Alignment Of Dipole Moments Research Articles

Prominent cycling reversibility and kinetics enabled by CaTiO3 protective layer on Zn metal for aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) have received considerable attention owing to their various advantages such as safety, low cost, simple battery assembly conditions, and high ionic conductivity. However, they still suffer from serious problems, including uncontrollable dendrite growth, corrosion, hydrogen evolution reaction (HER) from water decomposition, electrode passivation, and unexpected by-products. The creation of a uniform artificial nanocrystal layer on the Zn anode surface is a promising strategy for resolving these issues. Herein, we propose the use of a perovskite CaTiO3 (CTO) protective layer on Zn (CTO@Zn) as a promising approach for improving the performance of AZIBs. The CTO artificial layer provides an efficient pathway for Zn ion diffusion towards the Zn metal because of the high dielectric constant (εr = 180) and ferroelectric characteristics that enable the alignment of dipole moments and redistribute the Zn2+ ions in the CTO layer. By avoiding the direct contact of the Zn anode with the electrolyte solution, the uneven dendrite growth, corrosion, parasitic side reactions, and HER are mitigated, while CTO retains its mechanical and chemical robustness during cycling. Consequently, CTO@Zn demonstrates an improved lifespan in a symmetric cell configuration compared with bare Zn. CTO@Zn shows steady overpotential (∼68 mV) for 1500 h at 1 mA cm−2/0.5 mA h cm−2, excelling bare Zn. Moreover, when paired with the V2O5-C cathode, the CTO@Zn//V2O5-C full battery delivers 148.4 mA h g−1 (based on the mass of the cathode) after 300 cycles. This study provides new insights into Zn metal anodes and the development of high-performance AZIBs.

Intrinsic Out-Of-Plane and In-Plane Ferroelectricity in 2D AgCrS2 with High Curie Temperature.

2D ferroelectric materials have attracted extensive research interest due to potential applications in nonvolatile memory, nanoelectronics and optoelectronics. However, the available 2D ferroelectric materials are scarce and most of them are limited by the uncontrollable preparation. Herein, a novel 2D ferroelectric material AgCrS2 is reported that are controllably synthesized in large-scale via salt-assist chemical vapor deposition growth. By tuning the growth temperature from 800 to 900°C, the thickness of AgCrS2 nanosheets can be precisely modulated from 2.1 to 40nm. Structural and nonlinear optical characterizations demonstrate that AgCrS2 nanosheet crystallizes in a non-centrosymmetric structure with high crystallinity and remarkable air stability. As a result, AgCrS2 of various thicknesses display robust ferroelectric polarization in both in-plane (IP) and out-of-plane (OOP)directions with strong intercorrelation and high ferroelectric phase transition temperature (682 K). Theoretical calculations suggest that the ferroelectricity in AgCrS2 originates from the displacement of Ag atoms in AgS4 tetrahedrons, which changes the dipole moment alignment. Moreover, ferroelectric switching is demonstrated in both lateral and vertical AgCrS2 devices, which exhibit exotic nonvolatile memory behavior with distinct high and low resistance states. This study expands the scope of 2D ferroelectric materials and facilitates the ferroelectric-based nonvolatile memory applications.

Phonon dressing induced dipole moment alignment of nonpolar ions

Phonon dressing induced dipole moment alignment of nonpolar ions

Emergence of ferroelectricity in a nonferroelectric monolayer

Ferroelectricity in ultrathin two-dimensional (2D) materials has attracted broad interest due to potential applications in nonvolatile memory, nanoelectronics and optoelectronics. However, ferroelectricity is barely explored in materials with native centro or mirror symmetry, especially in the 2D limit. Here, we report the first experimental realization of room-temperature ferroelectricity in van der Waals layered GaSe down to monolayer with mirror symmetric structures, which exhibits strong intercorrelated out-of-plane and in-plane electric polarization. The origin of ferroelectricity in GaSe comes from intralayer sliding of the Se atomic sublayers, which breaks the local structural mirror symmetry and forms dipole moment alignment. Ferroelectric switching is demonstrated in nano devices fabricated with GaSe nanoflakes, which exhibit exotic nonvolatile memory behavior with a high channel current on/off ratio. Our work reveals that intralayer sliding is a new approach to generate ferroelectricity within mirror symmetric monolayer, and offers great opportunity for novel nonvolatile memory devices and optoelectronics applications.

Printable logic circuits comprising self-assembled protein complexes

This paper describes the fabrication of digital logic circuits comprising resistors and diodes made from protein complexes and wired together using printed liquid metal electrodes. These resistors and diodes exhibit temperature-independent charge-transport over a distance of approximately 10 nm and require no encapsulation or special handling. The function of the protein complexes is determined entirely by self-assembly. When induced to self-assembly into anisotropic monolayers, the collective action of the aligned dipole moments increases the electrical conductivity of the ensemble in one direction and decreases it in the other. When induced to self-assemble into isotropic monolayers, the dipole moments are randomized and the electrical conductivity is approximately equal in both directions. We demonstrate the robustness and utility of these all-protein logic circuits by constructing pulse modulators based on AND and OR logic gates that function nearly identically to simulated circuits. These results show that digital circuits with useful functionality can be derived from readily obtainable biomolecules using simple, straightforward fabrication techniques that exploit molecular self-assembly, realizing one of the primary goals of molecular electronics.

Polarized, V-Shaped, and Conjoined Biscoumarins: From Lack of Dipole Moment Alignment to High Brightness.

Eleven conjoined coumarins possessing a chromeno[3,4-c]chromene-6,7-dione skeleton have been synthesized via the reaction of electron-rich phenols with esters of coumarin-3-carboxylic acids, catalyzed by either Lewis acids or 4-dimethylaminopyridine. Furthermore, Michael-type addition to angular benzo[f]coumarins is possible, leading to conjugated helical systems. Arrangement of the electron-donating amino groups at diverse positions on this heterocyclic skeleton makes it possible to obtain π-expanded coumarins with emission either sensitive to, or entirely independent of, solvent polarity with large Stokes shifts. Computational studies have provided a rationale for moderate solvatochromic effects unveiling the lack of collinearity of the dipole moments in the ground and excited states. Depending on the functional groups present, the obtained dyes are highly polarized with dipole moments of ∼14 D in the ground state and ∼20–25 D in the excited state. Strong emission in nonpolar solvents, in spite of the inclusion of a NO2 group, is rationalized by the fact that the intramolecular charge transfer introduced into these molecules is strong enough to suppress intersystem crossing yet weak enough to prevent the formation of dark twisted intramolecular charge transfer states. Photochemical transformation of the dye possessing a chromeno[3,4-c]pyridine-4,5-dione scaffold led to the formation of a spirocyclic benzo[g]coumarin.

Morphology of dipolar Bose droplets

The ground state of a free standing, self-bound droplet comprising four hundred dipolar Bose particles with aligned dipole moments, with an additional purely repulsive two-body interaction, is investigated by Quantum Monte Carlo simulations. The focus here is on the evolution of the cluster as the effective range of the repulsive interaction is varied. We identify a “classical” regime, in which binding arises exclusively from the dipolar potential energy and the cluster is a quasi-one-dimensional filament, and a “quantum” regime of prolate droplets, held together to a significant degree by quantum-mechanical exchanges. The transition between the two regimes occurs abruptly.

Enhancing Mechanical Energy Transfer of Piezoelectric Supercapacitors

AbstractThe expected widespread use of wearable and other low‐power healthcare devices has triggered great interest in piezoelectric materials as a promising energy harvester. However, traditional piezoelectric materials suffer from poor interfacial energy transfer when used in self‐charging power cells. Herein, piezoelectric supercapacitors (PSCs) are engineered using MXene‐incorporated polymeric piezo separator and MXene (Ti3C2Tx) multilayered sheets as electrodes. The MXene‐blended polymer film showed considerable improvement with maximum output voltage of 28 V and current of 1.71 µA. The electromechanical properties studied by piezoelectric force microscopy suggest that the integration of MXene in polyvinylidene fluoride (PVDF) matrix induces the degree of dipole moment alignment, thereby improving the piezoelectric properties of PVDF. At the device level, the PSC featured the capacitance of 61 mF cm–2, the energy density of 24.9 mJ cm−2, the maximum power density of 1.3 mW cm−3, and the excellent long‐term cycling stability. A way is paved toward green, integrated energy harvesting and storing technology for next‐generation self‐powered implantable and wearable electronics.

Dielectric relaxation study of 1-pentanol–ethanol binary mixtures at 10 MHz–50GHz frequency range using TDR technique

ABSTRACT The dielectric measurements have been executed by making the use of time domain reflectometry (TDR) technique for 1-pentanol and ethanol in the pure form and for their binary liquid mixture in the frequency interim of 10 MHz–50 GHz at varying temperatures, respectively. The complex permittivity spectra studied show Debye behaviour and plotted as the function of frequency. The temperature-dependent dielectric constant and relaxation time values were estimated. The Kirkwood correlation factor (g eff) has also been studied to determine the alignment of dipole moments in mixture. The thermodynamic parameters and temperature-dependent behaviour of relaxation time, i.e. Arrhenius plot, have been studied.

Enhanced and Polarization-Dependent Coupling for Photoaligned Liquid Crystalline Conjugated Polymer Microcavities

Here we report the fabrication and optical characterization of organic microcavities containing liquid-crystalline conjugated polymers (LCCPs): poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), poly(9,9-dioctylfluorene) (PFO) and poly(2,7-(9,9-dihexylfluorene)-co-bithiophene) (F6T2) aligned on top of a thin transparent Sulfuric Dye 1 (SD1) photoalignment layer. We extract the optical constants of the aligned films using variable angle spectroscopic ellipsometry and fabricate metallic microcavities in which the ultrastrong coupling regime is manifest both for the aligned and non-aligned LCCPs. Transition dipole moment alignment enables a systematic increase in the interaction strength, with unprecedented solid-state Rabi splitting energies up to 1.80 eV for F6T2, the first to reach the visible spectrum; with an optical gap of 2.79 eV this also gives the highest-to-date organic microcavity coupling ratio, 65$\%$. We also demonstrate that the coupling strength is polarization-dependent with bright polaritons photoluminescence for TE polarization parallel to the transition dipoles and either no emission or weakly coupled emission from the corresponding TM polarization. The use of uniaxally aligned organic microcavities with switchable coupling strength offers exciting prospects for direct observations of ultrastrong coupling signatures, quantum simulation, polaritonics and condensation related phenomena.

Enhanced piezoelectric tactile sensing behaviors of high-density and low-damage CF4-plasma-treated IGZO thin-film transistors coated by P(VDF-TrFE) copolymers

Piezoelectric pressure sensing behaviors of high-density and low-damage CF4-plasma-treated indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) coated by poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) films have been investigated. The CF4 plasma treatment was performed on the IGZO channel by using an inductively coupled plasma (ICP) system with a quartz filter. Prior to the fabrication of devices, X-ray diffractometer (XRD) and atomic force microscopy (AFM) were applied to identify the enhancement in the crystallinity of P(VDF-TrFE) films on the plasma-fluorinated IGZO films. With the analyses of X-ray photoelectron spectroscopy (XPS), it is proved that the fluorine radicals reacted with the metal-oxygen bonds will increase the oxygen vacancies in IGZO films, contributing to an enhancement in field effect mobility (μFE) and drain current (IDS) of IGZO TFTs. Furthermore, the fluorine atoms diffused from the IGZO channel into the bottom SiO2 layer were confirmed by secondary ion-mass spectroscopy (SIMS), reducing the interfacial and oxide charges of the devices for a negative shift in threshold voltage (Vt). Under a 0.5-kg applied force press/release cyclic test, a 4.8-fold increase in drain current response of 1-min CF4-plasma-treated piezoelectric pressure sensors was optimized, because of the enhanced electrical behaviors of IGZO TFTs and an increase in aligned dipole moments of P(VDF-TrFE) copolymers. The promising results make the piezoelectric pressure sensors with high-density and low-damage CF4-plasma-treated IGZO TFTs coated by P(VDF-TrFE) copolymer suitable for future high-performance tactile sensing applications.

Atomically resolved domain boundary structure in lead zirconate-based antiferroelectrics

Domain boundary (DB) structures are of great importance for understanding the structure-property relationship in many ferroic crystals. Here, we present atomically resolved DB configurations in PbZrO3-based antiferroelectric ceramics. The Pb-cation displacement relative to B-site cations is precisely determined using aberration-corrected scanning transmission electron microscopy. We find that 90° DBs in undoped PbZrO3 can be as thin as one primitive cell of the perovskite structure, often appearing curved or zigzagged due to the complex dipole arrangement. In a chemically modified composition, Pb0.99Nb0.02[(Zr0.57Sn0.43)0.95Ti0.05]0.98O3, in which incommensurate modulations are present, the DB has a typical thickness of at least two primitive cells, with more or less aligned dipole moments. Our findings provide insights into establishing the structure-property relationship in antiferroelectrics, shedding light on the design and fabrication of domain-boundary electronics.

Local structure and orientational ordering in liquid bromoform

The neutron diffraction data of liquid bromoform (CHBr3) at 25°C was analysed using the Empirical Potential Structure Refinement technique in combination with H/D isotopic substitution. Compared to liquid chloroform (CHCl3), CHBr3 displays more spatially defined intermolecular contacts. A preference for polar stacking with collinear alignment of dipole moments is observed for the most closely approaching CHBr3 molecules, although to a lesser extent than in chloroform. Consistent with this, and in line with dielectric spectroscopy, the Kirkwood correlation factor from the structural model of CHBr3 is smaller than that of CHCl3. The net antiparallel alignment of dipole moments in CHBr3, as suggested by dielectric spectroscopy, must be due to weak but persistent long-range orientation correlations in CHBr3, which counteract the local polar stacking.

Patterned Supersolids in Dipolar Bose Systems

We study by means of first principle Quantum Monte Carlo simulations the ground state phase diagram of a system of dipolar bosons with aligned dipole moments, and with the inclusion of a two-body repulsive potential of varying range. The system is shown to display a supersolid phase in a relatively broad region of the phase diagram, featuring different crystalline patterns depending on the density and on the range of the repulsive part of the interaction (scattering length). The supersolid phase is sandwiched between a classical crystal of parallel filaments and a homogeneous superfluid phase. We show that a "roton" minimum appears in the elementary excitation spectrum of the superfluid as the system approaches crystallization.

High Exciton Diffusion Coefficients in Fused Ring Electron Acceptor Films.

Modest exciton diffusion lengths dictate the need for nanostructured bulk heterojunctions in organic photovoltaic (OPV) cells; however, this morphology compromises charge collection. Here, we reveal rapid exciton diffusion in films of a fused-ring electron acceptor that, when blended with a donor, already outperforms fullerene-based OPV cells. Temperature-dependent ultrafast exciton annihilation measurements are used to resolve a quasi-activationless exciton diffusion coefficient of at least 2 × 10-2 cm2/s, substantially exceeding typical organic semiconductors and consistent with the 20-50 nm domain sizes in optimized blends. Enhanced three-dimensional diffusion is shown to arise from molecular and packing factors; the rigid planar molecular structure is associated with low reorganization energy, good transition dipole moment alignment, high chromophore density, and low disorder, all enhancing long-range resonant energy transfer. Relieving exciton diffusion constraints has important implications for OPVs; large, ordered, and pure domains enhance charge separation and transport, and suppress recombination, thereby boosting fill factors. Further enhancements to diffusion lengths may even obviate the need for the bulk heterojunction morphology.

Infrared spectroscopy of jet-cooled HCCl singlet chlorocarbene diradical: CH stretching and vibrational coupling dynamics.

Quantum shot noise limited laser absorption methods are used to obtain first high-resolution infrared rovibrational spectra of jet cooled chlorocarbene (HCCl) diradical in a supersonic slit-jet discharge expansion spectrometer. The rotationally resolved absorption spectra of the C-H stretch ν1 fundamental are analyzed in the framework of a Watson non-rigid asymmetric rotor Hamiltonian model. Further analysis of the mid-infrared data reveals the additional presence of what has nominally been assigned as the combination band with one quantum of the H-C-Cl bend (ν2) and two quanta of the C-Cl stretch (2ν3). Rovibrational constants are obtained from least squares fits for each of the four excited vibrational states built on the ν1 fundamental and the combination mode for each 35Cl and 37Cl atom isotopologue. The four bands occur within a narrow spectral window, requiring detailed comparison of multiple spectral properties (e.g., rotational constant dependence on vibrational excitation, band types/transition dipole moment alignment in the body-fixed frame, etc.) to aid in the vibrational assignment. Indeed, the IR transition intensities arise from strong anharmonic mixing between the "bright" ν1 C-H stretch and "dark" H-C-Cl bend/C-Cl stretch combination modes, resulting in nearly equal amplitudes for the zeroth order and harmonic states. Finally, to aid the spectral search for HCCl in the interstellar medium, ground state two-line combination differences are combined with previous laser-induced fluorescence results to predict precision microwave transitions for HC35Cl and HC37Cl.

Fabrication of Energy-Boosted Triboelectric Nanogenerator Via Electric Field Assisted Thermal Nanoimprinting Process

Energy harvesting technologies, which scavenge and capture various types of abandoned energies from an ambient environment, have grown more comprehensive and crucial as they play a role to power the emerging mobile electronic systems and micro devices. Lots of energy harvesting technologies have been successfully demonstrated and explored based on photovoltaic effect, piezoelectric effect, electromagnetic effect and so forth. Recently, the eminent concept of the triboelectric nanogenerator (TENG), where operation mechanism is coupling of triboelectricity and electrostatic induction, has been proposed. The TENG is mainly composed of 1) the contact layer, where the triboelectric effect occurs, and 2) the electrode layer inducing movement of the electrical charges to generate electric current and power. Since its first demonstration, the TENG has been proven as one of the promising energy harvesting platforms due to its high accessibility, low manufacturing cost and high energy conversion efficiency compared with the other existing energy harvesting platforms. With those advantageous aspects, so far, the TENG has been widely applied to versatile applications such as biomedical monitoring system, self-powered sensor and portable power supply to drive wearable electronics. As above mentioned, although lots of potential applications of TENGs have been successfully demonstrated, for their reliable utilization as a practical power source, the electrical output performance of TENGs still needs to be further increased. From this point of view, enhancing the electrical output performance of the TENG has been one of the important issues in research fields from its first proposal to present. The simplest and most powerful way to enhance the electrical output performance of the TENG is based on formation of micro/nanoscale surface topographies on its contact layer inducing localized concentration of contact forces, which generates higher electrical charge amounts on its surface. As well as formation of topographies on its external surface, recently, the concept of modifying internal molecular arrangement has been suggested. For example, the synthesis of material where important derivatives are carbon increased the interface for charge storage by acting charge trapping sites. On top of that, the alignment of positive and negative charges referred to as poling process has been reported. During this poling or dipolar alignment, a large electric potential is applied across the material which induces the alignment of dipole and production of net positive charge. To be detailed, the maximized surface charge and charge difference between upper and bottom surface of material can produce the developed electrical energy compared with that of non-aligned material. In this respect, it has been considered as a potent strategy to increase the energy output of the TENG. Previously, we reported the one-step simple method to fabricate the advanced energy output TENG by using nanoimprinting process. Through thermal nanoimprint process, there are obvious advantages in terms of increasing energy output of the TENG, and practical commercialization. Firstly, the energy output of the TENG can be enhanced due to the formation of nano topographies on the contact layer of thermoplastic fluoropolymer. Secondly, in viewpoint of commercialization, the thermal nanoimprint is one-step fabrication, with coincidently replication of nano structure and integration of contact later with the electrode layer which are essential prerequisite components of TENG. Besides these merits, low cost and mass producible nanofabrication process present the application of practical commercialization. In this study, we first introduced the innovative strategy which is coupling process between nano imprint and poling process to maximize the electrical energy output performance of TENG based on the formation of nano-topographical surface on contact layer and modulation of the internal dipole moments of ferroelectric thermoplastic polymer. The most remarkable novelties are shown that energy output of TENG can be enhanced by achieving the alignment of dipole moments of polymer while taking advantages of fabricating the TENG by using the nanoimprint process. In aspects of the modulation of internal moments, the degree of alignment dipole moments is higher than when the conventional poling method is used. Compared with the conventional poling process, the method we suggested has distinct advantages. Given that the flexibility of thermoplastic polymer increased due to the elevated temperature, the alignment of dipole moments can be achieved more effectively. In addition, the electric field concentrated on each nano structure contributes to obtain the high portion of dipole moments alignment due to their higher electric field in comparison with when the electrode which has no nano-topograpies on surface is used to poling process. Lastly, based on these effects, the overall poling period is much shorter than that of conventional poling. Figure 1

Time-resolved stimulated emission depletion and energy transfer dynamics in two-photon excited EGFP.

Time and polarization-resolved stimulated emission depletion (STED) measurements are used to investigate excited state evolution following the two-photon excitation of enhanced green fluorescent protein (EGFP). We employ a new approach for the accurate STED measurement of the hitherto unmeasured degree of hexadecapolar transition dipole moment alignment α40 present at a given excitation-depletion (pump-dump) pulse separation. Time-resolved polarized fluorescence measurements as a function of pump-dump delay reveal the time evolution of α40 to be considerably more rapid than predicted for isotropic rotational diffusion in EGFP. Additional depolarization by homo-Förster resonance energy transfer is investigated for both α20 (quadrupolar) and α40 transition dipole alignments. These results point to the utility of higher order dipole correlation measurements in the investigation of resonance energy transfer processes.

Effect of Yb co-doping on the spectral properties of Er:YVO4 single crystal: A Judd Ofelt analysis

Single crystals of 0.7 at% Er:YVO4 co-doped with varied concentrations of Yb (1.5, 3.0 and 8.0 at%) were grown by optical floating zone technique. The absorption spectra of the grown crystal are characterized by the prominent absorption at 985 nm due to Yb ion and multiple absorption due to Er ions. The overall characteristic absorption for π-polarization (E||c) is stronger than that for σ-polarization (E┴c) due to alignment of dipole moments along c-direction. The line strength of all the transitions of Er ions decreases as the doping concentration of Yb increases. Judd Ofelt parameter Ω2, which strongly depends on the environment of ligand, decreases with increasing Yb concentration in the lattice. The value of spectroscopic quality factor was found to be nearly invariant (~ 1.80) with respect to the Yb doping concentration but better than that for Er doped YVO4 (~1.31) [1]. The radiative lifetime and emission cross-section of 4I13/2→4I15/2 transition of Er ions was also found to be independent of Yb doping concentration. This is one of the biggest advantages of Yb co-dopant as a good sensitizer in the Er:YVO4 as it results in high population density in upper level of Er ions making it. The emission cross-section of 4I13/2→4I15/2 line for excitation at 985 nm is ~ 2.33 × 10−20 cm2. Further, the values of emission cross-section for both the excitation at 808 nm (Er absorption line) and 985 nm (Yb absorption line) were found nearly same.

Voltage-Controlled Switching of Strong Light-Matter Interactions using Liquid Crystals.

We experimentally demonstrate a fine control over the coupling strength of vibrational light–matter hybrid states by controlling the orientation of a nematic liquid crystal. Through an external voltage, the liquid crystal is seamlessly switched between two orthogonal directions. Using these features, for the first time, we demonstrate electrical switching and increased Rabi splitting through transition dipole moment alignment. The C−Nstr vibration on the liquid crystal molecule is coupled to a cavity mode, and FT‐IR is used to probe the formed vibropolaritonic states. A switching ratio of the Rabi splitting of 1.78 is demonstrated between the parallel and the perpendicular orientation. Furthermore, the orientational order increases the Rabi splitting by 41 % as compared to an isotropic liquid. Finally, by examining the influence of molecular alignment on the Rabi splitting, the scalar product used in theoretical modeling between light and matter in the strong coupling regime is verified.