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In this study, we suggest a simple and effective one-pot hybrid reduction process for the mass production of high-quality reduced graphene oxide (rGO) by simultaneously doing deoxygenation and healing reactions. During the microwave-irradiated thermal reduction, intercalated benzene in the GO easily generates acetylene by pyrolysis; the released acetylene react with surrounding defect sites in the GO surface to successfully form new C–C bonds. As a result of the newly formed sp 2 -hybridized C–C bond in the rGO surface, the defect-repaired rGO (rGO-B) shows remarkably enhanced crystallinity (I D /I G ratio: rGO-B, 0.63; rGO-T, 1.08), thermal stability, and electrical properties over that of rGO prepared without a carbon-source supplement (rGO-T). Especially, compared to the rGO-T, the rGO-B had 4.4 times more carrier density and 18 times increased carrier mobility because of the restoration of defect sites in the rGO-B surface. The rGO-B exhibited six times higher electrical conductivity than did rGO-T because of the improved carrier mobility. These results obviously suggest that the reduction of GO by means of microwave-irradiated thermal reduction with a carbon-source supplement could be a powerful approach for commercial mass production of high-quality rGO because of its easy manufacturing approach. [Display omitted] [ABSTRACT FROM AUTHOR]

Poly(diallyldimethylammoium chloride) (PDDA)/acid or base modified graphene oxide (MGO) composite (PDDA/MGO)-based gas barrier films were prepared by layer-by-layer (LBL) assembly method on polyethylene terephthalate (PET) substrate using a spray coating assisted deposition. The effect of pH on the hydrogen gas permeability (H2GP) values of the different MGO-based films was investigated to determine the optimum pH value of the MGO solution for the preparation of PDDA/MGO-based LBL assembly. Accordingly, the different numbers of bilayers based LBL-assembled films were prepared using alternate deposition of PDDA and MGO solutions and the H2GP values were measured for those assemblies. The films were characterized by XRD, FT-IR, and Raman spectroscopy analyses. The morphology of the LBL-assembled film was observed by cross-sectional field emission scanning electron microscopy which confirms densely packed layered structure. The H2GP of six bilayers PDDA/MGO composite film is 5.7 cc/m2⋅d⋅atm, which is much lower than that of pure PET substrate (170.7 cc/m2⋅d⋅atm), indicating 96.7% decrease in H2GP. This result suggests that the PDDA/MGO composite film could be used as a potential candidate to fabricate hydrogen gas barrier coating material. [ABSTRACT FROM AUTHOR]

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young’s modulus, toughness, flexural strength and flexural modulus by ~ 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of ~ 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tanδ), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis. [ABSTRACT FROM AUTHOR]

A reduced graphene oxide (RGO)-NiFe 2 O 4 nanocomposite was synthesized by a simple one step hydrothermal approach and its application in the electrocatalytic oxidation of hydrazine was demonstrated. The as-synthesized nanocomposite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Thermogravimetric analysis, Field emission-scanning electron microscopy (FE-SEM), and Transmission electron microscopy (TEM). The FE-SEM and TEM image analyses revealed that the NiFe 2 O 4 nanoparticles were uniformly distributed on the RGO sheets with a diameter and length of ∼10 and ∼100 nm, respectively. The XPS analysis confirmed the ionic states of Ni and Fe to be Ni 3+ and Ni 2+ , and Fe 2+ and Fe 3+ , respectively. Further, the electrochemical activity of the RGO-NiFe 2 O 4 nanocomposite was investigated by studying the oxidation of hydrazine. The RGO-NiFe 2 O 4 modified glassy carbon electrode (GCE) showed an outstanding electrocatalytic activity towards the oxidation of hydrazine as compared to the NiFe 2 O 4 and RGO modified electrodes. The enhanced electrocatalytic activity is due to the synergistic effect between RGO and NiFe 2 O 4 . Using amperometry, the lowest detection limit of 200 nM was achieved with the RGO-NiFe 2 O 4 modified GCE. Therefore, the RGO-NiFe 2 O 4 modified GCE can be used for the electrochemical oxidation of hydrazine. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen gas barrier properties of polymeric materials are a critical determinant of their practical use in hydrogen gas storage and transportation container applications. We fabricated multi-layered films containing poly(diallyldimethylammonium) chloride (PDDA) and sulfonated polyvinylidene fluoride (SPVDF)-graphene oxide (GO) composites through layer-by-layer (LBL) assembly to enhance the hydrogen gas barrier properties. Polyethylene terephthalate (PET) substrate was rendered hydrophilic by treatment with aqueous sodium hydroxide solution prior to LBL assembly construction. Positively-charged PDDA and negatively-charged SPVDF or SPVDF/GO composites were assembled by spin-coating and were tightly packed by electrostatic attraction. LBL assemblies were characterized by Fourier transform infrared (FT-IR) spectroscopy and Field emission scanning electron microscopy (FE-SEM) analyses. Electrostatic LBL assembled PDDA/SPVDF-GO films showed improved mechanical and gas barrier properties compared to their respective PDDA/SPVDF LBL assemblies without GO. The hydrogen gas transmission rate (GTR) of a 16 bi-layer LBL assembly with 2wt.% GO was 11.7cc/m2 datm, which was much lower than that of PET substrate (329.1cc/m2 datm) and a one bi-layer LBL assembly without GO (277.9cc/m2 datm). The drastic decrease in GTR indicates that LBL assembled films are suitable for use in high hydrogen barrier applications. [Copyright &y& Elsevier]

Ternary nanocomposites (NCs) comprising Ag-Cu 2 O supported on glucose-reduced graphene oxide (rGO) with enhanced stability and visible light photocatalytic activity were synthesized via a facile and green approach using Benedict's solution and glucose solution at room temperature without the need of any toxic reagent, surfactant or any special treatment. Besides mild reducing capability to GO, glucose also induces the functionalization of rGO sheets, preventing the aggregation of reduced sheets and providing in situ stabilization to Cu 2 O. The resulting Ag-Cu 2 O/rGO NCs showed excellent photocatalytic efficiency for the photodegradation of methyl orange (MO), and the degradation rate was found to be higher than the pristine Cu 2 O and Cu 2 O/rGO NCs. Further, for the first time Ag-Cu 2 O/rGO NCs showed markedly enhanced photocatalytic efficiency for the photodegradation of phenol solution which is mainly attributed to its high electron injection rate and effective separation of electron–hole pairs. Thus, present strategy explores the facile synthesis way of varieties of Cu 2 O-based NCs materials using harmless reagents and their feasible applications. [ABSTRACT FROM AUTHOR]

In this study, a novel 4,4′-diaminostilbene-2,2′-disulfonic acid (DASDSA)-functionalized reduced graphene oxide (DASDSA-rGO) was prepared via simple refluxing method involving GO and DASDSA in the presence of ammonia solution followed by reduction with hydrazine hydrate. FTIR spectroscopy, Raman scattering, X-ray photoelectron spectroscopy (XPS), and XRD analyses confirmed the successful functionalization and reduction of GO in DASDSA-rGO. The FTIR and XPS analyses also confirmed covalent bond formation between DASDSA and graphene. The DASDSA spacer successfully minimized the restacking of rGO sheets as observed from FESEM analysis. Several redox transition states and SO 3 H groups of grafted DASDSA moieties provided excellent pseudocapacitance performance of the DASDSA-rGO electrode. The DASDSA-rGO electrode showed high specific capacitance ( C ) value of 1042 F g −1 at a current density of 1 A g −1 , good cycling stability (95% capacitance retention after 3000 cycles), and excellent rate capability in a three-electrode setup. The DASDSA-rGO (positive electrode) and rGO (negative electrode) were assembled to prepare an asymmetric supercapacitor (ASC) device. The power density values of the ASC device were calculated to be 650 and 7800 W kg −1 at energy density values of 37.37 and 23.78 W h kg −1 , respectively. The ASC device exhibited C value of 159 F g −1 at 1 A g −1 and displayed 86% retention in C after 8500 cycles. The EIS data of the three-electrode system and ASC device were fitted with Z-views to determine the different resistance components after a different number of charge–discharge cycles in a cycling stability test. [ABSTRACT FROM AUTHOR]

Nanocomposites of pluronic F127 modified reduced graphene oxide (PF127-rGO) with polyethylene glycol plasticize gum arabic (PGA) was prepared by evaporating an aqueous solution mixture of PF127-rGO and PGA. PF127-rGO was synthesized by the in-situ reduction of graphene oxide using hydrazine in presence of pluronic F127 and characterized by the Uv–Vis spectroscopy, transmission electron microscopy (TEM), wide angle x-ray scattering (WAXS), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Raman spectroscopy. The Uv–Vis and Raman spectroscopy results indicate that pluronic F127 functionalization does not hamper the structure of rGO, and TEM image indicates, the pluronic F127 anchored rGO sheets remain exfoliated in diluted aqueous solution of PF127-rGO. WAXS, FTIR and TGA studies confirms the functionalization of rGO with pluronic F127. PF127-rGO 2.5, PF127-rGO 5 and PF127-rGO 7.5 nanocomposites were fabricated, where the numbers represent the weight percentage of PF127-rGO with respect to PGA. The composite films were characterized by field emission scanning electron microscopy (FESEM), FTIR, WAXS and mechanical property study. FESEM and WAXS studies show good dispersion of PF127-rGO sheets in the PGA matrix. The FTIR results indicate a significant interaction between functional groups of PF127-rGO and functional groups of PGA. PF127-rGO 7.5 shows a 124% increase of stress at break and 185% increase of Young's modulus compared to pure PGA. [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) porous structure was designed based on carbon dot (CD)-supported copper sulphide (CuS)-decorated graphene oxide (GO) hydrogel for using in a high-performance asymmetric supercapacitor device to improve the specific capacitance, cyclic stability and energy density of CuS as well as GO based supercapacitors. CD coated CuS (CuS@CD) decorated GO hydrogels (CuS@CD-GOH) were prepared by a simple hydrothermal reaction at 180 °C and optimized through different spectroscopic, diffraction, microscopic and electrochemical analyses. CD acted as a stabilizer for the CuS nanoparticles and help to bind strongly CuS nanoparticles with GO inside the 3-D hydrogel structure. The CuS@CD-GOH exhibited high specific capacitance of 920 F g −1 at a current density of 1 A g −1 . The optimal CuS@CD-GOH was used as a positive electrode for the fabrication of asymmetric supercapacitor along with reduced GO as the negative electrode, which delivered the highest energy density up to 28 W h kg −1 along with long cycling life and retains up to 90% specific capacitance after 5000 cycles. The results are excellent in comparison to the reported CuS and composite GO hydrogel based supercapacitors. Thus, this work will provide a new insight of CuS and GO based composite 3-D structures for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Herein, reduced graphene oxide (rGO)/MnO 2 hybrid materials were prepared via a direct redox reaction between MnCl 2 and KMnO 4 on reduced graphene oxide (rGO) . A systematic study was carried out to understand the role of KMnO 4 . The morphology and microstructure of the as-prepared composite was characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman Spectroscopy. Results indicate that the concentrations of KMnO 4 have a detrimental effect on the distribution of MnO 2 nanoparticles on rGO sheets and hence on electrochemical properties. The electrochemical capacitive behavior of the as-prepared composite was investigated using cyclic voltammetry (CV), galvanostatic charge discharge, and electrochemical impedance spectroscopy (EIS) in 1 M Na 2 SO 4 aqueous electrolyte solution. At the optimum concentration of KMnO 4 , the as-prepared rGM-1 composite shows a high specific capacitance of 366 F/g at a scan rate of 10 mV/s. The composite also exhibits good electrocatalytic activity towards the oxidation of dopamine (DA), exhibiting a low detection limit of 2.3 × 10 −7 M with a wide linear range between 2.5 × 10 −7 M and 2.30 × 10 −4 M. Hence, the use of rGO/MnO 2 at an optimized concentration of KMnO 4 is a potential competitive candidate in supercapacitor and biosensor applications. [ABSTRACT FROM AUTHOR]

We demonstrate the sustainable production of H 2 O 2 without organic electron donors by a CdS-reduced graphene oxide (RGO) photocatalyst in sunlight with water and oxygen as resources. Photocatalysts were prepared with various amounts of RGO (0–30 wt.% with respect to CdS) by a hydrothermal method. A photocatalyst containing 20 wt.% RGO (CdS-G2) showed maximum activity, and the amount of H 2 O 2 produced (128 μM) was almost five times higher than that produced by CdS nanoparticles (27 μM) after 12 h sunlight irradiation. The results clearly revealed that the photocatalytic reaction mainly proceeds by two-electron reduction of oxygen rather than water oxidation on the catalyst surface. The effects of reaction temperature and pH on the production of H 2 O 2 were also investigated. We found that the production of H 2 O 2 was enhanced at lower temperature and pH. The concentration of H 2 O 2 reached to 164 and 156 μM with CdS-G2 at 10 °C and pH 2, respectively. [ABSTRACT FROM AUTHOR]

A super hydrogen barrier film was prepared via layer-by-layer self-assembly of graphene oxide (GO) and polyethyleneimine (PEI), and the effects of pH of the PEI solution on the performance of LBL films were studied in detail. Results show that the pH value of PEI solution has a significant influence not only on the adsorbed amount of self-assembly materials but also the stacking morphology of GO sheets. When the pH values of GO suspension and PEI solution are identical, the self-assembled film shows a superior hydrogen gas barrier performance under pH of 3.5. When the pH value of GO suspension was fixed and that of PEI solution was varied, the adsorbed amount of the film was increased and reached a maximum value when the pH of PEI solution was 12, and the film prepared under this condition had a 12.7% increase on thickness and a 55.5% decrease on its hydrogen transmission rate (H2TR). [ABSTRACT FROM AUTHOR]

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film. [ABSTRACT FROM AUTHOR]

Inhibiting the shuttle effect of soluble polysulfides (LiPSs) is critical to lithium–sulfur (Li–S) batteries. Nevertheless, the conventional separator fails to block immigration of LiPSs between electrodes. Herein, the enriched oxygen vacancies were stabilized with ruthenium doping on niobium oxide/three-dimensional reduced graphene oxide nanosphere (Nb 2 O 5−x /Ru-3DG) to prepare a functional separator layer for LiPSs diffusion prevention. The inhibition mechanism is unraveled by density functional theoretical calculations and experimental results. Li–S batteries with Nb 2 O 5−x /Ru-3DG-based separator displayed an excellent capacity of 700.3 mAh g−1 with a long-term stability of 1000 cycles and a high rate-performance of 533.2 mAh g−1 at 8 C. An industrial-level pouch cell delivered an outstanding specific capacity of 925.8 mAh g−1 with an exceptional flexibility. This study could open a new strategy to design materials with controlled defects and doping for LiPSs immobilization, enhanced catalytic activities for redox reaction, and other catalysts for energy conversion and storage devices. [Display omitted] • The Nb 2 O 5−x /Ru-3DG was fabricated via a two-step strategy with facile hydrothermal and controlled annealing methods. • Ru doping immobilized O vacancies by compensating coordination number and modulating electronic properties. • The coated layer effectively entrapped polysulfide and accelerated reaction kinetics for Li-S batteries. • Assembled Nb 2 O 5−x /Ru-3DG-based batteries delivered an excellent rate capacity and a long cycling stability. [ABSTRACT FROM AUTHOR]

Nanocomposites of polyacrylonitrile (PAN) with reduced graphene oxide (rGO) were prepared using a solution mixing technique employing polyvinyl phenol (PVP) as a compatibilizer. The PVP can facilitate composite formation by interacting with both rGO and PAN via π-π and H-bonding respectively. Various amounts of rGO were used to prepare PAN nanocomposites. The cross-sectional morphology of the composite films shows a uniform dispersion of rGO sheets in the PAN matrix. The Fourier transform infrared (FT-IR) studies revealed that good interaction of the rGO/PVP hybrid with PAN. The wide angle x-ray diffraction (WAXS) study confirms that the rGO sheets were uniformely dispersed as individual sheets in the PAN matrix. Thermogravimetric analysis shows enhanced thermal stability of the composite compared to pure PAN. The tensile strength and elastic modulus of the nanocomposites increased with increasing rGO content. A 102% enhancement in tensile strength and a 62.9% enhancement in elastic modulus were observed in the nanocomposite with 5% rGO. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N)-doped graphene (NG) sheets were prepared using (NH4)2CO3 and an aqueous dispersion of graphene oxide (GO) by an eco-friendly hydrothermal reaction. The in situ produced ammonia played an important role in the simultaneous nitrogen doping, the reduction and exfoliation of GO. The (NH4)2CO3/GO mass ratio and reaction temperature were varied to investigate the effects on the N doping level. The elemental analysis determined from the X-ray photoelectron spectroscopy showed that the nitrogen content of the NG was about 10.1at.% and the oxygen content decreased significantly due to the hydrothermal reduction of GO. The electrochemical performances of the NG sheets increased with increasing doped N content. The highest specific capacitance of 295Fg−1 at a current density of 5Ag−1 and the highest specific surface area of 412m2 g−1 were observed with the sample processed at 130°C. The retention of the specific capacitance was maintained at ∼89.8% after 5000 charge–discharge cycles. These results imply that NG sheets obtained by this simple eco-friendly approach are suitable for use in high performance energy storage electrode materials. [Copyright &y& Elsevier]

The storage of H 2 is one of the critical issues to be resolved to expand H 2 -based energy. Herein, MXene was employed in combination with GO for the first time for H 2 gas barrier coating on nylon 6 substrate (commonly used in storage tanks). A facile two-step method was acquired to covalently bond MXene and GO through 3-aminopropyl triethoxysilane (APTES) by employing carbodiimide reaction. The MXene-GO hybrid nanofiller (f -MXene-GO) exhibited a higher gallery gap between the nanosheets than that of the pristine MXene and GO. Besides, GO was also partially reduced by the amine functional groups of APTES. To the best of our knowledge, the stitching of MXene and GO using APTES has not yet been discussed in the literature. When f -MXene-GO was dispersed in poly (ethylene-co-acrylic acid) (EAA), a significant improvement in the mechanical properties was observed. An increase in the gallery gap between the MXene layers in f -MXene-GO/EAA nanocomposite as compared to MXene/EAA suggested the effectiveness of APTES grafting to enhance the interaction with EAA. MXene/EAA exhibited a higher H 2 gas barrier and mechanical properties than GO/EAA, whereas the adhesion of MXene/EAA to the nylon 6 substrate was weak. f -MXene-GO/EAA exhibited a judicious combination of both barrier and adhesion properties. The 10 wt% f -MXene-GO/EAA coated layer showed a very low H 2 permeability coefficient (0.03 cc.mm.m−2.d−1.atm−1) and a significant 89% reduction in the H 2 gas transmission rate with respect to nylon 6. [Display omitted] • MXene was stitched with graphene oxide (GO) by aminosilane for H 2 barrier application. • Hybrid MXene-GO/poly (ethylene-co-acrylic acid) was spray-coated on nylon 6 substrate. • Nanocomposite film showed a judicious combination of barrier and adhesion properties. • H 2 permeability coefficient was 0.03 cc.mm.m−2.d−1.atm−1 at 10 wt% filler loading. [ABSTRACT FROM AUTHOR]

Facile and a novel technique for bioinspired synthesis of silver nanoparticles (AgNPs) using an aqueous extract of mango (Mangifera indica) flower as stabilizing and reducing agent was demonstrated. The formation of AgNPs and AgNPs/rGO nanocomposites were confirmed through extensive experimental characterization and numerical analysis. Both, AgNPs and AgNPs/rGO nanocomposites showed excellent catalytic performance in catalytic hydrogenation of 4-nitrophenol and azo bond in dye molecules. The rGO supported Ag nanocomposites exhibited improved catalytic activity compared to AgNPs due to the enhancement of surface area. Electrochemical analysis of AgNPs/rGO nanocomposites showed specific capacitance (SC) of ∼532 F g−1 at a current density of 1.0 A g−1. About 92% retention in SC after 2000 charge-discharge cycles suggested long-term electrochemical cyclic stability as supercapacitor electrode materials. The biogenic nano-particles and composites implied that the rGO reinforced Ag excellent applicants as hydrogenation refining materials. All these observations demonstrated a novel, eco-cost effective and estimable candidates as hydrogenation refining materials and electrode materials. • Bioinspired silver nanoparticles/reduced graphene oxide nanocomposites. • This process is fast, easy, hazard free, and inexpensive. • Characterized by instrumental as well as theoretical study. • Efficient catalyst in hydrogenation of nitroarene and azo dye. • Relevant to the industrial wastewater purification and supply of energy. [ABSTRACT FROM AUTHOR]

The fabrication of low-cost, highly efficient, and earth-abundant electrocatalysts for oxygen reduction reaction is critical to produce clean and sustainable fuel through an electrochemical process. Herein, a facile hydrothermal technique is used for the synthesis of iron sulfide/graphene hybrid for oxygen reduction reaction. Morphological analysis of the resulting catalyst reveals that iron sulfide nanoparticles are homogeneously embedded on the surface of reduced graphene oxide sheet. Electrochemical analysis of the hybrid exhibits remarkably improved catalytic performance for oxygen reduction reaction while achieving half wave potential of +0.845 V and onset potential of +1.0 V (versus reversible hydrogen electrode), along with outstanding long-term stability under alkaline conditions. In addition, the methanol tolerance ability and stability of the hybrid exceed the benchmark platinum/carbon product in alkaline condition. These outstanding activities of the hybrid are attributed to the merits of the interaction between iron sulfide nanoparticles and graphene. The results suggest the practicability of metal sulfide as a low cost and efficient alternative catalyst of platinum for oxygen reduction reaction. Image 1 • Hydrothermal technique is used for fabricating a new iron sulfide/graphene hybrid. • The interaction of mesoporous iron sulfide and graphene produces excellent activity. • The hybrid outperforms Pt/C and other metal sulfide/graphene catalysts towards ORR. • The hybrid's stability and methanol tolerance are superior to Pt/C product. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen barrier properties are characteristic of polymeric materials prepared with graphene; thus, they can be considered as a good substitute for the metal body of the traditional hydrogen storage tank. Graphene oxide/polymer layer-by-layer self-assembling film based on noncovalent force shows good hydrogen gas barrier properties. However, the dense film structure can be broken when the film is placed in water environment, especially acidic or alkaline environment, which induces to the leak of the hydrogen gas. Herein, a modified graphene oxide/polyethyleneimine reactive layer-by-layer self-assembled film for the hydrogen barrier was fabricated by the covalent bond self-assembled technology. Graphene oxide was modified with ethylene glycol diglycidyl ether to introduce epoxy groups that can react with polyethyleneimine to form covalent bonds. The modification time, modification pH value, and the feed ratio of graphene oxide/ethylene glycol diglycidyl ether were investigated in detail. Results indicate that the self-assembled films were prepared by covalent bonds between polyethyleneimine and modified graphene oxide. When the modification time was 6 h, pH value was 2, and the feed ratio of graphene oxide/ethylene glycol diglycidyl ether was 0.05/0.23, the hydrogen transmission rate of 10-bilayer modified graphene oxide/polyethyleneimine self-assembled films was 289 cm3/m2·24 h·0.1 MPa, which was decreased by 78.8% compared to that of the polyethylene terephthalate substrate films (1365 cm3/m2·24 h·0.1 MPa). Furthermore, the modified graphene oxide/polyethyleneimine reactive layer-by-layer self-assembled films exhibit acid-resistance, alkali-resistance, salt-resistance and thermal-resistance properties. [ABSTRACT FROM AUTHOR]

Abstract Polyelectrolyte-decorated graphene with positive and negative charges was prepared using graphene oxide as a precursor along with polyallylamine hydrochloride and poly (styrenesulfonate sodium) as surface modifiers, respectively. Driven by an electrostatic interaction, the as-obtained polyelectrolyte-decorated graphene sheets were self-assembled via a layer-by-layer method, producing graphene based composite multilayers. Field emission scanning electron microscopy (FE-SEM) images showed that the surface of composite film exhibited a mass of characteristic wrinkles of graphene. Interestingly, the cross-sectional FE-SEM of the film exhibited an unstratified structure, indicating a good dispersion of graphene sheets in the composite film. The results of oxygen gas permeability testing demonstrated that the resulting composite films exhibited excellent oxygen gas barrier properties. The oxygen gas transmission rate (OTR) of the composite film with 24 bilayers was as low as 1.2 cm3 m-2 d-1∙atm−1, exhibiting potential for use in packaging applications. [ABSTRACT FROM AUTHOR]

A new series of boric acid (BA) induced cross-linked poly(vinyl alcohol-co-ethylene) (EVOH)/graphene oxide (GO) nanocomposite (EVOH/BA/GO) films are prepared using different amount of GO and BA with respect to EVOH. The EVOH/BA/GO nanocomposites are respectively coated on nylon films and stainless steel substrates by a typical spray coating method, followed by thermal and hydrazine vapor treatment for gas barrier and corrosion studies. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses confirm the formation of cross-linked nanocomposite through the formation of B–O–C bond. The field emission scanning electron microscopy analysis indicates the formation of homogeneous structure for these nanocomposites. The storage modulus (at 25 °C) and elastic modulus of EVOH/15BA/5GO-coated film with 15% BA and 5% GO are enhanced by 280 and 60%, respectively, in comparison to nylon film. EVOH/15BA/5GO-coated nylon film exhibits dramatic reduction of hydrogen (6.9) and oxygen gas (1.5) transmission rates (cc/m 2 ∙d∙atm) than pure nylon film. In addition, EVOH/15BA/5GO-coated stainless steel shows an ultralow corrosion current (0.294 μA/cm 2 ) and corrosion rate (3.43 × 10 −3  mm/year) than steel. A comparative study between EVOH/BA/GO and EVOH/GO is performed to examine the effect of the cross-linker on the different physical properties. [ABSTRACT FROM AUTHOR]

A novel carbon felt/nitrogen-doped reduced graphene oxide/paraffin wax ternary skeleton (CF/N−RGO/PW) is developed to enhance the tribological performances of monomer casting nylon-6 (MCPA6). FE−SEM results confirm the successful formation of the three-dimensional (3D) CF/N−RGO/PW skeleton, where N−RGO sheets are decorated on carbon fibers. Most importantly, the flexuous N−RGO sheets can accommodate PW to provide sufficient lubricity for MCPA6, working as ponds to store PW. On the other hand, abundant cracks are found along carbon fibers, working as ditches to transport PW onto the rubbing surface. Thus, the ternary CF/N−RGO/PW 3D skeleton exhibits a pond and ditch structure for the efficient storage and transportation of PW. In comparison with the neat MCPA6, the friction coefficient and wear loss of MCPA6/CF/N−RGO/PW decline by (83 and 65) %, respectively. Theoretical calculations based on density functional theory support the efficient adsorption of PW onto N−RGO. Therefore, the as-prepared MCPA6/CF/N−RGO/PW composite herein provides a new reference to prepare polymer composites with advanced tribological performance on account of the novel strategy of the storage and transportation of lubricants. [Display omitted] • A novel CF/N-RGO/PW ternary skeleton was developed for advanced tribological performances of MCPA6. • The ternary skeleton exhibits a unique ponds and ditches structure. • The excellent tribological performances were attributed to the efficient storage and transport of PW. • Theorotical calculation comfirmed the adsorption of PW by N-RGO sheets. [ABSTRACT FROM AUTHOR]

In this study, the organo-soluble dodecylamine amine (DDA)-modified reduced graphene oxide (DDA-rGO) was synthesized using two different grafting methods. DDA was covalently bonded with GO sheets by direct amidation processes in the presence of N,N′-Dicyclohexylcarbodiimide (DCC), followed by reduction with hydrazine hydrate to prepare the DDA-modified reduced GO (DDA-rGO1). Analogous DDA-modified rGO (DDA-rGO2) was prepared by modifying GO with DDA in the absence of DCC. The ultraviolet−visible spectra showed that the DMF dispersion of DDA-rGO1 and DDA-rGO2 followed Beer's law and their molar extinction coefficient values were calculated to be 64 and 44 mL mg −1 cm −1 , respectively. The AFM, TEM, and TGA confirm the higher amount of DDA attached in DDA-rGO1. These fillers with various loading amounts were successfully used to synthesize several composite films using polyurethane (PU) as matrix. All nanocomposites showed excellent improvement in mechanical and gas barrier properties than PU. DDA-rGO1-4/PU with 4 wt% DDA-rGO1 improved the tensile modulus ( E ) by 204% and reduced O 2 permeability ( P ) to 84% compared to PU. On other hand, DDA-rGO2-4/PU enhanced the E by 122% and declined P to 80% compared to PU. The DDA-rGO1 demonstrated a better reinforcing efficiency to improve the mechanical and gas barrier properties. [ABSTRACT FROM AUTHOR]

We report the simultaneous reduction, surface modification, and stitching of graphene oxide (GO) by ethylenediamine (EDA) and triethylenetetramine (TET) to boost the hydrogen gas barrier performance of polyurethane (PU) composite-coated nylon films. TEM and XRD analyses confirmed the formation of stitched EDA-modified GO (EDA-mGO) and TET-modified GO (TET-mGO) while FT-IR spectroscopy, Raman spectroscopy, and thermogravimetric analyses revealed the functionalization and reduction of GO by EDA and TET. EDA-mGO/PU and TET-mGO/PU composites were synthesized using different amounts of EDA-mGO and TET-mGO, respectively, and composites were deposited onto surface modified nylon films by spray coating to prepare hydrogen barrier films. FTIR, XRD, and FESEM analyses showed that both EDA-mGO and TET-mGO were uniformly dispersed into PU matrix. Cross-sectional FESEM showed strong adhesion between the nylon and composites. Coated films exhibited dramatic reduction in hydrogen gas transmission rate (H 2 GTR) and TET-mGO/PU with 22 wt% TET-mGO exhibited 93% decrease in H 2 GTR than bare nylon film. [ABSTRACT FROM AUTHOR]

A facile, cost effective and additive-free successive ionic layer adsorption and reaction (SILAR) technique is demonstrated to develop layer-by-layer (LbL) assembly of reduced graphene oxide (RGO) and MnO 2 (MnO 2 -RGO SILAR ) on a stainless steel current collector, for designing light-weight and small size supercapacitor electrode. The transmission electron microscopy and field emission scanning electron microscopy images shows uniform distribution of RGO and MnO 2 in the MnO 2 -RGO SILAR . The LbL (MnO 2 -RGO SILAR ) demonstrates improved physical and electrochemical properties over the hydrothermally prepared MnO 2 -RGO (MnO 2 -RGO Hydro ). The electrochemical environment of MnO 2 -RGO SILAR is explained by constant phase element in the high frequency region, and a Warburg element in the low frequency region in the Z-View fitted Nyquist plot. The equivalent circuit of the MnO 2 -RGO Hydro , displays the co-existence of EDL and constant phase element, indicating inhomogeneous distribution of MnO 2 and RGO by the hydrothermal technique. An asymmetric supercapacitor device is designed with MnO 2 -RGO SILAR as positive electrode, and thermally reduced GO (TRGO) as negative electrode. The designed cell exhibits high energy density of ∼88 Wh kg −1 , elevated power density of ∼23,200 W kg −1 , and ∼79% retention in capacitance after 10,000 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

Sulfonated polyaniline (SPANI) functionalized reduced graphene oxide (SPANI/G-1) was prepared by aniline initiated polymerization of m -aminobenzene sulfonic acid in presence of graphene oxide (GO), followed by reduction with hydrazine hydrate. Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy analyses confirmed successful surface modification of graphene using SPANI. The presence of sulfonic acid groups in SPANI accelerated the redox reaction and provided pseudocapacitance. SPANI/G-1 based electrode showed high specific capacitance of 1107 F g −1 at a current density of 1 A g −1 in a three electrode set up. An asymmetric supercapacitor (ASC) device was fabricated using SPANI/G-1 as positive electrode and chemically reduced GO (RGO) as a negative electrode. ASC showed specific capacitance of 157 F g −1 at a current density of 1.5 A g −1 and 94% retention in specific capacitance after 5000 charge-discharge cycles at a current density of 3.8 A g −1 . The ASC exhibited maximum energy density of 31.4 W h kg −1 and a large power density of 14,764 W kg −1 . Nyquist data of the device was fitted with Z-view and different components (solution resistance, charge-transfer resistance and Warburg elements) were calculated from the fitted curve. [ABSTRACT FROM AUTHOR]

Fabrication of high-performance graphene-based polymeric composites is challenging due to poor dispersion of graphene caused by restacking, weak interfacial bonding, and incompatibility of graphene with polymers. Herein, reduced graphene oxide (rGO)-based polyethyleneimine (PEI) composite (rGO/PEI) was synthesized by utilizing the unique roles of PEI as reducing agent and surface modifier to overcome the above-mentioned drawbacks of graphene. Composites with different graphene oxide (GO):HPEI ratios were used to prepare rGO-high molecular weight PEI (rGO/HPEI). For potential application as hydrogen gas barrier material, rGO/HPEI composites were coated onto the polyethylene terephthalate (PET) substrates through spray coating technique to prepare gas barrier films. Analogous rGO/LPEI (low molecular weight PEI) coated PET film was also prepared. The rGO/HPEI composite-coated films showed dramatic enhancement in hydrogen gas barrier properties and excellent tensile strength with high elongation at break as compared to PET and rGO/LPEI coated PET films. [ABSTRACT FROM AUTHOR]

Sulfonated poly (ether-ether-ketone) (SPEEK) was selected as a surface modifying agent to prepare non-covalently functionalized reduced graphene oxide (NFrGO) followed by the development of NFrGO/cellulose acetate (CA) nanocomposite (NFrGO-CANC) through solution mixing. The formation of the nanocomposite was governed via the hydrogen bonding interactions among the –SO 3 H group of NFrGO and –OH/-C O groups of CA. NFrGO-CANC was characterized by field emission scanning electron microscopy, FT-IR, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry analysis. The tensile strength of the NFrGO-CANC increased significantly with increasing NFrGO loading. The tensile strength and modulus of the NFrGO-CANC with 1.5 wt.% NFrGO were improved by ∼102 and 143%, respectively, compared to those of pure CA. The onset degradation temperature and oxygen gas barrier properties of the NFrGO-CANC also were enhanced with increasing NFrGO loading up to 1.5 wt.% compared to those of pure CA film. [ABSTRACT FROM AUTHOR]

Hexylamine (HA) functionalized reduced graphene oxide (RGO-HA) was prepared via the modification of graphene oxide (GO) with HA, followed by reduction with hydrazine hydrate. The structure of RGO-HA was confirmed using various characterization techniques. RGO-HA was easily dispersed in several organic solvents due to its hydrophobic nature. Accordingly, RGO-HA/polyurethane (PU) composites were synthesized using different amounts of RGO-HA for their potential application in the field of barrier materials. Fourier-transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXS) analysis, and field emission scanning electron microscopy (FESEM) showed that RGO-HA in PU was fully exfoliated and uniformly dispersed. The hydrogen gas barrier films were prepared by spray coating of RGO-HA/PU nanocomposite solutions on nylon films. Good attachment between the nylon surface and nanocomposite was confirmed by cross sectional field emission scanning electron microscopy. The nanocomposite coated nylon film having 43.3 wt% RGO-HA exhibited an 82% decrease in the hydrogen gas transmission rate (GTR) compared to a pure nylon film. The high reduction in GTR values of the coated films may motivate to use alkyl amine-modified reduced graphene oxide and PU nanocomposite for the future development of effective barrier materials. [ABSTRACT FROM AUTHOR]

Sulfonated poly(ether-ether-ketone) functionalized graphene oxide (SPG)/poly(vinylidene fluoride) (PVDF) composites have been prepared by a solvent evaporation technique. The –SO 3 H group of SPG interact with the >CF 2 dipole of PVDF to integrate graphene uniformly into a PVDF matrix. The cross-sectional field emission scanning electron microscopy micrograph shows folded-chain lamella of spherulitic PVDF crystallites spread outwards from the growth center. The spherulitic crystallites decrease with the incorporation of SPG into the PVDF matrix and the composite containing 3 wt.% SPG (SPG3) does not show spherulite, but fiber-like crystallites. Fourier transform infrared spectroscopy, wide angle X-ray scattering and differential scanning calorimetry (DSC) results suggest that piezoelectric β-polymorph formation begins with the incorporation of SPG into the PVDF matrix, and SPG3 shows the formation of the fully β-polymorph. DSC cooling curves show that SPG acts as an effective nucleating agent for the crystallization of PVDF. Study of the mechanical properties shows that there is a simultaneous enhancement of the stress and the strain at break indicating the enhanced toughness of the PVDF composites compared to pure PVDF. Young’s modulus increases 160% and the oxygen permeability coefficient decreases by 91% in the SPG3 composite film compared to pure PVDF. [ABSTRACT FROM AUTHOR]

Highlights: [•] NiCo2O4 were grown on RGO by in-situ synthesis process. [•] FE-SEM image revealed self-assembled layer by layer growth of NiCo2O4-RGO nanocomposite. [•] NiCo2O4-RGO nanocomposite exhibited synergetic effects on its electrochemical performance. [ABSTRACT FROM AUTHOR]

This study investigates the synthesis and application of boron nitride quantum dot (BNQD) covalently bonded reduced graphene oxide (rGO) hybrid materials as a novel electrode material for supercapacitors. Because of the p-doping as well as the enhanced hydrophilicity and interfacial bonding force enabled by the hybridization of amine-functionalized boron nitride quantum dot (A-BNQD) with rGO via the chemical coupling reaction, the A-BNQD/rGO shows improved charge carrier density, wettability of electrolyte, and durability. As a result of the synergistic effects, the A-BNQD/rGO as a supercapacitor electrode shows much higher specific capacitance compared to those of rGO and raw BNQD/rGO at a current density of 1 A g−1. Further, the A-BNQD/rGO shows high cycling stability, maintaining almost 94.38%, even after 10,000 cycles due to the enhanced interfacial bonding force between the A-BNQD and rGO. Besides, the fabricated symmetric supercapacitor exhibits high specific capacitance (90 F g−1@1 A g−1), an energy density (12.5 Wh kg−1@0.5 kW kg−1), and good cycling stability. This result suggested that the fabricated A-BNQD/rGO has great potential as electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Porous carbon materials with hierarchical features are the important materials to study the electrochemical properties for supercapacitor electrode application. Depending on the synthesis procedures and the carbon precursors used, these carbon materials possess different structures, and they are always associated with different amounts of various oxygen functional groups affecting the wettability, conductivity, and electrochemical performance. In this context, various electrochemical methods are adopted to study the charge storage contribution. Among them, separation of surface-controlled (capacitive) and diffusion-controlled currents from cyclic voltammetry (CV) curve by using the potential sweep method (PSM) is a preferred method. Herein, three-dimensional "Reduced Graphene Oxide-Carbon Nanofiber" (rGO-CNF) hybrid materials are fabricated by using different rGO:CNF ratios to study the effect of the composition of rGO and CNF in the charge storage behaviors. The structural, elemental, and electrochemical characterizations of the materials are performed to quantitatively study the surface-controlled (capacitive) and diffusion-controlled charge storage contributions in the rGO-CNF hybrid. It is found that the increase of rGO content in the hybrid material significantly affects the electrochemical properties of the hybrid materials. Image 1 • A hierarchical three-dimensional rGO-CNF material has been synthesized. • The rGO-CNF (1:1) shows a high specific capacitance of 316.50 F g−1 at 0.25 A g−1. • The rGO-CNF has both surface-controlled and diffusion-controlled charge storage contributions. • The surface-controlled and diffusion-controlled charge storage contributions have been deconvoluted. [ABSTRACT FROM AUTHOR]