  We have theoretically investigated the electronic and magnetic properties of
graphene whose zigzag edges are oxidized. The alteration of these properties by
adsorption of $\mathrm{H_{2}O}$ and $\mathrm{NH_3}$ molecules have been
considered. It was found that the adsorbed molecules form a cluster along the
oxidized zigzag edges of graphene due to interaction with the electro-negative
oxygen. Graphene tends to donate a charge to the adsorbates through the oxygen
atoms and the efficiency of donation depends on the intermolecular distance and
on the location of the adsorbed molecules relative to the plane of graphene. It
was found that by appropriate selection of the adsorbates, a controllable and
gradual growth of $p$-doping in graphene with a variety of adsorbed molecules
can be achieved.
