Effect of NaOH concentration on synthesis of cobalt oxide nanoparticles by pyridinium-based ionic liquid by co-precipitation method

In this study, nano-sized cobalt oxide samples were prepared by changing the NaOH concentration by co-precipitation using N-octyl pyridinium bromide [OPy][Br] ionic liquid in an aqueous medium. Properties of prepared nanostructures were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibration sample magnetometer (VSM), and ultraviolet-visible (UV-Visible) spectroscopy. XRD diffraction results show that with increasing NaOH concentration, the average size of crystals decreased. In this paper, the smallest particles in the range of 19 to 23 nm were obtained using 3 mmol NaOH. Using FE-SEM images, it can be seen that the particles have a spherical and plate-like shape. The value of Eg for the sample with the smallest crystal size of 17 nm has the highest bandgap energy of 3.01 electron volts. VSM analysis of the samples showed that all samples were ferromagnetic in nature and the saturation magnetization of the samples decreased with decreasing particle size.