UV-driven reversible switching of a roselike vanadium oxide film between superhydrophobicity and superhydrophilicity

We report the fabrication of a roselike nanostructured vanadium oxide (V₂O₅) film with photoinduced surface wettability switching by carrying out the drop-casting of a suspension of V₂O₅ particles synthesized with the sol-gel method. Although a pure V₂O₅ film is slightly hydrophilic, the addition of alkylamine renders the nanostructured V₂O₅ film superhydrophobic owing to the intercalation of alkyl chains between the V₂O₅ layers. UV exposure switches the wettability of the V₂O₅ surface to superhydrophilic with a water contact angle of almost 0°, and storage in the dark reconverts the irradiated surface back to its initial superhydrophobic state. This extraordinary wetting transition is ascribed to the cooperation between the photosensitivity of V₂O₅ and the surface roughness of its nanostructure, which has submicron- to micron-scale apertures. Our approach provides not only the possibility of producing large homogeneous or patterned surfaces with tunable wettability, but also potential uses in catalysts, electrodes, switchable smart devices, etc., in various fields for future industrial applications.