Method For Synthesis Of Graphene Research Articles

Laser‐Induced Graphene Composites for Printed, Stretchable, and Wearable Electronics

AbstractGraphene‐based composites have received attention as part of the drive towards next‐generation electronic and energy‐storage technologies. However, current graphene synthesis methods are limited by complex, time‐consuming, toxic, costly, and/or often low‐yield procedures. The synthesis of a novel stretchable graphene‐polyurethane‐poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate ink aimed at printing wearable electronics is reported. The procedure is based on low‐cost high‐yield production of high‐performance graphene ink produced by laser induction of polyimide film followed by harvesting the graphene. Screen printing is used to fabricate flexible and intrinsically stretchable micro‐supercapacitors (S‐MSCs) printed on different substrates. The resulting graphene‐based printed S‐MSCs display a remarkably high capacitive performance and attractive mechanical resiliency. High specific areal capacitance, above 23 mF cm−2, is achieved, which is the highest areal capacitance reported for highly stretchable, printed graphene supercapacitors. A repeated (200 cycles) stretchability beyond 100% is obtained while maintaining more than 85% of the S‐MSCs' original capacitance. This unique and highly scalable graphene ink synthesis method holds considerable promise for application in low‐cost graphene‐based chemical formulation, especially in the field of printed and wearable electronics toward multifunctional, energy‐storage systems capable of withstanding severe mechanical deformation while maintaining their optimal electrochemical performance.

(Keynote) Nanomaterials Transitions to Industry: Energy, Medicine and Devices

Discussed will be several nanotechnologies that have translated to industry. This will include graphene nanoribbons, graphene-nanotube hybrids, laser-induced graphene, bulk graphene synthesis methods, and other high surface area carbons. The materials are being used in electronic devices, batteries, anti-counterfeiting, medicine, oil recovery and other commercial platforms.

The influence of Graphene quality on performance of a Si/Graphene nanocomposite anode

ABSTRACTSi/Graphene nanoparticles represent attractive alternative anode materials for Lithium-ion batteries. Graphene nanosheets with different properties, including surface area, defect distance, and charge-transfer resistance, were fabricated and characterised in Si/Graphene nanocomposites formed by static-electric self-assembly then by an in-situ reduction process. Graphene nanosheets that exhibited the highest surface area, the shortest defect distance, and the lowest charge-transfer resistance demonstrated the best overall electrochemical performance, with a high initial discharge capacity of 2692 mAh g−1, good cycling performance of 1135 mAh g−1, at the 200th cycle at the current rate of 0.5 C. This work shows the preferable graphene quality for Si/Graphene nanocomposite anode and provides insights into the design of graphene nanocomposite electrodes, regardless of the graphene synthesis method.

Electrical Property of Graphene and Its Application to Electrochemical Biosensing.

Graphene, a single atom thick layer of two-dimensional closely packed honeycomb carbon lattice, and its derivatives have attracted much attention in the field of biomedical, due to its unique physicochemical properties. The valuable physicochemical properties, such as high surface area, excellent electrical conductivity, remarkable biocompatibility and ease of surface functionalization have shown great potentials in the applications of graphene-based bioelectronics devices, including electrochemical biosensors for biomarker analysis. In this review, we will provide a selective overview of recent advances on synthesis methods of graphene and its derivatives, as well as its application to electrochemical biosensor development. We believe the topics discussed here are useful, and able to provide a guideline in the development of novel graphene and on graphene-like 2-dimensional (2D) materials based biosensors in the future.

One-step low-temperature liquid phase method for synthesis of three-dimensional porous graphene and applications in supercapacitor

Three-dimensional porous graphene (3DPG) has been widely used as electrode material for supercapacitors due to its high conductivity and high specific surface area. Herein, 3DPG with controllable three-dimensional (3D) morphologies was successfully synthesized via using sodium ascorbate (SA) and ethylenediamine (EDA) by a one-step low-temperature method. The porous structure and reductive degree of the 3DPG can be tuned by adjusting the addition amount of reducing agent and pH value of graphene oxide (GO) suspension, and the pore size and specific capacitance of the 3DPG gradually increased with the suitable increase of EDA and SA. Moreover, we found that the alkaline environment is more conducive to the synthesis of 3DPG than acid environment. It is worth mentioning that the specific capacitance of the as-prepared 3DPG reached a high value for 169 F g−1 when the suitable addition amount of reducing agent and pH value was given.

A Review Paper on Graphene Coated Fibres

Graphene is now known as a super material because of its fascinating physical properties. Due to a great scope of research, it has now become a center of attraction of research scholars in physics, chemistry as well as materials science to study and explore its potential applications. In this paper, a brief review is presented on the various graphene synthesis methods and a short introduction of different types of fibres is discussed. Various studies have been carried out to obtain graphene coating on different fibres and observe the changes in their physical and chemical properties. This paper also provides the different types of coating methods used to form graphene layer on the fibres discussed.

Analysis of the low-temperature restoration process of graphene oxide based on in situ conductivity measurement

Graphene, a honeycomb network of sp2 carbon atoms, is expected to replace conventional materials in various fields, which makes it important to develop a high-throughput graphene synthesis method for industrial applications.

Review on graphene and its derivatives: Synthesis methods and potential industrial implementation

Graphene and its derivatives have gained significant attention of late due to their remarkable physicochemical properties. This review focuses firstly on the synthesis methods of graphene and its derivatives along with their attributes and characterization techniques. This is followed by a discussion of the potential industrial implementation of the synthesis routes. The potential industrial implementation of the graphene synthesis methods are reviewed using the key criteria of cost, process condition, yield, scalability, product quality and environmental impact. The literature data supported that synthesis routes such as oxidative exfoliation-reduction, liquid-phase exfoliation and chemical vapor deposition have the potential to be commercialized due to their ability to produce large amount of high quality graphene. Further development is necessary to overcome barriers such as environmental concerns and the high graphene cost.

Analysis of graphene films grown on copper foil at 845 °C by intermediate pressure chemical vapor deposition

Chemical vapor deposition (CVD) is the widely accepted method for synthesis of large area graphene from thermal decomposition of hydrocarbons. However, the high temperature (above 1000 °C) requirement is the major drawback of this technique. The present study is an effort towards growing graphene on copper foil using methane at a temperature of 845 °C without incorporation of any additional energy sources. This is achieved by tailoring the growth parameters at 8 mbar in thermal chemical vapor deposition. The effect of total pressure and the effect of growth-supporting gases on the growth and number of layers of graphene were analyzed to select a favorable deposition condition. Graphene formation and its uniformity were examined by Raman spectroscopy, SEM, optical microscopy, AFM and TEM analysis. No studies till date, have reported a growth temperature as low as 845 °C for complete graphene coverage on copper by thermal CVD using methane as the precursor. The low temperature can reduce the thermal budget for graphene production to a certain extent.

High degree reduction and restoration of graphene oxide on SiO2 at low temperature via remote Cu-assisted plasma treatment

A high throughput synthesis method of graphene has been required for a long time to apply graphene to industrial applications. Of the various synthesis methods, the chemical exfoliation of graphite via graphene oxide (GO) is advantageous as far as productivity is concerned; however, the quality of the graphene produced by this method is far inferior to that synthesized by other methods, such as chemical vapor deposition on metals. Developing an effective reduction and restoration method for GO on dielectric substrates has been therefore a key issue. Here, we present a method for changing GO deposited on a dielectric substrate into high crystallinity graphene at 550 °C; this method uses CH4/H2 plasma and a Cu catalyst. We found that Cu remotely catalyzed the high degree reduction and restoration of GO on SiO2 and the effect ranged over at least 8 mm. With this method, field-effect transistor devices can be fabricated without any post treatment such as a transfer process. This plasma treatment increased electron and hole mobilities of GO to 480 cm2 V−1 s−1 and 460 cm2 V−1 s−1 respectively; these values were more than 50 times greater than that of conventional reduced GO. Furthermore, the on-site conversion ensured that the shape of the GO sheets remained unchanged after the treatment. This plasma treatment realizes the high throughput synthesis of a desired shaped graphene on any substrate without any residue and damage being caused by the transfer process; as such, it expands the potential applicability of graphene.

A facile synthesis of porous graphene for efficient water and wastewater treatment

The use of two-dimensional graphene-based materials in water treatment has recently gained significant attention due to their unique electronic and thermal mobility, high surface area, high mechanical strength, excellent corrosion resistance and tunable surface chemistry. However, the relatively expensive, poor hydrophobicity, low adsorption capacity and recyclability, and complex post-treatment of the most pristine graphene frameworks limit their practical application. Here, we report a facile scalable method to produce highly porous graphene from reduced graphene oxide via thermal treatment without addition of any catalyst or use of any template. Comparing to conventional graphene counterparts, as-prepared porous graphene nanosheets showed evident improvement in hydrophobicity, adsorption capacity, and recyclability, making them ideal candidate materials for water treatment. Superhydrophobic and superoleophilic porous graphene prepared in this work has been demonstrated as effective absorbents for a broad range of ions, oils and organic solvents, exhibiting high selectivity, good recyclability, and excellent absorption capacities > 90%. The synthesis method of porous graphene reported in this paper is easy to implement, low cost and scalable. These attributes could contribute towards efficient and cost-effective water purification and pollution reduction.

Graphene supercapacitor with both high power and energy density

Supercapacitors, based on fast ion transportation, are specialized to provide high power, long stability, and efficient energy storage using highly porous electrode materials. However, their low energy density excludes them from many potential applications that require both high energy density and high power density performances. Using a scalable nanoporous graphene synthesis method involving an annealing process in hydrogen, here we show supercapacitors with highly porous graphene electrodes capable of achieving not only a high power density of 41 kW kg−1 and a Coulombic efficiency of 97.5%, but also a high energy density of 148.75 Wh kg−1. A high specific gravimetric and volumetric capacitance (306.03 F g−1 and 64.27 F cm−3) are demonstrated. The devices can retain almost 100% capacitance after 7000 charging/discharging cycles at a current density of 8 A g−1. The superior performance of supercapacitors is attributed to their ideal pore size, pore uniformity, and good ion accessibility of the synthesized graphene.

Engineering a PVD-Based Graphene Synthesis Method

Graphene is an important nanomaterial with extraordinary properties. An established physical vapor deposition (PVD) based Graphene synthesis method is engineered in order to demonstrate the versatility of the growth method with respect to the quality and number of layers of synthesized Graphene. A statistical method known as factorial Design-of-Experiments (DoE) is demonstrated in this paper to determine key factors for synthesis of Graphene on Copper (Cu) using amorphous carbon (a-C) as the solid carbon source. Both qualitative and quantitative analysis are performed to determine a suitable recipe. Carbon source thickness (which is a-C) annealing temperature and annealing duration are varied to study their effect on the growth. Annealing temperature and a-C thickness are found to be significant factors for growth feasibility in a PVD-based growth, whereas annealing time is found to play a crucial role in growing different number of layers of Graphene with different quality. The quality and number of layers of Graphene are verified by Raman characterization.

Black tea assisted exfoliation using a kitchen mixer allowing one-step production of graphene

A kitchen mixer is one of the possible tools for the exfoliation of graphene. While organic solvents such as NMP or DMF are suitable for the exfoliation of graphite, the majority are toxic and dangerously harmful when exposed to humans and the environment. Therefore, an alternative solvent must be proposed for green and sustainable production of graphene. In this initial work, we have developed a new synthesis method for graphene through the direct exfoliation of graphite in commercial black tea. We found that our maximum yield concentration of graphene is Y = 0.032 mg ml−l after 15 min of mixing. From the data of Raman, the level of defects in our produced graphene is suggested as being very minor (ID/IG = 0.17), despite possible graphene functionalization by oxygen groups in tea. Incorporation of our graphene into PMMA results in shifting the onset temperature from 300 °C to 326 °C, which impressively validates the potential of the produced graphene as a thermal reinforcement material for polymer composites.

Electron Mobility across Grain Boundaries in Graphene Synthesized using Chemical Vapor Deposition Process

Chemical vapor deposition (CVD) is currently the only method for large-scale synthesis of graphene. However, the CVD process introduces grain boundaries (GBs) when individual grains coalesce with various mismatch angles. These GBs contain atomic dislocations and defects, which are believed to alter graphene's mechanical, electrical, and thermal properties. Specifically, the GBs can act as “potential barriers” when charges move from one grain to neighboring grains. This barrier effect will not only change the electrical conductivity but also the thermal conductivity of graphene. Besides high-resolution, 3-dimensional topography images, Atomic force microscopy (AFM) can also obtain the electrical properties at the nanoscale. In this report, the potential barrier effect of graphene GBs is studied with AFM. During the experiment, the probe is brought into contact with the graphene while positively (or negatively) biased. This process injects net charges into the graphene. The electrostatic potential across the GBs can be measured by AFM as an indication of the potential barrier effect. GBs with lower potential difference correspond to lower potential barrier, and vice versa. The dependency of the barrier effect on the mismatch angles was also measured. Considering the 6 folds’ symmetry of graphene atomic lattice, the mismatch angle is in the range of 0° ∼ 30°, with 30° the maximum mismatch angle. Our results can be well fitted with a sinusoidal function with π/3 period, which supports our hypothesis that higher mismatch angle contains higher density of dislocations and defects that increase the potential barrier of GBs.

Germanium-Assisted Direct Growth of Graphene on Arbitrary Dielectric Substrates for Heating Devices.

Direct growth of graphene on dielectric substrates is a prerequisite to the development of graphene-based electronic and optoelectronic devices. However, the current graphene synthesis methods on dielectric substrates always involve a metal contamination problem, and the direct production of graphene patterns still remains unattainable and challenging. Herein, a semiconducting, germanium (Ge)-assisted, chemical vapor deposition approach is proposed to produce monolayer graphene directly on arbitrary dielectric substrates. By the prepatterning of a catalytic Ge layer, the graphene with desired pattern can be achieved conveniently and readily. Due to the catalysis of Ge, monolayer graphene is able to form on Ge-covered dielectric substrates including SiO2 /Si, quartz glass, and sapphire substrates. Optimization of the process parameters leads to complete sublimation of the catalytic Ge layer during or immediately after formation of the monolayer graphene, enabling direct deposition of large-area and continuous graphene on dielectric substrates. The large-area, highly conductive graphene synthesized on a transparent dielectric substrate using the proposed approach has exhibited a wide range of applications, including in both defogger and thermochromic displays, as already successfully demonstrated here.

Xenon Flash Lamp‐Induced Ultrafast Multilayer Graphene Growth

Optically induced annealing technology has provided promising strategies to synthesize graphene for future flexible electronics. Focused laser‐assisted methods have the capability of direct graphene growth, but have significant drawbacks such as small beam size, and locally different intrinsic properties caused by energy variations of each pulsed shot. Herein, a novel synthesis method of multilayer graphene (MLG) via xenon flash lamp with intense and achromatic light is presented. An extremely high temperature (over 1500 °C) by a single flash irradiation induces the MLG with about 15 layers in milliseconds time scale. Experimental and theoretical studies reveal characteristics of the MLG with I 2D/I G of 0.65 and average sheet resistance of 3.272 × 103 Ω sq−1 as well as photothermal interactions between flash and metal catalyst. The synthesized MLG is successfully transferred onto plastic substrates, demonstrating a new feasibility of the flash lamp system for next‐generation flexible electronics.

Chemical vapor deposition of graphene on insulating substrates and its potential applications

As the first two-dimensional crystal isolated in 2004, graphene has triggered numerous fundamental and technological studies because of its unique properties and a wide range of potential applications. To take these applications to an industrial level requires successful large scale growth of high quality graphene. Among popular methods for graphene synthesis, chemical vapor deposition (CVD) has received a lot of attention because of its relatively high yields, high quality and low cost in preparation of graphene. In addition, CVD is compatible with the existing silicon semiconductor processes, and exhibits potential for synthesis and applications of graphene at industrial scale. CVD graphene has been synthesized on various metal substrates such as ruthenium, iridium, platinum, nickel and copper. Though suitable for mass production, the need to transfer the graphene to different substrates has so far constrained its up-scaling to roll-to-roll production methods. However, CVD graphene on metal need transfer to insulating substrates for further device fabrication and characterization, and the extra transfer step inevitably causes the degradation of the graphene quality because of crack formation or resists residues. Researchers have developed some novel technologies aiming at reducing the influence of transfer process on the quality of graphene, but transfer process is still time-consuming and relatively expensive. An alternative to overcome the transfer difficulty is to synthesize graphene directly on insulating substrates. Epitaxial growth of graphene on single crystal SiC is one route towards mass production of graphene, however, single crystal SiC wafers are still very expensive. The search for better production techniques of graphene, in particular a transfer-free production method of high quality graphene, has intensified over the last few years. An amount of effective strategies have been utilized to realize the direct synthesis of high quality graphene on insulating substrates such as h-BN, silicon oxide, quartz, sapphire, SrTiO3 and even normal glass. Due to the lack of catalytic capability and carbon-dissolving ability in insulating substrates, the direct growth of graphene often associates with the problems of high nucleation density, small domain size, poor layer control and slow growth rate. As such, more research works should be conducted to explore the growth mechanism on the insulating substrates. In this paper, we reviewed recent progresses about direct growth of graphene on insulating substrates by chemical vapor deposition and its electronic applications. Firstly, we briefly discussed the newly progresses of graphene preparation and application. Great progress have been achieved in the field of direct synthesis of graphene on insulating substrates, however, there is still much room to improve further in many aspects, such as quality, domain size, layer and substrate suitability of graphene. We classified the growth strategies on insulating substrates into four groups: non-catalyst assisted method, plasma enhanced method, interface catalyzed growth and metal-vapor assisted growth. In each strategy, details of technology and merits were carefully discussed. In addition, we also introduced the typical applications of each strategy, which exhibits extraordinary prospect for improving our daily life. Finally, we shared our perspective views on future trend of this research field. We believe that with more and more efforts from the graphene-research community, technologies about direct synthesis of graphene on insulating substrates will be developed further. The future of directly grown graphene will become clearer in industrial applications.

Synthesis of Graphene-Based Sensors and Application on Detecting SF6 Decomposing Products: A Review.

Graphene-based materials have aroused enormous focus on a wide range of engineering fields because of their unique structure. One of the most promising applications is gas adsorption and sensing. In electrical engineering, graphene-based sensors are also employed as detecting devices to estimate the operation status of gas insulated switchgear (GIS). This paper reviews the main synthesis methods of graphene, gas adsorption, and sensing mechanism of its based sensors, as well as their applications in detecting SF6 decomposing products, such as SO2, H2S, SO2F2, and SOF2, in GIS. Both theoretical and experimental researches on gas response of graphene-based sensors to these typical gases are summarized. Finally, the future research trend about graphene synthesis technique and relevant perspective are also given.

Synergistic Ion Intercalations for High-Yield Synthesis of Li-Doped Graphene Nanosheets as an Efficient Electrocatalyst for Oxygen Reduction Reaction

A new electrochemical method for gram quantitative amount preparation of Li-doped graphene nanosheets was presented based on the one-pot cathodic exfoliation of a graphite electrode in an organic environment. Structural characterizations of synthesized graphene by FE-SEM and AFM indicate that graphene nanosheets have thickness lower than 4 nm, with a typical worm-like shape. Li-doped graphene nanoparticles show a superior electrocatalytic activity toward oxygen reduction reaction (ORR) without using any novel metals and losing stability during 3000 cycles. With a modification of the graphite configuration, the process can be used in a continuous manner, presenting a potentially scalable method for high-yield synthesis of few-layer graphene.