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An Electron Donor–Acceptor Complex-Driven Strategy Enables Initiation of Photoiniferter RAFT Polymerization from Amines, Carboxylic Acids, and Alcohols
No full textInternational audienceHere, we report a unified approach for the photoiniferter RAFT polymerization technique allowing the utilization of organic molecules with the most ubiquitous functional groups (amines, carboxylic acids, and alcohols) as initiators without significant limitations in substrate complexity providing close to complete α-end functionalization of synthesized polymers. Our catalytic system relies on a combination of visible light-induced electron donor-acceptor complex-driven initiation mechanism and photocontrolled radical polymerization to provide polymers with controlled molar mass, low dispersity, and targeted α-end functionality. Through this method, a wide range of diverse amines and carboxylic acids, including biorelevant and drug-like substrates, were effectively attached to polyacrylate backbone. In addition tothat, we have developed a reagent for effective initiation from complex amines and alcohols, which also provides a new dimension for the construction of conjugates with potentially biocleavable bridge between the α-end and polymer chain
Green polymerisation of renewable lignin-derived vinyl ketone monomer to form UV-degradable polymers
No full textInternational audienceWe report the synthesis of a novel aromatic vinyl ketone monomer (BioPVK) from an abundant product of lignin depolymerisation, syringaldehyde. We demonstrate that BioPVK can be homopolymerised and copolymerised with styrene (St) in green solvents (ethyl lactate or water) to produce UV-degradable polymers. The homopolymers produced showed good thermal properties with high stability (up to 370 °C) and high glass transition temperatures (91 °C), similar to that of polystyrene. After irradiation with UV-light for only 30 minutes, substantial loss in molar mass was observed by size exclusion chromatography demonstrating the degradability of these polymers in mild conditions. Furthermore, MALDI-TOF analysis revealed that UV-degradation produced small molecule aromatic compounds. Copolymerisation of BioPVK with styrene was performed as both a solution polymerisation in ethyl lactate and as a conventional emulsion polymerisation in water. As expected, the solution copolymers degraded under UV-light irradiation. The aqueous emulsion copolymerisation of BioPVK and St produced high molar mass UV-degradable copolymers (Mw of 172 kDa) as a colloidally stable latex in 2h. These high molar mass copolymers degraded readily in dilute solutions when irradiated with UV-light, but were less susceptible to degradation when cast as a solid film. This work provides progress into lignin-derived, UV-degradable, polymers and copolymers, offering industrially relevant and environmentally conscious degradable alternatives to current commodity plastics
Synthetic Diamond Materials for Emerging Quantum Technologies
No full textInternational audienceProgress in controlling diamond synthesis has made it possible to produce very pure crystals and to incorporate and control atomic impurities and carbon vacancies in the crystal lattice. The appropriate impurity-vacancy combinations can give rise to special defects known as color centers, such as the nitrogen-vacancy (NV) or the silicon-vacancy (SiV), which exhibit exceptional quantum properties with spins that are optically addressable. The use of diamond containing color centers has paved the way for the development of innovative quantum technologies, such as very high-resolution magnetometry and quantum information processing. Nevertheless, the development of quantum sensors at the nanometric scale remains one of the most interesting challenges. In this context, the development of a reliable nanoparticle synthesis technique that allows the desired defects to be incorporated and their quantum optical properties to be modulated is crucial. In this seminar, an efficient and recent method to produce diamond nanoparticles containing NV, SiV and germanium-vacancy (GeV) centers is proposed through direct plasma assisted chemical vapour deposition (CVD) growth. This technique allows good control of both nanoparticle growth processes and color centers formation. The optimization of the CVD nanodiamond growth process is presented, showing the impact of different plasma parameters and gas phasecomposition on nanoparticle crystallinity, size and shape. Morphological characterizations reveal the production of small (around 100 nm) and well faceted nanodiamond particles. In addition, the SiV and GeV color centers incorporation can be tuned within this material by varying the gas phase composition which emphasizes the high flexibility of the CVD growth technique. Finally, the quantum properties of the incorporated color centers have been successfully investigated under extreme pressure conditions (up to ~ 180 GPa) showing a monotonic blue shift of their optical zero-phonon line. Since their luminescence remains stable, SiV and GeV centers emerge as high-pressure nanosensors
Tantalum recovery from alkaline leachates based on magnesium hexatantalate intermediate precipitate
No full textInternational audienceExtraction of soluble Ta( v ) via precipitation with Mg( ii ) and recovery as Ta 2 O 5 solid
Drying Molybdate/Iron Hydroxide Interface Leading to Both Inner-and Outer-Sphere Surface Complexes Depending on Initial Concentrations
No full textInternational audienceDrying is ubiquitous. However, its influence on surface speciation has been seldom studied. Through an in situ Attenuated Total Reflection-Infrared (ATR-IR) spectroscopy analysis of the drying of molybdate solutions on a lepidocrocite particle film, the change in surface speciation is followed. No formation polymolybdates nor precipitate are observed upon drying at pH 8. An in situ washing of the dried solid/solution interface unveils the existence of surface outer-sphere and inner-sphere complexes. Decreasing the molybdate concentration highlights a saturation effect of the surface upon drying. Moreover, the careful analysis of substrate IR bands showed non-uniform drying which is an important insight to understand dehydration chemistry. The remaining molybdate ions at the surface as inner-sphere complexes are present as binuclear monodentate complexes stabilized by sodium
Multicomponent Synthesis on a Diiron Platform of Stable Ferrabenzenes with Promising Anticancer Activity
No full textInternational audienceAbstract Despite extensive research on metallabenzenes, ferrabenzenes have remained elusive, with only a single example reported to date, discovered accidentally. In this work, we present a reproducible, room‐temperature reaction on a diiron bis‐cyclopentadienyl platform, providing access to a class of four substituted ferrabenzenes ( 5a‐c ), stabilized by η 6 ‐coordination to a second iron fragment. This synthesis involves a one‐pot double C─C coupling of iminium, carbene (from a diazo compound), and carbon monoxide moieties, yielding ferra‐cyclohexadienone derivatives ( 4a‐c ), followed by O ‐alkylation with alkyl triflates. Experimental and computational studies enabled the proposal of a plausible reaction mechanism. Combined X‐ray crystallography, nuclear magnetic resonance (NMR), and computational data support the aromatic character of the ferrabenzene ring in compounds 5a‐c and, to a lesser extent, in their precursors 4a‐c . Complexes 4a‐c and 5a‐c were further characterized by IR spectroscopy, mass spectrometry, and IR spectroelectrochemistry. A selection of ferrabenzenes ( 5a , 5b , 5aEt ) revealed physicochemical properties suitable for biological applications, including permanent air stability, adequate aqueous solubility and stability, and balanced hydrophilic/lipophilic profile. These compounds exhibited potent cytotoxicity in vitro against three cancer cell lines, with 5aEt standing out for its pronounced activity, attributed to disruption of cell redox homeostasis, and marked selectivity compared to two noncancerous cell lines
Cotracking of Na+ and Br– Adsorption through Surface-Induced Quadrupolar Relaxation (SIQR): An Alternative to Zeta Potential Measurements for High Ionic Strengths (>0.1 M) and Nondispersed Liquid–Solid Mixtures
No full textInternational audienceWe compare traditional zeta potential measurements with a surface-induced quadrupolar relaxation-based approach to characterize the surface electric properties of oxides in aqueous media, particularly at high ionic strengths and solid contents where classical methods fail. Three oxide materials (two TiO2 and one α-alumina) were tested in 1 M NaBr aqueous solutions. Zeta potential measurements are expected to yield reliable isoelectric points (IEP) at moderate solid contents and up to 0.1 M ionic strengths. In contrast, NMR relaxation rate measurements, exploiting surface-induced quadrupolar relaxation (SIQR) of 81Br and 23Na, successfully provided IEP even at 1 M ionic strength and high solid content, although they are usually much more challenging under conditions suitable for conventional zeta potential measurements. Our NMR results correlated well with zeta potential trends at lower concentrations. Notably, TiO2_325 showed only acidic surface behavior, likely due to surface carbonate and/or phosphate groups. Surface acidity constants derived from NMR data allowed IEP estimation consistent with the literature values. This demonstrates that NMR relaxation rate measurements provide a robust alternative to zeta potential experiments under conditions where the latter are unreliable
Diagnosis, Characteristics, and Outcome of Selective Anti-polysaccharide Antibody Deficiencies In A Retrospective Cohort of 55 Adult Patients
No full textInternational audienceAbstract Selective anti-polysaccharide antibody deficiency (SPAD) predisposes to encapsulated bacterial infections. The diagnosis is challenging, and literature reports are scarce in adult patients, we therefore aim to describe the demographics, infectious complications, therapeutic strategies, and outcome of adult patients. We conducted a multicenter observational study involving 55 adult patients with SPAD. The median [interquartile range, IQR] age was 45 [36–60] years at diagnosis of SPAD, and 75% of patients were female. Twenty-one patients (38%) had a history of allergic and/or inflammatory disease, mainly asthma ( n = 12), and rheumatic diseases ( n = 6). Twelve patients (22%) were diagnosed after a single severe infection and 43 (78%) in a context of recurrent benign and/or severe infections. In the latter, the median time from first infections to diagnosis was 74.5 [33–167] months. Diagnostic delay was significantly higher in patients presenting with bronchiectasis than in those without (122 months [33–219.5] vs 24 months [14.5–74.5], p = 0.0042). In 22 patients (40%) receiving immunoglobulin replacement therapy (IgRT), the mean (min–max) frequency of antibiotic courses decreased from 7.9 (2–18) to 0.7 (0–2) courses per year ( p < 0.001) with a median follow-up period of 46 [27–73] months. Patients diagnosed after a single severe infection did not have any relapse during a median follow-up of 85 [80.5–104.5] months after diagnosis. Adult patients with SPAD have allergic or inflammatory disorders which could contribute to the diagnostic delay. IgRT is effective in preventing recurrent infections. Further studies are warranted to confirm if SPAD should be considered after a first unexplained severe bacterial infection
Impact of swift heavy ions irradiation on the microstructural and electrochemical properties of vanadium nitride thin films for micro-supercapacitors
No full textInternational audienceThe role of defects in pseudocapacitive electrode materials has been poorly investigated due to the poor control of their introduction in a pure phase material. Chemical defects are difficult to monitor although it seems they have an obvious influence on the electrochemical properties of the pristine material. The controlled introduction of defects should provide a more rational approach to understand their role in charge storage mechanisms. This study investigates the impact of swift heavy ions irradiation on the electrochemical properties of pseudocapacitive vanadium nitride (VN) thin films, a promising material for micro-supercapacitor electrodes. VN films were irradiated with 129 Xe 19+ ions at an energy of 70.95 MeV and a fluences up to 10 14 ions⋅cm -2 . The effects of irradiation were compared to those observed in a previous study using lower-energy As + ions (20-150 keV) [1]. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectrons spectroscopy (XPS) analyses revealed significant structural changes in the irradiated films, including densification, amorphization and oxidation of VN film surface. The electrochemical performance of the irradiated films was evaluated using cyclic voltammetry. While capacitance was reduced at low scan rates, a notable improvement was observed at high scan rates, which is attributed to the increase in electrical conductivity resulting from irradiation. This study deepens our understanding of the effects of high-energy ion irradiation on electrode materials and highlights the potential of this technique as a tool for guiding the development of more efficient energy storage devices
Phase Transformations in MOFs Induced by Adsorbate Exchange
No full textInternational audienceDeformation of nanoporous materials induced by gas adsorption is a ubiquitous phenomenon that plays important role in adsorption separations, gas and energy storage, nanosensors, actuators, secondary gas recovery and carbon dioxide sequestration in coal and shale reservoirs. One of the most prominent examples is the breathing phase transformation in metal-organic frameworks (MOF) associated with significant volume variations upon adsorption and desorption of guest molecules. Here, we present a theoretical framework for quantitative description of the breathing transitions upon adsorption of binary mixtures drawing on the practically important example of the displacement of methane by carbon dioxide in MIL-53 MOF. The proposed approach, that is based on the concept of the adsorption stress, reveals the mechanisms of the framework deformation and breathing phase transformation between the large pore (LP) and narrow pore (NP) conformations. We show that when the pure CH4 adsorption proceeds entirely in the LP phase, even a small addition of CO2 makes the LP phase unstable and triggers conversion to the NP phase, and the reverse NP-LP transformation occurs upon further displacement of CH4 by CO2. The theoretical predictions of adsorption and strain isotherms are confirmed by an agreement with the literature experimental studies performed on MIL-53 (Al) at different CH4-CO2 mixture pressures and temperatures. The proposed general approach is applicable to other flexible nanoporous structure and gas mixtures