Vapor-Phase Synthesis of Two-Dimensional Layered Gallium Chalcogenide Crystals

MasterThere has been rising interest in exploring two dimensional (2D) layered materials for future electronics and optics. Especially, atomically thin 2D materials exhibit new physical properties, compared with their bulk counterparts. Because of these features, 2D materials have the potentials to apply to next generation nanoelectronic devices. However there is a bottleneck for the application, which is a large size 2D material. There has been releasing a number of reports about large area 2D material’s growth, such as graphene, h-BN, TMDCs (MoS2, WSe2, NbSe2, TaS2, etc). However the research of 2D gallium chalcogenide is rarely reported and there is no report about growth of 2D gallium sulfide atomic layer. It is also 2D layered materials and its common formula is MX (M=Ga, X=S, Se, Te). In single layer, X-M-M-X are strongly bonded by covalent forces but each of layers are weakly bonded between neighbor layers by van der Waals forces. Recently, some groups prove that atomic layer Gallium chalcogenides have large band gap and exhibit fast response, high photoresponsivity, external quantum efficiency and good ON/OFF current ratio. So it is promising materials for application in high performance photodetectors, gas sensors and optoelectronic devices. For these applications, we synthesize large area gallium chalcogenide single layer films and various crystals, which have different thickness from few hundred nanometer to single layer, directly on SiO2/Si substrate using vapor phase synthesis. The gallium chalcogenides, synthesized from pure gallium and sulfur or selenium precursors, are characterized using raman spectroscopy and AFM depending on their thickness. From TEM, SEM analysis, we recognize the crystallinity, which shows the uniform single crystalline. Galliuim chalcogenide FET shows n-type semiconductor characteristic in GaS, p-type semiconductor characteristic in GaSe and similar electrical properties reported before. Our synthesis method can be used potentially for the synthesis of other 2D metal monochalcogenides and broaden the building blocks for the fabrication of 2D electronic and optoelectronic devices and provides the possibility of 2D gallium chalcogenide in applications

최인훈 소설의 이데올로기비판 담론 연구

학위논문(석사)--서울대학교 대학원 :국어국문학과 국문학전공,1998.Maste

Effects of rosiglitazone on SHBG, PPAR-γ gene, adiponectin & IL-6 in polycystic

의과학과/박사[한글] 다낭성난소증후군(polycystic ovary syndrome; PCOS)은 만성적인 무배란과 고안드로겐혈증을 특징으로 하며, 가임기 여성의 6-10%에서 발생하는 가장 흔한 여성 불임의 원인일 뿐 아니라, 젊은 여성에서 가장 흔한 내분비계 질환으로, PCOS 여성들의 50-80%에서 비만하고 다양한 정도의 인슐린 저항성을 보이며, 이러한 인슐린 저항성에 의해 제2형 당뇨병과 임신성 당뇨병, 고혈압, 이상지질혈증 및 죽상경화증의 위험성이 증가한다. 상당히 복합적인 병인을 가지고 있는 질환으로 인슐린저항성과 이에 따른 고인슐린혈증과 고안드로겐혈증 중 어떤 결함이 일차적 원인인지 확실하지 않으나, 많은 연구 결과들에서 인슐린이 당 수송과는 별도로 난소에 존재하는 인슐린 수용체를 통하여 난소의 안드로겐 생산을 자극하고 간에서 성호르몬 결합글로불린(sex hormone binding globulin: SHBG)을 감소시켜 혈중 유리테스토스테론의 농도를 증가시키면, 이렇게 증가된 안드로겐은 기질로 쓰여 부적절하게 조기에 고에스트로겐 환경을 조성하게 되어 난포의 발달을 억제하고, 미성숙 난포의 퇴화를 유도하는 기전으로 정리 해 볼 수 있겠다. 이러한 병인에 기초하여, 다낭성난소증후군의 치료는 식사요법과 적당량의 운동을 병행한 체중 조절과 인슐린저항성을 호전시키는 metformin이나 thiazolidinedione 계열의 약제를 고려한 각종 임상 연구 결과에서 인슐린 저항성의 개선과 성호르몬의 변화와 월경이상의 개선을 관찰할 수 있었으나, 그 상호 관련성의 실체나 기전에 관한 분자생물학적인 연구는 매우 적은 실정이다. 이에 본 연구에서는 가임기의 다낭성난소증후군 환자를 대상으로 rosiglitazone을 6개월간 투여하면서 신체 계측치, 총지방량, 인슐린 저항성을 나타내는 지표들과 adipocytokine의 혈중 그리고 지방조직에서의 발현 정도를 측정하여 인슐린 저항성의 개선 정도에 따라 배란 양상에 미치는 영향을 분자생물학적 기전의 면에서 알아보고자 하였다. 연세대학교 의과대학 영동세브란스병원 산부인과 외래에 내원하여 다낭성난소증후군으로 진단된 20세에서 35세 사이의 가임기 여성 30명을 대상으로 하여 내분비내과 외래에서 하루 4mg의 rosiglitazone을 6개월간 투여 받았다. 모든 대상 환자는 인위적인 체중 감소 식이 또는 운동 프로그램을 시행하지 않았다. 1개월 간격으로 외래 방문 할 때마다 환자의 신장, 체중, 허리 둘레 및 최종 월경일을 확인하였으며, 치료 전과 3개월 6개월 후에 10시간 이상 금식한 상태에서 채혈과 피하지방조직 생검(mini- subcutaneous liposuction method)을 시행 받았다. adiponectin과 leptin은 방사면역측정법(radioimmunoassay, RIA)으로 TNF-α와 IL-6는 효소 이용면역측정법(enzyme-linked immunosorbent assay, ELISA)으로 측정하였으며, 지방조직의 PPAR-γ, adiponectin, TNF-α, leptin의 발현 정도는 Northern blot analysis를 이용하여 측정하였다. SPSS 프로그램(SPSS/11.0)을 이용하여, Students paired & unpaired t-test, ANOVA test, Pearson linear correlation 및 multiple regression analysis를 통해 분석하였다. 대상 여성 30명 중에서 20명이 6개월간의 약물 복용 및 검사를 이행하였으며, 초반 3개월 중에 5명, 후반 3개월 중에 5명이 불순응으로 인하여 마치지 못하였다. rosiglitazone 6개월 치료 후에 체중(1.0kg, 2.1%), BMI (0.7kg/m2, 2.2%), 체지방량(0.5kg, 5.1%) 및 허리둘레는 증가하였으며, 혈장 인슐린, HOMA-IR score 및 유리지방산은 치료 3개월 후에 의미있게 감소하였다(각각 7.4 vs. 5.5uU/mL, p<0.05, 1.6 vs. 1.2, p<0.05, 595.38 vs. 394.58 meq/L, p<0.05). 또한, 치료 3개월 후에 혈장 adiponectin(6.7 vs. 15.1ug/mL, p<0.01)과 지방조직의 PPAR-γ gene(0.4 vs. 0.7, p<0.05)의 발현이 의미있게 증가하였다. rosiglitazone 치료 평균 2.6개월(77.4일) 후에 21명(70%)의 환자에서 월경 회복을 관찰할 수 있었으며, 치료 3개월 후에 혈청 성호르몬 결합글로불린(36.4 vs. 42.4nmol/L, p<0.01)의 증가와 6개월 후에 유리테스토스테론(2.2 vs. 1.7pg/mL, p<0.05)의 감소가 통계학적 의의를 보였다. rosiglitazone 6개월 투여 후 HOMA-IR score가 50% 이상 감소한 군(IS)과 50% 미만 감소한 군(IR)으로 구분하여 IS군 모두(100%)에서 월경을 회복하였으며, IR군에서는 53%만이 월경 회복 소견을 보였고, rosiglitazone 3개월 투여 후 HOMA-IR의 감소와 SHBG의 증가로 의미있는 인슐린 저항성 개선 이후에 6개월 째 유리테스토스테론이 의미있는 감소 소견을 보여 고안드로겐혈증보다는 인슐린 저항성이 다낭성난소증후군의 일차적인 병인임을 확인할 수 있었다. 6개월간의 인슐린 저항성 개선 정도에 따라 두 군(IS군: IR군)으로 분류한 결과, Δ HOMA-IR score(-63.57, 38.99%, p<0.05), Δ SHBG(72.73, 11.88%, p<0.01), Δ free T(-63.79, 9.90%, p<0.01)에서 의미 있는 차이를 보였다. 한편, IR군을 월경 회복 여부에 따라 세분하여 6개월간의 변화량을 관찰한 결과 무월경군에서 오히려 ΔHOMA- IR의 개선과 ΔPPAR-γ gene의 발현 감소 및 ΔSHBG의 감소 소견을 보이고 있어 예상과 다른 HOMA-IR score에 대해서 보다는 SHBG 변화량에 대한 다변량회귀분석을 시행하여, 지방 조직 Δ PPAR-γ gene 발현의 변화(β1=0.31,p<0.05)와 양의 상관관계, 혈장 Δadiponectn 변화(β2=0.30, p<0.05)와 양의 상관관계 및 혈장 Δ leptin의 변화(β3= -0.50, p<0.01)와는 음의 상관관계를 구할 수 있었다. 인슐린 저항성 개선 정도에 따른 두 군(IS군: IR군) 간에 adipocytokines의 변화량은 의미있는 차이를 보이지 않아, 각 인자의 변화량 간의 상관관계를 관찰하였을 때, adiponectin은 6개월간의 rosiglitazone투여 후에 그 농도가 의미있게 증가하였으며, 치료 전 농도는 체지방량, 허리둘레 및 HOMA-IR score와 음의 상관관계, SHBG와 양의 상관관계를 보이다가, rosiglitazone 투여 이후에는 그 관계가 역전되어 6개월 변화량은 체지방량 변화 %와 체질량지수 변화 %와 양의 상관관계, 유리 지방산 변화 %와 음의 상관관계를 보였으며, 오히려 IR군에서 높은 경향을 보이고 있어, 다낭성난소증후군 환자에서 adiponectin의 조절은 인슐린저항성 자체에 의해서 결정되지 않을 수도 있음을 유추하고 보상적인 반응의 맥락에서 이해할 수도 있겠다. IL-6는 6개월의 rosiglitazone 치료 후에 그 농도가 감소하는 경향을 보여주었으며, 치료 전 농도는 다른 인자와의 의미있는 관계를 보이지 않다가 rosiglitazone 투여 후 6개월 변화량은 오히려 HOMA-IR 변화량과 유리 지방산 변화량과 의미있는 음의 상관관계를 보였는데, IL- 6의 감소는 전반적으로는 인슐린 저항성의 개선에 기여하면서 지방분해를 유발하여 유리지방산의 에너지 이용을 촉진하는 양면성이 있어서 유리지방산의 감소에 따라 IL-6가 증가하며 증가된 IL-6는 난포의 면역 반응을 유발 하는데, 일부분 기여 할 수도 있음을 유추할 수 있겠다. 치료 전 임상적 특성을 살펴보았을 때 인슐린 저항성이 크게 개선되지 않은 IR군에서 오히려 체질량지수(26.62, 22.62kg/m2, p<0.05), 체지방량, 허리 둘레, HOMA-IR score(2.69, 1.20, p<0.05) 및 혈청 leptin 농도가 의미있게 낮았으며, 혈청 adiponectin(4.83, 7.31ug/mL, p<0.05)은 증가되어 있어 외국의 보고와 달리 우리나라에서는 비만하지 않은 다낭성난소증후군 환자에서 약물에 대한 반응이 떨어졌으며, IR군에서 월경 회복 여부에 따라 세분하여 월경이 회복되지 않은 군에서 치료 전 체질량지수가 역시 낮은 경향을 보였으며, PPAR-γ gene 발현이 높은 경향을 보였다. Rosiglitazone을 중등도 비만인에게 최소한 3개월 투여하면서 HOMA-IR score의 평균 10% 이상 감소 소견과 SHBG의 평균 40% 이상 증가 소견이 월경 회복을 예측하는 인자로 이용할 수 있음을 본 연구를 통하여 제시할 수 있으나, 좀 더 대규모의 연구가 필요하겠으며, 비만하지 않은 다낭성난소증후군 환자의 병인에 대해서도 좀 더 다각적인 연구가 필요하겠다. [영문]Characterized by chronic anovulation and hyperandrogenism, Polycystic Ovary Syndrome(PCOS) is a common endocrine disorder, affecting 6% to 10% of women of reproductive age. At least 50% of women with PCOS are obese. Insulin resistance and compensatory hyperinsulinemia are intrinsic features of the disorder. PCOS is also associated with an increased risk for type 2DM, hypertension, dyslipidemia and cardiovascular disease. The etiology of PCO is complex and incompletely understood. Accumulating data conclude that hyperinsulinemia and hyperandrogenemia are hormonal abnormalities, which disturb ovarian function. Contrary to the classical target tissues (muscles, liver, adipose tissues) of insulin action that have become resistant to insulin, the ovaries remain responsive to insulin throughout the interaction of its own receptor. So, excess insulin is capable of stimulating steroidgenesis and excessive androgen from the theca cell system. Reduction of hepatic sex hormone binding globulin (SHBG) production by insulin and the increase of unbound fraction of testosterone constitutes an important additional mechanism. This excess of androgens substrate leads to prematurely hyperestrogenic milieu in the developing follicle. It brings about inappropriate advancement of granulosa cell differentiation causing arrest of the follicle growth. Reduction of hyperinsulinemia appears of to be the key factor for the treatment of PCO. So, the use of insulin sensitizing drug seems reasonable. However, the study on the molecular pathogenesis between insulin resistance and ovulatory performance is few, the present study was thus undertaken to evaluate the effects of rosiglitazone on adipocytokines, PPAR-γ gene expression, SHBG and hyperandrogenism in polycystic ovary syndrome to the degree of impro vement of insulin resistance. Thirty women between ages of 20 and 35 yr, diagnosed PCOS, were recruited from the outpatient clinics of the Yonsei University Hospital, Korea. Each subject took a 4mg tablet rosiglitazone daily for 6 months. Subjects were put on a weight-maintaining diet and were allowed ad libitum activity without new exercise program. Body weight, height, waist circumference, menstrual pattern and side-effects were measured at each monthly out-patient visit. Blood sampling and abdominal subcutaneous adipose tissue biopsy through percutaneous mini-liposuction method were taken every 3 month. The expressions of PPAR-γ gene and adipocytokines of adipose tissue were measured by Northern blot analysis. The SPSS package was used for statistical analyses. Twenty subjects completed the protocol. Ten subjects (5 during early 3 months & 5 during later 3 months) declined to participate because they didn''t comply with the test procedures. The mean weight(1.0kg, 2.1%), BMI(0.7kg/m2, 2.2%), total body fat(0.5kg, 5.1%) and waist circumference of subjects, who were treated with 6 months-rosiglitazone, tended to increase comparing the values at baseline. During 3 month treatment, there were a significant decrease in insulin, HOMA score(1.6 vs. 1.3, p50% reduction to baseline group(IS, n=5) and HOMA <50% reduction to baseline group(IR, n=15) during 6months. Regular menstration was resumed in 5 subjects(100%) of IS group and 8 subjects(53%) in IR group. There were the significant decrease of free testosterone at 6 month and significant changes of HOMA and SHBG from 3 month. This showed insulin resistance was a primary role in this study rather than hyperandrogenemia. By unpaired t-test, % changes of parameters between 6 month and basal level were compared in 2 groups(IS: IR). There were significant differences in Δ HOMA IR(-63.57, 38.99%, p<0.05), Δ SHBG(72.73, 11.88%, p<0.01) and Δ free T(-63.79, 9.90%, p<0.01). Furthermore classifying IR group into IR-MR(menstraion resumed) and IR-MNR(menstraion not resumed), ΔHOMA-IR score, ΔPPAR gene expression and ΔSHBG decreased more in IR-MNR group. ΔHOMA-IR decrease means improvement of insulin resistance. The number of available samples is not enough to prove the effect of ΔPPAR gene expression. Thus ΔSHBG was a meaningful marker of insulin resistance and ovulatory performance in IR group. SHBG was negatively correlated with BMI, total body fat % and waist circumference and positively correlated with adiponectin. By multiple regression analysis, the following equation were extracted. ΔSHBG= -22.34+0.31 ΔPPAR-γ gene±0.30 Δadiponectin+(-0.50) Δleptin / (r=1.00, β1=0.31, p< 0.05, β2=0.30, p<0.05, β3= -0.50, p<0.01). There were no significant differences in adipocytokines(adipnectin, IL-6, TNF-α, leptin) between IS and IR group. So correlations in changes between 6 month and basal concentration of parameters were observed. There was a significant increase in adiponectin after 6months rosiglitazone treatment. Basal adiponectin concentration was negatively correlated with total body fat, waist circumference and HOMA-IR score and positively correlated with SHBG. Inversely,Δadiponectin concentration during rosiglitazone treatment was positively correlated with Δtotal body fat and ΔBMI and negatively correlated with Δfree fatty acid. Rather, Δadiponectin concentration tended to be higher in IR group. In the control of adiponectin levels in PCOS women, insulin sensitivity per se is unlikely to play a pivotal role. The levels of adiponectin might be the expression of a counter-regulatory or compensatory response. There was a decreasing tendency in IL-6 after 6M rosiglitazone treatment. Rather, ΔIL-6 concentration was negatively correlated with ΔHOMA-IR and Δfree fatty acid. IL-6 appears to increase energy expenditure at both the level of the CNS and periphery and are involved in follicular development as proinflammatory cytokines. As free fatty acid decreases, IL-6 increases. So the increase of ΔIL-6 might be involved in immune reaction of follicular development. To determine which factors are predictive of response to treatment, basal characteristics between IS:IR group were compared. Patients in IR group were less obese(BMI: 26.6, 22.6kg/m2, total body fat %: 35.6, 30.7%, leptin: 13.3, 5.8ng/mL, p<0.05) and had higher adiponectin levels(4.83, 7.31ug/mL, p<0.05) than IS group. Further study will be needed in the pathophysiology of non obese PCO patients. In summary, rosiglitazone therapy resulted in improvements in insulin sen- sitivity and ovulation in PCOS women. These changes occurred with minimal weight gain. The changes of adipose tissue PPAR-γ gene expression, plasma adiponectin, free fatty acid, IL-6, SHBG, and free testosterone may be the metabolic mediator of these results. A more complete understanding of the pathophysiology of PCOS will await direct studies of the effects of exogenous adiponectin and IL-6 on the reproductive axis of women, including those of PCOS.ope

향상된 전기화학적 특성을 가진 얼음 표면에서 합성한 전도성 고분자 연구

DoctorConducting polymers have been studied extensively in the past few decades due to various advantages such as high electrical conductivity, optical transparency, chemical stability, flexibility, and low cost. Recently, research to improve the electrical properties of conducting polymers for high performance in electronic devices are intensively conducted. Various studies have been reported to improve the conductivity of conducting polymers by controlling various factors such as the type of dopant, doping level, and conjugate length in the synthesis of conducting polymers. More recently, improving conductivity through the formation of nanostructure of conducting polymers has been attracted great attention. In order to synthesize conducting polymer nanostructures, various methods using hard templates and soft templates as well as conventional chemical oxidation polymerization have been reported. In particular, among them, the two-dimensional nanostructure has become important because it is advantageous for high-density integration of next-generation electronic devices to exhibit improved electron transport properties. Nevertheless, the synthesis of conducting polymers having two-dimensional nanostructure with high electrical conductivity have mainly based on methods using graphene oxide as templates. However, this approach showed difficulty in removing the template after synthesis, which made hard to obtain pure conducting polymer. It was also difficult to obtain reliable electrical properties over a large area due to the non-uniform distribution of functional groups of graphene oxide. To overcome this limitation, I synthesized conducting polymers using the ice surface as a template, where the ice template is easily removed in the next step. Consequently, pure two-dimensional conducting polymer nanosheets with high conductivity were obtained. In this dissertation, the role of crystallinity of the ice surface on the ice-templated conducting polymers are investigated, and new strategies for utilizing the ice-templated conducting polymers as the electrocatalyst, the virus filtration membrane are proposed. Chapter 1 provides an overall overview of ice-assisted chemistry for synthesizing functional materials using ice, and introduces current research trends on conducting polymers prior to introducing ice-templated conducting polymers. Research on conducting polymer-metal composites and porous conducting polymers are also included. Furthermore, research motivation and objectives of this dissertation are presented to develop the current research based on ice-assisted chemistry. Chapter 2 covers the study of the nanostructure and electrical properties of the ice-templated conducting polymers, and the study of a role of the crystallinity of the ice surface. Although the recently established ice-templated synthetic method of two-dimensional conducting polymers is evaluated as an environmentally friendly and easy-fabrication technology, the role of the crystallinity of the underlying ice surface remains unclear in determining the physicochemical and electrical properties of conducting polymers. In this study, crystallinity of ice is systematically controlled, and the electrical properties of conducting polymer nanosheets grown on the ice surface and the packing structure of conducting polymer crystals are studied in depth. Intriguingly, the crystallinity of the conducting polymer nanosheets resembled that of the ice surface, and it was confirmed that the higher the crystallinity of ice, the more predominantly anisotropic growth of the conducting polymer nanosheets in the face-on orientation. In addition, it was turned out that highly crystalline conducting polymer nanosheets led to more efficient charge transport due to improved degree of backbone ordering due to the pre-organized aniline moieties on the ice surface and strong polaron delocalization with the extended chain conformations. These results suggest that controlling the crystallinity of ice is simple but effective to control the electrical properties of conducting polymers. Chapter 3 describes the study of conducting polymer-platinum (Pt) nanoparticle composites based on ice-templated conducting polymers. Pt nanoparticles are well known as the most effective electrocatalysts for various electrochemical reactions. However, for commercially available Pt catalyst supported on carbon such as Pt/C catalyst, a high reaction temperature is generally required. And the particle agglomeration cannot be prevented, so that the catalytic activity decreases rapidly over time. Besides, carbon nanostructures such as graphene are even expensive. Thus, in this study, a new approach for the synthesis of uniform, high areal density Pt nanocrystals supported by ice-templated conducting polymers is presented. The key strategy is the use of ice-templated conducting polymers at the air-water interface as a platform to promote the nucleation of platinum. Highly crystalline Pt nanoparticles with a narrow size distribution of about 2.7 nm and a high electrochemically active surface area of 94.57 m2 g-1 were obtained. It showed good durability and excellent carbon monoxide tolerance. This approach suggests potential applications for the production of various other electrocatalysts with enhanced catalytic activity. Chapter 4 covers the study of the synthesis of two-dimensional porous conducting polymer nanosheets synthesized on the ice surface. In this study, the directional freezing is performed to the microplastics-containing solution and subsequently ice-templated synthesis is conducted on this microplastics-containing ice. This process leads to easy removal of microplastics in aqueous solution by detaching the synthesized conducting polymer nanosheets from the ice. The removal efficiency of microplastics was over 97 %. More importantly, while microplastics are being removed, porous two-dimensional conducting polymer nanosheets are synthesized with a solvent treatment process for removing the microplastics from the detached conducting polymer nanosheets. Intriguingly, the size of the pores could be easily tuned depending on the size of the microplastics. Then, porous conducting polymer nanosheets with 100 nm pores were utilized as the virus filtration membranes for coronavirus (SARS-CoV-2). As a result, high rejection rate up to 96.3 % was achieved. This approach is important in that it can remove microplastics in aqueous solution and simultaneously make porous conducting polymers with various pore sizes, which suggests a potential for variety of applications. Chapter 5 provides conclusions and perspectives based on these studies. Through these studies, the role of ice in ice-templated synthesis was investigated in more depth. 2D nanostructure of the ice-templated conducting polymers could be realized owing to the confinement provided by the quasi-liquid layer (QLL) on the ice surface. It was confirmed that the electrical properties and packing structure of the conducting polymers are greatly affected by the crystallinity of ice surface. Moreover, new advanced nanomaterials with high functionality and improved electrochemical properties were synthesized by utilizing ice-assisted chemistry, which showed high potential for application in various fields. Nevertheless, studies on the utilization of QLL on the ice surface are still lacking, which is ascribed to the difficulty in accurate identification and precise control of QLL. Thus, further studies are required to understand and utilize QLL on the ice surface, which may include the in-situ transmission electron microscopy and ultrafast X-ray scattering experiments. Such future studies will contribute to developing new advanced materials and expanding the scope of the ice-templated synthesis to various applications

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