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In this work, we propose an original strategy for the functionalization of aluminum nanoparticles (Al NPs), based on a combination of aryl diazonium salt chemistry and the photopolymerization iniferter method. It consists in grafting coupling agents, derived from diazonium salts, at the surface of Al NPs and in initiating the photopolymerization of methacrylic acid (MAA) directly from the surface. The hybrid NPs were fully characterized using XRD, TEM, TGA, and XPS. The results show that the obtained hybrids exhibit a core-double shell structure, the metallic core being preserved while a thin natural oxide layer and a strongly anchored organic shell surround it. The controlled and living character of the photopolymerization process allowed for the control of the polymer shell thickness with the polymerization time. Interestingly, the formation of compact aryl layers derived from the diazonium salts at the surface of Al NPs appears to provide an efficient protection against oxidation.

Surface characterisation of alloys before and after their interaction with proteins allows a more rational design of biomaterials. In this work, fibronectin adsorption on a Ti-based quasicrystals-forming alloy was studied by X-ray photoelectron spectroscopy (XPS) and compared to those obtained on pure titanium substrates (cp Ti). Different fibronectin (Fn) solution concentrations were tested in interaction with the quasi-crystalline/amorphous Ti45Zr38Ni17 composite. N 1s, C 1s, Ti 2p, Zr 3d and Ni 2p core level spectra were systematically recorded. The results indicate that fibronectin is chemically adsorbed on Ti45Zr38Ni17 as well as on cp Ti. The alloy surface composition and oxide thickness are not significantly changed in presence of the adsorbed protein. Data on the elemental distribution in the alloy surface obtained by XPS were completed by depth profiling with Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Surface saturation is clearly reached for Fn solution concentrations of 100–150 μg mL−1 for both surfaces. On the plateau, the equivalent protein thickness is 6 nm for Ti45Zr38Ni17 and 8 nm for cp Ti, both corresponding to one fibronectin monolayer. These results are in accordance with previous observations on osteoblasts adhesion, confirming the biocompatibility of Ti45Zr38Ni17. However, quasicrystals do not seem to influence the alloy surface reactivity.

Alloy 690 is a high-chromium nickel alloy widely used for steam generator tubes in pressurized water reactors. We have applied an optimized thermal oxidation treatment to alloy 690 consisting of 4 h at 500 °C (0.6 at% O2 in Ar) to make an improved diffusion barrier layer limiting the release of Ni during processing. The efficiency of such a treatment was tested by immersion in simulated pressurized water reactor primary water for 9 weeks. This work also explores the use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to characterize the oxidized films formed after different treatments. Reference spectra were acquired by analyzing thermally oxidized Ni, Cr, and Ni-30Cr samples as well as hydroxides and spinel powders [Ni(OH)2 and NiFe2O4]. ToF-SIMS spectra of model oxides have allowed the selection of a set of ionic intensity ratios to be used for data processing of the spectra and profiles, obtained after the different oxidation steps applied on alloy 690. Thus, the following information was obtained: (i) the oxide layer structure is triplex; (ii) an intermediate layer is composed of Cr2O3, on which surface coverage depends on treatment; (iii) the outer layer is Ni- and Fe-rich, whereas the inner layer is most probably constituted by a NiCr spinel oxide; and (iv) the total oxide layer grown during thermal oxidation is thinner than the one directly formed in primary water. If similar in thickness, the thermally grown oxide layer has a different composition once exposed to primary water. This ToF-SIMS strategy was very fruitful in such a surface tube characterization. Copyright © 2012 John Wiley & Sons, Ltd.

The control of the interface properties of titanium (Ti) and related alloys is of prime significance in dental implantology to enhance the biological compatibility of screws. In this work, we have investigated the use of electrochemical grafting of diazonium salts to modify the surface of titanium samples to propose a simple, low-cost, and reliable functionalization technique for titanium and titanium-based alloys. We have explored this electrochemical procedure by using two model salts in acidic aqueous solution, namely 4-nitrobenzenediazonium tetrafluoroborate (NBD) and 4-carboxybenzenediazonium tetrafluoroborate (CBD). A thorough chemical characterization of functionalized Ti surface enabled us to ascertain the presence of nitrophenyl or carboxyphenyl groups at titanium surfaces. The influence of the scan rate during the electrografting procedure on the properties of the modified surfaces was also analyzed by XPS. From our results, NBD is most probably electrografted according to an island-like model, as the equivalent thickness of the adsorbed layer, estimated from XPS measurements, is below one monolayer, while, CBD is electrografted in few multilayers of 2 to 3 nm thickness, depending on the scan rate used during electrografting.

The surface ageing of nickel electrodes was studied in the frame of the development of non-invasive biomedical devices, dedicated to the detection of sudomotor dysfunction manifested by an alteration of the ionic balance in human sweat. In this kind of technology, low voltage potentials with variable amplitudes are applied to nickel electrodes, placed on skin regions with a high density of sweat glands, and the electrical responses are measured. The trick is that nickel electrodes play alternately the role of anode and cathode, thus the analysis of the temporal evolution of the physico-chemical properties of nickel is of prime importance to ensure the good performance of the device. Electrochemical measurements coupled to surface chemical characterizations (X-ray photoelectron spectroscopy (XPS), Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS)) were performed on pure Ni samples, immersed in buffered chloride solutions mimicking human sweat. The shapes of voltammograms, recorded in a restricted anodic potential range, show that the nickel surface was gradually passivated as a function of the number of scans. This was confirmed by XPS data, with the formation of a 1 nm thick duplex layer composed by nickel hydroxide (outermost layer) and nickel oxide (inner layer). In a negative extended potential range, though the electrochemical behavior of electrodes was not modified upon cycling the potential, XPS data show that the inner layer was thickening, indicating a surface degradation of the nickel electrode. Below pitting potentials, adsorbed chloride was only hardly detected by XPS, and the surface composition of the nickel samples was similar after treatments in chloride or chloride-free buffered solutions. In a larger potential range enabling to reach the breakdown potential, the highly chemically sensitive ToF-SIMS characterization pointed out that the surface concentration of adsorbed chloride was higher in pits than elsewhere on the surface sample.

High temperature sulfidic corrosion has caused safety and reliability issues in refinery units for decades. The objective of the work was to investigate the kinetics of sulfidation under refinery conditions and to characterize, at the nanometer scale, the sulfide layers formed on different steels. The experiments were performed in an autoclave filled with a refinery high-sulfur crude oil at 300°C on XC18 carbon steel (Fe-0.18%C), P5 alloy steel (Fe-5% Cr-0.5%Mo) and 304L stainless steel (Fe-18% Cr-8%Ni). The duration of the test ranged from a few hours to a few days. The combination of X-ray diffraction and transmission electronic microscopy showed the presence of pyrrhotite (Fe 1-x S) on XC18, PS and 304L samples. For all alloys, the S 2p core level decomposition (X-ray photoelectron spectroscopy) proved the presence offive sulfur species on the surface: sulfide (main species), disulfide, elemental sulfur, sulfite and sulfate. On 304L, the presence of chromium oxide and nickel sulfide was revealed by XPS, whereas chromium sulfide was hardly detected. The macroscopic kinetics of sulfidation was followed by mass loss. The results showed that a parabolic law can fit the kinetics of sulfidation of XC18 and P5 steels. The kinetics of sulfidation of the adherent sulfide layer formed on 304L steel, determined from XPS measurements, follows a logarithmic law.

Nanometer-thick Al/SiC periodic multilayers, designed for the Extreme Ultra Violet (EUV) range, have been characterized by different techniques dedicated to such thin multilayers (each between 4 and 10 nm thick). In order to decrease the roughness and to improve the optical performances of the stacks, an ultrathin (2 nm) refractory metal layer has also been introduced, thus making Al/W/SiC and Al/Mo/SiC multilayer systems with three layers in period. The samples are deposited by magnetron sputtering. The stacks have a period ranging between 16 and 18 nm. Time-of-Flight SIMS (ToF-SIMS) is used here to determine the depth profiles of the different elements present within the multilayers. It is observed that the interfaces of the Al/W/SiC and Al/Mo/SiC multilayers are sharper than those of the Al/SiC system. X-ray emission spectroscopy (XES) is used to identify the chemical state of the Al and Si atoms within the multilayers and to check if there is any interfacial compound. The results show that there is no interaction between the Al and SiC layers leading to the formation of an interfacial compound. The results are confirmed by X-ray reflectivity (XRR) measurements. They show that the Al/SiC multilayers present large interfacial roughnesses, but the Al/W/SiC and Al/Mo/SiC multilayers have the lower roughness values. Copyright © 2010 John Wiley & Sons, Ltd.

In this work, kinetics data on adsorption of fibronectin (Fn) on passivated Ti surfaces (Ti quartz crystals) in phosphate buffered saline (PBS) solution were obtained from in situ investigations with electrochemical quartz crystal microbalance (EQCM): from experiments performed at 15 and 60 mg I -1 Fn solution concentrations, the maximum adsorption was reached within 30 min, and Fn adsorption seemed to be partially reversible, as about 15% of the initially adsorbed protein were removed upon PBS rinsing. The remaining amount of adsorbed Fn was around 1000 ng cm -2 and was similar for both protein concentrations in solution. Moreover, differences in kinetics were observed between the two concentrations: the initial adsorption rate was much larger at 60 mg l -1 than at 15 mg l -1 . Ex situ X-ray photoelectron spectroscopy (XPS) characterizations were used to examine the surface after adsorption under flow (EQCM measurements) or in static conditions: identification of the adsorbed protein and of the passivated TiO 2 layer on metallic Ti. With bulk Ti samples, an isotherm of adsorption of Fn in PBS was established on the basis of a selection of Fn solution concentrations and on the maximum time required to get a steady state, for a given concentration. The equivalent thicknesses of adsorbed Fn (d Fn (XPS), model of a continuous layer adsorbed on the passivated Ti samples) were estimated by XPS. At saturation, a plateau is reached corresponding to an equivalent thickness of 5.5 nm for Fn solution concentrations larger than 50 mg l -1 . The d Fn (XPS) values of the experiments performed under flow are in satisfactory agreement with the values determined from static adsorption experiments.

L'adsorption-desorption de deux proteines, l'albumine de serum bovin (BSA) et la fibronectine (Fn), a ete etudiee sur chrome et titane purs passives a pH 7,4 et 37 °C. Le trace des courbes de polarisation a permis de definir les domaines passifs du chrome et du titane, et de determiner l'influence des proteines adsorbees sur le comportement electrochimique des materiaux. Les mesures par microbalance a quartz electrochimique (EQCM) couplee a une cellule a circulation montrent que l'adsorption de BSA sur Cr ou Ti est un processus irreversible, tandis que l'adsorption de Fn sur Cr ou Ti est partiellement reversible, ce qui laisse supposer l'existence de molecules de Fn moins fortement liees a la surface que d'autres. En considerant un modele d'adsorption des proteines en ilots, la combinaison des resultats quantitatifs obtenus par EQCM et par spectroscopie de photoelectrons induits par rayons X (XPS) montre, dans le cas de la BSA, que la hauteur des ilots est plus faible sur Cr que sur Ti et que des taux de recouvrement plus eleves sont atteints sur Cr (a relier a d'eventuelles differences de conformation et/ou orientation de la BSA adsorbee). En revanche, l'adsorption de Fn est similaire sur Cr et sur Ti.

Among the great number of sol–gel prepared nanomaterials, TiO2 has attracted significant interest due to its high photocatalytic activity, excellent functionality, thermal stability and non-toxicity. The photocatalytic degradation of pollutants using un-doped and doped TiO2 nanopowders or thin films is very attractive for applications in environmental protection, as a possible solution for water purification. The present work describes a comparative structural and chemical study of un-doped TiO2 and the corresponding S- and Ag-doped materials. The photocatalytic activity was established by testing the degradation of organic chloride compounds from aqueous solutions. Sol–gel Ag-doped TiO2 coatings, prepared by co-gelation and sol–gel Ag-doped TiO2 coatings obtained from nanopowders were also compared. Their structural evolution and crystallization behaviour (lattice parameters, crystallite sizes, internal strains) with thermal treatment were followed by thermal analysis, X-ray diffraction, transmission electron microscopy, atomic force microscopy and specific surface areas measurements. X-ray photoelectron spectroscopy analyses were performed to characterize the surface composition and S or Ag speciation, which was used to interpret the catalytic data.

Two series of alkaline earth oxides (AEO) of Mg, Ca, and Sr doped with 5 mol% Nd2O3 have been synthesised by two procedures: (i) evaporation of nitrate solutions with subsequent nitrate decomposition (designated Ev) and (ii) sol–gel method (designated SG). The catalysts samples characterisation was performed by ICP chemical analysis, BET specific surface area measurement, FTIR spectroscopy, CO2 TPD, powder XRD, and XPS. The XRD data have shown presence of solid solutions of both Nd in AEO and of alkaline earth elements in Nd2O3. The structural defects that appeared under Nd incorporation into AEO lattice were studied by detailed XRD peak profiles analysis. They were agglomerated or dispersed, their relative amounts depending on the preparation procedure and on the alkaline-earth ion size match with Nd3+. The dispersed local defects were favored by the sol–gel method and by close cation radii dimensions, whereas Nd3+ agglomerates formed mainly on Mg-containing samples and were favored by evaporation. The catalyst basicity has been observed to follow the expected order Mg

The cleaning of protein-contaminated metallic surfaces is a major challenge for non-disposable devices used for biomedical applications and in the food industry. The objective of this work is to estimate the cleaning efficiency of sodium dodecyl sulfate (SDS) buffered at pH 7.4, as a function of temperature, for an immersion time of 15 h. Bovine serum albumin (BSA) is pre-adsorbed on pure Ti- and Cr-deposited quartz crystals. BSA adsorption and removal were investigated by X-ray photoelectron spectroscopy (XPS) and quartz crystal microbalance (QCM). Before cleaning, the amount of adsorbed BSA corresponds to one monolayer, and the oxide thickness is about 5 nm for the Cr quartz (Cr 3+ in oxide and hydroxide). For Ti quartz, the metal is not detected (10 nm or more of Ti 4+ in TiO 2 ). The C 1 s and N 1 s peaks indicate that the cleaning with SDS is achieved at 37 °C for Ti. For Cr, there are no significant changes from 37 to 60 °C. At 80 °C, the surface is partially cleaned (70% efficiency); at 90 °C, the surface cleaning with SDS is achieved (90% efficiency). The oxide layer of the chromium sample has not changed in composition and thickness. QCM measurements were performed at 37 °C. Switches between BSA and SDS solutions indicate that for Ti, SDS induces partial BSA removal (40% efficiency) after ∼20 min, while for Cr it seems that SDS adsorbs reversibly on the BSA layer, without any cleaning effect. Thus, QCM results are in agreement with XPS data obtained at the same temperature.

In this study, we have investigated the redox deactivation of a Ce/Pr mixed oxide supported on modified alumina. Two samples have been prepared by using silica- or lanthana-modified alumina as supports: 25% Ce 0.8 Pr 0.2 O 2-x /Al 2 O 3 -SiO 2 and 25% Ce 0.8 Pr 0.2 O 2-x /Al 2 O 3 -La 2 O 3 . The redox behavior was studied by reduction of the samples at selected temperatures, from 200 to 900 °C. Oxygen Storage Capacity (OSC) of reduced samples was measured by their reoxidation at 200 °C. The reduction degree attained by the supported mixed oxide, after reduction at temperatures up to 800 °C, increases in parallel for both samples. However, at 900°C, there is a decrease of OSC, which is moderate for silica-modified sample, while for lanthana-modified catalyst, the OSC is almost negligible. XPS analysis of the fresh samples shows that the redox state of cerium cations close to the surface is mainly +4, while praseodymium appears always as Pr 3+ . Samples reduced at different temperatures were also investigated by XPS. In the case of silica-modified alumina reduced at 900 °C, significant amounts of Ce 4+ can still be detected, which is in good agreement with the OSC value observed at that temperature. However, lanthana-modified sample reduced at 800 °C shows an important amount of Ce 3+ , being the only oxidation state observed for cerium after reduction at 900 °C. This is in good agreement with the strong drop in OSC observed for this latter sample, which can be thus attributable to the trapping of trivalent cations by the alumina, forming a stable perovskite-like aluminate, LnAlO 3 , as confirmed by X-Ray Diffraction (XRD).

The adsorption of albumin (BSA: bovine serum albumin) on passivated chromium surfaces was studied in deaerated sulphate solutions as a function of potential (in the passive state) and pH (from 4 to 10). In situ switch-flow cell EQCM measurements were coupled to ex situ XPS analyses. EQCM results showed that (i) the initial adsorption rate is about 3.3 ng cm −2 s −1 which corresponds to 3 × 10 10 molecules cm −2 s −1 , irrespective of the passive potential and pH, and (ii) the passive potential as well as the pH have no influence on the amount of adsorbed BSA (Δ m = 440 ± 70 ng cm −2 on the adsorption plateau). From the XPS N 1s and C 1s signals, which provide a fingerprint for the protein, it can be concluded that BSA is adsorbed on the Cr surface and is chemically intact. The XPS results show that (i) when increasing the passive potential, the oxide layer thickness increases (mean value: d ox = 2.2 ± 0.2 nm), and (ii) the passive film is not modified by the adsorption of protein. From combined EQCM and XPS data, a full coverage of the Cr surface by the adsorbed proteins ( γ = 1) is demonstrated at pH 4 (whatever the passive potential). The thickness of the continuous BSA layer ( h BSA ) is 3.3 ± 0.3 nm, which corresponds to one monolayer “side-on”, i.e . oriented parallel to the surface. At pH 5.5 and 10, the adsorbed proteins form islands. The surface coverage is much lower ( γ ∼ 0.5), and the height of the protein islands is significantly higher ( h BSA ∼ 6.5 nm). The results suggest a strong interaction (partially covalent) between the protein and the passivated chromium surface.

The paper presents two cerium doped lutetium silicate crystals: pyrosilicate Ce:Lu2Si2O7 (LPS) and Ce: Lu2(1-x)Y2xSiO5 (LYSO). These two crystals exhibit the expected requirements for gamma detection: high density and high atomic number, high scintillation light yield, good energy resolution and fast response. LPS and LYSO crystals doped with cerium were grown by the Czochralski process. The crystal growth parameters were studied and optimized. Development of scintillators requires good understanding of the scintillation process. The location within the forbidden band gap of the localized lanthanide energy levels is analyzed by time resolved spectroscopy and thermoluminescence studies.

The Mixed-Conduction Model (MCM) has been adapted to obtain the main kinetic and transport parameters for passive film growth on nickel-based alloys in high-temperature electrolytes. For the purpose, a procedure for the calculation of these parameters from electrochemical impedance spectroscopic data measured on Ni–15% and Ni–20%Cr alloys in 0.1 M Na2B4O7 at 300 °C in a wide potential range has been devised. The obtained sets of parameters have been used to successfully predict the steady-state current density versus potential dependence for the two Ni–Cr alloys, as well as the thickness versus time dependence for films grown on Alloy 600 at times ranging between a few minutes and a few thousand hours. The calculations are supported by results of previous XPS measurements of film growth on Alloy 600 showing that the barrier layer growing in the early stage consists of Cr2O3.

The formation of partial perfluoroalkyl or alkyl radicals from partial perfluoroalkyl or alkyl iodides (ICH2CH2C6F13 and IC6H13) and their reaction with surfaces takes place at low driving force (∼-0.5 V/SCE) when the electrochemical reaction is performed in acetonitrile in the presence of diazonium salts (ArN2(+)), at a potential where the latter is reduced. By comparison to the direct grafting of ICH2CH2C6F13, this corresponds to a gain of ∼2.1 V in the case of 4-nitrobenzenediazonium. Such electrochemical reaction permits the modification of gold surfaces (and also carbon, iron, and copper) with mixed aryl-alkyl groups (Ar = 3-CH3-C6H4, 4-NO2-C6H4, and 4-Br-C6H4, R = C6H13 or (CH2)2-C6F13). These strongly bonded mixed layers are characterized by IRRAS, XPS, ToF-SIMS, ellipsometry, water contact angles, and cyclic voltammetry. The relative proportions of grafted aryl and alkyl groups can be varied along with the relative concentrations of diazonium and iodide components in the grafting solution. The formation of the films is assigned to the reaction of aryl and alkyl radicals on the surface and on the first grafted layer. The former is obtained from the electrochemical reduction of the diazonium salt; the latter results from the abstraction of an iodine atom by the aryl radical. The mechanism involved in the growth of the film provides an example of complex surface radical chemistry.

We study the interface evolution of a series of periodic Co/Mo2C multilayers as a function of the annealing temperature up to 600{\textdegree}C. Different complementary techniques are implemented to get information on the phenomenon taking place at the interfaces of the stack. The periodical structure of Co/Mo2C multilayer is proven by Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles which demonstrate the formation of an oxide layer at both air/stack and stack/substrate interfaces. From Nuclear magnetic resonance (NMR) spectra, we observed the intermixing phenomenon of Co and C atoms for the as-deposited sample, and then at annealing temperature above 300{\textdegree}C Co and C atoms separate from their mixed regions. Comparison of NMR results between Co/Mo 2 C and Co/C references confirms this phenomenon. This is in agreement with x-ray emission spectroscopy (XES) measurements. Furthermore the calculation of the Co-C, Co-Mo and Mo-C mixing enthalpy using Miedema's model gives a proof of the demixing of Co and C atoms present within the stacks above 300{\textdegree}C. From the transmission electron microscopy (TEM) analysis, we found the presence of some crystallites within the as-deposited sample as well as the mainly amorphous nature of all layers. This is confirmed using x-ray diffraction (XRD) patterns which also demonstrate the growth of crystallites induced upon annealing., Published in Applied Surface Science 331, 8-16 (2015). http://dx.doi.org/10.1016/j.apsusc.2014.12.055

http://dx.doi.org/10.1051/mattech/2015016; International audience; Abstract – Effect of the chemical composition of fresh concrete pore solutions on the passiva-tion of mild steel. The passivity of reinforcing steel in concrete is generally attributed to the formation of a protective oxide layer on the steel surface due to the high alkalinity of the surrounding pore solution. The objective of this work was to study the influence of the chemical composition of fresh concrete pore solutions on the electrochemical behaviour and the surface chemical composition of C15 mild steel , used for reinforcement of building concrete. For that purpose , electrochemical measurements were performed at pH 13 in various simulated concrete pore solutions (CEM I , II and III) , as well as in the 0. 1 M NaOH reference solution , and were combined to surface analysis by XPS. The anodic polarization curves show the importance of steady-state measurements. The electrochemical impedance diagrams , plotted at the corrosion potential and at anodic potentials , show the presence of a protective passive layer on the steel surface with a thickness of about 2. 5 – 3 nm , in good agreement with XPS results. The pH is not the only determining parameter for predicting the corrosion behaviour of steel in concrete environments. Thus , the steady-state passive current density increases and the oxide layer becomes less protective with increasing sulfate concentration in solution. Furthermore , the strong protective nature of the passive layer in CEM III solution could be correlated to the presence of Fe 2+ on the steel surface .; – L ' alcalinité de la solution interstitielle contenue dans les pores du béton engendre la formation d ' une couche d ' oxyde protectricè a la surface des armatures métalliques. L ' objectif de ce travail est d ' ´ evaluer l ' influence de la composition chimique de la solution interstitielle de bétons jeunes sur la qualité du film d ' oxyde formé sur un acier doux C15. Pour ce faire , des mesures electrochimiques sont réalisées a pH 13 , dans différentes solutions interstitielles synthétiques (CEM I , II et III) , ainsi que dans une solution de référence NaOH 0 , 1 M et sont combinées a des analyses de surface par XPS. Les courbes de polarisation anodiques montrent l ' intérêt des mesures stationnaires. Les diagrammes d ' impédancé electrochimique , tracés au potentiel de corrosion et a potentiels anodiques , mettent en evidence la présence d ' une couche passive protectrice sur la surface d ' acier , dont l ' ´ epaisseur est de l ' ordre de 2 , 5 ` a 3 nm , en bon accord avec celle estimée par XPS. Le pH n ' est pas le seul param etre déterminant pour prédire le comportement a la corrosion de l ' acier. Ainsi , plus la concentration en sulfate en solution est importante , plus la densité de courant passif stationnaire est elevée et moins la solution est passivante. Par ailleurs , la présence de Fe 2+ a la surface du matériau pourrait en partie expliquer le fort pouvoir passivant de la solution CEM III.

The luminescence and scintillation properties of Cs 2 LiLuCl 6 :0.5%Ce 3+ are presented. Special attention is devoted to a 9.4 ns fast emission at 275 nm that can only be excited via the highest cubic field 5d e state of Ce. Contrary to Cs 3 LuCl 6 and Cs 2 LiYCl 6 , where the same type of fast emission was observed, the emission in Cs 2 LiLuCl 6 is still observed at room temperature. Assuming that the 5d e state is located inside the host conduction band (CB), we propose that the emission originates from a mixed state at or just below the bottom of the CB and ends at the 4f ground state of Ce 3+ . To proof this model we studied the thermal quenching of the anomalous luminescence and performed X-ray photoelectron spectroscopy. A model for a temperature-activated energy transfer from the anomalous state to the lowest 5d t excited state of Ce 3+ explains most of the results. Besides the 275 nm emission, the material shows 5d t –4f Ce 3+ emission at 370 and 406 nm and 2 ns fast core-valence luminescence when excited with 16–22 eV photons. The scintillation properties of Cs 2 LiLuCl 6 :Ce are briefly discussed.

Improved knowledge of the chemical composition of biomaterial surfaces and a better understanding of interactions between biomolecules and material surfaces will allow a more rational design of biomaterials. Surface characterisation of alloys before and after their interaction with proteins is an essential aspect of this approach. In this work, the interactions of fibronectin with stainless steel surfaces (Fe-17Cr alloy) were studied by X-ray photoelectron spectroscopy (XPS). Different solution concentrations of fibronectin were tested (0, 8, 60, 120 and 240 μg ml -1 ) in interaction with the stainless steel sample. N 1s, C 1s, Cr 2p and Fe 2p core level spectra were systematically recorded and compared. The results indicate that fibronectin is adsorbed on the stainless steel surface. The alloy surface composition and oxide thickness are almost unchanged (Fe 2 O 3 - Cr 2 O 3 + Cr(OH) 3 ) in presence of the protein, whatever the protein solution concentration. The isotherm of fibronectin adsorption at 37 °C was measured. A saturation is clearly reached for solution concentrations greater than 60 μg ml -1 . On the plateau, the equivalent protein thickness is 6.3 nm, corresponding to one fibronectin monolayer.

The surface basicity of pure ceria is strongly enhanced by the presence of the supported La2O3, the effect being very much influenced by the calcination temperature. X-ray diffraction (XRD), Raman spectroscopy, and La 3d5/2 XPS data for the different samples show a progressive incorporation of La3+ into the ceria lattice as the calcination temperature is increased. This structural change is considered to be responsible for the modifications that occurred in the basicity of the lanthana-modified ceria samples as revealed by temperature-programmed desorption-mass spectrometry (TPD-MS) of pre-adsorbed CO2. Copyright © 2006 John Wiley & Sons, Ltd.

The adsorption of bovine serum albumin (BSA), and its influence on the electrochemical behaviour in deaerated 0.05 M H 2SO4 solution of a ferritic stainless steel, Fe–17Cr, was studied by electrochemical methods (time dependence of the corrosion potential Ecor, polarization curves, EIS) and surface analysis techniques (PM-IRRAS, XPS). The electrochemical measurements show a corrosion inhibition by the BSA at Ecor. The charge transfer resistance decreases and hence the corrosion current of the alloy increases with immersion time at Ecor, but this phenomenon is much less marked in the presence of BSA. Impedance measurements performed after passivation of the alloy at 0 V versus SSE show that the presence of protein has no effect on the electrochemical behaviour of the passivated alloy surface. Surface analysis of the stainless steel samples by PM-IRRAS and XPS shows that chemically intact BSA molecules are adsorbed on the surface at Ecor and 0 V. The amount of adsorbed BSA is quite similar at both potentials. All these results demonstrate that the adsorption of BSA takes place on the Fe–17Cr surface both at the corrosion potential and in the passive region, and the BSA has a corrosion inhibition effect when the surface is not fully passivated. © 2005 Elsevier Ltd. All rights reserved.

The behaviour of dense nickel substrates coated by electrochemically deposited Co3O4 was analysed in Li2CO3–Na2CO3 under the usual molten carbonate fuel cell conditions. The cobalt oxide deposit reacts rapidly yielding LiCoO2, detected by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Nevertheless, after 1 h of immersion in the carbonate melt, XPS shows that, in the outermost layers (

The early stages of passivation in high temperature water of a nickel–chromium–iron alloy (Alloy 600) have been investigated by X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM). The samples (polycrystal Ni−16Cr−9Fe (wt. %) and single crystal Ni−17Cr−7Fe (1 1 1)) have been exposed for short time periods (0.4–8.2 min) to high temperature (325 °C) and high pressure water, under controlled hydrogen pressure, in a microautoclave designed to transfer the samples from and to the XPS spectrometer without air exposure. In the early stages of oxidation of the alloy (0.4–4 min), an ultra-thin oxide layer (about 1 nm) is formed, which consists of chromium oxide (Cr2O3), according to the Cr 2p3/2 core level spectrum. An outer layer of Cr(OH)3 with a very small amount of Ni(OH)2 is also revealed by the Cr 2p3/2, Ni 2p3/2, and O 1s core level spectra. At this early stage, there is a temporary blocking of the growth of Cr2O3. For longer exposures (4–8 min), the Cr2O3 inner layer becomes thicker, at the expense of the outer Cr(OH)3 layer. This implies the transport of Cr and Ni through the oxide layer, and release of Ni2+ in the solution. The structure of the ultra-thin oxide film formed on a single crystal Ni−17Cr−7Fe(1 1 1) alloy was analysed by STM in the constant current mode; STM images reveal that, in the early stages of oxidation, the oxide is crystalline, and the observed structure is consistent with the hexagonal structure of the oxygen sub-lattice in the basal plane (0 0 0 1) of α-Cr2O3.

Ammonia adsorption on Ni( 111) and on oxygen-pretreated Ni( 111) has been studied using metastable induced electron spectroscopy and ultraviolet photoelectron spectroscopy at room temperature. Both techniques allowed us to report on the electronic structure of the valence band. The nickel oxidation leads to the existence of an oxygen-adsorbed phase before NiO growth. So we compared the ammonia reaction toward three types of surfaces: Ni(111), NiO/Ni(111), and O-Ni(111). We observed different ammonia reactivities on these three types of surfaces at room temperature: ammonia molecules were molecularly adsorbed on Ni( 111), and were decomposed on oxygen-pretreated Ni(111). After surface heating, ammonia products were dissociated, and adsorbed hydroxyl groups were also seen on O-Ni(111). Above 450 K, no ammonia decomposition products were observed on NiO/Ni(111), whereas Ni(111) and the O-Ni(111) were covered by atomic nitrogen. Its coverage is higher on the O-Ni(111) surface than on the clean Ni(111) surface. This observation proves the high ammonia reactivity toward adsorbed oxygen. This study shows that the reactivity of oxygen atoms on Ni(111) toward ammonia depends on their characteristics (adsorbed oxygen or oxygen embedded into NiO).

A series of Ce–Mn composites with different compositions was prepared by co-precipitation. All samples were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). According to their size and chemical composition, two different kinds of particles were observed: (a) small crystallites of Ce–Mn solid solution ( 50 nm). These results were used to explain differences between the surface and bulk compositions of the samples as well as the specific surface area. Furthermore, from XPS studies, the presence of various Mn species with different oxidation states could be stated. This fact might clarify the exceptional catalytic behaviour of the samples for the catalytic wet oxidation of toxic organic compounds. Copyright  2004 John Wiley & Sons, Ltd.

The aim of this work was to investigate the initial stages of the SO 2 interaction with Ni(111) surfaces. SO 2 adsorption was performed at 1 x 10 -7 mbar, at room temperature, in a preparation chamber attached to the XPS analysis chamber. After each adsorption, the S 2p and O is core levels were analysed. Various S-containing adsorbed species were observed: S(ads) located at 162.0 ± 0.2 eV, and SO 3 (ads) at 166.7 ± 0.2 eV. A weak signal at 163.8 ± 0.3 eV is tentatively assigned to a small amount of S-O(ads). The data provided by the O is core level spectra have been used to confirm the nature of S-containing adsorbed species. Changes in the surface concentrations of the different adspecies as a function of exposure indicate that, first, SO 2 dissociates into S(ads) and O(ads), then SO 2 can either dissociate or combine with the available O(ads) to form SO 3 (ads). The surface saturation is reached after 12 L.

We have developed and elaborated a series of Mg/Co-based periodic multilayers to build efficient mirrors for the extreme ultraviolet (EUV) range. For s-polarized light and at 45° of grazing incidence, the reflectivity of as-deposited Mg/Co is 42.6% at 25.1 nm. X-ray emission spectroscopy and nuclear magnetic resonance measurements do not indicate any noticeable interdiffusion at the interfaces between layers. Scanning transmission electronic microscopy images attest the high structural quality of the stack. X-ray reflectivity (XRR) curves in the hard x-ray and EUV domains confirm this description and estimate a weak interfacial roughness (~ 0.5 nm). Taking advantage of the magnetic character of Co, we have performed resonant magnetic reflectivity measurements by scanning the photon energy around the Co L absorption edge for opposite circular polarizations. The magnetization profile of the Co layers within Co/Mg determined with an expected depth resolution of one monolayer confirms the interface abruptness. Scanning electron microscopy images and XRR curves give evidence of the thermal stability of Mg/Co up to 300 °C. From that value, a strong change in the sample morphology due to the delamination of the multilayer from the substrate occurs. This should account for the drastic reflectivity drop observed above this temperature. Starting from Mg/Co, we have inserted a Zr layer at one or at the other interface or at both interfaces to estimate the effect of the introduction of a third material within the period. We have found that Mg/Co/Zr is more efficient (50% of reflectivity) than Mg/Zr/Co and Mg/Zr/Co/Zr (~ 40%). Through time-of-flight secondary ion mass spectrometry depth profiling and NMR measurements, we have assigned this difference to an intermixing process when Co layers are deposited onto Zr layers.

In order to protect the state-of-the-art nickel cathode used in the molten carbonate fuel cell, electrochemical potentiostatic deposition, a cheap and low-temperature technique, has been used to produce a cobalt oxide coating. This process was optimised on nickel substrates, analysing thoroughly the effect of the imposed potential, electrolyte composition, pH, electrolysis duration and the pre-oxidation of the substrate. Thin and homogeneous cobalt oxide layers were elaborated, in particular, in nitrate media at pH 7.4 on a nickel substrate previously oxidised. The structure and morphology of the deposits were characterised either directly or after an annealing treatment, by X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. A cubic Co3O4 structure was identified, which is in agreement with the results obtained by cyclic voltammetry.