The Effect of Solvent on the Phase of Titanium Dioxide Deposited by Aerosol-assisted CVD

Titanium (IV) isopropoxide (TTIP) in methanol, ethanol, hexane, dichloromethane, and isopropanol solvents is used to deposit titanium dioxide thin films on glass and steel substrates at 550?degrees C using aerosol-assisted (AA)CVD. X-ray diffraction (XRD), and Raman spectra of the as-deposited films show that using methanol as the carrier solvent produces exclusively rutile films on steel, and predominantly rutile on glass substrates, while the use of the other solvents produces exclusively anatase phase on the steel under the same conditions. TiO2 is also deposited by AACVD from a mixture of ethanol and methanol solvents. As little as 15% of methanol in ethanol produces rutile as the predominant phase. Using a dye-ink test, the titanium dioxide thin films produced with ethanol are shown to be more active photocatalysts than films produced with methanol. All the films show photo-induced superhydrophilicity but, surprisingly, films stored in the dark have a water contact angle above 100 degrees.