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Iron Oxide Versus Fe _{55} Pt _{45} /Fe _{3} O _{4} : Improved Magnetic Properties of Core/Shell Nanoparticles for Biomedical Applications

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4 Author(s)
Varanda, L.C. ; Dept. de Fisico-Quim., Inst. de Quim. de Sao Carlos, Sao Carlos ; Imaizumi, M. ; Santos, F.J. ; Jafelicci, M.

In this paper, synthesis of the Fe55Pt45/Fe3O4 core/shell structured nanoparticles using the modified polyol process combined with the seed-mediated growth method is reported. Iron oxide shell thickness was tuned controlling the Fe(acac) 3/FePt seeds in the reaction medium. Annealing of the core/shell structure leads to iron-rich layer formation around the hard FePt phase in the nanoparticle core. However, the 2 nm Fe3O 4 shell thickness seems to be the limit to obtain the enhanced magnetization close to the alpha-Fe and preserving an iron oxide shell after annealing at 500degC for 30 min in a reducing atmosphere. The presence of both the oxide layer on nanoparticle surface and an intermediate iron-rich FePt layer after annealing promote strong decreases in the coercive field of the 2-nm-oxide shell thickness. These annealed nanoparticles were functionalized with dextran, presenting the enhanced characteristics for biomedical applications such as higher magnetization, very low coercivity, and a slightly iron oxide passivated layer, which leads an easy functionalization and decreases the nanoparticle toxicity.

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Magnetics, IEEE Transactions on  (Volume:44 ,  Issue: 11 )