Properties Of Graphene Materials Research Articles

Static analysis of foldable pressurized and thermally loaded cylindrical shell as an expander in sport equipment reinforced by G-Ori nanofillers

The present work investigates stress, strain and deformation analyses of a shear deformable cylindrical shell manufactures by a Copper (Cu) core reinforced with graphene origami auxetic metamaterial subjected to mechanical and thermal loads. The cylindrical models can be used in sport equipment especially in expander component. The effective material properties of the graphene origami auxetic reinforced Cu matrix are developed using micromechanical models cooperate both material properties of graphene and Cu in terms of local temperature, volume fraction and folding degree. The principle of virtual work is used to derive governing equations with accounting thermal loading.

Chasing Graphene-Based Anticancer Drugs: Where are We Now on the Biomedical Graphene Roadmap?

Graphene and graphene-based materials have attracted growing interest for potential applications in medicine because of their good biocompatibility, cargo capability and possible surface functionalizations. In parallel, prototypic graphene-based devices have been developed to diagnose, imaging and track tumor growth in cancer patients. There is a growing number of reports on the use of graphene and its functionalized derivatives in the design of innovative drugs delivery systems, photothermal and photodynamic cancer therapy, and as a platform to combine multiple therapies. The aim of this review is to introduce the latest scientific achievements in the field of innovative composite graphene materials as potentially applied in cancer therapy. The "Technology and Innovation Roadmap" published in the Graphene Flagship indicates, that the first anti-cancer drugs using graphene and graphene-derived materials will have appeared on the market by 2030. However, it is necessary to broaden understanding of graphene-based material interactions with cellular metabolism and signaling at the functional level, as well as toxicity. The main aspects of further research should elucidate how treatment methods (e.g., photothermal therapy, photodynamic therapy, combination therapy) and the physicochemical properties of graphene materials influence their ability to modulate autophagy and kill cancer cells. Interestingly, recent scientific reports also prove that graphene nanocomposites modulate cancer cell death by inducing precise autophagy dysfunctions caused by lysosome damage. It turns out as well that developing photothermal oncological treatments, it should be taken into account that near-infrared-II radiation (1000-1500 nm) is a better option than NIR-I (750-1000 nm) because it can penetrate deeper into tissues due to less scattering at longer wavelengths radiation.

Influence of morphological characteristics of graphene on its field emission properties

Graphene is one of the most potential field emission cathode materials due to its excellent electrical, thermal, and mechanical properties, as well as rich edge structures. In this paper, we study the growth parameters of graphene prepared by chemical vapor deposition, and prepare three kinds of morphologies of graphene: single-layer graphene, graphene islands, and graphene with buffer layers, and then we explore the influence of the morphological characteristics of graphene on its field emission properties, and analyze the mechanism of influence of the morphological characteristics of graphene on its field emission properties through COMSOL. Comparing with single-layer graphene, the turn-on field of graphene islands and that of graphene with buffer layers decrease to 5.55 V/μm and 5.85 V/μm, respectively. The current densities also increase to 40.3 μA/cm<sup>2</sup> and 26.4 μA/cm<sup>2</sup>, respectively. On the other hand, the field emission currents of single-layer graphene and graphene with buffer layers are more stable. In a 5-hour test, the current densities only decrease by 2% and 4%, respectively. COMSOL simulation shows that the morphological characteristics of graphene have significant influences on the electric field distribution characteristics and heat dissipation capacity. Graphene islands and graphene with buffer layers have exposed edges, leading to local electric field concentration, and thus improving field emission properties. The graphene islands are distributed discretely on the substrate, forming no continuous graphene film and lacking transverse heat dissipation channels, so the accumulation of heat will cause damage to the graphene emitter, and affect the stability of its field emission current. This study will be of great benefit to the understanding of the influence of the morphological characteristics of graphene on its field emission properties, and improving the field emission properties of graphene materials.

Bending and twisting behavior of multilayer graphene

In this work, multilayer graphene was chosen and modeled in ANSYS software. In the software, it was subjected to bending forces through various bend angles. In order to test for bending, the model is subjected to rigid support on the base side. Then a force is applied on the side on which the angle is provided to simulate Bending. Stress–strain plots were analyzed for various bending angles. The graphene sheet was also subjected to twist forces within the software. In order to test for torsion, the model is subjected to rigid support on both sides. Then a couple is applied on the opposite sides to simulate torsion. Torsional stress and strain measurements were analyzed. The trends were studied and correlations with the material properties of graphene were established. The quest is to identify a magic angle for bend and twist.

Spectro-geometric solutions for random vibration of functionally graded graphene platelet reinforced conical shells

This study delved into the random vibration characteristics of a conical shell constructed from a functionally graded graphene platelet-reinforced composite (FG-GPLRC) under the influence of basic acceleration excitation. The investigation employed a synthesis of two methodologies: the spectro-geometric method (SGM) and the pseudo-excitation method (PEM). Commencing with the application of the Halpin–Tsai micromechanics approach and the law of mixtures, the effective material characteristics of the FG-GPLRC structure were determined. Subsequently, the displacement field vector for the conical shell structure was established with SGM. By employing the framework of the first-order shear deformation theory (FSDT), the energy function of the FG-GPLRC conical shell was derived, with external random excitation energy being incorporated with PEM. To construct a dynamic model for the conical shell structure, the Rayleigh-Ritz method was applied, subjecting the energy function to variational extremization. This approach yielded a comprehensive dynamic representation. The validity of the proposed model was substantiated through comparison with existing literature and finite element method results. Ultimately, this study explored the influence of graphene material properties and geometric parameters of the conical shell on the random vibration characteristics of the FG-GPLRC conical shell.

Bending results of graphene origami reinforced doubly curved shell

The present work investigates higher order stress, strain and deformation analyses of a shear deformable doubly curved shell manufactures by a Copper (Cu) core reinforced with graphene origami auxetic metamaterial subjected to mechanical and thermal loads. The effective material properties of the graphene origami auxetic reinforced Cu matrix are developed using micromechanical models cooperate both material properties of graphene and Cu in terms of temperature, volume fraction and folding degree. The principle of virtual work is used to derive governing equations with accounting thermal loading. The numerical results are analytically obtained using Navier's technique to investigate impact of significant parameters such as thermal loading, graphene amount, folding degree and directional coordinate on the stress, strain and deformation responses of the structure. The graphene origami materials may be used in aerospace vehicles and structures and defence technology because of their low weight and high stiffness. A verification study is presented for approving the formulation, solution methodology and numerical results.

(Invited) Modification of Properties of N- and B-Doped Graphene by Heteroatom Functionalization

Since its discovery in 2004, the graphene has attracted great attention owing to its unique chemical bonding structure, which has excellent chemical, thermal, mechanical, electrical and optical properties. Due to the graphene being a zero band-gap material, it has a limited development in the field of nano electronics. Therefore, to broaden its application scope, it is very important to carry out a study on opening the band gap of graphene. One general strategy for achieving this goal is doping graphene with heteroatoms; in this approach, the properties of graphene are controlled by the nature of the dopant elements and by the percentage of doping being N-doped graphene is of n-type doping, while B-doped graphene is of p-type doping. Compared with that of the intrinsic graphene, the Fermi level of N doped graphene moves up 5 eV; on the contrary, the Fermi level of B doped graphene moves down 3 eV.However, it would be convenient to develop additional tools to achieve further control of the electronic properties of graphene materials. In this context, one of the possibilities would be to functionalize those dopant elements on the graphene sheet in such a way that the electron density and electronegativity of the heteroatom are effectively controlled. This objective could, in principle, be achieved by applying concepts from organic chemistry. Organic synthesis offers proven chemical reactions that are applicable to different types of nitrogen and boron compounds.In the work described here, we´ll present our results on the covalent functionalization of the nitrogen atom or boron atom of N-doped and B-doped graphene. In a simple strategy, electron-donating and -withdrawing groups present on aromatic rings can be used to modulate the electronic properties of the material.

Incident angle dependent tunable multiband infrared absorption based sensor

The effect of electromagnetic (EM) resonance in the graphene resonator and multiple reflections taking place in the dielectric spacer can provide the multiband infrared absorption. The intensity of resonance spectrum occurring due to the formation of EM dipoles in resonator can be controlled by patterning it using desired perturbation. The absorber response can be set with the multiple narrow and broad absorption peaks together by modulating the electrical properties of graphene material. The proposed absorber provides the incident angle dependent behavior with linear variation in the resonant wavelengths by maintaining the high absorption. This can provide a new way of tuning the antenna response by angle of incidence. The implemented absorber can provide the triple narrow bands which can be utilized for performing the refractive index sensing. The proposed absorber provides a significant value of sensing performance parameters including sensitivity, full-width-half-maxima, and figure-of-merit with the high value of quality factor. Moreover, the proposed absorber offers the ability of generating an extra narrow absorption band in the case of presence of sensing analyte of specific thickness and refractive index range making it highly sensitive for the detection of specific surroundings including the bio-cells, chemicals and humidity in the air. The broadband characteristics of the proposer absorber can be utilized in implementing the infrared EM shields and thermal storage components.

The mechanical, optical, and thermal properties of graphene influencing its pre-clinical use in treating neurological diseases.

Rapid progress in nanotechnology has advanced fundamental neuroscience and innovative treatment using combined diagnostic and therapeutic applications. The atomic scale tunability of nanomaterials, which can interact with biological systems, has attracted interest in emerging multidisciplinary fields. Graphene, a two-dimensional nanocarbon, has gained increasing attention in neuroscience due to its unique honeycomb structure and functional properties. Hydrophobic planar sheets of graphene can be effectively loaded with aromatic molecules to produce a defect-free and stable dispersion. The optical and thermal properties of graphene make it suitable for biosensing and bioimaging applications. In addition, graphene and its derivatives functionalized with tailored bioactive molecules can cross the blood-brain barrier for drug delivery, substantially improving their biological property. Therefore, graphene-based materials have promising potential for possible application in neuroscience. Herein, we aimed to summarize the important properties of graphene materials required for their application in neuroscience, the interaction between graphene-based materials and various cells in the central and peripheral nervous systems, and their potential clinical applications in recording electrodes, drug delivery, treatment, and as nerve scaffolds for neurological diseases. Finally, we offer insights into the prospects and limitations to aid graphene development in neuroscience research and nanotherapeutics that can be used clinically.

Recent Progress of Cement-Based Materials Modified by Graphene and Its Derivatives.

Graphene, with its excellent properties and unique structure, has been extensively studied in the context of modifiable cement-based materials. However, a systematic summary of the status of numerous experimental results and applications is lacking. Therefore, this paper reviews the graphene materials that improve the properties of cement-based materials, including workability, mechanical properties, and durability. The influence of graphene material properties, mass ratio, and curing time on the mechanical properties and durability of concrete is discussed. Furthermore, graphene's applications in improving interfacial adhesion, enhancing electrical and thermal conductivity of concrete, absorbing heavy metal ions, and collecting building energy are introduced. Finally, the existing issues in current study are analyzed, and the future development trends are foreseen.

Investigation of the effect of stainless-steel grain size on the continuity of graphene frictional behavior using molecular dynamics (MD) simulation

Nanograin refinement can improve the strength of stainless steel, but the substrate grain boundaries will cause graphene bulging, so it will affect the lubrication effect of graphene. In this study, the effect of stainless-steel grain size on the frictional strengthening behavior of graphene is investigated, and the mechanism of grain boundary distribution and grain boundary crossing on graphene friction strengthening behavior was revealed. A normal load constraint of 0.8 nN is set for the nano-friction process. Stainless steel grain size greater than or equal to 10 nm, the maximum friction force of graphene does not vary with grain size is about 6 nN. However, the friction strengthening behavior is discontinuous, and the friction force fluctuates significantly, which is not conducive to micromechanical structure lubrication. When the grain size of stainless steel is less than 10 nm, the frictional strengthening behavior is continuous and the friction force after strengthening will maintain small fluctuations. Since the small fluctuations of this stick–slip behavior are material properties of graphene and cannot be avoided, this state is already the ideal result for graphene lubrication. However, as the stainless-steel grain size continues to become smaller, the maximum friction of graphene will increase, which is not good for graphene lubrication. This means that after the grain size is less than 10 nm, the continuation of the grain refinement process for stainless steel will improve the strength of stainless steel, but will weaken the graphene lubrication efficiency. Moreover, the difficulty of the nanograin refinement process will be significantly increased. Therefore, the stainless-steel grain size of 7 nm by grain refinement is the best solution to balance the stainless-steel strength and graphene lubrication efficiency. With a grain size of 7 nm, the stainless-steel grain boundaries are densely distributed, and the graphene bulge area will occupy 65% of the total area, allowing for continuous frictional strengthening behavior. The maximum height of graphene bumps is 2.8 Å and the maximum friction force is about 7 nN. Meanwhile, the relationship between the grain size of stainless steel and the continuity of graphene frictional strengthening behavior was explored, and the mechanism of action of grain boundary crossing by modulating the height of graphene bulge and thus affecting the frictional maximum was revealed. The nano-friction simulation of stainless steel/graphene can clearly capture the details of the nano-friction process and the variation of friction values, providing a basis for nano-friction studies of graphene on polycrystalline material surfaces. The simulation can determine the range of stainless-steel grains that exhibit the best friction state with graphene. The simulation results also provide guidance for the refinement of stainless steel nanograins and insights for the application of nanocrystalline stainless steel/graphene in MEMS.

Beyond hydrophobisation: Deciphering the surprising reactivity of trimethylsilyl reagents towards graphene oxide

Trimethylsilylation of metal oxide surfaces (silica, titania…) is a common way to empower the handled supports with outstanding stability. This hydrophobisation prevailed in vital domains including chromatographic column, adsorption-based membranes and heterogeneous catalysis, where hydrolytic stability constituted a challenging issue. In spite of its benefits, trimethylsilylation of graphene oxide has been only sporadically investigated and this underlooked chemistry needs to be accurately addressed for further tailoring the surface properties of graphene materials. With this aim, we herein screened a set of commercially available trimethylsilyl reagents for end-cuping the surface of graphene oxide. Surprisingly, meticulous investigations show that these reagents behave primarily as nucleophiles and induce oxirane opening, with a diverging pattern depending on the functional group linked to trimethylsilyl fragments. Specifically: i) trimethylsilylchloride and trimethylsilyltriflate are not suitable because of the substantial side products formed under acidic conditions; ii) trimethylsilylimidazolium reacts rather through its imidazolium group with the simultaneous elimination of trimethylsilyl groups; iii) bis-silylated reagents like hexamethyldisilazane and N,O-bis-trimethylsilyl-trifluoroacetamide enable anchoring at least one functional arm while liberating the second trimethylsilyl moity. The introduced functionalities enhance the dispersion of the newly prepared graphenes in liquid medium, thereby broadening the library of solvents suitable for their handling and offering more possibilities for the ink processability. Regardless of the starting reagent, the resulting functionalisation do not compromise the anchoring ability of the graphene surface as illustrated by supporting InP/ZnS semiconductor nanocrystals. In the whole, these serendipitous findings challenge the conventional wisdom about the reactivity of trimethylsilyl reagents that was primarly associated to surface hydrophobisation, opening indeed new possibilities for graphene functionalisation and further use in materials science.

Implementing the circularly polarized THz antenna with tunable filtering characteristics

An ultra-wideband (UWB) terahertz (THz) antenna is designed and numerically analyzed. A technique is implemented for obtaining the filtering characteristics in the antenna response. A graphene sheet is placed in antenna structure for achieving the filtering response. The variation in the surface conductivity of the covered area by graphene sheet provides the variable field confinement in antenna structure. This way helps in generating the filtering characteristics in UWB response of antenna. Also, the variation in the electrical properties of graphene material provides the tunability in the generated notched frequency band. The antenna utilizes the feeding with the orthogonal stubs associated with it which helps in providing the circularly polarized response. Furthermore, the antenna operation is verified with the electrical circuit model.

Selective growth of graphene films on gallium-focused ion beam irradiated domains

Graphene, a single layer of carbon atoms tightly bound in a hexagonal honeycomb lattice to form a two-dimensional lattice, is a very interesting material with promising electronic, optical, chemical, and mechanical applicative potential [Geim and Novoselov, Nat. Mater. 6, 183 (2007)]. The properties of graphene make it suitable for a wide range of applications; however, its applicative future still depends on large scale technologies capable to robustly and reproducibly transfer its outstanding intrinsic properties into devices or complex structures. It must be recognized that a crucial technological problem, that still inhibits the applicability of high quality graphene material properties, is related to the patterning of this material using traditional top down instruments and lithographical methods. In this work, we will detail our investigations on applying a precise 30 keV Ga+ ion irradiation to selectively shape and modify a copper precursor surface for promoting the local growth of graphene surface domains. The morphology of these domains is investigated using scanning tunneling microscopy and spectroscopy to probe simultaneously the structural and the electronic properties at the atomic scale of the graphene films.

High-performance tri-band graphene plasmonic microstrip patch antenna using superstrate double-face metamaterial for THz communications

Abstract Recently, graphene-patch antennas have been widely used in communication technology, especially in THz applications due to the extraordinary properties of graphene material. Herein, a graphene-based rectangular microstrip patch antenna is designed on an FR4 substrate material (ɛr = 4.3). A single and double-faced superstrate MTM is placed upon the radiating patch for di erent purposes, such as enhancing the overall antenna performance, protecting the patch from environmental jeopardies, and generating a multiband resonance frequency. A single face superstrate triangle SRR unit was used to produce a dual-band frequency at 3.5 and 4.331 THz. The S 11 of the dual-band structure is achieved to be −26.78 dB and −46.25 dB with a bandwidth of 400 GHz and 460 GHz, respectively. The double face superstrate MTM unit cell of the triangle SRR printed on the opposite face gives another resonant frequency, so, triple frequency bands of 2.32, 3.35, and 4.38 THz with a wide impedance bandwidth of 230, 520, and 610 GHz, were generated, respectively. The double-face superstrate MTM not only enhances the antenna performance but also generates another resonant frequency that could be used in the next 6G communications. The proposed antenna is designed and optimized using two commercial 3D full-wave software, CST Microwave Studio and Ansoft HFSS, to validate the results.

Adsorption properties of graphene materials for pesticides: Structure effect

In recent years, the application of graphene materials to the adsorption of pesticides has attracted great research interests. However, to the best of our knowledge, there has been no report about the specific adsorption mechanism of graphene materials for pesticides with different structures. This study investigated the potential adsorption mechanism of graphene oxide (GO) and reduced graphene oxide (rGO) for three pesticides with different structures [Methomyl (Met; without aromatic rings), Acetamiprid (Ace; one aromatic ring) and Azoxystrobin (Azo, three aromatic rings)]. The operating variables including time, temperature and initial pesticide concentration were estimated and optimized with face-centered composite design (FCCD) through response surface methodology (RSM). Under optimal conditions, the calculated adsorption capacity of GO for Met, Ace and Azo was 106.22, 285.96 and 2896.84 mg/g; while that of rGO was 96.86, 357.65 and 2818.04 mg/g, respectively. The adsorption kinetics follows the pseudo second-order and Elovich models, while the adsorption isotherm can be well described by the Sips model. Thermodynamic study revealed that the adsorption process of the three pesticides onto GO or rGO was an exothermic and physical process. The adsorption was deduced to be synergistically driven by (1) the π-π conjugation between the sp2 region of adsorbent and the aromatic ring of pesticide molecules, (2) H-bonding and electrostatic interaction between heteroatoms in pesticide molecules and oxygen-containing functional groups on adsorption materials, and (3) H-bonding and π-π conjugation between pesticides. In general, this study provides important practical and theoretical implications for understanding the molecular mechanism underlying the adsorption of pollutants by GO or rGO and its practical application.

The shear strain energy fluctuations caused by random porosities in graphene based on the stochastic finite element model

Strain-induced deformation is a promising strategy to modify and functionalize the material properties of graphene. However, the impacts of random porosities are inevitable and complicated in the microstructure. In order to quantify and analyze the effects of random porosities in graphene under shear stress, the energy fluctuations and the equivalent elastic modulus are computed and recorded based on the stochastic finite element model. The finite element computation is combined with the Monte Carlo stochastic sampling procedure to distribute and propagate the random porosities in pristine graphene. Two different boundary conditions are taken into consideration and compared. Furthermore, the probability statistics of shear strain energy and equivalent elastic modulus are provided based on the comparison with the results of pristine graphene. The inhomogeneous spatial randomness is founded in the statistic records of shear strain energy. The sensitivity to the graphene chirality and boundary conditions are also shown for the porous graphene. The work in this paper provides important references for strain-induced engineering and artificial functionalization through topological vacancy control in graphene.

Surface- and nonlocality-dependent vibrational behavior of graphene using atomistic-modal analysis

Classical continuum theories are incapable of accurately describing the behavior of nanostructures due to their size dependence. Size-dependent effects such as surface and non-local are among these phenomena, and their study at the nano-scale is essential. Despite advances in modeling and characterization of graphene's material properties, the surface and nonlocality effects of circular graphene nano-plates have not been calibrated for continuum mechanics theories. Based on a hybrid model that combines the advantages of continuum and atomic models, the present study is primarily focused on developing a method for calculating and estimating the effect of these parameters. A non-local surface elasticity model for graphene has been developed using a modal analysis derived from molecular dynamics simulations based on genetic algorithm optimization. In this research, both asymmetric and axisymmetric linear vibrational modes are studied. The parameters of the model, including surface residual stress, surface elasticity, surface density, and size parameter, are extracted from the results of the atomistic modal. Subsequently, this hybrid atomistic-continuum model has been employed to characterize the vibrational behavior of graphene. Based on the conducted simulations, the surface elasticity model with the nonlocality effect is calibrated with the lowest error for all radii and vibration modes. Moreover, this research suggests using a non-local surface elasticity model for very small radii since its findings are remarkably similar to the molecular dynamics simulations for the same diameters. On the other hand, the error is highest for the continuum model that does not incorporate surface and non-local effects. The findings of this study can be valuable in evaluating the crucial parameters regarding the surface and non-local elasticity of two-dimensional structures.

A three-dimensional analysis of heat transfer based on mesoscopic method in nanoscale Si-MOSFET and Gr-FET

Thermal diffusion in the metal oxide semiconductor field effect transistor has received increased attention across a number of disciplines in recent years. This paper studies a three-dimensional (3D) heat conduction process in a MOSFET device based on Silicon (Si) and Graphene (Gr) materials. In order to perform analyses, a mesoscopic method was applied, based on lattice Boltzmann method (LBM) with D3Q15 model accounting the specularity parameter effects. The present study found that the maximal temperature is spotted at the interface whose value is 308.7 ​K and 324.5 ​K for the Gr-FET and Si-MOSFET, respectively, at t ​= ​30 ps and p ​= ​0.5. Also, the obtained results indicate that the specularity parameter has an important role in the phonon heat transport and thus in reducing the temperature in the nanotransistors. The preference of graphene device and the unique properties of graphene material make this material a good candidate for future nanoelectronics systems generation.

Influence of the Specific Surface Area of Graphene Nanoplatelets on the Capacity of Lithium-Ion Batteries.

In order to understand the influence of the morphological properties of graphene materials on the electrochemical performance of electrodes for lithium-ion batteries, three different graphene nanoplatelets with the increasing specific surface area (NP1: 296 m2 g−1, NP2: 470 m2 g−1, and NP3: 714 m2 g−1) were added in the electrode formulation in different ratios. Higher specific surface area graphene nanoplatelets (NP3) exhibit reversible capacity up to 505 mA h g−1 in the first discharge cycle (29.5% higher than that of graphite). Although significant irreversible capacity is shown for NP3, still higher reversible capacity is obtained compared to that of graphite electrode. The presence of micropores in the graphene structure benefits the lithiation. C-rate capability tests also show better performance of the graphene-based electrode. In this work, we demonstrate that graphene nanoplatelets with high specific surface area (714 m2 g−1) improve the electrochemical performance of Li-ion battery electrodes. The relationship between specific surface area, the presence of defects, and porosity is discussed.