A new type of molybdenum oxide crystal encapsulated inside a single-walled carbon nanotube

The crystal structure of a new type of molybdenum oxide crystal encapsulated in a single-walled carbon nanotube (CNT) was examined via diffraction and spectroscopic techniques using both X-rays and electron beams. This new type of molybdenum oxide crystal has a chemical bonding state of MoO3, as confirmed by X-ray absorption spectroscopy, and the MoO3 units exhibit axial symmetry, as clarified by electron diffraction from bundled and individual CNTs encapsulating the crystal. To obtain three-dimensional information on the structure, a cross-sectional sample was prepared using a conventional dimple and ion-mill method. High-resolution transmission electron microscopy images exhibit ring-like shapes that originated from the arrangement of the MoO3 units inside the CNTs, as observed along the tube axis. The units are spaced 0.36 nm from each other in a ring arrangement and the distance between each ring is 0.391 nm.