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Surface Properties of Titanium Dioxide

TIME:22-08-05    NUM:0

1. Super-hydrophilic surface

It is believed that the superhydrophilicity of TiO2 surface is due to the change of its surface structure under light conditions. Under ultraviolet light irradiation, electrons in the valence band of TiO2 are excited to the conduction band, electrons and holes migrate to the surface of TiO2, and electron-hole pairs are generated on the surface. The electrons react with Ti, and the holes react with the surface bridge oxygen ions, respectively forming Positive trivalent titanium ions and oxygen vacancies. At this time, the water in the air is dissociated and adsorbed in the oxygen vacancies to become chemically adsorbed water, and the chemically adsorbed water can further adsorb the water in the air to form a physical adsorption layer.

2. Surface hydroxyl

Compared with the metal oxides of other semiconductor semi-metal materials, the polarity of the Ti-O bond in TiO2 is larger, and the water adsorbed on the surface dissociates due to the polarization, and it is easy to form hydroxyl groups. Such surface hydroxyl groups can improve the performance of TiO2 as an adsorbent and various monomers, and provide convenience for surface modification.

3. Surface acidity and alkalinity

Al, Si, Zn and other oxides are often added to TiO2 during modification. Al or Si oxides have no obvious acidity and alkalinity when they exist alone, but when combined with TiO2, they show strong acidity and alkalinity, and solid superacid can be prepared.

4. Surface electrical properties

In a liquid (especially polar) medium, TiO2 particles will absorb opposite charges due to the surface charge and form a diffusion electric double layer, which increases the effective diameter of the particles. Repulsion, is conducive to the stability of the dispersion system. For example, the surface of TiO2 coated with Al2O3 has a positive charge, while the TiO2 treated with SiO2 has a negative charge.