Numerical analysis of superparamagnetic clusters distribution

Chrobak, A.; Haneczok, G.; Chełkowska, G.; Kassiba, A.; Ziółkowski, Grzegorz

doi:10.1002/pssa.201127016

Cited by 8 publications

(6 citation statements)

References 16 publications

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“…Additionally, to determine the distribution of magnetic moments, the Langevin granulometry technique was used. 29,30 Ultraviolet-visible (UV-Vis) spectra were recorded on a Hitachi Y-2910 spectrophotometer in the 190-700 nm range using aqueous solutions. MWCNT (1 mg) was introduced into water (10 mL) and sonicated with a horn sonicator (Hilsher UP200St, 200 W, 26 kHz) for 10 min.…”

Section: Characterization Of the Materialsmentioning

confidence: 99%

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

Tomczyk¹,

Boncel²,

Herman³

et al. 2020

IJN

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Purpose: Salicyl (Sal)-among other oxygen functionalities-multi-walled carbon nanotubes (MWCNTs) and their nanohybrids are investigated as promising contrast agents (CA) in magnetic resonance imaging (MRI) or drug delivery platforms, due to their unique properties. The preliminary results and the literature reports were the motivation to endow high r 2 relaxivities, excellent dispersibility in water, and biocompatibility to superparamagnetic MWCNTs nanohybrids. It was hypothesized that these goals could be achieved by, not described in the literature yet, two-stage oxygen functionalization of MWCNTs. Results: Two structurally different MWCNT materials differing in diameters (44 and 12 nm) and the iron content (4.7% and 0.5%) are studied toward the functionalization effect on the T 2 relaxometric properties. MWCNT oxidation is typically the first step of functionalization resulting in "first generation" oxygen functional groups (OFGs) on the surface. Until now, the impact of OFGs on the relaxivity of MWCNT was not truly recognized, but this study sheds light on this issue. By follow-up functionalization of oxidized MWCNT with 4-azidosalicylic acid through [2+1] cycloaddition of the corresponding nitrene, "second generation" of oxygen functional groups is grafted onto the nanohybrid, ie, Sal functionality. Conclusion: The introduced OFGs are responsible for an almost 30% increase in the relaxivity, which leads to remarkable r 2 relaxivity of 951 mM −1 s −1 (419 (mg/mL) −1 s −1), the unprecedented value reported to date for this class of CAs. Also, the resulting nanohybrids express low cytotoxicity and superb diffusion after subcutaneous injection to a mouse.

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Section: Characterization Of the Materialsmentioning

confidence: 99%

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

Tomczyk¹,

Boncel²,

Herman³

et al. 2020

IJN

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“…below or above the blocking temperature. For the unblocked state, the problem is quite easy but also requires applying sophisticated numerical methods, as described in [4]. Our development refers to the blocked superparamagnets in which energy barrier, related to the magnetic anisotropy, plays an important role.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…During last years we have developed numerical procedures and models used for such analysis [4,5]. The aim of this paper is a consistent presentation of our approach which can be applied not only in the case of determination of magnetic moments distribution but also in similar problems in which thermal activation plays an important role.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Analysis of Superparamagnetic Systems

Chrobak

Ziółkowski

2017

Acta Phys. Pol. A

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The paper refers to a kind of nanoscale characterization of superparamagnetic materials above and below the so-called blocking temperature. It is propose to apply the Stoner-Wohlfarth model of nanoparticles magnetization supplemented by the two-level kinetic model, determining behavior in T > 0. This approach allows determination of distribution of magnetic moments and energetic barriers of magnetic objects based on magnetization curves. In many cases, the determined distribution of magnetic moments can be recalculated into average size of the magnetic objects giving finally a nano/microscaled picture of the material. The proposed method was successfully used in characterization of diluted magnetics, nanocomposites, powders and even for human hemoglobin. In the paper the basic theory and its application to the nanoscale characterization is discussed in detail.

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“…As a numerical method, we propose the SA procedure supplemented with maximum of local entropy condition, which seems to be the most suitable because of some specific advantages (for details see Ref. ). The first one is the fact that SA algorithm does not require any preliminary assumptions of a shape and number of the separate components of a distribution, which is a unique feature among other fitting methods.…”

Section: Determination Of 2d Distribution Of Magnetic Nanoparticlesmentioning

confidence: 99%

“…Recently, we have developed the LG procedure by supplementing the so‐called SA algorithm with maximum of local entropy condition . The relevance of this original method was confirmed in the field of superparamagnetic and spin‐glass alloys , magnetic thin layers, as well as in some biological systems.…”

Section: Introductionmentioning

confidence: 99%

Determination of 2D distribution of magnetic nanoparticles derived from magnetization curves

Chrobak

Haneczok

2013

Phys. Status Solidi A

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This paper refers to determination of magnetic nanoparticles distribution as a function of both magnetic moment m and energy barrier E B . The original analysis consists in a numerical analysis of experimental M(H) curves determined at two different temperatures and is based on the Stoner-Wohlfarth model. As it was shown, the applied ''simulated annealing (SA)'' calculation algorithm with additional entropy maximum condition allows characteristic distribution profiles to be determined. Moreover, from the temperature shift of the profiles, the real positions of their homological points in m-E B space can be calculated. It should be emphasized that the novel approach does not require any preliminary assumption of a distribution shape and number of components. The proposed magnetic characterization was tested with the use of computergenerated as well as experimental M(H) curves. The obtained results confirm the efficiency of the method and its usefulness in analysis of hard magnetic powder systems.

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Numerical analysis of superparamagnetic clusters distribution

Cited by 8 publications

References 16 publications

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

<p>Oxygen Functional Groups on MWCNT Surface as Critical Factor Boosting T2 Relaxation Rate of Water Protons: Towards Improved CNT-Based Contrast Agents</p>

Nanoscale Analysis of Superparamagnetic Systems

Determination of 2D distribution of magnetic nanoparticles derived from magnetization curves

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