HAL Portal ESPCI (Ecole Supérieure de Physique et de Chimie Industrielles)
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Boosting Effect of Encapsulated Polyoxometalates in the Photocatalytic CO 2 Reduction by MOF-545
No full textInternational audienceAchieving efficient photocatalytic CO2 reduction is a current complex challenge, requiring the development of strategies that optimize not only the capture of photons but also the photoinduced charge separation and electron transfer processes. In this pursuit, we have immobilized polyoxometalates (POMs), specifically [SiW12O40] 4-(SiW12) and [W10O32] 4-(W10), within the Zr-based porphyrinic metal-organic framework (MOF) MOF-545 catalytic material with the purpose of maximizing its CO2 photoreduction activity. The resulting SiW12@MOF-545 and W10@MOF-545 composites were fully characterized by various techniques (IR spectroscopy, powder X-ray diffraction, N2 adsorption isotherms, HADDF-STEM) to confirm the POM's incorporation via impregnation. These characterizations were complemented by simulations in order to locate the POM into the MOF's cavities and identify host/guest interactions. In photocatalytic conditions, i.e. under visible-light irradiation and in CH3CN/TEOA 20:1 solution, the two SiW12@MOF-545 and W10@MOF-545 composites reduced CO2 to formate with 100% selectivity at rates of 669 and 1239 mol gMOF -1 h -1 , respectively. Remarkably, W10@MOF-545 showed around a 3-fold increase in activity compared to its POM-free counterpart. DFT calculations suggest that both POM guests can accept photoexcited electrons from the porphyrin linkers of MOF-545, allowing increased lifetime of the photogenerated holes in the MOF upon illumination, thus boosting TEOA oxidation by the porphyrinic MOF for subsequent CO2 reduction. Moreover, the calculations unveil the origin of the observed superior overall catalytic activity of W10@MOF-545 over SiW12@MOF-545 due to stronger thermodynamic driving force for charge separation, providing rational guidelines for future design of efficient photocatalysts.</div
Alkynyl Radicals, Myths and Realities
No full textInternational audienceThis Perspective deals with the organic chemistry of alkynyl radicals, a species that is ultimately still little known in the synthetic community. Starting with the first observations and characterizations of alkynyl radicals generated by various methodologies in the gas phase, we then particularly turned our attention to the implications of these highly reactive intermediates in organic synthesis and materials science. Mechanistic considerations have been provided, in particular, for the key steps of generating alkynyl radicals, which are mainly based on photochemical or thermal activation and single electron transfer processes. This Perspective should serve as a roadmap for the synthetic chemist in order to plan more reliably alkynylation reactions based on alkynyl radicals
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
Micropatterned hepatobiliary organoid for the study of the Canal of Hering
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: Projet de constitution d’une unité d'appui et de recherche (UAR)
No full textCe document présente le projet de création d’une Unité d’Appui et de Recherche (UAR) commune à l’ESPCI Paris PSL et à Chimie ParisTech PSL, dédiée à la conception et à la fabrication de prototypes d’instruments scientifiques. Cette structure, issue de la mutualisation des ateliers mécaniques de l’ESPCI, a pour mission de soutenir la recherche et l’enseignement dans les domaines de la physique, de la chimie et de la biologie, en offrant des compétences en conception mécanique, usinage, fabrication numérique et prototypage rapide.L’UAR vise à renforcer la mutualisation des moyens, à stabiliser les compétences techniques et à offrir un cadre de gouvernance clair et pérenne. Elle s’appuie sur un modèle économique transparent fondé sur une tarification auditable conforme aux recommandations du CNRS, favorisant ainsi la reconnaissance de son rôle dans les projets de recherche nationaux et partenariaux.En intégrant l’ensemble des laboratoires de l’ESPCI et de Chimie Paris, l’UAR contribuera à structurer durablement le soutien technique à la recherche au sein de PSL et à encourager une culture de conception collaborative et innovante
Self-locking and stability of the bowline knot
No full textInternational audienceWe investigate the self-locking of the bowline knot through numerical simulations, experiments, and theoretical analysis. Specifically, we perform two complementary types of simulations using the 3D finite-element method (FEM) and a reduced-order model based on the discrete-element method (DEM). For the FEM simulations, we develop a novel mapping technique that automatically transforms the centerline of the rod into the required knot topology prior to loading. In parallel, we conduct experiments using a nearly inextensible elastic rod tied into a bowline around a rigid cylinder. One end of the rod is pulled to load the knot while the other is left free. The measured force-displacement response serves to validate both the FEM and DEM simulations. Leveraging these validated computational frameworks, we analyze the internal tension profile along the rod's centerline, revealing that a sharp drop in tension concentrates around a strategic locking region, whose geometry resembles that observed in other knot types. By considering the coupling of tension, bending, and friction, we formulate a theoretical model inspired by the classic capstan problem to predict the stability conditions of the bowline, finding good agreement with our FEM and DEM simulations. Our methodology and findings offer new tools and insights for future studies on the performance and reliability of other complex knots
Giant mobility of surface-trapped ionic charges following liquid tribocharging
No full textInternational audienceThe sliding motion of aqueous droplets on hydrophobic surfaces leads to charge separation at the trailing edge, with implications from triple-line friction to hydrovoltaic energy generation. Charges deposited on the solid surface have been attributed to ions or electrons ripped off from the liquid drop. However, the dynamics and exact physicochemical nature of these surface-trapped charges remains poorly explored. Here, we take advantage of a scanning-based electrostatic mapping technique, to directly quantify the spatiotemporal dynamics of surface deposited charges in the wake of droplets sliding on hydrophobic surfaces. We confirm the ionic nature of these interfacially trapped charges, and evidence that they undergo very fast bidimensional diffusive transport, gliding with low friction at the solid/gas interface. We interpret our observations in the framework of molecular dynamics simulation of hydrated ions adsorbed on solid surfaces, revealing a peculiar transport mechanism limited by purely interfacial friction of the ionic solvation shell with the solid surface. By uncovering the unexpected dynamics of these ionic puddles—a distinct state of interfacial ionic matter—our findings have general implications for molecular-scale ionic transport, electrified matter, and wetting dynamics at interfaces
Kinetic Redox Shotgun Proteomics Reveals Specific Lipopolysaccharide Effects on Intestinal Epithelial Cells, Mitigated by a Mn Superoxide Dismutase Mimic
No full textInternational audienceOverproduction of reactive oxygen species and antioxidant superoxide dismutases (SOD1, SOD2) dysregulation contribute to chronic inflammation such as generated in inflammatory bowel diseases (IBD). A kinetic redox shotgun proteomic strategy (OcSILAC for Oxidized cysteine Stable Isotope Labelling by Amino acids in Cell culture) was used to explore the lipopolysaccharide (LPS) effects including LPS‐induced oxidation and inflammation cascades on a dedicated intestinal epithelial cell line (HT29‐MD2) together with the potential mitigating role of a Mn‐based SOD‐mimic Mn1 . While LPS induced transient oxidative damages at early times (15 min), cells incubated with Mn1 showed, in this time frame, a significantly reduced cysteine oxidation, highlighting Mn1 antioxidant properties. Over time, cysteine oxidation of LPS‐treated cells was counteracted by an overexpression of antioxidant proteins (SOD1, NQO1) and a late (6 h) preponderant increase in SOD2 level. Mn1 , when co‐incubated with LPS, attenuated the level of most LPS‐modified proteins, that is, proteins involved in the inflammatory response. Our results highlight Mn1 as a potentially effective antioxidant and anti‐inflammatory agent to consider in the treatment of IBD, as well as a useful tool for exploring the interconnection between oxidative stress and inflammation
Structure and properties of MOF composite sheets for CO2 adsorption
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