Titania (anatase) thin films were consolidated and hardened via UV irradiation when acidic precursor sols were diluted with 1-, 2-, and 3-carbon aliphatic alcohols. Titania sols were adjusted to pH values of 1.4, 2.3, or 3.1 and subsequently diluted with various mole fractions (X ROH) of alcohol prior to film deposition. Re-esterification of the titania film surface was confirmed by transmission FTIR (Fourier transform infrared) spectroscopic characterization. In the dark (absence of UV), proton-catalyzed oxidation of the alkoxide functional groups produced a unique monodentate formic acid ligand. This further oxidized to bidentate bicarbonate and carbonate complexes. Given an equivalent fluence of UV light (20 J cm -2, 254 nm), films became harder with increased proton concentration and X ROH- UV light promoted formic acid and carbonate/bicarbonate removal by photocatalytic oxidation. The rate of loss of formic acid/ bicarbonate species following UV irradiation increased with increasing proton concentration. With respect to carbon chain length, film hardness was found to follow MeOH > EtOH > nPrOH for pH 1.4 and X ROH = 0.48.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry