(372d) Luminescent RE:A2B2O7 and Core@Shell RE:A2B2O7@A'B'O3 Nanoparticles

Many rare earth compounds have photoluminescent characteristics for various important applications. In this study, a series of Eu³⁺ doped lanthanum zirconate (La₂Zr₂O₇) nanoparticles (NPs, 20 ± 5 nm in diameter) with cubic fluorite structure were facilely synthesized by a kinetically modified molten salt synthetic (MSS) process and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and photoluminescence spectra (PL). Under the excitation of 405 nm, intense red emission with high color purity was observed in these Eu³⁺ doped La₂Zr₂O₇ NPs. Moreover, the as-prepared Eu:La₂Zr₂O₇ NPs possess high concentration quenching, which is as high as ~32.5 mol% of europium dopants in the La₂Zr₂O₇ host. The corresponding concentration quenching mechanism was discussed as well. Our results confirm that the kinetically modified MSS process is a promising approach for preparing rare earth (RE) ions doped A₂B₂O₇ nanoparticles with uniform RE doping and high concentration quenching. In the next step, these nanoparticles were coated with A'B'O₃ shell in the next. We explored the effect of different experimental processing parameters on the structure, morphology and luminescence properties of these core@shell nanoparticles. They were characterized mainly using power x-ray diffraction, transmission and scanning electron microscopes. More importantly, their photoluminescence was carefully studied. The core nanoparticles possess a cubic fluoride crystal structure and high concentration quenching, which is as high as ~10% of europium dopants in the La₂Zr₂O₇ host due to the even distribution of Eu³⁺ ion enabled by our facile synthetic process. Moreover, the (La_1-xEu_x)₂Zr₂O₇@YBO₃ nanoparticles shows much stronger photoluminescence than the (La_1-xEu_x)₂Zr₂O₇ nanoparticles under the same measurement conditions. These special properties allow these nanoparticles as excellent candidates for broad applications in various devices, such as lighting devices and radiation detectors.