Dipolar Interactions Research Articles

Ring solids and supersolids in spherical shell-shaped dipolar Bose-Einstein condensates

We study the interplay between the anisotropy of the dipole-dipole interaction and confinement in a curved geometry by means of the extended Gross-Pitaevskii equation, which allows us to characterize the ground state of a dipolar Bose gas under the confinement of a bubble trapping potential. We do so in terms of the scattering length a and the number of particles. We observe the emergence of a wide variety of dipolar solids, consisting on arrangements of different number of droplets along a ring over the equator of the spherical shell confinement. We also show that the transition between the different phases of the system can be engineered by varying a, the number of particles or the radius of the trap, parameters, which can be experimentally tuned. Finally, we show the importance of working in microgravity conditions as gravity unstabilizes the observed dipolar solids. Published by the American Physical Society 2024

Structural, spectroscopy, nonlinear optical, and laser damage threshold analyses of sodium guanidinium bis(4-methylbenzenesulfonate) hydrate (NGMBS) crystal

Sodium guanidinium bis(4-methylbenzenesulfonate) hydrate (NGMBS) crystallized in the monoclinic crystal system with non-centrosymmetric space group P21. The mixed ionic crystal assembly was stabilized by N H⋯O hydrogen bonding involving guanidinium ion and with Na+ ions surrounded by aqua ligands and S–O oxygen atoms completing six coordination involving with coordinate covalent and ion–dipole interactions. A supramolecular assembly in two dimensions (along the a and b-axis) is possible by H-bonding which brought the Na+ within a distance of 3.6493 Å. The two 4-methylbenzenesulfonate ligands in one formula unit were not identical and exhibited structural variations. Hirshfeld analyses indicated significant interaction due to N⋯H, O⋯H, and Na+ … O. The vibrational bands were ascertained using FTIR. A cut-off wavelength of 273 nm and bandgap of 4.50 eV were estimated from UV–visible spectroscopy. The compound excited at 260 showed emission at 291 nm. Colour purity up to 95.62 % was estimated from chromaticity calculations. Kurtz-Perry's method confirmed that NGMBS showed NLO properties 1.5 times than KDP. The NGMBS crystal demonstrated superior resistance to LASER induced damage as compared to urea.

Sensing of nitrate/nitrite ions in aqueous medium using poly(m-aminophenol)/silver core–shell hybrid modified graphite electrode

A very facile methodology was developed for reliable sensing of nitrate/nitrite ions in the aqueous medium using poly(m-aminophenol)/silver core–shell hybrid coated graphite electrode. The hybrid consisting of a uniform silver nanoparticle core coated with a polymer shell, was synthesized by the thermal reduction of poly(meta-aminophenol) complex with silver mono-positive ions. This core–shell hybrid was fabricated on the tip of the graphite electrode by the drop-casting method and was used as a working electrode in a two electrode setup to study the sensing performance of nitrate/nitrite ions in aqueous medium. The sensitivity and limit of detection (LOD) of the sensor were determined as ∼ 190 mA mM-1cm−2 and ∼ 0.02 mM, respectively for the nitrate/nitrite anions. Very good selective response of poly(m-aminophenol)/silver core–shell hybrid towards nitrate/nitrite ions were also confirmed over the other common tested anions/cations. The mechanism of selective sensing of nitrate/nitrite by the core–shell hybrid has been explained on the basis of selective dipole interaction as well as hydrogen bonding interaction. A reliable result was verified with an accuracy of ∼ 99 ± 4 % for nitrate/nitrite ions in real water samples.

Probing energy transfer in luminescent CaMoO4:Tb3+ by steady state and decay dynamics

Polyvinylpyrrolidone functionalized CaMoO4:Tb3+ were synthesized hydrothermally. The formation of tetragonal phase CaMoO4:Tb3+ and morphology of nanoparticles are thoroughly studied with XRD, TEM and FT-IR spectroscopy. Nanophosphors show green emission of Tb3+ at 544 nm when excited at 290 nm due to MoO42− absorption. The energy transfer from the host MoO42− to the activator Tb3+ is occurred mainly through dipole-dipole interactions. The decay lifetime of MoO42− emission decreases from ∼13 to 1 μs with the increase in Tb3+ concentration indicating occurrence of energy transfer. This is further corroborated with the calculation of radiative and non-radiative decay rates. The quantum yield and CIE color chromaticity are also studied.

Giant Piezoelectric Effects of Topological Structures in Stretched Ferroelectric Membranes.

Freestanding ferroelectric oxide membranes emerge as a promising platform for exploring the interplay between topological polar ordering and dipolar interactions that are continuously tunable by strain. Our investigations combining density functional theory (DFT) and deep-learning-assisted molecular dynamics simulations demonstrate that DFT-predicted strain-driven morphotropic phase boundary involving monoclinic phases manifest as diverse domain structures at room temperatures, featuring continuous distributions of dipole orientations and mobile domain walls. Detailed analysis of dynamic structures reveals that the enhanced piezoelectric response observed in stretched PbTiO_{3} membranes results from small-angle rotations of dipoles at domain walls, distinct from conventional polarization rotation mechanism and adaptive phase theory inferred from static structures. We identify a ferroelectric topological structure, termed "dipole spiral," which exhibits a giant intrinsic piezoelectric response (>320 pC/N). This helical structure, possessing a rotational zero-energy mode, unlocks new possibilities for exploring chiral phonon dynamics and dipolar Dzyaloshinskii-Moriya-like interactions.

Low energy elastic and inelastic scattering of positrons from formic acid

This paper presents a detailed study of low energy positron scattering from formic acid, examining elastic scattering, electronic excitation and ionisation processes. Through detailed comparisons with previous experimental and theoretical data, it is clear that the picture for positron scattering from this target remains incomplete, with significant disagreement between experiment and theory in the comparisons of differential cross section data. Calculations of elastic electron scattering are unexpectedly in better agreement with the positron scattering experiments, and give some hints as to potential areas for improvement in the modelling of scattering for targets which tend to be dominated by dipole interactions.

Atom-magnon entanglement in a coupled cavity-magnon atom-optomechanical system

We propose an alternative way to realize macroscopic entanglement between an atomic ensemble and ferrimagnetic magnons in a hybrid cavity-magnon atom-optomechanics, in which a microwave cavity couples to the magnons via magnetic dipole interaction, and simultaneously couples to a standard optomechanical cavity with an ensemble of two-level atoms. We show that in experimental feasible parameters, the optomechanical entanglement can be transferred to the bipartite subsystems, which makes it possible to generate the macroscopic atom-magnon entanglement and genuine tripartite entanglement. We mainly analyze the effects of coupling strengths on the efficiency of the entanglement transfer and the generation of the atom-magnon entanglement. We find that by selecting appropriate coupling strengths, both the degree of the atom-magnon entanglement and its robustness against the environmental temperature are enhanced significantly.

Fully quantum-kinetic theory of the steady-state cooperative photoluminescence from two near-identical emitters

We have developed a theory of cooperative photoluminescence from two closely spaced particles using the density matrix method. The theory provides simulations of the photoluminescence excitation and emission spectra by nonidentical quantum emitters entangled by the dipole–dipole interaction in presence of a cw laser beam. The excitation spectra are shown to be consistent with all known experiments to date with pairs of coherently coupled organic molecules in thin solid layers. The simulations were performed with the use of the Bogoliubov–Born–Green–Kirkwood–Yvon (BBGKY) hierarchies for reduced density matrices and correlation operators of the quantum emitters and photonic subsystems. This method gives a straightforward way to describe the dipole–dipole coupling and entanglement of the emitters. We have also calculated the emission spectra to demonstrate the expected spectral patterns.

Polarizing Perspectives: Ion- and Dipole-Induced Dipole Interactions Dictate Bulk Nanobubble Stability.

The origin of the stability of bulk Nanobubbles (NBs) has been the object of scrutiny in recent years. The interplay between the surface charge on the NBs and the Laplace pressure resulting from the surface tension at the solvent-NB interface has often been evoked to explain the stability of the dispersed NBs. While the Laplace pressure is well understood in the community, the nature of the surface charge on the NBs has remained obscure. In this work, we aim to show that the solvent and the present ions can effectively polarize the NB surface by inducing a dipole moment, which in turn controls the NB stability. We show that the polarizability of the dispersed gas and the polarity of the dispersing solvent control the dipole-induced dipole interactions between the solvent and the NBs, and that, in turn, determines their stability in solution.

Twisted MoSe2 Homobilayer Behaving as a Heterobilayer.

Heterostructures (HSs) formed by the transition-metal dichalcogenide materials have shown great promise in next-generation (opto)electronic applications. An artificially twisted HS allows us to manipulate the optical and electronic properties. In this work, we introduce the understanding of the energy transfer (ET) process governed by the dipolar interaction in a twisted molybdenum diselenide (MoSe2) homobilayer without any charge-blocking interlayer. We fabricated an unconventional homobilayer (i.e., HS) with a large twist angle (∼57°) by combining the chemical vapor deposition (CVD) and mechanical exfoliation (Exf.) techniques to fully exploit the lattice parameter mismatch and indirect/direct (CVD/Exf.) bandgap nature. These effectively weaken the interlayer charge transfer and allow the ET to control the carrier recombination channels. Our experimental and theoretical results explain a massive HS photoluminescence enhancement due to an efficient ET process. This work shows that the electronically decoupled MoSe2 homobilayer is coupled by the ET process, mimicking a "true" heterobilayer nature.

Polyacrylonitrile as a binder realizes high-rate activated-carbon-based supercapacitors

Highly polar CN functional groups on polyacrylonitrile (PAN) facilitate strong hydrogen bonding and dipole-dipole interactions with hydroxyl groups on the surfaces of active materials and current collectors. Here we report that the strong interaction between PAN and carbon black (CB) particles facilitates a uniform distribution of CB particles within the electrode and forms a well-connected conductive network on the surface of active material particles. This significantly enhances electron transport within the electrode, offering superior rate performance and cycling stability beyond traditional binders like polyvinylidene fluoride (PVDF). Activated carbon (AC) electrodes containing 7.70 wt.% PAN binder (AC-7.7PAN) deliver areal capacitances over 0.60 F cm⁻2 at a scan rate of 500 mV s⁻1, and exhibits a high gravimetric energy density (Eg) of 26.20 Wh kg⁻1 and high areal energy density (Ea) of 0.33 mWh cm⁻2 at a current density of 1 A g⁻1. An AC-7.7PAN coin-cell supercapacitor maintains up to 62 % of its initial capacitance at a scan rate of 200 mV s⁻1, while a controlled AC-7.7PVDF coin-cell keeps only 37 % under the same conditions. The AC-7.7PAN coin-cell retains 91 % of its capacity even after 50,000 charge/discharge cycles at a constant current of 5 A g⁻1. The ability of PAN to evenly distribute conductive agents might be attractive for other power-type electrochemical electrodes, for which effective electron transport are extremely required.

Influence of resveratrol on the sorption of phosphorylated tau protein and MAPT on the PVDF membrane in a mouse model of Alzheimer’s disease

Alzheimer’s disease is a complex neurodegenerative disease based on various processes associated with the accumulation and aggregation of defective proteins. Among them, the particularly important ones are the following: amyloid-β, which is formed by the breakdown of amyloid precursor protein, the accumulation of hyperphosphorylated tau proteins inside neurons that form neurofibrillary tangles, and aberrant aggregation and inclusion formation of microtubule-associated protein tau (MAPT). APP/PS1 transgenic mice act as a model of Alzheimer’s disease and express mutant human genes that cause the accumulation of amyloid-β peptides in the brain. The goal of this work was a quantitative assessment of the level of p-tau231 in the brain of transgenic mice with a model of AD using the sorption method. The objectives of the study also included testing the ability of the natural polyphenol resveratrol to reduce the concentration of p-tau231 in the brain of transgenic mice and improve their cognitive functions. Western blot is a widely used method for the immunodetection and in vitro quantitative determination of proteins. Western blot allows separating proteins based on their molecular weight with the further transfer to an adsorption membrane. In this case, the proteins are transferred from the gel to the PVDF membrane using electrophoretic elution. This method involves placing a protein-containing polyacrylamide gel in direct contact with a PVDF membrane represented by a linear polymer with repetitive links -(CF2-CH2)-. Proteins transferred to the membrane are well-retained on its surface during the whole immunodetection process due to a combination of dipole and hydrophobic interactions. Western blot showed that mice with impaired protein aggregation accumulated significantly more MAPT and phosphorylated tau protein in the brain as compared to wild mice. In addition, in the course of the Morris water maze test, these mice showed cognitive deficits, which manifested both in the difficulty of finding the platform and more anxious behaviour, which confirmed pronounced thigmotaxis. The natural polyphenol resveratrol partially reversed cognitive deficits, although this effect was not associated with decreased levels of phosphorylated tau and MAPT.

Thermally enhanced luminescence and photoluminescence properties of green-emitting Lu2(1-x)Tb2x(WO4)3 phosphors

A series of Lu2(1-x)Tb2x(WO4)3 (x = 0.00–1.00) white powder materials were prepared by a high-temperature solid-phase method. The crystal structure, microscopic morphology, elemental composition, bandgap energy, photoluminescence properties, and thermal stability of luminescence of the prepared materials were analyzed and studied through room and high temperature X-ray diffraction patterns, field emission scanning electron microscopy images, energy energy-dispersive spectra and X-ray photoelectron spectra, diffuse reflectance spectra, room and high temperature photoluminescence spectra. Under 260 nm excitation, the green emitting Lu2(1-x)Tb2x(WO4)3 samples exhibited an optimum Tb3+ doping concentration at x = 0.30. Calculated results illustrate that the concentration quenching was mainly caused by dipole-dipole interaction. Lu1.98Tb0.02(WO4)3 phosphor exhibited thermally enhanced luminescence at 120 °C, with a maximum luminescence intensity of 254 % of the initial room temperature intensity. Lu1.4Tb0.6(WO4)3 phosphor exhibited thermally enhanced luminescence at 150 °C, with a maximum luminescence intensity of 109 % of the initial room temperature intensity. The mechanism of the thermally enhanced luminescence phenomenon is further discussed to be the adsorbed crystal water and the negative thermal expansion of the material. Thermally enhanced luminescence is of great significance in overcoming luminescent thermal quenching phenomenon, improving the luminescence efficiency, optimizing the material design, and so forth. It has potential applications in high-temperature lighting, display technology, temperature sensing, and optical anti-counterfeiting.

Polymer and micellar catalysis in d-fructose oxidation by imidazolium fluorochromate: A kinetic and mechanistic study

This work investigated the oxidation of d-fructose using imidazolium fluorochromate (IFC) as an oxidant and analyzed how sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG-400) affected the reaction kinetics. The process exhibited a unit-order dependence on IFC, d-fructose, and perchloric acid concentration. Perchloric acid was the primary source of hydrogen ions in the reaction mixture. The stoichiometry of the reaction indicated that 3 mol of d-fructose requires 4 mol of IFC. Acrylonitrile, a radical-generating species, did not impact the reaction rate, indicating the absence of a free radical intermediate. The reaction rate decreases as the Mn (II) ions concentration increases, suggesting the involvement of Cr (IV) species in the reaction. The dielectric value of the reaction medium (D) had an inverse effect on the rate, and the outcomes were consistent with the Amis (log k1 and 1/D) and Kirkwood plots (log k1 and (D-1/2D+1)), indicating the presence of dipole-dipole interactions in the process. SDS and PEG-400 catalyzed the reaction. The reaction showed significant catalysis before reaching the critical micelle concentration (CMC). However, the observed rate constants stabilized at higher SDS concentrations exceeding the CMC. Piszkiewicz's cooperativity model was employed to describe the surfactant catalysis, while the Benesi-Hildebrand equation was utilized to explain polymer catalysis. The activation parameters are ΔH† = 44.3 ± 1.3 kJ mol−1, and ΔS† = −133.4 ± 4.3 J K−1 mol−1. The products of the reaction have been identified by spectral analysis as d-arabinoniclactone and formic acid. The formation of an ester complex followed by its decomposition was proposed as the rate-limiting step in the proposed mechanistic reaction pathway.

Dispersion-Driven Cooperativity in Alkyl Perylene Diimide Oligomers: Insights from Density Functional Theory.

The cooperative mechanism is of paramount importance in the synthesis of supramolecular polymers with desired characteristics, including molecular mass, polydispersity, and morphology. It is primarily driven by the presence of intermolecular interactions, which encompass strong hydrogen bonding, metal-ligand interactions, and dipole-dipole interactions. In this study, we utilize density functional theory and energy decomposition analysis to investigate the cooperative behavior of perylene diimide (PDI) oligomers with alkyl chains at their imide positions, which lack the previously mentioned interactions. Our systematic examination reveals that dispersion interactions originating from the alkyl side-chain substituents play an important role in promoting cooperativity within these PDIs. This influence becomes even more pronounced for alkyl chain lengths beyond hexyl groups. The energy decomposition analysis reveals that the delicate balance between dispersion energy and Pauli repulsion energy is the key driver of cooperative behavior in PDIs. Additionally, we have developed a mathematical model capable of predicting the saturated binding energies for PDI oligomers of varying sizes and alkyl chain lengths. Overall, our findings emphasize the previously undervalued significance of dispersion forces in cooperative supramolecular polymerization, enhancing our overall understanding of the cooperative mechanism.

Charge Transfer and Intersystem Crossing in Compact Naphthalenediimide-Phenothiazine Triads: Synthesis and Study of the Photophysical Property with Transient Optical and Electron Paramagnetic Resonance Spectroscopic Methods.

In order to obtain a long-lived charge separation (CS) state in compact electron donor-acceptor molecular systems, we prepared a series of naphthalenediimide (NDI)-phenothiazine (PTZ) triads, with phenylene as the linker between the donor and acceptor. Conformation restriction is imposed to control the mutual orientation of the NDI and PTZ units by attaching methyl groups on the phenylene linker to tune the electronic coupling between the donor and the acceptor. Moreover, the PTZ moiety was oxidized to sulfoxide to tune the ordering of the CS state and the 3LE state (LE: locally excited state). UV-vis absorption spectra indicate electronic coupling between NDI with the phenylene linker as well as the PTZ units, manifested by the appearance of a charge-transfer (CT) absorption band, whereas this coupling is devoid in the triads with conformation restriction imposed. Fluorescence is strongly quenched in the triads compared to the reference compound, indicating electron transfer upon photoexcitation. Femtosecond transient absorption spectra indicate that the CS takes 0.8 ps, and then the 3LE state is formed by charge recombination in 83 ps. Nanosecond transient absorption (ns-TA) spectra show that the 3NDI state was observed in nonpolar solvents such as cyclohexane (triplet state lifetime: 95.7 μs), whereas the CS state was observed in more polar solvents. The CS state lifetimes are up to 1.2 μs (in toluene). Time-resolved electron paramagnetic resonance spectra of the triads in toluene consist of two types of signals: CS states (narrower signals, ∼10 mT) and 3LE states (broader signals, ∼50 to 200 mT). In the spectra of the triads containing PTZ, the CS state signals dominate, whereas for the triads containing oxidized PTZ, the 3NDI signals (zero-field splitting D ≈ 2000 MHz) prevail, both observations being in agreement with the ns-TA spectral studies. The electron spin polarization phase pattern of the 3NDI states of the triads indicates that the intersystem crossing (ISC) mechanism is spin-orbit charge-transfer ISC. Considering the 3CS state as ion pairs, the electron-exchange energy (J) is determined to be -39 to -59 MHz, and the electron spin dipolar interaction is 83-92 MHz.

Simultaneous control of carrier transport and film polarization of emission layers aimed at high-performance OLEDs

The orientation of a permanent dipole moment during vacuum deposition results in the occurrence of spontaneous orientation polarization (SOP). Previous studies reported that the presence of SOP in organic light-emitting diodes (OLEDs) lowers electroluminescence efficiency because electrically generated excitons are seriously quenched by SOP-induced accumulated charges. Thus, the SOP in a host:guest-based emission layer (EML) should be finely controlled. In this study, we demonstrate the positive effect of dipole-dipole interactions between polar host and polar emitter molecules on the OLED performance. We found that a small-sized polar host molecule that possesses both high molecular diffusivities and moderate permanent dipole moment, well cancels out the polarization formed by the SOP of the emitter molecules in the EML without a disturbance of the emitter molecules’ intrinsic orientation, leading to high-performance of OLEDs. Our molecular design strategy will allow emitter molecules to pull out the full potential of the EMLs in OLEDs.

Ribosome External Electric Field Regulates Metabolic Enzyme Activity: The RAMBO Effect.

Ribosomes bind to many metabolic enzymes and change their activity. A general mechanism for ribosome-mediated amplification of metabolic enzyme activity, RAMBO, was formulated and elucidated for the glycolytic enzyme triosephosphate isomerase, TPI. The RAMBO effect results from a ribosome-dependent electric field-substrate dipole interaction energy that can increase or decrease the ground state of the reactant and product to regulate catalytic rates. NMR spectroscopy was used to determine the interaction surface of TPI binding to ribosomes and to measure the corresponding kinetic rates in the absence and presence of intact ribosome particles. Chemical cross-linking and mass spectrometry revealed potential ribosomal protein binding partners of TPI. Structural results and related changes in TPI energetics and activity show that the interaction between TPI and ribosomal protein L11 mediate the RAMBO effect.

Quantum gate control of polar molecules with machine learning.

We propose a scheme for achieving basic quantum gates using ultracold polar molecules in pendular states. The qubits are encoded in the YbF molecules trapped in an electric field with a certain gradient and coupled by the dipole-dipole interaction. The time-dependent control sequences consisting of multiple pulses are considered to interact with the pendular qubits. To achieve high-fidelity quantum gates, we map the control problem for the coupled molecular system into a Markov decision process and deal with it using the techniques of deep reinforcement learning (DRL). By training the agents over multiple episodes, the optimal control pulse sequences for the two-qubit gates of NOT, controlled NOT, and Hadamard are discovered with high fidelities. Moreover, the population dynamics of YbF molecules driven by the discovered gate sequences are analyzed in detail. Furthermore, by combining the optimal gate sequences, we successfully simulate the quantum circuit for entanglement. Our findings could offer new insights into efficiently controlling molecular systems for practical molecule-based quantum computing using DRL.

Mechanism Study on the Effect of Surface Electrical Property on Microbial Membrane Formation Efficiency of TiO2-SiC Composite Filler in Recirculating Aquaculture System.

Recirculating aquaculture systems (RASs) offer significant advantages in aquaculture by markedly decreasing water usage and increasing culture density. A vital component within a RAS is the filler material, which serves as a surface for microbial colonization. Effective microbial treatment is crucial for the efficient operation of a RAS as it assists in purifying the wastewater generated within the system. Nevertheless, traditional fillers often show low efficiency in biofilm formation. The commercial silicon carbide used in this study is a foam ceramic filter with a density of about 0.4-0.55 g/cm3, a number of holes of about 10, and a through porosity of 80.9%, with a diameter of about 5 cm. This research investigates the utilization of a titanium dioxide-silicon carbide (TiO2-SiC) composite filler to improve the purification efficiency of ammonia nitrogen and chemical oxygen demand (COD) in aquaculture wastewater. The study involved the application of titanium dioxide films onto the surface of silicon carbide to produce the composite filler. This method takes advantage of the dipole interaction between titanium dioxide and microorganisms, which enhances biofilm culturing efficiency on the silicon carbide surface. The performance of three different fillers was assessed for their ability to purify aquaculture wastewater. Results showed that the TiO2-SiC composite filler was 1.67 times more effective in removing COD and 1.07 times more effective in removing ammonia nitrogen compared to using silicon carbide alone. These results demonstrate that the incorporation of a titanium dioxide coating substantially boosts the microbial colonization efficiency of silicon carbide, thereby enhancing the overall wastewater purification efficiency in RAS.