Field Of Electric Dipole Research Articles

Organic-Inorganic Interfacial Dipole Induced by Energy Level Alignment for Efficient Photocatalytic Sterilization.

Photocatalytic molecules are considered to be one of the most promising substitutions of antibiotics against multidrug-resistant bacterial infections. However, the strong excitonic effect greatly restricts their efficiency in antibacterial performance. Inspired by the interfacial dipole effect, a Ti3C2 MXene modified photocatalytic molecule (MTTTPyB) is designed and synthesized to enhance the yield of photogenerated carriers under light irradiation. The alignment of the energy level between Ti3C2 and MTTTPyB results in the formation of an interfacial dipole, which can provide an impetus for the separation of carriers. Under the role of a dipole electric field, these photogenerated electrons can rapidly migrate to the side of Ti3C2 for improving the separation efficiency of photogenerated electrons and holes. Thus, more electrons can be utilized to produce reactive oxygen species (ROS) under light irradiation. As a result, over 97.04% killing efficiency can be reached for Staphylococcus aureus (S. aureus) when the concentration of MTTTPyB/Ti3C2 was 50 ppm under 660 nm irradiation for 15 min. A microneedle (MN) patch made from MTTTPyB/Ti3C2 was used to treat the subcutaneous bacterial infection. This design of an organic-inorganic interface provides an effective method to minimize the excitonic effect of molecules, further expanding the platform of inorganic/organic hybrid materials for efficient phototherapy.

Columnar Macrocyclic Molecule Tailored Grain Cage to Stabilize Inorganic Perovskite Solar Cells with Suppressed Halide Segregation

AbstractSolidifying the soft lattice of all‐inorganic mixed‐halide perovskites is of great importance to restrain the notorious halide segregation under persistent light illumination. Herein, a multifunctional columnar macrocyclic molecule additive, namely cucurbituril into perovskite precursor to enhance the crystallization and reduce the defect density in the final perovskite film is introduced. Based on the theoretical calculation and simulation, the cucurbituril molecule with a strong double‐ended negatively‐charged cavity surrounded by terminated oxygen atoms not only coordinates with dangling Pb2+ ions to form host‐guest complexation but also induces an electric dipole field at perovskite grain boundary to effectively repel the iodide ion migration from the inside grain to the defective boundary, significantly suppressing the halide segregation and improving the device performance. As a result, the carbon‐based, all‐inorganic CsPbI2Br solar cell achieves an enhanced efficiency of 15.59% with great tolerance to environmental stresses. These findings provide new insights into the development of a novel passivation strategy with macrocyclic molecules for making high‐efficiency and stable perovskite solar cells.

A quantum sensor for atomic-scale electric and magnetic fields

The detection of faint magnetic fields from single-electron and nuclear spins at the atomic scale is a long-standing challenge in physics. While current mobile quantum sensors achieve single-electron spin sensitivity, atomic spatial resolution remains elusive for existing techniques. Here we fabricate a single-molecule quantum sensor at the apex of the metallic tip of a scanning tunnelling microscope by attaching Fe atoms and a PTCDA (3,4,9,10-perylenetetracarboxylic-dianhydride) molecule to the tip apex. We address the molecular spin by electron spin resonance and achieve ~100 neV resolution in energy. In a proof-of-principle experiment, we measure the magnetic and electric dipole fields emanating from a single Fe atom and an Ag dimer on an Ag(111) surface with sub-angstrom spatial resolution. Our method enables atomic-scale quantum sensing experiments of electric and magnetic fields on conducting surfaces and may find applications in the sensing of spin-labelled biomolecules and of spin textures in quantum materials.

Deploying a Dipole Electric Field at the CsPbI3 Perovskite/Carbon Interface for Enhancing Hole Extraction and Photovoltaic Performance.

Carbon-based CsPbI3 perovskite solar cells without hole transporter (C-PSCs) have achieved intense attention due to its simple device structure and high chemical stability. However, the severe interface energy loss at the CsPbI3/carbon interface, attributed to the lower hole selectivity for inefficient charge separation, greatly limits device performance. Hence, dipole electric field (DEF) is deployed at the above interface to address the above issue by using a pole molecule, 4-trifluoromethyl-Phenylammonium iodide (CF3-PAI), in which the ─NH3 group anchors on the perovskite surface and the ─CF3 group extends away from it and connects with carbon electrode. The DEF is proven to align with the built-in electric field, that is pointing toward carbon electrode, which well enhances hole selectivity and charge separation at the interface. Besides, CF3-PAI molecules also serve as defect passivator for reducing trap state density, which further suppresses defect-induced non-radiative recombination. Consequently, the CsPbI3 C-PSCs achieve an excellent efficiency of 18.33% with a high VOC of 1.144V for inorganic C-PSCs without hole transporter.

Gas Adsorption Mechanism on 2D Materials: The Hyperpolarizability Evolution Analyzed by Nonlinear Optics

AbstractWhile understanding the competitive adsorption behavior of gas sensor is important, it is yet to be unraveled. Especially for the influence of water molecules to the gas adsorbed on 2D materials. This study explores the potential of layered 2D materials as a candidate material for gas sensing, employing non‐destructive measurement, and second harmonic generation (SHG). The investigation focuses on analyzing oxygen, ammonia, and water vapor adsorbed on a WS2 surface by studying the evolutions in electric dipole and electric field. Leveraging the simplified bond hyperpolarizability model (SBHM), a foundation is established for gas sensors utilizing high‐quality 2D materials. This approach facilitates the detection of material modifications in response to environmental influences, including the inevitable water molecules. The obtained hyperpolarizability from SBHM exhibits remarkable consistency with Langmuir's adsorption model, confirming the physical adsorption in the system. In addition, the competitive effects between gases are explored by comparing experimental results with theoretical predictions based on Boltzmann distribution and density functional theory (DFT) calculations. This highlights the effectiveness of SHG and SBHM in studying gas adsorption on layered van der Waals materials.

Over 12% efficient CsSnI3 perovskite solar cells enabled by surface post-treatment with bi-functional polar molecules

Eco-friendly all-inorganic tin halide perovskite compounds have drawn significant attention for photovoltaic applications. Nevertheless, the non-radiative recombination derived from the uncoordinated Sn2+ cations at surface and the electron extraction barrier between different functional layers significantly impair the performance of perovskite device. Here we for the first time show that thiophene derivative, 3-thiophenemethylammonium iodide, as an interface modifier between the CsSnI3 perovskite surface and electron transport layer, can passivate defects and reduce the electron extraction potential barrier. The molecules of 3-thiophenemethylammonium iodide can autonomously inter-connect with uncoordinated Sn2+via lone electron pairs of the donated π electrons in electronic-rich thiophene molecule. Moreover, such interface modifier lowers the electron extraction potential barrier at the perovskite/electron transport layer junction in which an interface dipole electric field form. Consequently, the optimized planar solar cell with a structure of ITO/PEDOT:PSS/CsSnI3/ICBA/BCP/Ag, exhibited a power conversion efficiency of 12.05 % under AM 1.5G illumination condition. To the best of our knowledge, this is the highest efficiency for fully inorganic CsSnI3-based devices reported so far. This study represents an innovative approach to realize high-efficiency all-inorganic CsSnI3 perovskite solar cells.

Can the Dirac deltas in dipole fields be ignored in classical interactions?

When studying (or teaching) classical electromagnetism, one is bound to deal with the electric field of an ideal electric dipole, as well as its magnetic counterpart. A careful analysis then reveals that each of those fields must include, for consistency, a term proportional to a Dirac delta function localized at the position of the dipole. However, one is usually told not to worry about those terms since, as classical interactions always involve sources which are spatially separated, the Dirac-delta terms are only relevant for quantum mechanics, where they are directly related to important phenomena. In this work, we pose and solve a purely classical problem in electrostatics in which the Dirac-delta terms in the dipole fields are indispensable. It involves the computation of the interaction energy between a conductor with a spherical cavity and an (ideal) electric dipole located at the center of that cavity. We also solve its magnetic counterpart, replacing the conductor with a superconductor and the electric dipole with a magnetic one.

Sensing membrane voltage by reorientation of dipolar transmembrane peptides

Membrane voltage plays a vital role in the behavior and functions of the lipid bilayer membrane. For instance, it regulates the exchange of molecules across the membrane through transmembrane proteins such as ion channels. In this paper, we study the membrane voltage-sensing mechanism, which entails the reorientation of α-helices with a change in the membrane voltage. We consider a helix having a large electrical macrodipole embedded in a lipid bilayer as a model system. We performed extensive molecular dynamics simulations to study the effect of variation of membrane voltage on the tilt angle of peptides and ascertain the optimal parameters for designing such a voltage-sensing peptide. A theoretical model for the system is also developed to investigate the interplay of competing effects of hydrophobic mismatch and dipole-electric field coupling on the tilt of the peptide and further explore the parameter space. This work opens the possibility for the design and fabrication of artificial dipolar membrane voltage-sensing elements for biomedical applications.

Accurate Estimation of the Lateral Wave’s Contribution to the Radiated Fields of a Vertical Electric Dipole Embedded in a Lossy Half-Space

Accurate Estimation of the Lateral Wave’s Contribution to the Radiated Fields of a Vertical Electric Dipole Embedded in a Lossy Half-Space

Dynamically blocking leakage current in molecular tunneling junctions.

Molecular tunneling junctions based on self-assembled monolayers (SAMs) have demonstrated rectifying characteristics at the nanoscale that can hardly be achieved using traditional approaches. However, defects in SAMs result in high leakage when applying bias. The poor performance of molecular diodes compared to silicon or thin-film devices limits their further development. In this study, we show that incorporating "mixed backbones" with flexible-rigid structures into molecular junctions can dynamically block tunneling currents, which is difficult to realize using non-molecular technology. Our idea is achieved by the interaction between interfacial dipole moments and electric field, triggering structured packing in SAMs. Efficient blocking of leakage by more than an order of magnitude leads to a significant enhancement of the rectification ratio to the initial value. The rearrangement of supramolecular structures has also been verified through electrochemistry and electroluminescence measurements. Moreover, the enhanced rectification is extended to various challenging environments, including endurance measurements, bending of electrodes, and rough electrodes, thus demonstrating the feasibility of the dynamic behavior of molecules for practical electronic applications.

Discrimination of leucine and isoleucine via fragmentation by electromagnetic field.

We conduct comparative numerical studies of the effects of electric dipole field and electromagnetic radiation field on the amino acids leucine and isoleucine. Since they are structural isomers, distinguishing them by mass is a non-trivial task, while determination of protein structure can be crucial on many occasions. We emphasize the influence of the magnetic field of radiation by utilizing a modified basis sets with correction coefficients to the [Formula: see text] and [Formula: see text] orbitals following the Anisotropic Gaussian Type Orbitals method. Studying the electric potential of the isomers in dipole electric or electromagnetic fields proves that the different layout of leucine vs isoleucine is the main reason why some fragments could not be formed during chemical bond cleavage. Comparison of the chemical structure of the fragments created due to the decomposition of the isomers in the dipole electric or electromagnetic fields shows that their decomposition products are different. These findings can be used also for discrimination between the two isoleucine conformers, for which the cleavage starts at different values of the dipole electric field strength, as well as the products of the decomposition reaction are not identical. Our numerical calculations of the fragmentation outcomes, taking into account the magnetic field effects, can serve as a guidance for discrimination between the isomers/conformers. We applied the Becke's three-parameter hybrid functional approach with non-local correlation by Lee, Yang, and Parr ([Formula: see text]), together with the [Formula: see text] basis set as it is implemented in the GAUSSIAN09 quantum chemistry package in order to obtain the most stable conformers of leucine and isoleucine. We used the options provided by GAUSSIAN09 to add finite external field in order to perform the calculations of leucine and isoleucine in the electric dipole and electromagnetic fields. The Anisotropic Gaussian Type Orbitals method was used to obtain the correction coefficients which modify the original [Formula: see text] basis set in order to account for the effects of magnetic field of radiation. Results were visualized and the electrical potentials analyzed by the Molden visualization program.

Polarization-independent hollow nanocuboid metasurfaces with robust quasi-bound states in the continuum

All-dielectric metasurfaces supporting resonant quasi-bound states in the continuum (qBIC) offer an ideal platform for various applications relying on intense light–matter interaction in highly localized and enhanced fields. Here, we propose a dielectric metasurface composed of hollow GaP nanocuboid quadrumers periodically arranged on a silica substrate. The metasurface supports a qBIC resonant mode with an antiferroelectric field configuration, which is very robust to large perturbations of the cuboid structure thanks to its perpendicular electric dipole field profile. The perturbed quadrumer arrangement retains C4v symmetry, thus allowing for polarization-independent optical response for normally incident planewaves. In addition, the resonant mode dispersion is investigated, revealing interesting features, such as low birefringence along the ΓM contour of the Brillouin zone and very low dispersion for the TM polarization along the ΓX direction. The metasurface is designed to resonate close to 785nm, which is highly relevant for Raman spectroscopy, leveraging the strong field enhancement at the interface with the overlayer material. Moreover, its performance as a bulk refractometric sensor is discussed. The proposed dielectric metasurface is promising for emerging photonic phenomena where strong light–matter interaction plays a key role.

Proton acceleration with multi-peak energy spectra tailored by vortex laser

A novel flying cascaded acceleration mechanism is proposed to generate energetic proton beams with multi-peak energy spectra using a circularly polarized (CP) Laguerre–Gaussian (LG) laser pulse in three-dimensional particle-in-cell simulations. Simulations show that the protons are initially accelerated and compressed into the beam center via the radiation pressure of the CP LG (σz = −1) laser pulse. Then, they are tailored by flying dipolar electric fields in this LG laser, resulting in a multi-peak energy spectrum. Each shaped proton peak exhibits a narrow energy spread of ∼5% and high flux of ∼2 × 108 protons/MeV at giga-electron volts energy. Such a flying cascaded acceleration mechanism extends the energy spectra of proton beams from monoenergetic to multi-peak structure, thereby potentially enhancing the generation efficiency of monoenergetic proton beams for various applications, such as proton-induced spallation reactions, proton radiography, and proton therapy.

On an Analytical Representation of an Integral Related to the Fock Integral That Appears in Calculations of the Electromagnetic Fields of Dipole Sources at the Interface between Two Half-Spaces

Abstract—The Fock integral is called after Fock who introduced it for the theoretical analysis of the electromagnetic field of magnetic dipoles at the boundary of a uniform conducting (nonmagnetic) half-space and obtained its analytical expression in terms of cylindrical functions. Detailed analytical representations of integrals, where all components of the fields of the vertical and horizontal magnetic dipoles are expressed, are reported in [A.V. Veshev et al., 1971]. To obtain analytical expressions for similar integrals representing the components of the fields of electric dipoles in a similar model, it is necessary to consider not only the Fock integral but also another related integral conditionally called the Fock integral 1 whose analytical expression is still unknown. The aims of this work are to derive an inhomogeneous linear first-order differential equation for this integral with the corresponding boundary conditions and to obtain the analytical representation of the Fock integral 1 by solving this equation. The result of this work will allow one to simplify the simulation of fields in a uniform half-space and to improve the interpretation of electromagnetic data due to more accurate and reliable estimates of the normal field in such models of a host medium.

Unraveling the structure–property relationship of a chalcone-based push–pull molecule for optical limiting application in high-powered laser

In this work, the optical limiting response of a highly π-conjugated push–pull chalcone derivative (2E)-3-(2,3-dimethoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (abbreviated as 3DPNP) has been investigated. The structure–property relationship of 3DPNP was explored through spectroscopic investigation and quantum chemical computations. The existence of weak-non-covalent interactions and charge transfer species that responsible for the chemical stability of 3DPNP were studied by AIM and NBO analyses. The quantitative and qualitative analysis of vibrational and electronic contribution to non-linear optical (NLO) response of 3DPNP were discussed in detail. The normal vibrational modes associated with a change in the dipole moment, polarizability, first- and second-order hyperpolarizabilities of 3DPNP were identified using DFT calculations followed by potential energy distribution (PED) analysis using Gaussian 09 W software and Gar2ped program, respectively. The changes in the NLO parameters with respect to the varying frequencies and electric dipole fields were studied. The abrupt changes in the NLO properties were noticed when the frequency doubled, confirming the second harmonic generation (SHG) efficiency of 3DPNP. From the non-linear absorption and refraction studies through the z-scan experiment, the optical limiting threshold value of 3DPNP is determined to be 3.26 kJ/cm2, which shows the suitability of the material for optical limiting applications in the continuous wave (CW) laser regime.

Direct Measurement of the Local Density of Optical States in the Time Domain.

One of the most fundamental and relevant properties of a photonic system is the local density of optical states (LDOS) as it defines the rate at which an excited emitter dissipates energy by coupling to its surrounding. However, the direct determination of the LDOS is challenging as it requires measurements of the complex electric field of a point dipole at its own position. We introduce here a near-field setup which can measure the terahertz electric field amplitude at the position of a point source in the time domain. From the measured amplitude, the frequency-dependent imaginary component of the electric field can be determined and the LDOS can be retrieved. As a proof of concept, this setup has been used to measure the partial LDOS (the LDOS for a defined dipole orientation) as a function of the distance to planar interfaces made of gold, InSb, and quartz. Furthermore, the spatially dependent partial LDOS of a resonant gold rod has been measured as well. These results have been compared with analytical results and simulations. The excellent agreement between measurements and theory demonstrates the applicability of this setup for the quantitative determination of the LDOS in complex photonic systems.

Investigation on the near-field cutoff effect in a subwavelength plasma shell with near-zero permittivity.

Although the plasma-induced receiving and radiating near-field cutoff phenomena in the subwavelength regime are found of crucial importance in electromagnetic (EM) signal transmissions and plasma property studies, their mechanisms to a large extent remain unclear and undistinguished. In this paper, in the perspective of field and energy transfer, it is demonstrated that the cutoff in the near-field regime is completely different from that in the geometric optical regime. Results show that, for the receiving mode, epsilon-near-zero (ENZ) plasmas can be treated as a nearly ideal EM fluid, and thus, EM waves are restricted into the plasma channel. For the radiating mode, on the other hand, it is the destructive interference between the electric dipole fields of the antenna and the ENZ plasma that results in vanishing far-field radiation. As an important supplement to the existing cutoff theories, our results not only offer clearer physical insights into the near-field cutoff effect but also provide a helpful reference for cutoff-related practical applications in various frequency bands.

Space-Charging Interfacial Layer by Illumination for Efficient Sb2S3 Bulk-Heterojunction Solar Cells with High Open-Circuit Voltage

Solution-processed material systems for effective photovoltaic conversion are the key to low-cost and efficient solar cells. While antimony trisulfide (Sb2S3) is a promising photovoltaic absorber, solution-processed quality Sb2S3-based heterojunction systems for solar cells, particularly with an open-circuit voltage (Voc) higher than 0.70 V, are challenging issues. Here, a cadmium sulfide (CdS) interfacial engineering method is developed for the Sb2S3-based bulk-heterojunction (BHJ) solar cells with an efficiency of 6.14% and a Voc up to 0.76 V that is the highest one among solution-processed Sb2S3 solar cells. The prepared Sb2S3-based BHJ solar cells feature a Sb2S3 nanoparticle film interdigitated by a titania (TiO2) nanorod array with a nanostructured CdS shell as an interfacial layer on each TiO2 nanorod core. Upon understanding the interfacial interactions and band alignments in the TiO2-CdS-Sb2S3 system, the function of the CdS interfacial layer as a band-bended spatial spacer interacting strongly with both the TiO2 electron transporter and Sb2S3 absorber for increasing charge collecting efficiency is revealed; moreover, space-charging the band-bended CdS layer by illumination is found and a photogenerated interfacial dipole electric field model is proposed for understanding the high Voc subjected to the presence of the CdS interfacial layer. This work provides a conceptual guide for designing efficient inorganic heterojunction solar cells.

Optimizing Electromagnetic Interference Shielding of Ultrathin Nanoheterostructure Textiles through Interfacial Engineering.

Strong electromagnetic wave reflection loss concomitant with second emission pollution limits the wide applications of electromagnetic interference (EMI) shielding textiles. Decoration of textiles by using various dielectric materials has been found efficient for the development of highly efficient EMI shielding textiles, but it is still a challenge to obtain EMI shielding composites with thin thickness. A route of interfacial engineering may offer a twist to overcome these obstacles. Here, we fabricated a Ni nanoparticle/SiC nanowhisker/carbon cloth nanoheterostructure, where SiC nanowhiskers were deposited by a simple manufacturing method, namely, laser chemical vapor deposition (LCVD), directly grown on carbon cloth. Through directly constructing a Ni/SiC interface, we find that the formation of Schottky contact can influence the interfacial polarization associated with the generation of dipole electric fields, leading to an enhancement of dielectric loss. A striking feature of this interfacial engineering strategy is able to enhance the absorption of the incident electromagnetic wave while suppressing the reflection. As a result, our Ni/SiC/carbon cloth exhibits an excellent EMI shielding effectiveness of 68.6 dB with a thickness of only 0.39 mm, as well as high flexibility and long-term duration stability benefited from the outstanding mechanical properties of SiC nanowiskers, showing potential for EMI shielding applications.

Radiative Recombination Plasma Rate Coefficients for Multiply Charged Ions

Radiative recombination (RR) plasma rate coefficients are often applied to estimate electron densities and temperatures under quite different plasma conditions. Despite their frequent use, however, these rate coefficients are available only for selected (few-electron) ions and isoelectronic sequences, mainly because of the computational efforts required. To overcome this limitation, we report here a (relativistic) cascade model which helps compute fine-structure and shell-resolved as well as total RR plasma rate coefficients for many, if not most, elements of the periodic table. This model is based on Jac, the Jena Atomic Calculator, and supports studies on how the electron is captured in selected levels of the recombined ion, a relativistic (Maxwellian) electron distribution, or how the multipoles beyond the electric-dipole field in the electron-photon interaction affect the RR rate coefficients and, hence, the ionization and recombination dynamics of hot plasma. As a demonstration of this model, we compute, compare, and discuss different RR plasma rate coefficients for initially helium-like ions, with an emphasis especially on Fe24+ ions.