Reversible superhydrophilicity and hydrophobicity switching of V2O5 thin films deposited by magnetron sputtering

Highlights: • As-deposited V₂O₅ thin films are superhydrophilic. • Such V₂O₅ thin films turned into hydrophobic after days' of storage in air. • This change can be recovered by heating. • The main factor causing this change is proven to be air absorption. V₂O₅ thin films are well-known "smart" materials due to their reversible wettability under UV irradiation and dark storage. Their surfaces are usually hydrophobic and turn into hydrophilic under UV irradiation. However, the V₂O₅ thin films deposited by magnetron sputtering in present work are superhydrophilic and turned into hydrophobic after days' of storage in air. This change can be recovered by heating. The effects of many factors including surface roughness, irradiation from visible light, UV, & X-ray, and storage in air & vacuum on the reversible switching of wettability were investigated. The results show that air absorption is the main factor causing the film surface change from superhydrophilicity to hydrophobicity.