Electron Microscopy Center, South China University of Technology, Guangzhou 510640, China.
School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
Science. 2023 May 12;380(6645):633-638. doi: 10.1126/science.adg3183. Epub 2023 May 11.
Structural and compositional inhomogeneity is common in zeolites and considerably affects their properties. Thickness-limited lateral resolution, lack of depth resolution, and electron dose-constrained focusing limit local structural studies of zeolites in conventional transmission electron microscopy (TEM). We demonstrate that a multislice ptychography method based on four-dimensional scanning TEM (4D-STEM) data can overcome these limitations. Images obtained from a ~40-nanometer-thick MFI zeolite exhibited a lateral resolution of ~0.85 angstrom that enabled the identification of individual framework oxygen (O) atoms and the precise determination of the orientations of adsorbed molecules. Furthermore, a depth resolution of ~6.6 nanometers allowed probing of the three-dimensional distribution of O vacancies, as well as the phase boundaries in intergrown MFI and MEL zeolites. The 4D-STEM ptychography can be generally applied to other materials with similar high electron-beam sensitivity.
沸石中普遍存在结构和组成的非均一性，这对其性质有很大影响。传统透射电子显微镜（TEM）中，由于厚度限制的横向分辨率、缺乏深度分辨率以及电子剂量受限的聚焦，限制了对沸石的局部结构研究。我们证明，基于四维扫描 TEM（4D-STEM）数据的多层面相衬术方法可以克服这些限制。从40 纳米厚的 MFI 沸石获得的图像具有0.85 埃的横向分辨率，能够识别单个骨架氧（O）原子，并精确确定吸附分子的取向。此外，~6.6 纳米的深度分辨率允许探测 O 空位的三维分布，以及在共生长的 MFI 和 MEL 沸石中的相界。4D-STEM 相衬术可以普遍应用于具有类似高电子束灵敏度的其他材料。
