Photoinduced formation of reactive oxygen species in suspensions of titania mechanochemically synthesized from TiCl₄

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• 作者：Vlasta Brezová ; Peter Billik ; Zuzana Vrecková ; Gustav Plesch
• 关键词：Titanium dioxide ; Anatase ; Mechanochemical synthesis ; EPR spectroscopy ; Spin trapping ; Nitroxide radicals
• 刊名：Journal of Molecular Catalysis A: Chemical
• 出版年：2010
• 出版时间：15 July 2010
• 年：2010
• 卷：327
• 期：1-2
• 页码：101-109
• 全文大小：489 K

文摘

Titanium dioxide nanopowders were synthesized mechanochemically using TiCl₄ and (NH₄)₂CO₃ (series TC) or TiCl₄/(NH₄)₂CO₃ and Na₂SO₄–Na₂SO₄·10H₂O (series TCSM), as precursors and post-annealing in the temperature range 150–850 °C. Crystal structure and crystallite size of the titania nanomaterials were characterized by X-ray diffraction, and the optical properties of aqueous suspensions at various TiO₂ loadings were measured using UV/visible spectroscopy. The photoinduced activity was measured in situ by EPR spectroscopy applying a variety of experimental techniques (spin trapping, spin probes, 4-hydroxy-2,2,6,6-tetramethylpiperidine oxidation). In the series TC the presence of an NH₄Cl salt matrix, which was removed by decomposition to gaseous byproducts in the post-annealing process, leads to the formation of anatase nanocrystals with optimal size for high photoactivity (23–50 nm) at temperatures of 550 and 650 °C, and these titania samples are the most active in the photoinduced production of reactive oxygen species. The results found for TCSM series confirmed that the presence of a sulfate salt matrix (Na₂SO₄) during mechanochemical and annealing processes significantly hindered TiO₂ nanocrystallite growth, increased agglomerate formation in aqueous media and lowered the values of photonic efficiencies determined via paramagnetic species formation or termination.