Terahertz Circular Dichroism Spectroscopy of Molecular Assemblies and Nanostructures
Terahertz Circular Dichroism Spectroscopy of Molecular Assemblies and Nanostructures
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DOI：
10.1021/jacs.2c04817
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发表时间：
2022-12-09
影响因子：
15
通讯作者：
Kotov，Nicholas A.
中科院分区：
文献类型：
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作者：
Choi，Won Jin;Lee，Sang Hyun;Kotov，Nicholas A.
化学、物理、生物和材料工程学科使用各种手性光谱仪来探测分子和粒子中的几何和光学不对称。电子(ECD)和振动(VCD)圆二色谱是这些技术中最常见的，它们共同实现了能量在0.1到5.0 eV之间的电子和振动跃迁的研究。特征能量在0.001-0.01 eV范围内的振动态携带了多原子分子和晶体中分子间协同运动的有价值的信息。这些位于太赫兹(THz)光谱部分的振动跃迁对于复杂分子和材料的化学、物理和生物学变得越来越重要。然而，THz圆二色谱(TCD)的方法和硬件远远落后于用于紫外光、可见光、近红外和中红外光子的手性光谱。在这里，我们提供了TCD光谱学的理论基础、实际实施、比较评估和示范应用。我们发现，TCD峰的符号、强度和位置对分子晶体的三维结构和远程组织高度敏感，这为研究(生物)分子、其晶体和纳米级组装提供了独特的能力，并应用了新的数据处理方法。TCD还提供了一个方便的工具箱来识别新的物理现象，例如手性声子及其在纳米结构物质中的传播。我们还讨论了手性(纳米)晶体中观察到的手性声子的广泛研究，以及生物和纳米结构中TCD的新兴机器学习方法等主要挑战、新出现的机遇和未来的研究方向。生物分子结构中具有旋转成分的低频振动无处不在，再加上TCD光谱中峰的锐利，使得各种技术转换成为可能。
Chemical, physical, biological and materials engineering disciplines use a variety of chiroptical spectroscopies to probe geometrical and optical asymmetry in molecules and particles. Electronic (ECD) and vibrational (VCD) circular dichroism are the most common of these techniques and collectively enable the studies of electronic and vibronic transitions with energies between 0.1 and 5.0 eV. The vibrational states with characteristic energies in the range of 0.001–0.01 eV carry valuable information about concerted intermolecular motions in molecules and crystals involving multiple atoms. These vibronic transitions located in the terahertz (THz) part of the spectrum become increasingly more important for the chemistry, physics, and biology of complex molecules and materials However, the methodology and hardware of THz circular dichroism (TCD) are much less developed than the chiroptical spectroscopies for ultraviolet, visible, near- and mid infrared photons. Here we provide theoretical foundations, practical implementations, comparative assessments, and exemplary applications of TCD spectroscopy. We show that the sign, intensity, and position of TCD peaks are highly sensitive to the three-dimensional structure and long-range organization of molecular crystals, which offer unique capabilities to study (bio) molecules, their crystals, and nanoscale assemblies and apply the novel data processing methodologies. TCD also offers a convenient toolbox to identify new physical phenomena, such as chiral phonons and their propagation in nanostructured matter. We also discuss the major challenges, emerging opportunities and promising research directions, including broad investigation of chiral phonons observed in chiral (nano) crystals and emerging machine learning methodologies for TCD in biological and nanoscale structures. Ubiquity of low-frequency vibrations with rotational components in biomolecular structures, combined with sharpness of peaks in TCD spectra, enables a variety of technological translations.