Vol. 33, Supplement A (2017)

1.

WO₃-based semiconductor gas sensors were fabricated, and their sensing properties to methylmercaptan (CH₃SH) were examined in this study. The Ru loading on WO₃ increased the magnitude of CH₃SH response, and the response increased with a decrease in the operating temperature as well as with an increase in thickness of the Ru-loaded WO₃ films. In addition, the increase in porosity of the Ru-loaded WO₃ films, which were fabricated by utilizing polymethylmethacrylate microspheres as a template, was effective in improving the CH₃SH response, especially at a lower temperature of 150°C. The catalytic activities of CH₃SH oxidation over WO₃-based powders in wet air showed that CH₃SH was partially decomposed to produce an intermediate (dimethyl disulfide) at temperatures less than 330°C and the Ru loading on the WO₃ powder increased the catalytic activities. These results indicate that the positively charged adsorption of the intermediate onto the WO₃-based powders is one of important factors in promoting the magnitude of CH₃SH response at lower operating temperatures.

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2.

Effects of UV-light irradiation (peak wavelength: 365 nm) on sensing properties of oxide semiconductor sensors to different gases (hydrogen, ethanol, NO₂) have been investigated at 30°C in dry air. The responses of both pristine SnO₂ and 0.05 wt% Pd-loaded SnO₂ sensors to 6000 ppm H₂ decreased and those to 50 ppm ethanol increased with an increase in UV-light irradiation intensity. In addition, the Pd loading onto the SnO₂ surface was effective in improving the H₂ response under weak UV-light irradiation as well as the ethanol response under strong UV-light irradiation. On the other hand, UV-light irradiation reduced the response of a porous (pr-)In₂O₃ sensor to 5 ppm NO₂ and accelerated the response and recovery speeds at 30°C, and the 0.5 wt% Au loading onto the pr-In₂O₃ surface improved the NO₂ response, especially under weak UV-light irradiation. However, the NO₂ responses of pr-In₂O₃ sensors loaded with and without 0.5 wt% Au under UV-light irradiation at 30°C are not larger than those at elevated temperatures (no UV-light irradiation).

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3.

In this study, fundamental characteristics of semiconductor CO₂ sensors were investigated for integrated CO₂ sensors. As sensing materials, La₂O₃ and SnO₂ were employed. For the objective, La₂O₃SnO₂ stacked structures device having simple two facing electrodes with 500-μm spacing: #1 and the device having comb electrodes with 20-μm spacing: #2, were fabricated. In addition, SnO₂ with the various thicknesses in the range of 16 - 107 nm was deposited in #1. The resistance at 300°C in the synthesized air (N2: 80% + O2: 20%), Rair and that in the atmosphere with CO₂, RCO₂ were measured. The sensitivity was defined as the ratio of these resistances: Rair/RCO₂. The sensitivity for 1000 ppm of CO₂ of #1 increased as the SnO₂ thickness decreased. The sensitivity of #2 with 107 nm of SnO₂ thickness to 1000 ppm of CO₂ was higher than one of #1. These sensitivity differences were investigated in terms of the CO₂ concentration dependence and the electrode geometry based on the CO sensing model. As a result, it was suggested that the resistance near the interface with the electrodes contributes to the CO₂ responses.

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4.

In this study, we first report semiconductor CO₂ sensors integrated with MEMS hotplates (MHP). The MHP has bridge-type structure with the membrane area of 140 μm × 140 μm. The membrane consists of SiO₂ and SiN, and polycrystalline Si was used as a heater material. The MHP can reach 550°C at 5 V. The sensor consists of La₂O₃/SnO₂ stacked material with Pt interdigitated electrodes. The CO₂ sensitivity of the sensor for 1000 ppm CO₂ increased with increasing the operating temperature, reaching the maximum of 2.9 at 350°C, while the sensitivity decreased with further increasing temperature. Similar temperature dependence was observed in Ra. Because the change in Ra may originate from the density and ionization state of adsorbed oxygen, the results indicate that the adsorbed oxygen plays an important role in CO₂ sensing by the sensor in this study. Furthermore, it was confirmed that the limit of detection was 200 ppm at 400°C, at which the power consumption of the heater was about 20 mW. Consequently, a low-power MHP-based CO₂ sensor was demonstrated.

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特別講演

NTT DOCOMO is researching and developing self-health management using biological data in the health and medical care fields. Biological data reflecting individual differences can be obtained from biological gas contained in human breath and emitted from the skin’s surface without the pain of drawing blood, and that data can be applied to self-health management. We have developed three types of devices that measure biological gas components contained in breath or emitted from the skin’s surface for use as markers of fat metabolism, alcohol intoxication, and other conditions. These easy-to-use devices are expected to be useful in alleviating and preventing obesity, which can lead to all sorts of diseases and raise the risk of acquiring lifestyle-related diseases.

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5.

CO₂ sensing properties of alkali earth ferrite (MgFe₂O₄ and CaFe₂O₄) added with additional element, such as Si, Ti, Hf, Zr, La and Sm, were examined in the temperature range of 250 to 500 °C in dry air. At 300 °C, CO₂ sensitivity of CaFe₂O₄ was effectively improved by adding a small amount of impurity atoms such as Zr and Hf in comparison with unadded one. On the other hand, CO₂ sensitivities of MgFe₂O₄-based sensors were lower than those of CaFe₂O₄-based one. CO₂ sensitivity of the Zr-added CaFe₂O₄ sensor reached maximum at measuring temperature between 300 and 350 °C, and was estimated to be 2.9 times higher than that of pure CaFe₂O₄ powder. At 350 °C, for 5 mol% Zr-added CaFe₂O₄, the CO₂ sensitivity was the highest among the sensors examined.

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6.

Highly oxidative and reductive state of WO₃ and In₂O₃ coupled with NOx detection was studied by attaching the metal oxide electrode on an Sn0.9In0.1P2O7 electrolyte and by polarizing the electrode at 200 °C. During the polarization, insertion and release of H+ occurred at the WO₃ electrode and redox reaction of metal ions occurred at In₂O₃ electrode. Hydrogen tungsten bronze was not sensitive to NOx, however, WO₃ showed a comparable sensitivity toward NOx. The ohmic, charge-transfer, and gas-diffusion resistances changed by the exposition to NOx. The changes in NOx sensing property of In₂O₃ was observed when the polarity and applied voltage were changed. During cathodic polarization in the range of -0.5 to -1.5 V, the resistance of the sensor decreased when NOx were supplied to the sensor. On the other hand, the resistance increased by the supply, especially of NO₂ at -2.0 V. This phenomena attributed to the reduction of ions and functioned as selective adsorption sites especially for NO₂. Both electrodes were little affected by interference gases.

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7.

Cerium oxide is one of the most promising resistive oxygen sensing materials for use in fast-response sensors because the cerium oxide possesses high diffusion coefficient for oxygen so that oxygen vacancies can diffuse to whole bulk of cerium oxide and clear electrical resistance changes are obtained. Though pure cerium oxide possesses high impedance, the resistance of 10% Zr-doped cerium oxide (Ce_0.9Zr_0.1O₂; CeZr10) is roughly one tenth of that of pure cerium oxide with almost the same performance for oxygen sensor. In this study, we investigate sensing properties of CeZr10 to simulated exhaled gas and evaluation of CeZr10 using alternating current impedance analysis for developing as breath oxygen sensors.

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8.

Sensing properties of WO₃ with different amount of oxygen vacancy to hydrogen were examined using Au counter electrodes. WO_3-O2 with low amount of oxygen vacancy showed n-type semiconductor behavior. On the other hand, WO_3-H2 with many amount of oxygen vacancy showed p-type semiconductor behavior. This behavior suggests that hole is formed due to many amount of oxygen vacancy. The behavior of WO_3-Air was also depending on operating temperature. The WO_3-Air behaved as n-type behavior at the operating temperature of 300 and 250 oC as well as p-type behavior at the temperature of 200 oC. From above results, oxygen vacancies doped by three types of hydrothermal atmosphere were related to hydrogen detection.

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9.

Carbon nanohorns （CNHs） exhibit a high-surface-area architecture and have a large number of reactive carbon edge sites, which make them a promising candidate for a molecular adsorber. We have recently discovered a new nano-carbon material, "carbon nanobrush," （CNB） a fibrous aggregate composed of radially-assembled graphene-based single-walled nanotubules. CNB also has high surface area to volume ratios but has more than 10 times the electrical conductivity of CNHs. Due to these remarkable properties, they are expected to be a promising material for gas sensitive resistors. In this report, we examined the applicability of CNB for gas sensitive films by measuring the response to VOC gas exposures at the concentration between 200ppm and 4000ppm. We observed apparent resistive changes according to the VOC gas exposure, dependency on the gas concentrations, and the reversibility of the response. As a result, we confirmed applicability of CNB for the gas sensitive films.

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10.

Gas direct fired absorption chiller-heaters are used for the air conditioning of large buildings and factories. At present we carry out periodic safety inspections by a technical maintenance person, that is why there is a demand for an inexpensive monitor that can detect CO gas at any time. For this development we used an existing semiconductor CO gas sensor to which we added water- and heat- resistant structure to install it in a chimney flue. This sensor element alternates high temperature and low temperature cycle to detect CO. The drive was tested over a long period it showed stability and was able to detect CO. By utilizing the change ratio of this sensor resistance from the resistance in normal combustion as a relative response, this module can detect CO without any influence from other gases except CO gas. We found that the unburned flammable gas is transiently released at the time of ignition. Since this gas could cause a false alarm, we decided to use a way to turn off gas detection temporarily. We succeeded in developing a CO monitor for gas absorption chiller-heaters.

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11.

Nitrogen monoxide (NO) is an important bio-regulatory molecule, and high concentrations of NO are observed in the air exhaled by patients with asthma. Therefore we considered that a method to detect NO with both high sensitivity and high selectivity is required. We have already developed the NO sensing element using 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxil(PTIO) impregnated in a porous glass with 4 nm pore size, and have examined both the performance of the sensing element at 0.625 ppm NO atmosphere and the interference gases. In this work, we evaluated the kinetic reaction constant between the reagent and gaseous NO and obtained values for the solution system and the sensing element were 6.73×10^-3 Lmol-1min-1 and 1.21×10^-3 Lmol^-1min^-1, respectively. Despite the passive air sampling system of the proposed sensing element, the reaction constant of the sensing element was one-six of liquid’s one that was obtained in an active bubbling system. In addition, we also evaluated the sensing element’s performance by exposing to 0.167ppm NO. As a result, good linearity was observed between accumulated NO concentrations and the absorbance changes, that indicating the possibility of the detection with ppb.

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12.

Hydrogen gas sensor for leak detection is indispensable for wide spread use of hydrogen energy system. The authors propose catalyst-type hydrogen gas sensor using fiber Bragg gratings (FBG). Sensing principle is based on catalytic combustion heat and related thermal strain which makes shifts of center wavelength of the reflection spectra. In this study, Pt/SiO₂ catalyst film as a hydrogen-sensitive layer was obtained by using sol-gel method. The precursor solution was composed of hexachloroplatinic acid and commercially available silica precursor solutions. The molar ratio between the Si and Pt was fixed at 13:1. Small amount of this solution was dropped on the substrate and dried at room temperature. After that, the film was calcined at 500 ℃ in air. In order to enhance the sensitivity, this procedures were repeated and therefore thick hydrogen-sensitive films were obtained. It is found that sensor device having thick Pt/SiO₂ film showed high sensitivity at room temperature even in the low concentration range.

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13.

We have developed the catalytic combustion type hydrogen gas sensor showing high sensing performance even at moderate temperatures by incorporating a Pt loaded CeO₂–ZrO₂–SnO₂ solid solution as the H₂ gas oxidation catalyst. Since the present catalyst can oxidize H₂ gas completely even at 55°C, the sensor with a Pt loaded CeO₂–ZrO₂–SnO₂ solid solution showed superior H₂ gas sensing performance at the temperature as low as 55°C, which is substantially lower than that required for the operation of the sensors with the conventional H₂ oxidation catalysts such as Pt / Al₂O₃ or Pd / Al₂O₃.

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14.

In order to clarify the electrochemical behavior at detecting CO, polarization curves of a working electrode and a counter electrode of a solid electrolyte membrane type CO sensor were measured using Pt wire as a reference electrode. As with a liquid electrolyte membrane type sensor, short-circuit current between both electrodes in the air containing CO was confirmed to be approximately a half of diffusion limited current of a CO oxidation reaction on the working electrode.

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15.

Ammonia ( NH₃ ) is extremely toxic and harmful for environmental. Recently, NH₃ from urea is used for selective catalytic reduction (SCR) of NOx from diesel engines. Since little excess amount of NH₃ is required for high NOx conversion, leakage of ammonia is anticipated for the current urea NOx SCR system. Therefore, detection of NH₃ in exhaust gas line from diesel engines is an important subject. Various types sensor have been proposed for NH₃ detection. In particular, semiconductor type sensor or galvanic battery type sensor are popularly used. However, because of selectivity, maintenance and operating temperature, development of NH₃ sensor with more sensitive and selective is strongly required. In this study, we investigated NH₃ sensor based on oxygen pumping current and it was found that the cell using LaFeO₃ for NH₃ oxidation, LaGaO₃ doped with Ni for electrolyte, Au-In_0.95Sn_0.05O_1.5 (ITO) inactive electrode shows high sensitivity to NH₃ in air.

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16.

Human breath from a controlled human body contains <1 ppm NH₃, while that from a lever disease patient is known to increase to 50 ppm. Therefore NH₃ can be a biomarker in a non-invasive breath test for lever disease. In this study, potentiometric sensors aiming at detecting NH₃ in human breath were examined. Zirconia based sensor elements, i.e., NH₃, Pt/YSZ/Pt, air, detected an air-balanced 30ppm NH₃. Covering the Pt sensing electrode with hexagonal boron nitride (h-BN) supported catalysts (Pt, Pd, Ag) increased the EMF response. In particular, Ag loaded h-BN (Ag/h-BN) was the most effective catalyst, and the EMF response increased with an increase in the amount of Ag loading between 2 and10wt%. In the case of 10wt%Ag/h-BN, the EMF response value for 30ppm NH₃ was 60 mV and 90% response time was 220 s. However, Ag/h-BN was not significantly active for NH₃ decomposition. Therefore, it was deduced that the loaded Ag rather acts as NH₃ adsorption sites to condense NH₃ molecules in the catalyst layer. Humidification of NH₃ significantly reduced the EMF response compared to the dry NH₃ case.

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17.

Carbon monoxide (CO) is one of the most toxic gases in air pollution and human life. In previous researches, Cu-based materials have been used for CO sensors. In this study, an impedancemetric CO sensor using layered perovskite-type cuprates has been investigated. Layered perovskite-type La_2-xA’_xCu_1-yB’_yO₄ (A’ = Sr, Ba, Ce, B’ = Zr, x, y =0.1, 0.2) cuprate powders, which were used as a receptor material for CO sensor, were synthesized by a polymer precursor method. Thick-film devices prepared by screen-printing method were investigated by an AC impedance method at 300-500ºC. Among the Cu-based oxides tested, La_1.9Ce_0.1CuO₄ device showed good CO response which increasing with increasing CO concentrations at 400ºC, 50 Hz. According to XPS analysis, it could realize that the La_1.9Ce_0.1CuO₄　has a larger amount of Cu⁺ specie than the other oxides. It should consider that the Cu⁺ plays an important role in CO sensing.

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18.

It is well known that cocaine binding aptamer changes its conformation when it captures cocaine as a target molecule. Usually, cocaine aptamer is immobilized on gold electrode using gold-sulfur interaction to prepare cocaine sensor, which accompanies undesired aggregation and non-specific adsorption. We have already reported that these problems could be improved by simple heat treatment after immobilization. However, in systems that immobilize aptamers, since only one electron signal derived ferrocene molecule could be obtained from one aptamer that captures cocaine, it was difficult to amplify the signal and improve sensitivity. In this presentation, combining a ferrocene-modified cocaine-binding aptamer with a restriction enzyme exonuclease III that specifically degrades double-stranded DNA to release ferrocene molecule into the solution, we designed a new system in which ferrocene was amplified with an interdigitated array electrodes. The sensitivity of cocaine was improved compared with the immobilization systems.

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The conventional method for the diagnosis of infective diseases (the loop-mediated isothermal amplification (LAMP)) is limited for the detection time. Therefore, a biosensor using a quartz crystal is attracted for such infection diagnoses. The sensor with the quartz crystal is monitoring mass changes of targets in high frequency. However, the properties of polymer materials (DNA etc.) do not response to the vibration in the range of high frequency depend on molecular size. In this report, we are developing a new sensor using a piezoelectric polymer so called PolyVinylidene DiFluoride (PVDF). Because PVDF responses to a wide range of frequencies, the measuring at relaxation frequency is appropriate to detect micro mass changes of polymer (DNA etc.).

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20.

In this research, we developed a new reference electrode using poly vinylidene di fluoride (PVdF) binder and micro silica gel for thin layer chromatography to compatibilize two printed reference electrodes we have developed, a reference electrode with PDMS harden electrolyte layer and liquid junction layer having long lifetime, and a paper-based reference electrode indicated the stable potential fast. Using these materials, the electrolyte layer inside the reference electrode formed strong hydrophilic electrolyte layer, and kept KCl, leads to stable potential. We characterized this screen-printed reference electrode using potentiometry and cyclic voltammetry. As the result of potentiometry, the screen-printed reference electrode shift stable in 3 minutes from start, and kept stable for 5000 minutes.

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21.

In this study, we constructed a microfluidic channel on the chemical imaging sensor, which is capable of visualizing pH distribution. In our previous studies, the non-uniformity of signal photocurrent in the channel was a problem. In the present study, the ceiling of the channel was made of glass with conducting ITO to enhance the uniformity. Diffusion of ions across the boundary between two laminar flows was quantitatively measured in a Y-shaped channel and it was demonstrated that diffusion coefficients of ions with only a small difference in ionic radius could be distinguished.

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22.

Electrochemical wearable devices have been attracted attention as a device for evaluating the health condition by analysis of perspiration. Sodium ion is an excellent marker for electrolyte imbalance. In this study, we newly prepared a wearable potentiometric sodium ion sensor by transfer printing technique. The sensor was formed on a PET film, on which a releasing agent was coated, by screen-printing. Firstly, prior to perform the transfer printing, the responses of the screen-printed sensor on the PET film to sodium ion were evaluated by measuring the open circuit potential in a NaCl solution (0.1 - 100 mM). As a result, the sensor responded linearly by obeying the Nernst equation under 0.1 - 100 mM range. The slope of the calibration curve was 52.3 mV log₁₀[Na⁺]^-1. In addition, we evaluated the performances of the wearable sodium ion sensor.

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23.

An electrochemical sensing device based on the oxidation of an analyte on an electrode in a flow channel and deposition of silver in the other flow channel and subsequent coulometric measurement of the deposited silver was developed. To improve the detection limit, the effect of decreasing the number of electrodes in a microelectrode array for the deposition of silver and reducing the electrode area were examined. In the former case, measured charges did not decrease as long as there were a sufficient number of microelectrodes. On the other hand, no change in measured charges was observed in the latter case. In both cases, the background charge decreased by decreasing the number and area of the microelectrodes. Furthermore, a device with flow channels connected with two Ag/AgCl electrodes was used. The charge could be amplified by changing the potential of the Ag/AgCl electrodes.

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24.

Flow injection analysis (FIA) with amperometric determination of dissolved hydrogen molecule (H₂) was first developed using electrodeposited platinum particles on glassy carbon electrodes modified with nitrogen-containing functional groups (Pt-NMGC) as the working electrode. A glassy carbon (GC) electrode was covalently modified by electrochemical oxidation/reduction procedures. Intriguingly, the redox waves between hydrogen ion and H₂ at highly positive potential range were obtained by using Pt-NMGC electrode. The specific electrocatalytic activity for the electrode oxidation of H₂ has successfully been applied to the FIA of dissolved H₂. The typical current vs. time curve was obtained by the repetitive measurement of dissolved H₂, and the measurement of dissolved H₂ was finished completely in a short time (~20 sec.). A linear relationship was obtained between the oxidation current of H₂ and dissolved H₂ concentration. This indicates that our proposed technique can be used for the determination of the dissolved H₂ concentration.

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25.

Glucose oxidase (GOx)-immobilized electrodes were prepared by the combination of electrodeposition and photopolymerization. Methacryloyl choline chloride (NMA) were employed as photo-polymeriable methacrylates and were added in the enzyme-electrdeposition solution, in order to be entrapped in the enzyme film. In order to investigate the enzyme film formation behavior during the electrodeposition process, quartz crystal microbalance (QCM) technique was employed. QCM measurement results indicated that the amount of deposit increased continuously up to around 15 minutes, while the decrease of deposit was observed after that time. The amount of GOx immobilized on the electrode was also measured using Amplex Red Assay Kit and showed that the decrease of deposit was parallel with the decrease of GOx on the electrode. However, the amount of enzyme on the electrode started to increase again after electrodeposition time of 40 minutes. The glucose sensor sensitivity of the obtained electrode showed a good correlation with the amount of enzyme immobilized on the electrode.

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26.

A sensitive plant monitoring system with flexible boron-doped diamond (BDD) electrodes prepared from BDD powder and resin (Nafion or Vylon-KE1830) was investigated. The properties of the electrodes were compared with those of small BDD plate-type electrodes. While flexible BDD electrodes have wide potential windows, their cyclic voltammograms are not identical to those of the BDD plate. Further, the potential gap between a pair of electrodes attached to the plants changes as the plants are stimulated artificially with a finger touch, suggesting that the bioelectric potentials in the plant also changed, manifesting as changes in the potential gap between the electrodes. The BDD electrodes were assessed for their response reproducibility to a finger stimulus for 30 days. The plant monitoring system worked well with flexible BDD electrodes. Furthermore, the electrodes were stable and as reliable as the BDD plate electrodes in this study. Thus, a flexible and inexpensive BDD electrode system was successfully fabricated for monitoring the bioelectric potential changes in plants.

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27.

Previously we developed Leu-Gly-Arg-p-aminophenol (LGR-pAP) as a novel sub-strate of Limulus amebocyte lysate (LAL) assay for a simple amperometric detection of endotoxin. In this study we developed another substrates combined with two types of phenylenediamine derivatives alternative to pAP, p-amino-N-methylaniline (MPD) and N,N-dimethyl-p-phenylenediamine (DMPD). Both MPD and DMPD showed better temporal stability than pAP. In the voltammetric analysis, an oxidation peak was shown at 0.5 V vs Ag/AgCl in the case of 1mM LGR-pAP, LGR-MPD and LGR-DMPD in 0.1 M HEPES buffer (pH 7.8), while 0.2 V vs Ag/AgCl in the case of 1mM pAP, MPD and DMPD in the same buffer. From this result, we demonstrated endotoxin detection with amperometry at 0.3 V vs Ag/AgCl. A mixture of LAL reagent containing 1 mM substrate and endotoxin sample solution was incubated at 37°C for 1 h. Then, amperometry was conducted using glassy carbon disc electrode (1.0 mm in diameter) as a working electrode. By using this process, 10 endotoxin units L⁻¹ were detected.

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28.

Multi-walled carbon nanotubes (MWCNTs) were aligned in hydrogels using dielectrophoresis approach with horizontal and vertical orientation to interdigitated electrode array (IDA) chip. The horizontally aligned MWCNT embedded in PEG-DA hydrogel sheet was used as open-type bipolar electrode (MWCNT-oBPE) array. An external 180 VDC voltage was applied between two electrodes at the distance of 21 mm. The MWCNT-oBPE was set in a buffer solution containing [Ru(bpy)3]Cl2 and tripropylamine (TPA). Electrochemical luminescence was observed to show availability for oBPE-based biosensor. The vertically aligned MWCNT embedded in hydrogel sheet was designed for closed BPE (MWCNT-cBPE). In this case, Thermal gelation with 2,2'-Azobis(isobutyronitrile) (AIBN) was used instead of UV gelation. We confirmed vertical alignment by optical microscope.

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29.

Detection of microorganisms is crucial in a wide range of industries. Microarray testing is one of the promising methods for this purpose. However, it is time consuming and labor intensive. To address this issue, we established a novel microarray technology using the signaling array probe (SAP). The SAP comprises of fluorescent probe and quench probe, and generates fluorescent signal only when target DNA exists. We demonstrated the detection of two bacterial species, Staphylococcus aureus and Escherichia coli using the SAP-based microarray, on which both single strand- and double strand-DNA could be target DNA and any washing steps were not needed. This method would be useful to detect contaminated microorganisms in a variety of applications.

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30.

Detection and discrimination of bacteria are crucial in a wide range of industries including production of foods, cosmetics, and pharmaceuticals. Conventional methods for discrimination of bacteria are based on biochemical and/or genetic analyses. However, such methods are time-consuming and labor-intensive. To address this issue, we have developed a novel discrimination methodology using a lens-less imaging system, which is composed of a complementary metal oxide semiconductor (CMOS) sensor, medium agar plate and LED light. This lens-less imaging system has the advantage of wide field of view, enabling simultaneous tracking of the growth of multiple microcolonies. Morphological and growth characters of each microcolony are quantitatively examined by the image analysis, and a set of characteristic parameters (termed colony fingerprint) are extracted. Discrimination of bacteria is performed by multivariate analyses of the colony fingerprint. In this study, we applied this method for discrimination of five closely-related Staphylococcus species (S. aureus, S. epidermidis, S.　haemolyticus, S. saprophyticus, S. simulans). Using support vector machine (SVM) technique, and discrimination of theses bacteria was demonstrated with 100% of accuracy. Moreover, discrimination of S. aureus in the mixed culture with other bacterium Pseudomonas aeruginosa was also demonstrated. These results suggest that the colony fingerprint-based method is useful for discrimination of contaminated bacteria with high accuracy and robustness.

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31.

Drug-resistant enterobacteriaceae is of increasing global concern. Rapid detection and response are required for protecting from its propagation. For this issue, we have developed the Point-of-Care Testing (POCT)-oriented polymerase chain reaction (PCR) device which is driven by centrifugation assisted thermal convection. A cyclo-olefin polymer (COP) microfluidic chip, fabricated by injection molding, was integrated to a device that can control the temperature during chip rotation. The PCR solution could be driven by thermal convection and continuously exchanged high/low temperatures in a ring structured micro-channel without using a typical syringe pump. The flow rate was then able to be controlled by the relative gravity acceleration of the centrifugation device attached to the bottom of micro-channel. The on-chip DNA amplification of Imipenemase-6 (IMP-6), one of the genes responsible for carbapenem-resistance, was detected from 217fg of bacterial total DNA within 15min at 7G. In addition, we have successfully achieved the detection of blaIMP-6 from human stool samples. This result indicated that the easy and rapid PCR could be done without sample pre-treatment and technical proficiency of users.

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32.

An antibody, which can recognizes and binds a specific antigen, is applied for various purposes such as separation, purification, and sensing. Molecularly imprinted polymers (MIP) cannot only mimic the function of antibodies but also expedite and simplify to produce a receptor comparing with antibodies which are produced by immune response. We accomplished to synthesize nanometer-sized composite particle consisting of MIP based on O157-antigenic structure of enterohemorrhagic Escherichia coli (E. coli) O157 and encapsulated gold nanoparticles (Au NPs). The composite bound to E. coli O157 and enhanced light-scattering intensity of the cell owing to the optical properties of the Au NPs. Moreover, the composite shows excellent selectivity against other types of E. coli such as O26 and O rough. This composite as an artificial antibody and an optical label is expected to be applied for the detection of various kinds of bacterium including new threats by imprinting specific antigenic structure depending on bacterial species.

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33.

Heparin-imprinted polymer was grafted on graphite particles in fluidized bed reactor and paste electrodes were fabricated with the grafted particles. The electrodes have high homogeneity in heparin-sensitivity. The sensitivity to heparin in blood was same as that in physiological saline. The property is very feasible for disposable sensor for heparin in blood.

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34.

A bio-fluorometric imaging system (Sniff-cam) exploiting an enzymatic reaction was developed for measurement of gaseous acetaldehyde (AA) in exhaled breath. This system consisted of a highly sensitive camera, an ultraviolet-light emitting diode (UV-LED) array sheet and an alcohol dehydrogenase (ADH) immobilized mesh. Reduced Nicotinamide adenine dinucleotide (NADH) is consumed by the enzymatic reduction of AA with ADH, and its concentration is inverse-proportional to that of gaseous AA. In this system, the concentration of gaseous AA is quantitatively visualized with fluorescence intensities emitted from NADH by UV photo-excitation. The detection limit of 100 ppb with the high-selectivity for AA vapor was demonstrated in the sniff-cam. Finally, the Sniff-cam was applied to measure gaseous AA in exhaled breath after intake of an alcohol beverage, and a fluctuation of AA concentration with time was observed as alcohol metabolism.

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35.

Specific identification of enterohemorrhagic Escherichia coli was achieved using microspheres coated with overoxidized polypyrrole, and which recognized E. coli O157:H7 based on shape complementarity. It is a micrometer sized core-shell particle, composed of a gold coated core and a polymer complex shell. The thickness of polymer shell was controlled in a suitable level for cells imprinting. The microsphere has an approximative size compared to cells and well dispersed in aqueous media. These features can improve the interaction between microsphere and cells sufficiently, resulting specific, spontaneous, and efficient binding of E. coli O157:H7 through surface area effects. In addition, the microsphere recognized E. coli O157:H7 specifically with a high selectivity (over 10). The microspheres are an easy-to-use tool to detect and concentrate E. coli strains that cause food poisoning.

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36.

Heparin is the most important anticoagulant drug used during surgeries and extracorporeal therapies. Although the blood levels of heparin should be monitored continuously during the procedure to ensure the safety of the patient, there is currently no technique for measuring heparin in real time. This study describes the use of a molecularly imprinted polymer (MIP) as a recognition element in the development of a heparin sensor for real-time monitoring. An gold electrode grafted with a heparin-specific MIP by plasma-induced polymerization was used as a quartz crystal microbalance (QCM) sensor. The procedure of plasma initiated polymerization is as follows: (i) The gold electrode is treated by hexamethyldisiloxane plasma treatment for 1 min. (ii) The gold electrode solution is pour into the water solution for 12 h. The water solution heparin (template) contains (2-(methacryloxy)-ethyl)trimethylammonium chloride acrylamide (functional monomer), acrylamide, and N,N-methylenebisacrylamide (crosslimker). (iii) The gold electrode is washed by potassium chloride solution so as to remove the template. Non-imprinted polymer (NIP) is carried out like as the same procedure without template. The QCM measurement showed that the heparin-specific MIP bound to heparin and did not bind to chondroitin sulphate C which is heparin analog material. NIP did not bind to both of heparin and chondroitin sulfate C.

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37.

We investigated analytical procedure of bisphenol A based on enzyme linked immunosorbent assay (ELISA) using microfluidic device for ELISA. Formula of competitive immuno assay of bisphenol A in small amount of sample was investigated utilizing anti-bisphenol A antibody modified beads, which was introduced in a reaction chamber on a microchannel of the microfluidic device. To determine Bisphenol A in rat serum, solid phase extraction using molecularly imprinted polymer (MIP) was examined. Using the microfluidic device for ELISA and MIP, Bisphenol A in rat serum was determined in shorter time with much smaller volume of sample than conventional ELISA.

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特別講演

Various micro/nano surface-modification techniques such as photolithography, dip-pen lithography and micro-fluidic systems have been developed. And they were used to extend the functionalities of solid surfaces. While those approaches work in the “open space”, push–pull systems which work in solutions have recently drawn considerable attention. However, the confining flows performed by push–pull systems have realized only the dispense process, while microscale, region-selective chemical reactions have remained unattainable. This work reports a micro-chemical pen that enables region-selective chemical reactions for the micro/nano surface modification. The chemical pen is based on the principle of microfluidic laminar flows and the resulting mixing of reagents by the mutual molecular diffusion. The micro/nano scale diffusion layer performs as the working region of the surface modification. This report represents the first demonstration of an open micro reactor in which two different reagents react on a real solid sample. The multifunctional characteristics of the micro chemical pen are confirmed by different types of reactions in many research areas, including inorganic chemistry, polymer science, electrochemistry and biological sample treatment.

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38.

Over age 40 people have higher levels of a fragrant organic compound known as 2-nonenal on the skin. In this research, a 2-nonenal bio-sniffer (biochemical gas sensor) was constructed with a fluorometric device and demonstrated for measuring it from the neck skin surface. The bio-sniffer was composed by a flow-cell with an acetaldehyde dehydrogenase (ALDH) immobilized membrane, an optical fiber and a UV-LED excitation light source. NADH would be produced by the ALDH enzymatic reaction of 2-nonenal and the production volume is proportional to the concentration of 2-nonenal. Phosphate buffer, which contained NADH, was circulated into the flow-cell for supplying co-enzyme and removing the excessive substrates and products. The photo multiplier detects the change of the fluorescence intensity emitted from NADH. We also demonstrated that the alter value of fluorescence intensity was correlated with 2-nonenal concentration from 0.4 to 11 ppm. This calibration range includes the concentration of 2-nonenal on the skin of healthy young and old people. Finally, the 2-nonenal bio-sniffer was applied to measure the 2-nonenal of the skin of neck. This highly sensitivity bio-sniffer for 2-nonenal is expected to apply for the evaluation of age-related change in the concentration of body odor.

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39.

The flavoenzymes flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) and oxidase (FAD-GOx) do not undergo direct electron transfer (DET) at conventional electrodes, because the FAD cofactor is buried deeply (~1.4 nm) below the protein surface. We present a mediatorless DET between oxygen-insensitive FAD-GDH and single-walled carbon nanotubes (SWNTs). A glucose-concentration-dependent current (GCDC) is observed at the electrode with the combination of glycosylated FAD-GDH and debundled SWNTs; the GCDC due to an increase in the polarized potential during potential sweep voltammetry increases steeply (+0.1 V of onset, 1.2 mA cm-2 at +0.6 V 48 mM glucose) without the appearance of the FAD redox peak at –0.45 V. In the control experiment, the GCDC is not observed at the counterpart with debundled multi-walled carbon nanotubes (MWNTs). In the control experiment, the GCDC is observed at an analogous electrode based on oxygen-sensitive FAD-GOx with both of SWNT and MWNT in the presence of oxygen because oxygen acts as a natural and mobile mediator. Therefore, observation of the GCDC at the electrode with oxygen-insensitive FAD-GDH and debundled SWNTs provides evidence of mediatorless DET, even though oxygen is present. Details of the DET are discussed with respect to the recently reported crystallographic model of FAD-GDH. The three-dimensional globular FAD-GDH molecule is 4.5×5.6×7.8 nm, which is larger than the 1.2-nm diameter of an individual SWNT and smaller than the 10-nm diameter of an individual MWNT. Only individual SWNTs can be plugged into the groove of FAD-GDH, which is close to and within 1.0-nm of FAD, while maintaining their catalytic activity. Images obtained using transmission electron and atomic force microscopies support the stated configuration of FAD-GDH molecules and debundled SWNTs. We demonstrate that DET can be explained by quantum tunneling theory.

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40.

Preparation methods of immobilized alkaline phosphatase onto carbon fibers chemically treated were tried. The immobilized preparations were packed into a plastic column and then，this column was set into a flow-injection system. The system was applied to a flow-injection determination of zinc(II) ions based on an apoenzyme reactivation method. The performance characteristics of the flow system were reported.

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41.

Surface Plasmon Resonance (SPR) biosensor has been studied in our group for a practical application in small molecule detection. In this study, the indirect competitive inhibition immunoassay with secondary immunoreaction was investigated. It was known that the low affinity constant sensor surface provided the high sensitivity in the primary immunoreaction. Thus, it is inferred here that the affinity constant of the sensor surface also influences on the secondary immunoreaction. Past studies reported that the sensitivity of an immunoassay determined by the affinity constant of the immunosurface. Therefore, a low affinity and a high affinity sensor surface were fabricated for the kinetic study of the secondary immunoreaction. Aiming to achieve a high SPR response and a high sensitiveity, AuNP labeled secondary Ab was also used for the comparisonin in the secondary immunoreaction. A high response and a low limit of detection were found in the high affinity sensor surface, because it could be considered that the secondary antibody bonds to the tail of primary antibody.

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42.

Chromogranin A (CgA), which is one of the glycoproteins, is co-stored and co-released with catecholamines from storage granules in the adrenal medulla, or with the parathyroid gland. Although CgA is known as an important biomarker for monitoring in several diseases or psychophysical stress, the development of biosensor platforms for CgA detection is in their early stages. Toward that end, we decided to fabricate an organic field-effect transistor (OFET)-based immunosensor for human CgA (hCgA). The fabricated OFET device has an extended-gate electrode immobilized with an anti-CgA antibody. The titration results of hCgA showed that the electrical changes in the OFET characteristics. The sensitivity and selectivity suggest that the OFET-based immunosensor is potentially applied to the rapid detection of the glycoprotein concentration without any labeling.

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43.

We have been studying on non-enzyme type glucose sensors by using electrolytic manganese dioxide (EMD) as electrocatalyst, which do not require any expensive glucose oxidizing catalysts such as glucose oxidase or precious metal like platinum. However, the performance of the EMD electrode as glucose sensors is still not satisfactory to be substituted for the conventional sensors of enzyme electrode. In this study, glucose detectability of the EMD electrode is improved by adding surfactants into electrolytic bath for EMD preparation. Polyion complex coating on the EMD electrode is efficient to eliminate interference response to ascorbic and uric acids. Moreover, anodic oxidation mechanism of glucose is discussed with consideration of equilibrium of structural transition of glucose in aqueous solution.

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