  Longitudinal resolution and lateral sensitivity are decisive characteristics
that determine the suitability of a nanopore sensor for sequencing a strand of
DNA as well as other important polymers. Previous modeling of DNA induced ionic
current blockades in single atom thick graphene nanopores has shown these
nanopores to have sufficient longitudinal resolution to distinguish individual
nucleobases along the length of a DNA molecule. Here we experimentally focus on
the sensitivity to small changes in DNA diameter that can be discerned with
graphene nanopores. We show that remarkably large sensitivities (0.5 nA/A)are
obtained when the nanopore is tailored to have a diameter close to that of the
polymer of interest. Our results have been obtained with double-stranded DNA
(dsDNA). Smaller graphene nanopores that can be tuned to the diameter of
single-stranded DNA (ssDNA) for sequencing have only recently been
demonstrated. Our results indicate that nanopore sensors based on such pores
will provide excellent resolution and base discrimination, and will be robust
competitors to protein nanopores that have recently demonstrated sequencing
capability.
