Enhancement of chlorobenzene sensing by doping aluminum on nanotubes: A DFT study

Chlorobenzene (CB) is a harmful, aromatic volatile organic compound and has been demonstrated to be a primary precursor of dioxin formation in industrial processes. Single-walled carbon nanotubes (SWCNT) and boron nitride nanotubes (BNNT) have attracted tremendous attention in a wide range of applications, including chemical gas sensors. In this work, we studied the sensing behavior of both semiconducting (8, 0) SWCNT and BNNT via aluminum doping by using DFT calculations. Our results reveal that CB can only adsorb on pristine SWCNT and BNNT via physisorption, while the Al-doped nanotubes greatly enhance the adsorption energies of the CB molecule. This is caused by the electron donating from the Cl atom to the Al atom to form an Al-Cl dative bond. The strong interaction caused by this Al-Cl dative bond formation leads to the breaking of the partial-double-bond characteristic of the C-Cl bond of the CB molecule so that the adsorption energies of CB can be enhanced. Moreover, we also found that Al-doped (8,0) BNNT displays a huge conductivity increase because of the considerable change in the band gap value after detecting the CB molecule. Our results imply that the Al-doped nanotubes, especially Al-doped BNNT, might be highly sensitive to chlorine-containing species.