Planar Units Research Articles

Uncovering the Mechanism of Thermally Activated Delayed Fluorescence in Coplanar Emitters Using Potential Energy Surface Analysis

Planarized emitters exhibiting thermally activated delayed fluorescence (TADF) have attracted attention due to their narrow emission spectra, improved photostability, and high quantum yields, but with large singlet-triplet energy gaps (ΔEST) and no heavy atoms, the origin of their TADF remains a subject of debate. Here we prepare two isomeric, coplanar donor-acceptor compounds, with HMAT-2PYM performing dual TADF and room-temperature phosphorescence but with HMAT-4PYM exhibiting only prompt fluorescence. Although conventional TADF design principles suggest that neither isomer should exhibit TADF, we reveal differences in the excited state potential energy surfaces that enable spin-flip processes in only one isomer. We also find that hydrogen bonding is absent between the planar units of these emitters, despite earlier claims of intramolecular hydrogen bonding in similar compounds. Overall, this work demonstrates that potential energy surface analysis is a practical strategy for designing coplanar TADF materials that might otherwise be overlooked by conventional TADF design metrics.

The Sobolev Jordan-Schönflies problem

We consider the planar unit disk D as the reference configuration and a Jordan domain Y as the deformed configuration, and study the problem of extending a given boundary homeomorphism φ:∂D→onto∂Y as a Sobolev homeomorphism of the complex plane. Investigating such a Sobolev variant of the classical Jordan-Schönflies theorem is motivated by the well-posedness of the related pure displacement variational questions in the theory of Nonlinear Elasticity (NE) and Geometric Function Theory (GFT). Clearly, the necessary condition for the boundary mapping φ to admit a W1,p-Sobolev homeomorphic extension is that it first admits a continuous W1,p-Sobolev extension. For an arbitrary target domain Y this, however, is not sufficient. Indeed, first for each p<∞ we construct a Jordan domain Y and a homeomorphism φ:∂D→onto∂Y which admits a continuous W1,p-extension but does not even admit a W1,1-homeomorphic extension. Second, for a quasidisk target Y and the whole range of p, we prove that a boundary homeomorphism φ:∂D→onto∂Y admits a Wloc1,p-homeomorphic extension to C if and only if it admits a W1,p-extension to the unit disk. Quasidisks have been a subject of intensive study in GFT. They do not allow for singularities on the boundary such as cusps. Third, for any power-type cusp target there is a boundary homeomorphism from the unit circle whose harmonic extension has finite Dirichlet energy but does not have a homeomorphic extension in W1,2(D,C). Surprisingly, the Dirichlet integral (p=2) plays a unique role for the Sobolev Jordan-Schönflies Problem in the case of cusp targets. Even more, fourth we prove that if the target Y has piecewise smooth boundary, p≠2 and φ:∂D→onto∂Y has a W1,p-Sobolev extension to D, then it admits a homeomorphic extension to C in Wloc1,p(C,C). Fifth, if in addition Y is quasiconvex, then the one-sided Sobolev Jordan-Schönflies problem has a solution when p=2. Indeed, we show that the harmonic extension of φ:∂D→onto∂Y has a finite Dirichlet integral if and only if φ admits a homeomorphic extension h:D‾→ontoY‾ with finite Dirichlet energy.

Conductive C3NS Monolayer with Superior Properties for K Ion Batteries.

K-ion batteries (KIBs) have been considered as appealing alternatives to Li ion batteries due to the high abundance of K, their high working voltages, and allowing the use of mature LIB technology. Thus far, anode materials that can meet the rigorous requirements of KIBs are still rather rare. Here, we have identified a desirable anode material, a metallic C3NS monolayer with high stability, a high storage capacity of 980 mAh/g, a low diffusion barrier of 0.24 eV, and a low open-circuit voltage of 0.36 V, through first-principles calculations. Metallic C3NSKn (n = 1-3) can ensure a high electron conductivity during the charge/discharge process. Valence electrons of the N atom in a triangular bipyramid configuration favor the formation of a planar edge-sharing hexagonal C4N2 unit and delocalized π bonding with C 2p electrons. The lone pair electrons of the S atom induce strong interactions with K atoms, facilitating storage capacity. These interesting properties make the C3NS monolayer a promising anode for KIBs.

Geometric design and optimization of scissor-type deployable structures

Geometric design is the essential first step to ensure transformation of a structure from an undeployed to a deployed state and vice-versa. Typically, this is achieved using motion criteria to prevent interference of parts. This paper describes the geometric design procedure of axisymmetric deployable structures made of planar angulated scissor units. The geometric design parameters are optimized not just using motion criteria but also structural performance measures. The first part of this paper discusses the refinement of geometric parameters, namely, shape equation, number of vertical layers, number of sectors in plan, and rise-to-span ratio, to ensure minimum change in span during deployment. Analysis results showed that more number of vertical layers, more sectors, and a lower rise-to-span ratio led to minimal changes in base radius during deployment. A finite element analysis of a simplified slice model was used to validate the results by comparing with the full three-dimensional model results. Genetic Algorithm was used to find the optimum number of vertical layers and sectors in plan based on structural performance. This paper presents results of concurrent optimization of layout, elevation, and member sizes of deployable domes to meet stiffness criteria and to reduce self-weight.

Dihydrophenazine‐Based Conjugated Microporous Polymer Cathodes with Enhanced Electronic and Ionic Conductivities for High‐Performance Aluminum Dual‐Ion Batteries

AbstractIt is fundamentally challenging for cathode materials to achieve long life, high capacity, and fast kinetics in rechargeable aluminum batteries, due to the strong electrostatic interaction between Al3+ and the host materials. Herein, the redox‐active dihydrophenazine (Pz) is coupled with pyrene (Py) or biphenyl (Ph) to develop two conjugated microporous polymers of PyPz and PhPz as AlCl4−‐hosting cathodes for aluminum dual‐ion batteries (ADIBs). It is revealed that the planar Py unit endows PyPz with an extended conjugated skeleton and a higher surface area than PhPz produced from the Ph unit with a twisted structure, thus leading to a higher redox activity for PyPz. Hence, the PyPz cathode delivers a much higher capacity of 231 mAh g−1 than PhPz (137 mAh g−1). Its porous structure and insolubility also ensure PyPz shows a superior rate performance and exceptional cyclability over 100 000 cycles. Meanwhile, the feature of fast kinetics for AlCl4− storage also allows PyPz to operate well at not only a low temperature (−30 °C) but also a high areal capacity of 2.53 mAh cm−2. These findings suggest that redox‐active conjugated polymers are promising advanced organic cathodes for sustainable ADIBs, where the electrochemical performance can be significantly enhanced by rational structural design.

Printable assemblies of perovskite nanocubes on meter-scale panel.

Hierarchical assemblies of functional nanoparticles can have applications exceeding those of individual constituents. Arranging components in a certain order, even at the atomic scale, can result in emergent effects. We demonstrate that printed atomic ordering is achieved in multiscale hierarchical structures, including nanoparticles, superlattices, and macroarrays. The CsPbBr3 perovskite nanocubes self-assemble into superlattices in ordered arrays controlled across 10 scales. These structures behave as single nanoparticles, with diffraction patterns similar to those of single crystals. The assemblies repeat as two-dimensional planar unit cells, forming crystalline superlattice arrays. The fluorescence intensity of these arrays is 5.2 times higher than those of random aggregate arrays. The multiscale coherent states can be printed on a meter-scale panel as a micropixel light-producing layer of primary-color photon emitters. These hierarchical assemblies can boost the performance of optoelectronic devices and enable the development of high-efficiency, directional quantum light sources.

Achieving Large Second Harmonic Generation Effects via Optimal Planar Alignment of Triangular Units

AbstractTrigonal planar units with large polarizability anisotropy and high physicochemical stability are ideal structural units for exploring nonlinear optical (NLO) materials. Integrating the merits of two types of triangular‐like moieties, a family of second‐order NLO‐active hybrid halides, MATX (X = Cl (1), Br (2), and I (3)), are achieved. MATX crystallizes in a nonpolar space group of 2c but exhibits the optimal spatial arrangement and superior NLO performance. The low coordination planar trigonal AgX3 units enable segregation in layers of the three‐winged propeller‐like Me3TPA units. All of the layers are packed in a perfect parallel fashion, making the functional materials exhibit superior NLO performances, including the phase matchable behavior with strong SHG responses (6.2/1, 6.5/2, and 7.6/3 times that of potassium dihydrogen phosphate), large birefringence (0.232/1, 0.252/2 and 0.260/3 at 1064 nm), high laser damage threshold, wide transparent window, and easiness of crystal growth. The first‐principles calculations reveal that the coexistence of strong linear and nonlinear optical properties are ascribed to the synergistic effect of the trigonal moieties. This study points out a useful path for the rational design of excellent NLO materials.

Directed energy deposition-arc of aluminum-alloy curved-generatrix-shell pyramid lattice structure

The curved-generatrix-shell pyramid lattice structure (CPLS) is an important thermal insulation and load-bearing component of hypersonic vehicles (Mach>5). Directed energy deposition-arc (DED-Arc) is an effective method for fabricating CPLSs. In this study, the characteristics of a CPLS and the unit cells of the CPLS were analyzed in detail. The CPLS consisted of row-lattice unit cells along the axis of the curved-generatrix shell and column-lattice unit cells along the circumference. The strut inclination angles and strut lengths of different rows of each unit cell were different, in contrast to the previously reported planar unit cells. Based on the characteristics of the CPLS and unit cell, the curved-generatrix shell surface slicing method was used to obtain high-accuracy curved-generatrix-surface unit-cell deposition path points, and the initial position correction, variable process parameter values, and secondary deposition were used to control the droplet deposition amount to achieve the same layer height compensation. This ensured high-precision forming of the lattice struts. In this study, the fabrication of a CPLS was the ultimate goal. Thus, an eight-axis collaborative DED-Arc system composed of a six-axis robot and a two-axis positioner was adopted. The flip and rotation angles of the positioner were regulated so that the deposition plane of the formed struts was always horizontal, avoiding the flow of liquid metal in the molten pool. Finally, a large-size aluminum-alloy CPLS consisting of 23 rows of unit cells and 33 columns of unit cells was successfully fabricated using DED-Arc on the aluminum-alloy curved-generatrix shell. The maximum error of the lattice strut forming angle was within ±0.4°, and the maximum error of the forming strut length was within ±0.26 mm.

Phenine design for nanocarbon molecules.

With the name "phenine" given to 1,3,5-trisubstituted benzene for a fundamental trigonal planar unit to weave nanometer-sized networks, a series of curved nanocarbon molecules have been designed and synthesized. Since the 6π-phenine units were amenable to modern biaryl coupling reactions mediated by transition metals, concise syntheses of >400π-nanocarbon molecules were readily achieved. In addition, the phenine design allowed for installing of heteroatoms and/or transition metals doped at specific positions of the large π-systems of the nanocarbon molecules. Fundamental tools were also developed to specify and describe the locations of defects/dopants, quantify pyramidalizations of trigonal panels and estimate molecular Gauss curvatures of the discrete surface. Unique features of phenine nanocarbons, such as stereoisomerism, entropy-driven molecular assembly and effects of dopants on electronic/magnetic characteristics, were revealed during the first half-decade of investigations.

Planar D-σ-A type thermally activated delayed fluorescence material with Intra- and intermolecular charge transfer characteristics

Intramolecular charge transfer (intra-CT) and intermolecular charge transfer (inter-CT) are two general molecular design strategies of thermally activated delayed fluorescence (TADF) materials for organic light-emitting diodes (OLEDs). Herein, a diphenylamine (DPA) donor and a 2,4-diphenyl-1,3,5-triazine (TRZ) acceptor are connected by two planar units, non-conjugated 9,9-dimethyl-9H-xanthene (XA) and conjugated dibenzo[b,d]furan (FR), to give D-σ-A type emitter DPA-XA-TRZ and D-π-A type emitter DPA-FR-TRZ. Coexistence of intra- and inter-CT is found for DPA-XA-TRZ and is readily tuned by various doping concentrations owing to the non-conjugated linkage. In contrast, DPA-FR-TRZ shows a dominant intra-CT characteristic due to the strong molecular conjugation. The planar molecular skeleton of DPA-XA-TRZ could not only enhance intramolecular electronic coupling, but also reduce steric hindrance and shorten intermolecular distance to enhance inter-CT process. A maximum external quantum efficiency (EQEmax) of 21.9 % is achieved for the OLED device based on DPA-XA-TRZ, which is 2.5 times higher than that of DPA-FR-TRZ (8.4 %). DPA-XA-TRZ can also be utilized as an assistant host to sensitize multiple resonance TADF emitter DMAc-BN, and an EQEmax of 31.7 % is realized owing to its dual CT processes and high reverse intersystem crossing rate (kRISC), which is significantly superior to the conventional mCBP host and mCBP:PO-T2T exciplex cohost.

A bio-inspired 3D metamaterials with chirality and anti-chirality topology fabricated by 4D printing

ABSTRACT Artificial architected metamaterials equipped with unique mechanical and physical properties that are naturally inaccessible can be obtained by rational design. In this work, the innovative three-dimensional (3D) chiral and anti-chiral metamaterials are developed referring to the face-rotating polyhedral (FRP) structure present in the virus. Through assembling planar triangular units into the regular octahedron cells, several typical forms of chiral and anti-chiral metamaterials can be obtained by different assembly methods. By changing the topology parameters, the Poisson’s ratio can be adjusted between [0, 2.8]. The metamaterials are fabricated by 3D printing utilizing shape memory polymer, and the mechanical properties are analyzed via Finite Element Analysis (FEA) and experiments, including Young’s modulus, Poisson’s ratio, and tension-twist coupling behavior. In addition, target metamaterial with specific local deformation behavior is obtained by programmatic calculations and distributions to meet special requirements or achieve unique applications. The shape memory property endows the mechanical metamaterials with more potential applications.

From Phosphate Fluoride to Fluorophosphate: Design of Novel Ultraviolet/Deep-Ultraviolet Nonlinear Optical Materials for BePO3F with Optical Property Enhancement.

Fluorine-containing compounds have stimulated the exploration of ultraviolet/deep-ultraviolet nonlinear optical (NLO) materials. Alkali/alkaline-earth metal phosphates are one of the important potential systems as NLO materials, while the common small birefringence limits the phase-matching (PM) ability in the ultraviolet/deep-ultraviolet region. Herein, by applying a "fluorination synergy-induced enhancement of optical property" strategy, novel structures of phosphate fluoride/fluorophosphate in BePO3F with good thermodynamic/dynamic stability and promising NLO-related properties are discovered via performing crystal structure prediction combined with first-principles calculations. BePO3F-I-VI exhibit relatively large birefringence of 0.025, 0.048, 0.049, 0.049, 0.059, and 0.063 at 1064 nm, respectively. Simultaneously, BePO3F-I (Pc) is a new thermodynamically stable phosphate fluoride which possesses a wide band gap (Eg = 8.03 eV), large second-harmonic generation (SHG) coefficient (d11 = 0.67 pm/V, 1.7 × KDP), and the shortest PM wavelength of 292 nm. Other five thermodynamically metastable noncentrosymmetric (NCS) BePO3F structures (II-VI) belong to fluorophosphates and exhibit deep-ultraviolet PM wavelengths of 187, 183, 186, 188, and 196 nm. It reveals that the aligned nonbonding O 2p orbitals of [BeO2F2] and [PO4] units lead to a large SHG coefficient in the phosphate fluoride BePO3F-I. For fluorophosphates (BePO3F-II-VI), the synergy of [BeO3] planar units and [PO3F] units induces relatively large birefringence. Our research results provide an idea for exploring novel high-performance NLO materials.

Computational Exploration of Functional Nanoscale Carbonaceous Materials

Background: The unique ability of carbon to form a wide variety of allotropic modifications has ushered in a new era in material science. Tuning the properties of these materials by functionalization is a must-have tool for their design customized for a specific practical use. The exponentially growing computational power available to researchers allows for the prediction and thorough understanding of the underlying physicochemical processes responsible for the practical properties of pristine and modified carbons using the methods of quantum chemistry. Method: This review focuses on the computational assessment of the influence of functionalization on the properties of carbons and enabling desired practical properties of the new materials. The first section of each part of this review focuses on graphene with nearly planar units built from sp2- carbons. The second section discusses patterns of sp2-carbons rolled up into curved 3D structures in a variety of ways (fullerenes). The overview of other types of carbonaceous materials, including those with a high abundance of sp3-carbons, including nanodiamonds, can be found in the third section of each manuscript’s part. Conclusion: The computational methods are especially critical for predicting electronic properties of materials such as the bandgap, conductivity, optical and photoelectronic properties, solubility, adsorptivity, the potential for catalysis, sensing, imaging, and biomedical applications. We expect that introduction of defects to carbonaceous materials as a type of their functionalization will be a point of growth in this area of computational research.

A novel low-frequency multi-bandgaps metaplate: Genetic algorithm based optimization and experimental validation

Metaplates, i.e. 2D extruded structures made by a periodic repetition of unit cells that exhibit a complete and wide 3D bandgap, are attracting increasing interest thanks to the variety of emerging applications. In this work, an innovative planar unit cell suitable for metaplates is proposed and optimized through a genetic algorithm, to achieve wide and low frequency bandgaps. Four objective functions are employed to show the potentiality of the proposed topology with respect to the state of the art. Metaplates obtained through the periodic repetition of the optimized unit cells are then simulated and experimentally tested. High performance metaplates, endowed e.g. with a nondimensional opening frequency of 0.0029 and bandgap width equal to 95%, are here obtained, thus opening the path to challenging applications also in the world of Micro-Electro-Mechanical Systems (MEMS).

Energy dissipation and shock isolation using novel metamaterials

Dissipating kinetic energy from shock and vibration is an urgent requirement for various applications in aerospace to mechanical engineering. This paper proposes a series of innovative metamaterials with planar and cylindrical patterns for elastic energy dissipation and shock isolation. The planar unit cell with two axes of reflectional symmetry mainly consists of two V-shaped regions, four identical right triangle regions, and narrow regions. The stereometric and cylindrical unit cells are obtained through rotating and convolving methods. The mechanics of energy dissipation and shock isolation are systematically investigated with finite element analysis (FEA), and experiments. Results show that various mechanical responses of unit cells are obtained through tailoring combined geometric parameters and additional boundary conditions, and the planar unit cell has stronger bistability than the cylindrical one. Then, the designed multilayers metamaterials exhibit considerable energy dissipation via the snap-through induced hysteric force-displacement behaviors, whose performances are influenced by geometric parameters and the number of layers. Lastly, the designed metamaterials could effectively suppress the acceleration responses via the snap-through behaviors induced by elastic instability. The shock response process and corresponding deformation mechanics are investigated experimentally and numerically. The designed metamaterials have potential in shock and vibration engineering.

Laser cutting assisted fabrication of assembled solid-state supercapacitors based on polypyrrole coated paper

In this work, a simple process has been demonstrated to fabricate solid-state paper-based supercapacitors. A highly conductive paper was prepared through coating polypyrrole on cellulose paper by interfacial polymerization. Among the PPy/paper samples prepared using different Py concentrations of 0.5%, 1.0%, 2.0% and 2.5%, PPy/paper (1.0% Py) displayed the highest specific capacitance (247.4F/g at 0.01 V s−1) and a good flexibility: the conductivity could retain near the original value even after being bent 450 times. Then, the PPy/paper (1.0% Py) electrodes with desired shapes were manufactured easily by laser cutting. A thin solid-state planar supercapacitor unit was fabricated by assembling the two PPy/paper electrodes and polyvinyl alcohol/H3PO4 electrolyte, and it exhibited a capacity of 51.6 mF and a high areal specific capacitance of 12.9 mF cm−2. Furthermore, 8 supercapacitor units were connected in series and parallel to obtain a thin supercapacitor array generating a higher output voltage and capacity. The supercapacitor array was integrated with a flexible printed circuit board, and it lighted up 3 light-emitting diodes, even under bending conditions. This method can be used to scale up the fabrication of flexible integrated paper-based energy storage devices for various portable and wearable electronics.

Yin–Yang Complementarity Strategy Achieving Giant Optical Anisotropy in a Metal-free Birefringent Material C(NH2)3(HC4O4)

The Yin–Yang complementarity strategy was first proposed to successfully develop a superior metal-free birefringent material C(NH2)3(HC4O4), which was fabricated by two kinds of planar π-conjugated units containing triangle [C(NH2)3]+ cations and square [HC4O4]− anions. C(NH2)3(HC4O4) features a giant birefringence (0.313@546 nm), which is significantly enhanced compared to the commercially available birefringent materials.

Stimulus responsive luminescence and application of rotor type 1,1′-([2,2′-bithiophene]-3,3′-diyl)bis(ethan-1-one) and 3′-acetyl-[2,2′-bithiophene]-3-carbaldehyde as molecular rotors

Two dithiophene aldehyde/ketone derivatives are designed as luminescence molecular rotors, i.e., 1,1′-([2,2′-bithiophene]-3,3′-diyl)bis(ethan-1-one) (BTBE) and 3′-acetyl-[2,2′-bithiophene]-3-carbaldehyde (BTAC). Their absorption and luminescence properties, as well as the stimulus responsive luminescence characteristics of water spikes are studied in detail. In order to further explore relationship of luminescence and molecular structure, three reference compounds are also synthesized, named 1-(2-methylthiophen-3-yl)ethanone (MTE), 2-methylthiophene-3-carbaldehyde (MTC) and 4H-cyclohepta[1,2-b:7,6-b’]dithiophen-4-one (CDTO). BTBE and BTAC have two obvious absorption bands in the short wavelength region with peak wavelengths of about 212 nm and 260 nm, respectively, while there is a weak trailing type absorption band in the range of about 300–400 nm. Their fluorescence spectra show two luminescence bands in the range of 280–350 nm and 400–600 nm, respectively, and the latter is stronger. Compared with the absorption and luminescence spectra of the reference compounds, it is determined that two absorption bands of BTBE and BTAC in shorter wavelength region are derived from the single thiophene ring carbonyl planar unit, while the absorption band in longer region are derived from the integrated structure of dithiophene carbonyl. The fluorescence bands with peaks of about 300 nm and 470 nm originate respectively from the localized F-C vertical excited states (LE), i.e., the excited state from single planar thienyl-carbonyl unit, and integrated excited state (IE), i.e., the excited state from integrated di-thienyl-carbonyl rings linked covalently with less dihedral angle and greater degree of conjugation at excited state. The crystal structure data show that two thiophene rings possess larger dihedral angles in crystal states, 86.9° for BTBE and 60.8° for BTAC, respectively. However, theoretical calculation results prove the conformational stabilization energy changes little, less than 1.5 kcal/mol, as dihedral angle changes from 50° to 100°. Hydrogen bonding is sufficient to overcome the energy required for this conformational change. Therefore, both BTBE and BTAC can produce water stimulation response luminescence behavior. This stimulating response behavior of BTBE and BTAC can be applied to the preparation of water writable film materials.

Numerical simulation and analysis of the thermal stresses of a planar solid oxide electrolysis cell

ABSTRACT Hydrogen production using solid oxide electrolysis cells (SOECs) is a highly efficient and low-carbon pathway to generate high purity hydrogen. However, high working temperatures may result in high thermal stress due to a mismatch in the coefficient of thermal expansion (CTE) between components with a nonuniform temperature distribution. Serious stress concentration may lead to structural failure of the SOEC stack. Hence, this work investigated the thermal stress of SOECs through a three-dimensional planar SOEC unit model. A stress analysis method was proposed via a multi-physics coupling model of SOECs using Comsol Multiphysics software. The impacts of voltage, flow direction, water mole fraction, and operating pressure on the thermal stress were evaluated. Numerical results show that the highest maximum principal stress is located in the electrolyte in the SOEC unit. Raising the water mole fraction and the CTE of the electrolyte could reduce the thermal stress if the voltage is below the thermoneutral voltage.

Boron Incorporation in Silicate Melt: Pressure-induced Coordination Changes and Implications for B Isotope Fractionation

Ab initio molecular dynamics simulations have been employed to investigate the nature of boron incorporation in a haplobasalt melt at pressures up to 8 GPa. At ambient pressure, boron is predominantly incorporated as trigonal planar BO3 units. With increasing pressure, the proportion of tetrahedral BO4 increases markedly in parallel with increases in the coordination of other cations in silicate liquids. In contrast to studies of high-pressure boron-rich silicate glasses and liquids where boron units are polymerized, simulations of low B-concentration liquid here indicate that boron does not adopt a significant role as a network-forming cation. Marked changes in the proportion of BO4 in silicate melt at even moderate pressures (from 5 to 20%, over the pressure range 0–3 GPa) imply that pressure may significantly affect the extent of melt/fluid and melt/crystal boron isotope fractionation. This pressure-effect should be considered when using boron isotope data to elucidate processes occurring within the mantle.