Nanocomposites and nanomaterials

Enhancing hydroxyl radicals scavenging properties of CeO2-x nanocrysrtals by annealing, size reduction, pre-irradiation and doping
Pavel Maksimchuk, Kateryna Hubenko, Ganna Grygorova, Vladyslav Seminko, Svetlana Yefimova
Yu.V. Malyukin Department of Nanostructured Materials, Institute for Scintillation Materials National Academy of Sciences of Ukraine, 60 Nauky Ave., Kharkiv-61072, Ukraine 
E-mail: pavel.maksimchuk@gmail.com

Hydroxyl radicals (∙OH) are usually considered as the most dangerous type of reactive oxygen species formed inside the living cells that leads to increasing demand for antioxidant nanomaterials able to effective ∙OH elimination. Nanoceria (CeO2-x) has recommended itself as the one of the most potent ∙OH scavengers due to high content of Ce3+ ions and easy Ce3+↔Ce4+ switching making possible effective redox cycling. 
In the paper the direct connection between Ce3+ content and ∙OH scavenging ability is shown. The dependence of ∙OH scavenging properties on the content of Ce3+ ions in nanoceria was confirmed by the simultaneous study of luminescence spectra and nanoceria - ∙OH interaction processes. High temperature annealing, size reduction, doping of nanoceria by non-isovalent ions (Y3+) or by ions with smaller ionic radius (Zr4+) leads to increase of both Ce3+ content and antioxidant activity of nanoparticles. The same increase of ∙OH scavenging ability is observed at pre-irradiation of nanoceria (λ = 325 nm) which is accompanied by transfer of the part of Ce4+ ions to Ce3+ ones. The observed effects are caused by formation of additional oxygen vacancies at high temperature annealing, size reduction, doping or pre-irradiation providing increase in the number of sites (Ce3+-Vo-Ce3+ or Ce3+-Vo-Re3+) for ∙OH scavenging.
Remarkable ∙OH scavenging properties and reversible redox characteristics make Y3+- and Zr4+-doped and pre-irradiated ceria nanocrystals the potent materials for ∙OH scavenging in living cells.