Surface Investigation and Magnetic Behavior of Co Nanoparticles Prepared via a Surfactant-Mediated Polyol Process

This work reports on the structural and magnetic properties of 10 nm-sized Co nanoparticles, along with a surface investigation of chemi-adsorption of fatty acid-like oleic acid on their surfaces. The hexagonal close-packed superparamagnetic Co nanoparticles were prepared by a surfactant-mediated polyol process that consists of refluxing a solution of the metal precursor, using oleic acid in ethylene glycol. The nature of an adsorbed fatty acid on a Co nanoparticle surface was studied, using transmission electron microscopy and Fourier transform infrared spectroscopy techniques. The magnetic properties of the surfactant-capped and uncapped Co nanoparticles are compared. The surfactant-capped Co nanoparticles prepared by the modified polyol process show excellent superparamagnetic behaviors, with high magnetic susceptibility, negligible coercivity, and high saturation magnetization.