Chirality, single walled

Fig. 19. The energy gap FJ, for a general chiral single-wall carbon nanotube as a function of 100 kidt, where dt is the nanotube diameter in A [179].

G. Jia et al., Electronic structures and hydrogenation of a chiral single-wall (6, 4) carbon nanotube A density functional theory study. Chem. Phys. Lett. 418, 40 (2006)... 

Figure 16 Schematic representation of (a) armchair, (b) zigzag and (c) chiral single-walled nano tubes. (Reprinted with permission from Ref 91. 2002 American Chemical Society)...

Rikken proposed that the EMCA effect could also result from the simultaneous application of a magnetic field and a current to a crystal with an enantiomorphous space group, and that it is a universal property. He showed the existence of this effect in the case of chiral single-walled carbon nanotubes.For most of the investigated tubes, a dependence of the resistance is observed that is odd in both the magnetic field and the current. These observations confirm the existence of EMCA not only for a macroscopic chiral conductor but also for a molecular conductor with chirality on the microscopic level. 

Chang, T. (2007). Torsional Behavior of Chiral Single-Walled Carbon Nanotubes is Loading Direction Dependent. Appl. Phys. Lett., 90, 201910. 

Early transport measurements on individual multi-wall nanotubes [187] were carried out on nanotubes with too large an outer diameter to be sensitive to ID quantum effects. Furthermore, contributions from the inner constituent shells which may not make electrical contact with the current source complicate the interpretation of the transport results, and in some cases the measurements were not made at low enough temperatures to be sensitive to 1D effects. Early transport measurements on multiple ropes (arrays) of single-wall armchair carbon nanotubes [188], addressed general issues such as the temperature dependence of the resistivity of nanotube bundles, each containing many single-wall nanotubes with a distribution of diameters d/ and chiral angles 6. Their results confirmed the theoretical prediction that many of the individual nanotubes are metallic. 

Key Words—Single-wall, multi-wall, vibrational inodes, chiral nanotubes, electronic bands, tubule arrays. 

Fig. 2. By rolling up a graphene sheet (a single layer of ear-bon atoms from a 3D graphite erystal) as a cylinder and capping each end of the eyiinder with half of a fullerene molecule, a fullerene-derived tubule, one layer in thickness, is formed. Shown here is a schematic theoretical model for a single-wall carbon tubule with the tubule axis OB (see Fig. 1) normal to (a) the 6 = 30° direction (an armchair tubule), (b) the 6 = 0° direction (a zigzag tubule), and (c) a general direction B with 0 < 6 < 30° (a chiral tubule). The actual tubules shown in the figure correspond to (n,m) values of (a) (5,5), (b) (9,0), and (c) (10,5).

We have carried out a series of geometry optimizations on nanotubes with diameters less than 2 nm. We will present some results for a selected subset of the moderate band gap nanotubes, and then focus on results for an example chiral systems the chiral [9,2] nanotube with a diameter of 0.8 nm. This nanotube has been chosen because its diameter corresponds to those found in relatively large amounts by Iijima[7] after the synthesis of single-walled nanotubes. 

Experimental measurements to test these remarkable theoretical predictions of the electronic structure of carbon nanotubes are difficult to carry out because of the strong dependence of the predicted properties on tubule diameter and chirality. Ideally, electronic or optical measurements should be made on individual single-wall nanotubes that have been characterized with regard to diameter and chiral angle. Further ex-... 

Carbon nanotubes can have one, two, or many sidewalls and are referred to as single-, double-, or multi-walled nanotubes (SWNT, DWNT, or MWNT). Nanotubes can be metallic, or semi-conducting depending on the chirality of the tube. Single-walled nanotubes (SWNT) are about 1 nm in diameter, and hundreds of nanometers long, whereas multi-walled nanotubes (MWNT) are like nested... 

Bandow S, Asaka S, Saito Y, Rao AM, Grigorian L, Richter E, Eklund PC (1998) Effect of the growth temperature on the diameter distribution and chirality of single-wall carbon nanotubes. Physical Review Letters 80 3779-3782. 

SI Untreated single-walled Amorphous powder, chirality... 

Sundaram RM, Koziol KKK, Windle AH. Continuous direct spinning of fibers of single-walled carbon nanotubes with metallic chirality. AdvMater. 2011 Nov 16 23(43) 5064-8. 

Carbon nanotubes can be single walled (SWNT) or multi-walled (MWNT). SWNTs can be metallic or semiconducting, depending on their chirality. MWNTs contain several walls, so in combination they will tend to be metallic. In addition, as the band gap of semiconducting tubes varies inversely with their diameter, the larger diameter of MWNTs means that effectively most walls are metallic. 

Fig. 3 Representative examples of carbon nanomaterials. Empty cage fullerenes (a) Cgo, (b) C70 endohedral fullerenes (c) La2 fA-Cgo, (d) Lu3N 4-C8o, (e) graphene sheet, (f) zig-zag single wall carbon nanombe, (g) arm chair single wall carbon nanombe, (h) chiral carbon nanombes, (i) carbon nanohom, (j) carbon nanoonion...

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