A. Filankembo

Pierre and Marie Curie University - Paris 6, Paris, Ile-de-France, France

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Publications (14)37.97 Total impact

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    ABSTRACT: In this paper, copper nanocrystals are produced by using Cu(AOT)2−isooctane−water solution as a template. Even if the template does not change with various salt additions, the nanocrystal growth markedly depends on the salt used. It is demonstrated that chloride ions enable the growth of nanorods with an aspect ratio varying with chloride concentration. Conversely, only a slight amount of bromide ion is needed to increase the nanorod aspect ratio from 3 to 5 without any changes when increasing the bromide ion concentration. A rather large number of cubes are produced. Formations of nanorods and cubes are explained in terms of anion adsorption on (111) and (100) faces, respectively. By replacing chloride by other ions, the morphology of copper nanocrystals drastically changes. In all cases, the nanocrystals formed are fcc single crystals with a polyhedral shape or crystals composed of fcc tetrahedra (deformed or not) bounded by (111) faces. Some cylinders are formed by the connection of 2 different crystals with different 5-fold axes and/or with additional planes. This gives rise to various particle shapes.
    Journal of Physical Chemistry B - J PHYS CHEM B. 04/2003; 107(30).
  • A. Filankembo, M. P. Pileni
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    ABSTRACT: In the present Letter we demonstrate that particle shape can be controlled even if the macroscopic structure of the self-assembly used as a template remains unchanged. We demonstrate that the control of nanocrystal shape is influenced by the addition of salt while the same template is kept.
    Journal of Physical Chemistry B - J PHYS CHEM B. 06/2000; 104(25).
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    A Filankembo, M P Pileni
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    ABSTRACT: In this short paper, it is demonstrated that addition of various salts differing by their counter ions markedly changes the shape of copper metal nanocrystals. These follow the Hofmeister series. q 2000 Elsevier Science B.V. All rights reserved.
    Applied Surface Science 01/2000; 164:260-267. · 2.54 Impact Factor
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    ABSTRACT: In this paper we describe in detail the phase diagram Cu(AOT)2–water–isooctane in the oil rich region. The phase diagram is very rich. All the phases described are thermodynamically stable. In this paper we concentrate in the isotropic region obtained at rather large water content (29<w=[H2O]/[AOT]<40). A transition from interconnected cylinder to reverse micelles is observed. At high surfactant concentration the system does not have enough oil to solvate the surfactant alkyl chains and large aggregates made of interdigitated reverse micelles are surrounded by isolated water in oil droplets.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2000; 174:221-232. · 2.11 Impact Factor
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    ABSTRACT: Well-defined long Cu rods having a length of the order of 1 μm and diameters of several nanometers were prepared by reduction of copper compounds. After deposition on amorphous carbon films, high-resolution transmission electron microscopy and electron diffraction were performed in order to explain the structure of the rods. By applying computer simulations with multislice calculations, the particle structure was obtained. The rods were held to be truncated decahedra with a fivefold symmetry. It could be shown that most particles were oriented in the [001] direction with respect to the substrate for one of the five deformed tetrahedral subunits, i.e., the fivefold axis very often was parallel to the surface of the substrate. It was also proven that the Cu fcc bulk structure containing stacking faults had to be excluded as a possible structural model. Also, truncated icosahedral structures or icosahedra with additional intermediate planes did not serve to explain the experimental process. Icosahedra are often observed together with decahedral structures for particles with a spherical-like morphology. Due to the presence of surfactant, only growth in the direction of the fivefold axis of decahedra was possible, resulting in long needlelike rods.
    Physical Review B 01/2000; 61(7). · 3.66 Impact Factor
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    Advanced Materials 12/1999; 12(2):119 - 123. · 14.83 Impact Factor
  • Advanced Materials 11/1999; 11(16):1358 - 1362. · 14.83 Impact Factor
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    ABSTRACT: The phase behavior and microstructure of copper(II) bis(2-ethylhexyl) sulfosuccinate, Cu(AOT)2−isooctane−water, is determined over a wider domain than previously used. It is characterized by a rich variety of phases and microstructures. Equilibrium phases consisting of spontaneous thermodynamically stable emulsions in equilibrium with other microstructure phases are observed. These spontaneous emulsions are composed of supra-aggregates, lamellar spherulites in which the interior and exterior are phases of interconnected cylindrical nanostructures. In another part of the phase diagram, clumps of interdigitated micelles are surrounded by an interconnected cylinder phase. The phase boundaries emerge qualitatively from elementary considerations that require only notions of local and global packing constraints.
    Journal of Physical Chemistry B. 01/1999; 103(43):9176-9189.
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    Journal of Physical Chemistry B - J PHYS CHEM B. 01/1999; 103(43):9168-9175.
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    ABSTRACT: In this paper we demonstrate that growth of well-defined cylinders markedly depends on the ability of reactants to interact with the interface.
    Langmuir. 12/1998; 14(26).
  • M. P. Pileni, J. Tanori, A. Filankembo
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    ABSTRACT: An unusual phase diagram is presented. It is composed of copper(II) bis(2-ethylhexyl) sulfosuccinate Cu(AOT)2-isooctane-water. Keeping the concentration of the Cu(AOT)2-isooctane solution constant, increasing in the amount of water induces various phase transitions. At low water content, spherical and cylindrical reverse micelles are formed. By increasing the water content, a bicontinuous system appears. Further addition of water leads to the formation of planar and spherulite type lamellae. As more water is added only spherulites remain in the phase. Still further addition of water leads to a reappearance of an interconnected network and then reverse micelles.Syntheses performed in the various parts of the phase diagram show that the use of colloidal assemblies as templates favors the control of the shape of nanoparticles. Cylindrical metallic copper particles having the same size can be obtained in various parts of the phase diagram when the template is made of interconnected cylinders. A very low amount of cylinders (13%) is formed when the synthesis is performed in cylindrical reverse micelles. When the colloidal self-assembly is a mixture of several phases, various types of shapes can be obtained. In some cases, the polydispersity in size is so low that metallic particles are able to self-assemble in a hexagonal network. Multilayers can be observed and are arranged in a face centered cubic structure.
    Colloids and Surfaces A-physicochemical and Engineering Aspects - COLLOID SURFACE A. 01/1997; 123:561-573.
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    ABSTRACT: Well defined long Cu rods having a length of the order of 1 micron and diameters of several nanometers were prepared by reduction of copper compounds. After deposition on amorphous carbon films, HRTEM and electron diffraction were performed in order to explain the structure of the rods. By applying computer simulations with multislice calculations, the particle structure was obtained. The rods were held to be truncated decahedra with a 5-fold symmetry. It could be shown that most particles were oriented in the [001]-direction with respect to the substrate for one of the five deformed tetrahedral subunits, i.e., the 5-fold axis very often was parallel to the surface of the substrate. It was also proven that the Cu fcc bulk structure containing stacking faults had to be excluded as possible structural model. Also truncated icosahedral structures or icosahedra with additional intermediate planes did not serve to explain the experimental process. Icosahedra are often observed together with decahedral structures for particles with spherical-like morphology. Due to the presence of surfactant, only growth in the direction of the 5-fold axis of decahedra was possible resulting in long needle-like rods. PACS: 36.40.+d, 61.46.+w, 61.14.-x, 61.16.Bg
    Physical Review B, v.61, 4968-4974 (2000).