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Mechanochemical and Piezo‐Accelerated Stereoselective Synthesis of Isoindolinones
No full textInternational audienceIn this study, we report on the use of mechanochemistry for the synthesis of trifluoromethylated isoindolinones via a cascade radical sequence involving intermolecular addition/cyclization reactions of ynamides. This minimum solvent approach, involving liquid‐assisted grinding, provides the products in good yields with complete E stereoselectivity, contrasting with the E/Z mixtures obtained under previously reported photoredox conditions. Mechanistic investigations revealed two complementary activation pathways: mechanical activation alone can trigger the radical cascade, while the presence of piezoelectric materials (BaTiO 3 ) significantly accelerates product formation. Furthermore, we identified an unexpected role of Celite® as an abrasive agent that promotes metal leaching and enables alternative activation pathways. This methodology showcases mechanochemistry as a valuable alternative to photoredox catalysis for stereoselective radical transformations, with distinct mechanistic advantages that can be strategically exploited
Si–Ge Alloys as promising anodes for sulfide-based solid-state batteries: role of the powder morphology on performance
No full textInternational audienceAs the demand for safe, high-energy energy storage devices grows with the energy transition, all-solid-state batteries (ASSBs) have become the central focus of research. This pioneering study explores Si0.5Ge0.5 alloys as negative electrode for sulfur-based ASSBs, and how the morphology and electrode formulation protocols influence their electrochemical performance. Two distinct morphologies of Si0.5Ge0.5 alloys were synthesized via ball-milling (BM) and laser pyrolysis (LP). Composite electrodes were prepared using two different protocols: densification and casting. The distribution of the composite electrode components was analyzed using SEM/EDX. Electrochemical performance was evaluated in half-cells using argyrodite as the solid electrolyte, through galvanostatic cycling, derivative analysis, and electrochemical impedance spectroscopy (EIS). Particularly, for the LP-cast composite electrode, a high specific capacity of 1580 mAh g-1am was achieved at C/5, with 86% capacity retention after 45 cycles. Additionally, the electrochemical behavior and performance of both BM and LP Si0.5Ge0.5 alloys were compared to those in a liquid electrolyte system with a classical electrode formulation, revealing similar (de)lithiation mechanisms to those in solid-state configuration
A Fe-thiolate layered metal organic framework as a high-performance electrode material for potassium-ion batteries
No full textInternational audienceHere, we report a rare example of an Fe-based MOF capable of accommodating K ions electrochemically within its layered framework, achieving low polarization, high capacity utilization (similar to 0.8 electrons exchanged per Fe), and stable cycling performance. In situ Mössbauer spectroscopy and operando XRD analyses revealed that the observed electrochemical storage arises from the Fe/Fe redox couple with polyphasic transformations
La dynamique de transition de phase étudiée par la microscopie optique cryogénique dans un matériau moléculaire commutable Fe₂Co₂ à transfert de charge
No full textInternational audienceUnderstanding the phase transition mechanism in switchable materials is crucial for optimizing their properties. In this study, we present the thermal electron transfer -coupled spin transition (ETCST) mechanism, revealed through the cryogenic optical microscopy (OM) measurements on a cyanide-bridged square complex: where Tp is tris(pyrazolyl)borate and vbik, bis(1vinylimidazolyl)ketone. A one-step thermal ETCST of 1•ClO4 is observed using conventional techniques such as single crystal X-ray diffraction (SC-XRD) and bulk sample magnetic measurements. The ETCST is cooperative, with quite different transition temperatures for the single crystal (T1/2↑ = 251.5 K for heating and T1/2↓ = 243.5 K) and the bulk sample (T1/2↑ = 273 K and T1/2↓ = 255 K). In contrast, the direct visualization of the thermal ETCST in the single crystal of 1•ClO4 through OM and the subsequent image analysis disclose, for the first time, a phase transition of unexpected complexity. The ETCST progresses in three steps along the a, b and c axes, respectively: i) Initially, strip domains form and rapidly extend along the a-axis. ii) These domains then gradually widen in the b-axis covering the entire ab layer. iii) The final step involves a layerby-layer extension of ETCST along the c-axis. Structural analysis of 1•ClO4 reveals that two types of intermolecular interactions govern the two preferential propagation directions of ETCST. The first type, mediated by ClO4⁻ anion, drives the rapid propagation of ETCST along the a axis, occurring so rapidly that the conventional methods like magnetometry and SC-XRD are unable to detect it. The second type, along the b axis, involves the π-π stackings of vbik ligands, which contribute to the slower ETCST propagation in this direction. This mechanistic insight into the anisotropic propagation patterns of ETCST in 1•ClO4 underscores the role of intermolecular interactions in modulating the dynamics of molecular switching.La compréhension du mécanisme de transition de phase dans les matériaux commutables est essentielle à l'optimisation de leurs propriétés. Dans cette étude, nous présentons le mécanisme de transition de spin couplée au transfert thermique d'électrons (ETCST), révélé par des mesures de microscopie optique cryogénique (MO) sur un complexe carré ponté par du cyanure : {[Fe(Tp)(CN)3]2[Co(vbik)2]2}·2ClO4·2CH2Cl2 (1·ClO4), où Tp est le tris(pyrazolyl)borate et vbik, la bis(1-vinylimidazolyl)cétone. Une ETCST thermique en une étape de 1·ClO4 est observée à l'aide de techniques conventionnelles telles que la diffraction des rayons X sur monocristal (SC-DRX) et les mesures magnétiques sur échantillon massif. L'ETCST est coopératif, avec des températures de transition très différentes pour le monocristal (T1/2↑ = 251,5 K pour le chauffage et T1/2↓ = 243,5 K) et l'échantillon en vrac (T1/2↑ = 273 K et T1/2↓ = 255 K). En revanche, la visualisation directe de l'ETCST thermique dans le monocristal de 1·ClO4 à travers OM et l'analyse d'image ultérieure révèlent, pour la première fois, une transition de phase d'une complexité inattendue. L'ETCST progresse en trois étapes le long des axes a, b et c, respectivement : i) Initialement, des domaines en bande se forment et s'étendent rapidement le long de l'axe a. ii) Ces domaines s'élargissent ensuite progressivement dans l'axe b couvrant toute la couche ab. iii) L'étape finale implique une extension couche par couche de l'ETCST le long de l'axe c. L'analyse structurale de 1·ClO4 révèle que deux types d'interactions intermoléculaires régissent les deux directions de propagation préférentielles de l'ETCST. Le premier type, médié par l'anion ClO4⁻, entraîne la propagation rapide de l'ETCST le long de l'axe a, se produisant si rapidement que les méthodes conventionnelles comme la magnétométrie et la SC-XRD sont incapables de la détecter. Le second type, le long de l'axe b, implique les empilements π–π des ligands vbik, qui contribuent à la propagation plus lente de l'ETCST dans cette direction. Cette compréhension mécaniste des schémas de propagation anisotropes de l'ETCST dans 1·ClO4 souligne le rôle des interactions intermoléculaires dans la modulation de la dynamique de la commutation moléculaire
Copper‐Coordination Engineered Glassy Hydrogels Featuring Ultrastiffness and Structural Programmability
No full textInternational audienceGlassy hydrogels, which maintain a distinctive glassy state at ambient temperature, are appealing for engineering applications. Nevertheless, the existing glassy hydrogels often suffer from inferior strength, inadequate stiffness, and environmental stability caused by weak physical cross-linking. Herein, we present an ultrastiff and ultrastrong glassy hydrogel by introducing robust coordination bonds into a network composed of polyacrylic acid (PAA) and polyvinyl alcohol (PVA), using a copper acetate-assisted strategy. The presence of acetate anions creates a relatively alkaline environment, which deprotonates the carboxyl groups of PAA. This deprotonation exposes carboxylate groups that readily coordinate with copper ions, establishing a densely cross-linked network in the glassy state. The resultant glassy hydrogel exhibits record-breaking Young's modulus (469.7 MPa), tensile strength (19.2 MPa), and exceptional environmental stability. Moreover, the reversible softening and vitrification induced by the breakage and reforming of coordination bonds endows glassy hydrogel with structural programmability, allowing for the construction of integrated auxetic hydrogel (IAH). The IAH demonstrates enhanced mechanical properties compared to the auxetic skeleton alone while maintaining a negative Poisson's ratio over a wide strain range of 0-29%. This study provides a promising engineering route for the development of advanced glassy hydrogels
Engineering of diamond growth for high-end application: challenges and perspectives.
No full textInternational audienceDiamond is a transparent wide band gap material with outstanding optical and electronic properties that are attracting a lot of attention for the development of the next generation of devices. In addition to its exceptional properties, which are well known in the field of jewellery, for which it combines purity and brilliance, single crystal diamond provides also an ideal host material to incorporate different types of impurities that can drastically modify its properties. The use of dopants such as boron or phosphorous can for example allow tuning the electrical conductivity of the film up to the metallic conduction which could allow to produce highly boron doped substrates and develop vertical components for power electronic whose design and architecture for the realization of more complex function is simpler. In addition nitrogen are some of the elements that can be introduced in the crystal in order to create optically active centres such as the well-known NV (nitrogen-vacancy).In this presentation, we will focus more specifically on the production aspects of high purity and boron-doped or nitrogen-doped monocrystalline diamond films grown by chemical vapour deposition assisted by microwave plasma, highlighting all the constraints inherent to the targeted field of application. We will begin by showing the plasma conditions that are important to obtain in order to combine material quality and high growth rates, thereby limiting production costs. In the case of boron doping, particular attention will be paid to showing the plasma conditions which are essential to maintain in order to reach a sufficiently thick and doped film leading to on state resistances compatible with their use in vertical components. It will be shown in particular the importance of the gas composition to inject high microwave power allowing reaching high growth rate. With regard to nitrogen doping and the formation of NV colour centres, issues related to controlling their density and maximizing their coherence properties through precise engineering will be discussed. High amounts of NV are usually preferred in most sensing schemes but limits exist in the ability to control growth at high doping levels as well as to avoid interaction between nearby spins. Nuclear spins within the matrix itself might cause unwanted decoherence and growth of isotopically enriched materials allows considerably extending T2 times. In the same vein, magnetic sensitivity of a sensor based on NV ensembles can be considerably increased by producing diamond with NV centres having preferential orientation which can be obtained by using diamond substrates with specific crystallographic orientation such as (111) or (113). Lastly, we will describe the challenges ahead, in particular for the development of a diamond industry that requires the production of large single-crystal substrates. Indeed, significant success has been recently achieved in increasing the lateral size of the diamond films, by exploiting either a “mosaic” approach1 or heteroepitaxial growth on a foreign substrate2, and these techniques, associated to the development of growth strategies to reduce dislocation density are on the way allowing the first diamond wafers for electronics being on the verge of being commercialized at an industrial scale.Acknowledgements: this work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 101019234, RareDiamond), from the Quantera Project MAESTRO (ANR-22-QUA1-0003-07) and from ANR (Agence Nationale de la Recherche) through the projects Lapin113 (ANR-19-CE29-0017-04), Sinfonia (ANR-23-QUAC-0006-01), Trampoline ANR-22-CE51-0019) and the investment program for future Equipex e-Diamant (ANR-21-ESRE-0031).References1. S. Ohmagari, H. Yamada, N. Tsubouchi, H. Umezawa, A. Chayahara, A. Seki, F. Kawaii, H. Saitoh, and Y. Mokuno, Appl. Phys. Lett. 114 (2019), 082104 2. J.-C. Arnault, S. Saada, and V. Ralchenko, Physica Status Solidi (RRL) – Rapid Research Letters 16 (2022), 2100354
Le nettoyage à l'eau atténue-t-il la dégradation atmosphérique des verres instables du patrimoine ? Une étude expérimentale sur des verres modèles
No full textInternational audienceGlass curators often question how their treatments affect the long-term stability of historical glass. While damp cotton swabs are commonly used to remove surface salts and dust, the use of water remains controversial, particularly for heavily altered glass, due to concerns about worsening hydration. This study investigates the effect of water rinsing on an unstable soda-lime glass altered for six months (monoliths) and fifteen months (powders) at 35 °C and 85% relative humidity. Samples were then rinsed with Milli-Q water at 20 °C or 50 °C, and the monolithic glass was subsequently subjected to an additional 15 months of alteration under the same conditions. The glass surface was characterized by optical and scanning electron microscopy (SEM) as well as Raman spectroscopy to identify the nature of the salts. The evolution of the hydrated layer was assessed using transmission FTIR, Raman and solid-state NMR spectroscopies, ToF-SIMS, and thermogravimetric analysis (TGA). The results show that rinsing effectively removes surface salts—primarily sodium carbonate—and induces structural changes in the hydrated layer, promoting silicate network polymerization. Upon resuming alteration, rinsed monolithic samples exhibit no further degradation after the additional 15 months of alteration. These findings offer promising insights for conservation practices and may help curators refining their treatment strategies for altered glass.Les conservateurs de musée ayant en charge des objets en verre s'interrogent souvent sur l'impact de leurs traitements sur la stabilité à long terme de ces objets du patrimoine. Alors que des cotons-tiges humides sont couramment utilisés pour éliminer les sels présents en surface et la poussière, l'utilisation de l'eau reste controversée, en particulier pour les verres fortement altérés, en raison des craintes d'aggravation de l'hydratation. Cette étude examine l'effet du rinçage à l'eau sur un verre sodocalcique instable altéré pendant six mois (monolithes) et quinze mois (poudres) à 35 °C et 85 % d'humidité relative. Les échantillons ont ensuite été rincés avec de l'eau Milli-Q à 20 °C ou 50 °C, et le verre monolithique a ensuite été soumis à une altération supplémentaire de 15 mois dans les mêmes conditions. La surface du verre a été caractérisée par microscopie optique et électronique à balayage (MEB) ainsi que par spectroscopie Raman pour identifier la nature des sels. L'évolution de la couche hydratée a été évaluée à l'aide des spectroscopies FTIR en transmission, Raman et RMN à l'état solide, ToF-SIMS et analyse thermogravimétrique (TGA). Les résultats montrent que le rinçage élimine efficacement les sels de surface - principalement le carbonate de sodium - et induit des changements structuraux dans la couche hydratée, favorisant la polymérisation du réseau silicaté. Lors de la reprise de l'altération, les échantillons monolithiques rincés ne présentent plus de dégradation après 15 mois supplémentaires d'altération. Ces résultats offrent des perspectives prometteuses pour les pratiques de conservation et peuvent aider les conservateurs à affiner leurs stratégies de traitement du verre altéré
Detection and quantification of SF6 substitute g3 (C4F7N/CO2/O2) byproducts: An experimental and theoretical study
No full textInternational audienceSF6 is a most prevalent insulation gas widely used in the electrical industry worldwide, declared as one of six (GWP) global warming potential gases in the Kyoto Protocol held in 1999. The search to find alternatives to SF6 was challenging. In this regard, GE VERNOVA researchers proposed an insulation g3 gaseous mixture containing C4F7N/CO2/O2, which proved to be the most promising substitute for SF6. Thermoelectric stress in the circuit breaker decomposes the g3 (C3F7CN/CO2/O2) gas mixture in their corresponding byproducts. The byproducts could be toxic or corrosive in nature and should be identified and quantified with the help of GC-MS technology to maintain operator and instrument safety. For this instance, we developed the GC-MS and FTIR methodologies for the detection as well as quantification of prominent polluted gas molecules, ranging from ppm to % level. Furthermore, density functional theory (DFT) simulation could help us to determine the chemical reaction mechanism and their corresponding absorbed energies during the arcing process. Optimized GC-MS methodology gives us the range of byproducts, including CF4, C2F6, C3F8, CF3CN, C2F5CN, C2F2, (CN)2, CO, COF2, and (C2F7NH2O) amide, present in heavily arced g3 gas sample. Certain molecules, such as SiF(CH3)3, were also detected by the chemical reaction of the GC column with HF. Three standard gas samples containing CF4, C2F6, C3F8, CF3CN, and COF2 molecules in various concentration levels were employed for the calibration. The regression curve of the standard gases was established, and the slight movement of the curve was observed after the 60-day duration. However, the COF2 quantification was not possible by GC-MS due to the strong chemical reaction with column stationary phase and uneven peak area results in consecutive measurements. Thus, COF2 calibration via FTIR technology is established due to the utilization of only a gas cell in the infrared instrument without the interaction of the column with a standard sample for molecule separation. Furthermore, HF cannot be identified by GC-MS technology due to its limitation; therefore, we employ the GASTEC tube that quantifies the HF by color alternation and is also safe to use. Among all, CF4, C2F6, C3F8, CF3CN, C2F5CN, (CN)2, and COF2, HF are the main byproducts occurring during the breaking in a typical circuit breaker with a g3 gaseous mixture.The chemical reaction mechanism of g3 gas with the help of density functional theory is also investigated. Geometry optimization and transition state with one imaginary frequency were simulated by M062X hybrid functional with the combination of 6-311+G(d,p) basis sets, executed in Gaussian 16 software packages. Thermoelectric aging of the g3 gas mixture can open the various complicated channels of chemical reaction; nevertheless, we proposed the two main routes of decomposition coming from C4F7NO and C4F7NO2 intermediates, and a total of 34 and 6 chemical reactions can be obtained by their decomposition. Among the three primary dissociation reactions of the C4F7NO molecule, (R5) C4F7NO C3F3NO + CF4 and (R6) C4F7NO C2F5CN + CF2O, bond fission pathways are identified as the thermodynamically favorable route. The energy barrier values for these two reactions are 8.1 kcal mol-1 and 8.0 kcal mol-1, respectively. This paper could deliver a strong experimental and theoretical foundation for understanding the various natures of decomposition of byproducts in a diverse range generated during arcing in a typical circuit breaker
Synthesis of Mixed Phosphine–Phosphine Oxide Ligands by Rh(I)‐Catalyzed C─H Bond Alkylation
No full textInternational audienceAbstractThe design of phosphine ligands is pivotal in transition metal catalysis, enabling fine‐tuning of catalytic activity, selectivity, and stability. Hemilabile ligands, particularly mixed phosphine–phosphine oxide ligands, offer dynamic coordination, stabilizing reactive intermediates, and enhancing catalytic performance. Herein, we report an efficient Rh(I)‐catalyzed method for synthesizing these ligands via selective C─H bond alkylation of biarylphosphines, allowing the introduction of one or two hemilabile phosphine oxide side arms. The synthesized ligands exhibit remarkable reactivity in Pd‐catalyzed Buchwald–Hartwig coupling between 2‐chlorotoluene and gaseous ammonia, a challenging reaction due to ammonia's strong Lewis basicity. Among the ligands tested, DavePhosO showed complete conversion and 97% yield, highlighting the role of the hemilabile phosphine oxide unit in preventing formation of inactive palladium complexes
Coupling of X‐AES Transitions and XPS Photopeaks to Assess the Oxide Formation of Ga and in CuIn<sub>0.7</sub>Ga<sub>0.3</sub>Se<sub>2</sub> Material During Air Aging
No full textInternational audienceABSTRACTThe solar absorber Cu (In0.7Ga0.3)Se2 (CIGS) undergoes a process of evolution upon exposure to the atmosphere, resulting in the growth of oxide phases. This phenomenon can potentially affect the interfacial properties of CIGS, which in consequence may impact the efficiency of the solar cell. X‐ray photoelectron spectroscopy (XPS) is an appropriate method to analyze the degradation of CIGS upon air aging. However, many photopeaks and Auger lines of the constitutive elements are distributed along the energy scale, and the exact determination of the degradation within the CIGS absorber requires specific care to select peaks to consider to ensure that information arise from similar escape depths. In this study, we propose to investigate the kinetics of degradation of Ga and In at similar depths probed by coupling not only photopeaks but also X‐Auger electron spectroscopy (X‐AES) transitions in the absence of photopeaks in the same energy range. If photopeaks modeling is well established for In and Ga, a decomposition procedure of the X‐AES transitions must be developed. Both linear and nonlinear least square fitting were used and compared, starting to model CIGS, In2O3, and Ga2O3 references to deploy it after on Auger transitions measured on aged samples. Thanks to the determination of the degradation ratios (oxide phase over CIGS phase) at 3, 7, and 9 nm depth, we show that both In and Ga exhibit similar kinetic of oxide formation, which proceeds gradually by O penetration through the subsurface of the material, this penetration being more and more attenuated deeper.</p