Aging of Nanoscale Cerium Oxide in a Peroxide Environment: Its Influence on the Redox, Surface, and Dispersion Character

Nanoscale cerium oxide has demonstrated sub-stantial utility in biomedical applications. Among the various synthetic approaches, particles formed from addition of hydrogen peroxide have shown a unique functional and physicochemical character, suggesting an implication of the synthesis method in particle performance (e.g., free radical scavenging activity and modulation of oxygen metabolism). In this study, we observe the influence of particle aging in an aqueous peroxide environment for up to 8 weeks and identify three distinct material life stages (cluster/complex aggregation, condensation/hydrolysis, and mature particle redispersion). Particles are seen to undergo initial partial hydrolysis, leading to sedimentation within 24 h. After aging up to 4 weeks, the particles undergo a spontaneous redispersal into suspension with peroxy-phases transformed to oxide/oxy-hydroxides and age to a stable final product within 6 to 8 weeks. Further, these life stages are correlated with pH changes, allowing the in situ monitoring of particle aging and the mapping of the particle physicochemical character (i.e., morphology, aggregation character, and colloid phase composition) onto a pH vs time relation. Colloidal phases formed during these stages are characterized and compared against the fully aged, bio-active particles.

Automated summary

This study investigates the aging process of nanoscale cerium oxide particles in an aqueous peroxide environment, identifying three distinct material life stages. As the particles age, their properties change, eventually leading to the formation of a stable final product.