Luo Qi, Deng Xueshuang, Chen Wenhan, Guo Hai, Ou-Yang Wei, Chen Xiaohong, Huang Sumei
Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, School of Physics and Materials Science, East China Normal University, Shanghai 200062, P. R. China.
Department of Physics, Zhejiang Normal University, Jinhua, Zhejiang 321004, China.
J Nanosci Nanotechnol. 2018 Jul 1;18(7):5063-5073. doi: 10.1166/jnn.2018.15355.
We report a simple method for the fabrication of a three-layered plasmonic structure of silicon substrate-Au nanospheres-upconversion particles (UCNPs) that displays up to 101-fold fluorescence enhancement. Monodispersed pure hexagonal-phase NaYF4:Yb,Er core and NaYF4:Yb,Er@NaYF4 core@shell nanocrystals were prepared by a solvothermal method. Two dimensional (2D) assembled Au spheres were prepared on a Si substrate, and then, 2D arrays of UCNPs were deposited on the grown 2D monolayered Au spheres by a self-organizing process. The distance between plasmonic Au NPs and rare-earth (RE) core was finely adjusted by changing the undoped NaYF4 shell thickness. The UC emission enhancement shows a pronounced shell thickness dependence. For the non-plasmonic structured samples, a single peak in upconversion luminescence (UCL) enhancement was observed as the undoped NaYF4 shell thickness increases from 0 nm to 23.0 nm. In contrast, for the plasmonic structured samples, multi-oscillations in UCL enhancement were observed in the undoped NaYF4 shell thickness range of 0-23.0 nm, where the UCL enhancement factors of three bands (521 nm, 540 nm and 654 nm) are high up to 65, 101 and 61, respectively, at 19.6 nm-thick NaYF4 shell. The multi-oscillations in UCL enhancement in the plasmonic samples can be associated with plasmonic coupling between arrays of core-shell UCNPs with various sizes and the underlying 2D Au spheres. The related mechanisms of the UCL enhancements are discussed.
我们报道了一种制备硅基底-金纳米球-上转换粒子（UCNPs）三层等离子体结构的简单方法，该结构显示出高达101倍的荧光增强。通过溶剂热法制备了单分散的纯六方相NaYF4:Yb,Er核以及NaYF4:Yb,Er@NaYF4核壳纳米晶体。在硅基底上制备二维（2D）组装的金纳米球，然后通过自组装过程在生长的二维单层金纳米球上沉积UCNPs的二维阵列。通过改变未掺杂的NaYF4壳层厚度，可以精细调节等离子体金纳米粒子（NPs）与稀土（RE）核之间的距离。上转换（UC）发射增强表现出明显的壳层厚度依赖性。对于非等离子体结构的样品，随着未掺杂NaYF4壳层厚度从0 nm增加到23.0 nm，观察到上转换发光（UCL）增强中的一个单峰。相反，对于等离子体结构的样品，在未掺杂NaYF4壳层厚度为0 - 23.0 nm的范围内观察到UCL增强中的多次振荡，在19.6 nm厚的NaYF4壳层时，三个波段（521 nm、540 nm和654 nm）的UCL增强因子分别高达65、101和61。等离子体样品中UCL增强的多次振荡可能与具有不同尺寸的核壳UCNPs阵列与底层二维金纳米球之间的等离子体耦合有关。讨论了UCL增强的相关机制。
