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This paper describes preparation and characterization of magnetic core–shell nanoparticles with modulated magnetic core diameter and various thickness of the non-magnetic shell. Ag, Au and Cu are used as spacing layer metals. Nanoparticles were fabricated by the synthetic method based on modified seeds. During the preparation, the thicknesses of the core and shell were changed to control the influence of nanoparticles’ magnetic properties in respect to the composition and thickness of the spacer material. Obtained nanoparticles were examined by X-ray diffraction, transmission electron microscopy, infrared spectroscopy and differential scanning calorimetry. Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

Studies of the ferrite nanoparticles prepared by the chemical decomposition of iron chlorides with a various ratio ξ = Fe 3+ /Fe 2+ are herein presented. The microstructure and the magnetic properties have been studied by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Mössbauer spectroscopy (MS). The TEM studies show that the nanoparticles have almost a spherical shape with the diameter of (12 ± 2) nm for all samples. The measured XRD pattern was mainly composed of lines which were indexed with a cubic spinel structure. The analysis of the Mössbauer data shows that the microstructure of the nanoparticles consists of the core formed by nonstoichiometric magnetite and maghemite shell. A small amount of hematite, probably on the surface of the nanoparticles with ξ = 1.75, 2.0, was detected. At temperatures T ≤ 150 K the spin canting of surface maghemite with ξ = 2.25 was observed while for the samples with ξ = 1.75, 2.0 such effect was suppressed by the presence of hematite on the surface of the nanoparticles. Infield Mössbauer spectra with ξ = 1.75, 2.0 show that magnetic moments of the magnetite/maghemite core are parallel while magnetic moments of the surface hematite are perpendicular to the direction of the external magnetic field. [ABSTRACT FROM AUTHOR]

Highlights: [•] Core–shell nanoparticles with various shell layers were fabricated. [•] The influence on magnetic properties from layer composition was observed. [•] The influence on quality of layer from their composition was tested. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stability of magnetite nanoparticles in environmental solutions was tested. [•] The most aggressive model solutions were determined to be citric acid, acetic acid and white wine. [•] The chosen model solutions dissolve magnetic core (acids) or modifies mostly particle surface (wine). [ABSTRACT FROM AUTHOR]

Highlights: [•] Stability tests of core–shell nanoparticles were performed. [•] Various durability in studied solutions was observed. [•] The influence on magnetic properties from wetting solution was observed. [Copyright &y& Elsevier]

Highlights: [•] Organophosphorous compound modification of magnetic nanoparticles has been obtained. [•] Successful connection with trypsin via organophosphorous compounds has been tested. [•] Influence on modification from particles coating layer have been tested. [ABSTRACT FROM AUTHOR]

Abstract: In the present study Fe3O4 magnetic nanoparticles were synthesized by coprecipitation of Fe2+ and Fe3+ from chlorides. In the next step magnetite–gold core–shell nanoparticles were synthesized from HAuCl4 using an ethanol as a reducing agent. Finally, magnetic nanoparticles were functionalized by hexadecanethiol. The immobilization of biological molecules (trypsin and glucose oxidase) to the thiol-modified and unmodified magnetite–gold nanoparticles surface was tested. The resulting nanoparticles were characterized by infrared spectroscopy, differential scanning calorimetry, Mössbauer spectroscopy and transmission electron microscopy. [Copyright &y& Elsevier]

The ferrite magnetic nanoparticles with core-shell structures were obtained in two step preparation process. The Mössbauer spectra obtained for particles of pure maghemite or magnetite and two layered core-shell one the magnetite on maghemite and maghemite on magnetite are very different from each other. The presented results show that interparticle and intraparticle interaction plays important role in overall magnetic properties as well. [ABSTRACT FROM AUTHOR]

[Display omitted] • The influence of synthetic procedure on nanoparticles growth was tested. • The influence of dopant concentration on nanoparticles growth was established. • The correlation between particles growth condition and magnetic properties was achieved. The studies presented in this paper show the results of synthesis and physicochemical characterization of modified ferrite nanoparticles, which can be described by the general formula M x Fe 3-x O 4 (where x = 0.15 or 0.45) doped with Al3+, Cr3+, Cu2+ and Zn2+ ions. The nanoparticles were obtained through procedures using either water or organic environment. The aim of this study was to determine the influence of synthetic routine and doping on the quality of the obtained structure, morphology and magnetic properties of nanoparticles. Additionally, doping concentration of selected elements is a crucial influence on the crystallinity and magnetic properties of the obtained nanoparticles. Doped nanoparticles were synthesized by two chemical methods: co-precipitation of iron chlorides in a basic solution and thermal decomposition of iron(III) acetylacetonate in an organic high-boiling solvent. Obtained nanoparticles were characterized by transmission electron microscopy, energy dispersive X-ray, X-ray diffraction, porosimetry, infrared spectroscopy and Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]