Structure Of Graphene Research Articles

An environmentally sustainable ultrasonic-assisted exfoliation approach to graphene and its nanocompositing with polyaniline for supercapacitor applications

In the present work, a green high-yielding method for the preparation of graphene is introduced via ultrasonic-assisted liquid phase exfoliation (LPE) of graphite in a green solvent medium, since the common preparation method of graphene via graphite oxide is hazardous. A high concentration of 3.2 mg/ml graphene is achieved here in a comparatively short duration of 3 h ultrasonication. By using a mixed solvents strategy (acetophenone and isopropyl alcohol, 1:19 V/V), surface energy requirements needed for the exfoliation of graphite are satisfied here with acetophenone, where isopropyl alcohol further facilitated the exfoliation via non-conventional CH-π and OH-π interactions. Turbostratic graphene in high-yield (16 %) in a simple means of ultrasonic assisted LPE is the added attraction of the present procedure. The less-defective structure of graphene, its few-layered turbostratic nature, and edge functionalization of the sheets are evident from the material characterization via Raman spectroscopy, XRD, TEM-SAED, and XPS analyses. Here, we report a combination of the attractive conducting polymer polyaniline (PANI) with the as-prepared graphene for supercapacitor applications, where the PANI/graphene nanocomposites with different aniline concentrations (PANI1.125/G, PANI4.5/G, and PANI9/G) have been prepared via in-situ polymerization of aniline in the graphene dispersion. The structure and morphology of the nanocomposites are investigated using different characterization techniques which revealed that the molecular structure of the PANI is retained in the nanocomposites even with a strong interaction with graphene. FESEM and TEM images revealed the good coverage of graphene sheets with PANI that limit the volume change of PANI during the repeated charge-discharge processes. Electrochemical studies showed that PANI4.5/G has the highest specific capacitance of 126.16 mF/cm2 at a current density of 1 mA/cm2, resulting from the perfect combination of the pseudocapacitance behavior of the PANI along with the electrical double layer capacitance of graphene. A symmetric supercapacitor device is also fabricated with PANI4.5/G, which showed the highest areal capacitance of 116.38 mF/cm2 similar to that with three-electrode studies and also good cycling stability with 87 % capacitance retention in the specific capacitance after 6000 cycles. It also exhibited an energy density of 16 µWh/cm2 (0.29 Wh/kg) and a power density of 3.99 mW/cm2 (72.72 W/kg).

Adsorption of ethylene and 1-methylcyclopropene (1-MCP) on Al-doped graphene structure: A DFT study for gas sensing application

Ethylene is the ripening hormone of fruits and vegetables. 1-Methylcyclopropene (1-MCP) is used as the inhibitor of the ethylene actions for extending the postharvest shelf life of the plants. To control the ripening and extending the shelf life of the plants, the adsorption characteristics of ethylene and 1-MCP on Al-doped graphene structure (AlG) were investigated as a gas sensing application by density functional theory (DFT) calculations. The geometric structures were optimized, HOMO and LUMO, energy gap, adsorption energies, the density of states (DOS), electrostatic potential (ESP) and the global reactivities were calculated for different distances between the adsorbed ethylene or 1-MCP and the adsorbent AlG. Chemisorption and physisorption interactions were analyzed. For the chemisorption process of ethylene and 1-MCP on AlG, the adsorption energies were 19.34 kJ/mol and 56.53 kJ/mol, respectively. Whereas for the physisorption process, the adsorption energies of ethylene and 1-MCP were -60.16 kJ/mol and -7.32 kJ/mol, respectively. As a result, it was presented that the AlG structure has sufficient characteristics to be a good adsorbent and a gas sensor of ethylene and 1-MCP.

Graphene Monolayer Nanomesh Structures and Their Applications in Electromagnetic Energy Harvesting for Solving the Matching Conundrum of Rectennas.

In this paper, we investigate various graphene monolayer nanomesh structures (diodes) formed only by nanoholes, with a diameter of just 20 nm and etched from the graphene layer in different shapes (such as rhombus, bow tie, rectangle, trapezoid, and triangle), and their electrical properties targeting electromagnetic energy harvesting applications. In this respect, the main parameters characterizing any nonlinear device for energy harvesting are extracted from tens of measurements performed on a single chip containing the fabricated diodes. The best nano-perforated graphene structure is the triangle nanomesh structure, which exhibits remarkable performance in terms of its characteristic parameters, e.g., a 420 Ω differential resistance for optimal impedance matching to an antenna, a high responsivity greater than 103 V/W, and a low noise equivalent power of 847 pW/√Hz at 0 V.

Tailoring iron hexadecafluorophthalocyanine/GO nanocomposite separators for polysulfide adsorption and enabling fast electrochemical kinetics of Li-S batteries

The cycling stability of lithium-sulfur batteries is significantly compromised by the shuttle effect. Herein, we employed a preformed process to successfully load spherical nanoparticles of Iron hexadecafluorophthalocyanine (FePcF16) with sizes between 10 and 20 nm onto oxidized graphene sheets. The FePcF16 spherical particles with lithium and sulfur-affinitive sites maximally expose catalytically active sites, facilitating effective adsorption and catalysis of polysulfides (LiPSs). Density-functional theory (DFT) calculations suggest that the electron-rich fluorine substituents enhance the conjugation effect of FePcF16, facilitating electronic communication between the catalyst and graphene oxide (GO), achieving precise modulation of the electronic structure of Fe-N4 active centers. The electrochemical analysis demonstrates that the nanostructured and Fe-N4 site-containing FePcF16 integrated with the robust two-dimensional graphene structure synergistically facilitates both redox reactions and lithium affinity effects. Consequently, in extended cycling tests at 2 C, the initial discharge-specific capacity reached 857.7 mAh g−1. After 500 cycles, the capacity remained at 737.7 mAh g−1, with a minimal capacity decay rate of only 0.028 % per cycle.

A First Principles Study of Lithium Adsorption in Nanoporous Graphene

Recently, nanoporous graphene has attracted great interest in the scientific community. It possesses nano-sized holes; thus, it has a highly accessible surface area for lithium adsorption for energy storage applications. Defective graphene has been extensively studied. However, the lithium adsorption mechanism of nanoporous graphene is not clearly understood yet. Here, we present theoretical investigations on the lithium-ion adsorption mechanism in nanoporous graphene. We perform ab initio electronic structure calculations based on density functional theory. Lithium adsorption in a graphene nanopore is studied and adsorption sites are determined. We also study different lithium-ion distributions in graphene nanopores to determine the best lithium–nanoporous graphene structures for lithium-ion batteries. We show that lithium ions can be adsorbed in a graphene nanopore, even in a single layer of graphene. It is also shown that adding more nanopores to multilayer nanoporous graphene can result in higher Li storage capacity for new-generation lithium-ion batteries.

Nonlinear parametric generation and optical vortex transfer in graphene ensemble under Landau quantization

We explore the dynamics of nonlinear parametric generation and light beam propagation in a Landau-quantized graphene structure with three energy levels interacting with two laser pulses, utilizing the Maxwell-Bloch equations. By applying a laser field to one transition of the graphene sample while keeping the second beam initially absent, the distinctive preparation of the graphene sample, coupled with its weak interaction with laser radiation, results in the parametric generation of a new laser beam in a different transition. We investigate the influence of diverse system parameters on both the efficiency of the generated beam and the propagation dynamics of both beams. Our findings reveal that manipulating these parameters can induce oscillations in the intensity of propagated beams, mitigate absorption losses during propagation allowing for earlier relaxation, and enhance the efficiency of energy transfer from the initial to the generated beam. Additionally, we demonstrate the transfer of optical vortices within the graphene ensemble by introducing an optical vortex to the initial beam. This scheme holds promise for applications in high-dimensional quantum information processing.

Sliding-dependent electronic structures of alternating-twist tetralayer graphene

Sliding-dependent electronic structures of alternating-twist tetralayer graphene

Hybrid Powder‐Based Additive Manufacturing of Laser‐Induced Graphene 3D Architectures with Tunable Porous Microstructures from Waste Sources of Black Liquor and White Pollution

AbstractMacroscopic 3D‐controllable graphene (3D‐CG) architectures not only retain the intrinsic properties of graphene sheets but also exhibit structural advantages for pollutant adsorption and energy storage. This paper proposes a novel hybrid powder‐based additive manufacturing method to fabricate 3D biomass‐derived laser‐induced graphene (3D B‐LIG) structures with customizable geometries and microporous features. This method utilizes two waste sources as feedstock precursors for sustainable graphene production: “black liquor” (sodium lignosulfonate, NaLS) and “white pollution” (polypropylene, PP). Employing a computer‐aided design process, this method allows for the synchronous creation of various freeform macrostructures, with either identical or variable sections. To optimize the formability and processing efficiency of 3D B‐LIG, systematic studies have been conducted. These studies establish the relationship between processing parameters and the resulting structures by controlling the laser parameters and the mixing ratio of NaLS and PP. By leveraging tunable microporous structures with a maximized specific surface area of 485.3 m2 g−1, 3D B‐LIG demonstrates exceptional performance in pollutant adsorption (with a maximum adsorption capacity of 283.3 mg g−1 for methylene blue) and energy storage (with a gravimetric specific capacitance value of 194.9 F g−1).

Sequential carbonization of pig manure biogas residue into engineered biochar for diethyl phthalate removal toward environmental sustainability

Manure biogas residue has attracted increasing attention in waste recycling but faces substantial challenges because of its low carbon content, high ash content, and high heavy metal content. A novel sequential carbonization approach was proposed for recycling biogas residue; this approach consisted of pre-pyrolysis, activation with Ca(OH)2, and then activation with KOH. Pig manure-derived biogas residue was upcycled into engineered biochar (EB) with a high yield (26 %) and showed excellent performance in removing a typical plasticizer, diethyl phthalate (DEP). The proportion of carbon content greatly increased from 18 % (biogas residue) to 67 % (EB); however, the ash content decreased from 50 % (biogas residue) to 24 % (EB). The concentration of heavy metals decreased, and Zn had the largest decrease from 713 mg kg−1 to 61 mg kg−1 (p < 0.001). The sorption of DEP onto EB was rapid and reached equilibrium within 20 h. The developed specific surface area of EB was 1247 m2/g and provided abundant sorption sites for DEP; additionally, the sorption quantity reached 309 mg/g. The sorption capacity was dominated by surface adsorption. The oxygen-containing functional groups, graphene structure, porous structure, and hydrophobicity of EB contributed to the pore filling, hydrogen bonding, π–π stacking, and partitioning processes. Furthermore, the EB showed excellent practical application potential and great cycling stability. A sequential carbonization strategy was proposed to upcycle manure biogas residue into the EB for DEP removal; moreover, this strategy can aid in the attainment of environmental sustainability, including sustainable waste management and environmental pollution mitigation.

Strength and stability of π-π interaction between substituted benzene ring structures and graphene: Theoretical and molecular dynamics study

Adsorption between graphene and organic drug molecules attracts enormous attention for its wide application in drug delivery. π-π interaction, as one of the most important adsorption mechanisms, occurs between substituted benzene ring structure in organic drug molecule and graphene. This mechanism effectively prevents the degradation of molecular structure of drug, ensures its functional activity and promotes controlled release of drugs. It is worth noting that the type and quantity of substituents on the benzene ring have a significant impact on the strength and stability of π-π interactions. In this study, we cover features of eight kinds of substituents, and explore strength and stability of π-π interaction between graphene and substituted benzene ring structures from a mechanical perspective. The results demonstrate the advantages of substituents in enhancing adsorption strength. Electron-withdrawing substituents show more stronger enhancement effect than electron-donating substituents. Further research reveals that electrostatic interaction is the main enhancement mechanism for electron-withdrawing substituents. In addition, molecular dynamics simulations provide a comparison of adsorption stability among different substituents. Theoretical and simulation studies provide valuable mechanistic understanding of substituents in enhancing adsorption performance, contributing to the design and optimization of more targeting graphene carriers for drug molecules.

Highly Tunable Interlayer Coupling and Electronic Structures of Few-Layer Graphene with Pressure.

The interlayer electronic coupling is responsible for the electronic structure evolution from monolayer graphene to graphite and for the moiré potential in twisted bilayer graphene. Here we demonstrate that the interlayer transfer integral (hopping parameter) increases nearly 40% with a quite moderate pressure of ∼3.5 GPa, manifested by the resonance peak shift in the infrared spectra of all 2-10 L graphene. A simple model based on the Morse potential enabled us to establish the relationship between the transfer integral and pressure. Our work provides fundamental insights into the dependence of the electronic coupling on the interlayer distance.

Triple plasmon induced transparency based on multilayer graphene metamaterials

In this study, a novel multilayer terahertz metamaterial with four graphene sub-structures is designed to achieve dynamically tunable triple plasmon-induced transparency (PIT) due to interference among bright-bright modes. Coupled mode theory (CMT) and finite-difference time-domain (FDTD) simulations show a high degree of consistency in their results. Interestingly, enhanced transmission dips are observed when various graphene structures couple with the two longitudinal graphene strips at the bottom layer. Based on the dynamic modulation characteristics of graphene, the metamaterial demonstrates seven-band optical switching capabilities, achieving modulation depths (MD) of 94.6%, 88.1%, 90.8%, 90.8%, 90.4%, 86.6%, and 87.5%. Additionally, the proposed graphene metamaterial also shows excellent slow-light effects, with a group index reaching up to 1034. This proposed terahertz metamaterial holds significant theoretical implications for the development of dynamically integrated terahertz optoelectronic devices.

Precision defect integrated graphene as reliable support membrane for high-resolution cryo-transmission electron microscopy

Graphene is an excellent support film for high-resolution transmission electron microscopy (TEM) but its use with biological samples, notably in cryo-TEM, is hindered by its inherent hydrophobicity. Whereas surface treatments have been proposed to render graphene hydrophilic, they are often difficult to reproduce due to a lack of information on the structural changes that modify the wetting properties of graphene. This study aims to correlate the atomic structure of graphene with its wetting properties to allow a reproducible protocol to advance its application in cryo-TEM. We follow the change in the atomic structure of graphene as a function of low-energy hydrogen plasma treatment duration on monolayer graphene transferred onto TEM grids. With finely controlled plasma exposure, partial hydrogenation, monoatomic vacancies, and pores of a few nanometers are realized in the graphene. The introduction of defects (vacancies and pores) enables the formation of continuous layers of vitreous ice on TEM grids. Grids with defect-integrated graphene are reproduced and used in the vitrification of the mouse serotonin 5-HT3 receptor, a membrane protein. Single particle analysis of the membrane protein on graphene compared to conventional holey carbon film give insight into the strengths and discretions in using graphene membrane for protein structural studies.

Generative AI model trained by molecular dynamics for rapid mechanical design of architected graphene

Generative artificial intelligence (AI) is shown to be a useful tool to automatically learn from existing information and generate new information based on their connections, but its usage for quantitative mechanical research is less understood. Here, we focus on the structure-mechanics relationship of architected graphene as graphene with void defects of specific patterns. We use Molecular Dynamics (MD) to simulate uniaxial tension on architected graphene, extract the von Mises stress field in mechanical loading, and use the results to train a fine-tuned generative AI model through a Low-Rank Adaptation method. This model enables the freely designed architected graphene structures and predicts its associated stress field in uniaxial tension loading through simple descriptive language. We demonstrate that the fine-tuned model can be established with a few training images and can quantitatively predict the stress field for graphene with various defect geometries and distributions not included in the training set. We validate the accuracy of the stress field with MD simulations. Moreover, we illustrate that our generative AI model can predict the stress field from a schematic drawing of the architected graphene through image-to-image generation. These features underscore the promising future for employing advanced generative AI models in end-to-end advanced nanomaterial design and characterization, enabling the creation of functional, structural materials without using complex numerical modeling and data processing.

Laser micro/nano structuring of three-dimensional porous gradient graphene: Advanced heater for antibacterial surfaces and ion-selective electrode for sweat sensing

The development of three-dimensional (3D) gradient porous graphene (GPG) patterns, leveraging the remarkable properties and unique structure of graphene, has garnered considerable attention owing to their excellent electrochemical and electrothermal performances. Among the numerous graphene synthesis methods, laser-induced graphene (LIG) stands out as an eco-friendly and practical approach for creating patterned graphene structures on commercial films, with synthetic details varying depending on the application. Unlike conventional LIG with uniform geometric characteristics, we developed an innovative approach for circular line-scribed ultraviolet (UV)-LIG patterning; these approaches utilize a high overlapping factor and low power to achieve uneven graphitization. A comprehensive analysis of the 3D GPG was conducted via specific surface area measurements, contact angle analyses, sheet resistance measurements, X-ray photoelectron spectroscopy, and Raman spectroscopy. These 3D GPG structures exhibit large surface areas, low sheet resistance, and superior ion transport, thus improving heater and ion-selective electrode (ISE) performances. The fabricated 3D GPG heaters were successfully applied to antibacterial surfaces, and the ISEs were applied in a sweat sensor was demonstrated owing to the remarkable combination of high surface area, low electrical resistance, and unique 3D porous structure.

Prediction of cluster energy of lithium clusters from codescriptors with application in 2D porous graphene

A lithium metal anode has a high energy density, but its applications face numerous challenges, particularly the irregular deposition of lithium dendrites, which form due to the aggregation of lithium clusters, posing serious safety risks. Research has revealed that small lithium clusters have the potential to enhance the electrode potential in Lithium-ion batteries (LIBs), and cluster energy affects the stability of lithium clusters. Modern computational tools and DFT calculations of lithium clusters can provide invaluable insights into their chemical, physical, and structural properties. However, calculating structural properties through large-scale experiments can be time-consuming and expensive. To overcome the challenges inherent in studying lithium clusters, this study employs a novel approach. We construct molecular graphs for the most stable structures and leverage CoM Polynomial computations to generate codescriptors, enabling efficient and accurate predictions of cluster energy for diverse lithium cluster configurations. The curvilinear regression analysis filters out highly significant regression equations and highly predictive codescriptors. Additionally, we investigated two molecular structures of porous graphene, namely linear and triangular, and obtained topological codescriptors’ analytical expressions by utilizing the CoM Polynomial in each case. A deeper understanding of both lithium clusters and porous graphene properties is essential for optimizing LIBs’ performance and stability.

Electrochemical Synthesis of a Composite of Few-Layer Graphene Structures with PdNi-Alloy Nanoparticles and Its Electrocatalytic Activity in the Methanol Oxidation Reaction

Electrochemical Synthesis of a Composite of Few-Layer Graphene Structures with PdNi-Alloy Nanoparticles and Its Electrocatalytic Activity in the Methanol Oxidation Reaction

Regulating the evolution of interfacial species via B, N-codoped Pt sites for oxygen reduction electrocatalysis

The sluggish kinetics of the oxygen reduction reaction (ORR) poses significant limitations to the widespread application of the ORR in advanced energy systems. Here, we present a composite catalyst consisting of Pt nanoparticles immobilized on 3D B, N-doped graphene oxide (Pt/GO-BCN). Through X-ray absorption fine structure spectroscopy and synchrotron radiation infrared spectroscopy analyses, we discovered that the codoping of B and N significantly regulates the electronic structure of graphene and enhances the interaction between Pt nanoparticles and the supports. The electronic state-optimized 3D support promotes the uniform distribution of Pt nanoparticles with small size, forming a low-resistance interfacial environment to accelerate the cleavage of the *OOH species during the reaction process. The ORR activity and selectivity of Pt/GO-BCN significantly surpass those of commercial Pt/C catalysts, and excellent durability under long-term operation is achieved. These results provide a new avenue for the design of advanced Pt-based catalysts.

Temperature and inhomogeneous background affect plasmons in four-layer graphene structures

We employ the random-phase approximation to investigate the effects of temperature and the inhomogeneity of background dielectric on the collective excitations and respective broadening functions in 4-MLG structures. Computations present that the systems have four plasmon modes, corresponding to one in-phase and three out-of-phase oscillations of charged particles. We obtain that plasmon frequency and respective broadening functions behave as increasing functions of temperature with sufficiently large wave vectors. Dissimilarly, in small wave vector regions, the increase in temperature slightly decreases plasmon energy, but further increases in temperature increase this parameter. In addition, as the separation increases, both plasmon frequency and broadening functions significantly reduce, and the inhomogeneity of the dielectric background strongly decreases plasmon energy and its loss. We observe that both temperature and the environment's inhomogeneity should be considered in calculations.

Rapid Preparation of Porous Graphene by Microwave‐Assisted Chemical Etching for Electrochemical Energy Storage

AbstractPorous graphene materials possess a larger specific surface area and a more abundant presence of active sites compared to non‐porous graphene materials, resulting in enhanced electrochemical properties. The presence of in‐plane nanopores facilitates the transmission of ions and mass, further expanding the potential applications of graphene materials in electrochemical energy storage and various other fields. In this study, a rapid synthesis of porous graphene was achieved through a microwave‐assisted chemical etching method. With the aid of microwave radiation, the etchant efficiently reduced the oxygen‐containing groups within the graphene structure, consequently generating nanopores with an approximate diameter of 10 nm. By optimizing the microwave treatment parameters, including pretreatment time, etching time, amount of etchant H2O2, and microwave power, the area percentage of nanopores in the graphene material was controlled to enhance its electrochemical properties. Porous graphene materials exhibited excellent specific capacitance and rate capability, making it a promising material for capacitor applications. Moreover, the lower internal resistance of porous graphene, compared to non‐porous graphene, demonstrated the significant role of nanopores in enhancing the electrochemical performance. These findings highlight the potential of porous graphene for use in electrochemical energy storage.