Structural and Magnetic Properties of Iron Oxide Nanoparticles in Shells of Hollow Microcapsules Designed for Biomedical Applications

Lyubutin, I. S.; Starchikov, S. S.; Lin, Chun-Rong; Gervits, N.E.; Korotkov, N. Yu.; Букреева, Т. В.

doi:10.5562/cca2739

Cited by 11 publications

(3 citation statements)

References 20 publications

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“…However, one cannot exclude the formation of superparamagnetic ferric oxides during cathode preparation, which would contribute with a doublet overlapping with D1 signal from S1 sites. 37 To unveil this degeneracy, the spectra were acquired at 5 K, a temperature at which nano ferric-oxides contribute with a sextet component, 38,39 while the signal of S1 remains a doublet. 40 At 5 K, no sextet was visible for Fe0.5 while a sextet representing only 9 % of the absorption area, assigned to ferric oxide, appeared for Fe0.5cathode ( Figure S1c-d).…”

Section: Introductionmentioning

confidence: 99%

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Li¹,

Sougrati²,

Zitolo³

et al. 2020

Preprint

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While Fe-N-C materials are a promising alternative to platinum for catalyzing oxygen reduction in acidic polymer fuel cells, limited understanding of their operando degradation restricts rational approaches towards improved durability. Here we show that Fe-N-C catalysts initially comprising two distinct FeNx sites (S1 and S2) degrade via the transformation of S1 into iron oxides while the structure and number of S2 were unmodified. Structure-activity correlations drawn from end-of-test 57Fe Mössbauer spectroscopy reveal that both sites initially contribute to the ORR activity but only S2 significantly contributes after 50 h of operation. From in situ 57Fe Mössbauer spectroscopy in inert gas coupled to calculations of the Mössbauer signature of FeNx moieties in different electronic states, we identify S1 to be a high-spin FeN4C12 moiety and S2 a low- or intermediate spin FeN4C10 moiety. These insights lay the ground for rational approaches towards Fe-N-C cathodes with improved durability in acidic fuel cells.<br>

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Section: Introductionmentioning

confidence: 99%

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Li¹,

Sougrati²,

Zitolo³

et al. 2020

Preprint

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“…The values of magnetic hyperfine fields (H ef f ) of these sextets depend not only on the differences in local surroundings of iron nuclei corresponding to them but also on magnetic crystal sizes. The value H ef f decreases when crystals pass to single-domain (superparamagnet) condition, in which magnet locking temperature depends on crystal size [53]. Moreover, the smaller the crystal size is, the lower the value H ef f is down to its full disappearance.…”

Section: Fig 3 Size Distribution Of Cofe 2 O 4 Crystallites Obtained By the Methods Of Microreactor Synthesis With Continuously Impingingmentioning

confidence: 99%

Formation of cobalt ferrite nanopowders in an impinging-jets microreactor

Barashok¹,

Панчук²,

Семенов³

et al. 2021

Nanosystems: Phys. Chem. Math.

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The dependence of cobalt ferrite nanosized powder production process on the synthesis method and conditions was studied. The paper shows the possibility for producing nanocrystalline CoFe 2 O 4 with an average particle size of 12 nm under conditions of an impinging-jets microreactor at room temperature. The influence exerted by the parameters of process implementation in the microreactor on phase formation in the CoO-Fe 2 O 3 -H 2 O system was analyzed.

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“…The near neighbor coordination of A site around B site is closer The direct line shape fitting of the measured spectra showed that all iron ions are in tetrahedral A-site and octahedral B-sites. A third more broadening sextet (C) reflected a magnetically-disordered structural state which was obviously-corresponded to iron ions on the surface of the NPs [74,75], in addition to one doublet (D).…”

Section: Mössbauer Spectroscopymentioning

confidence: 99%

Unveiling the Effect of Zn2+ Substitution in Enrichment of Structural, Magnetic, and Dielectric Properties of Cobalt Ferrite

Maksoud

Elghandour

El-Sayyad

et al. 2020

J Inorg Organomet Polym

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This work reports the detailed structural characterization of Zn 2+ ion-substituted cobalt ferrite nanoparticles (CFO NPs; Co 1−x Zn x Fe 2 O 4 ; x = 0.00, 0.25, 0.50, and 0.75), prepared using a facile sol-gel method. It correlates structural changes with magnetic and dielectric properties. The as-synthesized samples were investigated by X-ray diffraction (XRD) analysis, BET surface area analyzer, energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Mössbauer spectroscopy, and impedance analyzer. The pristine sample (CFO) comprised of NPs with 25 nm size, which decreased up to 11 nm upon the formation of Zn 0.75 Co 0.25 Fe 2 O 4 . The N 2 adsorption-desorption isotherm of the prepared Zn 0.5 Co 0.5 Fe 2 O 4 sample confirmed the presence of a mesoporous structure. SEM images revealed that all prepared samples exhibited porous surface with honeycomb-like structures. The cationic distribution was described by Mössbauer spectra. The increment of Zn ions in the prepared samples resulted in sharp reduction of saturation magnetization and remanence values. The normal dielectric dispersion behavior was recorded and can be ascribed to the Maxwell-Wagner type polarization. Besides, the dielectric parameters varied by increasing Zn content in CFO NPs. This may be ascribed to O 2 vacancies and Fe 3+ ions in A-and B-sites. Dielectric studies revealed that, content of Zn ions beyond x = 0.25 was sufficient to reduce both dielectric constant and loss at low frequencies.

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Structural and Magnetic Properties of Iron Oxide Nanoparticles in Shells of Hollow Microcapsules Designed for Biomedical Applications

Cited by 11 publications

References 20 publications

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Formation of cobalt ferrite nanopowders in an impinging-jets microreactor

Unveiling the Effect of Zn2+ Substitution in Enrichment of Structural, Magnetic, and Dielectric Properties of Cobalt Ferrite

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