Vol. 27, Supplement A (2011)

1.

A microfluidic device for the determination of adenosine triphosphate (ATP) was developed for on-site freshness check of raw fish. Sample solutions containing ATP and another solution containing an enzyme substrate were handled in the form of plugs formed in a network of flow channels. To simplify structure and procedure for mixing solutions, a wider portion was formed in a flow channel to merge plugs. A row of plugs were ejected from each of branched flow channels, merged at the wider portion, and transported to an ATP biosensor located in the lower stream. ATP was detected using two enzymatic reactions involving glycerol kinase (GK) and glycerol-3-phosphate oxidase (G3PO). The current observed with solutions of different ATP concentrations showed distinctly different values. The device could also be used for freshness check of Jack mackerel.

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2.

In patients with inadequate renal function, toxins should be removed from their blood　by means of hemodialysis therapy. As the amount of dialysis has a strong impact on the health and mortality of patients, dialysis dose is evaluated from a quantity estimated from changes in urea concentration in blood. The urea concentration in blood has been measured by chemical analysis, but it takes ca. 90 min. As urea in blood is moved into dialysate through a filter named dialyzer, the accurate quantity of urea removed from blood is equal to the product of flow rate of dialysate and the time-integrated value of the urea concentration in dialysate. Therefore a urea sensor is expected to measure urea concentration in spent dialysate accurately and continuously. We have developed a compact urea sensor based on chemiluminescence using a micro-reactor. The chemiluminescence emitted by a reaction of urea with hypobromite is measured. The urea sensor has linear characteristics in a concentration range between 1 and 9 mM.

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3.

Imaging cytometry has been paid much attention as a powerful tool for high-content cell analysis in place of flow cytometry because it has an advantage for use in real-time imaging of cell populations at a single cell level. However, time-resolution is limited because a laser scanning is required to obtain 2-dimensional (2D) images. In order to overcome these obstacles, 2D image sensor-based analysis of cell populations has been proposed as one of possible approaches. In this study, 2D imaging of cell populations was investigated using complementary metal oxide semiconductor (CMOS) sensor by placing cell samples directly on the micro-lens array of the CMOS sensor. Furthermore, the CMOS sensor was integrated with microfluidic device. Cell introduction, entrapment, incubation and detection were implemented in a microfluidic assay within one integrated device. Our proposed cell analysis system will allow us to develop a novel miniaturized cytometer for high-throughput cell profiling.

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4.

An electrochemical flow cell has been developed for highly sensitive detection in microfluidic analytical systems. It consists of a single digitated Au electrode and a poly(dimethylsiloxane) rectangular channel that reversibly sealed onto a polystyrene substrate. For the construction of the flow cell, the dimensions of channel were optimized. The decrease in channel height and width increased the signal-to-noise (S/N) ratio although the decrease in channel width decreased the current because of reduction of the surface area of the electrode. Leak-tightness of the channel was also considered since the decrease in the channel cross section raises the pressure in the channel, resulting in leakage of a fluid. Next, the geometry of the single digitated electrode was examined. The spacing of finger electrodes was found to be responsible for the thickness of diffusion layer formed on each electrode. With an adequate spacing, the current was proportionally increased with the number of finger electrode, while the S/N ratio was kept at a constant value. Finally, the flow cell gave a superior detection limit (34 nM for ferrocyanide).

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5.

A flow-through reactor mounted with a planar net type of immobilized metalloenzyme preparations was fabricated and tested for flow-injection analysis of heavy metal ions based on the apoenzyme reactivation methods. A cyclic voltammogram based on the gold black net suggested to have much more surface area than that of the gold net.

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6.

Novel, simple and relatively highly sensitive reagentless inhibition-based amperometric flow biosensor for cyanide was developed by using horseradish peroxidase (HRP)-adsorbed carbon-felt (CF). The resulting HRP-adsorbed CF (HRP-CF) showed a sufficient bioelecrocatalytic activity for the O₂ reduction in the potential region from -0.15 to -0.5 V at pH 7.0, due to a direct electron transfer-based catalytic scheme via ferrous-HRP, compound III and ferric-HRP. This HRP-CF-catalyzed O₂ reduction was reversibly inhibited by cyanide, which enabled to fabricate a simple reagentless flow-biosensor for cyanide (i.e., no requirement of the ordinary substrate, H₂O₂, and electron transfer mediators). When air-saturated 0.1 M phosphate buffer (pH 7.0) was used as a carrier under the applied potential of −0.25 V vs. Ag/AgCl, the steady-state background-current due to the HRP-catalyzed O₂ reduction was reversibly inhibited by the cyanide injection, resulting in the peak-shape responses. The magnitude of the inhibition peak current linearly increased with increasing concentrations of cyanide up to 3 μM, and the detection limit was found to be 0.33 μM (S/N = 2). Apparent inhibition constant K'_i was estimated to be 2.13 μM.

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7.

Molecularly imprinted polymer (MIP) thin layers for bisphenol A were polymerized on a sputtered gold electrode by UV light irradiation for 2 – 30 min. Their thickness determined by QCM analyzer was 3.6 ±0.3 nm for 5min of irradiation and increased as the irradiation time increase to 30 min. AFM images of MIP modified surface suggested that the gold electrode was covered with MIP smooth layer. The responses to BPA and ascorbic acid of the gold electrode and MIP modified electrode anodic peak were compared and the electrode with MIP polymerized for 5min showed more selective to BPA than that for 2min.

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8.

Control of blood-coagulation is very important for safe operation of extra corporeal circulation. However suitable methodology for monitoring anticoagulant in blood is yet to be established. The purpose of this study is development of a sensor for level of heparin, which is the most well-used anticoagulant, using an electrode grafted with heparin-imprinted polymer. Indium-tin oxide (ITO) electrode was grafted with poly (methacryloxyethyl trimethylamine chloride-co-acrylamide-co-methylenebisacrylamide) in the presence of heparin. A cyclic voltammetry of ferrycyanide was performed with the grafted electrode. The anodic current was sensitive to the heparin. The change of current by heparin is reversible. Then the electrode grafted with the heparin-imprinted polymer is feasible for monitoring the heparin level.

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9.

We have designed a glucose-imprinted polymer (GIP) grafted on electrode using Activators ReGenerated by Electron Transfer-Atom Transfer Radical Polymerization (ARGET-ATRP) in the previous work. The anodic current at the polymer-grafted electrode was sensitive to glucose with high selectivity. The stability of anodic current of the electrode was estimated by cyclic voltammetry in this work. The current increased by exposing of the electrode in the atmosphere. The voltammogram at the exposed electrode was similar to that at non-treated electrode. It is suspectable that the grafted GIP layer was removed from the electrode surface. The results indicate that the ARGET-ATRP may be unsuitable method to prepare stable glucose sensor using molecularly imprinted polymer.

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10.

We have developed chemical sensors based on molecularly imprinted polymer and alkanethiol selfassembled monolayers. The molecularly imprinted polymer was prepared by electrochemical overoxidation of polypyrrole, which doped phosphate as a template. The monolayer based sensor was fabricated on a gold electrode and gold-coated quartz microbalance sensor and used for cholesterol sensing. Sensor systems developed based on the latter concept have been recently commercialized, and are validated for food cholesterol quantification.

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特別講演1

Photoelectrochemical reactions take place only for systems absorbing light, only when and where they are irradiated with light. These characteristics are exploited for biosensing based on photosynthetic activity of algae or phototaxis of flagellates, fabrication of sensor arrays on the basis of photocatalytic lithography, single-electrode algal sensor arrays, and chemical sensing based on localized surface plasmon resonance (LSPR).

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11.

We report on an amperometric biosensor that is based on a nanocomposite of carbon nanotubes (CNT), a nano-thin plasma-polymerized film (PPF), electron transfer moderator, and glucose dehydrogenase (GDH). A mixture of the GDH and a CNT film is sandwiched with 6-nm-thick acetonitrile PPFs. Under PPF layer was deposited onto a sputtered gold electrode. To facilitate the electrochemical communication between the CNT layer and GDH, CNT was treated with nitrogen plasma. The electron transfer play a role as the mediator in which the electron caused by enzymatic reaction transports to the electrode. As a result, the current increased and the polarized potential was reduced. The resulting device showed that the large oxidizing current response due to enzymatic reaction was observed at +0.2 V (vs. Ag/AgCl) polarized potential. The electron transfer mediator is phenothiazine.

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12.

Photo-exited current can be generated through a molecular interface between a photo-excited molecules and a semi-conductive electrode in appropriate condition. The reaction of photo-excited current generation is totally dependent on the interfacial energy reaction, which is in a highly fluctuated interfacial environment. The authors have developed site-specific electrochemical molecular immobilization method "EC tag method" for a preparation of ordered molecular layer on any of electro conductive material surface. Taking advantages of the EC tag method, synthesized sensor molecules were immobilized on a semi-conductor; fluorine doped tin oxide (FTO) surface. Output current can be obtained from the sensor molecule immobilized FTO when it was irradiated with laser light. The photo-excited current was clearly decreased when a ligand molecules were co-exist which was specifically bound to the affinity region of sensor molecule on FTO. The reason of the current decreasing is based on a occurring of steric hindrance by bound ligands which inhibit current transduction from photo-excited region to the FTO. The sensor can perform prompt and high sensitive affinity assay.

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13.

As immunoreaction has a high selectivity, various immunosensors have been reported. Especially, the sensors using antibody immobilized to the polymer material are widely used. However, the influence of immobilization condition on the characteristic of the antibody has not been understood in detail. Then, we immobilized the antibody on the surface of the polymer layer, and investigated the influence of the immobilization condition on the amount of the immobilized antibody and the reactivity with antigen. As a result, the amount of the immobilized antibody and of the binding antigen increased with the antibody concentration increased. Considering the reaction condition, some immobilized antibody lose the ability to bind antigen by the cohesion of the antibody. Moreover, the amount of the immobilized antibody increased with immobilization reaction pH values raised. On the other hand, the amount of the binding antigen decreased with pH values raised. These results show that the amount of immobilized antibody which has lost the ability to bind antigen increased with immobilization reaction pH values raised. The loss of ability to bind antigen is caused by cohesion.

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14.

Although carbon nanotube (CNT) showed the attractive properties for biosensor application, heterogeneity of as-synthesized CNTs was still limitation in order to get the designate and excellent characteristics. For example, about one-third of all possible single-walled CNTs exhibit metallic properties and the remaining two-thirds act as semiconductors. Recently, as-synthesized CNTs were sorted by metallic and semiconducting, using the technique of density-gradient ultracentrifugation. We report an amperometric biosensor based on the metallic CNTs. The configuration of the sensor was a nanocomposite of CNTs, a nano-thin plasma-polymerized film (PPF), oxidase (GOx). A mixture of the GOx and a CNT film is sandwiched with 6-nm-thick acetonitrile PPFs. Under PPF layer was deposited onto a sputtered gold electrode. To facilitate the electrochemical communication between the CNT layer and GOx, CNT was treated with nitrogen plasma. It showed the more than excellent sensor performance than that with semiconducting CNTs.

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15.

Subclinical mastitis is an infectious disease of dairy cows. To develop a diagnostic device for mastitis, we focused our attention to the increase of neutrophils in raw milk of mastitic cows. Since neutrophils secrete superoxide, it can be an indicator to estimate the number of active neutrophils. In this study, we designed a microfluidic channel in which neutrophils can be concentrated and separated from fat globules using the difference in specific gravity and specific adhesion of neutrophils to a P-selectin-coated surface. Neutrophils were eventually trapped in a micropillar working electrode with immobilized superoxide dismutase (SOD). Superoxide secreted from neutrophils was detected using the electrode. A linear relationship was observed between generated current and the number of neutrophils in raw milk. On-site diagnosis of subclinical mastitis was demonstrated using milk samples.

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16.

In this study, a rapid method for detection of Escherichia coli (E.coli) using the hand-held potentiostat and disposable electrical printed chip (DEP-chip) was demonstrated. E.coli bacteria is one of the indicator organisms for food safety. Detection of variant specific genes by polymerase chain reaction (PCR) has become a routine food safety testing for high sensitive detection of bacteria. Therefore, low cost, rapid and simple method for detection of PCR amplification has been required. Here we proposed the electrochemical method for E.coli detection without the purification of DNA. The bacteria cultures of various concentrations of E.coli were directly added in PCR solutions, and 2-step PCR (95.65℃ for 40cycles) were carried out. After PCR, the solutions were directly mixed into the Hoechst solutions, and droped onto the DEP chip. Electrochemical signals (linear sweep voltammogram) were recorded by the portable potentiostat. As the results, the oxidation peak current were decreased depending on the number of the added E.coli, moreover, from only one bacteria per reaction could be detected.

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17.

We have developed an electrochemical detection method for endotoxin based on Limulus amebocyte lysate (LAL) assay. A mixture of LAL reagent and endotoxin sample solution was incubated for 1 hr on an electrode chip device fabricated from diamond-like carbon coated glass substrate. The endotoxin activats the cascade reaction of zymogens containing in LAL to generate p-nitroaniline (pNA), which is not only a chromogenic compound but also an electrochemically active compound. The generated pNA was detected by differential pulse voltammetry. By using this process, 10 endotoxin units L⁻¹ were detected at room temperature. The concept of electrochemical endotoxin detection is expected to lead to a small, low cost and easy handling sensor to be able to use in clinics for on-site monitoring of potentially contaminated endotoxin in medical supplies including dialysis fluid, tissues for transplant and culture medium for assisted reproductive technique.

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18.

In this study, glutamate biosensor was constructed by electrochemical technique. The micro-planar electrodes of the sensor chip were manufactured by sputtering of platinum and silver onto the substrate surface. Glutamate biosensor was fabricated as follows: Glutamate oxidase solution (containing bovine serum albumin (BSA), dissolved in distilled water) with glutaraldehyde was placed onto the electrode surface of the sensor chip and then spread by spin-coater and furthermore was reacted (cross-linked by glutaraldehyde) for 24 hours in a refrigerator at 4 ℃. The electrochemical measurement was carried out in TES buffer (pH 7.5) containing 150 mM NaCl at room temperature. There was relationship between concentration of sodium glutamate and current value. The dynamic range of the sensor chip was 0.05 – 2 % (w/v) for sodium glutamate. Additionally, glutamate in Japanese soup stock (containing Miso soup) could be detected using this glutamate biosensor. We present a rapid, simple, high sensitivity and high acculacy biosensor of glutamate.

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19.

Phenylalanine (Phe) is an important essential amino acid and a biomarker of phenylketonuria. We have developed a phenylalanine sensor chip by co-immmobilization of phenylalanine dehydrogenase and diaphorase on a disposable gold electrode. However, a few redox-active compounds such as ascorbic acid in a blood sample interfere the precise measurement of Phe with the electrochemical enzyme sensor. In this study, we developed a phenylalanine sensing system that could eliminate the intererence from ascorbic acid by applying pre-electrolysis. Chronoamperometry with pre-electrolysis on the Phe sensor chip demonstrated the negligible interference current from ascorbic acid and the precise catalytic oxidation current for Phe. Detection range of this Phe sensing system was from 20 to 1000 μM. This sensor might be applicable to measure Phe in blood samples.

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20.

We have applied cell manipulation based on dielectrophoresis (DEP) to develop rapid and simple detection systems of cell surface antigen. CD33 expressed on HL-60 cell was used as a target antigen to develop detection systems based on the rapid manipulation. A suspension of the HL-60 was injected into the DEP device consisting of the indium-tin-oxide (ITO) substrate and ITO-bandelectrode immobilized with anti-CD33 antibody. The application of 10 MHz AC voltage (15 Vpp) forced most of the cells to form a line pattern on the microbands. Then, the frequency was switched from the frequency region with p-DEP to n-DEP (100 kHz). Some of the patterned cells moved to the gap region between the bandelectrodes 10 s after frequency was switched, indicating that the part of cells were irreversibly captured on bandelectrodes via the immunoreaction. The results suggested that the cells with CD33 cell surface antigen could be identified from the cell suspension and spatially separated.

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21.

Alkali-metal ions can be reversibly inserted / extracted into / from crystal lattices of alkali insertion materials. By applying this mechanism for the alkali-ion insertion materials, we have prepared all-solid-state ion-selective electrodes using alkali insertion materials; LiFePO₄, Na_0.33MnO₂, and KxMnO₂, covered with plasticized poly(vinyl chloride) (PVC) membrane containing ionophores. The electrodes show an ideal Nernstian response and good selectivity for each ion. Stability of electrode potential is also improved, which might correlate strongly with lowered electrode impedance. In this study, we examine the mechanisms of potential stabilization for the ion selective electrodes prepared with different insertion materials and components.

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22.

A new double electrode sensing system has been fabricated by piling microporous membrane electrodes which have 10 μm thicknesses. The each microporous electrode was prepared by sputtering of platinum onto precision membrane filters with sharply defined pore sizes. The electrolysis is performed when the sample solution flows through the membrane electrodes, and a generated species on the first working electrode (generator electrode) is instantaneously transported to the surface of the second working electrode (collector electrode) which is located at the downstream of the first one. The efficiency of electrolysis reaction on each electrode was nearly 100% when the micro- porous electrode with 0.4 μm pore size was used. The collection efficiencies (N) were also nearly 100%. The proposed double electrode system has a short transit time because of a short distance between the working electrodes. The proposed method is expected to be applied to various sensor systems because of easiness of its fabrication.

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23.

We have already developed fluorometric pH and oxygen sensor array by stamping fluorescence sensor dyes, FITC for pH sensing and ruthenium complex for dissolved oxygen sensing, using microcontact printing technologies. In this study, these sensor membranes were prepared inside a Y-shaped micro flow channel by using microcontact printing, and pH or oxygen distribution in the flow channel was imaged as fluorescence image by using a microscope equipped with a high speed laser confocal scanner unit. Response time (90% response) of the pH sensor investigated with phosphate solution of pH 4.5 and 9.3 was ca. 3 sec. Response time of the oxygen sensor was also the same. This response time might be permissible range for chemical imaging. Mixing of two different pH or oxygen concentration solutions in various mixing ratios could be successfully imaged as the changes of fluorescence intensity.

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24.

In this study, a scan-less fast chemical imaging sensor system was developed. The chemical imaging sensor, which is based on light-addressable potentiometric sensor (LAPS) is capable of visualizing the ion distribution on the sensor surface. The conventional chemical imaging sensor system requires a mechanism for the scanning of a light source to obtain chemical images, thus the high-speed chemical imaging has been prevented due to the limitation of the speed of mechanical movement. In the developed system, the mechanical stage and the light source were replaced by a 7 x 5 LED matrix array. Five LEDs on a line of the LED matrix were modulated by the oscillator array which consisted of five phase locked loop circuits was also implemented, and the scan-less fast chemical imaging was achieved at 10 fps by switching the line of the LED matrix.

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25.

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26.

In cytotoxic chemical screening, different cellular responses to chemicals due to different cellular conditions have been reported. Therefore, understanding the complexity and heterogeneity of cellular behavior requires techniques that can trace the temporal behavior of cells at single-cell resolution for minutes, hours, and even days. Further, it is necessary to monitor the biological responses of individual cells as opposed to bulk culture averages. We have introduced a high-density microcavity array with 10,000 microcavities (diameter 2 µm) which was designed for high efficient entrapment of single cells by applying negative pressure. Here, we integrated our microcavity array technology with current microfluidic gradient generating technology to develop a single-cell microfluidic gradient device. We used this new integrated system to evaluate the effects of chemical stimuli on individual cells and the applicability of this technology for chemical screening and cell viability analysis. We show that the integration of both technologies allowed easier and direct analysis of cells at both the bulk and single-cell levels, providing more analytical and accurate data evaluation.

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27.

An electrochemical device is fabricated for high-throughput electrochemical detection that consists of 32 row and 32 column electrodes on a single glass substrate. The row and column electrodes are connected to interdigitated array (IDA) electrodes to form 1024 (32 × 32) addressable sensors in the device. Electrochemical signals from each of the 1024 sensors were successfully acquired on the device within 1 min using redox cycling at individual IDA electrodes, which leads application of the device to comprehensive, high-throughput electrochemical detection such as enzyme-linked immunosorbent assay (ELISA), reported gene assay for monitoring gene expressions, and DNA analysis.

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28.

Highly sensitive, rapid and simple analysis of proteins is central to clinical diagnosis. Field effect transistor (FET) devices have considerable promise as electronic transducers for rapid and highly sensitive detection of biorecognition events. We have fabricated a stable antibody-modified FET for tumor marker detection. For the application of antibody-modified FETs in medical fields, multi-marker detection in blood serum is needed for improving the diagnostic sensitivity of cancer. However, there is a possibility that the charges of contaminating proteins adsorbed on the gate area lower the quantitativity of FET detection. In this study, to set a benchmark of detectable target proteins for FET multi-detection, relation between isoelectric points of target proteins and response quantity was evaluated. Then, bovine serum albumin was immobilized on the anti-α-fetoprotein (AFP) antibody-modified gate surface as a blocking agent, and quantitative detection of AFP in the blood serum using the anti-AFP antibody-modified FET was performed. We demonstrated that this developed anti-AFP antibody-modified FET had quantitative capability for AFP detection in the blood serum.

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29.

To develop high performance nitrate ion-selective field-effect transistors (ISFETs) to detect a human salivary nitrate, we have investigated sensing materialsand also polymer membrane materials. We prepared highly sensitive and selective prototype of FET NO₃^- checkers based on NO₃^--ISFETs using the suitable copper(I) complex as a nitrate-sensing material, 2-nitrophenyldodecylether (NPDDE) as a liquid membrane material (plasticizer) and poly(vinyl chloride) (PVC) as a conventional membrane material using the commercialized FET pH checker. We studied the sensor characteristics of prototype of FET NO₃^- checkers in detail. FET NO₃^- checkers showed linear characteristics from 10^-5.5 M to 10^-0.5 M with a response time of less than a few seconds. FET NO₃^- checkers also showed almost identical with the corresponding ion-selective electrodes as expected. FET NO₃^- checkers showed specific NO₃^- selectivity against coexisting major Cl^- in human saliva. So, we challenged to apply human saliva without pretreatment using direct potentiometry. Though we have a few human samples, we obtained relatively good correlation with the advanced ion chromatography.

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30.

Various biosensors using filed effect transistors (FETs) have been investigated because FET sensors are capable of rapid measurement and miniaturization. In this study, we investigated the use of lysine decarboxylase immobilized on the gate of FET to detect L-Lys molecules. In this system, the enzymatic decarboxylation of L-Lys consumes H⁺ and produces CO₂, both of which are expected to lead to FET responses based on pH change. With the LDC-immobilized FET, the sensitivity to pH change was 36.1mV/⊿pH. Moreover, L-Lys was detected with the sensitivity of -1.6mV/decade. These results were suggestive of the decrease in pH in the presence of L-Lys because of the production of CO₂. Here, the sensitivity to the detection of L-Lys was approximately twentieth compared with that to pH change, because pH change would be almost canceled by the consumption of H⁺ and the production of CO₂ in the reaction system.

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31.

Response characteristics to NO₂ of zirconia-based amperometric-type sensors using La-based perovskite oxide sensing-electrode were examined. Powders with La_1-xSr_xMO₃ (M=Mn, Co, x=0-0.6) were synthesized by means of spray pyrolysis method. The response current to NO₂ of the sensors increased with increasing the amount of Sr addition to Mn group perovskite-type oxide. On the other hand, the response current decreased with increasing the amount of Sr addition to Co group oxides. Among oxides studied, the sensor using La_0.8Sr_0.2MnO₃-SE showed the highest sensitivity to NO₂ as well as low base current even in the presence of O₂ (21 vol.%). Adsorption-desorption behavior of NO for the presented oxides was examined for analyzing the difference of sensing properties of these sensors.

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32.

In our previous study, sensing properties for CO in various gas atmospheres were studied with amperometric sensor using 10wt%Au-In_0.95Sn_0.05O_1.5 cathode, RuO₂-La_0.6Sr_0.4CoO₃ anode and La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ electrolyte. In this study, planar type CO sensor which was prepared anode and cathode on the same side was prepared and it was found that high sensitivity and selectivity was also exhibited on the planar type element. In particular, sensor is highly selective to CO and so selective detection of CO in exhaust gas from small boiler is expected by using this amperometric CO sensor.

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33.

We recently reported that the CO response of YSZ (yttria-stabilized zirconia) based sensor with ZnCr₂O₄ sensing electrode (SE) appeared via the addition of nano-sized Au particles (nano-Au) to the oxide sensing layer. In this study, therefore, the CO sensing characteristics of YSZ-based sensors using ZnCr₂O₄-SE added with sub-micron-sized (subµ-Au) or micron-sized Au particles (µ-Au) besides nano-Au were investigated and compared. As a result, the CO sensitivity was found to be highly depended on the size of Au particles. That is, it was increased with decreasing size of Au particles. Among examined, the sensor using ZnCr₂O₄ (+subµ-Au)-SE exhibited moderate response to CO at 550℃ in the presence of 5 vol.% H₂O. Furthermore, by measuring the potential difference between the (ZnCr₂O₄ (+subµ-Au))-SE and the undoped ZnCr₂O₄-SE, sensitivities to various gases were found to be negligible; demonstrating highly selective and sensitive response to CO at 550℃.

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34.

New type solid-electrolyte impedance-metric NOx (NOx ; NO, NO₂) sensor devices were designed by using oxide (Fe₂O₃, Co₃O₄, NiO, CuO, ZnO) as a receptor material, YSZ plate as a solid electrolyte transducer, respectively. The sensing performance of the impedance-metric NOx sensor was investigated for the detection of NOx (NO and NO₂ ) in the range 10～150ppm at 400 ºC. Nyquist plots of this sensor were measured at various concentrations of each NOx gases. The frequency was changed from 50 Hz to 5 MHz. The sensitivities of these sensors were influenced by the ability of receptor materials to detect the gas at different NOx concentration. The NiO/YSZ based compact impedance-metric sensor element showed excellent NOx sensing properties.

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35.

In this study, we investigated that interface between NASICON and oxide composite electrode plays a part as a sensing interface for detecting organic gases. Oxide ion conductor (BiCuVOx) was mixed with perovskite type oxide (La_0.6Sr_0.4Co_0.78Ni_0.02Fe_0.2O₃) and the obtained oxide composite was deposited as an electrode on NASICON disk by screen printing method. The resulting sensor responded to organic gases such as ethanol, formaldehyde, toluene and carbon monoxide at 400-500℃, but CO₂ had no effect on the sensor response. From this result, it was clear that the sensor response is not owing to gas response through interface of carbonate/NASICON shown in CO₂ sensor. In addition, it was found that the response (⊿EMF) to ethanol and formaldehyde was linear to the logarithm of gas concentration and increased with a decrease in operating temperature. Moreover, the response to ethanol increased with a decrease in electrode thickness. This means that the interface between NASICON and oxide composite electrode plays an important part as a sensing interface.

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36.

Sensors based on yttria-stabilized zirconia (YSZ) tubes and oxide sensing-electrodes (SE),　were developed with aspirations of selective and rapid detection of H₂. Cross sensitivities were also examined towards hydrocarbons, CO and NOx. Among five kinds of oxide-SE evaluated, the sensor using SnO₂-SE was found to give the highest sensitivity to H₂. However, the SnO₂-SE also showed high sensitivity to C₃H₆. In order to eliminate the C₃H₆ sensitivity of SnO₂-SE, a combined type sensor using (SnO₂ + 30 wt.% YSZ) and (NiO + 50 mol% TiO₂)-SE was fabricated. The fabricated combined type sensor exhibited selective response to H₂ as well as an acceptable 90% response and recovery rates both within the order of 30 s for H₂ leak detection. In addition, the sensitivity of the present sensor varied almost logarithmically with the H₂ concentration in the range of 20 – 800 ppm at 600℃ even in the presence of 5 vol.% H₂O.

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37.

Solid electrolyte type ammonia (NH₃) gas sensor was fabricated by using trivalent Al³⁺ ion conducting (Al_0.2Zr_0.8)_20/19Nb(PO₄)₃ solid electrolyte with NH₄⁺-β-gallate (NH₄⁺-Ga₁₁O₁₇) solid as the auxiliary sensing electrode and its ammonia gas sensing performance was investigated in humid atmosphere. Since the present sensor successfully showed such a superior sensing performance of continuous, quantitative and reproducible response with obeying the theoretical Nernst relationship even in high humidified atmosphere containing 4.2vol% H₂O at 230 ℃, it is greatly expected to be a practical on-site NH₃ gas sensing device.

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38.

Miniaturized rod-type yttria-stabilized zirconia (YSZ)-based gas sensors using oxide sensing-electrodes (SE) and Mn-based reference-electrodes (RE) were fabricated and their sensing performances in potentiometric/amperometric mode were evulated. It was found that during potentiometric evaluation the sensor comprised of a Mn-based RE and Cr₂O₃-SE gave comparatively high selectivity to hydrocarbons (HCs) saturated and unsaturated HCs at 550℃ under humid condition and exhibited similar values of sensitivity to both. The addition of 30 wt% NiCr₂O₄ to Cr₂O₃-SE significantly increased the sensitivitiy to HCs. Moreover, the sensitivity of the developed sensor showed linear dependence on the logarithm of HC concentration. Subsequently, the YSZ tube based sensor utilizing a planar-like sensor electrode geometry (i.e. all electrodes exposed to the sensing medium.) with In₂O₃-SE, Pt counter-electrode (CE) and Mn-based RE was examined in amperometric mode. This sensor exhibited large response and high selectivity to NO₂ with rather quick response and recovery time less than 10 s, and gave a linear Δcurrent change with increasing NO₂ concentration.

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特別講演2

It has passed for more than 40 years since a gas alarm for domestic use was born at 1969. Meanwhile, gas alarms have been improved depending on the needs of the time, such as a gas alarm is composed of a gas detective part and a separated outside buzzer or a gas inspection valve. In addition, a gas alarm detecting gas leakage and carbon monoxide gas and/or fire has been developed. Recently, the trend of the gas alarm research and development is the battery driving using the gas sensor, low power consumption applying MEMS technology. As the ubiquitous communication network is maintained, an additional function as the network terminal is demanded from the gas alarm. In this paper, the current states and the tasks of the gas alarm are described.

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39.

Lanthanoid based perovskite-type LnFeO₃ (Ln = La, Nd, Sm) oxide thick-film devices, which used as a receptor material, showed good sensing properties to C₂H₂. The thick-film devices could be fabricated with perovskite-type oxide fine powders by a polymer precursor method at 750℃ using metal nitrates as a starting material. The pastes mixed with oxides, PVP and α-turepntine oil were screen-printed on a Au-interdigitated electrode and sintered at 850ºC. Sensing properties to C₂H₂ of the perovskite thick-film devices were evaluated by an AC impedance method at 300 - 500 ℃, PO₂ = 0.21atm. The impedance changes to C₂H₂ of the thick-film devices revealed that sensor sensitivities were in the order of LnFeO₃: Ln = Sm > Nd > La. All sensor sensitivities were decreased with increasing measurement temperatures. Among the sensor devices tested, the SmFeO₃ thick-film sensor showed the best C₂H₂ sensing properties at 300℃.

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40.

Hydrogen gas promises to be a major clean fuel in the near future. Thus, sensors that can measure the concentrations of hydrogen gas over a wide dynamic range (e.g., 1-99.9%) are in demand for the production, storage, and utilization of hydrogen gas. However, it is difficult to directly measure hydrogen gas concentrations greater than 10% using conventional sensor. We report a simple sensor using an electrolyte made of proton conductive manganese dioxide (high purity of the ramsdellite crystal structure, RMO) that enables in-situ measurements of hydrogen gas concentration over a wide range of 0.1-99.9% at room temperature. We also report the electrochemical property of the RMO electrolyte as a proton conductive material.

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41.

This study describes a new CO sensor based on a proton exchange membrane at the temperature from 30 ℃ to 200 ℃. When polybenzimidazole(PBI) is used as the electrolyte membrane of fuel cell, the operating temperature seems to be at high temperature from 100 ℃ to 200 ℃. The purpose of this study is to evaluate the performance of PBI membranes at room temperature condition (30 ℃). Polarization curve was measured, and the short circuit current was used to detect the CO gas. The sensor performance was evaluated with different CO concentration and at different temperatures. The sensor outputs were compared using PBI and Nafion membrane at room temperature. As a result, PBI membrane was effective to operate the CO sensor at 30, 60, 140 ℃.

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42.

Utilization of porous silicon based optical interference filters in gas and vapor sensing applications has been studied for over a decade. It has been shown that with proper surface stabilization, simple sensing with reproducible results is possible. However, since the sensing method is based purely on measuring the redshift of the resonant stopband of the reflectance spectrum, the sensors suffer from limited selectivity and provide insufficient means for eliminating false positives. A possible way for increasing sensor selectivity might be obtained by increasing the number of measured sensing parameters. In this study, porous silicon rugate filters with multiple reflective stopbands were produced with an electrochemical etching process. Filters with different refractive index profiles were produced, and their gas sensing properties were evaluated. By employing various porosity profiles, the gas adsorption kinetics can be altered, which in turn affects the observed sensing properties of the filters. Ethanol vapor was used to test different designs, in order to provide proof of concept.

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43.

We have successfully measured the zone and nitrogen dioxide concentration distribution around small air deodorizer using developed method. The method is a combination of developed ozone/nitrogen dioxide detection sheet, image capturing of the sheet, and GRB analysis of the image. The color of the sheet changed when the sheet was exposed to ozone/nitrogen dioxide, and accumulated ozone/nitrogen dioxide concentration could be calculated form the RGB values of the digital image that was captured every 30 min. We found that the ozone and nitrogen dioxide emitted from the air deodorizer were located in a small area under clam conditions.

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44.

A clean energy system using hydrogen has been paid much attention. However, hydrogen is hazardous material because of its explosive nature. Therefore, the leakage detection of hydrogen is very important. The coloring reaction of the noble metal supported WO₃ thin films with the exposure to hydrogen gas is well-known. In this research, gasochromic response of WO₃ thin films as a hydrogen gas sensor was quantitatively evaluated at different humidity and ambient temperature condition. In dry condition, considerable change in transmitted light intensity was observed even in a concentration range less than 1% of hydrogen. However, the gasochromic reaction was seriously inhibited in the presence of humidity. At above a certain revel of humidity, the sensitivity remarkably deteriorated.

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45.

Recently, we reported that a compact type of electrochemical sensor^1-3) to detect blister agents such as mustard gas (HD) or lewisite (L1) using the carbon electrode modified with gold nanoparticles. In the present study, we will report on the development of HD sensor by using gold electrode prepared by sputtering it on the gas permeable membrane. The sensitivity of the sensor depended on the thickness of gold on the teflon membrane. So far, the most sensitive electrode was the 40Å-gold sputtered electrode. About 2.3 μA oxidation current was observed on the gold electrode (ca. 5.7 cm²) on the teflon film for 24 mg m^-3 of HD gas with the flow rate of 300 ml min^-1 at 0.2 V vs. gold black electrode in 9 M H₂SO₄, The response current decreased with the increase in the thickness of sputtered gold (> 40Å). We found that 20 Å of gold film was required for the detection of HD gas. The linear relationship of the signal to noise (S/N) vs. [HD] was obtained with the range till 24 mg m^-3 of HD.

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46.

Morphology of the sensing film plays an important role in gas sorption/desorption properties, and which results in the large effect on the performance of QCM-based gas sensors. Poly(N-isopropylacrylamide) (PNIPAM) membranes with different morphology, such as thin film, graft film, and nanosphere, were coated on the quartz crystal by various polymerization method, and their HCl gas sensing properties were investigated. The results show that the sensing properties are heavily affected by the morphology of the PNIPAM membranes. Among the sensors prepared, the sensor coated with nanospheres showed the fast and reversible response although the frequency shift due to the HCl gas sorption diminished.

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47.

Core (Au)-Shell (Pd) nanoparticles (mPd/Au, m: the weight ratio of Pd to Au), which were prepared by sonochemical reduction employing PdCl₂∙2NaCl and HAuCl₄ as noble-metal sources and polyethylene glycol monostearate as a reductant, were loaded on a mesoporous γ-alumina powder (m-Al₂O₃) and the gas-sensing properties of adsorption/combustion-type sensors fabricated with the powders (n(mPd/Au)/m-Al₂O₃ (n: the total amount of noble metals (Pd and Au) (wt%)) have been investigated in this study. The specific surface area of n(4Pd/Au)/m-Al₂O₃ powders remained almost unchanged by the amounts of noble metal loaded, while that of m-Al₂O₃ powders loaded with Pd and Au by impregnation method (n(mPd-Au)/m-Al₂O₃, m = 4) gradually increased with an increase in the amount of noble metal loaded. The responses of both n(4Pd/Au)/m-Al₂O₃ and n(mPd-Au)/m-Al₂O₃ sensors to ethanol and toluene in air tended to increase with an increase in the amounts of noble metal loaded, and the responses of n(4Pd/Au)/m-Al₂O₃ sensors were larger than those of n(4Pd-Au)/m-Al₂O₃ sensors. On the other hand, the response of both sensors to hexane was relatively small and independent of the amounts of noble metal loaded.

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48.

A novel Pt-Ti-O-gate Si-metal-insulator semiconductor field-effect transistor (MISFET) hydrogen gas sensor has been proposed by T.Usagawa and Y.Kikuchi, 2010. The sensors consist of unique gate structures composed of Ti and oxygen accumulated regions around Pt grains on top of a novel mixing layer of nanocrystalline TiOx and superheavily oxygen-doped amorphous Ti formed on SiO₂/Si substrates.　In this study we have investigated various as processed Pt/Ti-gate Si-MOSFETs in order to clarify the role of oxygen invasion into the Ti-layers. The thick Pt(45-90nm) with Ti(5nm)-gate Si- MOSFETs hydrogen gas sensors show very uniform wafer distributions of Vth with -0.26 V. It means that the oxygen invasion into Ti layer will be protected by thick Pt layer at least as processed states. On the other hand, air-annealed Pt(15 nm)/Ti(5 nm)-gate Si-MOSFETs at 400℃ for two hours shows higher average Vth with 1.076 V. The Vth difference for both FETs is 1.336V which is close to the work function difference, 1.32 eV, of Pt (5.65eV) and Ti (4.33eV). The device characteristics shows an evidence that the oxygen invade into Ti layer for thinner Pt gate FETs, but is protected for thicker Pt gate FETs.

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49.

It is well known that oxygen molecules adsorb as O^- on the surface of SnO₂ semiconductor particle and that such adsorption increases the electric resistance by the depletion layer formed inside the SnO₂ particles. In addition, it is also known that the humidity prohibit an oxygen adsorption, because the hydroxyl group forms on the adsorption site of oxygen. However, the effect of humidity on the electric properties of SnO₂ sensor such as the relationship between gas adsorption/reaction, humidity concentration and surface state of the crystallite, is still not clear sufficiently. In this study, we aimed to understand the influence of humidity on the electric properties of SnO₂ gas sensor through experiments. The SnO₂ sensor elements were investigated through the measurement of the electric resistance under different humidity and pre-treatment conditions. It was found that the electric resistance of SnO₂ under humid condition is lower than that under dry condition. In contrast, the electric resistance of the element after wet pre-treatment was higher than that after dry pre-treatment although they were measured under same condition. This result means that oxygen defects in SnO₂ particles are well compensated for by wet pre-treatment.

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50.

In this study, it was investigated that the effect of the dispersion state of Sn-containing sol solution on methane sensing properties. The median size of the sol decreased with increasing the hydrothermal pressure: ca. 45 nm in 1 MPa and ca. 15 nm in 15 MPa. These sol solutions were used as a sensor element to fabricate the tin oxide thin film on the gap of interdigitated Au or Pt electrodes. The increase of hydrothermal pressure contributed to increase sensor response to 3000 and 5000 ppm methane. Especially, the sensor response of microsensor with Au electrodes is higher than that with Pt electrodes, suggesting that the effect of hydrothermal pressure on the sensor response is independent on the composition of interdigitated electrodes. The average diameter of tin oxide nanoparticles calculated from TEM image was ranging from 8.5 (15 MPa) to 12 nm (1 MPa). The Pd loading to tin hydrate did not affect at all the sensor response.

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51.

A study on the application of V₂O₅/WO₃/TiO₂ (VWT) as the sensitive material for resistive-type SO₂ sensor is conducted, based on the fact that VWT is a well-known catalyst material for good selective catalytic nitrogen oxide reduction with a proven excellent durability in exhaust gases. The sensors fabricated in this study are planar ones with interdigitated electrodes of Au or Pt. The vanadium content of the utilized VWT is 1.5 or 3.0 wt%. The resistance of VWT decreases with an increasing SO₂ concentration in the range from 20 ppm to 5000 ppm. The best sensor response to SO₂ occurs at 400 ℃ using Au electrodes. The sensor response value is hardly dependent on the amount of added vanadium but it is dependent on the electrode materials.

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