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1.
The nature of the physical mechanisms responsible for the structural modification of the γ‐Fe2O3 nanoparticles under laser irradiation has been investigated by Raman spectroscopy. In situ micro‐Raman measurements were carried out on as‐prepared γ‐Fe2O3 nanoparticles about 4 nm in size as a function of laser power and on annealed γ‐Fe2O3 particles. A baseline profile analysis clearly evidenced that the phase transition from maghemite into hematite is caused by local heating due to laser irradiation with an increase of grain size of nanoparticles. This increasing was clearly determined by X‐ray diffraction from 4 nm in nanoparticles up to more than 177 nm beyond 900 °C in a polycrystalline state. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

2.
Magnetic iron oxide nanopowders are synthesized by the laser ablation of a target made of a coarse Fe2O3 powder. The geometric characteristics of the nanopowders and their yield are studied over a wide air pressure range ((1–34) × 104 Pa) in an evaporation chamber. The phase compositions of the nanopowders and the conditions under which their chemical composition is closest to magnetite Fe3O4 are determined. The specific saturation magnetization and the coercive force of some iron oxide nanoparticles are measured.  相似文献   

3.
In recent years, graphene‐incorporated micro‐/nanocomposites represent one of the hottest developing directions for the composite materials. However, a large number of active nanoparticles (NPs) are still in the unprotected state in most constructed graphene‐containing designs, which will seriously impair the effects of the graphene additives. Here, a fully protected Fe3O4‐based micro‐/nanocomposite (G/Fe3O4@C) is rationally developed by carbon‐boxing the common graphene/Fe3O4 microparticulates (G/Fe3O4). The processes and results of full protection are tracked in detail and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and nitrogen absorption–desorption isotherms, as well as scanning and transition electron microscopy. When used as the anode for lithium‐ion batteries, the fully protected G/Fe3O4@C exhibits the best lithium‐storage properties in terms of the highest rate capabilities and the longest cycle life compared to the common G/Fe3O4 composites and commercial Fe3O4 products. These much improved properties are mainly attributed to its novel structural features including complete protection of active Fe3O4 nanoparticles by the surface carbon box, a robust conductive network composed of nitrogen‐doped graphene nanosheets, ultra‐small Fe3O4 NPs of 4–5 nm, abundant mesopores to accommodate the volume variation during cycling, and micrometer‐sized secondary particles.  相似文献   

4.
The Verwey transition in Fe3O4 nanoparticles with a mean diameter of 6.3 nm is suppressed after capping the particles with a 3.5 nm thick shell of SiO2. By X‐ray absorption spectroscopy and its associated X‐ray magnetic circular dichroism this suppression can be correlated to localized Fe2+ states and a reduced double exchange visible in different site‐specific magnetization behavior in high magnetic fields. The results are discussed in terms of charge trapping at defects in the Fe3O4/ SiO2 interface and the consequent difficulties in the formation of the common phases of Fe3O4. By comparison to X‐ray absorption spectra of bare Fe3O4 nanoparticles in course of the Verwey transition, particular changes in the spectral shape could be correlated to changes in the number of unoccupied d states for Fe ions at different lattice sites. These findings are supported by density functional theory calculations.  相似文献   

5.
Shrines (or altars) are constructed in China for worshiping ancestors, Bodhisattva, and God of Wealth. In this work, pigments from the shrine of Kaiping Diaolou tower were analyzed by micro‐Raman spectroscopy, in conjunction with other analytical methods including scanning electron microscopy (SEM) with energy dispersive X‐ray spectroscopy (EDX) and X‐ray fluorescence (XRF). Paintings of the shrine were composed of 2–3 pigment layers and the total thickness was determined as about 200–300 µm by optical microscopy and SEM, indicating the fine painting skills applied in the construction of the shrine. The green pigments on the surface layer of the green fragment were identified as a mixture of lead phthalocyanine (PbPc) and cornwallite (Cu5(AsO4)2(OH)4) by XRF and micro‐Raman spectroscopy with two different excitation wavelengths (488 and 785 nm). Underneath the green layer, red and yellow ochre were found. The pigments on the surface layer of red and blue fragments were identified as hematite (Fe2O3) and lazurite or synthetic ultramarine [(Na8(Al6Si6O24)S3)], respectively. Finally, the pigments under the two surface layers were identified by EDX and micro‐Raman spectroscopy as chromium oxide (Cr2O3), gypsum (CaSO4·2H2O) and calcite (CaCO3). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

6.
We have deposited epitaxial iron oxide thin films on MgO(001) and LaAlO3(LAO)(001) substrates, resulting in different phase stabilities. Atomic force microscopy images revealed a smooth surface. Detailed X‐ray diffraction (XRD) measurements were performed to confirm the epitaxial growth and to analyze the atomic growth configuration. We found that (00l) oriented γ‐Fe2O3 was the stable phase on MgO(001) substrates, whereas $ (1\bar 102) $ oriented α‐Fe2O3 was stable on LAO(001). Magnetic hysteresis loop measurements revealed typical ferrimagnetic behavior for γ‐Fe2O3 on MgO, whereas the magnetization of α‐Fe2O3 on LAO was relatively small and consistent with an antiferromagnetic order. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
Lanathum (La)‐doped Fe3O4 magnetic nanoparticles were prepared in aqueous solution at room temperature, then La‐doped Fe3O4‐polyaniline (PANI) nanocomposites containing a dispersion of La‐doped Fe3O4 nanoparticles were synthesized via in‐situ polymerization of aniline monomer. The structure and properties of the synthesized samples were characterized with X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometry (ICPAES), and a vibrating sample magnetometer (VSM). The resulting particles of La‐doped Fe3O4 and La‐doped Fe3O4‐PANI were almost spherical with diameters ranging from 15 to 25 nm and 25 to 85 nm, respectively. The La‐doped Fe3O4‐PANI composite presented core‐shell structures; polyaniline covered the La‐doped Fe3O4 completely. The specific saturation magnetization of La‐doped Fe3O4‐PANI depended on the starting material of La‐doped Fe3O4. It increased with increasing amounts of La and Fe3O4 content.  相似文献   

8.
Powders of Fe–Mg–O nanocomposite particles have been grown using a novel chemical vapor synthesis approach that employs the decomposition of a metalorganic precursor inside the metal combustion flame. After annealing in controlled gas atmospheres composition distribution functions, structure and phase stability of the obtained magnesiowüstite nanoparticles are measured with a combination of techniques such as inductively coupled plasma‐optical emission spectroscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, and scanning and transmission electron microscopy. Complementary Mössbauer spectroscopy measurements reveal that depending on Fe loading and temperature of annealing either metastable and superparamagnetic solid solutions of Fe3+ ions in periclase (MgO) or phase separated mixtures of MgO and ferrimagnetic magnesioferrite (MgFe2O4) nanoparticles can be obtained. The described combustion technique represents a novel concept for the production of mixed metal oxide nanoparticles. Adressing the impact of selected annealing protocols, this study underlines the great potential of vapor phase grown non‐equilibrium solids, where thermal processing provides means to trigger phase separation and, concomitantly, the emergence of new magnetic properties.  相似文献   

9.
Magnetically contrasted granular hetero‐nanostructures are prepared by seed‐mediated growth in polyol, properly combining two oxide phases with different magnetic order, ferrimagnetic (F) partially oxidized magnetite Fe3−xO4 and antiferromagnetic (AF) cobalt oxide. Spinel Fe3−xO4 nanoparticles are first synthesized and then used as seeds for rock salt CoO nanocrystals growth. Three different hetero‐nanostructure designs are realized, acting on the content ratio between the seeds and the deposit's precursors during the synthesis. For all of them, the spinel and the rock salt phases are confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. Both phases are obtained in high‐crystalline quality with a net epitaxial relationship between the two crystallographic lattices. Mössbauer spectrometry confirms the cobalt cation diffusion into the spinel seeds, giving favorable chemical interfacing with the rock salt deposit, thus prevailing its heterogeneous nucleation and consequently offering the best condition for exchange‐bias (EB) onset. Magnetic measurements confirm EB features. The overall magnetic properties are found to be a complex interplay between dipolar interactions, exchange anisotropy at the F/AF interface, and magnetocrystalline anisotropy enhancement in the F phase, due to Co2+ diffusion into iron oxide's crystalline lattice. These results underline the powerfulness of colloidal chemistry for functional granular hetero‐nanostructured material processing.  相似文献   

10.
Raman spectroscopy, in principle, is an excellent technique for the study of molecular species developed on metal surfaces during electrochemical investigations. However, the use of the more common laser wavelengths such as the 514.5‐nm line results in spectra of less than optimal intensity, particularly for iron oxide compounds. In the present work, near‐resonance enhancement of the Raman spectra was investigated for the iron oxide and iron oxyhydroxide compounds previously reported to be present in the passive film on iron, using a tuneable dye laser producing excitation wavelengths between 560 and 637 nm. These compounds were hematite (α‐Fe2O3), maghemite (γ‐Fe2O3), magnetite (Fe3O4), goethite (α‐FeOOH), akaganeite (β‐FeOOH), lepidocrocite (γ‐FeOOH) and feroxyhyte (δ‐FeOOH). Optimum enhancement, when compared to that with the 514.5‐nm line, was obtained for all the iron oxide and oxyhydroxide standard samples in the low wavenumber region (<1000 cm−1) using an excitation wavelength of 636.4 nm. Particularly significant enhancement was obtained for lepidocrocite, hematite and goethite. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
A new method is reported for obtaining microspirals of iron‐based compounds by interfacial interaction. A thin film of Fe(OH)3 is obtained as a result of interaction between an aqueous solution of iron salts and gaseous ammonia. Upon drying, it is transformed into Fe(OH)3 microspirals with a diameter of up to 10 µm. These microspirals can be transformed into Fe2O3 microspirals by annealing in air. As a result of hydrogen reduction, Fe microspirals are formed. Both the annealing in air and that in hydrogen allow the retaining of the morphology. The material synthesized is characterized by electronic microscopy methods, X‐ray diffraction, diffuse reflectance Fourier transform infrared, and Mössbauer and photoelectron spectroscopies. The electrocatalytic properties of the electrode based on Fe2O3 microspirals as a catalyst of hydrogen evolution and the magnetic properties of Fe microspirals are tested. A hypothesis is proposed on the formation of microspirals by the gas–solution interface technique.  相似文献   

12.
The identification of iron sulfates on Mars by the Mars Exploration Rovers (MERs) and the Mars Reconnaissance Orbiter emphasized the importance of studying iron sulfates in laboratory simulation experiments. The copiapite group of minerals was suggested as one of the potential iron sulfates occurring on the surface and subsurface on Mars, so it is meaningful to study their spectroscopic features, especially the spectral changes caused by cation substitutions. Four copiapite samples with cation substitutions (Fe3+, Al3+, Fe2+, Mg2+) were synthesized in our laboratory. Their identities were confirmed by powder X‐ray diffraction (XRD). Spectroscopic characterizations by Raman, mid‐IR, vis‐NIR and laser‐induced‐breakdown spectroscopy (LIBS) were conducted on those synthetic copiapite samples, as these technologies are being (and will be) used in current (and future) missions to Mars. We have found a systematic ν1peak shift in the Raman spectra of the copiapite samples with cation substitutions, a consistent atomic ratio detection by LIBS, a set of systematic XRD line shifts representing structural change caused by the cation substitutions and a weakening of selection rules in mid‐IR spectra caused by the low site symmetry of (SO4)2− in the copiapite structures. The near‐infrared (NIR) spectra of the trivalent copiapite species show two strong diagnostic water features near 1.4 and 1.9 µm, with two additional bands near 2.0 µm. In the vis‐NIR spectra, the position of an electronic band shifts from 0.85 µm for ferricopiapite to 0.866 µm for copiapite, and this shift suggests the appearance of a Fe2+ electronic transition band near 0.9 µm. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

13.
For fundamental studies of the atmospheric corrosion of steel, it is useful to identify the iron oxide phases present in rust layers. The nine iron oxide phases, iron hydroxide (Fe(OH)2), iron trihydroxide (Fe(OH)3), goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (γ-FeOOH), feroxyhite (δ-FeOOH), hematite (α-Fe2O3), maghemite (γ-Fe2O3) and magnetite (Fe3O4) are among those which have been reported to be present in the corrosion coatings on steel. Each iron oxide phase is uniquely characterized by different hyperfine parameters from M?ssbauer analysis, at temperatures of 300K, 77K and 4K. Many of these oxide phases can also be identified by use of Raman spectroscopy. The relative fraction of each iron oxide can be accurately determined from the M?ssbauer subspectral area and recoil-free fraction of each phase. The different M?ssbauer geometries also provide some depth dependent phase identification for corrosion layers present on the steel substrate. Micro-Raman spectroscopy can be used to uniquely identify each iron oxide phase to a high spatial resolution of about 1 μm. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

14.
Monodisperse iron oxide nanoparticles (NPs) of 4 nm were obtained through high-temperature solution phase reaction of iron (III) acetylacetonate with 1, 2-hexadecanediol in the presence of oleic acid and oleylamine. The as-synthesized iron oxide nanoparticles have been characterized by X-ray diffraction, transmission electron microscopy, Mössbauer spectroscopy and magnetic measurements. The species obtained were Fe3O4 and/or $\upgamma$ -Fe2O3. These NPs are superparamagnetic at room temperature and even though the reduced particle size they show a high saturation magnetization (MS ≈ 90 emu/g).  相似文献   

15.
Iron oxide nanoparticle aggregated films were prepared using the excimer laser ablation technique by adopting an off-axis configuration and the gas condensation process. Sintered iron oxide (-Fe2O3) targets were ablated in oxygen ambient by an ArF excimer laser. The product of ablation comprised Fe2O3 at lower pressure and a mixture of Fe2O3 and FeO at higher pressure by X-ray-diffraction measurements. The maximum ambient oxygen pressure, PS(O2), at which the product composition was still a single Fe2O3 phase was higher for the higher-density target than for its lower-density counterpart. The target surface state affected the product composition only if the pressure was set to the pressure PS(O2) of 40 Pa for a high-density target. When the fluence was high (200 mJ/pulse, 3.3-mm2 spot size), the product composition varied at the initial stage of laser irradiation with the number of laser pulses from a mixture of Fe2O3 and FeO to only Fe2O3 along with the target surface morphological change from a grooved structure to a smooth surface. Product composition was practically independent of the number of pulses by low-fluence laser irradiation even at this particular pressure of 40 Pa. PACS 81.07.Bc; 81.15.Fg; 61.10.Nz  相似文献   

16.
Bursts of emissions of low‐energy electrons, including interatomic Coulomb decay electrons and Auger electrons (0–1000 eV), as well as X‐ray fluorescence produced by irradiation of large‐Z element nanoparticles by either X‐ray photons or high‐energy ion beams, is referred to as the nanoradiator effect. In therapeutic applications, this effect can damage pathological tissues that selectively take up the nanoparticles. Herein, a new nanoradiator dosimetry method is presented that uses probes for reactive oxygen species (ROS) incorporated into three‐dimensional gels, on which macrophages containing iron oxide nanoparticles (IONs) are attached. This method, together with site‐specific irradiation of the intracellular nanoparticles from a microbeam of polychromatic synchrotron X‐rays (5–14 keV), measures the range and distribution of OH radicals produced by X‐ray emission or superoxide anions () produced by low‐energy electrons. The measurements are based on confocal laser scanning of the fluorescence of the hydroxyl radical probe 2‐[6‐(4′‐amino)phenoxy‐3H‐xanthen‐3‐on‐9‐yl] benzoic acid (APF) or the superoxide probe hydroethidine‐dihydroethidium (DHE) that was oxidized by each ROS, enabling tracking of the radiation dose emitted by the nanoradiator. In the range 70 µm below the irradiated cell, radicals derived mostly from either incident X‐ray or X‐ray fluorescence of ION nanoradiators are distributed along the line of depth direction in ROS gel. In contrast, derived from secondary electron or low‐energy electron emission by ION nanoradiators are scattered over the ROS gel. ROS fluorescence due to the ION nanoradiators was observed continuously to a depth of 1.5 mm for both oxidized APF and oxidized DHE with relatively large intensity compared with the fluorescence caused by the ROS produced solely by incident primary X‐rays, which was limited to a depth of 600 µm, suggesting dose enhancement as well as more penetration by nanoradiators. In conclusion, the combined use of a synchrotron X‐ray microbeam‐irradiated three‐dimensional ROS gel and confocal laser scanning fluorescence microscopy provides a simple dosimetry method for track analysis of X‐ray photoelectric nanoradiator radiation, suggesting extensive cellular damage with dose‐enhancement beyond a single cell containing IONs.  相似文献   

17.
Herein, a novel heterogeneous nanoscale reducing agent for antibody cleavage, made of iron oxide nanoparticles, silica network, palladium on calcium carbonate (10%), and dithiothreitol (Fe3O4@Pd/CaCO3-DTT), is presented as a substantial alternative for traditional homogeneous analogues. Conventionally, antibody fragmentation is accomplished using reducing agents and proteases that digest or cleave certain portions of the immunoglobulin protein structure to provide active thiol sites for drug tagging aims. Then, dialysis process is needed to separate excess chemical structures and purify the reduced antibody. In this work, we have made an effort to design a suitable heterogeneous tool for protein cleavage and skip the dialysis process for purification of the reduced antibody. In this regard, firstly, various preparation methods including microwave irradiation, reflux and ultrasonication have been precisely compared, and it has been proven that the best result is obtained through 10 min ultrasound (US) irradiation using an US bath with 50 KHz frequency and 200 W L−1 power density. Then, all the necessary structural analyses have been done and thoroughly interpreted for the final product. Afterward, the catalytic performance of Fe3O4@Pd/CaCO3-DTT nanoscale system in the presence of US waves (50 KHz, 200 W) has been monitored using some disulphide derivatives. The NPs could be conveniently separated from the mixture through their substantial paramagnetic property. Thus, dialysis process in which various types of membranes are used is practically jumped after the reduction process. In this work, this is clearly demonstrated that there is a constructive synergistic effect between US waves and prepared Fe3O4@Pd/CaCO3-DTT nanoscale reducing agent. Ultimately, trastuzumab (anti HER-2) antibody has been used to test the performance of the prepared Fe3O4@Pd/CaCO3-DTT NPs in a real protein reduction reaction.  相似文献   

18.
Core–shell Cu/γ‐Fe2O3@C and yolk–shell‐structured Cu/Fe@γ‐Fe2O3@C particles are prepared by a facile synthesis method using copper oxide as template particles, resorcinol‐formaldehyde as the carbon precursor, and iron nitrate solution as the iron source via pyrolysis. With increasing carbonization temperature and time, solid γ‐Fe2O3 cores are formed and then transformed into Fe@γ‐Fe2O3 yolk–shell‐structured particles via Ostwald ripening under nitrogen gas flow. The composition variations are studied, and the formation mechanism is proposed for the generation of the hollow and yolk–shell‐structured metal and metal oxides. Moreover, highly graphitic carbons can be obtained by etching the metal and metal oxide nanoparticles through an acid treatment. The electrocatalytic activity for oxygen reduction reaction is investigated on Cu/γ‐Fe2O3@C, Cu/Fe@γ‐Fe2O3@C, and graphitic carbons, indicating comparable or even superior performance to other Fe‐based nanocatalysts.  相似文献   

19.
Interaction of sol–gel synthesized Ce–Ag‐codoped ZnO (CSZO) nanocrystals with (E)‐1‐(naphthalen‐1‐yl)‐2‐styryl‐1H‐phenanthro[9,10‐d]imidazole has been analysed. The synthesized nanocrystals and their composites with naphthyl styryl phenanthrimidazole have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray spectroscopy, X‐ray diffractometry, X‐ray photoelectron spectroscopy (XPS) lifetime and Fourier transform infrared spectroscopy and cyclic voltammetry. XPS shows doped silver and cerium in Ag0 and Ce4+ states, respectively. SEM and TEM images of CSZO nanoparticles show that they appear to be 3D trapezoid and cocoon‐like shape. The selected area electron diffraction pattern supports the nanocrystalline character of the synthesized material. The percentages of doping of cerium and silver in CSZO are 0.54 (at.) and 0.34 (at.), respectively. From the energy levels of the materials used in the imidazole–CSZO composite, the dominant CT direction has been analysed. Theoretical investigation shows that the binding energy and energy gap of the imidazole composites are highly dependent on the nature of the silver oxide cluster and that charge transfer in the imidazole–Ag4O4 composite is faster than the same in other composites. Molecular docking technique has also been carried out to understand the imidazole–DNA interactions. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
《Composite Interfaces》2013,20(3):259-274
Conducting copolymer poly(aniline-co-p-phenylenediamine) [poly(Ani-co-pPD)] and surface-modified magnetite (Fe3O4) composites were synthesized by ultrasonically-assisted chemical oxidative polymerization. Fe3O4 nanoparticles were surface-modified with silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS) in order that they would be well dispersed for the reaction process. It was also found that the aggregation of Fe3O4 nanoparticles could be reduced under ultrasonic irradiation. TEM analysis confirmed that the resulting poly(Ani-co-pPD)/Fe3O4 nanocomposite showed core–shell morphology, in which Fe3O4 nanoparticles were well dispersed. The incorporation of Fe3O4 in the nanocomposites was endorsed by FT-IR. The nanocomposites were also confirmed by UV-visible, TGA and XRD. Conductivity of the nanocomposites was found to be in the range of 7.02 × 10?4–6.54 × 10?6 S/cm. Higher saturated magnetization of 12 emu/g was observed for composite with 20% Fe3O4.  相似文献   

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