Peculiar surface–interface properties of nanocrystalline ceria–cobalt oxides were evidenced by X-ray diffraction, transmission electron microscopy and X-ray absorption spectroscopy. It was found that cobalt foreign cations modify the surface oxygen vacancies of ceria at the atomic level, inducing the exposure of well-defined reactive faces between the ceria-host and the cobalt oxide interface. These modifications of the surface–interface structure promoted a remarkable increase in the oxygen storage capacity of ceria nanocrystals.

In this study, we explore a new strategy to tailor the growth process of monodisperse nanocrystals. By means of X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, and X-ray absorption spectroscopy, it is found that the growth of ceria followed Ostwald ripening, and polydispersed ceria nanocrystals were obtained in a hydrothermal condition. With the addition of cobalt to the growing ceria nanocrystals, cobalt acted as a surface dopant and preferred to bind on the surface of large-sized ceria nanocrystals via Co–O–Ce bonds. The binding could modulate the Ostwald ripening process and narrow the size distribution. With the competition between cobalt dopants and Ce monomers onto the surface of nanocrystals, monodisperse cobalt-doped nanocrystals were formed. This route is expected to be applicable to a variety of monodisperse doped nanocrystals.

Ceria (CeO2) nanocrystals have unique and highly attractive properties that depend on the morphology and structure. In this paper, we demonstrate that by controlling the addition of copper to growing ceria nanocrystals it is possible to modulate the resulting structure properties. We show also by means of X-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence spectrometry, and X-ray absorption spectroscopy that copper configuration affects both the morphology and the electronic structure of cerium oxide nanocrystals. Indeed, external and internal copper doping on ceria nanocrystals leads to structural transitions, including a morphological transition from cubic to truncated octahedron, along with cerium valence changes. The results of this study, optimizing the structural properties of such nanocrystals, may certainly trigger new opportunities and, ultimately, new applications.