▎ 摘　　要

Solid-state nanopores, in particular graphene nanopores, are believed to have promising applications in DNA sequencing. Many efforts have been made in this research area, the ultimate goal is to extend the DNA translocation time and to achieve single-base resolution. Unfortunately, several factors in DNA sequencing are still not well understood. In this paper, we report a study on the effects of two main factors, the salt concentration and the bias voltage, on the corresponding ionic current. We propose a theoretical model to explore the relationship between the occupied nanopore area and the current. We demonstrate that the DNA translocation time can be prolonged by decreasing the bias voltage and by properly narrowing the nanopore diameter. We find that the reduction of the blockade current depends on the ratio of the unoccupied nanopore area to the total nanopore area.