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We investigated the effect of annealing temperature on magnetic properties of 2% and 10% Fe-doped BaTiO3. To understand the possible structural differences between samples treated at different annealing temperatures, and to correlate them with the magnetic properties, several characterization techniques, such as X-ray diffraction and X-ray absorption spectroscopic methods ( XANES and EXAFS) were employed. We found that the 2% Fe-doped BaTiO3 pseudocubic perovskite is paramagnetic regardless of the heat-treatment conditions. Initially paramagnetic 10% Fe-doped 6H-BaTiO3, treated at 1250°C, became ferromagnetic after additional annealing at higher temperature. We have crystalographically characterized the cation ordering processes in the 6H-BaTiO3 that occurred during the high-temperature annealing. The ferromagnetism that is induced in this stage is most probably associated with the observed diffusion processes but it extrinsic character still cannot be fully disregarded. [ABSTRACT FROM AUTHOR]

Iron insufficiency is a worldwide problem in human diets. In cereals like wheat, the bran layer of the grains is an important source of iron. However, the dietary availability of iron in wheat flour is limited due to the loss of the iron-rich bran during milling and processing and the presence of anti-nutrients like phytic acid that keep iron strongly chelated in the grain. The present study investigated the localization of iron and phosphorus in grain tissues of wheat genotypes with contrasting grain iron content using synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-proton-induced X-ray emission (micro-PIXE). X-ray absorption near-edge spectroscopy (XANES) was employed to determine the proportion of divalent and trivalent forms of Fe in the grains. It revealed the abundance of oxygen, phosphorus, and sulphur in the local chemical environment of Fe in grains, as Fe-O-P-R and Fe-O-S-R coordination. Contrasting differences were noticed in tissue-specific relative localization of Fe, P, and S among the different genotypes, suggesting a possible effect of localization pattern on iron bioavailability. The current study reports the shift in iron distribution from maternal to filial tissues of grains during the evolution of wheat from its wild relatives to the present-day cultivated varieties, and thus suggests the value of detailed physical localization studies in varietal improvement programmes for food crops. [ABSTRACT FROM AUTHOR]

ZnFeO bulk material shows a normal-spinel structure and a closely defined composition at Zn/Fe ≅ 0.5. However, the composition of zinc ferrite, prepared as nanoparticles, can be varied in a broad range without losing the single-phase spinel structure. In this article, structural mechanisms enabling this non-stoichiometry were studied using the X-ray absorption fine structure (EXAFS) in combination with X-ray diffractometry (XRD), transmission electron microscopy (TEM), and magnetic measurements. Nanoparticles with a narrow size distribution were synthesized using co-precipitation in water-in-oil microemulsions. First, the structure of the stoichiometric zinc-ferrite nanoparticles was studied in dependence of their size and the annealing temperature. EXAFS analysis showed that the degree of inversion x (as defined in the compound formula (ZnFe)[FeZn]O, with round and square brackets representing the tetrahedral and octahedral sites, respectively) increased with decreasing nanoparticles size. The structure of the stoichiometric nanoparticles and the nanoparticles of comparable size displaying Zn/Fe ratio of 0.2 (Fe-rich) and 0.7 (Zn-rich) were then compared. Analysis showed that the non-stoichiometry is structurally compensated predominantly in the core of the nanoparticle by the adjusted distribution of Zn and Fe ions over the two sublattices of the spinel structure. [ABSTRACT FROM AUTHOR]

Abstract: A Cr3+-modified natural zeolite sample from the deposit of Donje Jesenje (Croatia) was structurally studied using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXS), inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The analyses revealed the presence of up to 0.4wt% of chromium in the clinoptilolite crystals. The X-ray photoelectron spectroscopy depth analysis suggested a uniform distribution of chromium from the surface of the crystallites to the depth of 50(3)nm. The study of local environment of chromium by XANES (X-ray absorption near edge structure) showed that chromium cations in the sample were predominantly in the 3+ oxidation state. EXAFS (extended X-ray absorption fine structure) analysis revealed that Cr3+ cations bond to six oxygen atoms at the distance of 1.97(2)Å and two chromium atoms at the distance of 2.54(2)Å suggesting that Cr3+ cations most probably arrange in the zeolite pores in the form of small clusters of CrO6 octahedra. The chromium could not be completely desorbed from the sample after post-treatment with NaCl or HCl solutions thus indicating mostly irreversible sorption of chromium in the zeolite. [Copyright &y& Elsevier]

Abstract: Iron-containing hexagonal mesoporous aluminophosphate (FeHMA) was synthesised hydrothermally in a microwave oven in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The local environment of aluminium and phosphorus forming the aluminophosphate walls was studied by MAS NMR. The local environment of iron incorporated in HMA was investigated by X-ray absorption spectroscopy (XAS). X-ray absorption near edge structure (XANES) studies showed that iron in the as-synthesised and template-free FeHMA was present predominantly in the form of octahedrally coordinated Fe3+ ions. X-ray absorption fine structure (EXAFS) analyses confirmed that iron cations in the as-synthesised and template-free FeHMA were in octahedral coordination with the Fe–O distances of 1.97Å. Mössbauer spectroscopy revealed the presence of octahedrally coordinated Fe3+ and also tetrahedrally coordinated Fe2+ in the template-free FeHMA in the ratio of 4:1, which could not be detected by XANES. After the thermal treatment of template-free FeHMA at 427°C in vacuum the Mössbauer spectra showed that almost half of the iron cations present in the sample were tetrahedrally coordinated. The framework positions of tetrahedrally coordinated Fe2+ and octahedrally coordinated Fe3+ are suggested. [Copyright &y& Elsevier]

Pure phases of CoAPO-31 and MnAPO-31 were synthesized hydrothermally using di-n-propylamine as a structure-directing agent. The incorporation of manganese(II) and cobalt(II) into framework aluminum sites of AlPO4-31 was suggested from elemental, thermogravimetric and X-ray powder diffraction analysis. Isomorphous aluminum substitution with cobalt(II) was confirmed from static 31P NMR spectra. UV–VIS and XANES spectra revealed a partial oxidation of framework cobalt(II) and manganese(II) into cobalt(III) and manganese(III) in the calcined MeAPO-31 and thus the presence of redox centers in the products. The generation of acid sites (Brønsted and Lewis) in MeAPO-31 was supported by IR measurements of pyridine and by ammonium adsorption/desorption. The strength of the acid sites in the catalysts studied decreased in the following order: MnAPO-31>CoAPO-31>AlPO4-31. [Copyright &y& Elsevier]

• Alkali metal addition shortens the average copper-oxygen bond length. • Stronger binding of the oxygen leads to increased propylene oxide selectivity. • Na+ and Cs+ modification of 5CuO x /SiO 2 decrease the activation barrier for oxametallacycle ring closure. • Na+ and Cs+ modification of 5CuO x /SiO 2 increases the activation barrier for allylic hydrogen stripping. • The opposite effect is achieved by modification with Ca2+. This research focuses on epoxidation of propylene over pristine, Na, Ca and Cs modified CuO x /SiO 2 catalysts using O 2. The selectivity of the reaction is analyzed using a combination of catalytic tests, in-situ XAS and DFT calculations. The initially present subnanometer CuO clusters are present in all catalysts which re-disperse/flatten during reaction. During catalytic reaction, the Cu1+ becomes the predominant oxidation state. There is no correlation between propylene oxide (PO) selectivity and copper oxidation state. DFT analysis of the propylene reaction pathway revealed that Na, Cs, and Ca addition decreases the bonding strength of propylene to CuO and decreases the O 2 activation barrier, while simultaneously increase the exothermicity of O 2 dissociation. The Na induced Cu–O bond modification decreases the activation barrier from 0.87 to 0.71 eV for the oxametallacycle (OMC) ring closure (first step in the reaction pathway favoring selectivity towards PO) compared to pristine 5Cu catalyst. At the same time, we observed an increase (from 0.45 to 0.72 eV) of the barrier for the abstraction of allylic hydrogen. The opposite effect is achieved by Ca addition: the activation barrier for OMC ring closure increases to 1.08 eV and that for allylic hydrogen stripping decreases to 0.16 eV. [ABSTRACT FROM AUTHOR]

Zeolite Y was synthesized and modified with EDTA dealumination procedure. The modified zeolites were analyzed by X-ray diffraction, X-ray absorption spectroscopy, chemical analysis and water adsorption measurements. We demonstrated that dealumination with bulk organic acid such as EDTA is able to reduce the original intense water affinity. Furthermore, it was found that dealumination with EDTA, in contrast with steaming and HCl dealumination, provides fully controllable, predictable and secure process of Al removal from the zeolites' frameworks. The shift of the adsorption isotherm in the low partial pressure range represents an interesting result for adsorption-based applications. Image 1 • Zeolite Y dealumination by EDTA reveals "S-shaped" water sorption isotherm. • Bulky EDTA molecule causes dealumination only on particles' surface (silicon-rich shell). • Al XANES reveals significantly less Al(OH) 3 in EDTA-treated than in HCl-treated Y. • Hydrophobic character of EDTA-treated Y interesting for sorption-based applications. [ABSTRACT FROM AUTHOR]

Due to their adsorbent, ion exchange and catalytic properties zeolites are suitable for a variety of applications. We report on the photocatalytic activity of a readily available and inexpensive natural zeolite clinoptilolite (Z) containing SnO2 (Sn-Z). The Sn-Z samples with 3–15 wt. % of Sn were prepared by using a precipitation–deposition method. Powder X-ray diffraction analysis showed that the zeolite structure was unaffected by the introduction of the Sn-phase. Diffuse reflectance UV/VIS spectra of the Sn-Z samples confirmed the presence of SnO2 and X-Ray absorption spectroscopy analyses suggested that the SnO2 particles mainly resided on the surface of the clinoptilolite, while ATR-FTIR analysis gave some clues that part of the SnO2 phase was incorporated in the pores of the zeolite. The presence of SnO2 in Sn-Z increased both adsorption capacity and photocatalytic performance which could be partially explained by higher surface area and partially with an increased negative potential of the surface. Adsorption and total degradation of methylene blue (MB) for the Sn-Z with the highest amount of Sn (15 wt.%) was about 30% and 45%, respectively, suggesting a synergetic effect between SnO2 and the clinoptilolite lattice. Reusability tests showed that these catalysts present a promising material for water purification. [ABSTRACT FROM AUTHOR]

Summary: Lead (Pb) ranks among the most problematic environmental pollutants. Background contamination of soils is nearly ubiquitous, yet plant Pb accumulation is barely understood. In a survey covering 165 European populations of the metallophyte Arabidopsis halleri, several field samples had indicated Pb hyperaccumulation, offering a chance to dissect plant Pb accumulation.Accumulation of Pb was analysed in A. halleri individuals from contrasting habitats under controlled conditions to rule out aerial deposition as a source of apparent Pb accumulation. Several elemental imaging techniques were employed to study the spatial distribution and ligand environment of Pb.Regardless of genetic background, A. halleri individuals showed higher shoot Pb accumulation than A. thaliana. However, dose–response curves revealed indicator rather than hyperaccumulator behaviour. Xylem sap data and elemental imaging unequivocally demonstrated the in planta mobility of Pb. Highest Pb concentrations were found in epidermal and vascular tissues. Distribution of Pb was distinct from that of the hyperaccumulated metal zinc. Most Pb was bound by oxygen ligands in bidentate coordination.A. halleri accumulates Pb whenever soil conditions render Pb phytoavailable. Considerable Pb accumulation under such circumstances, even in leaves of A. thaliana, strongly suggests that Pb can enter food webs and may pose a food safety risk. [ABSTRACT FROM AUTHOR]

In this work, CuO x /SiO 2 catalysts were investigated in the propylene partial oxidation reaction. Ordered mesoporous silica (KIT-6) was used to deposit 1–10 wt. % copper and subsequently modified with Na, K and Ca. The synthesized materials were characterized by N 2 physisorption, XRD, TEM-EDS, CO 2 -TPD, operando UV/Vis DRS, operando XANES and pyridine DRIFT spectroscopy. Regardless of the CuO x loading, catalyst deactivation was observed during propylene oxidation reaction in non-modified catalysts, which was related to sintering of oligomeric [Cu-O-Cu] n species. Sintering of CuO x is strongly promoted under a reducing propylene atmosphere and related to the presence of Cu +1 . The resulting bulk CuO x promotes acrolein selectivity. We produced modified catalysts with finely dispersed alkali metal cations, associated with the subnanometer CuO x phase, resulting in a greatly stabilized morphology and catalytic activity. Operando XANES analysis revealed that a substantial fraction of Cu 2+ is transformed to Cu + during the propylene oxidation reaction (52–68%, depending on the modifying atom). Also, the dynamics of reaching the quasi steady oxidation state differ strongly. The kinetics of oxygen abstraction and replenishment are substantially different, indicative of modified chemistry of the nucleophilic oxygen species, present in 5CuNa catalyst in contrast to others (5Cu and 5CuCa). We propose that Cu + is not crucial for PO formation. Instead the electropositive Na + and K + decrease the nucleophilic strength of oxygen in CuO x , by attracting its electrons. Consequently, the catalytic action of oxygen changes from oxidative attack on the allylic hydrogen to oxygen insertion into the C C bond of propylene. This results in a noticeable selectivity shift from acrolein to propylene oxide. The effect of calcium on decreasing the nucleophilic character of O species in CuO x is negated by charge compensation by strongly adsorbed hydroxyl groups and Ca modification for PO selectivity is inefficient. Additionally we found, that further oxidation of propylene oxide is, most likely, the main factor determining high selectivity for CO x products. The alkali modification which increases the PO selectivity does not function via elimination of LAS, but exclusively through attenuation of nucleophilic character of oxygen species. [ABSTRACT FROM AUTHOR]

In this study, the particular effects of A-site donor doping, such as crystal-structure change, the secondary-phase formation and the grain-size decrease, in a lead-free piezoceramic material K 0.5 Na 0.5 NbO 3 (KNN) doped with Sr 2+ , were investigated. Extended X-ray absorption fine structure (EXAFS) analyses proved that Sr occupies the perovskite A-sublattice, and locally modifies the KNN monoclinic structure to cubic. Introducing Sr into the A-sublattice, as well as accounting for the charge-compensating A-site vacancies in the starting composition, causes increasing lattice disorder and microstrain, as determined from a Rietveld refinement of the synchrotron X-ray diffraction data. Above 2% Sr the system segregates the A-site vacancies in a secondary phase in order to release the chemical pressure, as revealed by Raman spectroscopy. All these effects result in an increasing number of low-angle grain boundaries that limit the grain growth and finally lead to a significant grain-size decrease. [ABSTRACT FROM AUTHOR]

Electrochemical reactions in the Li S batteries are considered as a multistep reaction process with at least 2–3 equilibrium states. Here we report a possibility of having a conversion of Li 2 S into sulfur without detectible formation of polysulfides. That was confirmed by using a novel material system consisting of carbon coated Li 2 S particles prepared by carbothermal reduction of Li 2 SO 4 . Two independent in operando measurements showed direct oxidation of Li 2 S into sulfur for this system, with almost negligible formation of polysulfides at potentials above 2.5 V vs. Li/Li + . Our results link the diversity of first charge profiles in the literature to the Li 2 S oxidation mechanism and show the importance of ionic wiring within the material. Furthermore, we demonstrate that the Li 2 S oxidation mechanism depends on the relative amount of soluble sulfur in the electrolyte. By controlling the type and the amount of electrolyte within the encapsulating carbon shell, it is thereby possible to control the reaction mechanism of Li 2 S activation. [ABSTRACT FROM AUTHOR]

Tartary buckwheat is a gluten-free crop with great potential as a wheat substitute. Iron (Fe) is an important mineral element in staple foods which is required in sufficient bioaccessible quantities. The aim of the study was to investigate how processing of grains into groats (hydrothermal processing to remove the husk) and sprouts (7-day-old seedlings) affected Fe speciation (Fe 2+ or Fe 3+ ), Fe ligand composition and Fe bioaccessibility to human Caco-2 cells. Groats contained the least Fe (23.8 ± 1.65 mg kg −1 ) and the lowest amounts of Fe 2+ (8%). Grains and sprouts had comparable Fe concentrations (78.2 ± 2.65 and 68.9 ± 2.73 mg kg −1 ) and similar proportions of Fe 2+ (15% and 18%). The main ligands for Fe in Tartary buckwheat material were phytate and citrate. Phytate was less abundant in sprouts, which did not correlate with greater Fe bioaccessibility. Iron bioaccessibility was 4.5-fold greater for grains than groats, suggesting that Fe is more bioaccessible in the husk than in the rest of the grain. [ABSTRACT FROM AUTHOR]

The Co–ferrite nanoparticles having a relatively uniform size distribution around 8 nm were synthesized by three different methods. A simple co-precipitation from aqueous solutions and a co-precipitation in an environment of microemulsions are low temperature methods (50 °C), whereas a thermal decomposition of organo-metallic complexes was performed at elevated temperature of 290 °C. The X-ray diffractometry (XRD) showed spinel structure, and the high-resolution transmission electron microscopy (HRTEM) a good crystallinity of all the nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) showed the composition close to stoichiometric (~CoFe2O4) for both co-precipitated nanoparticles, whereas the nanoparticles prepared by the thermal decomposition were Co-deficient (~Co0.6Fe2.4O4). The X-ray absorption near-edge structure (XANES) analysis showed Co valence of 2+ in all the samples, Fe valence 3+ in both co-precipitated samples, but average Fe valence of 2.7+ in the sample synthesized by thermal decomposition. The variations in cation distribution within the spinel lattice were observed by structural refinement of X-ray absorption fine structure (EXAFS). Like the bulk CoFe2O4, the nanoparticles synthesized at elevated temperature using thermal decomposition displayed inverse spinel structure with the Co ions occupying predominantly octahedral lattice sites, whereas co-precipitated samples showed considerable proportion of cobalt ions occupying tetrahedral sites (nearly 1/3 for the nanoparticles synthesized by co-precipitation from aqueous solutions and almost 1/4 for the nanoparticles synthesized in microemulsions). Magnetic measurements performed at room temperature and at 10 K were in good agreement with the nanoparticles’ composition and the cation distribution in their structure. The presented study clearly shows that the distribution of the cations within the spinel lattice of the ferrite nanoparticles, and consequently their magnetic properties are strongly affected by the synthesis method used. [ABSTRACT FROM AUTHOR]

Abstract: An aluminium-free Ti-Beta/SBA-15 composite material was prepared by the post-synthesis incipient wetness-deposition of different amounts of Ti-Beta nanoparticles solution on the SBA-15 matrix. The presence of crystalline nanoparticles in the solution, used for impregnation on SBA-15, was confirmed by HRTEM measurements. The hexagonal arrangement of the mesopores of SBA-15 was proven by XRD and TEM measurements. The presence and the deposition of Ti-incorporated zeolitic nanoparticles on the mesopore walls of SBA-15 were proven by nitrogen sorption analysis, IR spectroscopy and TG analysis. The X-ray absorption spectroscopy analysis of local environment of titanium incorporated in the new composite material showed that the product contained five fold coordinated framework titanium. These Ti sites can be oxidation titanium sites. [Copyright &y& Elsevier]

Abstract: Mesoporous silicate catalyst FeTUD-1 containing only isolated iron was synthesized. Local environment of iron was investigated by X-ray Absorption and Mössbauer spectroscopies. XANES (X-ray Absorption Near Edge Structure) studies show that iron in the as-synthesized and template-free FeTUD-1 is present in the form of Fe3+ ions in coordination geometries posses an inversion center. EXAFS (X-ray Absorption Fine Structure) analyses reveal that iron cations in the as-synthesized sample are coordinated to four oxygens at the distance of 1.87Å and in the template-free sample to one oxygen at 1.86Å and five oxygens at 2.0Å distances. Mössbauer spectroscopy proves the presence of iron in Fe3+ form in template-free sample. Moreover, it determines Fe3+ in two types of distorted octahedral coordinations. [Copyright &y& Elsevier]

Abstract: Thermally stable titanium-containing microporous/mesoporous composite (Ti, Al)-Beta/MCM-48 was synthesised hydrothermally in the presence of structure-directing agents cetyltrimethylammonium bromide (CTABr), polyoxyethylene(8) isooctylhexyl ether (Triton® X-114) and tetraethylammonium hydroxide (TEAOH) in the absence of sodium cations. The presence of both microporous and mesoporous phases was determined by XRD and HRTEM measurements and by the analysis of nitrogen adsorption isotherm based on the α-plot method. The mass percentage (μ) of the microporous material in the composite is approximately 6.5%. NMR investigations showed that acid sites related to framework aluminium were generated by calcination of the as-synthesised (Ti, Al)-Beta/MCM-48. Local environment of titanium incorporated into the microporous/mesoporous silicate material was investigated by X-ray absorption spectroscopy. XANES studies showed the presence of tetrahedrally-coordinated Ti4+ cations in the template-free sample. EXAFS analysis revealed that titanium cations were coordinated to four oxygens in the first coordination shell, to one oxygen at 1.73(1) Å and three oxygens at 1.86(1) Å. In the second coordination sphere three silicon atoms were found at distances 3.18(2) Å and 3.48(2) Å, respectively. These results indicated framework Ti and thus the presence of Ti oxidation centres within the composite material. [Copyright &y& Elsevier]

Abstract: Manganese-modified hexagonal mesoporous aluminophosphate (MnHMA) was synthesized hydrothermally in a microwave oven in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The mesoporous structure was elucidated by HRTEM. Local environment of aluminum and phosphorus forming the mesoporous aluminophosphate framework was studied by MAS NMR. The local environment of manganese incorporated in HMA was investigated by X-ray absorption spectroscopy. XANES studies show that manganese in the as-synthesized and template-free MnHMA is present in the form of Mn2+ and Mn3+ ions in the ratio 40–60%. EXAFS analyses revealed four oxygens in the first coordination sphere of manganese in the as-synthesized and template-free MnHMA at the distances 2.142(5)Å and 2.15(1)Å, respectively. EPR and ESEEM measurements revealed that Mn2+ in both as-synthesized and template-free products was located within the mesoporous aluminophosphate framework. [Copyright &y& Elsevier]

Abstract: Hydrothermally stable titanium containing microporous/mesoporous composite (Ti,Al)-Beta/MCM-41 was synthesized hydrothermally in the presence of structure-directing agents cetyltrimethylammonium bromide (CTABr) and tetraethyl ammonium hydroxide (TEAOH). XRD analysis and analysis of nitrogen adsorption isotherm confirmed the presence of micropores and mesopores in the composite. HRTEM microscopic studies revealed that micro- and mesoporosity of the composite was not due to the mechanical mixture of microporous (Ti,Al)-Beta and mesoporous (Ti,Al)-Beta/MCM-41. The local environment of titanium incorporated into the microporous/mesoporous silicate material was investigated by X-ray absorption spectroscopy. XANES studies showed the presence of tetrahedrally coordinated Ti4+ cations in the template-free sample. EXAFS analysis revealed that titanium cations were coordinated to four oxygens in the first coordination shell at a distance of 1.84Å. In the second coordination sphere one and two silicon atoms were found at the distances 3.12Å and 3.51Å, respectively. These results indicated framework Ti and thus the presence of Ti oxidation centers within the composite material. NMR investigations showed that Brønsted and Lewis acid sites related to framework aluminum were generated by the removal of potassium and sodium ions from the (Ti,Al)-Beta/MCM-41 pores. The new composite material was preliminarily tested in the oxidation reaction. Titanium leaching from the composite was not observed. [Copyright &y& Elsevier]

Abstract: Manganese containing MCM-41 was synthesised by the direct hydrothermal method (DHT) in the presence of cetyltrimethylammonium chloride (CTACl) as a template. The local environment of manganese incorporated in mesoporous silicate MCM-41 was investigated by XAS (X-ray Absorption Spectroscopy). XANES (X-ray Absorption Near Edge Structure) studies showed the coexistence of Mn2+ and Mn3+ cations in both, as-synthesised and template-free MnMCM-41 samples. The major part of manganese cations in the as-synthesised MnMCM-41 was Mn2+, while in the template-free MnMCM-41 the amount of Mn3+ was increased. EXAFS (X-ray Absorption Fine Structure) analyses revealed that major part of manganese cations in the as-synthesised MnMCM-41 were extra-framework with the Mn–O distance of 2.19Å. Manganese cations in the template-free MnMCM-41 were incorporated into the framework and coordinated to three oxygens in the first coordination shell, with two of them at a shorter distance of 1.92Å and one at a longer distance of 2.21Å. Pulsed ESR (Electron Spin Resonance) and ESEEM (Electron Spin-Echo Envelope Modulation) investigations were in agreement with the XANES and EXAFS results. [Copyright &y& Elsevier]

An extra-large pore iron-substituted aluminophosphate molecular sieve FeVPI-5 was synthesized. Elemental analysis indicated isomorphous substitution of aluminum by iron. X-ray absorption spectroscopy (XANES and EXAFS analyses) confirmed the incorporation of Fe(III) into the framework of VPI-5. The acidity tests of FeVPI-5, performed by IR spectroscopy using CO adsorption at low temperature on the oxidized and on the reduced material, gave evidence on redox behavior of framework iron in FeVPI-5. [Copyright &y& Elsevier]

Development of magnesium sulfur battery is accompanied with all known difficulties present in Li–S batteries, however with even more limited choice of electrolytes. In the present work, the influence of current collector on electrochemical mechanism was investigated in light of different reports where improved behavior was ascribed to electrolyte. Notable differences in cycling behavior are reported when Al current collector is replaced by Cu current collector independent of electrolyte. The initial reduction of sulfur follows similar reaction path no mater of current collector, but formation of MgS can be in competition with formation of CuS in the presence of Cu cations. With the subsequent cycling cells prepared from cathodes deposited on Cu current collector show decrease in the voltage and formation of single plateau during cycling. The change corresponds to the involvement of Cu into the reaction and formation of redox couple Mg/CuS as determined by Cu K-edge XANES measurements. Corrosion of Cu foil is identified by SEM and serves as a source of Cu cations for the chemical reaction between Cu and polysulfides. Mg/CuS redox couple shows improved cycling stability, but theoretical energy density is severely reduced due to substitution of S with CuS as cathode active material. Image 1 • Influence of current collectors on electrochemistry of Mg–S battery is shown. • Increased stability and rate capability can be achieved with Cu current collector. • Formation of CuS was confirmed when using Cu current collector. • Severe degradation of Cu current collector was observed in different electrolytes. • Cu current collectors can not be used in combination with sulfur cathode. [ABSTRACT FROM AUTHOR]

A γ-alumina support functionalized with transition metals is one of the most widely used industrial catalysts for the total oxidation of volatile organic compounds (VOCs) as air pollutants at higher temperatures (280-450 °C). By rational design of a bimetal CuFe-γ-alumina catalyst, synthesized from a dawsonite alumina precursor, the activity in total oxidation of toluene as a model VOC at a lower temperature (200-380 °C) is achieved. A fundamental understanding of the catalyst and the reaction mechanism is elucidated by advanced microscopic and spectroscopic characterizations as well as by temperature-programmed surface techniques. The nature of the metal-support bonding and the optimal abundance between Cu-O-Al and Fe-O-Al species in the catalysts leads to synergistic catalytic activity promoted by small amounts of iron (Fe/Al = 0.005). The change in the metal oxide-cluster alumina interface is related to the nature of the surfaces to which the Cu atoms attach. In the most active catalyst, the CuO 6 octahedra are attached to 4 Al atoms, while in the less active catalyst, they are attached to only 3 Al atoms. The oxidation of toluene occurs via the Langmuir-Hinshelwood mechanism. The presented material introduces a prospective family of low-cost and scalable oxidation catalysts with superior efficiency at lower temperatures.

Barium hexaferrite nanoplatelets (BHF NPLs) are permanent nanomagnets with the magnetic easy axis aligned perpendicular to their basal plane. By combining this specific property with optimised surface chemistry, novel functional materials were developed, e.g., ferromagnetic ferrofluids and porous nanomagnets. We compared the interaction of chemically different phosphonic acids, hydrophobic and hydrophilic with 1-4 phosphonic groups, with BHF NPLs. A decrease in the saturation magnetisation after functionalising the BHF NPLs was correlated with the mass fraction of the nonmagnetic coating, whereas the saturation magnetisation of the NPLs coated with a tetraphosphonic acid at 80 °C was significantly lower than expected. We showed that such a substantial decrease in the saturation magnetisation originates from the disintegration of BHF NPLs, which was observed with atomic-resolution scanning transmission electron microscopy and confirmed by a computational study based on state-of-the-art first-principles calculations. Fe K-edge XANES (X-ray absorption near-edge structure) and EXAFS (Extended X-ray absorption fine structure) combined with Fourier-transformed infrared (FTIR) spectroscopy confirmed the formation of an Fe-phosphonate complex on the partly decomposed NPLs. Comparing our results with other functionalised magnetic nanoparticles confirmed that saturation magnetisation can be exploited to identify the disintegration of magnetic nanoparticles when insoluble disintegration products are formed., (© 2023. The Author(s).)

Dry reforming of methane (DRM) is a promising way to convert methane and carbon dioxide into H 2 and CO (syngas). CeO 2 nanorods, nanocubes, and nanospheres were decorated with 1-4 wt % Ni. The materials were structurally characterized using TEM and in situ XANES/EXAFS. The CO 2 activation was analyzed by DFT and temperature-programmed techniques combined with MS-DRIFTS. Synthesized CeO 2 morphologies expose {111} and {100} terminating facets, varying the strength of the CO 2 interaction and redox properties, which influence the CO 2 activation. Temperature-programmed CO 2 DRIFTS analysis revealed that under hydrogen-lean conditions mono- and bidentate carbonates are hydrogenated to formate intermediates, which decompose to H 2 O and CO. In excess hydrogen, methane is the preferred reaction product. The CeO 2 cubes favor the formation of a polydentate carbonate species, which is an inert spectator during DRM at 500 °C. Polydentate covers a considerable fraction of ceria's surface, resulting in less-abundant surface sites for CO 2 dissociation.

Catalyst design is crucial for improving catalytic activity and product selectivity. In a bifunctional Ni/ZSM-5 zeolite type catalyst, catalytic properties are usually tuned via varying Al and Ni contents. While changes in acid properties associated with Al sites are usually closely investigated, Ni phases, however, receive inadequate attention. Herein, we present a systematic structural study of Ni in the Ni/ZSM-5 materials by using Ni K-edge XANES and EXAFS analyses, complemented by XRD and TEM, to resolve the changes in the local environment of Ni species induced by the different Al contents of the parent ZSM-5 prepared by a "green", template free technique. Ni species in Ni/ZSM-5 exist as NiO crystals (3-50 nm) and as charge compensating Ni 2+ cations. The Ni K-edge XANES and EXAFS results enabled the quantification of Ni-containing species. At a low Al to Si ratio ( n Al / n Si ≤ 0.04), the NiO nanoparticles predominate in the samples and account for over 65% of Ni phases. However, NiO is outnumbered by Ni 2+ cations attached to the zeolite framework in ZSM-5 with a high Al to Si ratio ( n Al / n Si = 0.05) due to a higher number of framework negative charges imparted by Al. The obtained results show that the number of highly reducible and active NiO crystals is strongly correlated with the framework Al sites present in ZSM-5 zeolites, which depend greatly on the synthesis conditions. Therefore, this kind of study is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified bifunctional catalysts., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

X-ray Raman spectroscopy (XRS) is an emerging spectroscopic technique that utilizes inelastic scattering of hard X-rays to study X-ray absorption edges of low Z elements in bulk material. It was used to identify and quantify the amount of carbonyl bonds in a cathode sample, in order to track the redox reaction inside metal-organic batteries during the charge/discharge cycle. XRS was used to record the oxygen K-edge absorption spectra of organic polymer cathodes from different multivalent metal-organic batteries. The amount of carbonyl bond in each sample was determined by modeling the oxygen K-edge XRS spectra with the linear combination of two reference compounds that mimicked the fully charged and the fully discharged phases of the battery. To interpret experimental XRS spectra, theoretical calculations of oxygen K-edge absorption spectra based on density functional theory were performed. Overall, a good agreement between the amount of carbonyl bond present during different stages of battery cycle, calculated from linear combination of standards, and the amount obtained from electrochemical characterization based on measured capacity was achieved. The electrochemical mechanism in all studied batteries was confirmed to be a reduction of double carbonyl bond and the intermediate anion was identified with the help of theoretical calculations. X-ray Raman spectroscopy of the oxygen K-edge was shown to be a viable characterization technique for accurate tracking of the redox reaction inside metal-organic batteries., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The microalgae Spirulina may be a popular dietary supplement rich in essential nutrients and vitamins, but oversight of the supplement industry, in general, remains limited, and increasing incidents of adulteration, misbranding, and undeclared ingredients together with misleading claims create potential risks. In response, this study characterized the elemental, amino acid and fatty acid content of commercially available Spirulina supplements in Slovenia using EDXRF, ICP-MS and GC-MS and compared the results with their nutritional declaration. The gathered data confirm that Spirulina supplements are a good source of calcium (0.15 to 29.5% of RDA), phosphorous (3.36-26.7% of RDA), potassium (0.5 to 7.69% of RDA) and selenium (0.01 to 38.6% of RDA) when consumed within recommended amounts. However, although iron contents were relatively high (7.64 to 316% of RDA), the actual bioavailability of iron was much lower since it was mainly present as the ferric cation. This study also confirms that pure Spirulina supplements are a good source of essential and non-essential amino acids, and ω-6 but not ω-3 polyunsaturated fatty acids. The presence of additives resulted in significant variation in nutrient content and, in some instances, lower product quality. Moreover, a high proportion (86.7%) of inappropriate declarations regarding the elemental content was observed. Overall, the study conclusions underline the need for a stricter control system for Spirulina -based supplements.

Combining the abundance and inexpensiveness of their constituent elements with their atomic dispersion, atomically dispersed Fe-N-C catalysts represent the most promising alternative to precious-metal-based materials in proton exchange membrane (PEM) fuel cells. Due to the high temperatures involved in their synthesis and the sensitivity of Fe ions toward carbothermal reduction, current synthetic methods are intrinsically limited in type and amount of the desired, catalytically active Fe-N 4 sites, and high active site densities have been out of reach (dilemma of Fe-N-C catalysts). We herein identify a paradigm change in the synthesis of Fe-N-C catalysts arising from the developments of other M-N-C single-atom catalysts. Supported by DFT calculations we propose fundamental principles for the synthesis of M-N-C materials. We further exploit the proposed principles in a novel synthetic strategy to surpass the dilemma of Fe-N-C catalysts. The selective formation of tetrapyrrolic Zn-N 4 sites in a tailor-made Zn-N-C material is utilized as an active-site imprint for the preparation of a corresponding Fe-N-C catalyst. By successive low- and high-temperature ion exchange reactions, we obtain a phase-pure Fe-N-C catalyst, with a high loading of atomically dispersed Fe (>3 wt %). Moreover, the catalyst is entirely composed of tetrapyrrolic Fe-N 4 sites. The density of tetrapyrrolic Fe-N 4 sites is more than six times as high as for previously reported tetrapyrrolic single-site Fe-N-C fuel cell catalysts.

The contribution of 1,8-dihydroxy naphthalene (DHN) melanin to cadmium (Cd) tolerance in two dark septate endophytes (DSE) of the genus Cadophora with different melanin content was investigated in vitro. The DSE isolate Cad#148 with higher melanin content showed higher tolerance to Cd than the less melanised Cad#149. Melanin synthesis was significantly reduced by Cd in both isolates with uninhibited melanin synthesis, in a dose-dependent manner. Inhibition of melanin synthesis by tricyclazole reduced the relative growth of Cad#148 exposed to Cd and did not affect Cad#149. Cd accumulation was not altered by tricyclazole in the two isolates, but it increased catalase and reduced glutathione reductase activity in more melanised Cad#148, indicating higher stress levels. In contrast, in Cad#149 the enzyme activity was less affected by tricyclazole, indicating a more pronounced role of melanin-independent Cd tolerance mechanisms. Cd ligand environment in fungal mycelia was analysed by extended EXAFS (X-ray absorption fine structure). It revealed that Cd was mainly bound to O- and S-ligands, including hydroxyl, carboxyl, phosphate and thiol groups. A similar proportion of S- and O- ligands (~35% and ~65%) were found in both isolates with uninhibited melanin synthesis. Among O-ligands two types with Cd-O-C- and Cd-O-P- coordination were identified. Tricyclazole altered Cd-O- ligand environment in both fungal isolates by reducing the proportion of Cd-O-C- and increasing the proportion of Cd-O-P coordination. DHN-melanin, among other tolerance mechanisms, significantly contributes to Cd tolerance in more melanised DSE fungi by immobilising Cd to hydroxyl groups and maintaining the integrity of the fungal cell wall., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Breeding and engineering of biofortified crops will benefit from a better understanding of bottlenecks controlling micronutrient loading within the seeds. However, few studies have addressed the changes in micronutrient concentrations, localization, and speciation occurring over time. Therefore, we studied spatial patterns of zinc and iron accumulation during grain development in two barley lines with contrasting grain zinc concentrations. Microparticle-induced-X-ray emission and laser ablation-inductively coupled plasma mass spectrometry were used to determine tissue-specific accumulation of zinc, iron, phosphorus, and sulfur. Differences in zinc accumulation between the lines were most evident in the endosperm and aleurone. A gradual decrease in zinc concentrations from the aleurone to the underlying endosperm was observed, while iron and phosphorus concentrations decreased sharply. Iron co-localized with phosphorus in the aleurone, whereas zinc co-localized with sulfur in the sub-aleurone. We hypothesize that differences in grain zinc are largely explained by the endosperm storage capacity. Engineering attempts should be targeted accordingly.

We used cathodoluminescence (CL) spectroscopy to characterize the oxygen vacancies (V O ) in ceria (CeO 2 ). The effects of the processing atmosphere and thermal quenching temperature on the nature and distribution of the intrinsic defects and on the spectroscopic behavior were investigated. The presence of polarons and associates of the polarons with the oxygen vacancies such as (V O •• -Ce Ce ' ) • is demonstrated. CL intensity quenching above a critical concentration of V O has been shown. Even though the emission centers in all samples are the same, their concentration changes with the oxygen partial pressure of the processing atmosphere. Deconvolution of the observed CL spectra shows that the emissions originating from the F 0 centers prevail over those of F + centers of V O when the defect concentration is high., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

In wheat ( Triticum aestivum L.), the awns-the bristle-like structures extending from lemmas-are photosynthetically active. Compared to awned cultivars, awnletted cultivars produce more grains per unit area and per spike, resulting in significant reduction in grain size, but their mineral element composition remains unstudied. Nine awned and 11 awnletted cultivars were grown simultaneously in the field. With no difference in 1000-grain weight, a larger calcium and manganese-but smaller iron (Fe) concentrations-were found in whole grain of awned than in awnletted cultivars. Micro X-ray absorption near edge structure analysis of different tissues of frozen-hydrated grain cross-sections revealed that differences in total Fe concentration were not accompanied by differences in Fe speciation (64% of Fe existed as ferric and 36% as ferrous species) or Fe ligands (53% were phytate and 47% were non-phytate ligands). In contrast, there was a distinct tissue-specificity with pericarp containing the largest proportion (86%) of ferric species and nucellar projection (49%) the smallest. Phytate ligand was predominant in aleurone, scutellum and embryo (72%, 70%, and 56%, respectively), while nucellar projection and pericarp contained only non-phytate ligands. Assuming Fe bioavailability depends on Fe ligands, we conclude that Fe bioavailability from wheat grain is tissue specific.

This study provides information on mercury (Hg) localization, speciation and ligand environment in edible mushrooms: Boletus edulis, B. aereus and Scutiger pes-caprae collected at non-polluted and Hg polluted sites, by LA-ICP-MS, SR-μ-XRF and Hg L 3 -edge XANES and EXAFS. Mushrooms (especially young ones) collected at Hg polluted sites can contain more than 100 μg Hg g -1 of dry mass. Imaging of the element distribution shows that Hg accumulates mainly in the spore-forming part (hymenium) of the cap. Removal of hymenium before consumption can eliminate more than 50% of accumulated Hg. Mercury is mainly coordinated to di-thiols (43-82%), followed by di-selenols (13-35%) and tetra-thiols (12-20%). Mercury bioavailability, as determined by feeding the mushrooms to Spanish slugs (known metal bioindicators owing to accumulation of metals in their digestive gland), ranged from 4% (S. pes-caprae) to 30% (B. aereus), and decreased with increasing selenium (Se) levels in the mushrooms. Elevated Hg levels in mushrooms fed to the slugs induced toxic effects, but these effects were counteracted with increasing Se concentrations in the mushrooms, pointing to a protective role of Se against Hg toxicity through HgSe complexation. Nevertheless, consumption of the studied mushroom species from Hg polluted sites should be avoided., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

A strain of Klebsiella oxytoca, isolated from acid pyrite-mine drainage, characteristically produces a ferric hydrogel, consisting of branched heptasaccharide repeating units exopolysaccharide (EPS), with metal content of 36 wt%. The high content of iron in the EPS matrix cannot be explained by a simple ferric ion bond to the sugar skeleton. The bio-generated Fe-EPS is investigated by X-ray absorption spectroscopy. Fe K-edge XANES analysis shows that iron is mostly in trivalent form, with a non-negligible amount of Fe(2+) in the structure. The Fe EXAFS results indicate that iron in the sample is in a mineralized form, prevalently in the form of nano-sized particles of iron oxides/hydroxides, most probably a mixture of different nano-crystalline forms. TEM shows that these nanoparticles are located in the interior of the EPS matrix, as in ferritin. The strain produces Fe-EPS to modulate Fe-ions uptake from the cytoplasm to avoid iron toxicity under anaerobic conditions. This microbial material is potentially applicable as iron regulator.