Methanol-sensing characteristics of zinc oxide nanotubes: quantum chemical study

Adsorption of a methanol molecule on a ZnO nanotube was investigated by using density functional calculations in terms of energetic, geometric, and electronic properties. The adsorption energy is found to be in the range of -23.4 to -220.7 kJ/mol. The electronic properties of the tube strongly depend on the orientation of the methanol on the nanotube surface. When the methanol attacks a hexagonal ring of the tube via its methyl hydrogens, the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap of the tube is significantly decreased from 2.27 to 1.53 eV, and, therefore, it becomes more conductive. This suggests that a pristine ZnO nanotube may generate an electrical signal in the presence of methanol molecules, making it a potential candidate for methanol detection.