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Sample records for graphene oxide membranes

  1. 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

  2. Graphene oxide membranes with tunable semipermeability in organic solvents.

    PubMed

    Huang, Liang; Li, Yingru; Zhou, Qinqin; Yuan, Wenjing; Shi, Gaoquan

    2015-07-01

    Graphene oxide membranes (GOMs) are mechanically stable in various organic solvents, and their nanochannels can be narrowed by thermal annealing or widened by solvation. Therefore, the semipermeability of GOMs can be easily modulated, and they can be used as "multipurpose membranes" for molecular sieving in organic media. PMID:25994919

  3. 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. PMID:26667828

  4. Structure of graphene oxide membranes in solvents and solutions

    NASA Astrophysics Data System (ADS)

    Klechikov, Alexey; Yu, Junchun; Thomas, Diana; Sharifi, Tiva; Talyzin, Alexandr V.

    2015-09-01

    The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite oxide powder samples. Intercalation of liquid dioxolane, acetonitrile, acetone, and chloroform into the GO membrane structure occurs with maximum one monolayer insertion (Type I), in contrast with insertion of 2-3 layers of these solvents into the graphite oxide structure. However, the structure of GO membranes expands in liquid DMSO and DMF solvents similarly to precursor graphite oxide (Type II). It can be expected that Type II solvents will permeate GO membranes significantly faster compared to Type I solvents. The membranes are found to be stable in aqueous solutions of acidic and neutral salts, but dissolve slowly in some basic solutions of certain concentrations, e.g. in NaOH, NaHCO3 and LiF. Some larger organic molecules, alkylamines and alkylammonium cations are found to intercalate and expand the lattice of GO membranes significantly, e.g. up to ~35 Å in octadecylamine/methanol solution. Intercalation of solutes into the GO structure is one of the limiting factors for nano-filtration of certain molecules but it also allows modification of the inter-layer distance of GO membranes and tuning of their permeation properties. For example, GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents.The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite

  5. Porous reduced graphene oxide membrane with enhanced gauge factor

    NASA Astrophysics Data System (ADS)

    Li, Jen-Chieh; Weng, Cheng-Hsi; Tsai, Fu-Cheng; Shih, Wen-Pin; Chang, Pei-Zen

    2016-01-01

    This paper shows that a porous structure for a reduced graphene oxide (rGO) membrane effectively enhances its gauge factor. A porous graphene-based membrane was synthesized in a liquid phase by combining a GO sheet with copper hydroxide nanostrands (CHNs). A chemical reduction treatment using L-ascorbic acid was utilized to simultaneously improve the conductivity of GO and remove the CHNs from each GO sheet. The intrinsic gauge factors of the porous rGO membrane with varying applied tensile strains were obtained and found to increase monotonically with the increased porosity of the rGO membrane. For a membrane porosity of 15.78%, the maximum gauge factor is 46.1 under an applied strain of less than 1%. The main mechanism behind the enhanced gauge factor is attributed to the structure of the porous rGO membrane. The relationships between the initial electrical resistance, tunneling distance, and gauge factor of the rGO membrane were found by adjusting the membrane porosity and the results completely confirmed the physical phenomena.

  6. 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

  7. 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). PMID:24675972

  8. 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.

  9. 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.

  10. Enabling graphene oxide nanosheets as water separation membranes.

    PubMed

    Hu, Meng; Mi, Baoxia

    2013-04-16

    We report a novel procedure to synthesize a new type of water separation membrane using graphene oxide (GO) nanosheets such that water can flow through the nanochannels between GO layers while unwanted solutes are rejected by size exclusion and charge effects. The GO membrane was made via layer-by-layer deposition of GO nanosheets, which were cross-linked by 1,3,5-benzenetricarbonyl trichloride, on a polydopamine-coated polysulfone support. The cross-linking not only provided the stacked GO nanosheets with the necessary stability to overcome their inherent dispensability in water environment but also fine-tuned the charges, functionality, and spacing of the GO nanosheets. We then tested the membranes synthesized with different numbers of GO layers to demonstrate their interesting water separation performance. It was found that the GO membrane flux ranged between 80 and 276 LMH/MPa, roughly 4-10 times higher than that of most commercial nanofiltration membranes. Although the GO membrane in the present development stage had a relatively low rejection (6-46%) of monovalent and divalent salts, it exhibited a moderate rejection (46-66%) of Methylene blue and a high rejection (93-95%) of Rhodamine-WT. We conclude the paper by emphasizing that the facile synthesis of a GO membrane exploiting the ideal properties of inexpensive GO materials offers a myriad of opportunities to modify its physicochemical properties, potentially making the GO membrane a next-generation, cost-effective, and sustainable alternative to the long-existing thin-film composite polyamide membranes for water separation applications. PMID:23488812

  11. 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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  14. Graphene oxide membrane for liquid phase organic molecular separation

    NASA Astrophysics Data System (ADS)

    Liu, Renlong; Arabale, Girish; Kim, Jinseon; Sun, Ke; Lee, Yongwoon; Ryu, Changkook; Lee, Changgu

    2015-03-01

    The selective permeation of organic solvents and water through graphene oxide (GO) membranes has been demonstrated. Water was found to permeate through GO membranes faster than various alcohols. The permeation rates of propanol are about 80 times lower than that of water. Taking advantage of the differences in the permeation rates, we separated water from the alcohols and obtained alcohols with high purity. For ethanol and 1-propanol, binary solutions of the alcohol and water were filtered efficiently to produce alcohols with concentration of about 97%. However, the selectivity of the filtration of methanol is significantly lower than those of the other alcohols. To understand the mechanism we followed the structural changes in the GO membranes by X-Ray diffraction analysis. From the X-ray diffraction results we speculate that the selectivity of the permeation of water and alcohols is closely related to the molecular sizes of the solvents and their polarity. In order to demonstrate the potential applications of this process for the selective removal of water from aqueous organic mixtures, we performed the separation of water from a bio-oil containing 73% of water. The majority of the water was filtered out resulting in a higher purity bio-oil.

  15. 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).

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

    PubMed

    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 cm(2)) 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

  17. 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

  18. 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. PMID:25046580

  19. 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

    2015-07-01

    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. PMID:26024066

  20. 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. PMID:26204850

  1. A graphene oxide membrane with highly selective molecular separation of aqueous organic solution.

    PubMed

    Huang, Kang; Liu, Gongping; Lou, Yueyun; Dong, Ziye; Shen, Jie; Jin, Wanqin

    2014-07-01

    A graphene oxide (GO) membrane is supported on a ceramic hollow fiber prepared by a vacuum suction method. This GO membrane exhibited excellent water permeation for dimethyl carbonate/water mixtures through a pervaporation process. At 25 °C and 2.6 wt % feed water content, the permeate water content reached 95.2 wt% with a high permeation flux (1702 g m(-2) h(-1)). PMID:24846755

  2. Low-Fouling Antibacterial Reverse Osmosis Membranes via Surface Grafting of Graphene Oxide.

    PubMed

    Huang, Xinwei; Marsh, Kristofer L; McVerry, Brian T; Hoek, Eric M V; Kaner, Richard B

    2016-06-15

    Azide-functionalized graphene oxide (AGO) was covalently anchored onto commercial reverse osmosis (RO) membrane surfaces via azide photochemistry. Surface modification was carried out by coating the RO membrane with an aqueous dispersion of AGO followed by UV exposure under ambient conditions. This simple process produces a hydrophilic, smooth, antibacterial membrane with limited reduction in water permeability or salt selectivity. The GO-RO membrane exhibited a 17-fold reduction in biofouling after 24 h of Escherichia coli contact and almost 2 times reduced BSA fouling after a 1 week cross-flow test compared to its unmodified counterpart. PMID:27231843

  3. Engineered crumpled graphene oxide nanocomposite membrane assemblies for advanced water treatment processes.

    PubMed

    Jiang, Yi; Wang, Wei-Ning; Liu, Di; Nie, Yao; Li, Wenlu; Wu, Jiewei; Zhang, Fuzhong; Biswas, Pratim; Fortner, John D

    2015-06-01

    In this work, we describe multifunctional, crumpled graphene oxide (CGO) porous nanocomposites that are assembled as advanced, reactive water treatment membranes. Crumpled 3D graphene oxide based materials fundamentally differ from 2D flat graphene oxide analogues in that they are highly aggregation and compression-resistant (i.e., π-π stacking resistant) and allow for the incorporation (wrapping) of other, multifunctional particles inside the 3D, composite structure. Here, assemblies of nanoscale, monomeric CGO with encapsulated (as a quasi core-shell structure) TiO2 (GOTI) and Ag (GOAg) nanoparticles, not only allow high water flux via vertically tortuous nanochannels (achieving water flux of 246 ± 11 L/(m(2)·h·bar) with 5.4 μm thick assembly, 7.4 g/m(2)), outperforming comparable commercial ultrafiltration membranes, but also demonstrate excellent separation efficiencies for model organic and biological foulants. Further, multifunctionality is demonstrated through the in situ photocatalytic degradation of methyl orange (MO), as a model organic, under fast flow conditions (tres < 0.1 s); while superior antimicrobial properties, evaluated with GOAg, are observed for both biofilm (contact) and suspended growth scenarios (>3 log effective removal, Escherichia coli). This is the first demonstration of 3D, crumpled graphene oxide based nanocomposite structures applied specifically as (re)active membrane assemblies and highlights the material's platform potential for a truly tailored approach for next generation water treatment and separation technologies. PMID:25942505

  4. 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

  5. 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. PMID:26978041

  6. Graphene-based membranes: status and prospects.

    PubMed

    Yoon, Hee Wook; Cho, Young Hoon; Park, Ho Bum

    2016-02-13

    Recently, graphene-based membranes have been extensively studied, represented by two distinct research directions: (i) creating pores in graphene basal plane and (ii) engineering nanochannels in graphene layers. Most simulation results predict that porous graphene membranes can be much more selective and permeable than current existing membranes, also evidenced by some experimental results for gas separation and desalination. In addition, graphene oxide has been widely investigated in layered membranes with two-dimensional nanochannels, showing very intriguing separation properties. This review will cover state-of-the-art of graphene-based membranes, and also provide a material guideline on future research directions suitable for practical membrane applications. PMID:26712638

  7. 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

    2016-03-01

    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. PMID:26849085

  8. 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. PMID:27517308

  9. Incorporating Zwitterionic Graphene Oxides into Sodium Alginate Membrane for Efficient Water/Alcohol Separation.

    PubMed

    Zhao, Jing; Zhu, Yiwei; He, Guangwei; Xing, Ruisi; Pan, Fusheng; Jiang, Zhongyi; Zhang, Peng; Cao, Xingzhong; Wang, Baoyi

    2016-01-27

    For the selective water-permeation across dense membrane, constructing continuous pathways with high-density ionic groups are of critical significance for the preferential sorption and diffusion of water molecules. In this study, zwitterionic graphene oxides (PSBMA@GO) nanosheets were prepared and incorporated into sodium alginate (SA) membrane for efficient water permeation and water/alcohol separation. The two-dimensional GO provides continuous pathway, while the high-density zwitterionic groups on GO confer electrostatic interaction sites with water molecules, leading to high water affinity and ethanol repellency. The simultaneous optimization of the physical and chemical structures of water transport pathway on zwitterionic GO surface endows the membrane with high-efficiency water permeation. Using dehydration of water/alcohol mixture as the model system, the nanohybrid membranes incorporating PSBMA@GO exhibit much higher separation performance than the SA membrane and the nanohybrid membrane utilizing unmodified GO as filler (with the optimal permeation flux of 2140 g m(-2) h(-1), and separation factor of 1370). The study indicates the great application potential of zwitterionic graphene materials in dense water-permeation membranes and provides a facile approach to constructing efficient water transport pathway in membrane. PMID:26765336

  10. 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. PMID:27214685

  11. 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

    2015-01-01

    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

  12. 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).

  13. 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

  14. Graphene and graphene oxide for desalination.

    PubMed

    You, Yi; Sahajwalla, Veena; Yoshimura, Masamichi; Joshi, Rakesh K

    2016-01-01

    There is a huge scope for graphene-based materials to be used as membranes for desalination. A very recent study has confirmed that 100% salt rejection can be achieved for commonly used ions by utilizing single layer nonporous graphene. However, the cost effective fabrication procedure for graphene oxide membranes with precise control of pore size can offer a practical solution for filtration if one can achieve 100% percent salt rejection. PMID:26615882

  15. 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

    2016-06-01

    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. PMID:27160324

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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.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

  17. 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

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

    PubMed

    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. PMID:27232262

  19. 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.

  20. Improving the hydrogen selectivity of graphene oxide membranes by reducing non-selective pores with intergrown ZIF-8 crystals.

    PubMed

    Wang, Xuerui; Chi, Chenglong; Tao, Jifang; Peng, Yongwu; Ying, Shaoming; Qian, Yuhong; Dong, Jinqiao; Hu, Zhigang; Gu, Yuandong; Zhao, Dan

    2016-06-21

    We report the intergrowth of ZIF-8 crystals on ultrathin graphene oxide (GO) membranes, which helps to reduce the non-selective pores of pristine GO membranes leading to gas selectivities as high as 406, 155, and 335 for H2/CO2, H2/N2, and H2/CH4 mixtures, respectively. PMID:27181340

  1. 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. PMID:25635511

  2. 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

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

    PubMed

    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

  4. 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.

  5. 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

  6. 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

    2016-01-01

    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

  7. 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. PMID:27158976

  8. 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.

  9. 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. PMID:26666712

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

    PubMed

    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

  11. 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. PMID:25682962

  12. 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. PMID:27399613

  13. 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. PMID:25875927

  14. 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

    2010-08-01

    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. PMID:20572256

  15. 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.

  16. Vacuolization in Cytoplasm and Cell Membrane Permeability Enhancement Triggered by Micrometer-Sized Graphene Oxide.

    PubMed

    Wu, Congyu; Wang, Chong; Zheng, Jing; Luo, Chao; Li, Yanfang; Guo, Shouwu; Zhang, Jingyan

    2015-08-25

    A deep understanding of the interaction of a graphene oxide (GO) sheet with cells at the molecular level may expedite its biomedical application and predict its new functions and adverse effects. Herein we inspect the interaction between micrometer-sized GO (mGO), commonly used in biomedical research, and cells at the molecular level through a variety of techniques. A major finding is that, instead of direct cellular penetration, the mGO sheets can stimulate the cellular response by interacting with the membrane protein and the membrane. Specifically, it is illustrated that even within a short exposure time the mGO sheets can induce the formation of vacuoles in the cytosolic compartment and enhance the cell permeability. The vacuolization is only observed in the cells that strongly express aquaporin (AQP1), indicating the specific interaction of the mGO with AQP1. Moreover, inhibition of the AQP1 activity prevents the formation of vacuoles, revealing that the interaction of the mGO with AQP1 occurs most probably at the vestibule of AQP1 at the extracellular side. Additionally, though the cell permeability was enhanced, it only improves the penetration of small molecules, not for macromolecules such as proteins. These findings are potentially valuable in cancer therapy because AQPs are strongly expressed in tumor cells of different origins, particularly aggressive tumors, and it will also be beneficial for drug transport across barrier membranes. PMID:26207693

  17. Interactions of Graphene Oxide with Model Cell Membranes: Probing Nanoparticle Attachment and Lipid Bilayer Disruption.

    PubMed

    Liu, Xitong; Chen, Kai Loon

    2015-11-10

    With the rapid growth in the application of graphene oxide (GO) in diverse fields, the toxicity of GO toward bacterial and mammalian cells has recently attracted extensive research attention. While several mechanisms have been proposed for the cytotoxicity of GO, the attachment of GO to cell membranes is expected to be the key initial process that precedes these mechanisms. In this study, we investigate the propensity for GO to attach to and disrupt model cell membranes using supported lipid bilayers (SLBs) and supported vesicular layers (SVLs) that are composed of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The deposition kinetics of GO on SLBs were determined using quartz crystal microbalance with dissipation monitoring and were observed to increase with increasing electrolyte (NaCl and CaCl2) concentrations, indicating that GO attachment to SLBs was controlled by electrostatic interactions. The GO deposition kinetics measured at elevated electrolyte concentrations were lower than mass-transfer-limited kinetics, likely due to the presence of hydration forces between GO and SLBs. Upon the attachment of GO to supported vesicles that were encapsulated with a fluorescent dye, dye leakage was detected, thus indicating that the lipid vesicles were disrupted. When the exposure of the SVL to the GO suspension was terminated, the leakage of dye decreased significantly, demonstrating that the pores on the lipid bilayers have a self-healing ability. PMID:26466194

  18. 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. PMID:26898192

  19. 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. PMID:24401025

  20. Novel sulfonated polyimide/zwitterionic polymer-functionalized graphene oxide hybrid membranes for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Cao, Li; Kong, Lei; Kong, Lingqian; Zhang, Xingxiang; Shi, Haifeng

    2015-12-01

    Hybrid membranes (SPI/ZGO) composed of sulfonated polyimide (SPI) and zwitterionic polymer-functionalized graphene oxide (ZGO) are fabricated via a solution-casting method for vanadium redox flow battery (VRB). Successful preparation of ZGO fillers and SPI/ZGO hybrid membranes are demonstrated by FT-IR, XPS and SEM, indicating that ZGO fillers is homogeneously dispersed into SPI matrix. Through controlling the interfacial interaction between SPI matrix and ZGO fillers, the physicochemical properties, e.g., vanadium ion barrier and proton transport pathway, of hybrid membranes are tuned via the zwitterionic acid-base interaction in the hybrid membrane, showing a high ion selectivity and good stability with the incorporated ZGO fillers. SPI/ZGO-4 hybrid membrane proves a higher cell efficiencies (CE: 92-98%, EE: 65-79%) than commercial Nafion 117 membrane (CE: 89-94%, EE: 59-70%) for VRB application at 30-80 mA cm-2. The assembled VRB with SPI/ZGO-4 membrane presents a stable cycling charge-discharge performance over 280 times, which demonstrates its excellent chemical stability under the strong acidic and oxidizing conditions. SPI/ZGO hybrid membranes show a brilliant perspective for VRB application.

  1. 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

    2016-02-01

    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. PMID:26710246

  2. 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

  3. 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

  4. 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.

  5. 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

  6. Enhancement of proton conductivity of chitosan membrane enabled by sulfonated graphene oxide under both hydrated and anhydrous conditions

    NASA Astrophysics Data System (ADS)

    Liu, Yahua; Wang, Jingtao; Zhang, Haoqin; Ma, Chuanming; Liu, Jindun; Cao, Shaokui; Zhang, Xiang

    2014-12-01

    In this study, sulfonated graphene oxide (SGO) nanosheets with controllable sulfonic acid group loading are synthesized via the facile distillation-precipitation polymerization, and then incorporated into chitosan (CS) matrix to prepare nanohybrid membranes. The microstructure and physicochemical properties of the resulting membranes are extensively investigated. Compared with CS control and GO-filled membranes, SGO-filled membranes attain enhanced thermal and mechanical stabilities due to the strong electrostatic attractions between -SO3H of SGO and -NH2 of CS, which inhibit the mobility of CS chains. Additionally, the inhibited mobility reduces the area swellings of SGO-filled membranes, reinforcing their structural stabilities. The incorporation of SGO generates acid-base pairs along CS-SGO interface, which work as facile proton-hoping sites and thus construct continuous and wide proton transfer pathways, yielding enhanced proton conductivities under both hydrated and anhydrous conditions. Meanwhile, the conductivity can be elevated by increasing the sulfonic acid group loading and content of SGO. Particularly, incorporating 2.0% S4GO can afford the nanohybrid membrane a 122.5% increase in hydrated conductivity and a 90.7% increase in anhydrous conductivity when compared with CS control membrane. The superior conduction properties then offered a significant enhancement in H2/O2 cell performances to the nanohybrid membranes, guaranteeing them to be promising proton exchange membranes.

  7. 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

  8. 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

  9. Facilitating the mechanical properties of a high-performance pH-sensitive membrane by cross-linking graphene oxide and polyacrylic acid

    NASA Astrophysics Data System (ADS)

    Jiang, Zaixing; Xia, Dan; Li, Yue; Li, Jun; Li, Qiang; Chen, Menglin; Huang, Yudong; Besenbacher, Flemming; Dong, Mingdong

    2013-08-01

    Graphene represents a two-dimensional material having extraordinary physical properties, which make it a prospective material for many applications. In particular, graphene oxide (GO), with abundant chemical functional groups, further extends the new functions of graphene-based materials. However, the preparation of GO materials through chemical reactions remains a challenge to materials science. Here, using suitable cross-linkable polymers, a GO-polyacrylic acid (PAA) composite membrane was prepared by a gel-desiccation approach. The fabricated membrane displays both well controlled mechanical characteristics and unique multiple pH response.

  10. 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.

  11. 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. PMID:26214126

  12. Enhanced performance of polyimide hybrid membranes for benzene separation by incorporating three-dimensional silver-graphene oxide.

    PubMed

    Dai, Shi-Qi; Jiang, Yang-Yang; Wang, Ting; Wu, Li-Guang; Yu, Xin-Yi; Lin, Jun-Ze; Shi, Shen-Xuan-Xiang

    2016-09-15

    Graphene oxide-Ag nanoparticle composites were prepared through impregnation reduction using different reactants. Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy analyses were performed to characterize differences in the morphologies of three different Ag-GO composites. Scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry analyses were also applied to evaluate the morphology and thermal stability of the hybrid membranes. Swelling-sorption and pervaporation experiments of benzene and cyclohexane were conducted to evaluate the separation performance of hybrid membranes containing different Ag-GO composites. Results demonstrated that small Ag nanoparticles generated through impregnation reduction using Ag(NH3)2(+) and PEG were homogeneously distributed in the hybrid membranes because of moderate reduction rate. The polymide (PI) hybrid membrane exhibited high separation performance. Increase in Ag content in the Ag-GO samples led to the formation of Ag particles on the GO surface; these particles enhanced the separation performance of the hybrid membranes. When Ag-GO samples with 15 mass percent added, the hybrid membrane showed the highest separation performance and its maximum separation factor in the pervaporation experiments reached 35. It is more than three times higher than that of the GO/PI hybrid membrane. Moreover, large Ag particles were formed and aggregated during the preparation and polymerization of Ag-GO samples with high Ag contents; these particles reduced the separation performance of the hybrid membranes. PMID:27295318

  13. 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. PMID:27376352

  14. 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

  15. 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. PMID:24219033

  16. 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.

  17. Adsorption of Cu(2+), Cd(2+) and Ni(2+) from aqueous single metal solutions on graphene oxide membranes.

    PubMed

    Tan, Ping; Sun, Jian; Hu, Yongyou; Fang, Zheng; Bi, Qi; Chen, Yuancai; Cheng, Jianhua

    2015-10-30

    Novel, highly ordered layered graphene oxide (GO) membranes with larger interlayer spacing were prepared by induced directional flow and were used as adsorbents for the removal of Cu(2+), Cd(2+) and Ni(2+) from aqueous solutions. The effects of pH, ionic strength, contact time, metal ion concentration and cycle time on Cu(2+), Cd(2+) and Ni(2+) sorption were investigated. The results indicated that the adsorption of Cu(2+), Cd(2+) and Ni(2+) onto GO membranes was greatly influenced by the pH and weakly affected by the ionic strength. The adsorption isotherms for Cu(2+), Cd(2+) and Ni(2+) were well fitted by the Langmuir model. The maximum adsorption capacities of the GO membranes for Cu(2+), Cd(2+) and Ni(2+) were approximately 72.6, 83.8 and 62.3 mg/g, respectively. The adsorption kinetics of Cu(2+), Cd(2+) and Ni(2+) onto GO membranes followed the pseudo-second-order model. The adsorption equilibrium was reached in a shorter time. The GO membranes can be regenerated more than six times based on their adsorption/desorption cycles, with a slight loss in the adsorption capacity. The results demonstrated that the GO membranes can be used as effective adsorbents for heavy metal removal from water. PMID:25978188

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

    PubMed

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

    2016-04-14

    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. PMID:27020773

  19. 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.

  20. 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

    2017-01-01

    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 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. PMID:27391314

  1. 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.

  2. 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

  3. 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

  4. 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. PMID:26221608

  5. 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.

  6. 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.

  7. 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.

  8. Preparation of graphene oxide doped eggshell membrane bioplatform modified Prussian blue nanoparticles as a sensitive hydrogen peroxide sensor.

    PubMed

    Mohammad-Rezaei, Rahim; Razmi, Habib; Dehgan-Reyhan, Sajjad

    2014-06-01

    This study describes the preparation and characterization of graphene oxide doped eggshell membrane (GO-ESM) as a novel electrochemical bioplatform for electroanalytical purposes. The GO-ESM bioplatform was prepared by incorporation of GO nano-sheets into the ESM via a facile sonication procedure. Field emission scanning electron microscopy and X-ray diffraction powder techniques were used to characterize the developed bioplatform. The electrochemistry of GO-ESM was investigated by decorating it on the surface of carbon ceramic electrode (CCE) by an O-ring. The GO-ESM platform was modified with Prussian blue (PB) via a facile dip-coating method. Then the resulted modified electrode (PB|GO-ESM|CCE) was used as a novel hydrogen peroxide electrochemical sensor. The fabricated electrode responds efficiently to H2O2 over the concentration range 125nM-195μM with a detection limit of 31nM (S/N=3) and sensitivity 8.8μAμM(-1)cm(-2). The PB|GO-ESM|CCE has been successfully applied to determination of H2O2 content in spiked milk samples. Due to good stability, environmental friendly, cheapness, nontoxic, well behaved electrochemical properties, and biocompatibility, the fabricated bioplatform has the promising future for practical applications. PMID:24742966

  9. 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. PMID:26302148

  10. Graphene Membranes for Atmospheric Pressure Photoelectron Spectroscopy.

    PubMed

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

    2016-05-01

    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. PMID:27082434

  11. 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.

  12. Realizing Synchronous Energy Harvesting and Ion Separation with Graphene Oxide Membranes

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    A synchronous ion separation and electricity generation process has been developed using G-O membranes. In addition to the size effect proposed prevsiouly, the separation of ions can be attributed to the different interactions between ions and G-O membranes; the generation of electricity is due to the confinement of G-O membranes, and the mobility difference of ions. Efficient energy transduction has been achieved with G-O membranes, converting magnetic, thermal and osmotic energy to electricity, distinguishing this material from other commercial semi-permeable membranes. Our study indicated that G-O membranes could find potential applications in the purification of wastewater, while producing electricity simultaneously. With G-O membranes, industrial magnetic leakage and waste heat could also be used to produce electricity, affording a superior approach for energy recovery.

  13. Realizing synchronous energy harvesting and ion separation with graphene oxide membranes.

    PubMed

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

    2014-01-01

    A synchronous ion separation and electricity generation process has been developed using G-O membranes. In addition to the size effect proposed prevsiouly, the separation of ions can be attributed to the different interactions between ions and G-O membranes; the generation of electricity is due to the confinement of G-O membranes, and the mobility difference of ions. Efficient energy transduction has been achieved with G-O membranes, converting magnetic, thermal and osmotic energy to electricity, distinguishing this material from other commercial semi-permeable membranes. Our study indicated that G-O membranes could find potential applications in the purification of wastewater, while producing electricity simultaneously. With G-O membranes, industrial magnetic leakage and waste heat could also be used to produce electricity, affording a superior approach for energy recovery. PMID:24984782

  14. Realizing Synchronous Energy Harvesting and Ion Separation with Graphene Oxide Membranes

    PubMed Central

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

    2014-01-01

    A synchronous ion separation and electricity generation process has been developed using G-O membranes. In addition to the size effect proposed prevsiouly, the separation of ions can be attributed to the different interactions between ions and G-O membranes; the generation of electricity is due to the confinement of G-O membranes, and the mobility difference of ions. Efficient energy transduction has been achieved with G-O membranes, converting magnetic, thermal and osmotic energy to electricity, distinguishing this material from other commercial semi-permeable membranes. Our study indicated that G-O membranes could find potential applications in the purification of wastewater, while producing electricity simultaneously. With G-O membranes, industrial magnetic leakage and waste heat could also be used to produce electricity, affording a superior approach for energy recovery. PMID:24984782

  15. 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

    2015-09-01

    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. PMID:26273843

  16. Mechanical properties of monolayer graphene oxide.

    PubMed

    Suk, Ji Won; Piner, Richard D; An, Jinho; Ruoff, Rodney S

    2010-11-23

    Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effective Young's modulus (207.6 ± 23.4 GPa when a thickness of 0.7 nm is used) as compared to the value reported for "pristine" graphene. The prestress (39.7-76.8 MPa) of the graphene oxide membranes obtained by solution-based deposition was found to be 1 order of magnitude lower than that obtained by others for mechanically cleaved graphene. The novel AFM imaging and FEM-based mapping methods presented here are of general utility for obtaining the elastic modulus and prestress of thin membranes. PMID:20942443

  17. 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. PMID:27479294

  18. 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. PMID:26197200

  19. Recent Developments in Graphene-Based Membranes: Structure, Mass-Transport Mechanism and Potential Applications.

    PubMed

    Sun, Pengzhan; Wang, Kunlin; Zhu, Hongwei

    2016-03-01

    Significant achievements have been made on the development of next-generation filtration and separation membranes using graphene materials, as graphene-based membranes can afford numerous novel mass-transport properties that are not possible in state-of-art commercial membranes, making them promising in areas such as membrane separation, water desalination, proton conductors, energy storage and conversion, etc. The latest developments on understanding mass transport through graphene-based membranes, including perfect graphene lattice, nanoporous graphene and graphene oxide membranes are reviewed here in relation to their potential applications. A summary and outlook is further provided on the opportunities and challenges in this arising field. The aspects discussed may enable researchers to better understand the mass-transport mechanism and to optimize the synthesis of graphene-based membranes toward large-scale production for a wide range of applications. PMID:26797529

  20. Manipulating Migration Behavior of Magnetic Graphene Oxide via Magnetic Field Induced Casting and Phase Separation toward High-Performance Hybrid Ultrafiltration Membranes.

    PubMed

    Xu, Zhiwei; Wu, Tengfei; Shi, Jie; Wang, Wei; Teng, Kunyue; Qian, Xiaoming; Shan, Mingjing; Deng, Hui; Tian, Xu; Li, Cuiyu; Li, Fengyan

    2016-07-20

    Hybrid membranes blended with nanomaterials such as graphene oxide (GO) have great opportunities in water applications due to their multiple functionalities, but they suffer from low modification efficiency of nanomaterials due to the fact that plenty of the nanomaterials are embedded within the polymer matrix during the blending process. Herein, a novel Fe3O4/GO-poly(vinylidene fluoride) (Fe3O4/GO-PVDF) hybrid ultrafiltration membrane was developed via the combination of magnetic field induced casting and a phase inversion technique, during which the Fe3O4/GO nanocomposites could migrate toward the membrane top surface due to magnetic attraction and thereby render the surface highly hydrophilic with robust resistance to fouling. The blended Fe3O4/GO nanocomposites migrated to the membrane surface with the magnetic field induced casting, as verified by X-ray photoelectron spectroscopy, elemental analysis, and energy dispersive X-ray spectroscopy. As a result, the novel membranes exhibited significantly improved hydrophilicity (with a contact angle of 55.0°) and water flux (up to 595.39 L m(-2) h(-1)), which were improved by 26% and 206%, 12% and 49%, 25% and 154%, and 11% and 33% compared with those of pristine PVDF membranes and PVDF hybrid membranes blended with GO, Fe3O4, and Fe3O4/GO without the assistance of magnetic field during membrane casting, respectively. Besides, the novel membranes showed high rejection of bovine serum albumin (>92%) and high flux recovery ratio (up to 86.4%). Therefore, this study presents a novel strategy for developing high-performance hybrid membranes via manipulating the migration of nanomaterials to the membrane surface rather than embedding them in the membrane matrix. PMID:27355273

  1. 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.

  2. 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%). PMID:27294568

  3. 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

  4. Substrate-Sensitive Graphene Oxidation.

    PubMed

    Zhang, Zhuhua; Yin, Jun; Liu, Xiaofei; Li, Jidong; Zhang, Jiahuan; Guo, Wanlin

    2016-03-01

    The inertness of graphene toward reaction with ambient molecules is essential for realizing durable devices with stable performance. Many device applications require graphene to contact with substrates, but whose impact on the chemical property of graphene has been largely overlooked. Here, we combine comprehensive first-principles analyses with experiments to show that graphene oxidation is highly sensitive to substrates. Graphene remains inert on SiO2 and hexagonal boron nitride but becomes increasingly weak against oxidation on metal substrates because of enhanced charge transfer and chemical interaction between them. In particular, Ni and Co substrates lead to spontaneous oxidation of graphene, while a Cu substrate maximally promotes the oxygen diffusion on graphene, with an estimated diffusivity 13 orders of magnitude higher than that on freestanding graphene. Bilayer graphene is revealed to have high oxidation resistance independent of substrate and thus is a better choice for high-performance nanoelectronics. Our findings should be extendable to a wide spectrum of chemical functionalizations of two-dimensional materials mediated by substrates. PMID:26884318

  5. Insight into the Nanoscale Mechanism of Rapid H2O Transport within a Graphene Oxide Membrane: Impact of Oxygen Functional Group Clustering.

    PubMed

    Ban, Shuai; Xie, Jing; Wang, Yajun; Jing, Bo; Liu, Bei; Zhou, Hongjun

    2016-01-13

    Realistic models of graphene oxide membranes were developed and validated to interpret the exceptional water permeation in association with X-ray photoelectron spectroscopy, thermogravimetric and differential scanning calorimetry analysis, and dynamic vapor sorption measurements. With respect to the GO oxidization level, surface distributions of functionalized domains were analyzed in line with TEM observations, and 3 types of interlayer domains in slit pores of GO membranes were identified. The hydrophilicity degrees of as-defined domains strongly influence their H2O uptake capacities. Calculated sorption enthalpies and isotherms are in good agreement with experimental data, and the results indicate the dominant role of dipole interactions. GO expansion shows a transition from the interstratification of an H2O monolayer to the accumulation of H2O multilayers at an interlayer distance of 0.8 nm. The evolution of both hydrogen bonds and H2O diffusivities suggests the existence of three types of H2O species with different binding states and molecular mobilities. The computed H2O permeability on the basis of sorption-diffusion theory supports the exceptional H2O transport capacity in GO membranes. PMID:26653332

  6. [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. PMID:25975033

  7. 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...

  8. 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. PMID:18763832

  9. 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.

  10. 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. PMID:26824511

  11. Biological applications of graphene oxide

    NASA Astrophysics Data System (ADS)

    Gürel, Hikmet Hakan; Salmankurt, Bahadır

    2016-03-01

    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.

  12. 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.

  13. 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. PMID:26806020

  14. 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.

  15. Optimizing Water Transport through Graphene-Based Membranes: Insights from Nonequilibrium Molecular Dynamics.

    PubMed

    Muscatello, Jordan; Jaeger, Frederike; Matar, Omar K; Müller, Erich A

    2016-05-18

    Recent experimental results suggest that stacked layers of graphene oxide exhibit strong selective permeability to water. To construe this observation, the transport mechanism of water permeating through a membrane consisting of layered graphene sheets is investigated via nonequilibrium and equilibrium molecular dynamics simulations. The effect of sheet geometry is studied by changing the offset between the entrance and exit slits of the membrane. The simulation results reveal that the permeability is not solely dominated by entrance effects; the path traversed by water molecules has a considerable impact on the permeability. We show that contrary to speculation in the literature, water molecules do not pass through the membrane as a hydrogen-bonded chain; instead, they form well-mixed fluid regions confined between the graphene sheets. The results of the present work are used to provide guidelines for the development of graphene and graphene oxide membranes for desalination and solvent separation. PMID:27121070

  16. 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. PMID:24206232

  17. 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.

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

    PubMed

    Park, Jaewoo; Bazylewski, Paul; Fanchini, Giovanni

    2016-05-14

    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. PMID:27098780

  19. 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.

  20. 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

    2016-06-01

    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. PMID:26554512

  1. 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.

  2. Highly Defective Graphene: The thinnest insulating membrane

    NASA Astrophysics Data System (ADS)

    Lherbier, Aurelien; Roche, Stephan; Restrepo, Oscar A.; Niquet, Yann-Michel; Delcorte, Arnaud; Charlier, Jean-Christophe

    2012-02-01

    The electronic structure and transport properties of two-dimensional highly defective sp2 graphene are investigated theoretically. Using classical molecular dynamics, large planes of highly defective graphene-based sheets are first generated. An accurate empirical tight-binding Hamiltonian is then elaborated, allowing the prediction of elastic mean free paths, conductivities, and charge mobilities using a real-space order-N Kubo-Greenwood method. In sharp contrast to pristine graphene, the highly defective sp2 carbon sheet displays high density of states close to the Dirac energy. However, the dynamics of the corresponding electronic wavepackets reveals extremely short mean free paths (below 1 nanometer) and quantum interferences, both yielding to particularly strong localization phenomena. Consequently, these highly defective graphene-based sheets, although exhibiting a metallic character through the density of states, are from an electronic transport perspective among the most insulating two-dimensional one-atom-thick membrane ever made.

  3. 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.

  4. Graphene can wreak havoc with cell membranes.

    PubMed

    Dallavalle, Marco; Calvaresi, Matteo; Bottoni, Andrea; Melle-Franco, Manuel; Zerbetto, Francesco

    2015-02-25

    Molecular dynamics--coarse grained to the level of hydrophobic and hydrophilic interactions--shows that small hydrophobic graphene sheets pierce through the phospholipid membrane and navigate the double layer, intermediate size sheets pierce the membrane only if a suitable geometric orientation is met, and larger sheets lie mainly flat on the top of the bilayer where they wreak havoc with the membrane and create a patch of upturned phospholipids. The effect arises in order to maximize the interaction between hydrophobic moieties and is quantitatively explained in terms of flip-flops by the analysis of the simulations. Possible severe biological consequences are discussed. PMID:25648559

  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 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.

  7. 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.

  8. 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. PMID:26477522

  9. Graphene oxide reduction by microwave heating

    NASA Astrophysics Data System (ADS)

    Longo, Angela; Carotenuto, Gianfranco

    2016-05-01

    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.

  10. Labyrinthine water flow across multilayer graphene-based membranes: Molecular dynamics versus continuum predictions

    NASA Astrophysics Data System (ADS)

    Yoshida, Hiroaki; Bocquet, Lydéric

    2016-06-01

    In this paper, we investigate the hydrodynamic permeance of water through graphene-based membranes, inspired by recent experimental findings on graphene-oxide membranes. We consider the flow across multiple graphene layers having nanoslits in a staggered alignment, with an inter-layer distance ranging from sub-nanometer to a few nanometers. We compare results for the permeability obtained by means of molecular dynamics simulations to continuum predictions obtained by using the lattice Boltzmann calculations and hydrodynamic modelization. This highlights that, in spite of extreme confinement, the permeability across the graphene-based membrane is quantitatively predicted on the basis of a continuum expression, taking properly into account entrance and slippage effects of the confined water flow. Our predictions refute the breakdown of hydrodynamics at small scales in these membrane systems. They constitute a benchmark to which we compare published experimental data.

  11. Labyrinthine water flow across multilayer graphene-based membranes: Molecular dynamics versus continuum predictions.

    PubMed

    Yoshida, Hiroaki; Bocquet, Lydéric

    2016-06-21

    In this paper, we investigate the hydrodynamic permeance of water through graphene-based membranes, inspired by recent experimental findings on graphene-oxide membranes. We consider the flow across multiple graphene layers having nanoslits in a staggered alignment, with an inter-layer distance ranging from sub-nanometer to a few nanometers. We compare results for the permeability obtained by means of molecular dynamics simulations to continuum predictions obtained by using the lattice Boltzmann calculations and hydrodynamic modelization. This highlights that, in spite of extreme confinement, the permeability across the graphene-based membrane is quantitatively predicted on the basis of a continuum expression, taking properly into account entrance and slippage effects of the confined water flow. Our predictions refute the breakdown of hydrodynamics at small scales in these membrane systems. They constitute a benchmark to which we compare published experimental data. PMID:27334184

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. Graphene-graphene oxide-graphene hybrid nanopapers with superior mechanical, gas barrier and electrical properties

    NASA Astrophysics Data System (ADS)

    Ouyang, Xilian; Huang, Wenyi; Cabrera, Eusebio; Castro, Jose; Lee, L. James

    2015-01-01

    Hybrid nanopaper-like thin films with a graphene oxide (GO) layer sandwiched by two functionalized graphene (GP-SO3H) layers were successfully prepared from oxidized graphene and benzene sulfonic modified graphene. The hybrid graphene-graphene oxide-graphene (GP-GO-GP) nanopapers showed combination of high mechanic strength and good electrical conductivity, leading to desirable electromagnetic interference shielding performance, from the GP-SO3H layers, and superior gas diffusion barrier provided by the GO layer. These GP-GO-GP nanopapers can be readily coated onto plastic and composite substrates by thermal lamination and injection molding for various industrial applications such as fuel cell and natural gas containers.

  18. Insulating behavior of an amorphous graphene membrane

    NASA Astrophysics Data System (ADS)

    Van Tuan, Dinh; Kumar, Avishek; Roche, Stephan; Ortmann, Frank; Thorpe, M. F.; Ordejon, Pablo

    2012-09-01

    We investigate the charge transport properties of planar amorphous graphene that is fully topologically disordered, in the form of sp2 threefold coordinated networks consisting of hexagonal rings but also including many pentagons and heptagons distributed in a random fashion. Using the Kubo transport methodology and the Lanczos method, the density of states, mean free paths, and semiclassical conductivities of such amorphous graphene membranes are computed. Despite a large increase in the density of states close to the charge neutrality point, all electronic properties are dramatically degraded, evidencing an Anderson insulating state caused by topological disorder alone. These results are supported by Landauer-Büttiker conductance calculations, which show a localization length as short as 5 nm.

  19. 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.

  20. Towards graphene bromide: bromination of graphite oxide

    NASA Astrophysics Data System (ADS)

    Jankovský, O.; Šimek, P.; Klimová, K.; Sedmidubský, D.; Matějková, S.; Pumera, M.; Sofer, Z.

    2014-05-01

    Halogenated graphene derivatives are interesting for their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of brominated graphene derivatives by the bromination of graphite oxides. Graphite oxides, prepared according to either the Hummers or Hofmann method, were brominated using bromine or hydrobromic acid under reflux or in an autoclave at elevated temperatures and pressures. The influence of both graphite oxide precursors on the resulting brominated graphenes was investigated by characterization of the graphenes, which was carried out using various techniques, including SEM, SEM-EDS, high-resolution XPS, FTIR, STA and Raman spectroscopy. In addition, the resistivity of the brominated graphenes was measured and the electrochemical properties were investigated by cyclic voltammetry. Although the brominated graphenes were structurally similar, they had remarkably different bromine concentrations. The most highly brominated graphene (bromine concentration above 26 wt%) exhibited a C/O ratio above 44 and partial hydrogenation. Brominated graphenes with such properties could be used for reversible bromine storage or as a starting material for further chemical modifications.Halogenated graphene derivatives are interesting for their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of brominated graphene derivatives by the bromination of graphite oxides. Graphite oxides, prepared according to either the Hummers or Hofmann method, were brominated using bromine or hydrobromic acid under reflux or in an autoclave at elevated temperatures and pressures. The influence of both graphite oxide precursors on the resulting brominated graphenes was investigated by characterization of the graphenes, which was carried out using various techniques, including SEM, SEM-EDS, high-resolution XPS, FTIR, STA and Raman spectroscopy. In addition, the resistivity of the brominated

  1. 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.

  2. 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.

  3. 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.

  4. Star polymer unimicelles on graphene oxide flakes.

    PubMed

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

    2013-08-01

    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. PMID:23883114

  5. 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. PMID:26204245

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

    PubMed

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

    2015-06-15

    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. PMID:25770934

  7. 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.

  8. Towards graphene iodide: iodination of graphite oxide

    NASA Astrophysics Data System (ADS)

    Šimek, Petr; Klímová, Kateřina; Sedmidubský, David; Jankovský, Ondřej; Pumera, Martin; Sofer, Zdeněk

    2014-11-01

    Halogenated graphene derivatives are interesting owing to their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of iodinated graphene derivatives by the iodination of graphite oxides prepared according to either the Hummers or Hofmann method. Both graphite oxides were iodinated by iodine or hydroiodic acid under reflux or in an autoclave at elevated temperatures (240 °C) and pressures (over 100 bar). The influence of both graphite oxide precursors on the properties of resulting iodinated graphenes was investigated by various techniques, including SEM, SEM-EDS, high-resolution XPS, FTIR, STA, and Raman spectroscopy. Electrical resistivity was measured by a standard four point technique. In addition, the electrochemical properties were investigated by cyclic voltammetry. Although the iodinated graphenes were structurally similar, they had remarkably different concentrations of iodine. The most highly iodinated graphenes (iodine concentration above 30 wt%) exhibited relatively high C/O ratios, confirming high degrees of reduction. Iodine is incorporated in the form of covalent bonds to carbon atoms or as polyiodide anions non-covalently bonded through the charge transfer reaction with the graphene framework. Iodinated graphenes with such properties could be used as the starting material for further chemical modifications or as flame-retardant additives.Halogenated graphene derivatives are interesting owing to their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of iodinated graphene derivatives by the iodination of graphite oxides prepared according to either the Hummers or Hofmann method. Both graphite oxides were iodinated by iodine or hydroiodic acid under reflux or in an autoclave at elevated temperatures (240 °C) and pressures (over 100 bar). The influence of both graphite oxide precursors on the properties of resulting iodinated graphenes was

  9. 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

  10. 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

  11. 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

    2016-06-01

    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. PMID:27199184

  12. Operation of staged membrane oxidation reactor systems

    DOEpatents

    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.

  13. 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.

  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. Nanoscale Tunable Reduction of Graphene Oxide for Graphene Electronics

    NASA Astrophysics Data System (ADS)

    Wei, Zhongqing; Wang, Debin; Kim, Suenne; Kim, Soo-Young; Hu, Yike; Yakes, Michael K.; Laracuente, Arnaldo R.; Dai, Zhenting; Marder, Seth R.; Berger, Claire; King, William P.; de Heer, Walter A.; Sheehan, Paul E.; Riedo, Elisa

    2010-06-01

    The reduced form of graphene oxide (GO) is an attractive alternative to graphene for producing large-scale flexible conductors and for creating devices that require an electronic gap. We report on a means to tune the topographical and electrical properties of reduced GO (rGO) with nanoscopic resolution by local thermal reduction of GO with a heated atomic force microscope tip. The rGO regions are up to four orders of magnitude more conductive than pristine GO. No sign of tip wear or sample tearing was observed. Variably conductive nanoribbons with dimensions down to 12 nanometers could be produced in oxidized epitaxial graphene films in a single step that is clean, rapid, and reliable.

  16. Dynamics of plasmon in graphene oxide

    NASA Astrophysics Data System (ADS)

    Javvaji, Brahmanandam; Mahapatra, D. R.; Raha, S.

    2015-04-01

    Dynamic effects of plasmon such as scattering with defect boundaries and oxygen impurities in the graphene oxide are investigated. Study of plasmon dynamics helps in understanding electronic, opto-electronic and biological applications of graphene based nanostructures. Tuning or control over such applications is made possible by graphene nanostructure engineering. We have modeled defects with increased smoothing of defect edge in graphene keeping area of the defect constant. Scattering of plasmons in graphene with defects is modeled using an electromagnetic field coupled inter-atomic potential approach with finite element discretization of the atomic vibrational and electromagnetic field degrees of freedom. Our calculations show π+σ plasmon red shifting under sharp defect edges whereas π plasmon show high extinction efficiency. Strong localization of electric fields near the sharp defect edges is observed. Observations on plasmons and its dynamics draws attention in designing novel optoelectronic devices and binders for bio-molecules.

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

    PubMed

    Wei, Xiaoding; Mao, Lily; Soler-Crespo, Rafael A; Paci, Jeffrey T; Huang, Jiaxing; Nguyen, SonBinh 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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.

  19. 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

  20. 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.

  1. 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. PMID:27033639

  2. 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.

  3. Temperature-Dependent Photoluminescence of Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Jadhav, S. T.; Rajoba, S. J.; Patil, S. A.; Han, S. H.; Jadhav, L. D.

    2016-01-01

    Graphene oxide thin films have been deposited by spray pyrolysis using graphene oxide powder prepared by modified Hummers method. These thin films were characterized by different physico-chemical techniques. The x-ray diffraction studies revealed the structural properties of GO (graphene oxide) while the Raman spectrum showed the presence of D and G and two-dimensional bands. The D/G intensity ratio for spray-deposited GO film is 1.10. The x-ray photoelectron spectroscopy showed 67% and 33% atomic percentages of carbon and oxygen, respectively. The ratio of O1s/C1s was found to be 0.49. The temperature-dependent photoluminescence of GO thin film and GO solution showed a blue emission.

  4. Epitaxially grown strained pentacene thin film on graphene membrane.

    PubMed

    Kim, Kwanpyo; Santos, Elton J G; Lee, Tae Hoon; Nishi, Yoshio; Bao, Zhenan

    2015-05-01

    Organic-graphene system has emerged as a new platform for various applications such as flexible organic photovoltaics and organic light emitting diodes. Due to its important implication in charge transport, the study and reliable control of molecular packing structures at the graphene-molecule interface are of great importance for successful incorporation of graphene in related organic devices. Here, an ideal membrane of suspended graphene as a molecular assembly template is utilized to investigate thin-film epitaxial behaviors. Using transmission electron microscopy, two distinct molecular packing structures of pentacene on graphene are found. One observed packing structure is similar to the well-known bulk-phase, which adapts a face-on molecular orientation on graphene substrate. On the other hand, a rare polymorph of pentacene crystal, which shows significant strain along the c-axis, is identified. In particular, the strained film exhibits a specific molecular orientation and a strong azimuthal correlation with underlying graphene. Through ab initio electronic structure calculations, including van der Waals interactions, the unusual polymorph is attributed to the strong graphene-pentacene interaction. The observed strained organic film growth on graphene demonstrates the possibility to tune molecular packing via graphene-molecule interactions. PMID:25565340

  5. Quantum description of nanoantenna properties of a graphene membrane

    NASA Astrophysics Data System (ADS)

    Firsova, N. E.; Firsov, Yu. A.

    2016-06-01

    We considered a graphene membrane irradiated by a weak activating periodic electric field in the terahertz range. We used the quantum approach based on the time-dependent density matrix method to analyze the graphene electromagnetic response. For this goal the exact solution was found for the graphene membrane density matrix equation in linear approximation on the external field. On this basis the induced current was studied and then we obtained the formula for quantum conductivity as a function of external field frequency and temperature. The found formula for the conductivity corrected the one obtained in 2007 by Gusynin, Sharapov and Carbotte (Phys. Rev. B, 75 (2007) 165407). The corrected formula allowed to see that the graphene membrane was an oscillating contour, its fundamental eigenfrequency coinciding with a singularity point of the conductivity. The obtained formula allowed us also to calculate the graphene membrane quantum inductivity and capacitance. So in effect we demonstrated that the graphene membrane could be used as an antenna or a transistor. It was shown also that its eigenfrequency could be tuned by doping as its value was found to depend on electrons concentration. It was obtained that the eigenfrequency could be tuned in a rather large terahertz-infrared frequency range as electrons concentration in graphene may differ considerably. The found dependence on concentration is consistent with experiments. The presented formula for conductivity can be used to correct the SPPs Dispersion Relation and for the description of radiation process. It would be useful to take the obtained results into account when constructing devices containing a graphene membrane nanoantenna. Such project could make it possible to create wireless communications among nanosystems. This would be a promising research area of energy harvesting applications.

  6. MnO2 nanotube-Pt/graphene mixture as an ORR catalyst for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Divya, P.; Ramaprabhu, S.

    2013-02-01

    In the present study, MnO2 nanotubes are synthesized by hydrothermal method and Pt/graphene by co reduction of hexachloroplatinic acid and graphite oxide. The formation of MnO2 nanotubes and Pt/graphene are confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy. MnO2 nanotubes are mixed with Pt/graphene is applied as the ORR catalyst in proton exchange membrane fuel cell. The single cell measurement is carried out after fabricating the membrane electrode assembly and polarization curves are recorded at different temperatures and the results are discussed.

  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. In-Situ ESEM and EELS Observation of Water Uptake and Ice Formation in Multilayer Graphene Oxide

    PubMed Central

    Daio, Takeshi; Bayer, Thomas; Ikuta, Tatsuya; Nishiyama, Takashi; Takahashi, Koji; Takata, Yasuyuki; Sasaki, Kazunari; Matthew Lyth, Stephen

    2015-01-01

    Graphene oxide (GO) is hydrophilic and swells significantly when in contact with water. Here, we investigate the change in thickness of multilayer graphene oxide membranes due to intercalation of water, via humidity-controlled observation in an environmental scanning electron microscope (ESEM). The thickness increases reproducibly with increasing relative humidity. Electron energy loss spectroscopy (EELS) reveals the existence of water ice under cryogenic conditions, even in high vacuum environment. Additionally, we demonstrate that freezing then thawing water trapped in the multilayer graphene oxide membrane leads to the opening up of micron-scale inter-lamellar voids due to the expansion of ice crystals. PMID:26133654

  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. Flexible Metal Oxide/Graphene Oxide Hybrid Neuromorphic Transistors on Flexible Conducting Graphene Substrates.

    PubMed

    Wan, Chang Jin; Liu, Yang Hui; Feng, Ping; Wang, Wei; Zhu, Li Qiang; Liu, Zhao Ping; Shi, Yi; Wan, Qing

    2016-07-01

    Flexible metal oxide/graphene oxide hybrid multi-gate neuromorphic transistors are fabricated on flexible conducting graphene substrates. Dendritic integrations in both spatial and temporal modes are emulated, and spatiotemporal correlated logics are obtained. A proof-of-principle visual system model for emulating Lobula Giant Motion Detector neuron is also investigated. The results are of great significance for flexible sensors and neuromorphic cognitive systems. PMID:27159546

  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

    2016-01-01

    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

  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. 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.

  14. Cytotoxicity of graphene oxide and graphene in human erythrocytes and skin fibroblasts.

    PubMed

    Liao, Ken-Hsuan; Lin, Yu-Shen; Macosko, Christopher W; Haynes, Christy L

    2011-07-01

    Two-dimensional carbon-based nanomaterials, including graphene oxide and graphene, are potential candidates for biomedical applications such as sensors, cell labeling, bacterial inhibition, and drug delivery. Herein, we explore the biocompatibility of graphene-related materials with controlled physical and chemical properties. The size and extent of exfoliation of graphene oxide sheets was varied by sonication intensity and time. Graphene sheets were obtained from graphene oxide by a simple (hydrazine-free) hydrothermal route. The particle size, morphology, exfoliation extent, oxygen content, and surface charge of graphene oxide and graphene were characterized by wide-angle powder X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, dynamic light scattering, and zeta-potential. One method of toxicity assessment was based on measurement of the efflux of hemoglobin from suspended red blood cells. At the smallest size, graphene oxide showed the greatest hemolytic activity, whereas aggregated graphene sheets exhibited the lowest hemolytic activity. Coating graphene oxide with chitosan nearly eliminated hemolytic activity. Together, these results demonstrate that particle size, particulate state, and oxygen content/surface charge of graphene have a strong impact on biological/toxicological responses to red blood cells. In addition, the cytotoxicity of graphene oxide and graphene sheets was investigated by measuring mitochondrial activity in adherent human skin fibroblasts using two assays. The methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, a typical nanotoxicity assay, fails to predict the toxicity of graphene oxide and graphene toxicity because of the spontaneous reduction of MTT by graphene and graphene oxide, resulting in a false positive signal. However, appropriate alternate assessments, using the water-soluble tetrazolium salt (WST-8), trypan blue exclusion, and reactive oxygen species assay reveal that the compacted graphene

  15. Thermal conductivity of graphene in corbino membrane geometry.

    PubMed

    Faugeras, Clement; Faugeras, Blaise; Orlita, Milan; Potemski, M; Nair, Rahul R; Geim, A K

    2010-04-27

    Local laser excitation and temperature readout from the intensity ratio of Stokes to anti-Stokes Raman scattering signals are employed to study the thermal properties of a large graphene membrane. The concluded value of the heat conductivity coefficient kappa approximately 600 W/(m.K) is smaller than previously reported but still validates the conclusion that graphene is a very good thermal conductor. PMID:20218666

  16. 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.

  17. 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. PMID:25877513

  18. 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.

  19. Optical properties of porphyrin: graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Harsha Vardhan Reddy, M.; Al-Shammari, Rusul M.; Al-Attar, Nebras; Lopez, Sergio; Keyes, Tia E.; Rice, James H.

    2014-08-01

    In this work we aim to (via a non-invasive functionalization approach) tune and alter the intrinsic features of optically "transparent" graphene, by integrating water-soluble porphyrin aggregates. We explore the potential to combine porphyrin aggregates and graphene oxide to assess the advantages of such as a composite compared to the individual systems. We apply a range of optical spectroscopy methods including photo-absorption, fluorescence assess ground-state and excited state interactions. Our studies show that comparing resonant Raman scattering with optical transmission and fluorescence microscopy that the presence of influences the microscopic structures of the resulting composites.

  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.

    PubMed

    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

  2. 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.

  3. Unimpeded Permeation of Water Through Helium-Leak-Tight Graphene-Based Membranes

    NASA Astrophysics Data System (ADS)

    Nair, R. R.; Wu, H. A.; Jayaram, P. N.; Grigorieva, I. V.; Geim, A. K.

    2012-01-01

    Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicrometer-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors, and gases, including helium, but these membranes 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 low-friction flow of a monolayer of water through two-dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water.

  4. Comparing graphene growth on Cu(111) versus oxidized Cu(111).

    PubMed

    Gottardi, Stefano; Müller, Kathrin; Bignardi, Luca; Moreno-López, Juan Carlos; Pham, Tuan Anh; Ivashenko, Oleksii; Yablonskikh, Mikhail; Barinov, Alexei; Björk, Jonas; Rudolf, Petra; Stöhr, Meike

    2015-02-11

    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

  5. 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

  6. Graphene oxide - Polyvinyl alcohol nanocomposite based electrode material for supercapacitors

    NASA Astrophysics Data System (ADS)

    Pawar, Pranav Bhagwan; Shukla, Shobha; Saxena, Sumit

    2016-07-01

    Supercapacitors are high capacitive energy storage devices and find applications where rapid bursts of power are required. Thus materials offering high specific capacitance are of fundamental interest in development of these electrochemical devices. Graphene oxide based nanocomposites are mechanically robust and have interesting electronic properties. These form potential electrode materials efficient for charge storage in supercapacitors. In this perspective, we investigate low cost graphene oxide based nanocomposites as electrode material for supercapacitor. Nanocomposites of graphene oxide and polyvinyl alcohol were synthesized in solution phase by integrating graphene oxide as filler in polyvinyl alcohol matrix. Structural and optical characterizations suggest the formation of graphene oxide and polyvinyl alcohol nanocomposites. These nanocomposites were found to have high specific capacitance, were cyclable, ecofriendly and economical. Our studies suggest that nanocomposites prepared by adding 0.5% wt/wt of graphene oxide in polyvinyl alcohol can be used an efficient electrode material for supercapacitors.

  7. Nano-Graphene Oxide for Cellular Imaging and Drug Delivery

    PubMed Central

    Sun, Xiaoming; Liu, Zhuang; Welsher, Kevin; Robinson, Joshua Tucker; Goodwin, Andrew; Zaric, Sasa

    2010-01-01

    Two-dimensional graphene offers interesting electronic, thermal, and mechanical properties that are currently being explored for advanced electronics, membranes, and composites. Here we synthesize and explore the biological applications of nano-graphene oxide (NGO), i.e., single-layer graphene oxide sheets down to a few nanometers in lateral width. We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments. We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration. The NGO sheets are found to be photoluminescent in the visible and infrared regions. The intrinsic photoluminescence (PL) of NGO is used for live cell imaging in the near-infrared (NIR) with little background. We found that simple physisorption via π-stacking can be used for loading doxorubicin, a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro. Owing to its small size, intrinsic optical properties, large specific surface area, low cost, and useful non-covalent interactions with aromatic drug molecules, NGO is a promising new material for biological and medical applications. PMID:20216934

  8. 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.

  9. 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

  10. Preparation and Properties of Graphene Oxide Modified Nanocomposite Hydrogels

    NASA Astrophysics Data System (ADS)

    Liu, Sihang; Huang, Mei

    2014-08-01

    Nanocomposite hydrogels with graphene oxide as chemical cross-linker were synthesized after graphene oxide being pretreated by methacryloyl chloride. Moreover, the mechanical behavior of nanocomposite hydrogels based on acrylamide (AAm) and graphene oxide (GO) was studied with different compositions. Experimental results of the swollen state properties of the nanocomposite hydrogels indicated that the addition of GO could effectively enhance the strength but lowers the swelling degree of nanocomposite hydrogels.

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

    PubMed

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

    2012-04-01

    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. PMID:22380625

  12. 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. PMID:25357231

  13. Graphene Oxide: Synthesis, Characterization, Electronic Structure, and Applications

    NASA Astrophysics Data System (ADS)

    Stewart, Derek A.; Mkhoyan, K. Andre

    While graphite oxide was first identified in 1855 [1, 2], the recent discovery of stable graphene sheets has led to renewed interest in the chemical structure and potential applications of graphene oxide sheets. These structures have several physical properties that could aid in the large scale development of a graphene electronics industry. Depending on the degree of oxidization, graphene oxide layers can be either semiconducting or insulating and provide an important complement to metallic graphene layers. In addition, the electronic and optical properties of these films can be controlled by the selective removal or addition of oxygen. For example, selective oxidationof graphene sheets could lead to electronic circuit fabrication on the scale of a single atomic layer. Graphene oxide is also dispersible in water and other solvents and this provides a facile route for graphene deposition on a wide range of substrates for macroelectronics applications. Although graphite oxide has been known for roughly 150 years, key questions remain in regards to its chemical structure, electronic properties, and fabrication. Answering these issues has taken on special urgency with the development of graphene electronics. In this chapter, we will provide an overview of the field with special focus on synthesis, characterization, and first principles analysis of bonding and electronic structures. Finally, we will also address some of the most promising applications for graphene oxide in electronics and other industries.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  15. Polyacrylonitrile fibers containing graphene oxide nanoribbons.

    PubMed

    Chien, An-Ting; Liu, H Clive; Newcomb, Bradley A; Xiang, Changsheng; Tour, James M; Kumar, Satish

    2015-03-11

    Graphene oxide nanoribbon (GONR) made by the oxidative unzipping of multiwalled carbon nanotube was dispersed in dimethylformamide and mixed with polyacrylonitrile (PAN) to fabricate continuous PAN/GONR composite fibers by gel spinning. Subsequently, PAN/GONR composite fibers were stabilized and carbonized in a batch process to fabricate composite carbon fibers. Structure, processing, and properties of the composite precursor and carbon fibers have been studied. This study shows that GONR can be used to make porous precursor and carbon fibers. In addition, GONR also shows the potential to make higher mechanical property carbon fibers than that achieved from PAN precursor only. PMID:25671488

  16. Stabilization of electrocatalytic metal nanoparticles at metal-metal oxide-graphene triple junction points.

    PubMed

    Kou, Rong; Shao, Yuyan; Mei, Donghai; Nie, Zimin; Wang, Donghai; Wang, Chongmin; Viswanathan, Vilayanur V; Park, Sehkyu; Aksay, Ilhan A; Lin, Yuehe; Wang, Yong; Liu, Jun

    2011-03-01

    Carbon-supported precious metal catalysts are widely used in heterogeneous catalysis and electrocatalysis, and enhancement of catalyst dispersion and stability by controlling the interfacial structure is highly desired. Here we report a new method to deposit metal oxides and metal nanoparticles on graphene and form stable metal-metal oxide-graphene triple junctions for electrocatalysis applications. We first synthesize indium tin oxide (ITO) nanocrystals directly on functionalized graphene sheets, forming an ITO-graphene hybrid. Platinum nanoparticles are then deposited, forming a unique triple-junction structure (Pt-ITO-graphene). Our experimental work and periodic density functional theory (DFT) calculations show that the supported Pt nanoparticles are more stable at the Pt-ITO-graphene triple junctions. Furthermore, DFT calculations suggest that the defects and functional groups on graphene also play an important role in stabilizing the catalysts. These new catalyst materials were tested for oxygen reduction for potential applications in polymer electrolyte membrane fuel cells, and they exhibited greatly enhanced stability and activity. PMID:21302925

  17. Highly oxidized graphene nanosheets via the oxidization of detonation carbon

    NASA Astrophysics Data System (ADS)

    Nepal, A.; Chiu, G.; Xie, J.; Singh, G. P.; Ploscariu, N.; Klankowski, S.; Sung, T.; Li, J.; Flanders, B. N.; Hohn, K. L.; Sorensen, C. M.

    2015-08-01

    A unique approach was developed to produce highly oxygenated graphene nanosheets (OGNs) by solution-based oxidation of the pristine graphene nanosheets (GNs) prepared via a controlled detonation of acetylene with oxygen. The produced OGNs are about 250 nm in size and are hydrophilic in nature. The C/O ratio was dramatically reduced from 49:1 in the pristine GNs to about 1:1 in OGNs, as determined by X-ray photoelectron spectroscopy. This C/O in OGNs is the least ever found in all oxidized graphitic materials that have been reported. Thus, the OGNs produced from the detonated GNs with such high degree of oxidation herein yield a novel and promising material for future applications.

  18. Growth of Epitaxial Oxide Thin Films on Graphene

    PubMed Central

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M.; Klein, Norbert; Alford, Neil M.; Petrov, Peter K.

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  19. Growth of Epitaxial Oxide Thin Films on Graphene.

    PubMed

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M; Klein, Norbert; Alford, Neil M; Petrov, Peter K

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  20. 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.

  1. 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.

  2. Quantum conductance of zigzag graphene oxide nanoribbons

    SciTech Connect

    Kan, Zhe; Nelson, Christopher; Khatun, Mahfuza

    2014-04-21

    The electronic properties of zigzag graphene oxide nanoribbons (ZGOR) are presented. The results show interesting behaviors which are considerably different from the properties of the perfect graphene nanoribbons (GNRs). The theoretical methods include a Huckel-tight binding approach, a Green's function methodology, and the Landauer formalism. The presence of oxygen on the edge results in band bending, a noticeable change in density of states and thus the conductance. Consequently, the occupation in the valence bands increase for the next neighboring carbon atom in the unit cell. Conductance drops in both the conduction and valence band regions are due to the reduction of allowed k modes resulting from band bending. The asymmetry of the energy band structure of the ZGOR is due to the energy differences of the atoms. The inclusion of a foreign atom's orbital energies changes the dispersion relation of the eigenvalues in energy space. These novel characteristics are important and valuable in the study of quantum transport of GNRs.

  3. 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.

  4. Molecular Dynamics Simulations of Graphene Oxide Frameworks

    SciTech Connect

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

    2013-01-01

    We use quantum mechanical calculations to develop a full set of force field parameters in order to perform molecular dynamics simulations to understand and optimize the molecular storage properties inside Graphene Oxide Frameworks (GOFs). A set of boron-related parameters for commonly used empirical force fields is determined to describe the non-bonded and bonded interactions between linear boronic acid linkers and graphene sheets of GOF materials. The transferability of the parameters is discussed and their validity is quantified by comparing quantum mechanical and molecular mechanical structural and vibrational properties. The application of the model to the dynamics of water inside the GOFs reveals significant variations in structural flexibility of GOF depending on the linker density, which is shown to be usable as a tuning parameter for desired diffusion properties.

  5. 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.

  6. 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.

  7. Graphene Oxide Nanosheets Disrupt Lipid Composition, Ca(2+) Homeostasis, and Synaptic Transmission in Primary Cortical Neurons.

    PubMed

    Bramini, Mattia; Sacchetti, Silvio; Armirotti, Andrea; Rocchi, Anna; Vázquez, Ester; León Castellanos, Verónica; Bandiera, Tiziano; Cesca, Fabrizia; Benfenati, Fabio

    2016-07-26

    Graphene has the potential to make a very significant impact on society, with important applications in the biomedical field. The possibility to engineer graphene-based medical devices at the neuronal interface is of particular interest, making it imperative to determine the biocompatibility of graphene materials with neuronal cells. Here we conducted a comprehensive analysis of the effects of chronic and acute exposure of rat primary cortical neurons to few-layer pristine graphene (GR) and monolayer graphene oxide (GO) flakes. By combining a range of cell biology, microscopy, electrophysiology, and "omics" approaches we characterized the graphene-neuron interaction from the first steps of membrane contact and internalization to the long-term effects on cell viability, synaptic transmission, and cell metabolism. GR/GO flakes are found in contact with the neuronal membrane, free in the cytoplasm, and internalized through the endolysosomal pathway, with no significant impact on neuron viability. However, GO exposure selectively caused the inhibition of excitatory transmission, paralleled by a reduction in the number of excitatory synaptic contacts, and a concomitant enhancement of the inhibitory activity. This was accompanied by induction of autophagy, altered Ca(2+) dynamics, and a downregulation of some of the main players in the regulation of Ca(2+) homeostasis in both excitatory and inhibitory neurons. Our results show that, although graphene exposure does not impact neuron viability, it does nevertheless have important effects on neuronal transmission and network functionality, thus warranting caution when planning to employ this material for neurobiological applications. PMID:27359048

  8. Reduction Kinetics of Graphene Oxide Determined by Temperature Programmed Desorption

    NASA Astrophysics Data System (ADS)

    Ventrice, Carl; Clark, Nicholas; Field, Daniel; Geisler, Heike; Jung, Inhwa; Yang, Dongxing; Piner, Richard; Ruoff, Rodney

    2009-10-01

    Graphene oxide, which is an electrical insulator, shows promise for use in several technological applications such as dielectric layers in nanoscale electronic devices or as the active region of chemical sensors. In principle, graphene oxide films could also be used as a precursor for the formation of large-scale graphene films by either thermal or chemical reduction of the graphene oxide. In order to determine the thermal stability and reduction kinetics of graphene oxide, temperature program desorption (TPD) measurements have been performed on multilayer films of graphene oxide deposited on SiO2/Si(100) substrates. The graphene oxide was exfoliated from the graphite oxide source material by slow-stirring in aqueous solution, which produces single-layer platelets with an average lateral size of ˜10 μm. From the TPD measurements, it was determined that the decomposition process begins at ˜80 ^oC. The primary desorption products of the graphene oxide films for temperatures up to 300 ^oC are H2O, CO2, and CO, with only trace amounts of O2 being detected. An activation energy of 1.4 eV/molecule was determined by assuming an Arrhenius dependence for the decomposition process.

  9. 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

    2015-01-01

    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

  10. 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.

  11. 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

  12. Mechanisms of polarization switching in graphene oxides and poly(vinylidene fluoride)-graphene oxide films

    NASA Astrophysics Data System (ADS)

    Jiang, Zhiyuan; Zheng, Guangping; Zhan, Ke; Han, Zhuo; Wang, Hao

    2016-04-01

    Polarization switching in graphene oxides (GOs) and poly(vinylidene fluoride) (PVDF)-GO nanocomposite is investigated by piezoelectric force microscopy (PFM). The dynamical switching results reveal that GO films exhibit ferroelectric and piezoelectric properties with two-dimensional characteristics. Abnormal polarization switching is observed in PVDF-GO films, which is promising for electronic applications.

  13. Graphene Oxide Nanosheets Reshape Synaptic Function in Cultured Brain Networks.

    PubMed

    Rauti, Rossana; Lozano, Neus; León, Veronica; Scaini, Denis; Musto, Mattia; Rago, Ilaria; Ulloa Severino, Francesco P; Fabbro, Alessandra; Casalis, Loredana; Vázquez, Ester; Kostarelos, Kostas; Prato, Maurizio; Ballerini, Laura

    2016-04-26

    Graphene offers promising advantages for biomedical applications. However, adoption of graphene technology in biomedicine also poses important challenges in terms of understanding cell responses, cellular uptake, or the intracellular fate of soluble graphene derivatives. In the biological microenvironment, graphene nanosheets might interact with exposed cellular and subcellular structures, resulting in unexpected regulation of sophisticated biological signaling. More broadly, biomedical devices based on the design of these 2D planar nanostructures for interventions in the central nervous system require an accurate understanding of their interactions with the neuronal milieu. Here, we describe the ability of graphene oxide nanosheets to down-regulate neuronal signaling without affecting cell viability. PMID:27030936

  14. 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.

  15. Gauge fields for rippled graphene membranes under central load

    NASA Astrophysics Data System (ADS)

    Barraza-Lopez, Salvador; Sloan, James V.; Pacheco, Alejandro A.; Horvath, Cedric M.; Wang, Zheng Fei

    2013-03-01

    Gauge fields on graphene are invariably expressed in the language of continuum elasticity. Following an approach where the atomic positions play the preponderant role, a model of strain on graphene was developed where all relevant quantities -including gauge fields- are directly expressed in terms of atomic displacements only. Suspended, rippled graphene membranes under cetral load by a sharp object were studied using this approach. The effects from both the pseudo-magnetic field and the deformation potential were included in calculations of the electron density at different spatial locations (the deformation potential acts as an on-site potential energy). The deformation potential -neglected without proper justification in many published works- appears to modify the electronic spectrum dramatically in a qualitative way. Discussion of experiments relevant to the model will also be given.

  16. X-ray Absorption Study of Graphene Oxide and Transition Metal Oxide Nanocomposites

    PubMed Central

    2015-01-01

    The surface properties of the electrode materials play a crucial role in determining the performance and efficiency of energy storage devices. Graphene oxide and nanostructures of 3d transition metal oxides were synthesized for construction of electrodes in supercapacitors, and the electronic structure and oxidation states were probed using near-edge X-ray absorption fine structure. Understanding the chemistry of graphene oxide would provide valuable insight into its reactivity and properties as the graphene oxide transformation to reduced-graphene oxide is a key step in the synthesis of the electrode materials. Polarized behavior of the synchrotron X-rays and the angular dependency of the near-edge X-ray absorption fine structures (NEXAFS) have been utilized to study the orientation of the σ and π bonds of the graphene oxide and graphene oxide–metal oxide nanocomposites. The core-level transitions of individual metal oxides and that of the graphene oxide nanocomposite showed that the interaction of graphene oxide with the metal oxide nanostructures has not altered the electronic structure of either of them. As the restoration of the π network is important for good electrical conductivity, the C K edge NEXAFS spectra of reduced graphene oxide nanocomposites confirms the same through increased intensity of the sp2-derived unoccupied states π* band. A pronounced angular dependency of the reduced sample and the formation of excitonic peaks confirmed the formation of extended conjugated network. PMID:25152800

  17. Porous Graphene as the Ultimate Membrane for Gas Separation

    SciTech Connect

    Jiang, Deen; Cooper, Valentino R; Dai, Sheng

    2009-01-01

    We investigate the permeability and selectivity of graphene sheets with designed subnanometer pores using first principles density functional theory calculations. We find high selectivity on the order of 10{sup 8} for H{sub 2}/CH{sub 4} with a high H{sub 2} permeance for a nitrogen-functionalized pore. We find extremely high selectivity on the order of 10{sup 23} for H{sub 2}/CH{sub 4} for an all-hydrogen passivated pore whose small width (at 2.5 {angstrom}) presents a formidable barrier (1.6 eV) for CH{sub 4} but easily surmountable for H{sub 2} (0.22 eV). These results suggest that these pores are far superior to traditional polymer and silica membranes, where bulk solubility and diffusivity dominate the transport of gas molecules through the material. Recent experimental investigations, using either electron beams or bottom-up synthesis to create pores in graphene, suggest that it may be possible to employ such techniques to engineer variable-sized, graphene nanopores to tune selectivity and molecular diffusivity. Hence, we propose using porous graphene sheets as one-atom-thin, highly efficient, and highly selective membranes for gas separation. Such a pore could have widespread impact on numerous energy and technological applications; including carbon sequestration, fuel cells, and gas sensors.

  18. Geometry controls conformation of graphene sheets: membranes, ribbons, and scrolls.

    PubMed

    Xu, Zhiping; Buehler, Markus J

    2010-07-27

    Graphene features a two-dimensional structure, where applications from electronic building blocks to reinforced composites are emerging, enabled through the utilization of its intriguing electrical, mechanical, and thermal properties. These properties are controlled by the structural makeup of graphene, which is known to display multiple morphologies that change under thermal fluctuations and variations of its geometry. However, as of now, a systematic understanding of the relationship between the conformation of graphene and its geometry remains unknown, preventing rational bottom-up design of materials, structures, and devices. Here, we present a conformational phase diagram for rectangular graphene sheets, defined by their geometry (size and aspect ratio), boundary conditions, and the environmental conditions such as supporting substrates and chemical modifications, as well as changes in temperature. We discover the occurrence of three major structural arrangements in membrane, ribbon, and scroll phases as the aspect ratio of the graphene nanoribbon increases. A theoretical and computational analysis of governing mechanisms for each conformation is provided. PMID:20597529

  19. 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.

  20. 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. PMID:26678843

  1. 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. PMID:26840791

  2. Luminomagnetic bifunctionality of Mn2+-bonded graphene oxide/reduced graphene oxide two dimensional nanosheets

    NASA Astrophysics Data System (ADS)

    Amandeep; Kedawat, Garima; Kumar, Pawan; Anshul, Avaneesh; Deshmukh, Abhay D.; Singh, Om Pal; Gupta, R. K.; Amritphale, S. S.; Gupta, Govind; Singh, V. N.; Gupta, Bipin Kumar

    2015-07-01

    Herein, we report the luminomagnetic bifunctional properties of two-dimensional (2D) Mn2+ bonded graphene oxide (GO)/reduced graphene oxide (RGO) nanosheets synthesized using a facile route of oxidation followed by a solvothermal reduction method. Photoluminescence (PL) studies (excited by different wavelengths) revealed that the resonant energy transfer between Mn2+ and sp3/sp2 clusters of GO/RGO is responsible for the enhancement of emissions. Moreover, pH-sensitive PL behaviors have also been investigated in detail. The ferromagnetic behavior is believed to arise due to defects in Mn2+ bonded GO composites. Thus, present reduction method provides a direct route to tune and enhance the optical properties of GO and RGO nanosheets bonded with Mn2+ ions, which creates an opportunity for various technological applications.Herein, we report the luminomagnetic bifunctional properties of two-dimensional (2D) Mn2+ bonded graphene oxide (GO)/reduced graphene oxide (RGO) nanosheets synthesized using a facile route of oxidation followed by a solvothermal reduction method. Photoluminescence (PL) studies (excited by different wavelengths) revealed that the resonant energy transfer between Mn2+ and sp3/sp2 clusters of GO/RGO is responsible for the enhancement of emissions. Moreover, pH-sensitive PL behaviors have also been investigated in detail. The ferromagnetic behavior is believed to arise due to defects in Mn2+ bonded GO composites. Thus, present reduction method provides a direct route to tune and enhance the optical properties of GO and RGO nanosheets bonded with Mn2+ ions, which creates an opportunity for various technological applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01095k

  3. Fast and fully-scalable synthesis of reduced graphene oxide.

    PubMed

    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

  4. 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

  5. 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.

  6. 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

    2015-12-01

    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. PMID:26574873

  7. Two-dimensional shape memory graphene oxide.

    PubMed

    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

  8. 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

  9. Sorption mechanisms of metals to graphene oxide

    NASA Astrophysics Data System (ADS)

    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.

  10. Two-dimensional shape memory graphene oxide

    NASA Astrophysics Data System (ADS)

    Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe

    2016-06-01

    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.

  11. Mechanical tearing of graphene on an oxidizing metal surface

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Graphene, the thinnest possible anticorrosion and gas-permeation barrier, is poised to transform the protective coatings industry for a variety of surface applications. In this work, we have studied the structural changes of graphene when the underlying copper surface undergoes oxidation upon heating. Single-layer graphene directly grown on a copper surface by chemical vapour deposition was annealed under ambient atmosphere conditions up to 400 °C. The onset temperature of the surface oxidation of copper is found to be higher for graphene-coated foils. Parallel arrays of graphene nanoripples are a ubiquitous feature of pristine graphene on copper, and we demonstrate that these form crucial sites for the onset of the oxidation of copper, particularly for ˜0.3-0.4 μm ripple widths. In these regions, the oxidation proceeds along the length of the nanoripples, resulting in the formation of parallel stripes of oxidized copper regions. We demonstrate from temperature-dependent Raman spectroscopy that the primary defect formation process in graphene involves boundary-type defects rather than vacancy or sp3-type defects. This observation is consistent with a mechanical tearing process that splits graphene into small polycrystalline domains. The size of these is estimated to be sub-50 nm.

  12. Graphene Oxide: A Fertile Nanosheet for Various Applications

    NASA Astrophysics Data System (ADS)

    Obata, Seiji; Saiki, Koichiro; Taniguchi, Takaaki; Ihara, Toshihiro; Kitamura, Yusuke; Matsumoto, Yasumichi

    2015-12-01

    Graphene oxide (GO) is chemically exfoliated graphene with various oxygen functional groups bound to its sp2 basal plane. GO is not only a precursor for graphene in large-scale production but provides a fertile platform for applications from electronics to biology owing to its outstanding characteristics. In this review, we introduce the preparation and reduction methods and discuss recent application examples on electrochemistry and biological sensors.

  13. 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. PMID:24418938

  14. Bulk preparation of holey graphene via controlled catalytic oxidation

    NASA Astrophysics Data System (ADS)

    Lin, Yi; Watson, Kent A.; Kim, Jae-Woo; Baggett, David W.; Working, Dennis C.; Connell, John W.

    2013-08-01

    Structural manipulation of the two dimensional graphene surface has been of significant interest as a means of tuning the properties of the nanosheets for enhanced performance in various applications. In this report, a straightforward and highly scalable method is presented to prepare bulk quantities of ``holey graphenes'', which are graphene sheets with holes ranging from a few to tens of nm in average diameter. The approach to their preparation takes advantage of the catalytic properties of silver (Ag) nanoparticles toward the air oxidation of graphitic carbon. In the procedure, Ag nanoparticles were first deposited onto the graphene sheet surface in a facile, controllable, and solvent-free process. The catalyst-loaded graphene samples were then subjected to thermal treatment in air. The graphitic carbons in contact with the Ag nanoparticles were selectively oxidized into gaseous byproducts, such as CO or CO2, leaving holes in the graphene surface. The Ag was then removed by refluxing in diluted nitric acid to obtain the final holey graphene products. The average size of the holes on the graphene was found to correlate with the size of the Ag nanoparticles, which could be controlled by adjusting the silver precursor concentration. In addition, the temperature and time of the air oxidation step, and the catalyst removal treatment conditions were found to strongly affect the morphology of the holes. Characterization results of the holey graphene products suggested that the hole generation might have started from defect-rich regions present on the starting graphene sheets. As a result, the remaining graphitic carbon structures on the holey graphene sheets were highly crystalline, with no significant increase of the overall defect density despite the presence of structural holes. Preliminary experiments are also presented on the use of holey graphene sheets as fillers for polymeric composites. The results indicated that these sheets might be better reinforcing

  15. 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. PMID:27127023

  16. Graphene versus oxides for transparent electrode applications

    NASA Astrophysics Data System (ADS)

    Sandana, V. E.; Rogers, D. J.; Teherani, F. Hosseini; Bove, P.; Razeghi, M.

    2013-03-01

    Due to their combination of good electrical conductivity and optical transparency, Transparent Conducting Oxides (TCOs) are the most common choice as transparent electrodes for optoelectronics applications. In particular, devices, such as LEDs, LCDs, touch screens and solar cells typically employ indium tin oxide. However, indium has some significant drawbacks, including toxicity issues (which are hampering manufacturing), an increasing rarefication (due to a combination of relative scarcity and increasing demand [1]) and resulting price increases. Moreover, there is no satisfactory option at the moment for use as a p-type transparent contact. Thus alternative materials solutions are actively being sought. This review will compare the performance and perspectives of graphene with respect to TCOs for use in transparent conductor applications.

  17. Graphene oxide aerogel-supported Pt electrocatalysts for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Duan, Jialin; Zhang, Xuelin; Yuan, Weijian; Chen, Hailong; Jiang, Shan; Liu, Xiaowei; Zhang, Yufeng; Chang, Limin; Sun, Zhiyuan; Du, Juan

    2015-07-01

    Graphene oxide aerogel (GOA) was prepared to serve as catalyst support for Pt nanoparticles for methanol electro-oxidation. Analyses by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were conducted to physically characterize the Pt/GOA catalyst. The results show that Pt/GOA has a 3D macroporous structure, which can not only accelerate mass transfer but also provide a larger efficient surface area for methanol oxidation. The results of electrochemical tests reveal that Pt/GOA has an electrochemical surface area as large as 95.5 m2 g-1, and its peak current density toward methanol oxidation is as high as 876 mA mg-1Pt.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Origin of the chemical and kinetic stability of graphene oxide.

    PubMed

    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

  3. 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.

  4. 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. PMID:23848277

  5. Contrast in electron-transfer mediation between graphene oxide and reduced graphene oxide.

    PubMed

    Hongthani, Wiphada; Patil, Avinash J; Mann, Stephen; Fermín, David J

    2012-08-27

    The properties of graphene oxide (GO) and DNA-stabilised reduced graphene-oxide (rGO) sheets as electron-transfer mediators in partially blocked electrodes are evaluated employing electrochemical impedance spectroscopy. Evidences obtained from UV/Vis, Raman and FTIR spectroscopies, as well as atomic force microscopy, confirm that the reduction of exfoliated GO single sheets by hydrazine yields partially reduced graphene oxide featuring a high defect density. Two-dimensional assemblies of GO and rGO were formed through electrostatic adsorption at Au electrodes, sequentially modified with 11-mercaptoundecanoic acid (MUA) and poly-diallyldimethylammonium chloride (PDADMAC). The MUA:PDADMAC generates a strong blocking layer to the electron-transfer reaction involving the ferri/ferrocyanide redox couple. This blocking behaviour is not significantly affected upon adsorption of GO. However, adsorption of a sub-monolayer of rGO decreases the charge-transfer resistance by more than two orders of magnitude. Analysis of cyclic voltammograms and impedance spectra suggests that electron transfer in rGO assemblies is mediated by occupied states located just below the redox Fermi energy of the probe. These findings are discussed in the context of on-going controversies regarding the electrochemical reactivity of sp(2)-carbon basal planes. PMID:22865797

  6. 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.

  7. Graphene oxide as a radical initiator: Free radical and controlled radical polymerization of sodium 4-vinylbenzenesulfonate with graphene oxide

    DOE PAGESBeta

    Voylov, Dmitry N.; Saito, Tomonori; Lokitz, Bradley S.; Uhrig, David; Wang, Yangyang; Agapov, Alexander L.; Holt, Adam P.; Bocharova, Vera; Kisliuk, Alexander; Sokolov, Alexei P.

    2016-01-19

    The free radical and controlled radical polymerization of sodium 4-vinylbenzenesulfonate using graphene oxide as a radical initiator was studied. This work demonstrates that graphene oxide can initiate radical polymerization in an aqueous solution without any additional initiator. Poly(sodium 4-vinylbenzenesulfonate) obtained via reversible addition fragmentation chain transfer polymerization had a controlled molecular weight with a very narrow polydispersity ranging between 1.01 and 1.03. Furthermore, the reduction process of graphene oxide as well as the resulting composite material properties were analyzed in detail.

  8. Carbocatalysts: graphene oxide and its derivatives.

    PubMed

    Su, Chenliang; Loh, Kian Ping

    2013-10-15

    Graphene oxide (GO) sheets are emerging as a new class of carbocatalysts. Conventionally, researchers exfoliate graphite oxide into submicrometer-sized, water-dispersible flakes to produce these sheets. The presence of oxygen functional groups on the aromatic scaffold of GO allows these sheets to mediate ionic and nonionic interactions with a wide range of molecules. GO shows remarkable catalytic properties on its own and when hybridized with a second material. It is a perfect platform for molecular engineering. This Account examines the different classes of synthetic transformations catalyzed by GO and correlates its reactivity with chemical properties. First, we raise the question of whether GO behaves as a reactant or catalyst during oxidation. Due to its myriad oxygen atoms, GO can function as an oxidant during anaerobic oxidation and become reduced at the end of the first catalytic cycle. However, partially reduced GO can continue to activate molecular oxygen during aerobic oxidation. Most importantly, we can enhance the conversion and selectivity by engineering the morphology and functionalities on the G/GO scaffold. GO can also be hybridized with organic dyes or organocatalysts. The photosensitization by dyes and facile charge transfer across the graphene interface produce synergistic effects that enhance catalytic conversion. Using GO as a building block in supramolecular chemistry, we can extend the scope of functionalities in GO hybrids. The presence of epoxy and hydroxyl functional groups on either side of the GO sheet imparts bifunctional properties that allow it to act as a structural node within metal-organic frameworks (MOFs). For example, known homogeneous molecular catalysts can be anchored on the GO surface by employing them as scaffolds linking organometallic nodes. We have demonstrated that porphyrin building blocks with GO can lead to facile four-electron oxygen transfer reactions. We have also evaluated the advantages and disadvantages of GO

  9. 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.

  10. 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}.