• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권3호
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• pp.107-110
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• 2006

We fabricated the monolayers onto QCM by self-assembly using viologen, which has been widely used as electron acceptor. A gold electrode of the QCM was cleaned by piranha solution and prepared the ethanol-acetonitrile(1:1) solution with 2 m mol/l viololgen compounding of pure hi gas. We determined the time dependence to resonant frequency shift during self-assembly process and the electrochemical behavior of the self-assembled viologen monolayers by cyclic voltammetry. With increasing scan rate, the redox peak current of the viologen increased linearly. This was signified that the redox reaction was reversible. The EQCM measurements revealed the anions transfer during redox reactions, respectively. From the EQCM data, the well-defined shape peaks were nearly equal charges by cyclic voltammetry.

• Bulletin of the Korean Chemical Society
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• 제19권11호
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• pp.1227-1232
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• 1998

The frequency response on the tip-sample distance in scanning electrochemical microscopy (SECM) that is combined with an electrochemical quartz crystal microbalance (EQCM) is described. The oscillation frequency of the EQCM increases rapidly when the SECM tip is very close to the substrate electrode surface. This frequency increase is reproducible regardless of the current feedback in SECM, which is attributed to the stress caused by the tip pressing the quartz crystal. It is useful to calibrate the tip-sample distance with respect to the frequency change when a combined system of SECM and EQCM (SECM-EQCM) is used. This method could be applied to several cases such as rigid metal electrode and non-conducting or partially conducting polymer coating prepared on the quartz crystal regardless of the feedback current.

• Nano
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• 제13권11호
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• pp.1850131.1-1850131.19
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• 2018

In this paper, an electrochemical sensor for epinephrine (EP), a neurotransmitter was developed by anchoring molecularly imprinted polymeric matrix (MIP) on the surface of gold-coated quartz crystal electrode of electrochemical quartz crystal microbalance (EQCM) using starch nanoparticles (Starch NP) - reduced graphene oxide (RGO) nanocomposite as polymeric format for the first time. Use of EP in therapeutic treatment requires proper dose and route of administration. Proper follow-up of neurological disorders and timely diagnosis of them has been found to depend on EP level. The MIP sensor was developed by electrodeposition of starch NP-RGO composite on EQCM electrode in presence of template EP. As the imprinted sites are located on the surface, high specific surface area enables good accessibility and high binding affinity to template molecule. Differential pulse voltammetry (DPV) and piezoelectrogravimmetry were used for monitoring binding/release, rebinding of template to imprinted cavities. MIP-coated EQCM electrode were characterized by contact angle measurements, AFM images, piezoelectric responses including viscoelasticity of imprinted films, and other voltammetric measurements including direct (DPV) and indirect (using a redox probe) measurements. Selectivity was assessed by imprinting factor (IF) as high as 3.26 (DPV) and 3.88 (EQCM). Sensor was rigorously checked for selectivity in presence of other structurally close analogues, real matrix (blood plasma), reproducibility, repeatability, etc. Under optimized conditions, the EQCM-MIP sensor showed linear dynamic ranges ($1-10{\mu}M$). The limit of detection 40 ppb (DPV) and 290 ppb (EQCM) was achieved without any cross reactivity and matrix effect indicating high sensitivity and selectivity for EP. Hence, an eco-friendly MIP-sensor with high sensitivity and good selectivity was fabricated which could be applied in "real" matrices in a facile manner.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2000년도 추계총회 및 학술발표회
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• pp.18-18
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• 2000

• 분석과학
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• 제8권3호
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• pp.383-389
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• 1995

A new approach for the measurement of the surface coverages of monomolecular films fabricated by spontaneous adsorption of thiol compounds on gold is described. It is based on the mass change measurement with EQCM for the reductive electrochemical desorption of thiol in aqueous KOH solution. The results were compared with that of charge calculation during electrochemical desorption. The surface coverage value for eicosanethiol agrees with that obtained by charge calculation of electrochemical reduction as well as that expected from a geometrical model of the compact monolayer.

• Bulletin of the Korean Chemical Society
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• 제17권1호
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• pp.39-42
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• 1996

A new oscillator for electrochemical quartz crystal microbalance (EQCM) was developed by using an operational amplifier without any LC component. The home-made EQCM using this oscillator showed only 0.02 Hz frequency noise at 0.3 s gate time when a 6 MHz AT-cut crystal was used. Pb underpotential deposition on gold substrate in nitric acid media was examined to demonstrate the performance of this EQCM. The derivative of frequency change could be obtained without averaging multiple scans.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1443-1444
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• 2012

• 한국전기전자재료학회논문지
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• 제19권3호
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• pp.246-249
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• 2006

We fabricated self-assembled monolayers(SAMs) onto quartz crystal microbalance(QCM) using viologen, which has been widely used as electron acceptor and electron transfer mediator. We determined the time dependence on resonant frequency shift during self-assembly process and observed the morphology of self-assembled monolayers by STM and investigated the electrochemical behavior of SAMs by cyclic voltammetry. Electrochemical deposition of viologen was investigated using electrochemical quartz crystal microbalance(EQCM). The redox reactions of viologen were highly reversible and the EQCM has been employed to monitor the electrochemically induced adsorption of SAMs during the redok reactions. The total frequency change was about 9.5 Hz, and 7.1 Hz. From the data, we could know the mass change was about 10.16 ng and 7.60 ng, respectively. Finally, the EQCM has been employed to monitor the electrochemically induced adsorption of self-assembled monolayers on Au surfaces.

• 전기화학회지
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• 제4권4호
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• pp.160-165
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• 2001

황산원자를 포함하는 mercapto화합물은 도금시 전착속도를 증가시키는 첨가제로 알려져 있는데, 이 중 4가지의 mercapto 화합물을 선정하여 농도를 변화시켜가며 Hull cell test, Haring-Blum cell test, cathodic polarization, EQCM(Electrochemical Quartz Crystal Microbalance)등을 이용하여 도금특성 및 throwing power를 알아보았다. Cathode polarization 및 EQCM을 통한 구리 전착량을 알아본 결과 4가지의 mercapto 화합물 중 3-mercapto-1-propanesulfonic acid가 activator로서 가장 적당하였으며, 그 농도가 20 ppm에서 throwing power를 증가시키고, 농도 및 활성 과전압이 오직 $Cl^-$만 포함되었을 때보다 cathodic scan시 100 mV 만큼 shift되어 증착속도를 증가시킴을 알 수 있었다.

• 전기화학회지
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• 제5권3호
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• pp.143-152
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• 2002

Self-assembled monolayer(SAM)로 변형된 금 전극 위로 폴리피롤의 전기화학적 석출 과정을 수용액 상태에서 in-situ EQCM (Electrochemical Quartz Crystal Microbalance)과 ex-situ AFM (Atomic Force Microscopy)을 이용하여 조사하였다. 금 전극에서 cyclic voltammetry로 살펴본 폴리머의 석출은 산화 제한 전위 (anodic limiting potential) 값에 매우 의존적이었으며 주사 횟수에는 의존하지 않았다. 제한 산화 전위가 0.8V (vs Ag | ArCl) 이상일 때 폴리머의 석출은 크게 증가하였다. 그리고 주사 횟수가 증가하면서 질량의 비이상적 변화가 관찰되었는데 이것은 폴리피롤 필름의 rearrangement가 원인이라고 생각된다. 1-dodecanethiol SAM 전극과 thiophene SAM전극에서는 폴리머가 3차원적으로 성장하며 필름의 rearrangement를 수반하였지만 BPUS $(Bis(\omega(N-pyrrolyl)-n-undecyl)disulfide)$ SAM 전극에서는 2차원적인 layer-by-layer 성장을 하고 필름의 rearrangement는 관찰되지 않았다. 폴리머가 급격하게 전극 면으로 석출되면 사슬 모양과 도너츠 모양의 폴리머를 만들며, 정류 상태에 이르면서 주름잡힌 폴리머 필름이 생성되는 것이 원자 힘 현미경 (Atomic Force Microscopy) 이미지로 관찰되었다.