Electronic-Mediated Slip Regulation at MoS₂-Water Interface via Self-Assembled Monolayers

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Reducing friction at solid-liquid interfaces is crucial for fluid transport and microfluidic devices.
• Microscopic mechanisms of friction reduction, particularly electronic effects, are not well understood.
• Molybdenum disulfide (MoS2) is a promising material for investigating interfacial phenomena.

Purpose of the Study:

• To investigate the impact of self-assembled monolayers (SAMs) on friction reduction at the MoS2-water interface.
• To explore the role of interfacial electronic properties in slip behavior.
• To elucidate the interplay between surface chemistry, hydrophobicity, and electronic effects on nanoscale friction.

Main Methods:

• Fabrication of MoS2 surfaces modified with SAMs.
• Spectroscopic analyses (e.g., photoluminescence) in air and aqueous environments.
• Surface potential measurements and density functional theory (DFT) simulations.
• Electrostatic gating experiments to decouple electronic and hydrophobic contributions.

Main Results:

• Achieved an order-of-magnitude enhancement in slip length at the MoS2-water interface using SAMs.
• Observed measurable changes in interfacial electronic properties of MoS2.
• Demonstrated that SAMs and interfacial water jointly modulate the electronic state of MoS2.
• Found that changes in surface electronic states and SAM-induced hydrophobicity govern slip behavior.
• Decoupled the contributions of hydrophobicity and electronic effects using electrostatic gating.

Conclusions:

• Interfacial electrons play a significant role in slip behavior at solid-liquid interfaces.
• SAMs can be used to tune both electronic properties and hydrophobicity for friction reduction.
• Findings provide insights into electronic effects governing nanoscale friction and offer strategies for interface engineering.