• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2229-2237
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• 2012

The two chelates based on calix[4]arene and thiacalix[4]arene have been synthesized and used as neutral ionophores for preparing PVC based membrane sensor selective to $Ho^{3+}$ ion. The addition of potassium tetrakis(4-chlorophenyl)borate (KTpClPB) and various plasticizers, viz., NDPE, o-NPOE, DOP, TEP and DOS have been found to improve significantly the performance of the sensors. The best performance was obtained with the sensor no. 6 having membrane of $L_2$ with composition (w/w) ionophore (2%): KTpClPB (4%): PVC (37%): NDPE (57%). This sensor exhibits Nernatian response with slope $21.10{\pm}0.3mV/decade$ of activity in the concentration range $3.0{\times}10^{-8}-1.0{\times}10^{-2}M\;Ho^{3+}\;ion$, with a detection limit of $1.0{\times}10^{-8}M$. The proposed sensor performs satisfactorily over a wide pH range of 2.8-10, with a fast response time (5 s). The sensor was also found to work successfully in partially non-aqueous media up to 25% (v/v) content of methanol, ethanol and acetonitrile, and can be used for a period of 4 months without any significant drift in potential. The electrode was also used for the determination of $Ho^{3+}$ ions in synthetic mixtures of different ions and the determination of the arsenate ion in different water samples.

• Bulletin of the Korean Chemical Society
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• 제30권10호
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• pp.2303-2308
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• 2009

A thiocyanate poly(vinyl chloride) (PVC) membrane electrode based on [1,2-bis(diphenylphosphino)ethane]dihalopalladium( II), [(dppe)$PdX_2$, X = Cl ($L^1$), X = I ($L^2$)] as active sensor has been developed. The diiodopalladium complex, [(dppe)$PdI_2](L^2$) displays an anti-Hofmeister selectivity sequence: $SCN^-\;>\;I^-\;>\;{ClO_4}^-\;>\;Sal^-\;>\;Br^-\;>\;{NO_2}^-\;>\;{HPO_4}^-\;>\;AcO^-\;>\;{NO_3}^-\;>\;{H_2PO_4}^-\;>\;{CO_3}^{2-}$. The electrode exhibits a Nernstian response (-59.8 mV/decade) over a wide linear concentration range of thiocyanate ($(1.0\;{\times}\;10^{-1}\;to\;5.0\;{\times}\;10^{-6}$ M), low detection limit ($(1.1\;{\times}\;10^{-6}$ M), fast response $(t_{90%}$ = 24 s), and applicability over a wide pH range (3.5∼11). Addition of anionic sites, potassium tetrakis[p-chlorophenyl] borate (KTpClPB) is shown to improve potentiometric anion selectivity, suggesting that the palladium complex may operate as a partially charged carrier-type ionophore within the polymer membrane phase. The reaction mechanism is discussed with respect to UV-Vis and IR spectroscopy. Application of the electrode to the potentiometric titration of thiocyanate ion with silver nitrate is reported.

• 센서학회지
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• 제30권3호
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• pp.175-180
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• 2021

In this paper, methods for improving the sensitivity of gas sensors to NO₂ gas are presented. A gas sensor was fabricated based on an SnO₂ nanowire network using the vapor-phase-growth method. In the gas sensor, the Au electrode was replaced with a fluorinedoped tin oxide (FTO) electrode, to achieve high sensitivity at low temperatures and concentrations. The gas sensor with the FTO electrode was more sensitive to NO₂ gas than the sensor with the Au electrode: notably, both sensors were based on typical SnO₂ nanowire network. When the Au electrode was replaced by the FTO electrode, the sensitivity improved, as the contact resistance decreased and the surface-to-volume ratio increased. The morphological features of the fabricated gas sensor were characterized in detail via field-emission scanning electron microscopy and X-ray diffraction analysis.

• Bulletin of the Korean Chemical Society
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• 제22권12호
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• pp.1345-1349
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• 2001

New quadruply-bridged calix[6]arenes (I-V) have been studied as cesium selective ionophores in poly(vinyl chloride) (PVC) membrane electrodes. PVC membranes were prepared with dioctyl sebacate (DOS) or 2-nitrophenyl octyl ether (o-NPOE) as the sol vent mediator and potassium tetrakis(p-chlorophenyl)borate as the lipophilic salt additive. These ionophores produced electrodes with near-Nernstian slope. The selectivity coefficients for cesium ion with respect to alkali, alkaline earth and ammonium ions have been determined. The lowest detection limit (logaCs+ = -6.3) and the higher selectivity coefficient (logkpotCs+,Rb+ = -2.1 by SSM, -2.3 by FIM for calix[6]arene I) for Cs+ have been obtained for membranes containing quadruply-bridged calix[6]arenes (I, Ⅱ, Ⅲ), which have no para t-butyl substituents on the bridging benzene ring.

• Journal of Electrochemical Science and Technology
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• 제3권4호
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• pp.178-184
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• 2012

A porous nickel (P-Ni) substrate was prepared by selective leaching of zinc from pressed pellets containing powders of Ni & Zn in 4 M NaOH solution. Anodic deposition of manganese oxide onto the porous Ni substrate ($MnO_x$/P-Ni) formed nano-flakes of manganese oxide layers as revealed in SEM studies. Pseudocapacitance of this oxide electrode was evaluated by cyclic voltammetry (CV) and chronopotentiometry (CHP) in 2 M NaOH solution. The specific capacitance of the Mn oxide electrode was as high as 1515 F $g^{-1}$, which was ten times higher than Mn oxide deposited on a flat Ni-ribbon. 80% of capacity was retained after 200 charge/discharge cycles. The system showed no loss of activity in dry form over period of days. The impedance studies indicated highly conducting $MnO_x$/P-Ni substance and the obtained specific capacitance from impedance data showed good agreement with the charge/discharge measurements.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.350-357
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• 2017

Purpose: In-situ monitoring of water quality is fundamental to most environmental applications. The high cost and long delays of conventional laboratory methods used to determine water quality, including on-site sampling and chemical analysis, have limited their use in efficiently managing water sources while preventing environmental pollution. The objective of this study was to develop an on-site water monitoring system consisting mainly of an Arduino board and a sensor array of multiple ion selective electrodes (ISEs) to measure the concentration of $NO_3$ ions. Methods: The developed system includes a combination of three ISEs, double-junction reference electrode, solution container, sampling system consisting of three pumps and solenoid valves, signal processing circuit, and an Arduino board for data acquisition and system control. Prior to each sample measurement, a two-point normalization method was applied for a sensitivity adjustment followed by an offset adjustment to minimize the potential drift that could occur during continuous measurement and standardize the response of multiple electrodes. To investigate its utility in on-site nitrate monitoring, the prototype was tested in a facility where drinking water was collected from a water supply source. Results: Differences in the electric potentials of the $NO_3$ ISEs between 10 and $100mg{\cdot}L^{-1}$ $NO_3$ concentration levels were nearly constant with negative sensitivities of 58 to 62 mV during the period of sample measurement, which is representative of a stable electrode response. The $NO_3$ concentrations determined by the ISEs were almost comparable to those obtained with standard instruments within 15% relative errors. Conclusions: The use of the developed on-site nitrate monitoring system based on automatic sampling and two-point normalization was feasible for detecting abrupt changes in nitrate concentration at various water supply sites, showing a maximum difference of $4.2mg{\cdot}L^{-1}$ from an actual concentration of $14mg{\cdot}L^{-1}$.

• 멤브레인
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• 제3권3호
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• pp.126-135
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• 1993

감응물질로 제4급 암모늄염을 사용하여 PVC를 지지체로 과염소산이온의 농도 $10^{-6}M$까지 측정가능한 이온 선택성 전극을 제작하였다. 감응물질의 화학적 구조와 함량, 가소제의 종류 및 막 두께에 따른 선형응답 범위와 Nernst의 기울기 등 전극특성을 검토하여, 최적 막조건을 구한 다음 측정가능 pH범위와 여러 방해이온에 대한 선택계수를 비교 검토하였다. 과염소산 이온선택성 전극에서 감응물질의 화학적 구조 즉, 알킬기의 탄소고리수가 증가할수록 선형응답 범위 등 전극 특성은 Aliquat 336P, TOAP, TDAP 및 TDDAP의 순서로 좋아졌다. 가소제는 DBP가 가장 좋았고, 감응물질의 양은 최적 함량 이상에서 적을수록 좋았다. 최적 막 조성은 TDDAP 9.09, PVC 30.3 및 DBP 60.61wt%이었고, 막두께 0.45mm이었다. 이 조건에서 선형응답 범위 $10^{-1}~1.2 {\times} 10^{-6}M$, 검출한계 $5.1{\times}10^{-7}M$ 및 Nernst기울기 $57mV/pClO_4$이었다. 막전위는 pH 4~11 범위에서 pH의 영향을 받지 않았으며, 선택계수 서열은 다음과 같았다. $SCN^->I^->NO_3^->Br^->ClO_3^->F^->Cl^->SO_4^{2-}$

• 한국세라믹학회지
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• 제30권10호
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• pp.819-822
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• 1993

The purpose of this paper is a investigation of sensing mechanism for the carbon monoxide gas in CuO infiltrated ZnO ceramics. Potential barriers between CuO and ZnO can explain the selective sensing of carbon monoxide gas in the physically contacted CuO/ZnO ceramics. A specimen having no potential barrier between CuO and ZnO was prepared to see whether the gas sensing mechanism is related to the potential barrier. CuO and ZnO was prepared to see whether the gas sensing mechanism is related to the potential barrier. CuO was painted on the non electrode sides of ZnO ceramics. The CuO painted ZnO ceramics showed that the sensitivityfor the carbon moxnoxide gas was 1.3 times as high as that for the hydrogen gas. It is almost same gas sensitivity as that of the CuO infiltrated ZnO ceramics.

• 대한화학회지
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• 제39권12호
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• pp.925-931
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• 1995

Nonactin을 이온운반체로 사용한 암모늄선택성 전극막 위에 urease를 고정시킨 형태의 요소센서는 혈액 중 여러가지 이온으로부터 방해작용을 받을 수 있다. 이 방해작용은고정화된 효소반응보다는 암모늄선택성 전극막 자체의 부적합한 선택성의 기인한 것이며 본 연구에서는 혈액 중의 요소를 측정할 경우 이들 방해이온에 의해 발생된 오차를 보정하고자 하였다. 이를 위해 혈액 속에 각 방해이온의 정상 평균농도를 포함하고 있는 용액을 검정용액으로 사용하여 이들 방해이온으로부터의 오차를 감소시키고자 하였다. 또한 칼륨이온선택성 전극을 부가적으로 사용하여 요소전극의 측정치를 보정하여 오차를 최소화하고자 하였다. 이와 같은 방법들에 의해 보정된 측정치의 오차는 보정하지 않았을 경우에 비해 현저히 감소함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제25권1호
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• pp.59-62
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• 2004

The ammonium ion-selective electrodes ($NH^+_4$-ISEs) based on the tetrahydrofuran(THF)-containing-16-crown-4 derivatives,1,4,6,9,11,14,16,19-tetraoxocycloeicosane ($L^1$) and 5,10,15,20,-tetramethyl-1,4,6,9,11,14,16,19-tetraoxocycloeicosane ($L^2$), were prepared and the electrode characteristics were tested. The conditioned $NH_4^+$-ISEs (E1) based on $L^1$ with TEHP as a plasticising solvent mediator gave best results with near-Nernstian slope of 53.9 mV/decade of activity, detection limit of $10^{-4.9}$ M, and enhanced selectivity coefficients for the $NH^+_4$ ion with respect to an interfering $K^+$ ion (log $K^{pot}_{NH_4^+,K^+}$ = -1.84). This result was compared to other ammonium ionophores reported previously, for example, that of nonactin (log $K^{pot}_{NH_4^+,K^+}$ = -0.92). The proposed electrode showed no significant potential changes in the range of 3.0 < pH < 9.0.