Preparation of Iron boride-silica core-shell nanoparticles with soft ferromagnetic properties

CHATREE SAIYASOMBAT; NATTASAMON PETCHSANG; I MING TANG; JOSE H HODAK

NANOTECHNOLOGY

Lugar: 085705; Año: 2008 vol. 19 p. 857051 - 857057

0957-4484

A one-pot aqueous chemical synthesis for silica passivated ferromagneticnanoparticles is presented. The average size of these particles is 90 ± 20 nm. The x-rayand electron diffraction revealed that the nanoparticles are mainly composed ofpolycrystalline iron boride. The broad x-ray diffraction peak leads to an averagecrystallite size of 1.8 nm which is much smaller that the overall size of the particles, andis consistent with the polycrystalline nature of the samples. Mössbauer spectroscopy andmagnetization experiments were used to establish the room temperature magneticproperties as well as the chemical nature of the particles. 2 Fe B dominates thecomposition of the nanoparticles, having a hyperfine field broadly distributed in the 10-33 T range. Alpha iron, the second ferromagnetic material identified in the particlesamounts to 4.6% of the composition. Finally, a paramagnetic phase accounting forapproximately 14.6% of the material of the particles was also detected. Thesenanoparticles contain a core with soft ferromagnetic properties surrounded by apassivating silica layer, and are suitable for magnetically targeted drug delivery andelectromagnetic induction heating applications.