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Bourvon H.,CEA Grenoble | Le Calvez S.,CEA Grenoble | Kanaan H.,CEA Grenoble | Meunier-Della-Gatta S.,CEA Grenoble | And 2 more authors.
Advanced Materials | Year: 2012

Quantum dot (QD) LEDs of high color purity, and low turn-on voltage and leakage current are prepared using a solvent free method. First, a monolayer of QDs is formed at the air/water interface, which is then transferred with a PDMS stamp onto the device. The method is applicable to large substrates and reduces materials consumption as compared to other deposition techniques. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Loi D.,European Synchrotron Radiation Facility | Mossa S.,CNRS Structure and Properties of Molecular Architectures Laboratory | Cugliandolo L.F.,University Pierre and Marie Curie
Soft Matter | Year: 2011

We follow the dynamics of an ensemble of interacting self-propelled semi-flexible polymers in contact with a thermal bath. We characterize the structure and dynamics of the passive system and as a function of the motor activity. We find that the fluctuation-dissipation relation allows for the definition of an effective temperature that is compatible with the results obtained by using a tracer particle as a thermometer. The effective temperature takes a higher value than the temperature of the bath when the effect of the motors is not correlated with the structural rearrangements they induce. Our data are compatible with a dependence upon the square of the motor strength (normalized by the average internal force) and they suggest an intriguing linear dependence on the tracer diffusion constant times the density of the embedding matrix. We show how to use this concept to rationalize the experimental results and suggest possible innovative research directions. © 2011 The Royal Society of Chemistry.


Loi D.,European Synchrotron Radiation Facility | Mossa S.,CNRS Structure and Properties of Molecular Architectures Laboratory | Cugliandolo L.F.,University Pierre and Marie Curie
Soft Matter | Year: 2011

We use molecular dynamics simulations to study the dynamics of an ensemble of interacting self-propelled semi-flexible polymers in contact with a thermal bath. Our intention is to model complex systems of biological interest. We find that an effective temperature allows one to rationalize the out-of-equilibrium dynamics of the system. This parameter is measured in several independent ways - from fluctuation-dissipation relations and by using tracer particles - and they all yield equivalent results. The effective temperature takes a higher value than the temperature of the bath when the effect of the motors is not correlated with the structural rearrangements they induce. We show how to use this concept to interpret experimental results and suggest possible innovative research directions. © The Royal Society of Chemistry 2011.


Gawrys P.,Warsaw University of Technology | Louarn G.,University of Nantes | Zagorska M.,Warsaw University of Technology | Pron A.,CNRS Structure and Properties of Molecular Architectures Laboratory
Electrochimica Acta | Year: 2011

Two electroactive polymeric arylene bisimides, namely poly[(4,7,10- trioxatrideca-1,13-diyl)-(1,4,5,8-naphthalenetetracarboxylic bisimide-N,N′-diyl)] and its perylene analogue - poly[(4,7,10- trioxatrideca-1,13-diyl)-(3,4,9,10-perylenetetracarboxylic bisimide-N,N′- diyl)] have been synthesized and studied by cyclic voltammetry, UV-vis-NIR as well as Raman spectroeletrochemistry. Contrary to low molecular weight arylene bisimides, which show a clear two electron, double-step electrochemical reduction (neutral form to radical anion and from radical anion to dianion), in the synthesized polymers multielectron transfers are observed, accompanied with a strong electrochromic effect. However, as probed by cyclic voltammetry, their first reduction step is retarded and covers a wider potential range. We attribute this effect to macromolecular nature of the compounds being reduced and their structural inhomogeneity caused by π-stacking induced nanoaggregation of bisimide segments of the polymer chains. The second redox step seems unaffected by the polymeric nature of the electroactive compounds and yields a reduction peak similar to that registered for low molecular weight bisimides. Raman spectroelectrochemical data, combined with the established vibrational model of the perylene derivative - (poly[(4,7,10-trioxatrideca-1,13- diyl)-(3,4,9,10-perylenetetracarboxylic bisimide-N,N′-diyl)]) - enabled us to determine the mechanism of the first step of the electrochemical reduction process. The electrochemically induced shifts of the Raman bands unequivocally show that the reduction process results in the transformation of the carbonyl group into a radical anion. The surplus negative charge is delocalized on the six-member imide ring with the aromatic core very little affected. © 2011 Elsevier Ltd. All rights reserved.


Pron A.,CNRS Structure and Properties of Molecular Architectures Laboratory | Gawrys P.,Warsaw University of Technology | Zagorska M.,Warsaw University of Technology | Djurado D.,CNRS Structure and Properties of Molecular Architectures Laboratory | Demadrille R.,CNRS Structure and Properties of Molecular Architectures Laboratory
Chemical Society Reviews | Year: 2010

This critical review discusses specific chemical and physicochemical requirements which must be met for organic compounds to be considered as promising materials for applications in organic electronics. Although emphasis is put on molecules and macromolecules suitable for fabrication of field effect transistors (FETs), a large fraction of the discussed compounds can also be applied in other organic or hybrid (organic-inorganic) electronic devices such as photodiodes, light emitting diodes, photovoltaic cells, etc. It should be of interest to chemists, physicists, material scientists and electrical engineers working in the domain of organic electronics (423 references). © 2010 The Royal Society of Chemistry.


Mizuno H.,Joseph Fourier University | Mossa S.,CNRS Structure and Properties of Molecular Architectures Laboratory | Barrat J.-L.,Joseph Fourier University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

Glasses exhibit spatially inhomogeneous elastic properties, which can be investigated by measuring their elastic moduli at a local scale. Various methods to evaluate the local elastic modulus have been proposed in the literature. A first possibility is to measure the local stress-local strain curve and to obtain the local elastic modulus from the slope of the curve or, equivalently, to use a local fluctuation formula. Another possible route is to assume an affine strain and to use the applied global strain instead of the local strain for the calculation of the local modulus. Most recently, a third technique has been introduced, which is easy to be implemented and has the advantage of low computational cost. In this contribution, we compare these three approaches by using the same model glass and reveal the differences among them caused by the nonaffine deformations. © 2013 American Physical Society.


Lyonnard S.,CNRS Structure and Properties of Molecular Architectures Laboratory | Gebel G.,CNRS Structure and Properties of Molecular Architectures Laboratory
European Physical Journal: Special Topics | Year: 2012

A molecular level understanding of structure and transport properties in fuel cell ionomer membranes is essential for designing new electrolytes with improved performance. Scattering techniques are suited tools for this purpose. In particular, neutron scattering, which has been extensively used in hydrogen-containing systems, is well adapted to investigate water-dependent complex polymeric morphologies. We report Small-Angle Neutron Scattering (SANS) studies on different types of fuel cell polymers: perfluorinated, radiation-grafted and sulfonated polyphosphazene membranes. We show that contrast variation methods can be efficiently employed to provide new insights on membrane microstructure and reveal ionic condensation effects. Neutrons have been used also as non-intrusive diagnosis tool to probe water properties and distribution inside membranes. Recently, in-situ neutronography and SANS experiments on operating fuel cells have been reported. In-plane cartography of water distribution at the surface of bipolar plates and water profiles across membrane thickness have been obtained and studied as a function of operating conditions. The last section of the article is devoted to the use of Quasi-Elastic Neutron Scattering to study water dynamics at molecular scale. We show that analysis with an appropriate sophisticated diffusion model allows to extract diffusion coefficients, characteristic times and length-scales of molecular motions. This quantitative information is fruitfully integrated in multi-scale modelling and usefully compared with numerical simulations. QENS also permits to compare alternative polymers and relate dynamical properties to chemical composition and membrane nanostructure. © 2012 EDP Sciences and Springer.


Fuchs J.,CNRS Structure and Properties of Molecular Architectures Laboratory | Fiche J.-B.,CNRS Structure and Properties of Molecular Architectures Laboratory | Buhot A.,CNRS Structure and Properties of Molecular Architectures Laboratory | Calemczuk R.,CNRS Structure and Properties of Molecular Architectures Laboratory | Livache T.,CNRS Structure and Properties of Molecular Architectures Laboratory
Biophysical Journal | Year: 2010

DNA microarrays find applications in an increasing number of domains where more quantitative results are required. DNA being a charged polymer, the repulsive interactions between the surface of the microarray and the targets in solution are increasing upon hybridization. Such electrostatic penalty is generally reduced by increasing the salt concentration. In this article, we present equilibrium-melting curves obtained from dedicated physicochemical experiments on DNA microarrays in order to get a better understanding of the electrostatic penalty incurred during the hybridization reaction at the surface. Various salt concentrations have been considered and deviations from the commonly used Langmuir adsorption model are experimentally quantified for the first time in agreement with theoretical predictions. © 2010 by the Biophysical Society.


Buhot A.,CNRS Structure and Properties of Molecular Architectures Laboratory
Macromolecules | Year: 2010

The viscosity η of polymer melts experimentally scales with the length L of the chains as a power law with an exponent b ≈ 3.4 larger than the prediction b = 3 from de Gennes' theory of reptation. This long-standing controversy is revisited within the repton and necklace models. Exact results from the rigid chain dynamics allow us to predict the leading order viscosities and renewal times for chains with fluctuating lengths and/or center-of-mass initial position fluctuations. The corrections to scaling are determined by numerical simulations to behave as L-1/2 in all cases. Such large effects may explain (a) the apparent exponent observed experimentally, (b) confirm the corrections due to the contour length fluctuations, and (c) highlight the importance of the relaxation of longitudinal modes. © 2010 American Chemical Society.


Reiss P.,CNRS Structure and Properties of Molecular Architectures Laboratory | Couderc E.,CNRS Structure and Properties of Molecular Architectures Laboratory | De Girolamo J.,CNRS Structure and Properties of Molecular Architectures Laboratory | Pron A.,CNRS Structure and Properties of Molecular Architectures Laboratory
Nanoscale | Year: 2011

This critical review discusses specific preparation and characterization methods applied to hybrid materials consisting of π-conjugated polymers (or oligomers) and semiconductor nanocrystals. These materials are of great importance in the quickly growing field of hybrid organic/inorganic electronics since they can serve as active components of photovoltaic cells, light emitting diodes, photodetectors and other devices. The electronic energy levels of the organic and inorganic components of the hybrid can be tuned individually and thin hybrid films can be processed using low cost solution based techniques. However, the interface between the hybrid components and the morphology of the hybrid directly influences the generation, separation and transport of charge carriers and those parameters are not easy to control. Therefore a large variety of different approaches for assembling the building blocks - conjugated polymers and semiconductor nanocrystals - has been developed. They range from their simple blending through various grafting procedures to methods exploiting specific non-covalent interactions between both components, induced by their tailor-made functionalization. In the first part of this review, we discuss the preparation of the building blocks (nanocrystals and polymers) and the strategies for their assembly into hybrid materials' thin films. In the second part, we focus on the charge carriers' generation and their transport within the hybrids. Finally, we summarize the performances of solar cells using conjugated polymer/semiconductor nanocrystals hybrids and give perspectives for future developments. © 2011 The Royal Society of Chemistry.

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