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Strain sensors for human health monitoring are of paramount importance in wearable medical diagnostics and personal health monitoring. Despite extensive studies, strain sensors with both high durability and stretchability are still desired, particularly with the stability for different environmental conditions. Here, we report a series of strain sensors possessing the graphene network with a high density of intermittent physical interconnections, which produces the relative resistance change by varying the overlap area between the neighboring graphene sheets under stretching and releasing, analogous to the slide rheostat working in electronics. Our in‐situ transmission electron microscope observation reveals the full recoverability of the structure from large deformation upon unloading for ensuring the exceptional cycle stability of our material on monitoring full‐range body movements. The stable response is also demonstrated over wide temperature range and frequency range, because the peculiar dynamic structure can be maintained through the self‐adjustment to the thermal expansion of the bulk material. Based on the working mechanism of graphene "slide rheostat," the sensing properties of the strain sensor are tailored by tuning the graphene network structure with different mass densities using different concentrations of graphene oxide dispersion, while the stretchability and sensitivity can be separately optimized for different application requirements. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • L-Tryptophan functionalized graphene quantum dots were prepared via a thermal cracking method. • Doping of L-Tryptophan effectively improves the luminescent properties of GQDs. • This quantum dots exhibit a good liner relationship between fluorescence response and pH variation of 4–12. • This quantum dots perform well in sensitivity to pH values in real water samples. Abstract L-Tryptophan (Trp) functionalized graphene quantum dots (Trp-GQDs) were prepared via a thermal cracking method, using Trp and citric acid (CA) as raw material. The as-obtained Trp-GQDs show stronger blue photoluminescence (PL) than simple graphene quantum dots (GQDs). The presence of Trp can obviously improve the luminescent properties of GQDs. The possible mechanism was investigated for the formation and luminescence properties of the Trp-GQDs. Furthermore, the Trp-GQDs exhibit a good liner relationship between fluorescence response and pH variation within the pH range of 4–12. More importantly, Trp-GQDs still perform well in sensitivity to pH values in real water samples. The results indicate that the probe shows great potential in pH detection. [ABSTRACT FROM AUTHOR]

Abstract An efficient photocatalyst consisting of nitrogen-doped graphene quantum dots (N-GQDs) dispersed on the surface of the three-dimensional hierarchical bismuth oxyhalide (BiOX, X = Br, Cl) was synthesized via a simple solvothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectrophotometer (DRS), and photoluminescence spectroscopy (PL). The N-GQDs play an important role in the improvement of photocatalytic performance because it significantly increases BiOX absorption of visible light and effectively traps photogenerated electrons to accelerate the separation of photogenerated electron-hole pairs. The superior activity of N-GQDs/BiOX was exhibited to the organic contaminant degradation under visible light. The 7 wt% N-GQDs/BiOBr and 7 wt% N-GQDs/BiOCl exhibited strong catalytic activity, in which RhB was almost completely removed after irradiation for 60 and 75 min, respectively. In our work, we provide a strategy that for improving the photocatalytic activity of BiOX with semiconductor quantum dots. [ABSTRACT FROM AUTHOR]

NiO nanoflakes are created with a simple hydrothermal method on 3D (three-dimensional) graphene scaffolds grown on Ni foams by microwave plasma enhanced chemical vapor deposition (MPCVD). Such as-grown NiO-3D graphene hierarchical composites are then applied as monolithic electrodes for a pseudo-supercapacitor application without needing binders or metal-based current collectors. Electrochemical measurements impart that the hierarchical NiO-3D graphene composite delivers a high specific capacitance of ≈1829 F g−1 at a current density of 3 A g−1 (the theoretical capacitance of NiO is 2584 F g−1). Furthermore, a full-cell is realized with an energy density of 138 Wh kg−1 at a power density of 5.25 kW kg−1, which is much superior to commercial ones as well as reported devices in asymmetric capacitors of NiO. More attractively, this asymmetric supercapacitor exhibits capacitance retention of 85% after 5000 cycles relative to the initial value of the 1st cycle. [ABSTRACT FROM AUTHOR]

Highlights: [•] We review recent progress on the studies of organic/graphene interfaces. [•] Organic molecular assembly structure on graphene surface prepared on different substrates. [•] Interfacial electronic properties between organic molecule and graphene. [•] Outlook on the development and application of organic/graphene interface in organic devices. [ABSTRACT FROM AUTHOR]

Surface doping can be a powerful way to modify the electronic properties of graphene with the unique potential to retain the excellent pristine properties of graphene. Here, we report an atomic surface doping method for graphene via dissociation of adsorbed precursor molecules of tetrafluorotetracyanoquinodimethane (F4-TCNQ) induced by hydrogen plasma treatment. Significantly, the location of the dopant N atoms can be pre-determined by the location and orientation of the F4-TCNQ molecule precursor on graphene, leading in principle to site-selective doping. Furthermore, the molecular precursor is stable under ambient conditions, satisfying an important consideration for patterning processes. [ABSTRACT FROM AUTHOR]

As a kind of cheap and easily available organic molecular with Faradic redox activity, quinones can well combined with carbon-materials by non-covalent π–π conjugation and remedy its shortcomings possessing relatively low specific capacitance. However, in previous studies, the combination of quinones and carbon-based materials often requires toxic organic solvent or high energy-consuming and interminable process, greatly hindering their practical application. Here we use water-soluble sodium anthraquinone-2-sulfonate (AQS) and graphene oxide (GO) solution as raw materials to directly obtain AQS composite reduced GO (AQS/rGO) hydrogels by chemical reduction, the whole process of which is performed at relatively low temperature and normal pressure, and only takes a short time, resulting in great promotion in sustainability and efficiency. The AQS/rGO hydrogel exhibiting a high specific capacitance of 387.43 F g−1 at 1 A g−1 and an excellent cycling stability of 91.11% after 10000 cycles at 10 A g−1, has a prodigious improvement for the pure graphene in all aspects. Besides, the maximum energy density of the asymmetric supercapacitor assembled by AQS/rGO-1 hydrogel reaches 15.98 W h kg−1 at the power density of 325.02 W kg−1. This work provide a new idea for the green and efficient preparation of graphene organic quinones composite and has an important significance for its practical application. • AQS can be combined with graphene sheet by non-covalent π-π conjugation. • The process of preparing AQS/rGO hydrogels is utrla-simple, green and efficient. • The AQS/rGO hydrogels exhibits superior electrochemical performance to pure graphene. • The asymmetric supercapacitor delivers high energy density. [ABSTRACT FROM AUTHOR]

Integrating a battery‐type electrode to build a hybrid supercapacitor is a promising approach to improve the overall energy density of a supercapacitor‐type energy storage device without sacrificing its power output. However, this strategy is usually achieved at the expense of cycling lifespan. In this work, a hybrid supercapacitor comprising Zn foil and porous carbon derived from chemical activated graphene (aMEGO) is developed, and the trade‐off between energy density and cycling life is well‐balanced by the utilization of 3 m Zn(CF3SO3)2 electrolyte with high Zn stripping/plating efficiency. Such a hybrid supercapacitor demonstrates an energy density of 106.3 Wh kg−1 and a power density of 31.4 kW kg−1, and significantly a wide operation voltage of 1.9 V is achieved in aqueous electrolyte. Benefitting from the high Zn stripping/plating efficiency, the Zn‐aMEGO hybrid‐supercapacitor also exhibits an ultralong cycling life up to 80 000 cycles with capacity retention of 93%, which is comparable to that of conventional electrochemical double‐layer capacitors. [ABSTRACT FROM AUTHOR]

It is demonstrated that dendrite growth and byproduct formation can be suppressed during Zn plating, and the competitive hydrogen evolution reaction is restrained by using a 3 m Zn(CF SB 3 sb SO SB 3 sb ) SB 2 sb electrolyte. Furthermore, based on this electrolyte, a novel hybrid supercapacitor comprising Zn foil and porous carbon derived from chemically activated graphene is developed which delivers high energy density and an ultra-long lifespan. Aqueous electrolytes, energy storage, graphene, hybrid supercapacitors, Zn metal anodes. [Extracted from the article]

3D hierarchical porous graphene (3D HPG) has recently captured significant attention due to its unique porosities, excellent electron transport capability, and multifunctionality. However, given that the traditional preparation method of 3D HPG is time-consuming, energy-consuming and seriously polluting, which seriously block its wide application. This study leveraged the capabilities of flash Joule heating (FJH) to ultrafast synthesize 3D porous flash graphene (3D PFG) with good dispersion and adsorption properties from bituminous coal (BC) within 21 s. The thermal shock generated by carbonate pyrolysis and the thermal expansion generated by Joule heating were used to produce the stable porous structure. Moreover, the specific surface area of 3D PFG was as high as 504 m2g−1, and displayed the characteristics of hierarchical porous structure of micropores, mesopores and macropores. The porous structure changes of 3D PFG synthesized by FJH under different carbonate ratios and different flash voltages were investigated, and the controllable synthesis conditions of hierarchical pore structures during FJH were obtained accordingly. As the experimental and simulation results show, the 3D PFG displays good dispersibility and good adsorption performance as adsorbent for methylene blue and methyl orange. This environmentally friendly synthetic process of FJH not only simplifies the preparation process of 3D HPG but also provides a valuable way for the high value-added utilization of coal. [Display omitted] • The flash Joule heating can heat the samples in situ. • It only takes 21 s to synthesize 3D porous flash graphene. • The removal rate of methylene blue is as high as 99%. [ABSTRACT FROM AUTHOR]

Graphene has a wide range of applications in anti-corrosion coatings due to its excellent barrier, shielding, and mechanical properties. However, traditional graphene synthesis methods, including the production of graphene oxide (GO) using Homer's method and then its reduction in the form of reduced graphene oxide (rGO) are time-consuming, energy-consuming, and environmentally polluting, which limits their application in anti-corrosion coatings. This study leveraged the capabilities of flash Joule heating (FJH) to synthesize flash coal-based graphene (FCBG) from Taixi anthracite (TA) within 200 ms without pretreatments or chemical reagents. The FJH had the advantages of low energy consumption and being environmentally friendly. Compared with the rGO, the FCBG prepared by FJH was characterized by fewer defects, larger carbon sheets, and a turbostratic structure. Moreover, carbon steel Q235 was used as the substrate to prepare anti-corrosion coatings by mixing FCBG at different flash voltages with epoxy resin (EP). Based on this, the electrochemical performance of different coatings was compared before and after salt spray corrosion. The results demonstrated that the FCBG composite anti-corrosion coating (EP/FCBG 190) prepared using EP and FCBG synthesized at 190 V in the FJH, displayed stronger corrosion resistance than the EP and rGO composite coating (EP/rGO). The FJH synthesis process provides a feasible route for improving the synthesis process of the anti-corrosion coatings and the high value-added utilization of coal. [Display omitted] • The flash Joule heating can heat the samples in situ. • It only takes 200 ms to synthesize flash coal-based graphene. • No pretreatment and chemicals required. • FCBG 190 has better corrosion resistance than rGO. [ABSTRACT FROM AUTHOR]

Graphene is electrochemically inert toward the oxygen evolution reaction (OER) owing to the zero-band property, nevertheless doping it with heteroatoms could modulate its electronic structure and increase its chemical reactivity. Notwithstanding the achieved progress, the overpotential of heteroatom doped graphene is still very large. Herein, we coat FeNiIr nanoalloys by nitrogen-doped graphene with core-shell structure (FeNiIr@NG) to further boost the OER activity on graphene surface. Because of the unique core-shell structure, FeNiIr@NG delivers high electrocatalytic OER activity and durability, even exceeding that of commercial IrO 2 electrocatalyst. Density functional theory calculations demonstrate that the nanoalloys core could transfer electron to outer graphene shells, which optimizes the electronic structure of graphene and balances the adsorption strength of OER intermediates, thereby triggering OER activity on the graphene surface. The OER activity on graphene surface is triggered through coating FeNiIr nanoalloys to modulate the electronic structure of graphene. Image 1 • The OER activity on graphene surface is triggered by coating FeNiIr with graphene. • This unique FeNiIr@NG core-shell catalyst exhibits better OER activity than IrO 2. • The adsorption strength of ∗ O, ∗OH and ∗OOH is depended on electronic structure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The MoS 2 /RGO and MoS 2 /Fe 3 O 4 hybrids are prepared by a facile synthesis route. • The MoS 2 /RGO and MoS 2 /Fe 3 O 4 hybrids with hetero-structures exhibit excellent microwave absorption properties. • Tailoring weight percentage and thickness tunes microwave absorption for high efficiency and broad bandwidth. • The mechanisms of high-performance microwave absorption of MoS 2 /RGO and MoS 2 /Fe 3 O 4 hybrids are elucidated. Abstract The two-dimensional (2D) transition metal dichalcogenide, molybdenum disulfide (MoS 2), has been demonstrated to be a new class of microwave absorption (MA) material due to its high specific surface area and peculiar electronic properties. However, its limited MA capacity and bandwidth require further improvement. MoS 2 /RGO composites with improved MA performance have been reported, but the complicated and inefficient preparation process also limits the application of MoS 2 /RGO composites. In this work, we prepare MoS 2 /RGO hetero-structure hybrid with excellent MA performance and broadened bandwidth by a facile one-step hydrothermal method. It is found that the highest reflection loss value of the sample-wax containing 40% MoS 2 /RGO is −49.41 dB at a thickness of 2.52 mm, and the bandwidth of RL values less than −10 dB can reach up to 13.36 GHz (from 4.64 to 18 GHz). Meanwhile, we investigate another strategy to prepare MoS 2 /Fe 3 O 4 hybrid with hetero-structures and their MA performance is studied for the first time. It is found that the highest reflection loss value of sample-wax containing 40% MoS 2 /Fe 3 O 4 is −42.57 dB at a thickness of 3.25 mm, and the bandwidth of RL values less than −10 dB can reach up to 12.73 GHz (from 5.27 to 18 GHz). Results obtained in this study open a new window for designing excellent MA materials for practical applications. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an affinity graphene nanosensor for detection of biomarkers in undiluted and non-desalted human serum. The affinity nanosensor is a field-effect transistor in which graphene serves as the conducting channel. The graphene surface is sequentially functionalized with a nanolayer of the polymer polyethylene glycol (PEG) and a biomarker-specific aptamer. The aptamer is able to specifically bind with and capture unlabeled biomarkers in serum. A captured biomarker induces a change in the electric conductivity of the graphene, which is measured in a buffer of optimally chosen ionic strength to determine the biomarker concentration. The PEG layer effectively rejects nonspecific adsorption of background molecules in serum while still allowing the aptamer to be readily accessible to serum-borne biomarkers and increases the effective Debye screening length on the graphene surface. Thus, the aptamer-biomarker binding sensitively changes the graphene conductivity, thereby achieving specific and label-free detection of biomarkers with high sensitivity and without the need to dilute or desalt the serum. Experimental results demonstrate that the graphene nanosensor is capable of specifically capturing human immunoglobulin E (IgE), used as a representative biomarker, in human serum in the concentration range of 50 pM–250 nM, with a resolution of 14.5 pM and a limit of detection of 47 pM. Graphical abstract Image 1 Highlights • A graphene FET nanosensor is used for IgE detection in human serum. • Functionlized PEG rejects nonspecific adsorption while increases the effective Debye length. • Aptamers are attached to PEG to recognize IgE molecules. • IgE in serum with a concentration range from 50 pM to 250 nM is successfully quantified. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) nanomaterials have become a new class of microwave absorption (MA) materials due to their high specific surface area and peculiar electronic properties. In this study, MoS 2 /graphene 2D hybrid nanosheets with isomorphic hetero-structures are prepared by liquid exfoliation and hydrothermal reaction. Their chemical composition and morphology are characterized and their MA properties are also investigated comprehensively. The minimum reflection loss (RL) value of an absorber containing wax and 20 wt% MoS 2 /graphene hybrid nanosheets (MoS 2 /GN) is −55.3 dB at a thickness of only 1.6 mm. The largest effective absorption bandwidth is up to 5.6 GHz for an absorber containing wax and 15 wt% MoS 2 /GN at a thickness of 2.2 mm. The enhanced MA performance of MoS 2 /GN is attributed to the high electrical conductivity of graphene and the multiple MoS 2 /graphene interfaces in the heterogeneous structures. The results suggest that those light-weight MoS 2 /graphene hybrid nanosheets are very promising materials for electromagnetic wave absorbing, which can exhibit broad effective absorption bandwidth in the absorber containing low loadings of MA materials at a small thickness. Besides, the facile preparation of MoS 2 /graphene hybrid nanosheets reported in this work provides a feasible and effective approach in the synthesis of high-performance 2D MA nanomaterials. [ABSTRACT FROM AUTHOR]

• Flash graphene form coal pitch via flash joule heating. • High temperature (3000 K) generate highly reactive radicals. • Free Radicals concentration was controlled by input energy. • Electric field reduce the reaction potential barrier. Most of the traditional graphene production processes were not only solvent-intensive but also time-and-energy-consuming. Flash Joule heating (FJH) is an efficient approach to green and scalable large-scale production of graphene. However, its reaction mechanism is not clear during the process of electric field and free radical on graphene generation. In this work, synthesis of coal pitch-based graphene by FJH under the coupling effect of temperature and electric field, and Raman spectroscopy and electron transient magnetic resonance were studied at different input energies. The results show that the input energy is positively correlated with the generated radicals and is beneficial for the quality improvement of graphene. In addition, the mechanism is explained using ReaxFF molecular dynamics and DFT calculations: Joule heat provides energy for the kinetics and thermodynamics of the reaction. High temperature (3000 K) can dissociate branch chains in coal tar molecules to generate highly reactive alkane and alkene radicals. Different cooling rates affect the quality of graphene generation. When the cooling rate is slow, the graphite microplates will grow in layers, and a multi-layer phenomenon will appear; when the cooling rate is fast, the generated graphene will be in a turbostratic order. At the same time, the DFT calculation shows that the coal tar molecules are ionized under the action of the electric field and are oriented and arranged to reduce the reaction potential barrier. [ABSTRACT FROM AUTHOR]

Mesoporous TiO 2 has attracted extensive research interest due to its promising application in photocatalysis, but which is inevitably diminished by the electro-hole pair recombination. The incorporation of graphene into mesoporous TiO 2 can improve the properties, there are however great challenges in realizing the full potential of graphene due to its poor dispersion in organic solvents and the hard nucleation of TiO 2 on its surface. Herein, we present a novel and easy approach for the synthesis of two-dimensional sandwich-like graphene-supported mesoporous TiO 2 hybrid sheets with tailored morphologies, uniform coverage and controllable pore diameters and surface areas, leading to improved photocatalytic performance in comparison with bare mesoporous TiO 2 spheres. [ABSTRACT FROM AUTHOR]

Abstract: The interfacial electronic structure of MoO3− x /graphene has been investigated using photoemission spectroscopy. The experimental data showed that upon deposition of MoO3− x , the Fermi level of graphene shifts downward gradually from its Dirac point due to the p-type doping effect. From the Fermi level shift of −0.28eV, the hole density of graphene was estimated to be 5.44×1012 cm−2. The formation of surface negative dipole due to electron transfer from graphene to the deposited MoO3− x films increased the sample′s work function. The existence of gap states in MoO3− x induced by oxygen vacancies greatly reduced the hole injection barrier at the MoO3− x /graphene interface. [Copyright &y& Elsevier]