Electrical Properties Research Articles

High-Pressure Polymorphism in Silver Ferrite Delafossite, AgFeO2.

The delafossites are a class of layered metal oxides that are notable for being able to exhibit optical transparency alongside an in-plane electrical conductivity, making them promising platforms for the development of transparent conductive oxides. Pressure-induced polymorphism offers a direct method for altering the electrical and optical properties in this class, and although the copper delafossites have been studied extensively under pressure, the silver delafossites remain only partially studied. We report two new high-pressure polymorphs of silver ferrite delafossite, AgFeO2, that are stabilized above ∼6 and ∼14 GPa. In situ X-ray diffraction and vibrational spectroscopy measurements are used to examine the structural changes across the two phase transitions. The high-pressure structure between 6 and 14 GPa is assigned as a monoclinic C2/c structure that is analogous to the high-pressure phase reported for AgGaO2. Nuclear resonant forward scattering reveals no change in the spin state or valence state at the Fe3+ site up to 15.3(5) GPa.

All-Oxide Metasurfaces Formed by Synchronized Local Ionic Gating.

Ionic gating of oxide thin films has emerged as a novel way of manipulating the properties of thin films. Most studies have been carried out on single devices with a three-terminal configuration but, by exploring the electrokinetics during the ionic gating, such a configuration with initially insulating films leads to a highly non-uniform gating response of individual devices within large arrays of the devices. We show that such an issue can be circumvented by the formation of a uniform charge potential by the use of a thin conducting underlayer. This synchronized local ionic gating allows for the simultaneous manipulation of the electrical, magnetic, and/or optical properties of large arrays of devices. Designer metasurfaces formed in this way from SrCoO2.5 thin films display anomalous optical reflection of light that relies on the uniform and coherent response of all the devices. Beyond oxides, almost any material whose properties can be controlled by the addition or removal of ions via gating can form novel metasurfaces using this technique. Our findings provide insights into the electrokinetics of ionic gating and a wide range of applications using synchronized local ionic gating. This article is protected by copyright. All rights reserved.

Electrical signature of heterogeneous human mesenchymal stem cells.

Human mesenchymal stem cells (hMSCs) have gained traction in transplantation therapy due to their immunomodulatory, paracrine, immune-evasive, and multipotent differentiation potential. The inherent heterogeneity of hMSCs poses a challenge for therapeutic treatments and necessitates the identification of robust biomarkers to ensure reproducibility in both in vivo and in vitro experiments. In this study, we utilized dielectrophoresis (DEP), a label-free electrokinetic phenomenon, to investigate the heterogeneity of hMSCs derived from bone marrow (BM) and adipose tissue (AD). The electrical properties of BM-hMSCs were compared to homogeneous mouse fibroblasts (NIH-3T3), human fibroblasts (WS1), and human embryonic kidney cells (HEK-293). The DEP profile of BM-hMSCs differed most from HEK-293 cells. We compared the DEP profiles of BM-hMSCs and AD-hMSCs and found that they have similar membrane capacitances, differing cytoplasm conductivity, and transient slopes. Inducing both populations to differentiate into adipocyte and osteoblast cells revealed that they behave differently in response to differentiation-inducing cytokines. Histology and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analyses of the differentiation-related genes revealed differences in heterogeneity between BM-hMSCs and AD-hMSCs. The differentiation profiles correlate well with the DEP profiles developed and indicate differences in the heterogeneity of BM-hMSCs and AD-hMSCs. Our results demonstrate that using DEP, membrane capacitance, cytoplasm conductivity, and transient slope can uniquely characterize the inherent heterogeneity of hMSCs to guide robust and reproducible stem cell transplantation therapies.

Recent advancements in bio-based dielectric and piezoelectric polymers and their biomedical applications.

The advent of polymer-based dielectrics marked a significant breakthrough in dielectric materials. However, despite their many advantages, they pose serious environmental threats. Therefore, in recent years, there has been growing interest in bio-based polymers as a sustainable alternative to traditional petroleum-based polymers. Their renewable nature and reduced environmental impact can fulfil the rising demand for eco-friendly substitutes. Beyond their ecological benefits, bio-based polymers also possess distinctive electrical properties that make them extremely attractive in a variety of applications. Considering these, herein, we present recent advancements in bio-based dielectric polymers and nanocomposites. First, the fundamental concepts of dielectric and polymer-based dielectric materials are covered. Then, we will delve into the discussion of recent advancements in the dielectric properties and thermal stability of bio-based polymers, including polylactic acid, polyhydroxyalkanoates, polybutylene succinate, starch, cellulose, chitosan, chitins, and alginates, and their nanocomposites. Other novel bio-based dielectric polymers and their distinct dielectric characteristics have also been pointed out. In an additional section, the piezoelectric properties of these polymers and their recent biomedical applications have been highlighted and discussed thoroughly. In conclusion, this paper thoroughly discusses the recent advances in bio-based dielectric polymers and their potential to revolutionize the biomedical industry while cultivating a more sustainable and greener future.

Crossover from Cooper-pair hopping to single electron hopping in Pbx(TiO 2)1-x granular films

Abstract The electrical transport properties of Pbx(TiO2)1-x (x being the Pb volume fraction and ranging from ~0.45 to ~0.69) granular films are investigated experimentally. The charging energy of the Pb granules is reduced to less than the superconducting gap of Pb granules for the low temperature insulating films by using high-k dielectric TiO2 as the insulating matrix. For the insulating films in the vicinity of the superconductor-insulator transition, Cooper-pair hopping governs the low-temperature hopping transport. For these films, the low-temperature magnetoresistance is positive at low field and the resistivity vs temperature for Cooper-pair hopping obeys an Efros-Shklovsii-type variable-range-hopping law. A crossover from Cooper-pair-dominated hopping to single-electron-dominated hopping is observed with decreasing x. The emergence of single-electron-dominated hopping in the more insulating films is due to the causation that the intergrain Josephson coupling becomes too weak for Cooper pairs to hop between adjacent Pb granules.

Large‐Area and Uniform Blade‐Coated Deep‐Blue Polymer Light‐Emitting Diodes Based on Triphenylethylene‐Encapsulated π‐Conjugated Polymer

AbstractEmerging large‐area flexible polymer light‐emitting diodes (PLEDs) are crucial for flat‐panel displays. The development of uniform, large‐area, flexible, and ultra‐deep‐blue PLEDs remains challenging owing to the lack of efficient and stable deep‐blue light‐emitting conjugated polymers with robust deep‐blue emission, excellent large‐scale solution‐processing capacity, and stable electrical properties. In this study, a multidimensional steric triphenylethylene (TPE) segment is introduced into the substitution side chain of polydiarylfluorenes (P‐F) for deep‐blue large‐area blade‐coated and flexible PLEDs. The encapsulation of backbone chains with extremely weak interchain π–π interactions facilitated the preparation of large‐area PLEDs via blade coating. Large‐area uniform P‐F films (16 cm2) are fabricated. Flexible PLEDs are fabricated with efficient deep‐blue emission (CIE: 0.15, 0.07) and a maximum brightness of 2314 cd m−2. Notably, the large‐area PLEDs exhibited a narrow‐band deep‐blue emission with a CIE of (0.15, 0.08) at ≈1000 mA cm−2 and an emitting area of 3.6 cm2. Furthermore, a preliminary patterned PLED array display with a pixel size of 800 × 1000 µm2 is successfully created, which exhibited stable and uniform deep‐blue light‐emitting pixel performance (CIE: 0.15 0.08). These results demonstrated the effectiveness of the TPE encapsulation strategy for large‐area PLEDs.

Effect of the mixing of s-wave and chiral p-wave pairing on electrical shot noise properties of normal metal/superconductor tunnel junctions

Abstract We study theoretically the electrical shot noise properties of tunnel junctions between a normal metal and a superconductor with the mixture of singlet $s$-wave and chiral triplet $p$-wave pairing due to broken inversion symmetry. We investigate how the shot noise properties vary as the relative amplitude between the two parity components in the pairing potential is changed. It is demonstrated that some characteristics of the electrical shot noise properties of such tunnel junctions may depend sensitively on the relative amplitude between the two parity components in the pairing potential, and some significant changes may occur in the electrical shot noise properties when the relative amplitude between the two parity components is varied from the singlet $s$-wave pairing dominated regime to the chiral triplet $p$-wave pairing dominated regime. In the chiral triplet $p$-wave pairing dominated regime, the ratio of noise power to electric current is close to $2e$ both in the in-gap and in the out-gap region. In the singlet $s$-wave pairing dominated regime, the value of this ratio is close to $4e$ in the inner gap region but may reduce to about $2e$ in the outer gap region as the relative amplitude of the chiral triplet pairing component is increased. The variations of the differential shot noise with the bias voltage also exhibit some significantly different features in different regimes. Such different features can serve as useful diagnostic tools for the determination of the relative magnitude of the two parity components in the pairing potential.

Contribution of (Bi0.45Y0.05)Na0.5ZrO3 to induced multiphase coexistence and enhanced piezoelectric properties of K0.5Na0.5NbO3 lead-free ceramics

In this study, new lead-free piezoelectric ceramics (1 − x)(K0.5Na0.5)NbO3 (KNN)–x(Bi0.45Y0.05)Na0.5ZrO3 (BYNZ) were prepared using the conventional solid-state method, and the relation between the doping amount of (Bi0.45Y0.05)Na0.5ZrO3 and its structural and electrical properties was investigated. Material characterization and structural analyses conducted using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy revealed that KNN–BYNZ ceramics formed single perovskite structures at 0 ≤ x ≤ 0.05 and a polycrystalline phase boundary (PPB) for the coexisting orthorhombic and tetragonal phases at 0.03 ≤ x ≤ 0.05. The ceramics exhibited desirable electrical properties at x = 0.04 (d33 = 305 pC/N, kp = 45.8 %, εr = 1316, tanδ = 2.4 %, Tc = 332 °C, Pr = 28.2 μC/cm2, and Ec = 1.07 kV/mm). These findings reveal that the introduction of BYNZ enables the effective formation of a PPB in the KNN-based ceramics to improve their electrical properties, and they exhibit potential for replacing lead-based piezoelectric ceramics in the market.

A comparative study of single and dual sintering processes of metal nanoparticles for flexible electronics application

The introduction of metallic nanoparticles (NPs) has revolutionized the fabrication of flexible electronic devices. Metallic NPs have numerous applications in the electronics industry due to their unique shape and size‐dependent properties compared to their bulk counterparts. However, the application of metallic NPs requires additional post‐processing procedures to remove stabilizing agents and additives, to achieve superior electrical conductivity. In this study, the sintering of printed metal NP patterns, including silver (Ag) and copper (Cu) NPs, fabricated on flexible polyimide substrates is explored using single and dual sintering methods. The single sintering methods involve exposing the printed metal NPs to either laser irradiation or thermal treatment. In the case of the dual sintering methods, one approach is to subject the printed metal patterns to thermal treatment followed by laser irradiation, while the other approach involves exposing the printed metal patterns to laser irradiation followed by thermal treatment. Moreover, this study identifies and compares the effects of these various sintering methods on the physical, electrical, chemical, and mechanical properties of the Ag and Cu NP patterns. Finally, the study suggests that dual sintering methods are more effective in improving the electrical conductivity and mechanical properties of the NP patterns under optimized sintering conditions.This article is protected by copyright. All rights reserved.

Nanodiamond Coating in Energy and Engineering Fields: Synthesis Methods, Characteristics, and Applications.

Nanodiamonds are metastable allotropes of carbon. Based on their high hardness, chemical inertness, high thermal conductivity, and wide bandgap, nanodiamonds are widely used in energy and engineering applications in the form of coatings, such as mechanical processing, nuclear engineering, semiconductors, etc., particularly focusing on the reinforcement in mechanical performance, corrosion resistance, heat transfer, and electrical behavior. In mechanical performance, nanodiamond coatings can elevate hardness and wear resistance, improve the efficiency of mechanical components, and concomitantly reduce friction, diminish maintenance costs, particularly under high-load conditions. Concerning chemical inertness and corrosion resistance, nanodiamond coatings are gradually becoming the preferred manufacturing material or surface modification material for equipment in harsh environments. As for heat transfer, the extremely high coefficient of thermal conductivity of nanodiamond coatings makes them one of the main surface modification materials for heat exchange equipment. The increase of nucleation sites results in excellent performance of nanodiamond coatings during the boiling heat transfer stage. Additionally, concerning electrical properties, nanodiamond coatings elevate the efficiency of solar cells and fuel cells, and great performance in electrochemical and electrocatalytic is found. This article will briefly describe the application and mechanism analysis of nanodiamonds in the above-mentionedfields.

Thickness‐Dependent Formation Capacity and Mechanism of Planar (β)‐Conformation in Polydiarylfluorenes for Stable Deep‐Blue Polymer Light‐Emitting Diodes

AbstractConjugated polymers with p‐orbital overlap show intramolecular‐conformation‐dependent photophysical and electrical properties. Compared to the non‐planar segments, the planar conformation segments have a relatively long effective conjugated length and rigid backbone structure, which are beneficial for the enhancement of optoelectronic properties. Herein, the effect of film thickness on the formation capacity of planar (β) conformations in polyfluorene (poly[4‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl]‐co‐[5‐(octyloxy)‐9,9‐diphenylfluorene‐2,7‐diyl], PODPF) for the fabrication of stable deep‐blue polymer light‐emitting diodes (PLEDs) is explored. Thickness‐tunable films with thicknesses ranging from 15 to 270 nm by controlling the concentration of precursor solution are prepared. The main observations are as follows. The PODPF chains in thin films are less likely to adopt the β conformations associated with the loose interchain packing in nano‐aggregates than those in thick films. Red‐shifted and well‐resolved emission spectra are observed for the annealed film with a high thickness, indicating the greater presence of β‐conformation segments. More interestingly, interchain aggregation is a necessary but not sufficient condition for the formation of β conformations. Finally, PLEDs based on β‐conformation segments have outstanding brightness, low turn‐on voltage, and stable deep‐blue electroluminescent behavior, confirming the unique advantage of planar conformation for optoelectronic applications.

Low‐Temperature Annealing of Asymmetrically Cold‐Rolled Electrolytic Tough‐Pitch Copper: Anneal Hardening and Bimodal Microstructure

In this research, 90% asymmetric unidirectional rolling and post‐annealing were applied to electrolytic tough‐pitch (ETP) copper. The effect of low‐temperature (200°C) annealing on the microstructure and texture evolution, mechanical, and electrical properties were investigated. Static recovery (SRV) was the main softening mechanism at the annealing time range of 1‐5 min. In contrast, complete static recrystallization (SRX) was observed after annealing for 10 min. Bimodal microstructure, consisting of coarse and fine grains was evolved for annealing times more than 10 minutes. With increasing the post‐annealing duration, the intensity of deformation and shear textures was continuously decreased, however, the recrystallization (Cube) orientation becomes stronger up to 11.2×R. After 1, 2, and 5 min of post‐annealing, the hardness, yield strength, tensile strength, ductility, and toughness of copper were higher than those of the 90% rolled sample due to annealing hardening. After 10 min of annealing, the hardness, yield strength, and tensile strength suddenly decreased and the ductility and toughness significantly enhanced owing to the complete recrystallization. With increasing the post‐annealing time, the fraction of flat surfaces was decreased and the fraction of ductile dimples was increased. With the post‐annealing time increasing from 1 to 120 min, the electrical conductivity gradually increased from 84.9%IACS to 96.7%IACS.This article is protected by copyright. All rights reserved.

Bioinspired Photoelectronic Synergy Coating with Antifogging and Antibacterial Properties.

Optically transparent glass with antifogging and antibacterial properties is in high demand for endoscopes, goggles, and medical display equipment. However, many of the previously reported coatings have limitations in terms of long-term antifogging and efficient antibacterial properties, environmental friendliness, and versatility. In this study, inspired by catfish and sphagnum moss, a novel photoelectronic synergy antifogging and antibacterial coating was prepared by cross-linking polyethylenimine-modified titanium dioxide (PEI-TiO2), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA). The as-prepared coating could remain fog-free under hot steam for more than 40 min. The experimental results indicate that the long-term antifogging properties are due to the water absorption and spreading characteristics. Moreover, the organic-inorganic hybrid of PEI and TiO2 was first applied to enhance the antibacterial performance. The Staphylococcus aureus and the Escherichia coli growth inhibition rates of the as-prepared coating reached 97 and 96% respectively. A photoelectronic synergy antifogging and antibacterial mechanism based on the positive electrical and photocatalytic properties of PEI-TiO2 was proposed. This investigation provides insight into designing multifunctional bioinspired surface materials to realize antifogging and antibacterial that can be applied to medicine and daily lives.

The role of annealing in optimizing the electrical, linear, and nonlinear optical properties ZIf-8@TiO2 films for possible use in photonic and optoelectronic devices

Abstract Here, we fabricate zeolitic imidazolate framework-8 (ZIF-8)–doped 5 wt. % nanosized TiO2 (ZIf-8@TiO2) thin films using a vapor coating unit. The effects of annealing up to 473 K on the physical characteristics of fabricated ZIf-8@TiO2 thin films were studied. XRD, FTIR, and UV-Vis spectroscopy were utilized to investigate the structural properties of the as-deposited and annealed samples. An increase of approximately 18% was observed in the electrical conductivity. As the annealing temperature increased, the light transmission decreased. This could be due to the growth or aggregation of TiO2 particles during annealing. Raising the annealing temperature by 100 K enhanced the refractive index (n) and energy gap (Eg) by approximately 33% and 8%, respectively. The decrease in ε1 and ε2 in response to the annealing temperature increase was due to the evaporation of MOF organic linkers. The nonlinear optical results indicated a dependence on the annealing temperatures that improved charge carrier mobility and coherent light-matter interactions. Our thesis findings can improve the overall performance and efficiency of optoelectronic devices.

Synergistic polarization engineering of dielectric towards low-voltage high-mobility solution-processed ultraflexible organic transistors

The emerging wearable skin-like electronics require the ultra-flexible organic transistor to operate at low voltage for electrical safety and energy efficiency and simultaneously enable high field-effect mobility to ensure the carrier migration ability and the switching speed of circuits. However, the currently reported low-voltage organic transistors generally present low mobility, originating from the trade-off between molecular polarity and surface polarity of the dielectrics. In this work, the orientation polarization of the dielectric is enhanced by introducing a flexible quaternary ammonium side chain, and the surface polarity is weakened by the shielding effect of the nonpolar methyl groups on the polar nitrogen atom. The resulting antisolvent QPSU dielectric enables the high-dielectric constant up to 18.8 and the low surface polarity with the polar component of surface energy only at 2.09 mJ/m2. Such a synergistic polarization engineering between orientation polarization and surface polarity makes the solution-processed ultraflexible transistors present the ultralow operational voltage down to −3 V, the ultrahigh charge-carrier mobility up to 8.28 cm2 V−1 s−1 at 1 Hz, excellent cyclic operational stability and long-term air stability. These results combined with the ultrathin thickness of transistor as low as 135 nm, the ultralight mass of 0.5 g/m2, the conformal adherence capability on human skin and 1-μm blade edge, and the strong mechanical robustness with stable electrical properties for 30,000 bending cycles, open up an available strategy to successfully realize low-voltage high-mobility solution-processed organic transistor, and presents the potential application of QPSU dielectric for the next-generation wearable imperceptible skin-like electronics.

Thermal and Electrical Properties of High-Temperature Proton-Conducting Cellulose Nanofibers Swollen with Protic Ionic Liquid

Thermal and Electrical Properties of High-Temperature Proton-Conducting Cellulose Nanofibers Swollen with Protic Ionic Liquid

Modification of LaB6 with ZrO2-Al2O3-TiO2 for Improvement of Density and Mechanical and Electrical Properties

Pure lanthanum hexaboride (LaB6) ceramics were prepared using powders of different grain sizes. The ceramics could reach a relative density of 98.2% at high temperatures and pressures, but had a low flexural strength (136.9 MPa). LaB6 ceramics were synthesized using ZrO2-Al2O3-TiO2 (ZAT) as sintering additives. The ceramics demonstrate high density and excellent mechanical properties. The hot pressure sintering (HPS) method was utilized in the synthesis of the ceramics. Investigations were conducted on the effects of ZAT content, as well as the effects of the sintering temperature and pressure on the sintering behavior, microstructure, and mechanical and electrical properties of LaB6 ceramics. LaB6 ceramics fabricated with a ZAT addition of 6 wt.%, at a sintering temperature of 1700 °C, and under a pressure of 50 MPa, exhibited superior sintering and electrical properties, including a relative density of 97%, a conductivity of 7.2 MS/m, a flexural strength of 281.5 MPa, and a Vickers hardness of 21.2 GPa. The LaB6 ceramics synthesized in this research exhibit promising potential as electron-emitting cathodes for field emission applications.

Modification of WS2 thin film properties using high dose gamma irradiation.

The tunability of the Transition Metal Dichalcogenide (TMD) properties has gained attention from numerous researchers due to their wide application in various fields including quantum technology. In the present work, WS2 has been deposited on fluorine doped tin oxide (FTO) substrate and its properties have been studied systematically. These samples were irradiated using gamma radiation for various doses, and the effect on structural, morphological, optical and electrical properties has been reported. The crystallinity of the material is observed to be decreased, and the results are well supported by X-ray diffraction, Raman spectroscopy techniques. The increase in grain boundaries has been supported by the agglomeration observed in the scanning electron microscopy micrographs. The XPS results of WS2 after gamma irradiation show evolution of oxygen, carbon, C=O, W-O and SO42- peaks, confirming the addition of impurities and formation of point defect. The gamma irradiation creates point defects, and their density increases considerably with increasing gamma dosage. These defects crucially altered the structural, optical and electrical properties of the material. The reduction in the optical band gap with increased gamma irradiation is evident from the absorption spectra and respective Tauc plots. The I-V graphs show a 1000-fold increase in the saturation current after 100 kGy gamma irradiation dose. This work has explored the gamma irradiation effect on the WS2 and suggests substantial modification in the material and enhancement in electrical properties. &#xD.

New insights into how temperature affects the electrical conductivity of clay-free porous rocks

Summary Geothermal energy is increasingly important for the global environment and for the sustainable development of our society. Electrical surveys are widely employed for the exploration of geothermal energy, because the electrical geophysical properties provide useful information about the fluids at depth. However, although quantitative interpretation of electrical survey data relies on the knowledge about the effects of temperature on the electrical properties of fluid-bearing rocks, it remains poorly understood about how temperature affects the electrical conductivity of clay-free porous rocks. We bridge this knowledge gap by measuring the electrical conductivity and porosity of five brine saturated clean Berea sandstones with temperature ranging between 25° C and 140° C, and analysing all the factors that impact the rock conductivity. We showed that the effects of surface conductivity on the temperature dependent electrical conductivity can be negligible, whereas the temperature induced variation in the porosity and pore structure quantitatively characterized in terms of cementation exponent can be more significant. We also found that temperature affects the electrical conductivity of brine saturated Berea sandstones by impacting the brine conductivity, and the pore structure and porosity of the samples, with their importance in a descending order. The results have provided new insights into how temperature affects the electrical conductivity of clay-free porous rocks, and will help to improve the quantitative interpretation of electrical survey data for the exploration of geothermal energy.

Electrorheological and magnetorheological properties of liquid composites based on polypyrrole nanotubes/magnetite nanoparticles

This research presents an in-depth exploration of the electrical and magnetic properties of a polypyrrole nanotubes/magnetite nanoparticles (PPyM) material embedded in a silicone oil matrix. A key finding of our study is the dual nature of the composite, i.e. it exhibits a behaviour akin to both electro- and magnetorheological suspensions. This unique duality is evident in its response to varying electric and magnetic field intensities. Our study focuses on examining the electrical properties of the composite, including its dielectric permittivity and dielectric loss factor. Additionally, we conduct an extensive analysis of its rheological behavior, with a particular emphasis on how its viscosity changes in response to electromagnetic stimuli. This property notably underscores the material’s dual-responsive nature. Employing a custom experimental design, we integrate the composite into a passive electrical circuit element subjected to alternating electric fields. This methodological approach allows us to precisely measure the material’s response in terms of resistance, capacitance, and charge under different field conditions. Our findings reveal substantial changes in the material’s electrical conductivity and rheological characteristics, which are significantly influenced by the intensity of the applied fields. These results enhance the understanding of electro-magnetorheological properties of PPyM-based magnetic composites, and also highlight their potential in applications involving smart materials. The distinct electrical, magnetic and rheological modulation capabilities demonstrated by this composite render it as promising candidate for advanced applications. These include sensory technology, actuation systems, and energy storage solutions.