Water-induced mica/ionic liquid interfacial nanostructure switches revealed by AFM

Area of Science:

• Surface Science
• Physical Chemistry
• Materials Science

Background:

• The interfacial structure between ionic liquids and solid surfaces is crucial for applications in lubrication, electrochemistry, and nanotechnology.
• Understanding the influence of environmental factors, such as water, on these interfaces is essential for predicting and controlling material behavior.

Purpose of the Study:

• To investigate the impact of controlled water content on the interfacial forces between mica and a pyrrolidinium-based ionic liquid.
• To elucidate the transition in force dominance from van der Waals attraction to double layer repulsion with increasing water concentration.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) within a glovebox environment to perform force curve measurements.
• Controlled introduction of small, precise amounts of water to the ionic liquid/mica system.

Main Results:

• Observed a distinct change in the long-range interfacial force beyond the short-range oscillatory structure.
• Demonstrated a transition from van der Waals attraction-dominated forces to double layer repulsion-dominated forces as water content increased.

Conclusions:

• Water acts as a significant modifier of the interfacial forces between ionic liquids and mica.
• The observed force switch highlights the sensitivity of ionic liquid interfaces to hydration levels, impacting their performance in various applications.