Titanium dioxide nanoparticles heavily doped with niobium: A light-induced electron paramagnetic resonance study

Light-induced electron paramagnetic resonance (EPR) spectra of titanium dioxide nanoparticles heavily doped with niobium(v) are studied. At low temperatures, the EPR signal caused by interband illumination is associated with paramagnetic Ti³⁺ sites in anatase, which, as the temperature rises above 210 K, are discharged to the non-paramagnetic Ti⁴⁺ state due to the escape of trapped photoelectrons and their recombination with holes. The temperature dependence of the integral EPR signal has a non-Curie character, especially in the temperature range where the discharge of Ti³⁺ centers is already significant.