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Bittova B.,ASCR Institute of Physics Prague | Vejpravova J.P.,ASCR Institute of Physics Prague | Kalbac M.,J. Heyrovsky Institute of Physical Chemistry | Burianova S.,ASCR Institute of Physics Prague | And 3 more authors.
Journal of Physical Chemistry C | Year: 2011

We have investigated the magnetic response of residual metal catalyst in the raw and super purified HiPco single wall carbon nanotubes (HiPco-raw and HiPco-SP SWCNTs). It has been shown that the residual metal catalyst is in the form of nanoparticles, even in the HiPco-SP SWCNTs that should contain a minimal amount of the metal. Mössbauer spectroscopy of the HiPco-raw SWCNTs proved the catalyst nanoparticles are in the form of Fe3C. Analysis of the synchrotron X-ray diffraction data provided an average diameter of nanoparticles about 1.9 nm. Magnetic studies by means of temperature dependence of magnetization, magnetization isotherms and susceptibility suggested that the nanoparticles obey the behavior of weakly interacting superparamagnetic systems in both samples. Further analysis of the data revealed a core-shell structure of the nanoparticles in the HiPco-raw nanotubes, with a magnetically oriented core and a paramagnetic shell, which is almost removed in the case of the HiPco-SP catalyst nanoparticles. © 2011 American Chemical Society. Source

Roiban L.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Hartmann L.,French National Center for Scientific Research | Hartmann L.,CEA Grenoble | Fiore A.,CEA Grenoble | And 7 more authors.
Nanoscale | Year: 2012

Highly oriented and nanostructured hybrid thin films made of regioregular poly(3-hexylthiophene) and colloidal CdSe nanocrystals are prepared by a zone melting method using epitaxial growth on 1,3,5-trichlorobenzene oriented crystals. The structure of the films has been analyzed by X-ray diffraction using synchrotron radiation, electron diffraction and 3D electron tomography to afford a multi-scale structural and morphological description of the highly structured hybrid films. A quantitative analysis of the reconstructed volumes based on electron tomography is used to establish a 3D map of the distribution of the CdSe nanocrystals in the bulk of the films. In particular, the influence of the P3HT-CdSe ratio on the 3D structure of the hybrid layers has been analyzed. In all cases, a bi-layer structure was observed. It is made of a first layer of pure oriented semi-crystalline P3HT grown epitaxially on the TCB substrate and a second P3HT layer containing CdSe nanocrystals uniformly distributed in the amorphous interlamellar zones of the polymer. The thickness of the P3HT layer containing CdSe nanoparticles increases gradually with increasing content of NCs in the films. A growth model is proposed to explain this original transversal organization of CdSe NCs in the oriented matrix of P3HT. © 2012 The Royal Society of Chemistry. Source

Hartmann L.,French National Center for Scientific Research | Hartmann L.,CEA Grenoble | Hartmann L.,Ecole Polytechnique Federale de Lausanne | Djurado D.,CEA Grenoble | And 10 more authors.
Macromolecules | Year: 2013

Highly oriented hybrid thin films composed of rod-shaped CdSe nanocrystals and poly(3-hexylthiophene) are prepared by mechanical rubbing. The orientation distribution of both CdSe nanorods and crystalline P3HT domains is determined by a combination of transmission electron microscopy (electron diffraction, low dose high-resolution TEM, and tomography), grazing incidence X-ray diffraction measurements, and UV-vis spectroscopy. After rubbing, P3HT crystalline domains show a preferential face-on orientation ((010) contact plane) and the chains align parallel to the rubbing direction. CdSe nanorods also align parallel to the rubbing direction, but the level of alignment is a function of their concentration in the polymer matrix: the lower their concentration, the higher the level of in-plane orientation of both the nanorods and the polymer chains. GIXD and electron diffraction suggest that CdSe nanorods adopt a preferential contact plane on the substrate after rubbing. The high in-plane alignment of the nanorods is mainly due to the orientation of the surrounding P3HT matrix. In particular, low dose HR-TEM shows that the local orientation of individual NRs matches the orientation of the surrounding π-stacked P3HT chains. For a high NR concentration, bundling of NRs into larger aggregates prevents their efficient alignment by rubbing. © 2013 American Chemical Society. Source

Langer R.,Karlsruhe Institute of Technology | Yu W.,Karlsruhe Institute of Technology | Wunsche L.,Karlsruhe Institute of Technology | Buth G.,Institute For Synchrotronstrahlung Iss | And 4 more authors.
Zeitschrift fur Anorganische und Allgemeine Chemie | Year: 2011

Four new copper chalcogenide clusters with trimethylsiloxy groups in the ligand shell have been synthesized and characterized by single-crystal X-ray diffraction. The compounds [Cu22Se6(S-C6H 4-OSiMe3)10(PPh3)8] (1), [Cu36Se8(S-C6H4-OSiMe 3)20(PPh3)8] (2) and [Cu 52Se20(S-C6H4-OSiMe 3)12(PPh3)11] (3) are core-shell-cluster, in which the heavy atom frameworks are built up of a copper selenide core which is partly surrounded by a copper thiolate shell. They were synthesized by the reaction of CuOAc and PPh3 with p-Me 3SiS-C6H4-OSiMe3 and Se(SiMe 3)2 in different ratios. The arrangements of the chalcogen atoms in 1 and 2 are similar to a close packing, while cluster 3 has a new unusual structural motif. In addition the analogous precursor p-Me 3SiSe-C6H4-OSiMe3 was synthesized and investigated in the cluster synthesis. The reaction with CuOAc, PPh 3 and Se(SiMe3)2 leads to the formation of the functionalized copper selenide cluster [Cu22Se6(Se-C 6H4-OSiMe3)10(PPh3) 8] (4). This compound is similar to 1 and consists of a Cu 22Se16 core instead of a Cu22Se 6S10 core. The functionalization of the cluster compounds with trimethylsiloxy-groups leads to a high solubility of these cluster. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Alaribe L.,FMF Freiburger Materialforschungszentrum | Disch C.,FMF Freiburger Materialforschungszentrum | Fauler A.,FMF Freiburger Materialforschungszentrum | Engels R.,Julich Research Center | And 6 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012

Currently, there is a great interest in the research and development of SrI 2:Eu 2+ scintillating crystals. The high light yield, high density (4.6 g/cm 3) and high effective atomic number (49.4) make the Eu 2+-activated SrI 2 suitable for use as x-ray and gamma ray detector. SrI 2:Eu 2+-single crystals were grown with the vertical Bridgman technique in silica ampoules to prevent melt hydration and oxygen contamination during the crystal growth. For measurements, crystals were hermetically encapsulated in aluminum containers with quartz glass optical windows. The radioluminescence spectra of the SrI 2:Eu 2+-samples show maximum at 431 nm and 432 nm for the 5% and 6% dopant concentrations respectively. The light yield of the bulk samples was up to 80 000 photons/MeV and up to 119 000 photons/MeV for a 360 μm sample integrated in an x-ray imaging setup. © 2011 IEEE. Source

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