Negative Electrostatic Field Research Articles

Magnetic Field Must Be Accompanied by Electric Field

 Not only the changing magnetic field produces an electric field, but also the static magnetic field is accompanied by an electric field. It is considered in the superposition principle of electrostatic field and the special relativity that the electric field around the moving electrons in permanent magnet still exists and presents length contraction in the direction of movement. Through experimental analysis, it is also considered that the motion states of two electric fields having same direction and opposite direction of motion cancel out each other. Based on the two above-mentioned basic concepts, it can be inferred that negative electrostatic field exists in the vicinity of cubic permanent magnet N and S pole surface edge while positive electrostatic field exists in the vicinity of side edge. In addition, the results of experimental verification are also introduced.

Dramatically promoted photocatalytic water splitting over InVO4 via extending hole diffusion length by surface polarization

Indium vanadate (InVO4) is considered to be a promising photocatalyst due to its strong absorption in the visible light region and potential to overall split water. However, it is hardly used for water splitting on account of its short diffusion length of holes. In this work, surface polarization based on inorganic acid modification was adopted to deal with above issue. The results show that the modified acid with hydroxyl groups would ionize in water, making InVO4 carry more negative charges. Such a surface polarization remarkably enhanced the activities, of which up to 21.74 μmol·g−1·h−1 for hydrogen generation and 13.18 μmol·g−1·h−1 for oxygen generation, respectively. The enhanced activities are mainly attributed to the induction of surface-carried negative electrostatic field, by which the holes were driven to the surface and its diffusion length was extended from ∼ 10 nm to ∼ 50 nm, while the electron tend to be transport to the inner. Thus, the charge carrier recombination was inhibited and more holes could arrive at the surface to generate oxygen, which is the rate-determining step of water splitting.

Electrostatic Interaction of Globins with Phospholipid Membranes

For the structures of sperm whale myoglobin (swMb), horse heart myoglobin (hhMb), hemoglobin I (HbI) from botfly Gasterophilus intestinalis (giHbI), and monomeric and dimeric hemoglobins HbI and HbII from Lucina pectinata mollusk (lpHbI and lpHbII), roles of electrostatic interactions in stabilization of native conformations of the heme cavity were analyzed, as well as their possible destabilization by interaction with the negatively charged phospholipid membranes. The native conformation of the heme cavity in these globins, both its proximal and distal parts, was shown to be sustained by a system of hydrogen bonds involving the proximal and distal protein residues, the heme propionates, and the nearby polar amino acids on the protein surface (His, Arg, Lys). The hydrogen bond network in the proximal part of the heme pocket controls the position of the Fe atom either outside or within the protoporphyrin plane, which affects the efficiency of ligand binding. In the distal part, the hydrogen bond network formed with the distal protein residue involved (HisE7 in swMb, hhMb, and giHbI and GlnE7 in lpHbII), should stabilize the conformation in which the protein can donate hydrogen to the O2 ligand. The hydrogen bond between the E7 distal residue and O2 ligand prevents rapid dissociation of the latter and plays an important role in the regulation of ligand affinity. The hydrogen bond networks found in the proximal and, especially, in the distal heme environments, must be disrupted when oxyglobin binds to the membrane surface. This disruption caused by interaction of negatively charged phospholipid heads with lysine or arginine residues exposed towards the membrane, altered local pH near the membrane, and the effect of negative electrostatic field of the membrane, can decrease the affinity of the protein for the O2 ligand, thus facilitating its dissociation at the physiological pO2 values in the cell.

Novel role of the phosphatidylinositol phosphatase Sac1 in membrane homeostasis and polarized growth in Candida albicans

Phosphoinositides (PIPs) are one kind of membrane components functioning in many intracellular processes, especially in signaling transduction and membrane transport. Phosphatidylinositide phosphatases (PIPases) are specifically important for the PIP homeostasis in cell. In our previous study, we have identified the actin-related protein CaSac1 in Candida albicans, while its functional mechanisms in regulating membrane homeostasis has not been identified. Here, we show that the PIPase CaSac1 is a main membrane-related protein and regulates hyphal polarization by governing phosphoinositide dynamic and plasma membrane (PM) electrostatic field. Deletion of CaSAC1 resulted in large-scale abnormal redistribution of phosphatidylinositide 4-phosphate (PI4P) from the endomembrane to the PM. This abnormality further led to disturbance of the PM's negative electrostatic field and abnormally spotted distribution of phosphatidylinositide 4,5-bisphosphate (PI(4,5)P2). These changes led to a severe defect in polarized hyphal growth, which could be diminished with recovery of the PM's negative electrostatic field by the anionic polymer polyacrylic acid (PAA). This study revealed that the PIPase CaSac1 plays an essential role in regulating membrane homeostasis and membrane traffic, contributing to establishment of polarized hyphal growth.

Surface adsorption configurations of H3PO4 modified TiO2 and its influence on the photodegradation intermediates of gaseous o-xylene

Abstract For the oxide-based photocatalysts, polyoxylic acid modification can affect their adsorption/desorption properties and further regulate photocatalytic reaction pathway, which is crucial for enhancing photocatalytic activity and selectivity. Herein, phosphoric acid modified TiO2 was synthesized by a facile impregnation-calcination method for photocatalytic degradation of gaseous o-xylene. According to FTIR, XPS, and EDS analysis, phosphoric acid was anchored on the surface of TiO2 successfully. The surface P atomic percentages for PT1 was 2.45%. The as-prepared phosphoric acid modified TiO2 (PTx) had a photocatalytic performance superior to that of commercial TiO2 and unmodified TiO2 (PT0), with increasing by 2.2 times at most. Interestingly, the phosphoric acid molecules strongly adsorbed on anatase TiO2 surface by forming H–O2C and =O–Ti5C chemical bonds according to the first principle calculations, which changed TiO2 surface properties (specific surface area and surface negative electrostatic field) and further improved adsorption and charge carrier separation and transfer, thus improving the photocatalytic activity. Additionally, according to the intermediates results, the relative abundance of intermediates shows obvious difference. Acetone was detected as the most abundant intermediates during o-xylene degradation for PT0, whereas that was o-methyl benzaldehyde for PT1, which could be ascribed to the difference of surface adsorption configuration of o-xylene. According to the temperature-programmed desorption (TPD) results, the surface modified by phosphoric acid could change the o-xylene adsorption configuration to favor its methyl oxidation (standing configuration), whereas the unmodified surface could be more favorable to the benzene ring-open reaction (lying configuration). This work will deepen the understanding of the relevance of surface modification and surface photocatalytic reaction, which also provides a feasible strategy to improve photocatalytic selectivity.

The Multiple Promotion Effects of Ammonium Phosphate-Modified Ag3PO4 on Photocatalytic Performance.

Phosphate () modification of semiconductor photocatalysts such as TiO2, C3N4, BiVO4, and etc. has been shown positive effect on the enhancement of photocatalytic performance. In the present study, we demonstrate a novel one-pot surface modification route on Ag3PO4 photocatalyst by ammonium phosphate [(NH4)3PO4], which combines modification with ammonium () etching to show multiple effects on the structural variation of Ag3PO4 samples. The modified Ag3PO4 photocatalysts exhibit much higher photocatalytic performance than bare Ag3PO4 for the degradation of organic dye solutions under visible light irradiation. It is indicated that the etching favors the surface transition from Ag3PO4 to metallic Ag nanoparticles, resulting in the fast capture of photogenerated electrons and the followed generation of radicals. The strongly adsorbed on the Ag3PO4 surfaces can further provide more negative electrostatic field, which improves the separation of photogenerated electron-hole pairs by inducing the holes to directly flow to the surface and then enhances the formation of reactive ·OH radicals. Furthermore, the photocatalytic performance of the modified Ag3PO4 photocatalysts can be optimized by monitoring the concentration of (NH4)3PO4 that is 1 mM.

Modeling diffusion processes in the presence of a diffuse layer at charged mineral surfaces: a benchmark exercise

The electrostatic properties of clay mineral surfaces play a significant role in their diffusion properties. The negative electrostatic potential field at clay mineral surfaces results in the presence of a diffuse layer that balances the mineral surface charge. The diffusion properties of the porosity fraction that is affected by this phenomenon are different from the diffusion properties of electroneutral bulk water. These properties have attracted growing interest from diverse communities in the past years, especially in the field of study of radioactive waste disposal. The influence of the diffuse layer can be described at the continuum scale by a set of equations that are formulated in terms of the Nernst-Planck equation. The number of codes that can handle the coupling between transport properties in clay affected by the presence of a diffuse layer in the porosity and chemical reactions is very limited, and no benchmark exercises have been published yet that make it possible to validate the numerical implementation of these equations in reactive transport codes. The present study proposes a set of benchmark exercises of increasing complexity that highlight caveats related to the finite difference (volume) treatment of the Nernst-Planck equation in the presence of a diffuse layer in heterogeneous systems. Once these problems are identified and solved, the codes PHREEQC, CrunchClay, and a new Fortran routine written for this study gave results in very good agreement for most of the benchmark exercises. When present, the differences in results were directly traceable to the differences in averaging methods at grid cell boundaries, and to the consideration or the omission of the activity gradient term in the Nernst-Planck equation.

Ion counting demonstrates a high electrostatic field generated by the nucleosome.

In eukaryotes, a first step towards the nuclear DNA compaction process is the formation of a nucleosome, which is comprised of negatively charged DNA wrapped around a positively charged histone protein octamer. Often, it is assumed that the complexation of the DNA into the nucleosome completely attenuates the DNA charge and hence the electrostatic field generated by the molecule. In contrast, theoretical and computational studies suggest that the nucleosome retains a strong, negative electrostatic field. Despite their fundamental implications for chromatin organization and function, these opposing views of nucleosome electrostatics have not been experimentally tested. Herein, we directly measure nucleosome electrostatics and find that while nucleosome formation reduces the complex charge by half, the nucleosome nevertheless maintains a strong negative electrostatic field. Our studies highlight the importance of considering the polyelectrolyte nature of the nucleosome and its impact on processes ranging from factor binding to DNA compaction.

2D Co-incorporated hydroxyapatite nanoarchitecture as a potential efficient oxygen evolution cocatalyst for boosting photoelectrochemical water splitting on Fe2O3 photoanode

The serious charge recombination together with the sluggish water oxidation kinetics have largely limited the practical application of hematite (Fe2O3) in photoelectrochemical (PEC) water splitting. Surface modification with oxygen evolution cocatalyst is an efficient strategy to address the both issues. Herein, a novel 2D oxygen evolution cocatalyst, namely Co-incorporated hydroxyapatite (Co-HAP) nanoarchitecture, was rationally designed and decorated on Fe2O3 photoanode. The resulting Co-HAP decorated Fe2O3 (Co-HAP/Fe2O3) exhibited excellent PEC water splitting with a high photocurrent density of 2.25 mA cm−2 at 1.23 V vs. RHE in neutral electrolyte, which is ca. 9.78 times that for bare Fe2O3. Moreover, the onset potential displayed a 200 mV cathodic shift, indicating an accelerated water oxidation kinetics over Fe2O3. PEC characterizations revealed Co-HAP could not only significantly improve the charge-separation efficiency but also could enhance the surface charge-separation efficiency in the bulk and on the surface of Fe2O3. Comprehensive investigations unveiled the interfacial negative electrostatic field and the increased electrical conductivity arising from Co-HAP decoration were of great benefit to improve the charge separation and inhibit surface charge recombination, while the 2D architecture of Co-HAP offered high surface area and abundant exposed Co active sites, ultimately boosted PEC water splitting over Fe2O3. Owing to the superior ion-exchange ability of HAP, the strategy presented here would open a new vane to explore highly efficient oxygen evolution cocatalyst.

An Insight into Electrostatic Field Effects on SO3 Adsorption by CaO with CO2, SO2 and H2O: A DFT Approach

ABSTRACT Because of the compulsory installation of electrostatic precipitators in coal-fired power plants, SO3 and particles in flue gas inevitably pass through areas with electric field and electric charge distributed. CaO is the highest alkaline content in fly ash and has strong interactions with SO3. Therefore, it is important to understand the effects of the electric field on the binding energies of SO3 and CaO. Density functional theory calculations were applied to examine the electrostatic field dependence of SO3 adsorption on the CaO(100) surface. The energetic, geometric and electronic nature of the modeled systems was analyzed. Trends of the adsorption energy variation in a positive or negative electrostatic field presented great differences. When the electrostatic field was small, it was observed that the required adsorption energy was reduced regardless of the positive or negative electrostatic field. With increased electrostatic field strength, the adsorption energy showed an increasing trend in a positive field, while the adsorption energy decreased in a negative field. The positive field enhanced the charge density changes of the surface O across the Ca around the OCaO, while the negative field enhanced the change of the charge density of the Ca below the OCaO. The SO42–-like structure accumulated electrons as a unit and the charge transfer of the SO42– increased with the incremental adsorption energy in a linear relationship. On the H pre-adsorbed surface, the total increment was much smaller than in previous cases in a positive field, and the total variation was negligible in a negative field.

A field-based disparity analysis of new 1,2,5-oxadiazole derivatives endowed with antiproliferative activity.

A series of 1,2,5-oxadiazoles were synthesized as new potential antiproliferative agents. The in vitro cytotoxic activity evaluation of title compounds through MTT assay revealed that some of them showed significant activity against the HCT-116 cancer cell line. The field-based disparity analysis provided indications about the electrostatic, hydrophobic, and shape features underlying the cytotoxicity, suggesting that increasing the negative electrostatic field on the heterocyclic core of the structure has positive effects on the activity. The structure-activity relationships (SAR) around a particular compound can be explained allowing for a structural rationale for the differences in activity. The SAR provided by this series of compounds can be exploited to carry out further lead optimization.

Enhanced Photoelectrochemical Performance of Porous Bi2MoO6 Photoanode by an Electrochemical Treatment

We report on the growth of porous Bi2MoO6 electrodes by first electrochemically depositing bismuth oxyiodide (BiOI) films and then thermally annealing the BiOI films with a molybdate solution. These Bi2MoO6 electrodes were tested as photoanodes for photoelectrochemical water oxidation. We found that the photoactivity of Bi2MoO6 electrode was largely improved after conducting a cyclic voltammetry treatment in 0.1 M phosphate buffer solution (pH 7.0). Through designed control experiments, XPS, FTIR and isoelectric point analyses, it was confirmed that phosphate anions (PO43−) modified the surface of Bi2MoO6 electrode during the cyclic voltammetry process and played a critical role in the enhancement of PEC performance. The performance improvement was attributed to the formation of a negative electrostatic field on the surface of Bi2MoO6 electrode after phosphate modification which resulted in the enhanced efficiency of charge separation.

Insights into electrolyte effects on photoactivities of dye-sensitized photoelectrochemical cells for water splitting

Dye-sensitized photoelectrochemical cell (DS-PEC) is an especially attractive method to generate hydrogen via visible light driven water splitting. Electrolyte, an essential component of DS-PEC, plays a great role in determining the photoactivities of devices for water splitting. When using phosphate buffer (pH=6.4) as electrolyte, the DS-PEC displayed much higher photoactivity than using 0.1M Na2SO4 (pH=6.4) as electrolyte. The insight is phosphate anion gathers together to form a negative electrostatic field on TiO2 surface, which increases the resistance in the TiO2/catalyst and electrolyte interface and validly reduces the charge recombination from TiO2 to the oxidized catalyst.

Simple synthesis of lithium-doped sulfated titania nanoparticles and their high visible light photocatalytic activity under negative bias electrostatic field

Li-doped TiO2/SO42− nanoparticles were successfully synthesized via a simple calcinination process in a vacuum environment using Ti(SO4)2 and LiBr as precursors, and were characterised by TEM, XRD, IR, DLS, XPS and UV-vis (DRS).

Nanocube-based hematite photoanode produced in the presence of Na2HPO4 for efficient solar water splitting

A thin film of α-Fe2O3 on FTO substrate has been synthesized from hydrothermal process in an aqueous solution of FeCl3 and Na2HPO4. A nanocube structure of α-Fe2O3 is observed within the formed hematite films and coated with phosphate ions on the surface. For comparison, another phosphate modified hematite film has been prepared by soaking the bare hematite film in Na2HPO4 solution. A negative electrostatic field can be built up on the surface of both phosphate modified hematite which will promote charge separation and extraction of photoexcited holes to the electrode surface. It is found that different types of phosphate complex exist in the hematite films, which has been determined by the isoelectric point (IEP) of the hematite films, and consequently influences the formation and strength of the electrostatic field. The effects of phosphate ions on the morphology, surface characteristics and the photoelectrochemical properties of the hematite thin films are investigated and the mechanism is proposed.

Refluxed electrons direct laser acceleration in ultrahigh laser and relativistic critical density plasma interaction

Refluxed electrons direct laser acceleration is proposed so as to generate a high-charge energetic electron beam. When a laser pulse is incident on a relativistic critical density target, the rising edge of the pulse heats the target and the sheath fields on the both sides of the target reflux some electrons inside the expanding target. These electrons can be trapped and accelerated due to the self-transparency and the negative longitudinal electrostatic field in the expanding target. Some of the electrons can be accelerated to energies exceeding the ponderomotive limit 1/2a02mc2. Effective temperature significantly above the ponderomotive scaling is observed. Furthermore, due to the limited expanding length, the laser propagating instabilities are suppressed in the interaction. Thus, high collimated beams with tens of μC charge can be generated.

The promotion effect of surface negative electrostatic field on the photogenerated charge separation of BiVO4 and its contribution to the enhanced PEC water oxidation.

The increased surface-carried negative charge of BiVO4 after phosphate modification prolongs the photogenerated charge carrier lifetime and improves the separation by inducing the holes to transfer to the surface, leading to the obvious enhancement of visible light activities for PEC water oxidation.

Bio-Template Mediated In Situ Phosphate Transfer to Hierarchically Porous TiO2 with Localized Phosphate Distribution and Enhanced Photoactivities

A localized phosphate distribution (LPD) was introduced for the first time into a porous TiO2 nanostructure by using a biotemplate synthetic strategy, that is, Staphylococcus aureus (S. aureus)-assisted in situ phosphate transfer. The resulting novel nanostructures have shown remarkable enhancement of photoactivities for both selective dye degradation and photoelectrochemical water reduction. Mechanistic understanding reveals that improved separation, directional transport, and less limited interface transfer of the photogenerated electron and hole may be achieved simultaneously within the LPD-modified TiO2 nanostructures because of the existence of the confined negative surface electrostatic field (NSEF) and the spatially oriented upward band bending (UBB). On the contrary, a homogeneous phosphate distribution (HPD) will greatly increase electron interface transfer resistance, which will cause the increase of recombination in bulk. The most important inspiration we can obtain herein is that a comprehensive consideration of the influence of nanostructure on all of the critical aspects of the carrier’s dynamics is needed during the rational design and construction of the advanced nanostructured photocatalyst systems. Considering the available resources for the synthesis and strong covalent interaction of phosphate with many other transition metal cations, the authors think that the novel strategy for a simultaneous optimization of the dynamic processes of the charge pairs by introducing LPD is promising for several applications including photocatalysis, photoelectrochemical hydrogen production, and solar cell.

A space charge motion simulation with FDTD method and application in negative corona electrostatic field analysis

In this paper, a finite difference time domain based simulation method is presented for the spatio-temporal analysis of space charge motion and the proposed method is applied to negative corona electrostatic field analysis. Drifting and diffusion motion equations of space charges are numerically solved and used in the simulation of corona discharges considering effects of impact ionization, electron attachment, ion–ion recombination and ion–electron recombination. The results obtained from the simulation are discussed.

Chemodynamics of Metal Complexation by Natural Soft Colloids: Cu(II) Binding by Humic Acid

The chemodynamics of Cu(II) complexation by humic acid is interpreted in terms of recently developed theory for permeable charged nanoparticles. Two opposing electric effects are operational with respect to the overall rate of association, namely, (i) the conductive enhancement of the diffusion of Cu(2+), expressed by a coefficient f(el), which accounts for the accelerating effect of the negative electrostatic field of the humic particle on the diffusive transport of metal ions toward it, and (ii) the ionic Boltzmann equilibration with the bulk solution, expressed by a factor f(B), which quantifies the extent to which Cu(2+) ions accumulate in the negatively charged particle body. These effects are combined in the probability of outer-sphere metal-site complex formation and the covalent binding of the metal ion by the complexing site (inner-sphere complex formation) as in the classical Eigen mechanism. Overall "experimental" rate constants for CuHA complex formation, k(a), are derived from measurements of the thermodynamic stability constant, K*, and the dissociation rate constant, k(d)*, as a function of the degree of metal ion complexation, θ. The resulting k(a) values are found to be practically independent of θ. They are also compared to theoretical values; at an ionic strength of 0.1 mol dm(-3), the rate of diffusive supply of metal ions toward the particles is comparable to the rate of inner-sphere complex formation, indicating that both processes are significant for the observed overall rate. As the ionic strength decreases, the rate of diffusive supply becomes the predominant rate-limiting process, in contrast with the general assumption made for complexes with small ligands that inner-sphere dehydration is the rate-limiting step. The results presented herein also resolve the discrepancy between experimentally observed and predicted dissociation rate constants based on the above assumption.