Single-Molecule Water Motion on h-BN and Graphene: A Paradigm Shift in Understanding the Behaviour of Water on 2D Material Interfaces

• DOI: 10.48550/arxiv.2502.11944
• Publication Date: 2025-02-17
• Authors: Paul Seiler; Anthony Payne; Neubi Francisco X...; Louie Slocombe; Marco Sacchi; Anton Tamtögl
• Keywords: Paradigm shift

Understanding water behaviour on 2D materials is crucial for sensing, microfluidics, and tribology. While water/graphene interactions are well studied, hexagonal boron nitride (h-BN) remains largely unexplored. Despite structural similarity to graphene, h-BN's slightly polar B-N bonds impart a large band gap, high thermal conductivity, chemical stability, making it promising electronics, lubricants, coatings. Moreover, existing studies often focus multilayer dynamics, overlooking single-molecular details. We bridge this gap by studying friction diffusion h-BN, comparing with graphene using helium spin-echo experiments ab initio calculations. Our findings show that h-BN/Ni follows complex rotational-translational dynamic, unlike graphene. conventional views treat motion as discrete jumps between equivalent adsorption sites, we demonstrate molecules rotate freely around their centre of mass. Although the binding energies h-BN similar, activation energy dynamics 2.5 times lower than implying much barrier molecular mobility. The fundamentally different characteristics which classical models cannot capture, underscores need rethink how model materials. our analysis reveals metal substrate strongly influences friction, showing markedly graphene/Ni, in stark contrast free-standing These challenge assumptions about material-water interactions, highlighting role effects chemistry material science offer insights designing next-generation microfluidic devices require precise mobility control.