Phase transformation of FeO/Fe3O4 core/shell nanocubes and facile synthesis of Fe3O4 nanocubes

A phase transformation induced by reduction in the γ-Fe2O3 nanocubes synthesized by oxidizing the corresponding FeO/Fe3O4 nanocubes was achieved in solution. Results from x-ray diffraction (XRD), color indication, and magnetic analysis strongly support this phase transformation. The γ-Fe2O3 nanocubes were transformed to Fe3O4 nanocubes within 260–300 °C range and the FeO/Fe3O4 nanospheres at 350 °C. The change in shape of the nanoparticles within the γ-Fe2O3→Fe3O4 transformation as observed from the transmission electron microscopy images was representative for entire the nanoparticles systems as confirmed by the XRD patterns of these nanoparticles in assembled state, suggesting a simple and novel route for synthesis of Fe3O4 nanocubes.