Immobilization of magnetic iron oxide nanoparticles on laponite discs – an easy way to biocompatible ferrofluids and ferrogels

Abstract

Magnetic nanocomposites containing iron oxide (maghemite – γ-Fe₂O₃) nanoparticles, embedded in a synthetic clay matrix (laponite) were prepared by a new one step chemical route and characterized by TEM, XRD, magnetization measurements, Mössbauer spectroscopy, DLS, and MRI measurements. The synthesis procedure leads to non-stoichiometric γ-Fe₂O₃ with a controllable content in the nanocomposite. Magnetic nanoparticles incorporated in the diamagnetic clay matrix exhibit a mean diameter of 13 nm and superparamagnetic behaviour with a high saturation magnetization achievable at low applied magnetic fields. The in-field Mössbauer spectra and ZFC/FC magnetization curves reveal a perfect ferrimagnetic ordering within nanoparticles with negligible spin frustration and interparticle interactions due to the incorporation of maghemite nanoparticles into the nanocrystalline laponite matrix, thus, significantly avoiding their clustering and agglomeration. Magnetic iron oxide nanoparticles embedded in the laponite matrix exhibit strong T₂-weighted MRI contrast. The γ-Fe₂O₃/laponite nanocomposite particles have a 200 nm hydrodynamic diameter and form very stable hydrosols and/or hydrogels depending on their concentration in water.