Titanium dioxide nanoparticles, surface and volume doped with such elements as carbon or nitrogen, are active in mineralization of various pollutants under visible light illumination [1, 2]. During the last years, published experimental and theoretical results indicated that these dopants generate localized energy levels (surface states) just above the valence band from which visible light excitation becomes feasible [1, 2], and the C- or N-doped titania exhibits a weak light absorption starting at about 550-700 nm. Presence of elemental carbon and also carbonate in C-doped materials was indicated by X-ray photoelectron spectra (XPS) [3]. C-doped materials were investigated in more detail by the EPR technique, allowed us to detect and characterize the paramagnetic defects and their changes [4]. However, the question about intermediates and certain mechanisms of photooxidation in the presence of such systems is still not solved.
This paper reports recent results on visible light photocatalysis on C- and N-doped TiO2 in comparison with published data. XPS and X-band EPR studies of the surface- and bulk-doped samples at temperatures 5-300K were carried out both in dark and under illumination at different wavelengths; kinetic curves were recorded. The nature of defects, their dynamics under illumination and probable mechanisms of photooxidation will be discussed.

1. S. Sakthivel, H. Kisch, Angew. Chem., 115, 5057 (2003).
2. S. Sakthivel, H. Kisch, ChemPhysChem, 4, 487 (2003).
3. S. Sakthivel, M. Janczarek, H. Kisch, J. Phys. Chem. B, 108, 19384 (2004).
4. E. Konstantinova, A. Kokorin, S. Sakthivel, et al., CHIMIA, 2008 (accepted).