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Polymer-based chromophore–catalyst assemblies for solar energy conversion
Leem Gyu,Sherman Benjamin D.,Schanze Kirk S. 나노기술연구협의회 2017 Nano Convergence Vol.4 No.37
The synthesis of polymer-based assemblies for light harvesting has been motivated by the multi-chromophore antennas that play a role in natural photosynthesis for the potential use in solar conversion technologies. This review describes a general strategy for using polymer-based chromophore–catalyst assemblies for solar-driven water oxidation at a photoanode in a dye-sensitized photoelectrochemical cell (DSPEC). This report begins with a summary of the synthetic methods and fundamental photophysical studies of light harvesting polychormophores in solution which show these materials can transport excited state energy to an acceptor where charge-separation can occur. In addition, studies describing light harvesting polychromophores containing an anchoring moiety (ionic carboxylate) for covalent bounding to wide band gap mesoporous semiconductor surfaces are summarized to understand the photophysical mechanisms of directional energy flow at the interface. Finally, the performance of polychromophore/catalyst assembly-based photoanodes capable of light-driven water splitting to oxygen and hydrogen in a DSPEC are summarized.
( Gyu Leem ) 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Photoinduced energy electron transfer processes are widely utilized in every aspect of photosynthesis and optical biosensor. The work aims to understand mechanisms and dynamics for the photoprocesses in colloidal solution and at the interfaces of mesoporous structured semiconductor and metal nanoparticle. We reported a series of polystyrene-based light harvesting polymers with pendant Ru chromophores (PS-Ru) and conjugated poly(phenylene ethynylene) (PPE) derivatives for the use of solar energy conversion and optical biosensor. The talk will present the findings of photophysical properties of PS-Ru coated mesoporous structured TiO2 nanoparticles and the quenching process of PPE polymer-Au nanoparticle pairs showing high Ksv ~ 1012 M-1, that enable sub-picomolar sensitivity in highly efficient polymer-based optical biosensors.
한국형 저상버스 복합소재 차체에 대한 비틀림 강성 평가
임송규(Song-Gyu Leem),김연수(Yeon-Su Kim),목재균(Jai-Kyun Mok),장세기(Se-ky Jang),조세현(Se-hyun Cho) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Low Floor buses have no steps to get on or get off the main cabin to provide the old and the handicapped with easy access. The car body for the low floor bus was designed to consider Korean physical standard, passenger capacity (standee, seated, handicapped), arrangement of vehicle components, and bus law or regulations. It was designed as an one body, without any reinforcement armature, which has light-weight sandwich constructions with glass epoxy skins, aluminum honeycomb cores and inner-frames. In this paper, torsion rigidity of the designed car body was evaluated and compared with that of a car body with reinforcement armatures in the cabin. Finite element method verified that the designed car body without reinforcement armatures could satisfy requirements of torsion rigidity.
Near - field photocurrent measurements on GaAs / AlGaAs multiple quantum wells
Jung Gyu Shin,Joo In Lee,Jae-Yong Leem,Sungkyu Yu 한국진공학회(ASCT) 2000 Journal of Korean Vacuum Science & Technology Vol.4 No.2
Near-field photocurrent experiments were performed for GaAs/AlGaAs MQWs at room temperature. Heavy hole and light hole related peaks are clearly resolved even under extremely low power of near-field excitation. By scanning laterally 2 ㎛×2 ㎛ area on the surface, minority carrier diffusion process in the well region was qualitatively studied.
Dohyun Leem,Jin‑Hwan Kim,Frédéric Barlat,Jung Han Song,Myoung‑Gyu Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2
An inverse approach based on the virtual fields method (VFM) is presented to identify the material hardening parametersunder dynamic deformation. This dynamic-VFM (D-VFM) method does not require load information for the parameteridentification. Instead, it utilizes acceleration fields in a specimen’s gage region. To investigate the feasibility of the proposedinverse approach for dynamic deformation, the virtual experiments using dynamic finite element simulations were conducted. The simulation could provide all the necessary data for the identification such as displacement, strain, and accelerationfields. The accuracy of the identification results was evaluated by changing several parameters such as specimen geometry,velocity, and traction boundary conditions. The analysis clearly shows that the D-VFM which utilizes acceleration fields canbe a good alternative to the conventional identification procedure that uses load information. Also, it was found that properdeformation conditions are required for generating sufficient acceleration fields during dynamic deformation to enhance theidentification accuracy with the D-VFM.
Cdo Interacts with APPL1 and Activates AKT in Myoblast Differentiation
Bae, Gyu-Un,Lee, Jae-Rin,Kim, Bok-Geon,Han, Ji-Won,Leem, Young-Eun,Lee, Hey-Jin,Ho, Seok-Man,Hahn, Myong-Joon,Kang, Jong-Sun The American Society for Cell Biology 2010 Molecular biology of the cell Vol.21 No.14
<P>Cell–cell interactions between muscle precursors are required for myogenic differentiation; however, underlying mechanisms are largely unknown. Promyogenic cell surface protein Cdo functions as a component of multiprotein complexes containing other cell adhesion molecules, Boc, Neogenin and N-cadherin, and mediates some of signals triggered by cell–cell interactions between muscle precursors. Cdo activates p38MAPK via interaction with two scaffold proteins JLP and Bnip-2 to promote myogenesis. p38MAPK and Akt signaling are required for myogenic differentiation and activation of both signaling pathways is crucial for efficient myogenic differentiation. We report here that APPL1, an interacting partner of Akt, forms complexes with Cdo and Boc in differentiating myoblasts. Both Cdo and APPL1 are required for efficient Akt activation during myoblast differentiation. The defective differentiation of Cdo-depleted cells is fully rescued by overexpression of a constitutively active form of Akt, whereas overexpression of APPL1 fails to do so. Taken together, Cdo activates Akt through association with APPL1 during myoblast differentiation, and this complex likely mediates some of the promyogenic effect of cell–cell interaction. The promyogenic function of Cdo involves a coordinated activation of p38MAPK and Akt via association with scaffold proteins, JLP and Bnip-2 for p38MAPK and APPL1 for Akt.</P>
( Young Gyu Kim ),( Byung Gu Kim ),( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.10
ZnO thin films were grown on Zn-deposited polyimide (PI) substrates using the sol-gel spin-coating method. The Zn seed layers were annealed at 200, 300, and 400 ℃. The annealing effects of the Zn seed layer on the structural and optical properties of the ZnO thin films were investigated for the first time. By adjusting the annealing temperature of the Zn seed layers, we achieved a significant enhancement in the crystallinity of the ZnO thin films. The ZnO thin film grown on a non-annealed Zn seed layer had a yellow/orange emission, whereas those grown on annealed ones had a green emission as well as lower defect-related deep-level emissions. The narrowest full width at half maximum of the near-band-edge emission was observed for the ZnO thin films grown on the Zn seed layers annealed at 200 and 300 ℃. We found that the structural and optical properties of the ZnO thin films grown on the Zn seed layer annealed at 400 ℃ were deteriorated, which could be attributed to considerable changes in the characteristics of the PI substrate at the annealing temperature of 400 ℃.
( Young Gyu Kim ),( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.6
We studied the dependence of the optical band gap energy and structural properties of the MgxZn1-xO (MZO) thin films on Mg concentration to explore applications in flexible optoelectronics. The MZO thin films were grown on muscovite mica substrates via sol-gel spin-coating. Their surface morphology was smoother and denser than that of ZnO thin film. The peaks were observed for the ZnO thin films at 31.7° and 34.4°, corresponding to the ZnO (100) and (002) planes, but the (100) peak did not appear when Mg was added. The (002) peak of the films was found to be increased with increasing Mg concentration. In the photoluminescence spectra, there were strong UV emissions in the range 3.25.3.45 eV and broad visible emissions were observed for the MZO thin films. The optical band gap calculated from the Tauc``s plot was blue-shifted with increasing Mg concentration. (Received August 13, 2015)