A5077920581- Liquid Crystal Research Advancements
- Surfactants and Colloidal Systems
- Material Dynamics and Properties
- Gold and Silver Nanoparticles Synthesis and Applications
- Photonic Crystals and Applications
- Pickering emulsions and particle stabilization
- Molecular spectroscopy and chirality
- Advanced Materials and Mechanics
- nanoparticles nucleation surface interactions
- Quasicrystal Structures and Properties
- Plant Reproductive Biology
- Block Copolymer Self-Assembly
- Advanced Fluorescence Microscopy Techniques
- Mesoporous Materials and Catalysis
- Biocrusts and Microbial Ecology
- Photonic and Optical Devices
- Lipid Membrane Structure and Behavior
- Laser-Ablation Synthesis of Nanoparticles
- Nanocluster Synthesis and Applications
- Molecular Junctions and Nanostructures
- Theoretical and Computational Physics
- Characterization and Applications of Magnetic Nanoparticles
- Polyoxometalates: Synthesis and Applications
- Polymer crystallization and properties
- Optical Polarization and Ellipsometry
Laboratoire de physique des Solides
2011-2024
Centre National de la Recherche Scientifique
2011-2024
Université Paris-Saclay
1992-2024
Centre Hospitalier d'Orsay
2021
Université Paris-Sud
2008-2020
Hetman Petro Sahaidachnyi National Army Academy
2017
Laboratoire de Réactivité de Surface
2010
Laboratoire de Chimie Physique
2007-2010
Sorbonne Université
2010
European Synchrotron Radiation Facility
2008
Colloidal crystals, made of large polystyrene particles (1.1 \ensuremath{\mu}m in diameter), are confined into a thin layer between two glass boundaries. When the thickness $h$ is increased progressively from zero, sequence structures $S(h)$ detected direct observations an optical microscope. These stacks $n$ square (\ensuremath{\square})---or triangular $(\ensuremath{\Delta})$---ordered layers. For $n<~7$,...
Abstract Blue Phases remained up to very recent years quite mysterious. First observations were done at the end of last century by Reinitzer in 1888 and Lehmann 1906. The precise nature these phases was a puzzling problem. At present it is firmly established that they are real not textures other phases. These observed narrow range temperature between isotropic cholesteric Up now, three different have been discovered. They appear following order increasing temperature:
Une serie de transitions structurelles a ete observee lors d'experiences consistant confiner des cristaux colloidaux dans un coin: ces consistent non seulement en changement du nombre couches cristallines mais aussi la structure meme l'interieur chacune couches. Pour expliquer cette serie, nous proposons modele d'empilement spheres dures ou, limite hautes pressions, l'etat d'equilibre correspond maximum densite volumique
We report the self-assembly of gold nanowires into hexagonal superlattices in liquid phase followed by situ small-angle X-ray scattering and give new insights their growth mechanism. The unprecedented large interwire distance 8 nm strongly suggests stabilization ultrathin a ligand's double layer composed oleylamine oleylammonium chloride. one-dimensional is discussed, opening perspectives toward control self-assemblies metallic nanowires.
The Frank-Kasper phases were already known in 1982 when quasi-crystals discovered, but their complex architectures are now considered as making a link between simple close-packed periodic structures and some quasi-periodic ones. These tetrahedrally close packed observed many materials from elements to intermetallics well self-assembled soft like micellar systems, dendritric liquid crystals, star polymers, more recently block copolymers or heated gold nanocrystal superlattices. We report here...
An efficient method to form 3D superlattices of gold nanoparticles inside oil emulsion droplets is presented. We demonstrate that this relies on Ostwald ripening, a well-known phenomenon occurring during the aging emulsions. The key point nanoparticle concentration smaller increasing very slowly with time, thus inducing crystallization into superlattices. Using oil-in-water emulsions doped hydrophobic nanoparticles, we for different types oils (toluene, cyclohexane, dodecane, and...
The amplitudes and the polarizations of different resonant reflections characterizing modulation orientational order in smectic liquid crystals are derived from molecular tensorial structure factor. In case a commensurate helicoidal modulation, our conclusions consistent with previous predictions Dimitrienko. We have extended Dimitrienko's prediction to incommensurate structures but nonhelicoidal modulations. compared estimated values for models modulations same period, experimental data...
Slow reduction of platinum salt in soft template made by direct hexagonal mesophases leads to Pt nanoballs with cells formed connected nanowires. The can be doped high concentrations (up 0.2 M) which relatively large quantities nanostructures.
Ultrathin Au nanowires were prepared following two routes: the reduction of lamellar phase [OY–AuICl] in an excess pure oleylamine and direct AuIII a solution hexane. The superiority chloride gold precursor isotropic environment is evidenced by small-angle X-ray scattering (SAXS) measurements. A reaction yield 75% observed, order magnitude higher than route involving phase. On basis detailed SAXS analysis, soft template role intermediate solid was discarded for nanowire growth. In case...
It is shown that higher degree exact differential forms on compact Riemannian $n$-manifolds possess continuous primitives whose uniform norm controlled by their $L^n$ norm. A contact sub-Riemannian analogue proven, with replaced Rumin forms.
Abstract Single‐crystalline platinum nanorods, monodisperse in diameter, are synthesized through a simple process at room temperature, cetyltrimethyl ammonium bromide (CTAB) solution. The complexation of the CTA + surfactant ion with tetrachloroplatinate presence hexanol leads to formation precipitate lamellar crystalline structure. reduction Pt II metal ions 0 is carried out using γ radiolysis. Transmission electron microscopy (TEM) observations nanoparticles extracted from solution, three...
A novel one-pot synthesis method to prepare gold nanorods of different aspect ratios using radiolysis is presented. The are synthesized by radiolytic reduction AuIII complexes in a micellar solution formed mixture cationic surfactants (cetyltrimethylammonium bromide and tetraoctylammonium bromide) the presence acetone silver ions. mechanisms formation discussed. can be trapped poly(vinyl alcohol) gel under irradiation. UV−visible absorption spectra nanorod solutions compared with...
This work reports the elaboration and structural study of new hybrid organic-inorganic materials constructed via coupling liquid-crystalline nonionic surfactants polyoxometalates (POMs). X-ray scattering polarized light microscopy demonstrate that these materials, highly loaded with POMs (up to 18 wt %), are nanocomposites lamellar structure (Lalpha), viscoelastic properties close those gels. The interpretation data strongly suggests located terminal -OH groups surfactants, within aqueous...
In this Letter, we show how advanced hierarchical structures of topological defects in the so-called smectic oily streaks can be used to sequentially transfer their geometrical features gold nanospheres. We use two kinds defects, 1D dislocations and 2D ribbon-like defects. The large trapping efficiency dislocation cores not only surpasses that elastically distorted zones around but also one defect. This enables formation a number aligned NP chains within quasi-fully filled without any...
We report the first experimental observation of a commensurate twist-grain-boundary smectic- $A$ phase $({\mathrm{TGB}}_{A})$. The number blocks per pitch is found to vary with temperature but independent thickness well aligned sample. For time variations distance between screw dislocations ${l}_{d}$ and grain boundaries ${l}_{b}$ have been determined in ${\mathrm{TGB}}_{A}$ phase. ratio ${l}_{b}{/l}_{d}$ be very close one predicted by Renn Lubensky. also structural study presumed chiral...
Interaction between hydrophobically-coated gold nanoparticles suspended in oil is usually described as the combination of strong attractive van der Waals attraction cores and interaction ligands. The latter expected to be purely repulsive if suspending medium a good solvent for ligands or partially bad solvent. By measuring structure factor interacting various solvents, we show that chemical affinity ligand with not only parameter controls conformation (small rigid long flexible molecules)...
Smectic blue phases are liquid crystalline which exhibit both three-dimensional-orientational order and smectic positional order. X-ray scattering experiments reveal that at least one of these is not cubic, as classical phases, but offers a hexagonal symmetry. A comparison the experimental patterns with given by double twist tubes sketched Kamien proposed.
Smectic blue phases ( BP(Sm)) are thermotropic liquid crystalline which exhibit both three-dimensional orientational order, such as classical phases, and smectic positional order. BP(Sm) appear the counterpart of twist grain boundary phases. X-ray scattering optical polarizing microscopy provide information on hexagonal cubic symmetries these new
Blue phases are frustrated systems characterized by a local constraint of double twist described mathematically in terms connection. We give rigourous construction such connection on any Riemannian 3-manifold using the Levi-Civita apply it to S 3 sphere which frustration is relieved. Using isomorphism between and unit quaternion group, we show that blue phase can be considered as nematic Lie algebra this group. This description enables an easy classification defects homotopy theory...
We study by synchrotron small-angle x-ray scattering highly aligned lamellar phases of a zwitterionic surfactant, doped with monodisperse and spherical hydrophobic inorganic particles as function particle concentration. Analysis the structure factor two-dimensional fluid formed in plane bilayer gives access to their membrane-mediated interaction, which is repulsive, contact value about 4kBT range 14 angstroms. Systematic application this technique should lead better understanding interaction...
A lamellar surfactant mesophase is used as a soft confinement medium for gold nanoparticles that are directly synthesized inside the by radiolytic reduction of salt incorporated into water medium. By increasing layer thickness mesophase, spherical size obtained. The same to synthesize in situ radiolysis nanorods (aspect ratio about 10). It also shown can be inserted simple mixing sufficiently swollen phase. In all cases, structure phase preserved presence nanoparticles.
We demonstrate a unique shear-induced crystallization phenomenon above the equilibrium freezing temperature in weakly swollen isotropic and lamellar mesophases with bilayers formed cationic-anionic mixed surfactant system. Synchrotron rheological X-ray diffraction study reveals transition to be reversible under shear (i.e., on stopping shear, nonequilibrium crystalline phase melts back mesophase). This is different from shear-driven below , which irreversible. Rheological optical...
Evaporation-induced self-assembly (EISA) is a versatile method for generating organized superstructures from colloidal particles, offering diverse design possibilities through the manipulation of colloid size, shape, substrate nature, and environmental conditions. While some work highlighted importance choice substrate, this parameter often overlooked in many EISA studies. In work, we compare lyotropic liquid crystals by on hydrophilic or hydrophobic substrates, acoustic levitation (absence...