Ionic Radii and Concentration Dependency of RE 3+ (Eu 3+ , Nd 3+ , Pr 3+ , and La 3+ )-Doped Cerium Oxide Nanoparticles for Enhanced Multienzyme-Mimetic and Hydroxyl Radical Scavenging Activity

The antioxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce 3+ active sites. In the present work, we report the impact of 5 mol % trivalent rare-earth-doped (RE 3+ = Eu 3+, Nd 3+, Pr 3+, and La 3+ ) CNPs on the oxidation state modulation and antioxidant property with respect to ionic radii. An increase in the lattice parameter, strain, and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNPs, La 3+ with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase, and hydroxyl radical (HO • ) scavenging activities. The kinetic parameters for the peroxidase and oxidase activities were found to be superior with K m = 0.217 and 0.261 mM, respectively, for 5 mol % La 3+ -doped CNPs. To divulge the role of dopant concentration on…