Optimizing the intrinsic properties of magnetic nanoparticles for magnetic hyperthermia is of considerable concern. In addition, the heating efficiency of the nanoparticles can be substantially influenced by dipolar interactions. Since adequate control of the intrinsic properties of magnetic nanoparticles is not straightforward, experimentally studying the complex interplay between these properties and dipolar interactions affecting the specific loss power can be challenging. Substituting zinc in magnetite structure is considered as an elegant approach to tune its properties. Here, we present experimental and numerical simulation results of magnetic hyperthermia studies using a series of zinc-substituted magnetite nanoparticles (ZnxFe1-xFe2O4, x = 0.0, 0.1, 0.2, 0.3 and 0.4). All experiments were conducted in linear regime and the results were inferred based on the numerical simulations conducted in the framework of the linear response theory. The results showed that depending on the nanoparticles intrinsic properties, interparticle interactions can have different effects on the specific loss power. When dipolar interactions were strong enough to affect the heating efficiency, the parameter σ = KeffV/kBT (Keff is the effective anisotropy and V the volume of the particles) determined the type of the effect. Finally, the sample x = 0.1 showed a superior performance with a relatively high intrinsic loss power 5.4 nHm2kg−1.
In this study, a
comprehensive characterization of iron oxide nanoparticles
synthesized by using a simple one-pot thermal decomposition route
is presented. In order to obtain monodisperse magnetite nanoparticles
with high saturation magnetization, close to the bulk material, the
molar ratios between the starting materials (solvents, reducing agents,
and surfactants) were varied. Two out of nine conditions investigated
in this study resulted in monodisperse iron oxide nanoparticles with
high saturation magnetization (90 and 93% of bulk magnetite). The
X-ray diffraction analyses along with the inspection of the lattice
structure through transmission electron micrographs revealed that
the main cause of the reduced magnetization in the other seven samples
is likely due to the presence of distortion and microstrain in the
particles. Although the thermogravimetric analysis, Raman and Fourier
transform infrared spectroscopies confirmed the presence of covalently
bonded oleic acid on the surface of all the samples, the particles
with higher polydispersity and the lowest surface coating molecules
showed the lowest saturation magnetization. Based on the observed
results, it could be speculated that the changes in the kinetics of
the reactions, induced by varying the molar ratio of the starting
chemicals, can lead to the production of the particles with higher
polydispersity and/or lattice deformation in their crystal structures.
Finally, it was concluded that the experimental conditions for obtaining
high-quality iron oxide nanoparticles, particularly the molar ratios
and the heating profile, should not be chosen independently; for any
specific molar ratio, there may exist a specific heating profile or
vice versa. Because this synthetic consideration has rarely been reported
in the literature, our results can give insights into the design of
iron oxide nanoparticles with high saturation magnetization for different
applications.
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