Cerium dioxide nanoparticles exhibit antioxidant properties by neutralizing free radicals and ROS [1]. In the process of laser ablation, it is possible to obtain cerium dioxide nanoparticles with surface structural defects that determine their antioxidant properties [2]. However, since the ablation method produces particles in a wide size range, it is of interest to separate nanodispersed solutions of ablated cerium dioxide particles into narrow-sized groups to study the dependence of the antioxidant properties of nanoparticles on their sizes.

Seven samples of nanodispersed aqueous solutions of cerium dioxide particles with different average sizes were obtained by sequential centrifugation. The average sizes of homogeneous spheres of ablated cerium dioxide nanoparticles in solutions were determined using SAXS. The efficiency of their antioxidant properties in the process of photocatalytic degradation of methylene blue in the presence of TiO₂ photocatalyst particles was determined using spectrophotometry.

For the solution samples, the average size of the homogeneous sphere varied from 30±0.5 nm to 41±0.5 nm. The results of the experiments showed that the samples with the smallest sizes exhibit pronounced antioxidant properties. This is due to the high concentration of structural defects on the surface of the nanoparticles and the large area of their specific surface. With an increase in the particle size, antioxidant activity was also observed, but to a lesser extent, which is due to the high crystallinity of the particles and a decrease in the width of the forbidden zone.

Thus, in this work, the production of systems of nanodispersed solutions of ablated cerium dioxide nanoparticles with a narrow-size distribution, characterized by different average sizes, is demonstrated. The influence of the size factor on the antioxidant properties of ablated cerium dioxide nanoparticles in a photocatalytic reaction is studied.