One-step solid state synthesis of capped γ - Fe 2 O 3 nanocrystallites (original) (raw)
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Three-stepped synthesis and characterization of magnetite and maghemite nanoparticles
On the basis of previous findings, here a novel, three-stepped approach is presented aimed at the synthesis of monodispersed superparamagnetic Fe 3 O 4 /γ-Fe 2 O 3 nanoparticles. In the first step of the approach, ferric nitrate nonahydrate, Fe(NO 3) 3 9H 2 O, was sterically hindered in the interstices and cavities of β-Cyclodextrin (β-CD) molecules, followed by a second step of polyol process. The resulting complex was then dispersed in polyethylene glycol (PEG) and the solution was thermally treated, finally yielding a combination of ferric nitrate and PEG in the form Fe(NO 3) 3 9H 2 O-PEG. In the last step, the ferric nitrate/PEG precursor was refluxed in a strong reductive environment, yielding the final superparamagnetic nanoparticles via a thermal decomposition process. The obtained particles were characterized by X-ray diffraction (XRD) and were confirmed to be a mixture of Fe 3 O 4 and/or γ-Fe 2 O 3. Fourier-transformed Infrared (FTIR) spectroscopy confirmed the presence of polyethylene glycol layer on the nanoparticle surface, along with Oleic Acid (OA) and oleylamine (OAm). High-resolution Transmission Electron Microscopy (HRTEM) confirmed satisfactory particle monodispersity, within a size range of 10-12 nm.
Magnetism and Mössbauer study of formation of multi-core γ-Fe2O3 nanoparticles
Journal of Magnetism and Magnetic Materials
A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (c-Fe 2 O 3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13 nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core c-Fe 2 O 3 nanoparticles show similar behavior to isolated particles of the same size.
Structural and Magnetic Properties of Monophasic Maghemite (γ-Fe 2 O 3) Nanocrystalline Powder
Structural and magnetic studies of monophasic maghemite (γ-Fe2O3) magnetic nanocrystallites (MNCs) synthesized by the co-precipitation chemical route are reported in this paper. For the synthesis, a starting precursor of magnetite (Fe3O4) in basic medium was oxidized at room temperature by adjusting the pH = 3.5 at 80˚C in an acidic medium without surfactants. X-ray diffraction (XRD) pattern shows widened peaks indicating nanometric size and Rietveld Refinement confirms only one single-phase assigned to γ-Fe2O3 MNCs. High Resolution Transmission Electron Microscopy (HR-TEM) demonstrates the formation of nanoparticles with diameter around D ≈ 6.8 ± 0.1 nm which is in good agreement with Rietveld Refinement (6.4 ± 1 nm). A selected area electron diffraction pattern was carried out to complement the study of the crystalline structure of the γ-Fe2O3 MNCs. M(H) measurements taken at different temperatures show almost zero coercivity and remanence indicating superparamagnetic domain and high magnetic saturation.
Synthesis of γ-Fe2O3 Nanoparticles Capped with Oleic Acid and their Magnetic Characterization
Iranian Journal of Science and Technology Transaction A-science, 2017
In recent years, superparamagnetic iron oxide nanoparticles have attracted a great attention due to their various biomedical applications, such as magnetic resonance imaging, targeted drug delivery, and hyperthermia. In this article, c-Fe 2 O 3 magnetic nanoparticles (Maghemite) were prepared in oleic acid media by co-precipitation method. The oleic acid, a monounsaturated fatty acid was used as the capping and stabilizing agent during the synthesis of the magnetic nanoparticles. Characterization of obtained nanoparticles were performed using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FTIR), and vibrating sample magnetometer (VSM). The crystallite size of c-Fe 2 O 3 nanoparticles was achieved in the range between 16.2 and 26.8 nm. The FESEM demonstrated the regular spheres of c-Fe 2 O 3 nanoparticles. The obtained nanoparticles were coated with oleic acid indicating by FTIR analysis. The resulted oleic acid-coated nanoparticles were shown superparamagnetic properties (*52 emu/g). This suggested method is simple and rapid to fabricate superparamagnetic nanoparticles which make them appropriate candidates for theranostic application in future studies.
Structural and Magnetic Properties of Monophasic Maghemite (γ-Fe2O3) Nanocrystalline Powder
Advances in Nanoparticles, 2014
Structural and magnetic studies of monophasic maghemite (γ-Fe2O3) magnetic nanocrystallites (MNCs) synthesized by the co-precipitation chemical route are reported in this paper. For the synthesis, a starting precursor of magnetite (Fe3O4) in basic medium was oxidized at room temperature by adjusting the pH = 3.5 at 80˚C in an acidic medium without surfactants. X-ray diffraction (XRD) pattern shows widened peaks indicating nanometric size and Rietveld Refinement confirms only one single-phase assigned to γ-Fe2O3 MNCs. High Resolution Transmission Electron Microscopy (HR-TEM) demonstrates the formation of nanoparticles with diameter around D ≈ 6.8 ± 0.1 nm which is in good agreement with Rietveld Refinement (6.4 ± 1 nm). A selected area electron diffraction pattern was carried out to complement the study of the crystalline structure of the γ-Fe2O3 MNCs. M(H) measurements taken at different temperatures show almost zero coercivity and remanence indicating superparamagnetic domain and high magnetic saturation.
Synthesis of γ–Fe2O3 nanoparticles with crystallographic and magnetic texture
International Journal of Engineering, Science and Technology, 2011
Maghemite (γ-Fe 2 O 3) nanoparticles are synthesized by chemical co-precipitation technique in AOT-microemulsion with a view to have possible application for biotagging. The investigations by means of X-ray diffraction, isothermal magnetization M (H) and 57 Fe Mössbauer Spectroscopy show that the particles are nonspherical, mostly of rod shape. The inter-particle interaction is so large that even a powder sample of thickness about 40 mg/cm 2 shows preferential orientation of magnetic moments in the plane of the sample. The saturation magnetization is much lower than the expected values for maghemite.
RSC Adv., 2014
Uniform 6-13 nm sized 0D superparamagnetic Fe 3 O 4 nanocrystals were synthesized by an aqueous 'coprecipitation method' under a N 2 atmosphere as a function of temperature to understand the growth kinetics. The crystal phases, surface charge, size, morphology and magnetic characteristics of assynthesized nanocrystals were characterized by XRD, Raman spectroscopy, FTIR, TG-DTA, BET surface area, dynamic light scattering along with zeta potential, HR-TEM, EDAX, vibrating sample magnetometry and Mössbauer spectroscopy. TEM investigation revealed highly crystalline spherical magnetite particles in the 8.2-12.5 nm size range. The kinetically controlled as-grown nanoparticles were found to possess a preferential (311) orientation of the cubic phase, with a highest magnetic susceptibility of $57 emu g À1. The Williamson-Hall technique was employed to evaluate the mean crystallite size and microstrain involved in the as-synthesized nanocrystals from the X-ray peak broadening. In addition to FTIR and Raman spectra, Rietveld structural refinement of XRD confirms the magnetite phase with 5-20% maghemite in the sample. VSM and Mössbauer spectral data allowed us to fit the magnetite/maghemite content to a core-shell model where the shell is 0.2-0.3 nm thick maghemite over a magnetite core. The activation energy of <10 kJ mol À1 calculated from an Arrhenius plot for the complex process of nucleation and growth by diffusion during synthesis shows the significance of the precipitation temperature in the size controlled fabrication processes of nanocrystals. Brunauer-Emmett-Teller (BET) results reveal a mesoporous structure and a large surface area of 124 m 2 g À1. Magnetic measurement shows that the particles are ferromagnetic at room temperature with zero remanence and zero coercivity. This method produced highly crystalline and dispersed 0D magnetite nanocrystals suitable for biological applications in imaging and drug delivery.
Nature communications, 2015
Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest-and more attractive-systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [Co(II)(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination-without nanoparticle aggregation and without complex dissociation-of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blockin...
Mössbauer study of formation of multi-core γ-Fe 2 O 3 nanoparticles Permalink
2017
A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (c-Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13 nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core c-Fe2O3 nanoparticles show similar behavior to isolated particles of the same size. 2017 Elsevier B.V. All rights reserved.
Protein-Directed Synthesis of γ-Fe2O3Nanoparticles and Their Magnetic Properties Investigation
Bulletin of the Korean Chemical Society, 2014
In this study, maghemite (γ-Fe 2 O 3) nanoparticles were produced using gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe 2 O 3 nanoparticles were characterized using XRD, FT-IR, TEM, SEM and VSM data. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced gelatin-Fe 3 O 4 nanocomposite were examined to prove the fundamental effect of gelatin; both as a capping agent in the nanoscale synthesis and as the director of the spinel γ-Fe 2 O 3 synthesis among possible Fe 2 O 3 crystalline structures.