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Magnetic Properties of Magnetite Formed by Biomineralization and Chemical Synthesis

100%
Timko M., Džarová A., Kopčanský P., Závišová V., Koneracká M., Kováč J., Šprincová A., Vaclavíková M., Ivaničová L., Vávra I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
573-576
EN
In this work, the magnetic properties of biologically produced magnetite (magnetosomes) by biomineralization process were compared to those of chemically synthesized Fe_3O_4. The coercivity of 185 Oe in magnetosomes is connected with the fact that the mean diameter is larger than critical size for transition from superparamagnetic to ferromagnetic behavior. A sharp magnetic transition at 105 K (Verwey transition) is clearly present in magnetosomes while in opposite, this transition is missing in Fe_3O_4.
2
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Magnetic Properties of Encapsulated Magnetite in PLGA Nanospheres

100%
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.
3
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Rhodamine 6G as a Mediator of Silver Nanoparticles Aggregation

88%
Kruszewski S., Cyrankiewicz M.
Acta Physica Polonica A
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2013
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vol. 123
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issue 6
965-969
EN
Surface-enhanced Raman scattering is the phenomenon where a huge increase of Raman scattering intensity from molecules situated close to the metal nanoobjects is observed. Our study is focused on the method of SERS-activation of silver nanoparticles and, in the future, the application of thus obtained SERS substrates for biomedical purposes. As expected, the intensity of Raman scattering from rhodamine 6G used here as a SERS probe strongly increase during the early stages of aggregation of silver sol. Moreover, the evolution of extinction spectra and changes in the degree of the colloid aggregation observed in DLS measurements point out that molecules of the dye do not participate passively in the aggregation process but greatly affect its course.
4
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Silver Nanoparticles as Enhancing Substrates for Raman and Fluorescence Spectroscopy

75%
Cyrankiewicz M., Wybranowski T., Kruszewski S.
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vol. 125
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issue 4A
A-11-A-15
EN
The enhancing properties of silver nanoparticles in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF) are studied in this work. The obtained results confirm that the partial aggregation of nanoparticles leads to a great increase of Raman scattering cross-section but there are significant differences in SERS-activity of colloidal silver treated with various aggregating compounds. The differences are interpreted through the analysis of both experimental and computational results. The same silver colloid covered with silica shell preventing the fluorescence quenching makes possible a several-fold increase in fluorescence emission. The effect strongly depends on thickness of the outer layer of nanoparticles. Geometrical parameters of nanoparticles (radius or radius and thickness of the adsorption layer in core-shell systems) are determined on the basis of the dynamic light scattering (DLS) data and extinction spectra analysis.
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