Synthesis Of High-quality Graphene Research Articles

Graphene-containing biocarbon from burlap waste: Property comparison with commercial grade graphene nanoplatelets

In this paper, we report a method for synthesizing high-yield graphene-containing biocarbon from burlap waste through a simple two-step carbonization process. The first step involves feedstock carbonization at 600 °C, followed by ball milling and then graphitization at 1200 °C using KOH. A comparative analysis between the obtained bio-graphene and commercial graphene revealed superior graphene properties of the burlap-based graphene. Notably, this bio-based graphene exhibited exceptional characteristics such as a very high BET surface area in the range of 1021 m²/g, low defect-to-graphene ratio of 0.12 in the Raman spectra, and an overall yield of 19% wt. These findings highlight the potential of burlap waste as a sustainable precursor for high-quality graphene synthesis and its potential for various applications.

Ultrafast alternating-current exfoliation toward large-scale synthesis of graphene and its application for flexible supercapacitors

To facilitate the transition of laboratory research to industrial applications, it is critical to establish a reliable protocol for the mass synthesis of high-quality graphene. Here, we present an efficient electrochemical intercalation-based exfoliation approach utilizing alternating current that allows for the production of sub-kilogram quantities of graphene. This strategy involves repeatedly intercalating foreign anions and cations into the interlayer gaps of dual-graphite electrodes, accelerating the graphite expansion process and maximizing the exfoliation efficiency of both electrodes while inhibiting excessive anodic oxidation. The exfoliation process leads to high-yield graphene nanosheets (92 %, primarily 1–3 layers) with minimal structural deterioration (ID/IG ratio of 0.05), high purity (2.1 at% oxygen), and outstanding electrical property (7.28 × 104 S m−1). Notably, our scaled-up manufacturing technique produces a record-breaking throughput of 135 g h−1, improving on the best-reported exfoliation efficiency with direct current by 35%. Furthermore, the as-made graphene demonstrates a large reversible capacity of 102 mF cm−2 for flexible supercapacitors, with robust cyclability with 99.5% after 10,000 cycles, excellent mechanical flexibility, and exceptional serial integration for adjustable voltage output. The efficient and scalable method presents a significant advancement in the large-scale manufacture of graphene, with potential for widespread industrial applications.

Ultrafast air-plasma reduction-exfoliation of graphene oxide aerogel at room temperature for capacitive deionization

Graphene produced by reducing graphene oxide has been an emerging candidate for capacitive deionization (CDI) and energy storage. However, the key factor for its commercial applications depends on the production methods that essentially determine its cost-effectiveness. Herein, we report a facile air-plasma method to achieve the highly efficient reduction of graphene oxide aerogel within 1 s, at room temperature, and without the need of any chemicals. It is demonstrated that by adjusting the plasma power ranging from 20 to 150 W, the interlayer distance between graphene layers, reduction degree (oxygen content), specific surface area, specific capacitance, and salt adsorption capacity can be tuned effectively for the obtained 3D graphene aerogel (GA). We also verify the validity of the air-plasma method for fabricating composite of GA with long Ag (or MnO2) nanowires, which can well maintain their unscathed 1D structure and redox activity for capturing ions. This air-plasma strategy, owing to its simplicity, time-saving and cost-effectiveness, opens a new pathway to large-scale synthesis of high-quality graphene with promising applications in CDI and beyond.

High quality synthesis of graphene by electrochemical exfoliation using methyl sulfonic acid media

High quality synthesis of graphene by electrochemical exfoliation using methyl sulfonic acid media

(Invited) Laser-Induced Graphene on Polymers: From Process Science to Applications

Nanocarbons like graphene and carbon nanotubes (CNTs) are promising for various applications including advanced electronic devices, novel energy systems, and next-generation healthcare diagnostics. This is owing to the excellent physical, chemical and electrochemical properties arising from the ordered atomic structure, the hierarchical nanoscale morphology, and tunable chemistry of nanocarbons. In particular, low-dimensional carbon electrodes for biosensors and neural interfaces have consistently been shown to have superior performance when compared to state-of-the-art metal electrodes. Nevertheless, major manufacturing challenges still hinder our ability to scalably produce graphene-based electrodes with tailored morphology and surface chemistry, especially on flexible substrates. While chemical vapor deposition (CVD) processes enable the synthesis of high quality graphene and CNTs, the extreme environments of high temperatures and hydrocarbon-rich gaseous atmosphere in such reactors limit the choice of substrates to silicon, quartz, metals or other rigid temperature-resistant materials. On the other hand, many emerging flexible devices require the fabrication of such nanocarbon electrodes on the surface of polymer substrates. Unlike different transfer technique of CVD-grown nanocarbons, this talk will focus on a unique bottom-up approach for directly growing different types of graphenic nanocarbons on polymer films by laser irradiation. The speaker will show how this direct-write process, often referred to as laser-induced graphene (LIG), can be controlled to produce spatially-varying morphologies and chemical compositions of LIG electrodes, by leveraging gradients of laser fluence. Moreover, a method will be introduced to control the heteroatom doping of these LIG electrodes based on controlling the molecular structure of the polymer being lased. Finally, a demonstration of these functional LIG electrodes as electrochemical biosensors will be presented for the detection of the neurotransmitter dopamine with nanomolar sensitivity.

Recent Advances in Transfer-Free Synthesis of High-Quality Graphene.

High-quality graphene obtained by chemical vapor deposition (CVD) technique holds significant importance in constructing innovative electronic and optoelectronic devices. Direct growth of graphene over target substrates readily eliminates cumbersome transfer processes, offering compatibility with practical application scenarios. Recent years have witnessed growing strategic endeavors in the preparation of transfer-free graphene with favorable quality. Nevertheless, timely review articles on this topic are still scarce. In this contribution, a systematic summary of recent advances in transfer-free synthesis of high-quality graphene on insulating substrates, with a focus on discussing synthetic strategies designed by elevating reaction temperature, confining gas flow, introducing growth promotor and regulating substrate surface is presented.

Synthesis of high-quality graphene by electrochemical anodic and cathodic co-exfoliation method

Large-scale preparation of high-quality graphene nanosheets at low cost is critical for advancing its industrial applications. Here we propose a fast electrochemical anode and cathode co-exfoliation method to synthesize high-yield solution-processable graphene. The chosen tetrabutylammonium hexafluorophosphate molecule, with superior electrochemical stability and oxygen-free feature, could efficiently enable simultaneous anion and cation intercalation while suppressing structural damage from anodic oxidation, resulting in minimally destructive exfoliation and high-efficiency graphene synthesis. After accurately regulating the intercalation chemistry, high-yield graphene (75% and 92% for anode and cathode, respectively) with uniform thickness distribution (>75%, 1–3 layers) was obtained. Meanwhile, as-prepared graphene has ultralow defect density (ID/IG < 0.052), significantly high C/O ratio (>46.6) and exceptional electrical conductivity (>4 × 104 S m−1). Remarkably, record high production rates (over 100 g h−1) are achieved in up-scaled fabrication process, and such graphene quality and exfoliation efficiency outperform most previously reported research. Furthermore, the graphene based flexible supercapacitor exhibits a high area capacitance of 95 mF cm−2, excellent rate capability, cycling performance with 99% after 10,000 cycles and robust mechanical flexibility. This efficient and scalable process will promote the mass production of high-quality graphene, which offers great potential applications in wearable electronics.

Morphology-Control Growth of Graphene Islands by Nonlinear Carbon Supply.

Controlling the morphology of graphene and other 2D materials in chemical vapor deposition (CVD) growth is crucial because the morphology reflects the crystal quality of as-synthesized nanomaterials in a certain way, and consequently it indirectly represents the physical properties of 2D materials such as bandgap, selective ion transportation, and impermeability. However, precise control of the morphology is limited by the complex formation mechanism and sensitive growth-environment factors of graphene. Therefore, the CVD synthesis of single-crystal hexagonal-shaped graphene islands with specific sizes is challenging. Herein, an unconventional nonlinear-carbon-supply growth strategy is proposed to realize controllable CVD growth of desired hexagonal graphene islands with specific sizes on Cu substrates. Large-area graphene films of isolated islands with desired densities, sizes, and distances between the islands aresuccessfully synthesized. Subsequently, the direct growth of a planar-tunnel-junction structure based on two parallel gapped graphene islands isachieved by specific adjustment of the growth and etching processes of graphene CVD synthesis. It is therefore demonstrated that the nonlinear-carbon-supply growth strategy is a reliable method for the synthesis of high-quality graphene and can facilitate the direct growth of graphene-based nanodevices in the future.

Graphene/Graphene Derivatives from Coal, Biomass, and Wastes: Synthesis, Energy Applications, and Perspectives

In the last decade, there has been a phenomenal development in the commercially viable, large-scale synthesis of graphene, a multifunctional advanced carbon nanomaterial, which is gaining popularity for its diverse range of applications, especially in energy storage, composites, sensors, and membranes. With the increasing demand, a large number of worldwide research efforts have been employed, resulting in a series of enormous breakthroughs both in its fundamental science and innovative applications. The earlier reviews on graphene show that the increase in the production yield is often accompanied by the generation of substandard graphene quality, making the process unsuited for commercialization. However, recent studies on graphene synthesis have shown the use of naturally available carbonaceous sources for the production of low-cost graphene derivatives is becoming an emerging trend in graphene research. In this present review, the most recent advances in the synthesis of high-quality graphene from solid carbon precursors, particularly abundant coal, biomass, and waste materials, have been extensively discussed along with their potential scalability for commercial production. The quality and yield of these graphene derivatives synthesized through different methods like chemical vapor deposition, exfoliation, laser-induced, microwave irradiation, and chemical methods are also examined to determine the best-suited synthetic methodology from the available literature. The utilization of graphene derivatives in the energy sector was further discussed, particularly in the emerging field of energy storage. Finally, the challenges and future prospects of this study are highlighted to have a better understanding of the current graphene production scenario, with an insight into the most efficient method for synthesizing high-purity low-cost graphene and their potential for scale-up and energy applications in the distant future.

Toward batch synthesis of high-quality graphene by cold-wall chemical vapor deposition approach

Toward batch synthesis of high-quality graphene by cold-wall chemical vapor deposition approach

Low-temperature synthesis of high-quality graphene by controlling the carbon-hydrogen ratio of the precursor

A furnace-free inductively coupled plasma chemical vapor deposition (ICP-PECVD) system, which does not require sample heating, was used to grow graphene at a temperature below 300 °C. This studies have found that under low-temperature PECVD growth conditions, liquid precursors are more suitable for preparing low-temperature graphene precursors than gaseous precursors.​​​​ Hence, benzene is used as a carbon precursor to obtain a sheet resistance of approximately 1.24 kΩ sq−1. In this research, it was discovered that the carbon-hydrogen ratio of the precursor molecule is an important factor while using PECVD to grow graphene. This factor affects the quality of graphene and the sheet resistance value —when the carbon–hydrogen ratio for the precursor molecule is 1:1, graphene has the high quality and lowest sheet resistance; when it is less than 1:2, the graphene that cannot be deposited has the worst quality and sheet resistance. Furthermore, we found that methane, a precursor often used to deposit graphene, will etch graphene under low-temperature conditions, and that acetylene can be used as a precursor to deposit graphene. It was further proven that the carbon–hydrogen ratio of the precursor molecules in the PECVD process caused the reduction in the graphene temperature.

Green Reduction of Graphene Oxide Involving Extracts of Plants from Different Taxonomy Groups

Graphene, a remarkable material, is ideal for numerous applications due to its thin and lightweight design. The synthesis of high-quality graphene in a cost-effective and environmentally friendly manner continues to be a significant challenge. Chemical reduction is considered the most advantageous method for preparing reduced graphene oxide (rGO). However, this process necessitates the use of toxic and harmful substances, which can have a detrimental effect on the environment and human health. Thus, to accomplish the objective, the green synthesis principle has prompted researchers worldwide to develop a simple method for the green reduction of graphene oxide (GO), which is readily accessible, sustainable, economical, renewable, and environmentally friendly. For example, the use of natural materials such as plants is generally considered safe. Furthermore, plants contain reducing and capping agents. The current review focuses on the discovery and application of rGO synthesis using extracts from different plant parts. The review aims to aid current and future researchers in searching for a novel plant extract that acts as a reductant in the green synthesis of rGO, as well as its potential application in a variety of industries.

Transistors based on solution-processed 2D materials for chemical and biological sensing

Two-dimensional (2D) materials have attracted signifcant attention due to their unique chemical and physical characteristics. The specific structures and large surface area of 2D materials lead to great potentials in sensing applications with the advantages of high sensitivity, high efficiency, and environmental friendliness. As a result, a great variety of devices have been developed based on 2D materials and utilized as electronic, chemical, biological, and even multifunctional sensors. Importantly, the high performance of these sensors is largely attributed to the synthetic strategies of high-quality 2D materials, where the exfoliation in the liquid phase is one of the most efficient methods. In this review, we firstly summarize the recent progress on the solution methods for the synthesis of high-quality graphene as well as non-carbon 2D materials. Then the main focus of this review article is shifted to the transistor-type sensors, especially the biosensors and chemical sensors, on the basis of these solution-processed 2D materials. In addition, the remaining challenges in this research field are discussed, and possible future directions of development are also proposed from the aspects of materials, processing, and devices.

Measurement of ultrafast carrier dynamics in multilayer MPCVD graphene

Graphene presents unique opto-electronic properties which makes it useful for a wide range of applications and devices, such as high-speed photodetectors, that rely on the relaxation dynamics of photoexcited charge carriers. These demand reliable and reproducible methods for synthesis of high quality graphene. Here we present ultrafast degenerate pump-probe measurements of multilayer graphene coatings grown by microwave plasma chemical vapour deposition (MPCVD) and analyse the impact of the synthesis growth time on the material’s nonequilibrium optical response.

The nucleation and growth of graphene under a controlled atmosphere during radio frequency-plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition (PECVD) has emerged as a potential method for the industrial synthesis of graphene due to its low growth temperature, energy savings and in situ graphene growth. Unlike traditional thermal chemical vapor deposition (TCVD), PECVD usually leads to rapid nucleation and growth of graphene from the promoting effect of plasma on the dissociation of the hydrocarbon precursor, resulting in a significantly higher nucleation density of graphene and small grain size, which reduces its electrical performance. Understanding and controlling graphene nucleation and growth during PECVD are of great significance for the synthesis of high-quality graphene. In this study, we noted that the nucleation density and grain size of graphene were significantly affected by various atmospheric conditions, including the Ar flow, H2/CH4 ratio and pressure. In particular, a higher H2/CH4 ratio notably decreased the nucleation density and enlarged the grain size from the effect of the H2 plasma. Furthermore, we studied the energies of the nucleation density, grain size and growth rate of graphene under various pressures by measuring the activation energy and demonstrated that low pressure and high growth temperature enabled to the growth of graphene with low nucleation and large grain size.

Copper acetate-facilitated transfer-free growth of high-quality graphene for hydrovoltaic generators

Direct synthesis of high-quality graphene on dielectric substrates without a transfer process is of vital importance for a variety of applications. Current strategies for boosting high-quality graphene growth, such as remote metal catalyzation, are limited by poor performance with respect to the release of metal catalysts and hence suffer from a problem with metal residues. Herein, we report an effective approach that utilizes a metal-containing species, copper acetate, to continuously supply copper clusters in a gaseous form to aid transfer-free growth of graphene over a wafer scale. The thus-derived graphene films were found to show reduced multilayer density and improved electrical performance and exhibited a carrier mobility of 8500 cm2 V−1 s−1. Furthermore, droplet-based hydrovoltaic electricity generator devices based on directly grown graphene were found to exhibit robust voltage output and long cyclic stability, in stark contrast to their counterparts based on transferred graphene, demonstrating the potential for emerging energy harvesting applications. The work presented here offers a promising solution to organize the metal catalytic booster toward transfer-free synthesis of high-quality graphene and enable smart energy generation.

Unique role of dimeric carbon precursors in graphene growth by chemical vapor deposition

Chemical vapor deposition has emerged as a promising approach for high-quality graphene synthesis. Graphene quality, including the defect density, the size of monocrystal domains, and the number of layers, depend on the growth conditions. The main experimental parameters include temperature, metal catalyst composition, growth atmosphere, and gaseous dynamics in the reaction chamber. Here we show, that even for the same growth conditions, simply changing carbon source from methane to ethane or acetylene yields drastically different growth mode that allows the production of single-crystal-like graphene on a polycrystalline metal foil substrate. This new single crystal growth mechanism does not require local supply of carbon precursors or special single crystal catalytic substrate that were introduced earlier. We assign the observed differences in the growth mechanism to formation of stable and mobile dimeric C2Hx intermediate species from ethane and acetylene, in contrast to less mobile CHx and C3Hx species formed from methane and propane.

New Insights into the Microstructural Analysis of Graphene Oxide.

To explore the impact of synthesis conditions (temperature and time) on the properties of developed Graphene Oxide (GO). A highly promising approach has been used for the synthesis of graphene oxide (GO) from graphite flakes using the modified Hummers method. Concentrated sulfuric acid was used as an intercalating agent and the oxidation was done with the help of potassium permanganate and hydrogen peroxide. The present method does not need expensive membranes for the filtration of Carbon and metalcontaining residues. The pre-cooling method is used to eradicate the explosive behavior of intermediate steps. The high quality of synthesized graphene oxides was confirmed by a series of characterization techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, and atomic force microscopy. The results indicated the presence of Oxygen-containing functional groups, and a rise in the Oxygen content confirmed the synthesis of high-quality graphene oxide. As per obtained experimental findings and subsequent analysis, the synthesized high-quality graphene oxide could be used in the design of membranes for water treatment applications.

Ion implantation assisted synthesis of graphene on various dielectric substrates

Direct synthesis of high-quality graphene on dielectric substrates is of great importance for the application of graphene-based electronics and optoelectronics. However, high-quality and uniform graphene film growth on dielectric substrates has proven challenging due to limited catalytic ability of dielectric substrates. Here, by employing a Cu ion implantation assisted method, high-quality and uniform graphene can be directly formed on various dielectric substrates including SiO2/Si, quartz glass, and sapphire substrates. The growth rate of graphene on the dielectric substrates was significantly improved due to the catalysis of Cu. Moreover, during the graphene growth process, the Cu atoms gradually evaporated away without involving any metal contamination. Furthermore, an interesting growth behavior of graphene on sapphire substrate was observed, and the results show the graphene domains growth tends to grow along the sapphire flat terraces. The ion implantation assisted approach could open up a new pathway for the direct synthesis of graphene and promote the potential application of graphene in electronics.

CVD growth of high-quality graphene over Ge (100) by annihilation of thermal pits

The physical and chemical state of the underlying germanium (Ge) substrate is crucial for the CVD synthesis of high-quality graphene. Here, we investigate the main causes responsible for formation of pit-like defects on Ge (100) and (111) surfaces, their elimination, and their influence on the quality of deposited graphene. Our data provides evidence of pit-like defects formation on Ge surfaces during thermal annealing at T ≥ 800 °C. We establish that the pits are due to preferential evaporation of residual Ge suboxides, and that their efficient removal would result in a pit-free surface. Oxide removal on HF, HCl and HBr treated surfaces is investigated using X-ray photoemission spectroscopy (XPS). The results confirm that in contrast to HF and HCl, HBr effectively eliminates GeO2 and Ge suboxides, providing pit-free surfaces, which enable CVD growth of high-quality graphene. Hence, we demonstrate that effective elimination of Ge suboxides enables the synthesis of graphene monolayers with excellent quality (ID/IG ∼ 0.2) as confirmed by Raman spectroscopy measurements. The experimental data provides clear corroboration for the role played by the Ge suboxides in the formation of thermal pits and the control of the graphene quality. Our findings lay the foundation for Ge substrates cleaning and the synthesis of high-quality graphene films for advanced applications.