Fluorinated Eu-doped SnO₂ nanostructures with simultaneous phase and shape control and improved photoluminescence

Fluorinated Eu-doped SnO₂ nanostructures with tunable morphology (shuttle-like and ring-like) are prepared by a hydrothermal method, using NaF as the morphology controlling agent. X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy are used to characterize their phase, shape, lattice structure, composition, and element distribution. The data suggest that Eu³⁺ ions are uniformly embedded into SnO₂ nanocrystallites either through substitution of Sn ⁴⁺ ions or through formation of Eu-F bonds, allowing for high-level Eu³⁺ doping. Photoluminescence features such as transition intensity ratios and Stark splitting indicate diverse localization of Eu³⁺ ions in the SnO₂ nanoparticles, either in the crystalline lattice or in the grain boundaries. Due to formation of Eu-F and Sn-F bonds, the fluorinated surface of SnO₂ nanocrystallites efficiently inhibits the hydroxyl quenching effect, which accounts for their improved photoluminescence intensity.