Department of Physics, OSED Center, Xiamen University, 422-19 South Siming Road, Xiamen, Fujian, 361005, China.
Small. 2016 Apr;12(15):2092-8. doi: 10.1002/smll.201502934. Epub 2016 Mar 3.
Metallic nanostructures are often used to enhance photoluminescence of nanomaterials based on local field enhancement with plasmons at metal surfaces. Here upconversion luminescence (UCL) enhancement of submicrometer-size NaGd0.3 Yb0.7 F4 :Er particles in cap-like metal cavities, formed by deposition of a silver film on the particles dispersed on glass substrates, is studied. UCL of the particles is shown to be influenced by not only the plasmon-enhanced local field but also the cavity modes. By varying the cavity size and location of the particles in the cavities, fluctuant variations of the UCL enhancement and electronic depopulation rate are observed in experiments. Typically, a maximum of 12-fold enhancement of the UCL intensity is obtained. Combining the results with numerical simulations, the phenomenon is ascribed to effects of metal quenching, plasmonic field enhancement, and the cavity modes for the excitation and emission photons. Finally it is verified that, for the cap-like submicrometer metal cavities, allocating the particles at the open mouths of the cavities is more advantageous to obtaining stronger enhancements of the particles' UCL. And the demonstrated structure is also convenient to fabricate for applications, e.g., in solar cells.
金属纳米结构通常用于增强基于金属表面等离子体局域场增强的纳米材料的光致发光。本文研究了在玻璃衬底上分散的粒子上沉积银膜形成帽状金属腔后，亚微米尺寸的 NaGd0.3 Yb0.7 F4:Er 粒子的上转换发光（UCL）增强。结果表明，粒子的 UCL 不仅受到等离子体增强局域场的影响，还受到腔模的影响。通过改变腔的大小和粒子在腔中的位置，在实验中观察到 UCL 增强和电子去激发速率的波动变化。通常，UCL 强度最大可增强 12 倍。将实验结果与数值模拟相结合，该现象归因于金属猝灭、等离子体场增强以及激发和发射光子的腔模的影响。最后验证了对于帽状亚微米金属腔，将粒子分配在腔的开口处更有利于获得更强的粒子 UCL 增强。所展示的结构也便于制造，例如在太阳能电池中。
