Preparation and characterization of water-soluble monodisperse magnetic iron oxide nanoparticles via surface double-exchange with DMSA

A simple, but efficient method for preparation of water-soluble iron oxide nanoparticles has been developed. Monodisperse Fe3O4 nanoparticles were synthesized by thermal decomposition of iron-oleate. Surface double-exchange of oleic acid capped monodisperse Fe3O4 nanoparticles with a familiar 2,3-dimercaptosuccinnic acid (HOOC–CH(SH)–CH(SH)–COOH, DMSA) was first performed in chloroform in the presence of triethylamine, and then this process was repeated in ethanol under the same conditions. The resulting Fe3O4 nanoparticles could be transferred into water to form stable magnetic fluid without post-treatment processes such as filtration and re-concentration. TEM images show that water-soluble Fe3O4 nanoparticles remain monodisperse and even form a monolayer of ordered assembly, and the results of TGA, VSM show that Fe3O4 nanoparticles via surface double-exchange possess more DMSA molecules through intermolecular disulfide cross-linking between DMSA, as confirmed by Raman spectra. Zeta potential measurements show that nanoparticles after surface double-exchange are negatively charged in the range of pH = 1–14, and stability assays exhibit their excellent stability in water and other physiological environments.