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Nanostructures & Spectroscopie
(46) Production(s) de l'année 2019
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pH-mediated control over the mesostructure of ordered mesoporous materials templated by polyion complex micelles
Auteur(s): Molina Emilie, Mathonnat M., Richard Jason, Lacroix-Desmazes Patrick, In M., Dieudonne-George P., Cacciaguerra Thomas, Gerardin Corine, Marcotte Nathalie
(Article) Publié:
Beilstein Journal Of Nanotechnology, vol. 10 p.144-156 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-01992289_v1
DOI: 10.3762/bjnano.10.14
WoS: 000455446300001
Exporter : BibTex | endNote
2 Citations
Résumé: Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak poly-acid-containing double-hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA), and a weak poly-base, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH.
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The individual double-walled carbon nanotubes; An experimental model system for studying coupling at the nanoscale :
Auteur(s): Sauvajol J.-L., Paillet M., Levshov D., Michel T., Tran H.-N., Parret R., Zahab A. A.
Conférence invité: "Modeling Nanostructures" in honor of Philippe Lambin (Namur, BE, 2019-01-31)
Ref HAL: hal-01982883_v1
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Résumé: Using an experimental approach that combines high-resolution electron microscopy, electron diffraction and optical spectroscopies, including Raman scattering, Rayleigh spectroscopy and photoluminescence, on individual, spatially isolated and suspended (free-standing) single-walled (SWNTs) and double-walled carbon nanotubes (DWNTs), we have been able to investigate their phonons characteristics and optical properties. In this talk, we present an overview of the most significant results obtained via this approach. Particular attention is paid to the study of DWNTs, a coaxial composite of two SWNTs, which provide a unique model system for studying coupling at the nanoscale. We show how such coupling, originating from the van der Waals interaction between the inner and outer nanotubes, plays a crucial role in determining the characteristics of the collective radial breathing-like modes and G modes in DWNTs (for a review see Ref. 1-2). The effects of quantum interference between different electronic transitions on the experimental behavior of the G-modes intensity are discussed [3]. It must be emphasized that the theoretical predictions of Philippe Lambin and his collaborators have been invaluable in understanding a lot of these experimental data [4].
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Une femme de science exceptionnelle : Mildred S. Dresselhaus
Auteur(s): San-Miguel Alfonso, Sauvajol J.-L.
(Article) Publié:
Reflets De La Physique, vol. 61 p.36-39 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02087924_v1
DOI: 10.1051/refdp/201961036
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Résumé: Première femme à avoir accédé au rang de professeur titulaire au Massachussetts Institute of Technology (MIT),Mildred Spiewak Dresselhaus, ou simplement Millie pourla plupart de ses collègues, est l’exemple d’un engagement passionnel et infatigable pour la science en général, la physique en particulier, et pour la reconnaissancede la place des femmes en science.Sa disparition le 20 février 2017 à l’âge de 86 ans, en pleine activité scientifique, a très profondément marqué les communautés de chercheurs engagés dansles nanosciences. Ses contributions à la compréhension du couplage entre propriétés électroniques,vibrationnelles et structurales, dans les différentes formesde carbone sont au centre du développement des nanomatériaux carbonés et de leurs applications.
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Probing the Intrinsic Vibrational and Optical Properties ofIndividual Chirality-Identified Carbon Nanotubes by Raman Spectroscopy
Auteur(s): Michel T., Levshov D., Zahab A. A., Sauvajol J.-L., Paillet M.
Chapître d'ouvrage: Handbook Of Carbon Nanomaterials:, vol. 10 p.chapter 10, pages 75-112 (2019)
Ref HAL: hal-02087885_v1
Exporter : BibTex | endNote
Résumé: The goal of this chapter is to review the main information derived from Raman spectroscopy on individual suspended (free-standing) chiralityidentified single-wall carbon nanotubes (SWCNTs) and double-wall carbonnanotubes (DWCNTs) with a special focus on the characteristics of their radial breathing modes and G modes, including their resonance conditions. ForSWCNTs, the different relationships between the radial breathing mode frequency and the inverse of the diameter illustrate the high sensitivity of individual suspended SWCNTs to their environmental conditions. The intrinsicprofiles of the optical longitudinal (LO) and transverse (TO) G modes are unambiguously identified both for metallic and semiconducting chiral and achiral SWCNTs, and the diameter dependence of the LO and TO frequencies are established. In DWCNTs, the intertube coupling, originating from the van der Waals interaction between the inner and outer tubes, plays an important role in determining the features/characteristics of the collectiveradial breathing-like modes and G modes.
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