Simple and low-temperature preparation of Co3O4 sphere-like nanoparticles via solid-state thermolysis of the [Co(NH3)6](NO3)3 complex

In this work, spinel-type Co3O4 spherical nanoparticles were easily prepared via decomposition of the hexamminecobalt(III) nitrate complex, [Co(NH3)6](NO3)3, at low temperature (200 °C). The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV–vis spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) specific surface area measurement and magnetic measurements. The results confirmed that pure single-phase Co3O4 nanoparticles with weak ferromagnetic behavior were obtained by this method. TEM images showed that the Co3O4 nanoparticles are sphere-like with an average diameter size of around 15 nm. The optical spectrum indicated two direct band gaps at 2.15 and 3.56 eV which are blue-shifted relative to reported values for the bulk sample. Using this fast and simple method, Co3O4 nanoparticles can be produced without expensive and toxic solvents or complicated equipment.