Shear and Young's Moduli of MoS₂ Nanotube Ropes

Abstract

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...

Nonlinear elastic behavior of two-dimensional molybdenum disulfide

“…Bulk MoS 2 is an indirect gap semiconductor with a band gap of 1.2 eV, but by reducing the number of layers one can modify the band structure and create a direct gap semiconductor 5,12,[18][19][20][21] . Recently, monolayers of MoS 2 have been investigated as materials for microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS) devices 5,7,12,17 . The low power dissipation of MoS 2 direct gap semiconductors and its low cost make it an ideal candidate for flexible electronic applications.…”

Tensile testing of individual glassy, rubbery and hydrogel electrospun polymer nanofibres to high strain using the atomic force microscope

“…In the three point configuration, a fibre with a high elastic modulus (E > ~100 GPa) and low aspect ratio (length: diameter< 5:1) will show purely bending behaviour. 53,68 In these cases the 3-point loading produces a linear F l -x curve in the elastic region. Fibres with a low modulus (E < ~10 GPa) and a high aspect ratio (> 30:1) are dominated by the axial tensile stretching of the fibre.…”

Elastic properties of suspended multilayer WSe2

“…48 Moreover, the mean value of E Y (167.3 6 6.7 GPa) for the multilayer WSe 2 membranes is smaller than that of multilayer MoS 2 ($330 GPa), 29 monolayer MoS 2 ($270 GPa), 30,31 monolayer WS 2 ($270 GPa), 31 roughly equal to one sixth of graphene ($1.0 TPa) 1,2 and carbon nanotube ($1.0 TPa), 49 and larger than that of MoS 2 nanotube ($120 GPa). 50 The possible reason for smaller Young's modulus of WSe 2 compared with 2D MoS 2 and WS 2 is that the charge transfer decrease and lattice constant increase in WSe 2 induces the weakening binding between the metal and chalcogen. 46 For a given geometry of NEMS, the resonant frequency will be lower if the Young's modulus of beam is lower or density is higher.…”