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Yongin, South Korea

Song S.H.,Korea Advanced Institute of Science and Technology | Park K.H.,Korea Advanced Institute of Science and Technology | Kim B.H.,Korea Advanced Institute of Science and Technology | Choi Y.W.,Korea Advanced Institute of Science and Technology | And 5 more authors.
Advanced Materials | Year: 2013

Homogeneous distribution of graphene flakes in a polymer matrix, still preserving intrinsic material properties, is key to successful composite applications. A novel approach is presented to disperse non-oxidized graphene flakes with non-covalent functionalization of 1-pyrenebutyric acid and to fabricate nanocomposites with outstanding thermal conductivity (∼1.53 W/mK) and mechanical properties (∼1.03 GPa). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Yang S.B.,Korea Advanced Institute of Science and Technology | Kong B.-S.,KCC Central Research Institute | Jung H.-T.,Korea Advanced Institute of Science and Technology
Journal of Physical Chemistry C | Year: 2012

We report a dual-coating method for the deposition of gold nanoparticles on single-walled carbon nanotubes (SWNTs) to improve the electrical conductivities of SWNT network films. The deposition is achieved via a two-step process: (i) pretreatment, mixing gold precursor (HAuCl4•3H2O) with a dispersion of SWNTs containing sodium cholate or sodium dodecyl sulfate surfactants, and (ii) post-treatment, immersion of SWNT network films functionalized with gold ions (Au3+) in a gold salt solution. SWNT films doubly hybridized with gold nanoparticles exhibited a 20% reduced sheet resistance in comparison with SWNT films that were post-treated with Au alone. Optical spectroscopy and UPS results show that such enhanced electrical properties can be attributed to additional p-type doping of the SWNTs upon treatment with gold. These results are important for the development of efficient transparent conducting SWNT films for optoelectronic device applications. © 2012 American Chemical Society. Source


Park K.H.,Korea Advanced Institute of Science and Technology | Kim B.H.,Korea Advanced Institute of Science and Technology | Song S.H.,Korea Advanced Institute of Science and Technology | Kwon J.,Korea Advanced Institute of Science and Technology | And 3 more authors.
Nano Letters | Year: 2012

The increasing demand for graphene has required a new route for its mass production without causing extreme damages. Here we demonstrate a simple and cost-effective intercalation based exfoliation method for preparing high quality graphene flakes, which form a stable dispersion in organic solvents without any functionalization and surfactant. Successful intercalation of alkali metal between graphite interlayers through liquid-state diffusion from ternary KCl-NaCl-ZnCl 2 eutectic system is confirmed by X-ray diffraction and X-ray photoelectric spectroscopy. Chemical composition and morphology analyses prove that the graphene flakes preserve their intrinsic properties without any degradation. The graphene flakes remain dispersed in a mixture of pyridine and salts for more than 6 months. We apply these results to produce transparent conducting (∼930 Ω at ∼75% transmission) graphene films using the modified Langmuir-Blodgett method. The overall results suggest that our method can be a scalable (>1 g/batch) and economical route for the synthesis of nonoxidized graphene flakes. © 2012 American Chemical Society. Source


Pham V.H.,University of Ulsan | Pham H.D.,University of Ulsan | Dang T.T.,University of Ulsan | Hur S.H.,University of Ulsan | And 4 more authors.
Journal of Materials Chemistry | Year: 2012

One of the major challenges in the chemical reduction of graphene oxide is increasing the C/O atomic ratio of the chemically converted graphene. In this paper, we report a simple and effective method to reduce aqueous suspensions of graphene oxide using nascent hydrogen generated in situ by the reaction between Al foil and HCl, Al foil and NaOH and Zn powder and NaOH. The nascent hydrogen-reduced graphene oxides (nHRGOs) were characterized by elemental analysis, UV-vis spectra, Raman spectra, X-ray photoelectron spectroscopy, thermogravimetric analysis and electrical conductivity measurements. The reduction efficiency of graphene oxide strongly depended on the reaction medium and the rate of nascent hydrogen generation. The best nHRGO achieved a C/O atomic ratio greater than 21 and a bulk electrical conductivity as high as 12500 S m -1, corresponding to the nascent hydrogen generated from the reaction between Al foil and HCl. Since nascent hydrogen could be produced on a metal surface upon oxidation in solution, other metals with low standard reduction potentials, such as Mg, Mn, and Fe, can be applied to reduce graphene oxide. © The Royal Society of Chemistry 2012. Source


Luan V.H.,University of Ulsan | Tien H.N.,University of Ulsan | Cuong T.V.,University of Ulsan | Kong B.-S.,KCC Central Research Institute | And 3 more authors.
Journal of Materials Chemistry | Year: 2012

In this study, 1-D Ag nanowires (NWs), 2-D chemically reduced graphene (CRG), and hybrid CRG-Ag NW fillers were investigated for use as conductive epoxy composites. By combining the 2-D CRG with 1-D Ag NWs, the percolation limit of the Ag NWs decreased from 30 wt% to 10 wt% and the electrical conductivity was dramatically enhanced because of the decreased tunneling resistance between the Ag NWs due to the thin 2-D conductive CRGs. Their thermal and mechanical properties were also improved due to the chemical crosslinking effects between CRGs and the hardener in the epoxy matrix as well as the physical crosslinking effects between nano-structures and polymer chains. The break strength of the CRG/Ag-NW/epoxy composite was 50% higher than that of the pure epoxy resin. © The Royal Society of Chemistry 2012. Source

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