Magnetic properties and hyperthermia behavior of iron oxide nanoparticle clusters

In this study, Iron Oxide nanoparticle clusters have been synthesized utilizing individual Fe3O4 nanoparticles with different sizes as building blocks. The synthesis was accomplished by encapsulation of the individual Fe3O4 nanoparticles in an oil in water emulsion via hydrophobic interactions between cetyltrimethylammonium bromide (CTAB) and the nanoparticle’s surface aliphatic capping agents. It has been observed that the time, temperature and CTAB concentration were three crucial factors for controlling the size, shape and collective behavior of the clusters. Powder X-Ray Diffraction study shows that both individual Fe3O4 and the corresponded nanoparticle clusters have the Fe3O4 cubic spinel structure. Dynamic Light Scattering (DLS) shows that the hydrodynamic diameter of cluster is in the range of 100 to 200 nm. Transmission electron microscopy (TEM) images illustrate that different sizes of clusters can be effectively synthesized by using different concentration of CTAB and the results are consistent with the DLS values. Magnetic measurements show that the saturation magnetization of clusters can be changed from 56.7 emu/g to 70.1 emu/g by just changing the size of primary individual nanoparticles from 7.1 nm to 11.5 nm. Also, the blocking temperatures for Fe3O4 clusters were increased to higher temperatures which confirms the stronger collective behavior in the case of larger nanoparticles. The magnetic hyperthermia behavior of the clusters has also been studied, and the data shows that the Specific Absorption Rate (SAR) values are increased by both the clustering and the size of the primary nanoparticles.