Crystalline Magnetite Research Articles

EPR Detection of Iron Storage in Rat Tissues After Simulated Microgravity Model

By a method of spectroscopy of electron paramagnetic resonance the tissues of rats after exposure of microgravity simulation (model of hindlimb unloading) were investigated. In the tissues of heart, lung, liver and muscles the signals of electron magnetic resonance (EMR) depending on orientation were detected. The temperature and orientation dependences of the signals were studied. Comprehensive analysis of the characteristics of the EMR signals made it possible to identify the source of the signals as a crystalline magnetite. Three types of anisotropic EMR signals corresponding to a variety of spatial forms of accumulation of biogenic magnetite were detected. The appearance of the signals after microgravity simulation indicates an alteration in iron metabolism and an abnormal accumulation of iron in the rat tissues.

High-resolution analytical imaging and electron holography of magnetite particles in amyloid cores of Alzheimer's disease.

Abnormal accumulation of brain metals is a key feature of Alzheimer’s disease (AD). Formation of amyloid-β plaque cores (APC) is related to interactions with biometals, especially Fe, Cu and Zn, but their particular structural associations and roles remain unclear. Using an integrative set of advanced transmission electron microscopy (TEM) techniques, including spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), nano-beam electron diffraction, electron holography and analytical spectroscopy techniques (EDX and EELS), we demonstrate that Fe in APC is present as iron oxide (Fe3O4) magnetite nanoparticles. Here we show that Fe was accumulated primarily as nanostructured particles within APC, whereas Cu and Zn were distributed through the amyloid fibers. Remarkably, these highly organized crystalline magnetite nanostructures directly bound into fibrillar Aβ showed characteristic superparamagnetic responses with saturated magnetization with circular contours, as observed for the first time by off-axis electron holography of nanometer scale particles.

Catalytic Ozonation of 4-Nitrophenol in the Presence of Magnetically Separable Titanium Dioxide – Magnetite Composite

<p>This paper deals with determining catalytic activities of titania (TiO<sub>2</sub>) with various crystalline structures and magnetite (Fe<sub>3</sub>O<sub>4</sub>) during mineralization of 4-nitrophenol in aqueous media by ozonation. Among the titania samples under study, amorphized TiO<sub>2</sub> was shown to have the highest catalytic activity, while magnetite was characterized by the lowest catalytic activity. A procedure is proposed to synthesize a magnetically separable composite (TiO<sub>2</sub>/Fe<sub>3</sub>O<sub>4</sub>) including amorphized titania and magnetite phases, which involves deposition of a catalytically active titania phase on preformed magnetite particles. We also studied the effect of mass ratio of titania and magnetite phases in the composite on its catalytic activity during 4-nitrophenol mineralization by ozonation. It was found that catalytic activity of composite increased as the amorphized titania phase was doped with magnetite phase up to 30% wt but as the magnetite portion in the composite catalyst was further increased, its activity decreased. According to Fourier transform infrared (FTIR) spectroscopy, content of catalytically active sites (hydroxyl groups of titania) in the composite catalyst decreases as compared to the pure phase of amorphized titania. Increase in catalytic activity of the composite as its magnetite content increases to 30% wt can be attributed to increase of accessibility of catalytically active sites (OH groups) for ozone, because specific surface area and total pore volume of the composite catalyst as determined by BET increase as compared to amorphized TiO<sub>2</sub> and catalytically active titania phase is located mostly on surface of magnetite particles which is indicated by scanning electron microscopy (SEM) results and electrophoretic light scattering (ELS) data. It was shown that the obtained composite catalyst of optimized composition, in spite of its fine particles, can be easily recovered from aqueous phase by magnetic field and used repeatedly in ozonation in order to promote water purification process.</p>

Fluorescent nanoparticles for drug delivery and theranostic

well crystalline magnetite cores within intact ferritin shells. The saturation magnetization (Ms), relaxivity, and peroxidase-like activity of synthesized M-HFn nanoparticles were monotonously increased with the size of ferrimagnetic cores. The M-HFn nanoparticles with largest core size of 5.3 nm exhibit the strongest saturation magnetization, the highest peroxidase activity in immunohistochemical staining, and the highest r2 of 321 mM −1 s, allowing to detect MDA-MB-231 breast cancer cells as low as 10 cells ml. This study indicates that M-HFn nanoparticles with larger ferrimagnetic core can significantly enhance the performance in MRI and staining of cancer cells.

Synthesis of functionalized magnetite nanoparticles to use as liver targeting MRI contrast agent

The aim of this research was the preparation of functionalized magnetite nanoparticles to use as a liver targeting contrast agent in magnetic resonance imaging (MRI). For this purpose, Fe3O4 nanoparticles were synthesized via the co-precipitation method. The synthesized nanoparticles were coated with silica via the Stober method and finally the coated nanoparticles were functionalized with mebrofenin. Formation of crystalline magnetite particles was confirmed by X-ray diffraction (XRD) analysis. The Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray analyzer (EDX) of the final product showed that silica had been effectively bonded onto the surface of the magnetite nanoparticles and the coated nanoparticles functionalized with mebrofenin. The magnetic resonance imaging of the functional nanoparticles showed that the Fe3O4–SiO2-mebrofenin composite is an effective MRI contrast agent for liver targeting.

Magnetic nanocomposites based on mesoporous silica for biomedical applications

In the present work we report the synthesis procedure of magnetic mesoporous SBA-15 silica materials with controlled morphology as potential composites for biomedical applications, mainly as scaffolds for bone tissue engineering. Different procedures and synthetic parameters are varied to control the physico-chemical, textural and magnetic properties of these materials. Our results show that magnetic mesoporous silica presents two-dimensional hexagonal symmetry with the presence of mesoporous cylindrical geometries, open at both ends, with magnetite nanoparticles in the channels as shown by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) micrographs. Determined by the Brunauer-Emmett-Teller (BET) method, these materials show a surface area above 150 m2/g, which assures a loading capacity higher than conventional ceramics. The presence of crystalline magnetite is corroborated by X-ray diffraction (XRD). The magnetisation cycles show no hysteresis or coercive forces, evidencing their superparamagnetic (SPM) behaviour, which is highly desirable for biomedical applications to avoid magnetic agglomeration of particles.

Polyethylene Glycol-Mediated Synthesis of Cubic Iron Oxide Nanoparticles with High Heating Power.

Iron oxide magnetic nanoparticles (IOMNPs) have been successfully synthesized by means of solvothermal reduction method employing polyethylene glycol (PEG200) as a solvent. The as-synthesized IOMNPs are poly-dispersed, highly crystalline, and exhibit a cubic shape. The size of IOMNPs is strongly dependent on the reaction time and the ration between the amount of magnetic precursor and PEG200 used in the synthesis method. At low magnetic precursor/PEG200 ratio, the cubic IOMNPs coexist with polyhedral IOMNPs. The structure and morphology of the IOMNPs were thoroughly investigated by using a wide range of techniques: TEM, XRD, XPS, FTIR, and RAMAN. XPS analysis showed that the IOMNPs comprise a crystalline magnetite core bearing on the outer surface functional groups from PEG200 and acetate. The presence of physisorbed PEG200 on the IOMNP surface is faintly detected through FT-IR spectroscopy. The surface of IOMNPs undergoes oxidation into maghemite as proven by RAMAN spectroscopy and the occurrence of satellite peaks in the Fe2p XP spectra. The magnetic studies performed on powder show that the blocking temperature (TB) of IOMNPs is around 300 K displaying a coercive field in between 160 and 170 Oe. Below the TB, the field-cooled (FC) curves turn concave and describe a plateau indicating that strong magnetic dipole-dipole interactions are manifested in between IOMNPs. The specific absorption rate (SAR) values increase with decreasing nanoparticle concentrations for the IOMNPs dispersed in water. The SAR dependence on the applied magnetic field, studied up to magnetic field amplitude of 60 kA/m, presents a sigmoid shape with saturation values up to 1700 W/g. By dispersing the IOMNPs in PEG600 (liquid) and PEG1000 (solid), it was found that the SAR values decrease by 50 or 75 %, indicating that the Brownian friction within the solvent was the main contributor to the heating power of IOMNPs.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1091-0) contains supplementary material, which is available to authorized users.

Потенційні продуценти біогенних магнітних наночастинок серед патогенних і умовно-патогенrх мікроорганізмів

Проблематика. Ускладнені форми інфекції при запальних процесах характеризуються зростанням резистентності мікрофлори до антибіотиків, що змушує шукати нові способи лікування, які б запобігали розвитку патогенних мікроорганізмів, підвищували місцевий імунітет і тим самим прискорювали регенеративні процеси. Мета. Метою роботи є класифікація патогенних та умовно-патогенних мікроорганізмів, які можуть бути потенційними продуцентами біогенних магнітних наночастинок (БМН), на предмет локалізації та властивостей БМН за допомогою методів порів­няльної геноміки з перспективою їх подальшого використання як магнітокерованих векторів для цільової доставки лікарських препаратів. Це дасть змогу використовувати методи гіпертермії для знешкодження патогенних та умовно-патогенних мікроорганізмів, які здатні до біомінералізації БМН, застосовуючи для нагріву клітин безпосередньо внутрішньоклітинні БМН цих мікроорганізмів. Методика реалізації. У роботі застосовано методи попарного та множинного вирівнювання з використанням вільної в доступі програми “BLAST” Національного центру біотехнологічної інформації. Результати. Виявлено, що такі штами, як E. coli (541-15), K. pneumoniae 342, C. perfringens str. 13 , P. fluorescens , є потенційними продуцентами саме кристалічного магнетиту, а мікроорганізми S. aureus RF122, S. suis BM407 , E. aerogenes KCTC 2190 , K. pneumoniae RYC492 , P. aeruginosa M18 можуть бути продуцентами внутрішньоклітинних аморфних БМН. Сила магнітодипольної взаємодії між БМН бактерій і БМН пухлин становить 10 - 7 –10 - 8 Н. Висновки. Пояснюється ефект знешкодження патогенних мікроорганізмів за допомогою методу магнітної гіпертермії за рахунок наявності БМН. Запропоновано використовувати для лікування гнійно-запальних процесів не тільки антибіотичні препарати, але й електромагнітні поля для тих мікроорганізмів, які є продуцентами БМН. Показано, що як вектори для цільової доставки лікарських препаратів доцільно використовувати мікроорганізми з природними магнітними властивостями, що зробить метод цільової доставки препаратів надійнішим та більш ефективним і зменшить його вартість.

Synthesis and characterization of Fe3O4/TiO2 magnetic and photocatalyst bifunctional core-shell with superparamagnetic performance

In this research a simple method has been presented to coat magnetic nanoparticles with TiO2. Firstly, Fe3O4 nanoparticles have been prepared using a co-precipitation method. Thereafter, in order to achieve particles with better dispersibility, the surface of Fe3O4 nanoparticles has been modified with the help of trisodium citrate as stabilizer. Afterward, Fe3O4 / TiO2 core-shell nanocomposites were synthesized by the Stober method. The prepared samples were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDS) analysis and vibrating sample magnetometer (VSM). XRD results show the formation of two compounds of crystalline magnetite and brookite-type TiO2 . TEM images confirmed the formation of their core-shell structure. The surface modification of magnetite nanoparticles using trisodium citrate was confirmed by FTIR analysis. Magnetic studies also indicated that prepared core-shells exhibit superparamagnetic behavior at room temperature. Combining this property with the photocatalytic ability of TiO2 could result in a synthesized nanocomposite with different medical and environmental applications.

Iron/Magnetite Nanoparticles as Magnetic Delivery Systems for Antitumor Drugs.

In this study we investigate on the possible use of a new kind of magnetic nanostructures as drug delivery systems for anticancer drugs. The starting particles are formed by an inner core of iron, coated by magnetite as a stabilizing, magnetic layer. These units are further coated by a poly(ethylenglycol) (PEG) layer to make them less prone to the attack by macrophages and to favour longer stays in the blood stream. The resulting particles consist of several magnetic cores encapsulated by a polymer layer around 5 nm thick. The crystal structure of the designed nanostructures, as determined by X-ray powder diffraction, is compatible with a crystalline magnetite component, whereas the magnetization hysteresis data indicate a superparamagnetic behavior. Both the initial susceptibility and the saturation magnetization are lower than for the bare magnetic cores, but still significant. Drug adsorption and release tests were performed on two anticancer drugs, namely 5-fluorouracil and doxorubicin. Both are found to adsorb on the particles, but only the latter appears to be released at a reasonable rate, which is found to be very slow for 5-fluorouracil.

Redox cycling of Fe(II) and Fe(III) in magnetite by Fe-metabolizing bacteria.

Microorganisms are a primary control on the redox-induced cycling of iron in the environment. Despite the ability of bacteria to grow using both Fe(II) and Fe(III) bound in solid-phase iron minerals, it is currently unknown whether changing environmental conditions enable the sharing of electrons in mixed-valent iron oxides between bacteria with different metabolisms. We show through magnetic and spectroscopic measurements that the phototrophic Fe(II)-oxidizing bacterium Rhodopseudomonas palustris TIE-1 oxidizes magnetite (Fe3O4) nanoparticles using light energy. This process is reversible in co-cultures by the anaerobic Fe(III)-reducing bacterium Geobacter sulfurreducens. These results demonstrate that Fe ions bound in the highly crystalline mineral magnetite are bioavailable as electron sinks and electron sources under varying environmental conditions, effectively rendering magnetite a naturally occurring battery.

Mössbauer characterization of feed coal, ash and fly ash from a thermal power plant

The aim of this work was apply 57Fe Transmission Mossbauer Spectroscopy at room temperature in order to study the occurrence of iron-containing mineral phases in: 1) feed coal; 2) coal ash, obtained in different stages of the ASTM D3174 standard method; and 3) fly ash, produced when coal is burned in the TERMOPAIPA IV thermal power plant localized in Boyaca, Colombia. According to obtained results, we can conclude the occurrence of pyrite and jarosite in the feed coal; Fe2+ and Fe3+ crystalline paramagnetic phases, superparamagnetic hematite and hematite in coal ash; Fe2+ and Fe3+ noncrystalline and crystalline phases, magnetite and hematite in fly ash. Precisely, for a basic understanding, this work discusses some the possible transformations that take place during coal combustion.

Size Dependent Heating Efficiency of Iron Oxide Single Domain Nanoparticles

The iron oxide nanoparticles have been synthesized by coprecipitation and solvothermal reduction methods. The particles obtained differ in size, the mean size of particles coprecipitated is of 13nm and the particles, prepared by solvothermal reduction method have a size of 20nm. Both kinds of nanoparticles demonstrate narrow particles sizes distribution. The particles which are prepared by coprecipitation method have narrow particles sizes distribution with mean size diameter of 13nm and the particles, prepared by solvothermal reduction method have a size of 20nm. The X-ray diffraction data analysis revealed that highly crystalline and single-phase magnetite nanoparticles are formed by solvothermal reduction technique, whereas coprecipitation leads to the formation of multi-phase composition of a magnetite (72%) and maghemite (28%). According to the size of nanoparticles obtained, they are in superparamagnetic state for iron oxides. The saturation magnetization of solvothermal prepared particles is higher than those for coprecipitated due to their higher crystallinity and phase purity. Nevertheless, the glycerol dispersion of particles coprecipitated shows higher SLP values than the dispersion of the particles, synthesized by solvothermal reduction method. The heating efficiency of nanoparticles based dispersions is explained by the particles size effect and properties of carrier medium.

Highly monodisperse low-magnetization magnetite nanocubes as simultaneous T(1)-T(2) MRI contrast agents.

We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 ± 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin canting effect. As a proof-of-concept demonstration, we showed their potential as dual contrast agents for both T1- and T2-weighted MRI via phantom studies, in vivo imaging and relaxivity measurements. Therefore, these low-magnetization magnetite nanocubes, while being non-toxic and bio-compatible, hold great promise as excellent dual-mode T1 and T2 contrast agents for MRI.

マグネタイトナノ粒子の水熱合成における応答曲面法を用いた粒子径制御

A hydrothermal synthesis process for preparing crystalline magnetite （Fe3O4） nanoparticles was statistically analyzed to control the particle size, using response surface methodology （RSM） based on design of experiments （DOE）. The influence of the experimental parameters （initial ferrous/ferric ion molar ratio, initial concentration of ferrous ions, and heating time） and their interactions on the particle growth was evaluated through the analysis of variance （ANOVA） for the dynamic light scattering diameter. Furthermore, the multiple linear regression analysis （MLRA） was performed, and then the three-dimensional response surface plots were obtained. The particle size was found to be affected by the experimental parameters, in particular, the interaction between the ferrous/ferric ion molar ratio and the concentration of ferrous ions, suggesting that the particle growth mechanism is altered depending on the amount of ferrous ions. The particle size can be successfully controlled to a given target level using the obtained analysis results.

Response Surface Methodology Study on Magnetite Nanoparticle Formation under Hydrothermal Conditions

In a hydrothermal preparation of crystalline magnetite (Fe3O4) nanoparticles, the influence of the experimental parameters (initial molar ratio of ferrous/ferric ions, initial concentration of ferrous ions, and heating time), and their interactions, on the particle formation was studied using response surface methodology (RSM), based on a statistical design of experiments (DOE). As indices indicating particle formation and crystallization, the variation in the particle diameter and crystallite size with the synthesis conditions was examined. The crystallite size was greatly affected by both the initial ferrous/ferric ion molar ratio and the heating time, whereas the particle diameter strongly depended on the heating time, and on the interaction between the initial ferrous/ferric ion molar ratio and the initial concentration of ferrous ions. The results from a statistical analysis suggest that the polycrystalline Fe3O4 nanoparticles form via crystal growth and/or thermal aggregation, after nucleation during hydrothermal treatment.

The facile fabrication of magnetite nanoparticles and their enhanced catalytic performance in Fischer-Tropsch synthesis.

Uniform and crystalline magnetite nanoparticles are facilely fabricated and utilized as an efficient catalyst in Fischer-Tropsch synthesis (FTS). The catalyst exhibits a high and stable activity with low methane selectivity, attributed to its remarkable structural and chemical stability at the realistic conditions of FTS.

Magnetic, X-ray and Mössbauer studies on magnetite/maghemite core–shell nanostructures fabricated through an aqueous route

Uniform 6–13 nm sized 0D superparamagnetic Fe3O4 nanocrystals were synthesized by an aqueous ‘co-precipitation method’ under a N2 atmosphere as a function of temperature to understand the growth kinetics. The crystal phases, surface charge, size, morphology and magnetic characteristics of as-synthesized 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 Mossbauer 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−1. 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 Mossbauer 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−1 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 m2 g−1. 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.

A miniaturized photoreactor based on a hollow-core metal cladding waveguide

We present a novel reactor based on the ultrahigh order modes in a hollow-core metal cladding waveguide (HCMW). Aqueous Fe2+/Fe3+ salt solutions in the hollow-core act as the HCMW guiding layer. Light power is induced into the guiding layer using the free-space coupling technique. A series of enhanced power points, considered to be optical trapping points, are formed because of the excitation of the ultrahigh-order modes. It is demonstrated that, at these optical trapping points, crystalline magnetite γ-Fe2O3 is synthesized after the deionized water is photolyzed into OH−. The magneto-optical effect of this γ-Fe2O3 is explored for potential applications.

Microwave-assisted nonaqueous sol–gel synthesis of highly crystalline magnetite nanocrystals

Microwave-assisted benzyl alcohol route, starting form Fe(III) acetylacetonate, was applied to obtain crystalline magnetite nanoparticles. In particular the effect of synthesis time on the physical and magnetic properties of the so obtained powders were evaluated. By means of this approach, monocrystalline magnetite particles with size ranging from 4 to 8 nm were obtained. The crystallinity increases as the microwave thermal treatment is increased and reaches almost 95 wt% with treatment time of 240 min. The size of the units individually responding to a magnetic field is slightly larger than the nanoparticle size, indicating partial aggregation of nanoparticles. Both the magnetization of powders and the effects of magnetic dipolar interaction increase with increasing heating time. All powders behave as weakly interacting superparamagnetic materials over an extended temperature interval.