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Self-Assembly of Plasmonic Nanoantenna–Waveguide Structures for Subdiffractional Chiral Sensing
ACS Nano ( IF 15.8 ) Pub Date : 2020-11-25 , DOI: 10.1021/acsnano.0c05240
Martin Rothe 1 , Yuhang Zhao 2 , Johannes Müller 1 , Günter Kewes 1 , Christoph T. Koch 1 , Yan Lu 2, 3 , Oliver Benson 1
Affiliation  

Spin-momentum locking is a peculiar effect in the near-field of guided optical or plasmonic modes. It can be utilized to map the spinning or handedness of electromagnetic fields onto the propagation direction. This motivates a method to probe the circular dichroism of an illuminated chiral object. In this work, we demonstrate local, subdiffraction limited chiral coupling of light and propagating surface plasmon polaritons in a self-assembled system of a gold nanoantenna and a silver nanowire. A thin silica shell around the nanowire provides precise distance control and also serves as a host for fluorescent molecules, which indicate the direction of plasmon propagation. We characterize our nanoantenna–nanowire systems comprehensively through correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging. Three-dimensional numerical simulations support the experimental findings. Besides our measurement of far-field polarization, we estimate sensing capabilities and derive not only a sensitivity of 1 mdeg for the ellipticity of the light field, but also find 103 deg cm2/dmol for the circular dichroism of an analyte locally introduced in the hot spot of the antenna–wire system. Thorough modeling of a prototypical design predicts on-chip sensing of chiral analytes. This introduces our system as an ultracompact sensor for chiral response far below the diffraction limit.

中文翻译:

等离子手征传感的等离子纳米天线-波导结构的自组装。

自旋动量锁定是在引导的光学或等离激元模式的近场中的特有效果。它可以用于将电磁场的旋转或旋向映射到传播方向。这激发了一种探测被照亮的手性物体的圆二色性的方法。在这项工作中,我们展示了金纳米天线和银纳米线自组装系统中光和传播的表面等离激元极化子的局域,亚衍射受限手性耦合。纳米线周围的二氧化硅薄壳提供了精确的距离控制,并且还充当荧光分子的主体,这些分子指示了等离子体激元的传播方向。我们通过相关的电子显微镜,能量色散X射线光谱,暗场和荧光成像来全面表征纳米天线-纳米线系统。三维数值模拟支持了实验结果。除了对远场极化进行测量之外,我们还估计了传感能力,不仅得出了光场椭圆率的1 mdeg灵敏度,还发现了103 deg cm 2 / dmol用于在天线线系统热点中局部引入的分析物的圆二色性。完整的原型设计建模可预测手性分析物的片上传感。这将我们的系统作为一种超紧凑型传感器用于手性响应,远远低于衍射极限。
更新日期:2021-01-26
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