Structure switch between α-Fe2O3, γ-Fe2O3 and Fe3O4 during the large scale and low temperature sol–gel synthesis of nearly monodispersed iron oxide nanoparticles

With same procedure and same starting materials, nearly monodispersed α-Fe2O3, γ-Fe2O3 and Fe3O4 nanoparticles were synthesized on an large scale of about 60 g in a single reaction through a low temperature sol–gel route. The simple preparation process includes the reactions between FeCl2 and propylene oxide in ethanol solution at boiling point to form a sol and the following drying of the sol. The different iron oxide phases can be obtained just by changing of the drying conditions for the sol solution. The strategy developed in this study offers important advantages over the conventional routes for the synthesis of α-Fe2O3, γ-Fe2O3 and Fe3O4 nanoparticles, showing potential for its application in industrial production of iron oxides.

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► α-Fe2O3, γ-Fe2O3 and Fe3O4 monodisperse nanoparticles were synthesized through a sol–gel route.
► The corresponding structure of iron oxide was obtained just by the changing of drying conditions.
► The preparation was carried at mild conditions on large scale due to the unique chemistry of epoxide.