Does adsorption in a single nanogroove exhibit hysteresis?

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Understanding fluid behavior in confined geometries is crucial for nanotechnology and materials science.
• Capillary condensation and adsorption isotherms are key phenomena in porous materials and thin films.
• Hysteresis in adsorption isotherms indicates complex fluid-interface interactions and phase transitions.

Purpose of the Study:

• To investigate the role of wetting properties in fluid adsorption hysteresis within a capped nanocapillary.
• To determine the conditions under which hysteresis occurs or is absent in nanogroove adsorption.
• To explore the influence of temperature and prewetting on adsorption isotherms.

Main Methods:

• Utilized fundamental measure density functional theory to model a simple fluid in a nanogroove.
• Simulated adsorption isotherms for a single, infinitely long nanogroove with long-range dispersion forces.
• Analyzed the impact of wetting temperature (T(w)) and prewetting phenomena on fluid behavior.

Main Results:

• Above the wetting temperature (T(w)), adsorption is a continuous process involving meniscus rise.
• Below T(w), fluid condensation exhibits a first-order transition, leading to hysteresis in adsorption isotherms.
• Hysteresis can also occur above T(w) due to prewetting on the nanogroove's side and bottom walls.

Conclusions:

• The wetting properties of the nanocapillary wall critically determine the presence or absence of adsorption hysteresis.
• Temperature plays a key role, with transitions occurring at or below the wetting temperature.
• Prewetting effects can induce hysteresis even in conditions where continuous adsorption is otherwise expected.