Properties Of Magnetic Microspheres Research Articles

Synthesis and properties of magnetic microspheres based on magnetite and hydrophilic polymers

Using emulsification technique, magnetic microspheres (MMS) were prepared from solutions of alginate, pectin, gelatin, chitosan and polyvinyl alcohol. Index of polidispersity of the microspheres was ≤ 0.1. The microspheres from gelatin, chitosan and polyvinyl alcohol covalently crosslinked with glutaraldehyde were resistant to sonication and hydrolysis at room temperature in buffer solution with pH 7.4. The microspheres containing superparamagnetic magnetite particles demonstrated no residual magnetization. After modification, chitosan and polyvinyl alcohol MMS were used for immunomagnetic separation of cells and germs.

Multifunctional PMMA@Fe₃O₄@DR Magnetic Materials for Efficient Adsorption of Dyes.

Magnetic porous microspheres are widely used in modern wastewater treatment technology due to their simple and quick dye adsorption and separation functions. In this article, we prepared porous polymethylmethacrylate (PMMA) microspheres by the seed-swelling method, followed by in situ formation of iron oxide (Fe3O4) nanoparticles within the pore. Then, we used diazo-resin (DR) to encapsulate the porous magnetic microspheres and achieve PMMA@Fe3O4@DR magnetic material. We studied the different properties of magnetic microspheres by different dye adsorption experiments before and after the encapsulation and demonstrated that the PMMA@Fe3O4@DR microspheres can be successfully used as a reusable absorbent for fast and easy removal of anionic and aromatic dyes from wastewater and can maintain excellent magnetic and adsorption properties in harsh environments.

Fabrication of Fe3O4/PAH/PSS@Pd core–shell microspheres by layer-by-layer assembly and application in catalysis

High performance magnetic Fe3O4/PAH/PSS@Pd core–shell microspheres are successfully synthesized via layer-by-layer self-assembly method. Fe3O4 cores with a rough surface are synthesized by hydrothermal method. Subsequently, Pd nanoparticle shells and Fe3O4/PAH/PSS@Pd microspheres are in situ simultaneously constructed by alternating immersion of Fe3O4 particles in PSS (poly(sodium 4-styrenesulfonate)) and PAH-Pd(II) (Poly(allylamine hydrochloride)-Pd(II)) solutions, followed by chemical reduction in NaBH4 solution. The structural and magnetic properties of microspheres are characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and vibrating sample magnetometer (VSM), respectively. These microspheres demonstrate excellent structural uniformity (190nm) and superior magnetization, leading to easy collection of microspheres using an external field. With highly active and stable Pd nanoparticle shells, these microspheres exhibit more efficient catalytic activity for the oxidation of benzyl alcohol.

Composition of ferrospinel phase and magnetic properties of microspheres and cenospheres from fly ashes

The methods of Mössbauer spectroscopy, magnetic measurements, chemical analysis, and thermodynamic calculation of the phase composition were used in systematic studies of oxide iron–aluminosilicate (SiO 2–Al 2O 3–Fe 2O 3) system in a wide range of its macrocomponent composition: 0.6–65.6 wt.% SiO 2; 0.05–20.5 wt.% Al 2O 3; 4.6–92.5 wt.% Fe 2O 3. These correspond to the composition of magnetic microspheres and cenospheres from fly ashes originated from powdered-coal combustion of five varieties of energy coals. It was established that the main phase governing the magnetic properties is magnetite with a defective structure. The microspheres saturation magnetization increases with the iron content range of 4.6–80.0 wt.% Fe 2O 3 is caused by the increase of the spinel phase content. The magnetization reduction in ferruginous microspheres with the high iron content (83.0–92.5 wt.% Fe 2O 3) is the result of the hematite–magnetite displacement.

Synthesis of Magnetic Microspheres with Controllable Structure via Polymerization‐Triggered Self‐Positioning of Nanocrystals

A facile and novel method for the synthesis of magnetite-polymer hybrid microspheres with controllable structure is reported. On the basis of the interactions between polymers and magnetic nanocrytals, which are coated with a primary oleic acid layer, a variety of magnetic microspheres with well-tailored structure are fabricated by carefully modulating polymerization and selecting components of composite microspheres; the evolvement of hierarchical structure, and the magnetic properties of microspheres were systematically studied. Importantly, the mechanism of polymerization-triggered self-positioning of magnetic nanocrystals is investigated.

Preparation and characterization of magnetic poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) microspheres

In this article, nano-magnetite particles (ferrofluid, Fe3O4) were prepared by chemical co-deposition method. A series of biodegradable triblock poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL, PCEC) copolymers were synthesized by ring-opening polymerization method from epsilon-caprolactone (epsilon-CL) initiated by poly(ethylene glycol) diol (PEG) using stannous octoate as catalyst. And the magnetic PCEC composite microspheres were prepared by solvent diffusion method. The properties of the ferrofluid, PCEC copolymer, and magnetic PCEC microspheres were studied in detail by SEM, VSM, XRD, Malvern Laser Particle Sizer, 1H-NMR, GPC, and TG/DTG. Effects of macromolecular weight and concentration of polymer, and the time for ultrasound dispersion on properties of magnetic microspheres were also investigated. The obtained magnetic PCEC microspheres might have great potential application in targeted drug delivery system or cell separation.

Magnetic properties of nanoparticles of cenospheres from energetic ashes

The application of magnetic cenospheres including ferrospinel nanoparticles as a “transport container” in medicine and biology is quite attractive. Their nanoscale size, high porosity, and well pronounced magnetic properties provide good consumer choice. In this contribution, we report on the magnetic properties of microspheres from energetic ashes of Ekibastuz coals.

Mössbauer and magnetic study of microspheres extracted from fly ashes of power stations

Phase composition of six narrow size fractions of microspheres extracted from fly ashes of Ekibastuz coals has been determined by Mossbauer spectroscopy. The basic phase is defect magnetite substituted by Al, Mg, and Ti ions. The magnetic properties of microspheres depend on the content of iron and its distribution over spinel positions.

Magnetic properties of nanostructured hollow microspheres

Computer simulations are presented to explore the magnetic and magnetomechanical properties of hollow microspheres consisting of a self-supporting shell of iron-oxide nanoparticles which were recently synthesized in experiment. The magnetic properties of the microspheres are governed by the dipolar interactions between the nanoparticles, leading to a complex vortex ground state structure with the magnetic moments aligned parallel to the surface. In magnetic fields, considerable deformations are observed that withstand external applied pressures.

Preparation of magnetic polystyrene microspheres with a narrow size distribution

AbstractA spraying suspension polymerization process for preparation of magnetic polystyrene microspheres with a narrow size distribution was proposed. The magnetite (Fe3O4) nanoparticles with hydrophobic shell were first prepared by a modified chemical coprecipitation method. Then the oil solution, composed of monomer styrene, crosslinker divinylbenzene, Fe3O4 nanoparticles, and initiator benzoyl peroxide, was sprayed into the poly(vinyl alcohol) aqueous solution by a pressure of nitrogen gas to form droplets. Finally, the droplets would be polymerized rapidly to magnetic polystyrene microspheres at the polymerization temperature. The morphology and magnetic properties of microspheres were examined using a scanning electron microscope and a vibrating sample magnetometer. The results showed that the magnetic microspheres had a narrow size distribution with mean diameter of around 10 μm and smooth surface, and the magnetic microspheres with saturation magnetization of 15.6 emu/g exhibited distinct superparamagnetic characteristics. Powder X‐ray diffraction was used to investigate the structure of the magnetite nanoparticles dispersed in the polystyrene matrix. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Magnetic hydrophilic methacrylate-based polymer microspheres for genomic DNA isolation

Carboxyl groups containing magnetic and non-magnetic microspheres were used in solid-phase reversible immobilization (SPRI) of genomic DNA. Magnetic non-porous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate)--P(HEMA-co-EDMA), poly(glycidyl methacrylate)--PGMA and P(HEMA-co-GMA) microspheres with hydrophilic properties were prepared by dispersion copolymerization of the respective monomers in the presence of colloidal iron oxides. DNA from chicken erythrocytes and DNA isolated from bacterial cells of Bifidobacterium longum was used for testing of adsorption/desorption properties of magnetic microspheres. The occurrence of false negative results in polymerase chain reaction (PCR) caused by the presence of extracellular inhibitors in DNA samples has been solved using SPRI. The P(HEMA-co-EDMA) and P(HEMA-co-GMA) microspheres were used for isolation of DNA from different dairy products followed by PCR identification of Bifidobacterium strains.