(388h) Effect of the Solid Substrates on the Topography and Molecular Conformation of Nanometer-Thick Ionic Liquid Films

Because of their extremely low volatility, non-flammability and other remarkable physicochemical properties, room temperature ionic liquids (RTILs) have attracted a lot of interests in the past two decades. Understanding the topography and molecular conformation of RTILs at RTIL-solid interfaces is critical to many important applications, including catalysis, lubrication, electrochemistry and photovoltaic power generation. To gain this understanding, an effective approach is to investigate the solid-supported nanometer-thick RTIL films, where the otherwise buried interface can be more easily characterized. In the current presentation, we report our recent experimental study on the nanometer-thick ionic liquid, 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (BMIM FAP), on various solid substrates including silica, mica and amorphous carbon. AFM results indicated a significant effect of the solid substrates on the topography of BMIM FAP nanofilms, which ranges from very smooth to “drop-on-layer” structure. Angle-resolved X-ray photoelectron spectroscopy (ARXPS) results provided valuable information on the molecular conformation at the interface. The difference in the topography and molecular conformation has been related to the different nature of solid-RTIL interaction.