Nicolas Solem, Claire Romanzin, Roland Thissen, Christian Alcaraz, Quentin Autret et leurs collaborateurs ont publié récemment un article dans The Journal of Physical Chemistry Letters:

Experimental Characterization of the Isomer-Selective Generation of the Astrochemically Relevant Hydroxymethylene Radical Cation (HCOH•+/DCOH•+)

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Interest in the observation and characterization of organic isomers in astronomical environments has grown rapidly with an increase in the sensitivity of detection techniques. Accurate modeling and interpretation of these environments require experimental isomer-specific reactivity and spectroscopic measurements. Given the abundance of formaldehyde (H2CO) in various astrophysical objects, the properties and reactivities of its cation isomers H2CO•+ and HCOH•+ are of significant interest. However, for the hydroxymethylene radical cation HCOH•+ (and its isotopologue DCOH•+), detailed reactivity studies have been limited by the lack of suitable experimental methods to generate this isomer with high purity. Here, potential approaches to the isomer-selective generation of HCOH•+ and DCOH•+ are characterized through differential reactivity measurements. While the dissociative photoionization of cyclopropanol (c-CH2CH2CHOH) is determined to be unsuitable, the dissociation of methanol-d3 (CD3OH) allows for the formation of DCOH•+ with a fractional abundance of >99% at photon energies below 14.8 eV. These results will allow future spectroscopic and reactivity measurements of HCOH•+/DCOH•+ to be conducted, laying the groundwork for future detection and incorporation into models of the interstellar medium.

Sana Aimeur, Xavier Serfaty, Tania Bizouarn, Laura Baciou et leurs collaborateurs ont publié récemment un article dans Journal of Biological Chemistry:

"Structural profiles of the full phagocyte NADPH oxidase unveiled by combining computational biology and experimental knowledge"

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The phagocyte NADPH oxidase (NOX2) is an enzyme, crucial for innate immune defense, producing reactive oxygen species necessary for pathogen destruction. Its activation requires the assembly of soluble proteins (p47phox, p40phox, p67phox, and Rac) with the membrane-bound flavocytochrome b558 (cytb558). We combined circular-dichroism analyses, with decades of experimental data, to filter structural models of the NADPH oxidase complex generated by the artificial intelligence program AlphaFold2 (AF2). The predicted patterns tend to closely resemble the active states of the proteins, as shown by the compact structure of the cytb558, whose dehydrogenase domain is stabilized closer to the membrane. The modeling of the interaction of p47phox with cytb558, which is the initial assembly and activation steps of the NADPH oxidase, enables us to describe how the C-terminus of p47phox interacts with the cytb558. Combining the AF2 cytb558 -p47phox model and its classical molecular dynamics simulations, we highlighted new hydrophobic lipid insertions of p47phox, particularly at residues Trp80-Phe81 of its PX domain. The AF2 models also revealed the implications of intrinsically disordered regions, such as the fragment between the PX domain and the SH3 regions of p47phox, in ensuring distant protein-protein and membrane-protein interactions. Finally, the AF2 prediction of the cytb558-Trimera model highlighted the importance of leaving Rac1 as a separate protein to reach an active state of the NADPH oxidase complex. Altogether, our step-by-step approach provides a structural model of the active complex showing how disordered regions and specific lipid and protein interactions can enable and stabilize the multi-subunit assembly.

Michel Heninger, Joël Lemaire, Antoine Pallandre et leurs collaborateurs ont publié récemment un article dans Journal of Physics D: Applied Physics:

VOCs conversion in He/H2O plasma produced in a micro-capillary tube at atmospheric pressure

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A non-equilibrium plasma is created in a micro-capillary quartz tube (800 µm of internal diameter), by a DC-pulsed micro-dielectric barrier discharge (micro-DBD) and the propagation of an ionisation wave, in mixtures of He/H2O/VOC at atmospheric pressure where the studied volatile organic compounds (VOCs) are representative of molecules belonging to different chemical families: alcohols (methanol, ethanol, isopropanol, tert-butanol), ketones (acetone), nitriles (acetonitrile), and aromatic hydrocarbons (toluene). The conversion efficiency of these VOCs is studied as a function of the applied voltage on the micro-DBD (or electrical energy deposited in the plasma) and of the initial concentration of the molecules in the range from 1 ppm up to 3000 ppm (depending on the molecule), with the help of high-resolution real-time mass spectrometry Fourier transform ion cyclotron resonance associated to chemical ionisation (CI-FTICR) using H3O+ as precursor ion. A variety of by-products resulting from the conversion of VOCs are identified and quantified, emphasising that the micro-capillary plasma is able to induce a complex chemical reactivity. A qualitative analysis of the involved kinetics, based on the existing literature, reveals that helium species (ions and metastable states) and radicals coming from the dissociation of the water molecules (O and OH) are the most probable candidates to explain the formation of all compounds detected by the CI-FTICR apparatus. Quenching processes of the metastable He(23S) by the VOCs, leading to the dissociation of the molecules, are suggested to explain some of the experimental results.

Zhiwen Jiang, Carine Clavaguéra, Sergey A. Denisov, Jun Ma et Mehran Mostafavi viennent de publier un article dans Journal of the American Society:

Role of Oxide-Derived Cu on the Initial Elementary Reaction Intermediate During Catalytic CO2 Reduction

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The catalytic role of oxide-derived Cu (OD-Cu) in promoting CO2 reduction (CO2R) to C2+ products has been appreciated for decades. However, the dynamic evolution of the surface oxidation states, together with their real correlation to the binding of reaction intermediates, remains unclear due to technical challenges. Here, we show the time-resolved spectroscopic signatures of key OD-Cu-CO2•– intermediates during catalytic CO2 reduction through one electron transfer from nanoseconds to seconds time scale. We generated the initial intermediate CO2•– radicals in the bulk solution and monitored the interfacial reaction kinetics with well-defined OD-Cu (Cu(0), Cu(I), and Cu(II)) nanoparticles. Combined with molecular simulations, transient absorption profiles analysis reveals that Cu(I) induced a faster CO2•– radical coupling reaction than Cu(0), whereas Cu(II) is only reduced to Cu(I) by the CO2•– radical. Furthermore, the newly developed multistep cumulative pulse methodology uncovered the transition in chemical states of mixed OD-Cu during radical coupling reactions. This pulse radiolysis study provides compelling evidence for the beneficial role of subsurface oxides in early time catalytic CO2 transformation.

Dominique Bazin et ses collaborateurs ont publié récemment un article dans Nephrology Image:

"Unveiling glomerular gold in oxalate nephropathy"

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An 82-year-old woman was admitted with acute kidney injury. Her medical history included type 2 diabetes, hypertension, ischemic stroke, rheumatoid arthritis, esophageal adenocarcinoma, and, recently, septic arthritis of the foot. Serum creatinine, previously normal, increased rapidly to 2.3 mg/dl and peaked at 3.8 mg/dl. Urinalysis, proteinuria, and kidney ultrasonography were normal. The kidney biopsy revealed lesions of acute tubular necrosis and crystalline deposits in the tubular lumens, birefringent in polarized light (Figure 1a and b). Unusual, small (1–3 μm), polarizing deposits were also observed in glomeruli (Figure 1b, arrows).

Roland Thissen a contribué à l'article "Astrochimie, dans les cuisines cosmiques" dans CNRS Le Journal.

Étudier la chimie du milieu interstellaire et récolter des indices sur l’origine de la vie sur Terre. Tel est l’objectif de l’astrochimie, une « jeune » science qui connaît depuis quelques années de formidables progrès.

https://lejournal.cnrs.fr/articles/astrochimie-dans-les-cuisines-cosmiques

"Enerzine" parle des travaux de Nawfal Ghazzal et ses collaborateurs !

Les énergies renouvelables connaissent un essor considérable, et la recherche s’intensifie pour développer des solutions durables. Une équipe de chercheurs français vient de réaliser une avancée significative dans le domaine de la production d’hydrogène vert, ouvrant la voie à de nouvelles perspectives énergétiques.

Des scientifiques de l’Institut de chimie physique (CNRS/Université Paris-Saclay) ont mis au point un système photocatalytique sans métaux nobles, s’inspirant du processus de photosynthèse des plantes. Le dispositif se révèle capable de transformer efficacement les protons de l’eau en dihydrogène, marquant ainsi une étape importante vers la production de carburants verts.
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Abderrahmane Tadjeddine participera à la 24 ème réunion annuelle de Annual Meeting of African Science Academies (AMASA 2024) qui se tiendra à Alger du 26 au 28/11/2024. Il donnera une key-note sur "Synchrotron radiation facility, an essential characterisation tool for science, innovation and technology".

Conférence de Julien Bobroff, physicien, professeur à l’Université Paris-Saclay.

Lundi 18 novembre -10h30 - Amphithéâtre du C2N

Quels sont les vrais enjeux de la vulgarisation aujourd'hui ? Pourquoi les chercheurs devraient à tout prix vulgariser eux-mêmes leurs recherches  ? Et dans ce cas, quels sont les bons formats ? Voilà quelques-unes des questions qui seront abordées.

CALL FOR PROPOSAL FOR THEMATIC PROGRAMS

Institut Pascal (IPa) promotes thematic programs to bring scientific communities together and help them explore pioneering ideas and establish new collaborations. IPa welcomes programs from all the scientific fields covered by Université Paris-Saclay, be they theoretical or experimental.

The spirit of the IPa initiative is to host programs of long duration (typically 2-3 weeks, up to a trimester), allowing researchers to devote the necessary time and energy to particularly challenging topics. These programs should favor brainstorming sessions that lead to innovative advancements.

Application details

https://www.universite-paris-saclay.fr/institut-pascal/

Deadline 9th December 2024

Une conférence organisée par la section locale Paris-Sud de la Société Française de Physique.

La conférence de Nathalie Palanque-Delabrouille "L'Univers sombre nous réserve-t-il de nouvelles surprises" aura lieu le jeudi 14 novembre 2024 à 16h à l'Auditorium Pierre Lehmann au bâtiment 200 du laboratoire IJCLab, sur le campus de l'Université Paris-Saclay. Elle sera également retransmise en direct via Zoom (lien fourni au moment de l'évènement).

Détails et lien

Le GdR EMIE organise à l'Observatoire des Hautes Provences un atelier "Spectroscopies d'intérêt astrophysique et observations à l’Observatoire de Haute- Provence" autour de la physique moléculaire appliquée à l’interprétation des données astrophysiques, et à la pratique des observations elles-même (incluant deux nuits d’observation à l’OHP).

Un des objectifs est de réunir et faire échanger des scientifiques dont le cœur de métier est centré autour de résultats observationnels, qu'il s'agisse de les produire, de les analyser, et enfin de les interpréter et exploiter.

Fete le savoir!!
La science pour tous autour d'un moment festif !

Le 30 novembre Journée fete le savoir sur le thème :
"Avons-nous les energies pour demain ? "

Où trouver l’énergie, les énergies du futur ? Quelles sont les nouvelles pistes aujourd’hui pour la capter, récupérer celle du soleil et la transformer en électricité , celle des océans en mouvement, du centre de la Terre , du végétal… verra-t-on bientôt sur Terre une nouvelle voix de génération d’énergie en faisant fusionner, les noyaux d’atomes hydrogène ?
Programme de la journée

CNRS Chimie met en lumière les travaux récents de Wahid Ullah, Cong Wang, Audrey Gayral, Maxime Vallet, Mohamed Nawfal Ghazzal et leurs collaborateurs.

"Une conversion biomimétique efficace du rayonnement solaire en hydrogène vert"

Des scientifiques viennent de synthétiser un système photocatalytique sans métaux nobles, s’inspirant de la photosynthèse, capable de transformer de manière particulièrement efficace les protons de l’eau en dihydrogène. Ce premier pas vers la production de carburants verts fait l’objet d’un article dans la revue Advanced Energy Materials.

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"Defect-Rich Graphdiyne Quantum Dots as Efficient Electron-Donors for Hydrogen Generation" Lien vers la publication.

CNRS Chimie met en lumière les travaux de Zhiwen Jiang, Sergey Denisov, Daniel Adjei, Mehran Mostafavi et leur collaborateur.

Face à l’urgence que pose leur accumulation dans l’environnement, la recherche se mobilise pour trouver des solutions de dégradation des PFAS. Une étude parue dans la revue Environmental Science and Technology et menée par des chimistes français et chinois montre que, en présence de sulfite, il est possible de multiplier par un facteur 15 la dégradation de petites molécules perfluoroalkylées par des rayonnements ionisants (radiolyse).

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"Overlooked Activation Role of Sulfite in Accelerating Hydrated Electron Treatment of Perfluorosulfonates"

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Eduarda Sangiogo Gil, David Lauvergnat et Federica Agostini ont publié récemment un article dans Journal of Chemical Physics

"Exact factorization of the photon–electron–nuclear wavefunction: Formulation and coupled-trajectory dynamics"

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"We employ the exact-factorization formalism to study the coupled dynamics of photons, electrons, and nuclei at the quantum mechanical level, proposing illustrative examples of model situations of nonadiabatic dynamics and spontaneous emission of electron–nuclear systems in the regime of strong light–matter coupling. We make a particular choice of factorization for such a multi-component system, where the full wavefunction is factored as a conditional electronic amplitude and a marginal photon–nuclear amplitude. Then, we apply the coupled-trajectory mixed quantum–classical (CTMQC) algorithm to perform trajectory-based simulations, by treating photonic and nuclear degrees of freedom on equal footing in terms of classical-like trajectories. The analysis of the time-dependent potentials of the theory along with the assessment of the performance of CTMQC allows us to point out some limitations of the current approximations used in CTMQC. Meanwhile, comparing CTMQC with other trajectory-based algorithms, namely multi-trajectory Ehrenfest and Tully surface hopping, demonstrates the better quality of CTMQC predictions."

Claire Romanzin, Roland Thissen, Christian Alcaraz et leurs collaborateurs ont publié un article dans PCCP

"Combined experimental and computational study of the reactivity of the methanimine radical cation (H2CNH˙+) and its isomer aminomethylene (HCNH2˙+) with propene (CH3CHCH2)"

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"The gas phase reactivity of the radical cation isomers H2CNH˙+ (methanimine) and HCNH2˙+ (aminomethylene) with propene (CH3CHCH2) has been investigated by measuring absolute reactive cross sections and product branching ratios, under single collision conditions, as a function of collision energy (in the range ∼0.07–11.80 eV) using guided ion beam mass spectrometry coupled with VUV photoionization for selective isomer generation. Experimental results have been merged with theoretical calculations to elucidate reaction pathways and structures of products. The H2CNH˙+ isomer is over a factor two more reactive than HCNH2˙+. A major channel from both isomers is production of protonated methanimine CH2NH2+via hydrogen-atom transfer reaction but, while H2CNH˙+ additionally gives charge and proton transfer products, the HCNH2˙+ isomer leads instead to protonated vinylimine CH2CHCHNH2+, produced alongside CH3˙ radicals. The reactions have astrochemical implications in the build up of chemical complexity in both the interstellar medium and the hydrocarbon-rich atmospheres of planets and satellites."

Liran Hu, Souad Abou Zeid, Samy Remita et leurs collaborateurs ont publié récemment un article dans Applied Surface Science

"One-pot radiolytically synthesized reduced graphene oxide-gold nanoparticles composites and exploration in energy storage"

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"Graphene and its composites are of primary importance, particularly in the field of energy storage. Numerous bottom-up and top-down methods have been proposed in the literature to produce these materials with enhanced physicochemical properties. Recently, an innovative and green methodology was developed based on ionizing radiation, allowing the quantitative synthesis of graphene oxide-based materials. With the aim to extend this strategy for the preparation of hybrid nanomaterials, the objective of this work was the one-pot synthesis of nanocomposites composed of reduced graphene oxide – gold nanoparticles (rGO-AuNPs) via gamma ray-induced radiolytic reduction. UV–Vis Absorption Spectroscopy, Fourier Transform Infrared Spectroscopy, Raman Spectroscopy and X-ray Photoemission Spectroscopy were utilized to comprehensively evaluate the reduction degree of graphene oxide and the formation of gold nanoparticles. Atomic Force Microscopy and Scanning Electron Microscopy were employed to obtain the morphological and topographical information on synthesized nanocomposites. Thermal properties were investigated by Thermogravimetric Analysis and electrical properties were investigated using Cyclic Voltammetry and Potentiostatic Charge and Discharge method. The results demonstrated the successful reduction of graphene oxide and gold ions through the drastic transformation of oxygen-containing functional groups and the formation of gold nanoparticles. Electrical characterization results highlighted the excellent electrical properties of radiosynthesized rGO-AuNPs composites and their great potential for supercapacitance application."

Zhiwen Jiang et Mehran Mostafavi ont publié récemment un article dans Nano Letters

"Direct Observation of the Reactivity of Electrons toward Gold Nanoparticles in Aqueous Solution"

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The catalytic activity of gold nanoparticles (AuNPs) has been widely acknowledged; however, Au NPs are considered to be highly inert as radiosensitizers in biological systems. This apparent discrepancy across different fields complicates the understanding of their interfacial reactivity, particularly in terms of electron transfer reactions. Here, we employ pulse radiolysis to determine the rate constants for the reactions of electrons with AuNPs in aqueous solution. Our investigation of AuNPs with different sizes and surface modifications demonstrates the potential influence of the AuNPs design on electron transfer reactions. These findings address long-standing mechanistic contradictions and underscore the significance of interfacial electron dynamics on AuNPs in both catalytic and biological processes.