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International audience; It is assumed that genetic diseases affecting the metabolism of cysteine and the kidney function lead to two different kinds of pathologies, namely cystinuria and cystinosis whereby generate L-cystine crystals. Recently, the presence of L-cysteine crystal has been underlined in the case of cystinosis. Interestingly, it can be strikingly seen that cystine ([-S-CH2-CH-(NH2)-COOH]2) consists of two cysteine (C3H7NO2S) molecules connected by a disulfide (S-S) bond. Therefore, the study of cystine and cysteine is important for providing a better understanding of cystinuria and cystinosis. In this paper, we elucidate the discrepancy between L-cystine and L-cysteine by investigating the theoretical and experimental infrared spectra (IR), X-ray diffraction (XRD) as well as Raman spectra aiming to obtain a better characterization of abnormal deposits related to these two genetic pathologies.

The reactivity of electrochemically-active molecular architectures immobilized on electrode surfaces was investigated by electrochemical-TERS, at relatively high potential sweep rate and on broad potential ranges. A complex electrochemical mechanism, involving reaction intermediates and multiple reaction paths, could be resolved on electroactive architectures based on nitrobenzene derivatives. Further EC-TERS investigations on these derivatives assembled as mono- or multilayers on the electrode surface emphasized the influence of the structure of the molecular assemblies on their reactivity. Under specific conditions, azo bonds formation between nitrobenzene derivatives observed by TERS can result from the electrochemical polarization/reaction, and not from photochemical processes.

International audience; Electrochemical Impedance Spectroscopy (EIS) is a powerful tool to assess and understand the degradation of Li-ion battery (LIB) performances during operation (i.e. upon charge and discharge cycles). The full interpretation of EIS diagrams associated to complex electrode/electrolyte interfaces is however tedious. An analytical solution for the electrochemical impedance of a porous electrode composed of spherical intercalation particles in contact with concentrated electrolyte is presented herein. The proposed model which is based on the concentrated solution theory previously developed but which also accounts for kinetic limitations, and both solution-phase and solid-phase diffusion limitations, can predict the EIS response of a porous electrode at any state of charge using a limited set of parameters. Moreover, the developed model can predict the optimal porosity of the electrode to be targeted during the manufacturing process for the best cycling performances depending on the composition of the electrode (volume fractions of active material, binder and conductive agent).

International audience; The examination of the urinary sediment of a 64-year-old woman showed the presence of three different types of crystals, all with unusual morphology, which could not be identified with bright field microscopy, polarized light, and the knowledge of urine pH (7.5). The use of microscopic infrared spectroscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy led to the identification of the three types of crystals as calcite, vaterite and aragonite, which are all variants of calcium carbonate crystals. This paper confirms the complex morphology and nature that urinary crystals may at times have and the utility of advanced infrared spectroscopy techniques for their identification.

International audience; The fundamental understanding of the electrode/electrolyte interfacial processes in lithium-sodium ion batteries (LIBs) and of their dynamics upon cycling is of prime importance for the development of new generation electrode materials. Operando analyses using the utmost sensitive techniques are required to produce an accurate depiction of the underlying processes at the origin of the battery performance decay. If enhanced Raman Spectroscopy through the use of signal nano-amplifiers (SHINs) shows the required sensitivity, its implementation in operando conditions and particularly on functional materials in contact with organic electrolytes remains challenging. This work through extensive optimization of SHINERS conditions for operando diagnosis of LIB materials, including the design of near-infrared active amplifiers and the control of the photon dose, demonstrates the possibility to track the dynamics of composition of the electrode/electrolyte interface upon cycling of LIB coin-cells and uncovers the origin of the irreversible capacity of tin electrodes proposed as alternative to graphite anodes.

International audience; Carcinogenic risk of tattoo inks remains unclear, and their composition is poorly regulated. Various types of carcinogenic compounds can be found in tattoo inks, including primary aromatic amines (PAA), cleavage products of organic azo colourants, found in coloured inks.1 Many cases of skin cancers occurring within tattoos have been reported, including cases of keratoacanthoma (KA) developed on red ink.2 Pathogenesis of KA on tattoos remains unclear and is probably due to multiple factors: trauma induced by the needle during the tattoo itself, inflammatory reactions, ultraviolet radiation, direct carcinogenicity of the tattoo inks and individual background

International audience; Nephrolithiasis is a major health concern in western countries. Herein, we propose a microfluidic based approach to mimic the physical and physicochemical conditions encountered in the collecting duct in a nephron where calcium oxalate (CaOx) precipitation occurs. Our objective is to understand the parameters involved in the formation of such crystals. The microfluidic platform is reversible, allowing interfacial characterizations using scanning electron microscopy imaging and Raman spectroscopy. CaOx crystalline phases and morphologies were studied with respect to hydrodynamics and physicochemical conditions within the channel and at the outlet. While calcium oxalate monohydrate (COM) crystals were dominant within the channel, at the outlet, the crystals were calcium oxalate dihydrate (COD) crystals, which agrees with medical observations. Decreasing the flow rate lowered down the induction time for CaOx formation and enhanced the occurrence of COD crystals. The kinetics of COM crystals growth studied in situ showed two regimes, an initial surface-limited reaction, followed by a transport-limited growth with a dependency of the kinetics on the position of the crystal in the channel. Numerical modeling of CaOx formation in a microchannel using an in-house model considering the chemical reactions involved allowed to confirm the experimental observations on the location of precipitate formation but also to quantitatively match the scaling law related to the early growth of precipitate particles. Finally, the effect of polyphenols naturally found in green tea (GT) on modulating CaOx crystallization was studied in the microfluidic device in different scenarios where GT was initially mixed in solution with the Ca and/or the Ox precursors. The formation of COD crystals rather than COM ones was always predominant; however, depending on the conditions, CaOx crystals of different morphologies could be observed, including COD crystals with an elongated (100) crystalline face and COM crystals with a round-shaped morphology with a concave crystalline face.

International audience; A rotaxane scaffold incorporating two dithiolaneanchoring units for the modification of gold surfaces hasbeen functionalized with multiple copies of a redox unit,namely ferrocene. Surface modification has been first assessedat the single molecule level by atomic force microscopy(AFM) and scanning tunneling microscopy (STM) imaging,while tip enhanced Raman spectroscopy (TERS) providedthe local vibrational signature of the ferrocenyl subunitsof the rotaxanes grafted onto the gold surface. Finally, oxidationof the redox moieties within a rotaxane scaffold graftedonto gold microelectrodes has been investigated by ultrafastcyclic voltammetry. Intramolecular electron hopping isindeed extremely fast in this system. Moreover, the kineticsof charge injection depends on the molecular coverage dueto the influence of intermolecular contacts on molecular motions.

International audience; To accompany the search for optimal materials in electrochemical supercapacitors, appropriate characterization tools to assess key parameters of newly developed electrodes are required. Here we demonstrate the capabilities of ac-mode electrogravimetry to study in details the capacitive charge storage mechanisms in electrochemically reduced graphene oxide (ERGO) thin film electrodes. The coupling of electrochemical impedance spectroscopy (EIS) with fast quartz crystal microbalance (QCM) complements classical electrochemical quartz crystal microbalance (EQCM) by capturing here the dynamics of the electroadsorption process, identifying charged moieties and detecting solvation effects. We evidenced the coelectroadsorption of two types of cationic species (fully and partially hydrated cations) in the potential range studied and the indirect intervention of free solvent molecules. Further kinetic information on electroadsorption is also obtained which leads to a full deconvolution of the global EQCM response at both gravimetric and temporal level. Through a fine analysis of the interactions of different cations of period one elements, Li+, Na+, and K+, with ERGO, we evidenced the critical role of solvation processes on the kinetics of electroadsorption, and provided an experimental proof to the phenomena that smaller ions are more tightly bound to their water molecules such that an inverse relationship exists between the dehydration energy and the ion size. Such gravimetric and dynamic subtleties are unreachable with classical tools and with EQCM method alone which permits us to suggest the ac-mode electrogravimetry as a baseline diagnostic tool to explore charge transfer mechanisms at the nanoscale.

Introduction Les tatouages sont largement repandus dans la population (17 % des Francais de > 15 ans). Les encres colorees injectees dans le derme sont destinees a demeurer a vie, entrainant une exposition a long terme a divers produits. Elles contiennent potentiellement des composes organiques carcinogenes, tels que des sels metalliques, des hydrocarbures et des amines aromatiques (AA). L’objectif de notre etude etait de detecter et de caracteriser les composes organiques presents au sein de keratoacanthomes (KA) developpes sur tatouages. Materiel et methodes Nous avons realise une etude retrospective sur 3 cas de keratoacanthomes sur tatouages diagnostiques en 2017 a l’hopital Bichat (Paris) ou a l’hopital universitaire d’Helsinki. Les donnees demographiques, la presentation clinique et la couleur de l’encre etaient collectees. Les biopsies cutanees etaient analysees en microscopie optique (MO), par spectroscopie Raman puis par fluorescence X classique et induite par rayonnement synchrotron. Resultats Les 3 patients, 1 femme (72 ans) et 2 hommes (53 et 55 ans) avaient developpe des KA uniques ou multiples, 1 a 4 semaines apres le tatouage. Les zones tatouees reactives etaient photo-exposees. Les encres utilisees provenaient de deux fournisseurs differents et etaient exclusivement rouge pour deux cas et rose pour un cas. L’analyse en MO montrait dans les trois cas la presence de massif tumoraux refoulant en leur peripherie l’encre du tatouage. L’analyse par fluorescence X revelait la presence de sels metalliques pour deux patients : goethite (FeO) dans un cas et zincite (ZnO) dans un autre. L’analyse par spectroscopie Raman revelait la presence d’un meme pigment rouge dans les trois cas, le PR170. Dans le cas ou l’encre utilisee etait rose, le PR170 etait associe a la presence de dioxyde de titane (TiO2) sous sa forme rutile ( Fig. B ), classiquement utilise comme agent eclaircissant. Discussion La majorite des cas de KA rapportes surviennent sur encre rouge. Leur survenue est probablement multifactorielle, liee a la toxicite des encres et a la reaction inflammatoire induite par le tatouage. Nous rapportons la premiere caracterisation de la composition d’encre de tatouage dans trois cas de KA et identifions la presence d’un meme pigment rouge, le PR170, soulignant sa forte imputabilitie dans la tumorigenese. Conclusion Ce pigment comporte une AA, compose dont la carcinogenicite est connue dans le cancer de la vessie. Cependant, contrairement a d’autres pigments, le PR170 ne fait pas partie a ce jour de la liste des agents carcinogenes a eviter chez l’homme. D’autres etudes utilisant ces techniques sur un plus grand nombre de tumeurs sur tatouage sont necessaires, afin de proposer des mesures d’evictions des composes organiques imputables.

Herein, we report tip-enhanced Raman spectroscopy (TERS) hyperspectral imaging under electrochemical control of a non-Raman-resonant molecular compound. A new setup combining a Scanning Tunneling Microscope (STM) and an optical coupling with high signal excitation and collection efficiency enables fast chemical imaging of an opaque functionalized electrode surface upon polarization. Variations in the TERS signal intensity up to 1.8 were observed across the surface, and correlated with topographic heterogeneities. These fluctuations, attributed to enhancement of the local electromagnetic field below the TERS tip, were used to estimate the lateral resolution of the produced hyperspectral image, which was found greater than 8 nm. This work represents an important step towards the use of electrochemical TERS imaging as a unique tool to unravel electrochemical processes at the nanoscale. Keywords: Tip enhanced Raman spectroscopy, Scanning Tunneling Microscopy, Nanospectroscopy, Electrochemistry, Plasmonics

INTRODUCTION AND OBJECTIVES:Diagnostic of urolithiasis composition is the keystone for prophylactic treatment of stone disease. To date, the gold standard for stone composition analysis remains the...

International audience; The present study proposes an alternative eco-friendly method to prepare a thin composite coating based on graphene embedded in siloxane polymers which can be used as application for the corrosion protection of steel. The nanocomposite coatings were elaborated by a dielectric barrier discharge using a nebulized colloidal suspension of graphene nanosheets (GNs) dispersed in hexamethyldisiloxane (HMDSO) used as the precursor for the polymer matrix. After obtaining a stable colloidal solution, it was nebulized into the plasma reactor to form a plasma polymer (pp) coating from HMDSO (ppHMDSO) in which GNs were incorporated (GN@ppHMDSO) on the mild steel substrate. The chemical structure of the hybrid coatings was characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectrometry. Raman spectra of GNs and GN@ppHMDSO coatings suggest the existence of charge transfer between the GNs and the HMDSO matrix. Furthermore, scanning electron microscopy confirms the synthesis of micro/nanocomposite with a fairly homogeneous dispersion of the GNs in the polymer matrix. The corrosion resistance of the samples was evaluated by electrochemical impedance spectroscopy which showed that the hybrid coatings GN@ppHMDSO deposited by a one-step atmospheric pressure plasma process, presented excellent anticorrosion performance with 99.99% of protection efficiency.

International audience; Importance: Calcific uremic arteriolopathy (CUA), a rare, potentially fatal, disease with calcium deposits in skin, mostly affects patients with end-stage renal disease who are receiving dialysis. Chemical composition and structure of CUA calcifications have been poorly described.Objectives: To describe the localization and morphologic features and determine the precise chemical composition of CUA-related calcium deposits in skin, and identify any mortality-associated factors.Design, Setting, and Participants: A retrospective, multicenter cohort study was conducted at 7 French hospitals including consecutive adults diagnosed with CUA between January 1, 2006, and January 1, 2017, confirmed according to Hayashi clinical and histologic criteria. Patients with normal renal function were excluded. For comparison, 5 skin samples from patients with arteriolosclerosis and 5 others from the negative margins of skin-carcinoma resection specimens were also analyzed.Main Outcomes and Measures: Localization and morphologic features of the CUA-related cutaneous calcium deposits were assessed with optical microscopy and field-emission-scanning electron microscopy, and the chemical compositions of those deposits were evaluated with μ Fourier transform infrared spectroscopy, Raman spectroscopy, and energy dispersive radiographs.Results: Thirty-six patients (median [range] age, 64 [33-89] years; 26 [72%] female) were included, and 29 cutaneous biopsies were analyzed. Calcific uremic arteriolopathy and arteriolosclerosis skin calcifications were composed of pure calcium-phosphate apatite. Calcific uremic arteriolopathy vascular calcifications were always circumferential, found in small to medium-sized vessels, with interstitial deposits in 22 (76%) of the samples. A thrombosis, most often in noncalcified capillary lumens in the superficial dermis, was seen in 5 samples from patients with CUA. Except for calcium deposits, the vessel structure of patients with CUA appeared normal, unlike thickened arteriolosclerotic vessel walls. Twelve (33%) patients died of CUA.Conclusions and Relevance: Calcific uremic arteriolopathy-related skin calcifications were exclusively composed of pure calcium-phosphate apatite, localized circumferentially in small to medium-sized vessels and often associated with interstitial deposits, suggesting its pathogenesis differs from that of arteriolosclerosis. Although the chemical compositions of CUA and arteriolosclerosis calcifications were similar, the vessels' appearances and deposit localizations differed, suggesting different pathogenetic mechanisms.

International audience; Gold electrodes were modified by silver and gold nanocrystals (NCs) that self-organize onto the surface. Their optical properties were explored by measuring electroreflectance spectra as a function of electrode potential. Below their oxidation potential, no shift of the reflectance maximum was observed for Ag NCs. This can be explained by a low inter-facial capacitance resulting from the impossibility for the electrolyte to penetrate into the hydrophobic layer created by the NCs dodecanethiol ligands. Conversely, a non-monotonous evolution was observed with the electrode potential for oleylamine capped Au NCs. This behavior is suggesting a less dense hydrophobic layer, allowing significant electrolyte penetration. Next, electroactive compounds were adsorbed on the the Au NCs assemblies and characterized by Raman spectroelectrochemistry. In the first system displaying a single electron transfer with no coupled chemical reaction, only the spectrum intensity changed, because oxidation generated a Raman resonant radical cation. The second study considered 4-nitrothiophenol, for which up to 6 electrons and 6 protons may be transferred. In this case, the nitro band disappeared upon reduction, and the spectrum displayed typical features of the formed 4-aminothiophenol.

In this work, cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques have been used to study the lithiation/delithiation of graphite using powder microelectrode in a 1.2 M LiPF6 in EC:EMC electrolyte. The advantage of using the powder microelectrode is the possibility to easily study graphite without any additive and determine electrochemical characteristics of Li-insertion. The use of cyclic voltammetry at very low scan rates allows to estimate the diffusion coefficient of lithium inside graphite. The exchange current density of graphite for several state of charge (SoC) has also been determined by EIS measurements. Moreover, the powder microelectrode is a useful tool to study the formation of the solid electrolyte interphase (SEI) on graphite either by cyclic voltammetry or EIS. Keywords: Graphite, Battery material, Cavity microelectrode, Cyclic voltammetry, Li-ion battery

Introduction L’AFF est une alopecie cicatricielle lymphocytaire consideree comme un sous-type clinique du LPP. Son incidence augmente de maniere significative dans les pays developpes depuis sa description en 1994. Les etudes cas-temoins trouvent de maniere repetee chez les patients une surrepresentation des sujets utilisant de maniere reguliere des ecrans solaires ou des cosmetiques sans rincage. Le dioxyde de titane, repandu dans les produits d’hygiene et cosmetiques d’usage quotidien pour ses proprietes physiques (pigment blanc, filtre UV), pourrait etre un trigger de l’inflammation dans l’AFF (pro-inflammatoire in vivo par voie orale). Nous avons realise un screening du titane (Ti) au sein des follicules pileux de patients atteints d’AFF, de LPP, et de temoins sains, par imagerie de nano-fluorescence X sur NANOSCOPIUM, la ligne d’imagerie X dur multimodal du synchrotron SOLEIL. Materiel et methodes Epilats de 5 patients AFF, 5 patients LPP en zone atteinte frontale avec controle interne en zone occipitale indemne de lesions, et 3 temoins sains en zone frontale et occipitale. Cheveu natif manipule par pince a mors en matiere plastique. Montage sur anneau en matiere plastique, maintien par vernis incolore. Deux acquisitions par cheveu, centrees sur le bulbe et la tige. Resolution minimale de 0,2um par pixel. Analyse des spectres a l’aide du logiciel PyMCA. Comparaison qualitative des images par 2 operateurs independants. Reperage du cheveu par le signal du Ca en vert, visualisation du Ti detecte en rouge. Comparaison semi-quantitative des signaux sur ImageJ (en cours). Determination de la forme cristalline par spectroscopie Raman. Resultats Presence d’amas de Ti sur l’ensemble des echantillons : a l’etat de traces chez les temoins, significativement plus important en nombre et taille des amas chez les sujets LPP et AFF. Gradient fronto-occipital decroissant chez les sujets de la presence de titane. Renforcement de la presence de Ti en regard du bulbe, focalement en regard du bulge (inconstant). Signature Raman de type TiO2-anatase (forme cristalline). Discussion Le Ti est detecte de maniere anormale au sein des follicules AFF et LPP. Sa presence a l’etat de traces chez les temoins temoigne d’une exposition ubiquitaire. L’existence d’un gradient fronto-occipital decroissant fait suspecter une exposition locale par les topiques appliques sur le front. Ces donnees permettent d’emettre l’hypothese du role du TiO2 comme trigger de l’inflammation dans l’AFF et du LPP chez des sujets predisposes. Elles mettent en lumiere l’importance de la voie folliculaire pour l’exposition aux substances pro inflammatoires ou aux perturbateurs endocriniens, permettant d’envisager d’autres hypotheses environnementales. Ces resultats sont a confirmer sur un effectif permettant d’atteindre une significativite statistique, et autoriseraient la mise en œuvre de mesures d’eviction.

International audience; Through the characterization of functional nanomaterials or of molecular architectures under operating conditions (in situ, operando), new insights in their working mechanism will be accessible. In this context, tip-enhanced Raman spectroscopy (TERS) which enables the extraction of precise chemical signatures at the nanoscale represents a great alternative to ultra-high vacuum analytical techniques. This review compiles the recent advances in in situ TERS characterizations and focuses on the strong potential of TERS to characterize the electrochemical processes taking place at the electrode/electrolyte interface.

International audience; Herein we present new substrates for surface-enhanced Ramanspectroscopy (SERS). The synthesis of colloidal nanoparticlesthrough an organometallic route allowed us to obtain gold,silver, or copper nanoparticles with well-controlled shapes andsizes (5–12 nm in diameter). The organization of these nanoparticlesinto large-scale 3D superlattices produces a very largenumber of “hot spots” at the origin of the signal enhancement.Each superlattice was studied individually to correlate its opticaland SERS properties to the thickness, the nanoparticlesizes, and the interparticle distance. This experimental and theoreticalstudy provides insights for the optimization andtuning of the SERS activity. Indeed, significant SERS amplificationcould be observed regardless of the nature of the metal.In addition, the SERS signal was homogeneous at the surfaceof the superlattices, which opens the route for a new approachin analytical SERS detection.

International audience; In the quest for analytical tools which enable the characterization of materials at the nanoscale and under the condition of their operation (in situ, operando), the emerging tip-enhanced Raman spectroscopy (TERS) now enters the spotlight. We demonstrate in this work that a TERS tip can be functionalized and partially insulated to be used as a microelectrode enabling electrochemical substrate enhanced Raman sectroscopy (EC-SERS) at a single hotspot. This “SERS at a tip” experiment enables one to capture the electrochemical transformation of a molecular layer self-assembled on a tapered gold microelectrode. The proposed setup and protocol open new perspectives in the characterization and development of complex redox architectures for molecular devices.

The experimental work involving the development and application of in situ liquid stages in the TEM was supported by the Chemical Imaging Initiative; under the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated by Battelle for the U.S. Department of Energy (DOE) under Contract DE-AC05-76RL01830. We thank Yongsoon Shin and Prabhakaran Munusamy for assistance with precursor solutions, and Ajay Karakoti for helpful discussions on solution synthesis chemistry for cerium oxide nanoparticles. A portion of the research was performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The SuperSTEM Laboratory is the U.K National Facility for Aberration-Corrected STEM, supported by the Engineering and Physical Sciences Research Council (PA).; International audience; Here we report radiation-induced formation of Ce(III) nanostructures in an in situ liquid cell for the transmission electron microscope (TEM). Small (

A novel experimental technique was developed to investigate HF formation in organic carbonate based electrolytes containing LiPF6. Using spectroscopic ellipsometry, aging and thermal decomposition of the electrolyte were monitored in a standard glass cell and in a polypropylene vessel. The amount of HF generated was determined by following the etching rate of a thin silicon dioxide layer on a silicon wafer in contact with the electrolyte. The material of cell construction clearly influenced the etching rate of the SiO2 sensor and affected the rate of degradation.

International audience; To use water as the source of electrons for proton or CO2 reduction within electrocatalytic devices, catalysts are required for facilitating the proton-coupled multi-electron oxygen evolution reaction (OER, 2 H2O→O2+4 H++4 e−). These catalysts, ideally based on cheap and earth abundant metals, have to display high activity at low overpotential and good stability and selectivity. While numerous examples of Co, Mn, and Ni catalysts were recently reported for water oxidation, only few examples were reported using copper, despite promising efficiencies. A rationally designed nanostructured copper/copper oxide electrocatalyst for OER is presented. This material derives from conductive copper foam passivated by a copper oxide layer and further nanostructured by electrodeposition of CuO nanoparticles. The generated electrodes are highly efficient for catalyzing selective water oxidation to dioxygen with an overpotential of 290 mV at 10 mA cm−2 in 1 m NaOH solution.

International audience; An ecofriendly chemical reduction of graphene oxide (GO) in water is reported. The reducing agent is an electrochemically reduced Keggin-type polyoxometalate (SiW12O405−). Moreover, this process leads to the fabrication of SiW12@rGO nanocomposite. This nanohybrid exhibits an electrochemical response which combines high faradic and capacitive currents due to high coverage of polyoxometalates on the rGO sheets. Therefore this material has strong potentiality for energy storage.

International audience; Implementation of Tip Enhanced Raman Spectroscopy in liquid is still a challenge. We demonstrate herein its feasibility in an upright illumination/collection configuration. Through a thin layer of organic solvent covering the sample, laser focussing on the tip is possible, enabling TERS imaging in liquid.

International audience; The effect of mixing calcium and oxalate precursors by diffusion at miscible liquid interfaces on calcium oxalate crystalline phases, and in physiological conditions (concentrations and flow rates), is studied using a microfluidic channel. This channel has similar dimensions as the collection duct in human kidneys and serves as a biomimetic model in order to understand the formation of pathological microcalcifications.

The mechanism of HF formation in LiPF6-based organic carbonate electrolytes S.F. Lux 1,2 , I.T. Lucas 2 , E. Pollak 2 , S. Passerini 1 , M. Winter 1 and R. Kostecki 2 University of Munster, Institute of Physical Chemistry, MEET laboratories, Corrensstr. 46, 48149 Munster, Germany Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA ABSTRACT Spectroscopic ellipsometry was used to study the time-dependent formation of HF upon the thermal degradation of LiPF 6 at 50°C in a lithium ion battery electrolyte containing ethylene carbonate and diethyl carbonate. The generated HF was monitored by following the etching rate of a 300 nm thick SiO 2 layer, grown on both sides of a silicon wafer substrate, as a function of the immersion time in the electrolyte at 50°C. It was found that the formation of HF starts after 70 hours of exposure time and occurs following several different phases. The amount of generated HF was calculated using an empirical formula correlating the etching rate to the temperature. Combining the results of the HF formation with literature data, a simplified mechanism for the formation of the HF involving LiPF 6 degradation, and a simplified catalytical reaction pathway of the formed HF and silicon dioxide is proposed to describe the kinetics of HF formation. KEYWORDS Lithium ion batteries, hydrofluoric acid, spectroscopic ellipsometry, LiPF 6 degradation Corresponding authors: Corresponding author: Simon Franz Lux

In situ atomic force microscopy (AFM) and spectroscopic ellipsometry were used to study the mechanism of organic carbonate electrolytes decomposition and surface layer (re)formation at β-Sn(001) and (100) single crystal electrodes. Interfacial phenomena were investigated at potentials above 0.8 V vs. Li/Li+, i.e. where no Sn–Li alloying takes place. The Sn(001) electrode tends to form a protective surface layer of electrolyte reduction products during the first cathodic CV scan, which effectively inhibits further reduction of the electrolyte upon cycling. In contrast, the Sn(100) electrode produces a thick, inhomogeneous and unstable surface layer. The observed significant difference of Sn reactivity toward the electrolyte as a function of Sn surface crystalline orientation suggests radically different reaction paths, reduction products, and properties of the surface film. Keywords: Li-ion battery, Sn anode, SEI layer, Single crystal electrode, Organic electrolyte

International audience; In the framework of urologic oncology, mini-invasive procedures have increased in the last few decades particularly for urothelial carcinoma. One of the essential elements in the management of this disease is still the diagnosis, which strongly influences the choice of treatment. The histopathologic evaluation of the tumor grade is a keystone of diagnosis, and tumor characterization is not possible with just a macroscopic evaluation. Even today intraoperative evaluation remains difficult despite the emergence of new technologies which use exogenous fluorophore. This study assessed an optical multimodal technique based on endogenous fluorescence, combining qualitative and quantitative analysis, for the diagnostic of urothelial carcinoma. It was found that the combination of two photon fluorescence, second harmonic generation microscopy, spectral analysis and fluorescence lifetime imaging were all able to discriminate tumor from healthy tissue, and to determine the grade of tumors. Spectral analysis of fluorescence intensity and the redox ratio used as quantitative evaluations showed statistical differences between low grade and high grade tumors. These results showed that multimodal optical analysis is a promising technology for the development of an optical fiber setup designed for an intraoperative diagnosis of urothelial carcinoma in the area of endourology.

We employed the Devanathan–Stachurski experimental methodology for direct measurement of the rate of lithium transport in metals that can be used as negative electrodes in lithium–ion batteries. The measured Li transport rate in aluminum appears to be in relatively good agreement with previously reported results obtained using standard electrochemical techniques. However, Li transport rate measurements in aluminum membranes of different thicknesses reveal anomalies with regard to the standard diffusion controlled mass transfer model. We attribute this effect to a complex Li transport mechanism in Al membranes upon alloying. Keywords: Lithium transport, Aluminum, Li–ion anode, Li–ion battery

Early stages of the solid electrolyte interphase (SEI) formation at a tin foil electrode in an ethylene carbonate (EC) based electrolyte were investigated by in situ AFM and cyclic voltammetry (CV) at potentials >0.7 V, i.e., above the potential of Sn–Li alloying. We detected and observed initial steps of the surface film formation at ∼2.8 V vs. Li/Li+ followed by gradual film morphology changes at potentials 0.7

A coarse-grain description of nanocolloidal suspensions in the presence of an added salt is presented here. It enables us to simulate trajectories of the nanoparticles from effective functions that depend on average densities of salt ions. In practice, the ion-averaged effective potential is used as input of a Brownian dynamics (BD) simulation. This potential may be derived by various methods, ranging from purely analytical to fully numerical ones. For the description of dynamical properties, this simulation also requires an effective diffusion coefficient that must be calculated or experimentally determined, and that accounts for the effects of microions on the mobility of the nanoparticles. The different versions of our coarse-graining procedure are applied to the case of a maghemite suspension, for which an explicit description of all ions would be very time-consuming.

International audience; This study demonstrates the unique capabilityof infrared near-field nanoscopy combined with Fouriertransform infrared spectroscopy to map phase distributionsin microcrystals of LixFePO4, a positive electrode material forLi-ion batteries. Ex situ nanoscale IR imaging provides directevidence for the coexistence of LiFePO4 and FePO4 phases inpartially delithiated single-crystal microparticles. A quantitativethree-dimensional tomographic reconstruction of the phasedistribution within a single microcrystal provides new insightsinto the phase transformation and/or relaxation mechanism,revealing a FePO4 shell surrounding a diamond-shaped LiFePO4 inner core, gradually shrinking in size and vanishing upondelithiation of the crystal. The observed phase propagation pattern supports recent functional models of LiFePO4 operationrelating electrochemical performance to material design. This work demonstrates the remarkable potential of near-field opticaltechniques for the characterization of electrochemical materials and interfaces.

Special issue in Honour of Pierre TURQ; International audience; We used several complementary experimental and theoretical tools to characterise the charge properties of well-definedmaghemite nanoparticles in solution as a function of the volume fraction. The radius of the nanoparticles is equal to 6 nm.The structural charge was measured from chemical titration and was found high enough to expect some counterions tobe electrostatically attracted to the surface, decreasing the apparent charge of the nanoparticle. Direct-current conductivitymeasurements were interpreted by an analytical transport theory to deduce the value of this apparent charge, denoted here by‘dynamic effective charge’. This dynamic effective charge is found to decrease strongly with the volume fraction. In contrast,the ‘static’ effective charge, defined thanks to the Bjerrum criterion and computed from Monte Carlo simulations turns outto be almost independent of the volume fraction. In the range of Debye screening length and volume fraction investigatedhere, double layers around nanoparticles actually interact with each other. This strong interaction between nanocolloidalmaghemite particles is probably responsible for the experimental dependence of the electrokinetic properties with the volumefraction.

The interaction of Li(+) with single and few layer graphene is reported. In situ Raman spectra were collected during the electrochemical lithiation of the single- and few-layer graphene. While the interaction of lithium with few layer graphene seems to resemble that of graphite, single layer graphene behaves very differently. The amount of lithium absorbed on single layer graphene seems to be greatly reduced due to repulsion forces between Li(+) at both sides of the graphene layer.

International audience; HF concentration and generation rate in organic LiPF6-based carbonate electrolytes at 60◦C was studied. Various compositions of linear and cyclic carbonates were used to determine the electrolyte degradation mechanism. Diethyl carbonate (DEC) has been identified as a promoter of HF formation, yielding 1 mmol/L of HF in 1 mol/L LiPF6 DEC after 200 hours at 60◦C. Prolonged aging of 1 mol/L LiPF6, EC:DEC electrolyte at room temperature results in a significantly lower HF formation rate with time. Spiking the aged electrolyte with 500 ppm of water restores the HF formation rate to a level typical for a freshly prepared electrolyte.

The objective of this effort was to correlate the local surface ionic conductance of a Nafion 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using direct-current voltammetry and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationship between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion membrane was examined.

International audience; We are interested here in the reactivity of magnetic nanoparticles at the electrode-electrolyte interface with the aim of the electrochemical synthesis of magnetic and conductive liquids (electronic conduction). The reactivity of charged colloidal particles occurs through a two steps process, the first being the approach toward the electrode with a possible adsorption phenomenon and the second step, the electron transfer. In this first paper we focus on the approach and the deposition of well-defined gamma-Fe2O3 nanoparticles onto conductive substrates like mercury and gold under different conditions in order to vary the interactions particle/substrate especially the electrostatic interactions. The approach of the particles near the electrodes is estimated from the electrochemical currents related to the transformation of the particles. This electrochemical method is validated by coupling several techniques on gold electrodes: direct imaging by atomic force microscopy and study of kinetics by reflectometry. The results show that the electrochemical currents are always associated to adsorption of the particles, so that the electrochemical method can be used to estimate the adsorption of the particles, thus to follow the kinetics. The influence of the electrostatics on the occurrence of adsorption highly depends on the nature of the substrate and on the nature of the colloidal suspension. (ions, pH, ionic strength): whereas electrostatics governs the deposits in some cases, it is totally dominated by other interactions in other cases. Therefore, it seems difficult to predict a priori the existence of adsorption. However, when a deposit occurs, the kinetics and the maximal coverage of the substrates are controlled by the electrostatic interactions between the particles already adsorbed and those, close to the interface, in the bulk of the solution.

In the present work, we focus on the surface charge properties of well-defined maghemite (gamma-Fe2O3) nanoparticles dispersed in water. Due to the acidic properties of surface groups, the nanoparticles surface can be positively or negatively charged depending on the pH. Consequently there are electrostatic repulsion forces between particles that allow stabilizing the suspensions in water. Acid-base titrations of the surface groups starting from acidic, alkaline and neutral pH are performed to access the dependence of the surface charge density with the pH. Titrations are followed by potentiometric and conductimetric measurements. Simultaneous zetametry measurements by acoustophoresis are implemented. The experimental curves are analyzed using several hypotheses, in particular we assume that the sites on the surface of the particles behave as weak diacids. The interpretation of the experimental determinations of the charge implies to take into account an electrostatic term due to the potential developed at the surface of the particles. Thanks to the complementarity of the potentio-conductimetric titrations and of the zetametry measurements, it is possible to better understand the phenomena of protonation and deprotonation of the colloidal particles as a function of the medium of dispersion (acidic, alkaline, neutral pH and nature of the counterions) and of the nature of the reagent.

International audience; We focus here on the effective charge of ionic micelles in aqueous solutions. First, we show that this quantity may be obtained by using an analytical transport theory based on the continuous solvent model to fit the experimental electrical conductivity of micellar solutions. In particular, we demonstrate the robustness of the fitting procedure on the example of real aqueous solutions of n-dodecyltrimethylammonium bromide and n-tetradecyltrimethylammonium chloride. Moreover, the approximate theoretical results are validated by a comparison to numerical simulations of Brownian dynamics. On the other hand, we propose to investigate the condensation properties of counterions on the micellar species by using Brownian dynamics. For that purpose, we have performed simulations of aqueous solutions that contain micellar species carrying their structural charge and the adequate number of counterions. We obtain a qualitative agreement between the fitted effective charges and the ones obtained by computing the mean number of bound counterions from numerical simulations.

International audience; Soft X-ray absorption spectroscopy with different probe depth wasemployed to characterize the solid electrolyte interphases (SEIs) formedon β-Sn single crystals with two different surface orientations. Based oncomparative studies of C- K , O- K , and F- K absorption spectra between theSEIs and reference samples, SEI on Sn (100) mainly consists of porousLi 2 CO 3 species with electrolyte uptake, while SEI on Sn (001) essentiallyconsists of LiF and organic molecules, with a small amount of –CO 3 andelectrolyte buried inside. Theoretical calculation suggests that Sn (001)surface is more reactive than (100), especially after air exposure. The reactive(001) surface facilitates the decomposition of LiPF 6 to form a LiF layer.In contrast, SEI on (100) surface is predominately from the typical decompositionof carbonate-based electrolyte. While the LiF passivates Sn (001)electrode after one cycle, the porous carbonate layer on (100) surface doesnot prevent further decomposition of electrolyte after many cycles. Thisleads to drastically different electrochemical behavior and morphology ofthe two SEIs. The result is a direct proof that surface properties of activematerials could strongly impact the SEI formation on electrodes even withthe same electrolyte. Such effect could lead to distinct SEI formation andelectrochemical performance.

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