How to decrease the agglomeration of magnetite nanoparticles and increase their stability using surface properties

The development of a variety of methodologies has been studied in order to obtain good dispersed nanoparticles in the medium without seriously affecting the magnetic and rheological properties of them. One of the areas of application that needs a material with controlled particle size and good stability is that of biomedical. In those applications are required to avoid the precipitation for promoting the biocompatibility and for obtaining a homogeneous nanoparticle size. In this paper Magnetite nanoparticles were synthesized by the Fast Injection Co-precipitation method. The magnetic nanoparticles were dispersed modifying their surface and, in this way, decreasing the agglomerate sizes and on the other hand favor the stability of the suspension. The surface modification was carried out by means of different coatings such as: sodium citrate, sodium metasilicate and colloidal silica from Tetraethyl Orthosilicate, obtained using the acid sol-gel process. The nanoparticles obtained were characterized by X-ray Diffraction, Vibrating Sample Magnetometer, Dynamic Light Scattering, Transmission Electron Microscope, Zeta Potential and Infrared Spectroscopy. An agglomerate size of nanoparticles around 100 and 200 nm was obtained, with good superparamagnetic properties. Also, by zeta potential measurements was found that the functional groups added by sodium metasilicate and tetraethyl orthosilicate generate repulsion among the superparamagnetic iron oxide nanoparticles increasing their zeta potential and stability of the suspensions. The main conclusion from this research is the establishment of a simple and very fast route to obtain stable and dispersed superparamagnetic nanoparticles with high stability at pH 7.4 that can be used in medical applications. This was achieved considering the difference in the isoelectric point, IEP, and of course in the net charge of both silica polymer and magnetite.