Nonaqueous synthesis of manganese oxide nanoparticles, structural characterization, and magnetic properties

The synthesis, structural characterization, and magnetic properties of crystalline manganese oxide nanoparticles are presented. The procedure is based on the reaction of benzyl alcohol with the two precursors: potassium permanganate KMnO4 and manganese(II) acetylacetonate Mn(acac)(2). Depending on the precursor used, the composition of the final product can be varied in such a way that in the case of KMnO4 mainly Mn3O4 is formed, whereas Mn(acac)(2) leads predominantly to MnO. Rietveld refinement of the XRD powder patterns, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and energy-dispersive X-ray (EDX) analysis, as well as electron energy loss spectroscopy (EELS) were employed for the structural characterization of the as-synthesized compounds. Especially the MnO manganosite nanocrystals exhibit some interesting features. HRTEM investigations point to the formation of a superstructure, which can be described as an ordered Mn vacancy cubic superstructure with the general formula of Mn0.875Ox and a lattice parameter of 8.888 A. The SQUID measurement proves a superparamagnetic behavior of the MnO nanoparticles.