The dynamic crossover in dielectric relaxation behavior of ice Ih

© the Owner Societies 2015. The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice Ih) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around Tc = 230 ± 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L-D orientational Bjerrum defects (at high temperature, T > Tc) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O+/OH- defects (at low temperature, T < Tc). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects

State of water in confinement near hydrophilic surfaces below the freezing temperature

The main goal of the research is to find a relationship between the dynamic and the structural properties of water in hydrated heterogeneous systems. The results of dielectric spectroscopy studies of hydrated matrixes of porous glasses, clays and hydrated powder of Lysozyme are presented in wide frequency and temperature intervals. It is shown that for all systems studied the low temperature relaxation process demonstrates Arrhenius kinetics and exhibits a Cole-Cole (CC) behavior. A new phenomenological approach has been recently presented (see Puzenko A, Ben Ishai P, Feldman Yu, Phys Rev Lett 105:037601, 2010) that clarifies the physical mechanism of the dipole-matrix interaction in complex systems (CS) underlying the CC behaviour. A comparison porous glass with clays helps one to understand the specific adsorbed water dynamics due to the variety in the distribution of hydration centers. © 2013 Springer Science+Business Media Dordrecht

The variety of states of adsorbed water in heterogeneous materials and their dielectric response

Whenever water interacts with another dipolar or charged entity, there exists a broadening of its dielectric relaxation peak. Often this broadening can be described by the phenomenological Cole-Cole (CC) spectral function. A new approach has been recently presented (A. Puzenko, P. Ben Ishai, and Y. Feldman, Phys. Rev. Letters 105, 037601-4 (2010)), which is based on the fractal nature of the time set of the interaction of the relaxing water dipoles with their encompassing matrix. It demonstrates a fundamental connection between the relaxation time, τ, the broadening parameter, α, and the Kirkwood-Froehlich correlation function B. The parameters B, τ and α were chosen as the coordinates of the new 3D space, wherein the evolution of the relaxation process, as a result of the variation of external macroscopic parameters (temperature, pressure etc.), will depict a trajectory. This trajectory is a result of the connection between the kinetic and the structural properties of water in the complex system. © 2013 American Institute of Physics

Dielectric relaxation of water in clay minerals

The study of confined water dynamics in clay minerals is a very important topic in aluminosilicate-surface chemistry. Aluminosilicates are among the most technologically versatile materials in industry today. Dielectric spectroscopy is a very useful method for investigating the structure and dynamics of water adsorbed on solid matrix surfaces and water in the vicinity of ions in solutions. Use of this method for the study of clay minerals has been underutilized to date, however. The main goal of the present research was to understand the relaxation mechanisms of water molecules interacting with different hydration centers in clay minerals, with a view to eventually control this interaction. Two types of natural layered aluminosilicates (clay minerals) montmorillonite with exchangeable K+, Co2+, and Ni2+ cations and kaolinite with exchangeable K+ and Ba2+ cations were examined by means of dielectric spectroscopy over wide ranges of temperature (from -121°C to +300°C) and frequency (1 Hz-1 MHz). An analysis of the experimental data is provided in terms of four distributed relaxation processes. The low-temperature relaxation was observed only in montmorillonites and could be subdivided into two processes, each related to a specific hydration center. The cooperative behavior of water at the interface was observed in the intermediate temperature region, together with a proton percolation. The dielectric properties of ice-like and confined water structures in the layered clay minerals were compared with the dielectric response observed in porous glasses. The spatial fractal dimensions of the porous aluminosilicates were calculated by two separate methods - from an analysis of the fractality found in photomicrographs and from the dielectric response

Effect of penetration enhancers on the dynamic behavior of phosphatidylcholine headgroups in liposomes

The results of a time-domain dielectric spectroscopy (TDDS) study of the effect of two skin penetration modulators on phosphatidylcholine (PC) bilayer vesicles are presented. The complex dielectric permittivity spectra of PC vesicle suspensions were described as the sum of two processes: the interfacial polarization of the bilayer and the reorientation of the zwitterionic PC headgroups in a plane approximately tangential to the bilayer surface. The influence of two additives (Azone and Transcutol) on the structure and dynamic behavior of PC headgroups of the bilayer vesicles was analyzed in terms of the interconnection of the dielectric spectra Cole-Davidson parameter, β, and the correlation factor, g, of the dielectric relaxation Kirkwood cell model. Analytically, these parameters are connected in the proposed model via the spatial distribution of headgroup dipole nonhomogeneities. In terms of the physical modulation of the polar surface phase, it appears that these additives can behave either as enhancers or as retarders. Their activity in this respect depends on the concentration of additive and temperature. © 2000 American Chemical Society

Электрон-избыточные металлoфенантроцианины – новый класс тетраазахромофорных комплексов d-элементов

Data of experimental and theoretical study (DFT method) of electron-rich metal phenanthrocyanines – new class of tetraazachromophore complexes of delements Pt2+, Pd2+, Rh3+, Cr3+, Co2+, Ni2+, Zn2+ and Cd2+ was presented. On basis of experimental data on electron absorption spectra (EAS) and quantum chemical calculations of EAS of model anion-radical 1,10-phenanthroline and electron-rich 1,10-phenanthroline complexes suggest of long-wave bands in EAS of metal phenanthrocyanines was made. Some general regularities of new metal phenanthrocyanines formation in C(sp2 )H-C(sp2 )H-coupling reactions of coordinated 1,10-phenanthrolines concerned with metal promotion and elementary electron and proton transfer processes in initialization stage of C(sp2 )H-C(sp2 )H-coupling was analysedредставлены результаты экспериментального и теоретического (методом DFT) исследования электрон-избыточных металлофенантроцианинов – нового класса тетраазахромофорных комплексов d-элементов Pt2+, Pd2+, Rh3+, Cr3+, Co2+, Ni2+, Zn2+ и Cd2+. Сделаны отнесения длинноволновых полос в ЭСП металлофенантроцианинов. Проанализированы некоторые общие закономерности образования новых металлофенантроцианинов в реакциях C(sp2 )H-C(sp2 )H-сочетания координированных 1,10-фенантролинов, связанные с металл-промотированием, а также с элементарными процессами электронного и протонного переноса на стадии инициирования C(sp2 )H-C(sp2 )H-сочетания

State of water in confinement near hydrophilic surfaces below the freezing temperature

The main goal of the research is to find a relationship between the dynamic and the structural properties of water in hydrated heterogeneous systems. The results of dielectric spectroscopy studies of hydrated matrixes of porous glasses, clays and hydrated powder of Lysozyme are presented in wide frequency and temperature intervals. It is shown that for all systems studied the low temperature relaxation process demonstrates Arrhenius kinetics and exhibits a Cole-Cole (CC) behavior. A new phenomenological approach has been recently presented (see Puzenko A, Ben Ishai P, Feldman Yu, Phys Rev Lett 105:037601, 2010) that clarifies the physical mechanism of the dipole-matrix interaction in complex systems (CS) underlying the CC behaviour. A comparison porous glass with clays helps one to understand the specific adsorbed water dynamics due to the variety in the distribution of hydration centers. © 2013 Springer Science+Business Media Dordrecht

State of water in confinement near hydrophilic surfaces below the freezing temperature

The main goal of the research is to find a relationship between the dynamic and the structural properties of water in hydrated heterogeneous systems. The results of dielectric spectroscopy studies of hydrated matrixes of porous glasses, clays and hydrated powder of Lysozyme are presented in wide frequency and temperature intervals. It is shown that for all systems studied the low temperature relaxation process demonstrates Arrhenius kinetics and exhibits a Cole-Cole (CC) behavior. A new phenomenological approach has been recently presented (see Puzenko A, Ben Ishai P, Feldman Yu, Phys Rev Lett 105:037601, 2010) that clarifies the physical mechanism of the dipole-matrix interaction in complex systems (CS) underlying the CC behaviour. A comparison porous glass with clays helps one to understand the specific adsorbed water dynamics due to the variety in the distribution of hydration centers. © 2013 Springer Science+Business Media Dordrecht

The dynamic crossover in dielectric relaxation behavior of ice Ih

© the Owner Societies 2015. The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice Ih) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around Tc = 230 ± 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L-D orientational Bjerrum defects (at high temperature, T > Tc) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O+/OH- defects (at low temperature, T < Tc). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects

Dielectric spectra broadening as a signature for dipole-matrix interactions. V. Water in protein solutions

© 2020 Author(s). In this paper, the fifth of our series focused on the dielectric spectrum symmetrical broadening of water, we consider the solutions of methemoglobin (MetHb) in pure water and in phosphate-buffered saline (PBS). The universal character of the Cole-Cole dielectric response, which reflects the interaction of water dipoles with solute molecules, was described in Paper I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)]. It enables the interpretation of the dielectric data of MetHb solutions in a unified manner using the previously developed 3D trajectory method driven by the protein concentration. It was shown that protein hydration is determined by the interaction of water dipoles with the charges and dipoles located on the rough surfaces of the protein macromolecules. In the case of the buffered solution, the transition from a dipole-charged to a dipole-dipole interaction with the protein concentration is observed {see Paper III [A. Puzenko et al., J. Chem. Phys. 137, 194502 (2012)]}. A new approach is proposed for evaluating the amount of hydration water molecules bounded to the macromolecule that takes into account the number of positive and negative charges on the protein's surface. In the case of the MetHb solution in PBS, the hydration of the solvent ions and their interaction with charges on the protein's surface are also taken into consideration. The difference in hydration between the two solutions of MetHb is discussed