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Accueil > Les équipes > Nanostructures/Semi-Conducteurs Organiques (NASCO) > Publications

Publications

publié le , mis à jour le

2016



  • A. Efrem, M. Courté, K. Wang, D. Fichou, et M. Wang, « Synthesis and characterization of γ-lactone-Pechmann dye based donor-acceptor conjugated polymers », Dyes and Pigments, vol. 134, p. 171-177.
    Résumé : A new acceptor moiety, γ-lactone-Pechmann dye is synthesized and used in the construction of two new conjugated D-A polymers. The optical and electrochemical characterization shows a broad absorption band extended to 1000 nm and narrow band gaps with deep LUMO energy levels. The chemical structures of the side chains appended from the donor units affect the intermolecular aggregation and the charge transport in thin-film field-effect transistors. The high degree of planarity, low bandgap, and strong electron accepting properties could make γ-lactone-Pechmann dye as a good candidate for the construction of conjugated D-A polymers.
    Mots-clés : Conjugated D-A polymers, Field-effect transistor, Lactone, Low bandgap, NASCO, Pechmann dye, POLE 2.

  • Z. Ku, N. H. Tiep, B. Wu, T. C. Sum, D. Fichou, et H. J. Fan, « Solvent engineering for fast growth of centimetric high-quality CH3NH3PbI3 perovskite single crystals », New Journal of Chemistry, vol. 40, nᵒ 9, p. 7261-7264.
    Résumé : Centimetre-scale CH3NH3PbI3 perovskite single crystals of high structural quality are grown by a new versatile method based on the use of a binary solvent mixture at a temperature as low as 70 degrees C. The growth rate is fast enough for a millimeter scale seed crystal to grow to the centimeter scale in a few hours.
    Mots-clés : crystallization, deposition, diffusion, electron, lead iodide perovskite, NASCO, organometal halide perovskites, performance, POLE 2, room-temperature, sensitized solar-cell, v hysteresis.

  • I. Minguez-Bacho, S. Rodriguez-Lopez, A. Climent-Font, D. Fichou, M. Vazquez, et M. Hernandez-Velez, « Variation of the refractive index by means of sulfate anion incorporation into nanoporous anodic aluminum oxide films », Microporous and Mesoporous Materials, vol. 225, p. 192-197.
    Résumé : The variation in the refractive index of nanoporous anodic aluminum oxide (AAO) films regarding the sulfur anion incorporation is studied in this work. For this purpose, different samples are grown under potentiostatic conditions at different voltages and concentrations of sulfuric acid in the electrolyte. The samples are analyzed by Rutherford backscattering spectroscopy and infrared spectrometry, confirming the presence of sulfate anions and water embedded into the nanoporous MO films. The incorporation of. sulfate ions into the alumina matrix varies from 63 up to 11.7% regarding aluminum content. We have studied Fabry-Perot optical interferences by shining incident monochromatic light in specular reflectance conditions. The reflected monochromatic light waves interact in internal reflectivity generating constructive and destructive interferences known as Fabry-Perot optical interferences. An iterative method based on the equation for constructive interferences conditions in thin films and Snell equations is developed in order to calculate the refractive index of the nanoporous AAO films as a function of the wavelength. The calculated refractive indices increase when the sulfur content of the nanoporous MO films decreases. The variation of the calculated refractive index is 0.08 and remains constant in the wavelength range 400-1200 nm. (C) 2015 Elsevier Inc. All rights reserved.
    Mots-clés : Anion incorporation, electrolyte, Fabry-Perot interferences, membranes, nanohole arrays, Nanoporous anodic alumina, nanotube arrays, NASCO, optical-properties, POLE 2, porous alumina, Refractive index, templates, thin-films, transmission, volume expansion.


  • H. Qi, J. Wolfe, D. Fichou, et Z. Chen, « Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst », Scientific Reports, vol. 6, p. 30882.
    Résumé : Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light.
    Mots-clés : NASCO, POLE 2.


  • V. Rajeshkumar, M. Courté, D. Fichou, et M. C. Stuparu, « Synthesis and Properties of Large Polycyclic Aromatic Hydrocarbons with Planar and Non-Planar Structural Motifs », European Journal of Organic Chemistry, vol. 2016, nᵒ 36, p. 6010-6014.
    Résumé : Implementation of non-planar aromatic motifs in the molecular design of π-conjugated materials represents a paradigm shift that is interesting from a fundamental research viewpoint but remains largely underdeveloped. To further facilitate this cause, we report on the synthesis and properties of two large polycyclic aromatic compounds (38 carbon atoms). In one compound the planar π-system pyrene is linked to bowl-shaped hydrocarbon corannulene through a C=C bond, which is referred to as “corannulene–vinylpyrene”. Photochemical treatment of this compound results in annulation of both aromatic nuclei and formation of the other large fused structure with ten six-membered aromatic rings, referred to as “corannulene–benzopyrene”. Photophysical and electrochemical studies reveal that the properties of these two structurally related hybrid materials arise from an extended π-conjugation between the planar and non-planar motifs and varies depending upon their molecular structure.
    Mots-clés : Annulation, Arenes, cyclization, Fused-ring systems, NASCO, POLE 2, polycycles.


  • V. Rajeshkumar, C. Marc, D. Fichou, et M. C. Stuparu, « Synthesis and Properties of a Buckybowl/Buckyball Dyad », Synlett, vol. 27, nᵒ 14, p. 2101-2104.
    Résumé : Thieme E-Books & E-Journals
    Mots-clés : NASCO, POLE 2.

  • C. Shen, D. Fichou, et Q. Wang, « Interfacial Engineering for Quantum-Dot-Sensitized Solar Cells », Chemistry-an Asian Journal, vol. 11, nᵒ 8, p. 1183-1193.
    Résumé : Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5%, far behind their molecular sensitizer counterparts (up to 13%). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs.
    Mots-clés : charge separation, detailed balance limit, high-efficiency, highly efficient, improved photovoltaic performance, nanostructures, NASCO, POLE 2, quantum dots, recombination control, renewable resources, sensitizers, solar cells, sulfide counter electrodes, thin-film, tio2 electrodes, zno nanowires.


  • C. Shen, D. Fichou, et Q. Wang, « Interfacial Engineering for Quantum-Dot-Sensitized Solar Cells », Chemistry – An Asian Journal, vol. 11, nᵒ 8, p. 1183-1193.
    Résumé : Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5 %, far behind their molecular sensitizer counterparts (up to 13 %). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs.
    Mots-clés : nanostructures, NASCO, POLE 2, quantum dots, renewable resources, sensitizers, solar cells.


  • I. Minguez-Bacho, M. Courté, H. J. Fan, et D. Fichou, « Conformal Cu 2 S-coated Cu 2 O nanostructures grown by ion exchange reaction and their photoelectrochemical properties », Nanotechnology, vol. 26, nᵒ 18, p. 185401.
    Résumé : Cuprous oxide Cu 2 O is a promising p-type semiconductor for photoelectrochemical (PEC) solar hydrogen generation because it has a suitable bandgap ( E g = 2.0–2.2 eV) and a band alignment adapted to water reduction. In addition, metallic Cu is earth-abundant thus making Cu 2 O a low-cost material. However, the reduction potential of Cu 2 O into metallic Cu (0.47 V versus RHE) is lower than that of water which induces a severe instability under irradiation in a PEC cell. Therefore, our recent efforts focused on the growth of a protective overlayer on top of Cu 2 O in order to stabilize Cu 2 O when used as a photocathode in an aqueous electrolyte. Among potential protective materials cuprous sulphide Cu 2 S is another p-type semiconductor with a 1.2 eV bandgap and an appropriate energy level alignment with Cu 2 O that would allow electrons flowing to the interface. We present here an original and simple method aimed at protecting a compact layer (CL) or nanowires (NWs) of Cu 2 O with a Cu 2 S coating. Our method is based on the ions exchange reaction (IER) of O 2− into S 2− at the surface of Cu 2 O itself in a solution-containing Na 2 S as the sulphur source. The local surface IER implies the formation of a conformal and uniform coating independently on the starting Cu 2 O morphology, CLs or NWs. As expected, coating Cu 2 O photocathodes by a conformal Cu 2 S layer improves their stability and PEC performances.
    Mots-clés : NASCO, POLE 2.

  • I. Minguez-Bacho, M. Courte, H. J. Fan, et D. Fichou, « Conformal Cu2S-coated Cu2O nanostructures grown by ion exchange reaction and their photoelectrochemical properties », Nanotechnology, vol. 26, nᵒ 18, p. 185401.
    Résumé : Cuprous oxide Cu2O is a promising p-type semiconductor for photoelectrochemical (PEC) solar hydrogen generation because it has a suitable bandgap (E-g = 2.0-2.2 eV) and a band alignment adapted to water reduction. In addition, metallic Cu is earth-abundant thus making Cu2O a low-cost material. However, the reduction potential of Cu2O into metallic Cu (0.47 V versus RHE) is lower than that of water which induces a severe instability under irradiation in a PEC cell. Therefore, our recent efforts focused on the growth of a protective overlayer on top of Cu2O in order to stabilize Cu2O when used as a photocathode in an aqueous electrolyte. Among potential protective materials cuprous sulphide Cu2S is another p-type semiconductor with a 1.2 eV bandgap and an appropriate energy level alignment with Cu2O that would allow electrons flowing to the interface. We present here an original and simple method aimed at protecting a compact layer (CL) or nanowires (NWs) of Cu2O with a Cu2S coating. Our method is based on the ions exchange reaction (IER) of O2- into S2- at the surface of Cu2O itself in a solution-containing Na2S as the sulphur source. The local surface IER implies the formation of a conformal and uniform coating independently on the starting Cu2O morphology, CLs or NWs. As expected, coating Cu2O photocathodes by a conformal Cu2S layer improves their stability and PEC performances.
    Mots-clés : atomic layer, cuprous sulphide, cuprous oxide, energy conversion, ion exchange reaction, nanomorphology, nanowire arrays, NASCO, photocathode, photoelectrochemistry, POLE 2, sensitized solar-cells, Stability, sulfide nanocrystals, thin-films, visible-light, water reduction.


  • I. Mínguez-Bacho, M. Courté, C. Shi, et D. Fichou, « Controlling the nanomorphology of thin conformal Cu2S overlayers grown on Cu2O compact layers and nanowires », Materials Letters, vol. 159, p. 47-50.
    Résumé : Thin conformal Cu2S overlayers are grown on Cu2O compact layers (CLs) and nanowires (NWs) by ion exchange reaction (IER). This method is based on the exchange of O2– into S2– ions at the surface of Cu2O in a solution-containing Na2S acting as the sulfur ions source. The Cu2S overlayers are grown under different experimental conditions by varying the Na2S concentration and the duration of the IER process, thus leading to different Cu2S nanomorphologies. In particular, when a concentration of 2 mM Na2S is used, hexagonal Cu2S nanocrystals are formed on the surface of both Cu2O CLs and NWs. These nanocrystals are of larger size at the ridges of the Cu2O cubes in CLs and at the tips of Cu2O in NWs. The high-quality crystal structure and composition of Cu2S are confirmed by high resolution transmission electron spectroscopy and X-ray photoluminescence spectroscopy.
    Mots-clés : Copper oxide, Copper sulfide, ion exchange reaction, nanomorphology, NASCO, Overlayer, POLE 2.

2014


  • G. H. V. Bertrand, L. Tortech, V. Gandon, C. Aubert, et D. Fichou, « Synthesis and photovoltaic performances in solution-processed BHJs of oligothiophene-substituted organocobalt complexes [(eta(4)-C-4(nT)(4))Co(eta(5)-C5H5)] », Chemical Communications, vol. 50, nᵒ 63, p. 8663-8666.
    Résumé : We describe an efficient synthetic route toward novel organocobalt complexes [(eta(4)-C-4(nT)(4))Co(eta(5)-C5H5)] with n = 1, 2, 3 thiophene rings. Solution-processed bulk heterojunctions solar cells based on CpCoCb(3T)(4):PCBM blends achieve power conversion efficiencies of up to 2.1%.
    Mots-clés : conversion efficiency, elements, heterojunction solar-cells, MACO, molecules, NASCO, open-circuit voltage, organic semiconductors, oxidation, phthalocyanines, POLE 1, POLE 2, polymers, srtio3.
    Pièce jointe

  • G. Y. Y. Chng, X. Sun, S. J. Cho, D. Rajwar, A. C. Grimsdale, et D. Fichou, « Synthesis and 2D self-assembly at the liquid-solid interface of novel H-bonding linear pi-conjugated oligomers terminated by uracil and melamine units », New Journal of Chemistry, vol. 38, nᵒ 6, p. 2407-2413.
    Résumé : We report here on the synthesis and 2D self-assembly of novel H-bonding linear it-conjugated oligomers terminated at both ends by either two uracil moieties (compound GR1) or by two melamine groups (compounds GR2 and GR3). The bis(uracil) GR1 compound was prepared by Sonogashira coupling of an ethynyturacil with a dihalobenzene and characterized spectroscopically. The synthesis of GR2 and GR3 was performed by Suzuki coupling of the dihalogenated benzene derivatives leading to the respective bisadducts which were then converted into the target bis-melamine derivatives by treatment with dicyanodimide. Self-assembly of the GR1 derivative is investigated at the liquid/graphite interface using scanning tunneling microscopy (STM). When deposited from n-tetradecane, GR1 forms a row-like structure stabilized by multiple terminal H-bonds between neighboring molecules. Co-adsorption of two n-tetradecane molecules per unit cell is also clearly identified. In turn, when deposited from 1-phenyloctane GR1 forms a complex quasi square-shaped open structure having asymmetric sides. One possible arrangement is that four phenyloctane molecules are co-adsorbed in-between GR1 rows similar to those formed from n-tetradecane, thus forming the two other sides of the square-shaped motif. From both solvents, the row-like 2D arrangements are governed by the multiple terminal H-bonds which create long-range alignments in one direction and by the van der Waals interdigitation of the dodecyl chains of the GR1 molecules that stabilize the network in a nearly perpendicular direction.
    Mots-clés : au(111), devices, graphite, molecular modules, monolayers, NASCO, POLE 2, surfaces, symmetry, trimesic acid.


  • M. Alaaeddine, Q. Zhu, D. Fichou, G. Izzet, J.E. Rault, N. Barrett, A. Proust, et L. Tortech, « Enhancement of photovoltaic efficiency by insertion of a polyoxometalate layer at the anode of an organic solar cell », Inorg. Chem. Frontiers, vol. 1, nᵒ 9, p. 682-688.
    Résumé : In this article the Wells–Dawson polyoxometalate K6[P2W18O62] is grown as an interfacial layer between indium tin oxide and bulk heterojunction of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The structure of the POM layers depends on the thickness and shows a highly anisotropic surface organization. The films have been characterized by atomic force microscopy and X-ray photoelectron spectroscopy (XPS) to gain insight into their macroscopic organization and better understand their electronic properties. Then, they were put at the anodic interface of a P3HT:PCBM organic solar cell and characterized on an optical bench. The photovoltaic efficiency is discussed in terms of the benefit of the polyoxometalate at the anodic interface of an organic photovoltaic cell.
    Mots-clés : E-POM, NASCO, POLE 2.

  • E. G. Petrov, A. Marchenko, O. L. Kapitanchuk, N. Katsonis, et D. Fichou, « Conductance Mechanism in a Linear Non-Conjugated Trimethyls

    ilyl-Acetylene Molecule: Tunneling Through Localized States », Molecular Crystals and Liquid Crystals, vol. 589, nᵒ 1, p. 3-17.
    Résumé : The conductance properties of 1,3-(trimethylsilyl)-1-tridecene-6,12-diyne, a non-conjugated trimethylsil-acetylene molecule have been investigated both experimentally and theoretically. Based on scanning tunnelling spectroscopy experiments, a discussion on the mechanisms controlling the charge transfer through this linear molecule is carried out. A specific property of the studied molecule is that it contains localized molecular orbitals. The shifts of the MOs energy levels caused by the applied voltage as well as a distant superexchange coupling between the respective localized MOs are shown to become determining in the formation of a nonlinear hole current through the molecule.
    Mots-clés : Charge transport mechanisms, conductance, current-voltage characteristics, density, devices, electron-transport, energy, junctions, localized states, monolayer, NASCO, organosilane, POLE 2, single-molecule, stm, transmission, wires.

  • H. Qi, J. Wolfe, D. Wang, H. J. Fan, D. Fichou, et Z. Chen, « Triple-layered nanostructured WO3 photoanodes with enhanced photocurrent generation and superior stability for photoelectrochemical solar energy conversion. », Nanoscale, vol. 6, nᵒ 22, p. 13457-62.
    Résumé : Unique nanorods/nanoparticles/nanoflakes (NRs/NPs/NFs) WO3 triple-layers are grown on a metallic W foil by a simple one-step anodization method. The triple-layered structure is formed through a self-organization process, the film thickness (up to 3 mum) being controlled by the anodization time. A first layer made of an array of WO3 densely-packed vertically-aligned NRs (1.2-1.4 mum in height) grow atop the tungsten foil, followed by a second layer of small NPs (50-80 nm) and finally a third layer made of rectangular NFs (200-300 nm). When irradiated by white light in a photoelectrochemical cell these WO3 triple-layers generate a photocurrent as high as 0.9 mA cm(-2) at 1.2 V/RHE. Moreover, we show that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.
    Mots-clés : NASCO, POLE 2.

  • T. Salim, J. Y. Lek, B. Braeuer, D. Fichou, et Y. M. Lam, « Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics (vol 16, pg 23829, 2014) », Physical Chemistry Chemical Physics, vol. 16, nᵒ 47, p. 26389-26389.


  • T. Salim, J. Y. Lek, B. Bräuer, D. Fichou, et Y. M. Lam, « Correction: Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics », Physical Chemistry Chemical Physics, vol. 16, nᵒ 47, p. 26389-26389.
    Résumé : Correction for ‘Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics’ by Teddy Salim et al., Phys. Chem. Chem. Phys., 2014, 16, 23829–23836.
    Mots-clés : NASCO, POLE 2.

2013


  • H. Bertrand, R. Guillot, M. - P. Teulade-Fichou, et D. Fichou, « Synthesis, Properties, and Remarkable 2D Self-Assembly at the Liquid/Solid Interface of a Series of Triskele-Shaped 5,11,17-Triazatrinaphthylenes (TrisK) », Chemistry-a European Journal, vol. 19, nᵒ 43, p. 14654-14664.
    Résumé : A series of 5,11,17-triazatrinaphthylene (TrisK) derivatives, large disk-like p-conjugated molecules with C-3h symmetry, has been synthesised by following an optimised synthetic pathway. The synthesis was performed by a four-step protocol based on the N-arylation of 1,3,5-tribromobenzene with appropriate anthranilate derivatives. This strategy permits the generation of either chlorinated (TrisK-Cl-OCn) or non-chlorinated (TrisK-H-OCn) alkoxy-substituted derivatives (OCnH2n+1 with n=3, 10, 12 and 16), thus providing additional versatility in the control of the structure-property relationships. The electronic properties of the various TrisK compounds have been characterised in solution by absorption and emission spectroscopies as well as cyclic voltammetry. The crystal structure of 2,8,14-propyloxy-5,11,17-triazatrinaphthylene TrisK-H-OC3 has been determined by X-ray diffraction analysis, which revealed the presence of stabilising weak intermolecular H bonds. Scanning tunnelling microscopy (STM) at the liquid/solid interface has revealed the remarkable 2D self-assembling properties of the TrisK compounds. In particular, it has shown that TrisK-H-OC12 forms three concomitant self-organised 2D phases with different row-packing arrangements. This 2D polymorphism arises from slow ordering due to the presence of three long dodecyloxy chains on the molecular backbone. Individual molecules can be imaged with spectacular intramolecular resolution, thus providing the possibility of correlating the STM features with the calculated charge density distribution.
    Mots-clés : FICHOU, NASCO, POLE 2.

  • C. Blouzon, F. Ott, L. Tortech, D. Fichou, et J. - B. Moussy, « Anti-ferromagnetic coupling in hybrid magnetic tunnel junctions mediated by monomolecular layers of alpha-sexithiophene », Applied Physics Letters, vol. 103, nᵒ 4, p. 042417.
    Résumé : We report here on the magnetic coupling taking place between Fe3O4 and Co layers across an organic monolayer of alpha-sexithiophene (6T). The controlled growth of 6T ultrathin films on epitaxial Fe3O4 surfaces allows to prepare highly homogeneous insulating layers with thicknesses in the range 0.5-2.0 monolayers (ML). A combined study using vibrating sample magnetometry and polarized neutron reflectivity reveals that hybrid Fe3O4/6T/Co tunnel junctions show different magnetic couplings depending on the 6T thickness. In particular, magnetic coupling between Fe3O4 and Co layers separated by 1 ML of 6T is consistent with anti-ferromagnetic coupling, opening new perspectives for controlling magnetization in organic spintronic devices. (C) 2013 AIP Publishing LLC.
    Mots-clés : co/ru, FICHOU, NASCO, order, organic semiconductors, POLE 2.

  • A. Nion, N. Katsonis, A. Marchenko, C. Aubert, et D. Fichou, « Influence of molecular length on the adsorption of linear trimethylsilylacetylene derivatives at the n-tetradecane/Au(111) interface: chemisorption vs. physisorption », New Journal of Chemistry, vol. 37, nᵒ 8, p. 2261-2265.
    Résumé : Adsorption of two trimethylsilylacetylene (TMSA) derivatives bearing linear alkyl chains of different lengths has been studied at the n-tetradecane/Au(111) interface. The lying or standing orientation of TMSA compounds on the gold surface shows that adsorption is not only controlled by the chemical reactivity of the molecules but also by their size.
    Mots-clés : au(111), COS, FICHOU, Gold, long, MACO, NASCO, organosilane, POLE 1, POLE 2, scanning-tunneling-microscopy, self-assembled monolayers, stm, surfaces.
    Pièce jointe

  • A. Pancotti, J. Wang, P. Chen, L. Tortech, C. - M. Teodorescu, E. Frantzeskakis, et N. Barrett, « X-ray photoelectron diffraction study of relaxation and rumpling of ferroelectric domains in BaTiO3(001) », Physical Review B, vol. 87, nᵒ 18, p. 184116.
    Résumé : The surface of a ferroelectric BaTiO3(001) single crystal was studied using synchrotron radiation induced x-ray photoelectron diffraction (XPD), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and low-energy electron diffraction (LEED). AFM, XPS, and LEED show that the surface is BaO terminated with a (1 x 1) reconstruction. The Ba 4d, Ti 2p, and O 1s XPD results were compared with multiple scattering simulations for out-of- (P+, P) and in-plane (P-in) polarizations using a genetic algorithm to determine atomic rumpling and interlayer relaxation. Linear combinations of the XPD simulations of the surface structure of each polarization state allow determination of the domain ordering. The best agreement with experiment is found for 55% P+, 38% P-, and 7% P-in. The rumpling is smaller at the surface than in the bulk, suggesting that both domain ordering and surface structural changes contribute to screening of the polarization.
    Mots-clés : NASCO, NSCO, POLE 2, surface.

2012


  • C. Afonso, D. Lesage, F. Fournier, V. Mancel, et J. - C. Tabet, « Origin of enantioselective reduction of quaternary copper D,L amino acid complexes under vibrational activation conditions », International Journal of Mass Spectrometry, vol. 312, p. 185-194.
    Résumé : Phenylglycine (Phg), a non natural amino acid was used as chiral selector for the distinction of L/D amino acids through enantioselective Cu-II reduction. The investigation of the chiral effects was performed based on the dissociation of copper quaternary complexes involving phenylglycine: [Cu-II,(Phg,AA(1),AA(2)-H)](+). The main cleavage was the competitive formal loss of Phg and [Phg-H](+) yielding the [Cu-II,(AA(1),AA(2)-H)](+) and [Cu-I,(AA(1),AA(2))](+) ions respectively. The later involving a stepwise process with CO2 loss and a concomitant Cu-II reduction. The relative extent of this competitive process appeared to be strongly enantioselective. This led us to explore the origin of the observed enantiomeric reduction from dissociations of copper AAs complexes. With this aim, smaller [Cu-II,(Phg,AA-H)](+) ternary complexes have been investigated and MSn tog

    ether with double resonance-IRMPD experiments have been conducted. The existence of zwitterions was considered in order explain the role of gas phase acidity and proton affinity on the enantioselective reduction. (C) 2011 Elsevier B.V. All rights reserved.
    Mots-clés : Amino acids, chiral recognition, chirality, chromatographic-separation, collision-induced dissociation, Copper, CSOB, diimine ligands, Double resonance, enantioselectivity, FICHOU, fragmentations, ft-icr, gas-phase complexes, irmpd, kinetic method, NASCO, POLE 2, POLE 3, proton affinities, quadrupole ion-trap, reduction, trap mass-spectrometer.


  • G. Bertrand, L. Tortech, D. Fichou, M. Malacria, C. Aubert, et V. Gandon, « An Improved Protocol for the Synthesis of [(η4-C4R4)Co(η5-C5H5)] Complexes », Organometallics, vol. 31, nᵒ 1, p. 126-132.
    Résumé : The reaction of bulky alkynes C2R2 with (?5-C5H5)Co(CO)(dimethyl fumarate) under microwave irradiation provides complexes of the type [(?4-C4R4)Co(?5-C5H5)] in good to excellent yields. This protocol represents a significant improvement over those reported previously. In particular, the formation of insertion products such as cyclopentadienones or cyclohexadienes can be avoided. In addition, because of the exceptional stability of (?5-C5H5)Co(CO)(dimethyl fumarate), the reactions can be carried out in crude solvents. The easy access to [(?4-C4R4)Co(?5-C5H5)] complexes stimulated a study of their reactivity, notably under cross-coupling conditions.
    Mots-clés : COS, FICHOU, MACO, NASCO, POLE 1, POLE 2.


  • D. Rajwar, X. Sun, S. J. Cho, A. C. Grimsdale, et D. Fichou, « Synthesis and 2D self-assembly at the liquid-solid interface of end-substituted star-shaped oligophenylenes », CrystEngComm, vol. 14, nᵒ 16, p. 5182-5187.
    Résumé : We report here on the synthesis and self-assembly of four star-shaped trigonal 1,3,5-tris-(1,1-biphenyl-4-yl)-benzene (TBB) derivatives substituted by different functional groups on the terminal positions of the three arms of the molecule: COOCH3 (1), COOH (2), NH2 (3), and CN (4). Self-assembly of the tries
    Mots-clés : FICHOU, NASCO, NSCO, POLE 2.

2011



  • H. Bertrand, F. Silly, M. - P. Teulade-Fichou, L. Tortech, et D. Fichou, « Locking the free-rotation of a prochiral star-shaped guest molecule inside a two-dimensional nanoporous network by introduction of chlorine atoms », Chemical Communications, vol. 47, nᵒ 36, p. 10091-10093.
    Résumé : Two star-shaped triazatrinaphthylene (TrisK) derivatives form highly-organized nanoporous honeycomb networks when adsorbed at the n-tetradecane/HOPG interface. STM reveals that replacing three H-atoms by three Cl-atoms in the chemical structure of the TrisK skeleton results in locking the free-rotation of th Molecule-based surface chemistry
    Mots-clés : NASCO, NSCO, POLE 2.

2010


  • S. Berny, L. Tortech, D. Fichou, S. Matzen, et J. - B. Moussy, « Organic-inorganic magnetic tunnel heterojunctions based on dithiapyrannylidene ultrathin films grown on Fe3O4(111) », Applied Physics Letters, vol. 97, nᵒ 25, p. 253303.
    Résumé : We report on the morphology, transport, and magnetic properties of ultrathin films of 4,4'-bis(diphenyl-2,6-thiapyrannylidene) (DITPY-Ph-4), a planar quinoid organic compound with potential applications in electronics. Atomic force microscopy (AFM) shows that highly homogeneous and continuous DITPY-Ph4 ultrathin films with thicknesses as low as 2 nm can be grown on epitaxial Fe3O4(111). Current-sensing AFM performed on ultrathin layers evidences an insulating behavior with a nonresonant tunneling conduction regime. Vibrating sample magnetometry achieved on Fe3O4/DITPY-Ph-4/Co organic-inorganic heterojunctions reveals the decoupling between the two magnetic electrodes and demonstrates that DITPY-Ph4 can be used to build magnetic tunnel junctions. (C) 2010 American Institute of Physics. [doi:10.1063/1.3529456]
    Mots-clés : NASCO, NSCO, POLE 2, semiconductors.

  • S. Berny, L. Tortech, M. Veber, et D. Fichou, « Dithiapyrannylidenes as Efficient Hole Collection Interfacial Layers in Organic Solar Cells », Acs Applied Materials & Interfaces, vol. 2, nᵒ 11, p. 3059-3068.
    Résumé : One inherent limitation to the efficiency of photovoltaic solar cells based on polymer/fullerene bulk heterojunctions (BHJs) is the accumulation of positive charges at the anodic interface. The unsymmetrical charge collection of holes and electrons dramatically decreases the short-circuit current. Interfacial layers (IFLs) such as poly (3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) have no effect on the unbalanced electron/hole transport across the BHJ. We report here on the use of dithiapyrannylidenes (DITPY), a new class of planar quinoid compounds, as efficient hole-transporting/electron-blocking layers in organic solar cells based on poly(3- hexylthiophene)/[6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM) BHJs. Inserting a 15-nm-thick IFL of 4,4'-bis(diphenyl-2,6- thiapyrannylidene) (DITPY-Ph(4)) between the indium-tin oxide electrode and the P3HT:PCBM BHJ prevents detrimental space charge effects and favors recombination limited currents. Current-sensing atomic force microscopy reveals a drastic increase of the hole-carrying pathways in DITPY-Ph(4) compared to PEDOT-PSS. In ambient conditions photovoltaic cells using DITPY-Ph(4) exhibit an 8% increase in the current density although the conversion efficiency remains slightly lower compared to PEDOT:PSS-based devices. Finally, we represent a detailed analysis of the photocurrent generation, showing that DITPY-Ph(4) IFLs induce a transition from unproductive space-charge-limited currents to recombination-limited currents.
    Mots-clés : charge-transport, conversion efficiency, current-sensing atomic force microscopy, electronic devices, injection, interfacial layers, light-emitting-diodes, NASCO, NSCO, organic solar cells, pedot-pss films, photocurrent generation, photovoltaic cells, photovoltaic devices, POLE 2, self-assembled monolayers, space-charge-limited current, thin-films.


  • P. Keg, A. Dell'Aquila, F. Marinelli, O. L. Kapitanchuk, D. Fichou, P. Mastrorilli, G. Romanazzi, G. P. Suranna, L. Torsi, Y. M. Lam, et S. G. Mhaisalkar, « Solution processable ter-anthrylene-ethynylenes semiconductors: thin film transistor properties and STM study on HOPG and Au(111) », Journal of Materials Chemistry, vol. 20, nᵒ 12, p. 2448-2456.
    Résumé : The article reports the properties of new solution processable 9,10-ter-anthrylene-ethynylenes functionalised with n-butyl (B3A) n-octyl (O3A) and 2-ethyl-hexyl (E3A) functional groups. The characterization of the oligomers as organic semiconductors in solution processed top-contact bottom-gate OTFT devices
    Mots-clés : NASCO, NSCO, POLE 2.


  • C. Marie, F. Silly, L. Tortech, K. Müllen, et D. Fichou, « Tuning the Packing Density of 2D Supramolecular Self-Assemblies at the Solid−Liquid Interface Using Variable Temperature », ACS Nano, vol. 4, nᵒ 3, p. 1288-1292.
    Résumé : The two-dimensional (2D) crystal engineering of molecular architectures on surfaces requires controlling various parameters related respectively to the substrate, the chemical structure of the molecules, and the environmental conditions. We investigate here the influence of temperature on the self-assembly of hexakis(n-dodecyl)-peri-hexabenzocoronene (HBC-C12) adsorbed on gold using scanning tunneling microscopy (STM) at the liquid/solid interface. We show that the packing density of 2D self-assembled HBC-C12 can be precisely tuned by adjusting the substrate temperature. Increasing the temperature progressively over the 20?50 °C range induces three irreversible phase transitions and a 3-fold increase of the packing density from 0.111 to 0.356 molecule/nm2. High-resolution STM images reveal that this 2D packing density increase arises from the stepwise desorption of the n-dodecyl chains from the gold surface. Such temperature-controlled irreversible phase transitions are thus a versatile tool that can then be used to adjust the packing density of highly ordered functional materials in view of applications in organic electronic devices.
    Mots-clés : NASCO, NSCO, POLE 2.

  • M. Mura, X. Sun, F. Silly, H. T. Jonkman, G. a. D. Briggs, M. R. Castell, et L. N. Kantorovich, « Experimental and theoretical analysis of H-bonded supramolecular assemblies of PTCDA molecules », Physical Review B, vol. 81, nᵒ 19, p. 195412.
    Résumé : Using a systematic method based on considering all possible hydrogen bond connections between molecules and subsequent density-functional theory (DFT) calculations, we investigated planar superstructures that the perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) molecules can form in one and two dimensions. Structures studied are mostly based on two molecule unit cells and all assemble in flat periodic arrays. We show that 42 different monolayer structures are possible, which can be split into eight families of distinct structures. A single representative of every family was selected and relaxed using DFT. We find square, herringbone and brick wall phases (among others) which were already observed on various substrates. Using scanning tunneling microscopy in ultrahigh vacuum, we also observed herringbone and square phases after sublimation of PTCDA molecules on the Au(111) surface at room temperature, the square phase being observed for the first time on this substrate. The square phase appears as a thin stripe separating two herringbone domains and provides a perfect structural matching for them. A similar structural formation serving as a domain wall between two other phases has been recently reported on the same surface formed by melamine molecules [F. Silly et al., J. Phys. Chem. C 112, 11476 (2008)]. Our theoretical analysis helps to account for these and other observed complex structures.
    Mots-clés : 3,4,9,10-perylenetetracarboxylic-dianhydride ptcda, au(111) surface, cyanuric acid, growth, homopairing possibilities, melamine, metal-surfaces, NASCO, networks, NSCO, organic thin-film, POLE 2, scanning-tunneling-microscopy.

  • X. Sun, H. T. Jonkman, et F. Silly, « Tailoring two-dimensional PTCDA-melamine self-assembled architectures at room temperature by tuning molecular ratio », Nanotechnology, vol. 21, nᵒ 16, p. 165602.
    Résumé : Engineering and tuning multi-component supramolecular self-assemblies on surfaces is one of the challenges of nanotechnology. We use scanning tunneling microscopy to investigate the influence of molecular ratio on the self-assembly of PTCDA-melamine structures on Au(111)-(22 x root 3). Our observations reveal that three different chiral supramolecular networks having a PTCDA:melamine ratio of 3:2, 1:2, 1:4 can be selectively created by tuning the ratio of molecules deposited on the surface. The 1:2 ratio network having melamine in excess has been observed previously but the 1:4 network has not yet been reported. In comparison, the multi-component 3:2 network having PTCDA in excess is a completely new structure.
    Mots-clés : au(111) surface, cyanuric acid, Fullerenes, nanoporous networks, nanostructures, NASCO, NSCO, POLE 2, scanning-tunneling-microscopy, solid-liquid interface, substrate, supramolecular network, thin-films.

  • X. Sun et F. Silly, « NaCl islands decorated with 2D or 3D 3,4,9,10-perylene-tetracarboxylic-dianhydride nanostructures », Applied Surface Science, vol. 256, nᵒ 7, p. 2228-2231.
    Résumé : The formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(1 1 1)-(22 x root 3) covered with NaCl islands has been studied using scanning tunneling microscopy (STM). Atomically resolved STM images show that NaCl grows as (1 0 0)-terminated layers on Au(1 1 1)-(22 x root 3). Local atomic hexagonal packing has also been observed in the NaCl(1 0 0) layer. At submonolayer NaCl coverage, PTCDA forms two-dimensional islands on the Au(1 1 1) surface and nucleate preferentially at the NaCl island step edges. When the Au surface is fully covered with NaCl layers, PTCDA molecules form three-dimensional molecular clusters decorating the step edges of NaCl layers. (C) 2009 Elsevier B.V. All rights reserved.
    Mots-clés : atomic-resolution, Crystalline orientation and texture, Fullerenes, growth, Molecular domain, nanocrystals, nanoparticles, Nanoscale pattern formation, NASCO, NSCO, POLE 2, Scanning tunneling microscopy, scanning-tunneling-microscopy, srtio3(001), Structure and morphology, supramolecular network, surfaces, thin-films.


  • M. Zhao, K. Deng, P. Jiang, S. - S. Xie, D. Fichou, et C. Jiang, « Binary-Component Self-Assembled Monolayer Comprising Tetrathiafulvalene and n-Tetradecane Molecules with Periodic Ordered Phase Separation Structures on a Highly Oriented Pyrolytic Graphite Surface », The Journal of Physical Chemistry C, vol. 114, nᵒ 3, p. 1646-1650.
    Résumé : A binary-component self-assembled monolayer (SAM) comprising tetrathiafulvalene (TTF) and n-tetradecane (n-C14H30) molecules has been investigated by a scanning tunneling microscope (STM) on a highly oriented pyrolytic graphite (HOPG) surface at room temperature. High-resolution STM images of the SAM reveal that the two different kinds of molecules spontaneously form periodic ordered strip-like phase separation structure on the HOPG substrate. The phenomenon can be qualitatively understood in terms of a phase field model, in which the interplay of three ingredients, including free energy of the binary component solution monolayer, phase boundary energy, and surface stress, is suggested to play an important role in determining the equilibrium sizes of strip-like domains of the TTF and n-C14H30 in the ordered phase separation structure. In addition, scanning tunneling spectrum (STS) measurements have also been performed by operating an STM tip to locate on the individual TTF or n-C14H30 molecule in the SAM on the HOPG substrate. The STS at the TTF molecule shows a distinct rectifying behavior, while at the n-C14H30 molecule it shows an intrinsic small current increase with the change of bias voltage and a slight asymmetry.
    Mots-clés : NASCO, NSCO, POLE 2.

2009



  • P. Jiang, K. Deng, D. Fichou, S. - S. Xie, A. Nion, et C. Wang, « STM Imaging ortho- and para-Fluorothiophenol Self-Assembled Monolayers on Au(111) », Langmuir, vol. 25, nᵒ 9, p. 5012-5017.
    Résumé : Self-assembled monolayers (SAMs) of para- and ortho-fluorothiophenol (p- and o-FTP) spontaneously formed on Au(111) substrate have been contrasted through investigation by a scanning tunneling microscope (STM) at room temperature. High-resolution STM imaging reveals that p-FTP adopts a 6 ? √3R30° molecule arrangement containing six molecules. Two different kinds of p-FTP molecule dimer line structures have been formed on Au(111) by intermolecular π?π stacking along ?112? substrate directions, besides a single p-FTP molecule line. In contrast, o-FTP molecules self-assemble into a much looser wave-like SAM, which can be described as a 5 ? 3√3R30° structure containing two molecules. Periodic density functional theory (DFT) calculations for the two systems suggest that these kinds of FTP molecules preferentially take the asymmetrical positions between 3-fold face-centered cubic (fcc) hollow and bridge sites on Au(111), tilting from the substrate surface. Theoretical simulation gives apparent average tilted angles of 58° and 68° for p-FTP and o-FTP with respect to the surface normal, respectively. This simulation shows that o-FTP is more inclined to lie down toward the Au(111) surface compared to p-FTP. The difference between p-FTP and o-FTP SAM structures can be qualitatively understood in terms of the variation of intermolecular dipole?dipole orientation. This suggests that, besides well-known Au?S and π?π interactions, electrostatic interactions including dipole?dipole, quadrupole?quadrupole, and dipole?quadrupole interactions might also play an important role in influencing the SAM structures formed by aromatic thiols with a permanent dipole moment.
    Mots-clés : NASCO, NSCO, POLE 2.


  • J. - B. Moussy, L. Tortech, F. Rengnez, S. Matzen, F. Ott, M. - J. Guittet, et D. Fichou, « Growth and magnetic behavior in hybrid organic–inorganic Ferrite/Alq3/Co heterostructures », Journal of Materials Chemistry, vol. 19, nᵒ 38, p. 6973-6976.
    Résumé : We report the growth and magnetic properties of AFe2O4/Alq3/Co heterostructures (A [[double bond, length as m-dash]] Fe, Co) containing a continuous Alq3 thin layer with a low roughness, down to a few nanometers, and we demonstrate the magnetic decoupling between AFe2O4 and Co electrodes showing the interest of...
    Mots-clés : NASCO, NSCO, POLE 2.


  • M. Mura, F. Silly, G. A. D. Briggs, M. R. Castell, et L. N. Kantorovich, « H-Bonding Supramolecular Assemblies of PTCDI Molecules on the Au(111) Surface », The Journal of Physical Chemistry C, vol. 113, nᵒ 52, p. 21840-21848.
    Résumé : Using a combination of scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV) and a systematic theoretical method based on considering all possible hydrogen bond connections between molecules with subsequent density functional theory (DFT) calculations, we studied supramolecular assemblies of highly symmetrical rectangular PTCDI molecules on the Au(111) surface. We show, using a systematic prediction procedure followed by ab initio density functional calculations, that just over 10 monolayer structures are possible assuming two molecules in the primitive cell, some of which would appear indistinguishable in the STM images. By breaking down these structures into distinct assemblies, we predict six possible phases. Two of these had been observed previously: a canted phase seen on a number of surfaces including Au(111) and a brick wall phase seen so far only on the NaCl(001) surface. Using STM imaging of PTCDI molecules on the Au(111) surface in ultrahigh vacuum, we discovered a completely new ?domino? phase, also predicted by our theory, in which molecules attach to each other rather like dominoes, to form squares repeated periodically across the surface. The interaction of the molecules with the gold surface seems to influence the orientation of the phases but not necessarily their stability.
    Mots-clés : NASCO, NSCO, POLE 2.

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  • L. Piot, C. Marie, X. Dou, X. Feng, K. Müllen, et D. Fichou, « Growth of Long, Highly Stable, and Densely Packed Worm-Like Nanocolumns of Hexa-peri-Hexabenzocoronenes via Chemisorption on Au(111) », Journal of the American Chemical Society, vol. 131, nᵒ 4, p. 1378-1379.
    Résumé : Long, highly stable, and densely packed edge-on nanocolumns of hexa-peri-hexabenzocoronenes spontaneously grow from solution as self-assembled monolayers chemisorbed on gold.
    Mots-clés : NASCO, NSCO, POLE 2.


  • L. Piot, F. Silly, L. Tortech, Y. Nicolas, P. Blanchard, J. Roncali, et D. Fichou, « Long-Range Alignments of Single Fullerenes by Site-Selective Inclusion into a Double-Cavity 2D Open Network », Journal of the American Chemical Society, vol. 131, nᵒ 36, p. 12864-12865.
    Résumé : We show by means of STM that C60 molecules can be trapped into specific sites of a 2D double-cavity open network, thus forming long-range alignments of single molecules. Since only one of the two cavities has the right size to host C60, the smallest cavity remains empty and is thus available to trap additional species of smaller size. This novel 2D supramolecular network opens new perspectives in the design of multicomponent guest?host architectures with electronic functionalities.
    Mots-clés : NASCO, NSCO, POLE 2.


  • A. Popoff et D. Fichou, « Weak intermolecular H-bonds as a tool to design 2D self-organized molecular architectures: Tailoring a “Scottish Tartan” open network », Journal of Molecular Structure, vol. 936, nᵒ 1-3, p. 156-161.
    Mots-clés : NASCO, NSCO, POLE 2.

2007

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