Preparation of single-crystal α-MnO2 nanorods and nanoneedles from aqueous solution

Single-crystal α-MnO2 nanorods and nanoneedles were prepared in H2SO4 solution by adding KMnO4 at temperature of 70-95 °C. The morphologies of the as-synthesized products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and high-resolution transmission electron microscopy. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and cryo-nitrogen adsorption measurements were also employed for characterization of the nanostructures. The results show that pure α-MnO2 nanorods with diameters of 12-20 nm and nanoneedles with diameters of 5-8 nm were synthesized by this technique. A high specific surface area of 165.8 m2/g was achieved for the α-MnO2 nanoneedles with a small diameter of 5 nm.