2D Honeycomb Research Articles

HKUST-1 in-situ loaded ultrastable covalently crosslinked agarose aerogel with solvothermal for highly efficient removal of methylene blue.

A new HKUST-1@covalently crosslinked agarose aerogel (HKUST-1@CCAGA) was synthesized for the highly effective elimination of Methylene Blue (MB). Firstly, the covalently crosslinked agarose aerogel (CCAGA) was obtained by hydrothermal crosslinking reaction with epichlorohydrin (ECH) as crosslinker, which remained stabilized under hydrothermal and solvothermal conditions. Then, HKUST-1 was made to bind to CCAGA by in situ solvothermal assays, and the HKUST-1 loading rate reached 47.4% based on thermogravimetric data and calculated using the cross over method. Meanwhile, the SEM exhibited the complete 3D honeycomb structure of CCAGA, and HKUST-1 particles uniformly distributed on its layers. Additionally, the specific surface area of HKUST-1@CCAGA can reached 648.59m2·g-1. The HKUST-1@CCAGA composite was utilized for MB removal, achieving a high adsorption capacity of 424.30mg·g-1 at pH8. The adsorption of MB was also maintained at 80% after 5cycles of the experiment. The composite aerogel exhibits good recyclability and has excellent adsorption capacity.

Graded metastructure design for linearly auxetic deformation under tension: From 2D honeycombs to 3D truncated cones

Mechanical metamaterials exhibit special properties that cannot be realized in traditional materials. To enable a metamaterial with a sequential Poisson’s ratio and controllable expansion, a 2D-graded hybrid re-entrant honeycomb is designed in this work by coupling graded re-entrant unit cells with negative and positive Poisson’s ratios. The correlation between Poisson’s ratio and structural location under tension is studied by finite element analysis and experiments. The influence of microstructural parameters, including base angle, height ratio, and internal angle, on the relationship between the Poisson’s ratio and structural location is systematically analyzed. The theoretical analysis shows that the 2D-graded hybrid metastructures exhibit auxetic behavior with a linearly declined Poisson’s ratio along the tensile direction due to the introduction of a height ratio, resulting in gradual expansion and elongation. Furthermore, adjusting the variation of internal angles at a small height ratio can enhance the negative Poisson’s ratio of the 2D-graded hybrid re-entrant honeycomb. Finally, a 3D-graded conical metastructure exhibiting linear auxeticity is constructed based on the 2D-graded lattice. Considering their designed linearity of deformation under tension, the 2D- and 3D-graded metastructures can facilitate the design of conical profiles for an extendable rocket nozzle and other deployable devices.

Emerging Anomalous Hall Effect in (111)‐Oriented Artificial Iridate Honeycomb Lattices

AbstractComplex Ir oxides provide a promising platform for investigating cooperativity and competition between Mott physics and spin‐orbit coupling in condensed matter physics. These materials have the potential to reveal intriguing phases, such as topological phases and the Kitaev spin liquid state, an exactly solvable S = 1/2 spin model describing Ir4+ ions on a 2D honeycomb lattice. However, experimental confirmation of such phases in iridate films has been hindered by the difficulty of preparing (111)‐oriented samples of the perovskite phase. Herein, by constructing SrIrO3/SrTiO3 superlattices on SrTiO3 (111) substrates, (111)‐oriented perovskite phase SrIrO3 films are achieved with the unprecedentedly large thickness of 6 unit cells. Electrical and magnetic characterizations reveal that these films exhibit anomalous Hall insulating behavior, significant charge fluctuations, and long‐range antiferromagnetic order. Moreover, these properties can be tuned by varying the thickness of the SrIrO₃ layer. These emergent phenomena underscore the complex interactions among spin‐orbit coupling, electron–electron correlations, and crystal structure in (111)‐oriented artificial iridate honeycomb lattices. Further, spin fractionalization and topological quantum spin liquid may be achieved by tuning the spin–orbit coupling and crystal field intensity from interface engineering.

Effective elastic properties of 3D lattice materials with intrinsic stresses: Bottom-up spectral characterization and constitutive programming

Analytical investigations to characterize the effective mechanical properties of lattice materials allow an in-depth exploration of the parameter space efficiently following an insightful, yet elegant framework. 2D lattice materials, which have been extensively dealt with in the literature following analytical as well as numerical and experimental approaches, have limitations concerning multi-directional stiffness and Poisson's ratio tunability. The primary objective of this paper is to develop mechanics-based formulations for a more complex analysis of 3D lattices, leading to a physically insightful analytical approach capable of accounting the beam-level mechanics of pre-existing intrinsic stresses along with their interaction with 3D unit cell architecture. We have investigated the in-plane and out-of-plane effective elastic properties to portray the physics behind the deformation of 3D lattices under externally applied far-field normal and shear stresses. The considered effect of beam-level intrinsic stresses therein can be regarded as a consequence of inevitable temperature variation, pre-stress during fabrication, inelastic and non-uniform deformation, manufacturing irregularities etc. Such effects can notably impact the effective elastic properties of lattice materials, quantifying which for 3D honeycombs is the central focus of this work. Further, from the material innovation viewpoint, the intrinsic stresses can be deliberately introduced to expand the microstructural design space for effective elastic property modulation of 3D lattices. This will lead to programming of effective properties as a function of intrinsic stresses without altering the microstructural geometry and lattice density. We have proposed a generic spectral framework of analyzing 3D lattices analytically, wherein the beam-level stiffness matrix including the effect of bending, axial, shear and twisting deformations along with intrinsic stresses can be coupled with the unit cell mechanics for obtaining the effective elastic properties.

Lattice Structures-Mechanical Description with Respect to Additive Manufacturing.

Lattice structures, characterized by their repetitive, interlocking patterns, provide an efficient balance of strength, flexibility, and reduced weight, making them essential in fields such as aerospace and automotive engineering. These structures use minimal material while effectively distributing stress, providing high resilience, energy absorption, and impact resistance. Composed of unit cells, lattice structures are highly customizable, from simple 2D honeycomb designs to complex 3D TPMS forms, and they adapt well to additive manufacturing, which minimizes material waste and production costs. In compression tests, lattice structures maintain stiffness even when filled with powder, suggesting minimal effect from the filler material. This paper shows the principles of creating finite element simulations with 3D-printed specimens and with usage of the lattice structure. The comparing of simulation and real testing is also shown in this research. The efficiency in material and energy use underscores the ecological and economic benefits of lattice-based designs, positioning them as a sustainable choice across multiple industries. This research analyzes three selected structures-solid material, pure latices structure, and boxed lattice structure with internal powder. The experimental findings reveal that the simulation error is less than 8% compared to the real measurement. This error is caused by the simplified material model, which is considering the isotropic behavior of the used material PA12GB (not the anisotropic model). The used and analyzed production method was multi jet fusion.

Pair-Density-Wave Superconductivity: A Microscopic Model on the 2D Honeycomb Lattice.

Pair-density wave (PDW) is a long-sought exotic state with oscillating superconducting order without external magnetic field. So far it has been rare in establishing a 2D microscopic model with PDW long-range order in its ground state. Here, we propose to study PDW superconductivity in a minimal model of spinless fermions (or spin-polarized electrons) on the honeycomb lattice with nearest-neighbor and next-nearest-neighbor interaction V_{1} and V_{2}, respectively. By performing a state-of-the-art density-matrix renormalization group study of this t-V_{1}-V_{2} model at finite doping on six-leg and eight-leg honeycomb cylinders, we show that the ground state exhibits PDW ordering (namely quasi-long-range order with a divergent PDW susceptibility). Remarkably this PDW state persists on the wider cylinder with 2D-like Fermi surfaces. To the best of our knowledge, this is probably the first controlled numerical evidence of PDW in systems with 2D-like Fermi surfaces.

Effect of Three-Dimensional auxetic honeycomb core on behavior of sound transmission loss in shallow sandwich cylindrical shell

The primary objective of this research is to examine the sound transmission loss (STL) in a shallow sandwich cylindrical shell featuring a 3D auxetic honeycomb core. Initially, the 3D elasticity theory was employed by applying the state vector method and extracting both local and global transfer matrices to calculate STL relations for the cylindrical shell, including the auxetic honeycomb core. Subsequently, boundary conditions were applied to calculate the unknowns, eventually leading to a relationship for calculating STL within the structure. The derived equations were numerically solved using MATLAB software. The validity of the results obtained using this method was examined by comparing them with the findings of other researchers. Moreover, a comparison was conducted involving a large ratio of the curvature radius to thickness, considering both the auxetic honeycomb core and aluminum with equal mass. The results demonstrate a significant increase in STL when utilizing this auxetic honeycomb core compared to a material with the same mass. Specifically, at a frequency of 2 Hz, a significant enhancement of about 29.44 % in STL is observed when increasing the core thickness from 10.39 mm to 20.39 mm. Furthermore, STL results have been obtained for various thicknesses, radius of curvature, and incident angles.

Equilibrium Moisture Mediated Esterification Reaction to Achieve Over 100% Lignocellulosic Nanofibrils Yield.

Lignocellulosic nanofibrils (LCNFs) isolation is recognized as an efficient strategy for maximizing biomass utilization. Nevertheless, achieving a 100% yield presents a formidable challenge. Here, an esterification strategy mediated by the equilibrium moisture in biomass is proposed for LCNFs preparation without the use of catalysts, resulting in a yield exceeding 100%. Different from anhydrous chemical thermomechanical pulp (CTMP0%), the presence of moisture (moisture content of 7wt%, denoted as CTMP7%) introduces a notably distinct process for the pretreatment of CTMP, comprising the initial disintegration and the post-esterification steps. The maleic acid, generated through maleic anhydride (MA) hydrolysis, degrades the recalcitrant lignin-carbohydrate complex (LCC) structures, resulting in esterified CTMP7% (E-CTMP7%). The highly grafted esters compensate for the mass loss resulting from the partial removal of hydrolyzed lignin and hemicellulose, ensuring a high yield. Following microfluidization, favorable LCNF7% with a high yield (114.4 ± 3.0%) and a high charge content (1.74 ± 0.09mmolg-1) can be easily produced, surpassing most previous records for LCNFs. Additionally, LCNF7% presented highly processability for filaments, films, and 3D honeycomb structures preparation. These findings provide valuable insights and guidance for achieving a high yield in the isolation of LCNFs from biomass through the mediation of equilibrium moisture.

Unraveling the enhanced sodium-storage mechanism in a strongly bonded 2D honeycomb borophene/boron phosphide heterostructure

The growing modern demand for battery capacity is driving the development of high-capacity metal-ion battery anodes for future energy storage. Two-dimensional (2D) material-based heterostructures have shown advantages as alternative anodes due to their enhanced adsorption capacity. The lightweight nature of honeycomb borophene (HB) is beneficial for serving as a high-capacity anode but is constrained by structural instability arising from electron deficiency. In this study, using first-principles calculations, we propose a HB/boron phosphide (BP) heterostructure as an anode for both lithium-ion batteries and sodium-ion batteries (SIBs). The heterostructure engineering not only stabilizes the HB structure but also leads to a bonding heterostructure instead of common van der Walls type. The HB/BP demonstrates robust structural stability and reversibility when multiple ions are stored. In addition, the HB/BP offers stable storage sites and low diffusion barriers for lithium (0.31 eV) and sodium (0.28 eV), indicating rapid charging–discharging performance. Notably, the predicted maximum sodium storage capacity reaches 2402 mAh/g, surpassing that of the constituent monolayers and most 2D heterostructures. The underlying mechanism for high storage capacity is elucidated through detailed charge image model analysis, offering atomistic-scale insights for constructing high-capacity anodes. All results suggest that the presented HB/BP is a promising anode candidate for SIBs and opens an avenue for stabilizing HB in energy storage.

Carbon-intercalated halloysite-based aerogel efficiently encapsulating phase change materials with excellent photothermal conversion and energy storage

Latent heat storage systems based on organic phase change materials (PCMs) are considered to be an efficient solar energy utilization strategy, but leakage vulnerability and insensitivity to sunlight of PCMs limit their further application in energy storage. In this work, a new hierarchical porous aerogel was constructed with the carbon intercalated halloysite nanotubes (CHNTs) as the assembly units for PCMs encapsulation to improve the load weight, stability and sunlight absorption. The CHNTs were first successfully synthesized through intercalation and carbonization, with the aim of increasing their specific surface area and sunlight absorption.Subsequently, the CHNTs/polyvinyl alcohol (PVA) aerogels with 3D honeycomb structure were prepared by self-assembly using a freeze-drying method, which can significantly promote the encapsulation ratio of lauric acid (LA) in the pores of both aerogels and CHNTs. The CHNTs can not only improve compressive strength of the aerogels and shape stability of the composite PCMs, but also enhance light absorption ability of the composites compared to pristine HNTs. As a support material, CHNTs aerogel (CHNP) loaded more than 92 wt% PCM (LA@CHNP) and exhibited an extremely high latent heat capacity (170.9 J/g). The LA@CHNP had good structural and thermal stability in 300 cycles without visible leakage. Besides, solar energy absorption increased from 43 % to 98 %, and the solar-to-thermal energy conversion efficiency increased to 95.88 %, which could be attributed to 3D porousness and carbon nanolayers of the CHNTs. We have successfully synthesized an eco-friendly and facile composite LA@CHNP, which will contribute to the design of advanced composites with excellent solar energy storage properties, and provide a new direction for the application of carbonized materials.

Light-element and purely charge-based topological materials

We examine a class of Hamiltonians characterized by interatomic, interorbital even-odd parity hybridization as a model for a family of topological insulators without the need for spin-orbit coupling. Non-trivial properties of these materials are exemplified by studying the topologically-protected edge states ofs-phybridized alkali and alkaline earth atoms in one and two-dimensional lattices. In 1D the topological features are analogous to the canonical Su-Schrieffer-Heeger model but, remarkably, occur in the absence of dimerization. Alkaline earth chains, with Be standing out due to its gap size and near particle-hole symmetry, are of particular experimental interest since their Fermi energy without doping lies directly at the level of topological edge states. Similar physics is demonstrated to occur in a 2D honeycomb lattice system ofs-pbonded atoms, where dispersive edge states emerge. Lighter elements are predicted using this model to host topological states in contrast to spin-orbit coupling-induced band inversion favoring heavier atoms.

Hazardous CO, NO, NH3 gases over boron and beryllium doped α-CN monolayers: A first principles study for sensing and removal applications

The exploration of two-dimensional (2D) honeycomb layered structure (HLS) has garnered significant attention due to their multifunctional properties, with diverse applications emerging in various fields. Motivated by the challenges posed by hazardous gases such as CO, NO, NH3 and inspired by the unique properties of 2D HLS this first principles study digs into the structural, electronic, and sensing properties of Boron and Beryllium doped α-CN monolayers. Rendering the structural and electronic variations induced by B and Be doping, our analysis reveals distinct functionalities for α-CN monolayers. Boron doping at the C-site exhibits promise for NO and NH3 sensing (with 73 % and 77 % increment in adsorption energies), while B-doping at the N-site enhances suitability for gas removal applications. Similarly, Be doping demonstrates effectiveness in gas removal across both C and N sites. Notably, the ultra-fast response (2.31 × 10−8 s) observed for NO adsorption over B-doped α-CN highlights its potential as a rapid sensor. Additionally, work function analysis suggests the suitability of B-doped α-CN for φ-type sensing in NH3 adsorption. These findings underscore the applicability of doped α-CN monolayers in gas sensing mechanisms.

Realization of Honeycomb Tellurene with Topological Edge States.

The two-dimensional (2D) honeycomb lattice has attracted intensive research interest due to the appearance of Dirac-type band structures as the consequence of two sublattices in the honeycomb structure. Introducing strong spin-orbit coupling (SOC) leads to a gap opening at the Dirac point, transforming the honeycomb lattice into a 2D topological insulator as a platform for the quantum spin Hall effect (QSHE). In this work, we realize a 2D honeycomb-structured film with tellurium, the heaviest nonradioactive element in Group VI, namely, tellurene, via molecular beam epitaxy. We revealed the gap opening of 160 meV at the Dirac point due to the strong SOC in the honeycomb-structured tellurene by angle-resolved photoemission spectroscopy. The topological edge states of tellurene are detected via scanning tunneling microscopy/spectroscopy. These results demonstrate that tellurene is a novel 2D honeycomb lattice with strong SOC, and they unambiguously prove that tellurene is a promising candidate for a room-temperature QSHE system.

Cover Picture: Exfoliatable Layered 2D Honeycomb Crystals of Host‐guest Complexes Networked by CH‐π Hydrogen Bonds (Angew. Chem. Int. Ed. 34/2024)

Cover Picture: Exfoliatable Layered 2D Honeycomb Crystals of Host‐guest Complexes Networked by CH‐π Hydrogen Bonds (Angew. Chem. Int. Ed. 34/2024)

Titelbild: Exfoliatable Layered 2D Honeycomb Crystals of Host‐guest Complexes Networked by CH‐π Hydrogen Bonds (Angew. Chem. 34/2024)

Titelbild: Exfoliatable Layered 2D Honeycomb Crystals of Host‐guest Complexes Networked by CH‐π Hydrogen Bonds (Angew. Chem. 34/2024)

Exfoliatable Layered 2D Honeycomb Crystals of Host‐guest Complexes Networked by CH‐π Hydrogen Bonds

AbstractStudies of graphene show that robust chemical bonds such as covalent bonds with trigonal‐planar atoms afford layered atomic 2D crystals possessing unique properties. Although layered molecular crystals are of interest to diversify elements and structures of 2D materials, the structural diversity of molecules as well as weak intermolecular interactions inevitably makes the design to be one‐off and individual. We herein report a versatile method to assemble layered molecular crystals. By developing a D3‐symmetry host at vertices to form a honeycomb layer, a diverse range of layered 2D host–guest crystals were obtained. Substituents on the host, elements/structures of the guest, the stereochemistry of the host and types of intercalants were diversified, which should allow for 6×32×3×2 combinations for structural diversification.

Exfoliatable Layered 2D Honeycomb Crystals of Host-guest Complexes Networked by CH-π Hydrogen Bonds.

Studies of graphene show that robust chemical bonds such as covalent bonds with trigonal-planar atoms afford layered atomic 2D crystals possessing unique properties. Although layered molecular crystals are of interest to diversify elements and structures of 2D materials, the structural diversity of molecules as well as weak intermolecular interactions inevitably makes the design to be one-off and individual. We herein report a versatile method to assemble layered molecular crystals. By developing a D3-symmetry host at vertices to form a honeycomb layer, a diverse range of layered 2D host-guest crystals were obtained. Substituents on the host, elements/structures of the guest, the stereochemistry of the host and types of intercalants were diversified, which should allow for 6×32×3×2 combinations for structural diversification.

Redox-active “Structural Pillar” molecular doping strategy towards High-Performance polyaniline-based flexible supercapacitors

To coordinate flexibility to electrodes without sacrificing their electrochemical properties is critical for the development of wearable supercapacitors (SCs). Polyaniline (PANI) is well-known pseudocapacitive electrode material due to its high conductivity and different oxidation states upon switchable structures. However, its rigid conjugated backbone and structural instability caused by repeated doping/de-doping during cycling severely impede its utilization in flexible SCs. Herein, we deploy a directional freezing and redox-active “structural pillar” molecular doping strategy to boost PANI-based flexible SCs with high performance. The directional freezing strategy constructs an interconnected 3D honeycomb hydrogel structure with PANI nanofibers, which guarantees fast ion diffusion and electron transport and meanwhile exposes abundant active sites. The large-sized dopant 2-amino-4-bromoanthraquinone-2-sulfonic acid sodium (AQNS) is used as the structural pillar to alleviate the structural instability of PANI during cycling and provides additional pseudocapacitance arising from its redox active quinone groups. Moreover, the negatively charged −SO3− on AQNS can further interact with H+ in the electrolyte to act as an internal proton reservoir, assisting the protonation of –NH- and −N = in PANI to facilitate its charge storage process. Consequently, the PANI-AQNS electrode achieves a high specific capacitance of 578 F g−1 at 1 A g−1 and its symmetric SCs exhibit a specific capacitance of 199 F g−1 at 0.5 A g−1 with an energy density of 13.61 W h kg−1 at a power density of 175 W kg−1. Upon 2000 cycles of dynamic deformations, the SCs can still maintain above 90 % of the initial capacitance, verifying their excellent flexibility-relevant property.

Nano-silicon embedded in 3D honeycomb carbon frameworks as a high-performance lithium-ion-battery anode

The fabrication of three-dimensional (3D) honeycomb carbon frameworks, incorporating embedded silicon (Si) nanoparticles (NPs), is successfully achieved through a facile method involving mixing, carbonization, and acid pickling. The as-prepared Si@PVPC composites exhibit excellent electrochemical performances due to reasons as follows. (1) Honeycomb channels supply enough space to accommodate the expansion of Si NPs and so structural integrity of 3D honeycomb carbon frameworks are maintained during lithiation/delithiation processes. (2) Honeycomb channels offers fast transfer paths for Li-ion diffusion. (3) 3D carbon frameworks afford reliable and stable electric contact points. As a result, Si@PVPC electrodes show a capacity of 1294.3 mAh g−1 at 2 A g−1 after 1400 cycles with a capacity retention of 85.5 %. Even at an ultrahigh current of 16 A g−1, Si@PVPC electrodes still show a capacity of 619.6 mAh g−1.

An Exploration of the Phonon Frequency Spectrum and Born–von Karman Periodic Boundary Conditions in 1D and 2D Lattice Systems Using a Computational Approach

Periodic boundary conditions (PBCs) are a pivotal concept in the treatment of ideal lattices of infinite extent as a finite lattice. Most undergraduate texts that delve into the analytical treatment of lattice dynamics solve the problem in the reciprocal space with an implicit assumption of PBCs. While the traditional approach centered in the reciprocal or [Formula: see text]-space is elegant for simple one-dimensional lattice structures, the method becomes mathematically cumbersome for more complex lattices with real-world applications, such as a honeycomb lattice involving a [Formula: see text] secular determinant. In this work, we have explored the solution of lattice dynamics in direct space numerically, by constructing unit cells through an explicit implementation of Born–von Karman PBCs and solving the lattice dynamical equations in the displacement–time domain using the fourth-order Runge–Kutta algorithm. The Fast Fourier Transform technique is then used to obtain the phonon frequency spectrum corresponding to the computed instantaneous displacements. The fidelity of the model is validated by the agreement of the computational results obtained for the phonon spectrum at high symmetry points in the Brillouin zone with the analytical values for the given problem. Initially, the dynamics and the phonon spectrum are explored for monatomic and diatomic linear lattices which serve to act as introductory cases for the approach before investigating the 2D monatomic square and honeycomb lattices using the nearest and next-nearest neighbor approximations. A short-range force constant model employing the central forces and angular forces is used for the monatomic square lattice to account for the interatomic interactions. Our computational approach is expected to be physically more intuitive for a student for visualizing the periodicity of a given lattice and understanding its related dynamics. The approach demonstrates the usage of Born–von Karman PBCs in constructing a unit cell that effectively captures the dynamics of a lattice system, complementing the traditional secular determinant formalism. The work also illustrates an instance of how the computer programming can be used as a tool to empower the students to explore abstract concepts in physics. A honing of programming and computational skills of students enables them to interact with dynamic models in physics and gain deeper insight into the real-world applications of physics principles. Target group of this work is the students and educators at undergraduate level who seek a thorough and didactic comprehension of lattice dynamics.