Micrometer-Scale Graphene-Based Liquid Cells of Highly Concentrated Salt Solutions for In Situ Liquid-Cell...

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• In situ liquid-cell transmission electron microscopy (TEM) is crucial for observing soft matter dynamics.
• Graphene liquid cells (GLCs) offer advantages like radical scavenging and high resolution over traditional silicon nitride cells.
• Previous studies noted challenges with GLC production stochasticity and compositional changes in encapsulated liquids.

Purpose of the Study:

• To investigate the reproducible formation of graphene-based liquid cells.
• To identify factors affecting the encapsulation of aqueous solutions in GLCs.
• To address limitations hindering the use of GLCs for pure water or dilute solutions.

Main Methods:

• Fabrication and characterization of graphene liquid cells with varying aqueous salt solution concentrations.
• Comparative analysis of GLC formation using conventional methods versus high-concentration solutions.
• Cooling experiments to assess ice formation and electron diffraction.
• Etch-pit method to confirm intrinsic defects in graphene.

Main Results:

• High reproducibility in nano- to micrometer-sized graphene-based liquid cell formation was achieved with concentrated aqueous salt solutions.
• Conventional fabrication methods yielded low success rates for water-encapsulated GLCs, with no ice diffraction observed.
• Intrinsic graphene defects were confirmed as a cause for poor encapsulation and potential leakage.
• Cell shrinkage and bubble area decrease indicated leakage of water and gas molecules from encapsulated cells.

Conclusions:

• Concentration of the encapsulated solution is key to reproducible graphene liquid cell formation.
• Intrinsic graphene defects impede the encapsulation of pure water and dilute solutions.
• Future work should focus on refining fabrication conditions and reducing graphene defects to enable GLCs for a wider range of aqueous samples.