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Effect of iron-group ions on the UV absorption of TiO2
1Kernazhitsky L., 1Shymanovska V., 1Naumov V., 2Chernyak V., 3Khalyavka T., 4Kshnyakin V.

1Institute of Physics of NAS, 46 Nauki Ave., 03650 Kyiv, Ukraine, 
2Kiev National University, 2/5 Acad. Glushkov Ave., 03122 Kyiv, Ukraine
3Institute for Sorption and Endoecology Problems of NAS, 31 Naumov Ave., 03142 Kyiv, Ukraine
4Sumy State Pedagogical University, 87 Romenska St., 40007 Sumy, Ukraine

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The UV absorption spectra of polydisperse rutile (TiO2) doped by transition metal cations Cr3+, Cu2+, Co2+  and Fe2+ are investigated at room temperature. It is shown that the fundamental absorption edge of TiO2 is determined by the two mechanisms of electron transitions: one of them represents a direct forbidden transition and the other an indirect allowed one. The fundamental band gap for the pure rutile is determined to be (delta)E = 3.013 eV. The absorption of Fe-doped TiO2 reveals spectral redistribution near the fundamental edge, while the absorption of Co-doped TiO2 is strictly similar to that of the pure rutile. Photocatalytic decomposition of organic safranine by means of TiO2 is also studied. It is found that the pure TiO2 has higher photocatalytic activity in comparison with the doped compounds. We suppose that the impregnation cations act as traps at the initial stage of reaction but their function changes to that of recombination centres as the photocatalytic process develops.

Keywords: titanium dioxide (rutile), transition metal cations, UV absorption spectroscopy, fundamental band gap, photocatalytic activity

PACS: 61.72.Uj, 71.55.Eq, 78.40.Fy, 82.30.Lp
UDC : 535.341
Ukr. J. Phys. Opt. 9197-207 
doi: 10.3116/16091833/9/3/197/2008
Received: 06.05.2008
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