Facile Preparation of Monodisperse CoO Nanocubes via Thermal Decomposition of Cobalt(II) Nitrate

Monodisperse CoO nanocubes have been successfully synthesized via a facile solvothermal decomposition of cobalt (II) nitrate in the presence of silver nitrate in oleylamine. The CoO nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). For these face-centered cubic (fcc) CoO nanoparticles, the exposed planes were indexed and the possible formation mechanism was tentatively discussed. As a reducing agent in the system, oleylamine molecules were oxidized by Ag+ ions followed by the formation of CoO species. Controlled experiments showed that monodisperse CoO nanocubes can be prepared in the presence of AgNO3 while CoO nanoparticls with irregular shapes can be obtained without the participation of AgNO3. It is reasonable to conclude that oxidized oleylamine was important factor to influence the growth rates of different crystal planes of CoO for their varied affinity between oxidized oleylamine molecules and crystal planes.