One-Dimensional NaSn₂F₅ Crystals Inside Single-Walled Carbon Nanotubes

Abstract

Crystals of NaSn2F5 were obtained from an aqueous solution. Their morphology and habitus were studied via scanning electron microscopy and X-ray phase diffraction analysis. The crystals obtained have a long prismatic shape with a very large aspect ratio (>100). The faceting of the crystal is represented by the (110) face, while the (100) face is practically absent. A nanocomposite incorporating one-dimensional (1D) NaSn2F5@SWCNT crystals was synthesized from the melt by means of the capillary wetting technique. The embedded fragment is represented by two planes of Sn cations, which provide contrast in high-resolution electron microscopy images. The cation plane is represented by the (110) crystallographic plane of the NaSn2F5 structure. The crystallographic direction [22¯3] coincides with the nanotube axis. The first layer of Sn cations forms a hexagonal network with Sn atoms at its nodes. The tin atoms in the second layer are arranged according to the closest spherical packing law in a plane, but with a distance between atoms that is two times greater than that in the first layer. Sn cations’ hexagon sizes are ~0.87 nm and ~0.69 nm in size. According to the Raman spectroscopy data, the nanocomposite behaves as an electron acceptor. The SWCNT diameter of 1.54 nm revealed using NaSn2F5@SWCNT Raman spectroscopy corresponds to their diameter in electron microscope images and the diameter used for modeling.

Keywords

• nanocomposite
• carbon nanotube
• 1D crystal
• electron microscopy
• structure modelling
• Raman spectroscopy