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End date: 2019 × Start date: 2010 × Type: Text × Publisher: Cambridge : RSC Publ. × Subject: Copper compounds ×

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    Colloidal PbS nanoplatelets synthesized via cation exchange for electronic applications
    (Cambridge : RSC Publ., 2019) Sonntag, Luisa; Shamraienko, Volodymyr; Fan, Xuelin; Samadi Khoshkhoo, Mahdi; Kneppe, David; Koitzsch, Andreas; Gemming, Thomas; Hiekel, Karl; Leo, Karl; Lesnyak, Vladimir; Eychmüller, Alexander
    In this work, we present a new synthetic approach to colloidal PbS nanoplatelets (NPLs) utilizing a cation exchange (CE) strategy starting from CuS NPLs synthesized via the hot-injection method. Whereas the thickness of the resulting CuS NPLs was fixed at approx. 5 nm, the lateral size could be tuned by varying the reaction conditions, such as time from 6 to 16 h, the reaction temperature (120 °C, 140 °C), and the amount of copper precursor. In a second step, Cu+ cations were replaced with Pb2+ ions within the crystal lattice via CE. While the shape and the size of parental CuS platelets were preserved, the crystal structure was rearranged from hexagonal covellite to PbS galena, accompanied by the fragmentation of the monocrystalline phase into polycrystalline one. Afterwards a halide mediated ligand exchange (LE) was carried out in order to remove insulating oleic acid residues from the PbS NPL surface and to form stable dispersions in polar organic solvents enabling thin-film fabrication. Both CE and LE processes were monitored by several characterization techniques. Furthermore, we measured the electrical conductivity of the resulting PbS NPL-based films before and after LE and compared the processing in ambient to inert atmosphere. Finally, we fabricated field-effect transistors with an on/off ratio of up to 60 and linear charge carrier mobility for holes of 0.02 cm2 V−1 s−1.
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    SET-LRP in biphasic mixtures of fluorinated alcohols with water
    (Cambridge : RSC Publ., 2018) Moreno, Adrian; Liu, Tong; Ding, Liang; Buzzacchera, Irene; Galià, Marina; Möller, Martin; Wilson, Christopher J.; Lligadas, Gerard; Percec, Virgil
    Biphasic-binary mixtures of 2,2,2-trifluoroethanol (TFE) or 2,2,3,3-tetrafluoropropanol (TFP) with water were used as reaction media to synthesize well-defined poly(methyl acrylate) (PMA) with chain end functionality close to 100% by SET-LRP. Non-activated Cu(0) wire was used as a catalyst, taking advantage of the Cu(0)-activation property that these fluorinated alcohols possess. Biphasic-binary mixtures of water, containing a ligand and Cu(II)Br2 either generated by disproportionation of Cu(I)Br or externally added, and an organic solvent, containing a monomer and a polymer, were studied. Two N-ligands were investigated: the classic tris(2-dimethylaminoethyl)amine (Me6-TREN) and tris(2-aminoethyl)amine (TREN), as a more economically attractive alternative for technological purposes. The results reported here support the replacement of Me6-TREN by TREN, taking into account the fact that the latter requires small loadings of an externally added Cu(II)Br2 deactivator and a ligand in the water phase to mediate a living radical polymerization process. Both catalytic systems ensure efficient SET-LRP processes with first order kinetics to high conversion, linear dependence of experimental Mn on conversion, narrow molecular weight distribution, and near-quantitative chain end functionality.