• Title, Summary, Keyword: graphene oxide

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Mechanisms of Na adsorption on graphene and graphene oxide: density functional theory approach

  • Moon, Hye Sook;Lee, Ji Hye;Kwon, Soonchul;Kim, Il Tae;Lee, Seung Geol
    • Carbon letters
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    • v.16 no.2
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    • pp.116-120
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    • 2015
  • We investigated the adsorption of Na on graphene and graphene oxide, which are used as anode materials in sodium ion batteries, using density functional theory. The adsorption energy for Na on graphene was -0.507 eV at the hollow sites, implying that adsorption was favorable. In the case of graphene oxide, Na atoms were separately adsorbed on the epoxide and hydroxyl functional groups. The adsorption of Na on graphene oxide-epoxide (adsorption energy of -1.024 eV) was found to be stronger than the adsorption of Na on pristine graphene. However, the adsorption of Na on graphene oxide-hydroxyl resulted in the generation of NaOH as a by-product. Using density of states (DOS) calculations, we found that the DOS of the Na-adsorbed graphene was shifted down more than that of the Na-adsorbed graphene oxide-epoxide. In addition, the intensity of the DOS around the Fermi level for the Na-adsorbed graphene was higher than that for the Na-adsorbed graphene oxide-epoxide.

Synthesis and Electrochemical Characterization of Reduced Graphene Oxide-Manganese Oxide Nanocomposites

  • Lee, Yu-Ri;Song, Min-Sun;Lee, Kyung-Min;Kim, In-Young;Hwang, Seong-Ju
    • Journal of Electrochemical Science and Technology
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    • v.2 no.1
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    • pp.1-7
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    • 2011
  • Nanocomposites of reduced graphene oxide and manganese (II,III) oxide can be synthesized by the freeze-drying process of the mixed colloidal suspension of graphene oxide and manganese oxide, and the subsequent heat-treatment. The calcined reduced graphene oxide-manganese (II,III) oxide nanocomposites are X-ray amorphous, suggesting the formation of homogeneous and disordered mixture without any phase separation. The reduction of graphene oxide to reduced graphene oxide upon the heat-treatment is evidenced by Fourier-transformed infrared spectroscopy. Field emission-scanning electronic microscopy and energy dispersive spectrometry clearly demonstrate the formation of porous structure by the house-of-cards type stacking of reduced graphene oxide nanosheets and the homogeneous distribution of manganese ions in the nanocomposites. According to Mn K-edge X-ray absorption spectroscopy, manganese ions in the calcined nanocomposites are stabilized in octahedral symmetry with mixed Mn oxidation state of Mn(II)/Mn(III). The present reduced graphene oxide-manganese oxide nanocomposites show characteristic pseudocapacitance behavior superior to the pristine manganese oxide, suggesting their applicability as electrode material for supercapacitors.

Nanoporous graphene oxide membrane and its application in molecular sieving

  • Fatemi, S. Mahmood;Arabieh, Masoud;Sepehrian, Hamid
    • Carbon letters
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    • v.16 no.3
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    • pp.183-191
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    • 2015
  • Gas transport through graphene-derived membranes has gained much interest recently due to its promising potential in filtration and separation applications. In this work, we explore Kr-85 gas radionuclide sequestration from natural air in nanoporous graphene oxide membranes in which different sizes and geometries of pores were modeled on the graphene oxide sheet. This was done using atomistic simulations considering mean-squared displacement, diffusion coefficient, number of crossed species of gases through nanoporous graphene oxide, and flow through interlayer galleries. The results showed that the gas features have the densest adsorbed zone in nanoporous graphene oxide, compared with a graphene membrane, and that graphene oxide was more favorable than graphene for Kr separation. The aim of this paper is to show that for the well-defined pore size called P-7, it is possible to separate Kr-85 from a gas mixture containing Kr-85, O2 and N2. The results would benefit the oil industry among others.

Graphene Oxide-based Direct Measurement of DNase I Activity with Single Stranded DNA

  • Gang, Jongback
    • Bulletin of the Korean Chemical Society
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    • v.35 no.9
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    • pp.2749-2752
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    • 2014
  • Recent studies have shown that single-stranded DNA adsorbed onto graphene oxide is protected from DNase I cleavage. However, double-stranded DNA bound to graphene oxide and could be digested by DNase I. To elucidate whether single-stranded DNA is protect from DNase I in the presence of graphene oxide, this study conducted DNase I digestion using single-stranded DNA and single-stranded DNA containing the duplex region in the presence of graphene oxide. Addition of DNase I resulted in restoration of the fluorescence emission that had been quenched when DNA was adsorbed to graphene oxide. It indicates that DNase I cleaved the adsorbed single-stranded DNA onto graphene oxide, which was sufficient for the detection of DNase I activity.

Development of AgNW/Reduced Graphene Oxide Hybrid Transparent Electrode with Long-Term Stability Using Plasma Reduction (플라즈마 환원 기술을 응용한 장수명의 은나노와이어/Reduced Graphene Oxide 하이브리드 투명전극 개발)

  • Jung, Sunghoon;Ahn, Wonmin;Kim, Do-Geun
    • Journal of the Korean institute of surface engineering
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    • v.49 no.1
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    • pp.87-91
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    • 2016
  • The development of high performance transparent electrode with flexibility have been required for flexible electronics. Here, we demonstrate the silver nanowire and reduced graphene oxide hybrid transparent electrode for replacing brittle indium-tin-oxide electrode by spray coating technique and plasma reduction. The spray coating system is applied to deposit silver nanowire and over coated graphene oxide films and it has a great potential to scale-up. The resistance of silver nanowire transparent electrode is reduced by 10% and the surface roughness is decreased after graphene oxide coating. The over-coated graphene oxide is successfully reduced by $H_2$ plasma treatment and it is effective in increasing the environmental stability of electrode. The lifetime of silver nanowire and reduced graphene oxide hybrid electrode at $85^{\circ}C$ of Celsius degree of temperature and 85% of relative humidity has much increased.

Recent trends in the synthesis of graphene and graphene oxide based nanomaterials for removal of heavy metals - A review

  • Lim, Jihn Yih;Mubarak, N.M.;Abdullah, E.C.;Nizamuddin, Sabzoi;Khalid, Mohammad;Inamuddin, Inamuddin
    • Journal of Industrial and Engineering Chemistry
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    • v.66
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    • pp.29-44
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    • 2018
  • The advanced synthesis and development of raw graphene based on various significant functionalization has been outstanding in the wastewater treatment compared to the other alternatives such as carbon nanotubes and other carbon nanomaterials. Nano size graphene is known to possess large surface area and some promising properties in terms of mechanical, electrical, chemical and magnetism. Besides, the graphene can be generated via both Top-down and Bottom-up methods such as chemical exfoliation, chemical vapour deposition and other techniques so that it can be further functionalized to form graphene oxide-based nanomaterials. Hence, graphene oxide-based nanomaterials are discovered to be useful in the application of heavy metal removal from wastewater. In short, this paper critically reviewed on the synthesis method of graphene and application of graphene oxide-based nanomaterials in the term of heavy metal removal. The advantages, drawbacks, comparison of the data efficiencies, and research requirements are further highlighted, elaborated and discussed detailly. Lastly, the future challenges of graphene are elaborated. Therefore, it can be guaranteed that the wastewater discharged should be detected with the minimum or none of the heavy metals so that minimum effects on the ecosystem is discovered.

Investigation of Charge Transfer between Graphene and Oxide Substrates

  • Min, Kyung-Ah;Hong, Suklyun
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.186.1-186.1
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    • 2014
  • Graphene, which is a 2-dimensional carbon material, has been attracting much interest due to its unique properties and potential applications. So far, many interesting experimental and theoretical works have been done concerning the electronic properties of graphene on various substrates. Especially, there are many experimental reports about doping in graphene which is caused by interaction between graphene and its supporting substrates. Here, we report the study of charge transfer between graphene and oxide substrates using density functional theory (DFT) calculations. In this study, we have investigated the charge transfer related with graphene considering various oxide substrates such as SiO2(0001) and MgO(111). Details in charge transfer between graphene and oxides are analyzed in terms of charge density difference, band structure and work function.

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Preparation of sulfonated reduced graphene oxide by radiation-induced chemical reduction of sulfonated graphene oxide

  • Jung, Chang-Hee;Hong, Ji-Hyun;Jung, Jin-Mook;Hwang, In-Tae;Jung, Chan-Hee;Choi, Jae-Hak
    • Carbon letters
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    • v.16 no.1
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    • pp.41-44
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    • 2015
  • We report the preparation of sulfonated reduced graphene oxide (SRGO) by the sulfonation of graphene oxide followed by radiation-induced chemical reduction. Graphene oxide prepared by the well-known modified Hummer's method was sulfonated with the aryl diazonium salt of sulfanilic acid. Sulfonated graphene oxide (SGO) dispersed in ethanol was subsequently reduced by ${\gamma}$-ray irradiation at various absorbed doses to produce SRGO. The results of optical, chemical, and thermal analyses revealed that SRGO was successfully prepared by ${\gamma}$-ray irradiation-induced chemical reduction of the SGO suspension. Moreover, the electrical conductivity of SRGO was increased up to 2.94 S/cm with an increase of the absorbed dose.

Fabrication and Characterization of Graphene Oxide/Alginate-based Graphite Fibers (그래핀 산화물/알지네이트 기반 그라파이트 섬유의 제조 및 특성)

  • Lim, Na-Young;Shim, Jin-Tae;Chung, Yong-Sik
    • Textile Science and Engineering
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    • v.55 no.6
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    • pp.407-414
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    • 2018
  • Graphene oxide can be prepared from graphene by introducing hydrophilic functional groups to facilitate dispersion in water. This process has attracted significant attention for production of fillers for polymer composite materials. Alginate is a natural polymer that can be used as a composite fiber matrix that is industrially applicable and is currently being studied for the development of novel materials. Graphene oxide/alginate composite fibers were prepared with various graphene oxide contents by wet spinning in a calcium chloride coagulation solution. To improve thermal and electrical properties, the graphene oxide/alginate fibers were reduced using hydrogen iodide and acetic acid. After low temperature carbonization over a graphite nickel catalyst, the yield of the carbonized alginate precursor increased from 20.3% to 36.1% upon addition of graphene oxide. After reduction and carbonization, XRD analysis showed the presence of a $2{\theta}=26.4^{\circ}$ peak arising from the (002) plane of the graphite structure. In addition, electrical conductivity increased from 225 to 13575 S/m, indicating that the composite fibers successfully incorporated graphite.

Graphene Oxide Thin Films for Nonvolatile Memory Applications

  • Kim, Jong-Yun;Jeong, Hu-Young;Choi, Hong-Kyw;Yoon, Tae-Hyun;Choi, Sung-Yool
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.9-9
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    • 2011
  • There has been strong demand for novel nonvolatile memory technology for low-cost, large-area, and low-power flexible electronics applications. Resistive memories based on metal oxide thin films have been extensively studied for application as next-generation nonvolatile memory devices. However, although the metal oxide-based resistive memories have several advantages, such as good scalability, low-power consumption, and fast switching speed, their application to large-area flexible substrates has been limited due to their material characteristics and necessity of a high-temperature fabrication process. As a promising nonvolatile memory technology for large-area flexible applications, we present a graphene oxide-based memory that can be easily fabricated using a room temperature spin-casting method on flexible substrates and has reliable memory performance in terms of retention and endurance. The microscopic origin of the bipolar resistive switching behaviour was elucidated and is attributed to rupture and formation of conducting filaments at the top amorphous interface layer formed between the graphene oxide film and the top Al metal electrode, via high-resolution transmission electron microscopy and in situ x-ray photoemission spectroscopy. This work provides an important step for developing understanding of the fundamental physics of bipolar resistive switching in graphene oxide films, for the application to future flexible electronics.

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