No description available.

In this thesis, we focused on understanding the synthesis of titanium dioxide (TiO2) films and nitrogen doped TiO2 films using an atmospheric pressure Dielectric Barrier Discharge (DBD). The first part of the work was dedicated to the deposition of TiO2 films by cold plasma DBD with titanium tetraisopropoxide as precursor in a single-step process at room temperature. The deposition rate was about 70 nm·min-1. The photocatalytic degradation rate for the degradation of methylene blue (MB) under ultra violet (UV) irradiation of the TiO2 film after annealing was close to a reference anatase TiO2 spin coated film. Moreover, the TiO2 films showed a good photocatalytic stability. The second part of the study focused on the optimization and the understanding of the effect of the plasma parameters (gas flow rate and power) on the morphology of the TiO2 films and on the investigation of the deposition mechanisms. The morphology of the film changed from granular to compact film by either increasing the total flow rate or decreasing the plasma power. In other words, adapting the energy density in the plasma allowed the control of the morphology of the TiO2 films. To our knowledge, it was the first time that the energy density parameters of the plasma were used to control the morphology of TiO2 films. The photocatalytic degradation rate for the degradation of MB under UV irradiation of the annealed TiO2 film turned out to be about 2 and 15 times higher than the one of the commercial TiO2 film and the as-deposited TiO2 films, respectively. In order to extend the light utilization to the visible light range, TiO2 films were doped with nitrogen using a room temperature argon/ammonia plasma discharge. XPS and SIMS results confirmed that the nitrogen has been incorporated in the TiO2 lattice mostly in Ti-N state. This was further confirmed by Raman spectroscopy and XRD. The plasma properties and the doping mechanism were studied by Optical Emission Spectroscopy. It is suggested that the NH radicals played a key role in the doping of TiO2. The concentration of nitrogen in the N-TiO2 coatings could be tuned by adapting the ratio of NH3 in the plasma or the plasma power. The band gap of our N-TiO2 coatings is lower than the one of undoped TiO2 coating. The photocatalytic degradation rate for N-TiO2 coating was more than 4 times higher than the one of the undoped TiO2 coating. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Diploma thesis Iron Functionalized Nanoparticles of Titanium Dioxide Lenka Volfová 2017, ABSTRACT Iron-functionalized TiO2 were obtained by hydrolysis of aqueous solutions of titanyl sulfate with addition of ferric nitrate with ammonium hydroxide and the reaction filtered and washed with hydrogen peroxide. The colloid solutions thus prepared were lyophilized and the products were subsequently annealed at three different temperatures of 650 řC, 800 řC and 950 řC. The prepared doped materials were characterized by powder X-ray diffractometry, electron microscopy, infrared spectroscopy, Mössbauer spectroscopy, UV/VIS spectroscopy, thermogravimetric analysis and differential thermal analysis, and measurement of the specific surface area. Photocatalytic activity was determined by measuring of the decomposition of kinetics of 4-chlorophenol in an aqueous solution in the ultraviolet and visible area. For comparison of activity in the UV area and in the visible area were used a previously prepared highly photoactive specimen and standard TiO2 from Kronos, respectively. Keywords: Doped titanium dioxide, nanostructure, X-ray diffraction, electron microscopy, Mössbauer spectroscopy, suppression of photoactivity