利用高温热分解法制备了LiLuF4∶Yb,Tm@LiGdF4核壳纳米晶。在980 nm激光激发下, 与未包覆的样品相比, LiLuF4∶Yb,Tm@LiGdF4核壳纳米晶的发光增强了15倍左右, 这主要是因为通过惰性壳层的包覆可以有效抑制表面猝灭效应。另外, 随着核中Yb3+离子的摩尔分数从20%增加到100%, 上转换发光强度逐渐增大, 最大增加了12.4倍左右。这主要是由于增加Yb3+离子的浓度可以增加纳米粒子对激发光的吸收和提高Yb3+到Tm3+的能量传递速率。所制备的LiYbF4∶2%Tm@LiGdF4核壳纳米晶的发光效率高达4%。

LiLuF4∶Yb,Tm@LiGdF4 core-shell nanoparticles were synthesized by high temperature thermal decomposition method. Under the excitation of980 nm near infrared (NIR) laser, the luminescence intensity of the core-shell nanoparticles can be enhanced by about 15 times in contrast to the pure LiLuF4 core. It is due to the passivating role of the inert-shell for protecting Tm3+ ions in the core from nonradiative decay caused by surface defects. The intensity of the UC emission of the nanocrystals increases (at most 12.4 times) as the mole fraction of Yb3+ ions increases from 20% to 100%, owing to the improvement of near-infrared absorption and energy-transfer from Yb3+ to Tm3+. LiYbF4∶2%Tm@LiGdF4 core-shell nanoparticles show a high absolute UC quantum yield of 4.0%.