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Pohang, South Korea

Kim J.Y.,Chonnam National University | Park K.,Chonnam National University | Bae S.Y.,Samsung | Kim G.C.,Jeonnam Nano Bio Research Center | And 2 more authors.
Journal of Materials Chemistry | Year: 2011

To investigate the relationship between the linker length and the catalytic activities of metal-decorated CNTs, three samples were prepared with different linker molecules, viz. NaSH, HSCH2CH2SH, and C 2H2N2S3. The structures of the prepared samples were characterized using transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The analysis of the TEM images and XRD patterns showed that the Pd nanoparticles strongly adhered to the outside of the CNTs, with average particle sizes of ∼3 nm, ∼5 nm, and ∼6 nm for samples A, B and C, respectively. The XPS spectra revealed that the Pd species on the Pd-decorated CNTs consisted of Pd0, Pd2+ and Pd4+. The oxidized Pd species were formed by the interaction of the electron-donor Pd 0 atoms with the electrophilic neighboring protons (H+) during the sample preparation. The oxidized Pd species become more abundant with increasing linker length, causing a decrease of their catalytic activities in organic and electrocatalytic reactions. Nevertheless, all of the samples exhibited higher activity in organic and electrocatalytic reactions than that of the reference systems. © 2011 The Royal Society of Chemistry.

Kim J.D.,Chonnam National University | Pyo A.,Chonnam National University | Park K.,Chonnam National University | Kim G.C.,Jeonnam Nano Bio Research Center | And 2 more authors.
Bulletin of the Korean Chemical Society | Year: 2013

We present here an efficient and simple method for preparation of highly active Pd heterogeneous catalyst (CNT-Pd), specifically by reaction of dichlorobis(triphenylphosphine)palladium (Pd(PPh3)2Cl 2) with thiolated carbon nanotubes (CNTs). The as-prepared CNT-Pd catalysts demonstrated an excellent catalytic activity for the carbon-carbon (C-C) cross-coupling reactions (i.e. Suzuki, Stille, and decarboxylative coupling reactions) under mild conditions. The CNT-Pd catalyst could easily be removed from the reaction mixture; additionally, in the decarboxylative coupling of iodobenzene and phenylpropiolic acid, it showed a six-times recyclability, with no loss of activity. Moreover, once its activity had decreased by repeated recycling, it could easily be reactivated by the addition of phosphine ligands. The remarkable recyclability of the decarboxylative coupling reaction is attributable to the high degree of dispersion of Pd catalysts in CNTs. Aggregation of the Pd catalysts is inhibited by their strong adhesion to the thiolated CNTs during the chemical reactions, thereby permitting their recycling. Copyright © 2005 KCSNET.

Park Y.,Kangwon National University | Kim N.H.,Kangwon National University | Cho S.B.,Agency for Defense Development | Kim J.M.,Agency for Defense Development | And 6 more authors.
Journal of Molecular Structure | Year: 2010

The passivating layer (also called the solid electrolyte interface, SEI) plays a key role in the performances of Li-ion batteries. In this work, we studied the surface reactions of Li[Ni0.31Co0.32Mn 0.28Al0.09]O2 with the organic electrolyte in the overcharge state by means of FTIR, XPS, XAS, and 2D correlation analysis. The FTIR and XPS results revealed that several types of compounds are formed on the cathode surface. These results also suggest that the organic solvents are decomposed to a greater extent than the Li-salt during the overcharge state. Based on the 2D correlation analysis, we can deduce the following sequence of events: 287.0 (due to C-O) → 290.0 (due to carbonate) → 288.5 (due to CO) → 291.5 (due to C-Fx) → 284.5 eV (due to CC or CH). © 2010 Elsevier B.V. All rights reserved.

Park K.-H.,Chonnam National University | Jin E.-M.,Chonnam National University | Gu H.-B.,Chonnam National University | Yoon S.-D.,Chonnam National University | And 2 more authors.
Applied Physics Letters | Year: 2010

Zirconia (ZrO2) nanofibers added mesoporous titania (TiO 2) photoelectrode has been synthesized for dye-sensitized solar cells to enhance the efficiency of cell. The ZrO2 nanofibers had reduced the resistance of the photoelectrode as well as enhancement of the absorption spectra in the ultraviolet (UV), visible, and near infrared (IR) region. The internal resistance of the photoelectrode is one of the important factor to affects the power conversion efficiency directly. The ZrO2 nanofibers provide the more photon harvest and optimal electron pathway. Finally, about 200% increases in conversion efficiency has been achieved. © 2010 American Institute of Physics.

Kim J.D.,Chonnam National University | Yun H.,Chonnam National University | Kim G.C.,Jeonnam Nano Bio Research Center | Lee C.W.,Chonnam National University | Choi H.C.,Chonnam National University
Applied Surface Science | Year: 2013

A facile approach to the synthesis of novel CNT-Ag and GO-Ag antibacterial materials, in which thiol groups are utilized as linkers to secure silver (Ag) nanoparticles to the CNT and GO surfaces without agglomeration, is reported. The resulting CNT-Ag and GO-Ag samples were characterized by performing TEM, XRD, Auger, XPS, and Raman measurements, which revealed that in these antibacterial materials size-similar and quasi-spherical Ag nanoparticles are anchored to the CNT and GO surfaces. The Ag nanoparticles in CNT-Ag and GO-Ag have narrow size distributions with average diameters of 2.6 and 3.5 nm respectively. The antibacterial activities of CNT-Ag and GO-Ag against Escherichia coli were assessed with the paper-disk diffusion method and by determining the minimal inhibitory concentrations (MICs). CNT-Ag was found to have higher antibacterial activity than the reference Ag colloid. Moreover, both CNT-Ag and GO-Ag retain more than 50% of their original antibacterial activities after 20 washes with detergent, which indicates their potential as antibacterial materials for laboratory and medical purposes. © 2013 Elsevier B.V. All rights reserved.

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