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Sample records for graphene oxide membranes

  1. Antibacterial activity of graphite, graphite oxide, graphene oxide, and reduced graphene oxide: membrane and oxidative stress.

    PubMed

    Liu, Shaobin; Zeng, Tingying Helen; Hofmann, Mario; Burcombe, Ehdi; Wei, Jun; Jiang, Rongrong; Kong, Jing; Chen, Yuan

    2011-09-27

    Health and environmental impacts of graphene-based materials need to be thoroughly evaluated before their potential applications. Graphene has strong cytotoxicity toward bacteria. To better understand its antimicrobial mechanism, we compared the antibacterial activity of four types of graphene-based materials (graphite (Gt), graphite oxide (GtO), graphene oxide (GO), and reduced graphene oxide (rGO)) toward a bacterial model-Escherichia coli. Under similar concentration and incubation conditions, GO dispersion shows the highest antibacterial activity, sequentially followed by rGO, Gt, and GtO. Scanning electron microscope (SEM) and dynamic light scattering analyses show that GO aggregates have the smallest average size among the four types of materials. SEM images display that the direct contacts with graphene nanosheets disrupt cell membrane. No superoxide anion (O(2)(•-)) induced reactive oxygen species (ROS) production is detected. However, the four types of materials can oxidize glutathione, which serves as redox state mediator in bacteria. Conductive rGO and Gt have higher oxidation capacities than insulating GO and GtO. Results suggest that antimicrobial actions are contributed by both membrane and oxidation stress. We propose that a three-step antimicrobial mechanism, previously used for carbon nanotubes, is applicable to graphene-based materials. It includes initial cell deposition on graphene-based materials, membrane stress caused by direct contact with sharp nanosheets, and the ensuing superoxide anion-independent oxidation. We envision that physicochemical properties of graphene-based materials, such as density of functional groups, size, and conductivity, can be precisely tailored to either reducing their health and environmental risks or increasing their application potentials. © 2011 American Chemical Society

  2. Scalable Production Method for Graphene Oxide Water Vapor Separation Membranes

    SciTech Connect

    Fifield, Leonard S.; Shin, Yongsoon; Liu, Wei; Gotthold, David W.

    2016-01-01

    ABSTRACT

    Membranes for selective water vapor separation were assembled from graphene oxide suspension using techniques compatible with high volume industrial production. The large-diameter graphene oxide flake suspensions were synthesized from graphite materials via relatively efficient chemical oxidation steps with attention paid to maintaining flake size and achieving high graphene oxide concentrations. Graphene oxide membranes produced using scalable casting methods exhibited water vapor flux and water/nitrogen selectivity performance meeting or exceeding that of membranes produced using vacuum-assisted laboratory techniques. (PNNL-SA-117497)

  3. Are vacuum-filtrated reduced graphene oxide membranes symmetric?

    NASA Astrophysics Data System (ADS)

    Tang, Bo; Zhang, Lianbin; Li, Renyuan; Wu, Jinbo; Hedhili, Mohamed Neijib; Wang, Peng

    2015-12-01

    Graphene or reduced graphene oxide (rGO) membrane-based materials are promising for many advanced applications due to their exceptional properties. One of the most widely used synthesis methods for rGO membranes is vacuum filtration of graphene oxide (GO) on a filter membrane, followed by reduction, which shows great advantages such as operational convenience and good controllability. Despite vacuum-filtrated rGO membranes being widely used in many applications, a fundamental question is overlooked: are the top and bottom surfaces of the membranes formed at the interfaces with air and with the filter membrane respectively symmetric or asymmetric? This work, for the first time, reports the asymmetry of the vacuum-filtrated rGO membranes and discloses the filter membranes' physical imprint on the bottom surface of the rGO membrane, which takes place when the filter membrane surface pores have similar dimension to GO sheets. This result points out that the asymmetric surface properties should be cautiously taken into consideration while designing the surface-related applications for GO and rGO membranes.Graphene or reduced graphene oxide (rGO) membrane-based materials are promising for many advanced applications due to their exceptional properties. One of the most widely used synthesis methods for rGO membranes is vacuum filtration of graphene oxide (GO) on a filter membrane, followed by reduction, which shows great advantages such as operational convenience and good controllability. Despite vacuum-filtrated rGO membranes being widely used in many applications, a fundamental question is overlooked: are the top and bottom surfaces of the membranes formed at the interfaces with air and with the filter membrane respectively symmetric or asymmetric? This work, for the first time, reports the asymmetry of the vacuum-filtrated rGO membranes and discloses the filter membranes' physical imprint on the bottom surface of the rGO membrane, which takes place when the filter

  4. Reduced Graphene Oxide Membranes for Ultrafast Organic Solvent Nanofiltration.

    PubMed

    Huang, Liang; Chen, Ji; Gao, Tiantian; Zhang, Miao; Li, Yingru; Dai, Liming; Qu, Liangti; Shi, Gaoquan

    2016-10-01

    Solvated reduced graphene oxide (S-rGO) membranes are stable in organic solvents, and strong acidic, alkaline, or oxidative media. They show high rejections to small molecules with charges the same as that of S-rGO coatings or neutral molecules larger than 3.4 nm, while retaining their high permeances to organic solvents.

  5. Are vacuum-filtrated reduced graphene oxide membranes symmetric?

    PubMed

    Tang, Bo; Zhang, Lianbin; Li, Renyuan; Wu, Jinbo; Hedhili, Mohamed Neijib; Wang, Peng

    2016-01-14

    Graphene or reduced graphene oxide (rGO) membrane-based materials are promising for many advanced applications due to their exceptional properties. One of the most widely used synthesis methods for rGO membranes is vacuum filtration of graphene oxide (GO) on a filter membrane, followed by reduction, which shows great advantages such as operational convenience and good controllability. Despite vacuum-filtrated rGO membranes being widely used in many applications, a fundamental question is overlooked: are the top and bottom surfaces of the membranes formed at the interfaces with air and with the filter membrane respectively symmetric or asymmetric? This work, for the first time, reports the asymmetry of the vacuum-filtrated rGO membranes and discloses the filter membranes' physical imprint on the bottom surface of the rGO membrane, which takes place when the filter membrane surface pores have similar dimension to GO sheets. This result points out that the asymmetric surface properties should be cautiously taken into consideration while designing the surface-related applications for GO and rGO membranes.

  6. Ultrathin Hollow Graphene Oxide Membranes for Use as Nanoparticle Carriers.

    PubMed

    Smith, Kurt B; Tomassone, Maria S

    2017-04-04

    We synthesize hollow spherical particles/membrane sacks of graphene oxide loaded with nanoparticles to be used as nanoparticles carriers, through a new method based on emulsion precipitation and sublimation of the cores. We vary the synthesis parameters, such as shear rate, pH, and graphene oxide and oil concentration ratios. Our results show a concentration dependent membrane thickness that varies between 3 and 25 nm depending on the concentration, and their mean diameters vary between 500 nm and 70 μm. In addition, polymeric nanoparticles are loaded inside the graphene oxide shells forming core-shell particles demonstrating that they can be used as carriers for nanoparticles. Our particles are characterized via laser diffraction, zeta potential, FE-SEM, TEM, BET, and AFM. Potential applications of this work include applications that benefit from core-shell structures and nanoparticle carriers, including drug formulation, catalysis, and electrochemical applications.

  7. Biomimetic Phospholipid Membrane Organization on Graphene and Graphene Oxide Surfaces: A Molecular Dynamics Simulation Study.

    PubMed

    Willems, Nathalie; Urtizberea, Ainhoa; Verre, Andrea F; Iliut, Maria; Lelimousin, Mickael; Hirtz, Michael; Vijayaraghavan, Aravind; Sansom, Mark S P

    2017-02-28

    Supported phospholipid membrane patches stabilized on graphene surfaces have shown potential in sensor device functionalization, including biosensors and biocatalysis. Lipid dip-pen nanolithography (L-DPN) is a method useful in generating supported membrane structures that maintain lipid functionality, such as exhibiting specific interactions with protein molecules. Here, we have integrated L-DPN, atomic force microscopy, and coarse-grained molecular dynamics simulation methods to characterize the molecular properties of supported lipid membranes (SLMs) on graphene and graphene oxide supports. We observed substantial differences in the topologies of the stabilized lipid structures depending on the nature of the surface (polar graphene oxide vs nonpolar graphene). Furthermore, the addition of water to SLM systems resulted in large-scale reorganization of the lipid structures, with measurable effects on lipid lateral mobility within the supported membranes. We also observed reduced lipid ordering within the supported structures relative to free-standing lipid bilayers, attributed to the strong hydrophobic interactions between the lipids and support. Together, our results provide insight into the molecular effects of graphene and graphene oxide surfaces on lipid bilayer membranes. This will be important in the design of these surfaces for applications such as biosensor devices.

  8. Origin of anomalous water permeation through graphene oxide membrane.

    PubMed

    Boukhvalov, Danil W; Katsnelson, Mikhail I; Son, Young-Woo

    2013-08-14

    Water inside the low-dimensional carbon structures has been considered seriously owing to fundamental interest in its flow and structures as well as its practical impact. Recently, the anomalous perfect penetration of water through graphene oxide membrane was demonstrated although the membrane was impenetrable for other liquids and even gases. The unusual auxetic behavior of graphene oxide in the presence of water was also reported. Here, on the basis of first-principles calculations, we establish atomistic models for hybrid systems composed of water and graphene oxides revealing the anomalous water behavior inside the stacked graphene oxides. We show that formation of hexagonal ice bilayer in between the flakes as well as melting transition of ice at the edges of flakes are crucial to realize the perfect water permeation across the whole stacked structures. The distance between adjacent layers that can be controlled either by oxygen reduction process or pressure is shown to determine the water flow thus highlighting a unique water dynamics in randomly connected two-dimensional spaces.

  9. Spectroscopic study of graphene oxide membranes exposed to ultraviolet light

    SciTech Connect

    Schwenzer, Birgit; Kaspar, Tiffany C.; Shin, Yongsoon; Gotthold, David W.

    2016-05-16

    Research on graphene oxide (GO) as anything but a precursor material for synthesizing graphene started to pick up in 20061,2 and was soon followed by a first report of freestanding GO membranes (also referred to as GO paper) from R. S. Ruoff’s group at Northwestern University.3 The first GO membranes were prepared by vacuum filtration. More recently, larger scale GO membranes have been prepared by tape casting4 and other methods.5 In step with the development of new fabrication techniques, GO membranes are now tested for a wide array of applications6 ranging from energy-related4,7 or biomedical8 applications to more conventional uses for filtration9 and dehumidification.10 For all these proposed and implemented applications it remains to be seen how sensitive each of them is with respect to chemical and physical changes of the GO membranes over time. In this study, we report the effects of UV exposure on 2D-hierarchically stacked (Fig. S1 in ESI†) GO membranes. Macroscopically observable changes, such as darkening and mechanical deformation, have been correlated to chemical changes at the molecular level through spectroscopic measurements. Not only do the results of this work offer insights into the stability of GO membranes under UV light, but the findings will enable researchers, who are studying the use of these materials for different applications, to better understand the shelf life and packaging requirements for GO membranes. Furthermore, our results demonstrate the feasibility of deep ultraviolet (DUV) photolithography for graphene oxide-based devices. This approach is readily scalable as opposed to previous reports on photolithographic patterned reduction of GO to graphene by AFM,11 electron-beam12 or with an extreme ultraviolet (λ = 46.9 nm) laser.13

  10. Tunable sieving of ions using graphene oxide membranes.

    PubMed

    Abraham, Jijo; Vasu, Kalangi S; Williams, Christopher D; Gopinadhan, Kalon; Su, Yang; Cherian, Christie T; Dix, James; Prestat, Eric; Haigh, Sarah J; Grigorieva, Irina V; Carbone, Paola; Geim, Andre K; Nair, Rahul R

    2017-04-03

    Graphene oxide membranes show exceptional molecular permeation properties, with promise for many applications. However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of ∼9 Å (ref. 4), which is larger than the diameters of hydrated ions of common salts. The cutoff is determined by the interlayer spacing (d) of ∼13.5 Å, typical for graphene oxide laminates that swell in water. Achieving smaller d for the laminates immersed in water has proved to be a challenge. Here, we describe how to control d by physical confinement and achieve accurate and tunable ion sieving. Membranes with d from ∼9.8 Å to 6.4 Å are demonstrated, providing a sieve size smaller than the diameters of hydrated ions. In this regime, ion permeation is found to be thermally activated with energy barriers of ∼10-100 kJ mol(-1) depending on d. Importantly, permeation rates decrease exponentially with decreasing sieve size but water transport is weakly affected (by a factor of <2). The latter is attributed to a low barrier for the entry of water molecules and large slip lengths inside graphene capillaries. Building on these findings, we demonstrate a simple scalable method to obtain graphene-based membranes with limited swelling, which exhibit 97% rejection for NaCl.

  11. Tunable sieving of ions using graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Abraham, Jijo; Vasu, Kalangi S.; Williams, Christopher D.; Gopinadhan, Kalon; Su, Yang; Cherian, Christie T.; Dix, James; Prestat, Eric; Haigh, Sarah J.; Grigorieva, Irina V.; Carbone, Paola; Geim, Andre K.; Nair, Rahul R.

    2017-07-01

    Graphene oxide membranes show exceptional molecular permeation properties, with promise for many applications. However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of ˜9 Å (ref. 4), which is larger than the diameters of hydrated ions of common salts. The cutoff is determined by the interlayer spacing (d) of ˜13.5 Å, typical for graphene oxide laminates that swell in water. Achieving smaller d for the laminates immersed in water has proved to be a challenge. Here, we describe how to control d by physical confinement and achieve accurate and tunable ion sieving. Membranes with d from ˜9.8 Å to 6.4 Å are demonstrated, providing a sieve size smaller than the diameters of hydrated ions. In this regime, ion permeation is found to be thermally activated with energy barriers of ˜10-100 kJ mol-1 depending on d. Importantly, permeation rates decrease exponentially with decreasing sieve size but water transport is weakly affected (by a factor of <2). The latter is attributed to a low barrier for the entry of water molecules and large slip lengths inside graphene capillaries. Building on these findings, we demonstrate a simple scalable method to obtain graphene-based membranes with limited swelling, which exhibit 97% rejection for NaCl.

  12. Separation of tritiated water using graphene oxide membrane

    SciTech Connect

    Sevigny, Gary J.; Motkuri, Radha K.; Gotthold, David W.; Fifield, Leonard S.; Frost, Anthony P.; Bratton, Wesley

    2015-06-28

    In future nuclear fuel reprocessing plants and possibly for nuclear power plants, the cleanup of tritiated water will be needed for hundreds of thousands of gallons of water with low activities of tritium. This cleanup concept utilizes graphene oxide laminar membranes (GOx) for the separation of low-concentration (10-3-10 µCi/g) tritiated water to create water that can be released to the environment and a much smaller waste stream with higher tritium concentrations. Graphene oxide membranes consist of hierarchically stacked, overlapping molecular layers and represent a new class of materials. A permeation rate test was performed with a 2-µm-thick cast Asbury membrane using mixed gas permeability testing with zero air (highly purified atmosphere) and with air humidified with either H2O or D2O to a nominal 50% relative humidity. The membrane permeability for both H2O and D2O was high with N2 and O2 at the system measurement limit. The membrane water permeation rate was compared to a Nafion® membrane and the GOx permeation was approximately twice as high at room temperature. The H2O vapor permeation rate was 5.9 × 102 cc/m2/min (1.2 × 10-6 g/min-cm2), which is typical for graphene oxide membranes. To demonstrate the feasibility of such isotopic water separation through GOX laminar membranes, an experimental setup was constructed to use pressure-driven separation by heating the isotopic water mixture at one side of the membrane to create steam while cooling the other side. Several membranes were tested and were prepared using different starting materials and by different pretreatment methods. The average separation result was 0.8 for deuterium and 0.6 for tritium. Higher or lower temperatures may also improve separation efficiency but neither has been tested yet. A rough estimate of cost compared to current technology was also included as an indication of potential viability of the process. The relative process costs were based on the rough size of facility to

  13. Ozonated graphene oxide film as a proton-exchange membrane.

    PubMed

    Gao, Wei; Wu, Gang; Janicke, Michael T; Cullen, David A; Mukundan, Rangachary; Baldwin, Jon K; Brosha, Eric L; Galande, Charudatta; Ajayan, Pulickel M; More, Karren L; Dattelbaum, Andrew M; Zelenay, Piotr

    2014-04-01

    Graphene oxide (GO) contains several chemical functional groups that are attached to the graphite basal plane and can be manipulated to tailor GO for specific applications. It is now revealed that the reaction of GO with ozone results in a high level of oxidation, which leads to significantly improved ionic (protonic) conductivity of the GO. Freestanding ozonated GO films were synthesized and used as efficient polymer electrolyte fuel cell membranes. The increase in protonic conductivity of the ozonated GO originates from enhanced proton hopping, which is due to the higher content of oxygenated functional groups in the basal planes and edges of ozonated GO as well as the morphology changes in GO that are caused by ozonation. The results of this study demonstrate that the modification of dispersed GO presents a powerful opportunity for optimizing a nanoscale material for proton-exchange membranes.

  14. Tunable water desalination across Graphene Oxide Framework membranes

    SciTech Connect

    Nicolai, Adrien; Sumpter, Bobby G; Meunier, V.

    2014-01-01

    The performance of graphene oxide framework (GOF) membranes for water desalination is assessed using classical molecular dynamics (MD) simulations. The coupling between water permeability and salt rejection GOF membranes is studied as a function of linker concentration n, thickness h and applied pressure DP. The simulations reveal that water permeability in GOF-(n,h) membranes can be tuned from 5 (n = 32 and h = 6.5 nm) to 400 L/cm2/day/MPa (n = 64 and h = 2.5 nm) and follows the law Cnh an . For a given pore size (n = 16 or 32), water permeability of GOF membranes increases when the pore spacing decreases, whereas for a given pore spacing (n = 32 or 64), water permeability increases by up to two orders of magnitude when the pore size increases. Furthermore, for linker concentrations n 32, the high water permeability corresponds to a 100% salt rejection, elevating this type of GOF membrane as an ideal candidate for water desalination. Compared to experimental performance of reverse osmosis membranes, our calculations suggest that under the same conditions of applied pressure and characteristics of membranes (DP 10 MPa and h 100 nm), one can expect a perfect salt rejection coupled to a water permeability two orders of magnitude higher than existing technologies, i.e., from a few cL/cm2/day/MPa to a few L/cm2/day/MPa.

  15. Tunable water desalination across graphene oxide framework membranes.

    PubMed

    Nicolaï, Adrien; Sumpter, Bobby G; Meunier, Vincent

    2014-05-14

    The performance of graphene oxide framework (GOF) membranes for water desalination is assessed using classical molecular dynamics (MD) simulations. The coupling between water permeability and salt rejection of GOF membranes is studied as a function of linker concentration n, thickness h and applied pressure ΔP. The simulations reveal that water permeability in GOF-(n,h) membranes can be tuned from ∼5 (n = 32 and h = 6.5 nm) to 400 L cm(-2) day(-1) MPa(-1) (n = 64 and h = 2.5 nm) and follows a Cnh(-αn) law. For a given pore size (n = 16 or 32), water permeability of GOF membranes increases when the pore spacing decreases, whereas for a given pore spacing (n = 32 or 64), water permeability increases by up to two orders of magnitude when the pore size increases. Furthermore, for linker concentrations n ≤ 32, the high water permeability corresponds to a 100% salt rejection, elevating this type of GOF membrane as an ideal candidate for water desalination. Compared to experimental performance of reverse osmosis membranes, our calculations suggest that under the same conditions of applied pressure and characteristics of membranes (ΔP ∼ 10 MPa and h ∼ 100 nm), one can expect a perfect salt rejection coupled to a water permeability two orders of magnitude higher than existing technologies, i.e., from a few cL cm(-2) day(-1) MPa(-1) to a few L cm(-2) day(-1) MPa(-1).

  16. Fabrication and Characterization of Graphene/Graphene Oxide-Based Poly(vinyl alcohol) Nanocomposite Membranes

    NASA Astrophysics Data System (ADS)

    Hieu, Nguyen Huu; Long, Nguyen Huynh Bach Son; Kieu, Dang Thi Minh; Nhiem, Ly Tan

    2016-05-01

    Graphene (GE)- or graphene oxide (GO)-based poly(vinyl alcohol) (PVA) nanocomposite membranes have been prepared by the solution blending method. Raman spectra and atomic force microscopy images confirmed that GE and GO were synthesized with average thickness of 0.901 nm and 0.997 nm, respectively. X-ray diffraction patterns indicated good exfoliation of GE or GO in the PVA matrix. Fourier-transform infrared spectra revealed the chemical fractions of the nanocomposite membranes. Differential scanning calorimetry results proved that the thermal stability of the nanocomposite membranes was enhanced compared with neat PVA membrane. Transmission electron microscopy images revealed good dispersion of GE or GO sheets in the PVA matrix with thickness in the range of 19 nm to 39 nm. As a result, good compatibility between GE or GO and PVA was obtained at 0.5 wt.% filler content.

  17. Molecular Insight into Water Desalination across Multilayer Graphene Oxide Membranes.

    PubMed

    Chen, Bo; Jiang, Haifeng; Liu, Xiang; Hu, Xuejiao

    2017-07-12

    Transport of ionic solutions through graphene oxide (GO) membranes is a complicated issue because the complex and tortuous structure inside makes it very hard to clarify. Using molecular dynamics (MD) simulations, we investigated the mechanism of water transport and ion movement across multilayer GO. The significant flow rate is considerably influenced by the structural parameters of GO membranes. Because of the size effect on a shrunken real flow area, there is disagreement between the classical continuum model and nanoscaled flow. To eliminate the variance, we obtained modified geometrical parameters from density analysis and used them in the developed hydrodynamic model to give a precise depiction of water flow. Four kinds of solutions (i.e., NaCl, KCl, MgCl2, and CaCl2) and different configurational GO sheets were considered to clarify the influence on salt permeation. It is found that the abilities of permeation to ions are not totally up to the hydration radius. Even though the ionic hydration shell is greater than the opening space, the ions can also pass through the split because of the special double-deck hydration structure. In the structure of GO, a smaller layer separation with greater offsetting gaps could substantially enhance the membrane's ability to reject salt. This work establishes molecular insight into the effects of configurational structures and salt species on desalination performance, providing useful guidelines for the design of multilayer GO membranes.

  18. Membrane of Functionalized Reduced Graphene Oxide Nanoplates with Angstrom-Level Channels

    PubMed Central

    Lee, Byeongho; Li, Kunzhou; Yoon, Hong Sik; Yoon, Jeyong; Mok, Yeongbong; Lee, Yan; Lee, Hong H.; Kim, Yong Hyup

    2016-01-01

    Membranes with atomic level pores or constrictions are valuable for separation and catalysis. We report a graphene-based membrane with an interlayer spacing of 3.7 angstrom (Å). When graphene oxide nanoplates are functionalized and then reduced, the laminated reduced graphene oxide (rGO) nanoplates or functionalized rGO membrane is little affected by an intercalated fluid, and the interlayer spacing of 3.7 Å increases only to 4.4 Å in wetted state, in contrast to the graphene oxide (GO) membrane whose interlayer spacing increases from 9 Å to 13 Å in wetted state. When applied to ion separation, this membrane reduced the permeation rate of small ions such as K+ and Na+ by three orders of magnitude compared to the GO membrane. PMID:27306853

  19. Ion sieving in graphene oxide membranes via cationic control of interlayer spacing.

    PubMed

    Chen, Liang; Shi, Guosheng; Shen, Jie; Peng, Bingquan; Zhang, Bowu; Wang, Yuzhu; Bian, Fenggang; Wang, Jiajun; Li, Deyuan; Qian, Zhe; Xu, Gang; Liu, Gongping; Zeng, Jianrong; Zhang, Lijuan; Yang, Yizhou; Zhou, Guoquan; Wu, Minghong; Jin, Wanqin; Li, Jingye; Fang, Haiping

    2017-10-09

    Graphene oxide membranes-partially oxidized, stacked sheets of graphene-can provide ultrathin, high-flux and energy-efficient membranes for precise ionic and molecular sieving in aqueous solution. These materials have shown potential in a variety of applications, including water desalination and purification, gas and ion separation, biosensors, proton conductors, lithium-based batteries and super-capacitors. Unlike the pores of carbon nanotube membranes, which have fixed sizes, the pores of graphene oxide membranes-that is, the interlayer spacing between graphene oxide sheets (a sheet is a single flake inside the membrane)-are of variable size. Furthermore, it is difficult to reduce the interlayer spacing sufficiently to exclude small ions and to maintain this spacing against the tendency of graphene oxide membranes to swell when immersed in aqueous solution. These challenges hinder the potential ion filtration applications of graphene oxide membranes. Here we demonstrate cationic control of the interlayer spacing of graphene oxide membranes with ångström precision using K(+), Na(+), Ca(2+), Li(+) or Mg(2+) ions. Moreover, membrane spacings controlled by one type of cation can efficiently and selectively exclude other cations that have larger hydrated volumes. First-principles calculations and ultraviolet absorption spectroscopy reveal that the location of the most stable cation adsorption is where oxide groups and aromatic rings coexist. Previous density functional theory computations show that other cations (Fe(2+), Co(2+), Cu(2+), Cd(2+), Cr(2+) and Pb(2+)) should have a much stronger cation-π interaction with the graphene sheet than Na(+) has, suggesting that other ions could be used to produce a wider range of interlayer spacings.

  20. The structure of graphene oxide membranes in liquid water, ethanol and water-ethanol mixtures.

    PubMed

    Talyzin, Alexandr V; Hausmaninger, Tomas; You, Shujie; Szabó, Tamás

    2014-01-07

    The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of "negative thermal expansion" and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes.

  1. Study on the separation performance of the multi-channel reduced graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Zhao, Yongjiao; Li, Chun; Fan, Xiaoyan; Wang, Jiesheng; Yuan, Guang; Song, Xinxiang; Chen, Jing; Li, Zhangde

    2016-10-01

    The multi-channel reduced graphene oxide membranes with separation function have been synthesized by a simple hydrothermal reduction method and vacuum filtration. In the as-synthesized membranes, the size, number, and type of the nanochannels can be controlled by the reduced temperature. The flux and retention rate of solution are investigated by filtering different size dye molecules. The interception and adsorption effect in the separation process are discussed. Furthermore, the sizes of the nanochannels in the membranes prepared by the different reduced temperatures are estimated. The results indicate that the multi-channel reduced graphene oxide membranes have potential application in water purification area.

  2. Large-area graphene-based nanofiltration membranes by shear alignment of discotic nematic liquid crystals of graphene oxide

    NASA Astrophysics Data System (ADS)

    Akbari, Abozar; Sheath, Phillip; Martin, Samuel T.; Shinde, Dhanraj B.; Shaibani, Mahdokht; Banerjee, Parama Chakraborty; Tkacz, Rachel; Bhattacharyya, Dibakar; Majumder, Mainak

    2016-03-01

    Graphene-based membranes demonstrating ultrafast water transport, precise molecular sieving of gas and solvated molecules shows great promise as novel separation platforms; however, scale-up of these membranes to large-areas remains an unresolved problem. Here we demonstrate that the discotic nematic phase of graphene oxide (GO) can be shear aligned to form highly ordered, continuous, thin films of multi-layered GO on a support membrane by an industrially adaptable method to produce large-area membranes (13 × 14 cm2) in <5 s. Pressure driven transport data demonstrate high retention (>90%) for charged and uncharged organic probe molecules with a hydrated radius above 5 Å as well as modest (30-40%) retention of monovalent and divalent salts. The highly ordered graphene sheets in the plane of the membrane make organized channels and enhance the permeability (71+/-5 l m-2 hr-1 bar-1 for 150+/-15 nm thick membranes).

  3. Selective Removal of Technetium from Water Using Graphene Oxide Membranes.

    PubMed

    Williams, Christopher D; Carbone, Paola

    2016-04-05

    The effective removal of radioactive technetium ((99)Tc) from contaminated water is of enormous importance from an environmental and public health perspective, yet many current methodologies are highly ineffective. In this work, however, we demonstrate that graphene oxide membranes may remove (99)Tc, present in the form of pertechnetate (TcO4(-)), from water with a high degree of selectivity, suggesting they provide a cost-effective and efficient means of achieving (99)Tc decontamination. The results were obtained by quantifying and comparing the free energy changes associated with the entry of the ions into the membrane capillaries (ΔFperm), using molecular dynamics simulations. Initially, three capillary widths were investigated (0.35, 0.68, and 1.02 nm). In each case, the entry of TcO4(-) from aqueous solution into the capillary is associated with a decrease in free energy, unlike the other anions (SO4(2-), I(-), and Cl(-)) investigated. For example, in the model with a capillary width of 0.68 nm, ΔFperm(TcO4(-)) = -6.3 kJ mol(-1), compared to ΔFperm(SO4(2-)) = +22.4 kJ mol(-1). We suggest an optimum capillary width (0.48 nm) and show that a capillary with this width results in a difference between ΔFperm(TcO4(-)) and ΔFperm(SO4(2-)) of 89 kJ mol(-1). The observed preference for TcO4(-) is due to its weakly hydrating nature, reflected in its low experimental hydration free energy.

  4. Molecule Channels Directed by Cation-Decorated Graphene Oxide Nanosheets and Their Application as Membrane Reactors.

    PubMed

    Long, Yong; Wang, Kai; Xiang, Guolei; Song, Kai; Zhou, Gang; Wang, Xun

    2017-04-01

    Highly selective macromembranes, fabricated by cation-decorated graphene oxide, exhibit an excellent selectivity toward a wide range of solvents. Mixed solvents are successfully separated, based on which a membrane reactor is designed to promote a series of chemical reactions. The cations bonding to the graphene oxide nanosheets are found to be responsible for this selectivity by cation-π, electrostatic interactions, and hydrogen bonding. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Electrochemically reduced graphene oxide / sulfonated polyether ether ketone composite membrane for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Seetharaman, S.; Ramya, K.; Dhathathreyan, K. S.

    2013-06-01

    A simple and effective method for the preparation of sulfonated polyether ether ketone (SPEEK) based composites with electrochemical reduced graphene oxide (EGO) as inorganic fillers has been described. The resulting dispersions are homogeneous and the cast membranes show significant improvement on tensile strength and thermal properties. It has high ionic conductivity and is cost effective making it a promising alternative membrane for electrochemical applications.

  6. Organic Fouling of Graphene Oxide Membranes and Its Implications for Membrane Fouling Control in Engineered Osmosis.

    PubMed

    Hu, Meng; Zheng, Sunxiang; Mi, Baoxia

    2016-01-19

    This study provides experimental evidence to mechanistically understand some contradicting effects of the characteristic properties of graphene oxide (GO), such as the high hydrophilicity, negative charge, strong adsorption capability, and large surface area, on the antifouling properties of GO membranes. Furthermore, this study demonstrates the effectiveness of forming a dense GO barrier layer on the back (i.e., porous) side of an asymmetric membrane for fouling control in pressure-retarded osmosis (PRO), an emerging engineered osmosis process whose advancement has been much hindered due to the severe irreversible fouling that occurs as foulants accumulate inside the porous membrane support. In the membrane fouling experiments, protein and alginate were used as model organic foulants. When operated in forward osmosis mode, the GO membrane exhibited fouling performance comparable with that of a polyamide (PA) membrane. Analysis of the membrane adsorption capacity showed that, likely due to the presence of hydrophobic regions in the GO basal plane, the GO membrane has an affinity toward organic foulants 4 to 5 times higher than the PA membrane. Such a high adsorption capacity along with a large surface area, however, did not noticeably aggravate the fouling problem. Our explanation for this phenomenon is that organic foulants are adsorbed mainly on the basal plane of GO nanosheets, and water enters the GO membrane primarily around the oxidized edges of GO, making foulant adsorption not create much hindrance to water flux. When operated in PRO mode, the GO membrane exhibited much better antifouling performance than the PA membrane. This is because unlike the PA membrane for which foulants can be easily trapped inside the porous support and hence cause severe irreversible fouling, the GO membrane allows the foulants to accumulate primarily on its surface due to the sealing effect of the GO layer assembled on the porous side of the asymmetric membrane support. Results

  7. Graphene oxide as a water dissociation catalyst in the bipolar membrane interfacial layer.

    PubMed

    McDonald, Michael B; Freund, Michael S

    2014-08-27

    Bipolar membranes are formed by the lamination of an anion- and cation-exchange layer. Upon a sufficient applied reverse bias, water molecules at the layer junction dissociate, generating OH(-) and H(+), which can be useful in electrodialysis and electrosynthesis applications. Graphene oxide has been introduced into bipolar membrane junctions (illustrated in the adjacent graphic) and is shown to be an efficient new water dissociation catalyst, lowering the overpotential by 75% compared to a control membrane. It was found that adjusting deposition conditions changes the nature of the graphene oxide films, leading to tunable membrane performance. Additionally, it is shown that their low overpotentials are stable, making for industrially viable, high-performance bipolar membranes.

  8. Enhanced Performance of Polyurethane Hybrid Membranes for CO2 Separation by Incorporating Graphene Oxide: The Relationship between Membrane Performance and Morphology of Graphene Oxide.

    PubMed

    Wang, Ting; Zhao, Li; Shen, Jiang-nan; Wu, Li-guang; Van der Bruggen, Bart

    2015-07-07

    Polyurethane hybrid membranes containing graphene oxide (GO) with different morphologies were prepared by in situ polymerization. The separation of CO2/N2 gas mixtures was studied using these novel membranes. The results from the morphology characterization of GO samples indicated that the oxidation process in the improved Hummers method introduced oxygenated functional groups into graphite, making graphite powder exfoliate into GO nanosheets. The surface defects on the GO sheets increased when oxidation increased due to the introduction of more oxygenated functional groups. Both the increase in oxygenated functional groups on the GO surface and the decrease in the number of GO layers leads to a better distribution of GO in the polymer matrix, increasing thermal stability and gas separation performance of membranes. The addition of excess oxidant destroyed the structure of GO sheets and forms structural defects, which depressed the separation performance of membranes. The hybrid membranes containing well-distributed GO showed higher permeability and permeability selectivity for the CO2. The formation of GO aggregates in the hybrid membranes depressed the membrane performance at a high content of GO.

  9. Crosslinking graphene oxide and chitosan to form scalable water treatment membranes

    NASA Astrophysics Data System (ADS)

    Mattei Sosa, Jose

    Graphene Oxide (GO) has emerged within the last decade as a next generation material for water treatment. Fabrication of graphene oxide membranes has been limited in scale and application due to repulsive hydration forces causing GO layers to electrostatically separate. In this study, chitosan is utilized to increase GO stability in the wet state through interactions with the negatively charged GO sheets (CSGO). This simple aqueous self-assembly allows scalable fabrication and enhanced stability for membrane applications in cross-flow. The CSGO membrane's performance was tested in a cross-flow reactor and challenged with methylene blue at concentrations ranging from 1 to 100 ppm at 345 kPa with fluxes ranging from 1 to 4.5 L/(m2 hr) with 100% removal by physical rejection. This work demonstrates that the CSGO composite matrix is a potential alternative to traditional polymeric membranes for water treatment using a renewable biopolymer and minimal chemical input.

  10. Small temperature coefficient of resistivity of graphene/graphene oxide hybrid membranes.

    PubMed

    Sun, Pengzhan; Zhu, Miao; Wang, Kunlin; Zhong, Minlin; Wei, Jinquan; Wu, Dehai; Zhu, Hongwei

    2013-10-09

    Materials with low temperature coefficient of resistivity (TCR) are of great importance in some areas, for example, highly accurate electronic measurement instruments and microelectronic integrated circuits. In this work, we demonstrated the ultrathin graphene-graphene oxide (GO) hybrid films prepared by layer-by-layer assembly with very small TCR (30-100 °C) in the air. Electrical response of the hybrid films to temperature variation was investigated along with the progressive reduction of GO sheets. The mechanism of electrical response to temperature variation of the hybrid film was discussed, which revealed that the interaction between graphene and GO and the chemical doping effect were responsible for the tunable control of its electrical response to temperature variation. The unique properties of graphene-GO hybrid film made it a promising candidate in many areas, such as high-end film electronic device and sensor applications.

  11. Large-area graphene-based nanofiltration membranes by shear alignment of discotic nematic liquid crystals of graphene oxide

    PubMed Central

    Akbari, Abozar; Sheath, Phillip; Martin, Samuel T.; Shinde, Dhanraj B.; Shaibani, Mahdokht; Banerjee, Parama Chakraborty; Tkacz, Rachel; Bhattacharyya, Dibakar; Majumder, Mainak

    2016-01-01

    Graphene-based membranes demonstrating ultrafast water transport, precise molecular sieving of gas and solvated molecules shows great promise as novel separation platforms; however, scale-up of these membranes to large-areas remains an unresolved problem. Here we demonstrate that the discotic nematic phase of graphene oxide (GO) can be shear aligned to form highly ordered, continuous, thin films of multi-layered GO on a support membrane by an industrially adaptable method to produce large-area membranes (13 × 14 cm2) in <5 s. Pressure driven transport data demonstrate high retention (>90%) for charged and uncharged organic probe molecules with a hydrated radius above 5 Å as well as modest (30–40%) retention of monovalent and divalent salts. The highly ordered graphene sheets in the plane of the membrane make organized channels and enhance the permeability (71±5 l m−2 hr−1 bar−1 for 150±15 nm thick membranes). PMID:26947916

  12. Graphene-based nafion nanocomposite membranes: enhanced proton transport and water retention by novel organo-functionalized graphene oxide nanosheets.

    PubMed

    Enotiadis, Apostolos; Angjeli, Kristina; Baldino, Noemi; Nicotera, Isabella; Gournis, Dimitrios

    2012-11-05

    Novel nanostructured organo-modified layered materials based on graphene oxide carrying various hydrophilic functional groups (-NH(2), -OH, -SO(3)H) are prepared and tested as nanofillers for the creation of innovative graphene-based Nafion nanocomposites. The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created. The pulsed field gradient NMR technique is used to measure the water self-diffusion coefficients. Remarkable behavior at temperatures up to 140 °C is observed for some composite membranes, thereby verifying the exceptional water retention property of these materials. Dynamic mechanical analysis shows that hybrid membranes are much stiffer and can withstand higher temperatures than pure Nafion.

  13. O-(carboxymethyl)-chitosan nanofiltration membrane surface functionalized with graphene oxide nanosheets for enhanced desalting properties.

    PubMed

    Wang, Jiali; Gao, Xueli; Wang, Jian; Wei, Yi; Li, Zhaokui; Gao, Congjie

    2015-02-25

    A novel O-(carboxymethyl)-chitosan (OCMC) nanofiltration (NF) membrane is developed via surface functionalization with graphene oxide (GO) nanosheets to enhance desalting properties. Using ring-opening polymerization between epoxy groups of GO nanosheets and amino groups of OCMC active layer, GO nanosheets are irreversibly bound to the membrane. The OCMC NF membranes surface-functionalized with GO nanosheets are characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, contact angle analyzer, and zeta potential analyzer. The membranes exhibit not only higher permeability but also better salt rejections than the pristine membranes and the commercial NF membranes; besides, the desalting properties are enhanced with the concentration of GO nanosheets increasing. Furthermore, the transport mechanism of GO-OCMC NF membranes reveals that the nanoporous structure of GO-OCMC functional layer and size exclusion and electrostatic repulsion of water nanochannels formed by GO nanosheets lead to the membranes possessing enhanced desalting properties.

  14. Protein corona mitigates the cytotoxicity of graphene oxide by reducing its physical interaction with cell membrane.

    PubMed

    Duan, Guangxin; Kang, Seung-gu; Tian, Xin; Garate, Jose Antonio; Zhao, Lin; Ge, Cuicui; Zhou, Ruhong

    2015-10-07

    Many recent studies have shown that the way nanoparticles interact with cells and biological molecules can vary greatly in the serum-containing or serum-free culture medium. However, the underlying molecular mechanisms of how the so-called "protein corona" formed in serum medium affects nanoparticles' biological responses are still largely unresolved. Thus, it is critical to understand how absorbed proteins on the surfaces of nanoparticles alter their biological effects. In this work, we have demonstrated with both experimental and theoretical approaches that protein BSA coating can mitigate the cytotoxicity of graphene oxide (GO) by reducing its cell membrane penetration. Our cell viability and cellular uptake experiments showed that protein corona decreased cellular uptake of GO, thus significantly mitigating the potential cytotoxicity of GO. The electron microscopy images also confirmed that protein corona reduced the cellular morphological damage by limiting GO penetration into the cell membrane. Further molecular dynamics (MD) simulations validated the experimental results and revealed that the adsorbed BSA in effect weakened the interaction between the phospholipids and graphene surface due to a reduction of the available surface area plus an unfavorable steric effect, thus significantly reducing the graphene penetration and lipid bilayer damaging. These findings provide new insights into the underlying molecular mechanism of this important graphene protein corona interaction with cell membranes, and should have implications in future development of graphene-based biomedical applications.

  15. Graphene Oxide as an Effective Barrier on a Porous Nanofibrous Membrane for Water Treatment.

    PubMed

    Wang, Jianqiang; Zhang, Pan; Liang, Bin; Liu, Yuxuan; Xu, Tao; Wang, Lifang; Cao, Bing; Pan, Kai

    2016-03-09

    A novel graphene oxide (GO)-based nanofiltration membrane on a highly porous polyacrylonitrile nanofibrous mat (GO@PAN) is prepared for water treatment applications. GO with large lateral size (more than 200 μm) is first synthesized through an improved Hummers method and then assembled on a highly porous nanofibrous mat by vacuum suction method. The prepared GO@PAN membrane is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectrum, X-ray diffraction, and so forth. The results show that graphene oxide can form a barrier on the top of a PAN nanofibrous mat with controllable thickness. The obtained graphene oxide layer exhibits "ideal" pathways (hydrophobic nanochannel) for water molecules between the well-stacked GO nanosheets. Water flux under an extremely low external pressure (1.0 bar) significantly increased due to the unique structure of the GO layer and nanofibrous support. Furthermore, the GO@PAN membrane shows high rejection performance (nearly 100% rejection of Congo red and 56.7% for Na2SO4). A hydrophilic-hydrophobic "gate"-nanochannel model is presented for explaining the water diffusion mechanism through the GO layer. This method for fabrication of the GO membrane on a highly porous support may provide many new opportunities for high performance nanofiltration applications.

  16. Free-Standing Graphene Oxide-Palygorskite Nanohybrid Membrane for Oil/Water Separation.

    PubMed

    Zhao, Xueting; Su, Yanlei; Liu, Yanan; Li, Yafei; Jiang, Zhongyi

    2016-03-01

    Graphene oxide (GO) is an emerging kind of building block for advanced membranes with tunable passageway for water molecules. To synergistically manipulate the channel and surface structures/properties of GO-based membranes, the different building blocks are combined and the specific interfacial interactions are designed in this study. With vacuum-assisted filtration self-assembly, palygorskite nanorods are intercalated into adjacent GO nanosheets, and GO nanosheets are assembled into laminate structures through π-π stacking and cation cross-linking. The palygorskite nanorods in the free-standing GOP nanohybrid membranes take a 3-fold role, rendering enlarged mass transfer channels, elevating hydration capacity, and creating hierarchical nanostructures of membrane surfaces. Accordingly, the permeate fluxes from 267 L/(m(2) h) for GO membrane to 1867 L/(m(2) h) for GOP membrane. The hydration capacity and hierarchical nanostructures synergistically endow GOP membranes with underwater superoleophobic and low oil-adhesive water/membrane interfaces. Moreover, by rationally imparting chemical and physical joint defense mechanisms, the GOP membranes exhibit outstanding separation performance and antifouling properties for various oil-in-water emulsion systems (with different concentration, pH, or oil species). The high water permeability, high separation efficiency, as well as superior anti-oil-fouling properties of GOP membranes enlighten the great prospects of graphene-based nanostructured materials in water purification and wastewater treatment.

  17. Strict molecular sieving over electrodeposited 2D-interspacing-narrowed graphene oxide membranes.

    PubMed

    Qi, Benyu; He, Xiaofan; Zeng, Gaofeng; Pan, Yichang; Li, Guihua; Liu, Guojuan; Zhang, Yanfeng; Chen, Wei; Sun, Yuhan

    2017-10-10

    To separate small molecules/species, it's crucial but still challenging to narrow the 2D-interspacing of graphene oxide (GO) membranes without damaging the membrane. Here the fast deposition of ultrathin, defect-free and robust GO layers is realized on porous stainless steel hollow fibers (PSSHFs) by a facile and practical electrophoresis deposition (ED) method. In this approach, oxygen-containing groups of GO are selectively reduced, leading to a controlled decrease of the 2D channels of stacked GO layers. The resultant ED-GO@PSSHF composite membranes featured a sharp cutoff between C2 (ethane and ethene) and C3 (propane and propene) hydrocarbons and exhibited nearly complete rejections for the smallest alcohol and ion in aqueous solutions. This demonstrates the versatility of GO based membranes for the precise separation of various types of mixtures. At the same time, a robust mechanical strength of the ED-GO@PSSHF membrane is also achieved due to the enhanced interaction at GO/support and GO/GO interfaces.Producing graphene oxide membranes with narrow channels is desirable for small molecule separations, but methods to narrow the 2D spacing typically result in membrane damage. Here the authors exploit electrophoresis-deposition to prepare GO membranes that are reduced in situ, leading to narrow and uniform 2D channels.

  18. Sulfonated graphene oxide/nafion composite membrane for vanadium redox flow battery.

    PubMed

    Kim, Byung Guk; Han, Tae Hee; Cho, Chang Gi

    2014-12-01

    Nafion is the most frequently used as the membrane material due to its good proton conductivity, and excellent chemical and mechanical stabilities. But it is known to have poor barrier property due to its well-developed water channels. In order to overcome this drawback, graphene oxide (GO) derivatives were introduced for Nafion composite membranes. Sulfonated graphene oxide (sGO) was prepared from GO. Both sGO and GO were treated each with phenyl isocyanate and transformed into corresponding isGO and iGO in order to promote miscibility with Nafion. Then composite membranes were obtained, and the adaptability as a membrane for vanadium redox flow battery (VRFB) was investigated in terms of proton conductivity and vanadium permeability. Compared to a pristine Nafion, proton conductivities of both isGO/Nafion and iGO/Nafion membranes showed less temperature sensitivity. Both membranes also showed quite lower vanadium permeability at room temperature. Selectivity of the membrane was the highest for isGO/Nafion and the lowest for the pristine Nafion.

  19. Evaluation of Humic Acid and Tannic Acid Fouling in Graphene Oxide-Coated Ultrafiltration Membranes.

    PubMed

    Chu, Kyoung Hoon; Huang, Yi; Yu, Miao; Her, Namguk; Flora, Joseph R V; Park, Chang Min; Kim, Suhan; Cho, Jaeweon; Yoon, Yeomin

    2016-08-31

    Three commercially available ultrafiltration (UF) membranes (poly(ether sulfone), PES) that have nominal molecular weight cut-offs (5, 10, and 30 kDa) were coated with graphene oxide (GO) nanosheets. Field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, confocal laser scanning microscopy, water contact angle measurements, and X-ray photoelectron spectroscopy were employed to determine the changed physicochemical properties of the membranes after GO coating. The water permeability and single-solute rejection of GO-coated (GOC) membranes for humic acid (HA) molecules were significantly higher by approximately 15% and 55%, respectively, compared to those of pristine UF membranes. However, the GOc membranes for single-solute tannic acid (TA) rejection showed similar trends of higher flux decline versus pristine PES membranes, because the relatively smaller TA molecules were readily adsorbed onto the membrane pores. When the mixed-solute of HA and TA rejection tests were performed, in particular, the adsorbed small TA molecules resulted in irreversible membrane fouling due to cake formation and membrane pore blocking on the membrane surface for the HA molecules. Although both membranes showed significantly higher flux declines for small molecules rejection, the GOc membranes showed better performance than the pristine UF membranes in terms of the rejection of various mixed-solute molecules, due to higher membrane recovery and antifouling capabilities.

  20. Graphene Oxide Membranes with Strong Stability in Aqueous Solutions and Controllable Lamellar Spacing.

    PubMed

    Xi, Yue-Heng; Hu, Jia-Qi; Liu, Zhuang; Xie, Rui; Ju, Xiao-Jie; Wang, Wei; Chu, Liang-Yin

    2016-06-22

    Graphene oxide (GO) membranes become emerging efficient filters for molecular or ionic separation due to their well-defined two-dimensional nanochannels formed by closely spaced GO sheets and tunable physicochemical properties. The stability of GO membranes in aqueous solutions is a prerequisite for their applications. Here we show a novel and easy strategy for fabricating GO membranes with strong stability in aqueous solutions and controllable lamellar spacing by simply doping with partially reduced graphene oxide (prGO) sheets. With our prGO-doping strategy, the interlayer stabilizing force in GO membranes is enhanced due to the weakened repulsive hydration and enhanced π-π attraction between GO sheets; as a result, the fabricated GO membranes are featured with controllable lamellar spacing and extraordinary stability in water or even strong acid and base solutions as well as strong mechanical properties, which will expand the application scope of GO membranes and provide ever better performances in their applications with aqueous solution environments.

  1. UV-Enhanced Sacrificial Layer Stabilised Graphene Oxide Hollow Fibre Membranes for Nanofiltration

    PubMed Central

    Chong, J. Y.; Aba, N. F. D.; Wang, B.; Mattevi, C.; Li, K.

    2015-01-01

    Graphene oxide (GO) membranes have demonstrated great potential in gas separation and liquid filtration. For upscale applications, GO membranes in a hollow fibre geometry are of particular interest due to the high-efficiency and easy-assembly features at module level. However, GO membranes were found unstable in dry state on ceramic hollow fibre substrates, mainly due to the drying-related shrinkage, which has limited the applications and post-treatments of GO membranes. We demonstrate here that GO hollow fibre membranes can be stabilised by using a porous poly(methyl methacrylate) (PMMA) sacrificial layer, which creates a space between the hollow fibre substrate and the GO membrane thus allowing stress-free shrinkage. Defect-free GO hollow fibre membrane was successfully determined and the membrane was stable in a long term (1200 hours) gas-tight stability test. Post-treatment of the GO membranes with UV light was also successfully accomplished in air, which induced the creation of controlled microstructural defects in the membrane and increased the roughness factor of the membrane surface. The permeability of the UV-treated GO membranes was greatly enhanced from 0.07 to 2.8 L m−2 h−1 bar−1 for water, and 0.14 to 7.5 L m−2 h−1 bar−1 for acetone, with an unchanged low molecular weight cut off (~250 Da). PMID:26527173

  2. UV-Enhanced Sacrificial Layer Stabilised Graphene Oxide Hollow Fibre Membranes for Nanofiltration.

    PubMed

    Chong, J Y; Aba, N F D; Wang, B; Mattevi, C; Li, K

    2015-11-03

    Graphene oxide (GO) membranes have demonstrated great potential in gas separation and liquid filtration. For upscale applications, GO membranes in a hollow fibre geometry are of particular interest due to the high-efficiency and easy-assembly features at module level. However, GO membranes were found unstable in dry state on ceramic hollow fibre substrates, mainly due to the drying-related shrinkage, which has limited the applications and post-treatments of GO membranes. We demonstrate here that GO hollow fibre membranes can be stabilised by using a porous poly(methyl methacrylate) (PMMA) sacrificial layer, which creates a space between the hollow fibre substrate and the GO membrane thus allowing stress-free shrinkage. Defect-free GO hollow fibre membrane was successfully determined and the membrane was stable in a long term (1200 hours) gas-tight stability test. Post-treatment of the GO membranes with UV light was also successfully accomplished in air, which induced the creation of controlled microstructural defects in the membrane and increased the roughness factor of the membrane surface. The permeability of the UV-treated GO membranes was greatly enhanced from 0.07 to 2.8 L m(-2) h(-1) bar(-1) for water, and 0.14 to 7.5 L m(-2) h(-1) bar(-1) for acetone, with an unchanged low molecular weight cut off (~250 Da).

  3. UV-Enhanced Sacrificial Layer Stabilised Graphene Oxide Hollow Fibre Membranes for Nanofiltration

    NASA Astrophysics Data System (ADS)

    Chong, J. Y.; Aba, N. F. D.; Wang, B.; Mattevi, C.; Li, K.

    2015-11-01

    Graphene oxide (GO) membranes have demonstrated great potential in gas separation and liquid filtration. For upscale applications, GO membranes in a hollow fibre geometry are of particular interest due to the high-efficiency and easy-assembly features at module level. However, GO membranes were found unstable in dry state on ceramic hollow fibre substrates, mainly due to the drying-related shrinkage, which has limited the applications and post-treatments of GO membranes. We demonstrate here that GO hollow fibre membranes can be stabilised by using a porous poly(methyl methacrylate) (PMMA) sacrificial layer, which creates a space between the hollow fibre substrate and the GO membrane thus allowing stress-free shrinkage. Defect-free GO hollow fibre membrane was successfully determined and the membrane was stable in a long term (1200 hours) gas-tight stability test. Post-treatment of the GO membranes with UV light was also successfully accomplished in air, which induced the creation of controlled microstructural defects in the membrane and increased the roughness factor of the membrane surface. The permeability of the UV-treated GO membranes was greatly enhanced from 0.07 to 2.8 L m-2 h-1 bar-1 for water, and 0.14 to 7.5 L m-2 h-1 bar-1 for acetone, with an unchanged low molecular weight cut off (~250 Da).

  4. Preparation of polyvinylidene fluoride nanofiber membrane and its antibacterial characteristics with nanosilver or graphene oxide.

    PubMed

    Hong, Byungpyo; Jung, Hyemin; Byun, Hongsik

    2013-09-01

    Polyvinylidene fluoride (PVdF) (Kynar 761) nanofibers were prepared by electrospinning at an external voltage of 6-10 kV, a traveling distance of 7-15 cm and flow rate of 0.4-1 ml/hr. Although the diameter of the fiber was not significantly changed, the electrospinning conditions affected the overall distribution of diameter. This is probably due to the interactions, both attraction and repulsion, of positive charges on polymer solutions and the electrically grounded collector. Especially, the effect of voltage on the distribution of diameter was investigated in this study. The final PVdF nanofiber membrane showed narrow pore-size distribution and high water flux compared with the commercial MF membrane. PVdF nanofiber membranes incorporated nanosilver or graphene oxide were also prepared as nanosilver and graphene have an antibacterial activity. It was found that more than 200 ppm of silver nanoparticles in the PVdF nanofiber had 99.9% of growth inhibition of Staphylococcus aureus and Klebsiella pneumonia. It was also found that 0.2 wt% of graphene oxide in the PVdF electrospinning solution had 99.6% of disinfection property to E-Coli.

  5. Graphene oxide membranes with high permeability and selectivity for dehumidification of air

    SciTech Connect

    Shin, Yongsoon; Liu, Wei; Schwenzer, Birgit; Manandhar, Sandeep; Chase-Woods, Dylan; Engelhard, Mark H.; Devanathan, Ram; Fifield, Leonard S.; Bennett, Wendy D.; Ginovska, Bojana; Gotthold, David W.

    2016-09-01

    Hierarchically stacked 2D graphene oxide (GO) membranes are a fascinating and promising new class of materials with the potential for radically improved water vapor/gas separation with excellent selectivity and high permeability. This paper details dehumidification results from flowing gas mixtures through free-standing GO membrane samples prepared by a casting method. The first demonstrated use of free-standing GO membranes for water vapor separation reveals outstanding water vapor permeability and H2O/N2 selectivity. Free-standing GO membranes exhibit extremely high water vapor permeability of 1.82 x 105 Barrer and a water vapor permeance of 1.01 x 10-5 mol/m2sPa, while the nitrogen permeability was below the system’s detection limit, yielding a selectivity >104 in 80% relative humidity (RH) air at 30.8 °C. The results show great potential for a range of energy conversion and environmental applications

  6. Biofouling Mitigation in Forward Osmosis Using Graphene Oxide Functionalized Thin-Film Composite Membranes.

    PubMed

    Perreault, François; Jaramillo, Humberto; Xie, Ming; Ude, Mercy; Nghiem, Long D; Elimelech, Menachem

    2016-06-07

    Forward osmosis (FO) is an emerging membrane process with potential applications in the treatment of highly fouling feedwaters. However, biofouling, the adhesion of microorganisms to the membrane and the subsequent formation of biofilms, remains a major limitation since antifouling membrane modifications offer limited protection against biofouling. In this study, we evaluated the use of graphene oxide (GO) for biofouling mitigation in FO. GO functionalization of thin-film composite membranes (GO-TFC) increased the surface hydrophilicity and imparted antimicrobial activity to the membrane without altering its transport properties. After 1 h of contact time, deposition and viability of Pseudomonas aeruginosa cells on GO-TFC were reduced by 36% and 30%, respectively, compared to pristine membranes. When GO-TFC membranes were tested for treatment of an artificial secondary wastewater supplemented with P. aeruginosa, membrane biofouling was reduced by 50% after 24 h of operation. This biofouling resistance is attributed to the reduced accumulation of microbial biomass on GO-TFC compared to pristine membranes. In addition, confocal microscopy demonstrated that cells deposited on the membrane surface are inactivated, resulting in a layer of dead cells on GO-TFC that limit biofilm formation. These findings highlight the potential of GO to be used for biofouling mitigation in FO.

  7. Extended friction elucidates the breakdown of fast water transport in graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Montessori, A.; Amadei, C. A.; Falcucci, G.; Sega, M.; Vecitis, C. D.; Succi, S.

    2016-12-01

    The understanding of water transport in graphene oxide (GO) membranes stands out as a major theoretical problem in graphene research. Notwithstanding the intense efforts devoted to the subject in the recent years, a consolidated picture of water transport in GO membranes is yet to emerge. By performing mesoscale simulations of water transport in ultrathin GO membranes, we show that even small amounts of oxygen functionalities can lead to a dramatic drop of the GO permeability, in line with experimental findings. The coexistence of bulk viscous dissipation and spatially extended molecular friction results in a major decrease of both slip and bulk flow, thereby suppressing the fast water transport regime observed in pristine graphene nanochannels. Inspection of the flow structure reveals an inverted curvature in the near-wall region, which connects smoothly with a parabolic profile in the bulk region. Such inverted curvature is a distinctive signature of the coexistence between single-particle zero-temperature (noiseless) Langevin friction and collective hydrodynamics. The present mesoscopic model with spatially extended friction may offer a computationally efficient tool for future simulations of water transport in nanomaterials.

  8. Reduced Graphene Oxide Bipolar Membranes for Integrated Solar Water Splitting in Optimal pH.

    PubMed

    McDonald, Michael B; Bruce, Jared P; McEleney, Kevin; Freund, Michael S

    2015-08-24

    The integration of light absorbers and catalysts for the water splitting process requires a membrane capable of both ion and electron management and product separation to realize efficient solar fuels systems. Bipolar membranes can maintain a pH gradient for optimal reaction conditions by the dissociation of water. Such membranes that contain graphene in the interfacial layer are fabricated by the chemical reduction of a uniformly deposited graphene oxide layer to convert sp(3) catalyst regions to sp(2) conductive regions. The resulting electrical and water dissociation properties are optimized by adjusting the exposure conditions, and treatments of less than 5 min render an interface that exceeds the conductivity requirements for integrated solar water splitting and increases the overpotential by <0.3 V. Integration with photoelectrodes is examined by characterizing the electrical interface formed between graphene and Si microwires, and we found that efficient Ohmic junctions are possible. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Reverse osmosis desalination of chitosan cross-linked graphene oxide/titania hybrid lamellar membranes

    NASA Astrophysics Data System (ADS)

    Deng, Hui; Sun, Penzhan; Zhang, Yingjiu; Zhu, Hongwei

    2016-07-01

    With excellent mass transport properties, graphene oxide (GO)-based lamellar membranes are believed to have great potential in water desalination. In order to quantify whether GO-based membranes are indeed suitable for reverse osmosis (RO) desalination, three sub-micrometer thick GO-based lamellar membranes: GO-only, reduced GO (RGO)/titania (TO) nanosheets and RGO/TO/chitosan (CTS) are prepared, and their RO desalination performances are evaluated in a home-made RO test apparatus. The photoreduction of GO by TO improves the salt rejection, which increases slowly with the membrane thickness. The RGO/TO/CTS hybrid membranes exhibit higher rejection rates of only about 30% (greater than threefold improvement compared with a GO-only membrane) which is still inferior compared to other commercial RO membranes. The low rejection rates mainly arise from the pressure-induced weakening of the ion-GO interlayer interactions. Despite the advantages of simple, low-cost preparation, high permeability and selectivity of GO-based lamellar membranes, as the current desalination performances are not high enough to afford practical application, there still remains a great challenge to realize high performance separation membranes for water desalination applications.

  10. Reverse osmosis desalination of chitosan cross-linked graphene oxide/titania hybrid lamellar membranes.

    PubMed

    Deng, Hui; Sun, Penzhan; Zhang, Yingjiu; Zhu, Hongwei

    2016-07-08

    With excellent mass transport properties, graphene oxide (GO)-based lamellar membranes are believed to have great potential in water desalination. In order to quantify whether GO-based membranes are indeed suitable for reverse osmosis (RO) desalination, three sub-micrometer thick GO-based lamellar membranes: GO-only, reduced GO (RGO)/titania (TO) nanosheets and RGO/TO/chitosan (CTS) are prepared, and their RO desalination performances are evaluated in a home-made RO test apparatus. The photoreduction of GO by TO improves the salt rejection, which increases slowly with the membrane thickness. The RGO/TO/CTS hybrid membranes exhibit higher rejection rates of only about 30% (greater than threefold improvement compared with a GO-only membrane) which is still inferior compared to other commercial RO membranes. The low rejection rates mainly arise from the pressure-induced weakening of the ion-GO interlayer interactions. Despite the advantages of simple, low-cost preparation, high permeability and selectivity of GO-based lamellar membranes, as the current desalination performances are not high enough to afford practical application, there still remains a great challenge to realize high performance separation membranes for water desalination applications.

  11. Electro- and Magneto-Modulated Ion Transport through Graphene Oxide Membranes

    PubMed Central

    Sun, Pengzhan; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Zhu, Hongwei

    2014-01-01

    The control of ion trans-membrane transport through graphene oxide (GO) membranes is achieved by electric and magnetic fields. Electric field can either increase or decrease the ion transport through GO membranes depending on its direction, and magnetic field can enhance the ion penetration monotonically. When electric field is applied across GO membrane, excellent control of ion fluidic flows can be done. With the magnetic field, the effective anchoring of ions is demonstrated but the modulation of the ion flowing directions does not occur. The mechanism of the electro- and magneto-modulated ion trans-membrane transport is investigated, indicating that the electric fields dominate the ion migration process while the magnetic fields tune the structure of nanocapillaries within GO membranes. Results also show that the ion selectivity of GO membranes can be tuned with the electric fields while the transport of ions can be enhanced synchronously with the magnetic fields. These excellent properties make GO membranes promising in areas such as field-induced mass transport control and membrane separation. PMID:25347969

  12. Development of a stable cation modified graphene oxide membrane for water treatment

    NASA Astrophysics Data System (ADS)

    Yu, Wenzheng; (Yet Yu, Tong; Graham, Nigel

    2017-12-01

    Membranes prepared from layers of graphene oxide (GO) offer substantial advantages over conventional materials for water treatment (e.g. greater flux), but the stability of GO membranes in water has not been achieved until now. In this study the behavior of GO membranes prepared with different quantities and species of cations has been investigated to establish the feasibility of their application in water treatment. A range of cation-modified GO membranes were prepared and exposed to aqueous solutions containing specific chemical constituents. In pure water, unmodified and Na-modified GO membranes were highly unstable, while GO membranes modified with multivalent cations were stable provided there were sufficient quantities of cations present; their relative capability to achieve GO stability was as follows: Al3+  >  Ca2+  >  Mg2+  >  Na+. It is believed that the mechanism of cross-linking, and membrane stability, is via metal-carboxylate chelates and cation-graphite surface interactions (cation-π interaction), and that the latter appears to increase with increasing cation valency. The instability of cation (Ca or Al)-modified GO membranes by NaCl solutions during permeation occurred as Na+ exchanged with the incorporated multivalent cations, but a high content of Al3+ in the GO membrane impeded Al3+/Na+ exchange and thus retained membrane stability. In solutions containing biopolymers representative of surface waters or seawater (protein and polysaccharide solutions), Ca-GO membranes (even with high Ca2+ content) were not stable, while Al-GO membranes were stable if the Al3+ content was sufficiently high; Al-formed membranes also had a greater flux than Ca-GO membranes.

  13. Pt nanoparticle-reduced graphene oxide nanohybrid for proton exchange membrane fuel cells.

    PubMed

    Park, Dae-Hwan; Jeon, Yukwon; Ok, Jinhee; Park, Jooil; Yoon, Seong-Ho; Choy, Jin-Ho; Shul, Yong-Gun

    2012-07-01

    A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) analysis, the face-centered cubic Pt NPs (3-5 nm in diameter) were homogeneously dispersed on the RGO nanosheets. The electrochemically active surface area and PEMFC power density of the Pt-RGO nanohybrid were determined to be 33.26 m2/g and 480 mW/cm2 (maximum values), respectively, at 75 degrees C and at a relative humidity (RH) of 100% in a single-cell test experiment.

  14. Atomistic understandings of reduced graphene oxide as an ultrathin-film nanoporous membrane for separations

    PubMed Central

    Lin, Li-Chiang; Grossman, Jeffrey C.

    2015-01-01

    The intrinsic defects in reduced graphene oxide (rGO) formed during reduction processes can act as nanopores, making rGO a promising ultrathin-film membrane candidate for separations. To assess the potential of rGO for such applications, molecular dynamics techniques are employed to understand the defect formation in rGO and their separation performance in water desalination and natural gas purification. We establish the relationship between rGO synthesis parameters and defect sizes, resulting in a potential means to control the size of nanopores in rGO. Furthermore, our results show that rGO membranes obtained under properly chosen synthesis conditions can achieve effective separations and provide significantly higher permeate fluxes than currently available membranes. PMID:26395422

  15. Atomistic understandings of reduced graphene oxide as an ultrathin-film nanoporous membrane for separations.

    PubMed

    Lin, Li-Chiang; Grossman, Jeffrey C

    2015-09-23

    The intrinsic defects in reduced graphene oxide (rGO) formed during reduction processes can act as nanopores, making rGO a promising ultrathin-film membrane candidate for separations. To assess the potential of rGO for such applications, molecular dynamics techniques are employed to understand the defect formation in rGO and their separation performance in water desalination and natural gas purification. We establish the relationship between rGO synthesis parameters and defect sizes, resulting in a potential means to control the size of nanopores in rGO. Furthermore, our results show that rGO membranes obtained under properly chosen synthesis conditions can achieve effective separations and provide significantly higher permeate fluxes than currently available membranes.

  16. Atomistic understandings of reduced graphene oxide as an ultrathin-film nanoporous membrane for separations

    NASA Astrophysics Data System (ADS)

    Lin, Li-Chiang; Grossman, Jeffrey C.

    2015-09-01

    The intrinsic defects in reduced graphene oxide (rGO) formed during reduction processes can act as nanopores, making rGO a promising ultrathin-film membrane candidate for separations. To assess the potential of rGO for such applications, molecular dynamics techniques are employed to understand the defect formation in rGO and their separation performance in water desalination and natural gas purification. We establish the relationship between rGO synthesis parameters and defect sizes, resulting in a potential means to control the size of nanopores in rGO. Furthermore, our results show that rGO membranes obtained under properly chosen synthesis conditions can achieve effective separations and provide significantly higher permeate fluxes than currently available membranes.

  17. Graphene Oxide Nanofiltration Membranes Stabilized by Cationic Porphyrin for High Salt Rejection.

    PubMed

    Xu, Xiao-Ling; Lin, Fu-Wen; Du, Yong; Zhang, Xi; Wu, Jian; Xu, Zhi-Kang

    2016-05-25

    Swelling has great influences on the structure stability and separation performance of graphene oxide laminate membranes (GOLMs) for water desalination and purification. Herein, we report cross-linked GOLMs from GO assembled with cationic tetrakis(1-methyl-pyridinium-4-yl)porphyrin (TMPyP) by a vacuum-assisted strategy. The concave nonoxide regions (G regions) of GO are used as cross-linking sites for the first time to precisely control the channel size for water permeation and salt ion retention. Channels around 1 nm are constructed by modulating the assembly ratio of TMPyP/GO, and these cross-linked GOLMs show high salt rejection.

  18. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances.

    PubMed

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-02-02

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.

  19. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

    NASA Astrophysics Data System (ADS)

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-02-01

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.

  20. Graphene Oxide Quantum Dots Covalently Functionalized PVDF Membrane with Significantly-Enhanced Bactericidal and Antibiofouling Performances

    PubMed Central

    Zeng, Zhiping; Yu, Dingshan; He, Ziming; Liu, Jing; Xiao, Fang-Xing; Zhang, Yan; Wang, Rong; Bhattacharyya, Dibakar; Tan, Timothy Thatt Yang

    2016-01-01

    Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation. PMID:26832603

  1. Constructing Ionic Liquid-Filled Proton Transfer Channels within Nanocomposite Membrane by Using Functionalized Graphene Oxide.

    PubMed

    Wu, Wenjia; Li, Yifan; Chen, Pingping; Liu, Jindun; Wang, Jingtao; Zhang, Haoqin

    2016-01-13

    Herein, nanocomposite membranes are fabricated based on functionalized graphene oxides (FGOs) and sulfonated poly(ether ether ketone) (SPEEK), followed by being impregnated with imidazole-type ionic liquid (IL). The functional groups (acidic group or basic group) on FGOs generate strong interfacial interactions with SPEEK chains and then adjust their motion and stacking. As a result, the nanocomposite membranes possess tunable interfacial domains as determined by its free volume characteristic, which provides regulated location for IL storage. The stored ILs act as hopping sites for water-free proton conduction along the FGO-constructed interfacial channels. The microstructure at SPEEK-FGO interface governs the IL uptake and distribution in nanocomposite membrane. Different from GO and vinyl imidazole functionalized GO (VGO), the presence of acidic (-SO3H) groups confers the p-styrenesulfonic acid functionalized GO (SGO) incorporated nanocomposite membrane loose interface and strong electrostatic attraction with imidazole-type IL, imparting an enhanced IL uptake and anhydrous proton conductivity. Nanocomposite membrane containing 7.5% SGO attains the maximum IL uptake of 73.7% and hence the anhydrous conductivity of 21.9 mS cm(-1) at 150 °C, more than 30 times that of SPEEK control membrane (0.69 mS cm(-1)). In addition, SGOs generate electrostatic attractions to the ILs confined within SGO-SPEEK interface, affording the nanocomposite membrane enhanced IL retention ability.

  2. Development of a nanocomposite ultrafiltration membrane based on polyphenylsulfone blended with graphene oxide

    NASA Astrophysics Data System (ADS)

    Shukla, Arun Kumar; Alam, Javed; Alhoshan, Mansour; Dass, Lawrence Arockiasamy; Muthumareeswaran, M. R.

    2017-02-01

    In the present study, graphene oxide (GO) was incorporated as a nanoadditive into a polyphenylsulfone (PPSU) to develop a PPSU/GO nanocomposite membrane with enhanced antifouling properties. A series of membranes containing different concentrations (0.2, 0.5 and 1.0 wt.%) of GO were fabricated via the phase inversion method, using N-methyl pyrrolidone (NMP) as the solvent, deionized water as the non-solvent, and polyvinylpyrrolidone (PVP) as a pore forming agent. The prepared nanocomposite membranes were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and were also characterized with respect to contact angle, zeta potential and porosity, mean pore radius, tortuosity and molecular weight cut-off (MWCO). Thermogravimetric analysis (TGA) and tensile testing were used to measure thermal and mechanical properties. The membrane performance was evaluated by volumetric flux and rejection of proteins, and antifouling properties. According to the results, the optimum addition of 0.5 wt% GO resulted in a membrane with an increased flux of 171 ± 3 Lm‑2h‑1 with a MWCO of ~40 kDa. In addition, the GO incorporation efficiently inhibited the interaction between proteins and the membrane surface, thereby improving the fouling resistance ability by approximately 58 ± 3%. Also, the resulting membranes showed a significant improvement in mechanical and thermal properties.

  3. The incorporation of graphene oxide into polysulfone mixed matrix membrane for CO2/CH4 separation

    NASA Astrophysics Data System (ADS)

    Zahri, K.; Goh, P. S.; Ismail, A. F.

    2016-06-01

    Carbon dioxide (CO2) is often found as the main impurity in natural gas, where methane (CH4) is the major component. The presence of CO2 in natural gas leads to several problems such as reducing the energy content of natural gas and cause pipeline corrosion. Thus it must be removed to meet specifications (CO2 ≤ 2 mol%) before the gas can be delivered to the pipeline. In this work, hollow fiber mixed matrix membrane (MMM) were fabricated by embedding graphene oxide (GO) into a polysulfone (PSf) polymer matrix to improve membrane properties as well as its separation performance towards CO2/CH4 gas. The membrane properties were investigated for pristine membrane and mixed matrix membrane filled with filler loading of 0.25%. The synthesized GO and properties of fabricated membranes were characterized and studied using TEM, AFM, XRD, FTIR and SEM respectively. The permeance of pure gases and ideal selectivity of CO2/CH4 gas were determined using pure gas permeation experiment. GO has affinity towards CO2 gas. The nanosheet structure creates path for small molecule gas and restricted large molecule gas to pass through the membrane. The incorporation of GO in PSf polymer enhanced the permeance of CO 2 and CO2/CH4 separation from 64.47 to 86.80 GPU and from 19 to 25 respectively.

  4. Development of a nanocomposite ultrafiltration membrane based on polyphenylsulfone blended with graphene oxide

    PubMed Central

    Shukla, Arun Kumar; Alam, Javed; Alhoshan, Mansour; Dass, Lawrence Arockiasamy; Muthumareeswaran, M. R.

    2017-01-01

    In the present study, graphene oxide (GO) was incorporated as a nanoadditive into a polyphenylsulfone (PPSU) to develop a PPSU/GO nanocomposite membrane with enhanced antifouling properties. A series of membranes containing different concentrations (0.2, 0.5 and 1.0 wt.%) of GO were fabricated via the phase inversion method, using N-methyl pyrrolidone (NMP) as the solvent, deionized water as the non-solvent, and polyvinylpyrrolidone (PVP) as a pore forming agent. The prepared nanocomposite membranes were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and were also characterized with respect to contact angle, zeta potential and porosity, mean pore radius, tortuosity and molecular weight cut-off (MWCO). Thermogravimetric analysis (TGA) and tensile testing were used to measure thermal and mechanical properties. The membrane performance was evaluated by volumetric flux and rejection of proteins, and antifouling properties. According to the results, the optimum addition of 0.5 wt% GO resulted in a membrane with an increased flux of 171 ± 3 Lm−2h−1 with a MWCO of ~40 kDa. In addition, the GO incorporation efficiently inhibited the interaction between proteins and the membrane surface, thereby improving the fouling resistance ability by approximately 58 ± 3%. Also, the resulting membranes showed a significant improvement in mechanical and thermal properties. PMID:28155882

  5. Selective gas diffusion in graphene oxides membranes: a molecular dynamics simulations study.

    PubMed

    Jiao, Shuping; Xu, Zhiping

    2015-05-06

    Designing membrane materials from one-atom-thick structures is highly promising in separation and filtration applications for the reason that they offer the ultimate precision in modifying the atomic structures and chemistry for optimizing performance, and thus resolving the permeation-selectivity trade-off. In this work, we explore the molecular dynamics of gas diffusion in the gallery space between functionalized graphene layers as well as within nanopores across the multilayers. We have identified highly selective gas permeation that agrees with recent experimental measurements and is promising for advancing gas separation technologies such as hydrogen separation, helium/nitrogen generation, and CO2 sequestration. The roles of structural and chemical factors are discussed by considering different types of gases including H2, He, CH4, N2, O2, CO, CO2, and H2O. The overall performance of graphene oxide membranes is also discussed with respect to their microstructures, and compared with recent experimental measurements. These understandings could advise high-performance gas-separation membrane development by engineering assemblies of two-dimensional layered structures.

  6. Graphene Oxide Induced Perturbation to Plasma Membrane and Cytoskeletal Meshwork Sensitize Cancer Cells to Chemotherapeutic Agents.

    PubMed

    Zhu, Jianqiang; Xu, Ming; Gao, Ming; Zhang, Zhihong; Xu, Yong; Xia, Tian; Liu, Sijin

    2017-03-28

    The outstanding physicochemical properties endow graphene materials (e.g., graphene oxide, GO) with beneficial potentials in diverse biomedical fields such as bioimaging, drug delivery, and biomolecular detection. GO recently emerged as a chemosensitizer; however, the detailed molecular basis underlying GO-conducted sensitization and corresponding biological effects are still elusive. Based on our recent findings that GO treatment at sublethal concentrations could impair the general cellular priming state, including disorders of plasma membrane and cytoskeleton construction, we aimed here to explore the mechanism of GO as a sensitizer to make cancer cells more susceptible to chemotherapeutic agents. We discovered that GO could not only compromise plasma membrane and cytoskeleton in J774A.1 macrophages and A549 lung cancer cells at sublethal concentrations without incurring significant cell death but also dampen a number of biological processes. Using the toxicogenomics approaches, we laid out the gene expression signature affected by GO and further defined those genes involved in membrane and cytoskeletal impairments responding to GO. The mechanistic investigation uncovered that the interactions of GO-integrin occurred on the plasma membrane and consequently activated the integrin-FAK-Rho-ROCK pathway and suppressed the expression of integrin, resulting in compromised cell membrane and cytoskeleton and a subsequent cellular priming state. By making use of this mechanism, the efficacy of chemotherapeutic agents (e.g., doxorubicin and cisplatin) could be enhanced by GO pretreatment in killing cancer cells. This study unveiled a feature of GO in cancer therapeutics: sensitizing cancer cells to chemotherapeutic agents by undermining the resistance capability of tumor cells against chemotherapeutic agents, at least partially, by compromising plasma membrane and cytoskeleton meshwork.

  7. Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation

    NASA Astrophysics Data System (ADS)

    Fang, Qile; Zhou, Xufeng; Deng, Wei; Zheng, Zhi; Liu, Zhaoping

    2016-09-01

    Graphene oxide (GO) based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. However, it’s still a challenge to prepare a freestanding GO-based membrane with high mechanical strength and structural stability which is prerequisite for separation application in aqueous solution. Here, a freestanding composite membrane based on bacterial cellulose (BC) and GO is designed and prepared. BC network provides a porous skeleton to spread GO sheets and uniformly incorporates into the GO layers, which endows the BC + GO composite membrane with well water-stability, excellent tensile strength, as well as improved toughness, guaranteeing its separation applicability in water environment. The resulting BC + GO membrane exhibits obviously discrepant permeation properties for different inorganic/organic ions with different size, and in particular, it can quickly separate ions in nano-scale from angstrom-scale. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation.

  8. Permselective graphene oxide membrane for highly stable and anti-self-discharge lithium-sulfur batteries.

    PubMed

    Huang, Jia-Qi; Zhuang, Ting-Zhou; Zhang, Qiang; Peng, Hong-Jie; Chen, Cheng-Meng; Wei, Fei

    2015-03-24

    Lithium-sulfur batteries hold great promise for serving as next generation high energy density batteries. However, the shuttle of polysulfide induces rapid capacity degradation and poor cycling stability of lithium-sulfur cells. Herein, we proposed a unique lithium-sulfur battery configuration with an ultrathin graphene oxide (GO) membrane for high stability. The oxygen electronegative atoms modified GO into a polar plane, and the carboxyl groups acted as ion-hopping sites of positively charged species (Li(+)) and rejected the transportation of negatively charged species (Sn(2-)) due to the electrostatic interactions. Such electrostatic repulsion and physical inhibition largely decreased the transference of polysulfides across the GO membrane in the lithium-sulfur system. Consequently, the GO membrane with highly tunable functionalization properties, high mechanical strength, low electric conductivity, and facile fabrication procedure is an effective permselective separator system in lithium-sulfur batteries. By the incorporation of a permselective GO membrane, the cyclic capacity decay rate is also reduced from 0.49 to 0.23%/cycle. As the GO membrane blocks the diffusion of polysulfides through the membrane, it is also with advantages of anti-self-discharge properties.

  9. Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation

    PubMed Central

    Fang, Qile; Zhou, Xufeng; Deng, Wei; Zheng, Zhi; Liu, Zhaoping

    2016-01-01

    Graphene oxide (GO) based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. However, it’s still a challenge to prepare a freestanding GO-based membrane with high mechanical strength and structural stability which is prerequisite for separation application in aqueous solution. Here, a freestanding composite membrane based on bacterial cellulose (BC) and GO is designed and prepared. BC network provides a porous skeleton to spread GO sheets and uniformly incorporates into the GO layers, which endows the BC + GO composite membrane with well water-stability, excellent tensile strength, as well as improved toughness, guaranteeing its separation applicability in water environment. The resulting BC + GO membrane exhibits obviously discrepant permeation properties for different inorganic/organic ions with different size, and in particular, it can quickly separate ions in nano-scale from angstrom-scale. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation. PMID:27615451

  10. Performance enhancement of polyvinyl chloride ultrafiltration membrane modified with graphene oxide.

    PubMed

    Zhao, Yuanyuan; Lu, Jiaqi; Liu, Xuyang; Wang, Yudan; Lin, Jiuyang; Peng, Na; Li, Jingchun; Zhao, Fangbo

    2016-10-15

    A novel polyvinyl chloride (PVC) membrane was modified with graphene oxide (GO) via phase inversion method to improve its hydrophilicity and mechanical properties. The GO presented a large amount of hydrophilic groups after the modification through the modified Hummers method. It was observed that with the addition of low fraction of GO powder, the GO/PVC hybrid membranes exhibited a significant enhancement in hydrophilicity, water flux, and mechanical properties. With optimal dosage (0.1wt%), the pure water flux of GO/PVC membrane increased from 232.6L/(m(2)hbar) to 430.0L/(m(2)hbar) and the tensile strength increased from 231.3cN to 305.3cN. The improved properties of the PVC/GO hybrid membranes are mainly attributed to the strong hydrophilicity of functional groups on the GO surface, indicating that GO has a promising candidate for modification of PVC ultrafiltration membranes in wastewater treatment.

  11. Graphene oxide based ultrafiltration membranes for photocatalytic degradation of organic pollutants in salty water.

    PubMed

    Pastrana-Martínez, Luisa M; Morales-Torres, Sergio; Figueiredo, José L; Faria, Joaquim L; Silva, Adrián M T

    2015-06-15

    Flat sheet ultrafiltration (UF) membranes with photocatalytic properties were prepared with lab-made TiO2 and graphene oxide-TiO2 (GOT), and also with a reference TiO2 photocatalyst from Evonik (P25). These membranes were tested in continuous operation mode for the degradation and mineralization of a pharmaceutical compound, diphenhydramine (DP), and an organic dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation. The effect of NaCl was investigated considering simulated brackish water (NaCl 0.5 g L(-1)) and simulated seawater (NaCl 35 g L(-1)). The results indicated that the membranes prepared with the GOT composite (M-GOT) exhibited the highest photocatalytic activity, outperforming those prepared with bare TiO2 (M-TiO2) and P25 (M-P25), both inactive under visible light illumination. The best performance of M-GOT may be due to the lower band-gap energy (2.9 eV) of GOT. In general, the permeate flux was also higher for M-GOT probably due to a combined effect of its highest photocatalytic activity, highest hydrophilicity (contact angles of 11°, 17° and 18° for M-GOT, M-TiO2 and M-P25, respectively) and higher porosity (71%). The presence of NaCl had a detrimental effect on the efficiency of the membranes, since chloride anions can act as hole and hydroxyl radical scavengers, but it did not affect the catalytic stability of these membranes. A hierarchically ordered membrane was also prepared by intercalating a freestanding GO membrane in the structure of the M-GOT membrane (M-GO/GOT). The results showed considerably higher pollutant removal in darkness and good photocatalytic activity under near-UV/Vis and visible light irradiation in continuous mode experiments.

  12. Flexible magnetic nanoparticles-reduced graphene oxide composite membranes formed by self-assembly in solution.

    PubMed

    Zhu, Guoxing; Liu, Yuanjun; Xu, Zheng; Jiang, Tian; Zhang, Chi; Li, Xun; Qi, Gang

    2010-08-02

    A facile and robust route for the pre-synthesized Fe(3)O(4) nanoparticles (NPs) exclusively assembled on both sides of reduced graphene oxide (RGO) sheets with tunable density forming two-dimensional NPs composite membranes is developed in solution. The assembly is driven by electrostatic attraction, and the nanocomposite sheets display considerable mechanical robustness, such as it can sustain supersonic and solvothermal treatments without NPs falling off, also, can freely float in solution and curl into a tube. The obtained two-dimensional composite grain membranes exhibit superparamagnetic behavior at room temperature but responds astutely to an external magnetic field. In addition, these magnetic composite membranes show an enhanced absorption capability for microwaves. The grain sheets are attractive for biomedical, sensors, environmental applications and electric-magnetic devices benefited from large surfaces, high magnetization moment, and superparamagnetic properties. The effective integration of oxide nanocrystals on RGO sheets provides a new way to design semiconductor-carbon nanocomposites for nanodevices or catalytic applications.

  13. Characterization of graphene membranes

    NASA Astrophysics Data System (ADS)

    O'Hern, Sean; Lee, Jongho; Jain, Tarun; Karnik, Rohit; Idrobo, Juan; Laoui, Tahar; Atieh, Motaz

    2011-11-01

    Graphene, which exhibits very high breaking strength, atomistic thickness, and the ability to maintain stable nanometer-scale pores, has the potential to be a superior membrane material in both liquid- and gas-phase separation processes. We have recently demonstrated high-quality transfer of ~1 cm2 LPCVD graphene from copper foil to 200 nm polycarbonate track etch membranes with less than 0.3% of the area constituting holes or tears in the graphene, which is essential for characterizing transport through graphene. Through gallium ion bombardment we have introduced nanometer-scale pores in the transferred graphene and will report on the molecular and ionic transport through these membranes. Funded by the Center for Clean Energy and Water at MIT and KFUPM.

  14. Graphene Oxide Membranes with Heterogeneous Nanodomains for Efficient CO2 Separations.

    PubMed

    Wang, Shaofei; Xie, Yu; He, Guangwei; Xin, Qingping; Zhang, Jinhui; Yang, Leixin; Li, Yifan; Wu, Hong; Zhang, Yuzhong; Guiver, Michael D; Jiang, Zhongyi

    2017-09-21

    Achieving high membrane performance in terms of gas permeance and carbon dioxide selectivity is an important target in carbon capture. Aiming to manipulate the channel affinity towards CO2 to implement efficient separations, gas separation membranes containing CO2 -philic and non-CO2 -philic nanodomains in the interlayer channels of graphene oxide (GO) were formed by intercalating poly(ethylene glycol) diamines (PEGDA). PEGDA reacts with epoxy groups on the GO surface, constructing CO2 -philic nanodomains and rendering a high sorption capacity, whereas unreacted GO surfaces give non-CO2 -philic nanodomains, rendering low-friction diffusion. Owing to the orderly stacking of nanochannels through cross-linking and the heterogeneous nanodomains with moderate CO2 affinity, a GO-PEGDA500 membrane exhibits a high CO2 permeance of 175.5 GPU and a CO2 /CH4 selectivity of 69.5, which is the highest performance reported for dry-state GO-stacking membranes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Graphene Oxide Nanosheets Stimulate Ruffling and Shedding of Mammalian Cell Plasma Membranes.

    PubMed

    Sun, Chao; Wakefield, Devin L; Han, Yimo; Muller, David A; Holowka, David A; Baird, Barbara A; Dichtel, William R

    2016-08-11

    Graphene oxide (GO) has attracted intense interest for use in living systems and environmental applications. GO's compatibility with mammalian cells is sometimes inferred from its low cytotoxicity, but such conclusions ignore non-lethal effects that will influence GO's utility. Here we demonstrate, with rat basophilic leukemia (RBL) cells, profound plasma membrane (PM) ruffling and shedding induced by GO using confocal and live cell fluorescence microscopy, as well as scanning electron microscopy. These membrane structures contain immunoglobulin E receptors, are resistant to detergents, and lack detectable fluorescence labeling of F-actin and fibronectin. The formation of these membrane structures correlates with a loss of contact inhibition between RBL cells. We observe similar cellular responses towards GO for NIH-3T3 fibroblast cells and MDA-MB-231 human breast cancer cells. These findings reveal a previously unreported cellular response towards foreign nanomaterials. Membrane ruffling and shedding raise fundamental questions about how GO interacts with the PM, as well as its potential to modulate cellular mechanosensing for tissue engineering, stem cell differentiation, and other biomedical applications.

  16. Effect of graphene oxide on affinity-immobilization of purple membranes on solid supports.

    PubMed

    Chen, Hsiu-Mei; Lin, Chi-Jung; Jheng, Kai-Ru; Kosasih, Aline; Chang, Jia-Yaw

    2014-04-01

    The effect of graphene oxide (GO) on the surface fabrication of purple membranes (PM) containing photosensitive bacteriorhodopsin is first reported in this study. GO was initially modified with biotin and then coupled with oxidized avidin to generate a GO-avidin complex, which was subsequently used as a linker to immobilize biotinylated PM (b-PM) onto amine-functionalized supports. Indium-tin-oxide glass coated with the GO-avidin complex was more hydrophilic than the electrode coated only with oxidized avidin, and the successive b-PM adsorption yielded a 1.4-fold higher (410 nA/cm(2)) photoelectric activity. AFM analysis on mica revealed that the GO-avidin complex layer had less surface roughness and dissipation energy than the pure oxidized avidin linker layer. For subsequent b-PM fabrication, GO addition not only reduced the stacking of immobilized b-PM patches but also improved their interior compactness and surface smoothness. This study demonstrates a convenient way to introduce GO into PM fabrication technology to provide enhanced surface morphology and photoelectric activity.

  17. Sulphonated imidized graphene oxide (SIGO) based polymer electrolyte membrane for improved water retention, stability and proton conductivity

    NASA Astrophysics Data System (ADS)

    Pandey, Ravi P.; Shahi, Vinod K.

    2015-12-01

    Sulphonated imidized graphene oxide (SIGO) (graphene oxide (GO) tethered sulphonated polyimide) has been successfully synthesized by polycondensation reaction using dianhydride and sulphonated diamine. Polymer electrolyte membranes (PEMs) are prepared by using SIGO (different wt%) and sulphonated poly(imide) (SPI). Resultant SPI/SIGO composite PEMs exhibit improved stabilities (thermal, mechanical and oxidative) and good water-retention properties (high bound water content responsible for proton conduction at high temperature by internal self-humidification). Incorporation of covalent bonded SIGO into SPI matrix results hydrophobic-hydrophilic phase separation and facile architecture of proton conducting path. Well optimized sulphonated poly(imide)/sulphonated imidized graphene oxide (15 wt%) (SPI/SIGO-15) composite membrane shows 2.24 meq g-1 ion-exchange capacity (IEC); 11.38 × 10-2 S cm-1 proton conductivity; 5.12% bound water content; and 10.52 × 10-7 cm2 s-1 methanol permeability. Maximum power density for pristine SPI membrane (57.12 mW cm-2) improves to 78.53 mW cm-2 for SPI/SIGO-15 membrane, in single-cell direct methanol fuel cell (DMFC) test at 70 °C using 2 M methanol fuel. Under similar experimental conditions, Nafion 117 membrane exhibits 62.40 mW cm-2 maximum power density. Reported strategy for the preparation of PEMs, offers a useful protocol for grafting of functionalized inorganic materials with in organic polymer chain by imidization.

  18. Synthesis and Characterization of Sulfonated Graphene Oxide Nanofiller for Polymer Electrolyte Membrane

    NASA Astrophysics Data System (ADS)

    Ch'ng, Y. Y.; Loh, K. S.; Daud, W. R. W.; Mohamad, A. B.

    2016-11-01

    In this study, sulfonated graphene oxide (SGO) nanocomposite were produced as potential nanofiller to improve the properties of polymer electrolyte membrane (PEM) for fuel cell applications. The GO is produced by modified Hummers's method and the as-synthesized GO was used to prepare SGO with three distinctive precursors, namely 3- mercaptomethoxysilane (MPTMS), sulfanilic acid (SA) and butane sultone (BS). The SGO samples were characterized with several physical characterization techniques (XRD, FTIR, SEM-EDX and XPS) to provide the insights into the morphology; the state of homogenization; the crystallography and the functional groups. The experimental result indicated that the sulfonic acid group has been successfully incorporated with GO and can be used as filler in PEM.

  19. High capacitive performance of flexible and binder-free graphene-polypyrrole composite membrane based on in situ reduction of graphene oxide and self-assembly.

    PubMed

    Zhang, Jintao; Chen, Peng; Oh, Bernice H L; Chan-Park, Mary B

    2013-10-21

    Exploiting flexible and binder-free electrode materials is of importance for the fast development of smart supercapacitor devices. A simple and effective strategy is demonstrated to fabricate a flexible composite membrane of reduced graphene oxide and polypyrrole nanowire (RGO-PPy) via in situ reduction of graphene oxide and self-assembly. More importantly, the shape and thickness of the membrane can be reasonably controlled by varying either the concentration of GO and PPy nanowires or the filtration volume. By direct coupling of two membrane electrodes, symmetric supercapacitors can be fabricated without the use of a binder and conductive additive. The supercapacitor is able to offer large areal capacitance (175 mF cm(-2)) and excellent cycling stability (~93% capacitance retention after 5000 charge-discharge cycles), thanks to the synergic integration between RGO sheets and PPy nanowires and the unique self-assembled porous structure.

  20. Enhanced Stability of Laminated Graphene Oxide Membranes for Nanofiltration via Interstitial Amide Bonding.

    PubMed

    Nam, Yoon Tae; Choi, Junghoon; Kang, Kyoung Min; Kim, Dae Woo; Jung, Hee-Tae

    2016-10-03

    Laminated graphene oxide (GO) has promising use as a membrane because of its high permeance, chemical and mechanical stability, as well as the molecular sieving effect of its interlayers. However, the hydrophilic surface of GO, which is highly decorated with oxygen groups, easily induces delamination of stacked GO films in aqueous media, thereby limiting the practical application. To stabilize GO films in aqueous media, we functionalized a polymer support with branched polyethylene-imine (BPEI). BPEI adsorbed intercalated into the stacked GO sheets via diffusion during filtration. The GO/BPEI membrane obtained exhibits high stability during sonication (>1 h duration, 40 kHz frequency) in water within a broad pH range (2-12). In contrast, the GO film spontaneously delaminated upon sonication. Furthermore, BPEI treatment did not affect the filtration performance of the GO film, as evidenced by the high rejection rates (>90%) for the dye molecules methylene blue, rose bengal, and brilliant blue and by their permeation rates of ca. 124, 34.8, 12.2, and 5.1%, respectively, relative to those of a typical GO membrane.

  1. High capacitive performance of flexible and binder-free graphene-polypyrrole composite membrane based on in situ reduction of graphene oxide and self-assembly

    NASA Astrophysics Data System (ADS)

    Zhang, Jintao; Chen, Peng; Oh, Bernice H. L.; Chan-Park, Mary B.

    2013-09-01

    Exploiting flexible and binder-free electrode materials is of importance for the fast development of smart supercapacitor devices. A simple and effective strategy is demonstrated to fabricate a flexible composite membrane of reduced graphene oxide and polypyrrole nanowire (RGO-PPy) via in situ reduction of graphene oxide and self-assembly. More importantly, the shape and thickness of the membrane can be reasonably controlled by varying either the concentration of GO and PPy nanowires or the filtration volume. By direct coupling of two membrane electrodes, symmetric supercapacitors can be fabricated without the use of a binder and conductive additive. The supercapacitor is able to offer large areal capacitance (175 mF cm-2) and excellent cycling stability (~93% capacitance retention after 5000 charge-discharge cycles), thanks to the synergic integration between RGO sheets and PPy nanowires and the unique self-assembled porous structure.Exploiting flexible and binder-free electrode materials is of importance for the fast development of smart supercapacitor devices. A simple and effective strategy is demonstrated to fabricate a flexible composite membrane of reduced graphene oxide and polypyrrole nanowire (RGO-PPy) via in situ reduction of graphene oxide and self-assembly. More importantly, the shape and thickness of the membrane can be reasonably controlled by varying either the concentration of GO and PPy nanowires or the filtration volume. By direct coupling of two membrane electrodes, symmetric supercapacitors can be fabricated without the use of a binder and conductive additive. The supercapacitor is able to offer large areal capacitance (175 mF cm-2) and excellent cycling stability (~93% capacitance retention after 5000 charge-discharge cycles), thanks to the synergic integration between RGO sheets and PPy nanowires and the unique self-assembled porous structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02381h

  2. Free-standing reduced graphene oxide/MnO2-reduced graphene oxide-carbon nanotube nanocomposite flexible membrane as an anode for improving lithium-ion batteries.

    PubMed

    Li, Yong; Ye, Daixin; Shi, Bin; Liu, Wen; Guo, Rui; Pei, Haijuan; Xie, Jingying

    2017-03-15

    To solve the barriers of poor rate capability and inferior cycling stability for the MnO2 anode in lithium ion batteries, we present a highly flexible membrane anode employing two-dimensional (2D) reduced graphene oxide sheets (rGO) and a three-dimensional (3D) MnO2-reduced graphene oxide-carbon nanotube nanocomposite (MGC) by a vacuum filtration and thermal annealing approach. All the components in the 2D/3D thin film anode have a synergistic effect on the improved performance. The initial discharge specific capacity of the electrode with the MnO2 content of 56 wt% was 1656.8 mA h g(-1) and remains 1172.5 mA h g(-1) after 100 cycles at a density of 100 mA g(-1). On enhancing the density to 200 mA g(-1), the membrane-electrode still exhibits a large reversible discharging capacity of ∼948.9 mA h g(-1) after 300 cycles. Moreover, the flexible Li-ion battery with a large area also shows excellent electrochemical performance in different bending positions, which provides the potential for wearable energy storage devices.

  3. Synthesis and performance of antifouling and self-cleaning polyethersulfone/graphene oxide composite membrane functionalized with photoactive semiconductor catalyst.

    PubMed

    Dizge, Nadir; Gonuldas, Hakan; Ozay, Yasin; Ates, Hasan; Ocakoglu, Kasim; Harputlu, Ersan; Yildirimcan, Saadet; Unyayar, Ali

    2017-02-01

    This study was performed to synthesize membranes of polyethersulfone (PES) blended with graphene oxide (GO) and PES blended with GO functionalized with photoactive semiconductor catalyst (TiO2 and ZnO). The antifouling and self-cleaning properties of composite membranes were also investigated. The GO was prepared from natural graphite powder by oxidation method at low temperature. TiO2 and ZnO nanopowders were synthesized by anhydrous sol-gel method. The surface of TiO2 and ZnO nanopowders was modified by a surfactant (myristic acid) to obtain a homogeneously dispersed mixture in a solvent, and then GO was functionalized by loading with these metal oxide nanopowders. The PES membranes blended with GO and functionalized GO into the casting solution were prepared via phase inversion method and tested for their antifouling as well as self-cleaning properties. The composite membranes were synthesized as 14%wt. of PES polymer with three different concentrations (0.5, 1.0, and 2.0%wt.) of GO, GO-TiO2, and GO-ZnO. The functionalization of membranes improved hydrophilicity property of membranes as compared to neat PES membrane. However, the lowest flux was obtained by functionalized membranes with GO-TiO2. The results showed that functionalized membranes demonstrated better self-cleaning property than neat PES membrane. Moreover, the flux recovery rate of functionalized membranes over five cycles was higher than that of neat membrane.

  4. High-flux graphene oxide nanofiltration membrane intercalated by carbon nanotubes.

    PubMed

    Han, Yi; Jiang, Yanqiu; Gao, Chao

    2015-04-22

    A sort of novel high-flux nanofiltration membrane was fabricated by synergistic assembling of graphene and multiwalled carbon nanotubes (MWNTs), in which graphene played the role of molecular sieving and MWNTs expanded the interlayer space between neighbored graphene sheets. The MWNT-intercalated graphene nanofiltration membrane (G-CNTm) showed a water flux up to 11.3 L m(-2) h(-1) bar(-1), more than 2 times that of the neat graphene nanofiltration membrane (GNm), while keeping high dye rejection (>99% for Direct Yellow and >96% Methyl Orange). The G-CNTm also showed good rejection ratio for salt ions (i.e., 83.5% for Na2SO4, 51.4% for NaCl). We also explored the antifouling performance of G-CNTm and GNm with bovine serum albumin (BSA), sodium alginate (SA) and humic acid (HA). Both G-CNTm and GNm possessed excellent antifouling performance for SA and HA but inferior for BSA because of the strong interaction between protein and graphene sheets.

  5. Synthesis and characterization of polysulfone/graphene oxide nano-composite membranes for removal of bisphenol A from water.

    PubMed

    Nasseri, Simin; Ebrahimi, Shima; Abtahi, Mehrnoosh; Saeedi, Reza

    2017-10-03

    Bisphenol A (BPA) is an emerging contaminant of water resources that disrupts endocrine function. Attempts are continuing to develop cost-effective methods to remove BPA from water environments. The aim of this study was to prepare and characterize polysulfone/graphene oxide nano-composite membranes for removal of BPA from water. Three membranes were synthetized using phase inversion method: polysulfone membrane as PSF and two polysulfone/graphene oxide nano-composite membranes with graphene oxide (GO) weight ratios of 0.4 and 1.0% as PSF/GO 0.4% and PSF/GO 1.0%, respectively. The membrane characteristics including morphology, surface roughness, pore size, zeta potential and presence of functional groups were determined using field emission scanning electron microscopy, atomic force microscopy, streaming potential, and attenuated total reflectance Fourier transform infrared spectroscopy techniques. Inclusion of GO remarkably increased permeate flux of the membranes, so that pure water flux of PSF, PSF/GO 0.4% and PSF/GO 1.0% at operating pressure of 2 bar was determined 226, 449 and 512 L/m(2) h, respectively. The membrane PSF/GO 0.4% with the most negative zeta potential (-10.46 mV) and the highest BPA removal efficiency was determined as the optimal membrane. The optimum conditions of input pressure, operating time, initial concentration of BPA, and pH for BPA removal efficiency by PSF/GO 0.4% were determined using surface response methodology to be 1.02 bar, 10.6 min, 7.5 mg/L, and 5.5, respectively. By optimizing the conditions of operating parameters, experimental BPA removal efficiency by PSF/GO 0.4% reached to as high as 93%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. A reduced graphene oxide nanofiltration membrane intercalated by well-dispersed carbon nanotubes for drinking water purification.

    PubMed

    Chen, Xianfu; Qiu, Minghui; Ding, Hao; Fu, Kaiyun; Fan, Yiqun

    2016-03-14

    In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for drinking water purification to retain the nanoparticles, dyes, proteins, organophosphates, sugars, and particularly humic acid. Experimentally, it is shown that the rGO-CNT hybrid NF membranes have high retention efficiency, good permeability and good anti-fouling properties. The retention was above 97.3% even for methyl orange (327 Da); for other objects, the retention was above 99%. The membrane's permeability was found to be as high as 20-30 L m(-2) h(-1) bar(-1). Based on these results, we can conclude that (i) the use of BCPs as a surfactant can enhance steric repulsion and thus disperse CNTs effectively; (ii) placing well-dispersed 1D CNTs within 2D graphene sheets allows an uniform network to form, which can provide many mass transfer channels through the continuous 3D nanostructure, resulting in the high permeability and separation performance of the rGO-CNT hybrid NF membranes.

  7. Dopamine crosslinked graphene oxide membrane for simultaneous removal of organic pollutants and trace heavy metals from aqueous solution.

    PubMed

    Wang, Jing; Huang, Tiefan; Zhang, Lin; Yu, Qiming Jimmy; Hou, Li'an

    2017-09-08

    A graphene oxide-polydopamine-(β-cyclodextrin) (GPC) ultrafiltration membrane was fabricated by using the method of drop-coating combined with vacuum filtration. The prepared GPC membrane was characterized with FTIR and XPS spectrophotometry and evaluated for its performances for the rejection of organic molecules (methylene blue) and adsorption of trace heavy metals (Pb(2+)) from aqueous solutions. The membrane exhibited an excellent rejection coefficient of 99.2% for methylene blue and the permeation flux was 12 L m(-2) h(-1) at 0.1 bar. The membrane also exhibited fast adsorption kinetics for Pb(2+) and the adsorption capacity was 101.6 mg g(-1) at a solution pH of 6. The performance of the membrane could almost be completely recovered after a simple clean and regeneration process. These results indicate that the GPC membrane has potential applications in treatment of complex industrial wastewater streams.

  8. Structural Engineering for High Sensitivity, Ultrathin Pressure Sensors Based on Wrinkled Graphene and Anodic Aluminum Oxide Membrane.

    PubMed

    Chen, Wenjun; Gui, Xuchun; Liang, Binghao; Yang, Rongliang; Zheng, Yongjia; Zhao, Chengchun; Li, Xinming; Zhu, Hai; Tang, Zikang

    2017-07-19

    Nature-motivated pressure sensors have been greatly important components integrated into flexible electronics and applied in artificial intelligence. Here, we report a high sensitivity, ultrathin, and transparent pressure sensor based on wrinkled graphene prepared by a facile liquid-phase shrink method. Two pieces of wrinkled graphene are face to face assembled into a pressure sensor, in which a porous anodic aluminum oxide (AAO) membrane with the thickness of only 200 nm was used to insulate the two layers of graphene. The pressure sensor exhibits ultrahigh operating sensitivity (6.92 kPa(-1)), resulting from the insulation in its inactive state and conduction under compression. Formation of current pathways is attributed to the contact of graphene wrinkles through the pores of AAO membrane. In addition, the pressure sensor is also an on/off and energy saving device, due to the complete isolation between the two graphene layers when the sensor is not subjected to any pressure. We believe that our high-performance pressure sensor is an ideal candidate for integration in flexible electronics, but also paves the way for other 2D materials to be involved in the fabrication of pressure sensors.

  9. Mussel-Inspired Architecture of High-Flux Loose Nanofiltration Membrane Functionalized with Antibacterial Reduced Graphene Oxide-Copper Nanocomposites.

    PubMed

    Zhu, Junyong; Wang, Jing; Uliana, Adam Andrew; Tian, Miaomiao; Zhang, Yiming; Zhang, Yatao; Volodin, Alexander; Simoens, Kenneth; Yuan, Shushan; Li, Jian; Lin, Jiuyang; Bernaerts, Kristel; Van der Bruggen, Bart

    2017-08-30

    Graphene-based nanocomposites have a vast potential for wide-ranging antibacterial applications due to the inherently strong biocidal activity and versatile compatibility of such nanocomposites. Therefore, graphene-based functional nanomaterials can introduce enhanced antibiofouling and antimicrobial properties to polymeric membrane surfaces. In this study, reduced graphene oxide-copper (rGOC) nanocomposites were synthesized as newly robust biocides via in situ reduction. Inspired by the emerging method of bridging ultrafiltration membrane surface cavities, loose nanofiltration (NF) membranes were designed using a rapid (2 h) bioinspired strategy in which rGOC nanocomposites were firmly codeposited with polydopamine (PDA) onto an ultrafiltration support. A series of analyses (SEM, EDS, XRD, XPS, TEM, and AFM) confirmed the successful synthesis of the rGO-Cu nanocomposites. The secure loading of rGOC composites onto the membrane surfaces was also confirmed by SEM and AFM images. Water contact angle results display a high surface hydrophilicity of the modified membranes. The PDA-rGOC functionalization layer facilitated a high water permeability (22.8 L m(-2) h(-1) bar(-1)). The PDA-rGOC modification additionally furnished the membrane with superior separation properties advantageous for various NF applications such as dye purification or desalination, as ultrahigh (99.4% for 0.5 g L(-1) reactive blue 2) dye retention and high salt permeation (7.4% for 1.0 g L(-1) Na2SO4, 2.5% for 1.0 g L(-1) NaCl) was achieved by the PDA-rGOC-modified membranes. Furthermore, after 3 h of contact with Escherichia coli (E. coli) bacteria, the rGOC-functionalized membranes exhibited a strong antibacterial performance with a 97.9% reduction in the number of live E. coli. This study highlights the use of rGOC composites for devising loose NF membranes with strong antibacterial and separation performance.

  10. Superhydrophilic graphene oxide@electrospun cellulose nanofiber hybrid membrane for high-efficiency oil/water separation.

    PubMed

    Ao, Chenghong; Yuan, Wei; Zhao, Jiangqi; He, Xu; Zhang, Xiaofang; Li, Qingye; Xia, Tian; Zhang, Wei; Lu, Canhui

    2017-11-01

    Inspired from fishscales, membranes with special surface wettability have been applied widely for the treatment of oily waste water. Herein, a novel superhydrophilic graphene oxide (GO)@electrospun cellulose nanofiber (CNF) membrane was successfully fabricated. This membrane exhibited a high separation efficiency, excellent antifouling properties, as well as a high flux for the gravity-driven oil/water separation. Moreover, the GO@CNF membrane was capable to effectively separate oil/water mixtures in a broad pH range or with a high concentration of salt, suggesting that this membrane was quite promising for future real-world practice in oil spill cleanup and oily wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Graphene oxide based nanohybrid proton exchange membranes for fuel cell applications: An overview.

    PubMed

    Pandey, Ravi P; Shukla, Geetanjali; Manohar, Murli; Shahi, Vinod K

    2017-02-01

    In the context of many applications, such as polymer composites, energy-related materials, sensors, 'paper'-like materials, field-effect transistors (FET), and biomedical applications, chemically modified graphene was broadly studied during the last decade, due to its excellent electrical, mechanical, and thermal properties. The presence of reactive oxygen functional groups in the grapheme oxide (GO) responsible for chemical functionalization makes it a good candidate for diversified applications. The main objectives for developing a GO based nanohybrid proton exchange membrane (PEM) include: improved self-humidification (water retention ability), reduced fuel crossover (electro-osmotic drag), improved stabilities (mechanical, thermal, and chemical), enhanced proton conductivity, and processability for the preparation of membrane-electrode assembly. Research carried on this topic may be divided into protocols for covalent grafting of functional groups on GO matrix, preparation of free-standing PEM or choice of suitable polymer matrix, covalent or hydrogen bonding between GO and polymer matrix etc. Herein, we present a brief literature survey on GO based nano-hybrid PEM for fuel cell applications. Different protocols were adopted to produce functionalized GO based materials and prepare their free-standing film or disperse these materials in various polymer matrices with suitable interactions. This review article critically discussed the suitability of these PEMs for fuel cell applications in terms of the dependency of the intrinsic properties of nanohybrid PEMs. Potential applications of these nanohybrid PEMs, and current challenges are also provided along with future guidelines for developing GO based nanohybrid PEMs as promising materials for fuel cell applications.

  12. Cysteamine- and graphene oxide-mediated copper nanoparticle decoration on reverse osmosis membrane for enhanced anti-microbial performance.

    PubMed

    Ma, Wen; Soroush, Adel; Luong, Tran Van Anh; Rahaman, Md Saifur

    2017-09-01

    In this work, copper nanoparticles (CuNPs) were decorated onto the polyamide RO membranes via in-situ reduction for biofouling mitigation. To increase CuNPs loading and improve anti-microbial properties of the membrane, cysteamine (Cys) and graphene oxide (GO), which contain different functional groups with high metal affinity, were applied as bridging agents between CuNPs and membrane surface via covalent bonding. The functionalization of Cys and GO linkers on membrane was confirmed by XPS and SEM analysis. By applying the linkers, the loading quantity of copper, in particular on Cys-modified membrane, was significantly improved and the particle size of CuNPs appeared smaller and had more uniform distribution. The GO medium increased the hydrophilicity of CuNP-decorated membranes, leading to an increase in water permeation with minor impact on membrane's salt rejection. Bacterial inactivation of the Cys-Cu- and GO-Cu-functionalized membranes was over 25% higher than that of the bare CuNP-coated surface, indicating enhanced bacterial inactivation benefiting from the application of linkers. After a CuNPs' release test, the membranes modified with Cys and GO retained larger quantities of CuNPs and showed better antimicrobial performance than that of bare CuNP-modified membranes. The successful regeneration of CuNPs after their depletion demonstrated the modified membranes' potential for long-term application. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Electricity generation and local ion ordering induced by cation-controlled selective anion transportation through graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Sun, Pengzhan; Deng, Hui; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Zhang, Yingjiu; Kang, Feiyu; Zhu, Hongwei

    2014-12-01

    A cation-controlled selective anion transportation through graphene oxide (GO) membranes is demonstrated in this work. The results reveal that the trans-membrane transport of different anions can be modulated by the corresponding cations. The diverse interactions among anions, cations, and the negatively charged GO membranes are responsible for selective anion permeation through GO membranes. During the ion penetration, electrical potential differences can be generated across drain and source as well as across GO membranes; based on this, the ion distributions around GO membranes can be determined. The results indicate that local ion ordering can be achieved by GO membranes. Interestingly, for the cases of KNO3, Ca(NO3)2, and Ba(NO3)2, alternate aggregations of metallic cations and NO3- anions can be formed around GO membranes, demonstrating the fantastic ability of these membranes for ordering the ions locally in solutions. In addition, based on the electrical potential differences generated by different salts, chlorides are demonstrated to be ideal sources for efficient practical electricity production compared to sulfates and nitrates, while the different voltage signals generated can be used to identify different source solutions for liquid sensing applications. These results indicate that GO membranes can find potential applications in membrane separation, energy generation, ion recognition, and local ion organizing.

  14. Selective trans-membrane transport of alkali and alkaline earth cations through graphene oxide membranes based on cation-π interactions.

    PubMed

    Sun, Pengzhan; Zheng, Feng; Zhu, Miao; Song, Zhigong; Wang, Kunlin; Zhong, Minlin; Wu, Dehai; Little, Reginald B; Xu, Zhiping; Zhu, Hongwei

    2014-01-28

    Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K(+), Mg(2+), Ca(2+), and Ba(2+)). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp(2) clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations.

  15. Graphene oxide exhibits broad-spectrum antimicrobial activity against bacterial phytopathogens and fungal conidia by intertwining and membrane perturbation

    NASA Astrophysics Data System (ADS)

    Chen, Juanni; Peng, Hui; Wang, Xiuping; Shao, Feng; Yuan, Zhaodong; Han, Heyou

    2014-01-01

    To understand the interaction mechanism between graphene oxide (GO) and typical phytopathogens, a particular investigation was conducted about the antimicrobial activity of GO against two bacterial pathogens (P. syringae and X. campestris pv. undulosa) and two fungal pathogens (F. graminearum and F. oxysporum). The results showed that GO had a powerful effect on the reproduction of all four pathogens (killed nearly 90% of the bacteria and repressed 80% macroconidia germination along with partial cell swelling and lysis at 500 μg mL-1). A mutual mechanism is proposed in this work that GO intertwinds the bacteria and fungal spores with a wide range of aggregated graphene oxide sheets, resulting in the local perturbation of their cell membrane and inducing the decrease of the bacterial membrane potential and the leakage of electrolytes of fungal spores. It is likely that GO interacts with the pathogens by mechanically wrapping and locally damaging the cell membrane and finally causing cell lysis, which may be one of the major toxicity actions of GO against phytopathogens. The antibacterial mode proposed in this study suggests that the GO may possess antibacterial activity against more multi-resistant bacterial and fungal phytopathogens, and provides useful information about the application of GO in resisting crop diseases.To understand the interaction mechanism between graphene oxide (GO) and typical phytopathogens, a particular investigation was conducted about the antimicrobial activity of GO against two bacterial pathogens (P. syringae and X. campestris pv. undulosa) and two fungal pathogens (F. graminearum and F. oxysporum). The results showed that GO had a powerful effect on the reproduction of all four pathogens (killed nearly 90% of the bacteria and repressed 80% macroconidia germination along with partial cell swelling and lysis at 500 μg mL-1). A mutual mechanism is proposed in this work that GO intertwinds the bacteria and fungal spores with a wide range

  16. Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets as Seeds for the Growth of Ultrathin Molecular Sieving Membranes.

    PubMed

    Hu, Yaoxin; Wei, Jing; Liang, Yan; Zhang, Huacheng; Zhang, Xiwang; Shen, Wei; Wang, Huanting

    2016-02-05

    A defect-free zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) membrane with a thickness of 100 nm was prepared using two-dimensional (2D) ZIF-8/GO hybrid nanosheets as seeds. Hybrid nanosheets with a suitable amount of ZIF-8 nanocrystals were essential for producing a uniform seeding layer that facilitates fast crystal intergrowth during membrane formation. Moreover, the seeding layer acts as a barrier between two different synthesis solutions, and self-limits crystal growth and effectively eliminates defects during the contra-diffusion process. The resulting ultrathin membranes show excellent molecular sieving gas separation properties, such as with a high CO2 /N2 selectivity of 7.0. This 2D nano-hybrid seeding strategy can be readily extended to the fabrication of other defect-free and ultrathin MOF or zeolite molecular sieving membranes for a wide range of separation applications.

  17. Controllable Preparation of Ultrathin Sandwich-Like Membrane with Porous Organic Framework and Graphene Oxide for Molecular Filtration

    PubMed Central

    Zhu, Yuanzhi; Xu, Danyun; Zhao, Qingshan; Li, Yang; Peng, Wenchao; Zhang, Guoliang; Zhang, Fengbao; Fan, Xiaobin

    2015-01-01

    Porous organic frameworks (POFs) based membranes have potential applications in molecular filtration, despite the lack of a corresponding study. This study reports an interesting strategy to get processable POFs dispersion and a novel ultrathin sandwich-like membrane design. It was accidentally found that the hydrophobic N-rich Schiff based POFs agglomerates could react with lithium-ethylamine and formed stable dispersion in water. By successively filtrating the obtained POFs dispersion and graphene oxide (GO), we successfully prepared ultrathin sandwich-like hybrid membranes with layered structure, which showed significantly improved separation efficiency in molecular filtration of organic dyes. This study may provide a universal way to the preparation of processable POFs and their hybrid membranes with GO. PMID:26455497

  18. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell

    PubMed Central

    Lei, M.; Wang, Z. B.; Li, J. S.; Tang, H. L.; Liu, W. J.; Wang, Y. G.

    2014-01-01

    Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8–1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study. PMID:25491655

  19. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell.

    PubMed

    Lei, M; Wang, Z B; Li, J S; Tang, H L; Liu, W J; Wang, Y G

    2014-12-10

    Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.

  20. Incorporation of Platinum and Gold Partially Reduced Graphene Oxide in Polymer Electrolyte Membrane Fuel Cells for Increased Carbon Monoxide Tolerance

    NASA Astrophysics Data System (ADS)

    Blackburn, Lee; Isseroff, Rebecca; Rafailovich, Miriam; Kang, Jaymo; Li, Hongfei; Gentleman, Molly; Qaio, Qaio

    Polymer Electrolyte Membrane Fuel Cells (PEMFCs) can potentially provide ``green'' energy but the platinum catalyst's susceptibility to carbon monoxide (CO) poisoning reduces output power. This project hypothesized that gold and platinum-partially reduced graphene oxide (Au/Pt-prGO) catalysts, incorporated into the electrodes and Nafion membrane of a PEMFC, will increase CO tolerance. Aliquots of graphene oxide (GO) were functionalized with platinum and/or gold nanoparticles. Partial reduction with NaBH4 prevented precipitation. Raman Spectroscopy and HRTEM verified the chemical identity, structure, and presence of the materials. Setups were tested in a PEM fuel cell with a gas feed containing 1000 ppm of CO, and averaged an output power >200% over the control, with the most effective sample, Pt-prGO Electrode + Membrane, yielding an output power ~250% greater than the control. Additionally, each setup's poisoned output power (PP) was compared to its highest possible output power (PM) . AuPt-prGO Electrode + Membrane produced 100% of its highest possible output power when poisoned, displaying 100% resistance to all CO poisoning at the resistances tested. Garcia MRSEC.

  1. A reduced graphene oxide nanofiltration membrane intercalated by well-dispersed carbon nanotubes for drinking water purification

    NASA Astrophysics Data System (ADS)

    Chen, Xianfu; Qiu, Minghui; Ding, Hao; Fu, Kaiyun; Fan, Yiqun

    2016-03-01

    In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for drinking water purification to retain the nanoparticles, dyes, proteins, organophosphates, sugars, and particularly humic acid. Experimentally, it is shown that the rGO-CNT hybrid NF membranes have high retention efficiency, good permeability and good anti-fouling properties. The retention was above 97.3% even for methyl orange (327 Da); for other objects, the retention was above 99%. The membrane's permeability was found to be as high as 20-30 L m-2 h-1 bar-1. Based on these results, we can conclude that (i) the use of BCPs as a surfactant can enhance steric repulsion and thus disperse CNTs effectively; (ii) placing well-dispersed 1D CNTs within 2D graphene sheets allows an uniform network to form, which can provide many mass transfer channels through the continuous 3D nanostructure, resulting in the high permeability and separation performance of the rGO-CNT hybrid NF membranes.In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for

  2. Aptamer-Conjugated Graphene Oxide Membranes for Highly Efficient Capture and Accurate Identification of Multiple Types of Circulating Tumor Cells

    PubMed Central

    2016-01-01

    Tumor metastasis is responsible for 1 in 4 deaths in the United States. Though it has been well-documented over past two decades that circulating tumor cells (CTCs) in blood can be used as a biomarker for metastatic cancer, there are enormous challenges in capturing and identifying CTCs with sufficient sensitivity and specificity. Because of the heterogeneous expression of CTC markers, it is now well understood that a single CTC marker is insufficient to capture all CTCs from the blood. Driven by the clear need, this study reports for the first time highly efficient capture and accurate identification of multiple types of CTCs from infected blood using aptamer-modified porous graphene oxide membranes. The results demonstrate that dye-modified S6, A9, and YJ-1 aptamers attached to 20–40 μm porous garphene oxide membranes are capable of capturing multiple types of tumor cells (SKBR3 breast cancer cells, LNCaP prostate cancer cells, and SW-948 colon cancer cells) selectively and simultaneously from infected blood. Our result shows that the capture efficiency of graphene oxide membranes is ∼95% for multiple types of tumor cells; for each tumor concentration, 10 cells are present per milliliter of blood sample. The selectivity of our assay for capturing targeted tumor cells has been demonstrated using membranes without an antibody. Blood infected with different cells also has been used to demonstrate the targeted tumor cell capturing ability of aptamer-conjugated membranes. Our data also demonstrate that accurate analysis of multiple types of captured CTCs can be performed using multicolor fluorescence imaging. Aptamer-conjugated membranes reported here have good potential for the early diagnosis of diseases that are currently being detected by means of cell capture technologies. PMID:25565372

  3. Aptamer-conjugated graphene oxide membranes for highly efficient capture and accurate identification of multiple types of circulating tumor cells.

    PubMed

    Viraka Nellore, Bhanu Priya; Kanchanapally, Rajashekhar; Pramanik, Avijit; Sinha, Sudarson Sekhar; Chavva, Suhash Reddy; Hamme, Ashton; Ray, Paresh Chandra

    2015-02-18

    Tumor metastasis is responsible for 1 in 4 deaths in the United States. Though it has been well-documented over past two decades that circulating tumor cells (CTCs) in blood can be used as a biomarker for metastatic cancer, there are enormous challenges in capturing and identifying CTCs with sufficient sensitivity and specificity. Because of the heterogeneous expression of CTC markers, it is now well understood that a single CTC marker is insufficient to capture all CTCs from the blood. Driven by the clear need, this study reports for the first time highly efficient capture and accurate identification of multiple types of CTCs from infected blood using aptamer-modified porous graphene oxide membranes. The results demonstrate that dye-modified S6, A9, and YJ-1 aptamers attached to 20-40 μm porous garphene oxide membranes are capable of capturing multiple types of tumor cells (SKBR3 breast cancer cells, LNCaP prostate cancer cells, and SW-948 colon cancer cells) selectively and simultaneously from infected blood. Our result shows that the capture efficiency of graphene oxide membranes is ~95% for multiple types of tumor cells; for each tumor concentration, 10 cells are present per milliliter of blood sample. The selectivity of our assay for capturing targeted tumor cells has been demonstrated using membranes without an antibody. Blood infected with different cells also has been used to demonstrate the targeted tumor cell capturing ability of aptamer-conjugated membranes. Our data also demonstrate that accurate analysis of multiple types of captured CTCs can be performed using multicolor fluorescence imaging. Aptamer-conjugated membranes reported here have good potential for the early diagnosis of diseases that are currently being detected by means of cell capture technologies.

  4. Graphene oxide exhibits broad-spectrum antimicrobial activity against bacterial phytopathogens and fungal conidia by intertwining and membrane perturbation.

    PubMed

    Chen, Juanni; Peng, Hui; Wang, Xiuping; Shao, Feng; Yuan, Zhaodong; Han, Heyou

    2014-01-01

    To understand the interaction mechanism between graphene oxide (GO) and typical phytopathogens, a particular investigation was conducted about the antimicrobial activity of GO against two bacterial pathogens (P. syringae and X. campestris pv. undulosa) and two fungal pathogens (F. graminearum and F. oxysporum). The results showed that GO had a powerful effect on the reproduction of all four pathogens (killed nearly 90% of the bacteria and repressed 80% macroconidia germination along with partial cell swelling and lysis at 500 μg mL(-1)). A mutual mechanism is proposed in this work that GO intertwinds the bacteria and fungal spores with a wide range of aggregated graphene oxide sheets, resulting in the local perturbation of their cell membrane and inducing the decrease of the bacterial membrane potential and the leakage of electrolytes of fungal spores. It is likely that GO interacts with the pathogens by mechanically wrapping and locally damaging the cell membrane and finally causing cell lysis, which may be one of the major toxicity actions of GO against phytopathogens. The antibacterial mode proposed in this study suggests that the GO may possess antibacterial activity against more multi-resistant bacterial and fungal phytopathogens, and provides useful information about the application of GO in resisting crop diseases.

  5. Fluidity evaluation of cell membrane model formed on graphene oxide with single particle tracking using quantum dot

    NASA Astrophysics Data System (ADS)

    Okamoto, Yoshiaki; Motegi, Toshinori; Iwasa, Seiji; Sandhu, Adarsh; Tero, Ryugo

    2015-04-01

    The lipid bilayer is the fundamental structure of plasma membranes, and artificial lipid bilayer membranes are used as model systems of cell membranes. Recently we reported the formation of a supported lipid bilayer (SLB) on graphene oxide (GO) by the vesicle fusion method. In this study, we conjugated a quantum dot (Qdot) on the SLB surface as a fluorescence probe brighter than dye-labeled lipid molecules, to qualitatively evaluate the fluidity of the SLB on GO by the single particle tracking method. We obtained the diffusion coefficient of the Qdot-conjugated lipids in the SLB on GO. We also performed the Qdot conjugation on the SLB containing a lipid conjugated with polyethylene glycol, to prevent the nonspecific adsorption of Qdots. The difference in the diffusion coefficients between the SLBs on the GO and the bare SiO2 regions was evaluated from the trajectory of single Qdot-conjugated lipid diffusing between the two regions.

  6. Fabrication of positively charged nanofiltration membrane via the layer-by-layer assembly of graphene oxide and polyethylenimine for desalination

    NASA Astrophysics Data System (ADS)

    Nan, Qian; Li, Pei; Cao, Bing

    2016-11-01

    Highly positively charged nanofiltration (NF) membranes have been prepared via a layer-by-layer (LbL) self-assembly technique using graphene oxide (GO) and polyethyleneimine (PEI). The high aspect ratio and unique 2D structure of GO nanosheets enabled them to be easily assembled on the membrane surface, and the intrinsic low resistant channels within the GO nanosheets resulted in a high water flux of the membrane. By assembled a PEI layer on the membrane outer surface, the composite membrane exhibited high positive charge and resulted in the high rejections to multivalent ions. The effects of deposition time, PEI and GO concentrations on separation performance of the NF membranes were detailed studied. The best performance among all the membranes was achieved with salt rejections of 93.9% and 38.1% for Mg2+ and Na+, and a water flux of 4.2 L/m2 h bar at 30 °C and 0.5 MPa. The attractive performance of these NF membranes showed a great potential in the industrial application of water softening.

  7. Fine-Tuning the Surface of Forward Osmosis Membranes via Grafting Graphene Oxide: Performance Patterns and Biofouling Propensity.

    PubMed

    Hegab, Hanaa M; ElMekawy, Ahmed; Barclay, Thomas G; Michelmore, Andrew; Zou, Linda; Saint, Christopher P; Ginic-Markovic, Milena

    2015-08-19

    Graphene oxide (GO) nanosheets were attached to the polyamide selective layer of thin film composite (TFC) forward osmosis (FO) membranes through a poly L-Lysine (PLL) intermediary using either layer-by-layer or hybrid (H) grafting strategies. Fourier transform infrared spectroscopy, zeta potential, and thermogravimetric analysis confirmed the successful attachment of GO/PLL, the surface modification enhancing both the hydrophilicity and smoothness of the membrane's surface demonstrated by water contact angle, atomic force microscopy, and transmission electron microscopy. The biofouling resistance of the FO membranes determined using an adenosine triphosphate bioluminescence test showed a 99% reduction in surviving bacteria for GO/PLL-H modified membranes compared to pristine membrane. This antibiofouling property of the GO/PLL-H modified membrane was reflected in reduced flux decline compared to all other samples when filtering brackish water under biofouling conditions. Further, the high density and tightly bound GO nanosheets using the hybrid modification reduced the reverse solute flux compared to the pristine, which reflects improved membrane selectivity. These results illustrate that the GO/PLL-H modification is a valuable addition to improve the performance of FO TFC membranes.

  8. Exploring the synergetic effects of graphene oxide (GO) and polyvinylpyrrodione (PVP) on poly(vinylylidenefluoride) (PVDF) ultrafiltration membrane performance

    NASA Astrophysics Data System (ADS)

    Chang, Xiaojing; Wang, Zhenxing; Quan, Shuai; Xu, Yanchao; Jiang, Zaixing; Shao, Lu

    2014-10-01

    Membrane surface and cross-sectional morphology created during membrane formation is one of the most essential factors determining membrane separation performance. However, the complicated interactions between added nanoparticles and additives influencing membrane morphology and performance during building membrane architectures had been generally neglected. In this study, asymmetric PVDF composite ultrafiltration (UF) membranes containing graphene oxides (GO) were prepared by using N-methyl pyrrolidone (NMP) as solvent and polyvinylpyrrodione (PVP) as the pore forming reagent. In the first time, the effects of mutual interactions between GO and PVP on membranes surface compositions, morphology and performance were investigated in detail. The variation in chemical properties of different membranes and hydrogen bonds in the membrane containing GO and PVP were confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle (CA) were utilized to clarify the synergetic effects of GO and PVP on morphologies and surface hydrophilicity of membranes. Besides, water flux, bovine serum albumin (BSA) rejection and attenuate coefficient were also determined to investigate filtration performance of various membranes. Compared with pure PVDF membrane, the comprehensive performance of PVDF/GO/PVP membrane has been obviously improved. The surface hydrophilicity and anti-fouling performance were enhanced by the synergistic effects of incorporated GO and PVP. When the PVP content was 0.25 wt.% and the GO content was 0.5 wt.%, the optimized performance can be obtained due to the formation of hydrogen bonds between GO and PVP.

  9. Graphene Trans-Electrode Membranes

    NASA Astrophysics Data System (ADS)

    Kuan, Aaron; Bo, Lu; Rollings, Ryan; Dressen, Don; Branton, Daniel; Golovchenko, Jene

    2014-03-01

    We report an electrical study of suspended single-layer graphene membranes separating reservoirs of electrolyte solution. Because the opposing reservoirs are separated only by an atomically thin membrane, the trans-conductance (ionic current response to a voltage across the membrane) is extremely sensitive to nanoscale defects in the membrane. This sensitivity allows the precise examination and characterization of intrinsic defects in graphene membranes, as well as engineered defects for devices. We will discuss methods for creating single nanopores or distributed defects in our graphene membranes, with the applications of nanopore DNA sequencing and water desalination in mind.

  10. Preparation of graphene oxide modified poly(m-phenylene isophthalamide) nanofiltration membrane with improved water flux and antifouling property

    NASA Astrophysics Data System (ADS)

    Yang, Mei; Zhao, Changwei; Zhang, Shaofeng; Li, Pei; Hou, Deyin

    2017-02-01

    Poly (m-phenylene isophthalamide)/graphene oxide (PMIA/GO) composite nanofiltartion (NF) membranes were prepared via a facile phase inversion method. Structures, surface properties and hydrophilicities of the membrane were analyzed using FT-IR, XPS, AFM, SEM, water contact angle and Zeta-potential measurements. FTIR spectra indicated the existence of hydrophilic carboxylic acid and hydroxyl groups in the GO molecules. SEM pictures revealed the large and finger-like micro-voids formed in the sublayer of the NF membranes after adding GO. The zeta-potential and water contact angle results proved that PMIA/GO composite membranes had more negatively charged and greater hydrophilic surfaces. The pure water flux of the PMIA/GO (0.3 wt% GO) composite membrane (125.2 (L/m2/h)) was 2.6 times as high as that of the pristine PMIA NF membrane (48.3 (L/m2/h)) at 0.8 MPa with slightly higher rejections to all tested dyes and better fouling resistance to bovine serum albumin (BSA). This study gave an effective method for preparing composite PMIA NF membranes with high water flux and excellent antifouling property, which showed potential application in water treatment.

  11. Biocompatibility of Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Kan; Ruan, Jing; Song, Hua; Zhang, Jiali; Wo, Yan; Guo, Shouwu; Cui, Daxiang

    2011-12-01

    Herein, we report the effects of graphene oxides on human fibroblast cells and mice with the aim of investigating graphene oxides' biocompatibility. The graphene oxides were prepared by the modified Hummers method and characterized by high-resolution transmission electron microscope and atomic force microscopy. The human fibroblast cells were cultured with different doses of graphene oxides for day 1 to day 5. Thirty mice divided into three test groups (low, middle, high dose) and one control group were injected with 0.1, 0.25, and 0.4 mg graphene oxides, respectively, and were raised for 1 day, 7 days, and 30 days, respectively. Results showed that the water-soluble graphene oxides were successfully prepared; graphene oxides with dose less than 20 μg/mL did not exhibit toxicity to human fibroblast cells, and the dose of more than 50 μg/mL exhibits obvious cytotoxicity such as decreasing cell adhesion, inducing cell apoptosis, entering into lysosomes, mitochondrion, endoplasm, and cell nucleus. Graphene oxides under low dose (0.1 mg) and middle dose (0.25 mg) did not exhibit obvious toxicity to mice and under high dose (0.4 mg) exhibited chronic toxicity, such as 4/9 mice death and lung granuloma formation, mainly located in lung, liver, spleen, and kidney, almost could not be cleaned by kidney. In conclusion, graphene oxides exhibit dose-dependent toxicity to cells and animals, such as inducing cell apoptosis and lung granuloma formation, and cannot be cleaned by kidney. When graphene oxides are explored for in vivo applications in animal or human body, its biocompatibility must be considered.

  12. Sulfonated polyimide/acid-functionalized graphene oxide composite polymer electrolyte membranes with improved proton conductivity and water-retention properties.

    PubMed

    Pandey, Ravi P; Thakur, Amit K; Shahi, Vinod K

    2014-10-08

    Sulfonated polyimide (SPI)/sulfonated propylsilane graphene oxide (SPSGO) was assessed to be a promising candidate for polymer electrolyte membranes (PEMs). Incorporation of multifunctionalized (-SO3H and -COOH) SPSGO in SPI matrix improved proton conductivity and thermal, mechanical, and chemical stabilities along with bound water content responsible for slow dehydration of the membrane matrix. The reported SPSGO/SPI composite PEM was designed to promote internal self-humidification, responsible for water-retention properties, and to promote proton conduction, due to the presence of different acidic functional groups. Strong hydrogen bonding between multifunctional groups thus led to the presence of interconnected hydrophobic graphene sheets and organic polymer chains, which provides hydrophobic-hydrophilic phase separation and suitable architecture of proton-conducting channels. In single-cell direct methanol fuel cell tests, SPI/SPSGO-8 exhibited 75.06 mW·cm(-2) maximum power density (in comparison with commercial Nafion 117 membrane, 62.40 mW·cm(-2)) under 2 M methanol fuel at 70 °C.

  13. Unimpeded permeation of water through biocidal graphene oxide sheets anchored on to 3D porous polyolefinic membranes

    NASA Astrophysics Data System (ADS)

    Mural, Prasanna Kumar S.; Jain, Shubham; Kumar, Sachin; Madras, Giridhar; Bose, Suryasarathi

    2016-04-01

    3D porous membranes were developed by etching one of the phases (here PEO, polyethylene oxide) from melt-mixed PE/PEO binary blends. Herein, we have systematically discussed the development of these membranes using X-ray micro-computed tomography. The 3D tomograms of the extruded strands and hot-pressed samples revealed a clear picture as to how the morphology develops and coarsens over a function of time during post-processing operations like compression molding. The coarsening of PE/PEO blends was traced using X-ray micro-computed tomography and scanning electron microscopy (SEM) of annealed blends at different times. It is now understood from X-ray micro-computed tomography that by the addition of a compatibilizer (here lightly maleated PE), a stable morphology can be visualized in 3D. In order to anchor biocidal graphene oxide sheets onto these 3D porous membranes, the PE membranes were chemically modified with acid/ethylene diamine treatment to anchor the GO sheets which were further confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and surface Raman mapping. The transport properties through the membrane clearly reveal unimpeded permeation of water which suggests that anchoring GO on to the membranes does not clog the pores. Antibacterial studies through the direct contact of bacteria with GO anchored PE membranes resulted in 99% of bacterial inactivation. The possible bacterial inactivation through physical disruption of the bacterial cell wall and/or reactive oxygen species (ROS) is discussed herein. Thus this study opens new avenues in designing polyolefin based antibacterial 3D porous membranes for water purification.3D porous membranes were developed by etching one of the phases (here PEO, polyethylene oxide) from melt-mixed PE/PEO binary blends. Herein, we have systematically discussed the development of these membranes using X-ray micro-computed tomography. The 3D tomograms of the extruded strands and

  14. Layer-by-layer assembly of graphene oxide nanosheets on polyamide membranes for durable reverse-osmosis applications.

    PubMed

    Choi, Wansuk; Choi, Jungkyu; Bang, Joona; Lee, Jung-Hyun

    2013-12-11

    Improving membrane durability associated with fouling and chlorine resistance remains one of the major challenges in desalination membrane technology. Here, we demonstrate that attractive features of graphene oxide (GO) nanosheets such as high hydrophilicity, chemical robustness, and ultrafast water permeation can be harnessed for a dual-action barrier coating layer that enhances resistance to both fouling and chlorine-induced degradation of polyamide (PA) thin-film composite (TFC) membranes while preserving their separation performance. GO multilayers were coated on the PA-TFC membrane surfaces via layer-by-layer (LbL) deposition of oppositely charged GO nanosheets. Consequently, it was shown that the conformal GO coating layer can increase the surface hydrophilicity and reduce the surface roughness, leading to the significantly improved antifouling performance against a protein foulant. It was also demonstrated that the chemically inert nature of GO nanosheets enables the GO coating layer to act as a chlorine barrier for the underlying PA membrane, resulting in a profound suppression of the membrane degradation in salt rejection upon chlorine exposure.

  15. Constructing proton-conductive highways within an ionomer membrane by embedding sulfonated polymer brush modified graphene oxide

    NASA Astrophysics Data System (ADS)

    Zhao, Liping; Li, Yifan; Zhang, Haoqin; Wu, Wenjia; Liu, Jindun; Wang, Jingtao

    2015-07-01

    Sulfonated polymer brush modified graphene oxide (SP-GO) fillers with controllable brush length are synthesized via the facile distillation-precipitation polymerization, and then incorporated into sulfonated poly(ether ether ketone) (SPEEK) matrix to fabricate composite membranes. The influences of SP-GO upon the microstructures, including thermal and mechanical properties, water uptake/swelling, proton conduction, H2 permeability and single PEMFC performances of composite membranes are intensively investigated. It is found that the SP-GO fillers are uniformly dispersed and tend to lie perpendicularly to the cross-section surface of the whole membrane, which allow SP-GO fillers creating inter-connected and broad ionic pathways through the sulfonic acid groups in polymer brushes. Meanwhile, the SP-GO fillers connect the ionic clusters in SPEEK matrix via interfacial interactions. In such a way, proton-transfer highways are constructed along the SPEEK/SP-GO interface, which lower the proton transfer activation energy and enhance the proton conductivities of the composite membranes under both hydrated and anhydrous conditions. Furthermore, elevating the brush length on SP-GO could further enhance the proton conductivity. Compared to SPEEK control membrane, a 95.5% increase in hydrated conductivity, an 178% increase in anhydrous conductivity and a 37% increase in maximum power density are obtained for the optimal composite membrane.

  16. High-Flux Graphene Oxide Membranes Intercalated by Metal-Organic Framework with Highly Selective Separation of Aqueous Organic Solution.

    PubMed

    Ying, Yunpan; Liu, Dahuan; Zhang, Weixin; Ma, Jing; Huang, Hongliang; Yang, Qingyuan; Zhong, Chongli

    2017-01-18

    Graphene oxide (GO) membranes assembled by single-atom thick GO nanosheets have displayed huge potential application both in gas and liquid separation processes due to its facile and large-scale preparation resulting from various functional groups, such as hydroxyl, carboxyl, and epoxide groups. Taking advantage of these characters, GO membranes intercalated by superhydrophilic metal-organic frameworks (MOFs) as strengthening separation fillers were prepared on modified polyacrylonitrile (PAN) support by a novel pressure-assisted self-assembly (PASA) filtration technique instead of traditional vacuum filtration method for the first time. The synthesized MOF@GO membranes were characterized with several spectroscopic techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), as well as scanning electron microscopy (SEM). Compared with GO membrane, these MOF@GO membranes combine the unique properties of MOF and GO and thus have significant enhancements of pervaporation (PV) permeation flux and separation factor simultaneously for ethyl acetate/water mixtures (98/2, w/w) through the PV process, which are also superior to the reported other kinds of membranes. Especially, for MOF@GO-0.3 membrane (corresponding MOF loading: 23.08 wt %), the increments are 159% and 244%, respectively, at 303 K, and the permeate water content can reach as high as 99.5 wt % (corresponding separation factor, 9751) with a high permeation flux of 2423 g m(-2) h(-1). Moreover, the procedures of both the synthesis of MOF and membranes preparation are environmentally friendly that only water was used as solvent. Such a nanosized MOF-intercalating approach may be also extended to other laminated membranes, providing valuable insights in designing and developing of advanced membranes for effective separation of aqueous organic solution through nanostructure manipulation of the nanomaterials.

  17. Optimized permeation and antifouling of PVDF hybrid ultrafiltration membranes: synergistic effect of dispersion and migration for fluorinated graphene oxide

    NASA Astrophysics Data System (ADS)

    Li, Mingming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Li, Jing; Lv, Hanming; Qian, Xiaoming; Jiao, Xiaoning

    2017-03-01

    Nanoparticles may have suffered from low modification efficiency in hybrid membranes due to embedding and aggregating in polymer matrix. In order to analyze the modification mechanisms of nanoparticle migration and dispersion on the properties of hybrid membranes, we designed different F/ O ratios ( R F/ O ) of fluorinated graphene oxide (FGO, diameter = 1.5 17.5 μm) by carbon tetrafluoride (CF4) plasma treatment GO for 3, 5, 10, 15, and 20 min and successfully prepared novel PVDF hybrid membranes containing FGO via the phase inversion method. After a prolonged plasma treatment, the R F/ O of FGO was enhanced sharply, indicating an increasing compatibility of FGO with the matrix, especially FGO-20 (GO treated for 20 min). FGO contents in the top layer, sublayer, and the whole of membranes were probed by X-ray photoelectron spectroscopy, energy-dispersive spectrometer, and indirect computation, respectively. In the top layer of membranes, FGO contents declined from 13.14 wt% (PVDF/GO) to 4.00 wt% (PVDF/FGO-10) and 1.96 wt% (PVDF/FGO-20) due to the reduced migration ability of FGO. It is worth mentioning that PVDF/FGO-10 membranes exhibited an excellent water flux and flux recovery rate (up to 406.90 L m-2 h-1 and 88.9%), which were improved by 67.3% and 14.6% and 52.5% and 24.0% compared with those of PVDF/GO and PVDF/FGO-20 membranes, respectively, although the dispersion and migration ability of FGO-10 was maintained at a moderate level. It indicated that the migration and dispersion of FGO in membranes could result in dynamic equilibrium, which played a key role in making the best use of nanomaterials to optimize membrane performance.

  18. Highly antifouling and antibacterial performance of poly (vinylidene fluoride) ultrafiltration membranes blending with copper oxide and graphene oxide nanofillers for effective wastewater treatment.

    PubMed

    Zhao, Chuanqi; Lv, Jinling; Xu, Xiaochen; Zhang, Guoquan; Yang, Yuesuo; Yang, Fenglin

    2017-11-01

    Innovation and effective wastewater treatment technology is still in great demand given the emerging contaminants frequently spotted from the aqueous environment. By blending with poly (vinylidene fluoride) (PVDF), the strong hydrophilic graphene oxide (GO) and antibacterial copper oxide (CuxO) were used as nanofillers to develop the novel, highly antifouling composite membranes via phase inversion process in our latest work. The existence and dispersion of GO and CuxO posed a significant role on morphologies, structures, surface composition and hydrophilicity of the developed composite membranes, confirmed by SEM, TEM, FTIR and XPS in depth characterization. The SEM images showed that the modified membranes presented a lower resistant structure with developed finger-like macrovoids and thin-walled even interconnected sponge-like pores after adding nanofillers, much encouraging membrane permeation. The XPS results revealed that CuxO contained Cu2O and CuO in the developed membrane and the Cu2O nanoparticles were dominant accounting for about 79.3%; thus the modified membrane specifically exhibited an efficient antibacterial capacity. Due to the hydrophilic and bactericidal membrane surface, the composite membranes demonstrated an excellent antifouling performance, including higher flux recovery rate, more resistant against accumulated contaminants and lower filtration resistance, especially lower irreversible resistance. The antifouling property, especially anti-irreversible fouling, was significantly improved, showing a significant engineering potential. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Positively charged graphene oxide nanoparticle: precisely label the plasma membrane of live cell and sensitively monitor extracellular pH in situ.

    PubMed

    Zhu, Huarui; Gao, Liang; Jiang, Xinglu; Liu, Ru; Wei, Yueteng; Wang, Yaling; Zhao, Yuliang; Chai, Zhifang; Gao, Xueyun

    2014-04-11

    Polyethylene glycol modified graphene oxide (GO-PEG) nanoparticles were prepared, which were positively charged and fairly stable in buffer solution. The GO-PEG nanoparticles possess a special affinity to the plasma membrane of live cells, and their yellowish-green fluorescence is sensitively responsive to the extracellular physiological solution in situ.

  20. A fully spray-coated fuel cell membrane electrode assembly using Aquivion ionomer with a graphene oxide/cerium oxide interlayer

    NASA Astrophysics Data System (ADS)

    Breitwieser, Matthias; Bayer, Thomas; Büchler, Andreas; Zengerle, Roland; Lyth, Stephen M.; Thiele, Simon

    2017-05-01

    A novel multilayer membrane electrode assembly (MEA) for polymer electrolyte membrane fuel cells (PEMFCs) is fabricated in this work, within a single spray-coating device. For the first time, direct membrane deposition is used to fabricate a PEMFC by spraying the short-side-chain ionomer Aquivion directly onto the gas diffusion electrodes. The fully sprayed MEA, with an Aquivion membrane 10 μm in thickness, achieved a high power density of 1.6 W/cm2 for H2/air operation at 300 kPaabs. This is one of the highest reported values for thin composite membranes operated in H2/air atmosphere. By the means of confocal laser scanning microscopy, individual carbon fibers from the gas diffusion layer are identified to penetrate through the micro porous layer (MPL), likely causing a low electrical cell resistance in the range of 150 Ω cm2 through the thin sprayed membranes. By spraying a 200 nm graphene oxide/cerium oxide (GO/CeO2) interlayer between two layers of Aquivion ionomer, the impact of the electrical short is eliminated and the hydrogen crossover current density is reduced to about 1 mA/cm2. The peak power density of the interlayer-containing MEA drops only by 10% compared to a pure Aquivion membrane of similar thickness.

  1. Effect of the incorporation of sulfonated chitosan/sulfonated graphene oxide on the proton conductivity of chitosan membranes

    NASA Astrophysics Data System (ADS)

    Shirdast, Abbas; Sharif, Alireza; Abdollahi, Mahdi

    2016-02-01

    Chitosan biopolymer (CS) has been attracting considerable interest as polymer electrolyte in fuel cells. However, proton conductivity of chitosan is low and it is necessary to enhance its conductivity. In this work, 10 wt% sulfonated chitosan (SCS) and different amounts of sulfonated graphene oxide (SGO) nanosheets are incorporated into a chitosan membrane to investigate their effects on the electrochemical properties of the membrane. The proton conductivity and methanol permeability tests conducted on the CS/SCS/SGO membranes show that the conductivity is increased by 454%, the permeability is reduced by 23% and hence the selectivity is increased by 650%, relative to the neat chitosan, at SGO content of 5 wt%. Furthermore, combined addition of SCS and SGO to chitosan causes much more proton conductivity enhancement than the individual additives due to the synergistic effect of SCS and SGO. The observed synergistic effect reveals the importance of the chemical functionality of chitosan and nanofillers in the formation of ionic cluster domains with enhanced size within the membranes for proton transport. Finally, a Nernst-Planck based model is applied to the experimental proton conductivity data in order to shed more light on the role of GOs in the proton conductivity mechanism of chitosan.

  2. Toxicity of graphene and graphene oxide nanowalls against bacteria.

    PubMed

    Akhavan, Omid; Ghaderi, Elham

    2010-10-26

    Bacterial toxicity of graphene nanosheets in the form of graphene nanowalls deposited on stainless steel substrates was investigated for both gram-positive and gram-negative models of bacteria. The graphene oxide nanowalls were obtained by electrophoretic deposition of Mg(2+)-graphene oxide nanosheets synthesized by a chemical exfoliation method. On the basis of measuring the efflux of cytoplasmic materials of the bacteria, it was found that the cell membrane damage of the bacteria caused by direct contact of the bacteria with the extremely sharp edges of the nanowalls was the effective mechanism in the bacterial inactivation. In this regard, the gram-negative Escherichia coli bacteria with an outer membrane were more resistant to the cell membrane damage caused by the nanowalls than the gram-positive Staphylococcus aureus lacking the outer membrane. Moreover, the graphene oxide nanowalls reduced by hydrazine were more toxic to the bacteria than the unreduced graphene oxide nanowalls. The better antibacterial activity of the reduced nanowalls was assigned to the better charge transfer between the bacteria and the more sharpened edges of the reduced nanowalls, during the contact interaction.

  3. Biomedical applications of graphene and graphene oxide.

    PubMed

    Chung, Chul; Kim, Young-Kwan; Shin, Dolly; Ryoo, Soo-Ryoon; Hong, Byung Hee; Min, Dal-Hee

    2013-10-15

    Graphene has unique mechanical, electronic, and optical properties, which researchers have used to develop novel electronic materials including transparent conductors and ultrafast transistors. Recently, the understanding of various chemical properties of graphene has facilitated its application in high-performance devices that generate and store energy. Graphene is now expanding its territory beyond electronic and chemical applications toward biomedical areas such as precise biosensing through graphene-quenched fluorescence, graphene-enhanced cell differentiation and growth, and graphene-assisted laser desorption/ionization for mass spectrometry. In this Account, we review recent efforts to apply graphene and graphene oxides (GO) to biomedical research and a few different approaches to prepare graphene materials designed for biomedical applications. Because of its excellent aqueous processability, amphiphilicity, surface functionalizability, surface enhanced Raman scattering (SERS), and fluorescence quenching ability, GO chemically exfoliated from oxidized graphite is considered a promising material for biological applications. In addition, the hydrophobicity and flexibility of large-area graphene synthesized by chemical vapor deposition (CVD) allow this material to play an important role in cell growth and differentiation. The lack of acceptable classification standards of graphene derivatives based on chemical and physical properties has hindered the biological application of graphene derivatives. The development of an efficient graphene-based biosensor requires stable biofunctionalization of graphene derivatives under physiological conditions with minimal loss of their unique properties. For the development graphene-based therapeutics, researchers will need to build on the standardization of graphene derivatives and study the biofunctionalization of graphene to clearly understand how cells respond to exposure to graphene derivatives. Although several

  4. Highly durable Pt/graphene oxide and Pt/C hybrid catalyst for polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Jung, Ju Hae; Park, Hyang Jin; Kim, Junbom; Hur, Seung Hyun

    2014-02-01

    We report a highly durable hybrid catalyst composed of Pt/graphene oxide (GO) and Pt/C catalyst for polymer electrolyte membrane fuel cell (PEMFC). The accelerated durability tests in half-cell and full cell systems shows that the addition of small amount of Pt/GO catalyst significantly enhances the durability of commercial Pt/C catalyst without sacrificing initial electrochemical active surface area (ECSA). The XRD and TEM analysis reveal that the GO not only exhibits the high resistance to Pt agglomeration but also prevents the Pt agglomeration in Pt/C catalyst by providing the anchoring sites of eluted metal ions. We believe that this simple and effective approach can open a new way to fabricate highly durable electrocatalyst for the commercialization of fuel cell vehicles.

  5. Applying graphene oxide nano-film over a polycarbonate nanoporous membrane to monitor E. coli by infrared spectroscopy.

    PubMed

    Singh, Krishna Pal; Dhek, Neeraj Singh; Nehra, Anuj; Ahlawat, Sweeti; Puri, Anu

    2017-01-05

    Nano-biosensors are excellent monitoring tools for rapid, specific, sensitive, inexpensive, in-field, on-line, and/or real-time detection of pathogens in foods, soil, air, and water samples. A variety of nano-materials (metallic, polymeric, and/or carbon-based) were employed to enhance the efficacy, efficiency, and sensitivity of these nano-biosensors, including graphene-based materials, especially graphene oxide (GO)-based materials. GO bears many oxygen-bearing groups, enabling ligand conjugation at the high density critical for sensitive detection. We have fabricated GO-modified nano-porous polycarbonate track-etched (PCTE) membranes that were conjugated to an Escherichia coli-specific antibody (Ab) and used to detect E. coli. The random distribution of nanopores on the PCTE membrane surface and the bright coating of the GO onto the membrane were confirmed by scanning electron microscope. Anti-E. coli β-gal Abs were conjugated to the GO surface via 1-ethyl-3,3-dimethylaminopropyl carbodiimide hydrochloride-N-hydroxysuccinimide chemistry; antibody coating was confirmed by the presence of a characteristic IR peak near 1600cm(-1). A non-corresponding Ab (anti-Pseudomonas) was used as a negative control under identical conditions. When E. coli interacted anti-E.coli β-gal with Ab-coated GO-nano-biosensor units, we observed a clear shift in the IR peak from 3373.14 to 3315cm(-1); in contrast, we did not observe any shift in IR peaks when the GO unit was coated with the non-corresponding Ab (anti-Pseudomonas). Therefore, the detection of E. coli using the described GO-nano-sensor unit is highly specific, is highly selective and can be applied for real-time monitoring of E. coli with a detection limit between 100μg/mL and 10μg/mL, similar to existing detection systems.

  6. Applying graphene oxide nano-film over a polycarbonate nanoporous membrane to monitor E. coli by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Krishna Pal; Dhek, Neeraj Singh; Nehra, Anuj; Ahlawat, Sweeti; Puri, Anu

    2017-01-01

    Nano-biosensors are excellent monitoring tools for rapid, specific, sensitive, inexpensive, in-field, on-line, and/or real-time detection of pathogens in foods, soil, air, and water samples. A variety of nano-materials (metallic, polymeric, and/or carbon-based) were employed to enhance the efficacy, efficiency, and sensitivity of these nano-biosensors, including graphene-based materials, especially graphene oxide (GO)-based materials. GO bears many oxygen-bearing groups, enabling ligand conjugation at the high density critical for sensitive detection. We have fabricated GO-modified nano-porous polycarbonate track-etched (PCTE) membranes that were conjugated to an Escherichia coli-specific antibody (Ab) and used to detect E. coli. The random distribution of nanopores on the PCTE membrane surface and the bright coating of the GO onto the membrane were confirmed by scanning electron microscope. Anti-E. coli β-gal Abs were conjugated to the GO surface via 1-ethyl-3,3-dimethylaminopropyl carbodiimide hydrochloride-N-hydroxysuccinimide chemistry; antibody coating was confirmed by the presence of a characteristic IR peak near 1600 cm- 1. A non-corresponding Ab (anti-Pseudomonas) was used as a negative control under identical conditions. When E. coli interacted anti-E.coli β-gal with Ab-coated GO-nano-biosensor units, we observed a clear shift in the IR peak from 3373.14 to 3315 cm- 1; in contrast, we did not observe any shift in IR peaks when the GO unit was coated with the non-corresponding Ab (anti-Pseudomonas). Therefore, the detection of E. coli using the described GO-nano-sensor unit is highly specific, is highly selective and can be applied for real-time monitoring of E. coli with a detection limit between 100 μg/mL and 10 μg/mL, similar to existing detection systems.

  7. Fabrication of Polyimide Membrane Incorporated with Functional Graphene Oxide for CO2 Separation: The Effects of GO Surface Modification on Membrane Performance.

    PubMed

    Wang, Ting; Cheng, Cheng; Wu, Li-Guang; Shen, Jiang-Nan; Van der Bruggen, Bart; Chen, Qian; Chen, Di; Dong, Chun-Ying

    2017-06-06

    Two kinds of isocyanate were used to modify graphene oxide (GO) samples. Then, polyimide (PI) hybrid membranes containing GO and modified GO were prepared by in situ polymerization. The permeation of CO2 and N2 was studied using these novel membranes. The morphology experiments showed that the isocyanate groups were successfully grafted on the surface of GO by replacement of the oxygen-containing functional groups. After modification, the surface polarity of the GO increased, and more defect structures were introduced into the GO surface. This resulted in a good distribution of more modified GO samples in the PI polymer matrix. Thus, the PI hybrid membranes incorporated by modified GO samples showed a high gas permeability and ideal selectivity of membranes. In addition, enhancement of the selectivity due to the solubility of CO2 played a major role in the increase in the separation performance of the hybrid membranes for CO2, although the diffusion coefficients for CO2 also increased. Both the higher condensability and the strong affinity between CO2 molecules and GO in the polymer matrix caused an enhancement of the solubility selectivity higher than the diffusion selectivity after GO surface modification.

  8. Graphene oxide induces plasma membrane damage, reactive oxygen species accumulation and fatty acid profiles change in Pichia pastoris.

    PubMed

    Zhang, Meng; Yu, Qilin; Liang, Chen; Liu, Zhe; Zhang, Biao; Li, Mingchun

    2016-10-01

    During the past couple of years, graphene nanomaterials were extremely popular among the scientists due to the promising properties in many aspects. Before the materials being well applied, we should first focus on their biosafety and toxicity. In this study, we investigated the toxicity of synthesized graphene oxide (GO) against the model industrial organism Pichia pastoris. We found that the synthesized GO showed dose-dependent toxicity to P. pastoris, through cell membrane damage and intracellular reactive oxygen species (ROS) accumulation. In response to these cell stresses, cells had normal unsaturated fatty acid (UFA) levels but increased contents of polyunsaturated fatty acid (PUFA) with up-regulation of UFA synthesis-related genes on the transcriptional level, which made it overcome the stress under GO attack. Two UFA defective strains (spt23Δ and fad12Δ) were used to demonstrate the results above. Hence, this study suggested a close connection between PUFAs and cell survival against GO. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Water and Molecular Transport across Nanopores in Monolayer Graphene Membranes

    NASA Astrophysics Data System (ADS)

    Jang, Doojoon; O'Hern, Sean; Kidambi, Piran; Boutilier, Michael; Song, Yi; Idrobo, Juan-Carlos; Kong, Jing; Laoui, Tahar; Karnik, Rohit

    2015-11-01

    Graphene's atomic thickness and high tensile strength allow it to outstand as backbone material for next-generation high flux separation membrane. Molecular dynamics simulations predicted that a single-layer graphene membrane could exhibit high permeability and selectivity for water over ions/molecules, qualifying as novel water desalination membranes. However, experimental investigation of water and molecular transport across graphene nanopores had remained barely explored due to the presence of intrinsic defects and tears in graphene. We introduce two-step methods to seal leakage across centimeter scale single-layer graphene membranes create sub-nanometer pores using ion irradiation and oxidative etching. Pore creation parameters were varied to explore the effects of created pore structures on water and molecular transport driven by forward osmosis. The results demonstrate the potential of nanoporous graphene as a reliable platform for high flux nanofiltration membranes.

  10. Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection.

    PubMed

    Kant, Ravi; Tabassum, Rana; Gupta, Banshi D

    2017-05-12

    Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

  11. Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

    NASA Astrophysics Data System (ADS)

    Kant, Ravi; Tabassum, Rana; Gupta, Banshi D.

    2017-05-01

    Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

  12. Toxicity of Graphene Shells, Graphene Oxide, and Graphene Oxide Paper Evaluated with Escherichia coli Biotests

    PubMed Central

    Efremova, Ludmila V.; Vasilchenko, Alexey S.; Rakov, Eduard G.; Deryabin, Dmitry G.

    2015-01-01

    The plate-like graphene shells (GS) produced by an original methane pyrolysis method and their derivatives graphene oxide (GO) and graphene oxide paper (GO-P) were evaluated with luminescent Escherichia coli biotests and additional bacterial-based assays which together revealed the graphene-family nanomaterials' toxicity and bioactivity mechanisms. Bioluminescence inhibition assay, fluorescent two-component staining to evaluate cell membrane permeability, and atomic force microscopy data showed GO expressed bioactivity in aqueous suspension, whereas GS suspensions and the GO-P surface were assessed as nontoxic materials. The mechanism of toxicity of GO was shown not to be associated with oxidative stress in the targeted soxS::lux and katG::lux reporter cells; also, GO did not lead to significant mechanical disruption of treated bacteria with the release of intracellular DNA contents into the environment. The well-coordinated time- and dose-dependent surface charge neutralization and transport and energetic disorders in the Escherichia coli cells suggest direct membrane interaction, internalization, and perturbation (i.e., “membrane stress”) as a clue to graphene oxide's mechanism of toxicity. PMID:26221608

  13. Toxicity of Graphene Shells, Graphene Oxide, and Graphene Oxide Paper Evaluated with Escherichia coli Biotests.

    PubMed

    Efremova, Ludmila V; Vasilchenko, Alexey S; Rakov, Eduard G; Deryabin, Dmitry G

    2015-01-01

    The plate-like graphene shells (GS) produced by an original methane pyrolysis method and their derivatives graphene oxide (GO) and graphene oxide paper (GO-P) were evaluated with luminescent Escherichia coli biotests and additional bacterial-based assays which together revealed the graphene-family nanomaterials' toxicity and bioactivity mechanisms. Bioluminescence inhibition assay, fluorescent two-component staining to evaluate cell membrane permeability, and atomic force microscopy data showed GO expressed bioactivity in aqueous suspension, whereas GS suspensions and the GO-P surface were assessed as nontoxic materials. The mechanism of toxicity of GO was shown not to be associated with oxidative stress in the targeted soxS::lux and katG::lux reporter cells; also, GO did not lead to significant mechanical disruption of treated bacteria with the release of intracellular DNA contents into the environment. The well-coordinated time- and dose-dependent surface charge neutralization and transport and energetic disorders in the Escherichia coli cells suggest direct membrane interaction, internalization, and perturbation (i.e., "membrane stress") as a clue to graphene oxide's mechanism of toxicity.

  14. Functionalized graphene and graphene oxide solution via polyacrylate coating.

    PubMed

    Saha, Arindam; Basiruddin, S K; Ray, S C; Roy, S S; Jana, Nikhil R

    2010-12-01

    Water soluble graphene with various chemical- and biofunctionalities is essential for their different applications. However, exfoliated graphenes are insoluble in water and water soluble graphene oxide precipitate if they are chemically reduced to graphene. We have developed a polyacrylate coating method for graphene oxide and then chemically reduced it into graphene. We found that polyacrylate coating can improve the colloidal stability of both graphene and graphene oxide. The coated graphene has been characterized using XPS, FTIR, XRD and micro-Raman spectroscopy. The primary amine present on the coating backbone has been used to derive glucose functionalized water soluble graphene. Various other functional graphenes can be anticipated from the polyacrylate coated graphene.

  15. Effect of incorporating graphene oxide and surface imprinting on polysulfone membranes on flux, hydrophilicity and rejection of salt and polycyclic aromatic hydrocarbons from water

    NASA Astrophysics Data System (ADS)

    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.

  16. The chemistry of graphene oxide.

    PubMed

    Dreyer, Daniel R; Park, Sungjin; Bielawski, Christopher W; Ruoff, Rodney S

    2010-01-01

    The chemistry of graphene oxide is discussed in this critical review. Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure. Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed. This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references).

  17. Graphene-Induced Pore Formation on Cell Membranes

    NASA Astrophysics Data System (ADS)

    Duan, Guangxin; Zhang, Yuanzhao; Luan, Binquan; Weber, Jeffrey K.; Zhou, Royce W.; Yang, Zaixing; Zhao, Lin; Xu, Jiaying; Luo, Judong; Zhou, Ruhong

    2017-02-01

    Examining interactions between nanomaterials and cell membranes can expose underlying mechanisms of nanomaterial cytotoxicity and guide the design of safer nanomedical technologies. Recently, graphene has been shown to exhibit potential toxicity to cells; however, the molecular processes driving its lethal properties have yet to be fully characterized. We here demonstrate that graphene nanosheets (both pristine and oxidized) can produce holes (pores) in the membranes of A549 and Raw264.7 cells, substantially reducing cell viability. Electron micrographs offer clear evidence of pores created on cell membranes. Our molecular dynamics simulations reveal that multiple graphene nanosheets can cooperate to extract large numbers of phospholipids from the membrane bilayer. Strong dispersion interactions between graphene and lipid-tail carbons result in greatly depleted lipid density within confined regions of the membrane, ultimately leading to the formation of water-permeable pores. This cooperative lipid extraction mechanism for membrane perforation represents another distinct process that contributes to the molecular basis of graphene cytotoxicity.

  18. Porphyrin-loaded liposomes and graphene oxide used for the membrane pore-forming protein assay and inhibitor screening.

    PubMed

    Liu, Zhongde; Long, Tengfei; Wu, Shuang; Li, Chong

    2015-08-21

    The interaction of planar aromatic molecules with the graphene oxide (GO) sheets is often marked by the fluorescence quenching of the former. Here, the α,β,γ,δ-tetrakis[4-(trimethylammoniumyl)phenyl]porphyrin (TAPP) molecules and the GO, corresponding to the energy donor and the acceptor respectively, are initially separated by encapsulating the TAPP molecules within the liposomes, to obstruct the formation of the self-assembled energy transfer-based quenching system. Upon disruption of the liposome membranes by the PLA2 or the α-toxin, the encapsulated TAPP molecules are released and subsequently result in significant fluorescence changes. Thus, a platform based on the fluorescence signal for monitoring the activity of the membrane pore-forming protein with advantages of high sensitivity and commonality was established. Using this strategy, we can detect the PLA2 and the α-toxin concentrations as low as 200 pM and 9.0 nM, respectively. Furthermore, by taking chlorpromazine and baicalin as the examples, we use the assay to evaluate the prohibition effects on the PLA2 and the α-toxin, and the IC50 values of chlorpromazine toward the PLA2 (9.6 nM) and that of baicalin toward the α-toxin (289.2 nM) were found to be 12.0 ± 0.62 μM and 26.9 ± 2.6 μM, respectively.

  19. Graphene-based structure, method of suspending graphene membrane, and method of depositing material onto graphene membrane

    DOEpatents

    Zettl, Alexander K.; Meyer, Jannik Christian

    2013-04-02

    An embodiment of a method of suspending a graphene membrane across a gap in a support structure includes attaching graphene to a substrate. A pre-fabricated support structure having the gap is attached to the graphene. The graphene and the pre-fabricated support structure are then separated from the substrate which leaves the graphene membrane suspended across the gap in the pre-fabricated support structure. An embodiment of a method of depositing material includes placing a support structure having a graphene membrane suspended across a gap under vacuum. A precursor is adsorbed to a surface of the graphene membrane. A portion of the graphene membrane is exposed to a focused electron beam which deposits a material from the precursor onto the graphene membrane. An embodiment of a graphene-based structure includes a support structure having a gap, a graphene membrane suspended across the gap, and a material deposited in a pattern on the graphene membrane.

  20. Reduced graphene oxide-NH2 modified low pressure nanofiltration composite hollow fiber membranes with improved water flux and antifouling capabilities

    NASA Astrophysics Data System (ADS)

    Li, Xipeng; Zhao, Changwei; Yang, Mei; Yang, Bin; Hou, Deyin; Wang, Tao

    2017-10-01

    Reduced graphene oxide-NH2 (R-GO-NH2), a kind of amino graphene oxide, was embedded into the polyamide (PA) layer of nanofiltration (NF) composite hollow fiber membranes via interfacial polymerization to enhance the permeate flux and antifouling properties of NF membranes under low pressure conditions. In addition, it could mitigate the poor compatibility issue between graphene oxide materials and PA layer. To evaluate the influence of R-GO-NH2 on the performance of the NF composite hollow fiber membrane, SEM, AFM, FTIR, XPS and Zeta potentials were used to characterize the membranes. The results indicated that the compatibility and interactions between R-GO-NH2 and PA layer were enhanced, which was mainly due to the polymerization reaction between amino groups of R-GO-NH2 and acyl chloride groups of TMC. Therefore, salts rejection of the current membranes was improved significantly, and the modified membranes with 50 mg/L R-GO-NH2 demonstrated highest performance in terms of the rejections, which were 26.9%, 98.5%, 98.1%, and 96.1%, for NaCl, Na2SO4, MgSO4, and CaCl2 respectively. It was found that with the R-GO-NH2 contents rasing from 0 to 50 mg/L, pure water flux increased from 30.44 ± 1.71 to 38.57 ± 2.01 L/(m2.h) at 2 bar. What's more, the membrane demonstrated improved antifouling properties.

  1. Graphene Oxide Quantum Dots Incorporated into a Thin Film Nanocomposite Membrane with High Flux and Antifouling Properties for Low-Pressure Nanofiltration.

    PubMed

    Zhang, Chunfang; Wei, Kaifang; Zhang, Wenhai; Bai, Yunxiang; Sun, Yuping; Gu, Jin

    2017-03-29

    Graphene oxide quantum dots (GOQDs), novel carbon-based nanomaterials, have attracted tremendous research interest due to their unique properties associated with both graphene and quantum dots. In the present study, thin film nanocomposite (TFN) membranes comprising GOQDs dispersed within a tannic acid (TA) film were fabricated by an interfacial polymerization reaction for low-pressure nanofiltration (NF). The resultant TA/GOQDs TFN membranes had measurably smoother and more hydrophilic, negatively charged surfaces compared to the similarly formed TA thin film composite (TFC) membrane. Owing to the loose active layer structure and the combination of Donnan exclusion and steric hindrance, the TA/GOQDs TFN membrane showed a pure water flux up to 23.33 L/m(2)·h (0.2 MPa), which was 1.5 times more than that of pristine TA TFC membrane, while high dye rejection to Congo red (99.8%) and methylene blue (97.6%) was kept. In addition, the TA/GOQDs TFN membrane presented better antifouling properties, which was ascribed to the favorable changes in membrane hydrophilicity, ζ-potential, and surface roughness. These results indicated the great potential of such membranes in wastewater treatment, separation, and purification in many industrial fields.

  2. Superpermeability of water through graphene based membranes

    NASA Astrophysics Data System (ADS)

    Raveendran Nair, Rahul; Joshi, Rakesh; Wu, Hengan; Narayanan, Jayaram; Grigorieva, Irina V.; Geim, Andre K.

    2013-03-01

    Permeation through nanometre-pore materials has been attracting unwavering interest due to fundamental differences in governing mechanisms at macroscopic and molecular scales, the importance of water permeation in living systems, and relevance for filtration and separation techniques. One of the most spectacular findings in this field was the observation that carbon nanotubes and other hydrophobic nanocapillaries allow anomalously fast permeation of gases and liquids and, in particular, of water. In this contribution we show that membranes made from graphene oxide which are impermeable to liquids, vapours and gases, including helium, but allow unimpeded permeation of water (H2O permeates through the membranes at least 1010 times faster than He). We attribute these seemingly incompatible observations to a nearly frictionless flow of a monolayer of water through two dimensional capillaries formed by closely spaced graphene sheets. The flow is driven by a large capillary-like pressure and normally limited only by evaporation from the wetted surface of the membranes. The permeation can be stopped by either reducing graphene oxide or inducing a reversible drying transition in low humidity, which narrow nanocapillaries in both cases. I will also give an overview of our latest results on ion permeation through these membranes.

  3. Bioinspired Underwater Superoleophobic Membrane Based on a Graphene Oxide Coated Wire Mesh for Efficient Oil/Water Separation.

    PubMed

    Liu, Yu-Qing; Zhang, Yong-Lai; Fu, Xiu-Yan; Sun, Hong-Bo

    2015-09-23

    Inspired from fish scales that exhibit unique underwater superoleophobicity because of the presence of micronanostructures and hydrophilic slime on their surface, we reported here the facile fabrication of underwater superoleophobic membranes by coating a layer of graphene oxide (GO) on commercially available wire meshes with tunable pore sizes. Using the wire mesh as a ready-made mask, GO-embellished mesh with open apertures (GO@mesh) could be readily fabricated after subsequent O2 plasma treatments from the back side. Interestingly, the congenital microstructures of the crossed microwires in combination with the abundant hydrophilic oxygen-containing groups of the GO layer endow the resultant GO@mesh with unique underwater superoleophobic properties. The antioil tests show that the underwater contact angles of various oils including both organic reagents (undissolved in water) and vegetable oil on GO@mesh exceed 150°, indicating the superoleophobic nature. In a representative experiment, a mixture of bean oil and water that imitates culinary sewage has been well separated with the help of our GO@mesh. GO-embellished wire meshes may find broad applications in sewage purification, especially for the treatment of oil contaminations.

  4. Strain and morphology of graphene membranes on responsive microhydrogel patterns

    SciTech Connect

    Shaina, P. R.; Jaiswal, Manu

    2014-11-10

    We study the configuration of atomically-thin graphene membranes on tunable microhydrogel patterns. The polyethylene oxide microhydrogel structures patterned by electron-beam lithography show increase in height, with a persistent swelling ratio up to ∼10, upon exposure to vapors of an organic solvent. We demonstrate that modifying the height fluctuations of the microhydrogel affects the strain and morphology of ultrathin graphene membrane over-layer. Raman spectroscopic investigations indicate that small lattice strains can be switched on in mechanically exfoliated few-layer graphene membranes that span these microhydrogel structures. In case of chemical-vapor deposited single-layer graphene, we observe Raman signatures of local depinning of the membranes upon swelling of microhydrogel pillars. We attribute this depinning transition to the competition between membrane-substrate adhesion energy and membrane strain energy, where the latter is tuned by hydrogel swelling.

  5. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

    PubMed

    Weatherup, Robert S; Eren, Baran; Hao, Yibo; Bluhm, Hendrik; Salmeron, Miquel B

    2016-05-05

    Atmospheric pressure X-ray photoelectron spectroscopy (XPS) is demonstrated using single-layer graphene membranes as photoelectron-transparent barriers that sustain pressure differences in excess of 6 orders of magnitude. The graphene serves as a support for catalyst nanoparticles under atmospheric pressure reaction conditions (up to 1.5 bar), where XPS allows the oxidation state of Cu nanoparticles and gas phase species to be simultaneously probed. We thereby observe that the Cu(2+) oxidation state is stable in O2 (1 bar) but is spontaneously reduced under vacuum. We further demonstrate the detection of various gas-phase species (Ar, CO, CO2, N2, O2) in the pressure range 10-1500 mbar including species with low photoionization cross sections (He, H2). Pressure-dependent changes in the apparent binding energies of gas-phase species are observed, attributable to changes in work function of the metal-coated grids supporting the graphene. We expect atmospheric pressure XPS based on this graphene membrane approach to be a valuable tool for studying nanoparticle catalysis.

  6. Bio-Conjugated CNT-Bridged 3D Porous Graphene Oxide Membrane for Highly Efficient Disinfection of Pathogenic Bacteria and Removal of Toxic Metals from Water.

    PubMed

    Nellore, Bhanu Priya Viraka; Kanchanapally, Rajashekhar; Pedraza, Francisco; Sinha, Sudarson Sekhar; Pramanik, Avijit; Hamme, Ashton T; Arslan, Zikri; Sardar, Dhiraj; Ray, Paresh Chandra

    2015-09-02

    More than a billion people lack access to safe drinking water that is free from pathogenic bacteria and toxic metals. The World Health Organization estimates several million people, mostly children, die every year due to the lack of good quality water. Driven by this need, we report the development of PGLa antimicrobial peptide and glutathione conjugated carbon nanotube (CNT) bridged three-dimensional (3D) porous graphene oxide membrane, which can be used for highly efficient disinfection of Escherichia coli O157:H7 bacteria and removal of As(III), As(V), and Pb(II) from water. Reported results demonstrate that versatile membrane has the capability to capture and completely disinfect pathogenic pathogenic E. coli O157:H7 bacteria from water. Experimentally observed disinfection data indicate that the PGLa attached membrane can dramatically enhance the possibility of destroying pathogenic E. coli bacteria via synergistic mechanism. Reported results show that glutathione attached CNT-bridged 3D graphene oxide membrane can be used to remove As(III), As(V), and Pb(II) from water sample at 10 ppm level. Our data demonstrated that PGLa and glutathione attached membrane has the capability for high efficient removal of E. coli O157:H7 bacteria, As(III), As(V), and Pb(II) simultaneously from Mississippi River water.

  7. Layer-by-layer assembly of graphene oxide on polypropylene macroporous membranes via click chemistry to improve antibacterial and antifouling performance

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen-Bei; Wu, Jing-Jing; Su, Yu; Zhou, Jin; Gao, Yong; Yu, Hai-Yin; Gu, Jia-Shan

    2015-03-01

    Polypropylene is an extensively used membrane material; yet, polypropylene membranes exhibit extremely poor resistance to protein fouling. To ameliorate this issue, graphene oxide (GO) nanosheets were used to modify macroporous polypropylene membrane (MPPM) via layer-by-layer assembly technique through click reaction. First, alkyne-terminated GO was prepared through esterification between carboxyl groups in GO and amide groups in propargylamine; azide-terminated GO was synthesized by the ring-opening reaction of epoxy groups in GO with sodium azide. Second, GO was introduced to the membrane by click chemistry. Characterizations of infrared spectra and X-ray photoelectron spectroscopy confirmed the modification. The sharply decreasing of static water contact angle indicated the improvement of the surface hydrophilicity for GO modified membrane. Introducing GO to the membrane results in a dramatic increase of water flux, improvements in the antifouling characteristics and antibacterial property for the membranes. The pure water flux through the 5-layered GO modified membrane is 1.82 times that through the unmodified one. The water flux restores to 43.0% for the unmodified membrane while to 79.8% for the modified membrane. The relative flux reduction decreases by 32.1% due to GO modification. The antibacterial property was also enhanced by two-thirds. These results demonstrate that the antifouling and antibacterial characteristics can be raised by tethering GO to the membrane surface.

  8. Integrating functional oxides with graphene

    NASA Astrophysics Data System (ADS)

    Hong, X.; Zou, K.; DaSilva, A. M.; Ahn, C. H.; Zhu, J.

    2012-08-01

    Graphene-oxide hybrid structures offer the opportunity to combine the versatile functionalities of oxides with the excellent electronic transport in graphene. Understanding and controlling how the dielectric environment affects the intrinsic properties of graphene is also critical to fundamental studies and technological development of graphene. Here we review our recent effort on understanding the transport properties of graphene interfaced with ferroelectric Pb(Zr,Ti)O3 (PZT) and high-κ HfO2. Graphene field effect devices prepared on high-quality single crystal PZT substrates exhibit up to tenfold increases in mobility compared to SiO2-gated devices. An unusual and robust resistance hysteresis is observed in these samples, which is attributed to the complex surface chemistry of the ferroelectric. Surface polar optical phonons of oxides in graphene transistors play an important role in the device performance. We review their effects on mobility and the high source-drain bias saturation current of graphene, which are crucial for developing graphene-based room temperature high-speed amplifiers. Oxides also introduce scattering sources that limit the low temperature electron mobility in graphene. We present a comprehensive study of the transport and quantum scattering times to differentiate various scattering scenarios and quantitatively evaluate the density and distribution of charged impurities and the effect of dielectric screening. Our results can facilitate the design of multifunctional nano-devices utilizing graphene-oxide hybrid structures.

  9. Molecular theory of graphene oxide.

    PubMed

    Sheka, Elena F; Popova, Nadezhda A

    2013-08-28

    Applied to graphene oxide, the molecular theory of graphene considers its oxide as a final product in the succession of polyderivatives related to a series of oxidation reactions involving different oxidants. The graphene oxide structure is created in the course of a stepwise computational synthesis of polyoxides of the (5,5) nanographene molecule governed by an algorithm that takes into account the molecule's natural radicalization due to the correlation of its odd electrons, the extremely strong influence of the structure on properties, and a sharp response of the molecule behavior on small actions of external factors. Taking these together, the theory has allowed for a clear, transparent and understandable explanation of the hot points of graphene oxide chemistry and suggesting reliable models of both chemically produced and chemically reduced graphene oxides.

  10. Highly effective permeability and antifouling performances of polypropylene non-woven fabric membranes modified with graphene oxide by inkjet printing and immersion coating methods.

    PubMed

    Zhao, Chuan-Qi; Xu, Xiao-Chen; Li, Rui-Yun; Chen, Jie; Yang, Feng-Lin

    2013-01-01

    In the current study, graphene oxide (GO)-modified polypropylene non-woven fabric (PP-NWF) membranes were prepared via inkjet printing and immersion coating methods. Scanning electron microscopy, Fourier transform infrared spectroscopy, contact angle measurements, pure water permeation (JPWP) and protein adsorption were tested to evaluate the impact of the GO nanosheet on the characteristics and performance of modified PP-NWF membranes. The results showed that the exfoliated GO nanosheets uniformly deposited on the membrane surface and firmly embedded into the interlaced fibers, resulting in the improvement of membrane hydrophilicity, permeability and antifouling properties comparing with original PP-NWF membranes. The GO-printed and GO-coated membranes had 113 and 188% higher fluxes, and 70.95 and 75.74% lower protein adsorptions than the original PP-NWF membranes, respectively. After cross-linked treatment, ultrasound processing was conducted to evaluate the stability of the modified PP-NWF membranes. The results demonstrated that there was almost no decrease in permeation after ultrasonic treatment indicating that the cross-linking treatment could enhance the immobilization of the GO nanosheets on and into the modified membranes.

  11. Shielding membrane surface carboxyl groups by covalent-binding graphene oxide to improve anti-fouling property and the simultaneous promotion of flux.

    PubMed

    Han, Jing-Long; Xia, Xue; Tao, Yu; Yun, Hui; Hou, Ya-Nan; Zhao, Chang-Wei; Luo, Qin; Cheng, Hao-Yi; Wang, Ai-Jie

    2016-10-01

    Graphene oxide (GO) is an excellent material for membrane surface modification. However, little is known about how and to what extent surface functional groups change after GO modification influence membrane anti-fouling properties. Carboxyl is an inherent functional group on polyamide or other similar membranes. Multivalent cations in wastewater secondary effluent can bridge with carboxyls on membrane surfaces and organic foulants, resulting in serious membrane fouling. In this study, carboxyls of a polydopamine (pDA)/1,3,5-benzenetricarbonyl trichloride (TMC) active layer are shielded by covalently-bound GO. The process is mediated by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS). For GO containing low quantities of carboxyls, X-ray photoelectron spectroscopy (XPS) and zeta potential analyzer test results reveal that the carboxyl density decreased by 52.3% compare to the pDA/TMC membrane after GO modification. Fouling experiments shows that the flux only slightly declines in the GO functionalized membrane (19.0%), compared with the pDA/TMC membrane (36.0%) after fouling. In addition, during GO modification process the pDA/TMC active layer also become harder and thinner with the aid of EDC/NHS. So the pure water permeability increases from 56.3 ± 18.2 to 103.7 ± 12.0 LMH/MPa. Our results provide new insights for membrane modification work in water treatment and other related fields.

  12. Nanometric Graphene Oxide Framework Membranes with Enhanced Heavy Metal Removal via Nanofiltration.

    PubMed

    Zhang, Yu; Zhang, Sui; Chung, Tai-Shung

    2015-08-18

    A novel dual-modification strategy, including (1) the cross-linking and construction of a GO framework by ethylenediamine (EDA) and (2) the amine-enrichment modification by hyperbranched polyethylenimine (HPEI), has been proposed to design stable and highly charged GO framework membranes with the GO selective layer thickness of 70 nm for effective heave metal removal via nanofiltration (NF). Results from sonication experiments and positron annihilation spectroscopy confirmed that EDA cross-linking not only enhanced structural stability but also enlarged the nanochannels among the laminated GO nanosheets for higher water permeability. HPEI 60K was found to be the most effective post-treatment agent that resulted in GO framework membranes with a higher surface charge and lower transport resistance. The newly developed membrane exhibited a high pure water permeability of 5.01 L m(-2) h(-1) bar(-1) and comparably high rejections toward Mg(2+), Pb(2+), Ni(2+), Cd(2+), and Zn(2+). These results have demonstrated the great potential of GO framework materials in wastewater treatment and may provide insights for the design and fabrication of the next generation two-dimensional (2D)-based NF membranes.

  13. Membrane properties and anti-bacterial/anti-biofouling activity of polysulfone–graphene oxide composite membranes phase inversed in graphene oxide non-solvent† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra25015g Click here for additional data file.

    PubMed Central

    Koseoglu-Imer, Derya Yuksel; Yilmaz-Deveci, Nurmiray; Mijakovic, Ivan; Koyuncu, Ismail

    2017-01-01

    A new and facile method for the fabrication of polysulfone–graphene oxide composite membranes is reported, where after casting, phase inversion is carried out with graphene oxide flakes (GO) in a coagulation bath. The membranes were characterized and the morphology was analysed using scanning electron microscopy. A bacterial inhibition ratio of 74.5% was observed with membranes fabricated from a very low concentration of di-water–GO non-solvent (0.048% of GO). The membranes were successfully tested for permeate flux and fouling resistance using activated sludge filtration from an MBR system. The observed trend shows that GO can operate as a protective barrier for membrane pores against the bacterial community. To our knowledge this is the first time where the immersion precipitation mechanism was carried out in a coagulation bath with GO flakes under continuous stirring. Using this method, a very low concentration of GO is required to fabricate membranes with conventional GO composite membrane properties and better selectivity. PMID:28496976

  14. Superflexibility of graphene oxide

    PubMed Central

    Poulin, Philippe; Jalili, Rouhollah; Neri, Wilfrid; Nallet, Frédéric; Colin, Annie; Wallace, Gordon; Zakri, Cécile

    2016-01-01

    Graphene oxide (GO), the main precursor of graphene-based materials made by solution processing, is known to be very stiff. Indeed, it has a Young’s modulus comparable to steel, on the order of 300 GPa. Despite its very high stiffness, we show here that GO is superflexible. We quantitatively measure the GO bending rigidity by characterizing the flattening of thermal undulations in response to shear forces in solution. Characterizations are performed by the combination of synchrotron X-ray diffraction at small angles and in situ rheology (rheo-SAXS) experiments using the high X-ray flux of a synchrotron source. The bending modulus is found to be 1 kT, which is about two orders of magnitude lower than the bending rigidity of neat graphene. This superflexibility compares with the fluidity of self-assembled liquid bilayers. This behavior is discussed by considering the mechanisms at play in bending and stretching deformations of atomic monolayers. The superflexibility of GO is a unique feature to develop bendable electronics after reduction, films, coatings, and fibers. This unique combination of properties of GO allows for flexibility in processing and fabrication coupled with a robustness in the fabricated structure. PMID:27647890

  15. Achieving enhanced hydrophobicity of graphene membranes by covalent modification with polydimethylsiloxane

    NASA Astrophysics Data System (ADS)

    Lei, Wei-Wei; Li, Hang; Shi, Ling-Ying; Diao, Yong-Fu; Zhang, Yu-Lin; Ran, Rong; Ni, Wei

    2017-05-01

    In this study, the graphene oxide was covalently modified by amino terminated polydimethylsiloxane (PDMS) through amidation reaction. And the membranes of the graphene oxide (GO), reduced graphene oxide (RGO) and PDMS-covalently modified graphene were prepared respectively by a vacuum filtration method, and the wettability of these membranes were investigated. Infrared spectroscopy, Raman, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetry analysis combined with dispersion ability indicated that PDMS chains were successfully grafted on the surface of graphene oxide sheets. The morphology of the prepared membranes had smooth surface and well-stacked structure in the cross-section indicated by the scanning electron microscope and EDS-mapping. The contact angle measurements indicated that the PDMS-modified graphene membrane with water contact angle 129.5° showed increased hydrophobicity compared with GO and RGO membranes.

  16. Functionalized graphene and graphene oxide solution via polyacrylate coating

    NASA Astrophysics Data System (ADS)

    Saha, Arindam; Basiruddin, Sk; Ray, S. C.; Roy, S. S.; Jana, Nikhil R.

    2010-12-01

    Water soluble graphene with various chemical- and biofunctionalities is essential for their different applications. However, exfoliated graphenes are insoluble in water and water soluble graphene oxide precipitate if they are chemically reduced to graphene. We have developed a polyacrylate coating method for graphene oxide and then chemically reduced it into graphene. We found that polyacrylate coating can improve the colloidal stability of both graphene and graphene oxide. The coated graphene has been characterized using XPS, FTIR, XRD and micro-Raman spectroscopy. The primary amine present on the coating backbone has been used to derive glucose functionalized water soluble graphene. Various other functional graphenes can be anticipated from the polyacrylate coated graphene.Water soluble graphene with various chemical- and biofunctionalities is essential for their different applications. However, exfoliated graphenes are insoluble in water and water soluble graphene oxide precipitate if they are chemically reduced to graphene. We have developed a polyacrylate coating method for graphene oxide and then chemically reduced it into graphene. We found that polyacrylate coating can improve the colloidal stability of both graphene and graphene oxide. The coated graphene has been characterized using XPS, FTIR, XRD and micro-Raman spectroscopy. The primary amine present on the coating backbone has been used to derive glucose functionalized water soluble graphene. Various other functional graphenes can be anticipated from the polyacrylate coated graphene. Electronic supplementary information (ESI) available: Details of XPS, XRD, AFM and FTIR of polymer coated GO and G and results of fluorescence quenching experiments. See DOI: 10.1039/c0nr00376j

  17. The Enzymatic Oxidation of Graphene Oxide

    PubMed Central

    Kotchey, Gregg P.; Allen, Brett L.; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A.; Tyurina, Yulia Y.; Klein-Seetharaman, Judith; Kagan, Valerian E.; Star, Alexander

    2011-01-01

    Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon – the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (~40 µM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, UV-Vis, EPR and FT-IR spectroscopy, TEM, AFM, SDS-PAGE, and GC-MS. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Due to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors. PMID:21344859

  18. The enzymatic oxidation of graphene oxide.

    PubMed

    Kotchey, Gregg P; Allen, Brett L; Vedala, Harindra; Yanamala, Naveena; Kapralov, Alexander A; Tyurina, Yulia Y; Klein-Seetharaman, Judith; Kagan, Valerian E; Star, Alexander

    2011-03-22

    Two-dimensional graphitic carbon is a new material with many emerging applications, and studying its chemical properties is an important goal. Here, we reported a new phenomenon--the enzymatic oxidation of a single layer of graphitic carbon by horseradish peroxidase (HRP). In the presence of low concentrations of hydrogen peroxide (∼40 μM), HRP catalyzed the oxidation of graphene oxide, which resulted in the formation of holes on its basal plane. During the same period of analysis, HRP failed to oxidize chemically reduced graphene oxide (RGO). The enzymatic oxidation was characterized by Raman, ultraviolet-visible, electron paramagnetic resonance, Fourier transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and gas chromatography-mass spectrometry. Computational docking studies indicated that HRP was preferentially bound to the basal plane rather than the edge for both graphene oxide and RGO. Owing to the more dynamic nature of HRP on graphene oxide, the heme active site of HRP was in closer proximity to graphene oxide compared to RGO, thereby facilitating the oxidation of the basal plane of graphene oxide. We also studied the electronic properties of the reduced intermediate product, holey reduced graphene oxide (hRGO), using field-effect transistor (FET) measurements. While RGO exhibited a V-shaped transfer characteristic similar to a single layer of graphene that was attributed to its zero band gap, hRGO demonstrated a p-type semiconducting behavior with a positive shift in the Dirac points. This p-type behavior rendered hRGO, which can be conceptualized as interconnected graphene nanoribbons, as a potentially attractive material for FET sensors.

  19. Surface Decoration of Amino-Functionalized Metal-Organic Framework/Graphene Oxide Composite onto Polydopamine-Coated Membrane Substrate for Highly Efficient Heavy Metal Removal.

    PubMed

    Rao, Zhuang; Feng, Kai; Tang, Beibei; Wu, Peiyi

    2017-01-25

    A new metal-organic framework/graphene oxide composite (IRMOF-3/GO) with high adsorption capacity of copper(II) (maximal adsorption amount = 254.14 mg/g at pH 5.0 and 25 °C) was prepared. Novel and highly efficient nanofiltration (NF) membrane can be facilely fabricated via surface decoration of IRMOF-3/GO onto polydopamine (PDA)-coated polysulfone (PSF) substrate. After decoration of IRMOF-3/GO, membrane surface potential increased from 6.7 to 13.1 mV at pH 5.0 and 25 °C. Due to the adsorption effect of IRMOF-3/GO and the enhancement of membrane surface potential, the prepared NF membrane (the loading amount of IRMOF-3/GO is ca. 13.6 g/m(2)) exhibits a highly efficient rejection of copper(II). The copper(II) rejection reaches up to ∼90%, while maintaining a relatively high flux of ∼31 L/m(2)/h at the pressure of 0.7 MPa and pH 5.0. Moreover, the membrane also presents an outstanding stability throughout the 2000 min NF testing period. Thus, the newly developed NF membrane shows a promising potential for water cleaning. This work provides a worthy reference for designing highly efficient NF membranes modified by metal-organic framework (MOF) relevant materials.

  20. On the biological performance of graphene oxide-modified chitosan/polyvinyl pyrrolidone nanocomposite membranes: In vitro and in vivo effects of graphene oxide.

    PubMed

    Mahmoudi, Nafiseh; Simchi, Abdolreza

    2017-01-01

    Nanofibrous structures that mimic the native extracellular matrix and promote cell adhesion have attracted considerable interest for biomedical applications. In this study, GO-modified nanofibrous biopolymers (GO) were prepared by electrospinning blended solutions of chitosan (80vol%), polyvinyl pyrrolidone (15vol%), polyethylene oxide (5vol%) containing GO nanosheets (0-2wt%). It is shown that GO nanosheets significantly change the conductivity and viscosity of highly concentrated chitosan solutions, so that ultrafine and uniform fibers with an average diameter of 60nm are spinnable. The GO-reinforced nanofibers with controlled pore structure exhibit enhanced elastic modulus and tensile strength (150-300%) with a controllable water permeability to meet the required properties of natural skins. Potential use of the GO-modified biocomposites for tissue engineering is demonstrated in mesenchymal stem cell lines extracted from rat's bone marrow. The biocompatibility assay and SEM imaging reveal that the nanofibrous structure promotes the attachment and maintained characteristic cell morphology and viability up to 72h. In-vivo evaluations in rats show that a faster and more efficient wound closure rate (about 33%) are attained for the 1.5% GO nanofibrous membrane as compared with control (sterile gauze sponges). Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Graphene oxide nanocolloids.

    PubMed

    Luo, Jiayan; Cote, Laura J; Tung, Vincent C; Tan, Alvin T L; Goins, Philip E; Wu, Jinsong; Huang, Jiaxing

    2010-12-22

    Graphene oxide (GO) nanocolloids-sheets with lateral dimension smaller than 100 nm-were synthesized by chemical exfoliation of graphite nanofibers, in which the graphene planes are coin-stacked along the length of the nanofibers. Since the upper size limit is predetermined by the diameter of the nanofiber precursor, the size distribution of the GO nanosheets is much more uniform than that of common GO synthesized from graphite powders. The size can be further tuned by the oxidation time. Compared to the micrometer-sized, regular GO sheets, nano GO has very similar spectroscopic characteristics and chemical properties but very different solution properties, such as surface activity and colloidal stability. Due to higher charge density originating from their higher edge-to-area ratios, aqueous GO nanocolloids are significantly more stable. Dispersions of GO nanocolloids can sustain high-speed centrifugation and remain stable even after chemical reduction, which would result in aggregates for regular GO. Therefore, nano GO can act as a better dispersing agent for insoluble materials (e.g., carbon nanotubes) in water, creating a more stable colloidal dispersion.

  2. Electrorheology of graphene oxide.

    PubMed

    Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin; Kim, Sang Guk

    2012-04-01

    Novel polarizable graphene oxide (GO) particles with oxidized groups on their edge and basal planes were prepared by a modified Hummers method, and their electro-responsive electrorheological (ER) characteristics when dispersed in silicone oil were examined with and without an electric field applied. The fibrillation phenomenon of this GO-based electro-responsive fluid was also observed via an optical microscope under an applied electric field. Both flow curves and dielectric spectra of the ER fluid were measured using a rotational rheometer and a LCR meter, respectively. Its viscoelastic properties of both storage and loss moduli were also examined using a vertical oscillation rheometer equipped with a high voltage generator, finding that the GO-based smart ER system behaves as a viscoelastic material under an applied electric field.

  3. Development of macroscopic nanoporous graphene membranes for gas separation

    NASA Astrophysics Data System (ADS)

    Boutilier, Michael; Hadjiconstantinou, Nicolas; Karnik, Rohit

    2015-11-01

    Nanoporous graphene membranes have the potential to exceed permeance and selectivity limits of existing gas separation membranes due to their atomic thickness and ability to support sub-nanometer pores for molecular sieving, while offering low resistance to flow. Gas separation by graphene nanopores has been demonstrated experimentally on micron-scale membranes, but scaling-up to larger sizes is challenging due to graphene imperfections and control of the selective nanopore size distribution. Using a model we developed for the inherent permeance of graphene, we designed a macroscopic graphene membrane predicted to be selectively permeable despite material imperfections. Micrometer-scale defects are sealed by interfacial polymerization and nanometer-scale defects are sealed by atomic layer deposition. The underlying support structure is tuned to further reduce the effects of leakage. Finally, ion bombardment followed by oxidative etching is used to create a high density of selective nanopores. SEM and TEM imaging are used to characterize the resulting membrane structure, and its performance is assessed by gas permeance and selectivity measurements. This work provides insight into gas flow through nanoporous graphene membranes and guides their future development.

  4. Single-Step Assembly of Multifunctional Poly(tannic acid)-Graphene Oxide Coating To Reduce Biofouling of Forward Osmosis Membranes.

    PubMed

    Hegab, Hanaa M; ElMekawy, Ahmed; Barclay, Thomas G; Michelmore, Andrew; Zou, Linda; Saint, Christopher P; Ginic-Markovic, Milena

    2016-07-13

    Graphene oxide (GO) nanosheets have antibacterial properties that have been exploited as a biocidal agent used on desalination membrane surfaces in recent research. Nonetheless, improved strategies for efficient and stable attachment of GO nanosheets onto the membrane surface are still required for this idea to be commercially viable. To address this challenge, we adopted a novel, single-step surface modification approach using tannic acid cross-linked with polyethylene imine as a versatile platform to immobilize GO nanosheets to the surface of polyamide thin film composite forward osmosis (FO) membranes. An experimental design based on Taguchi's statistical method was applied to optimize the FO processing conditions in terms of water and reverse solute fluxes. Modified membranes were analyzed using water contact angle, adenosine triphosphate bioluminescence, total organic carbon, Fourier transform infrared spectroscopy, ζ potential, X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy. These results show that membranes were modified with a nanoscale (<10 nm), smooth, hydrophilic coating that, compared to pristine membranes, improved filtration and significantly mitigated biofouling by 33% due to its extraordinary, synergistic antibacterial properties (99.9%).

  5. In Situ Photocatalytic Synthesis of Ag Nanoparticles (nAg) by Crumpled Graphene Oxide Composite Membranes for Filtration and Disinfection Applications.

    PubMed

    Jiang, Yi; Liu, Di; Cho, Minjung; Lee, Seung Soo; Zhang, Fuzhong; Biswas, Pratim; Fortner, John D

    2016-03-01

    Graphene oxide (GO) materials have demonstrated considerable potential in next-generation water treatment membrane-based technologies, which include antimicrobial applications. GO antimicrobial properties can be further enhanced by preloading or chemically generating surface-associated nanoscale silver particles (nAg). However, for these systems, enhanced antimicrobial functionality decreases over time as a function of Ag mass loss via dissolution (as Ag(+)). In this work, we demonstrate facile photocatalytic in situ synthesis of nAg particles by crumpled GO-TiO2 (GOTI) nanocomposites as an approach to (re)generate, and thus maintain, enhanced antimicrobial activity over extended operation times. The described photocatalytic formation process is highly efficient and relatively fast, producing nAg particles over a size range of 40 to 120 nm and with active (111) planes. Additionally, we show in situ surface-based photocatalyzed synthesis of nAg particles at the surface of GOTI nanocomposite membrane assemblies, allowing for simultaneous filtration and disinfection. With ca. 3 log inactivation for both Escherichia coli and Bacillus subtilis, the described membrane assemblies with in situ formed nAg demonstrate enhanced antimicrobial activity compared to the GOTI membrane surface or the support membrane alone. Under typical conditions, the working and operational time (Ag dissolution time) is calculated to be over 2 orders of magnitude higher than the loading (synthesis) time (e.g., 123 h versus 0.5 h, respectively). Taken together, results highlight the described material-based process as a potentially novel antifouling membrane technology.

  6. Anti-fouling and high water permeable forward osmosis membrane fabricated via layer by layer assembly of chitosan/graphene oxide

    NASA Astrophysics Data System (ADS)

    Salehi, Hasan; Rastgar, Masoud; Shakeri, Alireza

    2017-08-01

    To date, forward osmosis (FO) has received considerable attention due to its potential application in seawater desalination. FO does not require external hydraulic pressure and consequently is believed to have a low fouling propensity. Despite the numerous privileges of FO process, a major challenge ahead for its development is the lack of high performance membranes. In this study, we fabricated a novel highly-efficient FO membrane using layer-by-layer (LbL) assembly of positive chitosan (CS) and negative graphene oxide (GO) nanosheets via electrostatic interaction on a porous support layer. The support layer was prepared by blending hydrophilic sulfonated polyethersulfone (SPES) into polyethersulfone (PES) matrix using wet phase inversion process. Various characterization techniques were used to confirm successful fabrication of LbL membrane. The number of layers formed on the SPES-PES support layer was easily adjusted by repeating the CS and GO deposition cycles. Thin film composite (TFC) membrane was also prepared by the same SPES-PES support layer and polyamide (PA) active layer to compare membranes performances. The water permeability and salt rejection of the fabricated membranes were obtained by two kinds of draw solutions (including Na2SO4 and sucrose) under two different membrane orientations. The results showed that membrane coated by a CS/GO bilayers had water flux of 2-4 orders of magnitude higher than the TFC one. By increasing the number of CS/GO bilayers, the selectivity of the LbL membrane was improved. The novel fabricated LbL membrane showed better fouling resistance than the TFC one in the feed solution containing 200 ppm of sodium alginate as a foulant model.

  7. Superpermeable Atomic-Thin Graphene Membranes with High Selectivity.

    PubMed

    Wei, Gaoliang; Quan, Xie; Chen, Shuo; Yu, Hongtao

    2017-02-28

    Theoretical permeability of membrane is inversely proportional to its thickness, which indicates ultrathin membranes will be extremely permeable. Inspired by the atomic thickness of graphene, herein we report a four-layered graphene membrane with a thickness of about 2 nm. The ultrathin membrane is facilely fabricated by directly punching a complete graphene sheet through selective removal of some carbon atoms with metal oxide nanoparticles at high temperature. Their perpendicular pore channels spanning the whole thickness could, to a great extent, reduce hydrodynamic resistance for water transport. Experimental tests have revealed a flux of up to 4600 L m(-2) h(-1) of the membranes with a pore size of 50 nm and pore density of 1.0 × 10(7) cm(-2) at a pressure of 0.2 bar. This flux is 40-400 times higher than those of conventional ceramic membranes and track-etched membranes. The enhancement in water permeance is attributed to their atomic thickness and straight pore channels. High selectivity is also evidenced by selective separation of nanospheres with their narrowly distributed pores. These atomic-thin graphene membranes, in view of their outstanding permeability and selectivity, possess great potential as future advanced membranes and may inspire the design and development of other innovative membranes.

  8. Towards the Synthesis of Graphene Azide from Graphene Oxide.

    PubMed

    Halbig, Christian E; Rietsch, Philipp; Eigler, Siegfried

    2015-11-26

    In the last decades, organic azides haven proven to be very useful precursors in organic chemistry, for example in 1,3-dipolar cycloaddition reactions (click-chemistry). Likewise, azides can be introduced into graphene oxide with an almost intact carbon framework, namely oxo-functionalized graphene (oxo-G₁), which is a highly oxidized graphene derivative and a powerful precursor for graphene that is suitable for electronic devices. The synthesis of a graphene derivative with exclusively azide groups (graphene azide) is however still a challenge. In comparison also hydrogenated graphene, called graphene or halogenated graphene remain challenging to synthesize. A route to graphene azide would be the desoxygenation of azide functionalized oxo-G₁. Here we show how treatment of azide functionalized oxo-G₁ with HCl enlarges the π-system and removes strongly adsorbed water and some oxo-functional groups. This development reflects one step towards graphene azide.

  9. [Solidification of volatile oil with graphene oxide].

    PubMed

    Yan, Hong-Mei; Jia, Xiao-Bin; Zhang, Zhen-Hai; Sun, E; Xu, Yi-Hao

    2015-02-01

    To evaluate the properties of solidifying volatile oil with graphene oxide, clove oil and zedoary turmeric oil were solidified by graphene oxide. The amount of graphene oxide was optimized with the eugenol yield and curcumol yield as criteria. Curing powder was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The effects of graphene oxide on dissolution in vitro and thermal stability of active components were studied. The optimum solidification ratio of graphene oxide to volatile oil was 1:1. Dissolution rate of active components had rare influence while their thermal stability improved after volatile oil was solidified. Solidifying herbal volatile oil with graphene oxide deserves further study.

  10. Photochemical Transformation of Graphene Oxide in Sunlight

    EPA Science Inventory

    Graphene oxide (GO) is a graphene derivative that is more easily manufactured in large scale and used to synthesize reduced graphene oxide (rGO) with properties analogous to graphene. In this study, we investigate the photochemical fate of GO under sunlight conditions. The resu...

  11. Photochemical Transformation of Graphene Oxide in Sunlight

    EPA Science Inventory

    Graphene oxide (GO) is a graphene derivative that is more easily manufactured in large scale and used to synthesize reduced graphene oxide (rGO) with properties analogous to graphene. In this study, we investigate the photochemical fate of GO under sunlight conditions. The resu...

  12. Reduced graphene oxide molecular sensors.

    PubMed

    Robinson, Jeremy T; Perkins, F Keith; Snow, Eric S; Wei, Zhongqing; Sheehan, Paul E

    2008-10-01

    We demonstrate reduced graphene oxide as the active material for high-performance molecular sensors. Sensors are fabricated from exfoliated graphene oxide platelets that are deposited to form an ultrathin continuous network. These graphene oxide networks are tunably reduced toward graphene by varying the exposure time to a hydrazine hydrate vapor. The conductance change of the networks upon exposure to trace levels of vapor is measured as a function of the chemical reduction. The level of reduction affects both the sensitivity and the level of 1/ f noise. The sensors are capable of detecting 10 s exposures to simulants of the three main classes of chemical-warfare agents and an explosive at parts-per-billion concentrations.

  13. Graphene-Induced Pore Formation on Cell Membranes

    PubMed Central

    Duan, Guangxin; Zhang, Yuanzhao; Luan, Binquan; Weber, Jeffrey K.; Zhou, Royce W.; Yang, Zaixing; Zhao, Lin; Xu, Jiaying; Luo, Judong; Zhou, Ruhong

    2017-01-01

    Examining interactions between nanomaterials and cell membranes can expose underlying mechanisms of nanomaterial cytotoxicity and guide the design of safer nanomedical technologies. Recently, graphene has been shown to exhibit potential toxicity to cells; however, the molecular processes driving its lethal properties have yet to be fully characterized. We here demonstrate that graphene nanosheets (both pristine and oxidized) can produce holes (pores) in the membranes of A549 and Raw264.7 cells, substantially reducing cell viability. Electron micrographs offer clear evidence of pores created on cell membranes. Our molecular dynamics simulations reveal that multiple graphene nanosheets can cooperate to extract large numbers of phospholipids from the membrane bilayer. Strong dispersion interactions between graphene and lipid-tail carbons result in greatly depleted lipid density within confined regions of the membrane, ultimately leading to the formation of water-permeable pores. This cooperative lipid extraction mechanism for membrane perforation represents another distinct process that contributes to the molecular basis of graphene cytotoxicity. PMID:28218295

  14. Highly oxidized graphene oxide and methods for production thereof

    DOEpatents

    Tour, James M.; Kosynkin, Dmitry V.

    2016-08-30

    A highly oxidized form of graphene oxide and methods for production thereof are described in various embodiments of the present disclosure. In general, the methods include mixing a graphite source with a solution containing at least one oxidant and at least one protecting agent and then oxidizing the graphite source with the at least one oxidant in the presence of the at least one protecting agent to form the graphene oxide. Graphene oxide synthesized by the presently described methods is of a high structural quality that is more oxidized and maintains a higher proportion of aromatic rings and aromatic domains than does graphene oxide prepared in the absence of at least one protecting agent. Methods for reduction of graphene oxide into chemically converted graphene are also disclosed herein. The chemically converted graphene of the present disclosure is significantly more electrically conductive than is chemically converted graphene prepared from other sources of graphene oxide.

  15. Graphene-supported metal oxide monolith

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Biener, Juergen; Biener, Monika A.; Wang, Yinmin; Ye, Jianchao; Tylski, Elijah

    2017-01-10

    A composition comprising at least one graphene-supported metal oxide monolith, said monolith comprising a three-dimensional structure of graphene sheets crosslinked by covalent carbon bonds, wherein the graphene sheets are coated by at least one metal oxide such as iron oxide or titanium oxide. Also provided is an electrode comprising the aforementioned graphene-supported metal oxide monolith, wherein the electrode can be substantially free of any carbon-black and substantially free of any binder.

  16. Biological applications of graphene oxide

    SciTech Connect

    Gürel, Hikmet Hakan; Salmankurt, Bahadır

    2016-03-25

    Graphene as a 2D material has unique chemical and electronic properties. Because of its unique physical, chemical, and electronic properties, its interesting shape and size make it a promising nanomaterial in many biological applications. However, the lower water-solubility and the irreversible aggregation due to the strong π-π stacking hinder the wide application of graphene nanosheets in biomedical field. Thus, graphene oxide (GO), one derivative of graphene, has been used more frequently in the biological system owing to its relatively higher water solubility and biocompatibility. Recently, it has been demonstrated that nanomaterials with different functional groups on the surface can be used to bind the drug molecules with high affinity. GO has different functional groups such as H, OH and O on its surface; it can be a potential candidate as a drug carrier. The interactions of biomolecules and graphene like structures are long-ranged and very weak. Development of new techniques is very desirable for design of bioelectronics sensors and devices. In this work, we present first-principles spin polarized calculations within density functional theory to calculate effects of charging on DNA/RNA nucleobases on graphene oxide. It is shown that how modify structural and electronic properties of nucleobases on graphene oxide by applied charging.

  17. Simultaneous wastewater treatment and bioelectricity production in microbial fuel cells using cross-linked chitosan-graphene oxide mixed-matrix membranes.

    PubMed

    Holder, Shima L; Lee, Ching-Hwa; Popuri, Srinivasa R

    2017-05-01

    Microbial fuel cells (MFCs) are emerging technology for wastewater treatment by chemical oxygen demand (COD) reduction and simultaneous bioelectricity production. Fabrication of an effective proton exchange membrane (PEM) is a vital component for MFC performance. In this work, green chitosan-based (CS) PEMs were fabricated with graphene oxide (GO) as filler material (CS-GO) and cross-linked with phosphoric acid (CS-GO-P(24)) or sulfuric acid (CS-GO-S(24)) to determine their effect on PEM properties. Interrogation of the physicochemical, thermal, and mechanical properties of the cross-linked CS-GO PEMs demonstrated that ionic cross-linking based on the incorporation of PO4(3-) groups in the CS-GO mixed-matrix composites, when compared with sulfuric acid cross-linking commonly used in proton exchange membrane fuel cell (PEMFC) studies, generated additional density of ionic cluster domains, rendered enhanced sorption properties, and augmented the thermal and mechanical stability of the composite structure. Consequently, bioelectricity performance analysis in MFC application showed that CS-GO-P(24) membrane produced 135% higher power density than the CS-GO-S(24) MFC system. Simultaneously, 89.52% COD removal of primary clarifier municipal wastewater was achieved in the MFC operated with the CS-GO-P(24) membrane.

  18. Effective enhancement of gas separation performance in mixed matrix membranes using core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons

    NASA Astrophysics Data System (ADS)

    Xue, Qingzhong; Pan, Xinglong; Li, Xiaofang; Zhang, Jianqiang; Guo, Qikai

    2017-02-01

    Novel core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons (MWCNT@GONRs) nanohybrids were successfully prepared using a modified chemical longitudinal unzipping method. Subsequently, the MWCNT@GONRs nanohybrids were used as fillers to enhance the gas separation performance of polyimide based mixed matrix membranes (MMMs). It is found that MMMs concurrently exhibited higher gas selectivity and higher gas permeability compared to pristine polyimide. The high gas selectivity could be attributed to the GONRs shell, which provided a selective barrier and large gas adsorbed area, while the high gas permeability resulted from the hollow structured MWCNTs core with smooth internal surface, which acted as a rapid transport channel. MWCNT@GONRs could be promising candidates to improve gas separation performance of MMMs due to the unique microstructures, ease of synthesis and low filling loading.

  19. Graphene oxide as an anaerobic membrane scaffold for the enhancement of B. adolescentis proliferation and antagonistic effects against pathogens E. coli and S. aureus

    NASA Astrophysics Data System (ADS)

    Chen, Han-qing; Gao, Di; Wang, Bing; Zhao, Rui-fang; Guan, Ming; Zheng, Ling-na; Zhou, Xiao-yan; Chai, Zhi-fang; Feng, Wei-yue

    2014-04-01

    The impact of the gut microbiota on human health is widely perceived as the most exciting advancement in biomedicine. The gut microbiota has been known to play a crucial role in defining states of human health and diseases, and thus becomes a potential new territory for drug targeting. Herein, graphene oxide (GO) interaction with five common human gut bacteria, B. adolescentis, L. acidophilus, E. coli, E. faecalis, and S. aureus, was studied. It was shown that, in bacterial media, GO sheets were able to form effective, anaerobic membrane scaffolds that enhanced the antagonistic activity of B. adolescentis against the pathogens E. coli andS. aureus. Data obtained using bacterial growth measurements, colony counting and 16S rRNA gene sequencing consistently indicated that GO sheets promoted proliferation of gut bacteria, particularly for B. adolescentis. Scanning electron microscopy, atomic force microscopy images, and membrane potential measurements showed that cell membranes maintained their integrity and that no observable variations in cell morphology were induced after interaction with GO sheets, indicating good biocompatibility of GO. These results suggest the possibility of using GO sheets as efficient drug carriers in therapeutic applications to treat diseases related to the gut microbiota.

  20. Preparation and Characterization of Graphene Oxide Paper

    SciTech Connect

    Dikin,D.; Stankovich, S.; Zimney, E.; Piner, R.; Dommett, G.; Evmenenko, G.; Nguyen, S.; Ruoff, R.

    2007-01-01

    Free-standing paper-like or foil-like materials are an integral part of our technological society. Their uses include protective layers, chemical filters, components of electrical batteries or supercapacitors, adhesive layers, electronic or optoelectronic components, and molecular storage. Inorganic 'paper-like' materials based on nanoscale components such as exfoliated vermiculite or mica platelets have been intensively studied and commercialized as protective coatings, high-temperature binders, dielectric barriers and gas-impermeable membranes. Carbon-based flexible graphite foils composed of stacked platelets of expanded graphite have long been used in packing and gasketing applications because of their chemical resistivity against most media, superior sealability over a wide temperature range, and impermeability to fluids. The discovery of carbon nanotubes brought about bucky paper, which displays excellent mechanical and electrical properties that make it potentially suitable for fuel cell and structural composite applications. Here we report the preparation and characterization of graphene oxide paper, a free-standing carbon-based membrane material made by flow-directed assembly of individual graphene oxide sheets. This new material outperforms many other paper-like materials in stiffness and strength. Its combination of macroscopic flexibility and stiffness is a result of a unique interlocking-tile arrangement of the nanoscale graphene oxide sheets.

  1. Multilayer Nanoporous Graphene Membranes for Water Desalination.

    PubMed

    Cohen-Tanugi, David; Lin, Li-Chiang; Grossman, Jeffrey C

    2016-02-10

    While single-layer nanoporous graphene (NPG) has shown promise as a reverse osmosis (RO) desalination membrane, multilayer graphene membranes can be synthesized more economically than the single-layer material. In this work, we build upon the knowledge gained to date toward single-layer graphene to explore how multilayer NPG might serve as a RO membrane in water desalination using classical molecular dynamic simulations. We show that, while multilayer NPG exhibits similarly promising desalination properties to single-layer membranes, their separation performance can be designed by manipulating various configurational variables in the multilayer case. This work establishes an atomic-level understanding of the effects of additional NPG layers, layer separation, and pore alignment on desalination performance, providing useful guidelines for the design of multilayer NPG membranes.

  2. Ultrafast graphene oxide humidity sensors.

    PubMed

    Borini, Stefano; White, Richard; Wei, Di; Astley, Michael; Haque, Samiul; Spigone, Elisabetta; Harris, Nadine; Kivioja, Jani; Ryhänen, Tapani

    2013-12-23

    Sensors allow an electronic device to become a gateway between the digital and physical worlds, and sensor materials with unprecedented performance can create new applications and new avenues for user interaction. Graphene oxide can be exploited in humidity and temperature sensors with a number of convenient features such as flexibility, transparency and suitability for large-scale manufacturing. Here we show that the two-dimensional nature of graphene oxide and its superpermeability to water combine to enable humidity sensors with unprecedented response speed (∼30 ms response and recovery times). This opens the door to various applications, such as touchless user interfaces, which we demonstrate with a 'whistling' recognition analysis.

  3. Mesoporous metal oxide graphene nanocomposite materials

    DOEpatents

    Liu, Jun; Aksay, Ilhan A.; Kou, Rong; Wang, Donghai

    2016-05-24

    A nanocomposite material formed of graphene and a mesoporous metal oxide having a demonstrated specific capacity of more than 200 F/g with particular utility when employed in supercapacitor applications. A method for making these nanocomposite materials by first forming a mixture of graphene, a surfactant, and a metal oxide precursor, precipitating the metal oxide precursor with the surfactant from the mixture to form a mesoporous metal oxide. The mesoporous metal oxide is then deposited onto a surface of the graphene.

  4. Graphene as a prototype crystalline membrane.

    PubMed

    Katsnelson, Mikhail I; Fasolino, Annalisa

    2013-01-15

    The understanding of the structural and thermal properties of membranes, low-dimensional flexible systems in a space of higher dimension, is pursued in many fields from string theory to chemistry and biology. The case of a two-dimensional (2D) membrane in three dimensions is the relevant one for dealing with real materials. Traditionally, membranes are primarily discussed in the context of biological membranes and soft matter in general. The complexity of these systems hindered a realistic description of their interatomic structures based on a truly microscopic approach. Therefore, theories of membranes were developed mostly within phenomenological models. From the point of view of statistical mechanics, membranes at finite temperature are systems governed by interacting long-range fluctuations. Graphene, the first truly two-dimensional system consisting of just one layer of carbon atoms, provides a model system for the development of a microscopic description of membranes. In the same way that geneticists have used Drosophila as a gateway to probe more complex questions, theoretical chemists and physicists can use graphene as a simple model membrane to study both phenomenological theories and experiments. In this Account, we review key results in the microscopic theory of structural and thermal properties of graphene and compare them with the predictions of phenomenological theories. The two approaches are in good agreement for the various scaling properties of correlation functions of atomic displacements. However, some other properties, such as the temperature dependence of the bending rigidity, cannot be understood based on phenomenological approaches. We also consider graphene at very high temperature and compare the results with existing models for two-dimensional melting. The melting of graphene presents a different scenario, and we describe that process as the decomposition of the graphene layer into entangled carbon chains.

  5. Synthesizing High-Quality Graphene Membranes for Engineering Diffusion Barriers

    NASA Astrophysics Data System (ADS)

    Singha Roy, Susmit

    We demonstrate significant advances in the fundamental understanding and engineering of scalable graphene diffusion barriers. Experimental studies have established that defect-free non-scalable graphene is an excellent barrier material, however its scalable counterparts are still well behind in terms of performance. The latter's ability to perform as a barrier membrane is compromised primarily by the presence of three major problems - high density of defects, self-degradation in ambient environment and induced electrochemical oxidation of the underlying material. First, we develop an in-depth understanding of how diffusion occurs through monolayer graphene grown via chemical vapor deposition. It is shown that the atomic membrane is impenetrable in the pristine regions, however it is easily penetrated by oxygen and water at grain boundaries and intrinsic pinholes. Second, we study in detail the self-deterioration of graphene in ambient and quantify the evolution, kinetics, and energetics of the degradation process both in the pristine and intrinsically defective regions of graphene. It is also found that the degradation process is accelerated in the presence of water vapor. Third, we find that the overall defect density of a graphene membrane is primarily determined by the density of its intrinsic pinholes and grain boundaries. We demonstrate that the density on intrinsic pinholes can be significantly reduced by reducing the surface roughness of the growth substrate which is achieved by regulating the pre-growth annealing time and temperature. The density of the grain boundaries can be altered by varying the internucleation distance during the growth of the membrane. Fourth, when graphene is used as a corrosion barrier for metals, we establish that the electrochemical corrosion of the metal can be drastically reduced by adding an ultra-thin electrically insulating layer between the graphene and the metal. In addition, the barrier performance is enhanced greatly by

  6. Electrospun polyethylene terephthalate/graphene oxide nanofibrous membrane followed by HPLC for the separation and determination of tamoxifen in human blood plasma.

    PubMed

    Sereshti, Hassan; Bakhtiari, Sadjad; Najarzadekan, Hamid; Samadi, Soheila

    2017-09-01

    An electrospun polyethylene terephthalate/graphene oxide nanofibrous mat was fabricated and used as an effective and novel membrane for the solid-phase extraction of tamoxifen in human blood plasma samples before detection by high-performance liquid chromatography. The membrane was characterized by some identification techniques, such as FTIR spectroscopy, X-ray diffraction, and scanning electron microscopy. The effective variables of the extraction procedure including desorption condition (type and volume of the eluent), adsorbent dose, pH of sample solution, salt concentration, and sample loading time were investigated and their optimum values were obtained using one factor at a time methodology. Under the optimized conditions, the results showed wide linear concentration range of 5-2000 ng/mL with a determination coefficient of 0.992. The limits of detection and limits of quantification were 1.3 and 5.0 ng/mL, respectively. The intra-day and inter-day precisions were 3.4 and 4.6%, respectively. The method was successfully applied to determination of tamoxifen in the blood plasma samples and satisfactory relative recoveries (92.6-98.3 %) were achieved. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Porous graphene-based membranes for water purification from metal ions at low differential pressures

    NASA Astrophysics Data System (ADS)

    Park, Jaewoo; Bazylewski, Paul; Fanchini, Giovanni

    2016-05-01

    A new generation of membranes for water purification based on weakly oxidized and nanoporous few-layer graphene is here introduced. These membranes dramatically decrease the high energy requirements of water purification by reverse osmosis. They combine the advantages of porous and non-oxidized single-layer graphene, offering energy-efficient water filtration at relatively low differential pressures, and highly oxidized graphene oxide, exhibiting high performance in terms of impurity adsorption. In the reported fabrication process, leaks between juxtaposed few-layer graphene flakes are sealed by thermally annealed colloidal silica, in a treatment that precedes the opening of (sub)nanometre-size pores in graphene. This process, explored for the first time in this work, results in nanoporous graphene flakes that are water-tight at the edges without occluding the (sub)nanopores. With this method, removal of impurities from water occurs through a combination of size-based pore rejection and pore-edge adsorption. Thinness of graphene flakes allows these membranes to achieve water purification from metal ions in concentrations of few parts-per-million at differential pressures as low as 30 kPa, outperforming existing graphene or graphene oxide purification systems with comparable flow rates.

  8. Graphene Oxide and Thermally Exfoliated Graphene Cyanate Ester Resin Composites

    DTIC Science & Technology

    2013-05-01

    depending on the method of isolation from graphite and subsequent chemical and thermal treatments. Two forms of graphene, graphene oxide and thermally...The morphology, surface chemical functionality and thermal properties of graphene vary depending on the method of isolation from graphite and...chemical vapor deposition (CVD) 5 and epitaxial growth 6 ) and top-down (micromechanical cleavage 7 and graphite oxidation 8 , 9 ) methods . Bottom-up

  9. Low levels of graphene and graphene oxide inhibit cellular xenobiotic defense system mediated by efflux transporters.

    PubMed

    Liu, Su; Jiang, Wei; Wu, Bing; Yu, Jing; Yu, Haiyan; Zhang, Xu-Xiang; Torres-Duarte, Cristina; Cherr, Gary N

    2016-01-01

    Low levels of graphene and graphene oxide (GO) are considered to be environmentally safe. In this study, we analyzed the potential effects of graphene and GO at relatively low concentrations on cellular xenobiotic defense system mediated by efflux transporters. The results showed that graphene (<0.5 μg/mL) and GO (<20 μg/mL) did not decrease cell viability, generate reactive oxygen species, or disrupt mitochondrial function. However, graphene and GO at the nontoxic concentrations could increase calcein-AM (CAM, an indicator of membrane ATP-binding cassette (ABC) transporter) activity) accumulation, indicating inhibition of ABC transporters' efflux capabilities. This inhibition was observed even at 0.005 μg/mL graphene and 0.05 μg/mL GO, which are 100 times and 400 times lower than their lowest toxic concentration from cytotoxicity experiments, respectively. The inhibition of ABC transporters significantly increased the toxicity of paraquat and arsenic, known substrates of ABC transporters. The inhibition of ABC transporters was found to be based on graphene and GO damaging the plasma membrane structure and fluidity, thus altering functions of transmembrane ABC transporters. This study demonstrates that low levels of graphene and GO are not environmentally safe since they can significantly make cell more susceptible to other xenobiotics, and this chemosensitizing activity should be considered in the risk assessment of graphene and GO.

  10. Radio-frequency characteristics of graphene oxide

    NASA Astrophysics Data System (ADS)

    Kim, Whan Kyun; Jung, Young Mo; Cho, Joon Hyong; Kang, Ji Yoong; Oh, Ju Yeong; Kang, Hosung; Lee, Hee-Jo; Kim, Jae Hun; Lee, Seok; Shin, H. J.; Choi, J. Y.; Lee, S. Y.; Kim, Y. C.; Han, I. T.; Kim, J. M.; Yook, Jong-Gwan; Baik, Seunghyun; Jun, Seong Chan

    2010-11-01

    We confirm graphene oxide, a two-dimensional carbon structure at the nanoscale level can be a strong candidate for high-efficient interconnector in radio-frequency range. In this paper, we investigate high frequency characteristics of graphene oxide in range of 0.5-40 GHz. Radio-frequency transmission properties were extracted as S-parameters to determine the intrinsic ac transmission of graphene sheets, such as the impedance variation dependence on frequency. The impedance and resistance of graphene sheets drastically decrease as frequency increases. This result confirms graphene oxide has high potential for transmitting signals at gigahertz ranges.

  11. Anomalous Dynamical Behavior of Freestanding Graphene Membranes

    NASA Astrophysics Data System (ADS)

    Ackerman, M. L.; Kumar, P.; Neek-Amal, M.; Thibado, P. M.; Peeters, F. M.; Singh, Surendra

    2016-09-01

    We report subnanometer, high-bandwidth measurements of the out-of-plane (vertical) motion of atoms in freestanding graphene using scanning tunneling microscopy. By tracking the vertical position over a long time period, a 1000-fold increase in the ability to measure space-time dynamics of atomically thin membranes is achieved over the current state-of-the-art imaging technologies. We observe that the vertical motion of a graphene membrane exhibits rare long-scale excursions characterized by both anomalous mean-squared displacements and Cauchy-Lorentz power law jump distributions.

  12. Electromechanical piezoresistive sensing in suspended graphene membranes.

    PubMed

    Smith, A D; Niklaus, F; Paussa, A; Vaziri, S; Fischer, A C; Sterner, M; Forsberg, F; Delin, A; Esseni, D; Palestri, P; Östling, M; Lemme, M C

    2013-07-10

    Monolayer graphene exhibits exceptional electronic and mechanical properties, making it a very promising material for nanoelectromechanical devices. Here, we conclusively demonstrate the piezoresistive effect in graphene in a nanoelectromechanical membrane configuration that provides direct electrical readout of pressure to strain transduction. This makes it highly relevant for an important class of nanoelectromechanical system (NEMS) transducers. This demonstration is consistent with our simulations and previously reported gauge factors and simulation values. The membrane in our experiment acts as a strain gauge independent of crystallographic orientation and allows for aggressive size scalability. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity per unit area.

  13. Electronic structure of graphene oxide and reduced graphene oxide monolayers

    SciTech Connect

    Sutar, D. S.; Singh, Gulbagh; Divakar Botcha, V.

    2012-09-03

    Graphene oxide (GO) monolayers obtained by Langmuir Blodgett route and suitably treated to obtain reduced graphene oxide (RGO) monolayers were studied by photoelectron spectroscopy. Upon reduction of GO to form RGO C1s x-ray photoelectron spectra showed increase in graphitic carbon content, while ultraviolet photoelectron spectra showed increase in intensity corresponding to C2p-{pi} electrons ({approx}3.5 eV). X-ray excited Auger transitions C(KVV) and plasmon energy loss of C1s photoelectrons have been analyzed to elucidate the valence band structure. The effective number of ({pi}+{sigma}) electrons as obtained from energy loss spectra was found to increase by {approx}28% on reduction of GO.

  14. A review of recent advances in molecular simulation of graphene-derived membranes for gas separation

    NASA Astrophysics Data System (ADS)

    Fatemi, Seyyed Mahmood; Abbasi, Zeynab; Rajabzadeh, Halimeh; Hashemizadeh, Seyyed Ali; Deldar, Amir Noori

    2017-07-01

    To obtain an ideal membrane for gas separation the following three characteristics should be considered: the membrane should be as thin as possible, be mechanically robust, and have well-defined pore sizes. These features will maximize its solvent flux, preserve it from fracture, and guarantee its selectivity. These attractive properties of graphene-derived membranes introduce them as appropriate candidates for gas separation and gas molecular-sieving processes in nanoscale dimensions. The current effort has focused on two issues, including the review of the most newly progression on drilling holes in single graphene membranes for making ultrathin membranes for gas separation, and studying functionalized nanoporous sheet and graphene-derived membranes, including doped graphene, graphene oxide, fluorographene, and reduced graphene oxide from theoretical perspectives for making functional coatings for nano ultrafiltration for gas separation. We investigated the basic mechanism of separation by membranes derived from graphene and relevant possible applications. Functionalized nanoporous membranes as novel approach are characterized by low energy cost in realizing high throughput molecular-sieving separation.

  15. Measuring the proton selectivity of graphene membranes

    SciTech Connect

    Walker, Michael I.; Keyser, Ulrich F.; Braeuninger-Weimer, Philipp; Weatherup, Robert S.; Hofmann, Stephan

    2015-11-23

    By systematically studying the proton selectivity of free-standing graphene membranes in aqueous solutions, we demonstrate that protons are transported by passing through defects. We study the current-voltage characteristics of single-layer graphene grown by chemical vapour deposition (CVD) when a concentration gradient of HCl exists across it. Our measurements can unambiguously determine that H{sup +} ions are responsible for the selective part of the ionic current. By comparing the observed reversal potentials with positive and negative controls, we demonstrate that the as-grown graphene is only weakly selective for protons. We use atomic layer deposition to block most of the defects in our CVD graphene. Our results show that a reduction in defect size decreases the ionic current but increases proton selectivity.

  16. Graphene Oxides Show Angiogenic Properties.

    PubMed

    Mukherjee, Sudip; Sriram, Pavithra; Barui, Ayan Kumar; Nethi, Susheel Kumar; Veeriah, Vimal; Chatterjee, Suvro; Suresh, Kattimuttathu Ittara; Patra, Chitta Ranjan

    2015-08-05

    Angiogenesis, a process resulting in the formation of new capillaries from the pre-existing vasculature plays vital role for the development of therapeutic approaches for cancer, atherosclerosis, wound healing, and cardiovascular diseases. In this report, the synthesis, characterization, and angiogenic properties of graphene oxide (GO) and reduced graphene oxide (rGO) have been demonstrated, observed through several in vitro and in vivo angiogenesis assays. The results here demonstrate that the intracellular formation of reactive oxygen species and reactive nitrogen species as well as activation of phospho-eNOS and phospho-Akt might be the plausible mechanisms for GO and rGO induced angiogenesis. The results altogether suggest the possibilities for the development of alternative angiogenic therapeutic approach for the treatment of cardiovascular related diseases where angiogenesis plays a significant role.

  17. Synthesis and characterization of exfoliated graphene oxide

    NASA Astrophysics Data System (ADS)

    Muhamad, Ku Sarah Syahidah Ku; Mohamed, Faizal; Radiman, Shahidan; Hamzah, Ainon; Sarmani, Sukiman; Siong, Khoo Kok; Yasir, Muhammad Samudi; Rahman, Irman Abdul; Rosli, Nur Ratasha Alia Md.

    2016-11-01

    Graphene oxide has many applications such as in electronic devices, as storage energy device, biosensor, biomedical application, water purification, coating technology, as a composite and paper like materials. Hummer's method is one of the most common methods used in synthesizing graphene oxide. Graphene is different in size and structure because of oxidized layered of graphene oxide hence, the expanded interlayer structure of graphene oxide can be easily exfoliated by ultrasonication. We report on the preparation of exfoliated graphene oxide by using sonication method. Ultraviolet-visible spectrometer (UV-Vis) and Fourier-Transform Infrared Spectra Analyzer (FTIR) were used to characterize the exfoliated graphite oxide. Exfoliation of graphite oxide is conducted using water bath sonication. In order to confirm the chemical conformation and structure of the produced graphene oxide, FTIR and UV-Vis spectroscopy were utilized. Both peak of C=O and C-C bond are detected using UV-Vis and the results were confirmed using FTIR. Therefore, from this study, it can be concluded based on FTIR and UV-Vis spectral acquisition that graphene oxide can be produced by exfoliation of graphite oxide using water bath sonication.

  18. Graphene-graphene oxide floating gate transistor memory.

    PubMed

    Jang, Sukjae; Hwang, Euyheon; Lee, Jung Heon; Park, Ho Seok; Cho, Jeong Ho

    2015-01-21

    A novel transparent, flexible, graphene channel floating-gate transistor memory (FGTM) device is fabricated using a graphene oxide (GO) charge trapping layer on a plastic substrate. The GO layer, which bears ammonium groups (NH3+), is prepared at the interface between the crosslinked PVP (cPVP) tunneling dielectric and the Al2 O3 blocking dielectric layers. Important design rules are proposed for a high-performance graphene memory device: (i) precise doping of the graphene channel, and (ii) chemical functionalization of the GO charge trapping layer. How to control memory characteristics by graphene doping is systematically explained, and the optimal conditions for the best performance of the memory devices are found. Note that precise control over the doping of the graphene channel maximizes the conductance difference at a zero gate voltage, which reduces the device power consumption. The proposed optimization via graphene doping can be applied to any graphene channel transistor-type memory device. Additionally, the positively charged GO (GO-NH3+) interacts electrostatically with hydroxyl groups of both UV-treated Al2 O3 and PVP layers, which enhances the interfacial adhesion, and thus the mechanical stability of the device during bending. The resulting graphene-graphene oxide FGTMs exhibit excellent memory characteristics, including a large memory window (11.7 V), fast switching speed (1 μs), cyclic endurance (200 cycles), stable retention (10(5) s), and good mechanical stability (1000 cycles).

  19. Combination of graphene oxide-based solid phase extraction and electro membrane extraction for the preconcentration of chlorophenoxy acid herbicides in environmental samples.

    PubMed

    Tabani, Hadi; Fakhari, Ali Reza; Shahsavani, Abolfath; Behbahani, Mohammad; Salarian, Mani; Bagheri, Akbar; Nojavan, Saeed

    2013-07-26

    Combination of different extraction methods is an interesting and debatable work in the field of sample preparation. In the current study, for the first time, solid phase extraction combined with electro membrane extraction (SPE-EME) was developed for ultra-preconcentration and determination of chlorophenoxy acid herbicides in environmental samples using capillary electrophoresis (CE). In the mentioned method, first, a 100mL of chlorophenoxy acid herbicides (2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and 2-(4-chloro-2-methylphenoxy) propanoic acid (MCPP)) was passed through a column of graphene oxide as a solid phase, and then the adsorbed herbicides were eluted by 4.0mL of 8% acetic acid (HOAC) in methanol. Then, the elution solvent was evaporated and the herbicides residue was dissolved in 4.0mL of double distilled water (pH 9.0). Afterwards, the herbicides in 4.0mL of the aqueous solution were transferred to an EME glass vial. In the EME step, the herbicides were extracted from the sample solution into the basic acceptor solution (pH 13.0) under electrical potential, which was held inside the lumen of the fiber with 1-octanol as the supported liquid membrane (SLM). Under the optimized conditions, high enrichment factors were obtained in the range of 1950-2000. The limits of quantification (LOQs) and method detection limits (MDLs) were obtained in the range of 1.0-1.5 and 0.3-0.5ngmL(-1), respectively. Finally, the performance of the present method was evaluated for extraction and determination of chlorophenoxy acid herbicides in environmental samples.

  20. Tunable water desalination across Graphene Oxide Frameworks

    NASA Astrophysics Data System (ADS)

    Nicolai, Adrien; Meunier, Vincent

    2014-03-01

    ``Water, water, everywhere, nor any drop to drink.'' wrote Samuel Taylor Coleridge in 1798. Today's scientific advances in water desalination promise to change the second part of the sentence into ``and every drop to drink,'' by transforming sea water into fresh water and quench the thirst of 1.2B people facing shortages of water. To achieve this, the design of nanoporous materials with high water permeability and coupled with high salt rejection capacity is crucial. Graphene Oxide Frameworks (GOF) materials are a class of porous materials consisting of layers of graphene oxide sheets interconnected by linear boronic acid linkers. Water desalination across GOF is studied using classical Molecular Dynamics simulations. We used quantum mechanically obtained boron-related force field parameters to study the diffusion of water molecules inside bulk GOF. Properties, such as the self-diffusion coefficient of water molecules increases linearly with linker concentration n. Further, the desalination performance of GOF membranes reveals that the water permeability of GOF is several orders of magnitude higher than conventional membranes and an high water permeability can be coupled with a 100% efficiency of salt rejection by choosing the appropriate concentration n and thickness h.

  1. Liquid separation by a graphene membrane

    NASA Astrophysics Data System (ADS)

    Fileti, E. E.; Dalpian, G. M.; Rivelino, R.

    2010-12-01

    The behavior of liquids separated by a single graphene membrane has been studied with extensive molecular dynamics (MD) simulations at ambient conditions. With the help of appropriate empirical potentials, we have exploited two liquid phases forming distinct systems; say XGY, where G stands for graphene and X (Y) represents water (W), benzene (B), or acetonitrile (A). Our MD simulations revealed important changes in the wettability patterns of these liquids near the graphene surface. For instance, WGW exhibits strong density oscillations in a thin interfacial region with thickness of ˜2.4 nm. In the case of BGB and AGA the oscillating-density interfacial region extends beyond ˜3 nm and ˜5 nm, respectively, under ambient conditions. More interestingly, our findings indicate that a liquid at one side of the graphene sheet can affect the degree of wetting on the other side, by means of dispersion interactions through the graphene membrane. These systems can offer a useful framework to understand the structural as well as thermodynamic properties of interfaces by considering a real two-dimensional substrate.

  2. Graphene coatings: An efficient protection from oxidation

    NASA Astrophysics Data System (ADS)

    Topsakal, Mehmet; Sahin, Hasan; Ciraci, Salim

    2012-02-01

    We demonstrate that graphene coating can provide an efficient protection from oxidation by posing a high energy barrier to the path of oxygen atom, which could have penetrated from the top of graphene to the reactive surface underneath. Graphene bilayer, which blocks the diffusion of oxygen with a relatively higher energy barrier provides even better protection from oxidation. While an oxygen molecule is weakly bound to bare graphene surface and hence becomes rather inactive, it can easily dissociates into two oxygen atoms adsorbed to low coordinated carbon atoms at the edges of a vacancy. For these oxygen atoms the oxidation barrier is reduced and hence the protection from oxidation provided by graphene coatings is weakened. Our predictions obtained from the state of the art first-principles calculations of electronic structure, phonon density of states and reaction path will unravel how a graphene can be used as a corrosion resistant coating and guide further studies aiming at developing more efficient nanocoating materials.

  3. Synthesis and characterizations of graphene oxide and reduced graphene oxide nanosheets

    SciTech Connect

    Venkanna, M. Chakraborty, Amit K.

    2014-04-24

    Interest in graphene on its excellent mechanical, electrical, thermal and optical properties, it’s very high specific surface area, and our ability to influence these properties through chemical functionalization. Chemical reduction of graphene oxide is one of the main routes of preparation for large quantities of graphenes. Hydrazine hydrate used as reducing agent to prepare for the reduced graphene oxide (RGO). There are a number of methods for generating graphene and chemically modified graphene from natural graphite flakes, graphite derivative (such as graphite oxide) and graphite interaction compounds (i.e. expandable graphite). Here we review the use of colloidal suspensions of reduced graphene oxide (RGO) with large scalable, and is adaptable to a wide variety of applications. The graphene oxide (GO) and the reduced material (RGO) were characterized by XRD, UV-Vis spectroscopy, Thermo-gravimetric analysis (TGA), Raman spectroscopy and Field emission Scanning electron microscopy (FESEM) etc.

  4. In vitro and in vivo effects of graphene oxide and reduced graphene oxide on glioblastoma.

    PubMed

    Jaworski, Sławomir; Sawosz, Ewa; Kutwin, Marta; Wierzbicki, Mateusz; Hinzmann, Mateusz; Grodzik, Marta; Winnicka, Anna; Lipińska, Ludwika; Włodyga, Karolina; Chwalibog, Andrè

    2015-01-01

    Graphene and its related counterparts are considered the future of advanced nanomaterials owing to their exemplary properties. However, information about their toxicity and biocompatibility is limited. The objective of this study is to evaluate the toxicity of graphene oxide (GO) and reduced graphene oxide (rGO) platelets, using U87 and U118 glioma cell lines for an in vitro model and U87 tumors cultured on chicken embryo chorioallantoic membrane for an in vivo model. The in vitro investigation consisted of structural analysis of GO and rGO platelets using transmission electron microscopy, evaluation of cell morphology and ultrastructure, assessment of cell viability by XTT assay, and investigation of cell proliferation by BrdU assay. Toxicity in U87 glioma tumors was evaluated by calculation of weight and volume of tumors and analyses of ultrastructure, histology, and protein expression. The in vitro results indicate that GO and rGO enter glioma cells and have different cytotoxicity. Both types of platelets reduced cell viability and proliferation with increasing doses, but rGO was more toxic than GO. The mass and volume of tumors were reduced in vivo after injection of GO and rGO. Moreover, the level of apoptotic markers increased in rGO-treated tumors. We show that rGO induces cell death mostly through apoptosis, indicating the potential applicability of graphene in cancer therapy.

  5. In vitro and in vivo effects of graphene oxide and reduced graphene oxide on glioblastoma

    PubMed Central

    Jaworski, Sławomir; Sawosz, Ewa; Kutwin, Marta; Wierzbicki, Mateusz; Hinzmann, Mateusz; Grodzik, Marta; Winnicka, Anna; Lipińska, Ludwika; Włodyga, Karolina; Chwalibog, Andrè

    2015-01-01

    Graphene and its related counterparts are considered the future of advanced nanomaterials owing to their exemplary properties. However, information about their toxicity and biocompatibility is limited. The objective of this study is to evaluate the toxicity of graphene oxide (GO) and reduced graphene oxide (rGO) platelets, using U87 and U118 glioma cell lines for an in vitro model and U87 tumors cultured on chicken embryo chorioallantoic membrane for an in vivo model. The in vitro investigation consisted of structural analysis of GO and rGO platelets using transmission elec tron microscopy, evaluation of cell morphology and ultrastructure, assessment of cell viability by XTT assay, and investigation of cell proliferation by BrdU assay. Toxicity in U87 glioma tumors was evaluated by calculation of weight and volume of tumors and analyses of ultrastructure, histology, and protein expression. The in vitro results indicate that GO and rGO enter glioma cells and have different cytotoxicity. Both types of platelets reduced cell viability and proliferation with increasing doses, but rGO was more toxic than GO. The mass and volume of tumors were reduced in vivo after injection of GO and rGO. Moreover, the level of apoptotic markers increased in rGO-treated tumors. We show that rGO induces cell death mostly through apoptosis, indicating the potential applicability of graphene in cancer therapy. PMID:25759581

  6. Graphene membrane as a pressure gauge

    NASA Astrophysics Data System (ADS)

    Milovanović, S. P.; Tadić, M. Ž.; Peeters, F. M.

    2017-07-01

    Straining graphene results in the appearance of a pseudo-magnetic field which alters its local electronic properties. Applying a pressure difference between the two sides of the membrane causes it to bend/bulge resulting in a resistance change. We find that the resistance changes linearly with pressure for bubbles of small radius while the response becomes non-linear for bubbles that stretch almost to the edges of the sample. This is explained as due to the strong interference of propagating electronic modes inside the bubble. Our calculations show that high gauge factors can be obtained in this way which makes graphene a good candidate for pressure sensing.

  7. Twist-boat conformation in graphene oxides.

    PubMed

    Samarakoon, Duminda K; Wang, Xiao-Qian

    2011-01-01

    We have investigated the structural, electronic, and vibrational properties of graphene oxide based on first-principles density-functional calculations. A twist-boat conformation is identified as the energetically most favorable nonmetallic configuration for fully oxidized graphene. The calculated Raman G-band blue shift is in very good agreement with experimental observations. Our results provide important insight into structural and electronic characteristics that are useful for further development of graphene-based nanodevices.

  8. Graphene oxide reduction by microwave heating

    SciTech Connect

    Longo, Angela; Carotenuto, Gianfranco

    2016-05-18

    The possibility to prepare thermal reduced graphene oxide (Tr-GO) colloidal suspensions by microwave heating of graphene oxide (GO) suspensions in N-methyl-2-pyrrolidone (NMP) has been investigated. According to transmission electron microscopy (TEM) and absorption and emission spectroscopy characterization, such a type of thermal reduction does not lead to graphene quantum dots formation because only mono-functional oxygen-containing groups are removed.

  9. Nanocomposite of graphene and metal oxide materials

    DOEpatents

    Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

    2013-10-15

    Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10 C.

  10. Nanocomposite of graphene and metal oxide materials

    DOEpatents

    Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

    2012-09-04

    Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10C.

  11. Nanocomposite of graphene and metal oxide materials

    DOEpatents

    Liu, Jun; Aksay, Ilhan A.; Choi, Daiwon; Wang, Donghai; Yang, Zhenguo

    2015-06-30

    Nanocomposite materials comprising a metal oxide bonded to at least one graphene material. The nanocomposite materials exhibit a specific capacity of at least twice that of the metal oxide material without the graphene at a charge/discharge rate greater than about 10 C.

  12. Fluorescent biosensors enabled by graphene and graphene oxide.

    PubMed

    Zhang, Huan; Zhang, Honglu; Aldalbahi, Ali; Zuo, Xiaolei; Fan, Chunhai; Mi, Xianqiang

    2017-03-15

    During the past few years, graphene and graphene oxide (GO) have attracted numerous attentions for the potential applications in various fields from energy technology, biosensing to biomedical diagnosis and therapy due to their various functionalization, high volume surface ratio, unique physical and electrical properties. Among which, graphene and graphene oxide based fluorescent biosensors enabled by their fluorescence-quenching properties have attracted great interests. The fluorescence of fluorophore or dye labeled on probes (such as molecular beacon, aptamer, DNAzymes and so on) was quenched after adsorbed on to the surface of graphene. While in the present of the targets, due to the strong interactions between probes and targets, the probes were detached from the surface of graphene, generating dramatic fluorescence, which could be used as signals for detection of the targets. This strategy was simple and economy, together with great programmable abilities of probes; we could realize detection of different kinds of species. In this review, we first briefly introduced the history of graphene and graphene oxide, and then summarized the fluorescent biosensors enabled by graphene and GO, with a detailed account of the design mechanism and comparison with other nanomaterials (e.g. carbon nanotubes and gold nanoparticles). Following that, different sensing platforms for detection of DNAs, ions, biomolecules and pathogens or cells as well as the cytotoxicity issue of graphene and GO based in vivo biosensing were further discussed. We hope that this review would do some help to researchers who are interested in graphene related biosening research work. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Consecutive evaluation of graphene oxide and reduced graphene oxide nanoplatelets immunotoxicity on monocytes.

    PubMed

    Yan, Junyan; Chen, Liliang; Huang, Chih-Ching; Lung, Shih-Chun Candice; Yang, Lingyan; Wang, Wen-Cheng; Lin, Po-Hsiung; Suo, Guangli; Lin, Chia-Hua

    2017-05-01

    The biocompatibilities of graphene-family nanomaterials (GFNs) should be thoroughly evaluated before their application in drug delivery and anticancer therapy. The present study aimed to consecutively assess the immunotoxicity of graphene oxide nanoplatelets (GONPs) and reduced GONPs (rGONPs) on THP-1 cells, a human acute monocytic leukemia cell line. GONPs induced the expression of antioxidative enzymes and inflammatory factors, whereas rGONPs had substantially higher cellular uptake rate, higher levels of NF-κB expression. These distinct toxic mechanisms were observed because the two nanomaterials differ in their oxidation state, which imparts different affinities for the cell membrane. Because GONPs have a higher cell membrane affinity and higher impact on membrane proteins compared with rGONPs, macrophages (THP-1a) derived from GONPs treated THP-1cells showed a severer effect on phagocytosis. By consecutive evaluation the effects of GONPs and rGONPs on THP-1 and THP-1a, we demonstrated that their surface oxidation states may cause GFNs to behave differently and cause different immunotoxic effects. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Capillary zone electrophoresis of graphene oxide and chemically converted graphene.

    PubMed

    Müller, Marc B; Quirino, Joselito P; Nesterenko, Pavel N; Haddad, Paul R; Gambhir, Sanjeev; Li, Dan; Wallace, Gordon G

    2010-11-26

    The preparation of processable graphene oxide colloids called chemically converted graphene (CCG) involves the following steps: oxidation of graphite to form graphite oxide; exfoliation of graphite oxide to form graphene oxide (GO); and reduction of GO to form CCG. In this work, the exfoliation and reduction steps were monitored by capillary zone electrophoresis (CZE). CZE was performed in fused silica capillaries with UV absorbance at 230 nm (GO) and 270 nm (CCG) using 250 μM tetrapropylammonium hydroxide (pH 10.4). The results indicate that almost complete exfoliation of graphite oxide (0.05 wt%) and higher recovery of CCG were obtained by sonication at 50% power for more than 15 h. CZE is considered a valuable tool for the fractionation and analysis of GO nanoparticles and, hence, for the control of different steps in preparation of CCG. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

  15. Incorporation of Graphene-Related Carbon Nanosheets in Membrane Fabrication for Water Treatment: A Review

    PubMed Central

    Lawler, Jenny

    2016-01-01

    The minimization of the trade-off between the flux and the selectivity of membranes is a key area that researchers are continually working to optimise, particularly in the area of fabrication of novel membranes. Flux versus selectivity issues apply in many industrial applications of membranes, for example the unwanted diffusion of methanol in fuel cells, retention of valuable proteins in downstream processing of biopharmaceuticals, rejection of organic matter and micro-organisms in water treatment, or salt permeation in desalination. The incorporation of nanosheets within membrane structures can potentially lead to enhancements in such properties as the antifouling ability, hydrophilicy and permeability of membranes, with concomitant improvements in the flux/selectivity balance. Graphene nanosheets and derivatives such as graphene oxide and reduced graphene oxide have been investigated for this purpose, for example inclusion of nanosheets within the active layer of Reverse Osmosis or Nanofiltration membranes or the blending of nanosheets as fillers within Ultrafiltration membranes. This review summarizes the incorporation of graphene derivatives into polymeric membranes for water treatment with a focus on a number of industrial applications, including desalination and pharmaceutical removal, where enhancement of productivity and reduction in fouling characteristics have been afforded by appropriate incorporation of graphene derived nanosheets during membrane fabrication. PMID:27999364

  16. Incorporation of Graphene-Related Carbon Nanosheets in Membrane Fabrication for Water Treatment: A Review.

    PubMed

    Lawler, Jenny

    2016-12-19

    The minimization of the trade-off between the flux and the selectivity of membranes is a key area that researchers are continually working to optimise, particularly in the area of fabrication of novel membranes. Flux versus selectivity issues apply in many industrial applications of membranes, for example the unwanted diffusion of methanol in fuel cells, retention of valuable proteins in downstream processing of biopharmaceuticals, rejection of organic matter and micro-organisms in water treatment, or salt permeation in desalination. The incorporation of nanosheets within membrane structures can potentially lead to enhancements in such properties as the antifouling ability, hydrophilicy and permeability of membranes, with concomitant improvements in the flux/selectivity balance. Graphene nanosheets and derivatives such as graphene oxide and reduced graphene oxide have been investigated for this purpose, for example inclusion of nanosheets within the active layer of Reverse Osmosis or Nanofiltration membranes or the blending of nanosheets as fillers within Ultrafiltration membranes. This review summarizes the incorporation of graphene derivatives into polymeric membranes for water treatment with a focus on a number of industrial applications, including desalination and pharmaceutical removal, where enhancement of productivity and reduction in fouling characteristics have been afforded by appropriate incorporation of graphene derived nanosheets during membrane fabrication.

  17. Current applications of graphene oxide in nanomedicine

    PubMed Central

    Wu, Si-Ying; An, Seong Soo A; Hulme, John

    2015-01-01

    Graphene has attracted the attention of the entire scientific community due to its unique mechanical and electrochemical, electronic, biomaterial, and chemical properties. The water-soluble derivative of graphene, graphene oxide, is highly prized and continues to be intensely investigated by scientists around the world. This review seeks to provide an overview of the currents applications of graphene oxide in nanomedicine, focusing on delivery systems, tissue engineering, cancer therapies, imaging, and cytotoxicity, together with a short discussion on the difficulties and the trends for future research regarding this amazing material. PMID:26345988

  18. Application of hollow fiber membrane mediated with titanium dioxide nanowire/reduced graphene oxide nanocomposite in preconcentration of clotrimazole and tylosin.

    PubMed

    Sehati, Negar; Dalali, Nasser; Soltanpour, Shahla; Seyed Dorraji, Mir Saeed

    2015-11-13

    In this paper, TiO2 nanowires and TiO2 nanoparticles have been successfully anchored on graphene oxide (GO) nanosheets by a facile one-step hydrothermal method. The synthesized TiO2 NWs/RGO and TiO2 NPs/RGO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. After comparatively studying of the as-made nanocomposites, TiO2 NWs/RGO nanocomposite showed the best adsorbing performance and applied as an attractive efficient sorbent reinforced with microporous hollow fiber membrane through the sol-gel technology. In the following, the selected nanocomposite was utilized for simultaneous preconcentration and determination of clotrimazole and tylosin using high performance liquid chromatography (HPLC)-UV detection, respectively. In order to optimize the extraction conditions through affecting parameters (pH, stirring rate, salt addition, extraction time and volume of donor phase), response surface methodology (RSM) was employed as a powerful statistical technique. Under the optimal conditions, the limit of detection (S/N=3) of proposed HFSPME method, was 0.67 μg L(-1) for clotrimazole and 0.91 μg L(-1) for tylosin with good linear ranges of 1.7-8000.0 μg L(-1) and 4.0-6000.0 μg L(-1). The inter-day and intra-day relative standard deviations (RSD%) at 100 μg L(-1) concentration level were in the ranges of 2.10-3.58% for clotrimazole and 3.45-7.80% for tylosin (n=5), respectively. The proposed microextraction device was extended for determination of ultra trace amounts of target analytes in milk and urine samples with satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Can graphene oxide cause damage to eyesight?

    PubMed

    Yan, Lu; Wang, Yaping; Xu, Xu; Zeng, Chao; Hou, Jiangping; Lin, Mimi; Xu, Jingzhou; Sun, Fei; Huang, Xiaojie; Dai, Liming; Lu, Fan; Liu, Yong

    2012-06-18

    As graphene becomes one of the most exciting candidates for multifunctional biomedical applications, contact between eyes and graphene-based materials is inevitable. On the other hand, eyes, as a special organ in the human body, have unique advantages to be used for testing new biomedical research and development, such as drug delivery. Intraocular biocompatible studies on graphene-related materials are thus essential. Here, we report our recent studies on intraocular biocompatibility and cytotoxicity of graphene oxide (GO) both in vitro and in vivo. The successful preparation of GO nanosheets was confirmed using atomic force microscopy, contact angle analyzer, Fourier transform infrared spectroscopy, and Raman spectroscopy. The influence of GO on human retinal pigment epithelium (RPE) cells in terms of the cell morphology, viability, membrane integrity, and apoptosis was investigated using various techniques, including optical micrography, cell counting kit-8 (CCK-8) assay, lactate dehydrogenase (LDH) assay, and apoptosis assay. The addition of GO had little influence on cell morphology, but the change was visible after long-time culturing. RPE cells showed higher than 60% cell viability by CCK-8 assay in GO solutions and less than 8% LDH release, although a small amount of apoptosis (1.5%) was observed. In vitro results suggested good biocompatibility of GO to RPE cells with slight adverse influence, on the cell viability and morphology in long-time periods, along with aggregation of GO. Thus, some further studies are needed to clarify the cytotoxicity mechanism of GO. GO intravitreally injected eyes showed few changes in eyeball appearance, intraocular pressure (IOP), eyesight, and histological photos. Our results suggested that GO did not cause any significant toxicity to the cell growth and proliferation. Intravitreal injection of GO into rabbits' eyes did not lead to much change in the eyeball appearance, IOP, electroretinogram, and histological examination.

  20. Preparation of nanoporous graphene and the application of its nanocomposite membrane in propylene/propane separation

    NASA Astrophysics Data System (ADS)

    Sun, Hai-Xiang; Yuan, Bing-Bing; Li, Peng; Wang, Tao; Xu, Yan-Yan

    2015-11-01

    Chemically reduced graphene oxide containing hydroxyl groups and a wide size distribution of nanopores was prepared by a facile one-pot hydrothermal method. The resulting material was characterized by transmission electron microscopy (TEM), Raman spectroscopy, surface area measurement and attenuated total reflection infrared spectroscopy (ATR-FTIR), respectively. It was found that this reduced graphene oxide exhibited more clear nanopores and hydroxyl groups in the basal plane. Then the morphologies of the nanocomposite membrane incorporated into the nanoporous graphene were investigated through scanning electron microscopy (SEM), and the permeation test also was performed. Notably, the results showed that the nanocomposite membrane had a homogenous morphology and a better performance (separation factor 11.09) than polymer membrane in the separation of propylene/propane. This work demonstrates that nanoporous graphene exhibits great potential in the field of olefin/paraffin separation.

  1. Reducing agent free synthesis of graphene from graphene oxide

    NASA Astrophysics Data System (ADS)

    Kumar, R. Naresh; Shaikshavali, P.; Srikanth, Vadali V. S. S.; Sankara Rao, K. Bhanu

    2013-06-01

    Graphene is synthesized by microwave irradiation (MWI) of graphene oxide (GO) and subsequent sonication. MWI of GO is carried in a household microwave oven without using any reducing agents. Sonication of microwave irradiated GO is carried out in distilled water using a probe type sonicator. This method does not evolve any unsafe by-product gases which is otherwise the case when reducing agents are used in the reduction of GO to graphene. Moreover, due to its intrinsic nature, the method is scalable and cost effective. The synthesized product has been characterized as graphene using micro Raman scattering, x-ray diffraction and electron diffraction. Diffraction results show that the synthesized graphene is highly oriented.

  2. Star polymer unimicelles on graphene oxide flakes.

    PubMed

    Choi, Ikjun; Kulkarni, Dhaval D; Xu, Weinan; Tsitsilianis, Constantinos; Tsukruk, Vladimir V

    2013-08-06

    We report the interfacial assembly of amphiphilic heteroarm star copolymers (PSnP2VPn and PSn(P2VP-b-PtBA)n (n = 28 arms)) on graphene oxide flakes at the air-water interface. Adsorption, spreading, and ordering of star polymer micelles on the surface of the basal plane and edge of monolayer graphene oxide sheets were investigated on a Langmuir trough. This interface-mediated assembly resulted in micelle-decorated graphene oxide sheets with uniform spacing and organized morphology. We found that the surface activity of solvated graphene oxide sheets enables star polymer surfactants to subsequently adsorb on the presuspended graphene oxide sheets, thereby producing a bilayer complex. The positively charged heterocyclic pyridine-containing star polymers exhibited strong affinity onto the basal plane and edge of graphene oxide, leading to a well-organized and long-range ordered discrete micelle assembly. The preferred binding can be related to the increased conformational entropy due to the reduction of interarm repulsion. The extent of coverage was tuned by controlling assembly parameters such as concentration and solvent polarity. The polymer micelles on the basal plane remained incompressible under lateral compression in contrast to ones on the water surface due to strongly repulsive confined arms on the polar surface of graphene oxide and a preventive barrier in the form of the sheet edges. The densely packed biphasic tile-like morphology was evident, suggesting the high interfacial stability and mechanically stiff nature of graphene oxide sheets decorated with star polymer micelles. This noncovalent assembly represents a facile route for the control and fabrication of graphene oxide-inclusive ultrathin hybrid films applicable for layered nanocomposites.

  3. Graphene oxide: a carrier for pharmaceuticals and a scaffold for cell interactions.

    PubMed

    Durán, Nelson; Martinez, Diego Stéfani T; Silveira, Camila P; Durán, Marcela; de Moraes, Ana C M; Simões, Mateus B; Alves, Oswaldo L; Fávaro, Wagner J

    2015-01-01

    During the last ten years, graphene oxide has been explored in many applications due to its remarkable electroconductivity, thermal properties and mobility of charge carriers, among other properties. As discussed in this review, the literature suggests that a total characterization of graphene oxide must be conducted because oxidation debris (synthesis impurities) present in the graphene oxides could act as a graphene oxide surfactant, stabilizing aqueous dispersions. It is also important to note that the structure models of graphene oxide need to be revisited because of significant implications for its chemical composition and its direct covalent functionalization. Another aspect that is discussed is the need to consider graphene oxide surface chemistry. The hemolysis assay is recommended as a reliable test for the preliminary assessment of graphene oxide toxicity, biocompatibility and cell membrane interaction. More recently, graphene oxide has been extensively explored for drug delivery applications. An important increase in research efforts in this emerging field is clearly represented by the hundreds of related publications per year, including some reviews. Many studies have been performed to explore the graphene oxide properties that enable it to deliver more than one activity simultaneously and to combine multidrug systems with photothermal therapy, indicating that graphene oxide is an attractive tool to overcome hurdles in cancer therapies. Some strategic aspects of the application of these materials in cancer treatment are also discussed. In vitro studies have indicated that graphene oxide can also promote stem cell adhesion, growth and differentiation, and this review discusses the recent and pertinent findings regarding graphene oxide as a valuable nanomaterial for stem cell research in medicine. The protein corona is a key concept in nanomedicine and nanotoxicology because it provides a biomolecular identity for nanomaterials in a biological environment

  4. Theoretical investigation of gas separation in functionalized nanoporous graphene membranes

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Yang, Qingyuan; Zhong, Chongli; Li, Jinping

    2017-06-01

    Graphene has enormous potential as a membrane-separation material with ultrahigh permeability and selectivity. The understanding of mass-transport mechanism in graphene membranes is crucial for applications in gas separation field. We computationally investigated the capability and mechanisms of functionalized nanoporous graphene membranes for gas separation. The functionalized graphene membranes with appropriate pore size and geometry possess excellent high selectivity for separating CO2/N2, CO2/CH4 and N2/CH4 gas mixtures with a gas permeance of ∼103-105 GPU, compared with ∼100 GPU for typical polymeric membranes. More important, we found that, for ultrathin graphene membranes, the gas separation performance has a great dependence not only with the energy barrier for gas getting into the pore of the graphene membranes, but also with the energy barrier for gas escaping from the pore to the other side of the membranes. The gas separation performance can be tuned by changing the two energy barriers, which can be realized by varying the chemical functional groups on the pore rim of the graphene. The novel mass-transport mechanism obtained in current study may provide a theoretical foundation for guiding the future design of graphene membranes with outstanding separation performance.

  5. Bioinspired reduced graphene oxide nanosheets using Terminalia chebula seeds extract

    NASA Astrophysics Data System (ADS)

    Maddinedi, Sireesh Babu; Mandal, Badal Kumar; Vankayala, Raviraj; Kalluru, Poliraju; Pamanji, Sreedhara Reddy

    2015-06-01

    A green one step facile synthesis of graphene nanosheets by Terminalia chebula (T. chebula) extract mediated reduction of graphite oxide (GO) is reported in this work. This method avoids the use of harmful toxic reducing agents. The comparative results of various characterizations of GO and T. chebula reduced graphene oxide (TCG) provide a strong indication of the exclusion of oxygen containing groups from graphene oxide and successive stabilization of the formed reduced graphene oxide (RGO). The functionalization of reduced graphene oxide with the oxidized polyphenols causes their stability by preventing the aggregation. We also have proposed how the oxidized polyphenols are accountable for the stabilization of the formed graphene sheets.

  6. Oxidative stress-mediated antibacterial activity of graphene oxide and reduced graphene oxide in Pseudomonas aeruginosa.

    PubMed

    Gurunathan, Sangiliyandi; Han, Jae Woong; Dayem, Ahmed Abdal; Eppakayala, Vasuki; Kim, Jin-Hoi

    2012-01-01

    Graphene holds great promise for potential use in next-generation electronic and photonic devices due to its unique high carrier mobility, good optical transparency, large surface area, and biocompatibility. The aim of this study was to investigate the antibacterial effects of graphene oxide (GO) and reduced graphene oxide (rGO) in Pseudomonas aeruginosa. In this work, we used a novel reducing agent, betamercaptoethanol (BME), for synthesis of graphene to avoid the use of toxic materials. To uncover the impacts of GO and rGO on human health, the antibacterial activity of two types of graphene-based material toward a bacterial model P. aeruginosa was studied and compared. The synthesized GO and rGO was characterized by ultraviolet-visible absorption spectroscopy, particle-size analyzer, X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Further, to explain the antimicrobial activity of graphene oxide and reduced graphene oxide, we employed various assays, such as cell growth, cell viability, reactive oxygen species generation, and DNA fragmentation. Ultraviolet-visible spectra of the samples confirmed the transition of GO into graphene. Dynamic light-scattering analyses showed the average size among the two types of graphene materials. X-ray diffraction data validated the structure of graphene sheets, and high-resolution scanning electron microscopy was employed to investigate the morphologies of prepared graphene. Raman spectroscopy data indicated the removal of oxygen-containing functional groups from the surface of GO and the formation of graphene. The exposure of cells to GO and rGO induced the production of superoxide radical anion and loss of cell viability. Results suggest that the antibacterial activities are contributed to by loss of cell viability, induced oxidative stress, and DNA fragmentation. The antibacterial activities of GO and rGO against P. aeruginosa were compared. The loss of P. aeruginosa viability increased in a dose- and

  7. Oxidative stress-mediated antibacterial activity of graphene oxide and reduced graphene oxide in Pseudomonas aeruginosa

    PubMed Central

    Gurunathan, Sangiliyandi; Han, Jae Woong; Dayem, Ahmed Abdal; Eppakayala, Vasuki; Kim, Jin-Hoi

    2012-01-01

    Background Graphene holds great promise for potential use in next-generation electronic and photonic devices due to its unique high carrier mobility, good optical transparency, large surface area, and biocompatibility. The aim of this study was to investigate the antibacterial effects of graphene oxide (GO) and reduced graphene oxide (rGO) in Pseudomonas aeruginosa. In this work, we used a novel reducing agent, betamercaptoethanol (BME), for synthesis of graphene to avoid the use of toxic materials. To uncover the impacts of GO and rGO on human health, the antibacterial activity of two types of graphene-based material toward a bacterial model P. aeruginosa was studied and compared. Methods The synthesized GO and rGO was characterized by ultraviolet-visible absorption spectroscopy, particle-size analyzer, X-ray diffraction, scanning electron microscopy and Raman spectroscopy. Further, to explain the antimicrobial activity of graphene oxide and reduced graphene oxide, we employed various assays, such as cell growth, cell viability, reactive oxygen species generation, and DNA fragmentation. Results Ultraviolet-visible spectra of the samples confirmed the transition of GO into graphene. Dynamic light-scattering analyses showed the average size among the two types of graphene materials. X-ray diffraction data validated the structure of graphene sheets, and high-resolution scanning electron microscopy was employed to investigate the morphologies of prepared graphene. Raman spectroscopy data indicated the removal of oxygen-containing functional groups from the surface of GO and the formation of graphene. The exposure of cells to GO and rGO induced the production of superoxide radical anion and loss of cell viability. Results suggest that the antibacterial activities are contributed to by loss of cell viability, induced oxidative stress, and DNA fragmentation. Conclusion The antibacterial activities of GO and rGO against P. aeruginosa were compared. The loss of P

  8. Graphene tunnel junctions with aluminum oxide barrier

    NASA Astrophysics Data System (ADS)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2016-10-01

    We report a development of graphene tunnel junctions made by chemical vapor deposition grown graphene and sputtered aluminum insulating by an in-situ grown aluminum oxide. The thin oxide layer formed in between the metal layer and the two-dimensional material is a crucial part of a tunnel junction. We characterized surface morphology of oxide layers and studied tunneling spectra of lead and silver tunnel junctions to estimate the quality of the aluminum oxide. The Brinkman-Rowell-Dynes model was applied to fit the conductance-voltage plots to calculate the thickness of oxide layers. Junctions with graphene both on bottom and on top were fabricated and their tunneling properties were characterized after exposure to air for weeks to test time stability. Furthermore, the resistances of graphene tunnel junctions with aluminum oxide formed naturally and in an oxygen atmosphere were studied. Our results demonstrate that in-situ aluminum oxide is an effective barrier for graphene tunnel junctions. The methods of barrier formation enable the realization of more tunnel devices and circuits based on graphene.

  9. Charge transport-driven selective oxidation of graphene.

    PubMed

    Lee, Young Keun; Choi, Hongkyw; Lee, Changhwan; Lee, Hyunsoo; Goddeti, Kalyan C; Moon, Song Yi; Doh, Won Hui; Baik, Jaeyoon; Kim, Jin-Soo; Choi, Jin Sik; Choi, Choon-Gi; Park, Jeong Young

    2016-06-02

    Due to the tunability of the physical, electrical, and optical characteristics of graphene, precisely controlling graphene oxidation is of great importance for potential applications of graphene-based electronics. Here, we demonstrate a facile and precise way for graphene oxidation controlled by photoexcited charge transfer depending on the substrate and bias voltage. It is observed that graphene on TiO2 is easily oxidized under UV-ozone treatment, while graphene on SiO2 remains unchanged. The mechanism for the selective oxidation of graphene on TiO2 is associated with charge transfer from the TiO2 to the graphene. Raman spectra were used to investigate the graphene following applied bias voltages on the graphene/TiO2 diode under UV-ozone exposure. We found that under a reverse bias of 0.6 V on the graphene/TiO2 diode, graphene oxidation was accelerated under UV-ozone exposure, thus confirming the role of charge transfer between the graphene and the TiO2 that results in the selective oxidation of the graphene. The selective oxidation of graphene can be utilized for the precise, nanoscale patterning of the graphene oxide and locally patterned chemical doping, finally leading to the feasibility and expansion of a variety of graphene-based applications.

  10. Solvothermal reduction of graphene oxide in dimethylformamide

    NASA Astrophysics Data System (ADS)

    Kim, Sujin; Choi, Kwangrok; Park, Sungjin

    2016-11-01

    The reduction of graphene oxide (G-O) is one of the most promising methods for the large scale production of graphene-based materials. In this paper, we report a simple and non-toxic method to produce reduced graphene oxide (rG-O) by refluxing G-O in N, N-dimethylformamide without the aid of a reducing agent. The rG-O materials with high degrees of reduction are prepared and the levels of reduction are controlled using reflux time. Successful reduction is confirmed by combustion-based elemental analysis and X-ray photoelectron and Fourier transform infrared spectroscopy.

  11. Casein mediated green synthesis and decoration of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Maddinedi, Sireesh Babu; Mandal, Badal Kumar; Vankayala, Raviraj; Kalluru, Poliraju; Tammina, Sai Kumar; Kiran Kumar, H. A.

    This research is mainly focusing on one-step biosynthesis of graphene from graphene oxide and its stabilization using naturally occurring milk protein, casein. The synthesis of casein reduced graphene oxide (CRGO) was completed within 7 h under reflux at 90 °C with the formation of few layered fine graphene nanosheets. UV-Vis, XRD, XPS analysis data revealed the reduction process of the graphene oxide. Results of FT-IR, HPLC and TEM analysis have shown that the ensuing material consists of graphene decorated with casein molecules. Aspartic acid and glutamic acid residue present in casein molecules are responsible for the reduction of graphene oxide.

  12. Morphology and Electrical Characterization of Reduced Epitaxial Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Hu, Yike; Wu, Xiaosong; Sprinkle, Michael; Madiomanana, Nerasoa; Ruan, Ming; Berger, Claire; de Heer, Walter

    2009-03-01

    We present results for on-chip oxidation of epitaxial graphene and sequential reduction of the insulating graphene oxide layers. In our previous work , we have used the Hummer's method to oxidize epitaxial graphene and used electron beam exposure and heat treatment to reduce the epitaxial graphene oxide (EGO) band gap by changing the degree of oxidation. Here we further explore various oxidation and reduction methods on epitaxial graphene. EGO is characterized by atomic force microscopy, low-energy electron diffraction, ellipsometry, and Raman Spectrometry. Mobility measurements of patterned structures are presented where epitaxial graphene layers pads are seamlessly connected to EGO ribbons.

  13. Synthesis of free-standing MnO2/reduced graphene oxide membranes and electrochemical investigation of their performances as anode materials for half and full lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaojun; Wang, Gang; Wang, Hui

    2016-10-01

    MnO2 nanotubes/reduced graphene oxide (MnO2/RGO) membranes with different MnO2 contents are successfully synthesized by a facile two-step method including vacuum filtration and subsequent thermal reduction route. The MnO2 nanotubes obtained are 38 nm in diameter and homogeneously imbedded in RGO sheets as spacers. The synthesized MnO2/RGO membranes exhibit excellent mechanical flexibilities and free-standing properties. Using the membranes directly as anode materials for lithium batteries (LIBs), the membranes for half LIBs show superb cycling stabilities and rate performances. Importantly, the electrochemical performances of MnO2/RGO membranes show a strong dependence on the MnO2 nanotube contents in the hybrids. In addition, our results show that the hybrid membranes with 49.0 wt% MnO2 nanotube in half LIBs achieve a high reversible capacity of 1006.7 mAh g-1 after 100 cycles at a current density of 0.1 A g-1, which is higher lithium storage capacity than that of reported MnO2-carbon electrodes. Furthermore, the synthesized full cell (MnO2/RGO//LiCoO2) system also exhibit excellent electrochemical performances, which can be attributed to the unique microstructures of MnO2 and GRO, coupled with the strong synergistic interaction between MnO2 nanotubes and GRO sheets.

  14. Photochemical transformation of graphene oxide in sunlight (journal)

    EPA Science Inventory

    Graphene oxide (GO) is a graphene derivative that is more easily manufactured in large scale and used to synthesize reduced graphene oxide (rGO) with properties analogous to graphene. In this study, we investigate the photochemical fate of GO under sunlight conditions. The resu...

  15. Photochemical transformation of graphene oxide in sunlight (journal)

    EPA Science Inventory

    Graphene oxide (GO) is a graphene derivative that is more easily manufactured in large scale and used to synthesize reduced graphene oxide (rGO) with properties analogous to graphene. In this study, we investigate the photochemical fate of GO under sunlight conditions. The resu...

  16. Oxidation resistance of reactive atoms in graphene.

    PubMed

    Chisholm, Matthew F; Duscher, Gerd; Windl, Wolfgang

    2012-09-12

    We have found that reactive elements that are normally oxidized at room temperature are present as individual atoms or clusters on and in graphene. Oxygen is present in these samples but it is only detected in the thicker amorphous carbon layers present in the graphene specimens we have examined. However, we have seen no evidence that oxygen reacts with the impurity atoms and small clusters of these normally reactive elements when they are incorporated in the graphene layers. First principles calculations suggest that the oxidation resistance is due to kinetic effects such as preferential bonding of oxygen to nonincorporated atoms and H passivation. The observed oxidation resistance of reactive atoms in graphene may allow the use of these incorporated metals in catalytic applications. It also opens the possibility of designing and producing electronic, opto-electronic, and magnetic devices based on these normally reactive atoms.

  17. Oxidation Resistance of Reactive Atoms in Graphene

    SciTech Connect

    Chisholm, Matthew F; Duscher, Gerd; Windl, Wolfgang

    2012-01-01

    We have found that reactive elements that are normally oxidized at room temperature are present as individual atoms or clusters on and in graphene. Oxygen is present in these samples but it is only detected in the thicker amorphous carbon layers present in the graphene specimens we have examined. However, we have seen no evidence that oxygen reacts with the impurity atoms and small clusters of these normally reactive elements when they are incorporated in the graphene layers. First principles calculations suggest that the oxidation resistance is due to kinetic effects such as preferential bonding of oxygen to nonincorporated atoms and H passivation. The observed oxidation resistance of reactive atoms in graphene may allow the use of these incorporated metals in catalytic applications. It also opens the possibility of designing and producing electronic, opto-electronic, and magnetic devices based on these normally reactive atoms.

  18. Staged membrane oxidation reactor system

    DOEpatents

    Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

    2014-05-20

    Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

  19. Staged membrane oxidation reactor system

    DOEpatents

    Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

    2013-04-16

    Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

  20. Staged membrane oxidation reactor system

    DOEpatents

    Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

    2012-09-11

    Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

  1. Differential cytotoxic effects of graphene and graphene oxide on skin keratinocytes

    NASA Astrophysics Data System (ADS)

    Pelin, Marco; Fusco, Laura; León, Verónica; Martín, Cristina; Criado, Alejandro; Sosa, Silvio; Vázquez, Ester; Tubaro, Aurelia; Prato, Maurizio

    2017-01-01

    Impressive properties make graphene-based materials (GBMs) promising tools for nanoelectronics and biomedicine. However, safety concerns need to be cleared before mass production of GBMs starts. As skin, together with lungs, displays the highest exposure to GBMs, it is of fundamental importance to understand what happens when GBMs get in contact with skin cells. The present study was carried out on HaCaT keratinocytes, an in vitro model of skin toxicity, on which the effects of four GBMs were evaluated: a few layer graphene, prepared by ball-milling treatment (FLG), and three samples of graphene oxide (GOs, a research-grade GO1, and two commercial GOs, GO2 and GO3). Even though no significant effects were observed after 24 h, after 72 h the less oxidized compound (FLG) was the less cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 62.8 μg/mL (WST-8 assay) and 45.5 μg/mL (propidium iodide uptake), respectively. By contrast, the largest and most oxidized compound, GO3, was the most cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 5.4 and 2.9 μg/mL, respectively. These results suggest that only high concentrations and long exposure times to FLG and GOs could impair mitochondrial activity associated with plasma membrane damage, suggesting low cytotoxic effects at the skin level.

  2. Differential cytotoxic effects of graphene and graphene oxide on skin keratinocytes

    PubMed Central

    Pelin, Marco; Fusco, Laura; León, Verónica; Martín, Cristina; Criado, Alejandro; Sosa, Silvio; Vázquez, Ester; Tubaro, Aurelia; Prato, Maurizio

    2017-01-01

    Impressive properties make graphene-based materials (GBMs) promising tools for nanoelectronics and biomedicine. However, safety concerns need to be cleared before mass production of GBMs starts. As skin, together with lungs, displays the highest exposure to GBMs, it is of fundamental importance to understand what happens when GBMs get in contact with skin cells. The present study was carried out on HaCaT keratinocytes, an in vitro model of skin toxicity, on which the effects of four GBMs were evaluated: a few layer graphene, prepared by ball-milling treatment (FLG), and three samples of graphene oxide (GOs, a research-grade GO1, and two commercial GOs, GO2 and GO3). Even though no significant effects were observed after 24 h, after 72 h the less oxidized compound (FLG) was the less cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 62.8 μg/mL (WST-8 assay) and 45.5 μg/mL (propidium iodide uptake), respectively. By contrast, the largest and most oxidized compound, GO3, was the most cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 5.4 and 2.9 μg/mL, respectively. These results suggest that only high concentrations and long exposure times to FLG and GOs could impair mitochondrial activity associated with plasma membrane damage, suggesting low cytotoxic effects at the skin level. PMID:28079192

  3. Differential cytotoxic effects of graphene and graphene oxide on skin keratinocytes.

    PubMed

    Pelin, Marco; Fusco, Laura; León, Verónica; Martín, Cristina; Criado, Alejandro; Sosa, Silvio; Vázquez, Ester; Tubaro, Aurelia; Prato, Maurizio

    2017-01-12

    Impressive properties make graphene-based materials (GBMs) promising tools for nanoelectronics and biomedicine. However, safety concerns need to be cleared before mass production of GBMs starts. As skin, together with lungs, displays the highest exposure to GBMs, it is of fundamental importance to understand what happens when GBMs get in contact with skin cells. The present study was carried out on HaCaT keratinocytes, an in vitro model of skin toxicity, on which the effects of four GBMs were evaluated: a few layer graphene, prepared by ball-milling treatment (FLG), and three samples of graphene oxide (GOs, a research-grade GO1, and two commercial GOs, GO2 and GO3). Even though no significant effects were observed after 24 h, after 72 h the less oxidized compound (FLG) was the less cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 62.8 μg/mL (WST-8 assay) and 45.5 μg/mL (propidium iodide uptake), respectively. By contrast, the largest and most oxidized compound, GO3, was the most cytotoxic, inducing mitochondrial and plasma-membrane damages with EC50s of 5.4 and 2.9 μg/mL, respectively. These results suggest that only high concentrations and long exposure times to FLG and GOs could impair mitochondrial activity associated with plasma membrane damage, suggesting low cytotoxic effects at the skin level.

  4. Ultra-high Burst Strength of CVD Graphene Membranes

    NASA Astrophysics Data System (ADS)

    Wang, Luda; Boutilier, Michael; Kidambi, Piran; Karnik, Rohit; Microfluidics; Nanofluidics Research Lab Team

    2015-11-01

    Porous graphene membranes have significant potential in gas separation, water desalination and nanofiltration. Understanding the mechanical strength of porous graphene is crucial because membrane separations can involve high pressures. We studied the burst strength of CVD graphene membrane placed on porous support at applied pressures up to 100 bar by monitoring the gas flow rate across the membrane as a function of pressure. Increase of gas flow rate with pressure allowed for extraction of the burst fraction of graphene as it failed under increasing pressure. We also studied the effect of sub-nanometer pores on the ability of graphene to withstand pressure. The results showed that porous graphene membranes can withstand pressures comparable to or even higher than the >50 bar pressures encountered in water desalination, with non-porous CVD graphene exhibiting even higher mechanical strength. Our study shows that porous polycrystalline CVD graphene has ultra-high burst strength under applied pressure, suggesting the possibility for its use in high-pressure membrane separations. Principal Investigator

  5. Synthesis and properties of graphene oxide/graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Kapitanova, O. O.; Panin, G. N.; Baranov, A. N.; Kang, T. W.

    2012-05-01

    We report preparation of graphene oxide (GO)/graphene (G) nanostructures and their structural, optical and electrical properties. GO was synthesized through oxidation of graphite by using the modified Hummer's method, in which a long oxidation time was combined with a highly effective method for purifying the reaction products. The obtained GO was partially reduced (r-GO) by adding ascorbic acid and thermal annealing. An electrical reduction/oxidation process in r-GO under an electric field was used to form and control the GO/G nanostructures and the potential barrier at the interface. After the treatment, the ratio of the intensity of peak G (1578 cm-1) to that of peak D (1357 cm-1) in Raman spectra of the samples is increased, which is attributed to an increase in the ratio between the sp2 and sp3 regions. The electrical and the luminescence characteristics of the GO/G nanostructures were investigated.

  6. Formation of Self-Assembled Nanoscale Graphene/Graphene Oxide Photomemristive Heterojunctions using Photocatalytic Oxidation.

    PubMed

    Kapitanova, Olesya; Panin, Gennady; Cho, Hak; Baranov, Andrey; Kang, Tae

    2017-03-08

    Photocatalytic oxidation of graphene with ZnO nanoparticles was found to create self-assembled graphene oxide/graphene (G/GO) photosensitive heterostructures, which can be used as memristors. Oxygen groups released during photodecomposition of water molecules on the nanoparticles under ultraviolet light oxidized graphene locally forming the G/GO heterojunctions with ultra-high density. The G/GO nanostructures have non-linear current-voltage characteristics and switch the resistance in the dark and under white light, providing four resistive states at room temperature. Photocatalytic oxidation of graphene with ZnO nanoparticles, is proposed as an effective method for creating two-dimensional memristors with a photoresistive switching for the ultra-high capacity non-volatile memory.

  7. Plasticity and ductility in graphene oxide through a mechanochemically induced damage tolerance mechanism

    PubMed Central

    Wei, Xiaoding; Mao, Lily; Soler-Crespo, Rafael A.; Paci, Jeffrey T.; Espinosa, Horacio D.

    2015-01-01

    The ability to bias chemical reaction pathways is a fundamental goal for chemists and material scientists to produce innovative materials. Recently, two-dimensional materials have emerged as potential platforms for exploring novel mechanically activated chemical reactions. Here we report a mechanochemical phenomenon in graphene oxide membranes, covalent epoxide-to-ether functional group transformations that deviate from epoxide ring-opening reactions, discovered through nanomechanical experiments and density functional-based tight binding calculations. These mechanochemical transformations in a two-dimensional system are directionally dependent, and confer pronounced plasticity and damage tolerance to graphene oxide monolayers. Additional experiments on chemically modified graphene oxide membranes, with ring-opened epoxide groups, verify this unique deformation mechanism. These studies establish graphene oxide as a two-dimensional building block with highly tuneable mechanical properties for the design of high-performance nanocomposites, and stimulate the discovery of new bond-selective chemical transformations in two-dimensional materials. PMID:26289729

  8. In vitro studies of graphene oxide reinforced hydroxyapatite nanobiocomposite on human erythrocytes

    NASA Astrophysics Data System (ADS)

    Radha, G.; Rohith Vinod, K.; Venkatesan, Balaji; Vellaichamy, Elangovan; Balakumar, S.

    2017-05-01

    We report the interaction of graphene oxide reinforced hydroxyapatite (GO-HAp) nanocomposites with human erythrocytes. The hemocompatibility of GO-HAp found to be superior as compared to the pristine graphene oxide. It is found that the HAp nanoparticles on GO decrease the disruption of erythrocytes by minimizing the exposure of oxygen groups to phosphatidylcholine surface of erythrocyte membrane and it enhances hemocompatibility. Further, it is also found that the graphene oxide reinforced HAp nanobiocomposite enhances the metabolic activity of osteoblasts-like cells by promoting cell proliferation.

  9. Noncovalent Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications.

    PubMed

    Georgakilas, Vasilios; Tiwari, Jitendra N; Kemp, K Christian; Perman, Jason A; Bourlinos, Athanasios B; Kim, Kwang S; Zboril, Radek

    2016-05-11

    This Review focuses on noncovalent functionalization of graphene and graphene oxide with various species involving biomolecules, polymers, drugs, metals and metal oxide-based nanoparticles, quantum dots, magnetic nanostructures, other carbon allotropes (fullerenes, nanodiamonds, and carbon nanotubes), and graphene analogues (MoS2, WS2). A brief description of π-π interactions, van der Waals forces, ionic interactions, and hydrogen bonding allowing noncovalent modification of graphene and graphene oxide is first given. The main part of this Review is devoted to tailored functionalization for applications in drug delivery, energy materials, solar cells, water splitting, biosensing, bioimaging, environmental, catalytic, photocatalytic, and biomedical technologies. A significant part of this Review explores the possibilities of graphene/graphene oxide-based 3D superstructures and their use in lithium-ion batteries. This Review ends with a look at challenges and future prospects of noncovalently modified graphene and graphene oxide.

  10. Green reduction of graphene oxide using alanine.

    PubMed

    Wang, Jiabin; Salihi, Elif Caliskan; Šiller, Lidija

    2017-03-01

    There remains a real need for the easy, eco-friendly and scalable preparation method of graphene due to various potential applications. Chemical reduction is the most versatile method for the large scale production of graphene. Here we report the operating conditions for a one-step, economical and green synthesis method for the reduction of graphene oxide using a biomolecule (alanine). Graphene oxide was produced by the oxidation and exfoliation of natural graphite flake with strong oxidants using Hummers method (Hummers and Offeman, 1958), but the method was revised in our laboratory to set up a safe and environmentally friendly route. The reduction of graphene oxide was investigated using alanine at various operating conditions in order to set up optimum conditions (treatment time, temperature and concentration of the reagent). Samples have been characterized by using UV-Visible spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction analysis. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  11. Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles

    DTIC Science & Technology

    2012-12-01

    Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles by Matthew Ervin, Vinay Raju, Mary Hendrickson, and...Laboratory Adelphi, MD 20783-1197 ARL-TR-6289 December 2012 Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide...From - To) October 2011 to September 2012 4. TITLE AND SUBTITLE Carbon Nanotube/Graphene Supercapacitors Containing Manganese Oxide Nanoparticles

  12. Graphene-doped electrospun nanofiber membrane electrodes and proton exchange membrane fuel cell performance

    NASA Astrophysics Data System (ADS)

    Wei, Meng; Jiang, Min; Liu, Xiaobo; Wang, Min; Mu, Shichun

    2016-09-01

    A rational electrode structure can allow proton exchange membrane (PEM) fuel cells own high performance with a low noble metal loading and an optimal transport pathway for reaction species. In this study, we develop a graphene doped polyacrylonitile (PAN)/polyvinylident fluoride (PVDF) (GPP) electrospun nanofiber electrode with improved electrical conductivity and high porosity, which could enhance the triple reaction boundary and promote gas and water transport throughout the porous electrode. Thus the increased electrochemical active surface area (ECSA) of Pt catalysts and fuel cell performance can be expected. As results, the ECSA of hot-pressed electrospun electrodes with 2 wt% graphene oxide (GO) is up to 84.3 m2/g, which is greatly larger than that of the conventional electrode (59.5 m2/g). Significantly, the GPP nanofiber electrospun electrode with Pt loading of 0.2 mg/cm2 exhibits higher fuel cell voltage output and stability than the conventional electrode.

  13. Accelerated evaporation of water on graphene oxide.

    PubMed

    Wan, Rongzheng; Shi, Guosheng

    2017-03-29

    Using molecular dynamics simulations, we show that the evaporation of nanoscale volumes of water on patterned graphene oxide is faster than that on homogeneous graphene oxide. The evaporation rate of water is insensitive to variation in the oxidation degree of the oxidized regions, so long as the water film is only distributed on the oxidized regions. The evaporation rate drops when the water film spreads onto the unoxidized regions. Further analysis showed that varying the oxidation degree observably changed the interaction between the outmost water molecules and the solid surface, but the total interaction for the outmost water molecules only changed a very limited amount due to the correspondingly regulated water-water interaction when the water film is only distributed on the oxidized regions. When the oxidation degree is too low and some unoxidized regions are also covered by the water film, the thickness of the water film decreases, which extends the lifetime of the hydrogen bonds for the outmost water molecules and lowers the evaporation rate of the water. The insensitivity of water evaporation to the oxidation degree indicates that we only need to control the scale of the unoxidized and oxidized regions for graphene oxide to regulate the evaporation of nanoscale volumes of water.

  14. Multiscale mechanics of graphene oxide and graphene based composite films

    NASA Astrophysics Data System (ADS)

    Cao, Changhong

    The mechanical behavior of graphene oxide is length scale dependent: orders of magnitude different between the bulk forms and monolayer counterparts. Understanding the underlying mechanisms plays a significant role in their versatile application. A systematic multiscale mechanical study from monolayer to multilayer, including the interactions between layers of GO, can provide fundamental support for material engineering. In this thesis, an experimental coupled with simulation approach was used to study the multiscale mechanics of graphene oxide (GO) and the methods developed for GO study are proved to be applicable also to mechanical study of graphene based composites. GO is a layered nanomaterial comprised of hierarchical units whose characteristic dimension lies between monolayer GO (0.7 nm - 1.2 nm) and bulk GO papers (≥ 1 mum). Mechanical behaviors of monolayer GO and GO nanosheets (10 nm- 100 nm) were comprehensively studied this work. Monolayer GO was measured to have an average strength of 24.7 GPa,, orders of magnitude higher than previously reported values for GO paper and approximately 50% of the 2D intrinsic strength of pristine graphene. The huge discrepancy between the strength of monolayer GO and that of bulk GO paper motivated the study of GO at the intermediate length scale (GO nanosheets). Experimental results showed that GO nanosheets possess high strength in the gigapascal range. Molecular Dynamic simulations showed that the transition in the failure behavior from interplanar fracture to intraplanar fracture was responsible for the huge strength discrepancy between nanometer scale GO and bulk GO papers. Additionally, the interfacial shear strength between GO layers was found to be a key contributing factor to the distinct mechanical behavior among hierarchical units of GO. The understanding of the multiscale mechanics of GO is transferrable in heterogeneous layered nanomaterials, such as graphene-metal oxide based anode materials in Li

  15. Operation of staged membrane oxidation reactor systems

    SciTech Connect

    Repasky, John Michael

    2012-10-16

    A method of operating a multi-stage ion transport membrane oxidation system. The method comprises providing a multi-stage ion transport membrane oxidation system with at least a first membrane oxidation stage and a second membrane oxidation stage, operating the ion transport membrane oxidation system at operating conditions including a characteristic temperature of the first membrane oxidation stage and a characteristic temperature of the second membrane oxidation stage; and controlling the production capacity and/or the product quality by changing the characteristic temperature of the first membrane oxidation stage and/or changing the characteristic temperature of the second membrane oxidation stage.

  16. Nanoscale friction properties of graphene and graphene oxide

    SciTech Connect

    Berman, Diana; Erdemir, Ali; Zinovev, Alexander V.; Sumant, Anirudha V.

    2015-04-03

    Achieving superlow friction and wear at the micro/nano-scales through the uses of solid and liquid lubricants may allow superior performance and long-lasting operations in a range of micromechanical system including micro-electro mechanical systems (MEMS). Previous studies have indicated that conventional solid lubricants such as highly ordered pyrolitic graphite (HOPG) can only afford low friction in humid environments at micro/macro scales; but, HOPG is not suitable for practical micro-scale applications. Here, we explored the nano-scale frictional properties of multi-layered graphene films as a potential solid lubricant for such applications. Atomic force microscopy (AFM) measurements have revealed that for high-purity multilayered graphene (7–9 layers), the friction force is significantly lower than what can be achieved by the use of HOPG, regardless of the counterpart AFM tip material. We have demonstrated that the quality and purity of multilayered graphene plays an important role in reducing lateral forces, while oxidation of graphene results in dramatically increased friction values. Furthermore, for the first time, we demonstrated the possibility of achieving ultralow friction for CVD grown single layer graphene on silicon dioxide. This confirms that the deposition process insures a stronger adhesion to substrate and hence enables superior tribological performance than the previously reported mechanical exfoliation processes.

  17. Anomalous behaviour of magnetic coercivity in graphene oxide and reduced graphene oxide

    SciTech Connect

    Bagani, K.; Bhattacharya, A.; Kaur, J.; Rai Chowdhury, A.; Ghosh, B.; Banerjee, S.

    2014-01-14

    In this report, we present the temperature dependence of the magnetic coercivity of graphene oxide (GO) and reduced graphene oxide (RGO). We observe an anomalous decrease in coercivity of GO and RGO with decreasing temperature. The observation could be understood by invoking the inherent presence of wrinkles on graphene oxide due to presence of oxygen containing groups. Scanning electron microscopic image reveals high wrinkles in GO than RGO. We observe higher coercivity in RGO than in GO. At room temperature, we observe antiferromagnetic and ferromagnetic behaviours in GO and RGO, respectively. Whereas, at low temperatures (below T = 60–70 K), both materials show paramagnetic behaviour.

  18. In vivo nanotoxicological profile of graphene oxide

    NASA Astrophysics Data System (ADS)

    Durán, Marcela; Durán, Nelson; Fávaro, Wagner J.

    2017-06-01

    Graphene oxide, a widely studied nano materials, exhibits numerous beneficial effects in medical devices. The graphene sample Graphene oxide (GO):Single-layer graphene oxide, purity 99%, thickness 0.7-1.2 nm (AFM); ~300-800nm X&Y dimensions is the standard size <450 nm & 1-20 µm lateral dimensions from Cheap Tubes Inc., Bratleboro, USA was selected for this study. Characterization of GO and stability were previously studied. All the assays were carried out at a concentration of 1 mg/mL (stock suspension by ultrasonication)(stable 10 days). In this study the first parameter evaluated was in animal toxicity in acute and chronic responses. The second one was to observe the morphology and histological changes on major organs, like signs of inflammatory areas. A total of 25 rats (Fischer 344) were divide in 5 groups (n = 5 animals): negative control group (NCT); Positive cancer control group (PCCT); GO group-1 (GO 1); GO group-2 (GO 2) and GO group-3 (GO 3), with different concentrations of graphene oxide. All the groups were treated by via intra peritoneal (i.p) administration. Biochemical and histopathology results of acute toxicity showed no alterations. In the chronic toxicity was found deposit sections and morphology alterations in different tissues (inflammations). Genotoxicity was dose dependent of GO. This study gave us the limit concentrations of GO free for any biological study.

  19. Graphene oxide nanostructures modified multifunctional cotton fabrics

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, Karthikeyan; Navaneethaiyer, Umasuthan; Mohan, Rajneesh; Lee, Jehee; Kim, Sang-Jae

    2012-06-01

    Surface modification of cotton fabrics using graphene oxide (GO) nanostructures was reported. Scanning electron microscopic (SEM) investigations revealed that the GO nanostructure was coated onto the cotton fabric. The molecular level interaction between the graphene oxide and the cotton fabric is studied in detail using the Fourier transform infra-red (FTIR) spectra. Thermogravimetric analysis (TGA) showed that GO loaded cotton fabrics have enhanced thermal stability compared to the bare cotton fabrics. The photocatalytic activity of the GO-coated cotton fabrics was investigated by measuring the photoreduction of resazurin (RZ) into resorufin (RF) under UV light irradiation. The antibacterial activity was evaluated against both Gram-negative and Gram-positive bacteria and the results indicated that the GO-coated cotton fabrics are more toxic towards the Gram-positive ones. Our results provide a way to develop graphene oxide-based devices for the biomedical applications for improving health care.

  20. Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study.

    PubMed

    Li, Qibin; Xiao, Yitian; Shi, Xiaoyang; Song, Shufeng

    2017-09-07

    To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system.

  1. Rapid Evaporation of Water on Graphene/Graphene-Oxide: A Molecular Dynamics Study

    PubMed Central

    Li, Qibin; Xiao, Yitian; Shi, Xiaoyang; Song, Shufeng

    2017-01-01

    To reveal the mechanism of energy storage in the water/graphene system and water/grapheme-oxide system, the processes of rapid evaporation of water molecules on the sheets of graphene and graphene-oxide are investigated by molecular dynamics simulations. The results show that both the water/graphene and water/grapheme-oxide systems can store more energy than the pure water system during evaporation. The hydroxyl groups on the surface of graphene-oxide are able to reduce the attractive interactions between water molecules and the sheet of graphene-oxide. Also, the radial distribution function of the oxygen atom indicates that the hydroxyl groups affect the arrangement of water molecules at the water/graphene-oxide interface. Therefore, the capacity of thermal energy storage of the water/graphene-oxide system is lower than that of the water/graphene system, because of less desorption energy at the water/graphene-oxide interface. Also, the evaporation rate of water molecules on the graphene-oxide sheet is slower than that on the graphene sheet. The Leidenfrost phenomenon can be observed during the evaporation process in the water/grapheme-oxide system. PMID:28880207

  2. Thermal properties of graphite oxide, thermally reduced graphene and chemically reduced graphene

    NASA Astrophysics Data System (ADS)

    Jankovský, Ondřej; Sedmidubský, David; Lojka, Michal; Sofer, Zdeněk

    2017-07-01

    We compared thermal behavior and other properties of graphite oxide, thermally reduced graphene and chemically reduced graphene. Graphite was oxidized according to the Hofmann method using potassium chlorate as oxidizing agent in strongly acidic environment. In the next step, the formed graphite oxide was chemically or thermally reduced yielding graphene. The mechanism of thermal reduction was studied using STA-MS. Graphite oxide and both thermally and chemically reduced graphenes were analysed by SEM, EDS, elemental combustion analysis, XPS, Raman spectroscopy, XRD and BET. These findings will help for the large scale production of graphene with appropriate chemical composition.

  3. Tuning the underwater oleophobicity of graphene oxide coatings via UV irradiation.

    PubMed

    Li, Hang; Huang, Yi; Mao, Yating; Xu, Weiwei L; Ploehn, Harry J; Yu, Miao

    2014-09-07

    Ultraviolet (UV) irradiation was utilized to gradually modify the chemistry and structure of graphene oxide (GO) flakes, as confirmed by XPS and AFM. Ultrathin GO coatings/membranes, made of UV-irradiated flakes, showed tunable underwater oleophobicity. UV-treated, superoleophobic GO membranes exhibited excellent antifouling capability for oil/water separation.

  4. The Use of Confocal Raman Spectroscopy to Quantitatively Study the Interactions Between Immersive Water and Graphene/Graphene Oxide Surfaces

    NASA Astrophysics Data System (ADS)

    Narcross, Hannah; Jeon, Byung Ho; Lee, Jong-Won; Ryu, Chang Yeol

    2012-02-01

    The unique mechanical, chemical, optical, and electrical properties of graphene allow for many potential applications in biomaterials. Understanding and quantifying the surface interactions between graphene/graphene oxide and aqueous liquid is essential for the design of such graphene-based nanocomposites. Graphene sheets were produced by the mechanical exfoliation of graphite. We have used depth Confocal Raman Spectroscopy (CRM) profiles to measure graphene wettability using a water immersive objective lens, and demonstrated how surface energy between graphene/graphene oxide and immersive aqueous liquid can be affected to simultaneously measure the depth image profiles. Contact angles were also measured to further investigate the compatibility between graphene/graphene oxide and its environment.

  5. Graphene electrode modified with electrochemically reduced graphene oxide for label-free DNA detection.

    PubMed

    Li, Bing; Pan, Genhua; Avent, Neil D; Lowry, Roy B; Madgett, Tracey E; Waines, Paul L

    2015-10-15

    A novel printed graphene electrode modified with electrochemically reduced graphene oxide was developed for the detection of a specific oligonucleotide sequence. The graphene oxide was immobilized onto the surface of a graphene electrode via π-π bonds and electrochemical reduction of graphene oxide was achieved by cyclic voltammetry. A much higher redox current was observed from the reduced graphene oxide-graphene double-layer electrode, a 42% and 36.7% increase, respectively, in comparison with that of a bare printed graphene or reduced graphene oxide electrode. The good electron transfer activity is attributed to a combination of the large number of electroactive sites in reduced graphene oxide and the high conductivity nature of graphene. The probe ssDNA was further immobilized onto the surface of the reduced graphene oxide-graphene double-layer electrode via π-π bonds and then hybridized with its target cDNA. The change of peak current due to the hybridized dsDNA could be used for quantitative sensing of DNA concentration. It has been demonstrated that a linear range from 10(-7)M to 10(-12)M is achievable for the detection of human immunodeficiency virus 1 gene with a detection limit of 1.58 × 10(-13)M as determined by three times standard deviation of zero DNA concentration. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Rheology and microstructure of dilute graphene oxide suspension

    NASA Astrophysics Data System (ADS)

    Tesfai, Waka; Singh, Pawan; Shatilla, Youssef; Iqbal, Muhammad Z.; Abdala, Ahmed A.

    2013-10-01

    Graphene and graphene oxide are potential candidates as nanofluids for thermal management applications. Here, we investigate the rheological properties and intrinsic viscosity of aqueous suspension of graphene and use the measured intrinsic viscosity to determine the aspect ratio of graphene oxide. Dilute suspension of graphene oxide (0.05 to 0.5 mg/mL) exhibits a shear thinning behavior at low shear rates followed by a shear-independent region that starts at shear rate between 5 and 100/s depending on the concentration. This shear thinning behavior becomes more pronounced with the increase of particle loading. Moreover, AFM imaging of the dried graphene oxide indicates the evolution of irregular and thin low fractal aggregates of 0.3-1.8 nm thickness at lower concentrations to oblate compact structures of 1-18 nm thickness of nanosheets at higher concentration. These observations elucidate the microstructure growth mechanisms of graphene oxide in multiphase systems, which are important for nanofluids applications and for dispersing graphene and graphene oxide in composite materials. The suspension has a very high intrinsic viscosity of 1661 due to the high graphene oxide aspect ratio. Based on this intrinsic viscosity, we predict graphene oxide aspect ratio of 2445. While the classical Einstein and Batchelor models underestimate the relative viscosity of graphene oxide suspension, Krieger-Dougherty prediction is in a good agreement with the experimental measurement.

  7. Technical graphene (reduced graphene oxide) and its natural analog (shungite)

    NASA Astrophysics Data System (ADS)

    Sheka, E. F.; Golubev, E. A.

    2016-07-01

    The wide structure and chemical-composition spectrum of the main technological material of molecular graphenics—reduced graphene oxide (RGO)—is explained from a quantum-chemical standpoint. The proposed concept is used to consider the results of experimental investigations of a natural analog of RGO, namely, shungite carbon, by high-resolution electron microscopy and nanopoint energy dispersive spectral analysis. The results obtained are used to propose an atomic-microscopic model for the structure of shungite carbon.

  8. The effects of graphene oxide on green algae Raphidocelis subcapitata.

    PubMed

    Nogueira, P F M; Nakabayashi, D; Zucolotto, V

    2015-09-01

    Graphene represents a new class of nanomaterials that has attracted great interest due to its unique electrical, thermal, and mechanical properties. Once disposed in the environment, graphene can interact with biological systems and is expected to exhibit toxicological effects. The ecotoxicity of graphene and its derivatives, viz.: graphene oxide (GO) depends on their physicochemical properties, including purity, diameter, length, surface charge, functionalization and aggregation state. In this study we evaluated the effects of graphene oxide (GO) on green algae Raphidocelis subcapitata. The algae were exposed to different concentrations of GO pre-equilibrated for 24h with oligotrophic freshwater medium (20ml) during incubation in a growth chamber under controlled conditions: 120μEm(-2)s(-1) illumination; 12:12h light dark cycle and constant temperature of 22±2°C. Algal growth was monitored daily for 96h by direct cell counting. Reactive oxygen species level (ROS), membrane damage (cell viability) and autofluorescence (chl-a fluorescence) were evaluated using fluorescent staining and further analyzed by flow cytometry. The toxic effects from GO, as observed in algal density and autofluorescence, started at concentrations from 20 and 10μgmL(-1), respectively. Such toxicity is probably the result of ROS generation and membrane damage (cell viability). The shading effect caused by GO agglomeration in culture medium may also contribute to reduce algal density. The results reported here provide knowledge regarding the GO toxicity on green algae, contributing to a better understanding of its environmental behavior and impacts. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Charge transport-driven selective oxidation of graphene

    NASA Astrophysics Data System (ADS)

    Lee, Young Keun; Choi, Hongkyw; Lee, Changhwan; Lee, Hyunsoo; Goddeti, Kalyan C.; Moon, Song Yi; Doh, Won Hui; Baik, Jaeyoon; Kim, Jin-Soo; Choi, Jin Sik; Choi, Choon-Gi; Park, Jeong Young

    2016-06-01

    Due to the tunability of the physical, electrical, and optical characteristics of graphene, precisely controlling graphene oxidation is of great importance for potential applications of graphene-based electronics. Here, we demonstrate a facile and precise way for graphene oxidation controlled by photoexcited charge transfer depending on the substrate and bias voltage. It is observed that graphene on TiO2 is easily oxidized under UV-ozone treatment, while graphene on SiO2 remains unchanged. The mechanism for the selective oxidation of graphene on TiO2 is associated with charge transfer from the TiO2 to the graphene. Raman spectra were used to investigate the graphene following applied bias voltages on the graphene/TiO2 diode under UV-ozone exposure. We found that under a reverse bias of 0.6 V on the graphene/TiO2 diode, graphene oxidation was accelerated under UV-ozone exposure, thus confirming the role of charge transfer between the graphene and the TiO2 that results in the selective oxidation of the graphene. The selective oxidation of graphene can be utilized for the precise, nanoscale patterning of the graphene oxide and locally patterned chemical doping, finally leading to the feasibility and expansion of a variety of graphene-based applications.Due to the tunability of the physical, electrical, and optical characteristics of graphene, precisely controlling graphene oxidation is of great importance for potential applications of graphene-based electronics. Here, we demonstrate a facile and precise way for graphene oxidation controlled by photoexcited charge transfer depending on the substrate and bias voltage. It is observed that graphene on TiO2 is easily oxidized under UV-ozone treatment, while graphene on SiO2 remains unchanged. The mechanism for the selective oxidation of graphene on TiO2 is associated with charge transfer from the TiO2 to the graphene. Raman spectra were used to investigate the graphene following applied bias voltages on the graphene/TiO2

  10. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    NASA Astrophysics Data System (ADS)

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A.; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-03-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

  11. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration.

    PubMed

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A; Yoo, Jung Ho; Lee, Kyoung G; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-03-10

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

  12. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    PubMed Central

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-01-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties. PMID:26961409

  13. Nanoscale friction properties of graphene and graphene oxide

    DOE PAGES

    Berman, Diana; Erdemir, Ali; Zinovev, Alexander V.; ...

    2015-04-03

    Achieving superlow friction and wear at the micro/nano-scales through the uses of solid and liquid lubricants may allow superior performance and long-lasting operations in a range of micromechanical system including micro-electro mechanical systems (MEMS). Previous studies have indicated that conventional solid lubricants such as highly ordered pyrolitic graphite (HOPG) can only afford low friction in humid environments at micro/macro scales; but, HOPG is not suitable for practical micro-scale applications. Here, we explored the nano-scale frictional properties of multi-layered graphene films as a potential solid lubricant for such applications. Atomic force microscopy (AFM) measurements have revealed that for high-purity multilayered graphenemore » (7–9 layers), the friction force is significantly lower than what can be achieved by the use of HOPG, regardless of the counterpart AFM tip material. We have demonstrated that the quality and purity of multilayered graphene plays an important role in reducing lateral forces, while oxidation of graphene results in dramatically increased friction values. Furthermore, for the first time, we demonstrated the possibility of achieving ultralow friction for CVD grown single layer graphene on silicon dioxide. This confirms that the deposition process insures a stronger adhesion to substrate and hence enables superior tribological performance than the previously reported mechanical exfoliation processes.« less

  14. Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis.

    PubMed

    Najafpour, Mohammad Mahdi; Rahimi, Fahime; Fathollahzadeh, Maryam; Haghighi, Behzad; Hołyńska, Małgorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

    2014-07-28

    Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) ~ 2.6.

  15. Imaging height fluctuations in free-standing graphene membranes

    NASA Astrophysics Data System (ADS)

    Dorsey, Kyle; Miskin, Marc; Barnard, Arthur; Rose, Peter; Cohen, Itai; McEuen, Paul

    We present a technique based on multi-wavelength interference microscopy to measure the heights of observed ripples in free-standing graphene membranes. Graphene membranes released from a transparent substrate produce interference fringes when viewed in the reflection mode of an inverted microscope(Blees et. al. Nature 524 (7564): 204-207 (2015)). The fringes correspond to corrugation of the membrane as it floats near an interface. A single set of fringes is insufficient to uniquely determine the height profile, as a given fringe spacing can correspond to an increase or decrease in height by λ / 2 . Imaging at multiple wavelengths resolves the ambiguities in phase, and enables unique determination of the height profile of the membrane (Schilling et. al.Phys. Rev. E, 69:021901, 2004). We utilize this technique to map out the height fluctuations in free-standing graphene membranes to answer questions about fundamental mechanical properties of two-dimensional materials.

  16. Transferable graphene oxide films with tunable microstructures.

    PubMed

    Hasan, Saad A; Rigueur, John L; Harl, Robert R; Krejci, Alex J; Gonzalo-Juan, Isabel; Rogers, Bridget R; Dickerson, James H

    2010-12-28

    This report describes methods to produce large-area films of graphene oxide from aqueous suspensions using electrophoretic deposition. By selecting the appropriate suspension pH and deposition voltage, films of the negatively charged graphene oxide sheets can be produced with either a smooth "rug" microstructure on the anode or a porous "brick" microstructure on the cathode. Cathodic deposition occurs in the low pH suspension with the application of a relatively high voltage, which facilitates a gradual change in the colloids' charge from negative to positive as they adsorb protons released by the electrolysis of water. The shift in the colloids' charge also gives rise to the brick microstructure, as the concurrent decrease in electrostatic repulsion between graphene oxide sheets results in the formation of multilayered aggregates (the "bricks"). Measurements of water contact angle revealed the brick films (79°) to be more hydrophobic than the rug films (41°), a difference we attribute primarily to the distinct microstructures. Finally, we describe a sacrificial layer technique to make these graphene oxide films free-standing, which would enable them to be placed on arbitrary substrates.

  17. Preparation of nanoporous graphene sheets via free radical oxidation of graphene oxide and their application in lithium ion battery

    NASA Astrophysics Data System (ADS)

    Zhou, Xuejiao; Xu, Liangyou; Ma, Xiaohua

    2017-07-01

    Graphene is an attractive candidate for use as an electrode material in electrochemical energy storage due to its unique structure and excellent properties. Compared with graphene, nanoporous graphene is a superior electrode material, owing to the porous structure of its graphene sheets, which facilitates cross-plane lithium ion transportation and provides more binding sites for the lithium ions during the lithiation/delithiation process. In this work, we demonstrate a simple and efficient strategy for obtaining nanoporous graphene on a large scale. Nanoporous graphene can be generated through the oxidation of graphene oxide by H2O2 under high-power UV irradiation with a subsequent reduction process. The morphology, chemical composition and defects of the as-generated nanoporous graphene were studied. The electrochemical evaluation of the nanoporous graphene sheets showed that it delivered higher specific capacity and better charge/discharge rate capability compared with chemically reduced graphene sheets for use as an anode material in lithium ion batteries.

  18. Effects of nanofluids containing graphene/graphene-oxide nanosheets on critical heat flux

    NASA Astrophysics Data System (ADS)

    Park, Sung Dae; Won Lee, Seung; Kang, Sarah; Bang, In Cheol; Kim, Ji Hyun; Shin, Hyeon Suk; Lee, Dong Wook; Won Lee, Dong

    2010-07-01

    The superb thermal conduction property of graphene establishes graphene as an excellent material for thermal management. In this paper, we selected graphene/graphene oxide nanosheets as the additives in nanofluids. The authors interestingly found that the highly enhanced critical heat flux (CHF) in the nanofluids containing graphene/graphene-oxide nanosheets (GON) cannot be explained by both the improved surface wettability and the capillarity of the nanoparticles deposition layer. Here we highlights that the GON nanofluid can be exploited to maximize the CHF the most efficiently by building up a characteristically ordered porous surface structure due to its own self-assembly characteristic resulting in a geometrically changed critical instability wavelength.

  19. Tuning the electronic band gap of graphene by oxidation

    SciTech Connect

    Dabhi, Shweta D.; Jha, Prafulla K.

    2015-06-24

    Using plane wave pseudo potential density functional theory, we studied the electronic properties of graphene with different C:O ratio. In this work, we discussed the changes that occur in electronic band structure of graphene functionalized with different amount of epoxy group. Electronic band gap depends on C:O ratio in graphene oxide containing epoxy group. The present work will have its implication for making devices with tunable electronic properties by oxidizing graphene.

  20. Noninvasive Scanning Raman Spectroscopy and Tomography for Graphene Membrane Characterization

    NASA Astrophysics Data System (ADS)

    Wagner, Stefan; Dieing, Thomas; Centeno, Alba; Zurutuza, Amaia; Smith, Anderson D.; Östling, Mikael; Kataria, Satender; Lemme, Max C.

    2017-03-01

    Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane based nanoelectromechanical systems (NEMS). Here, chemical-vapor-deposited graphene is transferred onto target substrates to suspend it over cavities and trenches for pressure-sensor applications. The development of such devices requires suitable metrology methods, i.e., large-scale characterization techniques, to confirm and analyze successful graphene transfer with intact suspended graphene membranes. We propose fast and noninvasive Raman spectroscopy mapping to distinguish between freestanding and substrate-supported graphene, utilizing the different strain and doping levels. The technique is expanded to combine two-dimensional area scans with cross-sectional Raman spectroscopy, resulting in three-dimensional Raman tomography of membrane-based graphene NEMS. The potential of Raman tomography for in-line monitoring is further demonstrated with a methodology for automated data analysis to spatially resolve the material composition in micrometer-scale integrated devices, including free-standing and substrate-supported graphene. Raman tomography may be applied to devices composed of other two-dimensional materials as well as silicon micro- and nanoelectromechanical systems.

  1. Noninvasive Scanning Raman Spectroscopy and Tomography for Graphene Membrane Characterization

    PubMed Central

    2017-01-01

    Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane-based nanoelectromechanical systems (NEMS). Here, chemical-vapor-deposited graphene is transferred onto target substrates to suspend it over cavities and trenches for pressure-sensor applications. The development of such devices requires suitable metrology methods, i.e., large-scale characterization techniques, to confirm and analyze successful graphene transfer with intact suspended graphene membranes. We propose fast and noninvasive Raman spectroscopy mapping to distinguish between free-standing and substrate-supported graphene, utilizing the different strain and doping levels. The technique is expanded to combine two-dimensional area scans with cross-sectional Raman spectroscopy, resulting in three-dimensional Raman tomography of membrane-based graphene NEMS. The potential of Raman tomography for in-line monitoring is further demonstrated with a methodology for automated data analysis to spatially resolve the material composition in micrometer-scale integrated devices, including free-standing and substrate-supported graphene. Raman tomography may be applied to devices composed of other two-dimensional materials as well as silicon micro- and nanoelectromechanical systems. PMID:28140595

  2. Noninvasive Scanning Raman Spectroscopy and Tomography for Graphene Membrane Characterization.

    PubMed

    Wagner, Stefan; Dieing, Thomas; Centeno, Alba; Zurutuza, Amaia; Smith, Anderson D; Östling, Mikael; Kataria, Satender; Lemme, Max C

    2017-03-08

    Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane-based nanoelectromechanical systems (NEMS). Here, chemical-vapor-deposited graphene is transferred onto target substrates to suspend it over cavities and trenches for pressure-sensor applications. The development of such devices requires suitable metrology methods, i.e., large-scale characterization techniques, to confirm and analyze successful graphene transfer with intact suspended graphene membranes. We propose fast and noninvasive Raman spectroscopy mapping to distinguish between free-standing and substrate-supported graphene, utilizing the different strain and doping levels. The technique is expanded to combine two-dimensional area scans with cross-sectional Raman spectroscopy, resulting in three-dimensional Raman tomography of membrane-based graphene NEMS. The potential of Raman tomography for in-line monitoring is further demonstrated with a methodology for automated data analysis to spatially resolve the material composition in micrometer-scale integrated devices, including free-standing and substrate-supported graphene. Raman tomography may be applied to devices composed of other two-dimensional materials as well as silicon micro- and nanoelectromechanical systems.

  3. Macroscopic and spectroscopic investigations of the adsorption of nitroaromatic compounds on graphene oxide, reduced graphene oxide, and graphene nanosheets.

    PubMed

    Chen, Xiaoxiao; Chen, Baoliang

    2015-05-19

    The surface properties and adsorption mechanisms of graphene materials are important for potential environmental applications. The adsorption of m-dinitrobenzene, nitrobenzene, and p-nitrotoluene onto graphene oxide (GO), reduced graphene oxide (RGO), and graphene (G) nanosheets was investigated using IR spectroscopy to probe the molecular interactions of graphene materials with nitroaromatic compounds (NACs). The hydrophilic GO displayed the weakest adsorption capability. The adsorption of RGO and G was significantly increased due to the recovery of hydrophobic π-conjugation carbon atoms as active sites. RGO nanosheets, which had more defect sites than did GO or G nanosheets, resulted in the highest adsorption of NACs which was 10-50 times greater than the reported adsorption of carbon nanotubes. Superior adsorption was dominated by various interaction modes including π-π electron donor-acceptor interactions between the π-electron-deficient phenyls of the NACs and the π-electron-rich matrix of the graphene nanosheets, and the charge electrostatic and polar interactions between the defect sites of graphene nanosheets and the -NO2 of the NAC. The charge transfer was initially proved by FTIR that a blue shift of asymmetric -NO2 stretching was observed with a concomitant red shift of symmetric -NO2 stretching after m-dinitrobenzene was adsorbed. The multiple interaction mechanisms of the adsorption of NAC molecule onto flat graphene nanosheets favor the adsorption, detection, and transformation of explosives.

  4. Photoluminescence study in diaminobenzene functionalized graphene oxide

    SciTech Connect

    Gupta, Abhisek E-mail: cnssks@iacs.res.in; Saha, Shyamal K. E-mail: cnssks@iacs.res.in

    2014-10-15

    Being an excellent electronic material graphene is a very poor candidate for optoelectronic applications. One of the major strategies to develop the optical property in GO is the functionalization of graphene oxide (GO). In the present work GO sheets are functionalized by o-phenylenediamine to achieve diaminobenzene functionalized GO composite (DAB-GO). Formation of DAB-GO composite is further characterized by FTIR, UV, Raman studies. Excellent photoluminescence is observed in DAB-GO composite via passivation of the surface reactive sites by ring-opening amination of epoxides of GO.

  5. Thrombin aptasensing with inherently electroactive graphene oxide nanoplatelets as labels

    NASA Astrophysics Data System (ADS)

    Loo, Adeline Huiling; Bonanni, Alessandra; Pumera, Martin

    2013-05-01

    Graphene and its associated materials are commonly used as the transducing platform in biosensing. We propose a different approach for the application of graphene in biosensing. Here, we utilized graphene oxide nanoplatelets as the inherently electroactive labels for the aptasensing of thrombin. The basis of detection lies in the ability of graphene oxide to be electrochemically reduced, thereby providing a well-defined reduction wave; one graphene oxide nanoplatelet of dimension 50 × 50 nm can provide a reduction signal by accepting ~22 000 electrons. We demonstrate that by using graphene oxide nanoplatelets as an inherently electroactive label, we can detect thrombin in the concentration range of 3 pM-0.3 μM, with good selectivity of the aptamer towards interferences by bovine serum albumin, immunoglobulin G and avidin. Therefore, the inherently electroactive graphene oxide nanoplatelets are a material which can serve as an electroactive label, in a manner similar to metallic nanoparticles.

  6. Monolayer graphene as dissipative membrane in an optical resonator

    NASA Astrophysics Data System (ADS)

    Meyer, Hendrik M.; Breyer, Moritz; Köhl, Michael

    2016-12-01

    We experimentally demonstrate coupling of an atomically thin, free-standing graphene membrane to an optical cavity. By changing the position of the membrane along the standing-wave field of the cavity, we tailor the dissipative coupling between the membrane and the cavity, and we show that the dissipative coupling can outweigh the dispersive coupling. Such a system, for which controlled dissipation prevails dispersion, will prove useful for novel laser-cooling schemes in optomechanics. In addition, we have determined the continuous-wave optical damage threshold of free-standing monolayer graphene of 1.8(4) MW/cm^2 at 780 nm.

  7. Graphene quantum dots sensor for the determination of graphene oxide in environmental water samples.

    PubMed

    Benítez-Martínez, Sandra; López-Lorente, Ángela Inmaculada; Valcárcel, Miguel

    2014-12-16

    The paper proposes a simple and sensitive approach for the preconcentration and determination of graphene oxide (GO) in environmental samples by using fluorescent graphene quantum dots (GQDs). The method is based on the preconcentration of GO on a cellulose membrane and their subsequent elution prior to fluorescence analysis of the quenching effect produced on the GQD solution due to the hydrophobic interactions between GO and GQDs. The limit of detection was 35 μg·L(-1). The precision, for a 200 μg·L(-1) concentration of GO, is 5.16%. The optimized procedure has been successively applied to the determination of traces of GO in river water samples.

  8. Computational nanomaterials for novel desalination membrane design: Nanoporous graphene

    NASA Astrophysics Data System (ADS)

    Cohen-Tanugi, David; Grossman, Jeffrey C.

    2012-02-01

    We describe a novel approach for desalination based on nanoporous graphene. Our molecular dynamics calculations show that freestanding graphene patterned with nanometer-sized pores can act as an ultra-thin filtration membrane. Due to size exclusion and chemical interactions with the confining pores, salt ions can be blocked from permeating the membrane at sufficiently small pore diameters. Notably, the pore diameter and the chemical interactions at the water-membrane interface are most important criteria for this system's desalination performance. We will share insights from Molecular Dynamics calculations regarding the theoretical performance of this membrane system and the effects of chemical passivation of the graphene pores on the filtration dynamics. Although the narrow range of acceptable pore sizes suggests that further design innovations will be necessary at the molecular scale before large-scale applications are possible, our existing results predict that pressure requirements for this system can be made roughly competitive with commercial Reverse Osmosis.

  9. Quantum confinement-induced tunable exciton states in graphene oxide

    PubMed Central

    Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Lee, Jiyoul; Shin, Hyeon-Jin; Cole, Jacqueline M.; Shin, Taeho; Lee, Jaichan; Lee, Hangil; Su, Haibin

    2013-01-01

    Graphene oxide has recently been considered to be a potential replacement for cadmium-based quantum dots due to its expected high fluorescence. Although previously reported, the origin of the luminescence in graphene oxide is still controversial. Here, we report the presence of core/valence excitons in graphene-based materials, a basic ingredient for optical devices, induced by quantum confinement. Electron confinement in the unreacted graphitic regions of graphene oxide was probed by high resolution X-ray absorption near edge structure spectroscopy and first-principles calculations. Using experiments and simulations, we were able to tune the core/valence exciton energy by manipulating the size of graphitic regions through the degree of oxidation. The binding energy of an exciton in highly oxidized graphene oxide is similar to that in organic electroluminescent materials. These results open the possibility of graphene oxide-based optoelectronic device technology. PMID:23872608

  10. Wrinkled Surface-Mediated Antibacterial Activity of Graphene Oxide Nanosheets.

    PubMed

    Zou, Fengming; Zhou, Hongjian; Jeong, Do Young; Kwon, Junyoung; Eom, Seong Un; Park, Tae Jung; Hong, Suck Won; Lee, Jaebeom

    2017-01-18

    Surface wrinkles are commonly observed in large-scale of graphene films. As a new feature, the wrinkled surface of graphene films may directly affect bacterial viability by means of various interactions of bacterial cells with graphene sheets. In the present study, we introduce a wrinkled surface geometry of graphene oxide (GO) thin films for antibacterial application. Highly wrinkled GO films were formed by vacuum filtration of a GO suspension through a prestrained filter. Several types of wrinkled GO surfaces were obtained with different roughness grades determined by root-mean-square values. Antibacterial activity of the fabricated GO films toward three different bacterial species, Escherichia coli, Mycobacterium smegmatis, and Staphylococcus aureus, was evaluated in relation to surface roughness. Because of their nanoscopically corrugated nature, the wrinkled GO films exhibited excellent antibacterial properties. On the basis of our detailed observations, we propose a novel concept of the surrounded contact-based mechanism for antimicrobial activity of wrinkled GO films. It postulates formation of a mechanically robust GO surface "trap" that prompts interaction of bacteria with the diameter-matched GO sink, which results in substantial damages to the bacterial cell membrane. We believe that our approach uncovered a novel use of a promising two-dimensional material for highly effective antibacterial treatment.

  11. Oxide-on-graphene field effect biosensors

    NASA Astrophysics Data System (ADS)

    Wang, Bei; Liddell, Kristi; Wang, Junjie; Koger, Brandon; Keating, Christine; Zhu, J.

    2013-03-01

    Nanoelectronics-based detection schemes offer fast and label-free alternatives to bioanalysis. Here we report on the design, fabrication, and operation of ion-sensitive field-effect biosensors using large-area graphene sheets synthesized by chemical vapor deposition. The graphene transducer channel has a high carrier mobility of approximately 5000cm2/Vs. Our oxide-on-graphene design uses thin HfO2 and SiO2 films to passivate the graphene channel and electrodes from electrolyte and uses the top SiO2 surface for sensing and linker chemistry. The pH sensitivity of the bare SiO2 is measured to be 46mV/pH, in good agreement with literature results. We demonstrate the silanization of the SiO2 surface with aminopropyl-trimethoxysilane (APTMS). The pH sensitivity of the APTMS-functionalized SiO2 is measured to be 43mV/pH. By applying the solution gate voltage in pulse, we eliminate hysteresis in the transfer curve of the graphene channel, which is a common challenge in achieving high-solution detection using nanostructure-based field effect sensors. The amine-functionalized SiO2 surface can be further functionalized with bio-probes to perform the detection of specific binding events such as DNA hybridization.

  12. Influence of graphene oxide and reduced graphene oxide on the activity and conformation of lysozyme.

    PubMed

    Bai, Yitong; Ming, Zhu; Cao, Yuye; Feng, Shicheng; Yang, Hua; Chen, Lingyun; Yang, Sheng-Tao

    2017-03-08

    The dramatically different bio-effects of graphene and graphene oxide (GO) have been widely observed in diverse biological systems, which determine the applications and toxicity of graphene materials. To elucidate the mechanism at molecular level, it is urgent to investigate the enzyme-graphene interaction and its consequences. In this study, we comparatively studied the influence of GO and reduced GO (RGO) on the activity and conformation of lysozyme to provide better understandings of their different bio-effects. Both GO and RGO adsorbed large quantities of lysozyme after incubation. GO inhibited lysozyme activity seriously, while RGO nearly had no influence on the enzyme activity. The different inhibitions of enzyme activity could be explained by the lysozyme conformational changes, where GO induced more changes to the protein conformation according to UV-vis absorbance, far-UV circular dichroism spectra, intrinsic fluorescence quenching, and infrared spectra. Based on the spectroscopic changes of lysozyme, GO induced the loss of secondary structure and exposed the active site of lysozyme more to the aqueous environment. In addition, neither GO nor RGO induced the fibrillation of lysozyme after 12d incubation. The results collectively indicated that the oxidation degree significantly impacted the enzyme-graphene interaction. The implications to the designs of enzyme-graphene system for bio-related applications and the toxicological effects of graphene materials are discussed.

  13. Comparing Graphene Growth on Cu(111) versus Oxidized Cu(111)

    PubMed Central

    2015-01-01

    The epitaxial growth of graphene on catalytically active metallic surfaces via chemical vapor deposition (CVD) is known to be one of the most reliable routes toward high-quality large-area graphene. This CVD-grown graphene is generally coupled to its metallic support resulting in a modification of its intrinsic properties. Growth on oxides is a promising alternative that might lead to a decoupled graphene layer. Here, we compare graphene on a pure metallic to graphene on an oxidized copper surface in both cases grown by a single step CVD process under similar conditions. Remarkably, the growth on copper oxide, a high-k dielectric material, preserves the intrinsic properties of graphene; it is not doped and a linear dispersion is observed close to the Fermi energy. Density functional theory calculations give additional insight into the reaction processes and help explaining the catalytic activity of the copper oxide surface. PMID:25611528

  14. Casein mediated green synthesis and decoration of reduced graphene oxide.

    PubMed

    Maddinedi, Sireesh Babu; Mandal, Badal Kumar; Vankayala, Raviraj; Kalluru, Poliraju; Tammina, Sai Kumar; Kiran Kumar, H A

    2014-05-21

    This research is mainly focusing on one-step biosynthesis of graphene from graphene oxide and its stabilization using naturally occurring milk protein, casein. The synthesis of casein reduced graphene oxide (CRGO) was completed within 7h under reflux at 90°C with the formation of few layered fine graphene nanosheets. UV-Vis, XRD, XPS analysis data revealed the reduction process of the graphene oxide. Results of FT-IR, HPLC and TEM analysis have shown that the ensuing material consists of graphene decorated with casein molecules. Aspartic acid and glutamic acid residue present in casein molecules are responsible for the reduction of graphene oxide. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Highly controllable and green reduction of graphene oxide to flexible graphene film with high strength

    SciTech Connect

    Wan, Wubo; Zhao, Zongbin; Hu, Han; Gogotsi, Yury; Qiu, Jieshan

    2013-11-15

    Graphical abstract: Highly controllable and green reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant. Self-assembly of the as-made CCG sheets results in a flexible CCG film, of which the tensile strength strongly depends on the deoxygenation degree of graphene sheets. - Highlights: • Graphene was synthesized by an effective and environmentally friendly approach. • We introduced a facile X-ray diffraction analysis method to investigate the reduction process from graphene oxide to graphene. • Flexible graphene films were prepared by self-assembly of the graphene sheets. • The strength of the graphene films depends on the reduction degree of graphene. - Abstract: Graphene film with high strength was fabricated by the assembly of graphene sheets derived from graphene oxide (GO) in an effective and environmentally friendly approach. Highly controllable reduction of GO to chemical converted graphene (CCG) was achieved with sodium citrate as a facile reductant, in which the reduction process was monitored by XRD analysis and UV–vis absorption spectra. Self-assembly of the as-made CCG sheets results in a flexible CCG film. This method may open an avenue to the easy and scalable preparation of graphene film with high strength which has promising potentials in many fields where strong, flexible and electrically conductive films are highly demanded.

  16. Physiochemical and optical properties of chitosan based graphene oxide bionanocomposite.

    PubMed

    Kumar, Santosh; Koh, Joonseok

    2014-09-01

    In the present investigation an ecofriendly approach and a simple homogeneous solution casting method led to the development of biodegradable chitosan/graphene oxide bionanocomposites. The formation of bionanocomposite was confirmed by UV-vis, FT-IR, Raman spectroscopy, XRD, and further evaluated by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The circular dichroism (CD) study of chitosan/graphene oxide revealed that the intensity of the negative transition band at wavelength of 200-222 nm decreased with the different pH of chitosan/graphene oxide solutions. It was also found that the pH conditions affect the interaction between chitosan and graphene oxide. Optical properties of chitosan/graphene oxide are evaluated by photoluminescence (PL) spectroscopy which showed blue shift at excitation wavelength of 255 nm compared to graphene oxide. These results strongly suggest that the bionanocomposite materials may open new vistas in biotechnological, biosensor and biomedical applications.

  17. Synthesis and structural characterization of separate graphene oxide and reduced graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Aslam, M.; Kalyar, M. A.; Raza, Z. A.

    2016-10-01

    Graphene, being a unique carbon allotrope with a structure that is one atom thick, is known as a mysterious material in the current era due to its strange nature. It has attained global attention due to its amazing mechanical, electrical, thermal and optical properties. Recent progress has revealed that materials built with graphene can have a limitless impact on nanocomposites, electronic, optoelectronic and energy storage devices as well as chemical sensors. In the present study, graphite flakes were chemically oxidized in graphite oxide via the modified Hummers’ method, i.e. without adding sodium nitrate. The graphite oxide was exfoliated in distilled water by using an ultrasonic bath to fabricate graphene oxide nanosheets. The graphene was acquired through an inexpensive and large-scale production route to eliminate functional groups containing oxygen by using hydrazine monohydrate as a reducing agent. The reduced graphene oxide obtained through this route contained residual oxygen-functional groups which can act as active sites for gas molecular interaction and be used in a variety of applications like gas sensing. The prepared samples were analyzed using the dynamic light scattering technique, UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy and atomic force microscopy.

  18. Scalable Graphene-Based Membranes for Ionic Sieving with Ultrahigh Charge Selectivity.

    PubMed

    Hong, Seunghyun; Constans, Charlotte; Surmani Martins, Marcos Vinicius; Seow, Yong Chin; Guevara Carrió, Juan Alfredo; Garaj, Slaven

    2017-02-08

    Nanostructured graphene-oxide (GO) laminate membranes, exhibiting ultrahigh water flux, are excellent candidates for next generation nanofiltration and desalination membranes, provided the ionic rejection could be further increased without compromising the water flux. Using microscopic drift-diffusion experiments, we demonstrated the ultrahigh charge selectivity for GO membranes, with more than order of magnitude difference in the permeabilities of cationic and anionic species of equivalent hydration radii. Measuring diffusion of a wide range of ions of different size and charge, we were able to clearly disentangle different physical mechanisms contributing to the ionic sieving in GO membranes: electrostatic repulsion between ions and charged chemical groups; and the compression of the ionic hydration shell within the membrane's nanochannels, following the activated behavior. The charge-selectivity allows us to rationally design membranes with increased ionic rejection and opens up the field of ion exchange and electrodialysis to the GO membranes.

  19. Graphene oxide vs. reduced graphene oxide as carbon support in porphyrin peroxidase biomimetic nanomaterials.

    PubMed

    Socaci, C; Pogacean, F; Biris, A R; Coros, M; Rosu, M C; Magerusan, L; Katona, G; Pruneanu, S

    2016-02-01

    The paper describes the preparation of supramolecular assemblies of tetrapyridylporphyrin (TPyP) and its metallic complexes with graphene oxide (GO) and thermally reduced graphene oxide (TRGO). The two carbon supports are introducing different characteristics in the absorption spectra of the investigated nanocomposites. Raman spectroscopy shows that the absorption of iron-tetrapyridylporphyrin is more efficient on GO than TRGO, suggesting that oxygen functionalities are involved in the non-covalent interaction between the iron-porphyrin and graphene. The biomimetic peroxidase activity is investigated and the two iron-containing composites exhibit a better catalytic activity than each component of the assembly, and their cobalt and manganese homologues, respectively. The main advantages of this work include the demonstration of graphene oxide as a very good support for graphene-based nanomaterials with peroxidase-like activity (K(M)=0.292 mM), the catalytic activity being observed even with very small amounts of porphyrins (the TPyP:graphene ratio=1:50). Its potential application in the detection of lipophilic antioxidants (vitamin E can be measured in the 10(-5)-10(-4) M range) is also shown.

  20. Propylene/propane permeation properties of ethyl cellulose (EC) mixed matrix membranes fabricated by incorporation of nanoporous graphene nanosheets

    PubMed Central

    Yuan, Bingbing; Sun, Haixiang; Wang, Tao; Xu, Yanyan; Li, Peng; Kong, Ying; Niu, Q. Jason

    2016-01-01

    Nanopore containing graphene nanosheets were synthesized by graphene oxide and a reducing agent using a facile hydrothermal treatment in sodium hydroxide media. The as-prepared nanoporous graphene was incorporated into ethyl cellulose (EC) to prepare the mixed matrix membranes (MMMs) for C3H6/C3H8 separation. Transmission electron microscopy (TEM) photograph and X-ray photoelectron spectroscopy (XPS) analysis of nanoporous graphene nanosheets indicated that the structure of nano-pore was irregular and the oxygen-containing groups in the surface were limited. More importantly, the as-prepared MMMs presented better separation performance than that of pristine EC membrane due to simultaneous enhancement of C3H6 permeability and ideal selectivity. The ideal selectivity of the MMMs with 1.125 wt‰ nanoporous graphene content for C3H6/C3H8 increased from 3.45 to 10.42 and the permeability of C3H6 increased from 57.9 Barrer to 89.95 Barrer as compared with the pristine membrane. The presumed facilitated mechanism was that the high specific surface area of nanoporous graphene in polymer matrix increased the length of the tortuous pathway formed by nanopores for the gas diffusion as compared with the pristine graphene nanosheets, and generated a rigidified interface between the EC chains and fillers, thus enhanced the diffusivity selectivity. Therefore, it is expected that nanoporous graphene would be effective material for the C3H6/C3H8 separation. PMID:27352851

  1. Propylene/propane permeation properties of ethyl cellulose (EC) mixed matrix membranes fabricated by incorporation of nanoporous graphene nanosheets

    NASA Astrophysics Data System (ADS)

    Yuan, Bingbing; Sun, Haixiang; Wang, Tao; Xu, Yanyan; Li, Peng; Kong, Ying; Niu, Q. Jason

    2016-06-01

    Nanopore containing graphene nanosheets were synthesized by graphene oxide and a reducing agent using a facile hydrothermal treatment in sodium hydroxide media. The as-prepared nanoporous graphene was incorporated into ethyl cellulose (EC) to prepare the mixed matrix membranes (MMMs) for C3H6/C3H8 separation. Transmission electron microscopy (TEM) photograph and X-ray photoelectron spectroscopy (XPS) analysis of nanoporous graphene nanosheets indicated that the structure of nano-pore was irregular and the oxygen-containing groups in the surface were limited. More importantly, the as-prepared MMMs presented better separation performance than that of pristine EC membrane due to simultaneous enhancement of C3H6 permeability and ideal selectivity. The ideal selectivity of the MMMs with 1.125 wt‰ nanoporous graphene content for C3H6/C3H8 increased from 3.45 to 10.42 and the permeability of C3H6 increased from 57.9 Barrer to 89.95 Barrer as compared with the pristine membrane. The presumed facilitated mechanism was that the high specific surface area of nanoporous graphene in polymer matrix increased the length of the tortuous pathway formed by nanopores for the gas diffusion as compared with the pristine graphene nanosheets, and generated a rigidified interface between the EC chains and fillers, thus enhanced the diffusivity selectivity. Therefore, it is expected that nanoporous graphene would be effective material for the C3H6/C3H8 separation.

  2. Graphene oxide windows for in situ environmental cell photoelectron spectroscopy.

    PubMed

    Kolmakov, Andrei; Dikin, Dmitriy A; Cote, Laura J; Huang, Jiaxing; Abyaneh, Majid Kazemian; Amati, Matteo; Gregoratti, Luca; Günther, Sebastian; Kiskinova, Maya

    2011-08-28

    The performance of new materials and devices often depends on processes taking place at the interface between an active solid element and the environment (such as air, water or other fluids). Understanding and controlling such interfacial processes require surface-specific spectroscopic information acquired under real-world operating conditions, which can be challenging because standard approaches such as X-ray photoelectron spectroscopy generally require high-vacuum conditions. The state-of-the-art approach to this problem relies on unique and expensive apparatus including electron analysers coupled with sophisticated differentially pumped lenses. Here, we develop a simple environmental cell with graphene oxide windows that are transparent to low-energy electrons (down to 400 eV), and demonstrate the feasibility of X-ray photoelectron spectroscopy measurements on model samples such as gold nanoparticles and aqueous salt solution placed on the back side of a window. These proof-of-principle results show the potential of using graphene oxide, graphene and other emerging ultrathin membrane windows for the fabrication of low-cost, single-use environmental cells compatible with commercial X-ray and Auger microprobes as well as scanning or transmission electron microscopes.

  3. Colloidal Stability of Graphene Oxide Nanosheets in Aqueous Solutions

    NASA Astrophysics Data System (ADS)

    Guikema, Janice; Wang, Yung-Li; Chen, Kai

    2013-03-01

    Carbon-based nanomaterials are increasingly used in commercial products as well as in research and industrial applications. Due to its extraordinary properties, graphene has attracted intense research interest and has been demonstrated in many potential applications including solar cells, conductive ink, and transistors. Graphene oxide has also been studied extensively and has been used to produce biocompatible antibacterial paper. Chemical reduction of graphene oxide is commonly used to produce inexpensive graphene in large quantities. With the increasing use of graphene and graphene oxide in consumer products, these nanomaterials may inevitably be released to aqueous systems, resulting in potential risk to environmental ecosystems and human health. The fate and mobility of graphene and its oxides in aquatic systems is dependent on their colloidal stability. We will discuss our study of the early-stage aggregation kinetics of graphene oxide in aqueous solutions. We prepared a suspension of single-layer graphene oxide nanosheets in water and used time-resolved dynamic light scattering to study the influence of electrolytes and pH on the aggregation kinetics of the nanosheets. Atomic force microscopy was employed to further examine the graphene oxide nanosheets.

  4. Microorganism mediated synthesis of reduced graphene oxide films

    NASA Astrophysics Data System (ADS)

    Tanizawa, Y.; Okamoto, Y.; Tsuzuki, K.; Nagao, Y.; Yoshida, N.; Tero, R.; Iwasa, S.; Hiraishi, A.; Suda, Y.; Takikawa, H.; Numano, R.; Okada, H.; Ishikawa, R.; Sandhu, A.

    2012-03-01

    The wide-ranging industrial application of graphene and related compounds has led researchers to devise methods for the synthesis of high quality graphene. We recently reported on the chemical synthesis, patterning, and doping of graphene films by the chemical exfoliation of graphite into graphene oxide (GO) with subsequent chemical reduction into graphene films [1, 2]. Here, we describe a hybrid approach for the synthesis of reduced graphene sheets, where chemically derived GO was reduced by microorganisms extracted from a riverside near the University. Our procedure enabled the production of ~100 μm sized reduced graphene sheets, which showed excellent Raman spectra associated with high quality reduced graphene. We give a detailed account of the relationship between the type of microorganisms and the properties of the resulting reduced graphene.

  5. Internalization and cytotoxicity of graphene oxide and carboxyl graphene nanoplatelets in the human hepatocellular carcinoma cell line Hep G2.

    PubMed

    Lammel, Tobias; Boisseaux, Paul; Fernández-Cruz, Maria-Luisa; Navas, José M

    2013-07-12

    Graphene and graphene derivative nanoplatelets represent a new generation of nanomaterials with unique physico-chemical properties and high potential for use in composite materials and biomedical devices. To date little is known about the impact graphene nanomaterials may have on human health in the case of accidental or intentional exposure. The objective of this study was to assess the cytotoxic potential of graphene nanoplatelets with different surface chemistry towards a human hepatoma cell line, Hep G2, and identify the underlying toxicity targets. Graphene oxide (GO) and carboxyl graphene (CXYG) nanoplatelet suspensions were obtained in water and culture medium. Size frequency distribution of the suspensions was determined by means of dynamic light scattering. Height, lateral dimension and shape of the nanoplatelets were determined using atomic force and electron microscopy. Cytotoxicity of GO and CXYG nanoplatelets was assessed in Hep G2 cells using a battery of assays covering different modes of action including alterations of metabolic activity, plasma membrane integrity and lysosomal function. Induction of oxidative stress was assessed by measuring intracellular reactive oxygen species levels. Interaction with the plasma membrane, internalization and intracellular fate of GO and CXYG nanoplatelets was studied by scanning and transmission electron microscopy. Supplementing culture medium with serum was essential to obtain stable GO and CXYG suspensions. Both graphene derivatives had high affinity for the plasma membrane and caused structural damage of the latter at concentrations as low as 4 μg/ml. The nanoplatelets penetrated through the membrane into the cytosol, where they were concentrated and enclosed in vesicles. GO and CXYG accumulation in the cytosol was accompanied by an increase in intracellular reactive oxygen species (ROS) levels, alterations in cellular ultrastructure and changes in metabolic activity. GO and CXYG nanoplatelets caused dose

  6. Internalization and cytotoxicity of graphene oxide and carboxyl graphene nanoplatelets in the human hepatocellular carcinoma cell line Hep G2

    PubMed Central

    2013-01-01

    Background Graphene and graphene derivative nanoplatelets represent a new generation of nanomaterials with unique physico-chemical properties and high potential for use in composite materials and biomedical devices. To date little is known about the impact graphene nanomaterials may have on human health in the case of accidental or intentional exposure. The objective of this study was to assess the cytotoxic potential of graphene nanoplatelets with different surface chemistry towards a human hepatoma cell line, Hep G2, and identify the underlying toxicity targets. Methods Graphene oxide (GO) and carboxyl graphene (CXYG) nanoplatelet suspensions were obtained in water and culture medium. Size frequency distribution of the suspensions was determined by means of dynamic light scattering. Height, lateral dimension and shape of the nanoplatelets were determined using atomic force and electron microscopy. Cytotoxicity of GO and CXYG nanoplatelets was assessed in Hep G2 cells using a battery of assays covering different modes of action including alterations of metabolic activity, plasma membrane integrity and lysosomal function. Induction of oxidative stress was assessed by measuring intracellular reactive oxygen species levels. Interaction with the plasma membrane, internalization and intracellular fate of GO and CXYG nanoplatelets was studied by scanning and transmission electron microscopy. Results Supplementing culture medium with serum was essential to obtain stable GO and CXYG suspensions. Both graphene derivatives had high affinity for the plasma membrane and caused structural damage of the latter at concentrations as low as 4 μg/ml. The nanoplatelets penetrated through the membrane into the cytosol, where they were concentrated and enclosed in vesicles. GO and CXYG accumulation in the cytosol was accompanied by an increase in intracellular reactive oxygen species (ROS) levels, alterations in cellular ultrastructure and changes in metabolic activity. Conclusions

  7. Compositions comprising enhanced graphene oxide structures and related methods

    DOEpatents

    Kumar, Priyank Vijaya; Bardhan, Neelkanth M.; Belcher, Angela; Grossman, Jeffrey

    2016-12-27

    Embodiments described herein generally relate to compositions comprising a graphene oxide species. In some embodiments, the compositions advantageously have relatively high oxygen content, even after annealing.

  8. Laser trimming of graphene oxide for functional photonic applications

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaorui; Lin, Han; Yang, Tieshan; Jia, Baohua

    2017-02-01

    This article reviews the recent photonic applications on graphene oxide and reduced graphene oxide films via the direct laser printing method. Attention has been paid to the unique optical property modulations of graphene oxide films during the laser reduction process, which enable a wide range of functional photonic and optoelectronic devices. The exotic properties of graphene oxide during the laser reduction process, including the tunable dispersion relation, flexible patterning capability, surface functionalization possibility, wavefront shaping ability, and the mechanical robustness and strength, make it a promising integratable platform for the next-generation ultrathin, light-weight and flexible photonic and optoelectronic applications.

  9. Deformation of graphene on an oxidizing nickel surface: the role of graphene layer number

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    Few-layer graphene grown on nickel substrates by chemical vapour deposition is typically characterised by thickness inhomogeneity. In this work, we investigate the thickness-dependent changes induced in graphene during the surface oxidation of the underlying metal. Temperature-dependent Raman spectroscopy and scanning electron microscopy are used to monitor the lattice strain and defect formation induced in graphene, as well as the oxidation of Ni surface. Significant lattice strain is induced in thin layers of graphene (1-2 layers) during the oxidation process, for T > 400 °C. This is followed by the formation of boundary-type defects, and graphene loses structural integrity. In contrast, lattice strain induced in thicker graphene (up to 7 layers) during the metal surface oxidation is quite subdued. These thicker layers de-pin and remain structurally intact even after the underneath metal surface has oxidized.

  10. Zinc oxide doped graphene oxide films for gas sensing applications

    SciTech Connect

    Chetna, Kumar, Shani; Chaudhary, S.; Kapoor, A.; Garg, A.; Chowdhuri, A.; Dhingra, V.

    2016-05-06

    Graphene Oxide (GO) is analogous to graphene, but presence of many functional groups makes its physical and chemical properties essentially different from those of graphene. GO is found to be a promising material for low cost fabrication of highly versatile and environment friendly gas sensors. Selectivity, reversibility and sensitivity of GO based gas sensor have been improved by hybridization with Zinc Oxide nanoparticles. The device is fabricated by spin coating of deionized water dispersed GO flakes (synthesized using traditional hummer’s method) doped with Zinc Oxide on standard glass substrate. Since GO is an insulator and functional groups on GO nanosheets play vital role in adsorbing gas molecules, it is being used as an adsorber. Additionally, on being exposed to certain gases the electric and optical characteristics of GO material exhibit an alteration in behavior. For the conductivity, we use Zinc Oxide, as it displays a high sensitivity towards conduction. The effects of the compositions, structural defects and morphologies of graphene based sensing layers and the configurations of sensing devices on the performances of gas sensors were investigated by Raman Spectroscopy, X-ray diffraction(XRD) and Keithley Sourcemeter.

  11. Application of electrochemically reduced graphene oxide on screen-printed ion-selective electrode.

    PubMed

    Ping, Jianfeng; Wang, Yixian; Ying, Yibin; Wu, Jian

    2012-04-03

    In this study, a novel disposable all-solid-state ion-selective electrode using graphene as the ion-to-electron transducer was developed. The graphene film was prepared on screen-printed electrode directly from the graphene oxide dispersion by a one-step electrodeposition technique. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to demonstrate the large double layer capacitance and fast charge transfer of the graphene film modified electrode. On the basis of these excellent properties, an all-solid-state calcium ion-selective electrode as the model was constructed using the calcium ion-selective membrane and graphene film modified electrode. The mechanism about the graphene promoting the ion-to-electron transformation was investigated in detail. The disposable electrode exhibited a Nernstian slope (29.1 mV/decade), low detection limit (10(-5.8) M), and fast response time (less than 10 s). With the high hydrophobic character of graphene materials, no water film was formed between the ion-selective membrane and the underlying graphene layer. Further studies revealed that the developed electrode was insensitive to light, oxygen, and redox species. The use of the disposable electrode for real sample analysis obtained satisfactory results, which made it a promising alternative in routine sensing applications.

  12. Chair and twist-boat membranes in hydrogenated graphene.

    PubMed

    Samarakoon, Duminda K; Wang, Xiao-Qian

    2009-12-22

    Graphane is a two-dimensional system consisting of a single planar layer of fully saturated carbon atoms, which has recently been realized experimentally through hydrogenation of graphene membranes. We have studied the stability of chair, boat, and twist-boat graphane structures using first-principles density functional calculations. Our results indicate that locally stable twist-boat membranes significantly contribute to the experimentally observed lattice contraction. The band gaps of graphane nanoribbons decrease monotonically with the increase of the ribbon width and are insensitive to the edge structure. The implications of these results for future hydrogenated graphene applications are discussed.

  13. Realization of ferromagnetic graphene oxide with high magnetization by doping graphene oxide with nitrogen

    PubMed Central

    Liu, Yuan; Tang, Nujiang; Wan, Xiangang; Feng, Qian; Li, Ming; Xu, Qinghua; Liu, Fuchi; Du, Youwei

    2013-01-01

    The long spin diffusion length makes graphene very attractive for novel spintronic devices, and thus has triggered a quest for integrating the charge and spin degrees of freedom. However, ideal graphene is intrinsic non-magnetic, due to a delocalized π bonding network. Therefore, synthesis of ferromagnetic graphene or its derivatives with high magnetization is urgent due to both fundamental and technological importance. Here we report that N-doping can be an effective route to obtain a very high magnetization of ca. 1.66 emu/g, and can make graphene oxide (GO) to be ferromagnetism with a Curie-temperature of 100.2 K. Clearly, our findings can offer the easy realization of ferromagnetic GO with high magnetization, therefore, push the way for potential applications in spintronic devices. PMID:23995236

  14. Graphene Oxide Synthesis from Agro Waste

    PubMed Central

    Somanathan, Thirunavukkarasu; Prasad, Karthika; Ostrikov, Kostya (Ken); Saravanan, Arumugam; Mohana Krishna, Vemula

    2015-01-01

    A new method of graphene oxide (GO) synthesis via single-step reforming of sugarcane bagasse agricultural waste by oxidation under muffled atmosphere conditions is reported. The strong and sharp X-ray diffraction peak at 2θ = 11.6° corresponds to an interlayer distance of 0.788 nm (d002) for the AB stacked GOs. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) confirm the formation of the GO layer structure and the hexagonal framework. This is a promising method for fast and effective synthesis of GO from sugarcane bagasse intended for a variety of energy and environmental applications. PMID:28347038

  15. Graphene immobilized enzyme/polyethersulfone mixed matrix membrane: Enhanced antibacterial, permeable and mechanical properties

    NASA Astrophysics Data System (ADS)

    Duan, Linlin; Wang, Yuanming; Zhang, Yatao; Liu, Jindun

    2015-11-01

    Enzyme immobilization has been developed to address lots of issues of free enzyme, such as instability, low activity and difficult to retain. In this study, graphene was used as an ideal carrier for lysozyme immobilization, including graphene oxide (GO) immobilized lysozyme (GO-Ly) and chemically reduced graphene oxide (CRGO) immobilized lysozyme (CRGO-Ly). Herein, lysozyme as a bio-antibacterial agent has excellent antibacterial performance and the products of its catalysis are safety and nontoxic. Then the immobilized lysozyme materials were blended into polyethersulfone (PES) casting solution to prepare PES ultrafiltration membrane via phase inversion method. GO and CRGO were characterized by Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectrum (UV), X-ray diffraction (XRD), and transmission electron microscopy (TEM) and the immobilized lysozyme composites were observed by fluorescent microscopy. The results revealed that GO and CRGO were successfully synthesized and lysozyme was immobilized on their surfaces. The morphology, hydrophilicity, mechanical properties, separation properties and antibacterial activity of the hybrid membranes were characterized in detail. The hydrophilicity, water flux and mechanical strength of the hybrid membranes were significantly enhanced after adding the immobilized lysozyme. In the antibacterial experiment, the hybrid membranes exhibited an effective antibacterial performance against Escherichia coli (E. coli).

  16. Intracellular localization and toxicity of graphene oxide and reduced graphene oxide nanoplatelets to mussel hemocytes in vitro.

    PubMed

    Katsumiti, Alberto; Tomovska, Radmila; Cajaraville, Miren P

    2017-07-01

    Recently, graphene materials have attracted tremendous research interest due to their unique physicochemical properties that hold great promise in electronics, energy, materials and biomedical areas. Graphene oxide (GO) is one of the most extensively studied graphene derivatives. In order to improve GO electrical properties, nanoplatelets are chemically reduced, thus increasing nanoplatelet conductivity. This reduced GO (rGO) shows different properties and behavior compared to GO. Graphene-based wastes are expected to end up in the marine environment. Here we aimed to assess the potential toxic effects of GO and rGO to marine organisms by using in vitro assays with mussel (Mytilus galloprovincialis) hemocytes. Cells were exposed to a wide range of concentrations (up to 100mg/L) of GO (with and without polyvinylpyrrolidone-PVP as stabilizing agent: GO and GO-PVP) and rGO with PVP (rGO-PVP) to assess cytotoxicity and cell membrane integrity. Then, cells were exposed to sublethal concentrations of GO and rGO-PVP to assess their subcellular distribution through transmission electron microscopy (TEM) and to evaluate their effects on ROS production. GO, GO-PVP and rGO-PVP showed low and concentration-dependent cytotoxicity. rGO-PVP (LC50=29.902 and 33.94mg/L depending on the origin) was more toxic than GO (LC50=49.84 and 54.51mg/L depending on the origin) and GO-PVP (LC50=43.72mg/L). PVP was not toxic to hemocytes but increased bioavailability and toxicity of nanoplatelets. At TEM, GO and rGO-PVP nanoplatelets caused invaginations and perforations of the plasma membrane, which agrees with the observed decrease in cell membrane integrity. Nanoplatelets were internalized, at a higher extent for rGO-PVP than for GO, and found in the cytosol and in endolysosomal vesicles of hemocytes. Both GO and rGO-PVP increased ROS production at the highest sublethal concentration tested. In conclusion, GO, GO-PVP and rGO-PVP are not highly toxic to mussel cells but they cause membrane

  17. Graphene oxide overprints for flexible and transparent electronics

    SciTech Connect

    Rogala, M. Wlasny, I.; Kowalczyk, P. J.; Busiakiewicz, A.; Kozlowski, W.; Klusek, Z.; Sieradzki, Z.; Krucinska, I.; Puchalski, M.; Skrzetuska, E.

    2015-01-26

    The overprints produced in inkjet technology with graphene oxide dispersion are presented. The graphene oxide ink is developed to be fully compatible with standard industrial printers and polyester substrates. Post-printing chemical reduction procedure is proposed, which leads to the restoration of electrical conductivity without destroying the substrate. The presented results show the outstanding potential of graphene oxide for rapid and cost efficient commercial implementation to production of flexible electronics. Properties of graphene-based electrodes are characterized on the macro- and nano-scale. The observed nano-scale inhomogeneity of overprints' conductivity is found to be essential in the field of future industrial applications.

  18. Graphene oxide overprints for flexible and transparent electronics

    NASA Astrophysics Data System (ADS)

    Rogala, M.; Wlasny, I.; Dabrowski, P.; Kowalczyk, P. J.; Busiakiewicz, A.; Kozlowski, W.; Lipinska, L.; Jagiello, J.; Aksienionek, M.; Strupinski, W.; Krajewska, A.; Sieradzki, Z.; Krucinska, I.; Puchalski, M.; Skrzetuska, E.; Klusek, Z.

    2015-01-01

    The overprints produced in inkjet technology with graphene oxide dispersion are presented. The graphene oxide ink is developed to be fully compatible with standard industrial printers and polyester substrates. Post-printing chemical reduction procedure is proposed, which leads to the restoration of electrical conductivity without destroying the substrate. The presented results show the outstanding potential of graphene oxide for rapid and cost efficient commercial implementation to production of flexible electronics. Properties of graphene-based electrodes are characterized on the macro- and nano-scale. The observed nano-scale inhomogeneity of overprints' conductivity is found to be essential in the field of future industrial applications.

  19. Nitroxide-Functionalized Graphene Oxide from Graphite Oxide

    PubMed Central

    Avila-Vega, Yazmin I.; Leyva-Porras, Cesar C.; Mireles, Marcela; Quevedo-López, Manuel; Macossay, Javier; Bonilla-Cruz, José

    2013-01-01

    A facile method for preparing functionalized graphene oxide single layers with nitroxide groups is reported herein. Highly oxidized graphite oxide (GO=90.6%) was obtained, slightly modifying an improved Hummer’s method. Oxoammonium salts (OS) were investigated to introduce nitroxide groups to GO, resulting in a one-step functionalization and exfoliation. The mechanisms of functionalization/exfoliation are proposed, where the oxidation of aromatic alcohols to ketone groups, and the formation of alkoxyamine species are suggested. Two kinds of functionalized graphene oxide layers (GOFT1 and GOFT2) were obtained by controlling the amount of OS added. GOFT1 and GOFT2 exhibited a high interlayer spacing (d0001 = 1.12nm), which was determined by X-ray diffraction. The presence of new chemical bonds C-N (~9.5 %) and O-O (~4.3 %) from nitroxide attached onto graphene layers were observed by X-ray photoelectron spectroscopy. Single-layers of GOFT1 were observed by HRTEM, exhibiting amorphous and crystalline zones at a 50:50 ratio; in contrast, layers of GOFT2 exhibited a fully amorphous surface. Fingerprint of GOFT1 single layers was obtained by electron diffraction at several tilts. Finally, the potential use of these materials within Nylon 6 matrices was investigated, where an unusual simultaneous increase in tensile stress, tensile strain and Young’s modulus was observed. PMID:24347671

  20. Reduced graphene oxide by chemical graphitization.

    PubMed

    Moon, In Kyu; Lee, Junghyun; Ruoff, Rodney S; Lee, Hyoyoung

    2010-09-21

    Reduced graphene oxides (RG-Os) have attracted considerable interest, given their potential applications in electronic and optoelectronic devices and circuits. However, very little is known regarding the chemically induced reduction method of graphene oxide (G-O) in both solution and gas phases, with the exception of the hydrazine-reducing agent, even though it is essential to use the vapour phase for the patterning of hydrophilic G-Os on prepatterned substrates and in situ reduction to hydrophobic RG-Os. In this paper, we report a novel reducing agent system (hydriodic acid with acetic acid (HI-AcOH)) that allows for an efficient, one-pot reduction of a solution-phased RG-O powder and vapour-phased RG-O (VRG-O) paper and thin film. The reducing agent system provided highly qualified RG-Os by mass production, resulting in highly conducting RG-O(HI-AcOH). Moreover, VRG-O(HI-AcOH) paper and thin films were prepared at low temperatures (40 °C) and were found to be applicable to flexible devices. This one-pot method is expected to advance research on highly conducting graphene platelets.

  1. Growth and oxidation of graphene on Rh(111).

    PubMed

    Gotterbarm, Karin; Zhao, Wei; Höfert, Oliver; Gleichweit, Christoph; Papp, Christian; Steinrück, Hans-Peter

    2013-12-07

    The growth and oxidation of graphene supported on Rh(111) was studied in situ by high-resolution X-ray photoelectron spectroscopy. By variation of propene pressure and surface temperature the optimum growth conditions were identified, yielding graphene with low defect density. Oxidation of graphene was studied at temperatures between 600 and 1000 K, at an oxygen pressure of ~2 × 10(-6) mbar. The oxidation follows sigmoidal reaction kinetics. In the beginning, the reaction rate is limited by the number of defects, which represent the active sites for oxygen dissociation. After an induction period, the reaction rate increases and graphene is rapidly removed from the surface by oxidation. For graphene with a high defect density we found that the oxidation is faster. In general, a reduction of the induction period and a faster oxidation occur at higher temperatures.

  2. Room-temperature metastability of multilayer graphene oxide films.

    PubMed

    Kim, Suenne; Zhou, Si; Hu, Yike; Acik, Muge; Chabal, Yves J; Berger, Claire; de Heer, Walt; Bongiorno, Angelo; Riedo, Elisa

    2012-05-06

    Graphene oxide potentially has multiple applications. The chemistry of graphene oxide and its response to external stimuli such as temperature and light are not well understood and only approximately controlled. This understanding is crucial to enable future applications of this material. Here, a combined experimental and density functional theory study shows that multilayer graphene oxide produced by oxidizing epitaxial graphene through the Hummers method is a metastable material whose structure and chemistry evolve at room temperature with a characteristic relaxation time of about one month. At the quasi-equilibrium, graphene oxide reaches a nearly stable reduced O/C ratio, and exhibits a structure deprived of epoxide groups and enriched in hydroxyl groups. Our calculations show that the structural and chemical changes are driven by the availability of hydrogen in the oxidized graphitic sheets, which favours the reduction of epoxide groups and the formation of water molecules.

  3. Mechanical strength of nanoporous graphene as a desalination membrane.

    PubMed

    Cohen-Tanugi, David; Grossman, Jeffrey C

    2014-11-12

    Recent advances in the development of nanoporous graphene (NPG) hold promise for the future of water supply by reverse osmosis (RO) desalination. But while previous studies have highlighted the potential of NPG as an RO membrane, there is less understanding as to whether NPG is strong enough to maintain its mechanical integrity under the high hydraulic pressures inherent to the RO desalination process. Here, we show that an NPG membrane can maintain its mechanical integrity in RO but that the choice of substrate for graphene is critical to this performance. Using molecular dynamics simulations and continuum fracture mechanics, we show that an appropriate substrate with openings smaller than 1 μm would allow NPG to withstand pressures exceeding 57 MPa (570 bar) or ten times more than typical pressures for seawater RO. Furthermore, we demonstrate that NPG membranes exhibit an unusual mechanical behavior in which greater porosity may help the membrane withstand even higher pressures.

  4. New routes to graphene, graphene oxide and their related applications.

    PubMed

    Zhu, Yu; James, Dustin K; Tour, James M

    2012-09-18

    Recent research has focused upon the growth of the graphene, with a concentration on the synthesis of graphene and related materials using both solution processes and high temperature chemical vapor and solid growth methods. Protocols to prepare high aspect ratio graphene nanoribbons from multi-walled carbon nanotubes have been developed as well as techniques to grow high quality graphene for electronics and other applications where high quality is needed. Graphene materials have been manipulated and modified for use in applications such as transparent electrodes, field effect transistors, thin film transistors and energy storage devices. This review summarizes the development of graphene and related materials.

  5. Graphene and Graphene Oxide: Biofunctionalization and Applications in Biotechnology

    SciTech Connect

    Wang, Ying; Li, Zhaohui; Wang, Jun; Li, Jinghong; Lin, Yuehe

    2011-05-01

    Graphene is the basic building block of zero-dimensional fullerene, 1D carbon nanotubes, and 3D graphite. Graphene has a unique planar structure as well as novel electronic properties, which have attracted great interest from scientists. This review selectively analyzes current advances in the field of graphene bioapplications. In particular, the functionalization of graphene for biological applications, FRET-based biosensor development by using graphene-based nanomaterials, and the investigation of graphene for living cell studies have been summarized in more details. Future perspectives and possible challenges in this rapidly developing area are also discussed.

  6. Patterning graphene nanoribbons using copper oxide nanowires

    SciTech Connect

    Sinitskii, Alexander; Tour, James M.

    2012-03-05

    We present a fabrication technique for graphene nanoribbons (GNRs) that employs copper oxide nanowires as the etch masks. We demonstrate that these etch masks have numerous advantages: they can be synthesized simply by heating a copper foil in air, deposited on graphene from a solution, they are inert to oxygen plasma, and can be removed from the substrate by dissolution in mild acids. We fabricated GNRs in the device configuration and tested their electrical properties. Depending on the duration of the plasma etching, GNR devices exhibiting either standard ambipolar electric field effects or p-type transistor behaviors with ON-OFF ratios > 50 can be fabricated. The resulting devices based on narrow GNRs are demonstrated to exhibit promising electronic properties, which can be exploited in studies where GNR devices are required.

  7. Graphene oxide nanocomposites and their electrorheology

    SciTech Connect

    Zhang, Wen Ling; Liu, Ying Dan; Choi, Hyoung Jin

    2013-12-15

    Graphical abstract: - Highlights: • GO-based PANI, NCOPA and PS nanocomposites are prepared. • The nanocomposites are adopted as novel electrorheological (ER) candidates. • Their critical ER characteristics and dielectric performance are analyzed. • Typical ER behavior widens applications of GO-based nanocomposites. - Abstract: Graphene oxide (GO), a novel one-atom carbon system, has become one of the most interesting materials recently due to its unique physical and chemical properties in addition to graphene. This article briefly reviews a recent progress of the fabrication of GO-based polyaniline, ionic N-substituted copolyaniline and polystyrene nanocomposites. The critical electrorheological characteristics such as flow response and yield stress from rheological measurement, relaxation time and achievable polarizability from dielectric analysis are also analyzed.

  8. Nonlinear mechanics of graphene membranes and related systems

    NASA Astrophysics Data System (ADS)

    De Alba, Roberto

    Micro- and nano-mechanical resonators with low mass and high vibrational frequency are often studied for applications in mass and force detection where they can offer unparalleled precision. They are also excellent systems with which to study nonlinear phenomena and fundamental physics due to the numerous routes through which they can couple to each other or to external systems. In this work we study the structural, thermal, and nonlinear properties of various micro-mechanical systems. First, we present a study of graphene-coated silicon nitride membranes; the resulting devices demonstrate the high quality factors of silicon nitride as well as the useful electrical and optical properties of graphene. We then study nonlinear mechanics in pure graphene membranes, where all vibrational eigenmodes are coupled to one another through the membrane tension. This effect enables coherent energy transfer from one mechanical mode to another, in effect creating a graphene mechanics-based frequency mixer. In another experiment, we measure the resonant frequency of a graphene membrane over a wide temperature range, 80K - 550K, to determine whether or not it demonstrates the negative thermal expansion coefficient predicted by prevailing theories; our results indicate that this coefficient is positive at low temperatures - possibly due to polymer contaminants on the graphene surface - and negative above room temperature. Lastly, we study optically-induced self-oscillation in metal-coated silicon nitride nanowires. These structures exhibit self-oscillation at extremely low laser powers ( 1muW incident on the nanowire), and we use this photo-thermal effect to counteract the viscous air-damping that normally inhibits micro-mechanical motion.

  9. Preparation and characterization of graphene oxide encapsulated gold nanoparticles.

    PubMed

    Yun, Yong Ju; Song, Ki-Bong

    2013-11-01

    We present a simple approach for the fabrication of graphene oxide-encapsulated gold nanoparticles using graphene oxide sheet-wrapping via electrostatic self-assembly. By mixing bovine serum albumin molecule-functionalized gold nanoparticles with graphene oxide dispersion, positively charged bovine serum albumin/gold nanoparticles easily assembled with negatively charged graphene oxide sheets through electrostatic interaction. Transmittance electron microscopy, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy were used to confirm the encapsulation of graphene oxide on gold nanoparticles. Interestingly, graphene oxide sheets wrapping mainly occurs along the main body of single or a few gold nanoparticles. Additionally, by measuring the ultraviolet-visible spectroscopy spectrum, we found that the surface plasmon resonances band of the graphene oxide-encapsulated gold nanoparticles was found to become red-shifted compared to that of pristine gold nanoparticles, whereas similar to that of bovine serum albumin-coated gold nanoparticles. These results indicating that most of graphene oxide-encapsulated gold nanoparticles have good monodispersity and spherical shape. These resulting materials may potentially serve as a platform for plasmon resonance electron transfer spectroscopy or a probe for low level biosensing.

  10. Characterization of metal oxide layers grown on CVD graphene

    SciTech Connect

    Matsubayashi, Akitomo; Abel, Joseph; Prasad Sinha, Dhiraj; Lee, Ji Ung; LaBella, Vincent P.

    2013-03-15

    Growth of a fully oxidized aluminum oxide layer with low surface roughness on graphene grown by chemical vapor deposition is demonstrated. This is accomplished by the deposition of a 0.2 nm thick titanium seed layer on the graphene prior to the deposition of the aluminum under ultra high vacuum conditions, which was subsequently oxidized. The stoichiometry and surface roughness of the oxide layers were measured for a range of titanium and aluminum depositions utilizing ex situ x-ray photoelectron spectrometry and atomic force microscopy. These fully oxidized films are expected to produce good dielectric layers for use in graphene based electronic devices.

  11. Physical investigation of electrophoretically deposited graphene oxide and reduced graphene oxide thin films

    NASA Astrophysics Data System (ADS)

    Politano, Grazia Giuseppina; Versace, Carlo; Vena, Carlo; Castriota, Marco; Ciuchi, Federica; Fasanella, Angela; Desiderio, Giovanni; Cazzanelli, Enzo

    2016-11-01

    Graphene oxide and reduced graphene oxide thin films are very promising materials because they can be used in optoelectronic devices and in a growing range of applications such as touch screens and flexible displays. In this work, graphene oxide (GO) and thermally reduced graphene oxide (rGO) thin films, deposited on Ti/glass substrates, have been obtained by electrophoretic deposition. The morphological and the structural properties of the samples have been investigated by micro-Raman technique, X-ray reflectometry, and SEM analysis. In order to study the optical and electrical properties, variable angle spectroscopic ellipsometry and impedance analysis have been performed. The thermal annealing changes strongly the structural, electrical, and optical properties, because during the thermal processes some amount of sp3 bonds originally present in GO were removed. In particular, the annealing enhances the Ohmic behavior of the rGO film increasing its conductivity and the estimated optical density. Moreover, using electrophoretic deposition, we have found a higher value of optical density for GO thin films, not observed in GO films obtained with other deposition methods.

  12. Graphene oxide nanoribbons exhibit significantly greater toxicity than graphene oxide nanoplatelets.

    PubMed

    Chng, Elaine Lay Khim; Chua, Chun Kiang; Pumera, Martin

    2014-09-21

    Graphene oxide (GOs) has emerged in recent years as a versatile nanomaterial, demonstrating tremendous potential for multifunctional biomedical applications. GOs can be prepared by the top-down or bottom-up approach, which leads to a great variability of GOs being produced due to the different procedures and starting carbon sources adopted. This will have an effect on the physiochemical properties of GOs and their resultant toxic behavior. In this study, we examined the cytotoxicity of graphene-oxide nanoribbons (GONRs; ∼310 × 5000 nm) and graphene-oxide nanoplatelets (GONPs; 100 × 100 nm), prepared from the oxidative treatment of multi-walled carbon nanotubes (MWCNTs; ∼100 × 5000 nm) and stacked graphene nanofibers (SGNFs; 100 × 5000 nm), respectively. In vitro assessments revealed that the GONRs exhibited a much stronger cytotoxicity over the GONPs, and we correlated that observation with characterization data that showed GONRs to have a greater amount of carbonyl groups as well as greater length. Therefore, we put forward that the stronger toxic behavior of GONRs is a result of the synergistic effect between these two factors, and the type of carbon source used to prepare GOs should be carefully considered in any future bioapplications.

  13. Differences between graphene and graphene oxide in gelatin based systems for transient biodegradable energy storage applications

    NASA Astrophysics Data System (ADS)

    Landi, G.; Sorrentino, A.; Iannace, S.; Neitzert, H. C.

    2017-02-01

    A comparison between graphene flakes and graphene oxide as filler in gelatin based systems for low-cost transient biodegradable energy storage applications has been carried out. The two bio-composites have been prepared and characterized by rheological measurements, cyclic voltammetry measurements, chronopotentiometry measurements and impedance spectroscopy. Differences in dielectric and mechanical properties have been correlated to the different structural organizations determinate by the hydrophobic/hydrophilic character of the used filler. In particular, the addition of the graphene oxide to the gelatin causes an increase in the elastic modulus with a parallel increase in the mechanical stability with time as compared to the composites obtained by adding graphene. Conversely, the surface capacitance is slightly increased by the graphene oxide addition compared to the pure gelatin sample. On the other hand, the introduction of the graphene flakes into the gelatin leads to a marked increase of the dielectric properties of the resulting bio-composite.

  14. Fluorescence and Sensing Applications of Graphene Oxide and Graphene Quantum Dots: A Review.

    PubMed

    Zheng, Peng; Wu, Nianqiang

    2017-09-19

    Graphene oxide and graphene quantum dots are attractive fluorophores that are inexpensive, nontoxic, photostable, water-soluble, biocompatible, and environmentally friendly. They find extensive applications in fluorescent biosensors and chemosensors, in which they serve as either fluorophores or quenchers. As fluorophores, they display tunable photoluminescence emission and the "giant red-edge effect". As quenchers, they exhibit a remarkable quenching efficiency through either electron transfer or Förster resonance energy transfer (FRET) process. In this review, the origin of fluorescence and the mechanism of excitation wavelength-dependent fluorescence of graphene oxide and graphene quantum dots are discussed. Sensor design strategies based on graphene oxide and graphene quantum dots are presented. The applications of these sensors in health care, the environment, agriculture, and food safety are highlighted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Graphene oxide and H2 production from bioelectrochemical graphite oxidation

    NASA Astrophysics Data System (ADS)

    Lu, Lu; Zeng, Cuiping; Wang, Luda; Yin, Xiaobo; Jin, Song; Lu, Anhuai; Jason Ren, Zhiyong

    2015-11-01

    Graphene oxide (GO) is an emerging material for energy and environmental applications, but it has been primarily produced using chemical processes involving high energy consumption and hazardous chemicals. In this study, we reported a new bioelectrochemical method to produce GO from graphite under ambient conditions without chemical amendments, value-added organic compounds and high rate H2 were also produced. Compared with abiotic electrochemical electrolysis control, the microbial assisted graphite oxidation produced high rate of graphite oxide and graphene oxide (BEGO) sheets, CO2, and current at lower applied voltage. The resultant electrons are transferred to a biocathode, where H2 and organic compounds are produced by microbial reduction of protons and CO2, respectively, a process known as microbial electrosynthesis (MES). Pseudomonas is the dominant population on the anode, while abundant anaerobic solvent-producing bacteria Clostridium carboxidivorans is likely responsible for electrosynthesis on the cathode. Oxygen production through water electrolysis was not detected on the anode due to the presence of facultative and aerobic bacteria as O2 sinkers. This new method provides a sustainable route for producing graphene materials and renewable H2 at low cost, and it may stimulate a new area of research in MES.

  16. Graphene oxide and H2 production from bioelectrochemical graphite oxidation

    PubMed Central

    Lu, Lu; Zeng, Cuiping; Wang, Luda; Yin, Xiaobo; Jin, Song; Lu, Anhuai; Jason Ren, Zhiyong

    2015-01-01

    Graphene oxide (GO) is an emerging material for energy and environmental applications, but it has been primarily produced using chemical processes involving high energy consumption and hazardous chemicals. In this study, we reported a new bioelectrochemical method to produce GO from graphite under ambient conditions without chemical amendments, value-added organic compounds and high rate H2 were also produced. Compared with abiotic electrochemical electrolysis control, the microbial assisted graphite oxidation produced high rate of graphite oxide and graphene oxide (BEGO) sheets, CO2, and current at lower applied voltage. The resultant electrons are transferred to a biocathode, where H2 and organic compounds are produced by microbial reduction of protons and CO2, respectively, a process known as microbial electrosynthesis (MES). Pseudomonas is the dominant population on the anode, while abundant anaerobic solvent-producing bacteria Clostridium carboxidivorans is likely responsible for electrosynthesis on the cathode. Oxygen production through water electrolysis was not detected on the anode due to the presence of facultative and aerobic bacteria as O2 sinkers. This new method provides a sustainable route for producing graphene materials and renewable H2 at low cost, and it may stimulate a new area of research in MES. PMID:26573014

  17. Graphene oxide and H2 production from bioelectrochemical graphite oxidation.

    PubMed

    Lu, Lu; Zeng, Cuiping; Wang, Luda; Yin, Xiaobo; Jin, Song; Lu, Anhuai; Jason Ren, Zhiyong

    2015-11-17

    Graphene oxide (GO) is an emerging material for energy and environmental applications, but it has been primarily produced using chemical processes involving high energy consumption and hazardous chemicals. In this study, we reported a new bioelectrochemical method to produce GO from graphite under ambient conditions without chemical amendments, value-added organic compounds and high rate H2 were also produced. Compared with abiotic electrochemical electrolysis control, the microbial assisted graphite oxidation produced high rate of graphite oxide and graphene oxide (BEGO) sheets, CO2, and current at lower applied voltage. The resultant electrons are transferred to a biocathode, where H2 and organic compounds are produced by microbial reduction of protons and CO2, respectively, a process known as microbial electrosynthesis (MES). Pseudomonas is the dominant population on the anode, while abundant anaerobic solvent-producing bacteria Clostridium carboxidivorans is likely responsible for electrosynthesis on the cathode. Oxygen production through water electrolysis was not detected on the anode due to the presence of facultative and aerobic bacteria as O2 sinkers. This new method provides a sustainable route for producing graphene materials and renewable H2 at low cost, and it may stimulate a new area of research in MES.

  18. Effects of oxidation on the defect of reduced graphene oxides in graphene preparation.

    PubMed

    Hu, Yang; Song, Shaoxian; Lopez-Valdivieso, Alejandro

    2015-07-15

    The relationship between the defects of reduced graphene oxide (RGO) and the oxidation degree of graphite in the preparation of graphene with chemical conversion method has been studied in this work. This study was performed on an artificial graphite through the measurements of X ray diffraction, Raman spectroscopy and particle size analysis. The experimental results have shown that there indeed was a close relationship between the defects and the oxidation degree, which appeared in the form of S-type curve. Also, it was found that a low KMnO4 addition would lead to a partial oxidation of graphite, leaving defects mainly on the edges of RGO; with a high KMnO4 addition, the defects on RGO mostly appeared on the surfaces.

  19. Methylene blue adsorption on graphene oxide/calcium alginate composites.

    PubMed

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Wang, Yonghao; Wu, Shaoling; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2013-06-05

    Graphene oxide has been used as an adsorbent in wastewater treatment. However, the dispersibility in aqueous solution and the biotoxicity to human cells of graphene oxide limits its practical application in environmental protection. In this research, a novel environmental friendly adsorbent, calcium alginate immobilized graphene oxide composites was prepared. The effects of pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto calcium alginate immobilized graphene oxide composites were investigated. The equilibrium adsorption data were described by the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 181.81 mg/g. The pseudo-first order, pseudo-second order, and intraparticle diffusion equation were used to evaluate the kinetic data. Thermodynamic analysis of equilibriums indicated that the adsorption reaction of methylene blue onto calcium alginate immobilized graphene oxide composites was exothermic and spontaneous in nature. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Effect of ammonia plasma treatment on graphene oxide LB monolayers

    SciTech Connect

    Singh, Gulbagh; Botcha, V. Divakar; Narayanam, Pavan K.; Sutar, D. S.; Talwar, S. S.; Major, S. S.; Srinivasa, R. S.

    2013-02-05

    Graphene oxide monolayer sheets were transferred on Si and SiO{sub 2}/Si substrates by Langmuir-Blodgett technique and were exposed to ammonia plasma at room temperature. The monolayer character of both graphene oxide and plasma treated graphene oxide sheets were ascertained by atomic force microscopy. X-ray photoelectron spectroscopy and Raman spectroscopy revealed that ammonia plasma treatment results in enhancement of graphitic carbon content along with the incorporation of nitrogen. The conductivity of graphene oxide monolayers, which was in the range of 10{sup -6}-10{sup -7} S/cm, increased to 10{sup -2}-10{sup -3} S/cm after the ammonia plasma treatment. These results indicate that the graphene oxide was simultaneously reduced and N-doped during ammonia plasma treatment, without affecting the morphological stability of sheets.

  1. Green reduction of graphene oxide via Lycium barbarum extract

    NASA Astrophysics Data System (ADS)

    Hou, Dandan; Liu, Qinfu; Cheng, Hongfei; Zhang, Hao; Wang, Sen

    2017-02-01

    The synthesis of graphene from graphene oxide (GO) usually involves toxic reducing agents that are harmful to human health and the environment. Here, we report a facile approach for effective reduction of GO, for the first time, using Lycium barbarum extract as a green and natural reducing agent. The morphology and de-oxidation efficiency of the reduced graphene were characterized and results showed that Lycium barbarum extract can effectively reduce GO into few layered graphene with a high carbon to oxygen ratio (6.5), comparable to that of GO reduced by hydrazine hydrate (6.6). The possible reduction mechanism of GO may be due to the active components existing in Lycium barbarum fruits, which have high binding affinity to the oxygen containing groups to form their corresponding oxides and other by-products. This method avoided the use of any nocuous chemicals, thus facilitating the mass production of graphene and graphene-based bio-materials.

  2. Suitable chemical methods for preparation of graphene oxide, graphene and surface functionalized graphene nanosheets.

    PubMed

    Sheshmani, Shabnam; Fashapoyeh, Marzieh Arab

    2013-01-01

    This article presents the suitable chemical method for preparation of graphene oxide nanosheets. In order to examine the effects of HNO3/H2SO4 ratio on interlayer spacing and its comparison, the oxidation of graphite with HNO3 and H2SO4 in 1:2 and 1:3 volume ratios was done. Based on the reaction time and interlayer spacing, it was found that the optimum results were obtained when reaction was carried out with HNO3/H2SO4 in 1:3 volume ratio (using modified Staudenmaier method) for 4 days. Results showed that the modified Staudenmaier method improved efficiency exfoliation in oxidation process. Also, the chemical reduction of graphene oxide, which obtained using the modified Staudenmaier method, with hydroquinone and hydrazine hydrate was studied. The results indicate that use of hydrazine hydrate as the reducing agent was more beneficial than the hydroquinone. In continue, we describe the preparation of surface functionalized graphene nanosheets with octadecylamine. The products were characterized by Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Atomic force microscopy (AFM), Field emission-scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS).

  3. Multiplexed biomimetic lipid membranes on graphene by dip-pen nanolithography

    PubMed Central

    Hirtz, Michael; Oikonomou, Antonios; Georgiou, Thanasis; Fuchs, Harald; Vijayaraghavan, Aravind

    2013-01-01

    The application of graphene in sensor devices depends on the ability to appropriately functionalize the pristine graphene. Here we show the direct writing of tailored phospholipid membranes on graphene using dip-pen nanolithography. Phospholipids exhibit higher mobility on graphene compared with the commonly used silicon dioxide substrate, leading to well-spread uniform membranes. Dip-pen nanolithography allows for multiplexed assembly of phospholipid membranes of different functionalities in close proximity to each other. The membranes are stable in aqueous environments and we observe electronic doping of graphene by charged phospholipids. On the basis of these results, we propose phospholipid membranes as a route for non-covalent immobilization of various functional groups on graphene for applications in biosensing and biocatalysis. As a proof of principle, we demonstrate the specific binding of streptavidin to biotin-functionalized membranes. The combination of atomic force microscopy and binding experiments yields a consistent model for the layer organization within phospholipid stacks on graphene. PMID:24107937

  4. Multiplexed biomimetic lipid membranes on graphene by dip-pen nanolithography

    NASA Astrophysics Data System (ADS)

    Hirtz, Michael; Oikonomou, Antonios; Georgiou, Thanasis; Fuchs, Harald; Vijayaraghavan, Aravind

    2013-10-01

    The application of graphene in sensor devices depends on the ability to appropriately functionalize the pristine graphene. Here we show the direct writing of tailored phospholipid membranes on graphene using dip-pen nanolithography. Phospholipids exhibit higher mobility on graphene compared with the commonly used silicon dioxide substrate, leading to well-spread uniform membranes. Dip-pen nanolithography allows for multiplexed assembly of phospholipid membranes of different functionalities in close proximity to each other. The membranes are stable in aqueous environments and we observe electronic doping of graphene by charged phospholipids. On the basis of these results, we propose phospholipid membranes as a route for non-covalent immobilization of various functional groups on graphene for applications in biosensing and biocatalysis. As a proof of principle, we demonstrate the specific binding of streptavidin to biotin-functionalized membranes. The combination of atomic force microscopy and binding experiments yields a consistent model for the layer organization within phospholipid stacks on graphene.

  5. Local oxidation and reduction of graphene.

    PubMed

    Hong, Yi-Zhe; Chiang, Wei-Huan; Tsai, Hung-Chieh; Chuang, Min-Chiang; Kuo, Yan-Chien; Chang, Lo-Yueh; Chen, Chia-Hao; White, Jonathon-David; Woon, Wei-Yen

    2017-09-27

    Micrometer sized oxidation patterns were created in chemical vapor deposition grown graphene through scanning probe lithography (SPL) and then subsequently reduced by irradiation using a focused x-ray beam. Throughout the process, the films were characterized by lateral force microscopy, micro-Raman and micro-x-ray photoelectron spectroscopy. Firstly, the density of grain boundaries was found to be crucial in determining the maximum possible oxygen coverage with SPL. Secondly, the dominant factor in SPL oxidation was found to be the bias voltage. At low voltages, only structural defects are formed on grain boundaries. Above a distinct threshold voltage, oxygen coverage increased rapidly, with the duration of applied voltage affecting the final oxygen coverage. Finally, we found that, independent of initial conditions, types of defects or the amount of SPL oxidation, the same set of coupled rate equations describes the reduction dynamics with the limiting reduction step being C-C → C=C.

  6. The route to functional graphene oxide.

    PubMed

    Haubner, Kinga; Murawski, Jan; Olk, Phillip; Eng, Lukas M; Ziegler, Christoph; Adolphi, Barbara; Jaehne, Evelin

    2010-07-12

    We report on an easy-to-use, successful, and reproducible route to synthesize functionalized graphite oxide (GO) and its conversion to graphene-like materials through chemical or thermal reduction of GO. Graphite oxide containing hydroxyl, epoxy, carbonyl, and carboxyl groups loses mainly hydroxyl and epoxy groups during reduction, whereas carboxyl species remain untouched. The interaction of functionalized graphene with fluorescent methylene blue (MB) is investigated and compared to graphite, fully oxidized GO, as well as thermally and chemically reduced GO. Optical absorption and emission spectra of the composites indicate a clear preference for MB interaction with the GO derivatives containing a large number of functional groups (GO and chemically reduced GO), whereas graphite and thermally reduced GO only incorporate a few MB molecules. These findings are consistent with thermogravimetric, X-ray photoelectron spectroscopic, and Raman data recorded at every stage of preparation. The optical data also indicate concentration-dependent aggregation of MB on the GO surface leading to stable MB dimers and trimers. The MB dimers are responsible for fluorescence quenching, which can be controlled by varying the pH value.

  7. Graphene oxide as a photocatalytic material

    SciTech Connect

    Krishnamoorthy, Karthikeyan; Mohan, Rajneesh; Kim, S.-J.

    2011-06-13

    The photocatalytic characteristics of graphene oxide (GO) nanostructures synthesized by modified Hummer's method were investigated by measuring reduction rate of resazurin (RZ) into resorufin (RF) as a function of UV irradiation time. The progress of the photocatalytic reaction was monitored by change in color from blue (RZ) into pink (RF) followed by absorption spectra. It exhibited excellent photocatalytic activity, leading to the reduction of RZ in UV irradiation. The fitting of absorbance maximum versus time suggests that the reduction of RZ follow the pseudo first-order reaction kinetics. These results indicate that GO have great potential for use as a photocatalyst.

  8. Toxicology of Graphene Oxide Nanosheets Against Paecilomyces catenlannulatus.

    PubMed

    Li, Xiaoyu; Li, Fengbo; Gao, Zhimou; Fang, Lejin

    2015-07-01

    Graphene oxide (GO) nanosheets have been extensively investigated to fabricate the graphene in recent years. The migration of GO nanosheets into the environment could lead to the instability of biological system. In this study, the GO nanosheets were synthesized and were characterized by SEM, high resolution TEM, XRD, Raman, FTIR and XPS techniques. Toxicology testing of GO nanosheets against Paecilomyces catenlannulatus (P. catenlannulatus) was performed by measuring the efflux of cytoplasmic materials of P. catenlannulatus. Approximate 35 % of the bacteria could survive on the surface of GO nanosheets compared to the control sample (~92 %) within 3 h, indicating that GO nanosheets presented significantly antibacterial activities. It was observed that the concentration of RNA in the solution was obviously higher than that of control sample, which could be due to direct contact of the bacterial cell. The results showed that the damage of cell membrane of P. catenlannulatus was attributed to the direct contact of the P. catenlannulatus with the extremely sharp edges of GO nanosheets, which resulted in the P. catenlannulatus inactivation. The less resistant to the damage of cell membrane was observed with increasing of GO concentration and contact time.

  9. Graphene oxide, reduced graphene oxide and composite thin films NO2 sensing properties

    NASA Astrophysics Data System (ADS)

    Dunst, Katarzyna J.; Scheibe, Błażej; Nowaczyk, Grzegorz; Jurga, Stefan; Jasiński, Piotr

    2017-05-01

    A graphene oxide (GO), reduced graphene oxide (RGO) and poly(3,4-ethylenedioxytiophene)-reduced graphene oxide (PEDOT-RGO composite) gas sensors were successfully fabricated using an electrodeposition method. The electrodeposition was carried out in aqueous GO dispersions. In order to obtain RGO and PEDOT-RGO, the electrochemical reduction of GO and PEDOT-GO was carried out in 0.1 M KCl at constant potential of  -0.85 V. The GO, RGO and PEDOT-RGO composites were characterized by scanning and high resolution transmission electron microscopies with electron energy loss spectroscopy, Fourier-transform infrared and Raman spectroscopies. In this work the effect of GO electrochemical reduction process was discussed. The effects of the humidity and sensing response of GO, RGO and PEDOT-RGO to different gases were investigated. It was found out the PEDOT-RGO response to NO2 was much higher than to the other analyzed gases. The influence of the operating temperature on the gas sensing response was compared. The role of the polymer and RGO in PEDOT-RGO composite has been indicated. The results are discussed in light of recent literature on graphene sensors.

  10. Enhanced photothermal effect of plasmonic nanoparticles coated with reduced graphene oxide.

    PubMed

    Lim, Dong-Kwon; Barhoumi, Aoune; Wylie, Ryan G; Reznor, Gally; Langer, Robert S; Kohane, Daniel S

    2013-09-11

    We report plasmonic gold nanoshells and nanorods coated with reduced graphene oxide that produce an enhanced photothermal effect when stimulated by near-infrared (NIR) light. Electrostatic interactions between nanosized graphene oxide and gold nanoparticles followed by in situ chemical reduction generated reduced graphene oxide-coated nanoparticles; the coating was demonstrated using Raman and HR-TEM. Reduced graphene oxide-coated gold nanoparticles showed enhanced photothermal effect compared to noncoated or nonreduced graphene oxide-coated gold nanoparticles. Reduced graphene oxide-coated gold nanoparticles killed cells more rapidly than did noncoated or nonreduced graphene oxide-coated gold nanoparticles.

  11. Bottom-Up Preparation of Ultrathin 2D Aluminum Oxide Nanosheets by Duplicating Graphene Oxide.

    PubMed

    Huang, Zhifeng; Zhou, Anan; Wu, Jifeng; Chen, Yunqiang; Lan, Xiaoli; Bai, Hua; Li, Lei

    2016-02-24

    2D ultrathin aluminum oxide (2D-Al2O3) nanosheets are prepared by duplicating graphene oxide. An amorphous precursor of the hydroxide of aluminum is first deposited onto graphene oxide sheets, which are then converted into 2D-Al2 O3 nanosheets by calcination, while the graphene oxide is removed. The 2D-Al2O3 nanosheets have a large specific surface area and a superior adsorption capacity to fluoride ions.

  12. Breathable Vapor Toxicant Barriers Based on Multilayer Graphene Oxide.

    PubMed

    Spitz Steinberg, Ruben; Cruz, Michelle; Mahfouz, Naser G A; Qiu, Yang; Hurt, Robert H

    2017-06-27

    There is tremendous interest in graphene-based membranes as protective molecular barriers or molecular sieves for separation technologies. Graphene oxide (GO) films in the dry state are known to be effective barriers for molecular transport and to expand in the presence of moisture to create enlarged intersheet gallery spaces that allow rapid water permeation. Here we explore an application for GO membranes as water-breathable barrier layers for personal protective equipment, which are designed to allow outward perspiration while protecting the wearer from chemical toxicants or biochemical agents in the local environment. A device was developed to measure permeation rates of small-molecular toxicants in the presence of counter-current water flow simulating active perspiration. The technique was applied to trichloroethylene (TCE) and benzene, which are important environmental toxicants, and ethanol as a limiting case to model very small, highly water-soluble organic molecules. Submicron GO membranes are shown to be effective TCE barriers, both in the presence and absence of simulated perspiration flux, and to outperform current barrier technologies. A molecular transport model is developed, which suggests the limited toxicant back-permeation observed occurs not by diffusion against the convective perspiration flow in hydrophobic channels, but rather through oxidized domains where hydrogen-bonding produces a near-stagnant water phase. Benzene and ethanol permeation fluxes are higher than those for TCE, likely reflecting the effects of higher water solubility and smaller minimum molecular dimension. Overall, GO films have high water breathability relative to competing technologies and are known to exclude most classes of target toxicants, including particles, bacteria, viruses, and macromolecules. The present results show good barrier performance for some very small-molecule species, but not others, with permeation being favored by high water solubility and small

  13. Green conversion of graphene oxide to graphene nanosheets and its biosafety study

    PubMed Central

    Dasgupta, Adhiraj; Sarkar, Joy; Ghosh, Manosij; Bhattacharya, Amartya; Mukherjee, Anita; Chattopadhyay, Dipankar

    2017-01-01

    Chemical reduction of graphene oxide (GO) to graphene employs the use of toxic and environmentally harmful reducing agents, hindering mass production of graphene which is of tremendous technological importance. In this study we report a green approach to the synthesis of graphene, bio-reduced by crude polysaccharide. The polysaccharide reduces exfoliated GO to graphene at room temperature in an aqueous medium. Transmission electron microscopy image provides clear evidence for the formation of few layer graphene. Characterization of the resulting polysaccharide reduced GO by Raman spectroscopy, Fourier transform infrared spectroscopy and Energy dispersive X-ray analysis confirms reduction of GO to graphene. We also investigated the degree of biosafety of the reduced GO and found it to be safe under 100 μg/ml. PMID:28158272

  14. Green conversion of graphene oxide to graphene nanosheets and its biosafety study.

    PubMed

    Dasgupta, Adhiraj; Sarkar, Joy; Ghosh, Manosij; Bhattacharya, Amartya; Mukherjee, Anita; Chattopadhyay, Dipankar; Acharya, Krishnendu

    2017-01-01

    Chemical reduction of graphene oxide (GO) to graphene employs the use of toxic and environmentally harmful reducing agents, hindering mass production of graphene which is of tremendous technological importance. In this study we report a green approach to the synthesis of graphene, bio-reduced by crude polysaccharide. The polysaccharide reduces exfoliated GO to graphene at room temperature in an aqueous medium. Transmission electron microscopy image provides clear evidence for the formation of few layer graphene. Characterization of the resulting polysaccharide reduced GO by Raman spectroscopy, Fourier transform infrared spectroscopy and Energy dispersive X-ray analysis confirms reduction of GO to graphene. We also investigated the degree of biosafety of the reduced GO and found it to be safe under 100 μg/ml.

  15. Synthesis of Graphene Oxide by Oxidation of Graphite with Ferrate(VI) Compounds: Myth or Reality?

    PubMed

    Sofer, Zdeněk; Luxa, Jan; Jankovský, Ondřej; Sedmidubský, David; Bystroň, Tomáš; Pumera, Martin

    2016-09-19

    It is well established that graphene oxide can be prepared by the oxidation of graphite using permanganate or chlorate in an acidic environment. Recently, however, the synthesis of graphene oxide using potassium ferrate(VI) ions has been reported. Herein, we critically replicate and evaluate this new ferrate(VI) oxidation method. In addition, we test the use of potassium ferrate(VI) for the synthesis of graphene oxide under various experimental routes. The synthesized materials are analyzed by a number of analytical methods in order to confirm or disprove the possibility of synthesizing graphene oxide by the ferrate(VI) oxidation route. Our results confirm the unsuitability of using ferrate(VI) for the oxidation of graphite on graphene oxide because of its high instability in an acidic environment and low oxidation power in neutral and alkaline environments. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Adsorption of nitrogen oxides on graphene and graphene oxides: insights from density functional calculations.

    PubMed

    Tang, Shaobin; Cao, Zexing

    2011-01-28

    The interactions of nitrogen oxides NO(x) (x = 1,2,3) and N(2)O(4) with graphene and graphene oxides (GOs) were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the gas molecule-adsorbed graphene and GO were determined on the basis of first-principles calculations. The adsorption of nitrogen oxides on GO is generally stronger than that on graphene due to the presence of the active defect sites, such as the hydroxyl and carbonyl functional groups and the carbon atom near these groups. These active defect sites increase the binding energies and enhance charge transfers from nitrogen oxides to GO, eventually leading to the chemisorption of gas molecules and the doping character transition from acceptor to donor for NO(2) and NO. The interaction of nitrogen oxides with GO with various functional groups can result in the formation of hydrogen bonds OH⋅⋅⋅O (N) between -OH and nitrogen oxides and new weak covalent bonds C⋅⋅⋅N and C⋅⋅⋅O, as well as the H abstraction to form nitrous acid- and nitric acidlike moieties. The spin-polarized density of states reveals a strong hybridization of frontier orbitals of NO(2) and NO(3) with the electronic states around the Fermi level of GO, and gives rise to the strong acceptor doping by these molecules and remarkable charge transfers from molecules to GO, compared to NO and N(2)O(4) adsorptions on GO. The calculated results show good agreement with experimental observations.

  17. Voltage-induced reduction of graphene oxide

    NASA Astrophysics Data System (ADS)

    Faucett, Austin C.

    Graphene Oxide (GO) is being widely researched as a precursor for the mass production of graphene, and as a versatile material in its own right for flexible electronics, chemical sensors, and energy harvesting applications. Reduction of GO, an electrically insulating material, into reduced graphene oxide (rGO) restores electrical conductivity via removal of oxygen-containing functional groups. Here, a reduction method using an applied electrical bias, known as voltage-induced reduction, is explored. Voltage-induced reduction can be performed under ambient conditions and avoids the use of hazardous chemicals or high temperatures common with standard methods, but little is known about the reduction mechanisms and the quality of rGO produced with this method. This work performs extensive structural and electrical characterization of voltage-reduced GO (V-rGO) and shows that it is competitive with standard methods. Beyond its potential use as a facile and eco-friendly processing approach, V-rGO reduction also offers record high-resolution patterning capabilities. In this work, the spatial resolution limits of voltage-induced reduction, performed using a conductive atomic force microscope probe, are explored. It is shown that arbitrary V-rGO conductive features can be patterned into insulating GO with nanoscale resolution. The localization of voltage-induced reduction to length scales < 10 nm allows studies of reduction reaction kinetics, using electrical current obtained in-situ, with statistical robustness. Methods for patterning V-rGO nanoribbons are then developed. After presenting sub-10nm patterning of V-rGO nanoribbons in GO single sheets and films, the performance of V-rGO nanoribbon field effect transistors (FETs) are demonstrated. Preliminary measurements show an increase in electrical current on/off ratios as compared to large-area rGO FETs, indicating transport gap modulation that is possibly due to quantum confinement effects.

  18. Fast and fully-scalable synthesis of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Abdolhosseinzadeh, Sina; Asgharzadeh, Hamed; Seop Kim, Hyoung

    2015-05-01

    Exfoliation of graphite is a promising approach for large-scale production of graphene. Oxidation of graphite effectively facilitates the exfoliation process, yet necessitates several lengthy washing and reduction processes to convert the exfoliated graphite oxide (graphene oxide, GO) to reduced graphene oxide (RGO). Although filtration, centrifugation and dialysis have been frequently used in the washing stage, none of them is favorable for large-scale production. Here, we report the synthesis of RGO by sonication-assisted oxidation of graphite in a solution of potassium permanganate and concentrated sulfuric acid followed by reduction with ascorbic acid prior to any washing processes. GO loses its hydrophilicity during the reduction stage which facilitates the washing step and reduces the time required for production of RGO. Furthermore, simultaneous oxidation and exfoliation significantly enhance the yield of few-layer GO. We hope this one-pot and fully-scalable protocol paves the road toward out of lab applications of graphene.

  19. Fast and fully-scalable synthesis of reduced graphene oxide

    PubMed Central

    Abdolhosseinzadeh, Sina; Asgharzadeh, Hamed; Seop Kim, Hyoung

    2015-01-01

    Exfoliation of graphite is a promising approach for large-scale production of graphene. Oxidation of graphite effectively facilitates the exfoliation process, yet necessitates several lengthy washing and reduction processes to convert the exfoliated graphite oxide (graphene oxide, GO) to reduced graphene oxide (RGO). Although filtration, centrifugation and dialysis have been frequently used in the washing stage, none of them is favorable for large-scale production. Here, we report the synthesis of RGO by sonication-assisted oxidation of graphite in a solution of potassium permanganate and concentrated sulfuric acid followed by reduction with ascorbic acid prior to any washing processes. GO loses its hydrophilicity during the reduction stage which facilitates the washing step and reduces the time required for production of RGO. Furthermore, simultaneous oxidation and exfoliation significantly enhance the yield of few-layer GO. We hope this one-pot and fully-scalable protocol paves the road toward out of lab applications of graphene. PMID:25976732

  20. Enhanced Mechanical Properties of Graphene (Reduced Graphene Oxide)/Aluminum Composites with a Bioinspired Nanolaminated Structure.

    PubMed

    Li, Zan; Guo, Qiang; Li, Zhiqiang; Fan, Genlian; Xiong, Ding-Bang; Su, Yishi; Zhang, Jie; Zhang, Di

    2015-12-09

    Bulk graphene (reduced graphene oxide)-reinforced Al matrix composites with a bioinspired nanolaminated microstructure were fabricated via a composite powder assembly approach. Compared with the unreinforced Al matrix, these composites were shown to possess significantly improved stiffness and tensile strength, and a similar or even slightly higher total elongation. These observations were interpreted by the facilitated load transfer between graphene and the Al matrix, and the extrinsic toughening effect as a result of the nanolaminated microstructure.

  1. Transfer-free batch fabrication of large-area suspended graphene membranes.

    PubMed

    Alemán, Benjamín; Regan, William; Aloni, Shaul; Altoe, Virginia; Alem, Nasim; Girit, Caglar; Geng, Baisong; Maserati, Lorenzo; Crommie, Michael; Wang, Feng; Zettl, A

    2010-08-24

    We demonstrate a process for batch production of large-area (100-3000 microm(2)) patterned free-standing graphene membranes on Cu scaffolds using chemical vapor deposition (CVD)-grown graphene. This technique avoids the use of silicon and transfers of graphene. As one application of this technique, we fabricate transmission electron microscopy (TEM) sample supports. TEM characterization of the graphene membranes reveals relatively clean, highly TEM-transparent, single-layer graphene regions ( approximately 50% by area) and, despite the polycrystalline nature of CVD graphene, membrane yields as high as 75-100%. This high yield verifies that the intrinsic strength and integrity of CVD-grown graphene films is sufficient for sub-100 microm width membrane applications. Elemental analysis (electron energy loss spectroscopy (EELS) and X-ray energy-dispersive spectroscopy (EDS)) of the graphene membranes reveals some nanoscaled contamination left over from the etching process, and we suggest several ways to reduce this contamination and improve the quality of the graphene for electronic device applications. This large-scale production of suspended graphene membranes facilitates access to the two-dimensional physics of graphene that are suppressed by substrate interactions and enables the widespread use of graphene-based sample supports for electron and optical microscopy.

  2. Two-dimensional shape memory graphene oxide

    PubMed Central

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-01-01

    Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices. PMID:27325441

  3. Sorption mechanisms of metals to graphene oxide

    SciTech Connect

    Showalter, Allison R.; Duster, Thomas A.; Szymanowski, Jennifer E. S.; Na, Chongzheng; Fein, Jeremy B.; Bunker, Bruce A.

    2016-05-01

    Environmental toxic metal contamination remediation and prevention is an ongoing issue. Graphene oxide is highly sorptive for many heavy metals over a wide pH range under different ionic strength conditions. We present x-ray absorption fine structure (XAFS) spectroscopy results investigating the binding environment of Pb(II), Cd(II) and U(VI) ions onto multi-layered graphene oxide (MLGO). Analysis indicates that the dominant sorption mechanism of Pb to MLGO changes as a function of pH, with increasing inner sphere contribution as pH increases. In contrast, the sorption mechanism of Cd to MLGO remains constant under the studied pH range. This adsorption mechanism is an electrostatic attraction between the hydrated Cd+2 ion and the MLGO surface. The U(VI), present as the uranyl ion, changes only subtly as a function of pH and is bound to the surface via an inner sphere bond. Knowledge of the binding mechanism for each metal is necessary to help in optimizing environmental remediation or prevention in filtration systems.

  4. Green and Tunable Decoration of Graphene with Spherical Nanoparticles Based on Laser Ablation in Water: A Case of Ag Nanoparticle/Graphene Oxide Sheet Composites.

    PubMed

    He, Hui; Wang, Haibo; Li, Kai; Zhu, Jun; Liu, Jianshuang; Meng, Xiangdong; Shen, Xiaoshuang; Zeng, Xianghua; Cai, Weiping

    2016-02-23

    A simple and green strategy is presented to decorate graphene with nanoparticles, based on laser ablation of targets in graphene auqeous solution. Ag and graphene oxide (GO) are chosen as model materials. The surface of GO sheets is strongly anchored with spherical Ag nanoparticles. The density and size of the Ag nanoparticles can be easily tuned by laser ablation conditions. Further, the GO sheets can be decorated with other nanoparticles from simple metals or semiconductors to multicomponent hybrids. Additionally, the Ag nanoparticle/GO sheet colloids can be utilized as blocks to build three-dimensional structures, such as sandwich membranes by evaporation-induced self-assembly. These graphene-based composite materials could be very useful in catalysis, sensors, and nanodevices. Particularly, the Ag nanoparticle/GO sheet sandwich composite membranes exhibit excellent surface-enhanced Raman scattering performance and possess the huge potential in trace-detecting persistent organic pollutants in the environment.

  5. Nitrogen-doped reduced graphene oxide electrodes for electrochemical supercapacitors.

    PubMed

    Nolan, Hugo; Mendoza-Sanchez, Beatriz; Ashok Kumar, Nanjundan; McEvoy, Niall; O'Brien, Sean; Nicolosi, Valeria; Duesberg, Georg S

    2014-02-14

    Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.

  6. Graphene oxide decorated electrospun gelatin nanofibers: Fabrication, properties and applications.

    PubMed

    Jalaja, K; Sreehari, V S; Kumar, P R Anil; Nirmala, R James

    2016-07-01

    Gelatin nanofiber fabricated by electrospinning process is found to mimic the complex structural and functional properties of natural extracellular matrix for tissue regeneration. In order to improve the physico-chemical and biological properties of the nanofibers, graphene oxide is incorporated in the gelatin to form graphene oxide decorated gelatin nanofibers. The current research effort is focussed on the fabrication and evaluation of physico-chemical and biological properties of graphene oxide-gelatin composite nanofibers. The presence of graphene oxide in the nanofibers was established by transmission electron microscopy (TEM). We report the effect of incorporation of graphene oxide on the mechanical, thermal and biological performance of the gelatin nanofibers. The tensile strength of gelatin nanofibers was increased from 8.29±0.53MPa to 21±2.03MPa after the incorporation of GO. In order to improve the water resistance of nanofibers, natural based cross-linking agent, namely, dextran aldehyde was employed. The cross-linked composite nanofibers showed further increase in the tensile strength up to 56.4±2.03MPa. Graphene oxide incorporated gelatin nanofibers are evaluated for bacterial activity against gram positive (Staphylococcus aureus) and gram negative (Escherichia coli) bacteria and cyto compatibility using mouse fibroblast cells (L-929 cells). The results indicate that the graphene oxide incorporated gelatin nanofibers do not prevent bacterial growth, nevertheless support the L-929 cell adhesion and proliferation. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Functionalized single graphene sheets derived from splitting graphite oxide.

    PubMed

    Schniepp, Hannes C; Li, Je-Luen; McAllister, Michael J; Sai, Hiroaki; Herrera-Alonso, Margarita; Adamson, Douglas H; Prud'homme, Robert K; Car, Roberto; Saville, Dudley A; Aksay, Ilhan A

    2006-05-04

    A process is described to produce single sheets of functionalized graphene through thermal exfoliation of graphite oxide. The process yields a wrinkled sheet structure resulting from reaction sites involved in oxidation and reduction processes. The topological features of single sheets, as measured by atomic force microscopy, closely match predictions of first-principles atomistic modeling. Although graphite oxide is an insulator, functionalized graphene produced by this method is electrically conducting.

  8. Graphene oxide as an optimal candidate material for methane storage.

    PubMed

    Chouhan, Rajiv K; Ulman, Kanchan; Narasimhan, Shobhana

    2015-07-28

    Methane, the primary constituent of natural gas, binds too weakly to nanostructured carbons to meet the targets set for on-board vehicular storage to be viable. We show, using density functional theory calculations, that replacing graphene by graphene oxide increases the adsorption energy of methane by 50%. This enhancement is sufficient to achieve the optimal binding strength. In order to gain insight into the sources of this increased binding, that could also be used to formulate design principles for novel storage materials, we consider a sequence of model systems that progressively take us from graphene to graphene oxide. A careful analysis of the various contributions to the weak binding between the methane molecule and the graphene oxide shows that the enhancement has important contributions from London dispersion interactions as well as electrostatic interactions such as Debye interactions, aided by geometric curvature induced primarily by the presence of epoxy groups.

  9. Magnetism in graphene oxide induced by epoxy groups.

    SciTech Connect

    Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Cole, Jacqueline M.; Su, Haibin

    2015-04-27

    We have engineered magnetism in graphene oxide. Our approach transforms graphene into a magnetic insulator while maintaining graphene's structure. Fourier transform infrared spectroscopy spectra reveal that graphene oxide has various chemical groups (including epoxy, ketone, hydroxyl, and C-O groups) on its surface. Destroying the epoxy group with heat treatment or chemical treatment diminishes magnetism in the material. Local Density Approximation calculation results well reproduce the magnetic moments obtained from experiments, and these results indicate that the unpaired spin induced by the presence of epoxy groups is the origin of the magnetism. The calculation results also explain the magnetic properties, which is generated by the interaction between separated magnetic regions and domains. Our results demonstrate tunable magnetism in graphene oxide based on controlling the epoxy group with heat or chemical treatment.

  10. Magnetism in graphene oxide induced by epoxy groups

    SciTech Connect

    Lee, Dongwook; Seo, Jiwon; Zhu, Xi; Su, Haibin; Cole, Jacqueline M.

    2015-04-27

    We have engineered magnetism in graphene oxide. Our approach transforms graphene into a magnetic insulator while maintaining graphene's structure. Fourier transform infrared spectroscopy spectra reveal that graphene oxide has various chemical groups (including epoxy, ketone, hydroxyl, and C-O groups) on its surface. Destroying the epoxy group with heat treatment or chemical treatment diminishes magnetism in the material. Local density approximation calculation results well reproduce the magnetic moments obtained from experiments, and these results indicate that the unpaired spin induced by the presence of epoxy groups is the origin of the magnetism. The calculation results also explain the magnetic properties, which are generated by the interaction between separated magnetic regions and domains. Our results demonstrate tunable magnetism in graphene oxide based on controlling the epoxy group with heat or chemical treatment.

  11. Graphene oxide as an optimal candidate material for methane storage

    NASA Astrophysics Data System (ADS)

    Chouhan, Rajiv K.; Ulman, Kanchan; Narasimhan, Shobhana

    2015-07-01

    Methane, the primary constituent of natural gas, binds too weakly to nanostructured carbons to meet the targets set for on-board vehicular storage to be viable. We show, using density functional theory calculations, that replacing graphene by graphene oxide increases the adsorption energy of methane by 50%. This enhancement is sufficient to achieve the optimal binding strength. In order to gain insight into the sources of this increased binding, that could also be used to formulate design principles for novel storage materials, we consider a sequence of model systems that progressively take us from graphene to graphene oxide. A careful analysis of the various contributions to the weak binding between the methane molecule and the graphene oxide shows that the enhancement has important contributions from London dispersion interactions as well as electrostatic interactions such as Debye interactions, aided by geometric curvature induced primarily by the presence of epoxy groups.

  12. Flexible electrostatic nanogenerator using graphene oxide film

    NASA Astrophysics Data System (ADS)

    Tian, He; Ma, Shuo; Zhao, Hai-Ming; Wu, Can; Ge, Jie; Xie, Dan; Yang, Yi; Ren, Tian-Ling

    2013-09-01

    Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could significantly enhance the output voltage from 0.1 V to 2.0 V. The mechanism of our nanogenerator can be explained by an electrostatic effect, which is fundamentally different from that of previously reported piezoelectric and triboelectric generators. In this manuscript, we demonstrate flexible nanogenerators with large-area graphene based materials, which may open up new avenues of research with regard to applications in energy harvesting.Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could

  13. Magnetic resonance evidence of manganese-graphene complexes in reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Panich, Alexander M.; Shames, Alexander I.; Aleksenskii, Aleksandr E.; Dideikin, Artur

    2012-03-01

    We report on EPR and NMR study of reduced graphene oxide (RGO) produced by the Hummers method. We show that this RGO sample reveals isolated Mn2+ ions, which originate from potassium permanganate used in the process of the sample preparation. These ions form paramagnetic charge-transfer complexes with the graphene planes and contribute to the 13C spin-lattice relaxation.

  14. Origin of the Chemical and Kinetic Stability of Graphene Oxide

    PubMed Central

    Zhou, Si; Bongiorno, Angelo

    2013-01-01

    At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become – on average – endothermic by more than 0.6 eV. PMID:23963517

  15. Facile Access to Graphene Oxide from Ferro-Induced Oxidation

    NASA Astrophysics Data System (ADS)

    Yu, Chao; Wang, Cai-Feng; Chen, Su

    2016-01-01

    Methods allowing the oxidation of graphite to graphene oxide (GO) are vital important for the production of graphene from GO. This oxidation reaction has mainly relied on strong acid strategy for 174 years, which circumvents issues associated with toxicity of reagent and product, complex post-treatment, high cost and waste generation. Here, we report a green route for performing this oxidization reaction via a ferro-induced strategy, with use of water, potassium ferrate (Fe(VI)) and hydrogen peroxide (H2O2) as reagents, to produce about 65% yield of GO (vs. 40% for Hummers’ method, the most commonly used concentrated acid strategy) and non-toxic by-products. Moreover, GO produced from this new method shows equivalent performance to those reported previously. This H2SO4-free strategy makes it possible to process graphite into GO in a safe, low-cost, time-saving, energy-efficient and eco-friendly pathway, opening a promising avenue for the large-scale production of GO and GO-based materials.

  16. Facile Access to Graphene Oxide from Ferro-Induced Oxidation.

    PubMed

    Yu, Chao; Wang, Cai-Feng; Chen, Su

    2016-01-28

    Methods allowing the oxidation of graphite to graphene oxide (GO) are vital important for the production of graphene from GO. This oxidation reaction has mainly relied on strong acid strategy for 174 years, which circumvents issues associated with toxicity of reagent and product, complex post-treatment, high cost and waste generation. Here, we report a green route for performing this oxidization reaction via a ferro-induced strategy, with use of water, potassium ferrate (Fe(VI)) and hydrogen peroxide (H2O2) as reagents, to produce about 65% yield of GO (vs. 40% for Hummers' method, the most commonly used concentrated acid strategy) and non-toxic by-products. Moreover, GO produced from this new method shows equivalent performance to those reported previously. This H2SO4-free strategy makes it possible to process graphite into GO in a safe, low-cost, time-saving, energy-efficient and eco-friendly pathway, opening a promising avenue for the large-scale production of GO and GO-based materials.

  17. Facile Access to Graphene Oxide from Ferro-Induced Oxidation

    PubMed Central

    Yu, Chao; Wang, Cai-Feng; Chen, Su

    2016-01-01

    Methods allowing the oxidation of graphite to graphene oxide (GO) are vital important for the production of graphene from GO. This oxidation reaction has mainly relied on strong acid strategy for 174 years, which circumvents issues associated with toxicity of reagent and product, complex post-treatment, high cost and waste generation. Here, we report a green route for performing this oxidization reaction via a ferro-induced strategy, with use of water, potassium ferrate (Fe(VI)) and hydrogen peroxide (H2O2) as reagents, to produce about 65% yield of GO (vs. 40% for Hummers’ method, the most commonly used concentrated acid strategy) and non-toxic by-products. Moreover, GO produced from this new method shows equivalent performance to those reported previously. This H2SO4-free strategy makes it possible to process graphite into GO in a safe, low-cost, time-saving, energy-efficient and eco-friendly pathway, opening a promising avenue for the large-scale production of GO and GO-based materials. PMID:26818784

  18. Neutron scattering study of reduced graphene oxide of natural origin

    NASA Astrophysics Data System (ADS)

    Sheka, E. F.; Natkaniec, I.; Rozhkova, N. N.; Holderna-Natkaniec, K.

    2014-08-01

    This paper presents a direct confirmation of graphene-like configuration and first suggests the chemical composition of basic structural elements of shungite attributing the latter to reduced graphene oxide nanosheets with an average 11:1:3 (C:O:H) atomic content ratio.

  19. Probing Mechanical Properties of Chemical Vapor Deposition Graphene Membranes Using Indentation Methods

    NASA Astrophysics Data System (ADS)

    Lee, Gwan-Hyoung; Cooper, Ryan; An, Sungjoo; van der Zande, Arend; Petrone, Nicholas; Lee, Sunwoo; Hammerberg, Alex; Lee, Changgu; Crawford, Bryan; Kysar, Jeffrey; Hone, James

    2012-02-01

    Recent experimental studies have shown that two-dimensional pristine graphene is the strongest material ever measured. We used Atomic Force Microscopy (AFM) and Agilent G200 nanoindenter to measure the mechanical properties of graphene films obtained by Chemical Vapor Deposition (CVD). CVD graphene with different grain size and number of layers were produced in controlled synthetic conditions and transferred onto silicon dioxide substrate with holes of various diameters. Nano-indentation measurement revealed that stiffness and fracture strength of CVD graphene membranes are similar to those of pristine graphene membranes under the condition that suspended graphene membrane is within a single grain boundary without defects. Furthermore, elastic modulus and fracture strength of multi-layer graphene membranes increase with respect to the number of layers.

  20. Self assembly of functionalised graphene nanostructures by one step reduction of graphene oxide using aqueous extract of Artemisia vulgaris

    NASA Astrophysics Data System (ADS)

    Chettri, Prajwal; Vendamani, V. S.; Tripathi, Ajay; Pathak, Anand P.; Tiwari, Archana

    2016-01-01

    We report self assembly and organisation of graphene sheets to form a macroscopically ordered array of graphene layers using one step reduction of graphene oxide. Aqueous extract of dry leaves of Artemisia vulgaris is used for de-oxygenation of graphene oxide. The reduced graphene oxide samples are investigated for two different reflux times viz. for 6 h and 12 h. It is found that for an efficient reduction of graphene oxide and for the minimal damage to the crystal structure 6 h of reflux is the most favourable. Besides reducing graphene oxide, the phytomolecules also functionalise the graphene layers with electron withdrawing groups by virtue of which three dimensional nanostructures are formed on its surface.

  1. Graphitic carbon nitride/graphene oxide/reduced graphene oxide nanocomposites for photoluminescence and photocatalysis

    NASA Astrophysics Data System (ADS)

    Aleksandrzak, Malgorzata; Kukulka, Wojciech; Mijowska, Ewa

    2017-03-01

    The study presents a modification of graphitic carbon nitride (g-C3N4) with graphene oxide (GO) and reduced graphene oxide (rGO) and investigation of photoluminescent and photocatalytic properties. The influence of GO and rGO lateral sizes used for the modification was investigated. The nanomaterials were characterized with atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV-vis spectroscopy (DR-UV-vis) and photoluminescence spectroscopy (PL). PL revealed that pristine graphitic carbon nitride and its nanocomposites with GO and rGO emitted up-converted photoluminescence (UCPL) which could contribute to the improvement of photocatalytic activity of the materials. The photoactivity was evaluated in a process of phenol decomposition under visible light. A hybrid composed of rGO nanoparticles (rGONPs, 4-135 nm) exhibited the highest photoactivity compared to rGO with size of 150 nm-7.2 μm and graphene oxide with the corresponding sizes. The possible reason of the superior photocatalytic activity is the most enhanced UCPL of rGONPs, contributing to the emission of light with higher energy than the incident light, resulting in improved photogeneration of electron-hole pairs.

  2. Synthesis of high-performance graphene nanosheets by thermal reduction of graphene oxide

    SciTech Connect

    Wei, Ang; Wang, Jingxia; Long, Qing; Liu, Xiangmei; Li, Xingao; Dong, Xiaochen; Huang, Wei

    2011-11-15

    Graphical abstract: High-performance graphene nanosheets were synthesized by thermal reduction of graphene oxide under ethanol atmosphere. X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements indicate that the resulting graphene nanosheets can effectively restore its graphic structure in GO and present high mobility. Highlights: {yields} Graphene nanosheets were synthesized by reduction of GO under ethanol atmosphere. {yields} Raman and XPS results indicate the reduced graphene sheets have high-performance. {yields} Graphene sheets field-effect transistors present high mobility. -- Abstract: High-performance graphene nanosheets have been synthesized by thermal reduction of graphene oxide (GO) under ethanol atmosphere. The reduced GO nanosheets were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and electrical transport measurements, respectively. The results indicated that the thermal reduction of GO under ethanol atmosphere can effectively remove the oxygen-containing functional groups and restore its graphic structure compared to the ones obtained using hydrazine or hydrogen. The electrical measurements indicated that the electrical mobility of single-layer graphene sheet reduced under ethanol atmosphere at 900 {sup o}C can reach 29.08 cm{sup 2} V{sup -1} S{sup -1}.

  3. Synthesis of reduced graphene oxide/ZnO nanorods composites on graphene coated PET flexible substrates

    SciTech Connect

    Huang, Lei Guo, Guilue; Liu, Yang; Chang, Quanhong; Shi, Wangzhou

    2013-10-15

    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.

  4. Tailored Crumpling and Unfolding of Spray-Dried Pristine Graphene and Graphene Oxide Sheets.

    PubMed

    Parviz, Dorsa; Metzler, Shane D; Das, Sriya; Irin, Fahmida; Green, Micah J

    2015-06-10

    For the first time, pristine graphene can be controllably crumpled and unfolded. The mechanism for graphene is radically different than that observed for graphene oxide; a multifaced crumpled, dimpled particle morphology is seen for pristine graphene in contrast to the wrinkled, compressed surface of graphene oxide particles, showing that surface chemistry dictates nanosheet interactions during the crumpling process. The process demonstrated here utilizes a spray-drying technique to produce droplets of aqueous graphene dispersions and induce crumpling through rapid droplet evaporation. For the first time, the gradual dimensional transition of 2D graphene nanosheets to a 3D crumpled morphology in droplets is directly observed; this is imaged by a novel sample collection device inside the spray dryer itself. The degree of folding can be tailored by altering the capillary forces on the dispersed sheets during evaporation. It is also shown that the morphology of redispersed crumpled graphene powder can be controlled by solvent selection. This process is scalable, with the ability to rapidly process graphene dispersions into powders suitable for a variety of engineering applications.

  5. Biofabrication of a novel biomolecule-assisted reduced graphene oxide: an excellent biocompatible nanomaterial.

    PubMed

    Zhang, Xi-Feng; Gurunathan, Sangiliyandi

    Graphene has been shown much interest, both in academics and industry due to its extraordinary physical, chemical, and biological proprieties. It shows great promises in biotechnological and biomedical applications as an antibacterial and anticancer agent, nanocarrier, sensor, etc. However, many studies demonstrated the toxicity of graphene in several cell lines, which is an obstacle to its use in biomedical applications. In this study, to improve the biocompatibility of graphene, we used nicotinamide (NAM) as a reducing and stabilizing agent to catalyze the reduction of graphene oxide (GO) to reduced graphene oxide (rGO). The resulted smaller-sized GO (NAM-rGO) showed excellent biocompatibility with mouse embryonic fibroblast cells, evidenced by various cellular assays. Furthermore, NAM-rGO had no effect on mitochondrial membrane permeability and caspase-3 activity compared to GO. Reverse transcription polymerase chain reaction analysis allowed us to identify the molecular mechanisms responsible for NAM-rGO-induced biocompatibility. NAM-rGO significantly induced the expression of genes encoding tight junction proteins (TJPs) such as zona occludens-1 (Tjp1) and claudins (Cldn3) without any effect on the expression of cytoskeleton proteins. Furthermore, NAM-rGO enhances the expression of alkaline phosphatase (ALP) gene, and it does this in a time-dependent manner. Overall, our study depicted the molecular mechanisms underlying NAM-rGO biocompatibility depending on upregulation of TJPs and ALP. This potential quality of graphene could be used in diverse applications including tissue regeneration and tissue engineering.

  6. Biofabrication of a novel biomolecule-assisted reduced graphene oxide: an excellent biocompatible nanomaterial

    PubMed Central

    Zhang, Xi-Feng; Gurunathan, Sangiliyandi

    2016-01-01

    Graphene has been shown much interest, both in academics and industry due to its extraordinary physical, chemical, and biological proprieties. It shows great promises in biotechnological and biomedical applications as an antibacterial and anticancer agent, nanocarrier, sensor, etc. However, many studies demonstrated the toxicity of graphene in several cell lines, which is an obstacle to its use in biomedical applications. In this study, to improve the biocompatibility of graphene, we used nicotinamide (NAM) as a reducing and stabilizing agent to catalyze the reduction of graphene oxide (GO) to reduced graphene oxide (rGO). The resulted smaller-sized GO (NAM-rGO) showed excellent biocompatibility with mouse embryonic fibroblast cells, evidenced by various cellular assays. Furthermore, NAM-rGO had no effect on mitochondrial membrane permeability and caspase-3 activity compared to GO. Reverse transcription polymerase chain reaction analysis allowed us to identify the molecular mechanisms responsible for NAM-rGO-induced biocompatibility. NAM-rGO significantly induced the expression of genes encoding tight junction proteins (TJPs) such as zona occludens-1 (Tjp1) and claudins (Cldn3) without any effect on the expression of cytoskeleton proteins. Furthermore, NAM-rGO enhances the expression of alkaline phosphatase (ALP) gene, and it does this in a time-dependent manner. Overall, our study depicted the molecular mechanisms underlying NAM-rGO biocompatibility depending on upregulation of TJPs and ALP. This potential quality of graphene could be used in diverse applications including tissue regeneration and tissue engineering. PMID:27994461

  7. An in situ oxidation route to fabricate graphene nanoplate-metal oxide composites

    SciTech Connect

    Chen Sheng; Zhu Junwu; Wang Xin

    2011-06-15

    We report our studies on an improved soft chemical route to directly fabricate graphene nanoplate-metal oxide (Ag{sub 2}O, Co{sub 3}O{sub 4}, Cu{sub 2}O and ZnO) composites from the in situ oxidation of graphene nanoplates. By virtue of H{sup +} from hydrolysis of the metal nitrate aqueous solution and NO{sub 3}{sup -}, only a small amount of functional groups were introduced, acting as anchor sites and consequently forming the graphene nanoplate-metal oxide composites. The main advantages of this approach are that it does not require cumbersome oxidation of graphite in advance and no need to reduce the composites due to the lower oxidation degree. The microstructures of as-obtained metal oxides on graphene nanoplates can be dramatically controlled by changing the reaction parameters, opening up the possibility for processing the optical and electrochemical properties of the graphene-based nanocomposites. - graphical abstract: An improved soft chemical route to directly fabricate graphene nanoplate-metal oxide composites is reported from the in situ oxidation of graphene nanoplates. Highlights: > An improved soft chemical route to directly fabricate graphene nanoplate-metal oxide composites. > The microstructures can be controlled by changing the reaction parameters. > It does not require oxidation of graphite in advance and no need to reduce the composites due to the lower oxidation degree.

  8. Flexible electrostatic nanogenerator using graphene oxide film.

    PubMed

    Tian, He; Ma, Shuo; Zhao, Hai-Ming; Wu, Can; Ge, Jie; Xie, Dan; Yang, Yi; Ren, Tian-Ling

    2013-10-07

    Recently, graphene oxide (GO) super capacitors with ultra-high energy densities have received significant attention. In addition to their use in energy storage, GO capacitors might also have broad applications in renewable energy engineering, such as energy harvesting. Here, a flexible nanogenerator based on GO film is designed. A multilayer structure Al/PI/GO/PI/ITO is made on a flexible PET substrate. The GO nanogenerator could generate a peak voltage of 2 V with a current of 30 nA upon the repetitive application of a 15 N force with a frequency of 1 Hz. Moreover, the output voltage was increased to 34.4 V upon increasing the frequency of force application to 10 Hz. Compared with control samples, embedding GO film with a release structure into the device could significantly enhance the output voltage from 0.1 V to 2.0 V. The mechanism of our nanogenerator can be explained by an electrostatic effect, which is fundamentally different from that of previously reported piezoelectric and triboelectric generators. In this manuscript, we demonstrate flexible nanogenerators with large-area graphene based materials, which may open up new avenues of research with regard to applications in energy harvesting.

  9. Electronic transport properties in graphene oxide frameworks

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Cruz-Silva, E.; Meunier, V.

    2014-02-01

    The electronic transport properties in multiterminal graphene oxide framework (GOF) materials are investigated using a combination of theoretical and computational methods. GOFs make up four-terminal [origin=c]90H-shaped GNR-L-GNR junctions where sandwiched boronic acid molecules (L) are covalently linked to two graphene nanoribbons (GNRs) of different edge chiralities. The transport properties are governed by both tunneling and quasiresonant regimes. We determine how the presence of linker molecules affects the transport properties and establish that the through-molecule transport properties can be tuned by varying the chemical composition of the pillar molecules but are not significantly modified when changing the type of electrodes from zigzag GNRs to armchair GNRs. In addition, we find that in multilinker systems containing two parallel molecules in the device area, the coupling between the molecules can lead to both constructive and destructive quantum interferences. We also examine the inability of the classical Kirchhoff's superposition law to account for electron flow in multilinker GOF nanonetworks.

  10. An environment-friendly preparation of reduced graphene oxide nanosheets via amino acid.

    PubMed

    Chen, Dezhi; Li, Lidong; Guo, Lin

    2011-08-12

    Chemically modified graphene has been studied in many applications due to its excellent electrical, mechanical, and thermal properties. Among the chemically modified graphenes, reduced graphene oxide is the most important for its structure and properties, which are similar to pristine graphene. Here, we introduce an environment-friendly approach for preparation of reduced graphene oxide nanosheets through the reduction of graphene oxide that employs L-cysteine as the reductant under mild reaction conditions. The conductivity of the reduced graphene oxide nanosheets produced in this way increases by about 10(6) times in comparison to that of graphene oxide. This is the first report about using amino acids as a reductant for the preparation of reduced graphene oxide nanosheets, and this procedure offers an alternative route to large-scale production of reduced graphene oxide nanosheets for applications that require such material.

  11. Liquid crystallinity driven highly aligned large graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Lee, Kyung Eun; Oh, Jung Jae; Yun, Taeyeong; Kim, Sang Ouk

    2015-04-01

    Graphene is an emerging graphitic carbon materials, consisting of sp2 hybridized two dimensinal honeycomb structure. It has been widely studied to incorporate graphene with polymer to utilize unique property of graphene and reinforce electrical, mechanical and thermal property of polymer. In composite materials, orientation control of graphene significantly influences the property of composite. Until now, a few method has been developed for orientation control of graphene within polymer matrix. Here, we demonstrate facile fabrication of high aligned large graphene oxide (LGO) composites in polydimethylsiloxane (PDMS) matrix exploiting liquid crystallinity. Liquid crystalline aqueous dispersion of LGO is parallel oriented within flat confinement geometry. Freeze-drying of the aligned LGO dispersion and subsequent infiltration with PDMS produce highly aligned LGO/PDMS composites. Owing to the large shape anisotropy of LGO, liquid crystalline alignment occurred at low concentration of 2 mg/ml in aqueous dispersion, which leads to the 0.2 wt% LGO loaded composites.

  12. Electrochemically Exfoliated Graphene and Graphene Oxide for Energy Storage and Electrochemistry Applications.

    PubMed

    Ambrosi, Adriano; Pumera, Martin

    2016-01-04

    Top-down methods are of key importance for large-scale graphene and graphene oxide preparation. Electrochemical exfoliation of graphite has lately gained much interest because of the simplicity of execution, the short process time, and the good quality of graphene that can be obtained. Here, we test three different electrolytes, that is, H2 SO4 , Na2 SO4 , and LiClO4 , with a common exfoliation procedure to evaluate the difference in structural and chemical properties that result for the graphene. The properties are analyzed by means of scanning transmission electron microscopy (STEM), Raman spectroscopy, and X-ray photoelectron spectroscopy. We then tested the graphene materials for electrochemical applications, measuring the heterogeneous electron transfer (HET) rates with a Fe(CN)6 (3-/4-) redox probe, and their capacitive behavior in alkaline solutions. We correlate the electrochemical features with the presence of structural defects and oxygen functionalities on the graphene materials. In particular, the use of LiClO4 during the electrochemical exfoliation of graphite allowed the formation of highly oxidized graphene with a C/O ratio close to 4.0 and represents a possible avenue for the mass production of graphene oxide as valid alternative to the current laborious and dangerous chemical procedures, which also have limited scalability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Integrated oxidation membrane filtration process - NOM rejection and membrane fouling.

    PubMed

    Winter, J; Uhl, W; Bérubé, P R

    2016-11-01

    The extent and mechanisms by which organic matter in a solution can be retained and foul a membrane largely depends on the molecular weight of the material being filtered and the molecular weight cut-off (MWCO) of the membrane. The present study investigated the effect of the MWCO of a membrane and the molecular weight distribution of natural organic matter (NOM) in a source water on the increase in resistance to the permeate flux over time. Of particular interest was the effect of oxidation, applied prior to membrane filtration, on the predominant fouling mechanism. Oxidation can change the molecular weight distribution of organic matter in raw water, and therefore the ability of a membrane to retain this organic matter. Oxidation, using both ozonation and UV/H2O2, could effectively reduce the extent of fouling for higher MWCO membranes. However, neither oxidation approaches could effectively reduce the extent of fouling for lower MWCO membranes, likely because oxidation could not effectively oxidize lower molecular weight organic matter. Althoug the data indicated that the extent of fouling is increasing with the amount of DOC retained by the membrane, no statistically significant correlation was observed between these parameters. The results suggest that oxidation did not affect the predominant fouling mechanism. However, it did affect the molecular weight distribution of the organic matter retained by the membranes, and as a result, the resistance offered by the foulant cake layer.

  14. Coupling Graphene Sheets with Iron Oxide Nanoparticles for Energy Storage and Microelectronics

    DTIC Science & Technology

    2015-12-18

    superparamagnetic γ-Fe2O3 magnetic nanoparticles (MNP) to grapheme-based materials . The distance of the ligands to the graphene derivative surface can be...onto different types of graphene materials like reduced graphene oxide (rGO) nanoplatelets, chemically reduced graphene as well as electrochemically...transistors are also presented. 15. SUBJECT TERMS Graphene, Nanocomposites, Electromagnetic Materials , nanoparticles, Magneto

  15. Cytotoxicity assessment of graphene-based nanomaterials on human dental follicle stem cells.

    PubMed

    Olteanu, Diana; Filip, Adriana; Socaci, Crina; Biris, Alexandru Radu; Filip, Xenia; Coros, Maria; Rosu, Marcela Corina; Pogacean, Florina; Alb, Camelia; Baldea, Ioana; Bolfa, Pompei; Pruneanu, Stela

    2015-12-01

    Graphene-oxide (GO) and its most encountered derivatives, thermally reduced graphene oxide (TRGO) and nitrogen-doped graphene (N-Gr), were synthesized and structurally characterized by spectroscopic techniques, like Raman and (13)C MAS solid state NMR. Several biological effects (cytotoxicity, oxidative stress induction, and cellular and mithocondrial membrane alterations) induced by such graphene-based materials on human dental follicle stem cells were investigated. Graphene oxide shows the lowest cytotoxic effect, followed by the nitrogen-doped graphene, while thermally reduced graphene oxide exhibits high cytotoxic effects. Graphene oxide induces oxidative stress without causing cell membrane damage. Nitrogen-doped graphene shows a slight antioxidant activity; however, at high doses (20 and 40 μg/ml) it causes membrane damage. Both graphene oxide and nitrogen-doped graphene seem to be valuable candidates for usage in dental nanocomposites. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Epitaxial growth of crystalline polyaniline on reduced graphene oxide.

    PubMed

    Majumdar, Dipanwita; Baskey, Moni; Saha, Shyamal K

    2011-08-17

    Due to its unique electronic properties, graphene has already been identified as a promising material for future carbon based electronics. To develop graphene technology, the fabrication of a high quality P-N junction is a great challenge. Here, we describe a general technique to grow single crystalline polyaniline (PANI) films on graphene sheets using in situ polymerization via the oxidation-reduction of aniline monomer and graphene oxide, respectively, to fabricate a high quality P-N junction, which shows diode-like behavior with a remarkably low turn-on voltage (60 mV) and high rectification ratio (1880:1) up to a voltage of 0.2 V. The origin of these superior electronic properties is the preferential growth of a highly crystalline PANI film as well as lattice matching between the d-values [∼2.48 Å] of graphene and {120} planes of PANI.

  17. Graphene oxide: from fundamentals to applications

    NASA Astrophysics Data System (ADS)

    Perrozzi, F.; Prezioso, S.; Ottaviano, L.

    2015-01-01

    In this review, we discuss the fundamental characterization of graphene oxide (GO) and its future application perspectives. Morphology is discussed through optical microscopy, fluorescence microscopy, scanning electron microscopy, and atomic force microscopy studies. Chemical, structural, and vibrational properties are discussed through x-ray photoemission spectroscopy and Raman spectroscopy studies. Two easy characterization strategies, based on the correlation between x-ray photoemission spectroscopy and contact angle/optical contrast measurements are reported. Sensing and nano-biotechnology applications are discussed with focus on practical gas sensing and optical sensing, on the one hand, and on the toxicity issue of GO, on the other hand. Synthesis and post-synthesis treatments are also discussed, these latter with emphasis on lithography.

  18. Thermal actuation of graphene oxide nanoribbon mats

    NASA Astrophysics Data System (ADS)

    Oh, Jiyoung; Kozlov, Mikhail E.; Carretero-González, Javier; Castillo-Martínez, Elizabeth; Baughman, Ray H.

    2011-03-01

    Graphene oxide nanoribbons (GOr), obtained by chemically unzipping multi-walled carbon nanotubes, were assembled into macroscopic mats by vacuum filtration. These mats exhibited up to 1.6% reversible contraction when electrically heated at ambient. The experimentally derived work capacity of the mats was about 40 J/kg, which is similar to that of natural muscle. It was limited by the mechanical strength of mats and can be increased upon optimization of their preparation conditions. X-ray diffraction measurements indicated reversible changes in the interplanar spacing of GOr layers during heating. These dimensional changes can be associated with reversible adsorption/desorption of water molecules between GOr layers and used in thermally-driven high performance artificial muscles and moisture sensors.

  19. Graphene oxide-based antibacterial cotton fabrics.

    PubMed

    Zhao, Jinming; Deng, Bo; Lv, Min; Li, Jingye; Zhang, Yujie; Jiang, Haiqing; Peng, Cheng; Li, Jiang; Shi, Jiye; Huang, Qing; Fan, Chunhai

    2013-09-01

    Graphene oxide (GO) is an excellent bacteria-killing nanomaterial. In this work, macroscopic applications of this promising nanomaterial by fixing GO sheets onto cotton fabrics, which possess strong antibacterial property and great laundering durability, are reported. The GO-based antibacterial cotton fabrics are prepared in three ways: direct adsorption, radiation-induced crosslinking, and chemical crosslinking. Antibacterial tests show that all these GO-containing fabrics possess strong antibacterial property and could inactivate 98% of bacteria. Most significantly, these fabrics can still kill >90% bacteria even after being washed for 100 times. Also importantly, animal tests show that GO-modified cotton fabrics cause no irritation to rabbit skin. Hence, it is believed that these flexible, foldable, and re-usable GO-based antibacterial cotton fabrics have high promise as a type of new nano-engineered antibacterial materials for a wide range of applications.

  20. Optical and diamagnetic anisotropy of graphene oxide

    NASA Astrophysics Data System (ADS)

    Exarhos, A. L.; Vora, P. M.; Lou, Z.; Johnson, A. T.; Kikkawa, J. M.

    2009-03-01

    We have recently shown that graphene oxide (GO) emits a broad photoluminescence (PL) band in both solid and aqueous preparations. The origin of this PL is not yet well understood, but for absorptive and emissive optical processes originating in the two dimensional GO plane, one expects an in-plane polarization. Studies of optical anisotropy can therefore help to clarify the origin of the PL. Here we use a method of optical nanomagnetometry (Torrens, et al, JACS 129, p. 252 (2007)) to extract these quantities, also determining the magnetic anisotropy. We find that when aqueous preparations of GO are placed in a magnetic field, diamagnetically induced alignment leads to marked linear polarization anisotropy of absorbance and photoluminescence. By taking six optical measurements at each magnetic field, we are able to extract the intrinsic polarization anisotropies of optical absorption and emission of GO flakes and to quantify the orbital diamagnetic anisotropy. We discuss how these quantities give insight into electronic delocalization in these systems.

  1. Ultrahigh humidity sensitivity of graphene oxide

    PubMed Central

    Bi, Hengchang; Yin, Kuibo; Xie, Xiao; Ji, Jing; Wan, Shu; Sun, Litao; Terrones, Mauricio; Dresselhaus, Mildred S.

    2013-01-01

    Humidity sensors have been extensively used in various fields, and numerous problems are encountered when using humidity sensors, including low sensitivity, long response and recovery times, and narrow humidity detection ranges. Using graphene oxide (G-O) films as humidity sensing materials, we fabricate here a microscale capacitive humidity sensor. Compared with conventional capacitive humidity sensors, the G-O based humidity sensor has a sensitivity of up to 37800% which is more than 10 times higher than that of the best one among conventional sensors at 15%–95% relative humidity. Moreover, our humidity sensor shows a fast response time (less than 1/4 of that of the conventional one) and recovery time (less than 1/2 of that of the conventional one). Therefore, G-O appears to be an ideal material for constructing humidity sensors with ultrahigh sensitivity for widespread applications. PMID:24048093

  2. Graphene oxide film as solid lubricant.

    PubMed

    Liang, Hongyu; Bu, Yongfeng; Zhang, Junyan; Cao, Zhongyue; Liang, Aimin

    2013-07-10

    As a layered material, graphene oxide (GO) film is a good candidate for improving friction and antiwear performance of silicon-based MEMS devices. Via a green electrophoretic deposition (EPD) approach, GO films with tunable thickness in nanoscale are fabricated onto silicon wafer in a water solution. The morphology, microstructure, and mechanical properties as well as the friction coefficient and wear resistance of the films were investigated. The results indicated that the friction coefficient of silicon wafer was reduced to 1/6 its value, and the wear volume was reduced to 1/24 when using GO film as solid lubricant. These distinguished tribology performances suggest that GO films are expected to be good solid lubricants for silicon-based MEMS/NEMS devices.

  3. Hydrothermally reduced graphene oxide as a supercapacitor

    NASA Astrophysics Data System (ADS)

    Johra, Fatima Tuz; Jung, Woo-Gwang

    2015-12-01

    The supercapacitance behavior of hydrothermally reduced graphene oxide (RGO) was investigated for the first time. The capacitive behavior of RGO was characterized by using cyclic voltammetry and galvanostatic charge-discharge methods. The specific capacitance of hydrothermally reduced RGO at 1 A/g was 367 F/g in 1 M H2SO4 electrolyte, which was higher than that of RGO synthesized via the hydrazine reduction method. The RGO-modified glassy carbon electrode showed excellent stability. After 1000 cycles, the supercapacitance was 107.7% of that achieved in the 1st cycle, which suggests that RGO has excellent electrochemical stability as a supercapacitor electrode material. The energy density of hydrothermal RGO reached 44.4 W h/kg at a power density of 40 kW/kg.

  4. Polyelectrolyte/Graphene Oxide Barrier Film for Flexible OLED.

    PubMed

    Yang, Seung-Yeol; Park, Jongwhan; Kim, Yong-Seog

    2015-10-01

    Ultra-thin flexible nano-composite barrier layer consists of graphene oxide and polyelectrolyte was prepared using the layer-by-layer processing method. Microstructures of the barrier layer was optimized via modifying coating conditions and inducing chemical reactions. Although the barrier layer consists of hydrophilic polyelectrolyte was not effective in blocking the water vapor permeation, the chemical reduction of graphene oxide as well as conversion of polyelectrolyte to hydrophobic nature were very effective in reducing the permeation.

  5. Production of graphene oxide from pitch-based carbon fiber

    NASA Astrophysics Data System (ADS)

    Lee, Miyeon; Lee, Jihoon; Park, Sung Young; Min, Byunggak; Kim, Bongsoo; in, Insik

    2015-07-01

    Pitch-based graphene oxide (p-GO) whose compositional/structural features are comparable to those of graphene oxide (GO) was firstly produced by chemical exfoliation of pitch-based carbon fiber rather than natural graphite. Incorporation of p-GO as nanofillers into poly(methyl methacrylate) (PMMA) as a matrix polymer resulted in excellent mechanical reinforcement. p-GO/PMMA nanocomposite (1 wt.-% p-GO) demonstrated 800% higher modulus of toughness of neat PMMA.

  6. Production of graphene oxide from pitch-based carbon fiber.

    PubMed

    Lee, Miyeon; Lee, Jihoon; Park, Sung Young; Min, Byunggak; Kim, Bongsoo; In, Insik

    2015-07-09

    Pitch-based graphene oxide (p-GO) whose compositional/structural features are comparable to those of graphene oxide (GO) was firstly produced by chemical exfoliation of pitch-based carbon fiber rather than natural graphite. Incorporation of p-GO as nanofillers into poly(methyl methacrylate) (PMMA) as a matrix polymer resulted in excellent mechanical reinforcement. p-GO/PMMA nanocomposite (1 wt.-% p-GO) demonstrated 800% higher modulus of toughness of neat PMMA.

  7. Pd doped reduced graphene oxide for hydrogen storage

    NASA Astrophysics Data System (ADS)

    Das, Tapas; Banerjee, Seemita; Sudarsan, V.

    2015-06-01

    Pd nanoparticles dispersed reduced graphene oxide sample has been prepared by a simple chemical method using hydrazine as the reducing agent. Based on XRD and 13C MAS NMR studies it is confirmed that, Pd nanoparticles are effectively mixed with the reduced graphene oxide sample. Maximum hydrogen storage capacity has been estimated to be ˜1.36 wt % at 123K. Improved hydrogen storage capacity of Pd incorporated sample can be explained based on the phenomenon of spillover of atomic hydrogen.

  8. Pd doped reduced graphene oxide for hydrogen storage

    SciTech Connect

    Das, Tapas; Banerjee, Seemita; Sudarsan, V.

    2015-06-24

    Pd nanoparticles dispersed reduced graphene oxide sample has been prepared by a simple chemical method using hydrazine as the reducing agent. Based on XRD and {sup 13}C MAS NMR studies it is confirmed that, Pd nanoparticles are effectively mixed with the reduced graphene oxide sample. Maximum hydrogen storage capacity has been estimated to be ∼1.36 wt % at 123K. Improved hydrogen storage capacity of Pd incorporated sample can be explained based on the phenomenon of spillover of atomic hydrogen.

  9. Production of graphene oxide from pitch-based carbon fiber

    PubMed Central

    Lee, Miyeon; Lee, Jihoon; Park, Sung Young; Min, Byunggak; Kim, Bongsoo; In, Insik

    2015-01-01

    Pitch-based graphene oxide (p-GO) whose compositional/structural features are comparable to those of graphene oxide (GO) was firstly produced by chemical exfoliation of pitch-based carbon fiber rather than natural graphite. Incorporation of p-GO as nanofillers into poly(methyl methacrylate) (PMMA) as a matrix polymer resulted in excellent mechanical reinforcement. p-GO/PMMA nanocomposite (1 wt.-% p-GO) demonstrated 800% higher modulus of toughness of neat PMMA. PMID:26156067

  10. Graphene Oxide Nanoribbons Induce Autophagic Vacuoles in Neuroblastoma Cell Lines

    PubMed Central

    Mari, Emanuela; Mardente, Stefania; Morgante, Emanuela; Tafani, Marco; Lococo, Emanuela; Fico, Flavia; Valentini, Federica; Zicari, Alessandra

    2016-01-01

    Since graphene nanoparticles are attracting increasing interest in relation to medical applications, it is important to understand their potential effects on humans. In the present study, we prepared graphene oxide (GO) nanoribbons by oxidative unzipping of single-wall carbon nanotubes (SWCNTs) and analyzed their toxicity in two human neuroblastoma cell lines. Neuroblastoma is the most common solid neoplasia in children. The hallmark of these tumors is the high number of different clinical variables, ranging from highly metastatic, rapid progression and resistance to therapy to spontaneous regression or change into benign ganglioneuromas. Patients with neuroblastoma are grouped into different risk groups that are characterized by different prognosis and different clinical behavior. Relapse and mortality in high risk patients is very high in spite of new advances in chemotherapy. Cell lines, obtained from neuroblastomas have different genotypic and phenotypic features. The cell lines SK-N-BE(2) and SH-SY5Y have different genetic mutations and tumorigenicity. Cells were exposed to low doses of GO for different times in order to investigate whether GO was a good vehicle for biological molecules delivering individualized therapy. Cytotoxicity in both cell lines was studied by measuring cellular oxidative stress (ROS), mitochondria membrane potential, expression of lysosomial proteins and cell growth. GO uptake and cytoplasmic distribution of particles were studied by Transmission Electron Microscopy (TEM) for up to 72 h. The results show that GO at low concentrations increased ROS production and induced autophagy in both neuroblastoma cell lines within a few hours of exposure, events that, however, are not followed by growth arrest or death. For this reason, we suggest that the GO nanoparticle can be used for therapeutic delivery to the brain tissue with minimal effects on healthy cells. PMID:27916824

  11. Graphene Oxide Nanoribbons Induce Autophagic Vacuoles in Neuroblastoma Cell Lines.

    PubMed

    Mari, Emanuela; Mardente, Stefania; Morgante, Emanuela; Tafani, Marco; Lococo, Emanuela; Fico, Flavia; Valentini, Federica; Zicari, Alessandra

    2016-11-29

    Since graphene nanoparticles are attracting increasing interest in relation to medical applications, it is important to understand their potential effects on humans. In the present study, we prepared graphene oxide (GO) nanoribbons by oxidative unzipping of single-wall carbon nanotubes (SWCNTs) and analyzed their toxicity in two human neuroblastoma cell lines. Neuroblastoma is the most common solid neoplasia in children. The hallmark of these tumors is the high number of different clinical variables, ranging from highly metastatic, rapid progression and resistance to therapy to spontaneous regression or change into benign ganglioneuromas. Patients with neuroblastoma are grouped into different risk groups that are characterized by different prognosis and different clinical behavior. Relapse and mortality in high risk patients is very high in spite of new advances in chemotherapy. Cell lines, obtained from neuroblastomas have different genotypic and phenotypic features. The cell lines SK-N-BE(2) and SH-SY5Y have different genetic mutations and tumorigenicity. Cells were exposed to low doses of GO for different times in order to investigate whether GO was a good vehicle for biological molecules delivering individualized therapy. Cytotoxicity in both cell lines was studied by measuring cellular oxidative stress (ROS), mitochondria membrane potential, expression of lysosomial proteins and cell growth. GO uptake and cytoplasmic distribution of particles were studied by Transmission Electron Microscopy (TEM) for up to 72 h. The results show that GO at low concentrations increased ROS production and induced autophagy in both neuroblastoma cell lines within a few hours of exposure, events that, however, are not followed by growth arrest or death. For this reason, we suggest that the GO nanoparticle can be used for therapeutic delivery to the brain tissue with minimal effects on healthy cells.

  12. Synthesis of graphene oxide and reduced graphene oxide by needle platy natural vein graphite

    NASA Astrophysics Data System (ADS)

    Rathnayake, R. M. N. M.; Wijayasinghe, H. W. M. A. C.; Pitawala, H. M. T. G. A.; Yoshimura, Masamichi; Huang, Hsin-Hui

    2017-01-01

    Among natural graphite varieties, needle platy vein graphite (NPG) has very high purity. Therefore, it is readily used to prepare graphene oxide (GO) and reduced graphene oxide (rGO). In this study, GO and rGO were prepared using chemical oxidation and reduction process, respectively. The synthesized materials were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. XRD studies confirmed the increase of the interlayer spacing of GO and rGO in between 3.35 to 8.66 A°. AFM studies showed the layer height of rGO to be 1.05 nm after the reduction process. TEM micrographs clearly illustrated that the prepared GO has more than 25 layers, while the rGO has only less than 15 layers. Furthermore, the effect of chemical oxidation and reduction processes on surface morphology of graphite were clearly observed in FESEM micrographs. The calculated RO/C of GO and rGO using XPS analysis are 5.37% and 1.77%, respectively. The present study revealed the successful and cost effective nature of the chemical oxidation, and the reduction processes for the production of GO and rGO out of natural vein graphite.

  13. The role of water in resistive switching in graphene oxide

    SciTech Connect

    Rogala, M.; Kowalczyk, P. J.; Dabrowski, P.; Wlasny, I.; Kozlowski, W.; Busiakiewicz, A.; Pawlowski, S.; Dobinski, G.; Smolny, M.; Klusek, Z.; Lipinska, L.; Kozinski, R.; Librant, K.; Jagiello, J.; Grodecki, K.; Baranowski, J. M.; Szot, K.

    2015-06-29

    The resistive switching processes are investigated at the nano-scale in graphene oxide. The modification of the material resistivity is driven by the electrical stimulation with the tip of atomic force microscope. The presence of water in the atmosphere surrounding graphene oxide is found to be a necessary condition for the occurrence of the switching effect. In consequence, the switching is related to an electrochemical reduction. Presented results suggest that by changing the humidity level the in-plane resolution of data storage process can be controlled. These findings are essential when discussing the concept of graphene based resistive random access memories.

  14. Structure of graphene oxide dispersed with ZnO nanoparticles

    SciTech Connect

    Yadav, Rishikesh Pandey, Devendra K.; Khare, P. S.

    2014-10-15

    Graphene has been proposed as a promising two-dimensional nanomaterial with outstanding electronic, optical, thermal and mechanical properties for many applications. In present work a process of dispersion of graphene oxide with ZnO nanoparticles in ethanol solution with different pH values, have been studied. Samples have been characterized by XRD, SEM, PL, UV-visible spectroscopy and particles size measurement. The results analysis indicates overall improved emission spectrum. It has been observed that the average diameter of RGO (Reduced Graphene Oxide) decreases in presence of ZnO nanoparticles from 3.8μm to 0.41μm.

  15. Reduced graphene oxide based flexible organic charge trap memory devices

    NASA Astrophysics Data System (ADS)

    Rani, Adila; Song, Ji-Min; Jung Lee, Mi; Lee, Jang-Sik

    2012-12-01

    A nonvolatile organic transistor memory device was developed using layer-by-layer assembly of 3-aminopropyltriethoxysilane (APTES) and solution-processed, reduced graphene oxide (rGO) as the charge trapping layer on flexible substrates. Reduction of graphene oxide and successful adsorption of the rGO on APTES-covered substrates were confirmed. The organic memory devices based on rGO exhibited reliable programmable memory operations, confirmed by program/erase operations, data retention, and endurance properties. These methods can potentially play a significant role in the fabrication of next-generation flexible nonvolatile memory devices based on graphene materials.

  16. Effect of the graphene oxide reduction temperature on supercapacitor performance

    NASA Astrophysics Data System (ADS)

    Choi, Eunmi; Kim, Jaekwang; Cui, Yinhua; Choi, Kyuho; Gao, Yuan; Han, Seunghee; Pyo, Sung Gyu; Yoon, Songhun

    2017-07-01

    In this study, we investigated the influence of the reduction temperature on graphene oxide. After performing the thermal reduction at specific temperatures (200, 600, and 1000 °C), the morphological and crystallographic changes were investigated by several analysis methods. The reduced graphene oxides were used as supercapacitor electrodes and analyzed with various electrochemical techniques. The capacitance exhibited an increase up to 600 °C before decreasing abruptly at 1000 °C. This behavior was ascribed to the limited ionic accessibility into the compact graphene layer.[Figure not available: see fulltext.

  17. Controllably Inducing and Modeling Optical Response from Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Lombardo, Nicholas; Naumov, Anton

    Graphene, a novel 2-dimensional sp2-hybridized allotrope of Carbon, has unique electrical and mechanical properties. While it is naturally a highly conductive zero band gap semiconductor, graphene does not exhibit optical emission. It has been shown that functionalization with oxygen-containing groups elicits an opening of band gap in graphene. In this work, we aim to induce an optical response in graphene via controlled oxidation, and then explore potential origins of its photoluminescence through mathematical modeling. We employ timed ozone treatment of initially non-fluorescent reduced graphene oxide (RGO) to produce graphene oxide (GO) with specific optical properties. Oxidized material exhibits substantial changes in the absorption spectra and a broad photoluminescence feature, centered at 532 nm, which suggests the appearance of a band gap. We then explore a number of possible mechanisms for the origin of GO photoluminescence via PM3 and ab initio calculations on a functionalized single sheet of graphene. By adjusting modeling parameters to fit experimentally obtained optical transition energies we estimate the size of the sp2 graphitic regions in GO and the arrangement of functional groups that could be responsible for the observed emission.

  18. Adsorption of polycyclic aromatic hydrocarbons on graphene oxides and reduced graphene oxides.

    PubMed

    Sun, Yubing; Yang, Shubin; Zhao, Guixia; Wang, Qi; Wang, Xiangke

    2013-11-01

    Graphene has attracted increasing attention in multidisciplinary studies because of its unique physical and chemical properties. Herein, the adsorption of polycyclic aromatic hydrocarbons (PAHs), such as naphthalene (NAP), anthracene (ANT), and pyrene (PYR), on reduced graphene oxides (rGOs) and graphene oxides (GOs) as a function of pH, humic acid (HA), and temperature were elucidated by means of a batch technique. For comparison, nonpolar and nonporous graphite were also employed in this study. The increasing of pH from 2 to 11 did not influence the adsorption of PAHs on rGOs, whereas the suppressed adsorption of NAP on rGOs was observed both in the presence of HA and under high-temperature conditions. Adsorption isotherms of PAHs on rGOs were in accordance with the Polanyi-Dubinin-Ashtahhov (PDA) model, providing evidence that pore filling and flat surface adsorption were involved. The saturated adsorbed capacities (in mmol g(-1)) of rGOs for PAHs calculated from the PDA model significantly decreased in the order of NAP>PYR>ANT, which was comparable to the results of theoretical calculations. The pore-filling mechanism dominates the adsorption of NAP on rGOs, but the adsorption mechanisms of ANT and PYR on rGOs are flat surface adsorption.

  19. Application of graphene/graphene oxide in biomedicine and biotechnology.

    PubMed

    Zhou, Xianfeng; Liang, Feng

    2014-03-01

    Graphene, a truly two-dimensional (2D) and fully π-conjugated honeycomb network, exhibits many unique physical and chemical properties that are interesting in a wide range of areas. Since its discovery in 2004, graphene has been extensively studied in many different fields including nano-electronics, composite materials, energy research, catalysis and so on. Based on the fascinating action of members in the carbon family, notably zero dimensional (0D) fullerenes and one dimensional (1D) carbon nanotubes (CNTs) in biomedical areas, increasing number of reports have explored the potential of graphene for different biomedical and biotechnical applications since 2008. This manuscript aims to provide a summary of current research progress of graphene-based carbon materials in biosensing, drug (gene) delivery and tissue engineering, and discusses the opportunities and challenges in this rapidly growing field.

  20. Piezoresistive Properties of Suspended Graphene Membranes under Uniaxial and Biaxial Strain in Nanoelectromechanical Pressure Sensors

    PubMed Central

    2016-01-01

    Graphene membranes act as highly sensitive transducers in nanoelectromechanical devices due to their ultimate thinness. Previously, the piezoresistive effect has been experimentally verified in graphene using uniaxial strain in graphene. Here, we report experimental and theoretical data on the uni- and biaxial piezoresistive properties of suspended graphene membranes applied to piezoresistive pressure sensors. A detailed model that utilizes a linearized Boltzman transport equation describes accurately the charge-carrier density and mobility in strained graphene and, hence, the gauge factor. The gauge factor is found to be practically independent of the doping concentration and crystallographic orientation of the graphene films. These investigations provide deeper insight into the piezoresistive behavior of graphene membranes. PMID:27797484

  1. Simulation insights for graphene-based water desalination membranes.

    PubMed

    Konatham, Deepthi; Yu, Jing; Ho, Tuan A; Striolo, Alberto

    2013-09-24

    Molecular dynamics simulations were employed to study the transport of water and ions through pores created on the basal plane of one graphene sheet (GS). Graphene pore diameters ranged from 7.5 to 14.5 Å. Different pore functionalities were considered, obtained by tethering various functional groups to the terminal carbon atoms. The ease of ion and water translocation across the pores was monitored by calculating the potential of mean force along the direction perpendicular to the GS pore. The results indicate that effective ion exclusion can be achieved only using nonfunctionalized (pristine) pores of diameter ~7.5 Å, whereas the ions can easily penetrate pristine pores of diameters ~10.5 and 14.5 Å. Carboxyl functional groups can enhance ion exclusion for all pores considered, but the effect becomes less pronounced as both the ion concentration and the pore diameter increase. When compared to a carbon nanotube of similar pore diameter, our results suggest that GS pores functionalized with COO(-) groups are more effective in excluding Cl(-) ions from passing through the membrane. Our results suggest that narrow graphene pores functionalized with hydroxyl groups remain effective at excluding Cl(-) ions even at moderate solution ionic strength. The results presented could be useful for the design of water desalination membranes.

  2. Alkaline deoxygenated graphene oxide for supercapacitor applications: An effective green alternative for chemically reduced graphene

    NASA Astrophysics Data System (ADS)

    Perera, Sanjaya D.; Mariano, Ruperto G.; Nijem, Nour; Chabal, Yves; Ferraris, John P.; Balkus, Kenneth J.

    2012-10-01

    Graphene is a promising electrode material for energy storage applications. The most successful method for preparing graphene from graphite involves the oxidation of graphite to graphene oxide (GO) and reduction back to graphene. Even though different chemical and thermal methods have been developed to reduce GO to graphene, the use of less toxic materials to generate graphene still remains a challenge. In this study we developed a facile one-pot synthesis of deoxygenated graphene (hGO) via alkaline hydrothermal process, which exhibits similar properties to the graphene obtained via hydrazine reduction (i.e. the same degree of deoxygenation found in hydrazine reduced GO). Moreover, the hGO formed freestanding, binder-free paper electrodes for supercapacitors. Coin cell type (CR2032) symmetric supercapacitors were assembled using the hGO electrodes. Electrochemical characterization of hGO was carried out using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and ethylmethylimidazolium bis-(trifluoromethanesulfonyl)imide (EMITFSI) electrolytes. The results for the hGO electrodes were compared with the hydrazine reduced GO (rGO) electrode. The hGO electrode exhibits a energy density of 20 W h kg-1 and 50 W h kg-1 in LiTFSI and EMITFSI respectively, while delivering a maximum power density of 11 kW kg-1 and 14.7 kW kg-1 in LiTFSI and EMITFSI, respectively.

  3. Oxidation-assisted graphene heteroepitaxy on copper foil.

    PubMed

    Reckinger, Nicolas; Tang, Xiaohui; Joucken, Frédéric; Lajaunie, Luc; Arenal, Raul; Dubois, Emmanuel; Hackens, Benoît; Henrard, Luc; Colomer, Jean-François

    2016-11-10

    We propose an innovative, easy-to-implement approach to synthesize aligned large-area single-crystalline graphene flakes by chemical vapor deposition on copper foil. This method doubly takes advantage of residual oxygen present in the gas phase. First, by slightly oxidizing the copper surface, we induce grain boundary pinning in copper and, in consequence, the freezing of the thermal recrystallization process. Subsequent reduction of copper under hydrogen suddenly unlocks the delayed reconstruction, favoring the growth of centimeter-sized copper (111) grains through the mechanism of abnormal grain growth. Second, the oxidation of the copper surface also drastically reduces the nucleation density of graphene. This oxidation/reduction sequence leads to the synthesis of aligned millimeter-sized monolayer graphene domains in epitaxial registry with copper (111). The as-grown graphene flakes are demonstrated to be both single-crystalline and of high quality.

  4. Nanoscale pressure sensors realized from suspended graphene membrane devices

    SciTech Connect

    Aguilera-Servin, Juan; Miao, Tengfei; Bockrath, Marc

    2015-02-23

    We study the transport properties of graphene layers placed over ∼200 nm triangular holes via attached electrodes under applied pressure. We find that the injected current division between counter electrodes depends on pressure and can be used to realize a nanoscale pressure sensor. Estimating various potential contributions to the resistivity change of the deflected graphene membrane including piezoresistivity, changing gate capacitance, and the valley Hall effect due to the pressure-induced synthetic magnetic field, we find that the valley Hall effect yields the largest expected contribution to the longitudinal resistivity modulation for accessible device parameters. Such devices in the ballistic transport regime may enable the realization of tunable valley polarized electron sources.

  5. Nanoscale pressure sensors realized from suspended graphene membrane devices

    NASA Astrophysics Data System (ADS)

    Aguilera-Servin, Juan; Miao, Tengfei; Bockrath, Marc

    2015-02-01

    We study the transport properties of graphene layers placed over ˜200 nm triangular holes via attached electrodes under applied pressure. We find that the injected current division between counter electrodes depends on pressure and can be used to realize a nanoscale pressure sensor. Estimating various potential contributions to the resistivity change of the deflected graphene membrane including piezoresistivity, changing gate capacitance, and the valley Hall effect due to the pressure-induced synthetic magnetic field, we find that the valley Hall effect yields the largest expected contribution to the longitudinal resistivity modulation for accessible device parameters. Such devices in the ballistic transport regime may enable the realization of tunable valley polarized electron sources.

  6. Covalently Bonded Chitosan on Graphene Oxide via Redox Reaction

    PubMed Central

    Bustos-Ramírez, Karina; Martínez-Hernández, Ana L.; Martínez-Barrera, Gonzalo; de Icaza, Miguel; Castaño, Víctor M.; Velasco-Santos, Carlos

    2013-01-01

    Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. In this sense carbohydrates such as chitosan are extremely valuable because their functional groups play an important role in diversifying the applications of carbon nanomaterials. This paper reports the covalent attachment of chitosan onto graphene oxide, taking advantage of this carbohydrate at the nanometric level. Grafting is an innovative route to modify properties of graphene, a two-dimensional nanometric arrangement, which is one of the most novel and promising nanostructures. Chitosan grafting was achieved by redox reaction using different temperature conditions that impact on the morphology and features of graphene oxide sheets. Transmission Electron Microscopy, Fourier Transform Infrared, Raman and Energy Dispersive spectroscopies were used to study the surface of chitosan-grafted-graphene oxide. Results show a successful modification indicated by the functional groups found in the grafted material. Dispersions of chitosan-grafted-graphene oxide samples in water and hexane revealed different behavior due to the chemical groups attached to the graphene oxide sheet. PMID:28809348

  7. Covalently Bonded Chitosan on Graphene Oxide via Redox Reaction.

    PubMed

    Bustos-Ramírez, Karina; Martínez-Hernández, Ana L; Martínez-Barrera, Gonzalo; Icaza, Miguel de; Castaño, Víctor M; Velasco-Santos, Carlos

    2013-03-07

    Carbon nanostructures have played an important role in creating a new field of materials based on carbon. Chemical modification of carbon nanostructures through grafting has been a successful step to improve dispersion and compatibility in solvents, with biomolecules and polymers to form nanocomposites. In this sense carbohydrates such as chitosan are extremely valuable because their functional groups play an important role in diversifying the applications of carbon nanomaterials. This paper reports the covalent attachment of chitosan onto graphene oxide, taking advantage of this carbohydrate at the nanometric level. Grafting is an innovative route to modify properties of graphene, a two-dimensional nanometric arrangement, which is one of the most novel and promising nanostructures. Chitosan grafting was achieved by redox reaction using different temperature conditions that impact on the morphology and features of graphene oxide sheets. Transmission Electron Microscopy, Fourier Transform Infrared, Raman and Energy Dispersive spectroscopies were used to study the surface of chitosan-grafted-graphene oxide. Results show a successful modification indicated by the functional groups found in the grafted material. Dispersions of chitosan-grafted-graphene oxide samples in water and hexane revealed different behavior due to the chemical groups attached to the graphene oxide sheet.

  8. Graphene oxide/graphene vertical heterostructure electrodes for highly efficient and flexible organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Jia, S.; Sun, H. D.; Du, J. H.; Zhang, Z. K.; Zhang, D. D.; Ma, L. P.; Chen, J. S.; Ma, D. G.; Cheng, H. M.; Ren, W. C.

    2016-05-01

    The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability, and good compatibility with HIL materials (MoO3 in this work). Moreover, the conductivity of the heterostructure is not sacrificed compared to the pristine three-layer graphene electrodes, but is significantly higher than that of pristine two-layer graphene films. In addition to high flexibility, OLEDs with different emission colors based on the GO/G heterostructure TCEs show much better performance than those based on indium tin oxide (ITO) anodes. Green OLEDs with GO/G heterostructure electrodes have the maximum current efficiency and power efficiency, as high as 82.0 cd A-1 and 98.2 lm W-1, respectively, which are 36.7% (14.8%) and 59.2% (15.0%) higher than those with pristine graphene (ITO) anodes. These findings open up the possibility of using graphene for next generation high-performance flexible and wearable optoelectronics with high stability.The relatively high sheet resistance, low work function and poor compatibility with hole injection layers (HILs) seriously limit the applications of graphene as transparent conductive electrodes (TCEs) for organic light emitting diodes (OLEDs). Here, a graphene oxide/graphene (GO/G) vertical heterostructure is developed as TCEs for high-performance OLEDs, by directly oxidizing the top layer of three-layer graphene films with ozone treatment. Such GO/G heterostructure electrodes show greatly improved optical transmittance, a large work function, high stability

  9. Nematic phase formation in suspensions of graphene oxide

    NASA Astrophysics Data System (ADS)

    Fresneau, Nathalie; Campidelli, Stéphane

    The last decade has seen the rise of graphene. Graphene is a single layer of graphite; it can be obtained by direct liquid phase exfoliation of the latter through harsh sonication. This technique presents the disadvantage to produce small graphene flakes (typically in the 0.05 to 0.4 μm2 range for the monolayers) and multilayer graphene with uncontrolled thickness distributions. In order to improve the exfoliation process, one has to counter the strong van der Waals interactions between the carbon planes of graphite. This implies to increase the distance between two planes and it can be done, for example, by oxidizing graphite to introduce oxygen species in the graphenic planes. The fabrication of graphite oxide is known for almost 150 years, and it became popular again these last ten years. Generally, the oxidation of graphite is performed following a method described by Hummers in the 1950's and the material produced by this technique exfoliates quasi-spontaneously into monolayer species called graphene oxide (GO). The highly anisotropic shape of GO (several μm in length and width for a thickness of ca. 1 nm) combined with the presence of oxygenated functions on the sp2 carbon structure of graphene lead to the formation of a lyotropic liquid crystalline phase in water. Above a certain concentration of graphene flakes the gain in translational entropy for a long-range ordered phase outweighs the loss in rotational entropy, and the liquid crystal phase then forms. The value of the threshold is affected by the aspect ratio of the graphene flakes but other factors such as the interactions also play a strong role.

  10. Exceptionally strong and robust millimeter-scale graphene-alumina composite membranes.

    PubMed

    Berdova, Maria; Perros, Alexander Pyymaki; Kim, Wonjae; Riikonen, Juha; Ylitalo, Tuomo; Heino, Jouni; Li, Changfeng; Kassamakov, Ivan; Hæggström, Edward; Lipsanen, Harri; Franssila, Sami

    2014-09-05

    Graphene has attracted attention as a potential strengthening material and functional component in suspended membranes as utilized in micro and nanosystems. Development of a practical and scalable fabrication process is a necessary step to allow the exceptional material properties of graphene to be fully exploited in composite structures. Using standard and scalable microfabrication processes, we fabricated free-standing chemical vapor deposition monolayer graphene-reinforced Al2O3 composite membranes, 0.5 mm in diameter, that are strong and robust. Bulge tests revealed that the graphene reinforcement increased the membrane fracture strength by a factor of at least three and maximum sustainable strain from 0.28% to at least 0.69%. We show that the graphene-reinforced membranes are even tolerant to significant cracking without loss of membrane integrity. The graphene composite membranes' freestanding area of ∼ 200 000 μm(2) is almost a thousand times larger than suspended graphene membranes reported elsewhere. The presented graphene composite membranes may be seen as representing an interesting new class of durable composite materials warranting further study and having potential for broad applicability in a variety of fields.

  11. Headspace thin-film microextraction onto graphene membranes for specific detection of methyl(cyclopentadienyl)-tricarbonyl manganese in water samples by total reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Romero, V.; Costas-Mora, I.; Lavilla, I.; Bendicho, C.

    2016-12-01

    In this work, a novel analytical approach for determining methyl(cyclopentadienyl)-tricarbonyl (MMT) by total reflection X-ray fluorescence (TXRF) based on its trapping onto unmodified graphene membranes is described. Graphene membranes were synthesized by mild-thermal reduction of graphene oxide following drop-casting onto a glass substrate. High flexible and easy-to-handle graphene membranes with 10 mm diameter were obtained. In order to use the as-prepared membranes as extraction phases for headspace thin-solid film microextraction of MMT, they were fitted to quartz reflectors and placed onto the top of the glass vial containing the sample. Reflectors containing graphene membranes were directly used as sample carriers for TXRF analysis. Different parameters involved in the microextraction step were optimized in order to obtain the best performance. Detection and quantification limits were 18 and 60 ng L- 1 MMT, respectively. An enrichment factor of 265 was obtained. The method was successfully applied for the specific detection of MMT in different water samples and a certified reference material e.g., NWTM-27.2 fortified lake water. A recovery study was carried out on spiked water samples showing recoveries in the range 98-104% with a relative standard deviation of 4% (N = 5). In addition, speciation of manganese, i.e. MMT and Mn(II),in water samples can be accomplished since only volatile MMT is transferred to the headspace and retained onto graphene membranes.

  12. Reduction of graphene oxide to graphene, A study of changes in the atomic structure

    NASA Astrophysics Data System (ADS)

    Mittal, A.; Wagner, A.; Mattevi, C.; Chov, A.; Liao, K.; Macosko, C.; Chhowalla, M.; Mkhoyan, K. A.

    2012-02-01

    An economic method for large scale production of graphene is based on exfoliation of graphite into 1-atom thick sheets by oxidation, creating graphene oxide (GO) and subsequent reduction of GO into graphene. Reduced GO sheets approach the highly desired properties of graphene, such as electrical conductivity and mechanical strength, to various degrees, but not completely. To understand why, we must understand the nanostructure of the sheets. Different methods of reduction result in products that are similar to graphene, but these products retain some oxidized areas or contain regions with sp^3 bonded carbon. The concentration and distribution of these defects on the reduced GO sheet affect the properties of the 2D material. Here, we have characterized the atomic structure of GO and reduced GO via high resolution transmission electron microscopy, electron diffraction, and electron energy loss spectroscopy. Spectroscopic data taken during thermal reduction of GO shows changes in the fine structure of carbon K-edge as the carbon changes from an oxidized form to elemental amorphous carbon to graphite like form, clearly delineating the process of reduction of GO to graphene. Products of several other reduction methods are also characterized revealing information on electronic environment surrounding carbon atoms, distribution of crystalline areas, and oxygen removal from GO.

  13. Nanoporous Atomically Thin Graphene Membranes for Desalting and Dialysis Applications.

    PubMed

    Kidambi, Piran R; Jang, Doojoon; Idrobo, Juan-Carlos; Boutilier, Michael S H; Wang, Luda; Kong, Jing; Karnik, Rohit

    2017-09-01

    Dialysis is a ubiquitous separation process in biochemical processing and biological research. State-of-the-art dialysis membranes comprise a relatively thick polymer layer with tortuous pores, and suffer from low rates of diffusion leading to extremely long process times (often several days) and poor selectivity, especially in the 0-1000 Da molecular weight cut-off range. Here, the fabrication of large-area (cm(2) ) nanoporous atomically thin membranes (NATMs) is reported, by transferring graphene synthesized using scalable chemical vapor deposition (CVD) to polycarbonate track-etched supports. After sealing defects introduced during transfer/handling by interfacial polymerization, a facile oxygen-plasma etch is used to create size-selective pores (≤1 nm) in the CVD graphene. Size-selective separation and desalting of small model molecules (≈200-1355 Da) and proteins (≈14 000 Da) are demonstrated, with ≈1-2 orders of magnitude increase in permeance compared to state-of-the-art commercial membranes. Rapid diffusion and size-selectivity in NATMs offers transformative opportunities in purification of drugs, removal of residual reactants, biochemical analytics, medical diagnostics, therapeutics, and nano-bio separations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The composites based on plasticized starch and graphene oxide/reduced graphene oxide.

    PubMed

    Ma, Tiantian; Chang, Peter R; Zheng, Pengwu; Ma, Xiaofei

    2013-04-15

    The graphite was oxidized to prepare graphene oxide (GO), and GO was reduced by glucose to obtain reduced graphene oxide (RGO) sheet. There were abundant and residual oxygen-containing groups on GO and RGO, respectively. Compared to graphite, the GO and RGO sheets appeared flat and transparent, and the aqueous suspensions followed the Lambert-Beer's law well. The composites were also fabricated by using GO and RGO as the filler in plasticized-starch (PS) matrix. Because of more oxygen-containing groups, GO could form the stronger interaction with PS matrix than RGO. And GO/PS composites exhibited better tensile strength, elongation at break and moisture barrier than RGO/PS composites, but lower thermal stability. GO/PS composites could protect against UV light, while the conductivities of RGO/PS composites could reach 1.07×10(-4), 6.92×10(-4) and 0.01 S/cm, respectively stored at RH50, 75 and 100%.

  15. Biological reduction of graphene oxide using plant leaf extracts.

    PubMed

    Lee, Geummi; Kim, Beom Soo

    2014-01-01

    Two-dimensional graphene has attracted significant attention due to its unique mechanical, electrical, thermal, and optical properties. Most commonly employed methods to chemically reduce graphene oxide to graphene use hydrazine or its derivatives as the reducing agent. However, they are highly hazardous and explosive. Various phytochemicals obtained from different natural sources such as leaves and peels of a plant are used as reducing agents in the preparation of different gold, silver, copper, and platinum nanoparticles. In this study, seven plant leaf extracts (Cherry, Magnolia, Platanus, Persimmon, Pine, Maple, and Ginkgo) were compared for their abilities to reduce graphene oxide. The optimized reaction conditions for the reduction of graphene oxide were determined as follows. Type of plant: Cherry (Prunus serrulata), reaction time: 12 h, composition of the reaction mixture: 16.7% v/v of plant leaf extract in total suspension, and temperature: 95°C. The degree of reduction caused by Cherry leaf extract was analyzed by elemental analysis and X-ray photoelectron spectroscopy. The reduction of graphene oxide was also confirmed by ultraviolet-visible spectroscopy, Fourier transform-infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis.

  16. Graphene oxide and adsorption of chloroform: A density functional study

    NASA Astrophysics Data System (ADS)

    Kuisma, Elena; Hansson, C. Fredrik; Lindberg, Th. Benjamin; Gillberg, Christoffer A.; Idh, Sebastian; Schröder, Elsebeth

    2016-05-01

    Chlorinated hydrocarbon compounds are of environmental concerns, since they are toxic to humans and other mammals, and are widespread, and exposure is hard to avoid. Understanding and improving methods to reduce the amount of the substances are important. We present an atomic-scale calculational study of the adsorption of chlorine-based substance chloroform (CHCl3) on graphene oxide, as a step in estimating the capacity of graphene oxide for filtering out such substances, e.g., from drinking water. The calculations are based on density functional theory, and the recently developed consistent-exchange functional for the van der Waals density-functional method is employed. We obtain values of the chloroform adsorption energy varying from roughly 0.2 to 0.4 eV per molecule. This is comparable to previously found results for chloroform adsorbed directly on clean graphene, using similar calculations. In a wet environment, like filters for drinking water, the graphene will not stay clean and will likely oxidize, and thus adsorption onto graphene oxide, rather than clean graphene, is a more relevant process to study.

  17. Selective enrichment and desalting of hydrophilic peptides using graphene oxide.

    PubMed

    Jiang, Miao; Qi, Linyu; Liu, Peiru; Wang, Zijun; Duan, Zhigui; Wang, Ying; Liu, Zhonghua; Chen, Ping

    2016-08-01

    The wide variety and low abundance of peptides in tissue brought great difficulties to the separation and identification of peptides, which is not in favor of the development of peptidomics. RP-HPLC, which could purify small molecules based on their hydrophobicity, has been widely used in the separation and enrichment of peptide due to its fast, good reproducibility and high resolution. However, RP-HPLC requires the instrument and expensive C18 column and its sample capacity is also limited. Recently, graphene oxide has been applied to the adsorption of amino acids. However, the enrichment efficiency and selectivity of graphene oxide for peptides remain unclear. In this study, the adsorption efficiency and selectivity of graphene oxide and RP-C18 matrix were compared on trypsinized α-actin and also on tissue extracts from pituitary gland and hippocampus. For α-actin, there exhibit similar elution peaks for total trypsinized products and those adsorpted by GO and C18 matrix. But peptides adsorbed by GO showed the higher hydrophilic peaks than which adsorbed by C18 matrix. The resulted RP-HPLC profile showed that most of peptides enriched by graphene oxide were eluted at low concentration of organic solvent, while peptides adsorbed by RP-C18 matrix were mostly eluted at relatively high concentration. Moreover, mass spectrometry analysis suggested that, in pituitary sample, there were 495 peptides enriched by graphene oxide, 447 peptides enriched by RP-C18 matrix while in hippocampus sample 333 and 243 peptides respectively. The GRAVY value analysis suggested that the graphene oxide has a stronger adsorption for highly hydrophilic peptides compared to the RP-C18 matrix. Furthermore, the combination of these two methods could notably increase the number of identification peptides but also the number of predicted protein precursors. Our study provided a new thought to the role of graphene oxide during the enrichment of peptides from tissue which should be useful for

  18. Graphene oxide-MnO2 nanocomposite for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Muhammed Shafi, P.; Vishal, Jose K.; Chandra Bose, A.

    2016-09-01

    Increased depletion of fossil fuels along with global warming and climate change made the society to think about alternate green and sustainable energy sources and better energy storage devices. Extensive research has been performed on the development of solar cells, fuel cells, Lithium- ion battery and supercapacitors to combat the green house effect and its consequences, and to meet the increased energy crisis. Supercapacitors, also known as electrochemical capacitors are gained a great attention because of their pulse power supply, long cycle life (>100,000), simple principle and high dynamic of charge propagation. Its greater power density than lithium- ion battery and much larger energy density than conventional capacitors brought super capacitors to a promising energy storage device to meet the increased energy demands. Here we demonstrate supercapacitor electrode materials with graphene oxide (electric double layer capacitor) and α-MnO2 nanomaterial (pseudo-capacitor), as well as composite of these materials, which means that the bulk of the material undergoes a fast redox reaction to provide the capacitive response and they exhibit superior specific energies in addition to the carbon-based supercapacitors (double-layer capacitors). A simple soft chemical route is utilized to synthesize graphene oxide, α-MnO2 and graphene oxide-MnO2 composite. The phase and the structure of the synthesized materials are studied using X-ray diffractometry (XRD). The functional group and the presence of impurities are understood from Fourier transform infrared (FTIR) spectra. The capacitive properties of the graphene oxide, graphene oxide - MnO2 nanocomposite and α-MnO2 are tested with the help of cyclic voltammetry (CV) and galvanostatic charge - discharge techniques using 1 M Na2SO4 in aqueous solution as electrolyte. It was found that graphene oxide - MnO2 nanocomposite shows better electrochemical behaviour compared to individual graphene oxide and α-MnO2 nanomaterial.

  19. Ultraviolet photosensor based on few layered reduced graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Shelke, Nitin T.; Karche, B. R.

    2017-10-01

    Reduced graphene oxide (RGO), a two-dimensional (2D) system, has attracted much interest in photonic applications owing to its ability to absorb light over a broad wavelength. This leads to several studies on RGO-based photosensors. In this paper, chemical oxidation of graphite was carried out at room temperature for the preparation of large area reduced graphene oxide using a modified Hummer's method. The as-prepared reduced graphene oxide was characterized by XRD, Raman spectroscopy, FESEM, and TEM to confirm the absence of impurities and to ascertain their morphology. In addition, the as-prepared reduced graphene oxide for its possible application as UV photosensor is reported. The electric and optoelectronic properties of RGO based UV photosensor shows a fast response and recovery time of 1 s and 3 s; high photoresponsitivity (3.74 AW-1) and quantum efficiency (1274%) indicating that the graphene oxide is an important material for high performance photosensor. This work demonstrates the ultrafast photoresponse with high photoresponsivity, proving its potential as a promising material for optoelectronic devices.

  20. Interfacial Assembly of Graphene Oxide Sheets

    NASA Astrophysics Data System (ADS)

    Cote, Laura J.

    Scientific interest in graphene oxide (GO) sheets, the product of chemical oxidation and exfoliation of graphite powder, has resurged in recent years because GO is considered a promising precursor for the bulk production of graphene-based sheets for a variety of applications. In addition, GO can be viewed as an unconventional type of soft material as it is characterized by two abruptly different length scales. Its thickness is of typical molecular dimensions, measured to be about 1 nm by atomic force microscopy, but its lateral dimensions are that of common colloidal particles, ranging from nanometers to tens of microns. This high anisotropy leads to interesting fundamental colloidal interactions between the soft sheets which have practical implications in the solution processing and assembly of the material. This research therefore aims to use a variety of techniques to control these inter-sheet interactions to gain an understanding of the processing-structure relationships which ultimately determine the overall properties of the bulk GO assembly. GO is identified as a two-dimensional amphiphile with a unique edge-to-center arrangement of hydrophilic and hydrophobic groups, which has led to the demonstration of its pH- and size-dependent surface activity. The water surface is then utilized, as in the Langmuir-Blodgett technique, as an ideal substrate to tile up the GO sheets and study the interactions between them. Sheet-sheet interaction morphologies were successfully altered between wrinkled and overlapped states by pH tuning of sheet charge density, and the resulting structure-property relationships are explored. In addition, a novel flash-reduction and assembly process is described in which a simple photographic camera flash can rapidly and cleanly turn an insulating, well-stacked GO paper to a more open and fluffy conducting film. Lastly, the use of these research results as educational outreach platforms is highlighted. A variety of outlets, such as You

  1. Quaternized graphene oxide nanocomposites as fast hydroxide conductors.

    PubMed

    Zarrin, Hadis; Fu, Jing; Jiang, Gaopeng; Yoo, Skylar; Lenos, Jared; Fowler, Michael; Chen, Zhongwei

    2015-02-24

    Nanocomposites play a key role in performance improvements of hydroxide conductors employed in a wide range of alkaline-electrochemical systems such as fuel cells and metal-air batteries. Graphene oxide (GO) nanosheets are considered to be outstanding nanofillers for polymeric nanocomposites on account of their excellent physicochemical strength and electrochemical properties. In this work, a fast hydroxide conductor was developed on the basis of a chemically modified GO nanocomposite membrane. The high surface area of GO was functionalized with highly stable hydroxide-conductive groups using a dimethyloctadecyl [3-(trimethoxysilyl)propyl]ammonium chloride (DMAOP) precursor, named QAFGO, and then composed with porous polybenzimidazole PBI (pPBI) as a well-suited polymeric backbone. The nanocomposite exhibited outstanding hydroxide conductivity of 0.085 S cm(-1), high physicochemical strength, and electrochemical stability for 21 days. An alkaline fuel cell (AFC) setup was fabricated to determine the functionality of QAFGO/pPBI nanocomposite in an alkaline-based system. The high AFC performance with peak power density of 86.68 mW cm(-2) demonstrated that QAFGO/pPBI nanocomposite membrane has promising potential to be employed as a reliable hydroxide conductor for electrochemical systems working in alkaline conditions.

  2. First principles calculations of the electronic and chemical properties of graphene, graphane, and graphene oxide.

    PubMed

    Hernández Rosas, J J; Ramírez Gutiérrez, R E; Escobedo-Morales, A; Chigo Anota, Ernesto

    2011-05-01

    The electrical and chemical properties of graphene (C(24)H(12)), graphane (C(24)H(24)) and graphene oxide (C(54)H(17)+O+(OH)(3)+COOH) were studied through the density functional theory (DFT) at level of Local Density Approximation (LDA) using a model C(n)H(m) like. The optimized geometry, energy gap and chemical reactivity for the proposed carbon 2D models are reported. It was found that while the graphene and graphane structures have semiconductor behavior, the graphene oxide behaves as semi-metal. However, a transition from semi-mental to semiconductor is predicted if the carboxyl group (COOH) is removed from such structure. The chemically active sites are analyzed on the basis of the electrophilic Fukui functions for each structure.

  3. Graphene ``microdrums'' on a freestanding perforated thin membrane for high sensitivity MEMS pressure sensors

    NASA Astrophysics Data System (ADS)

    Wang, Qiugu; Hong, Wei; Dong, Liang

    2016-03-01

    We present a microelectromechanical system (MEMS) graphene-based pressure sensor realized by transferring a large area, few-layered graphene on a suspended silicon nitride thin membrane perforated by a periodic array of micro-through-holes. Each through-hole is covered by a circular drum-like graphene layer, namely a graphene ``microdrum''. The uniqueness of the sensor design is the fact that introducing the through-hole arrays into the supporting nitride membrane allows generating an increased strain in the graphene membrane over the through-hole array by local deformations of the holes under an applied differential pressure. Further reasons contributing to the increased strain in the devised sensitive membrane include larger deflection of the membrane than that of its imperforated counterpart membrane, and direct bulging of the graphene microdrum under an applied pressure. Electromechanical measurements show a gauge factor of 4.4 for the graphene membrane and a sensitivity of 2.8 × 10-5 mbar-1 for the pressure sensor with a good linearity over a wide pressure range. The present sensor outperforms most existing MEMS-based small footprint pressure sensors using graphene, silicon, and carbon nanotubes as sensitive materials, due to the high sensitivity.

  4. Nonlinear optical response of some Graphene oxide and Graphene fluoride derivatives

    NASA Astrophysics Data System (ADS)

    Liaros, Nikolaos; Orfanos, Ioannis; Papadakis, Ioannis; Couris, Stelios

    2016-12-01

    The nonlinear optical properties of two graphene derivatives, graphene oxide and graphene fluoride, are investigated by means of the Z-scan technique employing 35 ps and 4 ns, visible (532 nm) laser excitation. Both derivatives were found to exhibit significant third-order nonlinear optical response at both excitation regimes, with the nonlinear absorption being relatively stronger and concealing the presence of nonlinear refraction under ns excitation, while ps excitation reveals the presence of both nonlinear absorption and refraction. Both nonlinear properties are of great interest for several photonics, opto-fluidics, opto-electronics and nanotechnology applications.

  5. Graphene-based thin film supercapacitor with graphene oxide as dielectric spacer

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhang; Galpaya, Dilini; Notarianni, Marco; Yan, Cheng; Motta, Nunzio

    2013-08-01

    Thin film supercapacitors are produced by using electrochemically exfoliated graphene (G) and wet-chemically produced graphene oxide (GO). Either G/GO/G stacked film or sole GO film are sandwiched by two Au films to make devices, where GO is the dielectric spacer. The addition of graphene film can increase the capacitance about two times, compared to the simple Au electrode. It is found that the GO film has very high dielectric constant, accounting for the high capacitance. AC measurement reveals that the relative permittivity of GO is in the order of 104 within the frequency range of 0.1-70 Hz.

  6. Nano-rods of zinc oxide in nano-graphene

    NASA Astrophysics Data System (ADS)

    Ortiz, Pedro; Chavira, Elizabeth; Monroy, Marel; Elizalde, José; Santiago, Patricia; Sato, Roberto; Tejeda, Adriana; González, Guillermina; Novelo, Omar; Flores, Carlos

    2014-03-01

    It's of great interest to study the devices based on nano-ZnO and graphene, for their electromagnetic and optical properties to increase the efficiency of solar cells. The graphene multilayers synthesis was done by mechanosynthesis, grinding in a mechanical agate mortar. The zinc oxide nano-rods were synthesized from zinc acetate dihydrate, Ace, (Sigma Aldrich) and ethylene diamine, En, (Sigma Aldrich) with a 1:2 ratio of reagents En/Ace. The ZnO nano-rods in nano-tubes graphene were obtained by mechanosynthesis. The X-ray powder diffraction, shows the shift of C with PDF 12-0212 and ZnO, Zincite PDF 36-1451, both with hexagonal unit cell. The grain size and morphology of graphene (multilayers and nano-tubes), ZnO nano-rods and ZnO-graphene mixture (multilayers, nano-tubes) were observed by scanning electron microscope. Transmission electron microscope, corroborates shown in SEM. Raman spectroscopy, shows the shift of multilayer graphene and the ZnO nano-rods. In photoluminescence measurements, observe the change in intensity in the band defects. Magnetic properties characterization was carried out by Vibrating Sample Magnetometry. We conclude that graphite multilayers dislocated by cutting efforts, forming graphene nano-tubes and encapsulated ZnO nano-rods within graphene.

  7. Tuning the grade of graphene: Gamma ray irradiation of free-standing graphene oxide films in gaseous phase

    NASA Astrophysics Data System (ADS)

    Dumée, Ludovic F.; Feng, Chunfang; He, Li; Allioux, Francois-Marie; Yi, Zhifeng; Gao, Weimin; Banos, Connie; Davies, Justin B.; Kong, Lingxue

    2014-12-01

    A direct approach to functionalize and reduce pre-shaped graphene oxide 3D architectures is demonstrated by gamma ray irradiation in gaseous phase under analytical grade air, N2 or H2. The formation of radicals upon gamma ray irradiation is shown to lead to surface functionalization of the graphene oxide sheets. The reduction degree of graphene oxide, which can be controlled through varying the γ-ray total dose irradiation, leads to the synthesis of highly crystalline and near defect-free graphene based materials. The crystalline structure of the graphene oxide and γ-ray reduced graphene oxide was investigated by x-ray diffraction and Raman spectroscopy. The results reveal no noticeable changes in the size of sp2 graphitic structures for the range of tested gases and total exposure doses suggesting that the irradiation in gaseous phase does not damage the graphene crystalline domains. As confirmed by X-ray photoemission spectroscopy, the C/O ratio of γ-ray reduced graphene oxide is increasing from 2.37 for graphene oxide to 6.25 upon irradiation in hydrogen gas. The removal of oxygen atoms with this reduction process in hydrogen results in a sharp 400 times increase of the electrical conductivity of γ-ray reduced graphene oxide from 0.05 S cm-1 to as high as 23 S cm-1. A significant increase of the contact angle of the γ-ray reduced graphene oxide bucky-papers and weakened oxygen rich groups characteristic peaks across the Fourier transform infrared spectra further illustrate the efficacy of the γ-ray reduction process. A mechanism correlating the interaction between hydrogen radicals formed upon γ-ray irradiation of hydrogen gas and the oxygen rich groups on the surface of the graphene oxide bucky-papers is proposed, in order to contribute to the synthesis of reduced graphene materials through solution-free chemistry routes.

  8. Grain-boundary unzipping by oxidation in polycrystalline graphene

    NASA Astrophysics Data System (ADS)

    Alexandre, Simone; Lucio, Aline; Nunes, Ricardo

    2011-03-01

    The need for large-scale production of graphene will inevitably lead to synthesis of the polycrystalline material [1,2]. Understanding the chemical, mechanical, and electronic properties of grain boundaries in graphene polycrystals will be crucial for the development of graphene-based electronics. Oxidation of this material has been suggested to lead to graphene ribbons, by the oxygen-driven unzipping mechanism. A cooperative-strain mechanism, based on the formation of epoxy groups along lines of parallel bonds in the hexagons of graphene's honeycomb lattice, was proposed to explain the unzipping effect in bulk graphene In this work we employ ab initio calculations to study the oxidation of polycrystalline graphene by chemisorption of oxygen at the grain boundaries. Our results indicate that oxygen tends to segregate at the boundaries, and that the unzipping mechanism is also operative along the grain boundaries, despite the lack of the parallel bonds due to the presence of fivefold and sevenfold carbon rings along the boundary core. We acknowledge support from the Brazilian agencies: CNPq, Fapemig, and INCT-Materiais de Carbono.

  9. Highly Strong and Elastic Graphene Fibres Prepared from Universal Graphene Oxide Precursors

    NASA Astrophysics Data System (ADS)

    Huang, Guoji; Hou, Chengyi; Shao, Yuanlong; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang; Zhu, Meifang

    2014-02-01

    Graphene fibres are continuously prepared from universal graphene oxide precursors by a novel hydrogel-assisted spinning method. With assistance of a rolling process, meters of ribbon-like GFs, or GRs with improved conductivity, tensile strength, and a long-range ordered compact layer structure are successfully obtained. Furthermore, we refined our spinning process to obtained elastic GRs with a mixing microstructure and exceptional elasticity, which may provide a platform for electronic skins and wearable electronics, sensors, and energy devices.

  10. Highly Strong and Elastic Graphene Fibres Prepared from Universal Graphene Oxide Precursors

    PubMed Central

    Huang, Guoji; Hou, Chengyi; Shao, Yuanlong; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang; Zhu, Meifang

    2014-01-01

    Graphene fibres are continuously prepared from universal graphene oxide precursors by a novel hydrogel-assisted spinning method. With assistance of a rolling process, meters of ribbon-like GFs, or GRs with improved conductivity, tensile strength, and a long-range ordered compact layer structure are successfully obtained. Furthermore, we refined our spinning process to obtained elastic GRs with a mixing microstructure and exceptional elasticity, which may provide a platform for electronic skins and wearable electronics, sensors, and energy devices. PMID:24576869

  11. Unusual dielectric response in cobalt doped reduced graphene oxide

    SciTech Connect

    Akhtar, Abu Jahid; Gupta, Abhisek; Kumar Shaw, Bikash; Saha, Shyamal K.

    2013-12-09

    Intensive research on cobalt doped reduced graphene oxide (Co-RGO) to investigate the modification in graphene magnetism and spin polarization due to presence of transition metal atom has been carried out, however, its dielectric spectroscopy, particularly, how capacitance changes with impurity levels in graphene is relatively unexplored. In the present work, dielectric spectroscopy along with magneto-dielectric effect are investigated in Co-RGO. Contrary to other materials, here permittivity increases abruptly with frequency in the low frequency region and continues to increase till 10{sup 7} Hz. This unusual behavior is explained on the basis of trap induced capacitance created due to impurity levels.

  12. Knudsen effusion through polymer-coated three-layer porous graphene membranes.

    PubMed

    Boutilier, Michael S H; Hadjiconstantinou, Nicolas G; Karnik, Rohit

    2017-05-05

    Graphene membranes have the potential to exceed the permeance and selectivity limits of conventional gas separation membranes. Realizing this potential in practical systems relies on overcoming numerous scalability challenges, such as isolating or sealing permeable defects in macroscopic areas of graphene that can compromise performance and developing methods to create high densities of selective pores over large areas. This study focuses on a centimeter-scale membrane design, where leakage is reduced by substrate selection, permeable polymer film coating, and stacking of three independent layers of graphene, while (selective) pores are created by high density ion bombardment. The three-layer graphene provides high resistance to gas flow, which decreases with ion bombardment and results in selectivity consistent with Knudsen effusion. The results suggest that the permeable pores created in three layer graphene were larger than those required for molecular sieving and that designs based on single layer graphene may lend themselves more easily to molecular sieving of gases.

  13. Knudsen effusion through polymer-coated three-layer porous graphene membranes

    NASA Astrophysics Data System (ADS)

    Boutilier, Michael S. H.; Hadjiconstantinou, Nicolas G.; Karnik, Rohit

    2017-05-01

    Graphene membranes have the potential to exceed the permeance and selectivity limits of conventional gas separation membranes. Realizing this potential in practical systems relies on overcoming numerous scalability challenges, such as isolating or sealing permeable defects in macroscopic areas of graphene that can compromise performance and developing methods to create high densities of selective pores over large areas. This study focuses on a centimeter-scale membrane design, where leakage is reduced by substrate selection, permeable polymer film coating, and stacking of three independent layers of graphene, while (selective) pores are created by high density ion bombardment. The three-layer graphene provides high resistance to gas flow, which decreases with ion bombardment and results in selectivity consistent with Knudsen effusion. The results suggest that the permeable pores created in three layer graphene were larger than those required for molecular sieving and that designs based on single layer graphene may lend themselves more easily to molecular sieving of gases.

  14. A facile electrospinning method to fabricate polylactide/graphene/MWCNTs nanofiber membrane for tissues scaffold

    NASA Astrophysics Data System (ADS)

    Yang, Chunyu; Chen, Sihao; Wang, Jihu; Zhu, Tonghe; Xu, Gang; Chen, Zhichang; Ma, Xiaobiao; Li, Wenyao

    2016-01-01

    In this study, we have successfully prepared polylactide (PLA)/Graphene (G)/multiwalled carbon nanotubes (MWCNTs) solution by a solution-blending technique, and the different composition proportion of PLA/G/MWCNTs composite nanofiber membranes were produced via an electrospinning technique. The morphology, dispersion of graphene/MWCNTs, crystal structure and thermal stability of PLA/G/MWCNTs membranes were studied by SEM, TEM, XRD and TG, respectively. The results showed that the MWCNTs and graphene could disperse randomly into the fibers, and the introduction of graphene and MWCNTs did not mainly affect the crystal structure of PLA. TG test indicated that the addition of MWCNTs and graphene enhanced the thermal stability of the composites. Additionally, the presence of the graphene and MWCNTs in the PLA matrix had an obvious delaying effect on the degradation of PLA, which made PLA/G/MWCNTs nanofiber membrane have large potential in tissues scaffold.

  15. Graphene-graphite oxide field-effect transistors.

    PubMed

    Standley, Brian; Mendez, Anthony; Schmidgall, Emma; Bockrath, Marc

    2012-03-14

    Graphene's high mobility and two-dimensional nature make it an attractive material for field-effect transistors. Previous efforts in this area have used bulk gate dielectric materials such as SiO(2) or HfO(2). In contrast, we have studied the use of an ultrathin layered material, graphene's insulating analogue, graphite oxide. We have fabricated transistors comprising single or bilayer graphene channels, graphite oxide gate insulators, and metal top-gates. The graphite oxide layers show relatively minimal leakage at room temperature. The breakdown electric field of graphite oxide was found to be comparable to SiO(2), typically ~1-3 × 10(8) V/m, while its dielectric constant is slightly higher, κ ≈ 4.3. © 2012 American Chemical Society

  16. Facile Synthesis of Iron Oxide/Graphene Nanocomposites Using Liquid Phase Plasma Method.

    PubMed

    Lee, H; Park, Y K; Kim, S J; Kim, B J; An, K H; Kim, B H; Jung, S C

    2016-05-01

    Liquid phase plasma (LPP) method was applied, for the first time, to the impregnation of iron oxide nanoparticles onto graphene sheet. Iron oxide nanoparticles with the size of 50 nm were precipitated with uniform dispersion on the surface of graphene sheet. The amount of iron oxide nanoparticles precipitated on graphene sheets increased with increasing LPP process times. The XPS, Raman and EDX analyses showed that the iron oxide/graphene composites synthesized by the LPP process.

  17. Red photoluminescence BCNO synthesized from graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Kang, Yue; Chu, Zeng-yong; Ma, Tian; Li, Wei-ping; Zhang, Dong-jiu; Tang, Xiao-yu

    2016-01-01

    In this paper, we demonstrate the conversion of graphene oxide (GO) into boron carbon oxynitride (BCNO) hybrid nanosheets via a reaction with boric acid and urea, during which the boron and nitrogen atoms are incorporated into graphene nanosheets. The experimental results reveal that GO is important for the photoluminescence (PL) BCNO phosphor particles. More importantly, in this system, the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes (LEDs).

  18. Unfolding the damping behavior of multilayer graphene membrane in the low-frequency regime.

    PubMed

    Lahiri, Debrupa; Das, Santanu; Choi, Wonbong; Agarwal, Arvind

    2012-05-22

    The damping behavior of few-layered graphene membrane in the low-frequency regime of mechanical loading is investigated in the present study. Damping of graphene has significant applications in micro/nanoscale devices and macroscale dynamic systems for absorbing shock-generated energies. Damping behavior of graphene is experimentally evaluated, for the first time, by dynamic mechanical analysis at the nanoscale with cyclic mechanical loading in the range 0.1-50 μN applied at a frequency range of 10-250 Hz. This study reveals 260% higher damping on graphene membranes than a silicon surface. The damping shows excellent reproducibility and remains steady even after 100,000 cycles. The damping of multilayer graphene membrane, supported on a Si/SiO(2) substrate, shows a strong dependence on the frequency of cyclic loading. The mechanism governing impressive damping of a graphene membrane is elucidated by structural changes such as ripple formation, ripple wave propagation, and z-axis compression. Damping behavior of a graphene membrane in this low-frequency regime is also found to depend on the number of graphene layers and is explained as the interplay between in-plane sp(2) and out-of-plane van der Waals forces. These findings are important for establishing the potential of graphene for applications in macro- to nanoscale structures that require continuous absorption of shock waves without destruction/failure.

  19. The graphene oxide contradictory effects against human pathogens

    NASA Astrophysics Data System (ADS)

    Palmieri, Valentina; Carmela Lauriola, Maria; Ciasca, Gabriele; Conti, Claudio; De Spirito, Marco; Papi, Massimiliano

    2017-04-01

    Standing out as the new wonder bidimensional material, graphene oxide (GO) has aroused an exceptional interest in biomedical research by holding promise for being the antibacterial of future. First, GO possesses a specific interaction with microorganisms combined with a mild toxicity for human cells. Additionally, its antibacterial action seems to be directed to multiple targets in pathogens, causing both membranes mechanical injury and oxidative stress. Lastly, compared to other carbon materials, GO has easy and low-cost processing and is environment-friendly. This remarkable specificity and multi-targeting antibacterial activity come at a time when antibiotic resistance represents the major health challenge. Unfortunately, a comprehensive framework to understand how to effectively utilize this material against microorganisms is still lacking. In the last decade, several groups tried to define the mechanisms of interaction between GO flakes and pathogens but conflicting results have been reported. This review is focused on all the contradictions of GO antimicrobial properties in solution. Flake size, incubation protocol, time of exposure and species considered are examples of factors influencing results. These parameters will be summarized and analyzed with the aim of defining the causes of contradictions, to allow fast GO clinical application.

  20. Towards the Knittability of Graphene Oxide Fibres

    PubMed Central

    Seyedin, Shayan; Romano, Mark S.; Minett, Andrew I.; Razal, Joselito M.

    2015-01-01

    Recent developments in graphene oxide fibre (GO) processing include exciting demonstrations of hand woven textile structures. However, it is uncertain whether the fibres produced can meet the processing requirements of conventional textile manufacturing. This work reports for the first time the production of highly flexible and tough GO fibres that can be knitted using textile machinery. The GO fibres are made by using a dry-jet wet-spinning method, which allows drawing of the spinning solution (the GO dispersion) in several stages of the fibre spinning process. The coagulation composition and spinning conditions are evaluated in detail, which led to the production of densely packed fibres with near-circular cross-sections and highly ordered GO domains. The results are knittable GO fibres with Young’s modulus of ~7.9 GPa, tensile strength of ~135.8 MPa, breaking strain of ~5.9%, and toughness of ~5.7 MJ m−3. The combination of suitable spinning method, coagulation composition, and spinning conditions led to GO fibres with remarkable toughness; the key factor in their successful knitting. This work highlights important progress in realising the full potential of GO fibres as a new class of textile. PMID:26459866

  1. High Performance Graphene Oxide Based Rubber Composites

    NASA Astrophysics Data System (ADS)

    Mao, Yingyan; Wen, Shipeng; Chen, Yulong; Zhang, Fazhong; Panine, Pierre; Chan, Tung W.; Zhang, Liqun; Liang, Yongri; Liu, Li

    2013-08-01

    In this paper, graphene oxide/styrene-butadiene rubber (GO/SBR) composites with complete exfoliation of GO sheets were prepared by aqueous-phase mixing of GO colloid with SBR latex and a small loading of butadiene-styrene-vinyl-pyridine rubber (VPR) latex, followed by their co-coagulation. During co-coagulation, VPR not only plays a key role in the prevention of aggregation of GO sheets but also acts as an interface-bridge between GO and SBR. The results demonstrated that the mechanical properties of the GO/SBR composite with 2.0 vol.% GO is comparable with those of the SBR composite reinforced with 13.1 vol.% of carbon black (CB), with a low mass density and a good gas barrier ability to boot. The present work also showed that GO-silica/SBR composite exhibited outstanding wear resistance and low-rolling resistance which make GO-silica/SBR very competitive for the green tire application, opening up enormous opportunities to prepare high performance rubber composites for future engineering applications.

  2. High Performance Graphene Oxide Based Rubber Composites

    PubMed Central

    Mao, Yingyan; Wen, Shipeng; Chen, Yulong; Zhang, Fazhong; Panine, Pierre; Chan, Tung W.; Zhang, Liqun; Liang, Yongri; Liu, Li

    2013-01-01

    In this paper, graphene oxide/styrene-butadiene rubber (GO/SBR) composites with complete exfoliation of GO sheets were prepared by aqueous-phase mixing of GO colloid with SBR latex and a small loading of butadiene-styrene-vinyl-pyridine rubber (VPR) latex, followed by their co-coagulation. During co-coagulation, VPR not only plays a key role in the prevention of aggregation of GO sheets but also acts as an interface-bridge between GO and SBR. The results demonstrated that the mechanical properties of the GO/SBR composite with 2.0 vol.% GO is comparable with those of the SBR composite reinforced with 13.1 vol.% of carbon black (CB), with a low mass density and a good gas barrier ability to boot. The present work also showed that GO-silica/SBR composite exhibited outstanding wear resistance and low-rolling resistance which make GO-silica/SBR very competitive for the green tire application, opening up enormous opportunities to prepare high performance rubber composites for future engineering applications. PMID:23974435

  3. High performance graphene oxide based rubber composites.

    PubMed

    Mao, Yingyan; Wen, Shipeng; Chen, Yulong; Zhang, Fazhong; Panine, Pierre; Chan, Tung W; Zhang, Liqun; Liang, Yongri; Liu, Li

    2013-01-01

    In this paper, graphene oxide/styrene-butadiene rubber (GO/SBR) composites with complete exfoliation of GO sheets were prepared by aqueous-phase mixing of GO colloid with SBR latex and a small loading of butadiene-styrene-vinyl-pyridine rubber (VPR) latex, followed by their co-coagulation. During co-coagulation, VPR not only plays a key role in the prevention of aggregation of GO sheets but also acts as an interface-bridge between GO and SBR. The results demonstrated that the mechanical properties of the GO/SBR composite with 2.0 vol.% GO is comparable with those of the SBR composite reinforced with 13.1 vol.% of carbon black (CB), with a low mass density and a good gas barrier ability to boot. The present work also showed that GO-silica/SBR composite exhibited outstanding wear resistance and low-rolling resistance which make GO-silica/SBR very competitive for the green tire application, opening up enormous opportunities to prepare high performance rubber composites for future engineering applications.

  4. Photochemical transformation of graphene oxide in sunlight.

    PubMed

    Hou, Wen-Che; Chowdhury, Indranil; Goodwin, David G; Henderson, W Matthew; Fairbrother, D Howard; Bouchard, Dermont; Zepp, Richard G

    2015-03-17

    Graphene oxide (GO) is promising in scalable production and has useful properties that include semiconducting behavior, catalytic reactivity, and aqueous dispersibility. In this study, we investigated the photochemical fate of GO under environmentally relevant sunlight conditions. The results indicate that GO readily photoreacts under simulated sunlight with the potential involvement of electron-hole pair creation. GO was shown to photodisproportionate to CO2, reduced materials similar to reduced GO (rGO) that are fragmented compared to the starting material, and low molecular-weight (LMW) species. Kinetic studies show that the rate of the initially rapid photoreaction of GO is insensitive to the dissolved oxygen content. In contrast, at longer time points (>10 h), the presence of dissolved oxygen led to a greater production of CO2 than the same GO material under N2-saturated conditions. Regardless, the rGO species themselves persist after extended irradiation equivalent to 2 months in natural sunlight, even in the presence of dissolved oxygen. Overall, our findings indicate that GO phototransforms rapidly under sunlight exposure, resulting in chemically reduced and persistent photoproducts that are likely to exhibit transport and toxic properties unique from parent GO.

  5. Towards the Knittability of Graphene Oxide Fibres

    NASA Astrophysics Data System (ADS)

    Seyedin, Shayan; Romano, Mark S.; Minett, Andrew I.; Razal, Joselito M.

    2015-10-01

    Recent developments in graphene oxide fibre (GO) processing include exciting demonstrations of hand woven textile structures. However, it is uncertain whether the fibres produced can meet the processing requirements of conventional textile manufacturing. This work reports for the first time the production of highly flexible and tough GO fibres that can be knitted using textile machinery. The GO fibres are made by using a dry-jet wet-spinning method, which allows drawing of the spinning solution (the GO dispersion) in several stages of the fibre spinning process. The coagulation composition and spinning conditions are evaluated in detail, which led to the production of densely packed fibres with near-circular cross-sections and highly ordered GO domains. The results are knittable GO fibres with Young’s modulus of ~7.9 GPa, tensile strength of ~135.8 MPa, breaking strain of ~5.9%, and toughness of ~5.7 MJ m-3. The combination of suitable spinning method, coagulation composition, and spinning conditions led to GO fibres with remarkable toughness; the key factor in their successful knitting. This work highlights important progress in realising the full potential of GO fibres as a new class of textile.

  6. Towards the Knittability of Graphene Oxide Fibres.

    PubMed

    Seyedin, Shayan; Romano, Mark S; Minett, Andrew I; Razal, Joselito M

    2015-10-13

    Recent developments in graphene oxide fibre (GO) processing include exciting demonstrations of hand woven textile structures. However, it is uncertain whether the fibres produced can meet the processing requirements of conventional textile manufacturing. This work reports for the first time the production of highly flexible and tough GO fibres that can be knitted using textile machinery. The GO fibres are made by using a dry-jet wet-spinning method, which allows drawing of the spinning solution (the GO dispersion) in several stages of the fibre spinning process. The coagulation composition and spinning conditions are evaluated in detail, which led to the production of densely packed fibres with near-circular cross-sections and highly ordered GO domains. The results are knittable GO fibres with Young's modulus of ~7.9 GPa, tensile strength of ~135.8 MPa, breaking strain of ~5.9%, and toughness of ~5.7 MJ m(-3). The combination of suitable spinning method, coagulation composition, and spinning conditions led to GO fibres with remarkable toughness; the key factor in their successful knitting. This work highlights important progress in realising the full potential of GO fibres as a new class of textile.

  7. Graphene oxide-DNA based sensors.

    PubMed

    Gao, Li; Lian, Chaoqun; Zhou, Yang; Yan, Lirong; Li, Qin; Zhang, Chunxia; Chen, Liang; Chen, Keping

    2014-10-15

    Since graphene oxide (GO) is readily available and exhibits exceptional optical, electrical, mechanical and chemical properties, it has attracted increasing interests for use in GO-DNA based sensors. This paper reviews the advances in GO-DNA based sensors using DNA as recognition elements. In solution, GO is as an excellent acceptor of fluorescence resonance energy transfer (FRET) to quench the fluorescence in dye labeled DNA sequences. This review discusses the emerging GO-DNA based sensors related to FRET for use in the detection of DNA, proteins, metal ions, cysteine (Cys), and others. The application of the electrochemical GO-DNA based sensors is also summarized because GO possesses exceptional electrochemical properties. The detection mechanisms and the advantages of GO are also revealed and discussed. GO-DNA based sensors perform well at low cost, and high sensitivity, and provide low detection limits. Additionally, GO-DNA based sensors should appear in the near future as scientists explore their usefulness and properties. Finally, future perspectives and possible challenges in this area are outlined. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Sulfuric Acid Intercalated Graphite Oxide for Graphene Preparation

    PubMed Central

    Hong, Yanzhong; Wang, Zhiyong; Jin, Xianbo

    2013-01-01

    Graphene has shown enormous potential for innovation in various research fields. The current chemical approaches based on exfoliation of graphite via graphite oxide (GO) are potential for large-scale synthesis of graphene but suffer from high cost, great operation difficulties, and serious waste discharge. We report a facile preparation of graphene by rapid reduction and expansion exfoliation of sulfuric acid intercalated graphite oxide (SIGO) at temperature just above 100°C in ambient atmosphere, noting that SIGO is easily available as the immediate oxidation descendent of graphite in sulfuric acid. The oxygenic and hydric groups in SIGO are mainly removed through dehydration as catalyzed by the intercalated sulfuric acid (ISA). The resultant consists of mostly single layer graphene sheets with a mean diameter of 1.07 μm after dispersion in DMF. This SIGO process is reductant free, easy operation, low-energy, environmental friendly and generates graphene with low oxygen content, less defect and high conductivity. The provided synthesis route from graphite to graphene via SIGO is compact and readily scalable. PMID:24310650

  9. Sulfuric acid intercalated graphite oxide for graphene preparation.

    PubMed

    Hong, Yanzhong; Wang, Zhiyong; Jin, Xianbo

    2013-12-06

    Graphene has shown enormous potential for innovation in various research fields. The current chemical approaches based on exfoliation of graphite via graphite oxide (GO) are potential for large-scale synthesis of graphene but suffer from high cost, great operation difficulties, and serious waste discharge. We report a facile preparation of graphene by rapid reduction and expansion exfoliation of sulfuric acid intercalated graphite oxide (SIGO) at temperature just above 100°C in ambient atmosphere, noting that SIGO is easily available as the immediate oxidation descendent of graphite in sulfuric acid. The oxygenic and hydric groups in SIGO are mainly removed through dehydration as catalyzed by the intercalated sulfuric acid (ISA). The resultant consists of mostly single layer graphene sheets with a mean diameter of 1.07 μm after dispersion in DMF. This SIGO process is reductant free, easy operation, low-energy, environmental friendly and generates graphene with low oxygen content, less defect and high conductivity. The provided synthesis route from graphite to graphene via SIGO is compact and readily scalable.

  10. Enhanced sensitivity of a microfabricated resonator using a graphene-polystyrene bilayer membrane

    SciTech Connect

    Yun, Minhyuk; Lee, Eunho; Cho, Kilwon; Jeon, Sangmin

    2014-08-18

    A graphene layer was synthesized using chemical vapor deposition methods and a polystyrene solution was spin-cast onto the graphene film. The graphene-polystyrene bilayer membrane was attached between the two tines of a microfabricated quartz tuning fork (QTF). The modulus of the graphene-polystyrene bilayer was measured to be twice that of a pristine polystyrene membrane. Exposure of the membrane-coated QTF to ethanol vapor decreased the resonance frequency of the microresonator. The bilayer membrane-coated QTF produced a frequency change that was three times the change obtained using a polystyrene membrane-coated QTF, with a lower degree of degradation in the Q factor. The limit of detection of the bilayer membrane-coated QTF to ethanol vapor was determined to be 20 ppm.

  11. Molecular Sieving Across Centimeter-Scale Single-Layer Nanoporous Graphene Membranes.

    PubMed

    Boutilier, Michael S H; Jang, Doojoon; Idrobo, Juan-Carlos; Kidambi, Piran R; Hadjiconstantinou, Nicolas G; Karnik, Rohit

    2017-06-27

    Molecular sieving across atomically thin nanoporous graphene is predicted to enable superior gas separation performance compared to conventional membranes. Although molecular sieving has been demonstrated across a few pores in microscale graphene membranes, leakage through nonselective defects presents a major challenge toward realizing selective membranes with high densities of pores over macroscopic areas. Guided by multiscale gas transport modeling of nanoporous graphene membranes, we designed the porous support beneath the graphene to isolate small defects and minimize leakage through larger defects. Ion bombardment followed by oxygen plasma etching was used to produce subnanometer pores in graphene at a density of ∼10(11) cm(-2). Gas permeance measurements demonstrate selectivity that exceeds the Knudsen effusion ratio and scales with the kinetic diameter of the gas molecules, providing evidence of molecular sieving across centimeter-scale nanoporous graphene. The extracted nanoporous graphene performance is comparable to or exceeds the Robeson limit for polymeric gas separation membranes, confirming the potential of nanoporous graphene membranes for gas separations.

  12. Preparation and application of porous nitrogen-doped graphene obtained by co-pyrolysis of lignosulfonate and graphene oxide.

    PubMed

    Zhao, Hai-Bo; Wang, Wen-Dong; Lü, Qiu-Feng; Lin, Ting-Ting; Lin, Qilang; Yang, Haijun

    2015-01-01

    Nitrogen-doped graphene with in-plane porous structure was fabricated by simple co-pyrolysis of lignosulfonate and graphene oxide in the presence of urea. Lignosulfonate first performs as a dispersant adsorbed on the surface of graphene oxide to prevent the aggregation of graphene oxide sheets for preparing homogeneous nitrogen-containing precursor, and then acts as a porogen to render graphene sheets with nanopores in the pyrolysis process of the nitrogen-containing precursor. Urea was used as a nitrogen source to incorporate nitrogen atoms into graphene basal plane. The special nanoporous structure combined with nitrogen content of 7.41at.% endows the nitrogen-doped graphene electrode material with super capacitance up to 170Fg(-1), high rate performance, and excellent cycling stability.

  13. Phyto-reduction of graphene oxide using the aqueous extract of Eichhornia crassipes (Mart.) Solms

    NASA Astrophysics Data System (ADS)

    Firdhouse, M. Jannathul; Lalitha, P.

    2014-10-01

    The aqueous extract of Eichhornia crassipes was used as reductant to produce graphene from graphene oxide by refluxing method. The complete reduction of graphene oxide was monitored using UV-Vis spectrophotometer. Characterization of graphene was made through FTIR, XRD, and Raman spectroscopy analysis. The stability of graphene was studied by thermal gravimetric analysis and zeta potential measurements. The nature and surface morphology of the synthesized graphene was analyzed by transmission electron microscopy. The production of graphene using phytoextract as reductant emphasizes on the facile method of synthesis and greener nanotechnology.

  14. Factors controlling the size of graphene oxide sheets produced via the graphite oxide route.

    PubMed

    Pan, Shuyang; Aksay, Ilhan A

    2011-05-24

    We have studied the effect of the oxidation path and the mechanical energy input on the size of graphene oxide sheets derived from graphite oxide. The cross-planar oxidation of graphite from the (0002) plane results in periodic cracking of the uppermost graphene oxide layer, limiting its lateral dimension to less than 30 μm. We use an energy balance between the elastic strain energy associated with the undulation of graphene oxide sheets at the hydroxyl and epoxy sites, the crack formation energy, and the interaction energy between graphene layers to determine the cell size of the cracks. As the effective crack propagation rate in the cross-planar direction is an order of magnitude smaller than the edge-to-center oxidation rate, graphene oxide single sheets larger than those defined by the periodic cracking cell size are produced depending on the aspect ratio of the graphite particles. We also demonstrate that external energy input from hydrodynamic drag created by fluid motion or sonication, further reduces the size of the graphene oxide sheets through tensile stress buildup in the sheets.

  15. Toxicological effects of graphene oxide on adult zebrafish (Danio rerio).

    PubMed

    Souza, Jaqueline P; Baretta, Jéssica F; Santos, Fabrício; Paino, Ieda M M; Zucolotto, Valtencir

    2017-05-01

    Graphene exhibits unique physical and chemical properties that facilitate its application in many fields, including electronics and biomedical areas. However, the use of graphene and its derivatives could result in accumulation in aquatic environments, and the risks posed by these compounds for organisms are not completely understood. In this study, we investigated the effects of graphene oxide (GO) on adult zebrafish (Danio rerio). Experimental fish were exposed to 2, 10 or 20mgL(-1) GO, and the cytotoxicity, genotoxicity and oxidative stress were assessed. The morphology of the gills and liver tissues was also analyzed. Graphene oxide exposure led to an increase in the number of gill cells that were in early apoptotic and necrotic stages, but genotoxicity was not observed in blood cells. We also observed the generation of Reactive Oxygen Species (ROS) in gill cells. Structural analysis revealed injuries to gill tissues, including a dilated marginal channel, lamellar fusion, clubbed tips, swollen mucocytes, epithelial lifting, aneurysms, and necrosis. Liver tissues also presented lesions such as peripherally located nuclei. Furthermore, hepatocytes exhibited a non-uniform shape, picnotic nuclei, vacuole formation, cell rupture, and necrosis. Our results showed that sub-lethal doses of graphene oxide could be harmful to fish species and thus represent risks for the aquatic food chain. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Athermally photoreduced graphene oxides for three-dimensional holographic images

    PubMed Central

    Li, Xiangping; Ren, Haoran; Chen, Xi; Liu, Juan; Li, Qin; Li, Chengmingyue; Xue, Gaolei; Jia, Jia; Cao, Liangcai; Sahu, Amit; Hu, Bin; Wang, Yongtian; Jin, Guofan; Gu, Min

    2015-01-01

    The emerging graphene-based material, an atomic layer of aromatic carbon atoms with exceptional electronic and optical properties, has offered unprecedented prospects for developing flat two-dimensional displaying systems. Here, we show that reduced graphene oxide enabled write-once holograms for wide-angle and full-colour three-dimensional images. This is achieved through the discovery of subwavelength-scale multilevel optical index modulation of athermally reduced graphene oxides by a single femtosecond pulsed beam. This new feature allows for static three-dimensional holographic images with a wide viewing angle up to 52 degrees. In addition, the spectrally flat optical index modulation in reduced graphene oxides enables wavelength-multiplexed holograms for full-colour images. The large and polarization-insensitive phase modulation over π in reduced graphene oxide composites enables to restore vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Therefore, our technique can be leveraged to achieve compact and versatile holographic components for controlling light. PMID:25901676

  17. Optical conductivity of partially oxidized graphene from first principles

    SciTech Connect

    Nasehnia, F. Seifi, M.

    2015-07-07

    We investigate the geometry, electronic structure, and optical properties of partially oxidized graphene using density functional theory.