Zhao Fusheng, Arnob Md Masud Parvez, Zenasni Oussama, Li Jingting, Shih Wei-Chuan
Department of Electrical and Computer Engineering, University of Houston, 4800 Calhoun Road, Houston, TX 77204, USA.
Nanoscale Horiz. 2017 Sep 1;2(5):267-276. doi: 10.1039/c7nh00067g. Epub 2017 Jun 23.
We report the experimental observation and numerical modeling study of far-field plasmonic coupling (FFPC) in 2-dimensional polycrystalline plasmonic arrays consisting of "single crystalline" domains of a random size and orientation. Even though polycrystalline plasmonic arrays are routine products of low-cost nanosphere lithography (NSL), their FFPC behavior has not been well understood. Herein, FFPC observed from gold nanodisk (AuND) arrays fabricated using NSL appears, qualitatively, to be in keeping with that of highly regular nanoparticle arrays, where they induced cyclic modulations on the peak position and linewidth of the localized surface plasmon resonance (LSPR). Remarkable blue shifts as large as 1000 nm with nearly doubled linewidth were observed experimentally. Numerical modeling was systematically carried out and showed quantitative agreement with the experimental results. Using the modeling approach, the influences of array randomness and particle size on FFPC have been studied independently for the first time. Finally, two potential applications have been developed for FFPC-based LSPR tuning. Firstly, when AuND arrays are fabricated on flexible substrates, a novel transduction mechanism can be established between the LSPR peak position and the substrate strain. Owing to the far-field propagating nature, FFPC-based transduction can effectively extend the strain-tuning displacement range by an order of magnitude compared with those based on near-field coupling. Secondly, we show that FFPC leads to an LSPR peak within 1 μm for nanoporous gold disk arrays, which otherwise have a single particle LSPR peak beyond 1.5 μm. Such a significant FFPC-induced blue shift is critically important for compatibility with the use of silicon-based detectors.
我们报告了由随机尺寸和取向的“单晶”域组成的二维多晶等离子体阵列中远场等离子体耦合（FFPC）的实验观察和数值模拟研究。尽管多晶等离子体阵列是低成本纳米球光刻（NSL）的常规产物，但其FFPC行为尚未得到很好的理解。在此，通过NSL制备的金纳米盘（AuND）阵列观察到的FFPC，从定性上看，似乎与高度规则的纳米颗粒阵列的FFPC行为一致，在高度规则的纳米颗粒阵列中，它们会引起局部表面等离子体共振（LSPR）的峰值位置和线宽的周期性调制。实验观察到高达1000 nm的显著蓝移，线宽几乎翻倍。系统地进行了数值模拟，结果与实验结果在定量上吻合。利用该模拟方法，首次独立研究了阵列随机性和颗粒尺寸对FFPC的影响。最后，开发了基于FFPC的LSPR调谐的两个潜在应用。首先，当在柔性衬底上制备AuND阵列时，可以在LSPR峰值位置和衬底应变之间建立一种新型的转换机制。由于远场传播特性，与基于近场耦合的转换相比，基于FFPC的转换可以有效地将应变调谐位移范围扩展一个数量级。其次，我们表明FFPC导致纳米多孔金盘阵列的LSPR峰值在1μm以内，否则单个颗粒的LSPR峰值超过1.5μm。这种由FFPC引起的显著蓝移对于与硅基探测器的兼容性至关重要。
