Adsorption of DNA Nucleobases on Graphene Nanoribbon – Impact of Stone-Wales and Di-vacancy Defects*

Graphene has recently emerged as a promising low-dimensional material for electronic DNA sequencing. Most studies on the use of graphene for DNA sequencing were based on using pristine graphene. However, experimentally fabricated two-dimensional (2D) graphene has imperfections, among which are the Stone−Wales (SW) and divacancy (DV) defects. We studied the role of SW and DV defects on the electronic interactions of graphene nanoribbons (GNR) with DNA nucleobases. Using semilocal (PBE) and van der Waals-corrected density functional theory (vdW-DF2, Grimme-D2), we examined the binding energies of the nucleobases adsorbed on GNR surface.  Our results show that defected GNR exhibit slightly different binding energies for each nucleobase compared to pristine GNR. The calculated binding energies using PBE, Grimme-D2, and vdW-DF2 methods range from -0.06 to -0.10 eV, -0.55 to -0.80 eV, and -0.59 to -0.78 eV, respectively. The vdW-DF2 method captures vdW interactions effectively, with binding energies following the order G > A > C >T. These interactions lead to weak hybridization between nucleobases and the π-states of the GNR surface, including small interfacial dipole and a shift in the energy band gap. Furthermore, we explored the quantum transport properties of the GNR devices with different defect structures using non-equilibrium Green’s function (NEGF) approach. We found that SW and DV defects significantly alter the transmission spectra, suggesting potential applications for DNA nucleobase detection.