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Retransmitting Messages on Social Media in Disasters: Effects of Communication Tool Capabilities
No full textInternational audienceRetransmitted messages online can have profound effects on disaster response; however, existing literature provides an incomplete account of why messages are retransmitted on social media in disasters. In particular, there is a need to theorize the capabilities of the communication tools used for sending messages, because nowadays people can send messages online via different tools. This paper aims to theorize and explain how the capabilities of communication tools affect message retransmission by affecting the generation of message characteristics. To test our account, we collected and coded Twitter data from three disasters, and employed five logistic regressions to test our hypotheses. Our results confirm our expectations that compared to messages sent from desktops, messages sent from mobile devices are less likely to be helpful and verifiable, but are more likely to have visual attachments and expressions of anxiety
Improving the investigation of defects properties through temperature dependent Modulated Photoluminescence
No full textInternational audienceModulated Photoluminescence (MPL) has established itself as a key tool for defect characterization in semiconductor materials, as highlighted in Ref. { , }. Previous studies on high-frequency MPL have shown that the frequency dependence of the MPL phase can either be monotonic or exhibit a local minimum, forming a V-shape. The emergence of this feature in MPL spectra results from charge carrier capture and re-emission processes. In { }, simulations were conducted to study the impact of excitation power on the phase diagram, emphasizing the importance of multi-power characterization for identifying specific defect signatures.In this article, we focus on the temperature dependence of MPL phase Bode diagrams exhibiting a V-shape, which allowed us to extract three key defect parameters: the energy level position, defect density, and carrier capture cross-section of minority carriers. However, it is crucial to distinguish between V-shapes related to emission processes and those associated with carrier capture. Our study specifically addresses the latter through the analysis of experimental results obtained under realistic conditions.The analysis of the local phase shift minimum as a function of temperature enabled us to identify the essential defect properties. At low injection levels, the V-shape is mainly attributed to the re-emission of minority carriers by defects, a phenomenon particularly pronounced at high temperatures. In contrast, at high injection levels, other mechanisms influence the appearance of the V-shape, especially at low temperatures. These findings provide new insights into defect dynamics and their temperature-dependent behavior, offering a solid framework for interpreting experimental data in photovoltaic materials.From an experimental perspective, MPL measurements performed on multiple samples yielded significant results. For instance, in p-doped CIGS material, a defect located 0.13 eV below the conduction band was identified, aligning with literature data { }. Similarly, measurements on AlGaAs samples revealed a defect-relatedn activation energy of 0.11 eV. Preliminary analyses of additional samples also suggest the presence of phase shifts associated with multiple defects. Further investigations are planned to better characterize these defects and assess their combined impact on material performance
From α-pinene feedstock to value-added products: scalable and recyclable copper( ii ) catalysts for allylic oxidation
No full textInternational audienceα-Pinene is one of the most abundant and low-cost terpenes that can be used as an attractive and renewable feedstock for generating added-value products via allylic oxidation. Aiming to develop more sustainable catalytic materials for the functionalization of terpenes, in this work two new 2D coordination polymers (CPs), {[Cu2(μ-pdc)(μ3-pdc)(H2mdea)(H2O)2]·2H2O}n (Cu-mdea) and {[Cu2(μ-pdc)(μ3-pdc)(H3tipa)(H2O)2]·4H2O}n (Cu-tipa) {H2pdc = 3,4-pyridinedicarboxylic acid, H2mdea = N-methyldiethanolamine and H3tipa = triisopropanolamine} were synthesized via a self-assembly method under green conditions. These compounds were obtained from low-cost and environmentally tolerable reagents, and their scale-up process was also optimized in a ‘crystalline reactor’ from the milligram to gram scale. The obtained CPs were applied as efficient and recyclable heterogeneous catalysts for the mild oxidation of α-pinene. The effects of various reaction parameters, temperature-dependent and mechanistic features, and catalyst stability were investigated in detail, leading to up to 93% of α-pinene conversion with good yields of 4-tert-butylperoxy-2-pinene (42%) and verbenone (25%) as main oxidation products. This study extends the application of α-pinene as a renewable feedstock for the synthesis of value-added oxidation products using recyclable heterogeneous catalysts and mild reaction conditions
Molecular Catalyst Enables CO2 Electroreduction at 650 mA/cm2 CO Partial Current Density
No full textInternational audienceThe electrochemical reduction of CO2 to CO using renewable electricity offers a compelling pathway for greenhouse gas recycling. The two-electron, two-proton process is particularly attractive due to its operational simplicity and scalability, with copper-and silver-based nanomaterials being the most widely studied catalysts as the field approaches industrial maturity. However, achieving the necessary efficiency and stability for practical application remains a significant challenge. Recently, molecular catalysts immobilized on conductive surfaces with carbon-based inks have emerged as highly tunable hybrid systems capable of remarkable selectivity. In this work, we report that a straightforward cobalt phthalocyanine complex, simply modified with a single trimethylammonium group, delivers outstanding CO2-to-CO conversion rates and selectivity-reaching a Faradaic efficiency of 93% at a total current density of 700 mA/cm 2 (jCO 650 mA/cm 2 ) at neutral pH. Notably, CO selectivity above 90% was sustained for over 42 hours at 150 mA/cm 2 , illustrating the potential of simply designed molecular catalysts for large scale applications
Surrogate Modeling of Lithium‐Ion Battery Electrode Manufacturing by Combining Physics‐Based Simulation and Deep Learning
No full textInternational audienceOptimizing the manufacturing process of Lithium‐Ion Batteries (LIB. Finding efficient approaches that accelerate and replace time‐consuming, material scrap‐expensive trials‐and‐error optimization methods is a key area of research. This work presents a comprehensive LIB electrode manufacturing framework that combines physics‐based simulations with deep learning. This framework efficiently simulates the manufacturing process of LIB electrodes as a function of their formulation. This framework takes the form of a surrogate manufacturing model able to predict the impact of manufacturing parameters on the electrode microstructure and properties. The model is based on a regressor‐inspired variational autoencoder method. The analysis of the data and the predicted electrode functional metrics demonstrates the consistency of the approach with an electrode manufacturing model developed on the basis of physics. The reported framework holds significant promise in paving near real time optimization of LIB electrode manufacturing and supporting the optimization of battery cell design in pilot lines
Rapid C-S+ Bond Cleavage via 1,6-Benzyl Elimination for Traceless Modification of Bioactive Peptides
No full textInternational audiencePeptides and proteins are invaluable therapeutics and biological tools, where stimuli-responsive and fully reversible conjugation chemistry is essential to advances in drug delivery systems and chemical biology. However, methods that allow precise conjugation, efficient regulation of biochemical functions, and customized recovery of parent peptides remain underdeveloped. Here, we introduce a straightforward yet powerful reversible chemical strategy targeting methionine (Met), a widespread yet low abundance amino acid in peptides and proteins. By selectively alkylating Met-containing peptides under weakly acidic conditions, we form a stable C–S+ bond, which can be cleaved rapidly via 1,6-benzyl elimination upon stimulus. This versatile chemistry is demonstrated in diverse applications: (i) PEGylated prodrugs of antimicrobial peptides with reduced toxicity and enhanced enzymatic stability, (ii) esterase-responsive peptide–peptide inhibitor conjugates (PPICs) with improved cell membrane permeability and therapeutic effects, (iii) reversibly stapled peptides with switchable conformations for targeting both intra- and extracellular sites, and (iv) bioorthogonal control of C-terminal Met-caged neuropeptides. Overall, this work describes, for the first time, a valuable traceless modification strategy that promises to greatly benefit the peptide community and advance the field of chemical biology
Coupling differential voltage analysis and distribution of relaxation times II: Evaluating the impact of Si content in the degradation of coated NMC811/SiGr cells
No full textInternational audienceThe degradation of coated LiNi0.8Mn0.1Co0.1O2 (NMC811) cells with Silicon-Graphite (SiGr) composite anodes containing varying Si content is investigated using Differential Voltage Analysis (DVA), Incremental Capacity Analysis (ICA) and Distribution of Relaxation Times (DRT). ICA distinguishes Si from Gr specific degradation processes. It is observed an incomplete delithiation-related Si capacity loss in cells with 7 % and 11 % Si, which increases during early cycles and later stabilizes. Such behavior is not the reported permanent Si loss of active material, as the capacity of moderately and highly lithiated Si remains unchanged. Instead, a sudden rise in resistance at low states of charge is revealed. That is likely due to Si particle-particle contact loss during shrinkage, after particles are accommodated by a grown Solid Electrolyte Interphase (SEI) matrix and due to SEI cracks closure when particles contract. Data suggest a minimal threshold amount of Si may be necessary to trigger it, explained by Gr acting as electrical-contact keeper to Si particles. The proposed coupling of techniques made observable Si-driven effects in NMC811/SiGr cells, capacity fading primarily due to loss of lithium inventory and resistance increase dominated by the Si at lower voltages and by the NMC811 at medium and higher voltages
Substitution of Iron for Vanadium in Phosphate Fluoride Positive Electrode Materials for Na-Ion Batteries
No full textInternational audienceThe phosphate fluoride Na3V2(PO4)2F3 (NVPF) is an excellent positive electrode material for Na-ion batteries. It has already been researched extensively and can deliver a high specific energy and especially impressive power capabilities, which make it suitable for application in power tools. However, concerns exist about the widespread adoption of vanadium-based cathodes at a large scale. The phosphate fluoride framework can accommodate other metal ions, including the less expensive and abundant iron. However, the resulting compound performs poorly as an electrode material in Na-ion batteries. In this work, a substitutional series replacing vanadium with iron according to Na3V2−xFex(PO4)2F3 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 2.0) is successfully synthesized through a solid–state reaction. The crystal structure of all samples is investigated using high-resolution synchrotron X-ray diffraction (sXRD), showing that all of them crystallize in the orthorhombic Amam space group, with the difference between a and b unit cell parameters, however, decreasing with increasing Fe content. Neutron diffraction is used to reveal the distribution of vanadium and iron in the transition metal sites, while Mössbauer and Raman spectroscopy confirm the presence of high-spin FeIII, together with trivalent vanadium ions. Computational results based on density functional theory provide further insights on the voltage range of the (de)sodiation reaction of the x = 0.0, 1.0, and 2.0 compounds. The investigated materials are tested electrochemically in Na half cells. When the lower cutoff voltage allows for Fe reduction, all materials show significant reversible capacities in excess of ∼90 mA h g–1 (with the exception of the pure Fe compound). In the same voltage window as NVPF, the x = 0.2 sample is particularly promising, even showing a slightly higher reversible capacity of ∼110 mA h g–1 while keeping a voltage profile close to the one of the pure vanadium sample, indicating that at least 10% of the vanadium can be replaced by iron without significantly affecting the electrochemical performance
Iron‐Catalyzed [2+2+2] Cycloadditions for the Construction of Aromatic and Heteroaromatic Rings
No full textInternational audienceIn this review, the state‐of‐the‐art of iron‐catalyzed [2+2+2] cycloadditions applied to the formation of benzene, pyridine, and phosphabenzene derivatives is described. For decades important efforts have been made to highlight the role of iron as a powerful tool in catalysis, and this work summarizes the scope of iron‐catalyzed systems for the development of new, eco‐friendly, inexpensive, and practical processes for the synthesis of (hetero)aromatic rings
60 K wide hysteresis embracing room temperature in a fluorescent FeII spin transition complex
No full textInternational audienceThis work presents the synthesis and characterization of a new neutral mononuclear Fe(ii) spin transition (ST) complex, [FeII(L)2]0 (4Cl), where L is an asymmetrically substituted tridentate ligand 2-(3-(4-chlorophenyl)-1H-1,2,4-triazol-5-yl)-6-(1H-pyrazol-1-yl)pyridine. 4Cl exhibits a remarkably wide stable ST hysteresis loop ca. 60 K wide embracing room temperature (T up arrow 1/2 = 308 K and T down arrow 1/2 = 248 K). Detailed structural, calorimetric and spectroscopic investigations, including X-ray diffraction with Rietveld analysis, Raman spectroscopy, and photoluminescence, reveal the crucial role of subtle structural changes within the crystal lattice in driving the cooperative spin transition. The DFT energy framework analysis highlights the interplay of balanced stabilizing and destabilizing intermolecular interactions that contribute to the observed hysteresis. Furthermore, the fluorescent properties of 4Cl exhibit distinct changes in emission intensity and wavelength upon spin state switching with emission color change from sky blue in the high spin state to violet in the low spin state. The compound is the first example of the spin transition compound with bistable fluorescence response at room temperature