scholarly journals Underscreening in concentrated electrolytes

2017 ◽  
Vol 199 ◽  
pp. 239-259 ◽  
Author(s):  
Alpha A. Lee ◽  
Carla S. Perez-Martinez ◽  
Alexander M. Smith ◽  
Susan Perkin
Keyword(s):  
Interaction Energy ◽  
Surface Force ◽  
Differential Capacitance ◽  
Conventional Wisdom ◽  
Ion Concentration ◽  
Decay Length ◽  
Force Measurements ◽  
Screening Length ◽  
Concentrated Electrolytes ◽  
Bjerrum Length

Screening of a surface charge by an electrolyte and the resulting interaction energy between charged objects is of fundamental importance in scenarios from bio-molecular interactions to energy storage. The conventional wisdom is that the interaction energy decays exponentially with object separation and the decay length is a decreasing function of ion concentration; the interaction is thus negligible in a concentrated electrolyte. Contrary to this conventional wisdom, we have shown by surface force measurements that the decay length is an increasing function of ion concentration and Bjerrum length for concentrated electrolytes. In this paper we report surface force measurements to test directly the scaling of the screening length with Bjerrum length. Furthermore, we identify a relationship between the concentration dependence of this screening length and empirical measurements of activity coefficient and differential capacitance. The dependence of the screening length on the ion concentration and the Bjerrum length can be explained by a simple scaling conjecture based on the physical intuition that solvent molecules, rather than ions, are charge carriers in a concentrated electrolyte.

scholarly journals Long-range electrostatic screening in ionic liquids

2015 ◽  
Vol 112 (24) ◽  
pp. 7432-7437 ◽  
Author(s):  
Matthew A. Gebbie ◽  
Howard A. Dobbs ◽  
Markus Valtiner ◽  
Jacob N. Israelachvili
Keyword(s):  
Ionic Liquids ◽  
Long Range ◽  
Electrostatic Interactions ◽  
Biological Systems ◽  
Electrolyte Solutions ◽  
Ion Concentration ◽  
Decay Length ◽  
Diffuse Double Layer ◽  
High Concentration ◽  
Concentrated Electrolytes

Electrolyte solutions with high concentrations of ions are prevalent in biological systems and energy storage technologies. Nevertheless, the high interaction free energy and long-range nature of electrostatic interactions makes the development of a general conceptual picture of concentrated electrolytes a significant challenge. In this work, we study ionic liquids, single-component liquids composed solely of ions, in an attempt to provide a novel perspective on electrostatic screening in very high concentration (nonideal) electrolytes. We use temperature-dependent surface force measurements to demonstrate that the long-range, exponentially decaying diffuse double-layer forces observed across ionic liquids exhibit a pronounced temperature dependence: Increasing the temperature decreases the measured exponential (Debye) decay length, implying an increase in the thermally driven effective free-ion concentration in the bulk ionic liquids. We use our quantitative results to propose a general model of long-range electrostatic screening in ionic liquids, where thermally activated charge fluctuations, either free ions or correlated domains (quasiparticles), take on the role of ions in traditional dilute electrolyte solutions. This picture represents a crucial step toward resolving several inconsistencies surrounding electrostatic screening and charge transport in ionic liquids that have impeded progress within the interdisciplinary ionic liquids community. More broadly, our work provides a previously unidentified way of envisioning highly concentrated electrolytes, with implications for diverse areas of inquiry, ranging from designing electrochemical devices to rationalizing electrostatic interactions in biological systems.

Surface force measurements on picometer and piconewton scales

1990 ◽  
Vol 8 (4) ◽  
pp. 3502-3505 ◽  
Author(s):  
P. J. Bryant ◽  
H. S. Kim ◽  
R. H. Deeken ◽  
Y. C. Cheng
Keyword(s):  
Surface Force ◽  
Force Measurements

scholarly journals Anomalous Interfacial Structuring of a Non-Halogenated Ionic Liquid: Effect of Substrate and Temperature

2018 ◽  
Vol 2 (4) ◽  
pp. 60 ◽  
Author(s):  
Milad Radiom ◽  
Patricia Pedraz ◽  
Georgia Pilkington ◽  
Patrick Rohlmann ◽  
Sergei Glavatskih ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Surface Charge ◽  
Force Measurement ◽  
Surface Force ◽  
Solid Surfaces ◽  
Effect Of Temperature ◽  
Decay Length ◽  
Force Microscopy ◽  
Large Size ◽  
Atomic Force

We investigate the interfacial properties of the non-halogenated ionic liquid (IL), trihexyl(tetradecyl)phosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in proximity to solid surfaces, by means of surface force measurement. The system consists of sharp atomic force microscopy (AFM) tips interacting with solid surfaces of mica, silica, and gold. We find that the force response has a monotonic form, from which a characteristic steric decay length can be extracted. The decay length is comparable with the size of the ions, suggesting that a layer is formed on the surface, but that it is diffuse. The long alkyl chains of the cation, the large size of the anion, as well as crowding of the cations at the surface of negatively charged mica, are all factors which are likely to oppose the interfacial stratification which has, hitherto, been considered a characteristic of ionic liquids. The variation in the decay length also reveals differences in the layer composition at different surfaces, which can be related to their surface charge. This, in turn, allows the conclusion that silica has a low surface charge in this aprotic ionic liquid. Furthermore, the effect of temperature has been investigated. Elevating the temperature to 40 °C causes negligible changes in the interaction. At 80 °C and 120 °C, we observe a layering artefact which precludes further analysis, and we present the underlying instrumental origin of this rather universal artefact.

scholarly journals Screening length for finite-size ions in concentrated electrolytes

2019 ◽  
Vol 100 (4) ◽  
Author(s):  
Ram M. Adar ◽  
Samuel A. Safran ◽  
Haim Diamant ◽  
David Andelman
Keyword(s):  
Finite Size ◽  
Screening Length ◽  
Concentrated Electrolytes

Surface force measurements between cellulose surfaces using scanning probe microscopy

1997 ◽  
Vol 123-124 ◽  
pp. 369-374 ◽  
Author(s):  
Mark W. Rutland ◽  
Archie Carambassis ◽  
Gerold A. Willing ◽  
Ronald D. Neuman
Keyword(s):  
Scanning Probe Microscopy ◽  
Surface Force ◽  
Scanning Probe ◽  
Force Measurements ◽  
Probe Microscopy
Sign in / Sign up

Export Citation Format

Share Document