Preparation of Mn3O4 nanocrystallites by low-temperature solvothermal treatment of γ-MnOOH nanowires

The preparation of trimanganese tetroxide (Mn3O4) nanocrystallites from gamma-MnOOH nanowires under mild conditions has been achieved by two steps: first, gamma-MnOOH nanowires with a mean diameter of about 12 nm and lengths of up to several micrometers were directly prepared via hydrothermal reaction between KMnO4 and toluene in water at 180degreesC for 24 h; then, pure Mn304 nanocrystallites could be obtained by solvothermal treatment of the gamma-MnOOH nanowires in ethylenediamine (EDA) and ethylene glycol (EG) at 150degreesC for 24 h. It was found that the Mn3O4 product obtained in EDA comprised well-defined nanocrystallites with the size in the range of 15-35 nm, while the one obtained in EG consisted of aggregated nanoparticles with the size of less than 18 nm. The possible formation mechanism of nanocrystalline Mn3O4 in EDA and EG and reasons for the different effects of various solvents on the products were also proposed. (C) 2004 Elsevier Inc. All rights reserved.