Functional Three-Dimensional Graphene/Polymer Composites

Biomedical applications of graphene-based nanomaterials: recent progress, challenges, and prospects in highly sensitive biosensors

Graphene-based nanomaterials (graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, graphene-based nanocomposites, etc.) are emerging as an extremely important class of nanomaterials primarily because of their unique and advantageous physical, chemical, biological, and optoelectronic aspects. These features have resulted in uses across diverse areas of scientific research. Among all other applications, they are found to be particularly useful in designing highly sensitive biosensors. Numerous studies have established their efficacy in sensing pathogens and other biomolecules allowing for the rapid diagnosis of various diseases. Considering the growing importance and popularity of graphene-based materials for biosensing applications, this review aims to provide the readers with a summary of the recent progress in the concerned domain and highlights the challenges associated with the synthesis and application of these multifunctional materials.

Graphene (GNP) reinforced 3D printing nanocomposites: An advanced structural perspective

The influence of macro-micro structural design on the mechanical response of structural nanocomposites is substantial. The advancement of additive manufacturing especially three-dimensional (3-D) printing technology offers a promising avenue for the efficient and precise fabrication of multi-functional low-weight and high-strength nanocomposites. In contemporary discourse, there is a notable emphasis on carbon-based nanomaterials as nanofillers for structural composites due to their substantial specific surface area and exceptional load-bearing ability in mechanical structures. Notably, graphene, a distinctive two-dimensional (2-D) nanomaterial, exhibits very large elastic modulus and ultimate strength as well as remarkable plasticity. The utilization of graphene nanoparticles (GNPs) in the field of 3-D printing enables the production of intricate three-dimensional structures of varying sizes and configurations. This is achieved through the macro-assembly process, which facilitates the creation of a well-organized distribution of graphene and the establishment of a comprehensive physical network through precise micro-regulation. This paper presents an overview of multiscale structural composites that are strengthened by the incorporation of graphene and prepared by 3-D printing. The composites discussed in this study encompass graphene-polymer composites, graphene-ceramic composites, and graphene-metal composites. Furthermore, an analysis of the present obstacles and potential future advancements in this rapidly expanding domain is anticipated.

Three-Dimensional Graphene Sheet-Carbon Veil Thermoelectric Composite with Microinterfaces for Energy Applications

Over the years, various processing techniques have been explored to synthesize three-dimensional graphene (3DG) composites with tunable properties for advanced applications. In this work, we have demonstrated a new procedure to join a 3D graphene sheet (3DGS) synthesized by chemical vapor deposition (CVD) with a commercially available carbon veil (CV) via cold rolling to create 3DGS-CV composites. Characterization techniques such as scanning electron microscopy (SEM), Raman mapping, X-ray diffraction (XRD), electrical resistance, tensile strength, and Seebeck coefficient measurements were performed to understand various properties of the 3DGS-CV composite. Extrusion of 3DGS into the pores of CV with multiple microinterfaces between 3DGS and the graphitic fibers of CV was observed, which was facilitated by cold rolling. The extruded 3D graphene revealed pristine-like behavior with no change in the shape of the Raman 2D peak and Seebeck coefficient. Thermoelectric (TE) power generation and photothermoelectric responses have been demonstrated with in-plane TE devices of various designs made of p-type 3DGS and n-type CV couples yielding a Seebeck coefficient of 32.5 μV K-1. Unlike various TE materials, 3DGS, CV, and the 3DGS-CV composite were very stable at high relative humidity. The 3DGS-CV composite revealed a thin, flexible profile, good moisture and thermal stability, and scalability for fabrication. These qualities allowed it to be successfully tested for temperature monitoring of a Li-ion battery during charging cycles and for large-area temperature mapping.

One-step formation of three-dimensional interconnected T-shaped microstructures inside composites by orthogonal bidirectional self-assembly method

The fillers inside a polymer matrix should typically be self-assembled in both the horizontal and vertical directions to obtain 3-dimentional (3D) percolation pathways, whereby the fields of application can be expanded and the properties of organic-inorganic composite films improved. Conventional dielectrophoresis techniques can typically only drive fillers to self-assemble in only one direction. We have devised a one-step dielectrophoresis-driven approach that effectively induces fillers self-assembly along two orthogonal axes, which results in the formation of 3D interconnected T-shaped iron microstructures (3D-T CIP) inside a polymer matrix. This approach to carbonyl iron powder (CIP) embedded in a polymer matrix results in a linear structure along the thickness direction and a network structure on the top surface of the film. The fillers in the polymer were controlled to achieve orthogonal bidirectional self-assembly using an external alternating current (AC) electric field and a non-contact technique that did not lead to electrical breakdown. The process of 3D-T CIP formation was observed in real time using in situ observation methods with optical microscopy, and the quantity and quality of self-assembly were characterized using statistical and fractal analysis. The process of fillers self-assembly along the direction perpendicular to the electric field was explained by finite element analogue simulations, and the results indicated that the insulating polyethylene terephthalate (PET) film between the electrode and the CIP/prepolymer suspension was the key to the formation of the 3D-T CIP. In contrast to the traditional two-step method of fabricating sandwich-structured film, the fabricated 3D-T CIP film with 3D electrically conductive pathways can be applied as magnetic field sensor.

Engineering of zeolitic imidazolate frameworks based on magnetic three-dimensional graphene as effective and reusable adsorbent to enhance the adsorption and removal of caffeine from tea samples

As more and more adverse health effects of caffeine are being discovered, decaffeinated drinks are receiving increasing attention. In this work, a magnetic imidazole zeolite backbone compounded with three-dimensional graphene was successfully synthesized as a solid adsorbent using a layer-by-layer self-assembly technique, which can rapidly and effectively adsorb caffeine from tea. Meanwhile, the structure and properties of caffeine in tea were investigated by various physicochemical characterization tools. The analytical data showed that Fe3O4@3DGA@ZIF-8 had a specific surface area of 162.9754 m2/g and an adsorption capacity of up to 19.57 mg/g with a maximum adsorption rate of 96.55%, which could be maintained with good adsorption repeated utilization three times. The adsorption isotherm and the adsorption kinetic better fit with the Langmuir model and the preudo-second order kinetic model, respectively. Therefore, Fe3O4@3DGA@ZIF-8 is a good magnetic adsorbent for the separation and the effective removal of caffeine from tea sample.

From Forces to Assemblies: van der Waals Forces-Driven Assemblies in Anisotropic Quasi-2D Graphene and Quasi-1D Nanocellulose Heterointerfaces towards Quasi-3D Nanoarchitecture

In the pursuit of advanced functional materials, the role of low-dimensional van der Waals (vdW) heterointerfaces has recently ignited noteworthy scientific interest, particularly in assemblies that incorporate quasi-2D graphene and quasi-1D nanocellulose derivatives. The growing interest predominantly stems from the potential to fabricate distinct genres of quasi-2D/1D nanoarchitecture governed by vdW forces. Despite the possibilities, the inherent properties of these nanoscale entities are limited by in-plane covalent bonding and the existence of dangling π-bonds, constraints that inhibit emergent behavior at heterointerfaces. An innovative response to these limitations proposes a mechanism that binds multilayered quasi-2D nanosheets with quasi-1D nanochains, capitalizing on out-of-plane non-covalent interactions. The approach facilitates the generation of dangling bond-free iso-surfaces and promotes the functionalization of multilayered materials with exceptional properties. However, a gap still persists in understanding transition and alignment mechanisms in disordered multilayered structures, despite the extensive exploration of monolayer and asymmetric bilayer arrangements. In this perspective, we comprehensively review the sophisticated aspects of multidimensional vdW heterointerfaces composed of quasi-2D/1D graphene and nanocellulose derivatives. Further, we discuss the profound impacts of anisotropy nature and geometric configurations, including in-plane and out-of-plane dynamics on multiscale vdW heterointerfaces. Ultimately, we shed light on the emerging prospects and challenges linked to constructing advanced functional materials in the burgeoning domain of quasi-3D nanoarchitecture.

Countercation Engineering of Graphene-Oxide Nanosheets for Imparting a Thermoresponsive Ability

Graphene-oxide (GO) nanosheets, which are oxidized derivatives of graphene, are regarded as promising building blocks for functional soft materials. Especially, thermoresponsive GO nanosheets have been widely employed to develop smart membranes/surfaces, hydrogel actuators, recyclable systems, and biomedical applications. However, current synthetic strategies to generate such thermoresponsive GO nanosheets have exclusively relied on the covalent or non-covalent modification of their surfaces with thermoresponsive polymers, such as poly(N-isopropylacrylamide). To impart a thermoresponsive ability to GO nanosheets themselves, we focused on the countercations of the carboxy and acidic hydroxy groups on the GO nanosheets. In this study, we established a general and reliable method to synthesize GO nanosheets with target countercations and systematically investigated their effects on thermoresponsive behaviors of GO nanosheets. As a result, we discovered that GO nanosheets with Bu4N+ countercations became thermoresponsive in water without the use of any thermoresponsive polymers, inducing a reversible sol-gel transition via their self-assembly and disassembly processes. Owing to the sol-gel transition capability, the resultant dispersion can be used as a direct writing ink for constructing a three-dimensionally designable gel architecture of the GO nanosheets. Our concept of "countercation engineering" can become a new strategy for imparting a stimuli-responsive ability to various charged nanomaterials for the development of next-generation smart materials.

Dielectric Elastomers with Liquid Metal and Polydopamine-Coated Graphene Oxide Inclusions

Suspending microscale droplets of liquid metals like eutectic gallium-indium (EGaIn) in polydimethylsiloxane (PDMS) has been shown to dramatically enhance electrical permittivity without sacrificing the elasticity of the host PDMS matrix. However, increasing the dielectric constant of EGaIn-PDMS composites beyond previously reported values requires high EGaIn loading fractions (>50% by volume) that can result in substantial increases in density and loss of material integrity. In this work, we enhance permittivity without further increasing EGaIn loading by incorporating polydopamine (PDA)-coated graphene oxide (GO) and partially reduced GO. In particular, we show that the combination of EGaIn and PDA-GO within a PDMS matrix results in an elastomer composite with a high dielectric constant (∼10-57), a low dissipation factor (∼0.01), and rubber-like compliance and elasticity.

A wearable electrochemical fabric for cytokine monitoring

Wearable biosensors monitoring various biomarkers in sweat provide comprehensive and prompt profiling of health states at molecular levels. Cytokines existed in sweat with trace amounts play an important role in cellular activity modulation. Unfortunately, flexible and wearable biosensors for cytokine monitoring have not yet been achieved due to the limitation of membrane-based structure and sensing strategy. Herein, we develop a novel electrochemical fabric based on aptamer-functionalized carbon nanotube/graphene fibers for real-time and in situ monitoring of IL-6, a paramount cytokine biomarker for inflammation and cancer. This fabric system possesses flexibility, anti-fatigue ability and breathability for wearable applications and can apply to different body parts in various forms. Moreover, the electrochemical fabric can track other biomarkers by replacing the coupling aptamer, serving as a universal platform for sweat analysis. This fabric-based platform holds the potential to facilitate an intelligent and personalized health monitoring approach.

A Review on Graphene (GN) and Graphene Oxide (GO) Based Biodegradable Polymer Composites and Their Usage as Selective Adsorbents for Heavy Metals in Water

Water pollution due to heavy metal ions has become a persistent and increasing problem globally. To combat this, carbonaceous materials have been explored as possible adsorbents of these metal ions from solution. The problem with using these materials on their own is that their lifespan and, therefore, usability is reduced. Hence the need to mask them and an interest in using polymers to do so is picked. This introduces an improvement into other properties as well and opens the way for more applications. This work gives a detailed review of the major carbonaceous materials, graphene and graphene oxide, outlining their origin as well as morphological studies. It also outlines the findings on their effectiveness in removing heavy metal ions from water, as well as their water absorption properties. The section further reports on graphene/polymer and graphene oxide/polymer composites previously studied and their morphological as well as thermal properties. Then the work done in the absorption and adsorption capabilities of these composites is explored, thereby contrasting the two materials. This enables us to choose the optimal material for the desired outcome of advancing further in the utilization of carbonaceous material-based polymer composites to remove heavy metal ions from water.

Fluorescence anisotropy cytosensing of folate receptor positive tumor cells using 3D polyurethane-GO-foams modified with folic acid: molecular dynamics and in vitro studies

Integrated polyurethane (PU)-based foams modified with PEGylated graphene oxide and folic acid (PU@GO-PEG-FA) were developed with the goal of capturing and detecting tumor cells with precision. The detection of the modified PU@GO-PEG surface through FA against folate receptor-overexpressed tumor cells is the basis for tumor cell capture. Molecular dynamics (MD) simulations were applied to study the strength of FA interactions with the folate receptor. Based on the obtained results, the folate receptor has intense interactions with FA, which leads to the reduction in the FA interactions with PEG, and so decreases the fluorescence intensity of the biosensor. The synergistic interactions offer the FA-modified foams a high efficiency for capturing the tumor cell. Using a turn-off fluorescence technique based on the complicated interaction of FA-folate receptor generated by target recognition, the enhanced capture tumor cells could be directly read out at excitation-emission wavelengths of 380-450 nm. The working range is between 1×10 ² to 2×10 ⁴ cells mL ^-1 with a detection limit of 25 cells mL ^-1 and good reproducibility with relative standard deviation of 2.35%. Overall, findings demonstrate that the fluorescence-based biosensor has a significant advantage for early tumor cell diagnosis.

Self-Reporting Joule Heating Modulated Stiffness of Polymeric Nanocomposites for Shape Reconfiguration

Shape reconfigurable devices, e.g., foldable phones, have emerged with the development of flexible electronics. But their rigid frames limit the feasible shapes for the devices. To achieve freely changeable shapes yet keep the rigidity of devices for user-friendly operations, stiffness-tunable materials are desired, especially under electrical control. However, current such systems are multilayer with at least a heater layer and a structural layer, leading to complex fabrication, high cost, and loss of reprocessability. Herein, we fabricate covalent adaptable networks-carbon nanotubes (CAN-CNT) composites to realize Joule heating controlled stiffness. The nanocomposites function as stiffness-tunable matrices, electric heaters, and softening sensors all by themselves. The self-reporting of softening is used to regulate the power control, and the sensing mechanism is investigated by simulating the CNT-polymer chain interactions at the nanoscale during the softening process. The nanocomposites not only have adjustable mechanical and thermodynamic properties but also are easy to fabricate at low cost and exhibit reprocessability and recyclability benefiting from the dynamic exchange reactions of CANs. Shape and stiffness control of flexible display systems are demonstrated with the nanocomposites as framing material, where freely reconfigurable shapes are realized to achieve convenient operation, wearing, or storage, fully exploiting their flexible potential.

Directly Convert Carbonaceous Microspheres to Three-Dimensional Porous Carbon Microspheres with a Robust Self-Supporting Structure as a Metal-Free SERS Substrate for Online High-Throughput Analysis

It is of great significance for practical applications to directly convert readily available biomass carbon into three-dimensional (3D) porous carbon microspheres with a self-supporting structure. Herein, we report the convenient conversion of biomass carbon microspheres to hierarchical porous carbon microspheres (HP-CMSs) with a robust self-supporting framework structure. A general SiO₂-induced etching mechanism is proposed for the formation of the HP-CMSs. Benefiting from this robust 3D self-supporting frame structure, these HP-CMSs have outstanding mechanical, chemical, and thermal stability. As a metal-free surface-enhanced Raman scattering (SERS) substrate with an ultrahigh specific surface area (4216 m² g^-1) and a high density of active sites, the HP-CMSs exhibit high sensitivity with a detection limit of 10^-10 M and a Raman enhancement factor of 3.5 × 10⁶. By integrating the enrichment and sensing functions of the HP-CMSs in a microfluidic channel, online high-throughput SERS detection of 20 samples within 5 min is achieved in a single channel, and the relative standard deviation of the signals between samples is only 5.1%. The current work develops a convenient preparation method that converts sustainable biomass carbon to 3D hierarchical porous carbon and provides a potential material for sensing, energy, catalysis, and other fields.

High Performance of Functionalized Graphene Hydrogels Using Ethylenediamine for Supercapacitor Applications

High-performance supercapacitor (SC) electrodes typically require excellent rate capabilities, long cycle life, and high energy densities. In this work, ethylenediamine (EDA) functionalized graphene hydrogels (FGHs) with a high capacitor performance were prepared from graphene oxide (GO) dispersions using a two-step hydrothermal method. In addition, we used a very small amount of EDA to achieve the partial reduction and functional modification of GO, and the synthesized FGH-4 binder-free electrodes exhibited a high specific capacitance of −240 F/g at 1 A/g. We also successfully fabricated a symmetric SC device based on the FGH-4 electrode, with a wide voltage window of 3.0 V. More importantly, the as-assembled symmetric SC delivered a high specific energy of 39 Wh/kg at a specific power of 749 W/kg, while still maintaining its superior cycle life (retaining 88.09% of its initial capacitance after 10,000 cycles).

Graphene-Supported Naphthalene-Based Polyimide Composite as a High-Performance Sodium Storage Cathode

Electroactive acid anhydride with multicarbonyl is highly promising for electrochemical energy storage because of its high specific capacity and environmental benignity. Its low electrical conductivity and high dissolution in organic electrolyte, however, result in poor cycling and rate capabilities. Here, we report a naphthalene polyimide derivative (NPI) synthesized by using anhydride under condensation polymerization conditions, along with its composite with graphene (NPI-G) fabricated via in situ polymerization. The composite delivers a high reversible capacity and outstanding cycling stability and rate capability as a cathode for sodium-ion batteries (SIBs) owing to the formation of a polymer, the improvement in the electrical conductivity brought about by the highly dispersed graphene sheets, and the enhancement of structural stability resulting from the π-π stacking interaction between the phenyl groups of NPI and the six-member carbon rings of graphene. This investigation sheds light on the development, design, and screening of next-generation organic electrode materials with high performance for SIBs.

Fabrication, Structure, Performance, and Application of Graphene-Based Composite Aerogel

Graphene-based composite aerogel (GCA) refers to a solid porous substance formed by graphene or its derivatives, graphene oxide (GO) and reduced graphene oxide (rGO), with inorganic materials and polymers. Because GCA has super-high adsorption, separation, electrical properties, and sensitivity, it has great potential for application in super-strong adsorption and separation materials, long-life fast-charging batteries, and flexible sensing materials. GCA has become a research hotspot, and many research papers and achievements have emerged in recent years. Therefore, the fabrication, structure, performance, and application prospects of GCA are summarized and discussed in this review. Meanwhile, the existing problems and development trends of GCA are also introduced so that more will know about it and be interested in researching it.

Carbon-based aerogels for biomedical sensing: Advances toward designing the ideal sensor

Carbon based aerogels are special solid-state materials comprised of interconnected networks of 3D nanostructures with high amount of air-filled nanoporous. They expand the structural properties along with physicochemical characteristics of nanoscale construction blocks to macroscale, and incorporate distinctive attributes of aerogels, like large surface area, high porosity, and low density, with particular features of the different constituents. These features impart aerogels with rapid response signal, high selectivity, and ultra-sensitivity for sensing diverse targets in biomedical media. This has prompted researchers to develop a variety of aerogel-based sensors with encouraging achievements. Hence, this work outlines sensing applications of aerogel-based sensors with a comprehensive overview on the carbon aerogel hybrid materials and their analytical performances. Authors tried to list advantages and limitations of the developed approach and introduced more potent research for possible devices designing. We also point out some challenges and future perspectives related to the improvement of high-efficiency aerogel-based sensors.

Surface Engineering of Flower-Like Ionic Liquid-Functionalized Graphene Anchoring Palladium Nanocrystals for a Boosted Ethanol Oxidation Reaction

The development of low-cost and high-performance electrocatalyst-supporting materials is desirable and necessary for the ethanol oxidation reaction (EOR). Here, we report a facile and universal template-free approach for the first time to synthesize three-dimensional (3D) flower-like ionic liquid-functionalized graphene (IL-RGO). Then, the crystalline Pd nanoparticles were anchored on IL-RGO by a simple wet chemical growth method without a surfactant (denoted as Pd/IL-RGO). In particular, the IL is conducive to form a 3D flower-like structure. The optimized Pd/IL-RGO-2 presents a much-promoted electrocatalytic performance toward the EOR compared with commercial Pd/C catalysts, which is mainly derived from the grafted IL on RGO and the unique 3D flower-like structure. In detail, the IL can control, stabilize, and disperse the Pd nanocrystals as well as serving as the solvent and electrolyte in the microenvironment of the EOR, and the 3D flower-like structure endows the Pd/IL-RGO with high surface areas and rich opened channels, thereby kinetically accelerating the charge/mass transfers. Furthermore, density functional theory calculations reveal that the strong electronic interaction between Pd and IL-RGO generates a downshift of d_center for Pd and thereby enhances the durability toward CO-like intermediates and electrocatalytic reaction kinetics.

Composited Film of Poly(3,4-ethylenedioxythiophene) and Graphene Oxide as Hole Transport Layer in Perovskite Solar Cells

It is important to lower the cost and stability of the organic-inorganic hybrid perovskite solar cells (PSCs) for industrial application. The commonly used hole transport materials (HTMs) such as Spiro-OMeTAD, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and poly(3-hexylthiophene-2,5-diyl) (P3HT) are very expensive. Here, 3,4-ethylenedioxythiophene (EDOT) monomers are in-situ polymerized on the surface of graphene oxide (GO) as PEDOT-GO film. Compared to frequently used polystyrene sulfonic acid (PSS), GO avoids the corrosion of the perovskite and the use of H2O solvent. The composite PEDOT-GO film is between carbon pair electrode and perovskite layer as hole transport layer (HTL). The highest power conversion efficiency (PCE) is 14.09%.

Structural and Dipole-Relaxation Processes in Epoxy-Multilayer Graphene Composites with Low Filler Content

Multilayered graphene nanoplatelets (MLGs) were prepared from thermally expanded graphite flakes using an electrochemical technique. Morphological characterization of MLGs was performed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Raman spectroscopy (RS), and the Brunauer-Emmett-Teller (BET) method. DGEBA-epoxy-based nanocomposites filled with synthesized MLGs were studied using Static Mechanical Loading (SML), Thermal Desorption Mass Spectroscopy (TDMS), Broad-Band Dielectric Spectroscopy (BDS), and Positron Annihilation Lifetime Spectroscopy (PALS). The mass loading of the MLGs in the nanocomposites was varied between 0.0, 0.1, 0.2, 0.5, and 1% in the case of the SML study and 0.0, 1.0, 2, and 5% for the other measurements. Enhancements in the compression strength and the Young's modulus were obtained at extremely low loadings (C≤ 0.01%). An essential increase in thermal stability and a decrease in destruction activation energy were observed at C≤ 5%. Both the dielectric permittivity (ε1) and the dielectric loss factor (ε2) increased with increasing C over the entire frequency region tested (4 Hz-8 MHz). Increased ε2 is correlated with decreased free volume when increasing C. Physical mechanisms of MLG-epoxy interactions underlying the effects observed are discussed.

Electrical and Mechanical Properties of Sugarcane Bagasse Pyrolyzed Biochar Reinforced Polyvinyl Alcohol Biocomposite Films

Biochar obtained from the oxygen-deficient thermochemical processing of organic wastes is considered to be an effective reinforcing agent in biocomposite development. In the present research, biocomposite film was prepared using sugarcane bagasse pyrolyzed biochar and polyvinyl alcohol (PVA), and its electrical and mechanical properties were assessed. The biocomposite films were produced by varying content (5 wt.%, 8 wt.% and 12 wt.%) of the biochar produced at 400 °C, 600 °C, 800 °C and 1000 °C and characterized using X-Ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy. The experimental findings revealed that biochar produced at a higher pyrolyzing temperature could significantly improve the electrical conductance of the biocomposite film. A maximum electrical conductance of 7.67 × 10−2 S was observed for 12 wt.% addition of biochar produced at 1000 °C. A trend of improvement in the electrical properties of the biocomposite films suggested a threshold wt.% of the biochar needed to make a continuous conductive network across the biocomposite film. Rapid degradation of tensile strength was observed with an increasing level of biochar dosage. The lowest tensile strength 3.12 MPa was recorded for the film with 12 wt.% of biochar produced at 800 °C. Pyrolyzing temperature showed a minor impact on the mechanical strength of the biocomposite. The prepared biocomposites could be used as an electrically conductive layer in electronic devices.

A Review on the Production Methods and Applications of Graphene-Based Materials

Graphene-based materials in the form of fibres, fabrics, films, and composite materials are the most widely investigated research domains because of their remarkable physicochemical and thermomechanical properties. In this era of scientific advancement, graphene has built the foundation of a new horizon of possibilities and received tremendous research focus in several application areas such as aerospace, energy, transportation, healthcare, agriculture, wastewater management, and wearable technology. Although graphene has been found to provide exceptional results in every application field, a massive proportion of research is still underway to configure required parameters to ensure the best possible outcomes from graphene-based materials. Until now, several review articles have been published to summarise the excellence of graphene and its derivatives, which focused mainly on a single application area of graphene. However, no single review is found to comprehensively study most used fabrication processes of graphene-based materials including their diversified and potential application areas. To address this genuine gap and ensure wider support for the upcoming research and investigations of this excellent material, this review aims to provide a snapshot of most used fabrication methods of graphene-based materials in the form of pure and composite fibres, graphene-based composite materials conjugated with polymers, and fibres. This study also provides a clear perspective of large-scale production feasibility and application areas of graphene-based materials in all forms.

High-Performance Flexible Asymmetric Supercapacitor Paired with Indanthrone@Graphene Heterojunctions and MXene Electrodes

The energy density formula illuminated that widening the voltage window and maximizing capacitance are effective strategies to boost the energy density of supercapacitors. However, aqueous electrolyte-based devices generally afford a voltage window less than 1.2 V in view of water electrolysis, and chemically converted graphene yields mediocre capacitance. Herein, multi-electron redox-reversible, structurally stable indanthrone (IDT) π-backbones were rationally coupled with the reduced graphene oxide (rGO) framework to form IDT@rGO molecular heterojunctions. Such conductive agent- and binder-free film electrodes delivered a maximized capacitance of up to 345 F g^-1 in a potential range of -0.2 to 1.0 V. The partner film electrode-Ti₃C₂T_x MXene which worked in the negative potential range of -0.1 to -0.6 V-afforded a capacitance as large as 769 F g^-1. Thanks to the perfect complementary potentials of the IDT@rGO heterojunction positive electrode and Ti₃C₂T_x MXene negative partner, the polyvinyl alcohol/H₂SO₄ hydrogel electrolyte-based flexible asymmetric supercapacitor delivered an enlarged voltage window of 1.6 V and an impressive energy density of 17 W h kg^-1 at a high power density of 8 kW kg^-1, plus remarkable rate capability and cycling life (capacitance retention of ∼90% after 10000 cycles) as well as exceptional flexibility and bendability.

Effects of temperature and repeat layer spacing on mechanical properties of graphene/polycrystalline copper nanolaminated composites under shear loading

In the present study, the characteristics of graphene/polycrystalline copper nanolaminated (GPCuNL) composites under shear loading are investigated by molecular dynamics simulations. The effects of different temperatures, graphene chirality, repeat layer spacing, and grain size on the mechanical properties, such as failure mechanism, dislocation, and shear modulus, are observed. The results indicate that as the temperature increases, the content of Shockley dislocations will increase and the maximum shear stress of the zigzag and armchair directions also decreases. The mechanical strength of the zigzag direction is more dependent on the temperature than that of the armchair direction. Moreover, self-healing occurs in the armchair direction, which causes the shear stress to increase after failure. Furthermore, the maximum shear stress and the shear strength of the composites decrease with an increase of the repeat layer spacing. Also, the shear modulus increases by increasing the grain size of copper.

Versatile 3D reduced graphene oxide/poly(amino-phosphonic acid) aerogel derived from waste acrylic fibers as an efficient adsorbent for water purification

The fabrication of multifunctional materials to remove soluble heavy metal ions and dyes, as well as insoluble oils from waste water is urgently required, yet remains a daunting challenge because of difficulty in controlling their structure and property to satisfy various demands. Herein, for the first time, novel 3D reduced graphene oxide/poly(amino-phosphonic acid) (PAPA) aerogels (rGO/PAPAs) with different PAPA content were developed by solvothermal reduction of the graphene oxide and cross-linking with PAPA chain, and subsequently employed as versatile adsorbent for the removal of complex pollutants such as Cr(III) ion, methylene blue (MB) dye and various kinds of organic solvents from water. Benefiting from the synergistic effect of the reduced graphene oxide (rGO) sheet and PAPA component, as well as its unique 3D structure, the resultant aerogel (rGO/PAPA-2) gained amphiphilic, ultralight, and multifunctional properties. Thus, it showed a fast adsorption rate (within 15 min) and high adsorption capacity (up to 327.1 mg/g) for Cr(III) ion at an optimal pH of 5.5 due to its unique 3D network structure with abundant amino-phosphonic acid functional groups. The uptake of Cr(III) by rGO/PAPA-2 was fitted well with the Langmuir isotherm and pseudo-second-order kinetic model. The adsorption mechanism of Cr(III) onto rGO/PAPA-2 can be attributed to electrostatic attraction and surface complexation with APA groups. In addition, the rGO/PAPA-2 displayed an excellent adsorption performance for MB (694.5 mg/g) and several organic solvents (83.2 to 254.3 g/g). Moreover, the rGO/PAPA-2 exhibited a good regeneration (around 99%) and satisfactory recovery abilities for the tested adsorbates. Notably, PAPA chains can be easily prepared from waste acrylic fibers, making it become a cost effective but versatile candidate to prepare new material. Therefore, this work provides a new design strategy to fabricate the rGO/PAPA-2 aerogel with great prospect for sophisticated industrial wastewater cleanup.

Nanocomposite Materials Based on Electrochemically Synthesized Graphene Polymers: Molecular Architecture Strategies for Sensor Applications

The use of graphene and its derivatives in the development of electrochemical sensors has been growing in recent decades. Part of this success is due to the excellent characteristics of such materials, such as good electrical and mechanical properties and a large specific surface area. The formation of composites and nanocomposites with these two materials leads to better sensing performance compared to pure graphene and conductive polymers. The increased large specific surface area of the nanocomposites and the synergistic effect between graphene and conducting polymers is responsible for this interesting result. The most widely used methodologies for the synthesis of these materials are still based on chemical routes. However, electrochemical routes have emerged and are gaining space, affording advantages such as low cost and the promising possibility of modulation of the structural characteristics of composites. As a result, application in sensor devices can lead to increased sensitivity and decreased analysis cost. Thus, this review presents the main aspects for the construction of nanomaterials based on graphene oxide and conducting polymers, as well as the recent efforts made to apply this methodology in the development of sensors and biosensors.

Rock-Salt MnS0.5Se0.5 Nanocubes Assembled on N-Doped Graphene Forming van der Waals Heterostructured Hybrids as High-Performance Anode for Lithium- and Sodium-Ion Batteries

Manganese-based chalcogenides would be of latent capacity in serving as anodes for assembling lithium- and/or sodium-ion batteries (LIBs/SIBs) due to their large theoretical capacity, low price, and low-toxicity functionality, while the low electroconductivity and easy agglomeration behavior may impede their technical applications. Here, a solid-state solution of MnS_0.5Se_0.5 nanocubes in rock-salt phase has been synthesized for the first time at a relatively low temperature from the precursors of Mn(II) acetylacetonate with dibenzyl dichalcogens in oleylamine with octadecene, and the MnS_0.5Se_0.5 nanocubes have been assembled with N-doped graphene to form a new kind of heterostructured nanohybrids (shortened as MnS_0.5Se_0.5/N-G hybrids), which are very potential for the fabrication of metal-ion batteries including LIBs and/or SIBs. Investigations revealed that there have been dense vacancies generated and active sites increased via nonequilibrium alloying of MnS and MnSe into the solid-solution MnS_0.5Se_0.5 nanocubes with segregation and defects achieved in the low-temperature solution synthetic route. Meanwhile, the introduction of N-doped graphene forming heterojunction interfaces between MnS_0.5Se_0.5 and N-doped graphene would efficiently enhance their electroconductivity and avoid agglomeration of the active MnS_0.5Se_0.5 nanocubes with considerably improved electrochemical properties. As a result, the MnS_0.5Se_0.5/N-G hybrids delivered superior Li/Na storage capacities with outstanding rate performance as well as satisfactorily lasting stability (1039/457 mA h g^-1 at 0.1 A g^-1 for LIBs/SIBs). Additionally, full-cell LIBs of the anodic MnS_0.5Se_0.5/N-G constructed with cathodic LiFePO₄ (LFP) further confirmed the promising future for their practical application.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

Chirality has become an important research subject. The research areas associated with chirality are under substantial development. Meanwhile, graphene is a rapidly growing star material and has hard-wired into diverse disciplines. Rational combination of graphene and chirality undoubtedly creates unprecedented functional materials and may also lead to great findings. This hypothesis has been clearly justified by the sizable number of studies. Unfortunately, there has not been any previous review paper summarizing the scattered studies and advancements on this topic so far. This overview paper attempts to review the progress made in chiral materials developed from graphene and their derivatives, with the hope of providing a systemic knowledge about the construction of chiral graphenes and chiral applications thereof. Recently emerging directions, existing challenges, and future perspectives are also presented. It is hoped this paper will arouse more interest and promote further faster progress in these significant research areas.

Nucleation and growth dynamics of graphene grown by radio frequency plasma-enhanced chemical vapor deposition

We investigated the nucleation and grain growth of graphene grown on Cu through radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at different temperatures. A reasonable shielding method for the placement of copper was employed to achieve graphene by RF-PECVD. The nucleation and growth of graphene grains during PECVD were strongly temperature dependent. A high growth temperature facilitated the growth of polycrystalline graphene grains with a large size (~ 2 μm), whereas low temperature induced the formation of nanocrystalline grains. At a moderate temperature (790 to 850 °C), both nanocrystalline and micron-scale polycrystalline graphene grew simultaneously on Cu within 60 s with 50 W RF plasma power. As the growth time increased, the large graphene grains preferentially nucleated and grew rapidly, followed by the nucleation and growth of nanograins. There was competition between the growth of the two grain sizes. In addition, a model of graphene nucleation and grain growth during PECVD at different temperatures was established.

Induction of M2-Type Macrophage Differentiation for Bone Defect Repair via an Interpenetration Network Hydrogel with a GO-Based Controlled Release System

Recently, biomaterials with immune-regulating properties have emerged as crucial new platforms for bone tissue engineering. Inducing macrophages to differentiate into M2 subtype can reduce immune inflammatory response and accelerate tissue repair after implantation. An interpenetration network hydrogel is developed utilizing graphene oxide (GO)-carboxymethyl chitosan (CMC)/poly(ethylene glycol) diacrylate (PEGDA), in which two bioactive molecules, interleukin-4 (IL-4) and bone morphogenetic protein-2 (BMP-2), are loaded and released in a controlled manner to induce macrophages to differentiate into M2 type and enhance bone formation. These two factors are initially loaded with GO and then embedded into the CMC/PEGDA hydrogel for sustained release. Results indicate that the hydrogel shows enhanced mechanical stiffness, strength, and stability. The hydrogel loaded with IL-4 and BMP-2 significantly promotes both macrophage M2-type differentiation and bone marrow mesenchymal stem cell osteogenesis differentiation in vitro. Furthermore, in vivo studies show that the implantation of this hydrogel markedly reduces local inflammation while enhancing bone regeneration at 8 weeks post-implantation. In all, the findings suggest that hydrogel loaded with IL-4 and BMP-2 has synergistic effects on bone regeneration. Such an induction and immunomodulation system offers a promising strategy for the development of future bone immune regulation and tissue engineering applications.

A Facile and Scalable Approach in the Fabrication of Tailored 3D Graphene Foam via Freeze Drying

One of the challenges in the processing of advanced composite materials with 2D reinforcement is their extensive agglomeration in the matrix. 3D architecture of 2D graphene sheets into a Graphene Foam (GrF) assembly has emerged as an effective way to overcome agglomeration. The highly reticulated network of branches and nodes of GrF offers a seamless pathway for photon and electron conduction in the matrix along with improved mechanical properties. 3D GrF nano-filler is often fabricated by chemical vapor deposition (CVD) technique, which demands high energy, slow deposition rate, and restricting production to small scale. This work highlights freeze-drying (FD) technique to produce 3D graphene nanoplatelets (GNP) foam with a similar hierarchical structure to the CVD GrF. The FD technique using water as the main chemical in 3D GNP foam production is an added advantage. The flexibility of the FD in producing GNP foams of various pore size and morphology is elucidated. The simplicity with which one can engineer thermodynamic conditions to tailor the pore shape and morphology is presented here by altering the GNP solid loading and mold geometry. The FD 3D GNP foam is mechanically superior to CVD GrF as it exhibited 1280 times higher elastic modulus. However, thermal diffusivity of the FD GNP foam is almost 0.5 times the thermal diffusivity of the CVD GrF due to the defects in GNP particles and pore architecture. The versatility in GNP foam scalability and compatibility to form foam of other 1D and 2D material systems (e.g., carbon nanotubes, boron nitride nanotubes, and boron nitride nanoplatelets) brings a unique dimensionality to FD as an advanced engineering foam development process.

Carbon Nanomaterials for Biomedical Application

The use of carbon-based nanomaterials (CNs) with outstanding properties has been rising in many scientific and industrial application fields. These CNs represent a tunable alternative for applications with biomolecules, which allow interactions in either covalent or noncovalent way. Diverse carbon-derived nanomaterial family exhibits unique features and has been widely exploited in various biomedical applications, including biosensing, diagnosis, cancer therapy, drug delivery, and tissue engineering. In this chapter, we aim to present an overview of CNs with a particular interest in intrinsic structural, electronic, and chemical properties. In particular, the detailed properties and features of CNs and its derivatives, including carbon nanotube (CNT), graphene, graphene oxide (GO), and reduced GO (rGO) are summarized. The interesting biomedical applications are also reviewed in order to offer an overview of the possible fields for scientific and industrial applications of CNs.

Mechanism of Nanocomposite Formation in the Layer-by-Layer Single-Step Electropolymerization of π-Conjugated Azopolymers and Reduced Graphene Oxide: An Electrochemical Impedance Spectroscopy Study

This work presents a study of the formation mechanism of electrochemically deposited alternating layers of azopolymer and graphene oxide, as well as a systematic study of the physicochemical characteristics of the resulting nanocomposite films by electrochemical impedance spectroscopy. The nanocomposite films were constructed by cyclic electropolymerization, which allowed for the assembly of thin films with alternating azopolymers and reduced graphene oxide (rGO) layers in one step. Morphological characterizations were performed by atomic force microscopy and scanning electron microscopy and verified that the electrodeposition of the poly(azo-BBY) polymeric film occurred during the anodic sweep, and the deposition of graphene oxide sheets took place during the cathodic sweep. By analyzing the electrochemical impedance spectra using equivalent circuit models, variations in the resistance and capacitance values of the system were monitored as a function of the amount of electrodeposited material on the fluorine doped tin oxide electrode. In addition, the interfacial phenomena that occurred during the electroreduction of the rGO sheets were monitored with the same method.