Enhancement of upconversion emission of LaPO4:Er@Yb core-shell nanoparticles/nanorods
Enhancement of upconversion emission of LaPO4:Er@Yb core-shell nanoparticles/nanorods
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DOI：
10.1021/jp801978b
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发表时间：
2008-07-03
影响因子：
3.7
通讯作者：
Patra, Arnitava
中科院分区：
文献类型：
--
作者：
Ghosh, Pushpal;Oliva, Jorge;Patra, Arnitava
我们展示了通过溶液为基础的技术合成LaPO4:Er: yb掺杂的纳米颗粒/纳米棒和LaPO4:Er@Yb核壳纳米颗粒/纳米棒。提出并讨论了LaPO4: Er:Yb纳米棒/纳米颗粒形貌控制的机理。由于H-2(11/2) + S-4(3/2) -> I-4（15/2）和F-4(9/2) -> I-4（15/2）跃迁，分别观测到亮绿色（550 nm）和红色（670 nm）发射。掺杂纳米颗粒/纳米棒和核壳纳米颗粒/纳米棒在550 nm和670 nm发射波段的实验数据与斜率近似为2的直线拟合，证实了双光子吸收过程。掺杂LaPO4:Er: yb纳米粒子和LaPO4:Er@Yb核壳纳米粒子/纳米棒的上转换发射增强主要是由于表面相关效应的修饰。结果表明，随着纳米颗粒/纳米棒形状的改变，拉伸应变从+1.0%增加到+1.9%，而包覆纳米颗粒/纳米棒的晶格应变（压缩）发生逆转。值得一提的是，晶格应变随纳米晶体形状和表面涂层的变化而变化，上转换发射强度随拉伸晶格应变的减小而增大，随压缩应变的增大而增大。分析表明，晶格应变对稀土掺杂纳米晶体的上转换性能起着重要的作用。
We demonstrated the synthesis of LaPO4:Er:Yb-doped nanoparticles/nanorods and LaPO4:Er@Yb core-shell nanoparticles/nanorods by a solution-based technique. The mechanism related to morphology control of LaPO4: Er:Yb nanorods/nanoparticles is proposed and discussed. Bright-green (550 nm) and red (670 nm) emission were observed due to the transitions H-2(11/2) + S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2), respectively. The experimental data for 550- and 670-nm emission bands of doped nanoparticle/nanorod and core-shell nanoparticles/nanorods have been fit with a straight line with a slope of similar to 2, which confirms the two-photon absorption process. The enhancement of upconversion emission of LaPO4:Er:Yb-doped nanoparticles and LaPO4:Er@Yb core-shell nanoparticles/nanorods are mainly due to modifications of surface-related effects. It is found that the tensile strain increases from +1.0% to +1.9% with changing the shape from nanoparticle to nanorod and reversal of the lattice strain (compressive) is obtained for coated nanoparticle/nanorod. It is worth mentioning that the lattice strain varies with changing the shape and surface coating on nanocrystals and the upconversion emission intensity increases with decreasing the tensile lattice strain and it increases with increasing compressive strain. Analysis suggests that the lattice strain plays an important role in modification of the upconversion properties of the rare-earth-doped nanocrystals.