A simple one step approach to preparation of γ-MnOOH multipods and β-MnO2 nanorods

Multipod-like gamma-MnOOH and rod-like beta-MnO2 nanocrystals are synthesized by oxidization of manganese sulphate hydrate (MnSO4-H2O) using sodium chlorate (NaClO3) as an oxidizing agent in a simple hydrothermal reaction system in the absence of any templates, catalysts, or organic reagents. The powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize the as-prepared products. Based on the results of XRD and SEM, multipod-like gamma-MnOOH can be transformed into rod-like beta-MnO2 nanocrystals via one step synthetic route by simply increasing the reaction time while other conditions are kept constant. And a possible transfer mechanism via a nucleation-dissolution-anisotropic growth-recrystallization process is presented. (C) 2007 Elsevier B.V. All rights reserved.