Cheng Fei, Yang Xiaodong, Gao Jie
Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA.
Sci Rep. 2015 Sep 21;5:14327. doi: 10.1038/srep14327.
Infrared vibrational spectroscopy is an effective technique which enables the direct probe of molecular fingerprints, and such detection can be further enhanced by the emerging engineered plasmonic metamaterials. Here we experimentally demonstrate ultrasensitive detection and characterization of polymer molecules based on an asymmetric infrared plasmonic metamaterial, and quantitatively analyze the molecule detection sensitivity and molecule-structure interactions. A sharp, non-radiative Fano resonance supported by the plasmonic metamaterial exhibits strongly enhanced near-field, and the resonance frequency is tailored to match the vibrational fingerprint of the target molecule. By utilizing the near-field nature of the plasmonic excitation, significantly enhanced absorption signal of molecules in the infrared spectroscopy are obtained, enabling ultrasensitive detection of only minute quantities of organic molecules. The enhancement of molecular absorption up to 10(5) fold is obtained, and sensitive detection of molecules at zeptomole levels (corresponding to a few tens of molecules within a unit cell) is achieved with high signal-to-noise ratio in our experiment. The demonstrated infrared plasmonic metamaterial sensing platform offers great potential for improving the specificity and sensitivity of label-free, biochemical detection.
红外振动光谱是一种能够直接探测分子指纹的有效技术，而新兴的工程化等离子体超材料可以进一步增强这种检测能力。在此，我们通过实验展示了基于非对称红外等离子体超材料对聚合物分子的超灵敏检测与表征，并定量分析了分子检测灵敏度和分子 - 结构相互作用。等离子体超材料所支持的尖锐、非辐射性的法诺共振展现出强烈增强的近场，且共振频率经过调整以匹配目标分子的振动指纹。通过利用等离子体激发的近场特性，在红外光谱中获得了显著增强的分子吸收信号，从而能够超灵敏地检测仅微量的有机分子。在我们的实验中，实现了分子吸收增强高达10⁵倍，并且以高信噪比实现了zeptomole水平（对应于一个晶胞内几十分子）的分子灵敏检测。所展示的红外等离子体超材料传感平台在提高无标记生化检测的特异性和灵敏度方面具有巨大潜力。
