Infos Lab' septembre 2025

CNRS Chimie met en lumière les travaux récents de Hynd Remita et de ses collaborateurs

"Des nanoalliages d’or et de palladium pour booster la production d’hydrogène"

Produire de l’hydrogène vert à partir d’eau grâce à la lumière est une solution très attractive pour décarboner l’industrie. Cependant, elle requiert des photocalyseurs efficaces qui se passent de certains métaux critiques comme le platine. Combiner deux métaux moins critiques, surtout à l’échelle nanométrique pour en utiliser peu, telle est la stratégie mise au point par des chimistes français et mexicains.

Lien vers le communiqué de presse

"Enhanced Photocatalytic Activity of Surface-Modified TiO2 with Bimetallic AuPd Nanoalloys for Hydrogen Generation" Lien vers la publication dans Solar RRL

Dimitra Markovitsi a publié récemment un article dans ACS Omega: "On the Use of the Intrinsic DNA Fluorescence for Monitoring Its Damage: A Contribution from Fundamental Studies"

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Cet article a aussi mis en lumière par Life Sciences Université Paris-Saclay.

The assessment of DNA damage by means of appropriate fluorescent probes is widely spread. In the specific case of UV-induced damage, it has been suggested to use the emission of dimeric photoproducts as an internal indicator for the efficacy of spermicidal lamps. However, in the light of fundamental studies on the UV-induced processes, outlined in this review, this is not straightforward. It is by now well established that, in addition to photodimers formed via an electronic excited state, photoionization also takes place with comparable or higher quantum yields, depending on the irradiation wavelength. Among the multitude of final lesions, some have been fully characterized, but others remain unknown; some of them may emit, while others go undetected upon monitoring fluorescence, the result being strongly dependent on both the irradiation and the excitation wavelength. In contrast, the fluorescence of undamaged nucleobases associated with emission from ππ* states, localized or excitonic, appearing at wavelengths shorter than 330 nm is worthy of being explored to this end. Despite its low quantum yield, it is readily detected nowadays. Its intensity decreases due to the disappearance of the reacting nucleobases and the loss of exciton coherence provoked by the presence of lesions, independently of their type. Thus, it could potentially provide valuable information about the DNA damage induced, not only by UV radiation but also by other sanitizing or therapeutic agents.

Souad Abou Zeid, Rituporn Gogoi, Yamina Chouli, Samy Remita et leurs collaborateurs viennent de publier un article dans New Journal of Chemistry:

"Radiation induced reduction of graphene oxide: a dose effect study"

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In this paper, we present a novel approach for the preparation of reduced graphene oxide (rGO) through the radiolytical reduction of commercial graphene oxide (GO). The method is highly efficient and environmentally friendly compared to other synthetic routes. We conducted a detailed study on the influence of absorbed doses during the synthesis process. The reduction process for the production of rGO is induced by the radiolysis of water at ambient temperature and pressure, confirmed using several sophisticated techniques. Our results demonstrate the efficiency of the radiolytical process compared to conventional methods of GO reduction. The C/O ratio increased from 3.3 (GO) to 11.2 (rGO), surpassing those of other reduction methods. Additionally, the intensity ratio of D and G bands (ID/IG) increased for rGO due to an increase in order by reduction, implying the restoration of π-conjugation. Furthermore, the thermal stability of GO improved upon irradiation. Electrochemical measurements finally showed that our rGO exhibited a specific capacitance of 229.3 F g−1, indicating its high potential as a candidate for energy storage applications.

Zhiwen Jiang, Sergey Denisov, Daniel Adjei, Mehran Mostafavi et Jun Ma viennent de publier un article dans Environmental Science & Technology:

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

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Photoexcitation of sulfite (SO32–) is often used to generate hydrated electrons (eaq–) in processes to degrade perfluoroalkyl and polyfluoroalkyl substances (PFASs). Conventional consensus discourages the utilization of SO32– concentrations exceeding 10 mM for effective defluorination. This has hindered our understanding of SO32– chemistry beyond its electron photogeneration properties. In contrast, the radiation-chemical study presented here, directly producing eaq– through water radiolysis, suggests that SO32– plays a previously overlooked activation role in the defluorination. Quantitative 60Co gamma irradiation experiments indicate that the increased SO32– concentration from 0.1 to 1 M enhances the defluorination rate by a remarkable 15-fold, especially for short-chain perfluoroalkyl sulfonate (PFSA). Furthermore, during the treatment of long-chain PFSA (C8F17–SO3–) with a higher concentration of SO32–, the intermediates of C8H17–SO3– and C3F7–COO– were observed, which are absent without SO32–. These observations highlight that a higher concentration of SO32– facilitates both reaction pathways: chain shortening and H/F exchange. Pulse radiolysis measurements show that elevated SO32– concentrations accelerate the bimolecular reaction between eaq– and PFSA by 2 orders of magnitude. 19F NMR measurements and theoretical simulations reveal the noncovalent interactions between SO32– and F atoms, which exceptionally reduce the C–F bond dissociation energy by nearly 40%. As a result, our study offers a more effective strategy for degrading highly persistent PFSA contaminants.

Michèle Desouter-Lecomte et ses collaborateurs viennent de publier un article dans The Journal of Chemical Physics:

"Managing temperature in open quantum systems strongly coupled with structured environments".

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"In non-perturbative non-Markovian open quantum systems, reaching either low temperatures with the hierarchical equations of motion (HEOM) or high temperatures with the Thermalized Time Evolving Density Operator with Orthogonal Polynomials Algorithm (T-TEDOPA) formalism in Hilbert space remains challenging. We compare different ways of modeling the environment. Sampling the Fourier transform of the bath correlation function, also called temperature dependent spectral density, proves to be very effective. T-TEDOPA [Tamascelli et al., Phys. Rev. Lett. 123, 090402 (2019)] uses a linear chain of oscillators with positive and negative frequencies, while HEOM is based on the complex poles of an optimized rational decomposition of the temperature dependent spectral density [Xu et al., Phys. Rev. Lett. 129, 230601 (2022)]. Resorting to the poles of the temperature independent spectral density and of the Bose function separately is an alternative when the problem due to the huge number of Bose poles at low temperatures is circumvented. Two examples illustrate the effectiveness of the HEOM and T-TEDOPA approaches: a benchmark pure dephasing case and a two-bath model simulating the dynamics of excited electronic states coupled through a conical intersection. We show the efficiency of T-TEDOPA to simulate dynamics at a finite temperature by using either continuous spectral densities or only all the intramolecular oscillators of a linear vibronic model calibrated from ab initio data of a phenylene ethynylene dimer."

Samy Remita et ses collaborateurs ont publié récemment un article dans Chemosphere:

"Engineering the physical properties and photocatalytic activities of a β-ketoenamine COF using continuous flow synthesis"

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Covalent Organic Frameworks (COF) having conjugated backbone are an interesting class of metal-free, visible light active, heterogeneous photocatalysts. Interestingly, synthesis of COF using continuous flow process has emerged as an efficient, alternative method when compared to the traditional batch process. Here, we demonstrate the possibility to engineer the physical properties and hence the adsorption and catalytic activities of a β-ketoenamine COF by varying monomer flow rate and microreactor design during the continuous flow synthesis. Crystallinity of the COF increases on varying the monomer flow rate from 100 (S-100) to 500 (S-500) and up to 1000 μLmin-1 (S-1000), in an S-shaped microreactor, resulting in an enhanced surface area: 525, 722 and 1119 m2g-1 respectively. The photophysical properties of the COF are also found to vary significantly with the change in flow synthesis conditions. S-1000 is characterized by the highest adsorption of MB, due to its high surface area and accessible pores. On the other hand, S-500 shows the highest photocurrent, a low recombination of photogenerated charges and the lowest charge transfer resistance. Thus, S-500 is found to be the best photocatalyst for the removal of a model pollutant (methylene blue, MB). Further, enhanced photocatalytic removal of MB using S-500 could be achieved by performing the photocatalysis in continuous flow.

Dimitra Markovitsi et ses collaborateurs viennent de publier un article dans Chemical Science:

"Real-time observation of sub-100-fs charge and energy transfer processes in DNA dinucleotides"

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"Using as showcase the DNA dinucleotide 5′-dTpdG-3′, in which the thymine (T) is located at the 5′ end with respect to the guanine (G), we study the photoinduced electronic relaxation of coupled chromophores in solution with an unprecedented refinement. On the one hand, transient absorption spectra are recorded from 20 fs to 45 ps over the 330–650 nm range with a temporal resolution of 30 fs; on the other hand, quantum chemistry calculations determine the ground state geometry of the 4 possible conformers with stacked nucleobases, the associated Franck–Condon states, and map the relaxation pathways leading to excited state minima. Important spectral changes occurring before 100 fs are correlated with concomitant G+ → T− charge transfer and T → G energy transfer processes. The lifetime of the excited charge transfer state is only 5 ps and the absorption spectrum of a long-lived nπ*T state is detected. Our experimental results match the transient spectral properties computed for the anti–syn conformer of 5′-dTpdG-3′, which is characterized by the lowest ground state energy and differs from that encountered in B-form duplexes."

Les Graduate Schools Chimie, HeaDS et LSH vous invitent le mardi 24 septembre 2024 en salle 4000 du bâtiment Henri Moissan (salle 4000 HM1) ou en visio pour une matinée valorisation.

La thématique de cette matinée est la mise en place de partenariats entre laboratoires et entreprises.

Inscription en cliquant sur le lien suivant : https://admin-sphinx.universite-paris-saclay.fr/SurveyServer/s/GSLSH/Valo-Partenariats/questionnaire.htm

Atelier de Microscopie Confocale 2024

Du 7 au 11 octobre 2024. Plateforme Imagerie-gif, Gif-sur-Yvette

Date limite d'inscription: 20 septembre 2024
OBJECTIFS:

• Acquérir et renforcer les bases théoriques de la microscopie photonique
• Approfondir et maîtriser l'utilisation pratique d'un microscope plein champ et confocal
• Intégrer les principes et possibilités des nouvelles applications et développements en microscopie photonique
• Comprendre les complémentarités des techniques de la microscopie conventionnelle à la super-résolution

Programme et inscription

La journée scientifique annuelle GS Chimie qui aura lieu au bâtiment Henri Moissan 2, dans l'amphithéâtre Olivier Kahn, le jeudi 17 octobre.
Programme: l'olfaction, les ressources, les émotions, les sensations trigéminales, les ingrédients.
Inscription : https://admin-sphinx.universite-paris-saclay.fr/v4/s/pvy41g

DATAIA, l’institut d’intelligence artificielle de l’Université Paris-Saclay est l’un des neuf lauréats de l’appel à manifestation d’intérêt « IA-Cluster », pôles d’excellence en recherche et formation en intelligence artificielle.

Le Cluster DATAIA vise à atteindre trois objectifs :

• Construire un programme ambitieux, interdisciplinaire, mêlant recherche et innovation et capable de s'attaquer aux défis économiques et sociétaux posés par l’IA
• Former à l’IA les meilleurs étudiants, issus d’une variété de formations d’excellence qui doivent se transformer pour s’adapter aux métiers de demain et poursuivre leur ouverture à l’international
• Façonner un cluster agile, formant un continuum recherche-formation-innovation, décloisonnant les disciplines et capable de s’adapter aux évolutions rapides de l’intelligence artificielle.

Colloque de la MITI : Horizons interdisciplinaires : Découvrez - écoutez - discutez l'interdisciplinarité

Mardi 1 et mercredi 2 octobre
Auditorium Marie-Curie, CNRS, 3, rue Michel-Ange – Paris 16e

Ce colloque s'adresse à tous ceux qui sont impliqués dans des projets de recherche interdisciplinaire ou qui s'intéressent à cette approche novatrice.

Programme et inscription

La MITI lance en 2025 l’appel à projets « Osez l’interdisciplinarité ».

L’interdisciplinarité, la prise de risque et le caractère de rupture seront les critères clefs de la sélection des projets qui sera effectuée par le comité de pilotage de la MITI sous la présidence du Directeur Général Délégué à la Science. Une audition des candidats présélectionnés sera organisée au siège du CNRS en janvier 2025.

Le projet doit présenter en 7 pages maximum les motivations pour la mobilité thématique, les défis à lever, le caractère interdisciplinaire, les collaborations envisagées, les résultats attendus, la méthodologie employée et un budget détaillé.

Date limite de dépôt des candidatures : jeudi 07 novembre 2024 à midi (heure de Paris)

Détails et candidature

PEPR DIADEM – Appel à projets "Projets de Recherche Interdisciplinaires 2024"

Cet AAP comportera deux axes thématiques :

• Un axe thématique « Découverte accélérée de matériaux innovants et durables pour un Green Deal » en amont des applications pour les grandes transitions
• Un axe thématique « Accélération de la maîtrise des procédés de synthèse et de mise en forme » visant à construire ou renforcer une souveraineté technologique française.

Limite de dépôt des projets :
31/10/2024 à 11:00 CET

Détails sur le site de l'ANR