Dielectric Behavior Of Water Research Articles

Dielectric behavior of water in [bmim] [$$\hbox {Tf}_2$$N] room-temperature ionic liquid: molecular dynamic study

Dielectric behavior of water in [bmim] [$$\hbox {Tf}_2$$N] room-temperature ionic liquid: molecular dynamic study

Reply to the 'Comment on "Investigation of dielectric constants of water in a nano-confined pore"' by S. Mondal and B. Bagchi, RSC Adv., 2020, 10, DOI: 10.1039/D0RA02726J.

In our original work, the computation of the density of liquid in a silica hydrophilic nanopore was executed by the grand canonical Monte Carlo (GCMC) simulation to investigate the spatial dielectric properties of water in a confined phase. We found that the average values of the dielectric constants were very close and almost independent of the number of concentric radial shells. In response to the comment by S. Mondal and B. Bagchi, we clarify the issues of reproducibility of bulk value of the dielectric constant of water and dielectric anisotropy.

Tunable dielectric constant of water confined in graphene oxide nanochannels

Dielectric behavior of water in pristine and oxide graphene nanochannels with various separation has been investigated by means of molecular dynamic simulations. The motivation in performing this integrated set of simulations was to provide deep insight into the interaction between the size of the enclosure and the oxidation degree of the membrane sheets on the dielectric properties. It was shown that the dielectric constant of confined water decreased with the reduction of the space of the nanochannel because water molecules in such narrower environments were expected to exhibit a greater degree of spatial and orientational order. With the increase of the oxidation concentration, the influence of the wider interval space on the dielectric constant was greater than that of narrower nanochannls. For the widest channel (d = 1.2 nm), a decrease of dielectric constant was observed with the increase of oxidation concentration on the graphene bilayers, while a non-monotonous tendency of dielectric behavior appeared for the relatively narrow nanochannels (i.e. d = 0.6 nm and d = 0.9 nm). To understand the physical picture behind it, we computated the number of hydrogen bonds for the three nanochannels. Results showed that the number of HBs was the lowest in the 1.2 nm nanochannel, as well as the dynamic stability (corresponding the fastest decay rate), suggesting that water molecules are more unstable in this large nanochannel and then less orderly than in the 0.6 nm and 0.9 nm nanochannels.

Bottom-up derived flexible water model with dipole and quadrupole moments for coarse-grained molecular simulations.

Coarse-grained water models offer opportunities to study the molecular processes in water on spatial and temporal scales inaccessible to conventional atomic-level simulations. Such a model that can accurately describe the structural, electrostatic and thermodynamic properties of liquid water is difficult to derive but invaluable. Here, we present FlexDQ, a flexible three-site coarse-grained model, representing clusters of water molecules. This model was derived using a full bottom-up approach in which atomistic information of water molecules is processed using clustering techniques based on considerations of both energy and geometry and a mapping algorithm that encodes information of dipole and quadrupole moments of water clusters into coarsely grained interaction sites. Parameterization of FlexDQ was conducted consistently and systematically, augmented by these data. The resulting model reproduces not only dipolar and quadrupolar fluctuations of water clusters, but also their local structural correlations in the bulk phase and, to a good extent, pressure-related properties, dielectric permittivity and water-air interfacial properties that were not targeted for parameterization. The ability of our model to reproduce various properties of water has been shown to originate from its explicit treatment of electrostatics. Coupled with the popular MARTINI CG model, FlexDQ captures the entropy-enthalpy balance of hydrophobic interactions and describes the dielectric behavior of water at the water-membrane interface, yielding a positive internal electrostatic potential in membranes, which is otherwise difficult to reproduce using MARTINI alone. Together, the FlexDQ model and its development framework reported here show promise for studies on the biomolecules in water.

Dielectric characterization of water glucose solutions using a transmission/reflection line method

Abstract Diabetes mellitus (DM) is a disease that affects millions of people worldwide. In order to be managed, it requires the individuals to measure their blood glucose level in an uncomfortable way several times every day. Thereby, a reliable non-invasive, non-painful blood glucose monitoring system is desirable. Microwave technology has been regarded previously to develop such a sensor by dielectric means, but no clear dielectric characterization of blood glucose dielectric behavior has been hitherto shown. In this paper, a novel study of the effect on the dielectric behavior of water when glucose is added is presented, as a simplified case of blood glucose dielectric behavior. Different water glucose solutions have been dielectrically characterized using a transmission/reflection line method and the effect of the changes of the glucose level in the dielectric behavior has been discussed. Conclusions concerning the development of a non-invasive blood glucose sensor are offered and their validity is discussed.

Dielectric Properties of Water at Rutile and Graphite Surfaces: Effect of Molecular Structure

The dielectric properties of interfacial water adjacent to the surfaces of hydrophobic graphite and the 110 surface of hydrophilic rutile (α-TiO2) are investigated by means of nonequilibrium molecular dynamics simulations. The dielectric behavior of water is found to arise from its local density and molecular polarizability in response to an external field, and can be rationalized in terms of the number and strength of water–surface and water–water H-bonds. The interplay of local density and polarizability leads to a particularly strong dielectric response, exceeding the external field, of the water layer directly contacting the surfaces, while the second layer exhibits a reduced response. Consequently, dielectric profiles near surfaces cannot be correctly described by implicit solvent models valid for bulk water. The overscreening response of the contact water layer has been observed in previous simulation studies and implies the local permittivity (dielectric constant) of that layer is negative. However...

Lattice Approach to the Dielectric Permittivity of Water

A lattice theory, based on a quasi-chemical approach, has been combined with a semimacroscopical theory to calculate the permittivity of water. At low field strength the magnitude and the temperature dependency of the calculated permittivity agree with experimental data. The high-field dielectric behavior of water has also been studied. If the field strength increases, the permittivity goes through a maximum, which has not been found experimentally. This maximum is caused by the fact that orientation of dipoles in the field is strongly cooperative due to hydrogen bonding.

Dielectric behavior of water in biological solutions: studies on myoglobin, human low-density lipoprotein, and polyvinylpyrrolidone.

The dielectric behavior of the aqueous solutions of three widely differing macromolecules has been investigated: myoglobin, polyvinylpyrrolidone (PVP), and human serum low-density lipoprotein (LDL). It was not possible to interpret unambiguously the dielectric properties of the PVP solution in terms of water structure. The best interpretation of the dielectric data on the myoglobin and LDL solutions was that, in both cases, the macromolecule attracts a layer of water of hydration one or two water molecules in width. For LDL, this corresponds to a hydration factor of only 0.05 g/g, whereas for myoglobin the figure is nearer 0.6 g/g. With myoglobin, part of the water of hydration exhibits its dispersion at frequencies of a few GHz, and the rest disperses at lower frequencies, perhaps as low as 10-12 MHz. The approximate constancy of the width of the hydration shell for two molecules as dissimilar in size as LDL and myoglobin confirms that the proportion of water existing as water of hydration in a biological solution depends critically on the size of the macromolecules as well as on their concentration.

Effect of the nature of the metal on the dielectric properties of polar liquids at the interface with electrodes. A phenomenological approach

The dielectric behaviour of water, DMSO and ACN at the interface with transition and non-transition metals is examined by analysing the inner-layer capacity as a function of the metal surface chemical affinity. An, inner-layer capacity in the absence of metal-solvent specific interaction is defined and derived by graphical correlations. The permittivity of the surface phase of the solvent under these conditions is derived and analysed to elucidate the nature of the factors contributing to the dielectric behaviour at an interface. The capacity-potential curves for Fe, as a typical transition metal, are elaborated to investigate the orientation of the solvent on the surface and the applicability of the Gouy-Chapman-Stern model. Suggestions on the nature of the metal-water surface bond are given on the basis of the derived parameters. The structure of the double layer in ACN at transition metals is discussed in the light of recent measurements.

Dielectric behaviour of water adsorbed by partially dehydrated potassium chrome alum

Measurements of the real and imaginary parts of the complex dielectric constant have been made in the range 40 Hz–5 MHz during exposure of partially-dehydrated KCr alum, containing 6 of the original 12 moles of water of crystallization per mole KCr(SO4)2, to water vapour at 27 and 38°C. As the amount of water taken up by the residue increases, two regions of dispersion and absorption appear; the lower frequency region, characterized by a single relaxation time, is attributed to water of hydration formed during rehydration, and the higher frequency region, characterized by a distribution of relaxation times, is attributed to adsorbed water in equilibrium with water vapour. The relaxation times of the adsorbed water and water of hydration are compared with those for ice.

Dielectric behaviour of water adsorbed on partially dehydrated alums

Partial dehydration of NH4Fe, KCr, KAI, and NH4Al sulphate alums in vacuo, and their subsequent exposure to water vapour, have been investigated at 19–23° using dielectric measurements at 4·0 Mc./sec. Initial values of Iµ′ and Iµ″ relate to equilibrium water vapour pressure data, and are higher for crushed samples. Marked decreases in Iµ′ and Iµ″ occur in the early stages of the dehydration of NH4Fe and KCr alums, but not with KAl and NH4Al alums, and the curve of Iµ″ against time for the dehydration of NH4Fe alum shows a secondary maximum. Dehydrated NH4Fe and KAl alums sorb water more readily than the dehydrated KCr and NH4Al alums. Changes in Iµ″ during re-hydration are shown to reflect changes in adsorbed water and are independent of water of hydration. At constant re-hydration pressure, Iµ″ increases linearly with the equilibrium water vapour pressure of the original alum, indicating that adsorbed water is bound to the surface by a mechanism similar to that with which water of crystallisation is held inside the lattice. Changes in Iµ″ during re-hydration of dehydrated NH4Fe alum differ from previous results obtained with Rochelle salt.

Dielectric behavior of water adsorbed on zeolites in various ion-exchange forms

1. The dielectric behavior of the system of zeolite 0.6Mg0.3NH4NaA with adsorbed water was studied in a broad range of temperatures and frequencies. 2. The dependence of the activation energy upon the water content in zeolites 0.6Mg0.3NH4NaA and NaA permits us to believe that at sufficiently high contents of adsorbed water, it begins to form a structure, which depends upon the type of the cation. 3. At all the water contents studied, the dielectric relaxation time of the water molecules in a broad range of temperatures is greater for zeolite 0.6Mg0.3NH4NaA than for NaA.

Microwave Absorption and Molecular Structure in Liquids. LVI. Dielectric Behavior of Water and Heavy Water in Dioxane

The dielectric constants and losses of seven water—dioxane mixtures and six heavy-water—dioxane mixtures ranging in concentration from 5 to 58 mole % of water have been measured at wavelengths from 0.44 to 10.0 cm. The results are interpreted in terms of two partly superimposed noninteracting Debye dispersions. The high-frequency dispersion region for the water—dioxane mixtures corresponds to a relaxation time 4×10—12 sec, which is concentration independent, while the low-frequency dispersion region corresponds to a relaxation time which is concentration dependent and rises to a maximum at about 70 to 80 mole % water. The relaxation time 5.6×10—12 sec associated with the high-frequency dispersion region of the heavy-water—dioxane mixtures differs from the corresponding relaxation time for water—dioxane mixtures by a factor of (½)½. The low-frequency concentration-dependent relaxation time was found to be about 1.2 to 1.5 times greater than the corresponding relaxation time of the water—dioxane system. The high-frequency dispersion region is attributed either to the rotation of the OH (or OD) group about its hydrogen (or deuterium) bond or to over-all molecular relaxation. The low-frequency dispersion is attributed to the partial breaking and reforming of the hydrogen (or deuterium) bond. The rotational mechanism becomes a molecular libration in the extrapolating to pure water and contributes to the large atomic polarization observed.

Dielectric Behavior of Water Adsorbed on Solid Surface at Very Low Frequencies

Dielectric Behavior of Water Adsorbed on Solid Surface at Very Low Frequencies

Dielectric Behavior of Water at Microwave Frequencies

An extensive examination of the dielectric properties of water at microwave frequencies has been made. The results have been fitted to various functions which have been derived from the Cole and Cole dispersion equation and it is concluded that the relaxation process in water is characterized by a narrow spectrum of relaxation times.

The dielectric behaviour of water in water-dioxan mixtures

The dielectric behaviour of water in water-dioxan mixtures