Monolayer WS₂ Nanopores for DNA Translocation with Light-Adjustable Sizes

Area of Science:

• Materials Science
• Nanoscience
• Condensed Matter Physics

Background:

• Two-dimensional materials like tungsten disulfide (WS₂) offer unique electronic and optical properties.
• WS₂ monolayers possess a direct band gap and strong photoluminescence (PL), making them suitable for optoelectronics.
• Investigating low-dimensional systems requires precise control over material structures.

Purpose of the Study:

• To fabricate and characterize nanometer-size pores in suspended monolayer WS₂ membranes.
• To explore the electrical and optical properties of WS₂ nanopores for potential applications.
• To demonstrate the controlled growth and size tuning of WS₂ nanopores.

Main Methods:

• Fabrication of nanopores using a focused electron beam on suspended WS₂ membranes.
• Characterization via photoluminescence (PL) spectroscopy and aberration-corrected high-resolution scanning transmission electron microscopy (STEM).
• Ionic current measurements and DNA translocation experiments through the fabricated nanopores.

Main Results:

• Suspended WS₂ monolayers exhibit significantly enhanced PL intensity (10-15 times) compared to substrate-supported ones.
• Low-dose STEM imaging and electron beam drilling preserve the PL signal around the nanopores.
• WS₂ nanopores facilitate ionic conductance and DNA translocation, with controllable size growth under laser illumination.

Conclusions:

• Nanometer-size pores can be reliably fabricated in suspended WS₂ monolayers.
• The enhanced PL of suspended WS₂ and the preservation of optical properties around pores are crucial findings.
• WS₂ nanopores are promising for ionic sensing, DNA analysis, and atomically controlled nanopore engineering.