Vol. 17, Supplement B (2001)

Vol. 17, Supplement B (2001)

Proceedings of the 33rd Chemical Sensor Symposium
December 4-7, 2001

Abstracts

1A02
Construction of New Biosensor System Built up with pH Sensitive Insulating Polyprrole

Tetsuya Osaka

Department of Applied Chemistry, School of Science and Technology, Waseda University
3-4-1 Okubo, Shinjyuku-ku, Tokyo 169-8555, Japan

An Electrode modified with an insulating polyprrole (i-PPy) film formed by electropolymerization shows a good Nernstian response to pH. By combining the pH sensitive i-PPy modified electrode with the pH change during the enzymatic reaction of hydrolysis of bio-substance catalyzed by enzyme, a potentiometric biosensor could be fabricated. In particular, the biosensor using an electrode modified with a composite film of polyion complex (PIC) with i-PPy achieved highly sensitive detection of bio-substance such as urea in a batch analysis method. This system essentially was applied to various biosensors for many analytes accompanied with pH changes during the enzymatic reactions. A small and highly sensitive potentiometric biosensors for urea, creatinine, arginine, acetylcholine were obtained. The system was also applied to an amperometric biosensor based on pH-stat method. Furthermore, in order to enable the fast and continuous assay, a flow injection analysis system was constructed with PIC / i-PPy composite film modified electrode. This sensor demonstrated sensitivity of 120 mV decade-1 to urea, and was capable of assaying more than 15 samples per hour.

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1A05
Environmental Gas Sensors and Their Application

Duk-Dong Lee

School of Electronic & Electrical Engineering, Kyungpook National University

The natural atmospheric environment has become polluted and is rapidly deteriorating due to marked growth in industrial development and population. Thus the monitoring and controlling of atmospheric environmental in which various pollutants are contained is very important issue to prevent environmental disasters. This paper presents a brief overview of environmental gas sensors and their applications. The sensing properties of solid state gas sensors to environmental gases and their applications to monitoring systems will be summarized.

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1A09
Development of Thick Film Gas Sensors Using a Screen Printing Technique

Yoshinobu Matsuura

Figaro Engineering Inc.
1-5-11, Senbanishi, Mino, Osaka 562-8505, Japan

For fabrication of metal oxide semiconductor gas sensors, a screen printing method has advantages, such as to uniform sensor size, to miniaturize the sensor element, to form multielements on one chip, etc. We have developed various kinds of thick film gas sensors with this method so far. As an example, a low power consumption carbon monoxide sensor utilizing a pulse heating method, a dual type sensor with a water vapor sensing element as well as a gas sensing element to reduce influence of humidity, and a dual type sensor for air quarity control in a vehicle's cabin and a low power consumption methane sensor are described in this paper.

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1A10
Microstructure and CO Sensing Properties of SnO₂ Thin Films Derived from Chemically-Modified Sol-Gel Method

M. Shoyama* and N. Hashimoto*

*Ceramics Laboratory, Industrial Research Division, Mie Prefectural Science and Technology Promotion Center
788 Higashiakuragawa, Yokkaichi, Mie 510-0805, Japan

Microstructure and CO gas sensing properties of SnO₂ thin films prepared by a chemically-modified sol-gel method were evaluated. SnO₂ thin films were fabricated by spin-coating, and its sensing properties to CO gas were evaluated at temperatures of 200～500℃. As a result, addition of polyethylene glycol(PEG) to Sn precursor solution was much effective to decrease the particle size from 30nm (PEG-free) to 10nm (PEG 20wt%), and improved the sensitivity for CO gas. Maximum sensitivity (S=565) to CO (100ppm) was achieved at 500℃.

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1A11
CO Gas Selectivity of SnO₂-ZnO Composite Sensor

Won Jae Moon, Ji Haeng Yu, and Gyeong Man Choi

Department of Materials Science and Engineering Pohang University of Science and Technology
San 31, Hyoja-dong, Pohang 790-784, South Korea

For the selective detection of reducing gases (CO gas against H₂ gas, or vice-versa), SnO₂-ZnO composites were fabricated and the surface was coated with CuO. The electrical conductivity and the CO and the H₂ gas sensing properties of CuO-coated SnO₂-ZnO composites were examined between 80℃ and 450℃. The CuO, coated and thus doped to SnO₂, apparently acted as a catalyst and thus lowered the sensing temperature and slightly increased the sensitivity values for both CO and H₂ gases. The ZnO addition into CuO-doped SnO₂ increased the sensitivity to CO gas at low temperature and the sensitivity to H₂ gas at high temperature due to the combined effect of the microstructure and the composition. As a result, the high selectivity for CO gas was obtained between 150℃ and 250℃ while the high selectivity for H₂ gas was shown between 310℃ and 400℃, depending upon the ZnO content. As the content of ZnO increases above 3 mol%, the CO gas selectivity decreased.

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1A12
H₂ selective gas sensor based on MnO_x/In₂O₃

A. Katsuki, K. Fukui and H. Ishikawa

New Cosmos Electric Co., Ltd.
3-6-25, Mitsuya-Naka, Yodogawa-Ku, Osaka 532-0036, Japan

H₂ selective hot wire type semiconductor gas sensor based on a MnO_x/In₂O₃ system available for detection of H2 up to 2 vol% was developed in the present study. The effects of some metal oxides (Mn, Co,Cr) on the linearity of sensitivity vs. gas concentration curve of the sensor was investigated. In(OH)₃ was prepared from hydration of InCl₃ with aqueous ammonia, and pyrolyzed into In₂O₃(600℃, 4 h) in air. The In₂O₃ powder was distributed in a sphere(0.5 mmφ) to cover a platinum wire(20μmφ) coil that is a heater and a electrode for the semiconductor, and sintered at 600℃ for 2 h in air. The gas sensor had only two terminals. Each oxide of Mn, Cr or Co was added into the sintered layer through impregnation of aqueous solution of each nitride following by pyrolysis at 600℃ for 1 h in air. Further, the surface part of the sintered layer was converted to a silica-accumulated dense layer by chemical vapor deposition of hexiamethyldisiloxane. Each gas sensor was operated at ca. 480℃ by a bridge electric circuit. As a result, MnO_x gave a most improved linearity and a prominent resistance against H₂ of 2 vol%.

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1A14
High Stabilized Micro Gas Sensors with Single Electrode

Kap-Duk Song*, Yeung-Il Bang*, Sang-Mun Lee*, Yun-Su Lee*, Jeung-Soo Huh**, and Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
**Dept. of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea

Many metal oxide gas sensors have been developed for improving stability during last few decades. Their resistance of metal oxide gas sensor exposed to normal air changes continuously, therefore it may not be easily adaptable to measuring or detecting systems. In this paper, we propose new type of micro gas sensor with single electrode for improving stability and sensitivity. Generally, metal oxide gas sensors have two electrodes for heating and sensing. But this new type sensor has only a single electrode by forming a sensing material onto heating electrode. This micro gas sensor shows low resistance(a few hundred Ω) for parallel values of Pt resistance and SnO₂ sensing resistance. Therefore, it is appeared that the deviation of total resistance in the normal air condition is very low and so stability is improved. Pt as a heating and sensing electrode is sputtered on glass (pyrex 7440) substrate and SnO₂ sensing material is thermally evaporated on Pt electrode. SnO₂ is patterned by lift-off process and then thermally oxidized in O₂ condition for 1 hr., 600 ℃. The size of fabricated sensor is 1.9 × 2.1 mm2 As a result of CO gas sensing characteristics, this sensor shows 100 mV voltage output for 1000 ppm and linearity for wide range(0～20,000 ppm) of gas concentration. And the sensor shows a good recovery characteristics of 1 % deviation compared to initial resistance. The deviation of sensor resistance is about 5 % for 6 months and little influence for humidity of 90 R.H.%.

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1A15
GAS SENSORS BASED ON THE COMBINATION OF SILICON MICROMACHINING AND THICK FILM TECHNOLOGIES

A.A.Vasiliev*, A.V.Pisliakov*, M.Zen**, B.Margazin**, V.Guarniery**, G.Soncini**, G.Pignatel**.

*RRC Kurchatov Institute, Institute of Molecular Physics, **Instituto Trentino di Cultura, IRST
*123182, Moscow, Russia
**via Sommarive, Povo-Trento, 380050, Italy

The results of the application of combined technology for the manufacturing of metal oxide gas sensors are discussed. This technology includes the manufacturing of micromachined thin dielectric membrane with microheater used as a support for thick film metal oxide gas sensing layer. The optimization of geometry of the membrane enabled the fabrication of methane gas sensor with power consumption of ～25 mWatt. The application of pulsing heating with duty cycle of about 5 % enables average power consumption of the sensors of about 1 mW. Dielectric membrane withstands more than 5 millions of cycles of switching on and off. Two types of microheaters were studied. Polysilicon heater is characterized by drift of resistance of about 0.1 % per day at 400℃. Better results were obtained for Pt heater fabricated with the application of a modification of lift-off photolithography. Fast "thermal" response of membrane heater enables a very important modification of calibration of gas sensors without the utilization of calibrated gas mixture.

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1A17
Identification of odors using a sensor array with kinetic working temperature and Fourier spectrum analysis

K. Cai*, T. Maekawa and T. Takada

Cosmos Lab., New Cosmos Electric Co., Ltd.
3-6-25 Mitsuyanaka, Yodogawa-ku, Osaka 532-0036, Japan

A method for the identification of the odors using a sensor array driven dynamically has been developed, in which transient responses of the sensor array were used to recognize target odors. Fourier transform were used to transform the transient response curves of the sensor array into Fourier spectrums, and the patterns composed of some of magnitudes in the spectrums were used in the pattern recognition to identify the odors. An identification of odors with 3 kinds of 10% ethanol solutions of tea extract and 3 kinds of Japanese soy sauces was performed by the method. In consequence, the sample odors could be correctly recognized without any pretreatment device for separation of minor components from the main component.

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2A03
Detection of Odorous Compounds Using Tin Oxide Gas Sensors - Sensing Properties to Aliphatic Ketones -

Jun TAMAKI, Masaki SAKAGUCHI, Katsunori FUKUZAWA, Yoshifumi YAMAMOTO, and Masao MATSUOKA

Department of Applied Chemistry, Faculty of Science and Engineering, Ritsumeikan University
Kusatsu-shi, Shiga 525-8577, Japan

The sensing properties to 5 aliphatic ketones (2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, and 3-octanone) have been investigated for pure SnO2 and 17 kinds of modified SnO₂ sensors. Among various SnO₂ based sensors tested, ZnO- and WO₃-SnO₂ sensors showed high sensitivity to these ketones (S=20-50 to 10 ppm ketones at 400 ℃). The ZnO-SnO₂ sensor was non-selective sensor, where there was no remarkable difference in the sensitivity between these ketones. On the other hand, the WO₃-SnO₂ sensor exhibited 2.5-3 times higher sensitivity to 3-octanone than those to 2-ketones, suggesting the 3-octanone selective sensor. It is considered that these sensing properties result from the modification of catalytic properties due to metal oxide addition. From the results of oxidation of these ketones, it was found that the catalytic activity was decreased for ZnO- and WO₃-SnO₂. It seems that the decrease in oxidation activity induces the enhancement of sensitivity.

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2A04
Effects of Crystal Structures on Gas Sensing Properties of Nanocrystalline ITO Thick Films

Bong-Chull Kim*, Jae-Yeol Kim*, Chang-Hyun Shim**, Duk-Dong Lee** and Jeung-Soo Huh*

*Department of Metallurgical Engineering, Kyungpook National University
**School of Electronic and Electrical Engineering, Kyungpook National University
Taegu, Korea

Two kinds of nanocrystalline indium tin oxide (ITO) powders with different crystal structures - rhombohedral and cubic - were prepared using a coprecipitation process through the control of pH of a mixing solution and aging time after coprecipitation. The two powders have the same particle size of 15 nm in diameter but different morphologies (spherical for rhomboheral and rectangular for cubic). The gaseous ethanol sensing characteristics of the sensors prepared by the two ITO powders were quite different. The sensitivity of rhombohedral ITO sensor was high compared to that of the cubic ITO sensor across all temperatures. The reason for this is explained through the viewpoint of the binding energy as shown in XPS measurement and the surface structure relating to the crystal structure.

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2A05
Studies on the Mechanism of Conducting Polymer Sensor for Volatile Organic Compound

H. R. Hwang*, J. G. Roh*, D. D. Lee**, J. O. Lim***, J. Y. Lee****, J. S. Huh*

*Department of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu Taegu, Korea
**School of Electronic and Electrical Engineering, Kyungpook National University
Taegu Korea
***Medical Research Institute, Kyungpook National University
Taegu Korea
****Department of Textile Engineering, Sungkyunkwan University
suwon Korea

In this study, we fabricated chemically polymerized PPy and PANi films with different selectivity by controlling dedoping time. Additionally, the sensing properties and mechanism of VOCs adsorption to conducting polymers were investigated with contact angles measurement, a scanning probe microscope (SPM) and a UV-Vis-NIR spectrophotometer. Upon gas absorption, polypyrrole exhibited positive sensitivity while polyaniline had negative sensitivity. PPy film showed hydrophilic property and PANi film showed hydrophobic property. After gas absorption, the sensitivity increased as a function of the polarity of the absorbed molecules. These behaviors are due to the polar molecules absorbed with the movable polaron or free carrier, which then interrupts or generates the movement of polaron and carrier, and then changes the conductivity of the polymer. We found that conducting polymer sensors are very sensitive to the difference in polarity of gas molecules.

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2A06
Effects of Pre-doping and Post-annealing on Fluoroaluminum Phthalocyanine Thin Films for NO₂ Gas Sensing

X. Qian*, K. Hirayama**, K. Murakami** and K. Watanabe**

*Graduate School of Electronic Science and Technology, and **Research Institute of Electronics, Shizuoka University
3-5-1 Johoku, Hamamatsu-shi, Shizuoka 432-8011, Japan

The effects of NO₂ gas pre-doping and post-annealing treatments of the fluoroaluminium phthalocyanine (AlPcF) sublimed thin films were investigated on their NO₂ gas sensing behaviors. The NO₂ gas response/recovery characteristics have been improved significantly by the treatments. The improvement is interpreted in terms of the Langmuir's adsorption/desorption theory through a modification of the film microstructure.

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2A08
GAS SENSING PROPERTIES OF CARBON NANOTUBE COATED PIEZOELECTRIC QUARTZ CRYSTAL

Ching-San Lin*, Bee-Yu Wei*, Hong-Min Lin*, Hsin-Fu Lin* and Hong-Jen Lai**

*Department of Material Engineering, Tatung University
40 ChungShan N. Rd., Sec. 3, Taipei 104, Taiwan, R. O. C.
**Materials Research Laboratories, Industrial Technology Research Institute
Bldg 52, 195-5 Chung Hsing Rd., Section 4, Chutung, Hsinchu, Taiwan 310, R. O. C.

Carbon nanotube bundles are very good gas adsorbent materials due to their many adsorption sites. By depositing single wall carbon nanotube bundles on a piezoelectric quartz crystal, we demonstrated the gas sensing properties, which are utilized to detect the concentration of a flowing mixture gas by the signal of oscillation frequency change. The detected gases include carbon monoxide and hydrogen in air, and the detecting temperatures are from room temperature to 200℃. The sensor has the larger sensitivity at higher temperature, but is almost no response up to 100℃. The frequency change is increase when the sensor is exposed in the detected gases. The increase of frequency indicated a weight loss in carbon nanotube, which implied that the sensing mechanism is controlled by the desorption process. This implies the chemical reaction occurs between the surface adsorption of oxygen species and the detected gas that causes the oxygen desorption from the single wall carbon nanotube bundles.

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2A09
Large Voltage-Response of Pt-TiO_x-SiC Diode to Hydrogen Gas

Shinji Nakagomi, Hideyuki Watanabe, and Yoshihiro Kokubun

School of Science and Engineering, Ishinomaki Senshu University
Ishinomaki, 986-8580, Japan

The purpose of this contribution is to realize the hydrogen gas sensor device that has large voltage - response and to show the reason why the voltage - response is enlarged. The diode based on silicon carbide with Pt - thin TiO_x layer - SiC structure was fabricated. The current - voltage characteristics was compared in three types diodes without TiO_x layer and with 10 nm or 50 nm TiO_x layer. The dependence of the voltage difference, DV, between in H₂ ambient and in O₂ ambient at a constant forward current on the current level and on the temperature was studied. The DV of the diode without TiO_x layer is almost independent of the current. In contrast, the DV of the diode with TiO_x layer was increased with an increase in the forward current level. In the diode with 10 nm TiOx layer, the barrier height of the surface of SiC is lowered and the series resistance of the diode is also lowered when the diode is exposed to hydrogen gas. The change in the series resistance is due to the property of TiO_x layer sensitive to hydrogen. Using the Pt-thin TiO_x-SiC diode, the voltage response up to 3 volts was achieved at 300oC.

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2A10
Classification and quantification of mixed gases by a single semiconductor based on nonlinear dynamic response

Yo Kato, Kimiko Kato, Yasuhiro Setoguchi, Takeshi Nakahara

Figaro Engineering Inc.
1-5-11, Senbanishi, Mino, Osaka 562-8505, Japan

We propose a method of discrimination and quantification of mixed gases by a single semiconductor gas sensor, based on the information embedded in a nonlinear dynamic response. By applying a sinusoidal voltage to a heater attached to SnO₂, a characteristic time-dependent trace of the sensor resistance is obtained as a response to environmental gases. In order to evaluate the characteristic response in a quantitative manner, Fast Fourier Transform (FFT) is performed for the dynamic response. Higher harmonics, obtained by performing the FFT, were processed using a　 discrimination method and a multiple regression. For instance, we show that a mixture of ethanol and carbon monoxide (CO) gases can identify both components and also be quantified.

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2A11
Odor Recorder for Multi-component Odor Using Active Sensing System

T. Yamanaka, R. Matsumoto, T. Nakamoto, and T. Moriizumi

Department of Physical Electronics, Tokyo Institute of Technology
2-12-1, Ookayama, Meguro-ku, Tokyo 152-8552, Japan

An odor recorder has the capability of not only recording the recipes of odors electronically but also reproducing it anytime and anywhere once it obtains the recipe information. We present the new type of odor recorder for multi-component odors based on a solenoid valve system and the experiment on recording the recipes of five components in the apple flavor in this paper. Although four-component flavor had been successfully recorded and reproduced using odor blender consisted of several MFC(Mass Flow Controller)s in the previous work, it had been difficult to expand the number of components because a MFC is too expensive. Therefore, we have developed the new blender using solenoid valves controlled by delta-sigma modulation instead of MFCs. In this paper, we report the recorder for up to eight components using the new blender. Moreover, the appropriate sensors were selected based on the condition number of the sensor-array sensitivity matrix because the difference among sensor-array response patterns to the components should be larger as the number of the components increased. As a result, the recipes for five components were successfully determined using the active sensing system.

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2A12
Purification Characteristics of a Golden Pothos for Emitting Air-pollutants from a Plywood using Gas Sensors

Takashi Oyabu1, Takeshi Onodera2, Takashi Kamimiya3 and Kozaburo Takenaka4

1 Kanazawa University of Economics
Kanazawa 920-8620 Japan
2 Kyusyu University
3 Kanazawa University
4 Takenaka Garden Afforestation

Sick-house syndrome widely occurs in general domiciles. Its cause is from various types of chemical substances generated from building materials. The most prevalent chemicals are formaldehyde, toluene and xylene. It is well known that plants have purification capabilities for these chemicals in an indoor environment. It is strongly desired to reduce the pollution level for multiple chemical sensitivity in domiciles and buildings. Foliage plants are very effective in reducing the pollution concentration. In this study, the purification characteristics of golden pothos for the polluting chemicals emitted from a piece of building board are examined using two types of tin oxide gas sensors. The number of plant pots were also changed from 0 to 3 in the experiments. As for the results, pothos had high purification capabilities for those chemicals and the capabilities increased as the number of pots were added. The purification rate reached almost 100% at over three pots in a chamber experiment. The approximate function of the purification characteristic is derived using a fractional function. The system can introduce the pollution level in an indoor environment using this expression. It is felt that this model can be effective in estimating the level and the design of an indoor environment.

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2A13
CHEMICAL SENSORS FOR HEAVY METALS

Vinod Kumar Gupta

Department of Chemistry, University of Roorkee
Roorkee ? 247 667( Uttaranchal) India

Determination of heavy metals is important because most of these are toxic above certain permissible limits and are non-biodegradable. As a result of extensive research in this area, sensors are now commercially available for the determination of some metal ions. In the present talk an overview of the subject will be presented. A significant work has been done by us in this area and the results obtained for cadmium, cobalt, lead, mercury, molybdenum, uranium zinc, nickel, barium, strontium and copper sensors will be described.

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2A14
Technology of photocurable polymeric membranes for the integrated LAPS

Yu. Ermolenko*,**, T. Yoshinobu*, Yu. Mourzina**, K. Furuichi*, H. Iwasaki*, Yu. Vlasov and M. J. Schoning***,****

*The Institute of Scientific and Industrial Research, Osaka University
8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
**Dept. of Chemistry, St. Petersburg State University
Universitetskaya nab. 7/9, St. Petersburg 199034, Russia
***Institute of Thin Films and Interfaces, Research Centre Julich
D-52425 Julich, Germany
****University of Applied Sciences Aachen
Ginsterweg 1, D-52428 Julich, Germany

A new type of light-addressable potentiometric sensor (LAPS) has been developed by elaboration of the photocurable ion(biomolecule)-sensitive membranes in combination with the silicon-based electrochemical transducer. Compatibility of the photocurable matrix with the plasticizers commonly used in the PVC-based ion-selective membrane formulation has been established. The use of photocurable polymer based on mono- and bifunctional acrylates as entrapping membrane matrixes for ionophores and enzymes is exemplified here with the development and evaluation of K-, Li-, Ca-, urea- and butyrylcholine-LAPS.

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2A15
Deposition of hydrogen ion sensing membrane for ISFETs using atomic layer deposition technique

Young-Jin Kim, Young-Chul Lee, Byung-Ki Sohn

Sensor Technology Research Center., Kyungpook National University
1370 Sankyuk-dong, Daegu 702-701, Korea

This article presents atomic layer deposition (or ALD) technique[1] for deposition Al₂O₃ thin film as a hydrogen ion sensing membrane. Thin films deposited by ALD technique have many advantages, such as good uniformity, critical control of thickness, fine step coverage, elaborated structure, lower temperature process, high yield and good stoichiometry. Thus Al₂O₃ thin films, grown using ALD, have been applied for hydrogen ion sensing membrane of the pH-ISFETs[2]. And its sensing characteristics of the devices were investigated.

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2A16
Uranyl Ion Sensor Based on Selective Molecular Recognition of Calix[6]arene in Langmuir-Blodgett (LB) Monolayers

J.-H. Kim, J.-H. Park, G. Xuan, and S. Kang*

Department of Molecular Science and Technology, Ajou University
Suwon, 442-749 Korea
*Department of Electronic & Electrical Engineering Kyungpook National University
Taegu, 702-701 Korea

In this study Langmuir and LB monolayers of p-tert-butylcalix[6]arene (Cal-6) are constructed at the air-water interface and on various solid substrates respectively. Stable monolayers of Cal-6 were possible to construct by precise controlling intermolecular interaction and interaction with subphase. Surface pressure-area isotherm, Brewster angle microscopy (BAM) of Cal-6 in the Langmuir monolayer at the air-water interface, and FT-IR reflection-absorption spectroscopy (RAS) of LB monolayer indicated that Cal-6 aligned monomerically on a basic interface (pH 12) with the cavity oriented parallel to the surface normal. Cal-6 at the air-water interface and on solidsubstrates showed specific affinity toward Cs+ and uranyl ion. Visible reflection spectroscopy of the complex of Cal-6 with arsenazo III dye and surface-enhanced Raman spectroscopy (SERS) studies ofCal-6 uranyl ion complex indicated that Cal-6 forms 1 to 1 complex with uranyl ion. SERS spectra of 2-(4'-hydroxyphenylazo)-benzoic acid (HABA) showed the molecular recognition of Cal-6 by the upper rim in the LB monolayer.

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1B09
Integrated Bioanalytical Device for Measuring Biochemicals Released from Cultured Cells

Osamu Niwa1, Ryoji Kurita2, Katsuyoshi Hayashi1, Tsutomu Horiuchi1 and Keiichi Torimitsu3

1NTT Lifestyle & Environmental Technology Laboratories.
2NTT Advanced Technology
3NTT Basic Research Laboratories.
3-1 Morinosato, Wakamiya, Atsugi, Kanagawa 243-0198 Japan

Highly selective real-time measurement of bio-chemicals such as L-glutamate and histamine was achieved using microfluidic devices with electrochemical detection. The device consists of two glass plates which has two working, reference and counter electrodes arranged in parallel in a thin layer flow channel. The electrodes are made of graphite-like carbon film separated by a flow separator made of photoresist film. One electrode was modified with Os-polyvinylpyrridine mediator containing horseradish peroxidase (Os-gel-HRP) and BSA film containing oxidase enzymes such as glutamate and histamine oxidases. The other was modified with Os-gel-HRP and BSA without containing oxidase enzyme. Therefore, the differences of the currents at both electrodes should be due to the enzymatic reaction of the substrate. Two fused silica capillaries are connected to the end of the device to use as a sampling and connecting to the pump. The detection limit is greatly improved since baseline fluctuations resulting from pumping noise and electrostatic noise was canceled by the differential measurement. The current changes caused by the change in the double layer capacitance by adding other solution to stimulate the cells was also eliminated. As a result, the glutamate release from cultured rat cortex cells by KCl stimulation and histamine release from RBL 2H3 cells by BSA-dinitrophenol stimulation were continuously monitored using the devices.

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1B10
Application of Smell Chip Module for Breath Analysis in Liver Cirrhosis

Pin-Chao Hsu*, Ching-Yi Cheng**, Tzong-Zeng Wu**

*Gene Sole Biotechnology Co., Ltd., Taiwan
**Institute of Biotechnology, National Dong Hwa University, Taiwan
1, Sec. 2, Da Hsueh Rd., Shou-Feng, Hualien, Taiwan, R.O.C.

The distinctive odor exhaled from liver cirrhosis patients has been identified as those volatile organic compounds consisting of ammonia, short chain fatty acids and thiol compounds. Breath analysis has been gradually recognized as a powerful diagnostic method to reflect the pathological symptoms of liver diseases. In this study, we developed a specific smell chip module that consists of an array of piezoelectric quartz crystal devices immobilized with specific recognized materials for the detection from liver cirrhosis patients' breath. The recognized materials are four short peptide with specific sequences, and two organic chemicals (crown ether and polymer). In the clinical trial, we collect exhaled breath samples from cirrhosis patients and healthy volunteers as control. The data were analyzed by using principal component analysis. The result shows remarkably different cluster between cirrhosis patients and healthy volunteers. The specific smell chip module would become a popular non-invasive method for clinical diagnosis in the near future.

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1B11
Electrochemical Proteome Chip with Arrayed Electrodes

K. Kojima*, A. Hiratsuka**, K. Yano**, K. Ikebukuro**, H. Suzuki*, and I. Karube**

*Institute of Materials Science, University of Tsukuba
1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan
** RCAST, The University of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan

An arrayed electrochemical immuno chip for proteome analysis was microfabricated. The chip contained three-electrode systems consisting of arrayed thirty-six platinum working electrodes, two sets of Ag/AgCl reference and auxiliary electrodes formed on a glass substrate. An anti-α-fetoprotein (AFP) IgG as a model immunosensing element was immobilized in a matrix of hexamethyldisiloxane (HMDS) plasma-polymerized film (PPF). AFP was successfully detected following the procedures of the ELISA. The highly cross-linked matrix was extremely thin and adhered well to the electrode, which realized a fast response and high throughput analysis. Electrochemical crosstalk between neighboring sensing sites was negligible.

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1B13
BIOSENSING WITH THERMALLY-KILLED MICROBIAL CELLS

T. C. Tan

Department of Chemical & Environmental Engineering National University of Singapore
10, Kent Ridge Crescent, Singapore 119260

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1B14
NADP⁺ Sensor on Chrorella Ferredoxin / Ferredoxin-NADP⁺-Reductase Modified Indium Oxides

K. Nishiyama, H. Ikebe, Y. Mie, Y. Hoshide, H. Nagai and Isao Taniguchi

Department of Applied Chemistry & Biochemistry, Kumamoto University
2-39-1, Kurokami, Kumamoto 860-8555, Japan

Chrorella ferredoxin (ChFd) was immobilized electrostatically with the aid of cationic polypeptides such as poly-L-lysine (PLL) or poly-L-ornithine onto indium oxide electrodes. Clear redox waves of the immobilized ChFd was observed. In the presence of ferredoxin-NADP⁺-reductase (FNR) and NADP⁺, NADP⁺ was reduced to NADPH electrocatalytically at the modified electrode. Also, both ChFd and FNR were immobilized on the electrode, and the prepared ChFd / FNR modified electrode was applied to the NADP⁺ sensor.

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1B15
Cellular biosensing system for assessing chemicals with the inducible nitric oxide synthase cascade

K. Kamei*, T. Haruyama**, M. Mie*, Y. Yanagida*, E. Kobatake* and M. Aizawa*

*Department of Biological information, Graduate school of Bioscience and Biotechnology, Tokyo Institute of Technology
4259, Nagatsuta, Midori-ku, Yokohama, Japan, 226-8501
**Department of Biological Functions and Engineering, Graduate School of Life Science and Systems Engineering, Kyusyu Institute of Technology
1-1, Hibikino, Wakamatsu-ku, Kita-Kyusyu, Fukuoka, Japan, 808-0196

A cellular biosensing system has been constructed for assessing biological effects of chemicals as an animal test alternative. The system consists of a living cell cultured on a cell response detector. Nitric oxide (NO) was selected as a cell response indicator, because inducible NO synthase (iNOS) cascade is modulated by chemicals. The cell response detector consisted of a gold disk electrode (16 mm in diameter), on which a polyion complex layer was coated for fixing a cultured RAW264.7 cell layer, a Pt counter electrode and an Ag/AgCl reference electrode. NO released from stimulated cells was electrochemically determined by double potential step chronoamperometry (DPSCA). The responses of the cellular biosensing system were characterized with lipopolysaccharide (LPS) and interferon-g (IFN-g) as standard samples of immunomodulators. The cellular biosensing system could shorten measuring time to 600 ms and ensure that LPS and IFN-g modulated the iNOS expression cascade. These results show that the effects of chemicals on the iNOS cascade of the immune system could be assessed with this cellular biosensing system.

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1B16
Electrochemical, Cellular Biosensing Systems based on Locally Patterned Mammalian Cells

Matsuhiko Nishizawa, Kimiyasu Takoh, Yuki Takii, Hirokazu Kaji and Tomokazu Matsue*

Department of Biomolecular Engineering, Graduate School of Engineering Tohoku University
Sendai 980-8579 (Japan)

Patterns of mammalian cells (HeLa) were prepared on glass substrates, and the viability of the patterned cells was evaluated by SECM. The Micro-Contact-Printing method was used to make patterns of cell adhesion protein (fibronectin), at which adherent-type cells such as HeLa attach selectively and growth. The SECM imaging of oxygen over the patterned HeLa cells was achieved, the results indicating that the cells were living with uptake of oxygen. The respiration activity of cells was found to depend on their shape.

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1B17
A Comparison of a voltammetric electronic tongue and a lipid membrane taste sensor with respect to separation of detergent.

Patrik Ivarsson*,**, Yukiko Kikkawa***, Fredrik Winquist*, Cristina Krantz-Rulcker*, Nils-Erik Hojer**, Kenshi Hayashi***, Kioshi Toko***, Ingemar Lundstrom*

*S-SENCE (Swedish Sensor Centre) and Laboratory of Applied Physics, Linkoping University
SE-581 83 Linkopng, Sweden
**Asko Cylinda AB
SE-534 82 Vara, Sweden
***Graduate School of Information Science and Electrical Engineering, Kyushu University
Fukuoka 812-8581, Japan

Artificial senses have attracted more and more attention and interest during the last years. Examples of artificial sensors are electronic noses and electronic tongues. Many different methods have been developed, but they are all made up of an array of chemical sensors and the responses are treated with pattern recognition routines. The artificial senses are generally used to extract information of an attribute in the sample and not a specific single parameter. An attribute can for example be quality, condition, taste, or state of a process. The electronic nose is used for gas samples whereas electronic tongues are used for liquid samples. Regarding the electronic tongues, mainly three different techniques are used: the potentiometric methods of chalcogenide glass electrodes; lipid/polymer membranes; and the voltammetric method. Extensive research has been made and quite a few papers have been written concerning these different methods, but until now, no comparisons have been made. In the present contribution, a comparison between the voltammetric method and the lipid/polymer membrane method has been conducted. The voltammetric electronic tongue has been used to monitor quality of food and processes [1]. The lipid/polymer membrane electronic tongue, which is also called itaste sensori has mainly been used for measurements on tastes of foodstuff [2]. Twelve different detergents (six for automatic dishwashers and six for washing machines) were measured upon by both of the sensor systems. Principal Component Analysis (PCA) was used as evaluation of the two sensor systems. It was shown that the two sensor systems separated the detergents to somewhat different extents.

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2B01
Some methods to widen the scope of sensor materials for third-generation biosensors

Genxi Li

Department of Biochemistry and National Key Laboratory of Pharmaceutical Biotechnology, Nanjing University
Nanjing 210093, P. R. China

The third-generation biosensors are based on the direct electrical communication between enzymes and electrode surfaces. So, enzymes work in a potential window close to the redox potential of the enzymes themselves, which makes them less susceptible to interfering reactions. Another advantage is that the lack of mediators simplifies the reaction system. Therefore, the third-generation biosensors receive more and more interest. However, enzymes cannot be readily oxidized or reduced at an electrode surface because of the burying of the electroactive centers and the denaturation of the enzymes. So, while enzymes, the most commonly used sensor material, are made to be able to take direct electron transfer reactions, some methods to widen the scope of sensor materials for the third-generation biosensors have also been proposed, such as, function conversion to lead to novel enzyme activity for some proteins that can show feasible electron transfer reactivity, genetic engineering to alter the activity of enzymes, to make use of the interactions between specific species, to exploit new electrode substrate which can be directly used for sensor material, hybridization technique for DNA sensors to detect sequence-specific gene, chemical reactions at the electrode surface to produce desirable sensor material which is subsequently directly used for the fabrication of a biosensor, to take advantage of the electrochemical properties for sensor preparation although the properties are worthless for some other research purposes, medium engineering to enhance the electron transfer reactivity of the proteins, etc..

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2B02
Cellular NO Sensing Using Iron / Polyion complex Layered Electrode

Tetsuya HARUAYMA* and Masuo AIZAWA**

*Department of Biological Functions and Engineering, Kyushu Institute of Technology
Hibikino, Wakamatsu-ku (Kitakyushu Science and Research Park), Fukuoka 808-0196, Japan
**Department of Biological Information, Tokyo Institute of Technology
Nagatsuta, Midori-ku, Yokohama, 226-8501, Japan

Nitric oxide (NO) has become popular as an important regulation factor in various biological systems. However, NO is vary unstable gas substance in aqueous solution and is difficult to measure directly in aqueous solution. The authors have screened various NO specific substances to develop an in situ NO sensing system for primarily biological and medical uses and have found several types of NO sensing materials. Heat-treated cytochrome C (Cyt C) shows a remarkable catalytic activity against NO, which can be coupled with an electrochemical reaction for sensor out-put. Heat-treated CytC deposited on modified gold coated sheet responded to NO in an increase of cathodic current through electrochemical reduction of CytC (Fe ³⁺), when the electrode potential was controlled at 0 mV vs. Ag/AgCl. The dynamic range of the sensing system was 0.1 - 4 μM.

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2B03
FLOW INJECTION ANALYSIS OF TRACE UREA WITH AN ACID UREASE COLUMN

Yasuhiro Iida, Ayumi Koga, Noriko Hara and Ikuo Satoh

Kanagawa Institute of Technology
1030 Shimo-Ogino, Atsugi 243-0292, Japan

A spectrophotometric flow-injection analysis (FIA) with an acid urease column was applied to determination of trace urea in alcoholic beverages. A urea in alcoholic beverages is a precursor of an ethyl carbamate which may have the carcinogenicity. Therefore simple and useful method for determination of urea in alcohol drinks was demanded strongly. An acid urease, purified from NAGAPSHIN by a desalting process followed by ultra filtration, was covalently immobilized onto porous glass beads with controlled pore size and then, packed into a small polymer column. This flow-type of a biosensing system was assembled with a sample injection valve, the immobilized enzyme column, a gas-diffusion unit, and a flow-through quartz cell attached to a UV/VIS detector. Citrate buffer (50 mM, pH 5.0) as the carrier solution was continuously pumped through the system. Sample solutions were introduced into the system via a rotary injection valve. Ammonium ions produced in the enzymatic hydrolysis of urea were mixed with alkaline buffer (100 mM Na₂PO₄, pH 12.0), and the mixed solution was sent to the gas diffusion unit consisting of a double tubing structure. Thymol blue flowing in the Teflon tubing became colored due to ammonia diffusion across the Teflon tubing, and subsequent increase in absorbance at 596 nm due to the reaction was successively monitored. A wide, linear relationship was obtained between the concentration of urea (7.8 mM - 1.0 mM) and the change in absorbance. Effect of an ethanol coexisting in the substrate solutions on the response was investigated. This system for the determination of urea did not noticeably suffer from interference due to the urea containing ethanol up to 5 % concentration. These results demonstrate that this system should be promising to determination of urea in alcoholic beverages.

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2B04
Determination of Acetic Acid, Glycerol and Urea with Tri-enzyme/Polydimethylsiloxane-Bilayer-Coated Electrodes

F. Mizutani, Y. Sato, T. Sawaguch, and S. Yabuki

Biosensor Research Group, National Institute of Advanced Industrial Science and Technology
Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

An amperometric acetate-sensing electrode with high performance characteristics, such as high selectivity (e.g., free from the interference by ethanol and hydrogen peroxide) and high stability (usable for a month), was prepared by immobilizing acetate kinase, pyruvate kinase (PK) and pyruvate oxidase (PyOx) on a polydimethylsiloxane-coated oxygen electrode. By combining other ATP-dependent enzymes, glycerol kinase and urea amidolyase, with the PK/PyOx-based, ADP-measuring system, amperometric glycerol- and urea-sensing electrodes could respectively be prepared.

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2B05
Tyrosinase-immobilized carbon felt as a flow through bioelectrochemical detector for phenol, catechol and its inhibiting species.

Y. Hasebe, T. Shirai, and S. Uchiyama

Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology
1690, Fusaiji, Okabe, Saitama, 369-0293, Japan

　　　Flow amperometric biosensor for polyphenol compounds and tyrosinase inhibitors was developed using tyrosinase (polyphenol oxidase)-immobilized porous carbon felt (CF) as a flow through electrochemical detector. Tyroinase was covalently attached onto the surface of the cyanuric chloride-activated CF. Enzymatically produced o-quinone from catechol (or phenol) is electrochemically reduced back to catechol at the CF surface and reoxidized repeatedly. The cathodic peak current due to the reduction of o-quinone is proportional to the concentration of tyrosinase substrates. Among several tyrosinase substrates, highest response was obtained for catechol, and the response for phenol compounds was very small. Under the optimum operational condition (carrier 0.1 M phosphate buffer, pH 7.0, flow rate 1.3 ml min^-1, applied potential -0.2 V vs. Ag/AgCl), the detection limit of catechol was found to be 5 x10^-7 M. Moreover, this tyrosinase-CF based flow biosensor system could be applied to the determination of the tyrosinase inhibitors such as azide and benzoic acid.

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2B06
Amperometric Polyphenol Biosensor Based on Immobilization of Horseradish Peroxidase on Binary Thiol Self-assembled Monolayers

S. Imabayashi, M. Kashiwa, K. Mitomi, and M. Watanabe

Department of Advanced Materials Chemistry, Graduate School of Engineering Yokohama National University
Yokohama 240-8501, Japan

Amperometric polyphenol biosensor is prepared by covalently immobilizing horseradish peroxidase (HRP) on binary self-assembled monolayers (SAMs) of COOH- and OH-terminated alkanethiols on vapor-deposited gold electrodes. The effect of the structure and composition of SAM on the amount and state of immobilized HRP and the current response is examined by electrochemical methods and AFM. In phase-separated binary SAMs of mercaptoundecanol (MUOL) and mercaptopropionic acid, HPR is selectively immobilized on the COOH domains of binary SAMs as a monolayer state. From the dependence of the amount of immobilized HRP on the composition of homogeneously mixed binary SAMs of MUOL and mercaptoundecanoic acid, it is found that the surface density of COOH groups necessary for HRP immobilization is at least 0.4. The current response reflects the amount of immobilized HRP immobilized on the SAMs.

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2B08
Development of New Types of Solid Electrolytes and Realization of New Chemical Sensors with Advanced Concepts

N. Imanaka and G. Adachi

Materials Chemistry, Division for Research of Engineering Graduate School, Osaka University
2-1 Yamadaoka, Suita, Osaka 565-0871 Japan

The development of new functional materials, especially, solid electrolytes, has been systematically carried out and new types of sensors have been proposed with advanced concepts. In order to overcome the limitation of the conventional chemical sensors with monovalent ion conductors, multivalent cation conductors, such as divalent, trivalent and tetravalent cations were firstly developed and the multivalent solid electrolytes were combined with oxide anion conductor to fabricate a new advanced type of chemical sensors such gas species as CO₂, Cl₂, etc. In addition, for the practical gas sensing application, the water insoluble auxiliary electrode was also developed to realize an in-situ gas monitoring in emitted gas atmosphere.

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2B09
Influence of Humidity on a Potentiometric Cl₂ Gas Sensor Using a Na+ Ionic Conductor

Hiromichi AONO and Yoshihiko SADAOKA

Department of Materials Science and Engineering, Faculty of Engineering, Ehime University
Matsuyama-shi, Ehime, 790-8577, Japan

The influence of humidity in a test gas containing Cl₂ was investigated for a Cl₂ gas sensor using a Na+ conducting solid electrolyte. In the case of dried Cl₂ gas, the electron number n=1.86 for the reaction on the electrodes was very close to the theoretical value n=2.0. The EMF significantly decreased when water vapor was added to the Cl₂ measuring gas, because the Cl₂ gas concentration was reduced by the reaction with the H₂O gas. Based on the calibration curve observed under dry conditions, it is confirmed that the sensor can detect ppb levels of Cl₂ gas under ambient conditions. The EMF response was very fast even for the wet conditions.

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2B10
CO₂ Sensing mechanism for In₂O₃-attached NASICON sensor operative at room temperature

Kenji Obataa, Kengo Shimanoeb, Norio Miurac, Noboru Yamazoeb

aDepartment of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
bDepartment of Materials Science, Faculty of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
cAdvanced Science and Technology Center for Cooperative Research, Kyushu University,
Kasuga-shi, Fukuoka 816-8580, Japan

The NASICON (Na+ conductor, Na₃Zr₂Si₂PO₁₂) disk-based potentiometric devices attached with an In₂O₃ sensing electrode were investigated for their CO₂ sensing capability at room temperature. Although no auxiliary phase (carbonate or bicarbonate) was added intentionally to the device, the evidence supporting spontaneous formation of the auxiliary phase was obtained from the aging effects for the devices using different kinds of NASICON disks. As an extreme case, when the NASICON disk was washed in hot water, the resulting device could not acquire reasonable CO₂ sensing capability even after a heavy aging treatment. Remarkably the same device was made respondent to CO₂ very well by adding a small amount of NaHCO₃ or Li₂CO₃ to the sensing electrode, accompanied by corresponding changes in the number of reaction electrons per CO₂ (n).

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2B11
Carbon Dioxide Gas Sensors based on a Lithium Ionic Conductor Li₂TiSiO₅

M.Matsui and H.Uemura

Tokuyama Corporation
40,Wadai, Tsukuba-shi, Ibaraki 300-4247, Japan

Sodium ionic conductors such as NASICON (Na₃Zr₂Si₂PO₁₂) have been used as the solid electrolyte for the EMF (electromotive force) type CO₂ sensor. However, it has been hard to obtain sufficiently high quality in this type of sensor, partly due to the low humidity-resistance of NASICON and partly because of its poor initial response of the EMF to CO₂ pressure. For the purpose of improving the humidity-resistance and shortening the initial response time of the EMF of the solid electrolyte CO₂ sensors, Li₂Si₂O₅ is employed as the sensing material instead of NASICON. The humidity-resistance of Li₂Si₂O₅ is superior to that of NASICON. But the electrochemical reaction of Li₂Si₂O₅ does not follow the Nernst equation. Therefore, Ti replaces Si of Li₂Si₂O₅ and Li₂TiSiO₅ is synthesized. It is composed of the following electrochemical cell: CO₂+Air/Au+Li₂CO₃/Li₂TiSiO₅/Au/CO₂+Air The electrochemical reaction is in good agreement with the Nernst equation, and reacted electron is calculated as 2.04. The sensor fabricated with Li₂TiSiO₅ shows good linearity when it is exposed to an atmosphere of 90% relative humidity at 60℃. The initial 90% response of the EMF is steadied within 4min. These experimental results make it possible to use the sensor under a number of environmental conditions.

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2B13
Amperometric Hydrocarbon Sensor using Difference in Electrode Catalysis for Monitoring Exhaust Gas

Tatsumi Ishihara, Koji Kabemura, Hiroyasu Nishiguchi, and Yusaku Takita

Department of Applied Chemistry, Faculty of Engineering, Oita University
Dannoharu 700, Oita 870-1192, Japan

Amperometric hydrocarbon sensor using the difference in electrode catalysis was studied in this study for monitoring hydrocarbon in exhaust gas. Comparing simple mixed potential, current that is linearly changed with the concentration of hydrocarbon was observed on the solid electrolyte sensor using the different electrode catalysts. In particular, current at 1 V application was mainly affected by hydrocarbon but not oxygen when Pt and SnO₂ were used as active and inactive electrode for oxidation of hydrocarbon, respectively. Since the current linearly increased with increasing hydrocarbon, it is expected that the concentration of hydrocarbon in exhaust gas can be monitored with the current through the sensor element.　The current of the developed sensor is hardly changed by coexisting CO and H₂O and has small influence by O₂. Therefore, selective detection of hydrocarbon is expected. In addition, the sensitivity to hydrocarbon increased with increasing carbon number in hydrocarbon and the sensitivity to CH₄ is negligibly small. Consequently, the developed amperometric hydrocarbon sensor can detect hydrocarbon excepting CH₄. This is suitable property for the sensor for monitoring hydrocarbon in exhaust gas from the internal engines.

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2B14
A Study for Electrode Coating Material Base on Transition Metal Oxide of Carbon Monoxide Potentiometric Sensor

Ren-Jang Wu*, Cheng-Hung Hu**, Chuin-Tih Yeh** and Pi-Guey Su*

*Center for Measurement Standards, Industrial Technology Research Institute
Hsinchu, 300, Taiwan, R.O.C
**Department of Chemistry, National Tsing Hua University
Hsinchu, 30043, Taiwan, R.O.C

In this study, we investigate the solidelectrolyte type CO sensor in commercial design. Using 5% Y₂O₃ and 95% ZrO₂ as the conducting oxygen ion material, we plated two electrode with platinum on the same side of the substrate. The sensing layer covering upon anode is prepared by mixing metal oxide power, TEOS and glycol, the coating layer got a good adhesive effect. Variation the coating material on the anode by the transition metal, the Au/Co₃O₄ was selected the better metal oxide than others for its high sensitivity and lower working temperature. High dispersions of small Au particles on cobalt oxide are catalytic activators coating on the electrode in CO sensor. It offers the lower working temperature about 80 ℃ than using Co₃O₄ coating layer. TPR experimental figure reveals Au/Co₃O₄ has the weaker metal-oxide bond than Co₃O₄. Au has the electron donor effecting the lower temperature on Co₃O₄ using in CO sensor.

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2B15
Study of YSZ-based electrochemical sensors with a WO₃ electrode for high temperature applications

A. Dutta, N. Kaabbuathong, M. L. Grilli, E. Di Bartolomeo and E. Traversa

Department of Chemical Science and Technology, University of Rome "Tor Vergata", Via della Ricerca Scientifica
00133 Rome, Italy

In this work an investigation on potentiometric sensors based on yttria stabilized zirconia (YSZ) with WO₃ as sensing electrode is reported. The sensors were prepared using YSZ pellets painting metallic electrodes on both sides of the solid electrolyte and depositing on one electrode a thick film of WO₃ using a screen printing oil. The sensors were studied in the temperature range of 500-700℃ in presence of different concentrations of NO₂ and CO in air. The response to NO₂ was very stable with fast response time (20-40 s) at all the temperatures. The best sensitivity (18.8 mV/decade) was observed at 600℃. At the same temperature a cross-sensitivity of -15 mV/decade was also noted for CO gas. The response to CO showed negative values of electromotive force (EMF). The CO cross-sensitity was reduced using Au electrodes. The role played by WO₃ on the sensing electrode is discussed.

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2B16
AC Impedance Characterization and Sensing Mechanism of a Zirconia Based Conductive-type Oxygen Sensor

O.K.Tan*, W.Cao, and W.Zhu Sensors & Actuators Lab, Microelectronics Centre, School of EEE, Nanyang Technological University
50 Nanyang Avenue, Singapore 639798

The 0.2a-Fe₂O₃-0.8ZrO₂ solid solution was prepared using high-energy ball milling technique for low temperature oxygen gas sensing application. AC impedance spectra and thermally stimulated current (TSC) were characterized to investigate the conduction properties of the solid solution, 0.2a-Fe₂O₃-0.8ZrO₂, in air and nitrogen (carrier gas) respectively. It was found that the Arrhenius plots of sT versus 1000/T have two distinct gradients corresponding to two activation energies in the high and low temperature regimes. The transition temperature occurs at about 320℃ that corresponds to the optimal operating temperature of the gas sensor. It is believed that the high oxygen vacancy concentration present in the solid solution, 0.2a-Fe₂O₃-0.8ZrO₂, and the dissociation of the oxygen vacancy associated defect complexes at 320℃ are the critical factors for the high oxygen gas sensitivity at low operating temperature.

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2B17
Resistive Oxygen Gas Sensors Based on Fine Powders of Cerium Oxide Prepared by Mist Pyrolysis

N. Izu, W. Shin, and N. Murayama

Synergy Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST)
Moriyama-ku, Nagoya 463-8560, Japan

Recently, resistive-type oxygen gas sensors are drawing the attention again for new applications because of their simpler structure and smaller size. The disadvantage of the resistive-type sensors is the long response time against a change of oxygen partial pressure. The response time is expected to be shorter with decreasing the size of oxide powders. In the present work, cerium oxide thick films with an average particle size of 200 nm were prepared. Characterization of thick films was carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the sensing properties of the sensor were investigated. The thick film exhibited good adhesion. The SEM observation showed the neck growth and the three-dimensional network-structure of CeO₂ with no remarkable grain growth. The logarithm of sensor's output, which was electrical conductivity, was proportional to that of oxygen partial pressure in the range of 103 to 105 Pa. A response time (t90) with an average particle size of 200 nm was one tenth times shorter than that of 2000 nm after a sudden change of P(O₂) from 105 to 103 Pa. This result suggests that the response time of oxygen gas sensor is proportional to the particle size. The kinetics in the sensor seems to be controlled by surface reaction.

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1PA01
Solid-state Amperometric CO₂ Sensor using Li₂CO₃- Li₃PO₄-Al₂O₃

Ji-Sun Lee, Jong-Heun Lee, and Seong-Hyeon Hong

School of Materials Science and Engineering Seoul National University
Seoul 151-742, Korea

An amperometric CO₂ sensor was fabricated using a Li⁺-ion conductor. The Li⁺-ion pumping current of the cell was found to respond linearly to the CO₂ concentration ranging from 200 to 2000ppm at 400℃. Such a linear response of the amperometric CO₂ sensor demonstrates the possibility to detect a small change in CO₂ concentration reliably.

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1PA03
Planar CO₂ sensor using NASICON-glass composite thick film

Y. Miyachi*, T. Kida*, G. Sakai**, K. Shimanoe**, N. Yamazoe**

*Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan

**Department of Molecular and Material Sciences, Faculty of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan

Improvement of the density and mechanical strength of NASICON (Na⁺ conductor, Na₃Zr₂Si₂PO₁₂) thick films was attempted by the addition of glass-forming components for the purpose of fabricating a planar device combining a NASICON thick film with a layer of carbonate auxiliary phase. The powder of a precursor of NASICON was mixed with the glass-forming components in order to prepare the thick film of NASICON-glass mixture (30mm thick) on an alumina substrate. Analyses using SEM and XRD revealed that the glass-forming component added NASICON thick film after calcinations was densified well and consisted of crystalline NASICON and amorphous glass (broad XRD peaks). The resulting device responded sharply to CO₂ in dry air at 450 and 500℃. The EMF response was linear to the logarithm of CO₂ concentration (100-1000 ppm) at each temperature, although the slope of the Nernstian correlations at respective temperatures were slightly less steep than those of the device using a disk of NASICON.

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1PA04
Sensing Characteristics of NASICON Thick Film Sensor by Novel Fabrication Method

J.M. Chang*, J.S. Choi*, J.C. Bae*, K.D. Song**, Y.I. Bang**,D.D. Lee**, H.S. Kim***, and J.S. Huh*

*Department of Metallurgical Engineering, Kyungpook National University
Taegu, Korea
**School of Electronic and Electrical Engineering, Kyungpook National University
Taegu, Korea
***Department of Materials and Metallurgical Engineering, Sunchon National University
Sunchon, Korea

NASICON thick films, Na₃Zr₂Si₂PO₁₂, were prepared from ceramic slurry by a wet milling process. NASICON single phase has been obtained at 1150℃ for 3 hr 30 min, and its uniform grain size was 2 ～ 3 mm. We made simple structured planar CO₂ gas sensors with NASICON thick film (20 mm in thickness), Pt / NASICON / eutectic mixture (47.0 Na₂CO₃ : 25.6 K₂CO₃ : 27.4 CaCO₃ in wt%). Fabricated planar gas sensor shows good sensing characteristics for CO₂ at 200℃ and 400℃.

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1PA05
Preparation of Lithium Ionic Conductor by Ceramic Sheet and their CO₂ Sensing Characteristics

J.S. Choi*, J.M. Chang*, K.D. Song**, Y.I. Bang**, D.D. Lee**, H.S. Kim*** and J.S. Huh*

*Department of Metallurgical Engineering, Kyungpook National University
Taegu, Korea
**School of Electronic, Electrical Engineering, Kyungpook National University
Taegu, Korea
***Department of Materials and Metallurgical Engineering, Sunchon National University
Sunchon, Korea

Lithium ionic conductor films, Li₃Zr₂Si₂PO₁₂, were prepared from ceramic sheet by wet milling process. Lithium ionic conductor phases have been investigated by X-ray diffraction sintered at 1100℃ and 1150℃ for 3 hr 30 min, and its uniform grain size was 10 ～ 13 mm. We tried simple structured planar CO₂ gas sensors with lithium ionic conductor thick film (20 mm in thickness), Pt / Lithium ionic conductor / eutectic mixture (47.0 Na₂CO₃ : 25.6 K₂CO₃ : 27.4 CaCO₃ wt%). Fabricated planar gas sensor shows good sensing characteristic for CO₂ at 400℃.

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1PA06
A New Type of Nitrogen Monoxide Gas Sensor Applying Two Types of Solid Electrolyte with the Nitrate Based Auxiliary Electrode

A.Oda, N. Imanaka, and G. Adachi
Materials Chemistry, Division for Research of Engineering Graduate School, Osaka University
2-1 Yamadaoka, Suita, Osaka 565-0871 Japan

A new type of nitrogen monoxide (NO) gas sensor was fabricated by using divalent magnesium cation and divalent oxide anion conducting solid electrolytes with the nitrate based auxiliary electrode. A linear response was clearly observed between the sensor EMF output and the logarithm of the NO concentration and the relationship exactly obeys the Nernst equation. Here, a quantitative NO gas monitoring was successfully realized with a rapid, continuous and reproducible response and the installation of the present NO gas sensor at various NO gas exhausting sites is greatly expected.

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1PA07
Planar Electrochemical Sensors based on Yttria Stabilized Zirconia and Semiconducting Oxides

N. Kaabbuathong, A. Dutta, M. L. Grilli, E. Di Bartolomeo and E. Traversa

Department of Chemical Science and Technology, University of Rome "Tor Vergata"
Via della Ricerca Scientifica, 00133 Rome, Italy

In order to design functional sensors for pollutants' monitoring in automotive applications, gas sensing properties of electrochemical sensors based on planar Yttria Stabilized Zirconia (YSZ) were investigated in a high temperature range. Thick films electrodes of semiconducting oxides, WO₃ and LaFeO₃, were deposited together with a reference Pt electrode on commercial tape-casted YSZ. The whole device was exposed to the same atmosphere. YSZ conductivity was measured by electrochemical impedance spectroscopy (EIS). The sensing performance was studied at fixed temperatures and at different NO₂ and CO concentrations in the range 400-1000 ppm by means of electromotive force (EMF) measurements. Both the sensors exhibited very good performance as potentiometric sensors of NO₂ up to 700℃. A good response was also found to various concentration of CO in air. The EMF response to CO and NO₂ gas was in the opposite directions and opposite for LaFeO₃-and WO₃-based sensors.

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1PA08
Mixed-potential type N₂O sensor using stabilized zirconia and SnO₂-based sensing electrode

Masahiro Kugishimaa, Eiichi Kanazawaa, Kengo Shimanoeb, Yuichi Kanmurac, Yasutake Teraokad, Norio Miurae, and Noboru Yamazoeb

aInterdisciplinary, Graduate School of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
bFaculty of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
cFaculty of Medicine, Kagoshima University
Sakuragaoka, Kagoshima 890-8520, Japan
dFaculty of Engineering, Nagasaki University
Bunkyo-machi, Nagasaki 852-8521, Japan
eAdvanced Science and Technology Center for Cooperative Research, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan

A stabilized zirconia-based electrochemical device attached with a Sm₂O₃ or Bi₂O₃ loaded-SnO₂ sensing electrode was developed for monitoring nitrous oxide (N2O) in air. The electromotive force (EMF) of the device was almost linear to the logarithm of N₂O concentration in the range of 35-200 ppm at 475℃ with acceptable response rates. However, the EMF response at 475℃ decreased remarkably in the presence of water vapor. To improve this disturbance, working temperature was raised up to 600℃. The higher temperature operation was effective to eliminate the disturbance of water vapor. Especially, the device using Bi₂O₃ (0.5 wt.%)-SnO₂ exhibited fairly good sensing properties to 1000-5000 ppm N₂O at 600℃ in the presence of water vapor.

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1PA09
Solid Electrolyte SO_x Sensor Attached with Metal Sulfide Electrode

Noriko SOUDA and Youichi SHIMIZU*
Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology,
1-1 Sensui-cho, Tobata, Kitakyushu 804-8550, Japan

A solid electrolyte-based electrochemical sensor device has been investigated by using an Na₅DySi₄O₁₂ (:NADyCON)-based high performance solid electrolyte disc and some metal sulfide electrodes for the detection of sulfur dioxide in the concentration range between 20 and 200 ppm at 200 - 400 ℃. A metal sulfide element could be syntesized via solution route by using various homogeneous precipitaion methods. Among the various sensor devices tested, the CdS-based sensing device was found to show excellent sensing properties to SO₂ at 300 - 400℃. The EMF response of the CdS-based solid electrolyte sensor element was almost linear to the logarithm of SO₂ concentration in the range between 20 and 200 ppm, with a 90% response time to 100 ppm SO₂ of about 2 min at 400℃. 　　

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1PA10
SO₂ Gas Sensor Based on the Combination of Mg²⁺ Cation and O^2- Anion Conducting Solid Electrolytes with Water-insoluble Sulfate Auxiliary Electrode

K. Okamoto, N. Imanaka and G. Adachi

Materials Chemistry, Division for Research of Engineering Graduate School, Osaka University
2-1 Yamadaoka, Suita, Osaka 565-0871 Japan

A new type of SO₂ gas sensor was fabricated by the combination of a Mg²⁺ ion conducting solid electrolyte and an O^2- ion conducting stabilized zirconia with BaSO₄ as the auxiliary electrode. The output response was exactly equal to the Nernst equation and a 1:1 liinear relationship was obtained between the sensor output and the logarithm of the SO₂ gas content. Since the present sensor is composed of the materials which show a considerable high stability at elevated temperatures in reducing or oxidizing atmosphere, the sensor is greatly expected to be installed for the SO₂ gas monitoring at various sites in industry.

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1PA12
A Chemoresistor-type Hydrogen Gas Sensor Using Pt/WO₃ Thin Film

N. Yamamoto, S. Okazaki, H. Nakagawa, and S. Asakura

Department of Materials Science and Chemical Engineering , Yokohama National University
Tokiwadai 79-5 Hodogayaku, Yokohama 240-8501, Japan

A chemoresistor-type hydrogen gas sensor using Pt/WO₃ thin film was tried and characterized. In the presence of hydrogen gas, conductivity of Pt/WO₃ thin film prepared by a sol-gel method was sharply increased. It was indicated that tungsten bronze which is good electrical conductor was formed by the reaction of hydrogen with tungsten trioxide. The response time of the sensor to hydrogen (1 vol.%, N₂ balance) under the relative humidity of 100 % at room temperature is rapid, and it took about 10 sec. to change two orders of conductivity. The response time under humid condition is two times as fast as the response time under dry condition. When the sensor was exposed to oxygen(100 vol.%), the decrease in the conductivity was observed. The value decreased to about 10 % of the original conductivity within 20 sec. after exposure to humid oxygen. It took, however, almost 1 h. for the device to become an insulator. Conductivity of Pt/WO₃ under N₂ condition is higher than that of Pt/WO₃ under air condition. The difference could be attributed to the competition between hydrogen reduction and oxygen oxidation.

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1PA13
Thermoelectric Sensor for Hydrogen Gas Detection

W. Shin, N. Izu, and N. Murayama

Synergy Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST)
Moriyama-ku, Nagoya 463-8560, Japan

A sensor of thick film NiO doped with alkali ions was fabricated, coated with Pt as catalyst on the half of its surface. When this sensor is exposed to air mixed with the hydrogen gas, catalytic reaction heats up the Pt-coated surface, and then thermoelectric voltage appears across the hot and cold region of the oxide film. The thick oxide film is printed on the alumina substrate with a viscous paste, the mixture of the nickel oxide powders doped with alkali ions and organic vehicle. The printed film was fired at 1000 ℃ for 2 hr and then Pt thin film was deposited at room temperature by r. f. sputtering method. At temperature of 22 ℃, the sensor showed the built-up temperature difference and voltage signal of 0.12 ℃ and 0.087 mV, respectively, for the 100 ccm flow of 3 % hydrogen/air mixed gas. The non-contacting in-situ monitor for temperature used in this study enabled to measure Vs and temperature difference separately, and the calculated thermopower of oxide thick film was also discussed.

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1PA14
Application of Bio-electronic Nose on Odorant Detection

Hsin-Hsien Lu*, Tzong-Zeng Wu

*Department of R&D, Gene Sole Biotechnology Co., Ltd, Taiwan
Institute of Biotechnology, National Dong Hwa University
1, Sec. 2, Da Hsueh Rd., Shou-Feng, Hualien, Taiwan

The bio-electronic nose used in the study is composed of three major parts: recognized sensing layers, QCM transducer, and data processing software. The recognized materials included organic polymers and bio-mimic molecules. During the detection, mass loading was transformed into frequency shift. The results showed that the properties and concentrations of odorants were discriminated by radar plot. The bio-electronic nose could also effectively predict unknow odorant by using cluster analysis or principle component analysis (PCA). This bio-e nose might be applied widely in food industries, petrochemical plants, atmospheric pollutants detection, breath test and so on in the future

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1PA15
Pattern Classification of Gas Sensor Array with Online Retrainable RBF Network

Byung-Su Joo*, Sang-Mun Lee*, Yun-Su Lee*, Nak-Jin Choi*, Jong-Kyong Jung*, Joon-Boo Yu**, Minho Lee*, Hyung-Gi Byun***, Jeung-Soo Huh**, and Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea
**Dept. of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea
***Dept. of Information & Communication Engineering, Samchok National University
253 Gyodong, Samchok, Kangwondo 245-080, Korea

A variety of pattern recognition algorithms may be utilized for odours/gases classification [1,2]. These include an artificial neural network to classify pattern characteristics for gas sensor array. However, it has to meet forgetting problems, when new data set appear in the network. We proposed a new method of neural network, which is called retrainable radial basis function (RBF) network, to overcome the catastrophic forgetting problem for electronic nose application. In this paper, SnO₂-based sensing materials on a sensor array are SnO₂-Pt, SnO₂-La₂O₃, SnO₂-Au/Pd, and SnO₂-Pd-V₂O₅ using thick film process techniques. We used output patterns of gas sensor array as input patterns of retrainable RBF network. We ascertained that retrainable RBF is suitable neural network algorithm for electronic nose application. It was confirmed by experimental trails.

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1PA16
Study on the Module Chips for Breath Analysis of Patients with Renal Failure

Yu-Sheng Lin*, Tzong-Zeng Wu**, and Te-Chao Fang***

*Gene Sole Biotechnology Co., Ltd., Taiwan
**Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan
***Buddhist Tzu Chi General Hospital, Hualien, Taiwan

The distinctive odor from a patient's breath in renal failure has been identified as those volatile organic amines. Breath analysis is generally recognized as an efficient diagnostic method to reflect the level of uremic conditions. The modular biochip consists of two key components: one is the quartz crystal microbalance (QCM) device served as the transducer, and the other is the recognized material that oligo-peptides mimicked from olfactory receptor protein. In clinical tests, we collected the exhaled breath from uremic patients, healthy volunteers and air from the hemodialysis room into separated sampling bags. The exhaled breath was obtained before and after dialysis therapy for uremic patients. The data were analyzed by using hierarchical cluster analysis (HCA) and principle component analysis (PCA). The result showed a remarkable different cluster pattern between the uremic patients and healthy volunteers.

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1PA17
Design of DSP Core Processor for Improving of Learning Speed in Neural Network

Jong-Kyong Jung*, Nak-Jin Choi*, Byung-Su Joo*, Jae-Do Lee*, Hyung-Gi Byun***, Jeung-Soo Huh**, Duk-Dong Lee*

*School of Electronic, Electrical Engineering, Kyungpook Nat'l Univ.
1370 Sankyuk-dong, Puk-gu, Daegu 702-701, Korea
**Department of Metallurgical Engineering, Kyungpook Nat'l Univ.
1370 Sankyuk-dong, Puk-gu, Daegu 702-701, Korea
***Department of Information & Communication Engineering, Samchok Nat'l Univ.
Mt.253 Gyo-Dong, Samchok, Kangwon-Do 245-711, Korea

Recently, many researchers have been used pattern recognition technique of neural network or principal component analysis of statistical method to classify the gas species. We proposed design of arithmetic block for weight value computation to improve of learning speed in neural network. We used hardware description language, very high speed integrated circuit hardware description language (VHDL) to implement arithmetic block in neural network. Arithmetic block consists of three parts, that is, multiplier part, arithmetic logic unit part and register part. It was verified by synopsys synthesis and simulation tool. As a result, it takes only the recognition time of input value and confirmation time of out value.

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1PA18
Implementation of GAS sampling chamber and measuring hardware for capnograph system considering thermal noise EFFECT and time response characteristics

I. Y. Park*, S. K. Lee*, H. J. Park*, K. M. Kang**, S. G. Bae*, S. W. Kang*, J. H. Cho*

*School of Electrical Eng. and Computer Sci., Kyungpook National Univ.
Taegu, Korea
**Dept. of Sensor Eng., Kyungpook National Univ.
Taegu, Korea

Most capnograph systems that can indirectly determine the partial pressure of carbon dioxide in the blood of a patient are based on NDIR(non-dispersive infrared) absorption technology. As such an NDIR gas analyzing method requires an optical absorption chamber and signal processing hardware. Accordingly, this paper designed and implemented an NDIR type CO₂ gas chamber while considering the time response characteristics and lamp chopping frequency. In addition, signal processing hardware using two infrared sources was implemented to reduce the thermal background effect. The gas chamber and signal processing hardware has been tested using temperature variation and human expiration experiment. The results showed that the system could produce a stable output signal and discerning CO₂ gas concentration curve similar to a typical capnogram.

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1PA20
The Polymer Sensors with Different Electrodes for Volatile Organic Compounds

Byung-Soo Lee*, Kyung Mun Lee*, Jin-Gue Roh*, Ha-Ryong Hwang*, Chae-Gun Lim**, Youn-Soo Lee**, Jeong-Ok Lim***, Duk-Dong Lee**, Jeung Soo Huh*

*Department of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu Taegu, Korea
**School of Electronic and Electrical Engineering,
***Medical Research Institute, Kyungpook National University
Taegu Korea

The conventional polymer sensors are prepared by electropolymerization with the alumina plate as substrate and Pt as electrode. It is difficult to control the electrode pattern gap under millimeter size. We employed silicon wafer as the substrate and as electrodes variable metals such as copper, gold, aluminum and platinum by DC sputtering. The electrode pattern is the interdigitation. The pattern gaps were fixed 20mm, 30mm, and 50mm, respectively. When the sensors are exposed to the VOCs (Volatile Organic Compounds) gases, it shows good sensitivities, contrary to the conventional sensors. Higher sensitivities of Platinum and the Group I B metal electrode than ones of aluminum electrode were appeared. The Group 1 B metal electrode shows faster response than platinum electrode. The sensors were also characterized by the pattern gap.

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1PA21
NH₃ Sensing Characteristics of Conducting Polymer Sensor Fabricated by Chemical Polymerization

Byoung-Tae Kim*, Yun-Su Lee*, Chae-Gen Lim*, Byung-Su Joo*, Hwa-Ryong Hwang**, Jin-Kyu Roh** ,Jeung-Soo Huh**, Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
**Dept. of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea

The conducting polymer was used as gas sensor. It shows different characteristics for various polymerization methods. Most of the conducting polymer sensors, under development, were made by the electrochemical polymerization. In this paper, the conducting polymer sensors are fabricated by the trailblazing chemical polymerization method. We compared the chemical polymerization to electrical polymerization. The chemical polymerization sensors have better sensitivity than electrochemical polymerization in detecting the ammonia gas.

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1PA22
Effect of Matrix Polymer on the NH₃ Sensing Properties of Polyaniline Blend Films

M. Matsuguchi, K. Izumi, A. Okamoto, and Y. Sakai

Department of Applied Chemistry, Ehime University
Matsuyama, Ehime 790-8577, Japan

NH₃ gas-sensing characteristics of polyaniline-insulating matrix polymer blend films were investigated. The preparation method of the sensor coating proposed represented an easily performed and inexpensive method compared with that of electrochemical deposition. The conductivity of all sensors decreased with an increase in NH₃ concentration. The sensing characteristics depended on the type of matrix polymers. The polyaniline-poly(methyl methacrylate) or polyaniline-polysiloxane blend film protonated with bis(2-ethyl hexyl)hydrogen phosphate showed fast response and good reversibility. On the other hand, the conductivity increased with an increase in the relative humidity in the atmosphere. As a result, the coexistence of NH₃ and water molecules lead to the lowering of NH₃ sensitivity. The influence of water vapor on the sensor response was determined not only by the hydrophilicity of the matrix polymer but rather by the morphology of the film. It was proved that, by selecting the appropriate matrix polymer, the effect of coexisting water vapor can be controlled.

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1PA23
NO₂ Sensing Behavior of Phthalocyanine Thin Film Sensors

H. Yokoi, C. Hayashi*, T. Oshima*, H. Ogawa**, and Y. Sadaoka**

*R&D Center, NGK Spark Plug Co., Ltd.
2808, Iwasaki, Komaki, Aichi 485-8510, Japan
**Department of Materials Science and Engineering Facullty of Engineering, Ehime University
3, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan

NO₂ sensing behavior of thin films of phthalocyanines having various centrral metals (MPc, M=Co, Cu, Zn and Pb) has been investigated comparing with that of a SnO₂ thin film from the viewpoint of a sensor for air quality controls in automobile cabins. The MPc and SnO₂ thin films were deposited by vacuum sublimation and by sputtering on micromachined silicon substrates, respectively. Both thin film sensors were subjected to model gas tests and road tests to evaluate their NO₂ sensing performance. Among the MPc thin films tested, ZnPc and CuPc showed higher sensitivity to NO₂ than the others. That is, the sensitivity to NO₂ was high when the metal of which dx²-y² orbital was filled was selected. Although the model gas tests revealed that the recovery speeds after exposure of NO₂ gas to the base line of the MPc thin film sensors were slower than thatt of the SnO₂ thin film sensor, the road tests demonstrated that their response to the NO₂ gas of a short time heat cleaning with a built-in microheater before measurement and a co-existence of oxidizing and reducing gases in the ambient atmosphere that facilitates to release adsorbed gases on the MPc each other. It was concluded that MPc has a potential as a NO₂ sensing material of air quality sensors for automobile applications.

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1PA24
INVESTIGATIONS IN THE SENSING MECHANISMS OF PLASMA POLYMERIZED CoTPP AND CuTPP THIN FILMS

D.Sakthi Kumar, Kenji Nakamura, Hiromichi Noguchi, Shigeru Ishii, Kunihiro Kashiwagi and Yasuhiko Yoshida

Bio - Nano Electronics Research Center, Dept. of Applied Chemistry, TOYO University
Kawagoe, Saitama 350-8585, JAPAN

Sensing mechanisms of radio frequency plasma polymerized CoTPP and CuTPP thin films are discussed in this paper. From this studies it is found that plasma polymerized CoTPP thin film is a semiconductor with p-type characteristics and is useful to use as hydrogen peroxide sensor, and CoTPP and CuTPP plasma polymerized thin films can be used as glucose sensing materials also.

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1PA25
Conjugate Polymer Sensor for Volatile Organic Compounds

Jin Gyu Roh*, Kyung Mun Lee*, Byung Soo Lee*, Joon Boo Yu*, Ha Ryong Hwang*, Hyung Gi Byun**, Duk Dong Lee***, Jeong Ok Lim****, Jeung Soo Huh*

*Department of Metallurgical Engineering Kyungpook National University
1370 sankyuk-dong, Puk-gu Taegu, Korea (702-701)v **Department of Information and Communication Samchok National University
Samchok Kangwon-do, Korea (245-711)
***School of Electronic and Electrical Engineering,
****Medical Research Institute, Kyungpook National University
1370 sankyuk-dong, Puk-gu Taegu, Korea (702-701)

The sensors were made by polypyrrole and polyaniline deposition on Pt electrodes by silk screen printing on an alumina substrate. It is found that the degree of polymerization affects the sensitivity and degradation of the polymer films. The absolute sensitivity for benzene, chloroform and toluene increase in polar order. Six sensors were arrayed on a substrate to enhance the selectivity to VOC. Principal Components Analysis (PCA) were used to analyze the VOC sensing characteristics.

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1PA26
Implementation of VOCs recognition system using conducting polymer sensor array

Joon Boo Yu*, Jin Gyu Roh*, Ha Ryong Hwang*, Hyung Gi Byun**, Duk Dong Lee*** Jeong Ok Lim**** and Jeung Soo Huh*

*Department of Metallurgical Engineering Kyungpook National University
1370sankyuk-dong Puk-gu Taegu, Korea(702-701)
**Department of Information and Communication Samchok National University
Samchok Kangwon-do, Korea(245-711)
***School of Eletronic and Electrical Engineering,
****Medical Research Institute, Kyungpook National University
Puk-gu Taegu, Korea(702-701)

A sensor array with eight conducting polymer sensors was developed with the aim of recognizing VOCs, such as ethanol, benzene, and toluene. The system incorporates one-chip microprocessor-based interface that measures in situ the change of sensor resistances and then transfers data to a Notebook PC for classification. A variety of pattern recognition techniques may be utilized for VOCs classification. We adapted a simple and efficient 3-layer feed-forward back-propagation technique to recognize VOCs vapors. The VOCs recognition system, which was implemented by conducting polymer sensor array and microprocessor-based associated electronics, is capable of distinguishing VOCs vapors with up to 90% accuracy.

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1PA27
Gas-sensing Properties of n-Si/Polymer Thin Film Having a Heterojunction

Tsuyoshi Arakawa*, Kasue Takahashi* and Nobuhiro Okai*, Ryoichi Mochinaga**

*Department of Biological and Environmental Chemistry, Kyushu School of Engineering,Kinki University
Kayanomori 11-6,Iizuka,Fukuoka 820-8555,Japan
**Department of Materials Science and Engineering, Miyakonojo National College of Technology
473-1 Yoshio-Cho Miyakonojo,Miyazaki 885-8567,Japan

The I-V characteristics and sensing properties are investigated for an n-Si/polymer thin film which was formed by electrochemical polymerization of pyrole monomer or aniline monomer in the presence tetraethylammonium tetrafuluoroborate. The rectifying character was affected by the electrochemical polymerization time. The n-Si/polymer proved to be sensitive to the gas like NO₂ and NH₃ .

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1PA28
Fabrication of Optical Fiber Gas Sensor with Conducting Polymer

Yun-Su Lee*, Byoung-Tae Kim*, Chae-Gen Lim*, Sang-Mun Lee*, Kap-Duk Song*, Jeung-Soo Huh**, and Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
**Dept. of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea

Optical fiber sensors have been used in new technologies for detecting small amounts of chemical, gaseous species. In this work, new polymer-clad fiber coated with thin polymer layers have been developed. We select polymer for gas sensing material. Polymers were synthesized and chemically polymerized by using the distilled aniline. The optical property of polymer as sensing materials was analyzed by using UV-Vis-NIR. These layers have been prepared by using dip-coating technique. By using the dip-coating technique, the polymer is easily deposited on optical fiber. This material has been investigated for detecting gases. The light source were stabilized He-Ne laser at 635 nm and 1 mW. The light power transmitted through the fiber is measured with a spectroscope. By choosing a fixed incident angle, variation of light power transmitted through the fiber is detected as the gas is absorbed in the polymer layer. The transmitted light intensity through a polymer coated optical fiber decrease. NH₃ gas is used as testing gas. This optic fiber sensor has a good sensitivity to NH₃ gas. We hope that the optical fiber sensor effectively eliminates the limitation of conducting polymer sensors, which are based on conductivity measurements.

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1PA30
Changes In The Transmission Spectra of A TiO₂ Film-coated Glass Waveguide Induced By Refractive Index of Liquids

Zhi-mei Qi, Naoki Matsuda, Akiko Takatsu*, Kenji Kato*, and Kiminori Itoh**

Nanoarchitectonics Research Center, AIST
1-1-1 Higashi, Tsukuba 305-8565, Japan
*National Metrological Laboratory, AIST
1-1-4 Higashi, Tsukuba 305-8563, Japan
**Graduate School of Environment and Information Sciences, Yokohama National University
Yokohama 240-8501, Japan

A new optical method for sensing refractive index of liquids is proposed based on simultaneous changes in the light intensity and the wavelength range occurring in the transmission spectra of a potassium ion-exchanged (PIE) glass waveguide locally coated with a tapered TiO₂ film. Using the prism-coupling method the white light from a xenon lamp was launched into the single-mode PIE waveguide. In the region covered with the tapered TiO₂ film, adiabatic transition of the guided mode took place. The guided mode coupled into the TiO₂ film suffered a large surface-scattering loss that caused the signal disappearance and attenuation at different wavelengths. Owing to the superstrate index dependence of surface-scattering loss, the form of the transmission spectrum varies with changing the refractive index of liquids on the surface of the TiO₂ film. In this paper aqueous solutions of sugar were used as samples to demonstrate the refractive index response of the waveguide transmission spectrum. The new method is also expected to be able to detect biochemical interactions.

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2PA01
Simple Aqueous Processing for Fabrication of SnO₂ Nanosized Powder

N. Murayama, W. Shin, and N. Izu

Synergy Materials Research Center, National Institute of Advanced Industrial Science and Technology
Moriyama-ku, Nagoya 463-8560, Japan

M. Hayashi and S. Sago
R & D Center, Noritake Co. Ltd., Miyoshi 470-0293, Japan

A simple wet process has been developed for the fabrication of SnO₂ nanosized powders. The Sn-hydroxide, which was precipitated by the addition of NH₄OH to SnCl₄ aqueous solution, was mixed with carbon powders with a particle size of about 20 nm. The mixture was dried at 70 ℃ in air, and was calcined at 600 ℃ in air for 2 h. The carbon powders burned out and aggregation granules of SnO₂ nanosized powders were formed. The powder size was about 10-30 nm. Since SnO₂ powders were weakly bonded each other, the powders were easily disaggregated by ultrasonic vibration. Finally, SnO₂ powders with a size of 10-30 nm were obtained.

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2PA02
Characteristics of Tin Oxide Thin Films Prepared by Pulsed Laser Deposition Using SnO₂ Targets

Hiroharu Kawasaki, Yoshiaki Suda, Jun Namba, Keitarou Iwatsuji, Kenji Wada

Sasebo National College of Technology
1-1 Okishin, Sasebo, Nagasaki 857-1193, Japan

Tin oxide (SnO₂) thin films have been grown on Si(100) and Al₂O₃ substrates by pulsed KrF excimer (248 nm) laser deposition methods using SnO₂ targets. X-ray diffraction measurement showed that the almost amorphous microstructure transformed into a crystalline SnO₂ phase and preferred orientation varied from (101) to (110) on Si(100) with increasing oxygen gas pressure. This result suggests that oxygen gas pressure affects the phase formation, crystalline structure and preferred orientation of the films. Gas sensing properties of SnO₂ thin films by PLD method were also investigated over the temperature range 300～600℃, using 0.31vol%H₂ as a test gas. The oxygen gas pressure results in a notable change in gas sensing properties of SnO₂ thin films.

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2PA03
Detection of Odorous Compounds Using Tin Oxide Gas Sensors - Sensing Properties to Aliphatic Esters -

Yoshifumi NITTA , Jun TAMAKI , Yoshifumi YAMAMOTO and Masao MATSUOKA
Department of Applied Chemistry, Faculty of Science and Engineering, Ritsumeikan University
Kusatsu-shi, Shiga 525-8577, Japan

The sensing properties to aliphatic esters have been investigated for pure SnO₂ and 17 kinds of modified SnO₂ sensors. For all sensors examined, the sensitivities to ethyl esters (ethyl propionate-ethyl octanoate) hardly changed even when the carbon number of ester increased, while the sensitivities to various butyrates (ethyl butyrate-hexyl butyrate) increased with increasing carbon number of butyrate. On the other hand, the modification with metal oxide affected sensitivity as well as response-recovery characteristics. Especially, the addition of WO₃ and MoO₃ were effective to enhance the sensitivity. The catalytic properties of sensing materials were examined for the oxidation of various esters. The sensing properties were well interpreted in relation to the catalytic properties of sensing materials.

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2PA04
CO Adsorption Reaction on SnO₂-based CO Gas Sensors Modified with Surface Sulfate Species

Y. Nagano*, M. Morimitsu*†, M. Matsunaga*, Y. Ozaki**, and S. Suzuki***

*Department of Applied Chemistry, Kyushu Institute of Technology
Tobata, Kitakyushu 804-8550, Japan
**Tokuyama Corp.
Tokuyama, Yamaguchi 745-8648, Japan
***Figaro Engineering Inc.
Mino, Osaka 562-8505, Japan

The CO adsorption reactions on SnO₂ modified and unmodified with sulfate species were investigated by using FTIR. The samples for FTIR measurements were prepared by dipping a sintered SnO₂ disk into a sulfuric acid solution for a few seconds then heating at 600 ℃. The IR spectra were measured under air or CO atmospheres for the samples treated with different concentrations of sulfuric acid solutions. The absorbances of sulfate species and surface hydroxyl groups generated by the surface modification were examined in regard to the sulfuric acid concentration, and the correlation between those absorbances was discussed quantitatively. The absorbance of bicarbonate species produced by CO adsorption was also analyzed at different concentrations of sulfuric acid. The results indicated that sulfate species on SnO₂ surface increased with increasing concentration of sulfuric acid, accompanying the increases in surface hydroxyl groups and bicarbonate species. From the results, a possible mechanism for surface modification of SnO₂ with sulfate species was proposed. Given the modification mechanism, the variation in the active site for CO adsorption by the surface modification and its effect on the sensitivity to CO were discussed.

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2PA05
Gas Sensing Characteristics of SnO₂ Thin Film Fabricated by Sn/Pt/Sn/Pt Multi-Layer Thermal Oxidation

Chang-Hyun Shim*, O-shik Kwon*, Nak-Jin Choi*, Bong-Chull Kim**, Gi-Hong Rue*, Myung-Bok Lee*,Jeung-Soo Huh**, and Duk-Dong Lee*

* School of Electronic, Electrical & Computer Engineering Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Daegu, Korea
** School of Metallurgical Engineering Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Daegu, Korea

We propose a new method to prepare SnO₂ thin film with homogeneously dispersed Pt nano-crystallite via simple thermal oxidation of Sn/Pt/Sn/Pt multi-layer on alumina substrate. The stacked layer was prepared by thermal evaporation of Sn and sputtering of Pt, respectively. And we consequently oxidized the multi-layer film. The sensing film shows good sensitivity to iso-C₄H₁₀ gas as compared to a conventional Pt-added SnO₂ film, Pt sputtering after SnO₂ formation. Its surface phase and morphology were investigated using some surface characterization tools such as X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM). The gas sensing characteristics of the Pt-added SnO₂ thin films to the iso-C₄H₁₀ gas was systematically investigated at wide range of gas concentrations.

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2PA06
The Effect of Tin Black Filter Film on the Sensitivity of a SnO₂ Gas Sensor

O-Shik Kwon*, Sook-I Hwang*, Chang-Hyun Shim*, Gi-Hong Rue*, Bong-Chull Kim**, Jeung-Soo Huh**, and Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Taegu, Korea
**Department of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-dong, Puk-gu, Daegu 702-701, Korea

In this study, we investigated the effect of a thermally oxidized tin black filter on the sensitivity of SnO₂ gas sensor. Our sensor is composed of the oxidized tin black filter onto SnO₂ thin film. The tin black film was deposited in Ar atmosphere of 0.6 Torr by thermal evaporation. The SnO₂ sensing layer is prepared by metallic tin film thermal oxidation. Morphologically, the tin black film shows a high-porous and foam-structure. We investigated the microstructure of the films with scanning electron microscopy (SEM).

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2PA07
Mechanism for the Reduced Humidity Dependence of SnO₂-based CO Gas Sensors Modified with Surface Sulfate Species

M. Morimitsu*, Y. Nagano*, N. Ozaki*, M. Matsunaga*, Y. Ozaki**, and S. Suzuki***

*Department of Applied Chemistry, Kyushu Institute of Technology
Tobata, Kitakyushu 804-8550, Japan
**Tokuyama Corp.
Tokuyama, Yamaguchi 745-8648, Japan
***Figaro Engineering Inc.
Mino, Osaka 562-8505, Japan

The effects of ambient temperature and humidity on sensor resistance of SnO₂-based CO gas sensors modified and unmodified with sulfate species were investigated in order to clarify the mechanism for the reduced effects by the surface modification. The resistances in air or in 100 ppm CO for modified and unmodified sensors were compared under the conditions that both ambient temperature and humidity changed and that humidity changed under constant ambient temperature. The results indicated that the sensor resistance depended predominantly on humidity change, possibly due to the decrease in the amount of surface hydroxyl group. FTIR measurements of the modified and unmodified SnO₂ surface revealed that surface hydroxyl groups increased by the surface modification. Considering that CO adsorption reaction involves surface hydroxyl groups and the active adsorption site would depend on the amount of surface hydroxyl groups, a possible mechanism for the reduced humidity dependence of the sensor resistance by the modification with sulfate species was discussed.

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2PA08
Gas Sensing Characteristics of Tin Dioxide Film Using Porous Tin Black

Sook-I Hwang*, Chang-Hyun Shim*, O-Shik Kwon*, Bong-Chull Kim**, Gi-Hong Rue*, Jeung-Soo Huh**, Duk-Dong Lee*

*School of Electronic and Electrical Engineering, Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Taegu 702-701, Korea.
**Department of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Taegu 702-701, Korea

We proposed a new method to prepare tin oxide with an ultra porous structure and small grain size by thermal oxidation of tin black film. The tin black film was fabricated by thermal evaporation of metallic tin in an argon gas environment. After the deposition, tin black film was oxidized in the range of temperature, 600℃ ～ 700℃ in the oxygen ambient. The sensitivity of this device was investigated for iso-C₄H₁₀, CH₄, C₃H₈, and CO gases with the concentration of 1500ppm at various operating temperatures. The device showed an excellent sensitivity for iso-C₄H₁₀. The surface morphology and crystalline structure are investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM).

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2PA09
Molecular Orbital Analysis of Response of SnO₂ Gas Sensor for Aminic Gases

Akira Fujimoto*, Takeshi Kanashima** and Masanori Okuyama**

*Department of Electrical Engineering, Wakayama National College of Technology
77 Noshima, Nadacho, Gobo-shi 644-0023, Japan
**Department of Physical Science, Graduate School of Engineering Science, Osaka University
1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan

Response of SnO₂ gas sensor has been measured for aminic gases such as methylamine and ethylamine and compared with the response for alcoholic gases. Gas concentration dependence of SnO₂ gas sensor response for aminic and alcoholic gases was measured in the concentration range of 0 to 0.1 vol.%. Experimental results show that SnO₂ gas sensor has higher sensitivity for alcoholic gases than aminic gases. Heat of formations of SnO₂ cluster and aminic gases with various distances from cluster surface to aminic molecular were also calculated by molecular orbital method. It was shown that the aminic gases could be adsorbed to SnO₂ cluster surface with closer position than alcoholic gases. We suppose that the adsorption position of gas molecule have an effect on sensitivity of SnO₂ gas sensor.

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2PA11
WO₃ thin film for NO_x gas sensor prepared by pulsed laser deposition

Eiichi Hiraiwa, Fumiaki Mitsugi, Tomoaki Ikegami and Kenji Ebihara

Department of Electrical and Computer Engineering, Kumamoto University
Kurokami 2-39-1, Kumamoto 860-8555, Japan

Tungsten trioxide(WO₃) is a promising material for NO_x gas sensors. We report the crystal structure and the electrical response of the film in NO gas. We prepared WO₃ thin films on Al₂O₃ substrate using pulsed laser deposition (PLD) technique. The WO₃ thin film was fabricated at the oxygen pressure of 200 mTorr and the substrate temperature of 400 ℃. X-ray diffraction of the as- deposited film showed triclinic structure. The WO₃ thin film showed high sensitivity in 100 ppm NO at 150 °C.

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2PA12
NO_x Gas Sensor Using Tungsten Oxide (WO₃) Thin Film Prepared by Pulsed Laser Deposition

Yoshiaki Suda , Hiroharu Kawasaki, Jun Namba, Keitarou Iwatsuji, Kenji Wada*, Kenji Ebihara**, and Tamiko Ohshima**
Department of Electrical Engineering, Sasebo National College of Technology
1-2 Okishin, Sasebo, Nagasaki 857-1193, Japan
*Department of Chemistry and Biotechnology, Sasebo National College of Technology
1-1 Okishin, Sasebo, Nagasaki 857-1193, Japan
**Department of Electrical and Computer Engineering, Kumamoto University
Kurokami 2-39-1, Kumamoto, 860-0862, Japan

Tungsten oxide (WO₃) thin films have been deposited on silicon (100) and alumina substrates by using a pulsed excimer laser deposition method in oxygen gas. X-ray diffraction pattern shows that the polycrystalline WO₃ can be prepared. Gas sensing properties of WO₃ thin films are investigated over the temperature range 200-600℃ using 200ppmNO and 200ppmNO₂ containing dry air as test gases in a quartz cell. The maximum sensitivity of WO₃ film prepared at PO₂=10 Pa for 200ppm NO₂ is approximately 170 at the operating temperature of 400℃.

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2PA13
NO_x Sensing Properties of Al-doped ZnO Tick Film Sensors

K. Wada* and M. Egashira**

* Department of Chemistry and Biotechnology, Sasebo National College of Technology
1-1 Okishin-cho, Sasebo-shi, Nagasaki 857-1193, Japan
** Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

Al-doped ZnO thick film sensors were prepared by thermal decomposition of Zn(NO₃)₂ and Al(NO₃)₃ to be examined for the sensing properties to NO_x. The NO₂ sensitivity increased when the resistance considerably decreased with the Al-doping, and was maximal at 1.0 at.% Al. On the other hand, variations in NO₂ and NO sensitivity with operating temperature as well as with the doping amount of Al were very similar to each other, though the NO sensitivity was approximately a half of that to NO₂. In the temperature programmed desorption experiments after NO_x adsorption, the desorption peaks of NO_x species increased with increasing the Al-doping, and three peaks appeared at 210℃, 280℃ and 430℃ at the 5.0 at.% doping. The results suggest that the Al-doping promoted the NO_x adsorption and therefore the NO_x sensitivity.

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2PA14
NO_x Sensing Properties of Cr₂O₃-SnO₂ Sensors Fabricated by Slide-off Transfer Printing

Ayami Jono, Takeo Hyodo, Yasuhiro Shimizu and Makoto Egashira

Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

NO_x sensing properties of SnO₂-based thick-film sensors fabricated by a slide-off transfer printing method have been investigated as a function of additive amount of Cr₂O₃ in the temperature range 250-550℃. The Cr₂O₃ addition resulted in a drastic decrease in NO2 sensitivity on the whole, but in improvement of NO sensitivity up to 0.34 wt% Cr₂O₃. SnO₂ loaded with 0.34 wt% Cr₂O₃ exhibited the highest NO sensitivity at 250℃ among the sensors tested and the NO sensitivity was comparable to its NO₂ sensitivity. Thus, this sensor was confirmed to be the most suitable candidate as a total NO_x sensor.

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2PA15
NO_x Sensing Characteristics of ZnO-based Heterolayer Sensors Fabricated by Slide-Off Transfer Printing

A. Kawahara*, H. Katsuki* and M. Egashira**

*Fine Ceramic Division, Saga Ceramics Research Laboratory
Arita-machi, Nishimatsuura-gun, Saga 844-0024, Japan
**Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

Slide-off transfer sheets were fabricated from the paste stuffs of ZnO-, WO₃-, SnO₂-, and In₂O₃-based materials by a spin coating method. Uniform oxide films of 4-20 mm thick after firing at 800?C were obtained by controlling the spin speed (1000-4000 rpm). NO_x-sensing characteristics of the heterolayer sensors based on the pure oxides, noble metal-loaded SnO₂ and In₂O₃ (Au, Pt; 0.5wt%), and mixed oxides of ZnO-WO₃, SnO₂-WO₃, In₂O₃-WO₃ (equal weight ratio) were investigated at 300-500℃. Recovery characteristics of heterolayer sensors employing ZnO as the underlayer material as well as a single-layer ZnO sensor were much better than other sensors at 300-500℃. In addition these sensors exhibited comparatively high sensitivity; ZnO-WO₃/ZnO showed the maximum sensitivity of RNO/Rair=21.6 (800 ppm) and RNO₂/Rair=39.9 (81 ppm) at 300℃. Such sensing characteristics may be related with the catalytic activity and microstructure of the sensor materials.

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2PA16
Fabrication of WO₃ thin film from tungsten oxide-precursor sol suspension by a spin-coating method

Yong-Gyu Choi*, Go Sakai**, Kengo Shimanoe**, Norio Miura***, Noboru Yamazoe**

*Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
** Department of Materials Science, Faculty of Engineering Sciences, Kyushu University
***Advanced Science and Technology Center for Cooperative Research, Kyushu University

Sol suspensions of H₂WO₄.H₂O as a precursor of WO₃ were prepared from an aqueous solution of sodium tungstate by using an ion exchange method. The resulting sol suspension contained colloidal particles of about 30 nm in mean diameter with a narrow size distribution (25-35nm) and was found to be stable for a long time (1 month). As revealed by XRD analysis, the colloidal particles consisted of H₂WO₄.H₂O. The sol suspension, after being mixed with 0.4 mass% of carboxymethyl cellulose (CMC), could be spin-coated on an alumina substrate attached with comb-type Au electrodes. The thin films after sintering at 500℃ for 2h consisted of a densely packed stack of WO₃ grains of 50 nm in diameter and were fairly uniform in morphology.

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2PA17
PREPARATION OF MESOPOROUS TiO₂ FOR SENSOR APPLICATION

G. Sarala Devi, Takeo Hyodo, Yasuhiro Shimizu and Makoto Egashira

Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

Nanostructured TiO₂ powders have been prepared by employing sol-gel method with Ti(NO₃)₄ and polyethylene glycol (PEG) having different molecular weights. Gel powder dried at 100?C crystallized in rutile phase with a crystallite size of 12 nm in case of PEG600. Beyond the molecular weight of 600, the crystal phase was transformed to anatase, and pore volume and surface area increased with increasing the molecular weight of PEG. The finest nanosized TiO₂ gel powder was obtained in case of PEG6000 with a crystallite size of about 3.5 nm. Although both the pore volume and the surface area decreased after the calcination at elevated temperatures, a surface area of 66.3 m² g^-1 was obtained after the calcination at 600℃.

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2PA19
Effects of Particle Size on Gas Sensing Properties of Nanocrystalline ITO Thick Films

Jae-Yeol Kim*, Bong-Chull Kim*, Xiao-Long Zhu*, Chang-Hyun Shim** Duk-Dong Lee** and Jeung-Soo Huh*

*Department of Metallurgical Engineering, Kyungpook National University
Taegu 702-701, Korea
**School of Electronic and Electrical Engineering, Kyungpook National University
Taegu 702-701, Korea

In nano-sized materials, because the surface-to-bulk ratio is much greater than for coarse materials, surface properties become paramount, which makes these materials particularly appealing in applications in which such properties are exploited, as in gas sensors. The reduction of particle-size is one of the main factors enhancing the gas-sensing properties of semiconducting oxides, and indeed, sharp increases in sensitivity are expected when the particle size becomes smaller than the space-charge depth, according to currently accepted mechanisms. Therefore, the purpose of this work investigates the gas sensing characteristics in the nanocrystalline ITO thick films with various particle sizes. At first, we synthesized nano-sized ITO powders with particle size of 15 ～ 70 nm in an equivalent diameter. The crystal structures are cubic in all powders. The particle sizes were confirmed by X-ray peak broadening using the Scherrer equation and Brunauer-Emmett-Teller (BET) method. The samples were tested in various operating temperatures and gas concentrations. We measured the sensitivity of the ITO thick films from gas sensing results obtained in dry air and a target gas (C₂H₅OH diluted with air).

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2PA20
The application of block copolymer templated mesoporous silicate film for SPV Gas sensor

T. Yamada†, ‡, H. S. Zhou†*, H. Uchida§, W. Zhang§, M. Tomita￡, Y. Ueno￡, T. Ichino￡, I. Honma†, K. Asai‡, and T. Katsube§

† National Institute of Advanced Industrial Science and Technology (AIST)
AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
‡ Department of Quantum Engineering and Systems Science, Graduate School of Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
§ Department of Information and Computer Science, Faculty of Engineering, Saitama University
255 Shimo-okubo, Saitama, Saitama 338-0825, Japan
￡ NTT Lifestyle and Environmental Technology Laboratories, Nippon Telegraph and Telephone Corporation
3-1, Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan

Surface Photo Voltage semiconductor characterization technique have a great possibility to gas sensor application and the mesoporous materials also have a possibility to improve the gas adsorption property of SPV device due to its high surface area and pore channel alignment structure (mesostructure) property. We are succeeded in assembling mesoporous silicate film into SPV device, estimating the NO gas sensing property of them and finding the sensing property strongly depend on mesostructure.

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2PA22
First Principles Energy Band Calculation for ZnSb₂O₆ with Trirutile-Type Structure

M. Nonaka*, T. Tanizaki**, and S. Matsushima**

*Department of Earth Resources Engineering, Kyushu University
6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
** Department of Materials Chemistry, Kitakyushu National College of Technology
5-20-1 Shii, Kokuraminami-ku, Kitakyushu 802-0985, Japan

A first-principles energy band calculation has been carried out to clarify the electronic structure of ZnSb₂O₆ and also a molecular orbital calculation to analyze the chemical properties. The results show the presence of Sb 5sp and Zn 3d components in the valence band where O 2p dominates, suggesting that Sb-O and Zn-O bondings are not perfectly ionic but partially covalent. The conduction band is mainly constructed from the spatially spread Sb 5s orbitals and O 2p ones. Therefore, ZnSb₂O₆ crystal is expected to have large electron mobility with doping carriers.

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2PA23
Selective CO Detection of Zn₂SnO₄-based Gas Sensors

J. H. Yu and G. M. Choi

Department of Materials Science and Engineering Pohang University of Science and Technology
San 31, Hyoja-dong, Pohang 790-784, South Korea

The electrical and gas-sensing properties of undoped and CuO-doped Zn₂SnO₄ were investigated. In order to obtain an ohmic contact to Zn₂SnO₄, a ZnO layer was stacked on top of Zn₂SnO₄ and co-fired. CuO was coated by immersing the sintered sample in Cu solution. Both uncoated and CuO-coated samples showed the higher sensitivity to 200ppm CO gas than to 200ppm H₂ gas. The CuO-coated Zn₂SnO₄ showed much enhanced sensitivity and thus good selectivity for CO gas (SCO/SH2～6) compared to the undoped sample. The excellent selectivity of Zn₂SnO₄-based materials for CO gas was explained by the difference in the mechanisms of CO and H₂ oxidation.

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2PA24
Dilute CH₃SH Sensing Characteristics of Cd-M-O Complex Oxides (M=Ga, Fe, Cr, Mn, In and Sb) Thick Film Sensors

Xiangfeng CHU and Jun TAMAKI

Department of Applied Chemistry, Faculty of Science and Engineering, Ritsumeikan University
Kusatsu-shi, Shiga 525-8577, Japan

Cd-M-O complex oxides (M=Ga, Fe, Cr, Mn, In and Sb) were prepared by sol-gel or co-precipitation method. The thick film sensors of Cd-M-O complex oxides were subjected to the measurement of sensing characteristics to dilute CH₃SH. The effect of calcination temperature on the gas-sensing properties of Cd-M-O complex oxides was studied. The experiments illustrated that CdGa₂O₄ (calcined at 800℃ for 8h), CdFe₂O₄ (700℃, 4h) and Cd₂Sb₂O_6.8 (700℃, 4h) thick film sensors had high sensitivity and good selectivity to dilute CH₃SH at 300℃. However, CdIn₂O₄, CdCr₂O4 and CdMn₂O₄ thick film sensors showed very low sensitivity. Especially, the sensitivity of CdGa₂O₄ (800℃, 8h) thick film sensor attained as high as 20 even to 0.01 ppm CH₃SH.

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2PA25
Quantitative Analysis of Methylmercaptan by GC-MS in Marine Environments to Develop Semiconductor-Type Sensor

M. Nagaishi* and M. Egashira**

*Ceramic Research Center of Nagasaki
605-2, Hiekoba-go, Hasami-cho, Nagasaki 859-3726, Japan
** Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

Methylmercaptan, generated from the rot of aquatic animals or fish foods in marine environments such as shores or fish farms, was quantitatively analyzed by gas chromatography-mass spectrometry (GC-MS) using a polyethylene glycol capillary column of high polarity. To analyze environmental states around shores of Omura Bay and Sasebo Bay, gases were collected from several points generating bad smells. Methylmercaptan of about 1-3 ppb was detected by concentrating it using an adsorbent b,b-oxydipropionitrile. This level of methylmercaptan concentration may be detected with a semiconductor gas sensor 0.5 wt% Pt-SnO₂, which is known to have a sensitivity value of more than 10000 to 40 ppm methylmercaptan in air.

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2PA26
The Study and Application of PECVD Films on Impedance-Type Integrated Multifunctional Chemical Sensors

Ko-Shao Chen*, Ming-Shu Lee*, Mu-Rong Yang*, Ji-Yan Tian**, Feng-Yi Huang**, and Huang-Yuan Hung**

*Department of Materials Engineering, Tatung University
**Instrumentation Center of Tatung University
Taipei, Taiwan, ROC

Semiconductor manufacture technology was employed to fabricate the impedance-type integrated multifunctional sensitive devices on the Si wafer with Al electrodes. Tin oxide (SnO_x) organic-like thin films, as temperature sensors or intermediate layers, were deposited on the devices by plasma enhanced chemical vapor deposition (PECVD) of tetramethyltin (TMT) and O₂ mixing gas at low temperature. To enhance the humidity sensitive and stability, hydrophilic polymer films were introduced by UV-induced grafting polymerization. The more amount of TMT in mixing monomers during plasma deposition will tend to increase organic components in the deposited film and the surface exhibits hydrophobic. On the other hand, the less ratio of TMT gets a film with less organic nature. The optimal parameters for fabricating the temperature-sensitive layer are 50W, 10min., and TMT:O₂=20:20 mtorr as films prepared from the conditions contain higher Sn and relatively fewer C and O resulting in more hydrophilic, low impedance, and good temperature sensing properties. This optimal condition is also appropriate for the subsequent AAm grafting for humidity sensors. The acrylamide (AAm) grafting will get a hydrophilic surface and the impedance of the device decreases when related humidity (R.H.) increases monotonically. Therefore multi-sensors on the integrated multifunctional device using semiconductor processes on Si-wafer are feasible from this study.

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2PA27
A Micro Sensor for Polluting Gases and Floating Particles Using Semiconducting Thin Film

Tatsuya Yokoyama and Kazuhiro Hara

Department of Electrical Engineering, College of Engineering, Tokyo Denki University
2-2 Kanda-Nishikicho, Chiyodaku, Tokyo 101-8457, Japan

A micro sensor for polluting gases and organic floating particles has been developed. The sensor is composed of two parts: a sensing element and a micro heater. Both parts are fabricated by using thin film technology, IC fabrication process and micromachining technique. The sensing film has a double layered structure; the first layer is a Fe₂O₃-based thin film and the second layer is a SnO₂-based thin film. It is deposited on a SiO₂/Al₂O₃/SiO₂ diaphragm formed on a Si substrate. A thin film heater is also made on a similar diaphragm formed on another Si substrate. The sensing element and the heater are placed in parallel at a distance of about 50mm. The sensor is sensitive to NO_x, reducing gases, exhausted gases, cigarette smoke and organic floating particles such as pollen.

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2PA28
Gas-sensing Properties of Semiconductor Metal Oxides to Benzene and Chlorobenzene

Syoko Yamaguchi, Takeo Hyodo, Yasuhiro Shimizu and Makoto Egashira

Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

Sensing properties of several metal oxides to benzene and chlorobenzene have been investigated in the temperature range 200-600℃. Among the oxides tested, In₂O₃ exhibited the highest sensitivity to both benzene and chlorobenzene, and its sensitivity could be further improved by the addition of 6.0 wt% NiO, probably due to enhanced catalytic activity of a sensor material. In the chlorobenzene sensing, interference probably from partial decomposition products was obvious in case of a thinner sensor. The sensor with appropriate thickness was effective both for enhancing the sensitivity and for reducing the interference.

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2PA29
Implementation of Alert System for Indoor Toxic Gases by Temperature Modulation

Nak-Jin Choi*, Chang-Hyun Shim*, Kap-Duk Song*, Byung-Su Joo*, Yun-Su Lee*, Sang-Mun Lee*, Jong-Kyong Jung*, Hyung-Gi Byun**, Jeung-Soo Huh*** and Duk-Dong Lee*
*Department of Electronic and Electrical Engineering, Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Daegu, Republic of Korea
**Department of Information & Communication Eng. Samchok National University
253 Gyo-Dong, Samchok, Kangwon-Do, Republic of Korea
***Department of Metallurgical Engineering, Kyungpook National University
1370 Sankyuk-Dong, Puk-Gu, Daegu, Republic of Korea

We designed and fabricated two SnO₂ based sensing films (pure SnO₂ and SnO₂/Pt) and a Pt thin film for temperature sensor on an alumina substrate for implement of alert system in the indoor toxic gases. By controlling the heating power in the shape of trapezoid, we acquired a temperature profile and the four unique sensing response signals to test gases from both SnO₂ and SnO₂/Pt film. And then, we extracted various parameters from response signals. Finally we adapted a radial basis function (RBF) to classify signals among test gases. Using two sensing films and the proposed temperature modulation, we confirmed that our method was very effective in classifying indoor environment gases same as CO₂, C₃H₈ and C₄H₁₀.

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1PB01
Photoelectric Characteristics of pH-ISFET Based on AlN/SiO₂ Insulator Gate

Ying-Chung Chen*, Jung-Lung Chiang*, Jung-Chuan Chou**, Chien-Chuan Cheng***

* Department of Electrical Engineering, National Sun Yat-Sen University
Kaohsiung, Taiwan 804, R.O.C.
** Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.
*** Department of Electronic Engineering, De-Lin Institute of Technology
Tucheng, Taipei, Taiwan 236, R.O.C.

The optical characteristic is one of the important parameters of the ion sensitive field effect transistor (ISFET) devices. In this study, the aluminum nitride (AlN) thin film was selected as the gate insulator for pH sensing ISFETs. The AlN thin film was prepared by the sputtering technology and the relationship between the pH sensitivity and surface potential for the AlN gate ISFET device in various buffer solutions was studied. The results show that the pH response is superior linearity and the pH sensitivity is a super Nernstian response. In addition, the photoelectric characteristics from the current-voltage (I-V) curves under the various illumination have also demonstrated that the drain current increases with the increased light intensity for the AlN/SiO₂ gate ISFET device.

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1PB02
Study on Separative Structure Extended Gate pH-Sensitive Field Effect Transistor Based on WO₃ Thin Film

Jung-Lung Chiang*,**, Jung-Chuan Chou***, Ying-Chung Chen**

* Department of Electronic Engineering, Chung Chou Institute of Technology
Yuan-Lin, Chang-Hua,Taiwan 510, R.O.C.
** Department of Electrical Engineering, National Sun Yat-Sen University
Kaohsiung, Taiwan 804, R.O.C.
*** Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.

The novel structures of the WO₃/ITO glass and WO₃/SiO₂/p-Si were first investigated for pH sensing property. The separative structure of the extended gate field effect transistor (EGFET) was fabricated to connect with the gate of MOSFET devices(CD4007UB), and the structure of EGFET with the current-voltage (I-V) measurement system was utilized to measure the I-V curves. It was found that the separative structures have a pH sensing response in pH = 1～7 buffer solutions, and the sensitivities are 56.74 mV/pH and 49 mV/pH for the WO₃/ITO glass and the WO₃/SiO₂/p-Si sensing structures, respectively. KEYWORDS: MOSFET, WO₃, EGFET, Sensitivity, I-V.

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1PB03
pH-ISFET and Temperature Sensors on the Single Chip Using the CMOS VLSI Technology

Chung-We Pan, *Jung-Chuan Chou, **Tai-Ping Sun, Wen-Yaw Chung and Shen-Kan Hsiung

Institute of Electronic Engineering, Chung Yuan Christian University
Chung-Li, Taiwan 320, R. O. C.
*Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R. O. C.
**Institute of Electrical Engineering, National Chi Nan University
Nantou, Taiwan 545, R. O. C.

In this research, we use the extended gate fielld effect transistor (EGFET) to measure the pH value of the test solution. The EGFET will be influenced by the variations of the temperature; thus, we design a temperature sensor to monitor the system temperature. The chip was fabricated using the standard 0.5 mm DPDM n-well CMOS IC process of the UMC foundry company. The sensing area of the EGFET was 0.3mm x 0.3mm, and the layout are of the temperature sensor was 0.2mm x 0.2mm. Therefore, the temperature sensor is smaller than the EGFET and can reduce the layout are of the multi-sensor chip. The chip using the CMOS VLSI technology has many advantages such as mass manufacture, lower cost, small size, high yield and combine readout circuits to enhance the signal to noise ratio of the sensor. We design two sensors on the single chip to reduce the layyout area. The sensing membrane of the EGFET is SnO₂. The pH sensitivity was between 54 and 59mV/pH and from the IDS-VG characteristic curves of the SnO₂ EGFET, which has linear pH response and high pH sensitivity. The temperature sensitivity of our temperature sensor is about -1.51mV/℃ between 25℃ and 65℃, this temperature sensor has linear temperature response. Hence, this chip can monitor the pH value and temperature at the same time.

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1PB04
Extended-Gate FET Applied in the Disposable Urea Biosensor

Jia-Chyi Chen, *Jung-Chuan Chou, **Tai-Ping Sun, Wen-Yaw Chung and Shen-Kan Hsiung

Institute of Electronic Engineering, Chung Yuan Christian University
Chung-Li, Taiwan 320, R.O.C.
*Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Taiwan 640, R.O.C.
**Institute of Electrical Engineering, National Chi Nan University
Nantou, Taiwan 545, R.O.C.

The higher cost of the traditional ion-sensitive field effect transistor (ISFET) leads to the low competitiveness in the market. However, the configuration of the extended-gate field effect transistor (EGFET) can reduce the production cost exactly and then promote the competitiveness further. Besides, the configuration of the extended-gate field effect transistor can also reduce the influences of light, temperature and avoid being eroded by solutions. Therefore, the structure is suitable for developing the disposable biosensor. In this study, the extended-gate field effect transistor was applied in the disposable urea biosensor with a photocurable enzyme membrane, which was based on poly vinyl alcohol (PVA) with pendent styrylpyridinium groups (SbQ) to immobilize the urease. However, the polymerization with exposure to UV light can combine the photolithographic technique, which is a process of the semiconductor techniques. Therefore, the photocurable enzyme membranes can allow mass-production and have low cost. In our research, the urea biosensor has a linear response for concentrations of urea up to 60mg/dl at 5mM phosphate buffer solution pH 6.0 and the response time is about 5 minutes.

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1PB05
Light Effect of SnO₂/ITO Glass Extended Gate Field-Effect Transistors

Jing-Sheng Chiang, *Jung-Chuan Chou, **Tai-Ping Sun, Wen-Yaw Chung and Shen-Kan Hsiung

Department of Electronic Engineering, Chung Yuan Christian University
Chung-Li, Taiwan 320, R.O.C.
*Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Taiwan 640, R.O.C.
** Department of Electrical Engineering, National Chi Nan University
Nantou, Taiwan 545, R.O.C.

In the past, all the study of the light-induced effect of the ISFET focused on the open-gate structure, which both the sensitive film and the channel of the FET will be affected. So that, its light-induced variation is very large. In our research, we put emphasis on the light-induced effect of the tin oxide (SnO₂) sensitive gate EGFET (extended gate field effect transistor) based on ITO glass. First, we could find in this structure, EGFET, the light-induced variation was reduced. In addition, it could be sure that the light-induced variation was only caused by the sensitive film. We study the light behavior of the EGFET under the different light intensity and the pH values of the measuring environment. To obtain the light behavior, the sensitive thin film was dipped in the standard buffer phosphate solutions of pH 4, 7 and 10 in a dark box. According to these experiments, we can obtain that the light-induced effect of the EGFET is dependent on the pH value, which increases as the higher pH value. On the other hand, when the device was exposed for a long time, it would cause light-induced drift. Keywords: EGFET, light-induced variation, SnO2.

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1PB06
Study on the Drift and Hysteresis Effects of the Hydrogenated Amorphous Carbon Gate pH-ISFET

Jung-Chuan Chou, Hsjian-Ming Tsai

Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.

The hydrogenated amorphous carbon (a-C:H) or diamond-like carbon (DLC) is always used for protective layer, solar cell and field emission device because of their hardness, optical and electronic properties. The electrochemistry characteristics of the a-C:H are very well, especially for H+ and OH－ ions in the solution. Hence, the a-C:H film was been used for the sensing film of the pH-ISFET (ion sensitive field effect transistor) in this paper. We studied the phenomena of the hysteresis and drift for the pH-ISFET based on the a-C:H thin film and compared the performance of some kinds of the sensitive films listed on literatures. The a-C:H thin film was deposited by the plasma enhanced-low pressure chemical vapor deposition system (PE-LPCVD). According to the comparison with other materials, the a-C:H is good for using as the sensing film of the pH-ISFET. Keywords: Drift, Hysteresis, A-C:H pH-ISFET, Response.

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1PB07
Preparation and study on the urea biosensor based on the ISFET device

Jung Chuan Chou, Yen Sheng Wang

Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.

In this paper, we study and fabricate the urea biosensor based on the ion sensitive field effect transistor (ISFET) device. This structure has a lot of advantages, such as simple structure, easy fabrication, low cost, and simple package process. We use the hydrogenated amorphous carbon (a-C:H) sensitive film to design the pH sensor, and entrap the enzyme on the a-C:H sensitive film with immobilizing enzyme for manufacturing the optimum enzyme biosensors. And we immobile the urease on the ISFET with poly (vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) for designing the urea biosensor, which can measure urea concentration of the bloodstream. Keywords：urea biosensor, ion sensitive field effect transistor (ISFET), poly (vinyl alcohol) bearing styrylpyridinium (PVA-SbQ)

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1PB08
Preparation and Study on Drift and Hysteresis Properties of the Tin Oxide Gate ISFET by the Sol-Gel Method

Jung Chuan Chou and Yii Fang Wang

Institute of Electronics and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.

The drift and hysteresis are important factors that influence the output accuracy of the pH ion sensitive field effect transistor (pH-ISFET). In this paper, we use the sol-gel process to prepare the tin oxide (SnO₂) sensing membrane. Then, use the constant voltage constant current circuit and voltage-time recorder to record the output voltage of the SnO₂ gate pH-ISFET. The measurement of the drift was carried out separately in pH 1 to pH 9 buffer solutions for 12 hr. From the experimental results, we can find that the drift rate is increasing with pH value. We also use constant voltage constant current circuit to measure the hysteresis width of the SnO₂ gate pH-ISFET for pH loop pH 4-1-4-7-4 and pH 5-1-5-9-5 cycle loops for different loop times, respectively. From experimental results, we can conclude that the hysteresis width is proportional to the loop time. Keywords: Drift, hysteresis, SnO₂ gate pH-ISFET, sol-gel, constant voltage constant current circuit.

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1PB09
Design and Study on the Readout Circuit of the pH-ISFET Based on the Hydrogenated Amorphous Silicon

Jung Chuan Chou and Lan Pin Liao

Institute of Electronic and Information Engineering, National Yunlin University of Science and Technology
Touliu, Yunlin, Taiwan 640, R.O.C.

In this paper, we study and design the read out circuit of the ion sensitive field effect transistor (ISFET) based on the hydrogenated amorphous silicon (a-Si:H). And it was consisted of the analog circuit, A/D converter, and microcontroller. The design procedures of the system are the fundamental operation of the sensor device, design of the circuit, design of the software, fabrication and integration of the circuits. After all the read out circuit was finished, the measurement results were described in this paper. Keywords: hydrogenated amorphous silicon (a-Si:H), ion sensitive field effect transistor (ISFET), A/D converter.

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1PB10
Electroless Plating Technique to Fabricate High-sensitivity Pd/InP Hydrogen Sensors Based on Schottky Diode

Huey-Ing Chen*, Yen-I Chou, and Chien-Kang Hsiung

Department of Chemical Engineering, National Cheng Kung University
Tainan, Taiwan 70101, ROC

In this work, the electroless plating technique is employed to fabricate the Pd/InP hydrogen sensors based on the Schottky diodes. According to the thermionic emission analysis, the electroless plated Pd/InP diodes exhibit the barrier height of 584 meV. From the current-voltage (I-V) measurements, the diode currents present the excellent sensitivity on H₂. In addition, the H₂ sensing performances of Pd/InP diodes fabricated by electroless plating are also compared with those by thermal evaporation.

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1PB12
Examined the Absorption Properties of Organic Acids by Nanoparticles Coated Piezoelectric Quartz Crystal

Wen-Chang Chen*, Hong-Ming Lin**, and Yau-Ching Tsai***

*Department of Chemical Engineering, National Yunlin University of Science and Technology Touliu
Yunlin 640, Taiwan, R.O.C.
**Department of Materials Engineering, Tatung University
Taipei 104, Taiwan, R.O.C.
***Department of Bioengineering, Tatung University
Taipei 104, Taiwan, R.O.C.

Nanoparticles (NPs) of Au, Pt and TiO₂ have been directly coated on the Au electrode of piezoelectric quartz crystal (PQC) by gas condensation technique. After calcination, the response characteristics of NPs coated PQC sensors are examined with various kinds of organic acid solution. The results indicate that various NPs coated PQC sensors exhibits various response curves, depending on the kinds of acid solution and concentrations. The sensors also demonstrate an inherent reversible response to physical adsorption and a limitation of maximal adsorption amount of acid molecules. Among NPs coated PQC sensors, the nano TiO₂-coated PQC sensor has greater stability than that of Au or Pt-coated PQC sensor. However, the Pt-coated sensor has the greatest adsorption amount.

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1PB13
Plasma-polymerized-film Coated QCM Gas Sensor for Environmental Monitoring

H.Nanto*, Y.Hamaguchi*, S.Sanada*, K.Nobuyama*, T.Matsumoto**, K.Tanabe** and S.Kurosawa**

*Advanced Materials Science R&D Center, Kanazawa Institute of Technology
3-1 Yatsukaho, Mattou, Ishikawa 924-0838 Japan
**National Institute of Advanced Industrial Science and Technology
Tsukuba, Ibaraki 305-8566, Japan

In order to develop the sensor system for environmental monitoring, chemical sensors using quartz crystal microbalance (QCM) coated with acrylate-film with different functional groups, methacrolate-film with different functional groups and stylene-film as a molecular recognition membrane are prepared using plasma-polymerized chemical vapor deposition (CVD) method. It is found that the sensor response for various gases strongly depends on the functional group of molecular recognition membrame of the sensor. The stylene-film coated sensor exhibits no selectivity for specific gas and responds to various gases. It is also found that the stylene-film coated sensor in conjunction with principal component analysis is useful for identification of gas kinds in environmental monitoring.

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1PB14
Characteristic of Surface Acoustic Wave Gas Sensor with Resonator Structure

Long Wu★, Feng-Chih Chang★, Yu-Tang Shen★, Ming-Sheng Young★, and Alex C. S. Huang★★

★ Department of Electrical Engineering, National Cheng Kung University
Tainan, Taiwan, R.O.C.
★★ ftech Corporation, Taiwan, R. O. C.

Based on sensing requirement, the first condition for SAW device design is low insertion loss that promising whole oscillation circuit can work normally.[1] To match this requirement, we use 128^o rotated Y-cut LiNbO₃ as substrate and construct grating reflectors. This two-port SAW resonator is connected to an amplifier circuit in order to be an oscillator. The insertion loss of SAW device with 30 pairs grating reflections is 4 ～ 4.5dB, and that with 50 pairs grating reflectors is about 3.5dB. Upon theory of mass loading effect, SAW device may be regarded as ethanol vapor density sensor. The response due to changes in the medium density on the SAW transmission path causes transmission velocity change and resonant frequency shift. This is the basic principle of a SAW gas sensor. In order to increase sensitivity, coating stearic acid as sensing film on the transmission path is used. For different film depth, we discuss the responses of resonant frequency shift and find out the optimum. The selectivity up to 7.6×10^-2 Hz/ppm is obtained in this study. At last, the improvements of sensor system, range and stability are given.

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1PB15
The Sensing Properties of L-glutamic acid hydrochloride Coated on Surface Acoustic Wave Ammonia Gas Sensors

Chi-Yen Shen, Chun-Pu Huang, and Hsu-Chi Chuo

Department of Electrical Engineering, I-Shou University
Kaohsiung, 840, R.O.C.

The gas sensing properties of L-glutamic acid hydrochloride deposited onto 128^oYX-LiNbO₃ surface acoustic wave (SAW) delay line have been monitored in this study. The sensitivity, response time, reversibility, repeatability, and long-term stability of L-glutamic acid hydrochloride have been investigated. The SAW gas sensors based on L-glutamic acid hydrochloride demonstrate fairly sensitive and reversible toward ammonia gas with high repeatability. The detection limit of L-glutamic acid hydrochloride has been found to be less than 0.9 ppm ammonia in air. The long-term stability of L-glutamic acid hydrochloride is also superior. The response degrades at a rate of 0.01 ppm/day.

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1PB16
Application of Plasma Polymerized HMDSZ Films and Post Treatments on QCM to Humidity Sensors

Chen, K.-S.*, Wang, P.-Y.*, Yang, M.-R.*, Lin, C.-S.**, and Wu, T.-Z.***

*Department of Material Engineering, Tatung University
Taipei, Taiwan
** Institute of Biomedical Engineering, Yang-Ming University
Taipei, Taiwan
*** Department of Life Science and Institute of Biotechnology Dong Hwa University
Hualien, Taiwan

Quartz crystal microbalance (QCM) device is a piezoelectric sensor, characterized with its frequency variation with the change of mass due to surface adsorption. Moreover, the outstanding properties of QCM sensors, such as high sensitivity, selectivity and stability, have drawn a lot of attentions in decades. The plasma polymerization or modification, due to its excellent intrinsic properties, will be employed to introduce the hydrophilic surface for RH sensor or to provide an interlayer with abundant active sites for subsequent surface graft polymerization on QCM to improve hydrophilic properties. The monomer used in this study is hexamethyldisilazane (HMDSZ). This silicon organic-like thin film can be prepared by plasma polyermization. It also provided good adhesion to the substrate and had a uniform structure. To improve the surface wettability, plasma post-treatment (argon, or oxygen gas) or surface grafted-polymerization will be utilized to enhance hydrophilic property. QCM sensors modified by various surface modifications were accessed in humidity environments between 35%～85RH%. It was shown that the oscillating frequency of modified QCM sensors decreased remarkably as a result of adsorption of water vapor. The surface of QCM, modified by plasma-deposited film then grafted-AAm, had better sensitivity because of highly cross-linked structure. Its change of oscillating frequency decreased rapidly and stably from its apparent curve.

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1PB21
Amperometric Hydrogen-Phosphate Ion Sensor Using Perovskite-Type Oxide Thin-Film Electrode

Satoko Takase, Keiko Tsuchida, Miho Kawasaki, and Youichi Shimizu*

Department of Applied Chemistry, Faculty of Engineering, Kyushu Institute of Technology
1-1 Sensui-cho, Tobata, Kitakyushu 804-8550, Japan

Amperometric hydrogen-phosphate ion sensor based on perovskite-type oxide(La_1-xA'_xBO₃: A'= Ca, Sr, Ba, Ce, B= Cr, V, Mn, Fe, Co, Ni : x = 0～0.2)thin-films synthesized by an polymeric precursor method was investigated. Especially La_1-xA'_xCoO₃ systems obtained at 450～500℃ from metal nitrates, polymer and organic additives on a glass substrates with indium tin oxide electrode showed good amperometric responses to HPO₄^2- at the concentration between 5.0x10^-5~1.0x10^-3M. This sensor element showed high selectivity to HPO₄^2- among the examined anions of NO₃^-, Cl^-, and SCN^-.

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1PB22
Electrochromic Hydrogen-Phosphate Ion Sensor Using Metal-Oxide Thin-Film

Masayuki SHIOTSUKA, Satoko TAKASE, and Youichi SHIMIZU*

Department of Applied Chemistry, Kyushu Institute of Technology
1-1 Sensui-cho, Tobata, Kitakyushu 804-8550, Japan

Highly-sensitive hydrogen-phosphate ion sensor based on an electrochromism of NiO-based thin-film electrode was developed. Among the oxide thin-film tested, the 10 mol% Mn doped NiO thin-film electrode showed a remarkable change of absorbance at 400-800 nm, under applying an anodic potential at +0.80V vs. Ag/AgCl, which was depending on HPO₄^2- concentration. The change of the absorbance at 560 nm, the sensor signal, was almost linear to the logarithm of the HPO₄^2- concentration between 1.0x10^-6 and 1.0x10^-2 M. The 90% response time, when the electrode potential was changed from +0.80V to 0V vs. Ag/AgCl at 1.0x10^-3 M, was about 20 s at room temperature.

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1PB23
Dynamic Coating of Plastic Channels for High Throughput Characterization of Humic Substances in Microchip-based Capillary Electrophoresis

Xiaoling Wu, Hidenori Nagai, Shigeru Kurosawa, Sahori Takeda, Shin-ichi Wakida

National Institute of Advanced Industrial Science and Technology (AIST Kansai Center)
Ikeda, Osaka 563-8577, Japan

In present work the fluorescein isothiocyanate labeled humic substances were separated using plastic microchip based capillary gel electrophoresis (CGE) within a few minutes. The plastic microchips were modified using a dynamic coating method to improve the characterization of samples. Sodium dodecyl sulfate (SDS) coating were used to decrease efficiently the adsorption of humic substances and improve the separation efficiency of plastic chip.

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1PB24
A PVC Based Metalloporphyrin Membrane Potentiometric Sensor For Cobalt

V.K. Gupta1, Prashant Singh2 and Rajni Mangla1

1Department of Chemistry, University of Roorkee
Roorkee-247 667 (INDIA)
2Department of Chemistry, D.A.V. (P.G.) College
Dehradun-248 001 (INDIA)

A poly vinyl chloride (PVC) membrane sensor for cobalt (II) ions based on metalloporhyrin 5,10,15,20-tetrakis-(4-methoxyphenyl)porphyrinatocobalt(II) (TMOPP-Co) a membrane carrier was prepared. Different membranes having TMOPP-Co, PVC, plasticizers and anion excluder sodiumtetraphenyl borate (NaTPB) were prepared to work out the best composition. It was found that the membrane having the constituents TMOPP-Co, NaTPB and PVC in the ratio 2:1:100 (w/w) exhibits the best properties with a Nernstian response of 30.5 mV/decade of activity. The addition of plasticizers did not improve the response characteristics of the membrane. The working concentration of the membrane is 1.9x10^-5-1.0x10^-1 M over the pH range 1.9-5.8. It exhibits a fast response time of 20 s and has a life span of about 4 months. The utility of the sensor was also investigated in partially non-aqueous media using methanol-water, ethanol-water and acetone-water mixtures. The sensor works satisfactorily in mixtures having 15% (v/v) non-aqueous content without showing any considerable change in working concentration range of slope. The proposed electrode revealed high selectivity for Co²⁺ ions over alkali, alkaline earth, some transition and heavy metal ions. The sensor has been successfully used as an indicator electrode for the potentiometric titration of Co²⁺ against EDTA as well as for its quantitative determination in battery wastes. The results obtained agreed well with those obtained by AAS and ICP.

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1PB25
DICYCLOHEXANO-18-CROWN-6 AS ACTIVE MATERIAL IN PVC MATRIX MEMBRANE FOR THE FABRICATION OF CADMIUM SELECTIVE POTENTIOMETRIC SENSOR

Vinod K. Gupta* and Rajni Mangla

Department of Chemistry, Indian Institute of Technology Roorkee
Roorkee-247 667 (India)

PVC based membrane containing dicyclohexano-18-crown-6 (I) as active material along with sodium tetraphenyl borate (NaTPB) as an anion excluder and dibutyl phthalate as solvent mediator in the ratio 20:4:150:150 (I:NaTPB:DBP:PVC) exhibits good properties with a Nernstian response of 29.0±0.5 mV/decade of activity and a working concentration range of 2.1 x 10^-5 - 1.0 x 10^-1 M. The working pH range of the sensor is 1.9 - 7.0. It exhibits a fast response time as fast as 17 s and has a lifetime of about 6 months. The proposed sensor has good selectivity for cadmium over alkali, alkaline earth, some transition and heavy metal ions. The sensor works satisfactorily in mixtures having 10% (v/v) non-aqueous content without showing any considerable change in working concentration range of slope. Iit has been successfully used as an indicator electrode for the potentiometric titration of Cd²⁺ against EDTA as well as for its determination in waste waters.

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1PB26
Study on The Response of Micro pH-Sensor with Platinum Wire Electrode Modified by Plasma Polymerization

Tatsuhiko Yajima, Namie Harada and Shunichi Uchiyama

Department of Materials Science and Engineering, Graduate School of Engineering, Saitama Institute of Technology
Okabe, Saitama 369-0293, Japan

Toluene (TOL), ethylbenzene (EB) and p-xylene (p-XY) plasma polymerization thin films were found to be effective to prevent chloride ions from reaching the platinum electrode surface, whereas still occurring the rapid response to protons through plasma thin films. Deviations of the pH response of untreated platinum electrodes soaked in the solution containing some redox interferences were remarkably improved by the appropriate plasma chemical modification of the sensory electrode. Also, through this work, a diagnostic parameter, i.e. Pr_M^-1t_TR^-1, which plays a critical roll to determine the optimum plasma conditions to prepare an electrode that possesses the reasonable pH response characteristics in the linearity and the response time was found.

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1PB27
Development of a pH Microscope

Y. Ito

Research & Development Center, Shindengen Kogyo
10-13 Minamicho, Hanno-shi, Saitama, 357 Japan

The purpose of this work is to introduce a development of a practical pH-imaging sensor system of the Light-Addressable Potentiometric Sensor (LAPS) by applying the techniques with the SOS (Silicon on Sapphire) wafer and the high speed digital data processing. The developed pH imaging sensor system is like an inverted microscope. The system has a red laser diode that is driven by the alternatively modulated sinusoidal waves. The laser beam is focused and scanned by a scanner mirror of the Y axis and an AOD (Acousto-Optic Deflector ) of the X axis. Scanning area is 60mm X 80 mm. Sensor signals are detected by the high speed digital data processing. The developed instrument achieves 2 mm of mapping resolution, scanning speed of 1.4 ms/pixel in the measurement pixels of (512) X (512) .

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1PB28
Simultaneous Visualization of Multiple Ions by the Chemical Imaging Sensor

K. Furuichi*, T. Yoshinobu*, Yu. Ermolenko*,**, Yu. Mourzina**, H. Iwasaki*, and M. J. Schoning***,****

*The Institute of Scientific and Industrial Research, Osaka University
8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
**Dept. of Chemistry, St. Petersburg State University
Universitetskaya nab. 7/9, St. Petersburg 199034, Russia
***Institute of Thin Films and Interfaces, Research Centre Julich
D-52425 Julich, Germany
****University of Applied Sciences Aachen
Ginsterweg 1, D-52428 Julich, Germany

We propose the multiple ion imaging sensor, which can visualize the spatial distributions of more than one ion species. It is realized by integrating different kinds of ion-selective membranes on the sensing surface of the chemical imaging sensor. A photopolymerization technique was developed to fabricate the integrated stripe patterns of ion-selective polymer membranes containing different ionophores. Multiple ion imaging by a K⁺/Ca²⁺ ion imaging sensor is demonstrated.

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1PB30
Dissolved Carbon Dioxide Sensor using Fluoride Ion Conductive Solid Electrolyte

Naoko UEJOH and Ai MORI

Department of Chemistry, Biology and Marine Science, Faculty of Science, University of The Ryukyus
Okinawa 903-0213, Japan

A solid-state sensor using a fluoride ion conductive solid electrolyte (LaF₃) was investigated in order to determine its usefulness for dissolved carbon dioxide (CO₂) sensing applications. The sensor element was composed of the following electrochemical cell: (reference electrode) Au | LaF₃ | Au- Na₂CO₃-Li₂CO₃ (sensing electrode). Au sensing electrode was platinized by electrodeposition, an auxiliary phase of NaCO₃-LiCO₃ was immobilized on it by immersion in a series of solutions in the order of a saturated solution of NaCO₃ and LiCO₃, an albumin solution and a glutaraldehyde solution. The sensor element was found to respond to dissolved CO₂ in the phosphate buffer solution (pH 7.0, at 30 ℃). The electro motive force (emf) response varied logarithmically with a change in dissolved CO₂ concentration in the range from 180 to 1880 ppm, following a Nernst's equation. The Nernst's slope was about 29 mV / decade (n = 2.1). The response transients showed the sensor had good reversible characteristics and the 90 % response time was from 5 to 10 min. Influences of pH to the response of the sensor also were investigated.

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2PB01
Quantitative Detection of Suppression of Quinine-type Bitterness Using a Taste Sensor

S. Iiyama, H. Kuga, K. Goto, S. Ezaki and K. Toko*

Kyushu School of Engineering, Kinki University
Iizuka 820-8555, Japan
*Graduate School of Information Science and Electrical Engineering, Kyushu University
Fukuoka 812-8581, Japan

Suppression of bitterness was studied with a taste sensor which can detect taste in a manner similar to human gustatory sensation. The influence of sweet sucrose, salty NaCl, sour HCl and umami monosodium glutamate (MSG) on a bitter taste of quinine was examined with the sensor. Only sour substance out of four fundamental taste substances diminished the response of the sensor to bitter quinine. But the response of the sensor to bitter picric acid was not affected by sour substance. Food constituents such as glutamic acid, acetic acid, lactic acid, malic acid and citric acid were also effective to decrease the response to quinine. Acetic acid of 10 mM depressed the bitterness of quinine to a hundredth. The present method can be expected to provide a new method to measure the strength of bitterness in place of sensory evaluation.

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2PB02
Development of Lipid Membranes with Silicone Rubber for Taste Sensor

K. Tanaka, M. Iwakura, T. Onodera, T. Adachi and K. Toko

Graduate School of Information Science and Electrical Engineering, Kyushu University
6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan

Lipid membranes with silicone rubber (SR) were developed by mixing only lipids in SR. In this study, we prepared three kinds of lipid membranes and investigated their response characteristics for five basic taste qualities, i.e. sweet, salty, sour, bitter and umami taste. The first membrane is made of a lipid, dioctyl phosphate, the second membrane is made of trioctyl methyl ammonium chloride, and the third membrane contains the 5:5 molar mixture of these kinds of lipids. They are negatively charged, positively charged and noncharged, respectively. The response electric potential is different for different taste substances in each membrane and is different in other membranes. Furthermore, taste substances with the same basic taste had similar response patterns constructed from outputs of three kinds of membranes with each other, whereas those with the different taste had different patterns. However, response patterns for sweet substances are a little similar to those for umami taste substances. Improvement of this point will produce the taste sensor which can provide an objective scale for the human sensory expression. Use of taste sensor will lead to a new era of food and environmental science.

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2PB03
Electron transfer reaction of GOx hybrids modified with phenothiazine via poly(ethylene oxide) spacer on carboxyl residues

S. Aoki, K. Ishii, T. Ueki, K. Ban, S. Imabayashi and M. Watanabe

Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University
Yokohama 240-8501, Japan

Novel telechelic phenothiazine(PT)-bound poly(ethylene oxide)(PEO) oligomers having an amino end group for the covalent immobilization to the carboxylic residues, PT-PEO-NH₂, were synthesized and bonded to carboxylic residues on GO_x surface [GO_x-(PT-PEO-NH₂) hybrids]. Catalytic reactions of these hybrids were explored by electrochemical methods. The catalytic current increased with the number of modified PT-PEO-NH₂ and leveled off at a large number of PT-PEO-NH₂. The rate of current increment depends on the PEO chain length and exhibited a maximum for PT-PEO of molecular weight 3000. For the PT-PEO with a larger molecular weight, a maximum was observed for the current vs. number of modified PT relationship and the modified number at the maximum decreased with increasing the molecular weight of PT-PEO. The rate constant of the mediated FADH₂ oxidation, k_obs, calculated from the catalytic current ranges from 1.7 to 388 s^-1. These values are greater than our previous values for GO_x hybrids with PT attached to lysine residues via PEO. It was clarified that more effective electron transfer reaction between PT⁺ and FADH₂ can be achieved in GOx-(PT-PEO-NH₂) hybrids due to the PT modification to acidic amino acid residues, most of which are located closer to the FAD center than lysine residues.

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2PB04
Electron transfer reaction mechanisms of GO_x modified with electroactive phenothiazine group on surface residues

T. Ueki, K. Ban, S. Imabayashi, and M. Watanabe

Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University
Tokiwadai Hodogaya-ku Yokohama 240-8501, Japan

We have studied electrochemical properties of GOx-(PT-PEO) hybrids, in which poly(ethylene oxide) having on electroactive phenothiazine group at terminus is modified to surface lysine residues, in oxygen-free solutions containing excess glucose. Catalytic reactions of GOx-(PT-PEO) hybrids systems can be detected as a current at electrodes. The catalytic current of GOx-(PT-PEO) hybrids was changed depending on the number of mediators attached per GOx molecule and the PEO spacer length. A comparison of the catalytic current between GOx-(PT-PEO) hybrids and GOx-(PT-PA) hybrids, in which PT groups are directly attached on surface lysine residues of GOx, makes clear the importance of PEO spacer for rapid electron transfer. And the maximum catalytic current was obtained for GOx hybrid modified with PT-PEO of molecular weight 3000 (PT-PEO 3000), indicating the existence of the optimum PEO chain length for the intramolecular electron transfer from cofactor to PT groups. It should be emphasized that in spite of the lower diffusion coefficient of mediator attached to GOx-hybrid, the GOx-(PT-PEO 3000) hybrid reveals a higher catalytic current than the mixed system of GOx and freely diffusing PT-PEO 3000 because of the extremely fast reoxidation of FADH₂. This rapid electron transfer system can be applied to biosensors, the electrochemical control of enzymatic function, and the construction of oxidase enzyme systems without the influence of dioxygen in atmosphere.

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2PB05
Glucose Sensors Prepared by Layer-by-Layer Deposition of Platinum Black and Glucose Oxidase

Tomonori Hoshi, Shigehiro Takahashi, and Jun-ichi Anzai

Graduate School of Pharmaceutical Sciences, Tohoku University
Aramaki, Aoba-ku, Sendai 980-8578, JAPAN

A Platinum (Pt) electrode was immersed in glucose oxidase (GOx) solution (1 mg/ml in acetate buffer) for 30 min. GOx were spontaneously adsorbed on the electrode surface without loss of the catalytic activity. The electrode was then immersed in hexachloroplatinate solution for plating platinum black over the enzyme layer. Platinization was carried out by reducing hexachloroplatinate in the presence of lead acetate. The electrolytic reduction of hexachloroplatinate was performed galvanostatically: the deposition current was varied from -0.1 to 1.5 mA for 15 or 30 s. After platinization, the electrode was immersed in GOx solution for 30 min. This allowed GOx to form second enzyme layer on the platinum black. These procedures were carried out repeatedly and the effect of the deposition number on the amperometric response to glucose was studied. The amperometric response of the electrode to glucose was measured in phosphate buffer (pH 6.8) at room temperature. Enzymatically generated H₂O₂ was oxidized at +600 mV vs. Ag/AgCl electrode. It was found that the response current increased upon deposition of the first layer of Pt black though the amount of GOx unchanged. Cyclic voltammogram was also measured and found an obvious peak appeared around +200 mV. The electrode was then followed by deposition of GOx and Pt black, repeatedly. However, the response current has reached the peak after the second deposition of GOx or Pt black. Because of the thickness or density of the Pt black, glucose molecule may not be able to pass through the Pt layer.

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2PB06
Ferrocene-appended Polyelectrolyte Multilayer Film Coated Electrodes　for Biosensors

A. Liu and J. Anzai

Graduate School of Pharmaceutical Sciences, Tohoku University
Aramaki, Aoba-ku, Sendai 980-8578, Japan

A layer-by-layer self-assembly of ferrocene(Fc)-appended polyallylamine (PAA) or branched polyethylenimine (PEI) and polyanionic polyvinylsulfate, potassium salt (PVS) on a negatively charged thiol-modified gold electrode by electrostatic interaction is systematically studied. Fc-PAA /PVS or Fc-PEI/PVS film was obtained by alternately dipping the thiol-modified Au electrode into polyelectrolyte solutions. The Fc charge increases with the number of bilayers added. Dependence of peak current on the potential scan rate shows that as the number of bilayers increases, the electron transport within the multiilayer (PEM ) film becomes to obey different machanism. The electron-transfer reaction is rate-determining for the first several bilayers, and then changes to diffusion-control for the following bilayers. Fc-PAA and Fc-PEI can penetrate 3 or 4 PAH/PVS bilayers insulating spacers, respectively. Fc-PEI is faster in electron-relay than Fc-PAA. Ferrocene-containing PEM modified electrodes can electrocatalyze the oxidation of vitamin C (ascorbic acid) successfully.

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2PB07
Hydrogen Peroxide Sensor Based on Carbon Paste Electrode Containing a Metal Porphyrin Complex

Tomohisa Kasanuki*, Mitsuaki Kamiyama*, Hiromichi Noguchi**, Shigeru Ishii* and Yasuhiko Yoshida**

*Department of Applied Chemistry, Graduate School of Engineering, Toyo University
Kujirai, Kawagoe, Saitama 350-8585, JAPAN
**Bio-Nano Electronics Research Center, Toyo University
Kujirai, Kawagoe, Saitama 350-8585, JAPAN

Carbon paste (CP) electrodes containing a metal tetraphenylporphyrin (M-TPP; Me=Co, FeCl, Zn, Cu and Ni) were fabricated. Then, the response current at a given potential was measured in the usual manner at an H₂O₂ concentration of 10-70 mM in 0.1 M phosphate buffer solution using the CP electrode as a working electrode. The potential to be applied depended on M-TPP. The optimum potentials for the CP electrodes containing Co-TPP and FeCl-TPP, at which the response current increased linearly with the H₂O₂ concentration, were found to be -550 and -350 mV, respectively. On the other hand, the most preferable pH value, at which the same linear relation was observed, was 6.8 with these two electrodes. Since the cathodic electrode response is independent of the anodic discharge due to the components usually present in body fluids, a highly selective response to glucose might be expected for the CP electrodes on enzyme modification.

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2PB08
Histidine and Histamine Assay in Fish Meats Using Enzymatic Method

A. Yamamura*, Y. Sekiguchi*, T. Koyama*, K. Matsumoto*, and N. Kiba**

* Department of Applied Chemistry, Kanagawa Institute of Technology
1030 Shimo-ogino, Atsugi-shi, Kanagawa 246-0292, Japan
**Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Yamanashi University
4-37, Takeda, Kofu, Yamanashi 400-8511, Japan

A simple, selective and rapid method to determine the quantity of _L-histidine and histamine in fish meats was developed by utilizing two enzymes, _L-histidine oxidase [EC 1.4.3.-.] and histamine oxidase [EC 1.4.3.-.]. The quantity of L-histidine was determined by colorimetric analysis with 4- aminoantipyline, N-ethyl-N-2(2-hydroxy-3-sulfopropyl)-3, 5-dimethoxyaniline (DAOS), peroxidase [EC 1.11.1.7.] and L-histidine oxidase. The calibration curve for _L-histidine was linear from 1.0 to 5.0 mM. _L-Histidine concentration in tuna fish meats was 3.8 mmol/100g in the beginning, and increased together gradually with the refrigeration preservation days. The quantity of histamine was determined by chemiluminescent flow sensor with histamine oxidase and peroxidase. Histamine oxidase and peroxidase were co-immobilized covalently on tresylated hydrophilic vinyl polymer beads and packed into transparent PTFE, which was used as flow cell. One assay for histamine was done at intervals of 2 min without carryover. The calibration curve for histamine was linear from 0.1 to 50 mM. The response was reproducible within 1.25 % of the relative standard deviation when 115-replicate injections of 100 mM histamine were carried out. Histamine concentration in tuna fish meats was little in the beginning, and increased to 500 ppm after five days.

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2PB09
Amperometric sensing of histamine using mioglobin-adsorbed carbon felt electrode

S. Uchiyama, N. Kimura, Y.Hasebe

Department of Applied Chemistry, Saitama Institute of Technology
1690 Fusaiji, Okabe Saitama 369-0293,Japan

A dialyzed mioglobin adsorbs the carbon felt electrode surface and can suppress the cyclic voltammogram of ferrocyanide ion, because mioglobin covers the active sites of the electron transfer. On the bother hand, unpurified mioglobin does not influence these wave heights due to prior coordination of small molecule to the mioglobin. The active site of ferrocyanide ion redox reactions decreased by blocking of hydroxyl group on the carbon surface using dinitrobenzyl chloride, although des not decrease by blocking carbonyl group. This fact indicates that the active site contains hydroxyl group. The redox wave heights of ferrocyanide ion decreased in stepwise by successive addition of mioglobin, because mioglobin adsorbed to the carbon felt and active site should be blocked. We found that histamine and histidine react with the adsorbed mioglobin and can liberate mioglobin from the carbon felt surface. This fact indicates that the compound with bioaffinity to mioglobin can be measured by using mioglobin adsorbed carbon felt electrode if the recovered current heights of ferrocyanide ion are proportional to the added histamine or histidine.

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2PB10
Amperometric sensing of histamine using dialysis membrane covered silver electrode

S. Yamagata, Y. Hasebe, S. Uchiyama

Department of Applied Chemistry, Saitama Institute of Technology
1690 Fusaiji Okabe Saitama 369-0293, Japan

　 Histamine and histidine exhibit quasi-reversible redox waves at a silver electrode, and the optimum conditions of sensing these compounds such as pH or the electrode potential have been investigated. Histamine and histidine react with silver ion and the oxidation waves are sifted from those of silver to negative direction. The amperometric measurements of these compounds using a bare silver electrode were carried out and the steady-state current responses were obtained, but unfortunately the serious fluctuation of current response caused by convection of the sample solution are observed. This fact led us to try to get the stable current response by using dialysis membrane covered silver electrode. This study reveals that the oxidation potential of histamine is lower by 25 mV than that of histidine, and the selective amperometric measurement of histamine can be performed in the presence of histidine. The difference of the sensitivity between similar these compounds should be ascribed to the difference of equilibrium constants of the reactions of these compounds and silver ion. The present method applied to the determination of histidine contained in the fish meat juice.

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2PB11
Carbon-felt based flow amperometric biosensors: determination of glucose and lactate in real samples

T. Shirai, S. Uchiyama and Y. Hasebe

Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology
1690 Fusaiji, Okabe, Saitama, 369-0293, Japan

Flow amperometric biosensor for glucose and lactate was fabricated by coupling glucose oxidase (GOD) or lactate oxidase (LOD)-immobilized column reactor and the horseradish peroxidase (HRP)-based flow-through electrochemical H₂O₂ detector. HRP and the electron transfer mediator, thionine (TH) were co-immobilized onto porous carbon felt (CF) by cyanuric chloride and resulting elecrode (HRP-TN-CF) was used as working electrode of the flow electrochemical detector. The immobilized TN efficiently mediates electrons from the CF electrode to the redox active center of the HRP, and quite reproducible peak currents for the H₂O₂ were obtained. Under optimum operational conditions (applied potential; -0.1 V vs Ag/AgCl, injection volume; 200 ml, carrier flow rate; 1.5 ml/min, carrier pH; 8.0), linear determination range for the H₂O₂ is 0.1mM to ca. 0.1 mM (the detection limit of 1x10^-8 M). The sensitivity of H₂O₂ was 0.92mA/mM. The concentration-dependent peak current responses were also obtained for glucose and lactate, and the electrochemical interferences present in real samples (such as L-ascorbate, cysteine, uric acid and acetaminophen, 100 mM) induce no appreciable change, indicating that the present FIA system is applicable to the analysis of food and biological samples. The fundamental performance characteristics of the sensor (sensitivity, linear range, optimum pH, flow rate, response time, operational and storage stability) were investigated.

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2PB12
Amperometric Glucose Sensor Using Two Dimensional Cross-Linked Langmuir-Blodgett Films of Polysiloxane Copolymer

D. Kato 1, M. Masaike 1, M. Sakata 1, M. Kunitake 1, C. Hirayama 1, Y. Hirata 2, and F. Mizutani 2

1 Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University
2-39-1 Kurokami, Kumamoto 860-8555, Japan
2 National Institute of Advanced Industrial Science and Technology
1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

A novel amperometric glucose-sensing Pt electrode for detecting hydrogen peroxide, which is produced by the glucose oxidase (GOx) reaction, was constructed using H₂O₂-permselective films based on two-dimensional (2D) cross-linked polysiloxane Langmuir-Blodgett (LB) films. The electrode system consisted of polysiloxane LB films and a polyion complex layer between the GOx and glutaraldehyde as a permselective layer and an enzyme layer, respectively. 2D cross-linked polysiloxane LB films were placed on to the H₂O₂-permselective films in order to block other electroactive interferences, such as L-ascorbic acid, L-cysteine, uric acid and acetaminophen. Surprisingly, it was found that the 2D cross-linked siloxane monolayer was remarkably effective at eliminating the interfering responses and had a rapid response for glucose, even though the film was only a monolayer thick.

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2PB13
Amperometric Sensing System for the Detections of Urea and Glucose by the Combination of the pH-stat Method and Flow Injection Analysis

Y. Yamada*, T. Osaka*, and I. Satoh**

*Department of Applied Chemistry, School of Science and Engineering; Kagami Memorial Laboratory for Materials Science and Technology, Waseda University
Shinjuku-ku, Tokyo 169-0051, Japan
**Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of Technology
Atsugi-shi, Kanagawa 243-0292, Japan

A new type of amperometric sensing system for biological substances was designed and constructed based on the combination of the pH-stat method and the flow injection analysis (FIA). This system consists of an electrolysis path and a sample path. The pH change in the sample by enzymatic reaction is compensated by generated H⁺ or OH^- at the generation electrode (G.E.) by the electrolysis of the water in the electrolysis path. The magnitude of the applied current is used as the monitor to determine the concentration of substrates. In this system, the urea was measured sensitively and ideally from 100 mM to 800 mM. The stability of immobilized urease in the column was proved over 200 consecutive measurements. In addition, the response to urea was independent of the buffer concentration. Since the sample path was separated from the electrolysis path, no current responses of interfering substances were observed in the physiological level. Furthermore, this system was applied to glucose sensor, and the glucose measurement was achieved from 10 mM to 200 mM. Therefore, the high possibility of amperometric measurements of urea and glucose with merits of no dependency on buffer concentration and moreover, no influence of interfering substances was demonstrated. This new system is believed to have a potential to be widely applied to the measurements of various kinds of substances.

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2PB14
ENHANCED THE CONDUCTIVITY PROPERTIES OF AMPEROMETRIC BIOSENSOR BY METALLIC NANOPARTICLES

Jen-Hung Chuang＊, Hong-Min Lin＊＊, Wen-Chang Chen＊＊＊, and Thomas Y. Shen＊

＊ Apex Biotechnology Corp.
Industrial Park, Hsinchu 300, Taiwan, R.O.C.
＊＊ Department of Materials Engineering, Tatung University
Taipei 104, Taiwan, R.O.C.
＊＊＊ Dept. of Chem. Eng., National Yunlin Science and Technology University
Touliu City 630, Yunlin County, Taiwan, R.O.C.

There have been significant recent activities in the development of glucose oxidase (GDS) based electrodes for using in amperometric glucose sensors that can be used in various media, including whole blood. The electron transfer reaction and electron transport play an important role of amperometric biosensor. Nanocrystalline metal particles sizing in 1-100 nm show many special characteristics, such as quantum effect, surface effect, charging effect, and grain boundary effect, that are different from conventional bulk materials. Their unusual properties such as electrical conductivity and surface catalytic activity have become important areas of research. Screen-printed glucose biosensors, which can provide a rapid measurement of the glucose concentration in a fluid, are cost effective and now extensively used in clinical and research fields. However, there is a problem of measuring inaccuracy caused from the poor conductivity of carbon-ink used as electrodes. In this study, iron nanoparticles obtained by gas condensation method are used to modify the sensing surface of a screen-printed glucose biosensor. The electron conductive characteristics are examined by using the cyclic voltammetry. Results show that an excellent electron conductive characteristic, as well as an increase of the measuring accuracy, can be obtained.

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2PB15
Highly-sensitive determination of acetylcholinesterase activity based on the reductive desorption of thiol compound on silver electrodes

H. Matsuura＊, Y. Sato＊＊, T. Sawaguchi＊＊, F. Mizutani＊,＊＊

＊Department of Chemistry, University of Tsukuba
1-1-1 Tennou-dai, Tsukuba, Ibaraki 305-8571, Japan
＊＊Biosensor research group, National Institute of Advanced Industrial Science and Technology (AIST)
Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

In order to carry out the highly-sensitive determination of a thiol-producting catalyst acetylcholinesterase (AChE), we have developed a unique, "stripping-like" voltammetric method. Thiocholine, which was produced through the AChE-catalyzed hydrolysis of acetylthiocholine, formed a monolayer on a silver electrode surface. The thiolate on the electrode surface was then desorbed electrochemically. A cathodic peak for the reductive desorption was observed around -1150mV (vs. Ag/AgCl). The number of adsorbed thiocholine molecules was calculated from the charge for the peak. The charge increased in association with the increase of the AChE activity. The AChE activity as low as 0.01 U/l could be measured, the detection limit was 100-fold higher than that obtained conventional amperometric methods. Thus the present method has proved to be useful for the highly-sensitive determination of thiol-producing systems.

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2PB16
Electrochemical and Sensor Activities of Proteins Polymerized on Gold Nanocrystals

K. V. GOBI*,**, F. MIZUTANI*

*Biosensor Research Group, Institute of Molecular and Cell Biology, National Institute of Advanced Industrial Science and Technology
Tsukuba Cental 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305 8566, Japan
** Japan Science and Technology (JST), Japan.

Gold nanocrystals protected by monolayer of 3-mercaptopropionic acid were synthesized by a single-phase borohydride reduction reaction. Transmission electron micrograph shows that the average core diameter of the mercaptopropionic acid-monolayer protected nanocrystals, MPA:MPCs, is 2.96 nm. Electrochemical investigations of cytochrome c complexed with MPA:MPCs (cyt c/MPA:MPCs) revealed that cyt c, otherwise electrochemically non-active, shows a reversible redox wave on complexing with MPA protected gold nanocrystals. Cyclic voltammograms of cyt c/MPA:MPCs show a reversible redox wave at 0.06 V (vs. Ag|AgCl) and are diffusion-controlled. Rotated disk voltammograms of reduction of cyt c/MPA:MPCs show a limiting current that is under hydrodynamic mass-transport control and are consistent with a reversible one-electron transfer reaction. Cytochrome c complexed with MPA:MPCs shows anodic current response to the generation of superoxide radical at the electrode applied potential of 0.15 V. The superoxide radical sensing of cyt c/MPA:MPCs was investigated by chronoamperometry under hydrodynamic conditions.

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2PB17
APPLICATION OF AN ELECTROLYTIC DEVICE TO A FLOW-INJECTION ANALYSIS OF L-ASCORBATE

Yasuhiro Iida, Takuto Satoh, Takuya Kikuchi and Ikuo Satoh

Kanagawa Institute of Technology
1030 Shimo-Ogino, Atsugi 243-0292, Japan

Flow-injection amperometric determination of L-ascorbate was investigated with use of a laccase column. Laccase (EC 1. 10. 3. 1.) covalently immobilized onto porous glass beads was used as the recognition element for L-ascorbate. The biosensing system was assembled with the column unit and a flow-through type of an oxygen electrode for monitoring dissolved oxygen enzymatically consumed. Sample solutions were introduced into the system via a rotary injection valve. The catalytic activity of the enzyme-packed column was assessed by injecting 0.5 ml of L-ascorbate with various concentrations. L-Ascorbate was determined in a range of 0.05 - 20 mM, and a linear relationship was obtained in a range of 0.05 - 1.0 mM. In order to extend the linear range of the L-ascorbate determination, additional oxygen in the carrier stream should be provided for the laccase reaction. Not a chemical but physical method was employed to increase dissolved oxygen in the flow stream. Oxygen was electrolytically generated in the buffer stream by applying a constant current with use of a galvanostat. This electrolytic device was introduced between the pump and the damper in the system. By using this electrolytic device, more wide linear range of the L-ascorbate determination was obtained (0.05 - 2.0 mM). This study proposes a mediatorless method for determination of L-ascorbate by applying the electrolytic device to the system, and the device should be applicable to other oxidase reaction.

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2PB18
Preparation of L-Amino Acids Biosensor Based on an L-Amino Acid Oxidase-Immobilized Polyion Complex Membrane

S. Yabuki, F. Mizutani, and Y. Hirata

National Institute of Advanced Industrial Science and Technology
1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

L-Amino acid oxidase (LAAO)-immobilized polyion complex membrane was prepared on a glassy carbon (GC) electrode. Polystyrene sulfonate and poly-L-lysine solutions were successively placed on the GC electrode to prepare a polyion complex membrane. After drying, LAAO solution and glutaraldehyde solution were placed on the membrane to immobilize enzyme, and the enzyme/glutaraldehyde mixture was allowed to dry. The enzyme electrode was used for the detection of L-amino acids; +1 V vs. Ag/AgCl was applied on the base electrode to detect enzyme-produced hydrogen peroxide. For the L-phenylalanine, the lower detection limit was 5 μM, and the linear response range was up to 1 mM, and the response time was ～40 s. Responses to the other amino acids such as L-leucine and L-methionine were almost same magnitude to that to L-phenylalanine. These results indicate that the electrode could be used for the L-amino acids detection such as L-phenylalanine, L-leucine and L-methionine.

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2PB19
Improvement of Theanine Assay Using Laccase

Yoshinori Sekiguchi, Yoko Ohe, Akira Yamamura, Ikuo Satoh, and Kunio Matsumoto

Department of Applied Chemistry, Kanagawa Institute of Technology
1030 Shimoogino, Atsugi-shi, Kanagawa 246-0292, Japan

The ethylamine sensor by flow-injection analysis (FIA), native theanine hydrolase (EC 3.5.1.65), and laccase (EC 1.10.3.2) were employed for the improvement of assay method of theanine in green tea. The sensor was consisted of an immobilized ethylamine oxidase (EC 1.4.3.6) column and a hydrogen peroxide electrode, and was used for the ethylamine determination. Theanine was hydrolyzed by theanine hydrolase to corresponding ethylamine and L-glutamic acid. The ethylamine formed was measured amperometrically by using the ethylamine sensor. Ethylamine oxidase was immobilized covalently on beads of partially aminopropylated refractory brick and packed into column (30 mm × 4 mm i.d.). Some reducing substrates like polyphenol and ascorbic acid in samples were removed by enzymatic oxidation reaction with laccase or by adsorption method with poly(vinyl)poly(pyrrolidone) (PVPP) before the assay of theanine. The optimum laccase activity used for removal of them in samples and the treatment time were 165 mU /ml and 30 min at 37℃, respectively. The best condition for removal of reducing substrates was obtained by combination with laccase and PVPP. One assay for ethylamine was done at intervals of 2 min without carryover. The calibration curve of theanine was linear from 0.2 mM and 1 mM. The response was reproducible within 0.9 % of the relative standard deviation for 50-replicate injections of 0.5 mM ethylamine. The sensor was at least stable for 20 days. The present method gave good agreement (correlation coefficient of γ= 0.997) with the values obtained by High performance liquid chromatography (HPLC).

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2PB20
Biochemical Oxygen Demand (BOD) Sensor Using Oligotroph

Toshifumi SAKAGUCHI, Rumi IHARA and Tomoharu KUBO

Department of Biological and Environmental Chemistry Kyushu School of Engineering, Kinki University
11-6 Kayanomori, Iizuka, Fukuoka, Japan 820-8555

For detection of organic pollution in aquatic environments, newly isolated oligotrophic bacteria were used for the cell-immobilized membrane in the BODs sensing system. Four strains of oligotrophs were isolated from natural sediment and water samples in Ishigaki island (strains MA and MAK) or a natural spring well in Koganei, Tokyo (strains NU and NUK). Decrease of current due to the oxygen consumption was observed when these strains of oligotroph were used as the biological device in BODs system. Approximately 50 ppm of organic compounds could be detected as 0.2 mV current decrease (corresponding to 0.34 ppm oxygen decrease) by using the cell-immobilized membrane which was immobilized 0.3 mg (dry weight) of strain NUK cells.

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2PB21
Detection of Tetracycline Based on Its Inhibitory Effect to the Enzyme-Mimic Catalytic Activity of DNA/Ni (II) Complex

T. Gu, S. Uchiyama and Y. Hasebe

Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology
1690, Fusaji, Okaba, 369-0293, Japan

A flow injection analysis (FIA) system for the detection of DNA-binding antibiotics, tetracycline(TC), was developed by using DNA/Ni(II) complex-immobilized carbon felt (CF) as a sensing element. It was found that the DNA/Ni(II) complex exhibited enzyme-mimic catalytic activity for the air oxidation of thiol compounds. And the catalytic activity of the DNA/Ni(II) complex for the oxidation of aminoethanthiol (AET) was reversibly inhibited by the intercalation of TC within DNA-base pairs. Kinetic measurements implied that the TC inhibited the DNA/Ni(II) complex-catalyzed oxidation of AET according to the mixed type inhibition pattern. This phenomenon could be utilized for development of novel flow-type biosensing system for TC consisting with immobilized-DNA/Ni(II) complex reactor and Clark-type oxygen electrode detector. The peak-shape current responses were observed for TC using 0.1M Tris-HCl buffer containing AET as a carrier, and the magnitude of the peak current depended considerably upon the concentration of TC. The optimum conditions for TC detection such as Ni(II) concentration, AET concentration and carrier flow rate were evaluated. The calibration graph of TC exhibits the linear line in the concentration up to 1×10^-4M TC with detection limit of 1×10^-6 M.

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2PB22
SUBFEMTOMOLAR DETERMINATION OF ZINC(II) IONS 　　BASED ON AN APOENZYMATIC METHOD

Ikuo Satoh, Masayuki Kameyama, and Yasuhiro Iida

Kanagawa Institute of Technology
1030 Shimo-Ogino, Atsugi 243-0292, Japan

Ultratrace determination of zinc(II) ions with use of an apoenzymatic method was demonstrated.　Alkaline phosphatase immoblilized onto porous glass beads was packed into a small column and then used as a selective recognition element for zinc(II) ions. The flow-injection sensing system was assembled with a small polymer column containing the immobilized preparations and a flow-through cell attached to a UV/VIS detector. The catalytic activity was assessed by injecting 0.1 ml of 2.0 mM p-nitrophenyl phosphate(pH 8.0). The enzyme column was positively regenerated by introducing 100 mM 2,6-pyridine dicarboxylate solution into the system to remove zinc(II) ions coordinated in the active site of the enzyme molecules. Zinc(II) ions in subfemtomolar levels were photometrically determined through its activation of the apoenzyme, i.e., metal-free enzyme. Performance characteristics of the system was investigated.

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2PB23
Proline Sensor on the Basis of Electrochemiluminescence of Ruthenium(II) Complex

N. Egashira, J.Piao, R. Murayama, E. Hifumi, and T. Uda

School of Biosciences, Hiroshima Prefectural University
Shobara-shi, Hiroshima 727-0023, Japan

A proline sensor was prepared on the basis of ECL from a ruthenium complex using two protein-modified Au electrodes. With an electrode modified with albumin, the response intensity of proline, P, was 70% of histidine, H, while the responses were much weaker than those obtained with a bare Au electrode. In contrast, with an electrode modified with lysozyme, P showed almost the same strong response as that of the bare electrode and and the intensity for P was 15 times as strong as that of H and was the highest of all amino acids. A linear calibration curve for P was obtained in the concentration range of 1 x 10^-4 to 1 x 10^-6 M and the detection limit was 3 x 10^-7 M (S/N=3).

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2PB24
Application of simultaneous immunosensor for early detection of dengue virus

Li-Fang Huang*, Hui-Hua Yang***,Chih-Cheng Su*, Tzong-Zeng Wu* and Li-Kuang Chen***

*Gene Sole Biotechnology Co., Ltd.
*Institute of Biotechnology, National Dong Hwa University
Hualien, Taiwan
***Department of Emergency Medicine, Medical School Tzu Chi University

Dengue virus, mosquito-borne virus, is transmitted principally by Aedes aegypti mostly and it can cause dengue fever disease. If patients were under 15 years old or were re-infected by different serotype of dengue virus, they would be possible to turn class dengue fever into dengue hemorrhagic fever (DHF), which has higher mortality (about 15 - 20%). Although the diagnosis of dengue disease has been established such as HAI test, virus isolation, IgM ELISA methods and RT-PCR, there is still no effective method to satisfy the diagnosis during acute phase of dengue. For the prepare of immuno-chip to detect dengue disease, a monoclonal antibody against dengue virus was firstly produced. The antibodies were immobilized onto QCM electrode surface via glutaraldehyde coupling to form a specific immuno-chip. By comparing with conventional sandwich ELISA method, the result of immuno-chips showed hundred to thousand-fold higher in sensitivity and specificity. Not only the time required for the detection become shorter (about 30min), but the operation procedure and data interpretation was more simpler. Besides, the immuno-chip can detect dengue virus by detecting patient's sera during viremia stage. This technique will be helpful for the disease control and aid doctor to decide the necessary medical care to cure the illness at the early stage.

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2PB25
New Type Multilayers of SPR Sensor for Sensitization and Stabilization

S. Toyama*, T. Morihara**, M. Tsuge**, R. Usami**, and S. Kato*

*Research Institute, National Rehabilitation Center for the Disabled
4-1 Namiki, Tokorozawa, Saitama 359-8555, Japan
**Department of Applied Chemistry, Faculty of Engineering, Toyo University
2100 Nakanodai, Kujirai, Kawagoe, Saitama 350-0815, Japan

Optical properties, such as absorption angle, absorption width, and sensitivity for aqueous phase at the surface, of various multilayer SPR systems have been calculated. Multilayer composed of Ag-Au is suggested to exhibit medium properties between the single-layered Ag and Au systems. Furthermore, multilayer composed of MgF2-Au exhibits sharp absorption with less sensitivity than the single-layered Au system. More complicated multilayer systems, such as Ag-SiO₂-Ag, Ag-SiO₂-Au, Au-SiO₂-Ag, Au-SiO₂-Au, and Ag-PMMA-Au were conjectured to absorb S-wave as well as P-wave. The calculation suggested that the utilization of multilayers enables us not only to design SPR sensors with desired properties but also to select suitable materials for the new type SPR sensor.

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2PB26
DEVELOPMENT OF AN ECO-FRIENDLY SENSOR ELEMENT-(OPTICAL HCl DETECTION USING COMPOSITE FILMS OF TETRAPHENYLPORPHYRIN-BIODEGRADABLE POLYMER)

Katsuhiko NAKAGAWA*, Emi HOTANI*, Chikara TSUTSUMI*, Nobuki HAYASE* Michiaki MABUCHI*, Heru SUPRIYATNO**, and Yoshihiko SADAOKA**

*Department of Applied Chemistry and Biotechnology, Niihama National College of Technology
7-1, Yagumo-cho, Niihama 792-8580, Japan
**Department of Materials Science and Engineering, Faculty of Engineering, Ehime University
Bunkyo-cho-3, Matsuyama 790-0805, Japan

Composite films of 5,10,15,20-tetraphenylporphyrin(TPPH₂) embedded in various biodegradable polymer matrices(BPM) were prepared and their optical response to low ppm levels of HCl gas were examined in comparison with nonbiodegradable polymer matrices(NBPM). The absorbance of the Soret and Q-bands for BPM composite films are reversibly, more sensitive to low ppm levels of HCl gas than for NBPM composite films. Excellent sensitivity to low ppm levels of HCl gas and fast enzymatic degradation for TPPH₂-BPM composite films was achieved by using TPPH₂- poly(e-caprolactone)PCL composite.

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2PB27
In situ Observation of the Adsorption Behavior of Heme Proteins Using Slab Optical Waveguide Spectroscopy

Jose H. Santos*, Naoki Matsuda, Zhimei Qi, Akiko Takatsu and Kenji Kato

Nanoarchitectonics Research Center, AIST
Tsukuba Central 5, Tsukuba, Ibaraki, 305-8565, JAPAN

The adsorption behaviors of two important heme proteins, myoglobin and cytochrome c, were investigated using slab optical waveguide (SOWG) spectroscopy on both hydrophilic and hydrophobic surfaces under various solution conditions. The SOWG cell is composed of a quartz plate mounted on hollow silicone rubber sheet and supported with two prism couplers. The adsorbed protein film absorbed light from the evanescent field at the waveguide surface resulting to changes in the intensity of the outcoupled light. The light absorption patterns of both proteins are not only time dependent but also changes with pH and ionic strength implying that protein adsorption on quartz surface is affected by solution environment. At a neutral pH, cytochrome c preferred adsorption on hydrophilic over hydrophobic surfaces while the results for myoglobin showed slight bias towards hydrophobic surface. From a methodological point of view, it is found that SOWG spectroscopy using quartz plate is an appropriate tool for kinetic and mechanistic investigation of protein adsorption on flat surfaces.

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2PB28
Highly Sensitive Detection of Benzo(a)pyrene by Using SPR Immunosensor

N. Miura*, M. Sasaki*, G. Sakai**

*Advanced Science and Technology Center for Cooperative Research, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan
** Interdisciplinary Graduate School of Engineering Sciences, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan

Highly sensitive detection of benzo(a)pyrene (BaP) was achieved by using a surface-plasmon-resonance (SPR)-based immunosensor. A BaP-bovine serum albumin (BaP-BSA) conjugate (antigen) and an anti-BaP-BSA monoclonal antibody were prepared. The conjugate was immobilized on an Au thin-film of sensor chip by physical adsorption. The incident angle of the BaP-BSA immobilized sensor increased rapidly with increasing concentration of anti-BaP-BSA antibody up to ca. 30 mg/cm³ (ppm) and then increased meagerly above this concentration. The addition of BaP into the antibody solution was found to decrease the incident angle shift because of the inhibition effect of BaP. Based on this inhibiting principle, the present sensor was confirmed to detect BaP very sensitively in the concentration range of 0.1-300 ng/cm³ (ppb).

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2PB29
Detection of Cytochrome C by Means of Surface Plasmon Resonance Sensor

Tsutomu Ishihara and Tsuyoshi Arakawa

Department of Biological and Environmental Chemistry, Kyushu School of Engineering, Kinki University
Iizuka, Fukuoka 820-8555,Japan

We have studied the detection of cytochrome C by the use of surface plasmon resonance sensor on gold surfaces modified by alkyl thiols with different tail groups such as CH₃, NH₂ and CH₂OH. When the hexadecanethiol film was coated on gold surface, the incident angle changed from 23.1 to 53.2°. Moreover, the incident angle was changed from 53.2°to 63.6°by adding the phosphate buffer (PB) solution (pH=7.06). The shifts of the incident angle (Dq) were observed as on thiol thin film contacted with the cytochrome C solutions. The highest sensitivity was obtained on the thiol film having the hydrophobic group. The sensitivity decreased in the order CH₃>NH₂>CH₂OH.

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2PB30
A Novel SPR Chemical Sensor for Quality Control of Vinegar

H.Nanto*, Y.Hamagichi*, M.Komura*, Y.Sekikawa*, T.Miyatake*, E.Kusano*, Y.Oyabu** and A.Kinbara*

*Advanced Materials Science R&D Center, Kanazawa Institute of Technology
3-1 Yatsukaho, Mattou, Ishikawa 924-0838, Japan
**Kanazawa University of Economics
Kanazawa 920-8620, Japan

A chemical sensor based on surface plasmon resonance (SPR) with four channels is studied for quality control of the fermentation process of vinegar. Each channel of the SPR sensor responds to a change in quality of vinegar which is fermented for 1, 7 and 14 days, respectively. The responses of each channel of the SPR sensor clearly change with the number of fermentation days, indicating that the SPR sensor is useful for quality control in production of vinegar. The SPR sensor also responds to different vinegars such as "kome su", "junkome su" and "gousei su". This result suggests that the SPR sensor is also useful for identification of the types of vinegar.

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