• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.197-200
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• 2019

We report on electrochemical signal amplification using gap electrodes based on the redox cycling between gap electrodes. The distance between electrodes was controlled from $2{\mu}m$ to a few hundreds of nanometer by chemical deposition of reduced Au ion on the pre-defined electrodes. Enhanced redox current of ferri/ferrocyanide was obtained by redox cycling between the two working electrodes. The faradaic current is amplified about a thousand times in this redox system. Since the signal amplification is due to the shortened diffusion length between the two electrodes, the narrower the nanogap was, the better detection limit, calibration sensitivity, and dynamic range. The experimental results were discussed on the basis of the cyclic voltammetry (CV), atomic force microscope (AFM) and scanning electron microscope (SEM) measurements.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.353.2-353.2
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• 2016

We studied electrochemical detection of Botulinum neurotoxin, Vaccinia virus, and Streptococcus Pneumoniae based on nanogap device. Target bio substances were employed as representative targets of protein, virus, and bacteria, respectively. Redox current generated by ferri/ferrocyanide as an electroactive probe was enhanced according to gap distance which was controlled by surface-catalyzed chemical deposition. We found that enhanced electrochemical signal leads more sensitive signal changes according to selective interaction of target and its complementary elements on the electrode or gap area. In case of Botulinum neurotoxin, the redox signal showed a time-dependent increase due to cleavage of the immobilized peptide which blocked redox cycling. Redox cycling was also hindered by Vaccinia virus and Streptococcus Pneumoniae which were selectively immobilized in the gap area.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.365-365
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• 2016

3차원 갭 소자를 제작하고, 제작된 소자를 백시니아 바이러스의 전기화학적 검출에 이용하였다. 3차원 갭 전극은 하층 전극에 포토레지스트를 코팅하여 지지층을 형성한 후, 상층 전극을 부착을 통해 제작하였다. 상하층 전극사이로 분석물질인 ferricynide가 이동 할 수 있도록 유체채널을 도입하였고, 상하층 전극에 각각 산화, 환원 전위를 인가하여 ferricyanide/ferrocyanide에 의한 redox cycling이 일어나는 것을 확인하였다. 이 때, 발생한 redox 신호는 2차원 갭에서의 redox 신호와 비교했을 때 월등히 큰 것을 알 수 있었으며, 증폭된 redox 신호를 기반으로 백시니아 바이러스의 검출에 활용하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.364.2-364.2
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• 2016

본 연구에서는 3차원 갭 전극을 제작하고 이에 유체채널을 도입하여 전기화학적 분석을 수행하였다. 제작된 3차원 갭 전극은 전극의 배치가 상/하로 이루어져 있으며 전극 사이에는 포토레지스트가 간격을 유지하기 위해 코팅되었다. 상하층 전극사이로 분석물질인 ferricynide가 이동 할 수 있도록 유체채널을 도입하였고, 상하층 전극에 각각 산화, 환원 전위를 인가하면 ferricyanide/ferrocyanide에 의한 redox cycling이 일어나는 것을 확인 하였다. 이 때, 발생한 redox 신호는 2차원 갭에서의 redox 신호와 비교했을 때 월등히 큰 것을 확인하였으며, 증폭된 redox 신호를 기반으로 백시니아 바이러스의 검출 연구에 활용하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.82-89
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• 2006

The redox behaviors of anode-supported flat tube for solid oxide fuel cell has been studied. The mass change of the extruded NiO/YSZ anode flat tube during redox cycling was examined by thermogravimetric analysis(TGA). The result of TGA was shown a rapidly mass change in the range of $455\;-\;670^{\circ}C$ and the reoxidation of the NiO/YSZ anode was almost completed at $750^{\circ}C$. The starting temperature of reoxidation and the maximum temperature of oxidation rate decreased with increasing the reoxidation cycle, which is attributed to the increased porosity caused by volume change. Bending strengths of the NiO/YSZ anode after redox cycling were 96 - 80 MPa and the bending strength decreased slightly with increasing the redox cycle. On the other hand, the bending strength of the NiO/YSZ anode with electrolyte showed 130 MPa after first redox cycling but decreased rapidly with increasing the redox cycle. From the results of the bending test and the microstructure observation, we conclude that the crack initiation of the electrolyte-coated NiO/YSZ anode was induced easily at interface of electrolyte/anode tube and propagated cross the electrolyte.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.269-269
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• 2013

Redox cycling in between the two working electrodes in an electrochemical cell can lead a great signal enhancement. In this work, we report on a systematic examination of current amplification along with the decrease in the gap distance of a nanogap device which was fabricated by the combination of photo and chemical lithography [1]. The gap distance was controlled by the chemical lithographic process of surfacecatalyzed growth of metallic layer on pre-defined electrodes with wider initial gap. Enhancement of the redox current of ferri/ferrocyanide was observed upon gap distance reduction and the current is amplified about a thousand times in this redox system when the gap distance was decreased from 200 nm to 30 nm. The experimental results were discussed on the basis of the cyclic voltammetry (CV), atomic force microscopy (AFM) and scanning electron microscopy (SEM).

• Toxicological Research
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• v.12 no.2
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• pp.289-293
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• 1996

Our previous studies demonstrated that quinone (menadione) is cytotoxic to rat platelets. In an attempt to assess the relative contributions of redox cycling and/or arylation in quinone-induced cytotoxicity, we have studied three quinones with different mechanisms: 2, 3-dimethoxy-1, 4-naphthoquinone (DMNQ; pure redox cycler), menadione (both redox cycler and arylator), and 1, 4-benzoquinone (pure arylator). The order of redox cycling capacity in platelet rich plasma (PRP) isolated from rats was menadione>DMNQ>1, 4-benzoquonone, which was consistent with the previous studies using isolated hepatocytes. 1, 4-Benzoquinone was more toxic to rat platelets than menadione, while DMNQ did not cause cell death at all. Lactate dehydrogenase inhibition studies revealed that 1, 4-benzoquinone inhibited significantly in a time-dependent manner, while menadione and DMNQ did not at all. These results suggested that arylation by quinone compounds might play a critical role in quinone-induced cytotoxicity in rat platelets.

• Proceedings of the Zoological Society Korea Conference
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• 1994.10a
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• pp.245.2-245
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• 1994

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.237.2-237.2
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• 2015

본 연구에서는 포토레지스트 코팅과 전기도금 기술을 이용하여 3차원 갭을 가지는 전극을 제작하였다. 3차원 갭은 마이크로 전극이 배열된 하층과 벌크전극이 놓여진 상층으로 구성되었다. 갭의 크기는 하층 전극에 코팅된 포토레지스트의 두께와 하층 전극의 높이 차이로 결정되며, 코팅 두께가 다른 포토레지스트 ($3.5{\mu}m$, $1.25{\mu}m$)의 사용과 전기도금 기술을 병용하여 3차원 갭의 크기를 줄일 수 있다 (~150 nm). 제작한 3차원 갭 소자의 상 하층 전극에 각각 산화, 환원 전압을 인가함으로써, 유입된 ferricyanide의 redox cycling 을 유도 할 수 있음을 확인하였으며, 본 연구의 결과는 원자힘현미경 (AFM), 주사전자현미경 (SEM), 순환전압전류법 (CV) 및 시간대전류법 (CA)을 통해 분석 되었다.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2001.10b
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• pp.113-113
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• 2001