• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.262-267
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• 2016

In this study, we present an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic PtAu nanoparticles (NPs) on a multi-walled carbon nanotube (MWNT)-coated layer through dry plasma reduction. The NPs are stably and uniformly immobilized on the surface of MWNTs and the nanohybrid materials are applied to counter electrode (CE) of dye-sensitized solar cells (DSCs). The electrochemical properties of CEs are examined through cyclic voltammogram, electrochemical impedance spectroscopy, and Tafel measurements. As a result, both electrochemical catalytic activity and electrical conductivity are highest for PtAu/MWNT electrode. The DSC employing PtAu/MWNT CE exhibits power conversion efficiency of 7.9%. The efficiency is better than those of devices with MWNT (2.6%), AuNP/MWNT (2.7%) and PtNP/MWNT (7.5%) CEs.

• Journal of Life Science
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• v.31 no.9
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• pp.862-872
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• 2021

Recent studies on synthesis of metallic nanomaterials such as silver (Ag), gold (Au), platinum (Pt), cerium (Ce), zinc (Zn), and copper (Cu) nanoparticles (NPs) using plants and microbes are attracted researchers for their wide range of applications in the field of biomedical sciences. The plant contains abundant of bioactive contents such as flavonoids, alkaloids, saponins, steroids tannins and nutritionals components. Similarly, microbes produce bioactive metabolites, proteins and secretes valuable chemicals such as color pigments, antibiotics, and acids. Recently reported, biogenic synthesis of NPs in non-hazardous way and are promising candidates for biomedical applications such as antibacterial, antifungal, anti-cell proliferative and anti-plasmodia activity. All those activities are dose dependent, along with their shape and size also matters on potential of NPs. Microbes and plants are great source of metabolites, those useful in biomedical field, such metabolites or chemicals involved in synthesis of NPs in an ecofriendly way. NPs synthesized using microbes or plant materials are reveals more non-toxic, facile, and cost-effective compare to chemically synthesized NPs. In present review we are focusing on NPs synthesis using biological agents such as microbes (bacteria, fungi and algae) and plant, characterization using different techniques and their antibacterial applications on pathogenic Gram-positive and Gram-negative organisms.

• Food Engineering Progress
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• v.14 no.1
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• pp.49-53
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• 2010

Surface plasmon resonance (SPR) which is utilized in thin film refractometry-based sensors has been concerned on measurement of physical, chemical and biological quantities because of its high sensitivity and label-free feature. In this paper, an application of SPR to detection of alcohol content in wine and liquor was investigated. The result showed that SPR sensor had high potential to evaluate alcohol content. Nevertheless, food industry may need SPR sensor with higher sensitivity. Herein, we introduced a nano-technique into fabrication of SPR chip to enhance SPR sensitivity. Using Langmuir-Blodgett (LB) method, gold film with nano-structured surface was devised. In order to make a new SPR chip, firstly, a single layer of nano-scaled silica particles adhered to plain surface of gold film. Thereafter, gold was deposited on the template by an e-beam evaporator. Finally, the nano-structured surface with basin-like shape was obtained after removing the silica particles by sonication. In this study, two types of silica particles, or 130 nm and 300 nm, were used as template beads and sensitivity of the new SPR chip was tested with ethanol solution, respectively. Applying the new developed SPR sensor to a model food of alcoholic beverage, the sensitivity showed improvement of 95% over the conventional one.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.145-152
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• 2016

In this study, CuO was introduced on MWCNTs dispersed with Au nanoparticles to improve the glucose sensing capability of electrochemical biosensors. Nano-cluster shaped CuO was synthesized due to the presence of Au nanoparticle, which affects glucose sensing performance. The biosensor featuring CuO/Au@MWCNTs nanocomposite as an electrode material when 0.1 mole of CuO was synthesized showed the highest sensitivity of $504.1{\mu}A\;mM^{-1}cm^{-2}$, which is 4 times better than that of MWCNTs based biosensors. In addition, it shows a wider linear range from 0 to 10 mM and lower limit of detection (LOD) of 0.008 mM. These results demonstrate that CuO/Au@MWCNTs nanocomposite sensors are superior to other CuO based biosensors which are attributed that the nano-cluster shaped CuO is favorable for the electrochemical reaction with glucose molecules.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.80-80
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• 2008

바이오 센서 응용 연구에 많이 사용되는 금(Au) 나노 입자를 이용한 국소 표면 플라즈몬 공명(Localized Surface Plasmon Resonance, LSPR)에 의한 산란광을 검출하는데 주로 이용되는 암시야(dark field) 현미경 검출 방식에 관한 전산모사를 통하여 입사광의 입사 방식에 따른 산란광 세기를 정량적으로 분석하였다. 전산모사 기법으로는 국소 표면 플라즈몬 공명의 동역학적인 현상을 모사할 수 있는 유한차분시간영역(Finite Difference Time Domain, FDTD) 기법을 이용하였는데, 이러한 기법이 암시야 현미경 전산 모사에 유효함을 우선적으로 검증하였다. 암시야 현미경 검출 방식의 모사에서 입사 광원의 반사 입사 방식과 투과 입사 방식을 비교하였고, 각각의 방식에 서 입사광의 입사각에 따른 산랑광 세기를 계산하였다. 이러한 전산모사를 통하여 프리즘을 통한 내부 전반사(Total Internal Reflection, TIR) 방식에서 입사 광원의 임계각 근처에서 많이 발생하는 에바네슨트 장(evanescent field)을 결합하는 경우 산란광 세기가 증가함을 관찰하였고, 이러한 세기의 변화를 프레넬(Fresnel) 방정식에 의해 계산된 에바네슨트 장의 세기 분포와 비교 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.367.1-367.1
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• 2016

투명 전극은 유기 발광소자, 태양전지, 센서와 같은 다양한 분야에 응용되고 있으며, indium-tin-oxide(ITO)는 현재 다양한 소자의 투명 전극으로 가장 많이 사용하고 있다. 그러나 높은 가격과 유연성이 좋지 않은 ITO 소재를 대체하는 기술로 현재 금속 나노와이어를 사용하려는 시도가 진행되고 있다. 금속 나노 와이어 투명전극은 높은 전도성, 높은 광학적 투과율, 간단한 공정, 우수한 유연성 및 열 안정성의 장점을 가지고 있어 플렉서블 소자에 응용 가능성을 보여주고 있다. 본 연구에서는 금속 나노와이어 투명전극 기판 제작 방법과 이를 이용한 유기 쌍안정 메모리 소자의 전기적 특성을 관찰하였다. 세척한 PET 기판 위에 금속 나노와이어를 스핀코팅 방법으로 분산하고, 그 위에 금속 나노와이어의 표면 거칠기와 전도성을 증진하기 위해 PEDOT:PSS 층을 스핀코팅하여 플렉서블 투명전극을 제작하였다. 플렉서블 금속 나노와이어 투명전극 기판을 하부 전극으로 사용하고, 그 위에 금 나노입자가 포함된 유기물 층을 다시 한번 스핀코팅 방식으로 적층하였다. 마지막으로 알루미늄 상부 전극을 열 증착하여 비휘발성 메모리 소자를 제작하였다. 이렇게 제작된 소자의 전류-전압 측정 결과는 높은 전도도와 낮은 전도도의 차이를 갖는 전기적 특성을 확인할 수 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.243-244
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• 2012

산화아연 나노구조를 금을 금속촉매로 사용하여 실리콘 기판위에 기상이동법으로 성장하였다. 성장할 때 소스(source)와 기판 사이의 거리는 5에서 50 mm로 변화를 주며 아르곤과 산소 분위기에서 $900^{\circ}C$로 성장하였다. 산화아연 나노구조의 구조적 및 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), 그리고 photoluminescence (PL)를 이용하였다. 산화아연 나노구조는 나노선과 나노입자의 형태로 성장하였다. 산화아연 나노구조의 광학적 특성은 소스와 기판사이의 거리가 가까울수록 향상되었다. 특히, 소스와 기판사이의 거리가 5 mm 일 때, 산화아연 나노선이 관찰되었으며 XRD 와 PL 분석에서 나타난 반가폭 (full width at half maximum)은 $0.061^{\circ}$ 와 96 meV로써 가장 작았다. 산화아연 나노선은 산화아연 나노입자와 비교하여, 결정성 및 광학적 특성이 우수하였다.

• Analytical Science and Technology
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• v.23 no.2
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• pp.165-171
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• 2010

Glucose oxidase ($GOD_{ox}$) immobilized biosensor was fabricated by two methods. In one of the methods, gold nanoparticles (Au-NPs) prepared by ${\gamma}$-irradiation were loaded into the poly(maleic anhydride)-grafted multi-walled carbon nanotube, PMAn-g-MWCNT electrode via physical entrapment. In the other method, the Au-NPs were prepared by electrochemical reduction of Au ions on the surface of PMAn-g-MWCNT electrode and then GODox was immobilized into the Au-NPs. The $GOD_{ox}$ immobilized biosensors were tested for electrocatalytic activities to sense glucose. The sensing range of the biosensor based on the Au-NPs physically modified PMAn-g-MWCNT electrode was from $30\;{\mu}M$ to $100\;{\mu}M$ for the glucose concentration, and the detection limit was $15\;{\mu}M$. Interferences of ascorbic acid and uric acid were below 7.6%. The physically Au deposited PMAn-g-MWCNT paste electrodes appear to be good sensor in detecting glucose.

• Applied Chemistry for Engineering
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• v.29 no.1
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• pp.97-102
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• 2018

In this work, the surface of gold nanoparticles (AuNPs) was modified with small molecules including mercaptoundecanoic acid (MUA) and L-lysine for the development of highly sensitive lateral flow (LF) sensors. Uniformly sized AuNps were synthesized by a modified Turkevich-Frens method, showing an average size of $16.7{\pm}2.1nm$. Functionalized AuNPs were then characterized by transmission electron microscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The stable conjugation of AuNPs and antibodies was obtained at pH 7.07 and the antibody concentration of $10{\mu}g/mL$. The functionalized AuNP-based LF sensor exhibited lower detection limit of 10 ng/mL for hepatitis B surface antigens than that of using the bare AuNP-based LF sensor (100 ng/mL).

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.40-46
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• 2009

We present a method for spatially selective immobilization of functional materials, such as proteins and nanoparticles, onto pre-activated silicon surfaces by electrochemical reaction. Carboxymethylbenzendiazonium (CMBD) cations, being adsorbable on silicon surfaces through electrochemically reductive deposition, is used as an anchor molecule to prepare the pre-activated silicon surfaces. It is demonstrated that the use of BD reaction is very efficient for the selective immobilization because the functional materials are immobilized exclusively onto the pre-adsorbed CMBD region. The method is applied to immobilize gold nanoparticles on the selected nanowire of the nanowire array.