  Inspired by the recent successes in the development of two-dimensional based
gas sensors capable of single gas molecule detection, we investigate the
adsorption of gas molecules such as N2, NO, NO2, NH3, CO, CO2, CH4, SO2, and
H2S on silicene nanoribbons using density functional theory and nonequilibrium
Green's function methods. The most stable adsorption configurations, adsorption
sites, adsorption energies, charge transfer, quantum conductance modulation,
and electronic band structures of all studied gas molecules on SiNRs are
studied. Our results indicate that NO, NO2, and SO2 are chemisorbed on SiNRs
via strong covalent bonds, suggesting its potential application for disposable
gas sensors. In addition, CO and NH3 are chemisorbed on SiNRs with moderate
adsorption energy, alluding to its suitability as a highly sensitive gas
sensor. The quantum conductance is detectably modulated by chemisorption of gas
molecules which can be attributed to the charge transfer from the gas molecule
to the SiNR. Other studied gases are physisorbed on SiNRs via van der Waals
interactions. It is also found that the adsorption energies are enhanced by
doping SiNRs with either B or N atom. Our results suggest that SiNRs show
promise in gas molecule sensing applications.
