Fabrication of sub-nanometer pores on graphene membrane for ion selective transport

The ability to sieve ions through nanopores with high throughput has significant importance in seawater desalination and other separation applications. In this study, a plasma etching process has been demonstrated to be an efficient way to produce high-density nanopores on graphene membranes with tunable size in the sub-nanometer range. Besides the pore size, the nanopore density is also controllable through adjusting the exposure time of the sample to argon or oxygen plasma. The plasma-treated graphene membranes can selectively transport protons, Na and Cl ions. Density function theory calculations uncover that the sp and vacancy-type defects construct different energy barriers for different ions, which allow the defected graphene membrane to selectively transport ions. Our study indicates that oxygen plasma etching can be used as a very convenient and efficient method for fabricating a monolayer filtration graphene membrane with tunable sub-nanometer pores.