Ionic Liquid Structure in Thin Films

Abstract

Understanding molecular structure and organization of a fluid’s surface layers is important to control many heterogeneous electrochemical processes. Ionic liquids present an exciting opportunity to examine surface confined thin fluid films and extended interfacial systems that may prove useful for electrochemical applications. This work explores the behavior of thin (1-20 nm) ionic liquid films and bulk IL interfaces in contact with air and noble metal substrates. Thin IL films are introduced by a highly controlled emersion process. Bulk interfaces are prepared by immersing the metal electrode into an IL solution. Data from ellipsometry, vibrational spectroscopy, contact angle, and electrochemical measurements are reported for the thin films and bulk solution / metal interfaces. Results correlate film and interfacial thickness and molecular structure with the chemical nature of the IL components and substrates. We will be particularly interested in future studies showing the effects of common 'contaminents' (i.e. water) on IL instrfacial structure. Descriptors will include chemical interactions i.e. hydrophobic forces, hydrogen bonding, van der Waals, electrostatics, etc. These studies inform work in IL electrochemistry, IL modified materials, and new fabrication methods for tailored surfaces which are urgently desired.