Generalization of the post-collision interaction effect from gas-phase to solid-state systems demonstrated in thiophene and its polymers

We demonstrate experimentally and theoretically the presence of the post-collision interaction (PCI) effect in sulfur KL2,3L2,3 Auger electron spectra measured in the gas-phase thiophene and in solid-state organic polymers: polythiophene (PT) and poly(3-hexylthiophene-2,5-diyl), commonly known as P3HT. PCI manifests itself through a distortion and a blueshift of the normal Auger S KL2,3L2,3 spectrum when S 1s ionization occurs close to the ionization threshold. Our investigation shows that the PCI-induced shift of the Auger spectra is stronger in the solid-state polymers than in the gas-phase organic molecule. Theoretical modeling within the framework of the eikonal approximation provides good agreement with the experimental observations. In a solid medium, two effects influence the interaction between the photoelectron and the Auger electron. In detail, stronger PCI in the polymers is attributed to the photoelectron scattering in the solid, which overcompensates the polarization screening of electron charges which causes a reduction of the interaction. Our paper demonstrates the general nature of the PCI effect occurring in different media

X-ray induced ultrafast charge transfer in thiophene-based conjugated polymers controlled by core-hole clock spectroscopy

We explore ultrafast charge transfer (CT) resonantly induced by hard X-ray radiation in organic thiophene-based polymers at the sulfur K-edge. A combination of core-hole clock spectroscopy with real-time propagation time-dependent density functional theory simulations gives an insight into the electron dynamics underlying the CT process. Our method provides control over CT by a selective excitation of a specific resonance in the sulfur atom with monochromatic X-ray radiation. Our combined experimental and theoretical investigation establishes that the dominant mechanism of CT in polymer powders and films consists of electron delocalisation along the polymer chain occurring on the low-femtosecond time scale

Elaboration de systèmes électrocomutables à propriétés magnétiques (de la synthèse vers la fabrication de jonctions métal/molécule/métal)

Depuis la découverte de la conductivité pour le polyacétylène dopé, par Shirakawa, Mac Diarmid et Heeger dans les années 70, dont les travaux ont été couronnés du prix Nobel en 2000, les scientifiques ne cessent de développer de nouveaux polymères et oligomères conducteurs pour un large domaine d'applications, notamment pour l'électronique organique et moléculaire. Parallèlement, le magnétisme moléculaire a, depuis 25 ans, permis le développement de nouveaux systèmes à base d'aimants moléculaires, de chaînes aimants ou de complexes à transition de spin. Dans la même période, la découverte en 1988, par A. Fert et P. Grünberg (Prix Nobel 2007), de l'effet de magnétorésistance géante (GMR), a initié un développement rapide de la spintronique ou électronique de spin, basée sur des matériaux inorganiques L'évolution en parallèle de ces différents domaines de recherche a permis, comme le prédisait la loi de Moore, de réduire les systèmes de stockage de l'information de façon drastique. Cependant les découvertes faites dans ces deux domaines ne permettent pas à elles seules de contourner d'une part, la limite superparamagnétique et, d'autre part, de remplacer le silicium dans les dispositifs actuels. De manière étonnante peu d'exemples de justaposition de la spintronique et de l'électronique moléculaire ont été étudiés. Pourtant, l'alliance des propriétés des polymères conducteurs et des dispositifs magnétiques et/ou à transition de spin pourrait être une voie envisageable pour réduire encore la taille des dispositifs de stockage de l'information. C'est dans ce contexte que notre étude s'inscrit. Notre objectif a donc été de développer de nouveaux ligands -conjugués pour la synthèse de nouveaux composés organométalliques commutables, et aux propriétés magnétiques intéressantes. A plus long terme, l'objectif est d'être capable de commuter via le bras organique, les propriétés magnétiques de ces systèmes pour mimer un codage binaire "1/0".Since the discovery in the 70s, of conductivity in doped polyacetylene, by Shirakawa, Heeger and Mac Diarmid, whose work was crowned with the Nobel Prize in 2000, scientists continue to develop new polymers and oligomers for a wide range of applications, including molecular and organic electronics; In parallel, molecular magnetism has, for 25 years, allowed the development of new-systems-based molecular magnets, or magnets spin-crossover complex. In the same period, the discovery in 1988 by A. Fert and P. Grünberg (Nobel 2007), the giant magnetoresistance effect (GMR), initiated a rapid development of spintronics or spin electronics, based on inorganic materials. The parallel development of these three areas of research has, a predicted by Moore's law, reduce the storage systems of information drastically. But the discoveries made to not allow to circumvent, the superparamagnetic limit and, to replace silicon in current devices. Remarkably few examples of synergy between molecules and magnetics system have been studied. However, the alliance of conducting polumers properties and magnetic devices could be a feasible way to further reduce the size of storage devices information. This work has in the scientific context. Our aim was therefore to develop new -conjugated ligands for the synthesis of new organometallic switchables compounds, and developped interesting new magnetic devices. The purpose is to be able to switch via the organic moities, the magnetic properties of these systems to mimic a binary code "1/0".PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Electrochemical activation of molecular catalysts : from basics to applications

International audienceIn this article, the fundamental concepts of redox catalysis are first presented. While the one electron scheme provides general guidelines, it needs to be adapted when more complex systems involving several chemical reactions and electron transfer are concerned. Secondly, the structure of some bioinspired or biomimetic molecular catalysts for oxygen and proton reduction reactions is described. In that later case, a key aspect is to prevent degradation of the catalyst while keeping important turnover frequency, but also to keep the activity upon electrode functionalization

Electrografted Fluorinated Organic Ultrathin Film as Efficient Gate Dielectric in MoS 2 Transistors

International audienceDielectric films with nanometer thickness play a central role in the performances of field effect transistors (FETs). In this article, a new class of organic gate dielectric based on the electrochemical grafting of diazonium salts on metallic electrodes is investigated. The versatile diazonium salt strategy is a local and room-temperature process that provides robustness and performances. Moreover, this process produces ultrathin (4−8 nm) and smooth films. To prove their efficiency as gate dielectric, they were integrated in MoS 2 −FETs gate stacks. The devices display excellent switching behavior for reduced gate bias swing (down to 1 V) and suppressed hysteresis thanks to the highly hydrophobic nature of the fluorinated grafted film. Furthermore, the devices exhibit steep subthreshold slopes (as low as 110 mV/decade), demonstrating excellent gate coupling

Electro-grafted organic thin films in Nano-memristor device

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Synthesis of π‑Conjugated 2,2:6′,2″-Terpyridine-Substituted Oligomers Based on 3,4-Ethylenedioxythiophene

Dissymmetric π-conjugated monomers and oligomers incorporating 3,4-ethylenedioxythiophene (EDOT) units and bearing terpyridine end groups were synthesized in good yields through Vilsmeyer–Haak formylation followed by a reaction with 2-acetylpyridine in basic media or, for the longest oligomers, direct C–H bond arylation. They have a low HOMO–LUMO gap and are easily oxidized at low potentials. Upon complexation with cobalt(II) and iron(II) they yield new hybrid materials that can be used in various applications ranging from photovoltaics to spintronics

MoS2 Transistors with Electrografted Organic Ultrathin Film as Efficient Gate Dielectric

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MoS2 Transistors with Electrografted Organic Ultrathin Film as Efficient Gate Dielectric

International audienc

MoS2 Transistors with Electrografted Organic Ultrathin Film as Efficient Gate Dielectric

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