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© 2019 Elsevier BV. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (January 2019) in accordance with the publisher’s archiving policy, The morphology of Propyltrimethoxysilane films during the oscillatory growth mechanism is shown using Auger Electron Spectromicroscopy. While the link between oligomerisation of silane molecules on the substrate and the oscillatory growth mechanism has been proposed previously, here for the first time we show the presence of silane film islands through Auger Electron Spectromicroscopy elemental mapping of the substrate. Monitoring the morphology of the film at key peaks and throughout along the oscillatory curve reveals the formation of a stable thin, homogenous film along with the presence of islands approximately 20μm in diameter, whose numbers vary collectively during the adsorption/desorption mechanism. The measurable oscillations in silane substrate coverage has been directly linked to the repeated adsorption and desorption of silane islands on the aluminium substrate. The consequence of this mechanism is such that Propyltrimethoxysilane films behave most like a monolayer during the early stages of film growth, prior to siloxane oligomerisation.

The selectivity rules of sum frequency generation spectroscopy were exploited to determine propyl chain order during the time-dependent oscillatory adsorption of propyltrimethoxysilane (PTMS) and Langmuir-type growth of propyldimethylmethoxysilane (PDMMS). During the early stages of film growth, molecular packing density determines the extent of propyl chain defects within both films with high surface coverage resulting in a film with fewer defects. Following this, an ordered monolayer-like film stabilizes on the Al2O3 substrate for both silanes. Although this result is intuitive for the Langmuir-type growth of PDMMS, the stabilization of molecular ordering despite the continuing oscillation in PTMS surface coverage indicates the presence of a stable monolayer, while it is the oligomerized PTMS dendrimers which continue to desorb and readsorb to the substrate. We also reveal for the first time, the formation of a physisorbed bilayer during the self-assembly process of PTMS. The presence of this ordered, physisorbed bilayer on top of the covalently bound PTMS film plays a key role in the process of the molecular self-assembly mechanism and is proposed to enable further condensation of the covalently bound film.

Chalcopyrite, galena, and sphalerite commonly coexist with pyrite in sulfidic waste rocks. The aim of this work was to investigate their impact, potentially by galvanic interaction, on pyrite oxidation and acid generation rates under simulated acid and metalliferous drainage conditions. Kinetic leach column experiments using single-minerals and pyrite with one or two of the other sulfide minerals were carried out at realistic sulfide contents (total sulfide 47% for galena vs

The surface of pyrite exposed to the thermophilic archaeon Acidianus brierleyi was investigated to elucidate the impact of extracellular polymeric substances (EPS) and/or cells on mineral surface hydrophobicity. The interaction of cells with the surface of pyrite and the physicochemical properties of the mineral surface were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), captive bubble contact angle measurements and time of flight – secondary ion mass spectrometry (ToF-SIMS). The ToF-SIMS results show no clear evidence of EPS on the pyrite surface after exposure to A. brierleyi and further suggests significant contamination of the surface by the yeast extract included in the recommended A. brierleyi growth medium. It was found that the presence of yeast extract made it impossible to accurately determine the action of EPS on the surface, and potentially impeded chemical and biological reactions and interactions on the surface. Investigation of the impact of A. brierleyi on pyrite in the absence of yeast extract found up to 24° decrease in contact angle compared to the control after 2 h. It was found that A. brierleyi produced very little EPS and as such is unlikely to alter the surface through a contact mechanism, with little to no cell attachment observed on the pyrite surface. Thus removal of yeast extract may improve the application of this archaea to biomining applications.

The growth of silane films on plasma oxidized highly oriented pyrolytic graphite (HOPG) surfaces has been studied using wet chemical deposition of propyltrimethoxysilane (PTMS) and propyldimethylmethoxysilane (PDMMS). Scanning Auger microscopy (SAM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the chemical composition and morphology of the silane films. The effects of several deposition parameters were examined, including the necessity of oxidation of the HOPG surface, addition of water with the silane, and rinsing before curing. The optimal conditions needed to create a complete uniform film differ for the two silanes due to differences in their structures. Both silanes require an oxidized HOPG surface for a film to grow, the addition of water with PTMS results in a thicker film, while the addition of water with PDMMS decreases the film growth. Rinsing of both samples before curing removes physisorbed species, leaving only the covalently bonded film on the surface.

Cantilever devices have found applications in numerous scientific fields and instruments, including the atomic force microscope (AFM), and as sensors to detect a wide range of chemical and biological species. The mechanical properties, in particular, the spring constant of these devices is crucial when quantifying adhesive forces, material properties of surfaces, and in determining deposited mass for sensing applications. A key component in the spring constant of a cantilever is the plan-view shape. In recent years, the trapezoidal plan-view shape has become available since it offers certain advantages to fast-scanning AFM and can improve sensor performance in fluid environments. Euler beam equations relating cantilever stiffness to the cantilever dimensions and Young&rsquo, s modulus have been proven useful and are used extensively to model cantilever mechanical behaviour and calibrate the spring constant. In this work, we derive a simple correction factor to the Euler beam equation for a beam-shaped cantilever that is applicable to any cantilever with a trapezoidal plan-view shape. This correction factor is based upon previous analytical work and simplifies the application of the previous researchers formula. A correction factor to the spring constant of an AFM cantilever is also required to calculate the torque produced by the tip when it contacts the sample surface, which is also dependent on the plan-view shape. In this work, we also derive a simple expression for the torque for triangular plan-view shaped cantilevers and show that for the current generation of trapezoidal plan-view shaped AFM cantilevers, this will be a good approximation. We shall apply both these correction factors to determine Young&rsquo, s modulus for a range of trapezoidal-shaped AFM cantilevers, which are specially designed for fast-scanning. These types of AFM probes are much smaller in size when compared to standard AFM probes. In the process of analysing the mechanical properties of these cantilevers, important insights are also gained into their spring constant calibration and dimensional factors that contribute to the variability in their spring constant.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., A. ferrooxidans and their metabolic products have previously been explored as a viable alternative depressant of pyrite for froth flotation; however, the mechanism by which separation is achieved is not completely understood. Scanning electron microscopy (SEM), photoemission electron microscopy (PEEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and captive bubble contact angle measurements have been used to examine the surface physicochemical properties of pyrite upon exposure to A. ferrooxidans grown in HH medium at pH 1.8. C K-edge near edge X-ray absorption fine structure (NEXAFS) spectra collected from PEEM images indicate hydrophilic lipids, fatty acids and biopolymers are formed at the mineral surface during early exposure. After 168 h, the spectra indicate a shift towards protein and DNA, corresponding to an increase in cell population and biofilm formation on the surface, as observed by SEM. The Fe L-edge NEXAFS show gradual oxidation of the mineral surface from Fe(II) sulfide to Fe(III) oxyhydroxides. The oxidation of the iron species at the pyrite surface is accelerated in the presence of A. ferrooxidans and extracellular polymeric substances (EPS) as compared to HH medium controls. The surface chemical changes induced by the interaction with A. ferrooxidans show a significant decrease in surface hydrophobicity within the first 2 h of exposure. The implications of these findings are the potential use of EPS produced during early attachment of A. ferrooxidans, as a depressant for bioflotation., This work has been supported by the Australian Research Council under FT110100099. The authors acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy & Microanalysis Research Facility at the South Australian Regional Facility (SARF) SA Nodes, Flinders University, Adelaide University and the National Synchrotron Radiation Research Centre. We acknowledge travel funding provided by the International Synchrotron Access Program (ISAP) managed by the Australian Synchrotron AS_IA123_6566 and AS/IA133/7716.

There is currently poor understanding of metal removal by composites of bacteria and iron oxide minerals, even though they commonly co-occur and are among the most important sorbents in near-surface fluid–rock environments. This study evaluated Cu removal by composites of Anoxybacillus flavithermus and iron oxide over time during the addition, oxidation, and hydrolysis of Fe(II) aq and precipitation of the mineral, in comparison to Cu removal in the two single-sorbent end-member systems. In the absence of iron oxide, Cu removal by A. flavithermus was well described by a previously published surface complexation model, after inclusion of additional reactions describing aqueous complexation by exudate ligands released by the bacteria. In the absence of bacterial cells, Cu removal by iron oxide synthesized in the presence of the bacterial exudate ligands demonstrated the formation of ternary surface complexes. Removal of Cu by the A. flavithermus –iron oxide composites was ca. 20% greater than the prediction based on assumption of additivity in the two end-member systems. This non-additive behavior was attributed to (1) progressive physical blockage of bacterial surface sites by the iron oxide particles, (2) physical blockage of adsorption sites as a result of self-aggregation of the iron oxide particles, and (3) the reduction of Cu(II) to Cu(I) at the bacterial cell surface, as demonstrated by X-ray absorption spectroscopy. The extent of reduction of Cu(II) to Cu(I) was proportional to the concentration of solid phase Fe(II), suggesting that iron oxidation and copper reduction are linked. This study has shown that Cu removal by bacteria–iron oxide composites is greatly affected by redox processes such as Cu(II) reduction on the cell surface both by other bacterial surface ligands and the oxidation of sorbed Fe(II), as well as Fe(II) redox interactions, and aging effects of the mineral (i.e. surface site masking).

The surface chemical information of massive chalcopyrite electrode during electrochemical oxidation was studied by SXPS, NEXAFS and Raman spectroscopy. The electrochemical studies show that there was an activated region for chalcopyrite anodic dissolution between 550 and 630 mV (vs. Ag/AgCl), accompanied by two passive regions nearby. The spectroscopic studies suggest a thin film of non-stoichiometric sulfur-rich layer formed in the first passive region, likely to be responsible for the passivation. In the active region, S22 − species and covellite were also found, which could be the cause of the potential surge. When the potential was increased to 650 mV, another passive region appeared. At the same time, S22 − and covellite started to dissolve, leaving a highly metal deficient polysulfide and elemental sulfur layer on the chalcopyrite surface.

The surface electronic structure of (Fe,Ni)9S8 was investigated using synchrotron X-ray photoelectron spectroscopy (SXPS). SXPS S 2p and valence band (VB) spectra, collected as a function of photon energy, have resolved two distinct bulk states and two surface chemical states present at (Fe,Ni)9S8 fracture surfaces. The SXPS S 2p spectra show two distinct sulfur sites within the lattice that have been attributed to 4-coordinate sulfur at 161.7 eV, and 5-coordinate sulfur at 162.2 eV. Upon fracture, sulfur sites are exposed at multiple fracture planes and lose at least one bonding partner, resulting in surface 3-coordinate sulfur at 161.1 eV, and a slightly broader peak at 161.7 eV attributed to 4-coordinate sulfur surface monomer species overlapping the bulk 4-coordinate species. Significant asymmetric tail shapes were observed in each of the S 2p spectra and have been identified as ligand-to-metal charge transfer satellites (LMCT). A practical approach for curve fitting the (Fe,Ni)9S8 XPS spectra has been proposed.

SXPS (Synchrotron X-ray Photoelectron Spectroscopy) and NEXAFS (Near Edge X-ray Absorption Fine Structures) have been applied to study the surface chemical species of chalcopyrite leached by a moderate thermophilic consortia, Leptospirillum ferrooxidans and a mesophilic mixed culture of L. ferrooxidans , Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A sulfur-rich layer dominated by S n 2− developed with time, which was found to control the rate of bioleaching. Fe L 2,3 -edge NEXAFS and Fe 2 p spectra indicate the formation of jarosite during bioleaching. Thermophiles significantly enhanced the leaching efficiency, in which 1.34 g/L copper was dissolved in 25 days, while less than 0.3 g/L copper was released in 30 °C bioleaching. This was mostly caused by the increased abiotic reaction rate. The solution copper concentration in presence of L. ferrooxidans was higher than that with mesophilic mixed culture, which suggests the synergistic effect of mixed microorganisms did not play a comparably important role as temperature under the conditions used in this study. Explicit evidence of elemental sulfur was only found in samples leached by L. ferrooxidans by Raman spectroscopy. However, the formation of elemental sulfur does not significantly hinder the leach rate.

The effect of physisorbed and chemisorbed species on the time-dependent self-assembly mechanism of organosilane films has been investigated on aluminium oxide using X-ray Photoelectron Spectroscopy. The role of physisorbed species was determined through their removal using a simple rinsing procedure while monitoring film substrate coverage. Removing physisorbed species from Propyldimethylmethoxysilane films, shown to follow a Langmuir-type adsorption profile, reduces the substrate coverage initially but quickly results in coverages equivalent to films that did not undergo a rinsing procedure. This indicates that all Propyldimethylmethoxysilane molecules are covalently bound to the substrate following 15 s of film growth. Removing physisorbed species from films, which have been shown to follow an oscillatory adsorption profile, Propyltrimethoxysilane and Propylmethyldimethoxysilane, reveal the persistence of these oscillations despite a reduction in silane substrate coverage. These results not only confirm the presence of two thermodynamically favourable phases in the condensation equilibrium reaction as physisorbed and chemisorbed species, but also indicate that the desorption of species during film growth involves both states of chemical binding.

Biochar application to agricultural land has been proposed as a means for improving phosphorus (P) availability in soil. The purpose of the current study was to understand how pyrolysis temperature affects P speciation in biochar and how this affects availability of P in the amended soil. Biochar was produced at different temperatures from digestate solids. The primary species of P in digestate solids were simple calcium phosphates. However, a high co-occurrence of magnesium (Mg) and P, indicated that struvite or other magnesium phosphates may also be important species. At low temperatures, pyrolysis had little effect on P speciation; however, as the temperature increased above 600 °C, the P gradually became more thermo-dynamically stable in species such as apatite. At very high temperatures above 1000 °C, there were indications of reduced forms of P. Biochar production decreased the immediate availability of P in comparison with the original digestate solids. However, for biochar produced at low temperatures, availability quickly increased to the same levels as in the digestate solids. For biochar produced at higher temperatures, availability remained depressed for much longer. The low availability of P in the biochar produced at high temperatures can probably be explained by the formation of less soluble P species in the biochar. In contrast, the transient decrease of availability of the P in the biochar produced at low temperatures can be explained by mechanisms, such as sorption on biochar, which gradually decreases because of oxidation of the biochar surfaces or changes in pH around the biochar particles. Refereed/Peer-reviewed

The role of particle shape properties in determining flotation kinetics was investigated in this study. -150/+75 μm chalcopyrite was floated in a microflotation cell, and shape properties of the timed concentrates were quantified using a mineral liberation analyser - a mineralogical characterisation system based on automated scanning electron microscopy. It was found that, when floated in the absence of collector, particles with angular shape features reported to the concentrate faster than round particles. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) showed that angular particles also exhibited surface chemistry characteristics favourable for flotation. When particle floatabilities were high (i.e. when floated in the presence of potassium amyl xanthate), shape properties were not found to contribute significantly to the rates at which particles floated. © 2010 Elsevier Inc. All rights reserved.

The surface species present on two pure chalcopyrite samples (one with a smooth fracture surface; one with a rough fracture surface) and one heterogeneous sample containing both chalcopyrite and pyritehave been studied using synchrotron X-ray photoelectron spectroscopy (SXPS), near-edge X-ray Absorption Fluorescence Spectroscopy (NEXAFS), and time-of-flight secondary ion mass spectrometry (ToFSIMS).The measurements were performed for samples fractured in N2 and for samples subsequently exposed to pH 1 HCl solution for 2 h. The comparison of freshly fractured and solution exposed mineral surfaces has allowed for the investigation of the role of other mineral phases on the development of chalcopyrite surface species, and the role of chalcopyrite grain size on surface species development. Analysis of the chalcopyrite region of each sample indicates that increased surface roughness and the presence ofpyrite in intimate contact with chalcopyrite increases the formation of surface sulfur species that are implicated in the formation of passivating layers on leached chalcopyrite surfaces. ToF-SIMS analysis of the chalcopyrite and pyrite regions of the heterogeneous sample support the conclusions obtained from the synchrotron surface analysis experiments. Refereed/Peer-reviewed

Chalcopyrite, CuFeS2, is an important source of copper and is recovered from ore by the flotation process. Chalcopyrite is commonly associated with other metal sulfides, e.g. bornite, Cu5FeS4. In this study the effect of bornite on the oxidation and leaching of chalcopyrite has been investigated by probing the surface evolution of pure chalcopyrite, bornite, and heterogeneous samples containing both chalcopyrite and bornite using Synchrotron X-ray Photoelectron Spectroscopy (SXPS). Samples were freshly fractured in a N2 atmosphere and the resulting surfaces were oxidised in pH 9 KOH for 30 min or leached in pH 1 HCl for 2 h before being transferred into vacuum without leaving the N2 atmosphere. Analysis of the chalcopyrite region of each sample indicates that exposure to pH 9 for 30 min when bornite is present results in a decreased concentration of hydrophobic polysulfide species (from 43% to 36% of the total S 2p spectrum). In addition to this decrease in hydrophobic species, there is an increase in the amount of hydrophilic sulfate on the surface, from trace amounts to 3%. For those samples leached at pH 1 there was a small decrease in the amount of polysulfide species (43% to 39%), but also a slight increase in disulfide species (16% to 19%) indicating analteration to the oxidation process at low pH in the presence of bornite. Refereed/Peer-reviewed

Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study the Cuactivation of the (110) surface of sphalerites with Fe content varying from 0 to 14.79 wt%. Time resolvedAFM images show the development of surface oxidation products at high-energy step edges. These smallprotrusions evolve into larger conglomerates and finally full surface coverage with time. Surface morphologychanges show an increase in the number of cleavage steps and the size of precipitates as a functionof Fe concentration. Both of these factors contribute to the increased rate of Cu activation of high Fesphalerite as compared to low Fe sphalerite. XPS analysis of the sphalerites Cu activated for 1 h at pH 5,indicates an increased Cu concentration and the formation of disulphide and polysulphide that correlateswith an increase in bulk Fe content. Refereed/Peer-reviewed

To obtain a fundamental understanding of the population behaviour of Acidithiobacillus ferrooxidans at chalcopyrite and pyrite surfaces, the early stage attachment behaviour and biofilm formation by this bacterium on chalcopyrite (CuFeS2) and pyrite (FeS2) were studied by optical microscopy, Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The results indicate there was no significant difference in selectivity of bacterial attachment between chalcopyrite and pyrite. However, the result of ToF-SIMS analysis suggests that the surface of the pyrite was covered more extensively by biofilm than that of the chalcopyrite, which may indicate more extracellular polymeric substances (EPS) formation by bacterial cells growing on pyrite. EBSD and optical image analysis indicated that selectivity of bacterial attachment to chalcopyrite was not significantly affected by crystal orientation. The results also suggest that the bacterial population in defective areas of chalcopyrite was significantly higher than on the polished surfaces.

Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence., Wrapping bacterial cells with graphene oxide sheets using a vortex fluidic device (VFD) effectively limits cellular growth for a certain time period whilst sustaining biological activity. This simple and benign method in preparing such a composite material relies on the shear within the film in the device without compromising the cellular viability. In principle, the process is scalable for large volumes, for operating the VFD(s) under continuous flow mode. Moreover, acquiring SEM images was possible without pre-coating the composite material with a metallic film, with limited charging effects. This establishes the potential for interfacing material with graphene oxide, which could be extended to more conductive graphene layers, as an effective approach for simplifying characterization using SEM.

Chalcopyrite (CuFeS2) leaching in perchloric acid (HClO4) at an initial pH of one and a temperature of 85 °C has been examined. The rate of leaching of Cu and Fe increased progressively over the duration of the experiment. The Cu leach rate was initially greater (up to 24 h) but thereafter the leach rates for Cu and Fe were approximately equal. After 313 h 81% Cu release was achieved at which time the leach experiment was terminated. Only 25% of the available S was released into solution during the leaching process. Surface speciation over the duration of the leach was examined using X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy (SEM). As a result, a three-step reaction pathway is proposed. The first oxidation step involves the release of Cu and Fe into solution and the polymerisation of monosulfide (S2−) to polysulfide S n 2 - . The subsequent reduction step does not result in the release of cations to solution but does result in the reformation of surface S2− and other short chain polysulfides, which then on further oxidation restructure to form crystalline elemental sulfur (S0). This final oxidation step is accompanied by further cation release.

Conventional X-ray photoelectron spectroscopy (XPS) and synchrotron radiation XPS (SRXPS) were used to probe the chemical state properties of stibnite (Sb 2 S 3 ), a large-band-gap semiconductor of complex structure. The conventional spectra were obtained with a Kratos Axis Ultra XPS with magnetic confinement charge neutralization, which is very effective in minimizing both uniform charging and differential charging on this large-band-gap semiconductor. The narrow linewidths (much narrower than previously obtained) for single doublet fits (e.g. Sb 4d 5/2 of 0.57 eV and S 2p 3/2 of 0.63 eV) enabled the observation of a small peak on the low binding energy side of the Sb 3d and Sb 4d lines. With the aid of the very surface-sensitive Sb 4d SRXPS spectra, these low energy peaks are assigned to small Sb metal clusters at the surface after cleavage; the signal for these clusters increases with X-ray dose on the sample. A detailed analysis of the Sb 4d and S 2p linewidths concludes that the Sb 4d 5/2 linewidth is larger than expected based on the inherent linewidth of the instrument and the Sb 4d lifetime width, and on comparison with the As 3d linewidth (0.52 eV) for the analogous As 2 S 3 . Also, the S 2p 3/2 linewidth is substantially broader than the Sb 4d 5/2 linewidth. These larger than expected linewidths are due to two structurally distinct Sb atoms and three structurally distinct S atoms in the Sb 2 S 3 crystal structure. Accordingly, the Sb 4d and S 2p spectra have been fitted to two and three doublets respectively, and the linewidth for all peaks is 0.53 eV. Using recent molecular orbital calculations, the doublets have been assigned to the different structural Sb and S sites.

Nous avons synthetise la lazurite ayant une composition voisine de [Na 6 Ca 2 Al 6 Si 6 O 2 4 (S04,S) 2 ] en employant comme reactifs CaS + CaSO 4 dans des experiences hydrothermales sous pression et par reduction d'une feuille de Re dans des experiences avec piston-cylindre. Nous avons obtenu un echantillon bleu royal par recuit a 1200°C et 0.5 GPa; la trame de ce materiau est enrichie en Al (Al/Si entre 1.1 et 1.2), et il coexiste avec une petite quantite de sodalite incolore a faible teneur en soufre et contenant un excedant de Si. Le membre du groupe de la sodalite forme dans les experiences sans agent reducteur est la hauyne. Nous avons determine l'etat du soufre dans les produits de syntheses et dans la lazurite de l'Afghanistan et l'ile de Baffin, au Nunavut, par spectroscopie de l'absorption des rayons X pres du seuil K du soufre (XANES) et par spectroscopie photo-electronique des rayons X du S 2p (XPS). C'est le sulfate qui predomine parmi les especes de soufre dans tous les echantillons de lazurite, et nous decelons des quantites importantes mais subordonnees de sulfure en coordinence avec les cations Na + . De plus, il se trouve une fraction mineure de sulfite dans certains produits issus de l'appareil piston-cylindre, et de soufre natif dans les mineraux etudies. Les polysulfures ne depassent pas le seuil de detection. La lazurite naturelle differe de facon marquee de son equivalent synthetique en termes de composition chimique et des spectres XANES du seuil K du soufre et XPS du soufre 2p 3 / 2 , mais ces differences ne semblent pas exercer une grande influence sur le developpement de la couleur. Dans la hauyne synthetique, le soufre situe dans la cage structurale serait exclusivement sous forme de sulfate.

Sulfur and Ti 2p XPS and polarized S K- and L2,3- and Ti L2,3-edge XANES spectra have been obtained from oriented ribbon-like crystals of TiS3 grown by vapor transport. The S 2p XPS spectrum for (0 0 1) crystal faces has line widths of 0.53 eV and is completely accounted for by partially overlapped 2p3/2/2p1/2 doublets for sulfide (S2−) and disulfide ( S 2 2 - ) species, which are separate and independent entities in TiS3. Evidence of unsaturated surface states is lacking, consistent with a surface monolayer for the (0 0 1) growth face of disulfide atoms oriented with their charge-neutral sides outward. The S K-edge XANES spectra show pronounced anisotropy in the (0 0 1) plane of TiS3 crystals, associated with the photoelectron transition channel S 1 s → 3 p x σ u ∗ with the electric vector (E) parallel the a-axis (and the S–S bond of the disulfide group), and transitions to unoccupied antibonding orbitals of S–Ti bonds with E parallel to the b-axis (the direction of the well-known quasi-one-dimensional character of TiS3). The XPS and ultrasoft and soft X-ray region XANES spectra confirm the surface and near-surface structural integrity of TiS3.

The sulfur K and L2,3 x-ray absorption near-edge structure (XANES) spectra of FeS, CoS and NiS having the NiAs-type crystal structure have been measured. Theoretical analysis of the experimental data has been conducted by the full multiple-scattering approach. Good agreement between experimental and theoretical data is obtained for comparatively small clusters containing 19–37 atoms. There is no significant difference between S K-edge absorption spectra for the studied compounds calculated by G4XANES and FEFF8.2 packages. The electronic structure of NiS and CoS has been studied by analysing the distribution of calculated electronic states of the sulfides.

A comparative X-ray photoelectron spectrometric (XPS) study of the Fe 2p, S 2p and As 3d spectra of pristine, fractured surfaces of pyrite, marcasite, arsenopyrite and loellingite indicates systematic and predictable change to the surfaces of these minerals. Auto-redox and polymerization reactions stabilize uncompensated surfaces of these 3d transition metal-bearing dichalcogenides. The route to stabilization is predictable through consideration of bulk structure and electronegativity of the elements constituting the dichalcogenides. Stabilization occurs through reconstruction via polymerization of surface ligands, unless inhibited by intervening atoms or by large distances separating adjacent ligand dimers. The cubic structure of pyrite results in adjacent S dimers being separated by a distance about 50% greater than the S dimer bond length and Fe atoms are located sufficiently close to surface S atoms to inhibit S-polymer formation on (0 0 1) surfaces; polymerization on this surface consequently is minimal (if it occurs). The pyrite surfaces are consequently stabilized via an auto-redox reaction. Adjacent As dimers of loellingite (orthorhombic) are separated by a distance only 16% greater than the As dimer bond length and Fe atoms do not separate surface dimers from bulk dimers. Surface stabilization occurs via reconstruction with migration of surface As dimers toward the bulk and bonding with bulk As dimers to produce near-surface tetramers. Polymerization proceeds to such an extent that no surface monomers or dimers are detected at fracture surfaces. The crystal structure of marcasite is orthorhombic like loellingite but contains strongly electronegative S atoms (rather than As atoms). Its fracture surfaces are stabilized by both polymerization reactions (just as observed on loellingite surfaces) and by surface redox reactions (as on pyrite surfaces). The shortest distance separating adjacent S dimers is about 50% greater than the S–S dimer bond length in marcasite. This distance apparently diminishes appreciably the probablility of polymerization of surface S atoms thus allowing auto-redox reactions to occur. Polymerization and redox reactions stabilize Fe dichalcogenide surfaces. The extent to which each type of reaction proceeds is dependent upon bulk structure and electronegativity of the constituent atoms of the compound and favorable redox reaction energetics.

Pristine fractured surfaces of chalcopyrite (CuFeS2) have been studied using Synchrotron Radiation X-ray Photoelectron Spectroscopy and conventional X-ray Photoelectron Spectroscopy. These high-resolution spectra reveal for the first time three distinct contributions to the S 2 p spectrum. The main symmetric peak is located at 161.33 eV and is likely derived from fully coordinated bulk S atoms. A core-level shifted peak was observed at 160.84 eV and is attributed to surface monomeric species (S2−). A second broad contribution at 161.88 eV likely represents surface polymeric species (![Formula][1] ). The data suggest that surface polymers form where S-terminated surfaces such as the (111) plane are exposed during fracture. [1]: /embed/tex-math-1.gif

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)., The replacement of depressants used in sulfide mineral beneficiation, with bacteria and their metabolites, promises to reduce the environmental impact left by the mining industry. In this study, the attachment of Leptospirillum ferrooxidans, L.f, to chalcopyrite and pyrite was investigated through Scanning Electron Microscopy (SEM). The impact of selective attachment, bacterial growth conditions, and extracellular polymeric substances (EPS) was investigated through bio-flotation. L.f exhibits selective attachment to pyrite between 0 h and 168 h exposure via an indirect contact mechanism. Separation of chalcopyrite from pyrite was achieved through exposing the minerals for 72 h with an L.f culture grown on either HH media, chalcopyrite, or pyrite. The results produced 80.4, 43.4, and 47.4% recovery of chalcopyrite, respectively. However, EPS supernatant extracted from L.f grown on chalcopyrite, conditioned for 48 h, provided the best separation efficiency by the selective depression of pyrite resulting in 95.8% Cu recovery. Polysaccharide-rich EPS selectively attaches to pyrite within 48 h, depressing its floatability and ensuring successful separation with a PIPX collector., This work was funded by the Australian Research Council through FT110100099.

Gold was exposed to ethanol solutions containing 0.1 wt% 1-hexyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide (HMIM NTf2), an ionic liquid (IL). The resulting adsorbed layers were interrogated using X-ray photoelectron spectroscopy (XPS - both conventional and synchrotron-based) and spectroscopic ellipsometry. Ellipsometry indicated that the adsorbed layer thickness was smaller than the size of an IL ion pair, with an average determined layer thickness of 0.15 nm. This value indicates that the adsorbed layer on gold is most likely patchy. Conventional XPS revealed that the IL adsorbs irreversibly to gold, with equal amounts of anion and cation in the adsorbed layer. High signal-to-noise synchrotron XPS spectra permitted detailed deconvolution of the S 2p and N 1s peaks for the IL-treated gold, providing more information on adsorbed layer composition and structure. Spectra acquired as a function of X-ray exposure time indicate that non-interacting physisorbed IL components are preferentially removed at the expense of surface bound components, and that anion and cation are both present in the surface bound layer, and also in the layer above. A model structure for the IL adsorbed on gold is proposed.

Synchrotron-based X-ray photoemission electron microscopy (X-PEEM), X-ray photo-electron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and ultraviolet visible spectroscopy were used to characterize the flotation behaviour of chalcopyrite with xanthate at different processing conditions. The flotation recovery of chalcopyrite decreased from 97% under oxidative conditions (Eh ~ 385 mV SHE, pH 4) to 41% at a reductive potential of − 100 mV SHE (at pH 9). X-PEEM images constructed from the metal L3 absorption edges were used to produce near-edge X-ray absorption fine structure (NEXAFS) spectra from regions of interest, allowing the variability in mineral surface chemistry of each mineral particle to be analysed, and the effect of pulp potential (Eh) on the flotation of chalcopyrite to be determined. XPS, ToF-SIMS and NEXAFS analyses of chalcopyrite particles at oxidative conditions show that the surface was mildly oxidised and covered with adsorbed molecular CuEX. The Cu 2p XPS and Cu L2,3 NEXAFS spectra were dominated by CuI species attributed to bulk chalcopyrite and adsorbed CuEX. At a reductive potential of − 100 mV SHE, an increase in concentration of CuI and FeIII oxides and hydroxides was observed. X-PEEM analysis was able to show the presence of a low percentage of CuII oxides (CuO or Cu(OH)2) with predominantly CuI oxide (Cu2O) which is not evident in Cu 2p XPS spectra. Refereed/Peer-reviewed

The ultrasoft S L2,3 X-ray absorption near-edge structure (XANES) spectra of FeS, CoS and NiS having the NiAs-type crystal structure have been measured and theoretical analysis of the experimental data has been done on the basis of full multiple scattering theory. The distribution of local partial density of electronic states has been established. A special kind of hybridization between metal 3d and sulfur p states has been found: sulfur p states are “squeezed out” of the energy region of the maximum of metal d electronic states.

Artificial neural network (ANN) and a hybrid principal component analysis-artificial neural network (PCAANN) classifiers have been successfully implemented for classification of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) mass spectra collected from complex Cu-Fe sulphides (chalcopyrite, bornite, chalcocite and pyrite) at different flotation conditions. ANNs are very good pattern classifiers because of: their ability to learn and generalise patterns that are not linearly separable; their fault and noise tolerance capability; and high parallelism. In the first approach, fragments from the whole ToF-SIMS spectrum were used as input to the ANN, the model yielded high overall correct classification rates of 100% for feed samples, 88% for conditioned feed samples and 91% for Eh modified samples. In the second approach, the hybrid pattern classifier PCA-ANN was integrated. PCA is a very effective multivariate data analysis tool applied to enhance species features and reduce data dimensionality. Principal component (PC) scores which accounted for 95% of the raw spectral data variance, were used as input to the ANN, the model yielded high overall correct classification rates of 88% for conditioned feed samples and 95% for Eh modified samples. Refereed/Peer-reviewed

Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid−solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of

The adsorption of two modified dextrins (phenyl succinate dextrin – PS Dextrin; styrene oxide dextrin – SO Dextrin) on four different mineral surfaces has been studied using X-ray photoelectron spectroscopy (XPS), in situ atomic force microscopy (AFM) imaging, and captive bubble contact angle measurements. The four surfaces include highly orientated pyrolytic graphite (HOPG), freshly cleaved synthetic sphalerite (ZnS), and two surfaces produced through surface reactions of sphalerite: one oxidized in alkaline solution (pH 9, 1 h immersion); and one subjected to metal ion exchange between copper and zinc (i.e. copper activation: exposed to 1 × 10 −3 M CuSO 4 solution for 1 h). XPS measurements indicate that the different sphalerite surfaces contain varying amounts of sulfur, zinc, oxygen, and copper, producing substrates for polymer adsorption with a range of possible binding sites. AFM imaging has shown that the two polymers adsorb to a similar extent on HOPG, and that the two polymers display very different propensities for adsorption on the three sphalerite surface types, with freshly cleaved sphalerite encouraging the least adsorption, and copper activated and oxidized sphalerite encouraging significantly more adsorption. Contact angle measurements of the four surfaces indicate that synthetic sphalerite has a low contact angle upon fracture, and that oxidation on the timescale of one hour substantially alters the hydrophobicity. HOPG and copper-activated sphalerite were the most hydrophobic, as expected due to the carbon and di/poly-sulfide rich surfaces of the two samples, respectively. SO Dextrin is seen to have a significant impact on the wettability of HOPG and the surface reacted sphalerite samples, highlighting the difficulty in selectively separating sphalerite from carbonaceous unwanted minerals in flotation. PS Dextrin has the least effect on the hydrophobicity of the reacted sphalerite surfaces, whilst still significantly increasing the wettability of graphite, and thus has more potential for use as a polymer depressant in this separation.

Scanning photoemission microscopy (SPEM) has been applied to the investigation of homogeneous and heterogeneous metal sulfide mineral surfaces. Three mineral samples were investigated: homogeneous chalcopyrite, heterogeneous chalcopyrite with bornite, and heterogeneous chalcopyrite with pyrite. Sulfur, copper and iron SPEM images,i.e.surface-selective elemental maps with high spatial resolution acquired using the signal from the S 2pand Cu and Fe 3pphotoemission peaks, were obtained for the surfaces after exposure to different oxidation conditions (either exposed to air or oxidized in pH 9 solution), in addition to high-resolution photoemission spectra from individual pixel areas of the images. Investigation of the homogeneous chalcopyrite sample allowed for the identification of step edges using the topography SPEM image, and high-resolution S 2pspectra acquired from the different parts of the sample image revealed a similar rate of surface oxidation from solution exposure for both step edge and a nearby terrace site. SPEM was able to successfully distinguish between chalcopyrite and bornite on the heterogeneous sample containing both minerals, based upon sulfur imaging. The high-resolution S 2pspectra acquired from the two regions highlighted the faster air oxidation of the bornite relative to the chalcopyrite. Differentiation between chalcopyrite and pyrite based upon contrast in SPEM images was not successful, owing to either the poor photoionization cross section of the Cu and Fe 3pelectrons or issues with rough fracture of the composite surface. In spite of this, high-resolution S 2pspectra from each mineral phase were successfully obtained using a step-scan approach.

The structure of the liquid–vacuum interface in room temperature ionic liquids (ILs) is investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron X-ray photoelectron spectroscopy (SXPS). By varying the polar angle and comparing the results for the chosen ionic liquids, we identify the presence of a surface layer that is chemically different to the bulk. In particular, this layer: (i) is enriched by aliphatic carbon atoms from the saturated carbon chains of the anions and cations, and (ii) contains an unequal distribution of cations and anions in a direction normal to the surface. This unequal distribution creates a potential gradient which extends from the surface into the liquid. We show unequivocally that this layer is not due to the presence of impurities.

Synchrotron-based photoemission electron microscopy (PEEM; probing the surface region) and time-of-flight secondary ion mass spectrometry (ToF-SIMS; probing the uppermost surface layer) have been used to image naturally heterogeneous samples containing chalcopyrite (CuFeS2), pentlandite [(Ni,Fe)9S8] and monoclinic pyrrhotite (Fe7S8) both freshly polished and exposed to pH 9 KOH for 30 min. PEEM images constructed from the metal L3 absorption edges were acquired for the freshly prepared and solution-exposed mineral samples. These images were also used to produce near-edge X-ray absorption fine-structure spectra from regions of the images, allowing the chemistry of the surface of each mineral to be interrogated, and the effect of solution exposure on the mineral surface chemistry to be determined. The PEEM results indicate that the iron in the monoclinic pyrrhotite oxidized preferentially and extensively, while the iron in the chalcopyrite and pentlandite underwent only mild oxidation. The ToF-SIMS data gave a clearer picture of the changes happening in the uppermost surface layer, with oxidation products being observed on all three minerals, and significant polysulfide formation and copper activation being detected for pyrrhotite. Refereed/Peer-reviewed

Angle resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron XPS (SXPS) have been used to study the (110) surface of two Fe containing sphalerites cleaved in vacuo. The ARXPS S 2p and Zn 2p spectra collected from a low Fe (0.02 wt.%) sphalerite revealed a low binding energy peak when collected at low take off angles (20°). These peaks have been assigned as surface core-level shifts of ~ -0.46 eV and ~ +0.34 eV, respectively. The ARXPS and SXPS S 2p spectra collected from a high Fe (14.79 wt.%) sphalerite indicated the presence of a low binding energy peak resulting from a core level shift ~ -0.42 eV below the bulk S 2p line. A higher binding energy contribution, attributed to a second surface species, was found +0.47 eV above the bulk S 2p doublet. Comparison of the S 2p spectra collected from the two sphalerites, suggested that high Fe concentrations might induce surface reconstruction in the form of surface S dimers. The surface S dimers are likely to be concentrated at high energy step edges and defects. Refereed/Peer-reviewed

Fracture surfaces of a natural carrollite specimen have been characterised by synchrotron and conventional X-ray photo-electron spectroscopy and near-edge X-ray absorption spectroscopy. For the synchrotron X-ray measurements, the mineralsurfaces were prepared under clean ultra high vacuum and were unoxidised. The characterisation was undertaken primarily toestablish unequivocally the oxidation state of the Cu in the mineral, but also to obtain information on the electronic environ-ments of the Co and S, and on the surface species. Experimental and simulated Cu L2,3-edge absorption spectra confirmed anoxidation state of CuI, while Co 2pphotoelectron and Co L2,3absorption spectra were largely consistent with the CoIIIestab-lished previously by nuclear magnetic resonance spectroscopy. S 2pphotoelectron spectra provided no evidence for S to bepresent in the bulk in more than one state, and were consistent with an oxidation state slightly less negative than S–II. There-fore it was concluded that carrollite can be best represented by CuICoIII2(S4)–VII. The CuIoxidation state is in agreement withthat expected for Cu tetrahedrally coordinated by S, but is in disagreement with the CuIIdeduced previously from some mag-netic, magnetic resonance and Cu L-edge X-ray absorption spectroscopic measurements. A significant concentration of S spe-cies with core electron binding energies both lower and higher than the bulk value were formed at fracture surfaces, and theseentities were assigned to monomeric and oligomeric surface S species. The density of Cudstates calculated for carrollite dif-fered from that previously reported but was consistent with the observed Cu L3X-ray absorption spectrum. The initial oxi-dation of carrollite in air under ambient conditions was confirmed to be congruent, unlike the incongruent reaction undergoneby a number of non-thiospinel sulfide minerals. Refereed/Peer-reviewed

The reactivity of high-Fe containing sphalerite (Zn 1− x Fe x S), the major source of Zn, is of great interest for industrial applications. Since the initial reactivity depends on the physical and chemical properties of the surface, it is important to understand the structure of cleaved and fractured surfaces. Zn 1− x Fe x S zincblende (1 1 0) oriented samples cleaved in air and in vacuum were studied with medium energy ion scattering (MEIS) in order to study surface relaxation and reconstruction associated with the possible formation of S dimers. The experimental results are presented together with ion scattering Monte Carlo simulations that have been performed using the different models of the surface structure. The MEIS blocking patterns are different for the air- and vacuum-cleaved specimens. Models for the air-cleaved samples found S atoms in the first layer that are relaxed outwards by 0.08 A and Zn(Fe) atoms relaxed inwards by 0.51 A, with some lateral translation of both species. Results for the vacuum-cleaved sample indicate S atoms have been displaced laterally by 0.5 A at the surface. X-ray photoelectron spectroscopic (XPS) measurements provide evidence for a high binding energy species indicative of S–S bonds in the near-surface region that are consistent with the ion scattering structural data for both cleaving protocols.

Synchrotron XPS and Cu L2,3-edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its expected semiconductivity. The 2p binding energy for the 6-coordinate S atoms was found to be not detectably greater than that for the 4-coordinate S atoms, and surface species were not clearly discernible in either surface-optimized S 2p or Cu 2p spectra. The Cu 2p and Cu L2,3-edge spectra indicated that all Cu in the mineral was indisputably Cu(I). The Cu L2,3-edge spectra of relatively pure natural sphalerite treated with mildly acidic aqueous cupric solution revealed the presence of Cu(II) in the outermost layer of the fracture surfaces, but it was concluded that most of the Cu near the surface of the mineral was in formal oxidation state Cu(I), albeit with higher than normal d9character. The Cu(I) absorption peak was at an energy much lower than for the tetrahedrite absorption edge, but still consistent with Cu(I) in 4-fold coordination by S. The Cu(II) was consistent with Cu bonded both to S atoms in the outermost layer of the sphalerite and to O atoms in chemisorbed water. S 2p spectra determined at different photon energies revealed high binding energy components arising from oligosulfide-like environments in the outermost layers, but not necessarily in a completely restructured lattice and not in a Cu oligosulfide only. The data indicated some loss of Zn in addition to the Zn that had been replaced by Cu in the outermost layers of the sulfide lattice. The presence of these oligosulfide-like environments precluded the detection of S with formal oxidation state greater than (-II) that might have arisen only from Cu(I) in the S lattice. No evidence was obtained for the presence of Cu(II) in a sulfide lattice, but it was not possible to exclude the possibility of a very low concentration because of the presence of the Cu(II) bonded to both S and O at the surface of the treated sphalerite.Key words: tetrahedrite, sphalerite, copper uptake, XPS, NEXAFS.

High-resolution S L3,2-edge XANES spectra have been collected from a series of high-quality sphalerite samples. Each of the sphalerite samples examined has a characteristic iron concentration, and the range is from 3,2-edges are investigated by comparing ab initio calculated spectra with experimentally measured S L3,2-edge spectra collected from synthetic ZnS sphalerite. The theoretical and experimental data provide evidence that S 2p electron transitions to empty S 3s and S 3d states can occur across an energy range above the absorption edge. A chemical shift, associated with iron to sulphur bonds, is identified, and for the first time, a pre-edge feature associated with S–Fe bonding in sphalerite is observed.Key words: XANES, zincblende, sphalerite, characteristic iron content, S L-edge structure, ab initio calculated spectra, density of states, pre-edge peak.

Sulfide minerals contain sulphur in a large variety of coordination environments. Consequently, the S 2p XPS of various mineral surface states undergo different shifts in binding energy (BE) relative to the bulk, depending on the charge distribution on the surface. This in turn depends on the number, type and position of the atoms on the fracture surface, which is determined by the fracture mechanism. We have investigated three sulfide minerals: pyrite (tetrahedrally-coordinated S), chalcopyrite (tetrahedrally-coordinated S) and molybdenite (layered structure with trigonally-coordinated S). Comparison of conventional with surface sensitive synchrotron XPS shows that the S 2p spectrum displays two additional doublets at lower BE than the bulk signal for pyrite, and one doublet each at lower and at higher BE for chalcopyrite. Each of these signals is derived from surface states. Molybdenite shows no additional states. A BE shift to lower (higher) BE suggests a charge increase (decrease) on the S atoms relat...

The chemical state and local environment of sulfur in basaltic glasses from the eastern Galapagos rift and quenched laboratory experiments have been investigated by synchrotron-radiation S K-edge X-ray absorption near-edge structure (XANES) spectroscopy, using an energy-selective fl uorescence detector. We have also investigated sulfur in melts in the system 6NaAlSiO4–CaS– CaSO4 quenched from 1500°C and various reference compounds, using conventional fl uorescence yield and total-electron yield (TEY) recording modes. The S K-edge XANES spectrum of CaS dissolved in Na-aluminosilicate glass is dominated by a broad singlet edge-feature near 2475 eV, consistent with isolated SCan coordination polyhedra in the melt, whereas that of quenched end-member CaSO4-bearing melt is similar to XANES spectra of crystalline sulfates. The linear correlation between relative XANES area and wt% content of sulfur has been used to estimate the content of sulfur in samples of lazurite (5.6–6.3 wt% by EPMA), scapolite-group minerals (0.4 wt%) and the basaltic glasses (0.04–0.15 wt%). The S K-edge XANES spectra of basaltic glasses synthesized under reducing (WM and IQF solid oxygen-buffer) conditions are dominated by a single broad absorption peak at 2470–2482 eV in combination with a weak peak or shoulder at 2470–2471 eV, and are reproduced by mixing XANES spectra of FeS and alkaline-earth monosulfi des. The S K-edge XANES spectra for glasses from the eastern Galapagos rift are also dominated by S 2– , but one TEY spectrum shows possible thiosulfate and another, trace sulfate.

Nous avons utilise la spectroscopie photo-electronique des rayons X en rayonnement synchrotron (SRXPS) et la spectroscopie photo-electronique des rayons X conventionnelle (XPS) pour etudier une surface fractureetres fraiche de la bomite (Cu 5 FeS 4 ). A la suite de comparaisons de ces spectres a resolution elevee, nous demontrons pour la premiere fois quatre contributions distinctes au spectre de l'atome S 2p. Le pic symetrique principal du spectre de S 2p de la bomite est situe a environ 163.51 eV, et il est derive de la masse globale des atomes de S. La nature generalisee de cette contribution globale, par rapport aux autres sulfures de metaux de transition 3d tels la chalcopyrite, concorde avec la presence de huit sites S cristallographiquement distincts dans la structure, tous ces sites etant aussi energetiquement et structuralement distincts. Un second pic situe a 160.1 eV est attribuable a une espece de surface monomerique (S 2 - ) ayant une coordinence plus faible. La presence d'une seconde contribution de surface generalisee a 162.1 eV representerait l'espece polymerique de surface (S n 2 - ). La presence de polymeres de soufre de surface indique la stabilisation de la surface de la bomite suite a une fracture par la formation de liaisons S-S. D'apres ces donnees, les polymeres de surface semblent se former ou les surfaces polaires deviennent exposees lors du developpement d'une surface conchoidale. Un prolongement du spectre indiquant une energie de liaison elevee est presente a environ 163 eV et atteint environ 166 eV; son origine demeure incertaine. Les spectres conventionnels XPS de Cu 2p et de Fe 2p preleves a partir d'une surface de fracture tres fraiche revelent un pic de l'atome Cu 1 + centre a environ 932.2 eV et un pic du au Fe 3 + a l'etat de spin eleve centre a 708 eV.

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