Deposition Of Graphene Research Articles

Investigation of Electrochemical Fingerprints for Buzhong Yiqi Tang Extract Granules Using Diamond-Graphene Composite Electrode

This study presents a novel electrochemical fingerprinting method for Buzhong Yiqi Tang extract granules using a diamond-graphene composite electrode. The electrode was fabricated through chemical vapor deposition of graphene on high-pressure high-temperature synthetic diamond, resulting in a few-layer graphene coating as confirmed by Raman spectroscopy (I₂D/IG ratio ≈ 1.2) and XPS analysis (78% sp² C-C signal). Cyclic voltammetry revealed four anodic and three cathodic peaks, while differential pulse voltammetry provided enhanced resolution with eight distinct oxidation peaks. The method demonstrated high sensitivity (LODs 0.08-0.15mg/mL) and good linearity (R² > 0.995) over a concentration range of 0.5-10mg/mL. Comparison of fingerprints from individual herb extracts (Astragalus membranaceus, Panax ginseng, and Glycyrrhiza uralensis) elucidated the origins of major peaks in the Buzhong Yiqi Tang profile. Principal component analysis of fingerprints successfully differentiated between samples from three manufacturers, accounting for 87.3% of total variance. Strong correlations (r > 0.92) were observed between key DPV peak intensities and HPLC-determined concentrations of traditional chemical markers. The rapid analysis time, minimal sample preparation, and holistic representation of multiple electroactive components make this approach a promising complement to existing chromatographic methods for quality assessment of traditional Chinese medicine formulations.

Preparation and growth mechanism of high-quality multilayer graphene from simulated coal pyrolysis gas via chemical vapor deposition

Chemical vapor deposition (CVD) of graphene from coal pyrolysis gas provides new ways for both large-scale graphene preparation and high value-added utilization of coal. However, green, efficient and continuous preparation of high-quality multilayer graphene with both good uniformity and ideal structure characteristic remains a great challenge. Herein, we first investigated the influence of main carbonaceous species (CH4, C2H6, C3H8, CO2, and CO) in coal pyrolysis gas on the quality of CVD graphene products. The experimental results indicated that CO2 and CO have little effect on the growth of graphene, while methane as carbon source is conducive to obtain ideal graphene materials, propane and ethane could also influence structural defects and layer number of graphene products remarkably. On this basis, we designed a mixed gas of methane, ethane, and propane with optimized ratio as simulated coal pyrolysis gas, and successfully prepared high-quality multilayer graphene products on nickel foam from the as-designed simulated coal pyrolysis gas by CVD method. Notably, with a CH4:C2H6:C3H8 ratio of 2:1:1, the graphene products prepared from simulated coal pyrolysis gas outperformed that of raw coal pyrolysis gas in terms of physical structure, layer number, and quality uniformity. The corresponding I2D/IG value reached 0.97. The graphene growth process and mechanism were investigated and discussed macroscopically and microscopically. This work is of great significance for the intrinsic understanding of CVD growth of graphene from coal pyrolysis gas, and also inspires an efficient and environmentally friendly avenue for high-throughput, uniform production of high-quality graphene materials.

Fluid-Dynamics-Rectified Chemical Vapor Deposition (CVD) Preparing Graphene-Skinned Glass Fiber Fabric and Its Application in Natural Energy Harvest.

Graphene chemical vapor deposition (CVD) growth directly on target using substrates presents a significant route toward graphene applications. However, the substrates are usually catalytic-inert and special-shaped; thus, large-scale, high-uniformity, and high-quality graphene growth is challenging. Herein, graphene-skinned glass fiber fabric (GGFF) was developed through graphene CVD growth on glass fiber fabric, a Widely used engineering material. A fluid dynamics rectification strategy was first proposed to synergistically regulate the distribution of carbon species in 3D space and their collisions with hierarchical-structured substrates, through which highly uniform deposition of high-quality graphene on fibers in large-scale 3D-woven fabric was realized. This strategy is universal and applicable to CVD systems using various carbon precursors. GGFF exhibits high electrical conductivity and photothermal conversion capability, based on which a natural energy harvester was first developed. It can harvest both solar and raindrop energy through solar heating and droplet-based electricity generating, presenting promising potentials to alleviate energy burdens.

Chemical vapor deposition and applications of vertical graphene: Progress and prospects

Chemical vapor deposition and applications of vertical graphene: Progress and prospects

High Electrocatalytic Activities of the Electrochemically Exfoliated Graphene Deposited Carbon Paper Electrodes for Vanadium Redox Flow Batteries

The cost-effective and process-efficient preparation of highly electrocatalytic carbon electrodes on a large scale is crucial for enhancing the competitiveness of vanadium redox flow batteries (VRFBs). In this work, electrochemically exfoliated graphene oxides (Exf-GOs) are prepared form graphite foil at large scale with a multi-electrodes equipped continuous Exf-GOs production system. The Exf-GOs are deposited on the activated carbon paper (A-CP) substrate by a direct infiltration-deposition approach. Collective electro-kinetics analysis applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed that the resulting Exf-GO/A-CP electrodes exhibit two orders magnitude greater intrinsic electrocatalytic activities than the A-CP electrode for the VO2+/VO2 + redox reactions. A trade-off between the Exf-GO deposition amount and the open pore volume through the Exf-GO/A-CP electrodes was found that have critical impacts on the overall electro-kinetic performance of the electrodes. Compared to the A-CP electrode, the Exf-GO/A-CP electrode provided the VRFB with more than two-fold enhancements in the energy storage capacity and at least 10 – 15 % higher voltage and energy efficiencies. The results collectively demonstrate the high effectiveness of the Exf-GO/A-CP electrodes for VRFBs that can be prepared cost and process efficient approach at large scales.

Electrophoretic deposition of graphene coating on copper for improved thermoelectric performance of wire rods

Electrophoretic deposition of graphene coating on copper for improved thermoelectric performance of wire rods

Surface modification of mild steel to circumvent challenges in chemical vapour deposition of graphene coating for durable corrosion resistance

Graphene possesses unique combination of characteristics (i.e., inertness, impermeability and toughness) to qualify as ideal coating material for corrosion resistance, and graphene coatings on nickel and copper have been shown to provide excellent and durable corrosion resistances. However, growing graphene directly on mild steel by chemical vapour deposition (CVD), is prohibitively challenging due to high solubility of carbon in mild steel at high temperatures. The non-trivial challenge was circumvented through surface modification of steel by electroplating with Cu and Ni, accounting for the critical consideration, i.e., the inter-diffusivity of iron in nickel or copper. However, the key finding was that the undesirably high thicknesses of the electroplated Cu and Ni layers were detrimental, and optimization of their thicknesses was essential for successful deposition of the required quality graphene. The optimised thicknesses were derived on the basis of the fundamental diffusion calculations. The uniform multi-layered graphene coating on the suitably modified mild steel surface provided remarkable corrosion resistance in an aqueous chloride solution, and electrochemically validation of the corrosion durability for extended exposure (>1000 h) was characterised.

Challenges in Chemical Vapour Deposition of Graphene on Metallurgical Alloys Exemplified for NiTi Shape Memory Alloys

Atomically-thin two-dimensional (2D) materials like graphene have been suggested as ultimately thin corrosion barriers and functional coatings for modern metallurgical alloys. The challenges of chemical vapour deposition (CVD) of such 2D materials, particularly graphene, on modern metallurgical alloys are discussed and reviewed here, focusing on the key problems with the metallurgical alloys’ often limited catalytic activity towards 2D materials growth and the key need to preserve the metallurgical alloys’ bulk properties during the high temperature 2D materials CVD processes. Using graphene CVD on NiTi (Nitinol) shape memory alloys as a case study, we illustrate the constraints arising from low catalytic activity and tendency to form oxides due the Ti in the NiTi alloy in terms of graphene growth results. We show that, by using a scalable low-temperature CVD process at 650 to 750 °C, we can deposit fully covering carbon films on the NiTi, albeit at limited structural quality. Notably, we also demonstrate that our CVD process does not degrade the bulk microstructure of the NiTi during carbon deposition and, importantly, leaves the crystallographic shape memory effect evolution intact. This underscores the potential of CVD for depositing graphene films on NiTi alloys while emphasizing the necessity for further exploration of CVD conditions to achieve high-quality graphene deposits akin to those on prior widely investigated dedicated (often sacrificial) high-purity metal substrates such as Ni.

Development of an Innovative Biosensor Based on Graphene/PEDOT/Tyrosinase for the Detection of Phenolic Compounds in River Waters.

Phenolic compounds, originating from industrial, agricultural, and urban sources, can leach into flowing waters, adversely affecting aquatic life, biodiversity, and compromising the quality of drinking water, posing potential health hazards to humans. Thus, monitoring and mitigating the presence of phenolic compounds in flowing waters are essential for preserving ecosystem integrity and safeguarding public health. This study explores the development and performance of an innovative sensor based on screen-printed electrode (SPE) modified with graphene (GPH), poly(3,4-ethylenedioxythiophene) (PEDOT), and tyrosinase (Ty), designed for water analysis, focusing on the manufacturing process and the obtained electroanalytical results. The proposed biosensor (SPE/GPH/PEDOT/Ty) was designed to achieve a high level of precision and sensitivity, as well as to allow efficient analytical recoveries. Special attention was given to the manufacturing process and optimization of the modifying elements' composition. This study highlights the potential of the biosensor as an efficient and reliable solution for water analysis. Modification with graphene, the synthesis and electropolymerization deposition of the PEDOT polymer, and tyrosinase immobilization contributed to obtaining a high-performance and robust biosensor, presenting promising perspectives in monitoring the quality of the aquatic environment. Regarding the electroanalytical experimental results, the detection limits (LODs) obtained with this biosensor are extremely low for all phenolic compounds (8.63 × 10-10 M for catechol, 7.72 × 10-10 M for 3-methoxycatechol, and 9.56 × 10-10 M for 4-methylcatechol), emphasizing its ability to accurately measure even subtle variations in the trace compound parameters. The enhanced sensitivity of the biosensor facilitates detection and quantification in river water samples. Analytical recovery is also an essential aspect, and the biosensor presents consistent and reproducible results. This feature significantly improves the reliability and usefulness of the biosensor in practical applications, making it suitable for monitoring industrial or river water.

Fabrication of cemented carbides with bidirectional gradient structure via graphene deposition to simultaneously enhance surface hardness and toughness

The adoption of a continuous gradient in Co content stands as the foremost strategy for attaining heightened surface hardness and improved core toughness in cemented carbides. Nevertheless, the reduction in surface toughness stemming from a decreased Co content often precipitates premature surface failure of components. In this paper, WC-11Co powders was utilized as the precursor materials for fabricating a bidirectional gradient cemented carbide using the combined approach of low-temperature presintering and ultrasonic treatment techniques. The resultant cemented carbide exhibited a distinct gradient distribution, characterized by a forward gradient of graphene content, a reverse gradient of Co content, a forward gradient of WC grain size, and a forward gradient of residual compressive stress. The hardening and toughening mechanisms of the fabricated bidirectional gradient cemented carbides were comprehensively characterized and quantitatively discussed. The results provide compelling evidence that the gradient distribution of Co content plays a crucial role in attaining an impressive surface hardness of 1820 kgf/mm2. By utilizing the crack bridging mechanism of graphene, which efficiently exploits its strain transfer capabilities across a semi-coherent interface, in conjunction with the toughening effects of crack deflection and residual compressive stress, an exceptional surface fracture toughness of 17.62 MPa m1/2 is achieved. Additionally, the gradient layer exhibited a higher critical load for cracking. The present findings presents a novel strategy for the fabrication of high-performance ceramic-based composites.

Graphene synthesis by electromagnetic induction heating: Domain size and morphology control

In this paper we discuss the effect of hydrogen and methane content during low-pressure chemical vapor deposition (LPCVD) of graphene on inductively heated copper foils. By increasing the H2/CH4 ratio by a factor of 5 from 25 to 125, different graphene morphologies ranging from dendritic fractals to compact hexagonal islands are obtained. In addition, increasing the hydrogen concentration allows the nucleation rate to be slowed down by a factor of ∼10 thereby high-quality regular hexagonal graphene single crystals of significant size of 0.1 mm are found. From these measurements, we estimate the activation energy for graphene nucleation in low-pressure CVD (2 eV) and propose a phenomenological law for graphene nucleation. As compared to conventional CVD methods, considerable advantages of inductive heating are outlined, and some fundamental aspects of this approach are discussed.

Quantum Nature of Charge Transport in Inkjet-Printed Graphene Revealed in High Magnetic Fields up to 60T.

Inkjet-printing of graphene, iGr, provides an alternative route for the fabrication of highly conductive and flexible graphene films for use in devices. However, the contribution of quantum phenomena associated with 2D single layer graphene, SLG, to the charge transport in iGr is yet to be explored. Here, the first magneto-transport study of iGr in high magnetic fields up to 60 T is presented. The observed quantum phenomena, such as weak localization and negative magnetoresistance, are strongly affected by the thickness of the iGr film and can be explained by a combination of intra- and inter-flake classical and quantum charge transport. The quantum nature of carrier transport in iGr is revealed using temperature, electric field, and magnetic field dependences of the iGr conductivity. These results are relevant for the exploitation of inkjet deposition of graphene, which is of particular interest for additive manufacturing and 3D printing of flexible and wearable electronics. It is shown that printed nanostructures enable ensemble averaging of quantum interference phenomena within a single device, thereby facilitating comparison between experiment and underlying statistical models of electron transport.

Comparing the properties and growth of graphene on electrolytic and rolled Cu foils by chemical vapor deposition

In this work, we use electrolytic copper foils as substrates for the deposition of graphene by chemical vapor deposition. We investigate the effects of preannealing conditions, methane injection time, and temperature to synthesize graphene with a similar quality as when grown on cold-rolled copper. We find that the electrolytic copper foil’s annealing conditions and CH4 injection temperature determine the quality of graphene.

Deposition of vertical carbon nanostructures by microwave plasma source on nickel and alumina

Vertical carbon nanostructures on metal and ceramic substrates are deposited successfully using planar microwave plasma source at frequency of 2.45 GHz. The PECVD (Plasma Enhanced Chemical Vapor Deposition) with microwave surface wave discharge is applied because it produces a dense plasma providing efficient decomposition of the methane and creation of a large number of reactive particles which results in lower substrate temperature for graphene deposition compared to CVD method. Optimization of the gas mixture of H2, Ar and CH4, and the gas pressure in the chamber results in a homogeneous graphene structures deposition on the substrates of Ni-foil, Ni-foam and alumina ceramics at substrate temperatures ∼600 °C. The plasma parameters of surface wave discharge such as gas temperature, electron temperature and density are obtained by measuring OH-band and Ar-lines using optical emission spectroscopy. The morphology of the vertical carbon structures is obtained using SEM analysis and the characteristics of the graphene layers were determined by Raman spectroscopy.

Direct localized growth of graphene on a substrate: a novel nickel-catalyzed CVD process assisted by H2 plasma.

An original metal catalyzed CVD methodology assisted by hydrogen plasma for the direct deposition of few-layer graphene on a substrate is presented. Graphene is grown at 900 °C directly on the surface of the substrate of technological interest by carbon diffusion through a nickel film by using methane (CH4) as the carbon precursor. Hydrogen atoms in the H2-plasma downstream are used to promote the solubilization of carbon atoms in Ni, thus favouring the growth of graphene at the Ni/substrate interface. Structural and transport properties of the as-grown multilayer graphene films on SiO2/Si and quartz substrates are provided. We demonstrate the peculiarity of this approach for controlling the thickness and transport properties of as-grown graphene films using process-step times. Finally, the potential of the proposed methodology for the bottom-up direct growth of patterned graphene is demonstrated.

A microphysiological system for handling graphene related materials under flow conditions.

The field of nanotechnology has developed rapidly in recent decades due to its broad applications in many industrial and biomedical fields. Notably, 2D materials such as graphene-related materials (GRMs) have been extensively explored and, as such, their safety needs to be assessed. However, GRMs tend to deposit quickly, present low stability in aqueous solutions, and adsorb to plastic materials. Consequently, traditional approaches based on static assays facilitate their deposition and adsorption and fail to recreate human physiological conditions. Organ-on-a-chip (OOC) technology could, however, solve these drawbacks and lead to the development of microphysiological systems (MPSs) that mimic the microenvironment present in human tissues. In light of the above, in the present study a microfluidic system under flow conditions has been optimised to minimise graphene oxide (GO) and few-layer graphene (FLG) adsorption and deposition. For that purpose, a kidney-on-a-chip was developed and optimised to evaluate the effects of exposure to GO and FLG flakes at a sublethal dose under fluid flow conditions. In summary, MPSs are an innovative and precise tool for evaluating the effects of exposure to GRMs and other type of nanomaterials.

Optimization for Current-Enhanced Solid-Phase Deposition of Multi-Layer Graphene with High Crystallinity and Uniformity

Solid-phase deposition (SPD) is a preferable method to fabricate multi-layer graphene (MLG) for device applications since MLG can be deposited directly on substrates without transfer. Previously, we reported that current application during SPD enhances the MLG growth. In this study, we investigated the effects of applied current and heating rate on the crystallinity and uniformity of MLG precipitated from carbon (C) / nickel (Ni) structures. It was found that higher current and slower heating rate lead to improve the MLG crystallinity. Moreover, the uniformity was improved by the optimization of Ni and C thickness which could control the nucleation and growth of MLG during SPD. As a result, a uniform MLG with a high G/D ratio of 5.5 was obtained at a low temperature of 365 °C.

Ball milling‐assisted exfoliation and deposition to prepare few‐layer graphene/PVC nanocomposites with enhanced thermal stability

AbstractIt is still a great challenge to prepare high‐performance graphene/polymer nanocomposites by fully utilizing the large surface area, high tensile strength, and high thermal stability. Herein, a simple but efficient approach based on ball milling was developed to in situ exfoliate graphite into single‐layer graphene and simultaneously deposit them onto polyvinyl chloride (PVC) surface. Graphene/PVC nanocomposites were prepared via the plasticized molding and followed by hot pressing. Resulting from incorporation of highly exfoliated and evenly distributed graphene nanosheets, the obtained graphene/PVC nanocomposites displayed a significantly enhanced thermal stability. In contrast with neat PVC, the temperature of maximum weight loss (Tmax), glass transition temperature (Tg), and residual content of composite with 2.0 wt% graphene were increased by 10, 13°C, and 4.4%, respectively. Based on the deep analysis on heat releasing behavior and structure of residue, we proposed the related enhancing mechanism. Large‐area and highly exfoliated graphene sheets effectively inhibited the heat/mass transfer in composite system and prevented the degradation of PVC, as well as promoted the compact residue formation from polymer itself at high temperatures. In short, this work provided an environmentally friendly strategy to prepare high‐performance graphene/polymer nanocomposites with using low additive amount of single‐layer graphene.Highlights A simple graphite exfoliation method based on ball milling was proposed. Strong shearing and compact force induce graphene exfoliation and deposition. Graphene/PVC nanocomposites with enhanced thermal stability was prepared.

Development of Graphene-Based Functional Coating for the Surface Modification of Textiles

The objective of the presented research is to improve the ballistic performance of para-aramid woven fabric by deposition of graphene coatings directly on woven textile substrates. The improvement of mechanical properties of the ballistic fabric is attributed to the formation of a highly ordered layered structure and the efficient load transfer between the fabric fibers and the graphene nanosheets. The results of deposition of layered graphene coatings on woven textiles are discussed here. The pristine graphite directly subjected to a solvent treatment in this work, which resulted in the production of exfoliated graphene sheets in the form of a dispersion that allow immediate utilization obtained dispersion for deposition on the para-aramid samples. In order to prepare the dispersion, graphite flakes were first dispersed into liquid media followed by graphite intercalation (division into microlayers) and nano-layers exfoliation. Dipolar aprotic organic solvent DMAc (N,N-Dimethylacetamide) and Cyrene (Dihydrolevoglucosenone) as a bio-based alternative for dipolar aprotic solvents were used as main components of liquid media. At the final stage, a stable dispersion of isolated flakes by using two types of liquid medium was obtained. To study the effects of dip coating and rolling parameters, six kinds of samples with different pull-out speeds and compression ratios were prepared, and their functional properties were measured and compared.

Well-Dispersed Graphene Enhanced Lithium Complex Grease Toward High-Efficient Lubrication

Graphene as a lubricating additive holds great potential for industrial lubrication. However, its poor dispersity and compatibility with base oils and grease hinder maximizing performance. Here, the influence of graphene dispersion on the thickening effect and lubrication function is considered. A well-dispersed lubricant additive was obtained via trihexyl tetradecyl phosphonium bis(2-ethylhexyl) phosphate modified graphene ([P66614][DEHP]-G). Then lithium complex grease was prepared by saponification with 12-OH stearic acid, sebacic acid, and lithium hydroxide, using polyalphaolefin (PAO20) as base oil and the modified-graphene as lubricating additive, with the original graphene as a comparison. The physicochemical properties and lubrication performance of the as-prepared greases were evaluated in detail. The results show that the as-prepared greases have high dropping point and colloidal stability. Furthermore, modified-graphene lithium complex grease offered the best friction reduction and anti-wear abilities, manifesting the reduction of friction coefficient and wear volume up to 18.84% and 67.34%, respectively. With base oil overflow and afflux, well-dispersed [P66614][DEHP]-G was readily adsorbed to the worn surfaces, resulting in the formation of a continuous and dense graphene deposition film. The synergy of deposited graphene-film, spilled oil, and adhesive grease greatly improves the lubrication function of grease. This research paves the way for modulating high-performance lithium complex grease to reduce the friction and wear of movable machinery.