V. K. Klochkov

Spectroscopic Properties of Nanoceria Allowing Visualization of Its Antioxidant Action

Two distinct luminescence centers were revealed in ceria nanocrystals: first one – Ce3+ ions with 5d-4f luminescence at 390 nm, and second one – Ce4+–O2− complexes showing charge transfer (CT) luminescence at 630 nm. Intensity of Ce3+ luminescence depends directly on the concentration of oxygen vacancies in nanoceria and can be varied by means of change of both heat treatment atmosphere from oxidizing to reducing and the size of nanocrystal. Ce3+ luminescence can be used for visualization of the processes of interaction between ceria nanoparticles and reactive oxygen species using relative intensity of Ce3+ band as a measure of Ce4+/Ce3+ ratio during oxidation reaction.

Cerium Dioxide CeO2-x and Orthovanadate (Gd0.9Eu0.1VO4) Nanoparticles for Protection of Living Body from X-Ray Induced Damage

The effectiveness of CeO2−x and GdEuVO4 nanoparticles in radioprotection in model animals during radiation exposure has been shown. Nanoparticles were injected per os by two different schemes – once and during 15 days. For the 15-days scheme of GdEuVO4 nanoparticles injection during 30 days of observation the survival of animals irradiated with a dose of 6.0 Gy was 100 %; for ceria it was 90 % for ceria. It was revealed that 7.0 Gy radiation dose is lethal. These results can serve as a motivation to consider inorganic nanoparticles as the basis for new drugs possessing by radioprotective effect.

Energy migration processes in phosphate nanocrystals: Size and dimensionality dependence

Peculiarities of electronic excitation energy migration in phosphate nanocrystals with three-dimensional (EuPO4) and one-dimensional (EuP3O9) arrangement of regular ions under variation of concentration of both energy traps (Nd3+ ions) and scattering centres (La3+ ions) are discussed in the paper. Processes of energy migration in both EuPO4 and EuP3O9 nanocrystals are phonon-assisted ones due to absence of resonance between energy levels of adjacent Eu3+ ions. The distance of energy migration for both EuPO4 and EuP3O9 nanocrystals was found to be equal to tens of nanometres, however, for EuPO4 nanocrystals energy migration leads to stronger quenching of Eu3+ luminescence. For 10 nm EuPO4 nanocrystals sufficient hampering of energy migration is observed due to the depletion of the low-energy phonon spectrum as a result of the phonon confinement effect.

Radioprotective Effect of CeO2 and GdEuVO4 Nanoparticles in “In Vivo” Experiments

In experiments performed in vivo of the irradiation of rats, a strong radioprotective effect of nanoparticles based on orthovanadates of rare earth elements and cerium dioxide was found. The nanoparticles were injected per os by two different schemes - once and during 15 days. For the 15-days scheme of GdEuVO4 nanoparticles injection the survival of animals irradiated with a dose of 6.0 Gy was 100 % during 30 days of observation. Injection of CeO2 nanoparticles also effectively protects the bodies of rats from radiation. For an irradiation with the lethal dose of 7.0 Gy, the radioprotective effect of the nanoparticles is negligible.