Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, V6T 1Z1, Canada.
Nature. 2010 Nov 18;468(7322):422-5. doi: 10.1038/nature09540.
Chirality at the molecular level is found in diverse biological structures, such as polysaccharides, proteins and DNA, and is responsible for many of their unique properties. Introducing chirality into porous inorganic solids may produce new types of materials that could be useful for chiral separation, stereospecific catalysis, chiral recognition (sensing) and photonic materials. Template synthesis of inorganic solids using the self-assembly of lyotropic liquid crystals offers access to materials with well-defined porous structures, but only recently has chirality been introduced into hexagonal mesostructures through the use of a chiral surfactant. Efforts to impart chirality at a larger length scale using self-assembly are almost unknown. Here we describe the development of a photonic mesoporous inorganic solid that is a cast of a chiral nematic liquid crystal formed from nanocrystalline cellulose. These materials may be obtained as free-standing films with high surface area. The peak reflected wavelength of the films can be varied across the entire visible spectrum and into the near-infrared through simple changes in the synthetic conditions. To the best of our knowledge these are the first materials to combine mesoporosity with long-range chiral ordering that produces photonic properties. Our findings could lead to the development of new materials for applications in, for example, tuneable reflective filters and sensors. In addition, this type of material could be used as a hard template to generate other new materials with chiral nematic structures.
手性在分子水平上存在于多种生物结构中，如多糖、蛋白质和 DNA，它们负责许多独特的性质。在多孔无机固体中引入手性可能会产生新型材料，这些材料可用于手性分离、立体选择性催化、手性识别（传感）和光子材料。使用溶致液晶的自组装模板合成无机固体可获得具有明确定义的多孔结构的材料，但直到最近才通过使用手性表面活性剂将手性引入六方介孔结构。在手性更大的尺度上通过自组装赋予手性的努力几乎是未知的。在这里，我们描述了一种光子介孔无机固体的开发，该固体是由纳米纤维素形成的手性向列液晶的铸型。这些材料可以作为具有高表面积的独立膜获得。通过简单改变合成条件，膜的峰值反射波长可以在整个可见光谱和近红外光谱范围内变化。据我们所知，这些是第一个将介孔与长程手性有序结合产生光子特性的材料。我们的研究结果可能会导致开发用于可调反射滤波器和传感器等应用的新材料。此外，这种类型的材料可用作手性向列结构的其他新型材料的硬模板。
