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1

Mechanosynthesis and Sintering of Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) Solid Solutions

100%

Fabián M., Briančin J., Schutz T.

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vol. 126

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issue 4

951-953

EN

One-step mechanochemical approach was used to synthesize nanocrystalline Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) solid solutions. X-ray powder diffraction was utilized to characterize crystalline phases of as-prepared products. It was shown that the presence of yttrium suppresses the crystal growth. The effect of yttrium content on the grain size before and after sintering of green bodies at high temperatures was evaluated by means of scanning electron microscopy. The combination of one-step mechanochemical process and relatively low sintering temperatures resulted in preparation of ceria-based ceramics with wide scale of possible applications.

2

Photocatalytic Properties of Mechanochemically Synthesized Nanocrystalline ZnAl_2O_4 and CdSe

88%

Kostova N., Eliyas A., Fabián M., Achimovičová M., Baláž P.

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vol. 126

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issue 4

967-970

EN

Nanocrystalline powders of ZnAl_2O_4 and CdSe were prepared via mechanochemical synthesis. Powder slurries were coated as thin films on SiO_2 thin layer chromatography (TLC) sheet by capillary method. The photocatalytic activity of the film coating was tested in a self-made gas-phase flat-plate continuous-flow photocatalytic reactor with toluene as model air contaminant. The tested nanocrystalline ZnAl_2O_4 turned out to be poor oxidation photocatalyst under UV irradiation. CdSe displays considerable photocatalytic activity under visible light, where TiO_2 is inactive. The nonconventional one-step mechanochemical route to ZnAl_2O_4 and CdSe synthesis offers several advantages compared to traditional processing routes, including low-temperature solid state reactions at ambient temperature, absence of organic templates contamination and low expenses.

3

Mechanochemical Synthesis and Characterization of II-VI Nanocrystals: Challenge for Cytotoxicity Issues

64%

Baláž P., Jardin R., Dutková E., Sayagués M., Baláž M., Mojžišová G., Mojžiš J., Turianicová E., Fabián M.

Acta Physica Polonica A

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2012

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vol. 122

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issue 1

224-229

EN

CdSe@ZnS nanocrystals have been prepared by a two-step solid state mechanochemical synthesis. CdSe prepared from elements in the first step is mixed with ZnS synthesized from zinc acetate and sodium sulfide in the second step. The crystallite size of the new type CdSe@ZnS nanocrystals determined by X-ray diffraction Rietveld refined method was 35 nm and 10 nm for CdSe and ZnS, respectively. Energy dispersive/transmission electron microscopy/energy dispersive spectroscopy methods show good crystallinity of the nanoparticles and scanning electron microscopy elemental mapping illustrate consistent distribution of Cd, Se, Zn and S elements in the bulk of samples. UV-VIS spectra show an onset at 320 nm with calculated bandgap 3.85 eV. This absorption arises from the vibration modes of Zn-S bonds. The nanocrystals show the blue shift from the bandgap of bulk ZnS (3.66 eV). The synthesized CdSe@ZnS nanocrystals have been tested for dissolution, cytotoxicity and L-cysteine conjugation. The dissolution of Cd was less than 0.05 μg mL^{-1} (in comparison with 0.8 μg mL^{-1} which was evidenced for CdSe alone). The very low cytotoxic activity for selected cancer cell lines has been evidenced. CdSe@ZnS nanocrystals coated with L-cysteine are water-soluble and have a great potential in biomedical engineering as fluorescent labels.

4

Hall Effect in ZnO Extrinsic Structure

64%

Dolník B., Kurimský J., Marton K., Kolcun M., Tomčo L., Briančin J., Fabián M., Halama M., Vojtko M., Rajňák M.

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vol. 126

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issue 1

76-77

EN

Zinc oxide-based extrinsic composite was investigated. The sample was selected from a series of components of one production batch, prepared by standard sintering technology. The content of extrinsic elements in ZnO base was determined by SEM. Van der Pauw method with four-point electrode fixture was used for study of conducting phenomena in square-shaped sample. It is normaly preferred to assume the symmetric uniformity of the electrical properties of sample, for which sheet resistance, bulk resistivity and Hall mobility, sheet carrier density and carrier concentration can be calculated. When the uniformity of measured parameters is breached, the anisotropy in the arrangement of the internal structure may be the cause. There remains the question of whether the extrinsic ZnO material can be isotropic, regarding the electrical conductivity. Although the Hall effect has been measured, preliminary measurements indicate the presence of anisotropy in the measured samples. Before measurement the following phenomena should be taken into account: magneto-electric effect, photo-electric effect and the isothermal condition should be preserved. Paper discusses the uniformity deviations for the defined setup configurations for positive and negative magnetic field directions. Bulk resistivity has been calculated by numerical solution of van der Pauw equation. Large offset voltage during the measurement is discussed.

5

The Response of a Magnetic Fluid to Radio Frequency Electromagnetic Field

52%

Dolník B., Rajňák M., Cimbala R., Kolcunová I., Kurimský J., Balogh J., Džmura J., Petráš J., Kopčanský P., Timko M., Briančin J., Fabián M.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

946-948

EN

Electromagnetic pollution generated by the electrical devices has been regarded as a new form of pollution, harmful to the society as air and water pollution. The operation of electronic devices in a polluted electromagnetic environment has caused electromagnetic interference to become important concerns. Devices that are vulnerable to interference must often be shielded to protect them from the effects of electromagnetic interference. In this work we describe an interaction of a magnetic fluid based on transformer oil with alternating magnetic field. The magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Among the wide range of topics covered, we pay attention to an important field related to the absorption of electromagnetic field by magnetic fluid as a suitable candidate for applications where it is necessary to electrically isolate, remove excess of heat, and to shield electromagnetic fields. We present a method for the determination of shielding effectiveness of the magnetic fluid under high-frequency excitation conditions from 750 MHz to 3 GHz by means of magnetic near field measurements and analysis. Herein, we report the effect of magnetic volume fraction in the magnetic fluid and the effect of the sample thickness on the shielding effectiveness. We have found that the magnetic fluid has a frequency dependent "windows", characterized that either absorb the magnetic field, or facilitate penetration of the magnetic field through the barrier.

6

Characterization of Fe_3O_4 Magnetic Nanoparticles Modified with Dextran and Investigation of Their Interaction with Protein Amyloid Aggregates

52%

Koneracká M., Antošová A., Závišová V., Lancz G., Gažová Z., Šipošová K., Juríková A., Csach K., Kováč J., Tomašovičová N., Fabián M., Kopčanský P.

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issue 5

983-985

EN

Functionalised magnetic nanoparticles composed of Fe_3O_4 particles stabilised by sodium oleate and subsequently modified with dextran (MFDEX) were prepared by the co-precipitation method. Their morphology and particle size distribution were observed by scanning electron microscopy and photon cross correlation spectroscopy. In order to confirm the modification of magnetite surface with dextran physical techniques, including infrared spectroscopy, thermal analysis, and magnetic measurement, were used. Finally, the effect of MFDEX on amyloid fibrillar aggregates of human insulin and hen egg white lysozyme, typical amyloidogenic proteins, was investigated. In vitro interaction of MFDEX with protein amyloid fibrils resulted into destruction of amyloid aggregates. The anti-amyloid activity makes MFDEX of potential interest as therapeutic agent against amyloid-related diseases.

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Mechanosynthesis and Sintering of Ce_{1-x}Y_xO_{2-δ} (x ≤ 0.35) Solid Solutions

Photocatalytic Properties of Mechanochemically Synthesized Nanocrystalline ZnAl_2O_4 and CdSe

Mechanochemical Synthesis and Characterization of II-VI Nanocrystals: Challenge for Cytotoxicity Issues

Hall Effect in ZnO Extrinsic Structure

The Response of a Magnetic Fluid to Radio Frequency Electromagnetic Field

Characterization of Fe_3O_4 Magnetic Nanoparticles Modified with Dextran and Investigation of Their Interaction with Protein Amyloid Aggregates