Dipolar Interactions Research Articles

Viologen-Derived Covalent Organic Frameworks: Advancing PFAS Removal Technology with High Adsorption Capacity.

The escalating presence of per- and polyfluoroalkyl substances (PFAS) in drinking water poses urgent public health concerns, necessitating effective removal. This study presents a groundbreaking approach, using viologen to synthesize covalent organic framework nanospheres: MELEM-COF and MEL-COF. Characterized by highly crystalline features, these nanospheres exhibit exceptional affinity for diverse anionic PFAS compounds, achieving simultaneous removal of multiple contaminants within 30 min. Investigating six anionic PFAS compounds, MEL- and MELEM-COFs achieved 90.0-99.0% removal efficiency. The integrated analysis unveils the synergistic contributions of COF morphology and functional properties to PFAS adsorption. Notably, MELEM-COF, with cationic surfaces, exploits electrostatic and dipole interactions, with a 2500mg g-1 adsorption capacity-surpassing all reported COFs to date. MELEM-COF exhibits rapid exchange kinetics, reaching equilibrium within 30min. These findings deepen the understanding of COF materials and promise avenues for refining COF-based adsorption strategies.

Electronic Polarizability Tunes the Function of the Human Bestrophin 1 Cl- Channel.

Mechanisms of anion permeation within ion channels and nanopores remain poorly understood. Recent cryo-electron microscopy structures of the human bestrophin 1 Cl- channel (hBest1) provide an opportunity to evaluate ion interactions predicted by molecular dynamics (MD) simulations against experimental observations. Here, we implement the fully polarizable forcefield AMOEBA in MD simulations on different conformations of hBest1. This forcefield models multipole moments up to the quadrupole; therefore, it captures induced dipole and anion-π interactions. We show that key biophysical properties of the channel can only be simulated when electronic polarization is included in the molecular models and that Cl- permeation through the neck of the pore is achieved through hydrophobic solvation concomitant with partial ion dehydration. Furthermore, we demonstrate how such polarizable simulations can help determine the identity of ion-like densities within high-resolution cryo-EM structures and that neglecting polarization places Cl- at positions that do not correspond with their experimentally resolved location. Overall, our results demonstrate the importance of including electronic polarization in realistic and physically accurate models of biological systems, especially channels and pores that selectively permeate anions.

Dense dipole-dipole-coupled two-level systems in a thermal bath

The quantum dynamics of a dense and dipole-dipole-coupled ensemble of two-level emitters interacting via their environmental thermostat is investigated. The static dipole-dipole interaction strengths are being considered strong enough but smaller than the transition frequency. Therefore, the established thermal equilibrium of ensemble's quantum dynamics is described with respect to the dipole-dipole-coupling strengths. We have demonstrated the quantum nature of the spontaneously scattered light field in this process for weaker thermal baths as well as non-negligible dipole-dipole couplings compared to the emitter's transition frequency. Furthermore, the collectively emitted photon intensity suppresses or enhances depending on the environmental thermal baths' intensities. Published by the American Physical Society 2024

Electrically Controlled Photonic Circuits of Field-Induced Dipolaritons with Huge Nonlinearities

Electrically controlled photonic circuits hold promise for information technologies with greatly improved energy efficiency and quantum information processing capabilities. However, weak nonlinearity and electrical response of typical photonic materials have been two critical challenges. Therefore, hybrid electronic-photonic systems, such as semiconductor exciton polaritons, have been intensely investigated for their potential to allow higher nonlinearity and electrical control, with limited success so far. Here we demonstrate an electrically gated waveguide architecture for field induced dipolar polaritons that allows enhanced and electrically controllable polariton nonlinearities, enabling an electrically tuned reflecting switch (mirror) and transistor of the dipolar polaritons. The polariton transistor displays blockade and antiblockade by compressing a dilute dipolar-polariton pulse exhibiting very strong dipolar interactions. The large nonlinearities are explained using a simple density-dependent dipolar polarization field that very effectively screens the external electric field. We project that a quantum blockade at the single polariton level is feasible in such a device. Published by the American Physical Society 2024

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.

Harnessing Polar Interactions Tunes the Stability of Ultrathin Polymer Solution Films.

The stability of ultrathin (<100 nm) polymer films is essential in applications like protective coatings. On the contrary, their instability may actually be desirable for the emergence of self-assembled nanoscale patterns utilized in the fabrication of functional devices. Polymer solution films exhibit two distinct kinds of instabilities, viz., dewetting (long-wave) and decomposition (short-wave). Dewetting refers to the rupture of the continuous film to form isolated domains, while decomposition leads to phase separation within the polymer solution. The focus of this work is on leveraging polar interactions between the solute and solvent molecules to tune the stability of the film. A gradient dynamics-based thin film model is developed to investigate pattern formation in a thin polar polymer solution film. The Flory-Huggins theory is suitably modified by introducing a polar interaction parameter that depends upon the concentration of the polymer and the dipole moments of monomer (μ1) and solvent molecules (μ0). A linear stability analysis is performed to determine the characteristic length scale and growth rate of the instabilities. It is shown that the range of concentration space for the occurrence of the decomposition mode is directly affected by the Flory interaction parameter (χ0), μ0, and μ1, thereby serving as control parameters to tune the width of the concentration range. It is further shown that ignoring polar interactions may lead to incorrect predictions of the instability mode, including a complete loss of the decomposition mode. In addition, the long-wave dewetting length scale is found to decrease due to bulk dipolar interactions at higher polymer concentrations. Finally, numerical simulations are carried out to track the nonlinear evolution of the interface and concentration field for both the decomposition and dewetting modes of instability.

A novel tetra(4-pyridyl)porphyrin-palladium(0) functionalized polyacrylonitrile fiber as highly efficient and recyclable heterogeneous catalyst for the Heck reaction

A novel tetra(4-pyridyl)porphyrin-chelated palladium(0) nanoparticles functionalized polyacrylonitrile fiber (PANTPPF-Pd(0)) was prepared for the first time. Some necessary methods including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), etc. were used to verify the micro structure and properties of PANTPPF-Pd(0). Furthermore, with the Heck reaction chosen as a model reaction to determine the catalytic activity of PANTPPF-Pd(0), the experiment results shows that PANTPPF-Pd(0) can efficiently catalyze the Heck reaction with high yields (47–99%) in extensive substrate scope (46 examples) under non-solvent condition. Noteworthily, the average size of Pd(0) nanoparticles observed by transmission electron microscopy (TEM) slightly increased from 2.32 nm to 2.59 nm after recycled 8 times achieving an 99% isolated yield of Heck reaction catalyzed by PANTPPF-Pd(0), which proves that the PANTPPF-Pd(0) can maintain satisfactory recyclability. Finally, based on the π-π stacking interactions and dipolar-dipolar interaction between tetra(4-pyridyl)porphyrin moieties in PANTPPF-Pd(0) and substrates, a novel heterogeneous “capture-catalyze” mechanisms was proposed.

Recognition of monoamine neurotransmitters by cucurbiturils

Neurological disorders are linked to deficiencies in monoamine neurotransmitters (NTs) in the brain, and their inability to cross the blood–brain barrier (BBB) prevents their use as treatments. Encapsulating them within an appropriate host could present a potential remedy. Molecular dynamics (MD) simulations are employed to investigate the molecular recognition of protonated and neutral forms of five NTs and two dopamine (DP) analogs by cucurbit[n]urils (CBn). Binding free energies (ΔG), computed with the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method, reveal CB7 forms stable inclusion complexes with all studied NTs, driven by ion–dipole/dipole–dipole interactions between and the ammonium/amine in the NT with the carbonyl portal of CB7, as well as van der Waals interactions of the included catechol/heterocyclic ring. ΔG was more favorable (by ∼2–3 kcal.mol−1) for the DP analogs. MD simulations performed to study complexation between DP and CB6 and CB8 revealed 1:1 and 2:1 stoichiometries, respectively.

Energy transfer and color tunability in high-thermal-stability Dy3+/Tb3+ co-doped K3YF6 transparent oxyfluoride glass ceramics

The production process and comprehensive analysis of the co-doping of Dy3+ and Tb3+ in K3YF6 oxyfluoride glass-ceramics (GCs) are delved. The primary focus is on investigating the luminescent properties and energy transfer (ET) mechanisms within these systems. The embedding of well-formed K3YF6 nanocrystals within the matrix was verified through detailed analyses using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fine-tuning the Tb3+ concentration facilitated the achievement of tunable emission, ranging from a subtle yellow to a yellowish green hue, demonstrating the remarkable flexibility in color manipulation. Fluorescence analysis unmistakably demonstrates the occurrence of energy transfer occurring between Dy3+ and Tb3+ ions, attaining a peak energy transfer efficiency of 51.33 %. Additional analysis applying Dexter's energy transfer formula affirms that the fundamental mechanism of energy transfer between Dy3+ and Tb3+ ions is dipole-dipole interaction. The K3YF6 glass ceramics (GCs) incorporating Dy3+/Tb3+ nanocrystals exhibit a remarkable thermal stability, retaining 89.07 % of their original relative emission intensity at 423 K when stimulated by 350 nm light. These findings indicate that Dy3+/Tb3+ co-doped K3YF6 GCs hold significant potential in solid state lighting, positioning them as a candidate for future lighting.

Unconventional Light‐Matter Interactions Between Giant Atoms and Structured Baths with Next‐Nearest‐Neighbor Couplings

AbstractIn this paper, the unconventional light‐matter interactions between giant atoms and structured baths (i.e., lattices) are studied with either Hermitian or non‐Hermitian next‐nearest‐neighbor coupling terms. Essentially different dynamics of the atoms and the propagating field in the Hermitian and non‐Hermitian cases is revealed, which can be further engineered by tuning parameters such as the atomic transition frequency and the (synthetic) magnetic field associated to the coupling terms. The next‐nearest‐neighbor couplings play an important role in controlling the emission direction and the field distribution in the lattice, thus providing opportunities for tailoring exotic dipole–dipole interactions. The results in this paper have potential applications in, e.g., engineering unconventional quantum networks and simulating quantum many‐body systems.

The study of magnetoviscous effect of the ferrofluids considering magnetic dipole interactions

The study of magnetoviscous effect of the ferrofluids considering magnetic dipole interactions

MnO2-modified PEEK membrane for efficient oil-water separation and solar-assisted seawater desalination

Economic and efficient routes to achieve clean freshwater from oil-water mixtures and seawater have gained special attention to reduce the current water crisis, but still a challenge unsolved. Herein, poly (ether ether ketone) (PEEK) membrane, modified with MnO2 layer, has been prepared by facile hydrothermal method to address this issue aforementioned. Given the existence of PEEK and underwater superoleophobicity/underoil superhydrophilicity of MnO2, the composite membrane exhibits strong mechanic properties (tensile stress: 110.2 MPa) and high separation efficiencies (99.9 %) for different oil–water mixtures under gravity. Additionally, our membrane could also effectively separate immiscible oil mixtures according to the dipole–dipole interaction. Furthermore, firm chemical stability against dichloromethane, N, N-Dimethylformamide, 1 M NaOH, 1 M HCl, and 1 M NaCl has been achieved. Most importantly, our membrane displays durable evaporation efficiency (2.63 kg m-2h−1), high energy efficiency (85.9 %), and super salt tolerance under 1 sun irradiation, for solar-assisted seawater desalination.

Revisiting the governing equations of a magnetic suspension of polar particles: From microhydrodynamics analysis to rheological response

In this review, we describe a formulation for the stress tensor of a monodisperse magnetic suspension of polarized neutrally buoyant spheroidal particles suspended in a non-magnetic liquid. A magnetic suspension affords a rare example of a material for which the stress tensor is non-symmetric. The present formulation is based on a microhydrodynamics description of a spherical particle suspended in a Newtonian fluid subjected to magnetic forces and torques. The magnetic suspension is considered statistically homogeneous and treated as being a homogeneous equivalent fluid. Under this condition, a volume average over all particles in the carrier fluid is used in order to obtain the magnetization equation evolution and the constitutive equation for the stress tensor of the magnetic suspension, in particular the magnetic stress contribution. The average effects on the homogeneous continuum fluid due to particle pressure, particle dipole, and the applied magnetic field on each particle are computed by our constitutive equation. In this approach, the particles are not considered force or torque free since their permanent magnetization allows them to experience the effects of an applied magnetic field. The calculated stress tension can be used for modeling common flows of symmetric or non-symmetric magnetic fluids flowing in arbitrary geometries and in rheological applications for determination of important properties such as the rotational viscosity of non-symmetric magnetic fluids. The final expression of the constitutive equation for the stress tensor based on a particle scale approach presents some difference as compared with current constitutive models proposed in the current literature. Our constitutive equation considers the effect of a magnetic particle pressure, the average particle stresslet contribution in terms of an effective viscosity, the average particle rotlet in terms of a rotational viscosity, and a configurational tensor associated with dipole–dipole interactions. In addition, we discuss the situation in which the dipole moment of the particle is not frozen on it which leads to the necessity of an internal balance of angular momentum in a fluid element to close the governing equations of the model. An extension of the model for emulsions of polar deformable droplets is also proposed.

Second-harmonic generation of 2D materials excited by the Laguerre-Gaussian beam.

We theoretically study the second-harmonic generation (SHG) of two-dimensional (2D) materials excited by a Laguerre-Gaussian (LG) beam at normal incidence and provide a method to distinguish SHG induced by the electric dipole (ED) interaction and SHG induced by the electric quadrupole and magnetic dipole (EQ-MD) interaction by their different dependence on the LG beam parameters, including the effective spot area v02 and the order of orbital angular momentum (OAM) m. In an approximation of neglecting reflection and taking a beam radius to infinity, the intensity of the ED induced SHG is proportional to F m/v02 with Fm = 2-2|m|(2|m|)!/(π(|m|!)2), while the EQ-MD induced one is proportional to (4|m|+2)F m/v04. An in-plane isotropic substrate can strongly affect the signal amplitude but slightly change the v0 and m dependence. Our results provide an all-optical way to detect the OAM by SHG, as well as a theoretical basis for studying the EQ-MD induced SHG by the LG beams.

Influence of calcination temperature and particle size distribution on the physical properties of SrFe12O19 and BaFe12O19 hexaferrite powders

The paper deals with the economic optimisation of ferrite powder preparation during producing hard ferrite magnets. The magnetic properties of ferrites are investigated by replacing feedstock and reducing calcination temperature and particles in the order of tens of microns. The granulates about 8–10 mm in size were calcined for 2 h in the temperature range from 1100 °C to 1300 °C and additionally crushed and milled to an average particle size of about 80–90 µm. The scanning electron microscopy images confirmed the agglomerates of particles with different shapes and sizes in tens of µm. The X-ray diffraction measurements revealed that, besides the SrFe12O19 and BaFe12O19 phases, there was also the presence of 2–39% hematite. The highest values of maximum energy product (BH)max = 930 J/m3 and remanent magnetic induction Br = 72.8 mT were obtained at a calcination temperature of 1300 °C. The Henkel plots confirmed the presence of exchange-coupling and dipolar magnetic interactions at lower and higher magnetic fields, respectively. The strength of interactions was also dependent on the calcination temperature. Replacing strontium with barium led to a deterioration of the magnetic parameters, which were optimal at a lower calcination temperature (1100 °C). This phenomenon was partly overcome by reducing the mean particle size of Ba-based hexaferrites to 45–50 µm.

Reduced energies for thin ferromagnetic films with perpendicular anisotropy

We derive four reduced two-dimensional models that describe, at different spatial scales, the micromagnetics of ultrathin ferromagnetic materials of finite spatial extent featuring perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. Starting with a microscopic model that regularizes the stray field near the material’s lateral edges, we carry out an asymptotic analysis of the energy by means of [Formula: see text]-convergence. Depending on the scaling assumptions on the size of the material domain versus the strength of dipolar interaction, we obtain a hierarchy of the limit energies that exhibit progressively stronger stray field effects of the material edges. These limit energies feature, respectively, a renormalization of the out-of-plane anisotropy, an additional local boundary penalty term forcing out-of-plane alignment of the magnetization at the edge, a pinned magnetization at the edge, and, finally, a pinned magnetization and an additional field-like term that blows up at the edge, as the sample’s lateral size is increased. The pinning of the magnetization at the edge restores the topological protection and enables the existence of magnetic skyrmions in bounded samples.

Calculation of liquidus in eutectic alkali halide mixtures using thermodynamic perturbation theory

A statistical-thermodynamic model that makes it possible to describe with good accuracy phase equilibria between melt and crystal in binary alkali halide mixtures with common cations and anions is proposed. This model is based on the thermodynamic perturbation theory, which takes into account the charge-dipole contribution to the interionic interaction of binary molten salts using a multicomponent mixture of charged hard spheres as a reference system. Specific expressions for chemical potentials, taking into account the charge-induced dipole interaction in the molten phase, are presented within the developed approach. Considering binary eutectic mixtures NaF–NaCl, CsF–CsCl, NaF–CsF, and NaCl–CsCl as an example, the liquidus curves obtained in two series of calculations are shown: with the equation of state and without it. The discrepancies between the calculated and experimental data on the position of eutectic equilibrium for most of the considered mixtures do not exceed about 10 percent on the temperature scale and 5 percent on the composition when using only the tabulated values of ionic radii and polarizabilities without any adjustment.

Co‐Solvent Assisted Optimization of the CuSCN Hole Transport Layer for Enhancing the Efficiency of Ambient Processable Perovskite Solar Cells with Carbon Counter Electrodes

In recent perovskite solar cell (PSC) research, copper(I) thiocyanate (CuSCN) is an emerging inorganic hole transport layer (HTL) due to its suitable band gap, matched band edge positions with the perovskite and high stability under ambient conditions. However, being a coordination polymer typically requires sulfide‐based solvents that strongly interact with Cu(I) for dissolution. Dipropyl sulfide (DPS) is generally used where it is very sparingly soluble of about 10–12 mg mL−1, which leads to low surface coverage with pin‐holes on the surface responsible for the generation of defects at the perovskite–HTL interface. In this study, addition of the optimized amount 100 μL of co‐solvent Acetonitrile (ACN) increased the CuSCN dissolution from 10 to 35 mg mL−1. ACN can act as a Lewis‐base making it capable of donating electrons to a Lewis‐acid like Cu+ from CuSCN. ACN is a polar aprotic solvent due to its highly polar CN bond and by adding CuSCN the dipole–dipole interactions can stabilize the CuSCN molecules in solution. The device with architecture (FTO/c‐TiO2/mp‐TiO2/MAPbI3/CuSCN/carbon) showed the higher power conversion efficiency (PCE) of ≈11% with Voc of 1.01 V and Isc 24.65 mA cm−2 showing excellent stability stored under ambient atmosphere which retains 80% of its initial efficiency after 10 days.

The study on the magnetic interaction between the duel magnetic layers and the FINEMET ribbon

Due to the sensitive magnetic field response of the GMI effect, the peak field in magneto impedance curves obtained from the composite magnetic ribbons shows great dependence on the magnetic interaction, which has gained intensive attention in the study of the diversity and the mechanism of magnetic interaction. In this work, FINEMET/Fe20Ni80/SiO2/Fe20Ni80 composite ribbons with a fixed thickness of outer Fe20Ni80 layer (200 nm) and variable thickness ratio of the inner Fe20Ni80 and SiO2 layers, ranging from the 1:4 to 4:1 were prepared. Then the GMI response was utilized to investigate the influence of the exchange couple and the dipole interaction to magnetic properties of the base ribbon. The experimental results indicated that additional SiO2 layer can successfully induce slight magnetic differences of the two Fe20Ni80 layers, which results in the emergence of four-peak GMI profiles. Besides, the frequency-dependent nature of the peaks was explored, revealing that both dipole interaction and exchange couple influence the magnetic properties, contributing to the occurrence of four-peak GMI curves. Thus, the insights presented in this work are thought to be valuable for understanding the mechanisms of multilayer composite ribbons in future sensing applications.

Hydrogen Bonding in Amorphous Indomethacin.

Amorphous Indomethacin has enhanced bioavailability over its crystalline forms, yet amorphous forms can still possess a wide variety of structures. Here, Empirical Potential Structure Refinement (EPSR) has been used to provide accurate molecular models on the structure of five different amorphous Indomethacin samples, that are consistent with their high-energy X-ray diffraction patterns. It is found that the majority of molecules in amorphous Indomethacin are non-bonded or bonded to one neighboring molecule via a single hydrogen bond, in contrast to the doubly bonded dimers found in the crystalline state. The EPSR models further indicate a substantial variation in hydrogen bonding between different amorphous forms, leading to a diversity of chain structures not found in any known crystal structures. The majority of hydrogen bonds are associated with the carboxylic acid group, although a significant number of amide hydrogen bonding interactions are also found in the models. Evidence of some dipole-dipole interactions are also observed in the more structurally ordered models. The results are consistent with a distribution of Z-isomer intramolecular type conformations in the more disordered structures, that distort when stronger intermolecular hydrogen bonding occurs. The findings are supported by 1H and 2H NMR studies of the hydrogen bond dynamics in amorphous Indomethacin.