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International audience; For the first time, pristine ZnO nano-particles can be used as effective catalyst for water disinfection by killing and complete mineralization of two gram negative bacteria with direct solar light. Just like in earlier studies, pristine nano-size ZnO particles have shown anti-bacterial activity against two types of gram negative bacteria, E. coli and P. aeruginosa, where up to 20% of the former and 25% of the latter have been killed in the dark. Under direct solar radiation, the pristine ZnO particles readily catalyzed bacterial photo-degradation. While earlier studies were mostly limited to bacterial death and growth inhibition by pristine ZnO particles, the results describe for the first time how bacteria and their organic content can be completely photo-mineralized by direct solar radiations in 60 min. Only the bacterial cell wall fragments resisted the photo-degradation process. Under the reaction conditions, the degradation occurred by the UV tail of the direct solar light, where the ZnO nano-particles behaved as photo-catalysts. The results show the added value of using ZnO nano-particles as photo-catalysts in water disinfection strategies, leaving no resulting organic molecules in water.

International audience; This communication describes for the first time how nano-size particles, sensitized with natural dye molecules of anthocyanin, can be used as catalysts in photo-degradation of gram negative Escherichia coli bacteria in water. The naked ZnO nano-particles degraded up to 83% of the bacteria under solar simulator light, while the dye-sensitized particles increased the bacterial loss by ∼10%. Solar simulator light includes about 5% of UV tail (shorter than 400 nm) which means that both UV and visible light (longer than 400 nm) radiations could be involved. When a cut-off filter was used, the naked ZnO caused only 40% bacterial loss, in accordance with earlier literature that described killing of bacteria with ZnO particles both in the dark and under light. With the cut-off filter, the sensitized ZnO particles caused higher than 90% bacterial loss, which confirms sensitization of the ZnO particles to visible light. Moreover, the results show that the catalyzed photo-degradation process causes mineralization of the bacteria and their organic internal components which leach out by killing. The catalyst can be recovered and reused losing ∼10% of its activity each time due to mineralization of the dye molecules. However, catalyst activity can be totally regained by re-sensitizing it with the anthocyanin dye. The effects of different experimental conditions, such as reaction temperature, pH, bacterial concentration and catalyst amount together with nutrient broth and saline media, will be discussed together with the role of the sensitizer.

International audience; Electrodeposited CuSe film electrodes have been prepared onto FTO/glass by a facile method based on earlier methods described for other systems. The films were characterized, modified by annealing and further characterized. The films were then modified by coating with tetra(-4-pyridyl) pophyrinato-manganese (MnTPyP) complexes embedded inside commercial polyethylene (PE) matrices. The effects of modifications on different film properties, such as X-ray diffraction (XRD) patterns, surface morphology, photoluminescence (PL) spectra and electronic absorption spectra were investigated. Compared with other thin film electrode systems, very high photoelectrochemical (PEC) conversion efficiency values have been observed here. Pre-annealing the CuSe films at 150°C for 2 h, followed by attaching the MnTPyP/PE matrices remarkably enhanced their PEC characteristics. The conversion efficiency was significantly enhanced, from less than 1.0% to more than 15%. Fill factor (FF) was also enhanced from ∼30% to ∼80%. Values of open-circuit potential (VOC) and short-circuit current (JSC) were significantly enhanced. While annealing affects uniformity, particle inter-connection and surface texture of the CuSe films, the MnTPyP complex species behaves as an additional charge-transfer mediator across the film/electrolyte junction. Optimization of PEC characteristics, using different deposition times, different annealing temperatures, different annealing times and different redox couples, was also investigated.

Electrochromic nickel oxide (Ni 1− x O) pigment powder which was made from nickel acetate reacting with H 2 O 2 /urea solution followed by heat treatment of xerogels at 400 °C (24 h) was milled with zirconia beads in pure water or water with added nickel oxyhydroxy precipitate acting simultaneously as the dispersant and the coating binder. The corresponding pigment particle suspensions were spin coated on FTO glass and flexible ITO-PET foils, respectively, and cured at 150 °C. The optical properties of the deposited pigment coatings on FTO glass substrates were determined with an UV VIS spectrometer, providing total direct transmittance (TT), total diffuse transmittance (DT) and haze (in %). Haze increased with the coating thickness but did not exceed 4%. SEM micrographs of the deposited pigment coatings revealed that they consisted of agglomerated Ni 1− x O pigment with voids. Potential cycling of Ni 1− x O pigment coatings and Ni 1− x O thin films was performed in 1 M LiClO 4 /PC and 0.1 M TBA + triflate/PC electrolytes, revealing that the pigment coatings exhibited electrochemical and electrochromic activity also in lithium free (aprotic) electrolyte, while variations of the oxidation and reduction reaction peaks at various scan rates confirmed the presence of surface electrochemical reactions. The near-grazing incidence angle reflection–absorption spectroscopic technique (IR RA) was employed for identifying surface and inner-grain Ni–O stretching modes, the former being responsible for observed electrochemical properties, which was also demonstrated from the ex situ IR RA measurements performed for coatings charged/discharged in 1 M LiClO 4 /PC and 0.1 M TBA + triflate/PC electrolytes. The results disclosed in this study suggest that the electrochromic effect was not in direct correlation with the de-insertion/insertion of small ions into the NiO (bunsenite) grains but rather the pigment coatings behave similarly to nickel oxide electrochemical capacitors. The electrochromic response of a flexible EC devices made either of PEDOT (self-standing foil) or WO 3 and Ni 1− x O pigment coatings glued with PMMA based electrolytes without and with lithium salt were recorded for the demonstration of the possible practical application of wet deposited Ni 1− x O pigment coatings made as “electrochromic” paints.

International audience; Polycrystalline CdSe films have been deposited onto fluorine doped tin oxide (FTO/glass) substrates by three different techniques, electrochemical deposition (ECD), chemical bath deposition (CBD) and, for the first time, combined ECD and CBD (ECD/CBD). The films were comparatively characterized by photoluminescence spectra (PL), electronic absorption spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM micrographs show that the films involved rod shaped agglomerates with various lengths and widths. XRD patterns show that the three systems involved nano-sized CdSe particles with cubic type crystals. Based on Scherrer's equation, the ECD film showed larger particle size than the CBD film, while the ECD/CBD film showed largest particles among the series. Similarly, the band gap values varied for different films as CBD > ECD > ECD/CBD. Photo-electrochemical (PEC) characteristics, including photo-current density vs. voltage (J-V) plots, conversion efficiency (ƞ), fill factor (FF) and stability were all studied for different film electrodes. The films exhibited n-type behaviors with direct band gaps. The new ECD/CBD-CdSe electrode exhibited higher conversion efficiency (ƞ% ~ 4.40) than other counterparts. The results show the added value of combining ECD and CBD methods in enhancing PEC characteristics of CdSe film electrodes, even with no additional treatment.

International audience; High conversion efficiency (η) values have been obtained from modified CuS film electrodes electrochemically deposited onto Glass/FTO. The modification involved pre-annealing the film followed by coating with tetra(-4-pyridyl)porphyrinato manganese (MnTPyP+) ions embedded inside a polyethylene (PE) matrix. The Glass/FTO/CuS/MnTPyP/PE electrodes exhibited enhanced photo-electrochemical (PEC) characteristics under solar simulated illumination (5.6 mW/cm−2) in aqueous media, compared to the as-prepared Glass/FTO/CuS films which showed no PEC activity. Up to 17.4% efficiency and 85% fill factor (FF) values were obtained from the modified film electrodes. Such characteristics have not been widely known for metal chalcogenide based film electrodes before. Different pre-annealing temperatures were attempted and the 250 °C temperature, followed by quenching, showed favorable results. Different aqueous redox couples were studied and the environmentally safe FeCl2/FeCl3 aqueous system showed highest PEC characteristics. Effect of pre-annealing on film electrode characteristics is discussed. The MnTPyP/PE matrix behaves as charge transfer catalyst for the holes across the CuS film/liquid junction.

International audience; Aiming at enhancing the electrochromic properties of anodically colored NiOthinfilms, lithium doped NiOthinfilms were grown on FTO/glass substrates, by the pulsed laser deposition (PLD) method. Optimized conditions, namely a room temperature substrate under 10 Pa oxygen pressure were used. Comparison with undoped NiOthinfilms indicates that lithium doping deteriorates NiO cubic phase (1 1 1) preferred orientation and also induces lattice disorder. The investigation of the electrochromic properties of Li-Ni-O thinfilms in aqueous liquid electrolyte, 1 M KOH, on the one hand and in hydrophobic lithium conductive ionic liquid, 0.3 M LiTFSI in BMITFSI, on the other hand, demonstrates an improvement in the electrochromicperformances with lithium doping. Finally, electrochromicdevices built on the association of WO3 and Li-Ni-O thinfilms and using the above quoted ionic liquid blended with PMMA as electrolyte are reported. Good electrochromicperformances and neutral color are shown.

The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1-butyl-3-methylimidazolium cation (BMI+) and bis(trifluoromethane-sulfonyl)imide anion (TFSI−) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI-based systems, most lithium ions are shown to be coordinated within [Li(TFSI)2]− anionic clusters. The variation of the self-diffusion coefficients of the 1H, 19F, and 7Li nuclei, measured by pulsed-gradient spin-echo NMR (PGSE-NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI+ cations, TFSI− ‘free’ anions, and [Li(TFSI)2]− anionic clusters. This implies a negative transference number for lithium. Copyright © 2008 John Wiley & Sons, Ltd.

Background Photo-degradation of organic contaminants into non-hazardous mineral compounds is emerging as a strategy to purify water and environment. Tremendous research is being done using direct solar light for these purposes. In this paper we report on optimum conditions for complete mineralization of aqueous methyl orange using lab-prepared ZnO nanopowder catalyst under simulated solar light. Results Nano-scale ZnO powder was prepared in the lab by standard methods, and then characterized using electronic absorption spectra, photolumenscence emission (PL) spectra, XRD, and SEM. The powder involved a wurtzite structure with ~19 nm particles living in agglomerates. Photo-degradation progressed faster under neutral or slightly acidic conditions which resemble natural waters. Increasing catalyst concentration increased photodegradation rate to a certain limit. Values of catalyst turn over number and degradation percentage increased under higher light intensity, whereas the quantum yield values decreased. The photocatalytic efficiency of nano-ZnO powders in methyl orange photodegradation in water with solar light has been affected by changing the working conditions. More importantly, the process may be used under natural water conditions with pH normally less than 7, with no need to use high concentrations of catalyst or contaminant. The results also highlight the negative impact of possible high concentrations of CO2 on water purification processes. Effects of other added gaseous flows to the reaction mixture are also discussed. Conclusion ZnO nano-particles are useful catalyst for complete mineralization of organic contaminants in water. Photo-degradation of organic contaminants with ZnO nano-particles, methyl orange being an example, should be considered for future large scale water purification processes under natural conditions.

International audience; Rapid synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoribbons interleaved between the layers of crystalline V2O5 is achieved for the first time under microwave irradiation via the redox intercalative polymerization reaction of 3,4-ethylenedioxythiophene (EDOT) monomer and crystalline V2O5 at different time intervals...

Different modification techniques, namely, preheating, controlling the cooling rate and modification with tetra(-4-pyridyl)porphyrinatomanganese(III) have been used to enhance photoelectrochemical characteristics of n-GaAs electrodes in light-to-electricity conversions. Combination of such three techniques together yielded electrodes with better darkcurrent density vs potential plots and photocurrent density vs potential plots. Higher efficiency and stability were also observed for electrodes modified by such combined techniques.

Thermodynamic parameters and energy-band gap of a given metal oxide, are suitable measures of its stability. For this reason, direct correlations between energy-band gap or chemical hardness, and thermodynamic parameters (e.g. standard enthalpy of formation) have been constructed for different metal oxides. Furthermore, a simple relationship to calculate values of energy-band gaps, for metal oxides, from values of their enthalpies of formation, is presented here. When tested, an appreciable number of metal oxides from s- , p- and d-blocks well obeyed the relationship, while a number of metal oxides deviated. A qualitative theoretical account for such different behaviors is presented here.

We have established a novel method of inserting poly(3,4-ethylenedioxythiophene) (PEDOT) between the layers ofV2O5using a soft process of intercalation. The reaction takes place with the in situ polymerization of EDOT within the framework of crystallineV2O5with different nominal EDOT/V2O5ratios. The hybrids PEDOT/V2O5exhibit a high electrical conductivity

Poly(3,4-ethylene dioxythiophene) (PEDOT) has been inserted between the layers of crystallineV2O5via the in situ polymerization of EDOT within the framework of the oxyde. The insertion increases the bidimensionality of theV2O5host by the layer separation but results in a random layer stacking structure, leading to broadening of the energy state distribution. According to electrochemical measurements, the hybrids showed reversible specific capacities up to∼330mAh/g at 15mA/g between 2 and 4.4V vs.Li+/Li.

International audience; Successful preparation of tungsten oxide thin films on paper substrate, using a novel room temperature deposition method involving the connection of tungsten oxide nanoparticles by UV-irradiation, is reported. WO3 thin films, prepared from synthesized monoclinic WO3 powder as compared to commercial ones, show higher electrochemical activity and good cycling stability in 0.3 M trifluoromethanesulfonimide (HTFSI) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMITFSI) ionic liquid electrolyte versus Pt as counter electrode. Electrochromic performances of complete devices using Prussian Blue (PB) as complementary counter electrode and 0.3 M Lithium Bis(Trifluoromethanesulfonyl)Imide LiTFSI in BMITFSI plastified with polymethylmetacrylate (PMMA) membrane electrolyte are associated with a contrast in reflectance of 13%, from a yellow to a blue color.

International audience; A facile and low-cost strategy to improve stability and conversion efficiency of CdSe film electrodes prepared by chemical bath deposition (CBD) onto FTO/glass substrates, is described. The naked CdSe film electrodes, with band gap value 1.8 eV, photo-corroded under the photoelectrochemical (PEC) working conditions and exhibited no photocurrent. The CdSe film peeled out in short times. Attempts made to enhance stability and efficiency of naked CdSe electrodes, by chemical etching or pre-scratching the FTO surface with fine sand-paper, failed to improve film PEC characteristics. Annealing the glass/FTO/CdSe film also failed to improve its PEC stability or efficiency. When coated with the electro-active species Tetra(-4-pyridyl)porphyrinatomanganeseIII/II sulfate embedded inside polysiloxane films (MnPyP/Polysil) the CdSe films did not peel out under the PEC conditions. The coated electrode (glass/FTO/CdSe/MnPyP/Polysil) clearly exhibited photocurrents. Pre-annealing the naked CdSe film at 350 °C, followed by coating with MnPyP/Polysil further enhanced the electrode PEC characteristics. Additional heating of the prepared glass/FTO/CdSe/MnPyP/Polysil electrode at 120 °C also enhanced its PEC characteristics. The mode of action of the MnPyP/Polysil coating has been attributed to its ability to behave as a charge transfer catalyst at the solid/liquid interface. The new technique described here could also be potentially valuable for other types of thin film electrode materials.

International audience; Electrochromic (EC) performances of Ni3 + containing NiO thin films, called modified NiO thin films, prepared either by pulsed laser deposition or by chemical route are reported. When cycled in lithium based electrolyte, the comparison of the EC behavior of nonstoichiometric NiO thin films points out a larger optical contrast for the films synthesized by chemical route with the absence of an activation period on early electrochemical cycling due in particular to a larger porosity. Herein we demonstrate faster kinetics for modified NiO thin films cycled in lithium ion free electrolyte. Finally, X-ray absorption spectroscopy is used for a preliminary understanding of the mechanism involved in this original EC behavior linked to the film characteristics including their disorder character, the presence of Ni3 + and their porous morphology.

A model is proposed for the formation of degenerate semiconductors used as transparent electrodes. We propose that a degenerate semiconductor is, hypothetically, an oxide of formula Mn+On/2 doped with an oxide of formula (Mn+1+e)On/2. In this formula, Mn+1 and e symbolizes, respectively, the ionized donor center and the associated conduction-band electron. The electron affinity of both the matrix and the dopant have to be adjusted in order to combine an important transparency and conductivity. The calculation of the electron affinity is calculated on the basis of the electronegativity and of the chemical hardness of the oxides. An excellent fit is obtained for the already known materials and the model permits to forecast new materials.

A clear correlation between optical band gaps of oxides and the microscopic energies calculated from standard formation enthalpy or standard free energy related to one oxygen is demonstrated. This result is in agreement with the maximum chemical hardness principle proposed by Pearson (J. Am. Chem. Soc. 1987;64:561; J. Chem. Educ. 1999;76:267) and Parr and Chattaraj (J. Am. Chem. Soc. 1991;113:1854).

Micro-Raman spectroscopic analyses have been performed for the layered LiMnO 2 compound and its delithiated/relithiated derivatives in order to probe the effect of Li extraction/insertion on the local structure around manganese ion in this layered material. For this purpose, we have first tried to establish a spectroscopic measure for identifying the lithium manganates with closely related structures. From the detailed comparison among the Raman spectra of layered and spinel-structured lithium manganates, both phases can be easily differentiated from each other by using micro-Raman spectroscopy. Based on these experimental findings, we are able to conclude that the chemical or electrochemical deintercalation of lithium gives rise to the Mn migration into the interlayer lithium site, resulting in the creation of the spinel-like cation ordering. © 2001 The Electrochemical Society. All rights reserved.

Fluorine-doped tin dioxide (FTO) films were elaborated from a new Sn(IV) molecular precursor, the tert amyloxyfluorodipentan-2,4-dionatotin(IV) complex, to be used via the sol–gel route. Upon controlled hydrolysis in acetonitrile, a fluorinated polystannoxane was formed as a stable xerosol, which was characterized by multinuclear magnetic resonance and Mossbauer spectroscopies, elemental analysis, and thermogravimetry coupled to mass spectrometry. This xerosol was further dissolved in acetonitrile for depositing highly transparent films by the spin-coating and spray pyrolysis techniques. Film composition was determined by X-ray photoelectron spectroscopy, electron probe microanalysis and energy dispersive X-ray analysis. The F/Sn atomic ratio was 3% for spin-coated films and 10% for the sprayed films. A noticeable amount of carbon (C/Sn #10 at.%) was detected in the films whatever the deposition technique. In every case, the film resistivity was found to be larger than the one obtained from separate tin and fluorine precursors. This result was attributed to the excess of carbon and fluorine content in the oxide layers relieved from the xerosol.

A fluorine-doped nanocrystalline tin oxide has been prepared by thermolysis of xerosol derived from a single molecular precursor. A fluorine to tin atomic ratio, as high as 0.14, was estimated from the results of elemental analysis. The oxidation state of Sn and conducting properties were determined by Mossbauer spectroscopy and resistivity measurements. According to the electrochemical experiments, a reversible capacity up to ∼800 mAh/g has been achieved.

The electronic structures of the sesquioxide In 2 O 3 and Sn-doped In 2 O 3 are examined both self-consistently within the ab initio local density functional theory and using the non self-consistent extended Huckel method. A direct band gap and a wide dispersion of the bottom of the conduction band are obtained in the non-doped case. In the doped case, a narrow, half-filled band assigned to Sn is found at the bottom of the conduction band, in agreement with the metallic and transparent characteristics observed experimentally.

This paper reports on the deposition conditions and properties of WO 3 films used as electrochromic layer in a monolithic device on a plastic substrate. The deposition technique employed was roll-to-roll pulsed dc magnetron sputtering. The oxide was deposited at room temperature in an argon and oxygen plasma on a transparent conducting ITO layer previously coated on a PET film. The influence of deposition parameters such as pulse mode, total pressure and oxygen partial pressure has been investigated, in order to obtain the best compromise between a high deposition rate and adequate electro-optical properties. As expected, the deposition rate increases with decreasing total pressure and oxygen partial pressure. To control the coloring/bleaching behavior, lithium ions from an aprotic electrolyte have been intercalated in films. Films with thickness around 400 nm exhibit a contrast ratio of 9:1. The optical efficiency increases slightly with increasing total pressure and lies between 30–40 cm 2 C −1 . Further, the coloring and bleaching time decreases with increasing total pressure, coloring being faster than bleaching. This is consistent with UV–Vis ellipsometric measurements which reveal that the refractive index decreases with increasing total pressure. TEM investigations also confirm that films deposited at low total pressure exhibit a dense structure whereas those deposited at high-pressure exhibit a columnar structure.

The Li+/Co3+-codoped LiMn2O4 spinel was prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol–gel method, in order to investigate the changes of the electrochemical properties of the spinel LiMn2O4 on the amount of Li+/Co3+ ions. The FT-infrared spectra, chemical analysis, and Rietveld refinements of their XRD data revealed that the manganese ions in the 16d sites were replaced by both lithium and cobalt ions. Thus, the composition of obtained powders could be expressed as the new spinel formula (Li)[Mn2−xLix/4Co3x/4]O4, that is, (Li)[Mn3+1−3x/2Mn4+1+x/2Lix/4Co3+3x/4]O4. The inclusion of lithium and cobalt ions in 16d sites enhanced the electrochemical cyclability of LiMn2O4 at the expense of a reduction in the initial charge capacity. The improvement in cycling performance was mainly attributed to the suppression of Jahn–Teller distortion as shown in (Li)[Mn2−xLix]O4 and (Li)[Mn2−xCox]O4.

We have developed a novel nanocomposite material, PEDOT/V2O5 by inserting poly(3,4-ethylene dioxythiophene) PEDOT in V2O5 layers using oxidative polymerization/intercalation in air. A systematic study of the synthesis of the nanocomposites by direct in situ reaction of 3,4-ethylene dioxythiophene (EDOT) with V2O5 fine powder shows that upon intercalation, the interlayer spacing of V2O5 expands in two stages, i.e., first from 4.32 to 13.84 A and further to 19.04 A. The interlayer separation is consistent with the existence of two phases in the PEDOT/V2O5 system corresponding to the intercalation of one and two monolayers of PEDOT, respectively, in the V2O5 framework. The unique properties of the organo–inorganic composites are investigated by electronic conductivity measurements, X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and SEM. The application potential of these composites as cathode materials in rechargeable lithium batteries is also demonstrated by the electrochemical intercalation of lithium into the PEDOT/V2O5 nanocomposites, where an enhancement in the discharge capacity (240 mA h g−1) is observed compared to that (140 mA h g−1) observed for V2O5.

The effect of nickel substitution on the chemical bonding nature of spinel lithium manganate has been investigated by performing comparative X-ray absorption spectroscopic analyses for Ni- and Cr-substituted LiMn2-xMx O4 (M = Ni and Cr) compounds. The Mn K-edge X-ray absorption spectroscopic results presented here clarify that the replacement of Mn with Ni or Cr gives rise not only to the increase of the Mn oxidation state but also to the suppression of the tetragonal distortion in cubic spinel lattice. From the extended X-ray absorption fine structure analyses at the Ni and Cr K-edges, it has been confirmed that the substitution of nickel ion induces lower structural stability of the spinel lattice compared to that of chromium ion. Especially for the lithiated spinel phase, a remarkable tetragonal distortion is observed for the Ni-substituted case in contrast to the Cr-substituted one. On the basis of the present experimental findings, it is concluded that the substitution of Mn with Ni is less effective...

Hydrolysis and condensation of (CH3COCHCOCH3)2SnF(Otert-Am) and (CF3COCHCOCH3)2Sn(Otert-Am)2 gave soluble stannic oxo-oligomers or -polymers including fluorine and β-diketonate groups. Under thermal treatment in air at 550 °C, they yielded nanocrystalline fluorine-doped tin dioxide powders. The amount of remaining ligands in the xerosols depends on the hydrolysis ratio and on the nature of the solvent used, dimethylformamide (DMF) favoring ligand removal. The thermolytic reactions have been investigated by thermogravimetry coupled to mass spectrometry: (1) the β-diketonate ligands pyrolyze in two stages, at 200 and 320 °C, involving two different processes; (2) elimination of polar solvents of high boiling point, such as DMF, occurs up to 300 °C; (3) fluorine is lost as fluorhydric acid from 230 °C. The best strategy to prepare F-doped SnO2 materials by the sol−gel route is thus to start from precursors including Sn−F bonds and to use a polar aprotic solvent of low boiling point such as acetonitrile. It l...

Electrochromic tungsten oxide film was fabricated by a new soft chemistry route, in which the transparent conducting glass substrate was successively dip-coated with poly(acrylic acid) (PAA) and ammonium tungstate solutions. The as-coated composite layer of PAA/(NH4)2WO4·nH2O was dried at a low temperature (100 °C), and the ammonium tungstate component was polycondensed by acid treatment in 1 N HCl to form an electrochromic PAA/WO3 film. Transmission electron microscopy showed that the PAA/WO3 film contains regularly dispersed WO3 grains with an average size of ∼5 nm. According to the Auger depth profile analysis, the relative content of W, O, and C was quite homogeneous along the height of film. Depending on the concentration of PAA coating solution (1.0−3.0 wt %), the thickness and tungsten oxide content of the film were found to vary; therefore, the electrode property of the PAA/WO3 layer could easily be controlled. By using a 2.5 wt % PAA solution, an optimum electrochromic function was achieved with ...

Chromium-substituted LiMn1-xCrxO2 (0 ≤ x ≤ 0.15) oxides have been prepared by the ion-exchange reaction between α-NaMn1-xCrxO2 and LiBr. From the X-ray diffraction and infrared spectroscopic analyses, all of the present layered compounds are found to be crystallized with monoclinic structure. Additionally, the nitrogen adsorption−desorption isotherm measurements indicate a decrease in crystallite size induced by the replacement of Mn with Cr. According to the electrochemical measurements, the Cr-substituted compounds exhibit better electrochemical performance than the pristine LiMnO2. The effects of chromium substitution on the chemical bonding nature of LiMn1-xCrxO2 have been investigated by performing X-ray absorption spectroscopic (XAS) analyses. The Cr K-edge XAS results presented here clarify that the trivalent chromium ions are stabilized in the octahedral site of the (Mn,Cr)O2 layer before and after the electrochemical charge−discharge process. From the extended X-ray absorption fine structure anal...

Mn K-edge X-ray absorption spectroscopic (XAS) analyses have been performed to probe the evolution of electronic and crystal structures of layered LiMnO2 upon chemical and electrochemical delithiation/relithiation. According to the X-ray absorption near-edge structure studies, it becomes clear that the trivalent manganese ion in LiMnO2 is significantly oxidized by acid treatment and is not fully recovered by subsequent lithiation reaction with n-BuLi. The extended X-ray absorption fine structure results presented here demonstrate that the local structure around manganese in LiMnO2 is changed from a layered α-NaFeO2-type structure to a spinel-like one upon chemical delithiation reaction. It is also found from the XAS analyses for the cycled LiMnO2 that the electrochemical charge−discharge process gives rise not only to the partial oxidation of manganese ion but also to the migration of Mn into the interlayer lithium site, resulting in the coexistence of the layered structure and the spinel one. Such result...

The partial substitution of manganese by lithium and cobalt ions in 16d octahedral sites enhances the electrochemical cyclability of LiMn2O4upon cycling. The improvement in cycling performance is mainly attributed to the suppression of the Jahn–Teller distortion in the spinel structure. The as-doped spinel Mn oxide has been successfully used as cathode material in flat and flexible lithium battery.

Dialkoxydi(beta-diketonate)tin(IV) compounds react either with difluorodi(beta-diketonate)tin(IV) or with butanoyl fluoride to yield novel tin complexes Sn(OR(1))F(R(2)COCHCOR(2))(2) 1 (R(1) = tert-amyl, isopropyl, ethyl; R(2) = methyl, tert-butyl). Multinuclear (1)H, (13)C, (19)F, and (119)Sn NMR spectroscopic characterization showed that complexes 1 are octahedral in solution with a cis configuration for the fluorine and the alkoxide group. Kinetics of configurational rearrangements were studied by variable-temperature (13)C NMR spectroscopy. The hydrolytic behavior of 1 was determined for different hydrolysis ratios h = [H(2)O]/[1]. For R(1) = tert-amyl, a dimeric fluorinated species was mainly obtained for h = 0.5, and addition of 2 mol equiv of water led to a fluorinated stannic oxopolymer soluble in CH(3)CN. In the latter case, the powder obtained after solvent elimination and treatment in air at 550 degrees C consisted of crystalline SnO(2) cassiterite particles containing the required amount (3 mol %) of doping fluorine and exhibiting electronic conductivity comparable to that of Sn-doped In(2)O(3). Complexes 1 are the first precursors of F-doped SnO(2) materials prepared by the sol-gel route.

Systematic Mn 2p XPS and Mn K-edge XAS analyses together with the electrochemical measurement have been carried out for the spinel LiMn2O4 prepared at various sintering temperatures in order to elucidate an origin of the dependence of electrochemical properties on synthetic conditions. From the comparative experiments, it becomes clear that a lowering of synthetic temperature gives rise to an increase of structural disorder and of the average oxidation state of manganese, which is more prominent on the surface than in the bulk. Such results suggest that the modification of surface property induced by a decrease of particle size is closely related to the electrochemical performance. The nanocrystalline LiMn2O4 prepared at 250 °C shows excellent cyclability at the 3 V region compared to that of microcrystalline LiMn2O4 prepared at 700 °C. For the purpose of examining the evolution of the chemical bonding nature of inserted lithium, 7Li MAS NMR studies have been performed for both the spinel compounds before...

A micro-Raman spectroscopic study has been carried out to investigate the electrochromic process in a porous and nanocrystalline tungsten oxide film. The film was prepared by dipping the tin-doped indium oxide glass into an aqueous mixture solution of PAA (polyacrylic acid) and WO 3 –NH 4 OH. After heating at low temperature, around 100°C, the film was treated in 1 N HCl in order to achieve polycondensation, where the ammonium ion was replaced with a proton. In the micro-Raman spectra for the bleached and colored PAA–WO 3 films, it was evident that the coloration accompanies a peak reduction at ∼960 cm −1 and a peak enhancement at ∼810 cm −1 . Based upon the present Raman observation, we can confirm that the electrochromism of the nanocrystalline tungsten oxide is dominated by the grafting process, i.e., the surface modification of –W VI =O bonds into –W V =O (1− δ )+ — M δ + ( M =H, Li) ones.

This communication describes the synthesis of: (i) non toxic and low cost nanocrystalline electrode materials which can be advantageously prepared at low temperature; (ii) highly conductive electrolyte membranes formed by the nano-encapsulation within a poly (acrylonitrile)-based polymer matrix of a solution of LiPF6in organic solvants. The performances of rechargeable PLR (Plastic Lithium Rechargeable) batteries using the above mentioned components are presented.

Various LiMn2O4electrode materials, having different crystallite sizes ranging from ∼50Å to ∼500Å, have been investigated either in 3V or in 4V Li batteries. In agreement with our ≪electrochemical model≫, we have shown that nanocrystalline samples have much higher capacity, and cyclability than their microcrystalline homologue in the 3 V domain uniquely. A reverse trend is observed in the 4 V range, still in agreement with the model.

A new and simple method for the preparation of electrochromic tungsten oxide film is presented. This novel approach can be realized by introducing a nanoporous textured polyacrylic acid (PAA) layer between tungsten oxide layer and indium tin oxide (ITO) one by dip-coating process. Homogeneous film with a thickness of about 0.8 μm is made by single dipping a PAA-coated ITO glass in the WO3-NH4OH solution and shows an X-ray amorphous structure. During the cathodic and anodic processes by chronopotentiometry, the present films exhibit highly reversible electrochemical insertion of lithium ions; the corresponding inserted charge of 12.5 mC/cm2gives rise to a marked blue color yielding the change in optical density (AOD) of 0.65 at 550 nm and a coloration efficiency(η)of 51.8 cm2/C.

The thermoelectric power and Hall effect of Sn-or Ge-doped In2O3ceramics are investigated based on a comparative study. The metal-type conductivity in both the samples occurs when the carrier concentration exceeds ~1019cm-3. The carrier mobility is found to be higher for Ge-doped samples. The relation between the <> of the dopant element and its scattering cross section is also presented.

International audience; CdS thin films have been deposited onto FTO/glass substrates by two different techniques, electrochemical deposition (ECD) and chemical bath deposition (CBD). Feasibility of using these two film types in photoelectrochemical processes has been critically investigated here. The films were comparatively characterized by a number of techniques (solid state absorption spectra, solid state photoluminescence spectra, XRD and SEM). PEC characteristics of the electrodes, including current density-voltage (J-V) plots, conversion efficiency (η), stability and fill-factor (FF) were then studied. The results show that both systems involved nano-sized CdS particles living in coagulates. The ECD was thinner and more uniform than the CBD system. The CBD films were more effective in PEC processes than the ECD counterparts. Effect of annealing on characteristics of both electrode systems has been investigated. Annealing enhanced both film characteristics, but the CBD was affected to a higher extent, and the annealed CBD film was more effective than the ECD counterpart.

International audience; A new method to prepare CdS film electrodes, based on electrochemical deposition (ECD), followed by chemical bath deposition (CBD), is described. The ECD/CBD-CdS film electrodes combine the advantages of both ECD-CdS film (good adherence to FTO/glass substrate) and CBD-CdS film (suitable film thickness) together. The new ECD/CBD electrode showed higher photo-electrochemical (PEC) efficiency and stability than either ECD- or CBD-CdS film electrodes, especially after annealing. Inter-particle connection and uniformity of the ECD/CBD-CdS film were further enhanced by annealing. Consequently, the electrode PEC conversion efficiency and stability were enhanced. The combined preparation technique, followed by annealing, is potentially useful for future manufacturing of CdS and other film electrode systems.

International audience; Thin films of WO3 were prepared by surfactant assisted spray pyrolysis on F-doped SnO2 (FTO) conductive glass by using hexadecyltrimethylammonium bromide (HTAB) and polyethylene glycol (PEG400):HTAB as growth controlling agents. The surface tension of the spraying solutions was experimentally evaluated and was correlated with the deposition processes (nucleation and growth) of very smooth and homogenous films. The effect of the surfactant, alone and associated with PEG, on the structure (XRD), morphology (AFM), surface composition (XPS), FTIR and hydrophilicity (contact angle) were investigated and their influence on the electrochromic activity was discussed. Using surfactants and PEG, the coloration efficiency, transmission modulation and cycling stability of the WO3 thin films can be enhanced.

We propose an unconventional method to obtain fine-grained SnO2and WO3powders. It uses as precursors, polymer complexes between polyethylene oxide (POE) and SnCl4or WCl6respectively. By pyrolysis of these complexes in the 350-550℃ temperature range, metal-oxide powders possessing small crystallite sizes are obtained. They are free from water and hydroxyl group contaminations, which is an added advantage where the application of these materials to Li-batteries is concerned. We have, indeed, demonstrated that these powders show good ability to insert reversibly lithium ions in the Li/ Li+/SnO2(WO3) cells.

International audience; Calcination of cyclopentadienyltitanium-based organic-inorganic hybrid materials at 450-500 °C led to the formation of anatase titanium dioxide as white powders consisting of a porous network of aggregated nanoparticles, the nanoporosity detected being related to the inter-particle space. Depending on the calcination temperatures, the surface area of the titanium dioxide particles varied from 65 to 158 m(2) g(-1).

Indium oxide co-doped with tin and zinc (ITZO) ceramics have been successfully prepared by direct sintering of the powders mixture at 1300 °C. This allowed us to easily fabricate large highly dense target suitable for sputtering transparent conducting oxide (TCO) films, without using any cold or hot pressing techniques. Hence, the optimized ITZO ceramic reaches a high relative bulk density (∼ 92% of In 2 O 3 theoretical density) and higher than the well-known indium oxide doped with tin (ITO) prepared under similar conditions. All X-ray diagrams obtained for ITZO ceramics confirms a bixbyte structure typical for In 2 O 3 only. This indicates a higher solubility limit of Sn and Zn when they are co-doped into In 2 O 3 forming a solid-solution. A very low value of electrical resistivity is obtained for [In 2 O 3 :Sn 0.10 ]:Zn 0.10 (1.7 × 10 −3 Ω cm, lower than ITO counterpart) which could be fabricated to high dense ceramic target suing pressure-less sintering.