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Correction to “AMOEBA Polarizable Force Field for Molecular Dynamics Simulations of Glyme Solvents”
No full textInternational audienc
Individual solid-state nuclear spin qubits with coherence exceeding seconds
No full textInternational audienceThe ability to coherently control and read out qubits with long coherence times in a scalable system is a crucial requirement for any quantum processor. Nuclear spins in the solid state have shown great promise as long-lived qubits [1-3]. Control and readout of individual nuclear spin qubit registers has made major progress in the recent years using individual electron spin ancilla qubits addressed either electrically [4-6] or optically [7-11]. Here, we present a new platform for quantum information processing, consisting of 183 W nuclear spin qubits adjacent to an Er 3+ impurity in a CaWO4 crystal, interfaced via a superconducting resonator and detected using a microwave photon counter at 10 mK. We study two nuclear spin qubits with T * 2 of 0.8(2) s and 1.2(3) s and T2 of 3.4(4) s and 4.4(6) s, respectively. We demonstrate single-shot quantum non-demolition readout of each nuclear spin qubit using the Er 3+ spin as an ancilla. We introduce a new scheme for all-microwave single-and two-qubit gates, based on stimulated Raman driving of the coupled electron-nuclear spin system. We realize single-and two-qubit gates on a timescale of a few milliseconds, and prepare a decoherence-protected Bell state with a fidelity of 0.79 and T * 2 of 1.7(2) s. Our results are a proof-of-principle demonstrating the potential of solid-state nuclear spin qubits as a promising platform for quantum information processing. With the potential to scale to tens or hundreds of qubits, this platform has prospects for the development of scalable quantum processors with long-lived qubit
Polymères magnétiques à empreinte moléculaire en synthèse organique : du déroulement standard au dédoublement cinétique dynamique
No full textDynamic kinetic resolution (DKR) has emerged as a powerful approach for asymmetric synthesis, allowing the efficient conversion of a racemic mixture of a compound, easier to obtain, into a unique enantiomer. This significant improvement of standard kinetic resolution (KR), limited with a maximum of 50% conversion, proceeds through the selective transformation of one enantiomer by organometallic catalysis or biocatalysis and the racemization of the remaining one which can be converted in turn. The last few years have witnessed great improvements in the field of Molecularly Imprinted Polymers (MIPs), highly cross-linked macromolecular architectures capable of selective molecular recognition. MIPs exhibit excellent binding properties with affinity and selectivity often comparable to those of antibodies. Their combination with magnetic nanoparticles (Fe2O3) has conferred them new separation properties using a magnet. We propose here to design a new DKR system that simply combines enantiomer recognition by the magnetic MIP nanoparticles and racemization methods according to the substrate used. In other words, one enantiomer is trapped by magnetic MIP nanoparticles, the other one is racemized allowing the progressive shift of the equilibrium in the direction of formation of a single enantiomer. The polymer can then release the enantiomerically enriched product. Proofs of concept have already been established for standard KR, and then in the DKR. Extension to other examples of asymmetric resolution will be considered on the basis of our initial studies.La résolution cinétique dynamique est apparue comme une approche puissante pour la synthèse asymétrique, permettant la conversion efficace d'un mélange racémique d'un composé, plus facile à obtenir, en un énantiomère unique. Cette amélioration significative de la résolution cinétique standard, limitée à un maximum de 50% de conversion, passe par la transformation sélective d'un énantiomère par catalyse organométallique ou biocatalyse et la racémisation de l'autre qui peut être converti à son tour. Ces dernières années ont vu de grandes améliorations dans le domaine des polymères à empreinte moléculaire, des architectures macromoléculaires hautement réticulées capables de reconnaissance moléculaire sélective. Les MIP présentent d'excellentes propriétés de liaison avec une affinité et une sélectivité souvent comparables à celles des anticorps. Leur association avec des nanoparticules magnétiques (Fe2O3) leur a conféré de nouvelles propriétés de séparation par aimant. Nous proposons ici de concevoir un nouveau système DKR qui combine simplement la reconnaissance des énantiomères par les nanoparticules magnétiques MIP et les méthodes de racémisation selon le substrat utilisé. En d'autres termes, un énantiomère est piégé par des nanoparticules magnétiques de MIP, l'autre est racémisé permettant le déplacement progressif de l'équilibre dans le sens de la formation d'un seul énantiomère. Le polymère peut alors libérer le produit énantiomériquement enrichi. Des preuves de concept ont déjà été établies pour le KR standard, puis dans le DKR. L'extension à d'autres exemples de résolution asymétrique sera envisagée sur la base de nos premières études
Dual role of marine bacteria Pseudoalteromonas NCIMB 2021 in corrosion of mild steel in artificial seawater
No full textInternational audienceThe modifications in corrosion resistance and local surface modifications caused by the colonization of Pseudoalteromonas NCIMB 2021 bacteria on mild steel in artificial seawater were investigated using electrochemical techniques, Scanning Electron Microscopy and Time-of-Flight Secondary Ion Mass Spectrometry. A dual role of these bacteria on corrosion resistance was observed and characterized. While an improvement in corrosion resistance was obtained in the presence of the bacteria, the colonized surface is locally modified and once the bacteria are removed, the previously colonized areas are exposed, leading to enhanced localized corrosion.</div
Tracking Hg2+ adsorption by reduced graphene oxide in continuous flow by in situ techniques
No full textInternational audienceMercury pollution poses severe risks to environmental and public health due to its high toxicity and persistence. The use of physical adsorbents for heavy metal cation uptake is a straightforward solution for many applications, but a better fundamental understanding of the mechanism is crucial for rational improvement. We have investigated the adsorption of mercury ions on reduced graphene oxide (rGO) in real time by coupling continuous flow setups with in situ analytical techniques: X-ray absorption spectroscopy (XAS) and electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). The microfluidic setup provided a practical and efficient platform for mimicking realistic conditions, requiring minimal sample volumes and enabling continuous flow analysis, while the in situ XAS brought detailed atomic and electronic structural information, allowing for following changes in mercury ion coordination as adsorption proceeded. Similarly, EQCM-D followed the mass changes and viscoelastic properties of the rGO layer under dynamic flow conditions upon adsorption. The approach distinguished chemisorbed from physisorbed mercury cations, revealing a yet undescribed transition between the two forms. This enables a better understanding of the adsorption mechanisms and highlights the benefits of coupling microfluidic systems with advanced in situ techniques
Advanced CIGS-mesoporous TiO2 hybrid photocathode functionalized with cobalt quaterpyridine for solar-driven CO₂ reduction
No full textInternational audienceHybrid photocathodes that integrate inorganic semiconductors with molecular catalysts offer a promising strategy for photoelectrochemical CO2 reduction into value-added products. In this work, we present the design and characterization of a high-performance photocathode based on copper indium gallium sulfide (CIGSu), functionalized with a cobalt quaterpyridine (CoQPy) molecular catalyst. The device features a thin (5 nm) TiO2 protective layer deposited by atomic layer deposition (ALD) on CIGSu/CdS, followed by a mesoporous TiO2 layer formed under mild conditions using UV curing and low-temperature annealing (150°C). The mesoporous structure enables high CoQPy loading through chemisorption via phosphonic acid anchoring groups. Under simulated sunlight, the optimized photocathode delivers a photocurrent density of ca. 2 mA/cm² with 95% CO selectivity in carbonate buffer, double the 2 performance of systems using low-porosity TiO2. This work marks progress toward efficient, molecularly functionalized photocathodes for aqueous CO2 reduction
Unveiling capacity limitations of MnO2 in rechargeable Zn chemistry
No full textInternational audienceAqueous Zn–MnO2 batteries with mildly acidic electrolytes deliver attractive experimental capacities, however the underlying mechanisms remain elusive, particularly regarding the interactions of Zn2+ and H+ with MnO2, as well as the formation of Mn2+ and Zn4SO4(OH)6·xH2O (ZSH). Although these products are compatible with a two-electron dissolution mechanism, the observed first-discharge capacity is limited to approximately 300 mA h g−1 MnO2, close to that of a one-electron reaction. To address this contradiction, commonly used α-MnO2 nanowires were chosen as cathode material and investigated by a systematic multimodal and multiscale approach under operando or ex situ conditions to analyze the processes that occur during the first discharge. MnO2 dissolution into Mn2+ and ZSH precipitation were confirmed, and the formation of a disordered phase at the nanowire surface with the accumulation of Mn(III) was detected. An in-depth analysis indicates that such Mn(III) species correspond to protonated corner-sharing MnO2 octahedra, which, unlike the edge-sharing ones, are hindered from undergoing disproportion, limiting the MnO2 dissolution and explaining the reduced capacity. This comprehensive mechanistic understanding opens new pathways for the selection of the most appropriate MnO2 phases and the optimization of electrodes to improve the performance of aqueous Zn–MnO2 battery systems
Intracellular Monitoring of Luminescent Ag<sub>2</sub>S Nanoparticles in Fibroblasts
No full textInternational audienceInteraction between nanoparticles (NPs) and cells is a key concern in nanotechnology-based biomedical applications. This study investigates cytocompatible silver sulfide (Ag2S) quantum dots (QDs), which emit strongly in the second near-infrared (NIR II) region, for their potential in image-guided therapies. Since cellular microenvironments contain acidic pH, hydrogen peroxide (H2O2), and reactive oxygen species (ROS), which can affect luminescence, Ag2S NPs (AS NPs) coated with three ligands: DTDTPA (dithiolated diethylene triamine pentaacetic acid), 11MUA (11 mercaptoundecanoic acid), and PEG (polyethylene glycol) were studied in fibroblast cells over 9 days. Long term photoluminescence (PL) tracking showed distinct behavior. AS DTDTPA and AS 11MUA exhibited increasing uptake but decreasing PL, while AS PEG showed both enhanced PL and uptake over time. No significant changes in NP size or structure explained the PL differences. Exposure to H2O2 revealed that AS DTDTPA and AS 11MUA lost PL due to oxidation or shell detachment, reducing surface passivation. In contrast, AS PEG showed intensified PL, possibly from removal of metallic silver and increased PL lifetime. These results highlight time dependent PL changes in cellular and oxidative environments. DTDTPA and PEG coatings may act as ROS scavenger and promoter, respectively, while enabling NIR II imaging and offering insights into NP design for stable optical tracking and therapeutic use.</p
Deciphering the phosphorylation of chitosan through complementary <sup>1</sup>H and <sup>31</sup>P{<sup>1</sup>H} DOSY NMR
No full textInternational audienceChemical modification of chitosan through phosphorylation has gained significant attention for expanding its applications. However, confirming whether phosphorylating agents form covalent bonds with the chitosan backbone or remain as non-covalently associated species has remained challenging using conventional analytical techniques. The diffusion-ordered spectroscopy (DOSY) NMR of the complementary probes 1H and 31P nuclei was used for distinguishing among the results of three phosphorylating agents: phosphoric acid, phosphorous acid, and dimethyl phosphite. While conventional FTIR and common 1D/2D NMR spectroscopy experiments confirmed the presence of phosphorus-containing groups in all samples, DOSY NMR analysis revealed critical differences in molecular behavior. Chitosan backbone protons exhibited consistently low self-diffusion coefficients (4-9 × 10-12 m2/s) across all samples. Phosphorus species in samples treated with phosphoric acid and phosphorous acid displayed significantly higher diffusion coefficients (394-548 × 10-12 m2/s), indicating noncovalent association and freely diffusing in solution. In contrast, dimethyl phosphite treatment produced a 31P resonance at 30.3 ppm with a diffusion coefficient of 11 × 10-12 m2/s, closely matching the chitosan backbone protons values and providing strong evidence for covalent phosphorylation. This work establishes DOSY NMR of complementary probes as a reliable, quick, and simple method for distinguishing between covalent or noncovalent modification of biopolymers
Investigation of the adsorption and photodegradation of methylene blue in Fe-substituted methyl imogolite under UV-visible light
No full textInternational audienceImogolite, of formula (OH)₃Al₂O₃SiOH, is a nanotube composed of a curved gibbsite layer connected to isolated orthosilicate tetrahedrons with Si-OH groups pointing inward toward the tube cavity. This material has garnered significant attention due to its high water dispersibility, large specific surface area and ease of modification making it a promising candidate for applications such as adsorption, catalysis and gas storage. Recent studies have revealed a permanent polarization, with positive and negative charges spontaneously accumulating on the outer and inner tube walls1, respectively. This polarization facilitates electron-hole separation, which is critical for photocatalytic applications, driving our interest in using imogolite for pollutant photodegradation. However, classical aluminosilicate imogolite presents two key limitations: (i) the strong polarity of internal Si-OH groups hinders organic adsorption, and ii) its 5.4 eV bandgap restricts activation to UV light. To overcome these challenges, we synthesized methylated imogolite in which internal OH groups are replaced by CH3 hydrophobic functions and we substituted part of aluminum atoms with iron, varying the Al:Fe molar ratios of 20 to 40, which has been shown to decrease the bandgap2. Using methylene blue as a model organic pollutant, we investigated its adsorption within the nanotubes through in-situ infrared spectroscopy and isothermal adsorption curves. A notable shift of the Si-CH₃ IR band confirmed the adsorption of methylene blue inside the nanotubes.We then analyzed the photodegradation kinetics of methylene blue using GC and UV-Vis spectroscopy under different pH and concentration conditions. The iron-substituted imogolite demonstrated significantly enhanced degradation rates, with CO₂ production after 24 hours of light exposure being 4.5 times higher than that of the unsubstituted imogolite.1. E Poli et al., J. Phys: Condens. Matter, 2016, 28, 074003.2. E. Shafia et al., Micropor. Mesopor. Mat., 2016, 224, 229