Transformation of polyyne-containing carbon to nanoscale carbon tubules

Kawase, Noboru; Yasuda, Ayumu; Matsui, Taisuke; Yamaguchi, Chiharu; Matsui, Hisaji

doi:10.1016/s0008-6223(99)00016-0

Cited by 16 publications

(13 citation statements)

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“…Durch anschließendes Erhitzen des Films auf 600 °C oder 800 °C kombiniert mit Elektronenbestrahlung in einem Transmissionselektronenmikroskop wurden schließlich CNTs erhalten 203. 204 Die Anwendung dieses Ansatzes bleibt trotz aller Bemühungen und Erfolge limitiert, da zum einen nur perfluorierte Kohlenwasserstoffe als Vorstufenmoleküle in Frage kommen, zum anderen keinerlei strukturelle Kontrolle gegeben ist. Außerdem bleibt eine Unverträglichkeit mit den meisten funktionellen Gruppen bestehen, auch wenn die Verwendung von Amalgamverbindungen prinzipiell mildere Reaktionsbedingungen zulässt.…”

Section: Elektrochemische Carbonisierung Perfluorierter Kohlenwassunclassified

Halogenated Benzene Cation Radicals

Molski

Mollenhauer

Gohr

et al. 2012

Chemistry A European J

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The halogenated benzenes C(6)HF(5), 2,4,6-C(6)H(3)F(3), 2,3,5,6-C(6)H(2)F(4), C(6)F(6), C(6)Cl(6), C(6)Br(6), and C(6)I(6) were converted into their corresponding cation radicals by using various strong oxidants. The cation-radical salts were isolated and characterized by electron paramagnetic resonance (EPR) spectroscopy and by single-crystal X-ray diffraction. The thermal stability of the cation radicals increased with decreasing hydrogen content. As expected, the cation radicals [C(6)HF(5)](+) and 2,3,5,6-[C(6)H(2)F(4)](+) had structures with the same geometry as C(6)HF(5) and 2,3,5,6-[C(6)H(2)F(4)]. In contrast, the cation radicals [C(6)F(6)](+), [C(6)Cl(6)](+), and possibly also [C(6)Br(6)](+) exhibited Jahn-Teller-distorted geometries in the crystalline state. In the case of C(6)F(6)(+)Sb(2)F(11)(-), two low-symmetry geometries were observed in the same crystal. Interestingly, the structures of the cation radicals 2,4,6-[C(6)H(3)F(3)](+) and C(6)I(6)(+) did not exhibit Jahn-Teller distortions. DFT calculations showed that the explanation for the lack of distortion of these cations from the D(3h) or D(6h) symmetry of the neutral benzene precursor was different for 2,4,6-[C(6)H(3)F(3)](+) than for [C(6)I(6)](+).

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Section: Elektrochemische Carbonisierung Perfluorierter Kohlenwassunclassified

Halogenated Benzene Cation Radicals

Molski

Mollenhauer

Gohr

et al. 2012

Chemistry A European J

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“…The details have been presented in other publications. [33][34][35][36] For the preparation of the polyyne-containing carbons, poly-(tetrafluoroethylene) (PTFE) films are reduced electrochemically by a two-electrode method (anode, magnesium; cathode, stainless steel) under argon at 0 °C. The PTFE films (10 mm × 10 mm × 60 µm) are charged with a solvent containing supporting salts [tetrahydrofuran (THF), 30 mL; LiCl, 0.8 g; FeCl 2 , 0.48 g] in a flask.…”

Section: Methodsmentioning

confidence: 99%

“…[23][24][25][26][27][28] To circumvent experimental difficulties, computer simulations have also been applied. [29][30][31][32] A new technique for CNT formation, where polyynecontaining carbons are heated and irradiated by an electron beam, has been developed [33][34][35][36] and is applied here to the in situ TEM observation of CNT growth to elucidate the growth mechanism. The polyyne-containing carbons are prepared in the following scheme, where the reduction by the magnesium cation radical is tentatively assumed, 37 although it is not well understood as a reductant.…”

Section: Introductionmentioning

confidence: 99%

Carbon-Nanotube Formation Mechanism Based on in Situ TEM Observations

2002

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Carbon nanotubes (CNTs) have attracted much attention for their unique properties, although their formation mechanism is not well understood. The authors have been studying a technique to form CNTs by an electron beam that is carried out in a transmission electron microscope (TEM) and is compatible with in situ and real-time observation of the growth. The observation, where a precursor (polyyne-containing carbon) is heated and irradiated by an electron beam, shows that the growth occurs in two steps: rapid formation of rodlike carbon (first step) and slow graphitization of its wall (second step). The hollow inside the CNT is not formed in the first step and develops during the second. The formation mechanism is discussed in relation to in situ observations.

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“…[202] Postsynthetic annealing of the obtained films at 600 8C or 800 8C in combination with electron irradiation in a transmission electron microscope was reported to yield carbon nanotubes. [203,204] Despite these efforts, the scope of the electrochemical approach seems limited by the exclusive use of perfluorocarbon precursors, the lack of supramolecular control, and because the utilization of amalgamate reactants, while allowing for notably milder conditions in terms of temperature, is still incompatible with most functional groups.…”

Section: Electrochemical Carbonization Of Perfluorocarbonsmentioning

confidence: 99%

Nanostructured Carbonaceous Materials from Molecular Precursors

et al. 2010

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Nanostructured carbonaceous materials, that is, carbon materials with a feature size on the nanometer scale and, in some cases, functionalized surfaces, already play an important role in a wide range of emerging fields, such as the search for novel energy sources, efficient energy storage, sustainable chemical technology, as well as organic electronic materials. Furthermore, such materials might offer solutions to the challenges associated with the on-going depletion of nonrenewable energy resources or climate change, and they may promote further breakthroughs in the field of microelectronics. However, novel methods for their preparation will be required that afford functional carbon materials with controlled surface chemistry, mesoscopic morphology, and microstructure. A highly promising approach for the synthesis of such materials is based on the use of well-defined molecular precursors.

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Transformation of polyyne-containing carbon to nanoscale carbon tubules

Cited by 16 publications

References 0 publications

Halogenated Benzene Cation Radicals

Halogenated Benzene Cation Radicals

Carbon-Nanotube Formation Mechanism Based on in Situ TEM Observations

Nanostructured Carbonaceous Materials from Molecular Precursors

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