Surface Modification of Titanium Dioxide Thin Films and their Applications

Abstract

A low temperature and economical method i.e. sol-gel method has been adopted to prepare TiO2 sol. After the formation of TiO2 sol, thin films of TiO2 were prepared on the glass substrate by dip coating method. These films were formed both undoped and doped forms. The films were exposed in air plasma for varying time intervals to alter their surface properties. We observed a remarkable variation in the hydrophilic, optical and Photocatalytic properties of undoped and doped TiO2films after plasma treatment. The films coated on the surface of glass substrate when exposed to air plasma exhibited significant change in contact angle, which is basically a representative of wetting property. We found that the contact angle for deionized water and ethylene glycol reduced to considerable limits 3.02o and 1.85o from its initial value 54.40oand 48.82o, respectively. The variation in the hydrophilic property of films depends upon the dangling bonds and nanometer scale surface roughness created after plasma treatment. The variation in the surface roughness was estimated with the help of atomic force microscopy (AFM), which occurred from 4.6nm to 19.8nmwith the plasma exposure time. Further, the variation in the values of contact angle and surface roughness with increasing plasma exposure time reveal that not only the surface roughness but the dangling bonds also contribute to the hydrophilic property of surface modified TiO2 film. Based upon nanometer scale surface roughness and dangling bonds, a variation in the surface energy of TiO2 film was estimated which was found to increase from49.38 to 88.92mJ/m2. In order to investigate the variation in the surface chemistry, X-ray photoelectron spectroscopy (XPS) studies were carried out. These results show that there was an increase in the intensity of Ti2p and O1s, and a decrease in the intensity of C1s.