Spectroscopic study on spontaneously grown silver@ultra-thin cerium oxide nanostructures

Abstract

Ag@CeO₂ nanostructures have been recently reported to show unique catalytic properties but synthetic methods for them are limited. This study investigates microstructural characteristics of Ag@CeO₂ nanowires and nanoparticles with a spontaneously-grown ultra-thin ceria shell (∼0.5 nm), which were synthesized on CeO₂ substrate without using oxide precursors. Elemental mapping and line scanning by electron energy loss spectroscopy (EELS) suggest that the Ce in the CeO₂ substrate dissolved in the molten silver nitrate salt and was repelled to the surface of the Ag nanostructures to form continuous oxide shells during the growth of Ag single-crystals. X-ray absorption near edge structure (XANES) spectra verify that the valence of the Ce ions in the oxide layer was between Ce³⁺ and Ce⁴⁺.