Department of Physics, Birla Institute of Technology, Mesra, Ranchi - 835215, Jharkhand, India.
Analyst. 2019 Oct 22;144(21):6172-6192. doi: 10.1039/c9an00798a.
Terahertz time-domain spectroscopy (THz-TDS) is a non-invasive, non-contact and label-free technique for biological and chemical sensing as THz-spectra are less energetic and lie in the characteristic vibration frequency regime of proteins and DNA molecules. However, THz-TDS is less sensitive for the detection of micro-organisms of size equal to or less than λ/100 (where, λ is the wavelength of the incident THz wave), and molecules in extremely low concentration solutions (like, a few femtomolar). After successful high-throughput fabrication of nanostructures, nanoantennas were found to be indispensable in enhancing the sensitivity of conventional THz-TDS. These nanostructures lead to strong THz field enhancement when in resonance with the absorption spectrum of absorptive molecules, causing significant changes in the magnitude of the transmission spectrum, therefore, enhancing the sensitivity and allowing the detection of molecules and biomaterials in extremely low concentration solutions. Herein, we review the recent developments in ultra-sensitive and selective nanogap biosensors. We have also provided an in-depth review of various high-throughput nanofabrication techniques. We also discussed the physics behind the field enhancements in the sub-skin depth as well as sub-nanometer sized nanogaps. We introduce finite-difference time-domain (FDTD) and molecular dynamics (MD) simulation tools to study THz biomolecular interactions. Finally, we provide a comprehensive account of nanoantenna enhanced sensing of viruses (like, H1N1) and biomolecules such as artificial sweeteners which are addictive and carcinogenic.
太赫兹时域光谱（THz-TDS）是一种用于生物和化学传感的非侵入式、非接触式和无标记技术，因为 THz 光谱的能量较低，位于蛋白质和 DNA 分子的特征振动频率范围内。然而，THz-TDS 对于检测大小等于或小于 λ/100（其中，λ 是入射太赫兹波的波长）的微生物和极低浓度溶液中的分子（如，几个飞摩尔）的灵敏度较低。在成功进行纳米结构的高通量制造后，发现纳米天线对于增强传统 THz-TDS 的灵敏度是不可或缺的。这些纳米结构在与吸收分子的吸收光谱共振时会导致太赫兹场的强烈增强，从而导致传输光谱的幅度发生显著变化，从而提高了灵敏度并允许检测极低浓度溶液中的分子和生物材料。在此，我们综述了超灵敏和选择性纳米间隙生物传感器的最新进展。我们还深入回顾了各种高通量纳米制造技术。我们还讨论了亚皮肤深度和亚纳米大小纳米间隙中的场增强背后的物理原理。我们引入了有限差分时间域（FDTD）和分子动力学（MD）模拟工具来研究太赫兹生物分子相互作用。最后，我们全面介绍了纳米天线增强对病毒（如 H1N1）和生物分子（如人工甜味剂）的感应，这些物质具有成瘾性和致癌性。
