Doohun Kim

Korea Electrotechnology Research Institute-KERI, Tsau-liang-hai, Busan, South Korea

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Publications (31)201.06 Total impact

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    ABSTRACT: Anodization of valve metals and alloys is a powerful tool to control nanoscale architecture for many metal oxides. Except for aluminum, the most explored system is self-organized oxide formed on titanium, namely self-organized TiO2 nanotubes, because of the unique combination of geometry with the semiconductive nature of titania that is applicable in photocatalysis, light harvesting systems, electrochromic devices, batteries, matrices, templates, filtration membranes, and bio-compatible materials. In this contribution, we review recent advances in the formation of nanostructured oxides in the form of nanotubes, nanopores with a through-hole morphology, mesosponges, nanochannels and microcones grown on Ti, Nb, Ta, Zr, Hf, W, V and their alloys. We discuss mechanisms of their formation, key functional features, and describe their applications in various fields of chemistry and electrochemistry. (c) 2013 Elsevier Ltd. All rights reserved.
    Nano Today 06/2013; 8(3):235–264. DOI:10.1016/j.nantod.2013.04.010 · 18.43 Impact Factor
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    ABSTRACT: The paper reports on the use of a titanium oxide (TiO(2)) nanotube layer as a sensitive substrate for surface-assisted laser desorption-ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO(2) nanotubes morphology coupled to a controlled surface chemistry allowed desorption-ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO(2) nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO(2) layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO(2) layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process.
    The Analyst 05/2012; 137(13):3058-63. DOI:10.1039/c2an35207a · 3.91 Impact Factor
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    ABSTRACT: In the present work, we show that metallic Ti thin films on FTO glass can be completely anodized to a mesoporous oxide layer using a glycerol-K 2HPO 4 electrolyte at elevated temperatures (∼180 °C). This results in highly transparent mesoporous oxide coated electrodes that provide a significantly enhanced transparency compared with the classic nanoparticle layers or TiO 2 nanotube layers. We show that in electrochromic switching experiments these electrodes therefore exhibit a significantly higher contrast compared to other TiO 2 nanostructures. Moreover, this type of anodic titania layer is produced in a fluoride-free electrolyte and adheres very well to the FTO glass, both features that are highly beneficial in view of an application in electrochromic devices. © 2012 The Royal Society of Chemistry.
    Journal of Materials Chemistry 04/2012; 22(19). DOI:10.1039/c2jm31244a · 6.63 Impact Factor
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    ABSTRACT: An alloy containing 5 at.% of N was produced by arc melting of Ti and TiN powders. By anodization of the alloy in a 10 wt.% K 2HPO 4/glycerol electrolyte at 140 °, oxide mesosponge layers can be formed with thickness as up to several micrometers. X-ray photoelectron spectroscopy confirms nitrogen uptake in the oxide. Photoelectrochemical measurements show successful N-doping of these mesoporous anodic layers with a significant visible light photoresponse. © Springer-Verlag 2010.
    Journal of Solid State Electrochemistry 01/2012; 16(1). DOI:10.1007/s10008-010-1282-7 · 2.23 Impact Factor
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    Yang Yang, Doohun Kim, Patrik Schmuki
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    ABSTRACT: Straight to Ti-V movie: Binary oxide mesosponge layers were fabricated by self-organizing anodization of Ti-V alloys. The etched mesosponge layers exhibit a specific capacitance of 100-130 F g -1, with perfect reversibility and long-term stability. Such mesosponge structures greatly facilitate ion transport during rapid charge/discharge processes. Ti-V binary oxide mesosponge layers are promising candidates for applications in energy-storage devices. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - An Asian Journal 11/2011; 6(11):2916-9. DOI:10.1002/asia.201100488 · 3.94 Impact Factor
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    Yang Yang, Doohun Kim, Patrik Schmuki
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    ABSTRACT: Highly ordered V 2O 5 porous layers were fabricated from vanadium metal foils by self-organizing anodization. The defined porous structure of this material provides excellent lithium-ion transportation and intercalation/extraction properties. As a result the highly ordered porous structure shows a very good electrochromic performance with long term switching stability. © 2011 Elsevier B.V. All rights reserved.
    Electrochemistry Communications 11/2011; 13(11). DOI:10.1016/j.elecom.2011.08.045 · 4.29 Impact Factor
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    Yang Yang, Doohun Kim, Patrik Schmuki
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    ABSTRACT: Mixed V 2O 5-TiO 2 nanotube arrays were fabricated by self-organizing anodization of different Ti-V alloys. The mixed oxide nanotubes show switchable V-oxidation states and strong cathodic coloration. Already a low V content of ≈ 0.2 at.% significantly increases the electrochromic switching properties. Using a sample with 3 at.% V, very high electrochromic contrast can be established and a significantly lower switching onset voltage than for pure TiO 2 nanotubes is observed. At high V contents, although charge storage is increased, the improvement of contrast is diminished due to the strong background color of the sample. © 2011 Elsevier B.V. All Rights Reserved.
    Electrochemistry Communications 10/2011; 13(10). DOI:10.1016/j.elecom.2011.06.001 · 4.29 Impact Factor
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    ABSTRACT: Vanadium oxide layers with homogeneous nanoporous nanotubular morphology (see picture) were successfully fabricated by direct anodization of vanadium in fluoride electrolytes such as [TiF 6] 2- or [BF 4] -. The pore size and layer thickness can easily be controlled by tailoring the electrochemical conditions. Such nanotubular or porous structures are promising for the fabrication of lithium-ion insertion electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Angewandte Chemie International Edition 09/2011; 50(39):9071-5. DOI:10.1002/anie.201104029 · 11.34 Impact Factor
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    ABSTRACT: Highly ordered mixed V 2O 5-TiO 2 nanotubes can be formed by self-organizing anodization of Ti-V alloys with vanadium content of up to 18 at%. In the resulting oxide nanotube arrays, the vanadium is electrochemically switchable leading to a specific capacitance that can reach up to 220 F g -1 and an energy density of 19.56 Wh kg -1 with perfect reversibility and long-term stability. Thus these mixed oxide nanotubes may be considered as a promising candidate for supercapacitors. © 2011 The Royal Society of Chemistry.
    Chemical Communications 07/2011; 47(27). DOI:10.1039/c1cc11811k · 6.72 Impact Factor
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    ABSTRACT: In the present work, we report on the self-organized growth of TiO(2) layers consisting of a highly aligned nanochannel morphology. We show that an electrochemical anodization process of Ti in a hot glycerol/K(2)HPO(4) electrolyte can be adjusted to yield these self-organized TiO(2) structures. The channel diameter and length are controllable by the anodization parameters. This directional structure can, for example, find application in dye-sensitized solar cells.
    Chemical Communications 05/2011; 47(20):5789-91. DOI:10.1039/c1cc11160d · 6.72 Impact Factor
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    ABSTRACT: Nb-doped TiO(2) nanotube (with C(Nb) < 1 wt%) layers were successfully fabricated by self-ordered electrochemical anodization of Ti-Nb alloys. When used in dye-sensitized solar cells the efficiency enhanced by up to 30% compared to non-doped TiO(2) nanotubes. IMVS measurements indicate the beneficial effect to be due to lower recombination losses.
    Chemical Communications 02/2011; 47(7):2032-4. DOI:10.1039/c0cc04993j · 6.72 Impact Factor
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    ABSTRACT: Thick mesoporous tungsten oxide (WO 3) layers can be formed by anodization of tungsten in a 10 wt% K 2HPO 4/glycerol electrolyte, if the electrolyte temperature is around 80-100 °C. At 90 °C, a regular mesoporous WO 3 layer was grown up to a thickness of approximately 9 μm. This WO 3 mesosponge layer consists of typical feature sizes of 20-30 nm and pore widths of 10-30 nm. The photoresponse of different layer thicknesses and different annealing treatments was characterized in a photoelectrochemical cell. The highest photocurrents were observed with a 2.5 μm thick WO 3 layer annealed at 550 °C consisting of a mixture of orthorhombic, triclinic and monoclinic phases. Incident photon to current efficiencies (IPCEs) of the samples were 73.4% in a 1 M HClO 4 electrolyte and 167.5% for methanol photo-oxidation in 0.1 M CH 3OH/1 M HClO 4 electrolyte, at 1 V vs. Ag/AgCl under illumination at a wavelength of 420 nm. © 2010 Elsevier Ltd. All rights reserved.
    Electrochimica Acta 12/2010; 56(2). DOI:10.1016/j.electacta.2010.09.087 · 4.09 Impact Factor
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    ABSTRACT: We report on a simple and self-organizing process for the fabrication of TiO(2) nanochannel membranes with a channel width of 8-10 nm that can be used for size selective separation of macromolecules (proteins). The membrane, consisting of self-aligned oxide channels, is formed by complete anodization of a thin Ti foil under specific electrochemical conditions in a glycerol-phosphate electrolyte. Due to self-cleaning properties of TiO(2), clogged membranes (for example due to extended use) can easily be fully reopened and thus are reusable. As the TiO(2) after anodic formation directly contains anatase crystallites (the most photoactive TiO(2) crystal form) no thermal treatment of the membrane is required (avoiding the danger of thermally induced cracking).
    Journal of the American Chemical Society 06/2010; 132(23):7893-5. DOI:10.1021/ja102712j · 11.44 Impact Factor
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    ABSTRACT: In the present work, we produce 15 μm thick titania mesosponge layers (TMSL) by a Ti anodization/etching process and use the layers in dye-sensitized solar cells (DSCs). We show that the solar cell efficiency can considerably be improved by a TiCl4 hydrolysis treatment (increase of approx. 40% to an overall value of 4.9% under AM 1.5 illumination). This beneficial effect is due to the decoration of the ∼10 nm wide channels present in TMSL with TiO2 nanoparticles of approx. 3 nm diameter, which allow for a significantly higher specific dye loading of the TMS structure. © 2010 Elsevier B.V. All rights reserved.
    Electrochemistry Communications 04/2010; 12(4). DOI:10.1016/j.elecom.2010.02.003 · 4.29 Impact Factor
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    ABSTRACT: We report a process for the fabrication of an anatase TiO(2) mesosponge (TMS) layer by an optimized Ti anodization process in a hot glycerol electrolyte followed by a suitable etching process. Such layers can easily be grown to >10 microm thickness and have regular channels and structural features in the 5-20 nm range. The layers show high photocatalytic activity and are mechanically very robust. The layers therefore open new pathways to the wide field of TiO(2)(anatase) applications.
    Journal of the American Chemical Society 02/2010; 132(5):1478-9. DOI:10.1021/ja910045x · 11.44 Impact Factor
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    ABSTRACT: The present article reviews the current status of using TiO(2) nanotubes in Grätzel-type, dye-sensitized solar cells and extends the overview with the latest results and findings. Critical factors in tube geometry (length, diameter, top morphology), crystal structure (amorphous, anatase, rutile) as well as factors affecting dye loading or electron mobility are addressed. The highest solar cell efficiencies today for pure nanotube systems reach approximately 4% while for some mixed systems, around 7% has been reported. For both systems significant room for enhancement is anticipated and some key points and strategies for improvement are outlined.
    Nanoscale 01/2010; 2(1):45-59. DOI:10.1039/b9nr00131j · 6.74 Impact Factor
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    ABSTRACT: When anodic self-organized nanotube layers are formed on valve metals, often a disordered porous initiation layer is present on the tube tops. In the present work, we show that on the Formula nanotubes this layer can be triggered to self-peel and roll up in the nanosheets if the anodization is carried out at a sufficiently high voltage. An ultrasonic treatment allows to completely remove the nanosheet rolls and to obtain highly ordered nanotube layers. This finding is of high significance for any applications requiring defined tube tops.
    Electrochemical and Solid-State Letters 01/2010; 13:K73-K76. DOI:10.1149/1.3428513 · 2.15 Impact Factor
  • Angewandte Chemie International Edition 11/2009; 48(49):9326-9. DOI:10.1002/anie.200904455 · 11.34 Impact Factor
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    ABSTRACT: In the present work we investigate the effect of TiCl4 treatments on the photoconversion efficiency of TiO2 arrays used in dye sensitized solar cell. The results clearly show that by an appropriate treatment the decoration of the TiO2 nanotube arrays with TiO2 nanocrystallites of a typical size of 3 nm can be achieved. These particles can be converted to mixture of anatase and rutile phase by annealing in air. This decoration of the TiO2 nanotubes leads to a significantly higher specific dye loading and, for certain annealing treatments, to a doubling of the solar cell efficiency (in our case from 1.9% to 3.8% of AM 1.5 conditions) can be achieved. © 2009 Elsevier B.V. All rights reserved.
    Electrochemistry Communications 05/2009; 11(5). DOI:10.1016/j.elecom.2009.02.049 · 4.29 Impact Factor
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    ABSTRACT: Particle vs tube: The present paper systematically investigates a range of fundamental geometrical and structural features of TiO(2) nanotube layers and their effect on the dye-sensitized solar cell conversion efficiency, to deduce the most promising strategies for improvement. It is found that the performance of the cells strongly depends on the morphology and crystalline structure of the nanotubes.
    Chemistry - An Asian Journal 03/2009; 4(4):520-5. DOI:10.1002/asia.200800441 · 3.94 Impact Factor

Publication Stats

1k Citations
201.06 Total Impact Points

Institutions

  • 2013
    • Korea Electrotechnology Research Institute-KERI
      • Battery Research Center
      Tsau-liang-hai, Busan, South Korea
  • 2010–2012
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Department of Materials Science and Engineering
      Erlangen, Bavaria, Germany
  • 2008–2012
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany