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大腸菌膜・薬物相互作用を解析するためのイオンセンサシステムの開発

岡山大・薬

○勝 　孝、安田桂子、中川幸毅

DEVELOPMENT OF ION SENSOR SYSTEM FOR ANALYZING INTERACTION BETWEEN
DRUGS AND ESCHERICHIA COLI MEMBRANE

Takashi KATSU, Keiko YASUDA, and Hideki NAKAGAWA

Faculty of Pharmaceutical Sciences, Okayama University
Tsushima, Okayama 700-8530, Japan

The interaction between drugs and Escherichia coli membrane was
analyzed with ion sensor system composed of Ca2+, tetraphenylphosphonium (TPP+) and K+ electrodes. The Ca2+ electrode was used to examine the ability of the drugs to release Ca2+ from the outer membrane. The TPP+ electrode was used to examine the ability to permeabilize the outer membrane, since the uptake of TPP+ was > enhanced when the permeability barrier of the outer membrane was disrupted. The K+ electrode was used to examine permeabilization in the cytoplasmic membrane by monitoring the efflux of K+ in cytosol. Using the present senor system, we have demonstrated how the lipophilic moieties and the number of amino groups in drug molecules are important to induce outer membrane permeabilization.

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タンパク質薄膜の新規製造法の開発とバイオセンサーへの応用に関する研究

東北大薬

○安斉順一

THE DEVELOPMENT OF PROTEIN THIN FILMS FOR BIOSENDSOR APPLICATIONS

Jun-ichi ANZAI

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

Protein thin films have been developed on the basis of a biological affinity between binding proteins (avidin and lectin) and ligands (biotin and sugar) for constructing high-performance biosensors. Proteins which are tagged with biotin residues can be built into a layer-by-layer assembly through an alternate and repeated deposition of avidin and biotin-tagged protein on an solid surface. This technique was employed successfully for constructing enzyme and antibody biosensors. We also used concanavalin A as a prototype of lectin for constructing layered assemblies of proteins. In the lectin-based protein films, proteins were modified with sugar residues before use. It is a merit of the lectin-based protocol that one can use glycoproteins such as glucose oxidase (GOx) without any pretreatments because glycoproteins contain hydrocarbon chains intrinsically on the surface of the molecule. Thus, we can prepare a layer-by-layer assembly of GOx for developing glucose biosensors.

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ミクロ・マクロ構造制御による半導体ガスセンサの高性能化

長崎大工

清水康博

DEVELOPMENT OF HIGH PERFORMANCE SEMICONDUCTOR GAS SENSOR BY MICRO- AND MACRO-STRUCTURAL DESIGN

Yasuhiro SHIMIZU

Graduate School of Science and Technology, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan

This article reviews our approach aimed at improving and modifying the sensing properties of semiconductor gas sensors by specially designing micro- and micro-structure of sensors. The objective gases tested were trimethylamine and NH₃, but hydrogen sensitivity was also examined to establish suitable micro- and macro-structure of thick-film semiconductor as well as varistor-type gas sensors. Our new challenges in both controlling and designing the micro- and macro-structure of sensors are also reviewed with special emphasis on the potential advantages of a slide-off transfer printing method in fabricating heterolayer structure, unique H₂ sensing properties of an anodically oxidized TiO₂ film with Pd and Ti electrodes and novel preparation procedure of thermally stable mesoporous SnO₂ powders.

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自己組織化単分子膜による高感度非侵襲型コレステロールセンサの開発

山口大院理工

○岸本正義，池永 裕，椎木 弘，長岡 勉

DEVELOPMENT OF HIGH SENSITIVE NON-INVASIVE CHOLESTEROL SENSOR USING SELF-ASSEMBLED MONOLAYER

Masayoshi KISHIMOTO, Yutaka IKENAGA, Hiroshi SIIGI, and Tsutomu NAGAOKA

Division of Applied Chemistry, Graduate School of Science and Engineering,
Yamaguchi University,2-16-1 Tokiwadai,Ube755-8611

The detection of total cholesterol in a living body plays an important role in the clinical analysis of disease states. Now, the cholesterol analysis is carried out with an enzyme reaction in the clinical institutions. However, the enzyme method is troublesome due to the necessity of going to hospital and invasive collecting blood. Therefore, in this study we focus on the non-invasive measurement of cholesterol using molecularly imprinted self-assembled monolayer. The sensor using molecularly imprinted self-assembled monolayer shows a linear relationship with the concentration of cholesterol in the range of 0.1~1.0mM and a rapid response. The formation of cholesterol specific monolayers, their specificity, stability and reproducibility was examined and it has been applied for simple and speedy electrochemical sensor development.

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酵素固定化カーボンフェルトによるフロー型クーロメトリックバイオセンサ

埼玉工大工

○長谷部　靖、白井　貴行、内山　俊一

FLOW COULOMETRIC BIOSENSOR USING ENZYME-IMMBOLIZED CARBON FELT

Yasushi HASEBE, Takayuki SHIRAI and Shunichi UCHIYAMA

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

The flow-coulometric biosensor was designed using enzyme-immobilized porous carbon felt (CF) electrode as a flow-through coulometric detector. Horseradish peroxidase (HRP) and an electron transfer mediator, thionine (TN), were co-immobilized at the surface of cyanuric chloride-activated CF. The peak current responses for hydrogen peroxide based on HRP-TN assisted bioelectrocatalytic reduction of H2O2 was recorded and peak area was integrated by coulometer. The effect of various operational conditions on the coulometric efficiency was investigated. The coulometric efficiency was affected by TN-amount at the CF surface, carrier flow rate, applied potential, sample concentration and injection volume. The coulometric efficiency for 20 μM of H2O2 was found to be nealy 100 % under the following optimum conditions; applied potential; -0.05 V vs Ag/AgCl, carrier flow rate; 0.6 ml min-1, carrier pH; 8.0.

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pH感応性ゲルを利用したディスポーザブルバイオセンサ

筑波大物質工

○熊谷あゆみ、鈴木博章

A DISPOSABLE BIOSENSER USING A pH-SENSITIVE BIOCHEMOMECHANICAL GEL

Ayumi KUMAGAI, Hiroaki SUZUKI

Institute of Materials Science, University of Tsukuba,
1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan

A novel approach in constructing a disposable biosensor is proposed. By immobilizing glucose oxidase in a pH-sensitive copolymerized poly(N-isopropylacrylamide) / acrylic acid gel, a glucose-sensitive gel can be obtained. When the gel makes contact with a sample solution containing glucose, the pH of the gel decreases as a result of the enzymatic reaction inducing the collapse of the gel. The response time to shrinking change depended upon the activity of the enzyme and the concentration of glucose, although the final ratio of shrinkage settled approximately around the same value irrespective of their concentration. The transient stage can be used for sensing. The movement of the gel could be transduced into the movement of a colored solution in a flow channel with the help of a silicone rubber diaphragm. Clear dependence of the length of the colored solution on the concentration of glucose was observed. By measuring the change at a predetermined time, glucose concentration could be measured. The sensor will be an ultimate style of a disposable sensor, which does not necessitate any external circuits or spectroscopic procedures for detection.

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分子鋳型過酸化ポリピロール膜による人血清中の総胆汁酸計測

山口大院理工　

○椎木　弘，木島大介，長岡　勉

DETERMINATION OF TOTAL BILE ACIDS IN A HUMAN SERUM WITH MOLECULARLY IMPRINTED OVEROXIDIZED POLYPYRROLE FILM

Hiroshi SHIIGI, Daisuke KIJIMA, and Tsutomu NAGAOKA*

Molecular Recognition Engineering Course, Graduate School of Science and Engineering, Yamaguchi University,
Ube 755-8611, Japan

The electrochemical preparation of a molecularly imprinted overoxidized-polypyrrole (MIOPPy) film and its application
for bile acids sensor was presented here. The MIOPPy has been derived from taurocholic acid (TC)-doped polypyrrole
synthesized on a quartz crystal microbalance electrode. The extraction of TC (dedoping) by the overoxidation process
has created a pseudo shape-complementary cavity at the film surface. The resulting oPPy film exhibited a high
sensitivity to the bile acids, i.e. physiologically synthesized cholic acid, lithocholic acid, chenodeoxycholic acid,
deoxycholic acid, TC and artificially dehydrocholic acid, and showed a linear relationship between the resonance
frequency and in a wide range of the concentration of bile acids from 10-8 to 10-5 M. Development of this sensor
leads to simple detection of much affection without spectrometric procedure.

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ニュ−トン流体中における水晶振動子の振る舞い

鹿大工・産総研

〇吉本　稔、阿部　幸司、西上原　誠、黒澤　茂

Behavior of a quartz crystal microbalance in Newton liquid

Minoru Yoshimoto, Koji Abe, Makoto Nishikanbara, Shigeru Kurosawa

Department of Bioengineering, Faculty of Engineering, Kagoshima University,
1-21-40 Korimto, Kagoshima 890-0065, Japan
National Institute of Advanced Industrial Science and Technology (AIST)
1-1 Higashi, Tsukuba 305-8565, Japan

The effect of the immersion angle θ of the QCM in a Newton liquid was investigated using the impedance analyzer. In the QCM with the two faces in contact with a liquid, the resonant frequency shift ΔF was independent of θ and was dependent on only the number of faces in contact with a liquid. On the other hand, in the QCM with the one face in contact with a liquid, it became clear that ΔF depended on　θ, and had the largest value at θ = 90° and the smallest value at θ = 0°. We also presented the simple model of ΔF in the QCM with the one face in contact with a liquid on the basis of experimental results.

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抗C-反応性タンパク質(CRP)モノクローナル抗体と水晶振動子（QCM）によるCRPセンサの開発

産総研、日大院、NEDO

○中村美樹，黒澤　茂，愛澤秀信，朴　鍾元，戸塚光裕，山田和典，平田光男

IMMUNOSENSOR FOR C-REACTIVE PROTEIN (CRP) USING ANTI-CRP MONOCLONALANTIBODY IMMOBILIZED QCM

Miki NAKAMURA, Shigeru KUROSAWA, Hidenobu AIZAWA, Jong-Won PARK, Mitsuhiro TOZUKA, Kazunori YAMADA, Mitsuo HIRATA

National Institute of Advanced Industrial Science & Technology (AIST)
1-1 Higashi, Tsukuba-shi, 305-8565, Japan
Graduate School of Industrial Technology, Nihon University
1-2-1 Izumi-cho, Narashino-shi, 275-8575, Japan
New Energy and Industrial Technology Development Organization (NEDO)
3-1-1 Higashi Ikebukuro, Toshima-ku 170-6028, Japan

C-reactive protein (CRP) is well-known as a good marker protein for pneumonia in human blood, and is chosen as target molecule for this sensor. Anti-CRP monoclonal antibody is immobilized the activated QCM via covalent bonding. Oscillation frequency of QCM immobilized anti-CRP antibody is measured at each reaction step after wash pure water and then dry process under nitrogen gas. The range of CRP concentration is settled from 1 ng dL^-1 to 100 μg dL^-1. Frequency response of anti-CRP F(ab')₂ antibody immobilized QCM for CRP is two times larger than anti-CRP antibody immobilized QCM for CRP.

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水晶振動子と免疫ラテックスを用いたＦＤＰの測定

産総研、NEDO、武蔵工大院

○愛澤秀信，黒澤　茂，戸塚光裕，朴　鍾元，小林光一

NOVEL DETECTION OF FDP USING IMMUNIZED LATEX AND QUARTZ CRYSTAL MICROBALANCE

Hidenobu AIZAWA, Shigeru KUROSAWA, Mitsuhiro TOZUKA

National Institute of Advanced Industrial Science & Technology (AIST)
1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
New Energy and Technology Development Organization (NEDO)
3-1-1 Higashi Ikebukuro, Toshima-ku, Tokyo 170-6028, Japan
Musashi Institute of Technology
1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557, Japan

Fibrin and fibrinogen degradation products (FDP) are well-known as a good marker protein to detect a diagnosis of thrombosis in human serum. We constructed the FDP immunosensor to combine quartz crystal microbalance (QCM) with agglutination reaction of anti-FDP antibody immunized latex beads. Frequency response of QCM method and absorbance response of photometric method show good correlation

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DNA-Cu (II) COMPLEX FILM-MODIFIED ELECREODE FOR AMPEROMETRIC DETECTION OF
H2O2 AND OXIDASE-SUBSTRATES

○Tingting GU1, Yasushi HASEBE2, Shunichi UCHIYAMA2

1. Department of Material Science and Engineering, Graduate School of Engineering, Saitama Institute of Technology,
1690, Fusaiji, Okabe, Saitama 369-0293, Japan
2. Department of Applied Chemistry, Saitama Institute of Technology,
1690, Fusaiji, Okabe, Saitama, 369-0293, Japan

The novel enzyme-less H2O2-sensing electrode was fabricated using DNA-Cu (II) complex as a catalyst for reduction of H2O2. The polyion complex membrane cosisted with DNA-Cu (II) and polyallylamine (PAA) was prepared by simple cast method on a glassy carbon (GC) electrode. The electrochemical behavior of DNA-Cu(II)/PAA-modified electrode was characterized by cyclic voltammetry. The redox couple Cu(II)/Cu(I) was greatly changed in the presence of H2O2, due to the electrocatalytic reduction of H2O2. The steady-state current response to H2O2 observed at applied potential -0.2 V (vs. Ag/AgCl) was relatively rapid (< 20 s), and was proportional to the H2O2 concentration up to 0.5 mM with the detection limit of 0.1_M H2O2 (S/N = 3). Furthermore, this electrode was applicable to glucose sensing by co-immobilization of glucose oxidase (GOD) with DNA-Cu/PAA film, and the calibration curve of GOD/DNA-Cu/PAA-modified electrode was linear up to 2 mM with a detection limit of 20 μM.

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DNA stick -POC対応型DNAセンサーの開発-

北陸先端大院、北斗科学産業

○小林正昭、草川貴史、梶佐規子、森田資隆、民谷栄一

A NOVEL TOOL FOR POINT OF CARE 'DNA STICK'

Masaaki KOBAYASHI, Takashi KUSAKAWA, Sakiko KAJI, Yasutaka MORITA and Eiichi TAMIYA

School of Materials Science, Japan Advanced Institute of Science and Technology, Japan
Hokuto Science Industry Company

Recent days clinical diagnosis, a novel detection techniques is essentially required that are rapid, on-site, cheap, disposable and easy to use. Conventional medical examination takes long time to diagnose patient situation. On-site diagnoses not only shortens the hospital stay and also provide clear understanding of the disease. Clinical analysis at the site is called Point of Care Testing (POCT). This can be applied in home nursing, mobile gisoutal, as well as in hospital

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コプラナーPCBスクリーニング用ELISAシステムの開発

*エンバイオテック・ラボラトリーズ、**国立環境研、***大阪府立大院、****北陸先端大院

○奥山 亮*、竹中 宏誌*、西 和人＊、水上 春樹＊、滝上 英孝＊＊、小崎 俊司***、切畑 光統***、
宮武 和孝***、民谷 栄一****、酒井 伸一**、森田 昌敏**

DEVELOPMENT OF ENZYME-LINKED IMMUNOSORBENT ASSAY FOR THE PRE-SCREENING OF COPLANAR OLYCHLORINATED BIPHENYLS

Akira OKUYAMA*, Hiroshi TAKENAKA*, Kazuto NISHI*, Haruki MIZUKAMI*, Hidetaka TAKIGAMI**, Shunji KOZAKI***, Mitsunori KIRIHATA***, Kazutaka MIYATAKE***, Eiichi TAMIYA****, Shin-ichi SAKAI****, Masatoshi MORITA****

* EnBioTec Laboratories Co., Ltd., Koto-ku, Tokyo 135-8073, ** National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, *** Graduate School of Agricultural and Biological Sciences, Osaka Prefecture University, Sakai, Osaka 599-8231, **** Japan Advanced Institute of Science and Technology, nomi-gun, Ishikawa 923-12

Conventional methods for the analysis of dioxins using high resolution gas chromatography/mass spectrometry (GC/MS), are expensive and time consuming and require highly trained technicians. Therefore, alternative simple and cost-effective methods for the determination of these compounds are highly desired. One of the methods that may satisfy these requirements and be an efficient screening tool is an immunoassay method based on poly- or monoclonal antibodies. We have developed monoclonal antibodies against 2,3’,4,4’,5-pentachlorobiphenyl (IUPAC#: PCB #118)1). In this study, enzyme-linked immunosorbent assay (ELISA) system for coplanar polychlorinated biphenyls (co-PCBs) utilizing the monoclonal antibody was developed and validated. The investigation of the cross-reactivity for various related compounds suggested that the ELISA system was highly selective for co-PCB congeners. The sensitivity was 16.7 ng/mL of PCB #118 in DMSO. The average CVs of intra- and inter-!
!
assay were within 20 %, suggesting this system had the good reproducibility. The native PCB congeners would be difficult to be used as the standard in the ELISA system with respect to handling and disposal. We investigated the applicability of PCB derivative, methoxylated PCB as surrogate compound.

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タンパク質のin situ測定に適した蛍光免疫センサの開発

成蹊大工

○大岩佑子、青柳里果、工藤正博

FLUORESCENCE IMMUNOSENSOR FOR IN SITU MONITORING OF PROTEINS

S. AOYAGI, Y. OIWA and M. KUDO

Department of Applied Physics, Faculty of Engineering, Seikei University
3-4-1 Kitamachi Kichijoji, Musashino-shi, Tokyo 180-8633, Japan

Based on the enhancement of fluorescein isothiocyanate (FITC) fluorescence caused by reactions between proteins, we developed a reagent-less, regenerable and rapid immunosensing system to determine immunoglobulin G (IgG). Fluorescence internsity of the immobilized FITC-labeled protein A binds to IgG, the surrounding atmosphere of FITC becomes hydrophobic. Since the fluorescence intensity of fluorescent substances, generally, increase at a hydrophobic environment, FITC fluorescence internsity increases with the concentration of protein A bonding to IgG. Moreover, the immobilized FITC-labeled protein A responds to IgG repeatedly and its fluorescence-enhancement occurs as soon as IgG and protein A react.

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抗体固定ビーズを用いた免疫センサの光学測定法による安定性評価

徳島大工

○渕脇雄介、濱田浩幸、安澤幹人

STABILITY EVALUATION OF ANTIBODY-IMMOBILIZED COLUMN FOR IMMUNOSENSOR USING OPTICAL PROCEDURE

Yusuke FUCHIWAKI, Hiroyuki HAMADA, Mikito YASUZAWA

Department of Chemical Science and Technology, The University of Tokushima,
Tokushima-shi, Tokushima 770-8506,

　The stability of the antibody-immobilized beads packed column for immunosensor application was evaluated using an optical procedure. Agarose resin and glass beads were employed for the immobilization of the antibody and the antigen was labeled with fluorescein in order to determine the affinity of the immobilized antibody by fluorescent measurement. Luteininzing hormone (LH) and its IgG class monoclonal antibody (anti-LH) were employed. The stability of the anti-LH column was evaluated by repeating the acidic treatment (pH 3) that will reproduce the column by cleaving the antigen-antibody bond formed on the surface of the beads. Although, the affinity of the antibody immobilized column reduced slightly for the first five times, relatively good reproducible affinity was observed for more than ten repetitive measurements.

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バッテリ-駆動式携帯型SPR免疫センサシステム

富山大工

松島功治、八木澤壮平、北本和久、竹本純、○鈴木正康

BATTERY-DRIVEN PORTABLE SPR IMMUNOSENSOR SYSTEM

Koji MATSUSHIMA, Sohei YAGISAWA, Kazuhisa KITAMOTO, Atsushi TAKEMOTO, Masayasu SUZUKI

Department of Electric and Electronic Engineering, Faculty of Engineering,
Toyama University, Toyama-shi, Toyama 930-8555, Japan

A portable immunosensor system, which can be used without AC power supply, was developed for environmental field monitoring. A miniature SPR sensor chip, Spreeta(TM) was used as a transducer and its controller was modified so as to work with a 9 volts dry cell. The sensor was controlled by a lap-top PC which works with a battery. Hydrostatic pressure driven flow utilizing a Marionette bottle was used for a flow system. As a model compound of low molecular weight environmental pollutants, 2,4-dinitrophenol (DNP) was measured by using this sensor system. Anti-DNP antibody was immobilized onto the sensor surface of SPR sensor chip, and DNP was measured based on the competition between sample DNP and fixed number of labeled DNP.

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二単色光源による小型・高感度な光導波路表面プラズモンセンサの開発

静岡大工、スズキ

鈴木昭裕，松井義和，○近藤　淳，塩川祥子，鈴木和保

DEVELOPMENT OF A SIMPLE AND SENSITIVE WAVEGUIDE SURFACE PLASMON RESONANCE SENSOR

Akihiro SUZUKI, Jun KONDOH, Yoshikazu MATSUI, Showko SHIOKAWA, and Kazuyasu SUZUKI

Department of Systems Engineering, Faculty of Engineering, Shizuoka University
Hamamatsu-shi, Shizuoka 432-8561
Yokohama R&D Center, SUZUKI Mortor Corporation
Tsuzuki-ku, Yokohama 224-0046, Japan

We fabricated a cheap and simple optical waveguide SPR sensor system which used two LEDs and a photodiode instead of laser and spectroscope. The advantage of this sensor is to easily change in respect of refractive index of the waveguide and wavelength of the light source. And also, it is suitable for immobilization of the antibody and adsorption of the molecule, since the waveguide is the plane structure. In this study, high sensitivity was realized by designing the combination of two monochromatic light sources for considering refractive index range of the measuring samples.

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表面プラズモン共鳴法による2.4ジニトロフェノールの検出

産総研、武蔵工大院、NEDO

○戸塚光裕，黒澤茂，愛澤秀信，小林光一，樋口真弘

DETECTION OF 2,4-DINITROPHENOL (DNP) USING ANTI-DNP ANTIBODY IMMOBILIZED SURFACE PLASMON RESONANCE SENSOR CHIP

Mitsuhiro TOZUKA, Shigeru KUROSAWA, Hidenobu AIZAWA, Jong-Won PARK, Koichi KOBAYASHI

National Institute of Advanced Industrial Science & Technology (AIST)
1-1 Higashi, Tsukuba, 305-8565, Japan
Graduate School of Engineering, Musashi Institute of Technology
1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557, Japan
New Energy and Industrial Technology Development Organization (NEDO)
3-3-1 Higashi Ikebukuro, Toshima-ku, Tokyo 170-6028, Japan

Surface plasmon resonance (SPR) technique has been used as a signal transduction method for real-time biochemical reaction monitoring. The immunoreaction is most popular in its sensitivity and selectivity for environmental assays. We used 2,4-dinitropenol (DNP) as a model compound for dioxins. DNP-conjugated bovine serum albumin (DNP-BSA) induced immunoreaction with an anti-DNP monoclonal antibody immobilized SPR chip. We report DNP detection using a competitive reaction between DNP and DNP-BSA for anti-DNP monoclonal antibody immobilized SPR chip.

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SPR味センサとQCM匂センサを用いた日本酒の甘辛の評価

金沢工大、金沢星陵大^*

関川祐司、宮竹智樹、小村光弘、北出康人、竹井義法、南戸秀仁、草野英二、金原　粲、大薮多可志^*

DISCRIMINATION OF TYPES OF JAPANESE SAKE USING SPR TASTE SENSOR AND QCM ODOR SENSOR

Yuuji SEKIKAWA, Tomoki MIYATAKE, Mitsuhiro KOMURA, Yasuto KITADE, Yoshinori TAKEI, Hidehito NANTO, Eiji KUSANO, Akira KINBARA and Takashi OYABU^*

Advanced Materials Science R&D Center, Kanazawa Institute of Technology
^*Kanazawa Seiryou University

Quality of four types of Japanese sake is estimated using a surface plasmon resonance (SPR) taste sensor and a quartz crystal microbalance (QCM) sensor. The SPR taste sensor resonds to quality change of Japanese sake suchas sweetness and dry. On the other hand, QCM odor sensor responds to the alcohol content of Japanese sake. It is found that the discrimination of four types of Japanese sake can be possible by plotting the output of QCM odor sensor as a function of output of SPR taste sensor.

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色素固定化ヘテロコア型光ファイバの光伝搬特性

創価大学工学部

○関　篤志、片倉久和、甲斐俊典、伊賀光博、中澤　毅、渡辺一弘

LIGHT-PROPAGATION CHARACTERISTICS OF DYE-IMMOBILIZED HETERO-CORE FIBER OPTIC

Atsushi SEKI, Hisakazu KATAKURA, Toshinori KAI*, Mitsuhiro IGA*, Tsuyoshi
NAKAZAWA*, Kazuhiro WATANABE*

Department of Bioenginnering, *Department of Information systems, Faculty
of Engineering, Soka University
1-236 Tangi, Hachioji, Tokyo 192-8577 Japan

Dye was immobilized on the surface of hetero-core fiber optic by using
sol-gel method. The hetero-core portion of the fiber was immerzed in sol solution containing the dye, and the transmission loss of the white-propagating light was measured. When the hetero-core portion was dipped in sol solution containing cresol red, the propagation loss at 525nm was observed. Then, the gel matrix was formed by heating at 70 ℃. When the hetero-core portion of the fiber was immersed in NaOH solution, the propagation loss at 590-600 nm was observed. The leackage of the dye was not observed in a series of experiments. These results show that this fiber would be useful for a pH sensor as environmental and industrial monitoring.

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高感度薄膜複合光導波路の免疫センサへ応用

横浜国立大学院

〇アブリズ イミテ、許一太、黄修竹、雨宮　隆、伊藤公紀、

A THIN FILM COMPOSITE OPTICAL WAVEGUIDE APPLIED TO THE
HIGHLY SENSITIVE IMMUNOSENSOR

Abliz YIMIT^a,b, Yitai XU^a, Xiuzhu HUANG^a, Takashi AMEMIYA^a, Kiminori ITOH^a

^aGraduate School of Environment and Information Science,
Yokohama National University
Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan
^bDepartment of Chemistry, Xinjiang University
Urumqi, 830046, China

A highly sensitive thin film composite optical waveguide immunosensors were developed for immunoglobulin (antibody IgG) detection. Highly sensitive element (TiO2 film/PIE glass composite OWG) based on a titanium dioxide (TiO2) films were deposited onto the suface of potassium ion exchanged (PIE) glass optical waveguide (OWG) by RF sputtering. This system was applied to the affinity reaction between protein A and IgG; the sensing layer of the protein A was coated onto the composite OWG surface by chemical reaction. The experimental process and reversible response characteristics are reported in detail. The sensor has a short response time and high sensitivity (detection limit 70.0 pg/ml).

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誘電泳動を利用した微生物または細胞の分離フローシステムの開発

東北大院工・東北大学際セ

○尾形幸子、鈴木雅登、高橋透、西澤松彦、末永智一

Development of Delectrophoretic Microfluidic System for Separating Microorganisms such as Microbes and Cells

S. Ogataa, M. Suzukia, T. Takahashib, , M. Nishizawaa, T. Matsuea,

a; Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University,
07Aramaki-Aoba, Aoba-Ku, Sendai 980-8579, Japan
b; Center for Interdisciplinary Research, Tohoku University　
07Aramaki-Aoba, Aoba-Ku, Sendai, 980-8578, Japan　

Dielectrophoresis, the movement of particles in non-uniform ac electric field, has been used to separate and manipulate microbes or cells by utilizing the difference in their dielectric properties.　　In this study, by using the semiconductor processing technique, we integrated dielectrophoretic modular elements into microchannels of a fluidic microdevice to manipulate microbes and cells. The suspension solution was injected to the device, and ran through the flow channel with an interdigitated electrode array by a syringe pump. The array worked as an unit for capturing microbes and cells by the dielectrophoretic force. Different types of microbes or cells can be separated by applying an appropriate frequency to the array. We have achieved the separation of live and dead E. coli with the castellated microelectrodes.

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ストレスマーカー計測用マイクロ電気泳動チップ(I):カテコールアミン類の検討

産総研　ヒューマンストレスシグナル研究センター

○脇田慎一、呉 暁玲、吉野公三、松岡克典、二木鋭雄

MICRO CHIP BASED CAPILLARY ELECTROPHORESIS FOR STRESS MARKER MONITORING (I): CATECHOLAMINES

Shin-ichi WAKIDA, Xiaoling WU, Kohzoh YOSHINO, Katsunori MATSUOKA and Etsuo NIKI

Human Stress Signal Research Center, National Institute of Advanced Industrial Science and Technology (AIST),
Ikeda, Osaka 563-8577, Japan

High throughput microchip assay for catecholamines with laser induced fluorescence detection, which has several advantages for human-fluids monitoring. We optimized electrophoretic separation condition for disposable polymer chip and applied the human saliva before/after the tension-stress model. We demonstrated successfully the stress marker assay is useful using disposable microchip assay.

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集積型血液ガスセンサ

筑波大物質工、NTTマイクロシステムインテグレーション研*、国立循環器病セン ター**）

○王　シャウ文、鈴木博章、林　勝義*、砂川賢二**

INTEGRATED BLOOD GAS SENSORS

Xiaowen WANG, Hiroaki SUZUKI, Katsuyoshi HAYASHI*, Kenji SUNAGAWA**

Institute of Materials Science, University of Tsukuba, 1-1-1 Tennodai,
Tsukuba, Ibaraki 305-8573
*NTT Microsystem Integration Laboratories, 3-1 Morinosato Wakamiya,
Atsugi, Kanagawa, 243-0198
**National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka
565-8565

A needle-type micro Clark-type oxygen electrode was fabricated for in vivo monitoring of oxygen. The chip was 0.3 mm wide and 60 mm long. Electrode patterns were formed on a flexible polyimide substrate. The active area of the cathode was a circle of 25 μm, 50 μm, or 100 μm in diameter. The electrolyte layer was formed with a 20wt% polyvinylpyrrolidone solution containing 3 M KCl dissolved in 1 M Tris-HCl buffer solution (pH 8.5). A silicone rubber gas-permeable membrane was formed to cover the entire structure except for the pad. Clear response curves were obtained with a 90% response time less than 20s , calibration curves were linear in the clinically important range of the partial pressure of oxygen. The electrode showed lower flow dependence as the size of the cathode decreased.

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ELECTROCHEMICAL DETECTION OF OXALATE AT HYDROGEN-TERMINATED CONDUCTING
DIAMOND ELECTRODES

○Tata N. Rao, Bulusu V. Sarada, C. Terashima, T. A. Ivandini, Akira Fujishima

Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656

The electroctrochemical oxidation of oxalic acid was investigated at as-deposited highly boron-doped diamond thin-film electrodes in neutral aqueous medium. Cyclic voltammetry, flow injection analysis and high performance liquid chromatography with amperometry, were used in this work to study the electrochemical reactions and determination of oxalic acid. The
hydrogen termination of diamond electrode was found to be crucial for the detection of oxalate. Oxalate oxidizes at ~1.0 V vs. SCE in 0.1 M phosphate buffer. Calibration plots were linear from 100 nM to 20 mM (r2 = 0.9998) and the detection limit was 46 nM (S/N = 3). Highly reproducible results were obtained with an RSD below 5% for 5 injections of 100 nM oxalate. Detection
of oxalate in real urine samples was performed at diamond electrode after HPLC separation.

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カーボン電極表面に固定化されたウレアーゼの酸化還元に基づく活性制御

埼玉工大工

○内山俊一、長谷部靖

REDOX CONTROL OF UREASE ACTIVITY IMMOBILIZED TO THE CONDUCTING POLYMER ON THE CARBON FELT ELECTRODE

Shunichi UCHIYAMA, Yasushi HASEBE

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

The activity of urease varies by its redox reaction. Active urease has SH group that is essential to exhibit its activity, however, the oxidation agents such as quinone compounds can oxidize SH group in urease and S-S bond is produced, resulting in the loss of enzyme activity. The reduction potential of cystine was almost the same as that of the recovery of urease activity. In this work, it has been found that SH group of urease can be oxidized by not only chemical reaction but also the direct electrode oxidation of urease and the produced S-S bond can be reduced to SH group by chemical and electrode reactions, and the original enzyme activity is recovered. This research shows that the regulation of urease activity is easily possible by changing the electrode potential of the porous carbon felt immobilized urease. The variation of urease activity was monitored by ammonia or carbon dioxide electrode equipped with the urease immobilized carbon felt, and the ammonia or carbon oxide generated from urea can transfer through the carbon felt to reach the each gas permeable membrane. The combination of gas electrode with porous conducting material such as carbon can supply the novel device for the electrochemical investigation of enzyme activity.

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糖類センシングのための機能触媒電極

熊本大・工、松下電器産業（株）電池研＊

○谷口　功、Sami Ben Aoun, Gyeong Sook Bang, 古賀哲舟、＊外邨　正

CATALYTIC ELECTRODES FOR SENSING SUGARS

Isao TANIGUCHI, Sami BEN AOUN, Gyeong Sook BANG, Tesshu KOGA, and Tadashi SOTOMURA*

Department of Applied Chemistry and Biochemistry,
Faculty of Engineering, Kumamoto University,
2-39-1, Kuromami, Kumamoto 860-8555
*Battery Research Laboratory, Matsushita Electric Ind. Co. Ltd.

Electro-catalytic oxidation of sugars at various metal electrodes has been examined. On Pt and Au electrodes, for example, sugars were oxidized at rather negative potentials (-0.5 to -0.3 V vs. Ag/AgCl), but main oxidation products were glycolic acid (Pt) and gluconic acid (Au), respectively. On Au aldoses can be easily oxidized at negative potentials but no oxidation took place for ketoses. Also, on Au electrode no oxidation of gluconic acid took place at negative potential region. On the other hand, at positive potentials sugars can be oxidized at various metal electrodes and multi-electron oxidation occurs, meaning although selectivity of sugarsbecomes poor but sensitivity for detection of sugars increases. These results suggest that when suitable conditions (electrode material, applied potential etc.) are chosen, sensing systems for electrochemical detection of sugars can be prepared.

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ダイヤモンド電極を用いた尿中尿酸測定器の開発

科学技術振興事業団、東大院工

○斯波裕之、本多謙介、B. V. Sarada、T. N. Rao、堀熙一、藤嶋昭

DEVELOPMENT OF DEVICE FOR THE MEASUREMENT OF URIC ACID IN URINE BY THE USING OF DIAMOND ELECTRODE

Hiroyuki SHIBA, Kensuke HONDA, B. V. SARADA, T. N. RAO,
Hirokazu HORI, Akira FUJISHIMA

Japan Science and Technology Corporation
Department of Applied Chemistry, School of Engineering, the University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Uric acid (UA) has been detected at highly boron-doped diamond film electrode by the using of flow injection analysis. Ascorbic acid (AA) is usually present in urine. AA is interfering factor in the electrochemical analysis of UA. The oxidation current of UA and AA are usually overlapped. So UA is not able to detect exactly. But AA has two peaks by the use of diamond electrode in phosphate buffer solution. These peaks were dependent on the concentration of AA. So the part of electrochemical detection system has two diamond electrodes. One is for measurement of UA and AA. Another is the measurement for AA from the first peak. It is considered that this< method can remove the influence of AA for detection of UA. We aim at the development of electrochemical simple device for detection of UA in urine.

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ダイヤモンド電極表面に電析した酸化イリジウム電析量のセンサ応用への影響

東大院工

○寺島千晶、Tata N. Rao、B. V. Sarada、藤嶋　昭

ELECTROCHEMICAL CHARACTERISTICS OF ELECTRODEPOSITED IRIDIUM OXIDE ON
CONDUCTIVE DIAMOND ELECTRODES

Chiaki TERASHIMA, Tata N. RAO, B. V. SARADA, and Akira FUJISHIMA

Department of Applied Chemistry, School of Engineering, The University of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Boron-doped diamond (BDD) electrodes have been modified with iridium oxide (IrOx), which has shapes of either morphologically dispersed nanoparticles or thick layers, using the electrodeposition technique. Nanoparticle catalysts of IrOx for the oxidation of hydrogen peroxide on BDD, which are conductive materials but non-electroactive for hydrogen peroxide, followed a high sensitive detection less than 100 nM in flow injection conditions. Fully covered BDD electrodes with IrOx were investigated for the pH dependence of the open-circuit potential over a pH range of 2 to 12. Fast pH response, within 0.3 sec after sudden pH change, was obtained even in thick film, which presents good reproducibility for the super-Nernstian response.

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チロシナーゼ・ペルオキシダーゼ修飾電極を用いたフェノール誘導体の分離定量検出

東大生産研

○野津英男、立間　徹

SIMULTANEOUS DETERMINATION OF PHENOL DERIVATIVES BY USING TYROSINASE/PEROXIDASE-MODIFIED ELECTRODES

Hideo NOTSU, Tetsu TATSUMA

Institute of Industrial Science, University of Tokyo
4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

Most phenol derivatives are known as harmful and/or useful compounds. Many enzyme electrodes have been developed and used for the determination of phenol derivatives. However, monoenzyme electrodes suffer from a problem of selectivity. When a sample solution contains some different phenol derivatives, a monoenzyme electrode cannot determine them separately. As a solution for this problem, multienzyme systems may be envisaged. In the present work, weused tyrosinase and peroxidase, because both of them can oxidize catechol derivatives, while their enzymatic selectivities are different. Each corresponding enzyme electrode exhibited different sensitivities to different substrates. On the basis of the two responses from the two electrodes, catechol and cresol could be determined simultaneously.

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銀電極へのチオールの吸着/脱離を利用したアセチルコリンエステラーゼ活性測定とその有機リン系農薬検出への適用

筑波大化1・産総研2

○松浦宏昭1、佐藤　縁2、澤口隆博2、水谷文雄1,2

MEASUREMENT OF ACETYLCHOLINESTERASE ACTIVITY BASED ON THE CHEMISORPTION/DESORPTION-PROSESS OF THIOL COMPOUND ON A SILVER ELECTRODE AND ITS APPLICATION FOR DETECTION OF ORGANOPHOSPHORUS PESTICIDE

Hiroaki MATSUURA 1, Yukari SATO 2, Takahiro SAWAGUCHI 2, and Fumio MIZUTANI 1,2

1 Department of Chemistry, University of Tsukuba,
1-1-1 Tsukuba, Ibaraki 305-8571, Japan
2 National Institute of Advanced Industrial Science and Technology
Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

To the determination of ethylthiometon an organophosphorus pesticide, we have applied an adsorptive stripping voltammetric method: the activity change of acetylcholinesterase caused by ethylthiometon was measured by monitoring the chemisorption/reductive desorption-process of thiocholine on a silver surface. The decrease in the acetylcholinesterase by ethylthiometon, i.e., the decrease in the number of thiocholine molecules produced brought about the decrease in the number of adsorbed thiocholine molecules. Ethylthiometon could be determined in the concentration range from 0.01 to 0.2 ppm.

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白金ナノ微粒子分散炭素薄膜の作製と電気化学センサへの応用

¹NTTマイクロシステムインテグレーション研究所，²NTT-afty

○由　天艶¹，丹羽　修¹，富田雅人¹，廣野　滋²

SIMULTANEOUS DETERMINATION OF PHENOL DERIVATIVES BY USING TYROSINASE/PEROXIDASE-MODIFIED ELECTRODES

Tianyan YOU¹、Osamu NIWA¹、Masato TOMITA、Shigeru HIRONO²

¹NTT Mirosystem Integration Labs
3-1 Morinosato, Wakamiya, Atsugi, Kanagawa 243-0198, Japan
²NTT Afty Corporation
4-16-30 Shimorenjaku, Mitaka, Tokyo 181-0013, Japan

We prepared 6.5% atomic concentration platinum nanoparticles embedded in graphite-like carbon film (Pt-NEGCF) by a simple RF sputtering method. Both the structural and electrochemical characterization were studied. The Pt-NEGCF electrode has high electrocatalytic abiliity to detect hydrogen peroxide with a good stability. The potential of Pt-NEGCF for use as a biosensor electrode was also confirmed by determining acetylcholine (ACh) and choline (Ch)coupled with a microbore liquid chromatography (LC) and a post column enzyme reactor. A low detection limit of 2.5 fmol for ACh and Ch at Pt-NEGCF electrode was obtained.

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フルクトースデヒドロゲナーゼを固定化したポリ（メルカプト-p-ベンゾキノン）膜修飾電極のD-フルクトースセンサ特性

神奈川大工

）○山岸祐太、持田由幸、新井五郎

FRUCTOSE SENSORS USING AN ELECTRODE MODIFIED WITH FRUCTOSE DEHYDROGENASE(FDH) IMMOBILIZED IN POLY(QUINONE) FILM

Yuta YAMAGISHI, Yosiyuki MOCHIDA, Gorou ARAI

Department of Applied Chemistry, Kanagawa University
Kanagawa-ku, Yokohama 221-8686, Japan

Fructose dehydrogenase(FDH) was immobilized in a conductive redox polymer, poly(mercapto-p-benzoquinone), prepared on Au-electroplated glassy carbon electrode. The immobilization of the enzyme was carried out by an electropolymerization of mercaptohydroquinone in the presence of the enzyme. The enzyme could be immobilized in the polymer without loss of its native specificity. The enzyme electrode functioned well as a direct response type of sensor, where the polymer chain served as a conductive molecular chain between the active centers (PQQ) in the enzyme and the substrate electrode. The enzyme electrode responded to D-fructose over a concentration range of 0.1 mM to 10 mM. The time required to reach 95% of the steady-state currents were typecally less than 1.5 min after the addition of D-fructose.

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ダイヤモンドマイクロ電極での生体物質の電気化学的検出

東大院工

○Olivia Herlambang, Bulusu V. Sarada, Tata N. Rao, 藤嶋　昭

MINIATURIZATION OF DIAMOND MICROSENSOR SYSTEM FOR IN VIVO DETECTION

Olivia HERLAMBANG, Bulusu V. SARADA, Tata N. RAO, Akira FUJISHIMA

Department of Applied Chemistry, Undergraduate School of Engineering, The University of Tokyo,
Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Miniaturized diamond microsensor system was examined for several applications in electroanalysis including dopamine and serotonin detection. Dopamine, a neurotransmitter, was detected at miniaturized sensor system by use of amperometry with overoxidized poly pyrrole (OPPy)-modified BDD microfiber electrode as electrochemical detector. The limit of detection for dopamine was 0.5 nM with a linear dynamic range from 0.5 nM to 100μM. An< RSD of 5.4% was obtained for 5 injections of 0.5nM dopamine. Present sensor system improved the detection limit by two times compared to the previously described diamond microsensor. The detection of serotonin, another neurotransmitter was also investigated. The detection limit was 0.6 nM (S/N=3) with an RSD of 6.5% for 10 injections of 1 nM. The results obtained were reproducible indicating the absence of electrode surface deactivation due to adsorption of reaction products.

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Electrochemical Analysis of Pollutants with Capillary Electrophoresis using Diamond Electrode

D. Shin, B. V. Sarada, D. A. Tryk and A. Fujishima

Department of Applied Chemistry, School of Engineering, The University of
Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Highly boron-doped diamond microelectrodes were employed in an end-column electrochemical detector (ED) for capillary electrophoresis (CE), and their analytical performance as CE-ED was evaluated in a laboratory-made CE installation. The diamond-based CE-ED exhibited high separation efficiency for the detection of several catecholamines with excellent analytical< performance. Compared to carbon fiber electrodes, the diamond electrode shows better analytical performance with low noise levels and highly reproducible analysis for the environmental detection of chlorophenols and phenylureas.

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NASICONを用いた限界電流型NO2センサのパルス駆動

九大院総理工、*九大先端センター

〇島ノ江憲剛、早原信介、三浦則雄*、山添　�f

SODIUM NITRITE-REGENERATION TYPE PULSE WAVE-OPERATION OF AMPEROMETRIC NO2 SENSOR BASED ON NASICON (Na+ CONDUCTOR)

Kengo SHIMANOE, Shinsuke HAYAHARA*, Norio MIURA**, Noboru YAMAZOE

Department of Materials Science, Faculty of Engineering Sciences, Kyushu University,
Kasuga-shi, Fukuoka 816-8580, Japan
* Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University,
Kasuga-shi, Fukuoka 816-85 80, Japan
**Advanced Science and Technology Center for Cooperative Research, Kyushu University
Kasuga-shi, Fukuoka 816-8580, Japan

The amperometric NO2 sensor based on NASICON (Na+ conductor) consumes or accumulates NaNO2 on the counter or sensing electrode, respectively, resulting of a decay in the limiting current with time. In order to overcome this problem, the sensing electrode potential was swung between forward current bias (fb) and reverse current bias (rb) in pulses. Among the pulse wave patterns tested, the best was given by a combination among square waves of -200 mV (fb) for 15 s, +200 mV (rb) for 5 s, and 0 mV (rest) for 10 s. Under this condition, the sensor showed fairly good sensing properties to NO2 below 5 ppb. The current response to NO2 was totally independent of coexistent CO2, while water vapor caused the current response to increase slightly.

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ペロブスカイト型酸化物系電極を用いた固体電解質センサのNOx検知特性

九工大工

○高橋裕美、清水陽一

SENSING PROPERTIES OF SOLID ELECTROLYTE NOX SENSOR USING NASICON AND PEROVSKITE-TYPE OXIDE ELECTRODE

Hiromi TAKAHASHI and Youichi SHIMIZU

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

Solid electrolyte-based electrochemical devices fabricated with NASICON and perovskite-type
oxide electrodes have been systematically investigated for the detection of NOx ( NO, NO2
and N2O ) in the range 10-2000 ppm at 300-400?C. The elements attached with the
perovskite-type oxides [A1-xA'xBO3 ( A=La, Nd and Y, A'= Ca and Sr, B= Co, Cr, Fe, Ni, Mn and
Ru, x=0-0.4) or A2CuO4 ( A=La, Nd and Sm ) ] exhibited rather good performance for the
potentiometric sensing to NO as well as NO2 at 300-400?C. The EMF responses of these sensors
were almost liner to the logarithm of NO or NO2 concentration, while no response was observed
to N2O with them. Among the electrodes tested, the device attached with LaNiO3 or LaCrO3
electrode gave excellent NOx sensing properties.

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希土類酸化物を検出極に用いた新規な固体電解質型窒素酸化物ガスセンサ

大阪大学院工

○小田篤、田村真治、今中信人、足立吟也

A NEW SOLID ELECTROLYTE TYPE NITROGEN OXIDES GAS SENSOR WITH RARE EARTH OXIDE BASED AUXILIARY ELECTRODE

Atsushi ODA, Shinji TAMURA, Nobuhito IMANAKA, Gin-ya ADACHI

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

A new solid electrolyte type nitrogen oxides (NOx) gas sensor was fabricated by using multivalent cation and divalent oxide anion conducting solid electrolytes with the rare earth oxide based auxiliary electrode. The linear relationship between the sensor output and the logarithm of NOx content was obtained in the gas range from 200 to 2000 ppm, and the n value (1.04) calculated from the EMF slope was in good agreement with the theoretical one (n=1.00) for the sensor with Gd2O3+KNO2 as the auxiliary electrode. A quantitative NOx gas detection was successfully realized with a rapid, stable, continuous, and reproducible response and the present NOx gas sensor is greatly expected to be applied at various NOx gas emitting sites.

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酸化触媒電極を付与した混成電位式ＮＯxセンサの検知性能
　
（リケン*、九大先端センタ−**）

○ 小野敬*，**、長谷井政治*、国元晃*、三浦則雄**
　　
SENSING PERFORMANCES OF THE MIXED-POTENTIAL TYPE NOx SENSOR ATTACHED WITH OXIDATION-CATALYST ELECTRODE

Takashi ONO*，**， Masaharu HASEI*， Akira KUNIMOTO*， Norio MIURA**

* R & D Division， Riken Corporation，
Kumagaya-shi， Saitama 360-8522, Japan
**Advanced Science and Technology Center for Cooperative Research， Kyushu University，
Kasuga-shi， Fukuoka 816-8580, Japan

　 The mixed-potential type NOx sensor attached with an oxidation-catalyst electrode was fabricated by laminating and sintering YSZ green-sheets， on which an NOx sensing electrode consisting of metal oxide （Cr2O3）， an O2 sensing electrode， an NOx conversion electrode， Pt heaters， and a pair of thermocouples were printed． The sensor was capable of detecting low concentrations of total NOx． The use of an oxidation-catalyst electrode was found to decrease largely the interference of reducing gases （C3H8, CO） to the NOx sensivity． The results obtained here indicate that the present sensor has great possibility of being utilized as an on-board NOx sensor．

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固体電解質を用いた改質ガス中のCOセンシング：（II）抵抗型センサ
　
産総研、名大院環境

○橋本衷子、日比野高士、佐野　充
　　
DETECTION OF CO IN REFORMED GASES USING SOLID ELECTROLYTES: (II)RESISTOR-TYPE SENSOR

Atsuko HASHIMOTO, Takashi HIBINO, and Mitsuru SANO

Ceramics Research Institute, National Institute of Advanced Industrial Scienceand Technology
Moriyama-ku, Nagoya 463-8560, Japan
Graduate School of Environmental Studies, Nagoya University
Chikusa-ku, Nagoya 466-0804, Japan

Resistor-type sensor device using a samaria-doped ceria electrolyte with different working electrodes were fabricated for detecting carbon monoxide (CO) in reformed gases between 250 and 425℃. The electrochemical oxidation of H₂ over a Pd working electrode was the most sensitive to a reversible poisoning by 50-4000 ppm CO in the presence of 50% H₂, 10% CO₂ and 6% H₂O vapor, thus resulting in an increase in the electrode-reaction resistance at the electrode-electrolyte interface. There was a roughly linear relationship between the change in resistance and the logarithm of the CO concentration with 90% response and 90% recovery times of about 20 seconds. An improvement in the CO-sensing properties of the present sensor device, especially above 300℃, was also carried out by the addition of Au to the Pd working electrode.

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SURFACE PHOTO VOLTAGE OF MODIFIED MESOPOROUS SILICA FILM FOR NO2 GAS SENSOR

O Brian Yuliartoa, Keisuke Asaia, Takeo Yamadab, Hao-Shen Zhoub, and Itaru Honmab

a Department of Quantum Engineering and Systems Science, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
b Energy Material Group, Energy Electronic Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba-shi, Ibaraki 305-8568, Japan.


Modified mesoporous silica film was prepared by direct synthesis method using sol-gel and spin coating. The surface photo voltage (SPV) technique was then applied for the tin-modified silica mesoporous film for NO2 gas sensor. The sensor consists of Au/ modified mesoporous silica/ Si3N4/ SiO2/ Si/ Al. Clear response was obtained at the NO2 gas concentration as low as 1 ppm at room temperature. The changes in the average value and phase of the AC photocurrent, and the responsibility have been observed after exposure of NO2 gas to the film sample. Compared with those of the pure silica mesoporous film, modified mesoporous silica film showed enhanced sensitivity for NO2 gas sensor.

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シロキサン三次元網目構造に基づく高感度複合光導波路型ガスセンサ

横浜国大環境情報＊、新日鉄＊＊

○許一太＊、雨宮隆＊、伊藤公紀＊、山田紀子＊＊、濱田健＊＊

HIGHLY SENSITIVE COMPOSITE OPTICAL WAVEGUDIE GAS SENSOR BASED ON A
THREE-DIMENSIONAL SILOXANE STRUCTURE

Yitai XU*, Takashi AMEMIYA*, Kiminori ITOH*, Noriko YAMADA**, Takeshi HAMADA**

*Graduate School of Environment and Information Sciences, Yokohama National University,
Yokohama 240-8501, Japan
**Technical Development Bureau, Nippon Steel Corp.,
Futtsu City, Chiba Pref. 293-8511, Japan

A composite-type optical waveguide was applied to a gas sensor using a thin film of siloxane polymer which absorbs NO2 gas. The waveguide was prepared by using ion exchange (K+-doped base layer, about 2mm thick) and sputtering (TiO2 top layer, about 20nm thick, with slopes on both sides). A highly sensitive interferometer was constructed on the basis of the difference in cutoff thickness for TE and TM modes. Changes in thickness or refractive index taking place in the polymer film coated onto the TiO2 part induce phase shifts of the propagating lightwave. NO2 gas with concentration less than 1ppb was detected by measuring changes in the phase shift as a function of time. The response was reversible for low concentration, and irreversible for high concentration. The irreversible changes were attributed to the ion-pair formation in the film.

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フッ化アルミニウムフタロシアニン薄膜のNO₂ガス感知特性

静岡大学電子科研，電子工研

○向　前，村上健司，渡邉健蔵

NO₂ GAS SENSING PROPERTIES OF SUBSTITUTED ALUMINUMFLUORO PHTHALOCYANINE THIN FILMS

Qian XIANG, Kenji MURAKAMI, Kenzo WATANABE

Graduate School of Electronic Science and Technologies, and ^*Research Institute of Electronics, Shizuoka University
Hamamatsu-shi, Shizuoka 432-8011, Japan

Three novel substituted aluminumfluoro phthalocyanines (AlFPcRn), namely aluminumfluoro tetra-t-butyl-phthalocyanine [AlFPR₄, R=-C(CH₃)₃], aluminumfluoro octa-methyl-phthalocyanine [AlFPcR, R=-O(CH₂)₆CH(COOC₂H₅)₂] were synthesized and their NO₂ gas sensing properties have been investigated. The gas response/recovery characteristics are influenced by the substituents through their electron-donating and steric effects. The mono-substituted phthalocyanine (AlPcR) shows the best combination of gas sensing properties, i.e. the high sensitivity with good stability and reproducibility, for detecting a low concentration (1 ppm) of NO₂ gas.

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塩基性基を有する高分子膜を用いたQCM型簡易NO₂ガスセンサ

愛媛大工

○田中正教、松口正信

QCM-TYPE NO₂ GAS SENSOR USING POLYMERS WITH BASIC GROUPS

Masanori TANAKA, Masanobu MATSUGUCHI

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

A QCM-type NO₂ gas sensor was fabricated using various polymers with basic groups such as amino or amidegroups. It was found that NO₂ sorption in amino-functional polymers was irreversible process. This behavior was attributed to oxidation of amino groups by NO₂. On the other hand, for polymers having less basic amide groups, the sorption experiment performed at 70℃ exhibited fast response and good reversibility. Furthermore, sorption of other acidic gases such as 50 ppm of SO₂ and 20% of CO₂ was hardly observed, suggesting excellent selectivity towards NO₂. Among three amide-functional polymers used in this study, poly(N,N-dimetyl-acrylamide)(PDMAA) had the largest NO₂ sorption capacity and the estimated sensitivity as a QCM type sensor was approximately a few Hz/ppm at 70℃.

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プラズマ重合膜被覆水晶振動子を利用したガスセンシング

産総研、日大院、NEDO

○三浦英之，黒澤　茂，中村美樹，愛澤秀信，山田和典，平田光男

GAS SENSING USING PLASMA-POLYMERIZED FILMS COATED WITH QUARTZ CRYSTAL MICROBALANCE

Hideyuki MIURA^1,2, Shigeru KUROSAWA¹, Miki NAKAMURA^1,2, Hidenobu AIZAWA^1,3, Kazunori YAMADA², Mitsuo HIRATA<sup>2

1</sup>National Institute of Advanced Industrial Science & Technology (AIST)
Higashi, Tsukuba-shi 305-8565, Japan
²Graduate School of Industrial technology, Nihon University
1-2-1 Izumi-cho, Narashino-shi, 275-8575, Japan
³New Energy and Industrial Technology Development Organization (NEDO)
3-1-1 Higashi Ikebukuro, Toshima-ku, 170-6028, Japan

Molecular recognition components of gas sensor on quartz crystal microbalance (QCM) are prepared by plasma polymerization. Styrene, allylamine and acrylic acid serve as the monomers in the plasma polymerization. High sensitivity and good stability are found characteristic of the gas sensor in which plasma-polymerized (pp-) films are used.

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吸着燃焼を利用した有機ガスセンサ

矢崎総業、＊矢崎計器、＊＊長崎大工

○笹原隆彦、石原裕己、豊田和弘、砂山竜男、植松彰一、小沢　崇＊、荻野　薫＊、江頭　誠＊＊

A GAS SENSOR FOR VOLATILE ORGANIC COMPOUNDS BASED ON
ADSORPTION AND COMBUSTION

Takahiko SASAHARA, Hiroki ISHIHARA, Kazuhiro TOYODA, Tatsuo SUNAYAMA,
Shoichi UEMATSU, Takashi OZAWA*, Kaoru OGINO*, Makoto EGASHIRA**

Technical Center, Yazaki Co. Ltd., Susono-shi, Shizuoka 410-1194
*Gas Equipment Development Division, Yazaki Meter Co. Ltd., Tenryu-shi, Shizuoka 431-3393
**Faculty of Engineering, Nagasaki University, Nagasaki-shi, Nagasaki 852-8521

A catalytic combustion type gas sensor with low heat capacity employing Pd/Al2O3 was fabricated on a silicon substrate by micromachining and screen-printing. The sensor showed a large response peak before reaching a steady-state value upon pulse-driven heating for 0.4 s with a cycle of 1-30 s when volatile organic compounds such as alcohol and acid were contained in the environment, while hydrogen and methane did not show such a peak response but a simple increase to a steady-state value. The peak height or area increased with increasing the non-heating period (0.6-29.6 s) and also with the concentration of target gases. The unique peak response has likely arisen from the combustion of the volatile organic molecules adsorbed on the catalytic sensor material during the non-heating period. The response mechanism was supported by temperature programmed desorption experiments of C2H5OH adsorbed on the Pd/Al2O3 catalyst at 25℃.

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電界効果トランジスタに酸素酸塩補助相を接合したCO2センサ

九大院総理工

○後藤公平、小畑賢次、中田聖士、酒井　剛、島ノ江憲剛、山添　�f

FIELD EFFECT TRANSISTOR (FET) TYPE CO₂ SENSOR ATTACHED WITH Na₂CO₃ AUXILIARY PHASE

Kouhei GOTO, Kenji OBATA, Seiji NAKATA, Go SAKAI^*, Kengo SHIMANOE^*, Noboru YAMAZOE

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

It was tried to devise an FET type CO₂ sensor attached with Na₂CO₃ auxiliary phase. The selection (combination) of the Na⁺ ion-conducting layer to cover the gate area as well as the working electrode was found to be crucially important for realizing the CO₂ sensing capability at room temperature. When an Na⁺ type ion exchage membrane (Na⁺ conductor) mixed with Na₂CO₃ was combined with an Au sensing electrode, significant response to CO₂ was attained underhumid conditions. The CO₂sensitivity was improved remarkably by combining the membrane with a Na₂CO₃-mixed ITO layer (electrode). With this device, times of 90% response and 90% recovery to 3000 ppm CO2 at 30℃ were 2 and 4 min, respectively. The number of electrons(n) associated with the electrochemical reduction of CO₂ was slightly larger than 2.

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Si-MOSキャパシタ型H2センサの高温におけるアドミッタンス評価

石巻専修大理工　

○中込　真二、星　昭、國分　義弘

ADMITTANCE EVALUATION OF HYDROGEN SENSOR BASED ON SILICON MOS CAPACITOR IN HIGH TEMPERATURE CONDITION

Shinji NAKAGOMI, Akira HOSHI, Yoshihiro KOKUBUN

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

Hydrogen sensing properties of MOS capacitor based on Si were studied under high temperature condition. Firstly, the capacitance and conductance characteristics were measured in oxygen ambient and in hydrogen ambient. The voltage shift above 0.6 volts can be obtained at lower temperature than 200°C. Even at 300°C, the property change due to a change in ambient can be measured by using a frequency of MHz region. Secondly, behavior of interface-state was studied in higher temperature condition than 100°C using conductance method. The frequency variation of the admittance was measured at several constant bias voltages and temperatures to estimate the interface-state density and the relaxation time. The state density was increased in oxygen ambient with increasing temperature. In hydrogen ambient, an excess states were produced in the vicinity of Ec-0.4 eV. The excess states had larger time constant than that before exposure to hydrogen.

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ペロブスカイト型酸化物LnFeO3(Ln=La, Nd, Sm, Gd, and Dy)の表面状態とNO2ガス応答

愛媛大工・ローマ大・山形大理

○青野宏通、高須賀 悟、Enrico Traversa、坂本政臣、定岡芳彦

SURFACE STRUCTURE AND NO2 GAS SENSING PROPERTY OF PEROVSKITE LnFeO3 (Ln=La,
Nd, Sm, Gd, and Dy)

Hiromichi AONO, Satoru TAKASUKA, Enrico TRAVERSA, Masatomi SAKAMOTO, Yoshihiko SADAOKA

Department of Materials Science and Engineering, Faculty of Engineering,
Ehime University, Matsuyama 790-8577, Japan
Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor
Vergata, 00133 Roma, Italy
Department of Material and Biological Chemistry, Faculty of Science,
Yamagata University, Yamagata 990-8560, Japan

Perovskite-type LnFeO3 (Ln=La, Nd, Sm, Gd, and Dy) powders were prepared by the thermal decomposition of heteronuclear Ln[Fe(CN)6]・nH2O complexes. The prepared LnFeO3 showed a p-type semiconductive behavior and the highest enhancement of conductance due to NO2 exposure was observed for SmFeO3 sensor. The atomic ratio of adsorbed oxygen Oad increased with the surface coverage of Ln, expressed as Ln/(Ln+Fe). Experimentally, the atomic ratio of Ln/(Ln+Fe) was estimated to around 0.6 and the largest value, 0.65, was observed for SmFeO3. For SmFeO3, the distance between the central Sm ion and 4 oxygen is comparable with the sum of crystal radius of Sm3+(C.N.=6) and O2- but the distance between Sm ion and fifth and higher oxygen is longer than the expected distance form Shannonユcrystal radius. The highest sensitivity for NO2 observed for SmFeO3 would be mainly attributed to the divalency of Sm3+ in SmFeO3.

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高選択性NOxセンサの開発

エフアイエス

○坂本真理、花田真理子、森本聡

DEVELOPMENT OF HIGHLY SELECTIVE NOx GAS SENSOR

Mari SAKAMOTO, Mariko HANADA, Satoshi MORIMOTO

FiS Inc.
3-36-3 Kitazono, Itami-shi, Hyogo 664-0891, Japan

We have developed a thin film NOx (nitrogen oxides) sensor using an In-Sn oxide for the sensing material. By X-ray diffraction analysis, this sensor material is a mixture of ITO (Tin doped Indium Oxide) and tin dioxide. The NO2 sensitivity of the developed sensor has a maximum at 70% of Sn content, and the operation temperature of 300℃. This sensor has a high sensitivity to NOx even in a low concentration under 1ppm, and a high selectivity with small influences of other oxidizing gases and reducing gases. In addition, the humidity dependency of this sensor is quite low.

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In₂O₃系におい検知用センサ

新コスモス電機

○勝木　章、中村俊一、福井　清、石川　博

In₂O₃ BASED GAS SENSOR FOR ODDOR DETECTION

Akira KATSUKI, Syunichi NAKAMURA, Kiyoshi FUKUI and Hiroshi ISHIKAWA

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

A hot wire type semiconductor gas sensor with a low sensor power(ca.130mW) has been developed on the basis of In₂O₃ powder was sintered in a sphere (0.4 mm diameter) to cover a platinum wire(15 μm diameter) coil. CaO(2at% Ca) and Al₂O₃(2 at% Al) were added to the sintered In₂O₃ layer in order to modify chemical activity of In₂O₃. Further, a chemically inactive SiO₂ fine particles were deposited selectively on the surface layer of the In₂O₃ sintered layer by a CVD(5 min, 280℃) of hexamethyldisiloxane (HMDS)(9 vol%). As a result, the sensitivity to odor molecules was enhanced; at the same time, the sensitivity to odorless molecules was depressed. Thus, a gas sensor for detection of odor molecules was obtained. The manufacturing processes and the sensing characteristics of the gas sensor are investigated in details in this study.

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酸化インジウム系薄膜センサの低濃度塩素ガス検知に及ぼす水蒸気の影響

立命館大理工

○安永幸司、玉置　純、山本善史、松岡政夫

EFFECT OF WATER VAPOR ON DILUTE CHLORINE GAS SENSING OF INDIUM OXIDE-BASED THIN FILM SENSORS

Koji YASUNAGA, Jun TAMAKI, Yoshifumi YAMAMOTO, Masao MATSUOKA

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

In2O3 based thin film sensors were prepared by suspension dropping on SiO2/Si substrate equipped with Au microelectrodes, and the effect of water vapor on the sensing properties to dilute Cl2 gas was investigated at 250 ℃ .. In dry atmosphere (containing 9 ppm H2O), the La2O3 (3 wt%)-In2O3 sensor showed high sensitivities to 0.05-5 ppm Cl2. However, the sensitivity was steeply decreased when Cl2 concentration was decreased less than 0.05 ppm. The sensor exhibited opposite response (resistance decrease) to 0.02 ppm Cl2. The water vapor affected the Cl2 sensitivity in different way depending on the Cl2 concentration. The sensitivity to Cl2 lower than 0.2 ppm was decreased with increasing H2O concentration, while the sensitivity to Cl2 higher than 0.5 ppm was increased in the presence of 700-3000 ppm H2O. Moreover, with increasing H2O concentration, the response-recovery characteristics were improved and the opposite response to very dilute Cl2 gas (0.01-0.02 ppm) was not observed. It is considered that hydroxyl groups adsorbed on the sensor surface affect the adsorption-desorption behavior of Cl2.

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ガスセンサに応用可能なメソポーラスTiO₂の調製

長崎大工、インド化学技術研

○兵頭健生、ジー・サララ・デヴィ、于　春英、清水康博、江頭　誠

PREPARATION OF MESOPOROUS TiO₂ FOR GAS SENSOR APPLICATION

Takeo HYODO, G. Sarala DEVI^*, Chunying YU, Yasuhiro SHIMIZU and Makoto EGASHIRA

Faculty of Engineering, Nagasaki University
1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
^*Presently, Indian Institute of Chemical Technology
Hyderabad, India

Mesoporous TiO₂ powders have been prepared by employing a modified sol-gel method with polyethylene glycol (PEG) having different molecular weights. Among specimens prepared from Ti(NO₃)₄, mesoporous TiO₂ synthesized with PEG6000 (TiO₂(6000)) showed the largest specific surface area (299 and 66.3 m² g^-1 after heat treatment at 100 and 600℃, respectively). The loading of 0.5 mol% Nb₂O₅ to TiO₂(6000) gave it larger surface area (131 m² g^-1) and lower sensor resistance (ca. 1×10⁴ W at 450℃). The 0.5 mol% Nb₂O₅-loaded TiO₂(6000) sensor exhibited the highest H₂ and CO sensitivities among the sensors tested. Moreover, the treatment with phosphoric acid before calcination is found to be effective to maintain developed ordered mesoporous structure and high surface area of TiO₂ powders.

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長崎大工

○城野文美, 兵頭健生, 清水康博, 江頭　誠

PREPARATION OF LARGE MESOPOROUS SnO₂ AND GAS SENSOR APPLICATION

Ayami JONO, Takeo HYODO, Yashuhiro SHIMIZU and Makoto EGASHIRA

Faculty of Engineering, Nagasaki University,
1-14 Bunkyo-machi, Nasgasaki 852-8521, Japan

Attempts were made to prepare large mesoporous tin dioxide (lm-SnO₂) powders by employing SnCl₄ or SnCl2₂×2H₂O as an Sn-source and a block copolymer consisting of a hydrophilic-hydrophobic-hydrophilic block configuration as a surfactant. An increase in the concentration of the copolymer and hence the Sn-source in the precursor solution facilitate the formation of uniform large mesoporous structure with a sharp pore size distribution having a peak maximum around 4〜5 nm in diameter, after removal of the surfactant, especially when SnCl₂×2H₂O was employed. The surface area of the prepared lm-SnO₂ was as large as 230 m² g^-1 after calcinations at 400°C for 5 h and was sufficient for sensor application.

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メソポーラスシリカを用いたSurface Photo Voltage型NOxガスセンサ

産総研・埼玉大工*

○山田健郎・周　豪慎・本間　格・内田秀和*・勝部昭明*

An Application of Mesoporous Silicate for Surface Photo Voltage type NOx
gas sensor

Takeo YAMADA, Hao-shen ZHOU, Itaru HONMA, Hidekazu UCHIDA*, Teruaki KATSUBE*

Energy Electronics Institute, National Institute of Advanced Industrial Science and Technology (AIST),
Tsukuba-shi, Ibaraki 305-8568, Japan
*Department of Information and Computer Science, Faculty of Engineering, Saitama University,
Saitama-shi, Saitama 338-0825, Japan

The mesoporous materials SBA-15 and SBA-16 films from the self-assembled organic-inorganic compound materials are successfully prepared. These films are also successfully fabricated into the surface photo voltage (SPV) type gas sensor device as a gas adsorption insulator layer. These kinds of gas sensors device exhibit NO and NO2 gas sensing properties dependent on their mesoporous film structure. We are succeeded in indication about a possibility of mesoporous silicate films for the SPV type gas sensor application.

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イオン交換法により調製したWO3の粒子形状とNO2センサ特性との関係

九大院総理工、九大先端センター*

○崔　龍圭、酒井　剛、島ノ江憲剛、三浦則雄*、山添　�f

Relationship between particles morphology and NO2 sensing properties of WO3 sensor derived from ion-exchange 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
** Department of Materials Science, Faculty of Engineering Sciences, Kyushu University
***Advanced Science and Technology Center for Cooperative Research, Kyushu University

An aqueous sol of crystalline tungsten oxide dihydrate (WO3.2H2O) was prepared from Na2WO4 by an ion-exchange method. The centrifugal or ultrasonic treatment of the sol was found to affect the morphology of resultant WO3.2H2O gels, and therefore to affect also the NO2 sensing properties of the devices using the gels. When calcined at 300oC, the ultrasonically treated sample gave the most sensitive device at 200oC, which could respond to as low as 10 ppb NO2, while the sample subjected to centrifugal treatment for a prolonged time gave the highest sensitivity at 300oC. The sintering temperature was also found to affect the NO2 sensing properties through a change in the morphology of WO3 crystals.

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酸化タングステン薄膜センサの極低濃度NO2検知特性と膜厚効果

立命館大理工

○林　篤史、玉置　純、山本善史、松岡政夫

SENSING PROPERTIES TO DILUTE NITROGEN DIOXIDE AND THICKNESS EFFECT OF TUNGSTEN OXIDE THIN FILM SENSORS

Atsushi HAYASHI, Jun TAMAKI, Yoshifumi YAMAMOTO, Masao MATSUOKA

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

WO3 thin film sensors were prepared by suspension dropping on SiO2/Si substrates equipped with Au microelectrodes, and subjected to the detection of dilute NO2. The WO3 thin film with the thickness of ca. 0.6 μm showed t he extremely high sensitivity to dilute NO2 at 200 ℃ (for example, S=4.93 t o 0.1 ppm NO2). For this WO3 sensor, the Au electrodes (thickness：0.6 μm) were visible, inducing the easy access of NO2 molecules to a part between electrodes. Moreover, the high sensitivity suggests the possibility of environmental NO2 monitoring using WO3 thin film sensors. When the thickness increased larger than 0.6 μm, the upper part of WO3 film disturbe d the diffusion of NO2 molecules into inside, inducing the low sensitivity. On the other hand, the Au electrodes were always visible if the thickness of WO3 film was smaller than 0.6 μm. In this case, the thickness hardly af fected the sensing properties to NO2.

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