The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Hrubovčák, Pavol; Zeleňáková, A.; Zeleňák, Vladimı́r; Kováč, J.

doi:10.1016/j.jallcom.2015.07.044

Cited by 13 publications

(14 citation statements)

References 31 publications

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“…Hence, we decided to prepare a monodisperse core/shell Co/Au nanoparticle system and study its magnetocaloric properties. As it was demonstrated elsewhere [21], this system exhibits features of non-equilibrium dynamics induced by strong inter-particle interactions what leads to formation of superspin glass state. This work is the first attempt to apply scaling analysis of ∆S M (T ) [14] developed for bulk materials on nanoparticle system exhibiting superspin glass state in order to examine the characteristics of the phase transition.…”

supporting

confidence: 54%

Magnetocaloric effect and scaling analysis in superspin glass Co/Au nanoparticles

Hrubovcak,

Zelenakova,

Zelenak

et al. 2017

Preprint

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Bimetallic Co/Au (core/shell) nanoparticle system exhibiting transition form superparamagnetic (SPM) to superspin glass state (SSG) at low temperatures has been investigated with respect to its magnetocaloric properties. Peaks of magnetic entropy change vs. temperature dependences (∆SM (T )) have been observed at a temperature in the vicinity of SPM to SSG transition. Despite of significant thermal hysteresis of magnetization at low applied fields a master curve has been constructed from the ∆SM (T ) dependences employing scaling analysis. That confirms the investigated transition is of the second order type. Different values of critical exponents calculated from field dependence of relevant magnetocaloric response parameters in the proximity of critical temperature have been found for low and high applied fields. Moreover, the exponents exhibited significant disagreement with theoretical values characteristic of mean field theory as well as Ising models indicating distinct behavior of the SSG system at critical temperature.

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supporting

confidence: 54%

Magnetocaloric effect and scaling analysis in superspin glass Co/Au nanoparticles

Hrubovcak,

Zelenakova,

Zelenak

et al. 2017

Preprint

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“…Similar behavior has been revealed by Franco et al [6] in the Co/Ag nanoparticle system. However, the presence of superspin glass state instead of spin glass state has been documented in our system at low temperatures [8], thus further complementary measurements and data analysis is necessary to perform in order to verify the presence of the SOPT in studied Co/Au system. Nevertheless, the applicability of scaling analysis to nanoparticle system has been demonstrated and behavior resembling the spin glass transition was revealed in examined Co/Au nanoparticles.…”

Section: Resultsmentioning

confidence: 92%

“…Average particle and magnetic Co core size d ≈ 7 nm, d C ≈ 5 nm, respectively, was established. Details of synthesis, structural analysis and magnetic properties of the system have already been published elsewhere [8][9][10].…”

Section: Resultsmentioning

confidence: 99%

Scaling Analysis of the Magnetocaloric Effect in Co/Au Nanoparticles

et al. 2017

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The system of superparamagnetic Co/Au bimetallic nanoparticles of average diameter 7 nm was investigated with respect to its magnetocaloric properties. DC magnetic measurements revealed the presence of field dependent zero field cooled M (T ) maximum (6-8 K) and significant zero field cooled/field cooled irreversibility at low temperatures in the system. Documented thermal hysteresis disallow standard magnetic entropy change calculation from isothermal M (H) data, thus we attempted to employ zero field cooled M (T ) data for this purpose. Magnetic entropy change was calculated employing the Maxwell relation. In maximal field variation of 1 T relative high magnetic entropy change for nanoparticles ∆SM ≈ 0.7 J/(kg K) at T = 9 K was observed. The data collapsed onto single universal curve after proper axis rescaling.

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“…However, vesicle formation in cells suggests a certain degree of intoxication caused by the presence of the nanoparticles. MTT assay is closely connected with mitochondria in which formazan is produced [ 51 ]. For this reason, mitochondria of U87 MG cells were labeled with mitochondrial probe MTO.…”

Section: Resultsmentioning

confidence: 99%

Magnetic Characterization and Moderate Cytotoxicity of Magnetic Mesoporous Silica Nanocomposite for Drug Delivery of Naproxen

et al. 2021

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In this study, we describe the magnetic and structural properties and cytotoxicity of drug delivery composite (DDC) consisting of hexagonally ordered mesoporous silica, iron oxide magnetic nanoparticles (Fe2O3), and the drug naproxen (Napro). The nonsteroidal anti-inflammatory drug (NSAID) naproxen was adsorbed into the pores of MCM-41 silica after the ultra-small superparamagnetic iron oxide nanoparticles (USPIONs) encapsulation. Our results confirm the suppression of the Brownian relaxation process caused by a “gripping effect” since the rotation of the whole particle encapsulated in the porous system of mesoporous silica was disabled. This behavior was observed for the first time, to the best of our knowledge. Therefore, the dominant relaxation mechanism in powder and liquid form is the Néel process when the rotation of the nanoparticle’s magnetic moment is responsible for the relaxation. The in vitro cytotoxicity tests were performed using human glioma U87 MG cells, and the moderate manifestation of cell death, although at high concentrations of studied systems, was observed with fluorescent labeling by AnnexinV/FITC. All our results indicate that the as-prepared MCM-41/Napro/Fe2O3 composite has a potential application as a drug nanocarrier for magnetic-targeted drug delivery.

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The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Cited by 13 publications

References 31 publications

Magnetocaloric effect and scaling analysis in superspin glass Co/Au nanoparticles

Magnetocaloric effect and scaling analysis in superspin glass Co/Au nanoparticles

Scaling Analysis of the Magnetocaloric Effect in Co/Au Nanoparticles

Magnetic Characterization and Moderate Cytotoxicity of Magnetic Mesoporous Silica Nanocomposite for Drug Delivery of Naproxen

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