Imaging interfacial micro- and nano-bubbles by scanning transmission soft X-ray microscopy

Area of Science:

• Interface science
• Nanoscale phenomena
• Soft X-ray microscopy

Background:

• Interfacial gas nanobubbles are crucial in various physical and chemical processes.
• Understanding their stability and behavior at the solid/liquid interface is challenging.
• Previous studies suggest a length scale for nanobubble stability.

Purpose of the Study:

• To investigate the existence and behavior of interfacial gas nanobubbles.
• To determine the stability of nanobubbles confined between solid surfaces.
• To evaluate the suitability of STXM for nanobubble research.

Main Methods:

• Synchrotron-based scanning transmission soft X-ray microscopy (STXM) with nanometer resolution.
• Confining gas (SF6 and Ne) nanobubbles between silicon nitride windows.
• Observing nanobubble behavior during soft X-ray imaging.

Main Results:

• Stable interfacial gas nanobubbles with diameters smaller than 2.5 µm were observed.
• Larger nanobubbles exhibited instability and growth during imaging.
• The findings are consistent with a critical length scale for nanobubble stability.

Conclusions:

• STXM is a powerful technique for studying interfacial gas nanobubbles at the nanoscale.
• Nanobubble stability is dependent on their size, with a potential critical length scale.
• This research provides insights into gas aggregation phenomena at solid/water interfaces.