EAGER: Enhancing the Radical Scavenging Activity of Oxide Nanoparticles Beyond the Current Limits - an Unconventional Solution Through Multidisciplinary Science

The capability of nanoceria (CeO2) to scavenge free radicals is strongly related to the exposed particle surfaces and considerably constrained by the limited number of oxygen vacancies on the surface. The relatively immobile bulk vacancies in the particle core do not contribute to the observed redox activity and scavenging capacity of pure and doped-ceria nanoparticles. Novel scientific concept: We hypothesize that the surface activity of oxide nanoparticles can be enhanced by the participation of mobile bulk vacancies, which can allow for the continuous regeneration of surface oxygen vacancies. The oxygen ion diffusion in BaCeO3 with an open perovskite-type structure is more than 4 orders of magnitude higher than that in the closely-packed structure of CeO2. The correlation between the bulk ion mobility and the surface activities of oxide nanoparticles can be tested by exploring the scavenging efficiency of the highly ion-conducting BaCeO3 nanoparticles compared to the poor ion-conducting CeO2 nanoparticles. Nanoceria: Limited concentration of oxygen vacancies on the surface. No contribution from immobile bulk vacancies. Barium cerate nanoparticles: Enhanced scavenging capacity by the participation of mobile bulk vacancies. Continuous regeneration of surface oxygen vacancies. Ionic condcutivity: Higher lattice oxygen mobility of barium cerate. The proposed new concept will create a new paradigm for the emerging applications of oxide nanoparticles: (i) Real time selective biosensors: This novel scientific concept, through discovery of more active nanoparticles, will enable real-time monitoring of free radicals in live biological systems. Real time biosensors are being considered for medical applications to protect normal cells against the radiation damage, to preserve the health of the nervous system, and to inhibit inflammatory diseases. Furthermore, perovskite-type structures often exhibit very high proton uptake and proton conductivity and are expected to show selectivity in sensing hydroxyl and non-hydroxyl radicals. (ii) Nanoengineering photosynthesis: This novel scientific concept will enable long-term and stable photosynthesis functionality of biomimetic materials for solar harvesting and biochemical sensing. Cerium oxide nanoparticles are recently shown to enhance the photosynthetic activity of extracted plant chloroplast by trapping the reactive oxygen species before they damage the photosynthetic machinery. More effective nanoparticles with enhanced scavenging of photogenerated reactive oxygen species will pave new ways to engineer plant functions in synthetic materials that grow and repair themselves. (iii) Membranes & fuel cell vehicles: This novel scientific concept will enable effective scavenging of polymer-degradation-inducing free radicals that lead to the degradation of polymeric electrolyte membranes and failure of proton-exchange-membrane fuel cells.