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.

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.electrostatic interactions | intermolecular interactions | interfacial phenomena | Boltzmann distribution | activation energy E lectrolyte solutions are multicomponent liquids that are composed of ions (solutes) dissolved in a liquid phase (solvent), a classic example being salt water. Like any ideal mixture, the driving force for the dissolution of ions in electrolyte solutions is entropic. Unlike ideal mixtures, the long-range nature and high interaction free energy of the electrostatic interactions between ions ensures that the physical properties of all but the most dilute electrolyte solutions exhibit pronounced deviations from ideal behavior. These deviations primarily arise from the steric "crowding" of ions and the electrostatic correlation of ions, for example the formation of neutral ion pairs, both of which increase the range of electrostatic interactions, compared with ideal solutions (1). As a result, the development of a general conceptual picture of concentrated electrolyte solutions remains challenging. Nevertheless, electrolytes with high ionic concentrations are prevalent in biological systems (2) and technological applications, such as energy storage devices (3-5), so overcoming this challenge remains an important task.In this work, we study room-temperature ionic liquids (RTILs), ...

In this Article we described a ruthenium-catalysed carbonyl addition method for alcohol production via simple unsubstituted hydra-zone intermediates, but we inadvertently omitted the citation of two papers that had previously reported a similar carbanion reactivity 1,2. In these papers, the authors illustrated a series of substituted hindered hydrazones (for example, tert-butyl-, trityl-and diphenyl-4-pyri-dylmethyl) for additions to carbonyl compounds; however, to yield the target alcohols under these circumstances, the lithium salts of these hydrazones had to be pre-formed, with subsequent CC bond formation and removal of bulky substituents on azo-intermediates via radical decomposition. References 1. Baldwin, J. E. et al. Azo anions in synthesis: use of trityl-and diphenyl-4-pyridylmethylhydrazones for reductive C−C bond formation. Tetrahedron 42, 4235−4246 (1986). 2. Baldwin, J. E., Bottaro, J. C., Kolhe, J. N. & Adlington, R. M. Azo anions in synthesis. Use of trityl-and diphenyl-4-pyridylmethyl-hydrazones for reductive CC bond formation from aldehydes and ketones. J. Chem. Soc. Chem. Commun. 22−23 (1984). Addendum: Aldehydes as alkyl carbanion equivalents for additions to carbonyl compounds © 2 0 1 7 M a c m i l l a n P u b l i s h e r s L i m i t e d , p a r t o f S p r i n g e r N a t u r e. A l l r i g h t s r e s e r v e d .

Non-aqueous lithium-air batteries represent the next-generation energy storage devices with very high theoretical capacity. The benefit of lithium-air batteries is based on the assumption that the anodic lithium is completely reversible during the discharge-charge process. Here we report our investigation on the reversibility of the anodic lithium inside of an operating lithium-air battery using spatially and temporally resolved synchrotron X-ray diffraction and three-dimensional micro-tomography technique. A combined electrochemical process is found, consisting of a partial recovery of lithium metal during the charging cycle and a constant accumulation of lithium hydroxide under both charging and discharging conditions. A lithium hydroxide layer forms on the anode separating the lithium metal from the separator. However, numerous microscopic 'tunnels' are also found within the hydroxide layer that provide a pathway to connect the metallic lithium with the electrolyte, enabling sustained iontransport and battery operation until the total consumption of lithium.

Mussel foot proteins (Mfps) exhibit remarkably adaptive adhesion and bridging between polar surfaces in aqueous solution despite the strong hydration barriers at the solid-liquid interface. Recently, catechols and amines-two functionalities that account for >50 mol % of the amino acid side chains in surface-priming Mfps-were shown to cooperatively displace the interfacial hydration and mediate robust adhesion between mineral surfaces. Here we demonstrate that (1) synergy between catecholic and guanidinium side chains similarly promotes adhesion, (2) increasing the ratio of cationic amines to catechols in a molecule reduces adhesion, and (3) the catechol-cation synergy is greatest when both functionalities are present within the same molecule.

An in-depth knowledge of the interaction of water with amorphous silica is critical to fundamental studies of interfacial hydration water, as well as to industrial processes such as catalysis, nanofabrication, and chromatography. Silica has a tunable surface comprising hydrophilic silanol groups and moderately hydrophobic siloxane groups that can be interchanged through thermal and chemical treatments. Despite extensive studies of silica surfaces, the influence of surface hydrophilicity and chemical topology on the molecular properties of interfacial water is not well understood. In this work, we controllably altered the surface silanol density, and measured surface water diffusivity using Overhauser dynamic nuclear polarization (ODNP) and complementary silica-silica interaction forces across water using a surface forces apparatus (SFA). The results show that increased silanol density generally leads to slower water diffusivity and stronger silica-silica repulsion at short aqueous separations (less than ∼4 nm). Both techniques show sharp changes in hydration properties at intermediate silanol densities (2.0-2.9 nm). Molecular dynamics simulations of model silica-water interfaces corroborate the increase in water diffusivity with silanol density, and furthermore show that even on a smooth and crystalline surface at a fixed silanol density, adjusting the spatial distribution of silanols results in a range of surface water diffusivities spanning ∼10%. We speculate that a critical silanol cluster size or connectivity parameter could explain the sharp transition in our results, and can modulate wettability, colloidal interactions, and surface reactions, and thus is a phenomenon worth further investigation on silica and chemically heterogeneous surfaces.

The primary aim of this study was to investigate the "dilution effect", where dilution of the ionic concentration of the fluid injected into oil wells has been found to enhance oil recovery. We have measured crude oil/brine/carbonate surface (calcite) interactions using a variety of dynamic techniques including contact angles, surface forces apparatus, atomic force microscopy, interfacial tension, X-ray photoelectron spectroscopy, and other physical and chemical surface characterization techniques. The effects due to different brine (ionic electrolyte) solutions and temperatures, as well as the dynamics (timedependence) of these effects, were investigated. Ionic strengths varied from pure water to 350 000 ppm, and temperatures varied from 20 to 75 °C. We found that upon exchanging solutions (as occurs for waterflooding using dilute solutions), three different dynamic processes occur that have very different time scales: (1) the initial, rapid (seconds to minutes) physical ion exchange with the surfaces that locally changes the surface charge/potential and, hence, the double-layer and hydration forces, (2) the local electrochemical dissolution and restructuring of the surfaces (minutes to hours), which is also often accompanied by the desorption of preexisting organic−ionic layers on the mineral surface that come off as visible flakes with the oil, and (3) the largescale, diffusion-rate-controlled restructuring leading to macroscopic changes in rock morphology (months to years). We conclude that the "dilution effect" is in part due to the well-known colloidal interaction forces (electric double-layer, hydrophilic-hydration, and van der Waals). In addition, our experiments reveal (electro)chemical reactions involving dissolution, pitting, adsorption, and restructuring of the calcite surfaces, which increases their roughness (cf. the geological process of "pressure solution"). Both the colloidal forces and surface roughening and restructuring act to reduce the adhesion of the crude oil/brine interface to the calcite/brine interface (across the thin aqueous or "water" film), which in turn reduces the water-side contact angle (increasing the water-wettability and, presumably, oil recovery), with increasing dilution. These two contributionsreduced colloidal forces and surface rougheningappear to be essential for the "dilution effect" to be effective at all solution concentrations from formation water to pure water. We propose a semiquantitative model to explain the "dilution effect" based on a form of the wellestablished extended-Derjaguin−Landau−Verwey−Overbeek theory for the colloidal interactions between the crude oil and carbonate surface across brine of different concentrations and a modified Young−Dupréequation that accounts for the effects of surface roughness. We present the "dilution effect" in terms of "wettability maps" for the calculated (effective) adhesion energy of the crude oil/brine/carbonate system as a function of brine concentration (from formation water down to the infinite-dilution [i.e., pure ...

Nanoscale-resolved quantifications of almandine's (Fe 3 Al 2 (SiO 4 ) 3 ) dissolution rates across a range of pHs (1 ≤ pH ≤ 13)established using vertical scanning interferometryreveal that its dissolution rate achieves a minimum around pH 5. This minimum coincides with almandine's point of zero charge. These trends in almandine's dissolution can be estimated using the Butler−Volmer equation that reveals linkages between surface potentials and dissolution rates, demonstrating proton-and hydroxyl-promoted breakage of Si−O bonds. In contrast to well-polymerized silicates, the dissolution of almandine can also occur through the rupture of its cationic bonds. This behavior is reflected in the observed influences of irradiation on its dissolution kinetics. Molecular dynamics simulations highlight that irradiation induces alterations in the atomic structure of almandine by reducing the coordination state of the cations (Fe 2+ and Al 3+ ), thereby enhancing its reactivity by a factor of two. This is consistent with the minor change induced in the structure of almandine's silicate backbone, whose surface charge densities produce the observed pH dependence (and rate control) of dissolution rates. These findings reveal the influential roles of surface potential arising from solution pH and atomic scale alterations on affecting the reactivity of garnet-type silicates.