Spontaneous Cracking of Graphite Oxide Sheet on Oxygen Deficient ZnO Film

Graphite oxide （GO） is an important material of wide applications. Owing to its good mechanical property, the GO sheet is always expected to be stable and remains flat on various substrates. Here we demonstrate for the first time an unexpected behavior of the GO sheet on oxygen deficient ZnO film, namely the spontaneous cracking of the entire GO sheet into many small pieces. This unusual behavior has been carefully investigated by a series of control experiments and SEM, XPS and PL measurements. It is anticipated that the oxygen vacancies in the oxygen deficient ZnO film can annihilate epoxy groups of the GO sheet, resulting in the unzipping of the aligned epoxy groups on GO sheet. A prototype of the white light detector made from the cracked GO sheet is fabricated and the device demonstrates high stability and good reproducibility.

Theoretical Investigations on Graphite Oxide Immersed in Water or Methanol

Different structures of graphite oxide （GO） with and without water are optimized by density functional theory. Without H20 in interlayer space, the optimized interlayer distances are about 6A, smaller than the experimental values of 6.5-7A. On the other hand, the interlayer distances of hydrated graphite oxide structures are in good agreement with experimental observations. Based on the optimized GO structures, we then simulate the immersion of GO in water or methanol by molecular dynamics. For the dry GO, water and methanol molecules do not enter the nanopore. While for the hydrated GO, the liquid molecules enter the interlayer space and enlarge the interlayer distance, semi-quantitatively reproducing the experimental phenomena.

Enhanced dielectric permittivity of graphite oxide/polyimide composite films

Graphite oxide(GO) was prepared by the pressurized oxidation method and incorporated into polyimide(PI) matrix to fabricate high-k composite films by in-situ polymerization and subsequent thermal treatment. The results show that the as-prepared GO had good dispersion and compatibility in PI matrix due to the introduction of abundant oxygen-containing functional groups during the oxidation. The residual graphitic domains and the thermal treatment induced reduction of GO further enhanced the dielectric permittivity of the resulting GO–PI composites. The dielectric permittivity of the GO–PI composites exhibited a typical percolation behavior with a percolation threshold of 0.0347 of volume ratio and a critical exponent of 0.837. Near the percolation threshold, the dielectric permittivity of the GO–PI composite increased to 108 at 10~2 Hz and was 26 times that of the pure PI.

Catalytic Performance of Graphite Oxide Supported Au Nanoparticles in Aerobic Oxidation of Benzyl Alcohol： Support Effect

Various Au/GO catalysts were prepared by depositing Au nanoparticles on thermally- and chemically-treated graphite oxide （GO） supports using a sol-immobilization method. The surface chemistry and structure of GO supports were characterized by a series of analytical techniques including X-ray photoelectron spectroscopy, temperature-programmed desorption and Raman spectroscopy. The results show that thermal and chemical treatments have large influence on the presence of surface oxygenated groups and the crystalline structure of GO supports. A strong support effect was observed on the catalytic activity of Au/GO catalysts in the liquid phase aerobic oxidation of benzyl alcohol. Compared to the amount and the type of surface oxygen functional groups, the ordered structure of GO supports may play a more important role in determining the catalytic performance of Au/GO catalysts.

SYNTHESIS OF POLY(VINYL ACETATE)-INTERCALATED GRAPHITE OXIDE BY AN IN SITU INTERCALATIVE POLYMERIZATION

Graphite oxide, a pseudo-two-dimensional solid in bulk form, was synthesized from natural graphite powder by oxidization with KMnO4 in concentrated H2SO4. The poly(vinyl acetate)-intercalated graphite oxide nano-composite was prepared by an in situ intercalative polymerization reaction, in which n-octanol-graphite oxide intercalation compounds were first obtained, vinyl acetate monomer was then dispersed into the interlayer of modified graphite oxide, followed by thermal polymerization of the monomer. It was experimentally shown that the c-axis space of poly(vinyl acetate)-intercalated graphite oxide was increased to 0.115 nm, which suggested there existed a monolayer of poly(vinyl acetate) chain between the layers of graphite oxide. The nanocomposite was also characterized with thermal analysis and FT-IR spectrometry.

Preparation of N-doped graphite oxide for supercapacitors by NH_(3) cold plasma

In this work,N-doped graphite oxide(GO-P)was prepared by cold plasma treatment of GO using a mixture of NH_(3) and Ar as the working gas.When the ratios of NH_(3):Ar were 1:2,1:3,and 1:4,the specific capacitances of the GO-P(NH_(3):Ar=1:2),GO-P(NH_(3):Ar=1:3),and GO-P(NH_(3):Ar=1:4)were 124.5,187.7,and 134.6 F·g^(-1),respectively,which were 4.7,7.1,and 5.1 times that of GO at the current density of 1 A·g^(-1).The capacitance retention of the GO-P(NH_(3):Ar=1:3)was 80%when it was cycled 1000 times.The characterization results showed that the NH_(3)cold plasma could effectively produce N-doped GO and generate more active defects.The N/C ratio and the contents of pyridinic nitrogen and graphitic nitrogen of the GO-P(NH_(3):Ar=1:3)were the highest.These were conducive to providing pseudocapacitance and reducing the internal resistance of the electrode.In addition,the ID/IGof the GO-P(NH_(3):Ar=1:3)(1.088)was also the highest,indicating the highest number of defects.The results of discharge parameters measurement and in situ optical emission spectroscopy diagnosis of NH_(3) plasma showed that the discharge is the strongest when the ratio of NH_(3):Ar was 1:3,thereby the generated nitrogen active species can effectively promote N-doping.The N-doping and abundant defects were the keys to the excellent electrochemical performance of the GO-P(NH_(3):Ar=1:3).NH_(3) cold plasma is a simple and rapid method to prepare N-doped GO and regulate the N-doping to prepare high-performance supercapacitors.

In situ self-nucleophilic synthesis of nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porous structure for high-rate lithium ion batteries

It is the core to improve the electron/ion transfer features of Li_(4)Ti_(5)O_(12) for achieving high-rate anode in lithium ion batteries.By directly using graphite oxide powder,nano-Li_(4)Ti_(5)O_(12)/reduced graphite oxide composite with mesopore-oriented porosity is prepared through one-pot facile ball-milling method in this work.Synthesis mechanism underlying the self-nucleophilic effect of oxygen-containing functional groups in graphite oxide is substantiated.Reactants can intercalate into graphite oxide bulk and in-situ generate nanoparticles.Subsequently,graphite oxide with nanoparticles generated inside can obtain a mesopore-oriented porous structure under ball-milling.Furthermore,the synergistic effects of Li_(4)Ti_(5)O_(12) nanoparticles and mesopore-oriented porosity strengthen composites with rapid Li^(+)diffusion and electron conductive frameworks.The obtained optimal LTO/GO-1.75 composite displays excellent high-rate capability(136 mA·h/g at 7000 mA/g)and good cycling stability(a capacity retention of 72%after 1000 cycles at 7000 mA/g).Additionally,the reactants concentration in this demonstrated strategy is as high as 30 wt%−40 wt%,which is over 6 times that of traditional methods with GO suspensions.It means that the strategy can significantly increase the yield,showing big potential for large-scale production.

Supported Manganese Oxide on Graphite Oxide: Catalytic Oxidation of Nitrogen Oxide in Waste Gas

The catalytic oxidation of nitrogen oxide( NO) from waste gas was investigated using advanced oxidation process based on sulfate radicals. The manganese oxide immobilized on graphene oxide( GO) can activate peroxymonosulfate( PMS) for the oxidation of NO in waste gas. The Mn3O4 / GO catalyst system was characterized via X-ray diffraction( XRD), Fourier transform infrared spectrocopy( FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy( XPS), energy dispersive X-ray spectroscopy( EDS),and scanning electron microscope( SEM).The results showed that Mn3O4 was distributed on GO. The Mn3O4 /GO catalyst system exhibited efficient activity for NO oxidation when the Mn3O4 /GO catalyst had an optimum Mn3O4 loading. In addition,the best catalytic oxidation could be achieved within 60 min with 0. 25 mmol /L Mn3 O4 /GO catalyst, and2 mmol /L PMS dosage at 25 ℃. The catalysts also exhibited stable performance after several rounds of regeneration. Therefore,the results may have significant technical implication for utilizing Mn3O4 /PMS to oxidize NO for offgas treatment.

Analysis of CO_3O_4/ Mildly Oxidized Graphite Oxide(mGO)Nanocomposites of Mild Oxidation Degree for the Removal of Acid Orange 7

In this study,a series of Co_3O_4/ mildly oxidized graphite oxide(mGO) nanocatalysts(Co_3O_4/ mGO-l,Co_3O_4/ mGO-2 and Co_3O_4/mGO-3) were synthesized through solvothermal method and used as a mediator for the heterogeneous peroxymonosulfate(PMS)activation.The performance of CO_3O_4 / mGO/PMS system was investigated using acid orange 7(AO7).Results showed that Co_3O_4/mGO-3 had the best degradation efficiency of AO7 and the removal rate was above 90%in about 6 min.The phenomenon indicated the catalytic activity of Co_3O_4/mGO composites was related to the oxidation degree of graphite oxide(GO).In addition,experiments showed the content of Co_3O_4 had an effect on the catalytic activity.The composites were characterized with X-ray powder diffraction(XRD),FTIR,Raman,X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM).According to the charactrization and synergistic catalytic mechanism,the generation of Co—OH complexes found to be the initial step to activate PMS in the heterogeneous system of Co_3O_4/mGO hybrid.

Mechanism of Fume Suppression and Performance on Asphalt of Expanded Graphite for Pavement under High Temperature Condition

Fume suppression mechanisms and the effect of expanded graphite on the performance of asphalt were studied by applying infrared spectroscopy（FT-IR）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and comprehensive thermal analysis（TG, DSC）. The experimental results confirm that asphalt which is mixed with expandable graphite will expand in the process of hot mix, and the expanded graphite layer will swell by the light component in the asphalt. The light component in the asphalt and PAHs adsorption on expanded graphite surface or part of the plug in the expanded graphite layer between plates made nucleation crystallization growth. And the Van der Waals force and the bonding of the lattice can effectively restrain the asphalt fume release. Meanwhile, the expanding agent with oxidative can spread into the asphalt, leading to asphalt oxygenated and plastic abate, while the ductility decreases. Expanded graphite, SBS modifier and environment- friendly plasticizers are used to composite modified asphalt. According to asphalt fume release experiment, normal test of asphalt performance, Brookfield viscosity test, RTFOT test and asphalt mixture tests（high temperature stability, low temperature stability, water stability）, it has been proven that the modified asphalt’s performance is better than that of matrix asphalt and equivalent to that of SBS modified asphalt. Furthermore, it has good fume suppression effect.

Microstructure Evolution of Graphite Intercalated by TiO_2 and Its Photocatalytic Activity

An intercalative composite of graphite oxide （GO） as host intercalated by an object of TiO2 nanoparticles was obtained at low temperature by mixing GO with Ti（SO4）2 solution, and by another object of Ti2O3 while mixing with TiCl4 ethanol solution. Microstructures of the GO and its intercalative composites at different C/Ti ratio were studied by XRD, SEM, AFM and FF-IR, and the evolution of these lamellar structures was studied based on the temperature change. The photocatalytic activity of the intercalative composites was characterized according to the degradation of methyl orange. The intercalative composite formed by Ti（SO4）2 solution presents an excellent photocatalytic reactivity, while that formed by TiCl4 presents no observablly photocatalytic reactivity. The electric conductivity variation of different composites was checked, in order to investigate the role of the possible electron transfer between the graphite layer and TiO2 nanocrystal during TiO2 excited by UV light irradiation.

Effect of surface oxidation on the interfacial and mechanical properties in graphite/epoxy composites composite bipolar plates

Epoxy resin-reinforced graphite composites have found extensive application as bipolar plates in fuel cells for stationary power supplies,valued for their lightweight nature and exceptional durability.To enhance the interfacial properties between graphite and epoxy resin(EP),surface oxidation of graphite was carried out using diverse functional groups.Experimental assessments illustrated that the composites with graphite oxide resulted in heightened mechanical strength and toughness compared to pristine graphite,which could be attributed to the excellent interface connection.Moreover,these composites displayed remarkable conductivity while simultaneously retaining their mechanical attributes.Furthermore,molecular dynamics simulations outcomes unveiled that the inclusion of oxygen-containing functional groups on the graphite surface augmented the interfacial energy with EP,and the interface morphology between graphite and resin exhibited heightened stability throughout the stretching process.This simple and effective technique presents opportunities for improving composites interfaces,enabling high load transfer efficiency,and opens up a potential path for developing strong and tough composite bipolar plates for fuel cells.

High Performance Ultraviolet Photodetector Fabricated with ZnO Nanoparticles-graphene Hybrid Structures

Ultraviolet （UV） photodetector constructed by ZnO material has attracted intense research and commercial interest. However, its photoresistivity and photoresonse are still unsatisfied. Herein, we report a novel method to assemble ZnO nanoparticles （NPs） onto the reduced graphite oxide （RGO） sheet by simple hydrothermal process without any surfactant. It is found that the high-quality crystallized ZnO NPs with the average diameter of 5 nm are well dispersed on the RGO surface, and the density of ZnO NPs can be readily controlled by the concentration of the precursor. The photodetector fabricated with this ZnO NPs- RGO hybrid structure demonstrates an excellent photoresponse for the UV irradiation. The results make this hybrid especially suitable as a novel material for the design and fabrication of high performance UV photodector.

Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene

Pd/C catalysts were prepared by deposited Pd nanoparticles （NPs） on different carbon supports including activated carbon （AC）, graphite oxide （GO）, and reduced graphite oxide （rGO） using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.

The Prospective Two-Dimensional Graphene Nanosheets: Preparation, Functionalization, and Applications

Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties.With excellent electrical conductivity of 6000 S/cm, which is independent on chirality, graphene is a promising material for high-performance nanoelectronics, transparent conductor, as well as polymer composites. On account of its Young's Modulus of 1 TPa and ultimate strength of 130 GPa, isolated graphene sheet is considered to be among the strongest materials ever measured. Comparable with the single-walled carbon nanotube bundle,graphene has a thermal conductivity of 5000 W/(m·K), which suggests a potential application of graphene in polymer matrix for improving thermal properties of the graphene/polymer composite. Furthermore, graphene exhibits a very high surface area, up to a value of 2630 m^2/g. All of these outstanding properties suggest a wide application for this nanometer-thick, two-dimensional carbon material. This review article presents an overview of the significant advancement in graphene research: preparation, functionalization as well as the properties of graphene will be discussed. In addition, the feasibility and potential applications of graphene in areas, such as sensors, nanoelectronics and nanocomposites materials, will also be reviewed.

Pd nanoparticles immobilized on graphite oxide modified with a base: Highly efficient catalysts for selective hydrogenation of citral

In this work, the Pd-based catalysts were designed via immobilizing Pd nanoparticles on graphite oxide (GO) modified with organic base, 1,1,3,3-tetramethylguanidine (TMG), which was used for the selective hydrogenation of citral. These catalysts were characterized by various techniques including IR, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the Pd particles with size less than 5 nm were uniformly distributed throughout the support, and they were in the electron-deficient state due to the strong interactions with the modified support. The resultant Pd-TMG/GO catalyst displayed high efficiency for the selective hydrogenation of citral with a turnover frequency of 7100 h-1 as well as superior selectivity to citronellal of 89.6%. Moreover, the catalyst can be reused for five times without obvious activity loss, which may result from its stable structure.

Controllable synthesis of titania/reduced graphite oxide nanocomposites with various titania phase compositions and their photocatalytic performance

A facile method is presented for preparing TiO2/reduced graphite oxide （RGO） nanocomposites with phase-controlled TiO2 nanoparticles via redox reaction between the reductive titanium （III） precursor and graphite oxide （GO）, and a series of TiO2/RGO composites with various TiO2 phase compositions were obtained. In all the titania/RGO composites, the TiO2 nanoparticles were uniformly distributed on the surface of the RGO. The TiO2 consisted of anatase phase particles in the form of square-plates with edges less than 10 nm and the rutile phase nanorods in diameters less than 10 nm. The performances of the as-prepared TiO2/RGO composites were investigated on catalytically degrading phenol under visible light irradiation. The TiO2/RGO composites can effectively degrade phenol under visible light irradiation, and the phase composition of TiO2 in the composites significantly influences the activities of these catalysts.

Graphite oxide-catalyzed acetylation of alcohols and phenols

Graphite oxide （GO） was used as a catalyst for the reactions of alcohols and phenols with acetic anhydride. The acetates of primary and secondary alcohols were prepared in good to excellent yields in short reaction time under mild conditions. Electron deficient phenols could be converted to the corresponding acetates steadily. As an efficient catalyst, GO is easily available, cheap, moderately toxic and weakly acidic.

High Temperature Phase Transitions of Graphene Oxide Paper from Graphite Oxide Solution

Graphene oxide paper （GOP） can be prepared through simplified filtration of a graphite oxide solution. It possesses similar properties to graphene. In this study, the graphite oxide solution was synthesized from commercial graphite by means of Hummer＇s method. It corresponds to the dried GOP that was prepared by deposition on a cellulose filter. It is found that the mesophase of the dried graphene oxide papers obtained from the graphite was thermotropic hexagonal columnar liquid crystal. Its higher temperature transitions were found at 80 ℃, 150 ℃ and 170 ℃-180 ℃. Therefore, it could be used for thermal storage and conductive materials in the future.

Dehydrogenative Aromatization of Saturated Aromatic Compounds by Graphite Oxide and Molecular Sieves

Graphite oxide （GO） has attracted much attention of material and catalysis chemists recently. Here we describe a combination of GO and molecular sieves for the dehydrogenative aromatization. GO prepared through improved Hummers method showed high oxidative activity in this reaction. Partially or fully saturated aromatic compounds were converted to their corresponding dehydrogenated aromatic products with fair to excellent conversions and selectivities. As both GO and molecular sieves are easily available, cheap, lowly toxic and have good tolerance to various functional groups, this reaction provides a facile approach toward aromatic compounds from their saturated precursors