Detection of DNA homopolymer with graphene nanopore

Graphene nanopores hold great potential for applications such as molecular detection and DNA sequencing. Here, the authors present a fast and controllable way to fabricate sub-5-nm nanopores on a graphene membrane, with a process including two steps: (i) sputtering a large nanopore using a conventional, focused ion beam; and (ii) shrinking the large nanopore to under 5 nm using a scanning electron microscope. Conductance measurements confirm that the electron-beam-induced deposition of hydrocarbons not only shrinks the diameter of the nanopore but also increases its length. Furthermore, the authors report that using a salt gradient across the nanopore allows the detection of 3 nucleotide "C" and 3 nucleotide "G" homopolymer DNA strands based on differences in their physical dimensions.