Reversible switching of nanostructured cobalt hydroxide films from superhydrophobic to superhydrophilic state

摘要

Superhydrophobic cobalt hydroxide films with flower-like micro-nano structure prepared by chemical-bath deposition undergo a change in wettability from superhydrophobic to superhydrophilic state either by immersion in ethyl acetate or by heat treatment at 200°C and above. The superhydrophobicity of the film can be regained by immersion in an ethanolic solution of stearic acid. The superhydrophobicity is attributed to the combined effect of micro-nano binary surface morphology and the low surface energy of the self-assembled monolayer of stearic acid. It is proposed that switching from superhydrophobicity to superhydrophilicity is caused by removal of the adsorbed layer of stearic acid by solvent or heat treatment.