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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>
Neuroprotective Effects of Carpinus tschonoskii MAX on 6-Hydroxydopamine-Induced Death of PC12 Cells
( Sang Cheol Kim ),( Hee Kyoung Kang ),( Min Kyoung Kim ),( Ji Hoon Kang ),( Jin Won Hyun ),( Eun Sook Yoo ),( Jung Il Kang ),( Deok Bae Park ),( Hye Jin Boo ),( Young Sang Koh ) 한국응용약물학회 2010 Biomolecules & Therapeutics(구 응용약물학회지) Vol.18 No.4
The present study investigated the neuroprotective effect of Carpinus tschonoskii MAX and its intracellular protective mechanism on 6-hydroxydopamine (6-OHDA)-induced oxidative damage in PC12 cells. We found that pretreatment of PC12 cells with C. tschonoskii extract significantly inhibited the cell death induced by 6-OHDA in a dose dependent manner. C. tschonoskii extract decreased 6-OHDA-induced apoptotic events such as chromatin condensation, DNA fragmentation, the decrease of Bcl-2/Bax ratio, caspase-3 activation and PARP cleavage. C. tschonoskii extract also reduced generation of 6-OHDA-induced reactive oxygen species and nitric oxide. Furthermore, C. tschonoskii extract up-regulated the myocyte enhancer factor 2 D (MEF2D), a critical transcription factor for neuronal survival, and Akt activity, whereas it inhibited the activity of ERK1/2 and JNK. The results suggest that C. tschonoskii extract decreases 6-OHDA-induced oxidative stress and could prevent PC12 cell apoptosis induced by 6-OHDA via the up-regulation of MEF2D and Akt activity, and thus may have application in developing therapeutic agents for Parkinson`s disease.
Jung, In Hwan,Kim, Ji-Hoon,Nam, So Youn,Lee, Changjin,Hwang, Do-Hoon,Yoon, Sung Cheol American Chemical Society 2015 Macromolecules Vol.48 No.15
<P>We have synthesized a series of novel di(1-benzothieno) [3,2-b:2',3'-d]pyrrole (DBTP)-based conjugated polymers for organic photovoltaic devices. We first introduced DBTP moiety as an electron donating part in the conjugated polymer system to improve the open-circuit voltage (V-oc) in photovoltaic properties. The DBTP backbone has a fused ring structure with extended benzene rings at the end of the 4H-dithieno[3,2-b:2',3'-d]pyrrole (DTP) moiety. The synthesized DBTP-based polymers effectively enhanced V-oc compared to DTP-based polymers by decreasing the highest occupied molecular orbital (HOMO) energy levels of polymers without damaging other photovoltaic parameters. The alternation of DBTP and 3,6-dithien-2-yl-2,5-dialkylpyrrolo[3,4-c]p-yrrole-1,4-dione (DTDPP) formed a promising donor polymer, PDBTP4, exhibiting an excellent molar absorption coefficient of 17 600 L cm(-1) mol(-1) at the absorption maximum of 719 nm and a broad absorption covering 550-850 nm. PDBTP4:[6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) devices exhibited more than twice improved PCE of 6.80% with 0.28 V higher V-oc than DTP DTDPP polymer:PC71BM devices at the similar fabrication process. The benzene ring extension strategy is successfully working on the polymers containing strong electron donating DTP moiety. We believe that this approach can be used in other polymer systems showing a poor V-oc value.</P>
Jung, Min Wook,Myung, Sung,Song, Wooseok,Kang, Min-A,Kim, Sung Ho,Yang, Cheol-Soo,Lee, Sun Sook,Lim, Jongsun,Park, Chong-Yun,Lee, Jeong-O,An, Ki-Seok American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.16
<P>We have fabricated graphene-based chemical sensors with flexible heaters for the highly sensitive detection of specific gases. We believe that increasing the temperature of the graphene surface significantly enhanced the electrical signal change of the graphene-based channel, and reduced the recovery time needed to obtain a normal state of equilibrium. In addition, a simple and efficient soft lithographic patterning process was developed via surface energy modification for advanced, graphene-based flexible devices, such as gas sensors. As a proof of concept, we demonstrated the high sensitivity of NO<SUB>2</SUB> gas sensors based on graphene nanosheets. These devices were fabricated using a simple soft-lithographic patterning method, where flexible graphene heaters adjacent to the channel of sensing graphene were utilized to control graphene temperature.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-16/am502281t/production/images/medium/am-2014-02281t_0006.gif'></P>
Development of Knee Brace Hinge for the Optimization of Rotation Center in Femoro-tibio Joint
Cheol-Woong Kim(김철웅),Min-Hyung Park(박민형),Jung-Heum Yoon(윤정흠),Tae-Young Kim(김태영),Se-Hwan Park(박세환),Min-Sung Kang(강민성),Young-Kyu Yang(양영규),Kwang-Hyun Cho(조광현),Kwang-Seok Jang(장광석) 한국정밀공학회 2009 한국정밀공학회 학술발표대회 논문집 Vol.2009 No.10월
Sang Ho Rha,Un Ki Kim,Jisim Jung,Hyo Kyeom Kim,Yoon Soo Jung,Eun Suk Hwang,Yoon Jang Chung,Mijung Lee,Jung-Hae Choi,Cheol Seong Hwang IEEE 2013 IEEE transactions on electron devices Vol.60 No.3
<P>Asymmetric Schottky contact thin-film-transistors (ASC-TFTs) with an amorphous- In<SUB>2</SUB>Ga<SUB>2</SUB>ZnO<SUB>7</SUB> channel were fabricated, and their operation characteristics were examined. Ti, Ni, and Pt were evaluated as source/drain metal, and the variations in the device performance were analyzed in terms of energy level and bias polarity, which were carefully simulated to understand the influence of the contact properties on the device performance. The contact nature largely influenced the distribution of potential under the given gate and drain biases, as well as the accompanying carrier accumulation layer and current path formation. Schottky-type contact induced conduction path formation even on the back surface of the channel when drain voltage was high even with sufficiently high gate bias being applied. Based on these results, by applying different metal for each source and drain metal, ASC-TFTs integrating TFTs and Schottky diodes were fabricated, which showed a rectification ratio of drain current higher than 10<SUP>8</SUP> according to the bias direction. In addition, the transfer and output characteristics of ASC-TFTs were evaluated for various operation regimes, and the roles of the Schottky junction in device operation were studied in detail.</P>