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Binder‐free self‐standing hard carbon electrodes graphite‐coated by PE‐CVD to boost the efficiency of Na‐ion batteries
No full textInternational audienceThis work explores the use of plasma-enhanced chemical vapor deposition (PE-CVD) to deposit a C-coating on binder-free, selfstanding electrodes (SSEs). The C-coating consists of a nanocrystalline graphite thin film with crystalline domains measuring %14 nm. Regardless of the fabrication pyrolysis temperature of SSE, an increase in crystallite size and a reduction in interlayer space and defects is observed after C-coating and post-treatment at 1500 °C. Pyrolysis of the SSE at 900 °C induce better coverage with the nanographitic layer during PE-CVD , but prevents the development of closed pores during post-treatment at 1500 °C. In contrast, a large number of closed pores form when the SSE is pyrolyzed at 1500 °C. However, no difference in performance is observed between the C-coated SSE pyrolyzed at 900 and 1500 °C and post-annealed at 1500 °C, therefore, lower temperature can be advantageously used for the pyrolysis step. Nevertheless, post-treatment at 1500 °C is necessary to enhance performance. For both materials, the graphite coating minimized the undesirable reactions with the electrolyte, leading to more stable and conductive solid electrolyte interphase, which improves iCE (from 91.0% to 92.5%). A high reversible capacity of 320 mAh g À1 is also obtained, and the higher coating's conductivity is beneficial for rate capability
Low-temperature synthesis of mixed valence gold halide perovskites and exploration of their photoluminescence properties
No full textInternational audienceWe describe the structural and chemical properties of gold halide perovskites (Cs 2 Au I Au III X 6 , X = I, Br, Cl) synthesized at low temperatures. Photoluminescence shows bandgaps (1–1.4 eV), highlighting their potential for optoelectronic devices
Sensing diclofenac with DNA aptamers: an atomistic picture from molecular modelling
No full textInternational audienceWe developed a combined docking and classical molecular dynamics approach to study the origin of the sensitivity of an aptamer engineered to target diclofenac. Our simulations indicate that the sensitivity is associated with the folding substructure
In Situ High-Resolution Optical Microscopy Survey of the Initial Reactivity of Multiphase ZnAlMgSi Coating on Steel
No full textInternational audienceThe initial reactivity of a multiphase ZnAlMgSi coating with an Al content > 30 wt.% was studied by in situ reflective microscopy under alternating applied potentials +50 mV/−50 mV vs. open-circuit potential in 5 wt.% NaCl and 5 wt.% Na2SO4 aqueous solutions. In both environments, galvanic coupling between different coating phases and the anodic behavior decreased in the order binary ZnAl > binary Zn/Zn2Mg > Zn2Mg > Al(Zn); dendrites were evidenced for the coating exposed alone as well as in galvanic coupling with steel. Contrary to the observations known for Zn-rich ZnAlMg coatings, pure Zn2Mg was less reactive than the pure ZnAl phase, underlining the importance of the microstructure for reactivity. Si-needles were systematically cathodic, and Al(Zn) dendrites have shown cathodic behavior in some couplings. In the configuration of coupling with steel, corrosion started at the interfaces “binary ZnAl/steel substrate” or “binary ZnAl/Si particle”. The distribution and nature of the corrosion products formed during the experiment were assessed using X-ray microanalysis in scanning electron microscopy and confocal Raman microscopy. In the sulfate environment, a homogenous and stable corrosion product layer formed from the first steps of the degradation; this was in contrast to the chloride environment, where no surface film formed on the dendrites
Tunable Poly(butylene oxide)-stat-polyglycidol Copolymers for Microfluidic Assisted Nanoprecipitation Nanoparticle Design
No full textThe self-assembly of amphiphilic copolymers into well-defined nanoparticles depends on the interplay between polymer composition, solvent exchange kinetics, and processing conditions. In this study, we explore the anionic ring-opening copolymerization of 1,2-epoxybutane and ethoxyethyl glycidyl ether (EEGE) followed by a deprotection step to synthesize poly(butylene oxide)-stat-polyglycidol (PBO-stat-PG) copolymers with tunable amphiphilicity. Reactivity ratio analysis confirmed the formation of a gradient microstructure, with preferential incorporation of EEGE in the early polymerization stages. The copolymers were subsequently processed via bulk and microfluidic-assisted nanoprecipitation, and their self-assembly behavior was systematically investigated. Bulk nanoprecipitation demonstrated that the hydrophilic/hydrophobic balance plays a critical role in controlling nanoparticle formation, stability, and size distribution. Copolymers with 85/15 and 80/20 (BO/G) ratios exhibited the most favorable properties, leading to small, stable, and uniform nanoparticles, whereas excessive G content (≥70%) disrupted self-assembly, inducing irregular morphologies. To enhance nanoparticle homogeneity and minimize aggregation, hydrodynamic-flow-focusing (HFF) microfluidics with a fixed flow rate ratio and controlled mixing conditions were implemented. The highly reproducible microfluidic process enabled finer control over solvent exchange dynamics, leading to smaller and more monodisperse nanoparticles compared to bulk precipitation. The rapid solvent diffusion in the HFF system promoted fast nucleation, effectively reducing polydispersity and ensuring superior colloidal stability. This study establishes a direct correlation between copolymer composition, nanoprecipitation methods, and nanoparticle characteristics, providing a scalable and reproducible strategy for the design of well-defined amphiphilic nanostructures with a controlled hydrophilic/hydrophobic ratio. The optimized PBO-stat-PG nanoparticles present promising potential for biomedical applications, particularly in drug delivery, where controlled self-assembly and tailored hydrophilicity are crucial for performance
Fine-structure resolution of SiV color centers in CVD nanodiamonds via HPHT annealing
No full textInternational audienceDiamonds and nanodiamonds (NDs) containing quantum color centers, such as nitrogen-vacancy (NV) centers, have been widely studied in recent years for their promising applications across various fields, including cryptography and telecommunications, medical sciences, and sensing. In the context of sensing, recent studies on color centers such as silicon-vacancy (SiV) and germanium-vacancy (GeV) centers have shown great potential for measuring physical quantities like magnetic fields, temperature, and strain. This is due to their intense zero-phonon line (ZPL) optical signal, which accounts for about 80% of their total luminescence and is characteristic of group-IV color centers (G4V) [1]. In our recent papers, we demonstrated that as-grown CVD NDs containing SiV and GeV centers, featuring luminescent ZPLs and excellent photostability at room temperature, can function effectively as nanosensors under high stress and pressure conditions (up to 180 GPa) [2, 3]. To advance our research, in this work we investigate the optical properties of SiV centers in as-grown NDs at cryogenic temperatures. For SiV centers, which have spin 1/2, the fine structure should become accessible through the Jahn-Teller effect, which lifts the degeneracy at cryogenic temperatures (< 20 K). However, experiments on our as-grown NDs reveal significant spectral broadening even at around 9 K, caused by lattice strain, which prevents access to the optically addressable electronic spin states of the SiV center. To overcome this limitation, we propose an original post-treatment involving high-pressure and high-temperature (HPHT) annealing using the Paris–Edinburgh press. This approach allows the gradual increase of temperature and pressure allows for control over the undesired diamond-to-graphite phase transition. HPHT annealing experiments were conducted at the PSICHE beamline of Synchrotron SOLEIL [4], where X-ray diffraction and tomography analyses enabled precise monitoring of P-T parameters and made it possible for the first time to access single fine-structure transitions of SiV centers in such NDs.References[1] C. Bradac, et al., Nat. Commun. 10, 1 (2019). [2] B. Vindolet, et al., Phys. Rev. B 106, 214109 (2022).[3] M. De Feudis, et al., Adv. Mater. Interfaces 7, 1901408 (2019).[4] L. Henry et al., J. Synchrotron Rad. 29 (2022)
Metals recovery by supercritical CO2 processes: a focus on Li-ion battery metals extraction
No full textInternational audienceAs the demand for lithium-ion batteries (LIBs) continues to rise, recycling becomes essential to ensure a sustainable supply of critical raw materials while mitigating environmental impact. The European Union (EU) has set ambitious LIB recycling targets, emphasizing the need for innovative and cost-effective solutions. Although pyrometallurgical and hydrometallurgical processes currently dominate, emerging technologies such as supercritical carbon dioxide (scCO2)-based extraction offer promising alternatives. Continued research and investment in LIB recycling infrastructures are crucial to supporting the energy transition and securing raw material independence in the coming decades. This review begins with a general overview of LIBs, their end-of-life processes, and the market and geopolitical context of LIBs and electric vehicles (EVs). It then briefly presents the interactions between CO₂ and solutes, which play a key role in determining the solubility of substances in scCO₂. In the following, the current and potential uses of scCO₂ in the field of LIBs are reviewed, with particular attention to the extraction of metal, which represents a crucial and promising application of this green technology. This focus highlights the unique features and specific challenges associated with metal recovery using scCO₂. The main parameters influencing metal extraction, such as pressure, temperature, co-solvents, and complexing agents, are discussed. Finally, recent advances in the extraction of the metals contained in cathode active materials using scCO₂ are presented
Understanding Multi‐Stage Charge Storage on Nanoporous Carbons in Zn‐Ion Hybrid Capacitors
No full textInternational audienceAbstract Zn‐ion hybrid capacitors (ZIHCs) are promising high‐power energy storage devices. However, the underlying charge storage mechanisms, especially the influence of proton storage, remain poorly understood. Herein, the model porous carbons are synthesized having similar specific surface areas (SSAs) and surface chemistry but different pore sizes. They highlight the role of supermicropores and small mesopores (0.86–4 nm) enabling a high capacity of 198 mAh g −1 (capacitance of 446 F g −1 ), while larger mesopores (4–13 nm) significantly enhance cycling stability, exceeding 0.6 million cycles. Electrochemical studies, including EQCM analysis, reveal a 4‐stage charge‐storage process under cathodic polarization, comprising adsorption and desolvation of hydrated Zn 2+ ions, followed by water reduction, catalyzed by Zn 2+ , and formation of H ad . The rising pH leads to the formation of insoluble zinc hydroxysulfate hydrates (ZHS). Depending on the pore architecture, the precipitation of ZHS has different effects on the overall stability of cycling. The study overall: (i) presents a simplified method for pore control in carbon synthesis; (ii) discuss the effect of pore size on charge storage and cycling stability in respect of ZHS formation; (iii) sheds light on the charge storage mechanism indicating the important contribution of cation effect known from electrocatalysis on faradaic charge storage mechanism
Tellurium-Terminated MXene Synthesis via One-Step Tellurium Etching
No full textInternational audienceAbstract With the rapid development of two-dimensional MXene materials, numerous preparation strategies have been proposed to enhance synthesis efficiency, mitigate environmental impact, and enable scalability for large-scale production. The compound etching approach, which relies on cationic oxidation of the A element of MAX phase precursors while anions typically adsorb onto MXene surfaces as functional groups, remains the main prevalent strategy. By contrast, synthesis methodologies utilizing elemental etching agents have been rarely reported. Here, we report a new elemental tellurium (Te)-based etching strategy for the preparation of MXene materials with tunable surface chemistry. By selectively removing the A-site element in MAX phases using Te, our approach avoids the use of toxic fluoride reagents and achieves tellurium-terminated surface groups that significantly enhance sodium storage performance. Experimental results show that Te-etched MXene delivers substantially higher capacities (exceeding 50% improvement over conventionally etched MXene) with superior rate capability, retaining high capacity at large current densities and demonstrating over 90% capacity retention after 1000 cycles. This innovative synthetic strategy provides new insight into controllable MXene preparation and performance optimization, while the as-obtained materials hold promises for high-performance sodium-ion batteries and other energy storage systems
Tunable membrane-less dielectrophoretic microseparation by crossing interdigitated electrodes
No full textInternational audienceAbstract Separation is a crucial step in the analysis of living microparticles. In particular, the selective microseparation of phytoplankton by size and shape remains an open problem, even though these criteria are essential for their gender and/or species identification. However, microseparation devices necessitate physical membranes which complicate their fabrication, reduce the sample flow rate and can cause unwanted particle clogging. Recent advances in microfabrication such as High Precision Capillary Printing allow to rapidly build electrode patterns over wide areas. In this study, we introduce a new concept of membrane-less dielectrophoretic (DEP) microseparation suitable for large scale microfabrication processes. The proposed design involves two pairs of interdigitated electrodes at the top and the bottom of a microfluidic channel. We use finite-element calculations to analyse how the DEP force field throughout the channel, as well as the resulting trajectories of particles depend on the geometry of the system, on the physical properties of the particles and suspending medium and on the imposed voltage and flow rates. We numerically show that in the negative DEP regime, particles are focused in the channel mid-planes and that virtual pillars array leads either to their trapping at specific stagnation points, or to their focusing along specific lines, depending on their DEP mobility. Simulations allow to understand how particles can be captured and to quantify the particle separation conditions by introducing a critical DEP mobility. We further illustrate the principle of membrane-less DEP microseparation using the proposed setup, by considering the separation of a binary mixture of polystyrene particles with different diameters, and validate it experimentally