Ultrahigh-stability SnOX (X = S, Se) nanotubes with a built-in electric field as a highly promising platform for sensing NH3, NO and NO2: a theoretical investigation

Due to the confinement effect, nanotubes (NTs) are believed to be a highly promising platform for gas detection. In this work, combining density functional theory calculations with non-equilibrium Green's-function-based simulations, we systematically investigate the sensing performance of SnOX (X = S, Se) NTs toward NH3, NO, and NO2. Our results reveal that the novel SnOX NTs with a built-in electric field have ultrahigh stability and can be spontaneously formed from their monolayer counterparts. NH3 can be chemically captured by the inner side of the tube with moderate bonding strength. Combining this with a short recovery time and high sensitivity, SnOX NTs are believed to be a promising platform for sensing NH3. In contrast, NO and NO2 both interact physically with the NTs, and their different interaction mechanisms, i.e., electrostatic interactions and dipole–dipole interactions, account for the different sensing behavior. Due to the obvious perturbation of their electronic properties and ultrafast recovery time, SnOX NTs show high sensitivity toward NO2. However, due to the relatively weak interactions and relatively lower perturbation of their electronic properties, SnOX NTs show weak sensitivity toward sensing NO. The intrinsic dipole of the NTs is found to play different roles in detecting these N-containing polar gases. Transport calculations further verify that the SnOSe NTs are the most promising materials for sensing NH3 and NO2. Our results may provide a new idea for the artificial control and tailoring of the sensing performance based on the intrinsic dipole of the NTs.