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(179) Production(s) de l'année 2023
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Gelation and Re-entrance in Mixtures of Soft Colloids and Linear Polymers of Equal Size
Auteur(s): Parisi Daniele, Truzzolillo D., Slim Ali, Dieudonne-George P., Narayanan Suresh, Conrad Jacinta, Deepak Vishnu, Gauthier Mario, Vlassopoulos Dimitris
(Article) Publié:
Macromolecules, vol. 56 p.1818-1827 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04035012_v1
Ref Arxiv: 2212.05992
DOI: 10.1021/acs.macromol.2c02491
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Liquid mixtures composed of colloidal particles and much smaller non-adsorbing linear homopolymers can undergo a gelation transition due to polymer-mediated depletion forces. We now show that the addition of linear polymers to suspensions of soft colloids having the same hydrodynamic size yields a liquid-to-gel-to-re-entrant liquid transition. In particular, the dynamic state diagram of 1,4-polybutadiene star–linear polymer mixtures was determined with the help of linear viscoelastic and small-angle X-ray scattering experiments. While keeping the star polymers below their nominal overlap concentration, a gel was formed upon increasing the linear polymer content. Further addition of linear chains yielded a re-entrant liquid. This unexpected behavior was rationalized by the interplay of three possible phenomena: (i) depletion interactions, driven by the size disparity between the stars and the polymer length scale which is the mesh size of its entanglement network; (ii) colloidal deswelling due to the increased osmotic pressure exerted onto the stars; and (iii) a concomitant progressive suppression of the depletion efficiency on increasing the polymer concentration due to reduced mesh size, hence a smaller range of attraction. Our results unveil an exciting new way to tailor the flow of soft colloids and highlight a largely unexplored path to engineer soft colloidal mixtures.
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High-rectification near-field radiative thermal diode using Weyl semimetals
Auteur(s): Hu Yang, Liu Haotuo, Bing Yang, Shi Keshang, Antezza M., Wu Xiao-hu, Sun Yasong
(Article) Publié:
Physical Review Materials, vol. 7 p.035201 (2023)
DOI: 10.1103/PhysRevMaterials.7.035201
Résumé: Thermal diodes, which allow heat transfer in a preferential direction while being blocked in a reverse direction, have numerous applications in thermal management, information processing, energy harvesting, etc. Typical materials of thermal diodes in previous works include phase-change and magneto-optical materials. However, such thermal diodes depend highly on specific working temperatures or external magnetic fields. In this work, we propose a near-field radiative thermal diode (NFRTD) based on two Weyl semimetal (WSM) nanoparticles (NPs) mediated by a WSM planar substrate, which works without an external magnetic field and with flexible temperatures. Numerical results show that the maximum rectification ratio of NFRTD can be up to 2673 when the emitter is 200 K and receiver is 180 K, which exceeds the maximum value reported in some previous works by more than 10 times. The underlying physical mechanism is the strong coupling of the localized plasmon modes in the NPs and nonreciprocal surface plasmon polaritons in the substrate. In addition, we calculate the distribution of the Green's function and reflection coefficient to investigate nonreciprocal energy transfer in NFRTDs. Finally, we discuss the effects of momentum separation on the rectification performance of the NFRTD. This work demonstrates the great potential of WSMs in thermal rectification and paves a path for designing high-performance NFRTDs.
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Electromagnetic scattering by a partially graphene-coated dielectric cylinder: Efficient computation and multiple plasmonic resonances
Auteur(s): Jeyar Y., Antezza M., Guizal B.
(Article) Publié:
Physical Review E, vol. 107 p.025306 (2023)
DOI: 10.1103/PhysRevE.107.025306
Résumé: We present a numerical approach for the solution of electromagnetic scattering from a dielectric cylinder partially covered with graphene. It is based on a classical Fourier-Bessel expansion of the fields inside and outside the cylinder to which we apply ad hoc boundary conditions in the presence of graphene. Due to the singular nature of the electric field at the edges of the graphene sheet, we introduce auxiliary boundary conditions. The result is a particularly simple and efficient method allowing the study of diffraction from such structures. We also highlight the presence of multiple plasmonic resonances that we ascribe to the surface modes of the coated cylinder.
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Electrical monitoring of organic crystal phase transition using MoS2 field effect transistor
Auteur(s): Boulet Ilan, Pascal Simon, Bedu F., Ozerov Igor, Ranguis Alain, Leoni Thomas, Becker Conrad, Masson Laurence, Matkovic Aleksandar, Teichert Christian, Siri Olivier, Attaccalite Claudio
(Article) Publié:
Nanoscale Advances, vol. 5 p.1681-1690 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04001075_v1
DOI: 10.1039/d2na00817c
Exporter : BibTex | endNote
Résumé: Hybrid van der Waals heterostructures made of 2D materials and organic molecules exploit the high sensitivity of 2D materials to all interfacial modifications and the inherent versatility of the organic compounds. In this study, we are interested in the quinoidal zwitterion/MoS 2 hybrid system in which organic crystals are grown by epitaxy on the MoS 2 surface and reorganize in another polymorph after thermal annealing. By means of field-effect transistor measurements recorded in situ all along the process, atomic force microscopy and density functional theory calculations we demonstrate that the charge transfer between quinoidal zwitterions and MoS 2 strongly depends on the conformation of the molecular film. Remarkably, both the field effect mobility and the current modulation depth of the transistors remain unchanged which opens up promising prospects for efficient devices based on this hybrid system. We also show that MoS 2 transistors enable fast and accurate detection of structural modifications that occur during phases transitions of the organic layer. This work highlights that MoS 2 transistors are remarkable tools for on-chip detection of molecular events occurring at the nanoscale, which paves the way for the investigation of other dynamical systems.
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Hidden traces of chirality in the fluctuations of a fully unwound cholesteric
Auteur(s): Poy G.
(Article) Publié:
Soft Matter, vol. 19 p.1115-1130 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-03953472_v1
DOI: 10.1039/D2SM01646J
Exporter : BibTex | endNote
Résumé: Confinement and hydrodynamic interactions often play an important role in the fluctuation dynamics of soft matter systems, which can typically be studied using light scattering techniques. With experimental and theoretical methodologies, I demonstrate here that chirality is an additional critical parameter that leads to diverging decay times and correlation lengths in chiral liquid crystal cells with a fully unwound cholesteric helix. This study combines light scattering measurements made in a tailored microscope geometry and theoretical calculations of the decay dynamics of chiral orientational fluctuations---including hydrodynamics---to establish the existence of two soft chiral modes of fluctuations driving the destabilization of the unwound cholesteric. Despite the achirality of the equilibrium state of unwound cholesterics, this study indicates that chirality hides itself in the orientational fluctuation modes and plays a major role in their dynamics, which can be exploited to locally measure the strength of chirality in frustrated chiral liquid crystal cells.
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Polar nematic phase in short-chained fluorinated hydrogen-bonded liquid crystals
Auteur(s): Fouzai Malek, Dieudonne-George P., Guesmi Ahlem, Ben Hamadi Naoufel, Arfaoui Youssef, Soltani Taoufik, Chevalier Yves
(Article) Publié:
Journal Of Molecular Liquids, vol. 375 p.121307 (2023)
Ref HAL: hal-03978339_v1
DOI: 10.1016/j.molliq.2023.121307
Exporter : BibTex | endNote
Résumé: So as to investigate structure-activity relationships in hydrogen bonded liquid crystals, a new short-chained (7 carbon atoms) fluorinated hydrogen-bonded liquid crystal 4-heptyloxy-2-fluorobenzoic acid, 7OBAF, is prepared. Differential scanning calorimetry, polarized optical microscopy and X-ray diffraction disclose a phase sequence as two crystalline, a nematic and the isotropic phases. Dielectric spectroscopy of the nematic phase in the frequency range of 1 Hz–6 MHz reveals a low frequency mode ascribed to ferroelectric clusters. A high polarization is induced by an external electric field, in agreement with results of dielectric measurements. Such polarization increases as the alkyl chain length is shorter. Results of DFT calculations using the Maier–Meier relationship are consistent with the dielectric measurements; they reveal the parallel molecular distribution and provide the dipole moment, polarization anisotropy, birefringence and dielectric anisotropy. Intermolecular hydrogen bonds linking the fluorine substituent and the aromatic hydrogen atoms are also disclosed.
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Stability of the In-Plane Room Temperature van der Waals Ferromagnet Chromium Ditelluride and Its Conversion to Chromium-Interleaved CrTe 2 Compounds
Auteur(s): Purbawati Anike, Sarkar Suman, Pairis Sébastien, Kostka Marek, Hadj-Azzem Abdellali, Dufeu Didier, Singh Priyank, Bourgault Daniel, Nuñez-Regueiro Manuel, Vogel Jan, Renard Julien, Marty Läetitia
(Article) Publié:
Acs Applied Electronic Materials, vol. p. (2023)
Texte intégral en Openaccess :
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