• Journal of Sensor Science and Technology
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• v.1 no.2
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• pp.101-106
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• 1992

pH-ISFETs, the semiconductor pH sensors, were combined with immobilized enzyme membranes to prepare FET type urea and glucose sensors and its operational characteristics were investigated. Photolithography techniques were applied to immobilize enzymes on the $H^{+}$ sensing membrane of the pH-ISFET with photo-sensitive polymers, PVA-SbQ. Fabricated urea and glucose sensors could determine $0.5{\sim}50{\;}mg/dl$ urea concentrations and $10{\sim}1000{\;}mg/dl$ glucose concentrations, respectively.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.6-12
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• 1998

A FET(Field Effect Transistor) type dissolved $CO_2$ sensor based on Severinghaus type $CO_2$ sensor was fabricated by the photolithographic process. The sensor consists of Ag/AgCl reference electrode and membranes (hydrogel membrane and $CO_2$ gas permeable membrane) on the pH-ISFET base chip. Ag/AgCl reference electrode was fabricated as follows. Ag layer was thermally evaporated and then its upper surface was chemically chloridized into the AgCl. The hydrogel used as an internal electrolyte solution was fabricated by a photolithographic method using 2-hydroxyethyl methacrylate(HEMA) and acrylamide. $CO_2$ permeable membrane on the top of the hydrogel layer was formed by photolithographic process with UV-oligomer. The FET type $pCO_2$ sensor fabricated by photolithographic method showed good linearity within the concentration range of $10^{-3}{\sim}10^0mole/{\ell}$ of dissolved $CO_2$ in aqueous solution with high sensitivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.792-796
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• 2002

In this work, porous silicon(PS) layer is used as a sensing material to detect organic gases. To do this, PS sensors with membrane structure are fabricated. The sensors were made by applying the technologies of membrane formation by anisotropic etching of silicon, and PS layer formation by anodization in HF solution. From fabricated sensors, current-voltage (I-V) curves were measured against ethanol (called alcohol), methanol and acetone gases evaporated from 0.1 to 0.5% solution concentrations at $36^{\circ}C$. As the result, all curves showed rectifying behavior due to a diode structure between Si and PS, and the conductance of sensor devices increased largely with the organic solution concentration at high voltage of 5V.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.952-956
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• 1989

We experimentally investigated the mechanical and electrical characteristics of the poly vinyl alcohol(PVA) hydrogel which have attracted special interest as a mechanochemical material, and the applicability of the hydrogel membrane to a sensor for measuring large strain. As a result, the PVA hydrogel could be regarded as a Hookean elastic material and was treated as an electric resistance which was proportional to the tensile strain within a linearly elastic range.

• Journal of Sensor Science and Technology
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• v.30 no.5
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• pp.314-319
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• 2021

In this study, biomarkers were analyzed and segmented using tunable infrared gas sensors after performing the principal component analysis. The free spectral range of the device under test (DUT) was around 30 nm and DUT-5580 yielded the highest output voltage property among the others. The biomarkers (isoprophyl alcohol, ethanol, methanol, and acetone solutions) were sequentially mixed with deionized water and their mists were carried into the gas chamber using high-purity nitrogen gas. A total of 17 different mixed gases were tested with three tunable infrared gas sensors, namely DUT-3144, DUT-5580, and DUT-8010. DUT-8010 resolved the infrared absorption spectra of whole mixed gases. Based on the principal component analysis with each DUT and their combinations, each mixed gas and the trends in increasing gas concentration could be well analyzed when the contributions of the eigenvalues of the first and second were higher than 70% and 10%, respectively, and their sum was greater than 90%.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.193-197
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• 2014

The electrode for gas sensor was prepared by using pitch-based activated carbon fibers and polyvinyl alcohol (PVA) to investigate the toxic gas sensing characteristics. The physicochemical properties of activated carbon fibers electrode for gas sensor were analyzed with SEM and BET. Toxic gases sensing property of the electrode was also identified by different toxic gases such as $NH_3$, NO and $CO_2$. The specific surface area of activated carbon fibers electrode for gas sensor was decreased by 33% owing to PVA used as a binder compared with the activated carbon fibers. However, its pore size distribution of the ACF electrode was not greatly influenced by PVA. The activated carbon fibers electrode for gas sensor responded to toxic gases by electron hopping unlike semiconductor based gas sensors. In this study, activated carbon fibers electrode was decreased to 7.5% in resistance for the NH3 gas of the 100 ppm concentration and its $NH_3$ gas sensing property was confirmed the most excellent compared with other toxic gases.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1865-1872
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• 2011

This study investigates the sensitivity of a gas sensor to volatile organic compounds (VOCs) at various operating temperatures and catalysts. Nano-sized powdered $WO_3$ prepared by sol-gel and chemical precipitation methods was mixed with various metal oxides. Next, transition metals (Pt, Ru, Pd, and In) were doped on the surface of the mixture. Metal-$WO_3$ thick films were prepared using the screen-printing method. The physical and chemical properties of the films were studied by SEM/EDS, XRD, and BET techniques. The measured sensitivity to VOCs is defined as the ratio ($R_a/R_g$) of resistance ($R_{air}$) of $WO_3$ film in the air to resistance ($R_{gas}$) of $WO_3$ film in a VOCs test gas. The sensitivity and selectivity of the films were tested with various VOCs such as acetaldehyde, formaldehyde, methyl alcohol, and BTEX. The thick $WO_3$ film containing 1 wt % of Ru and 5 wt % of $SnO_2$ showed the best sensitivity and selectivity to acetaldehyde gas at an operating temperature of 300 $^{\circ}C$.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.655-658
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• 2015

The development of glucose biosensors has been attracting much attention because of their importance in monitoring glucose in the human body; such sensors are used to diagnose diabetes and related human diseases. Thanks to the high selectivity, sensitivity to glucose detection, and relatively low-cost fabrication of enzyme-immobilized electrochemical glucose sensors, these devices are recognized as one of the most intensively investigated glucose sensor types. In this work, ZnO nanofibers were synthesized using an electrospinning method with polyvinyl alcohol zinc acetate as precursor material. Using the synthesized ZnO nanofibers, we fabricated glucose biosensors in which glucose oxidase was immobilized on the ZnO nanofibers. The sensors were used to detect a wide range of glucose from 10 to 700 M with a sensitivity of $10.01nA/cm^2-{\mu}M$, indicating that the ZnO nanofiber-based glucose sensor can be used for the detection of glucose in the human body. The control of nanograins in terms of the size and crystalline quality of the individual nanofibers is required for improving the glucose-sensing abilities of the nanofibers.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.23-29
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• 2019

A copper tetracumylphenoxy phthalocyanine (CuPccp) thin film was formed on an organic insulator film by Langmuir-Blodgett (LB) deposition for gas sensor fabrication. To increase the reproducibility of film transfer, stearyl alcohol was used as a transfer promoter. The structural properties of the CuPccp layers were optically monitored through attenuated total reflection and polarization-modulated ellipsometry techniques. The average thickness of a single layer of the CuPccp LB film was measured to be 2.5 nm. Despite the role of the transfer promoter, the stability of the layer transfer was not sufficient to ensure homogeneity of the LB film. This was probably due to the presence of aggregates in the molecular structure of the CuPccp LB film. Nevertheless, copper phthalocyanine polymorphism can be greatly suppressed by the LB arrangement, which appears to contribute to the improvement of electrical conductivity. The p-type semiconductor characteristics were confirmed by Hall measurements from the CuPccp LB films.

• Journal of the Korean Institute of Gas
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• v.9 no.4 s.29
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• pp.26-29
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• 2005

In this paper, the solvent sensing properties of the metallophthalocyanine macrocyclic compounds(ZnPc) have been deposited as thin films by the spin-coated method and evaporated methods onto alumina substrates and quartz substrates. And then the spin-coated materials of Zinc phthalocyanine solutions blended with $N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,\;1-biphenyl-4,4'-diamine\;and/or\; Poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene-vinylene]$ solutions. The influences of the blended metallophthalocyanine macrocyclic compounds on the resistance have been measured and analysed in five different vapour organic compounds.