Adsorption of NH$_{2}$ on Graphene in the Presence of Primary Defects

The primary amine, NH$_{2}$, is of interest as a linker between graphene and organic molecules in novel biotechnologies using graphene platforms. We are using \textit{ab initio} electronic structure calculations to study NH$_{2}$ adsorption on graphene. We find that the adsorption energy on pristine graphene is on the order of 0.778 eV, a relatively weak bond. We are interested in situations in which the bonding of NH$_{2}$ is stronger and are studying systems in which NH$_{2}$ adsorbs near defects. We find the adsorption energy of a NH$_{2}$ molecule near a second NH$_{2}$ molecule is as high as 1.037 eV and that the adsorption near a substitutional N atom is 1.063 eV. We find that there is a RKKY-like interaction between the adsorbate molecules in the case of two NH$_{2}$. We will also give results for NH$_{2}$ adsorption near other defects.