Evolution of Nanostructured Manganese (Oxyhydr)oxides in Water through MnO4- Reduction

Manganese (oxyhydr)oxides are synthesized at low temperature (60 or 95 degrees C) from MnO4- reduction by S2O32- in water. Particles are characterized by X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy, and electron diffraction. The reactivity of S2O32- as a reducing agent is tuned by the temperature in order to selectively synthesize manganite gamma-MnOOH at 60 degrees C and hausmannite Mn3O4 at 95 degrees C. Feitknechtite-beta-MnOOH is identified as an intermediate phase during the formation of gamma-MnOOH. Twinned triangle-shaped feitknechtite particles are obtained and proposed to grow through nanorod self-assembly. The transformation of feitknechtite nanotriangles into manganite nanowires occurs through dissolution of the feitknechtite particle core and recrystallization on the edge of the feitknechtite nanotriangles.