Atomic imaging of molybdenum oxide nanowires with unique and complex periodicity by advanced electron microscopy.

Abstract

Crystalline Mo5O14 exhibits distinctive structural features such as tunnel structure and a pseudolamellar arrangement according to the ideal model. However, the spatial resolution of the conventional technique of transmission electron microscopy (TEM) is insufficient to distinguish the actual positions of atoms. In this work, we aimed to systematically analyze and identify the Mo5O14 nanowires fabricated by the chemical vapor deposition (CVD) process. Utilizing high-angle annular dark-field (HAADF), annular bright-field (ABF) and enhanced annular bright-field (E-ABF) within the scanning transmission electron microscope (STEM) mode reveals the structural features at the atomic scale. In addition, the ultrahigh resolution images have provided new insights to the [001] growth direction of the Mo5O14 nanowires with a tunnel structure throughout the nanowire. The cross-sectional images show the unique close-packed plane and atomic arrangement with a network of MoO6 octahedra and MoO7 pentagonal bipyramids. These results provide a new concept of atomic arrangement and benefit the realization of Mo5O14-type catalysts to be used in the selective oxidation process and batteries applications.