Fabrication of cobalt hollow microspheres via a PVP-assisted solvothermal process

•Solvothermal synthesis of cobalt hollow microspheres.•Water and ethanol mixed solution was used as solvent.•Surfactant of PVP played an important role.•Enhanced coercivity value of about 202 Oe.

Cobalt hollow microspheres were prepared by a surfactant-assisted solvothermal method in water and ethanol mixed solution. The outer diameter ranged from 1.5 to 2 μm, and the shell with average thickness of about 250 nm was constructed by smaller cobalt nanoparticles. The surfactant polyvinylpyrrolidone (PVP) was found to play an important role in the formation of such novel morphology. Room temperature magnetic measurement of the hollow microspheres demonstrated its enhanced ferromagnetic property with a coercivity of 202 Oe. The possible formation mechanism was also discussed. The result showed a potential application in ferrofluids and other related magnetic devices.

Graphical abstractCobalt hollow microspheres were prepared by a PVP-assisted solvothermal method in water and ethanol mixed solution, and such cobalt hollow structures possessed an enhanced coercivity value of about 202 Oe.Figure optionsDownload full-size imageDownload as PowerPoint slide