Fe3O4 Nanostructures Research Articles

Surfactantless synthesis of Fe3O4 magnetic nanobelts by a simple hydrothermal process

Fe3O4 nanobelts were prepared by a surfactantless hydrothermal process. FeCl2 and Na2CO3 were used as iron and alkali sources, respectively. X-ray diffraction and energy dispersive spectroscopy showed that the as-prepared product was pure cubic-phase Fe3O4 without any impurity. Scanning electron microscopy and transmission electron microscopy indicated that the Fe3O4 nanobelts had lengths of 400 to 1500nm and widths of 80 to 120nm. Investigations on the effects of other iron and alkali sources on the Fe3O4 nanostructures indicated that both FeCl2 and Na2CO3 were indispensable to the formation of Fe3O4 nanobelts. Magnetic analysis revealed that the Fe3O4 nanobelts had ferromagnetic behavior with a saturation magnetization of 74.54emug−1.

Facile fabrication and growth mechanism of 3D flower-like Fe3O4 nanostructures and their application as SERS substrates

A template-free solvothermal combined with precursor thermal transformation method has been developed for the preparation of flower-like Fe3O4 nanostructured hollow microspheres. The reaction mechanism and the self-assembly evolution process were studied, and it was found that the synthetic conditions for the precursor such as reaction time, urea concentration and non-aqueous media are all crucial for the formation of the flower-like hierarchical precursors. The flower-like Fe3O4 microspheres obtained by calcining the precursor in Ar gas exhibit superparamagnetic behavior and show relative high saturation magnetization at room temperature. To endow them with SERS activity, silver coating was conducted by magnetron sputtering. The obtained Fe3O4/Ag hybrid microflowers make a positive influence on the high sensitivity of SERS to 4-pyridinethiol (4-Mpy) and Rhodamine 6G (R6G) molecules when compared with the silver film substrates. More importantly, the detection limit of Fe3O4/Ag hybrid microflowers for R6G dye can reach up to 10−15 M, which meets the requirements of ultratrace detection of analytes using SERS. Thus, the SERS-active magnetic hybrids prepared in this work may possibly be used as an optical probe with magnetic function for application in high-sensitivity bioassays.

Hierarchical flower-like Fe3O4 and γ–Fe2O3 nanostructures: Synthesis, growth mechanism and photocatalytic properties

The present study describes a facile, economical and environment-friendly aqueous solution method of fabricating hierarchical flower-like Fe3O4 nanostructures under a moderate temperature (80 °C) and without the addition of any organic solvent or surfactant. The as-obtained products are characterized in detail. Control experiments demonstrate that the addition rate of reactants, H3PO4/FeSO4 molar ratio and reaction time influence the morphology of the products. Based on the experimental results, a possible growth mechanism for the formation of these hierarchical flower-like nanostructures is proposed. Well-defined flower-like γ–Fe2O3 nanostructures are also successfully obtained by the thermal treatment of the Fe3O4 sample. These as-prepared flower-like Fe3O4 and γ–Fe2O3 nanostructures are highly effective catalysts for the degradation of eriochrome black T (EBT) in aqueous solution with H2O2 as an oxidant and can be easily separated from the solution using an external magnetic field, exhibiting great potential in environmental cleanup applications.

Carbon Nanocapsules as Nanoreactors for Controllable Synthesis of Encapsulated Iron and Iron Oxides: Magnetic Properties and Reversible Lithium Storage

This paper reports the synthesis of carbon-encapsulated Fe3O4, γ-Fe2O3, and Fe nanostructures using FeOOH as a precursor and carbon nanocapsules (CNCs) as nanoreactors via controllable thermal transformation processes. The magnetic property investigation reveals that the as-synthesized Fe3O4-CNCs, γ-Fe2O3-CNCs, and Fe-C nanostructures all exhibit ferromagnetic behavior with quite high saturation magnetizations. Moreover, the Fe3O4-CNCs with a controlled carbon coating are prepared and their comparative lithium storage properties are investigated. It is found that optimized Fe3O4-CNCs exhibit high capacity and good cycling performance.

Magnetically separable iron oxide nanostructures-TiO2 nanofibers hierarchical heterostructures: controlled fabrication and photocatalytic activity

Novel hierarchical heterostructures of TiO2 nanofibers separately decorated with hematite (α-Fe2O3) or magnetite (Fe3O4) were prepared by combining the electrospinning technique and the hydrothermal method. Extensive characterizations of the resulting hierarchical heterostructures revealed that the secondary α-Fe2O3 or Fe3O4 nanostructures successfully grew on the surface of the primary TiO2 nanofibers substrates, thus integrating the magnetic and photocatalytic properties into the α-Fe2O3/TiO2 and Fe3O4/TiO2 hierarchical heterostructures. The component as well as morphology of the secondary α-Fe2O3 or Fe3O4 nanostructures could be further controlled by simply tuning the experimental parameters. Moreover, the magnetic properties and photocatalytic activities of the hierarchical heterostructures were systematically investigated. Electronic interactions between two semiconductors are the major contributing factor for the changed photoactivity. Most importantly, magnetic measurements showed that the Fe3O4/TiO2 hierarchical heterostructures were ferromagnetic and they could be separated and collected easily using a commercial magnet.

Fe3O4 nanostructures: synthesis, growth mechanism, properties and applications

Recent progress in research on Fe(3)O(4) nanocrystals has attracted much attention both for investigating fundamental nanomagnetism and their potential applications in nanocatalysis, biosensing, magnetic resonance imaging (MRI) contrast agents and drug delivery. In this feature article, we provide an overview of synthetic strategies and growth mechanisms of various Fe(3)O(4) nanostructures, discuss the uniqueness of associated properties, and illustrate their potential applications.

Superhydrophobic iron material surface with flower-like structures obtained by a facile self-assembled monolayer

A simple and economical route based on a K2CO3 mediated process was developed to synthesize three-dimensional (3D) flower-like Fe3O4 micro/nanoflakes on the surface of iron plates by a direct in-situ hydrothermal synthesis method. The prepared micro/nanoflakes were characterized by X-ray diffraction and scanning electron microscopy. It was found that the width of the nanoflakes ranges from 50 to 100 nm, and the length of the flakes is about 3 μm. The morphology of Fe3O4 nanostructures can be tuned from simple isolated nanoflakes to the ordered 3D flower-like shape by increasing the reaction temperature. The wettability of the surface with 3D flower-like micro/nanoflakes was changed from hydrophilicity to superhydrophobicity by chemical modification with vinyl tirethoxy-silane. The static contact angles for water on both of the modified surfaces were larger than 150°, which was closely related to the chemical modification and hierarchical structure. Furthermore, the surfaces retained good superhydrophobic stability in long-term storage as well, which should be critical to the application of iron materials in engineering.

Investigation of nanostructured Fe3O4 polypyrrole core-shell composites by X-ray absorbtion spectroscopy and X-ray diffraction using synchrotron radiation

In this article, we focus on the structural peculiarities of nanosized Fe3O4 in the core-shell nanocomposites obtained by polymerization of conducting polypyrrole shell around Fe3O4 nanoparticles. The local structure of Fe atoms was determined from the Extended X-ray Absorption Fine Structure analysis using our own package computer programs. An X-ray diffraction method that is capable to determine average particle size, microstrains, as the particle size distribution of Fe3O4 nanoparticles is presented. The method is based on the Fourier analysis of a single X-ray diffraction profile using a new fitting method based on the generalized Fermi function facilities. The crystallites size obtained by X-ray diffraction spectra analysis was estimated between 3.2 and 10.3 nm. Significant changes in the first and the second Fe coordination shell in comparison with standard bulk were observed. The global and local structure of the nanosized Fe3O4 are correlated with the synthesis conditions of the core-shell polypyrrole nanocomposites.

Fabrication and Characterization of Nanostructured Fe3O4 Electrodes for Lithium-Ion Batteries

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Controlled-synthesis, characterization, and magnetic properties of Fe3O4 nanostructures

Fe3O4 nanostructures with different morphologies, including uniform nanoparticles, nanorods and nanowire bundles, have been successfully synthesized via a facile hydrothermal route. Based on the observation of TEM images, the growth mechanism of one-dimensional Fe3O4 nanostructures is in accordance with Ostwald ripening process. From the hysteresis loops of as-prepared Fe3O4 products, we found that the morphology has great influence on the magnetic properties. The uniform Fe3O4 nanoparticles have higher saturation magnetization and lower coercivity than that of Fe3O4 nanorods and nanowires bundles. These phenomena attribute to the high shape anisotropy of nanorods and nanowire bundles, which prevent them from magnetizing in directions other than along their easy magnetic axes.

Synthesis of Fe3O4 nanostructures by backward plume deposition and influence of ambient gas pressure on their morphology

Iron oxide nanostructures with significantly fewer droplets were successfully synthesized by pulsed laser deposition using a special target–substrate geometry, which is coined backward plume deposition. The morphology of deposited nanostructures for backward plume deposition is found to be strongly controlled by the ambient gas pressure and changes from a thin film to an assemble of nanoclusters to nanoclusters with loosely bound floccule-like network with the increase in ambient gas pressure. The post-annealing considerably changes the structural properties of deposited materials, which were determined to be magnetite FCC-Fe3O4. It also causes the relaxation of long range stress in the film and hence leads to an increase in the saturation magnetization. The coercivity is found to decrease upon annealing due to the growth of randomly oriented Fe3O4 nanocrystallite as well as the relaxation of internal stress.

Mesoscopic Magnetic/Semiconductor Heterostructures

We report the experimental results of Fe and Fe3O4 nanostructures on GaAs(100) surfaces and hybrid Ferromagnetic/Semiconductor/Ferromagnetic (FM/SC/FM) spintronic devices. Element specific x-ray magnetic circular dichroism (XMCD) measurements have shown directly that Fe atoms on the GaAs(100)-4times6 surface are ferromagnetic. Within coverages of 2.5 to 4.8 ML superparamagnetic nanoclusters are formed and exhibiting strong uniaxial anisotropy, of the order of 6.0times105 erg/cm3. The coercivities of epitaxial Fe dot arrays films grown on GaAs(100) were observed to be dependent on the separation and size of the dots indicating that interdot dipolar coupling affects the magnetization processes in these dots. In addition Fe3O4 films grown on deformed GaAs(100) substrates have been observed to form nanostripes following the topography of the substrate and magneto-optical Kerr effect (MOKE) measurements showed that these nanostripes have uniaxial magnetic anisotropy with easy axis perpendicular to the length of the nanostripes. Meanwhile the FM/SC/FM vertical device has exhibited a biasing current dependent on MR characteristics, with a maximum change of 12% in the MR observed, indicating for the first time a large room temperature spin injection and detection

Large influence of the synthesis conditions on the physico-chemical properties of nanostructured Fe3O4

Magnetite synthesized via three different synthesis routes (coprecipitation process in aqueous media, electrochemical synthesis in presence of complexing agents and solid state reaction at high temperature) has been characterized by X-Ray diffraction, scanning electron microscopy, thermal analysis (TGA), FT-IR and Mossbauer spectroscopies. Although each procedure gave homogeneous magnetite powders, many differences could be seen in the physico-chemical properties of the samples mostly depending on the synthesis conditions. For instance, at least two factors seem to have a huge impact onto the Fe3O4 behaviour: the presence of hydration water molecules and the particle size of the powders since a superparamagnetic behaviour was observed with the thinnest particles, at room temperature, on the Mossbauer spectra via the appearance of line broadening and a pronounced central doublet.

Fe 3 O 4 nanowires synthesized by electroprecipitation in templates

We present an electrochemical technique for growing Fe3O4 nanostructures. Hydrazine and iron compounds in an aqueous solution undergo chemical reactions with hydroxides and form magnetite at the surface of the working electrode of an electrochemical cell. Growth of magnetite in nanoscale templates is demonstrated. X-ray diffraction, transmission electron microscopy, electrical transport measurements, and magnetometry confirm the nature of the deposit. Giant magnetoresistance was observed when the nanowires were granular.

Novel Nanopyramid Arrays of Magnetite

Pvramid-like Fe3O4 nanostructures (see Figure) are formed over large areas on alpha-Fe2O3(0001) substrates using a plasma-sputtering technique. No catalysts or templates are used in the reaction process. This nanostructure resembles Egyptian pyramids, possessing many layers and standing perpendicular to the substrate surface. These structures may have potential applications in constructing nanoscale magnetic and high-density storage devices.

Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures

Fe 3 O 4 nanowires have been fabricated based on Fe3O4 thin films grown on α-Al2O3 (0001) substrates using the hard mask and ion milling technique. Compared with thin films, the Fe3O4 nanowire exhibits a slightly sharper Verwey transition but pronounced anisotropic magnetoresistance properties in the film plane at low magnetic field. Detailed bias-dependence study of both the conductance and magnetoresistance curves for both the thin films and nanowires suggests that the electrical conduction in magnetite near and above the Verwey transition temperature is dominated by a tunneling mechanism across antiphase boundaries.