Redox enzyme-mimicking activities of CeO nanostructures: Intrinsic influence of exposed facets.

CeO nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce/Ce ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO NPs. Herein, CeO nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce/Ce ratio and oxygen vacancy content on the surfaces of as-synthesized CeO nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO nanostructures are greatly dependent on their exposed facets. CeO nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes.