Structure-color mechanism of iridescent cellulose nanocrystal films
Structure-color mechanism of iridescent cellulose nanocrystal films
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彩虹色纤维素纳米晶薄膜的结构-颜色机制
DOI：
10.1039/c4ra06268j
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发表时间：
2014-01-01
期刊：
影响因子：
3.9
通讯作者：
Lin, Fengying
中科院分区：
文献类型：
--
作者：
Liu, Dagang;Wang, Shuo;Lin, Fengying
硫酸盐纤维素纳米晶（CNCs）之间的手性和排斥相互作用对悬浮液或固化膜中液晶（CLC）相的形成具有重要影响。在这项工作中，一个简单的超声处理施加到改变结构和排斥相互作用的CNCs，从而调整所得薄膜的手性光学性能。结果表明，通过提高输入功率或延长老化时间来提高超声能量，可使虹彩薄膜的粒径减小，表面电荷密度降低，从而使虹彩薄膜的反射波长红移，反射间距增大。薄膜的光学性质遵循布拉格反射和薄膜干涉的规律。然而，过度的能量输入将导致根据表面电荷密度的水平的CNCs的多分散，从而导致由于多分布的轴内驱动力而形成多畴CLC而不是平面CLC。因此，建立了一个示意性的模型来描述结构转变，以及颜色的变化，并关联的介观行为的CNCs和静电排斥，氢键亲和力和手性的微观相互作用。因此，我们提供了一些有意义的信息，建立一个层次的组织组装从带电的刚性生物棒，并帮助认识的结构-颜色机制的多糖纳米晶体的固化膜。
Chirality and repulsion interactions among sulfate cellulose nanocrystals (CNCs) have vital impact on the formation of a cholesteric liquid crystal (CLC) phase in a suspension or solidified film. In this work, a facile sonication treatment was applied to change the structure and repulsion interactions of CNCs and consequently tune the chiroptical properties of the resultant films. The results show that increasing the sonication energy either by improving the input power or prolonging the aging time resulted in the reduction of particle size and surface charge density, thereby increasing the cholesteric pitch and redshifting the reflective wavelength of the iridescent films. The optical properties of the film followed the regulation of Bragg reflection and thin-film interference. However, an over-energy input would result in the multi-dispersion of the CNCs according to the level of the surface charge density, thus leading to the formation of polydomain CLC instead of planar CLC because of multi-distributed intra-axial drive forces. Hence, a schematic model was built up to describe the structure transition, as well as the color variation and to correlate the mesoscopic behavior of CNCs and the microscopic interactions of electrostatic repulsions, hydrogen bonding affinity and chirality. Hence, we provide some meaningful information on building up a hierarchical organization assembled from charged rigid biological rods, and help to recognize the structure-color mechanism of solidified films of polysaccharide nanocrystals.