Dielectric Constant of Liquids Confined in the Extended Nanospace Measured by a Streaming Potential Method

Morikawa, Kyojiro; Kazoe, Yutaka; Mawatari, Kazuma; Tsukahara, Takehiko; Kitamori, Takehiko

doi:10.1021/ac504141j

Cited by 42 publications

(40 citation statements)

References 39 publications

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“…The results of the mechanical and electrical tests reported in this work provide clear evidence that the ions in the layered nanostructures are trapped in a more regular structure compared to the liquid phase. A similar effect was experienced by Morikawa et al85 by measuring dielectric constant of water confined in an extended nanospace (10-1000 nm), and showing a significantly reduced value approximately 3 times lower than that for the bulk.The surface-induced formation of thin solid-like insulating IL nanostructures may have a strong impact on the behavior of nanotechnological systems and devices, in particular because such…”

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confidence: 81%

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Bovio¹,

Milani²,

Podestà

2017

Preprint

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We report on the modification of the electric properties of the imidazolium-based [BMIM][NTf2] ionic liquid upon surface confinement in the sub-monolayer regime. Solid-like insulating nanostructures of [BMIM][NTf2] spontaneously form on a variety of insulating substrates, at odd with the liquid and conductive nature of the same substances in the bulk phase. A systematic spatially resolved investigation by atomic force microscopy of the morphological, mechanical and electrical properties of [BMIM][NTf2] nanostructures showed that this liquid substance rearranges into lamellar nanostructures with a high degree of vertical order and enhanced resistance to mechanical compressive stresses and very intense electric fields, denoting a solid-like character. The morphological and structural reorganization has a profound impact on the electric properties of supported [BMIM][NTf2] islands, which behave like insulator layers with a relative dielectric constant between 3 and 5, comparable to those of conventional ionic solids, and significantly smaller than those measured in the bulk ionic liquid. These results suggest that in the solid-like ordered domains confined either at surfaces or inside the pores of the nanoporous electrodes of photo-electrochemical devices, the ionic mobility and the overall electrical properties can be significantly perturbed with respect to the bulk liquid phase, which would likely influence the<br>performance of the devices.<br>

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supporting

confidence: 81%

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Bovio¹,

Milani²,

Podestà

2017

Preprint

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“…The figure shows that this ramping of ε with the default parameters is too fast; we find that ε reaches the bulk limit within 3−4 Å of the surface, which is well within the first water bilayer. This rate of ramping is faster than the experimental 95 and theoretical investigations. 89,96 We also note that here, as illustrated by Figure 1, the ionic charge is unphysically close to the metal slab and a significant proportion lies in the region of vacuum permittivity.…”

Section: Acs Catalysismentioning

confidence: 79%

Challenges in Modeling Electrochemical Reaction Energetics with Polarizable Continuum Models

et al. 2018

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A major challenge in the modeling of electrochemical phenomena is the accurate description of the interface between an electrolyte and a charged conductor. Polarizable continuum models (PCM) have been gaining popularity because they offer a computationally inexpensive method of modeling the electrolyte. In this Perspective, we discuss challenges from using one such model which treats the ions using a linearized Poisson−Boltzmann (LPB) distribution. From a physical perspective, this model places charge unphysically close to the surface and adsorbates, and it includes excessively steep ramping of the dielectric constant from the surface to the bulk solvent. Both of these issues can be somewhat mitigated by adjusting parameters built into the model, but in doing so, the resultant capacitance deviates from experimental values. Likewise, hybrid explicit-implicit approaches to the solvent may offer a more realistic description of hydrogen bonding and solvation to reaction intermediates, but the corresponding capacitances also deviate from experimental values. These deviations highlight the need for a careful adjustment of parameters in order to reproduce not only solvation energies but also other physical properties of solid− liquid interfaces. Continuum approaches alone also necessarily do not capture local variations in the electric field from cations at the interface, which can affect the energetics of intermediates with substantial dipoles or polarizability. Finally, since the doublelayer charge can be varied continuously, LPB/PCM models provide a way to determine electrochemical barriers at constant potential. However, double-layer charging and the atomic motion associated with reaction events occur on significantly different timescales. We suggest that more detailed approaches, such as the modified Poisson−Boltzmann model and/or the addition of a Stern layer, may be able to mitigate some but not all of the challenges discussed.

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“…Such confined water was found to show unique properties differing from bulk water, e.g., higher viscosity, lower dielectric constant, enhancement of liquid conductivity, slower translational molecular motion, and higher protonic mobility compared with bulk water. [30][31][32][33][34][35] These results have suggested that local adsorbed water layers on surfaces and their electrostatic forces affect the collective behavior of bulklike hydration water in the nanochannel spaces.…”

Section: Introductionmentioning

confidence: 95%

Temperature and Size Effects on Structural and Dynamical Properties of Water Confined in 1 – 10 nm-scale Pores Using Proton NMR Spectroscopy

et al. 2017

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We were able to fill 1 -10 nm-scale silica pores with water by vapor condensation, and examined the freezing phenomena, structures, and molecular motions of the confined water in the temperature range from 293 to 188 K by 1 H-NMR spectroscopy. The results showed that almost all water molecules confined in 10 nm-scale pores were frozen and that approximately half of the water confined in 1 nm-scale pores existed in the liquid state even below the freezing point. The water adsorbed on the pore surfaces was estimated as a monolayer in 2.58 nm pores and bi-and tri-layers in 6.48 nm and larger pores, respectively. Furthermore, it was clarified from the proton relaxation rate ( 1 H-1/T1) measurements that the molecular motions of adsorbed water itself were restricted by nanoconfinement and were extremely dependent on the conditions of proton exchange and hydrogen bond rearrangements of the adsorbed water.

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Dielectric Constant of Liquids Confined in the Extended Nanospace Measured by a Streaming Potential Method

Cited by 42 publications

References 39 publications

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Challenges in Modeling Electrochemical Reaction Energetics with Polarizable Continuum Models

Temperature and Size Effects on Structural and Dynamical Properties of Water Confined in 1 – 10 nm-scale Pores Using Proton NMR Spectroscopy

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