Fabrication of hydrophilic magnetic nanoparticles

Abstract

Magnetic properties of nanoparticles (NPs) enable them to be oriented and self-assembled into nanostructures. Magnetic nanoparticles (MNPs) used in this study are magnetite (Fe3O4) NPs. These particles have great application potential in various fields including bioapplications. However, magnetites by their nature, have hydrophobic surfaces, hence cannot be used in aqueous media as bare particles. In order magnetites to be biocompatible, they need surface modifications. The surface modification this project aims involves coating them with SiO2. Silica-coating (Si-coating) can be achieved with two methods; "in situ" coating of magnetite NPs where both magnetite synthesis and Si-coating occur in the same reaction mixture, and coating of pre-prepared magnetite NPs where solid NPs are first dispersed, then coated with SiO2. In both methods the reaction takes place in aqueous cores of water-in-oil (w/o) microemulsion (ME). AOT is the surfactant used in all reactions, where n-heptane is the oil phase. The NP size is controlled by controlling the nanodroplet size within the ME. It has been observed that "in situ" method resulted in NPs where coating was more successful when compared with the "pre-prepared particles" method in AOT-stabilized reverse ME. The particles obtained were more polydispersed compared to the pre-prepared reaction.