Synthesis and characterization of Co_3O_4 nanoplates by simple thermolysis of the [Co(NH_3)_6]_2(C _2O_4)_3·4H_2O complex

摘要

Nanoplates of Co_3O_4 were selectively prepared through solid-state thermolysis of the [Co(NH_3)_6] _2(C_2O_4)_3·4H_2O complex at 350 C without the need for an expensive and toxic solvent/surfactant or complicated equipment. The product was characterized by thermal analysis (TGA/DTG/DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and magnetic measurements. The TEM images show that the product was formed mainly from square-like Co_3O_4 nanoplates with a length of 50 ～ 200 nm and thickness of 10-20 nm. The FT-IR, XRD, Raman, EDS and VSM results confirm that the as-prepared Co _3O_4 nanoplates are pure and single-phase with a weak ferromagnetic behavior that could be attributed to uncompensated surface spins and/or finite-size effects. The optical spectrum indicated two direct band gaps at 2.15 and 3.50 eV with a blue shift compared with the bulk samples. A plausible pathway for the formation of Co_3O_4 nanoplates from the [Co(NH_3)_6]_2(C_2O _4)_3·4H_2O complex was also proposed.