-
[show abstract]
[hide abstract]
ABSTRACT: Screen printing of graphene based ink shows promise for the integration of graphene within supercapacitor electrodes. A series of graphene/polyaniline inks are formulated, and screen printing is used to produce thin-film electrodes from these inks. Using these electrodes, supercapacitors are fabricated which exhibit high capacity, flexibility, and stability. These results provide an important step towards the industrial development of printable supercapacitors.
Advanced Energy Materials. 05/2013;
-
[show abstract]
[hide abstract]
ABSTRACT: An efficient synthesis of 2,7-dibromo- and diiodo-pyrene(4,5,8,19)-tetraones led to strong donors and acceptors based on pyrene. They are versatile building blocks for conjugated materials and can be further applied in molecular electronics.
Chemical Communications 04/2013; · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Electrostatic assembly between Fe3 O4 nanospheres and graphene oxide, and subsequent hydrothermal assembly with additional graphene sheets, leads to Fe3 O4 nanospheres encapsulated in the graphene shells and interconnected by the graphene networks. Such 3D Fe3 O4 /graphene foams exhibit enhanced lithium storage with excellent cycling performance and rate capability.
Advanced Materials 04/2013; · 13.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A series of soluble carbonyl-bridged heterotriangulenes, in which flexible n-dodecyl chains are attached through different spacers to the planar nitrogen-centered polycyclic core, have been synthesized. The introduction of triisopropylsilylethynyl moieties enabled, for the first time, the characterization of single-crystal columnar packing of a substituted heterotriangulene by X-ray crystallography. Electrochemical studies disclosed the carbonyl-bridged heterotriangulene core as a reasonably strong acceptor for a reversible two-electron transfer. The tendency of substituted heterotriangulenes to self-assemble in solution, on surfaces, and in the bulk appeared to sensitively depend on the nature of the lateral substituents, their steric demand, and the applied solution processing conditions. It can be concluded that 1) additional phenylene moieties between the heterotriangulene core and the n-dodecyl chains facilitate self-assembly by extending the π-conjugated polycyclic disc, 2) the rod-like ethynylene spacers introduce some additional flexibility and hence lower the overall aggregation tendency, and 3) the combination of both features in the phenylene-ethynylene moieties induces thermotropic liquid crystallinity.
Chemistry 04/2013; · 5.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Carbon-based films: Dopamine was used as the precursor for the facile yet controllable production of a highly stretchable transparent conductive film. The film synthesized is transparent and can reversibly withstand mechanical deformations (such as being stretched to 20 % for 100 cycles).
Angewandte Chemie International Edition 04/2013; · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Donor and acceptor substituents were introduced at pyrene's K-regions in order to engineer its optoelectronic properties. A study of the influence of the substitution pattern on the frontier orbitals as well as on the molecular packing is provided. A comparison with the pure donor and acceptor substituted pyrene derivatives highlights the strong impact of the presented donor-acceptor substitution.
Organic Letters 02/2013; · 5.86 Impact Factor
-
-
Yenny R. Hernandez,
Sebastian Schweitzer,
June-Seo Kim,
Ajit Kumar Patra,
Jan Englert,
Ingo Lieberwirth,
Andrea Liscio,
Vincenzo Palermo,
Xinliang Feng,
Andreas Hirsch,
Mathias Kläui, Klaus Müllen
[show abstract]
[hide abstract]
ABSTRACT: Carbon nanomaterials continue to amaze scientists due to their exceptional
physical properties. Recently there have been theoretical predictions and first
reports on graphene multilayers, where, due to the rotation of the stacked
layers, outstanding electronic properties are retained while the susceptibility
to degradation and mechanical stress is strongly reduced due to the multilayer
nature. Here we show that fully turbostratic multilayer graphitic
microstructures combine the high charge carrier mobilities necessary for
advanced electronic and spintronic devices with the robustness of graphitic
structures. Structural characterization of disk-shaped graphitic
microstructures using Raman spectroscopy and Transmission Electron Microscopy
(TEM) reveals Moir\'e and diffraction patterns corroborating their turbostratic
nature. Electronic transport characterization yields reproducible high
mobilities > 105 cm^2(Vs)^(-1) independent of the disks thickness, which is a
direct consequence of the electronic decoupling induced by the turbostratic
stacking.
01/2013;
-
[show abstract]
[hide abstract]
ABSTRACT: Selective solvent vapour annealing is used on a photovoltaic blend to enhance the interaction between the electron acceptor and the electron donor, simplifying thin films post-processing for photovoltaic applications. A remarkable improvement in the interfacial charge transfer in the bulk hetero-junction is attained, as measured by Kelvin Probe Force Microscopy.
Chemical Communications 01/2013; · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The two-dimensional diffusion of isolated molecular tracers at the water-n-alkane interface was studied with fluorescence correlation spectroscopy. The interfacial diffusion coefficients of larger tracers with a hydrodynamic radius of 4.0 nm agreed well with the values calculated from the macroscopic viscosities of the two bulk phases. However, for small molecule tracers with hydrodynamic radii of only 1.0 and 0.6 nm, notable deviations were observed, indicating the existence of an interfacial region with reduced effective viscosity and increased mobility.
Physical Review E 01/2013; 87(1-1):012403. · 2.26 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Light switch: A dendronized salt exhibiting photoswitchable conductivity was designed and synthesized. The salt consists of tetrabutylammonium cations and large, rigidly dendronized borate anions, each bearing eight photo-responsive azobenzene moieties. The conductivity of solutions of this salt can be reversibly switched by irradiation, owing to light-induced changes in the overall size of the dendronized anion and the density of its polyphenylene shell.
Angewandte Chemie International Edition 11/2012; · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The development of high-performance electrochemical energy storage and conversion devices, including supercapacitors, lithium-ion batteries, and fuel cells, is an important step on the road to alternative energy technologies. Carbon-containing nanomaterials (CCNMs), defined here as pure carbon materials and carbon/metal (oxide, hydroxide) hybrids with structural features on the nanometer scale, show potential application in such devices. Because of their pronounced electrochemical activity, high chemical and thermal stability and low cost, researchers areinterested in CCNMs to serve as electrodes in energy-related devices. Various all-carbon materials are candidates for electrochemical energy storage and conversion devices. Furthermore, carbon-based hybrid materials, which consist of a carbon component with metal oxide- or metal hydroxide-based nanostructures, offer the opportunity to combine the attractive properties of these two components and tune the behavior of the resulting materials. As such, the design and synthesis of CCNMs provide an attractive route for the construction of high-performance electrode materials. Studies in these areas have revealed that both the composition and the fabrication protocol employed in preparing CCNMs influence the morphology and microstructure of the resulting material and its electrochemical performance. Consequently, researchers have developed several synthesis strategies, including hard-templated, soft-templated, and template-free synthesis of CCNMs. In this Account, we focus on recent advances in the controlled synthesis of such CCNMs and the potential of the resulting materials for energy storage or conversion applications. The Account is divided into four major categories based on the carbon precursor employed in the synthesis: low molecular weight organic or organometallic molecules, hyperbranched or cross-linked polymers consisting of aromatic subunits, self-assembling discotic molecules, and graphenes. In each case, we highlight representative examples of CCNMs with both new nanostructures and electrochemical performance suitable for energy storage or conversion applications. In addition, this Account provides an overall perspective on the current state of efforts aimed at the controlled synthesis of CCNMs and identifies some of the remaining challenges.
Accounts of Chemical Research 10/2012; · 21.64 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An efficient synthesis of 9,10-dibromo-1,6,7,12-tetrachloro-perylene-3,4-dicarboxylic acid monoimides from easily available 1,6,7,12-tetrachloro-perylene-3,4,9,10-tetracarboxylic acid dianhydride is reported. Therefrom, unprecedented perylene monoimides with pronounced donor-acceptor character were obtained via twofold aromatic amination. The halogen substituents in the 1,6,7,12-positions of perylene were removed under basic conditions. To the best of our knowledge, this is the first efficient synthetic route toward 9,10-doubly functionalized perylene-3,4-dicarboxylic acid monoimides.
Organic Letters 10/2012; · 5.86 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A series of liquid crystalline organic dyes consisting of fluorenyl hexa-peri-hexabenzocoronene (FHBC) and diketopyrrolopyrrole (DPP) units was synthesised and characterised. Their thermotropic behaviour is a result of the strong π–π association between FHBC units while the DPP unit enhances light absorption. With small changes in the molecular structure, significant differences in molecular organisation were observed in solid state. In turn, the molecular arrangement led to variations in the semiconducting properties of these materials and, ultimately, their performance in organic solar cells.
Journal of Materials Chemistry 09/2012; 22:21131-21137. · 5.97 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A series of liquid crystalline organic dyes consisting of fluorenyl hexa-peri-hexabenzocoronene (FHBC) and diketopyrrolopyrrole (DPP) units was synthesised and characterised. Their thermotropic behaviour is a result of the strong π–π association between FHBC units while the DPP unit enhances light absorption. With small changes in the molecular structure, significant differences in molecular organisation were observed in solid state. In turn, the molecular arrangement led to variations in the semiconducting properties of these materials and, ultimately, their performance in organic solar cells.
Journal of Materials Chemistry 09/2012; 22:21131-21137. · 5.97 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Carbazole-containing porphyrinoid was synthesised for the first time via Suzuki-Miyaura cross-coupling reaction. Oxidation with MnO(2) yielded its porphyrin-state featuring macrocyclic aromaticity in exchange for the loss of the resonance energies of the benzene rings.
Chemical Communications 08/2012; 48(77):9640-2. · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A simplified prototype device of high-performance all-solid-state supercapacitors (ASSSs) based on 3D nitrogen and boron co-doped monolithic graphene aerogels (BN-GAs) is demonstrated for the first time. The resulting ASSSs show high specific capacitance, good rate capability, and enhanced energy density or power density.
Advanced Materials 07/2012; 24(37):5130-5. · 13.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Graphene, an individual two-dimensional, atomically thick sheet of graphite composed of a hexagonal network of sp(2) carbon atoms, has been intensively investigated since its first isolation in 2004, which was based on repeated peeling of highly oriented pyrolyzed graphite (HOPG). The extraordinary electronic, thermal, and mechanical properties of graphene make it a promising candidate for practical applications in electronics, sensing, catalysis, energy storage, conversion, etc. Both the theoretical and experimental studies proved that the properties of graphene are mainly dependent on their geometric structures. Precise control over graphene synthesis is therefore crucial for probing their fundamental physical properties and introduction in promising applications. In this Minireview, we highlight the recent progress that has led to the successful chemical synthesis of graphene with a range of different sizes and chemical compositions based on both top-down and bottom-up strategies.
Angewandte Chemie International Edition 07/2012; 51(31):7640-54. · 13.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Molecular modeling shows that longitudinal displacement of the backbones by a couple of ångströms has a profound impact on the electronic coupling mediating charge transport in a conjugated copolymer. These changes can be probed by monitoring the calculated X-ray scattering patterns and NMR chemical shifts as a function of sliding of the polymer chains and comparing them to experiment.
Advanced Materials 06/2012; · 13.88 Impact Factor
-
Periklis Papadopoulos,
Xu Deng,
Lena Mammen,
Dirk-Michael Drotlef,
Glauco Battagliarin,
Chen Li, Klaus Müllen,
Katharina Landfester,
Aranzazu Del Campo,
Hans-Jürgen Butt,
Doris Vollmer
Langmuir 06/2012; 28(26):10136-9. · 4.19 Impact Factor
