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International audience; We report the homoepitaxial growth of Cu2O thin films with tunable growth orientations on glass and silicon substrates using reactive sputtering. The importance of the initial growth stage on the subsequent development of specific orientations is detailed. Among the various deposition conditions, the total pressure is found to have a strong effect on the preferred orientation of Cu2O films: (1 0 0) at low pressure and (1 1 1) at high pressure. Furthermore, the texture of the deposited films is also influenced by that of a first Cu2O layer acting as a continuous seed layer. Effectively, using a two-step deposition procedure, a highly textured Cu2O thin film with controlled orientation can be formed independently of the deposition conditions. Provided that it has a sufficient thickness, this layer acts as a seed layer that determines the crystal orientation of a second layer grown even after air exposure and/or without specific cleaning of the surface prior to deposition. High-resolution transmission electron microscopy analyses evidence that the top layer grows in homoepitaxy with the seed layer with a microstructure consisting of single crystal columns crossing the interface between the layers.

International audience; Among trace metal pollutants, zinc is the major one in the rivers from the Paris urban area, such as the Orge River, where Zn concentration in the suspended particulate matter (SPM) can reach 2000 mg/kg in the most urbanized areas. In order to better understand Zn cycling in such urban rivers, we have determined Zn speciation in SPM as a function of both the seasonal water flow variations and the urbanization gradient along the Orge River. Using TEM/SEM-EDX and linear combination fitting (LCF) of EXAFS data at the Zn K-edge, we show that Zn mainly occurs as tetrahedrally coordinated Zn2+ sorbed to ferrihydrite (37-46%), calcite (0-37%), amorphous SiO2 (0-21%), and organic-P (0-30%) and as octahedrally coordinated Zn2+ in the octahedral layer of phyllosilicates (18-25%). Moreover, the Zn speciation pattern depends on the river flow rate. At low water flow, Zn speciation changes along the urbanization gradient: geogenic forms of Zn inherited from soil erosion decrease relative to Zn bound to organic-phosphates and amorphous SiO2. At high water flow, Zn speciation is dominated by soil-borne forms of Zn regardless the degree of urbanization, indicating that erosion of Zn-bearing minerals dominates the Zn contribution to SPM under such conditions.

Single-walled carbon nanotubes produced by the MER Corporation have been treated in an argon atmosphere at temperatures between 1400 and 2400°C. The modifications resulting from the heat treatment have been followed by adsorption volumetry and TEM measurements. 1600°C appears as a turning point for the high temperature treatments. Heating nanotubes up to 1600°C essentially results in the removal of metal particles. At higher temperatures the changes in morphology are predominant, and single-walled nanotubes packed in bundles are transformed into multi-walled nanotubes.

To reach a better understanding of the behavior of suspensions of charged colloidal platelets, takovite samples with a general formula Ni1-x, Alx(OH)2, Anz-x/z, yH2O, where An is an interlayer anion, were synthesized. These materials belong to the family of layered double hydroxides (also referred to as anionic clays). They can be easily prepared in the laboratory by coprecipitating mixed nickel and aluminum salts by NaOH. Their charge can be adjusted by changing the synthesis conditions, while the hydration properties can be modified by using various interlayer anions. On the basis of oscillatory measurements, rheological phase diagrams were obtained by plotting the sol−gel transition as a function of solid content and ionic strength for three monovalent anions: F-, Cl-, and NO3-. In all cases, the phase diagrams exhibit a negative slope, i.e., the sol−gel transition shifts toward lower solid contents for increasing ionic strength. The nature of the interlayer anion has a strong influence, the sol−gel l...

We present X-ray photoelectron spectroscopy (XPS) measurements of several Al–Cr–Fe samples which are mixtures of approximants of the decagonal phase. Some samples also contain a hexagonal γ-brass phase. Our purpose is to evaluate the effect of chemical composition, particularly Cr content, on the response of the surface to oxidation. Under mild conditions only aluminium oxidizes, but under extreme conditions (water immersion at room temperature, or oxygen exposure at high temperatures), chromium oxidizes as well. XPS data also provide a measure of the oxide thickness. Cr has no discernible effect on oxide thickness when the oxidizing environment is the gas phase, but provides significant protection against water immersion, where high concentrations of Cr reduce the thickness by as much as 40%. These results for the Al–Cr–Fe samples are compared with results for approximants and quasicrystals in other systems.

The dechlorination of alkyl and aryl (poly)chlorides is rapid and complete upon treatment with a new reduction system consisting of NaH as reagent, Ni–Al clusters as catalyst and t-BuOH as catalytic co-factor. The high efficiency of this combination is presumed to be due to the stabilization of the subnanometre nickel particles formed during reduction by the in-situ-generated alkoxide. Copyright © 2001 John Wiley & Sons, Ltd.

Des sediments synthetiques ont ete utilises pour etudier les mecanismes de solubilisation biologique du cadmium d'une hydroxyapatite au cours de la biodegradation aerobie de cellulose. Les sediments de synthese sont constitues d'une matrice siliceuse, d'une hydroxyapatite substituee ou non en cadmium, et de cellulose. Ils ont ete inocules avec une communaute microbienne issue d'un sediment naturel et incubes avec un milieu de culture en conditions controlees. La biodegradation de la cellulose est importante apres 53 jours pour les deux sediments (34 a 37 % du carbone organique initial). Simultanement, la solubilisation de Cd est importante et atteint 34 % du cadmium initialement present. Cette solubilisation est associee a une acidification importante du milieu, le pH passant de 6,7 a 4,5. La solubilisation de Cd apparait comme une consequence de la production de protons dans le milieu.

Finely dispersed nanocrystalline Pd x Cu 100− x (0≤ x ≤100 at.%) powders were obtained after chemical reduction of Pd(II) and Cu(II) metallic salts by activated alkaline hydride (NaH– t -BuONa) in tetrahydrofuran solvent at low temperature. The morphology and structure were characterized by transmission electron microscopy and revealed that this original chemical approach allows preparation of stable, single-phase nanoparticles of alloys with homogeneous distribution of chemical elements. The particle sizes were found in the range of 1–10 nm. Such nanostructured powders crystallize in the face centered cubic structure, and a linear evolution of the lattice parameter with the palladium atomic content was observed.

Lithium cannot be electrointercalated into graphite in an electrolyte containing propylene carbonate (PC) as the only solvent species. In order to improve the cycleability of graphite electrodes in the presence of PC two methods were used: use of solvent mixtures containing PC and halogen-substituted solvent molecules (α-bromo-γ-butyrolactone and methyl chloroformate); impregnation of the graphite electrode by halogenated solvents prior to cycling in PC-based electrolytes. It appears that the reversible capacity is increased by ∼10% when such halogenated solvent molecules are used. Moreover, the cycleability is dependent on the nature of lithium salt, the concentration of halogen solvent and the specific current.

The aim of this study is to determine the stages of appearance, morphology, crystallographic structure and chemical composition of otoconia during the inner ear development of an urodele amphibian, Pleurodeles waltl. The first otoconia are detected in the otocyst. Near hatching, calcitic otoconia are polyhedral in the saccule and cylindrical in the utricle. During the following stages, the saccular otoconia agglomerate and constitute a polyhedral calcitic otolith. At larval stage 44, aragonitic fusiform otoconia appear on the otolithic surface. At stage 52, X-ray diffraction analysis shows calcite and aragonite patterns. In adults, all the saccular otoconia are aragonitic. In contrast, the utricular otoconia do not show any modification up to adulthood. In the endolymphatic sac, otoconia appear at stage 45 and in the lagena at stage 49. They remain aragonitic up to adulthood. Energy dispersive X-ray spectroscopy (EDXS) elemental analysis of the otoconia reveals a high quantity of calcium with trace quantities of sodium, magnesium, phosphorus, sulfur, chlorine and potassium. However, magnesium and sulfur have a lower concentration in lagenar aragonitic otoconia than in utricular and saccular calcitic ones. As in adults, trace amounts of strontium are only found in aragonitic otoconia.

International audience; The electrochemical intercalation of sodium ions into pitch carbon fibres and natural graphite UF4 was studied using an electrolyte composed of ethylene carbonate as the solvent and NaClO4 as the salt. The reversible electrochemical capacity for a current equal to 7 μA mg−1 is negligible for graphite, a little bit higher for P100 fibres (28 mAh g−1) and reaches 55 mAh g−1 for P75 fibres. The sodium uptake can be increased by grinding our materials: the reversible capacity is then around 60 and 83 mAh g−1 for ground P100 and P75 carbon fibres, respectively. During the first reduction, a great part of the current is used for the formation of a passivating layer on the carbon surface. Analysis of this layer by transmission electron microscopy (TEM) has shown that it is composed of sodium carbonate Na2CO3 and alkylcarbonates ROCO2Na. Formation of Na2CO3 occurs at potentials in the 1–0.8 V range versus Na+/Na, and formation of sodium alkylcarbonates then follows at potentials below 0.8 V. TEM also revealed the presence of sodium chloride, attributed to NaClO4 reduction.

The electrochemical intercalation of lithium ions into graphite was studied in various electrolytes. The first cycle is accompanied by the irreversible process attributed to the formation of a passivating layer. The reduction of Cl–EC and EC begins at potentials equal to 1.7 and 0.9 V vs. Li+/Li, respectively. The electrochemical behaviour is considerably affected by the nature of the salt. Contrary to LiBF4, a good cycleability is obtained with LiClO4 and LiAsF6.

Resume Les microstructures des croutes Fe-Mn hydrogenetiques d'âge neogene prelevees sur la facade ouest-africainede l'Atlantique central et equatorial sont laminees. Trois types de lamines ont pu etre definis. Divers arguments, dont des observations sur coupes ultra-minces, indiquent que les lamines correspondent tres vraisemblablement a des voiles microbiens mineralises. L'etude conjointe d'enduits subactuels a actuels provenant de l'Atlantique et de la Mediterranee souligne l'analogie entre eeux-ci et les lamines des croutes. La mineralisation des biofilms se deroule en plusieurs etapes; l'enrichissement en fer et en silice precede l'incorporation de manganese. Le type de lamine reflete les conditions hydrologiques generales (activite des courants de fond, disponibilite en nutriments et en Mn), ainsi que les caracteristiques du micromilieu (microtopographie, Eh). Les faibles vitesses de croissance de ces depots polymetalliques pourraient s'expliquer par le mode de developpement des biofilms.

Polyparaphenylene powders are electrochemically reduced in LiCIO4-ethylene carbonate electrolyte. Intercalation of Li+ ions occurs and leads to the formation of Li0.5(C6H4) compounds. Side reactions due to the electrolyte decomposition are responsible for the important irreversible electrochemical capacity observed during the first charge-discharge cycles. The degradation products were analyzed by TEM and EELS between 2.85 and 0.75 V.

Electrochemical intercalation of sodium ions into poly( para -phenylene) (PPP) has been carried out in NaClO 4 —carbonate electrolytes (EC, PC and their mixture in the volumic ratio of 1/1). The same electrochemical behavior has been observed in the three electrolytes. The galvanostatic curves exhibit potential slope changes which are characteristic of multiphase system; this behavior is confirmed by cyclic voltammetry. Our experimental conditions allow the obtainment of rich compounds Na 0.5 (C 6 H 4 ) which do not contain co-inserted solvent molecules. This is due to a passivating layer formed at the electrode surface during the first discharge that prevents the co-insertion of solvent. Analysis of this layer by transmission electron microscopy reveals the presence of Na 2 CO 3 at potentials higher than 0.75 V and sodium alkylcarbonates at potentials lower than 0.75 V. A two-step mechanism of electrolyte decomposition is proposed by analogy with the case of the reduction of graphite in carbonate electrolytes containing LiClO 4 salt.

Polyindole obtained by oxidizing coupling of indole, C 8 NH 7 , was studied either in the doped or the undoped state by FT i.r., Raman and electron energy loss (EEL) spectroscopies. Interpretation of the vibrational modes was facilitated by comparison of the absorption spectra of polyindole and those of related molecules acting as standards. The change from the doped to the dedoped state of polyindole is accompanied by a reordering of the Π bonds of the system characterized by the disappearance of C  N bonds and the reappearance of NH bonds. Detailed analysis of the different spectral manifestations gives evidence for a monomer coupling involving the positions 2 and 3 of the carbon atoms.

Reversible electrochemical intercalation of unsolvated lithium into graphite previously treated either in LiClO4-ethylene carbonate (EC) or in LiClO4-dimethyl carbonate (DMC) solutions was carried out in a LiClO4-propylene carbonate (PC) electrolyte. Under these conditions, graphite exfoliation did not occur, allowing the graphite anode to cycle reversibly. The modifications of the structure and the morphology of the graphite during its reduction in PC-LiClO4 electrolyte was studied by transmission electron microscopy (electron diffraction, imaging) and X-ray diffraction studies.

Hydrotalcite compounds have been successfully prepared by successive infiltrations into the interstices of an ordered array of polystyrene spheres, subsequently removed by either dissolution or the...

International audience; One key challenge in inorganic mesoporous films is the development of oriented mesostructures with vertical channels, and even more challenging is their functionalization while maintaining accessible the selected surface groups. Combining the electrochemically assisted deposition of ordered and oriented azide-functionalized mesoporous silica with alkyne-azide click chemistry enables such nanostructured and vertically aligned hybrid films to be obtained with significant amounts of active organic functional groups, as illustrated for ferrocene and pyridine functions. A good level of mesostructural order was obtained, namely up to 40% of organosilane in the starting sol. The method could be applied to a wide variety of functional groups, thus offering numerous new opportunities for applications in various fields.

International audience; Al-Fe oxyhydroxy co-precipitates were synthesised by forced hydrolysis of Fe(NO3)(3)center dot 9H(2)O and Al(NO3)(3)center dot 9H(2)O solutions. Solids containing 0, 1, 10, 25, 50, 75, 90 mol% Al were characterised for composition, texture, mineral structure and local atomic environment. Cation substitution in the hydrous oxides was not observed. The solids consisted of hydrous ferric oxide (HFO) nuclei surrounded by Al-hydroxide. Below 50 mol% Al, unit particle size, high specific surface area and microporosity of HFO were preserved. Al-K-edge XANES showed ordered arrangements of Al-octahedra suggesting that some Al bound specifically to HFO surface sites. Above 50 mol%, Al precipitated in multiple layers around the nuclei and also as individual entities. The HFO nuclei exhibited the general characteristics of a 2-line ferrihydrite. However, as Al increased, the structure was slightly modified. While the symmetry of the FeO6 octahedra improved, the number of Fe-Fe linkages decreased, suggesting less polymerisation. An organisation of the Fe-octahedra, faintly resembling akaganeite, was expressed in Raman spectra. These changes in HFO structure were attributed to hindrance in the progressive olation/oxolation of the primary Fe-hydroxypolymers, caused by Al bound to the surface of nuclei. The presence of nitrate is suspected to have favoured the structural changes.

International audience; Lignin is a potential renewable material for the production of bio-sourced aromatic chemicals. We present the first hydrotreatment of lignin pyrolysis vapors, before any condensation, using inexpensive and sustainable iron-silica (Fe/SiO2) and iron-activated carbon (Fe/AC) catalysts. Lignin pyrolysis was conducted in a tubular reactor and vapors were injected in a fixed bed of catalysts (673 K, 1 bar) with stacks to investigate the profile of coke deposit. More than 170 GC-analyzable compounds were identified by GCxGC (heart cutting)/flame ionization detector mass spectrometry. Lignin oligomers were analyzed by very high resolution mass spectrometry, called the "petroleomic" method. They are trapped by the catalytic fixed bed and, in particular, by the AC. The catalysts showed a good selectivity for the hydrodeoxygenation of real lignin vapors to benzene, toluene, xylenes, phenol, cresols, and alkyl phenols. The spent catalysts were characterized by temperature-programmed oxidation, transmission electron microscopy (TEM), and N2 sorption. Micropores in the Fe/AC catalyst are completely plugged by coke deposits, whereas the mesoporous structure of Fe/SiO2 is unaffected. TEM images reveal two different types of coke deposit: 1) catalytic coke deposited in the vicinity of iron particles and 2) thermal coke (carbonaceous particles ≈1 μm in diameter) formed from the gas-phase growth of lignin oligomers. Lignin is fond of iron: Lignin is a promising source for renewable aromatics. Inexpensive iron-based catalysts are very selective for the direct hydrodeoxygenation of lignin pyrolysis vapors. Two types of coke deposit are revealed. Lignin oligomers are analyzed by very high resolution mass spectrometry.

International audience; To assess the effect of polymeric substances on the biomineralization and stabilization of green rust (GR), the effect of two organic polymers on the transformation of lepidocrocite (γ-FeOOH) to GR vs. magnetite in presence of Shewanella putrefaciens was investigated. These two polymers, generally used as flocculants, are polyacrylic acid (PAA), which bears negatively charged carboxylic groups at neutral pH and is expected to react with cationic hydrolyzed iron species, and polyacrylamide (PAM), which is a neutral polymer that may develop hydrogen bonds with iron nanocolloids. The bioreduction of lepidocrocite by S. putrefaciens was performed under conditions known to yield either magnetite or GR. Each operational condition of interest was investigated with various polymer concentrations from 0.6 to 60 mg g−1 Fe (10 to 1000 mg l−1). The final product was characterized using X-ray diffraction and electronic microscopy. The results showed that the formation of GR is favored, with respect to magnetite, to a lesser extent with PAM than with PAA. These results indicated that polymers influence the chemical stability of GR and/or guide the route of biomineralization. Polymer properties, in addition to silica and phosphate concentrations, are then critical parameters that control the secondary iron mineral biomineralization from iron-reducing bacteria.

International audience; Mn-doped zinc sulfide (Mn:ZnS) quantum dots stabilized by 3-mercaptopropionic acid (MPA) were synthesized at 100°C in basic aqueous solution using the nucleation-doping strategy. The optical properties and structure of the obtained Mn:ZnS d-dots have been characterized by UV-vis, photoluminescence (PL) and time-resolved PL spectroscopies, transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron spin resonance (ESR). The obtained nearly monodisperse Mn:ZnS@MPA QDs were found to be of spherical shape with an average diameter of ca. 2.5 nm and with a zinc-blende crystal structure. By varying the base (LiOH, NaOH, KOH, CsOH) used to deprotonate the MPA ligand and adjust the pH of the aqueous solution to 11, the PL emission wavelengths can be tuned within a relatively large optical window, from 567 to 594 nm. The variations of charge density near the surface of the QDs obtained by changing the cation associated to the MPA ligand and of the dopant location in the ZnS host are at the origin of the PL shifts observed. In order to improve the PL emission efficiency, a ZnS shell was subsequently overcoated around the Mn:ZnS core nanocrystals. With ZnS shell growth, the PL emission wavelength was restricted between 570 and 583 nm but PL quantum efficiency of Mn:ZnS/ZnS core/shell nanocrystals increased up to 18.4 %.

International audience; Nanocomposites have been processed following a wet-impregnation approach, by confined growth of nanoparticles of the spin crossover complex [Fe(Htrz)2(trz)](BF4) within pre-formed transparent mesoporous silica monoliths of well controlled porosity. The obtained materials were studied using numerous characterisation techniques to define the interplay between the porosity of the host matrix, the structure and morphology of the in situ elaborated nanoparticles, and the spin crossover properties of the composite. Transmission electron micrographs show monodisperse spherical nanoparticles of mean diameter 3.2(5) nm, homogeneously distributed within the pores of the silica monolith. Magnetic measurements, temperature dependent infrared, Raman, and M¨ossbauer spectroscopy confirm the spin transition behaviour of the nanocomposite, with a room temperature bistability and 65 K wide hysteresis.

International audience; The interaction between metallic iron and kaolinite was studied in conditions relevant to those that may be encountered in a high-level radioactive waste disposal facility in geological formation. Experiments were carried out under anoxic atmosphere at 90 C and in chloride solutions to simulate conditions close to disposal facilities. KGa-2 kaolinite was put in contact with powdered metallic iron in batch experiments for durations of 1, 3, and 9 months. Solutions extracted from the end-products were analyzed (pH, Eh, conductivity, and cation concentrations). End-products were characterized by a set of chemical (oxide analyses, CEC, EDXS) and mineralogical techniques (SEM, TEM, XRD, and FTIR), textural analyses (nitrogen adsorption and low-pressure argon adsorption), XPS, and Mossbauer spectroscopy. In another set of experiments the system was changed from anoxic to oxic conditions to evaluate the stability of the system in the presence of O-2.The interaction between metallic iron and kaolinite led to a fast initial reaction as major modifications took place during the first month. The partial oxidation of metallic iron resulted in a pH increase and negative Eh values. Iron was not found in solution but in two new Fe-rich phases: magnetite in very low amounts and a Fe-rich clay phase, belonging to the berthierine family. The Si and Al of the berthierine are derived from the partial alkaline dissolution of kaolinite, mostly along edge faces. TEM-EDXS local analyses showed that the composition of resulting particles consisted in mixtures of berthierine and kaolinite layers. Clay particles became thicker with the epitaxial growth of berthierine layers on the basal surfaces of pristine kaolinite.Neoformed berthierine was not stable in the presence of O-2 at 90 degrees C. Berthierine layers dissolved, iron was mobilized to form iron oxides and oxyhydroxides while kaolinite layers recrystallized from released Al and Si.

This study proposes a simple and innovative synthesis route for a goethite–calcite nanocomposite. This synthesis is summarised by three sequential precipitation reactions: (1) precipitation of nanosized acicular goethite (α-FeOOH) using a high OH/Fe molar ratio (=5); (2) instantaneous precipitation of portlandite (Ca(OH)2) by adding CaCl2 salt to a goethite alkaline suspension (2NaOH + CaCl2 → Ca(OH)2 + 2NaCl) and; (3) sub-micrometric calcite precipitation by injection of CO2 into a goethite–portlandite alkaline suspension (Ca(OH)2 + CO2 → CaCO3 + H2O). The XRD patterns have confirmed the goethite and calcite mineral composition in the composite precipitated at 30 and 70 °C. FESEM and TEM observations have revealed the formation of nanosized goethite particles well dispersed with sub-micrometric calcite particles, leading to an orange–brown colour nanocomposite with high specific surface area of around 92 m2/g for a composite synthesized at 30 °C and 45 m2/g for a composite synthesized at 70 °C. Both values were determined using the conventional BET method on N2 sorption isotherms. Finally, a goethite/calcite weight ratio equal to 0.8 in the composite was determined by Thermogravimetric Analysis (TGA). Additionally, some adsorption experiments carried out at two different pH values revealed that the goethite–calcite composite has a good sequestration capacity for Cu > Cd > As(III) > Se(IV) > As(V). Conversely, the Se(VI) did not show any chemical affinity with the goethite–calcite composite under the physico-chemical conditions studied. In practice, the goethite–calcite composite can neutralise acidic wastewater by slight calcite dissolution, enhancing the removal of heavy metals (e.g. Cu and Cd) at the calcite–solution interfaces.

International audience; Micro-gap discharges created in heptane between two platinum pin-electrodes produce platinum particles embedded in an amorphous carbon matrix which exhibits a short-range order. The platinum particles can be sorted by size. The largest ones (>100 nm in diameter) are created by emission of droplets from the liquid pool formed when the discharge hits the electrode surface. They are submitted to high stress levels by fast thermal quenching. The smallest ones (

Equipe 101 : Nanomagnétisme et électronique de spin; International audience; Large scale production of high quality CNT samples is still challenging. The presence of structural defects and metallic particles in pristine single walled carbon nanotubes (SWNTs) is responsible for the alteration of both their chemical stability and their magnetic and electrical properties. The commonly used purification procedures are based on multi-step treatments that are often too aggressive towards the CNTs, leading to disappointing yields. Here, we propose an alternative process that allows preparing high-quality and high-purity SWNT samples. The proposed process merely consists of heating up SWNT powder under high chlorine partial pressure and high temperature. These thermodynamic conditions favor high chlorine diffusion to metal impurities embedded in carbon shells thus inducing an avalanche process of metal chloride formation and sublimation. The purified samples have been characterized by transmission electron microscopy, thermogravimetric analysis, magnetic measurements and Raman spectroscopy. We show that the developed process combines selective elimination of catalytic impurities and high yields. More importantly, we show that this process preserves the quality of the resulting purified nanotubes.

Electrochemical intercalation of unsolvated lithium into pitch carbon fibres P100 and natural graphite UF4 has been carried out in LiClO4-ethylene carbonate electrolyte. The reversible electrochemical capacity for a current equal to 7 μA/mg is 260 mAh/g for P100 carbon fibres and about 350 mAh/g for UF4 graphite, respectively. During the first discharge (reduction) an electrochemical capacity greater than the theoretical value (372 mAh/g) corresponding to LiC6 is obtained. This excess of capacity can be related to the formation of a passivating layer on the carbon surface. Analysis of this layer by means of transmission electron microscopy (electron diffraction, electron energy loss spectroscopy, and imaging) and Fourier-transform infrared spectroscopy has shown that this layer is composed of lithium carbonate Li2CO3 and alkylcarbonates of lithium ROCO2Li. Formation of Li2CO3 occurs at potentials in the 1−0.8 V range versus Li + Li , and formation of lithium alkylcarbonates then follows at potentials below 0.8 V. We then attributed the voltage plateau at 0.9 V versus Li + Li observed in the electrochemical waves to the reduction of ethylene carbonate into Li2CO3. Transmission electron spectroscopy revealed the presence of lithium chloride in the electrolyte which appears as small rods.

Degradation of roots from beech trees was investigated by a novel approach: localization and elemental characterization of predominant brown substances were performed at ultrastructural scale using electron energy loss spectroscopy (EELS). This technique allowed us to detect light elements such as C and N, main constituents concerned in the degradation of plant tissues, within cellular constituents observed with a transmission electronic microscope, after having localized them by light microscopy. The results showed that there was no relationship between the brown pigmentation of the cellular substances and the presence of N, a relationship previously found in studies of degrading leaves. Other elements such as Si and Ca were also found to be involved in these root degradation processes. This approach seem powerful for detailed descriptions of the process of root degradation in soil.

The ESR characteristics of saturated alkali metal intercalated polyparaphenylene compounds [M y C 6 H 4 ] x with M = Na , K, Rb, Cs, were examined as a function of the nature of the intercalant and temperature. The peak-to-peak linewidth, ΔH pp , follows a Z α law ( Z = atomic number of M) with α = 2.3 ± 0.3. Evolution of ΔH pp with temperature T and atomic number Z shows that these compounds behave like metals and that the spin orbit interaction is the major cause of the broadening of the ESR signals.

The electro-oxidation of indole, C 8 NH 7 , in LiClO 4 -acetonitrile solution, leads to the formation of an electroactive polymer. This compound, in the doped state, was characterized by PEELS, XPS and FTIR spectroscopies. The sites of polymerization do not involve the benzene ring, but are rather on the 1 and 3 positions of the pyrrole ring. The most probable structure of ClO 4 − -doped polyindole is a regular alternance of 1,1–3,3 couplings.

Summary The authors have observed three different types of inclusions in hyphae of the endophyte: dense vacuolar granules, less dense and often diffuse vacuolar granules and granules included in small cytoplasmic vesicles. These inclusions were studied by cytochemical techniques and by energy electron loss spectroscopy. Dense granules correspond to polyphosphate granules already described by many authors. They contain phosphorus and calcium associated with a proteic fraction. Cytoplasmic granules and diffuse vacuolar granules are protein-rich inclusions without phosphorus and calcium. The authors suggest that the cytoplasmic inclusions are precursors of polyphosphate granules. These inclusions are contained in unknown origin vesicles. The diffuse protein-rich vacuolar granules are the remaining of polyphosphate granules after the transfer of phosphorus to the host. The polyphosphate granules are common in intracellular hyphae, but more rare and often absent in the hyphae of the arbuscule. For the authors,...

Tellurium and its alloys are used in many applications such as photoconductors, piezoelectric devices, thermoelectric generators and coolers [1]. For thermoelectric applications, the transport properties (thermal conductivity, electrical resistivity, Seebeck coefficient) of tellurium and its compounds can be improved by nanostructuring [2]. One-dimensional nanostructures like nanowires [3] and core-shell nanowires [4] are particularly promising due to the high phonon interface scattering and the blocking of the phonon conduction along the wire axis which lead to an increase of the thermoelectric conversion efficiency. Te nanowires can represent a base to create core-shell structures, being the core that could be further capped with a shell to get arrays of Te-based thermoelectric nanostructures like BiTe [5], AgTe [6] or LaTe [7]. Template assisted electrodeposition is a low cost technique widely used in literature for the synthesis of nanowires but implies several preparation steps and the removal of the template after the growth of the nanowires. The aim of this work is to develop a template free synthesis route that would be more convenient. For this purpose, Room-Temperature Ionic Liquids (RTILs) appear as promising solvents. Indeed, it has been highlighted that they can act as stabilizing agents for nanoparticles and nanostructured films synthesis [8]. In a previous work ([9]), our laboratory showed that Te nanowires can be obtained in an ionic liquid binary mixture: 1-ethyl-1-octyl-piperidinium bis(trifluoromethylsulfonyl)imide:1-ethyl-1-octyl-piperidinium bromide (EOPipTFSI:EOPipBr). In the present work, several morphologies were obtained by varying the synthesis parameters (applied fixed potential, Te(IV) concentration, electrolyte composition). Under charge transfer control, micrometer faceted grains are formed. Under diffusion control, the deposits are composed of nanowires, which are single crystalline as proven by SAED (Selected Area Electronic Diffraction) and TEM (Transmission Electron Microscopy) analyses. In highest tested overpotential conditions, nanowires turn progressively into crystallized hollow nanostructures (HNs) when the coulometric charge increases. This phenomenon is more accentuated at low concentration and disappears when using a soluble anode, showing that the formation of HNs is due to a limitation by species supply. The geometry of HNs, with a high surface to volume ratio, is particularly interesting to create high performances thermoelectric materials. Indeed, this geometry could further decrease the lattice part of the thermal diffusion coefficient by phonon confinement. By decreasing the bromide content of the electrolyte, hair-like single crystalline nanowires with a high aspect ratio can be obtained. HRTEM (High Resolution Transmission Electron Spectroscopy) analyses reveal a growth along the c-axis, with a smooth interface. No surface contaminants were observed by STEM (Scanning Transmission Electron Microscopy), proving that halogenide ions do not play the role of capping agents, unlike observed in other works [10]. References [1] Q. Wang et al, Adv. Mater. 2013, 25, 3915 [2] K.T. Kim et al, Adv. Powder Technol. 2011, 22, 566 [3] Caballero-Calero, O.; Martín-González, M., Scripta Materialia 2015, 10.1016/j.scriptamat.2015.04.020. [4] Poon, S. J.; Petersen, A. S.; Wu, D. Appl. Phys. Lett. 2013, 102. [5] Kang, J.; Roh, J. W.; Shim, W.; Ham, J.; Noh, J. S.; Lee, W. Advanced Materials 2011, 23, 3414. [6] Fang, H. Y.; Yang, H. R.; Wu, Y. Chemistry of Materials 2014, 26, 3322. [7] May, A. F.; Fleurial, J. P.; Snyder, G. J. Phys. Rev. B 2008, 78. [8] Z. Li et al, Current Opinion in Solid State and Materials Science 2008, 12, 1 [9] J. Szymczak et al.,Electrochem. Comm. 2012, 24, 57 [10] Al-Salman, R.; Sommer, H.; Brezesinski, T.; Janek, J. Chemistry of Materials 2015, 27, 3830. Figure 1: SEM (a) and HRTEM (b) images of Te nanostructures electrodeposited in EOPipTFSI ionic liquid Figure 1

International audience; The nature of the interaction between iron oxyhydroxide compounds and natural organic matter (NOM) may take various forms and is still a matter of debate. It is an important field to understand, especially for water treatment applications and for the knowledge of iron transport in the environment. The nature of association reached between iron oligomeric species and NOM is here investigated using Mössbauer spectroscopy and electron energy-loss spectroscopy (EELS) at the Fe-L3 edge. Raw water NOM taken from Moselle River (France), natural humic substances extracted from the riverine suspended matter, and a synthesized humic-like substance, are coagulated with iron nitrate according to a jar-test procedure. The results from Mössbauer spectroscopy indicate that Fe is present in an octahedral coordination environment, which is consistent with prior X-ray absorption spectroscopy reported in the literature. The areas beneath the peaks (Fe L3 edge) and the peak shapes of EELS spectra differ according to the origin of the organic matter, suggesting that various types of Fe populations can be distinguished using the EELS technique. Combining the selectivity of both Mössbauer spectroscopy for identifying trace, poorly crystalline Fe solids, oxidation state and of EELS for being able to characterize the population of Fe based on L-edge spectra, appears promising for characterizing Fe in systems containing NOM.

A 5% (wt/vol) whey protein isolate (WPI) dispersion (pH 6.5) with different concentrations of NaCl was submitted to dynamic heat treatment. Protein dispersions were characterized as to their rheological properties, particle sizes, morphology, denaturation temperatures, and protein surface hydrophobicity. At low ionic strength (

International audience; Water-dispersible CdS quantum dots (QDs) emitting from 510 to 650 nm were synthesized in a simple one-pot noninjection hydrothermal route using cadmium chloride, thiourea, and 3-mercaptopropionic acid (MPA) as starting materials. All these chemicals were loaded at room temperature in a Teflon sealed tube and the reaction mixture heated at 100 degrees C. The effects of CdCl2/thiourea/MPA feed molar ratios, pH, and concentrations of precursors affecting the growth of the CdS QDs, was monitored via the temporal evolution of the optical properties of the CdS nanocrystals. High concentration of precursors and high MPA/Cd feed molar ratios were found to lead to an increase in the diameter of the resulting CdS nanocrystals and of the trap state emission of the dots. The combination of moderate pH value, low concentration of precursors and slow growth rate plays the crucial role in the good optical properties of the obtained CdS nanocrystals. The highest photoluminescence achieved for CdS@MPA QDs of average size 3.5 nm was 20%. As prepared colloids show rather narrow particle size distribution, although all reactants were mixed at room temperature. CdS@MPA QDs were characterized by UV-vis and photoluminescence spectroscopy, powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectrometry and MALDI TOF mass spectrometry. This noninjection one-pot approach features easy handling and large-scale production with excellent synthetic reproducibility. Surface passivation of CdS@MPA cores by a wider bandgap material, ZnS, led to enhanced luminescence intensity. CdS@MPA and CdS/ZnS@MPA QDs exhibit high photochemical stability and hold a good potential to be applied in optoelectronic devices and biological applications.

Electrochemical reduction of graphite and fullerenes has been carried out in solid state cells operahng with solid polymer electrolytes based on poly(ethyleneoxide), GEO), complexed with lithium perchlorate. Low speed cyclic voltammetry, galvanostatic reduction and oxidation experiments give evidence for different successive redox states which appear during the cycling of both carbon materials. Preliminary electron diffraction studies have been performed on selected intercalated fullerenes

International audience; In wastewater treatment plants, optimizing bacterial flocculation and bacterial sludge dewatering requires a detailed understanding of the concommitant biological and physico-chemical processes governing the action of flocculating agent on living cells. Here we investigate the interactions between polyethyleneimine (PEI, 60000 g/mol) and Shewanella oneidensis MR-1 lacking or not the lipopolysaccharide (LPS) O-antigen surface structure. Flocculation tests were performed on bacteria with/without LPS O-antigen after being exposed to 0-100 mg/L PEI concentrations. Measurements of electrophoretic mobility and bacterial aggregates size were complemented by transmission electron micrographs and atomic force microscopy images. While low PEI concentrations (< 20 mg/L) lead to flocculation of both bare and LPS O-antigen-decorated bacterial strains, the lysis of bacterial membranes occurred at larger polymer concentrations for the latter, which highlights the protective role of LPS O-antigen against harmful PEI-mediated membrane alterations. Depending on polymer concentration, two types of bacterial aggregates are identified: one that solely integrates bacterial cells, and another that includes both cells and cell residues resulting from lysis (membrane and/or LPS fragments, and inner cell content materials). The latter is expected to significantly contribute to water entrapping in sludge and thus lower dewatering process efficiency.

International audience; In the Sinnamary Estuary (French Guiana), a dense red biofilm 15 grows on flooded surfaces. In order to characterize the iron oxides in this biofilm and to establish the nature of secondary minerals formed after anaerobic incubation, we conducted solid analysis and performed batch incubations. Elemental analysis indicated a major amount of iron as inorganic compartment along with organic matter. Solid analysis showed the presence of two ferric oxides ferrihydrite and lepidocrocite. Bacteria were abundant and represented more than 1011 cells g-1 of dry weight among which iron reducers were revealed. Optical and electronic microscopy analysis revealed than the bacteria were in close vicinity of the iron oxides. After anaerobic incubations with exogenous electron donors, the biofilm's ferric material was reduced into green rust, a FeII-FeIII 25 layered double hydroxide. This green rust remained stable for several years. From this study and previous reports, we suggest that ferruginous biofilms should be considered as a favorable location for GR biomineralization when redox conditions and electron donors availability are gathered.

International audience; Water-dispersible 1-thioglycerol-capped Mn-doped ZnSe quantum dots (QDs) were prepared in aqueous solution through the nucleation-doping method by using safe and low-cost inorganic salts as precursors. Influence of the Zn/Se ratio, precursors concentrations and reaction pH on the particle size, colloidal stability, and photoluminescence (PL) were investigated. Under optimal conditions, thioglycerol-capped ZnSe:Mn QDs with an average diameter of 3.5 nm and a PL quantum yield of 3.5% in water at neutral pH were produced. X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV- visible spectroscopy and spectrofluorometry have been used to characterize the crystal structure and the optical properties of the dots. Remarkable improvements of stability in biological medium and PL were achieved by introduction of a ZnO shell through basic hydrolysis of Zn(NO3)2. ZnO was found to eliminate the surface-trap state fromMn2+-doped ZnSe cores and enhance their PL quantum yield to 12%. Growth inhibition tests showed that core/shell ZnSe:Mn/ZnO@TG QDs do not exhibit any cytotoxicity toward E. coli bacterial cells up to a concentration of 0.14 mg/mL, indicating that these nanocrystals can be considered as building blocks for the synthesis of bioprobes for cells and tissues imaging.

International audience; Relatively monodisperse and highly luminescent Mn2+ -doped zinc blende ZnSe nanocrystals were synthesized in aqueous solution at 100 C using the nucleation-doping strategy. The effects of the experimental conditions and of the ligand on the synthesis of nanocrystals were investigated systematically. It was found that there were significant effects of molar ratio of precursors and heating time on the optical properties of ZnSe:Mn nanocrystals. Using 3-mercaptopropionic acid as capping ligand afforded 3.1 nm wide ZnSe:Mn quantum dots (QDs) with very low surface defect density and which exhibited the Mn2+-related orange luminescence. The post-preparative introduction of a ZnS shell at the surface of the Mn2+-doped ZnSe QDs improved their photoluminescence properties, resulting in stronger emission. A 2.5-fold increase in photoluminescence quantum yield (from 3.5 to 9%) and of Mn2+ ion emission lifetime (from 0.62 to 1.39 ms) have been observed after surface passivation. The size and the structure of these QDs were also corroborated by using transmission electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction.

International audience; Prussian Blue (PB) has been electrochemically grown through thin mesoporous silica films of novel generation, exhibiting regular arrays of hexagonally packed mesopores channels (3 nm in diameter) oriented perpendicular to the underlying electrode surface. Due to confinement effects, special care has to be taken to ensure effective permeability of PB precursors through the hard silica template, which was best achieved by pulsed electrodeposition from a high ionic strength medium (2 M KCl). Energy dispersive X-ray spectroscopy associated to electron microscopy was used to evidence the presence of PB in the vertically-aligned mesopores, which was also assessed by their electrocatalytic behavior towards H2O2 reduction.

International audience; Highly ordered and vertically oriented mesoporous silica films can be generated by electro-assisted self-assembly (EASA). The method involves the electrogeneration of hydroxide ions at an electrode surface immersed in an hydrolyzed sol solution (containing typically tetraethoxysilane, TEOS, and cetyltrimethylammonium bromide, CTAB) in order to catalyze polycondensation of the precursors and self-assembly of hexagonally packed one-dimensional channels that grow perpendicularly to the support. Vertically aligned mesostructures have been demonstrated by TEM imaging and by grazing incidence X-ray diffraction (GIXD), this latter technique enabling characterization of thin films directly on their underlying electrode surface. The influence of the electrosynthesis medium composition (precursor and surfactant concentrations, surfactant chain length) on the mesostructural order and film thickness has been thoroughly examined. It was shown that the highly ordered and oriented mesoporous silica films can be obtained over a wide composition of the starting sol (i.e., 10−200 mM CTAB and 50−350 mM TEOS) and that the lattice parameter can be moderately tuned by changing the chain length of the surfactant template. Thickness of these films can be accurately controlled by applying galvanostatic conditions and by varying the deposition time, which offer the versatility to be applied in the same way to electrodes of different nature without overpotential problems encountered in the potentiostatic mode. Thin mesoporous films are often covered with an additional byproduct made of particulate aggregates arising from bulk gelification at the electrode/solution interface. Getting aggregate-free thin films is possible by working in diluted solutions (i.e., [TEOS] < 125 mM and CTAB/TEOS ratio

Single-walled carbon nanotubes (SWCNTs) were functionalized in a three-step procedure. The first step is a radical reaction creating a covalent bond between the carbon nanotube surface and grafted p-methoxyphenyl functional groups. In a second step, a deprotection of the methoxy functions generates free alcohol groups and in the final step an esterification is done in order to install a double bond for further polymerization. Evidence that functionalization has actually occurred on the SWCNT sidewalls is furnished through investigations involving several complementary techniques (visual dispersion tests, transmission electron microscopy, thermal gravimetric analysis and adsorption volumetry). We show that surface properties of SWCNTs are changed throughout the chemical treatments and that the obtained level of functionalization is low. Incorporation of functionalized SWCNTs in a polymer (poly(methyl methacrylate)) matrix was done through an in situ polymerization process. Observations of the obtained composites using scanning and transmission electron microscopy illustrate that interactions between the SWCNT surface and the polymer matrix are improved.

International audience; A preliminary insight into metal cycling within the urban sewer was obtained by determining both the heavy metal concentrations (Cu, Zn, Pb, Cd, Ni, Cr) in sewage and sediments, and the nature of metal-bearing particles using TEM–EDX, SEM–EDX and XRD. Particles collected from tap water, sump-pit deposits, and washbasin siphons, were also examined to trace back the origin of some mineral species. The results show that the total levels in Cu, Pb, Zn, Ni, and Cr in sewage are similar to that reported in the literature, thus suggesting that a time-averaged heavy metal fingerprint of domestic sewage can be defined for most developed cities at the urban catchment scale. Household activities represent the main source of Zn and Pb, the water supply system is a significant source of Cu, and in our case, groundwater infiltration in the sewer system provides a supplementary source of Ni and Cd. Concentrations in heavy metals were much higher in sewer sediments than in sewage suspended solids, the enrichment being due to the preferential settling of metal-bearing particles of high density and/or the precipitation of neoformed mineral phases. TEM and SEM–EDX analyses indicated that suspended solids, biofilms, and sewer sediments contained similar heavy metal-bearing particles including alloys and metal fragments, oxidized metals and sulfides. Copper fragments, metal carbonates (Cu, Zn, Pb), and oxidized soldering materials are released from the erosion of domestic plumbing, whereas the precipitation of sulfides and the sulfurization of metal phases occur primarily within the household connections to the sewer trunk. Close examination of sulfide phases also revealed in most cases a complex growth history recorded in the texture of particles, which likely reflects changes in physicochemical conditions associated with successive resuspension and settling of particles within the sewer system.

The nature of phosphate phases present in suspended matter, biofilm, and sediment of Greater Nancy sewer system was investigated over a period of two years. The phosphate speciation was determined by two approaches: a direct identification of phosphorus mineral phases was conducted by Transmission Electron Microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS), whereas a chemical extraction of samples provided an estimate of phosphorus pools defined by the fractionation scheme. Quantitative analysis of 1340 individual particles by TEM–EDXS allowed to draw a picture of phosphate species distributions along the sewer system and over time. Amorphous Ca–phosphates (brushite, whitlockite, octacalcium phosphate, Mg-brushite, hydroxyapatite and carbapatite) were ubiquitous although brushite dominated upstream, and octacalcium phosphate and apatite prevailed downstream and in sediments. Al–Ca–phosphate minerals such as foggite, bearthite, gatumbaite, and crandallite appeared downstream and in biofilms. Ca–phosphate phase assemblages in the different locations of the sewer system were dependent on phase transformations from brushite to hydroxyapatite that were shown to be kinetically driven. The restriction of Al–Ca–phosphates to downstream of the sewer system was most probably related to the lower pHs measured at these sites. The pH dependency was confirmed by stability calculations. Chemical extractions were not reliable. TEM examination of extraction residues revealed the presence of neoformed Al–Ca–phosphate species that invalidated the fractionation scheme. Nonetheless, it confirmed that phosphate phases may undergo significant geochemical changes over a short time scale.