Synthesis and characterization of NiFe2O4@Co3O4 core-shell nanoparticles

Abstract Premade nickel ferrite (NiFe 2 O 4 ) nanoparticles were used as a core around which cobalt (II, III) oxide (Co 3 O 4 ) 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 Co 3 O 4 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 11.0 wt.% Co yielded a partial shell whilst a concentration of 7.6 wt.% Co yielded a uniform shell layer around most NiFe 2 O 4 nanoparticles. All particles with a Co 3 O 4 shell was obtained by following a two-step synthesis where 3.8 wt.% Co was used in each step to target a final loading of 7.7 wt.% Co. Whilst a concentration of 11.0 wt.% Co yielded a partial shell, the presence of Co 3 O 4 nanoparticles was also evidenced. A concentration of 19.1 wt.% Co resulted in the formation of separate Co 3 O 4 nanoparticles amongst the NiFe 2 O 4 nanoparticles.