Double-walled carbon nanotubes DWNTs

A single-walled carbon nanotube (S WNT) is a single graphene sheet rolled up in a seamless cylinder, whose diameter is of the order of few nanometers (Fig. 4.12). A double-walled carbon nanotube (DWNT) consists of rolled two graphene layers, and a multiwall carbon nanotube (MWNT) exhibits several co-axial rolls of graphene sheets, one sitting in each other and separated by about 0.35 nm. 

Double-walled carbon nanotubes (DWNTs), first observed in 1996, constitute a unique family of carbon nanotubes (CNTs). -2 DWNTs occupy a position between the single-walled carbon nanotubes (SWNTs) and the multiwalled carbon nanotubes (MWNTs), as they consist of two concentric cylinders of rolled graphene. DWNTs possess useful electrical and mechanical properties with potential applications. Thus, DWNTs and SWNTs have similar threshold voltages in field electron emission, but the DWNTs exhibit longer lifetimes.3 Unlike SWNTs, which get modified structurally and electronically upon functionalization, chemical functionalization of DWNTs surfaces would lead to novel carbon nanotube materials where the inner tubes are intact. The stability of DWNTs is controlled by the spacing of the inner and outer layers but not by the chirality of the tubes 4 therefore, one obtains a mixture of DWNTs with varying diameters and chirality indices of the inner and outer tubes. DWNTs have been prepared by several techniques, such as arc discharge5 and chemical vapor depo-... 

Figure 3.42 Growth mechanism for double-walled carbon nanotubes (DWNT).

Double-Walled Carbon Nanotubes (DWNT), 462 Multiwalled Carbon Nanotubes (MWNT), 463 Graphene, 464 Nanohoms, 465... 

Carbon nanotube is classified as single walled nanotubes (SWNTs), multiwalled nanotubes (MWNTs) and Double walled carbon nanotubes (DWNTs). 

Carbon nanotubes are one-dimensional carbon nanostructures with tubular morphology. Depending on the number of walls present in carbon nanotubes, these are named as single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and multi-walled carbon nanotubes (MWNTs). Each of these types have slightly different properties. For example, the electrical conductivity of pure SWNT is higher than that of DWNT and MWNT. Carbon nanotubes can be synthesized by arc discharge [11], laser ablation [12], catalytic CVD [13,14], etc. 

Rg. 1.8 Schematic diagrams of (a) a single-wall carbon nanotube (SWNT), (b) a multiwall carbon nanotube (MWNT), (c) a double-wall carbon nanotube (DWNT), and (d) a peapod nanotube consisting of an SWNT filled with fuUerenes (e.g., C ) (Reprinted with permission firom Dresselhaus et al. 2003, Copyright 2003 Elsevier)... 

Dense, vertically aligned double-walled carbon nanotubes (DWNTs) were grown on the surface of a sihcon tip by catalytic chemical vapor deposition (Step... 

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