• BMB Reports
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• v.38 no.5
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• pp.517-525
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• 2005

Solid phase peptide synthesis method, which was introduced by Merrifield in 1963, has spawned the concept of combinatorial chemistry. In this review, we summarize the present technologies of solid phase peptide synthesis (SPPS) that are related to combinatorial chemistry. The conventional methods of peptide library synthesis on polymer support are parallel synthesis, split and mix synthesis and reagent mixture synthesis. Combining surface chemistry with the recent technology of microelectronic semiconductor fabrication system, the peptide microarray synthesis methods on a planar solid support are developed, which leads to spatially addressable peptide library. There are two kinds of peptide microarray synthesis methodologies: pre-synthesized peptide immobilization onto a glass or membrane substrate and in situ peptide synthesis by a photolithography or the SPOT method. This review also discusses the application of peptide libraries for high-throughput bioassays, for example, peptide ligand screening for antibody or cell signaling, enzyme substrate and inhibitor screening as well as other applications.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.552-558
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• 1995

Stereolithography is a process used to rapidly produce polymer components directly from a computer-representation of the part. There are several considerations to be made for the efficient use of te process. Especially, the build-up orientation of part critically affect to the part accuracy, total build time and the volume of support structures. Te purpose of this study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, minimizing total build time, and the volume of supprot structures. The first factor is related to the area of surfaces which have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area with quantifying the process planning errors that the volume of materials is supposed to be removed or added to the part, and the optimal layer thickness for the SLA system whichcan hadle the variable layer thickness in different orientations achieved by rotating the given part to the specified finite directions. So the optimal part orientation is determined based on the user's selections of primary criterion and the optimal thickness of layers is calculated at any part orientations.

• Membrane Journal
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• v.17 no.1
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• pp.14-22
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• 2007

This is the research about the concentration of trace Magnolia flavor components in water by pervaporation. We have investigated the change of selectivity depending on support membrane structure and active layer thickness using prepared PVDF/PDMS composite membrane. Through the pure water flux test for PVDF support membrane, we could indirectly confirm that as the coagulation temperature decreases and the polymer concentration increases, the surface porosity and pore diameter decreases. Appling these results to transport mechanism, we could explain the effect of support membrane structure for the composite membrane. The selectivity increases as the thickness of PDMS active layer increases. We could know that there is a limitation to describe the transport on the active layer by Fick's law through these results.

• Carbon letters
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• v.11 no.1
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• pp.38-40
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• 2010

Carbon supported electrocatalysts are commonly used as electrode materials for polymer electrolyte membrane fuel cells(PEMFCs). These kinds of electrocatalysts provide large surface area and sufficient electrical conductivity. The support of typical PEM fuel cell catalysts has been a traditional conductive type of carbon black. However, even though the carbon particles conduct electrons, there is still significant portion of Pt that is isolated from the external circuit and the PEM, resulting in a low Pt utilization. Herein, new types of carbon materials to effectively utilize the Pt catalyst are being evaluated. Carbon nanofiber/activated carbon fiber (CNF/ACF) composite with multifunctional surfaces were prepared through catalytic growth of CNFs on ACFs. Nickel nitrate was used as a precursor of the catalyst to synthesize carbon nanofibers(CNFs). CNFs were synthesized by pyrolysising $CH_4$ using catalysts dispersed in acetone and ACF(activated carbon fiber). The as-prepared samples were characterized with transmission electron microscopy(TEM), scanning electron microscopy(SEM). In TEM image, carbon nanofibers were synthesized on the ACF to form a three-dimensional network. Pt/CNF/ACF was employed as a catalyst for PEMFC. As the ratio of prepared catalyst to commercial catalyst was changed from 0 to 50%, the performance of the mixture of 30 wt% of Pt/CNF/ACF and 70wt% of Pt/C commercial catalyst showed better perfromance than that of 100% commercial catalyst. The unique structure of CNF can supply the significant site for the stabilization of Pt particles. CNF/ACF is expected to be promising support to improve the performance in PEMFC.

• Membrane Journal
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• v.26 no.2
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• pp.146-151
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• 2016

Sulfonated poly (arylene ether sulfone) (SPAES) random copolymers have merits such as high proton conductivity, relatively low production cost, and thermochemical resistance when applied as polymer electrolyte membranes for fuel cells. However, it is difficult to directly employ SPAES copolymers into practical fuel cell membrane applications owing to their low chemical stability and dimensional instability under harsh operation conditions. A plausible solution is to impregnate SPAES copolymers into support films (e.g., electrospun polyimide support) with interconnected pore structures and high thermochemical toughness. In this study, a SPAES copolymer with a swivel group, which induces high free volume for fast ion transport, is chosen as ionomers to prepare pore-filling membranes (PFMs). The feasibility of the resulting membranes is evaluated via membrane characterizations.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.110-112
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• 2006

Membrane electrode assembly (MEA) for polymer electrolyte fuel cell (PEFC) are commonly prepared in the research laboratory by spraying, screen-printing and brushing catalyst slurry onto membrane or other support material like carbon paper or polyimide film in a batch style. These hand applications of the catalyst slurry are painstaking process with respect to precision of catalyst loading and reproducibility. It has been generally mentioned that the adoption of continuous process is very helpful to develop the reliable product. In the present work, we report the results of using continuous type coater with doctor-blade to coat catalyst slurry for preparing the MEA catalyst layers In a faster and highly reproducible fashion. We show that while expectedly faster than batch style, the machine coater requires the use of slurry of appropriate composition and a properly selected transfer decal material in order to achieve superior MEA plat lnw loading reproducibility. To make highly viscous catalyst slurry that is imperative for using coater, we use 40wt.% Nafion solution and minimize the content of organic solvent. And the choice of proper high surface area catalyst is important in the viewpoint of making well-dispersed slurry. After catalyst coating onto the support material, we transferred the catalyst layer to both sides of Nafion membrane by hot-pressing In this case, the degree of transfer was Influenced by hot-pressing condition including temperature, pressure, and time. To compare the transferring ability, we compared so many films and detaching papers. And among the support, polyethylene terephthalate(PET) film shows the prominent result.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.3
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• pp.223-229
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• 2013

Polymer Electrolyte Membrane Fuel Cell (PEMFC) is a power generation system to convert chemical energy of fuels and oxidants to electricity directly by electrochemical reactions. As a catalyst support for PEMFCs, carbon black has been generally used due to its large surface area and high electrical conductivity. However, under certain circumstances (start up/shut down, fuel starvation, ice formation etc.), carbon supports are subjected to serve corrosion in the presence of water. Therefore, it would be desirable to switch carbon supports to corrosion-resistive support materials such as metal oxide. $TiO_2$ has been attractive as a support with its stability in fuel cell operation atmosphere, low cost, commercial availability, and the ease to control size and structure. However, low electrical conductivity of $TiO_2$ still inhibits its application to catalyst support for PEMFCs. In this paper, to explore feasibility of $TiO_2$ as a catalyst support for PEMFCs, $TiO_2$ nanofibers were synthesized by electrospinning and calcinated at 600, 700, 800 and $900^{\circ}C$. Effects of calcination temperature on crystal structure and electrical conductivity of electrospun $TiO_2$ nanofibers were examined. Electrical conductivity of $TiO_2$ nanofibers increased significantly with increasing calcination temperature from $600^{\circ}C$ to $700^{\circ}C$ and then increased gradually with increasing the calcination temperature from $700^{\circ}C$ to $900^{\circ}C$. It was revealed that the remarkable increase in electrical conductivity could be attributed to phase transition of $TiO_2$ nanofibers from anatase to rutile at the temperature range from $600^{\circ}C$ to $700^{\circ}C$.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.7-12
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• 2024

The durability of the catalyst support has a significant effect on the durability of proton exchange membrane fuel cells (PEMFC). The accelerated durability evaluation of the catalyst support is performed at a high voltage (1.0 to 1.5 V), and the catalyst and ionomer binder in the catalyst layer are also deteriorated, hindering the evaluation of the durability of the support. The existing protocol (DOE protocol) was improved to find conditions in which the support, which is a durability evaluation target, deteriorates further. A protocol (MDOE) was developed in which the relative humidity was lowered by 35% and the number of voltage changes was reduced. After repeating the 1.0 ↔ 1.5 V voltage change cycle, the catalyst mass activitiy (MA), electrochemical active area (ECSA), electrical double layer capacity (DLC), Pt dissolution and particle growth were analyzed. Reaching 40% reduction in mass activity, the MDOE protocol took only 500 cycles, reducing the number of voltage changes compared to the DOE method and increasing the degradation of the carbon support by 50% compared to the DOE protocol.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.642-642
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• 2013

Graphene, two dimensional single layer of carbon atoms, has tremendous attention due to its superior property such as high electron mobility, high thermal conductivity and optical transparency. Especially, chemical vapor deposition (CVD) grown graphene has been used as a promising material for high quality and large-scale graphene film. Unfortunately, although CVD-grown graphene has strong advantages, application of the CVD-grown graphene is limited due to ineffective transfer process that delivers the graphene onto a desired substrate by using polymer support layer such as PMMA(polymethyl methacrylate). The transferred CVD-grown graphene has serious drawback due to remaining polymeric residues generated during transfer process, which induces the poor physical and electrical characteristics by a p-doping effect and impurity scattering. To solve such issue incurred during polymer transfer process of CVD-grown graphene, various approaches including thermal annealing, chemical cleaning, mechanical cleaning have been tried but were not successful in getting rid of polymeric residues. On the other hand, lithographical patterning of graphene is an essential step in any form of microelectronic processing and most of conventional lithographic techniques employ photoresist for the definition of graphene patterns on substrates. But, application of photoresist is undesirable because of the presence of residual polymers that contaminate the graphene surface consistent with the effects generated during transfer process. Therefore, in order to fully utilize the excellent properties of CVD-grown graphene, new approach of transfer and patterning techniques which can avoid polymeric residue problem needs to be developed. In this work, we carried out transfer and patterning process simultaneously with no polymeric residue by using a metal etch mask. The patterned thin gold layer was deposited on CVD-grown graphene instead of photoresists in order to make much cleaner and smoother surface and then transferred onto a desired substrate with PMMA, which does not directly contact with graphene surface. We compare the surface properties and patterning morphology of graphene by scanning electron microscopy (SEM), atomic force microscopy(AFM) and Raman spectroscopy. Comparison with the effect of residual polymer and metal on performance of graphene FET will be discussed.

• Polymer(Korea)
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• v.29 no.5
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• pp.501-507
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• 2005

Small intestinal submucosa (SIS) had been widely used as a biomaterial without immune rejection responses. SIS sponges prepared by crosslinking with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). SIS powders dissolved in $3\%(v/v)$ acetic acid aqueous solution for 48hrs and freeze-dried. EDC solution ($H_2O$ : ethanol = 5 : 95) as a crosslink agent was used in concentration of 100mM. In vitro, rat-BMSCs seeded in SIS sponges and induced the osteogenesis for 28 days. We have characterized the osteogenic potential of rat-BMSCs in SIS sponges by alkaline phosphatase activity(ALP), n assay, SEM and RT-PCR for osteogenic phenotype. In SEM, all morphology of SIS sponges was regular and showed interconnected pore structure. By RT-PCR analysis, we observed type I collagen expression. These results demonstrate osteogenic differentiation of rat-BMSCs. In conclusion, we confirmed that the morphology of surface, cross-section, and side of SIS sponges were highly porous with good interconnections between each pores, which can support the surface of cell growth, proliferation, and differentiation. This result indicates that SIS sponge is useful for osteogenesis of BMSCs.