Sugiyama Teruki, Lin Tung-Ming, Su Hao-Tse, Cheng An-Chieh, Sasaki Keiji
Department of Applied Chemistry and Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, 1001 University Rd., Hsinchu 300093, Taiwan.
Division of Materials Science, Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma 630-0192, Japan.
J Chem Phys. 2024 Feb 14;160(6). doi: 10.1063/5.0186018.
In this study, we conducted successful experiments on ethylenediamine sulfate (EDS), an organic compound, to investigate its enantioselectivity in chiral crystallization. We employed optical trapping with circularly polarized laser beams, using a continuous wave laser at 1064 nm. By focusing the laser at the air-solution interface of a heavy water-saturated EDS solution, the formation of sub-micrometer-sized chiral EDS crystals was verified. Two generated enantiomorphs (d-crystal and l-crystal) were identified by the rotating analyzer method. The enantioselectivity in the chiral crystallization of EDS was assessed through 30 to 60 times experiments conducted under various conditions of laser powers and polarization modes, utilizing the count of generated crystals for each enantiomorph in the evaluation. Circularly polarized lasers at a specific power created an imbalance in the generation probability of the enantiomorphs, resulting in crystal enantiomeric excess values of 23% and -30%. The enantioselectivity mechanism was explored from two perspectives: refractive index differences of two enantiomorphs and 3D helical optical forces. Study of the thermodynamic mechanism was insufficient to explain the outcomes. Conversely, the 3D helical optical force mechanism revealed that the forces acting on EDS clusters in solution induced helical fluid motion, driving EDS nucleation, with the helicity of fluid motion determining the crystal's chirality. This approach will present new insights into chirality in industrial and research fields, with potential applications in regard to improving optical resolution and addressing the origin of homochirality.
在本研究中，我们对有机化合物硫酸乙二胺（EDS）进行了成功的实验，以研究其在手性结晶中的对映选择性。我们使用1064 nm的连续波激光，采用圆偏振激光束进行光阱操作。通过将激光聚焦在重水饱和EDS溶液的气-液界面处，验证了亚微米级手性EDS晶体的形成。通过旋转分析器方法鉴定了两种生成的对映体（d-晶体和l-晶体）。在不同激光功率和偏振模式条件下进行了30至60次实验，利用评估中每种对映体生成晶体的数量，评估了EDS手性结晶中的对映选择性。特定功率的圆偏振激光导致对映体生成概率失衡，产生的晶体对映体过量值分别为23%和-30%。从两个角度探讨了对映选择性机制：两种对映体的折射率差异和三维螺旋光学力。对热力学机制的研究不足以解释实验结果。相反，三维螺旋光学力机制表明，作用于溶液中EDS团簇的力诱导了螺旋流体运动，驱动了EDS成核，流体运动的螺旋性决定了晶体的手性。这种方法将为工业和研究领域的手性提供新的见解，在提高光学分辨率和解决同手性起源方面具有潜在应用。
