• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1439-1444
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• 2006

A $Cu^{2+}$ ion-selective membrane microelectrode has been fabricated from poly vinyl chloride (PVC) matrix membrane containing a new symmetrical hexadentate Schiff,s base 2-{1-(E)-2-((Z)-2-{(E)-2-[(Z)-1-(2-hydroxyphenyl)ethylidene]hydrazono}-1-methylpropylidene)hydrazono]ethyl}phenol (HDNOS) as a neutral carrier, Potassium tetrakis(4-chlorophenyl) borate (KTpClPB) as an anionic excluder and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The microelectrode displays linear potential response in the concentration range of $1.0\;{\times}\;10^{-5}-1.0\;{\times}\;10^{-11}$ M of $Cu^{2+}$. The microelectrode exhibits a nice Nernstian slope of 25.9 ${\pm}$ 0.3 mV $decade^{-1}$ in the pH range of 3.1-8.1. The sensor has a relatively short response time in whole concentration ranges ($\sim$5 s). The detection limit of proposed sensor is $5.0\;{\times}\;10^{-12}$ M (320 pg/L), and it can be used over a period of eight weeks. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of $Cu^{2+}$ with EDTA. The proposed membrane electrode was used for the direct determining of $Cu^{2+}$ content in black and red pepper, and in waste water samples.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1298-1302
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• 2011

This study describes the development of an electrochemical array immunochip for the detection of IgG. Interdigitated immunochip platforms were fabricated by sputtering gold on a glass wafer by using MEMS process and then were coated with Eudragit S100, an enteric polymer, forming an insulating layer over the working area of immunochips. The breakdown of the polymer layer was exemplified by the catalytic action of urease which, in the presence of urea, caused an alkaline pH change. This subsequently caused an increase of the double layer capacitance of the underlying electrode. Used in conjunction with a competitive immunoassay format, this allowed the ratio of initial to final electrode capacitance to be directly linked with the concentration of analyte, i.e. IgG. Responses to IgG could be detected at IgG concentration as low as $250\;ngmL^{-1}$ and showed good linearity up to IgG concentration as high as $20\;{\mu}gmL^{-1}$.

• 센서학회지
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• 제19권4호
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• pp.306-312
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• 2010

We have detected deoxynivalenol(DON) using a metal-oxide-semiconductor field-effect-transistor(MOSFET)-based biosensor. The MOSFET-based biosensor is fabricated by a standard complementary metal-oxide-semiconductor(CMOS) process, and the biosensor's electrical characteristics were investigated. The output of the sensor was stabilized by employing a reference electrode that applies a fixed bias to the gate. Au which has a chemical affinity for thiol was used as the gate metal to immobilize a self-assembled monolayer(SAM) made of 16-mercaptohexadecanoic acid(MHDA). The SAM was used to immobilize anti-deoxynivalenol antibody. The carboxyl group of the SAM was bound to the anti- deoxynivalenol antibody. Anti-deoxynivalenol antibody and deoxynivalenol were bound by an antigen-antibody reaction. In this study, it is confirmed that the MOSFET-based biosensor can detect deoxynivalenol at concentrations as low as 0.1 ${\mu}g$/ml. The measurements were performed in phosphate buffered saline(PBS; pH 7.4) solution. To verify the interaction among the SAM, antibody, and antigen, surface plasmon resonance(SPR) measurements were performed.

• Nano
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• 제13권12호
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• pp.1850147.1-1850147.14
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• 2018

In this work, water-soluble and blue-emitting carbon nanodots (CDs) were synthesized from apple peels for the first time via one-step hydrothermal method. The synthetic route is facile, green, economical and viable. The as-prepared CDs were characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR), X-ray photoelectron (XPS), fluorescence and UV-Vis absorption spectroscopy in terms of their morphology, surface functional groups and optical properties. The results show that these CDs possessed ultrasmall size, good dispersivity, and high tolerance to pH, ionic strength and continuous UV irradiation. Significantly, the CDs had fast and reversible response towards temperature, and the accurate linear relationship between fluorescence intensity and temperature was used to design a novel nanothermometer in a broad temperature range from 5 to $65^{\circ}C$ facilely. In addition, the fluorescence intensity of CDs was observed to be quenched immediately by Cr(VI) ions based on the inner filter effect. A low-cost Cr(VI) ions sensor was proposed employing CDs as fluorescent probe, and it displayed a wide linear range from 0.5 to $200{\mu}M$ with a detection limit of $0.73{\mu}M$. The practicability of the developed Cr(VI) sensor for real water sample assay was also validated with satisfactory recoveries.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.184-188
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• 2008

본 연구는 산도 변화에 따라 색이 빠르게 변하는 특성을 가지고는 있는 반응성 염료(1,3-bisdicyanovinylindane)를 이용하여 신속하고 정확한 산성가스 검출을 위한 화학적 센서 제작을 위한 방법을 제안하였다. 반응성 염료(1,3-bisdicyanovinylindane)는 산성 상태에서 염료와 양성자의 해리되어 흡광도의 변화를 이용하면 손쉽게 미세화학센서를 제작 할 수 있었다. 또한, 반응성 염료는 수용액 상태에서 매우 안정적인 음전하를 지니고 있어 양전하를 지니는 고분자 전해질과 쉽게 layer-by-layer(LBL) 방법을 이용하여 다층 박막 구조를 쉽게 구현할 수 있었다. 먼저, 마이크로스탬프 위에 비반응성 염료와 양전하 고분자 전해질을 적층하여 다층박막을 형성한 후 센서기판에 프린팅한다. 이후 지시염료와 양전하 고분자 전해질을 다시 적층하여 최종 가스센서를 구현한다. 고안된 가스 센서는 산성가스와 반응을 통해 사용자에게 주의를 유도하는 해골 모양을 표현하여 실제 응용성을 보여주었다. 제시된 산성가스 감지센서는 첫째로 제작 과정이 매우 단순하며 저비용이고 둘째로 완성된 감지센서는 환원 과정을 통해 여러번 재사용될 수 있으며 마지막으로 센서 제작 공정이 매우 단순하며 수용액을 기반으로 하는 환경친화적 방법이다.

• 한국환경과학회지
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• 제13권3호
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• pp.245-250
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• 2004

The SBR(Sequencing Batch Reactor) process is ideally suited to treat high loading wastewater due to its high dilution rate. SBR operates by a cycle of periods consisting of filling, reacting, settling, decanting and idling. The react phases such as aeration or non-aeration, organic oxidation, nitrification, denitrification and other bio-logical reactions can be achieved in a reactor. Although the whole reactions can be achieved in a SBR with time distributing, it is hard to manage the SBR as a normal condition without recognizing a present state. The present state can be observed with nutrient sensors such as ${NH_{4}}^{+}-N$, ${NO_{2}}^{-}-N$, ${NO_{3}}^{-}-N} and ${PO_{4}}^{ 3-}-P.$ However, there is still a disadvantage to use the nutrient sensors because of their high expense and inconvenience to manage. Therefore, it is very useful to use common on-line sensors such as DO, ORP and pH, which are less expensive and more convient. Moreover, the present states and unexpected changes of SBR might be predicted by using of them. This study was conducted to get basic materials for making an inference of SBR process from ORP(oxidation reduction potential) of synthetic wastewater. The profiles of ORP, DO, and pH were under normal nitrification and denitrification were obtained to compare abnormal condition. And also, nitrite and nitrate accumulation were investigated during reaction of SBR. The bending point on ORP profile was not entirely in the low COD/NOx ratio condition. In this case, NOx was not entirely removed, and minimum ORP value was presented over -300mV. Under suitable COD/NOx ratio which complete denitrification was achieved, ORP bending point was observed and minimum ORP value was under -300m V. Under high COD/NOx ratio, ORP bending point was not detected at the first subcycle because of the fast denitrification and minimum ORP value was under -300mV at the time.

• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.43-47
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• 2008

The nickel and cobalt resistance of Cupriavidus metallidurans CH34 is mediated by the CnrCBA efflux pump encoded by the cnrYHXCBAT metal resistance determinant. The products of the three genes cnrYXH transcriptionally regulate expression of cnr. CnrY and CnrX are membrane-bound proteins, probably functioning as anti-sigma factors, whereas CnrH is a cnr-specific extracytoplasmic functions (ECF) sigma factor. The periplasmic domain of CnrX (residues 29-148) was cloned as a N-terminal His-tagged protein, expressed in Escherichia coli, and purified using affinity chromatography and gel filtration. The molecular mass was estimated to be about 13.6kDa by size exclusion chromatography, corresponding to a monomer. The tetragonal bipyramid crystals were obtained by mixing an equal volume of protein in 50mM Tris-HCl, pH 7.5, 1% glycerol, 100mM NaCl, 1mM DTT, and the reservoir solution of 15% w/v PEG 2000, 100mM lithium chloride at 277K in 2-4 days using hanging drop vapor diffusion. The protein concentration was 24mg/ml. The crystal that diffracted to $2.42{\AA}$ resolution belongs to space group $P4_1\;or\;P4_3$ with unit cell parameters of $a=b=32.14{\AA},\;c=195.31{\AA},\;{\alpha}={\beta}={\gamma}=90^{\circ}$, with one molecule of CnrX in the asymmetric unit.

• 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.

• KSBB Journal
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• 제21권4호
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• pp.279-285
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• 2006

본 연구에서는 trypsin을 모델 단백질로 하여 단백질 본연의 환성을 유지할 수 있는 고정화 방법을 찾기 위하여 공유결합방법과 친화력 결합방법을 이용하여 trypsin을 고정화 하였다. Streptavidin-biotin system을 이용한 고정화 방법은 bioactivity 유지측면에서 공유결합 방법보다 우수함을 확인하였다. 하지만 streptavidin-biotin system을 이용하였을 때 고정화 수율이 낮은 것은 해결해야 할 과제이다. 분자량이 다른 기질들(BAPNA, insulin, BSA)을 대상으로 고정화 trypsin의 부위 특이적 절단 특성을 분석한 결과 streptavidin-biotin에 의해 고정화된 trypsin이 절단효율도 높고 sequence coverage도 높은 것으로 확인되었다. 또한 공유결합된 trypsin은 견고한 분자구조를 나타낸 반면 streptavidin-biotin system으로 고정화된 trypsin은 유연성이 높은 것을 QCM-D를 이용하여 관찰할 수 있었다. 따라서 streptavidin-biotin system에 의한 고정화 방법에서 streptavidin-biotin 결합이 일종의 spacer arm 역할을 하면서 고정화된 trypsin의 분자유연성을 향상시켜 절단반응의 부위특이성과 절단수율을 향상시키는 것으로 판단되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1891-1893
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• 2004

이 논무에서는 유입식 변압를 대상으로 UHF 대역의 펄스신호를 검출하는 센서를 소개하고, 이를 이용한 방전 결함별 측정 결과를 소개한다. 측정결과는 기존의 PRPD법과 주파수 Domain과 위상 Domain에 대한 정보를 가지는 p-f-q 분석으로 측정 하였으며, 본 논문에서는 후자의 결과를 중심으로 서술 하였다.