Thermodynamics of Surface Nanobubbles

Area of Science:

• Thermodynamics
• Surface Science
• Nanotechnology

Background:

• Surface nanobubbles are intriguing phenomena observed on solid surfaces submerged in liquids.
• Understanding their thermodynamic stability is crucial for controlling their behavior and applications.

Purpose of the Study:

• To define and analyze the free energy of surface nanobubbles.
• To determine the conditions necessary for the thermodynamic stability of surface nanobubbles.

Main Methods:

• Defining free energy for a system of nanobubbles on a solid surface in a supersaturated solution.
• Analyzing plots of free energy versus the radius of curvature to identify a global minimum indicating stable equilibrium.
• Investigating the role of supersaturation and contact angle in nanobubble stability.

Main Results:

• Stable surface nanobubbles necessitate a supersaturated liquid solution.
• An anomalously high contact angle, measured through the liquid, is a key requirement for stability.
• The study explores the relationship between advancing/receding contact angles and thermodynamic equilibrium contact angles, considering a gas enrichment layer.

Conclusions:

• Supersaturation and high contact angles are essential for stable surface nanobubbles.
• The findings provide a thermodynamic framework for understanding surface nanobubble stability.
• This research contributes to the fundamental knowledge of interfacial phenomena at the nanoscale.