The adsorption of several common gas molecules over boron-, nitrogen-, aluminum-, and sulfur-doped graphene was theoretically studied using density-functional theory. B- and N-doped graphene retain a planar form, while Al and S atoms protrude out of the graphene layer. We find that only NO and NO2 bind to B-doped graphene, while only NO2 binds to S-doped graphene. Al-doped graphene is much more reactive and binds many more gases, including O2. We suggest that B- and S-doped graphene could be a good sensor for polluting gases such as NO and NO2.

Adsorption of molecular oxygen on B-, N-, Al-, Si-, P-, Cr- and Mn-doped graphene is theoretically studied using density-functional theory in order to clarify if O2 can change the possibility of using doped graphene for gas sensors, electronic, and spintronic devices. O2 is physisorbed on B-, and N-doped graphene with small adsorption energy and long distance from the graphene plane, indicating the oxidation will not happen; chemisorption is observed on Al-, Si-, P-, Cr- and Mn-doped graphene. The local curvature caused by the large bond length of X-C (X represents the dopants) relative to C-C bond plays a very important role in this chemisorption. The chemisorption of O2 induces dramatic changes of electronic structures and localized spin polarization of doped graphene, and in particular, chemisorption of O2 on Cr-doped graphene is antiferromagnetic. The analysis of electronic density of states shows the contribution of the hybridization between O and dopants is mainly from the p or d orbitals. Furthermore, spin density shows that the magnetization locates mainly around the doped atoms, which may be responsible for the Kondo effect. These special properties supply a good choice to control the electronic properties and spin polarization in the field of graphene engineering.

The adsorption of gas molecules on P-doped graphene (PG) was theoretically studied using density-functional theory in order to find the possibility of modulating electronic and magnetic ordering of graphene. H₂, H₂O, CO₂, CO, N₂ and NH₃ molecules are physisorbed, while NO, NO₂, SO₂ and O₂ molecules are strongly chemisorbed on PG through the formation of P-X (X = O, N, S) bonds. P dopant introduces global spin polarization into graphene with order of 1.05 μ(B). Chemisorption of NO₂ and SO₂ makes the spin polarization and projected density of states (PDOS) of molecules localized. NO also induces a partly localized spin state and O₂ an unpolarized system. Meanwhile, the systems of NO₂ and O₂ on PG are metallic, while NO and SO(2) on PG are half-metallic. Therefore, the properties of PG are strongly dependent on the types of molecules adsorbed, and the method of combining foreign atom doping followed by exposure to air is effective for the engineering of graphene.