B40 fullerene as a highly sensitive molecular device for NH3 detection at low bias: a first-principles study

The adsorption of small molecules (NH3, N-2, H-2 and CH4) on all-boron fullerene B-40 is investigated by density functional theory (DFT) and the non-equilibrium Green's function (NEGF) for its potential application in the field of single-molecular gas sensors. The high adsorption energies (-1.09 to -0.75 eV) of NH3 on different adsorption sites of the B-40 surface indicate that NH3 strongly chemisorbs to B-40. The charge transfer induced by the NH3 adsorption results in a modification of the density of states (DOS) of B-40 near the Fermi level, and therefore changes its electronic transport properties. For all possible adsorption sites, the adsorption of NH3 exclusively leads to a decrease of the conductance of B-40. Taking into consideration that the non-polar gas molecules (e.g. N-2, H-2 and CH4) are only physisorbed and show negligible effect on the conductance properties of B-40, we would expect that B-40 can be used as a single-molecular gas sensor to distinguish NH3 from non-polar gas molecules at low bias.