We report on the synthesis, structure, and self-assembly of single-wall subnanometer-diameter molybdenum disulfide tubes. The nanotubes are up to hundreds of micrometers long and display diverse self-assembly properties on different length scales, ranging from twisted bundles to regularly shaped "furry" forms. The bundles, which contain interstitial iodine, can be readily disassembled into individual molybdenum disulfide nanotubes. The synthesis was performed using a novel type of catalyzed transport reaction including C(60) as a growth promoter.

Due to their ease of fabrication and monodisperse, metallic nature, molybdenum-sulfur-iodine nanowires are an interesting alternative to carbon nanotubes for some applications. However very little is known about the solubility of these materials. In this work we have investigated the solubility of Mo(6)S(4.5)I(4.5) nanowire soot in a range of common solvents by performing sedimentation studies and microscopic and spectroscopic characterization. A sedimentation equation was derived showing that the concentration of any insoluble dispersed phase decreases exponentially with time. We find that in all solvents, Mo(6)S(4.5)I(4.5) nanowire soot contains three phases, two of which are insoluble with one stable phase. Microscopy and spectroscopy show that the first insoluble phase is associated mainly with spherical impurities and sediments rapidly out of solution resulting in purification. The second phase appears to consist of insoluble nanowire bundles and sediments more slowly, eventually leaving a stable dispersion of nanowire bundles. The stably dispersed bundles tend to be smaller than their insoluble counterparts. The best solvents studied were 2-propanol and dimethylformamide. Microscopy studies showed that, in the case of 2-propanol, sonication significantly reduced the bundle size relative to the unsonicated bulk. However, during sedimentation, large quantities of bundles were observed to reaggregate to form larger bundles which subsequently sedimented out of solution. In general, the sedimentation properties of the various phases did not vary significantly with concentration indicating that the insoluble nanowires are intrinsically insoluble. However, the diameter of the stably dispersed bundles decreased with concentration, until very small bundles consisting of only two or three nanowires were observed at concentrations below 0.003 mg/mL. In addition, stable composite dispersions were produced by mixing the nanowires with poly(vinylpyrrolidone) in 2-propanol opening the way for the formation of polymer/inorganic nanowire composites.

Large amounts of Li ions can be electrochemically intercalated into and controllably released by the channels between individual molybdenum selenide nanotubes (see Figure), forming the basis for a promising safe new battery electrode material. The use of dichalcogenide nanotubes rather than the more usual carbon is shown to have important advantages.

We report on the properties of a new air-stable nanowire material with the chemical formula Mo6S3I6. The distinguishing features of the material are rapid one-step synthesis, easy isolation and controllable dispersion into small-diameter wire bundles. Elemental analysis, x-ray diffraction, thermogravimetry, differential thermal analysis, Raman scattering and electron microscopy were used to characterize the material.

Moybdenum-based subnanometre diameter nanowires are easy to synthesize and disperse, and they exhibit a variety of functional properties in which they are superior to other one-dimensional materials. However, further progress in the understanding of physical properties and the development of new and specific applications have so far been impeded by the fact that their structure was not accurately known. Here we report on a combination of systematic x-ray diffraction and extended x-ray absorption fine structure experiments, and first-principles theoretical structure calculations, which are used to determine the atomic skeletal structure of individual Mo6S9−xIx (MoSIx) nanowires, their packing arrangement within bundles and their electronic band structure. From this work we conclude that the variations in functional properties appear to arise from different stoichiometry, not skeletal structure. A supplementary data file is available from http://stacks.iop.org/0957-4484/16/1578

pressure increases on the downstream side. A specimen for transmission electron microscopy (TEM) was prepared by sectioning a hybrid nanocomposite containing 10 wt.-% FS at ±100 C in a Reichert-Jung cryo-ultramicrotome. Electron-transparent sections measuring ca. 80 nm thick were imaged with a Zeiss EM902 electron spectroscopic microscope operated at an accelerating voltage of 80 kV and an energy loss of 0 eV. In the past decade, the discovery of fullerenes and carbon nanotubes as new forms of carbon has prompted the opening of an interesting and dynamic new field in physics, chemistry, and materials science because of their remarkable properties and a wide range of potential applications. With the discovery of tungsten disulfide (WS 2 ) and molybdenum disulfide (MoS 2 ) fullerene-like nanoparticles and tubular structures, [1,2] followed by the discovery of boron nitride (BN) nanotubes, [3] it was realized that fullerenes and carbon nanotubes represent only a small subset of a wide class of layered materials that can form C 60 -like particles, tubes, and other interesting morphologies.MoS 2 can be synthesized in a large variety of formsÐparti-cles, nanotubes, [1,2] multiwalled nanotubes [4] and alsoÐlike their carbon cousinsÐin the form of ropes, ribbons, and thin microtubes several micrometers in diameter and millimeters in length. [5] This richness in form promises potential applications going beyond those of carbon nanotubes. Recent theoretical calculations [6] predicted that MoS 2 nanotubes with diameters above 2 nm will all be semiconductors with a bandgap smaller than that of bulk MoS 2 . The size of this gap is a monotonous and smooth function of the tube's diameter and chirality. Zigzag tubes would even have a small direct gap, suggesting that they could be used for optoelectronics i.e., luminescent devices, which is not possible for carbon nanotubes. At this time, there are no theoretical calculations available on MoS 2 nanotubes with subnanometer diameters, such as the ones used in this study. Nevertheless, recent experimental findings indicate that these tubes are most likely all metallic. [7,8] Carbon nanotubes are always produced with a distribution of diameters and chiralities over which there is no real control. As a consequence, they have diverse electronic properties: semiconducting p-and n-tubes are produced along with metallic ones. Even a small change of diameter can drastically alter their electronic properties from metallic to semiconducting. In order to control the electronic properties of carbon nanotubes during production, complete control over their diameters is neededÐa feat that has not been achieved yet. A narrow distribution of diameter will still yield a mixture of metallic and semiconducting tubes. MoS 2 nanotubes on the other hand do not require perfect control over their diameters, because they are predicted to be semiconductors with a monotonous dependence of the bandgap on the diameter. Thanks to this, perfect control over their diameter is not needed: a narrow di...

Single wall carbon nanotubes (SWNT) were functionalized via addition of carbon radicals, which were generated by thermal decomposition of diacyl and dibenzoyl peroxides. Reaction products were investigated with TEM, Raman scattering, TGA, UV−Visible spectroscopy, FTIR, and 1H NMR. In Raman spectra of functionalized SWNT materials one of the radial breathing modes with a maximum at 260 cm-1 diminished completely. At the same time, the intensity ratio between the G- and D-bands decreased in comparison to that in the spectrum of raw SWNT material. From TGA measurements we conclude that SWNTs were derivatized up to 2.9−6.1 wt. % with functionalizing moieties. The loss of van Hove singularities in UV−Visible spectra of functionalized SWNTs also indicates a covalent modification of SWNTs.

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