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Flexible graphene-based paper is promising for wide applications due to its outstanding electrical and thermal conductivities. Graphene flakes with large size are usually known as the key factor for improved paper performance. However, we find that a combination of flakes with large and small sizes is more favorable for both electrical and thermal conductivities than pure large flakes. In this work, flexible paper with enhanced electrical and thermal properties was fabricated by mixing graphene flakes with various size distributions. Large-size graphene (LSG) flakes play the role of a backbone structure, whereas small-size graphene (SSG) flakes fill the voids in the paper without disturbing the high orientation. The physical properties of the as-prepared graphene papers with contents of SSG varying from 0 to 100% have been investigated. It is found that the electrical and thermal conductivities of the paper with 25 wt% SSG are both around 140% higher than that of pure LSG paper. Our results indicate that the lightweight and flexible graphene-based paper has great potential for lateral heat dissipation applications requiring heat movement in a particular direction. [ABSTRACT FROM AUTHOR]

This paper presents the nickel–cobalt nanoprickly particles (PNi2Co3) composited with graphene nanosheets (GNs) and carbon nanotubes (CNT), prepared via the one-pot hydrothermal method (PNi2Co3/GNs/CNT), as an efficacious nonprecious metal bifunctional electrocatalyst for both oxygen evolution and reduction reactions (OER/ORR). The study employs a comprehensive methodology, incorporating cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) analysis to characterize and assess the materials and electrochemical properties investigated in the article. The primary objective was to successfully prepare a bifunctional electrocatalyst, and the PNi2Co3/GNs/CNT material achieved this goal. It exhibited superior OER activity, durability, and resistance to crossover effects, by an overpotential (η) of 480 mV and a Tafel slope of 61 mV dec−1, significantly higher than those obtained for RuO2 nanoparticles (η = 970 mV, Tafel slope = 85 mV dec−1). A similar trend was observed for ORR, where the PNi2Co3/GNs/CNT displayed high activity with an n = 3.93, close to the activity of a Pt/C (20 wt%), commercial catalyst with n = 4. Careful analysis of the EIS results via suitable models, in conjunction with Tafel data, revealed that the enhanced activity originates mainly from two factors: (a) the large surface area of the Ni–Co nanoprickly alloy and graphene sheets, where the CNTs (as a spacer) helped graphene nanosheets to avoid restacking and decreasing the surface area, and (b) the synergistic effect between Ni–Co nanoprickly and carbon components (GNs and CNT) of the composite. [ABSTRACT FROM AUTHOR]

The material choice for electrical contacts fundamentally governs the breaking performance, safety, and reliability of electrical switches. In recent years, amid a rapid escalation in infrastructure development, an upsurge in living standards, and advancements in scientific and technological realms, there has been a burgeoning demand for increased load capacity within power distribution systems, thereby imposing novel demands on electrical contact materials. The advent of two-dimensional graphene, with its exceptional electrical conductivity, thermal conductivity, and mechanical attributes, has piqued the interest of researchers in the electrical contact field. This has spurred further research and development into innovative graphene-enhanced electrical contact materials. This paper presents a comprehensive review of the progression made in graphene-enhanced silver-based electrical contact materials over the recent years. It particularly delves into the application of graphene in silver-based contact substances, encompassing the most recent developments in graphene-enhanced contacts, the underlying principles and processes governing arc generation and erosion, the arc-resistant mechanisms inherent to graphene-enhanced contact materials, and provides a forward-looking perspective on the potential future of graphene-based contact materials. [ABSTRACT FROM AUTHOR]

Highly integrated and high-power devices place higher demands on the heat dissipation capability of heat sink components, and graphene meets the heat dissipation requirements due to its extremely high thermal conductivity of 5300 Wm−1 K−1 and good mechanical properties. Graphene by redox is one of the most promising methods for large-scale preparation of graphene; however, the quality of graphene prepared by different reduction processes varies. Herein, this paper presents a fast and efficient reduction process. Benzene was added as a reduction aid to increase the temperature from room to 2000 °C in 30 s and complete the reduction process. By this method, we obtained graphene with low defects and high thermal conductivity. The reduction process restored the lattice destroyed by the oxidation process, and the repaired material showed a higher crystallinity with a measured ID/IG of 0.18 (Ph-rGO-0, 0.58) and in-plane thermal conductivity of 510 ± 10 Wm−1 K−1. The in-plane thermal conductivity was increased by 262 Wm−1 K−1 compared with the film without benzene addition (Ph-rGO-0), which showed better homogeneous temperature performance and heat dissipation performance in practical applications. These results show the great potential for the application of graphene films prepared by this method in the field of heat dissipation materials. [ABSTRACT FROM AUTHOR]

Low-density aerogels have shown great potential as excellent oil–water separation materials in dealing with the growing problem of marine pollution, but they typically suffer from low oil adsorption capacity, complex process flow, expensive raw materials, and poor recyclability. In this paper, inexpensive industrial raw material melamine was introduced into the framework of graphene aerogels, which can be formed into gels (NGAs) in just one step. High-temperature carbonized nitrogen-doped graphene aerogels (N0.5CGAs-2) have the advantages of ultralow density, high porosity, repeatable compressibility, hydrophobicity, and excellent adsorption capacity. In addition, depending on the characteristics of the contaminants, N0.5CGAs-2 can be selected for different recycling methods and exhibits excellent reusability in cycling. It has a high application value for solving water pollution problems caused by oil spill accidents and chemical spills. [ABSTRACT FROM AUTHOR]

Nitrogen doping is an effective way to improve the electrical and catalytic properties of graphene. Here, we used a non-thermal plasma technique with AC rotating arc to prepare nitrogen-doped graphene. This method does not need catalyst and can produce nitrogen-doped graphene in the atmospheric environment by large scale. CH4 as the carbon source and N2 as the nitrogen source, nitrogen-doped graphene was obtained by plasma direct synthesis. The nitrogen content in the product was analyzed by X-ray photoelectron spectroscopy and the doping level was about 1.19 at.%. It was found that H2 and CO2 as carrier gases can change the nitrogen doping type and content. When there was only N2, pyrrolic N and graphitic N were the main forms in the graphene. The addition of H2 improved the selectivity of pyridinic N and pyrrolic N, but decreased the nitrogen doping content. CO2 significantly increased the selectivity of pyrrolic N and increased the nitrogen doping content. In addition, the formation mechanism of nitrogen-doped graphene was briefly described in this paper. The key in this plasma production technology is to understand the effect of carrier gas on nitrogen doping, which is also instructive for mass production in industry. [ABSTRACT FROM AUTHOR]

It has been shown that combining 2D materials in vertical or lateral heterostructures can significantly change and improve their electronic properties, making them more applicable for various purposes, e.g., nanoelectronics, spintronics, energy storage, catalysis etc. In this paper, we employ first principle calculations to investigate the influence of Li adsorption on lateral heterostructures composed of nanoribbons of graphene and hexagonal boron nitride. The results indicate the profound role of the nanoribbon interface. With respect to the sole graphene or boron nitride nanoribbons, Li atoms more strongly adsorb to their lateral interface due to the hybridization of electronic states. This leads to the severe changes in the electronic band structure. Our findings show that in the case of boron terminated zigzag nanoribbon interface, metallic character of the nanoribbon is changed upon Li adsorption. It opens an indirect bandgap of about 0.2 eV, showing that Li adsorption can be used for tuning electronic properties of the nanoribbons. [ABSTRACT FROM AUTHOR]

In this paper, a carbonized cotton fiber/graphene oxide hydrogel-juglone (CCF/GH-JUG) flexible binder-free electrode was fabricated by carbonization and hydrothermal process method for supercapacitors (SCs). The CCF substrate possess a layered three-dimensional porous structure, which can provide a conductive pathways for rapid electron transfer. The as-prepared electrode with outstanding electrochemical properties because of the introducing GH and juglone. Juglone, a renewable biomolecule, is immobilized onto reduced GH sheets due to the stable π-π interaction between the aromatic structure and the carbon scaffold, which shorten the ion diffusion distance, and ensure sufficient contact area between the electrode and the electrolyte, increasing and fast charge/discharge capability and the specific capacitance of the hybrid electrodes. The CCF/GH-JUG 8:3 not only electrode exhibits a high specific capacitance of 453.9 F g−1 at a current of 1 A g−1, but also shows good rate capability of 89.75% at a current of 10 A g−1 and high stability with 87.3% capacitance retention after 10,000 cycles. In addition, the assembled flexible supercapacitor possesses a high energy density of 33.72 Wh kg−1 with the power density of 0.124 kW kg−1 at a current of 0.5 A g−1, and expressing almost no decrease in the capacitance at different bending angles. Such three-dimensional macroporous graphene hydrogel with high capacitance and long-term stability have promising application prospects in energy storage devices for supercapacitors. [ABSTRACT FROM AUTHOR]

The heat transfer performance of the graphene network in the polymer is not so satisfactory due to the high interfacial thermal resistance between layered graphene. This paper constructs partially stacked graphene sheets models with random vacancies by the molecular dynamics to investigate the effect of vacancy coverage rate, stacking length and stacking forms on the heat transfer coefficient. The results indicate that the heat transfer coefficient of the whole system mainly depends on the effective thermal conductivity of the stacking region. As the vacancy coverage rate increases, the effective thermal conductivity of the stacking region increases rapidly and then decreases slowly due to the synthetic effect of the interfacial thermal resistance and in-plane thermal resistance. Further studies reveal the positive correlation between the stacking length and the effective thermal conductivity of the stacking region. However, the effective thermal conductivities of models with different stacking lengths converge to a similar value approximately at a high vacancy coverage rate. Finally, the stacking form is proved to have a slight influence on the effective thermal conductivity. This work is of practical importance for the design and application of graphene networks in composites materials. [ABSTRACT FROM AUTHOR]

The major challenges in the commercialization of spintronic devices lie in the high-dimensional materials with low spin-current generation efficiency and expensive fabrication processes. Recent discovery on the magnetoresistance (MR) phenomenon of graphene nanosheets could suggest that graphene-based materials can be excellent materials for spintronic devices. To develop two-dimensional materials with high MR at the low magnetic field and room temperature, we design and develop hybrid graphene nanosheets by using the matrix-assisted pulsed laser evaporation (MAPLE) technique. FeCo nanoparticles (NPs) are deposited onto the reduced graphene oxide (rGO) nanosheets in a stoichiometric manner by the MAPLE process. The density and size of FeCo NPs on rGO can be simply adjusted by varying the deposition time (t). Most importantly, with a limited FeCo ratio (0.4 at.%), MAPLE-prepared FeCo/rGO hybrid nanosheets display an MR phenomenon (MR up to 0.7%) at the low magnetic field (10 kOe) and room temperature. In this paper, we demonstrate that the MAPLE process can be used to produce hybrid graphene nanosheets with MR properties. The results of this work can contribute to the development of spintronic devices, e.g., ultra-thin MR sensors. [ABSTRACT FROM AUTHOR]

We demonstrate a functionalization strategy to improve the basic fluorescence properties and to systematically customize the bandgap properties of Graphene quantum dots (GQD) by functionalization with a well-known fluorophore called Dithienopyrrole derivative (DTPAN) whereby making them adequately acceptable for the suitable promising applications. We observed that the functionalization with DTPAN not only shifts the photoluminescence spectrum but also enhances the other inherent fluorescence properties. The functionalized material (DTPAN-fn-GQD) is used for the sensitive detection of Pb2+ ions in aqueous media. The detection of Pb2+ within the linear range of 0.5–40 nM was obtained with a limit of detection of 0.25 nM. Stern–Volmer analysis suggests that both static and dynamic mechanisms are active for the quenching process and further the Cyclic Voltammetry measurements along with DFT calculations of DTPAN-fn-GQD recommend the possibility of electron transfer from the HOMO of DTPAN to the LUMO of GQD upon photoexcitation. However, the presence of Pb2+ metal ions will perturbate this charge transfer process and lead to quenching of fluorescence. The sensor was applied efficiently to the determination of Pb2+ ions in real water samples. Paper strips based on the developed fluorescent probe were shown to be useful for rapid visual sensing, which can expand its potential ability for developing simple analytical devices. [ABSTRACT FROM AUTHOR]

A simple and effective xylitol-assisted mechanochemical stripping method has been used to peel graphite into graphene nanosheets (GNSs). Using xylitol as a ball milling aid can increase the shear force in the ball milling process and well get over the Van der Waals interlayer force between adjacent graphite layers. The prepared graphene has large horizontal size, thin thickness and high output. As a result, the performance of the batteries using the prepared GNSs as the negative electrode material is significantly better than that of industrial graphite. The initial capacity of GNSs electrode is 536 mAh·g−1, which is much more than that of commercial graphite electrode (296 mAh·g−1). After 550 cycles, the reversible capacity can still maintain at 500 mAh·g−1 with retention rate of 93.2%, which is also much higher than that of commercial graphite electrode (233 mAh·g−1 with retention rate of 78.7%). The xylitol-assisted mechanochemical exfoliation method designed in this paper offers a new method for large-scale preparation of GNSs with excellent electrochemical performance as the negative electrode material of lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Fabrication of effective photocatalyst using semiconductors and graphene or reduced graphene oxide has been regarded as one of the most promising task to attenuate the environmental pollution. This paper reports the synthesis of different nanocomposites of reduced graphene oxide–cadmium sulfide (RGO-CdS) with varying weight ratio of RGO by simple reflux condensation reaction, during which the reduction of graphene oxide (GO) and formation of CdS nanoparticles occur simultaneously. The combination of CdS nanoparticles (NPs) with the optimum amount of RGO gives a noticeable effect on the properties of the synthesized hybrid nanocomposites, such as enhanced optical, photocatalytic properties. The microscopic studies proved that with the increasing RGO content in the nanocomposites, the particle size decreases and got different shapes. These nanocomposites have been investigated separately as nanocatalyst for the reduction of Cr(VI) to Cr(III) in the presence of visible light irradiation and the catalytic activity depends on the pH of the medium and also the particle size of the CdS NPs which are supported by the band gap energy derived from Tauc's equation. The significant increase in photocatalytic performance of the RGO-CdS nanocomposite was attributed to high electron conductivity of the CdS NPs and RGO surface which facilitates charge separation and prolongs the lifetime of photogenerated electron–hole pairs by decreasing the recombination rate. Antibacterial and antiprotozoal activities have been investigated to determine the efficiency of these RGO-CdS nanocomposites on different bacterial and protozoan strains. [ABSTRACT FROM AUTHOR]

The fatigue failure of graphene plays an important role in determining the service life of many graphene-based nanodevices. In this paper, the fatigue behaviours of polycrystalline graphene are investigated by using molecular dynamics (MD) simulations. The results show that the fatigue process of polycrystalline graphene contains three stages, which, successively, are the initiation of microvoids, formation of large cracks and rapid propagation of cracks. The loading amplitude, grain size and temperature can greatly affect the fatigue properties. Evolutions of the mechanical and thermal transport properties of polycrystalline graphene during the fatigue process are also investigated by MD simulations. No significant changes are found in these material properties in the first two stages of fatigue. However, a dramatic decrease in the Young's modulus, tensile strength and thermal conductivity is found in the last stage. The large cracks occurring in the last stage are responsible for the reduced Young's modulus and tensile strength, because they can reduce the effective stiffness of polycrystalline graphene and induce the stress concentration in graphene. Meanwhile, large cracks also can reduce the heat flux and, meanwhile, increase the phonon scattering in polycrystalline graphene, both of which account for the reduced thermal conductivity observed in the last stage of fatigue. [ABSTRACT FROM AUTHOR]

The growth of graphene on Ni magnetic films is of great significance for graphene spintronics, whereas the existence of grain boundaries and twin crystal structures in Ni films is an obstacle for obtaining the large-scale and uniform graphene. In this paper, an epitaxial wafer-scale single-crystalline Ni(111) film with the flat and clean surface was successfully prepared on the commercial α-Al2O3(0001) substrate by a two-step method, which was demonstrated with several characterization methods. According to the abnormal grain growth mechanism, the clean and uniform sapphire surface plays a key role for the single crystallization of Ni films as it induces a weak interface energy difference between two atomic stacking structures (ABC and ACB), thus stimulating the evolution of Ni films from (111) out-of-plane textures to single crystals. Furthermore, an ultra-flat and wrinkle-free graphene monolayer was synthesized on the prepared Ni film, which further verified its high quality and effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, three series of heterostructures of 2D transition metal dichalcogenides (including MoS2, MoSe2, MoTe2, WS2, WSe2, and WTe2) sandwiched by graphene (Gr), h-BN, and g-C3N4, which will be referred to as Gr sandwich heterostructures (SHS), h-BN-SHS, and g-C3N4-SHS in the rest of this paper, have been systematically studied firstly by using first-principle calculations. Gr-SHS are found to hold stable structures with an expanded band gap when MoSe2 and WSe2 are used as interlayers, indicating potential applications to Hall switch sensors. With the same type of interlayers, the stable h-BN-SHS shows additionally good response to visible light. In addition to good response to the visible light, effective electron-hole separation is also observed in g-C3N4-SHS. Such properties suggest structures in this sandwich type may be applied in plentiful areas, such as photocatalyst and solar cells. Moreover, the number and density of catalytically active sites in SHS may be dramatically increased. Consequently, we hope our findings could provide guidance for both the design of advanced materials and the corresponding nano-devices. [ABSTRACT FROM AUTHOR]

In this paper, we present novel semi-permeable graphene-based membranes. Composite filters were designed and fabricated on polysulfone porous scaffolding using combinations of polycrystalline large-area High Strength Metallurgical Graphene (HSMG®), graphene oxide, hydrazine and an in-situ interfacial polymerized polyamide. The naturally occurring defects in HSMG® (which were tenths of a nanometer) were the clue in fabricating a filtering membrane. The performance of graphene membranes was evaluated in forward osmosis test. The prepared composites were proved to be semi-permeable membranes with great ions blocking efficiency (over 95%) and water flux only one order of magnitude lower than the commercial reverse osmosis membranes. The experiments' results demonstrated that the solutions proposed in this work indicate that graphene-based membranes can be used in water treatment technology. [ABSTRACT FROM AUTHOR]

Phase changing materials (PCM) release or absorb heat in high quantity when there is a variation in phase. PCMs show good energy storage density, restricted operating temperatures and hence find application in various systems like heat pumps, solar power plants, electronic devices, thermal energy storage (TES) systems. Though it has extensive usage in such a diverse range of systems, PCMs have some limitations like poor thermal conductivity, susceptibility to leakage during phase transformations. To overcome these shortcomings, phase changing composites (PCCs) were fabricated. PCCs are an amalgamation of filler material with PCMs to form a composite with those anticipated or desired properties. There are multiple factors like porosity, sealing performance, leaking holding capacity, shape stability, thermal conductivity that should be taken into consideration/account while fabricating PCCs. Having considered such factors, graphene, which has high thermal conductivity (2000–4000 W/m K) and high specific surface area (~ 2630 m2 g−1), acts as a suitable candidate for synthesizing an effective and efficient PCC. In its aerogel form, it is used as a conductive filler or form-stabilizer, to improve the thermal conductivity (~ 5.89 W/m K) and heat transfer of PCMs like reduced graphene oxide. Graphene aerogels, thus, are used in PCM as latent heat storage (LHS) for thermal energy storage systems. Many of the researchers have based their work focus on graphene aerogels in PCMs, significant roles of such PCCs, their advantages and disadvantages; this paper is an effort to elucidate those and provide further insight into TES systems in which LHS is explicitly used in PCMs and their practical aspect. [ABSTRACT FROM AUTHOR]

This work presents the synthesis of the noble nanocomposites of silica-coated calcium copper titanate-graphene (CCTO@SiO2-GO) by the established sol-gel method. This paper showed the decoration of CCTO@SiO2 NPs on the surface of graphene oxide and how the decoration/attachment depends on various environmental and instrumental factors like sonication time, stirring rate, centrifugation rpm and the thickness of silica shell coated on CCTO NPs. The prepared CCTO@SiO2-GO composites were characterized by suitable characterization techniques. FESEM and TEM confirmed the morphological study of nanocomposites and how the CCTO@SiO2 NPs are attached to the surface of GO sheet. FTIR has shown the presence of O-H, N-C groups which help in the formation of types of bonds between CCTO@SiO2 NPs and GO. This work further revealed an excellent result of a dielectric study, indicating that the best-decorated CCTO@SiO2 NPs over the surface of the GO sheet cause the increment of dielectric constant ε′ from 102 up to 105. Meanwhile, this study also suggested high loss ε″ up to 106 at a lower frequency, i.e. 20 Hz at RT which can be useful for microelectronic devices. This variance of dielectrics is due to the effect of polarization and decoration of CCTO@SiO2 NPs over the GO sheets. As the frequency increases from 20 Hz to 2 MHz, the dielectric constant ε′, as well as the loss of ε″, reached up to 102 values for the highest decorated material. Our study also clearly explained a uniform variation in dielectric constant ranges from 1 × 102 to 1.5 × 104 at a different temperature range from room temperature to 560 °C with a frequency range of 3 × 104 Hz to 2 × 106 Hz, and the value varies accordingly with the synthesis method. [ABSTRACT FROM AUTHOR]

In the present review, the recent progress in describing the intricacies of mechanical and thermal properties of all types of graphene- and modified graphene-based polymer nanocomposites has been comprehensively examined. The effectiveness of microscopy bouquet for the intrinsic characterization of graphene family and their composites was clearly demonstrated in this research. Furthermore, the utility of the dynamic mechanical analysis and thermo-gravimetric analysis employed for thermal characterization that has been reported by various researchers was exhaustively analyzed in this paper. This research primarily focused on the analyses of several good articles concerned with hybrid graphene composites and the synergetic effect of graphene with other nanofiller to assess its effect on the mechanical properties of its corresponding composites. Such systematic analysis of previous literatures imparted a direction to the researchers about the solution of improved interfacial properties as well as the enhanced dispersion into the vicinity of the matrix. This current research has suggested that the presence of the graphene filler even at very low loadings has shown considerable improvement in the overall mechanical properties of graphene. Further studies to optimize the value of the filler need to be addressed in order to gain complete understanding of the properties of graphene. The potential applications, current challenges, and future perspectives pertaining to these nanocomposites were elaborately discussed in the current study with regard to the multi-scale capabilities and promising developments of the graphene-family-based nanocomposites materials. [ABSTRACT FROM AUTHOR]

In this paper, SiC with the morphologies of both particles and whiskers was grown on graphite surface by chemical vapor reaction method under different pressure conditions. According to these experimental discoveries, designed experiments with different reaction pressures and temperatures were studied in detail, and then, the influence factors were analyzed in theory. The results show that the shapes of the formed SiC are influenced mainly by the total pressure of the system. Higher total pressure is in favor of larger concentration of CO and then tends to form SiC whiskers. In addition, temperature significantly affects the size of SiC, higher temperature results in shorter length and further quantity of the SiC whiskers as well as larger diameter of the SiC particles. Based on these results, controllable synthesis of silicon carbide whiskers and particles can be realized in accordance with the requirements of application. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the quantum capacitance and the integrated charge of graphene-based materials based on first-principles density functional theory calculations. Transition metals doped in a graphene plane will not move out of the graphene plane and will finally form an accurate symmetrical structure. Meanwhile, for transition metals doped out of plane, regardless of the positions that the metals were placed, they will conform to the same stable M-MV complexes eventually. Meanwhile, the introduction of N atoms makes the Al atom hybridization state tend to be consistent. Al3-NNN (the Al-embedded, nitrogen doped monovacancy graphene-based complexes, and the number of N atoms represents the number of N atoms surrounding the Al) and Al4-NNNN (Al-embedded, nitrogen doped divacancy graphene-based complexes) have the same Al atom hybridization, but it is different in the Al doped monovacancy graphene complexes (Al-MV) and the Al doped divacancy graphene complexes (Al-DV). In addition, we also found that both the Sc doped monovacancy graphene and the Al4-N (Al-embedded, nitrogen doped divacancy graphene-based complexes) can be used as candidates for the negative electrode materials of asymmetric supercapacitors. The results can provide valuable insights into the design and preparation of electrodes for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Fabrication of the polymer/graphene nanocomposites with high electro-mechanical properties is very challenging approach these days against the electromagnetic pollution. This paper mainly focused on the preparation of in situ reduced graphene oxide (IrGO) during melt blending of polycarbonate/ethylene-methyl acrylate [PC/EMA (95/5 wt/wt)] blend and graphene oxide to achieve enhanced electro-mechanical properties of the nanocomposites. It involves the reduction mechanism of graphene oxide with in the polymer matrix. The nanocomposites showed a significant improvement in mechanical stiffness owing to efficient stress transfer from matrix to filler. PC/EMA-IrGO nanocomposites with 15 phr loading of GO showed highest electromagnetic shielding effectiveness (− 30 dB) over the frequency range of X-band (8.2-12.4 GHz). This promising strategy of developing single-step PC/EMA-IrGO nanocomposites with enhanced electro-mechanical properties can also be used in large-scale technical and commercial applications. [ABSTRACT FROM AUTHOR]

Carbon-based nanostructures possess exceptional thermal properties and are being intensively explored as thermal management materials. In this paper, the thermal conductivities of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with vacancy defects are compared by using non-equilibrium molecular dynamics simulations. The results show that the vacancy defects markedly decrease the thermal conductivities of CNTs and GNRs. By analyzing the vibrational density of states and contributions of lattice vibrations, we demonstrate that the lower thermal conductivities of defective CNTs and GNRs are attributed to the depressions of longitudinal acoustic and transverse acoustic modes, respectively. In the temperature range of 200-600 K, the vacancies always have a weaker effect on heat transfer of GNR than that of CNT, which stems from the mode localization induced by the phonon scattering on GNR edges. In addition, the percentage change in thermal conductivity of CNT decreases with increasing temperature, while that of GNR is generally independent of temperature. This phenomenon is related to the sensitivity of lattice vibration contributions to temperature. The present work expands our understanding of vacancy effect on heat conduction in carbon-based nanostructures. [ABSTRACT FROM AUTHOR]

Graphene has attracted much attention and triggered extensive anti-corrosion applications due to its excellent electrochemical stability and robust barrier for molecules and ions. In this paper, a novel polypyrrole/reduced graphene oxide (PPy/rGO) nanocomposite was successfully prepared on carbon steel as an efficient protective coating for improving the anti-corrosion property. Graphene oxide (GO) was deposited onto carbon steel via potentiostatic technique, and PPy was obtained simultaneously by oxidation polymerization. Scanning cyclic voltammetry method was adopted to reduce GO into rGO to form PPy/rGO nanocomposite coating. Due to the synergistic effect of PPy and rGO, excellent anti-corrosion performance for carbon steel in simulated seawater was obtained. Impressively, the PPy/rGO-coated carbon steel showed 7.05 times higher corrosion resistance than that of bare carbon steel and revealed the excellent protection efficiency above 95.9%. The anti-corrosion mechanism of the PPy/rGO coating was also proposed. Our results suggested that the PPy/rGO composite coatings could serve as effectively protectors for anti-corrosion of seawater, therefore, they could envision potential applications in naval architecture and ocean engineering. [ABSTRACT FROM AUTHOR]

Polycrystalline graphene nanoribbons usually experience a brittle rupture before failure, and the irreversible breaking occurs in grain boundaries (GBs). In this paper, molecular dynamic simulations are conducted to study the fatigue properties of bi-crystal graphene nanoribbons under a periodic in-plane compression. It is found that ribbon edges rather than GBs dominate the dynamic stability when the ribbon width is smaller than 5 nm. The fatigue failure is closely related to the misorientation angle between two grains because of the distinct edge energy. It always starts from the edges with higher energy and results in a localized damage at the edges. [ABSTRACT FROM AUTHOR]

Due to the unique structures and properties of graphene and graphene-analogous two-dimensional (2D) nanosheets, numerous methods were developed to prepare these 2D nanosheets; however, it is still changeable to fabricate high-quality 2D nanosheets cost-effectively in large scale. Electrochemical exfoliation has emerged as an efficient and mild technology for the preparation of 2D nanosheets, and this paper reviewed the recent development of this strategy. Electrochemical exfoliation was divided into two main categories, anodic and cathodic exfoliation. The merits of each category were summarized and analyzed as well as drawbacks in detail. It provides an avenue to design and fabricate different kinds of high-quality 2D nanosheets cost-effectively in large scale for energy storage and conversion, catalysis, sensors, electronics and so on. [ABSTRACT FROM AUTHOR]

Graphene aerogel (GA) has wide applications in energy storage, catalysis, and adsorption. However, as a candidate for supercapacitor electrode, it suffers from low specific capacitance. In this paper, we conceived and conducted a two-step strategy to improve the electrochemical properties of GA: First, GA was selective functionalized with p-phenylenediamine. Then PANI was grafted onto GA by in situ polymerization. The results suggest that surface functionalization enhances the interface bonding between GA and PANI and charge transfer during electrode redox. As a result, the obtained GA/PANI composites, applied as the freestanding electrodes for supercapacitor, exhibit high specific capacitance (810 F/g at 1 A/g, 2.4 times of GA), good rate capability, and extraordinary cycling stability (83.2% of retention at 10 A/g after 10,000 cycles, 1.25 times of PANI/GA), indicating its great potential in the construction of high-performance energy-storage systems. [ABSTRACT FROM AUTHOR]

Here, we report a novel electrode structure with graphene and graphene-carbon black hybrids by electrospraying for polymer electrolyte membrane fuel cells. After syntheses of platinum (Pt)/partially reduced graphene oxide (rGO) and Pt/r-GO/carbon black (CB) hybrid electrocatalysts, suspensions of synthesized electrocatalyst inks were prepared with Nafion ionomer and poly(vinylidene fluoride- co-hexafluoropropylene) and electrosprayed over carbon paper to form electrodes. Electrosprayed catalyst layer exhibited uniform and small size Pt distribution. As the graphene content increases micrometer-sized droplet, pore formation and surface roughness of the electrode increase. Thus, an open porous electrode structure which is favorable for mass transport is achieved by electrospraying. The maximum power densities, 324 mW cm for Pt/rGO and 441 mW cm for Pt/rGO/CB electrosprayed electrodes, were achieved at a relatively low catalyst loading. [ABSTRACT FROM AUTHOR]

Graphene's invention has catalyzed many new material applications in different fields. It has been used in combination with different biopolymers to design nanocomposites with improved mechanical, thermal, electrical, as well as, gas-, and water vapor-barrier properties. This review focuses on the chemistry and synthesis of graphene oxide (GO) and sheds some light on the different ecological pathways available for graphene oxide synthesis and reduction. The major pathways for graphene incorporation into biopolymers include (1) solution intercalation, (2) melt intercalation, and (3) in situ polymerization. The fabrication, application, and mechanisms of bonding between biodegradable biopolymers, like poly (lactic acid), cellulose, starch, chitosan, alginates, polyamides, and other biodegradable materials, with different forms of graphene including graphene oxide (GO), reduced graphene oxide (RGO), graphene nanoplatelets (GNP), etc., are the focus of this review. The paper has been organized according to different methods of incorporating graphene derivatives into biopolymers, in order to highlight the mechanisms for chemical bonding-physical changes that biopolymers and graphene nanofillers undergo during the method of preparation and the impact of chemical changes on end use properties. The information has been assembled, so that new conclusions can be drawn from the available data. The mechanism of enhancement of functional properties is evaluated using techniques including fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and the synergy resulting from the use of different spectroscopic techniques is discussed beyond what the individual authors have been able to interpret often from a few techniques. Effectiveness of solvents used and reaction conditions have also been focused, in order to offer mechanistic understanding for the improvement of mechanical properties. The new observations and findings by comparing all relevant literature will help the reader to look at the whole spectrum of available methods and materials, in addition to focusing on the original biopolymer-graphene work. [ABSTRACT FROM AUTHOR]

This study focuses on a supercapacitor with displaying variations in color schemes depending on the level of energy storage. In this paper, hydrogen-bonded graphene/polyaniline (HbG/PANI) was successfully synthesized by electrochemical polymerization method. The results showed that the high capacitance (598 F g at 1.0 A g) and more excellent capacity retention were achieved for HbG/PANI as supercapacitor electrode than that of PANI (217 F g at 1.0 A g). In addition, the HbG/PANI also was exhibited fast (72 s) and reversible with the change of color at different potential (0-1 V) as electrochromic device. Excellent electrochemical properties were attributed mainly to the stable chemical bonding of HbG between PANI and ITO, which was conducive to the ion transport and electron conduction. Significantly, we proposed a smart supercapacitor and simultaneously monitored the level stored energy by visual change. The findings showed that the proposed supercapacitor with electrochromic function opens a new path for the future development of smart devices with visualized energy levels. [ABSTRACT FROM AUTHOR]

Graphene-based nanocomposites have been one of the most attractive electrode materials of supercapacitors. But in most cases, graphene-based nanocomposites always use single nanoparticle as active material, which cannot meet the increasing demand for next generation of energy storage devices. In the present paper, we prepared FeO-Ni(OH)/graphene nanocomposite by simple one-step hydrothermal method. The dual-particle system reveals a synergistic effect between FeO and Ni(OH), i.e., Ni(OH) can enhance the electrical conductivity of FeO, and then FeO can act as electrical conductivity bridges between Ni(OH) nanoparticles and RG. As a result, the FeO-Ni(OH)/graphene nanocomposite presents impressing electrochemical performance, including high specific capacitance (~857 F/g), good rate capability, and outstanding cycling stability (after 5000 cycles, 100 % retention). [ABSTRACT FROM AUTHOR]

In this paper, a simple one-step method, based on the hydrothermal technique, has been introduced to synthesize titanium dioxide/graphene-based nanocomposite. The titanium dioxide nanoparticles are prepared by solvothermal approach. The diethyl oxalate used in the process acts as capping agent, allowing the formation of titanium dioxide nanoparticles with a narrow-sized distribution (∼12 nm). TiO/GR nanocomposite shows a strong red-shift and a further narrowed band gap compared to pristine TiO. The addition of suitable amount of GO to TiO decreases the crystalline size of TiO (from 12 to 10) due to the homogeneous dispersion of the TiO nanostructures on GO sheets and inhibition of agglomerate of TiO nanostructures during synthesis process. Cyclic voltammetry was characterized to estimate the electrochemical properties of TiO/GR. The structure and morphology of the TiO nanostructures and nanocomposite were characterized with FT-IR, XRD, and Raman spectroscopies and SEM images. [ABSTRACT FROM AUTHOR]

In this paper, we adopted hot-pressing treatment to convert the regular reduced graphene oxide (RGO) from chemical exfoliation to the high-quality graphene (HQG), and then the HQG/poly vinylidene fluoride (PVDF) composite films were prepared by spin coating. The microstructural characterizations and property measurements revealed that (1) The HQG was free of defects and oxygen-containing functional groups on the surface, and exhibited a homogeneous dispersion and a well composite with PVDF; (2) The storage modulus of the HQG/PVDF composite was nearly twice higher than that of RGO/PVDF composite, and eight times higher than that of pure PVDF; and (3) The optimum additive amount of HQG with PVDF was at between 3 and 5 wt%. It is expected that the present HQG has a potential applications in polymer composites. [ABSTRACT FROM AUTHOR]

Recently, wearable electronic devices and human–computer interaction are developing prosperously, which expands the requirement of flexible sensing materials. Graphene and its derivatives with extraordinary advantages are highly attractive precursors. However, it is difficult to assemble graphene into macroscopic cubes with good fatigue resistance performance. Here, we propose an efficient way to manufacture a lamellar-structural rGO aerogel with enhanced stiffness and deflection of lamellae, by using MXene as a rigidity additive. The addition of MXene (Ti3C2Tx) improves the mechanical and fatigue resistance properties of the aerogel, making it super compressible and elastic. The highly stable structure of the aerogel can withstand extremely high compressive strain of 90% and long-term compression at 50% strain for at least 10,000 cycles. The lamellar structure makes a great contribution to achieve good sensing performance including high linear sensitivity, low testing limit, wide testing strain range and quick response. These features make the MXene/rGO aerogel a promising sensing material for flexible wearable devices to monitor the subtle and obvious biosignals of the human body movement. [ABSTRACT FROM AUTHOR]