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 reverse microemulsion method. ► The aspect ratio of core cobalt oxide nanocrystals were controlled from 1.3 to 10.5 by changing the reaction conditions. ► This method provides a relevant and directed approach to the design of new and novel core-shell structured nanoparticles.