  Innovative methodologies for reliably and inexpensively sequencing DNA can
lead to a new era of personalized medicine. In this work, we performed a
theoretical investigation of a nanogap-based all electronic DNA sequencing
device. To do so, we used a nitrogen-terminated nanogap on a graphene sheet
with the environment fully taken into account. Our investigation is performed
using a hybrid methodology combining quantum and classical mechanics coupled to
non-equilibrium Green's functions for solving the electron transport across the
device. The obtained results show that the DNA nucleotides can be both detected
and distinguished in such device, which indicates that it can be used as a DNA
sequencing device providing very high sensitivity and selectivity. Furthermore,
our results show that water plays a major role in electronic transport in
nanoscopic tunneling devices, not only from an electrostatics point of view,
but also by providing states that significantly increase the conductance in
nanogap-based DNA sequencing devices.
