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。

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.