A study on the photocatalytic properties of Ti-MCM-41 catalysts synthesized by two different methods of Ti incorporation

학위논문(석사) - 한국과학기술원 : 생명화학공학과, 2002.2, [ viii, 79 p. ]한국과학기술원 : 생명화학공학과

그래핀과 금속나노와이어 하이브리드를 이용한 고효율 그래핀 박막 제작에 관한 연구

학위논문(박사) - 한국과학기술원 : 생명화학공학과, 2014.8, [ viii, 96 p. ]Graphene is one of the most promising nanomaterials used in the fabrication of flexible transparent conductive films owing to its high charge carrier mobility of up to 200,000 cm2/Vs, its flexibility, and its high optical transparency. Despite intensive research efforts in this field, the conductivities of graphene films reported thus far remain very low, and the films are not yet suitable for replacing the transparent conducting films currently implemented in optoelectronic flexible foldable devices. In this study, the fabrication of highly efficient transparent conducting graphene films is demonstrated by hybridization with metal nanowires. Chemical vapor deposition (CVD) grown graphene films are hybridized with silver nanowires (AgNWs) below percolation threshold to improve their electrical properties and understand the role of AgNWs in polydomain graphene. Combination of chemical doping and hybridization with silver nanowires is performed to enhance significantly the conductivity of graphene films. Solution-processable reduced graphene oxide (RGO) films are hybridized with low density AgNWs to reduce the sheet resistance of RGO films without a little change of transmittance. Firstly, we demonstrate that the presence of a few one-dimensional (1D) metallic nanowires can significantly enhance the electrical conductance of a graphene film. Studies of the film’s optical birefringence, field-effect transistor (FET) transport properties, Raman spectra, and electrical resistance clearly showed that the improvements in the graphene film electrical conductance properties upon the addition of silver nanowires (AgNWs) did not result from the chemical doping properties of the AgNWs, but rather due to the connections among the domains in the graphene film facilitated by the AgNWs. The electrical conductance of the polydomain graphene was dramatically enhanced by more than 30% in the presence of the AgNWs. Thermal annealing of the graphene?AgNW hybrid films further enhan...한국과학기술원 : 생명화학공학과

4-펜텐-1,2,3-트리올의 입체선택적인 아민화 반응과 이를 이용한 (-)-아니 소마이신과 (+)-폴리옥사믹산의 합성

학위논문(석사) - 한국과학기술원 : 화학과, 1996.2, [ iii, 53 p. ]The double bond of (2S, 3S)-4-penten-1,2,3-triol 28, which was readily prepared from dimethyl L-tartrate in 67% overall yield, was iodoaminated stereoselectively by treating its tris(trichloroacetimidate) with iodine monobromide. Also that of (2R, 3S)-4-penten-1,2,3-triol 84, which was produced from lactone 87 in 68% overall yield, was functionalized into amino iodide stereoselectively by cyclizing its tris(trichloroacetimidate) with iodine. After acidic hydrolysis of the cyclized products followed by protection as t-butyl carbamate, the former and the latter stereoselectivity were determined to be 37: 1 and 38: 1 in favor of (2S, 3S, 4S)- and (2R, 3S, 4S)-4-amino-5-iodo-1,2,3-triol, respectively. Since (-)-anisomycin 30 and (+)-polyoxamic acid 31 contain the fucntional groups of carbamate 29, their syntheses were accomplished efficiently from 29. Carbamate 29 was converted into triol 112 via its protection as acetonide, aziridine formation and cuprate reaction. Cyclization of 112 into pyrrolidine 104 proceeded smoothly under Mitsunobu conditions in the presence of PPTS. The adjustment of its functional groups established the synthesis of (-)-anisomycin 30. Monosilylation followed by acetonide formation gave iodide 116. Treatment of 116 with acetate generated oxazolidinone, of which protection and hydrolysis provided alcohol 119. The synthesis of (+)-polyoxamic acid 31 was completed by oxidation of 119 followed by acidic hydrolysis.한국과학기술원 : 화학과

FR901483의 합성에 관한 연구와 N-아세틸뉴라민산의 합성, 라소놀라이드 A의 합성연구

학위논문(박사) - 한국과학기술원 : 화학과, 2000.2, [ vi, 163 p. ]Total synthesis of immunosuppressant FR901483 was attempted from the known cyclohexenone 30 via two synthetic approaches. In the first synthetic pathway, construction of piperidine ring was intended using 109-110,144-146 and 149. Oxazolines 88 and 141, possessing the requisite chiral amino group were obtained from the corresponding allylic alcohols 87a and 140 by iodine-promoted amidation, respectively. But electrophile-induced cyclization of 109-113, 144 and 146 or intramolecular 1,4-addition of amino group to the conjugated ester group in 144-146 and 149 did not give the desired piperidine compounds. Intramolecular amidation of allylic alcohol 157b afforded the undesired pyrrolidine compound 159b. In the second synthetic approach, the tertiary amino group was introduced by intramolecular cyclization of 175 and trichloroacetimidate prepared from 164 to provide the incorrect stereochemistry. Although the desired stereochemistry could be obtained with amidine 189 and oxazolidinone 193, hydrolysis of the generated cyclic urea failed. Synthesis of N-acetylneuraminic acid was accomplished from non-carbohydrate source using stereoselective phenylselenoamidation and dihydroxylation as key steps. Phenylselenonium ion-induced amidation of trichloroacetimidate derived from allylic alcohol 300a produced oxazoline 302. To achieve high diastereoselective dihydroxylation, oxazoline 302 was converted into oxazolidinone 305d, of which 2,4,6-trimethylbenzyl protecting group was installed because of its stability to subsequent basic hydrolysis. After transformation of trimethylbenzyl ether 305d to (-keto ester 244, its acidic hydrolysis furnished N-acetylneuraminic acid. The synthesis of macrocyclic lasonolide A was examined. In the first approach, formation of the ester bond was accomplished under Yamaguchi conditions between alcohol 337 and acid 338. But intramolecular Stille coupling of the resulting ester 336 was unsuccessful due to decomposition of vinyltin group in 337. A...한국과학기술원 : 화학과