Nanoscale multiple gaseous layers on a hydrophobic surface.

Area of Science:

• Surface Science
• Nanotechnology
• Physical Chemistry

Background:

• Understanding interfacial phenomena is crucial in various scientific fields.
• The nanoscale gas state at liquid-solid interfaces remains an area of active research.
• Previous studies have not detailed the multi-layered structure of interfacial gases.

Purpose of the Study:

• To investigate the nanoscale gas state at liquid interfaces with highly oriented pyrolytic graphite (HOPG).
• To characterize the formation and stability of interfacial gas layers.
• To explore the conditions that induce the formation of these gas layers.

Main Methods:

• Tapping-mode atomic force microscopy (AFM) was employed to probe the nanoscale gas structures.
• Experiments were conducted using water, acid, and salt solutions in contact with HOPG substrates.
• Controlled variations in temperature and solvent exchange were utilized to induce gas layer formation.

Main Results:

• For the first time, the formation of gas bilayers and trilayers at liquid-HOPG interfaces was observed.
• Gas layer formation was induced by local gas supersaturation via temperature gradients or ethanol-water exchange.
• Interfacial gas layers were found to be less stable than spherical bubbles, with a propensity to transform over time or upon AFM tip perturbation.

Conclusions:

• The study reveals a previously unreported multi-layered nanoscale gas structure at liquid-solid interfaces.
• Interfacial gas layer formation is controllable through specific environmental conditions.
• The dynamic transformation of gas layers into bubbles highlights the complex behavior of interfacial gases.