A Theoretical Study of a Single-Walled ZnO Nanotube as a Sensor for H2O Molecules

We have studied the property of single-walled ZnO nanotubes with adsorbed water molecules, and theoretically designed a new sensor for detecting water molecules using single-walled ZnO nanotubes using a combination of density functional theory and the non-equilibrium Green's function method. Details of the geometric structures and adsorption energies of the H sub(2)O molecules on the ZnO nanotube surface have been investigated. Our computational results demonstrate that the formation of hydrogen bonding between the H sub(2)O molecules and the ZnO nanotube, and adsorption energies of the H sub(2)O molecules on the ZnO nanotube are larger than the adsorption energies of other gas molecules present in the atmospheric environment. Moreover, the current-voltage curves of the ZnO nanotube with and without H sub(2)O molecules adsorbed on its surface are calculated, the results of which showed that the H sub(2)O molecules form stable adsorption configurations that could lead to the decrease in current. These results suggest that the single-walled ZnO nanotubes are able to detect and monitor the presence of H sub(2)O molecules by applying bias voltages.