Atomically sharp domain walls in ferroelectrics are considered as an ideal platform to realize easy-to-reconfigure nanoelectronic building blocks, created, manipulated and erased by external fields. ...However, conductive domain walls have been exclusively observed in oxides, where domain wall mobility and conductivity is largely influenced by stoichiometry and defects. Here, we report on giant conductivity of domain walls in the non-oxide ferroelectric GaV
S
. We observe conductive domain walls forming in zig-zagging structures, that are composed of head-to-head and tail-to-tail domain wall segments alternating on the nanoscale. Remarkably, both types of segments possess high conductivity, unimaginable in oxide ferroelectrics. These effectively 2D domain walls, dominating the 3D conductance, can be mobilized by magnetic fields, triggering abrupt conductance changes as large as eight orders of magnitude. These unique properties demonstrate that non-oxide ferroelectrics can be the source of novel phenomena beyond the realm of oxide electronics.
In the present work, we provide a dielectric study on two differently concentrated aqueous lysozyme solutions in the frequency range from 1MHz to 40GHz and for temperatures from 275 to 330K. We ...analyze the three dispersion regions, commonly found in protein solutions, usually termed β-, γ-, and δ-relaxations. The β-relaxation, occurring in the frequency range around 10MHz and the γ-relaxation around 20GHz (at room temperature) can be attributed to the rotation of the polar protein molecules in their aqueous medium and the reorientational motion of the free water molecules, respectively. The nature of the δ-relaxation, which is often ascribed to the motion of bound water molecules, is not yet fully understood. Here we provide data on the temperature dependence of the relaxation times and relaxation strengths of all three detected processes and on the dc conductivity arising from ionic charge transport. The temperature dependences of the β- and γ-relaxations are closely correlated. We found a significant temperature dependence of the dipole moment of the protein, indicating conformational changes. Moreover we find a breakdown of the Debye–Stokes–Einstein relation in this protein solution, i.e., the dc conductivity is not completely governed by the mobility of the solvent molecules. Instead it seems that the dc conductivity is closely connected to the hydration shell dynamics.
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► Temperature and concentration dependent dielectric spectra of a protein solution. ► Broad frequency range enabling detection of several dynamic processes. ► Calculation of effective dipole moment and hydrodynamic radius. ► Breakdown of the Debye-Stokes-Einstein relation. ► Temperature dependence of spectra covering all intrinsic relaxations.
Dielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of ...high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body.
The dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1
Hz to 40
GHz, information on all the typical dispersion regions of biological matter is obtained.
We find no evidence for a low-frequency relaxation (“
α-relaxation”) caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell–Wagner relaxation arising from the polarization of the cell membranes in the 1–100
MHz region (“
β-relaxation”) allows for the test of model predictions and the determination of various intrinsic cell properties. In the microwave region beyond 1
GHz, the reorientational motion of water molecules in the blood plasma leads to another relaxation feature (“
γ-relaxation”). Between
β- and
γ-relaxations, significant dispersion is observed, which, however, can be explained by a superposition of these relaxation processes and is not due to an additional “
δ-relaxation” often found in biological matter.
Our measurements provide dielectric data on human blood of so far unsurpassed precision for a broad parameter range. All data are provided in electronic form to serve as basis for the calculation of the absorption rate of electromagnetic radiation and other medical purposes. Moreover, by investigating an exceptionally broad frequency range, valuable new information on the dynamic processes in blood is obtained.
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► Dielectric spectra of human blood in dependence of temperature and hematocrit value. ► Broad frequency range (1
Hz–40
GHz) enabling detection of several dynamic processes. ► Detection of beta-, gamma-, and delta-dispersion. ► Calculation of dielectric properties of blood cells. ► Basis for calculation of absorption rates of electromagnetic radiation is provided.
The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high ...viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.
Intermolecular hydrogen bonds impede long-range (anti-)ferroelectric order of water. We confine H
O molecules in nanosized cages formed by ions of a dielectric crystal. Arranging them in channels at ...a distance of ~5 Å with an interchannel separation of ~10 Å prevents the formation of hydrogen networks while electric dipole-dipole interactions remain effective. Here, we present measurements of the temperature-dependent dielectric permittivity, pyrocurrent, electric polarization and specific heat that indicate an order-disorder ferroelectric phase transition at T
≈ 3 K in the water dipolar lattice. Ab initio molecular dynamics and classical Monte Carlo simulations reveal that at low temperatures the water molecules form ferroelectric domains in the ab-plane that order antiferroelectrically along the channel direction. This way we achieve the long-standing goal of arranging water molecules in polar order. This is not only of high relevance in various natural systems but might open an avenue towards future applications in biocompatible nanoelectronics.
Uhl
et al.
J. Chem. Phys
., 2019,
150
, 024504 studied the molecular dynamics of glycerol confined in a microporous zeolitic imidazolate framework (ZIF-8) with well-defined pore diameters of 1.16 nm ...by broadband dielectric spectroscopy. Of interest is a fast process in the central part of the pores identified as the α-relaxation of the confined supercooled glycerol with relaxation times
τ
α,conf
(
T
) reduced from
τ
α,bulk
(
T
) of bulk glycerol and having a temperature dependence different from the super-Arrhenius temperature of the latter. The focus of Uhl
et al.
was relating the confined molecular dynamics to the cooperativity length scales
L
corr
(
T
) of molecular motion above the glass transition, and deducing the limiting high-temperature value of the correlation length of about 1.22 nm. Not yet considered by anyone are the observed values of
τ
α,conf
(
T
) and temperature dependence. Since the cooperativity length scales
L
corr
(
T
) were found to be larger than the pore size of ZIF-8 over the temperature range studied and the density of the glycerol in the pore is possibly lower than the bulk, the cooperativity of the α-relaxation of glycerol confined in ZIF-8 is drastically reduced. Thus, within the framework of the Coupling Model (CM),
τ
α,conf
(
T
) should be nearly the same as the primitive relaxation time
τ
0
(
T
) for glycerol when devoid of intermolecular coupling and cooperativity. Consistent with the absence of cooperativity of the glycerol confined in ZIF-8, we find the calculated
τ
α,conf
(
T
) are either the same or slightly longer than the calculated values of
τ
0
(
T
). The quantitative prediction of the CM is verified. At this time we know of no other theory that can make such a quantitative prediction.
Relaxation times of glycerol confined in 1.16 nm ZIF pores found by Uhl
et al.
J. Chem. Phys.
, 2019,
150
, 024504 are explained quantitatively by the Coupling Model.
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