Strong Electrostatic Field Research Articles

Unraveling the nature of sensing in electrostatic MEMS gas sensors

This paper investigates the fundamental sensing mechanism of electrostatic MEMS gas sensors. It compares among the responsivities of a set of MEMS isopropanol sensors before and after functionalization, and in the presence and absence of electrostatic fields when operated in static and dynamic detection modes. In the static mode, we found that the sensors do not exhibit a measurable change in displacement due to added mass. On the other hand, bare sensors showed a clear change in displacement in response to isopropanol vapor. In the dynamic mode, functionalized sensors showed a measurable frequency shift due to the added mass of isopropanol vapor. In the presence of strong electrostatic fields, the measured frequency shift was found to be threefold larger than that in their absence in response to the same concentration of isopropanol vapor. The enhanced responsivity of dynamic detection allows the sensors to measure the vapor mass captured by the functional material, which is not the case for static detection. The detection of isopropanol by bare sensors in static mode shows that change in the medium permittivity is the primary sensing mechanism. The enhanced responsivity of dynamic mode sensors when operated in strong electrostatic fields shows that their sensing mechanism is a combination of a weaker added mass effect and a stronger permittivity effect. These findings show that electrostatic MEMS gas sensors are independent of the direction of the gravitational field and are, thus, robust to changes in alignment. It is erroneous to refer to them as ‘gravimetric’ sensors.

Self-Powered Autonomous Electrostatic Dust Removal for Solar Panels by an Electret Generator.

Solar panels often suffer from dust accumulation, significantly reducing their output, especially in desert regions where many of the world's largest solar plants are located. Here, an autonomous dust removal system for solar panels, powered by a wind-driven rotary electret generator is proposed. The generator applies a high voltage between one solar panel's output electrode and an upper mesh electrode to generate a strong electrostatic field. It is discovered that dust particles on the insulative glass cover of the panel can be charged under the high electrical field, assisted by adsorbed water, even in low-humidity environments. The charged particles are subsequently repelled from the solar panel with the significant Coulomb force. Two panels covered with sand dust are cleaned in only 6.6min by a 15cm diameter rotary electret generator at 1.6ms-1 wind speed. Experimental results manifest that the system can work effectively in a wide range of environmental conditions, and doesn't impact the panel performance for long-term operation. This autonomous system, with its high dust removal efficiency, simplicity, and low cost, holds great potential in practical applications.

Enhancing the Performance of GaN-Based Light-Emitting Diodes by Incorporating a Junction-Type Last Quantum Barrier

In this paper, an n-i-p-type GaN barrier for the final quantum well, which is closest to the p-type GaN cap layer, is proposed for nitride light-emitting diodes (LEDs) to enhance the confinement of electrons and to improve the efficiency of hole injection. The performances of GaN-based LEDs with a traditional GaN barrier and with our proposed n-i-p GaN barrier were simulated and analyzed in detail. It was observed that, with our newly designed n-i-p GaN barrier, the performances of the LEDs were improved, including a higher light output power, a lower threshold voltage, and a stronger electroluminescence emission intensity. The light output power can be remarkably boosted by 105% at an injection current density of 100 A/cm2 in comparison with a traditional LED. These improvements originated from the proposed n-i-p GaN barrier, which induces a strong reverse electrostatic field in the n-i-p GaN barrier. This field not only enhances the confinement of electrons but also improves the efficiency of hole injection.

Electrostatic Field in Contact‐Electro‐Catalysis Driven C−F Bond Cleavage of Perfluoroalkyl Substances

AbstractPerfluoroalkyl substances (PFASs) are persistent and toxic to human health. It is demanding for high‐efficient and green technologies to remove PFASs from water. In this study, a novel PFAS treatment technology was developed, utilizing polytetrafluoroethylene (PTFE) particles (1–5 μm) as the catalyst and a low frequency ultrasound (US, 40 kHz, 0.3 W/cm2) for activation. Remarkably, this system can induce near‐complete defluorination for different structured PFASs. The underlying mechanism relies on contact electrification between PTFE and water, which induces cumulative electrons on PTFE surface, and creates a high surface voltage (tens of volts). Such high surface voltage can generate abundant reactive oxygen species (ROS, i.e., O2⋅−, HO⋅, etc.) and a strong interfacial electrostatic field (IEF of 109~1010 V/m). Consequently, the strong IEF significantly activates PFAS molecules and reduces the energy barrier of O2⋅− nucleophilic reaction. Simultaneously, the co‐existence of surface electrons (PTFE*(e−)) and HO⋅ enables synergetic reduction and oxidation of PFAS and its intermediates, leading to enhanced and thorough defluorination. The US/PTFE method shows compelling advantages of low energy consumption, zero chemical input, and few harmful intermediates. It offers a new and promising solution for effectively treating the PFAS‐contaminated drinking water.

Electrostatic Field in Contact-Electro-Catalysis Driven C-F Bond Cleavage of Perfluoroalkyl Substances.

Perfluoroalkyl substances (PFASs) are persistent and toxic to human health. It is demanding for high-efficient and green technologies to remove PFASs from water. In this study, a novel PFAS treatment technology was developed, utilizing polytetrafluoroethylene (PTFE) particles (1-5 μm) as the catalyst and a low frequency ultrasound (US, 40 kHz, 0.3 W/cm2) for activation. Remarkably, this system can induce near-complete defluorination for different structured PFASs. The underlying mechanism relies on contact electrification between PTFE and water, which induces cumulative electrons on PTFE surface, and creates a high surface voltage (tens of volts). Such high surface voltage can generate abundant reactive oxygen species (ROS, i.e., O2⋅-, HO⋅, etc.) and a strong interfacial electrostatic field (IEF of 109~1010 V/m). Consequently, the strong IEF significantly activates PFAS molecules and reduces the energy barrier of O2⋅- nucleophilic reaction. Simultaneously, the co-existence of surface electrons (PTFE*(e-)) and HO⋅ enables synergetic reduction and oxidation of PFAS and its intermediates, leading to enhanced and thorough defluorination. The US/PTFE method shows compelling advantages of low energy consumption, zero chemical input, and few harmful intermediates. It offers a new and promising solution for effectively treating the PFAS-contaminated drinking water.

Modeling Field Electron Emission from a Flat Au (100) Surface with Density-Functional Theory

Field electron emission, or electron tunneling through a potential energy (PE) barrier under the influence of a strong electrostatic (ES) or radio frequency (RF) field, is of broad interest to the accelerator physics community. For example, it is the source of undesirable dark currents in resonant cavities, providing a limit to high-field operation. Field electron emission can also be applied to quasi-statically model electron emission induced by the electric field in a laser pulse. The classical approach to field electron emission is the Fowler–Nordheim (FN) framework, which incorporates a simplified PE profile and various assumptions. Here, we build a more realistic model using the PE and charge densities derived from a density-functional theory (DFT) calculation. We examine the correction factors associated with each model assumption. Compared to the FN framework, our results can be extended up to 80 GV/m, a limit that has been reached in laser-induced strong field emission scenarios.

Germination of bean seeds (Vigna unguiculata L. Walp.) in strong electric fields

This paper presents a tutorial for the germination of bean seeds (Vigna unguiculata L. Walp.) in strong electrostatic fields up to 1240 V/cm. The seeds were allowed to germinate under different electric field strengths for 48 h. Although most of such germination experiments did not show any visible effect, the field strength of 945 V/cm strongly increased the seedling's vigor during the early growth stage. In the end, 30 % more yield was obtained from stimulated seeds when compared to the control group. This article postulates for the first time a hypothesis of the mechanism of action of the electric field during germination. In biological cells of any species, water confined between narrow surfaces can undergo a phase transition that shifts its melting point to higher temperatures when an external electric field is applied. This effect has already been known as electrofreezing, and has been confirmed by several experimental and molecular modeling studies. As a consequence, the transport kinetics of molecules across cell organelle membranes might be altered, which in turn leads to different plant properties.With emphasis on the presented method, this work reports:•An inexpensive electric circuit for the generation of strong electric fields•Instructions regarding the setup and operation of an adequate germination chamber

Geometry effects on energy selective focusing of laser-driven protons with open and closed hemisphere-cone targets

Relativistically intense laser light interacting with solid density targets can accelerate protons to multi-MeV energies via the target normal sheath acceleration process. The use of hollow hemisphere targets with a hollow conical region to focus protons of selected energies, for applications such as isochoric heating of matter and for the fast ignition approach to inertial confinement fusion, is explored for laser intensity Wcm−2. Specifically, the effects of having the cone tip open or closed is investigated experimentally and via a programme of scaled particle-in-cell simulations. The open cone configuration is found to result in proton focusing in the energy range of 9 to 24 MeV, and produce an annular profile for higher energy components, up to 55 MeV, while the spatial distribution of lower energy components remains unchanged. By contrast, for the closed cone case, the focusing effect is diminished by the fields present on the inner wall of the cone tip. Simulations reveal that strong electrostatic and magnetic fields present on the inner surfaces of the target induce the focusing effect with the open cone, but also result in proton divergence in the case of the closed cone. Additionally, the simulations demonstrate the possibility to tailor the cone geometry to select the energy range over which the focusing occurs.

Self-assembly tourmaline@BiFeO3 composites with enhanced polarization for dual-selective C3H6O and H2S detection

Ferroelectric oxides with great polarization have attracted much attention due to the polarization modulated carrier behaviors causing high gas sensitivity in detecting hazardous toxic gases. In this work, tourmaline@BiFeO3 (T@BFO) composites were fabricated by the sol-gel method based on the electrostatic self-assembly strategy for the C3H6O and H2S detection. It is found that BFO nanoparticles are uniformly distributed on tourmaline due to the strong electrostatic field of tourmaline. In comparison with pure BFO, the T@BFO composites showed an improved gas sensitivity. More importantly, the sensor based on 3.0-T@BFO can effectively detect C3H6O at 150 °C and H2S at 210 °C in limits of detection as low as 50 and 7 ppb, respectively. The results exhibit that 3.0-T@BFO composites have lower activation energies (Eact) of C3H6O at 150 °C and H2S at 210 °C, which endow 3.0-T@BFO with dual-selectivity for C3H6O and H2S. The Ex-situ XPS and density functional theory calculations further reveal that tourmaline activates the sensing site of BFO to achieve selective adsorption of C3H6O at Bi, Fe, and oxygen vacancies sites and H2S at surface lattice oxygens, Fe and oxygen vacancies sites. These results provide an efficient strategy to design practice multifunctional and highly sensitive gas sensors for detecting hazardous toxic gases.

Influence of the Lateral Electrostatic Field on the Statistical Distribution of Charge Carriers in a Cylindrical Nanolayer of β-HgS

Analytical expressions are obtained for the wave functions and the energy spectrum of charge carriers in the β-HgS nanolayer of a cylindrical core/shell/shell β-CdS/ β-HgS/ β-CdS nanocomposite in the presence of a strong lateral uniform electrostatic field. It is shown that, under the influence of an external field, the position of the chemical potential of the electron-hole subsystem at absolute zero shifts to the bottom of the conduction band of the sample. The displacement value is determined by the intensity of the external field and increases linearly with increasing field. The concentration, internal energy, and heat capacity of the electronic subsystem of the β-HgS layer in the presence of a field are compared with similar values in the absence of a field. Calculations show that under identical conditions, the presence of an external field leads to an increase in the carrier concentration, which in turn leads to an increase in the internal energy and heat capacity of the system of electrons and holes in the layer.

Ultra-dispersed W-doped carbon nitride anchoring on ceramic via the regulation of electrostatic field for efficient degradation of cationic surfactant

To improve the dispersion and electronic transmission performance of carbon nitride (C3N4), an electrostatic field regulation strategy was developed for constructing an ultra-dispersed and high reactive W-doped C3N4/ceramic (W/C3N4@ceramic) composite, which was used as a photocatalyst for degrading low-concentration cetyltrimethylammonium bromide (CTAB) under visible light irradiation to achieve the goal of “enhanced enrichment/catalytic degradation”. The ceramic with strong electrostatic field can rapidly capture the interlayer electrons and break the hydrogen bonds in the lamellar skeletons of massive C3N4, leading to the structure of C3N4 from bulk to nanosheet. W/C3N4@ceramic exhibited outstanding adsorption capacity (CTAB removal rate of 68.2% within 30 min in the dark) and photocatalytic activity (CTAB degradation rate of 93.9% within 90 min under light irradiation), which were much higher than those adsorbed (21.9%) and photocatalyzed (46.6%) by W/C3N4. The improved photocatalytic activity can be ascribed to that the ultra-dispersed nanosheets shortened the charge transfer path to accelerate the transmission and separation efficiency of photogenerated charges and increase specific surface area to provide abundant active sites. Moreover, CTAB can be spontaneously adsorbed on the surface of ceramic driven by electrostatic field, thus accelerating the interfacial transport and promoting photocatalytic efficiency. This work provides a novel strategy for the development of efficient catalysts with enhanced adsorption capacity and photocatalytic activity.

Electra-electric induction for power generation by cutting through electric field lines

It is well known that cutting magnetic field lines leads to the generation of an induced current and induced electromotive force in a closed circuit coil, called as electromagnetic induction. In this paper, we found that rotating a closed circuit coil in a changing electric or electrostatic field could also generate an induced current and electromotive force in the coil without any external magnets. Here we call it Electra-electric induction (EEI). This interesting discovery will be of great significance both in theory and in applications. We deduced that both Maxwell’s displacement current and the Electra-electric induced current are generated by the changing electric field. One exists in space. The other exists and flows in the conductor. Maxwell’s displacement current is collected by a coil and flows in a conductor, which is the induced current. In addition, one can expect that the extremely strong electrostatic field near the high-voltage wire, as well as the strong electromagnetic field generated by the radiation of nuclear reactor or nuclear waste dumping, can be collected by the rotated coil driven by the windmill which results in a continuous induced current flow generated. This work likely opens up new possibilities for non-electromagnetic induction and provides a new idea for the generation and transmission mode of power energy.

Molecular insights into ions permeation and destruction behavior in methane hydrate driven by electrostatic fields

The formation and dissociation of gas hydrate can be promoted by different electrostatic field intensity, so it is considered as one of the potential technologies with great application value in hydrate exploitation, hydrate prevention in oil and gas wells and pipelines, and hydrate-related technologies. Generally, these technologies are used in the environment of ionic solution, resulting in the phenomenon of ion electrophoresis. The physical–chemical interaction between ions migration and hydrate is inevitable, but this interaction remains unclear. Herein, the crystal structure of methane hydrate infiltrated and destabilized by ions (K+, Na+, Li+, Ca2+, Mg2+, and Cl-) driven by electrostatic fields was shown through molecular dynamics (MD) simulation. Specifically, as the strength of the electrostatic field increases, the rate of diffusion and migration of ions in hydrate increases, accompanied by stronger destruction. Monovalent K+ migration is more effective in destroying hydrate structure under weak electrostatic fields, while divalent cations (Ca2+ and Mg2+) are more effective under strong electrostatic fields. The order of migration rate of ions in hydrate cages is K+ > Na+ > Li+ > Ca2+ > Mg2+. The difference of migration rate and destruction effect of ions in hydrate system is closely related to the hydration radius, hydration geometry, and hydration energy of ions. Dehydration and water molecular replacement occur in the process of hydrated ions driven by strong electrostatic fields entering the methane hydrate phase from the liquid phase. These molecular insights on the impacts of ions migration behavior on methane hydrate are beneficial for the application of electrostatic field in hydrate mining, safety of oil and gas pipeline transportation, and hydrate-related technologies.

Electroabsorption and Stark Fluorescence Spectroscopies of Thioflavin T.

Thioflavin T (ThT) is a typical fluorescent marker for detecting the formation of amyloid fibrils, because its fluorescence intensity increases by more than 2 orders of magnitude upon complexation with the fibrils. Strong electrostatic fields on protein surfaces are known to be a significant factor in chemical reactions and biological functions. Therefore, ThT bound to amyloid fibrils must experience strong electric fields. This study employed electroabsorption and Stark fluorescence spectroscopies to clarify the effects of external electric fields on the photophysics of ThT. The absorption spectrum shows two bands ascribed to locally excited (LE) and charge transfer (CT) states. Coupling between the LE and CT states is enhanced in the presence of an external electric field, resulting in fluorescence quenching. The electric field strength of the amyloid fibril surface was inferred from the fluorescence quenching efficiency of ThT.

Exceptional Hydrogen Diffusion Rate over Ru Nanoparticle-Doped Polar MgO(111) Surface.

Hydrogen (H) conductivity on oxide-based materials is crucially important in fuel cells and related catalysis. Here, this work measures the diffusion rate of H generated from Ru nanoparticles loaded on polar MgO(111) facet particles under H2 at elevated temperatures without moisture and compares it to conventional nonpolar MgO(110) for the first time by in situ quasielastic neutron scattering (QENS). The QENS reveals an exceptional diffusion rate on the polar facet via a proton (H+ ) hopping mechanism, which is an order of magnitude superior to that of typical H+ -conducting oxides. This work attributes this to the unique atomic arrangement of alternate layers of Mg cations and O anions of the polar MgO(111) where the strong electrostatic field of terminal oxygen anions facilitates protonic migration with a lower degree of local covalency.

Native frustrated Lewis pairs on core-shell In@InOxHy enhances CO2-to-formate conversion.

Strategies to efficiently activate CO2 by strongly inhibiting the competitive hydrogen evolution reaction process are highly desired for practical applications of the electrochemical CO2 reduction technique. Here, we assembled a core-shell In@InOxHy architecture on carbon black by one-step reduction of NaBH4 as a CO2-to-formate catalyst with high selectivity. The stable CO2-to-formate reaction originates from the creation of steritic frustrated Lewis pairs (FLPs) on the InOxHy shell with In-OVs (OVs, oxygen vacancies) Lewis acid, and In-OH Lewis base. During CO2 reduction, the electrochemically stable FLPs are capable of first capturing and stabilizing protons to protonate FLPs to In-H Lewis acid and In-OH2 Lewis base due to its strong steric electrostatic field; then, CO2 is captured and activated by the protonated FLPs to selectively produce formate. Our results demonstrated that FLPs can be created on the surface of oxyphilic single-metal catalysts efficient in accelerating CO2 reduction with high selectivity.

Atomistic modeling of the channeling process with radiation reaction force included

Methodology is developed that incorporates the radiative reaction force into the relativistic molecular dynamics framework implemented in the MBN Explorer software package. The force leads to a gradual decrease in the projectile’s energy ɛ due to the radiation emission. This effect is especially strong for ultra-relativistic projectiles passing through oriented crystals where they experience the action of strong electrostatic fields as has been shown in recent experiments. A case study has been carried out for the initial approbation of the methodology developed. Simulations of the processes of planar channeling and photon emission have been performed for 150 GeV positrons in a 200μm thick single oriented Si(110) crystal. Several regimes for the decrease in ɛ have been established and characterized. Further steps in developing the code to include the necessary quantum corrections are identified and possible algorithmic modifications are proposed.

Identification of Single Amino Acid Chiral and Positional Isomers Using an Electrostatically Asymmetric Nanopore.

Chirality is essential in nearly all biological organizations and chemical reactions but is rarely considered due to technical limitations in identifying L/D isomerization. Using OmpF, a membrane channel from Escherichia coli with an electrostatically asymmetric constriction zone, allows discriminating chiral amino acids in a single peptide. The heterogeneous distribution of charged residues in OmpF causes a strong lateral electrostatic field at the constriction. This laterally asymmetric constriction zone forces the sidechains of the peptides to specific orientations within OmpF, causing distinct ionic current fluctuations. Using statistical analysis of the respective ionic current variations allows distinguishing the presence and position of a single amino acid with different chiralities. To explore potential applications, the disease-related peptide β-Amyloid and its d-Asp1 isoform and a mixture of the icatibant peptide drug (HOE 140) and its d-Ser7 mutant have been discriminated. Both chiral isomers were not applicable to be distinguished by mass spectroscopy approaches. These findings highlight a novel sensing mechanism for identifying single amino acids in single peptides and even for achieving single-molecule protein sequencing.

A reactive molecular dynamics study of the effects of an electric field on n-dodecane combustion

A reactive Molecular Dynamics (MD) study of n-dodecane combustion at high temperatures under externally applied electrostatic fields is performed to investigate their effect on chemical kinetics. A local charge equilibration method is used to enable charge transfers up to the overlap of the atomic orbitals and introduce molecular polarization induced by an electric field. The atomic charges of an isolated n-dodecane molecule with and without external electrostatic fields are first compared with Density Functional Theory (DFT) computations, to assess the accuracy of the charge equilibration method and its ability to capture polarization. Then, the impact of external electrostatic fields on the reaction kinetics of fuel, oxidizer and products is studied for a range of ambient temperatures and densities. The activation energy and pre-exponential factor of Arrhenius-type reactions under various electrostatic fields are also investigated by performing Nudged Elastic Band (NEB) computations on selected reactions’ Minimum Energy Path (MEP) and by analysing the collision frequency, respectively. Results show that the atomic charge transfers due to close interactions and molecular polarisation are relatively weak in all investigated conditions, leading to the necessity of strong external electric fields to induce changes to chemical kinetics. The consumption rate of n-dodecane decreases for strong electrostatic fields, whereas for low values of the electrostatic field strength no clear trend is observed. In addition, at high temperature and density conditions, oxygen consumption increases under strong electrostatic fields, whereas the opposite trend is observed as the temperature and density decrease. NEB analysis shows alterations of the activation energy up to 2.3 kcal/mol for oxygen compound reactions with varying strength of the external electrostatic field. Furthermore, analysis of the translational, rotational and vibrational kinetic energy modes and collision frequency reveals the influence of translational motion and molecular stabilization on the reaction rates. The kinetics of oxygen molecules was found to be of primary importance to determine the reaction behaviour under external electrostatic fields, as oxygen molecules have a direct effect on the oxidation reactions and also indirectly affect n-dodecane pyrolysis when an electrostatic field is present. This study provides fundamental understanding of the interactions between heavy hydrocarbons and electrostatic fields for the development of future hybrid thermal-electrical technologies.

Exciting of Strong Electrostatic Fields and Electromagnetic Resonators at the Plasma Boundary by a Power Electromagnetic Beam

The interaction of an electromagnetic beam with a sharp boundary of a dense cold semi-limited plasma was considered in the case of a normal wave incidence on the plasma surface. The possibility of the appearance of an electrostatic field outside the plasma was revealed, the intensity of which decreased according to the power law with a distance from the plasma and the center of the beam. It was possible to form cavities with a reduced electron density, being each electromagnetic resonators, which probed deeply into the dense plasma and couldexist in a stable state for a long period.