Special Issue on Structure of Water at Interfaces and Its Control
Evaluation of Hydrophilic/Hydrophobic Properties and Wettability of Oxide Surfaces
2009 Volume 30 Issue 3 Pages 148-156
Details
2009 Volume 30 Issue 3 Pages 148-156
The interaction of H2O molecules with various oxide surfaces were investigated by using middle-infrared (MIR) and near-infrared (NIR) spectroscopies. The physicochemical properties of oxide surfaces such as hydrophilicity or hydrophobicity were then discussed from the viewpoint of the intermolecular hydrogen bonds in the H2O clusters. SiO2 surface showed hydrophobic property as compared to TiO2 or Al2O3 surfaces. However, smaller amount of H2O molecules on SiO2 surface can easily spread out to form H2O thin layer due to small contribution of intermolecular hydrogen bonds in the H2O clusters. As a result, such hydrophobic SiO2 surface shows high wettability. On the other hand, TiO2 or Al2O3 surfaces adsorbed large amounts of H2O and hydrocarbons because such polar molecules preferentially interact with such cationic (Ti4+ or Al3+) sites, showing both hydrophilic and oleophilic properties. However, larger amount of H2O molecules on the TiO2 or Al2O3 surfaces strongly interacted with each other to form aggregated bulky H2O clusters on the surfaces. As a result, such hydrophilic surfaces show low wettability.
