UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study
The photoinduced processes of pristine and Mg2+-doped anatase nanopowders with the exposed {0 0 1} facets synthesized by a solvothermal method, using HF as the capping agent, were investigated by EPR spectroscopy. The adsorbed fluoride ions on the {0 0 1} facets of the as-prepared anatase samples ha...
| Main Authors: | , , , , |
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| Format: | Journal Article |
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Academic Press
2015
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| Online Access: | http://hdl.handle.net/20.500.11937/50875 |
| _version_ | 1848758557433921536 |
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| author | Barbieriková, Z. Dvoranová, D. Sofianou, Maria Trapalis, C. Brezová, V. |
| author_facet | Barbieriková, Z. Dvoranová, D. Sofianou, Maria Trapalis, C. Brezová, V. |
| author_sort | Barbieriková, Z. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The photoinduced processes of pristine and Mg2+-doped anatase nanopowders with the exposed {0 0 1} facets synthesized by a solvothermal method, using HF as the capping agent, were investigated by EPR spectroscopy. The adsorbed fluoride ions on the {0 0 1} facets of the as-prepared anatase samples have been removed by NaOH washing (washed samples) or calcination at 600 °C (calcined samples). EPR spectra monitored at 100 K for the as-prepared and washed anatase nanopowders characterized with high percentage of the exposed {0 0 1} facets, evidenced the presence of paramagnetic signals attributed to the intrinsic Ti3+ centers with narrow-line axially symmetric spectrum (g⊥ = 1.988, g∥ = 1.956) and holes (O−) characterized with g-tensor g⊥ = 2.006, g∥ = 2.003 already before exposure. Upon in situ UV exposure under air, the intensity of EPR signals of Ti3+ and O− increased significantly and two additional signals compatible with the photogenerated O2− and O2H were observed. A series of indirect EPR techniques, e.g., spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO), hindered amine oxidation, or reduction of radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate), were applied to follow the reactions in the irradiated TiO2 dispersions. While in the irradiated aerated aqueous media all anatase samples revealed the generation of DMPO-OH spin-adduct, upon UV exposure of the as-prepared samples in deaerated acetonitrile, the formation of a unique EPR spectrum attributed to DMPO-F was found. The DMPO-F spin-adduct is most probably produced by the inverted spin trapping mechanism via interaction of DMPO+ with the surface fluorides. |
| first_indexed | 2025-11-14T09:45:53Z |
| format | Journal Article |
| id | curtin-20.500.11937-50875 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:45:53Z |
| publishDate | 2015 |
| publisher | Academic Press |
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| spelling | curtin-20.500.11937-508752017-09-28T04:34:28Z UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study Barbieriková, Z. Dvoranová, D. Sofianou, Maria Trapalis, C. Brezová, V. The photoinduced processes of pristine and Mg2+-doped anatase nanopowders with the exposed {0 0 1} facets synthesized by a solvothermal method, using HF as the capping agent, were investigated by EPR spectroscopy. The adsorbed fluoride ions on the {0 0 1} facets of the as-prepared anatase samples have been removed by NaOH washing (washed samples) or calcination at 600 °C (calcined samples). EPR spectra monitored at 100 K for the as-prepared and washed anatase nanopowders characterized with high percentage of the exposed {0 0 1} facets, evidenced the presence of paramagnetic signals attributed to the intrinsic Ti3+ centers with narrow-line axially symmetric spectrum (g⊥ = 1.988, g∥ = 1.956) and holes (O−) characterized with g-tensor g⊥ = 2.006, g∥ = 2.003 already before exposure. Upon in situ UV exposure under air, the intensity of EPR signals of Ti3+ and O− increased significantly and two additional signals compatible with the photogenerated O2− and O2H were observed. A series of indirect EPR techniques, e.g., spin trapping using 5,5-dimethyl-1-pyrroline N-oxide (DMPO), hindered amine oxidation, or reduction of radical cation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate), were applied to follow the reactions in the irradiated TiO2 dispersions. While in the irradiated aerated aqueous media all anatase samples revealed the generation of DMPO-OH spin-adduct, upon UV exposure of the as-prepared samples in deaerated acetonitrile, the formation of a unique EPR spectrum attributed to DMPO-F was found. The DMPO-F spin-adduct is most probably produced by the inverted spin trapping mechanism via interaction of DMPO+ with the surface fluorides. 2015 Journal Article http://hdl.handle.net/20.500.11937/50875 10.1016/j.jcat.2015.08.009 Academic Press restricted |
| spellingShingle | Barbieriková, Z. Dvoranová, D. Sofianou, Maria Trapalis, C. Brezová, V. UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title | UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title_full | UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title_fullStr | UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title_full_unstemmed | UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title_short | UV-induced reactions of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: An EPR study |
| title_sort | uv-induced reactions of mg2+-doped anatase nanocrystals with exposed {0 0 1} facets: an epr study |
| url | http://hdl.handle.net/20.500.11937/50875 |