Shape-controlled synthesis and luminescent properties of CeO ₂:Sm³⁺ nanophosphors

CeO₂:Sm³⁺ nanophosphors were synthesized by hydrothermal treatments of aqueous solutions containing cerium nitrate, samarium nitrate, and sodium hydroxide. The shape of the nanocrystals was controlled simply by changing the hydrothermal treatment temperature. Nanorods of CeO ₂:Sm³⁺ were obtained at 100 °C, whereas highly crystalline nanocubes were formed at a higher temperature of 180 °C. Photoluminescent properties of the nanophosphors were greatly influenced by their shapes. The as-prepared nanocubes exhibited much stronger orange-red emissions from Sm³⁺ than the as-prepared nanorods. A high-temperature treatment of the nanorods at 700 °C did not significantly enhance the emission intensity. The different photoluminescent properties were then examined by FTIR and Raman spectroscopy. Results showed that oxygen defects were the major reason for the inferior properties of the nanorods even after the high-temperature treatment. In contrast, the CeO₂:Sm³⁺ nanocubes were shown to be excellent nanophosphors prepared at 180 °C without any further treatment. CeO₂:Sm³⁺ nanorods and nanocubes were selectively synthesized by hydrothermal treatments of aqueous solutions. The nanocubes exhibited much better photoluminescent properties than the nanorods, which can be explained by shape-induced structural defects.