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There is considerable interest in the pH-dependent switchable biocatalytic properties of cerium oxide nanoparticles (CeNPs) in biomedicine, where these materials exhibit beneficial antioxidant activity against reactive oxygen species at neutral and basic physiological pH but cytotoxic prooxidant activity at acidic pathological pH. Oxygen vacancies play a key role in such biocatalytic activities. While the general characteristics of the role of oxygen vacancies are known, the mechanism of their action at the atomic scale under different pH conditions has yet to be elucidated. The present work applies density functional theory (DFT) calculations to interpret the pH-induced behavior of the stable {111} surface of CeO2 at the atomic scale. Analysis of the surface-adsorbed media species reveals the critical role of pH on the reversibility of the Ce3+ and Ce4+ redox equilibria and the formation and annihilation of the oxygen vacancies. Under acidic conditions, this reversible switching is hindered owing to incomplete volumetric filling of the oxygen vacancies by the oxygen in the water molecules, hence effective retention of the oxygen vacancies, and consequent inhibition of redox biomimetic reactions. Under neutral and basic conditions, the capacity for this reversible switching is preserved due to complete filling of the oxygen vacancies by the OH ions owing to their ready size accommodation, thereby retaining the capacity for performing redox biomimetic reactions cyclically.
There is considerable interest in the pH-dependent, switchable, biocatalytic properties of cerium oxide (CeO2) nanoparticles (CeNPs) in biomedicine, where these materials exhibit beneficial antioxidant activity against reactive oxygen species (ROS) a
It has been demonstrated in previous experimental and computational work that doping CeO2 with transition metals is an effective way of tuning its properties. However, each previous study on CeO2 doping has been limited to a single or a few dopants.
Oxygen vacancy formation energy is an important quantity for enabling fast oxygen diffusion and oxygen catalysis in technologies like solid oxide fuel cells. Both previous literature in various systems and our calculations in LaMnO3, La0.75Sr0.25MnO3
We use first-principles calculations to investigate the stability of bi-axially strained textit{Pnma} perovskite CaMnO$_3$ towards the formation of oxygen vacancies. Our motivation is provided by promising indications that novel material properties c
The iron(III) center in ferroelectric PbTiO3 together with an oxygen vacancy forms a charged defect associate, oriented along the crystallographic c-axis. Its microscopic structure has been analyzed in detail comparing results from a semi-empirical N