Nanoceria: factors affecting its pro- and anti-oxidant properties

Abstract

Nanoceria redox properties are affected by particle size, particle shape, surface chemistry, and other factors, such as additives that coat the surface, local pH, and ligands that can participate in redox reactions. Each CeO 2 crystal facet has a different chemistry, surface energy, and surface reactivity. Unlike nanoceria's industrial catalytic applications, biological and environment exposures are characterized by high water activity values and relatively high oxygen activity values. Electrochemical data show that oxygen levels, pH, and redox species affect its phase equilibria for solution and dissolution. However, not much is known about how the many and varied redox ligands in environmental and biological systems might affect nanoceria's redox behaviour, the effects of coated surfaces on redox rates and mechanisms, and whether the ceria solid phase undergoes dissolution at physiologically relevant pH and oxygen levels.Research that could answer these questions would improve our understanding of the links between nanoceria's redox performance and its morphology and environmental conditions in the local milieu.(111) FACE Dissociative water adsorption creates two types of hydroxyl on this face, Ce 1 -OH (sitting on top of a cerium atom) and Ce 3 -OH (sitting on top of the intersection of three co-shows the crystal facets investigated, the method, and the typical conditions considered. Several research groups have studied water adsorption 89-94 and hydroxyl stability 95 on nanoceria. Table 4. Computational studies of nanoceria. QCMD = quantum chemical molecular dynamics; DFT = density functional theory; SRPES = synchrotron radiation photoelectron spectroscopy. Condition Crystal facets Method Ref. Low water activity CO adsorption (110), slab

The yin: an adverse health perspective of nanoceria: uptake, distribution, accumulation, and mechanisms of its toxicity

“…To address if there are changes in the Ce 3+ /Ce 4+ ratio 43, 44 , electron energy loss spectrometry (EELS) of the surface of a 5 nm ceria was determined. It showed Ce 3+ enrichment, which was not changed after the nanoceria was in the vasculature of the rat’s brain for 20 h 16 .…”

Catalytic properties and biomedical applications of cerium oxide nanoparticles

“…The discussion of surface chemistry and material science in this review is also tied closely with another review in this special issue that asks broader questions about ceria and it uses in various applications 11 . A third closely related review discusses more of the nanoparticle aspects of cerium oxide that also relates to the catalytic nature of nanoceria that is presented in this work 12 . Since these works were developed in parallel, extensive cross-referencing is made difficult and thus the reader is encouraged to seek out information in all the reviews of this special issue on nanoceria.…”

Ceria Nanoparticles as Enzyme Mimetics

“…In a pervious review, Grulke and co-workers [80] listed several parameters, which could influence the oxidant properties of nanoceria. Another group [81] also disscussed some physicochemical changes of nanoceria in different environmental conditions.…”

“…[80,81] Nevertheless, nanoceria catalysts are generally considered to be more stable than the nature enzymes. Previous studies demonstrated that nanoceria possessed enzyme-like catalytic activity and were stable over a wide range of pH values and temperatures compared with natural enzyme horseradish peroxidase.…”

“…[91] The toxicological outcomes of nanoceria depend not only on the surface chemistry of nanoceria, but also on the local milieu. [21,80,92] Therefore, more studies are needed to understand the toxicologically relevant chemical/biological processes at the nano/bio interface. [93][94][95] More importantly, experimental and theoretical studies are both needed to fully understand the detailed catalytic mechanisms of nanoceria.…”