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  1. 54 Acta Physica Polonica A

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  1. 6 2018

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  5. 9 2012

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  1. 54 Kopčanský P.

  2. 41 Timko M.

  3. 20 Koneracká M.

  4. 19 Závišová V.

  5. 18 Tomašovičová N.

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1
Content available remote

The Effect of Polymer Immobilization on Magnetic Properties of Magnetosomes

100%
Timko M., Džarová A., Kovač J., Kopčanský P., Gojzewski H.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
995-997
EN
The anisotropy of several PVA/magnetosomes magnetically textured films has been investigated from the point of view of magnetic properties. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. On sample textured in magnetic field the magnetisation loop measurements were performed in dependence on the direction of the external magnetic field with respect to the texture axis. The results of hysteresis measurements show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanently textured film is obtained after solidification. The obtained values for magnetic remanence and coercivity were dependent on the external magnetic field orientation and the alignment effect of particle moments may be clearly seen which is in agreement with the theoretical model of magnetic particle chains.
2
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Synthesis and Characterization of Magnetoferritin

100%
Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1318-1320
EN
The paper presents detailed experimental study of synthesis and characterization a bioinorganic magnetic molecule - magnetoferritin. Magnetoferritin with loading of iron ions per protein molecule in the range from 300 to 3000 was prepared. Size distribution analysis (transmission electron microscopy, dynamic light scattering) shows spherical nanoparticles with particle size distribution from 2 to 12 nm, and hydrodynamic diameter from 12 to 25 nm. The thermomagnetic curves measured after cooling the sample in zero field (zero-field cooling) and under the presence of the measurement field (field cooling) show superparamagnetic behavior with the blocking temperature T_{b} from 22 to 60 K and the magnetization loops measured below T_{b} (at 2 K) show the hysteresis with coercive field from 20 to 30 kA/m depending on the concentration of the magnetic nanoparticles.
3
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Study of Composites Consisting of High-T_{c} Superconductor and Fine Magnetic Particles

100%
Timko M., Kopčanský P., Kováč J., Koneracká M., Plecháček V.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
389-392
EN
The composite systems as a mixture of fine magnetic particles of Fe_{3}O_{4} and superconducting powder such as Bi_{1.8}Pb_{0.2}Sr_{2}Ca_{2}Cu_{3}O_{10+x} were prepared. The influence of internal magnetic field (generated by magnetic particles) on the superconducting properties of prepared composites were studied as a function of concentration of magnetic particles and their magnetic state. The observed data both of the shielding and the Meissner effect were compared with corresponding linear combination of pure signals of magnetite and superconductor, respectively. The large differences were observed for demagnetized samples. It means that result must be discussed in the frame of the distribution of internal magnetic field created by the magnetic particles.
4
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Influence of Temperature on the Magneto-Dielectrics Effect of Oil-Based Ferrofluid

100%
Kúdelčík J., Hardoň Š., Bury P., Timko M., Kopčanský P.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
483-485
EN
The effect of temperature on the magneto-dielectrics behavior was studied by dielectric spectroscopy in the transformer oil-based ferrofluid with magnetic nanoparticles upon the effect of an external magnetic field. The frequency dependence of complex permittivity and dissipation factor were measured within the frequency range from 1 mHz to 10 kHz at different temperatures by a capacitance method. The dielectrics parameters were measured as a function of the external magnetic field in the range of 0-200 mT, parallel to the direction of the electric field as a function of temperature in the range of 15-35°C. The interaction between magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures which had influence on dielectric parameters. The dependence of these parameters at constant magnetic field on angle between the direction of the electric and magnetic fields (anisotropy) has been measured, too.
5
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Study of Structural Changes of Water-Based Magnetic-Fluid by Acoustic Spectroscopy

100%
Kúdelčík J., Hardoň Š., Bury P., Timko M., Kopčanský P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
919-921
EN
The effect of an external magnetic field on the changes in structural arrangement of magnetic nanoparticles in water based magnetic fluid was studied by acoustic spectroscopy. When a magnetic field is increased, the interaction between the magnetic field and the magnetic moments of nanoparticles leads to the orientation of magnetic nanoparticles and their following aggregation to long chains that cause the increase of acoustic attenuation. The attenuation of acoustic waves measured for jump changes of the magnetic field to 100, 200, and 300 mT at temperature 20°C showed that the changes of acoustic attenuation increased slowly to a stabilized state that after switching off the magnetic field decreased immediately to initial value. The dependence of attenuation of acoustic waves at constant magnetic field on angle between the wave vector and direction of the applied magnetic field (attenuation anisotropy) has been measured, too. The measured anisotropy of acoustic attenuation attested structural changes of magnetic fluid in the magnetic field.
6
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Study of Magnetic Fredericksz Transition in Ferronematics

100%
Kopčanský P., Koneracká M., Jadżyn J., Czechowski G., Żywucki B.
Acta Physica Polonica A
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1997
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vol. 92
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issue 2
437-440
EN
The magnetic Fredericksz transition in ferronematics (thermotropic nematic liquid crystals 7CB and MBBA combined with fine magnetic particles of a size 10 nm) as a function of concentration of magnetic particles was studied by using simple dielectric measurements. The increase of the threshold magnetic field is observed in 7CB based ferronematic while the decrease of threshold field in MBBA based ferronematic is observed when the concentration of magnetic particles is increased. Experimental results are discussed in the framework of Brochard, de Gennes and Burylov, Raikher theories.
7
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Thermal Analysis of Magnetic Polymer Nanospheres for Drug Targeting

87%
Juríková A., Csach K., Miškuf J., Koneracká M., Závišová V., Kopčanský P.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
990-992
EN
Poly(D,L-lactic-co-glycolic) acid (PLGA) polymer nanospheres loaded with different input amounts of anticancer drug taxol were prepared by the modified nanoprecipitation method. Magnetite was incorporated into the polymer nanospheres to impart them superparamagnetic properties. Thermal properties of the drug loaded magnetic polymer nanospheres were characterized using differential scanning calorimetry and thermogravimetric analysis. The solid state solubility of taxol in PLGA nanospheres and the influence of external magnetic field on their thermal stability were estimated. The investigations have revealed that the samples of dried taxol loaded magnetic PLGA nanospheres undergo mass loss at three stages during heating.
8
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Lysozyme Amyloid Fibrils Doped by Carbon Nanotubes

87%
Majorošová J., Tomašovičová N., Mitróová Z., Rajňák M., Girman V., Kopčanský P.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
588-590
EN
Production of new composites for the creation of modern materials with desired properties is the key feature of nanotechnology. Despite the well known advantages of magnetic nanoparticles, the aim of the present study was to synthesize lysozyme amyloid fibrils from hen egg white and subsequently doped this solution with single walled carbon nanotubes and with the magnetite Fe₃O₄ labelled single walled carbon nanotubes. Transmission electron microscopy and polarization optical microscopy were used to obtain the structural and dimensional information about samples. Measurements of magnetic properties indicate the considerable increase of the saturation magnetization for solutions included the magnetite nanoparticles.
9
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Influence of Magnetic Field on Dielectric Breakdown in Transformer Oil Based Ferrofluids

87%
Rajňák M., Dolník B., Marton K., Tomčo L., Molčan M., Kopčanský P., Timko M.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
248-249
EN
In this paper the experimental study of the breakdown field strength in a transformer oil based ferrofluid is reported. The experiments are conducted on five ferrofluid samples with different magnetic volume fraction. The influence of external magnetic field on the breakdown field strength is investigated, when a quasi-homogenous magnetic field was applied in parallel and perpendicular configuration in regard to the electric field. The obtained results are analysed in accordance to the electron charging of ferrofluid nanoparticles theory.
10
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SANS Study of Poly(ethylene glycol) Solutions in D_2O

87%
Lancz G., Avdeev M., Petrenko V., Garamus V., Koneracká M., Kopčanský P.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
980-982
EN
Poly(ethylene glycol) is used for coating of colloidal particles and other surfaces for gaining biocompatibility. Particularly, it can be introduced into magnetic fluids. The aim of the current study was to reveal the structural characteristics of poly(ethylene glycol) in neat D_2O using small-angle neutron scattering technique. Solutions of poly(ethylene glycol) (at temperature of 37°C) with different molecular weights in an interval of 400-20000 were investigated. It is concluded that at low concentrations (less than 2% of mass fraction) poly(ethylene glycol) molecules behave as Gaussian coils.
11
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Preparation and Complex Characterization of Magnetic Nanoparticles in Magnetic Fluid

87%
Kubovčíková M., Antal I., Kováč J., Závišová V., Koneracká M., Kopčanský P.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
268-269
EN
This paper deals with the preparation and complex characterization of magnetite nanoparticles (MNPs), stabilized with sodium oleate (SO), by the routine methods such as infrared spectroscopy (FTIR), magnetic measurements, scanning electron microscopy (SEM) and dynamic light scattering (DLS). The FTIR spectra showed that SO molecules were linked to MNPs through chemical bonding. Magnetic measurements proved that the MNPs are superparamagnetic in nature. Four different methods were used to determine the size and size distribution of the MNPs: SEM, DLS, differential centrifugal sedimentation (DCS) and magnetic measurements. SEM analysis showed a relatively narrow size distribution of roughly spherical MNPs with a mean diameter of 61 nm. DLS analysis confirmed monodispersed MNPs production with hydrodynamic diameter of 75 nm. The size distribution determined by DCS was found to be 69 nm. Finally, the calculated magnetic core diameter obtained from magnetization curve was 10 nm. The obtained results demonstrate that SO coated MNPs fulfil the requirements for a useful drug delivery system.
12
Content available remote

Physical Properties of Magnetite Nanoparticles Covered by 11-Mercaptoundecanoic Acid

87%
Timko M., Kopčanský P., Antalik M., Simsikova M., Valusova E., Molcan M., Kováč J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1321-1323
EN
We have investigated the magnetic behavior of magnetite nanoparticles covered by the 11-mercaptoundecanoic acid around magnetite core prepared by a standard co-precipitation method. The particles show superparamagnetic behavior at room temperature, with transition to a blocked state at blocking temperature 91 K estimated from zero field cooled and field cooled at 500 Oe experiment. The hysteresis loop measured at 293 K showed magnetization 32.8 emu/g at 50 kOe without any coercivity. The mean particle size (7.1 nm) was determined by fitting a magnetization curve obtained at 295 K assuming a log-normal size distribution.
13
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Temperature Effect on the Structure of Transformer Oil Based Magnetic Fluids Using Acoustic Spectroscopy

87%
Kúdelčík J., Bury P., Drga J., Kopčanský P., Závišová V., Timko M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1169-1171
EN
The changes in structural arrangement in transformer oil based magnetic fluids upon the effect of an external magnetic field and temperature were studied by acoustic spectroscopy. The attenuation of acoustic waves was measured as a function of an external magnetic field in the range of 0-300 mT, parallel to the direction of the field and as a function of temperature in the range of 15-35°C for various magnetic nanoparticles concentrations. The strong influence of the steeped magnetic field on the acoustic wave attenuation was detected and its hysteresis was observed, too. When a magnetic field is swept at a constant rate, the dominant interactions between the external magnetic field and the magnetic moment of the nanoparticles occur, leading to the aggregation of magnetic nanoparticles and clusters formation. However, the temperature of magnetic fluids has very important influence on the obtained dependences, where the mechanism of thermal motion acts against the cluster creation. The observed influences of magnetic field and temperature on the investigated magnetic liquids structure are discussed.
14
Content available remote

Viscosity Dependence of a Magnetic Fluid Nanoparticles Concentration

87%
Tóthová J., Kováč J., Kopčanský P., Rajňák M., Paulovičová K., Timko M., Józefczak A.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
278-279
EN
In this work we have studied the effect of temperature on the viscosity of magnetic fluids (MFs) based on the transformer oil ITO 100. The volume concentration of suspended magnetic particles (MPs) changed from 0.25 to 1%. Rheological characterization of MFs was performed using a vibroviscometer at working frequency of 30 Hz. The temperature dependence of the viscosity was measured in the temperature range from 20 up to 50 °C. The magnetization of different concentrations of MPs in MFs was determined by using the vibrating sample magnetometer.
15
Content available remote

Characterization of Carbon Nanotubes

87%
Jeníková M., Zakuťanská K., Kováč J., Girman V., Kopčanský P., Tomašovičová N.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
952-954
EN
The aim of the presented work was to characterize single-walled carbon nanotubes as well as multi-walled carbon nanotubes by transmission electron microscopy, the Raman spectroscopy and magnetization measurements to obtain information about their size, structure, and magnetic properties. We show that having different carbon nanotubes one can easily distinguish the single-wall or multi-wall carbon nanotubes and determine their quality. The obtained results show that carbon nanotubes can be diamagnetic or ferromagnetic depending on their structural parameters.
16
Content available remote

Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids

87%
Rajňák M., Kurimský J., Dolník B., Cimbala R., Paulovičová K., Kopčanský P., Timko M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
943-945
EN
In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.
17
Content available remote

Magnetic Birefringence Study of the Magnetic Core Structure of Ferritin

87%
Koralewski M., Pochylski M., Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1237-1239
EN
Magnetically induced optical birefringence (Δ n) was measured for magnetoferritin and horse spleen ferritin aqueous suspensions. The Δ n for magnetoferritin was described in the frame of the Langevin formalism taking into account distribution of core diameter. The established average magnetic dipole moment and core diameter is equal to about 460 μ_{B} and 3 nm, respectively. It was shown that magnetic birefringence and the Cotton-Mouton constant can be powerful parameters in identification of the magnetic core structure of ferritin, especially useful in biomedicine.
18
Content available remote

The Influence of Magnetic Particles on the Nematic Droplets Formation in Liquid Crystal

87%
Majorošová J., Gdovinová V., Tomašovičová N., Juríková A., Závišová V., Jadzyn J., Kopčanský P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
955-957
EN
In this work the thermotropic nematic liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanato-benzene (6CHBT) was dissolved in phenyl-isothiocyanate and doped with spherical magnetic particles with volume concentration ϕ₁=10¯⁴ and ϕ₂=10¯³. The influence of the volume concentration on the phase transitions from isotropic to nematic phase was studied by three experimental methods: optical microscopy, differential scanning calorimetry, and dielectric measurements. The obtained results confirmed the coexistence of isotropic and nematic phase, i.e. nematic or ferronematic droplets in isotropic phase in a wide temperature range between nematic and isotropic phase.
19
Content available remote

Magnetic Properties of Encapsulated Magnetite in PLGA Nanospheres

87%
Koneracká M., Závišová V., Timko M., Kopčanský P., Tomašovičová N., Csach K.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
595-598
EN
In this study, the biocompatible magnetic fluid was encapsulated in biodegradable polymer PLGA (poly D, L/lactide-co-glycolide acid) by the nanoprecipitation method. We characterized these spheres in terms of morphology, magnetite content and magnetic properties. The results showed good encapsulation with magnetite content 22wt% and magnetization 3.4 mT. The transmission electron microscopy and scanning electron microscopy images showed that magnetic particles have almost a spherical shape with approximate size 250 nm. Infrared spectroscopy and thermogravimetric analysis measurements were used to confirm incorporation of magnetic particles into the PLGA polymer.
20
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Thermal Analysis of Magnetic Nanoparticles Modified with Dextran

87%
Juríková A., Csach K., Miškuf J., Koneracká M., Závišová V., Kubovčíková M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1296-1298
EN
In the work the thermal behaviour of the magnetic nanoparticles modified with polysaccharide dextran of different weight ratios to the magnetite Fe_3O_4 was investigated using thermoanalytical methods - differential scanning calorimetry and thermogravimetric analysis. The adsorption of dextran on the magnetic nanoparticles was confirmed and the influence of the dextran amount in the modified magnetic fluid on the thermal decomposition of the complex system was studied. The results showed that magnetite catalyzed the thermal decomposition of dextran, the adsorbed dextran showed lower initial decomposition temperatures in comparison with the free one.
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