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Dive into the research topics where Isabelle Ly is active.

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Featured researches published by Isabelle Ly.


Langmuir | 2012

Polymorphism of Natural Fatty Acid Liquid Crystalline Phases

Hélène Fay; Steven Meeker; Juliette Cayer-Barrioz; Denis Mazuyer; Isabelle Ly; Frédéric Nallet; Bernard Desbat; Jean-Paul Douliez; Virginie Ponsinet; Olivier Mondain-Monval

We study the phase behavior in water of a mixture of natural long chain fatty acids (FAM) in association with ethylenediamine (EDA) and report a rich polymorphism depending on the composition. At a fixed EDA/FAM molar ratio, we observe upon dilution a succession of organized phases going from a lamellar phase to a hexagonal phase and, finally, to cylindrical micelles. The phase structure is established using polarizing microscopy, SAXS, and SANS. Interestingly, in the lamellar phase domain, we observe the presence of defects upon dilution, which SAXS shows to correspond to intrabilayer correlations. NMR and FF-TEM techniques suggest that these defects are related to an increase in the spontaneous curvature of the molecule monolayers in the lamellae. ATR-FTIR spectroscopy was also used to investigate the degree of ionization within these assemblies. The successive morphological transitions are discussed with regards to possible molecular mechanisms, in which the interaction between the acid surfactant and the amine counterion plays the leading role.


Bioresource Technology | 2017

Carbon nanotube fiber mats for microbial fuel cell electrodes

Brigitte Delord; Wilfrid Neri; Karen Bertaux; Alain Derré; Isabelle Ly; Nicolas Mano; Philippe Poulin

Novel carbon nanotube based electrodes of microbial fuel cells (MFC) have been developed. MFC is a promising technology for the wastewater treatment and the production of electrical energy from redox reactions of natural substrates. Performances of such bio-electrochemical systems depend critically on the structure and properties of the electrodes. The presently developed materials are made by weaving fibers solely comprised of carbon nanotubes. They exhibit a large scale porosity controlled by the weaving process. This porosity allows an easy colonization by electroactive bacteria. In addition, the fibers display a nanostructuration that promotes excellent growth and adhesion of the bacteria at the surface of the electrodes. This unique combination of large scale porosity and nanostructuration allows the present electrodes to perform better than carbon reference. When used as anode in a bioelectrochemical reactor in presence of Geobacter sulfurreducens bacteria, the present electrodes show a maximal current density of about 7.5mA/cm2.


Nanotechnology | 2016

Modified silver nanowire transparent electrodes with exceptional stability against oxidation

J Idier; Wilfrid Neri; Christine Labrugère; Isabelle Ly; Philippe Poulin; Rénal Backov

We report an easy method to prepare thin, flexible and transparent electrodes that show enhanced inertness toward oxidation using modified silver nanowires (Ag NWs). Stabilization is achieved through the adsorption of triphenylphosphine (PPh3) onto the Ag NW hybrid dispersions prior to their 2D organization as transparent electrodes on polyethylene terephtalate (PET) films. After 110 days in air (20 °C) under atmospheric conditions, the transmittance of the PET/Ag NW/PPh3 based films is nearly unchanged, while the transmittance of the PET/Ag NW-based films decreases by about 5%. The sheet resistance increases for both materials as time elapses, but the rate of increase is more than four times slower for films stabilized by PPh3. The improved transmittance and conductivity results in a significantly enhanced stability for the figure of merit σ dc/σ op. This phenomenon is highlighted in highly oxidative nitric acid vapor. The tested stabilized films in such conditions exhibit a decrease to σ dc/σ op of only 38% after 75 min, whereas conventional materials exhibit a relative loss of 71%. In addition, by contrast to other classes of stabilizers, such as polymer or graphene-based encapsulants, PPh3 does not alter the transparency or conductivity of the modified films. While the present films are made by membrane filtration, the stabilization method could be implemented directly in other liquid processes, including industrially scalable ones.


Applied Physics Letters | 2013

Conductivity of transparent electrodes made from interacting nanotubes

Laurent Maillaud; Cécile Zakri; Isabelle Ly; Alain Pénicaud; Philippe Poulin

Interactions in carbon nanotube (CNT) dispersions alter the morphology of films made from such dispersions. Weak attractive interactions induce an enhancement of the electrical conductivity. This phenomenon is observed in thin films that lie in a near percolated regime. Strong interactions instead induce a decrease of conductivity. In spite of strong morphological differences, the conductivity of thick films, away from percolated regimes, do not depend on interactions between the CNTs. These experiments support a recent theoretical scenario of the percolation of interacting rods and provide guidance for the optimal formulations of CNT inks in transparent electrode applications.


Liquid Crystals | 2016

A single parameter determines mesophase transitions in Swollen Liquid Crystals

Natacha Kinadjian; Frédéric Nallet; Isabelle Ly; Ahmed Bentaleb; Rénal Backov; Eric Prouzet

ABSTRACT We report how the control of a single parameter, the co-surfactant, determines the phase transitions of oil-in-water swollen liquid crystals (SLCs) prepared with cetyltrimethylammonium bromide (CTAB), from cubic to hexagonal, lamellar, and finally sponge-like structures. SLCs are complex mixtures (surfactant + co-surfactant + water + salt + oil) usually prepared to form hexagonal mesophases, with cell parameters tunable between 3 and 30 nm. These hexagonal mesophases were successfully used as nanoreactors to prepare a broad range of nanostructured materials. Because the potential of these mesophases as adaptive nanoreactors has not been extended to other liquid crystal geometries than the hexagonal, we studied in a first step the structure evolution of SLCs made with CTAB, cyclohexane, pentanol-1, water and different stabilising salts. We used small-angle X-ray scattering (SAXS), polarised light microscopy and Freeze-Fracture TEM to provide a partial phase diagram and list the different mesophases obtained as a function of composition. We report that the adjustment of a single parameter, the co-surfactant (pentanol-1), determines the phase transition between cubic, hexagonal, lamellar, and sponge-like structures, all other parameters such as the nature and concentration of salt, or amount of oil being constant. GRAPHICAL ABSTRACT


Langmuir | 2011

Freeze-Fracture TEM Imaging of Robust Order in Swollen Phases of Amphiphilic Diblock Copolymers

Benoît Maxit; Joanna Giermanska; Isabelle Ly; Denis Bendejacq; Olivier Mondain-Monval; Virginie Ponsinet

We report on the structures exhibited by two different diblock poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) copolymers in water, a selective solvent. Using a combination of X-ray scattering and freeze fracture-transmission electron microscopy (FF-TEM), we show that these structures can be widely swollen while retaining their initial morphology and a high degree of long-range order. The analysis of the FF-TEM pictures also evidences the presence of water crystallites of regular size and shape within the confined water domains. We relate the growth of these crystallites to the high local ionic strength of the water swelling the PAA brushes. Moreover, the confinement of the crystallites growth shows that the swollen phases have a very robust structure, potentially useful for confining colloidal particles.


Optical Materials Express | 2017

Shaping light spectra and field profiles in metal-coated monolayers of etched microspheres

Cristian Tira; Isabelle Ly; Renaud A. L. Vallée; Simion Astilean; Cosmin Farcau

Hybrid colloidal plasmonic-photonic crystals (HPPCs) are known for their interesting optical properties, which are relevant both fundamentally and for their applicative potential. The optical response of HPPCs is easily tunable from the visible to the infrared spectral range, while their fabrication, based on colloidal self-assembly, keeps production costs rather low. Both arguments make HPPCs a class of attractive functional materials. Here, we explore the optical properties of HPPCs obtained by gradual etching of a hexagonal close-packed monolayer of polystyrene microspheres, subsequently covered by a thin metal layer. We analyze the optical transmission characteristics of these etched colloidal crystals and HPPCs as a function of the etching degree. Finite-difference time-domain simulations allowed us to explain the correlations between the observed optical response and morphology. The transmission gap in bare colloidal crystals can be blue-shifted up to at least 50 nm, and its depth increased by more than 20%. In HPPCs on the other hand, it is possible to tune not only the wavelength of the enhanced plasmonic fields, but also their locations within the nanostructure. Thus, both spectra and near-field profiles can be fine-tuned in a controlled manner by plasma etching in these hybrid plasmonic-photonic structures, expanding the current understanding of the physical working principles of HPPCs and their applications.


Carbon | 2011

The effect of surface energy, adsorbed RGD peptides and fibronectin on the attachment and spreading of cells on multiwalled carbon nanotube papers

Guillaume Vidal; Brigitte Delord; Wilfrid Neri; Sébastien Gounel; Olivier Roubeau; C. Bartholome; Isabelle Ly; Philippe Poulin; Christine Labrugère; Elisabeth Sellier; Marie-Christine Durrieu; Joëlle Amédée; Jean-Paul Salvetat


Journal of Physical Chemistry C | 2016

Morphological Design of Gold Nanopillar Arrays and Their Optical Properties

Hanbin Zheng; Renaud A. L. Vallée; Isabelle Ly; Rui M. Almeida; Thomas Rivera; Serge Ravaine


ChemElectroChem | 2015

Wet-Spun Bioelectronic Fibers of Imbricated Enzymes and Carbon Nanotubes for Efficient Microelectrodes

Cintia Mateo-Mateo; Anne-Sophie Michardière; Sébastien Gounel; Isabelle Ly; Jad Rouhana; Philippe Poulin; Nicolas Mano

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Renaud A. L. Vallée

Centre national de la recherche scientifique

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Serge Ravaine

Centre national de la recherche scientifique

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