  Functionalized graphene offers great potential in the field of rapid
detection of gases at room temperature. We performed first-principles
calculations to study the suitability of 4-sulfobenzenediazonium salts (4SBD)
as bandgap modifier in graphene. The signature of unpaired spins is evidenced
near the Fermi level owing to the symmetry breaking of graphene sublattices.
4SBD-chemisorbed on graphene is found to be electronically sensitive to the
presence of ammonia NH3 with increasing gas concentration.
