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Carbon materials (e.g., pyrogenic carbon (PyC)) are widely used in agricultural soils and can participate in various biogeochemical processes, including iron (Fe) cycling. In soils, Fe(II) species have been proposed as the main active contributor to produce reactive oxygen species (ROS), which are involved in various biogeochemical processes. However, the effects of PyC on the transformation of different Fe species in soils and the associated production of ROS are rarely investigated. This study examined the influence of PyC (pyrolyzed at 300–700 °C) on Fe(II)/Fe(III) cycling and hydroxyl radical (·OH) production during redox fluctuations of paddy soils. Results showed that the reduction of Fe(III) in soils was facilitated by PyC during anoxic incubation, which was ascribed to the increased abundance of dissimilatory Fe(III)-reducing microorganisms (biotic reduction) and the electron exchange capacity of PyC (abiotic reduction). During oxygenation, PyC and higher soil pH promoted the oxidation of active Fe(II) species (e.g., exchangeable and low-crystalline Fe(II)), which consequently induced higher yield of ·OH and further led to degradation of imidacloprid and inactivation of soil microorganisms. Our results demonstrated that PyC accelerated Fe(II)/Fe(III) cycling and ·OH production during redox fluctuations of paddy soils (especially those with low content of soil organic carbon), providing a new insight for remediation strategies in agricultural fields contaminated with organic pollutants. Highlights: Pyrogenic carbon (PyC) with high EEC promoted active Fe(II) formation in anoxic paddy soils through abiotic and biotic mechanisms. Pyrolysis temperature affected the physiochemical properties of PyC, which regulated Fe cycling and ·OH production in soils. The enhanced production of ·OH led to microbial inactivation and organic pollutant degradation. [ABSTRACT FROM AUTHOR]

The chemical mixing at the "Al on Fe" and "Fe on Al" interfaces was studied by molecular dynamics simulations of the layer growth and by 57Fe Mössbauer spectroscopy. The concentration distribution along the layer growth direction was calculated for different crystallographic orientations, and atomically sharp "Al on Fe" interfaces were found when Al grows over (001) and (110) oriented Fe layers. The Al/Fe(111) interface is also narrow as compared to the intermixing found at the "Fe on Al" interfaces for any orientation. Conversion electron Mössbauer measurements of trilayers—Al/57Fe/Al and Al/57Fe/Ag grown simultaneously over Si(111) substrate by vacuum evaporation—support the results of the molecular dynamics calculations. [ABSTRACT FROM AUTHOR]

We report that the Ge1-xFexTe thin film exhibits spin-glass behavior when the Fe concentration increases to 0.08. A large bifurcation between the zero-field cooling and field cooling temperaturedependent magnetization was observed. The hysteresis loops after zero-field cooling and field cooling show an exchange bias effect. A time-dependent thermoremanent magnetization follows power-law decay, which confirms the existence of spin glass. The anomalous magnetotranport properties present a further evidence for spin-glass behavior and give a freezing temperature Tg~5K in the Ge0.92Fe0.08Te thin film. [ABSTRACT FROM AUTHOR]

Ferritin-like molecules show a remarkable combination of the evolutionary conserved activity of iron uptake and release that engage different pores in the conserved ferritin shell. It was hypothesized that pore selection and iron traffic depend on dynamic allostery with no conformational changes in the backbone. In this study, we detect the allosteric networks in Pseudomonas aeruginosa bacterioferritin (BfrB), bacterial ferritin (FtnA), and bullfrog M and L ferritins (Ftns) by a network-weaving algorithm (NWA) that passes threads of an allosteric network through highly correlated residues using hierarchical clustering. The residue-residue correlations are calculated in the packing-on elastic network model that introduces atom packing into the common packing-off model. Applying NWA revealed that each of the molecules has an extended allosteric network mostly buried inside the ferritin shell. The structure of the networks is consistent with experimental observations of iron transport: The allosteric networks in BfrB and FtnA connect the ferroxidase center with the 4-fold pores and B-pores, leaving the 3-fold pores unengaged. In contrast, the allosteric network directly links the 3-fold pores with the 4-fold pores in M and L Ftns. The majority of the network residues are either on the inner surface or buried inside the subunit fold or at the subunit interfaces. We hypothesize that the ferritin structures evolved in a way to limit the influence of functionally unrelated events in the cytoplasm on the allosteric network to maintain stability of the translocation mechanisms. We showed that the residue-residue correlations and the resultant long-range cooperativity depend on the ferritin shell packing, which, in turn, depends on protein sequence composition. Switching from the packing-on to the packing-off model reduces correlations by 35%-38% so that no allosteric network can be found. The influence of the side-chain packing on the allosteric networks explains the diversity in mechanisms of iron traffic suggested by experimental approaches. [ABSTRACT FROM AUTHOR]

We have used a table-top scale laser to dynamically compress iron at strain rates in excess of 109 s-1. Using an embedded ultrafast interferometer, we have measured corresponding free surface histories with a time resolution of approximately 10 ps. We have analyzed the surface histories using a method that accounts for nonsteady wave propagation and time-dependent material behavior. We show that at these strain rates, the α→∈ polymorphic transition begins within 100 ps after an initial very large (∼10 GPa) and mostly elastic compression and appears largely complete within a similar time thereafter. The corresponding deviatoric stress before the transition begins can exceed 3 GPa, while the transition stress itself is up to 25 GPa, nearly twice the value measured at low strain rates. We use these results to propose a systematic variation with loading time of the normal-stress/relative-volume curve followed by iron during rapid compression. [ABSTRACT FROM AUTHOR]

We have used a table-top scale laser to dynamically compress iron at strain rates in excess of 109 s-1. Using an embedded ultrafast interferometer, we have measured corresponding free surface histories with a time resolution of approximately 10 ps. We have analyzed the surface histories using a method that accounts for nonsteady wave propagation and time-dependent material behavior. We show that at these strain rates, the α→∈ polymorphic transition begins within 100 ps after an initial very large (∼10 GPa) and mostly elastic compression and appears largely complete within a similar time thereafter. The corresponding deviatoric stress before the transition begins can exceed 3 GPa, while the transition stress itself is up to 25 GPa, nearly twice the value measured at low strain rates. We use these results to propose a systematic variation with loading time of the normal-stress/relative-volume curve followed by iron during rapid compression. [ABSTRACT FROM AUTHOR]

We report on the electronic properties of Fe and Cr in n-type germanium studied using conventional and Laplace Deep Level Transient Spectroscopy techniques (LDLTS). Using Schottky barriers restricts the studies to levels located in the upper half of the band gap. However, by applying external optical excitation to generate minority carriers, the investigation is extended to the lower half of the band gap. Major findings already published by other authors are in several cases confirmed. However, new insight is revealed on the microscopic behavior of these two chemical species such as their interactions with hydrogen giving rise to the generation of complex-related levels in the band gap. For the Fe case, the small difference in energy of its two levels raises the question as to the possibility of negative-U character. [ABSTRACT FROM AUTHOR]

The structural, magnetic, transport, thermal, and magnetothermal properties of quaternary Heusler alloys Ni50Mn38-xFexSb12 have been studied. Powder x-ray diffraction and temperature dependence of magnetization studies reveal that with the addition of Fe in the Mn site, the martensitic transition shifts to low temperatures. It is also found that the martensitic transition becomes broader with the increase of Fe concentration. The metamagnetic transition in M(H) isotherms becomes very prominent in x = 2 and vanishes for x = 3 and 4. A maximum positive magnetic entropy change of 14.2 J/kg K is observed for x = 2 at 288 K for 50 kOe. Electrical resistivity data show an abrupt decrease across the martensitic transition in all the alloys, except x = 6, which does not have a martensitic transition. A maximum negative magnetoresistance of 21% has been obtained for x = 2 at 50 kOe. The same alloy also shows an exchange bias field of 288 Oe. [ABSTRACT FROM AUTHOR]

Results of first-principles simulations on both orthorhombic and monoclinic phases of CaFeO3 crystal are presented. The obtained atomic structures are consistent with x-ray diffraction data. The transition from a metallic orthorhombic to a narrow-gap semiconducting monoclinic phase is ascribed to the larger distortion of the Fe–O–Fe bond angle in the latter case. Calculations of Raman and optic active phonon modes at the Γ point of the Brillouin zone are performed and discussed. The isotopic substitution technique is applied to analyze the vibration modes obtained. The found charge/spin disproportionation is analyzed and compared with available experimental estimates. [ABSTRACT FROM AUTHOR]

Speciation analysis of Fe in single plagioclase crystals separated from two different gabbros was performed to understand the crystallization mechanisms of magnetite exsolution. Iron species in single crystals were measured using Fe K‐ and LIII‐edge X‐ray absorption fine structure (XAFS) analysis. The K‐edge pre‐edge analysis showed variation in the averaged valence state of Fe in plagioclase crystals even if they had been separated from the same gabbro that was further confirmed by the LIII‐edge analysis. The K‐edge pre‐dedge analysis also suggests the various degrees of contribution from tetrahedral Fe. The mixing of tetrahedral and octahedral Fe leads to an underestimation of the averaged valence state of Fe for the K‐edge pre‐edge analysis; thus, we adopted the LIII‐edge result for the valence state of Fe in plagioclase crystals. Iron K‐edge extended XAFS (EXAFS) analysis of two plagioclase crystals separated from the same gabbro clearly showed different coordination environments. A weakening of EXAFS oscillation was recognized in one sample, because two Fe–O bonds (Fe3+–O1 and Fe2+–O2) cancelled out the oscillations of each other. The EXAFS spectrum of the other plagioclase crystal suggested a homogeneous distribution of Fe. The content of exsolved magnetite in these crystals is nearly identical, indicating that the exsolution of magnetite in plagioclase crystal had been completed before the temperature decrease that stopped the ordering of Fe ions in tetrahedral sites. Key Points: Valence state of Fe in plagioclase varies among crystals separated from the same plutonic rockTwo different sites are confirmed as a host of Fe in plagioclase from the same rockLIII‐edge XANES is more suitable for speciation analysis because K‐edge XANES underestimate the contribution of tetrahedral Fe [ABSTRACT FROM AUTHOR]

Focuses on a study which determined the hyperfine parameters of the probe [sup57]iron nuclei using conversion electron Mössbauer spectroscopy. Experimental procedures; Description of the local states of iron implanted on titanium; Discussion and conclusion.

In this research, a novel magnetic mesoporous adsorbent with mixed phase of Fe2O3/Mn3O4 nanocomposite was prepared by a facile precipitating method and characterized extensively. The prepared nanocomposite was used as adsorbent for toxic methyl orange (MO) dye removal from aqua matrix considering its high surface area (178.27 m2/g) with high saturation magnetization (23.07 emu/g). Maximum dye adsorption occurs at solution pH 2.0 and the electrostatic attraction between anionic form of MO dye molecules and the positively charged nanocomposite surface is the main driving force behind this adsorption. Response surface methodology (RSM) was used for optimizing the process variables and maximum MO removal of 97.67% is obtained at optimum experimental condition with contact time, adsorbent dose and initial MO dye concentration of 45 min, 0.87 g/l and 116 mg/l, respectively. Artificial neural network (ANN) model with optimum topology of 3–5–1 was developed for predicting the MO removal (%), which has shown higher predictive ability than RSM model. Maximum adsorption capacity of this nanocomposite was found to be 322.58 mg/g from Langmuir isotherm model. Kinetic studies reveal the applicability of second‐order kinetic model with contribution of intra‐particle diffusion in this process. [ABSTRACT FROM AUTHOR]

The Hg 0 removal capacities of magnetospheres from fly ash collected from different power plants were investigated at a wide temperature range of 100–400 °C. The relationship between Hg 0 removal efficiency ( η T ) and iron content/species of magnetospheres was investigated. The magnetospheres attained the optimal Hg 0 removal capacity at 250 °C. The reaction temperature played an important role in Hg 0 adsorption and oxidation behaviors. At low reaction temperature (100 °C and 150 °C), the adsorption of Hg 0 played a predominant role in Hg 0 removal, while the Hg 0 removal mainly depended on the Hg 0 oxidation capacity at high temperature (200–400 °C). The Hg 0 removal capacity increased with the increase of iron content. The percentage of ferrospinel and hematite in magnetospheres is a key factor for determining the Hg 0 removal capacity as well. Hydrogen fluoride (HF) could remove the glass-phase materials on the magnetospheres and the active iron species embedded in the glass phase could be exposed and accessible. After fluorinated by HF, the Hg 0 removal capacity increased in different degree for different magnetospheres, which depended on the content of active iron species in raw magnetospheres. [ABSTRACT FROM AUTHOR]

Activated bleomycin (ABLM) is a drug-Fe(iii)-hydroperoxide complex kinetically competent in DNA attack (via H4′ abstraction). This intermediate is relatively stable, but its spontaneous conversion to ferric bleomycin (Fe(iii)·BLM) is poorly characterized because no observable intermediate product accumulates. The Fe(iii)·BLM formed cryophotolytically from ABLM and kept at 77 K was remarkably similar by EPR and ENDOR criteria to Fe(iii)·BLM formed from Fe(iii) + BLM solution. The notable ENDOR criteria were the ENDOR frequencies and features of orientation-selected, strongly hyperfine-coupled, exchangeable protons associated with the environs of the iron within ＜3.5 Å of paramagnetic Fe(iii) in Fe(iii)·BLM and ABLM. Cryophotolytic conversion of activated bleomycin to its ferric bleomycin product in the frozen solid is a sign that the reaction requires only constrained local proton rearrangements. We have characterized the metal–proton distances and orientations of the protons in that rearrangement, especially noting that these protons are of mechanistic importance in the ambient temperature conversion of ABLM to Fe(iii)·BLM in concert with a directed radical-forming attack on DNA. [ABSTRACT FROM AUTHOR]

Herein, we report a highly selective dual responsive chemosensor for detecting iron ion. The structural characterization of synthesized compounds was investigated on the basis of UV–vis, FTIR, 1 NMR, 13 NMR and Mass spectral data. The sensitivity and selectivity of RDFB toward Fe 3+ among different metal ions was examined by absorption, fluorescence, FTIR and mass spectral studies. Complexing with Fe 3+ ion leads to spirolactam ring opening of RDFB and consequently causes a color variation from colorless to red. Fe 3+ -specific binding to RDFB afford a 53-fold enhancement in fluorescence intensity and strong absorption in the visible range. The 1:1 binding mode was proposed on the basis of absorption, FTIR and MS studies. The HOMO and LUMO energy gap for RDFB and RDFB-Fe 3+ complex were found to be 3.782 eV and 1.875 eV suggesting that the interaction of Fe 3+ to RDFB reduces the HOMO-LUMO energy gap of the complex and stabilizes the system. The association constant of newly synthesized compound to the receptor is found to be 1.13 × 10 5 M −1 which further implying the potential of RDFB to acts as a selective chemosensor for Fe 3+ ions. Furthermore the reversibility of complexation of RDFB to Fe 3+ was also studied by conducting experiments against EDTA. [ABSTRACT FROM AUTHOR]

We report high-resolution density dependent intensity ratio measurements for middle charge states of iron in the extreme ultraviolet (EUV) spectral wavelength range of 160-200 Å. The measurements were performed at the Tokyo EBIT laboratory by employing a flat-field grazing incidence spectrometer installed on a low energy compact electron beam ion trap. The intensity ratios for several line pairs stemming from Fe X, Fe XI and Fe XII were extracted from spectra collected at the electron beam energies of 340 and 400 eV by varying the beam current between 7.5 and 12 mA at each energy. In addition, the effective electron densities were obtained experimentally by imaging the electron beam profile and ion cloud size with a pinhole camera and visible spectrometer, respectively. In this paper, the experimental results are compared with previous data from the literature and with the present calculations performed using a collisional-radiative model. Our experimental results show a rather good agreement with the calculations and previous reported results. [ABSTRACT FROM AUTHOR]

Fe-L and Ni-L X-ray spectra induced by electron impact were analyzed. The measurements were made on bulk samples using a commercial wavelength dispersive spectrometer, and the spectra were processed with a parameter optimization method previously developed. This procedure allowed for the determination of characteristic energies, relative transition probabilities and natural linewidths. The results obtained are compared to the data found in the literature, when available. Satellite and radiative Auger emissions were also analyzed, energy shifts and relative intensities being determined. Many of these parameters were determined for the first time, which was possible due to the robustness of the spectral processing method used. The line profile introduced here takes into account the differential attenuation at both sides of the absorption edge. [ABSTRACT FROM AUTHOR]

The structure of the outer and inner electron spectra of iron (2 p, 3 p, 3 s, and 3 d) and phosphorus (3 s and 3 p) atoms in FeP monophosphide is studied in detail by the X-ray photoelectron spectroscopy (XPS) method. On the basis of the analysis of the binding energy of electrons, as well as the parameters characterizing the structure of experimental spectra, a conclusion is made that Fe ( d ) cations in FeP are stabilized in a state with intermediate value of the total spin (IS, S = 3/2). The range of values of intra-atomic parameters (10 Dq, J ) is established in which the consideration of the high degree of covalence of Fe-P bonds may lead to the stabilization of (FeP) clusters in the IS state. [ABSTRACT FROM AUTHOR]

This research work focuses on the theoretical investigation of the upper critical magnetic field, HC2; Ginzburg-Landau coherence length, ξGL(T); and Ginzburg-Landau penetration depth, λGL(T), for the two-band iron based superconductors BaFe2(As1-xPx)2, NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductors BaFe2(As1-xPx)2, NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field, HC2; GL coherence length, ξGL; and GL penetration depth, λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel, HC2∥c, and perpendicular, HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field, HC2 versus the angle θ. Similarly, the phase diagrams of the GL coherence length, ξGL, and GL penetration depth, λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations. [ABSTRACT FROM AUTHOR]

In the present study, the self-diffusion process of nitrogen in pure iron nanocrystalline under strain conditions has been investigated by Molecular Dynamics (MD). The interactions between particles are modeled using Modified Embedded Atom Method (MEAM). Mean Square Displacement (MSD) of nitrogen in iron structure under strain is calculated. Strain is applied along [ 11 2 ̄ 0 ] and [ 0001 ] directions in both tensile and compression conditions. The activation energy and pre-exponential diffusion factor for nitrogen diffusion is comparatively high along [ 0001 ] direction of compressed structure of iron. The strain-induced diffusion coefficient at 973 K under the compression rate of 0.001 Å/ps along [ 0001 ] direction is about 6.72E−14 m 2 /s. The estimated activation energy of nitrogen under compression along [ 0001 ] direction is equal to 12.39 kcal/mol. The higher activation energy might be due to the fact that the system transforms into a more dense state when compressive stress is applied. [ABSTRACT FROM AUTHOR]

Presents a study which determined the influence of pressure on the Möbauer spectrum of a nearly stoichiometric sample of Fe[sub3]O[sub4] that exhibits no isomer shift induced splitting of the B-site patterns of the spectrum at 300 K. Procedure used to obtain the spectra; Basis for the adequacy of the fits; Factor attributed to the components of the B site.

The aim of this work is to reveal the results of the reaction of nepheline mineral with concentrated sulfuric acid. The valence states of iron atoms are determined in the nepheline and the reacted nepheline. The existence of iron containing magnetic particles in the sediment is shown. The differences in the lineshape are discussed also and are associated with a transfer from one phase to another of the magnetic particles. [ABSTRACT FROM AUTHOR]

The open question of crystal symmetry for YBaCuFeO5, still under debate, is resolved by using diffraction anomalous fine structure and resonant multi-beam X-ray diffraction at the Fe and Cu K edges. The different asymmetric intensity distributions observed at 7, 7.1305 and 8.9945 keV give direct evidence that the space group of YBaCuFeO5 should be P4/ mmm with the distance between Cu and apical O atoms longer than that between Fe and O atoms. This approach provides a direct way to resolve detailed structural symmetry which is indeterminate in conventional Bragg diffraction. [ABSTRACT FROM AUTHOR]

The open question of crystal symmetry for YBaCuFeO5, still under debate, is resolved by using diffraction anomalous fine structure and resonant multi-beam X-ray diffraction at the Fe and Cu K edges. The different asymmetric intensity distributions observed at 7, 7.1305 and 8.9945 keV give direct evidence that the space group of YBaCuFeO5 should be P4/ mmm with the distance between Cu and apical O atoms longer than that between Fe and O atoms. This approach provides a direct way to resolve detailed structural symmetry which is indeterminate in conventional Bragg diffraction. [ABSTRACT FROM AUTHOR]

The active site of the N2 fixing enzyme nitrogenase is a C-centred Fe7MoS cluster (FeMo-co) containing a trigonal prism of six Fe atoms connected by a central belt of three doubly-bridging S atoms. The trigonal faces of the prism are capped via triply-bridging S atoms to Fe1 at one end and Mo at the other end. One of the central belt atoms, S2B, considered to be important in the chemical mechanism of the enzyme, has been shown by Spatzal, Rees et al. to undergo substitution by CO, and also substitution by Se in the presence of SeCN−, under turnover conditions. Further, when turning over under C2H2 or N2/CO there is migration of Se to the other two belt bridging positions. These reactions are extraordinary, and unprecedented in metal chalcogenide cluster chemistry. Using density functional simulations, mechanisms for all of these reactions have been developed, involving the small molecules SCO, SeCO, C2H2S, C2H2Se, SeCN−, SCN− functioning as carriers of S and Se atoms. The possibility that the S2B bridge position is vacant is discounted, because the barrier to formation of a bridge-void intermediate with two contiguous three-coordinate Fe atoms is too large. A bridging ligand is retained throughout the proposed mechanisms. Intermediates with Fe–C(O)–S/Se–Fe cycles and with SCO/SeCO C-bound to Fe are predicted. The energetics of the reaction trajectories show them to be feasible and easily reversible, consistent with experiment. Alternative mechanisms involving intramolecular differential rotatory rearrangements of the cluster to scramble the Se bridges are also examined, and shown to be very unlikely. The implications of these new facets of the reactivity of the FeMo-co cluster are discussed: it is considered that they are unlikely to be part of the mechanism of the physiological reactions of nitrogenase. [ABSTRACT FROM AUTHOR]

With its historically long popularity in major structural applications, the use of iron (Fe) has also recently begun to be explored as an advanced functional material. For this purpose, it is more advantageous to use Fe as a porous structure, simply because it can provide a greater surface area and a higher reaction rate. This study uses a freeze-casting method, which consists of simple and low-cost processing steps, to produce Fe foam with a mean pore size of 10 μm. We examine the influences of various parameters ( i.e., mold bottom temperature, powder content, and sintering time) on the processing of Fe foam, along with its oxidation kinetics at 823 K (550 °C) with various heat-treatment times. We confirm that FeO and FeO oxide layers are successfully formed on the surface of Fe foam. With the Fe oxide layers as an active anode material, the Fe foam can potentially be used as a three-dimensional anode current collector for an advanced lithium-ion battery. [ABSTRACT FROM AUTHOR]

The iron selenidoantimonate(III) [Fe(phen)3]Sb6Se10 ( 1) (phen = 1, 10-phenanthroline) was prepared by reaction of Fe, Sb, Se, phen, and 1, 4-diazabicyclo[2.2.2]octane in MeOH and H2O mixed solvent under solvothermal conditions. 1 consists of a [Fe(phen)3]2+ cation and a two dimensional [Sb6Se10]2- anion. The [Sb6Se10]2- anion is constructed by SbSe3, SbSe4, and SbSe6 primary building blocks by corner- and edge-sharing, resulting Sb4Se4, Sb5Se5, and Sb6Se6 heterorings and a semi-cubic Sb4Se6 motif, which act as secondary building units. The octahedral SbSe6 primary unit and semi-cubic Sb4Se6 motif make compound 1 quite different from the thioantimonates(III). Compound 1 exhibits steep bandgap ( Eg) of 1.56 eV, indicating potential semiconducting property. The thermal stability of 1 was also investigated. [ABSTRACT FROM AUTHOR]

The iron selenidoantimonate(III) [Fe(phen)3]Sb6Se10 ( 1) (phen = 1, 10-phenanthroline) was prepared by reaction of Fe, Sb, Se, phen, and 1, 4-diazabicyclo[2.2.2]octane in MeOH and H2O mixed solvent under solvothermal conditions. 1 consists of a [Fe(phen)3]2+ cation and a two dimensional [Sb6Se10]2- anion. The [Sb6Se10]2- anion is constructed by SbSe3, SbSe4, and SbSe6 primary building blocks by corner- and edge-sharing, resulting Sb4Se4, Sb5Se5, and Sb6Se6 heterorings and a semi-cubic Sb4Se6 motif, which act as secondary building units. The octahedral SbSe6 primary unit and semi-cubic Sb4Se6 motif make compound 1 quite different from the thioantimonates(III). Compound 1 exhibits steep bandgap ( Eg) of 1.56 eV, indicating potential semiconducting property. The thermal stability of 1 was also investigated. [ABSTRACT FROM AUTHOR]

A comparative study of Raman spectra at room temperature of La 2/3 Ca 1/3 MnO 3 (LCMO) and La 2/3 Ca 1/3 Mn 0.97 F e0.03 O 3 (LCMFO) thin films, grown on monocrystalline substrates LaAlO 3 , is presented. The films were grown with thickness between 30 and 130 nm under identical deposition conditions by DC magnetron sputtering system at high O 2 pressure. In order to observe changes in the vibration modes of the lattice due to the substitution of Mn by Fe ions, we compared the different values of wave numbers obtained from the fittings of each Raman spectrum. The results show that the characteristic–and most intense-peak at ∼486 cm −1 corresponds to the substrate. In the LCMO thick films, Raman modes are very weak and mix up with the substrate one, whereas in LCMFO, these modes were found in three intervals around 220–250 cm −1 (υ 1 ), 450–520 cm −1 (υ 2 ) and 610–720 cm −1 (υ 3 ). A mode at ∼717 cm −1 is associated to structural disorder due to Fe doping effect. In both LCMO and LCMFO films, the conduction mechanism are related with electron localization and the electronic transition is mediated by phonons. According to the T* values from resistivity data fit (Variable Range Model -VRH), it is observed once more that the Fe doping relaxes the strain effects. [ABSTRACT FROM AUTHOR]

We developed a highly sensitive surface-enhanced Raman scattering (SERS) technique for determining Fe 3+ ions via synthesis of inositol hexaphosphate (IP 6 ) capped silver nanoparticles (AgNPs). IP 6 (1.98 nm thickness) coated on the surface of AgNPs not only provided a protection layer to stabilize silver substrate but also specifically anchoring sites of phosphates to capture Fe 3+ ions from aqueous solution. Rhodamine 6G (R6G) was used as a Raman indicator in this case and the scattering intensity of R6G in Raman probe increased with adding Fe 3+ ions. A possible mechanism is that IP 6 bound with Fe 3+ narrowed the gap of neighboring AgNPs to produce plenty of SERS “hot spots”. Due to the controllable aggregation of IP 6 @R6G–AgNPs by Fe 3+ , it presents a widely linear range of 11.2–39.2 ppm for analyzing the Fe 3+ ions. This Raman-based method for detecting Fe 3+ showed a high selectivity in the presence of other metal ions in same solution involving Mg 2+ , Cu 2+ , Ca 2+ , Pb 2+ , Co 2+ , Na + , Zn 2+ , K + , Li + , Mn 2+ and Fe 2+ . Under optimal conditions, the limit of detection (LOD) for SERS testing Fe 3+ could be down to 0.28 ppm. As a practical application, the Raman assay for the determination of Fe 3+ in river water was carried out. [ABSTRACT FROM AUTHOR]

We present the first measurements of the iron L2/3-edge of the compounds FeO, Fe2O3, and Fe3O4 at ambient pressure and of FeCO3 at high pressures of 2.4 and 40 GPa using a diamond anvil cell by X-ray Raman scattering spectroscopy, a bulk sensitive probe of soft X-ray absorption edges making use of hard X-rays. We show that the spectral shape of the Fe L2/3-edge can be analyzed quantitatively to reveal the oxidation state of iron in matter. Consequently, in situ X-ray Raman scattering spectroscopy at the iron L-edge at high pressure and temperature opens exciting perspectives to characterize the local coordination, oxidation, and spin state of iron at high pressure and temperature, conditions that are of relevance for e.g. geological sciences or chemical processing. [ABSTRACT FROM AUTHOR]

Aims.We present a multi-wavelength analysis of the evolved supernova remnants MCSNR J05067025 and MCSNR J0527-7104 in the Large Magellanic Cloud. Methods. We used observational data from XMM-Newton, the Australian Telescope Compact Array, and the Magellanic Cloud Emission Line Survey to study their broad-band emission and used Spitzer and Hi data to gain a picture of the environment into which the remnants are expanding. We performed a multi-wavelength morphological study and detailed radio and X-ray spectral analyses to determine their physical characteristics. Results. Both remnants were found to have bright X-ray cores, dominated by Fe L-shell emission, which is consistent with reverse shock-heated ejecta with determined Fe masses in agreement with Type Ia explosion yields. A soft X-ray shell, which is consistent with swept-up interstellar medium, was observed in MCSNR J0506-7025, suggestive of a remnant in the Sedov phase. Using the spectral fit results and the Sedov self-similar solution, we estimated the age of MCSNR J0506-7025 to be ~16-28 kyr, with an initial explosion energy of (0.07-0.84) × 1051 erg. A soft shell was absent in MCSNR J0527-7104, with only ejecta emission visible in an extremely elongated morphology that extends beyond the optical shell. We suggest that the blast wave has broken out into a low density cavity, allowing the shock heated ejecta to escape. We find that the radio spectral index of MCSNR J0506-7025 is consistent with the standard -0:5 for supernova remnants. Radio polarisation at 6 cm indicates a higher degree of polarisation along the western front and at the eastern knot with a mean fractional polarisation across the remnant of P ≅ (20 ± 6)%. Conclusions. The detection of Fe-rich ejecta in the remnants suggests that both resulted from Type Ia explosions. The newly identified Fe-rich cores in MCSNR J0506-7025 and MCSNR J0527-7104 make them members of the expanding class of evolved Fe-rich remnants in the Magellanic Clouds. [ABSTRACT FROM AUTHOR]

A novel atom-scale interfacial coordination assisted synthesis method for the textural engineering of three-dimensional (3D) Fe3O4–graphene oxide frameworks with hierarchical macro- and meso-porous structures is developed. [ABSTRACT FROM AUTHOR]

Motivated by the recent discovery of superconductivity in the iron-based ladder compound BaFe2S3 under high pressure, we derive low-energy effective Hamiltonians from first principles. We show that the complex band structure around the Fermi level is represented only by the Fe 3dxz (mixed with 3dxy) and 3dx²−y² orbitals. The characteristic band degeneracy allows us to construct a four-band model with the band unfolding approach. We also estimate the interaction parameters and show that the system is more correlated than the 1111 family of iron-based superconductors. Provided the superconductivity is mediated by spin fluctuations, the 3dxz-like band plays an essential role, and the gap function changes its sign between the Fermi surface around the Γ point and that around the Brillouin-zone boundary. [ABSTRACT FROM AUTHOR]

Effects of Fe doping on the structural, photoluminescence and optical properties of sol-gel derived ZnFeO (0 ≤ x ≤ 5) nanoparticles have been investigated. X-ray diffraction and HRTEM studies reveal a single phase wurtzite crystal structure without any secondary phase. The nanocrystalline nature of samples and their crystallinity have been confirmed by transmission electron microscopy measurements. Raman spectroscopy has been employed to study the crystalline quality and the structural disorder. The photoluminescence spectra display that all the samples have an violet emission peak centered at 416 nm, and 5 at. wt% Fe-doped ZnO nanoparticles have the strongest violet emission peak. These results suggest that 5 at. wt% Fe-incorporation can improve the crystalline quality and enhance the ultraviolet emission of ZnO nanoparticles. The optical band gap has been determined from optical absorption spectra. The optical band gap depends on Fe-doping level and on the microstructure of the samples, and is in the range of 3.20-3.47 eV. [ABSTRACT FROM AUTHOR]

A mild and operationally simple iron-catalyzed protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is described. Catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O2, α- and β-substituted styrenes were cleaved to afford benzaldehydes and aromatic ketones generally in high yields with excellent chemo-selectivity and very good functional group tolerance, including those containing radical-sensitive groups. With a-halo-substituted styrenes, the oxidation took place with concomitant halide migration to afford α-halo acetophenones. Various observations have been made, pointing to a mechanism in which both molecular oxygen i and the olefinic substrate coordinate to the iron center, leading to the formation of a dioxetane intermediate, which collapses to give the carbonyl product. [ABSTRACT FROM AUTHOR]

This work was attempted in order to provide a new and well-established approach for the quantification of Fe2+ sites in zeolites. The experimental procedure was based on carbon monoxide and nitrogen monoxide sorption in Fe-exchanged ZSM-5 zeolites with different pore hierarchies, which was followed by IR spectroscopy. The values of the absorption coefficients of the respective monocarbonyl Fe2+(CO) and mononitrosyl Fe2+(NO) IR bands were obtained. In turn, the concentrations of Fe(ii) moieties of various kinds were calculated and discussed with regard to the composition (Si/Al and Fe/Al ratios) of the zeolites studied. [ABSTRACT FROM AUTHOR]

In this article, a new feature-tuned artificial neural network (ANN) model has been developed for endmember classification of a hyperspectral image. This model is developed on the basis of using only the essential absorption bands of mineral spectra as opposed to using all the spectral bands of the hyperspectral image. This approach has the added advantages of reducing the dimensionality of input features to the ANN as well as inhibiting the influences of noisy bands for classification of endmembers. The proposed ANN model is trained using input features extracted from laboratory spectra ofinsitubulk ore materials collected from an existing iron ore deposit. The input features are basically the constituent absorption bands of mineral spectra where each absorption band is mathematically characterized by the centre, width, and strength parameters of a Gaussian curve. For extracting absorption bands from a mineral spectrum, a modified Gaussian model has been used. The application of this model also necessitates the design of a special template for the input layer ANN model. After training the model, its generalization property is assessed through a testing data set. The model has achieved nearly 97% of classification accuracy in a training set, and 71% of accuracy in a testing set. The trained model is then applied on Hyperion imagery collected over an iron ore deposit. All the endmember spectra of this deposit are classified into either vegetation or any of the ores or rock present in the deposit. None of the endmembers is classified into non-iron ore minerals. [ABSTRACT FROM AUTHOR]

Spinel-type Co3O4 has been reported to be the only transition metal oxide to date, which exhibits excellent catalytic activity for low temperature CO oxidation. But unfortunately, it is quickly deactivated by moisture. Here we report a Fe-doped Co3O4 spinel catalyst which demonstrates high activity and excellent moisture resistance for low temperature CO oxidation, especially at a low CO concentration of around 100 ppm which mimics the situations in automobile road tunnels and indoor parks. [ABSTRACT FROM AUTHOR]

Recent experiments show that GaN/AlGaN high-electron-mobility transistors suffer from significant current collapse, which is caused by an increase in the concentration of traps with energy levels 0.5-0.6 eV below the conduction-band edge. This increase in trap concentration is consistent with thermally activated defect diffusion, but the responsible defect complexes have not been identified. It has been suggested that the defect complex may contain iron because of the proximity of the Fedoped GaN substrate. Here, we report first-principles density-functional calculations of substitutional iron complexes, investigate their properties, and show that the FeGa-VN complex has properties that account for the observed degradation. [ABSTRACT FROM AUTHOR]

In this work, a non-covalent interaction of iron and metal-free meso-tetra (4-sulfonatophenyl) porphines (FeTPPS and TPPS, respectively) with high-quality single-layer graphene is studied by Raman spectroscopy. Such a kind of graphene functionalization is promising for a development of novel optoelectronic devices and sensors. Our results show that the central metal atom of porphyrin macrocycle, iron particularly, plays an important role in the integrity of FeTPPS on graphene surface; however, the predicted Raman enhancement is not significant. The interaction of metal-free TPPS with graphene leads to the deprotonation of TPPS molecules and higher Raman enhancement values. Moreover, initially deprotonated TPPS solutions after the adsorption onto the graphene surface demonstrate the appearance of new Raman bands and significantly enhanced Raman signals. We propose that a strong interaction between deprotonated TPPS and graphene is realized through pyrrole and desulfonated phenyl rings of closely located planar TPPS molecules on the graphene surface. The results show that both the protonation of porphyrin macrocycle and the existence of central metal atom are crucial for a formation of nanocomposites with defined electronic properties. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The cathode materials LiNi0.5Mn1.5O4 and LiNi0.4Fe0.2Mn1.4O4 were synthesized using a citric acid-assisted sol-gel method with a final calcination temperature of 1000 °C. An impurity phase exists in LiNi0.5Mn1.5O4 powders, which can be eliminated by substituting some of the Ni2+ and Mn4+ ions with Fe3+. The substitution of Fe into the spinel structure was confirmed by NMR and Mössbauer spectroscopy. The initial capacity of LiNi0.4Fe0.2Mn1.4O4 powder synthesized at 1000 °C (LNFMO) is slightly higher than that of LiNi0.5Mn1.5O4 powder synthesized at 1000 °C (LNMO). Additionally, its capacity retention of 92 % at room temperature after 300 cycles at C/2 charging-discharging rate between 3.5-5.0 V is higher than that of the Fe-free sample (79.5 %) under same conditions which could arise from the difference in their cycling mechanisms. In order to understand the structural evolution of these materials during electrochemical cycling, in situ studies under real operating conditions were performed. Measurements of initial powders in capillaries and in situ experiments during the first galvanostatic cycle were carried out by high resolution powder diffraction using synchrotron radiation. [ABSTRACT FROM AUTHOR]

The emission spectra of iron observed using a Grimm-type glow discharge in argon, argon with 0.3% v/v hydrogen and neon were studied to identify major excitation and ionization processes of iron ions in the plasma. Transition rate diagrams are given for iron ions in those discharges. These are particularly useful for describing situations in which the rate of radiative decay of excited states is comparable to or exceeds the rate of their collisional de-excitation. Relationships between transition rate diagrams and Boltzmann plots are discussed. The following processes were identified to be responsible for excitation of Fe II glow discharge spectra: charge transfer from argon/neon ions to ground state- and metastable iron atoms, Penning excitation of ground state- and metastable iron ions by argon metastables and collisional excitation by electrons of metastable iron ions. No evidence was found that local thermodynamic equilibrium exists for iron ions in a glow discharge plasma in any interval of excitation energies. Open questions remain concerning charge transfer excitation of iron, in particular about the range of energies in which the Fe II levels can be directly populated by charge transfer and about the conservation of spin in such reactions. [ABSTRACT FROM AUTHOR]

We report the realization of light emission from a Fe2+ doped ZnSe polycrystal with efficient pumping from a quantum cascade (QC) laser. The QC laser photon energy is near the absorption edge of the Fe2+:ZnSe with less than ~60 meV Stokes' shift. The Fe2+:ZnSe polycrystal shows an absorption band of ~2.2 - 5 μm in the mid-infrared (mid-IR) at room temperature, which narrows down to ~2.4-4.2 im at 80 K. Clear photoluminescence (PL) from 4.5 im to 6 μm are observed throughout the temperature range of 300 K to 80 K. At room temperature, the luminescence lifetime is about 0.38 ± 0.1 μs which increases up to 101 ± 2 μs at 118 K. This system transfers energy stored in the upper state of a QC laser with ~ps lifetime to the Fe2+:ZnSe with 105 to 108 times longer lifetime, at the cost of minute photon energy losses. [ABSTRACT FROM AUTHOR]

Using surface x-ray diffraction in combination with ab initio calculations we have studied the atomic structure of ultra-thin ZnO films deposited on Fe(l 10). In contrast to expectation that ZnO adopts the "graphitic" hexagonal Boron-nitride structure to the Wurtzite (WZ) structure is observed. Its formation is related to oxygen impurities in Fe(110) hollow sites inducing an anisotropic charge redistribution within the film which is characterized by a metallic surface. Our results provide a deeper understanding of depolarization mechanisms in ultrathin polar films at the atomic scale. [ABSTRACT FROM AUTHOR]

The development of a novel and straightforward procedure for the preparation of matrix-matched calibration standards for the quantitative imaging of iron (Fe) in biological tissues by laser ablation (LA)- ICP-MS with on-tissue internal standard addition is described. This simple approach enabled on-tissue addition of Rh as internal standard to samples (with heterogeneous Fe distribution) and calibrants (with homogeneous Fe distribution). This is achieved without altering the original Fe distribution of the sample. Calibration standards were prepared by full horizontal immersion of slides with mounted homogenised sheep brain tissue section into the corresponding solution containing 0.5, 0.75, 1, 5, 10 and 20 mg kg-1 Fe (each also containing 250 mg kg-1 Rh as IS) in pure methanol for 30 minutes (6 immersions, each for 5 minutes). Subsequent air-drying (bench drying at room temperature) for approximately 5 minutes was undertaken in between consecutive immersions, to prevent long-term exposure of the tissue to lipid degradation. Tissue-matched standards were characterised in-house for Fe composition, homogeneity and stability (at storage temperatures of -80 °C, -20 °C, 4 °C and 25 °C for up to 2 months) in order to investigate their suitability as calibrants for quantitative LA-ICP-MS. The homogeneity data suggested that the materials are homogeneous in terms of Fe and Rh distribution with RSDs (n = 30) of 8.3% and 4.7%, respectively. The Fe measurement precision was improved by approximately a factor of 2 when normalising 56Fe intensities to 103Rh intensities; the RSD (n = 30) for 56Fe/103Rh was 3.6%. The produced calibration standards were found to be stable when stored at room temperature for approximately 50 days, suggesting that they can be reused for multiple batches. Using LA coupled to double-focusing sector field ICP-MS in medium resolution mode (m/Dm = 4000), linear calibration over a range of 107 to 1519 mg kg-1 Fe (R² = 0.99) was achieved with a limit of detection of 1.84 mg kg-1 Fe. Assessment of the accuracy of the method for the quantitative imaging of Fe in tissues was undertaken by comparison of the LA-ICP-MS data with that obtained by micro-XRF; the average Fe concentrations in selected tissue regions obtained by using XRF fell within the window defined by the LA-ICP-MS values and their associated standard deviations. [ABSTRACT FROM AUTHOR]

We report herein the synthesis and physicochemical characterization of two mixed-ligand complexes of the following stoichiometric formulae: [Fe(phen)(ox)](NO)⋅2HO (1) and [Co(phen)(ox)](NO)⋅4HO (2) (as phen: 1,10-orthophenanthroline; ox: oxalate dianion). Both compounds have been prepared by slow evaporation at room temperature and characterized by single-crystal X-ray diffraction. They have been characterized by IR and UV-Vis spectra and thermoanalysis (TG and DTA) The structures of these compounds are highly symmetric. Indeed, the two compounds are isomorphous and crystallize in the orthorhombic space group Ibca. In each material, the M ion has a slightly distorted square bipyramidal environment, coordinated by one oxalate ion and two 1,10-orthophenanthroline ligands. Structural cohesion is established essentially by π- π interactions between the rings of phen groups and intermolecular O-H...O hydrogen bonds connecting the ionic entities and uncoordinated water molecules. Magnetic susceptibility measurements of (1) in the range 5-300 K exhibit paramagnetic behavior at high temperature. However, at low temperature, the magnetic data show the occurrence of weak antiferromagnetic intermolecular interactions between the local spins. [ABSTRACT FROM AUTHOR]

Core-shell structural magnetic nanocatalysts, involving carbon-coated magnetic Fe3O4 nanoparticles supported on graphene oxide sheets (mildly reduced graphene oxide (MRGO)/Fe3O4@C) and carbonaceous coatings on magnetic Fe3O4 nanoparticles (Fe3O4@C), for immobilizing metal (CuII, CoII, FeIII or VOIV)-salen complexes were prepared by a facile, green, and efficient chemical approach and first applied in the aerobic epoxidation of styrene with air as the oxidizing agent. The prepared catalysts were characterized by different techniques, such as XRD, TEM, FTIR spectroscopy, inductively coupled plasma atomic emission spectroscopy, TEM, thermogravimetric analysis, Raman spectroscopy, and X-ray photoelectron spectroscopy. The magnetic nanocatalysts MRGO/Fe3O4@C-salen-M (M=Cu, Co, Fe, or V) exhibited higher catalytic reactivity than that of the corresponding Fe3O4@C-salen-M (M=Cu, Co, Fe, or V) species possibly owing to site isolation, good dispersion of magnetic Fe3O4 nanoparticles, and an efficiently synergistic effect between the metal complexes and the supports. Furthermore, MRGO/Fe3O4@C-salen-Co exhibited up to 92.3 % conversion of styrene and 59.2 % selectivity to the styrene oxide upon using air as the oxidizing agent and showed good recoverability with negligible loss in activity and selectivity within successive runs owing to superparamagnetism. Most importantly, these materials can be easily recovered by simple magnetic separation. [ABSTRACT FROM AUTHOR]

[FeFe]-hydrogenases are the best natural hydrogen-producing enzymes but their biotechnological exploitation is hampered by their extreme oxygen sensitivity. The free energy profile for the chemical attachment of O2 to the enzyme active site was investigated by using a range-separated density functional re-parametrized to reproduce high-level ab initio data. An activation free-energy barrier of 13 kcal mol−1 was obtained for chemical bond formation between the di-iron active site and O2, a value in good agreement with experimental inactivation rates. The oxygen binding can be viewed as an inner-sphere electron-transfer process that is strongly influenced by Coulombic interactions with the proximal cubane cluster and the protein environment. The implications of these results for future mutation studies with the aim of increasing the oxygen tolerance of this enzyme are discussed. [ABSTRACT FROM AUTHOR]