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Nah, Yoon-Chae Materials Research Society of Korea 2011 한국재료학회지 Vol.21 No.12
The electrochromic properties of tungsten oxide films grown by RF sputtering were investigated. Among the sputter parameters, first the $Ar:O_2$ ratios were controlled with division into only an $O_2$ environment, 1:1 and 4:1. The structure of each film prepared by these conditions was studied by X-ray diffraction, X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. The sputter-deposited tungsten oxide films had an amorphous structure regardless of the $Ar:O_2$ ratios. The chemical compositions, however, were different from each other. The stoichiometric structure and low-density film was obtained at higher $O_2$ contents. Electrochemical tests were performed by cyclic voltammetry and chronoamperometry at 0.05 M $H_2SO_4$ solutions. The current density and charge ratio was estimated during the continuous potential and pulse potential cycling at -0.5 V and 1.8 V, respectively. The film grown in a higher oxygen environment had a higher current density and a reversible charge reaction during intercalation and deintercalation. The in-situ transmittance tests were performed by He-Ne laser (633 nm). At higher oxygen contents, a big transmittance difference was observed but the response speed was too slow. This was likely caused by higher film resistivity. Furthermore, the effect of sputtering pressure was also investigated. The structure and surface morphology of each film was observed by X-ray diffraction and scanning electron microscopy. A rough surface was observed at higher sputtering pressure, and this affected the higher transmittance difference and coloration efficiency.
Nah, Yoon-Chae,Ghicov, Andrei,Kim, Doohun,Berger, Steffen,Schmuki, Patrik American Chemical Society 2008 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.130 No.48
<P>The present work demonstrates that uniform and highly ordered arrays of TiO(2)-WO(3) nanotubes can be grown by anodization of Ti alloys in an ethylene glycol/fluoride based electrolyte under selected electrochemical conditions. These aligned mixed oxide nanotube structures are highly suitable for enhanced electrochromic reactions; in particular we show that already small amounts of WO(3) (such as 0.2 at%) present in the tube oxide drastically improve the electrochromic properties (contrast, onset potential, cycling stability) of nanotube layer based devices.</P>
Yoon-Seok Kang,Kwon-Pyo Hong,Dong-Chae Jung,Sungwon Hong,Jun-Ho Lee,Seung-Yeal Nah,Yoongho Lim,Dong-Ho Bae 한국식품과학회 2008 Food Science and Biotechnology Vol.17 No.1
This study was conducted to evaluate the hypotensive properties of the extract of Chinese balloon flower (Platycodon grandiflorum)’s root. In the studies for calcium channel-blocking using Xenopus oocytes, the ethanol-extract (26.2±5.2%) showed higher activity than water-extract. Twenty female rats were fed 25, 35, and 45 mg/kg BW/day of the ethanol-extract for 14 days to observe the changes in blood pressures and heart pulses. Ethanol-extract decreased the systolic, diastolic, and mean blood pressures of the rats. Especially, the rats fed with 45 mg/kg BW/day of the ethanol-extract showed significant decreases in the blood pressures. These results suggested that a decrease in blood pressures was due to the extension of a blood vessel with calcium channel-blocking by ethanol-extract of Chinese balloon flower. Forty %-ethanol showed the highest efficiency for ethanol-extraction of Chinese balloon flower.
American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.5
<P>Au nanoparticles and poly(3-hexylthiophene) (P3HT) composite films were prepared by electrodeposition of Au nanoparticles using pulse-current electrodeposition followed by the spin coating of P3HT and their enhanced electrochromic coloration was investigated. A relatively uniformed Au nanoparticle was obtained by the controlled electrodeposition on indium tin oxide (ITO) substrate and plasmon absorption band of Au nanoparticles were observed. Optical and electrochemical properties of Au/P3HT composite films were compared with the pure P3HT films. The enhanced electrochromic absorption of the composite films was observed due to the surface plasmon resonance of the Au nanoparticles.</P>
Synthesis of novel arylamine containing perfluorocyclobutane and its electrochromic properties
Lim, Bogyu,Nah, Yoon-Chae,Hwang, Jin-Taek,Ghim, Jieun,Vak, Doojin,Yun, Jin-Mun,Kim, Dong-Yu Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.16
<P>A new electrochromic oligomer based on an arylamine compound containing a perfluorocyclobutane (PFCB) ring has been synthesized <I>via</I> 2 + 2 cyclodimerization. A new N,N,N′,N′-tetraphenyl-biphenyl-4,4′-diamine (TPD) with PFCB (<B>TPD-PFCB</B>) showed high thermal stability with a decomposition temperature (T<SUB>d</SUB>) of 435 °C. Cyclic voltammograms of <B>TPD-PFCB</B> films coated onto an indium–tin oxide substrate showed two reversible redox steps during a potential scan between 0.7 and 1.2 V. The spectroelectrochemical series of <B>TPD-PFCB</B> films exhibited color change from colorless to yellow and then to greenish blue during the oxidation reaction of <B>TPD-PFCB</B>. This oligomer exhibited a high electrochromic coloration efficiency (602 cm<SUP>2</SUP>/C) and a comparable response speed (coloring and bleaching time at 700 nm were 0.71 and 0.12 s, respectively).</P> <P>Graphic Abstract</P><P>A new electrochromic oligomer based on an arylamine compound containing a PFCB ring has been synthesized <I>via</I> 2 + 2 cyclodimerization and its electrochromic properties investigated. The oligomer exhibited a high electrochromic coloration efficiency and a comparable response speed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b817303f'> </P>
열처리 및 바이올로젠 도입에 따른 TiO<sub>2</sub> 나노튜브의 전기변색 특성
차형철,나윤채,Cha, Hyeongcheol,Nah, Yoon-Chae 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.2
We demonstrate the electrochromic properties of $TiO_2$ nanotubes prepared by an anodization process and investigate the effects of heat treatment and viologen incorporation on them. The morphology and crystal structure of anodized $TiO_2$ nanotubes are investigated by scanning electron microscopy and X-ray diffraction. As-formed $TiO_2$ nanotubes have straight tubular layers with an amorphous structure. As the annealing temperature increases, the anodized $TiO_2$ nanotubes are converted to the anatase and rutile phases with some cracks on the tube surface and irregular morphology. Electrochemical results reveal that amorphous $TiO_2$ nanotubes annealed at $150^{\circ}C$ have the largest oxidation/reduction current, which leads to the best electrochromic performance during the coloring/bleaching process. Viologen-anchored $TiO_2$ nanotubes show superior electrochromic properties compared to pristine $TiO_2$ nanotubes, which indicates that the incorporation of a viologen can be an effective way to enhance the electrochromic properties of $TiO_2$ nanotubes.