Enhanced magnetic properties of carbon nanotubes and multilayer graphene decorated with Co 3 O 4

Here we report evidence of enhanced magnetic properties of carbon nanotubes (CNTs) and multilayer graphene (MLG) decorated with Co 3 O 4 nanoparticles (NPs). These 1∶1 CNTs/Co 3 O 4 and MLG/Co 3 O 4 nano-composites were prepared by a one-step ultrasonic treatment in sodium dodecylbenzene sulfonate (SDBS) surfactant. Structure and morphology of the composites were verified using X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopy. Magnetization (M) vs. magnetic field (H) measurements at room temperature in H up to 2.5 kOe showed that the measured M= MS at 2.5 kOe in both the CNT/Co 3 O 4 and MLG/Co 3 O 4 nanocomposites is enhanced by a factor of about 2.5 as compared to MS expected from the simple addition of MS measured for the two components of the nanocomposites. This is surprising since Co 3 O 4 is a paramagnet at room temperature. These enhanced magnetic properties in the nanocomposites likely result from contributions from Co 3+ ions which being in the low-spin S=0 state are non-magnetic in pristine Co 3 O 4 but become magnetic in the reduced crystalline symmetry of the interface layers in CNTs/Co 3 O 4 and MLG/Co 3 O 4 .