Synthesis and characterization of the CAT's eye-shaped CoO@SiO2 nanoshell aqueous colloids

The “cat's eye”-shaped CoO(core)@SiO2(shell) nanoshell was prepared by the reverse microemulsion method. The core cobalt oxide nanorods with controlled anisotropy were obtained by thermal decomposition of Co-(oleate)2 precursor. The Co-(oleate)2 precursor was synthesized by a simple complex reaction of cobalt chloride hexahydrate and sodium oleate molecules. The aspect ratio of cobalt oxide nanocrystals was controlled from 1.3 to 10.5 by changing the reaction conditions, such as the heating rate (0.5, 1.0, 2.0 and 4.0 °C/min) and crystal growth time (30, 60 and 120 min), during the reaction. The SiO2 coating on the surface of the core cobalt oxide nanorods was produced by hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) in the water phase of the reverse microemulsion system. The physicochemical characterizations of the obtained CoO@SiO2 nanoshell material were performed by X-ray diffraction (XRD) measurements, Fourier transform-infrared spectroscopy (FT–IR) and high resolution-transmission electron microscopy (HR–TEM).