Faculty of Materials Science and Engineering , Kunming University of Science and Technology , Kunming , Yunnan Province 650093 , People's Republic of China.
Department of Chemical and Materials Engineering , New Mexico State University , Las Cruces , New Mexico 88003 , United States.
ACS Nano. 2018 Apr 24;12(4):3623-3628. doi: 10.1021/acsnano.8b00741. Epub 2018 Apr 9.
Core-shell structure is an obvious concept to suppress surface-related deactivations in lanthanide-doped upconversion nanoparticles (UCNPs). However, no direct observation of atomic-scale surface restoration, which can improve the upconversion photoluminescence, has been reported. Here, we use aberration-corrected high-angle annular dark field scanning transmission electron microscopy to study the surface condition of KLuF:Yb,Er bare core UCNPs. Due to the very thin and uniform thickness of the UCNPs, we observe unambiguously that the recovery from surface defects enhances upconversion photoluminescence. Furthermore, the realization of dominant green lasing emission under pulsed laser excitation confirms the high crystallinity of the UCNPs.
核壳结构是抑制镧系掺杂上转换纳米粒子（UCNPs）表面相关失活的一个明显概念。然而，目前还没有直接观察到可以提高上转换荧光的原子尺度表面恢复的报道。在这里，我们使用了像差校正的高角度环形暗场扫描透射电子显微镜来研究 KLuF:Yb,Er 裸核 UCNPs 的表面状态。由于 UCNPs 的厚度非常薄且均匀，我们可以清楚地观察到表面缺陷的恢复增强了上转换荧光。此外，在脉冲激光激发下实现的主导绿光激光发射证实了 UCNPs 的高结晶度。
