A controllable one-pot hydrothermal synthesis of spherical cobalt ferrite nanoparticles: synthesis, characterization, and optical properties.

We herein report the controllable synthesis of spherical cobalt ferrite nanoparticles with average crystallite size in the range of 3.6-12.9 nm using a facile, eco-friendly, hydrothermal method. The hydrothermal treatment was carried out by utilizing cobalt nitrate, ferric nitrate, and ammonium hydroxide in the presence and absence of Arabic gum as a surfactant agent. The purity and crystallinity of the products were tuned by varying reaction conditions such as reaction time (0.5-8 h), reaction temperature (120-180 °C), percentage of ethylene glycol (0-100% (v/v)), pH (8-9.6), and amount of Arabic gum (0-2 g). We characterized the prepared products using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy analysis (EDS), selected area electron diffraction (SAED) patterns, and UV-visible diffuse reflectance spectra (DRS). The optimal hydrothermal treatment was performed at 180 °C and pH 9.6 for 4 h in aqueous media. The results also revealed that the as-prepared spinel cobalt ferrite nanoparticles have an estimated optical band gap energy in the range of 1.6-1.9 eV, indicating the semiconducting characteristics of the products.