Controlling the synthesis of CoO nanocrystals with various morphologies

A series of cubic CoO nanocrystals with various morphologies and sizes were obtained via the decomposition of cobalt(II) oleate complex at 280-320 degrees C in noncoordinating solvent octadecene containing dodecanol/oleic acid. The morphology of COO nanocrystals could be conveniently tuned by manipulating the decomposition rate of cobalt oleate with the introduction of activating reagent dodecanol or inhibiting reagent oleic acid into the reaction system. More specifically, the morphology of COO nanostructures can be tuned from the simple isolated tetrahedral shape to the complex 3D flowerlike shape by increasing the concentration of oleic acid, while with increasing concentration of dodecanol, the morphology of the COO structures can be tuned from the 3D nanoflower to isolated spheres. The structure and morphology of the obtained COO nanocrystals were characterized by X-ray diffraction (XRD) and by standard and high-resolution transmission electron microscopy (TEM and HRTEM), and the structural evolution and formation mechanism were also illustrated.