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In the present study, the ability of a modified CaCl2 zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms. The acid soils, either treated with Ca-Z or not, adsorbed higher amounts of Se(IV) than alkaline ones, whereas soils alone did not adsorb Se(VI) but impressively high adsorption of Se(VI) occurred in the Ca-Z-treated soils. Desorption of Se(IV) was higher from the Ca-Z-treated soils and especially from the acid soils. Higher distribution coefficients of desorption than the distribution coefficients of sorption were observed, clearly pointing to a hysteresis mechanism. The experimental data fitted with Langmuir and Freundlich isotherms. In the presence of Ca-Z, the Langmuir qm values increased indicating higher Se(IV) retention while Langmuir bL values decreased suggesting lower bonding strength and higher Se(IV) mobility. Overall, treating the soils with Ca-Z increased Se(IV) adsorption and mobility whereas it provided sites for Se(VI) adsorption that did not exist in the studied soils.

CuO nanowires were grown on Cu foils at 600 °C, coated with Cu and converted into Cu3N/Cu2O core–shell nanowires under NH3:H2 at 400 °C. The structural and optical properties are described in detail as well as its potential for energy applications.

Cu3N layers with a thickness of 40 nm were deposited by reactive sputtering using Ar: 10% N2 and 100% N2, after which they were annealed under NH3/H2 between 300 and 500 °C. These exhibited distinc...

Cu3N layers prepared by annealing, under NH3 O2 flow, of Cu sputtered on Si, fused SiO2, and soda lime glass were studied by Raman and N K edge Near Edge X ray Absorption Fine Structure NEXAFS spectroscopy. The annealing temperatures were ranging from 300 to 800 C. Benefiting from resonance effects on the Raman peak intensities when different excitation wavelengths are used, the contribution in the Raman signal of copper oxides, which provide peaks lying close to those of Cu3N, is more easily discriminated. The formation of Cu2O surface oxide is observed in almost all the samples even for annealing at low temperatures. CuO is generally formed at higher temperatures with the onset depending on the amount of O2 in the NH3 O2 mixture. However, high temperature is necessary to grow larger crystallites, as it is deduced from the decrease in the width of the high frequency Raman peak at ca. 650 cm amp; 8722;1 of Cu3N, in accordance with Scanning Electron Microscopy observations. The formation of CuO is accompanied by the creation of N2 trapped in the sample, which is directly detected by the NEXAFS measurements. N2 is most probably formed by the N atoms originating from the dissociation of the Cu N bonds

The effective stabilization of tannery sludge wastes is explored using X-Ray Absorption Fine Structure (XAFS) spectroscopies. Solidification of the Cr-rich waste was realized via vitrification of the incinerated sludge with silica and flux agents. It is demonstrated that the effective reduction of Cr(VI) and the structural role of Cr are strongly modulated by the chemical composition of the waste. Eskolaite microcrystallites are embedded in the silica matrix of all vitrified samples and the extent of microcrystalline formation is strongly related to the glass basicity. Both Cr(VI) and Cr(III) species are identified, corresponding to Cr(VI)O4 glass formers and Cr(III)O6 network modifiers. The toxic Cr(VI) prevails only in the glasses with the highest basicity index and lowest waste content, nevertheless it is safely incorporated and immobilized in the silica matrix. However, the detected abundance of Cr(VI) increases glass basicity and as a result, glass polymerization is hindered. Thermal treatment, a process that leads to glass-ceramics transforms almost all Cr(VI) to Cr(III), while eskolaite formation is promoted concurrently. Nevertheless, microcrystalline growth proceeds mainly via depletion of Cr(III) from the silica matrix and not from the reduced Cr(VI); yet, Cr-removal from the glass matrix does not impair the chemical stability of the devitrified products.

The exoskeleton of crustaceans consists of chitin biopolymers where the embedded inorganic biominerals, mainly CaCO3, affect strongly its mechanical properties. Raman and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies and Transmission Electron Microscopy (TEM) are applied to investigate the CaCO3 structure in various parts of the Calappa granulata crab exoskeleton. The shape of the main Raman peak of CaCO3 reveals the presence of two phases which are identified as calcite and amorphous calcium carbonate (ACC). The relative concentration of the two phases in various parts of the exoskeleton is determined from the area ratio under the corresponding peaks. The results of the Ca L3,2-edge NEXAFS analysis are in line with the Raman findings, since the energy separation of peaks that appear in the lower frequency region of the main L2 and L3 peaks due to crystal field splitting, is directly related to the percentage of the ACC phase in the total CaCO3 mineral content. The C K-edge spectra are used for the determination of the extent of calcification of the exoskeleton. Furthermore, dark and bright field TEM images reveal the presence of nanocrystallites with an average size of 20 nm. The structure of the nanocrystallites, as derived from the Selected Area Electron Diffraction patterns, is calcite. The results suggest that ACC plays a structural role in the exoskeleton of Calappa granulata.

Light absorption and charge transport in oxide semiconductors can be tuned by the introduction, during deposition, of a small quantity of foreign elements, leading to the improvement of the photoelectrocatalytic performance. In this work, both unmodified and vanadium-modified TiO2 thin films deposited by radio-frequency magnetron sputtering are investigated as photoanodes for photoelectrochemical water splitting. Following a structural characterization by X-ray diffraction, atomic force microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, photoelectrocatalysis is discussed based on ultrafast transient absorbance spectroscopy measurements. In particular, three different pump wavelengths from UV to the visible range are used (300, 390, and 530 nm) in order to cover the relevant photoactive spectral range of modified TiO2. Incident photon-to-current conversion efficiency spectra show that incorporation of vanadium in TiO2 extends water splitting in the visible range up to approximate to 530 nm, a significant improvement compared to unmodified TiO2 that is active only in the UV range less than or similar to 390 nm. However, transient absorbance spectroscopy clearly reveals that vanadium accelerates electron-hole recombination upon UV irradiation, resulting in a lower photon-to-current conversion efficiency in the UV spectral range with respect to unmodified TiO2. The new photoelectrocatalytic activity in the visible range is attributed to a V-induced introduction of intragap levels at approximate to 2.2 eV below the bottom of the conduction band. This is confirmed by long-living transient signals due to electrons photoexcited into the conduction band after visible light (530 nm) pulses. The remaining holes migrate to the semiconductor-electrolyte interface where they are captured by long-lived traps and eventually promote water oxidation under visible light.

The structural properties of InxGa1−xN epilayers, deposited on (0001) AlN templates by plasma-assisted molecular beam epitaxy, were studied by transmission electron microscopy and Raman spectroscopy, as a function of growth temperature. Single phase films with high indium content and well-ordered heteroepitaxial interfaces were attained at lower temperatures. Delayed plastic relaxation resulted in the structural stratification of high-temperature films due to the compositional pulling. Such films relaxed by a stacking fault mechanism, contrary to low temperature ones that exhibited relaxation by misfit dislocations. Despite the higher defect content of the former, their phonon mean free path was also higher, showing that alloying-induced fluctuations of the periodic potential constitute a more critical parameter. Cubic interfacial zones were suppressed at lower growth temperatures.This is part of a thematic issue on Nanoscale Materials Characterisation and Modeling by Advances Microscopy Methods -...

In-K-edge x-ray absorption fine structure (EXAFS), x-ray photoelectron, and Raman spectroscopy results are combined for a comprehensive study of InxGa1−xN layers with energy gaps extending over nearly the whole visible spectrum. The In–N and In–(In,Ga) distances determined by EXAFS are used for the derivation of the In–N bond ionicity as well as for the phonon frequency dependence of the LO and B12 modes, assessed by Raman, and the N 1s, In 3d5/2, Ga 3s, and Ga 2p1/2 electron binding energies on those distances. Phonon confinement due to perturbation of the periodic potential caused by the alloying is also quantified.

X-ray Absorption Fine Structure (XAFS) spectroscopies are implemented in a series of thermally treated vitrified industrial wastes in an effort to explain the structural role of Pb in the formation of stable, solidified products. In the vitrified wastes, Pb forms trigonal and tetragonal pyramids and acts as a network modifier. Consequently, Pb is successfully immobilized into a vitreous matrix. Devitrification promotes the formation of magnetoplumbite microcrystallites; nevertheless, the majority of Pb continues to modify the glassy network. The chemical stability of the vitroceramics correlates to the type of microcrystallites formed. Lead is safely trapped in both the crystalline and vitreous regions when microcrystalline growth proceeds via the depletion of both Pb and Fe from the silica matrix. However, if the formation of FexOy microcrystallites prevails, structural integrity is lost due to Fe removal, leading to a weak glassy network that can potentially permit the escape of Pb.

Journal of structural biology 195(1), 1-10(2016). doi:10.1016/j.jsb.2016.05.006, The exoskeleton of crustaceans consists mainly of calcium carbonate (CaCO$_3$) minerals and in many cases exhibits vivid colouration due to the presence of proteins rich in carotenoid chromophores. The exposure of aquatic animals in sea water results often in the incorporation of trace elements in their exoskeleton. The bonding configuration of Br and Sr trace elements in regions with different staining (white, orange and blue) of the exoskeleton of the Callinectes sapidus in crab claw are systematically investigated by a number of complementary spectroscopic techniques, including X-ray absorption fine structure spectroscopy (EXAFS), X-ray fluorescence, Raman and visible light reflectivity spectroscopies. It is found that Sr substitutes for Ca and the Sr/Ca ratio is constant along the claw. In the orange region that includes the claw fingers, CaCO$_3$ adopts a calcite-like structure, whereas in the blue and white regions, located in the palm of the claw, an aragonite-like structure dominates. On the other hand, Br, present only in the blue and orange stained parts of the claw, is bound to phenyl and/or phenol rings of amino acid residues, most probably to phenylalanine and/or tyrosine, of the chromophore protein., Published by Elsevier, San Diego, Calif.

The ability of a synthesized polyethylenimine - epichlorohydrin resin to remove Cr(VI) from aqueous solutions was investigated in absence (initial pH 2 to 7) and presence of background electrolytes (NaNO3 and Na2SO4 solutions of initial pH 3 and 6). The determined Cr-uptake was significantly higher than the one reported for the majority of other sorbents. The photo-metrically determined uptake data were modeled by the Langmuir, Redlich-Peterson, Langmuir-Freundlich, and Toth equations. The modeling results did not point out any preference to one specific model in terms of the goodness-of-fit and the prediction of maximum sorption capacity. The Cr-sorption kinetics was investigated at 15, 25, 35 and 45 oC using 51Cr-labeled solutions and ?-ray spectroscopy. The Cr-sorption was very fast at all studied temperatures and well reproduced by the pseudo-second order kinetics equation. Rate constant and activation energy values were calculated using the experimental data. The Cr-loaded resin was also examined by XRD, XPS, XAFS and SEM/EDS. The XPS and XAFS investigations indicated a partial reduction of Cr(VI) to Cr(III). The environmental compatibility of the Cr-loaded resin was examined using the EPA-TCLP method. The Cr-binding by the resin was very stable and regeneration attempts by HCl solutions of pH 3 were rather unsuccessful.

X-Ray Absorption Spectroscopies (XAFS) are employed in order to gather a thorough insight on the uptake mechanism of Cr(VI) by Fe3O4 nanoparticles under water treatment conditions. The XANES measurements identify that the reducing potential of Fe3O4 activates the precipitation of Cr(VI) in the form of insoluble and non-toxic Cr(III). However, electron donation from Fe(II) is responsible for its gradual consumption, resulting in the presence of a surface maghemite layer and the formation of structural vacancies. EXAFS analysis reveal that adsorption of Cr(III)-oxyanions occurs on sorption sites provided by the vacancies in the maghemite layer, where Cr(III) is involved in a bidentate binuclear (2E) geometry with Fe-octahedra while it also forms monodentate (1V) complexes with the Fe(III)O4 tetrahedra. The surface maghemitization along with the reduced Cr(III) adsorption into the vacancies, tracks the degree of Cr-reduction, since this surface structural modifications hinder Cr(VI) access to the Fe(II) ions of the magnetite nanoparticles. Thus, high surface coverage leads to the passivation of the reduction ability since physisorbed Cr(VI) is also detected through the formation of outer sphere complexes.

The delicate blue and green hue of ancient coloured beads from the Classical and Hellenistic period originate from the different transition metal (TM) ions added in the batch materials during glass production. The chemical composition in conjunction with the TM redox are fingerprints of the colour and vitrification process. We report on the structural and colouring/decolouring role of TM in blue and green-blue soda-lime beads from Thebes, central Greece dated back to the Classical and Hellenistic period using non-destructive X-Ray Absorption Fine Structure (XAFS) spectroscopies. Concerning the TMs redox and their consequent influence on colour, it is established that the major blue colourants are Co2+ and Cu2+, colourless Cu+ dominates in the blue beads, whereas chromophores Fe3+ and Cu2+ give rise to a green-blue hue. The Mn2+ content in the blue beads, whose occurrence is attributed to unintentional addition via the Co rich mineral colourant, counteracts the effect of the moderately higher content of Fe2+ in the raw materials. Based on the XAFS analysis results, we propose that the fractions of all TM under question (Mn, Fe, Co and Cu) were chosen and adjusted properly not only to control the desired colour, but also to ensure the stability of the glass matrix. Indeed, the integrity of the silica matrix should be further enhanced due to the presence of intermediate Fe oxides linking to Cu ions in either planar or linear geometry, while Mn and Co act as typical network formers.

The growth of GaN nanocrystals in an amorphous SiO2 matrix by sequential Ga and N implantation and rapid thermal annealing is reported. The effect of the implantation and annealing conditions on the distribution of the implanted ions, as well as the size, static disorder, and stability of the grown GaN nanocrystals, is studied by means of transmission electron microscopy, Rutherford backscattering spectrometry, Raman scattering, and extended X-ray absorption fine structure spectroscopies. It is found that the optimum temperature range for the post-implantation annealing of the nanocrystals, with a size that ranges from about 3 to 12 nm, is 1000–1100 °C. Higher temperatures result in the dissociation of the nanocrystals and out-diffusion of N and Ga, whereas lower temperatures are insufficient for the growth of GaN nanocrystals. Annealing for 30–90 s is optimum in order to avoid considerable loss of N and Ga. However, upon annealing at higher temperatures within the optimum range, up to 1100 °C, or for longer times, up to 120 s, larger GaN nanocrystals are grown and/or lower static disorder is observed.

International audience; The structural properties of Er-doped AlNO epilayers grown by radio frequency magnetron sputtering were studied by Extended X-ray Absorption Fine Structure (EXAFS) spectra recorded at the Er L 3 edge. The analysis revealed that Er substitutes for Al in all the studied samples and the increase in Er concentration from 0.5 to 3.6 at.% is not accompanied by formation of ErN, Er 2 O 3 or Er clusters. Simultaneously recorded X-ray Absorption Near Edge Structure (XANES) spectra verify that the bonding configuration of Er is similar in all studied samples. The Er-N distance is 2 constant at 2.18-2.19 Å i.e. approximately 15% larger than the Al-N bondlength, revealing that the introduction of Er in the cation sublattice causes considerable local distortion. The Debye-Waller factor, which measures the static disorder, of the second nearest shell of Al neighbors, has a local minimum for the sample containing 1% Er that coincides with the highest photoluminescence efficiency of the sample set.

Fossil bones and sediments from different horizons of the Upper Miocene paleontological site of Platania, Drama-Greece were studied using 238U, 235U, 232Th series and 40K measurements obtained by γ-spectroscopy. Additionally, SEM and XRF analysis was applied to bone and sediment samples while a lithological analysis of the sediments was also carried out. The 226Ra/238U ratios in the fossilization layers are attributed to the 238U depletion from the sediment and its incorporation into the fossils. The 226Ra/231Pa ratio indicates that the absorption of the isotopes started long before 4.2 Ma ago. The 232Th/40K profile demonstrate two distinct geological substrates, the lower corresponding to the Upper Miocene whereas the upper to the Upper Pleistocene-Holocene. Among them mediates a Mn-rich layer associated with the "Zanclean flood" during Pliocene. One layer above the "Glacial maximum event" during the Early Pleistocene was recorded. The natural radioactive sedimentary profile obtained reproduces the paleo-climatic conditions in Southeast Europe, which could be useful for the future.

In this work we present a molecular dynamics investigation of thermal transport in a silica-gallium nitride nanocomposite. A surprising enhancement of the thermal conductivity for crystalline volume fractions larger than 5% is found, which cannot be predicted by an effective medium approach, not even including percolation effects, the model systematically leading to an underestimation of the effective thermal conductivity. The behavior can instead be reproduced if an effective volume fraction twice larger than the real one is assumed, which translates into a percolation effect surprisingly stronger than the usual one. Such a scenario can be understood in terms of a phonon tunneling between inclusions, enhanced by the iso-orientation of all particles. Indeed, if a misorientation is introduced, the thermal conductivity strongly decreases. We also show that a percolating nanocomposite clearly stands in a different position than other nanocomposites, where thermal transport is dominated by the interface scattering and where parameters such as the interface density play a major role, differently from our case.

The high pressure response of type-I collagen from bovine Achilles tendon is investigated with micro-Raman spectroscopy. Fluorinert™ and methanol-ethanol mixtures were used as pressure transmitting media (PTM) in a diamond anvil cell. The Raman spectrum of collagen is dominated by three bands centred at approximately 1450, 1660 and 2930 cm-1 , attributed to C-H deformation, C=O stretching of the peptide bond (amide-I band) and C-H stretching modes respectively. Upon pressure increase, using Fluorinert™ as PTM, a shift towards higher frequencies of the C-H stretching and deformation peaks is observed. Contrary, the amide-I band peaks are shifted to lower frequencies with moderate pressure slopes. On the other hand, when using the alcohol mixture as PTM, the amide-I band exhibits more pronounced C=O bond softening, deduced from the shift to lower frequencies, suggesting a strengthening of the hydrogen bonds between glycine and proline residues of different collagen chains due to the presence of the polar alcohol molecules. Furthermore, some of the peaks exhibit abrupt changes in their pressure slopes at approximately 2 GPa, implying a variation in the compressibility of the collagen fibres. This could be attributed to a pitch change from 10/3 to 7/2, sliding of the tropocollagen molecules, twisting variation at the molecular level and/or elimination of the D-gaps induced by kink compression. All spectral changes are reversible upon pressure release, which indicates that denaturation has not taken place. Finally, a minor lipid phase contamination was detected in some sample spots. Its pressure response is also monitored.

The formation of wurtzite GaN nanoclusters in an amorphous silica matrix, via gallium and nitrogen ion implantation and rapid thermal annealing, is identified using Extended X Ray Absorption Fine Structure analysis. The mechanism and the crucial parameters that rule the formation of the nanoclusters are established by the use of molecular dynamics simulations. The dominant structural parameters are found to be the concentration of the silicon and oxygen vacancies that are formed during the implantation and the annealing temperature. It is concluded that annealing at 1400 K and 8% Ga/Si and 12% N/O ratios are needed for the formation of GaN nanoclusters. In addition to that, the GaN nanocluster formation is accomplished only when the vacancy concentrations of silicon and oxygen atoms are equal to 10% and 20%, respectively. Finally, the observation of various snapshots upon an increase of the annealing duration indicates the coalescence of smaller GaN nuclei towards larger ones, designating that the Ostwald...

Iron oxide nanoparticles were prepared using the simplest and most efficient chemical route, the coprecipitation, in the absence and the presence of three different and widely used surfactants. The purpose of this study is to investigate the possible influence of the different surfactants on the structure and therefore on the magnetic properties of the iron oxide nanoparticles. Thus, different techniques were employed in order to elucidate the composition and structure of the magnetic iron oxide nanoparticles. By combining transmission electron microscopy with X-ray powder diffraction and X-ray absorption fine structure measurements, we were able to determine and confirm the crystal structure of the constituent iron oxides. The magnetic properties were investigated by measuring the hysteresis loops where the surfactant influence on their collective magnetic behavior and subsequent AC magnetic hyperthermia response is apparent. The results indicate that the produced iron oxide nanoparticles may be considered as good candidates for biomedical applications in hyperthermia treatments because of their high heating capacity exhibited under an alternating magnetic field, which is sufficient to provoke damage to the cancer cells.

Manganese ferrite (MnFe2O4) nanoparticles of identical size (9 nm) and with different inversion degrees were synthesized under solvothermal conditions as a candidate theranostic system. In this facile approach, a long-chain amine, oleylamine, was utilized as a reducing and surface-functionalizing agent. The synthesized nanoparticles were shown to have a cubic-spinel structure as characterized by TEM and XRD patterns. Control over their inversion degree was achieved by a simple change of manganese precursor from Mn(acac)2 to Mn(acac)3. The variation in the inversion degree is ascribed to the partial oxidation of Mn(2+) to Mn(3+), as was evidenced by X-ray absorption near edge structure spectroscopy and extended X-ray absorption fine structure spectroscopy at both the Fe and Mn K-edges. The reduction of the inversion degree from 0.42 to 0.22 is close to the corresponding bulk value of 0.20 and led to elevated magnetization (65.7 emu g(-1)), in contrast to the Néel temperature, which was decreased owing to the weaker superexchange interactions between the tetrahedral and octahedral sites within the spinel structure. In order to evaluate the performance of these nanoprobes as a possible bifunctional targeting system, the (1)H NMR relaxation of the samples was tested together with their specific loss power under an alternating magnetic field as a function of concentration. The hydrophobic as prepared MnFe2O4 nanoparticles converted to hydrophilic nanoparticles with cetyltrimethylammonium bromide (CTAB). The MnFe2O4 nanoparticles, well-dispersed in aqueous media, were shown to have r2 relaxivity of up to 345.5 mM(-1) s(-1) and heat release of up to 286 W g(-1), demonstrating their potential use for bioapplications.

Earlymost Villafranchian fossil bones of an artiodactyl and a perissodactyl from the Milia excavation site in Grevena, Greece, were studied in order to evaluate diagenetic effects. Optical microscopy revealed the different bone types (fibro-lamellar and Haversian, respectively) of the two fragments and their good preservation state. The spatial distribution of bone apatite and soil-originating elements was studied using micro-X-ray fluorescence (µ-XRF) mapping and scanning electron microscopy. The approximate value of the Ca/P ratio was 2.2, as determined from scanning electron microscopy measurements. Bacterial boring was detected close to the periosteal region and Fe bearing oxides were found to fill bone cavities,e.g.Haversian canals and osteocyte lacunae. In the perissodactyl bone considerable amounts of Mn were detected close to cracks (the Mn/Fe weight ratio takes values up to 3.5). Goethite and pyrite were detected in both samples by means of metallographic microscopy. The local Ca/P ratio determined with µ-XRF varied significantly in metal-poor spots indicating spatial inhomogeneities in the ionic substitutions. XRF line scans that span the bone cross sections revealed that Fe and Mn contaminate the bones from both the periosteum and medullar cavity and aggregate around local maxima. The formation of goethite, irrespective of the local Fe concentration, was verified by the FeK-edge X-ray absorption fine structure (XAFS) spectra. Finally, SrK-edge extended XAFS (EXAFS) revealed that Sr substitutes for Ca in bone apatite without obvious preference to the Ca1or Ca2unit-cell site occupation.

The development of a single-phase Fe/Mn oxy-hydroxide (δ-Fe0.76Mn0.24OOH), highly efficient at adsorbing both As(III) and As(V), is reported. Its synthesis involves the coprecipitation of FeSO4 and KMnO4 in a kilogram-scale continuous process, in acidic and strongly oxidizing environments. The produced material was identified as a manganese feroxyhyte in which tetravalent manganese is homogeneously distributed into the crystal unit, whereas a second-order hollow spherical morphology is favored. According to this structuration, the oxy-hydroxide maintains the high adsorption capacity for As(V) of a single Fe oxy-hydroxide combined with enhanced As(III) removal based on the oxidizing mediation of Mn(IV). Ion-exchange between arsenic species and sulfates as well as the strongly positive surface charge further facilitate arsenic adsorption. Batch adsorption tests performed in natural-like water indicate that Mn(IV)-feroxyhyte can remove 11.7 μg As(V)/mg and 6.7 μg As(III)/mg at equilibrium pH 7, before residual concentration overcomes the regulation limit of 10 μg As/L for drinking water. The improved efficiency of this material, its low cost, and the possibility for scaling-up its production to industry indicate the high practical impact and environmental importance of this novel adsorbent.

The effect of 700 keV In implantation and subsequent annealing on GaN was studied by Rutherford Backscattering spectroscopy, Raman spectroscopy and nanο-indentation as a function of the ion fluence (F) ranging from 5 × 1013 to 1 × 1016 cm− 2. Symmetry allowed and disorder activated Raman scattering peaks were analyzed using the spatial correlation model, allowing their assignment to phonon branches of crystalline GaN or defects and the estimation of the corresponding phonon coherence length (L). The L values decrease abruptly at a critical fluence of approximately 2 × 1014 cm− 2. After a slight increase in the nano-hardness (H) and reduced elastic modulus (Er) values at low implantation fluences, they exhibit a steep reduction. These variations are accompanied by changes in the shape of the load–displacement curves, which are indicative of elasto-plastic behavior up to a critical F, whereas they approach the ideal plastic behavior at higher fluences. Annealing at 1000 °C of the sample implanted with 1 × 1015 ions/cm2 results in efficient recovery of its structural and nano-mechanical properties. However, annealing of specimens implanted at higher fluences causes partial recovery that starts mainly from the transition region between the heavily damaged and the underlying undamaged GaN. The highly correlated behavior of L, H and Er on the implantation fluence implies a common origin of the studied effects.

This study demonstrates an optimization procedure for the development of an Hg-specified adsorbent able to comply with the regulation limit for drinking water of 1 μg/L. On this purpose, the synthesis of Mn(IV)-feroxyhyte was modified to achieve high negative charge density by combining alkaline and extreme oxidizing conditions. In particular, precipitation of FeSO 4 at pH 9 and excess of KMnO 4 follows a very fast nucleation step providing a product with very small nanocrystal size (1–2 nm), high specific surface area (300 m 2 /g) and maximum negative charge density (1.8 mmol H + /g). The adsorbent was validated for Hg removal in batch experiments and column tests using natural-like water indicating an adsorption capacity as high as 2.5 μg/mg at equilibrium concentration 1 μg/L under reliable conditions of application. Importantly, the adsorption is an exothermic spontaneous process, resulting in the formation of inner sphere complexes by sharing both A-type and B-type oxygen atoms with the metal surface octahedral as revealed by the X-ray absorption fine structure results.

Synchrotron radiation micro-X-Ray Fluorescence (m-XRF), X-ray photoelectron (XPS) and X-ray Absorption Fine Structure (XAFS) spectroscopies are applied for the study of paleontological findings. More specifically the costal plate of a gigantic terrestrial turtle Titanochelon bacharidisi and a fossilized coprolite of the cave spotted hyena Crocuta crocuta spelaea are studied. Ca L2,3-edge NEXAFS and Ca 2p XPS are applied for the identification and quantification of apatite and Ca containing minerals. XRF mapping and XAFS are employed for the study of the spatial distribution and speciation of the minerals related to the deposition environment. Fil: Zougrou, I.M.. Aristotle University of Thessalonik; Grecia Fil: Katsikini, M.. Aristotle University of Thessalonik; Grecia Fil: Pinakidou, F.. Aristotle University of Thessalonik; Grecia Fil: Brzhezinskaya, M.. No especifíca; Fil: Papadopoulou, L.. Aristotle University of Thessalonik; Grecia Fil: Vlachos, Evangelos. Aristotle University of Thessalonik; Grecia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Tsoukala, E.. Aristotle University of Thessalonik; Grecia Fil: Paloura, E.C.. Aristotle University of Thessalonik; Grecia

The implementation of amorphous tetravalent manganese feroxyhyte (TMFx) nanoparticles, prepared via co-precipitation synthesis, as an efficient As(V)-removal material is investigated using X-ray absorption fine structure (XAFS) spectroscopy at the Fe-, Mn- and As-K-edges. The optimum synthesis conditions and chemical composition of the TMFx adsorbent were determined by the degree of polymerization in the adsorbents' microstructure. Under synthesis into mildly acidic conditions, the change in the polymerization of the metal-oxyhydroxyl chains (metal=Fe, Mn) provides more adsorption sites at edges and corner sites in the bonding environment of Fe and Mn, respectively, thereby enhancing As uptake. After exposure to As-polluted water, similar microstructural changes related to As-bidentate and monodentate geometries are generated: As(V) preferentially occupies the high energy adsorption sites ((2)C complexes) available in the Mn-oxyhydroxyl groups and the low energy edge sites offered by Fe ((2)E complexes). It is revealed that optimum arsenic-removal by TMFx occurs into mildly acidic synthesis pH and for iron to manganese molar ratio equal to 3.

X-ray absorption fine structure (XAFS) spectroscopy studies the modification of the X-ray absorption coefficient, above the absorption edge of a specific element, due to the presence of neighboring atoms and delivers information on materials nano- and electronic structure. The long-range translational symmetry is not a prerequisite, as in the case of diffraction-based techniques, which, along with the atom-specific character of XAFS, renders it a powerful tool for the study of nanomaterials.

GaN implanted with In, with fluencies (Φ) in the range of 1×1014 to 1×1016cm-2, is studied by means of X-ray absorption fine structure spectroscopy (XAFS). The heavily implanted samples, which are either highly defective or amorphous, are also studied after annealing at temperatures up to 1000 °C. The extended XAFS (EXAFS) spectra recorded at the Ga-K-edge reveal that the coordination numbers decrease with Φ while the Debye-Waller factors increase accordingly. Annealing at 1000 °C of the sample implanted with Φ = 1×1015cm-2recovers the coordination numbers and Debye-Waller factors to the values of the as-grown sample. Contrary to that, annealing even at 1000 °C does not induce recovery of the local coordination of Ga in the amorphized layers, although significant improvement in the EXAFS parameters is observed. In this case the detected undercoordination of Ga reveals loss of nitrogen after implantation and/or annealing. Annealing also improves the N-K-edge near edge (NEXAFS) spectra of the heavily implanted samples. More specifically, the NEXAFS peaks become sharper and the resonance lines that have been attributed to N-split-interstitials and N2 disappear even at low annealing temperatures. However, the absence of angular dependence of the NEXAFS spectra of the annealed layers, that became amorphous after the implantation, reveals the formation of randomly oriented microcrystallites. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The strain anisotropy of a-plane GaN epilayers is studied by polarization-dependent Raman spectroscopy. The intensity dependence of the A1(TO), E1(TO) and Raman peaks for an almost strain-free epilayer is well explained by using Raman tensors of C6v symmetry. However, the corresponding angular dependence for anisotropically strained GaN with |exx − eyy|∼6 × 10−3 (where x||a and y||m axes) dictates the use of a perturbation term of C2v symmetry that accounts for the orthorhombic distortion of the hexagonal unit cell. The consideration of this term elucidates the appearance of the mode for such epilayer orientations where it is forbidden by the hexagonal symmetry.

We report on the nanostructure of Ni and N in nanocomposite TiN-Ni films using extended (EXAFS) and near-edge (NEXAFS) X-Ray absorption fine structure spectroscopies at the Ni-K and N-K edges, respectively. The Ni content in the films, as determined by Rutherford backscattering analysis, varies between 0 and 21.5 at%. The Ni-K-edge EXAFS measurements disclose that the bonding environment of Ni is amorphous in all studied films. However, the local coordination of Ni changes as a function of the chemical composition. More specifically, Ni belongs both to a pure amorphous Ni phase, where the Ni–Ni bondlength is equal to 2.46–2.47 A (±0.01), while it also forms intermetallic TiNi bonds and the respective Ni–Ti bondlength is equal to 2.60–2.62 A (±0.02). The Ni–Ni and Ni–Ti bondlengths are equal among all studied samples and they are independent of the Ni content and the deposition temperature. On the contrary, the total coordination number of Ni in the 1st nearest neighbor shell, i.e. the sum of Ni and Ti atoms that comprise this shell, increases linearly with the Ni content and varies between 5.4 ± 0.7 and 13.1 ± 1.1. Finally, the N-K-NEXAFS results reveal that Ti forms crystalline TiN in all studied samples, independently of the N and Ti content in the films.

The nanostructure of Ti in TiN–Cu films, grown by pulsed laser deposition, is studied using Ti– K –NEXAFS spectroscopy. The characteristics of the NEXAFS spectra are strongly affected by both the different growth conditions and the Ti concentration in the films. More specifically, the area under the pre-edge peak is strongly correlated with the coordination number of Ti. It is found that in the TiN–Cu films grown from the intermetallic TiCu target, the area under the pre-edge peak decreases as the Ti concentration increases from 50 to 95 at.%. In the films grown from Ti and Cu elemental targets, the area under the pre-edge peak decreases as a function of the nitrogen partial pressure. The detected changes in the pre-edge peak can be attributed to the formation of Ti–Cu bonds.

We report on the distribution and local coordination of Fe and Ni in an Al matrix Fe–Ni composite, by means of X-ray Fluorescence mapping (XRF), micro- (μ-) and conventional Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies. The μ-XRF maps reveal that Fe segregates and forms Fe-rich islands which are depleted of Ni. The combined μ-EXAFS and EXAFS results reveal that both metals are bonded only to Al. More specifically, the Fe-rich islands are identified as FeAl 3 microcrystallites while in the Fe-poor regions, Fe belongs to an intermetallic FeAl phase. The bonding environment of Ni is also modified due to the variations in the distribution of the metals. In the region with high Ni concentration, i.e. Fe-poor regions, the Ni atoms are bonded to 10.5 ± 1.1 Al atoms that substitute Ni in fcc Ni. On the contrary, in the Ni-poor regions, where the Fe concentration exhibits maxima, the number of Al atoms in the first nearest shell of Ni is equal to 7.8 ± 0.9, i.e. in this region, Ni forms intermetallic NiAl. Finally, the atomic percentage of the Fe and Ni atoms that belong to the Fe-rich and Fe-poor islands is determined from the Fe- K and Ni- K edge EXAFS analysis. The majority of the Fe atoms (∼80 at%) belongs to the FeAl 3 microcrystallites, embedded into a FeAl matrix. On the contrary, the same atomic percentage of Ni atoms (∼50 at%), occupies sites in both the NiAl regions as well as in the matrix of the (Ni, Al) solid solution.

Micro-X-ray Fluorescence (μ-XRF) and Fe–K edge micro-X-ray Absorption Near Edge Structure (μ-XANES) spectroscopies are applied for the study of the distribution and the spatially-resolved bonding environment of Fe in human nails. The μ-XRF maps reveal that Fe forms islands where its concentration is up to six times higher than in the rest of the sample. Comparison of the map characteristics of two nails that belong to healthy and ill donors (affected by lung cancer), reveals that there is no significant variation in the size distribution of the Fe-rich inclusions contrary to their spatial density which is found higher in the nail of the ill donor. However, a relation between the variations of the spatial density and the illness can not be established due to the small number of the studied samples. The analysis of the Fe–K μ-XANES spectra reveals that the bonding environment of Fe varies between the samples and between different spots of the same sample with different Fe concentration. The characteristics of the pre-edge peak in the Fe–K XANES spectra indicate the presence of both Fe +3 and Fe +2 that participate in the formation of distorted octahedra. Finally, the area under the pre-edge peak depends linearly on the position of the absorption edge indicating variation of the Fe ligation between the samples and/or between different spots in the same sample.

The effect of Indium (In) implantation in n-type GaN is studied using Raman spectroscopy and Rutherford backscattering (RBS). The RBS analysis reveals that the 700 keV In implantation results in the formation of a subsurface defective region that extends to a depth of 400 nm. An abrupt increase (∼93%) of the maximum defect concentration is observed for fluences in the range 1.5 and 5×1014 cm-2. A further increase of the fluence to 5×1015 cm-2 renders the implanted layer amorphous. In the Raman spectra recorded in the backscattering geometry only the E22 peak is resolved since the A1(LO) is completely damped due to plasmon - phonon coupling. As the fluence increases, the characteristic sharp peaks of the as-grown sample broaden due to relaxation of the q-selection rules allowing phonons with q ≠ 0 to contribute in the Raman scattering. Furthermore, three additional broad peaks are detected in the implanted samples even after implantation with the fluence of 5×1013 cm-2. They are ascribed to disorder activated Raman scattering or acoustic overtones (300 cm-1, 420 cm-1) and the formation of point defects (670 cm-1), respectively. Rapid thermal annealing at 1000 °C causes partial recovery of the lattice. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

InxAl1-xN (0001) wurtzite layers with 0.2 0.45. In the case of the Al rich samples, an additional broad feature appears. The Raman spectra are fitted using the spatial correlation model providing the extent of the phonon confinement imposed by the alloy potential fluctuations is estimated. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on composition- and annealing-related modifications in the local bonding environment of Fe in a series of Fe- and Zn-rich composite quaternary materials whose composition models stabilized electric-arc furnace dust wastes. Application of X-ray absorption fine structure spectroscopies revealed that when [Fe 2 O 3 ] 3+ is a glass former, i.e. Fe belongs to tetrahedral sites into the vitreous matrix, independently of the annealing process and chemical composition. On the contrary, when [Fe 2 O 3 ] > 20 wt% the samples become vitroceramic. It is disclosed that a fraction of Fe 3+ occupies octahedral sites in Zn z Fe 3− x O 4 crystalline inclusions which are embedded into the glass matrix where the rest of Fe 3+ is bonded in tetrahedra. Furthermore, annealing of the samples with [Fe 2 O 3 ] ≥ 20 wt% at 900 °C induces devitrification, the samples become crystalline and Fe 3+ belongs to Zn n Fe 3− n O 4 where it forms both FeO 4 tetrahedra and FeO 6 octahedra.

The effect of chemical composition on the bonding environment of Cu, in a series of Ti1-x Cux and TiN/Cu films, is studied using X-Ray Absorption Spectroscopies (XAFS) at the Cu-K-edge. The EXAFS analysis reveals that in all studied samples Cu is amorphous. However, its bonding environment depends on the chemical composition. More specifically, in the Ti1-xCux films, Cu is coordinated with Ti and Cu and belongs both to intermetallic TiCu and to an amorphous Cu matrix. The coordination number of Cu, i.e., the sum of Ti and Cu first neighbours, increases systematically from 6.3 ± 0.7 to 10.6 ± 0.9 when the Cu content increases from 24.1 to 52.7 at%. On the contrary, in the TiN/Cu films, the type of atoms that consists the 1st nearest neighbour shell of Cu varies as a function of the Cu concentration. More specifically, in the TiN/Cu film with the lowest Cu content (27.3 at%), intermetallic TiCu is detected. At intermediate Cu concentration (37.8 at%), Cu is bonded to both Ti and Cu atoms. Finally, in the TiN/Cu film with the highest Cu content (67.7 at%), Cu is metallic.

We apply X-ray fluorescence (XRF) mapping and Fe-K X-ray absorption fine structure (XAFS) spectroscopies in order to determine the elemental distribution, the local coordination of Fe and the crystallization ratio of vitroceramic compounds that consist of Fe2O3, PbO, SiO2 and Na2O. The XRF maps reveal that Fe-rich inclusions are embedded into the vitreous matrix of the studied samples. The XAFS characterization results demonstrate that all quaternary samples are vitroceramic independently of the chemical composition and the Tcast. The EXAFS analysis reveals that only in the sample with 45 wt% Fe2O3 and Tcast = 1400 °C the microcrystalline inclusions consist of magnetite units. In all other vitroceramic samples the crystalline regions comprise both hematite and magnetite crystallites. The crystallization ratio is equal among all the vitroceramic samples, independent of the composition and Tcast. On the other hand, the increase in the concentration of hematite causes an elongation of the Fe–O bondlength in the FeO6 polyhedra and thus improves the symmetry of the FeO6 octahedra in the crystalline regions.

The effect of temperature on the bonding environment of indium in an InN epilayer is studied using X-ray absorption fine structure (EXAFS) spectroscopy. Shell-by-shell fitting of the EXAFS spectra reveals that, in the temperature range 80-245 K, the change in the nearest neighbour distances is smaller than the uncertainty of the measurement. The Debye-Waller factor of the second neighbouring shell (In-In pair) shows strong temperature dependence. Fitting using the Einstein model yields an Einstein temperature equal to 193 K + 5%. An alternative way of extracting information on the vibrational properties of the lattice is the simulation using the equation of motion method for the determination of the f Debye-Waller factors. The used values of 120 N/m and 50 N/m of the force constants for In-N and In-In bond stretching, respectively, simulate satisfactory the spectra measured at five different temperatures in the range 80-245 K.

We report on the bonding environment of In in In X Al i - x N (0.07 < x < 0.25) and InyGai-yN (0.7

The structural role, coordination geometry and valence of Fe in a series of Fe 2 O 3 –PbO–SiO 2 –Na 2 O glasses are studied by means of Fe-K-NEXAFS and EXAFS spectroscopies. Parameters for the study are the concentration of the Fe and Pb-oxides, the SiO 2 /Na 2 O ratio and the cast temperature. The EXAFS and NEXAFS results reveal that the role of Fe 3+ depends on the concentration of Fe 2 O 3 . More specifically, in most of the studied quaternary systems, the Fe 3+ ion is a glass former, i.e. the Fe atoms belong to FeO 4 tetrahedra that participate in the formation of the glassy network. The role of Fe as an intermediate oxide is identified only in one sample with 20 wt% Fe 2 O 3 , where ∼80 at.% of the Fe atoms are tetrahedrally coordinated with O atoms, while the remaining ∼20 at.% of the Fe atoms occupy octahedral sites. It is also revealed that the tetrahedral coordination of Fe in the vitreous matrix is destroyed when a number of parameters is altered, such as the T cast , the (Fe + Si)/O and the SiO 2 /Na 2 O ratio.

The effect of the composition and casting temperature on the structural role of Fe in a series of binary (Fe 2 O 3 –PbO and Fe 2 O 3 –Na 2 O) and ternary (Fe 2 O 3 –PbO–SiO 2 ) glass and glass ceramic materials is studied by means of X-ray fluorescence (XRF) mapping, X-ray absorption fine structure (XAFS) and Mossbauer spectroscopies. According to the Mossbauer results the majority of Fe exists in the Fe +3 state. The XRF maps reveal that Fe-rich islands evolve into the vitreous matrix of ternary samples that contain more than 40 wt% Fe 2 O 3 . In these samples the XAFS results disclose that 40–43 at.% of the Fe atoms belong to the Fe-rich microcrystalline islands formed by Fe x O y oxides. Furthermore, the structural role of Fe +3 in the ternary glasses is found to depend on the Fe 2 O 3 content. Finally in the binary Fe 2 O 3 –PbO systems the majority of Fe +3 is octahedrally coordinated in the Fe 2 O 3 and/or PbFe 12 O 19 crystalline phases.