Surface and photocatalytic properties of ZnO thin film prepared by sol–gel method

ZnO films were prepared on glass substrates by a sol–gel dip-coating technique. The films showed a polycrystalline phase without any preferable orientation. By decreasing the withdrawal speed, the surface of the ZnO films became denser because of a decrease in particle sizes. This reduces the distance between the supported solids under the water droplet that could increase the degree of the pinning effects, and leads to increase the water contact angle. Furthermore, these prepared ZnO films showed photocatalytic properties indicating by photocatalytic degradation of methylene blue under a blacklight illumination. By increasing the calcination temperature, the water contact angle value decreases due to the grain coalescence which increases the gap between these supported solids. On the other hand, this enhances the photocatalytic activity caused by the improving of the crystallinity and the surface roughness of ZnO thin films with an increase in calcination temperature.

► The denseness of the films increased when the withdrawal speed decreased.
► Photocatalytic activity improved with increased surface roughness.
► Reducing of the degree of the pinning effect produced a lower water contact angle.