Preparation And Luminescent Properties Of RE³⁺ Doped LaF₃ Nanoparticles

RE3+ doped inorganic–organic hybrid nanostructures have received much attention in recent years due to their strong luminescence sensitized by organic ligands via an energy transfer route. In this work, the preparation and photoluminescence properties of LaF3:Eu3+, LaF3:Tb3+ nanostructure phosphors and their inorganic–organic hybrid nanostructures were studied. The following three part results were obtained:(1)LaF3 nanoparticles were synthesized by a simple hydrothermal method and the process of Eu3+ doped LaF3 nanoparticles were used a new ion-exchange technique. After that, benzoic acid(BA) and 2-thenoyltrifluoroacetone(TTA) were selected as the sensitization attached to the LaF3:Eu3+ nanoparticles. XRD and TEM displays that as-prepared nanoparticles are pure hexagonal LaF3 nanoplates while dopant Eu3+ occupies a La3+ site with average width about 25-40 nm and thickness about 4-7 nm. FTIR spectra indicate that BA or TTA coordinate with LaF3:Eu3+ nanoparticles. The effect of Eu3+ doping concentrations on the luminescence properties of the LaF3:Eu3+ and organic(BA or TTA) capping concentrations on the luminescence properties of the LaF3:Eu3+ are described in Photoluminescence Spectrum(PL). The experiments indicate that luminescence intensity of BA or TTA capped LaF3:Eu3+ were enhanced dramatically due to energy transfer from the organic ligand. Finally, we talk about the schematic of energy transfer and the reason of luminescence enhancement.(2)Tb3+ doped LaF3(LaF3:Tb3+) is an important green light emitting material, but the low optical absorption cross-section of Tb3+ ions strongly limits its luminescence properties. In this work, we used an ion exchange method to prepare LaF3:Tb3+ based inorganic–organic hybrid nanostructures, which exhibited strong luminescence as aresult of luminescence sensitization, an energy transfer process from the organic ligands to the Tb3+ ions. The undoped LaF3 nanoparticles were first synthesized by a simple hydrothermal method, and Tb3+ ions were then ion exchanged into these LaF3 nanoparticles to form the LaF3:Tb3+ nanoparticles, which were then used to prepare the inorganic–organic hybrid nanostructures with benzoic acid. The LaF3:Tb3+ based inorganic–organic hybrid nanostructures had an emission intensity more than 44 times stronger than the as-prepared LaF3:Tb3+ nanoparticles. Dependence of their luminescence on the Tb3+ doping concentration and amount of organic ligands was studied in detail.(3) LaF3:Eu3+ nanoparticles were successfully synthesized by hydrothermal method and sensitized by benzoic acid(BA) and 2-thenoyltrifluoroacetone(TTA) together to form LaF3:Eu3+–BA–TTA inorganic-organic hybrid nanostructures. This hybrid nanostructures has realized stronger and especially broader e xcitation spectrum(200 nm- 420 nm) by energy transfer from organic ligands.