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Ferrocenylmethyl Benzoate류의 가용매분해에 대한 반응속도론적 연구
홍순영,김창석,원성준 漢陽大學校 自然科學硏究所 1996 自然科學論文集 Vol.15 No.-
여러 가지 p- 혹은 m- 치환 ferrocenylmethyl benzoate를 합성하였다. 이들 에스테르의 가용매 분해반응 속도를 여러 혼합비의 methanol, ethanol, acetone 및 1,4-dioxane 수용액에서 pH metric method로 측정하였다. 반응 속도는 용매의 유전상수가 클수록 빠르고 Kirkwood-Onsager 관계식에 잘 맞았다. Grunwald-Winstein 식을 적용시킬 때 substrate parameter m 값이 0.5 -0.6으로 나타나며 aprotic solvent에서 보다 protic solvent에서 약간 더 크게 나타났다. 이들 가용매 분해반응은 전자 끄는 치환기에 의해 촉진되며 Hammett 반응 상수가 +0.622 (80% EtOH)와 +0.882 (80% 1,4-dioxane)로 나타났다. 또한 이들 반응에 관여하는 몇 가지 활성화 parameter를 산출하였다. 이상의 반응 속도론적 연구결과로부터 이들 에스테르의 가용매 분해반응은 ?? (alkyl-oxygen fission)과 ?? (acyl-oxygen fission)의 혼합과정으로, 그러나 ??쪽이 약간 우세한 과정으로 진행한다는 사실을 알 수 있었다. Several ferrocenylmethyl p-or m- substituted benzoates were synthesized. Rates of solvolysis of these esters in aqueous methanol, ethanol, acetone or 1,4-dioxane of various compositions were measured by a pH metric method. Rates of reaction were increased with increasing dielectric constant of solvent and these reactions obeyed Kirkwood-Onsager equation well. Substrate parameter (m) derived from Grunwald-Winstein equation was found to be 0.4-0.6 in these solvolyses, and the value (m) in protic solvent was slightly larger than that in aprotic solvent. Reactions were accelerated by electron-withdrawing substituents and Hammett substituent constants (ρ) of +0.622 (in 80% EtOH) and +0.882 ( in 80% 1, 4-dioxane) were obtained. Some activation parameters relevant to these reactions were also calculated. From the observed kinetics, it was concluded that ferrocenylmethyl benzoates solvolyze by a combination of ?? (alkyl-oxygen fission) and ?? (acyl-oxygen fission) pathways, in which ?? mode predominates slightly over ?? mode.
Kim, Chang-Hyun,Bhak, Ghibom,Lee, Junghee,Sung, Sujin,Park, Sungjun,Paik, Seung R.,Yoon, Myung-Han American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.19
<P>Here, we report on charge-retention transistors based on novel protein-mediated Au nanoparticle (NP) arrays, with precise control over dimension and distribution. Individual NPs are coated with alpha-synuclein, an amyloidogenic protein responsible for Lewy body formation in Parkinson's disease. Subsequently, a monolayer of protein-NP conjugates is successfully created via a simple and scalable solution deposition to function as distributed nanoscale capacitors. Controllability over the film structure translates into the tunability of the electrical performance; pentacene-based organic transistors feature widely varying programmability and relaxation dynamics, providing versatility for various unconventional memory applications.</P>
이성준(Sungjun Lee),유창혁(Chang-Hyuk Yoo),이정훈(Junghoon Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
We report a highly selective and sensitive explosive sensor system based on a biological receptor. The sensor system employs a quartz crystal microbalance (QCM) whose sensing surface is functionalized with an anti-explosive oligo-peptide receptor. While other approaches with synthetic materials such as 4-mercapto phenol and Carbowax® has concerns over specificity because of additional interactions with polarized molecules including water and alcohols, the response of our biological receptor is highly selective to dinitrotoluene (DNT) which is an explosive marker molecule. We demonstrate that the sensor does not respond to other explosive analogues and polar molecules such as toluene, methanol, and ethanol. The oligopeptide receptor shows the sensitivity down to 1.8 ppm against the DNT. Our sensor system can be used for the direct detection of antipersonnel plastic mines for which the conventional approaches such as metal detector and ground penetrating radar (GPR) have difficulties.
Challenge beyond Graphene: Metal Oxide/Graphene/Metal Oxide Electrodes for Optoelectronic Devices
Kim, Sungjun,Kwon, Ki Chang,Park, Jae Yong,Cho, Hyung Won,Lee, Illhwan,Kim, Soo Young,Lee, Jong-Lam American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.20
<P>Graphene has shown strong potential to occupy transparent electrodes, replacing indium tin oxide (ITO). However, the commercialization of graphene is still limited 800 because of its poor chemical and electrical stability from 0 reaction with environmental factors or essential materials such as poly[3,4-(ethylenedioxy)thiophene]:poly(styrenesulfonate) (PEDOT:PSS). Here, we have demonstrated a multilayered electrode in which graphene is sandwiched between metal oxides (MOs) that have high stability and optical properties. The MOs overcoated graphene, and thereby protected it from desorption of chemical dopants. Because of the resulting chemical and electrical stability, the electrodes maintain low sheet resistance 2.4 times longer than bare graphene and 36 times longer than PEDOT:PSS-coated graphene. On the basis of optical simulations, we derive the design rules for highly transparent MO/graphene/MO stacks and demonstrate an optimized structure with a TiO2 and WO3 electrode that has high transmittance (96%) which exceeds those of ITO (87%) and graphene (90%). Using a TiO2/graphene/WO3 electrode in organic light-emitting diodes (lambda = 520 nm) instead of ITO or graphene anodes increases the cavity resonance and thereby increases power efficiencies by up to 30%. The MO/graphene/MO stacks designed will provide opportunities for commercialization of flexible electronics with graphene electrodes.</P>
Anatomic variations and MRI of the intermalleolar ligament.
Oh, Chang-Seok,Won, Hyung-Sun,Hur, Mi-Sun,Chung, In-Hyuk,Kim, Sungjun,Suh, Jin-Suck,Sung, Ki-Sun American Roentgen Ray Society 2006 American Journal of Roentgenology Vol.186 No.4
<P>OBJECTIVE: The purpose of this study was to identify the intermalleolar ligament morphologically and to correlate its shape with MR images. MATERIALS AND METHODS: Seventy-seven ankles were used in this study. After the intermalleolar ligament had been located in the posterior ankle space, its medial and lateral attaching sites were identified, and its length, width, and thickness were measured. MRI was performed on 26 ankles before they were dissected (20 specimens) or serially sectioned (six specimens). The serial sections were taken at a thickness of 2 mm in the sagittal and horizontal directions. RESULTS: The intermalleolar ligament was observed in 81.8% of the specimens and was composed of more than two bundles of fibers in all cases. The medial arising sites of the ligament were diverse (e.g., from the medial malleolus to the floor of the fibrous tunnel of the flexor hallucis longus). The ligament narrowed laterally and attached with the posterior talofibular ligament to the medial fossa of the lateral malleolus. Their morphologic shapes were also diverse, depending on their medial arising sites, the number of the composing fiber bundles, and the degree of bundle compactness. The intermalleolar ligament appeared as a thick string or as more than two fine parallel stripes on coronal MR images and as a linear structure on axial images. On sagittal images, the ligament appeared as scattered dots in the medial part and as a thin flat or nodular structure in the lateral part. CONCLUSION: The intermalleolar ligament seemed to be an almost invariably present anatomic entity with diverse morphologic features on MR images.</P>