The transmission electron microscope (TEM) images of a (C) SWCNT and (D) MWCNT [6–8]. Carbon nanotubes: structure and properties Carbon can bond in different ways to construct structures with completely different properties. The sp2
hybridization of carbon builds a layered construction with weak out-of-plane bonding of the van der Waals form and strong in-plane bounds. A few to a few tens of concentric cylinders with the regular periodic interlayer spacing locate around ordinary central hollow and made MWCNTs. The real-space analysis of multiwall nanotube images has shown a range of interlayer spacing (0.34 to 0.39 nm) [9]. Depending on the number of layers, the inner diameter of MWCNTs diverges from 0.4 nm up to a few nanometers HDAC inhibitor review and outer diameter varies characteristically from 2 nm up to 20 to 30 nm. Both tips of MWCNT usually have closed and the ends are capped by dome-shaped half-fullerene molecules (pentagonal defects), and axial size differs from 1 μm up to a few centimeter.
The role of the half-fullerene 5-Fluoracil in vivo molecules (pentagonal ring defect) is to help in closing of the tube at the two ends. On other hand, SWCNT diameters differ from 0.4 to 2 to 3 nm, and their length is typically of the micrometer range. SWCNTs usually can come together and form bundles (ropes). In a bundle structure, SWCNTs are hexagonally organized to form a crystal-like construction [3]. MWCNT and SWCNT structure Dependent on wrapping to a cylinder way, there are three different forms of SWCNTs such as armchair, chiral, and zigzag (Figure 2B). A SWCNT’s structure is characterized by a pair of indices (n, m) that describe the chiral vector and directly have an effect on electrical properties of nanotubes. The number of unit Tangeritin vectors in the honeycomb crystal lattice of graphene along two directions is determined by the integers n and m. As a common opinion, when m = 0, the nanotubes are named zigzag nanotubes; when n = m, the nanotubes are named armchair
nanotubes, and other state are called chiral. Figure 2 Different forms of SWNTs. (A) The chiral vector C also determines the tube diameter. (B) Models of three atomically perfect SWCNT structures [10]. The chiral vector C = na 1 + ma 2 (a1 and a2 are the base cell vectors of graphite) also determines the tube diameter d [4, 5], and this vector finds out the direction of rolling a graphene sheet (Figure 2A). Therefore, the diameter of a carbon tube can be calculated by where corresponds to the lattice constant in the graphite sheet. When n − m is a multiple of 3, then the nanotube is described as ‘metallic’ or highly conducting nanotubes, and if not, then the nanotube is a semimetallic or semiconductor. At all times, the armchair form is metallic, whereas other forms can make the nanotube a semiconductor.
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