SAXS study of chain-like structures formed by magnetic nanoparticles

Nanoparticles consisting of a magnetic core (γ-Fe2O3) and an organic shell were prepared by thermal decomposition of an iron carbonyl complex in the presence of oleic acid. The nanoparticles were then dispersed in cyclohexane to form a stable ferrofluid. These dispersions were investigated by means of Small Angle Scattering of X-rays (SAXS) and the data were interpreted according to a “pearl necklace” model, opportunely modified to account for the core-shell structure of the magnetic nanoparticles. The results of the fittings show that nearly monodisperse spherical particles with a radius of the magnetic core of about 3.9 nm and a shell of about 2 nm were obtained. These nanoparticles self-assemble in chain-like structures, even in the absence of an applied magnetic field.