The significance of multipole interactions for the stability of regular structures composed from charged particles

Identifying the forces responsible for stabilising binary particle lattices is key to the controlled fabrication of many new materials. Experiments have shown that the presence of charge can be integral to the formation of ordered arrays; however, a complete analysis of the forces responsible has not included many of the significant lattice types that may form during fabrication. A theory of many-body electrostatic interactions has been applied to six lattice stoichiometries, AB, AB2, AB3, AB4, AB5 and AB6, to show that induced multipole interactions can make a very significant (>80 %) contribution to the total lattice energy of arrays of charged particles. Particle radii ratios which favour global minima in electrostatic energy are found to be the same or a close match to those observed by experiment. Although certain lattice types exhibit local energy minima, the calculations show that many-body rather than two-body interactions are ultimately responsible for the structures observed by experiment. For a lattice isostructural with CFe4, a particle size ratio not previously observed is found to be particularly stable due to many-body effects.

Optical characterization and dispersion analyses of plasma polymerized methyl acrylate thin films

This work reports the structural characteristics, surface morphology, linear and nonlinear optical properties of 110 to 225 nm thick plasma polymerized methyl acrylate (PPMA) thin films. X-ray diffraction analyses confirm the amorphous nature of the films. Field emission scanning electron micrographs of the films display cluster-based surface morphology. Attenuated total reflectance Fourier transform infrared spectroscopy confirms the chemical structural changes in the films. The optical properties were studied based on the absorbance, transmittance, and reflectance spectra measured by an ultraviolet-visible spectrophotometer within the wavelength ranges from 200 to 800 nm. The direct optical band gap and Urbach values are increased from 3.66 to 3.83 eV and 0.28 to 0.45 eV, respectively with increasing film thickness. The extinction coefficient and refractive index were evaluated, and discussed a correlation between the refractive index and the optical bandgap. The real and imaginary dielectric constants, volume/surface energy loss functions and skin depth were deduced. The oscillator energies and parameters were analyzed using the concept of Wemple-DiDomenico and Sellmeier models, respectively for a single oscillator. Static linear refractive index for the studied films exhibits normal dispersion behavior with film thicknesses and satisfied Moss, Ravindra-Gupta, and Herve-Vandamme rules. The linear susceptibility, third-order nonlinear susceptibility and the non-linear refractive index are considerably reduced from 0.20, 29.5 × 10-14 esu, and 5.89 × 10-12 esu with increasing optical band gap energies. The outcomes from the analyses of PPMA demonstrated their potential for usage in electronic, optoelectronic, and non-linear device applications.

Biomass fly ash as nanofiller to improve the dielectric properties of low-density polyethylene for possible high-voltage applications

Flexible capacitive energy storage applications require polymer nanocomposites with high dielectric properties, which can be accomplished by addition of inorganic nanofillers to the polymer matrix. Low-density polyethylene (LDPE), known for its good dielectric characteristics and wide use in electrical insulation have been investigated for the desired applications. However, the improvement of its breakdown strength still continues with the use of various nanomaterials employed as nanofillers. In this study, a waste-derived material known as biomass fly ash (BFA) as a nanofiller to improve the dielectric properties of LDPE has been explored. BFA exhibits versatility in its composition with various metal oxides, making it an attractive choice as a nanofiller. The BFA-LDPE sheets were prepared using a conventional solvent mixing and subsequent hot-pressing process, incorporating BFA loadings ranging from 1 % to 4 wt%. The effects of different BFA loadings were carefully examined, and the synthesized nanocomposites were extensively characterized using various characterization methods, such as XRD, SEM, FTIR, TGA and dielectric constant measurements, to investigate the crystallographic properties, morphology, chemical composition, and thermal stability. Among all the nanocomposites, 4 wt%BFA-LDPE exhibited the highest dielectric constant, with a value of 11.58, compared to simple LDPE that had a dielectric constant of 8.33. This improvement is ascribed to the synergistic effects of different inorganic metal oxides (SiO2, MgO, and Fe2O3) present in BFA. The results showed a significant enhancement in dielectric properties, indicating that the waste-derived BFA can be purposefully applied as an effective nanofiller in the LDPE-based composites with even less than 4% loading for electrical insulating applications in future studies.

Laponite nanoparticle-crosslinked carboxymethyl cellulose-based injectable hydrogels with efficient underwater-specific adhesion for rapid hemostasis

Tissue adhesives have attracted intense and increasing interest due to their multiple biomedical applications. Despite the rapid development of adhesive hydrogels, huge challenges remain for materials that can ensure strong adhesion and seal hemostasis in aqueous and blood environments. To address this issue, we have developed an innovative design of PAA-based coacervate hydrogel with strong wet adhesion capability through a simple mixture of PAA copolymers with oxidized-carboxymethylcellulose (OCMC), and tannic acid (TA) as the main components, and structurally enhanced with natural clays (Laponite XLG). The absorbed TA provides solid adhesion to dry and wet substrates via multiple interactions, which endows the XLG-enhanced coacervate with the desired underwater adhesive strength. More importantly, the dielectric constant is introduced to evaluate the polarity of the tested samples, which may be used as guidance for the design of mussel-inspired adhesives with even better underwater adhesive properties. In vivo hemorrhage experiments further confirmed that the hydrogel adhesive dramatically shortened the hemostatic time to tens of seconds. Overall, the persistent adhesion and acceptable cytocompatibility of the hydrogel nanocomposite make it a promising alternative suture-free approach for rapid hemostasis at different length scales and is expected to be extended to clinical application for other organ injuries.

Orchestrating the impact of antisites and vacancy defects on the elastic and optoelectronic properties of boron arsenide

CONTEXT

Cubic boron arsenide (c-BAs), a semiconducting material with ultra-high thermal conductivity and carrier mobilities, has been studied using first-principles calculation. This study examined the elastic and optoelectronic properties of c-BAs. The challenge of subphase boron (B) formation in bulk form owing to the volatile nature of arsenic (As) makes it mandatory to calculate its optoelectronic properties, by producing vacancies and antisite defects with BAs (As atom on a B site) and AsB (B atom on an As site). The mechanical properties including bulk (B), shear (G) moduli, and Poison's ratio of all the systems were studied. It was found that mechanical instability of the structure is observed for the overall vacancy creation, arsenic substitution, and mutual antisite defects. Further, pristine c-BAs showed an indirect bandgap of 1.48 eV. Defect formation reduces the bandgap and shifts the absorption peaks, which improves the overall optoelectronic properties of the host material. In addition, B vacancy formation shows the maximum optical absorption and reflectivity and low energy loss, suggesting its potential applications for optoelectronic devices. The obtained anticipated data from this study is for the optoelectronic and elastic properties of c-BAs, for the device applications in photonics and electronics.

METHOD

In this paper, the elastic and optoelectronic properties of the pristine and defected c-BAs were systematically investigated using the Spanish Initiative for Electronic Simulations with Thousands of Atoms (SIESTA). The SIESTA program uses pseudopotentials in the norm-conserving nonlocal forms and pseudo-atomic orbital (PAO) basis set with a double-zeta potential (DZP) which are fundamental for calculating the Hamiltonian and overlap matrices in O(N) operations.

Temperature-dependent conduction mechanism of NiO@Carbon@Polypyrrole nanomaterial with EMI shielding characteristics

A simple hydrothermal technique and in-situ chemical oxidative polymerization of pyrrole monomer yield the functionalized NiO@C@PPy nanomaterial for electromagnetic shielding applications. The crystal structure, morphology, dielectric and electromagnetic shielding (EMI) performance in the X-band (8.2-12.4 GHz) is thoroughly studied. Impedance spectroscopy is utilized to study the electrical response of a NiO@C@PPy pellet. This study focuses on the modulations of relaxation time with frequency at different temperatures. In the NiO@C@PPy composite, a semiconductor-to-metal transition (SMT) is observed, at 328 K. The conduction mechanism of NiO@C@PPy is explained based on the carrier hopping transport model in Ni2+ and Ni3+ ions. It is evident from the activation energy value (Ea ≈ 0.32 eV) determined from impedance, conductivity, and dielectric data that the relaxation and conduction processes correspond to the same electro-active region. Using the variable range hopping (VRH) model localization length of the carrier is calculated to be 1.56 Å. The NiO@C@PPy sample demonstrated enhanced conductivity and low dielectric values which are vital in EMI shielding applications. Consequently, the electromagnetic interference shielding effectiveness is found to be 21.9 dB of NiO@C@PPy in the X-band frequency range. This composite material is a good candidate for high frequency shielding applications.

Enhancement of Ni-Zn ferrite nanoparticles parameters via cerium element for optoelectronic and energy applications

This work is concerned with fabricating ferrite nanoparticles of nickel-zinc with the chemical formula: Ni0.55Zn0.45Fe2-xCexO4, 0 ≤ x ≤ 0.011 by co-deposition technique and modifying their electrical, microscopic, spectroscopic, optical, electrical and dielectric properties as advanced engineering materials through doping with the cerium (Ce) element. XRD patterns displayed that the samples have a monophasic Cerium-Nickel-zinc (CNZ) spinel structure without other impurities for cerium concentration (x) ≤ 0.066. Both values of crystallite size and lattice parameters decrease from 33.643 to 23.137 nm and from 8.385 to 8.353 nm, respectively, with the increasing Ce ions substitution content from 0 to 0.066. SEM images indicate that grains of the fabricated compounds are smaller, more perfect, more homogeneous, and less agglomeration than those of the un-doped Ni-Zn nano-ferrites. The maximum intensity of first-order Raman spectral peaks (Eg, F2g(2), A1g(2), and A1g(1)) of CNZ ferrite nanoparticles are observed at about (330, 475, 650, 695) cm-1, respectively, that confirms the CNZ samples have the cubic spinel structure. The direct and indirect optical energy bandgaps of CNZ samples have a wide spectrum of values from semiconductors to insulators according to cerium concentration. The results showed that the values of dielectric constant, dielectric loss factor, and Ac conductivity and the conductivity transition temperature are sensitive to cerium ions content. AC conductivity exhibited by the CNZ samples has the semiconductor materials behavior, where the AC conductivity increases due to temperature or doping concentration. The results indicate that Ni0.55Zn0.45Fe1.944Ce0.066O4 ferrite nanoparticles may be selected for optoelectronic devices, high-frequency circuits, and energy storage applications.

Electrical and dielectric characteristics of molybdenum dioxide nanoparticles for high-performance electrocatalysis

As an attempt to improve the catalytic processes in different electrochemical systems, molybdenum dioxide nanoparticles were prepared using the hydrothermal method, and their electrical and dielectric properties were investigated. The nanoparticles were polycrystalline with an orthorhombic structure. AC electrical transport properties of the pressed disc were conducted over a temperature range of 303-423 K and a frequency range of 42-5 × 106 Hz. The AC conductivity follows Jonscher's universal dynamic law, and it has been determined that correlated barrier hopping (CBH) is the primary conduction mechanism. The maximum barrier height (W M ) was found to be 0.92 eV. The low activation energy showed that hopping conduction is the dominant mechanism of transporting current. The dielectric parameters were analyzed using both complex permittivity and complex electric modulus, with a focus on how they vary with temperature and frequency. At relatively high temperatures and low frequencies, the dielectric parameters showed a high-frequency dependence. The dielectric modulus showed that relaxation peaks move towards lower frequency when temperature increases. The dielectric relaxation activation energy, Δ E ω was determined to be 0.31 eV.

Electronic structure, theoretical power conversion efficiency, and thermoelectric properties of bismuth-based alkaline earth antiperovskites

CONTEXT

This research paper investigates the properties and potential applications of antiperovskite materials. Antiperovskites are a class of materials with a unique crystal structure, where the central atom is surrounded by a cage of anions. We review recent research on antiperovskite-based materials for energy storage, photovoltaics, catalysis, and sensors. We discovered that these materials display direct band gap semiconductors, strong absorption in the visible (VIS), ultra-violet (UV), and near infrared regions (NIR) based on their fundamental features, which is the most admirable quality that may be found in many optoelectronic devices. Both mechanical and thermodynamic stability have been confirmed for these materials. We discovered that these materials exhibit high figures of merit through the calculation of transport properties, which makes them a promising candidate for thermoelectric devices. It is anticipated that the proposed material BiPMg3, which has a theoretical efficiency of 11.5%, will make a suitable photovoltaic absorber. This paper highlights the potential of these materials for future technological advancements.

METHODS

Herein, we have used most authentic techniques to compute fundamental physical properties of these antiperovskites. Full-potential linear augmented plane wave (FP-LAPW) method has been used to investigate electronic, magnetic, optical properties, and make antiperovskites attractive for a variety of applications. In light of its implementation, we have checked the theoretical power conversion efficiency by first principles spectroscopic screening methodology, and inspect the fundamental physical parameters of antiperovskites, focusing on their potential as functional materials for energy and information technologies.

Structural and impedance spectroscopic investigations of eco-friendly alkali phosphoborate glass-ceramics containing zirconium ion

Glass-ceramics with novel composition xZrO2.7P2O5.19CaO.24Na2O.(50-x)B2O3 (x = 0, 2, 4, 6, and 8 mol%) have been synthesized using melt quench technique. The synthesized compositions were characterized and analyzed by X-ray diffraction, field emission scanning electron microscopy, infrared absorption, and impedance spectroscopy. X-ray diffraction profiles of prepared samples confirm the existence of phases corresponding to Na3Ca6(PO4)5 crystal (with crystallite size ~ 23 nm). Infrared absorbance spectra reveal the presence of phosphate and borate units (PO3, PO4, BO3, BO4) in the glass matrix. Different dielectric parameters such as dielectric loss, electric modulus, and tangent loss were evaluated. Their variations with temperature and frequency confirm the non- Debye relaxation behavior of prepared samples. A phenomenal description of the capacitive behavior was studied by considering the circuit having a parallel combination of constant phase element and bulk resistance. The conduction is found to be governed by overlapping large polaron tunneling (OLPT) and follow OLPT model. The results indicate that ZrO2 substituted alkali phosphoborate glass-ceramics can be used as eco-friendly and safe dielectric materials.

Investigation of CeO2 nanoparticles on the performance enhancement of InsulatingOils

Integrating nanotechnology in dielectric fluid significantly inhibits losses and boosts overall dielectric fluid performance. There has been research done on the effects of introducing various nanoparticles, such as titania, alumina, silica nanodiamonds, etc. In this paper, a novel nanoparticle, Ceria (CeO2), has been used, and its properties were examined using the FTIR (Fourier Transform Infrared) spectrum, the XRD (X-ray Diffraction) spectrum, the SEM (Scanning Electron Microscopy), and the TEM (Transmission Electron Microscopy). This paper illustrates an efficient dielectric fluid prepared by the successful dispersion of Cerium Oxide (CeO2) nanoparticles in various concentrations into four commercial oils, namely mineral oil, rapeseed oil, synthetic ester oil, and soybean oil, to enhance and improve their dielectric characteristics. The performance investigation emphasises breakdown strength enhancement and other dielectric properties of the colloidal solution comprising different nanoparticle (NP) concentrations. Various commercial oils are used as a base in nano-oil to diversify their applicability as dielectric fluids by measuring the correlation in dielectric parameters and statistically assessing their applicability with normal and Weibull distributions. The obtained experimental data sets were analyzed using the Statistics and Machine Learning Toolbox in MATLAB. The aging measurement has been done only on mineral oil, and results were matched using a predictive model of statistics and the Machine Learning Toolbox in MATLAB. Well-dispersed CeO2 NPs in the insulating oils lead to a significant increase in AC breakdown strength. The effect of ageing on the dielectric properties of nano oils yields better results than conventionally aged oil. It has been observed that the breakdown voltage is enhanced by up to 30% for mineral oil at an optimal concentration of 0.01 g/L, 9% for synthetic ester oil at 0.03 g/L, 18% for rapeseed oil at 0.02 g/L, and 19% for soybean oil at 0.03 g/L nanoparticle concentration. Following the dispersion of CeO2 nanoparticles, the dielectric constant of all insulating oils has also significantly improved. The overall experimental results are promising and show the potential of the CeO2 NPs-based nano oil as an efficient and highly performing dielectric oil for different power applications.

Dielectric studies for rare earth doped magnesium ferrite material

The aim of this study is to synthesize, characterize, and finally, electrical property measurement of the nano-particles of polycrystalline magnesium and iron ferrite doped with rare earth (RE) materials cerium and erbium (MgCexEryFe2-x-yO4) with a series x = 0.4, 0.6, 0.8 and y = 0.6, 0.4, 0.2 systematically to understand the electro-transport behavior. These series are prepared by using the sol-gel auto combustion method maintaining the pH of the solution at 7, i.e., in neutral condition in order to maintain the desired dielectric material properties. These grown materials were made into pellets by applying minimum hydrostatic pressure and then silver coated for electric measurements. The dielectric behavior of the desired series is studied with varying frequencies from 100 Hz to 120 MHz, and the results obtained are discussed in terms of the resistance, admittance, susceptance, dielectric constant, dielectric loss, and tangent loss using an impedance analyzer. The variation behaviors with respect to frequency are discussed systematically in an exhaustive manner, and the studies indicate that these materials may have possible incorporation to fabricate microwave antennas to reduce energy losses and eventual applications.

Active nanoceramic compound dipped in biopolymers to create composite coating for metallic implant surface

Biofunctionalization of an implant using functional ceramics with exceptional electrical characterization, such as BaTiO3 and SrTiO3, has gained considerable attention in creating a composite coating with bio-polymer to activate metal implant surfaces for bone tissue engineering applications and, at the same time, resist bacterial infection. A Ti-Zr alloy sample was created by powder technology, and then a coating was applied using the electrospinning technique. Individually, nanopowders of ceramic compounds such as nBaTiO3 and nSrTiO3 were added to a blend of polycaprolactone and chitosan to create composite solutions that could be converted into a nanofibrous coating layer using the electrospinning technique. The samples were analyzed for their morphology, chemical composition, surface roughness, dielectric constant, and wettability. The techniques employed were SEM, EDS, FTIR, an LCR meter, and a contact angle goniometer. The samples' cytocompatibility was assessed by examining the cell viability, ALP activity, proliferation, and attachment of MC3T3-E1 osteoblast cells on both coated and uncoated sample surfaces.The bacterial resistance assays were conducted against Staphylococcus aureus and Streptococcus mutans. The findings demonstrate a notable enhancement in the biocompatibility of the coated specimens following a week of cellular cultivation. The composite coating containing piezoelectric BaTiO3 has a dielectric constant Ɛr (16) close to dry human bone at 100HZ frequency. Cell proliferation increases dramatically with time in coated samples, and the improvement approaches 125.16% for (BA1) and 111.38% for (SR1) as compared to uncoated Ti-25Zr sample. Cell viability percentage for the coated samples is compared with bare Ti-25Zr, which has an 80.52 ± 1.97% crucial increase, while (BA1) has 181.63 ± 17.87 and (SR1) 170.09 ± 18.12%. No zone of inhibition was detected in the bacterial resistance test for the uncoated sample, while the samples with composite coating show an adequate and comparable inhibitory zone. The composite nano-fiber has a strong biocompatibility, and the coating process is simple and economical, holding potential for use in orthodontic and orthopedic bone regeneration applications.

Permittivity measurements for raw and boiled quinoa seeds versus temperature, bulk density, and moisture content

Quinoa is a nutrient-rich pseudocereal that is gaining popularity in European countries since it is gluten-free and an interesting source of fat, proteins, minerals, and amino acids. However, up to date, the electric permittivity of quinoa seeds has not been measured and, therefore, this hampers the possibility of designing optimized recipes for its microwave processing. In this work, the permittivity of both raw and boiled quinoa seeds is measured around 2.45 GHz at several conditions for temperature, moisture content, and bulk density. The grain kernel permittivity is also estimated from the Complex Refractive Index (CRI) mixture equation and different bulk density measurements. The obtained results show different temperature behaviours for raw and boiled seeds, whereas the permittivity of quinoa seeds versus moisture content and bulk density was as expected: the permittivity (both the dielectric constant and loss factor) levels increased as the observed variables did. From the measured data, it can be concluded that both raw and boiled quinoa can be processed with microwave technology, although care must be taken with raw quinoa grain kernels since the permittivity increases significantly with temperature, and a thermal runaway may occur.

Progress in theoretical study of lead-free halide double perovskite Na2AgSbX6 (X = F, Cl, Br, and I) thermoelectric materials

CONTEXT

Herein, we have studied progressively novel metal lead-free halide double perovskite renewable energy materials. Due to their potential use in electronic devices, researchers have investigated these materials with a lot of interest. From the electronic structure, we have found that these are the indirect band gap semiconductors within the range between 1.273 and 3.986 eV. Optical parameters such as dielectric constant, electrical conductivity, and absorption coefficient have also been investigated, which have shown that these materials have potential use in photovoltaics. We have checked stability issues by thermodynamic parameters and phonon spectra. We have found them thermally stable; however, the phonon spectra show their dynamical instability and except for Na₂AgSbF₆ and Na₂AgSbI₆, the remaining compounds are weak in mechanical stability. For another futuristic purpose, thermoelectric parameters such as Seebeck coefficient, power factor, and figure of merit have also been calculated, which again verifies that these materials may be very useful in thermoelectric devices. Most of the parameters have been computed for the first time.

METHODS

We have performed this computational work using WIEN2k simulation code, which is based on the full-potential linearized augmented plane wave (FP-LAPW) technique. It is one of the most reliable techniques to calculate the photovoltaic properties of semiconducting perovskites. The interaction between ion-core and valence electrons was dealt with within the PAW technique as implemented in Vienna Ab initio Simulation Package (VASP).

Effect of carbons' structure and type on AC electrical properties of polymer composites: predicting the percolation threshold of permittivity through different models

The AC electrical properties of EVA- and NBR-based composites filled with different conductive fillers were investigated. Result shows several magnitudes of increment in AC electrical conductivity and dielectric permittivity after the addition of these conductive fillers, indicating that these materials can be used as supercapacitors. The magnitude of increment was varied according to polymer and filler types. Herein, we also have tested the applicability of different sigmoidal models to find out the percolation threshold value of permittivity for these binary polymer composite systems. It is observed that except sigmoidal-Boltzmann and sigmoidal-dose-response models, other sigmoidal models exhibit different values of percolation threshold when considered for any particular polymer composite system. The paper discusses the variation in results of percolation threshold with an emphasis on the advantages, disadvantages and limitations of these models. We also have applied the classical percolation theory to predict the percolation threshold of permittivity and compared with all the reported sigmoidal models. To judge the unanimous acceptability of these models, they tested vis-à-vis the permittivity results of various polymer composites reported in published literature. To comprehend, all the models except the sigmoidal-logistic-1 model were successfully applicable for predicting the percolation threshold of permittivity for polymer composites.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00396-023-05120-2.

The structural, biological and dielectric properties of Sr, Mg and Zn doped silicate ceramics

The current work examines the structural and biological characteristics of doped Zn, Mg, and Sr. Na₂O-CaO-Si₂O-P₂O₅ silicate ceramics synthesized by the solid state method. The undoped sample showed amorphous behavior after sintering at the 800 ^OC while doping of SrO, MgO and ZnO induce crystal growth; and a single phase of Parawollastonite (JCPDS# 00-043-1460) was identified in both doped samples. The strontium doped sample showed the highest value of the dielectric as compared to other three samples. The Sr doped sample had higher dielectric value because the size of Sr²⁺ is greater than Ca⁺² so it will possess the higher polarizing power. Conductivity of Zn and Sr doped samples increased with increase in frequency and Mg doped decrease with increase in frequency. Bioactivity test confirmed that doped samples were more bioactive as compared to undoped samples, and Sr doped sample showed superior bioactivity as compared to other samples.

All-Organic Hyper-Crosslinked Polymer/Polyimide Composite Films with Ultralow High-Frequency Dielectric Constant

The ever-increasing demand for high-speed communication at high frequency promotes the rapid development of low dielectric polymer films. Aromatic polyimide (PI) has been widely used as the main dielectrics in the flexible circuit board due to its excellent dielectric, mechanical and thermal properties. Nevertheless, the dielectric constant of PI films at high frequency range (several GHz) is relatively high and can not satisfy the requirement high-frequency communication. On this basis, we synthesized a hyper-crosslinked polymer (HCP) and fabricated all-organic HCP/PI composite films through a physical blending method. The porous structure of HCP is helpful to reduce the dielectric constant of PI matrix. The effects of HCP loadings on the dielectric, mechanical and thermal properties of HCP/PI composite films were systematically investigated. The dielectric constants of the composite films can be reduced to 1.6-1.8 in the frequency range of 8.2-9.6 GHz when the HCP content reached 10 wt%. The proposed method in this work is simple and effective to reduce the dielectric constant of PI and can be easily extended to other organic component filled PI systems. This article is protected by copyright. All rights reserved.

A mini-review on the dielectric properties of cellulose and nanocellulose-based materials as electronic components

Cellulose-based materials have the advantages of renewable, non-toxic, flexible, and strong mechanical properties, so it of is great significance to study the dielectric properties of cellulose-based materials. In this paper, we summarized the factors influencing the dielectric properties of cellulose and nanocellulose-based dielectric and the ways to change the dielectric properties, mainly exploring the methods to improve the dielectric constant of cellulose-based dielectric materials. Cellulose and nanocellulose-based dielectric need to improve the hygroscopic property, increase the flexibility and reduce dielectric loss of the composite materials. This review summarizes the current state-of-art progress of new dielectric materials for green energy storage and flexible electronic devices.

Measurement of human skin moisture via high-frequency spectroscopy

High-frequency spectroscopy (HFS) is an analytical method that is sensitive to slight changes in the dielectric properties of materials. Since water has high permittivity, HFS can be used to detect changes in water content in materials. In this study, we employed HFS to measure human skin moisture during a water sorption-desorption test. Skin without any treatment showed a resonance peak at approximately 1150 MHz. Furthermore, the peak shifted to lower frequency immediately after the application of water to the skin and gradually returned to its original frequency as time progressed. The resonance frequency obtained via least-squares fitting showed that the applied water remained in the skin after 240 s from the beginning of the measurement. These results illustrated that HFS measurements can monitor the progression of decreasing moisture content in human skin during a water sorption-desorption test.

Effects of barium titanate on the dielectric constant, radiopacity, and biological properties of tricalcium silicate-based bioceramics

This study evaluated the effect of barium titanate (BT) on the dielectricity, radiopacity, and biological properties of tricalcium silicate (C3S). C3S/BT samples were prepared with varying proportions of BT (0, 20, 40, and 60 wt%; referred to as BT00, BT20, BT40, and BT60, respectively). Dielectric constant and radiopacity were measured. Cytocompatibility was evaluated on human dental pulp cells. After surgical procedures on rat mandible, immunohistochemistry and Masson's trichrome staining were performed. The dielectric constant increased with higher proportions of BT (p<0.05). BT40 and BT60 satisfied the clinical guideline of radiopacity. There were no significant differences among groups in the cytocompatibility tests (p>0.05). New bone was observed well, along with the expressions of the dentin matrix protein 1 (DMP1), osteocalcin (OC), and osteonectin (ON) in BT40 and BT60. Conclusively, the contents of 40-60 wt% of BT in C3S provided proper radiopacity, favorable cytocompatibility, and beneficial effect on bone regeneration.

Comprehensive evaluation of end-point free energy techniques in carboxylated-pillar[6]arene host-guest binding: II. regression and dielectric constant

End-point free energy calculations as a powerful tool have been widely applied in protein-ligand and protein-protein interactions. It is often recognized that these end-point techniques serve as an option of intermediate accuracy and computational cost compared with more rigorous statistical mechanic models (e.g., alchemical transformation) and coarser molecular docking. However, it is observed that this intermediate level of accuracy does not hold in relatively simple and prototypical host-guest systems. Specifically, in our previous work investigating a set of carboxylated-pillar[6]arene host-guest complexes, end-point methods provide free energy estimates deviating significantly from the experimental reference, and the rank of binding affinities is also incorrectly computed. These observations suggest the unsuitability and inapplicability of standard end-point free energy techniques in host-guest systems, and alteration and development are required to make them practically usable. In this work, we consider two ways to improve the performance of end-point techniques. The first one is the PBSA_E regression that varies the weights of different free energy terms in the end-point calculation procedure, while the second one is considering the interior dielectric constant as an additional variable in the end-point equation. By detailed investigation of the calculation procedure and the simulation outcome, we prove that these two treatments (i.e., regression and dielectric constant) are manipulating the end-point equation in a somehow similar way, i.e., weakening the electrostatic contribution and strengthening the non-polar terms, although there are still many detailed differences between these two methods. With the trained end-point scheme, the RMSE of the computed affinities is improved from the standard ~ 12 kcal/mol to ~ 2.4 kcal/mol, which is comparable to another altered end-point method (ELIE) trained with system-specific data. By tuning PBSA_E weighting factors with the host-specific data, it is possible to further decrease the prediction error to ~ 2.1 kcal/mol. These observations along with the extremely efficient optimized-structure computation procedure suggest the regression (i.e., PBSA_E as well as its GBSA_E extension) as a practically applicable solution that brings end-point methods back into the library of usable tools for host-guest binding. However, the dielectric-constant-variable scheme cannot effectively minimize the experiment-calculation discrepancy for absolute binding affinities, but is able to improve the calculation of affinity ranks. This phenomenon is somehow different from the protein-ligand case and suggests the difference between host-guest and biomacromolecular (protein-ligand and protein-protein) systems. Therefore, the spectrum of tools usable for protein-ligand complexes could be unsuitable for host-guest binding, and numerical validations are necessary to screen out really workable solutions in these 'prototypical' situations.

Fabrication, characterization and application of electrospun polysulfone membrane for phosphate ion removal in real samples

Due to simplicity and flexibility, electrospinning technique can produce many types of fibers at nanoscale via different operational parameters for various applications including industrial wastewater treatment, air filtration and so on. Nonetheless, the study on the electrospinning operational parameter is very limited and many researchers are still using trial-and-error method to design their targeted fiber. In this study, a series of electrospun polysulfone (PSF; 20% w/v) nanofibrous membranes that made up from different ratios of dimethylformamide (DMF) and tetrahydrofuran (THF) mixtures in order to achieve different dielectric constant (ϵ) of solvent system. The fabricated PSF nanofibers were characterized by field emission scanning electron microscopy (FESEM), tensile strength tester and contact angle measurement. The THF-DMF binary solvent system with ϵ = 16.33 to 27.97 produced a smooth surface electrospun PSF nanofibers, while THF mono solvent system (ϵ = 7.60) and DMF mono solvent system (ϵ = 36.70) produced a rough and porous surface electrospun PSF nanofibers. This finding is contradicted with the common finding in which only a binary solvent is able to fabricate a rough or grooved surface electrospun nanofibers. In addition, the dielectric constant can be another key factor, besides boiling point and solubility of binary solvent system, that induces phase separation in the polymeric solution jet and eventually fabricate non-smooth surface electrospun nanofibers. The fabricated electrospun PSF nanofibrous membranes showed high efficiency in phosphate removal.

Development of Fluorescently Labeled Self-Emulsifying Drug Delivery Systems (SEDDS) for Prolonged Stability, In Vitro Sustained Release and Cellular Uptake

AIM

In this study, four fluorescein hydrophobic ionic complexes were formed with the cationic polymers Eudragit RS, Eudragit RL, Eudragit E, and polyethyleneimine (PEI) to provide fluorescein sustained release, sustained cellular uptake, and stability.

METHODS

Complexes were loaded in a self-emulsifying drug delivery system (SEDDS) composed of 40% Tween 80, 20% Kolliphor EL, 15% 2-n-Octyl-1-dodecanol, and 25% dipropylene glycol. SEDDS were investigated regarding their size, polydispersity index (PDI), zeta potential, and cytotoxicity. Fluorescein release from SEDDS was performed in phosphate buffer (pH 6.8 and pH 8) and the released fluorescein was evaluated for cellular uptake. Moreover, fluorescein from all of the SEDDS pre-concentrates was released at different time points to check its long-term stability over six months.

RESULTS

The average fluorescein load in SEDDS was 0.045%. SEDDS showed an average droplet size of 24.9 ± 1.6 nm with PDI ≤ 0.3. SEDDS complexes diluted 1:100 increased the zeta potential from -7.3 mV to +3.7 mV and provided > 85% cell viability. An 92.27 ± 3.18% fluorescein exhibited a few seconds of immediate release when used as control or PEI complex in SEDDS. On the contrary, Eudragit-fluorescein complexes in SEDDS showed sustained release of 87.01 ± 5.22% fluorescein in ≤ 70 min with 22.19 ± 14.56% and 59.27 ± 16.57% released at 10 min in pH 6.8 and pH 8 release media, respectively. Comparatively, the medium at pH 6.8 maintained a significantly improved sustained fluorescein release (p ≤ 0.001). Furthermore, Eudragit RS/RL compared to Eudragit E significantly exhibited a slower fluorescein release rate from SEDDS (p ≤ 0.01). The cellular uptake of the released fluorescein was 72.4 ± 8.2% for all SEDDS complexes after 3 h. Eudragit complexes compared to PEI complex in SEDDS significantly showed more sustained fluorescein cellular uptake at 1 h and 2 h (p ≤ 0.001). However, SEDDS complexes showed the longest fluorescein stability with PEI after six months, whereas fluorescein stability for SEDDS containing fluorescein as Eudragit complex and control showed 39.1% and 82.5% fluorescence decrease, respectively after three months.

CONCLUSION

In the developed SEDDS, the presence of hydrophobic ionic complexes can significantly promote longer stability and sustained cellular uptake of fluorescein while releasing in a sustained manner.

Dielectric constants of organic pollutants determine their strength for enhancing microbial iron reduction

Physicochemical properties are essential characteristics of organic compounds, which not only impact the fate of organic pollutants but also determine their application in biological processes. Here, we first found that the dielectric constants (ɛ) of organic pollutants negatively correlated to their strength for enhancing microbial Fe(III) reduction. Those with lower ɛ values than 2.61 potentially promoted the above process following the sequence carbon tetrachloride (CT) > benzene > toluene > tetrachloroethylene (PCE) due to their different ability to deprotonate the phosphorus-related groups on the outer cell membrane of iron-reducing bacteria Shewanella oneidensis MR-1 (MR-1). The stronger deprotonation of phosphorus-related groups induced more negative charge of cell surface and more strongly increased cell membrane permeability and consequently stimulated faster release of flavin mononucleotide (FMN) as an electron shuttle/cofactor for Fe(III) reduction. These findings are significant for understanding the biogeochemistry in multi-organic contaminated subsurface and providing knowledge for remediation strategies and current production.

Investigation of electrical properties of eco-friendly vegetable oil blended with bioactive compound

Oxidative stability of prototypical groundnut oil (GO) and mustard oil (MO) blended with a significant characteristic addition of antioxidants, α-tocopherol (α-T) and TBHQ (tert-butyl hydroquinone), at different concentrations was analysed. α-T (natural) and TBHQ (synthetic) antioxidants at a different concentrations from 0 to 20 mg/L were blended with GO and MO to prepare 18 samples. Compositional analysis of groundnut oil and mustard oil was carried out using gas chromatography and mass spectra (GCMS). Electrical properties like dielectric constant, tanδ, specific resistance etc. were investigated at frequencies from 1 Hz to 10 MHz for the modified samples. Thermal properties like breakdown voltage, flash and fire points and viscosity of all samples were also premeditated. It was observed that dielectric constant (ε') of GO reduces from 3.58 to 2.82 with the addition of α-T but increases to 3.29 with the addition of TBHQ, whereas in MO, dielectric constant increases from 2.93 to 3.38 with the addition of α-T and rises to 3.27 with the addition of TBHQ at 15 mg/L. The synergistic effect of antioxidants in regulating the insulation nature of the oil is found to be more effective with α-tocopherol compared to TBHQ in GO. Higher breakdown voltage and more stability were observed in oil with the addition of antioxidant (TBHQ) in low concentration. The study would be useful in the selection of eco-friendly coolants in engineering and industry.

Effect of solvent polarity on the Ultrasound Assisted extraction and antioxidant activity of phenolic compounds from habanero pepper leaves (Capsicum chinense) and its identification by UPLC-PDA-ESI-MS/MS

Phenolic compounds are secondary metabolites involved in plant adaptation processes. The development of extraction procedures, quantification, and identification of this compounds in habanero pepper (Capsicum chinense) leaves can provide information about their accumulation and possible biological function. The main objective of this work was to study the effect of the UAE method and the polarity of different extraction solvents on the recovery of phenolic compounds from C. chinense leaves. Quantification of the total phenolic content (TPC), antioxidant activity (AA) by ABTS⁺ and DPPH radical inhibition methods, and the relation between the dielectric constant (ε) as polarity parameter of the solvents and TPC using Weibull and Gaussian distribution models was analyzed. The major phenolic compounds in C. chinense leaves extracts were identified and quantified by UPLC-PDA-ESI-MS/MS. The highest recovery of TPC (24.39 ± 2.41 mg GAE g^-1 dry wt) was obtained using MeOH (50%) by UAE method. Correlations between TPC and AA of 0.89 and 0.91 were found for both radical inhibition methods (ABTS⁺ and DPPH). The Weibull and Gaussian models showed high regression values (0.93 to 0.95) suggesting that the highest phenolic compounds recovery is obtained using solvents with "ε" values between 35 and 52 by UAE. The major compounds were identified as N-caffeoyl putrescine, apigenin, luteolin and diosmetin derivatives. The models presented are proposed as a useful tool to predict the appropriate solvent composition for the extraction of phenolic compounds from C. chinense leaves by UAE based on the "ε" of the solvents for future metabolomic studies.

Zinc substitution effect on the structural, spectroscopic and electrical properties of nanocrystalline MnFe2O4 spinel ferrite

This paper reports the structural, morphological, spectroscopic, dielectric, ac conductivity, and impedance properties of nanocrystalline Mn1-xZnxFe2O4. The nanocrystalline Mn-Zn ferrites were synthesized using a solvent-free combustion reaction method. The structural analysis using X-ray diffraction (XRD) pattern reveals the single-phase of all the samples and the Rietveld refined XRD patterns confirmed the cubic-spinel structure. The calculated crystallite size values increase from 8.5 nm to 19.6 nm with the Zn concentration. The surface morphological analysis using field emission scanning electron microscopy and the transmission electron microscopy confirms the nano size of the prepared ferrites. X-ray photoelectron spectroscopy was used to study the ionic state of the atoms present in the samples. Further, the high-resolution Mn 2p, Zn 2p, Fe 2p, and O 1s spectra of Mn1-xZnxFe2O4 does not result in the appearance of new peaks with Zn content, indicating that the Zn substitution does not change the ionic state of Mn, Zn, Fe, and O present in nanocrystalline Mn1-xZnxFe2O4. The investigated electrical properties show that the dielectric constant, tan δ and ac conductivity gradually decrease with increasing Zn substitution and the sample Mn0 · 2Zn0 · 8Fe2O4 has the lowest value of conductivity at 303 K. The ac conductivity measured at different temperatures shows the semiconducting nature of the ferrites. The impedance spectra analysis shows that the contribution of grain boundary is higher compared with the grain to the resistance. The obtained results suggest that the Zn substituted manganese ferrite nanoparticles can act as a promising candidate for high-frequency electronic devices applications.

Water Layer at Hydrophobic Surface: Electrically Dead but Dynamically Alive?

The origin of the anomalous low value of the static dielectric constant (SDC) of confined water has been addressed and unearthed. While the low value is partly due to the different dielectric boundaries, a significant role is played by the "electrically dead layer" (EDL). As the observed dielectric constant is the harmonic mean of the grid-wise SDCs, the first layer, having the smallest SDC, makes a disproportionately large contribution. This enhanced contribution, in turn, arises from the orientationally ordered surface water molecules. They exhibit reduced fluctuations in collective dipole moment, as the molecules remain partly caged due to water-surface interactions. This phenomenon is found to be universal. We study the structure and dynamics of the water molecules which characterize the EDL. We demonstrate that while the EDL remains alive at a molecular level, with a finite residence time, it displays time scales not substantially different compared to the distant water layers.

Delving into the properties of polymer nanocomposites with distinctive nano-particle quantities, for the enhancement of optoelectronic devices

The study focusses on synthesis and modification of structural, optical and electrical characteristics of nanostructured titanium dioxide anatase embedded Poly(methyl methacrylate) (PMMA) nanocomposite with different weight percentages (0.03, 0.06, 0.12, 0.18 and 0.24%) by the solvent casting method. Modification in the morphology of PMMA nanocomposites with an increasing amount of titanium dioxide anatase is studied by using a field emission scanning electron microscope (FE-SEM). Micrograms of FE-SEM show spherical shaped nanoparticles distribution in PMMA nanocomposites thin films. In optical characterization, transmission, optical band gaps, the real and imaginary part of dielectric constant, linear susceptibility, optical conductivity, refractive index and extinction coefficient are calculated using experimental data. It is observed that the optical band gap has an overall decreasing trend with increasing the weight percentage of TiO₂ (anatase) in PMMA nanocomposites. It is also found that values of all electrical parameters decrease with increasing the weight percentage of TiO₂ (anatase) in PMMA nanocomposites. All wavelength depending parameters are investigated in the wavelength range from 190 nm to 2700 nm. Single oscillator model is used to analyze the refractive index dispersion and estimation of the oscillator energy and dispersion energy of the films. The study is applicable to optical sensors and other optoelectronic devices.

Geochemical and electrical characterization of heavy metals in contaminated soils

The present work is conducted in the industrial district south of greater Cairo (ElTabbin area). Some heavy metals like Mn, Co, Ni, Cu, Zn, Pb, Cr, Ba, Cd, Mo were determined in polluted soils during May, 2018. At the study area, results displayed that average heavy metals concentrations differ considerably. They are decreased from Mn to Cd (Mn > Ba > Zn > Cr > Ni > Co > Pb > Cu > Mo > Cd). The average ranges as follows: Mn (255.8–31448.2 ppm); Ba (145.2–17545.6 ppm); Zn (53.3–1589.9 ppm); Cr (26.7–311.3 ppm); Ni (29.7–114.1 ppm); Co (13.2–39.8 ppm); Pb (5.7–77.4 ppm); Cu (7.6–35.2 ppm); Mo (0.1–15.9 ppm) and Cd (0–1.5 ppm), respectively. ElTabbin area has heavy manufacturing activity at Egypt. ElTabbin area was chosen as a model for that contamination.

Electrical characteristics of some specimens from El- Tebbin area, Egypt, were taken and measured electrically at frequency range (10⁻³ to 100 kHz). Major and heavy elements were measured at specimens. Specimens were classified to three categories according to electrical properties. The changes were the consequence of change in minor and major mineral composition in the specimens. Electrical properties were able to recognize different specimens according to different levels of contaminants in the specimens. Texture, tortuosity and minor elements of heavy elements are the controlling factors that control electrical properties at specimens. High values concentration of Mn, Ni, and Zn heavy elements increases conductivity while the high concentration of Pb and Cu heavy elements decreases the conductivity. The mixing up of these different minor and major minerals and elements at specimen may lead to the change of conductivity values. The main controlling factors of the major elements are the Fe₂O₃ and SiO₂, while the main controlling factors of the minor elements are the Mn and Pb. Our main objective is to study mixing up of the different minor and major minerals and elements on electrical properties of rocks.

Rapid and label-free metamaterial-based biosensor for fatty acid detection with terahertz time-domain spectroscopy

A rapid method for detecting fatty acids (FAs) using terahertz time-domain spectroscopy (THz-TDS) technology combined with a metamaterial-based THz sensor was developed. We measured the THz responses to oleic acid, linoleic acid and α-linoleic acid with different numbers of double-bond, α-linoleic acid and γ-linoleic acid with different conformations. In addition, in order to explore the reason for the observed redshifts of the resonance frequencies of the four FAs, the dielectric constants of the FAs were measured in the THz region. Furthermore, the four fatty acids were also attempted to be identified by Raman spectroscopy, which was difficult to accomplish unambiguously because of the effect of fluorescence. This result thus demonstrates the power and usefulness of metamaterial-assisted THz-TDS in the rapid determination of the FAs, and its potential as a versatile tool for investigation of biological metabolism, and for food product quality, safety inspection and control.

Microwave-absorbing properties of cathode material during reduction roasting for spent lithium-ion battery recycling

As a hazardous material to the environment and human health, spent lithium-ion batteries need to be recycled in a reasonable way. To explore the effect of microwave heating on spent lithium-ion batteries (LIBs) recycling, the microwave-absorbing properties of a spent cathode powder (LiNi_xCo_yMn_zO₂) were studied by measuring its dielectric properties from 25-900 °C at 2450 MHz under different conditions (temperature, carbon dose and apparent density). X-ray diffraction and thermogravimetric analysis (TGA) were used to study decomposition and reduction reactions in the heating process. The results indicated that the cathode material has good microwave-absorbing properties over the entire temperature range (25-900 °C), especially when mixed with carbon. As the reduction reactions proceed, the dielectric properties of the material increase rapidly from 600 °C, which means that microwave heating can promote a carbothermal reduction reaction. The effect of the carbon dose on the dielectric properties indicates that the carbothermal reduction reaction can fully occur when the carbon dose reaches 18%. Furthermore, the best microwave-absorbing performance can be achieved when the apparent density of the material is 1.41 g/cm³. These studies have established a basis for research towards the direct recovery of lithium from LIBs by microwave reduction roasting.

Rheological and Dielectric Behavior of 3D-Printable Chitosan/Graphene Oxide Hydrogels

The effect of concentration, temperature, and the addition of graphene oxide (GO) nanosheets on the rheological and dielectric behavior of chitosan (CS) solutions, which influences the formation of the blend materials for various applications including 3D printing and packaging, was studied. Among tested acid solutions, the rheological behavior of 1% CS in acetic and lactic acid solutions was found to be similar, whereas the hydrochloric acid solution showed an abnormal drop in the dynamic moduli. Oscillatory rheology confirmed a distinct gel point for the CS solutions at below 10 °C. Both the G' and G″ of the solutions increased with the loading concentrations of GO between 0.5 and 1%, and it marginally dropped at the loading concentration of 2%, which is consistent with AFM observation. The steady-shear flow data fitted the Carreau model. Dielectric property measurement further confirmed that both the dielectric constant, ε' and the loss factor, ε″ for the CS in hydrochloric acid solutions behaved differently from others. Addition of GO significantly improved both ε' and ε″, indicating an improvement in the dielectric properties of CS/GO solutions. The dispersion of GO into the CS matrix was assessed by measuring XRD, FTIR, and microscopy of the film prepared from the solutions. Furthermore, the inclusion of GO into CS solution containing pluronic F127 (F127) base for potential 3D printing application showed positive results in terms of the printing accuracy and shape fidelity of the printed objects (films and scaffolds). The optimized composition with homogeneous particle distribution indicated that up to ∼50 mg/mL GO concentration (w/v of F127 base) was suitable to print both films and scaffolds for potential biomedical applications.

Electrical detection of blood cells in urine

Available methods for detecting blood in the urine (hematuria) can be problematic since results can be influenced by many factors in patients and in the lab settings, resulting in false positive or false negative results. This necessitates the development of new, accurate and easy-access methods that save time and effort. This study demonstrates a label-free and accurate method for detecting the presence of red and white blood cells (RBCs and WBCs) in urine by measuring the changes in the dielectric properties of urine upon increasing concentrations of both cell types. The current method could detect changes in the electrical properties of fresh urine over a short time interval, making this method suitable for detecting changes that cannot be recognized by conventional methods. Correcting for these changes enabled the detection of a minimum cell concentration of 10² RBCs per ml which is not possible by conventional methods used in the labs except for the semi-quantitative method that can detect 50 RBCs per ml, but it is a lengthy and involved procedure, not suitable for high volume labs. This ability to detect very small amount of both types of cells makes the proposed technique an attractive tool for detecting hematuria, the presence of which is indicative of problems in the excretory system.

Relaxation dynamics of l-alanine in water medium investigated by dielectric relaxation spectroscopy

The complex dielectric permittivity of L-alanine in aqueous medium at different concentrations and different temperatures were measured in the microwave (0.02 < ν/GHz < 20) frequency region by using open-ended coaxial probe technique. From the reflection coefficient and impedance data, the real and imaginary part of the dielectric permittivity values is determined. It is observed that there is a decrease in the real part of the dielectric permittivity up to certain frequency and an increase in the imaginary part of the dielectric permittivity with increase in the molar concentration of L-alanine in water medium. Based on the experimental data the average relaxation time values are calculated and its behavior is analyzed in terms of bound water and free water molecules. The theoretical dipole moment of L-alanine is calculated at gaseous state as well as in aqueous medium by using PCM and IEFPCM model at HF, DFT/B3LYP and MP2 calculations using 6-311G* basis set. Analysis between experimentally determined parameters and computed dipole moments were discussed. The mean molecular polarizability is calculated from the Lippincott δ function potential model and compared with the Le Fèvre method of polarizability values.

Dielectric properties of carrots affected by ultrasound treatment in water and oil medium simulated systems

The ultrasound treatment of vegetables can damage their tissue structure and release water and soluble solids altering the dielectric properties of the material. Changes in the dielectric properties will influence the microwave processing of ultrasound pretreated material. In order to investigate the effect of ultrasound pretreatment on dielectric properties, carrots were ultrasonicated in simulated water and oil systems. Microwave heating and microwave-assisted vacuum frying of carrot slices were also completed to explore the relation between dielectric properties of microwave pretreated samples and microwave absorption. Ultrasound of carrots in water simulated system showed that ε' and ε″ of carrots tended to decrease with the increase of ultrasonic power (from 480 W to 640 W) and time (from 10 min to 30 min). Ultrasound treatment of carrots in salt solutions increased ε' and ε″ of carrots. The combined pretreatment of microwave blanching with ultrasound in salt solutions increased ε″ (from 19.72 to 29.90). Conversely, in oil simulated system, the ε' and ε″ of carrots also decreased as the ultrasonication power and time increased. Besides, the dielectric properties decreased as the temperature of oil medium increased from 35 °C to 75 °C. With improved dielectric properties, the dehydration rate during frying of carrot increased due to the enhanced microwave absorption. Therefore, the combined pretreatment of microwave blanching with ultrasound in salt solutions largely improved the dielectric properties of carrots, and reducing the required time of microwave vacuum frying.

Modelling, characterization and quality analysis of heated oil using electric moment and chemical properties

The effect of temperature (30-90 °C) on the electrical parameter: dielectric constant (ε_r) of Sunflower, Olive and Corn oil exposed to three cycles of heating to frying temperature (175 ± 5 °C) was studied to exhibit the quality analysis of oil. Dielectric constant of heated oil was measured using designed inter-digitated electrode capacitor at different frequency (10 kHz-5 MHz) and temperature (30-90 °C). Dielectric constant (ε_r) of oil samples increases with cycles of heating. Variation of dielectric constant with frequency was premeditated using quadratic equation and the dependency factor was observed to be R² > 0.914. Chemical kinetic dielectric constant with temperature was studied using Arrhenius law and observed that activation energy increases with cycles of heating. Andrade's equation was also fitted with the variation of ε_r with temperature and the dependency factor (R² between 0.978 to 0.999) was observed to be highly correlated. Experiential physical properties like density, refractive index and ε_r were significantly correlated with the pragmatic peroxide value. The observed relation between ε_r with chemical property divulges the suitability of measured dielectric constant in real time and continuous evaluation of edible oil quality analysis in food industry.

Dielectric properties for selected wall material in the development of microwave-encapsulation-drying

Dielectric properties study is important in understanding the interaction between materials within electromagnetic field. By knowing and understanding the dielectric properties of materials, an efficient and effective microwave heating process and products can be designed. In this study, the dielectric properties of several encapsulation wall materials were measured using open-ended coaxial probe method. This method was selected due to its simplicity and high accuracy. All materials exhibited similar behavior. The result inferred that β-cyclodextrin (BC), starch (S), Arabic (GA) and maltodextrin (M) with various dextrose equivalent exhibited effective encapsulation wall materials in microwave encapsulation-drying technique owing to loss tangent values which were higher than 0.1 at general application frequency of 2.45 GHz. Thus, these were found to be suitable as wall material to encapsulate the selected core material in this microwave encapsulation-drying method. On contrary, sodium caseinate showed an ineffective wall material to be used in microwave encapsulation-drying. The differences in the values of dielectric constant, loss factor and loss tangent were found to be contributed by frequency, composition and bulk density.

Dielectric study of Clove oil

Dielectric properties of clove oil were determined using an impedance gain phase analyzer (HP 4194 A) at discrete frequencies between 10 kHz and 3 MHz and a range of temperature between 25 °C and 45 °C. A micro processor controller based temperature controller (Julabo F-25) was used for keeping the temperature of clove oil constant. Dielectric constant of the sample is found to decrease with increase in frequency and temperature, while dielectric loss decreases with increase in frequency but increases with increase in temperature. Penetration depth has been calculated with the help of dielectric data and is found to decrease with increase in frequency.

Enabling Simultaneous Extreme Ultra Low-k in Stiff, Resilient, and Thermally Stable Nano-Architected Materials

Low dielectric constant (low-k) materials have gained increasing popularity because of their critical role in developing faster, smaller, and higher performance devices. Their practical use has been limited by the strong coupling among mechanical, thermal, and electrical properties of materials and their dielectric constant; a low-k is usually attained by materials that are very porous, which results in high compliance, that is, silica aerogels; high dielectric loss, that is, porous polycrystalline alumina; and poor thermal stability, that is, Sr-based metal-organic frameworks. We report the fabrication of 3D nanoarchitected hollow-beam alumina dielectrics which k is 1.06-1.10 at 1 MHz that is stable over the voltage range of -20 to 20 V and a frequency range of 100 kHz to 10 MHz. This dielectric material can be used in capacitors and is mechanically resilient, with a Young's modulus of 30 MPa, a yield strength of 1.07 MPa, a nearly full shape recoverability to its original size after >50% compressions, and outstanding thermal stability with a thermal coefficient of dielectric constant (TCK) of 2.43 × 10^-5 K^-1 up to 800 °C. These results suggest that nanoarchitected materials may serve as viable candidates for ultra low-k materials that are simultaneously mechanically resilient and thermally and electrically stable for microelectronics and devices.

Effects of Environmental Factors and Metallic Electrodes on AC Electrical Conduction Through DNA Molecule

BACKGROUND

Deoxyribonucleic acid (DNA) is one of the best candidate materials for various device applications such as in electrodes for rechargeable batteries, biosensors, molecular electronics, medical- and biomedical-applications etc. Hence, it is worthwhile to examine the mechanism of charge transport in the DNA molecule, however, still a question without a clear answer is DNA a molecular conducting material (wire), semiconductor, or insulator? The answer, after the published data, is still ambiguous without any confirmed and clear scientific answer. DNA is found to be always surrounded with different electric charges, ions, and dipoles. These surrounding charges and electric barrier(s) due to metallic electrodes (as environmental factors (EFs)) play a substantial role when measuring the electrical conductivity through λ-double helix (DNA) molecule suspended between metallic electrodes. We found that strong frequency dependence of AC-complex conductivity comes from the electrical conduction of EFs. This leads to superimposing serious incorrect experimental data to measured ones.

METHODS

At 1 MHz, we carried out a first control experiment on electrical conductivity with and without the presence of DNA molecule. If there are possible electrical conduction due to stray ions and contribution of substrate, we will detected them. This control experiment revealed that there is an important role played by the environmental-charges around DNA molecule and any experiment should consider this role.

RESULTS AND DISCUSSION

We have succeeded to measure both electrical conductivity due to EFs (σ _ENV) and electrical conductivity due to DNA molecule (σ _DNA) independently by carrying the measurements at different DNA-lengths and subtracting the data. We carried out measurements as a function of frequency (f) and temperature (T) in the ranges 0.1 Hz < f < 1 MHz and 288 K < T < 343 K. The measured conductivity (σ _MES) portrays a metal-like behavior at high frequencies near 1 MHz. However, we found that σ _DNA was far from this behavior because the conduction due to EFs superimposes σ _DNA, in particular at low frequencies. By measuring the electrical conductivity at different lengths: 40, 60, 80, and 100 nm, we have succeeded not only to separate the electrical conduction of the DNA molecule from all EFs effects that surround the molecule, but also to present accurate values of σ _DNA and the dielectric constant of the molecule ε'_DNA as a function of temperature and frequency. Furthermore, in order to explain these data, we present a model describing the electrical conduction through DNA molecule: DNA is a classical semiconductor with charges, dipoles and ions that result in creation of localized energy-states (LESs) in the extended bands and in the energy gap of the DNA molecule.

CONCLUSIONS

This model explains clearly the mechanism of charge transfer mechanism in the DNA, and it sheds light on why the charge transfer through the DNA can lead to insulating, semiconducting, or metallic behavior on the same time. The model considers charges on DNA, in the extended bands, either could be free to move under electric field or localized in potential wells/hills. Localization of charges in DNA is an intrinsic structural-property of this solitaire molecule. At all temperatures, the expected increase in thermal-induced charge is attributed to the delocalization of holes (or/and electrons) in potential hills (or/and potential wells) which accurately accounts for the total electric and dielectric behavior through DNA molecule. We succeeded to fit the experimental data to the proposed model with reasonable magnitudes of potential hills/wells that are in the energy range from 0.068 eV.

Composition, Microstructure, and Electrical Properties Control of the Powders Synthesized by Sol-Gel Auto-Combustion Method Using Citric Acid as the Fuel

Nanocrystalline lithium ferrite Li _0.5 Fe _1.7 Mg _0.8 O ₄ powders were synthesized by the sol-gel auto-combustion method from the corresponding metal nitrates using citric acid as fuel.The results from XRD, SEM, and AC electrical conductivity studies are summarized as follows: The results of XRD analysis showed that all the samples were formed in single-phase cubic spinel structure at different annealing temperatures from 300 to 700 °C for 2 h. The lattice parameter was found to decrease on increasing the temperature. The microstructure of lithium ferrite powders was temperature dependent. The particle size was increased with the annealing temperature. AC electrical properties were investigated using the super-linear power law and activation energies were calculated for all compositions. The electron mobility in Li _0.5 Fe _1.7 Mg _0.8 O ₄ samples ranged from 0.05 to 0.29 eV, which clearly indicated that the present lithium ferrites have semiconductor-like behavior. The frequency exponent "s" of lithium ferrite lies in the range 0.5 < s < 1, which confirms the electron hopping between Fe ^2 + and Fe ^3 + ions.

The effect of solvent polarity on wormlike micelles using dipropylene glycol (DPG) as a cosolvent in an anionic/zwitterionic mixed surfactant system

HYPOTHESIS

The behavior/properties of micellar solutions are governed by Coulombic interactions that are influenced by the polarity of the surfactant head groups, hydrophobic tails, and solvent molecules. The addition of co-solvent should have a direct impact on solvent polarity and the size of the micelles are expected to decrease accordingly.

EXPERIMENTS

In this study, a mixed surfactant system is studied composed of a common anionic surfactant, sodium laureth sulfate-1, modified by a zwitterionic surfactant, cocamidopropyl betaine in deuterated water. In this system, worm-like micelles (WLMs) are formed. The influence of a co-solvent, dipropylene glycol (DPG) in the present of high salt content, is investigated. DPG primarily modifies the dielectric constant of the solvent.

FINDINGS

It was found that the addition of DPG slightly decreased the micelle radius, but dramatically reduced the persistence length as well as the contour length of the micelles. The relative dependence of contour length on salt concentration is not significantly changed. Thus, it is shown that the self-assembled structure can be tuned by adjusting solvent polarity without affecting the relative tunability of the WLM/ellipsoidal structure through counter ion concentration.

Micellar dipolar rearrangement is sensitive to hydrophobic chain length: Implication for structural switchover of piroxicam

The interfacial properties of the membrane are exceptionally vital in drug-membrane interaction. They not only select out a particular prototropic form of the drug molecule for incorporation, but are also potent enough to induce structural switchover of these drugs in several cases. In this work, we quantitatively monitored the change in dipolar rearrangement of the micellar interface (as a simplified membrane mimic) by measuring the dielectric constant and dipole potential with the micellization of SDS at pH 3.6. The dielectric constant and dipole potential were measured utilizing the fluorescence of polarity sensitive probe, pyrene and potential-sensitive probe, di-8-ANEPPS, respectively. Our study demonstrates that the change in dipolar rearrangement directly influences the switchover equilibrium between the anionic and neutral from of piroxicam. We have further extended our work to evaluate the effect of hydrophobic chain length of the surfactants on the dipolar rearrangement and its effect on the structural switchover of piroxicam. It is interesting that the extent of switchover of piroxicam is directly correlated with the dipolar rearrangement induced bythe varying hydrophobic chain length of the surfactants. To the best of our knowledge, our results constitute the first report to show the dependence of dipole potential on the hydrophobic chain length of the surfactant and demonstrate that the dipolar rearrangement directly tunes the extent of structural switchover of piroxicam, which was so far only intuitive. We consider that this new finding would have promising implication in drug distribution and drug efficacy.

Predicting water-to-cyclohexane partitioning of the SAMPL5 molecules using dielectric balancing of force fields

Alchemical transformation of solutes using classical fixed-charge force fields is a popular strategy for assessing the free energy of transfer in different environments. Accurate estimations of transfer between phases with significantly different polarities can be difficult because of the static nature of the force fields. Here, we report on an application of such calculations in the SAMPL5 experiment that also involves an effort in balancing solute and solvent interactions via their expected static dielectric constants. This strategy performs well with respect to predictive accuracy and correlation with unknown experimental values. We follow this by performing a series of retrospective investigations which highlight the potential importance of proper balancing in these systems, and we use a null hypothesis analysis to explore potential biases in the comparisons with experiment. The collective findings indicate that considerations of force field compatibility through dielectric behavior is a potential strategy for future improvements in transfer processes between disparate environments.

Continuum Electrostatics Approaches to Calculating pKas and Ems in Proteins

Proteins change their charge state through protonation and redox reactions as well as through binding charged ligands. The free energy of these reactions is dominated by solvation and electrostatic energies and modulated by protein conformational relaxation in response to the ionization state changes. Although computational methods for calculating these interactions can provide very powerful tools for predicting protein charge states, they include several critical approximations of which users should be aware. This chapter discusses the strengths, weaknesses, and approximations of popular computational methods for predicting charge states and understanding the underlying electrostatic interactions. The goal of this chapter is to inform users about applications and potential caveats of these methods as well as outline directions for future theoretical and computational research.

Experimental investigation of electro-rheological properties of modeled vegetable oils

Vegetable oil becomes polarized on oxidation and polymerization resulting in the formation of peroxide, triglycerides, etc. The quality and reusable state were investigated for sunflower, sesame, rice bran oil and model oil with the addition of oleic acid (2, 4 and 6 %) and antioxidants (citric and tert-Butyl hydroquinone-TBHQ). Excessive reclaims of cooking oil produce toxic by-products due to chemical breakdown that induce the production of polar compounds in oil. To determine the consumable fitness, variations of dielectric constant are observed at different temperatures (29 to 70 °C) and frequencies (1 to 10(7)Hz) for the cooking oil. Physical parameters, such as viscosity and density associated with the saturated and unsaturated fatty acid, are also measured at different temperatures to determine the quality of oil. Dielectric constant and viscosity are correlated and analyzed using a newly developed equation with high correlation constant (R (2)  = 0.998) for oil added with citric acid. Oil added with 2-4 % of oleic acid is observed to have high determination coefficient (R (2)  > 0.92). A lowest correlation (R (2)  = 0.6-0.7) was observed for the oil added with TBHQ. The present study also states that addition of TBHQ to oil does not impede oxidation reaction. Besides, even the shelf life of the oil could not be enhanced and may produce adverse effects in human health.

EPR and impedance spectroscopic investigations on lithium bismuth borate glasses containing nickel and vanadium ions

Glasses having composition 7NiO∙23Li2O∙20Bi2O3∙50B2O3, 7V2O5∙23Li2O∙20Bi2O3∙50B2O3 and x(2NiO∙V2O5)∙(30-x)Li2O∙50B2O3∙20Bi2O3 (with x=0, 2, 5, 7 & 10 mol%) prepared through melt-quench route are explored by analyzing density, impedance spectroscopy and electron paramagnetic resonance (EPR). It is found that both density and molar volume increase with an increase in substitution of 2NiO∙V2O5 in the base glass matrix. Different dielectric parameters viz. dielectric loss (ε), electrical modulus (M), loss tangent (tanδ) etc. are evaluated and their variations with frequency and temperature are analyzed which reveals that these glasses exhibit a non-Debye relaxation behavior. A phenomenal description of the capacitive behavior is obtained by considering the circuitry as a parallel combination of bulk resistance (Rb) and constant phase element (CPE). The conduction mechanism is found to follow Quantum Mechanical Tunneling (QMT) model. Spin Hamiltonian Parameters (SHPs) and covalency rates are calculated from the EPR spectra of vanadyl ion. The observed EPR spectra confirmed that V(4+) ion exists as vanadyl ion in the octahedral coordination with tetragonal compression.

The structural stability and catalytic activity of DNA and RNA oligonucleotides in the presence of organic solvents

Organic solvents and apolar media are used in the studies of nucleic acids to modify the conformation and function of nucleic acids, to improve solubility of hydrophobic ligands, to construct molecular scaffolds for organic synthesis, and to study molecular crowding effects. Understanding how organic solvents affect nucleic acid interactions and identifying the factors that dominate solvent effects are important for the creation of oligonucleotide-based technologies. This review describes the structural and catalytic properties of DNA and RNA oligonucleotides in organic solutions and in aqueous solutions with organic cosolvents. There are several possible mechanisms underlying the effects of organic solvents on nucleic acid interactions. The reported results emphasize the significance of the osmotic pressure effect and the dielectric constant effect in addition to specific interactions with nucleic acid strands. This review will serve as a guide for the selection of solvent systems based on the purpose of the nucleic acid-based experiments.