Charged iodide in chains behind the highly efficient iodine doping in carbon nanotubes

Abstract

The origin of highly efficient iodine doping of carbon nanotubes is not well understood. Relying on firstprinciples calculations, we found that iodine molecules (I 2 ) in contact with a carbon nanotube interact to form monoiodide or/and polyiodide from two and three I 2 as a result of removing electrons from the carbon nanotube (p-type doping). Charge per iodine atom for monoiodide ion or iodine atom at end of iodine chain is significantly higher than that for I 2 . This atomic analysis extends previous studies showing that polyiodide ions are the dominant dopants. Moreover, we observed isolated I atoms in atomically resolved transmission electron microscopy, which proves the production of monoiodide. Finally, using Raman spectroscopy, we quantitatively determined the doping level and estimated the number of conducting channels in high electrical conductivity fibers composed of iodine-doped double-wall carbon nanotubes.

Effective Doping of Single-Walled Carbon Nanotubes with Polyethyleneimine

“…Regarding the electrical characteristics, similarly to classical semiconductors, surface modification can be exercised on nanocarbon to boost its electrical conductivity via doping [ 11 , 12 ]. Alternatively, the doping species can also be accommodated in the inner cavity of the CNTs [ 13 , 14 , 15 ].…”

Tailoring of Double‐Walled Carbon Nanotubes for Formaldehyde Sensing through Encapsulation of Selected Materials

“…As it has already been established that iodine induces p‐type doping of SWNTs, creating charge carriers in the SWNTs walls and as a result, the semiconducting SWNTs become metallic, whereas metallic SWNTs become even more metallic due to increased density of carriers (holes) . The same effect was evidenced in iodine‐doped DWNTs, it is, therefore, logical to assume that zinc iodide filling results in p‐type doping of DWNTs, which explains the decrease in response. The increase in response observed for unfilled DWNTs when formaldehyde was introduced can be explained as follows: unfilled DWNTs are composed of a mixture of semiconducting and metallic DWNTs with the latter being predominant, and hence, the dominating conduction is due to electrons (n‐type).…”

Structure of inorganic nanocrystals confined within carbon nanotubes

“…The temperature dependence of the frequency of the tangential modes of CNTs has also been evidenced (Se, Te, HgTe, PbI 2 [69]) to depend on the filling of the nanotubes, and can thus be used to demonstrate that CNTs are filled or empty, without requiring TEM observation. Charge transfer of CNTs due to doping effect was also evidenced by Raman spectroscopy in the case of filling with iodine [70,71], leading to p-doping of the nanotubes. Fig.…”