Synthesis Of Few-layer Graphene Research Articles

Feasibility of online optical diagnostics during gas-phase synthesis of few-layer graphene based on elastic light scattering measurements

Gas-phase synthesis is a promising method for scalable production of high-quality free-standing few-layer graphene (FLG) particles. This study assesses the feasibility of elastic light scattering in characterizing particle morphology and distinguishing FLG from soot-like particles that may also be produced concurrently during gas-phase synthesis. FLG particle morphology is modeled based on tomographic electron microscopy images of FLG particles produced within a plasma reactor, whereas synthetic soot particles are generated via a cluster–cluster aggregation algorithm based on morphological parameters typical of flame soot. Light scattering properties of ensembles of synthetic FLG and soot particles are simulated via the discrete dipole approximation (DDA) and the multi-sphere T-matrix method, respectively. Angle-resolved scattering properties of ensembles of FLG and soot particles are analyzed to evaluate the feasibility of scattering-based diagnostics and identify potential measurement configurations for characterizing particle morphology. Overall, certain scattering properties, especially the depolarization ratio, are observed to be sensitive to the distinctive morphological aspects of FLG and soot, which highlights the promise of light scattering-based diagnostics for characterizing morphology during gas-phase synthesis of FLG.

A bio-inspired approach for the synthesis of few-layer graphene using beetle defensive gland extract.

Graphene exhibits remarkable properties and holds substantial promise for diverse applications. Its unique combination of thermal, chemical, physical, and biological properties makes it an appealing material for a wide range of uses. But, the lack of an economical and environmentally friendly approach to synthesize good-quality graphene represents an immense challenge for the scientific community. What makes this research unique is the utilization of the defensive gland extract from the beetle species Luprops tristis (Order: Coleoptera, Family: Tenebrionidae) to synthesize a few layers of graphene (FLG). This innovative incorporation of natural resources and exploration of biologically inspired methods provides an eco-friendly and cost-effective alternative to conventional graphene production techniques. The exfoliated graphene displayed antimicrobial effects against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, with particularly potent bactericidal activity. Additionally, the cytotoxicity assay demonstrated the anti-cancer properties of biosynthesized graphene against Daltons Lymphoma Acetic (DLA) cells.

Synthesis of few-layer graphene through simultaneous ultrasonication and electrochemical exfoliation in a Bronsted acidic ionic liquid [NMP] [HSO4] aqueous electrolyte for NH3 vapor sensing

Synthesis of few-layer graphene through simultaneous ultrasonication and electrochemical exfoliation in a Bronsted acidic ionic liquid [NMP] [HSO4] aqueous electrolyte for NH3 vapor sensing

High-purity graphene and carbon nanohorns prepared by base-acid treated waste tires carbon via direct current arc plasma

As the accumulation of waste tires continues to rise year by year, effectively managing and recycling these discarded materials has become an urgent global challenge. Among various potential solutions, pyrolysis stands out due to its superior environmental compatibility and remarkable efficiency in transforming waste tires into valuable products. Thus, it is considered the most potential method for disposing these tires. In this work, waste tire powder is pyrolyzed at 560 °C to yield pyrolysis carbon black, and meanwhile, the purification effects of base-acid solutions on pyrolysis carbon black are discussed. High-purity few-layer graphene flakes and carbon nanohorns are synthesized by a direct current arc plasma with H2 and N2 as buffer gases and high-purity pyrolysis carbon black as raw material. Under an H2 atmosphere, hydrogen effectively terminates the suspended carbon bonds, preventing the formation of closed structures and facilitating the expansion of graphene sheets. During the preparation of carbon nanohorns, the nitrogen atoms rapidly bond with carbon atoms, forming essential C–N bonds. This nitrogen doping promotes the formation of carbon-based five-membered and seven-membered rings and makes the graphite lamellar change in the direction of towards negative curvature. Consequently, such change facilitates the formation of conical structures, ultimately yielding the coveted carbon nanohorns. This work not only provides an economical raw material for efficient large-scale synthesis of few-layer graphene and carbon nanohorns but also broadens the intrinsic worth of pyrolysis carbon black, which is beneficial to improving the recycling value of waste tires.

Synthesis of Few-Layer Graphene by Ball-Milling for Oxygen Reduction: Kinetics and Mechanistic Insights

Synthesis of Few-Layer Graphene by Ball-Milling for Oxygen Reduction: Kinetics and Mechanistic Insights

Relevance of C/O ratios in the gas-phase synthesis of freestanding few-layer graphene

In microwave-plasma synthesis of few-layer graphene from hydrocarbon precursors, the carbon-to-oxygen and the carbon-to-hydrogen ratios are known to influence the product ratio of graphene to amorphous soot-like particles. While the role of oxygenated hydrocarbons and water as oxygen-supplying species has been studied before, in this paper, we compare the effect of carbon dioxide, molecular oxygen, and nitrous oxide mixed with ethylene to systematically change the C/O ratio while keeping the hydrogen supply constant. Ex situ powder analysis, emission spectroscopy, gas chromatography, and simple reaction kinetics simulations are employed to evaluate and describe the synthesis process. Additionally, thermophoretically sampled nanomaterials are collected close after the first particle inception and analyzed ex situ. The results show that molecular oxygen and nitrous oxide increase the graphene fraction with decreasing C/O ratios and pure graphene is reached at 2:1.5. The decrease in C/O ratio results in an overall decrease in solid carbon yield. With carbon dioxide, pure graphene cannot be generated at a C/O ration of 2:1.5, although a similar reduction of the particle yield is observed. Thermophoretic sampling showed that the specific mixture of carbon allotropes is already defined a few cm downstream to the plasma zone. Emission spectroscopy shows that carbon dioxide forms carbon species during its decomposition in the plasma, we hypothesize that these released carbon species might influence the environment for local nucleation of solid carbon. Thus, the C/O ratio and available carbon fraction for growth cannot always be used to tailor the carbon microstructure. Moreover, the source of oxygen atoms also seems to have an effect on the resultant microstructure.

One pot green synthesis of few-layer graphene (FLG) by simple sonication of graphite and Azardirachta Indica resin in water for high-capacity and excellent cyclic behavior of rechargeable lithium-ion battery

A simple, green, and eco-friend route is employed for the preparation of few-layer graphene using Azardirachta Indica resin (AZIr) in water. In addition, the preparation of the solvent (AZIr) for the exfoliation of graphene involves various steps, including vacuum filtration and surface tension optimization by the capillary rise method. It has been demonstrated that the 4 h sonication effectively exfoliated graphite to form a Few-Layer Graphene (FLG) sheet. Structural, morphological, and surface topographical analysis were performed using X-ray diffraction, Raman spectrum, FTIR spectrum, atomic force microscopy, and Scanning electron microscope. The as-prepared FLG was demonstrated as anode material for lithium-ion batteries¸ exhibiting a high initial capacity of 464 mAh g−1 at 0.1C and excellent cyclic performance of 527 mAh g−1 at 200th cycle with 100 % capacity retention. The maximum capacity of 281 mAh g−1 was achieved when tested at a high current rate of 10C. These results suggest that few-layer graphene is a promising material for high-performance Li-ion battery applications.

Evolution of particle size and morphology in plasma synthesis of few-layer graphene and soot

This paper examines the evolution of particle size and morphology of plasma-synthesized carbonaceous nanoparticles for various reactants, reactant concentrations, reactor temperatures, and positions within the reactor. Aerosol particles were characterized at various positions downstream from the plasma zone by spatially-resolved thermophoretic sampling and transmission electron microscopy, Raman spectroscopy, and by in situ time-resolved laser-induced incandescence. Depending on the carbon-bearing reactant (ethanol or toluene) and its concentration, either pure few-layer graphene (FLG) or soot-like particles, or a mixture of both, were generated. The initial carbon nucleation has been found to commence less than 12.4 cm downstream from the plasma nozzle. In the case of FLG formation, particles show an increasing level of crumpling with increasing distance downstream from the plasma zone. The process was numerically simulated with a 1D plug-flow reactor model employing a joint population balance model for graphitic and amorphous-like particles (FLG and soot-like, respectively). The simulation includes modified versions of inception, hydrogen-abstraction-carbon-addition (HACA), and polycyclic-aromatic hydrocarbon (PAH) adsorption models adapted from a pre-existing soot model. The simulations showed that the ratio of HACA/PAH adsorption determined by post-plasma C2H2 is the main factor that affects the soot-to-FLG ratio. This is also consistent with experimental observations as reducing the rate at which carbon precursor is supplied to the reactor leads to less C2H2 in the post-plasma zone, which results in less PAH adsorption, and consequently suppressed soot formation in favor of FLG synthesis.

Self-propagating combustion synthesis of few-layer graphene for supercapacitors from CO and Mg

Graphene is considered as a promising electrode material for supercapacitors due to its large specific surface area, excellent electrical conductivity and so on. In this paper, few-layer graphene is prepared by self-propagating combustion reaction between CO and metal magnesium, using powder MgO as deposition template. Graphene with a high specific surface area of up to 928 m 2 g −1 replicates the morphological feature of powder MgO. Raman spectroscopy analysis demonstrates that the graphene layer decreases when the dosage of MgO template is increased. The specific capacitance of as-prepared sample exhibits the highest specific capacitance of 222 F g −1 at the current density of 1 A g −1 in EMI [TFSI] electrolyte. The sample demonstrates a "double high" performance with high specific energy density and high specific power density. A high energy density of 76.3 Wh kg −1 can be achieved at a specific power density of 1.75 kW kg −1 , and it can still remain 48.6 Wh kg −1 when the specific power density reaches a high level of 35 kW kg −1 . • Self-propagating combustion reaction synthesis graphene. • Synthesis graphene from CO and Mg. • Synthesized graphene has good structural properties. • Excellent capacitive performances in the electrolyte of EMI [TFSI].

Electrochemical synthesis of few layer graphene in subcritical electrolyte

A novel top-down approach to the graphene synthesis combining electrochemical ion intercalation and supercritical fluid intercalation is proposed. Potentiostatic intercalation of BF4- anion into highly-oriented pyrolytic graphite in a subcritical electrolyte based on a CO2/acetonitrile mixture in a specially designed 3-electrode high-pressure electrochemical cell has been performed. The intercalation stage of the anion inside working electrode made of highly-oriented pyrolytic graphite is studied by means of Raman spectroscopy. The dispersed solid particles contained in the electrolyte have been analyzed after the intercalation and high-pressure cell decompression by means of atomic force and transmission electron microscopies. As a result, few (2−4) layers graphene flakes with partial crystallinity have been detected in the electrolyte. Additionally, the intercalated graphite electrode has been ultrasonicated, which also resulted in the formation of few layer graphene stacks with lower lateral dimensions and higher thickness.

Industrial molasses waste in the performant synthesis of few-layer graphene and its Au/Ag nanoparticles nanocomposites. Photocatalytic and supercapacitance applications

In view of clean environment, the industry needs to address multiple demands at different levels of production and processes via the sustainable approach including recycling or smart use of produced waste. On the other hand, a development and success of green energy requires the crucial materials synthesized via efficient, sustainable methodology. Herein, the green, simple, easily scalable, fast, and highly efficient synthesis of few-layer graphene (FLG) and its composites with Au and Ag nanoparticles using a waste is presented. The FLG synthesis based on the exfoliation of graphite runs in water in the presence of industrial co-product, molasses, which next also shows performant reductive properties during Ag and Au NPs formation. The decreased size of NPs deposited on FLG indicates the synergetic effect of molasses and FLG, exhibiting the add role of FLG/molasses as metal stabilizer species. The NPs/FLG composites are efficient photocatalysts of bisphenol (BisA) degradation in the presence of peroxy-monosulfate (PMS) activator. The Au/FLG (PVDF) and Ag/FLG (PVDF) based electrodes reveal as well relatively high gravimetric capacitance, 205 Fg-1 and 729 Fg-1. The presented approach is much worthy to be further applied in the synthesis of other layered materials as well as other non-noble supported metallic systems.

Co/Mg Self-Propagating Combustion Synthesis of Few-Layer Graphene for Supercapacitors

Co/Mg Self-Propagating Combustion Synthesis of Few-Layer Graphene for Supercapacitors

Phenomenological model of synthesis of few-layer graphene (FLG) by the selfpropagating high-temperature synthesis (SHS) method from biopolymers

A phenomenological model for the synthesis of few-layer graphene (FLG) nanosheets by the method of self-propagating high-temperature synthesis (SHS) from starch, lignin, and other biopolymers is considered. We suggested that polysaccharides, in particular starch, could be an acceptable source of native cycles for the SHS process. The carbonization of biopolymers under the conditions of the SHS process was chosen as the basic method of synthesis. Chemical reactions, under the conditions of the SHS process, proceed according to a specific mechanism of nonisothermal branched-chain processes, which are characterized by the joint action of two fundamentally different process-accelerating factors - avalanche reproduction of active intermediate particles and self-heating. It is shown that the proposed model can explain the production of few-layer graphene nanosheets with linear dimensions of tens of microns and a thickness of several graphene layers.

Conductivity/Electrochemical Study of Polyvinyl pyrrolidone-Poly(vinyl alcohol)/I3\u2212 Thin Film Electrolyte for Integrated Dye-Sensitized Solar Cells and Supercapacitors

The current era focuses not only on producing solar energy but also preserving it for future use. Dye-sensitized solar cells (DSSC) and supercapacitors (SC) are such energy-based devices. DSSCs capture the solar energy and SCs store this captured energy. A natural anthocyanin dye extracted from Garcinia indica (kokum fruit) was used in the DSSCs. SnO2, one of the promising electrode materials for DSSC, was synthesized via a microwave technique. Blend polymer electrolytes (BPE) were prepared through a solution casting technique. A polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blend with varying concentrations of potassium iodide, along with iodine dopant, was prepared as a BPE electrolyte composition. The best of the PVA-PVP/KI composition was chosen using Nyquist plots of electrochemical impedance spectroscopy (EIS). Varying the temperature, the dielectric and conductivity study of the chosen composition was studied in detail. A fast/single-step synthesis technique, namely a laser-engraved approach, was used for few-layer graphene synthesis. This graphene serves as a common platform for the DSSC-SC integrated device: as a counter electrode in DSSC and graphene-graphene symmetric electrode in SC. A DSSC-SC integrated device was fabricated and characterized using various analytical and microscopy techniques. The integrated device showed a 0.42 fill factor and 0.56% efficiency. The discharge time for integrated DSSC-SC cells was found to be increased threefold.Graphical

Smart “Sticky Note” for strain and temperature sensing using few-layer graphene from exfoliation in red spinach solution

The synthesis of few-layer graphene from graphite typically uses N, N methyl pyrrolidone (NMP) or dimethylformamide (DMF) due to the strong affinity of both solvents for graphite. However, NMP and DMF are known as carcinogens and a long-time exposure to these substances may subject users to potential risk of major health issue later. Therefore, a replacement with dispersing solvent that is not only harmless but also able to exfoliate graphite at an excellent concentration yield must be outlined for a sustainable mass-production of graphene. In this work, we have successfully exfoliated graphite to few-layer graphene with a recorded yield concentration of up to 0.75°mg/ml (2.5°h) just by using extracted red spinach/water mixture as an exfoliating medium. The prepared graphene was found to possess less structural defect (ID/IG: 0.5) and high C/O ratio (6.8) and can be used further as an electrical conductive ink for smart “Sticky Note” sensor. The fabricated device was able to detect strain and temperature with gauge factor and temperature coefficient resistance of 23.5 and −32.14 × 10-4°Ω/°;C, respectively. We believe that this study would be useful for the preparation of environmental-friendly graphene that is not only strain and thermally sensitive but also producible at low -cost.

Two-step synthesis of few layer graphene using plasma etching and atmospheric pressure rapid thermal annealing

A two-step process using halogen based plasma etching combined with atmospheric pressure rapid thermal annealing has been used to synthesize few layer graphene films on 6H-SiC (0001) surfaces. In this process, the 6H-SiC substrates were etched under different plasma conditions to produce a carbon rich surface layer. This was followed by rapid thermal annealing in a flow of atmospheric pressure Ar to produce the graphene films. The effects of different etching conditions, heating rates, and average and maximum annealing temperatures were investigated. Changes in surface and near-surface composition after each step were characterized by x-ray photoelectron spectroscopy and overall film quality was assessed using Raman spectroscopy. Film defects associated with this synthesis method included a buffer layer between the SiC substrate and graphene as well as oxygen-based defects on the graphene surface. Electrical characterization of these films was performed using both two and four point methods. In the two point measurements, these films exhibited back-to-back Schottky behavior from which the Schottky barrier height, carrier density and mobility were determined. The four point measurements were used to determine the contact and film resistivity as well as the transfer length.

Synthesis of in situ N‐, S‐, and B‐doped few‐layer graphene by chemical vapor deposition technique and their superior glucose electrooxidation activity

At present, N-, S-, and B-doped grapheme-modified indium tin oxide (ITO) electrodes are produced and doping method effect on the glucose electrooxidation is investigated. Firstly, few-layer graphene is produced by chemical vapor deposition (CVD) method. Then, N, S, and B doping is carried out after graphene produced by CVD to prepare N-doped, B-doped, and S-doped few-layer graphene. N, S, and B doping is carried out by two different ways as (a) doping after synthesis of few-layer graphene and (b) in situ doping during few-layer graphene production. These materials are characterized by X-ray diffraction, scanning electron microscopy-energy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). One could note that graphene and nitrogen networks are clearly visible from SEM images. Raman spectra show that B, N, and S are doped on few-layer graphene/ITO successfully. XPS results of graphene, N-doped graphene, and in situ N-doped graphene reveal that graphene and nitrogen atoms used in the preparation of the electrodes obtain mainly in their elemental state. Then, these N-, S-, B-doped and in situ N-, S-, B-doped few-layer graphene materials are coated onto indium tin oxide (ITO) to obtain N-, S-, B-doped and in situ N-, S-, B-doped ITO electrodes for glucose (C6H12O6) electrooxidation. C6H12O6 electrooxidation measurements are investigated with cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements. As a result, in situ N-doped few-layer graphene/ITO electrode displays the best C6H12O6 electrooxidation activity with 9.12 mA.cm−2 current density compared with other N-, S-, B-doped graphene and in situ doped S and B grapheme-modified ITO electrodes. Furthermore, this current density value for in situ N-doped few-layer graphene/ITO is highly above the values reported in the literature. In situ N-doped few-layer graphene/ITO electrode is a promising electrode for C6H12O6 electrooxidation because it exhibits the best electrocatalytic activity, stability, and resistance compared with other electrodes.

Green sonochemical synthesis of few-layer graphene in instant coffee

Abstract In this work, we reported for the first time the use of bath sonication of graphite in instant coffee to produce few-layered graphene flakes. The sonication of graphene in instant coffee allows facile production of graphene flakes in a green medium and avoids the application of commonly used organic exfoliating solvents such as Dimethylformamide or N, N methyl pyrrolidone. We verified the presence of graphene flakes in the resulting supernatant using local maximum UV spectrum (269 nm) and performed thickness and length measurements of said graphene flakes by atomic force microscopy and transmission electron microscopy. The defect and purity of exfoliated graphene flakes were investigated using Raman spectroscopy (ID/IG = 0.85) and X-ray photon spectroscopy (C/O = 2.6) meanwhile Fourier transform infrared spectroscopy was used to identify the functional group attached to graphene. The production of graphene flakes in coffee was shown to have a time exponent factor of 1.07, which impressively is higher than the time exponent factor for typical sonication in a solvent and surfactant.

Development of High Purity, Few-Layer Graphene Synthesis by Electric Arc Discharge Technique

Development of High Purity, Few-Layer Graphene Synthesis by Electric Arc Discharge Technique

Green and facile synthesis of few-layer graphene via liquid exfoliation process for Lithium-ion batteries

A green and facile method using jet cavitation (JC) was utilized to prepare few layer graphene (FLG) derived from artificial graphite delamination without adding any strong acids and oxidants. The JC method not only provides high quality FLG with high yield but also demonstrate excellent electrochemical performance as anode materials for Li-ion batteries. Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) as well as BET isotherms and XPS are carried out in this study. The results of atomic force microscopy (AFM) further revealed that up to 85% of the prepared FLG were less than 10 layers. This exfoliation process happened mainly due to the cavitation-induced intensive tensile stress acting on the layered materials. Electrochemical measurements demonstrate that graphite anode delivered only 240 mAh/g while FLG anode achieved more than 322 mAh/g at 5C rate test. These results indicate that JC method not only paves the way for cheaper and safer production of graphene but also holds great potential applications in energy-related technology.