Environmentally hazardous gas sensing ability of MoS₂-nanotubes: an insight from the electronic structure and transport properties

Herein we have investigated the ability of the (6,6) MoS₂-nanotube (NT) to sense environmentally hazardous electrophilic and nucleophilic gases using density functional theory (DFT). CO, CO₂, H₂O and NH₃ gases were chosen for adsorption on the (6,6) MoS₂-NT and different adsorption parameters such as adsorption energy, projected density of states (PDOS), band structure and structural changes after adsorption were evaluated. Nucleophilic gases NH₃ and H₂O showed a fairly high amount of electron density transfer from gas molecules to the NT while the opposite trend was realized for electrophilic gases CO and CO₂. Among the four gases, H₂O has the highest amount of adsorption energy (-1.74 eV) and a moderately high amount of charge transfer from H₂O to the NT. Gas sensing behaviour was further rationalized from the enhanced I-V characteristics of gas adsorbed nanotubes compared to pristine ones. Analysis of results revealed that the (6,6) MoS₂-NT showed a decent level of gas sensing properties towards CO, CO₂, H₂O and NH₃ gases, and high selectivity for H₂O makes the MoS₂-NT superior to previously reported MoS₂-monolayer in this matter. These results suggest the possibility of fabrication of highly efficient MoS₂-NT based gas sensors for environmentally hazardous gases.