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Poisson-Nernst-Planck charging dynamics of an electric double layer capacitor: symmetric and asymmetric binary electrolytes
No full textInternational audienceA parallel plate capacitor containing an electrolytic solution is the simplest model of a supercapacitor, or electric double layer capacitor. Using both analytical and numerical techniques, we solve the Poisson-Nernst-Planck equations for such a system, describing the mean-field charging dynamics of the capacitor, when a constant potential difference is abruptly applied to its plates. Working at constant total number of ions, we focus on the physical processes involved in the relaxation and, whenever possible, give its functional shape and exact time constants. We first review and study the case of a symmetric binary electrolyte, where we assume the two ionic species to have the same charges and diffusivities. We then relax these assumptions and present results for a generic strong (i.e. fully dissociated) binary electrolyte. At low electrolyte concentration, the relaxation is simple to understand, as the dynamics of positive and negative ions appear decoupled. At higher electrolyte concentration, we distinguish several regimes. In the linear regime (low voltages), relaxation is multi-exponential, it starts by the build-up of the equilibrium charge profile and continues with neutral mass diffusion, and the relevant time scales feature both the average and the Nernst-Hartley diffusion coefficients. In the purely nonlinear regime (intermediate voltages), the initial relaxation is slowed down exponentially due to increased capacitance, while bulk effects become more and more evident. In the fully nonlinear regime (high voltages), the dynamics of charge and mass are completely entangled and, asymptotically, the relaxation is linear in time
Étude comparative du blanchiment réducteur et oxydant de papiers lignocellulosiques naturellement vieillis
No full textInternational audienceMit zunehmendem Alter versauern lignozellulosehaltige Papiere – die auf Holzfasern basieren – sie vergilben und werden sehr brüchig, was eine große Herausforderung für die Konservierung darstellt. Das Bleichen ist eine kurative Behandlung, die hauptsächlich dazu dient, die Bräunung des Papiers zu mildern und so den Zugang zu seinem historischen oder künstlerischen Inhalt zu ermöglichen. Die Literatur zum Thema Papierbleiche ist umfangreich, und das Fehlen standardisierter Protokolle erschwert den Vergleich der Ergebnisse. Darüber hinaus konzentrieren sich diese Studien häufig auf Zellulosepapiere, die kein oder nur wenig Lignin enthalten. Um diese Probleme zu beheben, haben wir die Auswirkungen der reduktiven und oxidativen Bleichung auf die Farbe, den pH-Wert, die Wasseraufnahme und die mechanische Festigkeit von zwei natürlich gealterten Lignocellulosepapieren verglichen.With natural ageing, wood pulp papers acidify, yellow and become very fragile, all of which pose a major preservation challenge. Bleaching is a remediation treatment primarily used to increase the brightness of paper, thereby enabling access to its historical or artistic content. Literature on paper bleaching is vast and the lack of standardised protocols makes it difficult to compare the results. Moreover, these studies often focus on papers containing no or little lignin. To tackle these issues, we compared the impact of reductive and oxidative bleaching on two naturally aged lignocellulosic papers' color, pH, water absorption and mechanical strength.Avec le vieillissement naturel, les papiers lignocellulosiques - à base de pâte de bois- s'acidifient, jaunissent et deviennent très fragiles, ce qui constitue un défi majeur de conservation. Le blanchiment est un traitement curatif principalement mis en oeuvre pour atténuer le brunissement du papier, permettant ainsi d'accéder à son contenu historique ou artistique. La littérature sur le blanchiment du papier est vaste et l'absence de protocoles standardisés rend difficile la comparaison des résultats. De plus, ces études se concentrent souvent sur des papiers cellulosiques, ne contenant pas ou peu de lignine. Pour remédier à ces problèmes, nous avons comparé l'impact du blanchiment réducteur et oxydatif sur la couleur, le pH, l'absorption d'eau et la résistance mécanique de deux papiers lignocellulosiques vieillis naturellement
Quasiliving Cationic Polymerization of Isobutylene with FeCl 3 × i PrOH as Co‐Initiator in Toluene: A Step Toward Greener Process
No full textInternational audienceA quasiliving carbocationic polymerization of isobutylene (IB) in toluene using DiCumCl/FeCl 3 × i PrOH initiating system at −80°C is investigated. The optimal composition of catalytic complex is found to be FeCl 3 ×1.0 i PrOH, while at lower content of i PrOH in a complex side reactions occur resulting in generation of monofunctional polyisobutylene (PIB) fraction. The experiments at different monomer to initiator ratios in conjunction with chain extension experiment confirm the quasiliving nature of the polymerization resulting in well‐defined difunctional low molecular weight PIB (M n from 1200 to 7000 g⋅mol −1 , Đ < 1.3). Synthesis of higher molecular weight PIB in toluene leads to the gelation of the polymerization system, hence, the toluene/ n ‐hexane 50:50 v/v mixture is successfully used for the synthesis of PIB with M n up to 52 000 g⋅mol −1 with low dispersity Đ < 1.3. In addition, one‐pot syntheses of end‐functional PIB are conducted in toluene resulting in vinylidene‐ and hydroxyl‐terminated PIBs with near quantitative functionality
Metallocarbonyl bromomaleimide derivatives for thiol bioconjugation and disulfide bridging: spectroscopic and biological properties
No full textInternational audienceMetallocarbonyl mono- and dibromomaleimides are potent fluorogenic reagents for thiol group modification, protein disulfide rebridging, and CO delivery to cancer cells
Multidisciplinary Preclinical Investigations on Ferrocenyl, Ruthenocenyl, and Benzyl Derivatives of Niridazole as New Drug Candidates against Schistosomiasis
No full textInternational audienceSchistosomiasis affects hundreds of millions of people worldwide, yet its chemotherapeutic treatment is based on the only drug available‐praziquantel (PZQ). The development of alternative treatment options is urgent, not only due to the threat of drug resistance, but also because the drawbacks of PZQ, such as its inactivity against juvenile stages, contribute to its incomplete cure rates, thus requiring repeated treatment. This study presents the design, synthesis, characterization, and biological evaluation of 10 novel organometallic derivatives of the old schistosomicide, niridazole. The in vitro characterization of the derivatives on different life stages of Schistosoma mansoni showed that the activity profile of niridazole could be modified and extended. One ferrocenoyl derivative showed promising activity against all life cycle stages of S. mansoni . Two ferrocenyl and one ruthenocenyl derivatives also displayed higher potency against adult schistosomes than niridazole. In conclusion, valuable information could be gained on the structure–activity relationship of the different organometallic modifications, which could be used to design a second generation of derivatives with further improved activity profiles
Impact of Disorder, Porosity, and Surface Chemistry of Salt Templated Carbons on Capacitance
No full textInternational audienceThe necessity of tailoring the structure/texture of carbons to improve the performance of aqueous-based electrical double-layer capacitors (EDLCs) is emphasized. A green soft-salt templating approach allowed the preparation of a series of porous carbons for this target. The EDLCs operating in 1M Li 2 SO 4 demonstrated a maximum capacitance of 244 F g -1 at 1.6 V (CsCl/KCl-T), long-term cycle life (288 h for LiCl/KCl-T), and a specific energy exceeding 10 Wh kg -1 . The physicochemical properties of carbons have been correlated with capacitance, retention, and stability. The investigation by Raman spectroscopy revealed that carbons with the increased disorder, thus, higher I D /I G ratio, are in accord with enhanced capacitance. Active surface area (ASA) values, related to carbon defects, perfectly supported the Raman findings. Surface functionality, i.e., the phenol/ether and carboxyl groups are found to affect capacitance. The carbons showed a predominance of micropores, with a specific surface area (SSA) ranging from 2640 to 1453 m 2 g -1 . In sum, I D /I G , SSA, ASA, and volume of micropores are in linear proportion with capacitance at various regimes. However, the most ordered and less porous materials provided better lifespan performance. Therefore, a good compromise is required to satisfy both high capacitance and the long cycle life of EDLCs
Structural insights into nanofibers formed by templated polymerization-induced self-assembly through combined SANS and AFM characterizations
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Do Micropower Sources Meet the Needs of the Internet of Things?
No full textInternational audienceAbstract The rapid global adoption of the Internet of Things (IoT), combined with the ongoing trend toward device miniaturization, has marked the emergence of compact, connected technologies. However, as device dimensions continue to decrease, power sources remain a critical bottleneck. Micropower sources (<1 cm 2 ) must balance the inherent trade‐off between physical size and achievable energy and power densities. Although advances in materials and design are steadily improving performance within small form factors, a comprehensive assessment of how well current micropower technologies meet the energy and power requirements of modern IoT devices is still lacking. This Perspective aims to: 1) define the opportunity space for miniaturized energy storage systems within IoT technologies, 2) survey the commercial and research landscape of micropower sources, and 3) critically evaluate whether current micropower solutions fulfill the demands of existing and emerging IoT applications
Cationization of fac-[Mn(CO)<sub>3</sub>(<sup>R</sup>bpy)Br] complexes with ammonia: direct access to water-soluble photoinduced CO releasing molecules
No full textInternational audienceA new family of water-soluble photoinduced CO-releasing molecules (PhotoCORMs) having the general structure fac-[Mn(CO)3(Rbpy)Br)(NH3)]Br (bpy= 2,2’-bipyridine; R= -H, -Me, -tBu, -OMe, -NO2, -CF3, -CONH2) has been synthesized in good yield by reaction between the corresponding [Mn(CO)3(Rbpy)Br] complexes and methanolic ammonia. Photolysis experiments and myoglobin assay were performed on all the complexes and unambiguously demonstrated that they rapidly release from one to three CO molecules upon blue light irradiation
A Multi-Technique Machine Learning Workflow for Optimizing the Manufacturing Process of Functional Layers in Electrochemical Energy Devices
No full textInternational audienceIn this presentation we will share our latest developments revolving around the utilization of Artificial Intelligence/Machine Learning techniques to optimize the manufacturing process of functional layers in lithium ion batteries (electrodes) and polymer electrolyte membrane fuel cells (gas diffusion layers -GDL-). We have used several machine learning techniques (including unsupervised, supervised and deep learning techniques) to predict the influence of manufacturing process parameters (e.g. slurry formulation, drying temperature, electrode calendering degree, GDL fiber diameter) on the properties of the functional layers (e.g. conductivity, tortuosity factor, porosity). We have also applied deep learning techniques in order to derive surrogate models mimicking the behavior of physics-based numerical models simulating the manufacturing process of the electrodes. The so-derived machine learning models are then used in combination with optimization algorithms in order to perform inverse design of the manufacturing processes, i.e. predicting which manufacturing parameters we need to adopt in order to maximize and/or minimize given properties. In this presentation, we review these developments, including the different workflows that we designed and discuss our manufacturing digitalization vision towards accelerated design of functional layers for electrochemical energy device applications. We believe that this approach gives the promise to reduce costs and save time in the industrialization of these devices towards a more sustainable world