Dipolar Interactions Research Articles

Tuning Surface Organic Structures by Small Gas Molecules through Catassembly and Coassembly.

The field of molecular assembly has seen remarkable advancements across various domains, such as materials science, nanotechnology, and biomedicine. Small gas molecules serve as pivotal modulators, capable of altering the architecture of assemblies via tuning a spectrum of intermolecular forces including hydrogen bonding, dipole-dipole interactions, and metal coordination. Surface techniques, notably scanning tunneling microscopy and atomic force microscopy, have proven instrumental in dissecting the structural metamorphosis and characteristic features of these assemblies at an unparalleled single-molecule resolution. Recent research has spotlighted two innovative approaches for modulating surface molecular assemblies with the aid of small gas molecules: "catassembly" and "coassembly". This Perspective delves into these methodologies through the lens of varying molecular interaction types. The strategies discussed here for regulating molecular assembly structures using small gas molecules can aid in understanding various complex assembly processes and structures and provide guidance for the further fabrication of complex surface structures.

Entanglement and quantum coherence of two YIG spheres in a hybrid Laguerre–Gaussian cavity optomechanics

We theoretically investigate continuous variable entanglement and macroscopic quantum coherence in the hybrid L–G rotational cavity optomechanical system containing two YIG spheres. In this system, a single L–G cavity mode and both magnon modes (which are due to the collective excitation of spins in two YIG spheres) are coupled through the magnetic dipole interaction whereas the L–G cavity mode can also exchange orbital angular momentum (OAM) with the rotating mirror (RM). We study in detail the effects of various physical parameters like cavity and both magnon detunings, environment temperature, optorotational and magnon coupling strengths on the bipartite entanglement and the macroscopic quantum coherence as well. We also explore parameter regimes to achieve maximum values for both of these quantum correlations. We also observed that the parameters regime for achieving maximum bipartite entanglement is completely different from macroscopic quantum coherence. So, our present study shall provide a method to control various nonclassical quantum correlations of macroscopic objects in the hybrid L–G rotational cavity optomechanical system and have potential applications in quantum sensing, quantum meteorology, and quantum information science.

Fluorinated Poly(thiophene-based aryl piperidinium) Anion-Exchange Membranes Containing Dual Cation–Dipole Interactions for Alkaline Fuel Cells

Fluorinated Poly(thiophene-based aryl piperidinium) Anion-Exchange Membranes Containing Dual Cation–Dipole Interactions for Alkaline Fuel Cells

Enhanced Quantum Control of Individual Ultracold Molecules Using Optical Tweezer Arrays

Control over the quantum states of individual molecules is crucial in the quest to harness their rich internal structure and dipolar interactions for applications in quantum science. In this paper, we develop a toolbox of techniques for the control and readout of individually trapped polar molecules in an array of optical tweezers. Starting with arrays of up to eight Rb and eight Cs atoms, we assemble arrays of RbCs molecules in their rovibrational and hyperfine ground state with an overall efficiency of 48(2)%. We demonstrate global microwave control of multiple rotational states of the molecules and use an auxiliary tweezer array to implement site-resolved addressing and state control. We show how the rotational state of the molecule can be mapped onto the position of Rb atoms and use this capability to readout multiple rotational states in a single experimental run. Further, using a scheme for the midsequence detection of molecule formation errors, we perform rearrangement of assembled molecules to prepare small defect-free arrays. Finally, we discuss a feasible route to scaling to larger arrays of molecules. Published by the American Physical Society 2024

Integrating K+ into Eu and Tb doped GdCa4O(BO3)3: A dual study on photoluminescence and structure

In this study, we investigate the structural and photoluminescence (PL) properties of rare-earth-doped GdCa4O(BO3)3 (GdCOB) phosphors, specifically focusing on the spectral behaviour induced by doping with Eu³⁺ and Tb³⁺ ions. The powder X-ray diffraction (XRD) spectra confirm the formation of a monoclinic phase. The XRD data were also refined by a Rietveld refinement method. The existence of B, O, Ca, Gd, Tb, Eu and K elements was verified by EDS spectra. We introduce a detailed examination of the charge compensation process using Kröger-Vink notation to clarify the mechanisms essential for tailoring the optical properties of the phosphors. The PL excitation spectrum of GdCOB:Eu3+, monitored at 611 nm, reveals sharp excitation peaks at 319, 361, 380, and 392 nm, corresponding to 7F0→5H3, 7F0→5D4, 7F0→7F0, and 7F0→5L6 transitions, respectively. The PL spectrum under excitation of 392 nm exhibits that phosphors doped with Eu3+ a significant red emission at 611 nm, which is attributed to the 5D₀→7F₂ transition. This emission intensity is particularly enhanced at non-centrosymmetric sites of the Eu³⁺ ions. Similarly, the PL excitation spectrum of GdCOB:Tb3+, monitored at 552 nm, displays distinct excitation peaks at 316, 341, 353, and 379 nm, which correspond to the transitions 7F₆→5D₀, 7 F₆→5L₇, 7F₆→5D₂, and 7F₆→5D₃, respectively. Tb³⁺-doped phosphors display a bright green emission, with a dominant peak at 552 nm, resulting from the 5D₄→7F₅ transition. Additionally, the introduction of K⁺ ions as co-dopants results in modifications to the local environments of Eu³⁺ and Tb³⁺ ions. These changes allow for fine-tuning of the emission peaks, significantly enhancing the luminescent output of the phosphors. Optimal doping concentrations of 5 mol% for Eu³⁺ and 1 mol% for Tb³⁺ enhance luminescent intensity and prevent concentration quenching. This phenomenon, often resulting in reduced PL intensity at higher dopant levels, is primarily due to dipole-dipole interactions, consistent with Dexter's theory of energy transfer. Strategic modulation of doping concentrations, coupled with a deep understanding of energy transfer mechanisms are critical for the development of advanced luminescent materials Our analysis of the Commission de l′Eclairage (CIE) chromaticity coordinates reveals enhanced energy transfer dynamics in rare-earth-doped borates, facilitating the tuning of luminescent properties. These results not only deepen our understanding of the fundamental physics governing such phosphors but also open pathways for the development of optoelectronic applications requiring consistent color output, such as LED technologies and solid-state lighting.

The Unprecedented Biodegradable Polyzwitterion: A Removal-Free Patch for Accelerating Infected Diabetic Wound Healing.

Zwitterionic polymers have emerged as an important class of biomaterials to construct wound dressings and antifouling coatings over the past decade due to their excellent hydrophilicity. However, all the reported zwitterionic polymers are non-degradable because of non-cleavable carbon-carbon bonding backbones, and must be removed periodically after treatment to avoid hypoxia in the wound, thus leading to potential secondary injury. In this work, we fabricate a biodegradable polyzwitterion patch for the first time by ring-opening polymerization of carboxybetaine dithiolane (CBDS), which is self-crosslinked via inter-amide hydrogen bonds and zwitterionic dipole-dipole interactions on the side chains. The unprecedented polyCBDS (PCBDS) patch demonstrates enough ductility owing to the intermolecular physical interactions to fully cover irregular wounds, also showing excellent biodegradability and antifouling performance resulted from the existence of disulfide bonds and carboxybetaine groups. Besides, the PCBDS degradation-induced released CBDS owns potent antioxidant and antibacterial activities. This PCBDS patch is used as a diabetic wound dressing, inhibiting bacterial adhesion on the external surface, and its degradation products can exactly kill bacteria and scavenge reactive oxygen species at the wound site to regulate local microenvironment, including regulation of cytokine express and macrophage polarization, accelerating infected diabetic wound repair and also avoiding the potential secondary injury. This article is protected by copyright. All rights reserved.

Ambient N[tbnd]N bond weakening hydrogenation by utilizing the highly defective Cu3BiS3/MnO2 electrocatalyst for ammonia yield above 3 mg/h.cm2: The N2-nano dipole interaction micromechanism

This study introduces a novel Cu3BiS3/MnO2 composite catalyst for the electrochemical nitrogen reduction reaction (eNRR) to address challenges in sustainable ammonia production, aiming to replace the energy-intensive Haber-Bosch process. The ternary Cu3BiS3/MnO2 catalyst exhibited impressive results, achieving a high ammonia yield rate of 3604 µg h−1cm−2 and a significant Faradaic efficiency of 31.4 % at −0.75 V vs. RHE in a 0.5 M Na2SO4 solution, while only 446 µg h−1cm−2 from binary metal CuMn(2:3). This success was attributed to abundant cation and anion defects with multiple valence charges in the Cu3-xBiS3/MnO2-y catalyst, created by introducing the third metal, Bi, into the binary CuMn system. These defects served as trapping centers for dynamic nitrogen molecule activation and facilitated charge transport, enhancing the eNRR process. This study underscores the potential of highly defective Cu3-xBiS3/MnO2-y as an efficient and sustainable catalyst for electrochemical nitrogen fixation, offering a greener approach to ammonia production.

Magnetic Assembly of Magnetite/Perovskite Hybrid Nanorods for Circularly Polarized Luminescence

AbstractMagnetic fields are uniquely valuable for creating colloidal nanostructured materials, not only providing a means for controlled synthesis but also guiding their self‐assembly into distinct superstructures. In this study, a magnetothermal process for synthesizing hybrid nanostructures comprising ferrimagnetic magnetite nanorods coated with fluorescent perovskite nanocrystals is reported and their magnetic assembly into superstructures capable of emitting linear and circularly polarized light are demonstrated. Under UV excitation, the superstructures assembled in a liner magnetic field produce linear polarized luminescence, and those assembled in a chiral magnetic field exhibit strong circularly polarized luminescence (CPL) with a glum value up to 0.44 (±0.004). The CPL is believed to originate from the dipolar interaction between neighboring perovskite nanocrystals attached to the chiral assemblies and the chiral‐selective absorption of the perovskite emission by the magnetite phase. The magnetic synthesis and assembly approaches and the resulting distinctive chiral superstructures are anticipated to open up new avenues for designing diverse functional chiroptical devices.

Determination of Binding Constants for the Complexes Between Heavy Metal Ions and Cucurbit[n]uril

AbstractOne of the major concerns worldwide is the rapid increase in water pollution with hazardous heavy metals. The Cucurbit[n]uril (CB[n]) structure provides an inner hydrophobic cavity accessible through two electrostatically negative portals with polar carbonyl groups, allowing for charged ion–dipole interaction between cationic species with excellent binding affinities. In this work we selected CB[5], and CB[7] for the titrimetric and electrochemical evaluation of the heavy metal complexes formed with Copper(II), Cadmium(II) and Lead(II). The host–guest interaction was found by either attenuation of the redox peaks, the formation of a new peak, or the slight shift in the redox peaks of the heavy metal ions. Titration data were obtained for CB[n] with the heavy metal solutions to determine the molar coefficient of binding. The stoichiometry of the complexes was 1 : 1 by Job′s plot. We calculated the binding constants using the Benesi–Hildebrand method achieving relatively good binding constants (K) ranging from (1.80±0.14)×105–(4.98±0.13)×105 M−1. The results showed that the complexes of Cadmium(II) and Lead(II) with both CB[5] and CB[7] are highly stable in aqueous media. Copper(II) was able to bind to the smaller sized portal of CB[5], whereas with CB[7] the heavy metal ion could not form a favourable complex. This phenomenon suggests that the CB[5] is an ideal host at forming stable host–guest interactions than their larger homologue.

Generation of out-of-plane ferroelectric behavior in a one-atom-thick monolayer

Ferroelectricity with out-of-plane polarization has so far been found in several two-dimensional (2D) materials, including monolayers comprising three to five planes of atoms, e.g. α-In2Se3 and MoTe2. Here, we explore the generation of out-of-plane polarization within a one-atom-thick monolayer material, namely hexagonal boron nitride. We performed density-functional-theory calculations to explore inducing ferroelectric-like distortions through incorporation of isovalent substitutional impurities that are larger than the host atoms. This disparity in bond lengths causes a buckling of the h-BN, either up or down, which amounts to a dipole with two equivalent energies and opposing orientations. We tested several impurities to explore the magnitude of the induced dipole and the switching energy barrier for dipole inversion. The effects of strain, dipole–dipole interactions, and vertical heterostructures with graphene are further explored. Our results suggest a highly-tunable system with ground state antiferroelectricity and metastable ferroelectricity. We expect that this work will help foster new ways to include functionality in layered 2D-material-based applications.

Direct measurement of repulsive and attractive pair potentials using pairs of optical traps

We present a technique for measuring the interactions between pairs of colloidal particles in two optical traps. This method is particularly suitable for measuring strongly attractive potentials, an otherwise challenging task. The interaction energy is calculated from the distribution of inter-particle separations by accounting for the contribution from the optical traps with arbitrary trap profiles. The method is simple to implement and applicable to different types of pair potentials and optical trapping geometries. We apply the method to measure dipolar pair interactions in experiments with paramagnetic colloids in external magnetic fields. We obtain consistent and accurate results in all regimes, from strongly attractive to repulsive potentials. By means of computer simulations, we demonstrate that the proposed method can be successfully applied to systems with complex pair interactions characterized by multiple attractive and repulsive regimes, which are ubiquitous in soft and biological matter.

Cooperative effects in dense cold atomic gases including magnetic dipole interactions

We theoretically investigate cooperative effects in cold atomic gases exhibiting both electric and magnetic dipole-dipole interactions, such as occurs, for example, in clouds of dysprosium atoms. After introducing a general framework capturing both the quantum degenerate and nondenegerate cases, we focus on the emergence of tailorable spin models in the quantum nondegenerate regime. In the low-excitation limit, we provide analytical and numerical results detailing the effect of magnetic interactions on the directionality of scattered light and characterize sub and superradiant effects. Published by the American Physical Society 2024

Dipole-dipole interactions and the origin of ferroelectric ordering in polar nematics

ABSTRACT A molecular origin of the ferroelectric ordering in the nematic phase is considered in detail considering a model based on electrostatic interaction between permanent molecular dipoles modulated by the anisotropic molecular shape. It is shown that a contribution to the total free energy of the long-range tail of the dipole-dipole interaction potential defines the total electrostatic energy of the system which depends on the sample shape and on the boundary conditions. This contribution may strongly affect the transition into the ferroelectric phase. However, the dipole-dipole interaction itself can hardly be responsible for the ferroelectric ordering in nematic liquid crystals for any reasonable values of the molecular dipole. A more promising model which combines dipole-dipole interaction and short-range orientational-translational correlations is also considered.

Optimizing Performance of PVC Gel Actuators: Temperature Influence and Characterizations

PVC gels are in high demand for actuators, so choosing the optimal route for preparing PVC gel is crucial. In this study, PVC gel samples were prepared using polymer PVC, plasticizer Di-butyl adipate (DBA), and solvent tetrahydrofuran (THF) at temperatures ranging from 40°C to 70°C. The samples obtained at different temperatures were labeled as PVC40, PVC50, PVC60, and PVC70. Rheological properties of all PVC gel samples were analyzed, revealing, that the rheological behavior of the PVC70 gel sample differed significantly from the others due to THF evaporation at 70°C, resulting in inadequate PVC gel preparation. However, PVC40, PVC50, and PVC60 gel samples were chosen for further characterizations, including scanning electron microscopy (SEM), actuation, and mechanical properties evaluation. Moreover, a self-assembled setup was fabricated using electrodes and PVC gel to test the performance of the planar actuator. The maximum displacement of PVC60 was measured at approximately 0.74 mm, with a response time of 0.75 sec under an applied voltage of 1000V. It was observed that the homogeneity of the gel and the solubility of the raw materials, based on resin were influenced by the reaction temperature, suggesting that uniformity could be achieved through dipole-dipole interactions or hydrogen bonding between PVC and DBA (Cl-H…. O=C). Finally, our findings have the potential to contribute to the development of innovative PVC gel actuators.

Binding of Phosphate Species to Ca2+ and Mg2+ in Aqueous Solution.

Phosphate derivatives and their interaction with metal cations are involved in many important biological phenomena, so an accurate characterization of the phosphate-metal interaction is necessary to properly understand the role of phosphate-metal contacts in mediating biological function. Herein, we improved the standard 12-6 Lennard-Jones (LJ) potential via the usage of the 12-6-4 LJ model, which incorporates ion-induced dipole interactions. Via parameter scanning, we fine-tuned the 12-6-4 LJ polarizability values to obtain accurate absolute binding free energies for the phosphate anions H2PO4-, HPO42-, PO43- coordinating with Ca2+ and Mg2+. First, we modified the phosphate 12-6-4 LJ parameters to reproduce the solvation free energies of the series of phosphate anions using the thermodynamic integration (TI) method. Then, using the potential mean force (PMF) method, the polarizability of the metal-phosphate interaction was obtained. We show that the free energy profiles of phosphate ions coordinated to Ca2+ and Mg2+ generally show similar trends at longer metal-phosphate distances, while the absolute binding energy values increased with deprotonation. The resulting parameters demonstrate the flexibility of the 12-6-4 LJ-type nonbonded model and its usefulness in accurately describing cation-anion interactions.

Ultrafast Self-Healing Elastomer with Closed-Loop Recyclability.

The loss of function after prolonged periods of use is inevitable for all materials including plastics. Hence, self-healing capabilities are a key development to prolong the service lifetime of materials. One of such self-healing capabilities can be achieved by integrating dynamic bonds such as boronic ester linkages into polymeric materials, however the rate of self-healing in these materials is insufficient and current methods to accelerate it are limited. In this study, we report the rational design, synthesis and characterization of a fluorinated elastomer (FBE15) that utilizes enhanced interaction between polymer chains afforded by strong dipole-dipole interactions from -CF3, which showed a significant increase in binding energy to -7.71 Kcal/mol from -5.51 Kcal/mol, resulting in increased interaction between the boronic ester linkages and improving self-healing capabilities of boronic ester materials, drastically reducing the time required for stress relaxation by 900 %. The bulk elastomer is capable of ultrafast self-healing in a one-click fashion that can happen in mere seconds, which can then be stretched to 150 % of its original length. By utilising the dynamic cross-linking, FBE15 is also capable of both mechanical reprocessing into the same materials and chemical recycling into its starting materials, respectively, further allowing reconstruction of the elastomers that have comparable properties to the original ones at the end of its service lifespan.

Multiple non-covalent interactions for mechanically robust and electrically detachable liquid-free poly(ionic liquids) ionoadhesives

Ionoadhesives hold great potentials for detachment and replacement of bonding components by virtue of the interfacial electrochemistry reactions of ion carriers, but previous ionoadhesives suffer from liquid leakage and conflict between mechanical properties and ionic conductivity. Here, a liquid-free and nanophase separated poly(ionic liquids) ionoadhesive (PIA) is designed through establishing multiple non-covalent interactions (NCIs) including weak ion–dipole interactions, moderate lithium bonds and strong electrostatic interactions. As a result, the physical crosslinked networks in PIAs are effectively strengthened that ensures the mechanical performances under static state; the breaking-reforming events of the multiple NCIs are beneficial for dissipating energy to resist external deformations that endows the PIAs with outstanding dynamic stability; the multiple NCIs also induce the orientation of nanophases that enables the PIAs to be reinforced via cyclic mechanical training. Benefiting from the high ionic conductivity, the PIAs exhibit extraordinary electrically detaching behavior under DC voltages since the occurrence of rapid interfacial electrochemistry reactions that facilitates the formation of gases and nanoparticles at the bonding interfaces. This work proposes a new rational design of electrically detachable ionoadhesives with excellent comprehensive performances that demonstrate great potentials in recycle and reuse of the bonding components and reduce the waste of industrial resources.

Characteristic Curves of Polar Fluids: (I) The Two-Center Lennard–Jones Plus Dipole Fluid

Brown’s characteristic curves of polar fluids were studied using molecular simulation and molecular-based equation of state. The focus was on elucidating the influence of dipole interactions and the molecule elongation on the characteristic curves. This was studied using the symmetric two-center Lennard–Jones plus point dipole (2CLJD) model fluid class. This model class has two parameters (using Lennard–Jones reduced units), namely the elongation and the dipole moment. These parameters were varied in the range relevant for real substance models that are based on the 2CLJD model class. In total, 43 model fluids were studied. Interestingly, the elongation is found to have a stronger influence on the characteristic curves compared to the dipole moment. Most importantly, the characteristic curve results for the 2CLJD fluid are fully conform with Brown’s postulates (which were originally derived for simple spherical dispersive fluids). The independent predictions from the computer experiments and the theory are found to be in reasonable agreement. From the molecular simulation results, an empirical correlation for the characteristic curves of the 2CLJD model as a function of the model parameters was developed and also applied for modeling real substances. Additionally, the intersection points of the Charles and Boyle curve with the vapor-liquid equilibrium binodal and spinodal, respectively, were studied.

Atomic physics on a 50-nm scale: Realization of a bilayer system of dipolar atoms.

Controlling ultracold atoms with laser light has greatly advanced quantum science. The wavelength of light sets a typical length scale for most experiments to the order of 500 nanometers (nm) or greater. In this work, we implemented a super-resolution technique that localizes and arranges atoms on a sub-50-nm scale, without any fundamental limit in resolution. We demonstrate this technique by creating a bilayer of dysprosium atoms and observing dipolar interactions between two physically separated layers through interlayer sympathetic cooling and coupled collective excitations. At 50-nm distance, dipolar interactions are 1000 times stronger than at 500 nm. For two atoms in optical tweezers, this should enable purely magnetic dipolar gates with kilohertz speed.

Evolution mechanism of the core-shell to homogeneous microstructure in immiscible alloy by semi-solid treatment under a high magnetic field

Immiscible alloys possess broad industrial applications, but the presence of immiscible gaps makes them highly susceptible to the formation of segregated microstructures, thus, a new method for obtaining a uniform distribution of fine minor separated phases needs to be explored. The present work focuses on the evolution mechanism of a CuCo immiscible alloy with a core-shell microstructure during semi-solid isothermal processing under a high magnetic field. The results showed that the microstructure changes from the core-shell structure of the initial sample to homogeneous microstructure after semi-solid treatment, regardless of whether a magnetic field is applied. The mechanism of microstructure evolution of the alloy during semi-solid treatment was revealed through in-situ experiment, in which Ostwald ripening and coalescence mechanisms led to grain coarsening, grain boundary remelting caused grain dissociation, and ultimately the grains underwent spheroidization. However, as a high magnetic field was applied, the average radius of the Co-rich particles decreased, and the particles were aligned in the direction of the magnetic field, forming a chain-like microstructure due to dipole-dipole interactions between the grains. The CuCo immiscible alloy with a uniform microstructure after semi-solid treatment exhibited a higher microhardness and saturation magnetization. This study offers a novel perspective for designing immiscible alloys with homogeneous microstructures as well as chain-like microstructures by utilizing semi-solid treatment combined with a magnetic field.