Graphene Honeycomb Research Articles

Free vibrational mode shapes and frequencies of sandwich folded plates standing on folded foundation and structured by auxetic honeycomb core and FG-GPLRC coating layers

In this article, for the first time, the free vibration and modal shapes of sandwich folded plate with honeycomb core are studied. The current article investigates the free vibrational mode shapes and frequencies of sandwich folded plate made of auxetic honeycomb core and graphene platelet-reinforced functionally graded composite (FG-GPLRC) coating layers which standing on the normal-shear folded supports. The structures are supported by normal-shear folded supports. The negative Poisson’s ratio exhibited by honeycomb materials results in distinct physical and mechanical properties, profoundly impacting the behavior of structures constructed from this material. While structures with basic shapes like rectangular, circular, and spherical configurations find limited applications across various industries, the versatility of folded structures makes them highly suitable for a wide range of industrial applications, given their more complex geometries. Dynamic equations are formulated within the framework of the first-order shear deformation theory (FSDT) for each flat section of the folded plate. The continuous equality conditions for displacements, rotations, and stresses at the junction edges of the two flat sections are rigorously satisfied. To effectively solve these equations, a robust numerical technique known as the generalized differential quadrature method (GDQM) is employed specifically tailored for the 2D analysis of folded plates. Furthermore, the study investigates the influence of various parameters, including material properties and geometry, on the frequencies and mode shapes of the folded structures, shedding light on the intricate interplay between these factors in shaping the dynamic response of the structures.

Graphene-based Nanomaterials As Catalysts for the Synthesis of Medicinally Privileged Heterocycles: Importance and Outlook

: Catalysis is an integral part of sustainable and green chemical processes. During the last two decades, the wonder 2D carbon material with honeycomb structure, graphene, and other functionalized graphenes have emerged as extremely versatile and robust nanomaterials in heterogeneous catalysis. The incredible catalytic efficacy of such carbon nanomaterials relies on their unique physicochemical properties, including large surface area, diverse catalytic active sites, multiple chemical functionalities, tunable electron density, synergistic effect, etc., making them noteworthy as metal-free catalysts and catalytic supports. : The article presents an overview of the catalytic applications of various graphene-based nanomaterials (GBNs), either metal-free or embedded with metal/metal oxide NPs, in synthesizing medicinally privileged heterocyclic compounds. It also summarizes the general methodologies for preparing graphene and various GBNs, their chemical structures, characterization techniques, and discussions on the potential active sites that are responsible for wider catalytic activity. Overall discussions unequivocally establish a promising paradigm for uncovering more innovative graphene-based materials and their subsequent applications in diverse fields, including heterogeneous catalysis.

Topological regulations of Stone-Wales graphene

Designed synthesis of graphene-based materials containing Stone-Wales defects represents a promising strategy for graphene modification, because of their highly diverse structures and tunable properties. In graphene-based materials, Stone-Wales defects are caused by the in-plane atomic rearrangement and re-linkage of graphene's honeycomb structure. The resultant Stone-Wales graphene's are topoisomers of graphene. Topology is naturally a major factor in regulating the structures and properties of Stone-Wales graphene, but the regulation rules are mostly unclear. In this study, 478 low-energy Stone-Wales graphene allotropes with diverse topology are predicted using topology-based global optimization, for which the thermodynamic, electronic, and elastic properties are evaluated using the first-principles calculations. The dependencies of the predicated physical properties on topological quantities and patterns are explicitly determined. The current study may lay the groundwork for design, synthesis, and property tuning of graphene-based materials.

High-performance flexible piezoelectric sensors based on honeycomb graphene macro-film exploiting auxetic mechanical property

Flexible piezoelectric sensors have received widespread attention in wearable electronics for their ability to convert mechanical energy into electrical energy, while the insufficient output power and complex preparation process have limited their application. In this work, several honeycomb structures based on graphene macro-film (GAMF) were created via laser engraving, which can utilize negative Poisson’s ratio (NPR) properties to improve the output electric performance of flexible piezoelectric sensors. The effect of different electrode materials on the piezoelectric output was investigated in the experiments and compared with the theoretical equations, indicating that the output power of the sensor could be enhanced up to 142 % by improving the materials auxetic mechanical properties. The stability tests have proven that the sensors can operate effectively for a long time under different operating conditions. Moreover, the optimized sensor shows powerful potential for monitoring human movements such as finger tapping, joint bending, and foot stepping. This work opens up a new development path for the preparation of convenient and high-performance wearable electronic devices.

Prediction of mechanical properties of phagraphene nanosheets and nanotubes: A molecular dynamics study

Phagraphene (PhaG), a recently discovered carbon allotrope, deviates from graphene's honeycomb lattice by featuring a distinctive unit cell composed of 20 carbon atoms arranged in a pentagonal-hexagonal-heptagonal ring sequence. This unique structure imparts mechanical properties comparable to graphene. In this investigation, Molecular Dynamics simulations are employed to estimate the mechanical characteristics of both nanosheets and nanotubes in their pristine and defective states. The study delves into the impact of defects, by introducing two types of defects—vacancies and Stone-Wales defects—into these nanostructures. Among these, Type-1 vacancies and Type-2 and Type-3 Stone-Wales defects prove dominant. It is determined from the results that nanosheets exhibit an average elastic modulus of approximately 0.8 TPa and an ultimate strength of 95 GPa, demonstrating an anisotropic nature. Phagraphene nanotubes (PhaNT), modeled through the revolution of atomic Cartesian coordinates of nanosheets, display an elastic modulus close to 0.9 TPa and an ultimate strength of 250 GPa. Additionally, this study investigates the impact of temperature on the mechanical properties of Phagraphene nanostructures. The findings reveal that as the temperature increases, there is a decrease in the tensile strength of both nanosheets and nanotubes. This temperature-dependent behavior provides valuable insights into the thermal stability and performance of Phagraphene nanostructures, further contributing to our understanding of their mechanical response under varying environmental conditions. The precision of the results is observed when nanosheets, each comprising 2800 or more carbon atoms, and nanotubes, each composed of 4500 or more carbon atoms, undergo testing under a tensile strain rate of 109/s.

A photoelectrochemical cytosensor based on a Bi2S3-MoS2 heterojunction-modified reduced oxide graphene honeycomb film for sensitive detection of circulating tumor cells.

A novel photoelectrochemical (PEC) cytosensor for the ultrasensitive detection of circulating tumor cells (CTCs) was developed. The bio-inspired reduced graphene oxide (rGO) honeycomb film photoelectrode was fabricated via a "breath figure" method, followed by the self-assembly of a Bi2S3-MoS2 heterojunction. The resulting Bi2S3-MoS2 heterojunction-modified rGO honeycomb film was employed as a sensing matrix for the first time. Compared to the smooth rGO film, the significant enhanced photocurrent of the photoelectrode under visible light was attributed to its improved visible light absorption, increased surface area and enhanced separation efficiency of photo-generated electron-hole pairs, which met the requirements of the PEC sensor for detecting larger targets. By virtue of the photocurrent decrease due to the steric hindrance of MCF-7 cells, which were captured by an aptamer immobilized on the surface of the photoelectrode, a cytosensor for detecting CTCs was achieved, showing a wide linear range of 10-1 × 105 cells per mL and a low detection limit of 2 cells per mL. Furthermore, MCF-7 cells in human serum were determined by this PEC biosensor, exhibiting great potential in the clinical detection of CTCs.

Entanglement and quantum correlations in the honeycomb graphene lattice within the Hubbard model

Entanglement and quantum correlations in the honeycomb graphene lattice within the Hubbard model

Buckling Stability and Vibration Characteristics of Functionally Graded Graphene Platelet-Reinforced Composites Multi-Arc Concave Honeycomb Sandwich Panels Under Thermal Loading

The utilization of functionally graded graphene platelet-reinforced composites (FG-GPLRC) and honeycomb sandwich constructions is prevalent in the field of engineering. Therefore, it is crucial to investigate the buckling and vibration properties of these materials under heat circumstances. This paper specifically focuses on the vibration and thermal buckling characteristics of a novel multi-arc concave honeycomb sandwich plate (MACHSP) equipped with an adjustable positive-negative Poisson’s ratio. The governing equations of motion for the system are derived based on the first-order shear deformation theory in conjunction with Hamilton’s principle. The formulation of the system’s characteristic equation involves the establishment of displacement functions that satisfy distinct boundary conditions. Using computational programming, natural frequencies, mode shapes, and critical buckling temperatures of MACHSP with three different FG-GPLRC distributions under thermal influences are determined. Subsequently, these results are compared with outcomes from finite element simulations and findings from previously published literature. Additionally, the amplitude-frequency response characteristics of the structure under harmonic excitation are analyzed, followed by a discussion of the impact of structural parameters on its buckling and vibration characteristics. The results indicate that the established theoretical model for predicting the buckling and vibration characteristics of MACHSP with FG-GPLRC distribution aligns well with simulation models and prior research. In contrast to solid plates, MACHSP not only achieves a substantial reduction in weight but also demonstrates a significant increase in natural frequency. Furthermore, graphene platelets have the potential to enhance the structure’s natural frequency values and critical buckling temperatures. Lastly, various structural parameters exert a notable influence on the structure’s performance.

Strength and Deformation Behavior of Graphene Aerogel of Different Morphologies

Graphene aerogels are of high interest nowadays since they have ultralow density, rich porosity, high deformability, and good adsorption. In the present work, three different morphologies of graphene aerogels with a honeycomb-like structure are considered. The strength and deformation behavior of these graphene honeycomb structures are studied by molecular dynamics simulation. The effect of structural morphology on the stability of graphene aerogel is discussed. It is shown that structural changes significantly depend on the structural morphology and the loading direction. The deformation of the re-entrant honeycomb is similar to the deformation of a conventional honeycomb due to the opening of the honeycomb cells. At the first deformation stage, no stress increase is observed due to the structural transformation. Further, stress concentration on the junctions of the honeycomb structure and over the walls occurs. The addition of carbon nanotubes and graphene flakes into the cells of graphene aerogel does not result in a strength increase. The mechanisms of weakening are analyzed in detail. The obtained results further contribute to the understanding of the microscopic deformation mechanisms of graphene aerogels and their design for various applications.

Mechanistic Insights on Functionalization of Graphene with Ozone.

The exposure of graphene to O3 results in functionalization of its lattice with epoxy, even at room temperature. This reaction is of fundamental interest for precise lattice patterning, however, is not well understood. Herein, using van der Waals density functional theory (vdW-DFT) incorporating spin-polarized calculations, we find that O3 strongly physisorbs on graphene with a binding energy of -0.46 eV. It configures in a tilted position with the two terminal O atoms centered above the neighboring graphene honeycombs. A dissociative chemisorption follows by surpassing an energy barrier of 0.75 eV and grafting an epoxy group on graphene reducing the energy of the system by 0.14 eV from the physisorbed state. Subsequent O3 chemisorption is preferred on the same honeycomb, yielding two epoxy groups separated by a single C-C bridge. We show that capturing the onset of spin in oxygen during chemisorption is crucial. We verify this finding with experiments where an exponential increase in the density of epoxy groups as a function of reaction temperature yields an energy barrier of 0.66 eV, in agreement with the DFT prediction. These insights will help efforts to obtain precise patterning of the graphene lattice.

Flexible SiO2/rGO aerogel for wide-angle broadband microwave absorption

Graphene aerogel has been a promising microwave absorber due to ultralow density and strong dielectric loss ability. However, its intrinsic brittleness, and poor absorbing properties because of impedance mismatch severely hinders practical engineering applications. Herein, flexible silica fibers with excellent impedance matching properties were introduced into graphene honeycomb structures to co-construct a dual-structure aerogel (GS) by eco-friendly and low-cost technology. The unique dual-structure significantly enhances its resilience, enabling it to rebound after 1000 cycles of 75% compression. In addition, it can withstand 450 times of 180° folding and 360° rotation without damage, featuring remarkable flexibility and reliability. Furthermore, the simulation and experimental results indicate that GS has excellent wave absorbing performance. When the thickness is 6 mm, the effective absorption bandwidth is 32.55 GHz; when the thickness increases to 10 mm, the reflection loss is less than −8 dB in the range of 2.79–40 GHz. Moreover, the reflection loss remains almost constant when the oblique incidence angle ranges from 5° to 45°, which further demonstrates the critical role of impedance matching in enhancing the microwave absorption performance. These superior characteristics make GS an ideal candidate for many microwave absorption applications such as flexible electronics and aerospace.

Quantum Phase Transition in Magnetic Nanographenes on a Lead Superconductor.

Quantum spins, also known as spin operators that preserve SU(2) symmetry, lack a specific orientation in space and are hypothesized to display unique interactions with superconductivity. However, spin-orbit coupling and crystal field typically cause a significant magnetic anisotropy in d/f shell spins on surfaces. Here, we fabricate atomically precise S = 1/2 magnetic nanographenes on Pb(111) through engineering sublattice imbalance in the graphene honeycomb lattice. Through tuning the magnetic exchange strength between the unpaired spin and Cooper pairs, a quantum phase transition from the singlet to the doublet state has been observed, consistent with the quantum spin models. From our calculations, the particle-hole asymmetry is induced by the Coulomb scattering potential and gives a transition point about kBTk ≈ 1.6Δ. Our work demonstrates that delocalized π electron magnetism hosts highly tunable magnetic bound states, which can be further developed to study the Majorana bound states and other rich quantum phases of low-dimensional quantum spins on superconductors.

Highly efficient quantum heat engine operating at maximum power in the α-T3 lattice

The α−T3 lattice, an interpolation of graphene's honeycomb lattice and the dice lattice, has drawn a lot of attention. Herein, the thermoelectric properties of the α−T3 lattice based junction are investigated. The parameter φ and the gate voltage Vg can be utilized for adjusting thermoelectric properties. Without the mass term Δ, the efficiency at maximum power η is relatively low, similar to two-dimensional graphene. When Δ is introduced, the initially flat band warps and disperses, resulting in a band gap between the distorted flat band and the conduction (valence) band. In this case, the maximum power and η are both greatly enhanced and are adjustable by Vg and φ. With high output power, η can be higher than 0.3 Carnot efficiency. As a result, it is suggested that the α−T3 lattice will be utilized to create a highly efficient quantum heat engine.

Bending and eigenfrequency analysis of glass fiber reinforced honeycomb sandwich shell panels containing graphene-decorated with graphene quantum dots

The present study employs a finite element (FE) formulation to examine the free vibration and bending analyses of sandwich shells made of a glass fiber reinforced polymer (GFRP) composite honeycomb core and graphene decorated with graphene quantum dots (GDGQD) reinforced by GFRP composite face layers. The mechanical characteristics of the GFRP composites with GDGQD reinforcement were evaluated using experimental tests. The FE formulation was developed to compute the vibration and bending responses of the sandwich shells via MATLAB software. The Lagrange method is used for dynamic analysis, whereas the principle of potential energy is used for static analysis. The FE model's validity is compared to numerical data reported in the literature in terms of frequencies and deflection, and the results demonstrate excellent agreement. The impacts of the end conditions, core-to-facesheet thickness ratio, curvature ratios, and weight percent of GDGQD are studied further in relation to the bending and dynamic properties of GFRP sandwich shells.

Nonlinear vibration analysis of sandwich plates with honeycomb core and graphene nanoplatelet-reinforced face-sheets

Nonlinear vibration analysis of sandwich plates with honeycomb core and graphene nanoplatelet-reinforced face-sheets

Imprinting Sensor Based on Honeycomb Graphene Oxide for the Determination of Echinacoside in Complex Samples

Echinacoside(ECH) is a phenylethanoid glycoside compound with various pharmacological activity in Chinese medicine. The development of convenient, efficient and sensitive analysis methods for ECH in complex samples in vitro and in vivo has considerable application value. In this study, honeycomb graphene oxide (H-GO) with highly conductivity and nanoscale defect-like structure was successfully prepared by combustion method. It was used as a modified material for flexible electrode (ITO-PET), and then activated in alkaline solution to construct a nanomaterial modified electrode (aH-GO/ITO-PET). The imprinted sensor (MIP/aH-GO/ITO-PET) was further constructed by simple electropolymerization and elution. Under optimized conditions, the sensor achieves sensitive detection of ECH in a wide linear range of 0.1 ∼ 100 μM, with a detection limit as low as 1.6 nM (S/N = 3), and has good repeatability, stability and anti-interference. It has been successfully used for the direct detection of ECH in Cistanche deserticola Ma wine and rat plasma.

Honeycomb graphene–polyaniline nanocomposites as novel electrode materials for high-performance supercapacitors

Honeycomb graphene–polyaniline (HG–PANI) nanocomposites are synthesized through a facile electrostatic self-assembly approach, and the obtained material is characterized as the electrode for supercapacitor applications.

First-principles study of surface modification of CuSe

Original bulk phases of two-dimensional atomic crystal materials are layered. However, a few relevant researches show that some of two-dimensional material crystals have non-layered bulk phases. In this work we investigate monolayer CuSe which is non-layered, belonging in a new kind of honeycomb graphene analogue. Monolayer CuSe is not suitable for application in electronic devices because of its metallic nature. In order to find new two-dimensional atomic crystal materials with excellent performance suitable for application in electronic devices, we change CuSe from metal to semiconductor through external atom modification. The first principles study of density functional theory is conducted to ascertain the energy band structure of monolayer CuSe after second periodic atoms have been added to the top, center and bridge sites. The characteristics of monolayer CuSe with addition of Li or B atoms are studied, including energy band structure, the density of states, differential charge density, and crystal orbital Hamiltonian population. The results show that after adding Li atoms to CuSe, the CuSe transforms from metallic to semiconductive property at all three positions, and Li atom is more easily to be modified in the hexagonal center of CuSe, with band gap being about 1.77 eV, the Fermi level biased towards the top of the valence band. The CuSe with addition of Li atoms exhibits a p-type semiconductor property, so it is a direct bandgap semiconductor. Adding B atom to the top of Cu atom can also make CuSe semiconductive, with a band gap of about 1.2 eV, the conduction band minimum at the <i>K</i> point, and the valence band maximum at the <i>Γ</i> point. The CuSe with addition of B atoms belongs in an indirect band gap semiconductor, and the Fermi energy level is biased towards the conduction band minimum, exhibiting the characteristics of an n-type semiconductor. According to the results of differential charge density and crystal orbital Hamiltonian population, the B atom is bound to the top of the monolayer CuSe with the B-Se polar covalent bond. The first principle study reveals the realization of metal-to-semiconductor transition from monolayer CuSe to Cu<i>X</i>Se (<i>X</i> = Li, B), and the calculation results also show that CuSe with addition of Li atoms or B atoms is likely to be used in future electronic devices.

Theory of triangulene two-dimensional crystals

Abstract Equilateral triangle-shaped graphene nanoislands with a lateral dimension of n benzene rings are known as [n] triangulenes. Individual [n] triangulenes are open-shell molecules, with single-particle electronic spectra that host n − 1 half-filled zero modes and a many-body ground state with spin S = ( n − 1 ) / 2 . The on-surface synthesis of triangulenes has been demonstrated for n = 3 , 4 , 5 , 7 and the observation of a Haldane symmetry-protected topological phase has been reported in chains of [3]triangulenes. Here, we provide a unified theory for the electronic properties of a family of two-dimensional honeycomb lattices whose unit cell contains a pair of triangulenes with dimensions n a , n b . Combining density functional theory and tight-binding calculations, we find a wealth of half-filled narrow bands, including a graphene-like spectrum (for n a = n b = 2 ), spin-1 Dirac electrons (for n a = 2 , n b = 3 ), p x , y -orbital physics (for n a = n b = 3 ), as well as a gapped system with flat valence and conduction bands (for n a = n b = 4 ). All these results are rationalized with a class of effective Hamiltonians acting on the subspace of the zero-energy states that generalize the graphene honeycomb model to the case of fermions with an internal pseudospin degree of freedom with C 3 symmetry.

Electrochemical performance of honeycomb graphene prepared from acidic graphene oxide via a chemical expansion method

• Simple, low-energy and scalable one-step chemical expansion of graphene. • High-yield (>90%) preparation of of nanocrystalline chemically expanded graphene. • Specific capacity of 283.8F·g −1 at 1 A·g −1 , and excellent rate capability. • Excellent capacity retention of ≈87% after 5000 cycles at 20 A·g −1. High-performance electrode materials are particularly important for the next-generation of supercapacitors with enhanced specific capacity and cycle stability. In this study, a simple and scalable thermal expansion method is used to convert acidic graphite oxide (AGO) into chemically expanded graphene (CEG) nanostructure, with a honeycomb morphology consisting of 2–3 graphene layers. The CEG produced by the thermal expansion of AGO under modified conditions of time and duration (CEG-2) exhibits a substantially large specific surface area of around 388 m 2 ·g −1 , in comparison to value of 6 m 2 ·g −1 recorded on the virgin superconducting graphite powder. This provides the CEG-2 material with an excellent specific capacitance of 283.8F·g −1 , recoded at 1 A·g −1 . The cycle stability of CEG-2 is characterized to be highly desirable with a retention rate of around 87% after 5000 cycles. The results obtained suggest the enhanced electrochemical performance of CEG.