Cole-Cole Relaxation Model Research Articles

Design and analysis of a metamaterial based biosensor to determine blood glucose concentration

In this paper, a biosensor utilizing metamaterials is designed and simulated to detect blood glucose concentration. The proposed sensor comprised of a microstrip patch antenna designed on a Rogers RT5880 substrate. A circular-shaped complementary split ring resonator (CSRR) cell is integrated onto the patch of the antenna which acts as the sensing region. The sensor is analyzed in order to ascertain the blood glucose concentration ranging from 50-300 mg/dL in a human finger model. The sensing parameter is amplitude of reflection coefficient, which exhibits variation in response to alterations in the dielectric characteristics of the sample being tested. The Cole-Cole relaxation model is employed to predict the dielectric properties of different finger tissues. An analysis of the characteristics of the CSRR was conducted to illustrate its significance in the realm of glucose detection. The glucose level is determined through the utilization of a linear regression model that describes the relationship between the reflection coefficient of the sensor and glucose level. The sensor demonstrates an impressive sensitivity of 1.792 dB per (mgdL<sup>-1</sup>) and has the ability of determining glucose levels with a good accuracy, as verified by the application of Clarke error grid. This sensor exhibits enhanced performance compared to some other recent glucose sensors.

Dielectric and transport properties of Mn-modified bismuth sodium strontium titanate composite

The structural, dielectric and transport properties of modified Bismuth Sodium Titanate (BNT) are reported. Mn and Sr-modified BNT (Bi0.35Na0.35Sr0.3Ti0.9Mn0.1O3) was synthesized by a solid-state reaction route. Structural analysis based on Rietveld refinement of X-ray diffraction data confirms the single-phase characteristic without change of hexagonal crystal structure with R3C space group of BNT. The dielectric characteristics of the modified BNT are recorded in the frequency range of 20 Hz to 1 MHz at temperatures of 50 °C and 200 °C. Using the frequency-dependent, real and imaginary parts of the dielectric constant, ϵ′(ω)-ϵ″(ω) dipolar and hopping conduction-based carrier polarization properties are discussed. The dipole parameters such as relaxation time, static and high-frequency dielectric constant etc. are estimated by using Cole-Cole relaxation model.

Impact of Gamma-Irradiated SiR-Al2O3 Nanocomposites and Degradation Diagnosis Using LIBS Method

The present study elucidates the impact of gamma irradiation on the thermal properties of silicone rubber nanocomposite insulation. Contact angle measurements, water droplet-initiated corona discharge studies and laser-induced breakdown spectroscopy (LIBS) studies are combined to provide a better understanding of the materials dielectric and thermal properties subjected to different irradiation dosages. The results show that the contact angle and the water-droplet initiated corona inception voltage decrease with increasing nanofiller content and gamma irradiation dosage. Analysis of the dielectric properties of the material following gamma irradiation, shows that the Cole-Cole double relaxation model fits well with the permittivity measured at different temperatures for both virgin and gamma-irradiated specimens. The coefficient of thermal expansion, deduced from the measured dielectric parameters, decreases with the increase of alumina nanofiller content and with the dosage of gamma irradiation. LIBS studies indicate that the ablation depth of the virgin and gamma-irradiated specimens becomes smaller when the filler content is increased. The coefficient of thermal expansion correlates directly with the plasma temperature measured using LIBS spectra of the nanocomposite material for non-irradiated and irradiated specimens.

Analysis of the effect of low dye concentration for electrical system applications of reactive red 45 dye loaded hydrogels

Structural, optical and dielectric properties determining the conduction mechanism were investigated using appropriate measurement techniques to determine the suitability of low-concentrations (LC) (1000 μL, 500 μL, 250 μL and 125 μL) reactive red 45 (RR-45) dye loaded hydrogels for electrical circuit applications. The UV spectra of the all samples displayed a fluctuating behaviour depending on the concentration. It was found that the dielectric plane plots for all the samples are compatible with the Cole-Cole relaxation model and correspond to an equivalent electrical circuit (RC) representing with the impedance circuit in the Smith Chart. It was concluded that RR-45 dye loaded hydrogels could be a suitable material for electrodes used in electroencephalography and electrocardiography systems due to the decrease of the real part of complex dielectric constant and impedance values with increasing frequency. The s-parameter for the samples, which determines the conductivity mechanism, was calculated separately for different regions.

Interpretation of the giant dielectric constant in the single crystal of the CH3NH3PbBr3 perovskite

The dielectric studies of the CH3NH3PbBr3 single crystal were conducted in wide frequency and temperature ranges. The giant dielectric constant (up to 106) which was obtained at low frequencies based on these measurements was considered according to the induced polarization of the electrodes caused by the migration of ions and also the intrinsic polarization included in the hybrid network. Various temperature and frequency evolution regimes were shown and considered for the electrical conductivity (σ′(ω,T),σ″(ω,T)) and the dielectric functions (ε′(ω,T),ε″(ω,T)). In accordance with the Cole-Cole relaxation model and the Debye relaxation theory, pertinent phenomenological approaches were used in order to examine the included dielectric properties as well as the conductivity behavior. Hence, at high temperatures, the migration of the CH3NH3+ ions augments electrode polarization in the low-frequency range. At intermediate frequencies, however, ion hopping results in a modified Cole-Cole relaxation model at high temperatures and in a Debye-type relaxation at low temperatures. This study indicates the correlation between the giant dielectric constant whose activation energy depends on the polar CH3NH3+ ions and the alternating current conductivity enforced by ion migration.

Relaxation behavior in low-frequency complex conductivity of sands caused by bacterial growth and biofilm formation by Shewanella oneidensis under a high-salinity condition

Complex electrical conductivity is increasingly used to monitor subsurface processes associated with microbial activities because microbial cells mostly have surface charges and thus electrical double layers. Although highly saline environments are frequently encountered in coastal and marine sediments, there are limited data available on the complex conductivity associated with microbial activities under a high-salinity condition. Therefore, we have developed the spectral responses of complex conductivity of sand associated with bacterial growth and biofilm formation under a highly saline condition of approximately 1% salinity and approximately 2 S/m pore water conductivity with an emphasis on relaxation behavior. A column test is performed, in which the model bacteria Shewanella oneidensis MR-1 are stimulated for cell growth and biofilm formation in a sand pack, whereas the complex conductivity is monitored from 0.01 Hz to 10 kHz. The test results indicate that the real conductivity increases in the early stage due to the microbial metabolites and the increased surface conduction with cell growth but soon begin to decrease because of the reduction of charge passages due to bioclogging. However, the imaginary conductivity significantly increases with time, and clear bell-shaped relaxation behaviors are observed with the peak frequency of 0.1–1 Hz, associated with the double-layer polarization of cells and electrically conductive pili and biofilms. The Cole-Cole relaxation model appears to capture such relaxation behaviors well, and the modeling results indicate gradual increases in normalized chargeability and decreases in relaxation time during bacterial growth and biofilm formation in the highly saline condition. Comparison with previous literature confirms that the high-salinity condition further increases the normalized chargeability, whereas it suppresses the phase shift and thus the imaginary conductivity. Our results suggest that the complex conductivity can effectively capture microbial biomass formation in sands under a highly saline condition.

Investigation of a partially fluorinated chiral antiferroelectric liquid crystalline material with large negative dielectric anisotropy

Liquid crystal is a state of matter that has both liquid-like fluidity and crystal-like ordering in varying degrees. In this work, we study 4-{[(2S)-octan-2-yloxy]carbonyl}phenyl4′-{4-[(2,2,3,3,4,4,4-heptafluorobutanoyl)oxy]butoxy}-[1,1′-biphenyl]-4-carboxylate, a partially fluorinated chiral liquid crystalline compound. The mesomorphic studies of the compound highlight the existence of polar smectic phases. The molecular geometry, chemical reactivity, nonlinear optics, and charge dynamics are investigated by density functional theoretical calculations. The structural characterization of the compound is performed through vibrational spectroscopy. Dielectric spectroscopy highlights five collective relaxation processes that perfectly fit the modified Cole-Cole relaxation model. The compound 3F4Bi exhibits a bandgap of 4.05 eV, high birefringence (0.16), optical nonlinearity, and a large negative dielectric anisotropy for the tilted ferroelectric phase. The compound could be used as an optically active component to form ferroelectric multi-component mixtures.

Spatiotemporal geo-electrical sensing of a Pluronic-coated cobalt ferrite nanoparticle slug in natural sand flow-through columns

Rising industrial interest in the application of nanomaterials for the remediation of contaminated sites has led to concern over the environmental fate of the nanoremediation agents used. A critical requirement in evaluating and understanding nanoparticle (NP) behaviour in porous media is the development of analytical methods capable of in situ monitoring of complex NP transport dynamics. Spectral induced polarization (SIP), a non-invasive geo-electrical technique, offers a promising tool for detecting and quantifying NPs in soil and aquifer media. However, its application for monitoring the spatial migration and attachment behaviour of NPs remains uninvestigated. Here, we present results from flow-through experiments where we monitored the transport of cobalt ferrite nanoparticles (CoFe-NPs) coated with Pluronic, an amphiphilic polymer, in natural aquifer sand columns. We coupled concentration breakthrough curve analysis with SIP monitoring and reactive transport modeling to relate spatiotemporal NP concentration distributions to geo-electrical signals. Changes in the real (σ′) conductivity at three different locations along the columns closely correlated with model-computed total (solid plus aqueous phase) NP concentrations during the propagation of a NP slug. The imaginary conductivity (σ″) correlated closely with the arrival of the NP-slug. However, during the receding front, bimodal σ″-signal peak behaviour was observed propagating through the columns, indicating the existence of complex in situ NP transport dynamics, potentially revealing the rupture of nanoclusters upon straining and their effect on bulk charge storage that may not be obvious from breakthrough curve data alone. Fitting of a double Cole-Cole relaxation model yielded distinct shifts in relaxation time (τ) associated with the polarization of smaller length-scale particles. Post-NP pulse τ and σ″ did not return to pre-injection values; these lingering signals were caused by retained NP concentrations as low as 8.8 mg kg−1. Our results support the applicability of SIP for spatial and temporal monitoring of NP distributions, with implications for the investigation of NP transport and nanoremediation strategies.

Evaluation of the effect of dose change of Fe3O4 nanoparticles on electrochemical biosensor compatibility using hydrogels as an experimental living organism model

Morphological, structural, optical and dielectric properties, which provide important information about the technological applications of pure and different dose (2.5%, 5.0%, 7.5% and 10.0%) Fe3O4 nanoparticles (NPs) doped hydrogels were analyzed in detail in this study. The complex dielectric parameters of all the samples are related to the electrode/interface polarization (grain boundary), dielectric relaxation and grain effects in accordance with the Maxwell-Wagner theory and Brownian motion in the broadband frequency regions. Experimental plane plots of the complex electrical modulus for all the samples are explained by the Havriliak and Negami relaxation model represented by two relaxation times (α and γ) associated with resistances created by grain boundary (α) and grain (γ). In the high frequency region, complex electrical modulus plane plots of all the samples were compatible with the Cole-Cole relaxation model corresponding to the equivalent electrical circuit (RC) in the Smith Chart diagram. Koop's theory and electron hopping mechanism formed between Fe3+ and Fe2+ ions in the octahedral lattice are effective on the electrical conductivity values of the samples. As the molarity of Fe3O4 NPs increased, the logarithmic conductivity values of all samples, which a function of the angular frequency and defined by the Jonscher Power Law, Nearly Constant Loss and Super Linear Power Law conductivity mechanisms, were generally increased. From the experimental results, it was concluded that the hydrogels with high doses of Fe3O4 NPs can be used as an electrochemical biosensor in bio-systems since it has the high dielectric, capacitance, low impedance and conductivity values.

Mesomorphic, electro-optic and dielectric behaviour of a semi-fluorinated chiral liquid crystalline material forming polar smectic phases

Attributed to the superior dielectric and electro-optical properties, ferroelectric liquid crystals have a wide implementation to display industries and academic communities. In this work, we attempt to study the mesomorphic, vibrational, dielectric, and electro-optical behaviour of a semi-fluorinated chiral liquid crystal. The chemical name of the compound is (2S)-octan-2-yl-3-fluoro-4’-[4-({6-[(2,2,2-trifluoroacetyl)oxy]hexyl}oxy)phenyl]-[1,1′-biphenyl]-4-carboxylate (acronym 1F6T(2F)). The compound is identified as a smectogen exhibiting antiferroelectric, ferroelectric and orthogonal paraelectric mesophases. The compound has a lateral dipole moment of 2.63 debye, electrical bandgap of 4.21 eV, and a non-vanishing first-order static hyperpolarizability. The dielectric studies underline three different types of collective relaxation processes which are readily modelled by the modified Cole-Cole relaxation model. Employing reverse current technique, the spontaneous polarization, rotational viscosity, and response time are calculated for the compound.

Dielectric and electric properties as a tool to investigate the coagulation mechanism during sludge treatment

ABSTRACTThe analysis of the complex permittivity, electrical complex modulus and the hopping conductivity have been employed in order to investigate the impacts of calcium oxide during sludge treatment in textile such as coagulation process. In this context, impedance measurement was performed on five samples, including raw sludge and four compositions containing different amounts of calcium oxide: 2%, 3%, 4% and 5% (w/w). The dielectric spectra of each composition were described by the summation of a power law and a Cole-Cole relaxation model. The relaxation time and the magnitude of the dielectric relaxation obtained from the analysis of dielectric properties showed an increase up to 3% of these parameters with the addition of calcium oxide. Above this critical value, both parameters showed a very small change, suggesting that the aggregation became more stable. In addition, the evolution of the hopping conductivity reached a minimum value at this critical amount (3%). This evolution was well described by a double power law, which allowed us to estimate the optimal amount of the calcium oxide to achieve coagulation process. The analysis of the dielectric properties was found useful in monitoring aggregation processes that occur during the coagulation mechanism in textile sludge.

Understanding the dielectric properties of pressboard material thermally aged in Dibenzyl Disulphide (DBDS) included transformer oil

Surface Discharge Inception Voltage (SDIV) of unaged and copper sulphide diffused Oil Impregnated Pressboard (OIP) material was studied by adopting Ultra High Frequency (UHF) technique. Copper sulphide diffusion into OIP material was carried out by thermal aging of pressboard material in Dibenzyl Disulphide (DBDS) added transformer oil. The SDIV reduces with increase of thermal aging temperature. The current pulse injected in positive and negative half cycle during the surface discharge of the AC shows the rise time of 0.8ns and 1ns respectively. The FFT analysis of UHF signal measured during surface discharge process has shown frequency content in the range 0.7–1.2 GHz with its dominant frequency at 0.9 GHz. The life of the charge presented on the pressboard increases with thermal aged specimen. Energy dispersive spectroscopy (EDS) analysis of OIP material indicates presence of copper and sulphur content. Frequency Domain Dielectric Spectroscopy (FDDS) studies indicate the permittivity(er), dissipation factor (tan(δ)), conductivity (σdc) increases and relaxation time (τ), coefficient (α) decrease with OIP material (in air / Nitrogen) aged at higher temperature in DBDS added transformer oil. Cole-Cole double relaxation model was used to understand the dielectric parameters of copper sulphide diffused OIP material. The DC conductivity of pressboard material aged in DBDS included transformer oil follows Arrhenius law and the activation energy decreases with increase in temperature of thermal aging.

1D Cole-Cole inversion of TEM transients influenced by induced polarization

Effects of induced polarization (IP) can have an impact on time-domain electromagnetic measurements (TEM) and may lead to sign reversals in the recorded transients. To study these IP effects on TEM data, a new 1D inversion algorithm was developed for both, the central-loop and the separate-loop TEM configurations using the Cole-Cole relaxation model. 1D forward calculations for a homogeneous half-space were conducted with the aim of analyzing the impacts of the Cole-Cole parameters on TEM transients with respect to possible sign reversals. The forward modelings showed that the variation of different parameters have comparable effects on the TEM transients. This leads to an increasing number of equivalent models as a result of inversion calculations. Subsequently, 1D inversions of synthetic data were performed to study the potentials and limitations of the algorithm regarding the resolution of the Cole-Cole parameters. In order to achieve optimal inversion results, it was essential to error-weight the data points in the direct vicinity of sign reversals. The obtained findings were eventually adopted on the inversion of real field data which contained considerable IP signatures such as sign reversals. One field data set was recorded at the Nakyn kimberlite field in Western Yakutiya, Russia, in the central-loop configuration. Another field data set originates from a waste site in Cologne, Germany, and was measured utilizing the separate-loop configuration.

Dielectric relaxation analysis of Pb(Zr0.54,Ti0.46)O3 thin films: Electric field dependence

350 nm-thick Perovskite PbZr0.54Ti0.46O3 (PZT) thin films were deposited on Al2O3 substrates by sputtering with and without an additional 10-nm-thick TiOx buffer layer. X-ray diffraction patterns showed that in presence of TiOx buffer layer, PZT film was highly oriented along the (111) direction film, whereas the unbuffered, counterpart was polycrystalline. A full wave electromagnetic analysis using a vector finite element method was performed to determine the tunability and the complex permittivity up to 67 GHz. A comparison between the electromagnetic analysis and Cole-Cole relaxation model was proposed. Through an original study of the relaxation time as a function of the electric field, values, such as 2 ps and 0.6 ps, were estimated for EDC = 0 kV/cm and 235 kV/cm, respectively, and in both cases (111)-PZT and polycrystalline-PZT. The distribution of relaxation times is found to be larger for (111)-PZT film, which is probably related to the film microstructure.

Stabilization of water structure in ammonium hydrogenphosphate solutions

Radio-frequency permittivity and dielectric loss of (NH4)2 HPO4 solutions at 288–308 K in the water permittivity dispersion region (7.5–25 GHz) are studied. Low-frequency electrical conductivities of these solutions are measured, and ionic losses at high frequencies are calculated. The analysis is carried out in terms of the Cole-Cole relaxation model. Static dielectric constants ɛs and the activation times τ and thermodynamic parameters of activation (ΔH ɛ ++ , ΔG ɛ ++ , and TΔS ɛ ++ ) for the dielectric relaxation of the solutions are calculated. The values of ɛs decrease in response to increasing salt concentration at all temperatures. The increasing τ and ΔH ɛ ++ values indicate the stabilization of water structure in solutions where the anion and cation are hydrophilically hydrated.

Broadband Dielectric Spectroscopy Analysis of Dielectric Properties of Barium Titanate Ceramics

The complex dielectric behaviors of ferroelectric barium titanate (BT) ceramics were investigated. The dielectric properties were studied as a function of temperature and frequency using broadband dielectric spectrometer. The results show that the maximum value of dielectric constant occurs at 500nm BT ceramics, which is approximately 7,500; the dielectric loss is lower than 0.03 with the temperature varying from 225 K to 450 K. Dielectric constant and dielectric loss experience three dielectric peaks corresponding to rhombohedral to orthorhombic, tetragonal and cubic transitions. With the frequency ranges from 1 MHz to 1 GHz, the dielectric relaxation is apparently present. The relaxation process obeys Cole-Cole relaxation model at high temperature and conforms to Debye relaxation model when the temperature far lower than Curie temperature. The relaxation time is the order magnitude of ~10-9s obtained by Havriliak-Negami function fitting, which is very consistent with theoretical calculation.

Dielectric frequency response of oil-paper composite insulation modified by nanoparticles

The research on dielectric frequency response of oil-paper composite insulation modified by nanoparticles has been carried out in order to seek possible way to improve insulation properties thereof. Before and after nanoparticles being added, the dielectric frequency responses of oil-paper composite insulation with different moisture contents at different temperatures have been measured within the frequency from 0.1 mHz to 1 MHz. The Cole-Cole relaxation model has been used to analyzing the measured data. The results show that the variation rules of insulation condition can be indicated by the parameters of relaxation model. By adding nanoparticles, a new low frequency relaxation appeared.

Terahertz dielectric response of ferroelectric baxsr1-xtio3thin films

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

Dielectric permittivity and relaxation of aqueous cesium iodide solutions

The high-frequency dielectric permittivity and losses of CsI solutions were studied at 288–323 K in the range of water dielectric permittivity dispersion (7–25 GHz). The low-frequency electrical conductivity of these solutions was measured, and ionic losses at high frequencies were calculated. The Debye or Cole-Cole relaxation model was used for describing the spectra. The low-frequency limits of these relaxation region were calculated, which are the static dielectric constants ɛS and well as dielectric relaxation times (τ) and activation enthalpies (ΔH ɛ ++ ). The ɛS values decrease in going from water to a solution. In concentrated solutions, the slope of the plot of ɛS versus temperature become zero. The decrease in τ and gDH ɛ ++ is evidence of the structure-breaking effect of ions on water. At elevated temperatures (313 K), the decrease in τ is minimal. At 323 K, τ slightly increases in going from water to a solution.

Comparison of complex permittivities of isotonic colloids containing single‐wall carbon nanotubes of varying chirality

The application of bio-compatible, conductive nanoparticles in combination with radiofrequency (RF) irradiation to raise tissue temperatures between 40 and 60 °C for hyperthermia and ablation spurred interest in the complex permittivities of isotonic nanoparticle-based colloids. Nanoparticles with large aspect ratios and high permittivities increase the bulk permittivity of the colloid and RF losses at the macroscopic scale. The complex permittivities of isotonic colloids with and without single-wall carbon nanotubes (SWCNTs) containing either metallic, semiconducting, or mixed chiralities were measured from 20 MHz to 1 GHz at room temperature. The colloids were made with one of three different isotonic solvents: phosphate buffered saline (PBS), and Dulbecco's modified eagle medium (DMEM) with and without 0.5% weight/volume bovine serum albumin to simulate cytosol and blood, respectively. The concentration of elemental carbon from the SWCNTs in the colloids ranged from 16 to 17 mM. The permittivities were corrected for electrode polarization effects by fitting the data to the Cole-Cole relaxation model with a constant phase angle element. The presence of SWCNTs increased both the real and imaginary components of the permittivities of the colloids. For all three solvents, the direct current (DC) components of the real and imaginary permittivities were greatest for the colloids containing the mixed chirality SWCNTs, followed by the colloids with semiconducting SWCNTs, and then metallic SWCNTs.