A Novel Synthesis and Characterization Studies of Magnetic Co3O4 Nanoparticles.

Cobalt oxide (Co3O4) nanoparticles were synthesized by microwave combustion method (MCM) using urea as the fuel. For the purpose of comparison, they are also prepared by conventional combustion method (CCM). The prepared samples were examined by using X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), UV-Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). XRD analysis indicated that the as-prepared samples have well-crystalline cubic phase. HR-TEM images showed that Co3O4 nanoparticles have sphere-like structure with an average particle size in the range of 20-25 nm (MCM) and 45-50 nm (CCM). Optical properties of Co3O4 nanoparticles revealed the presence of two band gap (1.89 and 2.54 eV (MCM), 1.68 and 2.38 eV (CCM)) values, which in turn confirmed the semi-conducting properties. VSM measurements revealed a small hysteresis loop at room temperature thus indicating a weak ferromagnetism.