Lucie Arberet, Lea-Maria Ibele, Alain Tchapla, Federica Agostini, Sylvie Héron et leurs collaborateurs ont publié récemment un article dans Journal of Molecular Structure: "Structural elucidation of the main coloured compounds of Justicia spicigera based on experimental and computational electronic features"

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In continued efforts to characterise the dye extracted from Justicia spicigera leaves, the two main coloured compounds were isolated. In this study, a multi-analytical techniques characterisation of their structures was carried out by HRMS, NMR, vibrational (IR and Raman) and electronic (UV–Vis absorption and fluorescence) spectroscopies, completed by computational studies. Two unreported compounds from the phenoxazone (aka phenoxazine-3-one) family were identified, the 2-amino-7‑hydroxy-8‑methoxy-3H-phenoxazin-3-one, a positional isomer of the already described perisbivalvin B and the 2-N-(4‑hydroxy-γ-glutamyl)-7‑hydroxy-8‑methoxy-3H-phenoxazin-3-one. The simulated UV–Vis absorption and fluorescence spectra of the suggested structures showed good agreement with the experimental ones, supporting the structural elucidation and giving more insights into the chemistry of these compounds.

Isabelle Lampre, Christophe Humbert, Hynd Remita et leurs collaborateurs ont publié récemment un article dans Journal of Physics and Chemistry of Solids: "Radiation-induced photoluminescence enhancement of zinc oxide and zinc oxide- polyvinyl alcohol nanocomposite: A green and controllable approach for tailor-made optoelectronics"

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The structural and optical properties of gamma-ray-irradiated ZnO and ZnO-PVA nanocomposites, synthesized via a one-pot method, were investigated. The samples were analyzed before and after irradiation at doses up to 26 kGy using UV–Vis spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and surface frequency generation spectroscopy. X-ray diffraction confirmed the hexagonal wurtzite structure of ZnO, while electron microscopy revealed the embedment of 40 nm ZnO nanoparticles into the PVA matrix. Shifts and decreased ratio of the CH2–CH2 FT-IR vibrations at 1420 cm−1 and combined CH2–CH2/CH2–O–CH2 stretching at 1143 cm−1 indicated not only polymer matrix dislocation resulting from incorporation of ZnO nanoparticles in the PVA matrix but also cross-linking of the polymer chains upon irradiation. Surface frequency generation spectroscopy further confirmed PVA adherence and bonding to ZnO surfaces. Photoluminescence studies revealed significant changes in the energy and intensity of the near-band-edge emission of irradiated ZnO nanoparticles attributed to the annealing of surface defects. UV–Vis spectroscopy of ZnO-PVA showed a dose-dependent absorption increase at 280 nm, suggesting polymer cross-linking. Additionally, the intensity of the blue photoluminescent peak located around 445 nm increased with irradiation dose indicating dose-dependent enhancement of ZnO-PVA bonding. These findings demonstrate that gamma-ray irradiation effectively modifies the optical and surface properties of ZnO-based materials, enhancing their performance for applications in flexible optoelectronics, light-emitting devices, and environmental sensors. The ability to precisely control material properties through irradiation offers new opportunities for developing advanced functional materials with improved performance and sustainability.

Nicolas Solem, Roland Thissen, Claire Romanzin, Christian Alcaraz et leurs collaborateurs ont publié récemment un article dans ACS Earth and Space Chemistry: "Possible Hydrocarbon Chemical Growth Routes from l-C3H+ in Dense Molecular Clouds"

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The C3H+ cation plays a pivotal role within the chemical network of dense interstellar clouds. Its relatively slow reaction with molecular hydrogen (H2) suggests that reactions with other species, particularly small hydrocarbons, may play a significant role. In this study, we measured the absolute reaction cross sections of C3H+ with acetylene (C2H2) and the two isomers of C3H4 (allene and propyne). To facilitate the implementation of our experimental data into astrochemical models, we converted the reaction cross sections into rate constants. No temperature dependency was observed for all of the investigated channels. The reaction rates for C3H+ with C2H2 and C3H4, yielding C5H2+ and C4H3+, respectively, are in good agreement with existing data. However, we report a previously unidentified channel in the reaction with C3H4, leading to protonated acetylene C2H3+ with a 30% yield compared to the major product, C4H3+.

Claire Romanzin, Nicolas Solem, Roland Thissen, Christian Alcaraz et leurs collaborateurs ont publié récemment un article dans ACS Earth and Space Chemistry: "The Experimental Rate Constant of the S+(2D) + H2 Reaction"

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Endothermic reactions such as S+(4S) + H2 are not expected to play a significant role in the chemistry of the interstellar medium (ISM). However, in some specific environments, such as photon-dominated regions (PDR), UV radiation may catalyze the reaction by providing enough internal energy to reactants to overcome endothermicity. For instance, it was recently shown that the vibrational excitation of H2 greatly enhances the reactivity of C+ and S+ with H2, explaining the presence of their respective hydrides CH+ and SH+ in these regions. However, vibrational excitation of H2 is not a unique way to enhance the reactivity by UV radiation. Electronic excitation is an alternative way to effectively inject a huge amount of internal energy into the system, thus favoring reactivity. In this work, we will address how electronic excitation of the sulfur cation can strongly enhance the production of SH+. This is done by measuring experimentally the cross section of the title reaction for collision energies from 50 meV up to several eV and comparing the results with theoretical predictions in the 0.001–3 eV range. The reaction cross section is then used to derive the rate constant for a wide range of temperatures.

Le journal du CNRS via le "Focus Sciences" met en lumière le projet "Réactivité Ultrarapide des Biomolécules sous Irradiation" - RUBI coordonné par Aurélien de la Lande et financé par l’Agence nationale de la recherche (ANR).

Comprendre les effets de l’irradiation passe par l’exploration des phénomènes ultrarapides. En modélisant les mouvements atomiques et électroniques à des échelles de temps infimes, les scientifiques lèvent le voile sur la dynamique moléculaire qui se joue juste après l’impact d’un rayonnement intense sur des molécules biologiques (ADN, protéines…). 

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Cet évènement sur la thématique des réactions ion-molécule pour l'astrochimie s'est déroulé à l'Institut Pascal - Université Paris-Saclay du 7 au 18 avril 2025 et a remporté un franc succès. 

Organisé par Roland Thissen et ses collaborateurs, cet événement a reçu le support de l'Institut Pascal, de la GS Chimie, de la GS physique et de Soleil Synchrotron. 

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A cette occasion, un séminaire grand public a aussi été proposé par Daniela Ascenzi (Department of Physics - University of Trento - Italy) « Gas phase astrochemistry: from lab to the interstellar space and planetary systems » le mercredi 9 avril 2025.

La journée des doctorants "PhD Day" de l'ICP aura lieu le 2 juin en salle Magat. Communications orales, session poster et traditionnel barbecue, le programme arrive bientôt !

Sylwia Ptasinska Professeur à l'Université de Notre Dame (Radiation Laboratory) sera présente à l'ICP en tant que professeur invitée du 3 au 16 juin. Elle donnera un séminaire intitulé: "Radiation-Induced Molecular Changes as a Probe for Low-Temperature Plasma Chemistry".

Ce  séminaire aura lieu mercredi 4 juin  à 14h salle  Magat.

FOCUS#4 se tiendra le jeudi 12 juin 2025 à l'Ecole Polytechnique L'objectif de FOCUS est de fédérer la communauté du plateau de Saclay (IP-Paris et Université Paris-Saclay) travaillant sur des thématiques scientifiques abordant les dynamiques ultrarapides (ou presque). Programme et inscription :

https://focus.sciencesconf.org/resource/page/id/5

The 33rd Miller Conference on Radiation Chemistry will be held in Dubrovnik, Croatia, from October 5 to 10, 2025. A Workshop for Early Career Scientists will precede the conference on October 5, running from morning to evening. Information and registration

CNRS Chimie met en lumière les travaux récents de Xiaojiao Yuan, Girlie Eunice Lopez, Viet-Dung Duong, Samy Remita, Hynd Remita et leurs collaborateurs.

"La lumière pour scinder l’eau grâce à des nanoparticules de polymère"

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"Semiconducting Overoxidized Polypyrrole Nano-Particles for Photocatalytic Water Splitting"

CNRS Chimie met en lumière les travaux récents de Zhiwen Jiang, Carine Clavaguéra, Sergey A. Denisov, Jun Ma & Mehran Mostafavi

Des chercheurs révèlent le rôle crucial du cuivre et ses mécanismes d’action dans les premières étapes de réduction du CO₂ en produits à haute valeur ajoutée. L’étude, qui combine radiolyse pulsée et simulations moléculaires, montre quelles espèces de catalyseur de cuivre sont les plus efficaces et pourquoi. Une étape clé vers la valorisation durable du CO2 et une économie circulaire du carbone.

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

Nicolas Solem, Claire Romanzin et Roland Thissen ont publié récemment un article dans ACS Earth and Space Chemistry: "CN– and C3N– Reactivity with Formic and Acetic Acid, Acetaldehyde, and Methanol"

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The anion-molecule reactivity of CN– and C3N–, produced by dissociative electron attachment of the respective bromide precursors, with four oxygenated molecules has been investigated in a guided ion beam mass spectrometer, and absolute reaction cross-sections are derived as a function of collision energy. The four targets are formic acid, acetic acid, acetaldehyde, and methanol. Exothermic and endothermic proton transfer has been observed as the main reaction channel, with differences in cross-section between the two anions. Oxidation of the anions is also observed, forming OCN– and OC3N–, for both anions and limited to the targets with endothermic proton transfer for CN–. This reaction requires several rearrangements and, therefore, a long-lived complex to proceed. Other complex-mediated products are observed for C3N– but not for CN–, interpreted as the ability to proceed through a long-lived complex because of less easy proton transfer for C3N–. Comparison between the present results at low-collision energy, models, and previous studies are producing a coherent picture. Several products observed with C3N– were missing formation enthalpies. Using the experimental exothermic behavior, it was possible to determine the upper limit values for enthalpies for the formation of OC3N– (0.39 ± 0.25 eV), [H2OC3N]− (0.39 ± 0.25 eV), C4N– (0.65 ± 0.25 eV), and CH3C3N– (3.52 ± 0.25 eV).

Lea Maria Ibele, Eduarda Sangiogo Gil, Evaristo Villaseco Arribas et Federica Agostini ont publié récemment un article dans Physical Chemistry Chemical Physics: "Simulations of photoinduced processes with the exact factorization: state of the art and perspectives Physical Chemistry Chemical Physics"

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This perspective offers an overview of the applications of the exact factorization of the electron–nuclear wavefunction to the domain of theoretical photochemistry, where the aim is to gain insights into the ultrafast dynamics of molecular systems via simulations of their excited-state dynamics beyond the Born–Oppenheimer approximation. The exact factorization offers an alternative viewpoint to the Born–Huang representation for the interpretation of dynamical processes involving the electronic ground and excited states as well as their coupling through the nuclear motion. Therefore, the formalism has been used to derive algorithms for quantum molecular-dynamics simulations where the nuclear motion is treated using trajectories and the electrons are treated quantum mechanically. These algorithms have the characteristic features of being based on coupled and on auxiliary trajectories, and have shown excellent performance in describing a variety of excited-state processes, as this perspective illustrates. We conclude with a discussion on the authors' point of view on the future of the exact factorization.

Dimitra Markovitsi et ses collaborateurs ont publié récemment un article dans Biomolecules:

"Factors Affecting the Population of Excited Charge Transfer States in Adenine/Guanine Dinucleotides: A Joint Computational and Transient Absorption Study"
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There is compelling evidence that the absorption of low-energy UV radiation directly by DNA in solution generates guanine radicals with quantum yields that are strongly dependent on the secondary structure. Key players in this unexpected phenomenon are the photo-induced charge transfer (CT) states, in which an electric charge has been transferred from one nucleobase to another. The present work examines the factors affecting the population of these states during electronic relaxation. It focuses on two dinucleotides with opposite orientation: 5′-dApdG-3′ (AG) and 5′-dGpdA-3′ (GA). Quantum chemistry calculations determine their ground state geometry and the associated Franck–Condon states, map their relaxation pathways leading to excited state minima, and compute their absorption spectra. It has been shown that the most stable conformer is anti-syn for AG and anti-anti for GA. The ground state geometry governs both the excited states populated upon UV photon absorption and the type of excited state minima reached during their relaxation. Their fingerprints are detected in the transient absorption spectra recorded with excitation at 266 nm and a time resolution of 30 fs. Our measurements reveal that in the large majority of dinucleotides, chromophore coupling is already operative in the ground state and that the charge transfer process occurs within ~120 fs. The competition among various relaxation pathways affects the quantum yields of the CT state formation in each dinucleotide, which are estimated to be 0.18 and 0.32 for AG and GA, respectively.

Ba Lich Pham, Alireza Ranjbari, Abderrahmane Tadjeddine, Christophe Humbert et leurs collaborateurs ont publié un article dans Symmetry: "Sum-Frequency Generation Spectroscopy at Aqueous Electrochemical Interfaces"

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The electrochemical interface (EI) is the determining factor in the yield and mechanism of sustainable energy storage and conversion systems due to its intrinsic functionality as a dynamic junction with the symmetry breaking of the molecular arrangement for complex reaction fields of mass transport and heterogeneous electron transfer. At the EI, the externally applied potential stimulus drives the formation of the electrical double layer (EDL) and governs the adsorption of interfacial adsorbate species in aqueous electrolyte solutions. Water and its aqueous electrolyte systems are integral and quintessential elements in the technological innovation of various fields such as environmental sciences, electrocatalysis, photocatalysis, and biochemistry. Although deciphering the structure and orientation of water molecules at the electrode–electrolyte interface in a quantitative analysis is of utmost importance, assessing chemical phenomena at the buried EI was rather challenging due to the intricacy of selecting interface-specific methodologies. Based on the non-centrosymmetry of the interfaces’ electronic properties, sum-frequency generation (SFG) spectroscopy has been manifested to be specifically well suited for probing the EI with detailed and comprehensive characteristics of adsorbates’ chemical structures and electrochemical events. In this review, we holistically engage in a methodical and scrupulous assessment of the fundamental EDL models and navigate towards the connection of the renowned Stark effect and potential dependence of SFG spectra at heterogeneous electrode–electrolyte interfaces. We dissect the development, advantages, and available geometrical configurations of in situ SFG spectroscopy in harnessing the EI. A broad spectrum of applications in unraveling the water orientations and rationalizing the convoluted mechanism of fuel-generated electrocatalytic reactions with particular encumbrances and potential resolutions is underscored by leveraging SFG spectroscopy.

La région Ile de France a attribué une subvention de 895 000 € dans le cadre de l’appel à projet SESAME2024 au projet porté par l’Institut de Chimie Physique en partenariat avec de laboratoires de l’Université Paris-Saclay, de la région Ile de France et européens pour la mise à niveau de la plateforme de spectroscopie IRMPD CLIO/SMAS.  Cette subvention permettra l’achat de lasers IR pour la plateforme et l’installation de deux nouveaux spectromètres de masse de type piège à ions dont un à très haute résolution et à très haut champ magnétique. La plateforme CLIO/SMAS de l’ICP est fortement impliquée dans de réseaux nationaux tels que l’Infrastructure de recherche Infranalytics et le PEPR LUMA qui soutiennent également ce projet.

Contact: Debora Scuderi

Bravo à Raphaël Vangheluwe qui effectue sa thèse dans le groupe ThéoSim pour avoir gagné le prix du meilleur poster dans le cadre du Colloque Alain Bouyssy.

"Accelerating the exploration of nanoclusters structures with machine learning inerfaced with particle swarm optimisation"

Ce colloque s'est tenu le 12 décembre 2024 et a été organisé par la Graduate School de Physique de l'Université Paris-Saclay.