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Origin and characterization of cyclodepsipeptides: Comprehensive structural approaches with focus on mass spectrometry analysis of alkali‐cationized molecular species
No full textInternational audienceAbstract Cyclodepsipeptides (CDPs) represent a huge family of chemically and structurally diverse molecules with a wide ability for molecular interactions. CDPs are cyclic peptide‐related natural products made up of both proteinogenic and nonproteinogenic amino acids linked by amide and ester bonds. The combined use of different analytical methods is required to accurately determine their integral structures including stereochemistry, thus allowing deeper insights into their often‐intriguing bioactivities and their possible usefulness. Our goal is to present the various methods developed to accurately characterize CDPs. Presently, Marfey's method and NMR (nuclear magnetic resonance) are still considered the best for characterizing CDP configuration. Nevertheless, electrospray‐high resolution tandem mass spectrometry (ESI‐HRMS/MS) is of great value for efficiently resolving CDP's composition and sequences. For instance, recent data shows that the fragmentation of cationized CDPs (e.g., [M + Li] + and [M + Na] + ) leads to selective cleavage of ester bonds and specific cationized product ions ( b series) useful to get unprecedented sequence information. Thus, after a brief presentation of their structure, biological functions, and biosynthesis, we also provide a historic overview of these various analytical approaches as well as their advantages and limitations with a special emphasis on the emergence of methods based on HRMS/MS through recent fundamental works and applications
Stereoselective Redox Switching between Möbius and Hückel Aromatic π Systems in a Three-Type Chirality Totem
No full textInternational audienc
Sodium hydrosulfide hydrate as sodium precursor for low-cost synthesis of Na3SbS4 ionic conductor
No full textInternational audienceSolid-state batteries (SSBs), an alternative to liquid-electrolyte lithium/sodium batteries, are a hot topic of research in the field of electrochemical energy storage. Sodium tetrathioantimonate Na3SbS4, a promising sodium ion-conductor solid electrolyte, can be synthesized via solution chemistry; a suitable, less energy-consuming and efficient method for mass production compared to dry processes (solid-solid reactions, mechanochemistry). The current work proposes to replace anhydrous sodium sulfide (Na2S, Na-precursor) with sodium hydrosulfide (NaSH.xH2O), a cheaper product that considerably reduces the cost of material production, a limiting factor from an up-scaling
Hopper flows of dense suspensions: a 2D microfluidic model system
No full textInternational audienceAbstract Flows of particles through bottlenecks are ubiquitous in nature and industry, involving both dry granular materials and suspensions. However, difficulties in precisely controlling particle properties in conventional set-ups hinder the full understanding of these flows in confined geometries. Here, we present a microfluidic model set-up to investigate the flow of dense suspensions in a two-dimensional hopper channel. Particles with controlled properties such as shape and deformability are in situ fabricated with a photolithographic projection method and compacted at the channel constriction using a Quake valve. The set-up is characterised by examining the flow of a dense suspension of hard, monodisperse disks through constrictions of varying widths. We demonstrate that the microfluidic hopper discharges particles at a constant rate under both imposed pressure and flow rate. The discharge of particles under imposed flow rate follows a Beverloo-like scaling, while it varies nonlinearly with particle size under imposed pressure. Additionally, we show that the statistics of clog formation in our microfluidic hopper follow the same stochastic laws as reported in other systems. Finally, we show how the versatility of our microfluidic model system can be used to investigate the outflow and clogging of suspensions of more complex particles
Sputtered molybdenum nitride films for asymmetric micro-supercapacitors in aqueous electrolyte
No full textData availabilityData for this article, including SEM, XRD, XPS, Raman, XAS, AFM, electrochemical cycling, EPR, electrical conductivity, bulk density measurements are available at the following URL https://nextcloud.univ-lille.fr/index.php/s/qRqJ4mo4aWYq45rInternational audienceHere we investigated the electrochemical performance of molybdenum nitride films as an efficient electrode for asymmetric micro-supercapacitors. Molybdenum nitride films were successfully deposited and optimized by reactive magnetron sputtering. On the one hand, the tuning of several deposition parameters (pressure, gas flow rates) allows obtaining molybdenum nitride electrode with high porosity and high electrical conductivity. On the other hand, Operando X-ray diffraction, operando Raman spectroscopy and operando X-ray absorption spectroscopy are combined to unveil the charge storage process in 1 M KOH aqueous electrolyte. These measurements clearly reveal the role of molybdenum oxide species in the pseudocapacitive mechanism at the oxide/electrolyte interface. High volumetric capacitance up to 624 F·cm⁻³ with excellent capacitance retention of 95 % over 20 000 cycles was achieved in 1 M KOH
Transport of soft matter in complex and confined environments
No full textInternational audienceBrownian motion provides a bedrock for the understanding of soft condensed matter and, therefore, of the physical description of the microscopic biological world. Inspired by this domain, and combining softness with hydrodynamic energy inputs, new physical modes of nanoscale organization and transport may now be accessible
Self‐assembled silicon@silica metasurfaces with high‐quality resonances in the infrared
No full textInternational audience2D assemblies of resonant dielectric particles constitute promising materials for the next generation of photonic devices, thanks to their low optical losses and intense electromagnetic response. However, bottom‐up synthesis methods present many difficulties when targeting metasurface applications, particularly due to the high degree of positional disorder and the size dispersion of the resonant particles. This work presents the fabrication of core–shell silicon@silica particles with multipolar resonances in the visible and near‐infrared. These resonant particles are then assembled at an air–water interface into a semi‐ordered array with islands of crystallinity. The assembly is deposited on quartz and the optical properties are characterized with ellipsometry and optical microscopy. The effective medium of this material appears to display a magnetic resonance with a high‐quality factor at ≈945 nm, as demonstrated by a Lorentzian resonance in the permeability. Thus, this is the first bottom‐up synthesis of silicon particle assemblies known to generate optical magnetism, giving promise for the scalable production of high‐performance metasurfaces, in spite of the imperfections associated with bottom‐up fabrication
Tailored Synthesis of Conformal Si‐Al Coatings on TiO2 Nanotubes for Hybrid Negative Electrodes of Lithium‐Ion Batteries
No full textInternational audienceAn original synthesis route has been developed to optimize silicon's utility in replacing graphite as anode material in Li‐ion batteries. This involves blending silicon with aluminium to enhance its conductivity. The silicon‐aluminium is co‐deposited on a nanoporous titanium dioxide nanotube matrix, which serves as an active current collector, thereby eliminating the need for inactive binders and ensuring robust mechanical stability during cycling. The nanostructured negative electrode is fabricated through two electrochemical synthesis steps: first, the anodization of a titanium foil, followed by the co‐electrodeposition of silicon and aluminium using a room temperature ionic liquid electrolyte. This co‐electrodeposition enables the in‐situ integration of aluminium into the silicon deposit. The resulting Si‐Al/TiO2 nanotube nanocomposite anode exhibits improved cyclic stability and enhanced rate capability. The observed enhancement in battery electrochemical performance underscores the significance of this electrochemical process in fabricating such nanostructured silicon negative composite electrodes
Fluorine as a key element in solid-state chemistry of mixed anions 3d transition metal-based materials for electronic properties and energy
No full text"ADC - Accord Couperin / American Chemical Society (2024-2026)"International audienceMixed anion compounds containing fluorine and based on 3d transition elements represent a class of materials with significant interest in solid-state chemistry. Indeed, their highly varied chemical composition, structural diversity, and the resulting electronic properties provide a rich playground for imagining new applications in the field of energy. The anions and the chemical bonds they form with the 3d transition elements are at the heart of this review. Key parameters such as electronegativity, hardness, and polarizability are introduced and discussed to better understand the charge capacity of the anion and the bonds formed in the solid. Oxyfluorides represent the most studied family due to the size similarity of the two anions, and part of the review is dedicated to the specific synthesis of these materials by systematically adjusting the fluorine content within various structures and analyzing the electronic and electrochemical properties of these compositions. The final sections focus on materials with structures often exhibiting a two-dimensional character, where ionic blocks coexist with covalent layers, such as fluorochalcogenides, fluoropnictides, and fluorotetrelides. The compositions and structures are systematically correlated with the electronic properties
Crystallization of Manganese(V) Oxides by Hydroflux Synthesis: Control of Anisotropic Growth and Electrochemical Stability
No full textInternational audienceDespite intriguing optical, magnetic, and redox properties, inorganic materials containing pentavalent manganese (Mn V ) are rare and could never be designed as shape-controlled crystals, which limits the ability to tune properties. Herein, we explore alkali hydroxide mixtures with controlled water content, namely, hydrofluxes, to demonstrate phase, shape, and nanostruc-ture control of Mn(V) oxides. We demonstrate speciation among KSrMn V O 4 , Sr 5 (Mn V O 4 ) 3 OH, and SrMn IV O 3 with the water and strontium content and the nature of the alkali cation of the hydroxide salt. We then provide evidence of the key role of water in enabling shape and nanostructure control, which we relate to the preferential interaction of water with specific c rystal f acets o f the hydroxyapatite Sr 5 (Mn V O 4 ) 3 OH, and to the impact of water on precursor solubility in water-poor hydrofluxes. We then show that nanostructured Mn(V) hydroxyapatite possesses an acid-base redox stability window, enabling electrochemical operation in strongly oxidative conditions. By correlating the fundamental knowledge of hydrofluxes with crystallization mechanisms, this work sheds light on the possibilities offered by hydrofluxes for crystal shape, size, and property control.Manganese can be found in various oxidation states in solidstate materials from 0 to +7. 1 Despite its low stability and scarcity, pentavalent manganese(V) is the origin of important properties. It can be used to design colorful blue or green pigments. 2,3 Mn(V) compounds have been considered as laser materials 4 and also raise interest due to intriguing magnetic properties. 5,6 Mn(V) is also involved in the oxygen-evolving complex for the production of dioxygen during photosynthesis. 7,8 This suggests that Mn(V) compounds could find interest for use in water oxidation electrocatalysis provided that they can be used in conditions where the oxidation state and structural features are maintained. To date, the electrochemical properties of Mn(V) compounds, especially their pH-potential stability window, have not been evaluated, so the feasibility of using Mn(V) compounds for electrochemical applications remains an open question.Inorganic compounds containing pentavalent manganese (Mn V ) are scarce due to their low stability. 9 Currently reported manganese oxides built on Mn(V) are Ba</div