Researchers at Islamic Azad University (Tabriz Branch), Iran, noticed the key effect of different crystal structures, namely anatase and rutile, of titanium oxide nanoparticles on its pollutant degrading power while investigating photocatalytic activity of titanium oxide nanoparticles. Photocatalytic activity of semiconductor oxides is proved to encourage the degradation of both organic and inorganic pollutants.
Once a beam of light with appropriate wavelength hits the surface of semiconductor oxide, pairs of electron-hole are generated. In fact, the electron acts as an intensive reducing agent while the hole exhibits considerable oxidative properties.
Mohammad A. Behnejadi and his colleagues studied photocatalytic activity of commercial titanium dioxide nanoparticles of different sizes and crystalline shape in degrading a typical pollutant of textile industry.
The researchers first prepared commercial titanium dioxide nanoparticles in different sizes and crystalline shape and characterized them to analyze their morphologies and structures. Next, they tested the effectiveness of the prepared samples in degrading of pollutant compounds.
Results of this research underscored the important effect of crystalline size and structure on photocatalytic activity of the particles. In other words, by combining anatase and rutile phases of titanium oxide nanoparticles, the separation of electron from hole succeeds better and therefore the particles become more photocatalytically active.
In addition, the comparison between two commercial samples with approximately identical phase combinations but different sizes revealed that reduction in particle size would not cause any significant rise in catalytic activity.
For further information on this work, please consult the Journal of Environmental Science and Health Part A, volume 43, pages 460 to 467.