Feasibility of pristine, Al-doped and Ga-doped Boron Nitride nanotubes for detecting SF4 gas: A DFT, NBO and QTAIM investigation

In this work, a molecular level study on the adsorption of SF4 gas onto pristine Boron Nitride (BN) nanotube, BN nanotube doped with Al (BN(Al)) and BN nanotube doped with Ga (BN(Ga)) has been done using density functional theory (DFT) methods. PBEPBE, B3LYP-D3 and M06-2X functionals along with 6-31G(d) and 6-31 + G(d) basis sets were implemented. QTAIM, NBO, ESP and NCI analyses are performed to explore the nature of the nanotube/SF4 intermolecular interactions. Adsorption energies (E-ads) reveal that, the adsorption tendency of SF4 on nanotubes is in the order of: BN(Al) > BN(Ga) > pristine-BN which is completely in agreement with ESP and NCI analyses results. QTAIM, NBO, ESP and NCI analyses demonstrate that, the interactions of SF4 and BNNTs are more closed-shell (noncovalent) in nature. In other words, considered nanotubes can detect SF4 gas in a simple physisorption process. Total density of state (DOS) analysis also shows that, the Al and Ga atoms doped on BNNT decrease HOMO-LUMO band gap, and therefore, has a substantial influence on the electric properties of decorated nanotube. Generally, it was found that, the sensitivity of Al and Ga doped nanotubes toward SF4 gas are substantially more than that of the pristine BN nanotube.