Effect of CeO2 Nanoparticles on Hydroxyl Radicals in EPR Studies of the Photodegradation of Methylene Blue under Influence of Red Light

The antioxidant properties of cerium dioxide nanoparticles synthesized by the hydrothermal method are studied both by optical photometry and by EPR spectroscopy. It was found that with increasing intensity of irradiation of methylene blue with red light, the antioxidant activity of CeO2 nanoparticles improve. The greatest antioxidant activity is achieved at a concentration of CeO2 particles in solution from 5 mM to 10 mM. Increasing a concentration of CeO2 nanoparticles above 20 mM leads to deterioration in their antioxidant properties. It has been shown that in an alkaline medium the antioxidant activity of nanoparticles increases significantly, but with a decrease in pH to 3, CeO2 nanoparticles exhibit weak pro-oxidant properties due to more active generation of O2•− radicals.