Simple preparation of ferromagnetic Co3O4 nanoparticles by thermal dissociation of the [CoII(NH3)6](NO3)2 complex at low temperature

Co3O4 nanoparticles were prepared using [Co(NH3)6](NO3)2 as a starting material via a solid-state thermal decomposition route at low temperature (150°C). The product was characterized by thermal analysis (thermogravimetric/derivative thermogravimetric/differential thermal analysis), X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller specific surface area measurement, UV-visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, and magnetic measurements. The results confirmed that the nanoparticles are highly pure Co3O4 with weak ferromagnetic properties. TEM images showed that the Co3O4 nanoparticles have an average diameter size of around 13 nm. The optical spectrum indicated two direct bandgaps at 2.3 and 3.2 eV which are blueshifted relative to reported values for the bulk sample. By this fast and simple method, Co3O4 nanoparticles can be produced without expensive and toxic solvents or complicated equipment.