Effect Of External Electric Field Research Articles

External electric field effect on electronic properties and charge transfer in CoI2/NiI2 spinterface

AbstractElectronic structure and spin‐related properties of CoI2/NiI2 heterostructure were studied by means of density functional theory. It was shown that the electronic structure at the Fermi level can be characterized by a band gap. The effect of the external electric field on charge transfer and electronic properties of the CoI2/NiI2 interface was investigated, and it was found that band gap width depends on the strength of the applied electric field, switching its nature from semiconducting to a half‐metallic one. An easy control of the electronic properties and promising spin‐polarized nature of the CoI2/NiI2 spinterface allows the heterostructure to be used in spin‐related applications.

Exploring response of Li2 molecule to external electric field: A DFT and SAC-CI study

Quantum chemical calculations are performed using Gaussian16W Software to theoretically investigate the response of Li2 molecule to external electric field. Ground state properties of Li2 molecule in the presence of electric field are modelled using Density Functional Theory(CAM-B3LYP/[6-311++G(3df,3pd)]) while excited states are modelled using Symmetry Adapted Cluster Configuration Interaction theory and 6-311++G∗∗ basis set. The effect of external electric field on ground state properties including structural (bond length, total energy, harmonic vibrational frequency and rotational constant), electronic (dipole moment and polarizability) and thermodynamic (vibrational contribution to partition function, thermal energy, entropy and specific heat capacity) properties is reported. External electric field modifies the charge distribution within the molecule and hence its molecular properties. Potential energy curves and transition dipole moments of 22 states (13Singlet + 9Triplet) are also reported. The computed parameters agree well with the experimental data wherever the later is available.

Spectrum and Physical Properties of C70 Under the External Electric Field

Fullerene C70 has a broad application prospect. It is of great significance for investigating the properties of fullerene C70 under the external electric field. The dipole moment, energy gap and infrared spectrum of fullerene C70 molecule under external electric field (0–0.040 atomic units) are studied with density functional theory at B3PW91/3-21G level. The dipole moment increases almost linearly from 0.005 to 65.005 Debye and the energy gap decreases continuously. The effect of external electric field on the infrared spectrum is great and it can be found that certain vibrational mode become active due to the symmetry reduction due to the external electric field. Meanwhile, the ultraviolet–visible absorption spectra, the excitation wavelength, the excitation energy, and oscillator strength of first fourteen excited states of fullerene C70 under the external electric field are also studied with the time-dependent density functional theory at B3PW91/3-21G level. It is found that the absorption peak of fullerene C70 occurs red shift from 504.78 to 736.39 nm. The excitation energy decreases rapidly and the excitation wavelength increases a lot with the external electric field. The results can offer an important reference to use external electric field to tune the properties of fullerene C70.

Valley- and spin-dependent quantum Hall states in bilayer silicene

The Hall conductivity $\sigma_{xy}$ of many condensed matter systems presents a step structure when a uniform perpendicular magnetic field is applied. We report the quantum Hall effect in buckled AB-bottom-top bilayer silicene and its robust dependence on the electronic valley and spin-orbit coupling. With the unique multi-valley electronic structure and the lack of spin degeneracy, the quantization of the Hall conductivity in this system is unlike the conventional sequence as reported for graphene. Furthermore, the conductivity plateaux take different step values for conduction ($2e^2/h$) and valence ($6e^2/h$) bands since their originating valleys present inequivalent degeneracy. We also report the emergence of fractions under significant effect of a uniform external electric field on the quantum Hall step structure by the separation of orbital distributions and the mixing of Landau levels from distinct valleys. The valley- and spin-dependent quantum Hall conductivity arises from the interplay of lattice geometry, atomic interaction, spin-orbit coupling, and external magnetic and electric fields.

Effect of substrate surface on DR-19 films deposition process with using EFA-PVD method

The Disperse Red 19 (DR-19) with its conjugated chain structure is known to offer great potential for photonic device applications, such as optical switching and optical data storage. This researches aim to study surfactant effect of silane substrate and the effect of external electric field applied during the deposition process on properties of the resulted DR-19 film. This researches using Electric Field Assisted Physical Vapor Deposition (EFA-PVD) method. The characterization of the film structure was performed by means of XRD. The deposited molecular orientation was characterized with UV-Vis spectroscopic measurement. Based on these spectroscopic data, it is shown that anchoring mechanism with hydrogen bonding does occurred between DR-19 molecule and silane substrate responsible of the stability of the fabricated film. Result of this research show that DR-19 films have been obtained which exhibit crystalline structure with the molecules deposited in parallel polar orientation perpendicular to the silane substrate surface and regular head to tail stacking when increasing external electric field. This is understood to be result of the formation of strong hydrogen bonding acting as the anchoring mechanism.

DEVELOPMENT OF "KERR EFFECT" DEVICES TO MEASURE URINE GLUCOSE LEVELS OF DIABETES MELITUS (DM) PATIENTS

<p>The development of the "Kerr Effect" device has been carried out to measure urine glucose levels of Diabetes Mellitus (DM) patients by applying an external electric field of two parallel plate capacitors. The purpose of this research was to design and construct a new "Kerr Effect" device to measure urine glucose levels of DM patients, to determine the effects of external electric fields and glucose concentrations on light polarization. The measurement of the polarization changes was done by emitting polarized light through a glucose standard solution sample and urine samples of DM patients. In this measurement, the sample was irradiated with an external electric field (0 kV / m - 80 kV / m) of parallel plate capacitors, and the changes of light polarization in the sample were observed. The obtained data of the measurement have been collected and plotted as a graph. The results showed that as the electric field increased the changes in polarization have a tendency to increase. In addition, the amount of glucose concentration in the urine also affected the magnitude of the change in the rotational polarization angle of the light. Therefore, the changes in the rotational polarization angle increase linearly due to the influence of the external electric field and the concentration of glucose in the urine.</p>

Biaxial strain and external electric field effects on the electronic structure of hydrogenated GaN monolayer

Abstract We investigate systematically the electronic properties of fully hydrogenated GaN (HGaNH) monolayer under effects of the biaxial strain and external electric field. Results assert that the pristine GaN monolayer is an indirect semiconductor with a band gap of 1.933 eV. Band structures indicate that the N-p and Ga-p states are the main contributors to the valence and conduction bands near Fermi level, respectively. The full hydrogenation can induce an increase of this parameter to 3.019 eV, with H-s state being present in both valence and conduction bands. Interestingly, the HGaNH monolayer transforms from indirect to direct gap as a consequence of GaN hydrogenation. Based on results, the electronic band gap of HGaNH monolayer shows sensitivity to the biaxial strain and external electric field. Therefore, these factors can be used to effectively tune the electronic properties of HGaNH monolayer in order to make it more suitable for optoelectronic applications.

Precise near-wall pH measurement in pressure-driven and electrically-driven flows using nanoscale laser-induced fluorescence imaging

The present study developed a near-wall pH measurement technique based on nanoscale laser-induced fluorescence to evaluate the spatio-temporal distributions of pH in the vicinity of a glass-solution interface. Fluorescein sodium salt, a pH-sensitive dye, was dissolved in working fluids and excited by an evanescent wave generated by total internal reflection of a laser beam. Near-wall pH distributions were determined based on a ratiometric calibration using a high-pH buffer solution (pH ⩾ 10) as a reference. The proposed technique was applied to both pressure-driven and electroosmotic flows to investigate the effects of interfacial potential and external electric field on proton concentration. The near-wall pH in pressure-driven flow was lower than the bulk pH by ~0.2 due to the local excess of protons attracted towards the negatively charged glass wall. This pH shift was especially noticeable in solutions with low ionic strength, which indicates that the near-wall pH is closely related to the thickness of the electric double layer. The pH shift in electroosmotic flow was smaller than that in pressure-driven flow by ~0.02 and decreased with electric field strength. In addition, a time-series measurement clearly visualized the temporal change in non-uniform pH distributions in electroosmotic flow at a spatial resolution of 5.2 × 5.2 µm. The measurement uncertainty was estimated to be 0.16 pH unit at 95% confidence level. These results demonstrated the feasibility of the present technique to evaluate spatio-temporal proton concentrations within the space 10–100 nm away from a solid–liquid interface. The proposed technique will therefore contribute to quantitative investigations into electrostatic interactions and ion transport in developing nanoscale electrochemical transport techniques and devices in, for example, biochemical analysis and water purification.

Theoretical study of methane adsorption and C─H bond activation over Fe‐embedded graphene: Effect of external electric field

The effect of an external electric field (EF) on the methane adsorption and its activation on iron-embedded graphene (Fe-GPs) are investigated by using the M06-L density functional method. The EF is applied in the perpendicular direction to the graphene in the range of -0.015 to +0.015 a.u. with the interval of 0.005 a.u. The effects of EF on the adsorption, transition state and product complexes of the methane activation reaction are revealed. The binding energies of methane on Fe site in Fe-GPs are increased from -12.9 to -15.3, -18.1 and -21.5 kcal/mol for the negative EF of -0.005, -0.010 and -0.015, respectively. By applying positive EF, the activation barriers for methane activation are reduced in range of 3-8 kcal/mol (around 12-31%) and the reaction energies are more exothermic. The positive EF kinetically favors the reaction compared to the system without EF. The adsorption and activation of methane on Fe-GPs can be easily tuned by adjusting the external electric field for various applications. © 2019 Wiley Periodicals, Inc.

Tunable electronic structures in BP/MoSSe van der Waals heterostructures by external electric field and strain

Motivated by the successful preparations and extraordinary properties of blue phosphorus (BP) and Janus MoSSe monolayer, we constructed the van der Waals (vdW) heterostructures composed of BP and Janus MoSSe monolayer denoted by BP-SMoSe and BP-SeMoS, respectively, investigated their electronic structures and the effects of external electric field and strain. We find that the BP-SMoSe vdW heterostructure exhibits type-I band alignment, while the BP-SeMoS vdW heterostructure shows type-II band alignment. Moreover, the bandgap and band alignment of BP-SMoSe and BP-SeMoS vdW heterostructures can be tuned effectively by applying external electric field and strain. The results indicate that these BP/MoSSe vdW heterostructures will have great applications in multi-functional device.

Control of nonlinear refractive index of AuNPs doped with nematic liquid crystal under external electric field

The nonlinear refractive index of gold nanoparticles (Au NPs) doped with nematic liquid crystal (NLC) is determined using Z-scan technique. The Au NPs were synthesized by laser ablation (Nd: YAG laser at 1064 nm) dispersed in liquid deionized water and then mixed by nematic liquid crystal. The effect of external electric field onto the nonlinear refractive index of the Au NPs was investigated using a close aperture Z-scan technique. It’s found experimentally, that the nonlinear refractive index of the Au NPs doped with E7 can be varied by changing both the compositional percentage of Au NPs and NLC molecules. The obtained nonlinear refractive index of the samples showed that E7 NLC can act as a good material for controlling the third order nonlinear coefficient due to its large nonlinear optical properties.

Analysis of double diffusive convection in electroosmosis regulated peristaltic transport of nanofluids

In-depth understanding of flow and pumping characteristics of the nanofluids in a narrow fluidic channel is required for accurate control of micropumps. The present paper studies the nanofluids flow driven by the combined effects of peristaltic pumping and external electric field through microchannel. Double diffusive convection in nanofluids is examined. Buoyancy effects due to change in temperature, solute concentration and nanoparticle volume fraction are also taken into account. Poisson–Boltzmann, momentum, energy, solute concentration, and nanoparticle volume fraction equations are considered to govern the nanofluids flow. Governing equations are simplified under the lubrication theory and Debye-Hückel linearization. Influences of Joule heating, electric double layer thickness, electroosmostic velocity, Grashof numbers, thermophoresis and Brownian motion on flow characteristics, pumping characteristics, and skin friction coefficient are computed using Mathematica software. Trapping phenomenon is also examined under the effects of pertinent parameters. Present analysis reveals that flow characteristics and pumping characteristics improve with negative Joule heating effects. The findings of present analysis can be utilized in clinical implications like drug delivery systems, cell therapeutics, and particles filtrations etc.

Tuning the electronic structure of 2D materials by strain and external electric field: Case of GeI2 monolayer

Strain and external electric field effect on electronic structure of GeI2 monolayer has been investigated using first principles calculations. The obtained results indicate that GeI2 monolayer is an indirect semiconductor with band gap value of 2.188 eV. With biaxial strain, the band gap of considered material increases slightly with compression up to −6% and then it decreases and shows abrupt drop for strain −9% to −12%, whereas it just shows decreasing trend with tensile strain. In case of uniaxial strain, the band gap value increases nearly linearly under the effect of considered strain range. The weak external electric field has no significant effect on the band gap of GeI2 monolayer, while with E = ±0.6 (eV/Å/e), the band gap decreases considerably as I-6s state in conduction band moves to the lower energy levels.

A continuum study of layer analysis for single species ion transport inside double-layered graphene sheets with various separations

We investigate the formation of thin ionic layers driven by electro-osmotic forces, that are commonly found in micro- and nano-channels. Recently, multi-layers have been reported in the literature. However, the relation between classical Debye layers and multi-layers, which is a practically and fundamentally important question, was previously unexplained. Here, we fill this gap by using a continuum approach to investigate the flow of lithium ions inside double-layered graphene sheets. Fluid flow, charge conductivity and thermal stability will be investigated. We show that the separation and strength of forces between the sheets, the external electric field and thermal effects determine the topology of the ionic layers between the graphene sheets.

Simultaneous Effects of Hydrostatic Pressure and External Electric Field on the Energy Spectra of Two Donors in a Strained Zinc Blende GaN/AlGaN Quantum Dot

The energy spectrum of two donors in a strained GaN quantum dot embedded in Al\(_x\)Ga\(_{1-x}\)N has been investigated under the influence of hydrostatic pressure and external electric field. Our calculations are carried out using variational principle within the single band effective mass approximation by means of dot radius, hydrostatic pressure, and electric field. The numerical results show that the binding energy of two donors increase, attains a maximum value, and then decreases as the quantum dot radius increases for any electric field. Moreover, the binding energy of two donors increases with the pressure for any size of dot. Our results are compared with existing literature.

Effect of External Electric Field on the Electronic Structure and Aromaticity of Cr(CO)3(η6-C6H6) Complex

In the present research, the modified Perdew–Wang exchange and correlation (MPW1PW91) quantum chemical method was applied to determine the impact of external electric field on the total energy, dipole moment, the energies of frontier orbitals, HOMO–LUMO gaps, and aromaticity of the Cr(CO)3(η6-C6H6) complex. Percentage compositions of frontier orbitals have been calculated in terms of the specific groups in the absence and presence of external electric field. Moreover, variation of the global reactivity descriptors was examined in response to changes in the electric field. The nucleus independent chemical shift (NICS) values have been used to assess the aromaticity of the complex.

External electric field effects on chemical structure and reactivity

AbstractIn recent years, external electric fields (EEFs) have captured some spotlight as novel effectors of chemical change. EEFs directly impact the structure of molecular systems. For example, aligning an electric field along a specific bond‐axis leads to either shortening or elongation of the bond (and ultimately bond breaking). Furthermore, EEFs enable unprecedented control over chemical reactivity. Orienting an electric field along the so‐called “reaction‐axis,” the direction in which the electrons reorganize during the conversion from reactant to product, leads to catalysis or inhibition and can induce mechanistic crossover from concerted to stepwise reactions. Off‐reaction‐axis orientation enables control over the stereoselectivity of reactions and disables forbidden–orbital mixing. Two‐directional fields enable control over both reactivity and selectivity. In this advanced review, we offer an overview of this rapidly evolving research field with a focus on the valence bond modeling of EEF effects and the insight it offers. A wide variety of examples will be considered and a link to the experiment will be made throughout. We end by offering some perspectives in which we postulate that, as experimental techniques continue to mature, EEFs could potentially become a generally applicable “zapping” tool to facilitate elaborate chemical syntheses.This article is categorized under:Structure and Mechanism > Reaction Mechanisms and Catalysis

The Influence of Electric Field on the Adhesion Characteristics of the Polychloroprene-Shungite System

The effect of temperature and external electric field on the adhesion characteristics in the polychloroprene-schungite system was investigated. It is shown that an increase in temperature and orientation of macromolecules of polychloroprene in an external electric field significantly increase the bond strength between the studied components. The detected effects are explained from the viewpoint of the possibility of direct chemical interaction ofshungite with polychloroprene macromolecules oriented in a certain way in the region of an adhesive compound formation. This is facilitated by the structural features of schungite (the presence of paramagnetic centers, fullerene-like structures, metal oxides) and polychloroprene in shungite, as well as by the creation of the most optimal modes for implementing this interaction. To assess the strength of the interaction between polychloroprene and the surface of shungite we used a method for determining the stress of exfoliation of a polymer film from the surface of a shungite plate. It was established that the greatest effect in strengthening the bond between polychloroprene and the surface of shungite is achieved when a polymer film is formed from a solution in carbon tetrachloride on a negative electrode (cathode). The strength of the bond between shungite and the polychloroprene film formed on the cathode is more than two times higher than this parameter when forming the same film on the anode. The energy expended during the peeling of a film formed on the cathode is twice the energy of exfoliation from the shungite plate of the film formed on the anode. The analysis of the change in the supramolecular structure of polychloroprene in the polychloroprene-shungite system as a result of the orientational influence of an external electrostatic field was carried out using the temperature dependence of the tangent of the dielectric loss angle of the systems under study. It is shown that a polychloroprene film formed in an electrostatic field has a more ordered structure compared to a similar sample formed without a field. This fact is evidenced by the shift of the maxima toward higher temperatures in the relaxation spectra of the dipole polarization for the system formed without the field, and the system formed on the cathode. The polychloroprene film containing finely dispersed shungite as a filler and formed on the cathode is characterized by an increased value of the tangent of dielectric loss angle and an increased number of peaks of dipole relaxation in the temperature range studied.

The interaction of 5-fluorouracil with graphene in presence of external electric field: a theoretical investigation

In current research, the interaction between 5-fluorouracil (FU), as an anticancer drug, and graphene was studied in the M062X/6-311G(d,p) level of theory. The external electric field effects on the total energy, dipole moment, the energies corresponding to frontier orbitals and HOMO–LUMO gap of the fluorouracil···graphene molecule. Furthermore, the analysis of interaction of the 5-FU with graphene was carried out through the energy decomposition analysis (EDA). There were excellent linear relationships between electronic spatial extent (ESE), frontier orbital energies and energy of interaction with external electric field strength.

Tuning the electronic and magnetic properties of Mn-doped graphene by gas adsorption and effect of external electric field: First-principles study

The effect of gas molecule (H2CO, NO, NO2, O2 and SO2) adsorption on the electronic and magnetic properties of Mn-doped graphene (MnG) is investigated by first-principles calculations in the framework of density functional theory (DFT). Our study reveals that after H2CO, NO, NO2 and SO2 adsorption, MnG transforms from half-metal to semiconductor, and this transformation indicates that MnG’s conductivity is changed significantly. Meanwhile, O2 adsorption has no influence on MnG’s original electronic property. Therefore, the substrate of MnG is highly sensitive to H2CO, NO, NO2 and SO2. The reconfiguration of electron distribution caused by gas adsorption dramatically alters the spin polarization distribution of the combined system, that is, NO2 and H2CO adsorption leads to local spin polarization, whereas O2, NO and SO2 adsorption result in complete spin polarization. In addition, the external electric field (E-field) is varied from −0.50 V/Å to +0.50 V/Å then applied to the adsorption system. A strong interaction is observed between gas and MnG with a positive E-field as reflected in the enhancement of adsorption energy. The interaction is obviously weakened by introducing the E-field in the negative direction. Hence, the adsorption strength and sensitivity of gas on MnG can be effectively tuned by the E-field. The results can serve as useful references for the design of graphene-based gas sensor.