Planar Layer Research Articles

Outer Helmholtz plane adsorption regulation to achieve low-concentration of pure propylene carbonate solvent electrolytes compatible with graphite anode

The low melting point and high polarity of propylene carbonate (PC) make it an ideal solvent for electrolytes of lithium-ion batteries (LIBs), but the incompatibility with graphite anode hinders the application. In the present study, a new method is developed to solve this problem from a new viewpoint. Introduction of saturated LiNO3 (0.14 mol L‒1) into pure PC electrolyte containing lithium salt with normal concentration (1.38 mol L‒1) leads to a perfect compatibility with graphite anode. Li/Graphite cell using this pure PC electrolyte shows a reversible capacity of 350.0 mAh g‒1 and a 200-cycle capacity retention of 96.3 %. Further mechanism study and theoretical computation indicate that the NO3‒ anions are adsorbed to outer Helmholtz plane of the electric double layer at the graphite anode interface. This changes the Li+ solvation structure in the electric double layer, facilitating the Li+ desolvation process hence resulting in high compatibility with the graphite anode. The most prominent advantage of the present strategy is that, because of the adsorption of NO3‒ anions to the outer Helmholtz plane, the compatibility with graphite anode could be improved by introduction of tiny amount of Li salt without large change of the bulk phase properties of the electrolyte. This work provides a new understanding of the compatibility from the viewpoint of outer Helmholtz plane, which might deliver new insights for the optimization of electrolytes for LIBs.

Fabrication and Characterization of Biocompatible Multilayered Elastomer Hybrid with Enhanced Water Permeation Resistance for Packaging of Implantable Biomedical Devices

This study presents the synthesis and characterization of hexadecyl-modified SiO2 (HD-SiO2) nanoparticles and their application in the fabrication of a multilayered elastomer hybrid sheet to enhance water resistance in implantable biomedical devices. The surface modification of SiO2 nanoparticles was confirmed via FT-IR and TGA analyses, showing the successful grafting of hydrophobic hexadecyl groups. FE-SEM and DLS analyses revealed spherical HD-SiO2 nanoparticles with an average size of 360 nm. A multilayered elastomer hybrid sheet, consisting of a PDMS-based circuit-protecting body, a water resistance layer of HD-SiO2, a planarization layer, and a biocompatible layer of polydopamine, was fabricated and characterized. The water resistance layer exhibited superhydrophobic properties, with a water contact angle of 154.7° and a 27% reduction in water vapor transmission rate (WVTR) compared to the circuit-protecting body alone. The device packaged with both the circuit-protecting body and water resistance layer demonstrated a tenfold increase in operational lifespan in water medium compared to the device without the water resistance layer. Cytotoxicity and cell proliferation tests on human dermal fibroblast cells (HDFn) confirmed the biocompatibility of the multilayered sheet, with no significant cytotoxicity observed over 48 h.

Effects of Anisotropy, Convection, and Relaxation on Nonlinear Reaction-Diffusion Systems

The effects of relaxation, convection, and anisotropy on a two-dimensional, two-equation system of nonlinearly coupled, second-order hyperbolic, advection–reaction–diffusion equations are studied numerically by means of a three-time-level linearized finite difference method. The formulation utilizes a frame-indifferent constitutive equation for the heat and mass diffusion fluxes, taking into account the tensorial character of the thermal diffusivity of heat and mass diffusion. This approach results in a large system of linear algebraic equations at each time level. It is shown that the effects of relaxation are small although they may be noticeable initially if the relaxation times are smaller than the characteristic residence, diffusion, and reaction times. It is also shown that the anisotropy associated with one of the dependent variables does not have an important role in the reaction wave dynamics, whereas the anisotropy of the other dependent variable results in transitions from spiral waves to either large or small curvature reaction fronts. Convection is found to play an important role in the reaction front dynamics depending on the vortex circulation and radius and the anisotropy of the two dependent variables. For clockwise-rotating vortices of large diameter, patterns similar to those observed in planar mixing layers have been found for anisotropic diffusion tensors.

Solvent-vapor-assisted crystallization of covalent organic framework films for CO2/CH4 separation

Abstract Covalent organic framework (COF) films were prepared using alternating vapor deposition of precursors followed by solvent vapor annealing. When an as-deposited film was annealed in appropriate solvent vapors, the prepared COF film exhibited an “onion-like” structure. This result opens a way to synthesize COF films with highly ordered planar layers through the interaction between layers. The CO2/CH4 separation performance of COF film was significantly improved due to the decrease in defects caused by crystallization.

Half-metallic behavior and anisotropy of two-dimensional MoSi2N4/ScSi2N4 heterojunction

Heterojunctions formed by stacking different two-dimensional monolayer materials typically have tunable electronic properties, which will greatly broaden the application prospects of 2D materials in electron devices. In this paper, the structures, electron properties, and anisotropy of MoSi2N4/ScSi2N4 heterojunctions formed by stacking MoSi2N4 monolayer with semiconductor properties and ScSi2N4 monolayer with half-metallic properties have been systematically studied. The results show that Type-Ⅰ configuration has the most stable structure in terms of total energy, binding energy, phonon spectrum and molecular dynamics among the three configurations formed by MoSi2N4/ScSi2N4 heterojunctions. The MoSi2N4/ScSi2N4 heterojunction has robust half-metallic behavior and tensile anisotropy at equilibrium. At the same time, MoSi2N4/ScSi2N4 heterojunction can still maintain stable ferromagnetic and half-metallic properties under large interlayer distance changes. Studies of magnetic anisotropy show that the direction of hard axis for MoSi2N4/ScSi2N4 heterojunction is perpendicular to the 2D layer plane. The tunable properties of MoSi2N4/ScSi2N4 heterojunction provides promising exploration for novel 2D materials.

Local Orientation Transitions to a Lying Helix State in Negative Dielectric Anisotropy Cholesteric Liquid Crystal

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed from a planar Grandjean texture, with the helix axis perpendicular to the layer plane, to states with a lying helix, when the helix axis is parallel to the layer plane and perpendicular to the electrode stripes. It was found that the relaxation time of the induced state in the Grandjean zones, corresponding to two or more half-turns of the helix, significantly exceeded the relaxation time for the first Grandjean zone with one half-turn. An analysis of experimentally observed and numerically simulated textures shows that slow relaxation to the initial state in the second Grandjean zone, as well as in higher-order zones, is associated with the formation of local topologically equivalent states. In these states, the helix has a reduced integer number of helix half-turns throughout the layer thickness or unwound into the planar alignment state.

Epitaxy of GaSe Coupled to Graphene: From In Situ Band Engineering to Photon Sensing.

2D semiconductors can drive advances in quantum science and technologies. However, they should be free of any contamination; also, the crystallographic ordering and coupling of adjacent layers and their electronic properties should be well-controlled, tunable, and scalable. Here, these challenges are addressed by a new approach, which combines molecular beam epitaxy and in situ band engineering in ultra-high vacuum of semiconducting gallium selenide (GaSe) on graphene. In situ studies by electron diffraction, scanning probe microscopy, and angle-resolved photoelectron spectroscopy reveal that atomically-thin layers of GaSe align in the layer plane with the underlying lattice of graphene. The GaSe/graphene heterostructure, referred to as 2semgraphene, features a centrosymmetric (group symmetry D3d) polymorph of GaSe, a charge dipole at the GaSe/graphene interface, and a band structure tunable by the layer thickness. The newly-developed, scalable 2semgraphene is used in optical sensors that exploit the photoactive GaSe layer and the built-in potential at its interface with the graphene channel. This proof of concept has the potential for further advances and device architectures that exploit 2semgraphene as a functional building block.

Oscillatory excitation of Faraday waves on the interface of immiscible fluids in a slotted channel

Recent studies of the oscillatory dynamics of the interface between fluids in Hele–Shaw cells have revealed a new type of instability termed the “oscillatory Saffman instability” in the case of fluids with high-viscosity contrast. The present study is dedicated to the experimental investigation of the dynamics of the interface between low-viscosity fluids of different densities oscillating in a vertical narrow channel. It is discovered that as the amplitude of oscillations increases, a threshold excitation of parametric oscillations of the interface in the form of a standing wave is observed in the plane of the fluid layer. This phenomenon bears a resemblance to Faraday waves, but the dependence of the standing wave wavelength on the oscillation frequency does not align with the classical dispersion relation for low-viscosity fluids. The damping effect of viscous boundary layers near the cell walls and the out-of-plane curvature of the oscillating interface leads to a decrease in the natural frequency of oscillations. The experiments demonstrate a significant role of the dimensionless layer thickness. With its decrease (increase in the dimensionless out-of-plane interface curvature), the threshold oscillation acceleration rises in accordance with a power law. To the best of the authors' knowledge, this type of instability has been discovered and studied for the first time. Another important finding is the excitation of intense time-averaged vortical flows in the channel plane within the supercritical region. The physical mechanism underlying the excitation of the time-averaged vortices is clarified, and the dimensionless parameters that govern their intensity are identified.

Effect of surface alignment on electric-field-induced phase transitions in blue phases

This study investigates the critical electric field thresholds required for phase transitions in the blue phases of liquid crystals (BPs) confined within vertical field switching cells. BPs are attractive for electro-optical applications due to their polarization-independent response and fast switching times; however; challenges remain regarding their limited temperature stability and previously reported high operational voltages. We employ a combined approach of polarized optical microscopy and electrical impedance analysis to identify the electric field thresholds triggering BP transitions to focal conic domains in cells with and without planar polyimide alignment layers. We show that surface alignment layers stabilize the blue phases and allow for higher applied electric fields before transitioning into the focal conic state. This suggests the possibility of a wider operational voltage range in thinner cells with alignment layers. These findings significantly improve our understanding of BPs, addressing key challenges and paving the way for their integration into advanced photonic devices, based on the CMOS technology.

Microstructural Instability and Its Effects on Thermoelectric Properties of SnSe and Na-Doped SnSe.

Effects of thermal cycling on the microstructure and thermoelectric properties are studied for the undoped and Na-doped SnSe samples using X-ray computed tomography and property measurements. It is observed that thermal cycling causes significant cracks to develop, which decrease both the electrical and lattice thermal conductivities but do not affect the thermopower. The zT values are drastically reduced after the repeated heat treatment. It is important to account for density changes during cycling to obtain accurate values of the thermal conductivity. Even before thermal cycling, the spark-plasma sintered (SPS) samples have a significant number of microcracks. The orientation of cracks within the SPS pellets and their effect on the microstructure are influenced by the presence of a Na-rich impurity. The SnSe and Sn0.995Na0.005Se samples without the impurity develop cracks and exhibit grain growth parallel to the pellet surface, which is also the plane of the 2D SnSe layers. The Sn0.97Na0.03Se sample containing the impurity develops cracks that are orthogonal to the pellet surface. Such an orientation of cracks in Sn0.97Na0.03Se inhibits grain growth. All samples appear mechanically unstable after thermal cycling.

Experimental study on hydraulic fracture propagation behavior in heterogeneous shale formations

The study of fracture propagation in heterogeneous shale is a crucial prerequisite for the investigation of heterogeneous cluster and perforation parameters optimization. In this paper, we conduct a physical simulation fracturing experiment on heterogeneous shale to investigate the effects of various influencing factors, such as shale bedding, near-wellbore fractures, lithological changes, and the presence of fractures surrounding the perforation hole, on fracture propagation law and morphology. Our research demonstrates that during shale fracturing, shear dislocation typically occurs between layers, resulting in the separation of different layer planes. The main fracture primarily propagates through layers in a stepped manner. The presence of sandstone in heterogeneous shale significantly impedes fracturing fractures, causing significant distortion and deviation. As the scale of natural fractures increases, it tends to cause the fracturing fracture to twist and change direction. The natural fractures network can also lead to the distortion of fracturing fractures, albeit to a lesser extent than large-scale natural fractures. The presence of micro fractures parallel to the perforation axis surrounding the perforation hole enhances the ability of the main fracturing fractures to pass through natural fractures.

Influence of Rotation and Viscosity on Parallel Rolls of Electrically Conducting Fluid

Rayleigh–Bénard convection is a fundamental fluid dynamics phenomenon that significantly influences heat transfer in various natural and industrial processes, such as geophysical dynamics in the Earth’s liquid core and the performance of heat exchangers. Understanding the behavior of conductive fluids under the influence of heating, rotation, and magnetic fields is critical for improving thermal management systems. Utilizing the Boussinesq approximation, this study theoretically examines the nonlinear convection of a planar layer of conductive liquid that is heated from below and subjected to rotation about a vertical axis in the presence of a magnetic field. We focus on the onset of stationary convection as the temperature difference applied across the planar layer increases. Our theoretical approach investigates the formation of parallel rolls aligned with the magnetic field under free–free boundary conditions. To analyze the system of nonlinear equations, we expand the dependent variables in a series of orthogonal functions and express the coefficients of these functions as power series in a parameter ϵ. A solution for this nonlinear problem is derived through Fourier analysis of perturbations, extending to O(ϵ8), which allows for a detailed visualization of the parallel rolls. Graphical results are presented to explore the dependence of the Nusselt number on the Rayleigh number (R) and Ekman number (E). We observe that both the local Nusselt number and average Nusselt number increase as the Ekman number decreases. Furthermore, the flow appears to become more deformed as E decreases, suggesting an increased influence of external factors such as rotation. This deformation may enhance mixing within the fluid, thereby improving heat transfer between different regions.

The Improvement of Luminous Uniformity of Large-Area Organic Light-Emitting Diodes by Using Auxiliary Electrodes

The study developed a large emission area of flexible blue organic light-emitting diodes (BOLED) on a polyethylene terephthalate/ Indium tin oxide (PET/ITO) substrate using a polycyclic skeleton ν-DABNA Thermally Activated Delayed Fluorescence (TADF) material. Initially, a 1 × 1 cm2 blue OLED was fabricated to optimize the layer thickness. The blue OLED structure consisted of PET/ITO/HATCN/TAPC/UBH-21:ν-DABNA/TPBi/LiF/Al. However, as the emission area increased to 3.5 × 3.5 cm2, the current density decreased due to the resistance of PET/ITO, leading to luminance non-uniformity. To address this issue, auxiliary Au lines were added to the ITO anode to enhance current injection. Despite this, when the Au lines reached a thickness of 30 nm, average light emission was disrupted. To improve the luminescence characteristics of large-area PET/ITO OLEDs, a capping and planarization layer of PEDOT:PSS was applied. Grid uniformity revealed a significant increase in overall luminance uniformity from 74.1% to 87.4% with the addition of auxiliary Au lines. Further increases in grid line density slightly reduced uniformity but enhanced brightness, resulting in brighter, flexible, large-area blue OLED lighting panels.

Rationalizing the Influence of Small-Molecule Dopants on Guanine Crystal Morphology.

Many spectacular optical phenomena in animals are produced by reflective assemblies of guanine crystals. The crystals comprise planar H-bonded layers of π-stacked molecules with a high in-plane refractive index. By preferentially expressing the highly reflective π-stacked (100) crystal face and controlling its cross-sectional shape, organisms generate a diverse array of photonic superstructures. How is this precise control over crystal morphology achieved? Recently, it was found that biogenic guanine crystals are composites, containing high quantities of hypoxanthine and xanthine in a molecular alloy. Here, we crystallized guanine in the presence of these dopants and used computations to rationalize their influence on the crystal morphology and energy. Exceptional quantities of hypoxanthine are incorporated into kinetically favored solid solutions, indicating that fast crystallization kinetics underlies the heterogeneous compositions of biogenic guanine crystals. We find that weakening of H-bonding interactions by additive incorporation elongates guanine crystals along the stacking direction-the opposite morphology of biogenic crystals. However, by modulation of the strength of competing in-plane H-bonding interactions, additive incorporation strongly influences the cross-sectional shape of the crystals. Our results suggest that small-molecule H-bond disrupting additives may be simultaneously employed with π-stack blocking additives to generate reflective platelet crystal morphologies exhibited by organisms.

Controllable adjustment of Ta and Cu material removal rate in TSV tantalum-based barrier layer planarization process

Controllable adjustment of Ta and Cu material removal rate in TSV tantalum-based barrier layer planarization process

Obtaining in-situ reacted Fe–W–Ni–Cr–Cu high-entropy alloy within the interlayer of dissimilar Cf/SiC-GH3536 joint by designing non-high-entropy Cu–Ti–W composite filler

In aerospace applications, the development of high-entropy alloys (HEAs) filler is an effective strategy to obtain reliable Cf/SiC nozzles and GH3536 thrust chambers components. Considering the high costs and extended preparation times with HEA fillers, utilizing non-HEA fillers to generate HEAs within brazing seam offers significant advantages. This study successfully joined Cf/SiC with GH3536 using a non-HEA Cu–Ti–W composite filler that facilitated the in-situ formation of Fe–W–Ni–Cr–Cu HEA during the brazing process. Furthermore, the formation and accompanying martensite phase transformation were revealed. The microstructure characteristic of W reinforcements/HEA/Cu(s,s) was ultimately formed in the brazing seam. The atomic structure of the HEA, confirmed to be hexagonal close-packed, was elucidated using spherical aberration-corrected transmission electron microscopy. Additionally, a martensite phase transformation was observed in the HEA, involving two adjacent layers of (0 0 0 1) atomic planes that sheared and move a3 distance alon g [10–10] in opposite directions, resulting in the formation of M-HEA. The inclusion of HEA and M-HEA in the Cf/SiC-GH3536 joint, brazed with Cu–Ti–W composite filler, increased its shear strength to 84.8 MPa, which was 2.15 times higher than that of joints without the W reinforcements. This study offers new insights into the design of composite fillers and the application of HEAs.

Optically transparent coplanar wideband antenna for vehicular communication

SummaryThe presented state of the art is a novel coplanar optically transparent antenna designed to operate in extended GSM, L‐band, and UWB applications for vehicular communication. The presented radiator operates using a coplanar waveguide feed mechanism without a separate ground plane layer with a minimal conductive surface to enhance the transparency of the proposed antenna. The proposed antenna design has dimensions of 40 × 20 mm2, and a transparent material of soda–lime glass is used as a substrate with a dielectric constant of 7. The radiating element over the substrate is the conductive film fluorine‐doped tin oxide (FTO) with a sheet resistance of 7 Ω/sq. The operating frequency range of the designed antenna is from 0.86 to 14.45 GHz, which encloses the E‐GSM (900 MHz), L‐band (1–2 GHz), and UWB (3.1–10.6 GHz) frequencies. The peak gains at the operating frequencies are 1, 1.6, and 4.34 dBi, respectively. The designed antenna is fabricated and measured, and the performance metrics are plotted and compared. Since the transparent antenna is designed, the tendency of a substance to conduct light is measured as the optical transmittance, and it is calculated as 95% in the glass reference and 82% in the air reference.

Sulfur and Wavy-Stacking Boosted Superior Lithium Storage in 2D Covalent Organic Frameworks.

2D conjugated covalent organic frameworks (c-COFs) provide an attractive foundation as organic electrodes in energy storage devices, but their storage capability is long hindered by limited ion accessibility within densely π-π stacked interlayers. Herein, two kinds of 2D c-COFs based on dioxin and dithiine linkages are reported, which exhibit distinct in-plane configurations-fully planar and undulated layers. X-ray diffraction analysis reveals wavy square-planar networks in dithiine-bridged COF (COF-S), attributed to curved C─S─C bonds in the dithiine linkage, whereas dioxin-bridged COF (COF-O) features densely packed fully planar layers. Theoretical and experimental results elucidate that the undulated stacking within COF-S possesses an expanded layer distance of 3.8 Å and facilitates effective and rapid Li+ storage, yielding a superior specific capacity of 1305 mAh g-1 at 0.5 A g-1, surpassing that of COF-O (1180 mAh g-1 at 0.5 A g-1). COF-S also demonstrates an admirable cycle life with 80.4% capacity retention after 5000 cycles. As determined, self-expanded wavy-stacking geometry, S-enriched dithiine in COF-S enhances the accessibility and redox activity of Li storage, allowing each phthalocyanine core to store 12 Li+ compared to 8 Li+ in COF-O. These findings underscore the elements and stacking modes of 2D c-COFs, enabling tunable layer distance and modulation of accessible ions.

The Aspects of Dimensionality in the Analysis of Raman Spectra of 2D Materials

Two-dimensional crystals are a class of materials in which an individual layer is indefinitely extended in two dimensions. Each layer is the molecular unit in the crystalline lattice. The nature of interlayer/intermolecular interaction is poorly understood. However, it defines physical properties such as carrier mobility, thermal conductivity, photoluminescence, etc. The vibrational properties of 2D materials are described based on triperiodic space groups. However, the triperiodic space groups do not apply to the description of these structures. The 17 two-dimensional groups in triperiodic space groups do not allow the existence of a third dimension. Therefore, if structures are not planar, the approach is inappropriate. The way to describe such structures is using the diperiodic groups in three dimensions. The well-known 2D materials are graphite, graphene, chalcogenide of Ga, Mo, W, and other elements. The crystalline As2S3 belongs to a class of 2D materials. The unit cell contains two layers with ten atoms in each layer, and it is similar to a structure of metal chalcogenide (MoS(Se)2, WS(Se)2). A bond length of 2.24 A is within the layer, and 3.56 A is between the layers. This interlayer/intralayer bond length ratio (= 1.59) corresponds to a significant difference in bond strengths. Center-zone optical phonons in crystalline As2S3 have been investigated by Raman scattering in a wide temperature range for two polarizations in the layer plane (ac). The crystal's and individual layers' symmetry are different, defining different selection rules for optical phonons. According to the crystallographic data, crystal symmetry is monoclinic with 20 atoms in a unit cell and is P21/n (C2h 5). The axis b, perpendicular to the layers, is the only unique axis of the crystal. Therefore, all phonons in the ac plane should be indistinguishable. The layer symmetry is orthorhombic in the diperiodic space group in three dimensions, in which a, b, and c axes are axes of symmetry with a space group of Pnm21 (C2v 7). The intensity of Raman bands in the layer plane shows strong polarization dependence, indicating layer symmetry's dominance. Interlayer interaction is weak, and as a result, low-frequency Raman bands appear in the spectra. The position of these bands defines the strength of interlayer interaction. The data presented provides an understanding of the structural motives of 2D As2S3 and may predict the optical/electronic properties of similar 2D materials based on Raman spectra.

Polyphenol-Enabled 2D Nanopatch for Enhanced Nasal Mucoadhesion and Immune Activation.

The advancement of effective nasal mucoadhesive delivery faces challenges due to rapid mucociliary clearance (MCC). Conventional studies have employed mucoadhesive materials, mainly forming spherical nanoparticles, but these offer limited adhesion to the nasal mucosa. This study hypothesizes that a 2D nanoscale structure utilizing adhesive polyphenols can provide a superior strategy for countering MCC, aligning with the planar mucosal layers. We explore the use of tannic acid (TA), a polyphenolic molecule known for its adhesive properties and ability to form complexes with biomolecules. Our study introduces an unprecedented 2D nanopatch, assembled through the interaction of TA with green fluorescent protein (GFP), and cell-penetrating peptide (CPP). This 2D nanopatch demonstrates robust adhesion to nasal mucosa and significantly enhances immunoglobulin A secretions, suggesting its potential for enhancing nasal vaccine delivery. The promise of a polyphenol-enabled adhesive 2D nanopatch signifies a pivotal shift from conventional spherical nanoparticles, opening new pathways for delivery strategies through respiratory mucoadhesion.