Modulating the Catalytic Activity of Cerium Oxide Nanoparticles with the Anion of the Precursor Salt

In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by the presence of counterions. We first employed various precursor cerium(III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, and sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•2– from reduction of NO3– in CNPs synthesized from Ce(III) nitrate). Physicochemical properties of these CNPs, e.g., dispersion stability, hydrodynamic size, signature surface chemistry, superoxide dismutase (SOD)-mimetic activity, and oxidation potentials, were found to be significantly affected by the anions of the precursor salts. CNPs synthesized from Ce(III) nitrate and Ce(III) chloride exhibited higher extent of SOD-mimetic activities. Therefore, these CNPs were studied extensively employing in situ ultraviolet (UV)–visible spectroe...