Synthesis Of Graphene Nanosheets Research Articles

Synthesis of graphene nanosheets from coffee ground waste and its incorporation to mixed-phase TiO2 as photocatalyst in anthracene degradation

The increasing level of coffee consumption in Indonesia causes a significant amount of coffee ground waste as landfill, leading to serious environmental problems on account of phenol derivatives and acidic compounds as its constituents. Containing high carbon content, waste coffee ground is a favourable biomass candidate to be converted into carbon-based material, such as graphene nanosheet (GN). Having wide surface area, graphene derivatives can be used to modify surface of many materials, such as TiO2. The aim of this study is to synthesize graphene-modified TiO2 with a mixed anatase:rutile phase (9:1) and to analyse its photocatalytic activity towards the photodegradation of anthracene, in comparison with unmodified TiO2. UV-DRS analysis showed a significant decrease in the band gap of TiO2/GN-A (2.78 eV) compared with TiO2 (3.00 eV), leading to an increase in photocatalytic activity (Kt TiO2 = 7.26 × 10-4 min−1; Kt TiO2/GN-A = 3.43 × 10-3 min−1). All in all, the synthesized photocatalyst materials presented promising potential to be applied as photocatalysts in photodegradation of organic compounds.

The role of biocatalysts in the synthesis of graphene nanosheets from sub-bituminous coal

The synthesis of graphene nanosheets (GNs) from sub-bituminous coal aims to increase the added value of coal in a cheap, easy and proclaimed this method on an industrial scale. The addition of biocatalyst (BFS) in the pyrolysis process can reduce the reactive temperature of the pyrolysis process so that the combustion reaction runs better at low temperatures of 200-300℃. Followed by hydrothermal carbonization of coal at 180℃ for 6 h with the addition of pyrolysis liquid smoke. Filter the results and exfoliate using 24 kHz ultrasonication for 30 min. Then centrifuge at 10,000 rm for 10 min to separate the solids. Wash the solids with deionized water to obtain a neutral pH. Using FESEM and TEM to obtain the morphological characteristics of GNs, structural characterization was studied using XPS, FTIR, and XRD. The GNs produced using BFS yielded 7–8 layers of Graphene, and a crystal size of 2.7 nm showing promising efficiency from the methodology used.

Graphene Nanostructures by Pulsed Laser Ablation in Liquids: A Review

High-quality graphene has demonstrated remarkable mechanical, thermal, electronic, and optical properties. These features have paved the road for the introduction of graphene into numerous applications such as optoelectronics and energy devices, photodegradation, bioimaging, photodetectors, sensors, and biosensors. Due to this, graphene research has accelerated exponentially, with the aim of reaching a sustainable large-scale production process of high-quality graphene that can produce graphene-based technologies at an industrial scale. There exist numerous routes for graphene fabrication; however, pulsed laser ablation in liquids (PLAL) has emerged as a simple, fast, green, and environmentally friendly method as it does not require the use of toxic chemicals. Moreover, it does not involve the use of expensive vacuum chambers or clean rooms. However, the great advantage of PLAL is its ability to control the size, shape, and structure of the produced nanostructures through the choice of laser parameters and liquid used. Consequently, this review will focus on recent research on the synthesis of graphene nanosheets and graphene quantum dots via PLAL and the effect of experimental parameters such as laser wavelength, pulse width, pulse energy, repetition rate, irradiation time, and liquid media on the produced nanostructures. Moreover, it will discuss extended PLAL techniques which incorporate other methods into PLAL. Finally, different applications that utilize nanostructures produced by PLAL will be highlighted. We hope that this review will provide a useful guide for researchers to further develop the PLAL technique and the fabrication of graphene-based materials.

On the transition of reaction pathway during microwave plasma gas‐phase synthesis of graphene nanosheets: From amorphous to highly crystalline structure

AbstractFourier‐transform infrared spectroscopy and proton‐transfer‐reaction–mass spectrometry are used in a complementary way to study gas‐phase processes during decomposition of ethanol in a microwave plasma torch. Decomposition products (C, C2 and simple hydrocarbons) reassemble into higher hydrocarbons and graphene nuclei and further grow into graphene nanosheets (GNS). Depending on microwave power, ethanol flow rate and molecular gas admixture, the material structure changes from amorphous to crystalline. The presence of C2n + 1H y species was found to be responsible for the formation of defects in the GNS structure. O2 and H2 admixtures change the gas temperature axial profile and consequently modify reaction pathways influencing growth and production rate of GNS. Determination of reaction pathway selectivity enables us to predict whether high‐quality or defective GNS are produced.

Synthesis of graphene nanosheets by the electrical explosion of graphite powder confined in a tube

The electrical explosion method, due to its simplicity and high efficiency, has attracted significant attention in graphene synthesis. Generally, graphite rods and carbon fibers are used to form graphene by electrical explosions in a liquid medium. In the present work, the preparation of graphene from graphite powder in a tube by electrical explosions was proposed. A certain amount of graphite powder was confined in a tube and electrically exploded in an argon atmosphere. The diameter of the constraint tube affected the microstructure of the as-prepared products (graphite nanosheets and few-layer graphene) under the charging voltage of 14 kV. When the diameter of the constraint tube was 3 mm, explosive products were mainly composed of few-layer graphene. The collision degree between graphite powder particles and the diameter of the constraint tube were the key factors to form graphene by electrical explosions. The underlying mechanism governing the generation of graphene was carefully illustrated. Moreover, a self-designed device for electrical explosions was developed.

Greener approach towards the synthesis of graphene nanosheet and its application in supercapacitor

Green synthetic method for the graphene sheet’s production has precisely attracted the researcher’s interest. Currently, most of the conventional practices for graphene oxide (GO) reduction into reduced graphene oxide (RGO) included chemical reduction using highly toxic and hazardous reducing agents. In this respect, here we are introducing a facile, sustainable, economically feasible, and green method to graphene sheet’s synthesis by reducing the GO using natural monoterpenoid thymol. The phenolic groups present in thymol have the ability to convert exfoliated GO to RGO under reflux condition. The quality of the T-RGO was confirmed using characterization techniques. The electrochemical results showed that the T-RGO has a high specific capacitance and energy density of 400 F g−1 and 55 W h kg−1, respectively, at a current density of 1 A g−1. These characterization data obtained show that this green approach holds an excellent standpoint in the synthesis of energy-storage graphene materials.

Effect of synthesis conditions on methylene blue adsorption capacity of electrochemically preparated graphene

This report presents the effect of synthesis conditions on the synthesis of graphene nanosheets via electrochemical exfoliation method for adsorbing methylene blue from aqueous solution. Oxygen-containing functional groups and defects in the material were characterized by Raman and X-ray photoelectron spectroscopy (XPS). As a result, by using voltage of 15 V, (NH4)2SO4 (5%, 250 mL) and KOH (7.5%, 250 mL), the obtained material showed the highest MB adsorption capacity due to the high densities of oxygen-containing groups and defects comparison to other conditions.

Chemistry and Mechanism of One-Step Formation of Graphene from Agrowaste

The one-step synthesis of high-quality graphene derivatives via CVD process has gained considerable importance nowadays for high-performance electronics and sensors. However, the use of harsh chemicals, high temperature, sensitivity, and the problem of separation of graphene from the substrate, motivated the one-step synthesis of graphene from a non-graphitic precursor, bypassing the use of graphite. In this paper, we have reported for the first time, the synthesis of graphene nanosheets from sugarcane bagasse at the normal atmospheric condition in a single step, avoiding the formation of GO. Here, the pyrolysis of sugarcane bagasse was carried out in the temperature range of 250-450o C in the presence of sodium hydroxide. The results suggested that even the low temperature (250–450o C) facilitated the development of graphitic planes via condensation and aromatization of the glucose monomers present in the precursor. The XRD pattern showed 2θ at around 25o in each case, which confirmed the formation of graphene instead of GO. The FESEM, TEM, and EDX analysis proved the formation of few-layer nanosheets of graphene from carbon-rich waste precursors in a single step.

Synthesis of graphene nanosheets by emitted black carbon and its sustainable applications

Abstract An approach has been made to convert Black carbon (BC) into two-dimensional novel Graphene nanosheets (GNS) by simpler approach carried-out for the conversion of facile using Black carbon (BC) by purging Catalytic-Chemical vapor deposition (C-CVD) technique. Iron and Nickel (Fe-Ni) bi-metallic catalyst supports 92 % GNS yield, as opposed to other lower yields method and using less-cost effective catalysts. The synthesized GNS is employed for the photo-catalytic degradation of Rhodamine-B (RhB) in addition with Janus Green (JG) in a single step which resolves two organic dye contaminant issues with non-toxic molecular intermediates at the same time, under influence of solar light exposure. The Anti-bacterial properties activity of selected gram-negative and gram-positive and fungal activity was systematically achieved. GNS is highly stable and shows less toxicity against the Human embryonic kidney (HEK-293) cell lines and safer to the environment. Furthermore, regeneration efficiency of GNS, which was still at its higher value even after five consecutive cycles of recycling testing, GNS can perform the quite superior result than the earlier reported studies on structurally altered graphene and other graphitic based materials. The fusion of these investigations introduces a new course, promising way to achieve the new era in environmental remediation and utilization of these materials in future eco-friendly approaches.

Boron-doped graphene/TiO2 nanotube-based aqueous lithium ion capacitors with high energy density

Graphene and its derivatives have gained tremendous research interest for energy storage because of their high capacitance and structural stability. However, the synthesis of graphene nanosheets with high electrochemical activity remains a great challenge. Herein, boron-doped graphene (BG)/TiO2 nanotube array/Ti multilayer films were constructed by growing BG sheets on the TiO2 nanotubes. The high electrochemical activity of BG sheets and electronic transfer capability of TiO2 nanotubes led to good structural stability and energy-storage capability. The as-fabricated capacitors with two BG/TiO2/Ti electrodes in a CMC/LiCl gel electrolyte could realize a wide operational voltage of 2.6 V and deliver a high energy density of 221.8 Wh∙kg−1 at 5.98 kW kg−1, which still remains 102.4 Wh∙kg−1 as the power density increased to 35.1 kW kg−1. These devices show very high electrochemical lifespans, with approximately 91.3% retention after 10000 charge/discharge cycles.

Synthesis of graphene nanosheets using Camellia sinensis and its electrochemical behavior for energy storage application

Graphene nanosheets were successfully synthesized by modified Hummer's method using Camellia sinensis extract as a reducing agent, without hydrogen peroxide and any other hazardous solution. X-ray diffraction peak seen at ~3.4 Å interplanar spacing confirms the presence of sp2 carbon bonds. Raman spectra and morphological studies revealed the formation of multilayered graphene sheets. The peak broadening seen in FTIR spectra clearly supports the elimination of oxygen content in these green synthesized graphene sheets besides Raman spectra. The charge transfer resistance of 9.55 Ω obtained in Nyquist plot indicates the good conductivity of graphene. In cyclic voltammetry, a maximum specific capacitance value of 666 F/g is obtained at a scan rate of 5 mV/s. This higher capacitive behavior of the sp2 carbon lattice graphene nanosheets find future application in supercapacitors.

Synthesis of GNS-MnS hybrid nanocomposite for enhanced electrochemical energy storage applications

With high power density and promising possibilities for high energy density, the electrochemical capacitor has become an indispensable energy storage device to satisfy the future energy demands. Here in, we report on synthesis of graphene nanosheets (GNS) supported manganese sulfide (MnS) hybrid (GNS-MnS) nanocomposite by a simple, facile hydrothermal process. The resultant GNS-MnS hybrid nanocomposite with robust electronic amalgamation facilitates swift transfer of both ions and electrons across the interface between electrode surface and electrolyte ions than pristine MnS. Benefiting from the better conduction along with improved active sites of the MnS in GNS-MnS hybrid nanocomposite, a high ratio surface/near-surface reactions is dominated by high specific capacity even at high current rate. As such, the GNS-MnS hybrid nanocomposite exhibited a maximum specific capacitance of 792 F g−1 at 2 A g−1 along with better retention rate of 58% at 15 A g−1, is significantly higher than that of pristine MnS (423 F g−1 at 2 A g−1 and 37% retention at 15 A g−1). In addition, the fabricated symmetric GNS-MnS hybrid nanocomposite cell delivered a high energy density of 25 W h kg−1 and power density of 7160 W kg−1. Moreover, specific capacitance of 91.1% is retained after 15000th cycles with columbic efficiency of ∼100% at 20 A g−1. The remarkable electrochemical performance of GNS-MnS hybrid nanocomposite electrode demonstrated its potential as a key material for developing high energy supercapacitors.

Synthesis of Graphene Nanosheets through Spontaneous Sodiation Process

Graphene is one of the emerging materials in the nanotechnology industry due to its potential applications in diverse areas. We report the fabrication of graphene nanosheets by spontaneous electrochemical reaction using solvated ion intercalation into graphite. The current literature focuses on the fabrication of graphene using lithium metal. Our procedure uses sodium metal, which results in a reduction of costs. Using various characterization techniques, we confirmed the fabrication of graphene nanosheets. We obtained an intensity ratio (ID/IG) of 0.32 using Raman spectroscopy, interlayer spacing of 0.39 nm and our XPS results indicate that our fabricated compound is relatively oxidation free.

Enhancing Graphene Concentration in Organic Solvents with Salts and Additives

The synthesis of graphene nanosheets by liquid-phase exfoliation of graphite in organic solvents is reported. The graphene concentration was enhanced with addition of salts and additives in organic solvents. Additives and salts intercalate into the edges of graphite which enhances graphene concentration significantly. It was found that by adding phenophthalein in cyclohexanone (CYN) organic solvent the graphene yield was increased nine times from 0.005 mg/ml to 0.045 mg/ml. Addition of organic and in-organic salt also affects the graphene concentration in organic solvents. It has been found that with addition of sodium citrate organic salt, the graphene concentration in dimethyl sulfoxide (DMSO) organic solvent was increased from 0.002 to 0.015 mg/ml. In 1-methyl-2-pyrrolidinone (NMP) organic solvent the effect of addition of anthracene in enhancing the graphene concentration was most prominent. The enhanced graphene concentration can be used for making graphene films and composites for various applications such as field effect transistors, flexible supercapacitors etc

One-step synthesis of graphene nanosheets through explosive process

ABSTRACTHerein, we report a facile process to prepare graphene nanosheets through explosive method. The explosive products were characterized by using XRD, TEM, AFM, Raman and XPS. The results show that the obtained materials have a perfect sheet-like structure, and vary in the two-dimensional plane at the macron scale and in thickness at the nanoscale. This technique may offer a low-cost, energy-saving, and efficient way to prepare graphene materials.

Solar light reduced Graphene as high energy density supercapacitor and capacitive deionization electrode

Graphene is a promising electrode material for high performance supercapacitors and capacitive deionization applications. Our present work is focused on the synthesis of graphene nanosheets by the reduction of graphite oxide using focused solar irradiation. The as prepared graphene nanosheets are characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopic (FTIR) techniques for surface, structural and functional group analysis. Electrochemical properties are studied using cyclic voltammetry and galvanostatic charge-discharge method. The fabricated supercapacitor cell shows high specific capacitance of 265.9 and 187.1Fg−1 with 6M KOH and ionic liquid electrolyte (EMIMBF4), respectively. High energy density of 58.5WhKg−1 has been obtained for EMIMBF4 electrolyte. The electrosorption studies were also performed to study the effect of deionization behaviour of the prepared graphene under flow in between electrodes technique. The electrosortion capacity of 22.4mg/g has been obtained for 100mM NaCl (∼5844mg/l) solution at the applied voltage of 1V.

Novel aluminum-graphene and aluminum-graphite metallic composite materials: Synthesis and properties

A novel method of creating new lightweight, aluminum-metallic, composite materials under halides melt at temperatures 973–1073 К under air atmosphere is proposed. The method for synthesizing aluminum-based metallic composite materials, containing up to 2 wt. % graphene sheets uniformly distributed in a metal matrix, is entirely new, having no analogies in current science and practice. The synthesis of graphene nanosheets in a metal matrix is one-step, simultaneous process, taking place directly in molten aluminum under alkali halides melt without the necessity of a separate stage of synthesis and introduction of graphene. This has the potential to facilitate the inexpensive synthesis of aluminum-graphene composites with a high concentration of graphene.The aluminum-graphene composites formed according to this method are characterized by a high uniformity of graphene films with linear dimensions from 100 nm to 50 μm and a thickness from one to three nm in the metal bulk.No aluminum carbide forms under synthesis; the aluminum-graphene and aluminum-graphite composites are resistant to corrosion in NaCl solution.The hardness, strength and ductility of aluminum-graphene composites are at least 2–3 times higher than the initial aluminum material, proportional to the concentration of graphene.

A facial solvothermal reduction route for the production of Li4Ti5O12/graphene composites with enhanced electrochemical performance

A simple and scalable solution fabrication process preparing Li4Ti5O12/graphene anode material for lithium-ion batteries is the focus of this paper. The aforementioned graphene sheets are attached tightly to lithium titanate particles under the action of solvothermal treatments, which provide a highly conductive network for electron transportation. It is worth mentioning that the synthesis of graphene nanosheets from graphite oxide has been adapted to allow for a more cost-efficient, environmentally friendly, and scalable production method. Electrochemical tests reveal that electrodes with a graphene content of 3wt% present a Li-ion storage specific capacity of 184mAh/g at 0.1C, and the specific capacity maintains at 158mAh/g even after 50 cycles. Moreover, spinel-type Li4Ti5O12 can also be fabricated via hydrothermal processes in a shorter time and at a lower temperature compared to solid-state synthesis. This low energy and environmentally friendly method of preparing Li4Ti5O12/graphene lends itself to a variety of applications, ranging from portable electronic devices to electric vehicles and energy storage devices.

Ferritin-mediated biomimetic synthesis of bimetallic Au–Ag nanoparticles on graphene nanosheets for electrochemical detection of hydrogen peroxide

We demonstrated a biomimetic green synthesis of bimetallic Au – Ag nanoparticles (NPs) on graphene nanosheets (GNs). The spherical protein, ferritin ( Fr ), was bound onto GNs and served as the template for the synthesis of GN / Au – Ag nanohybrids. The created GN / Au – Ag nanohybrids were further utilized to fabricate a non-enzymatic amperometric biosensor for the sensitive detection of hydrogen peroxide ( H 2 O 2), and this biosensor displayed high performances to determine H 2 O 2 with a detection limit of 20.0 × 10-6 M and a linear detection range from 2.0 μM to 7.0 mM.

Effect of Oxidation Condition on the Synthesis of Graphene Nanosheets and the Electrical Properties of Poly (Trimethylene Terephthalate) Composites Prepared Using these Nanosheets

Graphene nanosheets (GNSs) with different oxygen contents crucially affect the performance of polymer composites. In this study, we compared GNSs prepared from graphite oxide (GO) using three different concentrations of potassium permanganate and thermal reduction of GO at 1050 °C. The structural properties of GO and GNSs were investigated by Fourier transform infrared spectroscopy and Raman spectroscopy. Moreover, an effective coagulation method was used to prepare poly (trimethylene terephthalate) (PTT) composites filled with well-dispersed GNSs by selecting suitable solvents for solution blending. The electrical properties of PTT/GNSs were investigated to reveal the effect of oxygen content of GNSs.