Wang Ruiqian, Xu Wendao, Chen Dinghao, Zhou Ruiyun, Wang Qi, Gao Weilu, Kono Junichiro, Xie Lijuan, Ying Yibin
College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
Key Laboratory of on Site Processing Equipment for Agricultural Products, Ministry of Agriculture and Rural Affairs, Zhejiang University, Hangzhou 310058, China.
ACS Appl Mater Interfaces. 2020 Sep 9;12(36):40629-40634. doi: 10.1021/acsami.0c06503. Epub 2020 Aug 26.
Terahertz (THz) electromagnetic waves strongly interact with complex molecules, making THz spectroscopy a promising tool for high-sensitivity molecular detection, especially for biomedical applications. Metamaterials are typically used for enhancing THz-molecule interactions to achieve higher sensitivities. However, a primary challenge in THz molecular sensing based on metallic metamaterials is the limited tunability of optical constants of metals. Here, we present an ultrahigh-sensitivity molecular sensor based on carbon nanotube (CNT) THz metamaterials. The sensor, consisting of a CNT cut-wire array on a Si substrate prepared by a novel two-step method, exhibits a reflectance resonance whose frequency strongly varies with the substrate composition, geometries of periodic arrays, and analyte composition. We used this sensor to detect glucose, lactose, and chlorpyrifos-methyl molecules, achieving limit-of-detection values of 30, 40, and 10 ng/mL (S/N = 3), respectively, higher than that of metallic metamaterials by 2 orders of magnitude. We attribute this ultrahigh sensitivity to the high conductivity of CNTs and the efficient adsorption of the target analyte by CNTs through van der Waals forces and π-π stacking. These easy-to-fabricate CNT-based THz metamaterials pave the way for versatile and reliable ultrahigh-sensitivity THz molecular detection.
太赫兹（THz）电磁波与复杂分子有强烈相互作用，这使得太赫兹光谱成为高灵敏度分子检测的一种很有前景的工具，特别是在生物医学应用方面。超材料通常用于增强太赫兹与分子的相互作用以实现更高的灵敏度。然而，基于金属超材料的太赫兹分子传感的一个主要挑战是金属光学常数的可调性有限。在此，我们展示了一种基于碳纳米管（CNT）太赫兹超材料的超高灵敏度分子传感器。该传感器由通过一种新颖的两步法在硅衬底上制备的碳纳米管切割线阵列组成，呈现出一种反射共振，其频率随衬底成分、周期性阵列的几何形状以及分析物成分而强烈变化。我们使用该传感器检测葡萄糖、乳糖和甲基毒死蜱分子，分别实现了30、40和10 ng/mL（S/N = 3）的检测限，比金属超材料高出2个数量级。我们将这种超高灵敏度归因于碳纳米管的高导电性以及碳纳米管通过范德华力和π-π堆积对目标分析物的有效吸附。这些易于制造的基于碳纳米管的太赫兹超材料为通用且可靠的超高灵敏度太赫兹分子检测铺平了道路。
