ИСТИНА

In recent years, semiconductor nanomaterials are all time in the center of attention of re-searchers. Their structural, electrophysical, and optoelectronic properties are being ac-tively studied. Such an increased interest in these objects is primarily due to their unique properties, which, first of all, include quantum-size and size effects. The latter manifests itself always when we move from bulk material to nanoparticle ensembles, and is expressed in a sharp increase in the specific surface area (several 100 m2 per gram of substance). The presence of such a huge specific surface makes nanomaterials a good model object for studying the fundamental laws of adsorption processes, the nature and properties of defects on the surface of nanocrystals and, moreover, opens up the prospect for new practical applications of nanostructured semiconductors. EPR spectroscopy is a generally recognized powerful method for studying semiconductor nanoparticles. We have proposed new, unique EPR-based methods for studying semiconductor nanomaterials: a method for the control of the generation of singlet oxygen and determining its concentration in ensembles of Si nanoparticles, which is based on a change in the relaxation times of spin centers; determination of the band structure of nanooxide semiconductors (energy level position of defect, band gap); detection of charge carrier separation and accumu-lation in nanoheterostructures. In this work we have studied TiO2 nanocrystals, TiO2 based nanoheterostructures (TiO2/MoO3, TiO2/WO3, TiO2/V2O5, TiO2/MoO3/V2O5) and TiO2 based microspheres (TiO2/MoO3, TiO2/WO3, TiO2/V2O5, TiO2/MoO3/V2O5) using our new EPR-based methods. Energy diagrams of the investigated oxides with energy level position in the band gap are proposed. We have revealed the effect of separation and accumulation of photoexcited electrons and holes in TiO2 based nanogeterostructures. These results can be useful for understanding the mechanism of photocatalytic reactions and further practical ap-plications of the TiO2 based nanomaterials.