A study of factors that change the wettability of titania films

The effect of several pretreatment methods on the wettability of polycrystalline titania-coated glass (Pilkington Activ) and plain glass are investigated. UV/ozone, immersion in aqua regia, and heating (T > 500 degrees C) render both substrates superhydrophilic (i.e., water contact angle (CA) < 5 degrees). The dark recovery of the contact angles of these superhydrophilic substrates, monitored after treatment in either an evacuated or an ambient atmosphere, led to marked increases in CA. Ultrasound treatment of superhydrophilic Activ and glass samples produced only small increases in CA for both substrates, but rubbing the samples with a cloth produced much larger increases. The results of this study are discussed in the context of the current debate over the mechanism of the photo-induced superhydrophilic effect.