Electrochemical Reaction in Single Layer MoS₂: Nanopores Opened Atom by Atom

Abstract

Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate resolution toward DNA sequencing. Among them, molybdenum disulfide (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 subnanometer 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.

Single-layer MoS2 nanopores as nanopower generators

“…8d). Considerable energy could also be generated by exploiting parallelization, with multiple small pores or even a continuous porous structure within a large area of single-layer MoS 2 membrane 26 , which could be scaled up for mass production using the ECR pore-fabrication technique 16 or plasma-based defect creation 27 .…”

“…Nanofluidic measurements. Nanofluidic transport experiments are performed as described 16 . The nanopore chips are mounted in a custom-made polymethylmethacrylate chamber, and then wetted with an H 2 O:ethanol (1:1) solution.…”

“…12). We use our MoS 2 nanopore generator to power a MoS 2 transistor, thus demonstrating a self-powered nanosystem.MoS 2 nanopores have already demonstrated better water-transport behaviour than graphene 13,14 owing to the enriched hydrophilic surface sites (provided by the molybdenum) that are produced following either irradiation with transmission electron microscopy (TEM) 15 or electrochemical oxidation 16 . The osmotic power is generated by separating two reservoirs containing potassium chloride (KCl) solutions of different concentrations with a freestanding MoS 2 membrane, into which a single nanopore has been introduced 13 .…”

“…1c) or by the recently demonstrated electrochemical reaction (ECR) technique 16 . With a typical nanopore diameter in the range 2-25 nm, a stable LETTER RESEARCH osmotic current can be expected, owing to the long time required for the system to reach equilibrium.…”

Nano-structured interface of graphene and h-BN for sensing applications

“…In recent studies [16], nanopores were created on SiN membranes and it was claimed that it is possible to control the stability, size and also the shape of the nanopores, using transmission electron microscope (TEM). Another technique, using electrochemical reaction (ECR) [17], can create a nanopore in 2D materials with ann atom-by-atom control, and this technique has been applied on both graphene and MoS 2 .…”