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Sample records for graphene surface preparation

  1. The Preparation of Graphene

    Chen Yanyan

    2015-01-01

    Graphene has unique structure and possesses excellent physical and chemical properties, and it has received a great deal of attention in related research fields. The quality, quantity and application of graphene are related to its preparation methods. At present the bottleneck of graphene research is that both high-quality and large quantity of graphene could not be obtained simultaneously and the reason is that the basic mechanism of graphene formation has mot been wel understood.

  2. Novel Graphene-Gold Hybrid Nanostructures Constructed via Sulfur Modified Graphene: Preparation and Characterization by Surface and Electrochemical Techniques

    Shervedani, Reza Karimi; Amini, Akbar

    2014-01-01

    range, from 1.0 to 12.0 mM and 0.1 to 8.0 mM glucose, with a detection limit of 9.3 and 4.1 μM and high sensitivity, 47.6 μA mM −1 cm −2 and 45.0 kΩ/log(C glucose /mM) obtained by voltammetry and electrochemical impedance spectroscopy (EIS), respectively. According to the results obtained by analysis of the EIS experimental data, the source of enhanced activity was found to be originated from the synergistic effect of GNs and AuNPs, the role of ATP mediating assembling of GNs-AuNPs hybrid on GCE, and the increase in the surface roughness. This work opens up a new and facile way for direct preparation of metal nanoparticles embedded in GNs, which will enable exciting opportunities in advanced applications based on graphene-metal hybrids like electrocatalysis for energy conversion and highly sensitive modifier films for electrochemical sensors and biosensors

  3. Carbon Papers and Aerogels Based on Graphene Layers and Chitosan: Direct Preparation from High Surface Area Graphite.

    Barbera, Vincenzina; Guerra, Silvia; Brambilla, Luigi; Maggio, Mario; Serafini, Andrea; Conzatti, Lucia; Vitale, Alessandra; Galimberti, Maurizio

    2017-12-11

    In this work, carbon papers and aerogels based on graphene layers and chitosan were prepared. They were obtained by mixing chitosan (CS) and a high surface area nanosized graphite (HSAG) in water in the presence of acetic acid. HSAG/CS water dispersions were stable for months. High resolution transmission electron microscopy revealed the presence of few graphene layers in water suspensions. Casting or lyophilization of such suspensions led to the preparation of carbon paper and aerogel, respectively. In X-ray spectra of both aerogels and carbon paper, peaks due to regular stacks of graphene layers were not detected: graphene with unaltered sp 2 structure was obtained directly from graphite without the use of any chemical reaction. The composites were demonstrated to be electrically conductive thanks to the graphene. Chitosan thus makes it possible to obtain monolithic carbon aerogels and flexible and free-standing graphene papers directly from a nanosized graphite by avoiding oxidation to graphite oxide and successive reduction. Strong interaction between polycationic chitosan and the aromatic substrate appears to be at the origin of the stability of HSAG/CS adducts. Cation-π interaction is hypothesized, also on the basis of X-ray photoelectron spectroscopy findings. This work paves the way for the easy large-scale preparation of carbon papers through a method that has a low environmental impact and is based on a biosourced polymer, graphene, and water.

  4. Preparation and Characterization of Graphene

    Xu Man

    2015-01-01

    Full Text Available The homogeneous-dispersed graphene oxide was prepared by the improved Hummers method, which would be reduced to graphene with the reducing agent called hydrazine hydrate. The X-ray diffraction, Infrared spectroscopy, Raman spectra and Transmission electron microscopy were used to analysis the phase, morphology and structure of the graphene and graphene oxide. The results show that the graphene oxide and reduced graphene oxide prepared via this method, whose degree of oxidation and reduction are high; Also obtained a higher well-disperses and less structural imperfection of the graphene that was manufactured in the reducing system that added ammonia reduction

  5. Green Preparation of Epoxy/Graphene Oxide Nanocomposites Using a Glycidylamine Epoxy Resin as the Surface Modifier and Phase Transfer Agent of Graphene Oxide.

    Tang, Xinlei; Zhou, Yang; Peng, Mao

    2016-01-27

    In studies of epoxy/graphene oxide (GO) nanocomposites, organic solvents are commonly used to disperse GO, and vigorous mechanical processes and complicated modification of GO are usually required, increasing the cost and hindering the development and application of epoxy nanocomposites. Here, we report a green, facile, and efficient method of preparing epoxy/GO nanocomposites. When triglycidyl para-aminophenol (TGPAP), a commercially available glycidyl amine epoxy resin with one tertiary amine group per molecule, is used as both the surface modifier and phase transfer agent of GO, GO can be directly and rapidly transferred from water to diglycidyl ether of bisphenol A and other types of epoxy resins by manual stirring under ambient conditions, whereas GO cannot be transferred to these epoxy resins in the absence of TGPAP. The interaction between TGPAP and GO and the effect of the TGPAP content on the dispersion of GO in the epoxy matrix were investigated systematically. Superior dispersion and exfoliation of GO nanosheets and remarkably improved mechanical properties, including tensile and flexural properties, toughness, storage modulus, and microhardness, of the epoxy/GO nanocomposites with a suitable amount of TGPAP were demonstrated. This method is organic-solvent-free and technically feasible for large-scale preparation of high-performance nanocomposites; it opens up new opportunities for exploiting the unique properties of graphene or even other nanofillers for a wide range of applications.

  6. Water on graphene surfaces

    Gordillo, M C [Departamento de Sistemas Fisicos, Quimicos y Naturales, Facultad de Ciencias Experimentales, Universidad Pablo de Olavide, Carretera de Utrera, km 1, E-41013 Sevilla (Spain); Marti, J, E-mail: cgorbar@upo.e, E-mail: jordi.marti@upc.ed [Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, B4-B5 Campus Nord, E-08034 Barcelona, Catalonia (Spain)

    2010-07-21

    In this paper, we summarize the main results obtained in our group about the behavior of water confined inside or close to different graphene surfaces by means of molecular dynamics simulations. These include the inside and outside of carbon nanotubes, and the confinement inside a slit pore or a single graphene sheet. We paid special attention to some thermodynamical (binding energies), structural (hydrogen-bond distributions) and dynamic (infrared spectra) properties, and their comparison to their bulk counterparts.

  7. The preparation and graphene surface coating NaTi_2(PO_4)_3 as cathode material for lithium ion batteries

    Li, Na; Wang, Yanping; Rao, Richuan; Dong, Xiongzi; Zhang, Xianwen; Zhu, Sane

    2017-01-01

    Graphical abstract: The NaTi_2(PO_4)_3/graphene composite is used directly as cathode electrode material for lithium-ion battery by using metal lithium as an anode electrode. Meanwhile, the electrochemical properties of the composite in this system is firstly studied in detail. The NaTi_2(PO_4)_3/graphene composite exhibits the better rate and cyclic performance than NaTi_2(PO_4)_3, which is ascribed to its stable 3-D framework and the enhanced electronic conduction resulting from the graphene sheets surface modification. - Highlights: • The graphene coated NaTi_2(PO_4)_3 was prepared by a simple sol-gel method followed by calcination. • The electrochemical properties of the NaTi_2(PO_4)_3/graphene composite was firstly studied in detail when used as cathode electrode material for lithium-ion batteries. • The electrochemical reaction mechanism of NaTi_2(PO_4)_3/graphene composite was investigated by ex situ XRD. - Abstract: The graphene coated NaTi_2(PO_4)_3 has been fabricated via a simple sol-gel process followed by calcination. The NaTi_2(PO_4)_3/graphene (NTP/G) composite is used directly as cathode electrode material for lithium-ion battery and the electrochemical properties of the composite in this system is firstly studied in detail. In the charge-discharge process, two Li"+ can occupy octahedral M (2) site and be reversibly intercalated into the 3D framework of NTP through the ion conduction channel where almost all of Na"+ are immobilized to sustain the framework. At 5C rate, the capacity retention of the NTP/G composite after 800 cycles is still up to 82.7%. The superior electrochemical properties of NTP/G is ascribed to its stable 3-D framework and the enhanced electronic conduction resulting from the graphene sheets surface modification.

  8. Alloyed surfaces: New substrates for graphene growth

    Tresca, C.; Verbitskiy, N. I.; Fedorov, A.; Grüneis, A.; Profeta, G.

    2017-11-01

    We report a systematic ab-initio density functional theory investigation of Ni(111) surface alloyed with elements of group IV (Si, Ge and Sn), demonstrating the possibility to use it to grow high quality graphene. Ni(111) surface represents an ideal substrate for graphene, due to its catalytic properties and perfect matching with the graphene lattice constant. However, Dirac bands of graphene growth on Ni(111) are completely destroyed due to the strong hybridization between carbon pz and Ni d orbitals. Group IV atoms, namely Si, Ge and Sn, once deposited on Ni(111) surface, form an ordered alloyed surface with √{ 3} ×√{ 3} -R30° reconstruction. We demonstrate that, at variance with the pure Ni(111) surface, alloyed surfaces effectively decouple graphene from the substrate, resulting unstrained due to the nearly perfect lattice matching and preserves linear Dirac bands without the strong hybridization with Ni d states. The proposed surfaces can be prepared before graphene growth without resorting on post-growth processes which necessarily alter the electronic and structural properties of graphene.

  9. The preparation and graphene surface coating NaTi{sub 2}(PO{sub 4}){sub 3} as cathode material for lithium ion batteries

    Li, Na; Wang, Yanping; Rao, Richuan; Dong, Xiongzi [Department of Chemical and Chemical Engineering, Hefei normal University, Hefei, Anhui 230601 (China); Zhang, Xianwen, E-mail: 18326056237@163.com [Institute of Advanced Energy Technology & Equipment, Hefei University of Technology, 193 Tunxi Road, Hefei, Anhui 230009 (China); Zhu, Sane, E-mail: sdjnlina@163.com [Department of Chemistry and Materials Engineering, Hefei University, Hefei, Anhui 230601 (China)

    2017-03-31

    Graphical abstract: The NaTi{sub 2}(PO{sub 4}){sub 3}/graphene composite is used directly as cathode electrode material for lithium-ion battery by using metal lithium as an anode electrode. Meanwhile, the electrochemical properties of the composite in this system is firstly studied in detail. The NaTi{sub 2}(PO{sub 4}){sub 3}/graphene composite exhibits the better rate and cyclic performance than NaTi{sub 2}(PO{sub 4}){sub 3}, which is ascribed to its stable 3-D framework and the enhanced electronic conduction resulting from the graphene sheets surface modification. - Highlights: • The graphene coated NaTi{sub 2}(PO{sub 4}){sub 3} was prepared by a simple sol-gel method followed by calcination. • The electrochemical properties of the NaTi{sub 2}(PO{sub 4}){sub 3}/graphene composite was firstly studied in detail when used as cathode electrode material for lithium-ion batteries. • The electrochemical reaction mechanism of NaTi{sub 2}(PO{sub 4}){sub 3}/graphene composite was investigated by ex situ XRD. - Abstract: The graphene coated NaTi{sub 2}(PO{sub 4}){sub 3} has been fabricated via a simple sol-gel process followed by calcination. The NaTi{sub 2}(PO{sub 4}){sub 3}/graphene (NTP/G) composite is used directly as cathode electrode material for lithium-ion battery and the electrochemical properties of the composite in this system is firstly studied in detail. In the charge-discharge process, two Li{sup +} can occupy octahedral M (2) site and be reversibly intercalated into the 3D framework of NTP through the ion conduction channel where almost all of Na{sup +} are immobilized to sustain the framework. At 5C rate, the capacity retention of the NTP/G composite after 800 cycles is still up to 82.7%. The superior electrochemical properties of NTP/G is ascribed to its stable 3-D framework and the enhanced electronic conduction resulting from the graphene sheets surface modification.

  10. Ultrasonic-assisted preparation of graphene oxide carboxylic acid polyvinyl alcohol polymer film and studies of thermal stability and surface resistivity.

    Li, Yongshen; Li, Jihui; Li, Yuehai; Li, Yali; Song, Yunan; Niu, Shuai; Li, Ning

    2018-01-01

    In this paper, flake graphite, nitric acid and acetic anhydride are used to prepare graphene oxide carboxylic acid (GO-COOH) via an ultrasonic-assisted method, and GO-COOH and polyvinyl alcohol polymer (PVA) are used to synthesize graphene oxide carboxylic acid polyvinyl alcohol polymer (GO-COOPVA) via the ultrasonic-assisted method, and GO-COOPVA is used to manufacture graphene oxide carboxylic acid polyvinyl alcohol polymer film (GO-COOPVA film) via a solidification method, and the structure and morphology of GO-COOH, GO-COOPVA and GO-COOPVA film are characterized, and the thermal stability and surface resistivity are measured in the case of the different amount of GO-COOH. Based on the characterization and measurement, it has been successively confirmed and attested that carboxyl groups implant on 2D lattice of GO to form GO-COOH, and GO-COOH and PVA have the esterification reaction to produce GO-COOPVA, and GO-COOPVA consists of 2D lattice of GO-COOH and the chain of PVA connected in the form of carboxylic ester, and GO-COOPVA film is composed of GO-COOPVA, and the thermal stability of GO-COOPVA film obviously improves in comparison with PVA film, and the surface resistivity of GO-COOPVA film clearly decreases. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Preparation of Reduced Graphene Oxides as Electrode Materials for Supercapacitors

    Bai, Yaocai

    2012-06-01

    Reduced graphene oxide as outstanding candidate electrode material for supercapacitor has been investigated. This thesis includes two topics. One is that three kinds of reduced graphene oxides were prepared by hydrothermal reduction under different pH conditions. The pH values were found to have great influence on the reduction of graphene oxides. Acidic and neutral media yielded reduced graphene oxides with more oxygen-functional groups, lower specific surface areas but broader pore size distributions than those in basic medium. Variations induced by the pH changes resulted in great differences in the supercapacitor performance. The graphene produced in the basic solution presented mainly electric double layer behavior with specific capacitance of 185 F/g, while the other two showed additional pseudocapacitance behavior with specific capacitance of 225 F/g (acidic) and 230 F/g (neutral), all at a constant current density of 1A/g. The other one is that different reduced graphene oxides were prepared via solution based hydrazine reduction, low temperature thermal reduction, and hydrothermal reduction. The as- prepared samples were then investigated by UV-vis spectroscopy, X-ray diffraction, Raman spectroscopy, and Scanning electron microscope. The supercapacitor performances were also studied and the hydrothermally reduced graphene oxide exhibited the highest specific capacitance.

  12. Synthesis of transfer-free graphene on cemented carbide surface.

    Yu, Xiang; Zhang, Zhen; Liu, Fei; Ren, Yi

    2018-03-19

    Direct growth of spherical graphene with large surface area is important for various applications in sensor technology. However, the preparation of transfer-free graphene on different substrates is still a challenge. This study presents a novel approach for the transfer-free graphene growth directly on cemented carbide. The used simple thermal annealing induces an in-situ transformation of magnetron-sputtered amorphous silicon carbide films into the graphene matrix. The study reveals the role of Co, a binding phase in cemented carbides, in Si sublimation process, and its interplay with the annealing temperature in development of the graphene matrix. A detailed physico-chemical characterisation was performed by structural (XRD analysis and Raman spectroscopy with mapping studies), morphological (SEM) and chemical (EDS) analyses. The optimal bilayer graphene matrix with hollow graphene spheres on top readily grows at 1000 °C. Higher annealing temperature critically decreases the amount of Si, which yields an increased number of the graphene layers and formation of multi-layer graphene (MLG). The proposed action mechanism involves silicidation of Co during thermal treatment, which influences the existing chemical form of Co, and thus, the graphene formation and variations in a number of the formed graphene layers.

  13. Surface acoustic wave propagation in graphene film

    Roshchupkin, Dmitry; Plotitcyna, Olga; Matveev, Viktor; Kononenko, Oleg; Emelin, Evgenii; Irzhak, Dmitry; Ortega, Luc; Zizak, Ivo; Erko, Alexei; Tynyshtykbayev, Kurbangali; Insepov, Zinetula

    2015-01-01

    Surface acoustic wave (SAW) propagation in a graphene film on the surface of piezoelectric crystals was studied at the BESSY II synchrotron radiation source. Talbot effect enabled the visualization of the SAW propagation on the crystal surface with the graphene film in a real time mode, and high-resolution x-ray diffraction permitted the determination of the SAW amplitude in the graphene/piezoelectric crystal system. The influence of the SAW on the electrical properties of the graphene film was examined. It was shown that the changing of the SAW amplitude enables controlling the magnitude and direction of current in graphene film on the surface of piezoelectric crystals

  14. Graphene growth and stability at nickel surfaces

    Lahiri, Jayeeta; S Miller, Travis; J Ross, Andrew; Adamska, Lyudmyla; Oleynik, Ivan I; Batzill, Matthias

    2011-01-01

    The formation of single-layer graphene by exposure of a Ni(111) surface to ethylene at low pressure has been investigated. Two different growth regimes were found. At temperatures between 480 and 650 deg. C, graphene grows on a pure Ni(111) surface in the absence of a carbide. Below 480 deg. C, graphene growth competes with the formation of a surface Ni 2 C carbide. This Ni 2 C phase suppresses the nucleation of graphene. Destabilization of the surface carbide by the addition of Cu to the surface layer facilitates the nucleation and growth of graphene at temperatures below 480 deg. C. In addition to the growth of graphene on Ni substrates, the interaction between graphene and Ni was also studied. This was done both experimentally by Ni deposition on Ni-supported graphene and by density functional theory calculation of the work of adhesion between graphene and Ni. For graphene sandwiched between two Ni-layers, the work of adhesion between graphene and the Ni substrate was found to be four times as large as that for the Ni-supported graphene without a top layer. This stronger interaction may cause the destruction of graphene that is shown experimentally to occur at ∼200 0 C when Ni is deposited on top of Ni-supported graphene. The destruction of graphene allows the Ni deposits to merge with the substrate Ni. After the completion of this process, the graphene sheet is re-formed on top of the Ni substrate, leaving no Ni at the surface.

  15. Preparation and charaterization of Pt/functionalized graphene and its electrocatalysis for methanol oxidation

    Liang, Qingsheng; Zhang, Li; Cai, Maolin; Li, Yong; Jiang, Kun; Zhang, Xin; Shen, Pei Kang

    2013-01-01

    Water-dispersible 8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (PyS)-functionalized graphene (PyS-graphene) sheets were prepared by a π–π interaction method, in which the aromatic organic molecules of PyS were reacted with graphene. The PyS-graphene sheets were used as Pt nanoparticle support to prepare a Pt/PyS-graphene catalyst for direct methanol fuel cells. The prepared materials were characterized by ultraviolet spectrometry (UV–vis), Fourier transform infrared spectrometry (FT-IR), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy (SERS), and transmission electron microscopy (TEM). The electrocatalytic properties of the catalysts for methanol oxidation were evaluated by cyclic voltammetry (CV). The Pt/PyS-graphene catalysts were found to have higher electrocatalytic activity for methanol oxidation than Pt/graphene catalyst. This finding can be attributed to the introduction of negative sulfonic (SO 3 − ) groups to the graphene sheet surface, which makes the graphene sheets dispersible in water. Consequently, the Pt nanoparticles were uniformly and securely deposited onto the graphene sheet surface. These results suggested that the sulfonic group-modified water-dispersible graphene sheets can be used to improve the electrocatalytic activity of catalysts for fuel cells

  16. Preparation of Reduced Graphene Oxides as Electrode Materials for Supercapacitors

    Bai, Yaocai

    2012-01-01

    Reduced graphene oxide as outstanding candidate electrode material for supercapacitor has been investigated. This thesis includes two topics. One is that three kinds of reduced graphene oxides were prepared by hydrothermal reduction under different

  17. Surface enhanced Raman spectroscopy on a flat graphene surface

    Xu, Weigao; Ling, Xi; Xiao, Jiaqi; Dresselhaus, Mildred S.; Kong, Jing; Xu, Hongxing; Liu, Zhongfan; Zhang, Jin

    2012-01-01

    Surface enhanced Raman spectroscopy (SERS) is an attractive analytical technique, which enables single-molecule sensitive detection and provides its special chemical fingerprints. During the past decades, researchers have made great efforts towards an ideal SERS substrate, mainly including pioneering works on the preparation of uniform metal nanostructure arrays by various nanoassembly and nanotailoring methods, which give better uniformity and reproducibility. Recently, nanoparticles coated with an inert shell were used to make the enhanced Raman signals cleaner. By depositing SERS-active metal nanoislands on an atomically flat graphene layer, here we designed a new kind of SERS substrate referred to as a graphene-mediated SERS (G-SERS) substrate. In the graphene/metal combined structure, the electromagnetic “hot” spots (which is the origin of a huge SERS enhancement) created by the gapped metal nanoislands through the localized surface plasmon resonance effect are supposed to pass through the monolayer graphene, resulting in an atomically flat hot surface for Raman enhancement. Signals from a G-SERS substrate were also demonstrated to have interesting advantages over normal SERS, in terms of cleaner vibrational information free from various metal-molecule interactions and being more stable against photo-induced damage, but with a comparable enhancement factor. Furthermore, we demonstrate the use of a freestanding, transparent and flexible “G-SERS tape” (consisting of a polymer-layer-supported monolayer graphene with sandwiched metal nanoislands) to enable direct, real time and reliable detection of trace amounts of analytes in various systems, which imparts high efficiency and universality of analyses with G-SERS substrates. PMID:22623525

  18. Factors influencing graphene growth on metal surfaces

    Loginova, E; Bartelt, N C; McCarty, K F [Sandia National Laboratories, Livermore, CA (United States); Feibelman, P J [Sandia National Laboratories, Albuquerque, NM (United States)], E-mail: mccarty@sandia.gov

    2009-06-15

    Graphene forms from a relatively dense, tightly bound C-adatom gas when elemental C is deposited on or segregates to the Ru(0001) surface. Nonlinearity of the graphene growth rate with C-adatom density suggests that growth proceeds by addition of C atom clusters to the graphene edge. The generality of this picture has now been studied by use of low-energy electron microscopy (LEEM) to observe graphene formation when Ru(0001) and Ir(111) surfaces are exposed to ethylene. The finding that graphene growth velocities and nucleation rates on Ru have precisely the same dependence on adatom concentration as for elemental C deposition implies that hydrocarbon decomposition only affects graphene growth through the rate of adatom formation. For ethylene, that rate decreases with increasing adatom concentration and graphene coverage. Initially, graphene growth on Ir(111) is like that on Ru: the growth velocity is the same nonlinear function of adatom concentration (albeit with much smaller equilibrium adatom concentrations, as we explain with DFT calculations of adatom formation energies). In the later stages of growth, graphene crystals that are rotated relative to the initial nuclei nucleate and grow. The rotated nuclei grow much faster. This difference suggests firstly, that the edge-orientation of the graphene sheets relative to the substrate plays an important role in the growth mechanism, and secondly, that attachment of the clusters to the graphene is the slowest step in cluster addition, rather than formation of clusters on the terraces.

  19. Mn3O4 nanoparticles embedded into graphene nanosheets: Preparation, characterization, and electrochemical properties for supercapacitors

    Wang Bei; Park, Jinsoo; Wang Chengyin; Ahn, Hyojun; Wang, Guoxiu

    2010-01-01

    Mn 3 O 4 /graphene nanocomposites were synthesized by mixing graphene suspension in ethylene glycol with MnO 2 organosol, followed by subsequent ultrasonication processing and heat treatment. The as-prepared product consists of nanosized Mn 3 O 4 particles homogeneously distributed on graphene nanosheets, which has been confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis. Atomic force microscope analysis further identified the distribution of dense Mn 3 O 4 nanoparticles on graphene nanosheets. When used as electrode materials in supercapacitors, Mn 3 O 4 /graphene nanocomposites exhibited a high specific capacitance of 175 F g -1 in 1 M Na 2 SO 4 electrolyte and 256 F g -1 in 6 M KOH electrolyte, respectively. The enhanced supercapacitance of Mn 3 O 4 /graphene nanocomposites could be ascribed to both electrochemical contributions of Mn 3 O 4 nanoparticles, functional groups attached to graphene nanosheets, and significantly increased specific surface area.

  20. Preparation and study of properties of dispersed graphene oxide

    Evgeniya Seliverstova

    2015-09-01

    Full Text Available Ability of graphene oxide to form stable dispersion in organic solvents was studied in this work. As it was shown, sonication of graphene leads to the decreas of the particle size. Stability of prepared graphene dispersions was studied upon measurements of distribution of number of the particles via size and change of optical density of the solutions with time. It was found that graphene oxide forms a more stable dispersion in tetrahydrofuran and dimethylformamide than in chloroform and acetone.

  1. Excellent electrochemical performance of graphene-silver nanoparticle hybrids prepared using a microwave spark assistance process

    Shanmugharaj, A.M.; Ryu, Sung Hun

    2012-01-01

    Highlights: ► A simple synthesis route is explored in preparing graphene-metal nanoparticle hybrids using cost effective microwave radiation process. ► Electrochemical performance of the synthesized graphene-silver nanoparticle hybrids have been compared with graphite and silver nanoparticle based anode materials. ► Graphene-silver nanoparticle hybrid exhibits stable charge/discharge characteristics of 714 mAh g −1 and it is significantly higher compared to natural graphite and silver based electrodes. - Abstract: A simple method is described for the synthesis of graphene-silver nanoparticle hybrids from graphite and silver precursors using microwave spark ignition process. Adding ecofriendly free radical initiators, in the presence of hydrogen peroxide solution leads to the expansion of graphite to graphene nanosheets. Simultaneously, silver ions intercalated between the graphene layers are reduced to silver nanocrystals leading to the development of graphene-silver nanoparticle hybrids. Transmission electron microscopic (TEM) studies reveal the successful formation of graphene-silver nanoparticle hybrids. X-ray diffraction (XRD) shows that the silver nanoparticles formed on the graphene surfaces are face centered cubic crystals. The surface composition and functional groups present on the graphene-silver nanoparticle hybrids are corroborated using X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FT-IR). The lithium storage capacity of the synthesized material, when used as an anode material for rechargeable lithium secondary batteries is investigated. Its first specific discharge capacity is observed to be 580 mAh g −1 and this has been increased to 827 mAh g −1 , by incorporating the silver nanoparticles between the graphene platelets. The reversible capacity of the graphene-silver nanoparticle hybrids is observed to be 714 mAh g −1 , which is significantly higher compared to that of graphene (420 mAh g −1

  2. Surface preparation of niobium

    Kneisel, P.

    1980-01-01

    Any discussion of surface preparation for superconducting rf-surfaces is certainly connected with the question what is the best recipe for achieving high Q-values and high break-down fields. Since the break-down in a cavity is not understood so far and because several mechanisms play a role, it also is not possible to give one recipe which always works. Nevertheless in the past certain preparation techniques for niobium surfaces have been developed and certain rules for preparation can be applied. In the following the to-days state of the art will be described and it is attempted to give a short description of the surface in conjunction with the methods of surface treatments, which generally can be applied to niobium cavities. (orig./WTR)

  3. Formation of graphene on Ru(0001) surface

    Pan Yi; Shi Dong-Xia; Gao Hong-Jun

    2007-01-01

    We report on the formation of a graphene monolayer on a Ru(0001) surface by annealing the Ru(0001) crystal.The samples are characterized by scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES). STM images show that the Moiré pattern is caused by the graphene layer mismatched with the underlying Ru(0001) surface and has an N × N superlattice. It is further found that the graphene monolayer on a Ru(0001) surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru(0001) surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.

  4. Preparation of three-dimensional graphene foam for high performance supercapacitors

    Yunjie Ping

    2017-04-01

    Full Text Available Supercapacitor is a new type of energy-storage device, and has been attracted widely attentions. As a two dimensional (2D nanomaterials, graphene is considered to be a promising material of supercapacitor because of its excellent properties involving high electrical conductivity and large surface area. In this paper, the large-scale graphene is successfully fabricated via environmental-friendly electrochemical exfoliation of graphite, and then, the three dimensional (3D graphene foam is prepared by using nickel foam as template and FeCl3/HCl solution as etchant. Compared with the regular 2D graphene paper, the 3D graphene foam electrode shows better electrochemical performance, and exhibits the largest specific capacitance of approximately 128 F/g at the current density of 1 A/g in 6 M KOH electrolyte. It is expected that the 3D graphene foam will have a potential application in the supercapacitors.

  5. Preparation of 3D graphene-based architectures and their applications in supercapacitors

    Zhuxian Yang

    2015-12-01

    Full Text Available Three dimensional (3D graphene-based architectures such as 3D graphene-based hydrogels, aerogels, foams, and sponges have attracted huge attention owing to the combination of the structural interconnectivities and the outstanding properties of graphene which offer these interesting structures with low density, high porosity, large surface area, stable mechanical properties, fast mass and electron transport. They have been extensively studied for a wide range of applications including capacitors, batteries, sensors, catalyst, etc. There are several reviews focusing on the 3D graphene-based architectures and their applications. In this work, we only summarise the latest development on the preparation of 3D graphene-based architectures and their applications in supercapacitors, with emphasis on the preparation strategies.

  6. The Preparation and Property of Graphene /Tin Oxide Transparent Conductive Film

    SUN Tao

    2017-02-01

    Full Text Available Graphene doped tin oxide composites were prepared with SnCIZ·2HZ 0 and graphene oxide as raw materials with sol-gel method and then spincoated on the quartz glass to manufacture a new transparent conductive film. The composite film was characterized with X-ray diffraction(XRDand scanning electron microscopy(SEM analysis. XRD results show that the graphene oxide was successfully prepared with Hummers method. The graphene layers and particulate SnOZ can be clearly observed in SEM photos. The transmittance and conductivity of the thin films were tested with ultraviolet visible spectrophotometer and Hall effect measurement. The results show that the transmittivity of composite film in visible region is more than 90% and surface square resistance is 41 S2/口.The graphene/ SnOZ film exhibits a higher performance in transparence and conductivity than commercial FTO glass.

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

    Zhi Yang; Rungang Gao; Nantao Hu; Jing Chai; Yingwu Cheng; Liying Zhang; Hao Wei; Eric Siu-Wai Kong; Yafei Zhang

    2012-01-01

    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.

  8. Preparation of graphene by electrical explosion of graphite sticks.

    Gao, Xin; Xu, Chunxiao; Yin, Hao; Wang, Xiaoguang; Song, Qiuzhi; Chen, Pengwan

    2017-08-03

    Graphene nanosheets were produced by electrical explosion of high-purity graphite sticks in distilled water at room temperature. The as-prepared samples were characterized by various techniques to find different forms of carbon phases, including graphite nanosheets, few-layer graphene, and especially, mono-layer graphene with good crystallinity. Delicate control of energy injection is critical for graphene nanosheet formation, whereas mono-layer graphene was produced under the charging voltage of 22.5-23.5 kV. On the basis of electrical wire explosion and our experimental results, the underlying mechanism that governs the graphene generation was carefully illustrated. This work provides a simple but innovative route for producing graphene nanosheets.

  9. An economic route to mass production of graphene oxide solution for preparing graphene oxide papers

    Liou, Yan-Jia; Tsai, Bo-Da; Huang, Wu-Jang, E-mail: wjhuang@mail.npust.edu.tw

    2015-03-15

    Highlights: • Graphene oxide paper can be prepared from synthesized graphene sheet containing carbon materials. • Graphene oxide paper can be used as a phase change materials for thermal storage. • To prepare graphene oxide paper from synthesized graphene sheet containing carbon materials could highly reduce the cost. - Abstract: Graphene oxide paper (GOP) is a composite material fabricated from graphene oxide (GO) solution. In addition, it can be a novel and potential material for application on the separation of water vapor from gaseous steam or larger alkali ions from aqueous solution. GOP could be used as electricity and thermal storage materials. The preparation of GO commonly uses high purity natural or artificial graphite. It is difficult to prepare GOP from artificial graphite powder due to the cost of $1,450 US/ton. In this study, we tried to prepare GOPs from homemade graphene sheets containing carbon materials (GSCCMs) and evaluate the thermal properties of GSCCM derived GOPs. Results show that GSCCM derived GOPs have a higher phase transition temperature, and the average mesophase phase change enthalpy is 9.41 J/g, which is 2.87 times higher than graphite derived GOP. Therefore, to prepare GOP from GSCCMs could highly reduce the cost.

  10. Effects of various surfactants on the dispersion stability and electrical conductivity of surface modified graphene

    Uddin, Md. Elias [WCU Program, Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Kuila, Tapas [Surface Engineering and Tribology, CSIR – Central Mechanical Engineering Research Institute, Durgapur 721 302 (India); Nayak, Ganesh Chandra [Department of Applied Chemistry, ISM Dhanbad, Dhanbad 826 004, Jharkhand (India); Kim, Nam Hoon [Department of Hydrogen and Fuel Cell Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Ku, Bon-Cheol [Institute of Advanced Composite Materials, Korea Institute of Science and Technology, Dunsan-ri, Bongdong-eup, Wanju-gun, Jeollabuk-do 864-9 (Korea, Republic of); Lee, Joong Hee, E-mail: jhl@chonbuk.ac.kr [WCU Program, Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Department of Hydrogen and Fuel Cell Engineering, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of)

    2013-06-15

    Highlights: ► Water dispersible graphene has been prepared using ionic and non-ionic surfactants. ► XPS and FTIR spectra analysis confirm surface modification and reduction of GO. ► The highest water dispersibility is observed in the graphene modified with of SDBS. ► The best properties of modified graphene is achieved with GO/surfactant ratio of two. -- Abstract: Ionic and non-ionic surfactant functionalized, water dispersible graphene were prepared to investigate the effects on the dispersion stability and electrical conductivity of graphene. In this study, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate and 4-(1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol (Triton X-100) were used as ionic and non-ionic surfactants. The effects of surfactant concentrations on the dispersibility and electrical conductivity of the surface modified graphene were investigated. The dispersion stability of SDBS functionalized graphene (SDBS-G) was found to be best in water at 1.5 mg ml{sup −1}. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis indicate that the presence of surfactants does not prevent the reduction of graphene oxide (GO). These measurements also demonstrated that the surfactants were present on the surface of graphene, resulting in the formation of functionalized graphene. The thickness of different functionalized graphene was measured by Atomic force microscopy and varied significantly with different surfactants. The thermal properties of the functionalized graphene were also found to be dependent on the nature of the surfactants. The electrical conductivity of SDBS-G (108 S m{sup −1}) was comparatively higher than SDS and Triton X-100 functionalized graphene.

  11. Gas loading of graphene-quartz surface acoustic wave devices

    Whitehead, E. F.; Chick, E. M.; Bandhu, L.; Lawton, L. M.; Nash, G. R.

    2013-08-01

    Graphene was transferred to the propagation path of quartz surface acoustic wave devices and the attenuation due to gas loading of air and argon measured at 70 MHz and 210 MHz and compared to devices with no graphene. Under argon loading, there was no significant difference between the graphene and non-graphene device and the values of measured attenuation agree well with those calculated theoretically. Under air loading, at 210 MHz, there was a significant difference between the non-graphene and graphene devices, with the average value of attenuation obtained with the graphene devices being approximately twice that obtained from the bare quartz devices.

  12. Surface adhesion properties of graphene and graphene oxide studied by colloid-probe atomic force microscopy

    Ding Yanhuai; Zhang Ping; Ren Huming; Zhuo Qin; Yang Zhongmei; Jiang Xu; Jiang Yong

    2011-01-01

    Surface adhesion properties are important to various applications of graphene-based materials. Atomic force microscopy is powerful to study the adhesion properties of samples by measuring the forces on the colloidal sphere tip as it approaches and retracts from the surface. In this paper we have measured the adhesion force between the colloid probe and the surface of graphene (graphene oxide) nanosheet. The results revealed that the adhesion force on graphene and graphene oxide surface were 66.3 and 170.6 nN, respectively. It was found the adhesion force was mainly determined by the water meniscus, which was related to the surface contact angle of samples.

  13. Graphene Emerges as a Versatile Template for Materials Preparation.

    Li, Zhengjie; Wu, Sida; Lv, Wei; Shao, Jiao-Jing; Kang, Feiyu; Yang, Quan-Hong

    2016-05-01

    Graphene and its derivatives are emerging as a class of novel but versatile templates for the controlled preparation and functionalization of materials. In this paper a conceptual review on graphene-based templates is given, highlighting their versatile roles in materials preparation. Graphene is capable of acting as a low-dimensional hard template, where its two-dimensional morphology directs the formation of novel nanostructures. Graphene oxide and other functionalized graphenes are amphiphilic and may be seen as soft templates for formatting the growth or inducing the controlled assembly of nanostructures. In addition, nanospaces in restacked graphene can be used for confining the growth of sheet-like nanostructures, and assemblies of interlinked graphenes can behave either as skeletons for the formation of composite materials or as sacrificial templates for novel materials with a controlled network structure. In summary, flexible graphene and its derivatives together with an increasing number of assembled structures show great potentials as templates for materials production. Many challenges remain, for example precise structural control of such novel templates and the removal of the non-functional remaining templates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Modified Unzipping Technique to Prepare Graphene Nano-Sheets

    Al-Tamimi, B. H.; Farid, S. B. H.; Chyad, F. A.

    2018-05-01

    Graphene nano-sheets have been prepared via unzipping approach of multiwall carbon nanotubes (MWCNTs). The method includes two chemical-steps, in which a multi-parameter oxidation step is performed to achieve unzipping the carbon nanotubes. Then, a reduction step is carried out to achieve the final graphene nano-sheets. In the oxidation step, the oxidant material was minimized and balanced with longer curing time. This modification is made in order to reduce the oxygen-functional groups at the ends of graphene basal planes, which reduce its electrical conductivity. In addition, a similar adjustment is achieved in the reduction step, i.e. the consumed chemicals is reduced which make the overall process more economic and eco-friendly. The prepared nano-sheets were characterized by atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. The average thickness of the prepared graphene was about 5.23 nm.

  15. Preparation of Composited Graphene/PEDOT:PSS Film for Its Possible Application in Graphene-based Organic Solar Cells

    YU; Yue; LI; Meicheng; CHU; Lihua; YU; Hakki; Wodtke; A.M.; ZHAO; Yan; ZHANG; Zhongmo

    2015-01-01

    The interface between graphene and organic layers is a key factor responsible for the performance of graphene-based organic solar cells(OSCs). In this paper, we focus on coating PEDOT:PSS onto the surface of graphene. We demonstrate two approaches, applying UV/Ozone treatment on graphene and modifying PEDOT:PSS with Zonyl, to get a PEDOT:PSS well-coated graphene film. Our results prove that both methods can be effective to solve the interface issue between graphene and PEDOT: PSS. Thereby it shows a positive application of the composited graphene/PEDOT:PSS film on graphene-based OSCs.

  16. Surface characterization of graphene based materials

    Pisarek, M.; Holdynski, M.; Krawczyk, M.; Nowakowski, R.; Roguska, A.; Malolepszy, A.; Stobinski, L.; Jablonski, A.

    2016-01-01

    Highlights: • Two kind of samples: commercial graphene on Cu substrate and rGO flakes. • EPES applied to measure the IMFPs in graphene based materials. • Characterization by various techniques like: FE-SEM, AFM, XPS, AES and REELS. • EPES IMFPs for rGO deviated up to 14% from IMFPs calculated using the optical data. - Abstract: In the present study, two kind of samples were used: (i) a monolayer graphene film with a thickness of 0.345 nm deposited by the CVD method on Cu foil, (ii) graphene flakes obtained by modified Hummers method and followed by reduction of graphene oxide. The inelastic mean free path (IMFP), characterizing electron transport in graphene/Cu sample and reduced graphene oxide material, which determines the sampling depth of XPS and AES were evaluated from relative Elastic Peak Electron Spectroscopy (EPES) measurements with the Au standard in the energy range 0.5–2 keV. The measured IMFPs were compared with IMFPs resulting from experimental optical data published in the literature for the graphite sample. The EPES IMFP values at 0.5 and 1.5 keV was practically identical to that calculated from optical data for graphite (less than 4% deviation). For energies 1 and 2 keV, the EPES IMFPs for rGO were deviated up to 14% from IMFPs calculated using the optical data by Tanuma et al. [1]. Before EPES measurements all samples were characterized by various techniques like: FE-SEM, AFM, XPS, AES and REELS to visualize the surface morphology/topography and identify the chemical composition.

  17. Surface characterization of graphene based materials

    Pisarek, M., E-mail: mpisarek@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Holdynski, M.; Krawczyk, M.; Nowakowski, R.; Roguska, A. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Malolepszy, A. [Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, 00-065 Warsaw (Poland); Stobinski, L. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, 00-065 Warsaw (Poland); Jablonski, A. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland)

    2016-12-01

    Highlights: • Two kind of samples: commercial graphene on Cu substrate and rGO flakes. • EPES applied to measure the IMFPs in graphene based materials. • Characterization by various techniques like: FE-SEM, AFM, XPS, AES and REELS. • EPES IMFPs for rGO deviated up to 14% from IMFPs calculated using the optical data. - Abstract: In the present study, two kind of samples were used: (i) a monolayer graphene film with a thickness of 0.345 nm deposited by the CVD method on Cu foil, (ii) graphene flakes obtained by modified Hummers method and followed by reduction of graphene oxide. The inelastic mean free path (IMFP), characterizing electron transport in graphene/Cu sample and reduced graphene oxide material, which determines the sampling depth of XPS and AES were evaluated from relative Elastic Peak Electron Spectroscopy (EPES) measurements with the Au standard in the energy range 0.5–2 keV. The measured IMFPs were compared with IMFPs resulting from experimental optical data published in the literature for the graphite sample. The EPES IMFP values at 0.5 and 1.5 keV was practically identical to that calculated from optical data for graphite (less than 4% deviation). For energies 1 and 2 keV, the EPES IMFPs for rGO were deviated up to 14% from IMFPs calculated using the optical data by Tanuma et al. [1]. Before EPES measurements all samples were characterized by various techniques like: FE-SEM, AFM, XPS, AES and REELS to visualize the surface morphology/topography and identify the chemical composition.

  18. Localized Surface Plasmons in Vibrating Graphene Nanodisks

    Wang, Weihua; Li, Bo-Hong; Stassen, Erik

    2016-01-01

    in graphene disks have the additional benefit to be highly tunable via electrical stimulation. Mechanical vibrations create structural deformations in ways where the excitation of localized surface plasmons can be strongly modulated. We show that the spectral shift in such a scenario is determined...... by a complex interplay between the symmetry and shape of the modal vibrations and the plasmonic mode pattern. Tuning confined modes of light in graphene via acoustic excitations, paves new avenues in shaping the sensitivity of plasmonic detectors, and in the enhancement of the interaction with optical emitters...

  19. A roadmap to high quality chemically prepared graphene

    Gengler, Regis Y N; Spyrou, Konstantinos; Rudolf, Petra, E-mail: r.gengler@rug.n, E-mail: p.rudolf@rug.n [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen (Netherlands)

    2010-09-22

    Graphene was discovered half a decade ago and proved the existence of a two-dimensional system which becomes stable as a result of 3D corrugation. It appeared very quickly that this exceptional material had truly outstanding electronic, mechanical, thermal and optical properties. Consequently a broad range of applications appeared, as the graphene science speedily moved forward. Since then, a lot of effort has been devoted not only to the study of graphene but also to its fabrication. Here we review the chemical approaches to graphene production, their advantages as well as their downsides. Our aim is to draw a roadmap of today's most reliable path to high quality graphene via chemical preparation.

  20. A roadmap to high quality chemically prepared graphene

    Gengler, Regis Y N; Spyrou, Konstantinos; Rudolf, Petra

    2010-01-01

    Graphene was discovered half a decade ago and proved the existence of a two-dimensional system which becomes stable as a result of 3D corrugation. It appeared very quickly that this exceptional material had truly outstanding electronic, mechanical, thermal and optical properties. Consequently a broad range of applications appeared, as the graphene science speedily moved forward. Since then, a lot of effort has been devoted not only to the study of graphene but also to its fabrication. Here we review the chemical approaches to graphene production, their advantages as well as their downsides. Our aim is to draw a roadmap of today's most reliable path to high quality graphene via chemical preparation.

  1. Electrostatic Deposition of Large-Surface Graphene

    Charles Trudeau

    2018-01-01

    Full Text Available This work describes a method for electrostatic deposition of graphene over a large area using controlled electrostatic exfoliation from a Highly Ordered Pyrolytic Graphite (HOPG block. Deposition over 130 × 130 µm2 with 96% coverage is achieved, which contrasts with sporadic micro-scale depositions of graphene with little control from previous works on electrostatic deposition. The deposition results are studied by Raman micro-spectroscopy and hyperspectral analysis using large fields of view to allow for the characterization of the whole deposition area. Results confirm that laser pre-patterning of the HOPG block prior to cleaving generates anchor points favoring a more homogeneous and defect-free HOPG surface, yielding larger and more uniform graphene depositions. We also demonstrate that a second patterning of the HOPG block just before exfoliation can yield features with precisely controlled geometries.

  2. Surface characterization of graphene based materials

    Pisarek, M.; Holdynski, M.; Krawczyk, M.; Nowakowski, R.; Roguska, A.; Malolepszy, A.; Stobinski, L.; Jablonski, A.

    2016-12-01

    In the present study, two kind of samples were used: (i) a monolayer graphene film with a thickness of 0.345 nm deposited by the CVD method on Cu foil, (ii) graphene flakes obtained by modified Hummers method and followed by reduction of graphene oxide. The inelastic mean free path (IMFP), characterizing electron transport in graphene/Cu sample and reduced graphene oxide material, which determines the sampling depth of XPS and AES were evaluated from relative Elastic Peak Electron Spectroscopy (EPES) measurements with the Au standard in the energy range 0.5-2 keV. The measured IMFPs were compared with IMFPs resulting from experimental optical data published in the literature for the graphite sample. The EPES IMFP values at 0.5 and 1.5 keV was practically identical to that calculated from optical data for graphite (less than 4% deviation). For energies 1 and 2 keV, the EPES IMFPs for rGO were deviated up to 14% from IMFPs calculated using the optical data by Tanuma et al. [1]. Before EPES measurements all samples were characterized by various techniques like: FE-SEM, AFM, XPS, AES and REELS to visualize the surface morphology/topography and identify the chemical composition.

  3. Probing Interfacial Processes on Graphene Surface by Mass Detection

    Kakenov, Nurbek; Kocabas, Coskun

    2013-03-01

    In this work we studied the mass density of graphene, probed interfacial processes on graphene surface and examined the formation of graphene oxide by mass detection. The graphene layers were synthesized by chemical vapor deposition method on copper foils and transfer-printed on a quartz crystal microbalance (QCM). The mass density of single layer graphene was measured by investigating the mechanical resonance of the QCM. Moreover, we extended the developed technique to probe the binding dynamics of proteins on the surface of graphene, were able to obtain nonspecific binding constant of BSA protein of graphene surface in aqueous solution. The time trace of resonance signal showed that the BSA molecules rapidly saturated by filling the available binding sites on graphene surface. Furthermore, we monitored oxidation of graphene surface under oxygen plasma by tracing the changes of interfacial mass of the graphene controlled by the shifts in Raman spectra. Three regimes were observed the formation of graphene oxide which increases the interfacial mass, the release of carbon dioxide and the removal of small graphene/graphene oxide flakes. Scientific and Technological Research Council of Turkey (TUBITAK) grant no. 110T304, 109T209, Marie Curie International Reintegration Grant (IRG) grant no 256458, Turkish Academy of Science (TUBA-Gebip).

  4. Dichlorobenzene: an effective solvent for epoxy/graphene nanocomposites preparation.

    Wei, Jiacheng; Saharudin, Mohd Shahneel; Vo, Thuc; Inam, Fawad

    2017-10-01

    It is generally recognized that dimethylformamide (DMF) and ethanol are good media to uniformly disperse graphene, and therefore have been used widely in the preparation of epoxy/graphene nanocomposites. However, as a solvent to disperse graphene, dichlorobenzene (DCB) has not been fully realized by the polymer community. Owing to high values of the dispersion component ( δ d ) of the Hildebrand solubility parameter, DCB is considered as a suitable solvent for homogeneous graphene dispersion. Therefore, epoxy/graphene nanocomposites have been prepared for the first time with DCB as a dispersant; DMF and ethanol have been chosen as the reference. The colloidal stability, mechanical properties, thermogravimetric analysis, dynamic mechanical analysis and scanning electron microscopic images of nanocomposites have been obtained. The results show that with the use of DCB, the tensile strength of graphene has been improved from 64.46 to 69.32 MPa, and its flexural strength has been increased from 97.17 to 104.77 MPa. DCB is found to be more effective than DMF and ethanol for making stable and homogeneous graphene dispersion and composites.

  5. Effect of preparation methods on dispersion stability and electrochemical performance of graphene sheets

    Chen, Li, E-mail: chenli1981@lut.cn; Li, Na; Zhang, Mingxia; Li, Pinnan; Lin, Zhengping

    2017-05-15

    Chemical exfoliation is one of the most important strategies for preparing graphene. The aggregation of graphene sheets severely prevents graphene from exhibiting excellent properties. However, there are no attempts to investigate the effect of preparation methods on the dispersity of graphene sheets. In this study, three chemical exfoliation methods, including Hummers method, modified Hummers method, and improved method, were used to prepare graphene sheets. The influence of preparation methods on the structure, dispersion stability in organic solvents, and electrochemical properties of graphene sheets were investigated. Fourier transform infrared microscopy, Raman spectra, transmission electron microscopy, and UV–vis spectrophotometry were employed to analyze the structure of the as-prepared graphene sheets. The results showed that graphene prepared by improved method exhibits excellent dispersity and stability in organic solvents without any additional stabilizer or modifier, which is attributed to the completely exfoliation and regular structure. Moreover, cyclic voltammetric and electrochemical impedance spectroscopy measurements showed that graphene prepared by improved method exhibits superior electrochemical properties than that prepared by the other two methods. - Graphical abstract: Graphene oxides with different oxidation degree were obtained via three methods, and then graphene with different crystal structures were created by chemical reduction of exfoliated graphene oxides. - Highlights: • Graphene oxides with different oxidation degree were obtained via three oxidation methods. • The influence of oxidation methods on microstructure of graphene was investigated. • The effect of oxidation methods on dispersion stability of graphene was investigated. • The effect of oxidation methods on electrochemical properties of graphene was discussed.

  6. Effect of preparation methods on dispersion stability and electrochemical performance of graphene sheets

    Chen, Li; Li, Na; Zhang, Mingxia; Li, Pinnan; Lin, Zhengping

    2017-01-01

    Chemical exfoliation is one of the most important strategies for preparing graphene. The aggregation of graphene sheets severely prevents graphene from exhibiting excellent properties. However, there are no attempts to investigate the effect of preparation methods on the dispersity of graphene sheets. In this study, three chemical exfoliation methods, including Hummers method, modified Hummers method, and improved method, were used to prepare graphene sheets. The influence of preparation methods on the structure, dispersion stability in organic solvents, and electrochemical properties of graphene sheets were investigated. Fourier transform infrared microscopy, Raman spectra, transmission electron microscopy, and UV–vis spectrophotometry were employed to analyze the structure of the as-prepared graphene sheets. The results showed that graphene prepared by improved method exhibits excellent dispersity and stability in organic solvents without any additional stabilizer or modifier, which is attributed to the completely exfoliation and regular structure. Moreover, cyclic voltammetric and electrochemical impedance spectroscopy measurements showed that graphene prepared by improved method exhibits superior electrochemical properties than that prepared by the other two methods. - Graphical abstract: Graphene oxides with different oxidation degree were obtained via three methods, and then graphene with different crystal structures were created by chemical reduction of exfoliated graphene oxides. - Highlights: • Graphene oxides with different oxidation degree were obtained via three oxidation methods. • The influence of oxidation methods on microstructure of graphene was investigated. • The effect of oxidation methods on dispersion stability of graphene was investigated. • The effect of oxidation methods on electrochemical properties of graphene was discussed.

  7. Slip length crossover on a graphene surface

    Liang, Zhi, E-mail: liangz3@rpi.edu [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Keblinski, Pawel, E-mail: keplip@rpi.edu [Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2015-04-07

    Using equilibrium and non-equilibrium molecular dynamics simulations, we study the flow of argon fluid above the critical temperature in a planar nanochannel delimited by graphene walls. We observe that, as a function of pressure, the slip length first decreases due to the decreasing mean free path of gas molecules, reaches the minimum value when the pressure is close to the critical pressure, and then increases with further increase in pressure. We demonstrate that the slip length increase at high pressures is due to the fact that the viscosity of fluid increases much faster with pressure than the friction coefficient between the fluid and the graphene. This behavior is clearly exhibited in the case of graphene due to a very smooth potential landscape originating from a very high atomic density of graphene planes. By contrast, on surfaces with lower atomic density, such as an (100) Au surface, the slip length for high fluid pressures is essentially zero, regardless of the nature of interaction between fluid and the solid wall.

  8. Electronic structure of graphene on Ni surfaces with different orientation

    Pudikov, D.A.; Zhizhin, E.V.; Rybkin, A.G.; Rybkina, A.A.; Zhukov, Y.M.; Vilkov, O. Yu.; Shikin, A.M.

    2016-01-01

    An experimental study of the graphene, synthesized by propylene cracking on Ni surfaces with different orientation: (100) and (111), using angle-resolved photoemission, has been performed. It has been shown that graphene on Ni(111) had a perfect lateral structure due to consistency of their lattices, whereas graphene/Ni(100) consisted of a lot of domains. For both systems electronic structure was quite similar and demonstrated a strong bonding of graphene to the underlying Ni surface. After Au intercalation the electronic structure of graphene in both systems was shifted to the Fermi level and became linear in the vicinity of the K point of the Brillouin zone. - Highlights: • Graphene on Ni(111) is well-ordered, whereas on Ni(100) – multi-domain. • Graphene on Ni(111) and Ni(100) is strongly bonded with substrate. • Intercalation of Au atoms restores the linearity in dispersion and makes graphene quasi-free on both Ni(100) and Ni(111).

  9. Direct Measurement of the Surface Energy of Graphene.

    van Engers, Christian D; Cousens, Nico E A; Babenko, Vitaliy; Britton, Jude; Zappone, Bruno; Grobert, Nicole; Perkin, Susan

    2017-06-14

    Graphene produced by chemical vapor deposition (CVD) is a promising candidate for implementing graphene in a range of technologies. In most device configurations, one side of the graphene is supported by a solid substrate, wheras the other side is in contact with a medium of interest, such as a liquid or other two-dimensional material within a van der Waals stack. In such devices, graphene interacts on both faces via noncovalent interactions and therefore surface energies are key parameters for device fabrication and operation. In this work, we directly measured adhesive forces and surface energies of CVD-grown graphene in dry nitrogen, water, and sodium cholate using a modified surface force balance. For this, we fabricated large (∼1 cm 2 ) and clean graphene-coated surfaces with smooth topography at both macro- and nanoscales. By bringing two such surfaces into contact and measuring the force required to separate them, we measured the surface energy of single-layer graphene in dry nitrogen to be 115 ± 4 mJ/m 2 , which was similar to that of few-layer graphene (119 ± 3 mJ/m 2 ). In water and sodium cholate, we measured interfacial energies of 83 ± 7 and 29 ± 6 mJ/m 2 , respectively. Our work provides the first direct measurement of graphene surface energy and is expected to have an impact both on the development of graphene-based devices and contribute to the fundamental understanding of surface interactions.

  10. Antioxidant Deactivation on Graphenic Nanocarbon Surfaces

    Liu, Xinyuan [ORNL; Sen, Sujat [Brown University; Liu, Jingyu [Brown University; Kulaots, Indrek [Brown University; Geohegan, David B [ORNL; Kane, Agnes [Brown University; Puretzky, Alexander A [ORNL; Rouleau, Christopher M [ORNL; More, Karren Leslie [ORNL; Palmore, G. Tayhas R. [Brown University; Hurt, Robert H. [Brown University

    2011-01-01

    This article reports a direct chemical pathway for antioxidant deactivation on the surfaces of carbon nanomaterials. In the absence of cells, carbon nanotubes are shown to deplete the key physiological antioxidant glutathione (GSH) in a reaction involving dissolved dioxygen that yields the oxidized dimer, GSSG, as the primary product. In both chemical and electrochemical experiments, oxygen is only consumed at a significant steady-state rate in the presence of both nanotubes and GSH. GSH deactivation occurs for single- and multi-walled nanotubes, graphene oxide, nanohorns, and carbon black at varying rates that are characteristic of the material. The GSH depletion rates can be partially unified by surface area normalization, are accelerated by nitrogen doping, and suppressed by defect annealing or addition of proteins or surfactants. It is proposed that dioxygen reacts with active sites on graphenic carbon surfaces to produce surface-bound oxygen intermediates that react heterogeneously with glutathione to restore the carbon surface and complete a catalytic cycle. The direct catalytic reaction between nanomaterial surfaces and antioxidants may contribute to oxidative stress pathways in nanotoxicity, and the dependence on surface area and structural defects suggest strategies for safe material design.

  11. Surface patterning of multilayer graphene by ultraviolet laser irradiation in biomolecule sensing devices

    Chang, Tien-Li, E-mail: tlchang@ntnu.edu.tw; Chen, Zhao-Chi

    2015-12-30

    Graphical abstract: - Highlights: • Direct UV laser irradiation on multilayer graphene was discussed. • Multilayer graphene with screen-printed process was presented. • Surface patterning of multilayer graphene at fluence threshold was investigated. • Electrical response of glucose in sensing devices can be studied. - Abstract: The study presents a direct process for surface patterning of multilayer graphene on the glass substrate as a biosensing device. In contrast to lithography with etching, the proposed process provides simultaneous surface patterning of multilayer graphene through nanosecond laser irradiation. In this study, the multilayer graphene was prepared by a screen printing process. Additionally, the wavelength of the laser beam was 355 nm. To perform the effective laser process with the small heat affected zone, the surface patterns on the sensing devices could be directly fabricated using the laser with optimal control of the pulse overlap at a fluence threshold of 0.63 J/cm{sup 2}. The unique patterning of the laser-ablated surface exhibits their electrical and hydrophilic characteristics. The hydrophilic surface of graphene-based sensing devices was achieved in the process with the pulse overlap of 90%. Furthermore, the sensing devices for controlling the electrical response of glucose by using glucose oxidase can be used in sensors in commercial medical applications.

  12. Thermophoretically driven water droplets on graphene and boron nitride surfaces

    Rajegowda, Rakesh; Kannam, Sridhar Kumar; Hartkamp, Remco; Sathian, Sarith P.

    2018-05-01

    We investigate thermally driven water droplet transport on graphene and hexagonal boron nitride (h-BN) surfaces using molecular dynamics simulations. The two surfaces considered here have different wettabilities with a significant difference in the mode of droplet transport. The water droplet travels along a straighter path on the h-BN sheet than on graphene. The h-BN surface produced a higher driving force on the droplet than the graphene surface. The water droplet is found to move faster on h-BN surface compared to graphene surface. The instantaneous contact angle was monitored as a measure of droplet deformation during thermal transport. The characteristics of the droplet motion on both surfaces is determined through the moment scaling spectrum. The water droplet on h-BN surface showed the attributes of the super-diffusive process, whereas it was sub-diffusive on the graphene surface.

  13. Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer.

    Kafiah, Feras; Khan, Zafarullah; Ibrahim, Ahmed; Atieh, Muataz; Laoui, Tahar

    2017-01-21

    In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm.

  14. Layer Dependence of Graphene for Oxidation Resistance of Cu Surface

    Yu-qing Song; Xiao-ping Wang

    2017-01-01

    We studied the oxidation resistance of graphene-coated Cu surface and its layer dependence by directly growing monolayer graphene with different multilayer structures coexisted,diminishing the influence induced by residue and transfer technology.It is found that the Cu surface coated with the monolayer graphene demonstrate tremendous difference in oxidation pattern and oxidation rate,compared to that coated with the bilayer graphene,which is considered to be originated from the strain-induced linear oxidation channel in monolayer graphene and the intersection of easily-oxidized directions in each layer of bilayer graphene,respectively.We reveal that the defects on the graphene basal plane but not the boundaries are the main oxidation channel for Cu surface under graphene protection.Our finding indicates that compared to putting forth efforts to improve the quality of monolayer graphene by reducing defects,depositing multilayer graphene directly on metal is a simple and effective way to enhance the oxidation resistance of graphene-coated metals.

  15. Graphene aerogels

    Pauzauskie, Peter J; Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H; Biener, Juergen

    2015-03-31

    Graphene aerogels with high conductivity and surface areas including a method for making a graphene aerogel, including the following steps: (1) preparing a reaction mixture comprising a graphene oxide suspension and at least one catalyst; (2) curing the reaction mixture to produce a wet gel; (3) drying the wet gel to produce a dry gel; and (4) pyrolyzing the dry gel to produce a graphene aerogel. Applications include electrical energy storage including batteries and supercapacitors.

  16. Optical transparency of graphene layers grown on metal surfaces

    Rut’kov, E. V.; Lavrovskaya, N. P.; Sheshenya, E. S.; Gall, N. R.

    2017-01-01

    It is shown that, in contradiction with the fundamental results obtained for free graphene, graphene films grown on the Rh(111) surface to thicknesses from one to ~(12–15) single layers do not absorb visible electromagnetic radiation emitted from the surface and influence neither the brightness nor true temperature of the sample. At larger thicknesses, such absorption occurs. This effect is observed for the surfaces of other metals, specifically, Pt(111), Re(1010), and Ni(111) and, thus, can be considered as being universal. It is thought that the effect is due to changes in the electronic properties of thin graphene layers because of electron transfer between graphene and the metal substrate.

  17. Optical transparency of graphene layers grown on metal surfaces

    Rut’kov, E. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Lavrovskaya, N. P. [State University of Aerospace Instrumentation (Russian Federation); Sheshenya, E. S., E-mail: sheshenayket@gmail.ru; Gall, N. R. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2017-04-15

    It is shown that, in contradiction with the fundamental results obtained for free graphene, graphene films grown on the Rh(111) surface to thicknesses from one to ~(12–15) single layers do not absorb visible electromagnetic radiation emitted from the surface and influence neither the brightness nor true temperature of the sample. At larger thicknesses, such absorption occurs. This effect is observed for the surfaces of other metals, specifically, Pt(111), Re(1010), and Ni(111) and, thus, can be considered as being universal. It is thought that the effect is due to changes in the electronic properties of thin graphene layers because of electron transfer between graphene and the metal substrate.

  18. Preparation of Composited Graphene/PEDOT:PSS Film for Its Possible Application in Graphene-based Organic Solar Cells

    YU Yue; LI Meicheng; CHU Lihua; YU Hakki; Wodtke A M; ZHAO Yan; ZHANG Zhongmo

    2015-01-01

    The interface between graphene and organic layers is a key factor responsible for the performance of gra-phene-based organic solar cells (OSCs). In this paper, we focus on coating PEDOT:PSS onto the surface of graphene. We demonstrate two approaches, applying UV/Ozone treatment on graphene and modifying PEDOT:PSS with Zonyl, to get a PEDOT:PSS well-coated graphene film . Our results prove that both methods can be effective to solve the interface issue between graphene and PEDOT: PSS. Thereby it shows a positive application of the composited gra-phene/PEDOT:PSS film on graphene-based OSCs.

  19. Molecularly engineered graphene surfaces for sensing applications: A review

    Liu, Jingquan; Liu, Zhen; Barrow, Colin J.; Yang, Wenrong

    2015-01-01

    Highlights: • The importance of surface chemistry of graphene materials is clearly described. • We discuss molecularly engineered graphene surfaces for sensing applications. • We describe the latest developments of these materials for sensing technology. - Abstract: Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis

  20. Molecularly engineered graphene surfaces for sensing applications: A review

    Liu, Jingquan, E-mail: jliu@qdu.edu.cn [College of Chemical Science and Engineering, Laboratory of Fiber Materials and Modern Textile, The Growing Base for State Key Laboratory, Qingdao University, Qingdao (China); Liu, Zhen; Barrow, Colin J. [Centre for Chemistry and Biotechnology, Deakin University, Geelong, VIC 3217 (Australia); Yang, Wenrong, E-mail: wenrong.yang@deakin.edu.au [Centre for Chemistry and Biotechnology, Deakin University, Geelong, VIC 3217 (Australia)

    2015-02-15

    Highlights: • The importance of surface chemistry of graphene materials is clearly described. • We discuss molecularly engineered graphene surfaces for sensing applications. • We describe the latest developments of these materials for sensing technology. - Abstract: Graphene is scientifically and commercially important because of its unique molecular structure which is monoatomic in thickness, rigorously two-dimensional and highly conjugated. Consequently, graphene exhibits exceptional electrical, optical, thermal and mechanical properties. Herein, we critically discuss the surface modification of graphene, the specific advantages that graphene-based materials can provide over other materials in sensor research and their related chemical and electrochemical properties. Furthermore, we describe the latest developments in the use of these materials for sensing technology, including chemical sensors and biosensors and their applications in security, environmental safety and diseases detection and diagnosis.

  1. Graphene surface plasmon polaritons with opposite in-plane electron oscillations along its two surfaces

    Liang, Huawei; Ruan, Shuangchen; Zhang, Min; Su, Hong; Li, Irene Ling

    2015-01-01

    We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices

  2. Graphene surface plasmon polaritons with opposite in-plane electron oscillations along its two surfaces

    Liang, Huawei; Ruan, Shuangchen, E-mail: scruan@szu.edu.cn; Zhang, Min; Su, Hong; Li, Irene Ling [Shenzhen Key Laboratory of Laser Engineering, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060 (China)

    2015-08-31

    We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices.

  3. Synthesis and characterization of graphene layers prepared by low-pressure chemical vapor deposition using triphenylphosphine as precursor

    Mastrapa, G.C.; Maia da Costa, M.E.H. Maia [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Larrude, D.G., E-mail: dunigl@vdg.fis.puc-rio.br [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Freire, F.L. [Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900, Rio de Janeiro, RJ (Brazil); Brazilian Center for Physical Research, 22290-180, Rio de Janeiro, RJ (Brazil)

    2015-09-15

    The synthesis of a single-layer graphene using a low-pressure Chemical Vapor Deposition (CVD) system with triphenylphosphine as precursor is reported. The amount of triphenylphosphine used as precursor was in the range of 10–40 mg. Raman spectroscopy was employed to analyze samples prepared with 10 mg of the precursor, and these spectra were found typical of graphene. The Raman measurements indicate that the progressive degradation of graphene occurs as the amount of triphenylphosphine increases. X-ray photoelectron spectroscopy measurements were performed to investigate the different chemical environments involving carbon and phosphorous atoms. Scanning electron microscopy and transmission electron microscopy were also employed and the results reveal the formation of dispersed nanostructures on top of the graphene layer, In addition, the number of these nanostructures is directly related to the amount of precursor used for sample growth. - Highlights: • We grow graphene using the solid precursor triphenylphosphine. • Raman analysis confirms the presence of monolayer graphene. • SEM images show the presence of small dark areas dispersed on the graphene surface. • Raman I{sub D}/I{sub G} ratio increases in the dark region of the graphene surface.

  4. Green approach for preparation of reduced graphene oxide decorated with gold nanoparticles and its optical and catalytic properties

    Šimšíková, M., E-mail: michaela.simsikova@ceitec.vutbr.cz [CEITEC BUT, Brno University of Technology, Technická 10, 616 69 Brno (Czech Republic); Bartoš, M. [CEITEC BUT, Brno University of Technology, Technická 10, 616 69 Brno (Czech Republic); Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic); Keša, P. [Department of Biochemistry, Faculty of Science, P.J. Šafárik University, Šrobárova 2, 041 54 Košice (Slovakia); Department of Biophysics, Institute of Experimental Physics, SAS, Watsonova 47, 040 01 Košice (Slovakia); Šikola, T. [CEITEC BUT, Brno University of Technology, Technická 10, 616 69 Brno (Czech Republic); Institute of Physical Engineering, Brno University of Technology, Technická 2, 616 69 Brno (Czech Republic)

    2016-07-01

    Graphene oxide (GO) was reduced and modified by gold nanoparticles using aqueous leaf extract of green tea. Successful formation of gold nanoparticles (AuNPs) on graphene oxide surface was determined by scanning electron microscopy (SEM). Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared analyses (FT-IR) have been used to demonstrate the behavior of complex of reduced graphene oxide with gold nanoparticles (rGO-AuNPs), the removal of oxygen-containing groups from the graphene, and subsequent formation of reduced graphene oxide (rGO). We also demonstrated the change of optical properties of GO after the reduction and formation of gold nanoparticles on its surface by UV–vis spectroscopy and fluorescence spectroscopy. The positive impact of rGO-AuNPs composite on safranin T reduction in the presence of NaBH{sub 4} without light irradiation was examined, as well. The dye decolorization was observed within 60 min which highlights the exceptional catalytic potential of the rGO-AuNPs. - Highlights: • Reduction of GO was performed by an environmentally friendly approach. • Gold nanoparticles were prepared by self-assembly on the graphene oxide surface. • Surface properties were enhanced after the formation of gold nanoparticles. • Optical properties have been changed after the graphene reduction and formation of gold nanoparticles. • The decolorization of safranin T was observed within 60 min.

  5. Green approach for preparation of reduced graphene oxide decorated with gold nanoparticles and its optical and catalytic properties

    Šimšíková, M.; Bartoš, M.; Keša, P.; Šikola, T.

    2016-01-01

    Graphene oxide (GO) was reduced and modified by gold nanoparticles using aqueous leaf extract of green tea. Successful formation of gold nanoparticles (AuNPs) on graphene oxide surface was determined by scanning electron microscopy (SEM). Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared analyses (FT-IR) have been used to demonstrate the behavior of complex of reduced graphene oxide with gold nanoparticles (rGO-AuNPs), the removal of oxygen-containing groups from the graphene, and subsequent formation of reduced graphene oxide (rGO). We also demonstrated the change of optical properties of GO after the reduction and formation of gold nanoparticles on its surface by UV–vis spectroscopy and fluorescence spectroscopy. The positive impact of rGO-AuNPs composite on safranin T reduction in the presence of NaBH_4 without light irradiation was examined, as well. The dye decolorization was observed within 60 min which highlights the exceptional catalytic potential of the rGO-AuNPs. - Highlights: • Reduction of GO was performed by an environmentally friendly approach. • Gold nanoparticles were prepared by self-assembly on the graphene oxide surface. • Surface properties were enhanced after the formation of gold nanoparticles. • Optical properties have been changed after the graphene reduction and formation of gold nanoparticles. • The decolorization of safranin T was observed within 60 min.

  6. Epitaxial graphene-encapsulated surface reconstruction of Ge(110)

    Campbell, Gavin P.; Kiraly, Brian; Jacobberger, Robert M.; Mannix, Andrew J.; Arnold, Michael S.; Hersam, Mark C.; Guisinger, Nathan P.; Bedzyk, Michael J.

    2018-04-01

    Understanding and engineering the properties of crystalline surfaces has been critical in achieving functional electronics at the nanoscale. Employing scanning tunneling microscopy, surface x-ray diffraction, and high-resolution x-ray reflectivity experiments, we present a thorough study of epitaxial graphene (EG)/Ge(110) and report a Ge(110) "6 × 2" reconstruction stabilized by the presence of epitaxial graphene unseen in group-IV semiconductor surfaces. X-ray studies reveal that graphene resides atop the surface reconstruction with a 0.34 nm van der Waals (vdW) gap and provides protection from ambient degradation.

  7. High photoactive and visible-light responsive graphene/titanate nanotubes photocatalysts: preparation and characterization.

    Qianqian, Zhai; Tang, Bo; Guoxin, Hu

    2011-12-30

    A series of graphene/titanate nanotubes (TNTs) photocatalysts using graphene and nanoscale TiO(2) or P25 as original materials were fabricated by hydrothermal method. Both low hydrothermal temperature and proper amount of graphene are propitious to better photoactivity. The photocatalytic activities of these nanocomposites far exceed that of P25, pure TNTs and reported TiO(2)-based nanocomposites for the degradation of Rhodamine-B under visible-light irradiation. These prepared photocatalysts were characterized by TEM, XRD, XPS, BET, FTIR and UV-vis diffuse reflection spectra, and the results indicate that the outstanding photoactivities in visible-light region result from sensitization effect of graphene rather than impurity level in the band gap of TNTs. Furthermore, large BET surface areas of these photocatalysts (almost 10 times larger than that of previously reported graphene/TiO(2) nanoparticles) evidently enhance their absorption abilities and photocatalytic performances (the rate constants of degrading Rhodamine-B are at least 5 times higher than that of previously reported photocatalysts). These photocatalysts show good stability, and their photoactivities do not obviously decrease after four times of repeated uses. A detailed photocatalytic mechanism is suggested, as well. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Surface modification of multilayer graphene using Ga ion irradiation

    Wang, Quan, E-mail: wangq@mail.ujs.edu.cn [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Shao, Ying; Ge, Daohan; Ren, Naifei [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yang, Qizhi [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013 (China); State key laboratory of Robotics, Chinese Academy of Sciences, Shengyang 110000 (China)

    2015-04-28

    The effect of Ga ion irradiation intensity on the surface of multilayer graphene was examined. Using Raman spectroscopy, we determined that the irradiation caused defects in the crystal structure of graphene. The density of defects increased with the increase in dwell times. Furthermore, the strain induced by the irradiation changed the crystallite size and the distance between defects. These defects had the effect of doping the multilayer graphene and increasing its work function. The increase in work function was determined using contact potential difference measurements. The surface morphology of the multilayer graphene changed following irradiation as determined by atomic force microscopy. Additionally, the adhesion between the atomic force microscopy tip and sample increased further indicating that the irradiation had caused surface modification, important for devices that incorporate graphene.

  9. Mechanical tearing of graphene on an oxidizing metal surface

    George, Lijin; Gupta, Aparna; Shaina, P R; Jaiswal, Manu; Gupta, Nandita Das

    2015-01-01

    Graphene, the thinnest possible anticorrosion and gas-permeation barrier, is poised to transform the protective coatings industry for a variety of surface applications. In this work, we have studied the structural changes of graphene when the underlying copper surface undergoes oxidation upon heating. Single-layer graphene directly grown on a copper surface by chemical vapour deposition was annealed under ambient atmosphere conditions up to 400 °C. The onset temperature of the surface oxidation of copper is found to be higher for graphene-coated foils. Parallel arrays of graphene nanoripples are a ubiquitous feature of pristine graphene on copper, and we demonstrate that these form crucial sites for the onset of the oxidation of copper, particularly for ∼0.3–0.4 μm ripple widths. In these regions, the oxidation proceeds along the length of the nanoripples, resulting in the formation of parallel stripes of oxidized copper regions. We demonstrate from temperature-dependent Raman spectroscopy that the primary defect formation process in graphene involves boundary-type defects rather than vacancy or sp"3-type defects. This observation is consistent with a mechanical tearing process that splits graphene into small polycrystalline domains. The size of these is estimated to be sub-50 nm. (paper)

  10. Mechanical tearing of graphene on an oxidizing metal surface.

    George, Lijin; Gupta, Aparna; Shaina, P R; Das Gupta, Nandita; Jaiswal, Manu

    2015-12-11

    Graphene, the thinnest possible anticorrosion and gas-permeation barrier, is poised to transform the protective coatings industry for a variety of surface applications. In this work, we have studied the structural changes of graphene when the underlying copper surface undergoes oxidation upon heating. Single-layer graphene directly grown on a copper surface by chemical vapour deposition was annealed under ambient atmosphere conditions up to 400 °C. The onset temperature of the surface oxidation of copper is found to be higher for graphene-coated foils. Parallel arrays of graphene nanoripples are a ubiquitous feature of pristine graphene on copper, and we demonstrate that these form crucial sites for the onset of the oxidation of copper, particularly for ∼0.3-0.4 μm ripple widths. In these regions, the oxidation proceeds along the length of the nanoripples, resulting in the formation of parallel stripes of oxidized copper regions. We demonstrate from temperature-dependent Raman spectroscopy that the primary defect formation process in graphene involves boundary-type defects rather than vacancy or sp(3)-type defects. This observation is consistent with a mechanical tearing process that splits graphene into small polycrystalline domains. The size of these is estimated to be sub-50 nm.

  11. Atomic and electronic structure of a copper/graphene interface as prepared and 1.5 years after

    Boukhvalov, D. W.; Bazylewski, P. F.; Kukharenko, A. I.; Zhidkov, I. S.; Ponosov, Yu. S.; Kurmaev, E. Z.; Cholakh, S. O.; Lee, Y. H.; Chang, G. S.

    2017-12-01

    We report the results of X-ray spectroscopy and Raman measurements of as-prepared graphene on a high quality copper surface and the same materials after 1.5 years under different conditions (ambient and low humidity). The obtained results were compared with density functional theory calculations of the formation energies and electronic structures of various structural defects in graphene/Cu interfaces. For evaluation of the stability of the carbon cover, we propose a two-step model. The first step is oxidation of the graphene, and the second is perforation of graphene with the removal of carbon atoms as part of the carbon dioxide molecule. Results of the modeling and experimental measurements provide evidence that graphene grown on high-quality copper substrate becomes robust and stable in time (1.5 years). However, the stability of this interface depends on the quality of the graphene and the number of native defects in the graphene and substrate. The effect of the presence of a metallic substrate with defects on the stability and electronic structure of graphene is also discussed

  12. Localized in situ polymerization on graphene surfaces for stabilized graphene dispersions.

    Das, Sriya; Wajid, Ahmed S; Shelburne, John L; Liao, Yen-Chih; Green, Micah J

    2011-06-01

    We demonstrate a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets. Graphene sheets show great promise as strong, conductive fillers in polymer nanocomposites; however, difficulties in dispersion quality and interfacial strength between filler and matrix have been a persistent problem for graphene-based nanocomposites, particularly for pristine graphene. With this in mind, a physisorbed polymer layer is used to stabilize graphene sheets in solution. To create this protective layer, we formed an organic microenvironment around dispersed graphene sheets in surfactant solutions, and created a nylon 6, 10 or nylon 6, 6 coating via interfacial polymerization. Technique lies at the intersection of emulsion and admicellar polymerization; a similar technique was originally developed to protect luminescent properties of carbon nanotubes in solution. These coated graphene dispersions are aggregation-resistant and may be reversibly redispersed in water even after freeze-drying. The coated graphene holds promise for a number of applications, including multifunctional graphene-polymer nanocomposites. © 2011 American Chemical Society

  13. Preparation of an antibacterial, hydrophilic and photocatalytically active polyacrylic coating using TiO2 nanoparticles sensitized by graphene oxide.

    Nosrati, Rahimeh; Olad, Ali; Shakoori, Sahar

    2017-11-01

    In recent years more attentions have been paid for preparation of coatings with self-cleaning and antibacterial properties. These properties allow the surface to maintain clean and health over long times without any need to cleaning or disinfection. Acrylic coatings are widely used on various surfaces such as automotive, structural and furniture which their self-cleaning and antibacterial ability is very important. The aim of this work is the preparation of a polyacrylic based self-cleaning and antibacterial coating by the modification of TiO 2 as a coating additive. TiO 2 nanoparticles were sensitized to the visible light irradiation using graphene oxide through the preparation of TiO 2 /graphene oxide nanocomposite. Graphene oxide was prepared via a modified Hummers method. TiO 2 /graphene oxide nanocomposite was used as additive in a polyacrylic coating formulation. Hydrophilicity, photocatalytic and antibacterial activities as well as coating stability were evaluated for TiO 2 /graphene oxide modified polyacrylic coating and compared with that of pristine TiO 2 modified and unmodified polyacrylic coatings. TiO 2 /graphene oxide nanocomposite and polyacrylic coating modified by TiO 2 /graphene oxide additive were characterized using FT-IR, UV-Vis, XRD, and FESEM techniques. The effect of TiO 2 /graphene oxide composition and its percent in the coating formulation was evaluated on the polyacrylic coating properties. Results showed that polyacrylic coating having 3% W TiO 2 /graphene oxide nanocomposite additive with TiO 2 to graphene oxide ratio of 100:20 is the best coating considering most of beneficial features such as high photodecolorization efficiency of organic dye contaminants, high hydrophilicity, and stability in water. According to the results, TiO 2 is effectively sensitized by graphene oxide and the polyacrylic coating modified by TiO 2 /graphene oxide nanocomposite shows good photocatalytic activity under visible light irradiation. Copyright © 2017

  14. Solvothermal tuning of photoluminescent graphene quantum dots: from preparation to photoluminescence mechanism

    Qi, Bao-Ping; Zhang, Xiaoru; Shang, Bing-Bing; Xiang, Dongshan; Zhang, Shenghui

    2018-02-01

    Solvothermal synthesis was employed to tune the surface states of graphene quantum dots (GQDs). Two series of GQDs with the particle sizes from 2.6 to 4.5 nm were prepared as follows: (I) GQDs with the same size but different oxygen degrees; (II) GQDs with different core sizes but the similar surface chemistry. Both the large sizes and the high surface oxidation degrees led to the redshift photoluminescence (PL) of GQDs. Electrochemiluminescence (ECL) spectra from two series of GQDs were all in accordance with their PL spectra, respectively, which provided good evidence for the conjugated structures in GQDs responsible for PL. [Figure not available: see fulltext.

  15. Nitrogen-doped graphene prepared by a transfer doping approach for the oxygen reduction reaction application

    Mo, Zaiyong; Zheng, Ruiping; Peng, Hongliang; Liang, Huagen; Liao, Shijun

    2014-01-01

    Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm-2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.

  16. Solvent exfoliated graphene for reinforcement of PMMA composites prepared by in situ polymerization

    Wang, Jialiang; Shi, Zixing; Ge, Yu; Wang, Yan; Fan, Jinchen; Yin, Jie

    2012-01-01

    Graphene (GP)-based polymer nanocomposites have attracted considerable scientific attention due to its pronounced improvement in mechanical, thermal and electrical properties compared with pure polymers. However, the preparation of well-dispersed and high-quality GP reinforced polymer composites remains a challenge. In this paper, a simple and facile approach for preparation of poly(methyl methacrylate) (PMMA) functionalized GP (GPMMA) via in situ free radical polymerization is reported. Fourier transform infrared (FTIR), X-ray photoelectron spectra (XPS), Raman, transmission electron microscope (TEM) and thermogravimetric analysis (TGA) are used to confirm the successful grafting of PMMA chains onto the GP sheets. Composite films are prepared by incorporating different amounts of GPMMA into the PMMA matrix through solution-casting method. Compared with pure PMMA, PMMA/GPMMA composites show simultaneously improved Young's modulus, tensile stress, elongation at break and thermal stability by addition of only 0.5 wt% GPMMA. The excellent reinforcement is attributed to good dispersion of high-quality GPMMA and strong interfacial adhesion between GPMMA and PMMA matrix as evidenced by scanning electron microscope (SEM) images of the fracture surfaces. Consequently, this simple protocol has great potential in the preparation of various high-performance polymer composites. Highlights: ► Functionalization of solvent exfoliated graphene by in situ polymerization. ► A simple and scalable method for preparing high-quality graphene. ► Functionalized graphene can be well-dispersed and have a strong interfacial adhesion with the polymer matrix. ► The nanocomposites exhibit a remarkable improvement of thermal and mechanical properties.

  17. Exciting Graphene Surface Plasmon Polaritons through Light and Sound Interplay

    Farhat, Mohamed; Guenneau, Sé bastien; Bagci, Hakan

    2013-01-01

    We propose a concept that allows for efficient excitation of surface plasmon spolaritons (SPPs) on a thin graphene sheet located on a substrate by an incident electromagnetic field. Elastic vibrations of the sheet, which are generated by a flexural wave, act as a grating that enables the electromagnetic field to couple to propagating graphene SPPs. This scheme permits fast on-off switching of the SPPs and dynamic tuning of their excitation frequency by adjusting the vibration frequency (grating period). Potential applications include single molecule detection and enhanced control of SPP trajectories via surface wave patterning of graphene metasurfaces. Analytical calculations and numerical experiments demonstrate the practical applicability of the proposed concept.

  18. Exciting Graphene Surface Plasmon Polaritons through Light and Sound Interplay

    Farhat, Mohamed

    2013-12-05

    We propose a concept that allows for efficient excitation of surface plasmon spolaritons (SPPs) on a thin graphene sheet located on a substrate by an incident electromagnetic field. Elastic vibrations of the sheet, which are generated by a flexural wave, act as a grating that enables the electromagnetic field to couple to propagating graphene SPPs. This scheme permits fast on-off switching of the SPPs and dynamic tuning of their excitation frequency by adjusting the vibration frequency (grating period). Potential applications include single molecule detection and enhanced control of SPP trajectories via surface wave patterning of graphene metasurfaces. Analytical calculations and numerical experiments demonstrate the practical applicability of the proposed concept.

  19. Passivated graphene transistors fabricated on a millimeter-sized single-crystal graphene film prepared with chemical vapor deposition

    Lin, Meng-Yu; Lee, Si-Chen; Lin, Shih-Yen; Wang, Cheng-Hung; Chang, Shu-Wei

    2015-01-01

    In this work, we first investigate the effects of partial pressures and flow rates of precursors on the single-crystal graphene growth using chemical vapor depositions on copper foils. These factors are shown to be critical to the growth rate, seeding density and size of graphene single crystals. The prepared graphene films in millimeter sizes are then bubbling transferred to silicon-dioxide/silicon substrates for high-mobility graphene transistor fabrications. After high-temperature annealing and hexamethyldisilazane passivation, the water attachment is removed from the graphene channel. The elimination of uncontrolled doping and enhancement of carrier mobility accompanied by these procedures indicate that they are promising for fabrications of graphene transistors. (paper)

  20. Preparation of Ni(OH)2-graphene sheet-carbon nanotube composite as electrode material for supercapacitors

    Liu, Y.F.; Yuan, G.H.; Jiang, Z.H.; Yao, Z.P.; Yue, M.

    2015-01-01

    Highlights: • CNT is introduced into graphene to prevent restacking by solvothermal reaction. • Ethanol as a low cost and green solvent is used in solvothermal reaction. • Ni(OH) 2 nanosheets were chemically precipitated into GS-CNT to increase the capacitance. - Abstract: Ni(OH) 2 -graphene sheet-carbon nanotube composite was prepared for supercapacitance materials through a simple two-step process involving solvothermal synthesis of graphene sheet-carbon nanotube composite in ethanol and chemical precipitation of Ni(OH) 2 . According to N 2 adsorption/desorption analysis, the Brunauer–Emmett–Teller surface area of graphene sheet-carbon nanotube composite (109.07 m 2 g −1 ) was larger than that of pure graphene sheets (32.06 m 2 g −1 ), indicating that the added carbon nanotubes (15 wt.%) could prevent graphene sheets from restacking in the solvothermal reaction. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Ni(OH) 2 nanosheets were uniformly loaded into the three-dimensional interconnected network of graphene sheet-carbon nanotube composite. The microstructure enhanced the rate capability and utilization of Ni(OH) 2 . The specific capacitance of Ni(OH) 2 -graphene sheet-carbon nanotube composite was 1170.38 F g −1 at a current density of 0.2 A g −1 in the 6 mol L −1 KOH solution, higher than those provided by pure Ni(OH) 2 (953.67 Fg −1 ) and graphene sheets (178.25 F g −1 ). After 20 cycles at each current density (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 A g −1 ), the capacitance of Ni(OH) 2 -graphene sheet-carbon nanotube composite decreased 26.96% of initial capacitance compared to 74.52% for pure Ni(OH) 2

  1. Facile Dry Surface Cleaning of Graphene by UV Treatment

    Kim, Jin Hong; Haidari, Mohd Musaib; Choi, Jin Sik; Kim, Hakseong; Yu, Young-Jun; Park, Jonghyurk

    2018-05-01

    Graphene has been considered an ideal material for application in transparent lightweight wearable electronics due to its extraordinary mechanical, optical, and electrical properties originating from its ordered hexagonal carbon atomic lattice in a layer. Precise surface control is critical in maximizing its performance in electronic applications. Graphene grown by chemical vapor deposition is widely used but it produces polymeric residue following wet/chemical transfer process, which strongly affects its intrinsic electrical properties and limits the doping efficiency by adsorption. Here, we introduce a facile dry-cleaning method based on UV irradiation to eliminate the organic residues even after device fabrication. Through surface topography, Raman analysis, and electrical transport measurement characteristics, we confirm that the optimized UV treatment can recover the clean graphene surface and improve graphene-FET performance more effectively than thermal treatment. We propose our UV irradiation method as a systematically controllable and damage-free post process for application in large-area devices.

  2. The influence of the preparation conditions on structure and optical properties of solid films of graphene oxide

    Seliverstova, E; Ibrayev, N; Dzhanabekova, R; Gladkova, V

    2016-01-01

    In this study, we investigated the physico-chemical properties of graphene oxide monolayers at the interface water-air. Monolayers were formed by the spreading of dispersion of graphene oxide in acetone and THF. It was found than graphene monolayers are in the “liquid” state on the surface of subphase. Monolayers were transferred onto solid substrates according to Langmuir-Blodgett (LB) method. SEM images show that the films have an island structure. The films obtained from acetone solutions are more uniform, which makes them more promising in terms of their use as conductive coatings. Absorption spectrum of graphene LB films exhibits a broad band in the ultraviolet and visible region of the spectrum. The optical density of the film obtained from acetone solution is greater than the optical density of the film prepared from THF. In the visible region of the spectrum both films have high transparency. (paper)

  3. Preparation and Investigation of the Microtribological Properties of Graphene Oxide and Graphene Films via Electrostatic Layer-by-Layer Self-Assembly

    Yongshou Hu

    2015-01-01

    Full Text Available Graphene oxide (GO films with controlled layers, deposited on single-crystal silicon substrates, were prepared by electrostatic self-assembly of negatively charged GO sheets. Afterward, graphene films were prepared by liquid-phase reduction of as-prepared GO films using hydrazine hydrate. The microstructures and microtribological properties of the samples were studied using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, UV-vis absorption spectroscopy, water contact angle measurement, and atomic force microscopy. It is found that, whether GO films or graphene films, the adhesion force and the coefficients of friction both show strong dependence on the number of self-assembled layers, which both allow a downward trend as the number of self-assembled layers increases due to the interlayer sliding and the puckering effect when the tip slipped across the top surface of the films. Moreover, in comparison with the GO films with the same self-assembled layers, the graphene films possess lower adhesion force and coefficient of friction attributed to the difference of surface functional groups.

  4. Preparation and characterization of graphene/turbostratic carbon derived from chitosan film for supercapacitor electrodes

    Hanappi, M. F. Y. M.; Deraman, M.; Suleman, M.; Othman, M. A. R.; Basri, N. H.; Nor, N. S. M.; Hamdan, E.; Sazali, N. E. S.; Tajuddin, N. S. M.

    2018-04-01

    Electrochemical capacitors or supercapacitors are the potential energy storage devices which are known for having higher specific capacitance and specific energy than electrolytic capacitors. Electric double-layer capacitors (EDLCs) also referred as ultracapacitors is a class of supercapacitors that employ different forms of carbon like activated carbon, CNT, graphene etc., as electrodes. The performance of the supercapacitors is determined by its components namely electrolyte, electrode, etc. Carbon electrodes with high surface area and desired pore size distribution are always preferred and which can be tailored by varying the precursor and method of preparation. In recent years, owing to their low cost, ease of synthesis, high stability and conductivity, the activated carbons derived from biomass precursors have been investigated as potential electrode material for the EDLCs. In this report, we present the preparation and characterization of graphene/turbostratic carbon monolith (CM) electrodes from the carbon grains (CGs) obtained by carbonization (under the flow of nitrogen, N2 gas and over a temperature range from 600 °C to 1000 °C) of biomass precursor chitosan film. The procedure to prepare the chitosan film is described elsewhere. The carbon grains are characterized using Raman spectroscopy (RS) and X-ray diffraction (XRD). We expect that the CGs would have the similar characteristics as graphene and would be a potential electrode material for EDLCs application.

  5. Electrochemical preparation of poly(methylene blue)/graphene nanocomposite thin films

    Erçarıkcı, Elif; Dağcı, Kader; Topçu, Ezgi; Alanyalıoğlu, Murat

    2014-01-01

    Highlights: • Poly(MB)/graphene thin films are prepared by a simple electrochemical approach. • Graphene layers in the film show a broad band in visible region of absorbance spectra. • Morphology of composite films indicates both disordered and ordered regions. • XRD reveals that nanocomposite films include rGO layers after electropolymerization process. • Chemically prepared graphene is better than electrochemically prepared graphene for electrooxidation of nitrite. - Abstract: Poly(methylene blue)/graphene nanocomposite thin films were prepared by electropolymerization of methylene blue in the presence of graphene which have been synthesized by two different methods of a chemical oxidation process and an electrochemical approach. Synthesized nanocomposite thin films were characterized by using cyclic voltammetry, UV–vis. absorption spectroscopy, powder X-ray diffraction, and scanning tunneling microscopy techniques. Electrocatalytical properties of prepared poly(methylene blue)/graphene nanocomposite films were compared toward electrochemical oxidation of nitrite. Under optimized conditions, electrocatalytical effect of nanocomposite films of chemically prepared graphene through electrochemical oxidation of nitrite was better than that of electrochemically prepared graphene

  6. Mn{sub 3}O{sub 4} nanoparticles embedded into graphene nanosheets: Preparation, characterization, and electrochemical properties for supercapacitors

    Wang Bei [School of Mechanical, Materials and Mechatronic Engineering and Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia)] [Department of Chemistry and Forensic Science, University of Technology, Sydney, City Campus, Broadway, Sydney, NSW 2007 (Australia); Park, Jinsoo [School of Materials Science and Engineering, Gyeongsang National University, 900 Gazwa-dong, Jinju, Gyeongnam 660 -701 (Korea, Republic of); Wang Chengyin [Department of Chemistry and Forensic Science, University of Technology, Sydney, City Campus, Broadway, Sydney, NSW 2007 (Australia); Ahn, Hyojun [School of Materials Science and Engineering, Gyeongsang National University, 900 Gazwa-dong, Jinju, Gyeongnam 660 -701 (Korea, Republic of); Wang, Guoxiu, E-mail: Guoxiu.Wang@uts.edu.a [School of Mechanical, Materials and Mechatronic Engineering and Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia)] [Department of Chemistry and Forensic Science, University of Technology, Sydney, City Campus, Broadway, Sydney, NSW 2007 (Australia)

    2010-09-01

    Mn{sub 3}O{sub 4}/graphene nanocomposites were synthesized by mixing graphene suspension in ethylene glycol with MnO{sub 2} organosol, followed by subsequent ultrasonication processing and heat treatment. The as-prepared product consists of nanosized Mn{sub 3}O{sub 4} particles homogeneously distributed on graphene nanosheets, which has been confirmed by field emission scanning electron microscopy and transmission electron microscopy analysis. Atomic force microscope analysis further identified the distribution of dense Mn{sub 3}O{sub 4} nanoparticles on graphene nanosheets. When used as electrode materials in supercapacitors, Mn{sub 3}O{sub 4}/graphene nanocomposites exhibited a high specific capacitance of 175 F g{sup -1} in 1 M Na{sub 2}SO{sub 4} electrolyte and 256 F g{sup -1} in 6 M KOH electrolyte, respectively. The enhanced supercapacitance of Mn{sub 3}O{sub 4}/graphene nanocomposites could be ascribed to both electrochemical contributions of Mn{sub 3}O{sub 4} nanoparticles, functional groups attached to graphene nanosheets, and significantly increased specific surface area.

  7. Investigation of CVD graphene topography and surface electrical properties

    Wang, Rui; Pearce, Ruth; Gallop, John; Patel, Trupti; Pollard, Andrew; Hao, Ling; Zhao, Fang; Jackman, Richard; Klein, Norbert; Zurutuza, Amaia

    2016-01-01

    Combining scanning probe microscopy techniques to characterize samples of graphene, a selfsupporting, single atomic layer hexagonal lattice of carbon atoms, provides far more information than a single technique can. Here we focus on graphene grown by chemical vapour deposition (CVD), grown by passing carbon containing gas over heated copper, which catalyses single atomic layer growth of graphene on its surface. To be useful for applications the graphene must be transferred onto other substrates. Following transfer it is important to characterize the CVD graphene. We combine atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM) to reveal several properties of the transferred film. AFM alone provides topographic information, showing ‘wrinkles’ where the transfer provided incomplete substrate attachment. SKPM measures the surface potential indicating regions with different electronic properties for example graphene layer number. By combining AFM and SKPM local defects and impurities can also be observed. Finally, Raman spectroscopy can confirm the structural properties of the graphene films, such as the number of layers and level of disorder, by observing the peaks present. We report example data on a number of CVD samples from different sources. (paper)

  8. Hydrophobic and optical characteristics of graphene and graphene oxide films transferred onto functionalized silica particles deposited glass surface

    Yilbas, B. S.; Ibrahim, A.; Ali, H.; Khaled, M.; Laoui, T.

    2018-06-01

    Hydrophobic and optical transmittance characteristics of the functionalized silica particles on the glass surface prior and after transfer of graphene and graphene oxide films on the surface are examined. Nano-size silica particles are synthesized and functionalized via chemical grafting and deposited onto a glass surface. Graphene film, grown on copper substrate, was transferred onto the functionalized silica particles surface through direct fishing method. Graphene oxide layer was deposited onto the functionalized silica particles surface via spin coating technique. Morphological, hydrophobic, and optical characteristics of the functionalized silica particles deposited surface prior and after graphene and graphene oxide films transfer are examined using the analytical tools. It is found that the functionalized silica particles are agglomerated at the surface forming packed structures with few micro/nano size pores. This arrangement gives rise to water droplet contact angle and contact angle hysteresis in the order of 163° and 2°, respectively, and remains almost uniform over the entire surface. Transferring graphene and depositing graphene oxide films over the functionalized silica particles surface lowers the water droplet contact angle slightly (157-160°) and increases the contact angle hysteresis (4°). The addition of the graphene and graphene oxide films onto the surface of the deposited functionalized silica particles improves the optical transmittance.

  9. Continuous Reduced Graphene Oxide Film Prepared by Stitching of Nanosheets at the Interface of Two Immiscible Solutions

    Sohn, Young Ku; Kim, Seog K.; Min, Bong Ki

    2011-01-01

    RGO sheets dispersed in water are prepared by chemical reduction of GO using ascorbic acid. By mixing and sonication of submicron-size RGO sheets in two immiscible liquids (e. g., chloroform and water) for the first time we have prepared a continuous large-area RGO film at the interface. In other words, we have shown that aggregated RGO sheets could be fully stretched at the interface to form a continuous film. The RGO film has been characterized by SEM, TEM, UV-vis absorption, XPS and Raman. The film exhibits high flexibility, transparency, and very long-term stability without forming aggregations. Without requiring vapor deposition, a special instrument, or a filtration followed by a removing the filter paper one could easily achieve a continuous RGO-film in any laboratories. Our solution-based method is much simpler and cost-effective, and very good for large scale mass production. This finding could boost real applications of graphene in laboratory and industry, and provide a new methodology for the fabrication of large-area continuous graphene films. Graphene, an atom-thick two-dimensional (2D) honeycomb lattice sheet of sp 2 -bonded carbon atoms, has recently been emerged as a new promising material in various fields. Because of its gigantic charge carrier mobility it could be applied to field-effect transistors as a substitute of silicon. Due to its transparency and high electrical conductivity, it could be used as a substitute of ITO electrode in solar cells and light-emitting diodes. Other superior properties include large surface area, flexibility, strength, stiffness, and thermal conductivity. These provides wide applications of graphene including supercapa-citor, battery, sensor, storage and drug delivery. For real applications, large-scale of graphene sheets or films needs to be prepared. Large-area (orders of centimeters) graphene films have recently been fabricated using a chemical vapor deposition (CVD) method on various metal substrates. This

  10. Preparation of dispersible graphene through organic functionalization of graphene using a zwitterion intermediate cycloaddition approach

    Zhang, Xiaoyan; Browne, Wesley R.; Feringa, Ben L.

    2012-01-01

    Highly functionalized graphene were obtained through a zwitterion intermediate cycloaddition onto exfoliated graphene flakes under new reaction conditions. The functionalized graphene obtained formed stable dispersions in common solvents, including dimethylformamide (DMF), CHCl3 and water. Its

  11. High performance supercapacitor using N-doped graphene prepared via supercritical fluid processing with an oxime nitrogen source

    Balaji, S. Suresh; Elavarasan, A.; Sathish, M.

    2016-01-01

    Graphical abstract: N-doped graphene prepared via supercritical fluid processing with oxime nitrogen source (DMG) showed enhanced performance in electrochemical supercapacitor application. A maximum specific capacitance of 286 F g"−"1 at a current density of 0.5 A/g was achieved with a high specific capacity retention of 98% after 1000 cycles at 5 A/g. - Highlights: • N-functionalised graphene synthesized via supercritical fluid processing. • DMG, an oxime based nitrogen precursor. • Maximum specific capacitance of 286 F/g at 0.5 A/g in aqueous solution. • Pyridinic as well as quarternary nitrogen for enhanced capacitance. - Abstract: Heteroatom doped graphene has been proved for its promising applications in electrochemical energy storage systems. Here, nitrogen (N) doped graphene was prepared via two different techniques namely supercritical fluid assisted processing and hydrothermal heat treatment using dimethylglyoxime (DMG) as an oxime nitrogen precursor. The FT-IR and Raman spectra showed the N-containing functional group in the graphene. The XRD analysis revealed the complete reduction of graphene oxide during the supercritical fluid processing. The elemental analysis and X-ray photoelectron spectroscopy revealed the amount and nature of N-doping in the graphene, respectively. The surface morphology and physical nature of the samples were analyzed using scanning and transmission electron microscopic analysis. The electrochemical performance of prepared electrode materials was evaluated using cyclic voltammetry, galvanostatic charge-discharge analysis and electrochemical impedance spectroscopy. The N-doped graphene prepared via supercritical fluid assisted processing exhibit enhanced capacitive behaviour with a maximum specific capacitance of 286 F g"−"1 at a current density of 0.5 A/g. The cycling studies showed 98% specific capacity retention with 100% coulombic efficiency over 1000 cycles at 5 A/g. The enhanced specific capacitance of N

  12. Surface-Induced Hybridization between Graphene and Titanium

    Hsu, Allen L. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States).; Koch, Roland J. [Technische Universitat, Chemnitz (Germany); Ong, Mitchell T. [Stanford Univ., CA (United States); Fang, Wenjing [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Hofmann, Mario [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Kim, Ki Kang [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States).; Seyller, Thomas [Technische Universitat, Chemnitz (Germany); Dresselhaus, Mildred S. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Reed, Evan J. [Stanford Univ., CA (United States); Kong, Jing [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Palacios, Tomás [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States)

    2014-08-26

    Carbon-based materials such as graphene sheets and carbon nanotubes have inspired a broad range of applications ranging from high-speed flexible electronics all the way to ultrastrong membranes. However, many of these applications are limited by the complex interactions between carbon-based materials and metals. In this work, we experimentally investigate the structural interactions between graphene and transition metals such as palladium (Pd) and titanium (Ti), which have been confirmed by density functional simulations. We find that the adsorption of titanium on graphene is more energetically favorable than in the case of most metals, and density functional theory shows that a surface induced p-d hybridization occurs between atomic carbon and titanium orbitals. This strong affinity between the two materials results in a short-range ordered crystalline deposition on top of graphene as well as chemical modifications to graphene as seen by Raman and X-ray photoemission spectroscopy (XPS). This induced hybridization is interface-specific and has major consequences for contacting graphene nanoelectronic devices as well as applications toward metal-induced chemical functionalization of graphene.

  13. Photocatalytic activities of heterostructured TiO2-graphene porous microspheres prepared by ultrasonic spray pyrolysis

    Yang, Jikai; Zhang, Xintong; Li, Bing; Liu, Hong; Sun, Panpan; Wang, Changhua; Wang, Lingling; Liu, Yichun

    2014-01-01

    Highlights: • USP method is used to prepare TiO 2 -graphene porous microspheres. • XPS shows GO sheets in the composites has been reduced to graphene. • TiO 2 -graphene microspheres display a red-shifted absorption edge. • PL spectra indicate graphene can accept the photoexcited electrons from TiO 2 . • TiO 2 -graphene shows higher photocatalytic activity than TiO 2 under solar light. -- Abstract: TiO 2 -graphene porous microspheres were prepared by ultrasonic spray pyrolysis (USP) of aqueous suspension of graphene oxide containing TiO 2 nanoparticles (Degussa P25). The composite microspheres were characterized with SEM, XPS, photoluminescence, Raman and UV–Vis absorption spectra. TiO 2 -graphene porous microspheres displayed higher photocatalytic activity for the degradation of methylene blue solution than pristine TiO 2 microspheres under the irradiation of Xe lamp, and the highest activity was obtained at a weight percentage of graphene around 1%. The effect of graphene on photocatalytic activity of porous microsphere was discussed in terms of the enhanced charge separation by TiO 2 -graphene heterojunction, increased absorption of the visible light, as well as the possible hindrance of mass transportation in microspheres

  14. Graphene-reinforced aluminum matrix composites prepared by spark plasma sintering

    Wen-ming Tian; Song-mei Li; Bo Wang; Xin Chen; Jian-hua Liu; Mei Yu

    2016-01-01

    Graphene-reinforced 7055 aluminum alloy composites with different contents of graphene were prepared by spark plasma sinter-ing (SPS). The structure and mechanical properties of the composites were investigated. Testing results show that the hardness, compressive strength, and yield strength of the composites are improved with the addition of 1wt% graphene. A clean, strong interface is formed between the metal matrix and graphene via metallurgical bonding on atomic scale. Harmful aluminum carbide (Al4C3) is not formed during SPS processing. Further addition of graphene (above 1wt%) results in the deterioration in mechanical properties of the composites. The agglomeration of graphene plates is exacerbated with increasing graphene content, which is the main reason for this deterioration.

  15. Tuning the deposition of molecular graphene nanoribbons by surface functionalization

    Konnerth, R.; Cervetti, C.; Narita, A.; Feng, X.; Müllen, K.; Hoyer, A.; Burghard, M.; Kern, K.; Dressel, M.; Bogani, L.

    2015-07-01

    We show that individual, isolated graphene nanoribbons, created with a molecular synthetic approach, can be assembled on functionalised wafer surfaces treated with silanes. The use of surface groups with different hydrophobicities allows tuning the density of the ribbons and assessing the products of the polymerisation process.

  16. Investigation of surface potentials in reduced graphene oxide flake by Kelvin probe force microscopy

    Negishi, Ryota; Takashima, Kai; Kobayashi, Yoshihiro

    2018-06-01

    The surface potential (SP) of reduced graphene oxide (rGO) flakes prepared by thermal treatments of GO under several conditions was analyzed by Kelvin probe force microscopy. The low-crystalline rGO flakes in which a significant amount of oxygen functional groups and structural defects remain have a much lower SP than mechanically exfoliated graphene free from oxygen and defects. On the other hand, the highly crystalline rGO flake after a thermal treatment for the efficient removal of oxygen functional groups and healing of structural defects except for domain boundary shows SP equivalent to that of the mechanically exfoliated graphene. These results indicate that the work function of rGO is sensitively modulated by oxygen functional groups and structural defects remaining after the thermal reduction process, but is not affected significantly by the domain boundary remaining after the healing of structural defects through the thermal treatment at high temperature.

  17. Fabrication of high surface area graphene electrodes with high performance towards enzymatic oxygen reduction

    Di Bari, Chiara; Goñi-Urtiaga, Asier; Pita, Marcos; Shleev, Sergey; Toscano, Miguel D.; Sainz, Raquel; De Lacey, Antonio L.

    2016-01-01

    High surface area graphene electrodes were prepared by simultaneous electrodeposition and electroreduction of graphene oxide. The electrodeposition process was optimized in terms of pH and conductivity of the solution and the obtained graphene electrodes were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical methods (cyclic voltammetry and impedance spectroscopy). Electrodeposited electrodes were further functionalized to carry out covalent immobilization of two oxygen-reducing multicopper oxidases: laccase and bilirubin oxidase. The enzymatic electrodes were tested as direct electron transfer based biocathodes and catalytic currents as high as 1 mA/cm 2 were obtained. Finally, the mechanism of the enzymatic oxygen reduction reaction was studied for both enzymes calculating the Tafel slopes and transfer coefficients.

  18. Surface-enhanced Raman spectra on graphene

    Ek Weis, Johan; Vejpravová, Jana; Verhagen, Timotheus; Melníková Komínková, Zuzana; da Costa, Sara; Kalbáč, Martin

    2018-01-01

    Roč. 49, č. 1 (2018), s. 168-173 ISSN 0377-0486 R&D Projects: GA MŠk LL1301; GA ČR(CZ) GA15-01953S; GA MŠk(CZ) LM2015073 Grant - others:GA MŠk(CZ) CZ.02.1.01/0.0/0.0/16_013/0001821 Institutional support: RVO:61388955 ; RVO:68378271 Keywords : charge transfer * graphene * graphene-plasmon interaction Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 2.969, year: 2016

  19. Harmonics radiation of graphene surface plasmon polaritons in terahertz regime

    Li, D., E-mail: dazhi_li@hotmail.com [Institute for Laser Technology, Suita, Osaka 565-0871 (Japan); Wang, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Nakajima, M. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Hashida, M. [Advanced Research Center for Beam Science, ICR, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Wei, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Miyamoto, S. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Ako, Hyogo 678-1205 (Japan)

    2016-06-03

    This letter presents an approach to extract terahertz radiation from surface plasmon polaritons excited in the surface of a uniform graphene structure by an electron beam. A sidewall configuration is proposed to lift the surface plasmon mode to be close to the light line, so that some of its harmonics have chances to go above the light line and become radiative. The harmonics are considered to be excited by a train of periodic electron bunches. The physical mechanism in this scheme is analyzed with three-dimensional theory, and the harmonics excitation and radiation are demonstrated through numerical calculations. The results show that this technique could be an alternative to transform the surface plasmon polaritons into radiation. - Highlights: • An approach to extract terahertz radiation from graphene surface plasmon polaritons is presented. • A sidewall configuration is proposed to lift the surface plasmon mode. • Harmonics of surface plasmon polaritons are possible to radiate.

  20. Nature of the surface states at the single-layer graphene/Cu(111) and graphene/polycrystalline-Cu interfaces

    Pagliara, S.; Tognolini, S.; Bignardi, L.; Galimberti, G.; Achilli, S.; Trioni, M. I.; van Dorp, W. F.; Ocelik, V.; Rudolf, P.; Parmigiani, F.

    2015-01-01

    Single-layer graphene supported on a metal surface has shown remarkable properties relevant for novel electronic and optoelectronic devices. However, the nature of the electronic states derived from unoccupied surface states and quantum well states, lying in the real-space gap between the graphene

  1. Functionalization of graphene and grafting of temperature-responsive surfaces from graphene by ATRP 'on water'

    Ren Lulu; Huang Shu; Zhang Chao; Wang Ruiyu [Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science (China); Tjiu, Weng Weei [Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A-STAR) (Singapore); Liu Tianxi, E-mail: txliu@fudan.edu.cn [Fudan University, State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science (China)

    2012-06-15

    Water-dispersible graphene with temperature-responsive surfaces has successfully been synthesized by grafting poly(N-isopropylacrylamide) (PNIPAM) from graphene via surface-initiated atom transfer radical polymerization (ATRP). First, graphene surfaces are functionalized with aminophenol groups by diazonium reaction on water. Subsequently, bromoisobutyrate groups are covalently attached to the phenol-functionalized graphene (G-OH) surface by esterification of 2-bromoisobutyrate with the hydroxyl groups, forming bromoisobutyrate-functionalized graphene (G-Br). Finally, PNIPAM is then grafted from G-Br via ATRP. Data from Raman spectroscopy, {sup 1}H NMR, and transmission electron microscopy (TEM) confirm that PNIPAM chains grow from graphene by ATRP. Thermogravimetric analysis shows that the amount of PNIPAM grown from the graphene increases with the increase of monomer ratios. TEM images also show that functionalized polymer structures (PNIPAM cluster or agglutination) on graphene sheets can be well tuned by controlled polymerization. The obtained graphene-PNIPAM (G-PNIPAM) composite has PNIPAM surface which is highly sensitive to the temperature change. This temperature-responsive and water-dispersible G-PNIPAM composite may find potential applications in environmental devices as well as controlled release drug delivery.

  2. Raman Spectroscopy Study of Annealing-Induced Effects on Graphene Prepared by Micromechanical Exfoliation

    Song, Ji Eun; Ko, Taeg Yeoung; Ryu, Sun Min

    2010-01-01

    Raman spectroscopy was combined with AFM to investigate the effects of thermal annealing on the graphene samples prepared by the widely used micromechanical exfoliation method. Following annealing cycles, adhesive residues were shown to contaminate graphene sheets with thin molecular layers in their close vicinity causing several new intense Raman bands. Detailed investigation shows that the Raman scattering is very strong and may be enhanced by the interaction with graphene. Although the current study does not pinpoint detailed origins for the new Raman bands, the presented results stress that graphene prepared by the above method may require extra cautions when treated with heat or possibly solvents. Since its isolation from graphite, graphene has drawn a lot of experimental and theoretical research. These efforts have been mostly in pursuit of various applications such as electronics, sensors, stretchable transparent electrodes, and various composite materials. To accomplish such graphene-based applications, understanding chemical interactions of this new material with environments during various processing treatments will become more important. Since thermal annealing is widely used in various research of graphene for varying purposes such as cleaning, nanostructuring, reactions, etc., understanding annealing-induced effects is prerequisite to many fundamental studies of graphene. In this regard, it is to be noted that there has been a controversy on the cause of the annealing-induced hole doping in graphene

  3. Preparation of functional composite materials based on chemically derived graphene using solution process

    Kim, M; Hyun, W J; Mun, S C; Park, O O

    2015-01-01

    Chemically derived graphenes were assembled into functional composite materials using solution process from stable solvent dispersion. We have developed foldable electronic circuits on paper substrates using vacuum filtration of graphene nanoplates dispersion and a selective transfer process without need for special equipment. The electronic circuits on paper substrates revealed only a small change in conductance under various folding angles and maintained an electronic path after repetitive folding and unfolding. We also prepared flexible. binder-free graphene paper-like materials by addition of graphene oxide as a film stabilizer. This graphene papers showed outstanding electrical conductivity up to 26,000 S/m and high charge capacity as an anode in lithium-ion battery without any post-treatments. For last case, multi-functional thin film structures of graphene nanoplates were fabricated by using layer-by-layer assembly technique, showing optical transparency, electrical conductivity and enhanced gas barrier property. (paper)

  4. Channel surface plasmons in a continuous and flat graphene sheet

    Chaves, A. J.; Peres, N. M. R.; da Costa, D. R.; Farias, G. A.

    2018-05-01

    We derive an integral equation describing surface-plasmon polaritons in graphene deposited on a substrate with a planar surface and a dielectric protrusion in the opposite surface of the dielectric slab. We show that the problem is mathematically equivalent to the solution of a Fredholm equation, which we solve exactly. In addition, we show that the dispersion relation of the channel surface plasmons is determined by the geometric parameters of the protrusion alone. We also show that such a system supports both even and odd modes. We give the electrostatic potential and the intensity plot of the electrostatic field, which clearly show the transverse localized nature of the surface plasmons in a continuous and flat graphene sheet.

  5. Graphene prepared by one-pot solvent exfoliation as a highly sensitive platform for electrochemical sensing

    Wu, Can; Cheng, Qin [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wu, Kangbing, E-mail: kbwu@hust.edu.cn [Key Laboratory for Large-Format Battery Materials and System, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wu, Gang [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, Qing, E-mail: qing_li_2@brown.edu [Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2014-05-01

    Highlights: • Graphene was prepared by one-step solvent exfoliation as superior electrode material. • Compared with RGO, prepared graphene exhibited stronger signal enhancement. • A widespread and highly-sensitive electrochemical sensing platform was constructed. - Abstract: Graphene was easily obtained via one-step ultrasonic exfoliation of graphite powder in N-methyl-2-pyrrolidone. Scanning electron microscopy, transmission electron microscopy, Raman and particle size measurements indicated that the exfoliation efficiency and the amount of produced graphene increased with ultrasonic time. The electrochemical properties and analytical applications of the resulting graphene were systematically studied. Compared with the predominantly-used reduced graphene oxides, the obtained graphene by one-step solvent exfoliation greatly enhanced the oxidation signals of various analytes, such as ascorbic acid (AA), dopamine (DA), uric acid (UA), xanthine (XA), hypoxanthine (HXA), bisphenol A (BPA), ponceau 4R, and sunset yellow. The detection limits of AA, DA, UA, XA, HXA, BPA, ponceau 4R, and sunset yellow were evaluated to be 0.8 μM, 7.5 nM, 2.5 nM, 4 nM, 10 nM, 20 nM, 2 nM, and 1 nM, which are much lower than the reported values. Thus, the prepared graphene via solvent exfoliation strategy displays strong signal amplification ability and holds great promise in constructing a universal and sensitive electrochemical sensing platform.

  6. Graphene on metal surfaces and its hydrogen adsorption

    Andersen, Mie; Hornekær, L.; Hammer, B.

    2012-01-01

    The interaction of graphene with various metal surfaces is investigated using density functional theory and the meta-generalized gradient approximation (MGGA) M06-L functional. We demonstrate that this method is of comparable accuracy to the random-phase approximation (RPA). With M06-L we study...... large systems inaccessible to RPA with H adsorbed on graphene on a selected strongly (Ni) and a selected weakly (Pt) interacting substrate. Very stable graphane-like clusters, where every other C atom binds to a H atom above and every other to a metal atom below, are found on both substrates...

  7. Preparation of water-soluble graphene nanoplatelets and highly conductive films

    Xu, Xuezhu; Zhou, Jian; Jestin, Jacques; Colombo, Veronica; Lubineau, Gilles

    2017-01-01

    This paper tackles the challenge of preparation stable, highly concentrated aqueous graphene dispersions. Despite tremendous recent interest, there has been limited success in developing a method that ensures the total dispersion of non

  8. Infrared beam-steering using acoustically modulated surface plasmons over a graphene monolayer

    Chen, Paiyen; Farhat, Mohamed; Askarpour, Amir Nader; Tymchenko, Mykhailo; Alù , Andrea

    2014-01-01

    We model and design a graphene-based infrared beamformer based on the concept of leaky-wave (fast traveling wave) antennas. The excitation of infrared surface plasmon polaritons (SPPs) over a 'one-atom-thick' graphene monolayer is typically

  9. Surface engineering of graphene-based nanomaterials for biomedical applications.

    Shi, Sixiang; Chen, Feng; Ehlerding, Emily B; Cai, Weibo

    2014-09-17

    Graphene-based nanomaterials have attracted tremendous interest over the past decade due to their unique electronic, optical, mechanical, and chemical properties. However, the biomedical applications of these intriguing nanomaterials are still limited due to their suboptimal solubility/biocompatibility, potential toxicity, and difficulties in achieving active tumor targeting, just to name a few. In this Topical Review, we will discuss in detail the important role of surface engineering (i.e., bioconjugation) in improving the in vitro/in vivo stability and enriching the functionality of graphene-based nanomaterials, which can enable single/multimodality imaging (e.g., optical imaging, positron emission tomography, magnetic resonance imaging) and therapy (e.g., photothermal therapy, photodynamic therapy, and drug/gene delivery) of cancer. Current challenges and future research directions are also discussed and we believe that graphene-based nanomaterials are attractive nanoplatforms for a broad array of future biomedical applications.

  10. Fluorinated Graphene Prepared by Direct Fluorination of N, O-Doped Graphene Aerogel at Different Temperatures for Lithium Primary Batteries

    Xu Bi

    2018-06-01

    Full Text Available Fluorinated graphene (FG has been a star material as a new derivative of graphene. In this paper, a series of fluorinated graphene materials are prepared by using N, O-doped graphene aerogel as precursor via a direct fluorination method, and the effect of fluorination temperature on the FG structure is investigated. The prepared FG samples are systematically characterized by scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. It is found that the structure of FG, including features such as layer size, chemical composition, chemical bond state of the component elements, etc., is significantly related to the fluorination temperature. With the change of the fluorination temperature, fluorine atoms enter the graphene framework by a substitution process of the N, O-containing groups, including residual phenol, ether, carbonyl groups, or C–N groups, and the addition to CC bonds, subsequently forming a fluoride with different fluorine contents. The fluorine content increases as the fluorination temperature increases from 200 °C to 300 °C, but decreases at a fluorination temperature of 350 °C due to the decomposition of the fluorinated graphene. The prepared FG samples are used as cathode material for lithium primary batteries. The FG sample prepared at 300 °C gives a high specific capacity of 632 mAh g−1 and a discharge plateau of 2.35 V at a current density of 10 mA g−1, corresponding to a high energy density of 1485 Wh kg−1.

  11. Scattering of surface plasmons on graphene by a discontinuity in surface conductivity

    Rejaei, Behzad; Khavasi, Amin

    2015-01-01

    The scattering of graphene surface plasmons from an arbitrary, one-dimensional discontinuity in graphene surface conductivity is treated analytically by an exact solution of the quasi-static integral equation for surface current density in the spectral domain. It is found that the reflection and transmission coefficients are not governed by the Fresnel formulas obtained by means of the effective medium approach. Furthermore, the reflection coefficient generally exhibits an anomalous reflection phase, which has so far only been reported for the particular case of reflection from abrupt edges. This anomalous phase becomes frequency-independent in the regime where the effect of inter-band transitions on graphene conductivity is negligible. The results are in excellent agreement with full-wave electromagnetic simulations, and can serve as a basis for the analysis of inhomogeneous graphene layers with a piecewise-constant conductivity profile. (paper)

  12. A facile and scalable method to prepare carbon nanotube-grafted-graphene for high performance Li-S battery

    Wang, Q. Q.; Huang, J. B.; Li, G. R.; Lin, Z.; Liu, B. H.; Li, Z. P.

    2017-01-01

    A carbon nanotube-grafted-graphene (CNT-g-Gr) is developed for enhancements of electrical conduction and polysulfide (PS) absorption to improve rate performance and cycleability of lithium-sulfur battery. The CNT-g-Gr is prepared through CNT growth on Ni-deposited graphene sheet which is fabricated via pyrolysis of glucose in a molten salt. The obtained CNT-g-Gr shows much higher specific surface area and PS adsorption capability than graphene. The in-situ formed Ni nanoparticles on graphene sheet not only serve as the catalytic sites for CNT growth, but also function as the anchor-sites for polar PS absorption. The CNT-g-Gr contributes a superb PS adsorption capability arising from graphene and CNT absorbing weakly-polar PS species, and Ni nanoparticles absorbing the species with stronger polarity. The resultant Li-S battery with the CNT-g-Gr shows excellent cycleability and rate performance. A stable discharge capacity of 900 mAh g-1 (with low capacity degradation rate) and a rate capacity of 260 mAh g-1 at 30 C discharge rate have been achieved.

  13. Using glucosamine as a reductant to prepare reduced graphene oxide and its nanocomposites with metal nanoparticles

    Li Chuanbao; Wang Xingrui; Liu Yu; Wang Wei; Wynn, Jeanne; Gao Jianping

    2012-01-01

    A green and facile approach of producing reduced graphene oxide (RGO) by the reduction of graphene oxide (GO) with a monosaccharide medicine glucosamine (GL) was developed. The effect of several factors on the GO reduction, including pH, the weight ratio of GL/GO, and the reaction temperature was studied. The deoxygenation process was monitored with UV–Vis absorption spectroscopy, and the reducing degree of GO was determined with X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy. Au nanoparticles (about 3.3–4.2 nm) (AuNPs)/RGO and Ag nanoparticles (about 6 nm) (AgNPs)/RGO materials were prepared in two different ways using the above reduction method. They were then used to catalyze the Suzuki–Miyaura coupling reaction of phenyl halide and phenylboronic acid to produce biphenyl, and the highest yield of biphenyl for AuNPs/RGO was 99 %. In addition, the AgNPs/RGO materials exhibited a surface-enhanced Raman scattering effect, and some RGO peaks were enhanced. This approach opens up a new, practical, and green reducing method to prepare RGO for large-scale practical application.

  14. Preparation and electrochemical characterization of MnOOH nanowire-graphene oxide

    Wang Lin; Wang Dianlong

    2011-01-01

    Highlights: → MnOOH nanowire-graphene oxide composites are prepared by hydrothermal reaction in distilled water or 5% ammonia aqueous solution at 130 deg. C, with MnO 2 -graphene oxide composites which are synthesized by a redox reaction between KMnO 4 and graphene oxide. → MnO 2 is deoxidized to MnOOH on graphene oxide through hydrothermal reaction without any extra reductants. → It is found that the electrochemical resistance of MnOOH nanowire-graphene oxide composites decreases and the capacitance increases to 76 F g -1 when hydrothermal reaction is conducted in ammonia aqueous solution. → MnOOH nanowire-graphene oxide composites prepared by hydrothermal reaction in 5% ammonia aqueous solution have excellent capacitance retention ratio at scan rate from 5 mV s -1 to 40 mV s -1 . - Abstract: MnOOH nanowire-graphene oxide composites are prepared by hydrothermal reaction in distilled water or 5% ammonia aqueous solution at 130 deg. C with MnO 2 -graphene oxide composites which are synthesized by a redox reaction between KMnO 4 and graphene oxide. Powder X-ray diffraction (XRD) analyses and energy dispersive X-ray analyses (EDAX) show MnO 2 is deoxidized to MnOOH on graphene oxide through hydrothermal reaction without any extra reductants. The electrochemical capacitance of MnOOH nanowire-graphene oxide composites prepared in 5% ammonia aqueous solution is 76 F g -1 at current density of 0.1 A g -1 . Moreover, electrochemical impedance spectroscopy (EIS) suggests the electrochemical resistance of MnOOH nanowire-graphene oxide composites is reduced when hydrothermal reaction is conducted in ammonia aqueous solution. The relationship between the electrochemical capacitance and the structure of MnOOH nanowire-graphene oxide composites is characterized by cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). The results indicate the electrochemical performance of MnOOH nanowire-graphene oxide composites strongly depends on their

  15. Preparation of Ni(OH){sub 2}-graphene sheet-carbon nanotube composite as electrode material for supercapacitors

    Liu, Y.F. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); College of Environmental and Chemical Engineering, Heilongjiang University of Science and Technology, Harbin 150022 (China); Yuan, G.H., E-mail: ygh@hit.edu.cn [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Jiang, Z.H., E-mail: jiangzhaohua@hit.edu.cn [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Yao, Z.P. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Yue, M. [Shenzhen BTR New Energy Materials INC., Shenzhen 528206 (China)

    2015-01-05

    Highlights: • CNT is introduced into graphene to prevent restacking by solvothermal reaction. • Ethanol as a low cost and green solvent is used in solvothermal reaction. • Ni(OH){sub 2} nanosheets were chemically precipitated into GS-CNT to increase the capacitance. - Abstract: Ni(OH){sub 2}-graphene sheet-carbon nanotube composite was prepared for supercapacitance materials through a simple two-step process involving solvothermal synthesis of graphene sheet-carbon nanotube composite in ethanol and chemical precipitation of Ni(OH){sub 2}. According to N{sub 2} adsorption/desorption analysis, the Brunauer–Emmett–Teller surface area of graphene sheet-carbon nanotube composite (109.07 m{sup 2} g{sup −1}) was larger than that of pure graphene sheets (32.06 m{sup 2} g{sup −1}), indicating that the added carbon nanotubes (15 wt.%) could prevent graphene sheets from restacking in the solvothermal reaction. The results of field emission scanning electron microscopy and transmission electron microscopy showed that Ni(OH){sub 2} nanosheets were uniformly loaded into the three-dimensional interconnected network of graphene sheet-carbon nanotube composite. The microstructure enhanced the rate capability and utilization of Ni(OH){sub 2}. The specific capacitance of Ni(OH){sub 2}-graphene sheet-carbon nanotube composite was 1170.38 F g{sup −1} at a current density of 0.2 A g{sup −1} in the 6 mol L{sup −1} KOH solution, higher than those provided by pure Ni(OH){sub 2} (953.67 Fg{sup −1}) and graphene sheets (178.25 F g{sup −1}). After 20 cycles at each current density (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 A g{sup −1}), the capacitance of Ni(OH){sub 2}-graphene sheet-carbon nanotube composite decreased 26.96% of initial capacitance compared to 74.52% for pure Ni(OH){sub 2}.

  16. Preparation of Graphene-Modified Acupuncture Needle and Its Application in Detecting Neurotransmitters

    Tang, Lina; Du, Danxin; Yang, Fan; Liang, Zhong; Ning, Yong; Wang, Hua; Zhang, Guo-Jun

    2015-06-01

    We report a unique nanosensing platform by combining modern nanotechnology with traditional acupuncture needle to prepare graphene-modified acupuncture needle (G-AN), and using it for sensitive detection of neurotransmitters via electrochemistry. An electrochemical deposition method was employed to deposit Au nanoparticles (AuNPs) on the tip surface of the traditional acupuncture needle, while the other part of the needle was coated with insulation paste. Subsequently, the G-AN was obtained by cyclic voltammetry reduction of a graphene oxide solution on the surface of the AuNPs. To investigate the sensing property of the G-AN, pH dependence was measured by recording the open circuit potential in the various pH buffer solutions ranging from 2.0 to 10.0. What’s more, the G-AN was further used for detection of dopamine (DA) with a limit of detection of 0.24 μM. This novel G-AN exhibited a good sensitivity and selectivity, and could realize direct detection of DA in human serum.

  17. Photoinduced hydrophobic surface of graphene oxide thin films

    Zhang Xiaoyan; Song Peng; Cui Xiaoli

    2012-01-01

    Graphene oxide (GO) thin films were deposited on transparent conducting oxide substrates and glass slides by spin coating method at room temperature. The wettability of GO thin films before and after ultraviolet (UV) irradiation was characterized with water contact angles, which increased from 27.3° to 57.6° after 3 h of irradiation, indicating a photo-induced hydrophobic surface. The UV–vis absorption spectra, Raman spectroscopy, X-ray photoelectron spectroscopy, and conductivity measurements of GO films before and after UV irradiation were taken to study the mechanism of photoinduced hydrophobic surface of GO thin films. It is demonstrated that the photoinduced hydrophobic surface is ascribed to the elimination of oxygen-containing functional groups on GO molecules. This work provides a simple strategy to control the wettability properties of GO thin films by UV irradiation. - Highlights: ► Photoinduced hydrophobic surface of graphene oxide thin films has been demonstrated. ► Elimination of oxygen-containing functional groups in graphene oxide achieved by UV irradiation. ► We provide novel strategy to control surface wettability of GO thin films by UV irradiation.

  18. Hydrophobic cotton textile surfaces using an amphiphilic graphene oxide (GO) coating

    Tissera, Nadeeka D.; Wijesena, Ruchira N.; Perera, J. Rangana; Nalin de Silva, K.M.; Amaratunge, Gehan A.J.

    2015-01-01

    Graphical abstract: - Highlights: • Different GO dispersions were prepared by sonicating different amounts of GO in water. Degree of exfoliation of these GO sheets in water was analyzed using Atomic Force Microscopy (AFM). • AFM results obtained showed higher the GO concentration on water more the size of GO sheets and lesser the degree of exfoliation. • GO with different amounts was deposited on cotton fabric using simple dyeing method. • High GO loading on cotton increase the surface area coverage of the textile fibers with GO sheets. This led to less edge to mid area ratio of grafted GO sheets. • As contribution of mid area of GO increase on fiber surface cotton fabric becomes more hydrophobic. • Amphiphilic property of GO sheets was used to lower the surface energy of the cotton fibers leading to hydrophobic property. - Abstract: We report for the first time hydrophobic properties on cotton fabric successfully achieved by grafting graphene oxide on the fabric surface, using a dyeing method. Graphite oxide synthesized by oxidizing natural flake graphite employing improved Hummer's method showed an inter layer spacing of ∼1 nm from XRD. Synthesized graphite oxide was exfoliated in water using ultrasound energy to obtain graphene oxide (GO). AFM data obtained for the graphene oxide dispersed in an aqueous medium revealed a non-uniform size distribution. FTIR characterization of the synthesized GO sheets showed both hydrophilic and hydrophobic functional groups present on the nano sheets giving them an amphiphilic property. GO flakes of different sizes were successfully grafted on to a cotton fabric surface using a dip dry method. Loading different amounts of graphene oxide on the cotton fiber surface allowed the fabric to demonstrate different degrees of hydrophobicity. The highest observed water contact angle was at 143° with the highest loading of graphene oxide. The fabric surfaces grafted with GO also exhibits adhesive type hydrophobicity

  19. Building up Graphene-Based Conductive Polymer Composite Thin Films Using Reduced Graphene Oxide Prepared by γ-Ray Irradiation

    Siyuan Xie

    2013-01-01

    Full Text Available In this paper, reduced graphene oxide (RGO was prepared by means of γ-ray irradiation of graphene oxide (GO in a water/ethanol mix solution, and we investigated the influence of reaction parameters, including ethanol concentration, absorbed dose, and dose rate during the irradiation. Due to the good dispersibility of the RGO in the mix solution, we built up flexible and conductive composite films based on the RGO and polymeric matrix through facile vacuum filtration and polymer coating. The electrical and optical properties of the obtained composite films were tested, showing good electrical conductivity with visible transmittance but strong ultraviolet absorbance.

  20. Preparation and supercapacitor performance of assembled graphene fiber and foam

    Jing Li

    2016-06-01

    Full Text Available Graphene-based materials have been full of vigor and tremendous potentiality for application in supercapacitors due to its variety of unique properties such as electronic properties, simple synthesis, etc. In developing new macroscopic nanostructured graphene materials for supercapacitors, considerable efforts have been made by the scientist including our research group. In this account, we describe our development of the construction of the assembled graphene especially fiber and foam, which have great potential in addressing the challenges in the synthesis of graphene-based electrode materials for supercapacitors. As the supercapacitors are reviewed in this article, they are accordant with the rapid development of flexible, lightweight, and wearable-electronic devices, overcoming the major some drawbacks of conventional bulk supercapacitors. We hope that this summary will benefit the further research of graphene-based materials for the applications in electrochemical energy storage devices and beyond.

  1. Large-scale uniform bilayer graphene prepared by vacuum graphitization of 6H-SiC(0001) substrates

    Wang, Qingyan; Zhang, Wenhao; Wang, Lili; He, Ke; Ma, Xucun; Xue, Qikun

    2013-03-01

    We report on the preparation of large-scale uniform bilayer graphenes on nominally flat Si-polar 6H-SiC(0001) substrates by flash annealing in ultrahigh vacuum. The resulting graphenes have a single thickness of one bilayer and consist of regular terraces separated by the triple SiC bilayer steps on the 6H-SiC(0001) substrates. In situ scanning tunneling microscopy reveals that suppression of pit formation on terraces and uniformity of SiC decomposition at step edges are the key factors to the uniform thickness. By studying the surface morphologies prepared under different annealing rates, it is found that the annealing rate is directly related to SiC decomposition, diffusion of the released Si/C atoms and strain relaxation, which together determine the final step structure and density of defects.

  2. Strong composite films with layered structures prepared by casting silk fibroin-graphene oxide hydrogels

    Huang, Liang; Li, Chun; Yuan, Wenjing; Shi, Gaoquan

    2013-04-01

    Composite films of graphene oxide (GO) sheets and silk fibroin (SF) with layered structures have been prepared by facile solution casting of SF-GO hydrogels. The as-prepared composite film containing 15% (by weight, wt%) of SF shows a high tensile strength of 221 +/- 16 MPa and a failure strain of 1.8 +/- 0.4%, which partially surpass those of natural nacre. Particularly, this composite film also has a high modulus of 17.2 +/- 1.9 GPa. The high mechanical properties of this composite film can be attributed to its high content of GO (85 wt%), compact layered structure and the strong hydrogen bonding interaction between SF chains and GO sheets.Composite films of graphene oxide (GO) sheets and silk fibroin (SF) with layered structures have been prepared by facile solution casting of SF-GO hydrogels. The as-prepared composite film containing 15% (by weight, wt%) of SF shows a high tensile strength of 221 +/- 16 MPa and a failure strain of 1.8 +/- 0.4%, which partially surpass those of natural nacre. Particularly, this composite film also has a high modulus of 17.2 +/- 1.9 GPa. The high mechanical properties of this composite film can be attributed to its high content of GO (85 wt%), compact layered structure and the strong hydrogen bonding interaction between SF chains and GO sheets. Electronic supplementary information (ESI) available: XPS spectrum of the SF-GO hybrid film, SEM images of lyophilized GO dispersion and the failure surface of GO film. See DOI: 10.1039/c3nr00196b

  3. Ultrasound-assisted preparation of electrospun carbon nanofiber/graphene composite electrode for supercapacitors

    Dong, Qiang; Wang, Gang; Hu, Han; Yang, Juan; Qian, Bingqing; Ling, Zheng; Qiu, Jieshan

    2013-12-01

    Electrospun carbon nanofiber/graphene (CNF/G) composites are prepared by in situ electrospinning polymeric nanofibers with simultaneous spraying graphene oxide, followed by heat treatment. The freestanding carbon nanofiber web acts as a framework for sustaining graphene, which helps to prevent the agglomeration of graphene and to provide a high conductivity for the efficient charge transfer to the pores. The as-obtained CNF/G composite exhibits a specific capacitance of 183 F g-1, which is approximately 1.6 times higher than that of the pristine CNF. The results have demonstrated that the high performance of the CNF/G composite is due to the novel structure and the synergic effect of graphene and the carbon nanofibers.

  4. Novel strategy for the preparation of graphene-encapsulated mesoporous metal oxides with enhanced lithium storage

    Lin, Rong; Yue, Wenbo; Niu, Fangzhou; Ma, Jie

    2016-01-01

    As potential anode materials for lithium-ion batteries, mesoporous metal oxides show high reversible capacities but relatively poor cycle stability due to the structural collapse during cycles. Graphene-encapsulated mesoporous metal oxides may increase the electronic conductivity of the composite as well as stabilize the mesostructure of metal oxides, thereby enhancing the electrochemical performance of mesoporous metal oxides. Herein we describe a novel strategy for the preparation of graphene-encapsulated mesoporous metal oxides (SnO_2, Mn_3O_4), which exhibit superior electrochemical performance compared to pure mesoporous metal oxides. Moreover, some mesoporous metal oxides may be further reduced to low-valence metal oxides when calcined in presence of graphene. Mesoporous metal oxides with high isoelectric points are not essential for this synthesis method since metal oxides are connected with graphene through mesoporous silica template, thus expanding the types of graphene-encapsulated mesoporous metal oxides.

  5. Silver Fiber Fabric as the Current Collector for Preparation of Graphene- Based Supercapacitors

    Mehrabi-Matin, Bahareh; Shahrokhian, Saeed; Iraji-zad, Azam

    2017-01-01

    Highlights: • For the first time, silver fiber fabric (SFF) is employed as a current collector.. • rGO is electrophoretically deposited on the surface of SFF. • The electrodes are prepared in various EP deposition times. • The rGO/SFF-10 shows a higher capacitive performance of 172 mF/cm 2 at 4 mA/cm 2 . • The rGO/SFF-10 exhibits of 97% capacitance retention after 5000 cycles. - Abstract: During the past few years, a considerable attention has been devoted to the development of textile- based energy storage devices and wearable electronics applications. In this paper, for the first time, we report a flexible high performance graphene-based supercapacitor using silver fiber fabric as the current collector. The silver fiber fabric offers remarkable advantages such as light weight, mechanical flexibility and ease of integration with electronic textiles, which well-suited for wearable energy storage devices. A new hybrid material of graphene-silver fiber fabric (rGO/SFF) was prepared through a facile electrophoretic deposition of graphene and being used as a binder-free flexible supercapacitor electrode. In order to obtain the optimum condition, the effect of deposition time was investigated and a duration time of 10 minute was selected as an optimum condition. The as-prepared binder-free electrode based on rGO/SFF-10 showed excellent electrochemical performance in the three-electrode configuration using KOH (3 M) as the supporting electrolyte, with the highest capacity of 172 mF/cm 2 at 4 mA/cm 2 and a capacitance retention of 97% after 5000 charge−discharge cycles. The high performance of rGO/SFF electrode is associated to the superior conductivity, high mechanical flexibility as well as good electrochemical stability of the silver fiber fabrics. The results suggest that the prepared electrode is a promising candidate for wearable energy storage applications due to its advantageous properties and the ease of preparation.

  6. Simple method to transfer graphene from metallic catalytic substrates to flexible surfaces without chemical etching

    Ko, P J; Takahashi, H; Sakai, H; Thu, T V; Okada, H; Sandhu, A; Koide, S

    2013-01-01

    Graphene shows promise for applications in flexible electronics. Here, we describe our procedure to transfer graphene grown on copper substrates by chemical vapor deposition to polydimethylsiloxane (PDMS) and SiO 2 /Si surfaces. The transfer of graphene was achieved by a simple, etching-free method onto flexible PDMS substrates.

  7. Propagation of liquid surface waves over finite graphene structured arrays of cylinders

    2011-01-01

    Based on the multiple scattering method,this paper investigates a benchmark problem of the propagation of liquid surface waves over finite graphene (or honeycomb) structured arrays of cylinders.Comparing the graphene structured array with the square structured and with triangle structured arrays,it finds that the finite graphene structure can produce more complete band gaps than the other finite structures,and the finite graphene structure has less localized ability than the other finite structures.

  8. Preparation of magnetic Ni@graphene nanocomposites and efficient removal organic dye under assistance of ultrasound

    Zhao, Chuang; Guo, Jianhui; Yang, Qing; Tong, Lei; Zhang, Jingwei; Zhang, Jiwei; Gong, Chunhong; Zhou, Jingfang; Zhang, Zhijun

    2015-01-01

    Graphical abstract: Reduced graphene oxide/Ni microspheres, being prepared under ultrasound conditions, exhibit a better removal efficiency to decolorize RhB with ultrasonic-assisted decolorization process. - Highlights: • One-step synthesis of Ni@graphene microspheres under ultrasound conditions. • During the ultrasonic process, graphene oxide was reduced and Ni nanoparticles were formed and anchored on graphene sheets. • The products exhibit excellent performance for fast and efficient removal of dye contaminants. • The nanocomposites can be easily separated from solution by a magnet. - Abstract: In this article, we report a facile one-step synthesis of Ni@graphene nanocomposite microspheres (NGs) in hydrazine hydrate solution under ultrasound conditions. During the ultrasonic process, graphene oxide (GO) was reduced effectively under mild conditions and Ni nanoparticles were simultaneously formed and anchored on graphene sheets, which act as spacers to keep the neighboring sheets separated. The target products exhibit excellent performance for fast and efficient removal of dye contaminants, rhodamine B (RhB) in aqueous solution, under assistance of ultrasound. Finally, the nanocomposites can be easily separated from solution by a magnet. Furthermore, higher content of graphene can be produced under sonication, which facilitates faster and more efficient removal of organic contaminates in the solution. The nanocomposites were also characterized by scanning electron microscopy, Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and thermogravimetric analysis.

  9. Preparation of magnetic Ni@graphene nanocomposites and efficient removal organic dye under assistance of ultrasound

    Zhao, Chuang; Guo, Jianhui; Yang, Qing; Tong, Lei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Jingwei, E-mail: jwzhang@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Zhang, Jiwei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Gong, Chunhong [College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004 (China); Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Zhou, Jingfang, E-mail: jingfang.zhou@unisa.edu.au [Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Zhang, Zhijun [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

    2015-12-01

    Graphical abstract: Reduced graphene oxide/Ni microspheres, being prepared under ultrasound conditions, exhibit a better removal efficiency to decolorize RhB with ultrasonic-assisted decolorization process. - Highlights: • One-step synthesis of Ni@graphene microspheres under ultrasound conditions. • During the ultrasonic process, graphene oxide was reduced and Ni nanoparticles were formed and anchored on graphene sheets. • The products exhibit excellent performance for fast and efficient removal of dye contaminants. • The nanocomposites can be easily separated from solution by a magnet. - Abstract: In this article, we report a facile one-step synthesis of Ni@graphene nanocomposite microspheres (NGs) in hydrazine hydrate solution under ultrasound conditions. During the ultrasonic process, graphene oxide (GO) was reduced effectively under mild conditions and Ni nanoparticles were simultaneously formed and anchored on graphene sheets, which act as spacers to keep the neighboring sheets separated. The target products exhibit excellent performance for fast and efficient removal of dye contaminants, rhodamine B (RhB) in aqueous solution, under assistance of ultrasound. Finally, the nanocomposites can be easily separated from solution by a magnet. Furthermore, higher content of graphene can be produced under sonication, which facilitates faster and more efficient removal of organic contaminates in the solution. The nanocomposites were also characterized by scanning electron microscopy, Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and thermogravimetric analysis.

  10. Water-dispersible triethylenetetramine-functionalized graphene: Preparation, characterization and application as an amperometric glucose sensor

    Ren, Qunxiang; Feng, Li; Fan, Ronghua; Ge, Xin; Sun, Yingying, E-mail: syyxiluda@hotmail.com

    2016-11-01

    The triethylenetetramine-functionalized graphene (TFGn) was prepared using graphene oxide (GO) and triethylenetetramine as raw materials through a one-step reaction under alkaline condition. The triethylenetetramine not only acted as cross-linker to combine GO, but also as reductant of GO. The TFGn was characterized by its ultraviolet spectrum (UV), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM). The results showed that triethylenetetramine was successfully grafted onto the surface of the GO through covalent bonding between amine and epoxy groups. The resultant TFGn was uniformly dispersed in water over several weeks, suggesting that the introduction of amino groups greatly increased the hydrophilicity of TFGn. The triethylenetetramine-functionalized graphene was then applied to fabricate glucose biosensors with IO{sub 4}{sup −} oxidized glucose oxidase (GOx) through layer-by-layer (LBL) self-assembly by the covalent bonding between the aldehyde groups of GOx and amino groups of TFGn. The gold electrodes modified with the (GOx/TFGn){sub n} multilayer films were studied by cyclic voltammetry (CV) and showed outstanding electrocatalytical response to the oxidation of glucose when ferrocenemethanol was used as an artificial redox mediator. The response increased with an increasing number of GOx/TFGn bilayers, indicating that the analytical performance, such as the sensitivity of the glucose biosensor, could be adjusted by tuning the number of deposited GOx/TFGn bilayers. The linear response range of the biosensor constructed with six bilayers of GOx/TFGn to the concentration of glucose can extend to at least 8 mM with a sensitivity of 19.9 μA mM{sup −1} cm{sup −2}. In addition, the sensor exhibited good stability due to the covalent interactions between the GOx and TFGn. - Highlights: • Water-dispersible triethylenetetramine

  11. Facile preparation of graphene by high-temperature electrolysis and its application in supercapacitor.

    Jiao, Chen-Xu; Xing, Bao-Yan; Zhao, Jian-Guo; Geng, Yu; Li, Zuo-Peng

    2014-01-01

    Graphene is well known owing to its astonishing properties: stronger than diamond, more conductive than copper and more flexible than rubber. Because of its potential uses in industry, researchers have been searching for less toxicity ways to make graphene in large amount with lower cost. We demonstrated an efficient method to prepare graphene by high temperature electrolysis technique. High resolution scanning electron microscopy and raman spectroscopy were used to characterize the microstructure of graphene. Graphene was assembled into the supercapacitor and its performance of electrochemical capacitor was investigated by constant current charge and discharge, cyclic voltammetry and AC impedance. The results showed that the micro-morphology of the prepared graphene was multilayer and it was favorable when the electrolytic voltage was 1.5 V. When the current density is 1 mA/cm(2), the specific capacitance of the graphene supercapacitor can reach 78.01 F/g in 6 mol/L KOH electrolyte, which was an increase of 114% compared with 36.43 F/g of conventional KOH electrolyte.

  12. Facile approach to prepare Pt decorated SWNT/graphene hybrid catalytic ink

    Mayavan, Sundar, E-mail: sundarmayavan@cecri.res.in [Centre for Innovation in Energy Research, CSIR–Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India); Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701 (Korea, Republic of); Mandalam, Aditya; Balasubramanian, M. [Centre for Innovation in Energy Research, CSIR–Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India); Sim, Jun-Bo [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701 (Korea, Republic of); Choi, Sung-Min, E-mail: sungmin@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon, 305-701 (Korea, Republic of)

    2015-07-15

    Highlights: • Pt NPs were in situ synthesized onto CNT–graphene support in aqueous solution. • The as-prepared material was used directly as a catalyst ink without further treatment. • Catalyst ink is active toward methanol oxidation. • This approach realizes both scalable and greener production of hybrid catalysts. - Abstract: Platinum nanoparticles were in situ synthesized onto hybrid support involving graphene and single walled carbon nanotube in aqueous solution. We investigate the reduction of graphene oxide, and platinum nanoparticle functionalization on hybrid support by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The as-prepared platinum on hybrid support was used directly as a catalyst ink without further treatment and is active toward methanol oxidation. This work realizes both scalable and greener production of highly efficient hybrid catalysts, and would be valuable for practical applications of graphene based fuel cell catalysts.

  13. Direct transfer of multilayer graphene grown on a rough metal surface using PDMS adhesion engineering

    Jang, Heejun; Kang, Il-Suk; Lee, Youngbok; Cha, Yun Jeong; Yoon, Dong Ki; Ahn, Chi Won; Lee, Wonhee

    2016-09-01

    The direct transfer of graphene using polydimethylsiloxane (PDMS) stamping has advantages such as a ‘pick-and-place’ capability and no chemical residue problems. However, it is not easy to apply direct PDMS stamping to graphene grown via chemical vapor deposition on rough, grainy metal surfaces due to poor contact between the PDMS and graphene. In this study, graphene consisting of a mixture of monolayers and multiple layers grown on a rough Ni surface was directly transferred without the use of an adhesive layer. Liquid PDMS was cured on graphene to effect a conformal contact with the graphene. A fast release of graphene from substrate was achieved by carrying out wet-etching-assisted mechanical peeling. We also carried out a thermal post-curing of PDMS to control the level of adhesion between PDMS and graphene and hence facilitate a damage-free release of the graphene. Characterization of the transferred graphene by micro-Raman spectroscopy, SEM/EDS and optical microscopy showed neither cracks nor contamination from the transfer. This technique allows a fast and simple transfer of graphene, even for multilayer graphene grown on a rough surface.

  14. Preparation of Reduced Graphene Oxide/MnO Composite and Its Electromagnetic Wave Absorption Performance

    Yuan, Jiangtao; Li, Kunzhen; Liu, Zhongfei; Jin, Shaowei; Li, Shikuo; Zhang, Hui

    2018-02-01

    The composite containing reduced graphene oxide and MnO nanoparticles (RGO/MnO) has been prepared via a one step pyrolysis method. The MnO nanoparticles were uniformly dispersed on the surface of RGO nanosheets forming MnO/RGO composite. The composite displays a maximum absorption of ‒38.9 dB at 13.5 GHz and the bandwidth of reflection loss corresponding to -10 dB can reach 4.9 GHz (from 11.5 to 16.4 GHz) with a coating layer thickness of only 2 mm. Therefore, the obtained RGO/MnO composite a perfect lightweight and high-performance electromagnetic wave absorbent.

  15. Preparation of Phosphonic Acid Functionalized Graphene Oxide-modified Aluminum Powder with Enhanced Anticorrosive Properties

    He, Lihua; Zhao, Yan; Xing, Liying; Liu, Pinggui; Wang, Zhiyong; Zhang, Youwei; Liu, Xiaofang

    2017-07-01

    To improve the anticorrosive performance of aluminum powder, a common functional filler in polymer coatings, we report a novel method to prepare graphene oxide modified aluminum powder (GO-Al) using 3-aminoproplyphosphoic acid as "link" agent. The GO nanosheets were firstly functionalized with 3-aminoproplyphosphoic acid (APSA) by the reaction of amine groups of APSA and the epoxy groups of GO. Subsequently, a layer of GO nanosheets uniformly and tightly covered the surface of flaky aluminum particle though the strong linking strength between -PO(OH)2 functional groups of the modified GO and aluminum. The hydrogen evolution experiment suggests that the GO attached on the aluminum powder could effectively improve the anticorrosive performance of the pigments.

  16. Generation of Electricity at Graphene Interface Governed by Underlying Surface Dipole Induced Ion Adsorption

    Yang, Shanshan; Su, Yudan; Wu, Qiong; Zhang, Yuanbo; Tian, Chuanshan

    Aqueous droplet moving along graphene surface can produce electricity This interesting phenomenon provided environment-friendly means to harvest energy from graphene interface in contact with sea wave or rain droplets. However, microscopically, the nature of charge adsorption at the graphene interface is still unclear. Here, utilizing sum-frequency spectroscopy in combined with measurement of electrical power generation, the origin of charge adsorption on graphene was investigated. It was found that the direct ion-graphene interaction is negligibly small, contrary to the early speculation, but the ordered surface dipole from the supporting substrate, such as PET, is responsible for ion adsorption at the interface. Graphene serves as a conductive layer with mild screening of Coulomb interaction when aqueous droplet slips over the surface. These results pave the way for optimization of energy harvesting efficiency of graphene-based device.

  17. Preparation and Characterization of Graphene-Based Magnetic Hybrid Nano composite

    Jashiela Wani Jusin; Madzlan Aziz

    2016-01-01

    Graphene-based magnetic hybrid nano composite has the advantage of exhibiting better performance as platform or supporting materials to develop novel properties of composite by increasing selectivity of the targeted adsorbate. The hybrid nano material was prepared by mixing and hydrolysing iron (II) and iron (III) salt precursors in the presence of GO dispersion through coprecipitation method followed by in situ chemical reduction of GO. The effect of weight loading ratio of Fe to GO (4:1, 2.5:1, 1:1 and 1:4) on structural properties of the hybrid nano materials was investigated. The presence of characteristic peaks in FTIR spectra indicated that GO has been successfully oxidized from graphite while the decrease in oxygenated functional groups and peaks intensity evidenced the formation of hybrid nano materials through the subsequent reduction process. The presence of characteristic peaks in XRD pattern denoted that magnetite nanoparticles disappeared at higher loading of GO. TEM micrograph showed that the best distribution of iron oxide particles on the surface of hybrid nano material occurred when the loading ratio of Fe to GO was fixed at 2:5 to 1. The reduced graphene oxide (RGO) sheets in the hybrid materials showed less wrinkled sheet like structure compared to GO due to exfoliation and reduction process during the synthesis. The layered morphology of GO degrades at higher concentrations of iron oxide. (author)

  18. Preparation of polyaniline/graphene oxide nanocomposite for the application of supercapacitor

    Gui, Dayong; Liu, Chunliang; Chen, Fengying; Liu, Jianhong

    2014-01-01

    Graphene oxide was synthesized by an improved Hummers method. Three polyaniline (PANI)/graphene oxide (GO) nanocomposite electrode materials were prepared from aniline (ANI), GO, and ammonium persulfate (APS) by chemical polymerization with the mass ratio (m ANI :m GO ) 1000:1, 100:1, and 10:1 in ice water, respectively. The crystal structure and the surface topography of all materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and scanning electron microscopy (SEM). The electrochemical properties of the composite were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and the impedance spectroscope, respectively. The test results show that the composites have similar and enhanced cyclic voltammetry performance compared with pure PANI based electrode material. The PANI/GO composite synthesized with the mass ratio (m ANI :m GO ) 1000:1 possessed excellent capacitive behavior with a specific capacitance as high as 355.2 F g −1 at 0.5 A g −1 in 1 mol L −1 H 2 SO 4 electrolyte due to the unique morphology of Mace-like PANI/GO composite, and after 1000 cycles, the specific capacitance of the composite still has 285.8 F g −1 . These results demonstrate exciting potentials of the composite for high performance supercapacitors or other power source system.

  19. Preparation of graphene-enhanced nickel-phosphorus composite films by ultrasonic-assisted electroless plating

    Yu, Qian; Zhou, Tianfeng; Jiang, Yonggang; Yan, Xing; An, Zhonglie; Wang, Xibin; Zhang, Deyuan; Ono, Takahito

    2018-03-01

    To improve the mechanical properties of nickel-phosphorus (Ni-P) mold material for glass molding, an ultrasonic-assisted electroless plating method is proposed for the synthesis of graphene-enhanced nickel-phosphorus (G-Ni-P) composite films on heat-resistant stainless steel (06Cr25Ni20). Graphene flakes are prepared by an electrochemical exfoliation method. The surface roughness of the as-plated G-Ni-P composite plating is Ra 2.84 μm, which is higher than that of the Ni-P plating deposited using the same method. After annealing at 400 ºC for 2 h, the main phase of the G-Ni-P composite is transformed to crystalline Ni3P with an average grain size of 32.8 nm. The Vickers hardness and Young's modulus of the G-Ni-P composite are increased by 8.0% and 8.2% compared with the values of Ni-P, respectively. The detailed plating process is of great significance for the fabrication of G-Ni-P mold materials with enhanced mechanical properties.

  20. Graphene oxide powders with different oxidation degree, prepared by synthesis variations of the Hummers method

    Guerrero-Contreras, Jesus; Caballero-Briones, F.

    2015-01-01

    Graphene oxide (GO) powders with different oxidation degree estimated through the relative intensity of the infrared absorption bands related to oxygen containing groups were prepared through variations of the Hummers method. The GO powders were analyzed by Transmission Electron Microscopy, Energy dispersive spectroscopy, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Raman spectroscopy, X-ray Diffraction, UV–VIS spectroscopy and Electrical Resistance measurements. Several square micron GO sheets with low wrinkling were obtained. Oxygen to carbon ratio is around 0.2 in all the samples although a strong variance in the relative intensity of the oxygen related infrared bands is evident. Thus, the oxidation degree was estimated from the FTIR measurements using the quotient between the C–O related bands area to the total area under the spectra. FTIR shows presence of hydroxyl (–OH), epoxy (C–O–C), carboxyl (–COOH) and carbonyl (C=O) moieties and evidence of intermolecular interactions between adjacent groups. These interactions influence the exfoliation degree, the absorbance of the GO suspensions, as well as the electrical resistance, while the crystalline domain sizes, estimated from XRD and Raman do not show a noticeable behavior related with the composition and molecular structure. The results indicate that the electrical resistance is influenced mainly by the surface chemistry of the GO powders and not only by the O/C ratio. The control of the surface chemistry of GO powders would allow their use as additives in organic bulk heterojunction solar cells with enhanced photoconversion efficiency. - Highlights: • Powders of graphene oxide with different oxidation degree were prepared through variations of the Hummers method. • Raman spectroscopy and XRD demonstrated similar crystallite domain size in the samples. • Electrical resistance, exfoliation degree and optical absorption depend on the molecular structure.

  1. Graphene oxide powders with different oxidation degree, prepared by synthesis variations of the Hummers method

    Guerrero-Contreras, Jesus; Caballero-Briones, F., E-mail: fcaballero@ipn.mx

    2015-03-01

    Graphene oxide (GO) powders with different oxidation degree estimated through the relative intensity of the infrared absorption bands related to oxygen containing groups were prepared through variations of the Hummers method. The GO powders were analyzed by Transmission Electron Microscopy, Energy dispersive spectroscopy, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, Raman spectroscopy, X-ray Diffraction, UV–VIS spectroscopy and Electrical Resistance measurements. Several square micron GO sheets with low wrinkling were obtained. Oxygen to carbon ratio is around 0.2 in all the samples although a strong variance in the relative intensity of the oxygen related infrared bands is evident. Thus, the oxidation degree was estimated from the FTIR measurements using the quotient between the C–O related bands area to the total area under the spectra. FTIR shows presence of hydroxyl (–OH), epoxy (C–O–C), carboxyl (–COOH) and carbonyl (C=O) moieties and evidence of intermolecular interactions between adjacent groups. These interactions influence the exfoliation degree, the absorbance of the GO suspensions, as well as the electrical resistance, while the crystalline domain sizes, estimated from XRD and Raman do not show a noticeable behavior related with the composition and molecular structure. The results indicate that the electrical resistance is influenced mainly by the surface chemistry of the GO powders and not only by the O/C ratio. The control of the surface chemistry of GO powders would allow their use as additives in organic bulk heterojunction solar cells with enhanced photoconversion efficiency. - Highlights: • Powders of graphene oxide with different oxidation degree were prepared through variations of the Hummers method. • Raman spectroscopy and XRD demonstrated similar crystallite domain size in the samples. • Electrical resistance, exfoliation degree and optical absorption depend on the molecular structure.

  2. Local charge transport properties of hydrazine reduced monolayer graphene oxide sheets prepared under pressure condition

    Ryuzaki, Sou; Meyer, Jakob Abild Stengaard; Petersen, Søren Vermehren

    2014-01-01

    Charge transport properties of chemically reduced graphene oxide (RGO) sheets prepared by treatment with hydrazine were examined using conductive atomic force microscopy. The current-voltage (I-V) characteristics of monolayer RGO sheets prepared under atmospheric pressure followed an exponentially...

  3. Methanol electrocatalytic oxidation on Pt nanoparticles on nitrogen doped graphene prepared by the hydrothermal reaction of graphene oxide with urea

    Xu, Xiao; Zhou, Yingke; Yuan, Tao; Li, Yawei

    2013-01-01

    A facile hydrothermal reaction of graphene oxide with urea was used to produce nitrogen doped graphene, and Pt nanoparticles were deposited on the obtained nitrogen doped graphene by the NaBH 4 reduction route. The morphology and microstructure of the synthesized catalysts were characterized by transmission electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy, while the functional groups on the surface of the catalysts were investigated by the Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectra. Cyclic voltammetry, chronoamperometry and electrochemical impedance techniques were carried out to evaluate the methanol electrocatalytic oxidation activity and durability of Pt catalysts supported on the nitrogen doped graphene. The results showed that nitrogen doping and reduction of GO were achieved simultaneously by the facile hydrothermal reaction, which had beneficial effects for the deposition process and electrocatalytic activity of Pt nanoparticles. The Pt catalysts supported on the nitrogen doped graphene substrate presented excellent activity and durability of methanol oxidation reaction, which might be promising for application in direct methanol fuel cells

  4. Polymer Adsorption on Graphite and CVD Graphene Surfaces Studied by Surface-Specific Vibrational Spectroscopy.

    Su, Yudan; Han, Hui-Ling; Cai, Qun; Wu, Qiong; Xie, Mingxiu; Chen, Daoyong; Geng, Baisong; Zhang, Yuanbo; Wang, Feng; Shen, Y R; Tian, Chuanshan

    2015-10-14

    Sum-frequency vibrational spectroscopy was employed to probe polymer contaminants on chemical vapor deposition (CVD) graphene and to study alkane and polyethylene (PE) adsorption on graphite. In comparing the spectra from the two surfaces, it was found that the contaminants on CVD graphene must be long-chain alkane or PE-like molecules. PE adsorption from solution on the honeycomb surface results in a self-assembled ordered monolayer with the C-C skeleton plane perpendicular to the surface and an adsorption free energy of ∼42 kJ/mol for PE(H(CH2CH2)nH) with n ≈ 60. Such large adsorption energy is responsible for the easy contamination of CVD graphene by impurity in the polymer during standard transfer processes. Contamination can be minimized with the use of purified polymers free of PE-like impurities.

  5. In situ one-pot preparation of reduced graphene oxide/polyaniline composite for high-performance electrochemical capacitors

    Chen, Nali; Ren, Yapeng; Kong, Peipei; Tan, Lin; Feng, Huixia; Luo, Yongchun

    2017-01-01

    Highlights: • A new method to prepare reduced graphene oxide/polyaniline composite is developed. • Aniline serves as a reduction for graphene oxide under weak alkali condition. • Different characterizations confirm that GO can be effectively reduced by aniline. • A high specific capacitance of 524.4 F·g"−"1 is obtained at 0.5 A·g"−"1. - Abstract: Reduced graphene oxide/polyaniline (rGO/PANI) composites are prepared through an effective in situ one-pot synthesis route that includes the reduction of graphene oxide (GO) by aniline under weak alkali condition via hydrothermal method and then followed by in situ polymerization of aniline. X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope are employed to reveal that GO is successfully reduced by aniline under weak alkali condition and PANI can be deposited on the surfaces of reduced graphene oxide (rGO) sheets. The effect of rGO is optimized by tuning the mass ratios of aniline to GO to improve the electrochemical performance of rGO/PANI composites. The maximum specific capacitance of rGO/PANI composites achieves 524.4 F/g with a mass ratio of aniline to GO 10:1 at a current density of 0.5 A/g, in comparison to the specific capacitance of 397 F/g at the same current density of pure PANI. Particularly, the specific capacity retention rate is 81.1% after 2000 cycles at 100 mv/s scan rate, which is an improvement over that of pure PANI (55.5%).

  6. In situ one-pot preparation of reduced graphene oxide/polyaniline composite for high-performance electrochemical capacitors

    Chen, Nali [College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, Gansu (China); State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, Gansu (China); Ren, Yapeng; Kong, Peipei; Tan, Lin [College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, Gansu (China); Feng, Huixia, E-mail: fenghx@lut.cn [College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, Gansu (China); Luo, Yongchun, E-mail: luoyc@lut.cn [State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, Gansu (China)

    2017-01-15

    Highlights: • A new method to prepare reduced graphene oxide/polyaniline composite is developed. • Aniline serves as a reduction for graphene oxide under weak alkali condition. • Different characterizations confirm that GO can be effectively reduced by aniline. • A high specific capacitance of 524.4 F·g{sup −1} is obtained at 0.5 A·g{sup −1}. - Abstract: Reduced graphene oxide/polyaniline (rGO/PANI) composites are prepared through an effective in situ one-pot synthesis route that includes the reduction of graphene oxide (GO) by aniline under weak alkali condition via hydrothermal method and then followed by in situ polymerization of aniline. X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope are employed to reveal that GO is successfully reduced by aniline under weak alkali condition and PANI can be deposited on the surfaces of reduced graphene oxide (rGO) sheets. The effect of rGO is optimized by tuning the mass ratios of aniline to GO to improve the electrochemical performance of rGO/PANI composites. The maximum specific capacitance of rGO/PANI composites achieves 524.4 F/g with a mass ratio of aniline to GO 10:1 at a current density of 0.5 A/g, in comparison to the specific capacitance of 397 F/g at the same current density of pure PANI. Particularly, the specific capacity retention rate is 81.1% after 2000 cycles at 100 mv/s scan rate, which is an improvement over that of pure PANI (55.5%).

  7. Tunable antenna radome based on graphene frequency selective surface

    Qu, Meijun; Rao, Menglou; Li, Shufang; Deng, Li

    2017-09-01

    In this paper, a graphene-based frequency selective surface (FSS) is proposed. The proposed FSS exhibits a tunable bandpass filtering characteristic due to the alterable conductivity of the graphene strips which is controlled by chemical potential. Based on the reconfigurable bandpass property of the proposed FSS, a cylindrical antenna radome is designed using the FSS unit cells. A conventional omnidirectional dipole can realize a two-beam directional pattern when it is placed into the proposed antenna radome. Forward and backward endfire radiations of the dipole loaded with the radome is realized by properly adjusting the chemical potential. The proposed antenna radome is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems when the gain of a conventional antenna needs to be enhanced.

  8. A comparison of the microstructures and electrochemical capacitive properties of 2 graphenes prepared by arc discharge method and chemical method

    Zhang, H.; Yang, Y. [Research Inst. of Chemical Defense, Beijing (China); Univ. of Science and Technology, Beijing (China); Cao, G.; Xu, B. [Research Inst. of Chemical Defense, Beijing (China)

    2010-07-01

    In this study, 2 kinds of graphene materials were prepared using both arc discharge and chemical methods. The pore structures and electrochemical capacitive properties of the materials were investigated. A mesopore structure was obtained for the graphene prepared using the arc discharge method, with a capacitance of 12.9 F/g and a high rate capability when used in electrochemical applications. The graphene prepared with the chemical method demonstrated a more highly developed micropore structure and capacitances greater than 70 F/g. However, rate performance for the graphene was normal. 2 figs.

  9. Density functional theory prediction for diffusion of lithium on boron-doped graphene surface

    Gao Shuanghong; Ren Zhaoyu; Wan Lijuan; Zheng Jiming; Guo Ping; Zhou Yixuan

    2011-01-01

    The density functional theory (DFT) investigation shows that graphene has changed from semimetal to semiconductor with the increasing number of doped boron atoms. Lithium and boron atoms acted as charge contributors and recipients, which attracted to each other. Further investigations show that, the potential barrier for lithium diffusion on boron-doped graphene is higher than that of intrinsic graphene. The potential barrier is up to 0.22 eV when six boron atoms doped (B 6 C 26 ), which is the lowest potential barrier in all the doped graphene. The potential barrier is dramatically affected by the surface structure of graphene.

  10. Polydopamine-mediated surface-functionalization of graphene oxide for heavy metal ions removal

    Dong, Zhihui; Zhang, Feng; Wang, Dong; Liu, Xia; Jin, Jian

    2015-01-01

    By utilizing polydopamine (PD) nano-thick interlayer as mediator, polyethylenimine (PEI) brushes with abundant amine groups were grafted onto the surface of PD coated graphene oxide (GO) uniformly via a Michael-Addition reaction and produced a PEI–PD/GO composite nanosheets. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions as compared to PEI-coated GO and pure GO. The adsorption capacities for Cu 2+ , Cd 2+ , Pb 2+ , Hg 2+ are up to 87, 106, 197, and 110 mg/g, respectively. To further make the GO based composite operable, PEI–PD/RGO aerogel was prepared through hydrothermal and achieved a high surface area up to 373 m 2 /g. Although the adsorption capacity of PEI–PD/RGO aerogel for heavy metal ions decreases a little as compared to PEI–PD/GO composite dispersion (38, 32, 95, 113 mg/g corresponding to Cu 2+ , Cd 2+ , Pb 2+ , and Hg 2+ , respectively), it could be recycled several times in a simple way by releasing adsorbed metal ions, indicating its potential application for cleaning wastewater. - Graphical abstract: Polyethylenimine (PEI) brushes were grafted onto the surface of graphene oxide (GO) uniformly via a Michael-Addition reaction between the PEI and polydopamine interlayer coated on GO surface. The PEI–PD/GO composite exhibited an improved performance for adsorption of heavy metal ions compared to PEI-coated GO and pure GO. - Highlights: • We prepared polyethylenimine grafted polydopamine-mediated graphene oxide composites. • Introduction of PD layer increases metal ions adsorption capacity. • PEI–PD/RGO aerogel exhibited a superior adsorption performance. • PEI–PD/RGO aerogel can be recycled several times in a simple way

  11. Preparation of water-soluble graphene nanoplatelets and highly conductive films

    Xu, Xuezhu

    2017-08-11

    This paper tackles the challenge of preparation stable, highly concentrated aqueous graphene dispersions. Despite tremendous recent interest, there has been limited success in developing a method that ensures the total dispersion of non-oxidized, defect-free graphene nanosheets in water. This study successfully demonstrates that few-layer graphene nanoplatelets (GNPs) can form highly concentrated aqueous colloidal solutions after they have been pretreated in a low-concentration inorganic sodium-hypochlorite and sodium-bromide salted aqueous solvent. This method retains the graphitic structure as evidenced by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Vacuum-filtrated freestanding films demonstrate an electrical conductivity as high as 3000 S m−1. This dispersion technique is believed to be applicable not only for GNPs, but also for dispersing other types of graphitic materials, including fullerenes, single/double/multi-walled carbon nanotubes, graphene nanoribbons and etc.

  12. Preparation of polyvinyl alcohol graphene oxide phosphonate film and research of thermal stability and mechanical properties.

    Li, Jihui; Song, Yunna; Ma, Zheng; Li, Ning; Niu, Shuai; Li, Yongshen

    2018-05-01

    In this article, flake graphite, nitric acid, peroxyacetic acid and phosphoric acid are used to prepare graphene oxide phosphonic and phosphinic acids (GOPAs), and GOPAs and polyvinyl alcohol (PVA) are used to synthesize polyvinyl alcohol graphene oxide phosphonate and phosphinate (PVAGOPs) in the case of faint acidity and ultrasound irradiation, and PVAGOPs are used to fabricate PVAGOPs film, and the structure and morphology of GOPAs, PVAGOPs and PVAGOPs film are characterized, and the thermal stability and mechanical properties of PVAGOPs film are investigated. Based on these, it has been proved that GOPAs consist of graphene oxide phosphonic acid and graphene oxide phosphinic acid, and there are CP covalent bonds between them, and PVAGOPs are composed of GOPAs and PVA, and there are six-member lactone rings between GOPAs and PVA, and the thermal stability and mechanical properties of PVAGOPs film are improved effectively. Copyright © 2018 Elsevier B.V. All rights reserved.

  13. Comparative effects of graphene and graphene oxide on copper toxicity to Daphnia magna: Role of surface oxygenic functional groups.

    Liu, Yingying; Fan, Wenhong; Xu, Zhizhen; Peng, Weihua; Luo, Shenglian

    2018-05-01

    Although the risk of graphene materials to aquatic organisms has drawn wide attention, the combined effects of graphene materials with other contaminants such as toxic metals, which may bring about more serious effects than graphene materials alone, have seldom been explored. Herein, the effects of graphene (GN) and graphene oxide (GO, an important oxidized derivative of graphene) on copper (Cu) toxicity to Daphnia magna were systematically investigated. The results indicated that GN remarkably increased the Cu accumulation in D. magna and enhanced the oxidative stress injury caused by Cu, whereas did not significantly alter D. magna acute mortality within the tested Cu concentrations (0-200 μg L -1 ). On the contrary, GO significantly decreased the Cu accumulation in D. magna and alleviated the oxidative stress injury caused by Cu. Meanwhile, the presence of GO significantly reduced the mortality of D. magna when Cu concentration exceeded 50 μg L -1 . The different effects of GN and GO on Cu toxicity were possibly dependent on the action of surface oxygenic functional group. Because of the introduction of surface oxygenic functional groups, the adsorption ability to metal ions, stability in water and interaction mode with organisms of GO are quite different from that of GN, causing different effects on Cu toxicity. This study provides important information on the bioavailability and toxicity of heavy metals as affected by graphene materials in natural water. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection.

    Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

    2014-05-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ~4 nm and the length is 18-66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R(2)=0.998), and the detection limit is 3.32×10(-7) M (S/N=3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Hydrogen atom addition to the surface of graphene nanoflakes: A density functional theory study

    Tachikawa, Hiroto, E-mail: hiroto@eng.hokudai.ac.jp

    2017-02-28

    Highlights: • The reaction pathway of the hydrogen addition to graphene surface was determined by the DFT method. • Binding energies of atomic hydrogen to graphene surface were determined. • Absorption spectrum of hydrogenated graphene was theoretically predicted. • Hyperfine coupling constant of hydrogenated graphene was theoretically predicted. - Abstract: Polycyclic aromatic hydrocarbons (PAHs) provide a 2-dimensional (2D) reaction surface in 3-dimensional (3D) interstellar space and have been utilized as a model of graphene surfaces. In the present study, the reaction of PAHs with atomic hydrogen was investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of atomic hydrogen to graphene nanoflakes. PAHs with n = 4–37 were chosen, where n indicates the number of benzene rings. Activation energies of hydrogen addition to the graphene surface were calculated to be 5.2–7.0 kcal/mol at the CAM-B3LYP/6-311G(d,p) level, which is almost constant for all PAHs. The binding energies of hydrogen atom were slightly dependent on the size (n): 14.8–28.5 kcal/mol. The absorption spectra showed that a long tail is generated at the low-energy region after hydrogen addition to the graphene surface. The electronic states of hydrogenated graphenes were discussed on the basis of theoretical results.

  16. The role of graphene-based sorbents in modern sample preparation techniques.

    de Toffoli, Ana Lúcia; Maciel, Edvaldo Vasconcelos Soares; Fumes, Bruno Henrique; Lanças, Fernando Mauro

    2018-01-01

    The application of graphene-based sorbents in sample preparation techniques has increased significantly since 2011. These materials have good physicochemical properties to be used as sorbent and have shown excellent results in different sample preparation techniques. Graphene and its precursor graphene oxide have been considered to be good candidates to improve the extraction and concentration of different classes of target compounds (e.g., parabens, polycyclic aromatic hydrocarbon, pyrethroids, triazines, and so on) present in complex matrices. Its applications have been employed during the analysis of different matrices (e.g., environmental, biological and food). In this review, we highlight the most important characteristics of graphene-based material, their properties, synthesis routes, and the most important applications in both off-line and on-line sample preparation techniques. The discussion of the off-line approaches includes methods derived from conventional solid-phase extraction focusing on the miniaturized magnetic and dispersive modes. The modes of microextraction techniques called stir bar sorptive extraction, solid phase microextraction, and microextraction by packed sorbent are discussed. The on-line approaches focus on the use of graphene-based material mainly in on-line solid phase extraction, its variation called in-tube solid-phase microextraction, and on-line microdialysis systems. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Preparation of graphene/nile blue nanocomposite: Application for oxygen reduction reaction and biosensing

    Shervedani, Reza Karimi; Amini, Akbar

    2015-01-01

    Highlights: •New nanocomposite is synthesized by electrochemical polymerization of Nile blue and reduction of GO on GCE. •The nanocomposite is characterized by SEM, UV–vis and electrochemical methods. •High electrocatalytic activity was observed for O 2 reduction on GNs-NB nanocomposite. •GCE-GNs-NB poly was tested successfully for immobilization of GOx and detection of glucose. -- Abstract: Nile blue/graphene (NB-GNs) nanocomposite was synthesized for the first time via a green and effective one-step electrochemical method, allowing to reduce graphene oxide (GO) and NB on the glassy carbon electrode (GCE) simultaneously and construct GCE-GNs-NB poly composite. The composite was characterized by scanning electron microscopy (SEM), UV–Vis spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical results obtained in the absence of any redox probe, where NB was active, allowed to trace step-by-step addition of the NB-GNs nanocomposite onto the GCE electrode surface, supporting formation of the GCE-GNs-NB poly composite. The electrocatalytic activity of the as-prepared GCE-GNs-NB poly towards O 2 reduction was studied in neutral medium. The results revealed excellent electrocatalytic performance for two-electron reduction of oxygen, suggesting its potential application as metal-free electrocatalysts for O 2 reduction reaction. Application of the GCE-GNs-NB poly in electrochemical biosensing was demonstrated by immobilization of glucose oxidase (GOx) on the surface of GCE-GNs-NB poly , and then, using it for sensing of glucose. The biosensor exhibited a linear response, from 0.2 to 2.0 mM glucose, with a low detection limit, 2.1 μM, and high sensitivity, 67.0 μA mM −1 cm −2 , obtained by cyclic voltammetry method. The proposed biosensor was successfully tested for determination of glucose in blood serum samples

  18. A roadmap to high quality chemically prepared graphene

    Gengler, Regis Y. N.; Spyrou, Konstantinos; Rudolf, Petra

    2010-01-01

    Graphene was discovered half a decade ago and proved the existence of a two-dimensional system which becomes stable as a result of 3D corrugation. It appeared very quickly that this exceptional material had truly outstanding electronic, mechanical, thermal and optical properties. Consequently a

  19. A green method of graphene preparation in an alkaline environment

    Štengl, Václav; Henych, Jiří; Bludská, Jana; Ecorchard, Petra; Kormunda, M.

    2015-01-01

    Roč. 24, MAY (2015), s. 65-71 ISSN 1350-4177 R&D Projects: GA ČR(CZ) GA14-05146S Institutional support: RVO:61388980 Keywords : Alkaline environment * Exfoliation * Graphene * Ultrasound Subject RIV: CA - Inorganic Chemistry Impact factor: 4.556, year: 2015

  20. Preparation of electrochemically reduced graphene oxide/multi-wall ...

    graphene nanosheets with other carbon based nanos- tructures has been ... was coated on the pretreated GCE evenly and dried at ... Tablets or Rutin Tablets was ground into powder in an ... ing mode of epoxy or alkoxy at ∼1050 cm. −1 and.

  1. Step driven competitive epitaxial and self-limited growth of graphene on copper surface

    Lili Fan

    2011-09-01

    Full Text Available The existence of surface steps was found to have significant function and influence on the growth of graphene on copper via chemical vapor deposition. The two typical growth modes involved were found to be influenced by the step morphologies on copper surface, which led to our proposed step driven competitive growth mechanism. We also discovered a protective role of graphene in preserving steps on copper surface. Our results showed that wide and high steps promoted epitaxial growth and yielded multilayer graphene domains with regular shape, while dense and low steps favored self-limited growth and led to large-area monolayer graphene films. We have demonstrated that controllable growth of graphene domains of specific shape and large-area continuous graphene films are feasible.

  2. Structure and electronic properties of graphene on ferroelectric LiNbO{sub 3} surface

    Ding, Jun, E-mail: dingjun@haue.edu.cn [College of Science, Henan University of Engineering, Zhengzhou 451191 (China); Wen, LiWei; Li, HaiDong [College of Science, Henan University of Engineering, Zhengzhou 451191 (China); Zhang, Ying, E-mail: yingzhang@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China)

    2017-05-25

    Highlights: • Interface structure of graphene on O terminated LiNbO{sub 3} surface. • Asymmetry gap around Dirac point. • Berry phase calculations confirm a valley Hall effect. - Abstract: We investigate the structural and electronic properties of graphene on the O terminated LiNbO{sub 3}(001) surface by density functional theory simulations. We observe that the first graphene layer is covalent bonded with the surface O atoms and buckles a lot. While considering second layer graphene upon the first layer, it almost recovers the planar structure and the interface interaction breaks the AB sublattice symmetry which leads to a valley Hall effect. Our results reveal the interface structure of graphene-ferroelectric heterostructure and provide the way for valleytronic applications with graphene.

  3. Improved catalytic activity of cobalt core–platinum shell nanoparticles supported on surface functionalized graphene for methanol electro-oxidation

    Zhang, Mingmei; Li, Yuan; Yan, Zaoxue; Jing, Junjie; Xie, Jimin; Chen, Min

    2015-01-01

    Poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene supported bimetallic catalysts of shell platinum on core cobalt (Co@Pt/PDDA-G) are synthesized using a two-step procedure involving the microwave synthesis method and replacement method. TEM indicate that a uniform dispersion of Co@Pt nanoparticles on PDDA functionalized graphene have the average particle size of 1.9 nm. The composite is applied to electrocatalysis for methanol oxidation. And the electrochemical surface areas of the as-prepared Co@Pt/PDDA-G, Pt supported on PDDA-graphene (Pt/PDDA-G), Co@Pt supported on graphene (Co@Pt/G) are evaluated by cyclic voltammetry, which are calculated to be 105.6 m 2 g −1 Pt , 92.8 m 2 g −1 Pt , and 83.4 m 2 g −1 Pt , with respect to 37.8 m 2 g −1 Pt of commercial Pt/C (TKK) catalyst. The current being examined by chronoamperometry reach a constant at 23 mA mg −1 for Co@Pt/PDDA–G catalyst, which is roughly 3.3-fold higher than that of commercial Pt/C catalyst. The electrochemical tests show that the activity and stability of Co@Pt supported on PDDA-G is highly better than the widely used Pt supported on PDDA-graphene sheets, also better than that of Co@Pt on unfunctional graphene with the same Pt content on the electrode. This improved activity could be attributed to not only the PDDA playing a crucial role in the dispersion and stabilization of Co@Pt on graphene, but also the high use ratio of Pt for its shell structure and the electronic effect of the underlying metal and Pt surface layer

  4. Preparation of three-dimensional nitrogen-doped graphene layers by gas foaming method and its electrochemical capactive behavior

    Hao, Junnan; Shu, Dong; Guo, Songtao; Gao, Aimei; He, Chun; Zhong, Yayun; Liao, Yuqing; Huang, Yulan; Zhong, Jie

    2016-01-01

    Highlights: • A three-dimensional porous graphene layers was prepared via a gas foaming method. • Melamine was the nitrogen source to synthesize the N-doped 3D graphene layers. • The specific surface area of 3D N-doped graphene material is as high as 1196 m 2 g −1 . • The 3D N-doped graphene specific capacitance is 335 F g −1 in three-electrode system. • The energy density of 3D N-doped graphene reaches 58.1 Wh kg −1 in a symmetric cell. - Abstract: A porous graphene layers with a three-dimensional structure (3DG) was prepared via a gas foaming method based on a polymeric predecessor. This intimately interconnected 3DG structure not only significantly increases the specific surface area but also provides more channels to facilitate electron transport. In addition, 3D N-doped (3DNG) layers materials were synthesized using melamine as a nitrogen source. The nitrogen content in the 3DNG layers significantly influenced the electrochemical performance. The sample denoted as 3DNG-2 exhibited a specific capacitance of 335.2 F g −1 at a current density of 1 A g −1 in a three-electrode system. Additionally, 3DNG-2 exhibited excellent electrochemical performance in aqueous and organic electrolytes using a two-electrode symmetric cell. An energy density of 58.1 Wh kg −1 at a power density of 2500 W kg −1 was achieved, which is approximately 3 times that (19.6 Wh kg −1 ) in an aqueous electrolyte in a two-electrode system. After 1000 cycles, the capacity retention in aqueous electrolyte was more than 99.0%, and this retention in organic electrolytes was more than 89.4%, which demonstrated its excellent cycle stability. This performance makes 3DNG-2 a promising candidate as an electrode material in high-power and high-energy supercapacitor applications.

  5. Influence of nanoparticle–graphene separation on the localized surface plasmon resonances of metal nanoparticles

    Masoudian Saadabad, Reza, E-mail: masoudian-reza@yahoo.com, E-mail: rms@mail.usb.ac.ir; Aporvari, Ahmad Shafiei [University of Sistan and Baluchestan, Department of Physics (Iran, Islamic Republic of); Shirdel-Havar, Amir Hushang [Golestan University, Department of Physics (Iran, Islamic Republic of); Havar, Majid Shirdel [University of Kashan, Department of Physics (Iran, Islamic Republic of)

    2016-01-15

    We develop a theory to model the interaction of graphene substrate with localized plasmon resonances in metallic nanoparticles. The influence of a graphene substrate on the surface plasmon resonances is described using an effective background permittivity that is derived from a pseudoparticle concept using the electrostatic method. For this purpose, the interaction of metal nanoparticle with graphene sheet is studied to obtain the optical spectrum of gold nanoparticles deposited on a graphene substrate. Then, we introduce a factor based on dipole approximation to predict the influence of the separation of nanoparticles and graphene on the spectral position of the localized plasmon resonance of the nanoparticles. We applied the theory for a 4-nm-radius gold nanosphere placed near 1.5 nm graphene layer. It is shown that a blue shift is emerged in the position of plasmon resonance when the nanoparticle moves away from graphene.

  6. Localized surface plasmon resonance properties of Ag nanorod arrays on graphene-coated Au substrate

    Mu, Haiwei; Lv, Jingwei; Liu, Chao; Sun, Tao; Chu, Paul K.; Zhang, Jingping

    2017-11-01

    Localized surface plasmon resonance (LSPR) on silver nanorod (SNR) arrays deposited on a graphene-coated Au substrate is investigated by the discrete dipole approximation (DDA) method. The resonance peaks in the extinction spectra of the SNR/graphene/Au structure show significantly different profiles as SNR height, and refractive index of the surrounding medium are varied gradually. Numerical simulation reveals that the shifts in the resonance peaks arise from hybridization of multiple plasmon modes as a result of coupling between the SNR arrays and graphene-coated Au substrate. Moreover, the LSPR modes blue-shifts from 800 nm to 700 nm when the thickness of the graphene layer in the metal nanoparticle (NP) - graphene hybrid nanostructure increases from 1 nm to 5 nm, which attribute to charge transfer between the graphene layer and SNR arrays. The results provide insights into metal NP-graphene hybrid nanostructures which have potential applications in plasmonics.

  7. Surface-directed molecular assembly of pentacene on monolayer graphene for high-performance organic transistors.

    Lee, Wi Hyoung; Park, Jaesung; Sim, Sung Hyun; Lim, Soojin; Kim, Kwang S; Hong, Byung Hee; Cho, Kilwon

    2011-03-30

    Organic electronic devices that use graphene electrodes have received considerable attention because graphene is regarded as an ideal candidate electrode material. Transfer and lithographic processes during fabrication of patterned graphene electrodes typically leave polymer residues on the graphene surfaces. However, the impact of these residues on the organic semiconductor growth mechanism on graphene surface has not been reported yet. Here, we demonstrate that polymer residues remaining on graphene surfaces induce a stand-up orientation of pentacene, thereby controlling pentacene growth such that the molecular assembly is optimal for charge transport. Thus, pentacene field-effect transistors (FETs) using source/drain monolayer graphene electrodes with polymer residues show a high field-effect mobility of 1.2 cm(2)/V s. In contrast, epitaxial growth of pentacene having molecular assembly of lying-down structure is facilitated by π-π interaction between pentacene and the clean graphene electrode without polymer residues, which adversely affects lateral charge transport at the interface between electrode and channel. Our studies provide that the obtained high field-effect mobility in pentacene FETs using monolayer graphene electrodes arises from the extrinsic effects of polymer residues as well as the intrinsic characteristics of the highly conductive, ultrathin two-dimensional monolayer graphene electrodes.

  8. Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application

    Kaushik, Priya Darshni; Ivanov, Ivan G.; Lin, Pin-Cheng; Kaur, Gurpreet; Eriksson, Jens; Lakshmi, G.B.V.S.; Avasthi, D.K.; Gupta, Vinay; Aziz, Anver; Siddiqui, Azher M.; Syväjärvi, Mikael; Yazdi, G. Reza

    2017-01-01

    Highlights: • For the first time the gas sensing application of SHI irradiated epitaxial graphene on SiC is explored. • Surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles. • Existence of an optimal fluence which maximize the gas sensing response towards NO_2 and NH_3 gases. - Abstract: In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 × 10"1"3 ions/cm"2). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and spintronic

  9. Surface functionalization of epitaxial graphene on SiC by ion irradiation for gas sensing application

    Kaushik, Priya Darshni, E-mail: kaushik.priyadarshni@gmail.com [Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping (Sweden); Department of Physics, Jamia Millia Islamia, New Delhi, 110025 (India); Ivanov, Ivan G.; Lin, Pin-Cheng [Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping (Sweden); Kaur, Gurpreet [Department of Physics and Astrophysics, University of Delhi, Delhi, 110007 (India); Eriksson, Jens [Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping (Sweden); Lakshmi, G.B.V.S. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, 110067 (India); Avasthi, D.K. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi, 110067 (India); Amity Institute of Nanotechnology, Noida 201313 (India); Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi, 110007 (India); Aziz, Anver; Siddiqui, Azher M. [Department of Physics, Jamia Millia Islamia, New Delhi, 110025 (India); Syväjärvi, Mikael [Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping (Sweden); Yazdi, G. Reza, E-mail: yazdi@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping (Sweden)

    2017-05-01

    Highlights: • For the first time the gas sensing application of SHI irradiated epitaxial graphene on SiC is explored. • Surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles. • Existence of an optimal fluence which maximize the gas sensing response towards NO{sub 2} and NH{sub 3} gases. - Abstract: In this work, surface functionalization of epitaxial graphene grown on silicon carbide was performed by ion irradiation to investigate their gas sensing capabilities. Swift heavy ion irradiation using 100 MeV silver ions at four varying fluences was implemented on epitaxial graphene to investigate morphological and structural changes and their effects on the gas sensing capabilities of graphene. Sensing devices are expected as one of the first electronic applications using graphene and most of them use functionalized surfaces to tailor a certain function. In our case, we have studied irradiation as a tool to achieve functionalization. Morphological and structural changes on epitaxial graphene layers were investigated by atomic force microscopy, Raman spectroscopy, Raman mapping and reflectance mapping. The surface morphology of irradiated graphene layers showed graphene folding, hillocks, and formation of wrinkles at highest fluence (2 × 10{sup 13} ions/cm{sup 2}). Raman spectra analysis shows that the graphene defect density is increased with increasing fluence, while Raman mapping and reflectance mapping show that there is also a reduction of monolayer graphene coverage. The samples were investigated for ammonia and nitrogen dioxide gas sensing applications. Sensors fabricated on pristine and irradiated samples showed highest gas sensing response at an optimal fluence. Our work provides new pathways for introducing defects in controlled manner in epitaxial graphene, which can be used not only for gas sensing application but also for other applications, such as electrochemical, biosensing, magnetosensing and

  10. Evolution of interfacial intercalation chemistry on epitaxial graphene/SiC by surface enhanced Raman spectroscopy

    Ferralis, Nicola; Carraro, Carlo

    2014-01-01

    Highlights: • H-intercalated epitaxial graphene–SiC interface studied with surface enhanced Raman. • Evolution of graphene and H–Si interface with UV-ozone, annealing and O-exposure. • H–Si interface and quasi-freestanding graphene are retained after UV-ozone treatment. • Enhanced ozonolytic reactivity at the edges of H-intercalated defected graphene. • Novel SERS method for characterizing near-surface graphene–substrate interfaces. - Abstract: A rapid and facile evaluation of the effects of physical and chemical processes on the interfacial layer between epitaxial graphene monolayers on SiC(0 0 0 1) surfaces is essential for applications in electronics, photonics, and optoelectronics. Here, the evolution of the atomic scale epitaxial graphene-buffer-layer–SiC interface through hydrogen intercalation, thermal annealings, UV-ozone etching and oxygen exposure is studied by means of single microparticle mediated surface enhanced Raman spectroscopy (smSERS). The evolution of the interfacial chemistry in the buffer layer is monitored through the Raman band at 2132 cm −1 corresponding to the Si-H stretch mode. Graphene quality is monitored directly by the selectively enhanced Raman signal of graphene compared to the SiC substrate signal. Through smSERS, a simultaneous correlation between optimized hydrogen intercalation in epitaxial graphene/SiC and an increase in graphene quality is uncovered. Following UV-ozone treatment, a fully hydrogen passivated interface is retained, while a moderate degradation in the quality of the hydrogen intercalated quasi-freestanding graphene is observed. While hydrogen intercalated defect free quasi-freestanding graphene is expected to be robust upon UV-ozone, thermal annealing, and oxygen exposure, ozonolytic reactivity at the edges of H-intercalated defected graphene results in enhanced amorphization of the quasi-freestanding (compared to non-intercalated) graphene, leading ultimately to its complete etching

  11. Evolution of interfacial intercalation chemistry on epitaxial graphene/SiC by surface enhanced Raman spectroscopy

    Ferralis, Nicola, E-mail: ferralis@mit.edu [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Carraro, Carlo [Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720 (United States)

    2014-11-30

    Highlights: • H-intercalated epitaxial graphene–SiC interface studied with surface enhanced Raman. • Evolution of graphene and H–Si interface with UV-ozone, annealing and O-exposure. • H–Si interface and quasi-freestanding graphene are retained after UV-ozone treatment. • Enhanced ozonolytic reactivity at the edges of H-intercalated defected graphene. • Novel SERS method for characterizing near-surface graphene–substrate interfaces. - Abstract: A rapid and facile evaluation of the effects of physical and chemical processes on the interfacial layer between epitaxial graphene monolayers on SiC(0 0 0 1) surfaces is essential for applications in electronics, photonics, and optoelectronics. Here, the evolution of the atomic scale epitaxial graphene-buffer-layer–SiC interface through hydrogen intercalation, thermal annealings, UV-ozone etching and oxygen exposure is studied by means of single microparticle mediated surface enhanced Raman spectroscopy (smSERS). The evolution of the interfacial chemistry in the buffer layer is monitored through the Raman band at 2132 cm{sup −1} corresponding to the Si-H stretch mode. Graphene quality is monitored directly by the selectively enhanced Raman signal of graphene compared to the SiC substrate signal. Through smSERS, a simultaneous correlation between optimized hydrogen intercalation in epitaxial graphene/SiC and an increase in graphene quality is uncovered. Following UV-ozone treatment, a fully hydrogen passivated interface is retained, while a moderate degradation in the quality of the hydrogen intercalated quasi-freestanding graphene is observed. While hydrogen intercalated defect free quasi-freestanding graphene is expected to be robust upon UV-ozone, thermal annealing, and oxygen exposure, ozonolytic reactivity at the edges of H-intercalated defected graphene results in enhanced amorphization of the quasi-freestanding (compared to non-intercalated) graphene, leading ultimately to its complete etching.

  12. Anticoagulation and endothelial cell behaviors of heparin-loaded graphene oxide coating on titanium surface

    Pan, Chang-Jiang, E-mail: panchangjiang@hyit.edu.cn [Jiangsu Provincial Key Laboratory for Interventional Medical Devices, Huaiyin Institute of Technology, Huai' an 223003 (China); Pang, Li-Qun [Department of General Surgery, Huai' an First People' s Hospital, Nanjing Medical University, Huai' an 223300 (China); Gao, Fei [Zhejiang Zylox Medical Devices Co., Ltd., Hangzhou 310000 (China); Wang, Ya-Nan; Liu, Tao; Ye, Wei; Hou, Yan-Hua [Jiangsu Provincial Key Laboratory for Interventional Medical Devices, Huaiyin Institute of Technology, Huai' an 223003 (China)

    2016-06-01

    Owing to its unique physical and chemical properties, graphene oxide (GO) has attracted tremendous interest in many fields including biomaterials and biomedicine. The purpose of the present study is to investigate the endothelial cell behaviors and anticoagulation of heparin-loaded GO coating on the titanium surface. To this end, the titanium surface was firstly covered by the polydopamine coating followed by the deposition of the GO coating. Heparin was finally loaded on the GO coating to improve the blood compatibility. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated that the heparin-loaded GO coating was successfully created on the titanium surface. The scanning electron microscopy (SEM) images indicated that a relative uniform GO coating consisting of multilayer GO sheets was formed on the substrate. The hydrophilicity of the titanium surface was enhanced after the deposition of GO and further improved significantly by the loading heparin. The GO coating can enhance the endothelial cell adhesion and proliferation as compared with polydopamine coating and the blank titanium. Loading heparin on the GO coating can significantly reduce the platelet adhesion and prolong the activated partial thromboplastin time (APTT) while not influence the endothelial cell adhesion and proliferation. Therefore, the heparin-loaded GO coating can simultaneously enhance the cytocompatibility to endothelial cells and blood compatibility of biomaterials. Because the polydopamine coating can be easily prepared on most of biomaterials including polymer, ceramics and metal, thus the approach of the present study may open up a new window of promising an effective and efficient way to promote endothelialization and improve the blood compatibility of blood-contact biomedical devices such as intravascular stents. - Highlights: • Heparin-loaded graphene oxide coating was

  13. Generation of Graphene Surface Plasmons and Their Applications in Beam Steering

    Farhat, Mohamed; Chen, Pai Yen; Guenneau, Sebastien; Bagci, Hakan

    2015-01-01

    We propose a novel concept that uses mechanical and electronic properties of graphene to efficiently couple light to surface plasmon polaritons. A graphene-based infrared beam-former based on the concept of surface leaky-wave is also discussed

  14. Generation of Graphene Surface Plasmons and Their Applications in Beam Steering

    Farhat, Mohamed

    2015-01-01

    We propose a novel concept that uses mechanical and electronic properties of graphene to efficiently couple light to surface plasmon polaritons. A graphene-based infrared beam-former based on the concept of surface leaky-wave is also discussed. © OSA 2015.

  15. Toward intrinsic graphene surfaces: a systematic study on thermal annealing and wet-chemical treatment of SiO2-supported graphene devices.

    Cheng, Zengguang; Zhou, Qiaoyu; Wang, Chenxuan; Li, Qiang; Wang, Chen; Fang, Ying

    2011-02-09

    By combining atomic force microscopy and trans-port measurements, we systematically investigated effects of thermal annealing on surface morphologies and electrical properties of single-layer graphene devices fabricated by electron beam lithography on silicon oxide (SiO(2)) substrates. Thermal treatment above 300 °C in vacuum was required to effectively remove resist residues on graphene surfaces. However, annealing at high temperature was found to concomitantly bring graphene in close contact with SiO(2) substrates and induce increased coupling between them, which leads to heavy hole doping and severe degradation of mobilities in graphene devices. To address this problem, a wet-chemical approach employing chloroform was developed in our study, which was shown to enable both intrinsic surfaces and enhanced electrical properties of graphene devices. Upon the recovery of intrinsic surfaces of graphene, the adsorption and assisted fibrillation of amyloid β-peptide (Aβ1-42) on graphene were electrically measured in real time.

  16. Nitrogen-doped graphene network supported copper nanoparticles encapsulated with graphene shells for surface-enhanced Raman scattering

    Zhang, Xiang; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun; Zhao, Naiqin; He, Chunnian

    2015-10-01

    In this study, we demonstrated nitrogen-doped graphene network supported few-layered graphene shell encapsulated Cu nanoparticles (NPs) (Cu@G-NGNs) as a sensing platform, which were constructed by a simple and scalable in situ chemical vapor deposition (CVD) technique with the assistance of a self-assembled three-dimensional (3D) NaCl template. Compared with pure Cu NPs and graphene decorated Cu NPs, the graphene shells can strengthen the plasmonic coupling between graphene and Cu, thereby contributing to an obvious improvement in the local electromagnetic field that was validated by finite element numerical simulations, while the 3D nitrogen-doped graphene walls with a large surface area facilitated molecule adsorption and the doped nitrogen atoms embedded in the graphene lattice can reduce the surface energy of the system. With these merits, a good surface enhanced Raman spectroscopy (SERS) activity of the 3D Cu@G-NGN painting film on glass was demonstrated using rhodamine 6G and crystal violet as model analytes, exhibiting a satisfactory sensitivity, reproducibility and stability. As far as we know, this is the first report on the in situ synthesis of nitrogen-doped graphene/copper nanocomposites and this facile and low-cost Cu-based strategy tends to be a good supplement to Ag and Au based substrates for SERS applications.In this study, we demonstrated nitrogen-doped graphene network supported few-layered graphene shell encapsulated Cu nanoparticles (NPs) (Cu@G-NGNs) as a sensing platform, which were constructed by a simple and scalable in situ chemical vapor deposition (CVD) technique with the assistance of a self-assembled three-dimensional (3D) NaCl template. Compared with pure Cu NPs and graphene decorated Cu NPs, the graphene shells can strengthen the plasmonic coupling between graphene and Cu, thereby contributing to an obvious improvement in the local electromagnetic field that was validated by finite element numerical simulations, while the 3D nitrogen

  17. Preparation of a Leaf-Like BiVO4-Reduced Graphene Oxide Composite and Its Photocatalytic Activity

    Shimin Xiong

    2017-01-01

    Full Text Available We prepared a unique leaf-like BiVO4-reduced graphene oxide (BiVO4-rGO composite with prominent adsorption performance and photocatalytic ability by a single-step method. Multiple characterization results showed that the leaf-like BiVO4 with average diameter of about 5 um was well dispersed on the reduced graphene oxide sheet, which enhanced the transportation of photogenerated electrons into BiVO4, thereby leading to efficient separation of photogenerated carriers in the coupled graphene-nanocomposite system. The characterization and experiment results also indicated that the outstanding adsorption ability of such composite was closely associated with the rough surface of the leaf-like BiVO4 and doped rGO. The surface photocurrent spectroscopy and transient photocurrent density measurement results demonstrated that the doped rGO enhanced separation efficiency and transfer rate of photogenerated charges. As a result, the BiVO4-rGO exhibited higher photocatalytic capacity toward the degradation of rhodamine B dye under visible-light irradiation compared with pure BiVO4 and P25.

  18. Green preparation using black soybeans extract for graphene-based porous electrodes and their applications in supercapacitors

    Chu, Hwei-Jay; Lee, Chi-Young; Tai, Nyan-Hwa

    2016-08-01

    Adopting an in situ construction strategy, green reduction of graphene oxide (GO) and the formation of an open porous structure are simultaneously completed in a one-pot process using an aqueous extract of an anthocyanin-containing plant, black soybean, as a green reducing agent. The reduced GO prepared by the aqueous extract of black soybean (BRGO), and the hydrogel of BRGO are characterized to better understand the nature of BRGO and the evolution of BRGO from GO. Graphene-based porous electrodes for supercapacitors are fabricated using the BRGO hydrogel as a primary material, and the electrochemical performance of the electrodes are further improved when the BRGO porous electrodes are treated in a microwave oven. Owing to the formation of uniformly dispersed nanoparticles on the graphene surface during the microwave treatment, the electrical conductivity of the electrodes improves by four orders of magnitude and the electroactive surface area also increases by over four times, as a consequence, the capacitance is significantly enhanced, reaching a capacitance of 268.4 F g-1 at a charging current of 0.1 A g-1.

  19. Chemical preparation of graphene-based nanomaterials and their applications in chemical and biological sensors.

    Jiang, Hongji

    2011-09-05

    Graphene is a flat monolayer of carbon atoms packed tightly into a 2D honeycomb lattice that shows many intriguing properties meeting the key requirements for the implementation of highly excellent sensors, and all kinds of proof-of-concept sensors have been devised. To realize the potential sensor applications, the key is to synthesize graphene in a controlled way to achieve enhanced solution-processing capabilities, and at the same time to maintain or even improve the intrinsic properties of graphene. Several production techniques for graphene-based nanomaterials have been developed, ranging from the mechanical cleavage and chemical exfoliation of high-quality graphene to direct growth onto different substrates and the chemical routes using graphite oxide as a precusor to the newly developed bottom-up approach at the molecular level. The current review critically explores the recent progress on the chemical preparation of graphene-based nanomaterials and their applications in sensors. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Electronic and structural characterizations of unreconstructed {0001} surfaces and the growth of graphene overlayers

    Emtsev, Konstantin

    2009-01-01

    The present work is focused on the characterization of the clean unreconstructed SiC{0001} surfaces and the growth of graphene overlayers thereon. Electronic properties of SiC surfaces and their interfaces with graphene and few layer graphene films were investigated by means of angle resolved photoelectron spectroscopy, X-ray photoelectron spectroscopy and low energy electron diffraction. Structural characterizations of the epitaxial graphene films grown on SiC were carried out by atomic force microscopy and low energy electron microscopy. Supplementary data was obtained by scanning tunneling microscopy. (orig.)

  1. Aqueous preparation of polyethylene glycol/sulfonated graphene phase change composite with enhanced thermal performance

    Li, Hairong; Jiang, Ming; Li, Qi; Li, Denian; Chen, Zongyi; Hu, Waping; Huang, Jing; Xu, Xizhe; Dong, Lijie; Xie, Haian; Xiong, Chuanxi

    2013-01-01

    Highlights: • We report an aqueous preparation technique of PEG/graphene phase change composite. • Hydrophilic sulfonated graphene (SG) nanosheets were synthesized. • Large increase in thermal conductivity is attained at low SG loading. • High latent heat is retained due to the low filler loading. • Affinity between SG and PEG contributes to the enhanced thermal performance. - Abstract: A polyethylene glycol (PEG)/sulfonated graphene (SG) phase change composite with enhanced thermal performance was prepared by solution processing in aqueous medium. It is remarkable that the addition of only 4 wt.% of SG to PEG could lead to a four times higher increase in thermal conductivity and a slight decrease in the phase change enthalpy, which is attributed to the formation of efficient thermal conductive network within the PEG matrix relevant to the excellent thermal property and unique 2-dimensional morphology of graphene as well as strong interface affinity between PEG matrix and SG nanosheets. The aqueous preparation technique is expected to pioneer a new way to prepare environment friendly organic phase change materials, and the production of PEG/SG composites is potentially scalable due to the facile fabricating process

  2. Physicochemical properties of hybrid graphene-lead sulfide quantum dots prepared by supercritical ethanol

    Tavakoli, Mohammad Mahdi; Tayyebi, Ahmad; Simchi, Abdolreza; Aashuri, Hossein; Outokesh, Mohmmad; Fan, Zhiyong

    2015-01-01

    Recently, hybrid graphene-quantum dot systems have attracted increasing attention for the next-generation optoelectronic devices such as ultrafast photo-detectors and solar energy harvesting. In this paper, a novel, one-step, reproducible, and solution-processed method is introduced to prepare hybrid graphene-PbS colloids by employing supercritical ethanol. In the hybrid nanocomposite, PbS quantum dots ( 3 nm) are decorated on the reduced graphene oxide (rGO) nanosheets ( 1 nm thickness and less than 1 micron lengths). By employing X-ray photoelectron and Raman and infrared spectroscopy techniques, it is shown that the rGO nanosheets are bonded to PbS nanocrystals through carboxylic bonds. Passivation of {111} planes of PbS quantum dots with rGO nanosheets is demonstrated by employing density function theory. Quenching of the photoluminescence emission of PbS nanocrystals through coupling with graphene sheets is also shown. In order to illustrate that the developed preparation method does not impair the quantum efficiency of the PbS nanocrystals, the photovoltaic efficiency of solar cell device is reported and compared with oleic acid-capped PbS colloidal quantum dot solar cells. By employing the "Hall effect" measurement, it is shown that the carrier mobility is significantly increased (by two orders of magnitudes) in the presence of graphene nanosheets.

  3. Multifunctional surface modification of silk fabric via graphene oxide repeatedly coating and chemical reduction method

    Cao, Jiliang; Wang, Chaoxia

    2017-05-01

    Multifunctional silk fabrics with electrical conductive, anti-ultraviolet and water repellent were successfully prepared by surface modification with graphene oxide (GO). The yellow-brown GO deposited on the surface of silk fabric was converted into graphitic black reduced graphene (RGO) by sodium hydrosulfite. The surface properties of silk fabrics were changed by repeatedly RGO coating process, which have been proved by SEM and XPS. The SEM results showed that the RGO sheets were successive form a continuously thin film on the surface of silk fabrics, and the deposition of GO or RGO also can be proved by XPS. The electrical conductivity was tested by electrical surface resistance value of the silk fabric, the surface resistance decreased with increasing of RGO surface modification times, and a low surface resistance value reached to 3.24 KΩ cm-1 after 9 times of modification, indicating the silk obtained excellent conductivity. The UPF value of one time GO modification silk fabric (silk-1RGO) was enhanced significantly to 24.45 in comparison to 10.40 of original silk. The contact angle of RGO coating silk samples was all above of 120°. The durability of RGO coated silk fabrics was tested by laundering. The electrical surface resistance of silk-4RGO (65.74 KΩ cm-1), silk-6RGO (15.54 KΩ cm-1) and silk-8RGO (3.86 KΩ cm-1) fabrics was up to 86.82, 22.30 and 6.57 KΩ cm-1 after 10 times of standard washing, respectively. The UPF value, contact angle and color differences of RGO modified silk fabric slightly changed before and after 10 times of standard washing. Therefore, the washing fastness of electric conduction, anti-ultraviolet and water repellent multifunctional silk fabrics was excellent.

  4. Facile hydrothermal preparation of recyclable S-doped graphene sponge for Cu2+ adsorption

    Zhao, Lianqin; Yu, Baowei; Xue, Fumin; Xie, Jingru; Zhang, Xiaoliang; Wu, Ruihan; Wang, Ruijue; Hu, Zhiyan; Yang, Sheng-Tao; Luo, Jianbin

    2015-01-01

    Graphical abstract: S-doped graphene sponge was prepared via hydrothermal treatment, where S-doped graphene sponge had an adsorption capacity of 228 mg/g for Cu 2+ . - Highlights: • S-doped graphene sponge was prepared by hydrothermal treatment for heavy metal adsorption. • S-doped graphene sponge had a huge adsorption capacity for Cu 2+ , which was 40 times higher than that of active carbon. • S-doped graphene sponge could be easily regenerated by washing with acidic thiourea. - Abstract: Graphene sponge (GS) has been widely employed for water purification, but adsorption capacity loss frequently occurs during the formation of spongy structure. In this study, we reported the hydrothermal preparation of S-doped GS for the removal of Cu 2+ with a huge adsorption capacity of 228 mg/g, 40 times higher than that of active carbon. The adsorption isotherm could be well fitted into the Freundlich model with a K F value of 36.309 (L/mg) 1/n . The equilibrium adsorption could be fully achieved in the first 5 min. In the thermodynamics study, the negative ΔG indicated that the adsorption was spontaneous and physisorption in nature. The positive ΔH implied that the adsorption was endothermic. The changes of both pH and ionic strength had no apparent influence on the adsorption. S-doped GS could be easily regenerated by washing with acidic thiourea. Moreover, S-doped GS could be used for the adsorption of other heavy metal ions, too. The implication to the applications of S-doped GS in water treatment is discussed

  5. Preparation of multilayer graphene sheets and their applications for particle accelerators

    Tatami, Atsushi; Tachibana, Masamitsu; Yagi, Takashi; Murakami, Mutsuaki

    2018-05-01

    Multilayer graphene sheets were prepared by heat treatment of polyimide films at temperatures of up to 3000 °C. The sheets consist of highly oriented graphite layers with excellent mechanical robustness and flexibility. Key features of these sheets include their high thermal conductivity in the in-plane direction, good mechanical properties, and high carbon purity. The results suggest that the multilayer graphene sheets have great potential for charge stripping foils that persist even under the highest ion beam intensities irradiation and can be used for accelerator applications.

  6. Supercapacitors based on highly dispersed polypyrrole-reduced graphene oxide composite with a folded surface

    Wang, Anqi; Zhou, Xi; Qian, Tao; Yu, Chenfei; Wu, Shishan; Shen, Jian

    2015-08-01

    Highly dispersed polypyrrole particles were decorated on reduced graphene oxide sheets using a facile in situ synthesis route. The prepared composite, which obtained a folded surface, shows remarkable performance as the electrode material of supercapacitors. The specific capacitance reaches 564.1 F g-1 at a current density of 1 A g-1 and maintains 86.4 % after 1000 charging-discharging cycles at a current density of 20 A g-1, which indicates a good cycling stability. Furthermore, the prepared supercapacitor demonstrates an ultrahigh energy density of 50.13 Wh kg-1 at power density of 0.40 kW kg-1, and remains of 45.33 Wh kg-1 even at high power density of 8.00 kW kg-1, which demonstrate that the hybrid supercapacitor can be a promising energy storage system for fast and efficient energy storage in the future.

  7. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

    Huang, Linhong [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Hou, Keyu; Jia, Xiao [Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Pan, Haibo, E-mail: hbpan@fzu.edu.cn [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); Institute of Research for Functional Materials, Fuzhou University, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China); College of Chemistry and Chemical Engineering, Qishan Campus, Fuzhou University, Fuzhou, Fujian 350108 (China); Du, Min [Fujian Key Lab of Medical Instrument and Pharmaceutical Technology, Yishan Campus, Fuzhou University, Fuzhou, Fujian 350002 (China)

    2014-05-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R{sup 2} = 0.998), and the detection limit is 3.32 × 10{sup −7} M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity.

  8. Preparation of novel silver nanoplates/graphene composite and their application in vanillin electrochemical detection

    Huang, Linhong; Hou, Keyu; Jia, Xiao; Pan, Haibo; Du, Min

    2014-01-01

    Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ∼ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R 2 = 0.998), and the detection limit is 3.32 × 10 −7 M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination. - Highlights: • Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate. • Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin. • The composite with good dispersion exhibits enhanced surface area and good catalysis. • Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity

  9. Transfer printing of graphene strip from the graphene grown on copper wires

    Su, Ching-Yuan; Fu Dongliang; Lu, Ang-Yu; Liu, Keng-Ku; Xu Yanping; Juang, Zhen-Yu; Li, Lain-Jong

    2011-01-01

    A simple, cost-effective and lithography-free fabrication of graphene strips for device applications is demonstrated. The graphene thin layers were directly grown on Cu wires, followed by Cu etching and transfer printing to arbitrary substrates by a PDMS stamp. The Cu wires can be arranged on the PDMS stamp in a desired pattern; hence, the substrates can receive graphene strips with the same pattern. Moreover, the preparation of graphene strips does not involve conventional lithography; therefore, the surface of the graphene strip is free of residual photoresists, which may be useful for studies requiring clean graphene surfaces.

  10. Surface study of platinum decorated graphene towards adsorption of NH_3 and CH_4

    Rad, Ali Shokuhi; Pazoki, Hossein; Mohseni, Soheil; Zareyee, Daryoush; Peyravi, Majid

    2016-01-01

    To distinguish the potential of graphene sensors, there is a need to recognize the interaction between graphene sheet and adsorbing molecules. We used density functional theory (DFT) calculations to study the properties of pristine as well as Pt-decorated graphene sheet upon adsorption of NH_3 and CH_4 on its surface to exploit its potential to be as gas sensors for them. We found much higher adsorption, higher charge transfer, lower intermolecular distance, and higher orbital hybridizing upon adsorption of NH_3 and CH_4 gas molecules on Pt-decorated graphene compared to pristine graphene. Also our calculations reveal that the adsorption energies on Pt-decorated graphene sheet are in order of NH_3 >CH_4 which could be corresponded to the order of their sensitivity on this modified surface. We used orbital analysis including density of states as well as frontier molecular orbital study for all analyte-surface systems to more understanding the kind of interaction (physisorption or chemisorption). Consequently, the Pt-decorated graphene can transform the existence of NH_3 and CH_4 molecules into electrical signal and it may be potentially used as an ideal sensor for detection of NH_3 and CH_4 in ambient situation. - Highlights: • Pt-decorated graphene was investigated as an adsorbent for NH_3 and CH_4. • Much higher adsorption of NH_3 and CH_4 on Pt-decorated graphene than pristine graphene. • Higher adsorption of NH_3 compared to CH_4 on Pt-decorated graphene. • Pt influences the electronic structure of graphene.

  11. One-pot preparation of unsaturated polyester nanocomposites containing functionalized graphene sheets via a novel solvent-exchange method

    This paper reports a convenient one-pot method integrating a novel solvent-exchange method into in situ melt polycondensation to fabricate unsaturated polyester nanocomposites containing functionalized graphene sheets (FGS). A novel solvent-exchange method was first developed to prepare graphene oxi...

  12. Three-dimensional assemblies of graphene prepared by a novel chemical reduction-induced self-assembly method

    Zhang, Lianbin; Chen, Guoying; Hedhili, Mohamed N.; Zhang, Hongnan; Wang, Peng

    2012-01-01

    In this study, three-dimensional (3D) graphene assemblies are prepared from graphene oxide (GO) by a facile in situ reduction-assembly method, using a novel, low-cost, and environment-friendly reducing medium which is a combination of oxalic acid

  13. Electrochemical Properties of Graphene-vanadium Oxide Composite Prepared by Electro-deposition for Electrochemical Capacitors

    Jeong, Heeyoung; Jeong, Sang Mun

    2015-01-01

    The nanostructural graphene/vanadium oxide (graphene/V 2 O 5 ) composite with enhanced capacitance was synthesized by the electro-deposition in 0.5 M VOSO 4 solution. The morphology of composites was characterized using scanning electron microscopy (SEM), x-ray diffraction pattern (XRD), and x-ray photoelectron spectroscopy (XPS). The oxidation states of the electro-deposited vanadium oxide was found to be V 5+ and V 4+ . The morphology of the prepared graphene/V 2 O 5 composite exhibits a netlike nano-structure with V 2 O 5 nanorods in about 100 nm diameter, which could lead a better contact between electrolyte an electrode. The composite with a deposition time of 4,000 s exhibits the specific capacitance of 854 mF/cm 2 at a scan rate of 20 mV/s and the capacitance retention of 53% after 1000 CV cycles

  14. Infrared beam-steering using acoustically modulated surface plasmons over a graphene monolayer

    Chen, Paiyen

    2014-09-01

    We model and design a graphene-based infrared beamformer based on the concept of leaky-wave (fast traveling wave) antennas. The excitation of infrared surface plasmon polaritons (SPPs) over a \\'one-atom-thick\\' graphene monolayer is typically associated with intrinsically \\'slow light\\'. By modulating the graphene with elastic vibrations based on flexural waves, a dynamic diffraction grating can be formed on the graphene surface, converting propagating SPPs into fast surface waves, able to radiate directive infrared beams into the background medium. This scheme allows fast on-off switching of infrared emission and dynamic tuning of its radiation pattern, beam angle and frequency of operation, by simply varying the acoustic frequency that controls the effective grating period. We envision that this graphene beamformer may be integrated into reconfigurable transmitter/receiver modules, switches and detectors for THz and infrared wireless communication, sensing, imaging and actuation systems.

  15. Perfect-absorption graphene metamaterials for surface-enhanced molecular fingerprint spectroscopy

    Guo, Xiangdong; Hu, Hai; Liao, Baoxin; Zhu, Xing; Yang, Xiaoxia; Dai, Qing

    2018-05-01

    Graphene plasmon with extremely strong light confinement and tunable resonance frequency represents a promising surface-enhanced infrared absorption (SEIRA) sensing platform. However, plasmonic absorption is relatively weak (approximately 1%-9%) in monolayer graphene nanostructures, which would limit its sensitivity. Here, we theoretically propose a hybrid plasmon-metamaterial structure that can realize perfect absorption in graphene with a low carrier mobility of 1000 cm2 V-1 s-1. This structure combines a gold reflector and a gold grating to the graphene plasmon structures, which introduce interference effect and the lightning-rod effect, respectively, and largely enhance the coupling of light to graphene. The vibration signal of trace molecules can be enhanced up to 2000-fold at the hotspot of the perfect-absorption structure, enabling the SEIRA sensing to reach the molecular level. This hybrid metal-graphene structure provides a novel path to generate high sensitivity in nanoscale molecular recognition for numerous applications.

  16. Room temperature Zinc-metallation of cationic porphyrin at graphene surface and enhanced photoelectrocatalytic activity

    Zeng, Rongjin; Chen, Guoliang; Xiong, Chungang; Li, Gengxian; Zheng, Yinzhi; Chen, Jian; Long, Yunfei; Chen, Shu

    2018-03-01

    A stable zincporphyrin functionalized graphene nanocomposite was prepared by using positively charged cationic porphyrin (5,10,15,20-tetra(4-propyl pyridinio) porphyrin, TPPyP) and successive reduced graphene oxide (rGO) with tuned negative charge. The nanocomposite preparation was accompanied first by distinct electrostatic interactions and π-π stacking between TPPyP and rGO, and followed by fast Zinc-metallation at room temperature. In contrast to free TPPyP with Zn2+, the incorporation reaction is very slow at room temperature and heating or reflux conditions are required to increase the metallation rate. While at the surface of rGO nanosheet, the Zinc-metallation of TPPyP was greatly accelerated to 30 min at 25 °C in aqueous solution. The interaction process and composites formation were fully revealed by significant variations in UV-vis absorption spectra, X-ray photoelectron spectra (XPS) measurements, atomic force microscope (AFM) images, and fluorescence spectra. Furthermore, photoelectrochemical activity of resultant rGO/TPPyP-Zn nanocomposites was evaluated under visible-light irradiation, and enhancement of the photoelectrocatalytic reduction of CO2 was achieved.

  17. Preparation and property of UV-curable polyurethane acrylate film filled with cationic surfactant treated graphene

    Xu, Jinghong; Cai, Xia; Shen, Fenglei, E-mail: shenfenglei@suda.edu.cn

    2016-08-30

    Highlights: • The non-covalent modification of graphene maintains the intrinsic structure of graphene compared with the covalent functionalization of graphene. • The initial degradation temperature of nanocomposite film increases by 57 °C which is much higher than that of PUA nanocomposite previously reported. • The nanocomposite film exhibits improved dielectric property and electrical conductivity. • The outstanding performance of CTAB-G/PUA films will open up enormous opportunities for applications in various regions such as high temperature or electrical field. - Abstract: The preparation of nanocomposite films composed of UV-curable polyurethane acrylate (PUA) and modified graphene were demonstrated in this paper. Cetyl trimethyl ammonium bromide modified graphene (CTAB-G) was prepared via intercalation of cationic surfactant and subsequently incorporated into PUA by UV curing technology. Fourier transform infrared spectra, wide-angle X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the structure and morphology of CTAB-G, as well as CTAB-G/PUA nanocomposite films. The results revealed that the CTAB-G sheets were layer-by-layer structure and dispersed uniformly in PUA matrix. Thermal gravimetric analysis showed that the thermal stabilities of UV-curable PUA nanocomposite films in this work were much higher than that of PUA nanocomposites previously reported. Dynamic mechanical analysis indicated that the dynamic mechanical properties of nanocomposite films were greatly enhanced in the presence of modified graphene sheets. In addition, the CTAB-G/PUA nanocomposite films exhibited improved dielectric properties and electrical conductivities compared with the pure PUA.

  18. Preservation of the Pt(100) surface reconstruction after growth of a continuous layer of graphene

    Nilsson, Louis; Andersen, Mie; Bjerre, Jacob

    2012-01-01

    Scanning tunneling microscopy shows that a layer of graphene can be grown on the hex-reconstructed Pt(100) surface and that the reconstruction is preserved after growth. A continuous sheet of graphene can be grown across domain boundaries and step edges without loss of periodicity or change in di...

  19. Preparation of BiVO4-Graphene Nanocomposites and Their Photocatalytic Activity

    Xuan Xu

    2014-01-01

    Full Text Available We prepared BiVO4-graphene nanocomposites by using a facile single-step method and characterized the material by x-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse-reflection spectroscopy, and three-dimensional fluorescence spectroscopy. The results show that graphene oxide in the catalyst was thoroughly reduced. The BiVO4 is densely dispersed on the graphene sheets, which facilitates the transport of electrons photogenerated in BiVO4, thereby leading to an efficient separation of photogenerated carriers in the coupled graphene-nanocomposite system. For degradation of rhodamine B dye under visible-light irradiation, the photocatalytic activity of the synthesized nanocomposites was over ∼20% faster than for pure BiVO4 catalyst. To study the contribution of electrons and holes in the degradation reaction, silver nitrate and potassium sodium tartrate were added to the BiVO4-graphene photocatalytic reaction system as electron-trapping agent and hole-trapping agent, respectively. The results show that holes play the main role in the degradation of rhodamine B.

  20. High surface area graphene-supported metal chalcogenide assembly

    Worsley, Marcus A.; Kuntz, Joshua D.; Orme, Christine A.

    2017-04-25

    Disclosed here is a method for hydrocarbon conversion, comprising contacting at least one graphene-supported assembly with at least one hydrocarbon feedstock, wherein the graphene-supported assembly comprises (i) a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds and (ii) at least one metal chalcogenide compound disposed on the graphene sheets, wherein the chalcogen of the metal chalcogenide compound is selected from S, Se and Te, and wherein the metal chalcogenide compound accounts for at least 20 wt. % of the graphene-supported assembly.

  1. Preparation of hyperbranched poly (amidoamine)-grafted graphene nanolayers as a composite and curing agent for epoxy resin

    Gholipour-Mahmoudalilou, Meysam; Roghani-Mamaqani, Hossein; Azimi, Reza; Abdollahi, Amin

    2018-01-01

    Thermal properties of epoxy resin were improved by preparation of a curing agent of poly (amidoamine) (PAMAM) dendrimer-grafted graphene oxide (GO). Hyperbranched PAMAM-modified GO (GD) was prepared by a divergent dendrimer synthesis methodology. Modification of GO with (3-Aminopropyl)triethoxysilane (APTES), Michael addition of methacrylic acid, and amidation reaction with ethylenediamine results in the curing agent of GD. Then, epoxy resin was cured in the presence of different amounts of GD and the final products were compared with ethylenediamine-cured epoxy resin (E) in their thermal degradation temperature and char contents. Functionalization of GO with APTES and hyperbranched dendrimer formation at the surface of GO were evaluated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and thermogravimetric analysis (TGA) results. TGA results showed that the weight loss associated with chemical moieties in GONH2, GOMA, and GD is estimated to be 10.1, 12.2, and 14.1%, respectively. Covalent attachment of dendrimer at the surface of GO increases its thermal stability. TGA also showed that decomposition temperature and char content are higher for composites compared with E. Scanning and transmission electron microscopies show that flat and smooth graphene nanolayers are wrinkled in GO and re-stacking and flattening of nanolayers is observed in GD.

  2. Metals on graphene and carbon nanotube surfaces: From mobile atoms to atomtronics to bulk metals to clusters and catalysts

    Sarkar, Santanu C.; Moser, Matthew L.; Tian, Xiaojuan; Zhang, Xixiang; Al-Hadeethi, Yas Fadel; Haddon, Robert C.

    2014-01-01

    , and the next generation energy devices. We touch on chemical vapor deposition (CVD) graphene grown on metals, the reactivity of its surface, and its use as a template for asymmetric graphene functionalization chemistry (ultrathin Janus discs). We highlight some

  3. Ab initio study of friction of graphene flake on graphene/graphite or SiC surface

    Gulseren, Oguz; Tayran, Ceren; Sayin, Ceren Sibel

    Recently, the rich dynamics of graphene flake on graphite or SiC surfaces are revealed from atomic force microcopy experiments. The studies toward to the understanding of microscopic origin of friction are getting a lot of attention. Despite the several studies of these systems using molecular dynamics methods, density functional theory based investigations are limited because of the huge system sizes. In this study, we investigated the frictional force on graphene flake on graphite or SiC surfaces from pseudopotential planewave calculations based on density functional theory. In both cases, graphene flake (24 C) on graphite or SiC surface, bilayer flake is introduced by freezing the top layer as well as the bottom layer of the surface slab. After fixing the load with these frozen layers, we checked the relative motion of the flake over the surface. A minimum energy is reached when the flake is moved on graphene to attain AB stacking. We also conclude that edge reconstruction because of the finite size of the flake is very critical for frictional properties of the flake; therefore the saturation of dangling bonds with hydrogen is also addressed. Not only the symmetric configurations remaining parameter space is extensively studied. Supported by TUBITAK Project No: 114F162. This work is supported by TUBITAK Project No: 114F162.

  4. Three-dimensional assemblies of graphene prepared by a novel chemical reduction-induced self-assembly method

    Zhang, Lianbin

    2012-01-01

    In this study, three-dimensional (3D) graphene assemblies are prepared from graphene oxide (GO) by a facile in situ reduction-assembly method, using a novel, low-cost, and environment-friendly reducing medium which is a combination of oxalic acid (OA) and sodium iodide (NaI). It is demonstrated that the combination of a reducing acid, OA, and NaI is indispensable for effective reduction of GO in the current study and this unique combination (1) allows for tunable control over the volume of the thus-prepared graphene assemblies and (2) enables 3D graphene assemblies to be prepared from the GO suspension with a wide range of concentrations (0.1 to 4.5 mg mL-1). To the best of our knowledge, the GO concentration of 0.1 mg mL-1 is the lowest GO concentration ever reported for preparation of 3D graphene assemblies. The thus-prepared 3D graphene assemblies exhibit low density, highly porous structures, and electrically conducting properties. As a proof of concept, we show that by infiltrating a responsive polymer of polydimethylsiloxane (PDMS) into the as-resulted 3D conducting network of graphene, a conducting composite is obtained, which can be used as a sensing device for differentiating organic solvents with different polarity. © 2012 The Royal Society of Chemistry.

  5. Preparation of graphene oxide/polypyrrole/multi-walled carbon nanotube composite and its application in supercapacitors

    Wang, Bin; Qiu, Jianhui; Feng, Huixia; Sakai, Eiichi

    2015-01-01

    Highlights: • A novel method for synthesizing graphene oxide/polypyrrole/multi-walled nanotube composites. • Investigation of the effects of the mass ratio of GO, CM and Py on the capacitance of prepared composites. • Excellent electrochemical performance of PCMG composites. - Abstract: We report a novel method for preparing graphene oxide/polypyrrole/multi-walled carbon nanotubes (MWCNTs) composites (PCMG). The MWCNTs are treated by sulfuric acid, nitric acid and thionyl chloride, and then composite with graphene oxide and PPy by in suit polymerization. Transition electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results show that in 3-D structure of PCMG composites, PPy chains act as the “bridge” between graphene oxide and chlorinated-MWCNTs. Electrochemical tests reveal that the PCMG1-1 composite has high capacitance of 406.7 F g −1 at current density of 0.5 A g −1 , and the capacitance retention of PCMG1-1 composite is 92% after 1000 cycles

  6. Preparation and Application of Water-in-Oil Emulsions Stabilized by Modified Graphene Oxide

    Xiaoma Fei

    2016-08-01

    Full Text Available A series of alkyl chain modified graphene oxides (AmGO with different alkyl chain length and content was fabricated using a reducing reaction between graphene oxide (GO and alkyl amine. Then AmGO was used as a graphene-based particle emulsifier to stabilize Pickering emulsion. Compared with the emulsion stabilized by GO, which was oil-in-water type, all the emulsions stabilized by AmGO were water-in-oil type. The effects of alkyl chain length and alkyl chain content on the emulsion properties of AmGO were investigated. The emulsions stabilized by AmGO showed good stability within a wide range of pH (from pH = 1 to pH = 13 and salt concentrations (from 0.1 to 1000 mM. In addition, the application of water-in-oil emulsions stabilized by AmGO was investigated. AmGO/polyaniline nanocomposite (AmGO/PANi was prepared through an emulsion approach, and its supercapacitor performance was investigated. This research broadens the application of AmGO as a water-in-oil type emulsion stabilizer and in preparing graphene-based functional materials.

  7. Excitation of surface electromagnetic waves in a graphene-based Bragg grating.

    Sreekanth, Kandammathe Valiyaveedu; Zeng, Shuwen; Shang, Jingzhi; Yong, Ken-Tye; Yu, Ting

    2012-01-01

    Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc.

  8. Preparation of RHA-silica/graphene oxide nanocomposite for removal of nickel ions from water

    Tien, Tran Thi Thuy; Tu, Tran Hoang; Thao, Huynh Nguyen Phuong; Hieu, Nguyen Huu

    2017-09-01

    In this study, silica was synthesized from rice husk ash (RHA-SiO2) by precipitation method. Graphene oxide (GO) was prepared by modified Hummers method. RHA-SiO2/GO nanocomposite was fabricated by in-situ one-step method using 3-Aminopropyltriethoxysilane (APS) as a coupling agent. The nanocomposite was characterized by using X-ray Fluorescence, X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and Brunauer-Emmett-Teller (BET) specific surface area. The adsorption of RHA-SiO2/GO for Ni2+ ions from water was investigated and compared with the precursors. Ultraviolet-visible (UV-Vis) spectroscopy was used to quantify the amount of the initial and the residual Ni2+ concentration. The maximum adsorption capacity of the nanocomposite for Ni2+ calculated from Langmuir isotherm model, which was 256.4 mg/g. In addition, the adsorption data were well-fitted to the pseudo-second-order kinetic equation. Accordingly, this study demonstrated that RHA-SiO2/GO could be used as a highly efficient adsorbent for removal Ni2+ ions from aqueous solution.

  9. Retraction: Graphene-SnO2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism.

    Simpson, Anna

    2017-09-20

    Retraction of 'Graphene-SnO 2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism' by Qingxiu Wang et al., Phys. Chem. Chem. Phys., 2014, 16, 19351-19357.

  10. Carbon out-diffusion mechanism for direct graphene growth on a silicon surface

    Kim, Byung-Sung; Lee, Jong Woon; Jang, Yamujin; Choi, Soon Hyung; Cha, Seung Nam; Sohn, Jung Inn; Kim, Jong Min; Joo, Won-Jae; Hwang, Sungwoo; Whang, Dongmok

    2015-01-01

    Direct growth of graphene on silicon (Si) through chemical vapor deposition has predominantly focused on surface-mediated processes due to the low carbon (C) solubility in Si. However, a considerable quantity of C atoms was incorporated in Si and formed Si 1−x C x alloy with a reduced lattice dimension even in the initial stage of direct graphene growth. Subsequent high temperature annealing promoted active C out-diffusion, resulting in the formation of a graphitic layer on the Si surface. Furthermore, the significantly low thermal conductivity of the Si 1−x C x alloy shows that the incorporated C atoms affect the properties of a semiconductor adjacent to the graphene. These findings provide a key guideline for controlling desirable properties of graphene and designing hybrid semiconductor/graphene architectures for various applications

  11. Bloch Surface Waves Using Graphene Layers: An Approach toward In-Plane Photodetectors

    Richa Dubey

    2018-03-01

    Full Text Available A dielectric multilayer platform was investigated as a foundation for two-dimensional optics. In this paper, we present, to the best of our knowledge, the first experimental demonstration of absorption of Bloch surface waves in the presence of graphene layers. Graphene is initially grown on a Cu foil via Chemical Vapor Deposition and transferred layer by layer by a wet-transfer method using poly(methyl methacrylate, (PMMA. We exploit total internal reflection configuration and multi-heterodyne scanning near-field optical microscopy as a far-field coupling method and near-field characterization tool, respectively. The absorption is quantified in terms of propagation lengths of Bloch surface waves. A significant drop in the propagation length of the BSWs is observed in the presence of graphene layers. The propagation length of BSWs in bare multilayer is reduced to 17 times shorter in presence of graphene monolayer, and 23 times shorter for graphene bilayer.

  12. Preparation and characterization of antibacterial electrospun chitosan/poly (vinyl alcohol)/graphene oxide composite nanofibrous membrane

    Yang, Shuai; Lei, Peng; Shan, Yujuan; Zhang, Dawei

    2018-03-01

    In this paper, chitosan (CS)/poly (vinyl alcohol) (PVA)/graphene oxide (GO) composite nanofibrous membranes were prepared via electrospinning. Such nanofibrous membranes have been characterized and investigated for their morphological, structural, thermal stability, hydrophilic and antibacterial properties. SEM images showed that the uniform and defect-free nanofibers were obtained and GO sheets, shaping spindle and spherical, were partially embedded into nanofibers. FTIR, XRD, DSC and TGA indicated the good compatibility between CS and PVA. There were strong intermolecular hydrogen bonds between the chitosan and PVA molecules. Contact angle measurement indicated that while increasing the content of GO, the distance between fibers increased and water drop showed wetting state on the surface of nanofibrous membranes. As a result, the contact angle decreased significantly. Meanwhile, good antibacterial activity of the prepared nanofibrous membranes were exhibited against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.

  13. Preparation of Three-Dimensional Graphene Foams Using Powder Metallurgy Templates.

    Sha, Junwei; Gao, Caitian; Lee, Seoung-Ki; Li, Yilun; Zhao, Naiqin; Tour, James M

    2016-01-26

    A simple and scalable method which combines traditional powder metallurgy and chemical vapor deposition is developed for the synthesis of mesoporous free-standing 3D graphene foams. The powder metallurgy templates for 3D graphene foams (PMT-GFs) consist of particle-like carbon shells which are connected by multilayered graphene that shows high specific surface area (1080 m(2) g(-1)), good crystallization, good electrical conductivity (13.8 S cm(-1)), and a mechanically robust structure. The PMT-GFs did not break under direct flushing with DI water, and they were able to recover after being compressed. These properties indicate promising applications of PMT-GFs for fields requiring 3D carbon frameworks such as in energy-based electrodes and mechanical dampening.

  14. Preparation of ceramic materials for surface characterization

    Zipperian, D.C.

    1989-01-01

    This paper discusses how microstructural preparation permits a microscopic analysis of a material's internal structure, which is related to the physical properties of the material. Today, numerous microstructural quantitative and qualitative measurements are commonly utilized. Several of these include phase determination, phase hardness, phase distribution, grain size and shape, and porosity and size distribution. The most widely used surface characterization techniques are optical microscopy, electron microscopy, and x-ray microscopy. Optical microscopy includes both transmitted-and reflected-light techniques and requires a surface preparation prior to analysis. Transmitted-light microscopy samples require thinning and polishing of both sides of the sample, whereas reflected light techniques require polishing of only one side of the sample

  15. Structure and Properties of Nanocomposites based on PTT-block-PTMO Copolymer and Graphene Oxide prepared by in Situ Polymerization

    Paszkiewicz, Sandra; Szymczyk, Anna; Špitalský, Zdenko; Mosnáček, Jaroslav; Kwiatkowski, Konrad; Rosłaniec, Zbigniew

    2014-01-01

    Poly(trimethylene terephthalate-block-tetramethylene oxide) (PTT-PTMO) copolymer/graphene oxide nanocomposites were prepared by in situ polymerization. From the SEM and TEM images of PTT-PTMO/GO nanocomposite, it can be seen that GO sheets are clearly well-dispersed in the PTT-PTMO matrix. TEM images also showed that graphene was well exfoliated into individual sheets, suggesting that in situ polymerization is a highly efficient method for preparing nanocomposites. The influence of GO on the ...

  16. Preparation and properties of in situ amino-functionalized graphene oxide/polyimide composite films

    Lu, Yunhua; Hao, Jican; Xiao, Guoyong; Chen, Lin; Wang, Tonghua; Hu, Zhizhi

    2017-11-01

    The pure light-colored and transparent polyimide (PI) film was prepared from aromatic dianhydride 4,4‧-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and diamine 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) in the solvent of DMAc via two-step method. Graphene oxide (GO) was in situ grafted with 6FAPB and directly used as a functional inorganic nanofiller to further synthesize poly(amic acid) (PAA)/GO solution. Then, PI/GO composite films with different loadings of GO were prepared by the thermal imidization. The mechanical, thermal, optical, electrical, surface properties, and electrochemical behavior were characterized. The FTIR and XPS results indicate that amino groups can be successfully grafted on the surface of GO. The tensile strength and Young's modulus of the PI-1.0%GO composite film were increased to 118.4 MPa and 2.91 GPa, respectively, which was an approximate improvement of 30.8% and 39.9% compared with pure PI film. These PI/GO composites showed around 256 °C for the glass transition temperature, and around 535 °C for the 5% thermal decomposition temperature, respectively. However, the optical transmittance was significantly decreased from 81.5% (pure PI) to 0.8% (PI-1.0%GO). Besides, the electrical conductivity increased from 1.6 × 10-13 S/m (pure PI) to 2.5 × 10-9 S/m (PI-1.0%GO). Furthermore, when the incorporation of GO was 1.0 wt%, an obvious reduction from 1.08% (pure PI) to 0.65% in the water uptake was observed for the PI/GO composite films, and the water surface contact angle raised from 72.5° (pure PI) to 83.5°. The electrochemical behavior showed that the ability of oxygen atom on the imide ring to gain and loss electron was increased due to incorporation of GO. These results indicated that the strong interfacial interaction between GO and PAA as well as uniform dispersion of GO in PI matrix were benefit to improve the mechanical, thermal, electrical properties and so on. The in situ amino-functionalized approach

  17. Preparation and characterization of porous reduced graphene oxide based inverse spinel nickel ferrite nanocomposite for adsorption removal of radionuclides

    Lingamdinne, Lakshmi Prasanna; Choi, Yu-Lim [Department of Environmental Engineering, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Kim, Im-Soon [Graduate School of Environmental Studies, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Yang, Jae-Kyu [Ingenium College of Liberal Arts, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Koduru, Janardhan Reddy, E-mail: reddyjchem@gmail.com [Graduate School of Environmental Studies, Kwangwoon University, Seoul, 139-701 (Korea, Republic of); Chang, Yoon-Young, E-mail: yychang@kw.ac.kr [Department of Environmental Engineering, Kwangwoon University, Seoul, 139-701 (Korea, Republic of)

    2017-03-15

    Highlights: • Novel porous Ferromagnetic, GONF and Superparamagnetic, rGONF preparation. • The nanosize particles GONF (41.14 nm) and rGONF (32.16 nm) preparation. • Adsorption mechanism and modeling developments for radionuclides. • Zeta potential and surface site density of nanocomposites for comparison. - Abstract: For the removal of uranium(VI) (U(VI)) and thorium(IV) (Th(IV)), graphene oxide based inverse spinel nickel ferrite (GONF) nanocomposite and reduced graphene oxide based inverse spinel nickel ferrite (rGONF) nanocomposite were prepared by co-precipitation of GO with nickel and iron salts in one pot. The spectral characterization analyses revealed that GONF and rGONF have a porous surface morphology with an average particle size of 41.41 nm and 32.16 nm, respectively. The magnetic property measurement system (MPMS) studies confirmed the formation of ferromagnetic GONF and superparamagnetic rGONF. The adsorption kinetics studies found that the pseudo-second-order kinetics was well tune to the U(VI) and Th(IV) adsorption. The results of adsorption isotherms showed that the adsorption of U(VI) and Th(IV) were due to the monolayer on homogeneous surface of the GONF and rGONF. The adsorptions of both U(VI) and Th(IV) were increased with increasing system temperature from 293 to 333 ± 2 K. The thermodynamic studies reveal that the U(VI) and Th(IV) adsorption onto GONF and rGONF was endothermic. GONF and rGONF, which could be separated by external magnetic field, were recycled and re-used for up to five cycles without any significant loss of adsorption capacity.

  18. Increasing the doping efficiency by surface energy control for ultra-transparent graphene conductors.

    Chang, Kai-Wen; Hsieh, Ya-Ping; Ting, Chu-Chi; Su, Yen-Hsun; Hofmann, Mario

    2017-08-22

    Graphene's attractiveness in many applications is limited by its high resistance. Extrinsic doping has shown promise to overcome this challenge but graphene's performance remains below industry requirements. This issue is caused by a limited charge transfer efficiency (CTE) between dopant and graphene. Using AuCl 3 as a model system, we measure CTE as low as 5% of the expected values due to the geometrical capacitance of small adsorbate clusters. We here demonstrate a strategy for enhancing the CTE by a two-step optimization of graphene's surface energy prior to AuCl 3 doping. First, exposure to UV ozone modified the hydrophilicity of graphene and was found to decrease the cluster's geometric capacitance, which had a direct effect on the CTE. Occurrence of lattice defects at high UV exposure, however, deteriorated graphene's transport characteristics and limited the effectiveness of this pretreatment step. Thus, prior to UV exposure, a functionalized polymer layer was introduced that could further enhance graphene's surface energy while protecting it from damage. Combination of these treatment steps were found to increase the AuCl 3 charge transfer efficiency to 70% and lower the sheet resistance to 106 Ω/γ at 97% transmittance which represents the highest reported performance for doped single layer graphene and is on par with commercially available transparent conductors.

  19. Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

    Mansour, Ahmed

    2017-05-23

    Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

  20. Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu

    Ruffino, F., E-mail: francesco.ruffino@ct.infn.it; Cacciato, G.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Universitá di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2014-02-28

    A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.

  1. Hybrid Doping of Few-Layer Graphene via a Combination of Intercalation and Surface Doping

    Mansour, Ahmed; Kirmani, Ahmad R.; Barlow, Stephen; Marder, Seth R.; Amassian, Aram

    2017-01-01

    Surface molecular doping of graphene has been shown to modify its work function and increase its conductivity. However, the associated shifts in work function and increases in carrier concentration are highly coupled and limited by the surface coverage of dopant molecules on graphene. Here we show that few-layer graphene (FLG) can be doped using a hybrid approach, effectively combining surface doping by larger (metal-)organic molecules, while smaller molecules, such as Br2 and FeCl3, intercalate into the bulk. Intercalation tunes the carrier concentration more effectively, whereas surface doping of intercalated FLG can be used to tune its work function without reducing the carrier mobility. This multi-modal doping approach yields a very high carrier density and tunable work function for FLG, demonstrating a new versatile platform for fabricating graphene-based contacts for electronic, optoelectronic and photovoltaic applications.

  2. Graphene Based Terahertz Absorber Designed With Effective Surface Conductivity Approach

    Andryieuski, Andrei; Pizzocchero, Filippo; Booth, Tim

    Young field of terahertz (THz) science and technology demands new materials and devices, such as filters, modulators, polarization converters and absorbers. Graphene, a recently discovered single-atom-thick material, provides exciting properties for functional terahertz applications. Graphene...... conductivity and how to use it in optical design. We demonstrate a tunable THz perfect absorber, which consists of continuous graphene various structured graphene metamaterials above a metal mirror. Changing the Fermi level from 0 eV to 0.5 eV allows for drastic changes in absorbance from less than 0.1 to 1...

  3. Physical deoxygenation of graphene oxide paper surface and facile in situ synthesis of graphene based ZnO films

    Ding, Jijun; Wang, Minqiang; Zhang, Xiangyu; Ran, Chenxin; Shao, Jinyou; Ding, Yucheng

    2014-01-01

    In-situ sputtering ZnO films on graphene oxide (GO) paper are used to fabricate graphene based ZnO films. Crystal structure and surface chemical states are investigated. Results indicated that GO paper can be effectively deoxygenated by in-situ sputtering ZnO on them without adding any reducing agent. Based on the principle of radio frequency magnetron sputtering, we propose that during magnetron sputtering process, plasma streams contain large numbers of electrons. These electrons not only collide with argon atoms to produce secondary electrons but also they are accelerated to bombard the substrates (GO paper) resulting in effective deoxygenation of oxygen-containing functional groups. In-situ sputtering ZnO films on GO paper provide an approach to design graphene-semiconductor nanocomposites

  4. Preparation of Ag–AgBr/TiO2–graphene and its visible light photocatalytic activity enhancement for the degradation of polyacrylamide

    Rong, Xinshan; Qiu, Fengxian; Zhang, Chen; Fu, Liang; Wang, Yuanyuan; Yang, Dongya

    2015-01-01

    Highlights: • Ag–AgBr/TiO 2 –graphene (AATG) composite photocatalyst was prepared. • AATG was applied to photocatalytic degradation of polyacrylamide (PAM). • Degradation condition such as mass ratio of TiO 2 /graphene, dose, pH and time, was investigated. • The AATG composite photocatalyst can be separated from system effectively and easily. • The prepared AATG exhibits significant photocatalytic activity after five successive recycles. - Abstract: In current work, TiO 2 was modified by Ag/AgBr semiconductor and graphene to enhance its photocatalytic activity for the degradation of polyacrylamide (PAM). Ag–AgBr/TiO 2 –graphene (AATG) composite photocatalysts were prepared by the deposition–precipitation method combining a subsequent calcination process. The structure, surface morphology and chemical composition of AATG composite photocatalysts were investigated by XRD, XPS, DRS, PL, SEM, EDS, TEM, and HRTEM methods. XRD and XPS results show that Ag 0 is generated from Ag + under visible light irradiation. Degradation of PAM was chosen to evaluate photocatalytic activity using AATG composite as photocatalysts. The conditions such as mass ratio of TiO 2 /graphene, catalyst dose, pH and contact time, were investigated for the degradation of PAM. Possible pathway and mechanism were proposed for photocatalytic degradation of PAM over AATG composite photocatalyst under visible light irradiation. The prepared AATG composite photocatalyst can be separated from system effectively and easily; and exhibits significant photocatalytic activity after five successive recycles, which confirmed that the components of the AATG are not photo decomposed and the structure is stable during the photocatalytic process

  5. Comparative facile methods for preparing graphene oxide-hydroxyapatite for bone tissue engineering.

    Raucci, M G; Giugliano, D; Longo, A; Zeppetelli, S; Carotenuto, G; Ambrosio, L

    2017-08-01

    Motivated by the success of using graphene oxide (GO) as a nanofiller of composites, there is a drive to search for this new kind of carbon material as a bioactive component in ceramic materials. In the present study, biomineralized GO was prepared by two different approaches, represented by in situ sol-gel synthesis and biomimetic treatment. It was found that in the biocomposites obtained by the sol-gel approach, the spindle-like hydroxyapatite nanoparticles, with a diameter of ca. 5 ± 0.37 nm and a length of ca. 70 ± 2.5 nm, were presented randomly and strongly on the surface. The oxygen-containing functional groups, such as hydroxyl and carbonyl, present on the basal plane and edges of the GO sheets, play an important role in anchoring calcium ions, as demonstrated by FT-IR and TEM investigations. A different result was obtained for biocomposites after biomimetic treatment: an amorphous calcium phosphate on GO sheet was observed after 5 days of treatment. These different approaches resulted in a diverse effect on the proliferation and differentiation of osteogenic mesenchymal stem cells. In fact, in biocomposites prepared by the sol-gel approach the expression of an early marker of osteogenic differentiation, ALP, increases with the amount of GO in the first days of cell culture. Meanwhile, biomimetic materials sustain cell viability and proliferation, even if the expression of alkaline phosphatase activity in a basal medium is delayed. These findings may provide new prospects for utilizing GO-based hydroxyapatite biocomposites in bone repair, bone augmentation and coating of biomedical implants and broaden the application of GO sheets in biological areas. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  6. Absorption and reflectivity of the lithium niobate surface masked with a graphene layer

    O. Salas

    2017-01-01

    Full Text Available We performed simulations of the interaction of a graphene layer with the surface of lithium niobate utilizing density functional theory and molecular dynamics at 300K and atmospheric pressure. We found that the graphene layer is physisorbed on the lithium niobate surface with an adsorption energy of -0.8205 eV/(carbon-atom. Subsequently, the energy band structure, the optical absorption and reflectivity of the new system were calculated. We found important changes in these physical properties with respect to the corresponding ones of a graphene layer and of a lithium niobate crystal.

  7. Controlling Short-Range Interactions by Tuning Surface Chemistry in HDPE/Graphene Nanoribbon Nanocomposites.

    Sadeghi, Soheil; Zehtab Yazdi, Alireza; Sundararaj, Uttandaraman

    2015-09-03

    Unique dispersion states of nanoparticles in polymeric matrices have the potential to create composites with enhanced mechanical, thermal, and electrical properties. The present work aims to determine the state of dispersion from the melt-state rheological behavior of nanocomposites based on carbon nanotube and graphene nanoribbon (GNR) nanomaterials. GNRs were synthesized from nitrogen-doped carbon nanotubes via a chemical route using potassium permanganate and some second acids. High-density polyethylene (HDPE)/GNR nanocomposite samples were then prepared through a solution mixing procedure. Different nanocomposite dispersion states were achieved using different GNR synthesis methods providing different surface chemistry, interparticle interactions, and internal compartments. Prolonged relaxation of flow induced molecular orientation was observed due to the presence of both carbon nanotubes and GNRs. Based on the results of this work, due to relatively weak interactions between the polymer and the nanofillers, it is expected that short-range interactions between nanofillers play the key role in the final dispersion state.

  8. Novel MnOOH–graphene nanocomposites: Preparation, characterization and electrochemical properties for supercapacitors

    Mei, Jun; Zhang, Long, E-mail: zhanglongzhl@163.com

    2015-01-15

    In this paper, we report a simple and controlled synthesis of novel MnOOH–graphene nanocomposites with a one-step facile hydrothermal method. It is template-free and easy to reproduce. Electrochemical properties are investigated in different media. The values of specific capacitance achieved are 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. The assembly of multiple branched MnOOH and graphene flakes results in synergistic effects, forming new electron transfer channels to accelerate electron transfer and provide the pseudocapacitance to increase the overall capacitance. The novel composites have potential applications in the fields of supercapacitors, lithium battery and so on. - Graphical abstract: The MnOOH–graphene nanocomposites shows better specific capacitance with the values achieved 112 F g{sup −1} in 1 M Na{sub 2}SO{sub 4} and 165 F g{sup −1} in 6 M KOH electrolyte, respectively. - Highlights: • Novel MnOOH–graphene nanocomposites were prepared by a one-step hydrothermal method. • The assembly can form new electron transfer channels to accelerate electron transfer. • The capacitive and rate performances are enhanced in both neutral and alkaline medium.

  9. Novel MnOOH–graphene nanocomposites: Preparation, characterization and electrochemical properties for supercapacitors

    Mei, Jun; Zhang, Long

    2015-01-01

    In this paper, we report a simple and controlled synthesis of novel MnOOH–graphene nanocomposites with a one-step facile hydrothermal method. It is template-free and easy to reproduce. Electrochemical properties are investigated in different media. The values of specific capacitance achieved are 112 F g −1 in 1 M Na 2 SO 4 and 165 F g −1 in 6 M KOH electrolyte, respectively. The assembly of multiple branched MnOOH and graphene flakes results in synergistic effects, forming new electron transfer channels to accelerate electron transfer and provide the pseudocapacitance to increase the overall capacitance. The novel composites have potential applications in the fields of supercapacitors, lithium battery and so on. - Graphical abstract: The MnOOH–graphene nanocomposites shows better specific capacitance with the values achieved 112 F g −1 in 1 M Na 2 SO 4 and 165 F g −1 in 6 M KOH electrolyte, respectively. - Highlights: • Novel MnOOH–graphene nanocomposites were prepared by a one-step hydrothermal method. • The assembly can form new electron transfer channels to accelerate electron transfer. • The capacitive and rate performances are enhanced in both neutral and alkaline medium

  10. Growth of graphene from SiC{0001} surfaces and its mechanisms

    Norimatsu, Wataru; Kusunoki, Michiko

    2014-01-01

    Graphene, a one-atom-layer carbon material, can be grown by thermal decomposition of SiC. On Si-terminated SiC(0001), graphene nucleates at steps and grows layer-by-layer, and as a result a homogeneous monolayer or bilayer can be obtained. We demonstrate this mechanism both experimentally and theoretically. On the C-face (000 1-bar ), multilayer graphene nucleates not only at steps, but also on the terraces. These differences reflect the distinct differences in the reactivity of these faces. Due to its high quality and structural controllability, graphene on SiC{0001} surfaces will be a platform for high-speed graphene device applications. (paper)

  11. Facile synthesis of graphene on dielectric surfaces using a two-temperature reactor CVD system

    Zhang, C; Man, B Y; Yang, C; Jiang, S Z; Liu, M; Chen, C S; Xu, S C; Sun, Z C; Gao, X G; Chen, X J

    2013-01-01

    Direct deposition of graphene on a dielectric substrate is demonstrated using a chemical vapor deposition system with a two-temperature reactor. The two-temperature reactor is utilized to offer sufficient, well-proportioned floating Cu atoms and to provide a temperature gradient for facile synthesis of graphene on dielectric surfaces. The evaporated Cu atoms catalyze the reaction in the presented method. C atoms and Cu atoms respectively act as the nuclei for forming graphene film in the low-temperature zone and the zones close to the high-temperature zones. A uniform and high-quality graphene film is formed in an atmosphere of sufficient and well-proportioned floating Cu atoms. Raman spectroscopy, scanning electron microscopy and atomic force microscopy confirm the presence of uniform and high-quality graphene. (paper)

  12. Effect of strain on geometric and electronic structures of graphene on a Ru(0001) surface

    Sun Jia-Tao; Du Shi-Xuan; Xiao Wen-De; Hu Hao; Zhang Yu-Yang; Li Guo; Gao Hong-Jun

    2009-01-01

    The atomic and electronic structures of a graphene monolayer on a Ru(0001) surface under compressive strain are investigated by using first-principles calculations. Three models of graphene monolayers with different carbon periodicities due to the lattice mismatch are proposed in the presence and the. absence of the Ru(0001) substrate separately. Considering the strain induced by the lattice mismatch, we optimize the atomic structures and investigate the electronic properties of the graphene. Our calculation results show that the graphene layers turn into periodic corrugations and there exist strong chemical bonds in the interface between the graphene N x N superlattice and the substrate. The strain does not induce significant changes in electronic structure. Furthermore, the results calculated in the local density approximation (LDA) are compared with those obtained in the generalized gradient approximation (GGA), showing that the LDA results are more reasonable than the GGA results when only two substrate layers are used in calculation.

  13. Surface-modified reduced graphene oxide electrodes for capacitors by ionic liquids and their electrochemical properties

    Kim, Jieun; Kim, Seok

    2014-01-01

    Highlights: • Reduced graphene oxide surface was modified by introduction of ionic liquids. • Microstructure and capacitance of modified electrode were dependent on the ionic liquids contents. • Modification gives electrode better charge transport and higher specific capacitance. • Modified electrode showed the better capacitive performance such as rate capability and cycle stability. - Abstract: In this work, reduced graphene oxide (rGO)/ionic liquids (IL) composites with different weight ratios of IL to rGO were synthesized by a simple method. In these composites, IL contributed to the exfoliation of rGO sheets and to the improvement of the electrochemical properties of the resulting composites by enhancing the ion diffusion and charge transport. The structure of the composites was examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The TEM images showed that IL was coated on the surface of rGO in a translucent manner. The electrochemical analysis of the prepared composites was carried out by performing cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). Among the prepared composites, the one with a weight ratio of rGO to IL of 1:7 showed the highest specific capacitance of 147.5 F g −1 at a scan rate of 10 mV s −1 . In addition, the rate capability and cycle performance of the composites were enhanced compared to pristine rGO. These enhanced properties make the composites suitable as electrode materials for the better performance supercapacitors

  14. PEGylated graphene oxide elicits strong immunological responses despite surface passivation

    Luo, Nana; Weber, Jeffrey K.; Wang, Shuang; Luan, Binquan; Yue, Hua; Xi, Xiaobo; Du, Jing; Yang, Zaixing; Wei, Wei; Zhou, Ruhong; Ma, Guanghui

    2017-02-01

    Engineered nanomaterials promise to transform medicine at the bio-nano interface. However, it is important to elucidate how synthetic nanomaterials interact with critical biological systems before such products can be safely utilized in humans. Past evidence suggests that polyethylene glycol-functionalized (PEGylated) nanomaterials are largely biocompatible and elicit less dramatic immune responses than their pristine counterparts. We here report results that contradict these findings. We find that PEGylated graphene oxide nanosheets (nGO-PEGs) stimulate potent cytokine responses in peritoneal macrophages, despite not being internalized. Atomistic molecular dynamics simulations support a mechanism by which nGO-PEGs preferentially adsorb onto and/or partially insert into cell membranes, thereby amplifying interactions with stimulatory surface receptors. Further experiments demonstrate that nGO-PEG indeed provokes cytokine secretion by enhancing integrin β8-related signalling pathways. The present results inform that surface passivation does not always prevent immunological reactions to 2D nanomaterials but also suggest applications for PEGylated nanomaterials wherein immune stimulation is desired.

  15. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    Cuevas, Mauro, E-mail: cuevas@df.uba.ar [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Ingeniería y Tecnología Informática, Universidad de Belgrano, Villanueva 1324, C1426BMJ, Buenos Aires (Argentina); Grupo de Electromagnetismo Aplicado, Departamento de Física, FCEN, Universidad de Buenos Aires and IFIBA, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires (Argentina)

    2016-12-09

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  16. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    Cuevas, Mauro

    2016-01-01

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  17. Synthesis and electronic properties of chemically functionalized graphene on metal surfaces

    Grüneis, Alexander

    2013-01-01

    A review on the electronic properties, growth and functionalization of graphene on metals is presented. Starting from the derivation of the electronic properties of an isolated graphene layer using the nearest neighbor tight-binding (TB) approximation for π and σ electrons, the TB model is then extended to third-nearest neighbors and interlayer coupling. The latter is relevant to few-layer graphene and graphite. Next, the conditions under which epitaxial graphene can be obtained by chemical vapor deposition are reviewed with a particular emphasis on the Ni(111) surface. Regarding functionalization, I first discuss the intercalation of monolayer Au into the graphene/Ni(111) interface, which renders graphene quasi-free-standing. The Au intercalated quasi-free-standing graphene is then the basis for chemical functionalization. Functionalization of graphene is classified into covalent, ionic and substitutional functionalization. As archetypical examples for these three possibilities I discuss covalent functionalization by hydrogen, ionic functionalization by alkali metals and substitutional functionalization by nitrogen heteroatoms.

  18. Controlling the growth of epitaxial graphene on metalized diamond (111) surface

    Cooil, S. P.; Wells, J. W.; Hu, D.; Evans, D. A.; Niu, Y. R.; Zakharov, A. A.; Bianchi, M.

    2015-01-01

    The 2-dimensional transformation of the diamond (111) surface to graphene has been demonstrated using ultrathin Fe films that catalytically reduce the reaction temperature needed for the conversion of sp 3 to sp 2 carbon. An epitaxial system is formed, which involves the re-crystallization of carbon at the Fe/vacuum interface and that enables the controlled growth of monolayer and multilayer graphene films. In order to study the initial stages of single and multilayer graphene growth, real time monitoring of the system was preformed within a photoemission and low energy electron microscope. It was found that the initial graphene growth occurred at temperatures as low as 500 °C, whilst increasing the temperature to 560 °C was required to produce multi-layer graphene of high structural quality. Angle resolved photoelectron spectroscopy was used to study the electronic properties of the grown material, where a graphene-like energy momentum dispersion was observed. The Dirac point for the first layer is located at 2.5 eV below the Fermi level, indicating an n-type doping of the graphene due to substrate interactions, while that of the second graphene layer lies close to the Fermi level

  19. Creation of nanopores on graphene planes with MgO template for preparing high-performance supercapacitor electrodes

    Wang, Huanjing; Sun, Xiuxia; Liu, Zonghuai; Lei, Zhibin

    2014-05-01

    Creation of nanopores on graphene planar sheets is of great significance in promoting the kinetic diffusion of electrolyte and enhancing the utilization efficiency of graphene planar sheets. Herein, we developed a facile chemical vapor deposition strategy to prepare highly porous graphene with flake-like MgO as template and ferrocene as the carbon precursor. The graphene layers show a highly porous structure with small mesopores of 4-8 nm, large mesopores of 10-20 nm and additional macropores of 100-200 nm. These nanopores on graphene sheets provide numerous channels for fast ion transport perpendicular to the 2D basal plane, while the good powder conductivity ensures an effective electron propagation within the 2D graphene plane. As a result, a specific capacitance of 303 F g-1, an areal capacitance up to 17.3 μF cm-2 and a nearly tenfold shorter time constant were achieved when compared with those of nonporous and stacked graphene electrodes. The method demonstrated herein would open up an opportunity to prepare porous graphene for a wide applications in energy storage, biosensors, nanoelectronics and catalysis.Creation of nanopores on graphene planar sheets is of great significance in promoting the kinetic diffusion of electrolyte and enhancing the utilization efficiency of graphene planar sheets. Herein, we developed a facile chemical vapor deposition strategy to prepare highly porous graphene with flake-like MgO as template and ferrocene as the carbon precursor. The graphene layers show a highly porous structure with small mesopores of 4-8 nm, large mesopores of 10-20 nm and additional macropores of 100-200 nm. These nanopores on graphene sheets provide numerous channels for fast ion transport perpendicular to the 2D basal plane, while the good powder conductivity ensures an effective electron propagation within the 2D graphene plane. As a result, a specific capacitance of 303 F g-1, an areal capacitance up to 17.3 μF cm-2 and a nearly tenfold shorter time

  20. One-step electrochemical approach for the preparation of graphene wrapped-phosphotungstic acid hybrid and its application for simultaneous determination of sunset yellow and tartrazine

    Gan Tian; Sun Junyong; Cao Shuqin; Gao Fuxing; Zhang Yuxia; Yang Yingqin

    2012-01-01

    Highlights: ► Graphene layer–wrapped PTA hybrid is one–step electropolymerized onto GCE surface. ► Graphene–PTA/GCE is used for simultaneous detection of sunset yellow and tartrazine. ► The oxidation mechanisms of sunset yellow and tartrazine were studied. ► Sunset yellow and tartrazine contents in soft drink samples are successfully determined. - Abstract: We have demonstrated a one-step and effective electrochemical method to prepare graphene (GN) layer-wrapped phosphotungstic acid (PTA) hybrid on the surface of glassy carbon electrode (GCE) using graphene as an electron transfer mediator. The PTA coupled with graphene provides good selectivity and high sensitivity for the simultaneous determination of two synthetic food colorants, sunset yellow and tartrazine, exhibiting as well-defined oxidation peaks in differential pulse voltammetry with a peak potential separation of ca. 260 mV. The detection limit was found to be 0.5 μg L −1 for sunset yellow and 30.0 μg L −1 for tartrazine. The interference of some common food additives was studied and it was concluded that application of this method for the determination of sunset yellow and tartrazine in several commercial soft drink samples led to satisfactory results. This study provides useful further evidences for the development of portable sensors for food additives.

  1. Preparation of Graphene Sheets by Electrochemical Exfoliation of Graphite in Confined Space and Their Application in Transparent Conductive Films.

    Wang, Hui; Wei, Can; Zhu, Kaiyi; Zhang, Yu; Gong, Chunhong; Guo, Jianhui; Zhang, Jiwei; Yu, Laigui; Zhang, Jingwei

    2017-10-04

    A novel electrochemical exfoliation mode was established to prepare graphene sheets efficiently with potential applications in transparent conductive films. The graphite electrode was coated with paraffin to keep the electrochemical exfoliation in confined space in the presence of concentrated sodium hydroxide as the electrolyte, yielding ∼100% low-defect (the D band to G band intensity ratio, I D /I G = 0.26) graphene sheets. Furthermore, ozone was first detected with ozone test strips, and the effect of ozone on the exfoliation of graphite foil and the microstructure of the as-prepared graphene sheets was investigated. Findings indicate that upon applying a low voltage (3 V) on the graphite foil partially coated with paraffin wax that the coating can prevent the insufficiently intercalated graphite sheets from prematurely peeling off from the graphite electrode thereby affording few-layer (graphene sheets in a yield of as much as 60%. Besides, the ozone generated during the electrochemical exfoliation process plays a crucial role in the exfoliation of graphite, and the amount of defect in the as-prepared graphene sheets is dependent on electrolytic potential and electrode distance. Moreover, the graphene-based transparent conductive films prepared by simple modified vacuum filtration exhibit an excellent transparency and a low sheet resistance after being treated with NH 4 NO 3 and annealing (∼1.21 kΩ/□ at ∼72.4% transmittance).

  2. Understanding the growth mechanism of graphene on Ge/Si(001) surfaces.

    Dabrowski, J; Lippert, G; Avila, J; Baringhaus, J; Colambo, I; Dedkov, Yu S; Herziger, F; Lupina, G; Maultzsch, J; Schaffus, T; Schroeder, T; Kot, M; Tegenkamp, C; Vignaud, D; Asensio, M-C

    2016-08-17

    The practical difficulties to use graphene in microelectronics and optoelectronics is that the available methods to grow graphene are not easily integrated in the mainstream technologies. A growth method that could overcome at least some of these problems is chemical vapour deposition (CVD) of graphene directly on semiconducting (Si or Ge) substrates. Here we report on the comparison of the CVD and molecular beam epitaxy (MBE) growth of graphene on the technologically relevant Ge(001)/Si(001) substrate from ethene (C2H4) precursor and describe the physical properties of the films as well as we discuss the surface reaction and diffusion processes that may be responsible for the observed behavior. Using nano angle resolved photoemission (nanoARPES) complemented by transport studies and Raman spectroscopy as well as density functional theory (DFT) calculations, we report the direct observation of massless Dirac particles in monolayer graphene, providing a comprehensive mapping of their low-hole doped Dirac electron bands. The micrometric graphene flakes are oriented along two predominant directions rotated by 30° with respect to each other. The growth mode is attributed to the mechanism when small graphene "molecules" nucleate on the Ge(001) surface and it is found that hydrogen plays a significant role in this process.

  3. In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

    Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

    2015-09-15

    Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Reduction Expansion Synthesis as Strategy to Control Nitrogen Doping Level and Surface Area in Graphene

    Russell Canty

    2015-10-01

    Full Text Available Graphene sheets doped with nitrogen were produced by the reduction-expansion (RES method utilizing graphite oxide (GO and urea as precursor materials. The simultaneous graphene generation and nitrogen insertion reactions are based on the fact that urea decomposes upon heating to release reducing gases. The volatile byproducts perform two primary functions: (i promoting the reduction of the GO and (ii providing the nitrogen to be inserted in situ as the graphene structure is created. Samples with diverse urea/GO mass ratios were treated at 800 °C in inert atmosphere to generate graphene with diverse microstructural characteristics and levels of nitrogen doping. Scanning electron microscopy (SEM and transmission electron microscopy (TEM were used to study the microstructural features of the products. The effects of doping on the samples structure and surface area were studied by X-ray diffraction (XRD, Raman Spectroscopy, and Brunauer Emmet Teller (BET. The GO and urea decomposition-reduction process as well as nitrogen-doped graphene stability were studied by thermogravimetric analysis (TGA coupled with mass spectroscopy (MS analysis of the evolved gases. Results show that the proposed method offers a high level of control over the amount of nitrogen inserted in the graphene and may be used alternatively to control its surface area. To demonstrate the practical relevance of these findings, as-produced samples were used as electrodes in supercapacitor and battery devices and compared with conventional, thermally exfoliated graphene.

  5. Synthesis and characterization of electrochemically-reduced graphene

    Graphene has superior electrical conductivity than graphite and other allotropes of carbon because of its high surface area and chemical tolerance. Electrochemically processed graphene sheets were obtained through the reduction of graphene oxide from hydrazine hydrate. The prepared samples were heated to different ...

  6. In vitro assessment of activity of graphene silver composite sheets ...

    Purpose: To synthesize graphene-based silver nanocomposites and evaluate their antimicrobial and anti-Tomato Bushy Stunt Virus (TBSV) activities. Methods: A graphene-based silver composite was prepared by adsorbing silver nanoparticles AgNPs to the surfaces of graphene oxide (GO) sheets. Scanning electron ...

  7. Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

    Sun, Jie; Lindvall, Niclas; Yurgens, August; Nam, Youngwoo; Cole, Matthew T.; Teo, Kenneth B. K.; Woo Park, Yung

    2014-01-01

    A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000 °C growth temperature

  8. Control of the graphene growth rate on capped SiC surface under strong Si confinement

    Çelebi, C.; Yanık, C.; Demirkol, A.G.; Kaya, İsmet İ.

    2013-01-01

    Highlights: ► Graphene is grown on capped SiC surface with well defined cavity size. ► Graphene growth rate linearly increases with the cavity height. ► Graphene uniformity is reduced with thickness. - Abstract: The effect of the degree of Si confinement on the thickness and morphology of UHV grown epitaxial graphene on (0 0 0 −1) SiC is investigated by using atomic force microscopy and Raman spectroscopy measurements. Prior to the graphene growth process, the C-face surface of a SiC substrate is capped by another SiC comprising three cavities on its Si-rich surface with depths varying from 0.5 to 2 microns. The Si atoms, thermally decomposed from the sample surface during high temperature annealing of the SiC cap /SiC sample stack, are separately trapped inside these individual cavities at the sample/cap interface. Our analyses show that the growth rate linearly increases with the cavity height. It was also found that stronger Si confinement yields more uniform graphene layers.

  9. Surface-enhanced Raman scattering of dipolar molecules by the graphene Fermi surface modulation with different dipole moments

    Zhang, Mingjia; Leng, Yandan; Huang, Jing; Yu, JiaoJiao; Lan, Zhenggang; Huang, Changshui

    2017-12-01

    We report the modulation of Raman scattering spectrum of chromophore/graphene hybrids by tunning the molecular polarization with different terminal groups (methyl, methoxy, nitrile, and two nitros). Based on the density functional theory, the specific dipole moment values of the chromophore molecules are calculated. An obvious surface-enhanced Raman scattering (SERS) was observed and the scattering intensity of molecule increases with enlarged dipole moment. According to the analysis of G band Raman shifts of graphene, the enhancement of the Raman signal can be attributed to strong electronic coupling between graphene and chromophore, which is closely related with the modulation of graphene Fermi surface by changing the dipole moment of the molecule. Besides, the optimization of the ground state geometry and the binding energy of the hybrids were also calculated with the Density Functional Based Tight Bonding (DFTB) method, which confirms that the enhanced Raman scattering of molecules on graphene arises from the improved energy level matching between graphene Fermi surface and molecular band, further providing a new way to design novel SERS devices.

  10. The crystal orientation relation and macroscopic surface roughness in hetero-epitaxial graphene grown on Cu/mica

    Qi, J L; Nagashio, K; Nishimura, T; Toriumi, A

    2014-01-01

    Clean, flat and orientation-identified graphene on a substrate is in high demand for graphene electronics. In this study, the hetero-epitaxial graphene growth on Cu(111)/mica(001) by chemical vapor deposition is investigated to check the applicability for top-gate insulator research on graphene, as well as graphene channel research, by transferring graphene on to SiO 2 /Si substrates. After adjusting the graphene growth conditions, the surface roughness of the graphene/Cu/mica substrate and the average smoothed areas are ∼0.34 nm and ∼100 μm 2 , respectively. The orientation of graphene in the graphene/Cu/mica substrate can be identified by the hexagonal void morphology of Cu. Moreover, we demonstrate a relatively high mobility of ∼4500 cm 2 V −1 s −1 in graphene transferred on the SiO 2 /Si substrate. These results suggest that the present graphene/Cu/mica substrate can be used for top-gate insulator research on graphene. (papers)

  11. Preparation and characterization of green graphene using grape seed extract for bioapplications

    Yaragalla, Srinivasarao [Center for Advanced Materials, Qatar University, Doha (Qatar); International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686560, Kerala (India); Rajendran, Rajakumari; Jose, Jiya [International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686560, Kerala (India); AlMaadeed, Mariam A., E-mail: m.alali@qu.edu.qa [Center for Advanced Materials, Qatar University, Doha (Qatar); Kalarikkal, Nandakumar, E-mail: nkkalarikkal@mgu.ac.in [International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686560, Kerala (India); School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, 686560, Kerala (India); Thomas, Sabu, E-mail: sabupolymer@yahoo.com [International and Inter University Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, 686560, Kerala (India); School of Chemical Sciences, Mahatma Gandhi University, Kottayam, 686560, Kerala (India)

    2016-08-01

    The development of functionalized graphene materials concerning health and environmental aspects via green approaches is currently the most recent topic in the field of nanoscience and nanotechnology. Herein, we report the green reduction of graphene oxide (GO) to reduced graphene oxide (RGO) using grape seed extract (GSE). Structural properties of the prepared RGO were investigated using Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetric analysis (TGA), UV–Visible spectroscopy and X-ray diffraction analysis. These all characterization techniques clearly revealed that the RGO has been successfully prepared. Moreover, the average thickness (4.2 nm) of RGO layers was also confirmed by transmission electron microscopy (TEM). Optical properties such as band gap and photoluminescence of the synthesized RGO were evaluated. The band gap of RGO was found to be 3.84 eV and it showed emission in the visible region. Efficient antimicrobial activity against Escherichia coli and Staphylococcus aureus was observed with 4 μg ml{sup −1} & 5 μg ml{sup −1} of RGO and also the cell wall damage of these strains has been proved by atomic force microscopy (AFM). The in vitro study of RGO (500 μg) disclosed the effective anti-proliferative activity (88%) against HCT-116 cell lines. - Highlights: • Grape seed extract was used for the reduction of graphene oxide. • Detailed structural analysis of RGO was done. • Excellent antimicrobial activity with 4 and 5 μg ml{sup −1} was reported. • Anti-inflammatory activity of RGO was reported. • Excellent anti-cancer activity was reported with just 500 μg of RGO.

  12. Preparation of Graphene Quantum Dots and Their Application in Cell Imaging

    Jie Zhang

    2016-01-01

    Full Text Available Objective. This study aims to increase the fluorescence quantum yield by improving the conditions of preparing graphene quantum dots (GQDs through the solvothermal route and observe the GQDs performance in imaging oral squamous cells. Methodology. The following experimental conditions of GQDs preparation through the solvothermal route were improved: graphene oxide (GO/N-N dimethyl formamide (DMF ratio, filling percentage, and reaction time. A fluorescence spectrophotometer was used to measure photoluminescence, and the peak values were compared. Methylthiazolyldiphenyl-tetrazolium (MTT bromide was used to detect the cytotoxicity of GQDs, which was compared with that of cadmium telluride quantum dots (CdTe QDs. GQDs were cultured with tongue cancer cells. After the coculture, a laser scanning confocal microscope (LSCM was used to observe cell imaging. Results. The optimal conditions of GQD preparation through the solvothermal route included the following: 10 mg/mL GO/DMF ratio, 80% filling percentage, 12 h reaction time, and 17.4% fluorescence quantum yield. As the cell concentration increased, the GQD and CdTe QD groups exhibited a decreasing cell survival rate, with the decrease in the CdTe QD group being more significant. The LSCM observations showed bright green fluorescence images. Conclusion. The improved experimental conditions increased the fluorescence quantum yield of GQDs. In this study, the prepared GQDs exhibited low cytotoxicity level and satisfactory cell imaging performance.

  13. In situ chemical oxidative polymerization preparation of poly(3,4-ethylenedioxythiophene)/graphene nanocomposites with enhanced thermoelectric performance.

    Xu, Kongli; Chen, Guangming; Qiu, Dong

    2015-05-01

    Three different in situ chemical oxidative polymerization routes, that is, (A) spin-coating and subsequent liquid layer polymerization, (B) spin-coating followed by vapor phase polymerization, and (C) in situ polymerization and then post-treatment by immersion in ethylene glycol (EG), have been developed to achieve poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (PEDOT/rGO) nanocomposites. As demonstrated by scanning electron microscopic and energy-dispersive X-ray spectroscopic techniques, PEDOT has been successfully coated on the surface of the rGO nanosheets by each of the three preparation routes. Importantly, all of the nanocomposites display a greatly enhanced thermoelectric performance (power factors) relative to those of the corresponding neat PEDOT. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Surface study of gallium- and aluminum- doped graphenes upon adsorption of cytosine: DFT calculations

    Shokuhi Rad, Ali; Zareyee, Daryoush; Peyravi, Majid; Jahanshahi, Mohsen

    2016-01-01

    Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.

  15. Surface study of gallium- and aluminum- doped graphenes upon adsorption of cytosine: DFT calculations

    Shokuhi Rad, Ali, E-mail: a.shokuhi@gmail.com [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Zareyee, Daryoush [Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Peyravi, Majid; Jahanshahi, Mohsen [Faculty of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2016-12-30

    Highlights: • P1 and P4 are the most stable adsorption configurations for cytosine. • NBO analysis show n-type semiconductor property for both Al- and Ga-doped graphenes. • Important changes in the HOMO and LUMO of doped graphene upon adsorption of cytosine. • Increase in the conductivity of system when cytosine is adsorbed on doped graphenes. - Abstract: The adsorption of cytosine molecule on Al- and Ga- doped graphenes is studied using first-principles density functional theory (DFT) calculations. The energetically most stable geometries of cytosine on both Al- and Ga- doped graphenes are determined and the adsorption energies are calculated. The net charge of transfer as well as local charge of doped atoms upon adsorption of cytosine are studied by natural bond orbitals (NBO) analysis. Orbital hybridizing of complexes was searched by frontier molecular orbital theory (FMO), and density of states (DOS). Depending on the side of cytosine, there are four possible sites for its adsorption on doped graphene; denoted as P1, P2, P3, and P4, respectively. The order of binding energy in the case of Al-doped graphene is found as P1 > P4 > P3 > P2. Interestingly, the order in the case of Ga-doped graphene changes to: P4 ∼ P1 > P3 > P2. Both surfaces show superior adsorbent property, resulting chemisorption of cytosine, especially at P1 and P4 position configurations. The NBO charge analysis reveals that the charge transfers from Al- and Ga- doped graphene sheets to cytosine. The electronic properties of both surfaces undertake important changes after cytosine adsorption, which indicates notable change in its electrical conductivity.

  16. Hierarchical On-Surface Synthesis of Deterministic Graphene Nanoribbon Heterojunctions

    Bronner, Christopher; Durr, Rebecca A.; Rizzo, Daniel J.; Lee, Yea-Lee; Marangoni, Tomas; Kalayjian, Alin Miksi; Rodriguez, Henry; Zhao, William; Louie, Steven G.; Fischer, Felix R.; Crommie, Michael F.

    2017-01-01

    Bottom-up graphene nanoribbon (GNR) heterojunctions are nanoscale strips of graphene whose electronic structure abruptly changes across a covalently bonded interface. Their rational design offers opportunities for profound technological advancements enabled by their extraordinary structural and electronic properties. Thus far the most critical aspect of their synthesis, the control over sequence and position of heterojunctions along the length of a ribbon, has been plagued by randomness in mo...

  17. Enhanced CO2 Adsorption by Nitrogen-Doped Graphene Oxide Sheets (N-GOs Prepared by Employing Polymeric Precursors

    Abdulaziz Ali Alghamdi

    2018-04-01

    Full Text Available Nitrogen-doped graphene oxide sheets (N-GOs are prepared by employing N-containing polymers such as polypyrrole, polyaniline, and copolymer (polypyrrole-polyaniline doped with acids such as HCl, H2SO4, and C6H5-SO3-K, which are activated using different concentrations of KOH and carbonized at 650 °C; characterized using SEM, TEM, BET, TGA-DSC, XRD, and XPS; and employed for the removal of environmental pollutant CO2. The porosity of the N-GOs obtained were found to be in the range 1–3.5 nm when the KOH employed was in the ratio of 1:4, and the XRD confirmed the formation of the layered like structure. However, when the KOH employed was in the ratio of 1:2, the pore diameter was found to be in the range of 50–200 nm. The SEM and TEM analysis reveal the porosity and sheet-like structure of the products obtained. The nitrogen-doped graphene oxide sheets (N-GOs prepared by employing polypyrrole doped with C6H5-SO3-K were found to possess a high surface area of 2870 m2/g. The N-GOs displayed excellent CO2 capture property with the N-GOs; PPy/Ar-1 displayed ~1.36 mmol/g. The precursor employed, the dopant used, and the activation process were found to affect the adsorption property of the N-GOs obtained. The preparation procedure is simple and favourable for the synthesis of N-GOs for their application as adsorbents in greenhouse gas removal and capture.

  18. An Analytical Model for Adsorption and Diffusion of Atoms/Ions on Graphene Surface

    Yan-Zi Yu

    2015-01-01

    Full Text Available Theoretical investigations are made on adsorption and diffusion of atoms/ions on graphene surface based on an analytical continuous model. An atom/ion interacts with every carbon atom of graphene through a pairwise potential which can be approximated by the Lennard-Jones (L-J potential. Using the Fourier expansion of the interaction potential, the total interaction energy between the adsorption atom/ion and a monolayer graphene is derived. The energy-distance relationships in the normal and lateral directions for varied atoms/ions, including gold atom (Au, platinum atom (Pt, manganese ion (Mn2+, sodium ion (Na1+, and lithium-ion (Li1+, on monolayer graphene surface are analyzed. The equilibrium position and binding energy of the atoms/ions at three particular adsorption sites (hollow, bridge, and top are calculated, and the adsorption stability is discussed. The results show that H-site is the most stable adsorption site, which is in agreement with the results of other literatures. What is more, the periodic interaction energy and interaction forces of lithium-ion diffusing along specific paths on graphene surface are also obtained and analyzed. The minimum energy barrier for diffusion is calculated. The possible applications of present study include drug delivery system (DDS, atomic scale friction, rechargeable lithium-ion graphene battery, and energy storage in carbon materials.

  19. Contact Angle Hysteresis on Graphene Surfaces and Hysteresis-free Behavior on Oil-infused Graphite Surfaces

    Wu, Cyuan-Jhang; Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Woon, Wei-Yen [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Sheng, Yu-Jane, E-mail: yjsheng@ntu.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Tsao, Heng-Kwong, E-mail: hktsao@cc.ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Department of Physics, National Central University, Jhongli 320, Taiwan (China)

    2016-11-01

    Highlights: • Contact angle hysteresis(CAH) on four graphitic surfacesisinvestigated. • The hysteresis loopof water drops on the polished graphite sheetshowsparticularly small receding contact angle. • The significant CAH observed on CVD graphene and highly oriented pyrolytic graphite is attributed mainly to adhesion hysteresis. • An oil-infused surface of a graphite sheet is produced by imbibition of hexadecane into its porous structure. • The hysteresis-free property for water drops on such a surface is examined and quantitatively explained. - Abstract: Contact angle hysteresis (CAH) on graphitic surfaces, including chemical vapor deposition (CVD) graphene, reduced electrophoretic deposition (EPD) graphene, highly oriented pyrolytic graphite (HOPG), and polished graphite sheet, has been investigated. The hysteresis loops of water drops on the first three samples are similar but the receding contact angle is particularly small for the polished graphite sheet.The significant CAH observed on CVD graphene and HOPG associated with atom-scale roughness has to be attributed mainly to adhesion hysteresis (surface relaxation), instead of roughness or defects.The difference of the wetting behavior among those four graphitic samples has been further demonstrated by hexadecane drops. On the surface of HOPG or CVD graphene,the contact line expands continuously with time, indicating total wetting for which the contact angle does not exist and contact line pinning disappears. In contrast, on the surface of reduced EPD graphene, spontaneous spreading is halted by spikes on it and partial wetting with small contact angle (θ≈4°) is obtained. On the surface of polished graphite sheet, the superlipophilicity and porous structure are demonstrated by imbibition and capillary rise of hexadecane. Consequently, an oil-infused graphite surface can be fabricated and the ultralow CAH of water (∆θ≈2°) is achieved.

  20. Preparation of Ultrahigh Molecular Weight Polyethylene/Graphene Nanocomposite In situ Polymerization via Spherical and Sandwich Structure Graphene/Sio2 Support

    Su, Enqi; Gao, Wensheng; Hu, Xinjun; Zhang, Caicai; Zhu, Bochao; Jia, Junji; Huang, Anping; Bai, Yongxiao

    2018-04-01

    Reduced graphene oxide/SiO2 (RGO/SiO2) serving as a novel spherical support for Ziegler-Natta (Z-N) catalyst is reported. The surface and interior of the support has a porous architecture formed by RGO/SiO2 sandwich structure. The sandwich structure is like a brick wall coated with a graphene layer of concreted as skeleton which could withstand external pressures and endow the structure with higher support stabilities. After loading the Z-N catalyst, the active components anchor on the surface and internal pores of the supports. When the ethylene molecules meet the active centers, the molecular chains grow from the surface and internal catalytic sites in a regular and well-organized way. And the process of the nascent molecular chains filled in the sandwich structure polymerization could ensure the graphene disperse uniformly in the polymer matrix. Compared with traditional methods, the porous spherical graphene support of this strategy has far more advantages and could maintain an intrinsic graphene performance in the nanocomposites.

  1. Graphene-SnO2 nanocomposites decorated with quantum tunneling junctions: preparation strategies, microstructures and formation mechanism.

    Wang, Qingxiu; Wu, Xianzheng; Wang, Lijun; Chen, Zhiwen; Wang, Shilong

    2014-09-28

    Tin dioxide (SnO2) and graphene are versatile materials that are vitally important for creating new functional and smart materials. A facile, simple and efficient ultrasonic-assisted hydrothermal synthesis approach has been developed to prepare graphene-SnO2 nanocomposites (GSNCs), including three samples with graphene/Sn weight ratios = 1 : 2 (GSNC-2), 1 : 1 (GSNC-1), and graphene oxide/Sn weight ratio = 1 : 1 (GOSNC-1). Low-magnification electron microscopy analysis indicated that graphene was exfoliated and adorned with SnO2 nanoparticles, which were dispersed uniformly on both the sides of the graphene nanosheets. High-magnification electron microscopy analysis confirmed that the graphene-SnO2 nanocomposites presented network tunneling frameworks, which were decorated with the SnO2 quantum tunneling junctions. The size distribution of SnO2 nanoparticles was estimated to range from 3 to 5.5 nm. Comparing GSNC-2, GSNC-1, and GOSNC-1, GOSNC-1 was found to exhibit a significantly better the homogeneous distribution and a considerably smaller size distribution of SnO2 nanoparticles, which indicated that it was better to use graphene oxide as a supporting material and SnCl4·5H2O as a precursor to synthesize hybrid graphene-SnO2 nanocomposites. Experimental results suggest that the graphene-SnO2 nanocomposites with interesting SnO2 quantum tunneling junctions may be a promising material to facilitate the improvement of the future design of micro/nanodevices.

  2. Dry-cleaning of graphene

    Algara-Siller, Gerardo; Lehtinen, Ossi; Kaiser, Ute; Turchanin, Andrey

    2014-01-01

    Studies of the structural and electronic properties of graphene in its pristine state are hindered by hydrocarbon contamination on the surfaces. Also, in many applications, contamination reduces the performance of graphene. Contamination is introduced during sample preparation and is adsorbed also directly from air. Here, we report on the development of a simple dry-cleaning method for producing large atomically clean areas in free-standing graphene. The cleanness of graphene is proven using aberration-corrected high-resolution transmission electron microscopy and electron spectroscopy

  3. Dry-cleaning of graphene

    Algara-Siller, Gerardo [Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Albert-Einstein-Allee 11, Ulm 89081 (Germany); Department of Chemistry, Technical University Ilmenau, Weimarer Strasse 25, Ilmenau 98693 (Germany); Lehtinen, Ossi; Kaiser, Ute, E-mail: ute.kaiser@uni-ulm.de [Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Albert-Einstein-Allee 11, Ulm 89081 (Germany); Turchanin, Andrey [Faculty of Physics, University of Bielefeld, Universitätsstr. 25, Bielefeld 33615 (Germany)

    2014-04-14

    Studies of the structural and electronic properties of graphene in its pristine state are hindered by hydrocarbon contamination on the surfaces. Also, in many applications, contamination reduces the performance of graphene. Contamination is introduced during sample preparation and is adsorbed also directly from air. Here, we report on the development of a simple dry-cleaning method for producing large atomically clean areas in free-standing graphene. The cleanness of graphene is proven using aberration-corrected high-resolution transmission electron microscopy and electron spectroscopy.

  4. Preparation of reduced graphene oxide/meso-TiO_2/AuNPs ternary composites and their visible-light-induced photocatalytic degradation n of methylene blue

    Yang, Yongfang; Ma, Zheng; Xu, Lidong; Wang, Hefang; Fu, Nian

    2016-01-01

    Graphical abstract: Reduced graphene oxide/meso-TiO_2/AuNPs (RGO/meso-TiO_2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO_2/AuNPs under a hydrothermal condition. The RGO/meso-TiO_2/AuNPs ternary composites show high photocatalytic activity toward MB. - Highlights: • RGO/meso-TiO_2/AuNPs were obtained by addition of graphene oxide to meso-TiO_2/AuNPs. • Au NPs in the mesopores of meso-TiO_2 reduce the recombination of charge carriers. • RGO covered with the surface of the meso-TiO_2 enhance the adsorption of MB. • RGO/meso-TiO_2/AuNPs composites show high photocatalytic performance toward MB. - Abstract: Reduced graphene oxide/meso-TiO_2/AuNPs (RGO/meso-TiO_2/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO_2/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO_2/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO_2/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO_2 and meso-TiO_2/AuNPs.

  5. Preparation of reduced graphene oxide/meso-TiO{sub 2}/AuNPs ternary composites and their visible-light-induced photocatalytic degradation n of methylene blue

    Yang, Yongfang; Ma, Zheng; Xu, Lidong [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Wang, Hefang, E-mail: whf0618@163.com [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Fu, Nian, E-mail: funian3678@163.com [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); College of Physics Science and Technology of Hebei University, Baoding 071002 (China)

    2016-04-30

    Graphical abstract: Reduced graphene oxide/meso-TiO{sub 2}/AuNPs (RGO/meso-TiO{sub 2}/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO{sub 2}/AuNPs under a hydrothermal condition. The RGO/meso-TiO{sub 2}/AuNPs ternary composites show high photocatalytic activity toward MB. - Highlights: • RGO/meso-TiO{sub 2}/AuNPs were obtained by addition of graphene oxide to meso-TiO{sub 2}/AuNPs. • Au NPs in the mesopores of meso-TiO{sub 2} reduce the recombination of charge carriers. • RGO covered with the surface of the meso-TiO{sub 2} enhance the adsorption of MB. • RGO/meso-TiO{sub 2}/AuNPs composites show high photocatalytic performance toward MB. - Abstract: Reduced graphene oxide/meso-TiO{sub 2}/AuNPs (RGO/meso-TiO{sub 2}/AuNPs) ternary composites were prepared via the addition of graphene oxide to the dispersion of meso-TiO{sub 2}/AuNPs under hydrothermal conditions. The structure and the morphology of the RGO/meso-TiO{sub 2}/AuNPs materials were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The photocatalytic activity of RGO/meso-TiO{sub 2}/AuNPs was evaluated by degradation of methyl blue (MB) under visible-light illumination. The ternary composites present an extended light absorption range, efficient charge separation properties, high adsorption ability for MB and high photocatalytic degradation activity of MB compared to the meso-TiO{sub 2} and meso-TiO{sub 2}/AuNPs.

  6. Preparation and characterization of ZnO/graphene nanocomposite for improved photovoltaic performance

    Jayabal, P.; Gayathri, S.; Sasirekha, V.; Mayandi, J.; Ramakrishnan, V.

    2014-11-01

    Zinc oxide (ZnO) nanoparticles and ZnO/graphene (ZG) nanocomposite were synthesized via simple chemical route and its application as a photoanode for dye-sensitized solar cell (DSSC) was demonstrated. The prepared ZnO and ZG were structurally characterized by X-ray diffraction and micro-Raman techniques. The scanning electron micrograph of ZG revealed the spherical-shaped ZnO nanoparticles of particle size 160 nm was anchored on the two-dimensional graphene sheets. UV-Vis absorption spectroscopy showed that the ZG nanocomposite has enriched visible light absorption. The DSSCs were fabricated using the synthesized ZnO and ZG nanocomposite as photoanode and the effect of low-cost organic dyes on the photovoltaic performances of the solar cells were investigated. Comprehensive performances of ZG are better than that of ZnO-based DSSCs. The ZG DSSCs show power conversion efficiency (PCE) of 1.5 and 0.98 % for RB and EY sensitized electrodes, respectively. Moreover, the ZG dominates in many aspects due to the presence of graphene.

  7. Preparation and characterization of flexible lithium iron phosphate/graphene/cellulose electrode for lithium ion batteries.

    Wang, Yan; He, Zhen-Yu; Wang, Yao-Xuan; Fan, Cong; Liu, Chen-Ren-Lang; Peng, Qi-Ling; Chen, Jin-Ju; Feng, Zhe-Sheng

    2018-02-15

    In this work, a free-standing flexible composite electrode was prepared by vacuum filtration method with LiFePO 4 , graphene and nanofibrillated cellulose (NFC). Compared with the pure LiFePO 4 electrode, the resulting flexible composite (LiFePO 4 /graphene/NFC) electrode showed excellent mechanical flexibility, and possessed an enhanced initial discharge capacity of 151 mA h/g (0.1 C) and a good capacity retention rate with only 5% loss after 60 cycles due to suitable electrolyte wettability at the interface. Furthermore, the NFC and graphene formed a three-dimensional conductive framework, which provided high-speed electron conduction in the composite and reduced electrode polarization during charging-discharging processes. Moreover, the composite electrode could endure bending tests up to 1000 times, highlighting preferable mechanical strength and durability. These results demonstrated that the as-fabricated electrodes could be applied as flexible electrodes with an embedded power supply. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Preparation and characterization of polymer nanocomposites based on PVDF/PVC doped with graphene nanoparticles

    I.S. Elashmawi

    Full Text Available Novel nanocomposites based on PVDF/PVC blend containing graphene oxide nanoparticles (GO were prepare using sonicator. IR analysis revealed that the addition of GO prompts a crystal transformation of α-phase of PVDF. The change of the structural before and after adding GO to PVDF/PVC were studied by X-ray diffraction. A decrease in activation energy gap from UV data was observed with increasing GO content, implying a variation of reactivity as a result of reaction extent. The variation of ε′ with frequency is nearly the same as that of ε″. At higher frequencies, the decrease of both ε′ and ε″ becomes nearly constant. The dispersion at lower frequencies ε′ of ε′ polarization is of Maxwell–Wagner interfacial polarization but at higher frequencies, it levels off. The behavior of conductivity (σAC tends to acquire constant values approaching it DC values. The values of σAC was increased after doped GO with exponential increase after the critical value of frequency. All nanocomposites behaved the same fashion revealing that a higher number of polarons were getting added to conducting pool in composites as graphene content was increased. Conduction mechanism appeared to be getting expedited with increasing frequency due to fact that increase in frequency enhances polaron hopping frequency. Keywords: Nanocomposites, Graphene oxide, FT-IR, X-ray, AC conductivity

  9. Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111/Si(111

    Abe Shunsuke

    2010-01-01

    Full Text Available Abstract Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111 thin films on Si(111 has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D2-TPD and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111/Si(111 is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001 proceeds.

  10. The Preparation of Graphene Reinforced Poly(vinyl alcohol Antibacterial Nanocomposite Thin Film

    Yuan-Cheng Cao

    2015-01-01

    Full Text Available Methylated melamine grafted polyvinyl benzylchloride (mm-g-PvBCl was prepared which was used as additive in poly(vinyl alcohol (PVA and graphene nanosheets (GNs were used to reinforce the mechanical strength. Using casting method, antimicrobial nanocomposite films were prepared with the polymeric biocide loading lever of 1 wt%, 5 wt%, and 10 wt%. Thermogravimetric analysis (TGA characterization revealed the 2.0 wt% of graphene content in resultant nanocomposites films. XRD showed that the resultant GNs 2 theta was changed from 16.6 degree to 23.3 degree. Using Japanese Industry Standard test methods, the antimicrobial efficiency for the loading lever of 1 wt%, 5 wt%, and 10 wt% was 92.0%, 95.8%, and 97.1%, respectively, against gram negative bacteria E. coli and 92.3%, 99.6%, and 99.7%, respectively, against the gram positive S. aureus. These results indicate the prepared nanocomposite films are the promising materials for the food and drink package applications.

  11. Preparation of graphene/polyaniline nanocomposites by gamma radiation for supercapacitor

    Cai Xiaosheng; Zhang Qilu; Peng Jing; Li Jiuqiang; Zhai Maolin

    2014-01-01

    Graphene was prepared from graphite oxide (GO) with surfactants by gamma irradiation, and then mixed with polyaniline to produce the composites. The structure characterization was investigated using (FTIR), thermalgravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), and the electrochemical properties of the composites were measured. The results show that the cationic surfactant can promote the reduction of GO. The specific capacitance of the composite materials reaches 435 F/g at 0.1 A/g showing potential for use in supercapacitors. (authors)

  12. Preparation of silver nanoparticles/graphene nanosheets as a catalyst for electrochemical oxidation of methanol

    Han, Kun; Miao, Peng; Tang, Yuguo, E-mail: tangyg@sibet.ac.cn [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Tong, Hui; Zhu, Xiaoli [Laboratory of Biosensing Technology, School of Life Sciences, Shanghai University, Shanghai 200444 (China); Liu, Tao; Cheng, Wenbo [Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou 215163 (China)

    2014-02-03

    In this report, silver nanoparticles (AgNPs) decorated graphene nanosheets have been prepared based on the reduction of Ag ions by hydroquinone, and their catalytic performance towards the electrochemical oxidation of methanol is investigated. The synthesis of the nano-composite is confirmed by transmission electron microscope measurements and UV-vis absorption spectra. Excellent electrocatalytic performance of the material is demonstrated by cyclic voltammograms. This material also contributes to the low peak potential of methanol oxidation compared with most of the other materials.

  13. Surface enhanced Raman spectroscopy platform based on graphene with one-year stability

    Tite, Teddy [Univ Lyon, UJM-Saint-Etienne, CNRS, Laboratoire Hubert Curien UMR 5516, 18 rue Professeur Benoit Lauras, F-42000 Saint-Etienne (France); Barnier, Vincent [Ecole Nationale Supérieure des Mines, CNRS, Laboratoire Georges Friedel UMR 5307, 158 cours Fauriel, F-42023 Saint-Etienne (France); Donnet, Christophe, E-mail: Christophe.Donnet@univ-st-etienne.fr [Univ Lyon, UJM-Saint-Etienne, CNRS, Laboratoire Hubert Curien UMR 5516, 18 rue Professeur Benoit Lauras, F-42000 Saint-Etienne (France); Loir, Anne–Sophie; Reynaud, Stéphanie; Michalon, Jean–Yves; Vocanson, Francis; Garrelie, Florence [Univ Lyon, UJM-Saint-Etienne, CNRS, Laboratoire Hubert Curien UMR 5516, 18 rue Professeur Benoit Lauras, F-42000 Saint-Etienne (France)

    2016-04-01

    We report the synthesis, characterization and use of a robust surface enhanced Raman spectroscopy platform with a stable detection for up to one year of Rhodamine R6G at a concentration of 10{sup −6} M. The detection of aminothiophenol and methyl parathion, as active molecules of commercial insecticides, is further demonstrated at concentrations down to 10{sup −5}–10{sup −6} M. This platform is based on large scale textured few-layer (fl) graphene obtained without any need of graphene transfer. The synthesis route is based on diamond-like carbon films grown by pulsed laser deposition, deposited onto silicon substrates covered by a Ni layer prior to diamond-like carbon deposition. The formation of fl-graphene film, confirmed by Raman spectroscopy and mapping, is obtained by thermal annealing inducing the diffusion of Ni atoms and the concomitant formation of nickel silicide compounds, as identified by Raman and Auger electron spectroscopies. The textured fl-graphene films were decorated with gold nanoparticles to optimize the efficiency of the SERS device to detect organic molecules at low concentrations. - Highlights: • Synthesis of graphene film from amorphous carbon by pulsed laser deposition with nickel catalyst • Large scale textured graphene with nanoscale roughness obtained through nickel silicide formation • Films used for surface enhanced Raman spectroscopy detection of organophosphate compounds • Stability of the SERS platforms over up to one year.

  14. Sonochemical Preparation and Subsequent Fixation of Oxygen-Free Graphene Sheets at N,N-Dimethyloctylamine-Aqua Boundary

    Elena A. Trusova

    2018-01-01

    Full Text Available In this study, the syntheses of oxygen-free graphene sheets and the method of its fixation at an oil-aqua interface were presented. The graphene sheets were prepared by exfoliation of synthetic graphite powder in an aqua-organic medium under ultrasound irradiation. N,N-Dimethyloctylamine- (DMOA- aqua emulsion was used as the liquid medium, and pH was equal to 3. The obtained graphene nanosuspension was fractionated by sedimentation and decanted according to the weight. The graphene nanoparticle fractions, differing in configuration and number of layers, have been characterized using transmission electron microscopy (TEM, electron diffraction, HRTEM, Raman spectroscopy, and electron energy loss spectroscopy (EELS. It was found that using a DMOA-aqua mixture as the liquid medium in ultrasonic treatment of synthetic graphite leads to the formation of oxygen-free 1-2-layer graphene sheets attached to the DMOA-aqua interface. The proposed method differs from known ones by using a small amount of more environmentally friendly organic substances. It allows to obtain large quantities of oxygen-free graphene, and finally unconverted graphite can be directed for reuse. The proposed method allows to obtain both 2D graphene sheets with micron linear dimensions and 3D packages with a high content of defects. Both these species are in demand in areas related to the development of new materials with unique electrophysical properties.

  15. Efficient preparation of highly hydrogenated graphene and its application as a high-performance anode material for lithium ion batteries

    Chen, Wufeng; Zhu, Zhiye; Li, Sirong; Chen, Chunhua; Yan, Lifeng

    2012-03-01

    A novel method has been developed to prepare hydrogenated graphene (HG) via a direct synchronized reduction and hydrogenation of graphene oxide (GO) in an aqueous suspension under 60Co gamma ray irradiation at room temperature. GO can be reduced by the aqueous electrons (eaq-) while the hydrogenation takes place due to the hydrogen radicals formed in situ under irradiation. The maximum hydrogen content of the as-prepared highly hydrogenated graphene (HHG) is found to be 5.27 wt% with H/C = 0.76. The yield of the target product is on the gram scale. The as-prepared HHG also shows high performance as an anode material for lithium ion batteries.

  16. Three-dimensional graphene networks: synthesis,properties and applications

    Yanfeng Ma; Yongsheng Chen

    2015-01-01

    Recently, three-dimensional graphene/graphene oxide(GO) networks(3DGNs) in the form of foams,sponges and aerogels have atracted much atention. 3D structures provide graphene materials with high speciic surface areas, large pore volumes, strong mechanical strengths and fast mass and electron transport,owing to the combination of the 3D porous structures and the excellent intrinsic properties of graphene.his review focuses on the latest advances in the preparation, properties and potential applications of 3D micro-/nano-architectures made of graphene/GO-based networks, with emphasis on graphene foams and sponges.

  17. Interactions of Graphene Oxide Nanomaterials with Natural Organic Matter and Metal Oxide Surfaces

    Interactions of graphene oxide (GO) with silica surfaces were investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Both GO deposition and release were monitored on silica- and poly-l-lysine (PLL) coated surfaces as a function of GO concentration a...

  18. Eco-friendly preparation of large-sized graphene via short-circuit discharge of lithium primary battery.

    Kang, Shaohong; Yu, Tao; Liu, Tingting; Guan, Shiyou

    2018-02-15

    We proposed a large-sized graphene preparation method by short-circuit discharge of the lithium-graphite primary battery for the first time. LiC x is obtained through lithium ions intercalation into graphite cathode in the above primary battery. Graphene was acquired by chemical reaction between LiC x and stripper agents with dispersion under sonication conditions. The gained graphene is characterized by Raman spectrum, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM) and Scanning electron microscopy (SEM). The results indicate that the as-prepared graphene has a large size and few defects, and it is monolayer or less than three layers. The quality of graphene is significant improved compared to the reported electrochemical methods. The yield of graphene can reach 8.76% when the ratio of the H 2 O and NMP is 3:7. This method provides a potential solution for the recycling of waste lithium ion batteries. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Hydrogen atom addition to the surface of graphene nanoflakes: A density functional theory study

    Tachikawa, Hiroto

    2017-02-01

    Polycyclic aromatic hydrocarbons (PAHs) provide a 2-dimensional (2D) reaction surface in 3-dimensional (3D) interstellar space and have been utilized as a model of graphene surfaces. In the present study, the reaction of PAHs with atomic hydrogen was investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of atomic hydrogen to graphene nanoflakes. PAHs with n = 4-37 were chosen, where n indicates the number of benzene rings. Activation energies of hydrogen addition to the graphene surface were calculated to be 5.2-7.0 kcal/mol at the CAM-B3LYP/6-311G(d,p) level, which is almost constant for all PAHs. The binding energies of hydrogen atom were slightly dependent on the size (n): 14.8-28.5 kcal/mol. The absorption spectra showed that a long tail is generated at the low-energy region after hydrogen addition to the graphene surface. The electronic states of hydrogenated graphenes were discussed on the basis of theoretical results.

  20. Raman spectroscopy of few-layer graphene prepared by C2–C6 cluster ion implantation

    Wang, Z.S.; Zhang, R.; Zhang, Z.D.; Huang, Z.H.; Liu, C.S.; Fu, D.J.; Liu, J.R.

    2013-01-01

    Few-layer graphene has been prepared on 300 nm-thick Ni films by C 2 –C 6 cluster ion implantation at 20 keV/cluster. Raman spectroscopy reveals significant influence of the number of atoms in the cluster, the implantation dose, and thermal treatment on the structure of the graphene layers. In particular, the graphene samples exhibit a sharp G peak at 1584 cm −1 and 2D peaks at 2711–2717 cm −1 . The I G /I 2D ratios higher than 1.70 and I G /I D ratio as high as 1.95 confirm that graphene sheets with low density of defects have been synthesized with much improved quality by ion implantation with larger clusters of C 4 –C 6

  1. Toward High Carrier Mobility and Low Contact Resistance:Laser Cleaning of PMMA Residues on Graphene Surfaces

    Yuehui Jia; Xin Gong; Pei Peng; Zidong Wang; Zhongzheng Tian; Liming Ren; Yunyi Fu; Han Zhang

    2016-01-01

    Poly(methyl methacrylate)(PMMA) is widely used for graphene transfer and device fabrication.However,it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of device performance.How to eliminate contamination and restore clean surfaces of graphene is still highly demanded.In this paper,we present a reliable and position-controllable method to remove the polymer residues on graphene films by laser exposure.Under proper laser conditions,PMMA residues can be substantially reduced without introducing defects to the underlying graphene.Furthermore,by applying this laser cleaning technique to the channel and contacts of graphene fieldeffect transistors(GFETs),higher carrier mobility as well as lower contact resistance can be realized.This work opens a way for probing intrinsic properties of contaminant-free graphene and fabricating high-performance GFETs with both clean channel and intimate graphene/metal contact.

  2. Molecular simulation insights on the in vacuo adsorption of amino acids on graphene oxide surfaces with varying surface oxygen densities

    Rahmani, Farzin; Nouranian, Sasan, E-mail: sasan@olemiss.edu; Mahdavi, Mina [University of Mississippi, Department of Chemical Engineering (United States); Al-Ostaz, Ahmed [University of Mississippi, Department of Civil Engineering (United States)

    2016-11-15

    In this fundamental study, a series of molecular dynamics simulations were performed in vacuo to investigate the energetics and select geometries of 20 standard amino acids (AAs) on pristine graphene (PG) and graphene oxide (GO) surfaces as a function of graphene surface oxygen density. These interactions are of key interest to graphene/biomolecular systems. Our results indicate that aromatic AAs exhibit the strongest total interactions with the PG surfaces due to π-π stacking. Tryptophan (Trp) has the highest aromaticity due to its indole side chain and, hence, has the strongest interaction among all AAs (−16.66 kcal/mol). Aliphatic, polar, and charged AAs show various levels of affinity to the PG sheets depending on the strength of their side chain hydrophobic interactions. For example, arginine (Arg) with its guanidinium side chain exhibits the strongest interaction with the PG sheets (−13.81 kcal/mol) following aromatic AAs. Also, glycine (Gly; a polar AA) has the weakest interaction with the PG sheets (−7.29 kcal/mol). When oxygen-containing functional groups are added to the graphene sheets, the π-π stacking in aromatic AAs becomes disrupted and perfect parallelism of the aromatic rings is lost. Moreover, hydrogen bonding and/or electrostatic interactions become more pronounced. Charged AAs exhibit the strongest interactions with the GO surfaces. In general, the AA-GO interactions increase with increasing surface oxygen density, and the effect is more pronounced at higher O/C ratios. This study provides a quantitative measure of AA-graphene interactions for the design and tuning of biomolecular systems suitable for biosensing, drug delivery, and gene delivery applications.

  3. Free-standing graphene films prepared via foam film method for great capacitive flexible supercapacitors

    Zhu, Yucan; Ye, Xingke; Tang, Zhonghua; Wan, Zhongquan; Jia, Chunyang

    2017-11-01

    Recently, graphene films have always attracted attention due to their excellent characteristics in energy storage. In this work, a novel graphene oxide (GO) film with excellent mechanical properties, whose thickness was regulated simply via changing the concentration of the surfactant, was successfully prepared by foam film method. After chemical reduction, the reduced GO (rGO) films have excellent electrical conductivity of ∼172 S cm-1. Moreover, the supercapacitors based on the rGO films exhibit satisfied capacitive performance of ∼56 mF cm-2 at 0.2 mA cm-2 in 6 M KOH aqueous solution. Meanwhile, the flexible all solid state supercapacitors (FSSCs) based on the rGO films also show great volumetric capacitance of ∼2810 mF cm-3 at 12 mA cm-3 (∼1607 mF cm-3 at 613 mA cm-3) with polyvinyl alcohol-KOH gel electrolyte. Besides, after 10000 cycles and continuously bent to 180° for 300 times, the volumetric capacitance of the FSSC remains at 81.4% and 90.4% of its initial capacitance value, respectively. Therefore, the free-standing rGO films prepared via foam film method could be considered as promising electrode materials for high performance flexible supercapacitors.

  4. Electronic and structural characterizations of unreconstructed {l_brace}0001{r_brace} surfaces and the growth of graphene overlayers

    Emtsev, Konstantin

    2009-06-03

    The present work is focused on the characterization of the clean unreconstructed SiC{l_brace}0001{r_brace} surfaces and the growth of graphene overlayers thereon. Electronic properties of SiC surfaces and their interfaces with graphene and few layer graphene films were investigated by means of angle resolved photoelectron spectroscopy, X-ray photoelectron spectroscopy and low energy electron diffraction. Structural characterizations of the epitaxial graphene films grown on SiC were carried out by atomic force microscopy and low energy electron microscopy. Supplementary data was obtained by scanning tunneling microscopy. (orig.)

  5. Photocurrent enhancement of graphene photodetectors by photon tunneling of light into surface plasmons

    Maleki, Alireza; Cumming, Benjamin P.; Gu, Min; Downes, James E.; Coutts, David W.; Dawes, Judith M.

    2017-10-01

    We demonstrate that surface plasmon resonances excited by photon tunneling through an adjacent dielectric medium enhance the photocurrent detected by a graphene photodetector. The device is created by overlaying a graphene sheet over an etched gap in a gold film deposited on glass. The detected photocurrents are compared for five different excitation wavelengths, ranging from {λ }0=570 {{nm}} to {λ }0=730 {{nm}}. Although the device is not optimized, the photocurrent excited with incident p-polarized light (which excites resonant surface plasmons) is significantly amplified in comparison with that for s-polarized light (without surface plasmon resonances). We observe that the photocurrent is greater for shorter wavelengths (for both s- and p-polarizations) with increased photothermal current. Position-dependent Raman spectroscopic analysis of the optically-excited graphene photodetector indicates the presence of charge carriers in the graphene near the metallic edge. In addition, we show that the polarity of the photocurrent reverses across the gap as the incident light spot moves across the gap. Graphene-based photodetectors offer a simple architecture which can be fabricated on dielectric waveguides to exploit the plasmonic photocurrent enhancement of the evanescent field. Applications for these devices include photodetection, optical sensing and direct plasmonic detection.

  6. A process to enhance the specific surface area and capacitance of hydrothermally reduced graphene oxide

    Alazmi, Amira

    2016-08-26

    The impact of post-synthesis processing in reduced graphene oxide materials for supercapacitor electrodes has been analyzed. A comparative study of vacuum, freeze and critical point drying was carried out for hydrothermally reduced graphene oxide demonstrating that the optimization of the specific surface area and preservation of the porous network are critical to maximize its supercapacitance performance. As described below, using a supercritical fluid as the drying medium, unprecedented values of the specific surface area (364 m2 g−1) and supercapacitance (441 F g−1) for this class of materials have been achieved.

  7. Spin torque on the surface of graphene in the presence of spin orbit splitting

    Ji Chen

    2013-06-01

    Full Text Available We study theoretically the spin transfer torque of a ferromagnetic layer coupled to (deposited onto a graphene surface in the presence of the Rashba spin orbit coupling (RSOC. We show that the RSOC induces an effective magnetic field, which will result in the spin precession of conduction electrons. We derive correspondingly the generalized Landau-Lifshitz-Gilbert (LLG equation, which describes the precessional motion of local magnetization under the influence of the spin orbit effect. Our theoretical estimate indicates that the spin orbit spin torque may have significant effect on the magnetization dynamics of the ferromagnetic layer coupled to the graphene surface.

  8. A process to enhance the specific surface area and capacitance of hydrothermally reduced graphene oxide

    Alazmi, Amira; El Tall, Omar; Rasul, Shahid; Hedhili, Mohamed N.; Patole, Shashikant P.; Da Costa, Pedro M. F. J.

    2016-01-01

    The impact of post-synthesis processing in reduced graphene oxide materials for supercapacitor electrodes has been analyzed. A comparative study of vacuum, freeze and critical point drying was carried out for hydrothermally reduced graphene oxide demonstrating that the optimization of the specific surface area and preservation of the porous network are critical to maximize its supercapacitance performance. As described below, using a supercritical fluid as the drying medium, unprecedented values of the specific surface area (364 m2 g−1) and supercapacitance (441 F g−1) for this class of materials have been achieved.

  9. A facile and green preparation of reduced graphene oxide using Eucalyptus leaf extract

    Li, Chengyang; Zhuang, Zechao; Jin, Xiaoying; Chen, Zuliang

    2017-11-01

    In this paper, a green and facile synthesis of reduced graphene oxide (GO) by Eucalyptus leaf extract (EL-RGO) was investigated, which was characterized with ultraviolet-visible spectroscopy (UV), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Thermal gravimetric analysis (TG). Eucalyptus leaf extract also play both reducing and capping stabilizing agents prepared EL-RGO as shown a good stability and electrochemical properties. This approach could provide an alternative method to prepare EL-RGO in large-scale production. Moreover, the good electrochemical property and biocompatibility can be used in various applications. In addition, the merit of this study is that both the oxidized products and the reducing agents are environmental friendly by green reduction.

  10. High-Surface-Area Nitrogen-Doped Reduced Graphene Oxide for Electric Double-Layer Capacitors.

    Youn, Hee-Chang; Bak, Seong-Min; Kim, Myeong-Seong; Jaye, Cherno; Fischer, Daniel A; Lee, Chang-Wook; Yang, Xiao-Qing; Roh, Kwang Chul; Kim, Kwang-Bum

    2015-06-08

    A two-step method consisting of solid-state microwave irradiation and heat treatment under NH3 gas was used to prepare nitrogen-doped reduced graphene oxide (N-RGO) with a high specific surface area (1007 m(2)  g(-1) ), high electrical conductivity (1532 S m(-1) ), and low oxygen content (1.5 wt %) for electrical double-layer capacitor applications. The specific capacitance of N-RGO was 291 F g(-1) at a current density of 1 A g(-1) , and a capacitance of 261 F g(-1) was retained at 50 A g(-1) , which indicated a very good rate capability. N-RGO also showed excellent cycling stability and preserved 96 % of the initial specific capacitance after 100 000 cycles. Near-edge X-ray absorption fine-structure spectroscopy results provided evidenced for the recovery of π conjugation in the carbon networks with the removal of oxygenated groups and revealed chemical bonding of the nitrogen atoms in N-RGO. The good electrochemical performance of N-RGO is attributed to its high surface area, high electrical conductivity, and low oxygen content. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Surface structure deduced differences of copper foil and film for graphene CVD growth

    Tian, Junjun [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Hu, Baoshan, E-mail: hubaoshan@cqu.edu.cn [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Wei, Zidong; Jin, Yan [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Luo, Zhengtang [Department of Chemical and Biomolecular Engineering, The Hongkong University of Science and Technology, Kowloon (Hong Kong); Xia, Meirong [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Pan, Qingjiang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Heilongjiang University, Harbin 150080 (China); Liu, Yunling [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)

    2014-05-01

    Highlights: • We demonstrate the significant differences between Cu foil and film in the surface morphology and crystal orientation distribution. • The different surface structure leads to the distinctive influences of the CH₄ and H₂ concentrations on the thickness and quality of as-grown graphene. • Nucleation densities and growth rate differences at the initial growth stages on the Cu foil and film were investigated and discussed. Abstract: Graphene was synthesized on Cu foil and film by atmospheric pressure chemical vapor deposition (CVD) with CH₄ as carbon source. Electron backscattered scattering diffraction (EBSD) characterization demonstrates that the Cu foil surface after the H₂-assisted pre-annealing was almost composed of Cu(1 0 0) crystal facet with larger grain size of ~100 μm; meanwhile, the Cu film surface involved a variety of crystal facets of Cu(1 1 1), Cu(1 0 0), and Cu(1 1 0), with the relatively small grain size of ~10 μm. The different surface structure led to the distinctive influences of the CH₄ and H₂ concentrations on the thickness and quality of as-grown graphene. Further data demonstrate that the Cu foil enabled more nucleation densities and faster growth rates at the initial growth stages than the Cu film. Our results are beneficial for understanding the relationship between the metal surface structure and graphene CVD growth.

  12. Experimental and Theoretical Studies on Corrosion Inhibition of Niobium and Tantalum Surfaces by Carboxylated Graphene Oxide

    Valbonë Mehmeti

    2018-05-01

    Full Text Available The corrosion of two different metals, niobium and tantalum, in aqueous sulfuric acid solution has been studied in the presence and absence of carboxylated graphene oxide. Potentiodynamic measurements indicate that this nanomaterial inhibits corrosion due to its adsorption on the metal surfaces. The adsorbed layer of carboxylated graphene hinders two electrochemical reactions: the oxidation of the metal and the transport of metal ions from the metal to the solution but also hydrogen evolution reaction by acting as a protective barrier. The adsorption behavior at the molecular level of the carboxylated graphene oxide with respect to Nb, NbO, Ta, and TaO (111 surfaces is also investigated using Molecular Dynamic and Monte Carlo calculations.

  13. A facile approach to prepare crumpled CoTMPyP/electrochemically reduced graphene oxide nanohybrid as an efficient electrocatalyst for hydrogen evolution reaction

    Ma, Juanjuan, E-mail: majj0518@hotmail.com [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); School of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore (Singapore); Liu, Lin; Chen, Qian; Yang, Min [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Wang, Danping [School of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore (Singapore); Tong, Zhiwei [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Chen, Zhong, E-mail: aszchen@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore (Singapore)

    2017-03-31

    Highlights: • Crumpled CoTMPyP/ERGO hybrid was successfully prepared by a facile two-step process. • CoTMPyP nanoaggregates are homogeneously distributed over the graphene surface. • CoTMPyP/ERGO hybrid film shows good electrocatalytic activity and stability for HER. - Abstract: Elaborate design and synthesis of efficient and stable non-Pt electrocatalysts for some renewable energy related conversion/storage processes are one of the major goals of sustainable chemistry. Herein, we report a facile method to fabricate Co porphyrin functionalized electrochemically reduced graphene oxide (CoTMPyP/ERGO) thin film by direct assembly of oppositely charged tetrakis(N-methylpyridyl) porphyrinato cobalt (CoTMPyP) and GO nanosheets under mild conditions followed by an electrochemical reduction procedure. STEM analysis confirms that CoTMPyP nanoaggregates are homogeneously distributed over the graphene surface. The electrochemical properties of CoTMPyP/ERGO were investigated by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy. The results demonstrate that CoTMPyP/ERGO nanohybrid film can serve as excellent electrocatalyst for hydrogen evolution in alkaline solution with high activity and stability. The intimate contact and efficient electron transfer between CoTMPyP and ERGO, as well as the crumpled structure, contribute to the improvement of the electrocatalytic performance.

  14. Preparation of LiMn2O4 Graphene Hybrid Nanostructure by Combustion Synthesis and Their Electrochemical Properties

    Dinesh Rangappa

    2014-10-01

    Full Text Available The LiMn2O4 graphene hybrid cathode material has been synthesized by spray drying combustion process. The spinel structure cubic phase LiMn2O4 graphene hybrid material was prepared by spray drying process at 120 ℃ and subsequent heat treatment at 700 ℃ for 1 hour. The result indicates that the spinel shaped LiMn2O4 particles wrapped with graphene sheets were formed with particle size in the range of 60-70 nm. The charge-discharge measurement indicates that the LiMn2O4 graphene hybrid material shows an improved discharge capacity of 139 mAh/g at 0.1C rate. The pristine LiMn2O4 nano crystals present only about 132 mAh/g discharge capacity. The LiMn2O4 graphene hybrid samples show good cyclic performance with only 13% of capacity fading in 30 cycles when compared to the pristine LiMn2O4 that shows 22% of capacity fading in 30 cycles. The capacity retention of the LiMn2O4 graphene hybrid samples is about 10% higher than the pristine cycle after 30 cycles.

  15. Simultaneous surface and depth neural activity recording with graphene transistor-based dual-modality probes.

    Du, Mingde; Xu, Xianchen; Yang, Long; Guo, Yichuan; Guan, Shouliang; Shi, Jidong; Wang, Jinfen; Fang, Ying

    2018-05-15

    Subdural surface and penetrating depth probes are widely applied to record neural activities from the cortical surface and intracortical locations of the brain, respectively. Simultaneous surface and depth neural activity recording is essential to understand the linkage between the two modalities. Here, we develop flexible dual-modality neural probes based on graphene transistors. The neural probes exhibit stable electrical performance even under 90° bending because of the excellent mechanical properties of graphene, and thus allow multi-site recording from the subdural surface of rat cortex. In addition, finite element analysis was carried out to investigate the mechanical interactions between probe and cortex tissue during intracortical implantation. Based on the simulation results, a sharp tip angle of π/6 was chosen to facilitate tissue penetration of the neural probes. Accordingly, the graphene transistor-based dual-modality neural probes have been successfully applied for simultaneous surface and depth recording of epileptiform activity of rat brain in vivo. Our results show that graphene transistor-based dual-modality neural probes can serve as a facile and versatile tool to study tempo-spatial patterns of neural activities. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. An Ideal Electrode Material, 3D Surface-Microporous Graphene for Supercapacitors with Ultrahigh Areal Capacitance

    Chang, Liang; Stacchiola, Dario J.; Hu, Yun Hang

    2017-01-01

    The efficient charge accumulation of an ideal supercapacitor electrode requires abundant micropores and its fast electrolyte-ions transport prefers meso/macropores. But, current electrode materials cannot meet both requirements, resulting in poor performance. We creatively constructed three-dimensional cabbage-coral-like graphene as an ideal electrode material, in which meso/macro channels are formed by graphene walls and rich micropores are incorporated in the surface layer of the graphene walls. The unique 3D graphene material can achieve a high gravimetric capacitance of 200 F/g with aqueous electrolyte, 3 times larger than that of commercially used activated carbon (70.8 F/g). Furthermore, it can reach an ultrahigh areal capacitance of 1.28 F/cm"2 and excellent rate capability (83.5% from 0.5 to 10 A/g) as well as high cycling stability (86.2% retention after 5000 cycles). The excellent electric double-layer performance of the 3D graphene electrode can be attributed to the fast electrolyte ion transport in the meso/macro channels and the rapid and reversible charge adsorption with negligible transport distance in the surface micropores.

  17. Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide

    Wu, Qiong; Sun, Ying; Ma, Pinyi; Zhang, Di; Li, Shuo; Wang, Xinghua; Song, Daqian

    2016-01-01

    A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL"−"1, which is 32 times lower than that of graphene oxide-based biosensor. - Highlights: • A sensitive and versatile SPR biosensor was constructed for detection of pig IgG. • Biofunctional gold nanostars were used to amplify the response signals. • The strategy employed carboxyl-functionalized graphene oxide as biosensing substrate. • The detection limit of the proposed biosensor is 32 times lower than that of graphene oxide-based biosensor.

  18. Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide

    Wu, Qiong; Sun, Ying; Ma, Pinyi; Zhang, Di; Li, Shuo; Wang, Xinghua; Song, Daqian, E-mail: songdq@jlu.edu.cn

    2016-03-24

    A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL{sup −1}, which is 32 times lower than that of graphene oxide-based biosensor. - Highlights: • A sensitive and versatile SPR biosensor was constructed for detection of pig IgG. • Biofunctional gold nanostars were used to amplify the response signals. • The strategy employed carboxyl-functionalized graphene oxide as biosensing substrate. • The detection limit of the proposed biosensor is 32 times lower than that of graphene oxide-based biosensor.

  19. Carbohydrazide-dependent reductant for preparing nitrogen-doped graphene hydrogels as electrode materials in supercapacitor

    Jiang, Man [Resources and Environmental Engineering, Shandong University of Technology, Zibo 255049 (China); Xing, Ling-Bao, E-mail: lbxing@sdut.edu.cn [School of Chemical Engineering, Shandong University of Technology, Zibo 255049 (China); Zhang, Jing-Li; Hou, Shu-Fen; Zhou, Jin; Si, Weijiang; Cui, Hongyou [School of Chemical Engineering, Shandong University of Technology, Zibo 255049 (China); Zhuo, Shuping, E-mail: zhuosp_academic@yahoo.com [School of Chemical Engineering, Shandong University of Technology, Zibo 255049 (China)

    2016-04-15

    Graphical abstract: - Highlights: • Three-dimensional nitrogen-doped graphene hydrogels (NGHs) were prepared. • Carbohydrazide was used as reducing and doping agents. • NGHs exhibited relatively good electrochemical properties in supercapacitor. • NGHs with different doping of N demonstrated different performances in supercapacitors. - Abstract: Three-dimensional (3D) nitrogen-doped graphene hydrogels (NGHs) are designed and synthesized in an efficient and fast way by using a strong reductant of carbohydrazide as reducing and doping agent in an aqueous solution of graphene oxide (GO). The transformation of GO suspension to the hydrogels can be completed in 1 h, which can be confirmed by X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). With adding different amounts of carbohydrazide, the obtained NGHs behave different doping of N and unlike performances in supercapacitors, which can be demonstrated by elemental analysis and X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), N{sub 2} sorption experiments, and electrochemical measurements, respectively. According to the network architectures, the NGHs all exhibited high specific capacitance, NGHs-1, NGHs-2, NGHs-5 and NGHs-10 showed specific capacitance at 167.7, 156.8, 140.4 and 119.3 F g{sup −1} at 1 A g{sup −1} in KOH electrolyte. The specific capacitance can still be maintained for 80.5, 79.5, 80.3 and 78.6% with an increase of the discharging current density of 10 A g{sup −1}, respectively. More interestingly, the NGHs-1 based supercapacitor also exhibited good electrochemical stability and high degree of reversibility in the long-term cycling test (81.5% retention after 4000 cycles).

  20. Carbohydrazide-dependent reductant for preparing nitrogen-doped graphene hydrogels as electrode materials in supercapacitor

    Jiang, Man; Xing, Ling-Bao; Zhang, Jing-Li; Hou, Shu-Fen; Zhou, Jin; Si, Weijiang; Cui, Hongyou; Zhuo, Shuping

    2016-01-01

    Graphical abstract: - Highlights: • Three-dimensional nitrogen-doped graphene hydrogels (NGHs) were prepared. • Carbohydrazide was used as reducing and doping agents. • NGHs exhibited relatively good electrochemical properties in supercapacitor. • NGHs with different doping of N demonstrated different performances in supercapacitors. - Abstract: Three-dimensional (3D) nitrogen-doped graphene hydrogels (NGHs) are designed and synthesized in an efficient and fast way by using a strong reductant of carbohydrazide as reducing and doping agent in an aqueous solution of graphene oxide (GO). The transformation of GO suspension to the hydrogels can be completed in 1 h, which can be confirmed by X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FT-IR). With adding different amounts of carbohydrazide, the obtained NGHs behave different doping of N and unlike performances in supercapacitors, which can be demonstrated by elemental analysis and X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), N_2 sorption experiments, and electrochemical measurements, respectively. According to the network architectures, the NGHs all exhibited high specific capacitance, NGHs-1, NGHs-2, NGHs-5 and NGHs-10 showed specific capacitance at 167.7, 156.8, 140.4 and 119.3 F g"−"1 at 1 A g"−"1 in KOH electrolyte. The specific capacitance can still be maintained for 80.5, 79.5, 80.3 and 78.6% with an increase of the discharging current density of 10 A g"−"1, respectively. More interestingly, the NGHs-1 based supercapacitor also exhibited good electrochemical stability and high degree of reversibility in the long-term cycling test (81.5% retention after 4000 cycles).

  1. Biocompatibility of poly(lactic acid) with incorporated graphene-based materials

    Pinto, Artur Moreira; Moreira, Susana Margarida Gomes; Gonçalves, Inês; Gama, F. M.; Mendes, Adélio; Magalhães, Fernão D.

    2013-01-01

    The incorporation of graphene-based materials has been shown to improve mechanical properties of poly(lactic acid) (PLA). In this work, PLA films and composite PLA films incorporating two graphene-based materials – graphene oxide (GO) and graphene nanoplatelets (GNP) – were prepared and characterized regarding not only biocompatibility, but also surface topography, chemistry and wettability. The presence of both fillers changed the films surface topography, increasing the roughness, and modif...

  2. Optimization of Graphene Conductive Ink with 73 wt% Graphene Contents.

    Xu, Chang-Yan; Shi, Xiao-Mei; Guo, Lu; Wang, Xi; Wang, Xin-Yi; Li, Jian-Yu

    2018-06-01

    With the pace of development accelerating in printed electronics, the fabrication and application of conductive ink have been brought into sharp focus in recent years. The discovery of graphene also unfolded a vigorous research campaign. In this paper, we prepared graphene conductive ink and explored the feasibility of applying the ink to flexible paper-based circuit. Since experimental study concentrating upon ink formulation was insufficient, orthogonal test design was used in the optimization of preparation formula of conductive ink for the first time. The purpose of this study was to determine the effect of constituent dosage on conductivity of graphene conductive ink, so as to obtain the optimized formula and prepare graphene conductive ink with good conductivity. Characterization of optimized graphene conductive ink we fabricated showed good adhesion to substrate and good resistance to acid and water. The graphene concentration of the optimized ink reached 73.17 wt% solid content. Particle size distribution of graphene conductive ink was uniform, which was about 1940 nm. Static surface tension was 28.9 mN/m and equilibrium contact angle was 23°, demonstrating that conductive ink had good wettability. Scanning Electron Microscope (SEM) analysis was also investigated, moreover, the feasibility of lightening a light-emitting diode (LED) light was verified. The graphene conductive ink with optimized formula can be stored for almost eight months, which had potential applications in flexible paper-based circuit in the future.

  3. Tuning the Reactivity of Graphene by Surface Phase Orientation

    Plšek, Jan; Kovaříček, Petr; Valeš, Václav; Kalbáč, Martin

    2017-01-01

    Roč. 23, č. 8 (2017), s. 1839-1845 ISSN 0947-6539 R&D Projects: GA ČR(CZ) GAP208/12/1062; GA MŠk(CZ) LM2015073 Grant - others:AVČR PPPLZ(CZ) L200401551 Institutional support: RVO:61388955 Keywords : chemical-vapor-deposition * fluorinated graphene * raman-spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 5.317, year: 2016

  4. Evolution effects of the copper surface morphology on the nucleation density and growth of graphene domains at different growth pressures

    Hedayat, Seyed Mahdi [Transport Phenomena & Nanotechnology Lab., School of Chemical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of); Karimi-Sabet, Javad, E-mail: j_karimi@alum.sharif.edu [NFCRS, Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of); Shariaty-Niassar, Mojtaba, E-mail: mshariat@ut.ac.ir [Transport Phenomena & Nanotechnology Lab., School of Chemical Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of)

    2017-03-31

    Highlights: • Manipulation of the Cu surface morphology in a wide range by electropolishing treatment. • Comparison of the nucleation density of graphene at low pressure and atmospheric pressure CVD processes. • Controlling the evolution of the Cu surface morphology inside a novel confined space. • Growth of large-size graphene domains. - Abstract: In this work, we study the influence of the surface morphology of the catalytic copper substrate on the nucleation density and the growth rate of graphene domains at low and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) processes. In order to obtain a wide range of initial surface morphology, precisely controlled electropolishing methods were developed to manipulate the roughntreess value of the as-received Cu substrate (RMS = 30 nm) to ultra-rough (RMS = 130 nm) and ultra-smooth (RMS = 2 nm) surfaces. The nucleation and growth of graphene domains show obviously different trends at LPCVD and APCVD conditions. In contrast to APCVD condition, the nucleation density of graphene domains is almost equal in substrates with different initial roughness values at LPCVD condition. We show that this is due to the evolution of the surface morphology of the Cu substrate during the graphene growth steps. By stopping the surface sublimation of copper substrate in a confined space saturated with Cu atoms, the evolution of the Cu surface was impeded. This results in the reduction of the nucleation density of graphene domains up to 24 times in the pre-smoothed Cu substrates at LPCVD condition.

  5. Evolution effects of the copper surface morphology on the nucleation density and growth of graphene domains at different growth pressures

    Hedayat, Seyed Mahdi; Karimi-Sabet, Javad; Shariaty-Niassar, Mojtaba

    2017-01-01

    Highlights: • Manipulation of the Cu surface morphology in a wide range by electropolishing treatment. • Comparison of the nucleation density of graphene at low pressure and atmospheric pressure CVD processes. • Controlling the evolution of the Cu surface morphology inside a novel confined space. • Growth of large-size graphene domains. - Abstract: In this work, we study the influence of the surface morphology of the catalytic copper substrate on the nucleation density and the growth rate of graphene domains at low and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) processes. In order to obtain a wide range of initial surface morphology, precisely controlled electropolishing methods were developed to manipulate the roughntreess value of the as-received Cu substrate (RMS = 30 nm) to ultra-rough (RMS = 130 nm) and ultra-smooth (RMS = 2 nm) surfaces. The nucleation and growth of graphene domains show obviously different trends at LPCVD and APCVD conditions. In contrast to APCVD condition, the nucleation density of graphene domains is almost equal in substrates with different initial roughness values at LPCVD condition. We show that this is due to the evolution of the surface morphology of the Cu substrate during the graphene growth steps. By stopping the surface sublimation of copper substrate in a confined space saturated with Cu atoms, the evolution of the Cu surface was impeded. This results in the reduction of the nucleation density of graphene domains up to 24 times in the pre-smoothed Cu substrates at LPCVD condition.

  6. Surface study of platinum decorated graphene towards adsorption of NH{sub 3} and CH{sub 4}

    Rad, Ali Shokuhi, E-mail: a.shokuhi@gmail.com [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Pazoki, Hossein; Mohseni, Soheil [Department of Chemical Engineering, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Zareyee, Daryoush [Department of Chemistry, Qaemshahr Branch, Islamic Azad University, Qaemshahr (Iran, Islamic Republic of); Peyravi, Majid [Faculty of Chemical Engineering, Babol University of Technology, Babol (Iran, Islamic Republic of)

    2016-10-01

    To distinguish the potential of graphene sensors, there is a need to recognize the interaction between graphene sheet and adsorbing molecules. We used density functional theory (DFT) calculations to study the properties of pristine as well as Pt-decorated graphene sheet upon adsorption of NH{sub 3} and CH{sub 4} on its surface to exploit its potential to be as gas sensors for them. We found much higher adsorption, higher charge transfer, lower intermolecular distance, and higher orbital hybridizing upon adsorption of NH{sub 3} and CH{sub 4} gas molecules on Pt-decorated graphene compared to pristine graphene. Also our calculations reveal that the adsorption energies on Pt-decorated graphene sheet are in order of NH{sub 3} >CH{sub 4} which could be corresponded to the order of their sensitivity on this modified surface. We used orbital analysis including density of states as well as frontier molecular orbital study for all analyte-surface systems to more understanding the kind of interaction (physisorption or chemisorption). Consequently, the Pt-decorated graphene can transform the existence of NH{sub 3} and CH{sub 4} molecules into electrical signal and it may be potentially used as an ideal sensor for detection of NH{sub 3} and CH{sub 4} in ambient situation. - Highlights: • Pt-decorated graphene was investigated as an adsorbent for NH{sub 3} and CH{sub 4}. • Much higher adsorption of NH{sub 3} and CH{sub 4} on Pt-decorated graphene than pristine graphene. • Higher adsorption of NH{sub 3} compared to CH{sub 4} on Pt-decorated graphene. • Pt influences the electronic structure of graphene.

  7. Preparation and characterization of three-dimensional scaffolds based on hydroxypropyl chitosan-graft-graphene oxide.

    Sivashankari, P R; Moorthi, A; Abudhahir, K Mohamed; Prabaharan, M

    2018-04-15

    Hydroxypropyl chitosan (HPCH), a water soluble derivative of chitosan, is widely considered for tissue engineering and wound healing applications due to its biocompatibility and biodegradability. Graphene oxide (GO) is a carbon-based nanomaterial which is capable of imparting desired properties to the scaffolds. Hence, the integration of GO into HPCH could allow for the production of HPCH-based scaffolds with improved swelling character, mechanical strength, and stability aimed at being used in tissue engineering. In this study, hydroxypropyl chitosan-graft-graphene oxide (HPCH-g-GO) with varying GO content (0.5, 1, 3 and 4wt.%) was prepared using HPCH and GO as a tissue engineering scaffold material. The formation of HPCH-g-GO was confirmed by FTIR and XRD analysis. Using the HPCH-g-GO as a matrix material and glutaraldehyde as a crosslinking agent, the three dimensional (3D) porous scaffolds were fabricated by the freeze-drying method. The HPCH-g-GO scaffolds exhibited uniform porosity as observed in SEM analysis. The pore size and porosity reduced as the content of GO was increased. These scaffolds presented good swelling capacity, water retention ability, mechanical strength and in vitro degradation properties. The HPCH-g-GO scaffolds irrespective of their GO content demonstrated good cell viability when compared to control. Altogether, these results suggest that HPCH-g-GO scaffolds can be used as potential tissue engineering material. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Preparation of graphene oxide-manganese dioxide for highly efficient adsorption and separation of Th(IV)/U(VI).

    Pan, Ning; Li, Long; Ding, Jie; Li, Shengke; Wang, Ruibing; Jin, Yongdong; Wang, Xiangke; Xia, Chuanqin

    2016-05-15

    Manganese dioxide decorated graphene oxide (GOM) was prepared via fixation of crystallographic MnO2 (α, γ) on the surface of graphene oxide (GO) and was explored as an adsorbent material for simultaneous removal of thorium/uranium ions from aqueous solutions. In single component systems (Th(IV) or U(VI)), the α-GOM2 (the weight ratio of GO/α-MnO2 of 2) exhibited higher maximum adsorption capacities toward both Th(IV) (497.5mg/g) and U(VI) (185.2 mg/g) than those of GO. In the binary component system (Th(IV)/U(VI)), the saturated adsorption capacity of Th(IV) (408.8 mg/g)/U(VI) (66.8 mg/g) on α-GOM2 was also higher than those on GO. Based on the analysis of various data, it was proposed that the adsorption process may involve four types of molecular interactions including coordination, electrostatic interaction, cation-pi interaction, and Lewis acid-base interaction between Th(IV)/U(VI) and α-GOM2. Finally, the Th(IV)/U(VI) ions on α-GOM2 can be separated by a two-stage desorption process with Na2CO3/EDTA. Those results displayed that the α-GOM2 may be utilized as an potential adsorbent for removing and separating Th(IV)/U(VI) ions from aqueous solutions. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Density functional theory study of elemental mercury adsorption on boron doped graphene surface decorated by transition metals

    Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Wongnongwa, Yutthana [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210 (Thailand); Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathum Thani 12120 (Thailand)

    2016-01-30

    Graphical abstract: Decoration of Pd{sub 4}-A (square planar) on B-doped graphene significantly promotes Hg{sup 0} adsorption, a single site of Pd{sub 4} cluster on BDG could strongly adsorb up to six Hg atoms. - Highlights: • Transition metal atom and cluster binds strongly on B-doped graphene surface. • Decoration of transition metal on B-doped graphene significantly promotes Hg{sup 0} adsorption. • Adsorption strength of Hg{sup 0} atom on metal decorated B-doped graphene: Pd > Pt > Ru > W > Cu. • One site decorated Pd4 cluster adsorbed Hg{sup 0} strongly up to six atoms.

  10. Preparation of graphene oxide-wrapped carbon sphere@silver spheres for high performance chlorinated phenols sensor

    Gan, Tian, E-mail: gantsjy@163.com [College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000 (China); State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China); Lv, Zhen; Sun, Junyong; Shi, Zhaoxia; Liu, Yanming [College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000 (China)

    2016-01-25

    Highlights: • Hierarchical CS@Ag@GO composite was obtained by a simple solution route. • Signal amplification is achieved for sensitive detection of chlorinated phenols. • The low-cost method exhibits wide concentration range and acceptable accuracy. • The method can be successfully applied to detect chlorinated phenols in waters. - Abstract: A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment. The CS@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity, which was further mechanically protected by graphene oxide (GO) nanolayers to fabricate intriguing configuration, which was beneficial for efficiently preventing the aggregation and oxidation of AgNPs and improving the electrical conductivity through intimate contact. By immobilizing this special material on electrode surface, the CS@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The tailored structure, fast electron transfer ability and facile preparation of CS@Ag@GO made it a promising electrode material for practical applications in phenols sensing.

  11. Detection of DNA hybridization using graphene-coated black phosphorus surface plasmon resonance sensor

    Pal, Sarika; Verma, Alka; Raikwar, S.; Prajapati, Y. K.; Saini, J. P.

    2018-05-01

    In this paper, graphene-coated black phosphorus at the metal surface for the detection of DNA hybridization event is numerically demonstrated. The strategy consists of placing the sensing medium on top of black phosphorus-graphene-coated SPR which interfaces with phosphate-buffered saline solution carrying single-stranded DNA. Upon hybridization with its complementary DNA, desorption of the nanostructures takes place and thus enables the sensitive detection of the DNA hybridization event. The proposed sensor exhibits a sensitivity (125 ο/RIU), detection accuracy (0.95) and quality factor (13.62 RIU-1) for complementary DNA. In comparison with other reported papers, our suggested sensor provides much better performance. Thus, this label-free DNA detection platform should spur off new interest towards the use of black phosphorus-graphene-coated SPR interfaces.

  12. Enhancement in sensitivity of graphene-based zinc oxide assisted bimetallic surface plasmon resonance (SPR) biosensor

    Kumar, Rajeev; Kushwaha, Angad S.; Srivastava, Monika; Mishra, H.; Srivastava, S. K.

    2018-03-01

    In the present communication, a highly sensitive surface plasmon resonance (SPR) biosensor with Kretschmann configuration having alternate layers, prism/zinc oxide/silver/gold/graphene/biomolecules (ss-DNA) is presented. The optimization of the proposed configuration has been accomplished by keeping the constant thickness of zinc oxide (32 nm), silver (32 nm), graphene (0.34 nm) layer and biomolecules (100 nm) for different values of gold layer thickness (1, 3 and 5 nm). The sensitivity of the proposed SPR biosensor has been demonstrated for a number of design parameters such as gold layer thickness, number of graphene layer, refractive index of biomolecules and the thickness of biomolecules layer. SPR biosensor with optimized geometry has greater sensitivity (66 deg/RIU) than the conventional (52 deg/RIU) as well as other graphene-based (53.2 deg/RIU) SPR biosensor. The effect of zinc oxide layer thickness on the sensitivity of SPR biosensor has also been analysed. From the analysis, it is found that the sensitivity increases significantly by increasing the thickness of zinc oxide layer. It means zinc oxide intermediate layer plays an important role to improve the sensitivity of the biosensor. The sensitivity of SPR biosensor also increases by increasing the number of graphene layer (upto nine layer).

  13. Ionic liquid assisted mechanochemical preparation and electrochemical performance of graphene nanosheets/polypyrrole composite for supercapacitor

    Lu, X.J.; Zhang, X.G.; Yang, S.D.; Hao, L. [Nanjing Univ. of Aeronautics and Astronautics (China). College of Material Science and Engineering

    2010-07-01

    Carbons, metal oxides, and conducting polymers are the main materials used to construct supercapacitor electrodes. As a conducting polymer, polypyrrole (PPy) is both environmentally friendly and has high capacitive characteristics. In this study, an ionic liquid (IL) assisted mechanochemical technique was used to prepare a graphene nanosheet (GNS) PPy composite. 1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeC1{sub 4}]) was used as a bifunctional IL, as both the dispersant of the GNS and as the oxidant of the PPy. The specific capacitance of the GNS, PPy, and GNS-PPy composites were calculated. Results of the study suggested that the superior performance of the GNS-PPy composite was caused by the synergistic effect between the GNS and PPy. Use of the GNS as a supporting material provided a relatively large area on which to deposit PPy particles, which allowed more PPy to participate in faradaic redox reactions. Electrical conductivity was also improved. 2 refs., 1 fig.

  14. Physical Properties Investigation of Reduced Graphene Oxide Thin Films Prepared by Material Inkjet Printing

    Veronika Schmiedova

    2017-01-01

    Full Text Available The article is focused on the study of the optical properties of inkjet-printed graphene oxide (GO layers by spectroscopic ellipsometry. Due to its unique optical and electrical properties, GO can be used as, for example, a transparent and flexible electrode material in organic and printed electronics. Spectroscopic ellipsometry was used to characterize the optical response of the GO layer and its reduced form (rGO, obtainable, for example, by reduction of prepared layers by either annealing, UV radiation, or chemical reduction in the visible range. The thicknesses of the layers were determined by a mechanical profilometer and used as an input parameter for optical modeling. Ellipsometric spectra were analyzed according to the dispersion model and the influence of the reduction of GO on optical constants is discussed. Thus, detailed analysis of the ellipsometric data provides a unique tool for qualitative and also quantitative description of the optical properties of GO thin films for electronic applications.

  15. Application of indigenously prepared graphene oxide on onion in combination with gamma irradiation

    Khade, H.D.; Gadly, T.; Jain, M.P.; Ghosh, S.K.

    2017-01-01

    Onion (Allium cepa), a commonly used vegetable, it ranks third in the global production of major vegetables. Due to its delicious taste, flavour and pungency used in many culinary preparations and it has several medicinal properties also. The preservation of onion is a major thrust area since a long ago. In this study farm fresh onions of kharif season were harvested from farms nearby town of Dist. Satara, Maharashtra and were used for study. Variety named Lonand (Agri Dark Red (ADR)) were selected for study. Graphene oxide was sprayed and dried at ambient temperature for half an hour. Suitably packed in nylon mesh bag having capacity 3 Kg. Gamma radiation dose 70 Gy were given at Food package irradiator, FIPLY (dose rate 3.5 Gy/Min) at the centre

  16. Preparation of three dimensional graphene foam–WO3 nanocomposite with enhanced visible light photocatalytic activity

    Azimirad, R.; Safa, S.

    2015-01-01

    Three dimensional graphene foam (3D GF) was synthesized by chemical vapor deposition (CVD) on a nickel foam skeleton. After dissolving the nickel foam, the obtaining 3D GF was used as a highly porous conductive substrate for nucleation and growth of WO 3 particles. Scanning electron microscopy (SEM) and Raman spectroscopy was employed to ensure the quality of the prepared GFs and to judge about the 3D GF–WO 3 chemical structure. The WO 3 characteristic Raman peaks centered at 726, and 809 cm −1 are slightly broadened and displaced to lower wavelength in the 3D GF–WO 3 nanocomposite, as compared to the corresponding peaks of the bare tungsten oxide. This phenomenon confirms the formation of W–C and W–O–C bonds in composite material which is important for faster transferring the photoexcited electrons to graphene 3D network as an exceptional electron acceptor. The 3D GF−WO 3 composite material was applied in photocatalytic degradation of Rhodamine B dye. It was observed that the annealed samples show an excellent photocatalytic performance relative to the as-prepared 3D GF−WO 3 samples and bare WO 3 , which is ascribed to the lower electron/hole recombination through the formation of W–C and W–O–C bonds. - Highlights: • 3D GF synthesized by CVD on a nickel foam as a highly porous conductive substrate. • WO 3 nanoparticles coated on 3D GF by dip-coating. • 3D GF−WO 3 shows an excellent photocatalytic degradation of Rhodamine B dye. • Better photocatalytic properties assigned to the formation of W–C and W–O–C bonds

  17. A facile strategy for the reduction of graphene oxide and its effect on thermal conductivity of epoxy based composites

    F. Xie

    2016-06-01

    Full Text Available A facile and efficient approach to reduce graphene oxide with Al particles and potassium hydroxide was developed at moderate temperature and the graphene/epoxy composite was prepared by mould casting method. The as-prepared graphene has been confirmed by Transmission electron microscopy, Fourier transform infrared spectrometer, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Thermal gravimetric analysis. This provides a new green way to synthesize graphene with high surface area and opens another opportunity for the production of graphene. Effects of graphene on thermal conductivity, thermal stability and microstructures of the epoxy-based composite were also investigated. The results showed that thermal conductivity of the composite exhibited a remarkable improvement with increasing content of graphene and thermal conductivity could reach 1.192 W/(m*K when filled with 3 wt% graphene. Moreover, graphene/epoxy composite exhibits good thermal stability with 3 wt% graphene.

  18. Density functional study of TaSin (n = 1-3, 12) clusters adsorbed to graphene surface

    Guo Ping; Zheng Lin; Zheng Jiming; Zhang Ruizhi; Yang Luna; Ren, Zhaoyu

    2011-01-01

    A plane-wave density functional theory (DFT) calculations have been performed to investigate structural and electronic properties of TaSi n (n = 1-3, 12) clusters supported by graphene surface. The resulting adsorption structures are described and discussed in terms of stability, bonding, and electron transfer between the cluster and the graphene. The TaSi n clusters on graphene surface favor their free-standing ground-state structures. Especially in the cases of the linear TaSi 2 and the planar TaSi 3 , the graphene surface may catalyze the transition of the TaSi n clusters from an isomer of lower dimensionality into the ground-state structure. The adsorption site and configuration of TaSi n on graphene surface are dominated by the interaction between Ta atom and graphene. Ta atom prefers to adsorb on the hollow site of graphene, and Si atoms tend to locate on the bridge site. Further, the electron transfer is found to proceed from the cluster to the surface for n = 1 and 2, while its direction reverses as n > 2. For the case of TaSi, chemisorption is shown to prevail over physisorption as the dominant mode of surface-adsorbate interaction by charge density analysis.

  19. Hydrophilic Graphene Preparation from Gallic Acid Modified Graphene Oxide in Magnesium Self-Propagating High Temperature Synthesis Process

    Cao, Lei; Li, Zhenhuan; Su, Kunmei; Cheng, Bowen

    2016-10-01

    Hydrophilic graphene sheets were synthesized from a mixture of magnesium and gallic acid (GA) modified graphene oxide (GO) in a self-propagating high-temperature synthesis (SHS) process, and hydrophilic graphene sheets displayed the higher C/O ratio (16.36), outstanding conductivity (~88900 S/m) and excellent water-solubility. GO sheets were connected together by GA, and GA was captured to darn GO structure defects through the formation of hydrogen bonds and ester bonds. In SHS process, the most oxygen ions of GO reacted with magnesium to prevent the escape of carbon dioxide and carbon monoxide to from the structure defects associated with vacancies, and GA could take place the high-temperature carbonization, during which a large-area graphene sheets formed with a part of the structure defects being repaired. When only GO was reduced by magnesium in SHS process, and the reduced GO (rGO) exhibited the smaller sheets, the lower C/O ratio (15.26), the weaker conductivity (4200 S/m) and the poor water-solubility because rGO inevitably left behind carbon vacancies and topological defects. Therefore, the larger sheet, less edge defects and free structure defects associated with vacancies play a key role for graphene sheets good dispersion in water.

  20. Promising applications of graphene and graphene-based nanostructures

    Nguyen, Bich Ha; Hieu Nguyen, Van

    2016-06-01

    The present article is a review of research works on promising applications of graphene and graphene-based nanostructures. It contains five main scientific subjects. The first one is the research on graphene-based transparent and flexible conductive films for displays and electrodes: efficient method ensuring uniform and controllable deposition of reduced graphene oxide thin films over large areas, large-scale pattern growth of graphene films for stretchble transparent electrodes, utilization of graphene-based transparent conducting films and graphene oxide-based ones in many photonic and optoelectronic devices and equipments such as the window electrodes of inorganic, organic and dye-sensitized solar cells, organic light-emitting diodes, light-emitting electrochemical cells, touch screens, flexible smart windows, graphene-based saturated absorbers in laser cavities for ultrafast generations, graphene-based flexible, transparent heaters in automobile defogging/deicing systems, heatable smart windows, graphene electrodes for high-performance organic field-effect transistors, flexible and transparent acoustic actuators and nanogenerators etc. The second scientific subject is the research on conductive inks for printed electronics to revolutionize the electronic industry by producing cost-effective electronic circuits and sensors in very large quantities: preparing high mobility printable semiconductors, low sintering temperature conducting inks, graphene-based ink by liquid phase exfoliation of graphite in organic solutions, and developing inkjet printing technique for mass production of high-quality graphene patterns with high resolution and for fabricating a variety of good-performance electronic devices, including transparent conductors, embedded resistors, thin-film transistors and micro supercapacitors. The third scientific subject is the research on graphene-based separation membranes: molecular dynamics simulation study on the mechanisms of the transport of

  1. Superamphiphobic Surfaces Prepared by Coating Multifunctional Nanofluids.

    Esmaeilzadeh, Pouriya; Sadeghi, Mohammad Taghi; Bahramian, Alireza; Fakhroueian, Zahra; Zarbakhsh, Ali

    2016-11-23

    Construction of surfaces with the capability of repelling both water and oil is a challenging issue. We report the superamphiphobic properties of mineral surfaces coated with nanofluids based on synthesized Co-doped and Ce-doped Barium Strontium Titanate (CoBST and CeBST) nanoparticles and fluorochemicals of trichloro(1H,1H,2H,2H-perfluorooctyl)silane (PFOS) and polytetrafluoroethylene (PTFE). Coating surfaces with these nanofluids provides both oil (with surface tensions as low as 23 mN/m) and water repellency. Liquids with high surface tension (such as water and ethylene glycol) roll off the coated surface without tilting. A water drop released from 8 mm above the coated surface undergoes first a lateral displacement from its trajectory and shape deformation, striking the surface after 23 ms, bouncing and rolling off freely. These multifunctional coating nanofluids impart properties of self-cleaning. Applications include coating surfaces where cleanliness is paramount such as in hospitals and domestic environments as well as the maintenance of building facades and protection of public monuments from weathering. These superamphiphobic-doped nanofluids have thermal stability up to 180 °C; novel industrial applications include within fracking and the elimination of condensate blockage in gas reservoirs.

  2. Enhanced photocatalytic activity of ZnO–graphene nanocomposites prepared by microwave synthesis

    Herring, Natalie P.; Almahoudi, Serial H.; Olson, Chelsea R.; El-Shall, M. Samy

    2012-01-01

    This work reports a simple one-step synthesis of ZnO nanopyramids supported on reduced graphene oxide (RGO) nanosheets using microwave irradiation (MWI) of zinc acetate and GO in the presence of a mixture of oleic acid and oleylamine. The rapid decomposition of zinc acetate by MWI in the presence of the mixture of oleic acid and oleylamine results in the formation of hexagonal ZnO nanopyramids. GO has a high affinity for absorbing MWI, which results in a high local heating effect around the GO nanosheets and facilitates the reduction of GO by the oleylamine. The RGO nanosheets act as heterogeneous surface sites for the nucleation and growth of the ZnO nanopyramids. Using ligand exchange, the ZnO–RGO nanocomposites can be dispersed in an aqueous medium, thus allowing their use as photocatalysts for the degradation of the malachite green dye in water. The ZnO–RGO nanocomposites show enhanced photocatalytic activity for the degradation of the dye over the unsupported ZnO nanopyramids. The enhanced activity is attributed to efficient charge transfer of the photogenerated electrons in the conduction band of ZnO to graphene. This enhances the oxidative pathway of the holes generated in the valence band of ZnO which can effectively lead to the degradation and mineralization of the malachite green. The ZnO nanopyramids supported on RGO could have improved performance in other photocatalytic reactions and also in solar energy conversion.

  3. Powder, paper and foam of few-layer graphene prepared in high yield by electrochemical intercalation exfoliation of expanded graphite.

    Wu, Liqiong; Li, Weiwei; Li, Peng; Liao, Shutian; Qiu, Shengqiang; Chen, Mingliang; Guo, Yufen; Li, Qi; Zhu, Chao; Liu, Liwei

    2014-04-09

    A facile and high-yield approach to the preparation of few-layer graphene (FLG) by electrochemical intercalation exfoliation (EIE) of expanded graphite in sulfuric acid electrolyte is reported. Stage-1 H2SO4-graphite intercalation compound is used as a key intermediate in EIE to realize the efficient exfoliation. The yield of the FLG sheets (papers made of the FLG flakes retain excellent conductivity (≈24,500 S m(-1)). Three-dimensional (3D) graphene foams with light weight are fabricated from the FLG flakes by the use of Ni foams as self-sacrifice templates. Furthermore, 3D graphene/Ni foams without any binders, which are used as supercapacitor electrodes in aqueous electrolyte, provide the specific capacitance of 113.2 F g(-1) at a current density of 0.5 A g(-1), retaining 90% capacitance after 1000 cycles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Graphene quantum dots prepared from glucose as optical sensor for glucose

    Shehab, Mona, E-mail: mona_shehab@alexu.edu.eg [Materials Science Department, Institute of Graduate Studies & Research, Alexandria University (Egypt); General Bureau of Beheira Governorate, Damanhour, Beheira 22111 (Egypt); Ebrahim, Shaker; Soliman, Moataz [Materials Science Department, Institute of Graduate Studies & Research, Alexandria University (Egypt)

    2017-04-15

    Quantum Dots (QDs) show promise materials for many technological applications. In this work we utilized a simple route to prepare graphene quantum dots (GQDs) using glucose carbonization. GQDs functionalized with phenylboronic acid receptors were employed as a sensing material for a nonenzymatic glucose sensor. Photoluminance spectra of GQDs were used as a property of optical sensor for glucose. GQDs considered as a good sensing probe because of its low toxicity, high photoluminance, water solubility and excelent photochemical properties. The prepared GQDs were characterized using UV-visible, Raman and photoluminance spectroscopies, X-ray diffraction and high resolution transmission electron microscopy (HRTEM). HRTEM micrographs confirmed the preparation of 7–10 nm GQDs and the emission peak of the GQDs appeared at 450 nm. The developed sensor has linear response to glucose over a concentration range of 4–40 mM with a correlation coefficient of 0.97 and a low detection limit of approximately 3.0 mM.

  5. Preparation and electrochemistry of graphene nanosheets–multiwalled carbon nanotubes hybrid nanomaterials as Pd electrocatalyst support for formic acid oxidation

    Yang Sudong; Shen Chengmin; Lu Xiangjun; Tong Hao; Zhu Jiajia; Zhang Xiaogang; Gao Hongjun

    2012-01-01

    Highlights: ► Graphene nanosheets–MWCNTs (GNS–CNTs) composites as Pd electrocatalysts support were synthesized by in situ reduction method. ► The direct electrooxidation of HCOOH is improved on the GNS–CNTs based catalyst. ► Both activity and durability of GNS–CNTs based catalyst are improved greatly. ► Pd/GNS–CNTs catalysts exhibit excellent performance when the mass ratio of GO to CNTs is 5:1. - Abstract: Graphene nanosheets–MWCNTs (GNS–CNTs) composites were synthesized by in situ reduction method, and then palladium nanoparticles (NPs) were supported on the GNS–CNTs by a microwave-assisted polyol process. Microstructure measurements showed that the graphene nanosheets and the CNTs formed a uniform nanocomposite with CNTs absorbed on the graphene nanosheets surface and/or filled between the graphene nanosheets. Compared to Pd/Vulcan XC-72R carbon, Pd/GNS, or Pd/CNTs catalysts, the Pd/GNS–CNTs catalysts exhibit excellent electrocatalytic activity and stability for formic acid electro-oxidation when the mass ratio of GO to CNTs is 5:1. The superior performance of Pd/GNS–CNTs catalysts may arise from large surface area utilization for NPs and enhanced electronic conductivity of the supports. Therefore, the GNS–CNTs composite should be a promising carbon material for application as electrocatalyst support in fuel cells.

  6. Microwave-irradiated preparation of reduced graphene oxide-Ni nanostructures and their enhanced performance for catalytic reduction of 4-nitrophenol

    Qiu, Hanxun; Qiu, Feilong; Han, Xuebin; Li, Jing; Yang, Junhe

    2017-01-01

    Highlights: • Nickel nanoparticle-decorated reduced graphene-oxide nanostructures were prepared by an environmentally friendly, one-pot strategy via an efficient microwave irradiation approach. • Upon microwave irradiation, the composites could be prepared within only a few hundred seconds, much faster than using the widely used traditional hydrothermal methods that may take tens of hours generally. • The nanostructure exhibits superior catalytic activity and selectivity towards transforming the highly toxic nitroaromatic compounds to industrially useful intermediates • The corresponding kinetic reaction rate constant (κ) is even four-fold compared to pure Ni nanoparticles. - Abstract: Here we report an environmentally friendly, one-pot strategy toward preparation of nickel nanoparticle-decorated reduced graphene-oxide (Ni-RGO) nanostructures, by employing Ni(AC) 2 as nickel source and ethylene glycol as both solvent and reducing agent via a facile microwave irradiation heating approach. The results show that Ni nanoparticles with an average diameter of around 40 nm are homogeneously anchored onto the surface of RGO sheets. As compared to the pure Ni nanoparticles and RGO sheets, Ni-RGO composites with over 64 wt% loading of Ni nanoparticles possess superior catalytic activities and selectivity toward the reduction of 4-nitrophenol. The corresponding kinetic reaction rate constant (defined as κ) is even four-fold compared to pure Ni nanoparticles. Such promising composites show great potential for friendly treatment of industrial waste containing nitrophenol in a simple, sustainable and green way.

  7. Microwave-irradiated preparation of reduced graphene oxide-Ni nanostructures and their enhanced performance for catalytic reduction of 4-nitrophenol

    Qiu, Hanxun, E-mail: hxqiu@usst.edu.cn; Qiu, Feilong; Han, Xuebin; Li, Jing; Yang, Junhe, E-mail: jhyang@usst.edu.cn

    2017-06-15

    Highlights: • Nickel nanoparticle-decorated reduced graphene-oxide nanostructures were prepared by an environmentally friendly, one-pot strategy via an efficient microwave irradiation approach. • Upon microwave irradiation, the composites could be prepared within only a few hundred seconds, much faster than using the widely used traditional hydrothermal methods that may take tens of hours generally. • The nanostructure exhibits superior catalytic activity and selectivity towards transforming the highly toxic nitroaromatic compounds to industrially useful intermediates • The corresponding kinetic reaction rate constant (κ) is even four-fold compared to pure Ni nanoparticles. - Abstract: Here we report an environmentally friendly, one-pot strategy toward preparation of nickel nanoparticle-decorated reduced graphene-oxide (Ni-RGO) nanostructures, by employing Ni(AC){sub 2} as nickel source and ethylene glycol as both solvent and reducing agent via a facile microwave irradiation heating approach. The results show that Ni nanoparticles with an average diameter of around 40 nm are homogeneously anchored onto the surface of RGO sheets. As compared to the pure Ni nanoparticles and RGO sheets, Ni-RGO composites with over 64 wt% loading of Ni nanoparticles possess superior catalytic activities and selectivity toward the reduction of 4-nitrophenol. The corresponding kinetic reaction rate constant (defined as κ) is even four-fold compared to pure Ni nanoparticles. Such promising composites show great potential for friendly treatment of industrial waste containing nitrophenol in a simple, sustainable and green way.

  8. Graphene nanosheets preparation using magnetic nanoparticle assisted liquid phase exfoliation of graphite: The coupled effect of ultrasound and wedging nanoparticles.

    Hadi, Alireza; Zahirifar, Jafar; Karimi-Sabet, Javad; Dastbaz, Abolfazl

    2018-06-01

    This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic Fe 3 O 4 nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of Fe 3 O 4 particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of Fe 3 O 4 particle separation from graphene solution which arises from the magnetic nature of Fe 3 O 4 nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, Fe 3 O 4 nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Graphene from the chemistry lab; Graphen aus dem Chemielabor

    Muellen, Klaus [Max-Planck-Institut fuer Polymerforschung, Mainz (Germany)

    2012-08-15

    A material being discovered eight years ago and consisting of carbon with only one layer of atoms could revolutionize the electronics. So far, there are no suitable methods of preparation. From this point, the author of the contribution under consideration reports on the direct deposition of graphene on a metal surface with the formation of samples having a diameter of ten nanometers. Also graphene ribbons with a predetermined width or shape could be produced.

  10. Microstructure and tensile properties of bulk nanostructured aluminum/graphene composites prepared via cryomilling

    Li, J.L., E-mail: ljlhpu123@163.com; Xiong, Y.C.; Wang, X.D.; Yan, S.J.; Yang, C.; He, W.W.; Chen, J.Z.; Wang, S.Q.; Zhang, X.Y.; Dai, S.L.

    2015-02-25

    In order to develop high strength metal–matrix composites with acceptable ductility, bulk nanostructured aluminum–matrix composites reinforced with graphene nanoflakes were fabricated by cryomilling and hot extrusion processes. Microstructure and mechanical properties were characterized and determined using transmission electron microscopy, electron dispersion spectroscopy, as well as static tensile tests. The results show that, with an addition of only 0.5 wt% graphene nanoflakes, the bulk nanostructured aluminum/graphene composite exhibited increased strength and unsubdued ductility over pure aluminum. Besides, the mechanical properties of the composites with higher content of graphene nanoflakes were also measured and investigated. Above 1.0 wt% of graphene nanoflakes, however, this strengthening effect sharply dropped due to the clustering of graphene nanoflakes. Furthermore, the optimal addition of graphene nanoflakes into the nanocrystalline aluminum matrix was calculated and discussed.

  11. 3D graphene preparation via covalent amide functionalization for efficient metal-free electrocatalysis in oxygen reduction

    Ahmed, Mohammad Shamsuddin; Kim, Young-Bae

    2017-02-01

    3D and porous reduced graphene oxide (rGO) catalysts have been prepared with sp3-hybridized 1,4-diaminobutane (sp3-DABu, rGO-sp3-rGO) and sp2-hybridized 1,4-diaminobenzene (sp2-DABe, rGO-sp2-rGO) through a covalent amidation and have employed as a metal-free electrocatalyst for oxygen reduction reaction (ORR) in alkaline media. Both compounds have used as a junction between functionalized rGO layers to improve electrical conductivity and impart electrocatalytic activity to the ORR resulting from the interlayer charge transfer. The successful amidation and the subsequent reduction in the process of catalyst preparation have confirmed by X-ray photoelectron spectroscopy. A hierarchical porous structure is also confirmed by surface morphological analysis. Specific surface area and thermal stability have increased after successful the amidation by sp3-DABu. The investigated ORR mechanism reveals that both functionalized rGO is better ORR active than nonfunctionalized rGO due to pyridinic-like N content and rGO-sp3-rGO is better ORR active than rGO-sp2-rGO due to higher pyridinic-like N content and π-electron interaction-free interlayer charge transfer. Thus, the rGO-sp3-rGO has proven as an efficient metal-free electrocatalyst with better electrocatalytic activity, stability, and tolerance to the crossover effect than the commercially available Pt/C for ORR.

  12. Preparation and performance of a novel gel polymer electrolyte based on poly(vinylidene fluoride)/graphene separator for lithium ion battery

    Liu, Jiuqing; Wu, Xiufeng; He, Junying; Li, Jie; Lai, Yanqing

    2017-01-01

    Poly(vinylidenefluoride)/graphene (PVDF/graphene) gel polymer electrolyte is prepared via non-solvent induced phase separation (NIPS) technique for lithium ion battery application. The effect of graphene on the ion conductivity is investigated by AC impedance measurement. The relationship among the chemical structure, PVDF crystallinity, the graphene on macroporous formation and the ion conductivity are investigated. The results indicate that the graphene disperses homogenously in PVDF, and it also increases the porosity and decreases the crystallinity of the PVDF. At the same time, the unique structure increases the liquid uptake capability of PVDF/graphene polymer electrolyte. The ionic conductivity of the PVDF/graphene polymer electrolyte increases significantly from 1.85 mS cm"−"1 in pristine PVDF to 3.61 mS cm"−"1 with 0.002 wt% graphene. It is found that graphene not only increases the ionic conductivity but also markedly enhances the rate capability and the cycling performances of coin cell. This study shows that PVDF/graphene gel polymer electrolyte is a very promising material for lithium ion batteries.

  13. Aqueous Exfoliation of Graphite into Graphene Assisted by Sulfonyl Graphene Quantum Dots for Photonic Crystal Applications.

    Zeng, Minxiang; Shah, Smit A; Huang, Dali; Parviz, Dorsa; Yu, Yi-Hsien; Wang, Xuezhen; Green, Micah J; Cheng, Zhengdong

    2017-09-13

    We investigate the π-π stacking of polyaromatic hydrocarbons (PAHs) with graphene surfaces, showing that such interactions are general across a wide range of PAH sizes and species, including graphene quantum dots. We synthesized a series of graphene quantum dots with sulfonyl, amino, and carboxylic functional groups and employed them to exfoliate and disperse pristine graphene in water. We observed that sulfonyl-functionalized graphene quantum dots were able to stabilize the highest concentration of graphene in comparison to other functional groups; this is consistent with prior findings by pyrene. The graphene nanosheets prepared showed excellent colloidal stability, indicating great potential for applications in electronics, solar cells, and photonic displays which was demonstrated in this work.

  14. Graphene as a high impedance surface for ultra-wideband electromagnetic waves

    Aldrigo, Martino; Costanzo, Alessandra [Department of Electrical, Electronic, and Information Engineering “Guglielmo Marconi” – DEI, University of Bologna, Viale del Risorgimento, 2, 40132 Bologna (Italy); Dragoman, Mircea [National Institute for Research and Development in Microtechnology (IMT), P.O. Box 38-160, 023573 Bucharest (Romania); Dragoman, Daniela [Department of Physics, University of Bucharest, P.O. Box MG-11, 077125 Bucharest (Romania)

    2013-11-14

    The metals are regularly used as reflectors of electromagnetic fields emitted by antennas ranging from microwaves up to THz. To enhance the reflection and thus the gain of the antenna, metallic high impedance surfaces (HIS) are used. HIS is a planar array of continuous metallic periodic cell surfaces able to suppress surface waves, which cause multipath interference and backward radiation in a narrow bandwidth near the cell resonance. Also, the image currents are reduced, and therefore the antenna can be placed near the HIS. We demonstrate that graphene is acting as a HIS surface in a very large bandwidth, from microwave to THz, suppressing the radiation leakages better than a metal.

  15. The effect of surface characteristics of reduced graphene oxide on the performance of a pseudocapacitor

    Chang, M S; Kim, T; Kang, J H; Park, J; Park, C R

    2015-01-01

    In this research, we have analyzed the electrochemical characteristics of the different rGO/Co 3 O 4 composites prepared by controlling the rGO surface characteristics and its relationship between the growth of Co 3 O 4 nanoparticles and the performance of the pseudocapacitor. Reduced graphene oxide/cobalt oxide (rGO/Co 3 O 4 ) nanocomposites of different morphologies were prepared through the simple hydrothermal method. First, different kinds of graphite precursors, crumpled and planar with different properties, were used to determine the most suitable substrate to grow Co 3 O 4 nanoparticles. As a result, rGO/Co 3 O 4 composite synthesized from planar graphite shows a higher specific capacitance of 207.2, 170.1, and 141.5 Fg −1 at 1, 2, and 5 Ag −1 than the one prepared from crumpled graphite. In the second part, planar graphite, confirmed to be the most suitable substrate from the previous part, was oxidized under various oxidation conditions to increase the oxygen functional groups attached on the GO surfaces and observed to see how it affects the growth of Co 3 O 4 nanoparticles and its influence on the electrochemical performance of the rGO/Co 3 O 4 pseudocapacitor. As a result, the one with the largest amount of functional groups had the Co 3 O 4 nanoparticles well dispersed and grown on the rGO substrate in small nanoparticle sizes, as small as 5.9 nm, leading to an improved electrochemical performance. Thus, the specific capacitance with the least amount of oxygen functional groups are 207.2, 170.1, and 141.5 Fg −1 and for the largest amount of functional groups are 411.5, 371.4, and 292.7 Fg −1 , at 1, 2, and 5 Ag −1 respectively. This approach could become a guideline for the ideal fabrication of rGO/metal oxide composite for further research involving rGO based pseudocapacitors. (paper)

  16. Searching for magnetism in hydrogenated graphene: Using highly hydrogenated graphene prepared via birch reduction of graphite oxides

    Eng, A.Y.S.; Poh, H. L.; Šaněk, F.; Maryško, Miroslav; Matějková, Stanislava; Šofer, Z.; Pumera, M.

    2013-01-01

    Roč. 7, č. 7 (2013), s. 5930-5939 ISSN 1936-0851 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 ; RVO:61388963 Keywords : hydrogenated graphene * graphane * graphite oxide * ferromagnetism Subject RIV: BM - Solid Matter Physics ; Magnetism; CF - Physical ; Theoretical Chemistry (UOCHB-X) Impact factor: 12.033, year: 2013

  17. Manipulation of surface plasmon resonance of a graphene-based Au aperture antenna in visible and near-infrared regions

    Wan, Yuan; An, Yashuai; Tao, Zhi; Deng, Luogen

    2018-03-01

    Behaviors of surface plasmon resonance (SPR) of a graphene-based Au aperture antenna are investigated in visible and near-infrared (vis-NIR) regions. Compared with the SPR wavelength of a traditional Au aperture antenna, the SPR wavelength of the graphene-based Au aperture antenna shows a remarkable blue shift due to the redistribution of the electric field in the proposed structure. The electric field of the graphene-based Au aperture antenna is highly localized on the surface of the graphene in the aperture and redistributed to be a standing wave. Moreover, the SPR of a graphene-based Au aperture antenna is sensitive to the thickness and the refractive index of the dielectric layer, the graphene Fermi energy, the refractive index of the environment and the polarization direction of the incident light. Finally, we find the wavelength, intensity and phase of the reflected light of the graphene-based Au aperture antenna array can be actively modulated by varying the graphene Fermi energy. The proposed structure provides a promising platform for realizing a tunable optical filter, a highly sensitive refractive index sensor, and other actively tunable optical and optoelectronic devices.

  18. Dry transfer of chemical-vapor-deposition-grown graphene onto liquid-sensitive surfaces for tunnel junction applications

    Feng, Ying; Chen, Ke

    2015-01-01

    We report a dry transfer method that can tranfer chemical vapor deposition (CVD) grown graphene onto liquid-sensitive surfaces. The graphene grown on copper (Cu) foil substrate was first transferred onto a freestanding 4 μm thick sputtered Cu film using the conventional wet transfer process, followed by a dry transfer process onto the target surface using a polydimethylsiloxane stamp. The dry-transferred graphene has similar properties to traditional wet-transferred graphene, characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and electrical transport measurements. It has a sheet resistance of 1.6 ∼ 3.4 kΩ/□, hole density of (4.1 ∼ 5.3) × 10 12 cm −2 , and hole mobility of 460 ∼ 760 cm 2 V −1 s −1 without doping at room temperature. The results suggest that large-scale CVD-grown graphene can be transferred with good quality and without contaminating the target surface by any liquid. Mg/MgO/graphene tunnel junctions were fabricated using this transfer method. The junctions show good tunneling characteristics, which demonstrates the transfer technique can also be used to fabricate graphene devices on liquid-sensitive surfaces. (paper)

  19. Preparation and tribological properties of MoS2/graphene oxide composites

    Song, Haojie; Wang, Biao; Zhou, Qiang; Xiao, Jiaxuan; Jia, Xiaohua

    2017-10-01

    A hydrothermal route is developed for the synthesis of MoS2/graphene oxide (GO) composites based on the hydrothermal reduction of Na2MoO4 and GO sheets with L-cysteine. The MoS2/GO composites in improving friction and wear of the sunshine oil on sliding steel surfaces under low or high applied load were demonstrated. In tests with sliding steel surfaces, the sunshine oil that contains small amounts of MoS2/GO composites exhibited the lowest specific friction coefficient and wear rate under all of the sliding conditions. Scanning electron microscopy and energy dispersive spectrometer performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of MoS2/GO composites could be attributed to their good dispersion stability and extremely thin laminated structure, which allow the MoS2/GO composites to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

  20. Surface enhanced infrared absorption spectroscopy for graphene functionalization on copper

    Matulková, I.; Kovaříček, Petr; Šlouf, Miroslav; Němec, I.; Kalbáč, Martin

    2017-01-01

    Roč. 124, NOV 2017 (2017), s. 250-255 ISSN 0008-6223 R&D Projects: GA ČR(CZ) GA15-01953S; GA MŠk LL1301; GA MŠk(CZ) LM2015073 Grant - others:AVČR PPPLZ(CZ) L200401551; GA MŠk(CZ) CZ.02.1.01/0.0/0.0/16_013/0001821 Institutional support: RVO:61388955 ; RVO:61389013 Keywords : chemical-vapor-deposition * diazonium salts * raman-spectroscopy * covalent functionalization * seira spectroscopy * grown graphene Subject RIV: CF - Physical ; Theoretical Chemistry; CD - Macromolecular Chemistry (UMCH-V) OBOR OECD: Physical chemistry; Polymer science (UMCH-V) Impact factor: 6.337, year: 2016

  1. Effects of reducibility of graphene oxide nanosheets on preparation of AgNPs/GO nanocomposites and their electrocatalytic performance

    Dou, Yanpeng; Peng, Junjun, E-mail: john-peng@whu.edu.cn; Li, Wei; Li, Ming; Liu, Huihong; Zhang, Hanmin [Wuhan Textile University, College of Chemistry and Chemical Engineering (China)

    2015-12-15

    Silver nanoparticles/graphene oxide (AgNPs/GO) nanocomposites were prepared in a solution of AgNO{sub 3} and GO. The GO serves not only as a reductant but also as a substrate to support the as-reduced silver nanoparticles. The reducibility of GO was investigated by analyzing the influence factors such as pH, duration, the reaction temperature, and the weight ratio of AgNO{sub 3} and GO in the AgNP/GO nanocomposite mixture, which were evaluated by the UV–vis absorption spectroscopy. The results demonstrated that Ag nanoparticles with an average diameter of 5–10 nm were uniformly dispersed on the surface of GO nanosheets under the optimum synthesis conditions of pH between 8 and 11, weight ratio of AgNO{sub 3} and GO between 55 % and 60 %, and at 80 °C for 6 h. Moreover, the obtained AgNPs/GO nanocomposites exhibit good electrocatalytic activity for the reduction of p-nitrophenol to 4-(hydroxyamino) phenol.

  2. Preparation of tetraethylenepentamine modified magnetic graphene oxide for adsorption of dyes from aqueous solution

    Tang, Xiaosheng [Hubei Normal University (China); Tang, Ping; Liu, Liangliang, E-mail: liuliangliang@caas.cn [Chinese Academy of Agricultural Sciences, Changsha (China)

    2018-05-01

    In this study, tetraethylenepentamine modified magnetic graphene oxide nanomaterial (TMGO) was prepared and characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and vibration sample magnetometer (VSM). All the characterizations proved that the modification and preparation of TMGO were successful. The TMGO nanomaterial was used in the adsorption of Acid Red 18 (AR) in aqueous solution. The parameters like pH of solution, adsorption kinetics and isotherms were all investigated. The results indicated that the TMGO nanomaterial had satisfied adsorption ability and the maximum adsorption capacity was 524.2 mg g{sup -}'1 at 45 °C and pH 6. The adsorption capacity remained at 91.8% of the initial value after five cycles. The adsorption process with AR was found through fitting the pseudo-second-order kinetics equations and the Freundlich adsorption model. The experimental results demonstrated that the TMGO nanomaterial could be rapidly extracted from the medium and had a good adsorption ability to remove dyes in wastewater. (author)

  3. Preparation and surface labeling of murine eosinophils

    Burgess, A.W.; Cruise, K.M.; Mitchell, G.F.; Watt, S.M.

    1980-01-01

    Eosinophilic polymorphonuclear leukocytes were isolated from the peritoneal cavity of BALB/c mice infected with the parasite Mesocestoides corti. Approximately 4 x 10 7 eosinophils (purity, 50%) could be harvested from each mouse. A high yield and purity of eosinophils was obtained from the peritoneal cells of infected male BALB/c mice using density centrifugation on a gradient of slightly hypotonic colloidal silica sol (Percoll). After initial irradiation of the mice to lower the lymphocyte contamination, subsequent density gradient (and where nescessary sedimentation velocity) centrifugation yielded 10 8 eosinophils (purity >95%) from six to eight mice. It was also possible to isolate small numbers of eosinophils (2 x 10 4 cells/minute, purity >99%) without irradiating the mice. This could be achieved by separating the density gradient purified peritoneal cells by light-scatter on a Becton-Dickinson cell sorter (FACS II). Analysis of proteins extracted from eosinophils using polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed a group of high molecular weight proteins (between 250K and 160K) which were not as distinctive in the neutrophil profile. Surface labeling was performed, before the cell separation, by using 125 I and 1,3,4,6-tetrachloro-3α,6α-diphenylglycoluril. Only five 125 I-labeled proteins were detected initially (all with apparent molecular weights >50,000). No 125 I appeared to be associated with actin under the conditions used for surface labeling. Four of the eosinophil surface labeled proteins corresponded to surface labeled proteins on neutrophils, but the major surface component of the eosinophils (MW 79,000) appeared to be smaller than the major neutrophil protein (MW 90,000). (author)

  4. Preparation of a Microspherical Silver-Reduced Graphene Oxide-Bismuth Vanadate Composite and Evaluation of Its Photocatalytic Activity

    Mao Du

    2016-03-01

    Full Text Available A novel Ag-reduced graphene oxide (rGO-bismuth vanadate (BiVO4 (AgGB ternary composite was successfully synthesized via a one-step method. The prepared composite was characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM, energy dispersive X-ray (EDX, Brunauer-Emmett-Teller (BET surface area measurement, Raman scattering spectroscopy, and ultraviolet-visible diffuse-reflection spectroscopy (UV-vis DRS. The results showed that bulk monoclinic needle-like BiVO4 and Ag nanoparticles with a diameter of approximately 40 nm formed microspheres (diameter, 5–8 μm with a uniform size distribution that could be loaded on rGO sheets to facilitate the transport of electrons photogenerated in BiVO4, thereby reducing the rate of recombination of photogenerated charge carriers in the coupled AgGB composite system. Ag nanoparticles were dispersed on the surface of the rGO sheets, which exhibited a localized surface plasmon resonance phenomenon and enhanced visible light absorption. The removal efficiency of rhodamine B dye by AgGB (80.2% was much higher than that of pure BiVO4 (51.6% and rGO-BiVO4 (58.3% under visible light irradiation. Recycle experiments showed that the AgGB composite still presented significant photocatalytic activity after five successive cycles. Finally, we propose a possible pathway and mechanism for the photocatalytic degradation of rhodamine B dye using the composite photocatalyst under visible light irradiation.

  5. Surface Preparation for Microdebonding Analysis of Composites

    Kahraman, Ramazan; Mandell, J. F.

    1999-01-01

    The bond strength between fibers and matrix is an essential property of all composite materials and it must be measured accurately to be able to correlate it with the composite behavior. There are several factors affecting its measurement. This paper discusses the polishing and load application aspects of the indentation test technique for fibre-matrix bond strength determination in polymer and ceramic matrix composites. Different polishing procedures are suggested for polymer and ceramic surfaces for obtaining a smooth surface which is a must for the test results to be reliable. The geometry of the fibers tested was also found to affect the analysis results. For best results, fibers with similar size and which are similarly surrounded by other fibers should be tested. Care should be taken during load application on a fiber for the loading probe not to approach the fiber circumference. The force should be applied in a small increments as possible, however starting from a high enough level to prevent fiber breakage due to surface damage from several loading steps. (Author)

  6. Facile hydrothermal preparation of titanium dioxide decorated reduced graphene oxide nanocomposite

    Chang, Betty Yea Sze; Huang, Nay Ming; An’amt, Mohd Nor; Marlinda, Abdul Rahman; Norazriena, Yusoff; Muhamad, Muhamad Rasat; Harrison, Ian; Lim, Hong Ngee; Chia, Chin Hua

    2012-01-01

    A simple single-stage approach, based on the hydrothermal technique, has been introduced to synthesize reduced graphene oxide/titanium dioxide nanocomposites. The titanium dioxide nanoparticles are formed at the same time as the graphene oxide is reduced to graphene. The triethanolamine used in the process has two roles. It acts as a reducing agent for the graphene oxide as well as a capping agent, allowing the formation of titanium dioxide nanoparticles with a narrow size distribution (~20 nm). Transmission electron micrographs show that the nanoparticles are uniformly distributed on the reduced graphene oxide nanosheet. Thermogravimetric analysis shows the nanocomposites have an enhanced thermal stability over the original components. The potential applications for this technology were demonstrated by the use of a reduced graphene oxide/titanium dioxide nanocomposite-modified glassy carbon electrode, which enhanced the electrochemical performance compared to a conventional glassy carbon electrode when interacting with mercury(II) ions in potassium chloride electrolyte. PMID:22848166

  7. Effects of Cu intercalation on the graphene/Ni(111) surface: density-functional calculations

    Kwon, Se Gab; Kang, Myung Ho

    2012-01-01

    The Cu-intercalated graphene/Ni(111) surface has been studied by using density-functional theory calculations. We find that (1) the intercalation-induced decoupling between graphene and the Ni(111) substrate begins sharply at a Cu coverage of about 0.75 ML, (2) at the optimal Cu coverage of 1 ML, graphene recovers an almost ideal Dirac-cone band structure with no band gap, and (3) the Dirac point is located at 0.17 eV below the Fermi level, indicating a small charge transfer from the substrate. Cu thus plays essentially the same role as Au in realizing quasi-free-standing graphene by intercalation. Our charge character analysis shows that the Dirac-cone bands near the Fermi level reveal a weakening of their π character when crossing the Ni d bands, suggesting that the resulting low Dirac-cone intensity could possibly be the origin of the recent photoemission report of a relatively large band gap of 0.18 eV.

  8. Graphene nanoribbons exfoliated from graphite surface dislocation bands by electrostatic force

    Sidorov, Anton N; Ouseph, P J; Sumanasekera, Gamini; Bansal, Tanesh

    2010-01-01

    We have developed a novel technique to produce long and narrow graphene ribbons with smooth edges. This technique is free of any chemical treatments and involves a combination of two steps: (i) creation of surface dislocation ribbons by high velocity clusters impacting the graphite surface and (ii) electrostatic transferring of the dislocation ribbons to a desired substrate. The width of the ribbons can be controlled by varying the impact velocity of a cluster jet stream from a gas jet impactor. The electrical transport properties were investigated on the ribbons in field effect transistor (FET) configuration. The p-type behavior observed under ambient conditions was found to be reversed upon annealing at 180 deg. C in a vacuum of 10 -7 Torr. Charge transfer effects were observed when the degassed graphene was exposed to N 2 O and NH 3 .

  9. Quantum-mechanical interference in charge exchange between hydrogen and graphene-like surfaces

    Romero, M; Iglesias-García, A; Goldberg, E C

    2012-01-01

    The neutral to negative charge fluctuation of a hydrogen atom in front of a graphene surface is calculated by using the Anderson model within an infinite intra atomic Coulomb repulsion approximation. We perform an ab initio calculation of the Anderson hybridization function that allows investigation of the effect of quantum-mechanical interference related to the Berry phase inherent to the graphene band structure. We find that consideration of the interaction of hydrogen on top of many C atoms leads to a marked asymmetry of the imaginary part of the hybridization function with respect to the Fermi level. Consequently, Fano factors larger than one and strongly dependent on the energy around the Fermi level are predicted. Moreover, the suppression of the hybridization for energies above the Fermi level can explain the unexpected large negative ion formation measured in the scattering of protons by graphite-like surfaces. (paper)

  10. Facile preparation of superhydrophobic surface with high adhesive ...

    Glass substrates modified by carbon/silica composites are fabricated through a two-step process for the preparation of a superhydrophobic surface (water contact angle ≥ 150°). Carbon nanoparticles were first prepared through a deposition process on glass using a hydrothermal synthesis route, then the glass was ...

  11. Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

    Feng Lili

    2011-01-01

    Full Text Available Abstract In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future.

  12. Preparation of surface enhanced Raman substrate and its characterization

    Liu, Y.; Wang, J. Y.; Wang, J. Q.

    2017-10-01

    Surface enhanced Raman spectroscopy (SERS) is a fast, convenient and highly sensitive detection technique, and preparing the good effect and repeatable substrate is the key to realize the trace amount and quantitative detection in the field of food safety detection. In this paper, a surface enhanced Raman substrate based on submicrometer silver particles structure was prepared by chemical deposition method, and characterized its structure and optical properties.

  13. Preparation and Electrochemical Properties of Graphene/Epoxy Resin Composite Coating

    Liao, Zijun; Zhang, Tianchi; Qiao, Sen; Zhang, Luyihang

    2017-11-01

    The multilayer graphene powder as filler, epoxy modified silicone resin as film-forming agent, anticorrosion composite coating has been created using sand dispersion method, the electrochemical performance was compared with different content of graphene composite coating and pure epoxy resin coating. The open circuit potential (OCP), potentiodynamic polarization curves (Tafel Plot) and electrochemical impedance spectroscopy (EIS) were tested. The test results showed that the anti-corrosion performance of multilayer graphene added has improved greatly, and the content of the 5% best corrosion performance of graphene composite coating.

  14. One-step approach to prepare magnetic iron oxide/reduced graphene oxide nanohybrid for efficient organic and inorganic pollutants removal

    Thakur, Suman; Karak, Niranjan, E-mail: karakniranjan@yahoo.com

    2014-04-01

    An environmentally friendly effective technique was demonstrated to prepare iron oxide/reduced graphene oxide nanohybrid (IO/RGO) at room temperature by using banana peel ash aqueous extract as the base source and Colocasia esculenta leaves aqueous extract as the reducing agent. The nanohybrid was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy and thermal studies. The results indicated the decoration of superparamagnetic IO nanoparticles on the surface of the RGO. Both organic and inorganic pollutants were effectively removed from the contaminated water (for Pb{sup 2+} and Cd{sup 2+} within 10 min, whereas for tetrabromobisphenol A within 30 min) by IO/RGO. The study revealed that adsorption followed pseudo-second order kinetics and isotherms were well described by the Langmuir model in all the cases. The thermodynamics parameters (ΔG°, ΔS° and ΔH°) were calculated from the temperature dependent isotherms and indicated that the adsorptions were endothermic and spontaneous. - Highlights: • Eco-friendly one step preparation of iron oxide/reduced graphene oxide nanohybrid. • The nanohybrid has excellent pollutants removal capacity from contaminated water. • Superparamagnetic iron oxide nanoparticles help in easy recycle. • The adsorption processes of pollutants are endothermic and spontaneous.

  15. One-step approach to prepare magnetic iron oxide/reduced graphene oxide nanohybrid for efficient organic and inorganic pollutants removal

    Thakur, Suman; Karak, Niranjan

    2014-01-01

    An environmentally friendly effective technique was demonstrated to prepare iron oxide/reduced graphene oxide nanohybrid (IO/RGO) at room temperature by using banana peel ash aqueous extract as the base source and Colocasia esculenta leaves aqueous extract as the reducing agent. The nanohybrid was characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, transmission electron microscopy, vibrating sample magnetometry, Raman spectroscopy and thermal studies. The results indicated the decoration of superparamagnetic IO nanoparticles on the surface of the RGO. Both organic and inorganic pollutants were effectively removed from the contaminated water (for Pb 2+ and Cd 2+ within 10 min, whereas for tetrabromobisphenol A within 30 min) by IO/RGO. The study revealed that adsorption followed pseudo-second order kinetics and isotherms were well described by the Langmuir model in all the cases. The thermodynamics parameters (ΔG°, ΔS° and ΔH°) were calculated from the temperature dependent isotherms and indicated that the adsorptions were endothermic and spontaneous. - Highlights: • Eco-friendly one step preparation of iron oxide/reduced graphene oxide nanohybrid. • The nanohybrid has excellent pollutants removal capacity from contaminated water. • Superparamagnetic iron oxide nanoparticles help in easy recycle. • The adsorption processes of pollutants are endothermic and spontaneous

  16. Silver-graphene oxide based plasmonic spacer for surface plasmon-coupled fluorescence emission enhancements

    Badiya, Pradeep Kumar; Srinivasan, Venkatesh; Sathish Ramamurthy, Sai

    2017-06-01

    We report the application of single layered graphene oxide (SLGO) and silver decorated SLGO (Ag-SLGO) as plasmonic spacer material for obtaining enhanced fluorescence from a Rhodamine 6G (Rh6G) radiating dipole in a surface plasmon-coupled emission platform. To this end, we have decorated SLGO with biphasic silver nanoparticles using an in situ deposition technique to achieve 112-fold fluorescence enhancements.

  17. Dispersive and Covalent Interactions between Graphene and Metal Surfaces from the Random Phase Approximation

    Olsen, Thomas; Yan, Jun; Mortensen, Jens Jørgen

    2011-01-01

    We calculate the potential energy surfaces for graphene adsorbed on Cu(111), Ni(111), and Co(0001) using density functional theory and the random phase approximation (RPA). For these adsorption systems covalent and dispersive interactions are equally important and while commonly used approximations...... for exchange-correlation functionals give inadequate descriptions of either van der Waals or chemical bonds, RPA accounts accurately for both. It is found that the adsorption is a delicate competition between a weak chemisorption minimum close to the surface and a physisorption minimum further from the surface....

  18. A General Strategy for the Preparation of Carbon Nanotubes and Graphene Oxide Decorated with PdO Nanoparticles in Water

    Hongkun He

    2010-07-01

    Full Text Available The preparation of carbon nanotube (CNT/PdO nanoparticles and graphene oxide (GO/PdO nanoparticle hybrids via a general aqueous solution strategy is reported. The PdO nanoparticles are generated in situ on the CNTs and GO by a one-step “green” synthetic approach in aqueous Pd(NO32 solution under ambient conditions without adding any additional chemicals. The production of PdO is confirmed by energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. The morphologies of the resulting CNT/PdO and GO/PdO nanohybrids are characterized by transmission and/or scanning transmission electron microscopy. PdO nanoparticles with an average size of 2–3 nm in diameter are decorated evenly along the surfaces of CNTs and GO. This synthesis strategy is demonstrated to be compatible for 1 CNTs with different modifications, including pristine, oxidized, and polymer-functionalized CNTs; 2 different types of CNTs, including single-walled carbon nanotubes (SWCNTs, double-walled carbon nanotubes (DWCNTs, and multiwalled carbon nanotubes (MWCNTs; and 3 different shapes of carbon materials, including tubular CNTs and planar GO. The as-prepared CNT/PdO and GO/PdO nanohybrids can be transformed into CNT/Pd and GO/Pd nanohybrids by reduction with NaBH4, and can then be used as a heterogeneous catalyst in the catalytic reduction of 4-nitrophenol.

  19. One-step preparation of N-doped graphene/Co nanocomposite as an advanced oxygen reduction electrocatalyst

    Bai, Fo; Huang, Hao; Tan, Yanlei; Hou, Changmin; Zhang, Ping

    2015-01-01

    Graphical abstract: N-doped graphene/Co nanocomposites were synthesized through one-step pyrolysis process and the product exhibits high performance for ORR and excellent stability in alkaline medium. - Highlights: • N-doped graphene/Co nano-composite is directly synthesized by a one-step method from Co(NO3)2∙6H2O, glucose and dicyandiamide (DCDA). • The electrocatalytic performance of as-prepared NG/Co-0.5 shows the peak potential positively shifts about 10 mV than commercial Pt/C electrode. • The material shows an excellent stability and tolerance to methanol poisoning effects in alkaline medium. - Abstract: N-doped graphene/Co nanocomposites (NG/Co NPs) have been prepared by a simple one-step pyrolysis of Co(NO 3 ) 2 ∙6H 2 O, glucose and dicyandiamide (DCDA). The products with nitrogen doped and suitable graphitic degree perform high electrocatalytic activity (with the reduction peak at −0.099 V vs Ag/AgCl) and near four-electron selectivity for the oxygen reduction reaction (ORR), with excellent stability and durability in alkaline medium comparable to a commercial Pt/C catalyst. Owing to the superb ORR performance, low cost and facile preparation, the catalysts of NG/Co NPs have great potential applications in fuel cells, metal-air batteries and ORR-related electrochemical industries

  20. Surface Modification of Graphene Oxides by Plasma Techniques and Their Application for Environmental Pollution Cleanup.

    Wang, Xiangxue; Fan, Qiaohui; Chen, Zhongshan; Wang, Qi; Li, Jiaxing; Hobiny, Aatef; Alsaedi, Ahmed; Wang, Xiangke

    2016-02-01

    Graphene oxides (GOs) have come under intense multidisciplinary study because of their unique physicochemical properties and possible applications. The large amount of oxygen-containing functional groups on GOs leads to a high sorption capacity for the removal of various kinds of organic and inorganic pollutants from aqueous solutions in environmental pollution cleanup. However, the lack of selectivity results in difficulty in the selective removal of target pollutants from aqueous solutions in the presence of other coexisting pollutants. Herein, the surface grafting of GOs with special oxygen-containing functional groups using low-temperature plasma techniques and the application of the surface-modified GOs for the efficient removal of organic and inorganic pollutants in environmental pollution are reviewed. This paper gives an account of our research on the application of GO-based nanomaterials in environmental pollution cleanup, including: (1) the synthesis and surface grafting of functional groups on GOs, summarizing various types of low-temperature plasma techniques for the synthesis of graphene/GOs; and (2) the application of graphene/GOs and their composites for the efficient removal of organic and inorganic pollutants from aqueous solutions, including the interaction mechanism according to recently published results. © 2015 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Stable Nafion-functionalized graphene dispersions for transparent conducting films

    Liu Yangqiao; Gao Lian; Sun Jing; Wang Yan; Zhang Jing

    2009-01-01

    Nafion was used for the first time to aid in preparing stable graphene dispersions in mixed water/ethanol (1:1) solvents via the reduction of graphite oxide using hydrazine. The dispersion was characterized by ultraviolet-visible (UV-vis) spectra, transmission electron microscopy, zeta potential analysis, etc. It was found that for Nafion-to-graphene ratios higher than 5:1, graphene solutions with concentrations up to 1 mg ml -1 and stabilities of over three months were obtained. It was proposed that the Nafion adsorbed onto the graphene by the hydrophobic interaction of its fluoro-backbones with the graphene layer and imparted stability by an electrosteric mechanism. Furthermore, transparent and conductive films were prepared using these highly stable Nafion-stabilized graphene dispersions. The prepared Nafion-graphene films possess smooth and homogeneous surfaces and the sheet resistance was as low as 30 kΩ/sq for a transmittance of 80% at 550 nm, which was much lower than for other graphene films obtained by chemical reduction. X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the p-doping of the graphene by Nafion. It was expected that this p-doping effect, as well as the high dispersing ability of Nafion for graphene and the connection of the sp 2 domains by residual Nafion combined to produce good properties of the Nafion-graphene films.

  2. Preparation and properties of novel epoxy/graphene oxide nanosheets (GON) composites functionalized with flame retardant containing phosphorus and silicon

    Li, Kuo-Yi; Kuan, Chen-Feng; Kuan, Hsu-Chiang; Chen, Chia-Hsun; Shen, Ming-Yuan; Yang, Jia-Ming; Chiang, Chin-Lung

    2014-01-01

    2-(Diphenylphosphino)ethyltriethoxy silane (DPPES) was grafted onto the surface of graphene oxide nanosheets (GON) via a condensation reaction. X-ray photoelectron spectroscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and Raman spectroscopy verify that DPPES did not only covalently bond to GON as a functionalization moiety, but partly restored its conjugated structure as a reducing agent. DPPES on graphene sheets oxide was observed by transmission electron microscopy, and contributed to the favorable dispersion of DPPES-GON in nonpolar toluene. Additionally, the flame retardancy and thermal stability of epoxy/DPPES-GON nanocomposites that contain various weight fractions of DPPES-GON were studied using the limiting oxygen index test, UL-94 test and by thermogravimetric analysis in nitrogen. The composites containing 10 wt% DPPES-GON can pass V-0 rating in UL-94 test. Adding 10 wt% DPPES-GON in epoxy greatly increased the char yield and LOI by 42% and 80%, respectively. Epoxy/DPPES-GON nanocomposites with phosphorus, silicon and graphene layer structures were found to exhibit much greater flame retardancy than neat epoxy. The synergistic effects among silicon, phosphorus and GON can improve the flame retardancy of epoxy resin. - Highlights: • Flame retardant was grafted on the surface of graphene oxide nanosheets (GON) by the condensation reaction. • The synergistic effect between silicon, phosphorus and GON improved the flame retardance of epoxy resin. • Epoxy composites have excellent flame retardance at low additive concentrations

  3. Control of the microstructure and surface chemistry of graphene aerogels via pH and time manipulation by a hydrothermal method.

    García-Bordejé, E; Víctor-Román, S; Sanahuja-Parejo, O; Benito, A M; Maser, W K

    2018-02-15

    Three-dimensional graphene aerogels of controlled pore size have emerged as an important platform for several applications such as energy storage or oil-water separation. The aerogels of reduced graphene oxide are mouldable and light weight, with a porosity up to 99.9%, consisting mainly of macropores. Graphene aerogel preparation by self-assembly in the liquid phase is a promising strategy due to its tunability and sustainability. For graphene aerogels prepared by a hydrothermal method, it is known that the pH value has an impact on their properties but it is unclear how pH affects the auto-assembly process leading to the final properties. We have monitored the time evolution of the chemical and morphological properties of aerogels as a function of the initial pH value. In the hydrothermal treatment process, the hydrogel is precipitated earlier and with lower oxygen content for basic pH values (∼13 wt% O) than for acidic pH values (∼20 wt% O). Moreover, ∼7 wt% of nitrogen is incorporated on the graphene nanosheets at basic pH generated by NH 3 addition. To our knowledge, there is no precedent showing that the pH value affects the microstructure of graphene nanosheets, which become more twisted and bent for the more intensive deoxygenation occurring at basic pH. The bent nanosheets attained at pH = 11 reduce the stacking by the basal planes and they connect via the borders, hence leading eventually to higher pore volumes. In contrast, the flatter graphene nanosheets attained under acidic pH entail more stacking and higher oxygen content after a long hydrothermal treatment. The gravimetric absorption capacity of non-polar solvents scales directly with the pore volume. The aerogels have proved to be highly selective, recyclable and robust for the absorption of nonpolar solvents in water. The control of the porous structure and surface chemistry by manipulation of pH and time will also pave the way for other applications such as supercapacitors or batteries.

  4. Aromatic graphene

    Das, D. K., E-mail: gour.netai@gmail.com [Department of Metallurgical and Material Science Engineering, National Institute of Technology Durgapur-713209, West Bengal (India); Sahoo, S., E-mail: sukadevsahoo@yahoo.com [Department of Physics, National Institute of Technology Durgapur-713209, West Bengal (India)

    2016-04-13

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  5. Aromatic graphene

    Das, D. K.; Sahoo, S.

    2016-01-01

    In recent years graphene attracts the scientific and engineering communities due to its outstanding electronic, thermal, mechanical and optical properties and many potential applications. Recently, Popov et al. [1] have studied the properties of graphene and proved that it is aromatic but without fragrance. In this paper, we present a theory to prepare graphene with fragrance. This can be used as scented pencils, perfumes, room and car fresheners, cosmetics and many other useful household substances.

  6. Preparation and microwave-infrared absorption of reduced graphene oxide/Cu-Ni ferrite/Al2O3 composites

    De-yue, Ma; Xiao-xia, Li; Yu-xiang, Guo; Yu-run, Zeng

    2018-01-01

    Reduced graphene oxide (RGO)/Cu-Ni ferrite/Al2O3 composite was prepared by solvothermal method, and its properties were characterized by SEM, x-ray diffraction, energy-dispersive x-ray spectroscopy and FTIR. The electromagnetic parameters in 2-18 GHz and mid-infrared (IR) spectral transmittance of the composite were measured, respectively. The results show that Cu0.7Ni0.3Fe2O4 nanoparticles with an average size of tens nanometers adsorb on surface of RGO, and meanwhile, Al2O3 nanoparticles adhere to the surface of Cu0.7Ni0.3Fe2O4 nanoparticles and RGO. The composite has both dielectric and magnetic loss mechanism. Its reflection loss is lower than -19 dB in 2-18 GHz, and the maximum of -23.2 dB occurs at 15.6 GHz. With the increasing of Al2O3 amount, its reflection loss becomes lower and the maximum moves towards low frequency slightly. Compared with RGO/Cu-Ni ferrite composites, its magnetic loss and reflection loss slightly reduce with the increasing of Al2O3 amount, and the maximum of reflection loss shifts from a low frequency to a high one. However, its broadband IR absorption is significantly enhanced owing to nano-Al2O3. Therefore, RGO/Cu-Ni ferrite/Al2O3 composites can be used as excellent broadband microwave and IR absorbing materials, and maybe have broad application prospect in electromagnetic shielding, IR absorbing and coating materials.

  7. ZnS-Graphene nanocomposite: Synthesis, characterization and optical properties

    Pan Shugang [Key Laboratory for Soft Chemistry and Functional Materials, Nanjing University of Science and Technology, Ministry of Education, Nanjing 210094 (China); Liu Xiaoheng, E-mail: xhliu@mail.njust.edu.cn [Key Laboratory for Soft Chemistry and Functional Materials, Nanjing University of Science and Technology, Ministry of Education, Nanjing 210094 (China)

    2012-07-15

    A ZnS-Graphene nanocomposite was prepared by a facile one-step hydrothermal method using zinc nitrate hexahydrate, ethylenediamine and carbon disulfide as precursors, graphene oxide as a template. The composite was characterized by X-ray power diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier transform infrared, Raman spectra and fluorescence spectroscopy. The results show that graphene oxide was reduced to graphene in the hydrothermal reaction process. Simultaneously, the graphene sheets in the composite are exfoliated and decorated with ZnS nanoparticles. Furthermore, Raman and fluorescence properties of the composite were observed. ZnS-Graphene nanocomposite displays surface-enhanced Raman scattering activity for graphene oxide, and fluorescence enhancement property compared with pure ZnS sample. - Graphical abstract: Approach of reaction makes the reduction of grapheme oxide and the deposition of Zns on the grapheme sheets occur simultaneously and overcomes the aggregation of the grapheme sheets and Zns. Highlights: Black-Right-Pointing-Pointer Graphene oxide is reduced to graphene in the hydrothermal reaction process. Black-Right-Pointing-Pointer ZnS nanoparticles are attached onto the almost transparent graphene sheets. Black-Right-Pointing-Pointer ZnS-Graphene system shows surface-enhanced Raman scattering (SERS) activity. Black-Right-Pointing-Pointer ZnS-Graphene system displays relatively better fluorescence property than pure ZnS.

  8. Preparation, characterization, and antibacterial activity of silver nanoparticle-decorated graphene oxide nanocomposite.

    Shao, Wei; Liu, Xiufeng; Min, Huihua; Dong, Guanghui; Feng, Qingyuan; Zuo, Songlin

    2015-04-01

    In this work, we report a facile and green approach to prepare a uniform silver nanoparticles (AgNPs) decorated graphene oxide (GO) nanocomposite (GO-Ag). The nanocomposite was fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, and X-ray photoelectron spectroscopy (XPS), which demonstrated that AgNPs with a diameter of approximately 22 nm were uniformly and compactly deposited on GO. To investigate the silver ion release behaviors, HEPES buffers with different pH (5.5, 7, and 8.5) were selected and the mechanism of release actions was discussed in detail. The cytotoxicity of GO-Ag nanocomposite was also studied using HEK 293 cells. GO-Ag nanocomposite displayed good cytocompatibility. Furthermore, the antibacterial properties of GO-Ag nanocomposite were studied using Gram-negative E. coli ATCC 25922 and Gram-positive S. aureus ATCC 6538 by both the plate count method and disk diffusion method. The nanocomposite showed excellent antibacterial activity. These results demonstrated that GO-Ag nanocomposite, as a kind of antibacterial material, had a great promise for application in a wide range of biomedical applications.

  9. Experimental study of the effect of the reduced graphene oxide films on nucleate boiling performances of inclined surfaces

    Kim, Ji Hoon; Kong, Byeong Tak [Incheon National University, Incheon (Korea, Republic of); Kim, Ji Min [POSTECH, Pohang (Korea, Republic of); and others

    2016-05-15

    For the enhancing the CHF, surface coating techniques are available. Yang et al. performed small scale boiling experiments for the vessel lower head, which was coated by aluminum/copper micro particles. Recently, graphene has received much attention for applications in thermal engineering due to its large thermal conductivity. Ahn et al. used a silicon dioxide substrate, which was coated graphene films, as a heating surface during pool boiling experiments. The graphene films inhibited the formation of hot spots, increasing the CHF. For applying novel material 'Graphene' in nuclear industry, here we investigated the effects of graphene film coatings on boiling performances. The experimental pool boiling facility, copying the geometry of lower head of reactor, was designed for verifying orientation effects. The effects of graphene films coating on varied inclined heater surfaces were investigated. The CHF values were increased at every case, but the increased amounts were decreased for downward heater surfaces. At the downward-facing region, however, coating the RGO films would change the CHF mechanisms and boiling heat transfer performances. Generally, RGO films, made by colloidal fabrication, has defects on each flakes.

  10. Experimental study of the effect of the reduced graphene oxide films on nucleate boiling performances of inclined surfaces

    Kim, Ji Hoon; Kong, Byeong Tak; Kim, Ji Min

    2016-01-01

    For the enhancing the CHF, surface coating techniques are available. Yang et al. performed small scale boiling experiments for the vessel lower head, which was coated by aluminum/copper micro particles. Recently, graphene has received much attention for applications in thermal engineering due to its large thermal conductivity. Ahn et al. used a silicon dioxide substrate, which was coated graphene films, as a heating surface during pool boiling experiments. The graphene films inhibited the formation of hot spots, increasing the CHF. For applying novel material 'Graphene' in nuclear industry, here we investigated the effects of graphene film coatings on boiling performances. The experimental pool boiling facility, copying the geometry of lower head of reactor, was designed for verifying orientation effects. The effects of graphene films coating on varied inclined heater surfaces were investigated. The CHF values were increased at every case, but the increased amounts were decreased for downward heater surfaces. At the downward-facing region, however, coating the RGO films would change the CHF mechanisms and boiling heat transfer performances. Generally, RGO films, made by colloidal fabrication, has defects on each flakes.

  11. One-step oxidation preparation of unfolded and good soluble graphene nanoribbons by longitudinal unzipping of carbon nanotubes

    Hu, Xiaolin; Hu, Yizhen; Huang, Jindan; Zhou, Ning; Liu, Yuhan; Wei, Lin; Chen, Xin; Zhuang, Naifeng

    2018-04-01

    A simple one-step method to prepare graphene nanoribbon (GNR) is reported in this paper. Compared with water steam etching, the oxidation and co-etching of dilute sulfuric acid can result in the more complete longitudinal unzipping of carbon nanotube, although there is no other strong oxidant. As-prepared GNRs are more flat and have more oxygenated functional groups along the edge. Moreover, they can steadily disperse in a water system. These make them suitable as a carrier for supporting palladium (Pd) nanoparticles. The Pd/GNR composite exhibits a superior electrocatalytic activity for ethanol oxidation.

  12. Surface preparation for the heteroepitactic growth of ceramic thin films

    Norton, M.G.; Summerfelt, S.R.; Carter, C.B.

    1990-01-01

    The morphology, composition, and crystallographic orientation of the substrate influence the nucleation and growth of deposited thin films. A method for the preparation of controlled, characteristic surfaces is reported. The surfaces are suitable for the heteroepitactic growth of thin films. When used in the formation of electron-transparent thin foils, the substrates can be used to investigate the very early stages of film growth using transmission electron microscopy. The substrate preparation involves the cleaning and subsequent annealing to generate a surface consisting of a series of steps. The step terraces are formed on the energetically stable surface, and controlled nucleation and growth of films at step edges is found. The substrate materials prepared using this technique include (001) MgO, (001) SrTiO 3 , and (001) LaAlO 3

  13. Uniform hexagonal graphene flakes and films grown on liquid copper surface.

    Geng, Dechao; Wu, Bin; Guo, Yunlong; Huang, Liping; Xue, Yunzhou; Chen, Jianyi; Yu, Gui; Jiang, Lang; Hu, Wenping; Liu, Yunqi

    2012-05-22

    Unresolved problems associated with the production of graphene materials include the need for greater control over layer number, crystallinity, size, edge structure and spatial orientation, and a better understanding of the underlying mechanisms. Here we report a chemical vapor deposition approach that allows the direct synthesis of uniform single-layered, large-size (up to 10,000 μm(2)), spatially self-aligned, and single-crystalline hexagonal graphene flakes (HGFs) and their continuous films on liquid Cu surfaces. Employing a liquid Cu surface completely eliminates the grain boundaries in solid polycrystalline Cu, resulting in a uniform nucleation distribution and low graphene nucleation density, but also enables self-assembly of HGFs into compact and ordered structures. These HGFs show an average two-dimensional resistivity of 609 ± 200 Ω and saturation current density of 0.96 ± 0.15 mA/μm, demonstrating their good conductivity and capability for carrying high current density.

  14. Acoustically-driven surface and hyperbolic plasmon-phonon polaritons in graphene/h-BN heterostructures on piezoelectric substrates

    Fandan, R.; Pedrós, J.; Schiefele, J.; Boscá, A.; Martínez, J.; Calle, F.

    2018-05-01

    Surface plasmon polaritons in graphene couple strongly to surface phonons in polar substrates leading to hybridized surface plasmon-phonon polaritons (SPPPs). We demonstrate that a surface acoustic wave (SAW) can be used to launch propagating SPPPs in graphene/h-BN heterostructures on a piezoelectric substrate like AlN, where the SAW-induced surface modulation acts as a dynamic diffraction grating. The efficiency of the light coupling is greatly enhanced by the introduction of the h-BN film as compared to the bare graphene/AlN system. The h-BN interlayer not only significantly changes the dispersion of the SPPPs but also enhances their lifetime. The strengthening of the SPPPs is shown to be related to both the higher carrier mobility induced in graphene and the coupling with h-BN and AlN surface phonons. In addition to surface phonons, hyperbolic phonons polaritons (HPPs) appear in the case of multilayer h-BN films leading to hybridized hyperbolic plasmon-phonon polaritons (HPPPs) that are also mediated by the SAW. These results pave the way for engineering SAW-based graphene/h-BN plasmonic devices and metamaterials covering the mid-IR to THz range.

  15. Surface plasmon polariton amplification in semiconductor-graphene-dielectric structure

    Dadoenkova, Yuliya S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Novgorod State University, Veliky Novgorod (Russian Federation); Donetsk Institute for Physics and Technology, Donetsk (Ukraine); Moiseev, Sergey G. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Ulyanovsk (Russian Federation); Abramov, Aleksei S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kadochkin, Aleksei S.; Zolotovskii, Igor O. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences, 32A Leninskiy Prosp., 119991, Moscow (Russian Federation); Fotiadi, Andrei A. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Universite de Mons (Belgium)

    2017-05-15

    A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing-down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Green chemistry approach for the synthesis of biocompatible graphene

    Gurunathan, Sangiliyandi; Han, Jae Woong; Kim, Jin-Hoi

    2013-01-01

    Background Graphene is a single-atom thick, two-dimensional sheet of hexagonally arranged carbon atoms isolated from its three-dimensional parent material, graphite. One of the most common methods for preparation of graphene is chemical exfoliation of graphite using powerful oxidizing agents. Generally, graphene is synthesized through deoxygenation of graphene oxide (GO) by using hydrazine, which is one of the most widespread and strongest reducing agents. Due to the high toxicity of hydrazine, it is not a promising reducing agent in large-scale production of graphene; therefore, this study focused on a green or sustainable synthesis of graphene and the biocompatibility of graphene in primary mouse embryonic fibroblast cells (PMEFs). Methods Here, we demonstrated a simple, rapid, and green chemistry approach for the synthesis of reduced GO (rGO) from GO using triethylamine (TEA) as a reducing agent and stabilizing agent. The obtained TEA reduced GO (TEA-rGO) was characterized by ultraviolet (UV)–visible absorption spectroscopy, X-ray diffraction (XRD), particle size dynamic light scattering (DLS), scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). Results The transition of graphene oxide to graphene was confirmed by UV–visible spectroscopy. XRD and SEM were used to investigate the crystallinity of graphene and the surface morphologies of prepared graphene respectively. The formation of defects further supports the functionalization of graphene as indicated in the Raman spectrum of TEA-rGO. Surface morphology and the thickness of the GO and TEA-rGO were analyzed using AFM. The presented results suggest that TEA-rGO shows significantly more biocompatibility with PMEFs cells than GO. Conclusion This is the first report about using TEA as a reducing as well as a stabilizing agent for the preparation of biocompatible graphene. The proposed safe and green method offers substitute routes for large-scale production of graphene

  17. Preparation, characterization, Raman, and terahertz spectroscopy study on carbon nanotubes, graphene nano-sheets, and onion like carbon materials

    Abouelsayed, A.; Anis, Badawi; Hassaballa, Safwat; Khalil, Ahmed S.G.; Rashed, Usama M.; Eid, Kamal A.; Al-Ashkar, Emad; El hotaby, W.

    2017-01-01

    We present the optical properties of carbon nanotubes, graphene nanosheets, and onion like carbon (OLC) samples with different cages size in wide frequency range from 0.06 to 1650 THz. The samples were characterized by high resolution transmission electron microscope (HRTEM), Raman, and UV–Vis-IR-THz spectroscopy. The broad absorption bands centered at around 10, 3, 2.5, 1.5, and 1.8 THz for SWCNTs, MWCNTs, graphene nanosheets, large cages (OLC 1 ), and small cages (OLC 2 ) samples, respectively, are assigned to plasmon resonance due to the localization of free carriers in a finite length. For SWCNTs, both the plasmon band position and the Drude weight (D) are located at higher values as compared with MWCNTs, graphene nanosheets, and OLC sample, suggesting that the dimensionality of the system plays a major role regarding the carrier mobility of the graphene structure. The differences in the estimated values of D, the Fermi energy (E f ), and density of carriers (N) in case of OLC samples can be due to the variation in sizes of the cages and the variation of the defects in the structure of the outermost layers of cages, where each cages consist of multi-layers of graphene enclosed one into another. - Highlights: • Preparation and spectroscopic studies on carbonaceous materials were performed. • Drude-Lorentz model were used for fitting the optical conductivity spectra. • The plasmonic resonances have been observed in THz frequency range. • The charge density N has been effected by disordered of the grapheme structure. • The σ DC values is decreased in case of 2D carbonaceous materials.

  18. Preparation, characterization, Raman, and terahertz spectroscopy study on carbon nanotubes, graphene nano-sheets, and onion like carbon materials

    Abouelsayed, A., E-mail: as.abouelsayed@gmail.com [Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouth St. (fromer El Tahrir St.), Dokki, P.O. 12622, Giza (Egypt); Anis, Badawi [Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouth St. (fromer El Tahrir St.), Dokki, P.O. 12622, Giza (Egypt); Hassaballa, Safwat [Physics Department, Faculty of Science, Al-Azhar University, Cairo 11884 (Egypt); Khalil, Ahmed S.G. [Center for Environmental and Smart Technology, Fayoum University, Fayoum (Egypt); Egypt Nanotechnology Center, Cairo University, Giza (Egypt); Arab Academy for Science, Technology and Maritime Transport, Smart Village Campus, Giza (Egypt); Rashed, Usama M. [Physics Department, Faculty of Science, Al-Azhar University, Cairo 11884 (Egypt); Eid, Kamal A.; Al-Ashkar, Emad; El hotaby, W. [Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouth St. (fromer El Tahrir St.), Dokki, P.O. 12622, Giza (Egypt)

    2017-03-01

    We present the optical properties of carbon nanotubes, graphene nanosheets, and onion like carbon (OLC) samples with different cages size in wide frequency range from 0.06 to 1650 THz. The samples were characterized by high resolution transmission electron microscope (HRTEM), Raman, and UV–Vis-IR-THz spectroscopy. The broad absorption bands centered at around 10, 3, 2.5, 1.5, and 1.8 THz for SWCNTs, MWCNTs, graphene nanosheets, large cages (OLC{sub 1}), and small cages (OLC{sub 2}) samples, respectively, are assigned to plasmon resonance due to the localization of free carriers in a finite length. For SWCNTs, both the plasmon band position and the Drude weight (D) are located at higher values as compared with MWCNTs, graphene nanosheets, and OLC sample, suggesting that the dimensionality of the system plays a major role regarding the carrier mobility of the graphene structure. The differences in the estimated values of D, the Fermi energy (E{sub f}), and density of carriers (N) in case of OLC samples can be due to the variation in sizes of the cages and the variation of the defects in the structure of the outermost layers of cages, where each cages consist of multi-layers of graphene enclosed one into another. - Highlights: • Preparation and spectroscopic studies on carbonaceous materials were performed. • Drude-Lorentz model were used for fitting the optical conductivity spectra. • The plasmonic resonances have been observed in THz frequency range. • The charge density N has been effected by disordered of the grapheme structure. • The σ{sub DC} values is decreased in case of 2D carbonaceous materials.

  19. Effect of preparation conditions on physicochemical, surface and catalytic properties of cobalt ferrite prepared by coprecipitation

    El-Shobaky, G.A., E-mail: elshobaky@yahoo.co [Physical Chemistry Department, National Research Center, Dokki, Cairo (Egypt); Turky, A.M.; Mostafa, N.Y.; Mohamed, S.K. [Chemistry Department, Faculty of Science, Suez Canal University, Ismailia 41522 (Egypt)

    2010-03-18

    Cobalt ferrite nanoparticles were prepared via thermal treatment of cobalt-iron mixed hydroxides at 400-600 {sup o}C. The mixed hydroxides were coprecipitated from their nitrates solutions using NaOH as precipitating agent. The effects of pH and temperature of coprecipitation and calcination temperature on the physicochemical, surface and catalytic properties of the prepared ferrites were studied. The prepared systems were characterized using TG, DTG, DTA, chemical analysis, atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), energy dispersive X-ray (EDX) as well as surface and texture properties based on nitrogen adsorption-desorption isotherms. The prepared cobalt ferrites were found to be mesoporous materials that have crystallite size ranges between 8 and 45 nm. The surface and catalytic properties of the produced ferrite phase were strongly dependent on coprecipitation conditions of the mixed hydroxides and on their calcination temperature.

  20. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

    van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano

    2016-01-01

    Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy image...

  1. Metals on graphene and carbon nanotube surfaces: From mobile atoms to atomtronics to bulk metals to clusters and catalysts

    Sarkar, Santanu C.

    2014-01-14

    In this Perspective, we present an overview of recent fundamental studies on the nature of the interaction between individual metal atoms and metal clusters and the conjugated surfaces of graphene and carbon nanotube with a particular focus on the electronic structure and chemical bonding at the metal-graphene interface. We discuss the relevance of organometallic complexes of graphitic materials to the development of a fundamental understanding of these interactions and their application in atomtronics as atomic interconnects, high mobility organometallic transistor devices, high-frequency electronic devices, organometallic catalysis (hydrogen fuel generation by photocatalytic water splitting, fuel cells, hydrogenation), spintronics, memory devices, and the next generation energy devices. We touch on chemical vapor deposition (CVD) graphene grown on metals, the reactivity of its surface, and its use as a template for asymmetric graphene functionalization chemistry (ultrathin Janus discs). We highlight some of the latest advances in understanding the nature of interactions between metals and graphene surfaces from the standpoint of metal overlayers deposited on graphene and SWNT thin films. Finally, we comment on the major challenges facing the field and the opportunities for technological applications. © 2013 American Chemical Society.

  2. Preparation of graphene and the research of dielectric properties of graphene/PVDF composites%石墨烯的制备及石墨烯/PVDF合材料介电性能的研究

    宋洪松; 刘大博

    2011-01-01

    The fully oxidized graphite oxide was prepared by Staudenmaier method, and single layer of graphene was obtained through the thermal expansion mechanism. The oxide degree and oxygen containing functional groups of graphite oxide had been investigated by FT-IR, TC, XRD, etc; the existence of graphene had been proved by XRD. The graphene/PVDF nanocomposites had been prepared by ultrasonic processing and mixture method. Dielectric results showed graphene could imporve dielectric constant of PVDF.and when the quality ratio of graphene got 0.25%, the permittivity of composite got to 16, which was 1.7 times of pure PVDF. And a novel ideal of graphene's application and preparation high charge storage density capacitor of low cost was expolred.%通过Staudenmaier法制备了完全氧化的氧化石墨(GO),并通过高温热膨胀制备了单层石墨烯(graphene).用FT-IR、TG和XRD对GO的氧化程度、含氧官能团进行了表征;Graphene的XRD测试结果证明了单层石墨的存在.利用超声共混法制备了graphene/PV DF介电纳米复合材料.介电性能的测试表明:Graphene的加入使PVDF介电常数大幅提高,当graphene添加量为0.25%(质量分数)时,材料介电常数接近16,是纯PVDF的1.7倍,这为石墨烯的应用和低成本介电复合材料的制备提供了新思路.

  3. Redox reaction between graphene oxide and In powder to prepare In2O3/reduced graphene oxide hybrids for supercapacitors

    Xu, Xiaoyang; Wu, Tao; Xia, Fengling; Li, Yi; Zhang, Congcong; Zhang, Lei; Chen, Mingxi; Li, Xichuan; Zhang, Li; Liu, Yu; Gao, Jianping

    2014-11-01

    A facile and quick route for the chemical reduction of graphene oxide (GO) using In powder as a reductant has been established. The reduction of GO by In powder is traced by UV-visible absorption spectroscopy, and the obtained reduced graphene oxide (rGO) is analyzed. The In3+ ions produced during the reaction between the GO and the In powder are chemically transformed to In2O3 and then form In2O3/rGO hybrids. The In2O3/rGO hybrids are used as electrode materials and their electrochemical performance are studied using cyclic voltammetry and galvanostatic charge/discharge. The In2O3/rGO hybrids demonstrate excellent electrochemical performance and their highest specific capacitance is 178.8 F g-1 which is much higher than that of either In2O3 or rGO. In addition, the In2O3/rGO hybrids are also very stable.

  4. Radiation preparation of graphene/carbon nanotubes hybrid fillers for mechanical reinforcement of poly(vinyl alcohol) films

    Ma, Hui-Ling; Zhang, Long; Zhang, Youwei; Wang, Shuojue; Sun, Chao; Yu, Hongyan; Zeng, Xinmiao; Zhai, Maolin

    2016-01-01

    Graphene/carbon nanotubes (G/CNTs) hybrid fillers were synthesized by γ-ray radiation reduction of graphene oxide (GO) in presence of CNTs. The obtained hybrid fillers with three-dimensional (3D) interconnected network structure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Poly(vinyl alcohol) (PVA) composite films with enhanced mechanical properties and thermal stability were subsequently prepared by solution blending of G/CNTs with PVA matrix. The tensile strength and Young's modulus of PVA composite films containing 1 wt% G/CNTs were measured to be 81.9 MPa and 3.9 GPa respectively, which were 56% and 33.6% higher than those of pure PVA. These substantial improvements could be attributed to the interconnected 3D structure of G/CNTs, homogeneous dispersion as well as the strong hydrogen-bonding interaction between G/CNTs and PVA macromolecular chains.

  5. Preparation of layered graphene and tungsten oxide hybrids for enhanced performance supercapacitors.

    Xing, Ling-Li; Huang, Ke-Jing; Fang, Lin-Xia

    2016-11-01

    Tungsten oxide (WO 3 ), which was originally poor in capacitive performance, is made into an excellent electrode material for supercapacitors by dispersing it on graphene (Gr). The obtained Gr-WO 3 hybrids are characterized by X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy and scanning electron microscopy techniques, and evaluated as electrode materials for high-performance supercapacitors by cyclic voltammetry, galvanostatic charge-discharge curves and electrochemical impedance spectroscopy. A great improvement in specific capacitance is achieved with the present hybrids, from 255 F g -1 for WO 3 nanoparticles to 580 F g -1 for Gr-WO 3 hybrids (scanned at 1 A g -1 in 2 M KOH over a potential window of 0 to 0.45 V). The Gr-WO 3 hybrid exhibits an excellent high rate capability and good cycling stability with more than 92% capacitance retention over 1000 cycles at a current density of 5 A g -1 . The enhancement in supercapacitor performance of Gr-WO 3 is not only attributed to its unique nanostructure with large specific surface area, but also its excellent electro-conductivity, which facilitates efficient charge transport and promotes electrolyte diffusion. As a whole, this work indicates that Gr-WO 3 hybrids are a promising electrode material for high-performance supercapacitors.

  6. Preparation and properties of highly conductive palmitic acid/graphene oxide composites as thermal energy storage materials

    Mehrali, Mohammad; Latibari, Sara Tahan; Mehrali, Mehdi; Indra Mahlia, Teuku Meurah; Cornelis Metselaar, Hendrik Simon

    2013-01-01

    PA/GO (palmitic acid/graphene oxide) as PCMs (phase change materials) prepared by vacuum impregnation method, have high thermal conductivity. The GO (graphene oxide) composite was used as supporting material to improve thermal conductivity and shape stabilization of composite PCM (phase change material). SEM (Scanning electronic microscope), FT-IR (Fourier transformation infrared spectroscope) and XRD (X-ray diffractometer) were applied to determine microstructure, chemical structure and crystalloid phase of palmitic acid/GO composites, respectively. DSC (Differential scanning calorimeter) test was done to investigate thermal properties which include melting and solidifying temperatures and latent heat. FT-IR analysis represented that the composite instruction of porous palmitic acid and GO were physical. The temperatures of melting, freezing and latent heats of the composite measured through DSC analysis were 60.45, 60.05 °C, 101.23 and 101.49 kJ/kg, respectively. Thermal cycling test showed that the form-stable composite PCM has good thermal reliability and chemical stability. Thermal conductivity of the composite PCM was improved by more than three times from 0.21 to 1.02. As a result, due to their acceptable thermal properties, good thermal reliability, chemical stability and great thermal conductivities, we can consider the prepared form-stable composites as highly conductive PCMs for thermal energy storage applications. - Highlights: • Novel composite PCM with high thermal conductivity and latent heat storage. • New thermal cycling test for thermal reliability of composite PCMs. • Increasing thermal conductivity of composite PCM with graphene oxide. • Increasing thermal stability of phase change material by adding graphene oxide

  7. Preparation of hollow Zn2SnO4 boxes@C/graphene ternary composites with a triple buffering structure and their electrochemical performance for lithium-ion batteries

    Huang, Haijian; Huang, Ying; Wang, Mingyue; Chen, Xuefang; Zhao, Yang; Wang, Ke; Wu, Haiwei

    2014-01-01

    Highlights: • A new hollow Zn 2 SnO 4 boxes@C/graphene ternary composites were synthesized through two hydrothermal processes followed by a calcined process for the first time. • The structure, morphology and electrochemical properties of the ternary composites were investigated by means of XRD, FTIR, Raman, BET, BJH, SEM, TEM, and electrochemical measurements. • The hollow Zn 2 SnO 4 boxes@C/graphene ternary composites were proved to have a triple buffering nanostructure. The hollow interior of the Zn 2 SnO 4 boxes, the carbon coating layer on the surface of the boxes and the 3D carbon network constructed by the graphene sheets can work together to effectively improve the electrochemical performance of the material. • The hollow Zn 2 SnO 4 boxes@C/graphene ternary composites show an enhanced electrochemical performance (726.9 mAh g −1 at a current density of 300 mA g −1 after 50 cycles) and high rate capability compared with the hollow Zn 2 SnO 4 boxes@graphene binary composites, the hollow Zn 2 SnO 4 boxes@C binary composites, the hollow Zn 2 SnO 4 boxes and the solid Zn 2 SnO 4 cubes. - Abstract: Hollow Zn 2 SnO 4 boxes@C/graphene ternary composites with a three-dimensional triple buffering structure are prepared by two hydrothermal processes followed by a calcined process. The structure, morphology and electrochemical properties of the ternary composites were investigated by means of XRD, FTIR, Raman, BET, BJH, SEM, TEM, and electrochemical measurements. The hollow Zn 2 SnO 4 boxes are coated with carbon layer and then supported by graphene sheets to form a 3D carbon conductive network. Compared with the hollow Zn 2 SnO 4 boxes@graphene binary composites, the hollow Zn 2 SnO 4 boxes@C binary composites, the hollow Zn 2 SnO 4 boxes and the solid Zn 2 SnO 4 cubes, the hollow Zn 2 SnO 4 boxes@C/graphene ternary composites show an enhanced electrochemical performance (726.9 mAh g −1 at a current density of 300 mA g −1 after 50 cycles) and high rate

  8. One-step Fabrication of Cellulose/Graphene Conductive Paper

    KaiWen Mou; LuMing Yang; HuangWei Xiong; RuiTao Cha

    2017-01-01

    In this study,a straightforward,one-step wet-end formation process was employed to prepare cellulose/graphene conductive paper for antistatic packing materials.Cationic polyacrylamide was introduced into the cellulose/graphene slurry to improve the graphene loading on the surfaces of the cellulose fibers.The effect of the super calender process on the properties of the cellulose/graphene conductive paper was investigated.When 55 wt% graphene was added,the volume resistivity of the cellulose/graphene conductive paper was 94.70 Ω·cm,decreasing to 35.46 Ω·cm after the super calender process.The cellulose/graphene conductive paper possessed excellent anti-static ability and could be used as an anti-static material.

  9. Microwave-irradiated preparation of reduced graphene oxide-Ni nanostructures and their enhanced performance for catalytic reduction of 4-nitrophenol

    Qiu, Hanxun; Qiu, Feilong; Han, Xuebin; Li, Jing; Yang, Junhe

    2017-06-01

    Here we report an environmentally friendly, one-pot strategy toward preparation of nickel nanoparticle-decorated reduced graphene-oxide (Ni-RGO) nanostructures, by employing Ni(AC)2 as nickel source and ethylene glycol as both solvent and reducing agent via a facile microwave irradiation heating approach. The results show that Ni nanoparticles with an average diameter of around 40 nm are homogeneously anchored onto the surface of RGO sheets. As compared to the pure Ni nanoparticles and RGO sheets, Ni-RGO composites with over 64 wt% loading of Ni nanoparticles possess superior catalytic activities and selectivity toward the reduction of 4-nitrophenol. The corresponding kinetic reaction rate constant (defined as κ) is even four-fold compared to pure Ni nanoparticles. Such promising composites show great potential for friendly treatment of industrial waste containing nitrophenol in a simple, sustainable and green way.

  10. Enzymatic sensing of glucose in artificial saliva using a flat electrode consisting of a nanocomposite prepared from reduced graphene oxide, chitosan, nafion and glucose oxidase

    Rabti, Amal; Argoubi, Wicem; Raouafi, Noureddine

    2016-01-01

    We report on the preparation of a nanoporous flat electrode by drop casting a nanocomposite consisting of reduced graphene oxide (rGO) and chitosan onto a polyester substrate. An underlying conductive surface is not required. The nanocomposite was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The 3D network of the composite was used as a scaffold for the immobilization of glucose oxidase (GOx). A well-defined signal related to direct GOx electrochemistry was registered and used to monitor levels of glucose. The resulting biosensor displays a linear response to glucose with a detection limit of 5 μM (at an S/N ratio of 3) and a sensitivity of 41.7 μA⋅mM"−"1∙cm"−"2. The sensor was applied to the determination of glucose in artificial saliva. (author)

  11. Improvement of graphene field-effect transistors by hexamethyldisilazane surface treatment

    Chowdhury, Sk. Fahad; Sonde, Sushant; Rahimi, Somayyeh; Tao, Li; Banerjee, Sanjay; Akinwande, Deji

    2014-01-01

    We report the improvement of the electrical characteristics of graphene field-effect transistors (FETs) by hexamethyldisilazane (HMDS) treatment. Both electron and hole field-effect mobilities are increased by 1.5 × –2×, accompanied by effective residual carrier concentration reduction. Dirac point also moves closer to zero Volt. Time evolution of mobility data shows that mobility improvement saturates after a few hours of HMDS treatment. Temperature-dependent transport measurements show small mobility variation between 77 K and room temperature (295 K) before HMDS application. But mobility at 77 K is almost 2 times higher than mobility at 295 K after HMDS application, indicating reduced carrier scattering. Performance improvement is also observed for FETs made on hydrophobic substrate–an HMDS-graphene-HMDS sandwich structure. Raman spectroscopic analysis shows that G peak width is increased, G peak position is down shifted, and intensity ratio between 2D and G peaks is increased after HMDS application. We attribute the improvements in electronic transport mainly to enhanced screening and mitigation of adsorbed impurities from graphene surface upon HMDS treatment.

  12. Preparation, characterization, and nonlinear optical properties of hybridized graphene @ gold nanorods nanocomposites

    Guo, Jia; Ning, Tingyin; Han, Yanshun; Sheng, Yingqiang; Li, Chonghui; Zhao, Xiaofei; Lu, Zhengyi; Man, Baoyuan; Jiao, Yang; Jiang, Shouzhen

    2018-03-01

    The methods of chemical vapor deposition (CVD) and seed-mediated growth were used to obtain graphene and gold nanorods (GNRs), respectively. We fabricate graphene @ gold nanorods (G@GNRs) nanocomposites by successively using dropping and transferring methods Through SEM, Raman spectra and TEM analysis, the number of graphene layers is 6-7. The diameter of gold nanorods (GNRs) is about 10 nm and the average aspect ratio is 6.5. In addition, we systematically investigate their nonlinear optical responses by using open-aperture Z-scan technique. In contrast with graphene and GNRs, the G@GNRs nanocomposites exhibit excellent nonlinear optical response with a modulation depth of about 51% and a saturable intensity of about 6.23 GW/cm2. The results suggest that the G@GNRs nanocomposites could potentially be used as an optical modulator in pulsed laser generation.

  13. Preparation and characterization of graphene-based vanadium oxide composite semiconducting films with horizontally aligned nanowire arrays

    Jung, Hye-Mi; Um, Sukkee

    2016-01-01

    Highly oriented crystalline hybrid thin films primarily consisting of Magnéli-phase VO 2 and conductive graphene nanoplatelets are fabricated by a sol–gel process via dipping pyrolysis. A combination of chemical, microstructural, and electrical analyses reveals that graphene oxide (GO)-templated vanadium oxide (VO x ) nanocomposite films exhibit a vertically stacked multi-lamellar nanostructure consisting of horizontally aligned vanadium oxide nanowire (VNW) arrays along the (hk0) set of planes on a GO template, with an average crystallite size of 41.4 Å and a crystallographic tensile strain of 0.83%. In addition, GO-derived VO x composite semiconducting films, which have an sp 3 /sp 2 bonding ratio of 0.862, display thermally induced electrical switching properties in the temperature range of − 20 °C to 140 °C, with a transition temperature of approximately 65 °C. We ascribe these results to the use of GO sheets, which serve as a morphological growth template as well as an electrochemically tunable platform for enhancing the charge-carrier mobility. Moreover, the experimental studies demonstrate that graphene-based Magnéli-phase VO x composite semiconducting films can be used in advanced thermo-sensitive smart sensing/switching applications because of their outstanding thermo-electrodynamic properties and high surface charge density induced by the planar-type VNWs. - Highlights: • VO x -graphene oxide composite (G/VO x ) films were fabricated by sol–gel process. • The G/VO x films mainly consisted of Magnéli-phase VO 2 and reduced graphene sheets. • The G/VO x films exhibited multi-lamellar textures with planar VO x nanowire arrays. • The G/VO x films showed the thermo-sensitive electrical switching properties. • Effects of GOs on the electrical characteristics of the G/VO x films were discussed.

  14. One-pot preparation of PEDOT:PSS-reduced graphene decorated with Au nanoparticles for enzymatic electrochemical sensing of H{sub 2}O{sub 2}

    Mercante, Luiza A., E-mail: lamercante@gmail.com [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Facure, Murilo H.M. [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Center for Exact Sciences and Technology, Federal University of São Carlos (UFSCar), 13565-905, São Carlos, SP (Brazil); Sanfelice, Rafaela C.; Migliorini, Fernanda L.; Mattoso, Luiz H.C. [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Correa, Daniel S., E-mail: daniel.correa@embrapa.br [National Laboratory for Nanotechnology in Agribusiness (LNNA), Embrapa Instrumentation, 13560-970, São Carlos, SP (Brazil); Center for Exact Sciences and Technology, Federal University of São Carlos (UFSCar), 13565-905, São Carlos, SP (Brazil)

    2017-06-15

    Highlights: • Hybrid ternary nanocomposite PEDOT:PSS-rGO-AuNPs is developed by a one-step approach. • Horseradish peroxidase is used to build a novel hybrid biomaterial. • The PEDOT:PSS-rGO-AuNPs-HRP displays excellent electrochemical activity toward the reduction of H{sub 2}O{sub 2}. • A significant low detection limit of 0.08 μM and wider linear range is achieved. • The constructed electrode is used detecting H{sub 2}O{sub 2} in real samples. - Abstract: The development of novel graphene-based nanocomposites is a hotspot in materials science due to their unique optical, electronic, thermal, mechanical and catalytic properties for varied applications. The present work reports on the development of a graphene-based ternary nanocomposite of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), reduced graphene oxide and gold nanoparticles (PEDOT:PSS-rGO-AuNPs) for the detection of hydrogen peroxide (H{sub 2}O{sub 2}). The hybrid nanocomposite showed superior electrochemical properties and higher stability compared to each individual component as electrode materials, showing a synergistic effect between PEDOT, rGO and AuNPs. The nanocomposite was obtained via a facile one-step approach and was assembly with horseradish peroxidase (HRP). The PEDOT:PSS-rGO-AuNPs-HRP modified electrode has been used for the amperometric detection of H{sub 2}O{sub 2} and exhibited a high sensitivity of up to 677 μA mM{sup −1} cm{sup −2}, with a wide linear range from 5 to 400 μM and a low detection limit of 0.08 μM (S/N = 3). This developed enzymatic biosensor showed to be highly stable and unresponsive to potentially interfering substances, and it could be used for sensing H{sub 2}O{sub 2} in real samples, including tap water and bovine milk samples. These enhanced sensing performance could be ascribed to the intimate contact of AuNPs onto the rough surface of the PEDOT:PSS-rGO nanocomposite, which has a high electrical conductivity and large surface area, providing

  15. Preparation of flower-like TiO{sub 2} sphere/reduced graphene oxide composites for photocatalytic degradation of organic pollutants

    Kim, Tae-Woong [Department of Chemistry, Inha University, 100 Inharo, Incheon 402-751 (Korea, Republic of); Park, Mira [Department of Organic Materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kim, Hak Yong [Department of BIN Convergence technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, 100 Inharo, Incheon 402-751 (Korea, Republic of)

    2016-07-15

    In this study, novel flower-like TiO{sub 2} sphere (FTS)/reduced graphene oxide (rGO) composites (FTS-G) were synthesized via a hydrothermal method. The photocatalytic performance of the FTS-G composites was evaluated through the photodegradation of rhodamine B (Rh B) and trichloroethylene (TCE) under simulated solar light irradiation. The rGO to FTS ratio in the composites significantly affected photocatalytic activity. The photocatalytic activities of FTS-Gs in the degradation of Rh B and TCE were superior to that of pure FTS. Of all the FTS-G composites tested, FTS-G with 1 wt% rGO (FTS-G-1) had the greatest photocatalytic activity, while FTS-G composites with rGO contents over 1 wt% had lower photocatalytic activities. Additionally, it is expected that the synthesis of FTS with a high specific surface area and well-developed pore structure and simultaneous conversion of GO to graphene-like rGO without the use of strong reducing agents could be a promising strategy to prepare other carbon-based flower-like TiO{sub 2} sphere composite photocatalysts. - Graphical abstract: Schematic illustration of high photocatalytic activity for FTS-G composites. Display Omitted.

  16. The Sliding Wear and Friction Behavior of M50-Graphene Self-Lubricating Composites Prepared by Laser Additive Manufacturing at Elevated Temperature

    Liu, Xiyao; Shi, Xiaoliang; Huang, Yuchun; Deng, Xiaobin; Lu, Guanchen; Yan, Zhao; Zhou, Hongyan; Xue, Bing

    2018-03-01

    M50 steel is widely applied to manufacture aircraft bearings where service lives are mainly determined by the friction and wear behaviors. The main purpose of this study is to investigate the tribological behaviors and wear mechanisms of M50-1.5 wt.% graphene composites (MGC) prepared by laser additive manufacturing (LAM) (MGC-LAM) sliding against Si3N4 ball from 25 to 550 °C at 18 N-0.2 m/s. XRD, EPMA, FESEM, and EDS mapping were conducted to understand the major mechanisms leading to the improvement in the sliding behavior of MGC-LAM. The results indicated that MGC-LAM showed the excellent friction and wear performance at 25-550 °C for the lower friction coefficient of 0.16-0.52 and less wear rate of 6.1-9.5 × 10-7 mm3 N-1 m-1. Especially at 350 °C, MGC-LAM obtained the best tribological performance (0.16, 6.1 × 10-7mm3 N-1 m-1). It was attributed to the dense coral-like microstructure, as well as the formed surface lubricating structure which is composed of the upper uniform lubricating film with massive graphene and the underneath compacted layer.

  17. Selective Dispersive Solid Phase Extraction of Ser-traline Using Surface Molecularly Imprinted Polymer Grafted on SiO2/Graphene Oxide

    Faezeh Khalilian

    2017-01-01

    Full Text Available A surface molecularly imprinted dispersive solid phase extraction coupled with liquid chromatography–ultraviolet detection is proposed as a selective and fast clean-up technique for the determination of sertraline in biological sample. Surface sertraline-molecular imprinted polymer was grafted and synthesized on the SiO2/graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and progen, respectively. Non-imprinted polymer was also prepared for comparing purposes. The properties of the molecular imprinted polymer were characterized using field emission-scanning electron microscopy and Fourier transform infrared spectroscopy methods. The surface molecular imprinted polymer was utilized as an adsorbent of dispersive solid phase extraction for separation and preconcentration of sertraline. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the non-imprinted polymer was examined in absence and presence of competitive drugs. Sertraline calibration curve showed linearity in the ranges 1–500 µg L-1. The limits of detection and quantification under optimized conditions were obtained 0.2 and 0.5 µg L-1. The within-day and between-day relative standard deviations (n=3 were 4.3 and 7.1%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 92%.

  18. Spectra investigation on surface characteristics of graphene oxide nanosheets treated with tartaric, malic and oxalic acids.

    Teng, Xiyao; Yan, Manqing; Bi, Hong

    2014-01-24

    The surface characteristics of graphene oxide nanosheets (GO) treated respectively with tartaric acid, malic acid and oxalic acid, have been investigated by mainly using optical spectroscopic methods including Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible (UV-Vis) absorption and Raman spectroscopy. Additionally, the electrochemical property of the products has also been studied. The data revealed that oxygen-containing groups such as OH, COOH and CO on the GO surface have been almost removed and thus reduced graphene oxide nanosheets (RGN) were obtained. Interestingly, the number of sp(2) domains of RGN increases as treated by tartaric acidsurface conjugated degree alteration. We claim that the difference in both SH and IC among these acids is the main reason for the diverse surface characteristics as well as the improved Cs of the RGN. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Temperature-tunable wettability on a bioinspired structured graphene surface for fog collection and unidirectional transport.

    Song, Yun-Yun; Liu, Yan; Jiang, Hao-Bo; Li, Shu-Yi; Kaya, Cigdem; Stegmaier, Thomas; Han, Zhi-Wu; Ren, Lu-Quan

    2018-02-22

    We designed a type of smart bioinspired wettable surface with tip-shaped patterns by combining polydimethylsiloxane (PDMS) and graphene (PDMS/G). The laser etched porous graphene surface can produce an obvious wettability change between 200 °C and 0 °C due to a change in aperture size and chemical components. We demonstrate that the cooperation of the geometrical structure and the controllable wettability play an important role in water gathering, and surfaces with tip-shaped wettability patterns can quickly drive tiny water droplets toward more wettable regions, so making a great contribution to the improvement of water collection efficiency. In addition, due to the effective cooperation between super hydrophobic and hydrophilic regions of the special tip-shaped pattern, unidirectional water transport on the 200 °C heated PDMS/G surface can be realized. This study offers a novel insight into the design of temperature-tunable materials with interphase wettability that may enhance fog collection efficiency in engineering liquid harvesting equipment, and realize unidirectional liquid transport, which could potentially be applied to the realms of microfluidics, medical devices and condenser design.

  20. Hydrogen intercalation of single and multiple layer graphene synthesized on Si-terminated SiC(0001) surface

    Sołtys, Jakub; Piechota, Jacek; Ptasinska, Maria; Krukowski, Stanisław

    2014-01-01

    Ab initio density functional theory simulations were used to investigate the influence of hydrogen intercalation on the electronic properties of single and multiple graphene layers deposited on the SiC(0001) surface (Si-face). It is shown that single carbon layer, known as a buffer layer, covalently bound to the SiC substrate, is liberated after hydrogen intercalation, showing characteristic Dirac cones in the band structure. This is in agreement with the results of angle resolved photoelectron spectroscopy measurements of hydrogen intercalation of SiC-graphene samples. In contrast to that hydrogen intercalation has limited impact on the multiple sheet graphene, deposited on Si-terminated SiC surface. The covalently bound buffer layer is liberated attaining its graphene like structure and dispersion relation typical for multilayer graphene. Nevertheless, before and after intercalation, the four layer graphene preserved the following dispersion relations in the vicinity of K point: linear for (AAAA) stacking, direct parabolic for Bernal (ABAB) stacking and “wizard hat” parabolic for rhombohedral (ABCA) stacking

  1. Preparation of polymer brushes grafted graphene oxide by atom transfer radical polymerization as a new support for trypsin immobilization and efficient proteome digestion.

    Guo, Cong; Zhao, Xinyuan; Zhang, Wanjun; Bai, Haihong; Qin, Weijie; Song, Haifeng; Qian, Xiaohong

    2017-08-01

    Highly efficient protein digestion is one of the key issues in the "bottom-up" strategy-based proteomic studies. Compared with the time-consuming solution-based free protease digestion, immobilized protease digestion offers a promising alternative with obviously improved sample processing throughput. In this study, we proposed a new immobilized protease digestion strategy using two kinds of polymer-grafted graphene oxide (GO) conjugated trypsin. The polymer brush grafted GO was prepared using in situ polymer growth on initiator-functionalized GO using surface-initiated atom transfer radical polymerization (SI-ATRP) and characterized by AFM, TEM, TGA, and XPS. The polymer brush grafted GO supports three-dimensional trypsin immobilization, which not only increases the loading amount but also improves accessibility towards protein substrates. Both of the two types of immobilized trypsin provide 700 times shorter digestion time, while maintaining comparable protein/peptide identification scale compared with that of free trypsin digestion. More interestingly, combined application of the two types of immobilized trypsin with different surface-grafted polymers leads to at least 18.3/31.3% enhancement in protein/peptide identification compared with that obtained by digestion using a single type, indicating the potential of this digestion strategy for deeper proteome coverage using limited mass spectrometer machine hour. We expect these advantages may find valuable application in high throughput clinical proteomic studies, which often involve processing of a large number of samples. Graphical abstract Preparation of polymer brushes grafted and trypsin immobilized graphene oxide and its application in proteome digestion and mass spectrometry identification.

  2. Facile Synthesis of Nitrogen Doped Graphene Oxide from Graphite Flakes and Powders: A Comparison of Their Surface Chemistry.

    Yokwana, Kholiswa; Ray, Sekhar C; Khenfouch, Mohammad; Kuvarega, Alex T; Mamba, Bhekie B; Mhlanga, Sabelo D; Nxumalo, Edward N

    2018-08-01

    Nitrogen-doped graphene oxide (NGO) nanosheets were prepared via a facile one-pot modified Hummer's approach at low temperatures using graphite powder and flakes as starting materials in the presence of a nitrogen precursor. It was found that the morphology, structure, composition and surface chemistry of the NGO nanosheets depended on the nature of the graphite precursor used. GO nanosheets doped with nitrogen atoms exhibited a unique structure with few thin layers and wrinkled sheets, high porosity and structural defects. NGO sheets made from graphite powder (NGOp) exhibited excellent thermal stability and remarkably high surface area (up to 240.53 m2 ·g-1) compared to NGO sheets made from graphite flakes (NGOf) which degraded at low temperatures and had an average surface area of 24.70 m2 ·g-1. NGOf sheets had a size range of 850 to 2200 nm while NGOp sheets demonstrated obviously small sizes (460-1600 nm) even when exposed to different pH conditions. The NGO nanosheets exhibited negatively charged surfaces in a wide pH range (1 to 12) and were found to be stable above pH 6. In addition, graphite flakes were found to be more suitable for the production of NGO as they produced high N-doping levels (0.65 to 1.29 at.%) compared to graphite powders (0.30 to 0.35 at.%). This study further demonstrates that by adjusting the amount of N source in the host GO, one can tailor its thermal stability, surface morphology, surface chemistry and surface area.

  3. Chemistry at the dirac point of graphene

    Sarkar, Santanu

    Graphene holds great potential as an electronic material because of its excellent transport properties, which derive from its unique Fermi surface and ballistic conductance. It exhibits extremely high mobility [~250,000 cm*2/(V*s)]. Despite its extraordinary properties, the absence of a band-gap in graphene makes it unsuitable for its use as an active element in conventional field effect transistors (FETs). Another problem with pristine graphene is its lack of solution processability, which inhibits it applications in numerous fields such as printed electronics, transparent conductors, nano-biodevices, and thin film technologies involving fuel cells, capacitors and solar cells. My thesis is focused on addressing theses issue by application of covalent chemistry on graphene. We have applied the Kolbe electro-oxidation strategy to achieve an efficient quasi-reversible electrochemical grafting of the naphthylmethyl radicals to graphene. The method facilitates reversible bandgap engineering in graphene and preparation of electrochemically erasable organic dielectric films. We have discovered that the zero-band-gap electronic structure of graphene enables it to function as either the diene or the dienophile in the Diels-Alder (DA) reaction, and this versatile synthetic method offers a powerful strategy for the reversible modification of the electronic properties of graphene under very mild conditions. We show that the application of the Diels-Alder (DA) chemistry to graphene, which is capable of simultaneous formation of a pair of sp3-carbon centers (balanced divacancies) in graphene, can selectively produce DA-modified graphene FET devices with mobility between 1,000-6,000 cm2V-1s-1 (with a variable range hopping transport mechanism). Most of the covalent chemistry applied on graphene leads to the change in hybridization of graphene sp2 carbon to sp3 (destructive hybridization) and the FET devices based on such covalently modified graphene shows a drastic reduction of

  4. A novel sensitive Cu(II) and Cd(II) nanosensor platform: Graphene oxide terminated p-aminophenyl modified glassy carbon surface

    Gupta, Vinod Kumar; Yola, Mehmet Lütfi; Atar, Necip; Ustundag, Zafer; Solak, Ali Osman

    2013-01-01

    Graphical abstract: - Highlights: • We electrochemically prepared sensor based on graphene oxide. • The prepared electrode was characterized by using various techniques. • The proposed nanosensor showed good stability, selectivity and high sensitivity. • The proposed nanosensor electrode was used for the analysis of Cd(II) and Cu(II). - Abstract: Graphene oxide (GO) based glassy carbon (GC) electrode has been prepared. Firstly, p-nitrophenyl (NP) modified GC (NP/GC) electrode was prepared via the electrochemical reduction of its tetraflouroborate diazonium salt. After the formation of NP/GC electrode, the negative potential was applied to NP/GC electrode to reduce the nitro groups to amine. p-Aminophenyl (AP) modified GC (AP/GC) electrode was immersed into a graphene oxide solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide. Hence, we constructed GO terminated AP modified GC (GO/AP/GC) electrode. NP/GC, AP/GC and GO/AP/GC electrodes were characterized sequentially using cyclic voltammetry (CV) in the presence of 1.0 mM of potassium ferricyanide in 0.1 M KCl. In addition, GO and GO/AP/GC surfaces were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The GO/AP/GC electrode was used for the analysis of Cd(II) and Cu(II) ions by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) and Cu(II) ions were 1.0 × 10 −11 –5.0 × 10 −10 M and 3.3 × 10 −12 M (S/N = 3), respectively

  5. Effect of incorporating graphene oxide and surface imprinting on polysulfone membranes on flux, hydrophilicity and rejection of salt and polycyclic aromatic hydrocarbons from water

    Kibechu, Rose Waithiegeni; Ndinteh, Derek Tantoh; Msagati, Titus Alfred Makudali; Mamba, Bhekie Briliance; Sampath, S.

    2017-08-01

    We report a significant enhancement of hydrophillity of polysulfone (Psf) membranes after modification with graphene oxide (GO) as a filler followed by surface imprinting on the surface of GO/Psf composite imprinted membranes (CIMs). The surface imprinting on the GO-Psf membrane was employed in order to enhance its selectivity towards polycyclic aromatic hydrocarbons (PAHs) in water. The CIMs were prepared through a process of phase inversion of a mixture of graphene oxide and polysulfone (Psf) in N-methylpyrrolidone (NMP). Fourier-transform spectroscopy (FT-IR) of the imprinted showed new peaks at 935 cm-1 and 1638 cm-1 indicating success in surface imprinting on the GO-Psf membrane. The CIM also showed improvement in flux from 8.56 LM-2 h-1 of unmodified polysulfone membrane to 15.3 LM-2 h-1 in the CIM, salt rejection increased from 57.2 ± 4.2% of polysulfone membrane to 76 ± 4.5%. The results obtained from the contact angle measurements showed a decrease with increase in GO content from 72 ± 2.7% of neat polysulfone membrane to 62.3 ± 2.1% of CIM indicating an improvement in surface hydrophilicity. The results from this study shows that, it is possible to improve the hydrophilicity of the membranes without affecting the performance of the membranes.

  6. Natural printed silk substrate circuit fabricated via surface modification using one step thermal transfer and reduction graphene oxide

    Cao, Jiliang; Huang, Zhan; Wang, Chaoxia

    2018-05-01

    Graphene conductive silk substrate is a preferred material because of its biocompatibility, flexibility and comfort. A flexible natural printed silk substrate circuit was fabricated by one step transfer of graphene oxide (GO) paste from transfer paper to the surface of silk fabric and reduction of the GO to reduced graphene oxide (RGO) using a simple hot press treatment. The GO paste was obtained through ultrasonic stirring exfoliation under low temperature, and presented excellent printing rheological properties at high concentration. The silk fabric was obtained a surface electric resistance as low as 12.15 KΩ cm-1, in the concentration of GO 50 g L-1 and hot press at 220 °C for 120 s. Though the whiteness and strength decreased with the increasing of hot press temperature and time slowly, the electric conductivity of RGO surface modification silk substrate improved obviously. The surface electric resistance of RGO/silk fabrics increased from 12.15 KΩ cm-1 to 18.05 KΩ cm-1, 28.54 KΩ cm-1 and 32.53 KΩ cm-1 after 10, 20 and 30 washing cycles, respectively. The results showed that the printed silk substrate circuit has excellent washability. This process requires no chemical reductant, and the reduction efficiency and reduction degree of GO is high. This time-effective and environmentally-friendly one step thermal transfer and reduction graphene oxide onto natural silk substrate method can be easily used to production of reduced graphene oxide (RGO) based flexible printed circuit.

  7. Tailored lithium storage performance of graphene aerogel anodes with controlled surface defects for lithium-ion batteries

    Shan, Hui; Xiong, Dongbin; Li, Xifei; Sun, Yipeng; Yan, Bo; Li, Dejun; Lawes, Stephen; Cui, Yanhua; Sun, Xueliang

    2016-01-01

    Graphical abstract: - Highlights: • The graphene aerogel (GA) with controllable surface defects was synthesized. • The graphene aerogel anodes showed high specific capacity and excellent cyclability. • Surface defects on the GA significantly function for lithium storage. • This study can extend the application of the graphene anodes for LIBs. - Abstract: Three dimensional self-assembled graphene aerogel (GA) anode materials with some surface defects have been successfully generated through a facile hydrothermal procedure using graphene oxide as precursor. The morphologies and textural properties of as-obtained GA were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman and other spectroscopy techniques. The surface defects and electrical conductivities of GA can be controlled by adjusting the hydrothermal reaction time. The results indicate that GA with a reaction time of 6 h exhibits extremely high reversible capacity (1430 mAh g"−"1 at the current density of 100 mA g"−"1) and superior rate capability (587 mAh g"−"1 at 800 mA g"−"1) with excellent cycling stability (maintaining a reversible capacity of 960 mAh g"−"1 at 100 mA g"−"1 after 100 cycles). It is demonstrated that the 3D porous network with increased defect density, as well as the considerable electrical conductivity, results in the excellent electrochemical performance of the as-made GA anodes in lithium-ion batteries.

  8. Preparation of graphene oxide/poly (3,4-ethylenedioxytriophene): Poly (styrene sulfonate) (PEDOT:PSS) electrospun nanofibers

    Efelina, Vita; Widianto, Eri; Rusdiana, Dadi; Nugroho, A. A.; Kusumaatmaja, Ahmad; Triyana, Kuwat; Santoso, Iman

    2016-01-01

    Graphene oxide (GO)/Poly (3,4-Ethylenedioxytriophene):Poly (styrene Sulfonate) (PEDOT:PSS) nanofibers have been successfully fabricated by a simple electrospinning technique to develop conductive nanofibers with polyvinyl alcohol (PVA) act as a carrier solution. Graphene oxide has been synthesized by Hummer’s method and has been confirmed by Raman Spectroscopy, FTIR and UV-Vis Spectroscopy. GO/PEDOT:PSS composite nanofibers. The structural and morphological properties were characterized by Scanning Electron Microscopy (SEM). The result of SEM show that GO/PEDOT:PSS nanofibers has a relatively uniform morphology nanofiber with diameter between 180 nm - 340 nm with smooth nanofiber surface. The produced nanofibers from this study can be utilized for various applications such as flexible, conductive and transparent electrode.

  9. Preparation of graphene oxide/poly (3,4-ethylenedioxytriophene): Poly (styrene sulfonate) (PEDOT:PSS) electrospun nanofibers

    Efelina, Vita; Widianto, Eri [Department of Physics, Universitas Gadjah Mada, Sekip Utara BLS.21 Yogyakarta, 55281 Indonesia (Indonesia); Rusdiana, Dadi [Department of Physical Education, Universitas Pendidikan Indonesia, Bandung (Indonesia); Nugroho, A. A. [Department of Physics, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung (Indonesia); Kusumaatmaja, Ahmad; Triyana, Kuwat; Santoso, Iman, E-mail: iman.santoso@ugm.ac.id [Department of Physics, Universitas Gadjah Mada, Sekip Utara BLS.21 Yogyakarta, 55281 Indonesia (Indonesia); Nanomaterials Research Group, Universitas Gadjah Mada,, Sekip Utara, Yogyakarta (Indonesia)

    2016-04-19

    Graphene oxide (GO)/Poly (3,4-Ethylenedioxytriophene):Poly (styrene Sulfonate) (PEDOT:PSS) nanofibers have been successfully fabricated by a simple electrospinning technique to develop conductive nanofibers with polyvinyl alcohol (PVA) act as a carrier solution. Graphene oxide has been synthesized by Hummer’s method and has been confirmed by Raman Spectroscopy, FTIR and UV-Vis Spectroscopy. GO/PEDOT:PSS composite nanofibers. The structural and morphological properties were characterized by Scanning Electron Microscopy (SEM). The result of SEM show that GO/PEDOT:PSS nanofibers has a relatively uniform morphology nanofiber with diameter between 180 nm - 340 nm with smooth nanofiber surface. The produced nanofibers from this study can be utilized for various applications such as flexible, conductive and transparent electrode.

  10. Spatial variation of the number of graphene layers formed on the scratched 6H-SiC(0 0 0 1) surface

    Osaklung, J. [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900 (Thailand); Euaruksakul, C. [Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics, CHE, Bangkok 10400 (Thailand); Meevasana, W., E-mail: worawat@g.sut.ac.th [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics, CHE, Bangkok 10400 (Thailand); Songsiriritthigul, P. [School of Physics, Suranaree University of Technology, Nakhon Ratchasima 30000 (Thailand); Synchrotron Light Research Institute, Nakhon Ratchasima 30000 (Thailand); Thailand Center of Excellence in Physics, CHE, Bangkok 10400 (Thailand)

    2012-03-01

    The unique properties of graphene can vary greatly depending on the number of graphene layers; therefore, spatial control of graphene thickness is desired to fully exploit these properties in promising new devices. Using low energy electron microscopy (LEEM), we investigate how scratches on the surface of 6H-SiC(0 0 0 1) affect the epitaxial growth of graphene. Oscillations in the LEEM-image intensity as a function of electron energy (I-V LEEM analysis) show that the number of graphene layers clearly differs between regions of scratched and smooth substrate. The extent of the thicker graphene layers formed above scratches is found to be significantly larger than the width of the scratch itself. This finding can be implemented as an additional technique for spatially modulating graphene thickness.

  11. Preparation of surface–modified lanthanum fluoride–graphene oxide nanohybrids and evaluation of their tribological properties as lubricant additive in liquid paraffin

    Yang, Cuizhen; Hou, Xiao; Li, Zhiwei; Li, Xiaohong; Yu, Laigui; Zhang, Zhijun

    2016-01-01

    Highlights: • Oleic acid was selected as the modifier according to similar miscibility principle. • OA–LaF_3–GO nanohybrids were successfully prepared by surface modification technology. • OA–LaF_3–GO nanohybrids prove excellent antiwear and friction-reducing capacities. - Abstract: Oleic acid surface–modified Lanthanum trifluoride–graphene oxide (OA–LaF_3–GO) nanohybrids were successfully prepared by surface modification technology. The morphology and phase structure of as-prepared samples were analyzed by means of X-ray diffraction and transmission electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry and thermogravimetry. The results revealed that OA were bonded onto the surface of LaF_3–GO nanohybrids. Subsequently, the tribological properties of OA–LaF_3–GO nanohybrids as lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined on a scanning electron microscope with an energy dispersive spectrometer. Tribological results showed that OA–LaF_3–GO nanohybrids had excellent friction reduction and antiwear ability at the loading of 0.5 wt.% OA–LaF_3–GO nanohybrids, compared to liquid paraffin alone. The results of energy dispersive spectrometer revealed that improved tribological properties resulted from OA–LaF_3–GO could transfer to the rubbed steel surface and decompose to form protective layers, which help to improve tribological properties.

  12. Preparation of surface–modified lanthanum fluoride–graphene oxide nanohybrids and evaluation of their tribological properties as lubricant additive in liquid paraffin

    Yang, Cuizhen; Hou, Xiao; Li, Zhiwei, E-mail: zhiweili@henu.edu.cn; Li, Xiaohong; Yu, Laigui; Zhang, Zhijun

    2016-12-01

    Highlights: • Oleic acid was selected as the modifier according to similar miscibility principle. • OA–LaF{sub 3}–GO nanohybrids were successfully prepared by surface modification technology. • OA–LaF{sub 3}–GO nanohybrids prove excellent antiwear and friction-reducing capacities. - Abstract: Oleic acid surface–modified Lanthanum trifluoride–graphene oxide (OA–LaF{sub 3}–GO) nanohybrids were successfully prepared by surface modification technology. The morphology and phase structure of as-prepared samples were analyzed by means of X-ray diffraction and transmission electron microscopy, Fourier transform infrared spectrometry, Raman spectrometry and thermogravimetry. The results revealed that OA were bonded onto the surface of LaF{sub 3}–GO nanohybrids. Subsequently, the tribological properties of OA–LaF{sub 3}–GO nanohybrids as lubricant additive in liquid paraffin were evaluated with a four-ball machine, and the morphology and elemental composition of worn steel surfaces were examined on a scanning electron microscope with an energy dispersive spectrometer. Tribological results showed that OA–LaF{sub 3}–GO nanohybrids had excellent friction reduction and antiwear ability at the loading of 0.5 wt.% OA–LaF{sub 3}–GO nanohybrids, compared to liquid paraffin alone. The results of energy dispersive spectrometer revealed that improved tribological properties resulted from OA–LaF{sub 3}–GO could transfer to the rubbed steel surface and decompose to form protective layers, which help to improve tribological properties.

  13. Direct preparation of a graphene oxide modified monolith in a glass syringe as a solid-phase extraction cartridge for the extraction of quaternary ammonium alkaloids from Chinese patent medicine.

    Liang, Xiaojing; Wang, Licheng; Wang, Shuai; Li, Yijing; Guo, Yong

    2017-11-01

    Packed cartridges have been widely used in solid-phase extraction. However, there are still some drawbacks, such as they are blocked easily and the method is time-consuming. In view of the advantages of monoliths, a monolithic extraction material has been directly synthesized in a glass syringe without any gap between the monolith and syringe inner wall. The monolithic syringe was modified with graphene oxide by loading graphene oxide dispersion onto it. The content of graphene oxide and the surface topography of the monolith have been evaluated by elemental analysis and scanning electron microscopy, respectively, which confirmed the successful modification. This prepared graphene oxide-modified monolithic syringe was directly used as a traditional solid-phase extraction cartridge. As expected, it shows good permeability and excellent capability for the extraction of quaternary ammonium alkaloids. The sample loading velocity (1-6 mL/min) does not affect the recovery. Under the optimal conditions, good linearities (R = 0.9992-0.9998) were obtained for five quaternary ammonium alkaloids, and the limits of detection and quantification were 0.5-1 and 1-2 μg/L, respectively. The proposed method was successfully applied for the analysis of quaternary ammonium alkaloids in Chinese patent medicine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. From surface to volume plasmons in hyperbolic metamaterials: General existence conditions for bulk high-k waves in metal-dielectric and graphene-dielectric multilayers

    Zhukovsky, Sergei; Andryieuski, Andrei; Sipe, John E.

    2014-01-01

    -dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high- k waves...

  15. HIGH VELOCITY THERMAL GUN FOR SURFACE PREPARATION AND TREATMENT

    I.A. Gorlach

    2012-01-01

    Full Text Available Many surface preparation and treatment processes utilise compressed air to propel particles against surfaces in order to clean and treat them. The effectiveness of the processes depends on the velocity of the particles, which in turn depends on the pressure of the compressed air. This paper describes a thermal gun built on the principles of High Velocity Air Fuel (HVAF and High Velocity Oxy Fuel (HVOF processes. The designed apparatus can be used for abrasive blasting, coating of surfaces, cutting of rocks, removing rubber from mining equipment, cleaning of contaminations etc.

  16. The promising application of graphene oxide as coating materials in orthopedic implants: preparation, characterization and cell behavior

    Zhao, Changhong; Lu, Xiuzhen; Liu, Johan; Zanden, Carl

    2015-01-01

    To investigate the potential application of graphene oxide (GO) in bone repair, this study is focused on the preparation, characterization and cell behavior of graphene oxide coatings on quartz substrata. GO coatings were prepared on the substrata using a modified dip-coating procedure. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy results demonstrated that the as-prepared coatings in this study were homogeneous and had an average thickness of ∼67 nm. The rapid formation of a hydroxyapatite (HA) layer in the simulated body fluid (SBF) on GO coated substrata at day 14, as proved by SEM and x-ray diffraction (XRD), strongly indicated the bioactivity of coated substrata. In addition, MC3T3-E1 cells were cultured on the coated substrata to evaluate cellular activities. Compared with the non-coated substrata and tissue culture plates, no significant difference was observed on the coated substrata in terms of cytotoxicity, viability, proliferation and apoptosis. However, interestingly, higher levels of alkaline phosphatase (ALP) activity and osteocalcin (OC) secretion were observed on the coated substrata, indicating that GO coatings enhanced cell differentiation compared with non-coated substrata and tissue culture plates. This study suggests that GO coatings had excellent biocompatibility and more importantly promoted MC3T3-E1 cell differentiation and might be a good candidate as a coating material for orthopedic implants. (paper)

  17. Preparation and characterisation of glass surfaces for experimental purposes

    Serruys, Y.

    1986-01-01

    Experimental investigation of glasses, applied especially to the prevision of the behaviour of vitrified nuclear wastes, requires the preparation of well-defined and reproducibles surfaces, in order to separate the investigated phenomena from artifacts due to surface anomalies and to allow a valuable comparison between results obtained in different laboratories. The aim of the present report is to determine which characters, both physical and chemical, of glass surfaces, have to be controlled, because of their influence upon the investigated phenomena or the experimental processes employed in the investigation. A method is then presented for a surface preparation giving good guaranties of quality and reproducibility. The physical and chemical aspects of surface characterisation are successively considered. The relevant characters and their importance are described, then the corresponding techniques of characterisation are reviewed and it has been attempted to propose a set of techniques allowing a characterisation as complete as possible for laboratory purposes. A preparation method for experimental sample, aiming to satisfy all the previously defined criteria, is then proposed, and present results obtained with this method are described [fr

  18. Preparation, characterisation and critical flux determination of graphene oxide blended polysulfone (PSf) membranes in an MBR system.

    Ravishankar, Harish; Roddick, Felicity; Navaratna, Dimuth; Jegatheesan, Veeriah

    2018-05-01

    Microfiltration membranes having different blends of graphene-oxide (GO) (0-1 wt%) and Polysulfone (PSf) (15-20 wt%) were prepared using the classical non-solvent induced phase inversion process. The prepared membranes were characterised for their structural morphology, surface properties, mechanical strength, porosity and pure water flux. Based on the initial characterisation results, four membranes (15 wt% PSf, 15 wt% PSf + 0.25 wt% GO, 15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) were chosen for critical flux study, that was conducted using flux-step method in a lab scale MBR system. In order to study the application potential of GO blended membranes, the critical flux of each membrane was evaluated in two operational modes i.e., continuous and intermittent modes with backwash. The membranes with maximal GO concentration (15 wt% PSf + 1 wt% GO and 20 wt% PSf + 1 wt% GO) showed higher critical flux (16.5, 12.8 L/m 2 h and 19, 15 L/m 2 h for continuous and intermittent mode, respectively). It was observed that the operational modes did not have a significant effect on the critical flux of the membranes with low GO concentration (15 wt% PSf and 15 wt% PSf + 0.25 wt% GO), indicating a minimal of 1 wt% GO was required for an observable effect that favoured intermittent mode of operation. Through these results, ideal operating condition was arrived (i.e., flux maintained at 6.4 L/m 2 h operated under intermittent mode) and the membranes 15 wt% PSf and 15 wt% PSf + 1 wt% GO were studied for their long-term operation. The positive effect of GO on filtration time, cleaning frequency and against fouling was demonstrated through long term TMP profile of the membranes, indicating the suitability of GO blended membrane for real time wastewater treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. The influence of adherent surface preparation on bond durability

    Rider, A.N.; Arnott, D.R.; Olsson-Jacques, C.L.

    1999-01-01

    Full text: One of the major factors limiting the use of adhesive bonding is the problem associated with the production of adhesive joints that can maintain their initial strength over long periods of time in hostile environments. It is well known that the adherent surface preparation method is critical to the formation of a durable adhesive bond. Work presented in this paper focuses on the critical aspects of the surface preparation of aluminium employed for the manufacture of aluminium-epoxy joints. The surface preparation procedure examined is currently employed by the RAAF for repairs requiring metal to adhesive bonding. The influence of each step in the surface preparation on the ultimate bond durability performance of the adhesive joint is examined by a combination of methods. Double cantilever wedge style adhesive joints are loaded in mode 1 opening and then exposed to a humid environment. X-ray photoelectron spectroscopy (XPS) and contact angle measurements of the aluminium adherent before bonding provides information about the adherent surface chemistry. XPS is also employed to analyse the surfaces of the bonded specimens post failure to establish the locus of fracture. This approach provides important information regarding the properties influencing bond durability as well as the bond failure mechanisms. A two step bond degradation model was developed to qualitatively describe the observed bond durability performance and fracture data. The first step involves controlled moisture ingress by stress induced microporosity of the adhesive in the interfacial region. The second step determines the locus of fracture through the relative dominance of one of three competitive processes, viz: oxide degradation, polymer desorption, or polymer degradation. A key element of the model is the control exercised over the interfacial microporosity by the combined interaction of stress and the relative densities of strong and weak linkages at the metal to adhesive interface

  20. Attenuation of the in vitro neurotoxicity of 316L SS by graphene oxide surface coating

    Tasnim, Nishat; Kumar, Alok; Joddar, Binata

    2017-01-01

    A persistent theme in biomaterials research comprises of surface engineering and modification of bare metallic substrates for improved cellular response and biocompatibility. Graphene Oxide (GO), a derivative of graphene, has outstanding chemical and mechanical properties; its large surface to volume ratio, ease of surface modification and processing make GO an attractive coating material. GO-coatings have been extensively studied as biosensors. Further owing to its surface nano-architecture, GO-coated surfaces promote cell adhesion and growth, making it suitable for tissue engineering applications. The need to improve the long-term durability and therapeutic effectiveness of commercially available bare 316L stainless steel (SS) surfaces led us to adopt a polymer-free approach which is cost-effective and scalable. GO was immobilized on to 316L SS utilizing amide linkage, to generate a strongly adherent uniform coating with surface roughness. GO-coated 316L SS surfaces showed increased hydrophilicity and biocompatibility with SHSY-5Y neuronal cells, which proliferated well and showed decreased reactive oxygen species (ROS) expression. In contrast, cells did not adhere to bare uncoated 316L SS meshes nor maintain viability when cultured in the vicinity of bare meshes. Therefore the combination of the improved surface properties and biocompatibility implies that GO-coating can be utilized to overcome pertinent limitations of bare metallic 316L SS implant surfaces, especially SS neural electrodes. Also, the procedure for making GO-based protective coatings can be applied to numerous other implants where the development of such protective films is necessary. - Highlights: • GO was immobilized on to 316L SS utilizing carbodiimide chemistry to generate a strong adherent uniform nano coating. • GO-modified surfaces showed increased hydrophilicity and biocompatibility with SH5YSY cells cultured atop these surfaces. • Proliferation and alignment of the cells with the

  1. Attenuation of the in vitro neurotoxicity of 316L SS by graphene oxide surface coating

    Tasnim, Nishat; Kumar, Alok; Joddar, Binata, E-mail: bjoddar@utep.edu

    2017-04-01

    A persistent theme in biomaterials research comprises of surface engineering and modification of bare metallic substrates for improved cellular response and biocompatibility. Graphene Oxide (GO), a derivative of graphene, has outstanding chemical and mechanical properties; its large surface to volume ratio, ease of surface modification and processing make GO an attractive coating material. GO-coatings have been extensively studied as biosensors. Further owing to its surface nano-architecture, GO-coated surfaces promote cell adhesion and growth, making it suitable for tissue engineering applications. The need to improve the long-term durability and therapeutic effectiveness of commercially available bare 316L stainless steel (SS) surfaces led us to adopt a polymer-free approach which is cost-effective and scalable. GO was immobilized on to 316L SS utilizing amide linkage, to generate a strongly adherent uniform coating with surface roughness. GO-coated 316L SS surfaces showed increased hydrophilicity and biocompatibility with SHSY-5Y neuronal cells, which proliferated well and showed decreased reactive oxygen species (ROS) expression. In contrast, cells did not adhere to bare uncoated 316L SS meshes nor maintain viability when cultured in the vicinity of bare meshes. Therefore the combination of the improved surface properties and biocompatibility implies that GO-coating can be utilized to overcome pertinent limitations of bare metallic 316L SS implant surfaces, especially SS neural electrodes. Also, the procedure for making GO-based protective coatings can be applied to numerous other implants where the development of such protective films is necessary. - Highlights: • GO was immobilized on to 316L SS utilizing carbodiimide chemistry to generate a strong adherent uniform nano coating. • GO-modified surfaces showed increased hydrophilicity and biocompatibility with SH5YSY cells cultured atop these surfaces. • Proliferation and alignment of the cells with the

  2. Fabrication of new magnetite-graphene nanocomposite and comparison of its laser-hyperthermia properties with conventionally prepared magnetite-graphene hybrid

    Tayyebi, Ahmad; Moradi, Shahab; Azizi, Fatemeh; Outokesh, Mohammad; Shadanfar, Kamran; Mousavi, Seyed Sadjad

    2017-01-01

    A single step supercritical method was introduced for synthesis of “magnetite - reduced graphene oxide (M-rGO)” composite in supercritical methanol. Modified surface, smaller size, lesser cytotoxicity, and homogenous dispersion of Fe 3 O 4 nanoparticles on the graphene surface were advantages of this new M-rGO composite in comparison to the materials synthesized by conventional wet chemical method (M-GO). Nanocomposites were injected in tissue equivalent phantoms of agarose gel in 10 mg/g dosage, and were irradiated by a 1600 mW laser beam at wavelength of 800–810 nm. The M-rGO and M-GO were found to be the most and the least efficient samples for increasing the temperature of the phantom. As for mathematical analysis of the heating process, a heat transfer model was developed and solved by the COMSOL Multiphysics software. Results showed an appreciable agreement with the experiments and revealed enhancement in thermal conductivity and light absorption coefficient of tissue by injecting of M-rGO sample. Our findings showed that M-rGO is a promising material for laser hyperthermia, which can deposit adequate heat dose with desirable effect in the tumorous cells in a short period. - Highlights: • Synthesis of magnetic Fe 3 O 4 -rGO with modified surface, smaller size and lesser cytotoxicity in supercritical methanol. • Development of a heat transfer model for prediction of tissue temperature in hyperthermia process. • Enhancement in thermal conductivity and light absorption coefficient of tissue by injecting of new magnetic Fe 3 O 4 -rGO. • Application of the nanocomposits in efficient laser hyperthermia in the tumorous cells.

  3. Fabrication of new magnetite-graphene nanocomposite and comparison of its laser-hyperthermia properties with conventionally prepared magnetite-graphene hybrid

    Tayyebi, Ahmad [Department of Energy Engineering, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Moradi, Shahab [Department of Energy Engineering, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Azizi, Fatemeh [Department of Energy Engineering, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Outokesh, Mohammad, E-mail: Outokesh@sharif.ir [Department of Energy Engineering, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of); Shadanfar, Kamran [Medical Committee of Handball Federation of Islamic Republic of Iran, Tehran (Iran, Islamic Republic of); Mousavi, Seyed Sadjad [Department of Energy Engineering, Sharif University of Technology, P.O. Box 11365-8639, Tehran (Iran, Islamic Republic of)

    2017-06-01

    A single step supercritical method was introduced for synthesis of “magnetite - reduced graphene oxide (M-rGO)” composite in supercritical methanol. Modified surface, smaller size, lesser cytotoxicity, and homogenous dispersion of Fe{sub 3}O{sub 4} nanoparticles on the graphene surface were advantages of this new M-rGO composite in comparison to the materials synthesized by conventional wet chemical method (M-GO). Nanocomposites were injected in tissue equivalent phantoms of agarose gel in 10 mg/g dosage, and were irradiated by a 1600 mW laser beam at wavelength of 800–810 nm. The M-rGO and M-GO were found to be the most and the least efficient samples for increasing the temperature of the phantom. As for mathematical analysis of the heating process, a heat transfer model was developed and solved by the COMSOL Multiphysics software. Results showed an appreciable agreement with the experiments and revealed enhancement in thermal conductivity and light absorption coefficient of tissue by injecting of M-rGO sample. Our findings showed that M-rGO is a promising material for laser hyperthermia, which can deposit adequate heat dose with desirable effect in the tumorous cells in a short period. - Highlights: • Synthesis of magnetic Fe{sub 3}O{sub 4}-rGO with modified surface, smaller size and lesser cytotoxicity in supercritical methanol. • Development of a heat transfer model for prediction of tissue temperature in hyperthermia process. • Enhancement in thermal conductivity and light absorption coefficient of tissue by injecting of new magnetic Fe{sub 3}O{sub 4}-rGO. • Application of the nanocomposits in efficient laser hyperthermia in the tumorous cells.

  4. Low-temperature aluminum reduction of graphene oxide, electrical properties, surface wettability, and energy storage applications.

    Wan, Dongyun; Yang, Chongyin; Lin, Tianquan; Tang, Yufeng; Zhou, Mi; Zhong, Yajuan; Huang, Fuqiang; Lin, Jianhua

    2012-10-23

    Low-temperature aluminum (Al) reduction is first introduced to reduce graphene oxide (GO) at 100-200 °C in a two-zone furnace. The melted Al metal exhibits an excellent deoxygen ability to produce well-crystallized reduced graphene oxide (RGO) papers with a low O/C ratio of 0.058 (Al-RGO), compared with 0.201 in the thermally reduced one (T-RGO). The Al-RGO papers possess outstanding mechanical flexibility and extremely high electrical conductivities (sheet resistance R(s) ~ 1.75 Ω/sq), compared with 20.12 Ω/sq of T-RGO. More interestingly, very nice hydrophobic nature (90.5°) was observed, significantly superior to the reported chemically or thermally reduced papers. These enhanced properties are attributed to the low oxygen content in the RGO papers. During the aluminum reduction, highly active H atoms from H(2)O reacted with melted Al promise an efficient oxygen removal. This method was also applicable to reduce graphene oxide foams, which were used in the GO/SA (stearic acid) composite as a highly thermally conductive reservoir to hold the phase change material for thermal energy storage. The Al-reduced RGO/SnS(2) composites were further used in an anode material of lithium ion batteries possessing a higher specific capacity. Overall, low-temperature Al reduction is an effective method to prepare highly conductive RGO papers and related composites for flexible energy conversion and storage device applications.

  5. A dataset for preparing pristine graphene-palladium nanocomposites using swollen liquid crystal templates

    Vats, Tripti; Siril, Prem Felix

    2017-12-01

    Pristine graphene (G) has not received much attention as a catalyst support, presumably due to its relative inertness as compared to reduced graphene oxide (RGO). In the present work, we used swollen liquid crystals (SLCs) as nano-reactors for graphene-palladium nanocomposites synthesis. The 'soft' confinement of SLCs directs the growth of palladium (Pd) nanoparticles over the G sheets. In this dataset we include all the parameters and details of different techniques used for the characterization of G, SLCs and synthesized G-Pd nanocomposites. The synthesized G-palladium nanocomposites (Pd-G) exhibited improved catalytic activity compared with Pd-RGO and Pd nanoparticles, in the hydrogenation of nitrophenols and C-C coupling reactions.

  6. Method for preparing microstructure arrays on the surface of thin film material

    Wang, Peng; Tang, Bo; Zhang, Lianbin

    2017-01-01

    Methods are provided for growing a thin film of a nanoscale material. Thin films of nanoscale materials are also provided. The films can be grown with microscale patterning. The method can include vacuum filtration of a solution containing the nanostructured material through a porous substrate. The porous substrate can have a pore size that is comparable to the size of the nanoscale material. By patterning the pores on the surface of the substrate, a film can be grown having the pattern on a surface of the thin film, including on the top surface opposite the substrate. The nanoscale material can be graphene, graphene oxide, reduced graphene oxide, molybdenum disulfide, hexagonal boron nitride, tungsten diselenide, molybdenum trioxide, or clays such as montmorillonite or lapnotie. The porous substrate can be a porous organic or inorganic membrane, a silicon stencil membrane, or similar membrane having pore sizes on the order of microns.

  7. Method for preparing microstructure arrays on the surface of thin film material

    Wang, Peng

    2017-02-09

    Methods are provided for growing a thin film of a nanoscale material. Thin films of nanoscale materials are also provided. The films can be grown with microscale patterning. The method can include vacuum filtration of a solution containing the nanostructured material through a porous substrate. The porous substrate can have a pore size that is comparable to the size of the nanoscale material. By patterning the pores on the surface of the substrate, a film can be grown having the pattern on a surface of the thin film, including on the top surface opposite the substrate. The nanoscale material can be graphene, graphene oxide, reduced graphene oxide, molybdenum disulfide, hexagonal boron nitride, tungsten diselenide, molybdenum trioxide, or clays such as montmorillonite or lapnotie. The porous substrate can be a porous organic or inorganic membrane, a silicon stencil membrane, or similar membrane having pore sizes on the order of microns.

  8. Transport of Dirac fermions on the surface of strong topological insulator and graphene

    Kundu, Arijit

    2012-06-14

    In this dissertation I study electronic transport through Dirac Fermions on the surface of strong topological insulator and graphene. I start by reviewing the physics of topological insulator and graphene and the low energy effective theory for the electronic states of the surface of a 3D strong topological insulator and graphene. Using this theory the electronic structure of the surface states of strong topological insulators of geometries with large surface to bulk ratio like nanowire and thin film are obtained. Then the energy spectrum and the spin-parity structure of the eigenstates for a finite size topological insulator quantum dot of the shape of a nanotube are considered. Numerical calculations show that even at the lowest energy scales, the ''spin-surface locking'' is broken, that is, the spin direction in a topologically protected surface mode is not locked to the surface. The calculations also show the existence of ''zero-momentum'' modes, and sub-gap states localized near the ''caps'' of the dot. Both the energy spectrum and the spin texture of the eigenstates are basically reproduced from an analytical surface Dirac fermion description. The results are compared to microscopic calculations using a tight-binding model for a strong topological insulator in a finite-length nanowire geometry, which shows qualitative similarity. Then, a theoretical study of electron-phonon scattering effects in thin films made of a strong topological insulator is presented. Phonons are modeled by isotropic elastic continuum theory with stress-free boundary conditions, and the interaction with the helical surface Dirac fermions is mediated by the deformation potential. The temperature-dependent electrical resistivity ρ(T) and the quasi-particle decay rate Γ(T) observable in photo-emission are computed numerically. The low and high-temperature power laws for both quantities are obtained analytically. Detailed

  9. Synthesis of reduced graphene oxide/ZnO nanorods composites on graphene coated PET flexible substrates

    Huang, Lei; Guo, Guilue; Liu, Yang; Chang, Quanhong; Shi, Wangzhou

    2013-01-01

    Graphical abstract: - Highlights: • ZnO nanorods synthesized on CVD-graphene and rGO surfaces, respectively. • ZnO/CVD-graphene and ZnO/rGO form a distinctive porous 3D structure. • rGO/ZnO nanostructures possibility in energy storage devices. - Abstract: In this work, reduced graphene oxide (rGO)/ZnO nanorods composites were synthesized on graphene coated PET flexible substrates. Both chemical vapor deposition (CVD) graphene and reduced graphene oxide (rGO) films were prepared following by hydrothermal growth of vertical aligned ZnO nanorods. Reduced graphene sheets were then spun coated on the ZnO materials to form a three dimensional (3D) porous nanostructure. The morphologies of the ZnO/CVD graphene and ZnO/rGO were investigated by SEM, which shows that the ZnO nanorods grown on rGO are larger in diameters and have lower density compared with those grown on CVD graphene substrate. As a result of fact, the rough surface of nano-scale ZnO on rGO film allows rGO droplets to seep into the large voids of ZnO nanorods, then to form the rGO/ZnO hierarchical structure. By comparison of the different results, we conclude that rGO/ZnO 3D nanostructure is more desirable for the application of energy storage devices

  10. Preparation and Characterization of Graphene Oxide-Modified Sapium sebiferum Oil-Based Polyurethane Composites with Improved Thermal and Mechanical Properties

    Guiying Wu

    2018-01-01

    Full Text Available Bio-based polyurethane (PU composites with superior thermal and mechanical properties have received wide attention. This is due to the recent rapid developments in the PU industry. In the work reported here, novel nano-composites with graphene oxide (GO-modified Sapium sebiferum oil (SSO-based PU has been synthesized via in situ polymerization. GO, prepared using the improved Hummers method from natural graphene (NG, and SSO-based polyol with a hydroxyl value of 211 mg KOH/g, prepared by lipase hydrolysis, were used as raw materials. The microstructures and properties of GO and the nano-composites were both characterized using Fourier transform infrared spectroscopy (FTIR, Raman spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, thermogravimetric analysis (TGA, differential scanning calorimetry (DSC, and tensile tests. The results showed that GO with its nano-sheet structure possessed a significant number of oxygen-containing functional groups at the surface. The nano-composites containing 1 wt % GO in the PU matrix (PU1 exhibited excellent comprehensive properties. Compared with those for pure PU, the glass transition temperature (Tg and initial decomposition temperature (IDT of the PU1 were enhanced by 14.1 and 31.8 °C, respectively. In addition, the tensile strength and Young’s modulus of the PU1 were also improved by 126% and 102%, respectively, compared to the pure PU. The significant improvement in both the thermal stability and mechanical properties for PU/GO composites was attributed to the homogeneous dispersion and good compatibility of GO with the PU matrix. The improvement in the properties upon the addition of GO may be attributable to the strong interfacial interaction between the reinforcing agent and the PU matrix.

  11. Enhanced catalytic hydrogenation activity of Ni/reduced graphene oxide nanocomposite prepared by a solid-state method

    Li, Yizhao; Cao, Yali; Jia, Dianzeng

    2018-01-01

    A simple solid-state method has been applied to synthesize Ni/reduced graphene oxide (Ni/rGO) nanocomposite under ambient condition. Ni nanoparticles with size of 10-30 nm supported on reduced graphene oxide (rGO) nanosheets are obtained through one-pot solid-state co-reduction among nickel chloride, graphene oxide, and sodium borohydride. The Ni/rGO nanohybrid shows enhanced catalytic activity toward the reduction of p-nitrophenol (PNP) into p-aminophenol compared with Ni nanoparticles. The results of kinetic research display that the pseudo-first-order rate constant for hydrogenation reaction of PNP with Ni/rGO nanocomposite is 7.66 × 10-3 s-1, which is higher than that of Ni nanoparticles (4.48 × 10-3 s-1). It also presents superior turnover frequency (TOF, 5.36 h-1) and lower activation energy ( E a, 29.65 kJ mol-1) in the hydrogenation of PNP with Ni/rGO nanocomposite. Furthermore, composite catalyst can be magnetically separated and reused for five cycles. The large surface area and high electron transfer property of rGO support are beneficial for good catalytic performance of Ni/rGO nanocomposite. Our study demonstrates a simple approach to fabricate metal-rGO heterogeneous nanostructures with advanced functions.

  12. Bulk functionalization of graphene using diazonium compounds and amide reaction

    Peng, Chang; Xiong, Yuzi; Liu, Zhibo; Zhang, Fan; Ou, Encai; Qian, Jiangtao; Xiong, Yuanqin; Xu, Weijian

    2013-09-01

    An efficient and convenient method is applied to introduce varieties of simple functionalities onto the graphene surface for the bulk preparation, which begins with pristine graphite that does not require initial oxidative damage of the graphene basal planes. Diazonium compounds functionalized reaction is demonstrated and it successfully prevented the aggregation of graphene for which providing solubility in high polar organic media or even in volatile solvents such as ethanol and acetone. This approach is complemented by the phenyl carboxylic diazonium salt functionalized graphene (PCFG) attachment of a symmetrically substituted zinc phthalocyanine (PCFG-Pc) using the amide reaction, which is used for the covalent introduction of a complex phthalocyanine molecule.

  13. Graphene Paper Based Nanomaterials for Electrochemical Sensing and Energy Conversion

    Zhang, Minwei

    of graphene-based materials to real world, graphene nanosheets must be assembled into macroscopic architecture with desired structures and functionality. To this end, graphene oxide (GO) is a very useful building block because it contains a significant number of oxygen-containing groups on the planar surface...... of hydrogen peroxide (H2O2). Graphene paper was finally explored as a sacrificial template for the synthesis of 2D ultra-fined nanostructured porous metal oxide (MO), as described in Chapters 6-8. In Chapter 6, we demonstrated that crystalline MO can be prepared by using GO papers as sacrificial templates...

  14. Terahertz modulation based on surface plasmon resonance by self-gated graphene

    Qian, Zhenhai; Yang, Dongxiao; Wang, Wei

    2018-05-01

    We theoretically and numerically investigate the extraordinary optical transmission through a terahertz metamaterial composed of metallic ring aperture arrays. The physical mechanism of different transmission peaks is elucidated to be magnetic polaritons or propagation surface plasmons with the help of surface current and electromagnetic field distributions at respective resonance frequencies. Then, we propose a high performance terahertz modulator based on the unique PSP resonance and combined with the metallic ring aperture arrays and a self-gated parallel-plate graphene capacitor. Because, to date, few researches have exhibited gate-controlled graphene modulation in terahertz region with low insertion losses, high modulation depth and low control voltage at room temperature. Here, we propose a 96% amplitude modulation with 0.7 dB insertion losses and ∼5.5 V gate voltage. Besides, we further study the absorption spectra of the modulator. When the transmission of modulator is very low, a 91% absorption can be achieved for avoiding damaging the source devices.

  15. Effect of Graphene Oxide (GO) on the Surface Morphology & Hydrophilicity of Polyethersulfone (PES)

    Junaidi, N. F. D.; Khalil, N. A.; Jahari, A. F.; Shaari, N. Z. K.; Shahruddin, M. Z.; Alias, N. H.; Othman, N. H.

    2018-05-01

    Membrane has been widely used in water and wastewater treatment. One of the major issues related membrane separation is concentration polarization or fouling, which can lead to a decline of flux and premature failure of membrane. However, fouling can be controlled by modification of membrane properties such as morphology and hydrophilicity. In this work, a modification of polymeric membrane, polyethersulfone (PES) was carried out using graphene oxide in order to attain high antifouling characteristics. Graphene oxide (GO) was added at different compositions ranging from (0.1 wt%-1.0 wt%). GO was synthesized using modified Hummers’ method and characterized using XRD and FTIR prior to using it as additive for the PES membrane. The prepared PES-GO composite membranes were characterized using FTIR and SEM, Contact angle measurement and pure water flux test were then conducted to investigate the hydrophilicity of the PES-GO membranes. It was found that the additions of GO has significantly improved the hydrophilicity of the membranes.

  16. Disturbance induced by surface preparation on instrumented indentation test

    Li, Yugang; Kanouté, Pascale; François, Manuel

    2015-01-01

    Surface preparation, which may induce considerable sample disturbance, plays an important role in instrumented indentation test (IIT). In this study, the sample disturbance (mainly divided into residual stresses and plastic strain) induced by the surface preparation process of instrumented indentation test specimens were investigated with both experimental tests and numerical simulations. Grazing incidence X-ray diffractions (GIXRD) and uniaxial tensile tests were conducted for characterizing the residual stresses and high plastic strain in the top surface layers of a carefully mechanically polished indentation sample, which, in the present work, is made of commercially pure titanium. Instrumented indentation tests and the corresponding finite element simulations were performed as well. For comparison, a reference sample (carefully mechanically polished & electrolytically polished) which represents the raw material was prepared and tested. Results showed that a careful mechanical polishing procedure can effectively reduce the level of residual stresses induced by this process. However, the high plastic strain in the surface region imposed by the polishing process is significant. The induced plastic strain can affect a depth up to 5 µm, which is deeper than the maximum penetration depth h max (3 µm) used for the instrumented indentation tests. In the near surface layer (in the range of depth about 350 nm), the plastic strain levels are fairly high. In the very top layer, the plastic strain was even estimated to reach more than 60%. The simultaneous use of indentation tests and numerical simulations showed that the existence of high plastic strain in the surface region will make the load vs depth (P–h) curve shift upwards, the contact hardness (H) increase and the contact stiffness (S) decrease

  17. Disturbance induced by surface preparation on instrumented indentation test

    Li, Yugang, E-mail: yugang.li@utt.fr [Université de Technologie de Troyes (UTT), ICD-LASMIS, UMR CNRS 6281, 12, rue Marie Curie-CS 42060, 10010 Troyes Cedex (France); Kanouté, Pascale, E-mail: pascale.kanoute@onera.fr [Université de Technologie de Troyes (UTT), ICD-LASMIS, UMR CNRS 6281, 12, rue Marie Curie-CS 42060, 10010 Troyes Cedex (France); The French Aerospace Lab (ONERA), DMSM/MCE, 29 avenue de la Division Leclerc-BP 72, F-92322 Chatillon Cedex (France); François, Manuel, E-mail: manuel.francois@utt.fr [Université de Technologie de Troyes (UTT), ICD-LASMIS, UMR CNRS 6281, 12, rue Marie Curie-CS 42060, 10010 Troyes Cedex (France)

    2015-08-26

    Surface preparation, which may induce considerable sample disturbance, plays an important role in instrumented indentation test (IIT). In this study, the sample disturbance (mainly divided into residual stresses and plastic strain) induced by the surface preparation process of instrumented indentation test specimens were investigated with both experimental tests and numerical simulations. Grazing incidence X-ray diffractions (GIXRD) and uniaxial tensile tests were conducted for characterizing the residual stresses and high plastic strain in the top surface layers of a carefully mechanically polished indentation sample, which, in the present work, is made of commercially pure titanium. Instrumented indentation tests and the corresponding finite element simulations were performed as well. For comparison, a reference sample (carefully mechanically polished & electrolytically polished) which represents the raw material was prepared and tested. Results showed that a careful mechanical polishing procedure can effectively reduce the level of residual stresses induced by this process. However, the high plastic strain in the surface region imposed by the polishing process is significant. The induced plastic strain can affect a depth up to 5 µm, which is deeper than the maximum penetration depth h{sub max} (3 µm) used for the instrumented indentation tests. In the near surface layer (in the range of depth about 350 nm), the plastic strain levels are fairly high. In the very top layer, the plastic strain was even estimated to reach more than 60%. The simultaneous use of indentation tests and numerical simulations showed that the existence of high plastic strain in the surface region will make the load vs depth (P–h) curve shift upwards, the contact hardness (H) increase and the contact stiffness (S) decrease.

  18. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

    2014-06-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al2O3 and Fe3O4, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  19. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

    2014-01-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al 2 O 3 and Fe 3 O 4 , on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  20. Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

    Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An, E-mail: lian2010@lut.cn

    2014-06-01

    A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

  1. Surface Preparation of InAs (110 Using Atomic Hydrogen

    T.D. Veal

    2002-06-01

    Full Text Available Atomic hydrogen cleaning has been used to produce structurally and electronically damage-free InAs(110 surfaces.  X-ray photoelectron spectroscopy (XPS was used to obtain chemical composition and chemical state information about the surface, before and after the removal of the atmospheric contamination. Low energy electron diffraction (LEED and high-resolution electron-energy-loss spectroscopy (HREELS were also used, respectively, to determine the surface reconstruction and degree of surface ordering, and to probe the adsorbed contaminant vibrational modes and the collective excitations of the clean surface. Clean, ordered and stoichiometric  InAs(110-(1×1 surfaces were obtained by exposure to thermally generated atomic hydrogen at a substrate temperature as low as 400ºC.  Semi-classical dielectric theory analysis of HREEL spectra of the phonon and plasmon excitations of the clean surface indicate that no electronic damage or dopant passivation were induced by the surface preparation method.

  2. As-grown graphene/copper nanoparticles hybrid nanostructures for enhanced intensity and stability of surface plasmon resonance

    Li, Yun-Fei; Dong, Feng-Xi; Chen, Yang; Zhang, Xu-Lin; Wang, Lei; Bi, Yan-Gang; Tian, Zhen-Nan; Liu, Yue-Feng; Feng, Jing; Sun, Hong-Bo

    2016-11-01

    The transfer-free fabrication of the high quality graphene on the metallic nanostructures, which is highly desirable for device applications, remains a challenge. Here, we develop the transfer-free method by direct chemical vapor deposition of the graphene layers on copper (Cu) nanoparticles (NPs) to realize the hybrid nanostructures. The graphene as-grown on the Cu NPs permits full electric contact and strong interactions, which results in a strong localization of the field at the graphene/copper interface. An enhanced intensity of the localized surface plasmon resonances (LSPRs) supported by the hybrid nanostructures can be obtained, which induces a much enhanced fluorescent intensity from the dye coated hybrid nanostructures. Moreover, the graphene sheets covering completely and uniformly on the Cu NPs act as a passivation layer to protect the underlying metal surface from air oxidation. As a result, the stability of the LSPRs for the hybrid nanostructures is much enhanced compared to that of the bare Cu NPs. The transfer-free hybrid nanostructures with enhanced intensity and stability of the LSPRs will enable their much broader applications in photonics and optoelectronics.

  3. "Turn-on" fluorescence detection of lead ions based on accelerated leaching of gold nanoparticles on the surface of graphene.

    Fu, Xiuli; Lou, Tingting; Chen, Zhaopeng; Lin, Meng; Feng, Weiwei; Chen, Lingxin

    2012-02-01

    A novel platform for effective "turn-on" fluorescence sensing of lead ions (Pb(2+)) in aqueous solution was developed based on gold nanoparticle (AuNP)-functionalized graphene. The AuNP-functionalized graphene exhibited minimal background fluorescence because of the extraordinarily high quenching ability of AuNPs. Interestingly, the AuNP-functionalized graphene underwent fluorescence restoration as well as significant enhancement upon adding Pb(2+), which was attributed to the fact that Pb(2+) could accelerate the leaching rate of the AuNPs on graphene surfaces in the presence of both thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Consequently, this could be utilized as the basis for selective detection of Pb(2+). With the optimum conditions chosen, the relative fluorescence intensity showed good linearity versus logarithm concentration of Pb(2+) in the range of 50-1000 nM (R = 0.9982), and a detection limit of 10 nM. High selectivity over common coexistent metal ions was also demonstrated. The practical application had been carried out for determination of Pb(2+) in tap water and mineral water samples. The Pb(2+)-specific "turn-on" fluorescence sensor, based on Pb(2+) accelerated leaching of AuNPs on the surface of graphene, provided new opportunities for highly sensitive and selective Pb(2+) detection in aqueous media.

  4. The Surface Imprinted Polystyrene Beads Prepared via Emulsion Templates

    Guo Xiang CHENG; Guang Ling PEI; Ling Gang ZENG; Li Yong ZHANG; Chao LIU

    2004-01-01

    In this paper, the surface imprinted cross-linked polystyrene beads were prepared via suspension polymerization with styrene (St), divinylbezene (DVB), polyvinyl alcohol (PVA1788), the mixture of Span 85 and xylene or the mixture of Span 85 and paraffin as monomer, cross-linking agent, dispersion stabilizer and templates, respectively. The results indicate that there are dense cavities on the surface of beads, and the diameter and density of cavity are related with the composition and amount of emulsion template. The forming mechanism of cavity from thermodynamics and dynamics was proposed.

  5. EDITORIAL: Epitaxial graphene Epitaxial graphene

    de Heer, Walt A.; Berger, Claire

    2012-04-01

    Graphene is widely regarded as an important new electronic material with interesting two-dimensional electron gas properties. Not only that, but graphene is widely considered to be an important new material for large-scale integrated electronic devices that may eventually even succeed silicon. In fact, there are countless publications that demonstrate the amazing applications potential of graphene. In order to realize graphene electronics, a platform is required that is compatible with large-scale electronics processing methods. It was clear from the outset that graphene grown epitaxially on silicon carbide substrates was exceptionally well suited as a platform for graphene-based electronics, not only because the graphene sheets are grown directly on electronics-grade silicon carbide (an important semiconductor in its own right), but also because these sheets are oriented with respect to the semiconductor. Moreover, the extremely high temperatures involved in production assure essentially defect-free and contamination-free materials with well-defined interfaces. Epitaxial graphene on silicon carbide is not a unique material, but actually a class of materials. It is a complex structure consisting of a reconstructed silicon carbide surface, which, for planar hexagonal silicon carbide, is either the silicon- or the carbon-terminated face, an interfacial carbon rich layer, followed by one or more graphene layers. Consequently, the structure of graphene films on silicon carbide turns out to be a rich surface-science puzzle that has been intensively studied and systematically unravelled with a wide variety of surface science probes. Moreover, the graphene films produced on the carbon-terminated face turn out to be rotationally stacked, resulting in unique and important structural and electronic properties. Finally, in contrast to essentially all other graphene production methods, epitaxial graphene can be grown on structured silicon carbide surfaces to produce graphene

  6. Preparation of novel CdS-graphene/TiO2 composites with high ...

    materials science since the discovery of carbon nanotubes and C60 (Geim and ... the various semiconduc- tors, titanium dioxide (TiO2) is known to be a good photo- ..... CdS-graphene/TiO2 to absorb more photons, which will enhance the ...

  7. .beta.-Cyclodextrin-epichlorohydrin polymer/graphene oxide nanocomposite: preparation and characterization

    Heydari, A.; Sheibani, H.; Hronský, V.; Janigová, I.; Šlouf, Miroslav; Šiffalovič, P.; Chodák, I.

    2018-01-01

    Roč. 72, č. 5 (2018), s. 1299-1313 ISSN 0366-6352 Institutional support: RVO:61389013 Keywords : beta-cyclodextrin * graphene oxide * hydrogels Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 1.258, year: 2016

  8. Chemical Preparation of Graphene Materials Results in Extensive Unintentional Doping with Heteroatoms and Metals

    Chua, C. K.; Ambrosi, A.; Sofer, Z.; Macková, Anna; Havránek, Vladimír; Tomandl, Ivo; Pumera, M.

    2014-01-01

    Roč. 20, č. 48 (2014), s. 15760-15767 ISSN 1521-3765 R&D Projects: GA MŠk(XE) LM2011019; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389005 Keywords : doping * graphene * heteroatoms * oxidation * synthetic methods Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  9. Microstructural investigation of aluminum-graphene nano platelets composites prepared by powder metallurgy

    Sreearravind, M.; Peddavarapu, Sreehari; Raghuraman, S.

    2018-04-01

    Recently, Graphene has attracted a large variety of scientific communities due to its inimitable properties. Typically, Graphene Nanoplatelets (GNPs) are ideal reinforcements for the production of nanocomposites due to its excellent mechanical properties for strength enhancement. This paper reports the Aluminum-Graphene Nanoplatelets (Al/GNPs) composites synthesized through powder metallurgy method. The microstructural investigation was carried out to study the GNPs integration on the Al matrix. For this study, the samples Al-2wt% GNPs, Al-3wt% GNPs and Al- 4wt% GNPs are high-energy ball milled at 200rpm and sintered at 500°C,550°C, and 600°C. Microstructural characterization is carried out with optical microscopy, Scanning electron microscopy. Rockwell hardness test is conducted to evaluate the hardness behavior in Al/GNPs. Microstructural analysis revealed the homogeneous dispersion of GNPs in the Al matrix in all the samples. It is observed that the existence of the graphene nanoparticles and the rise of their concentrations in the aluminum matrix (2 wt.% to 4 wt.%) as reinforcement in addition to rising the sintering temperature (450°C to 600°C) greatly improve the mechanical properties of Al/GNPs composites.

  10. Preparation of graphene by using an intense cavitation field in a pressurized ultrasonic reactor

    Štengl, Václav

    2012-01-01

    Roč. 18, č. 44 (2012), s. 14047-14054 ISSN 0947-6539 Institutional support: RVO:61388980 Keywords : cavitation field * graphene * nanostructures * ultrasound * X-ray diffraction Subject RIV: CA - Inorganic Chemistry Impact factor: 5.831, year: 2012

  11. Surface plasmon resonance induced reduction of high quality Ag/graphene composite at water/toluene phase for reduction of H2O2

    Zhang Fengjun; Zhang Kehua; Xie Fazhi; Liu Jin; Dong Hongfei; Zhao Wei; Meng Zeda

    2013-01-01

    Highlights: ► The Ag/graphene composites have been successfully synthesized in two-phase solvent. ► The surface plasmon resonance of Ag can reduce GO with high deoxygenation and low defect. ► The Ag particles were uniformly distributed on graphene surface. ► The Ag/graphene composites obtained show high superior electrical properties for reduction of H 2 O 2 . - Abstract: Surface plasmon resonance induced synthesis of Ag/graphene composites from Ag/graphene oxide (Ag/GO) in a two-phase (water–toluene) solvent was reported. Transmission electron microscopy (TEM) results revealed that the Ag nanoparticles with size of 5–8 nm were trimly distributed on reduced graphene oxide sheets. Raman and X-ray photoelectron spectroscopy (XPS) have demonstrated low defect density and high deoxygenation degree of graphene in Ag/graphene composite. The excellent structure and morphology of Ag/graphene composites contributed to superior electrical properties for reduction of H 2 O 2 .

  12. Composites of Graphene Nanoribbon Stacks and Epoxy for Joule Heating and Deicing of Surfaces.

    Raji, Abdul-Rahman O; Varadhachary, Tanvi; Nan, Kewang; Wang, Tuo; Lin, Jian; Ji, Yongsung; Genorio, Bostjan; Zhu, Yu; Kittrell, Carter; Tour, James M

    2016-02-10

    A conductive composite of graphene nanoribbon (GNR) stacks and epoxy is fabricated. The epoxy is filled with the GNR stacks, which serve as a conductive additive. The GNR stacks are on average 30 nm thick, 250 nm wide, and 30 μm long. The GNR-filled epoxy composite exhibits a conductivity >100 S/m at 5 wt % GNR content. This permits application of the GNR-epoxy composite for deicing of surfaces through Joule (voltage-induced) heating generated by the voltage across the composite. A power density of 0.5 W/cm(2) was delivered to remove ∼1 cm-thick (14 g) monolith of ice from a static helicopter rotor blade surface in a -20 °C environment.

  13. Monitoring the on-surface synthesis of graphene nanoribbons by mass spectrometry

    Zhang, Wen

    2017-06-14

    We present a mass spectrometric approach to monitor and characterize the intermediates of graphene nanoribbon (GNR) formation by chemical vapor deposition (CVD) on top of Au(111) surfaces. Information regarding the repeating units, lengths, and termini can be obtained directly from the surface sample by a modified matrix assisted laser desorption/ionization (MALDI) method. The mass spectrometric results reveal ample oxidative side reactions under CVD conditions which can, however, be diminished drastically by introduction of protective H2 gas at ambient pressure. Simultaneously, addition of hydrogen extends the lengths of the oligophenylenes and thus the final GNRs. Moreover, the prematurely formed cyclodehydrogenation products during the oligomer growth can be assigned by the mass spectrometric method. The obtained mechanistic insights provide valuable information for optimizing and upscaling the bottom-up fabrication of GNRs. Given the important role of GNRs as semiconductors, the mass spectrometric characterization provides a readily available tool to improve and characterize their structural perfection.

  14. The peeling behaviour of a graphene sheet on a nano-scale corrugated surface

    Chen, Hao; Chen, Shaohua

    2013-01-01

    The peeling process and average peeling force of a graphene (GE) sheet on a corrugated surface are investigated using molecular dynamics simulation. It is found that the peeling behaviour varies with the substrate surface roughness and the peeling angle. Three kinds of typically peeling behaviours include (a) GE sheet directly passing the valley of the substrate roughness; (b) bouncing off from the substrate; and (c) continuously peeling off similarly to that on a flat substrate. As a result, the average peeling force is strongly dependent of the peeling behaviours. Furthermore, some interesting phenomena are caught, such as partial detaching and partial sliding of GE sheet in the valley of the substrate roughness, which are mainly due to the effects of pre-tension in GE sheet and the reduction of friction resistance. The results in this paper should be useful for the design of nano-film/substrate systems. (paper)

  15. Transfer of Chemically Modified Graphene with Retention of Functionality for Surface Engineering.

    Whitener, Keith E; Lee, Woo-Kyung; Bassim, Nabil D; Stroud, Rhonda M; Robinson, Jeremy T; Sheehan, Paul E

    2016-02-10

    Single-layer graphene chemically reduced by the Birch process delaminates from a Si/SiOx substrate when exposed to an ethanol/water mixture, enabling transfer of chemically functionalized graphene to arbitrary substrates such as metals, dielectrics, and polymers. Unlike in previous reports, the graphene retains hydrogen, methyl, and aryl functional groups during the transfer process. This enables one to functionalize the receiving substrate with the properties of the chemically modified graphene (CMG). For instance, magnetic force microscopy shows that the previously reported magnetic properties of partially hydrogenated graphene remain after transfer. We also transfer hydrogenated graphene from its copper growth substrate to a Si/SiOx wafer and thermally dehydrogenate it to demonstrate a polymer- and etchant-free graphene transfer for potential use in transmission electron microscopy. Finally, we show that the Birch reduction facilitates delamination of CMG by weakening van der Waals forces between graphene and its substrate.

  16. Ternary hybrid polymeric nanocomposites through grafting of polystyrene on graphene oxide-TiO{sub 2} by surface initiated atom transfer radical polymerization (SI-ATRP)

    Kumar, Arvind; Bansal, Ankushi; Behera, Babita; Jain, Suman L.; Ray, Siddharth S., E-mail: ssray@iip.res.in

    2016-04-01

    A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO{sub 2}-PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO{sub 2} (GO-TiO{sub 2}) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO{sub 2} as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO{sub 2}-PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. - Highlights: • Nanocomposite of ternary hybrid of GO-TiO{sub 2} with polystyrene. • PS is surface grafted on GO-TiO{sub 2}. • Polymer chain lengths are well regulated by SI-ATRP living polymerization. • Thermal stability of this hybrid is relatively high.

  17. Ternary hybrid polymeric nanocomposites through grafting of polystyrene on graphene oxide-TiO_2 by surface initiated atom transfer radical polymerization (SI-ATRP)

    Kumar, Arvind; Bansal, Ankushi; Behera, Babita; Jain, Suman L.; Ray, Siddharth S.

    2016-01-01

    A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO_2-PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO_2 (GO-TiO_2) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO_2 as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO_2-PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. - Highlights: • Nanocomposite of ternary hybrid of GO-TiO_2 with polystyrene. • PS is surface grafted on GO-TiO_2. • Polymer chain lengths are well regulated by SI-ATRP living polymerization. • Thermal stability of this hybrid is relatively high.

  18. In situ deposition of graphene nanosheets on wood surface by one-pot hydrothermal method for enhanced UV-resistant ability

    Wan, Caichao; Jiao, Yue; Li, Jian

    2015-01-01

    Graphical abstract: - Highlights: • The graphene/wood nanocomposites were fabricated via a mild fast one-pot hydrothermal method. • Graphene nanosheets were in situ deposited on the surface of the wood matrix. • The incorporation of graphene nanosheets results in the improvement in the thermal stability of the graphene/wood. • The graphene/wood exhibits superior UV resistance performance. - Abstract: Graphene nanosheets were successfully in situ deposited on the surface of the wood matrix via a mild fast one-pot hydrothermal method, and the resulting hybrid graphene/wood (GW) were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and thermogravimetric analysis (TGA). According to the results, the wood matrix was evenly coated by dense uninterrupted multilayer graphene membrane structure, which was formed by layer-by-layer self-assembly of graphene nanosheets. Meanwhile, the graphene coating also induced significant improvement in the thermal stability of GW in comparison with that of the original wood (OW). Accelerated weathering tests were employed to measure and determine the UV-resistant ability of OW and GW. After about six hundred hours of experiments, the surface color change of GW was much less than that of OW; besides, the Fourier transform infrared spectroscopy (FTIR) analysis also proved the less significant changes in surface chemical compositions of GW. The results both indicated that the graphene coating effectively protected wood surface from UV damage. Therefore, this class of GW composite might be expected to be served as high-performance wooden building material for outdoor or some particular harsh environments like strong UV radiation regions use

  19. Flat Graphene-Enhanced Electron Transfer Involved in Redox Reactions.

    Pan, Meilan; Zhang, Yanyang; Shan, Chao; Zhang, Xiaolin; Gao, Guandao; Pan, Bingcai

    2017-08-01

    Graphene is easily warped in the out-of-plane direction because of its high in-plane Young's modulus, and exploring the influence of wrinkled graphene on its properties is essential for the design of graphene-based materials for environmental applications. Herein, we prepared wrinkled graphene (WGN-1 and WGN-2) by thermal treatment and compared their electrochemical properties with those of flat graphene nanosheets (FGN). FGN exhibit activities that are much better than those of wrinkled graphene nanosheets (WGN), not only in the electrochemical oxidation of methylene blue (MB) but also in the electrochemical reduction of nitrobenzene (NB). Transformation ratios of MB and NB in FGN, WGN-1, and WGN-2 were 97.5, 80.1, and 57.9% and 94.6, 92.1, and 81.2%, respectively. Electrochemical impedance spectroscopy and the surface resistance of the graphene samples increased in the following order: FGN reaction charges transfer faster across the reaction interfaces and along the surface of FGN than that of WGN, and wrinkles restrict reaction charge transfer and reduce the reaction rates. This study reveals that the morphology of the graphene (flat or wrinkle) greatly affects redox reaction activities and may have important implications for the design of novel graphene-based nanostructures and for our understanding of graphene wrinkle-dependent redox reactions in environmental processes.

  20. Scalable Synthesis of Freestanding Sandwich-structured Graphene/Polyaniline/Graphene Nanocomposite Paper for Flexible All-Solid-State Supercapacitor

    Xiao, Fei; Yang, Shengxiong; Zhang, Zheye; Liu, Hongfang; Xiao, Junwu; Wan, Lian; Luo, Jun; Wang, Shuai; Liu, Yunqi

    2015-03-01

    We reported a scalable and modular method to prepare a new type of sandwich-structured graphene-based nanohybrid paper and explore its practical application as high-performance electrode in flexible supercapacitor. The freestanding and flexible graphene paper was firstly fabricated by highly reproducible printing technique and bubbling delamination method, by which the area and thickness of the graphene paper can be freely adjusted in a wide range. The as-prepared graphene paper possesses a collection of unique properties of highly electrical conductivity (340 S cm-1), light weight (1 mg cm-2) and excellent mechanical properties. In order to improve its supercapacitive properties, we have prepared a unique sandwich-structured graphene/polyaniline/graphene paper by in situ electropolymerization of porous polyaniline nanomaterials on graphene paper, followed by wrapping an ultrathin graphene layer on its surface. This unique design strategy not only circumvents the low energy storage capacity resulting from the double-layer capacitor of graphene paper, but also enhances the rate performance and cycling stability of porous polyaniline. The as-obtained all-solid-state symmetric supercapacitor exhibits high energy density, high power density, excellent cycling stability and exceptional mechanical flexibility, demonstrative of its extensive potential applications for flexible energy-related devices and wearable electronics.

  1. Scalable synthesis of freestanding sandwich-structured graphene/polyaniline/graphene nanocomposite paper for flexible all-solid-state supercapacitor.

    Xiao, Fei; Yang, Shengxiong; Zhang, Zheye; Liu, Hongfang; Xiao, Junwu; Wan, Lian; Luo, Jun; Wang, Shuai; Liu, Yunqi

    2015-03-23

    We reported a scalable and modular method to prepare a new type of sandwich-structured graphene-based nanohybrid paper and explore its practical application as high-performance electrode in flexible supercapacitor. The freestanding and flexible graphene paper was firstly fabricated by highly reproducible printing technique and bubbling delamination method, by which the area and thickness of the graphene paper can be freely adjusted in a wide range. The as-prepared graphene paper possesses a collection of unique properties of highly electrical conductivity (340 S cm(-1)), light weight (1 mg cm(-2)) and excellent mechanical properties. In order to improve its supercapacitive properties, we have prepared a unique sandwich-structured graphene/polyaniline/graphene paper by in situ electropolymerization of porous polyaniline nanomaterials on graphene paper, followed by wrapping an ultrathin graphene layer on its surface. This unique design strategy not only circumvents the low energy storage capacity resulting from the double-layer capacitor of graphene paper, but also enhances the rate performance and cycling stability of porous polyaniline. The as-obtained all-solid-state symmetric supercapacitor exhibits high energy density, high power density, excellent cycling stability and exceptional mechanical flexibility, demonstrative of its extensive potential applications for flexible energy-related devices and wearable electronics.

  2. Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

    Li, Mingji, E-mail: limingji@163.com [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Guo, Wenlong [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Hongji, E-mail: hongjili@yeah.net [Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xu, Sheng [School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072 (China); Qu, Changqing; Yang, Baohe [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2014-10-30

    Highlights: • The capacitance of graphene/tantalum (Ta) wire electrodes is firstly reported. • Graphene was grown on the Ta surface by hot-filament chemical vapor deposition. • Graphene/Ta wire structure is favorable for fast ion and electron transfer. • The graphene/Ta wire electrode shows high capacitive properties. - Abstract: This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3–3.4 nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10 mm and a diameter of 0.6 mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1 M Na{sub 2}SO{sub 4} aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5 F g{sup −1} at current density of 0.5 A g{sup −1}. The capacitance remains at about 84% after 1000 cycles at 10 A g{sup −1}. The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices.

  3. Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

    Li, Mingji; Guo, Wenlong; Li, Hongji; Xu, Sheng; Qu, Changqing; Yang, Baohe

    2014-01-01

    Highlights: • The capacitance of graphene/tantalum (Ta) wire electrodes is firstly reported. • Graphene was grown on the Ta surface by hot-filament chemical vapor deposition. • Graphene/Ta wire structure is favorable for fast ion and electron transfer. • The graphene/Ta wire electrode shows high capacitive properties. - Abstract: This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3–3.4 nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10 mm and a diameter of 0.6 mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1 M Na 2 SO 4 aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5 F g −1 at current density of 0.5 A g −1 . The capacitance remains at about 84% after 1000 cycles at 10 A g −1 . The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices

  4. Surface-Enhanced Raman Scattering Activity of Ag/graphene/polymer Nanocomposite Films Synthesized by Laser Ablation

    Siljanovska Petreska, G.; Blazevska-Gilev, J.; Fajgar, Radek; Tomovska, R.

    2014-01-01

    Roč. 564, AUG 1 (2014), s. 115-120 ISSN 0040-6090 Grant - others:NATO SfP(US) 984399 Institutional support: RVO:67985858 Keywords : laser ablation * surface-enhanced raman scattering * nanocomposite s * graphene * rhodamine 6G Subject RIV: CH - Nuclear ; Quantum Chemistry Impact factor: 1.759, year: 2014

  5. Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

    Kumar, Mohan; Swamy, B.E. Kumara; Asif, M.H. Mohammed; Viswanath, C.C.

    2017-01-01

    Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO_4 followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE. The

  6. Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

    Kumar, Mohan [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Swamy, B.E. Kumara, E-mail: kumaraswamy21@yahoo.com [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Asif, M.H. Mohammed [Nanoscience and Technology, Kuvempu University, Shankaraghatta, 577451, Shimoga, Karnataka (India); Viswanath, C.C. [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India)

    2017-03-31

    Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO{sub 4} followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE

  7. Screening-induced surface polar optical phonon scattering in dual-gated graphene field effect transistors

    Hu, Bo, E-mail: hubo2011@semi.ac.cn

    2015-03-15

    The effect of surface polar optical phonons (SOs) from the dielectric layers on electron mobility in dual-gated graphene field effect transistors (GFETs) is studied theoretically. By taking into account SO scattering of electron as a main scattering mechanism, the electron mobility is calculated by the iterative solution of Boltzmann transport equation. In treating scattering with the SO modes, the dynamic dielectric screening is included and compared to the static dielectric screening and the dielectric screening in the static limit. It is found that the dynamic dielectric screening effect plays an important role in the range of low net carrier density. More importantly, in-plane acoustic phonon scattering and charged impurity scattering are also included in the total mobility for SiO{sub 2}-supported GFETs with various high-κ top-gate dielectric layers considered. The calculated total mobility results suggest both Al{sub 2}O{sub 3} and AlN are the promising candidate dielectric layers for the enhancement in room temperature mobility of graphene in the future.

  8. Surface Plasmon Resonance based sensing of lysozyme in serum on Micrococcus lysodeikticus-modified graphene oxide surfaces.

    Vasilescu, Alina; Gáspár, Szilveszter; Gheorghiu, Mihaela; David, Sorin; Dinca, Valentina; Peteu, Serban; Wang, Qian; Li, Musen; Boukherroub, Rabah; Szunerits, Sabine

    2017-03-15

    Lysozyme is an enzyme found in biological fluids, which is upregulated in leukemia, renal diseases as well as in a number of inflammatory gastrointestinal diseases. We present here the development of a novel lysozyme sensing concept based on the use of Micrococcus lysodeikticus whole cells adsorbed on graphene oxide (GO)-coated Surface Plasmon Resonance (SPR) interfaces. M. lysodeikticus is a typical enzymatic substrate for lysozyme. Unlike previously reported sensors which are based on the detection of lysozyme through bioaffinity interactions, the bioactivity of lysozyme will be used here for sensing purposes. Upon exposure to lysozyme containing serum, the integrity of the bacterial cell wall is affected and the cells detach from the GO based interfaces, causing a characteristic decrease in the SPR signal. This allows sensing the presence of clinically relevant concentrations of lysozyme in undiluted serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Preparation of XH-3001 floodgate type of calibration surface sources

    Lin Hui; Zhang Fenglan

    2005-10-01

    The preparation of a large sized (active area: 100 mm x 150 mm) calibration sources by oxide film filling of aluminum is introduced. The influence of current densities, oxidation time, filling time, the pH, the concentration and the consumption of filling solution on surface emission rate of the source is studied. The surface emission rate, adhensiveness and uniformity of the source are also tested. The testing results indicate that the surface emission rate of source is 1500-3500 (2π·s) -1 , the uniformity of the source is better than ±10%, the activity of the source removed with wipe test is less than 200 Bq. The large sized source have been used for calibrating the apparatus in Qinshan Nuclear Power Station. (authors)

  10. Surface preparation and coupling in plastic scintillator dosimetry

    Ayotte, Guylaine; Archambault, Louis; Gingras, Luc; Lacroix, Frederic; Beddar, A. Sam; Beaulieu, Luc

    2006-01-01

    One way to improve the performance of scintillation dosimeters is to increase the light-collection efficiency at the coupling interfaces of the detector system. We performed a detailed study of surface preparation of scintillating fibers and their coupling with clear optical fibers to minimize light loss and increase the amount of light collected. We analyzed fiber-surface polishing with aluminum oxide sheets, coating fibers with magnesium oxide, and the use of eight different coupling agents (air, three optical gels, an optical curing agent, ultraviolet light, cyanoacrylate glue, and acetone). We prepared 10 scintillating fiber and clear optical fiber light guide samples to test different coupling methods. To test the coupling, we first cut both the scintillating fiber and the clear optical fiber. Then, we cleaned and polished both ends of both fibers. Finally, we coupled the scintillating fiber with the clear optical fiber in either a polyethylene jacket or a V-grooved support depending on the coupling agent used. To produce more light, we used an ultraviolet lamp to stimulate scintillation. A typical series of similar couplings showed a standard deviation in light-collection efficiency of 10%. This can be explained by differences in the surface preparation quality and alignment of the scintillating fiber with the clear optical fiber. Absence of surface polishing reduced the light collection by approximately 40%, and application of magnesium oxide on the proximal end of the scintillating fiber increased the amount of light collected from the optical fiber by approximately 39%. Of the coupling agents, we obtained the best results using one of the optical gels. Because a large amount of the light produced inside a scintillator is usually lost, better light-collection efficiency will result in improved sensitivity

  11. Increasing the Thermal Conductivity of Graphene-Polyamide-6,6 Nanocomposites by Surface-Grafted Polymer Chains: Calculation with Molecular Dynamics and Effective-Medium Approximation.

    Gao, Yangyang; Müller-Plathe, Florian

    2016-02-25

    By employing reverse nonequilibrium molecular dynamics simulations in a full atomistic resolution, the effect of surface-grafted chains on the thermal conductivity of graphene-polyamide-6.6 (PA) nanocomposites has been investigated. The interfacial thermal conductivity perpendicular to the graphene plane is proportional to the grafting density, while it first increases and then saturates with the grafting length. Meanwhile, the intrinsic in-plane thermal conductivity of graphene drops sharply as the grafting density increases. The maximum overall thermal conductivity of nanocomposites appears at an intermediate grafting density because of these two competing effects. The thermal conductivity of the composite parallel to the graphene plane increases with the grafting density and grafting length which is attributed to better interfacial coupling between graphene and PA. There exists an optimal balance between grafting density and grafting length to obtain the highest interfacial and parallel thermal conductivity. Two empirical formulas are suggested, which quantitatively account for the effects of grafting length and density on the interfacial and parallel thermal conductivity. Combined with effective medium approximation, for ungrafted graphene in random orientation, the model overestimates the thermal conductivity at low graphene volume fraction (f 10%). For unoriented grafted graphene, the model matches the experimental results well. In short, this work provides some valuable guides to obtain the nanocomposites with high thermal conductivity by grafting chain on the surface of graphene.

  12. Preparation of Bioactive Titanium Surfaces via Fluoride and Fibronectin Retention

    Carlos Nelson Elias

    2012-01-01

    Full Text Available Statement of Problem. The chemical or topographic modification of the dental implant surface can affect bone healing, promote accelerated osteogenesis, and increase bone-implant contact and bonding strength. Objective. In this work, the effects of dental implant surface treatment and fibronectin adsorption on the adhesion of osteoblasts were analyzed. Materials and Methods. Two titanium dental implants (Porous-acid etching and PorousNano-acid etching followed by fluoride ion modification were characterized by high-resolution scanning electron microscopy, atomic force microscopy, and X-ray diffraction before and after the incorporation of human plasma fibronectin (FN. The objective was to investigate the biofunctionalization of these surfaces and examine their effects on the interaction with osteoblastic cells. Results. The evaluation techniques used showed that the Porous and PorousNano implants have similar microstructural characteristics. Spectrophotometry demonstrated similar levels of fibronectin adsorption on both surfaces (80%. The association indexes of osteoblastic cells in FN-treated samples were significantly higher than those in samples without FN. The radioactivity values associated with the same samples, expressed as counts per minute (cpm, suggested that FN incorporation is an important determinant of the in vitro cytocompatibility of the surfaces. Conclusion. The preparation of bioactive titanium surfaces via fluoride and FN retention proved to be a useful treatment to optimize and to accelerate the osseointegration process for dental implants.

  13. Enhancing the specificity of polymerase chain reaction by graphene oxide through surface modification: zwitterionic polymer is superior to other polymers with different charges

    Zhong, Yong; Huang, Lihong; Zhang, Zhisen; Xiong, Yunjing; Sun, Liping; Weng, Jian

    2016-01-01

    Graphene oxides (GOs) with different surface characteristics, such as size, reduction degree and charge, are prepared, and their effects on the specificity of polymerase chain reaction (PCR) are investigated. In this study, we demonstrate that GO with a large size and high reduction degree is superior to small and nonreduced GO in enhancing the specificity of PCR. Negatively charged polyacrylic acid (PAA), positively charged polyacrylamide (PAM), neutral polyethylene glycol (PEG) and zwitterionic polymer poly(sulfobetaine) (pSB) are used to modify GO. The PCR specificity-enhancing ability increases in the following order: GO-PAA Pfu DNA polymerase. Our data demonstrate that the size, reduction degree and surface charge of GO affect the specificity of PCR. Based on our results, zwitterionic polymer-modified GO may be used as an efficient additive for enhancing the specificity of PCR. PMID:27956830

  14. Analysis of ultraviolet exposure effects on the surface properties of epoxy/graphene nanocomposite films on Mylar substrate

    Clausi, Marialaura; Santonicola, M. Gabriella; Schirone, Luigi; Laurenzi, Susanna

    2017-05-01

    In this paper, we present a study of the effects generated by exposure to UV-C radiation on nanocomposite films made of graphene nanoplatelets dispersed in an epoxy matrix. The nanocomposite films, at different nanoparticle size and concentration, were fabricated on Mylar substrate using the spin coating process. The effects of UV-C irradiation on the surface hydrophobicity and on the electrical properties of the epoxy/graphene films were investigated using contact angle measurements and electrical impedance spectroscopy, respectively. According to our results, the UV-C irradiation selectively degrades the polymer matrix of the nanocomposite films, giving rise to more conductive and hydrophobic layers due to exposure of the graphene component of the composite material. The results presented here have important implications in the design of spacecraft components and structures destined for long-term space missions.

  15. A study on the upward and downward facing pool boiling heat transfer characteristics of graphene-modified surface

    Kim, Ji Hoon; Ahn, Ho Seon; Kim, Ji Min

    2016-01-01

    Recently, graphene, carbon in two dimensions, were highlighted as a good heat transfer materials, according to its high thermal conductivity. Lateral conduction and water absorption into the structure helped graphene films to inhibit the formation of hot spots, which means increasing of critical heat flux (CHF) and boiling heat transfer coefficient (BHTC) performances. In this study, we report a promising increase of CHF and BHTC results with 2D graphene films. Furthermore, we tried to observe bubble behavior via high-speed visualization to investigate a relationship between bubble behavior and pool boiling performances in downward facing boiling. The effect of graphene film coating on the pool boiling performances of upward and downward facing heater surface were examined. 2D- and 3D- graphene film showed good enhancement results on the CHF (by 111% and 60%) and BHTC (by 40% and 20-25%) performances. Bubble behavior change was significant factor on the CHF and BHTC performances in downward facing boiling. The amount of evaporation heat flux was calculated from the velocity, bubble diameter, frequency, orientation angle and superheat that the post-products of the high-speed visualization

  16. Nickel tungstate (NiWO4) nanoparticles/graphene composites: preparation and photoelectrochemical applications

    Hosseini, Seyyedamirhossein; Farsi, Hossein; Moghiminia, Shokufeh; Zubkov, Tykhon; Lightcap, Ian V.; Riley, Andrew; Peters, Dennis G.; Li, Zhihai

    2018-05-01

    Nickel tungstate/graphene composite was synthesized in various compositions with application of a hydrothermal method. Chemical composition and morphology of each sample was studied via application of x-ray diffraction and transmission electron microscopy techniques. In the continuous, a photosystem was obtained by deposition of composite sample on a fluorine-doped tin oxide electrode with application of electrophoretic method. Electrode morphology was studied by employment of atomic force microscopy and SEM techniques. Eventually, light conversion properties and involved mechanism of fabricated photosystem was studied with application of the Mott–Schottky method. Our results confirmed that the optimum ratio between graphene and nickel tungstate is in the regime of 1:1.

  17. Graphene-based electrochemical supercapacitors

    WINTEC

    been great interest in graphene, which constitutes an entirely new class of carbon. Electrical characteriza- tion of single-layer graphene has been reported. 12,13. We have investigated the use of graphene as elec- trode material in electrochemical supercapacitors. For this purpose, we have employed graphene prepared.

  18. Fabrication of a single layer graphene by copper intercalation on a SiC(0001) surface

    Yagyu, Kazuma; Tochihara, Hiroshi; Tomokage, Hajime; Suzuki, Takayuki; Tajiri, Takayuki; Kohno, Atsushi; Takahashi, Kazutoshi

    2014-01-01

    Cu atoms deposited on a zero layer graphene grown on a SiC(0001) substrate, intercalate between the zero layer graphene and the SiC substrate after the thermal annealing above 600 °C, forming a Cu-intercalated single layer graphene. On the Cu-intercalated single layer graphene, a graphene lattice with superstructure due to moiré pattern is observed by scanning tunneling microscopy, and specific linear dispersion at the K ¯ point as well as a characteristic peak in a C 1s core level spectrum, which is originated from a free-standing graphene, is confirmed by photoemission spectroscopy. The Cu-intercalated single layer graphene is found to be n-doped

  19. Graphene-epoxy flexible transparent capacitor obtained by graphene-polymer transfer and UV-induced bonding.

    Sangermano, Marco; Chiolerio, Alessandro; Veronese, Giulio Paolo; Ortolani, Luca; Rizzoli, Rita; Mancarella, Fulvio; Morandi, Vittorio

    2014-02-01

    A new approach is reported for the preparation of a graphene-epoxy flexible transparent capacitor obtained by graphene-polymer transfer and UV-induced bonding. SU8 resin is employed for realizing a well-adherent, transparent, and flexible supporting layer. The achieved transparent graphene/SU8 membrane presents two distinct surfaces: one homogeneous conductive surface containing a graphene layer and one dielectric surface typical of the epoxy polymer. Two graphene/SU8 layers are bonded together by using an epoxy photocurable formulation based on epoxy resin. The obtained material showed a stable and clear capacitive behavior. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Preparation of Shape-Controlled Graphene/Co3O4 Composites for Supercapacitors

    Chen, Jun; Chen, Ningna; Feng, Xiaomiao; Hou, Wenhua

    2016-09-01

    Graphene/Co3O4 nanocomposites with different morphologies were fabricated by hydrothermal method. The morphology of nanocomposites was characterized by scanning electron microscopy. These composites could be used as the electrode materials for supercapacitors. The eletrochemical behavior of the composite was tested by cyclic voltammetry and galvanostatic charge-discharge measurements in 1.0 mol/L KOH solution. The results showed that the graphene/Co3O4 nanopetal composite exhibited excellent electrochemical performance. The specific capacitance value could reach up to 714 F/g at a scan rate of 2 mV/s. Besides, the capacitance of the graphene/Co3O4 nanopetal composite was 841 F/g at a current density of 0.1 A/g. After galvanostatic charge-discharge 1000 laps at the current density of 0.4 A/g, the specific capacitance could keep 96.7% of original capacitive value, demonstrating its good cycling stability.

  1. Preparation of reduced graphene oxide/gelatin composite films with reinforced mechanical strength

    Wang, Wenchao; Wang, Zhipeng; Liu, Yu; Li, Nan; Wang, Wei; Gao, Jianping

    2012-01-01

    Highlights: ► We used and compared different proportion of gelatin and chitosan as reducing agents. ► The mechanical properties of the films are investigated, especially the wet films. ► The cell toxicity of the composite films as biomaterial is carried out. ► The water absorption capabilities of the composite films also studied. -- Abstract: Graphene oxide (GO) was reduced by chitosan/gelatin solution and added to gelatin (Gel) to fabricate reduced graphene oxide/gelatin (RGO/Gel) films by a solvent-casting method using genipin as cross-linking agent. The structure and properties of the films were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The addition of RGO increased the tensile strength of the RGO/Gel films in both dry and wet states, but decreased their elongation at break. The incorperation of RGO also decreased the swelling ability of the films in water. Cell cultures were carried out in order to test the cytotoxicity of the films. The cells grew and reproduced well on the RGO/Gel films, indicating that the addition of RGO has no negative effect on the compatibility of the gelatin. Therefore, the reduced graphene oxide/gelatin composite is a promising biomaterial with excellent mechanical properties and good cell compatibility.

  2. Preparation and supercapacitance performance of manganese oxide nanosheets/graphene/carbon nanotubes ternary composite film

    Tang, Qianqiu; Sun, Minqiang; Yu, Shuangmin; Wang, Gengchao

    2014-01-01

    Graphical abstract: - Highlights: • The MnO 2 nanosheets/graphene/MWCNT composite film with a porous sandwich structure was fabricated through a filtration-directed self-assembly. • The introduction of graphene and MWCNT restricts dense stacking of MnO 2 nanosheets. • Ternary composite film exhibits impressive electrochemical performance compared to pure MnO 2 nanosheets. - Abstract: A novel MnO 2 nanosheets/graphene nanosheets/carboxylic multi-walled carbon nanotubes (MONS/GNS/cMWCNT) ternary composite film was fabricated through a filtration-directed self-assembly method. The Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images showed the porous sandwiched structure of MONS/GNS/cMWCNT with GNS providing a conductive substrate and cMWCNT functioning as a vertical electron pathway. The X-ray diffraction (XRD) and Raman spectra further confirmed that the introduction of GNS and cMWCNT restricted the serious aggregation of MONS, resulting in a higher specific area (691 m 2 g −1 ). As a result, the MONS/GNS/cMWCNT composite film exhibited higher specific capacitance (248 Fg −1 at 1 Ag −1 in 1 M Na 2 SO 4 ), better rate performance (66.9% capacitance retention from 0.2 to 10 Ag −1 ) and cycling stability (86.5% retention after 3000 cycles) compared with those of pure dried MnO 2 nanosheets

  3. Graphene Electrodes

    Pizzocchero, Filippo

    The production of graphene and the other 2D materials is presented in the beginning of this thesis. Micromechanical exfoliation is the best method for obtaining relatively small and top quality samples. The invention of Graphene Finder simplifies the procedure of finding the exfoliated flakes...... in copper thin films is studied and found to be detrimental for the growth of graphene. The modified synthesis of rGO is introduced, as rGO represents a cheap alternative to CVD for large scale production of graphene. The transfer of flakes is performed by several methods, such as with PVA/PMMA support, CAB...... wedging and the pick-up technique with hBN. Several important improvements of the pick-up technique are introduced. These allowed us to transfer any 2D crystals and patterned graphene flakes with PMMA residues. We also developed the drop-down technique, which is used to release any crystal on the surface...

  4. Surface decoration with MnO{sub 2} nanoplatelets on graphene/TiO{sub 2} (B) hybrids for rechargeable lithium-ion batteries

    Li, Xinlu, E-mail: lixinlu@cqu.edu.cn; Zhang, Yonglai; Zhong, Qineng; Li, Tongtao; Li, Hongyi; Huang, Jiamu

    2014-09-15

    Graphical abstract: - Highlights: • The surface of graphene/TiO{sub 2} (B) hybrids is decorated by ultrathin MnO{sub 2} nanoplatelets. • MnO{sub 2}@graphene/TiO{sub 2} (B) composites exhibit high specific surface area of 283.9 m{sup 2} g{sup −1}. • The reversible capacity of graphene/TiO{sub 2} (B) hybrids is greatly improved by surface decoration with low content of MnO{sub 2}. - Abstract: Hierarchically ultrathin MnO{sub 2} nanoplatelets are decorated on the surface of graphene-based TiO{sub 2} (B) hybrids by a facile water-bath reaction to fabricate MnO{sub 2}@graphene/TiO{sub 2} (B) composites. The multi-component composites show high specific surface area of 283.9 m{sup 2} g{sup −1}, facilitating the electrochemical reactions with solvented lithium ions in the enlarged interface area. The reversible capacity of the composites remains 243 mA h g{sup −1} after 150 cycles, with capacity retention of 83.5%. In comparison with graphene/TiO{sub 2} (B) hybrids, the MnO{sub 2}@graphene/TiO{sub 2} (B) composites perform better rate capability, suggesting that surface decoration with MnO{sub 2} nanoplatelets can be a promising strategy to enhance the electrochemical performance of anode materials for lithium ion batteries.

  5. Preparation of Bimetallic Pd-Co Nanoparticles on Graphene Support for Use as Methanol Tolerant Oxygen Reduction Electrocatalysts

    R. N. Singh

    2012-12-01

    Full Text Available Graphene-supported (40-x wt% Pd x wt% Co (0≤x≤13.33 alloys/composites have been prepared by a microwave-assisted polyol reduction method and been investigated for their structural and electrocatalytic properties for the oxygen reduction reaction (ORR in 0.5 M H2SO4 at 298 K. The study demonstrated that the bimetallic Pd-Co composite nanoparticles are, in fact, alloy nanoparticles with fcc crystalline structure. Partial substitution of Pd by Co (from 3.64 to 13.33 wt% in 40 wt% Pd/graphene decreases the lattice parameter as well as the crystallite size and increases the apparent catalytic activity, the latter, however, being the greatest with 8 wt% Co. The ORR activity of the active 32 wt% Pd 8wt% Co is found to be considerably low when it was deposited on the support multiwall carbon nanotubes under similar conditions. The rotating disk electrode study indicated that the ORR on 32 wt% Pd 8 wt% Co/GNS in 0.5 M H2SO4 follows approximately the four-electron pathway.

  6. Tuning TiO2 nanoparticle morphology in graphene-TiO2 hybrids by graphene surface modification

    Sordello, Fabrizio; Zeb, Gul; Hu, Kaiwen; Calza, Paola; Minero, Claudio; Szkopek, Thomas; Cerruti, Marta

    2014-05-01

    We report the hydrothermal synthesis of graphene (GNP)-TiO2 nanoparticle (NP) hybrids using COOH and NH2 functionalized GNP as a shape controller. Anatase was the only TiO2 crystalline phase nucleated on the functionalized GNP, whereas traces of rutile were detected on unfunctionalized GNP. X-Ray Photoelectron spectroscopy (XPS) showed C-Ti bonds on all hybrids, thus confirming heterogeneous nucleation. GNP functionalization induced the nucleation of TiO2 NPs with specific shapes and crystalline facets exposed. COOH functionalization directed the synthesis of anatase truncated bipyramids, bonded to graphene sheets via the {101} facets, while NH2 functionalization induced the formation of belted truncated bipyramids, bonded to graphene via the {100} facets. Belted truncated bipyramids formed on unfunctionalized GNP too, however the NPs were more irregular and rounded. These effects were ascribed to pH variations in the proximity of the functionalized GNP sheets, due to the high density of COOH or NH2 groups. Because of the different reactivity of anatase {100} and {101} crystalline facets, we hypothesize that the hybrid materials will behave differently as photocatalysts, and that the COOH-GNP-TiO2 hybrids will be better photocatalysts for water splitting and H2 production.We report the hydrothermal synthesis of graphene (GNP)-TiO2 nanoparticle (NP) hybrids using COOH and NH2 functionalized GNP as a shape controller. Anatase was the only TiO2 crystalline phase nucleated on the functionalized GNP, whereas traces of rutile were detected on unfunctionalized GNP. X-Ray Photoelectron spectroscopy (XPS) showed C-Ti bonds on all hybrids, thus confirming heterogeneous nucleation. GNP functionalization induced the nucleation of TiO2 NPs with specific shapes and crystalline facets exposed. COOH functionalization directed the synthesis of anatase truncated bipyramids, bonded to graphene sheets via the {101} facets, while NH2 functionalization induced the formation of belted

  7. Surface-enhanced Raman scattering from graphene covered gold nanocap arrays

    Long, Kailin; Luo, Xiaoguang; Nan, Haiyan; Du, Deyang; Zhao, Weiwei; Ni, Zhenhua; Qiu, Teng

    2013-11-01

    This work reports an efficient method to fabricate large-area flexible substrates for surface enhanced R