Magnetic domain interactions of Fe3O4 nanoparticles embedded in a SiO2 matrix

Abstract

Currently, superparamagnetic functionalized systems of magnetite (Fe3O4) nanoparticles (NPs) are promising options for applications in hyperthermia therapy, drug delivery and diagnosis. Fe3O4 NPs below 20 nm have stable single domains (SSD), which can be oriented by magnetic field application. Dispersion of Fe3O4 NPs in silicon dioxide (SiO2) matrix allows local SSD response with uniaxial anisotropy and orientation to easy axis, 90° <001> or 180° <111>. A successful, easy methodology to produce Fe3O4 NPs (6–17 nm) has been used with the Stöber modification. NPs were embedded in amorphous and biocompatible SiO2 matrix by mechanical stirring in citrate and tetraethyl orthosilicate (TEOS). Fe3O4 NPs dispersion was sampled in the range of 2–12 h to observe the SiO2 matrix formation as time function. TEM characterization identified optimal conditions at 4 h stirring for separation of SSD Fe3O4 in SiO2 matrix. Low magnetization (Ms) of 0.001 emu and a coercivity (Hc) of 24.75 Oe indicate that the embedded SSD Fe3O4 in amorphous SiO2 reduces the Ms by a diamagnetic barrier. Magnetic force microscopy (MFM) showed SSD Fe3O4 of 1.2 nm on average embedded in SiO2 matrix with uniaxial anisotropy response according to Fe3+ and Fe2+ electron spin coupling and rotation by intrinsic Neél contribution.

Magnetic Iron Oxide Nanoparticles: Synthesis, Characterization and Functionalization for Biomedical Applications in the Central Nervous System

“…The selected literature was classified into four main groups:Methods of synthesis of IONPs [13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56]Characterization of IONPs [57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,…”

“…Characterization of IONPs [57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85]…”

“…The effect of size on magnetic properties of Fe 3 O 4 NPs embedded in SiO 2 matrix was studied by Fuentes-Garcia and colleagues, showing that the coercive force becomes zero for a critical size of about 20 nm [79].…”

“…The accumulation of NPs in the tumor cells was evaluated by means of histological studies and such SPIONs exhibited enhanced properties for the targeted delivery of chemotherapy and for the delineation of the tumor mass in the brain. Moreover, the synthesis strategy described in [79] (IONPs stabilized SiO 2 matrix) avoided agglomeration phenomena and the characterization by SQUID revealed an effective magnetic excitation to produce hyperthermia.…”

Indirect magnetic force microscopy

“…MFM has been utilized to characterize a variety of magnetic nanoparticles 2–4 and decipher between magnetic and non-magnetic nanoparticles. 5 For superparamagnetic nanoparticles, MFM has been especially useful to evaluate magnetic moment, 6,7 magnetic anisotropy, 8 magnetization curves 9 and the effect of aggregation 10,11 in particles. Applications of MFM have also extended to evaluate biological samples 12 such as ferritin proteins, 13,14 cells labeled with magnetic particles, 15 and magnetic (iron) deposits in bacteria 16,17 and in mammalian tissues.…”