Mao Wenting, Bao Chao, Han Lu
School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, Shanghai Jiao Tong University, Shanghai200240, China.
School of Chemical Science and Engineering, Tongji University, Shanghai200092, China.
Microsc Microanal. 2021 Jun 30:1-11. doi: 10.1017/S1431927621012149.
The precise structural solution of crystals on a mesostructural scale is challenging due to the difficulties in obtaining electron diffraction and the complicated relationship between the crystal structure factors (CSFs) and the conventional underfocus phase-contrast transmission electron microscopy (TEM) images due to the large unit cell and the complex structures. Here, we present the structural investigation of mesostructured crystals via the combination of electron crystallographic Fourier synthesis and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that only relies on the mass-thickness contrast. The three-dimensional electrostatic potential is reconstructed from the amplitudes and phases extracted from the Fourier transforms of the corresponding HAADF-STEM images and merged into a set of CSFs. This method is verified on silica scaffolds following a shifted double-diamond surface network with space group I41/amd. The results indicate that electron crystallography reconstruction by HAADF-STEM images is more suitable and accurate in determining the structure in comparison with conventional TEM electron crystallography reconstruction. This approach transfers the contrast of mesostructured crystals to images more accurately and the relationship between the Fourier transforms of HAADF-STEM images and the CSFs is more intuitive. It shows great advantages for the structural solution of crystals on the mesostructural scale.
由于在获得电子衍射方面存在困难，且由于大晶胞和复杂结构导致晶体结构因子（CSF）与传统欠焦相衬透射电子显微镜（TEM）图像之间存在复杂关系，因此在介观结构尺度上精确解析晶体的结构具有挑战性。在此，我们通过结合仅依赖于质量厚度对比度的电子晶体学傅里叶合成和高角度环形暗场扫描透射电子显微镜（HAADF-STEM），展示了对介观结构晶体的结构研究。从相应HAADF-STEM图像的傅里叶变换中提取的振幅和相位重建三维静电势，并将其合并为一组CSF。该方法在具有空间群I41/amd的移位双菱形表面网络的二氧化硅支架上得到验证。结果表明，与传统TEM电子晶体学重建相比，通过HAADF-STEM图像进行电子晶体学重建在确定结构方面更合适、更准确。这种方法将介观结构晶体的对比度更准确地转移到图像上，并且HAADF-STEM图像的傅里叶变换与CSF之间的关系更直观。它在介观结构尺度上的晶体结构解析方面显示出巨大优势。
