Na+ and K+ ion selectivity by size-controlled biomimetic graphene nanopores

Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K+ channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K+ and Na+ channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K+, the smaller radius of Na+ leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 A between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na+ and K+ ions.