David Visontai

Graphene sculpturene nanopores for DNA nucleobase sensing

To demonstrate the potential of nanopores in bilayer graphene for DNA sequencing, we computed the current-voltage characteristics of a bilayer graphene junction containing a nanopore and found that they change significantly when nucleobases are transported through the pore. To demonstrate the sensitivity and selectivity of example devices, we computed the probability distribution PX(β) of the quantity β representing the change in the logarithmic current through the pore due to the presence of a nucleobase X (X = adenine, thymine, guanine, or cytosine). We quantified the selectivity of the bilayer-graphene nanopores by showing that PX(β) exhibits distinct peaks for each base X. To demonstrate that such discriminating sensing is a general feature of bilayer nanopores, the well-separated positions of these peaks were shown to be present for different pores, with alternative examples of electrical contacts.

A study of planar anchor groups for graphene-based single-molecule electronics.

To identify families of stable planar anchor groups for use in single molecule electronics, we report detailed results for the binding energies of two families of anthracene and pyrene derivatives adsorbed onto graphene. We find that all the selected derivatives functionalized with either electron donating or electron accepting substituents bind more strongly to graphene than the parent non-functionalized anthracene or pyrene. The binding energy is sensitive to the detailed atomic alignment of substituent groups over the graphene substrate leading to larger than expected binding energies for -OH and -CN derivatives. Furthermore, the ordering of the binding energies within the anthracene and pyrene series does not simply follow the electron affinities of the substituents. Energy barriers to rotation or displacement on the graphene surface are much lower than binding energies for adsorption and therefore at room temperature, although the molecules are bound to the graphene, they are almost free to move along the graphene surface. Binding energies can be increased by incorporating electrically inert side chains and are sensitive to the conformation of such chains.