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AC Field-Induced Polymer Electroluminescence with Single Wall Carbon Nanotubes
Sung, Jinwoo,Choi, Yeon Sik,Kang, Seok Ju,Cho, Sung Hwan,Lee, Tae-Woo,Park, Cheolmin American Chemical Society 2011 NANO LETTERS Vol.11 No.3
<P>We developed a high-performance field-induced polymer electroluminescence (FPEL) device consisting of four stacked layers: a top metal electrode/thin solution-processed nanocomposite film of single wall carbon nanotubes (SWNTs) and a fluorescent polymer/insulator/transparent bottom electrode working under an alternating current (AC) electric field. A small amount of SWNTs that were highly dispersed in the fluorescent polymer matrix by a conjugate block copolymer dispersant significantly enhanced EL, and we were able to realize an SWNT-FPEL device with a light emission of approximately 350 cd/m<SUP>2</SUP> at an applied voltage of ±25 V and an AC frequency of 300 kHz. The brightness of the SWNT-FPEL device is much greater than those of other AC-based organic or even inorganic ELs that generally require at least a few hundred volts. Light is emitted from our SWNT-FPEL device because of the sequential injection of field-induced holes and then electron carriers through ambipolar carbon nanotubes under an AC field, followed by exciton formation in the conjugated organic layer. Field-induced bipolar charge injection provides great material design freedom for our devices; the energy level does not have to be aligned between the electrode and the emission layer, and the balance of the carrier injected and transported can be altered in contrast to that in conventional organic light-emitting diodes, leading to an extremely cost-effective and unified device architecture that is applicable to all red−green−blue fluorescent polymers.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-3/nl103458g/production/images/medium/nl-2010-03458g_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl103458g'>ACS Electronic Supporting Info</A></P>
Transparent, Low-Electric-Resistance Nanocomposites of Self-Assembled Block Copolymers and SWNTs
Sung, Jinwoo,Jo, Pil Sung,Shin, Hyein,Huh, June,Min, Byung Gil,Kim, Dong Ha,Park, Cheolmin WILEY-VCH Verlag 2008 Advanced Materials Vol.20 No.8
<B>Graphic Abstract</B> <P>A transparent PS-b-P4VP copolymer/SWNTs nanocomposite film is used as both source and drain electrode in a pentacene OTFT with transmittance and electricresistance values of 85% and 6000 Ω/□, respectively. The low electric resistance of the film is achieved by the selective doping of HAuCl<SUB>4</SUB> in P4VP cores of the self-assembled block copolymer micelles, which simultaneously provides sufficientstability for the SWNTs suspension. <img src='wiley_img/09359648-2008-20-8-ADMA200701535-content.gif' alt='wiley_img/09359648-2008-20-8-ADMA200701535-content'> </P>
Control of SWNT Dispersion by Block Copolymers with a Side-Chain Polarity Modifier
Sung, Jinwoo,Park, Jae Man,Choi, U-Hyeok,Huh, June,Jung, Bumsuk,Min, Byung Gil,Ahn, Cheol Hee,Park, Cheolmin WILEY-VCH Verlag 2007 Macromolecular Rapid Communications Vol.28 No.2
<P>The dispersion of single-walled carbon nanotubes (SWNTs) in a non-polar solvent is controlled with a series of polystyrene-block-polybutadiene-block-polystyrene (PSBS) block copolymers that contain cholesteryl chloroformate (CC) in side-chains. Esterification of CC with the partially hydroxylated polybutadiene (PB) blocks allows one to tune the polarity of the block copolymers, which decreases with the amount of CC attached. An excellent dispersion of weak polar SWNTs is observed with PSBS that contains a partially hydroxylated PB block. The dispersion is then significantly deteriorated when the amount of non-polar CC moieties increases in the block copolymers. A good dispersion is achieved with a polymer that gives rise to strong SWNT–polymer interactions, which ensures contact of the polymer molecules with the nanotube surface, rather than a good solubility of the polymer dispersant in solvent. The stability of the SWNTs in solution arises from unique needle-like nanowires of the block copolymer aligned perpendicular to the nanotube axis.</P><P> <img src='wiley_img/10221336-2007-28-2-MARC200600669-gra001.gif' alt='wiley_img/10221336-2007-28-2-MARC200600669-gra001'> </P>
Sung, Jinwoo,Huh, June,Choi, Ji‐,Hyuk,Kang, Seok Ju,Choi, Yeon Sik,Lee, Geun Tak,Cho, Junhan,Myoung, Jae‐,Min,Park, Cheolmin WILEY‐VCH Verlag 2010 Advanced Functional Materials Vol.20 No.24
<P><B>Abstract</B></P><P>Ultrathin composite films consisting of mixtures of metallic (m‐) and semiconducting (s‐) single‐walled carbon nanotubes (SWNTs) with a conjugated block copolymer are developed from a solution‐based process. The electronic properties of the films are precisely controlled from metallic to semiconducting to insulating. The tunability of the electronic composite sheets is mainly attributed to (1) the efficient dispersion of SWNTs with a conjugated block copolymer in solution, (2) the control of the number of nanotubes by centrifugation, and (3) the individually networked deposition of SWNTs embedded in the conjugated block copolymer on the target substrate by spin‐coating. A highly reliable field‐effect transistor with a networked composite film is realized with a specific range of tube density and a high on/off current ratio of approximately 10<SUP>6</SUP> which resulted from the Schottky barriers evolved between the individual m‐ and s‐SWNTs in the network. There is also great freedom when choosing both the gate dielectrics and source‐drain electrodes for transistors containing the composite films. Furthermore, the fabricated electronic composites are highly transparent, flexible, and chemically robust and thus, they can be conveniently micropatterned by photolithography, as well as by unconventional transfer printing techniques.</P>
Antioxidant Content and Properties of Commonly Consumed Dried Vegetables in Korea
Jinwoo Yang, Jeehye Sung, Hyeonmi Ham, Hyemin Han, and Junsoo Lee 忠北大學校 農業科學硏究所 2015 農業科學硏究 Vol.31 No.1
This study evaluated the antioxidant content and activity of fourteen different indigenous Korean vegetables, as well as the relationship between antioxidant content and activity. DPPH and ABTS radical scavenging activities, through their inhibitory effect on lipid peroxidation, as well as their reducing power, have been used to investigate the antioxidant activity of 14 vegetables extracts. Polyphenolic and flavonoid concentrations were measured using spectrophotometric methods. Ascorbic acid analysis was carried out using HPLC. The polyphenolic, flavonoid and ascorbic acid concentrations were measure to be 0.24-11.34, 0.0079-10.84 and 0-71.35 mg·100 g-1, respectively. The extracts of Aster scaber Thunb, Capsicum annuum L. leaves, Cirsium setidens, and Morus alba leaves demonstrated significantly high level of antioxidant activity and higher antioxidant content. In addition, these vegetables demonstrated significant positive correlations between antioxidant activity and polyphenolic and flavonoid content. However, no relationship was found between antioxidant activity and ascorbic acid. Therefore, polyphenolic and flavonoid compounds are major antioxidants in vegetables. Our results could have a direct impact on vegetable consumption by increasing consumer awareness of the health benefits of vegetables.
Jinwoo Sung 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.S1
Comparative studies on mechanical properties and cutting performance of Cr-Al-Si-N coated micro tool for high speed machining applications were performed. Quaternary Cr-Al-Si-N coatings, in which Si was incorporated into Cr-Al-N, were synthesized onto WC-Co substrates using a hybrid system of an arc ion plating (AIP) and DC magnetron sputtering techniques. The high hardness of Cr-Al-Si-N coatings was related to the composite microstructure consisting of fine CrN crystallites and amorphous Si3N4. The hardness values of the Cr-Al-Si-N (~55 GPa) coatings were significantly increased compared with those of Cr-Al-N (~24 GPa) coatings. Cutting tests were carried out to evaluate the performances of micro endmill coated tool in high-speed cutting conditions. Consequently, the quaternary Cr-Al-Si (8.7 at.%)-N coated micro end-mill under dry machining showed good cutting performance in micro end-milling process of AISI D2 work material (HRC 24).
성진우(JinWoo Sung),이영주(YoungJoo Lee),최윤근(YounKeun Choi),박찬열(ChanYeol Park) 한국콘텐츠학회 2007 한국콘텐츠학회 종합학술대회 논문집 Vol.5 No.2_2
클러스터 시스템을 관리하기 위하여 모니터링 툴(S/W)이 필요하지만, 소규모 클러스터 시스템에 적합하고 관리자가 필요로 하는 기능을 갖춘 모니터링 툴을 결정하는 것은 쉽지가 않다. 본 문서는 인피니밴드 네트워크 스위치를 사용한 소규모 SMP 클러스터 시스템을 위하여 개발한 모니터링 툴의 설계와 구현 내용을 기술하였다. 모니터링 툴의 기능은 계산노드, 인피니밴드 스위치 그리고 작업관리 스케줄러(PBS)의 작업을 모니터링한다. System manager needs monitoring tool(S/W) to manage cluster system. But, it is difficult to decide suitable monitoring tool for small SMP cluster system. This document described design of monitoring tool(mon) and development. Mon is monitoring tool for small SMP cluster system using InfiniBand network switch. Function of this tool is monitoring such as computing nodet? node), Infiniband network switch and monitoring of PBS job.