不同壳层厚度的LaF3：Eu3+/LaF3核壳结构纳米颗粒制备及发光性质

表面缺陷会使纳米材料的发光中心产生严重的猝灭，而适当厚度的同质包覆层会减少其猝灭。本文利用共沉淀法合成了LaF₃：Eu³⁺纳米颗粒和LaF₃：Eu³⁺/LaF₃核壳结构纳米颗粒，研究了颗粒的晶体结构、形貌以及不同壳层厚度对发光性能的影响。研究发现：LaF₃：Eu³⁺核心和LaF₃：Eu³⁺/LaF₃核壳结构均为六方结构。包覆同质壳层可以提高稀土离子的发光性能，包覆厚度的不同导致LaF₃：Eu³⁺/LaF₃核壳结构的荧光强度与衰减时间均发生改变。其原因是未掺杂的LaF₃壳层可以将发光中心Eu³⁺离子与LaF₃：Eu³⁺核心的表面隔离，进而减少表面对发光中心的猝灭，提高材料的发光性能。这种修饰作用与壳层厚度相关。

Synthesis and Luminescence Properties of LaF3：Eu3+/LaF3 Core/Shell Nanoparticles with Different Shell Thickness

Coating the nanoparticles with a homogeneous shell is a feasible strategy to reduce energy losses on the nanoparticle surface. Eu³⁺ doped hexagonal LaF₃ nanoparticles with a mean size of 7~8 nm were prepared by co-precipitation method. After coating the LaF₃:Eu³⁺ core particles with the undoped LaF₃, the enhancement of Eu³⁺ emission in LaF₃:Eu³⁺/LaF₃ core-shell nanoparticles was discovered. In comparison with the LaF₃:Eu³⁺ core, the luminescence lifetime of Eu³⁺ emission in core-shell nanoparticles was increased. The decay curves of LaF₃:Eu³⁺/LaF₃ core/shell nanoparticles with different thickness had also been studied. The increase of the luminescence lifetime of Eu³⁺ emission resulted from the effective shielding of the luminescence center Eu³⁺ ions from LaF₃:Eu³⁺ core, the quenching at or near the surface of the nanoparticles was reduced.