Sakamoto Y, Kaneda M, Terasaki O, Zhao D Y, Kim J M, Stucky G, Shin H J, Ryoo R
Department of Physics and CIR, Tohoku University, Sendai, Japan.
Nature. 2000 Nov 23;408(6811):449-53. doi: 10.1038/35044040.
Mesostructured composite materials, with features ranging from 20 to 500 A in size, are obtained by the kinetically controlled competitive assembly of organic and inorganic species into nanostructured domains. Short-range order is limited, and long-range order is determined by weak forces such as van der Waals or hydrogen-bonding. Three-dimensional mesoporous materials obtained by removing the organic phase are of particular interest for applications such as catalysis and chemical sensing or separation, for which structural features such as cavity shape, connectivity and ordered bimodal porosity are critical. But atomic-scale structural characterization by the usual diffraction techniques is challenging for these partially ordered materials because of the difficulty in obtaining large (> 10 microm) single crystals, and because large repeat spacings cause diffraction intensities to fall off rapidly with scattering angle so that only limited small-angle data are available. Here we present a general approach for the direct determination of three-dimensional mesoporous structures by electron microscopy. The structure solutions are obtained uniquely without pre-assumed models or parametrization. We report high-resolution details of cage and pore structures of periodically ordered mesoporous materials, which reveal a highly ordered dual micro- and mesoscale pore structure.
介观结构复合材料的尺寸范围为20至500埃，是通过有机和无机组分动力学控制的竞争组装进入纳米结构域而获得的。其短程有序受到限制，长程有序由范德华力或氢键等弱力决定。通过去除有机相获得的三维介孔材料对于催化、化学传感或分离等应用特别有意义，对于这些应用而言，诸如孔腔形状、连通性和有序双峰孔隙率等结构特征至关重要。但是，由于难以获得大尺寸（>10微米）的单晶，并且由于大的重复间距导致衍射强度随散射角迅速下降，以至于只能获得有限的小角数据，因此利用常规衍射技术对这些部分有序材料进行原子尺度的结构表征具有挑战性。在此，我们提出一种通过电子显微镜直接测定三维介孔结构的通用方法。无需预先假设模型或参数化即可唯一地获得结构解。我们报告了周期性有序介孔材料的笼状和孔结构的高分辨率细节，这些细节揭示了高度有序的双微观和介观尺度孔结构。
