• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.146-147
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• 2007

A universal four-point contact measurement method, has an advantage of non-existence of contact resistance, is demonstrated by the experiments with carbon nanotubes and ZnO nanowire. Ti/Au and Pt are tried to compare the influence of contact resistance between two different metals. These metals are selected to make Ohmic contact and Schottky contact originated from their different work functions. For precise experiments, Ti/Au and Pt are separately evaporated to form double 'four-point contact electrodes' on CNTs or ZnO, and the voltage-current characteristics are measured. This method can be applied to universal resistivity measurement for nanotubes and nanowires.

• Journal of the Korean Applied Science and Technology
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• v.21 no.3
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• pp.214-224
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• 2004

Although the structure of carbon nanotubes is important factor characterizing its properties, it is very difficult to control the structure of carbon nanotubes (MWNTs) and to predict the range of their diameter, which is the primary factor of MWNTs' physical properties. We tried to control the diameter of MWNTsby governing the feed injection temperature of floating catalyst method. The structure of MWNTs was influenced by the phase change of ferrocene fed as the catalyst,. The carbon nanotubes were very narrow at injection temperatures close to the sublimation pt. of ferrocene, in which most MWNTs had diameters in the range of 20$^{\sim}$30 nm. At injection temperatures between the boiling pt. and melting pt. of ferrocene, the diameters became larger and had broad distribution. However, at injection temperatures higher than the boiling pt., the diameters became narrow again and had very uniform distribution.

• Journal of Powder Materials
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• v.22 no.5
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• pp.326-330
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• 2015

In this study, we demonstrate the photoelectrochromic devices composed of $TiO_2$ and $WO_3$ nanostructures prepared by anodization method. The morphology and the crystal structure of anodized $TiO_2$ nanotubes and $WO_3$ nanoporous layers are investigated by SEM and XRD. To fabricate a transparent photoelectrode on FTO substrate, a $TiO_2$ nanotube membrane, which has been detached from Ti substrate, is transferred to FTO substrate and annealed at $450^{\circ}C$ for 1 hr. The photoelectrode of $TiO_2$ nanotube and the counter electrode of $WO_3$ nanoporous layer are assembled and the inner space is filled with a liquid electrolyte containing 0.5 M LiI and 5 mM $I_2$ as a redox mediator. The properties of the photoelectrochromic devices is investigated and Pt-$WO_3$ electrode system shows better electrochromic performance compared to $WO_3$ electrode.

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.377-383
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• 2007

We describe the fabrication and characterization of a doubly clamped multi-walled carbon nanotube (MWNT). The device was assembled by an application of electric field in solution. The MWNT was clamped on end of metal trench electrodes in solution and deposited with additional platinum (Pt) on edge of electrode for firmly suspending the MWNT by focused ion beam (FIB). The MWNTs range of diameter and length were 100 to 150 nm and 1.5 to $2{\mu}m$, respectively. Electrical characteristics of fabricated devices were measured by I-V curve and impedance analysis. The mechanical deformation was observed by resistivity in high air pressure. Resonant frequency around 6.8 MHz was detected and resistivity was linearly varied according to the magnitude of air pressure. This device could have potential applications in nanoelectronics and various sensors.

• Journal of the Korean Ceramic Society
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• v.54 no.6
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• pp.535-538
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• 2017

Here we report the tunable electrical properties and chemical sensor of single-walled carbon nanotubes (SWCNTs) network-based devices with a functionalization technique. Formation of highly aligned SWCNT structures is made on $SiO_2/Si$ substrates using a template-based fluidic assembly process. We present a Platinum (Pt)-nanocluster decoration technique that reduces the resistivity of SWCNT network-based devices. This indicates the conversion of the semiconducting SWCNTs into metallic ones. In addition, we present the Hydrogen Sulfide ($H_2S$) gas detection by a redox reaction based on SWCNT networks functionalized with 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) as a catalyst. We summarize current changes of devices resulting from the redox reactions in the presence of $H_2S$. The semiconducting (s)-SWCNT device functionalized with TEMPO shows high gas response of 420% at 60% humidity level compared to 140% gas response without TEMPO functionalization, which is about 3 times higher than bare s-SWCNT sensor at the same RH. These results reflect promising perspectives for real-time monitoring of $H_2S$ gases with high gas response and low power consumption.

• Rapid Communication in Photoscience
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• v.1 no.2
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• pp.67-67
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• 2012

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1379-1385
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• 2018

The hand held voltammetry systems searched diabetic assay using glucose sensor of fluorine nafion doped carbon nanotube electrode (FCNE). An inexpensive graphite carbon pencil was used as an Ag/AgCl reference and Pt counter electrode. Upon combining and using three electrode systems, optimum square wave (SW) stripping results were attained to 1.0-9.0 ug/L with 8 points. Statistic RSD precision was of 6.02 % with n=15 in 0.1 mg/L glucose. After a total of 200 second accumulation times, analytical detection limit of 0.8 ug/L was obtained. This developed technique was applied to urine samples from diabetic patients urine for fluid analysis, it was determined that the sensor can be used with a diagnostics in the ex vivo of live cells and non treated biological fluid.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.227.1-227.1
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• 2010

본 연구는 자외선 영역의 흡수로 전자 정공의 전하쌍을 생성함으로써 광전압 및 전류를 일으키는 티타니아 물질을 금속지지체 표면에 양극산화로 튜브형 $TiO_2$(anodized tubular $TiO_2$; ATT)로 제조한 후 나노크기의 금속 혹은 $WO_3$입자를 담지하여 광감응 재료로 활용하였다. 이는 기존의 입자나 콜로이드 형태로 광촉매 물질을 고정화하여 사용한 재료의 탈리현상 및 효율저하를 극복하기 위함이다. ATT는 전해질 내에 전기화학적 에칭율과 화학적 용해율의 비율에 의해 나노튜브 길이 성장에 영향을 미치는데 이를 유기 전해질과 불산 전해질을 사용하여 정전압 혹은 정전류의 조건에서 다양한 길이의 $TiO_2$ 나노튜브를 제조하였다. 여기에 전기분해담지(electrolytic deposition; ELD)를 통하여 정전류 조건에서 다양한 금속(Pt, Pd, Ru)을 나노크기의 형태로 담지하여 광촉매 내 생성된 전자 정공의 재결합을 줄이고자 하였고 $WO_3$의 담지를 통하여 가시광 감응을 높이고자 하였다. 제조된 여러 조건의 시료는 SEM과 EDAX를 통하여 형태와 길이, 담지량을 확인 하고 XRD를 이용하여 열처리 온도에 따른 결정화상태를 확인하였으며 광전류 측정 및 Cr(VI)의 광환원과 MB의 광분해를 통하여 광효율을 관찰하였다. 금속이 도핑되었을 경우 순수 ATT보다 보통 3배의 흡착률과 UV광원 아래 2배의 광효율을 관찰할 수 있었는데 이 중 Pt의 담지가 가장 효율이 좋았으며 흡착률에서는 담지량의 증가에 따른 증가선을 관찰 할 수 있었으나 광원 사용시 3%담지율에서 최적을 확인 할 수 있었다. 또한 $TiO_2$외 가시광감응 활성을 높이기 위한 다양한 광촉매제조가 진행 중에 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.411.2-411.2
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• 2016

직접 메탄올 연료전지 (DMFCs)는 친환경적이고 낮은 작동 온도로 인한 빠른 구동, 높은 에너지 밀도 등 다양한 장점을 가지고 있어 차세대 에너지 변환소자로 많은 관심을 받고 있다. 직접 메탄올 연료전지는 메탄올을 연료로 사용하며, 메탄올이 보유하고 있는 화학적 에너지를 전기 에너지로 변환하는 장치로써 음극에서는 백금 촉매로 인한 메탄올 산화반응, 양극에서는 환원 반응이 일어나며 전기화학적 구동을 하게 된다. 하지만 일산화탄소 피독으로 인한 촉매 활성 저하, 메탄올의 cross over, 백금 촉매 사용으로 인한 고비용 등의 문제점을 가지고 있다. 따라서 많은 연구자들이 백금 사용량을 줄이고 백금 촉매를 고르게 분포하기 위해 값이 저렴하고 넓은 비표면적을 갖는 탄소계 (graphite, graphene, carbon nanotube, carbon nanofiber 등) 지지체 재료를 도입하고 있다. 이 중 탄소나노섬유 (carbon nanofibers, CNFs)는 우수한 전기전도도와 열적/화학적 안정성을 가지고 있으며, 특히 넓은 비표면적을 가지고 있어 백금 촉매의 지지체로서 많은 연구가 진행되고 있다[1]. 따라서 우리는 전기방사법을 활용하여 넓은 비표면적을 보유하는 다공성 탄소나노섬유를 성공적으로 합성하였다. 또한, 이를 백금 촉매의 지지체로 도입하여 직접 메탄올 연료전지를 위한 다공성 탄소나노섬유에 담지된 고분산성 백금 촉매를 제조하였다. 제조한 다공성 탄소나노섬유의 형상 및 구조 분석은 주사전자 현미경 (field-emission scanning electron microscopy)와 투과전자 현미경 (transmission electron microscopy)를 이용하여 분석하였고, 결정구조와 화학적 결합상태는 X-선 회절분석 (X-ray diffraction) 및 X-선 광전자 분광법 (X-ray photoelectron spectroscopy)를 이용하여 규명하였다. 전기화학적 특성은 순환 전압 전류법 (cyclic voltammetry)를 이용하였다. 이러한 실험 결과들을 바탕으로 다공성 탄소나노섬유에 담지된 고분산성 백금 촉매의 자세한 특성을 본 학회에서 다루도록 하겠다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.111.2-111.2
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• 2010

One-dimensional nanostructures such as carbon nanotubes could be ideal templates for formation of metallic nanoparticles. Furthermore, bimetallic component nanoparticles have recently been interesting issues for having high catalytic activity. This work provides both a facile method to synthesize bimetallic catalysts via N atoms of carbon nanotubes and also a picture about how to design the optimal bimetallic catalyst for hydrogen generation from the hydrogen storage material. In principle, the ratio of one component to another component could be generically extended to fabricate the high-performance bimetallic catalysts on host nanostructures. Indeed, we demonstrate that the bimetallic catalyst composed of the optimum composition results in the excellent hydrogen generation property from an aqueous borane ammonia solution, thus being capable of satisfying the Depart of Energy in USA target required for many advanced applications even with the small amount of our bimetallic catalysts attached onto the N-doped carbon nanotubes. This high hydrogen generation rate is found to be attributed to the optimal distance between active Pt and cheap Ni atoms for effective hydrogen generation.