Synthesis and characterization of NiFe2O4@Co3O4 core-shell nanoparticles

Abstract

Premade nickel ferrite (NiFe2O4) nanoparticles were used as a core around which cobalt (II, III) oxide (Co3O4) was grown. In an attempt to vary the shell thickness, the concentration of Co used was varied. It was found that the concentration of Co did dictate whether Co3O4 formed on the surface but not its thickness. Additionally, it was established that a two-step synthesis route was needed to synthesize the core-shell material. Concentrations below 11.0wt.% Co yielded a partial shell whilst a concentration of 7.6wt.% Co yielded a uniform shell layer around most NiFe2O4 nanoparticles. All particles with a Co3O4 shell was obtained by following a two-step synthesis where 3.8wt.% Co was used in each step to target a final loading of 7.7wt.% Co. Whilst a concentration of 11.0wt.% Co yielded a partial shell, the presence of Co3O4 nanoparticles was also evidenced. A concentration of 19.1wt.% Co resulted in the formation of separate Co3O4 nanoparticles amongst the NiFe2O4 nanoparticles.