  First-principles calculations based on density functional theory (DFT) have
been employed to investigate the structural, electronic, and gas-sensing
properties of pure, defected, and doped germanene nanosheets. Our calculations
have revealed that while a pristine germanene nanosheet adsorbs CO2 weakly, H2S
moderately, and SO2 strongly, the introduction of vacancy defects increases the
sensitivity significantly which is promising for future gas-sensing
applications.Mulliken population analysis imparts that an appreciable amount of
charge transfer occurs between gas molecules and a germanene nanosheet which
supports our results for adsorption energies of the systems. The enhancement of
the interactions between gas molecules and the germanene nanosheet has been
further investigated by density of states.Projected density of states provides
detailed insight of the gas molecules contribution in the gas-sensing
system.Additionally, the influences of substituted dopant atoms such as B, N,
and Al in the germanene nanosheet have also been considered to study the impact
on its gas sensing ability. There was no significant improvement found in doped
gas sensing capability of germanene over the vacancy defects, except for CO2
upon adsorption on N-doped germanene.
