MAGNETIC HYPERTHERMIA AND MAGNETIC DYNAMIC RESPONSE OF AQUEOUS SUSPENSION OF FE3O4 NANOPARTICLES COATED WITH OLEIC ACID/CHITOSANE

CORAL, D.F.; P. MENDOZA-ZELIS; LASALLE, V. ; NICOLAS, P. ; FERREIRA, M.L.; M.B. FERNANDEZ VAN RAAP

Buenos Aires

Congreso; X Latin Americam Workshop on Magnetism ans Magnetic Materials and theri Applications; 2013

The issue on whether dynamic properties of magnetic colloids retrieved from magnetic measurement of low ac-eld ampli-tudes and frequencies can be extrapolated to analyzed Specic Absorption Rate (SAR) data acquired at higher amplitudesand frequencies excitation elds is addressed. The dynamic response of two colloids of magnetite coated with oleic acid(OA-MAG) and chitosan (CS) in water, displaying high and low heat power release (85 and 5 W/gFe3O4) at frequency f of267 kHz and eld amplitude of 52 kA/m, were analyzed. Both colloids are the same in terms of carrier liquid, surfactantand magnetic phase composition. The colloids were prepared by nanoprecipitation under the same experimental condition.The same amount of CS was used to hydrophilize OA-MAG nanoparticles (2/3 of CS/OA-MAG w/w) previously synthesizedwith dierent mass ratio of oleic acid to magnetite (1/1 and 4/1), resulting in mean sizes (d) of 10.02.9 and 13.43.6 nm(TEM) and hydrodynamic sizes of 168 and 460 nm (DLS) respectively. From out of phase a.c susceptibility temperaturedependence "(T), acquired in the frequency range from 5 to 104 Hz and eld amplitude of 80 A/m, attempt time  o andenergy barrier Ea was obtained and used to analyzed SAR data within the linear response theory. Results indicate that thenanoparticles in both colloids relax by Neel mechanism. Simulations of g(d)"( (d)), using magnetic core size distributiong(d) inferred from VSM, and " size dependence, introduced by Neel relaxation time and evaluated at a xed frequencycoincident with SAR experiment, were calculated. For the colloid displaying high dissipation, the maximum of the simulatedcurve is close to the mean magnetic core size, while for the other colloid is far away. Dipolar magnetic interactions are notnegligible in the case of 10 nm nanoparticles, and their inuence in the dissipation is also discussed.