Nonmonotonic evolution of the blocking temperature in dispersions of superparamagnetic nanoparticles

Serantes, David; Baldomir, D.; Pereiro, Manuel; Hoppe, Cristina Elena; Rivadulla, F.; Rivas, José

doi:10.1103/physrevb.82.134433

Cited by 25 publications

(25 citation statements)

References 15 publications

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“…This may lead to an increase of T B in comparison with the blocking temperature of non-interacting NP samples. This phenomenon has been discussed in previous works (Hoppe et al 2008;Serantes et al 2010b). In fact, based on the mean size of the iron-oxide NPs, lower blocking temperatures than the observed ones would be expected in the absence of interactions.…”

Section: Resultssupporting

confidence: 65%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical crosslinking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical crosslinking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

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Section: Resultssupporting

confidence: 65%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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“…blocking temperature is above the working temperature). 42 Thus, it is implicit that the thermal energy is much lower than the anisotropy energy. This condition is usually reached experimentally for particles of several tens of nm in diameter under fields of hundreds of kHz in frequency.…”

Section: Methodsmentioning

confidence: 99%

A Single Picture Explains Diversity of Hyperthermia Response of Magnetic Nanoparticles

et al. 2015

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Progress in the design of nanoscale magnets for localized hyperthermia cancer therapy has been largely driven by trial-and-error approaches, for instance, by changing of the stoichiometry composition, size, and shape of the magnetic entities. So far, widely different and often conflicting heat dissipation results have been reported, particularly as a function of the nanoparticle concentration. Thus, achieving hyperthermia-efficient magnetic ferrofluids remains an outstanding challenge. Here we demonstrate that diverging heat-dissipation patterns found in the literature can be actually described by a single picture accounting for both the intrinsic magnetic features of the particles (anisotropy, magnetization) and experimental conditions (concentration, magnetic field). Importantly, this general magnetic-hyperthermia scenario also predicts a novel non-monotonic concentration dependence with optimum heating features, which we experimentally confirmed in iron oxide nanoparticle ferrofluids by fine-tuning the particle size. Overall, our approach implies a magnetic hyperthermia trilemma that may constitute a simple strategy for development of magnetic nanomaterials for optimal hyperthermia efficiency.

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“…This could be understood considering the high similarity in the morphology of the NPs distribution (as discussed in the previous section). This behaviour was, nevertheless, very different from that observed for ideally dispersed systems [47][48]. Finally, T B and peak broadening were observed in samples prepared with bigger NPs, which can be easily explained by the increase in anisotropy and strength of dipolar interactions expected for higher NPs volumes (Figure 8).…”

Section: Magnetic Propertiesmentioning

confidence: 77%

Superparamagnetic nanocomposites obtained by dispersion of ultrafine magnetic iron oxide nanoparticles in poly(3-hydroxybutyrate)

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Hoppe

et al. 2014

European Polymer Journal

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Nonmonotonic evolution of the blocking temperature in dispersions of superparamagnetic nanoparticles

Cited by 25 publications

References 15 publications

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

A Single Picture Explains Diversity of Hyperthermia Response of Magnetic Nanoparticles

Superparamagnetic nanocomposites obtained by dispersion of ultrafine magnetic iron oxide nanoparticles in poly(3-hydroxybutyrate)

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