전기화학적 분석, 자외선-가시광선 분광법 및 주사 터널링 현미경을 이용한 헤테로폴리산 촉매의 산화환원 특성연구

학위논문 (박사)-- 서울대학교 대학원 : 화학생물공학부, 2015. 2. 송인규.Heteropolyacids (HPAs) are polymeric metal-oxide clusters that exhibit the diverse range of structures and compositions. Because of their robust structures and unique redox properties, HPAs have been widely employed as catalysts for several redox reactions. Catalytic oxidations over HPAs have been extensively studied over the past few decades and mixed-addenda HPAs have attracted recent attention due to the variety in stoichiometric combinations and outstanding redox natures. Physicochemical properties and catalytic activity of mixed-addenda HPAs can be easily tuned at molecular level by changing the constituent elements including counter-cation, central heteroatom, or framework addenda atom. Because a number of elements including metals, semimetals, and even non-metals could be incorporated into the HPA frameworks, a number of mixed-addenda HPAs with different structures can be designed as a candidate for promising oxidation catalyst. In this work, several series of transition metal-substituted HPAs were designed and synthesized. They were investigated by several experimental techniques including electrochemical analysis, UV-visible spectroscopy, and scanning tunneling microscopy (STM) in order to elucidate the effect of transition metal-substitution on redox properties and catalytic activities in oxidation catalysis. Furthermore, reliabilities of absorption edge energy and negative differential resistance (NDR) peak voltage as alternative parameters for the reducibility were also examined. First, molybdenum-substituted H6P2W18-xMoxO62 (x=0, 3, 9, 15, 18) Wells-Dawson HPAs were prepared by etherate method to elucidate the effect of molybdenum-substitution on the redox properties and catalytic activity of Wells-Dawson-type tungstophosphates. Electrochemical measurements were conducted to elucidate the redox properties of HPAs. Several tungsten-based redox transitions were observed in the cyclic voltammogram of H6P2W18O62. However, H6P2Mo18O62 exhibited molybdenum-based redox transitions. Interestingly, molybdenum-substituted Wells-Dawson HPAs showed an additional molybdenum-centered redox transition at more positive potential. First electron reduction potentials increased with increasing molybdenum-substitution. UV-visible spectroscopy measurements were conducted to probe the electronic structure of bulk H6P2W18-xMoxO62 (x=0, 3, 9, 15, 18) Wells-Dawson HPAs. Absorption edge energy determined from the linear fit of [F(R∞)•hν]1/2 (Tauc plot) decreased with increasing molybdenum content. Scanning tunneling microscopy (STM) measurements were performed for the further investigation about the local surface electronic structure of H6P2W18-xMoxO62 (x=0, 3, 9, 15, 18) Wells-Dawson HPAs. In STM measurements, two-dimensional self-assembled HPA arrays were observed. Tunneling spectra taken at bright corrugations showed a distinctive current-voltage responses, referred to as negative differential resistance (NDR) phenomenon. NDR peak voltage appeared at less negative voltage with increasing the molybdenum content. Gas-phase oxidative dehydrogenation of ethanol to acetaldehyde was carried out as a model reaction to probe the oxidation catalysis of H6P2W18-xMoxO62 (x=0, 3, 9, 15, 18) Wells-Dawson HPAs. Yield for acetaldehyde (oxidation product) increased with increasing molybdenum content. Among the tested catalysts, H6P2Mo18O62 with the highest reduction potential showed the best catalytic performance. In order to explore the effect of group 5 metal (V and Nb)-substitution on redox properties and catalytic activity of Wells-Dawson-type tungstophosphates. α2-K7P2W17V1O62 and α2-K7P2W17Nb1O62 Wells-Dawson HPAs were synthesized via direct incorporation of transition metal into the mono-lacunary species to yield the selectively-substituted structures. α-K6P2W18O62 and α2-K6P2W17Mo1O62 were also prepared for the comparison. In the electrochemical analysis, molybdenum- and vanadium-substituted Wells-Dawson tungstophosphates showed additional molybdenum- and vanadium-based redox transitions, respectively, at more positive potential. However, niobium-substituted Wells-Dawson tungstophosphates showed significantly shifted redox transitions. First electron reduction potential increased in the order of α2-K7P2W17Nb1O62 α-K6P2W18O62 > α2-K6P2W17Mo1O62 > α2-K7P2W17V1O62. STM images clearly showed the formation of self-assembled and well-ordered HPA arrays on HOPG surface. The trend of NDR peak voltage was also well consistent with that of absorption edge energy. Gas-phase oxidative dehydrogenation of benzylamine was carried out as a model reaction to probe oxidation catalysis. Yield for dibenzylimine (oxidation product) increased in the order of α2-K7P2W17Nb1O62 < α-K6P2W18O62 < α2-K6P2W17Mo1O62 < α2-K7P2W17V1O62. Heteropolytungstates with different central atom, α-HnXW12O40 (X=Co2+, B3+, Si4+, and P5+) Keggin HPAs were prepared to elucidate the effect of central atom on the redox properties and catalytic activity. All α-HnXW12O40 HPAs exhibited well-defined reversible and stepwise tungsten-centered redox transitions during the electrochemical measurements. First electron reduction potential increased in the order of α-H6CoW12O40 α-H5BW12O40 > α-H4SiW12O40 > α-H3PW12O40. The trend of NDR peak voltage was also well consistent with that of absorption edge energy. Among the tested, PO43- anion with smaller negative charge and lager size was the most effective to enhance the reducibility. Another series of heteropolytungstates containing AsO43- as a central unit were also examined to elucidate the effect of transition metal-substitution on the redox properties and catalytic activities of Wells-Dawson-type tungstoarsenates. A series of α-K6As2W18-xMoxO62 (x=0-3) Wells-Dawson HPAs were prepared via direct incorporation of transition metal into the mono-, di-, and tri-lacunary species. In electrochemical analysis, α-K6As2W18O62 exhibited four tungsten-centered redox transitions. However, molybdenum-substituted α-K6As2W18-xMoxO62 (x=1-3) exhibited an additional molybdenum-centered redox transition at more positive potential. First electron reduction potential increased with increasing molybdenum content. Absorption edge energy determined by UV-visible spectroscopy decreased with increasing molybdenum content. It is interesting to note that NDR peak voltage appeared at less negative voltage with increasing molybdenum content. These results are nearly same with the results in the series of H6P2W18-xMoxO62 (x=0, 3, 9, 15, 18). Gas-phase oxidative dehydrogenation of benzyl alcohol was carried out as a model reaction to track the oxidation catalysis. Yield for benzaldehyde (oxidation product) increased with increasing molybdenum content. Furthermore, group 5 metal-substituted α2-K7As2W17V1O62 and α2-K7As2W17Nb1O62 Wells-Dawson HPAs were synthesized via direct incorporation of transition metal into the mono-lacunary species to yield the selectively-substituted structures. α-K6As2W18O62 and α2-K6As2W17Mo1O62 were also prepared for the comparison. In the electrochemical analysis, molybdenum- and vanadium-substituted Wells-Dawson tungstoarsenates showed additional molybdenum- and vanadium-based redox transitions, respectively, at more positive potential. However, niobium-substituted Wells-Dawson tungstoarsenates showed significantly shifted redox transitions. First electron reduction potential increased in the order of α2-K7As2W17Nb1O62 α-K6As2W18O62 > α2-K6As2W17Mo1O62 > α2-K7As2W17V1O62. Gas-phase oxidative dehydrogenation of benzylamine was carried out as a model reaction to track the oxidation catalysis. Yield for dibenzylimine (oxidation product) increased in the order of α2-K7As2W17Nb1O62 < α-K6As2W18O62 < α2-K6As2W17Mo1O62 < α2-K7As2W17V1O62. In summary, several series of transition metal-substituted HPA catalysts with different addenda atoms, central atoms, contents, and structures were prepared, characterized, and applied to the model reactions in order to elucidate the redox properties and catalytic activities in oxidation catalysis. Reliabilities of absorption edge energy and NDR peak voltage as alternative parameters for the redox properties were also examined. It was found that redox properties were easily tunable by changing constituent elements. In addition, it could be concluded that redox properties of HPAs, which is closely related to the electronic structure, play an important role to determine the catalytic activities in the oxidation catalysis and absorption edge energy and NDR peak voltage can be utilized as alternative parameters to estimate the reducibility of HPAs.Chapter 1. Introduction 1 1.1. Heteropolyacids (HPAs) 1 1.2. Characteristics of HPAs 5 1.2.1. General properties and applications 5 1.2.2. Redox properties 10 1.3. Oxidation catalysis over HPAs 13 Chapter 2. Experimental 16 2.1. Mo(VI)-substituted Wells-Dawson-type tungstophosphates 16 2.1.1. Preparation 16 2.1.2. Characterization 17 2.1.2.1. Formation of HPA structure 17 2.1.2.2. Electrochemical analysis 17 2.1.2.3. UV-visible spectroscopy 18 2.1.2.4. Scanning tunneling microscopy 18 2.1.3. Catalytic test (oxidative dehydrogenation of ethanol) 20 2.2. V(V) and Nb(V)-substituted Wells-Dawson-type tungstophosphates 21 2.2.1. Preparation 21 2.2.1.1. Preparation of tungstophosphate (α-K6P2W18O62) 21 2.2.1.2. Preparation of mono-lacunary tungstophosphate (α2-K10P2W17O61) 22 2.2.1.3. Preparation of α2-K7P2W17M1O62 (M=V and Nb) 22 2.2.2. Characterization 24 2.2.2.1. Formation of HPA structure 24 2.2.2.2. Electrochemical analysis 24 2.2.2.3. UV-visible spectroscopy 25 2.2.2.4. Scanning tunneling microscopy 25 2.2.3. Catalytic test (oxidative dehydrogenation of benzylamine) 27 2.3. Keggin-type heteropolytungstates with different central atom 28 2.3.1. Preparation 28 2.3.1.1. Preparation of α-H3PW12O40 and α-H4SiW12O40 28 2.3.1.2. Preparation of α-H5BW12O40 28 2.3.1.3. Preparation of α-H6CoW12O40 29 2.3.2. Characterization 30 2.3.2.1. Formation of HPA structure 30 2.3.2.2. Electrochemical analysis 30 2.3.2.3. UV-visible spectroscopy 31 2.3.2.4. Scanning tunneling microscopy 31 2.4. Mo(VI)-substituted Wells-Dawson-type tungstoarsenates 32 2.4.1. Preparation 32 2.4.1.1. Preparation of α-K6As2W18O62 32 2.4.1.2. Preparation of mono-lacunary tungstoarsenate (α2-K10As2W17O61) 33 2.4.1.3. Preparation of di-lacunary tungstoarsenate (α-K11HAs2W16O59) 33 2.4.1.4. Preparation of tri-lacunary tungstoarsenate (α-Na12As2W15O56) 33 2.4.1.5. Preparation of α-K6As2W18-xMoxO62 (x=1-3) 34 2.4.2. Characterization 35 2.4.2.1. Formation of HPA structure 35 2.4.2.2. Electrochemical analysis 35 2.4.2.3. UV-visible spectroscopy 36 2.4.2.4. Scanning tunneling microscopy 36 2.4.3. Catalytic test (oxidative dehydrogenation of benzyl alcohol) 38 2.5. V(V) and Nb(V)-substituted Wells-Dawson-type tungstoarsenates 39 2.5.1. Preparation 39 2.5.1.1. Preparation of α2-K7As2W17V1O62 39 2.5.1.2. Preparation of α2-K7As2W17Nb1O62 39 2.5.2. Characterization 41 2.5.2.1. Formation of HPA structure 41 2.5.2.2. Electrochemical analysis 41 2.5.2.3. UV-visible spectroscopy 42 2.5.3. Catalytic test (oxidative dehydrogenation of benzyl amine) 43 Chapter 3. Results and Discussion 44 3.1. Mo(VI)-substituted Wells-Dawson-type tungstophosphates 44 3.1.1. Formation of HPA structure 44 3.1.2. Characterization 50 3.1.2.1. Cyclic voltammetry 50 3.1.2.2. UV-visible spectroscopy 53 3.1.2.3. Scanning tunneling microscopy 56 3.1.3. Catalytic test 64 3.2. V(V) and Nb(V)-substituted Wells-Dawson-type tungstophosphates 67 3.2.1. Formation of HPA structure 67 3.2.2. Characterization 74 3.2.2.1. Cyclic voltammetry 74 3.2.2.2. UV-visible spectroscopy 76 3.2.2.3. Scanning tunneling microscopy 79 3.2.3. Catalytic test 85 3.3. Keggin-type heteropolytungstates with different central atom 89 3.3.1. Formation of HPA structure 89 3.3.2. Characterization 93 3.3.2.1. Cyclic voltammetry 93 3.3.2.2. UV-visible spectroscopy 96 3.3.2.3. Scanning tunneling microscopy 98 3.4. Mo(VI)-substituted Wells-Dawson-type tungstoarsenates 101 3.4.1. Formation of HPA structure 101 3.4.2. Characterization 107 3.4.2.1. Cyclic voltammetry 107 3.4.2.2. UV-visible spectroscopy 109 3.4.2.3. Scanning tunneling microscopy 111 3.4.3. Catalytic test 117 3.5. V(V) and Nb(V)-substituted Wells-Dawson-type tungstoarsenates 119 3.5.1. Formation of HPA structure 119 3.5.2. Characterization 125 3.5.2.1. Cyclic voltammetry 125 3.5.2.2. UV-visible spectroscopy 127 3.5.3. Catalytic test 132 Chapter 4. Conclusions 134 Bibliography 139 초 록 146Docto

Consecutive Jailed- and Kissing-Corsair Technique: Side Branch Protection and Dilation during Stent Implantation

The primary concern in percutaneous coronary intervention for bifurcation lesions is occlusion of a side branch after stenting of a main branch, especially in high-risk patients. We describe a novel technique, consecutive jailed- and kissing-Corsair technique, using a Corsair microcatheter for protection of side branches in bifurcation lesions.ope

Rapid Regrowth of Left Atrial Myxoid Fibrosarcoma Considered to be Myxoma after Surgical Resection

Malignant primary cardiac tumors are rare with the most common type among them being sarcomas. However, a myxoid sarcoma in the heart is very rare and differentiating it from from cardiac myxoma is often difficult. Here, we report a case of rapid regrowth of a left atrial tumor after surgical resection that was finally diagnosed as cardiac myxoid fibrosarcoma. An 82-year-old man, who underwent resection of a cardiac tumor 3 months ago, presented with severe dyspnea and peripheral edema. He was diagnosed with a mitral valve obstruction due to the regrowth of a huge left atrial tumor. The patient had a second resection and the resected tumor was finally diagnosed as myxoid fibrosarcoma.ope

Constrictive Pericarditis Long after a Gunshot Wound

Constrictive pericarditis is an uncommon post-inflammatory disorder characterized by a variably thickened, fibrotic, and frequently calcified, pericardium. Etiology of the constriction can occur for many reasons. Although foreign bodies are not the common cause of constrictive pericarditis, the long-term presence of foreign bodies, like bullets, is presumed to cause chronic constrictive pericarditis even after a very long asymptomatic period. A 69-year-old patient with atrial flutter was admitted to the hospital. A cardiac computed tomography showed a bullet located adjacent to the right atrium. The transthoracic echocardiography showed a thickened pericardium and septal bouncing motion, which were compatible with constrictive pericarditis. The history of the patient revealed an injury by gunshot during the Korean War in 1950. Radiofrequency ablation of the atrial flutter was performed, and after ablation, the bullet was removed surgically. The patient was discharged home after surgery without complications.ope

Metallic foreign body in heart mimicking moderator band

A foreign body in heart is rare, but it is more frequently encountered than the past as iatrogenic causes are increasing. Clinicians should be aware that foreign body could be mistaken for normal structure of heart. In order for accurate diagnosis, multi-imaging modalities should be used for information of exact location, mobility and hemodynamic effects. A decision to intervene should be made based on potential harms harbored by foreign bodies. Endovascular retrieval should be considered as an option. However, when fatal complications occur or when foreign bodies are embedded deeply, a surgical removal should be attempted.ope

Two Cases of Mushroom Poisoning by Podostroma Cornu-Damae

Podostroma cornu-damae is a rare fungus that houses a fatal toxin in its fruit body. In this case report, two patients collected and boiled the wild fungus in water, which they drank for one month. One patient died, presenting with desquamation of the palms and soles, pancytopenia, severe sepsis and multiple organ failure. The other patient recovered after one month of conservative care after admission. We found a piece of Podostroma cornu-damae in the remaining clusters of mushrooms. Mushroom poisoning by Podostroma cornu-damae has never been previously reported in Korea.ope

Late Gadolinium Enhancement in Cardiac MRI in Patients with Severe Aortic Stenosis and Preserved Left Ventricular Systolic Function Is Related to Attenuated Improvement of Left Ventricular Geometry and Filling Pressure after Aortic Valve Replacement

BACKGROUND AND OBJECTIVES: WE INVESTIGATED ECHOCARDIOGRAPHIC PREDICTORS: left ventricular (LV) geometric changes following aortic valve replacement (AVR) according to the late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) in patients with severe aortic stenosis (AS) and preserved LV systolic function. SUBJECTS AND METHODS: We analyzed 41 patients (24 males, 63.1±8.7 years) with preserved LV systolic function who were scheduled to undergo AVR for severe AS. All patients were examined with transthoracic echocardiography (TTE), CMR before and after AVR (in the hospital) and serial TTEs (at 6 and 12 months) were repeated. RESULTS: The group with LGE (LGE+) showed greater wall thickness (septum, 14.3±2.6 mm vs. 11.5±2.0 mm, p=0.001, posterior; 14.3±2.5 mm vs. 11.4±1.6 mm, p<0.001), lower tissue Doppler image (TDIS', 4.4±1.4 cm/s vs. 5.5±1.2 cm/s, p=0.021; TDI E', 3.2±0.9 cm/s vs. 4.8±1.4 cm/s, p=0.002), and greater E/e' (21.8±10.3 vs. 15.4±6.3, p=0.066) than those without LGE (LGE-). Multivariate analysis show that TDI e' (odds ratio=0.078, 95% confidence interval=0.007-0.888, p=0.040) was an independent determinant of LGE+. In an analysis of the 6- and 12-month follow-up compared with pre-AVR, LGE- showed decreased LV end-diastolic diameter (48.3±5.0 mm vs. 45.8±3.6 mm, p=0.027; 48.3±5.0 mm vs. 46.5±3.4 mm, p=0.019). Moreover, E/e' (at 12 months) showed further improved LV filling pressure (16.0±6.6 vs. 12.3±4.3, p=0.001) compared with pre-AVR. However, LGE+ showed no significant improvement. CONCLUSION: The absence of LGE is associated with favorable improvements in LV geometry and filling pressure. TDI E' is an independent determinant of LGE in patients with severe AS and preserved LV systolic function.ope

Economic Analysis of Defective Prediction System Using Virtual Metrology

학위논문 (석사)-- 서울대학교 대학원 : 산업·조선공학부, 2012. 2. 이창훈.성공적인 공정 관리를 위해서는 불량률의 감소와 수율의 향상이 핵심 목표가 된다. 이것은 비용의 감소 및 생산량의 증대로 이루어진다. 최근에는 가상계측기법(Virtual Metrology Technique)라는 기법이 도입되어 실제 계측 및 검사를 대체하고 있다. 가상계측기법이란 공정 과정에서 발생한 기기 정보 및 센서 자료를 데이터마이닝기법으로 분석하여 제품의 특성치를 예측하는 기법이다. 실제 계측 및 검사에 소요되는 비용을 줄이고 시간을 절약함으로서 생산량 확대에 효과적일 수 있다. 공정 관리자의 입장에서 높은 예측력이 보장된 가상계측시스템의 도입은 공정관리에 긍정적인 효과를 항상 기대할 수 있다. 하지만, 경영자의 입장에서 전체 기업의 운영비용을 고려해야 하기 때문에 시스템의 효과를 분석할 수 있는 도구가 필요하다. 그래서 본 연구는 가상계측시스템의 도입하기 전에 시스템의 경제성을 분석하여 경영자의 의사 결정을 지원할 수 있는 정보를 제공함이 목적이다. 연구는 가상계측시스템이 도입될 수 있는 공정의 예시를 제시하고, 각 공정은 M/M/1모형을 따르는 것으로 가정하여 모형화 하였고, Flow Line공정의 생산량 및 총 소요 비용을 예측할 수 있는 분석적인 모델을 개발하였다. 그리고 가상계측시스템이 적용되지 않은 공정과 적용된 공정의 모형에서 총 비용을 성능 척도로 설정하였다. 각 변수에 따른 추세 분석 및 성능 척도의 값의 비교를 통하여 가상계측시스템의 경제적 효과를 분석하였다.For successful process control, reducing fraction defectives and improving yields have to be core objectives. To reduce the proves costs, Papers recently published suggest a new system which is called "Virtual Metrology(VM)". VM is function to reduce a number of real measurements of products in inspection and save time and cost. VM seems to be effective for that cases but effectiveness cannot be figure out until it is actually working. So we investigate a methodology of estimating an economic effect of a VM system installed and operated in the production process. For the purpose, we consider various cases and developed general analytic models of a flow line system. These models are applied for non-VM and VM installed systems. By analyzing an increment trend of these two models and comparing them, the decision of an investment can be supported.Maste

(A)Study on the development of the real-time localized image enhancement techniques for the digital lateral cephalometric radiograph

학위논문(박사)--서울대학교 대학원 :치의학과 치과교정학전공,2006.Docto

유년기 골격성 Ⅲ급 부정교합자에서 이모장치의 효과에 관한 유한요소분석법적 연구

학위논문(석사)--서울대학교 대학원 :치의학과 치과교정학전공,1998.Maste