Influence of laser modification of TiO2 films for its photocatalytic properties

The photocatalytic activity of TiO2 layer modified by laser radiation is discussed in the paper. Commercially available nanopowder P25(Degussa) was used, which consists of a mixture of anatase and rutile - two crystallographic forms of TiO2. The spin-coating technique was applied to produce thin layers on glass. After drying and calcination the layer was thermally modified using a pulsed (6 ns) Nd:YAG laser (FHG 266 nm). This caused a clearly visible surface darkening effect. The XRD spectra show that phase change transition (from anatase to rutile) took place partially. This was also confirmed by Raman spectra. The main peak of Raman-spectra shifts from 142,84 to 145,22 cm(-1), probably due to decreasing size of TiO2 nanoparticles or more probably due to a defects generation in nanocrystallite structure. Defects have been reported in the literature as surface oxygen depletion and generation valance states Ti3+ and Ti4+. Eventually, kinetics of methylene-blue decay and CO2 to methane conversion were examined. In both cases an increase of catalytic activity was observed.