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

Abstract

Reducing friction at the solid-liquid interfaces is critical for improving the efficiency of fluid transport, underwater equipment, and microfluidic devices. While macroscopic strategies have achieved significant friction reduction, experimental investigation into the underlying microscopic mechanisms remains limited, especially from atomic and electronic perspectives. In this work, an order-of-magnitude enhancement in slip length at the MoS₂-water interface is achieved via self-assembled monolayers (SAMs), accompanied by measurable changes in interfacial electronic properties. Spectroscopic analyses performed in both air and aqueous environments reveal that the electronic state of MoS₂ is jointly modulated by SAMs and interfacial water. Exciton recombination behavior under optical excitation serves as an indirect probe of interfacial electron transfer. Combined surface potential measurements and density functional theory simulations indicate that changes in surface electronic states may influence charge density which, along with SAM-induced hydrophobicity, governs the observed slip behavior. Electrostatic gating experiments further decouples the contribution of substrate hydrophobicity, enabling a more precise interpretation of the interfacial electronic influence. These findings suggest that interfacial electrons contribute to slip behavior at solid-liquid interfaces and offer valuable insights into electronic effects in nanoscale friction.