  Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate
resolution toward DNA sequencing. Among them, molybdenum disulphide (MoS2)
shows long-term stability as well as superior sensitivity enabling high
throughput performance. The traditional method of fabricating nanopores with
nanometer precision is based on the use of focused electron beams in
transmission electron microscope (TEM). This nanopore fabrication process is
time-consuming, expensive, not scalable and hard to control below 1 nm. Here,
we exploited the electrochemical activity of MoS2 and developed a convenient
and scalable method to controllably make nanopores in single-layer MoS2 with
sub-nanometer precision using electrochemical reaction (ECR). The
electrochemical reaction on the surface of single-layer MoS2 is initiated at
the location of defects or single atom vacancy, followed by the successive
removals of individual atoms or unit cells from single-layer MoS2 lattice and
finally formation of a nanopore. Step-like features in the ionic current
through the growing nanopore provide direct feedback on the nanopore size
inferred from a widely used conductance vs. pore size model. Furthermore, DNA
translocations can be detected in-situ when as-fabricated MoS2 nanopores are
used. The atomic resolution and accessibility of this approach paves the way
for mass production of nanopores in 2D membranes for potential solid-state
nanopore sequencing.
