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Iron-based compounds with a ThMn12-type structure have the potential to bridge the gap between ferrites and high performance Nd2Fe14B magnets. From the point of view of possible applications, the main advantage is their composition, with about 10 wt.% less rare earth elements in comparison with the 2:14:1 phase. On the other hand, the main issue delaying the development of Fe-rich alloys with a ThMn12-type structure is their structural stability. Therefore, various synthesis methods and stabilizing elements have been proposed to stabilize the structure. In this work, the influence of increasing Nd substitution on the phase constitution of Zr0.4−xNdxCe0.6Fe10Si2 (0 ≤ x ≤ 0.3) alloys was analyzed. X-ray diffraction and 57Fe Mössbauer spectrometry were used as the main methods to derive the stability range and destabilization routes of the 1:12 structure. For the arc-melted samples, an increase in the lattice parameters of the ThMn12-type structure was observed with the simultaneous growth of bcc-(Fe,Si) content with increasing Nd substitution. After isothermal annealing, the ThMn12-type structure (and the coexisting bcc-(Fe,Si)) were stable over the whole composition range. While the formation of a 1:12 phase was totally suppressed in the as-cast state for x = 0.3, further heat treatment resulted in the growth of about 45% of the ThMn12-type phase. The results confirmed that the stability range of ThMn12-type structure in the Nd-containing alloys was well improved by other substitutions and the heat treatment, which in turn, is also needed to homogenize the ThMn12-type phase. After further characterization of the magnetic properties and optimization of microstructure, such hard/soft magnetic composites can show their potential by exploiting the exchange spring mechanism. [ABSTRACT FROM AUTHOR]

Two new 3D porphyrin-based metal organic frameworks were obtained by solvothermally reacting iron(iii) chloride, a free base (5,10,15,20-tetrakis[4-(2,3,4,5-tetrazolyl)phenyl]porphyrin) (H2TTPP) and either pyrazine or 1,4-diazabicyclo[2.2.2]octane (DABCO). Both MOFs displayed a 3-D open framework of the fry topology, where the inorganic building unit is a chain of corner-sharing FeN4O2 octahedra and the porphyrinic linker is metallated with iron during the reaction course, with the N-donor base bridging the iron of the porphyrinic cores. Through thorough structural and spectroscopic analyses of the pyrazine containing material the chemical formula [FeIIpzTTP(FeII1−xDMF1−xFeIIIxOHx)]n was inferred (x≥ 0.25). Whereas the already reported carboxylate analogue is built up from a pure iron(iii) inorganic chain, here spectroscopic and structural studies evidenced a mixed valence iron(ii/iii) state, evidencing that, in agreement with the HSAB theory, the substitution of a carboxylate function by a tetrazolate one allows redox tuning. Finally, both materials feature one-dimensional channels of ca. 8 × 12 Å within the structures with permanent microporosity. [ABSTRACT FROM AUTHOR]

Abstract: The hydrothermal synthesis, using tris-(2-ethylamino)amine (tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H3O)2·[H3 tren]2·(FeF6)2·(FeF5(H2O))·2H2O (I), [H3 tren]2·(FeF6)2·(FeF2(H2O)4)·8H2O (II) and [H3 tren]2·(FeF6)·(F)3·H2O (III), are reported. I, II, and III are triclinic (P-1), monoclinic (P21/c) and orthorhombic (I222), respectively. The structure of I is built up from isolated FeF6 and FeF5(H2O) distorted octahedra separated by triprotonated [H3 tren]3+ cations, disordered H3O+ cations and H2O molecules. In II, FeIIIF6 and neutral [FeIIF2(H2O)4] octahedra form, together with [H3 tren]3+ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF6 octahedra, fluoride anions F− connected to [H3 tren]3+ cations and extra fluoride anions F− disordered with H2O molecules. All [H3 tren]3+ cations have a “spider” type conformation. 57Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results. [Copyright &y& Elsevier]

The new compound FeIII(OH)[C6H2(CO2)2(CO2H)2]·xH2O (with x=0.88) is the first ferric carboxylate with a 3D open structure that has been synthesized up to now. Its structure is built up from chains of octahedra connected by carboxylate ligands; it displays small channels filled by water molecules. The removal of water molecules was studied by Mössbauer spectroscopy which set up defaults of water molecules in the crystal. Magnetic measurements indicate an antiferromagnetic behavior at low temperature, but also a metamagnetic transition for an applied magnetic field larger than 0.5 T. [Copyright &y& Elsevier]

The advancement of lithium-ion batteries (LIBs) with high performance is crucial across various sectors, notably in space exploration. This advancement hinges on the development of innovative cathode materials. Our research is dedicated to pioneering a new category of cathodes using fluorinated multimetallic materials, with a specific focus on diverging from the traditional Ni, Co, and Mn-based NMC chemistries by substituting nickel and manganese with copper and iron which are more sustainable elements. Our goal is also to enhance the robustness of cathodes upon cycling by substituting oxygen with fluorine as the metal-ligand. To achieve this, an intimate composite blend of CuF2 and FeF3, through the multimetallic template fluorination (MMTF) methodology using a layered double hydroxide (LDH) as a precursor has been designed. Each of these components was carefully selected for its distinct attributes, including high redox potential, elevated energy density, substantial theoretical capacity, and improved cyclability. The composition denoted as (Cu1.5Co0.5)2+(Fe0.75Al0.25)3+ has been selected for fluorination because it maximizes Fe3+ and Cu2+ amount in the screened LDHs. Subsequently, this particular LDH was fluorinated through solid-gas fluorination at different temperatures (200, 350, and 500 °C) using gaseous molecular fluorine (F2). A comprehensive characterization of these materials using various techniques, including X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and inductively coupled plasma analyses (ICP-AES) was conducted, and the evolution of LDH upon fluorination has revealed an intermediate porous texture particularly sensitive to hydration. Two original crystallographic phases are else obtained by fluorination: one formed by the hydration of the amorphous intermediate compound: Cu3Fe1.5Al0.5F12(H2O)12 an anti-perovskite structure and another stabilized through the combination of solid gas fluorination and LDH precursor yielding an original CoFeF5-type phase. Raman operando during cyclic voltammetry measurement applied on a sample fluorinated at 500 °C and used as a cathode in front of lithium metal was finally conducted to validate redox activity and mechanism. [ABSTRACT FROM AUTHOR]

The high-power ultrasonic irradiation of preformed magnetite (Fe3O4) nanoparticles in the presence of monoelectronic Ce-containing ceric ammonium nitrate [CeIV(NH4)2(NO3)6] oxidant in MeCOMe afforded hydrophilic 50 nm-sized colloidal, highly stable maghemite (γ-Fe2O3) nanoparticles. An "inorganid' Ce atom doping of the NP surface has been proposed in order to rationalize the observed nanoparticle antiaggregation phenomenon. Quite importantly, this method did not require the use of any organic ligand and/or polymer for the passivation of the nanoparticle surface. [ABSTRACT FROM AUTHOR]

The improvement of the Total Isomerization Process (TIP) for the production of high‐quality gasoline with the ultimate goal of reaching a Research Octane Number (RON) higher than 92 requires the use of specific sorbents to separate pentane and hexane isomers into classes of linear, mono‐ and di‐branched isomers. Herein we report the design of a new multi‐cage microporous Fe(III)‐MOF (referred to as MIP‐214, MIP stands for materials of the Institute of Porous Materials of Paris) with a flu‐e topology, incorporating an asymmetric heterofunctional ditopic ligand, 4‐pyrazolecarboxylic acid, that exhibits an appropriate microporous structure for a thermodynamic‐controlled separation of hydrocarbon isomers. This MOF produced via a direct, scalable, and mild synthesis route was proven to encompass a unique separation of C5/C6 isomers by classes of low RON over high RON alkanes with a sorption hierarchy: (n‐hexane≫n‐pentane≈2‐methylpentane>3‐methylpentane)low RON≫(2,3‐dimethylbutane≈i‐pentane≈2,2‐dimethylbutane)high RON following the adsorption enthalpy sequence. We reveal for the first time that a single sorbent can efficiently separate such a complex mixture of high RON di‐branched hexane and mono‐branched pentane isomers from their low RON counterparts, which is a major achievement reported so far. [ABSTRACT FROM AUTHOR]

The improvement of the Total Isomerization Process (TIP) for the production of high‐quality gasoline with the ultimate goal of reaching a Research Octane Number (RON) higher than 92 requires the use of specific sorbents to separate pentane and hexane isomers into classes of linear, mono‐ and di‐branched isomers. Herein we report the design of a new multi‐cage microporous Fe(III)‐MOF (referred to as MIP‐214, MIP stands for materials of the Institute of Porous Materials of Paris) with a flu‐e topology, incorporating an asymmetric heterofunctional ditopic ligand, 4‐pyrazolecarboxylic acid, that exhibits an appropriate microporous structure for a thermodynamic‐controlled separation of hydrocarbon isomers. This MOF produced via a direct, scalable, and mild synthesis route was proven to encompass a unique separation of C5/C6 isomers by classes of low RON over high RON alkanes with a sorption hierarchy: (n‐hexane≫n‐pentane≈2‐methylpentane>3‐methylpentane)low RON≫(2,3‐dimethylbutane≈i‐pentane≈2,2‐dimethylbutane)high RON following the adsorption enthalpy sequence. We reveal for the first time that a single sorbent can efficiently separate such a complex mixture of high RON di‐branched hexane and mono‐branched pentane isomers from their low RON counterparts, which is a major achievement reported so far. [ABSTRACT FROM AUTHOR]

A simple one-pot synthesis was utilized to prepare Mn-doped maghemite nanoparticles. A homogenized mixture of Mn- and Fe-acetylacetonates was heated in air atmosphere at 300 °C to produce Mn-doped maghemite. XRD showed only the presence of a spinel crystal structure with a linear increase of the unit-cell volume up to 20 mol% of the Mn dopant. Possible structural changes with increased Mn doping are briefly discussed.57Fe Mössbauer spectra recorded at 77 K were fitted with two sextets of lines corresponding to Fe3+ ions at A-tetrahedral and B-octahedral sites in maghemite. FE SEM images showed that Mn-doped maghemite nanoparticles were of good uniformity, with the crystallite size varying from 24 to 35 nm, as determined by XRD. [ABSTRACT FROM AUTHOR]

Microscopic and spectroscopic analyses were conducted on steel/bentonite interface samples removed from four in situ experiments that were carried out in three underground research laboratories at different temperatures and under different hydraulic and geochemical conditions. The results provide valuable information about the corrosion processes occurring in high‐level radioactive waste repositories. Systematic patterns can be deduced from the results, irrespective of carbon steel grade, type of bentonite and its degree of compaction, geochemical environment or experimental setup. Thus, a clear dependence of the corrosion rates on temperature and exposure period, as well as on the availability of H2O and O2 provided by the surrounding bentonite buffer, is observed. Furthermore, Fe(II) ions released by corrosion interact with the structural Fe in the clay. Recent developments highlight the usefulness of reactive transport modelling in understanding the coupled corrosion and Fe–clay interaction processes. [ABSTRACT FROM AUTHOR]

In this work, we investigate the effect of the reaction environment and the in situ formation of an iron precursor on the synthesis of iron oxide nanoparticles (IONPs) through thermal decomposition. Spherical IONPs with a spinel Fe3−xO4 structure were synthesized reproducibly through the thermal decomposition of iron stearate (Fe(stearate)2) assisted by oleic acid in octyl ether or eicosene solvents under air. Under similar conditions and by adjusting only the reaction environment, namely under argon, core–shell FeO@Fe3−xO4 NPs with the same sizes were obtained. On the other hand, the thermal decomposition of iron oleate (Fe(oleate)3) in the presence of a mixture of oleic acid and sodium oleate, under air and argon, leads to the formation of cubic-shaped NPs with a similar FeO@Fe3−xO4 structure. Cubic NPs with a homogenous Fe3−xO4 composition were synthesized from the iron oleate formed in situ from FeCl3·6H2O and sodium oleate reactants, which was immediately decomposed. The composition and shape dependence on the experimental conditions, i.e. atmosphere and iron complex, is discussed. The synthesized NPs were characterized by combining several techniques including transmission electron microscopy (TEM), scanning-TEM, X-ray diffraction (XRD) and 57Fe Mössbauer spectrometry. The correlation between the crystalline composition and the magnetic properties was investigated by carrying out magnetization measurements as a function of the applied field and temperature. The spherical and cubic-shaped NPs with a core–shell structure display exchange bias coupling due to the interaction between the antiferromagnetic (AFM) core and the ferrimagnetic (FiM) layer at the surface, while the Fe3−xO4 NPs exhibit a saturation magnetisation lower than that for the bulk counterpart due to the oxidation effects and the presence of a spin canted layer at their surface. [ABSTRACT FROM AUTHOR]

The catalytic properties of a chemically stable iron porphyrin MOF were evaluated in a reaction with ethyl diazoacetate. In contrast to its homogeneous counterpart, an Fe-porphyrin-MOF features a different reaction pathway leading to the formation of pyrazoline due to the confinement of catalytic sites within the MOF network. Unexpectedly, a sharp increase of the selectivity from 35% (run 1) to 86% (run 5) occurs upon catalyst recycling. [ABSTRACT FROM AUTHOR]

The thermal stability of Fe-8P (wt.%) ball milled powders was investigated by differential scanning calorimetry X-ray diffraction and 57Fe Mössbauer spectrometry. The effect of structural disorder is evidenced in the DSC thermogram by the presence of a large exothermic reaction consists of several overlapping peaks and spread over the temperature range (150-700)°C. The result of the Rietveld refinement of the XRD patterns indicates that during the annealing of the powders up to 210°C, three phases are observed: α-Fe(P), solid solution Fe3P and FeP phosphides. The Mössbauer spectra analyses show that the paramagnetic FeP phosphide phase is the only product after the annealing (∼ 2%). The annealing at 450°C leads to a mixture of α-Fe(P) solid solution, Fe3P nanophase and a small amount of a paramagnetic FexP (1 < x < 2) phosphide phase (∼ 3%) in addition to iron oxides. [ABSTRACT FROM AUTHOR]

The hydrothermal syntheses, structures, and magnetism of two new pyrochlore oxides of compositions (Na0.60Bi1.40)(Fe1.06Mn0.17Bi0.77)O6.87 and (K0.24Bi1.51)(Fe1.07Mn0.15Bi0.78)O6.86 are described. With preparation at 200 °C for 6 h in solutions of sodium or potassium hydroxide, the alkali metals introduced from these mineralizers are essential to the synthesis of the phases. The average long-range order of the pyrochlore structure, with space group Fd3m, was investigated and refined against X-ray and neutron diffraction data, and it was shown that disorder is present in both the metal and coordinating oxygen positions, along with metal-mixing across both the A and B sites of the structure. XANES analysis confirms the presence of Mn4+, mixed valence Bi3+ and Bi5+, and Fe3+, the last also verified by 57Fe Mössbauer spectroscopy. Magnetic measurements show a lack of long-range magnetic ordering that is typical of geometrically frustrated pyrochlores. The observed glasslike interactions occur at low temperatures, with the onset temperature depending upon the magnitude of the applied external field. Variable temperature X-ray diffraction shows that these pyrochlores are metastable and collapse on heating at ca. 395 °C, which suggests that their formation by conventional solid-state synthesis would be impossible. [ABSTRACT FROM AUTHOR]

Understanding the redox characteristic of the host geological layer is vital for radioactive waste management. In order to predict the radionuclides behavior during their release it must be thoroughly evaluated. This redox property could be affected by hydrogen gas which arises from the anaerobic corrosion of the stainless steel container. In this study, reduction methods using hydrogen gas or sodium dithionite as a reductive agent were tested on reference synthetic montmorillonites with various Fe(III) contents. The reduced samples were systematically studied with 57 Fe transmission Mössbauer spectrometry. After reduction with H 2 (g) in dry conditions, the Mössbauer spectra are characterized by hyperfine parameters located between those for Fe(III) and Fe(II), compared to reduction in water suspension with Na 2 S 2 O 4 (aq) and H 2 (g) which gives standard Fe(II) hyperfine parameters. The former results with dry H 2 (g) highlight an incomplete reduction and the possibility to have a Fe(III)–Fe(II) system with one-electron sharing. A natural clayrock sample, the Callovo-Oxfordian (COx), was also considered. The results above allowed its reduction to be evaluated. Much attention has also been focused on the modeling of the hyperfine spectra because of COx structure complexity. In addition, a hyperfine parameter data base was developed for a variety of Fe components based on an extensive literature review. This database provides additional statistical order to the study. This study highlights also that Mössbauer spectrometry remains a useful and non-destructive method to determine the reduction process and the reduction capacity of a reactant. Therefore we could estimate the redox property of the rock to evaluate and predict radionucleide behavior for nuclear waste management. [ABSTRACT FROM AUTHOR]

A magnetocaloric effect with wide tunability was observed in melt-spun amorphous Gd65Fe15-xCo5+xAl10Si5 (x = 0, 5, 10) alloys of different Fe/Co ratios. Their magnetic properties were compared with those of the previously investigated parent alloy Gd65Fe10Co10Al15. The glassy structure of the melt-spun samples was confirmed by X-ray diffraction (XRD) and 57Fe Mössbauer spectrometry. Their Curie temperatures (TC) were between 155 and 195 K and increased significantly with decreasing Co content. The highest value of the magnetic entropy change ΔSM = − 6.8 J/kg K was obtained for Gd65Fe5Co15Al10Si5, when the magnetic field was increased from 0 to 5 T. Refrigerant capacity (RC) takes values close to 700 J/kg for the whole series of the alloys. The occurrence of the second-order phase transition and the conformity of the magnetic behavior with the mean field model were concluded on the basis of the analysis of the universal curves and the values of the exponent n (ΔSM ∝ Hn). [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of [H3 dien]·(FeF6)·H2O (I) and [H3 dien]·(CrF6)·H2O (II) are obtained by solvothermal synthesis under microwave heating. I is orthorhombic (Pna21) with a=11.530(2)Å, b=6.6446(8)Å, c=13.787(3)Å, V=1056.3(2)Å3 and Z=4. II is monoclinic (P21 /c) with a=13.706(1)Å, b=6.7606(6)Å, c=11.3181(9)Å, β=99.38(1)°, V=1034.7(1)Å3 and Z=4. The structure determinations, performed from single crystal X-ray diffraction data, lead to the R 1/wR 2 reliability factors 0.028/0.066 for I and 0.035/0.102 for II. The structures of I and II are built up from isolated FeF6 or CrF6 octahedra, water molecules and triprotonated amines. In both structures, each octahedron is connected by hydrogen bonds to six organic cations and two water molecules. The iron-based compound is also characterized by 57Fe Mössbauer spectrometry: the hyperfine structure confirms the presence of Fe3+ in octahedral coordination and reveals the existence of paramagnetic spin fluctuations. [Copyright &y& Elsevier]

[FeIII(H2O)(O3P– (CH2)–CO2)] or MIL-49 was hydrothermally synthesized under autogenous pressure at 170°C for 48 h. Its bidimensional structure was solved from single-crystal X-ray diffraction in the monoclinic space group P21/c (No.14). Cell parameters are a =9.3836(3) A˚, b=6.3798(3) A˚, c=10.1371(3) A˚, β=111.891(2)°, Z=4, and V=563.10(4) A˚3. Reliability factors of the structure refinement are R1(F)=0.0470 and wR2(F2)=0.1297 for 1036 reflections with I>2σ(I). The structure of MIL-49 is based on inorganic units built up from two edge-sharing [FeO5(H2O)] octahedra and two carboxymethylphosphonate groups. The connection of these units leads to the formation of hybrid sheets. A dangling oxygen atom from the carboxy function points toward the interlayer space and is responsible for hydrogen bonding with adjacent layers. Magnetic measurements and 57Fe Mo¨ssbauer study reveal an antiferromagnetic ordering below TN=25(1) K which becomes canted below 11(1) K. [ABSTRACT FROM AUTHOR]

Discusses the hydrothermal synthesis, structure and magnetic properties of a novel monodimensional iron phosphate. Representation of a series of amine-templated oxyfluoronated metallophosphates with open structures in the ULM-n family; Supposition of the extent of oligomeric condensation of ULM-n as controlled by the charge density of the amines.

Fe-glycolate wires with micrometer-scale lengths can be synthesized by the polyol process. Although the as-produced wires are in the paramagnetic state at room temperature, they are transformed into ferrimagnetic iron oxides and ferromagnetic metallic iron wires by reductive annealing. The shape of the wires is unchanged by reductive annealing, and it is possible to control the magnetic properties of the resulting wire-shaped ferri/ferromagnets by adjusting the annealing conditions. Consequently, the reductive annealing of polyol-derived Fe-glycolate wires is an effective material-processing route for the production of magnetic wires. [ABSTRACT FROM AUTHOR]

Hetero-nanostructures based on magnetic contrast oxides have been prepared as highly dense nanoconsolidates. Cobalt ferrite-cobalt oxide core-shell type nanoparticles (NPs) were synthesized by seed mediated growth in polyol and subsequently consolidated by Spark Plasma Sintering (SPS) at 500 °C for a few minutes while applying a uniaxial pressure of 100 MPa. It is interesting to note that the exchange bias feature observed in the core-shell NPs is reproduced in their ceramic counterparts, or even attenuated. A systematic structural characterization was then carried out to elucidate the decrease in the exchange magnetic field, involving mainly advanced X-ray diffraction, zero-field and in-field 57Fe Mössbauer spectrometry, magnetic measurements and electron microscopy. [ABSTRACT FROM AUTHOR]

The present study investigates the magnetic properties of spherical monodispersed maghemite (γ-Fe2O3) nanoparticles coated with multiple silica (SiO2) layers of different thicknesses, forming core-shell multifunctional nanomaterials. This study was performed using a combination of local probe techniques (Mössbauer spectrometry) and magnetization measurements. At room temperature, both techniques confirm the superparamagnetic state of the samples, even after being coated with the SiO2 shells. The zero-field-cooling-field-cooling magnetization curves of the silica-coated γ-Fe2O3 nanomaterials with different shell thicknesses allow the evaluation of the intensity of the interparticle dipole-dipole interactions. We estimate the interparticle energy within the framework of dipolar interaction models and relate it with the hyperfine parameters. We further observe that this dipole-dipole interaction increases the superparamagnetic energy barrier, which largely depends on the interparticle distance. Finally, we consider the effect of spin canting at the surface ('dead layer') of uncoated γ-Fe2O3 nanoparticles manifested by a layer of ∼0.5(1) nm. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • γ-irradiation was explored for the synthesis of magnetic iron oxide/Au NPs. • A redox reaction occurs between solid-state Fe(OH) 2 and Au3+ ions. • Obtained nanostructures consist of feroxyhyte nanodiscs decorated with AuNPs. • Feroxyhyte@Au material shows a high catalytic activity for the reduction of 4-NP. γ-irradiation was used as an effective and environmentally friendly technique for the synthesis of magnetic iron oxide/Au nanostructures. Firstly, alkaline iron(III) precursor solutions, in the presence of 2-propanol and DEAE-dextran, were purged with nitrogen and γ-irradiated to doses of 14 and 75 kGy, which resulted in the reduction of Fe3+ to Fe2+ ions and formation of Fe(II)/Fe(III) or Fe(II) iron (hydr)oxide phases. After irradiation, gold nanoparticles (AuNPs) were attached to the surface of the magnetic nanostructures by in situ reduction of Au3+ with radiolytically formed Fe2+. At 75 kGy, simultaneous oxidation of Fe(OH) 2 formed on irradiation and reduction of Au3+ led to the formation of superparamagnetic feroxyhyte (δ-FeOOH) nanodiscs decorated with well distributed, 11–24 nm AuNPs. The experiments performed with and without Fe(III) precursor and 2-propanol or tert -butanol as scavenger and in different atmospheres (N 2 , N 2 O) confirmed the main role of Fe2+ in Au3+ reduction. The catalytic activity of the δ-FeOOH/Au nanostructures was tested for the reduction of 4-nitrophenol to 4-aminophenol. Increasing the amount of added Au3+ enhanced the catalytic activity of the samples, but up to a certain amount depending on the size of formed AuNPs. [ABSTRACT FROM AUTHOR]

The effects of weathering and decompaction on the Opalinus Clay in northern Switzerland were studied on the basis of a 146 m long drillcore profile. Below 6 m of Quaternary sediments, the rock down to 16 m depth is affected by partial or complete dissolution of siderite, calcite, pyrite and organic matter, with goethite as the only identified product. The reduction level of Fe (Fe2+/Fe tot) in the rock increases with depth from <20% to >80% in unweathered rock below 24 m. Porosity reaches 0.39 in the shallowest samples before dropping to normal values of around 0.13 below 30 m. Pore-water composition obtained by rock squeezing evolves with depth from fresh water of the Ca-SO 4 -HCO 3 type to a 10–12 g/L Na-SO 4 -Cl type in unweathered rock below 40 m. Ground-water samples taken in the weathered zone indicate reducing conditions at present and therefore reflect a remaining redox buffering capacity even in the strongly oxidised rock. The interpretation of the rock properties, in conjunction with the chemical and isotopic signatures of ground and pore waters, suggests that substantial weathering occurred primarily during stages with a lower ground-water table in the Pleistocene, providing access to oxygen via gas diffusion across the partially unsaturated zone. Three evolutionary stages can be distinguished: 1) Long-term pyrite oxidation during Pleistocene surface exposure under dry climate and diffusive transport of SO 4 2− into the formation. This explains the higher SO 4 2− pore-water concentrations even in the unweathered rock at depth when compared to regional data from deep boreholes. 2) Build-up of the curved Cl− and water-isotope diffusion profiles since ∼50–60 ka with a depth penetration of 40–80 m. 3) Holocene rise of the water table, leading to self sealing of fractures and the establishment of a diffusive regime in the weathered zone. Under saturated conditions, the depth penetration of rock oxidation is quite limited, which illustrates the substantial buffering capacity of the Opalinus Clay against external geochemical disturbances. • Weathering effects include increased porosity, mineral dissolution and precipitation of goethite • Weathering occurred mainly during arid periods with low water table and oxygen supply via fractures • The fracture system self sealed upon Holocene rise of the water table, a diffusive system developed • Surface effects on pore-water composition reach depths of 50–80 m, well below the weathered zone • The Opalinus Clay has a high redox buffering capacity even in the weathered zone. [ABSTRACT FROM AUTHOR]

The reactivity of potassium or sodium hexacyanoferrate(II) with transition-metal layered simple hydroxides (LSHs) has been investigated to evaluate the possibility of inserting Prussian Blue analogues (PBAs) into magnetic copper(II) LSHs. This report shows how such a reaction led, unexpectedly, to the direct formation of PBA nanoparticles, the layered hydroxide serving as a metal-ion reservoir. The lamellar structure of the starting LSH collapses and copper-iron PBA nanoparticles were obtained as well-defined cubic structures stacked in layers. In addition to structural and magnetic characterization, the reaction mechanism was investigated by 57Fe Mössbauer spectrometry and X-ray photoemission spectroscopy. The layered copper hydroxide acetate turns out to be a smart precursor of well-shaped PBA nanoparticle layers through pseudomorphic replication. [ABSTRACT FROM AUTHOR]

The exploration of the composition space diagram of the FeF3/ZnF2-Hamtetraz-HFaq system (Hamtetraz = 5-aminotetrazole) by solvothermal synthesis at 160 °C for 72 h in dimethylformamide (DMF) has evidenced five new hybrid fluorides (1-5); the structures are characterized from single crystal X-ray diffraction data. [Hdma]·(ZnFeIII(H2O)4F6) (1) and [Hdma]·[Hgua]2·(FeIIIF6) (2) contain anionic inorganic chains (1) or isolated octahedra (2) weakly hydrogen bonded (Class I hybrids) to dimethylammonium (Hdma) and/or guanidinium (Hgua) cations which are produced from the tetrazole ligand and solvent decomposition. [Hdma]2·[Hgua]·[NH4]·[ZnFeIIIF5(amtetraz)2]2 (3), [Hdma]2·[Zn1.6FeII0.4FeIIIF6(amtetraz)3] (4), and [Hdma]·[Zn4F5(amtetraz)4] (5) are considered as Class II hybrids in which the (amtetraz)− anions are strongly linked to divalent metal cations via N-M bonds. In 3, ∞{[NH4]·[ZnFeIIIF5(amtetraz)2]2} layers are separated by [Hdma]+ and [Hgua]+ cations. 4 and 5 exhibit three-dimensional (3D) hybrid networks that contain small cavities where [Hdma]+ cations are inserted. A porous 3D metal-organic framework intermediate is evidenced from the thermogravimetric analysis and X-ray thermodiffraction of 5. [ABSTRACT FROM AUTHOR]

The exploration of the FeF3/FeF2-Hamtetraz-HF system in dimethylformamide by solvothermal synthesis evidences two isostructural 3D hybrid fluoroferrates. They are prepared from the same starting mixture at two different synthesis temperatures: 120 °C for [Hdma]·(Fe4IIFeIIIF8(H2O)2(amtetraz)4) (1) and 140 °C for [Hdma]1.5·(Fe4.5IIFe0.5IIIF7(H2O)(HCOO)(amtetraz)4) (2). Both compounds are characterized by single crystal X-ray diffraction, X-ray thermodiffraction, TGA analysis, Mössbauer spectrometry and SQUID magnetometry. They crystallize in the monoclinic system and are built from two distinct chains connected by aminotetrazolate anions. The first chain ∞(FeIIFN4) is common to 1 and 2 and can be found in numerous fluorides. In the second chain ∞(Fe3X12) (X = F, N, O), iron cations adopt both valence states Fe(ii)/Fe(iii). The hydrolysis of DMF implies the formation of a [Hdma]+ cation and a (HCOO)− anion. The presence of Fe3+ in both phases is evidenced by 57Fe Mössbauer spectrometry. The magnetic properties are studied and two transitions from a paramagnetic regime to a long range ordered state below 30 K and 5 K are identified. [ABSTRACT FROM AUTHOR]

Three new [H 2 amtaz ] + iron fluorides are synthesized at 160 °C under microwave heating from FeF 2 , FeF 3 , 3-amino-1,2,4-triazole (H amtaz ), HF aqueous solution and ethanol. The exploration of this system shows that the dimensionality of the inorganic networks increases with the HF/(H amtaz ) ratio in the starting solution. The structures of [H 2 amtaz ] 3 ·(Fe III F 6 ) (0D) and [H 2 amtaz ] 2 ·(Fe III F 5 ) (1D), obtained for HF/(H amtaz ) ratios equal to 1 and 2.3, are built up from monoprotonated organic cations and isolated FeF 6 octahedra or ∞ [FeF 5 ] chains, respectively. For HF/(H amtaz ) = 8, ∞ [Fe III 2 Fe II F 10 (H 2 amtaz ) 2 ] layers (2D), resulting from the association of Fe II F 4 N 2 entities and ∞ [FeF 5 ] chains, appear in Fe III 2 Fe II F 10 (H 2 amtaz ) 2 . Interestingly, these puckered HTB-type layers are neutral. The 57 Fe Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in Fe III 2 Fe II F 10 (H 2 amtaz ) 2 ; their proportions 0.65(1)/0.35(1) at 77 K are in fair agreement with the ratio deduced from the crystallographic determination. The presence of dominant antiferromagnetic interactions in Fe III 2 Fe II F 10 (H 2 amtaz ) 2 as evidenced by magnetization measurements, combined to the cationic topology favors a highly frustrated magnetic structure in the HTB-type layers which results in a very large Θ P / T N ratio (the Curie–Weiss paramagnetic temperature is Θ P = −350 K while the magnetic order temperature is T N = 18 K). [ABSTRACT FROM AUTHOR]

Reaction of iron(IIII)chloride with the free base tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) in the presence of different bases leads to the formation of a series of iron/porphyrin metal-organic frameworks. Such a crystal engineering approach led to the obtaining of four structures presenting three different topologies and inorganic secondary building units. Depending on the synthesis conditions, isolated FeIII octahedra, diiron(II) paddle wheel dimers, or extended [FeIII(OH)O4]n chains could be obtained in a controlled manner. The influence of the synthetic conditions on the final structure and the oxidation state of iron is discussed. Stability of the porous solids towards air and water is studied, and their intrinsic porosity is assessed. [ABSTRACT FROM AUTHOR]

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (AlFeIIIFeIIMgLiMn)(SiAl)O(OH)] and chlorite CCa-2 from Flagstaff Hill, California [USA; (SiAl)(AlFeIIIMgFeIIMnCa)O(OH)]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738-4749, ) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature. [ABSTRACT FROM AUTHOR]

We report, for the first time, the synthesis of magnetically contrasted oxide-based core-shell nanoparticles using the polyol process. Iron oxide nanoparticles were first prepared by forced hydrolysis of iron acetate salt in a polyol and were then recovered by centrifugation and re-dispersed in a fresh cobalt acetate polyol solution. The microstructure of the resulting powder was finely characterized combining X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Interestingly, the produced particles appeared to be of a very high crystalline quality with a perfect epitaxy between the spinel-like iron oxide core and the rock-salt-like cobalt monoxide shell, leading to a substantial exchange bias at low temperatures. As a consequence, a net blocking temperature, T, increase was measured on the superparamagnetic iron oxide cores when they were coated by CoO, reaching a T value of 298 K, very close to room temperature. [ABSTRACT FROM AUTHOR]

The solvothermal reactions of an equimolar mixture of FeF2 and FeF3 with Htaz (1,2,4-triazole), aqueous HF and DMF (dimethylformamide) at 120 °C yielded a series of new hybrid fluoroferrates (1–5). Their structures were characterized by either single crystal or powder X-ray diffraction data analysis. Both classes of hybrid networks were observed according to the Fen+/Htaz/HF starting ratio: class I for 1 and 2 and class II for 3, 4 and 5. Four compounds, [Hdma]·(Fe2(H2O)4F6) (1), [Hdma]·(Fe2(H2O)4F6)·0.5H2O (2), Fe2F5(Htaz) (3) and [Hdma]·(Fe2F5(H2O)(Htaz)(taz)) (4), exhibit both Fe(ii) and Fe(iii) oxidation states while [Hdma]·(Fe2F5(taz)2) (5) contains only Fe(iii) cations. [Hdma]·(Fe2(H2O)4F6) (1) and [Hdma]·(Fe2(H2O)4F6)·0.5H2O (2) contain anionic inorganic chains of alternating corner-sharing Fe(ii) and Fe(iii) octahedra; they are weakly hydrogen bonded to dimethylammonium cations [Hdma]+ which are formed by the in situ hydrolysis of DMF. The structure of Fe2F5(Htaz) (3) exhibits a three dimensional inorganic network resulting from the association of HTB planes of corner sharing FeIIF4N2 and FeIIIF6 octahedra. [Hdma]·(Fe2F5(H2O)(Htaz)(taz)) (4) and [Hdma]·(Fe2F5(taz)2) (5) reveal two original two-dimensional sheets. In 4, the deprotonated and neutral amines connect trinuclear Fe3F10N6 units of corner-sharing octahedra and mononuclear FeN4(H2O)2 octahedra. Infinite Fe2F5(taz)2 layers in 5 are built up from dinuclear species connected by deprotonated amines along two perpendicular directions. The thermal behavior and Mössbauer spectrometry results are detailed for the first tridimensional mixed valence hybrid fluoroferrate (3). [ABSTRACT FROM AUTHOR]

The stability of clay minerals is an important factor in assessing the durability of containment barriers for deep waste storage. In that context, the complete thermodynamic data set of three 2:1 ferro-magnesian clay minerals have been determined at 1 bar and from 2 to 520 K, using calorimetric methods. The studied clay samples were, respectively, the Na-saturated saponite Sap-Ca-1, Na0.394 K0.021Ca0.038(Si3.569Al0.397Fe0.0343+)(Mg2.948Fe0.0212+Mn0.001)O10(OH)2, the Ca-saturated nontronite NAu-1, Ca0.247K0.020(Si3.458Al0.542)(Mg0.066Fe1.6883+Al0.268Ti0.007)O10(OH)2, and the Ca-saturated Santa Olalla vermiculite, Ca0.445(Si2.778Al1.222)(Al0.192Mg2.468Fe0.2263+Fe0.0282+Ti0.018Mn0.007)O10(OH)2. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K. The heat capacities were measured between 2 and 520 K, using low-temperature adiabatic calorimetry, heat-pulse calorimetry, and differential scanning calorimetry. The standard entropies and the Gibbs free energies of formation at 298.15 K have been calculated from these values. Finally, the equilibrium constants at 298.15 K have been determined. A comparison between these experimental data and estimated values obtained from prediction models available in the literature enabled the most usual calculation methods available to date to be assessed for each thermodynamic property. [ABSTRACT FROM AUTHOR]

Mixed-metal iron--vanadium analogues of the 1,4-benzenedicarboxylate (BDC) metal--organic framework MIL-53 have been synthesized solvothermally in N,N'-dimethylformamide (DMF) from metal chlorides using initial Fe:V ratios of 2:1 and 1:1. At 200°C and short reaction time (1 h), materials (Fe,V)II/IIIBDC(DMF1--xFx) crystallize directly, whereas the use of longer reaction times (3 days) at 170°C yields phases of composition [(Fe,V)III0.5(Fe,V)0.5II(BDC)(OH,F)]0.5-·0.5DMA+ (DMA = dimethylammonium). The identity of the materials is confirmed using high-resolution powder X-ray diffraction, with refined unit cell parameters compared to known pure iron analogues of the same phases. The oxidation states of iron and vanadium in all samples are verified using X-ray absorption near edge structure (XANES) spectroscopy at the metal K-edges. This shows that in the two sets of materials each of the vanadium and the iron centers are present in both +2 and +3 oxidation states. The local environment and oxidation state of iron is confirmed by 57Fe Mössbauer spectrometry. Infrared and Raman spectroscopies as a function of temperature allowed the conditions for removal of extra-framework species to be identified, and the evolution of μ2-hydroxyls to be monitored. Thus calcination of the mixed-valent, mixed-metal phases [(Fe,V)III0.5(Fe,V)0.5II(BDC)(OH,F)]0.5-·0.5DMA+ yields single-phase MIL-53-type materials, (Fe,V)III(BDC)(OH,F). The iron-rich, mixed-metal MIL-53 shows structural flexibility that is distinct from either the pure Fe material or the pure V material, with a thermally induced pore opening upon heating that is reversible upon cooling. In contrast, the material with a Fe:V content of 1:1 shows an irreversible expansion upon heating, akin to the pure vanadium analogue, suggesting the presence of some domains of vanadium-rich regions that can be permanently oxidized to V(IV). [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline Fe–44Co–6Mo (wt.%) powders have been prepared by high-energy ball milling from elemental Fe, Co and Mo pure powders in a P7 planetary ball mill. The obtained powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Mössbauer spectrometry techniques. The influence of milling process and Mo substitution for Co in equiatomic FeCo have been examined in order to study structural evolution and formation mechanism of nanostructured Fe(CoMo) solid solution. XRD results show the formation of a BCC Fe(CoMo) solid solution (a = 0.2874 nm) where unmixed nanocrystalline Mo with a BCC structure is embedded. Disordered Fe(CoMo) solid solution is characterized by a broad hyperfine magnetic field distribution with two regions centered at B 1 = 35.0 T and B 2 = 30.7 T, respectively, attributed to disordered Fe(Co) solid solution and CoMo enriched environments. Prolonged milling and Mo addition cause the decrease of average hyperfine magnetic field while the average isomer shift remains nearly constant. [Copyright &y& Elsevier]

Abstract: We present a numerical study of the magnetic structure of nanostructured iron fluoride, using the Monte Carlo Metropolis simulated annealing technique and a classical Heisenberg Hamiltonian with superexchange angle dependent interactions. The parameters are adjusted on experimental results, and the atomic structure and topology taken from a previous atomistic model of grain boundaries in the same system. We find perfect antiferromagnetic crystalline grains and a disordered magnetic configuration (speromagnetic) at the grain boundary, in agreement with experimental features. Both the lowest magnetic energy and the rate of magnetic frustration are found to be dependent on the relative disorientation of crystalline grains, i.e. on the cationic topology. We conclude on possible extensions of the model. [Copyright &y& Elsevier]

A nanopyrite/greigite composite was synthesized by reacting FeCl3 and NaHS in a ratio of 1:2 (Wei et al. 1996). Following this procedure, the obtained solid phases consisted of 30-50 nm sized particles containing 28% of greigite (Fe2+Fe3+2S4) and 72% pyrite (FeS2). Batch reactor experiments were performed with selenite or selenate by equilibrating suspensions containing the nanosized pyrite-greigite solid phase at different pH-values and with or without the addition of extra Fe2+. XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe2) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se0, the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system. [ABSTRACT FROM AUTHOR]

Abstract: The intracellular biosynthesis of superparamagnetic (blocking temperature 5.6K) 2-lines ferrihydrite (Fh2L) nanoparticles was observed within living Euglena gracilis microalgae. [Copyright &y& Elsevier]

Superparamagnetic ferrite nanoparticles (MFe2O4, where M = Fe, Co, Mn) were synthesized through a novelone-stepaqueous coprecipitation method based on the use of a new type of alkalineagent: the alkanolamines isopropanolamine and diisopropanolamine.The role played by the bases on the particles’ size, chemicalcomposition, and magnetic properties was investigated and compareddirectly with the effect of the traditional inorganic base NaOH. Thenovel MFe2O4nanomaterials exhibited high colloidalstability, particle sizes in the range of 4–12 nm, and superparamagneticproperties. More remarkably, they presented smaller particle sizes(up to 6 times) and enhanced saturation magnetization (up to 1.3 times)relative to those prepared with NaOH. Furthermore, the nanomaterialsexhibited improved magnetic properties when compared with nanoferritesof similar size synthesized by coprecipitation with other bases orby other methods reported in the literature. The alkanolamines wereresponsible for these achievements by acting both as alkaline agentsand as complexing agents that controlled the particle size duringthe synthesis process and improved the spin rearrangement at the surface(thinner magnetic “dead” layers). These results opennew horizons for the design of water-dispersible MFe2O4nanoparticles with tuned properties through a versatile andeasily scalable coprecipitation route. [ABSTRACT FROM AUTHOR]

Abstract: Stacking faults probability, structure and microstructure parameters of different phases of ball milled Fe–50%Co powders have been quantitatively evaluated by X-ray diffraction profile analysis. It is observed that after short milling time, Co is found to undergo an allotropic transformation from FCC to HCP form. The Rietveld whole profile fitting results reveal an increase of the stacking fault probability with increasing milling time and that twin faults are more prevalent than deformation ones. In addition to the reduction of crystallite size to the nanometer level and the increase of internal strain, prolonged milling leads to the formation of a BCC Fe(Co) solid solution with a high dislocations density (3.8×1017 m−2). [Copyright &y& Elsevier]

The synthesis on the gram scale and characterization of a series of flexible functionalized iron terephthalate MIL-53(Fe) type solids are reported. Chemical groups of various polarities, hydrophilicities, and acidities (-Cl, -Br, -CF3, -CH3, -NH2, -OH, -CO2H) were introduced through the aromatic linker, to systematically modify the pore surface. X-ray powder diffraction (XRPD), molecular simulations, thermogravimetric analyses, and in situ IR and 57Fe Mössbauer spectrometries indicate some similarities with the pristine MIL-53(Fe) solid, with the adoption of the narrow pore form for all solids in both the hydrated and dry forms. Combined XRPD and computational structure determinations allow concluding that the geometry of the pore opening is predominantly correlated with the intraframework interactions rather than the steric hindrance of the substituent. Only (MIL-53(Fe)-(CF3)2) exhibits a nitrogen accessible porosity (SBET ≈ 100 m2 g-1). The adsorption of some liquids leads to pore openings showing some very specific behaviors depending on the guest-MIL-53(Fe) framework interactions, which can be related to the energy difference between the narrow and large pore forms evaluated by molecular simulation. [ABSTRACT FROM AUTHOR]

Bentonite, a common smectite-rich buffer material, is in direct contact with corroding steel in many high-level radioactive waste repository designs. The interaction of iron with the smectite-rich clay may affect its swelling and sealing properties by processes such as alteration, redox reactions and cementation. The chemical interactions were investigated by analysing the Fe/clay interfaces of eight bentonite blocks which had been exposed to temperatures up to 130 °C for five years in the ABM2 borehole at the Äspö Hard Rock Laboratory managed by the Swedish Nuclear Fuel and Waste Management Co (SKB). Eleven interface samples were characterised by high spatial resolution methods, including scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and μ-Raman spectroscopy as well as by "bulk" methods X-ray diffraction, X-ray fluorescence and 57Fe Mössbauer spectrometry. Corrosion induced an iron front of 5–20 mm into the bentonite, except for the high-Fe bentonite where no Fe increase was detected. This Fe front consisted mainly of ferric (oxyhydr)oxides in addition to the structural Fe in the smectite fraction which had been partially reduced by the interaction process. Fe(II) was also found to extend further into the clay, but its nature could not be identified. The consistent behaviour is explained by the redox evolution, which shifts from oxidising to reducing conditions during the experiment. No indication of smectite alteration was found. [ABSTRACT FROM AUTHOR]

Abstract: The redox properties of FeII adsorbed onto a series of FeIII (oxyhydr)oxides (goethite, lepidocrocite, nano-sized ferric oxide hydrate (nano-FOH), and hydrous ferric oxide (HFO)) have been investigated by rest potential measurements at a platinum electrode, as a function of pH (−log10[H+]) and surface coverage. Using the constant capacitance surface complexation model to describe FeII adsorption onto these substrates, theoretical values of the suspension redox potential (E H) have been computed, under the assumption that FeII adsorption occurs at crystal growth sites of the substrate surface. Good agreement between calculated and experimental E H values is observed for nano-FOH and HFO, however the redox potentials measured for lepidocrocite and goethite are significantly more oxidizing than predicted. Mössbauer spectroscopic analysis of 57FeII adsorbed onto HFO and goethite shows that in both cases the adsorbed 57FeII is incorporated into the crystal structure of the substrate, in broad agreement with the thermodynamic model, but is almost completely oxidized to 57FeIII. The mechanism by which the adsorbed 57FeII is oxidized is not resolved in this work, but is thought to be due to electron transfer to the substrate, rather than a net oxidation of the suspension. The disagreement between experimental and calculated rest potential measurements in the goethite and lepidocrocite systems is thought to be due to the poor electrochemical equilibration of these suspensions with the platinum electrode, rather than a failure of the thermodynamic model. The model developed for the redox potential of adsorbed FeII allows direct assessment of the reactivity of this species towards oxidized pollutants. [Copyright &y& Elsevier]

Hundred nanometers outer diameter multi-walled carbon nanotubes have been used as suitable host template for synthesizing CoFe2O4 nanowires encapsulated inside nanotubes under mild conditions, i.e. 100 °C and atmospheric pressure, with a high filling yield of the nanotubes, using an aqueous nitrate precursor solution and the confinement effect provided by the surrounding walls. The formation of caps near the tube tips at the beginning of the nitrate decomposition led to consider each nanotube as a closed nanoreactor, in which the reaction conditions could be far different from the macroscopic conditions outside the tube. The structure of the CoFe2O4 nanowires could be continuously changed from a disordered hair-like dendritic structure at 100 °C to highly crystallized domains when increasing the temperature. A material with high coercivity at room temperature for small particles of about 25 nm in diameter was obtained by submitting the nanowires to an Ar treatment at 550 °C for 2 h. [Copyright &y& Elsevier]

The two-dimensional (2D) iron trimellitate [Fe(H[sub 2]O)[sub 2](C[sub 9]O[sub 6]H[sub 4])]·H[sub 2]O, labeled MIL-67, has been obtained under hydrothermal conditions (473 K, 48 h). In the 2D structure of MIL-67, the Fa[sup 2+] ions display two different octahedral environments: [FeO[sub 4](H[sub 2]O)[sub 2]] and [FeO[sub 2](H[sub 2]O)[sub 4]]. These octahedra share an apical water molecule to form infinite chains. The chains are linked by partly deprotonated C[sub 9]O[sub 6]H[sub 4, sup 2-] anions to give hybrid organic-inorganic layers; the remaining acidic-CO[sub 2]H group is dangling in the interlayer space. Below 8(1) K, MIL-67 displays a canted antiferromagnetic behavior, according to analyses via magnetic measurements and Mössbauer spectroscopy. Crystal data for MIL-67 are as follows: triclinic; space group P&1macr; (No. 2), with a = 6.9671(2) Å, b = 7.3089(3) Å, c = 12.5097(3) Å, α = 78.758(1)°, β = 89.542(2)°, and γ = 65.197(1)°; volume V = 565.21(3) ų; and Z = 2. [ABSTRACT FROM AUTHOR]

Magnetic polymer gels are a new promising class of nanocomposite gels. In this work, magnetic PEO/iron oxide nanocomposite hydrogels were synthesized using the one-step γ-irradiation method starting from poly(ethylene oxide) (PEO) and iron(III) precursor alkaline aqueous suspensions followed by simultaneous crosslinking of PEO chains and reduction of Fe(III) precursor. γ-irradiation dose and concentrations of Fe3+, 2-propanol and PEO in the initial suspensions were varied and optimized. With 2-propanol and at high doses magnetic gels with embedded magnetite nanoparticles were obtained, as confirmed by XRD, SEM and Mössbauer spectrometry. The quantitative determination of γ-irradiation generated Fe2+ was performed using the 1,10-phenanthroline method. The maximal Fe2+ molar fraction of 0.55 was achieved at 300 kGy, pH = 12 and initial 5% of Fe3+. The DSC and rheological measurements confirmed the formation of a well-structured network. The thermal and rheological properties of gels depended on the dose, PEO concentration and initial Fe3+ content (amount of nanoparticles synthesized inside gels). More amorphous and stronger gels were formed at higher dose and higher nanoparticle content. The properties of synthesized gels were determined by the presence of magnetic iron oxide nanoparticles, which acted as reinforcing agents and additional crosslinkers of PEO chains thus facilitating the one-step gel formation. [ABSTRACT FROM AUTHOR]

A new metal organic framework (MOF) built up from non-toxic iron and the therapeutically active linker nicotinic acid, with pellagra-curative, vasodilating, and antilipemic properties, has been isolated and characterised viasingle crystal methods. The release of the therapeutic agent, which is a constituent of the framework, is achieved through the degradation of the hybrid phase, under simulated physiological conditions, allowing for the delivery of the bioactive molecule. [ABSTRACT FROM AUTHOR]

Cobalt ferrite ferrimagnetic nanoparticles (NPs) are prepared and used in this work as seeds to grow a thin antiferromagnetic poly‐ and nanocrystalline CoO shell. The major purpose is to study systematically the characteristics of the as‐produced powders, making emphasis on their internal crystallographic arrangement and their magnetic properties. 57Fe Mössbauer spectrometry evidences an evolution of the cation distribution among the spinel lattice in the cobalt ferrite core during the core–shell NPs processing. High‐resolution transmission electron microscopy shows a perfect epitaxy between the face‐centered cubic lattices of the spinel core and the rock‐salt shell. Finally, the measurements of 7T‐field‐cooled magnetic hysteresis loops at low temperature (5 K) of the composite particles exhibit a strong exchange bias coupling with an exchange field, µ0HE, of 365 mT and an enhanced coercive field, µ0HC, of 1395 mT. These values are very high compared to those of differently prepared CoO‐based oxide composite NPs and for which a giant exchange‐bias is reported. These features are attributed to the favorable material processing conditions offered by the polyol process in terms of crystalline quality, particularly at the interfaces, and for the pinning action exerted by the CoO phase on the magnetization of the CoFe2O4 phase. Oxide‐based core–shell like nanoparticles are produced by the polyol process. Their advanced structural and microstructural characterization highlighted their very exceptional crystallographic quality, making them able to exhibit giant EB feature. [ABSTRACT FROM AUTHOR]