Hydrophilicity and photocatalytic activity of self-cleaning porous TiO2 thin films on glass

The porous TiO2 thin films deposited on glass surface were prepared from alkoxide solutions containing polyethylene glycol(PEG) by a dip-coating technique, The effects of PEG addition to the precursor solution on the photocatalytic activity and hydrophilicity of the resultant thin films were studied, The larger the amount of PEG, the larger the adsorbed hydroxyl content in the as-prepared porous thin films, the better the hydrophilicity. The contact angle between water and the porous TiO2 thin films declines to zero, The glass with porous TiO2 thin films possesses self-cleaning function and is easily washed. However, the transmittance of the glass with porous TiO2 thin films decreases due to the enhancement of light scattering of the larger pores(400 nm), The photocatalytic degradation experiments show that methyl orange aqueous solution was efficiently decolorized in the presence of the porous TiO2 thin films by illumination with a 125 W high pressure mercury lamp. The photocatalytic activity of the TiO2 thin films is obviously enhanced by the PEG addition to the precursor solutions. On the other hand, when the amount of PEG reaches 2.0 g, the photocatalytic activity will drop.