Polarization Electric Field Research Articles

Design and fabrication of Gr/Ag-coated tilted grating sensor for ultra-sensitive detection of DNA hybridization

A graphene sensitized biosensor based on 6° tilted fiber Bragg grating (TFBG) was proposed. The introduction of the graphene coating boosted the sensitivity and stability of the Ag/TFBG sensor, and improved the probe loading and molecular capture of the sensitized layer. A quantitative analytical model was proposed to calculate the hybridization efficiency and maximum sensor response of DNA single base mismatch. The results showed that the kinetic affinity response of the Gr/Ag/TFBG sensor was stably demonstrated with a dissociation constant (kd=9.392 ± 0.178·10−3 min−1) and the detection limit of DNA was as low as 3 pM. This indicates that the sensor has the ability to distinguish single base mutations quantitatively in real time. The surface modification, probe binding and DNA hybridization were characterized based on atomic force microscopy (AFM) and Raman detection spectrum detection system. A 3D diversity analysis model for TFBG sensors was innovatively proposed based on COMSOL. The multi-mode coupling and polarization response analysis of the inner core, the electric field distribution and polarization transmission mode of the sensitized layer, and the polarization gain brought by graphene are systematically described. Excellent bioanalytical capabilities combined with well-established analytical methods make prepared sensor promising for high-throughput screening of genetic variants and disease markers.

Topological edge and corner states based on the transformation and combination of photonic crystals with square lattice

The topological edge state (TES) and the topological corner state (TCS) have provided new method of manipulating the behavior of light. In this paper, we propose topological photonic crystals (PCs) with C4 symmetry, and the electric field distribution and polarization of eigenmodes are investigated via the finite element method. Through the lattice transformation, different Zak phases and polarizations of eigenmodes in the PCs can be obtained. Further, one-dimensional TES and zero-dimensional TCS with strong robustness are realized by the combination of PCs with different Zak phases. This work paves a new way for manipulating the behavior of light based on the properties of TES and TCS, which will promote the development of the integrated optical field.

Conjugate Effect of the 2011 Tohoku Reflected Tsunami‐Driven Gravity Waves in the Ionosphere

AbstractThis study presents the conjugate ionospheric disturbances triggered by the 2011 Tohoku‐Oki reflected tsunami oceanic waves using the ground‐based Global Navigation Satellite System (GNSS) total electron content (TEC) observations. We found that the equatorward and westward propagating nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) occurred over Japan and Australia simultaneously following the tsunami oceanic waves reflected by the Emperor Seamount Chain in the northern hemisphere. The atmospheric gravity waves driven by reflected tsunami oceanic waves are hypothesized to be the source to trigger the conjugate MSTIDs by transporting the polarization electric fields along the field line to the conjugate hemisphere. Moreover, only the southwestward propagating MSTIDs have this conjugate effect, which could be due to the wavefront orientation. The Perkins instability could also be involved in the interhemispheric coupling process. This study provides the first observational evidence that the reflected tsunami can induce conjugate ionospheric disturbances through electrodynamic forcing.

Fluid pumping by liquid metal droplet utilizing ac electric field.

We report a unique phenomenon in which liquid metal droplets (LMDs) under a pure ac electric field pump fluid. Unlike the directional pumping that occurs upon reversing the electric field polarity under a dc signal, this phenomenon allows the direction of fluid motion to be switched by simply shifting the position of the LMD within the cylindrical chamber. The physical mechanism behind this phenomenon has been termed Marangoni flow, caused by nonlinear electrocapillary stress. Under the influence of a localized, asymmetric ac electric field, the polarizable surface of the position-offset LMD produces a net time-averaged interfacial tension gradient that scales with twice the field strength, and thus pumps fluid unidirectionally. However, the traditional linear RC circuit polarization model of the LMD/electrolyte interface fails to capture the correct pump-flow direction when the thickness of the LMD oxide skin is non-negligible compared to the Debye length. Therefore, we developed a physical description by treating the oxide layer as a distributed capacitance with variable thickness and connected with the electric double layer. The flow profile is visualized via microparticle imaging velocimetry, and excellent consistency is found with simulation results obtained from the proposed nonlinear model. Furthermore, we investigate the effects of relevant parameters on fluid pumping and discuss a special phenomenon that does not exist in dc control systems. To our knowledge, no previous work addresses LMDs in this manner and uses a zero-mean ac electric field to achieve stable, adjustable directional pumping of a low-conductivity solution.

Composition dependent crossover from ferroelectric to relaxor-ferroelectric in NBT-ST-KNN ceramics

Composition driven crossover from ferroelectric (FE) to relaxor-ferroelectric (RFE) is systematically investigated in (0.8-x)(Na0.5Bi0.5)TiO3-0.2SrTiO3-x(K0.5Na0.5)NbO3 (NBT-ST-xKNN) ceramics in the light of ferroelectric and dielectric (ε) response. The appearance of constricted polarization-electric field loop and double current density-electric field peaks in the proximity of x = 0.02 suggests a co-existence of FE and RFE phases. The system attains a maximumε ∼4200 and tan δ < 0.1 at x = 0.02. Broad ε(T) peaks reveal a greater degree of disorder due to KNN substitution and their deconvolution demonstrates three different relaxation/polarization processes related to low and high-temperature nanodomains. The composition with x = 0.1 exhibits maximum broadness in ε(T) profiles resulting in a temperature-insensitive permittivity variation of ±15% (ε125 °C,100kHz∼2007) over a span of ∼280 °C. A remarkably low (TCε)100kHz of −75 ppm/°C is also achieved for x = 0.1 from 100 to 300 °C proposing it to be a potential capacitor material.

Improved electric-field-induced strain and strong photoluminescence properties in novel Er3+-modified 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 multifunctional ceramics

Recently, the progress of electronic devices toward miniaturization has strongly promoted development of multifunctional materials possessing multiple desirable properties. In this study, we develop and fabricate 0.93Bi0.5Na0.5TiO3-0.07BaTiO3-xEr multifunctional ceramics which show simultaneously considerable electric-field-induced strain and bright green light emission properties. With the introduction of Er3+, the ceramics gradually transform from non-ergodic relaxor phase to ergodic relaxor phase which could reversibly transform to ferroelectric phase under the electric field. As a result, with improving Er3+ content, the shape of the polarization-electric field loops of the ceramics become pinched, and it is obvious that the negative strain disappears while the positive strain gradually increases and reaches a maximum value 0.46% at x = 1.2 mol%. Besides, After the ceramics are poled, the light emission peak are greatly enhanced attributed to the decreased crystal symmetry and increased domain size, and is the strongest at x = 1.2 mol%. These results indicate that 0.93Bi0.5Na0.5TiO3-0.07BaTiO3-xEr ceramics are good candidates for developing multifunctional optoelectronic devices.

Enhancement of piezoelectric catalysis of Na0.5Bi0.5TiO3 with electric poling for dye decomposition

In this work, the performance of solid-phase sintered Na 0.5 Bi 0.5 TiO 3 ceramic powder catalyst is investigated for Rhodamine B (RhB) dye decomposition under different electric poling fields. As a result of the vibration excitation, the piezoelectric catalytic decomposition ratio of the poled Na 0.5 Bi 0.5 TiO 3 for RhB dye wastewater increases from 10.84% to 51.32% as the electric poling field increases from 0 to 0.5 kV/mm. The improved piezoelectric catalytic activity could be attributed to a rise in the piezoelectric performance of Na 0.5 Bi 0.5 TiO 3 after electric poling. The addition of the different types of radical scavengers in piezoelectric catalysis further proves that a large amount of superoxide-free radicals and a small number of hydroxyl radicals participate in the catalytic reaction. Our results demonstrate that electric poling, as a simple and effective method of improving piezoelectric catalysis, has potential applications in dye-containing wastewater treatment.

The structural, dielectric, electrocaloric, and energy storage properties of lead-free Ba0·90Ca0·10Zr0·15Ti0·85O3

Lead-free ferroelectric materials with Electrocaloric Effect (ECE) and recoverable energy (W rec ) represent a major breakthrough in the technological race for manufacturing low-cost and eco-friendly smart multifunctional devices. Here, guided by the benefits resulting from successive ferroelectric-ferroelectric (F–F) and ferroelectric-pseudo cubic (F-PC) transitions including broad operational temperature span, lead-free Ba 0·90 Ca 0·10 Zr 0·15 Ti 0·85 O 3 (BCZT) ferroelectric ceramic located near the phase convergence region was prepared using the conventional solid-state solution. In this study, the systematic investigation of structural and microstructural properties via X-Ray Powder Diffraction (XRPD), scanning electron microscopy (SEM), temperature-dependence Raman spectroscopy and dielectric properties confirm the formation of a pure perovskite material which undergoes consecutive R 3 c - R 3 m , R 3 m - Amm 2, Amm 2- P 4 mm (F–F) phase transitions followed by (F-PC) transition in a wide temperature range centered around room temperature (RT). Polarization-Electric field (P-E) measurements, revealed the coexistence of Positive Electro-Caloric Effect (PECE) and Negative Electro-Caloric Effect (NECE) in a wide temperature span of [-40 °C, 95 °C]. More interestingly, we reached a large absolute temperature change (ΔT) and EC coefficient (ξ) values of (5.505 °C, 1.847 KmmkV −1 ), (0.861 °C, 0.289 KmmkV −1 ) and (1.897 °C, 0.637 Kmm kV −1 ) registered respectively at about −5, 42.5 and 74.5 °C under an electric field of 29.80 kVcm −1 . This work will promote further studies on lead-free BCZT ceramics towards multifunctional environmentally-friendly material promising for solid-state cooling technology.

Self‐Poled Heteroepitaxial Bi(1−x)DyxFeO3 Films with Promising Pyroelectric Properties

AbstractPyroelectric materials are very promising for thermal energy harvesting applications. To date, lead‐based systems are the foremost studied materials in this field. A facile and simple metal organic chemical vapor deposition route is applied for the fabrication of lead‐free, high quality, epitaxial Bi(1−x)DyxFeO3 (x = 0, 0.06, 0.08, 0.11) thin films deposited on conductive SrTiO3:Nb (100) single crystal substrates. The films are studied by structural, morphological, compositional, and functional characterization. The correlation between the Dy‐doping amount and the dielectric properties is thoroughly investigated. Unipolar polarization–electric field loops and permittivity measurements show the important impact of Dy on ferroelectric, dielectric, and pyroelectric properties. Dy doping increases considerably the dielectric response, but much more the pyroelectric coefficient, up to a concentration of 8% Dy. The films are self‐poled, which is an ideal situation for pyroelectric applications. The best figure of merit for pyroelectric energy harvesting, FE, is 82 J m−3 K−2, showing a factor increase of 2.6 as compared to the undoped film of the sample series. It constitutes a factor 4.5 improvement as compared to previous results obtained on BiFeO3 based thin films.

A facile synthesis of Al-doped BaTiO3 thin films by a hydrothermal-galvanic couple method on TiAlN film electrodes

Al-doped barium titanate (ABT) thin films were produced by a facile hydrothermal-galvanic couple (HT-GC) method using ternary TiAlN seeding layers. TiAlN thin films serving as the working electrode were deposited onto Si substrates by reactive unbalanced magnetron sputtering. HT-GC synthesis was conducted in the alkaline solutions consisting of 0.5 M Ba(CH3COOH)2 and 2 M NaOH. Although no external power sources were applied, substantial galvanic currents occurred during the synthesis. X-ray diffraction patterns show that cubic ABT films were formed over TiAlN. Field-emission scanning electronic microscopy revealed ABT films exhibiting hemispherical grains over the nitride surface with single-layered structures. X-ray photoelectron spectroscopy verified Al doping in the obtained ABT coatings. Reaction paths and formation mechanisms of the ABT coatings were also proposed. Moreover, the ABT thin films possessed higher residual polarization (Pr) and piezoelectricity coefficient (d33) compared with un-doped BaTiO3 (BTO), deduced from polarization–electric field loops results. The deduced Pr-value for BTO thin films was 0.8 μC/cm2 and could be enhanced to 1.6 μC/cm2 for ABT thin films, meanwhile the value of d33 for BTO films was 13 ± 1 pC/N and increased to 18 ± 1 pC/N for ABT films. Such a facile synthesis of ABT thin films may bring in more technological applications such as piezoelectric and triboelectric materials in the hybrid nanogenerator, and non-volatile ferroelectric random access memory.

On the High-Resolution Discretization of the Maxwell Equations in a Composite Tape and the Heating Effects Induced by the Dielectric Losses

Electromagnetic field propagation inside composite materials represents a challenge where fiber-scale simulation remains intractable using classical simulation methods. The present work proposes an original 3D simulation with a mesh resolution fine enough to resolve the fiber scale, thanks to the use of Proper Generalized Decomposition (PGD)-based space decomposition, which avoids the necessity of considering homogenized properties and considers the richest description of the involved physics from the solution of the Maxwell equations. This high-resolution simulation enables comparing the electromagnetic field propagation in a composite part, depending on the considered frequency and the fiber’s/wave polarization’s relative orientation. The electromagnetic fields are then post-processed to identify the heat generation terms and- the resulting induced thermal field. The results prove the ability of the PGD-based discretization to attain extremely high levels of resolution, the equivalent of 1010 finite-element degrees of freedom. The obtained results show an enhanced wave penetration when the electric field polarization coincides with the fiber orientation. On the contrary, when the electric field is polarized along the normal to the fiber orientation, both the penetration and the associated heating reduce significantly, compromising the use of homogenized models, rendering them unable to reproduce the observed behaviors.

Periodic Electro-Optical Characteristics of PDLC Film Driven by a Low-Frequency Square Wave Voltage

The electro-optical features of the PDLC films applied with a low-frequency square wave voltage were investigated. The transmittance curves indicated the double frequency of the applied voltage at 0–50 Hz, which resulted from the relaxation of an internal electric field polarized by ions in LC droplets. When the local electric field was reversed, the internal polarization electric field could be maintained and superimposed on the local electric field. The relaxation of the internal polarized electric field resulted in the relaxation of the transmittance. Furthermore, the transmittance curves changed with the frequency of the applied voltage.

Preparation of efficient piezoelectric PVDF–HFP/Ni composite films by high electric field poling

Abstract Poly(vinylidene fluoride) (PVDF) and its copolymers have been widely studied due to their excellent piezoelectricity and ferroelectricity. In this study, composite films are prepared by adding Ni nanoparticles (0.00–0.3 wt%) into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) matrix by solution casting, uniaxial stretching, and high electric field poling. It is found that when the maximum electric field E max for poling is 130 MV m−1, the calibrated open circuit voltage of the pure PVDF–HFP films reaches 3.12 V, which is much higher than those poled by a lower electric field (70 MV m−1: 1.40 V; 90 MV m−1: 2.29 V). This result shows that the effect of poling on the generated output voltage is decisive. By adding 0.1 wt% Ni nanoparticles, it increases to 3.84 V, 23% higher than that of the pure PVDF–HFP films. To further understand the enhancement mechanism, the effects of Ni nanoparticles on initial crystallization, uniaxial stretching, and high electric field poling are investigated by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, and differential scanning calorimetry.

Electric Field Coupling in the S-Scheme CdS/BiOCl Heterojunction for Boosted Charge Transport toward Photocatalytic CO2 Reduction

Step-scheme (S-scheme) photocatalysts have received much attention owing to the enhanced photocatalytic redox ability. However, the carrier transport driven only by the interfacial electric field of the S-scheme heterojunction is not efficient enough to satisfy the highly active CO2 reduction. In this study, we realize the coupling of multiple electric fields and the accelerating of charge transfer in the CdS/BiOCl heterojunction by regulating the contact interface of CdS and BiOCl. The photoreduction CO2 test results show that all composites exhibit a higher photocatalytic activity than pure CdS and BiOCl, indicating the inherent advantages of the S-scheme heterojunction. More importantly, the CdS/BiOCl composites (Cx-B001) assembled by the {001}-facet-exposed BiOCl nanosheets show significantly boosted photocatalytic activity compared to the counterpart (Cx-B010) constructed by the {010}-facet-exposed BiOCl nanosheets. The enhanced CO2 reduction activity of Cx-B001 is attributed to the more effective charge transport, which is synergistically driven by the electric field at the heterojunction interface and the polarization electric field in the BiOCl phase. This work may provide some useful insights into the design of highly efficient S-scheme photocatalysts.

Toward high‐efficiency stable 2D/3D perovskite solar cells by incorporating multifunctional CNT:TiO2 additives into 3D perovskite layer

AbstractThe power conversion efficiency (PCE) of 2D/3D perovskite solar cells (PSCs) is still significantly low compared with 3D PSCs due to the poor charge transport ability of 2D perovskite thin films and a large number of defects in 3D thin films. Herein, to address these two issues, multifunctional TiO2 nanoparticles (NPs)‐modified carbon nanotubes (CNT:TiO2) additives are incorporated into 3D perovskite layer for the first time, and demonstrate three positive effects for CNT:TiO2 material application: firstly, it passivates the defect state of the 3D perovskite layer and enhances the charge mobility of the 3D layer; secondly, its interaction with the 2D film increases the conductivity of the 2D layer and produces the interface polarization electric field to promote the hole extraction. As a consequence, not only the PCE of the optimized 2D/3D PSCs with the CNT:TiO2 is greatly improved to 22.7% from 19.8% of the control PSCs, but also the stability is significantly improved.image

A geometric approach to decoding molecular structure and dynamics from photoionization of isotropic samples.

We propose a geometric approach to the description and analysis of photoelectron angular distributions resulting from isotropic samples in the case of few-photon ionization by electric fields of arbitrary polarization. This approach formulates the standard photoionization observables - the bl,m expansion coefficients of the photoelectron angular distribution, in terms of geometrical properties of the vector field D⃑(k⃑) ≡ 〈k⃑|d⃑|0〉 describing the electronic transition from a bound state |0〉 into a scattering state |k⃑〉 - the photoionization transition dipole. Besides revealing selection rules for the enantio-sensitivity of bl,m coefficients in multiphoton ionization, our approach yields very compact expressions for both chiral and achiral molecules revealing how the molecular rotational invariants couple to the rotational invariants of the setup defined by the electric field polarization and the arrangement of photoelectron detectors. We apply this approach to one-photon ionization and find that the forward-backward asymmetry parameter b1,0, emerging exclusively in chiral molecules and encoded in the field B⃑(k⃑) ≡ iD⃑*(k⃑) × D⃑(k⃑), is sensitive only to the components of D⃑(k⃑) perpendicular to k⃑, while the regular asymmetry parameter b2,0 emerging in chiral and achiral molecules is sensitive only to the component of D⃑(k⃑) parallel to k⃑. Next, we analyze resonantly enhanced two-photon ionization and show that b0,0 and b1,0 can be written in terms of an effectively stretched D⃑(k⃑), and how b1,0 and b3,0 can be used to probe B⃑(k⃑).

Surface polarization of BiOI to boost photoelectrochemical signal transduction for high-performance bioassays.

Surface-hydroxylation-induced polarization (SHIP) was shown to promote the cathodic photoelectrochemical (PEC) communication of bismuth oxyiodide with doxorubicin (Dox) by as much as three orders of magnitude. This SHIP tactic was used to establish a polarization electric field (PEF) that not only negatively shifted the conduction band (CB) edge but also promoted the dynamic migration of photogenerated electrons of BiOI to Dox. The tactic underlies a pioneering way to boost signal transduction, and hence offers fresh opportunities for high-performance bioassays.

Mn–Nb co-doping in barium titanate ceramics by different solid-state reaction routes for temperature stable and DC-bias free dielectrics

BaTi1-2xMnxNbxO3 (x = 0, 0.05 and 0.10) ceramics were fabricated by either one-step calcination or two-step calcination with the first calcination of BaTi1-2xMnxO3-δ and the second calcination with Nb2O5 addition, and the effect of the calcinations on crystal structure, microstructure, and electrical properties was investigated. With the Mn and Nb substitution, the crystal system of BaTiO3 changed to a pseudo-cubic, the temperature dependence of the dielectric constant was flattened, and the polarization-electric field (P-E) loops became almost linear. At x = 0.10, compared with the one-step calcined ceramics with a remaining hexagonal phase and higher dielectric loss at high temperatures, the two-step calcined ceramics had a single-phase perovskite structure, the dielectric constants of 575–345 at temperatures between 25 and 150 °C with smaller dielectric loss, and the dielectric constants estimated from the slopes of the P-E loop of ∼650 at 0 kV/cm and ∼500 at 100 kV/cm at room temperature. BaTiO3+xMnO2+x/2Nb2O5 ceramics were also fabricated at x = 0.05 and 0.10, but they were less dense and had a secondary phase. These results suggest that the two-step calcined BaTi1-2xMnxNbxO3 ceramics with x = 0.10 can be a candidate material for temperature stable, DC-bias free capacitor applications.

Synergizing Internal Electric Field and Ferroelectric Polarization of Bifeo3/Znin2s4 Z-Scheme Heterojunction for Photocatalytic Overall Water Splitting

Synergizing Internal Electric Field and Ferroelectric Polarization of Bifeo3/Znin2s4 Z-Scheme Heterojunction for Photocatalytic Overall Water Splitting

Modeling of polyvinylidene fluoride nanocomposite utilizing BaTiO3@SiO2 for energy storage

Polymer-based nano dielectrics are attracting great attention in the research world. Such materials, primarily for embedded capacitors, offer greater feasible energy storage alternatives. This research aims to analyze the distribution of electric field in binary and core–shell BaTiO3@SiO2 structures of polyvinylidene fluoride (PVDF) nanocomposites with various filler concentrations of nanofibers using COMSOL Multiphysics® software-based finite element method. The core–shell structures enhanced the electric field strength and polarization as compared to binary nanocomposites. The novelty of the work is the design of the interface layer on the surface of nanoparticles was beneficial in reducing the local electric field in the filler/ polymer matrix system. According to a finite element simulation, the SiO2 shell may effectively reduce the electric field contrast between the polymer matrix and the BaTiO3 filler. The PVDF/BaTiO3@SiO2 nanocomposites show a maximum electric field strength of 380 MV/m, which is about 2.5 times larger than PVDF/BT nanocomposites under both the same filler content of 2.5 wt% and applied voltage. This work provides a prosperous path to achieving large-performance capacitors.