Simple and low-temperature synthesis of NiO nanoparticles through solid-state thermal decomposition of the hexa(ammine)Ni(II) nitrate, [Ni(NH3)6](NO3)2, complex

NiO nanoparticles with an average size of about 12 nm were easily prepared via the thermal decomposition of hexa(ammine)Ni(II) nitrate complex, [Ni(NH₃)₆](NO₃)₂, at low temperature of 250 °C. The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and magnetic measurement. The magnetic measurement revealed a small hysteresis loop at room temperature, confirming a superparamagnetic (weak ferromagnetic) nature of the synthesized NiO nanoparticles. Indeed, the NiO nanoparticles prepared by this method could be an appropriate semiconductor material due to the optical band gap of 3.35 eV which shows a red shift in comparison with the previous reports. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.