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In 5G era, integration and miniaturization of electronic components lead to increasing challenges in thermal management. Materials with high thermal conductivity and flexibility are strongly desired for dissipating heat locally generated in such devices. Due to its extraordinary thermal conducting performance, graphene has been exhibiting great potential in thermal management. In this work, composite films based on graphene oxide and poly‐naphthylamine (gGO/PNA) with enhanced thermal conducting performance have been achieved by employing poly (naphthylamine) (PNA) as repairing additives to restore topological defects of graphene oxide (GO). Specifically, gGO/PNA films are prepared with a facile operation of vacuum filtration followed by an elevated temperature treatment. The optimal thermal conductivity (κ) of gGO/PNA reaches to 1016.03 W m−1 K−1, 31.3% enhancement over that of the pristine graphene one. The thermal conducting performance test demonstrates the film an efficient heat‐dissipation ability from a heat‐generating LED bulb. Furthermore, the film exhibits excellent flexibility, making it survival from a 1000‐cycle bending test. This finding may promote the development of heat‐spreading materials and their applications in thermal management of highly integrated electronics. [ABSTRACT FROM AUTHOR]

Heat dissipation in time is essential for long-term reliability of electrical devices. Graphene, with superior thermal conductivity and excellent flexibility, exhibits a potential to substitute currently used graphite film for thermal management. In this work, a free-standing film with enhanced thermal conductivity and better flexibility was achieved by a facile and environmentally friendly in situ polymerization. The ‘molecular welding’ strategy was introduced for preparation of graphitized graphene oxide/polyaniline (gGO/PANI) hybrid film, and the uniformly distributed PANI, serving as a solder, connected adjacent graphene sheets and filled in air voids of GO films. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and Raman spectroscopy were used to determine the structure of PANI and the interaction between GO and PANI. The in-plane thermal conductivity of gGO/PANI film is enhanced by 38% to 1019.7 ± 0.1 W m−1 K−1 with addition of 12 wt% PANI, compared with that of pristine gGO film. Besides, the gGO/PANI film shows better flexibility than gGO film after 180° bending for 500 times. [ABSTRACT FROM AUTHOR]

A simple one-step pyrolysis strategy has been developed to prepare molybdenum dioxide supported on nitrogen-doped graphene (MoO2/NG) as electrocatalyst for oxygen reduction reactions (ORR). Homogeneous anchoring of MoO2 nanoparticles on nitrogen-doped graphene was achieved for the composite synthesized at 500 °C (MoO2/NG-500). For the first time, the MoO2/NG composite manifests considerable electrocatalytic activity for ORR in alkaline solution, with the onset potential of 0.91 V and the peak potential of 0.73 V. Furthermore, the MoO2/NG catalyst outperforms commercial Pt/C catalyst in terms of the electrochemical durability for ORR. The facile fabrication, reasonable ORR activity and excellent stability endow our MoO2/NG catalyst with great promise in application of cost-effective fuel cells. [ABSTRACT FROM AUTHOR]

A new contact model between Zn xCd1− xS nanorods and reduced graphene oxide (RGO) was obtained by rational formation of ultrathin Zn0.5Cd0.5S (ZCS) nanorods on RGO through a facile oleylamine-DMSO mediated synthesis approach. The 1 D/2 D model of ZCS/RGO provides a strong contact line-to-line interface, which is not only conducive for the fast collection and transfer of photogenerated electrons but also stabilizes the ultrathin nanorod structure of ZCS. The photocatalytic test results indicated that the ZCS/RGO nanocomposites exhibit significantly enhanced photocatalytic H2 evolution rate and cycling stability under visible light compared with free ZCS and the physical mixture of ZCS and RGO. [ABSTRACT FROM AUTHOR]

Highlights: [•] The size of the GO sheets was up to ~100μm in lateral size. [•] The UL-GO sheets were transferred onto flexible substrates through soft transfer printing method. [•] The reduced UL-GO films by HI have layered architectures and exhibit high electrical conductivity and transparency. [•] The technique proposed to produce flexible TCFs is inexpensive and tunable for mass production. [ABSTRACT FROM AUTHOR]

With the development of integrated devices, the local hot spot has become a critical problem to guarantee the working efficiency and the stability. In this work, we proposed an innovative approach to deliver graphene foam/polyaniline@epoxy composites (GF/PANI@EP) with improvement in the thermal and mechanical property performance. The graphene foam was firstly modified by the grafting strategy of p-phenylenediamine to anchor reactive sites for further in-situ polymerization of PANI resulting in a conductive network. The thermal conductivity (κ) and electromagnetic interference shielding (EMI) performance of the optimized GF/PANI4:1@EP is significantly enhanced by 238% and 1184%, respectively, compared to that of pristine EP with superior reduced modulus and hardness. Such a method to deliver GF composites can not only solve the agglomeration problem in traditional high content filler casting process, but also provides an effective way to build up conductive network with low density for thermal management of electronic devices. [ABSTRACT FROM AUTHOR]

It is difficult to keep the balance of high quality and high yield for graphene quantum dots (GQDs). Because the quality is uncontrollable during cutting large 2D nanosheets to small 0D nanodots by top-down methods and the yield is low for GQDs with high quality obtained from bottom-up strategy. Here, aphanitic graphite (AG), a low-cost graphite contains a large amount of small graphite nanocrystals with size of about 10 nm is used as the precursor of graphene oxide quantum dots (GO-QDs) for the first time. GO-QDs with high yield and high quality were successfully obtained directly by liquid phase exfoliating AG without high strength cutting. The yield of these GO-QDs can reach up to 40 wt. %, much higher than that obtained from flake graphite (FG) precursor (less than 10 wt. %). The size of GO-QDs can be controlled in 2–10 nm. The average thickness of GO-QDs is about 3 nm, less than 3 layer of graphene sheet. Graphene quantum dots (GQDs) with different surface properties can be easily obtained by simple hydrothermal treatment of GO-QDs, which can be used as highly efficient fluorescent probe. Developing AG as precursor for GQDs offers a way to produce GQDs in a low-cost, highly effective and scalable manner. [ABSTRACT FROM AUTHOR]

In order to obtain acetone sensor with excellent sensitivity, selectivity, and rapid response/recovery speed, graphene-like ZnO/graphene oxide (GO) nanosheets were synthesized using the wet-chemical method with an additional calcining treatment. The GO was utilized as both the template to form the two-dimensional (2-D) nanosheets and the sensitizer to enhance the sensing properties. Sensing performances of ZnO/GO nanocomposites were studied with acetone as a target gas. The response value could reach 94 to 100 ppm acetone vapor and the recovery time could reach 4 s. The excellent sensing properties were ascribed to the synergistic effects between ZnO nanosheets and GO, which included a unique 2-D structure, large specific surface area, suitable particle size, and abundant in-plane mesopores, which contributed to the advance of novel acetone vapor sensors and could provide some references to the synthesis of 2-D graphene-like metals oxide nanosheets. [ABSTRACT FROM AUTHOR]

Nitrogen doped graphene quantum dots (NGQDs) were successfully prepared via a hydrothermal method using citric acid and urea as the carbon and nitrogen precursors, respectively. Due to different post-treatment processes, the obtained NGQDs with different surface modifications exhibited blue light emission, while their visible-light absorption was obviously different. To further understand the roles of nitrogen dopants and N-containing surface groups of NGQDs in the photocatalytic performance, their corresponding composites with TiO2 were utilized to degrade RhB solutions under visible-light irradiation. A series of characterization and photocatalytic performance tests were carried out, which demonstrated that NGQDs play a significant role in enhancing visible-light driven photocatalytic activity and the carrier separation process. The enhanced photocatalytic activity of the NGQDs/TiO2 composites can possibly be attributed to an enhanced visible light absorption ability, and an improved separation and transfer rate of photogenerated carriers. [ABSTRACT FROM AUTHOR]

A novel isotype heterojunction ultraviolet photodetector was fabricated by growing n-ZnO nanorod arrays on n-GaN thin films and then spin-coated with graphene quantum dots (GQDs). Exposed to UV illumination with a wavelength of 365 nm, the time-dependent photoresponse of the hybrid detectors manifests high sensitivity and consistent transients with a rise time of 100 ms and a decay time of 120 ms. Meanwhile, an ultra-high specific detectivity (up to ~ 1012 Jones) and high photoresponsivity (up to 34 mA W−1) are obtained at 10 V bias. Compared to the bare heterojunction detectors, the excellent performance of the GQDs decorated n-ZnO/n-GaN heterostructure is attributed to the efficient immobilization of GQDs on the ZnO nanorod arrays. GQDs were exploited as a light absorber and act like an electron donor to effectively improve the effective carrier concentration in interfacial junction. Moreover, appropriate energy band alignment in GQDs decorated ZnO/GaN hybrids can also be a potential factor in facilitating the UV-induced photocurrent and response speed. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate the potential use of asphalt emulsions as a binder for the preparation of polycrystalline graphite. An emulsion mixing method was adopted to create the natural microcrystalline graphite and asphalt binder mixture, and graphite samples with a bulk density of 1.7g/cm3 and a flexural strength of ca. 22MPa were prepared. This approach is advantageous because of the uniformity of the asphalt coating, and it also reduces the use of coal tar pitch. [Copyright &y& Elsevier]

• A Ni(OH)F@GF core-sheath fiber was synthesized. • Effective fiber-shaped nonenzymatic glucose sensors were prepared with Ni(OH)F@GF core-sheath fibers. • The high performance is due to synergistic effects of Ni(OH)F and graphene. Fiber-shaped sensors have great application prospects in wearable electronic devices for tracking the physiological dynamics of the human body. In this paper, we report the synthesis of a unique core-sheath fiber composed of graphene fiber and F-doped nickel hydroxide (Ni(OH)F@GF). The core-sheath fibers are used as electrodes to make flexible fibrous non-enzymatic glucose microsensors. The as-prepared fiber-shaped microsensor shows excellent performance in the electrochemical detection of glucose with an excellent sensitivity of 595.3 μA mM−1 cm−2 and a wide linear range of 0.01–7.66 mM. This microsensor also exhibits fast response time (3 s), a low detection limit (1 μM) and good selectivity. [ABSTRACT FROM AUTHOR]

Fiber-shaped supercapacitors are an essential component for making wearable electronics and smart textiles. Despite the significant progress in this area, it is still a challenge to develop large capacitance, high energy density fiber-shaped supercapacitors for energy storage applications. Herein, we report a unique core-sheath fiber comprising graphene core and radially-aligned tungsten disulfide sheath via a one-step hydrothermal method. Two such fibers were used as electrodes for making an all solid fiber-shaped supercapacitor. This device has an areal capacitance as large as 270.36 mF cm−2 and volumetric capacitance as high as 54.07 F cm−3 (energy density 16.86 μWh cm−2). The graphene core ensures the fiber to have high conductivity, while the sheath nanosheet array creates numerous active sites and enables fast ion diffusion. The electrode material with a high capacitance, long-term stability, and excellent flexibility may form a novel candidate for the development of high-performance energy storage fibers. Image 1 • A rGOF@WS 2 core-sheath fiber was synthesized via a one-step hydrothermal method. • The flexible fiber-shaped supercapacitor with rGOF@WS 2 core-sheath electrodes has high capacitance and energy. • The high performance is due to the unique core-sheath structure and synergistic effects of graphene and WS 2. [ABSTRACT FROM AUTHOR]

Flexible fiber-shaped supercapacitors have broad application prospects in wearable and portable electronics and smart textiles, however, often suffered from their relatively low capacitance and energy density. In this paper, a unique core-shell fiber composed of graphene fiber and radially-aligned molybdenum disulfide nanosheet arrays (GF/MoS 2) has been rationally designed and prepared. The morphology and structure of well-designed core-shell fibers were studied by Raman, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopic (EDX) elemental mapping. All-solid-state, fiber-shaped symmetric supercapacitors were constructed by packaging two parallel GF/MoS 2 core-shell fibers with PVA/H 2 SO 4 electrolyte. Owing to the synergistic effects between graphene and MoS 2 , the fiber-shaped supercapacitor exhibits an enhanced areal capacitance up to 189.73 mF cm−2 and a high energy density of 14.665 μW h cm−2. The fibrous supercapacitors also exhibit good stability and flexibility. This work provides a strategy to design core-shell fibrous electrodes for high performance fiber-shaped supercapacitors, which also holds great potential for future flexible electronic devices. The fabrication processes for the GF/MoS 2 core-shell fiber. Image 1 • Radially-aligned MoS 2 arrays are grown on the surface of graphene fiber, forming a unique core-shell fiber. • The introduction of MoS 2 arrays can greatly improve the performance of fiber-shaped supercapacitors. • The enhanced performance of GF/MoS 2 is due to its structure and the synergistic effects of graphene and MoS 2. [ABSTRACT FROM AUTHOR]

As a promising active material for supercapacitor, graphene suffers serious restack, which reduces the surface area utilization of electrodes. Porous crumpled graphene (PCG) with hierarchical pore structure is designed in this paper. The spherical morphology of porous crumpled graphene effectively prevents it from restack, and thus dramatically promotes the utilization of pores on the graphene sheets. As electrode in supercapacitor, the specific capacitance per surface area is as high as 20.7 μF cm −2 due to the high surface utilization efficiency, which is much higher than that of the traditional activated carbon (6.0 μF cm −2 ) and porous graphene (6.5 μF cm −2 ), approaching the theoretical value of 20.9 μF cm −2 . [ABSTRACT FROM AUTHOR]

With the development of high-power electronics and portable devices at a noticeable rate, thermal dissipation becomes challenging and critical to the performance of these devices. It greatly promotes the research and development of thermal dissipation materials. Due to its extremely high in-plane thermal conductivity, graphene have shown great potential in thermal management. In this work, a subtle “molecular welding” strategy was realized for the fabrication of flexible, ultrathin, but highly conductive graphitized-graphene/polyimide (g-GO/PI) hybrid films. PI was applied as a solder to weld the micron-sized graphene platelets up through the covalent bonding and to fill up the voids between the graphene layers. This is believed as the key to the considerable enhancement of the in-plane thermal conductivity of g-GO/PI hybrid films. It was worth noting that an enhancement of 21.9% in the in-plane thermal conductivity was achieved for the “molecular welded” g-GO/PI hybrid film as compared to the pristine g-GO film. The proposed “molecular welding” conception provides not only a promising way to the development of the next-generation graphene-based film for thermal management, but also an effective technique to fabricate functional materials with GO or graphene nanoplatelets in other fields. [ABSTRACT FROM AUTHOR]

Silanized graphene oxide (SGO) reinforced organofunctional silane composite coatings were fabricated on galvanized steel substrates. A mixture of silane precursors were employed to prepare the composite matrix. The graphene oxide surfaces were functionalized by tetraethoxysilane molecules to improve its compatibility with the silane matrix. The protective properties of the composite coatings were significantly improved compared with the neat silane coatings. The composite coatings exhibited the highest protective properties with the addition of 0.2 wt% of SGO. Silanized graphene provided a physical barrier to the corrosive molecules. [ABSTRACT FROM AUTHOR]

A polyaniline/graphene composite with covalently-bond is synthesized by a novel approach. In this way, graphene oxide is functionalized firstly by introducing amine groups onto the surface with the reduction of graphene oxide in the process and then served as the anchor sites for the growth of polyaniline (PANI) via in-situ polymerization. The composite material is characterized by electron microscopy, the resonant Raman spectra, X-ray diffraction, transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical properties of the composite are measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charging/discharging. With the functionalization process, the graphene/polyaniline composite electrode exhibits remarkably enhanced electrochemical performance with specific capacitance of 489 F g −1 at 0.5 A g −1 , which is superior to those of its individual components. The outstanding electrochemical performance of the hybrid can be attributed to its covalently synergistic effect between graphene and polyaniline, suggesting promising potentials for supercapacitors. [ABSTRACT FROM AUTHOR]

Graphene oxide, mildly reduced graphene oxide (RGO) and functionalized graphene were added to waterborne polyurethane (PU) matrix as the anticorrosive reinforcement, respectively. The anticorrosive properties of the graphene oxide and its derivatives reinforced PU composite coatings were characterized by Electrochemical Impedance Spectroscopy (EIS) and salt spray tests. The dispersion states of graphene in PU matrix varied with the chemical states of graphene. The correlations between the chemical states, dispersion states of graphene, and anticorrosive properties of the composite coatings were discussed. The superior anticorrosive properties of the graphene reinforced PU composite coatings were achieved by the addition of 0.2 wt% of RGO. The EIS results showed that the under-painting corrosion did not occur after 235 h immersion in 3.5 wt% NaCl electrolyte and the impedance modulus at 0.1 Hz remained at 10 9 Ω, barely changed for 235 h. [ABSTRACT FROM AUTHOR]

Mesocarbon microbeads (MCMBs) are attractive precursors for high-density, high-strength polycrystalline graphite due to their self-sintering capability. They have the shape of a standard sphere and stack in a completely random orientation during compaction, thereby leading to an isotropic texture. In this paper, MCMB-based graphite shows better isotropic property than commercial nuclear graphite, as demonstrated by a coefficient of thermal expansion-based isotropy ratio of 1.00. It was found that variations in apparent density within block are approximately 2–5% in graphitized artifacts. The variation of flexural strength within block is small, revealing excellent homogeneity of MCMB-based graphite. Density distribution measurement indicates that artifacts produced in the same batch also have low variation from block to block. Furthermore, the flexural strength of this material is greatly influenced by heat treatment temperature and mean particle size. The fracture mechanism is also shown by a detail examination of fracture surfaces. These results may help to gain a better understanding of MCMB-based graphite. [ABSTRACT FROM AUTHOR]

Ni(OH) 2 nanoflakes were successfully synthesized with a facile hydrothermal method on 3D (three-dimensional) graphene grown by atmospheric pressure chemical vapor deposition (APCVD). The hydrothermal temperature and time were optimized to improve the performance of the composite as a binder-free supercapacitor electrode. The Ni(OH) 2 /3D graphene composite synthesized at 180 °C for 3 h shows high specific capacitance of 1450 F/g at a current density of 5 A/g. Even when the discharge current density increases to 60 A/g, a specific capacitance of 1196 F/g is still retained, highlighting the remarkable rate capability of our composite electrode. It also shows good capacity retention of 78 % after 1000 charge-discharge cycles, presenting the excellent cycle stability. These impressive results suggest that the composite is a promising electrode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Direct current electro-deposition is a promising method to synthesis graphene oxide (GO) reinforced copper matrix composites with improved comprehensive property. The microstructure of deposited material largely determines the properties of composites. Here, the effect of current density and GO concentration in electrolyte on microstructure, thermal and mechanical properties of the fabricated composites by electro-deposition were systematically investigated. With optimization of current density and the GO concentration, GO was highly reduced and uniformly dispersed in copper matrix. Compared with pure copper foil, the thermal conductivity of the composite foil was up to 503.39 W m−1 K−1, the maximum hardness reached 3.32 GPa and the ultimate tensile strength and elongation of the composite foil were increased by 22.8% and 2.8% respectively. The simultaneously enhancement in thermal and mechanical properties of the composites can be ascribed to the positive role of GO reinforcement in microstructure refinement and its partly reduction during electro-deposition. [ABSTRACT FROM AUTHOR]

In recent years, graphene has attracted a lot of attention as a reinforcement to enhance aluminum (Al) matrix composites due to its two dimensional structure and excellent mechanical properties. However, there are still some obstacles that limit the performance of the composites, such as uniform distribution of graphene oxide (GO) and the interfacial bonding between GO and Al matrix. In this work, Cu2+ ions acting as a bonding bridge were added into GO/Al powder suspension to improve the distribution of GO sheets on Al powder via a simple electrostatic adsorption method. Then, vacuum hot-pressing sintering was applied to fabricate bulk composites, and their mechanical properties were investigated. The results showed that doping 3 wt% Cu2+ ions illustrated the best dispersion of GO on the surface of Al powder, meanwhile GO was maximally reduced. Compared with unreinforced Al, the hardness, compressive strength and flexural strength of the 3 wt% Cu-doped bulk composite were increased by 121%, 120% and 28%, respectively. However, the mechanical properties were deteriorated after doping 5 wt% Cu2+ ions, due to the aggregation of GO on the surface of Al powder. This was attributed that Cu2+ ions had a critical coagulation concentration in aqueous GO suspensions. It was expected this work could offer some useful information for preparing graphene reinforced metal composites. • GO distribution was enhanced by doping Cu2+ ions in GO/Al aqueous suspension. • GO was in situ further reduced by doping Cu2+ ions during the adsorption. • Mechanical properties of GO/Al composites were increased by doping Cu2+ ions. [ABSTRACT FROM AUTHOR]