Manish Shankla and Aleksei Aksimentiev.
Modulation of molecular flux using a graphene nanopore capacitor.
Journal of Physical Chemistry B, 121:3724-3733, 2016.
SHAN2016-AA
Modulation of ionic current flowing through nanoscale pores is one of the
fundamental biological processes. Inspired by nature, nanopores in synthetic
solid-state membranes are being developed to enable rapid analysis of biological
macromolecules and to serve as elements of nanofludic circuits. Here, we
theoretically investigate ion and water transport through a graphene–insulator–
graphene membrane containing a single, electrolyte-filled nanopore. By means
of all-atom molecular dynamics simulations, we show that the charge state of
such a graphene nanopore capacitor can regulate both the selectivity and the
magnitude of the nanopore ionic current. At a fixed transmembrane bias, the
ionic current can be switched from being carried by an equal mixture of cations
and anions to being carried almost exclusively by either cationic or anionic
species, depending on the sign of the charge assigned to both plates of the
capacitor. Assigning the plates of the capacitor opposite sign charges can either
increase the nanopore current or reduce it substantially, depending on the
polarity of the bias driving the transmembrane current. Facilitated by the
changes of the nanopore surface charge, such ionic current modulations are
found to occur despite the physical dimensions of the nanopore being an order
of magnitude larger than the screening length of the electrolyte. The ionic
current rectification is accompanied by a pronounced electro-osmotic effect that
can transport neutral molecules such as proteins and drugs across the solid-
state membrane and thereby serve as an interface between electronic and
chemical signals.
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