Controlled hydrothermal synthesis of triangular CeO2 nanosheets and their formation mechanism and optical properties

Triangular nanosheets have been successfully synthesized via controlling the morphology of CeCO3OH precursors by a facile hydrothermal technique. The reaction temperature, reaction time and the amount of ethylenediamine were systematically investigated. XRD, TG-DSC, FTIR, SEM, TEM, XPS, Raman scattering, UV-vis and Photoluminescence (PL) spectra were employed to characterize the samples. The results showed that the triangular CeO2 nanosheets owned a fluorite cubic structure and mesocrystal structure, the bundle-like structures gradually transform into nanosheets with the increase of the reaction time, and the number of sides of nanosheets decreases with the increase of reaction temperature. The possible formation mechanism related to a defect driven dissolution-recrystallization was proposed, which might afford some guidance for the synthesis of other sheet-like nanostructures. It is also found that there is a red-shifting in the band gap of the material compared to bulk one, which is mainly attributed to the influences of the Ce3+ ions, oxygen vacancies and the change of morphology. The triangular nanosheets and bundle-like structures exhibited similar emission peaks of room temperature photoluminescence and the emission intensity increases with the increase of the concentration of oxygen vacancies. (C) 2016 Elsevier B.V. All rights reserved.