• 전기화학회지
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• 제13권2호
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• pp.132-137
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• 2010

본 연구는 KOH 전해질에서 전기화학적으로 석출된 망간 산화물이 산소 환원 반응에 미치는 전기화학적 촉매 역할에 대해 고찰하였다. 나노 사이즈 망간 산화물들은 Glassy carbon(GC), Gold(Au) 그리고 Titanium(Ti)로 이루어진 전극에 전해방식으로 석출시켰으며, 각 전극 표면에 나노 사이즈로 균일하게 분포되어 있는 것이 SEM 관찰을 통해서 확인되었다. 망간산화물의 한 종류인 $\gamma$-MnOOH는 산소 환원반응에 수반되는 4-electron 반응에서 촉매 역할을 하는 것을 확인하였다. 망간산화물이 전기화학적으로 석출된 전극들은 전해석출을 하지 않은 전극들에 비해서 양극 전위가 낮아지는 것을 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.23-27
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• 2003

Molecular self-assembled of surfactant viologen are of recent interest because they can from functional electrodes as well as micellar assemblies, which can be profitably utilized for display devices, photoelectrochemical studies and electrocatalysis as electron acceptor or electron mediator. Fromherz et al studied the self-assembly of thiol and disulfide derivatives of viologens bearing long n-alkyl chains on Au electrode surface. The electrochemical behavior of self-assembled viologen monolayer has been investigated with QCM, which has been known as nano-gram order mass detector. The self-assembly process of viologen was monitored using resonant frequency$({\Delta}F)$ and resonant resistance(R). The redox process of viologen was observed with resonant frequency $({\Delta}F)$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1520-1522
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• 2003

Molecular self-assembled of surfactant viologen are of recent interest because they can from functional electrodes as well as micellar assemblies, which can be Profitably utilized for display devices, photoelectrochemical studies and electrocatalysis as electron acceptor or electron mediator. Fromherz et al studied the self-assembly of thiol and disulfide derivatives of viologens bearing long n-alkyl chains on Au electrode surface. The electrochemical behavior of self-assembled viologen monolayer has been investigated with QCM, which has been known as nano-gram order mass detector. The self-assembly process of viologen was monitored using resonant frequency (${\Delta}$F) and resonant resistance (R). The redox process of viologen was observed with resonant frequency (${\Delta}$F).

• Journal of Microbiology and Biotechnology
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• 제16권4호
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• pp.505-510
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• 2006

A gallocyanine-bound nanoporous titanium dioxide electrode system was investigated to carry out a mediated enzyme reaction. Gallocyanine was bound either directly or through an aminopropylsilane linker to the film of nanoporous titanium dioxide and used as a mediator for nitrate reductase in the mediated enzymatic nitrate reduction. The electrode with the aminopropylsilane linker showed 20% higher efficiency of electron transfer at the same potential than that directly linked. The prepared electrodes showed $0.26{\mu}mol/h$ nitrate reduction at a $100mm^2$ surface of the electrode, and linear current response on nitrate ion concentration up to 1.0 mM, which is very useful as a biosensor of nitrate ion in water.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1436-1437
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• 2006

탄소 나노튜브는 기계적인 강도가 크고, 표면적이 넘으며 전기전도도가 우수할 뿐만 아니라 화학적으로도 안정하기 때문에 최근 여러분야에 적용하려는 연구가 활발히 진행되고 있는 나노물질이다. 특히 바이오센서에서 탄소 나노튜브는 작업 전극의 활성을 증대시키는 물질로써, 안정적인 효소 고정화에 기여하는 reservior로써 그리고 반응에서 생성된 전자를 전극에 효과적으로 전달하는 매개체로써 이용되고 있다. 본 연구에서는 다중벽 탄소 나노튜브(multi-walled carbon nanotube ; MWNT)를 화학처리하여 작용기를 유도한 후 효소와 반응시킨 용액으로 스크린 프린팅 방법으로 제작된 탄소전극의 표면을 개질하는 방법으로 바이오센서를 제작하였다. 이렇게 제작된 바이오센서를 탄소 나노튜브를 이용하지 않은 바이오 센서와 전기화학적으로 분석한 결과 감도가 약 3배정도 증가하는 결과를 얻을 수 있었다. 이것은 효소반응 시 발생된 전자가 나노튜브를 통해서 전극에 효과적으로 전달됨을 의미한다.

• Bulletin of the Korean Chemical Society
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• 제22권11호
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• pp.1192-1196
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• 2001

A diaphorase enzyme electrode for the catalytic reduction of NAD+ , the oxidized form of nicotinamide adenine dinucleotide, has been prepared. The enzyme layer grew spontaneously over an aminoethanethiol self assembled monolayer on a go ld plate electrode. The growth was accomplished by simply dipping the electrode covered by the aminoethanethiol monolayer into a solution containing both glutaraldehyde and diaphorase. We suggested that the glutaraldehyde as a cross-linking reagent was attached to the amino groups of the aminoethanethiol monolayer and the diaphorase enzyme molecules were bound to free aldehyde groups of the glutaraldehyde. Further attachments of the enzyme molecules over the bound enzyme molecules continued with the bridging of the glutaraldehyde. In frequency measurements with a quartz crystal microbalance, the frequency decrease was much more than it was for that of the enzyme monolayer formation, and an enzyme layer thicker than a monolayer was formed. The modified electrode was employed to reduce NAD+ , using diffusional methyl viologen as an electron transfer mediator. The NAD+ was electrocatalytically reduced, and the catalytic current was almost equivalent to that with the multilayered electrode of ten enzyme layers.

• Korean Chemical Engineering Research
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• 제61권4호
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• pp.635-644
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• 2023

Due to the rapid development of the livestock industry, particularly due to residual pharmaceutical antibiotics, environmental populations have been negatively affected. Herein, we report a ZnO/melamine-functionalized carboxylic-rich graphene oxide (ZFG) photocatalyst for visible light-driven photocatalytic degradation of tetracycline hydrochloride in aqueous solutions. The properties of the photocatalysts were evaluated by XRD, FTIR, XPS, Fe-SEM, HR-TEM, TGA, Raman spectroscopy, UV-Vis spectroscopy, zeta potential, and electrochemical measurements. The photocatalytic activity was measured using high-performance liquid chromatography. The photocatalytic properties of the ZFG photocatalyst evaluated against the tetracycline hydrochloride (TCH) antibiotic under visible light irradiation showed superior photodegradation of 96.27% within 60 min at an initial pH of 11. The enhancement of photocatalytic degradation was due to the introduction of functionalized graphene, which increases the light-harvesting capability and molecular adsorption capability in addition to minimizing the recombination rate of photogenerated charge carriers due to its role as an electron acceptor and mediator.

• Journal of Microbiology and Biotechnology
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• 제22권10호
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• pp.1406-1411
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• 2012

5,5'-Dithiobis(2-nitrobenzoic acid) (DTNB) was selected as an electron transfer mediator and was covalently immobilized onto high porosity carbon cloth to employ as a working electrode in an electrochemical $NAD^+$-regeneration process, which was coupled to an enzymatic reaction. The voltammetric behavior of DTNB attached to carbon cloth resembled that of DTNB in buffered aqueous solution, and the electrocatalytic anodic current grew continuously upon addition of NADH at different concentrations, indicating that DTNB is immobilized to carbon cloth effectively and the immobilized DTNB is active as a soluble one. The bioelectrocatalytic $NAD^+$ regeneration was coupled to the conversion of L-glutamate into ${\alpha}$-ketoglutarate by L-glutamate dehydrogenase within the same microreactor. The conversion at 3 mM monosodium glutamate was very rapid, up to 12 h, to result in 90%, and then slow up to 24 h, showing 94%, followed by slight decrease. Low conversion was shown when substrate concentration exceeding 4 mM was tested, suggesting that L-glutamate dehydrogenase is inhibited by ${\alpha}$-ketoglutarate. However, our electrochemical $NAD^+$ regeneration procedure looks advantageous over the enzymatic procedure using NADH oxidase, from the viewpoint of reaction time to completion.

• 한국재료학회지
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• 제22권3호
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• pp.130-135
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• 2012

We present a method of graphene synthesis with high thickness uniformity using the thermal chemical vapor deposition (TCVD) technique; we demonstrate its application to a grid supporting membrane using transmission electron microscope (TEM) observation, particularly for nanomaterials that have smaller dimensions than the pitch of commercial grid mesh. Graphene was synthesized on electron-beam-evaporated Ni catalytic thin films. Methane and hydrogen gases were used as carbon feedstock and dilution gas, respectively. The effects of synthesis temperature and flow rate of feedstock on graphene structures have been investigated. The most effective condition for large area growth synthesis and high thickness uniformity was found to be $1000^{\circ}C$ and 5 sccm of methane. Among the various applications of the synthesized graphenes, their use as a supporting membrane of a TEM grid has been demonstrated; such a grid is useful for high resolution TEM imaging of nanoscale materials because it preserves the same focal plane over the whole grid mesh. After the graphene synthesis, we were able successfully to transfer the graphenes from the Ni substrates to the TEM grid without a polymeric mediator, so that we were able to preserve the clean surface of the as-synthesized graphene. Then, a drop of carbon nanotube (CNT) suspension was deposited onto the graphene-covered TEM grid. Finally, we performed high resolution TEM observation and obtained clear image of the carbon nanotubes, which were deposited on the graphene supporting membrane.

• Journal of Chest Surgery
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• 제32권11호
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• pp.978-983
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• 1999

Background: Complement activation with transpulmonary leukocyte sequestration is considered a main mediator leading to ischemia-reperfusion lung(I-R) injury. We studied the role of leukocytes in the formation of I-R injury in ovine cardiopulmonary bypass(CPB) model with a membrane oxygenator. Material and Method: Five sheep were used. CPB circuitry consisted of a roller pump(American Optical Corp., Greenwich, CT, USA) and a membrane oxygenator(UNIVOX-IC, Bentley, Baxter Health Corp, Irvine, CA, USA). The CPB time was fixed at 120 min. Ten minutes after the start of CPB, total CPB was established. Thereafter a total CPB of 100 min was performed, followed by another 10 min of partial CPB. The CPB was discontinued and the animals were fully recovered. For measuring left and right atrial leukocyte counts, blood samples were taken before thoracotomy, 5 min and 109 in after the start of CPB, and 30 min and 120 min after weaning. C3a was measured before thoracotomy, 109 min after the start of CPB, and 30 min and 120 min after weaning. Plasma malondialdehyde(MDA) was checked before thoracotomy, 109 min after the start of CPB, and 30 min after weaning. One to two grams of lung tissue were taken for water content measurement before thoracotomy, 109 min after the start of CPB, and 30 min after weaning. Lung biopsy specimens were examined by light and electron microscopy. Result: Of 5 animals, 4 survived the experimental procedures. Of these, 3 animals survived on a long-term basis. No significant differences in transpulmonary gradients of leukocyte were found and no significant complement activation was expressed by C3a levels. MDA level did not show significant changes related to lung reperfusion despite an increase after the start of CPB. On both light and electron microscopic examinations, mild to moderate acute lung change was observed. Interstitial edema, leakage of erythrocytes into the alveolar space and endothelial cell swelling were the main findings. Water content of the lung showed a slight increase after the start of CPB, but there was no statistical significance. Conclusion: These findings indicate that ischemia-repersusion lung injury may not be from complement activation-leukocyte sequestration but from another source of oxygen free radicals related to CPB.