Synthesis and Characterization of Co₃O₄ Nanoparticles by Thermal Treatment Process

Abstract

The simple preparation of Co₃O₄ nanoparticles from a solid metallorganic molecular precursor [bis(salicylaldehydeato)cobal(II)]; [Co(sal)₂] has been achieved via two simple steps: firstly, the [Co(sal)₂] precursor was precipitated from the reaction of cobalt(II) acetate and salicylaldehyde; in propanol under nitrogen condition; then, cubic phase Co₃O₄ nanoparticles with the size of mostly 20–30 nm could be produced by thermal treatment of the [Co(sal)₂] in air at 500 °C for 5 h. The as-synthesized products were characterized by powder XRD, FT-IR, TEM and SEM. The results confirm that the resulting oxide was pure single-crystalline Co₃O₄ nanoparticles. The optical absorption spectrum indicates that the direct band gaps of Co₃O₄ nanoparticles are 1.53 and 2.02 eV. The optical property test indicates that the absorption peak of the nanoparticles shifts towards short wavelength, and the blue shift phenomenon might be ascribed to the quantum effect. The hysteresis loops of the obtained samples reveal the ferromagnetic behaviors the enhanced coercivity (H _c ) and decreased saturation magnetization (M _s ) in contrast to their respective bulk materials.