LaF3 and LaF3:Ln3+ (Ln = Eu, Tb) hierarchical microstructures: synthesis, characterization and photoluminescence

Without any templates or surfactants, large-scale 3D persimmon-shaped hierarchical LaF3 and LaF3:Ln3+ (Ln = Eu, Tb) have been synthesized via a simple hydrothermal route using organic tetrafluroborate complexes N(C4H9)4BF4 as the fluoride source. The phase and morphology of the products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The SEM and TEM results indicate the 3D persimmon-shaped hierarchical microstructures are constructed by numerous nanodisks with mean thickness of 50 nm. It is found that several factors, including the fluoride sources, molar ratio of reagents and the reaction time, play crucial roles in the formation of the multilayer stacked structures. Detailed studies indicate that the layer-by-layer self-assembly of nanodisks is responsible for the formation of 3D hierarchical structures. The possible mechanism of the crystal growth and assembled procedure are also proposed. Furthermore, the photoluminescent properties of LaF3:Ln3+ (Ln = Eu, Tb) are studied, which exhibit orange-red (Eu3+:5D0–7F1,2,3,4) and green (Tb3+, 5D4–7F3,4,5,6) emission, respectively.