Composites with Separated Metallic SWNTs

Metallic SWNTs are of extremely high electrical conductivity, with the theoretical value estimated as high as 10 S It is also well-established 

The superior conductivity of separated metallic SWNTs was also verified in the transparent conductive PEDOTiPSS composites. A suspension of the separated metallic SWNTs or the pre-separation nanotube mixture in DMSO was mixed with aqueous PEDOTiPSS for spray coating on to glass substrate. 

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Figure 6.8 Electrical conductivity and surface resistivity comparison. Upper panel electrical conductivity results of P3HT/SWNT composite films depending on (left) different amounts of pre-separated ( ) and separated metallic (O) nanotube samples, and (right) their corresponding effective metallic SWNT contents in the films (dashed line the best fit in terms of the percolation theory equation). Lower panel Surface resistivity results of PEDOT PSS/SWNT films on glass substrate with the same 10 wt% nano tube content (O pre-separated purified sample and T separated metallic SWNTs and for comparison, blank PEDOT PSS without nano tubes) but different film thickness and optical transmittance at 550 nm. Shown in the inset are representative films photographed with tiger paw print as background.

The thickness of the composite films reflected by transmittance was controlled by spraying different volumes of nanotube suspension. Again, the composite films with enriched metallic SWNTs were consistently and substantially more conductive than those with non-separated SWNTs (and both better than the films with neat PEDOT PSS, Figure 6.8). ... 

Arc discharge [25] is initially used for producing C60 fullerenes. Nanotubes are produced by arc vaporization of two carbon rods placed in a chamber that is filled with low pressure inert gas (helium, argon). The composition of the graphite anode determines the type of CNTs produced. A pure graphite anode produce preferably MWNT while catalyst (Fe, Co, Ni, Y or Mo) doped graphite anode produces mainly SWNT. This technique normally produces a complex mixture of components, and requires further purification to separate the CNTs from the soot and the residual catalytic metals present in the crude product. 

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