  We studied the electronic and the structural properties of amino acids
(alanine, glycine, and histidine) attached to graphene oxide (GO) by peptide
bonding, via plane wave pseudopotential total-energy calculations within the
local spin density approximation (LSDA). The HOMO-LUMO gap, the Hirshfeld
charges, and the equilibrium geometrical structures exhibit keen variations
depending on the species of the attached amino acid. The GO-amino acid system
appears to be a good candidate as a biosensor.
