title: π+-π+stacking of imidazolium cations enhances molecular layering of room temperature ionic liquids at their interfaces.
abstract: The interfacial structure of room temperature ionic liquids (RTILs) controls many of the unique properties of RTILs, such as the high capacitance of RTILs and the efficiency of charge transport between RTILs and electrodes. RTILs have been experimentally shown to exhibit interfacial molecular layering structures over a 10 Å length scale. However, the driving force behind the formation of these layered structures has not been resolved. Here, we report ab initio molecular dynamics simulations of imidazolium RTIL/air and RTIL/graphene interfaces along with force field molecular dynamics simulations. We find that the π+-π+interaction of imidazolium cations enhances the layering structure of RTILs, despite the electrostatic repulsion. The length scales of the molecular layering at the RTIL/air and RTIL/graphene interfaces are very similar, manifesting the limited effect of the substrate on the interfacial organization of RTILs.
authors.affiliation: International Center for Quantum Materials, Peking University, 5 Yiheyuan Road, Haidian, Beijing 100871, China and Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany. nagata@mpip-mainz.mpg.de.
authors.forename: Fujie
authors.initials: F
authors.lastname: Tang
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Ohto
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyoku, Kyoto 606-8502, Japan.
authors.forename: Taisuke
authors.initials: T
authors.lastname: Hasegawa
authors.affiliation: Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany. nagata@mpip-mainz.mpg.de.
authors.forename: Mischa
authors.initials: M
authors.lastname: Bonn
authors.affiliation: Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany. nagata@mpip-mainz.mpg.de.
authors.forename: Yuki
authors.identifier: http://orcid.org/0000-0001-9727-6641
authors.initials: Y
authors.lastname: Nagata