  We characterize the transport properties of functionalized graphene
nanoribbons using extensive first-principles calculations based on density
functional theory (DFT) that encompass both monovalent and divalent ligands,
hydrogenated defects and vacancies. We find that the edge metallic states are
preserved under a variety of chemical environments, while bulk conducting
channels can be easily destroyed by either hydrogenation or ion or electron
beams, resulting in devices that can exhibit spin conductance polarization
close to unity.
