Search

Three-dimensional (3D) graphene is a promising active component for various engineering fields, but its performance is limited by the hidebound electrical conductivity levels and hindered electrical transport. Here we present a novel approach based on interlayer engineering, in which graphene oxide (GO) nanosheets are covalently functionalized with varied molecular lengths of diamine molecules. This has led to the creation of an unprecedented class of 3D graphene with highly adjustable electronic properties. Theoretical calculations and experimental results demonstrate that ethylenediamine, with its small diameter acting as a molecular bridge for facilitating electron transport, has the potential to significantly improve the electrical conductivity of 3D graphene. In contrast, butylene diamine, with its larger diameter, has a reverse effect due to the enlarged spacing of the graphene interlayers, resulting in conductive degradation. More importantly, the moderate conductive level of 3D graphene can be achieved by combining the interlayer spacing expansion effect and the π-electronic donor ability of aromatic amines. The resulting 3D graphene exhibits highly tunable electronic properties, which can be easily adjusted in a wide range of 2.56–6.61 S·cm−1 compared to pristine GO foam (4.20 S·cm−1). This opens up new possibilities for its use as an active material in a piezoresistive sensor, as it offers remarkable monitoring abilities. [ABSTRACT FROM AUTHOR]

Graphene aerogel (GA), with low density, high conductivity, and good mechanical properties, has important application potentials in the field of flexible electronics. Here, a balanced approach was developed in this work: Graphene oxide (GO) nanosheets were induced to assemble into a homogeneous porous hydrogel under alkali induction, and then, the oxygen-containing functional groups of GO were removed by reductant of formamidine sulfonic acid (FAS). Besides, the hydrogel of GA precursor can be quickly dried at a high temperature (150 °C) within 30 min to obtain pure GA of FGA. After further calcination, the obtained aerogel of AFGA with ordered structure has ultralow density (3.88 mg/cm3), high conductivity (7.4 S/m), supercompression recovery performance (99%), high sensitivity (S = 0.83 kPa−1), large reversible compression cycle performance (200 cycles under 90% strain), and high fatigue resistance (10,000 cycles under 70% strain), which presents excellent piezoresistive properties and can find wide applications in piezoresistive sensors as the high-performance sensing material. [ABSTRACT FROM AUTHOR]

In this article, a hybrid of reduced graphene oxide (rGO) sheets decorated by zinc oxide (ZnO) particles was synthesized by a simple hydrothermal method, and its thermosetting polyimide (TPI) composites were prepared by an in situ polymerization method. The mechanical and tribological properties of the ZnO–rGO/TPI composite under dry sliding conditions were studied. The compression strength and modulus of 0.8 wt% ZnO–rGO/TPI composite reached 120.67 ± 2 MPa and 1.77 ± 0.06 GPa, which were 28.1% and 51.3% higher than those of TPI, respectively. The wear rate of 0.8 wt% ZnO–rGO/TPI was also reduced to 1.54 × 10−8 mm3 N−1 m−1 at 100 N load, which is about two order of magnitude lower than that of TPI. Compared with the addition of GO alone, the results also demonstrate more significant enhancements in mechanical and tribological properties of TPI by ZnO–rGO hybrid. Furthermore, the tribological mechanism exploration indicates that the "particle‐on‐plane" structure and chemical bonding between ZnO and rGO lead to the crack suppression and strength increment, contributing to the extraordinary improvement of mechanical and tribological properties. Thus, this ZnO–rGO/TPI composite presents promising potential as high‐performance tribological materials under dry‐sliding conditions in industrial applications. [ABSTRACT FROM AUTHOR]

Highlights • The hydrazine hydrate modified FG (HFG) has excellent demulsification efficiency. • HFG presented superior demulsification performances ranging from acidic to alkaline conditions. • There exist strong electrostatic attraction and π–π interaction between HFG and oil droplets. Abstract A series of functional fluorinated graphene (FG) materials including urea modified FG (UFG), alkali modified FG (AFG) and hydrazine hydrate modified FG (HFG) with different fluorine contents were prepared and introduced as demulsifiers for efficient separation of oil from oil-in-water (O/W) emulsion. Their demulsification performances were evaluated by measuring oil absorbance in separated water phase. Effects of demulsifier dosage, pH of wastewater and the NaCl concentration on demulsification efficiency have been studied detailedly. The demulsification mechanism was also explored. Results showed that demulsification efficiency increased with the decrease of fluorine content of functional FG and the oil concentration in the separated water phase decreased to the lowest value when the 600 mg/L HFG was added into the wastewater. In particular, the HFG has superior demulsification performances ranging from acidic to alkaline conditions. The strong π–π interaction and electrostatic attraction between HFG and oil droplets promote the separation of oil from oily wastewater. Besides, the HFG also presents high demulsification efficiency at different concentrations of NaCl wastewater solution, suggesting the excellent salt resistance. This work indicates that the HFG is a simple and highly efficient demulsifier to separate the oil from the oily wastewater in a wide range of pH levels. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Herein, Mn-MOF/RGOn composites have been successfully synthesized using terephthalic acid non-covalent functionalized graphene oxide (GO) sheets acting as efficient nucleation sites and structure-directing templates to direct the growth of MOFs. The electrochemical performance of the Mn-MOF/RGOn composite electrode was much better than that of the pristine Mn-MOF when used as a candidate anode material for lithium-ion batteries due to the synergetic advantages of RGO and Mn-MOF, improved electrical conductivity, and mechanical flexibility of Mn-MOF. Especially, the Mn-MOF/RGO10 composite electrode maintains a reversible discharge capacity of 715 mA h g−1 with a capacity retention of 98% after 100 cycles at 100 mA g−1 and also exhibits a high discharge capacity of 485 mA h g−1 at 300 mA g−1, 432 mA h g−1 at 500 mA g−1 while still maintaining 348 mA h g−1 at 1000 mA g−1 after 500 cycles, which is greatly higher as compared to that of the pure Mn-MOF material as expected. [ABSTRACT FROM AUTHOR]

Inspired by the vision that incommensurately stacked multilayers can extend the already superior lubricating properties of two-dimensional (2D) nanomaterials, reduced graphene oxide/molybdenum disulfide (RGO/MoS 2 ) heterostructures with different compositions are synthesized by a facile one-pot hydrothermal method for lubrication purpose. Two feed ratios for the graphene oxide and MoS 2 precursors are designed to explore the relation among morphology, chemical composition and lubrication performances of the synthesized heterostructures. In the case of high loading amount of MoS 2 on RGO, the novel structure of cocked MoS 2 nanosheets provides extra steric hindrance effect to restrain the aggregate and settlement tendency when dispersed in paraffin oil. By comparing the tribological results, it is found that RGO/MoS 2 heterostructures have better lubricating properties with lower coefficient of friction (0.09 in oil lubrication as additive and 0.02 in vacuum as coating) and higher wear resistance than single and physically mixed forms of RGO or MoS 2 . The proposed reason to this enhanced performance is the lower shear strength arising from the intrinsic lattice mismatch between RGO and MoS 2 . [ABSTRACT FROM AUTHOR]

We report a graphene/cobalt selenide (rGO/CoSe2) composite as an anode material for lithium-ion batteries. The prepared composite shows a wrinkled morphology with the CoSe2 nanoparticles tightly anchored/wrapped on/in the rGO sheets. The rGO/CoSe2 composite exhibits enhanced electrochemical performance with higher capacity, better rate capability, and cycling performance compared to pure CoSe2. The rGO/CoSe2 composite delivers a high initial reversible capacity of 726 mAh g−1 and a very high capacity of 1577 mAh g−1 after 200 cycles at a current density of 200 mA g−1 (0.38 C). The rGO sheets in the composite play important roles for the improvement in electrochemical properties, for example, the rGO sheet not only enhances the electrical conductivity of the whole electrode, but also alleviates the structure degradation caused by volume expansion of CoSe2 during discharge/charge processes, resulting in improved lithium-storage performances. [ABSTRACT FROM AUTHOR]

In this work, we report a simple self-assembly way to prepare ceria/graphene oxide (CeO 2 /GO) composite films on silicon (Si) substrates, which exhibit significant enhancement on tribological performances compared with Si substrates and GO films. Specifically, the friction coefficient is reduced drastically to the one-third of that of Si substrates. What’s more, the antiwear lifetime is markedly prolonged to ∼8 h under a high applied load of 2 N, which is over seven times longer than that of GO films. It is expected that the CeO 2 /GO composite films may find wide applications in nano/microelectromechanical systems as high-performance solid lubricating films, due to their facile and low cost preparation, nano-scale thickness, lower friction coefficient and desired antiwear lifetime. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni/RGO composites were successfully synthesized through a simple solvothermal method. [•] The attached Ni nanoparticles can efficiently inhibit the aggregation of RGO nanosheets and provide pseudocapacitance. [•] Ni/RGO–2 exhibits the highest specific capacitance of 547.3 F g−1 at 1 A g−1 in 2M KOH. [•] Ni/RGO–2 can maintain 81% of initial capacity after a continuous 1000 times of cycling. [Copyright &y& Elsevier]

Abstract: A simple and rapid one-pot process is developed for the synthesis of reduced graphene oxide/cobalt hydroxide (rGO/Co(OH)2) composite. The morphology and microstructure of the composite are examined by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Both morphology and element analyses confirm that Co(OH)2 nanoparticles are homogeneously and tightly attached on the surfaces of rGO. The electrochemical performances of the rGO/Co(OH)2 composite as electrode materials for supercapacitors are systematically investigated. A synergistic effort built from the excellent properties of graphene and fine structure of the composite guarantees its superior capacitive performances than those of pure rGO and Co(OH)2. The specific capacitance of the rGO/Co(OH)2 composite reaches 474 F g−1 at a current density of 1 A g−1 and this value can even retain 300 F g−1 at a high current density of 10 A g−1, showing a relatively good rate capability. Moreover, the specific capacitance of this electrode still remains 90% after 1000 times of cycling, demonstrating a good cycle stability of this composite. [Copyright &y& Elsevier]

In this work, a facile hydrothermal method has been developed to synthesize a three-dimensional porous birnessite manganese dioxide hierarchical structure (pMHs) using thermally reduced graphene oxide paper as a sacrificing template. The morphology, microstructure, and thermal stability of the obtained samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms, and thermal gravimetric analysis. Furthermore, the electrochemical properties of the pMHs as an electrode material for supercapacitor were investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in 1 M Na2SO4 electrolyte, and a specific capacitance of 194 F g−1 was achieved at a current density of 0.1 A g−1. The long-term stability implies that the synthesized pMHs is a good candidate as an electrode material for SCs. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a promising solid lubricant for moving mechanical systems to implement reliable and effective lubrication due to its easy modification and excellent tribological properties. However, obtaining highly dense GO coatings simultaneously with high hardness and extensibility is still a challenge for available self-assembly techniques, and these characteristics are beneficial to tribological properties. Inspired by the advanced abrasion resistance system of mussel byssus threads, a surprisingly simple and versatile metal ions (namely Fe2+ and Fe3+ ions) directed self-assembly strategy has been developed to rapidly fabricate GO coatings. GO as a solid lubricant is highly sensitive to the interface structure and test environment. Consequently, the influence of the valence state of iron ions on the macroscopic tribological properties of GO-based coatings in air, nitrogen gas and vacuum environments are comparatively investigated. The results show that the GO-Fe3+ coating with a highly compact characteristic and unique granular microarchitecture resulting in higher hardness and strain capacity displays a lower friction coefficient and remarkable wear resistance than the GO-Fe2+ coating. Additionally, because water molecules generate strong hydrogen bonding gradually disrupting the ordered layered structure, both GO-Fe2+ and GO-Fe3+ coatings exhibit a higher friction coefficient in air than in nitrogen gas and vacuum. [Display omitted] • Graphene oxide coatings with enhancing mechanical properties and tribological properties via chemical cross-linking are made by a facile and versatile bioinspired iron ions induced self-assembly strategy. • Compared with GO-Fe2+ coating induced by Fe2+ ions, stronger affinity ability between GO nanosheets and Fe3+ ions are prone to achieve much compact GO-Fe3+ coating. • GO-Fe3+ coating with unique granular micro-architecture resulting in higher hardness and strain capacity displays superior tribological properties than GO-Fe2+ coating. • GO coatings have superior tribological properties in dry nitrogen gas and vacuum environments than that in humid air environments due to their easier to form orderly layered structures. [ABSTRACT FROM AUTHOR]

Abstract Three-dimensional holey reduced graphene oxide/MnO 2 composites, which possess in-plane pores-containing graphene sheets and three-dimensional interconnection porosity, are fabricated via multiple steps including preparation of solution processible holey graphene oxide, hydrothermal-induced self-assembly of holey graphene oxide to form three-dimensional holey reduced graphene oxide, and deposition of MnO 2 onto holey reduced graphene oxide. By changing the immersion time of the holey reduced graphene oxide into the KMnO 4 aqueous solution, a series of three-dimensional holey reduced graphene oxide/MnO 2 composites are synthesized. Specially, the composite prepared with immersion time of 3 h presents remarkable performances for supercapacitor application, which exhibits a high specific capacitance of 192.2 F g−1 at a current density of 0.5 A g−1 and a good capacitance retention of 79% after 5000 times of charge/discharge cycling at a current density of 1 A g−1. The reasons for the enhanced electrochemical performance are investigated by various structural characterization and electrochemical measurement technologies. The results demonstrate that the unique porous structure, proper specific surface area, pore size distribution and electrical conductivity are ascribed to the good electrochemical performance of the prepared composite. The convenient preparation method and good electrochemical performance of this composite make it an attractive electrode material for supercapacitors. Graphical abstract Image 1 Highlights • Holey graphene oxide was prepared by a facile acid-assisted defect-etching approach. • 3DHG and 3DHG/MnO 2 with interconnected hierarchical porous networks were constructed. • 3DHG/MnO 2 exhibited an enhanced electrochemical performance as supercapacitor electrode material. [ABSTRACT FROM AUTHOR]

With the broader application of intelligent sensors in various complex conditions, sensing materials with better mechanical and conductive properties as well as higher temperature adaptability are required. For this purpose, a GO/PVA/MXene (GPM) composite aerogel was designed and prepared via a two-step strategy, including self-assembly and vacuum-assisted dip-coating processes. The as-prepared GPM has a unique structure composed of hierarchical GO network skeleton and MXene coating, endowing it with high Young's modulus (11.2 kPa) and compressibility (90%). Demonstrated with the finite element (FE) simulation, the elasticity and toughness of the GPM are originated from the hierarchical microstructure and the improved thickness of shells. Besides, the GPM exhibits a long-term durability of 5,000 compression cycles at 50% strain, a high sensitivity of 1.744 kPa−1, and a rapid response time of 4.5 ms. Further application examples reveal that the pressure sensor based on GPM has superior physiological signal capture capability, realizing fingertip pulse and temporal artery detections. Moreover, the GPM aerogel possesses high thermal insulation efficiency, resulting in good temperature adaptability in harsh environments from −196 °C to 300 °C. The sensitive pressure sensors should have the potential application in many fields of intelligent factories, complex militaries, and space discoveries. A GO/PVA/MXene (GPM) composite aerogel was designed via a two-step strategy, including self-assembly and vacuum-assisted dip-coating processes. The GPM has a unique structure composed of hierarchical GO skeleton and MXene coating, endowing it with high Young's modulus (11.2 kPa) and compressibility (90%). Besides, the GPM exhibits long-term durability of 5,000 compression cycles at 50% strain, high sensitivity of 1.744 kPa−1, and a rapid response time of 4.5 ms. Moreover, the GPM aerogel possesses high thermal insulation efficiency, resulting in temperature adaptability in harsh environments from −196 °C to 300 °C. [Display omitted] • PVA was used to modulate the microstructure of the GO skeleton for obtaining the hierarchical GPM aerogel. • MXene coating endows GPM aerogel with the excellent mechanical and conductive property. • GPM-based sensor exhibits superb detection capability and wide temperature adaptability. [ABSTRACT FROM AUTHOR]

Herein, a facile hydrothermal self-assembling strategy is employed to prepare a reduced graphene oxide (rGO) aerogel with a multi-scale hierarchical cellular structure inspired by deep-sea glass sponge. This hierarchical cellular structure of the rGO aerogel, obtained by changing the carbon wall to cellular structure, can be broken down into six levels from the nano- to the macro-scale. Remarkably, the rGO aerogel, with multi-step reductions, shows significant flexibility and toughness under extra-high compressions: 99.9% of the original height is remained after 20 000 compression cycles at a high strain of 90%, whereas 79.8% of height is still preserved after 10 000 compression cycles at an extreme strain of 99%. Moreover, the rGO aerogel demonstrates outstanding compressive strength: the stress of 1.5 MPa under 99% strain and the ratio of strength to density of 177 kPa cm3 mg−1, which overcomes the shortcoming of low stress tolerance for general graphene aerogels. In addition, the rGO aerogel shows high electrical conductivity of 42.7 S m−1 and exceptionally stable current signal response even after tens of thousands of compression cycles under extreme strain (99%). The outstanding properties of this graphene aerogel demonstrate its promising potential as a piezoresistive sensor with high stability and wide detection range. [Display omitted] • Sponge skeleton-like graphene aerogel is obtained by hydrothermal self-assembling. • Superelastic and recycle stability at 99% strain of 10,000 compression cycles. • Great compressive strength (1.5 MPa) and strength-density ratio (177 kPa cm3 mg−1). • Electrical conductivity of 42.7 S m−1 and stable current response at 99% strain. • High-performance wearable piezoresistive sensor for detecting human movements. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is a layered lubricant with high performance, but its application is limited by complex synthesis and relatively low resistance to environmental moisture. In this study, a simple and versatile self-assembly method was developed to prepare GO coatings with thicknesses ranging from the nanometer to micrometer scale. The results indicate that tribological performance is significantly influenced by ambient humidity. During friction, water molecules tend to form hydrogen bonds with oxygen functional groups and defects on GO nanosheets, destroying the ordered layer structure and thus degrading tribological performance. In addition, the further incorporation of lubricating oil is beneficial for achieving lower friction attributed to the synergistic effect of GO coating and oil film that serves as a moisture repellent. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) presents great potential in lubricating and anticorrosive coatings. However, the durability of GO coatings is seriously limited due to its typical brittleness. Cellulose nanofiber (CNF) is a kind of versatile natural material, which is widely used as nanofillers to enhance the mechanical and anticorrosive properties of various matrix materials. In this work, graphene oxide-cellulose nanofiber (GO-CNF) composite coatings with different CNF mass fractions were fabricated on stainless steel substrates by spraying technique. The results of nanoindentation and tribological tests indicate that GO-10.0 wt% CNF composite coating presents the optimum mechanical and tribological properties, with low coefficient of friction (COF<0.2) and long service life of more than 10,000 cycles. In addition, electrochemical corrosion behavior and salt spray experiments demonstrate that the GO-40.0 wt% CNF composite coating can still maintain excellent anticorrosive properties and integrity after one week of long-term corrosion. This result shows that a certain amount of CNF can effectively improve the anticorrosive properties and enhance the protective effect of GO coatings. This strategy of enhancing the tribological and anticorrosive properties by introducing CNF into GO coatings provides a simple and rapid route for developing graphene-based functional coatings for practical engineering applications. [Display omitted] • The graphene oxide-cellulose nanofiber (GO-CNF) composite coating was constructed by spraying method. • The wear-resistant life of GO-10.0 wt% CNF coating reaches more than 10000 cycles. • The good mechanical properties and friction interface film play a key role in lubrication and long-life service. • The GO-40.0 wt% CNF coating with dense brick-mud structure shows the best anti-corrosion properties. • (More highlights in detail are listed in the cover letter). [ABSTRACT FROM AUTHOR]

The introduction of fluorine into graphene endows it with unusual physical and chemical properties. Developing a valid and safe fluorinating method and advancing the fundamental understanding of fluorination mechanism are highly anticipated. Here, a photochemical route for synthesizing fluorinated graphene oxide via one-step ultraviolet (UV) irradiation using F-TEDA-BF4 ( Selectfluor ) as fluorinating reagent is reported. The results suggest that, unlike the general view, the oxygenic groups are not contributed to the reactivity of graphene. An electrophilic fluorination mechanism including UV induced electronic excitation and single electron transfer process is put forward. [ABSTRACT FROM AUTHOR]

In this work, large-size and ultra-thin two-dimensional (2D) zirconia nanosheets (ZrO 2 NSs) were firstly synthesized by wet chemical template method, and then graphene oxide-zirconia nanosheets (GO-ZrO 2 NSs) composite coating with excellent wear-resistance and friction-reduction performances was constructed. The friction and wear tests indicated the GO-ZrO 2 NSs coating presents the lowest friction coefficient of less than 0.12 and the highest service life of more than 20,000 cycles among the prepared series of coatings in air environment under conditions of 0.25 N and 0.02 m/s. Compared with the GO-ZrO 2 nanoparticles (GO-ZrO 2 NPs) coating, its excellent tribological properties are related to the 2D-2D interlayer sliding structure, which can share the normal pressure and the easy friction-induced formation of amorphous transfer film. [Display omitted] • 2D-2D GO-ZrO 2 NSs coating was formed by chemical-template method and dip coating. • This work can make up the gap in the tribological properties of GO and ZrO 2 NSs composite. • The COF and service life of GO-ZrO 2 NSs coating are better than GO-ZrO 2 NPs coating. • 2D-2D interlayer slipping plays an important role in wear-resistance enhancement. [ABSTRACT FROM AUTHOR]

The development of novel electrode materials with high energy density and long cycling life is critical to realize electrochemical capacitive energy storage for practical applications. In this paper, the hybrids of nickle cobalt sulfide/multi-wall carbon nanotubes (NiCo 2 S 4 /MWCNTs) with different contents of MWCNTs are prepared using a facile one-pot solvothermal reaction. As novel active materials for supercapacitors, the electrochemistry tests show that the hybrid of NiCo 2 S 4 /MWCNTs-5 is able to deliver a high specific capacitance of 2080 F g −1 at the current density of 1 A g −1 , even superior rate capability of 61% capacitance retention after a 20-fold increase in current densities, when the content of MWCNTs is up to 5%. More importantly, an asymmetric supercapacitor assembled by NiCo 2 S 4 /MWCNTs-5 as positive electrode and reduced graphene oxide (rGO) as negative electrode delivers a high energy density of 51.8 Wh Kg −1 at a power density of 865 W kg −1 , and 85.7% of its initial capacitance is retained at the current density of 4 A g −1 after 5000 charge-discharge cycles, exhibiting potential prospect for practical applications. [ABSTRACT FROM AUTHOR]

Water-soluble and blue luminescent graphene fluoroxide quantum dots (GFOQDs) with tunable fluorine coverage and size were effectively synthesized from exfoliated fluorinated graphene (FG) by sacrificing certain fluorine to improved solubility and reaction activity. Morphology investigation indicates that the obtained GFOQDs possess narrow size distribution and the average size is 2.5–3.5 nm. Chemical composition analysis confirms that besides C–F covalent bonds, C–O bonds in the forms of hydroxyl and carbonyl co-exist on the structure of GFOQDs. Moreover, photoluminescence performance research considering the surface state and size has also been conducted, and as anticipated in carbon-based quantum dots the GFOQDs exhibit excitation wavelength-dependent properties. Additionally, rather different from other graphene quantum dots (GQDs) that are often susceptible to pH without additional surface passivation, the GFOQDs themselves are poised to resist pH effects and display stable luminescence in both acid and alkali conditions. These results indicate that our method not only opens up a new avenue to prepare GQDs decorated with fluorine and oxygen, but also can find practical applications in novel GQDs-based devices that require water solubility while keep chemical stability and resistance against pH. [ABSTRACT FROM AUTHOR]

Abstract: Fluorine and oxygen co-doped graphene with controllable element coverage was effectively synthesized through simultaneously fluorinating and reducing graphene oxide by pyrolysis of fluorinated graphite. Morphology investigation indicates that the doped graphene is of few-layered thickness, and the prepared films exhibit layered structure through cross-section. Chemical composition analysis confirms that fluorine has been grafted onto graphene scaffold through C F covalent bond, and the doping level can be readily manipulated just by adjusting the reaction temperature. The structural changes of graphene induced by the controllable doping thus facilitate the tunable electrical property, which can be tuned over several orders of magnitude. These results indicate our method is not only potentially useful to tailor the chemical surface and electronic structure of graphene, but also can find applications in novel electronic devices based on graphene co-doped with different dopants. [Copyright &y& Elsevier]

In this work, a lubricating hetero-film (GS-PTFE) was constructed through Al3+-induced self-assembly of graphene oxide (GO) and SiO 2 nanoparticles, and in-situ transfer from polytetrafluoroethane (PTFE) counterpart, which is a simple and surprisingly versatile method. With directly replacing counterpart by GCr15 ball, the tribological results at load of 1 N and frequency of 1 Hz demonstrate that hetero-film exhibits longer wear lives than GS and GO-PTFE film under multi-environments (air, dry N 2 , humidity), especially not worn out within 1 × 104 cycles in 50% humidity. The long durability mainly depends on shielding and lubrication of PTFE, high mechanical strength of GO, rolling effect of SiO 2 , and secondary transfer film. The transfer lubrication theories of PTFE on GO-based film can offer technical guidance for exploiting high-performance bearing cage. [Display omitted] • Counterpart replacing strategy is employed to construct GS-PTFE hetero-film. • GS-PTFE hetero-film has long service life under air, N 2 and humid multi-environments. • The lubrication mechanism of PTFE intercalating and shielding was presented. • Transfer lubrication offers novel idea for designing bearing cage materials. [ABSTRACT FROM AUTHOR]

Here, we report a uniform and thickness controllable Ti 3 C 2 -graphene oxide (GO) nanocomposite film on the silicon substrate prepared by electrophoretic deposition (EPD) for the first time. The effects of deposition voltage on the thickness and tribological performance of Ti 3 C 2 -GO films are investigated. Tribological test results indicate that the nanocomposite film deposited under 35 V exhibites remarkable friction reduction and wear resistance. Namely, the average friction coefficient of Ti 3 C 2 -GO nanocomposite film is reduced by 76% compared with the bare silicon and the wear volume reduced by 94% and 86%, respectively, compared with GO and Ti 3 C 2 films. The improved tribological properties of Ti 3 C 2 -GO nanocomposite films are proposed to be the in-situ formation of tribo-film and the synergy effect between Ti 3 C 2 and GO. A uniform Ti 3 C 2 -graphene oxide nanocomposite film was prepared by a facile electrophoretic deposition method and its tribological properties under ambient conditions were systematically investigated. [Display omitted] • Ti 3 C 2 -GO nanocomposite films were successfully prepared by a facile electrophoretic deposition (EPD) method. • Through the EPD method, high quality films with uniform surface and controllable thickness were obtained. • Ti 3 C 2 -GO film significantly reduced the average friction coefficient and wear volume. • The improved tribological properties of Ti 3 C 2 -GO films are owing to the formation of tribo-film and synergy effect. [ABSTRACT FROM AUTHOR]

• A lamellar GOCr coating is constructed by an ultrafast self-assembly method. • Oxygen-containing groups and structural defects of coating are tuned by hydrazine reduction. • In air, the best lubrication is achieved by balancing functional groups and defects. • In vacuum, the lubrication performance is mainly influenced by defects. Graphene oxide (GO) coating is a potential candidate for improving friction-reduction and wear-resistance capabilities of moving mechanical systems. However, GO coating with diversity of oxygen-containing groups and defects on GO nanosheets dramatically affect its lubrication application. In this work, a facile, green, and ultrafast self-assembly method based on metal coordination interaction has been developed to construct lamellar GOCr coatings. Moreover, hydrazine vapor reduction was selected to tune the oxygen-containing functional groups and defects in a controllable manner while with minimal damage to the substrate. The macro-tribological behavior of the prepared coatings is investigated in both air and vacuum environments to explore the roles of oxygen-containing functional groups and defects on their tribological performances. The results show that, the oxygen-containing functional groups and unstable defect sites with high chemical activity can form hydrogen bonds with water molecules in air, leading to quick lubrication failure. Therefore, the prepared coating exhibits the best lubrication performance when the oxygen-containing functional groups and defects on GO nanosheets reach an optimal balance. In contrast, the lubrication performance of all coatings in vacuum is better than that in air environment, strongly demonstrating that the lubrication property is mainly influenced by defects due to the absence of water molecules in vacuum environment. [ABSTRACT FROM AUTHOR]