Super-chiral vibrational spectroscopy with metasurfaces for high-sensitive identification of alanine enantiomers
Super-chiral vibrational spectroscopy with metasurfaces for high-sensitive identification of alanine enantiomers
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DOI：
10.1063/5.0012331
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发表时间：
2020-09-08
影响因子：
4
通讯作者：
Tsuruta, Kenji
中科院分区：
文献类型：
--
作者：
Iida, Takumi;Ishikawa, Atsushi;Tsuruta, Kenji
对映异构体的手性性质可以通过圆二色性（CD）光谱来表征，但是这种技术即使使用复杂的光学仪器也通常遭受弱信号。等离子体超颖表面的最近演示表明，分子的手性相互作用可以被设计，从而大大简化了具有高传感能力的测量系统。在这里，通过利用超表面的超手性场，我们实验证明了高灵敏度的振动CD光谱丙氨酸对映体，最小的手性氨基酸。在线性极化激发下，由交错排列的Au纳米棒组成的超表面在1600 cm（-1）处选择性地产生左手和右手超手征场，其光谱与丙氨酸的官能团振动重叠。在傅里叶变换红外光谱仪的测量中，D-和L-丙氨酸的镜像对称CD光谱被清楚地观察到取决于超颖表面的旋向性，实现了小手性分子的可靠鉴定。相应的数值模拟揭示了潜在的共振旋光相互作用的等离子体模式的超颖表面和丙氨酸的振动模式。我们的方法展示了一种高灵敏度的振动CD光谱技术，为先进的红外检测技术开辟了一个可靠的手性传感平台。
Chiral nature of an enantiomer can be characterized by circular dichroism (CD) spectroscopy, but such a technique usually suffers from weak signal even with a sophisticated optical instrument. Recent demonstrations of plasmonic metasurfaces showed that chiroptical interaction of molecules can be engineered, thereby greatly simplifying a measurement system with high sensing capability. Here, by exploiting super-chiral field in a metasurface, we experimentally demonstrate high-sensitive vibrational CD spectroscopy of alanine enantiomers, the smallest chiral amino acid. Under linearly polarized excitation, the metasurface consisting of an array of staggered Au nano-rods selectively produces the left- and right-handed super-chiral fields at 1600cm(-1), which spectrally overlaps with the functional group vibrations of alanine. In the Fourier-transform infrared spectrometer measurements, the mirror symmetric CD spectra of D- and L-alanine are clearly observed depending on the handedness of the metasurface, realizing the reliable identification of small chiral molecules. The corresponding numerical simulations reveal the underlying resonant chiroptical interaction of plasmonic modes of the metasurface and vibrational modes of alanine. Our approach demonstrates a high-sensitive vibrational CD spectroscopic technique, opening up a reliable chiral sensing platform for advanced infrared inspection technologies.