Shape-influenced magnetic properties of CoO nanoparticles

Using a wet chemical approach, CoO nanospheres, nanorings, nanoflowers, and nanowires of different sizes were generated. Among those, nanorings show ferromagnetic behavior below 6 K while the nanospheres remain paramagnetic. X-ray photoelectron spectroscopy for Co 2p, 3p, and 3s core-levels indicates the paramagnetic high-spin Co(II) electronic configuration. This finding reveals the optical, electronic, and magnetic behavior of CoO nanoparticles (NPs) that opens new opportunities for future applications as catalysts precursors for making pigments, lithium-ion battery materials, or as solid-state sensors as anisotropy source for magnetic recording.Graphical abstractUsing a wet chemical approach, CoO nanospheres, nanorings, nanoflowers, and nanowires of different sizes were generated. Among those, nanorings show ferromagnetic behavior below 6 K while the nanospheres remain paramagnetic. X-ray photoelectron spectroscopy for Co 2p, 3p, and 3s core-levels indicates the paramagnetic high-spin Co(II) electronic configuration. This finding reveals the optical, electronic, and magnetic behavior of CoO nanoparticles (NPs) that opens opportunities for future applications as catalysts precursors for making pigments, lithium-ion battery materials, or as solid-state sensors as anisotropy source for magnetic recording.