysis [20], anti-ultraviolet protection [21] and chemical sensor [22].…”