Enhanced magnetic properties of carbon nanotubes and multilayer graphene decorated with Co3O4

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
.