Presentation Information
[16a-M_B104-1][The 10th Thin Film and Surface Physics Division Paper Award Speech] Molecular-Resolution Imaging of Ionic Liquid/Alkali Halide Interfaces with Varied Surface Charge Densities via Atomic Force Microscopy
Yifan Bao1, Yuto Nishiwaki1, Touma Kawano1, Toru Utsunomiya1, Hiroyuki Sugimura1, 〇Takashi Ichii1 (1.Kyoto Univ.)
Keywords:
ionic liquid,atomic force microscopy,solid-liquid interface
Ionic liquids (ILs) form solvation structures at charged interfaces, typically described by alternating cation/anion layers due to "overscreening." However, their behavior on surfaces with near-zero or extremely high surface charge density is less understood. In this study, we investigated IL solvation structures on nearly zero-charged RbI(100) and highly charged RbI(111) surfaces using frequency modulation atomic force microscopy (FM-AFM) with atomic resolution. For the RbI(100) surface, alternating cation and anion layers were observed, supporting the overscreening model even at near-zero surface charges and reconciling previous experimental conflicts. In contrast, on the RbI(111) surface, we identified a unique solvation structure consisting of two consecutive counterion layers, which aligns with the theoretically predicted "crowding" phenomenon. These findings provide critical experimental evidence for the response of IL solvation layers to varying surface charges, particularly highlighting the transition from overscreening to crowding.