On-line monitoring of laser modification of titanium dioxide using optical surface second harmonic

TiO2 photocatalysis is a promising technology for the destruction of organic pollutants in both waste and potable waters with the mineralisation of a wide range of compounds having been reported. TiO2 has many advantages over other semiconductors, it is highly photoreactive, cheap, non-toxic, chemically and biologically inert, and photostable. The photocatalytic activity of TiO2 has been shown to depend upon many criteria including the ratio of anatase/rutile crystal phase, particle size and oxidation state. This paper reports the use of optical surface second harmonic generation (SSHG) to monitor modifications in TiO2 powder induced following laser treatment. SSHG is a non-contact, non-destructive technique, which is highly sensitive to both surface chemical and physical changes. Results show that three different SSH intensities were observable as the TiO2 samples were irradiated with the laser light. These regions were related to changes in chemical characteristics and particle size of the TiO2 powder.