Planar Alignment of Graphene Sheets by a Rotating Magnetic Field for Full Exploitation of Graphene as a 2D Material
Planar Alignment of Graphene Sheets by a Rotating Magnetic Field for Full Exploitation of Graphene as a 2D Material
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DOI：
10.1002/adfm.201805255
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发表时间：
2018-11-14
影响因子：
19
通讯作者：
Bao, Jiming
中科院分区：
文献类型：
--
作者：
Lin, Feng;Yang, Guang;Bao, Jiming
为了将其优异的各向异性性质从微观的个体结构转移到宏观的集体组装，需要盘状纳米材料的平面排列。然而，与棒状纳米结构相比，这种通过电场或磁场进行取向的取向是具有挑战性的，因为它们具有额外的取向自由度。这里报道了利用一对小的NdFeB磁体产生的旋转磁场实现悬浮石墨烯的平面对准，并展示了高的光学各向异性和潜在的新型器件应用。与静磁场作用下的部分取向石墨烯悬浮液相比，平面取向石墨烯悬浮液显示出近乎完美的有序参数、高得多的双折射和各向异性的吸收/透射率。盘状纳米材料组装的一个独特特征是，观察到的有序参数和光学性质可以从各向同性到部分和完全排列，这取决于实验构型。通过在紫外光固化的聚合物树脂中固定和图案化定向石墨烯，我们进一步展示了一种全石墨烯永久显示器，该显示器在透射式或反射式模式下显示出广角、高暗亮对比度，而不需要任何偏振光学。能够在所有三个维度上控制石墨烯的取向并为其绘制图案，开启了石墨烯的新探索和广泛的设备应用。
Planar alignment of disc-like nanomaterials is required to transfer their superior anisotropic properties from microscopic individual structures to macroscopic collective assemblies. However, such alignment by electrical or magnetic field is challenging due to their additional degrees of orientational freedom compared to that of rod-like nanostructures. Here, the realization of planar alignment of suspended graphene sheets using a rotating magnetic field produced by a pair of small NdFeB magnets and subsequent demonstration of high optical anisotropy and potential novel device applications is reported. Compared to partially aligned sheets with a static magnetic field, planar aligned graphene suspensions exhibit a near-perfect order parameter, much higher birefringence and anisotropic absorption/transmission. A unique feature of discotic nanomaterial assemblies is that the observed order parameter and optical property can vary from isotropic to partial and complete alignment depending on the experimental configuration. By immobilizing and patterning aligned graphene in a UV-curable polymer resin, we further demonstrated an all-graphene permanent display, which exhibits wide-angle, high dark-bright contrast in either transmission or reflection mode without any polarizing optics. The ability to control and pattern graphene orientation in all three dimensions opens up new exploration and broad device applications of graphene.