Unbalanced Charges Research Articles

Self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO heterostructure with Schottky junction for regulating BIEF to enhance microwave absorption

Currently, heterogenous interface engineering on absorbers is shown to boost the electromagnetic wave absorption (EMA) performance effectively. However, challenges remain in investigating the mechanisms by studying heterojunctions between heterogeneous interfaces. Herein, a self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO (MZCZ) heterostructure with abundant Schottky heterogenous interfaces generating a controllable built-interface electric field (BIEF) effect is fabricated to achieve exceptional EMA ability. The formative BIEF between the unbalanced distribution charges promotes charge separation and migration, increasing polarization loss. Fortunately, the obtained MZCZ1 exhibits the reflection loss (RL) value of −69.78 dB under the ultralow thickness of 1.501 mm and the optimal minimum RL (RLmin) value of −74.41 dB, respectively. The excellent performance can be ascribed to the multiple polarization loss, conduction loss, natural resonance, and exchange resonance characteristics. Moreover, by the Computer Simulation Technology (CST) software, the designed circular cone and circular truncated cone periodicity structure with the MZCZ1 absorber both exhibit a super-wide effective absorption bandwidth (EAB) covering the whole C, X, and Ku band. This study can pioneer a novel approach to developing functional EMA materials and provide a valuable direction for further study of EMA mechanisms at heterogeneous interfaces.

The behavior of surfactant microemulsion in clay-hosted nanopores

The utilization of microemulsions to boost well productivity is gaining traction, particularly in unconventional shale wells during fracturing. However, the subsequent behavior and stability of microemulsions remain less clear, especially in clay-hosted nanopores where clay minerals exhibit unbalanced surface charges. This study employs the molecular dynamics (MD) approach to characterize the behavior and stability of microemulsion droplets through clay-hosted nanopores with different surface chemistries and salinities in shales, under typical reservoir pressures and temperatures. Our findings reveal that in the bulk, microemulsion droplets remain stable across all salinities. Yet, depending on the surface chemistry (charge distribution) in clays, the stability of microemulsion droplets becomes contingent on salinity. When clay surfaces are charge-balanced or have a moderate imbalance, microemulsion droplets remain stable. However, with a strong charge imbalance, induced local electric fields in the slit pore affect the fluids, leading to the essential role of both the electric field and clay surface in breaking the microemulsion droplet. Increasing salinity results in the formation of an electrical double layer, diminishing the strength of the electric field, and preserving the stability of microemulsion droplets. This modeling-based work enhances our comprehension of salinity variations' impact on microemulsions in charged clay hosted nanopores. Notably, this is the inaugural study combining and assessing microemulsion sensitivity to salinity and pore surface chemistry, thereby broadening possibilities for the effective delivery of EOR agents to shales.

Engineering of Molecular Bridge on Buried Interface via Ferrocene Carboxylic Acid for High Performance Perovskite Light‐Emitting Devices

AbstractQuasi‐two‐dimensional (Quasi2D) perovskite materials gained widespread attention due to whose unique and highly desirable luminescence properties. However, the behavior of perovskite lightemitting diodes (PeLEDs) is prejudiced by inefficient cascading energy transfer of perovskite film and unbalanced charges injection. Here, ferrocene carboxylic acid (FcAd) is employed between hole transport layer (HTL) and perovskite layer as a molecular bridge to solve the current problems of PeLEDs. Ferrocene units can bond with [PbBr6]4−, forming one‐dimensional (1D) intermediate phases of FcPbBr3 at the interface, which can manipulate the growth kinetics of perovskite and reconstruct the phase distribution. Therefore, due to the suppression of low dimensional phase content, not only is the cascaded energy transfer of PEA2(CsPbBr3)2PbBr4 films effectively achieved, but also the quasi‐2D perovskite's work function is reduced. Additionally, Pb2+ coordinated with the carboxyl group of FcAd, inducing an electric dipole effect that leads to an further upward shift of the perovskite energy level. Eventually, the synergy achieves a significant tailoring between the perovskite and HTL energy exhibits the most excellent external quantum efficiency (EQE) exceeds 27% and optimal brightness exceeds 240000 cd m−2. Therefore, the preparation method will provide an effective strategy to widen the color gamut of next‐generation displays.

Modulation of Structural, Electronic, and Optical Properties of Titanium Nitride Thin Films by Regulated In Situ Oxidation

Epitaxial titanium nitride (TiN) and titanium oxynitride (TiON) thin films have been grown on sapphire substrates using a pulsed laser deposition (PLD) method in high-vacuum conditions (base pressure <3 × 10-6 T). This vacuum contains enough residual oxygen to allow a time-independent gas phase oxidation of the ablated species as well as a time-dependent regulated surface oxidation of TiN to TiON films. The time-dependent surface oxidation is controlled by means of film deposition time that, in turn, is controlled by changing the number of laser pulses impinging on the polycrystalline TiN target at a constant repetition rate. By changing the number of laser pulses from 150 to 5000, unoxidized (or negligibly oxidized) and oxidized TiN films have been obtained with the thickness in the range of four unit cells to 70 unit cells of TiN/TiON. X-ray photoelectron spectroscopy (XPS) investigations reveal higher oxygen content in TiON films prepared with a larger number of laser pulses. The oxidation of TiN films is achieved by precisely controlling the time of deposition, which affects the surface diffusion of oxygen to the TiN film lattice. The lattice constants of the TiON films obtained by x-ray diffraction (XRD) increase with the oxygen content in the film, as predicted by molecular dynamics (MD) simulations. The lattice constant increase is explained based on a larger electrostatic repulsive force due to unbalanced local charges in the vicinity of Ti vacancies and substitutional O. The bandgap of TiN and TiON films, measured using UV-visible spectroscopy, has an asymmetric V-shaped variation as a function of the number of pulses. The bandgap variation following the lower number of laser pulses (150-750) of the V-shaped curve is explained using the quantum confinement effect, while the bandgap variation following the higher number of laser pulses (1000-5000) is associated with the modification in the band structure due to hybridization of O2p and N2p energy levels.

Fire-resistant iron-based phosphates/phosphorus-doped carbon composites derived from phytic acid-treated metal organic frameworks as high-efficiency microwave absorbers

Considering the electromagnetic pollution in harsh environments, it is vital to prepare multifunctional microwave absorbers to broaden their application fields. Herein, fire-resistant iron-based phosphates/phosphorus-doped carbon composites were annealed from phytic acid-treated metal organic frameworks. Through tailoring the dosage of phytic acid used in the preparation process, composites with diverse morphologies, crystal structures, electric and microwave absorption properties are obtained. When the dosage of phytic acid used reaches 4 mL, the obtained composite, Fe2P4O12/phosphorus-doped carbon, possesses the best microwave absorption performance with a minimum reflection loss of −67.6 dB (2.0 mm) and an effective absorption bandwidth of 5.76 GHz (2.1 mm, 12.24–18 GHz). The microwave attenuation could be mainly attributed to the high conductivity brought by phosphorus-doped carbon, and polarization relaxations triggered by dipoles, functional groups, and unbalanced charges at interfaces. Specifically, the charge density distribution, obtained with density functional theory (DFT), suggests the occurrence of intense charge transfer and formation of internal electric field at P-carbon, O-carbon, and iron-based phosphates/phosphorus-doped carbon interfaces. Meanwhile, the as-prepared iron-based phosphates/phosphorus-doped carbon composites possess good fire-resistant property. The work provides a novel idea to construct multifunctional materials with high-efficient microwave absorption to broaden their application fields.

Micellization, aggregation, and gelation of polystyrene-block-poly(ethylene oxide) in cosolvents added with hydrochloric acid

The micellization, aggregation, and gelation of the polystyrene-block-poly(ethylene oxide) block copolymer in solutions were quantitatively analyzed by small-angle X-ray scattering. The content and concentration of added hydrochloric acid influence the micellization, aggregation, and gelation of a polystyrene-block-poly(ethylene oxide) block copolymer in tetrahydrofuran/water and dimethylformamide/water cosolvents added with hydrochloric acid. The polystyrene-block-poly(ethylene oxide) block copolymer forms spherical micelles with screened Coulomb repulsions when dispersed in tetrahydrofuran/water cosolvents added with hydrochloric acid. The screened Coulomb repulsion arises from the poly(ethylene oxide) shells bound with protonated water and surrounded by unbalanced negative charges. If excessive water is introduced from hydrochloric acid, the non-solvent quality of tetrahydrofuran/water cosolvent predominantly causes aggregation of spherical micelles. Such screened Coulomb repulsions do not form for core-shell cylinders dispersed in dimethylformamide/water added with hydrochloric acid. Hydrochloric acid tends to form complexes with dimethylformamide. The length of core-shell cylinders can increase with the increased content of hydrochloric acid. Long core-shell cylinders favorably form three-dimensional networks through inter-cylinder entanglement. Furthermore, the absence of screened Coulomb repulsions makes entangled cylinders more compact to strongly trap the liquid phase. Thus, gels occurred in dimethylformamide/water cosolvents with added hydrochloric acid. Nevertheless, the content of added hydrochloric acid should be finely controlled. Adding a large amount of hydrochloric acid prohibits network formation and instead favors kinetically trapped rigid cylinders. This study has demonstrated that finely controlling solvent quality by additives provides a physical design strategy for fabricating cylindrical micelles with tunable properties in solutions. This should offer the fundamental understanding of self-assembly for potential applications of block copolymer micelles.

Theoretical study on the output of contact-separation triboelectric nanogenerators with arbitrary charging and grounding conditions

Nanogenerators of contact-separation mode have been studied comprehensively both from the theoretical perspective and for practical applications. Compared with the in-situ charging through contact electrification during each cycle of operation, pre-charging has shown its advantages and benefits of less wear, longer lifetime, high stability, improved output power, good controllability and repeatability. In this work, universal formulas are derived for the output of contact-separation mode triboelectric nanogenerators (TENG), which is applicable to arbitrary charging conditions including the triboelectrification, pre-charging, and even those with unbalanced charges on the two counterparts of dielectric layers. The formula is also validated and appropriate to various grounding conditions of the two conductive terminals. A systematic study is conducted on various combinations of device configurations, charging conditions and grounding settings to compare the results derived from the universal formula proposed in this work with that of previous work as well as the simulated results based on finite element modeling. The applicability of the universal formula is verified by the simulated results and it also consists with the conventional formula for TENGs under specific settings. The universal formula proposed in this work can operate as not only a convenient tool to derive the output of contact-separation TENGs with known charging and grounding conditions, but also a guidance for the fabrication and experiment of contact-separation TENGs to improve its output performance with a given configuration of device.

Effect of Magnetic Field on Different Opening Processes of Multi-Break Vacuum Gaps

Vacuum gap saturation of single break can be solved by multiple breaks in series. In different breaking processes, the unbalanced energy and charges injected into the breaks lead to unbalanced voltage distribution. The purpose of this paper was to compare the voltage distribution under the regulation of magnetic field in different opening process. The magnetic fields with 3 ms width were applied at the point 3 ms before current through zero. Comparing with no axial magnetic field, the voltage distribution unbalances deceased both in synchronous and asynchronous opening processes. Under the condition that the arcing time of high-voltage break remained at 6.6 ms and the magnitude of axial magnetic fields was 60 mT, voltage distributions of high-voltage break were approximately proportional to the arcing times of the low-voltage break from 3.4 ms to 6.6 ms. It demonstrated that axial magnetic fields could effectively improve the voltage distribution of multi-break vacuum circuit breakers in synchronous and asynchronous opening processes.

Migration of Constituent Protons in Hybrid Organic-Inorganic Perovskite Triggers Intrinsic Doping.

The crucial separation of photocarriers in solar cells can be efficiently driven by contacting semiconductor phases with differing doping levels. Here we show that intrinsic doping surges in methylammonium lead iodide (MAPbI3) crystals as a response to environmental basicity. MAPbI3 crystals were passivated with polybases to induce the deprotonation of its methylammonium ions (MA+). Stable crystals showed marked increases in photoluminescence and radiative decay, attributed to the presence of unbalanced charges acting as doped carriers. This emulates in a controlled manner the proton-withdrawing conditions of polycrystalline films, where excess basic precursors are found between grains. Raman spectroscopy showed the collective alignment of MA+ cations within the intrinsically doped lattices, thus revealing the buildup of electric fields. On this basis, we propose a mechanism for the formation of doping-gradients toward grain boundaries, potentially explaining the extended photocarrier lifetimes and diffusion lengths observed in perovskite solar cells.

Electrostatic Effects on the Internal Dynamics of Redox-Sensitive Microgel Systems

Microgels are flexible entities with a number of properties which can be tailored for a variety of applications. For redox-sensitive PNIPAM-based microgels involved in this study, the size and effective charge of microgels can be manipulated by electrochemical means. The electrochemical switching is implemented via interaction of redox-sensitive counterions (hexacyanoferrates: HCF) with oppositely charged (cationic) thermoresponsive microgels. Effects on the internal dynamics upon uptake of HCF and increased hydrophobicity with temperature are investigated with neutron spin echo spectroscopy. The polymer segmental dynamics is well described by the Zimm model. Unbalanced charges (in absence of HCF) apparently shorten the polymer length acting like confined discontinuity points (pinning). This effect vanishes in the presence of HCF. The ability of multivalent ferricyanides to bind several monovalent polymer charges at the same time produces an apparent secondary network. This effective bridging makes the dynamics slower analogous to an increase in cross-linker density. In support of this picture, an enhanced viscosity of the medium, where the polymer chains move, was obtained by the fitting.

Synergistic effect of oxygen and nitrogen functionalities for graphene-based quantum dots used in photocatalytic H2 production from water decomposition

Surface intact nitrogen-doped graphene oxide quantum dots (iNGO-QDs), which are based on the abundant elements C, H, O, and N, exhibit outstanding photocatalytic performance in H2 production through water decomposition. In this study, we synthesize the iNGO-QDs by thermally treating graphene oxide sheets in NH3 with subsequent ultrasonic exfoliation. The iNGO-QDs exhibit sizes of 2 to 6nm and consist of approximately 3 graphitic layers. Nitrogen doping in QD synthesis repairs the vacancy-type defects of GO and introduces n-type conductivity to compensate for the unbalanced charges on p-type GO, thereby suppressing leaks of photogenerated charges. Coexistence of p- and n-domains in the iNGO-QDs may form photochemical diodes to facilitate charge separation. Under visible light illumination, the iNGO-QDs steadily catalyze the production of H2 from an aqueous solution containing triethanolamine. When deposited with Pt as the cocatalyst, the iNGO-QDs exhibit high activity in H2 generation at an apparent quantum yield of 12.8% under monochromatic light (420nm) irradiation. The high activity of the iNGO-QDs can be attributed to the synergistic effect of the oxygen and nitrogen functionalities in facilitating charge separation and transfer.

Nowcasting the lightning activity in Peninsular Malaysia using the GPS PWV during the 2009 inter-monsoons

&lt;p&gt;The spatial and temporal radio wave delay of the Global Positioning System (GPS) signal can be manipulated to estimate the precipitable water vapor (PWV) which favorable for meteorological applications. A rapid change of the water vapor amount was a precondition for the unbalanced atmospheric charges, which noticeably associated with the development of convective cloud as a lightning chamber. According to this fact, GPS derived PWV will be utilized to nowcasting the lightning event for the next couple of hours. The variances of PWV of four-selected station of the Peninsular Malaysia during the past two inter-monsoons events in May and November 2009 were analyzed. To clarify the response, the changes of PWV in hourly Δ (max-min) before the lightning event was investigated with minimum value 2 mm and is maintained at least three consecutive hours. There are 177 samples were extracted from this method and 69% of the sample showed the lightning occurrence with an average duration was after the six consecutive hours. The lightning day with 2 mm Δ was also higher than the fair weather of 6.3%. These findings suggest that the GPS data can be proposed further as a guide to nowcast the occurrence of lightning activity.&lt;/p&gt;

Surface screening of written ferroelectric domains in ambient conditions

We have combined Piezoresponse Force Microscopy and Kelvin Probe Force Microscopy (KPFM) to study screening charge dynamics in written domains on PbZr0.2Ti0.8O3 (PZT) thin film surfaces under a controlled environment and at variable temperature. The screening dynamics decayed exponentially on a timescale of tens of minutes, consistently with what we expected for water-mediated surface diffusion of ionic species. Variable-temperature KPFM measurements showed variations in surface potential due to temporary unbalanced surface screening charges. Low humidity experiments revealed gradual incorporation of positive charges onto the surface, even in a non-reactive environment (N2), as well as deceleration of the screening dynamics upon reversal of the temperature variation. Our work may serve as a guide for future studies on the dynamics and nature of adsorbates on polarized PZT thin films.

The crystal structure of a lyxose-bridged dimolybdate: a redetermination of the first monosaccharide–metal complex’s structure

The crystal structure of the first monosaccharide–metal complex ever reported, a β- d-lyxofuranose-bridged dimolybdate [Taylor, G. E.; Waters, J. M. Tetrahedron Lett. 1981, 22, 1277–1278] was re-determined since the original work shows unbalanced charges, and thus an unclear protonation state of the lyxose ligand. As a result, the complex was found to be a monoanion whose charge is balanced by an ammonium counterion. The lyxose O5 atom is non-deprotonated, and the carbohydrate ligand is trianionic due to deprotonation of the O1, O2 and O3 hydroxy functions.

First Principles Investigation of Mineral Component of Bone: CO3 Substitutions in Hydroxyapatite

First principles calculations are used to investigate carbonated hydroxyapatite, a naturally occurring mineral and also the inorganic component of animal bone. Two types of carbonate substitution are studied: A-type in which the carbonate ion substitutes for an OH and B-type where the substitution is for a phosphate. Both types have unbalanced charges and various forms of charge compensation are treated. The methods, which are based on density functional theory and first principles pseudopotentials, yield equilibrium atomic arrangements, changes in lattice parameters, and total energies for different types of substitution. When calculated energies of selected stable compounds are used, the formation energies of different carbonate substitutions with accompanying charge compensation defects can be compared. The results indicate that compact complexes are energetically favored, and a B-type material with charge compensation by a calcium vacancy together with a hydrogen atom which bonds to a neighboring phosphate is the most stable of all those considered.

Passive Propagation of Transmembrane Potential Induced by Intrinsic Capacitances of Myocardium Bioelectrolytes during Its Electrical Defibrillation

External and implantable electric cardioverters/ defibrillators (ECD) are subject to continuous upgrading: the size and weight are reduced, whereas the energy transmitted to myocardium tissue is increased by optimization of the electric pulse shape; functional capacities for detection of the moment of exposure to electric pulse, documentation of the operating modes, and information exchange (including remote exchange) with medical personnel and patient (in portable models) are being improved [1, 3, 12]. Optimization of the medico-technical characteristics of modern ECDs and development of new models of ECDs are impossible without understanding the main bioelectrical characteristics of the process of defibrillation. However, in spite of extensive research in this field, there is still no acceptable unified theory of the mechanism (mechanisms) of defibrillation that can explain the majority of experimental findings. In particular, it is presently uncertain why a bipolar electric pulse is more effective for defibrillation [8]. Understanding of the mechanism of response of myocardium cells to external electrical effect of an electrode positioned at a distance significantly larger than several millimeters would provide a particularly deep insight into the mechanism of electrical defibrillation. On one hand, the mechanism of this response is due to passive propagation of transmembrane potential (TMP) deep into the myocardium during the exposure to the external electric pulse. This suggestion is supported by a large body of experimental findings. On the other hand, in accordance with theoretical models of electrophysical properties of myocardium, passive propagation of TMP during exposure to the external electric effect of an electrode positioned at a distance larger than several millimeters is impossible [10, 14]. This problem has been a subject of extensive research [10, 11]. Various theoretical models of passive propagation of TMP have been suggested to solve this problem. These models consider the conductive properties of the area of contact of myocyte cytoplasms, curvature of myocardium fibers, and heterogeneity of myocardial tissue at microscopic and macroscopic levels [5-7, 9-11, 13, 14, 17-19]. Nevertheless, the problem of determination of the predominant mechanism of defibrillation remains unsolved [10, 11]. The goal of this work was to describe the mechanism of passive propagation of TMP within the framework of bidomain description of the electrophysical properties of myocardium. According to this description, propagation of TMP is due to the intrinsic capacitances of bioelectrolytes [16]. This mechanism is due to the fact that both external and internal bioelectrolytes may have unbalanced (by absolute value) electric charges with respect to one another. In addition, these charges can sufficiently rapidly diffuse along bioelectrolytes, thereby contributing to the TMP due to electric induction. One of the advantages of this mechanism is that it is based on fundamental electrophysical properties of myocardium as a bidomain medium.

An improved method to estimate intrinsic small signal parameters of a gaas mesfet from measured dc characteristics

This investigation offers a technique to predict the ac behavior of mm wavelength GaAs metal semiconductor field effect transistors by using dc characteristics. To predict the intrinsic equivalent circuit parameters of the device from dc data, the measured dc characteristics are first simulated by employing a nonlinear dc model. The effects of biasing on the device ac parameters are evaluated for its low-noise applications. An improvement greater than 10% in predicting the ac response of the device is observed. The concept of depletion layer modification caused by the transverse electric field inside the channel is introduced for accurate Miller's capacitor modeling. It is assumed that with increased device biasing there are more unbalanced positive charges in the gate depletion toward the drain-side of the Schottky barrier. The electric field lines originated by these uncompensated charges induce an opposite charge density in the gate electrode. This modifies the gate biasing and hence the Schottky barrier depletion. As a result, the values of intrinsic ac device parameters change. It is observed that an accurate dc modeling is key to predicting an accurate ac small signal equivalent circuit of a device.

Black diholes in five dimensions

Using a generalized Weyl formalism, we show how stationary, axisymmetric solutions of the four-dimensional vacuum Einstein equation can be turned into static, axisymmetric solutions of five-dimensional dilaton gravity coupled to a two-form gauge field. This procedure is then used to obtain new solutions of the latter theory describing pairs of extremal magnetic black holes with opposite charges, known as black diholes. These diholes are kept in static equilibrium by membranelike conical singularities stretching along two different directions. We also present solutions describing diholes suspended in a background magnetic field, and with unbalanced charges.

Removing distortions from charge balance functions

Charge balance functions provide insight into critical issues concerning hadronization and transport in heavy-ion collisions by statistically isolating charge/anti-charge pairs which are correlated by charge conservation. However, distortions from residual interactions and unbalanced charges cloud the observable. Within the context of simple models, the significance of these effects is studied by constructing balance functions in both relative rapidity and invariant relative momentum. Methods are presented for eliminating or accounting for these distortions.

Black diholes with unbalanced magnetic charges

We present a technique that can be used to generate a static, axisymmetric solution of the Einstein-Maxwell-dilaton equations from a stationary, axisymmetric solution of the vacuum Einstein equations. Starting from the Kerr solution, Davidson and Gedalin have previously made use of this technique to obtain a pair of oppositely charged, extremal dilatonic black holes, known as a black dihole. In this paper, we shall instead start from the Kerr-NUT (Newman-Unti-Tamburino) solution. It will be shown that the new solution can also be interpreted as a dihole, but with the black holes carrying unbalanced magnetic charges. The effect of the NUT parameter is to introduce a net magnetic charge into the system. Finally, we uplift our solution to ten dimensions to describe a system consisting of $D6$ and anti--$D6$-branes with unbalanced charges. The limit in which they coincide agrees with a solution recently derived by Brax et al.