Influence of atmospheric water vapour on electrical performance of carbon nanotube fibres

Carbon nanotube assemblies are expected to find application in many areas of technology. Therefore, it is of paramount importance to understand and predict their performance in different ambient conditions. Here, we explore the influence of air exposure on the electrical conduction in carbon nanotube fibres and films produced via floating catalyst chemical vapour deposition. We recognise that on top of the previously well-explored oxygen doping effect these macroscopic materials are also significantly affected by humidity. The adsorption of water vapour causes an increase in the weight of the assemblies, increase in electrical conductivity at room temperature or changes in the resistance-temperature dependence at low temperatures. It is suggested that the water vapour is mainly adsorbed by the standard clustering mechanisms observed in other carbon materials, but the mechanisms responsible for the improvement in electrical performance are much more debatable. We present a strong indication that the carbon nanotubes are neither n-doped nor p-doped by water molecules and provide further discussion on the potential role of water in the electrical transport of carbon nanotube assemblies.