Does water dope carbon nanotubes?

Abstract

We calculate the long-range perturbation to the electronic charge density of carbon nanotubes (CNTs) as a result of the physisorption of a water molecule. We find that the dominant effect is a charge redistribution in the CNT due to polarisation caused by the dipole moment of the water molecule. The charge redistribution is found to occur over a length-scale greater than 30 Å, highlighting the need for large-scale simulations. By comparing our fully first-principles calculations to ones in which the perturbation due to a water molecule is treated using a classical electrostatic model, we estimate that the charge transfer between CNT and water is negligible (no more than 10 −4 e per water molecule). We therefore conclude that water does not significantly dope CNTs, a conclusion that is consistent with the poor alignment of the relevant energy levels of the water molecule and CNT. Previous calculations that suggest water n-dopes CNTs are likely due to the misinterpretation of Mulliken charge partitioning in small supercells.

Switchable changes in the conductance of single-walled carbon nanotube networks on exposure to water vapour

“…It has been previously reported that water induces n-type 65,66 or p-type 56,[67][68][69] responses from carbon nanotubes, causing a change in the conductance of ropes and bundles. The study by Bell et al 70 suggested that this effect is attributable to electrostatic interactions. The permanent dipole moment of water induces a polarisation of electronic charge density in the nanotube over a long range (3 nm).…”

Room temperature vanadium dioxide–carbon nanotube gas sensors made via continuous hydrothermal flow synthesis

“…6a). The sensitivity of carbon nanotubes to water vapour is well reported [66][67][68] . As the nanotubes contribute significantly towards conduction in the composites, any interactions inducing changes in conductance of the tubes, will have a large overall effect on the resistance of the sensor, which may have been the cause of the larger responses to water.…”

Electronic transport calculations in the onetep code: Implementation and applications

“…This gives greater flexibility in the sense of allowing the study of inter-tube conductance between CNTs of different chiralities. This and a detailed analysis of inter-tube scattering in CNT networks will be provided elsewhere [56].…”