Self-cleaning properties of zirconium dioxide thin films

Here we focused on the fundamental study of self-cleaning properties of zirconium dioxide films, including photoinduced alteration of surface hydrophilicity, photocatalytic and photoinduced bactericidal activities. The accent was made on the factors influencing the photoinduced hydrophilic conversion such as surface acidity and spectral composition of light for the surface photoexcitation. The studies on photoinduced hydrophilic conversion of the ZrO2 thin film were carried out using the contact angle measurements and XPS method. The experimental data demonstrate the very different hydrophilic behavior of the hydrated surface depending on the spectral region of photoexcitation corresponding to intrinsic or extrinsic ZrO2 absorption. This is explained by the difference in the concentration of photoelectrons and photoholes which participate in the photo-induced surface processes. It is suggested that hole-trapping species such as surface hydroxyl groups and adsorbed water molecules play a crucial role in the photoinduced superhydrophilic transition. The effect of the electron-acceptor and electron-donor gas atmospheres on the aging of the surface superhydrophilicity is found to be in agreement with this conclusion. The photochemical activity of ZrO2 coatings was tested by photodegradation of stearic acid. The antibacterial properties are investigated against Escherichia coli. The ZrO2 thin films reveal self-cleaning properties and can be successfully used as biomedical or construction material.