Publications by authors named "Youn Sik Lee"

A linear-shaped small organic molecule (E)-4-(5-(3,5-dimethoxy-styryl)thiophen-2-yl)-7-(5″-hexyl-[2,2':5',2″-terthiophen]-5-yl)benzo[c][1,2,5]thiadiazole (MBTR) comprising a benzothiadiazole (BTD) acceptor linked with the terminal donors bithiophene and dimethoxy vinylbenzene through a π-bridge thiophene was synthesized and analyzed. The MBTR efficiently tuned the thermal, absorption, and emission characteristics to enhance the molecular packing and aggregation behaviors in the solid state. The obtained optical bandgap of 1.

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The majority of the vitamin D that is present in the blood binds to vitamin D binding protein (VDBP) and circulates in the form of a complex (VDBP-Complex). Knowing the level of vitamin D in the body is crucial for vitamin D-related treatments so that the right dosage of vitamin D can be given. In other words, it is essential to distinguish between the protein VDBP and the complex form bound to vitamin D.

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In the semiconductor manufacturing process, metallic contaminants remain on the surface of the silicon wafer, which has a serious effect on the physical and electrical characteristics of the semiconductor device. In particular, silver has high electrical conductivity and large reducibility, and it is not easily removed causing a great deal of damage in small amounts. Therefore, it is important to prevent contamination by lowering the silver ion concentration in the etching agent in the wet etching process.

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In this work, we report a feasible fabrication of NiCoS nanotree-like structures grown from the Ni nanoparticle (NP)-doped reduced graphene oxides (Ni-rGO) by a simple hydrothermal method. It is found that the presence of Ni NPs on the surface of the rGOs initiates growth of the NiCoS nanotree flocks with enhanced interfacial compatibility, providing excellent cyclic stability and rate performance. The resulting NiCoS/Ni-rGO nanocomposites exhibit a superior rate performance, demonstrating 91.

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One-pot synthesis of mixed-valence manganese oxide (MnO)/potassium ion-doped reduced graphene oxide (rGO) composites for efficient electrochemical supercapacitors is introduced. Using manganese nitrate and potassium permanganate as co-precursors for the MnO and by directly annealing the rGO without tedious purification steps, as described herein, MnO/rGO composites with a high specific capacitance of 1955.6 F g at a current density of 1 A g are achieved.

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Although a thiourea-immobilized polystyrene sorbent has been reported to exhibit high Ag sorption capacity (135mg/g), it is not stable under the acidic conditions commonly employed for desorption. In this research, we synthesized novel thiourea-immobilized polystyrene (TA-PS) nanoparticles to be highly acid resistant via a two-step procedure from polystyrene nanoparticles: acetylation and the subsequent immobilization of thiourea. We investigated the influences of pH, contact time, and initial concentration of AgNO solution on the Ag sorption of the polymer nanoparticles and estimated the maximum Ag sorption capacity to be 190±5mg/g at a pH of 6.

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We have synthesized water-soluble polymer, poly[(9,9-bis((6'-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene))-alt-bisphenylfumaronitrile]dibromide (AHF-alt-PFN), the polymer typically obtained by the Suzuki type of polymerization reaction and shows good solubility in methanol. Bulk heterojunction polymer solar cells (BHJ-PSCs) fabricated by using water soluble conjugated polymer and positive (Cs+) and negative (F-, CO2-(3)) charge ions doping as an interfacial layer for poly(3-hexylthiophene):phenyl-C61 butyric acid methyl ester (P3HT:PCBM). We have achieved an enhancement of the short circuit density and power conversion efficiency in solar cell by introducing poly(AHF-alt-PFN) layer between the active layer and the cathode metal.

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Poly N-isopropyl acrylamide (PNI) radically polymerized in aqueous solution in the presence of graphene oxide (GO) can significantly change the properties of the resulting solution from a regular polymer solution to a soft solid with a GO content of only 0.176 wt% (3 wt% with respect to PNI). However, these properties require the presence of both grafting and supramolecular interactions between polymer chains and hydrophilic groups on GO (-OH, -COOH), proven by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction and spectroscopy (XRD) and Raman spectra.

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Reports on the development of polymer adsorbents for microwave-assisted desorption of nonpolar volatile organic compounds (VOCs) are rare. In this study, we synthesized macroporous polymeric adsorbents with hydrophilic methyl pyridinium units for microwave-assisted desorption of nonpolar VOCs. The benzene adsorption and desorption properties of the adsorbents were investigated under both dry and humid conditions.

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To improve the performance of organic solar cells, various methods have been used to increase the light absorbance and electron transfer efficiency or decrease the internal resistance of the device. In this article, red dyes of phosphorescent materials are used to improve the performance of bulk heterojunction organic solar cells based on MDMO-PPV and PCBM. Solar cell devices doped with different red dyes showed higher performances in terms of current, voltage and conversion efficiency than those without red dyes.

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Natural rubber (NR) nanocomposites filled with carbon nanotubes (CNT) and organoclay (O-MMT) were prepared by melt mixing, and their vulcanization, mechanical, thermal and flammability properties were characterized. The obtained results were compared with those of carbon black (CB) and pure NR composites. The incorporation of OC reduced drastically the cure times, when compared with CNT and CB-reinforced compounds.

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Background: The diagnosis of hepatitis C virus (HCV) infection is screened by anti-HCV enzymelinked immunosorbant assay (ELISA) and confirmed by recombinant immunoblotting assay (RIBA) or HCV RT-PCR. We attempted to evaluate the results between anti-HCV ELISA and a qualitative HCV RT-PCR.

Methods: Four hundred and twenty patients who were tested with anti-HCV ELISA and HCV RTPCR, simultaneously, from January 2002 to June 2005 were enrolled in this study.

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Mammalian serine protease HtrA2/Omi has been known as an apoptosis inducer involved inactivation of caspase-dependent as well as caspase-independent cell death. Recent studies with the HtrA2/Omi mutant and knockout mouse models, however, suggested that HtrA2/Omi might play a protective role in neurons. It is important to establish a transgenic mouse model with neuron-specific overexpression of HtrA2/Omi to clarify the physiological function of mammalian HtrA2/Omi in neurons.

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