Abstract
In this work, a simple one-step thermal oxidation process was established to achieve a significant surface increase in {110} and {111} nanofacets on well-defined, pure and Pr-doped, ceria nanocubes. More importantly, without changing most of the bulk properties, this treatment leads to a remarkable boost of their enzymatic activities: from the oxidant (oxidase-like) to antioxidant (hydroxyl radical scavenging) as well as the paraoxon degradation (phosphatase-like) activities. Such performance improvement might be due to the thermally generated sawtoothlike {111} nanofacets and defects, which facilitate the oxygen mobility and the formation of oxygen vacancies on the surface. Finally, possible mechanisms of nanoceria as artificial enzymes have been proposed in this manuscript. Considering the potential application of ceria as artificial enzymes, this thermal treatment may enable the future design of highly efficient nanozymes without changing the bulk composition.
Highlights
Natural enzymes play a crucial role in catalyzing almost all biochemical reactions in biological systems
Since the pioneering studies by Seal et al and Perez et al on nanoceria’s functions as artificial enzymes, more investigations have been focused on tuning its enzymelike kinetics and performance.[9,13−17] Previous studies indicate that ceria with controlled morphologies presents outstanding properties, different from those of conventional ceria particles.[9,18,19]
Knowing the importance in catalysis of crystal defects on edges and corners of nanoparticles, this study provides us an easy tool in order to control nanofacets of ceria nanocubes with a view to manipulating their enzymatic activities
Summary
Natural enzymes play a crucial role in catalyzing almost all biochemical reactions in biological systems Their catalytic efficiency is extraordinary in terms of selectivity, yield, and reaction rate. Because of their restraint in denaturation conditions, stability and cost, for a long time people have been intending to find a substitution of enzymes using inorganic materials, that is, artificial enzymes.[1] Recent developments in nanomaterial synthesis and characterization have triggered many scientists to study them as artificial enzymes.[1−3] A number of nanomaterials, such as CeO2,4 Au,[5] Fe3O4,6,7 carbon nanotubes,[8] etc., have demonstrated multienzyme-mimic functions of oxidase,[9] peroxidase,[8] superoxide dismutase, and phosphatase.[10,11] Previous studies have shown that the enzymelike activities depend on the size, morphology, composition, and surface coating of nanomaterials, and their activities can be tuned by controlling these parameters.[1,2,12]. Doping ceria with other elements, such as other lanthanides or aliovalent cationic metal dopants, can enhance the redox properties of ceria due to an increase in the concentration of oxygen vacancies and oxygen mobility in ceria.[18,21,22] In particular, Pr can greatly improve the oxygen storage capacity of ceria because of its redox Pr3+/Pr4+ couple.[21,23,24]
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