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Evgen V Govor, Karrar Al-Ameed, Indranil Chakraborty, Carla S Coste, Olena Govor, Yiannis Sanakis, John E McGrady, Raphael G Raptis
One-electron reduction of a pyrazolate-bridged triangular Fe3 (μ3 -O) core induces a cascade wherein all three metal centers switch from high-spin Fe(3+) to low-spin Fe(2.66+) . This hypothesis is supported by spectroscopic data ((1) H-NMR, UV-vis-NIR, infra-red, (57) Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters...
December 5, 2016: Angewandte Chemie
Weizhao Yin, Lizhi Huang, Emil Bjerglund Pedersen, Cathrine Frandsen, Hans Christian B Hansen
Layered Fe(II)-Fe(III) hydroxides (green rusts, GRs) are efficient reducing agents against oxidizing contaminants such as chromate, nitrate, selenite, and nitroaromatic compounds and chlorinated solvents. In this study, we adopted a buffered precipitation approach where glycine (GLY) was used in the synthesis of sulfate-interlayered GR (GRSO4) by aerial oxidation of Fe(II) or co-precipitation by adding Fe(III) salt to an aqueous solution of Fe(II) at constant pH. In both the oxidation and the co-precipitation methods pure crystalline GRSO4 was precipitated in the presence of 70mM GLY (pH 8...
November 22, 2016: Journal of Colloid and Interface Science
Guoyin Shen, Ho Kwang Mao
Pressure profoundly alters all states of matter. The symbiotic development of ultrahigh-pressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields...
November 22, 2016: Reports on Progress in Physics
Magdalena Kaczmarska, Dominika Żydek, Justyna Wilkłacz-Potoczny, Maria Fornal, Tomasz Grodzicki, Elżbieta Kochowska, Krzysztof Kozak, Łukasz Gocal, Władysław Pohorecki, Krzysztof Matlak, Józef Korecki, Květoslava Burda
Our aim was to study the influence of low doses (0.2-4 μGy) of α radiation on the stability of human erythrocytes isolated from healthy and diabetic erythrocytes. Absorption spectroscopy was used to measure the level of red blood cell (RBC) hemolysis, along with Mössbauer spectroscopy, which is a highly specific method suited to monitoring various hemoglobin forms. States of hemoglobin are sensitive to a homeostatic imbalance in red blood cells. Changes in the membrane skeleton organization of irradiated erythrocytes isolated from healthy donors were studied using atomic force microscopy (AFM)...
November 16, 2016: Microscopy Research and Technique
Christian Suchomski, Ben Breitung, Ralf Witte, Michael Knapp, Sondes Bauer, Tilo Baumbach, Christian Reitz, Torsten Brezesinski
Magnetic nanocrystals with a narrow size distribution hold promise for many applications in different areas ranging from biomedicine to electronics and energy storage. Herein, the microwave-assisted sol-gel synthesis and thorough characterization of size-monodisperse zinc ferrite nanoparticles of spherical shape is reported. X-ray diffraction, (57)Fe Mössbauer spectroscopy and X-ray photoelectron spectroscopy all show that the material is both chemically and phase-pure and adopts a partially inverted spinel structure with Fe(3+) ions residing on tetrahedral and octahedral sites according to (Zn0...
2016: Beilstein Journal of Nanotechnology
Yao Cheng, Shi-Hui Yang, Michael Lan, Chih-Hao Lee
Several observations of the Nb long-lived Mossbauer phenomena are presented, in consequence of an irradiation increased by an order of magnitude compared with previous work. These are 1) two β decays of (182)Ta and (92m)Nb are enhanced, i.e., (182)Ta is now 200 times faster than in previous results while (92m)Nb is twice as fast as normal; 2) γs emitted from two β decays compete to eject electrons in a winner-takes-all rule, rather than by superposition; 3) abrupt spectral changes reveal three decay phases of (182)Ta; 4) the biphoton γγ of (93m)Nb is released from the sample for the first time; 5) the γγ distribution is narrow, in contrast to the broad γγ spectrum obtained from independent nuclei; 6) Nb K-lines super-radiate along the long sample axis; 7) collective scattering of multipolar MeV γs...
November 8, 2016: Scientific Reports
Anna Bourliva, Lambrini Papadopoulou, Elina Aidona, Konstantinos Simeonidis, George Vourlias, Eamonn Devlin, Yiannis Sanakis
The mineralogy, morphology, and chemical composition of magnetic fractions separated from fly ashes (FAs) originating from Greek lignite-burning power plants was investigated. The oral bioaccessibility of potentially harmful elements (PHEs) from the fly ash magnetic fractions (FAMFs) was also assessed using in vitro gastrointestinal extraction (BARGE Unified Bioaccessibility Method, UBM). The FAMFs isolated were in the range 4.6-18.4%, and their mass specific magnetic susceptibility ranged from 1138 × 10(-8) to 1682 × 10(-8) m(3)/kg...
November 4, 2016: Environmental Science and Pollution Research International
Denis A Proshlyakov, John McCracken, Robert P Hausinger
A wide range of spectroscopic approaches have been used to interrogate the mononuclear iron metallocenter in 2-oxoglutarate (2OG)-dependent oxygenases. The results from these spectroscopic studies have provided valuable insights into the structural changes at the active site during substrate binding and catalysis, thus providing critical information that complements investigations of these enzymes by X-ray crystallography, biochemical, and computational approaches. This mini-review highlights taurine hydroxylase (taurine:2OG dioxygenase, TauD) as a case study to illustrate the wealth of knowledge that can be generated by applying a diverse array of spectroscopic investigations to a single enzyme...
November 3, 2016: Journal of Biological Inorganic Chemistry: JBIC
Masataka Kinoshita, Hideaki Sakai, Naoaki Hayashi, Yoshinori Tokura, Mikio Takano, Shintaro Ishiwata
The effects of Rh and Ru doping for SrFeO3 , a helimagnetic metal with a cubic perovskite structure, are studied by magnetic and resistivity measurements. Although SrRhO3 is a paramagnetic metal and SrRuO3 is a ferromagnetic one, the Rh doping induces a nearly ferromagnetic metallic state, whereas the Ru doping induces a spin-glass insulating state. Mössbauer measurements evidence a marked difference between SrFe0.8 Rh0.2 O3 and SrFe0.8 Ru0.2 O3 in the formal valences of Fe, which are estimated to be 4+ and 3...
November 2, 2016: Angewandte Chemie
Takafumi Yamamoto, Hiroshi Ohkubo, Cédric Tassel, Naoaki Hayashi, Shota Kawasaki, Taku Okada, Takehiko Yagi, James Hester, Maxim Avdeev, Yoji Kobayashi, Hiroshi Kageyama
The effect of lanthanoid (Ln = Nd, Sm, Ho) substitution on the structural and physical properties of the infinite-layer iron oxide SrFeO2 was investigated by X-ray diffraction (XRD) at ambient and high pressure, neutron diffraction, and (57)Fe Mössbauer spectroscopy. Ln for Sr substituted samples up to ∼30% were synthesized by topochemical reduction using CaH2. While the introduction of the smaller Ln(3+) ion reduces the a axis as expected, we found an unusual expansion of the c axis as well as the volume...
November 1, 2016: Inorganic Chemistry
Fernande Grandjean, Louise Samain, Gary J Long
This review deals with our long-range goal of determining why the Prussian blue pigments, typically either the "soluble" KFe(III)[Fe(II)(CN)6]·xH2O or the alternative "insoluble" Fe[Fe(II)(CN)6]3·xH2O compounds, used by artists from shortly after the discovery of Prussian blue in 1704 and well into the early twentieth century, often fade when exposed to light. In order to achieve this goal it was decided that first, for comparison purposes, we had to prepare and fully characterize Prussian blues prepared by various, often commercially successful, synthetic methods...
November 1, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Nicole Kindermann, Anne Schober, Serhiy Demeshko, Nicolai Lehnert, Franc Meyer
Flavo-diiron nitric oxide reductases (FNORs) are a subclass of nonheme diiron proteins in pathogenic bacteria that reductively transform NO to N2O, thereby abrogating the nitrosative stress exerted by macrophages as part of the immune response. Understanding the mechanism and intermediates in the NO detoxification process might be crucial for the development of a more efficient treatment against these bacteria. However, low molecular weight models are still rare, and only in a few cases have their reductive transformations been thoroughly investigated...
October 27, 2016: Inorganic Chemistry
Léa Gustin, Yoshiteru Hosaka, Cédric Tassel, Tomoko Aharen, Yuichi Shimakawa, Hiroshi Kageyama, John B Wiley
Synthesis, characterization, and thermal modification of the new layered perovskite FeLa2Ti3O10 have been studied. FeLa2Ti3O10 was prepared by ion exchange of the triple-layered Ruddlesden-Popper phase Li2La2Ti3O10 with FeCl2 at 350 °C under static vacuum. Rietveld refinement on synchrotron X-ray diffraction data indicates that the new phase is isostructural with CoLa2Ti3O10, where Fe(II) cations occupy slightly compressed/flattened interlayer tetrahedral sites. Magnetic measurements on FeLa2Ti3O10 display Curie-Weiss behavior at high temperatures and a spin-glass transition at lower temperatures (<30 K)...
October 26, 2016: Inorganic Chemistry
Chao Wang, Chongyang Zhao, Lianrui Hu, Hui Chen
Cyanobacterial aldehyde-deformylating oxygenase (cADO) is a nonheme diiron enzyme that catalyzes the conversion of aldehyde to alk(a/e)ne, an important transformation in biofuel research. In this work, we report a highly desired computational study for probing the mechanism of cADO. By combining our QM/MM results with the available (57)Fe Mössbauer spectroscopic data, the gained detailed struc-tural information suggests construction of asymmetry from the symmetric diiron cofactor in aldehyde substrate and O2 activation...
October 24, 2016: Journal of Physical Chemistry Letters
Valeriy Yu Verchenko, Sergei S Sokolov, Alexander A Tsirlin, Alexey V Sobolev, Igor A Presniakov, Mikhail A Bykov, Maria A Kirsanova, Andrei V Shevelkov
A new ternary telluride, Fe3-δAs1-yTe2, was synthesized from elements at 600 °C. It crystallizes in the hexagonal P63/mmc space group with the unit cell parameters a = 3.85091(9) Å and c = 17.1367(4) Å for δ = 0.3 and y = 0.04. Its layered crystal structure contains partially occupied intralayer and interlayer Fe positions, which give rise to significant nonstoichiometry: Fe3-δAs1-yTe2 was found to possess the homogeneity range of 0.25 < δ < 0.45 and y = 0.04. Regions of local vacancy ordering alternate with regions of randomly distributed vacancies, so that the ordering of Fe atoms and vacancies is not complete in the average structure...
October 3, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Wojciech Szczerba, Jan Żukrowski, Marek Przybylski, Marcin Sikora, Olga Safonova, Aleksey Shmeliov, Valeria Nicolosi, Michael Schneider, Tim Granath, Maximilian Oppmann, Marion Straßer, Karl Mandel
The maximum magnetisation (saturation magnetisation) obtainable for iron oxide nanoparticles can be increased by doping the nanocrystals with non-magnetic elements such as zinc. Herein, we closely study how only slightly different synthesis approaches towards such doped nanoparticles strongly influence the resulting sub-nano/atomic structure. We compare two co-precipitation approaches, where we only vary the base (NaOH versus NH3), and a thermal decomposition route. These methods are the most commonly applied ones for synthesising doped iron oxide nanoparticles...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Fernande Grandjean, Gary J Long
The proportionality constant, α, between the observed isomer shifts and the calculated electron probability density at the iron nucleus has been reevaluated in terms of the correct experimental isomer shifts relative to α-iron and their corresponding accuracy, which should be considered in the linear regression fit yielding α. The iron-57 excited state nuclear quadrupole moment, Q, is not a "relative" value and its widely accepted experimental value is 0.16(1) × 10(-28) m(2) as also confirmed by nuclear model calculations...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Dianne J Xiao, Julia Oktawiec, Phillip J Milner, Jeffrey R Long
Metal-organic frameworks are a new class of heterogeneous catalysts in which molecular-level control over both the immediate and long-range chemical environment surrounding a catalytic center can be readily achieved. Here, the oxidation of cyclohexane to cyclohexanol and cyclohexanone is used as a model reaction to investigate the effect of a hydrophobic pore environment on product selectivity and catalyst stability in a series of iron-based frameworks. Specifically, expanded analogues of Fe2(dobdc) (dobdc(4-) = 2,5-dioxido-1,4-benzenedicarboxylate) were synthesized and evaluated, including the biphenyl derivative Fe2(dobpdc) (H4dobpdc = 4,4'-dihydroxy-[1,1'-biphenyl]-3,3'-dicarboxylic acid), the terphenyl derivative Fe2(dotpdc) (H4dotpdc = 4,4''-dihydroxy-[1,1':4',1''-terphenyl]-3,3''-dicarboxylic acid), and three modified terphenyl derivatives in which the central ring is replaced with tetrafluoro-, tetramethyl-, or di-tert-butylaryl groups...
October 5, 2016: Journal of the American Chemical Society
Sergey M Aksenov, Nikita V Chukanov, Vyacheslav S Rusakov, Taras L Panikorovskii, Ramiza K Rastsvetaeva, Ramil R Gainov, Farit G Vagizov, Konstantin A Lyssenko, Dmitry I Belakovskiy
Vesuvianite containing 5.85 wt% TiO2 from an Alpine-cleft-type assemblage outcropped near Alchuri, Shigar Valley, Northern Areas, Pakistan, has been investigated by means of electron microprobe analyses, gas-chromatographic analysis of H2O, X-ray powder diffraction, single-crystal X-ray structure refinement, (27)Al NMR, (57)Fe Mössbauer spectroscopy, IR spectroscopy and optical measurements. Tetragonal unit-cell parameters are: a = 15.5326 (2), c = 11.8040 (2) Å, space group P4/nnc. The structure was refined to final R1 = 0...
October 1, 2016: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
M Shopska, D Paneva, G Kadinov, Z Cherkezova-Zheleva, I Mitov, M Iliev
The biogenic iron oxide/hydroxide materials possess useful combination of physicochemical properties and are considered for application in various areas. Their production does not require special investments because these compounds are formed during cultivation of neurophilic iron bacteria. Bacteria from genus Leptothrix develop intensively in the Sphaerotilus-Leptothrix group of bacteria isolation medium and feeding media of Fedorov and Lieske. These media are different in their composition which determined the present study as an attempt to clear up the reasons that define the differences in the composition of the laboratory-obtained biomasses and the natural biomass finds...
October 1, 2016: Applied Biochemistry and Biotechnology
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