Dimitrov Botyo, Bukharina Daria, Poliukhova Valeriia, Nepal Dhriti, McConney Michael E, Bunning Timothy J, Tsukruk Vladimir V
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States.
Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio 45433, United States.
ACS Appl Opt Mater. 2024 Nov 21;2(12):2540-2550. doi: 10.1021/acsaom.4c00386. eCollection 2024 Dec 27.
In this work, twisted helical cellulose nanocrystals films with preprogrammed circular polarization and near-infrared reflectance are fabricated via a blade-based 3D printing method. The films are composed of stacked nanoscale slabs with high birefringence from unidirectionally organized cellulose nanocrystals. By changing the printing director, we achieved two types of films: twisted helical stacks and anisotropic Bragg stacks. These films are highly transparent and clear, and the achiral anisotropic Bragg stack shows near-infrared spectral region reflectance (1.3-1.4 μm). In contrast, the twisted helical films show concurrent left- and right-handed circularly polarized properties, as opposed to left-handed natural cellulose nanocrystals films. We observe dual chiroptical properties with circular dichroism peaks due to circular Bragg reflectance in the visible region and suggest that the circularly polarized properties are extended to the near-infrared region. These observations prompted us to explore the transition between anisotropic Bragg stacks and continuous helical films via simulations. We show that the printed twisted films can act as optical metamaterials with dual helicity and fill the gap between known photonic structures-the conventional continuous chiral nematic material with a chiroptical appearance and the achiral Bragg stack with a controlled photonic bandgap. These printed twisted stacked films hold the potential of larger-scale printed ordering of unique anisotropic nanostructures for circularly polarized-sensitive photonic, thermal, and energy management applications.
在这项工作中，通过基于刮刀的3D打印方法制备了具有预编程圆偏振和近红外反射率的扭曲螺旋纤维素纳米晶体薄膜。这些薄膜由堆叠的纳米级平板组成，这些平板由单向排列的纤维素纳米晶体具有高双折射。通过改变打印方向，我们获得了两种类型的薄膜：扭曲螺旋堆叠和各向异性布拉格堆叠。这些薄膜高度透明且清晰，非手性各向异性布拉格堆叠在近红外光谱区域（1.3 - 1.4μm）显示出反射率。相比之下，扭曲螺旋薄膜显示出同时具有左旋和右旋圆偏振特性，这与左旋天然纤维素纳米晶体薄膜不同。我们观察到由于可见区域的圆形布拉格反射而产生的具有圆二色性峰的双旋光特性，并表明圆偏振特性扩展到了近红外区域。这些观察结果促使我们通过模拟探索各向异性布拉格堆叠和连续螺旋薄膜之间的转变。我们表明，打印的扭曲薄膜可以作为具有双螺旋度的光学超材料，并填补已知光子结构之间的空白——具有旋光外观的传统连续手性向列材料和具有可控光子带隙的非手性布拉格堆叠。这些打印的扭曲堆叠薄膜具有为圆偏振敏感的光子、热和能量管理应用进行更大规模打印独特各向异性纳米结构有序排列的潜力。
