Solid-state thermal decomposition of the [Co(NH3)5CO3]NO3·0.5H2O complex: A simple, rapid and low-temperature synthetic route to Co3O4 nanoparticles

Co3O4 nanoparticles were easily prepared via the decomposition of the pentammine(carbonato)cobalt(III) nitrate precursor complex [Co(NH3)5CO3]NO3·0.5H2O at low temperature (175 °C). The product was characterized by thermal analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area measurements and magnetic measurements. The FT-IR, XRD, Raman and EDX results indicated that the synthesized Co3O4 nanoparticles are highly pure and have a single phase. The TEM analysis revealed nearly uniform and quasi-spherical Co3O4 nanoparticles with an average particle size of approximately 10 nm. The optical absorption spectrum of the Co3O4 nanoparticles showed two direct band gaps of 2.18 and 3.52 eV with a red shift in comparison with previous reported values. The prepared Co3O4 nanoparticles showed a weak ferromagnetic behaviour that could be attributed to uncompensated surface spins and/or finite-size effects. Using the present method, Co3O4 nanoparticles can be produced without expensive organic solvents and complicated equipment. This simple, rapid, safe and low-cost synthetic route can be extended to the synthesis of other transition-metal oxides.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► [Co(NH3)5CO3]NO3·0.5H2O complex was used for preparing pure Co3O4 nanoparticles. ► Co3O4 nanoparticles were prepared at low temperature of 175 °C. ► Co3O4 nanoparticles show a weak ferromagnetic behaviour at room temperature. ► The method is simple, low-cost and suitable for the production of Co3O4.