Well-dispersed cobalt magnetic nanoparticles incorporated into 3D mesoporous graphene

Abstract

The cobalt nanoparticles (Co NPs) incorporated into mesoporous graphene (Co/MG) were prepared via electrostatic interaction between cobalt hydrate ion and exfoliated graphene oxide, further utilizing tri-block co-polymer P123 as a soft-template for the self-assembly process, followed by carbothermal reduction in an argon atmosphere. The particle size and crystal phase of the Co/MG were confirmed by HR-TEM and XRD, which showed the formation of a face-centered cubic cobalt phase and well-dispersed Co NPs with a narrow size distribution of (10.8 +/- 3.5) nm. In addition, most of the Co NPs structures in Co/MG were only slightly oxidized, with remaining Co metal. The EDS and TGA verified the contents of cobalt inside MG. The Raman spectra showed restoration of the graphitic structure after Co NPs were introduced to MG. Further, pore parameters exhibited that the synthesized Co/MG maintained its mesoporosity (S-BET = (683 +/- 99) m(2) g(-1)), suggesting Co NPs were well embedded into the MG structure. The magnetic properties of the Co/MG were measured and implied that the obtained sample has ferromagnetic behavior at 300 K with an excellent value of saturation magnetism (154.3 emu g(-1); 1.88 wt% Co). The results demonstrated that even small amounts of Co NPs can be influenced by an external magnetic field.