Many fascinating device applications of chiral nematic materials are determined by their helical axis orientations. Cellulose nanocrystals (CNCs) self-assemble producing left-handed chiral nematic films with predominant planar textures. While varied techniques have been exploited to tune the helical axis orientations, it remains challenging to produce concentrically aligned chiral nematic state. Herein, the authors report novel findings that left-handed chiral nematic CNC films formed with homeotropic concentric helix orientations in the planar textures can be realized by local radial magnetic field-directed self-assembly of CNCs. These chiral nematic CNC films display left-handed circular polarization patterns and transform spontaneous luminescence to right-handed circularly polarized luminescence on both film plane and lateral surfaces owing to the underlying photonic bandgaps. These plane-lateral chiroptical properties can be tuned simultaneously from the visible to the near-infrared spectral regime. Their work presents a step towards the development of self-organized chiroptical materials encoded with complex polarization features for photonic applications.

中文翻译：

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局部磁场在手性向列纤维素纳米晶体薄膜中的同心同心螺旋取向

手性向列材料的许多引人入胜的器件应用是由它们的螺旋轴方向决定的。纤维素纳米晶体 (CNC) 自组装产生具有主要平面纹理的左手手性向列薄膜。虽然已经利用各种技术来调整螺旋轴方向，但产生同心对齐的手性向列状态仍然具有挑战性。在这里，作者报告了新的发现，即在平面纹理中具有垂直同心螺旋取向的左手手性向列 CNC 薄膜可以通过 CNC 的局部径向磁场定向自组装来实现。由于潜在的光子带隙，这些手性向列 CNC 薄膜显示左旋圆偏振模式，并在薄膜平面和侧面上将自发发光转换为右旋圆偏振发光。这些平面横向手性光学特性可以同时从可见光谱区调整到近红外光谱区。他们的工作向开发用于光子应用的复杂偏振特征编码的自组织手性材料迈出了一步。