Dielectric spectroscopy of some heteronuclear amino alcohol complexes (original) (raw)
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Dielectric properties of some cadmium and mercury amino alcohol complexes at low temperatures
Journal of the Serbian Chemical Society, 2002
The dielectric properties of some cadmium and mercury amino alcohol complexes were studied within the temperature range of 100-300 K at the frequencies of 100, 300 and 1000 kHz. The polarization mechanisms are suggested and the dependence of both e and tg d on both temperature and frequency are analyzed. The analysis of the data reveals semi-conducting features based mainly on the hopping mechanism.
Impedance spectroscopy and alternating-current (AC) conductivity (r AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (s 0) and loss in the material, with increasing temperature. For each temperature , a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of r AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The r AC value at different frequencies increased linearly with temperature.
Dielectric Relaxation Studies of Decanol Complexes with Amines using Time Domain Reflectometry
The dielectric relaxation studies for decanol-amine mixtures over the frequency range of 10 MHz – 10 GHz have been carried out using pico-second time domain reflectometry technique. The dielectric quantities like the static dielectric constant (ε0m) and the dielectric constants at infinite frequency (ε∞m) were obtained. The relaxation time (τ), the effective Kirkwood correlation factor (geff), the excess dielectric parameter such as excess dielectric permittivity (ε E) and excess inverse relaxation time (1/τ) E were calculated. The thermodynamic properties (Fτ) of the mixtures of decanol with diethyl amine, n-butylamine, triethylamine, aniline and pyridine were evaluated. The Bruggeman factor shows large variation with volume fraction of aromatic amines. The (geff) is almost unity for amines and > 1 for decanol with diethylamine, triethylamine, aniline and pyridine mixtures, showing a parallel orientation of the dipoles. The studies suggest that these amines effectively break the -clusters of decanol and form specific complexes without any charge transfer. It is observed that the values of the enthalpy of activation (Fτ) for the dielectric relaxation always greater than the theoretically predicted values for all the mixtures studied.
Dielectric Study of Aqueous Solutions of Alanine and Phenylalanine
Journal- Chinese Chemical Society Taipei
Dielectric relaxation measurements on aqueous solutions of alanine and phenylalanine were carried out using time domain reflectometry (TDR) at 25, 30, 35, and 40 °C in the frequency range from 10 MHz to 20 GHz. Aqueous solutions of alanine and phenylalanine are prepared for five different molar concentrations of the respective amino acid. For all the solutions considered, only one relaxation peak was observed in this frequency range. The relaxation peaks shift to lower frequency with an increase in alanine and phenylalanine molar concentration. The molar enthalpy of activation and molar entropy of activation show endothermic interactions.
Temperature dependence of the microwave dielectric properties of \gamma$$-aminobutyric acid
Scientific Reports, 2021
The GABA molecule is the major inhibitory neurotransmitter in the mammalian central nervous system. Through binding to post-synaptic neurons, GABA reduces the neuronal excitability by hyperpolarization. Correct binding between the GABA molecules and its receptors relies on molecular recognition. Earlier studies suggest that recognition is determined by the geometries of the molecule and its receptor. We employed dielectric relaxation spectroscopy (DRS) to study the conformation and dielectric properties of the GABA molecule under physiologically relevant laboratory conditions. The dielectric properties of GABA investigated have given us new insights about the GABA molecule, such as how they interact with each other and with water molecules at different temperatures (22°C and 37.5°C). Higher temperature leads to lower viscosity, thus lower relaxation time. The change in the GABA relaxation time due to concentration change is more associated with the solution viscosity than with the G...
Dielectric spectroscopy of organic solvents ofvarying polarity
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The dielectric constant and the conductivity for several organic solvents of varying polarity and for colloidal suspensions are measured using dielectric spectroscopy as a function of frequency, over the frequency range 0.1 Hz to 100 kHz. These measurements are carried out for organic solvents of different polarities: cyclohexyl bromide (CHB), castor oil, cis+trans-decahydronaphtalene (decalin) and decane. In addition, dielectric spectroscopy is carried out for polymethylmethacrylate (PMMA) colloidal spheres in the intermediate polar mixture of cyclohexy bromide (C 6 H 11 Br,(CHB)) and 20% cis+trans-decalin by volume. The primary result in this thesis is the examination of electrode polarization effects, which were observed at low frequency in CHB and CHB-decalin mixtures. A
Indian Journal of Physics, 2012
The mechanism of dipolar complexation involving TBP and three alcohols namely 1-hexanol, 1-heptanol and 1-octanol in an apolar medium benzene is investigated by three direct methods using dielectric measurement data at frequency 455 kHz and at temperature 303.16 K. The parameters evaluated in these systems are the interaction dipole moment, induced polarization and apparent complex formation constant for thermodynamically most favoured stoichi-ometry of 1:1 complexes. Two conclusions resulted from the study. Firstly, the complexation is predominantly due to polarization effect involving charge redistribution and secondly, the complex formation is most favoured in 1-hexanol system.