A practicable model of a carbon nanotube-based ionic sensor

We introduce a model for using carbon nanotubes (CNTs) as selective room temperature aqueous ionic sensors and present calculations of how the current–voltage characteristics change as a function of ion adsorption. We were able to predict how changes in the band-structure of the CNTs manifest themselves in measurable external electrical parameters, such as conductivity. The mechanism by which the electronic properties are modified is by radial distortion of the nanotube caused by the mutual repulsion of the ions that have been adsorbed onto a thin insulating ligand shell. Depending on the chirality of the nanotube, the radial distortion is found to cause very different types of changes to the current–voltage behavior. For the case of zigzag nanotubes, at fixed bias, the current is found be modulated as a function of amount of adsorbed charge.