Germanene nanotube electroresistive molecular device for detection of NO2 and SO2 gas molecules: a first-principles investigation

We explore the electronic properties of germanene nanotubes (GeNTs) using first-principles calculations with the non-equilibrium Green's function technique. The adsorption of two different gases, namely NO2 and SO2, onto GeNT is investigated using van der Waals density functional technique. Moreover, the change in the band gap-energy is noticed upon interaction of small NO2 and SO2 gas molecules. The shift in the peaks is observed in the conduction band upon adsorption of small NO2 and SO2 molecules on the GeNT. The calculated adsorption energies range from -0.156 to -0.609eV. The transmission spectrum showed that the transition of electrons is prominent for SO2 molecules rather than NO2 molecules onto the GeNT. In addition, the electron density diagram also indicate that a transfer of electrons occurs among the gas molecules and the GeNT electroresistive molecular device. The I-V characteristics of GeNT device clearly reveal the change in the current, which varies in the magnitude from 10(-9) to 10(-6)A upon adsorption of gas molecules on GeNT device. Thus, we suggest that germanene nanotube molecular device can be employed for the detection of NO2 and SO2 small molecules.