Two-dimensional self-assembly of DNA base molecules on Cu(111) surfaces

We present scanning tunneling microscope images of the self-assembled nucleic-acid base molecules on the surfaces of Cu(111). The images reveal that the chemical inertness of the Cu(111) substrate allows the molecules to diffuse over the surface to self-assemble themselves spontaneously into their own unique structure: adenine into one-dimensional (1D) molecular chains, thymine into 2D islands, guanine into 2D square lattices, and cytosine into 1D zig-zag molecule-cluster networks. We find that molecular orbital calculations reproduce some of the observed self-assembly, and suggest that base-base interaction induced by hydrogen bonding is essential to this phenomenon.