Heat Generation by Magnetic Losses of Fe3O4 Nanoparticles for Magnetic Fluid Hyperthermia

M VASQUEZ MANSILLA; ENIO LIMA JR.; E DE BIASI; M L MOJICA PISCIOTTI; H TROIANE; F EFFENBERG; L M ROSSI; R D ZYSLER

Rome, Italy

Conferencia; X International Conference on Nanostructured Materials – NANO2010; 2010

In Magnetic Fluid Hyperthermia (MFH) therapy the energy absorption by magnetic nanoparticles in the presence of an alternating field increases locally the temperature of a targeting tissue. Basically, the mechanism for magnetic losses in superparamagnetic nanoparticles are the thermal relaxation of their magnetic moments (Neel and Brown relaxation) Instead, the hysteresis losses are frequently negligible. Concerning the thermal relaxation mechanism, the absorption will depends of the size, magnetic anisotropy, hydrodynamic radius, and magnetic interactions. In the present work, we show results on the Specific Absorption Rate (SAR) measurements of Fe3O4 nanoparticles produced by thermal decomposition of Fe(acac)3 in the presence of surfactants and dispersed in an organic solvent. We have studied the effects of diameter, grain size distribution, crystallinity and agglomeration on the heat capability of Fe3O4 Nanoparticles. Two sets of samples were growth in sucessive synthesis procedure using smaller particles as seeds. In the first set we have monodisperse and noninteracting nanoparticles, while in the second one we observe agglomerated nanoparticles (large hydrodynamic radius) with wider grains size distribution. Heat conversion mechanism based in the Soner-Wohlfarth hysteresis losses must to be added to the Neel-Brown mechanisms to explain our experimental data. In the forme mechanisms the heat hability of monodomain nanoparticle can be calculated considering the dependence of the remanence and coercive field with the frequency and amplitude of the applied ac magnetic field. The results and discussion presented herein will allow us to optimize the SAR conditions aiming to the use of this nanometric system in MFH protocols. We have observed a maximun value of SAR = 50 W/G for applying field of 100 kHz and 160 Oe.