title: Long range electrostatic forces in ionic liquids.
abstract: Ionic liquids are pure salts that are liquid under ambient conditions. As liquids composed solely of ions, the scientific consensus has been that ionic liquids have exceedingly high ionic strengths and thus very short Debye screening lengths. However, several recent experiments from laboratories around the world have reported data for the approach of two surfaces separated by ionic liquids which revealed remarkable long range forces that appear to be electrostatic in origin. Evidence has accumulated demonstrating long range surface forces for several different combinations of ionic liquids and electrically charged surfaces, as well as for concentrated mixtures of inorganic salts in solvent. The original interpretation of these forces, that ionic liquids could be envisioned as "dilute electrolytes," was controversial, and the origin of long range forces in ionic liquids remains the subject of discussion. Here we seek to collate and examine the evidence for long range surface forces in ionic liquids, identify key outstanding questions, and explore possible mechanisms underlying the origin of these long range forces. Long range surface forces in ionic liquids and other highly concentrated electrolytes hold diverse implications from designing ionic liquids for energy storage applications to rationalizing electrostatic correlations in biological self-assembly.
authors.affiliation: Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA. magebbie@stanford.edu.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Gebbie
authors.affiliation: Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QZ, UK. susan.perkin@chem.ox.ac.uk.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Smith
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, UK. jacob@engineering.ucsb.edu.
authors.forename: Howard A
authors.initials: HA
authors.lastname: Dobbs
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Alpha A
authors.initials: AA
authors.lastname: Lee
authors.affiliation: School of Chemistry, F11, The University of Sydney, NSW 2006, Australia.
authors.forename: Gregory G
authors.identifier: http://orcid.org/0000-0002-6893-1253
authors.initials: GG
authors.lastname: Warr
authors.affiliation: Faculty of Pharmacy, Universite de Montreal, Montreal, QC, Canada.
authors.forename: Xavier
authors.initials: X
authors.lastname: Banquy
authors.affiliation: Interface Chemistry and Surface Engineering, Max Planck Institut fur Eisenforschung GmbH, Dusseldorf, 40237, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Valtiner
authors.affiliation: Surface and Corrosion Science, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden. mark@kth.se and SP Chemistry Materials and Surfaces, SE 114 86 Stockholm, Sweden.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Rutland
authors.affiliation: Department of Chemical Engineering, University of California, Santa Barbara, CA 93106, UK. jacob@engineering.ucsb.edu.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Israelachvili
authors.affiliation: Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QZ, UK. susan.perkin@chem.ox.ac.uk.
authors.forename: Susan
authors.initials: S
authors.lastname: Perkin
authors.affiliation: Priority Research Centre for Advanced Fluid Interfaces, Newcastle Institute for Energy and Resources, The University of Newcastle, Australia. rob.atkin@newcastle.edu.au.
authors.forename: Rob
authors.identifier: http://orcid.org/0000-0001-8781-7854
authors.initials: R
authors.lastname: Atkin