Facile Synthesis Of Graphene Research Articles

Facile synthesis of graphene oxide/Fe3O4 nanocomposite for electrochemical sensing on determination of dopamine

Dopamine concentration abnormalities in the body can cause various disorders and diseases such as Parkinson's, Tourette's syndrome, and depression. In this study, graphene oxide (GO) was combined with Fe3O4 to sensitively and selectively detect dopamine. The performance was evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The results of testing with CV on the solution [Fe(CN)6] showed that a modification with GO gave a maximum effective surface area value of 0.0127 cm2, proving that GO can increase the effective area and conductivity of the sensor. DPV testing shows that dopamine detection using GO/Fe3O4 has a linear range at a concentration of 1–10 μM with a detection limit of 0.48 μM and a quantification limit of 1.6 μM. GO/Fe3O4 also shows good selectivity where the peak current is separated by 0.245 V with ascorbic acid, which is the closest interference compound.

Facile synthesis of graphene oxide-polyaniline-copper cobaltite (GO/PANI/CuCo2O4) hybrid nanocomposite for supercapacitor applications

A novel type ternary GO/PANI/CuCo2O4 composite for electrode material was successfully synthesized and ensured by different characterizations such as XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), FE-SEM (Field emission scanning electron microscopy), and EDS (Energy-dispersive X-ray spectroscopy). The interconnected morphology of ternary GO/PANI/CuCo2O4 indicates superior electrochemical performance. Ternary GO/PANI/CuCo2O4 displayed the maximum specific capacitance of 741.39 F/g at 1 mV/s scan rate and 312.72 F/g at 1 A/g current density using three-electrode and symmetric two-electrode system, respectively. The ternary GO/PANI/CuCo2O4 electrode based symmetric device had specific energy of 62.54 Wh/kg at 1 A/g current density and specific power of 5997.61 W/kg at 20 A/g. The systems have a wide potential window of 1.2 V, which is beneficial for the energy density. The ternary material electrode also has the lowest value of charge transfer resistance (Rct) as 12.23 Ω and relatively good specific capacitance of 84.25% after 5000 cycles. The excellent electrochemical nature of ternary GO/PANI/CuCo2O4 is mainly because of the synergistic effect which has brought this material to the spotlight for the supercapacitor application.

Facile Synthesis of Graphene Oxide/Titanate Nanotube Composites and Their Application for Cobalt(II) Removal

In this work, the novel graphene oxide/titanate nanotubes (GTNT) composites were synthesized through a facile and high-yield alkaline hydrothermal method. SEM, TEM, XRD, BET, and TGA/DTA were applied to study the morphology and structure of the GTNT composites. The results show that a huge number of titanate nanotubes are closely attached to the graphene sheet structure and overlap each other. This hierarchical morphology endows the GTNT composites with not only the high specific surface area of 236.9 m2/g but also abundant porous structure, both of which are benefit for Co(II) adsorption. The batch adsorption experiments demonstrate that the GTNT composites have a high adsorption capacity and rapid kinetics for Co(II) adsorption (10 min for equilibrium). The adsorption capacity of the GTNT composites reaches 211.1 mg/g. The adsorption kinetics of the GTNT composites fits well to the pseudo-second-order model, while the adsorption isotherm of which fits well to the Langmuir model. The adsorption performance of Co(II) ions on the GTNT composites has a great relationship with the pH value, in the pH range of 1–7, the Co(II) adsorption capacity of the GTNT composites greatly increases with the increase of the pH value. In addition, the effect of coexisting anions on fluoride removal is also investigated. Na+, K+, and Mg2+ ions have shown a negligible effect on the Co(II) adsorption efficiency of the GTNT composites. However, the existences of Cu2+, Cd2+, and Pb2+ ions would clearly have an effect on the Co(II) adsorption of the GTNT composites. The adsorption mechanism is also discussed. It is believed that the GTNT composites can be considered as a potential functional material for removing the radioactive metals containing wastewater.

Facile Synthesis of Graphene with Fast Ion/Electron Channels for High-Performance Symmetric Lithium-Ion Capacitors.

With the battery-type anode and capacitor-type cathode, lithium-ion capacitors (LICs) are expected to exhibit both high energy and high power density but suffer from the mismatch of the electrode reaction kinetics and capacity. Herein, to alleviate the mismatch between the two electrodes and synergistically enhance the energy/power density, we design a method of microwave irradiation reduction to prepare graphene-based electrode material (MRPG/CNT) with fast ion/electron pathway. The three-dimensional structure of CNT intercalation to graphene inhibits the restacking of graphene sheets and improves the conductivity of the electrode material, resulting a rapid ion and electron diffusion channel. Due to its specific properties, MRPG/CNT materials can be used as both anode and cathode electrodes of LICs at the same time. As anode, MRPG/CNT shows a high capacity of 1200 mAh g-1 as well as high rate performance. As cathode, MRPG/CNT displays a high capacity of 108 mAh g-1 and the capacity retention of 100% after 8000 cycles. Coupling the prelithiated MRPG/CNT anode with MRPG/CNT cathode gives a full-graphene-based symmetric LIC, which achieves a high energy density of 232.6 Wh kg-1 at 226.0 W kg-1, 111.2 Wh kg-1 at the ultrahigh power density of 45.2 kW kg-1, and superior capacity retention of 86% after 5000 cycles. The structure design of this electrode provides a new strategy for alleviating the mismatch of LIC electrodes and constructing high-performance symmetrical LICs.

A facile synthesis of graphene oxide/locust bean gum hybrid aerogel for water purification

Graphene oxide/locust bean gum (GO/LBG) aerogels, synthesized in an ice crystal template without using any chemical modifiers, were used for the treatment of water pollution. Various characterization results showed that GO/LBG aerogel exhibited a network-like three-dimensional (3D) structure with large specific surface area. The adsorption data revealed that GO/LBG aerogels with GO/LBG mass ratio of 1:4 (GO/LBG-1 aerogels) exhibited more prominent adsorption properties for Rhodamine-B (RhB, 514.5 mgg−1) than Indigo Carmine (IC, 134.6 mgg−1). Simultaneously, GO/LBG-1 aerogels could selectively remove RhB from a binary mixed solution of RhB-IC dyes. Furthermore, GO/LBG-1 aerogels also displayed excellent reusability and could still reach 92.4 % after ten cycles. Based on the above results, GO/LBG-1 aerogel could be considered as an ideal adsorbent with potential application value for removing water-soluble RhB from wastewater.

Facile synthesis of graphene paper/polypyrrole nanocomposite as electrode for flexible solid-state supercapacitor

A green and facile method was adopted to fabricate graphene paper (GrP) decorated with polypyrrole (PPy) as supercapacitor electrode material. Polypyrrole was deposited on GrP at room temperature via one-step electropolymerization of 5% pyrrole with 0.5 M H2SO4 as electrolyte solution in a three-electrode configuration using GrP, platinum wire, and Ag/AgCl (1 M KCl), as working electrode, counter electrode and reference electrode, respectively. Different cyclic voltammetry (CV) deposition cycles (1, 3, 5, 8, 10 and 15) were applied under constant potentials in the range of 0.0 to 1.0 V at a scan rate of 30 mV/s. Successful electropolymerization of PPy onto GrP was confirmed via analytical (FT-IR, XPS and Raman spectroscopies), electrochemical (CV, electrochemical impedance spectroscopy), and morphological (scanning electron microscopy) characterizations of the fabricated GrP-PPy nanocomposite. Based on the CV data obtained in a three-electrode system, among the as-prepared electrodes those prepared with eight deposition cycles of PPy (GrP-PPy/8) produced the best supercapacitance performance. A flexible asymmetric all-solid-state supercapacitor device (AASD) was fabricated with GrP-PPy/8 as positive electrode and GrP as negative electrode. The areal capacitance of the AASD was as high as 128.9 mF/cm2 at current density of 0.1 mA/cm2. The AASD also exhibited excellent energy density (16.1 mWh/cm2) and power density (180 mW/cm2); and its cyclic stability was over 85% after 5,000 consecutive galvanostatic charge/discharge cycles. These results point to a novel and fast route to fabricate free-standing and flexible supercapacitor devices.

Facile Synthesis of Graphene from Waste Tire/Silica Hybrid Additives and Optimization Study for the Fabrication of Thermally Enhanced Cement Grouts.

This work evaluates the effects of newly designed graphene/silica hybrid additives on the properties of cementitious grout. In the hybrid structure, graphene nanoplatelet (GNP) obtained from waste tire was used to improve the thermal conductivity and reduce the cost and environmental impacts by using recyclable sources. Additionally, functionalized silica nanoparticles were utilized to enhance the dispersion and solubility of carbon material and thus the hydrolyzable groups of silane coupling agent were attached to the silica surface. Then, the hybridization of GNP and functionalized silica was conducted to make proper bridges and develop hybrid structures by tailoring carbon/silica ratios. Afterwards, special grout formulations were studied by incorporating these hybrid additives at different loadings. As the amount of hybrid additive incorporated into grout suspension increased from 3 to 5 wt%, water uptake increased from 660 to 725 g resulting in the reduction of thermal conductivity by 20.6%. On the other hand, as the concentration of GNP in hybrid structure increased, water demand was reduced, and thus the enhancement in thermal conductivity was improved by approximately 29% at the same loading ratios of hybrids in the prepared grout mixes. Therefore, these developed hybrid additives showed noticeable potential as a thermal enhancement material in cement-based grouts.

Facile synthesis of graphene oxide/palygorskite composites for Pb(II) rapid removal from aqueous solutions.

As a kind of earth-abundant and cheap natural clay mineral, palygorskite (Pal) was facilely modified by grafting with graphene oxide (GO) to fabricate GO/Pal composites for rapid removal of Pb(II) from aqueous solutions. The results of characterization confirmed that the GO/Pal composites were successfully grafted between GO sheets and Pal nanorods. The effects of pH, adsorbent dosage, adsorption time, initial Pb(II) concentration and temperature on the adsorption of Pb(II) onto the GO/Pal composites as adsorbents were systematically investigated. The maximum adsorption capacity over 106.6 mg/g was obtained within a short adsorption time of less than 1 h even at 298.15 K. The adsorption of Pb(II) was a fast process that more accurately followed the pseudo-second-order kinetic equation. This process also could be described better with the Langmuir equation model than the Freundlich model. The negative values of ΔG° and the positive values of ΔH° and ΔS° indicated that it was a spontaneous, endothermic and entropy-increasing adsorption process. Compared with pristine Pal and GO powders, such the GO/Pal composites as a cost-efficient and eco-friendly adsorbents could significantly improve the adsorption properties of Pb(II) and would have potential application in the industrial wastewater treatment for rapid removal of Pb(II).

Facile Synthesis of Graphene on Cu Nanowires via Low-Temperature Thermal CVD for the Transparent Conductive Electrode

We report on the application of graphene (Gr)/copper (Cu) shell/core nanowires (NWs) as a transparent conducting electrode (TCE) for optoelectronic devices. First, we optimize the synthesis conditi...

Facile Synthesis of Graphene Encapsulated Co₂SnO₄ Nanoparticles as Enhanced Anode Materials for Lithium-Ion Batteries.

A graphene encapsulated Co2SnO4 nanoparticles (Co2SnO4 NPs@rGO) was synthesized via the analogous mechanism of electrostatic interactions followed by thermal treatment. The Co2SnO4 NPs were uniformly encapsulated in the graphene sheets. As an anode material for rechargeable lithium batteries Co2SnO4 NPs@rGO exhibits enhanced cyclability and rate performance compared with free Co2SnO4 NPs. Even after 200 cycles, it still delivered large reversible capacity of 1037.9 mA h g-1 at 200 mA g-1. The excellent electrochemical performance should be associated with the uniform encapsulation of Co2SnO4 NPs by graphene sheets, which could not only effectively buffer the volume expansion and prevent the aggregation of the Co2SnO4 NPs but maintain good electrical conductivity of the whole electrode during the discharge/charge process.

Facile synthesis of graphene oxide/PVA nanocomposites for laser optical limiting: band gap analysis and dielectric constants

Casting technique was used to prepare nanocomposites of polyvinyl alcohol (PVA) and graphene oxide (GO). GO has been set up by Hummer’s method and characterized by SEM and X-ray spectroscopy. Samples have been designed to contain a different weight percent of GO as follows: (0.370, 0.926, 1.852, 2.778, 3.704, 9.259 wt%) inside PVA matrix under the homogenous ultrasonic system to have a highly dispersed GO in PVA matrix. The nanocomposites were described and analyzed by utilizing different methods such as UV–Vis–NIR, dielectric studies at room temperature and optical limiting properties. It is shown that the influence of the nanofiller leads to the increase in the absorption values while diminishing the optical band gap of both direct and indirect transition. The dielectric constant (e′) and the dielectric loss (e″) were studied within the frequency range from 3 kHz to 10 MHz and were found to be depending on the GO contents. The conduction mechanism for the studied samples can be described by the correlated barrier hopping. PVA/GO nanocomposites showed good optical limiting properties. The synthesized GO-doped PAV can be used in electronic and optoelectronic applications especially in battery electrolyte and dye-sensitized solar cells.

Facile synthesis of graphene via reduction of graphene oxide by artemisinin in ethanol

The preparation of reduced graphene oxide (RGO) by chemical reduction of graphene oxide (GO) usually involves highly toxic reducing agents which are harmful to the environment and human health. In this paper, a mediated facile and relative green approach for the preparation of RGO in ethanol using artemisinin as a reducing agent is reported for the first time. The morphology and de-oxidation efficiency of the obtained RGO were characterized by transmission electron microscope (TEM), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). The results showed that artemisinin can effectively reduce GO into few-layered RGO with a high carbon to oxygen ratio (11.7). The mechanism for elimination of oxygen-containing functional groups decorated on GO nanosheets by artemisinin was proposed. The important features of relatively environmentally friendly and facile operation procedures endow this approach with great promise in the mass production of RGO and various graphene-based materials, especially for biomaterials.

Wet mechanochemical approach assistance to the green synthesis of graphene sheet at room temperature and in situ anchored with MnO2 in a green method

In this study, we report a green and eco-friendly method for direct synthesis of graphene sheet from natural graphite under simple conditions and in situ anchored with MnO2 via an environmental route. A wet mechanochemical approach is used to exfoliate the graphite to graphene sheet by using citric acid as a non-toxic and friendly intercalator agent instead of strongly corrosive acids such as sulfuric and nitric acids at the shortest time and environmental condition. We carried out various microscopic and spectroscopic measurements such as UV–visible spectroscopy, Fourier transform Infrared (FT-IR), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) Atomic Force Microscopy (AFM) and Handle Raman Microscopy to confirm the exfoliation of natural graphite to graphene under mild condition. Moreover, we took nanoindentation test for investigation of mechanical properties of graphene sheets. The hardness and elastic modulus obtained from this analysis are about 4.1 and 37.2 GPa, receptivity. At the following work, one pot preparation of graphene-MnO2 nanocomposite can be performed on the large scale and be utilized in a wide variety of applications. This synthesis, which is economically suitable, is performed without any reduction agent and much purification. Facile synthesis of graphene and graphene-MnO2 nanocomposite via a green and simple way makes it scalable to apply in many fields.

Green and facile synthesis of graphene nanosheets/K3PW12O40 nanocomposites with enhanced photocatalytic activities

K3PW12O40 is a promising polyoxometalate photocatalyst for the removal of organic pollutants from water. However, two main disadvantages of poor adsorptive performance and high recombination rate of photogenerated electron-hole pair hinder its practical applications. In this paper, a new graphene nanosheets/K3PW12O40 nanocomposite has been synthesized via a green photoreduction strategy, being low-cost and scalable production. Characterizations show that K3PW12O40 nanoparticles with 60nm or so have been successfully deposited on the graphene nanosheets. As a kind of photocatalyst, the binary graphene nanosheets/K3PW12O40 nanocomposite displays improved photocatalytic activity compared to pure K3PW12O40. This improvement is ascribed to the introduction of graphene nanosheets in the nanocomposite, which could increase adsorptive property and reduce the recombination of electron-hole pairs.

Facile synthesis of Graphene Oxide/Double-stranded DNA composite liquid crystals and Hydrogels

Investigation of the interactions between graphene oxide (GO) and biomolecules is very crucial for the development of biomedical applications based on GO. This study reports the first observation of the spontaneous formation of self-assembled liquid crystals and three-dimensional hydrogels of graphene oxide with double-stranded DNA by simple mixing in an aqueous buffer media without unwinding double-stranded DNA to single-stranded DNA. The GO/dsDNA hydrogels have shown controlled porosity by changing the concentration of the components. The strong binding between dsDNA and graphene is proved by Raman spectroscopy.

Facile synthesis of graphene using a biological method

A new, facile, low cost, environmentally safe process is demonstrated for the production of few layer graphene by liquid phase exfoliation of graphite using extracts of medicinal plants in water.

Facile Synthesis of Graphene via Direct Water-Sodium Dodecylbenzenesulfonate Exfoliation

Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science,University of Malaya, 50603 Kuala Lumpur, MalaysiaIn this study, a mild, one-step electrochemical exfoliation was demonstrated for the synthesis ofgraphene with the assistance of water and a surfactant, particularly sodium dodecylbenzenesul-fonate and sodium dodecyl sulphate. Different types of water-surfactant solutions in different con-centrations could influence the exfoliation of graphite rods. From one to several layers of grapheneflakes (with a thickness of approximately 1 nm) could be produced directly after sonication. AFMimages showed that the flake diameters from this source were typically small. Raman and IRspectroscopic analyses of the dispersed phase suggested that the exfoliation of graphene sheetswas accomplished. The flakes were also characterized using field emission scanning electronmicroscopy, X-ray diffraction, and cyclic voltammetry techniques. Further improvements in thismethodology may pave the way to develop green, cost-effective, and large-scale production meth-ods for graphene sheets.

Facile synthesis of graphene on single mode fiber via chemical vapor deposition

Direct deposition of graphene film on the standard single mode fiber is offered using a Cu-vapor-assisted chemical vapor deposition system. The gas flow of H2 and Ar before the growth process plays a crucial role for the direct deposition of the graphene film and the layers of the graphene can be controlled by the growth time. With a large gas flow, Cu atoms are carried off with the gas flow and hard to deposit on the surface of the single mode fiber before the growth process. Consequently, uniform graphene film is obtained in this case. On the contrary, with a lower one, Cu atoms is facile to deposit on the surface of the single mode fiber and form nanodots acting as active catalytic sites for the growth of carbon nanotubes. This method presents us a promising transfer-free technique for fabrication of the photonic applications.

Facile synthesis of graphene by pyrolysis of poly(methyl methacrylate) on nickel particles in the confined microzones

In this work, multi-layer graphene has been prepared by pyrolyzing poly(methyl methacrylate) (PMMA) on nickel microparticles in the confined microzones formed by organophilic montmorillonite (OMT). Gram-scale of product can be obtained per day by using this method. The obtained graphene was evaluated by scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Pyrolytic conditions such as the system composition of the composites, reaction temperature and the size of catalyst are important parameters affecting the morphology and yield of the final product. Based on the experimental observations and reported literatures, a possible formation process is discussed. The synthesis method of graphene is simple, low-cost, and scalable, which is promising for the application in many fields.