Papers by Keyword: Magnetic Nanoparticle

Abstract: Faraday rotation (FR) and magnetic circular dichroism (MCD) of nanocomposite structures based on potassium-aluminum-germanium-boron glasses co-doped with Fe and rare earth (RE) or Y+Bi oxides have been studied. Formation of magnetic nanoparticles as a result of the glass heat treatment ensures them magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, glasses keep transparence in visual spectral range owing to low paramagnetic oxides concentration. FR and MCD spectra of the heat treated glasses are shown to be very close to those of γ-Fe2O3 and practically independent of the RE element nature for the light wave energies lower than 22000 cm-1. For higher energies, the MCD spectrum shape depends strongly on RE what evidences the different origin of magneto-optical effects in two spectral ranges.

Abstract: Nanocrystalline lithium-substituted manganese-zinc ferrites Li0.5xMn0.4Zn0.6-xFe2+0.5xO4 were prepared by the sol-gel autocombustion method. X-ray diffraction analysis (XRD) confirmed that samples are single-phase and that only a spinel phase is present. The saturation magnetization increases while the cell parameter of the cubic phase decreases with Li concentration. Magnetic permeability and dielectric permittivity of all samples were measured at room temperature as a function of frequency. Reflection loss calculations show that the prepared samples are good electromagnetic wave absorbers in microwave range. Li substitution plays an important role in changing the structural and magnetic properties of these MnZn ferrites.

Abstract: NiCuZn ferrites were prepared by the sol-gel self-combustion method. Nanosized, homogeneous and highly reactive powders were obtained at relatively low temperatures. In present work the variations of structural, magnetic, and microwave properties of NiCuZn ferrite nanoparticles were studied as a function of the annealing temperature. The analysis of XRD patterns showed that only the spinel phase is present. Cell parameters slightly vary with thermal treatment while a crystalline size increases. Magnetic nanoparticles were mixed with an epoxy resin for reflectivity studies with a microwave vector network analyzer using the microwave-guide method in the range of 7.5 to 13.5GHz. Static saturation magnetization value (measured by SQUID) and microwave absorption show clear dependence on the annealing temperature/particle size and the absorption maximum moves towards the higher frequencies with an increase in the average size of the particles.

Abstract: The Fe3O4 magnetic nanoparticles were prepared through co-precipitation of Fe3+ and Fe2+ with ammonium hydroxide. The initially obtained Fe3O4 nanoparticles were then coated by gold in solution of chloroauric acid through connecting of 3-aminopropyropyl thriethoxysilane (3-APTES) and the obtained Fe3O4@Au nanoparticles were further characterized by X-ray photoelectron spectrum (XPS). During the process, the influences of chloroauric acid, reducing agent, coupling agent and nanoparticles of Fe3O4 were studied. The results showed that core-shell structure Fe3O4@Au particles have diameters of about 20nm in size synthesized from sodium citrate as reducing agent with 10.08 emu/g of saturation magnetization.

Abstract: In this study, the magnetic nanoparticles derivatized with dual functional moieties of dodecyl and mercapto were prepared, which characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), surface area and pore size determination, fourier transform infrared spectrometry (FT-IR) and water contact angle analysis. The new material was proved to be an effective sorbent for environmental remediation.

Abstract: Heavy metal ions are increasingly being released into environment, leading to serious pollution and significant health problems to human being. To address the adverse effects posed by them, in the present study, a remediation method by magnetic nanoparticles was proposed. The magnetic particles were synthesized by a solvothermal process first. Then they were derivatized with dual functional moieties of amino- and mercapto- by reacting with aminopropyl-triethoxysilane and mercaptopropyl-triethoxysilane simultaneously. The prepared material was characterized by infrared spectrometry and elemental analysis. Both functional groups of amino- and mercapto- were present within the material. Since amino- and mercapto- have high affinity for heavy metal ions, the material can be used to retrieve these ions from water samples. Pb2+ and Mn2+ were used as model analytes to evaluate the effectiveness of the material. It is found that, after 60 min adsorption, the ions were almost total removed from the sample solution.

Abstract: Superparamagnetic maghemite nanoparticles were successfully produced using Massart’s procedure. Nanocomposites consisting of the synthesized maghemite nanoparticles and silica were produced by dispersing the as-synthesized maghemite nanoparticles into the silica xerogel, which was prepared by sol-gel technique. The system was then heated for 3 days at 140oC. A variety of weight ratios of Fe2O3/SiO2 was investigated. The nanocomposites were characterized using TGA, XRD, TEM and AGM. TGA thermogram showed one significant weight loss at around 250oC. It was caused by dehydration and evaporation of solvent from sol-gel process. XRD showed that the dispersed particles were still maghemite. TEM micrographs showed that the maghemite nanoparticles were in spherical shape and they were homogeneously incorporated in the silica matrix. The values of magnetization at 10kOe applied field were in the range of 1.79emu/g to 9.53emu/g depending of the Fe2O3/SiO2 ratio. Reduction of average crystallite size of dispersed maghemite particles was observed after encapsulation process. Increasing weight ratio of Fe2O3/SiO2 caused increase of the average crystallite size of maghemite nanoparticles.

Abstract: In this work, iron oxide nanoparticles (~5 nm) embedded in a chitosan polymer film, were synthesized. In order to obtain this nanostructured material, firstly a homogenous film of Fe(II)-chitosan was prepared. The resulting composite film has a thickness of ~140μm. Iron oxide nanoparticles were in-situ synthesized by treating the composite film with H2O2 under alkaline conditions. The morphological analysis by Transmission Electron Microscopy (TEM) shows the nanoparticles were embedded and stabilized in chitosan polymer film. The magnetic behavior was studied by magnetization measurements. The magnetization curves at room temperature showed that iron oxide nanoparticles have a superparamagnetic behavior.

Abstract: Ferromagnetic or superparamagnetic nanocrystallites, stabilized in carbon matrix, were prepared by the procedure comprising formation of the appropriate metal acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer. The pyrolysis products were in a form of beads, which contained in their volume randomly distributed nanocrystallites. The nanocrystallites had various composition, magnetic properties and sizes ranging from few to tens of nanometers, depending on the element type. Application of this procedure stabilizes the nanostructure and enables processing of nanoparticles within a narrow window of sizes. The magnetic parameters depend on the crystallite size, determined by their chemical composition. The nanocrystallites pyrolysed at 773 K exhibited ferromagnetic properties for Co and Fe, and superparamagnetic behaviour for the Ni. The nanocrystallites can potentially be applied as sensors for tagging the biological substances or for targeted drug delivery.

Abstract: Magnetic nanoparticles have been used extensively as drug delivery materials in recent years [1,2]. The present research goal is to treat bone diseases (such as osteoporosis and infection) by using surface modified magnetic nanoparticles. Magnetite (Fe3O4) and maghemite (Fe2O3) were synthesized and coated with calcium phosphate (CaP). The resulting nanoparticles were treated hydrothermally to change the crystalline properties of CaP. Nanoparticles were characterized via transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). TEM was also used to study the uptake of nanoparticles into osteoblasts (OB) and bacteria. OB proliferation experiments were conducted after 1, 3 and 5 days in the presence of the various iron oxide nanoparticles alone and CaP coated iron oxide magnetic nanoparticles. OB proliferation experiments were also conducted after 1, 3 and 5 days in the presence of various concentrations of CaP coated nanoparticles to examine a possible concentration dependent trend on OB density. Staph epidermidis were incubated with different doses of Fe3O4 to determine the effect of these nanoparticles on bacteria activity. Results of this in vitro study demonstrated greater OB functions and inhibited bacteria functions in the presence of select magnetic nanoparticles. In summary, the results of this study showed that magnetic nanoparticles should be further studied for various orthopedic applications.