The alteration of the structural properties and photocatalytic activity of TiO2 following exposure to non-linear irradiation sources

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

“…Other workers have also reported the generation of Ti 3+ sites in TiO 2 samples on irradiation with short wavelength UV light, with the TiO 2 samples changing to a characteristic blue colour [17]. We have also confirmed the presence of Ti 3+ in our laser irradiated samples using ESR spectroscopy [2]. These species are formed following band gap excitation of the samples.…”

“…Since the SSH is sensitive to many parameters influencing the photocatalytic activity of TiO 2 (crystal structure, oxidation state, particle size), it has therefore been demonstrated to be a powerful tool for monitoring these changes when TiO 2 was exposed to laser irradiation. So far only the enhanced photocatalytic activity of heavily treated P25 has been reported [2,3]. It would be interesting to study the photocatalytic activity of the TiO 2 during the different stages of modifications.…”

“…These properties are usually determined using surface analysis methods such as XPS, XRD or TEM, which require significant sample preparation and must be operated under vacuum. Recently Lee et al reported a modification of crystal structure and oxidation state of TiO 2 powders, which also changed in colour from white to blue grey, following exposure to pulsed laser light [2,3]. Further work has shown that the laser induced alterations were dependent on the exposure parameters i.e.…”

Recent Overview of Solar Photocatalysis and Solar Photo-Fenton Processes for Wastewater Treatment

“…Mineralization of organic compounds (conversion to CO 2 and mineral acids) by the TiO 2 solar photocatalytic process depends directly on the synthesis method of the catalyst [121][122][123][124][125][126], type of doping materials [11,112,113,[117][118][119][120], annealing temperature [127][128][129][130][131], catalyst load [132][133][134][135], pollutant concentration [136][137][138][139], and pH of the aqueous solution [140][141][142]. There are other parameters like reaction temperature, reactor configuration (geometry), reactor material, air sparging in the reactor solution, and the solar radiation intensity (solar concentration ratio) [143] that are important too in the TiO 2 solar photocatalytic process.…”

“…Introduction of such energy levels in the band gap induces the red shift in the band gap transition and the visible light absorption through a charge transfer between a dopant and conduction band (or valence band) [112]. Nevertheless, these changes depend on the nature of dopants, synthesis methods, annealing process, dopant concentration, and dopant distribution [11,112,113,[117][118][119][120].…”