4.8 Article

Super-resolved Optical Mapping of Reactive Sulfur-Vacancies in Two-Dimensional Transition Metal Dichalcogenides

Journal

ACS NANO
Volume 15, Issue 4, Pages 7168-7178

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsnano.1c00373

Keywords

2D materials; defects; super-resolution; thiol chemistry; sulfur vacancy; interface

Funding

  1. Swiss National Science Foundation (SNSF) [BIONIC BSCGI0_ 157802]
  2. CCMX project (Large Area Growth of 2D Materials for device integration)
  3. Swedish Research Council [VR 2018-06764]
  4. U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0019112]
  5. U.S. Department of Energy (DOE) [DE-SC0019112] Funding Source: U.S. Department of Energy (DOE)
  6. Swedish Research Council [2018-06764] Funding Source: Swedish Research Council

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Transition metal dichalcogenides (TMDs) are a class of exciting semiconducting two-dimensional (2D) materials, where defects and their molecular interactions with the environment can significantly impact their properties. In this study, a new mapping method was demonstrated to locate sulfur-deficient defects in 2D-TMDs in aqueous solutions using fluorescence labeling with thiol chemistry. This approach allows precise localization of defects and control over Foster resonance energy transfer (FRET) process, revealing grain boundaries and line defects, as well as investigating binding kinetics under varying pH conditions.
Transition metal dichalcogenides (TMDs) represent a class of semiconducting two-dimensional (2D) materials with exciting properties. In particular, defects in 2D-TMDs and their molecular interactions with the environment can crucially affect their physical and chemical properties. However, mapping the spatial distribution and chemical reactivity of defects in liquid remains a challenge. Here, we demonstrate large area mapping of reactive sulfur-deficient defects in 2D-TMDs in aqueous solutions by coupling single-molecule localization microscopy with fluorescence labeling using thiol chemistry. Our method, reminiscent of PAINT strategies, relies on the specific binding of fluorescent probes hosting a thiol group to sulfur vacancies, allowing localization of the defects with an uncertainty down to 15 nm. Tuning the distance between the fluorophore and the docking thiol site allows us to control Foster resonance energy transfer (FRET) process and reveal grain boundaries and line defects due to the local irregular lattice structure. We further characterize the binding kinetics over a large range of pH conditions, evidencing the reversible adsorption of the thiol probes to the defects with a subsequent transitioning to irreversible binding in basic conditions. Our methodology provides a simple and fast alternative for large-scale mapping of nonradiative defects in 2D materials and can be used for in situ and spatially resolved monitoring of the interaction between chemical agents and defects in 2D materials that has general implications for defect engineering in aqueous condition.

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