Mechanochemical synthesis of MnZn ferrite nanoparticles suitable for biocompatible ferrofluids

Mn0.4Zn0.6Fe2O4 nanoparticles (NPs) were synthesized by the mechanochemical method, starting from elemental oxides. Structural and magnetic properties of the NPs were investigated by X ray diffraction (XRD), vibrating sample magnetometry (VSM) and both scanning and transmission electron microscopy (SEM and TEM). XRD measurements show that MnZn ferrite is already present after 15 min of milling. After milling for 120 min, the resulting powder is almost completely single-phase without the need of any thermal treatment. Magnetization curves for samples with different milling times show saturation magnetizations ranging from 12.2 emu/g -after 15 min to 50.3 emu/g -after 120 min. Coercive field and remanent magnetization are negligible for all samples, in agreement with a superparamagnetic behavior. NPs with mean size of 8 nm were separated by centrifugation and were coated with chitosan for the preparation of a ferrofluid, which showed good stability for 12 h. The Intrinsic Loss Parameter (MP) of this fluid indicates that the mechanochemical method can be a good alternative for the synthesis of the usual Fe-oxides ferrofluids used in hyperthermia. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.