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https://www.readbyqxmd.com/read/28745500/discriminating-catalytically-active-fenx-species-of-atomically-dispersed-fe-n-c-catalyst-for-selective-oxidation-of-c-h-bond
#1
Wengang Liu, Leilei Zhang, Xin Liu, Xiaoyan Liu, Xiaofeng Yang, Shu Miao, Wentao Wang, Aiqin Wang, Tao Zhang
Nanostructured Fe-N-C materials represent a new type of "platinum-like" non-noble metal catalysts for various electrochemical reactions and organic transformations. However, no consensus has been reached on the active sites of the Fe-N-C catalysts because of their heterogeneity in particle size and composition. In this contribution, we have successfully prepared atomically dispersed Fe-N-C catalyst, which exhibited high activity and excellent reusability for the selective oxidation of C-H bond. A wide scope of substrates including aromatic, heterocyclic, and aliphatic alkanes were smoothly oxidized at room temperature and the selectivity of corresponding products reached as high as 99%...
July 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28741934/mixed-spin-diamond-chain-cu2fepo4f4-h2o-4-with-a-noncollinear-spin-order-and-possible-successive-phase-transitions
#2
Hongcheng Lu, Naoaki Hayashi, Yuki Matsumoto, Hiroshi Takatsu, Hiroshi Kageyama
A diamond spin chain system, one of the one-dimensional frustrated lattices, is known to exhibit novel properties, but experimental studies have been exclusively confined to materials with a single spin component. Here, we report on the synthesis, structure, and magnetic properties of a new diamond chain compound Cu2FePO4F4(H2O)4 1 composed of mixed-spins of Cu(2+) (S = 1/2 × 2) and Fe(3+) (S = 5/2). Compound 1 crystallizes in the space group C2/c of the monoclinic crystal system with a = 7.7546(4) Å, b = 12...
July 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28738659/sample-treatment-in-m%C3%A3-ssbauer-spectroscopy-for-protein-related-analyses-nondestructive-possibilities-to-look-inside-metal-containing-biosystems
#3
Alexander A Kamnev, Anna V Tugarova
In this review, the unique possibilities are considered of the (57)Fe transmission (TMS) and (57)Co emission (EMS) variants of Mössbauer (nuclear γ-resonance) spectroscopy as nondestructive techniques with minimal sample preparation/treatment and a significant analytical potential, with a focus on the analysis of cation-binding sites in metalloproteins. The techniques are shown to provide unique structural and quantitative information on the coordination microenvironment, the chemical state and transformations of the Mössbauer nuclides in sophisticated metal-containing proteins, including those within complicated supramolecular structures, and in microbial cells or tissues...
November 1, 2017: Talanta
https://www.readbyqxmd.com/read/28737797/cation-distribution-dependent-magnetic-properties-in-cocr2-xfexo4-x-0-1-to-0-5-exafs-m%C3%A3-ssbauer-and-magnetic-measurements
#4
D Kumar, A Banerjee, A Mahmoud, Chandana Rath
In this report, we have examined the evolution of the structure and rich magnetic transitions such as a paramagnetic to ferrimagnetic phase transition at the Curie temperature (TC), spiral ordering temperature (TS) and lock-in temperature (TL) observed in the CoCr2O4 spinel multiferroic after substituting Fe. The crystal structure, microstructure and cation distribution among the tetrahedral (A) and octahedral (B) sites in the spinel lattice are characterised by X-ray diffraction, transmission electron microscopy, Extended X-ray Absorption Fine Structure (EXAFS) and Mössbauer spectroscopy...
July 24, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28735529/spinel-ferrite-core-shell-nanostructures-by-a-versatile-solvothermal-seed-mediated-growth-approach-and-study-of-their-nanointerfaces
#5
Marco Sanna Angotzi, Anna Musinu, Valentina Mameli, Andrea Ardu, Claudio Cara, Daniel Niznansky, Huolin L Xin, Carla Cannas
An easy, low-cost, repeatable seed-mediated growth approach in solvothermal condition has been proposed to synthesize bimagnetic spinel ferrite core-shell heterostructures in the 10-20 nm particle size range. Cobalt ferrite and manganese ferrite nanoparticles (CoFe2O4 and MnFe2O4) have been coated with isostructural spinel ferrites like maghemite/magnetite, MnFe2O4 and CoFe2O4 with similar cell parameters to create different heterostructures. The conventional study of the structure, morphology and composition has been combined with advanced techniques in order to achieve details on the interface at the nanoscale level...
July 23, 2017: ACS Nano
https://www.readbyqxmd.com/read/28726913/mechanistic-insights-into-dioxygen-activation-oxygen-atom-exchange-and-substrate-epoxidation-by-asqj-dioxygenase-from-quantum-mechanical-molecular-mechanical-calculations
#6
Xudan Song, Jiarui Lu, Wenzhen Lai
Herein, we use in-protein quantum mechanical/molecular mechanical (QM/MM) calculations to elucidate the mechanism of dioxygen activation, oxygen atom exchange and substrate epoxidation processes by AsqJ, an Fe(II)/α-ketoglutarate-dependent dioxygenase (α-KGD) using a 2-His-1-Asp facial triad. Our results demonstrated that the whole reaction proceeds through a quintet surface. The dioxygen activation by AsqJ leads to a quintet penta-coordinated Fe(IV)-oxo species, which has a square pyramidal geometry with the oxo group trans to His134...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28723082/mixed-valency-in-a-3d-semiconducting-iron-fluoranilate-coordination-polymer
#7
Ryuichi Murase, Brendan F Abrahams, Deanna M D'Alessandro, Casey G Davies, Timothy A Hudson, Guy N L Jameson, Boujemaa Moubaraki, Keith S Murray, Richard Robson, Ashley L Sutton
A pair of coordination polymers of composition (NBu4)2[M2(fan)3] (fan = fluoranilate; M = Fe and Zn) were synthesized and structurally characterized. In each case the compound consists of a pair of interpenetrating three-dimensional, (10,3)-a networks in which metal centers are linked by chelating/bridging fluoranilate ligands. Tetrabutylammonium cations are located in the spaces between the two networks. Despite the structural similarity, significant differences exist between (NBu4)2[Fe2(fan)3] and (NBu4)2[Zn2(fan)3] with respect to the oxidation states of the metal centers and ligands...
July 19, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28723078/covalency-competition-in-the-quadruple-perovskite-cdcu3fe4o12
#8
Ikuya Yamada, Akihiko Takamatsu, Naoaki Hayashi, Hidekazu Ikeno
Cadmium ions (Cd(2+)) are similar to calcium ions (Ca(2+)) in size, whereas the Cd(2+) ions tend to form covalent bonds with the neighboring anions because of the high electronegativity. The covalent Cd-O bonds affect other metal-oxygen bonds, inducing drastic changes in crystal structures and electronic states. Herein, we demonstrate high-pressure synthesis, crystal structure, and properties of a new quadruple perovskite CdCu3Fe4O12. This compound exhibits an electronic phase transition accompanying a charge disproportionation of Fe ions without charge ordering below ∼200 K, unlike charge-disproportionation transition with rock-salt-type charge ordering for CaCu3Fe4O12...
July 19, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28722013/stability-of-iron-bearing-carbonates-in-the-deep-earth-s-interior
#9
Valerio Cerantola, Elena Bykova, Ilya Kupenko, Marco Merlini, Leyla Ismailova, Catherine McCammon, Maxim Bykov, Alexandr I Chumakov, Sylvain Petitgirard, Innokenty Kantor, Volodymyr Svitlyk, Jeroen Jacobs, Michael Hanfland, Mohamed Mezouar, Clemens Prescher, Rudolf Rüffer, Vitali B Prakapenka, Leonid Dubrovinsky
The presence of carbonates in inclusions in diamonds coming from depths exceeding 670 km are obvious evidence that carbonates exist in the Earth's lower mantle. However, their range of stability, crystal structures and the thermodynamic conditions of the decarbonation processes remain poorly constrained. Here we investigate the behaviour of pure iron carbonate at pressures over 100 GPa and temperatures over 2,500 K using single-crystal X-ray diffraction and Mössbauer spectroscopy in laser-heated diamond anvil cells...
July 19, 2017: Nature Communications
https://www.readbyqxmd.com/read/28713215/a-high-spatial-resolution-synchrotron-m%C3%A3-ssbauer-study-of-the-tazewell-iiicd-and-esquel-pallasite-meteorites
#10
Roberts Blukis, Rudolf Rüffer, Aleksandr I Chumakov, Richard J Harrison
Metallic phases in the Tazewell IIICD iron and Esquel pallasite meteorites were examined using (57)Fe synchrotron Mössbauer spectroscopy. Spatial resolution of ~10-20 μm was achieved, together with high throughput, enabling individual spectra to be recorded in less than 1 h. Spectra were recorded every 5-10 μm, allowing phase fractions and hyperfine parameters to be traced along transects of key microstructural features. The main focus of the study was the transitional region between kamacite and plessite, known as the "cloudy zone...
May 2017: Meteoritics & Planetary Science
https://www.readbyqxmd.com/read/28702640/a-simple-high-yield-synthesis-of-high-purity-h%C3%A3-gg-carbide-%C3%AF-fe5c2-nanoparticles-with-extraordinary-electrochemical-properties
#11
Ondřej Malina, Petr Jakubec, Josef Kašlík, Jiří Tuček, Radek Zbořil
Iron carbides are of eminent interest in both fundamental scientific research and in the industry owing to their properties such as excellent mechanical strength and chemical inertness. They have been found very effective in Fischer-Tropsch synthesis exploring heterogeneous catalysis for the production of chemicals such as liquid fuel and they have also been employed as successful promoters for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). However, so far there have been only a few reports on the application of iron carbide nanoparticles in the field of electrochemical sensing...
July 27, 2017: Nanoscale
https://www.readbyqxmd.com/read/28695249/first-study-on-iron-complexes-in-blood-and-organ-samples-from-thalassaemic-and-normal-laboratory-mice-using-m%C3%A3-ssbauer-spectroscopy
#12
George Charitou, Vlassis Petousis, Charalambos Tsertos, Yannis Parpottas, Marina Kleanthous, Marios Phylactides, Soteroula Christou
Measurements of iron complexes and iron stores in the body are crucial for evaluation and management of chelation therapy targeted against iron accumulation or overload in blood and organs. In this work, blood and tissue samples from one normal and one thalassaemic laboratory mouse were studied using (57)Fe Mössbauer spectroscopy at 78 K for the first time. In contrast to human patients, these laboratory mice did not receive any medical treatment, thus the iron components present in the samples are not altered from their natural state...
July 10, 2017: European Biophysics Journal: EBJ
https://www.readbyqxmd.com/read/28691111/density-functional-calculations-for-prediction-of-57-fe-m%C3%A3-ssbauer-isomer-shifts-and-quadrupole-splittings-in-%C3%AE-diketiminate-complexes
#13
Sean F McWilliams, Emma Brennan-Wydra, K Cory MacLeod, Patrick L Holland
The relative ease of Mössbauer spectroscopy and of density functional theory (DFT) calculations encourages the use of Mössbauer parameters as a validation method for calculations, and the use of calculations as a double check on crystallographic structures. A number of studies have proposed correlations between the computationally determined electron density at the iron nucleus and the observed isomer shift, but deviations from these correlations in low-valent iron β-diketiminate complexes encouraged us to determine a new correlation for these compounds...
June 30, 2017: ACS Omega
https://www.readbyqxmd.com/read/28685326/ferruginous-compounds-in-the-airborne-particulate-matter-of-the-metropolitan-area-of-belo-horizonte-minas-gerais-brazil
#14
Fernanda Vasconcelos Fonseca Tavares, José Domingos Ardisson, Paulo César Horta Rodrigues, José Domingos Fabris, Luis Eugenio Fernandez-Outon, Vanusa Maria Delage Feliciano
Samples of soil, iron ore, and airborne particulate matter (size <10 μm) were analyzed with the main goal of investigating the differentiating physicochemical properties of their ferruginous compounds. These data were used to identify whether the sources of airborne particulate matter in the metropolitan area of Belo Horizonte, Minas Gerais, Brazil, are either from natural origin, as, for instance, re-suspension of particles from soil, or due to anthropogenic activities, meaning that it would be originated from the many iron ore minings surrounding the metropolitan area...
July 6, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28685126/characterization-of-ferrite-nanoparticles-for-preparation-of-biocomposites
#15
Urszula Klekotka, Magdalena Rogowska, Dariusz Satuła, Beata Kalska-Szostko
Ferrite nanoparticles with nominal composition Me0.5Fe2.5O4 (Me = Co, Fe, Ni or Mn) have been successfully prepared by the wet chemical method. The obtained particles have a mean diameter of 11-16 ± 2 nm and were modified to improve their magnetic properties and chemical activity. The surface of the pristine nanoparticles was functionalized afterwards with -COOH and -NH2 groups to obtain a bioactive layer. To achieve our goal, two different modification approaches were realized. In the first one, glutaraldehyde was attached to the nanoparticles as a linker...
2017: Beilstein Journal of Nanotechnology
https://www.readbyqxmd.com/read/28677977/synthesis-and-electronic-ground-state-properties-of-pyrrolyl-based-iron-pincer-complexes-revisited
#16
Nico Ehrlich, Markus Kreye, Dirk Baabe, Peter Schweyen, Matthias Freytag, Peter G Jones, Marc D Walter
The pyrrolyl-based iron pincer compounds [((tBu)PNP)FeCl] (1), [((tBu)PNP)FeN2] (2), and [((tBu)PNP)Fe(CO)2] (3) were prepared and structurally characterized. In addition, their electronic ground states were probed by various techniques including solid-state magnetic susceptibility and zero-field (57)Fe Mössbauer and X-band electron paramagnetic resonance spectroscopy. While the iron(II) starting material 1 adopts an intermediate-spin (S = 1) state, the iron(I) reduction products 2 and 3 exhibit a low-spin (S = (1)/2) ground state...
July 17, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28677041/degradation-of-the-cyanotoxin-microcystin-lr-using-iron-based-photocatalysts-under-visible-light-illumination
#17
Changseok Han, Libor Machala, Ivo Medrik, Robert Prucek, Radina P Kralchevska, Dionysios D Dionysiou
In this study, a simple and low-cost method to synthesize iron(III) oxide nanopowders in large quantity was successfully developed for the photocatalytic degradation of microcystin-LR (MC-LR). Two visible light-active iron(III) oxide samples (MG-9 calcined at 200 °C for 5 h and MG-11 calcined at 180 °C for 16 h) with a particle size of 5-20 nm were prepared via thermal decomposition of ferrous oxalate dihydrate in air without any other modifications such as doping. The synthesized samples were characterized by X-ray powder diffraction, (57)Fe Mössbauer spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller (BET) specific surface area analysis, and UV-visible diffuse reflectance spectroscopy...
July 4, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28671654/simple-methods-for-the-preparation-of-non-noble-metal-bulk-electrodes-for-electrocatalytic-applications
#18
Kai Junge Puring, Stefan Piontek, Mathias Smialkowski, Jens Burfeind, Stefan Kaluza, Christian Doetsch, Ulf-Peter Apfel
The rock material pentlandite with the composition Fe4.5Ni4.5S8 was synthesized via high temperature synthesis from the elements. The structure and composition of the material was characterized via powder X-ray diffraction (PXRD), Mössbauer spectroscopy (MB), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and energy dispersive X-ray spectroscopy (EDX). Two preparation methods of pentlandite bulk electrodes are presented. In the first approach a piece of synthetic pentlandite rock is directly contacted via a wire ferrule...
June 21, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28668640/spectroscopic-studies-of-the-cytochrome-p450-reaction-mechanisms
#19
REVIEW
Piotr J Mak, Ilia G Denisov
The cytochrome P450 monooxygenases (P450s) are thiolate heme proteins that can, often under physiological conditions, catalyze many distinct oxidative transformations on a wide variety of molecules, including relatively simple alkanes or fatty acids, as well as more complex compounds such as steroids and exogenous pollutants. They perform such impressive chemistry utilizing a sophisticated catalytic cycle that involves a series of consecutive chemical transformations of heme prosthetic group. Each of these steps provides a unique spectral signature that reflects changes in oxidation or spin states, deformation of the porphyrin ring or alteration of dioxygen moieties...
June 28, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28661224/experimental-study-on-magnetic-characteristics-of-coal-fly-ash-at-different-combustion-temperatures
#20
Daojie Liu, Xin Wu, Yiwei Du, Li Sun
Two different coals containing iron minerals combusted in a drop tube furnace at different temperatures. The ash samples collected were analyzed in detail to investigate the transformation behaviours of iron-bearing minerals and the magnetic characteristic of coal fly ash (FA). Vibrating sample magnetometer (VSM) was used to analyze magnetic characteristics of the ash samples and Mössbauer spectroscopy was employed to analyze the iron-bearing components in FA. The results indicate that combustion temperature does not significantly affect the crystals phases formed in FA, but does change the relative content of crystals...
June 29, 2017: Environmental Technology
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