Functionalization-induced improvement in magnetic properties of Fe3O4 nanoparticles for biomedical applications
Dattatri K. Nagesha, Brian D. Plouffe, Minh Phan, Laura H. Lewis, Srinivas Sridhar, and Shashi K. Murthy
Journal of Applied Physics 105, 07B317 (2009)
Fe3O4 were synthesized nanoparticles by thermal decomposition method with oleic acid as the surfactant, and to make them suitable for aqueous environments, dopamine ligand exchange was carried out on the particles. SQUID magnetometry confirmed superparamagnetic behavior in the nanoparticles. A surprising and significant increase in the remanence MR, saturation magnetization MS, and blocking temperature TB of the particles was found after dopamine functionalization, even though TEM and XRD studies revealed no change in the particles' size and/or structure. The results are consistent with an increase in the magnetic size of the nanoparticle core induced by the dopamine ligand exchange process. These effects are tentatively attributed to surface bonding effects that alter the canted magnetic state of the Fe3O4 nanoparticles.