Tuning Growth Modes of Ceria-Based Nanocubes by a Hydrothermal Method

Abstract

We control two growth modes, Ostwald ripening (OR) and oriented attachment (OA), to yield ceria nanocubes by a simple hydrothermal method, using an oleate modified precursor. Using a Ce(III) salt as an initial material, the OA mode is highly activated to form ceria nanocubes with well-developed (002) facets (ca. 8 nm), while OA growth is not allowed so that smaller nanocubes (ca. 5 nm) were formed if Ce(IV) salt is used for the synthesis. A combination analysis by X-ray photoelectron spectroscopy and Fourier transform IR indicates that the surface of ceria nanocubes synthesized with Ce(III) precursor have surface valence (Ce3+) sites coordinating with oleate through bidentate bonding. We propose that the difference in Ce3+ from the grain interior (Ce4+) provides the high surface energy needed to activate the OA growth mode. The luminescence spectra of ceria nanocubes grown by OA rather resemble those of a microcrystalline sample, suggesting the presence of a nonstoichiometric ceria phase, such as Ce2O3, a...