Characterization of surface properties of titanium dioxide by inverse gas chromatography

The surface energy and acid/base constants of three kinds of titanium dioxide (TiO₂) were measured by inverse gas chromatography (IGC) to investigate the effect of organic treatment on the surface properties of TiO₂. The non-polar surface energy of the samples were calculated by using different molecular probes at different temperatures. The results indicate that non-polar surface energy $ \gamma\mathrm{_s^d} $of TiO₂ decreases with the increase of organic cladding amount at the same temperature (within the testing temperature range). As the temperature increases, $ \gamma\mathrm{_s^d} $of TiO₂ decreases. Meanwhile, the acid-base component of surface energy was studied by using polar molecules as probe molecules, revealing that the surface of titanium dioxide is amphoacid. Since the surface of TiO₂ presents acidic, the reaction between organic agents and the hydroxyl groups on the surface of TiO₂ leads to the decrease in the surface acid sites and thus the surface acidity of TiO₂. However, when excessive organic agent is added, some hydroxyl groups generated by organic agents hydrolyzation would not react with TiO₂, resulting in the increment of TiO₂ surface acidity.