A set of cerium dioxide nanoparticles (CeO2NPs) was synthesized by precipitation in water-alcohol solutions under conditions when the physical-chemical parameters of synthesized NPs were controlled by changing the ratio of the reaction components. The size of CeO2NPs is controlled largely by the dielectric constant of the reaction solution. An increase of the percentage of Ce3+ions at the surface was observed with a concomitant reduction of the NP sizes. All synthesized CeO2NPs possess relatively high positive values of zeta-potential (ζ > 40 mV) suggesting good stability in aqueous suspensions. Analysis of the valence- and size-dependent rate of hydrogen peroxide decomposition revealed that catalase/peroxidase-like activity of CeO2NPs is higher at a low percentage of Ce3+at the NP surface. In contrast, smaller CeO2NPs with a higher percentage of Ce3+at the NP surface display a higher oxidase-like activity.

Department of Solid State Chemistry 5 1 Vernadskii Institute of General and Inorganic Chemistry of the NAS of Ukraine 32 34 Palladina Ave Kyiv 03142 Ukraine

Department of Surface and Plasma Science Faculty of Mathematics and Physics Charles University 5 Holešovičkách 2 Prague 8 18000 Czech Republic

Institute of Experimental Physics Slovak Academy of Sciences Watsonova 47 Kosice 040 01 Slovakia

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