Ionic Radii and Concentration Dependency of RE³⁺ (Eu³⁺, Nd³⁺, Pr³⁺, and La³⁺)-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 Ce³⁺ active sites. In the present work, we report the impact of 5 mol % trivalent rare-earth-doped (RE³⁺ = Eu³⁺, Nd³⁺, Pr³⁺, and La³⁺) 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, La³⁺ 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 Kₘ = 0.217 and 0.261 mM, respectively, for 5 mol % La³⁺-doped CNPs. To divulge the role of dopant concentration on the structur…