Study of the ferrofluid drying process for morphological and nanostructutal characterization

Abstract

A drying method suitable for the study of the morphological and structural properties of colloidal magnetic systems, including a contrast agent used in Magnetic Resonance Imaging (MRI) is described. We tested three alternative ferrofluid drying methods: drying at 70°C in nitrogen atmosphere; drying in air at 70°C; and drying by liophylization using an MRI marker in the form of a colloidal suspension (Endorem™ - Guebert). X-ray diffraction (XRD), and transmission electron microscopy (TEM) were applied to each characterization method. The XRD allowed the observation of the possible physical-chemical changes of the stabilizers and also Fe3O4, present in the system. The morphology and nanoparticles size distribution was analyzed by TEM. Among the drying methods examined in this study, the liophylization has shown to be the more adequate one for the nanoparticles (FE3O4) morphological study and nanostructural characterization, because the structure of the nanoparticles was maintained the same as in the suspension. The drying procedures performed at 70°C in the atmospheres of nitrogen and air let to the coalescence and growth of the nanoparticles, as well as some degradation has been noticed in some of the stabilizers.