Physisorption of nucleobases on graphene: Density-functional calculations

We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density-functional theory framework, with additional calculations utilizing Hartree-Fock plus second-order Møller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: $\mathrm{G}>\mathrm{A}\approx \mathrm{T}\approx \mathrm{C}>\mathrm{U}$, with the equilibrium configuration being rather similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step toward a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally.

Figure 1

(Color online) Potential energy surface (PES) plot (in eV) for guanine on graphene. Qualitatively similar PES plots were obtained for the other four nucleobases. Approximately, a $3\times 3$ repetition of the unit cell is shown. The energy difference between peak and valley is approximately $0.10\mathrm{eV}$. The energy barriers separating adjacent global minima have heights of about $0.04–0.05\mathrm{eV}$, depending on the direction of translocation.

Figure 2

(Color online) Equilibrium geometry of nucleobases on top of graphene: (a) guanine, (b) adenine, (c) thymine, (d) cytosine, and (e) uracil.

Figure 3

(Color online) Plot of the relative total energy (black squares), exchange-correlation energy [blue (dark gray) diamonds], and kinetic energy [red (gray) triangles] of guanine (top panel) and adenine (bottom panel) adsorbed on graphene calculated as a function of the displacement from their respective equilibrium position.