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Minerals are reported to dominate the electrical properties of honey and indicate its botanical and geographical origins. In this study, Electrochemical Impedance Spectroscopy (EIS) was used to assess the relation between mineral elements, electrical properties and botanical origin using three honey varieties - Citrus sp., Eucalyptus sp., and Erica sp. These varieties are identified through pollen analysis and market labelling. Flame atomic absorption and emission spectroscopies were used to quantify the concentrations of eight elements (potassium, sodium, calcium, magnesium, manganese, zinc, copper, and iron). Among all the mineral elements, potassium showed a consistent correlation with impedance. The potassium estimation in honey and standard solutions (calibration curve) had similar sensitivities of 153.43 nF/mM and 132.68 nF/mM, respectively. Additionally, the analysis revealed that potassium dominates the mineral composition, with the other species present in minimal quantities. The EIS technique showed high sensitivity to potassium and other ionisable species, making it possible to classify the botanical origin of these three honey types. The EIS technique proved to be both time and cost effective, yielding a classification rate higher than that achieved by analysing mineral composition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Molecularly imprinted polymers (MIPs) are synthetic receptors made by template-assisted synthesis. MIPs might be ideal receptors for sensing devices, given the possibility to custom-design selectivity and affinity toward a targeted analyte and their robustness and ability to withstand harsh conditions. However, the synthesis of MIP is an inherently random process that produces a statistical distribution of binding sites, characterized by a variety of affinities. This is verified both for bulk MIP materials and for MIP's thin layers. In the present work, we aimed at assessing the effects of inhomogeneous versus homogeneous imprinted binding sites on electrochemical sensing measurements, and the possible implications on the sensor's performance. In the example of an Electrochemical Impedance Spectroscopy (EIS) sensor for the 17β-estradiol (E2) hormone, the scenario of inhomogeneous binding sites was studied by modifying electrodes with an E2-MIP polyaniline (PANI) thin layer, called the "Imprinted PANI layer". In contrast, the condition of discrete and uniform binding sites was epitomized by electrodes modified with a thin PANI layer purposedly doped with E2-MIP nanoparticles (nanoMIPs), which were referred to as "nanoMIP-doped PANI". The behaviors of the two EIS sensors were compared. Interestingly, the sensitivity of the nanoMIP-doped PANI was almost twice with respect to that of the imprinted PANI layer, strongly suggesting that the homogeneity of the binding sites has a fundamental role in the sensor's development. The nanoMIP-doped PANI sensor, which showed a response for E2 in the range 36.7 pM-36.7 nM and had a limit of detection of 2.86 pg/mL, was used to determine E2 in wastewater.

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (C m ) at this interface with the gate voltage V gate ≈ 0.1 V follows approximate laws C m ~T 1.2 and C m ~T 0.11 (T is V gate period) in frequency ranges (1000-50,000) Hz and (0.02-300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (C int ) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (C m ) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (C dl ) and by the graphene quantum capacitance (C q ), and it also implies that C int is mostly charged. We have also found a voltage dependence of C m below 10 Hz, which is likely related to the voltage dependence of C q . The observation of this effect only at low frequencies indicates that C q relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges.

The rapid and sensitive detection of bacterial contaminants using low-cost and portable point-of-need (PoN) biosensors has gained significant interest in water quality monitoring. Cell-imprinted polymers (CIPs) are emerging as effective and inexpensive materials for bacterial detection as they provide specific binding sites designed to capture whole bacterial cells, especially when integrated into PoN microfluidic devices. However, improving the sensitivity and detection limits of these sensors remains challenging. In this study, we integrated CIP-functionalized stainless steel microwires (CIP-MWs) into a microfluidic device for the impedimetric detection of E. coli bacteria. The sensor featured two parallel microchannels with three-electrode configurations that allowed simultaneous control and electrochemical impedance spectroscopy (EIS) measurements. A CIP-MW and a non-imprinted polymer (NIP)-MW suspended perpendicular to the microchannels served as the working electrodes in the test and control channels, respectively. Electrochemical spectra were fitted with equivalent electrical circuits, and the charge transfer resistances of both cells were measured before and after incubation with target bacteria. The charge transfer resistance of the CIP-MWs after 30 min of incubation with bacteria was increased. By normalizing the change in charge transfer resistance and analyzing the dose-response curve for bacterial concentrations ranging from 0 to 10 7 CFU/mL, we determined the limits of detection and quantification as 2 × 10 2 CFU/mL and 1.4 × 10 4 CFU/mL, respectively. The sensor demonstrated a dynamic range of 10 2 to 10 7 CFU/mL, where bacterial counts were statistically distinguishable. The proposed sensor offers a sensitive, cost-effective, durable, and rapid solution for on-site identification of waterborne pathogens.

Crevice corrosion in modular taper junctions of hip or knee replacements using cobalt-chrome-molybdenum (CoCrMo) alloys remains a clinical concern. Non-mechanically-driven corrosion has been less explored compared to mechanically assisted crevice corrosion. This study hypothesized that solution chemistry within crevices, inflammation, and cathodic electrode potential shifts during fretting result in low pH and generate reactive oxygen species (ROS), affecting oxide film behavior. This study investigated how resistance and capacitance of the CoCrMo oxide film (i.e., corrosion resistance) are modified in simulated in vivo crevice environments of modular taper junctions. Six solutions were evaluated (two pH levels: 1 and 7.4 and four hydrogen peroxide (H 2 O 2 ) concentrations: 0, 0.001, 0.01 and 0.1 M). R p versus voltage and Mott-Schottky plots were created from symmetry-based electrochemical impedance spectroscopy (sbEIS). At pH 1, the semiconductor transition to p-type occurs at more anodic potentials and higher flat band potentials were found. H 2 O 2 decreased the flat band potential and slope in the Mott-Schottky plot. Higher H 2 O 2 in pH 7.4 solution significantly modified the oxide film, leading to increased donor density (p = 0.0004) and a 150-fold reduction in R p in the cathodic potential range at -1 V (p = 0.0005). The most unfavorable condition (0.1 M H 2 O 2 pH 1) resulted in a 250-fold lower resistance compared to phosphate buffered saline (PBS) pH 7.4 at -1 V (p = 0.0013). This study highlights the corrosion susceptibility of CoCrMo under adverse chemical and potential conditions, identifying increased defects in the oxide film due to ROS, hydrogen ions and electrode potential. STATEMENT OF SIGNIFICANCE: Corrosion of cobalt chrome molybdenum alloy caused by direct chemical attack in the crevice region of hip replacements, such as modular taper junctions, remains a clinical concern. The junction environment contains adverse chemical compositions, including high acidity and reactive oxygen species (ROS) due to inflammatory responses against the corrosion products. We simulate inflammatory environments with different pH levels and hydrogen peroxide, representative of ROS. We employ electrochemical impedance spectroscopy and apply stepwise voltage over the range induced by tribocorrosion processes. We relate the effect of adverse chemical components on corrosion and semiconducting behavior of the oxide film using Mott-Schottky analysis. This study shows how pH and ROS concentration compromises the oxide film potentially leading to non-mechanically induced corrosion., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jeremy L. Gilbert: Consultant for Smith and Nephew, Exactech, Naples Hospital. Research support to Clemson from The Food and Drug Administration, Bayer Inc, and Ceramtech. Owner, Syracuse Biomaterials Company, LLC. Editor-in-Chief of Journal of Biomedical Materials Research – Part B: Applied Biomaterials, J Wiley and Sons, and member of the council of Society For Biomaterials. Hwaran Lee and Mike A. Kurtz: no conflicts., (Copyright © 2024 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

In the present study the authors' main goal is to avoid the corrosive attack of the chloride ions of 3.5% NaCl solution in saline medium on the mild steel (MS), by addition of small amount of a new derivative of the hydrazide called ligand (HL), as a corrosion inhibitor. This study had been achieved by employing different electrochemical measurements such as, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP) methods. The results of the electrochemical test (OCP), showed that, the open circuit potential of the mild steel in saline solution, was guided to more positive direction in presence of the ligand (HL), at its ideal concentration (1 × 10 -3  M), compared to the (OCP), of the mild steel in absence of (HL). The results of the electrochemical methods, EIS and PDP presented that, the ligand (HL), was acted as a good corrosion inhibitor for hindering the corrosion process of the mild steel in 3.5% sodium chloride, as it was recorded a good percentage of the inhibition efficiency (77.45%, 53.41%, by EIS and PDP techniques respectively), at its optimum concentration (1 × 10 -3  M). Also, the corrosion rate of the mild steel in the saline medium without (HL), was listed about (0.0017 mm/year), while in existence of (HL), was decreased to a value about (0.00061 mm/year). As well, some of electrical properties of (HL), and its derivative [Pd(II), Cr(III), and Ru(III)], complexes were investigated such as; the activation energy (E a(ac) ), which recorded values in the range of 0.02-0.44 (eV) range and electrical conductivity which listed values at room temperature in the range of 10 -5 -10 -8  S.cm -1 . The results of the AC and DC electrical conductivity measurements for (HL), and its derivative [Pd(II), Cr(III) and Ru(III)] complexes indicate semiconducting nature which suggests that these compounds could be used in electronic devices. Also, the complexes exhibited higher conductivity values than (HL). Photophysical studies showed good florescence properties of HL that indicated that it can be used to determine most of the drugs with no fluorescence properties by quenching and calculating quantum yield. Moreover, the hydrazide ligand (HL), has shown selectivity as an active anticancer candidate drug for both breast and colon cancer in humans. Density function theory demonstrated that, the frontier molecular orbital HOMOs of the complexes have exhibited similar behavior and the charge density has localized in the metallic region of all the studied complexes. Also, the values of the energy gap of the ligand (HL), and its complexes Pd(II), Cr(III) and Ru(III), had been arranged in this order HL > Cr(III) > Ru(III) > Pd(II). All characterization using different spectroscopic techniques were reported to elucidate the proposed structures such as; thermal analysis, elemental analysis of C, H, and N atoms, spectral analysis using IR, UV, 1 H NMR techniques, scanning electron microscopy and energy dispersive X-ray analyses., (© 2024. The Author(s).)

The future development of advanced molecular systems with controlled rotation requires the development of an effective methodology for assessing the rotational performance of artificial machine components. We identified two patterns of the dielectric behavior for polar rotators in a static non-polar framework of sizable crystal showing relations between the spectral and molecular-level features of solid-state rotary motion. Various functionalization of phenylene rotors with a fluorine atom(s) changed rotational performance from high to low with rotational barriers ranging from 6.06 to 11.84 kcal mol -1 . The meta-F-substitution favored rotator-rotator contacts allowing for the implementation of fast rotary motion. Contrary, the presence of rotator-stator contacts inhibited independent rotator dynamics leading to opposite spectral behavior in terms of temperature evolution of loss peak amplitude. Our observations, supported by an analysis based on an asymmetric double well-potential model, show that easily noticeable spectral differences encoded some molecular-level information important for the implementation of rotary motion., (Creative Commons Attribution license.)

Protein-surfactant interaction is a dynamic interplay of electrostatic and hydrophobic forces that ensues from the folding of a protein. We employ impedance spectroscopy (IS), a label-free method, to investigate the unfolding and refolding of human serum albumin (HSA), a globular plasma protein, in the presence of two surfactants: polysorbate-20 (Tween-20), a nonionic surfactant, and sodium dodecyl sulfate (SDS), an anionic surfactant. The equivalent electrical analog circuit was predicted from impedance spectra of HSA in an aqueous solution at physiological pH and room temperature, focusing on varying the concentration of codissolved surfactants. A change in the dielectric constant (ε ' ) and ionic conductivity (κ) is observed by comparing the surfactant-treated protein samples to the bare surfactant solutions to assess the conformational changes induced by surfactants in HSA. Far-UV circular dichroism analysis revealed a decrease in α-helices and an increase in β-sheets and random coils upon SDS addition, which were reversed by Tween-20. Dynamic light scattering supported the findings by measuring changes in the hydrodynamic diameter ( d h ) of HSA. Unfolding and refolding of HSA with surfactants were also observed through photoluminescence spectroscopy by examining the microenvironment surrounding the single tryptophan ( W ) within the protein, and the thermodynamic parameters were obtained using the modified Stern-Volmer equation. Our research explores the intriguing domain of protein-surfactant interactions, offering insights with promising applications across diverse biological processes and IS as a suitable alternative technique for investigating protein conformational changes by studying the electrical response of the samples.

Microbioreactors increase information output in biopharmaceutical screening applications because they can be operated in parallel without consuming large quantities of the pharmaceutical formulations being tested. A capillary wave microbioreactor (cwMBR) has recently been reported, allowing cost-efficient parallelization in an array that can be activated for mixing as a whole. Although impedance spectroscopy can directly distinguish between dead and viable cells, the monitoring of cells in suspension within bioreactors is challenging because the signal is influenced by the potentially varying properties of the culture medium. In order to address this challenge, an impedance sensor consisting of two sets of microelectrodes in a cwMBR is presented. Only one set of electrodes was covered by a two-photon cross-linked hydrogel to become insensitive to the influence of cells while remaining sensitive to the culture medium. With this impedance sensor, the biomass of Saccharomyces cerevisiae could be measured in a range from 1 to 20 g L -1 . In addition, the sensor can compensate for a change in the conductivity of the suspension of 5 to 15 mS cm -1 . Moreover, the two-photon cross-linking of hydroxyethyl starch methacrylate hydrogel, which has been studied in detail, recommends itself for even much broader sensing applications in miniaturized bioreactors and biosensors.

Background: Fluid overload (FO) subjects patients with severe aortic stenosis (AS) to increased risk for heart failure and death after valve replacement and can be objectively quantified using bioimpedance spectroscopy (BIS)., Objectives: The authors hypothesized that in AS patients with concomitant FO, BIS-guided decongestion could improve prognosis and quality of life following transcatheter aortic valve replacement (TAVR)., Methods: This randomized, controlled trial enrolled 232 patients with severe AS scheduled for TAVR. FO was defined using a portable whole-body BIS device according to previously established cutoffs (≥1.0 L and/or ≥7%). Patients with FO (n = 111) were randomly assigned 1:1 to receive BIS-guided decongestion (n = 55) or decongestion by clinical judgment alone (n = 56) following TAVR. Patients without FO (n = 121) served as a control cohort. The primary endpoint was the composite of hospitalization for heart failure and/or all-cause death at 12 months. The secondary endpoint was the change from baseline to 12 months in the Kansas City Cardiomyopathy Questionnaire., Results: The occurrence of the primary endpoint at 12 months was significantly lower in the BIS-guided vs the non-BIS-guided decongestion group (7/55 [12.7%, all deaths] vs 18/56 [32.1%, 9 hospitalizations for heart failure and 9 deaths]; HR: 0.36; 95% CI: 0.15-0.87; absolute risk reduction = -19.4%). Outcomes in the BIS-guided decongestion group were identical to the euvolemic control group (log-rank test, P = 0.7). BIS-guided decongestion was also associated with a higher increase in the Kansas City Cardiomyopathy Questionnaire score from baseline compared to non-BIS-guided decongestion (P = 0.001)., Conclusions: In patients with severe AS and concomitant FO, quantitatively guided decongestive treatment and associated intensified management post-TAVR was associated with improved outcomes and quality of life compared to decongestion by clinical judgment alone. (Management of Fluid Overload in Patients Scheduled for Transcatheter Aortic Valve Replacement [EASE-TAVR]; NCT04556123)., Competing Interests: Funding Support and Author Disclosures This study was supported by the Austrian Society of Cardiology. Dr Dannenberg has received consulting fees from Abbott; and has received educational grants from Edwards Lifesciences. Dr Kammerlander has received speaker fees from Bayer and Boehringer Ingelheim; has received advisory board honoraria from Boehringer Ingelheim; and has received research grants from Pfizer. Dr Hengstenberg has received proctoring/speaker fees from Boston Scientific and Edwards Lifesciences; and has received institutional research grants from Abbott, Boston Scientific, Edwards Lifesciences, and Medtronic). Dr Mascherbauer has received proctor fees from Abbott and Edwards Lifesciences; has received consulting fees from Boston Scientific, Edwards Lifesciences, and Shockwave Medical; and has received educational grants from Abbott, Boston Scientific, and Edwards Lifesciences. Dr Nitsche has received speaker fees/institutional research grants from Pfizer; and has received advisory board honoraria from Prothena). All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The rapid and accurate detection of SARS-CoV-2, particularly its spike receptor-binding domain (S-RBD), was crucial for managing the COVID-19 pandemic. This study presents the development and optimization of two types of aptasensors: quartz crystal microbalance (QCM) and electrochemical sensors, both employing thiol-modified DNA aptamers for S-RBD detection. The QCM aptasensor demonstrated exceptional sensitivity, achieved by optimizing aptamer concentration, buffer composition, and pre-treatment conditions, with a limit of detection (LOD) of 0.07 pg/mL and a linear range from 1 pg/mL to 0.1 µg/mL, and a significant frequency change was observed upon target binding. The electrochemical aptasensor, designed for rapid and efficient preparation, utilized a one-step modification process that reduced the preparation time to 2 h while maintaining high sensitivity and specificity. Electrochemical impedance spectroscopy (EIS) enabled the detection of S-RBD concentrations as low as 132 ng/mL. Both sensors exhibited high specificity, with negligible non-specific interactions observed in the presence of competing proteins. Additionally, the QCM aptasensor's functionality and stability were verified in biological fluids, indicating its potential for real-world applications. This study highlights the comparative advantages of QCM and electrochemical aptasensors in terms of preparation time, sensitivity, and specificity, offering valuable insights for the development of rapid, sensitive, and specific diagnostic tools for the detection of SARS-CoV-2 and other viruses.

Human activity is the cause of the continuous and gradual grooving of environmental contaminants, where some released toxic and dangerous compounds cannot be degraded under natural conditions, resulting in a serious safety issue. Among them are the widely occurring water-soluble perfluoroalkyl and polyfluoroalkyl substances (PFAS), sometimes called "forever chemicals" because of the impossibility of their natural degradation. Hence, a reliable, expressive, and simple method should be developed to monitor and eliminate the risks associated with these compounds. In this study, we propose a simple, express, and portable detection method for water-soluble fluoro-alkyl compounds (PFOA and GenX) using mutually complementary methods: electrochemical impedance spectroscopy (EIS) and surface-enhanced Raman spectroscopy (SERS). To implement our method, we developed special substrates based on porous silicon with a top-deposited plasmon-active Au layer by subsequently grafting -C 6 H 4 -NH 2 chemical moieties to provide surface affinity toward negatively charged water-soluble PFAS. Subsequent EIS utilization allows us to perform semiquantitative detection of PFOA and GenX up to 10 -10  M concentration because surface entrapping of PFAS leads to a significant increase in the electrode-electrolyte charge-transfer resistance. However, distinguishing by EIS whether even PFAS were entrapped was impossible, and thus the substrates were subsequently subjected to SERS measurements (allowed by surface plasmon activity due to the presence of a porous Au layer), clearly indicating the appearance of characteristic C-F vibration bands., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Our research addresses the pressing need for environmental sensors capable of large-scale, on-site detection of a wide array of heavy metals with highly accurate sensor metrics. We present a novel approach using electrochemically polished (ECP) carbon screen-printed electrodes (cSPEs) for high-sensitivity detection of cadmium and lead. By applying a range of techniques, including scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, we investigated the impact of the electrochemical potential scan range, scan rate, and the number of cycles on electrode response and its ability to detect cadmium and lead. Our findings reveal a 41 ± 1.2% increase in voltammogram currents and a 51 ± 1.6% decrease in potential separations ( n = 3), indicating a significantly improved active electrode area and kinetics. The impedance model elucidates the microstructural and electrochemical property changes in the ECP-treated electrodes, showing an 88 ± 2% ( n = 3) decrease in the charge transfer resistance, leading to enhanced electrode electrical conductivity. A bismuth-reduced graphene oxide nanocomposite-modified, ECP-treated electrode demonstrated a higher cadmium and lead sensitivity of up to 5 ± 0.1 μAppb -1 cm -2 and 2.7 ± 0.1 μAppb -1 cm -2 ( n = 3), respectively, resulting in sub-ppb limits of detection in spiked deionized water samples. Our study underscores the potential of optimally ECP-activated electrodes as a foundation for designing ultrasensitive heavy metal sensors for a wide range of real-world heavy metal-contaminated waters.

Recently, various biosensors based on odorant-binding proteins (OBPs) were developed for the detection of odorants and pheromones. However, important data gaps exist regarding the sensitive and selective detection of aldehydes with various carbon numbers. In this work, an OBP2a-based electrochemical impedance spectroscopy (EIS) biosensor was developed by immobilizing OBP2a on a gold interdigital electrode, and was characterized by EIS and atomic force microscopy. EIS responses showed the OBP2a-based biosensor was highly sensitive to citronellal, lily aldehyde, octanal, and decanal (detection limit of 10 -11  mol/L), and was selective towards aldehydes compared with interfering odorants such as small-molecule alcohols and fatty acids (selectivity coefficients lower than 0.15). Moreover, the OBP2a-based biosensor exhibited high repeatability (relative standard deviation: 1.6%-9.1 %, n = 3 for each odorant), stability (NIC declined by 3.6 % on 6th day), and recovery (91.2%-96.6 % on three real samples). More specifically, the sensitivity of the biosensor to aldehydes was positively correlated to the molecular weight and the heterocyclic molecule structure of the odorants. These results proved the availability and the potential usage of the OBP2a-based EIS biosensor for the rapid and sensitive detection of aldehydes in aspects such as medical diagnostics, food and favor analysis, and environmental monitoring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Campylobacter jejuni is a common foodborne pathogen found in poultry that can cause severe life-threatening illnesses in humans. It is important to detect this pathogen in food to manage foodborne outbreaks. This study reports a novel impedimetric phage protein-based biosensor to detect C. jejuni NCTC 11168 at 100 CFU/mL concentrations using a genetically engineered receptor-binding phage protein, FlaGrab, as a bioreceptor. The electrochemical impedance spectroscopy (EIS) technique was employed to measure changes in resistance upon interaction with C. jejuni . The sensitivity of the phage protein-immobilized electrode was assessed using the various concentrations of C. jejuni NCTC 11168 ranging from 10 2 -10 9 colony forming units (CFU)/mL). The change transfer resistance of the biosensor increased with increasing numbers of C. jejuni NCTC 11168 cells. The detection limit was determined to be approximately 10 3 CFU/mL in the buffer and 10 2 CFU/mL in the ex vivo samples. Salmonella enterica subsp. enterica serotype Typhimurium-291RH and Listeria monocytogenes Scott A were used as nontarget bacterial cells to assess the specificity of the developed biosensor. Results showed that the developed biosensor was highly specific toward the target C. jejuni NCTC 11168, as no signal was observed for the nontarget bacterial cells.

Microbiologically Influenced Corrosion (MIC) poses a significant challenge to various industries, leading to substantial economic losses and potential safety hazards. Despite extensive research on the MIC resistance of various materials, there is a lack of studies focusing on High Chromium White Iron (HCWI) alloys, which are widely used in wear-resistant applications. This study addresses this knowledge gap by providing a comprehensive investigation of the MIC resistance of three HCWI alloys with varying chromium contents (22 wt%, 30.7 wt%, and 21 wt%) in the presence of Pseudomonas aeruginosa (P. Aeruginosa), a common bacterial species associated with MIC. The alloys were exposed to an artificial seawater medium inoculated with P.Aeruginosa for 14 days, and their corrosion behaviour was evaluated using electrochemical techniques, surface analysis, and microscopy. Electrochemical Impedance Spectroscopy (EIS) results revealed that the alloy with the highest chromium content (A2, 30.7 wt% Cr) exhibited superior MIC resistance compared to the other alloys (A1, 22 wt% Cr and M1, 21 wt% Cr). The enhanced performance of alloy A2 was attributed to the formation of a more stable and protective passive film, as well as the development of a more compact and less permeable biofilm. The EIS data, interpreted using equivalent circuit models, showed that alloy A2 had the highest charge transfer resistance and the lowest biofilm capacitance, indicating a more effective barrier against corrosive species. Bode plots further confirmed the superior corrosion resistance of alloy A2, with higher impedance values and phase angles at low frequencies compared to alloys A1 and M1. Scanning Electron Microscopy (SEM) and optical microscopy analyses corroborated these findings, showing that alloy A2 had the lowest pit density and size after 14 days of exposure. The insights gained from this study highlight the critical role of chromium content in the MIC resistance of HCWI alloys and have significant implications for the design and selection of materials for applications prone to microbial corrosion., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Tan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Technological development of microwave treatment and detection techniques for lung cancer requires accurate and comprehensive knowledge of the microwave dielectric properties of human lung tissue. We characterize the dielectric properties of room temperature human lung tissue from 0.5 to 10 GHz for three lung tissue groups: normal, fibroelastotic, and malignant. We fit a two-pole Debye model to the measured frequency-dependent complex permittivity and calculate the median Debye parameters for the three groups. We find that malignant lung tissue is approximately 10% higher in relative permittivity and conductivity compared to normal lung tissue; this trend matches previously reported normal versus malignant data for other biological tissues. There is little contrast between benign lung tissue with fibroelastosis and malignant lung tissue. We extrapolate our data from room temperature to 37 °C using a temperature-dependence model for animal lung tissue and use the Maxwell-Garnett dielectric mixing model to predict the dielectric properties of inflation-dynamic human lung tissue; both approximations correspond with previously reported dielectric data of bovine and porcine lung tissue., (Creative Commons Attribution license.)

In this research, we investigate the impact of varying machining parameters [depth of cutting (mm) and spindle rotation speed (rpm)] on the microstructure and electrochemical behavior of Ti6Al4V-ELI dental implants. This comprehensive study employs an approach, leveraging potentiodynamic methods and electrochemical impedance spectroscopy, to analyze corrosion behavior in a phosphate-buffered saline solution. To further deepen our understanding of corrosion kinetics, we used an alternating current circuit model, based on a simple Randles equivalent circuit. This model elucidates the corrosion interface interactions of the Ti6Al4-V-ELI alloy implant within the PBS solution. In addition, our research delves into the microstructural implications of different machining parameters, utilizing scanning electron microscopy and X-ray diffraction (XRD) techniques to reveal significant phase changes. The changes in texture were examined qualitatively by comparing the intensities of the peaks of the XRD pattern. A detailed correlation analysis further links the machining parameters with the corrosion properties of dental implants, offering a comprehensive perspective rarely explored in the existing literature. The results obtained for the three samples showed that the corrosion resistance would be higher by increasing the machining depth and the spindle rotation and that the corrosion current would be lower. As a result, a lower corrosion rate was obtained. Finally, experimental results from electrochemical analyses are compared and discussed.

Recent advancements in polymer science and manufacturing technologies triggered new developments of porous materials used for mitigating heat losses, such as thermal insulating polymeric foams. The major bottleneck in the optimization of these products, however, remains the absence of analytical methods able to scrutinize their large design space reasonably quickly and cost-effectively. This manuscript targets the paucity of data for polymeric foams by illustrating, at a proof-of-principle level, that several well-established analytical methods including optical microscopy, pycnometry, dielectric spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance can be exploited for an extensive, yet logistically efficient, characterization of these materials. The purpose of this study is thus introducing an experimental platform for the characterization of market foam products and for the development of new polymeric foams with pore sizes that are particularly relevant for industrial and residential thermal insulation. Since this work introduces several new methodologies, it may be used as a guide for both laboratory users and specialists in the field, who may further improve the herein proposed experimental concepts., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Catalin Gainaru reports financial support was provided by US Department of Energy. S. Shrestha reports financial support was provided by US Department of Energy. A. Tamraparni reports financial support was provided by US Department of Energy. D. Howard reports financial support was provided by US Department of Energy. T. Saito reports financial support was provided by US Department of Energy. D. Hun reports financial support was provided by US Department of Energy. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

Additively manufactured (AM) Ti-6Al-4V devices are implanted with increasing frequency. While registry data report short-term success, a gap persists in our understanding of long-term AM Ti-6Al-4V corrosion behavior. Retrieval studies document β phase selective dissolution on conventionally manufactured Ti-6Al-4V devices. Researchers reproduce this damage in vitro by combining negative potentials (cathodic activation) and inflammatory simulating solutions (H 2 O 2 -phosphate buffered saline). In this study, we investigate the effects of these adverse electrochemical conditions on AM Ti-6Al-4V impedance and selective dissolution. We hypothesize that cathodic activation and H 2 O 2 solution will degrade the oxide, promoting corrosion. First, we characterized AM Ti-6Al-4V samples before and after a 48 h -0.4 V hold in 0.1 M H 2 O 2 /phosphate buffered saline. Next, we acquired nearfield electrochemical impedance spectroscopy (EIS) data. Finally, we captured micrographs and EIS during dissolution. Throughout, we used AM Ti-29Nb-21Zr as a comparison. After 48 h, AM Ti-6Al-4V selectively dissolved. Ti-29Nb-21Zr visually corroded less. Structural changes at the AM Ti-6Al-4V oxide interface manifested as property changes to the impedance. After dissolution, the log-adjusted constant phase element (CPE) parameter, Q, significantly increased from -4.75 to -3.84 (Scm -2 (s) α ) (p = .000). The CPE exponent, α, significantly decreased from .90 to .84 (p = .000). Next, we documented a systematic decrease in oxide polarization resistance before pit nucleation and growth. Last, using k-means clustering, we established a structure-property relationship between impedance and the surface's dissolution state. These results suggest that AM Ti-6Al-4V may be susceptible to in vivo crevice corrosion within modular taper junctions., (© 2023 The Authors. Journal of Biomedical Materials Research Part A published by Wiley Periodicals LLC.)

Intense use of microbial cells in biotechnological production requires rapid methods to monitor bacterial growth online and analyze the regulation of microbial metabolic activity. Some details of metabolic activity are examined conventionally, by changing the concentration of nutrient medium components, the concentration of metabolites, the pH, the respiratory activity, and other variables. In this case, the set of variables used may turn out insufficient and a number of critical points of the control process will remain in the shadow. The enzymatic catalysis in the bacterial cell is accompanied by a redistribution of charges inside the cell and, therefore, may lead to a change in its electrophysical characteristics. Ideally, researchers should use structurally intact and metabolically undisturbed growing cells to fully understand the enzymatic processes in microbes. Electrophysical analysis, based on the study of cells as electrophysical objects and on the measurement of their polarization characteristics, is a new approach to assessing the intravital physiological variables of cells and their heterogeneity. This article describes the theoretical principles of electrophysical analysis of bacteria and shows the possibilities of methods for examining the metabolic status of bacteria.

Dielectric properties and structure of initial nanocomposite based on porous glass with embedded ferroelectric NaNO2 and nanocomposite identical to that but having a TiO2-modified pore surface, have been studied over a temperature range 300 – 450 K (on cooling) and frequency one 0.1 – 3∙106 Hz. X-ray spectroscopy of the samples exhibited that NaNO2 was in the ferroelectric phase in both composites and the percentage of crystalline NaNO2 increased in the pores of the modified one. An increase in permittivity and conductivity was observed in the TiO2-modified nanocomposite. Two relaxation processes were identified and their nature was established. The charge polarization at the interfaces was found to make the main contribution to the dielectric response of the both nanocomposites. The DC-conductivity of both composites was estimated and its activation energies were determined. An activation energy change observed in a vicinity of 400 K was attributed to the phase transition to the low-temperature phase of NaNO2. The possibility to control the properties of nanocomposites through modifying the interfaces was shown.

This paper studies the dielectric spectra of solid solutions (SS) of the system (1 − x − y)NaNbO3–[Formula: see text]KNbO3 –[Formula: see text]CdNb2O6 [Formula: see text]= 0.075, [Formula: see text]= 0.05 ÷ 0.30 in the temperature range (10 ÷ 900) K. The formation of a local maximum was established in the interval (260 ÷ 300) K at small [Formula: see text] values, which, as KNbO3 increases, is gradually blurred and becomes an inflection point. Detected in SS with [Formula: see text] = 0.05 ÷ 0.10, the shift of the maxima of dependences [Formula: see text]′/ [Formula: see text]0([Formula: see text]) and [Formula: see text]′′/[Formula: see text]0 ([Formula: see text]), depending on the frequency of the electric field at the temperature ranges (300 ÷ 304) K and (258 ÷ 271) K, is not related to relaxation. This anomaly may indicate a crystallographic disorder to A and B positions. The conclusion is made about the expediency of using the obtained results for the development of functional ferroactive materials.

Flame-resistant polymer composites were prepared based on polyvinyl alcohol (PVA) as a polymer matrix and a polyphosphonate as flame retardant. Oxalic acid was used as crosslinking agent. LiClO4, BaTiO3, and graphene oxide were also incorporated into PVA matrix to increase the ionic conductivity. The obtained film composites were investigated by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and microscale combustion tests. Incorporating fire retardant (PFRV), BaTiO3, and graphene oxide (GO) into a material results in increased resistance to fire when compared to the control sample. A thermogravimetric analysis revealed that, as a general trend, the presence of PFRV and BaTiO3 nanoparticles enhances the residue quantity at a temperature of 700 °C from 7.9 wt% to 23.6 wt%. Their dielectric properties were evaluated with Broad Band Dielectric Spectroscopy. The electrical conductivity of the samples was determined and discussed in relation to the LiClO4 content. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. Out of the various composites tested, the composite containing 35 wt% of LiClO4 exhibits the highest alternating current (AC) conductivity, with a measured value of 2.46 × 10−3 S/m. Taking into consideration all the aspects discussed, these improved composites are intended for utilization in the manufacturing of Li-Ion batteries.

Nematic–nematic transitions in a highly polar nematic compound are studied, in thick cells in which the molecules are aligned parallel to the substrates but perpendicular to the applied electric field, using dielectric spectroscopy in the frequency range 1 Hz to 10 MHz over a wide temperature range. The studied compound displays three nematic phases under cooling from the isotropic phase: ubiquitous nematic N; high polarizability NX; and ferroelectric nematic NF. Two collective processes were observed. The dielectric strength and relaxation frequency of one of the processes P2 showed a dependence on the thickness of the cell. The process P1 is the amplitude mode, while the process P2 is the phason mode.

Two neutral copper(I) halide complexes ([Cu(BTU)2X], X = Cl, Br) were prepared by the reduction of the corresponding copper(II) halides (chloride or bromide) with a benzoylthiourea (BTU, N-(3,4-diheptyloxybenzoyl)-N′-(4-heptadecafluorooctylphenyl)thiourea) ligand in ethanol. The two copper(I) complexes show a very interesting combination of 2D supramolecular structures, liquid crystalline, emission, and 1D ionic conduction properties. Their chemical structure was ascribed based on ESI–MS, elemental analysis, IR, and NMR spectroscopies (1H and 13C), while the mesomorphic behavior was analyzed through a combination of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and powder X-ray diffraction (XRD). These new copper(I) complexes have mesomorphic properties and exhibit a hexagonal columnar mesophase over a large temperature range, more than 100 K, as evidenced by DSC studies and POM observations. The thermogravimetric analysis (TG) indicated a very good thermal stability of these samples up to the isotropization temperatures and over the whole temperature range of the liquid crystalline phase existence. Both complexes displayed a solid-state emission with quantum yields up to 8% at ambient temperature. The electrical properties of the new metallomesogens were investigated by variable temperature dielectric spectroscopy over the entire temperature range of the liquid crystalline phase. It was found that the liquid crystal phases favoured anhydrous proton conduction provided by the hydrogen-bonding networks formed by the NH…X moieties (X = halide or oxygen) of the benzoylthiourea ligand in the copper(I) complexes. A proton conductivity of 2.97 × 10−7 S·cm−1 was achieved at 430 K for the chloro-complex and 1.37 × 10−6 S·cm−1 at 440K for the related bromo-complex.

Rapeseed is one of the most important sources of vegetable oil worldwide. Knowledge of the dielectric properties of rapeseed may be beneficial for moisture content determination and the optimization of microwave treatment processes. The aim of this research was to examine the complex dielectric permittivity spectra of rapeseed of moisture content from 8.3% to 16.1%. The measurements were performed in the 20 MHz–3 GHz frequency range with the use of a vector network analyzer and a coaxial transmission-line cell. The real part of dielectric permittivity significantly depended on the water content of the seeds. The obtained spectra were modeled with the use of a three-pole Debye model with bulk electrical conductivity. Because the highest-frequency pole was found near the high-frequency measurement band limit, the spectra were additionally modeled with the use of an approximate ABC model with two in-band Debye poles. The determined model parameters were found to be highly dependent on the water content of the seeds. The relations between these parameters and water content were analyzed. [ABSTRACT FROM AUTHOR]

Measurement of the complex permittivity of a substance in a wide frequency range, for example, from 10 mHz to 100 kHz, provides useful information on the dielectric properties of the substance. In this regard, some of such dielectric properties can be analyzed more clearly if we pay attention to the frequency spectra of electric modulus, which is a reciprocal of complex relative permittivity. Especially, the imaginary part of the electric modulus can be a powerful tool for dielectric materials research. In this paper, this fact is demonstrated clearly by showing abundant examples acquired by the author's laboratory. First, the equations of electric modulus that hold for various dielectric relaxation processes, including their derivation, are shown in an easy‐to‐understand manner. After that, for several insulating polymers, actual measurement examples of broadband complex permittivity spectra are shown, up to frequencies of about 100 kHz and a much broader range up to several THz. In the first example of showing permittivity spectra, polyamide exhibits an incredibly high relative permittivity value of 106 at high temperatures such as 200 °C at a frequency as low as 10 mHz. This is a result of the phenomenon often called electrode polarization. In other words, if electric charge carriers accumulate in an insulator facing a nearby electrode and have the polarity opposite to that of the electrode, the permittivity of the insulator goes up. In such a case, the dielectric loss factor usually shows a very high value in the low‐frequency range and decreases in inverse proportion to the frequency. This reflects the fact that the charge carriers are transported, and the conductivity can be derived from this frequency dependence much more easily with apparently higher reliability than measuring the dc leakage current. Furthermore, it is shown that the coefficient of thermal expansion can be estimated from the permittivity spectra relatively accurately for several polymers that satisfy the necessary condition. Next, taking examples in electric modulus spectra measured in important insulating polymers such as engineering ones, it is demonstrated that the processes of dielectric polarization and relaxation, which are difficult to see in permittivity spectra, can be recognized obviously. Moreover, the effects of the addition of nanosized or microsized fillers to epoxy resin on its thermal property and filler‐induced inhomogeneity are analyzed using the electric modulus spectra measured in these samples. The effects of thermal aging treatment and simultaneous aging treatment with heat and radiation on the degradation of cross‐linked polyethylene are also analyzed by paying attention to the frequency spectra of its imaginary electric modulus. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The molecular dynamics of two addition type polynorbornenes, exo‐PNBSi and PTCNSi1, bearing microporosity has been investigated by broadband dielectric spectroscopy, fast scanning calorimetry, and neutron scattering. Both polymers have the same side groups but different backbones. Due to their favorable transport properties, these polymers have potential applications in separation membranes for gases. It is established in literature that molecular fluctuations are important for the diffusion of small molecules through polymers. For exo‐PNBSi, two dielectric processes are observed, which are assigned to Maxwell/Wagner/Sillars (MWS) process due to blocking of charge carriers at internal voids or pore walls. For PTCNSi1, one MWS‐polarization process is found. This points to a bimodal pore‐size distribution for exo‐PNBSi. A glass transition for exo‐PNBSi and for PTCNSi1 could be evidenced for the first time using fast scanning calorimetry. For Tg and the corresponding apparent activation energy, higher values were found for PTCNSi1 compared to exo‐PNBSi. For both polymers, the neutron scattering data reveal one relaxation process. This process is mainly assigned to methyl group rotation probably overlayed by carbon–carbon torsional fluctuations. [ABSTRACT FROM AUTHOR]

This paper describes a novel dielectric spectroscopic technique to investigate the milk freshness and adulterated agents using a customized, open-ended, coaxial probe. An inversely proportional relationship was found between temperature and shelf-life and the real part of the complex permittivity (e') of the samples at 0.1-3GHz. At 2GHz, a linear relationship was found in e' and e", storage time, and water content. In addition, total of five adulterants' agents were investigated and a linear relationship was found between both e' and e" parts, and their concentrations (R² > 0.99). This approach could be the potential basis of rapid online milk quality monitoring in milk production facilities. [ABSTRACT FROM AUTHOR]

The influence of various types of nanoparticle fillers with the same diameter of 20 nm were separately incorporated into a single component impregnating resin based on a polyesterimide (PEI) matrix and its subsequent changes in complex relative permittivity were studied. In this paper, nanoparticles of Al 2 O 3 and ZnO were dispersed into PEI (with 0.5 and 1 wt.%) to prepare nanocomposite polymer. Dielectric frequency spectroscopy was used to measure the dependence of the real and imaginary parts of complex relative permittivity within the frequency range of 1 mHz to 1 MHz at a temperature range from +20 °C to +120 °C. The presence of weight concentration of nanoparticles in the PEI resin has an impact on the segmental dynamics of the polymer chain and changed the charge distribution in the given system. The changes detected in the 1 H NMR spectra confirm that dispersed nanoparticles in PEI lead to the formation of loose structures, which results in higher polymer chain mobility. A shift of the local relaxation peaks, corresponding to the α -relaxation process, and higher mobility of the polymer chains in the spectra of imaginary permittivity of the investigated nanocomposites was observed. [ABSTRACT FROM AUTHOR]

In the dielectric spectroscopy of aqueous systems containing ions, the dielectric loss spectrum is affected by the contribution of the direct current (DC) conductivity σ, which sometimes significantly overlaps the dielectric relaxations related to the slow dynamics of water molecules distributing in sub-GHz frequency range. We have demonstrated a practical procedure based on the Kramersâ€"Kronig (KK) relations to exclude the contribution of DC conductivity from the experimentally obtained dielectric spectrum. Examples of the KK transform for the spectrum of ultrapure water and aqueous solution of protein (lysozyme) showed the feasibility of our method. [ABSTRACT FROM AUTHOR]

Determining the aging state of low-voltage nuclear power plant cables using a nondestructive and reliable condition monitoring technique is highly desirable as the cables experience multiple aging stresses during the service period. This paper deals with the implementation and investigation of such nondestructive techniques, which can detect the overall aging state of low-voltage instrumentation and control (I&C) cables, which are subjected to accelerated thermal aging. The dielectric spectroscopy, extended voltage response, and polarization–depolarization current as nondestructive electrical aging techniques were used for the investigation purpose, while the elongation at break was also adopted as a mechanical measurement and for comparison. Prominent variations in the electrical parameters for the insulation and jacket were observed, whereas the elongation at break for both materials also decreased under thermal aging. Based on the electrical techniques, aging markers were selected that showed a strong correlation with the aging and elongation at break, proving the ability of the adopted electrical methods as a nondestructive condition monitoring technique. [ABSTRACT FROM AUTHOR]

A procedure was developed for fractionating P-2 food-grade wax to obtain a close-cut component with increased content of С20–24n-alkanes. The wax fractionation was performed by centrifugation of its hexane solutions. An SL/8R programmable refrigerator centrifuge ensuring the relative centrifugal acceleration of 12 108g in the temperature interval from 40 to –10°C was used. At low temperatures, high-melting wax components were separated in the form of a precipitate in rotor test tubes. Low-melting components, including С20–24n-alkanes, were concentrated in hexane in the form of a solution. In the course of centrifugation, low-melting wax components became also enriched in isoparaffin and paraffin–naphthene hydrocarbons. The wax fractionation efficiency was evaluated by gas–liquid chromatography and by dielectric and IR spectroscopy. The optimum conditions of wax centrifugation from its hexane solutions were determined: relative centrifugal acceleration 12 108g and dilution of P-2 wax with the solvent in 2 : 1 to 4 : 1 weight ratio. The optimum centrifugation temperature is 5–9°С. Under these conditions, the content of С20–24n-alkanes in the low-melting fractions relative to the initial wax increases from 27.7 to 43.6–47.6 wt % at a yield of up to 45.5–66.0 wt %. The low-melting wax component, in contrast to the initial P-2 wax and high-melting wax component, does not contain a doublet in the IR spectrum at 728 cm–1. A correlation equation relating the variation of the dielectric permittivity Δε of the waxes with temperature, Δε/Δt, in the region of their crystallization, Δt, to the hydrocarbon composition of P-2 wax and its fractions was obtained: Δε/Δt = 0.0009(C11+/∑(СIP + СPN) + 0.0065) (R2 = 0.909). The values of Δ?/?t and hence the performance of paraffins in the low-temperature region of their active expansion is the higher, the higher is their total Cε/Δt and hence the performance of paraffins in the low-temperature region of their active expansion is the higher, the higher is their total C11+n-alkane content and the lower is the content of crystallizing isoparaffin and paraffin–naphthene hydrocarbons ∑(СIP + СPN). [ABSTRACT FROM AUTHOR]

Broadband dielectric spectroscopy (BDS) was applied to study polarization phenomena in alkaline silicate glasses, in particular, properties and structure of subsurface (anodic) polarized layers forming in poling with deposited film electrodes of different structures. A model of poled glasses which does not contradict experimental data is proposed. In accordance with the model, a poled glass is presented as two resistor‐capacitor circuits in a series connection, one of which is the polarized layer and another is the rest of the sample. It is found that the electric properties of the layers essentially depend on the structure of the anodic electrode used in glass poling. It is also shown that the dielectric response of poled glass samples is mainly determined by the electric properties of the submicron polarized layers and this gives an opportunity to reveal specific properties of the layers rather than ones of the glass sample bulk. Revealed temperature dependence of DC conductivity of the polarized layers obeys Arrhenius's law, and determining activation energy does not depend on the electrode. Finally, it is noted that today above‐mentioned information about polarized layers can be obtained only by BDS. [ABSTRACT FROM AUTHOR]

The detection of toxic insecticides is a major scientific and technological challenge. In this regard, imidacloprid is a neonicotinoid that is a systemic insecticide that can accumulate in agricultural products and affect human health. This work aims to study the properties of chitosan–TiO2 nanocomposites in which nanoparticles with high surface area serve as molecular recognition sites for electroanalytical imidacloprid detection. We show that the best sensitivity to imidacloprid was obtained using a modified electrode with a chitosan–TiO2 nanocomposite with a 40 wt.% of TiO2 nanoparticles. By using a three-phase effective permittivity model which includes chitosan, TiO2, an interface layer between nanoparticles and a matrix, we showed that nanocomposites with 40 wt.% of TiO2 the interface volume fraction reaches a maximum. At higher nanoparticle concentration, the sensitivity of the sensor decreases due to the decreasing of the interface volume fraction, agglomeration of nanoparticles and a decrease in their effective surface area. The methodology presented can be helpful in the design and optimization of polymer-based nanocomposites for a variety of applications. [ABSTRACT FROM AUTHOR]

Glass-forming ability is one of the most desired properties of organic compounds dedicated to optoelectronic applications. Therefore, finding general structure–property relationships and other rules governing vitrification and related near-glass-transition phenomena is a burning issue for numerous compound families, such as Schiff bases. Hence, we employ differential scanning calorimetry, broadband dielectric spectroscopy, X-ray diffraction and quantum density functional theory calculations to investigate near-glass-transition phenomena, as well as ambient- and high-pressure molecular dynamics for two structurally related Schiff bases belonging to the family of glycine imino esters. Firstly, the surprising great stability of the supercooled liquid phase is shown for these compounds, also under high-pressure conditions. Secondly, atypical self-organization via bifurcated hydrogen bonds into lasting centrosymmetric dimers is proven. Finally, by comparing the obtained results with the previous report, some general rules that govern ambient- and high-pressure molecular dynamics and near-glass transition phenomena are derived for the family of glycine imino esters. Particularly, we derive a mathematical formula to predict and tune their glass transition temperature (Tg) and its pressure coefficient (dTg/dp). We also show that, surprisingly, despite the presence of intra- and intermolecular hydrogen bonds, van der Waals and dipole–dipole interactions are the main forces governing molecular dynamics and dielectric properties of glycine imino esters. [ABSTRACT FROM AUTHOR]

It is a longstanding question whether universality or specificity characterize the molecular dynamics underlying the glass transition of liquids. In particular, there is an ongoing debate to what degree the shape of dynamical susceptibilities is common to various molecular glass formers. Traditionally, results from dielectric spectroscopy and light scattering have dominated the discussion. Here, we show that nuclear magnetic resonance (NMR), primarily field-cycling relaxometry, has evolved into a valuable method, which provides access to both translational and rotational motions, depending on the probe nucleus. A comparison of 1H NMR results indicates that translation is more retarded with respect to rotation for liquids with fully established hydrogen-bond networks; however, the effect is not related to the slow Debye process of, for example, monohydroxy alcohols. As for the reorientation dynamics, the NMR susceptibilities of the structural (α) relaxation usually resemble those of light scattering, while the dielectric spectra of especially polar liquids have a different broadening, likely due to contributions from cross correlations between different molecules. Moreover, NMR relaxometry confirms that the excess wing on the high-frequency flank of the α-process is a generic relaxation feature of liquids approaching the glass transition. However, the relevance of this feature generally differs between various methods, possibly because of their different sensitivities to small-amplitude motions. As a major advantage, NMR is isotope specific; hence, it enables selective studies on a particular molecular entity or a particular component of a liquid mixture. Exploiting these possibilities, we show that the characteristic Cole–Davidson shape of the α-relaxation is retained in various ionic liquids and salt solutions, but the width parameter may differ for the components. In contrast, the low-frequency flank of the α-relaxation can be notably broadened for liquids in nanoscopic confinements. This effect also occurs in liquid mixtures with a prominent dynamical disparity in their components. [ABSTRACT FROM AUTHOR]

Abstract (1−x)K0.5Na0.5NbO3−xBi(Zn2/3Nb1/3)O3 ((1−x)KNN−xBZN, x = 0.010, 0.015, 0.020, 0.025, and 0.030) lead-free ceramics were fabricated via a traditional solid-state method. The crystal structure, microstructure, dielectric, and conductivity behavior of this system were studied. Combined with X-ray diffraction (XRD) patterns, Rietveld refinement, and dielectric spectroscopy, an orthorhombic phase was determined for x = 0.010, an orthorhombic-tetragonal mixed phase was identified for x = 0.015, and a rhombohedral symmetry appears in 0.020 ⩽ x ⩽ 0.030. Both 0.98KNN−0.02BZN and 0.975KNN−0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent (tanδ) in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic. The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly, then drop sharply, and finally decline slowly, which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.

• Modulation in dielectric relaxations of ferroelectric liquid crystal (SCE9) by the dopant bent-core mesogen derived from the oxadiazole bisaniline moiety. • Dielectric studies confirm modulation in Goldstone mode, p-UHM and soft mode of ferroelectric liquid crystal by dopant bent-core mesogen. • SmC*-SmA* phase transition of ferroelectric liquid crystal is highly dependent on concentration of dopant bent-core mesogen. The modulation in dielectric relaxations of a conventional ferroelectric liquid crystal (FLC, SCE9) material by doping the bent-core mesogen (BCM) derived from the oxadiazole bisaniline moiety has been greatly investigated using frequency-temperature dependent dielectric spectroscopy. The application of probing ac voltage (i.e., oscillating voltage, 800 mV) has clearly shown the presence of partially unwound helical mode (p -UHM) along with Goldstone mode (GM). However, the temperature-dependent dielectric studies further demonstrate that p -UHM gets merged with GM at higher temperatures and hence becomes difficult to observe it separately. It appears that doping of BCM into FLC leads to the suppression of p -UHM at lower temperature, but with the increase in the concentration of dopant beyond a certain point, p -UHM mode reappears. Moreover, the significant decrement (∼9 °C) in SmC*-SmA* phase transition temperature of FLC with increase in the dopant BCM concentration up to 3 wt%. We believe that such studies would be certainly useful for the understanding of the plausible interaction between two different shaped mesogens (i.e., rod and bent-core) present in the mixture and could pave the way forward to the use of one type of mesogen in the modulation of the dielectric properties of other mesogen. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNFs) nanocomposites were prepared using poly(methylmethacrylate- co -methacrylic acid) (PMMA- co -MAA) to investigate the macromolecular mobility within the composite, with particular focus on the effect of H-bonding. Dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) were used to fully characterize the molecular mobility for which the effect of the introduction of H-bond forming moieties and the addition of CNFs (5 and 15 wt%) were assessed. Despite similar T g values (determined by Differential Scanning Calorimetry), a deeper analysis of the relaxation times associated with the α-relaxation evidenced a significant effect induced by CNFs, which is in fact slowing down the macromolecular relaxation processes. The activation energy of the β-relaxation remained unchanged despite the introduction of MAA units in the main chain and the successive addition of CNFs. However, the latter led to the appearance at low frequencies of a new β'-relaxation correlated with the interactions between the CNF surface -OH groups and the -COOH groups of the matrix. The γ-relaxation showed a 45 % increase in activation energy from PMMA to PMMA- co -MAA + CNF nanocomposites regardless of the CNF content, due to the possibility of CNFs to interact and hinder the motion of the main chain methyl groups in α position. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Shortwave infrared micro spectroscopy (SWIR) enables the measurement of water rotational relaxation time. • Water relaxation time measured by SWIR agrees with that measured by dielectric spectroscopy up to 100psec within 20% accuracy. • SWIR allows the sub-zero measurement of water relaxation time in solutions where ice and solution form a slurry. The shortwave infrared spectroscopy (SWIR) is the noble method which allows to evaluate the rotational relaxation time of water (RRTW) in a sample. Because SWIR requires the reference sample of pure water, the measurement temperature is limited only at above 0 °C. In this study, we expanded this temperature limitation of SWIR by using alternative reference solutions with freezing points below 0 °C, including sugar and glycerol solutions. The results showed that some reference sample solutions are useable for evaluating RRTW in samples below 0 °C. It was found that RRTW in solution measured by newly proposed SWIR agrees with RRTW measured by dielectric spectroscopy in 10% accuracy when it is shorter than 100psec. [ABSTRACT FROM AUTHOR]