Engineering porous and compact two-dimensional nanoarchitectures on surfaces taking advantage of bisterpyridine-derivatives self-assembly

International audienceThe self-assembly of two bis-terpyridine derivatives is experimentally investigated at the nanometer scale. Scanning tunneling microscopy (STM) reveals that two-dimensional compact and porous nanoarchitectures can be engineered by changing the length of terpyridine spacer; i.e. a benzene ring or a quaterthiophene (4T) unit. In both cases the molecular nanoarchitecture appears to be stabilized by double hydrogen-bonds between molecular terpyridine groups. The STM images suggest however that terpyridine groups adopt different conformations, s-cis and s-trans as well as s-trans and s-trans conformations, in the two self-assembled organic layers

Visible and near-infrared organic photosensitizers comprising isoindigo derivatives as chromophores: synthesis, optoelectronic properties and factors limiting their efficiency in dye solar cells

The development of ruthenium-free organic photosensitizers showing panchromatic absorption up to the near-infrared (NIR) region for application in dye-sensitized solar cells (DSSCs) is still scarce. Among the sensitizers with absorption beyond 700 nm and developed for DSSCs, only zinc-phthalocyanine and boron-dibenzopyrromethene-based dyes have been able to reach efficiencies as high as 6%. Here we report metal-free organic dyes based on isoindigo, thieno-isoindigo or benzo-thieno-isoindigo chromophores that absorb in the UV-visible and NIR spectral range up to 900 nm. These molecules, that exhibit purple, blue, or green hues, were used to sensitize TiO2 mesoporous electrodes in order to fabricate DSSCs with an iodide/triiodide-based electrolyte. Advanced photophysical characterizations, including charge extraction, transient photovoltage, and laser transient absorption spectroscopy experiments, combined with density functional theory modeling and computational investigations allow us to fully unravel the interfacial processes at the origin of the solar cell performances and to identify the limiting factors. A power conversion efficiency as high as 7% associated with a Jsc close to 19 mA cm−2 was obtained with one of the dyes, which is comparable to those of the best panchromatic organic dyes reported so far. We also demonstrate in this work that the Voc of the solar cells is linearly correlated to the dipolar moments of the oxidized dyes, the molecules possessing larger dipoles leading to the highest Voc value

Influence of Redox Couple on the Performance of ZnO Dye Solar Cells and Minimodules with Benzothiadiazole-Based Photosensitizers

ZnO-based dye-sensitized solar cells exhibit lower efficiencies than TiO2-based systems despite advantageous charge transport dynamics and versatility in terms of synthesis methods, which can be primarily ascribed to compatibility issues of ZnO with the dyes and the redox couples originally optimized for TiO2. We evaluate the performance of solar cells based on ZnO nanomaterial prepared by microwave-assisted solvothermal syn- thesis, using three fully organic benzothiadiazole-based dyes YKP- 88, YKP-137, and MG-207, and alternative electrolyte solutions with the I−/I3−, Co(bpy)32+/3+, and Cu(dmp)21+/2+ redox couples. The best cell performance is achieved for the dye−redox couple combination YKP-88 and Co(bpy)32+/3+, reaching an average −− efficiency of 4.7% and 5.0% for the best cell, compared to 3.7% and 3.9% for the I /I3 couple with the same dye. Electrical impedance spectroscopy highlights the influence of dye and redox couple chemistry on the balance of recombination and regeneration kinetics. Combined with the effects of the interaction of the redox couple with the ZnO surface, these aspects are shown to determine the solar cell performance. Minimodules based on the best systems in both parallel and series configurations reach 1.5% efficiency for an area of 23.8 cm2.Área de Química Físic

GRAVITY: observing the universe in motion

GRAVITY is the second generation VeryLarge Telescope Interferometer instrument for precision narrow-angle as -trometry and interferometric imaging.With its fibre-fed integrated optics,wavefront sensors, fringe tracker, beamstabilisation and a novel metrologyconcept, GRAVITY will push the sensitivity and accuracy of astrometry andinterferometric imaging far beyond whatis offered today. Providing precisionastrometry of order 10 microarcseconds,and imaging with 4-milliarcsecondresolution, GRAVITY will revolutionisedynamical measurements of celestialobjects: it will probe physics close tothe event horizon of the Galactic Centreblack hole; unambiguously detect andmeasure the masses of black holesin massive star clusters throughout theMilky Way; uncover the details of massaccretion and jets in young stellarobjects and active galactic nuclei; andprobe the motion of binary stars, exoplanets and young stellar discs. Theinstrument capabilities of GRAVITY areoutlined and the science opportunitiesthat will open up are summarised

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI

The GRAVITY instrument has been revolutionary for near-infrared interferometry by pushing sensitivity and precision to previously unknown limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer (VLTI) in GRAVITY+, these limits will be pushed even further, with vastly improved sky coverage, as well as faint-science and high-contrast capabilities. This upgrade includes the implementation of wide-field off-axis fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser guide stars in an upgraded facility. GRAVITY+ will open up the sky to the measurement of black hole masses across cosmic time in hundreds of active galactic nuclei, use the faint stars in the Galactic centre to probe General Relativity, and enable the characterisation of dozens of young exoplanets to study their formation, bearing the promise of another scientific revolution to come at the VLTI.Comment: Published in the ESO Messenge

Classification des techniques de frappe en football et modélisation des réussites en compétition (l'exemple des passes d'élimination de l'expert)

Le travail s'inscrit dans une approche technologie du football. Il vise avant tout à constituer un outil de caractérisation in situ des pratiques de frappe de balle des footballeurs. La classification est élaborée par aller-retours : elle se crée dans l'interaction entre les variables empiriques issues de l'analyse de discours d'experts sur des situations vécues de frappe de balle en compétition, et celles validées par les sciences du contrôle moteur. Cet outil se veut exhaustif. Il a pour vocation d'embrasser l'ensemble des gestuelles de frappe de balle du joueur, quel que soit son niveau de maîtrise ou de pratique. Le travail s'attache ensuite, à partir de la grille d'analyse constituée, à formaliser les techniques d'exécution les plus adaptées aux passes à fonction d'élimination de l'adversaire au plus haut niveau de compétition. Ces configurations de recherche du déséquilibre de l'adversaire , caractérisées par des espaces fugitifs, imposent au passeur un conflit vitesse/précision au plan de la réalisation motrice. La gestion de cette pression temporelle constitue un obstacle majeur à la réussite des tentatives des experts. L'étude définit, par l'intermédiaire d'une modélisation statistique, les principes moteurs pertinents pour la réussite de ces passes spécifiques en compétition adulte professionnelle et élite 13ans. Ces règles techniques novatrices, transversales aux deux populations, expriment l'utilité sociale du travail. Elles ouvrent des perspectives didactiques en termes d'optimisation des passes à l'entraînement et de formation des professionnels de demain.RENNES2-BU Centrale (352382101) / SudocSudocFranceF

Etude rétrospective sur une année, de la prise en charge des cas de paludisme à l'Hôpital d'Instruction des Armées Desgenettes (à propos de 40 cas et revue de la littérature)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-Bib. Serv.Santé Armées (751055204) / SudocSudocFranceF

S-Shaped Conformation of the Quaterthiophene Molecular Backbone in Two-Dimensional Bisterpyridine-Derivative Self-Assembled Nanoarchitecture

International audienceThe conformation and the two-dimensional self-assembly of 4′-(3′,4″-dihexyloxy-5,2′:5′,2″:5″,2‴-quater-thien-2,5‴-diyl)-bis(2,2′:6′,2″-terpyridine) molecules are theoretically and experimentally investigated. This molecular building block forms a hydrogen-bonded chiral supramolecular nanoarchitecture on graphite at the solid/liquid interface. Scanning tunneling microscopy (STM) shows that the molecule adopts an S-shaped conformation in this structure. DFTB+ calculations reveal that this conformation is not the lowest-energy conformation. The molecular nanoarchitecture appears to be stabilized by hydrogen bonding as well as van der Waals interactions. I-, Land nd D-shaped molecular conformations are, however, locally observed at the domain boundary, but these conformations do not self-assemble into organized 2D structures. ■ INTRODUCTION Engineering novel organic/inorganic interfaces thought the self-assembly of functionalized molecules 1−11 is attracting an enormous amount of research interest due to its expected applications in nanotechnology. 12−14 The electronic properties of a self-assembled organic or hybrid layer can be drastically affected by the organization of its building blocks at the interface with a conductive surface. 15,16 Controlling the arrangement of the building nanoblock at the nanoscale is therefore a key parameter governing the properties of the interface. Hydrogen bonding is a particularly appealing interaction governing molecular self-assembly due to the strength, the high selectivity, and the directionality of this binding. 17−27 Carboxylic groups can be used to strengthen molecular self-assembly because these substituents are expected to lead to the formation of double hydrogen bonds (O−H···O) between neighboring molecules. This strategy has been successfully used to achieve the formation of self-assembled porous and compact nanoachitectures. 28−31 An alternative consists of functionalizing the molecular skeleton with pyridine units instead of carboxylic groups. Pyridine is also expected to drive molecular self-assembly through the formation of double hydrogen bonds (C−H···N) between neighboring molecules. Intense effort has recently been devoted to the synthesis of pyridine-based molecular building blocks. 32,33 Hydrogen-bonded densely packed and porous nanoarchitectures have been engineered using pyridine-based molecular building blocks. 34,35 The review of Wild et al. summarized the recent research effort in synthezising π-conjugated 2,2′:6′,2″-terpyr-idine ligands for application in the fields of supramolecular and coordination chemistry and materials science. 32 The pyridine groups are expected to drive molecular self-assembly through hydrogen bonding or metal coordination whereas the spacer unit is carrying the electronic properties or the active part of the molecular building block. Among the possible spacer units, oligothiophenes are very interesting because their chemistry is now well known to tune their electronic, optical, and redox properties for applications in organic electronics