Intrinsic Dipole Moment Research Articles

Investigating the role of internal electric fields on interfacial charge transfer dynamics in 2D MoSTe/WSeTe heterojunction for photocatalytic water splitting

Introducing the degrees of freedom brought by intrinsic dipole moments into heterojunctions allows for effective manipulation through the combination of different interfaces, thus offering more possibilities for designing high-performance photocatalysts. The influence of internal electric fields (EIN) in Janus materials on heterojunction interface charges is a crucial aspect of understanding the intrinsic mechanisms of charge transfer at interfaces. To address this, we construct four contact modes of MoSTe/WSeTe heterojunctions, considering the work function difference as a mediator to quantify two different electric fields. It is estimated that the influence of the interfacial electric field (EIF) on interfacial charge transfer is approximately 1.6 times that of the EIN (pointing outwards the interface). Moreover, the direction of the EIN varies, resulting in different impacts on interface charges. Subsequently, we also discuss the conditions under which different charge transfer modes are formed at different contact surfaces. On the other hand, the heterojunction of the Te-S mode can serve as a direct Z-Scheme photocatalyst for overall water splitting, and the presence of vacancies is necessary to address the issue of surface passivation. Our study not only refines the intrinsic mechanism of interfacial charge transfer in Janus-based heterojunctions but also predicts a direct Z-Scheme photocatalyst capable of achieving overall water splitting.

The effects of plant flavones on the membrane boundary potential and lipid packing stress

Here we have revealed the effects of different plant flavones on the physicochemical properties of model lipid membranes. We have demonstrated that baicalein increases the boundary potential of membranes composed of phosphatidylcholine, while wogonin does not affect it. Other flavones tested reduce membrane boundary potential, with this ability increasing among scutellarein, chrysin, apigenin, morin, fisetin, and luteolin. Molecular dynamics simulations demonstrate connection of alteration in boundary potential with the preferential orientation of intrinsic flavone dipole moments in membranes. We have also shown that flavones reduce the melting point of phosphatidylcholine, and this ability increases in the series of luteolin, morin, wogonin, scutellarein, apigenin, baicalein, chrysin, and fisetin. The introduction of baicalein, chrysin and fisetin also leads to a significant decrease in the sharpness of the lipid phase transition. We have hypothesized that the localization of flavones in the glycerol backbone or in the C1-C8 methylene region of lipid hydrocarbon chains leads to an increase in the area per lipid and, as a consequence, to an expansion of the lipid melting peak. Replacement of neutral phosphatidylcholine with negatively charged phosphatidylserine affects the membrane-modifying activity of flavones which given the externalization of phosphatidylserine on the surface of cancer cells may be crucial in the flavone anticancer effects.

Accelerated Electron-Hole Separation at the Organic-Inorganic Anthracene/Janus MoSSe Interface.

Organic light-absorbing materials with two-dimensional semiconductor layers as contact electrodes are promising for efficient and flexible low-cost solar cells. Considering anthracene as an absorber and a MoSSe Janus monolayer, we use non-adiabatic molecular dynamics to show that electron transfer from anthracene to MoSSe is faster on the Se side than the S side. The transfer from anthracene to MoS2 and MoSe2 monolayers takes intermediate times. As a rule, we find that a shorter adsorption distance produces a stronger donor-acceptor coupling. The smaller distance on the Se side is rationalized by the attractive force between the intrinsic dipole moment of the Janus structure and that of the molecule induced due to adsorption. Quantum coherence also affects the transfer time. The study provides detailed insights into adsorption of molecules on Janus structures and the resulting electronic and electron vibrational interactions. The results suggest that the dipole interaction plays an important role in the thermodynamic stability, alignment of electronic levels, and electron vibrational dynamics.

Functionalized MBenes as promising anode materials for high-performance alkali-ion batteries: a first-principles study

The discovery of novel electrode materials based on two-dimensional (2D) structures is critical for alkali metal-ion batteries. Herein, we performed first-principles computations to investigate functionalized MXenes, Mo2BT2 (T = O, S), which are also regarded as B-based MXenes, or named as MBenes, as potential anode materials for Li-ion batteries and beyond. The pristine and T-terminated Mo2BT2 (T = O, S) monolayers reveal metallic character with higher electronic conductivity and are thermodynamically stable with an intrinsic dipole moment. Both Mo2BO2 and Mo2BS2 monolayers exhibit high theoretical Li/Na/K storage capacity and low ion diffusion barriers. These findings suggest that functionalized Mo2BT2 (T = O, S) monolayers are promising for designing viable anode materials for high-performance alkali-ion batteries.

Synergistic polarity interaction and structural reconstruction in Bi2MoO6/C3N4 heterojunction for enhancing piezo-photocatalytic nitrogen oxidation to nitric acid

Constructing heterojunctions has emerged as a widely embraced strategy for augmenting piezo-photocatalytic activities. However, the synergistic pressure response, the construction of charge transfer, polar direction sites and active site are often left in the basket. Here, the carboxylated C3N4 and Bi2MoO6 S-scheme heterostructure was elaborately designed for piezo-photocatalytic nitrogen oxidation towards nitric acid. Extensive research evidence proves that Bi-COOH interaction between Bi2MoO6 and g-C3N4 leads to the occurrence of polarity interaction and structural reconstruction. Those initiatives facilitate the efficient distribution of charges and acts as a pathway for carrier migration, thereby promoting charge transfer and the large intrinsic dipole moment. Furthermore, the combination of polarity interaction and structural reconstruction strengthens N2 polarization and electron transfer, facilitating the breaking of NN bonds and reducing activation energy. Consequently, the optimal BCO-3 catalyst revealed outstanding nitric acid production rates of 5930 μg g−1 h−1 under the stimulation of ultrasonic and light illumination, which is 3.66 times higher than that of C3N4-Bi2MoO6 heterostructure and superiors to various piezo-photocatalysts. Our research endeavors present promising prospects for the design of advanced catalysts and contribute to a profound comprehension of molecular activation processes in heterojunction.

Highly Stable Lithium Metal Batteries Enabled by Tuning the Molecular Polarity of Diluents in Localized High-Concentration Electrolytes.

Electrolyte plays a crucial role in ensuring stable operation of lithium metal batteries (LMBs). Localized high-concentration electrolytes (LHCEs) have the potential to form a robust solid-electrolyte interphase (SEI) and mitigate Li dendrite growth, making them a highly promising electrolyte option. However, the principles governing the selection of diluents, a crucial component in LHCE, have not been clearly determined, hampering the advancement of such a type of electrolyte systems. Herein, the diluents from the perspective of molecular polarity are rationally designed and developed. A moderately fluorinated solvent, 1-(1,1,2,2-tetrafluoroethoxy)propane (TNE), is employed as a diluent to create a novel LHCE. The unique molecular structure of TNE enhances the intrinsic dipole moment, thereby altering solvent interactions and the coordination environment of Li-ions in LHCE. The achieved solvation structure not only enhances the bulk properties of LHCE, but also facilitates the formation of more stable anion-derived SEIs featured with a higher proportion of inorganic species. Consequently, the corresponding full cells of both Li||LiFePO4 and Li||LiNi0.8Co0.1Mn0.1O2 cells utilizing Li thin-film anodes exhibit extended long-term stability with significantly improved average Coulombic efficiency. This work offers new insights into the functions of diluents in LHCEs and provides direction for further optimizing the LHCEs for LMBs.

Organic cations in halide perovskite solid solutions: exploring beyond size effects.

Halide perovskites are a class of materials of consolidated optoelectronic and electrochemical applications, reaching efficiencies compared to established materials in respective fields. In this scenario, the design and understanding of composition-structure-property relations is imperative. In solid solutions containing mixed cations, some direct relations between the sizes of the substituents and the properties of perovskites are generally observed. However, in several cases, these relations are not observed, implying that other characteristics of these cations play a major role. Despite its importance, this understanding has not been comprehensively deepened. To address this issue, we synthesized and characterized the structure, electrical behavior, and stability of methylammonium lead iodide-based perovskites with equal amounts of the substituents guanidinium, ethylammonium, and acetamidinium. These three large organic cations have essentially equal sizes but other remarkably different characteristics, such as the number of N-H bonds, intrinsic dipole moment, and order of C-N bonds. Herein, we show that these cations have dramatically different effects over important fundamental and applied properties of resulting perovskites, including the orthorhombic-to-tetragonal and tetragonal-to-cubic phase transitions, microstructural development, ionic conductivity, I-V hysteresis, electronic carrier mobility, and stability against light-induced degradation. These effects are correlated with the characteristics of the large substituent cations and help pave the way for a better rational chemical design of halide perovskites.

PVDF/fluorescent carbon dots electrospun nanofibers with synergistic dipole alignment and multifunctional sensing applications

The development of novel multifunctional materials has been attracting continuous attention in recent years. In this work, fluorescent carbon dots (CDs) with a designed quasi-molecular structure were introduced into polyvinylidene fluoride (PVDF) nanofibers to realize electro-mechano-photoluminescence coupling effects. The N-H and O-H groups in the CDs formed hydrogen bonds with C-F groups in PVDF, which not only ensured the uniform arrangement of the CDs in the nanofiber matrix, but also facilitated the polarization of the PVDF. The β phase in PVDF was improved from 80% to 86% by doping of the CDs. Moreover, due to the asymmetric molecular structure of the carbon dot, it possessed an intrinsic dipole moment of 4.62 Debye. The self-assembly of the CDs on the nanofibers with a similar energy-favorable conformation improved the long-range spatial ordering in the nanocomposite. The CDs could also act as working dipoles, and contributed to the piezoelectric output of the whole device. Under a repeated finger imparting, the output voltage was enhanced from 6 V of the pure PVDF to 15 V of the nanocomposite. Furthermore, the CDs endowed the fiber with fluorescence capacity. The composite nanofiber exhibited bright fluorescence with excellent homogeneity. Through monitoring of the fluorescent intensity, visualized strain sensing and information encryption could be realized, which showed high potential of the nanofiber as a multifunctional nanocomposite.

Bipolar ferromagnetic semiconductors and dipole-modulated magnetism in two-dimensional Janus transition metal dihalides

Two-dimensional (2D) transition metal dihalides (TMDHs) have attracted great interest owing to their unique magnetic and semiconductor properties. Compared with the mirror/inversion symmetric materials, 2D Janus materials possess vertical intrinsic dipole moment, which offer a versatile platform for the fundamental physics and future spintronic devices. Here, we systematically explore the magnetic and electronic properties of the 2D Janus transition metal dihalides MXY (M = Co and Ni; X ≠ Y = Cl, Br, and I) monolayers and bilayers by using density functional theory. The monolayer CoClBr, NiClBr, and NiBrI are bipolar ferromagnetic semiconductors that possess the valence and conduction band edges of different spin channels. The magnetism of the bilayer CoClBr, NiClBr, and NiBrI is highly dependent on the accumulated dipole moments of the two adjacent layers. When the dipole moments in both layers are aligned in the same direction and the accumulated dipole moments are nonzero, the systems are antiferromagnetic half semiconductors. However, when the dipole moments in the two layers are opposite and the accumulated dipole moments are zero, the systems are A-type antiferromagnetic semiconductors. Our findings are helpful to understand the magnetism of Janus TMDHs and guide experiments in exploring their potential application in spintronic devices.

Intrinsic Nonlinear Hall Effect and Gate-Switchable Berry Curvature Sliding in Twisted Bilayer Graphene.

Though the observation of the quantum anomalous Hall effect and nonlocal transport response reveals nontrivial band topology governed by the Berry curvature in twisted bilayer graphene, some recent works reported nonlinear Hall signals in graphene superlattices that are caused by the extrinsic disorder scattering rather than the intrinsic Berry curvature dipole moment. In this Letter, we report a Berry curvature dipole induced intrinsic nonlinear Hall effect in high-quality twisted bilayer graphene devices. We also find that the application of the displacement field substantially changes the direction and amplitude of the nonlinear Hall voltages, as a result of a field-induced sliding of the Berry curvature hotspots. Our Letter not only proves that the Berry curvature dipole could play a dominant role in generating the intrinsic nonlinear Hall signal in graphene superlattices with low disorder densities, but also demonstrates twisted bilayer graphene to be a sensitive and fine-tunable platform for second harmonic generation and rectification.

Nuclear DFT electromagnetic moments in heavy deformed open-shell odd nuclei

Within the nuclear DFT approach, we determined the magnetic dipole and electric quadrupole moments for paired nuclear states corresponding to the proton (neutron) quasiparticles blocked in the π11/2− (ν13/2+) intruder configurations. We performed calculations for all deformed open-shell odd nuclei with 63≤Z≤82 and 82≤N≤126. Time-reversal symmetry was broken in the intrinsic reference frame and self-consistent shape and spin core polarizations were established. We determined spectroscopic moments of angular-momentum-projected wave functions and compared them with available experimental data. We obtained good agreement with data without using effective g-factors or effective charges in the dipole or quadrupole operators, respectively. We also showed that the intrinsic magnetic dipole moments, or those obtained for conserved intrinsic time-reversal symmetry, do not represent viable approximations of the spectroscopic ones.

Construction of spontaneously polarized ceramic via synergistic mechanical activation‒Biomimetic mineralization for activating air and water

Spontaneously polarized crystals with intrinsic electric dipole moment have attracted immense interest as excellent functional materials for extensive applications. It is of great significance to engineer sustainable spontaneously polarized materials with fascinating characteristics and performance for activating air and water. Herein, a novel strategy based on the synergy of mechanical activation (MA) and biomimetic mineralization (BM) was created to construct spontaneously polarized ceramic. MA induced the structural damage of clay and promoted the dissolution of ions and the release of free proteins, contributing to the formation of silicate precursor in BM process. After high temperature firing, the silicate precursor in clay was converted to form KCa3AlCa3Si4O16 (hexagonal crystal system, L6 symmetry type, and P63 space group) in the resulting spontaneously polarized ceramic. The non-centrosymmetric structure of KCa3AlCa3Si4O16 and the high intrinsic electric dipole moments contributed by K(1) polyhedrons resulted in high spontaneous polarization (0.2322 μC/cm2) and far-infrared emissivity (0.951) of spontaneously polarized ceramic. In air, spontaneously polarized ceramic can activate H2O and O2 molecules to form negative air ions owing to surface electric field. In water, spontaneously polarized ceramic can disaggregate large water clusters to form small water clusters ascribed to surface electric field and far-infrared emission; water pH can be regulated from weak acidity to approximate neutrality via the capture of electrons by H+ ions to produce releasable hydrogen gas. This work provides great promise for rational design and synthesis of spontaneously polarized materials for functional applications.

The mechanism of pyroelectricity in polar material hemimorphite

It is known that a crystal structure and symmetry determine the physical properties of materials. Lattice distortion can strongly affect the symmetry of the crystal structure. Polar materials show changes in polarization with temporal fluctuations of temperature due to the asymmetry. As a polar crystal, hemimorphite shows excellent pyroelectric properties. However, to date, there are a few studies on its intrinsic physical properties, and the mechanism of its pyroelectricity remains unclear. In this paper, single-crystal x-ray diffraction measurement was carried out to obtain the atomic positions at 100–400 K. Furthermore, the electric dipole moments of [ZnO4] and [SiO4] polyhedrons along a, b, and c axes have been calculated. The calculated pyroelectric coefficient derived from the intrinsic electric dipole moment was compared with the experimental measurement. The results indicate that the pyroelectric coefficients of hemimorphite at different temperatures mainly come from the variation of the electric dipole moment of [ZnO4] and [SiO4] polyhedrons along the c axis. The electric dipole moment changes as a function of temperature from 100 to 400 K, which is induced by the random lattice distortion. It is found that pyroelectricity is strongly correlated with the random lattice distortion. The establishment of the relationship between lattice distortion and pyroelectricity helps us to regulate the specific electrical parameters of the material, which may lead to future work in energy harvesting and further properties.

Polar Layered Bismuth‐Rich Oxyhalide Piezoelectrics Bi4O5X2 (XBr, I): Efficient Piezocatalytic Pure Water Splitting and Interlayer Anion‐Dependent Activity

AbstractPiezocatalytic pure water splitting for H2 evolution carries the virtues of efficacious utilization of mechanical energy, easy operation, and high value‐added products, while lacking desirable piezoelectrics for high chemical energy production. Here, two polar layered bismuth‐rich oxyhalides Bi4O5X2 (XBr, I) thin nanosheets (≈4 nm) are first exploited as efficient piezocatalysts to be capable of dissociating pure water. The unique asymmetrical layered structures of Bi4O5X2 (XBr, I) composed of the interleaved [Bi4O5]2+ layer and double X− ions slabs along the [1 0 1_] orientation cause large intrinsic dipole moment, excellent piezoelectricity and easy deformation. Without any cocatalyst and sacrificial agent, Bi4O5Br2 and Bi4O5I2 thin nanosheets display remarkable piezocatalytic H2 production rate of 1149.0 and 764.5 µmol g−1 h−1, respectively, standing among the best piezocatalysts, accompanied by H2O2 and hydroxyl radicals (·OH) as oxidative products. The smaller radius and higher electronegativity of interleaved Br than I cause a more strongly polar crystal structure in Bi4O5Br2, contributing to the higher piezocatalytic activity compared to Bi4O5I2. This study broadens the scope of piezoelectric materials applied to sustainable energy catalysis by efficiently converting mechanical energy and illustrates the importance of crystal configuration and composition in fabricating efficient piezocatalytic systems.

Experimental review of octupole correlations in the A≈80 mass region

This review presents the nuclei with octupole correlations in the [Formula: see text] mass region. The status of experimental data on the behavior of the energy displacement, the [Formula: see text] transition probability and intrinsic electric dipole moment have been reviewed. The evolutions of the octupole strength with the numbers of protons and neutrons are discussed.

The study on the dielectric properties of structural changes of surfactant aqueous solution by molecular dynamics simulation

Dielectric constant is an important physical and chemical property of liquid in regulating solute–solvent interaction and solvation microstructure. Herein this work deals with the procedure for calculating dielectric property based on the raw data of molecular dynamics (MD) simulation. The fluctuations of the dipole moment and current which are obtained from MD can be directly related to the frequency-dependent permittivity. In this article, we have taken the sodium dodecyl sulfate (SDS) aqueous micelle system containing free charges as an example, and the dielectric behavior of micellar systems with different structures were studied. In the high frequency range, the response of positive and negative ions is shielded due to the intrinsic dipole moment polarization of the molecule. At low frequencies, the static dielectric constant can reveal the microstructral transformation of the micelles properly. Our results show that the dielectric constant is closely related to the atomic structure of the micelles, and the static dielectric constant could serve as an important method to determine the microscopic phase change process.

First-principles prediction of two-dimensional Janus XMInZ[formula omitted](X [formula omitted] Cl, Br, I; M [formula omitted] Mg, Ca; and Z [formula omitted] S, Se, and Te) with promising spintronic and photocatalytic properties

Janus two-dimensional (2D) materials with asymmetric structures and intrinsic dipole moments have recently drawn enormous attention due to their appealing performance in diverse fields of nanoelectronics, optoelectronics, spintronics, and photocatalytic water splitting. In this paper, we propose a novel 2D Janus family named XMInZ2(X = Cl, Br, I; M = Mg, Ca; and Z = S, Se, and Te) and investigate their properties employing first-principles calculations. Using phonon dispersion, seventeen compounds of the predicted XMInZ2 monolayers are proved to be dynamically stable. The electronic band structures reveal that all stable XMInZ2 monolayers are direct bandgap semiconductors among which XMgInZ2 have larger bandgaps than XCaInZ2 monolayers. Lack of mirror symmetry gives rise to distinct Rashba spin-splitting (RSS) at Γ point of conduction bands in most XMInZ2 monolayers and the largest Rashba coefficient (αRΓC= 1.112 eVÅ) belongs to BrCaInTe2. Furthermore, comparing the projected band structures with and without the spin–orbit coupling (SOC) effect, it is found that the inclusion of SOC leads to band inversion between the lower conduction band (LCB) and upper valence band (UVB) of ICaInS2 monolayer. In terms of photocatalytic properties, some Janus XMInZ2 monolayers possess appropriate band edge positions for overall water splitting owing to their intrinsic dipole moments. Particularly, BrMgInTe2, BrCaInTe2, and ICaInTe2 due to their smaller bandgaps, larger solar light absorptions, and efficient separation and transport of electrons and holes are superior photocatalysts for water splitting. These explorations can pave the way for the design of highly efficient spintronic and photocatalytic devices.

Electronegative diversity induced localized built-in electric field in a single phased MoSxSeyNz for selectivity-enhanced visible photocatalytic CO2 reduction

How to passivate the recombination in a photocatalyst is a big challenge to achieve efficient photocatalytic CO2 reduction. Besides the heterojunction strategy, the design of intrinsic built-in electric field in a single phased photocatalyst can facilitate the transport while it does not introduce extra side reactions induced by the unbalanced photocarriers. This work utilizes the electronegative diversity between chalcogens and non-chalcogen element in a quarternary transition metal dichalcogenide of MoSxSeyNz to define localized built-in electric fields. It has been revealed that the nitrogen induced intrinsic dipole moments and potential energy have strenghthened the built-in electric fields, promoting the separation of photocarriers and the gathering of electrons around N sites, which has been found to improve the adsorption of intermediate products and lower the energy for methanol-oriented photoproduction route. Finally, the MoSxSeyNz has improved the photoproduction of methanol reduced from CO2 by 162%.

Surface-Enhanced Raman Spectroscopy (SERS) Chemical Enhancement in the Vibronically Coupled Langmuir Layer of Mixed Dichalcogenide 1T-MoSSe with Adsorbed R6G

Transition-metal dichalcogenides based on different chalcogen atoms give origins to many new phenomena due to symmetry breaking and exhibit better physicochemical characteristics than pristine dichalcogenides. In this work, the formation of a perfectly tiled uniform monolayer of MoSSe using the Langmuir–Blodgett (LB) technique under ambient conditions is demonstrated. The aligned monolayer of the 1T phase depicts a film thickness of 1.2–2.4 nm corresponding to a single to a bilayer of MoSSe. The LB-prepared substrates are subsequently used for Raman sensing of R6G. The presence of MoSSe quenches the fluorescence of the R6G. Regarding surface-enhanced Raman spectroscopy sensitivity, 1T MoSSe could sense R6G up to picomolar concentrations with an enhancement factor of ∼6 × 106. This is 3 to 4 orders higher than the corresponding sulfide or the selenide analogues (1T MoS2 and 1T MoSe2). This increased sensitivity of 1T MoSSe is attributed to a large number of active sites with intrinsic dipole moment and high electronic conductivity, which leads to strong substrate-analyte vibronic coupling. Absorption and Raman spectroscopy confirms the static coupling between the substrates and R6G molecules. First principle density functional theory calculations reveal high density of states near the Fermi level in the case of distorted 1T MoSSe as compared to the pristine sulfide or selenide with less energy difference between the highest occupied molecular orbital of R6G and the Fermi level of 1T MoSSe. This might result in a facile charge transfer during the photoinduced charge transfer-driven chemical mechanism leading to a strong coupling of the metal–analyte complex, thus resulting in significant Raman enhancement.

Properties of CF3SO2F under the influence of external electric field: A DFT study

With the deterioration of global greenhouse effect, CF3SO2F (Trifluoromethanesulphonyl Fluoride) has become an alternative gas of SF6 (Sulfur Hexafluoride). CF3SO2F has environmentally friendly characteristics and has been widely concerned. In this work, we analyze the electric field level of the discharge in the dielectric and the direction of the molecular intrinsic dipole moment. Density functional theory and time-dependent density functional theory are used to calculate the molecular structure parameters, dipole moments, frontier orbitals and excited states at corresponding electric field levels and in specific electric field directions. C2F5SO2F and C3F7SO2F, as by-products in the synthesis of CF3SO2F, are studied together to explore the influence of carbon atom number on molecular properties. As a result, the molecular structure is clearly changed under the electric field and the molecular bond length strongly depended on the electric field. The HOMO is mainly contributed by O atoms and the LUMO is mainly contributed by S atoms. When the electric field in the -z-axis direction is applied, the HOMO energies of molecules increase, especially for C3F7SO2F molecule, and the ionization potentials decrease correspondingly. The reduced ionization potentials facilitate the liberation of electrons from the molecule and the propagation of the streamer. The excitation energy of each molecule in each excited state decreases with the increasing of electric field intensity. Therefore, during the preparation process of CF3SO2F molecule, C3F7SO2F molecule should be reduced or removed as much as possible to prevent the reduction of dielectric insulation strength. The finding of this study is beneficial to the performance improvement and application research of CF3SO2F.