Shao Wei, Chen Guanying, Damasco Jossana, Wang Xianliang, Kachynski Aliaksandr, Ohulchanskyy Tymish Y, Yang Chunhui, Ågren Hans, Prasad Paras N
Opt Lett. 2014 Mar 15;39(6):1386-9. doi: 10.1364/OL.39.001386.
In this work, we report on efficient visible and near-IR upconversion emissions in colloidal hexagonal-phase core/shell NaYF4:Er(3+)/NaYF4 nanoparticles (∼38 nm) under IR laser excitation at 1523 nm. Varying amounts of Er(3+) dopants were introduced into the core NaYF4:Er(3+) nanoparticles, revealing an optimized Er(3+) concentration of 10% for the highest luminescent efficiency. An inert epitaxial shell layer of NaYF4 grown onto the core of the NaYF4:Er(3+) 10% nanoparticle increased its upconversion emission intensity fivefold due to suppression of surface-related quenching mechanisms, yielding the absolute upconversion efficiency to be as high as ∼3.9±0.3% under an excitation density of 18 W/cm(2). The dependence of the intensity of upconversion emission peaks on laser excitation density in the core/shell nanoparticle displayed "saturation effects" at low excitation density in the range of 1.5-18 W/cm(2), which again demonstrates high upconversion efficiency.
在本工作中，我们报道了在1523 nm红外激光激发下，胶体六方相核壳结构NaYF4:Er(3+)/NaYF4纳米颗粒（约38 nm）中高效的可见光和近红外上转换发射。将不同量的Er(3+)掺杂剂引入到核NaYF4:Er(3+)纳米颗粒中，结果表明，对于最高的发光效率，Er(3+)的优化浓度为10%。在10%的NaYF4:Er(3+)纳米颗粒的核上生长一层惰性外延NaYF4壳层，由于抑制了与表面相关的猝灭机制，其上转换发射强度提高了五倍，在18 W/cm(2)的激发密度下，绝对上转换效率高达约3.9±0.3%。核壳纳米颗粒中上转换发射峰强度对激光激发密度的依赖性在1.5 - 18 W/cm(2)的低激发密度范围内表现出“饱和效应”，这再次证明了高上转换效率。
