• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.833-837
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• 2004

DeniLite$^{TM}$ laccase immobilized platinum electrode was used for amperometric detection of hydroquinone (HQ) and homogentisic acid (HGA) by means of substrate recycling. In case of HQ, the obtained sensitivity is 280 nA/ ${\mu}$M with linear range of 0.2-35 ${\mu}$M ($r^2$ = 0.998) and detection limit (S/N = 3) of 50 nM. This high sensitivity can be attributed to chemical amplification due to the cycling of the substrate caused by enzymatic oxidation and following electrochemical regeneration. In case of HGA, the obtained sensitivity is 53 nA/ ${\mu}$M with linear range of 1-50 $[\mu}M\;(r^2$ = 0.999) and detection limit of 0.3 ${\mu}$M. The response times ($t_{90%}$) are about 2 seconds for the two substrates and the long-term stability is 60 days for HQ and around 40-50 days for HGA with retaining 80% of initial activities. The very fast response and the durable long-term stability are the principal advantages of this sensor. pH studies show that optimal pH of the sensor for HQ is 6.0 and that for HGA is 4.5-5.0. This shift of optimal pH towards acidic range for HGA can be attributed to the balance between enzyme activity and accessibility of the substrate to the active site of the enzyme.

• Bulletin of the Korean Chemical Society
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• 제18권11호
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• pp.1149-1152
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• 1997

An enzyme electrode for the amperometric measurement of urea was prepared by co-immobilizing L-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane attached to a glassy carbon electrode. The reduced nicotinamide adenine dinucleotide(NADH) was used as the electroactive species. The electrochemical oxidation of NADH was monitored at +1.0 volt vs. Ag/AgCl. The enzyme-immobilized electrode was linear over the range of 2.0 × 10-5 to 2 × 10-4 M. The response time of the electrode was approximately 3 min. and the optimum pH of the enzyme immobilized membrane was pH 7.4-7.6 (Dulbcco's buffer solution). It was stable for at least two weeks or 50 assays. There was no interference from other physiological species, except from high levels of ascorbic acid.

• 한국입자에어로졸학회지
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• 제10권2호
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• pp.53-59
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• 2014

Palladium (Pd) nanoparticles attached graphene (GR) composite was synthesized for an enhanced glucose biosensor. Aerosol spray pyrolysis (ASP) was employed to synthesize the GR-Pd composite using a colloidal mixture of graphene oxide (GO) and palladium chloride ($PdCl_2$) precursor. The effects of the weight ratio of the Pd/GR on the particle properties including the morphology and crystal structure were investigated. The morphology of GR-Pd composites was generally the shape of a crumpled paper ball, and the average composite size was about $1{\mu}m$. Pd nanoparticles less than 20 nm in diameter were deposited on GR sheets and the Pd nanoparticles showed clear crystallinity. The characteristic of the glucose biosensor fabricated with the as-prepared GR-Pd composite was tested through cyclic voltammetry measurements. The biosensor exhibited a high current flow as well as clear redox peaks, which resulted in a superior ability of the catalyst in terms of an electrochemical reaction. The highest sensitivity obtained from the amperometric response of the glucose biosensor was $14.4{\mu}A/mM{\cdot}cm^2$.

• 전기학회논문지
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• 제57권11호
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• pp.2006-2010
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• 2008

In this paper, we fabricated a biosensor for detecting hydrogen peroxide and investigated the sensing property. We prepared a viologen and hemoglobin modified gold electrode using self-assembly and layer by layer method. The electrochemical property of the viologen derivative was characterized in 0.1 M $NaClO_4$ electrolyte solution by cyclic voltammetry. The modified electrode showed reversible electrochemical properties and high stability. From the results, the viologen can act as a charge transfer mediator for access to the electrode surface. The catalytic characteristics of the designed sensor proved that hemoglobin has been kept in its natural structure and can retain its biological activity. The designed biosensor showed a fast amperometric response, excellent linearity and low detection limit. In addition, it had high sensitivity, good reproducibility and stability.

• 전기화학회지
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• 제15권4호
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• pp.249-255
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• 2012

크레아티닌 센서의 생체시료 측정 시 가장 심각한 방해 작용을 발생하는 물질인 크레아틴을 효과적으로 제거하기 위하여 creatine kinase와 adenosine triphosphate를 사용한 두 번째 효소층을 도입하여 크레아틴에 대한 방해작용을 현저히 감소시켰다. 또한 평면형 소형 크레아티닌 센서를 개발하기 위해 탄소전극 표면에 Pt black(Pt-B)을 도입하여 표면적을 증가시킴으로써 전기화학적 감응 특성을 증가시킨 스크린 프린팅 방식의 Pt-B/C 전극을 제작하였다. 최적화된 소형 크레아티닌 센서를 흐름계 카트리지에 장착하여 미지시료를 측정한 결과 5% 이내의 오차 범위 내에서 우수한 측정 정확성과 재현성을 보임을 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제9권1호
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• pp.28-36
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• 2018

Metal-organic frameworks have recently been considered very promising modifiers in electrochemical analysis due to their unique characteristics among which tunable pore sizes, crystalline ordered structures, large surface areas and chemical tenability are worth noting. In the present research, $Cu(btec)_{0.5}DMF$ was electrodeposited on the surface of glassy carbon electrode at room temperature under cathodic potential and was initially used as the active materials for the detection of $H_2O_2$. The cyclic voltammogram of $Cu(btec)_{0.5}DMF$ modified GC electrode shows distinct redox peaks potentials at +0.002 and +0.212 V in 0.1 M phosphate buffer solution (pH 6.5) corresponding to $Cu^{(II)}/Cu^{(I)}$ in $Cu(btec)_{0.5}DMF$. Acting as the electrode materials of a non-enzymatic $H_2O_2$ biosensor, the $Cu(btec)_{0.5}DMF$ brings about a promising electrocatalytic performance. The high electrocatalytic activity of the $Cu(btec)_{0.5}DMF$ modified GC electrode is demonstrated by the amperometric response towards $H_2O_2$ reduction with a wide linear range from $5{\mu}M$ to $8000{\mu}M$, a low detection limit of $0.865{\mu}M$, good stability and high selectivity at an applied potential of -0.2 V, which was higher than some $H_2O_2$ biosensors.

• 공업화학
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• 제21권6호
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• pp.689-693
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• 2010

톨루엔에 녹인 천연고무를 탄소가루의 결합재로 사용하여 바이오센서를 제작하였을 때, 반죽은 용매가 증발한 후 기계적 물성을 보였다. 이 특성은 탄소반죽전극 실용화의 선행 조건을 만족시키는 것으로, 이 특성의 활용성을 살펴보기 위하여 과산화수소 정량을 위한 바이오센서를 제작하고, 그것의 전기화학적인 정량 및 정성적 특성을 파악하기 위하여 여러 가지 속도론적 파라메타, 즉 대칭인자(0.37), 교환전류밀도($i_0$, $0.075mAcm^{-2}$), 이중층의 축전용량($C_d$, $9.7{\times}10^{-3}F$), 시간상수(${\tau}_A$, 0.92 s), 최대전류($i_{max}$, $5.92{\times}10^{-7}Acm^{-2}$), Michaelis 상수($K_M$, $1.99{\times}10^{-3}M$) 및 기타 상수들을 도출하였다. 이 실험적 결과는 천연고무가 탄소가루의 결합재로 활용될 수 있음을 보여 주었다.

• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.385-390
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• 2002

Laccase could be successfully assembled on an amine-derivatized platinum electrode by glutaraldehyde coupling. The enzyme layer formed on the surface does not communicate electron directly with the electrode, but the enzymatic activity of the surf ace could be followed by electrochemical detection of enzymatically oxidized products. The well-known laccase substrates, ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) and PPD (p-phenylenediamine) were used. ABTS can be detected down to 0.5 ${\mu}M$ with linear response up to 15 ${\mu}M$ and current sensitivity of 75 nA/ ${\mu}M.$ PPD showed better response with detection limit of 0.05 ${\mu}M$, linear response up to 20 ${\mu}M$, and current sensitivity of 340 nA/ ${\mu}M$ with the same electrode. The sensor responses fit well to the Michaelis-Menten equation and apparent $K_M$ values are 0.16 mM for ABTS and 0.055 mM for PPD, which show the enzymatic reaction is the rate-determining step. The laccase electrode we developed is very stable and more than 80% of initial activity was still maintained after 2 months of uses.

• 전기화학회지
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• 제13권1호
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• pp.50-56
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• 2010

Multi-wall carbon nano-tube(MWCNT)를 이용해 screen printed carbon electrodes(SPCEs)을 제작하여 혈당센서의 선택성과 감도가 증가됨을 확인 할 수 있었다. 효소촉매반응을 위한 탄소전극으로의 전자이동의 매개체로 8족 금속 원소인 오스뮴을 중심금속으로 일차 아민을 포함하는 피리딘(pyridine) 리간드를 배위시켜 $[Os(dme-bpy)_2(4-aPy)Cl]^{+/2+}$를 합성하였다. 합성된 오스뮴 착물은 순환 전압전류법을 포함한 다양한 전기화학분석방법을 이용하여 전기적 성질을 조사하였다. 전기적 흡착방법을 이용하여 일차 아민을 갖는 착화합물을 전극위에 고정화 하였다. 오스뮴이 고정화된 MWCNT-SPCEs는 일반적인 carbon electrode보다 약 100배가량의 오스뮴이 흡착됨을 확인 할 수 있었다. (${\tau}_0=2.0\;{\times}\;10^{-9}\;mole/cm^2$) 마지막으로 당(Glucose)과 당 분해효소(Glucose Oxidase, GOx)에 의한 촉매반응의 전류를 확인하였고, 당 농도에 따라 선형 변화하는 전류의 양도 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권10호
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• pp.449-452
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• 2005

We fabricated an electrochemical detector (ECD) to catalyze redox reaction efficiently by electrodepositing Prussian blue (PB) on the indium tin oxide (ITO) electrode. Capillary electrophoresis (CE) and amperometric method were used. We investigated the PB surface properties by topography from atomic force microscopy (AFM). Also PB film thickness calibration with respect to deposition time and voltage was used to get better PB surFace. The PB thin film of dense and smooth surface could catalyze redox reaction efficiently. Comparing with CE-ECD microchip using bare-lTO electrode, proposed CE-ECD microchip using PB deposited electrode has shown better sensitivity by determining the detected peak current from the electropherograms while the concentration of tested analyzes was maintained the same. It is verified that detection limit can be lowered for 0.01 mM of dopamine and catechol respectively.