Pyrolysis synthesis of magnetic εε- and ββ-MnO2 nanostructures and the polymorph discrimination

The concentration of the Mn(NO3)2 solution has significant influence on the morphologies and the phases of the MnO2 products. A large number of εε- MnO2 nanowires were prepared via a simple pyrolysis under lower reaction concentration. The nanowires have lengths up to tens of micrometers and diameters in the range of 20–100 nm. The ββ- MnO2 nanobundles and nanoflowers were prepared by increasing the concentration of Mn(NO3)2 solution. The superparamagnetism of εε- MnO2 nanowires and paramagnetism of ββ- MnO2 nanoflowers indicate their potential applications in magnetic materials.