Abstract
Magnetic nanoparticles (NPs) are especially interesting for several biomedical applications due to their chemical surface, especially for targeted cancer imaging and therapeutics. In order to realize these applications, it is important to know their magnetic properties among other complementary properties that help to improve the understanding of the synthesis process. In this work, we report the magnetic properties of polyethyleneimine-coated magnetite (PEI-Fe3O4) NPs synthesized by a one-step method via the co-precipitation method and using PEI as a stabilizer. Transmission electron microscopy (TEM) images revealed agglomerated magnetic nanoparticles with an average size of ∼10 nm; meanwhile, the X-ray diffraction (DRX) analysis confirmed a pure magnetite phase. The study of magnetic properties shows a superparamagnetic system with coexistence of non-interacting single NPs with a low blocking temperature (∼35 K) and interacting NPs in the aggregates with a higher blocking temperature (>150 K), in which the interparticle interactions of magnetic cores dominate over surface spin disorder. The interaction between the surface spin-disorder layer and NP core was found to be weak, related to a weak exchange bias effect. A maximum specific loss power (SLP) value of 70 W g−1 was obtained (f = 571 kHz and H = 23.87 kA m−1) indicating that the magnetic response plays a crucial role in determining the heating efficiency for future applications.
Highlights
Iron oxide magnetic NPs with an appropriate biocompatible coating to improve colloidal stability[1] and a good biocompatibility or low cytotoxicity are increasingly used in many biomedical applications including protein separation,[2] drug and gene delivery,[3] magnetic resonance imaging (MRI)[4] and magnetic hyperthermia therapy.[5,6]
It is important to consider the in uence of the surface, interface effects such as surface spin disorder, defects, breaking of exchange bonds, changes in the surface atom coordination number,[9] and the distance among magnetic nanoparticles (MNPs) assemblies that leads to interparticle interactions[10] that can dominate over single domain nanoparticles response and affect the heating efficiency
polyethylenimine branched (PEI)-coated Fe3O4 NPs of narrow size distribution and mean size of $10 nm were successfully synthesized by a one-step coprecipitation route
Summary
Iron oxide magnetic NPs with an appropriate biocompatible coating to improve colloidal stability[1] and a good biocompatibility or low cytotoxicity are increasingly used in many biomedical applications including protein separation,[2] drug and gene delivery,[3] magnetic resonance imaging (MRI)[4] and magnetic hyperthermia therapy.[5,6]. It is important to consider the in uence of the surface, interface effects such as surface spin disorder, defects, breaking of exchange bonds, changes in the surface atom coordination number,[9] and the distance among MNPs assemblies that leads to interparticle interactions[10] that can dominate over single domain nanoparticles response and affect the heating efficiency. 17) the authors reported that there is an intrinsic single-particle property, as the large magnetic anisotropy of the g-Fe2O3 shell with a spin glass-like behavior or a possibly disordered magnetic state no related to the interparticle interaction.[18] the observed EB effect in ultrasmall $2 nm MnFe2O4 NPs has been assigned to the exchange coupling between core and surface spins at the interface and the interparticle exchange coupling.[16] In magnetite NPs of 40 nm a spin-glass like behavior with a freezing temperature of $35 K was determined and could be observed in both, the in-phase and the out-phase magnetic susceptibility curves.[19] These characteristics can be tuned during the synthesis process. The phase, crystal structure, and magnetic properties were characterized by X-ray diffraction, transmission electron microscopy, dc, and ac magnetic measurement and power absorption for future applications in magnetic hyperthermia
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