Synthesis of single-crystalline α-MnO2 nanotubes and structural characterization by HRTEM

Single-crystalline α-MnO2 nanotubes were synthesized by hydrothermal method. The growth of α-MnO2 nanotubes is through the formation of the core (γ-MnO2)-shell (α-MnO2) nanofibers, and then through the formation of the cavity by the dissolution of the core. The outer and the inner diameters of as-synthesized nanotubes are in the range from 13.3 to 39.2 nm, and from 2.0 to 10.8 nm, respectively. The lattice images on the wall and in the center correspond to the (2 2 0), and the (2 1 1) interplanar spacing of the tetragonal-structure α-MnO2.