Cryo-EM Visualization of Nanobubbles in Aqueous Solutions

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Surface nanobubble detection is established using techniques like atomic force microscopy (AFM) and optical microscopy.
• Direct detection of nanobubbles within bulk solutions remains a significant challenge in current scientific methodologies.

Purpose of the Study:

• To develop and demonstrate a novel method for the direct visualization of nanobubbles in aqueous solutions.
• To characterize the properties and behavior of bulk nanobubbles using advanced imaging techniques.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was utilized to image nanobubbles in aqueous solutions.
• Nitrogen nanobubbles were generated via a chemical reaction and subsequently trapped in amorphous ice for observation.

Main Results:

• Cryo-electron microscopy successfully visualized nanobubbles within the bulk solution, confirming theoretical predictions.
• Observed nanobubbles did not appear near the air-water interface, suggesting diffusion away from the bulk.
• An estimated diffusion coefficient for the nanobubbles was determined to be in the range of 30–250 μm²/s.

Conclusions:

• Cryo-electron microscopy provides a viable method for the direct detection and study of bulk nanobubbles.
• The findings suggest that bulk nanobubbles can diffuse to and potentially escape through the air-water interface.
• This technique opens new avenues for understanding nanobubble behavior in various liquid environments.