Vol. 33, Supplement B (2017)

1.

CO sensing properties of NASICON (Na₃Zr₂Si₂PO₁₂)-based solid electrolyte-type gas sensors attached with Pt mixed with a metal oxide (MO: Bi₂O₃, CeO₂, Cr₂O₃, CuO, Fe₂O₃, In₂O₃, La₂O₃, Mn₂O₃, NiO, V₂O₅, WO₃) as a sensing electrode (Pt(15MO), the additive amount of MO: 15 wt%) and Pt as a counter electrode, which were denoted as Pt(15MO)/Pt, were examined at operating temperature in the range of −10~300°C. The magnitude of responses to 300 ppm CO of the examined sensors except for the Pt(15MO)/Pt (MO: Fe₂O₃ and In₂O₃) were the largest at 30°C. Among them, the Pt(15Bi₂O₃)/Pt and Pt(15Cr₂O₃)/Pt sensors showed relatively large CO response with a change in electromotive force to a positive direction at 30°C, while the Pt(15CeO₂)/Pt sensor showed relatively large negative CO response at 30°C. The Pt(15MO)/Pt sensors (MO: Bi₂O₃, CeO₂, Cr₂O₃) also showed the clear CO responses even at the temperature below freezing point. Among them, the Pt(15Bi₂O₃)/Pt sensor showed relatively large CO response (ca. −148 mV) with quick response and recovery behavior even at −10°C. The CO response mechanism of the sensors was discussed based on mixed potential theory.

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2.

Graphene oxide (GO) is a two-dimensional carbon nanosheet with various oxygen functional groups. GO has been attracting much attention as a material that can be applied in a wide range of applications such as capacitors and solar cells, because GO has unique electrical properties. Here, we report the development of solid electrolyte gas sensor using proton conductivity of GO. GO was synthesized by the Hummers’ method, and the GO membrane was prepared by vacuum filtration of the obtained solution. The GO membrane exposed to humid air showed good proton-conducting properties at room temperature, as confirmed by hydrogen concentration cell measurements, complex impedance analyses, and proton pumping. The gas sensor using the GO membrane with a platinum-supporting carbon (Pt/C) sensing electrode showed a high hydrogen response at room temperature. The sensing mechanism is explained by the mixed-potential theory. Our results showed the possibility of GO which can electrochemically detect hydrogen leakage without external heating.

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3.

CO-sensing properties of potentiometric gas sensors using an anion-conducting polymer (ACP) as an electrolyte and metal oxide (MO) loaded with and without a noble metal (N) as a sensing-electrode material (EC(nN/MO) or EC(MO), respectively, MO: Bi₂O₃, CeO₂ or SnO₂, n: the loading amount of a noble metal (0.5–10 wt%), N = Ag, Au, Ir, Rh, Ru, Pt) have been investigated in wet synthetic air (57%RH) at 30°C. All the EC(MO) sensors showed quite small responses to both CO and H₂. The N loading onto MO was effective in improving the CO response in some cases, and the Au and Pt loading onto SnO₂ especially enhanced the CO response of the EC(SnO₂) sensor. In addition, the CO responses of all the EC(nPt/SnO₂) sensors showed a good linear relationship with CO concentration. Among them, the H₂ responses of the EC(nPt/SnO₂) (n = 0.5–5.0) sensors were much smaller than their CO responses, indicating their excellent CO selectivity against H₂.

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4.

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, exhaled NH₃ can be a biomarker in a non-invasive breath test for lever disease. We reported that 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 and10 wt%. However, Ag-loading tended to increase the sensor response time. In this study, a beads-milling technique was applied to increase surface area of the h-BN powder. It was found that increasing surface area of the h-BN powder significantly enhance the sensor response and decrease the sensor response time.

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5.

These days, disease diagnostics using breath analysis have attracted a lot of attentions as a non-invasive method. Therefore, it has been coming very important to develop high performance gas sensors for maker gases, i. e., ammonia, acetone, toluene, etc. It is well known that hydro-sodalites show high ion-exchange capacity, tunable surface charge, and large surface area. In this study, we have focused on the use of hydro-sodalite as a new receptor for an impedancemetric solid-electrolyte gas sensor. Hydro-sodalites, Na₈(AlSiO₄)₆(OH)₂ and NA₈(AlSiO₄)₆Cl₂, powders could be synthesized by a hydrothermal method. It was found that the impedance response of the Na₈(AlSiO₄)₆Cl₂ / Na₅DySi₄O1₂ sensor device showed high sensitivity and selectivity to NH₃ at 400ºC, 50 Hz.

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6.

We have applied the platinum-titanium-oxygen (Pt-Ti-O) gate silicon-metal-insulator-semiconductor field-effect transistors (Si-MISFETs) hydrogen gas sensor to gas sensing study for H₂S, NH₃, CH₃OH, C₂H₅OH gases. We demonstrated the H₂S gas response for wide concentration range from 500ppm to 10ppm at operation temperature of 200C. The H₂S gas response shows steep threshold operation-temperature around 180 C. As the Pt-Ti-O gate Si-MISFETs are operated around 115 C for H₂ gas sensing, it is possible to discriminate H₂S gases and H₂ gases. The high threshold temperature will be an advantage for H₂S gas sensing compared with previous 100nm-thick Pd-gate MOSFETs H₂S gas sensors, which work at a low temperature of 70 C. The sensing characteristics of our Pt-Ti-O gate structures to NH₃, CH₃OH, and C₂H₅OH gases were much different from the previous simple Pd-gate or Pt-gate Si-MOSFETs. The sensor responses of our Pt-Ti-O gate structures to 500ppm NH₃ gas exposures showed no response at 115C, 320mV Vth shift at 185C, and 360mV Vth shift at 220C. These NH₃ sensing behavior is much different from the hitherto-developed Pt-gate Si-MOSFETs sensors,which showed large sensing amplitude like 400~800 mV depending operation temperature between 70~200C. We also investigate CH₃OH, and C₂H₅OH gas sensing.

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特別講演

Chemical biosensors to measure taste and smell have made rapid progress recently. They are named electronic tongues (e-tongues) and noses (e-noses), respectively. A taste sensor, which is a kind of e-tongue, has a property of global selectivity that implies ability to decompose taste into five basic taste qualities (sourness, sweetness, bitterness, saltiness, umami) and quantify them without identifying each chemical substance. Each sensor electrode of the taste sensor is specific to each taste quality. This sensor has been applied to many kinds of foods such as beer, coffee, tea, meat, rice, milk and wine. It can provide a scale of taste, and can be utilized to produce new foods and medicines or control/monitor their qualities.
E-noses are chemical biosensors to detect smell of foods, perfumes and circumstance. Whereas various types of materials and methods are reported, an “electronic dog nose” based on both surface plasmon resonance (SPR) and an antigen–antibody interaction is explained here. The detecting surface is chemically modified by a self-assembled monolayer. As a result, TNT was detected at about 6 ppt using the optimized surface with indirect competitive assay. In the near future, mobile phones mounting the above kinds of e-tongues and e-noses will be developed.

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7.

Ethylene (C₂H₄) gas, which is a essential material in petrochemical industry, leads to the potential for explosion accidents, because of its high flammability (explosive limits: 2.7 vol. % in the air), Thus, a C₂H₄ gas sensor is required to detect C₂H₄ leakage for preventing the following accidents. In this study, a new catalytic combustion-type C₂H₄ gas sensor was developed by using Pt-loaded CeO₂-ZrO₂-ZnO (CZZn) solid solution as a C₂H₄ oxidizing catalyst. The sensor employing 10wt%Pt/CZZn catalyst responded to C₂H₄ gas smoothly and reproducibly with linear response to C₂H₄ gas concentration change even at 135°C.

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8.

The catalytic activity and gas sensing property of Pd-loaded Al₂O₃ (Pd/AL) and Pd and LaMnO₃ co-loaded Al₂O₃ (Pd/LM/AL) to detect hydrocarbons, especially isobutane and methane were investigated. For gas sensing properties, the combustion type MEMS gas sensor was driven by pulse-heating mode to reduce the power consumption. The isobutane conversion using Pd/LM/AL showed higher catalytic activity than that using Pd/AL at 300oC, because Pd of Pd/LM/AL was more dispersed in the particles than that of Pd/AL. On the other hand, however, the sensor response to isobutane using Pd/AL was higher than that using Pd/LM/AL. Thus, it is indicated that the distribution state of Pd particles such as particles aggregation and chemical state affect to the thermal conductivity of sensing layers and the enhancement of the sensor response.

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9.

Ammonia gas is one of the useful gas species in the industrial field. However, ammonia gas is very toxic, and the ammonia gas sensor showing the exact gas detection with a rapid response is greatly requested for prevening the serious accidents. In this study, we fabricated the catalytic combustion-type sensor which can detect NH₃ at low temperature by incorporating a Pt-loaded　appatite-type La₁₀Si₆O₂₇ solid solution as the NH₃ oxidizing catalyst. The sensor showed the superior sensing performance of smooth and rapid response to NH₃ gas at 200°C. Moreover, since the present sensor exhibited linear response to the NH₃ gas concentration change, it is expected that the sensor can detect NH₃ quantitatively at around 200°C.

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10.

Sensing properties of adsorption/combustion-type gas sensors utilizing mesoporous alumina co-loaded with 10 wt% noble metal and 10 wt% metal oxide, (10N/10MO/mp-Al₂O₃, N: noble metal (Pd or Pd), MO: metal oxide (Bi₂O₃ or CeO₂)) to volatile organic compounds (VOCs, ethanol or 1-hexanol in this study) have been investigated and their sensor-signal profiles have been analyzed by differential and integral processing. The sensor-signal profiles to ethanol and 1-hexanol were drastically dependent on the kind of N and MO loaded onto the mp-Al₂O₃, and 10Pt/10CeO₂/mp-Al₂O₃ and 10Pd/10CeO₂/mp-Al₂O₃ sensors showed the largest dynamic responses to ethanol and 1-hexanol, which probably originated from flash combustion (450°C) of adsorbed partially decomposed products and/or polycondensates produced at 150°C, respectively. In addition, the differential processing obviously differentiated their dynamic-response behavior. On the other hand, the integral processing of static responses revealed that the catalytic-combustion activities of ethanol and 1-hexanol over mp-Al₂O₃ largely depended on the kind of loaded MO (Bi₂O₃ or CeO₂).

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11.

Calorimetric gas sensors take advantages of micro-machined devices using the heat of combustion reaction generated on catalytic metals and inflammable gas. Micro-thermoelectric array sensors (TAS) have been developed for the ppm level gas detection, which includes H₂, CO, and CH₄ in human breath, heating catalyst combustor temperatures by using micro heaters built on the membrane of the sensor device. For the purpose of simultaneous detection of the gases in exhaled breath, an array sensor of thermoelectric devices with 3 different combustion catalysts is developed. Using the micro-heaters the temperatures of the Pd/Al₂O₃, Au/Co₃O₄ and Pt/Al₂O₃ catalysts were controlled for the selective combustion of CH₄, CO and H₂, respectively, and the gas sensing performance of the sensor for the simulated breath of the gas mixture including 100 ppm H₂, 25 ppm CO, 50 ppm CH₄, and 199 ppm CO₂ in air is investigated.

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12.

It is well known that sensing properties of a polyaniline (PANI) gas sensor depend on the morphology of the PANI film. In this study, the surface-grafted PANI film was fabricated and its sensing properties towards NH₃ gas were investigated. Fabrication of the grafted PANI sensor was performed in two steps. First, parylene A was deposited by chemical vapor deposition onto an alumina substrate having a pair of interdigitated gold electrodes. Second, polyaniline was then immobilized onto the parylene A surface by oxidative graft polymerization of aniline. The response of the grafted sensor was approximately five times larger than that of the simply deposited (non-grafted) sensor. Also, the grafted sensor was fabricated in several conditions. Among the sensors tested, the grafted sensor prepared in 0.5 M H₂SO₄ for 24 hours had much higher response. However, the there was little difference in the reversibility of the grafted sensors, irrespective of fabrication conditions.

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13.

A novel optic sensor using platinum-loaded tungsten oxide (Pt/WO₃) and silicon microring-resonator (MRR) for detection of hydrogen gas at room temperature was proposed and examined. The sensing principle is based on the resonant wavelength shift caused by the change in optical properties of hydrogen sensitive layer. 140 pm resonant wavelength shift was observed when the sensor was exposed to 4 vol.% H₂/N₂ for 5 minutes, however, according to the optical microscope image of the surface of it, the part of microring was not completely covered with Pt/WO₃. Maybe it was because this part was so small that the surface tension of Pt/WO₃ precursor prevented to entirely cover it. We think this sensor will be much more sensitive if the microring portion is fully covered with Pt/WO₃ by mixing a surfactant into its precursor.

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14.

Poly(N-isopropylacrylamide) (PNIPAM) nanoparticle films were fabricated easily at room temperature on the surface of a quartz resonator by using a cononsolvency effect. The surface morphology of the films was observed by SEM and nanoparticles with the diameter of several hundreds nm were successfully formed. Moreover, images obtained at high magnification(×500k) revealed that these nanoparticles were secondary particles formed by aggregation of primary particles (about 10 nm in diameter). The amount of HCl gas adsorption of PNIPAM nanoparticle films increased in proportion to the PNIPAM loading on the resonator surface, while the reversibility was unexpectedly less than 90%.

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15.

CO₂ sensing properties of Zr-added CaFe₂O₄ powders prepared from a malic acid complex (MAC) and a polymerized complex (PC) methods were examined in the temperature range of 250 to 450 °C in dry air. In the MAC method, the CO₂ sensitivity of Zr-added CaFe₂O₄ powder was higher than that of unadded CaFe₂O₄ powder and it reached maximum at measuring temperature from 300 to 350 °C. On the other hand, Zr-added CaFe₂O₄ powder in the PC method had a low CO₂ sensitivity as well as the unadded one.

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16.

MEMS-type gas sensor, for which benefits of the pulse heating are not only reduction of power consumption but also its specific sensing performance, was investigated the effect of the pulse heating condition on the sensing property. In this pulse heating, sensor signal includes the transformation of the unsteady state to the steady state. Sensing properties to H₂, CO and C₇H₈ gases were measured and compared within such transformation. As a result, it was found that the resistance change in 1 pulse heating strongly depends on the kind of gas and the rest time. Thus, the measurements of resistance change during a one pulse were discussed for high sensitivity and selectivity in gas detection.

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17.

Detection of trace amounts of hydrogen in vacuum conditions is essential in reusable space transportation systems and for safety control in manned space exploration. We evaluated the H₂ detection in vacuum conditions by a novel gas sensor using sintered ceria (cerium oxide) nanoparticles. The results show that sensor resistance depended on H₂ and O₂ partial pressure ratios at any pressure from 10-5 Pa to atmospheric pressure. We conclude that the ceria resistance does not depend on total pressure but on H₂ and O₂ adsorption. The increase in sensor resistance resulted from a decrease in oxygen vacancies dependent on the O₂ storage of ceria at a high O₂ partial pressure. On the other hand, H₂ dissociated and formed a cluster with ceria oxygen atoms when the H₂ partial pressure was higher than the O₂ partial pressure. Sensor resistance markedly decreased in these conditions because Ce₃+ with free electrons were generated. In summary, the proposed sensor can convert gas adsorption into an electrical signal even in vacuum conditions, and has the potential to be a highly durable device with high sensitivity.

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18.

We propose a novel sensing device for small olfactory chip which can be installed on mobile such as smart phone. Three kinds of the gas-sensitive films were separately deposited on surface potential sensor arrays, which is integrated in a single chip with the area of 7.3 mm². The chip has 128 × 128 elements with the element size of 37.30 × 37.30 μm², and the manufactured device was exposure to three gases, ethanol, ammonia, acetic acid. The output voltage changes -17 to -41, -58 to -115, and -19 to -58 mV depending on ethanol, ammonia, and acetic acid, respectively. Response pattern of three gases can be obtained from the comparison of voltage difference by the type of film. Furthermore, the time responses have been proposed to be used for gas identification. These results indicate the promising property of the proposed device as a small olfaction chip.

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Exhaled breath air includes a lot of volatile organic compounds (VOCs) related to halitosis, metabolism, and diseases. It will be easy to check the health condition if the breath analysis, one of the noninvasive analysis, will be improved to monitor the specific VOCs related to them. Especially for diseases, it is expected as a screening method leading to early detection. In this study, we developed semiconductive gas sensors and exhaled breath VOCs monitoring systems using the gas sensors for screening lung cancer. The exhaled breath VOCs monitoring systems consist of Tenax TA as a gas condensing unit, two GC columns, and two semiconductive gas sensors as detectors. We used Pt, Pd, and Pd-loaded SnO₂ (Pt,Pd,Au/SnO₂) sensors for detecting various VOCs. The target VOCs were selected according to the results of GC/MS analysis. In statistical analyses, we firstly carried out the t-test and the correlation coefficient analysis, and compared the results from the GC/MS and the exhaled breath VOCs monitoring system. Next, we carried out the support vector machine algorithm (SVM) for other target VOCs with high percentage of correct answers, and prepared the second version of exhaled breath VOCs monitoring system.

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20.

An electrochemical detection system for DNA has been investigated based on the current increase due to the catalytic oxidation of hydrogen peroxide with platinum deposited by the electrochemical reduction of chloro-2,2':6',2''-terpyridine platinum (II) chloride dihydrate (Pt complex) on a screen-printed carbon electrode. The platinum deposited on the screen-printed carbon electrode that has shown no catalytic activity for oxidation of hydrogen peroxide gives rise to catalytic activity. Cyclic voltammetry was used to reduce the Pt complex to deposit platinum metal on the carbon electrode. The oxidation current of hydrogen peroxide increased with increasing concentration of the Pt complex in the electrolytic deposition. The intercalation of the Pt complex into double-stranded DNA (dsDNA) decreased the concentration of free Pt complex and caused a decrease in the diffusion coefficient of the intercalated Pt complex. Moreover, the reduction of Pt complex was inhibited due to steric hindrance. Thus, the oxidation current for hydrogen peroxide by platinum deposited on the carbon electrode decreased with an increase in the concentration of dsDNA. The present procedure is absolutely simple without the need of the immobilization of DNA. Furthermore, the use of inexpensive screen-printed carbon electrodes will allow for the development of disposable sensing systems.

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21.

In this study, an organic-inorganic nanostructure that was composed of polyaniline (PANI) and gold nanoparticles has been prepared. The presence of PANI offered us a potential application as electrochemical label for bacteria. Therefore, we have attempted to use this nanostructure as an electrochemical label for E. coli O157:H7 cell which is the leading cause of foodborne diseases. It is well known that the specific antibody-antigen reaction is one of the most effective ways for bacteria detection. So, the anti-E. coli O157:H7 antibody was immobilized on the nanostructure to ensure the specific binding to the target cells. It was confirmed that the antibody-modified nanostructure bound selectively to the target bacteria by using a dark-field microscopy. The bacterial detection was carried out by differential pulse voltammetry (DPV). The results showed that the electrochemical response based on the nanostructure was obtained for the pathogenic E. coli O157:H7 while there was no response for other types of bacteria.

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22.

Surface Plasmon Resonance (SPR) biosensor has been developed for a practical application in small molecule detection. However, the real sample may contain many kinds of inhibitors. There are challenges for real sample analysis, even though the high sensitivity was realized in an ideal condition. In this study, the indirect competitive inhibition immunoassay with secondary immunoreaction was employed for detection of beta agonist. Although the sensitivity of 150 ppq (fg mL-1) was achieved, SPR did not respond to the monoclonal antibody of beta agonist in non-pretreated urine. First, the pH was adjusted by mixing with PBS buffer solution (1:1). The pH of sample solution became always 7.4 by the buffer effect. Next, the filtration methods for urine of cows were investigated. It was found that the filtration using pore size could not remove inhibitors. But, the inhibitors were totally removed by the filter modified with functional group such as –CH₃, -NH₂, or –COOH. It was noticed that the COOH-modified silica filter showed the best performance. It was almost comparable sensitivity to that in PBS buffer solution. It will be discussed that the mechanism of inhibitors in urine.

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23.

Graphite particles grafted with a polymer imprinted with unfractionated heparin and kneaded with silicone oil to fabricate a paste electrode. The redox current at of ferrocyanide at the paste electrode was sensitive to unfractionated heparin and low molecular weight heparin but was insensitive to chondroitin sulfate C. The contact angle of saline on the surface of the paste electrode was decreased by addition of heparin but insensitive to chondroitin sulfate C. The results indicate that the sensing of heparin by the molecularly imprinted polymer on graphite paste electrode controls the effective area of the paste electrode by oil movement.

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24.

Finely cut fragments from cucumber’s peels immobilized onto carbon fibers chemically treated were prepared. The disk type of the immobilized preparations were packed into a small plastic column and then，this column was assembled into a flow-injection system. The system was applied to a flow-injection determination of L-ascorbate based on an amperometric monitoring of decrease in amounts of dissolved oxygen in the substrate solutions. The performance characteristics of the flow system were reported.

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25.

A platinum electrode with a mesoporous structure was prepared by electrodeposition of the platinum. The mesoporous platinum electrode showed a large electrochemical active surface. In the glucose solution, the obtained electrode show reductive peak at around 0.35 V vs. Ag/AgCl in the cyclic voltammograms, which was not observed in the electrolyte of 0.5 M H₂SO₄ solution. The peak current value show a good linear relationship with the concentration of not only D- but also L-glucose in the range between 2 mM and 10 mM. Glucose sensing using cyclic voltammograms in the mixed solution of D-, and L-glucose solution with the constant glucose concentration (5 mM), showed that the peak current value slightly increase with increasing the ratio of L-glucose. Therefore, the influence of L-glucose should be taken into account for a more accurate detection of D-glucose with the mesoporous Pt. Therefore, the influence of L-glucose should be taken into account for a more accurate detection of D-glucose with the mesoporous Pt.

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26.

Horseradish peroxidase (HRP) was physically adsorbed onto plastic formed carbon (PFC) electrode together with various redox-active organic dyes. Bioelectrocatalytic reduction current to H₂O₂ were increased by co-adsorption of some redox-active dyes. In the case of phenazine and phenoxazine dyes, typical mediated currents were observed. However, in the case of phenothiazine (PTZ) dyes such as thionine (TN) and methylene blue (MB), the PTZ facilitated direct electron transfer (DET), and the DET-based bioelectrocatalytic reduction current to H₂O₂ increased. Glucose oxidase (GOx) was further adsorbed onto the HRP/PTZ-PFC electrodes, and the resulting bi-enzyme electrode (GOx/HRP/PTZ-PFC) showed cathodic responses to glucose in a concentration depending manner. When the electrode was changed to carbon-felt (CF), essentially similar behavior was observed, and these sensors allowed highly sensitive and selective determinations of H₂O₂ and glucose.

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27.

A stable dispersed solution of glucose oxidase (GOx) and carbon nanotube (CNT) was prepared using gellan gum and was applied as a solution for electrodeposition. Both GOx and CNT was successfully immobilized on Pt-Ir electrode by applying a constant potential of 1.3 V（vs. Ag/AgCl）, while it was followed by o-phenylenediamine electropolymerization in order to fabricate a stable enzyme-immobilized electrode. The obtained electrode performed as a glucose sensor with high sensor sensitivity. This indicate that the introduction of CNT in GOx-immobilized film increased the efficiency of electron transfer between the electrode and generated hydrogen peroxide. In addition, the reproductivity of electrode fabrication was satisfactorily improved by the use of gellan gum as a dispersing agent.

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清山賞受賞講演1

We have been studying nanocarbon film electrodes formed by some sputtering methods. The film provides a nanocrystalline sp² and sp³ mixed bond structure with an atomically flat surface and high conductivity without doping. The film electrode has excellent properties including a low background current, a wide potential window, and little surface fouling, while maintaining relatively high electrode activity for various (bio) molecules. These characteristics allow the detection of (bio)molecules (e.g., all DNA bases and cerebral gliotransmitter), especially ultratrace amount of biomolecules, which are difficult to measure at conventional carbon electrodes. The nanocarbon film surface can be also easily modified with other atoms/nanoparticle without losing its ultraflatness. For example, we developed electrochemically stable fluorinated nanocarbon (F-nanocarbon) film by CF₄ plasma treatment. We successfully used F-nanocarbon film electrode for selective detection of hydrophobic antioxidants (vitamin E) and highly-sensitive detection of LPS. Our developed nanocarbon film-based electrodes can extend ability to detect analytes, which are difficult to detect at conventional carbon electrodes.

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清山賞受賞講演2

We have developed various kinds of gas sensors in which the rare earth containing materials were strategically selected as the key component of the sensor for realizing the superior sensing performances such as high gas selectivity, high durability, and low temperature operation. Although we have developed the solid electrolyte-type CO₂, SO₂, NO_x, Cl₂, and NH₃ gas sensors and the catalytic combustion-type CO and H₂ gas sensors, I introduce, here, the water durable solid electrolyte-type NH₃ gas sensor and the low temperature operable catalytic combustion-type CO gas sensor.

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28.

In this study, highly sensitive bio-sniffers (gas phase biosensor) for analysis of breath acetone and IPA were constructed and demonstrated. Secondary alcohol dehydrogenase (S-ADH) can reduce acetone to isopropanol (IPA) and oxidize nicotinamide adenine dinucleotide (NAD⁺ to NADH) in a weak acid environment. Furthermore, S-ADH can reversely oxidize IPA to acetone and reduce NADH to NAD⁺ in an alkaline condition. NADH has unique optical property that it emits fluorescence at 490 nm when it is exposed to 340 nm ultraviolet lights. Therefore, the acetone sniffer detected the decrease of NADH fluorescence to determine the concentration of gaseous acetone and the IPA sniffer measured the increase of NADH. The bio-sniffers were composed of an UV–LED, a photomultiplier tube and an optical fiber probe equipped with a flow-cell and enzyme immobilized membrane. Buffer (pH 7.0 or pH 8.5) solution containing coenzyme (NAD⁺ or NADH) was circulated in the flow-cell. Both bio-sniffers showed rapid response, highly sensitivity and selectivity to acetone/IPA in the gas phase. The analysis of breath acetone in healthy volunteers found higher concentrations when during the fasting. Additionally, the IPA in exhaled air of healthy subjects observed the concentration of 15.4±11.3 ppb, which was consisted with other researches.

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29.

Methyltransferase from Aeropyrum pernix was constructed and the active properties were investigated. A. pernix is known as hyperthermophilic archaea and the methyltransferase will have a thermostability, therefore, the methyltransferase can be expected for industrial applications. On the other hand, there is little knowledge of methyltransferase from archaea. APE_0872.1 is a gene in A. pernix genome and is presumed to be a gene encoding DNA(cytosin-5) methyltransferase by homology search. The sequence is homologous to motif I, IV, VI, VIII, and X region of Dnmt I which is known as a DNA methyltransferase of human. And more, A. pernix has a APEK I encoded by a gene of restriction enzyme which recognize GCWGC. From the view point of the restriction modification system, it is considered that DNA methyltransferase of A. pernix will recognize the sequence of GCWGC. However, there is no report of the recognition sequence and thermostability about a protein encoded APE_0872.1. Therefore, in this study, we investigate the properties.

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30.

Cells of Salmonella enterica contaminate food and cause foodborne illnesses. It takes long time to detect the existence of S. enterica because of enrichment and several times of separation cultures from samples. Bacterial cells can be isolated in microchamber on a microfluidic disc for single cell isolation, which was developed in our group. Through the PCR of the gene using fluorescent probe the amplicon of the gene in the isolated cell can be detected on the disc and small numbers of S. enterica cells were detected selectively by PCR of invA gene. The aim of this study is rapid detection of S. enterica spiked to chicken meat, as a model of food, by PCR of invA gene on the disc. The collected bacteria from the meat was mixed with PCR reagents and applied to the disc, and single cell isolation and PCR was performed. PCR amplicon of each micro chamber was detected by a fluorescent microscope. The number of the microchamber with PCR amplicon depended on the concentration of S. enterica cells. On a microfluidic disc we could successfully detect S. enterica cells at range of 10⁴ -10⁵ CFU/g within 8 hours including enrichment culture.

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31.

Circulating tumor cells (CTCs) are defined as tumor cells circulating in the peripheral blood of patients with metastatic cancer. CTCs could provide useful information regarding malignancy, metastatic property of primary tumor and its response to anticancer agent. However, it is still extremely difficult to cultivate CTCs and examine multiple anticancer agents toward identical CTCs. This could be due to the lack of knowledge of division and proliferation behavior of CTCs. The critical difficulty in investigation of CTC proliferation is that cell division events of CTCs are very rare, and thus conventional microscopy might overwork them. Additionally, it is essential that CTCs are discriminated from the blood cells which contaminate CTCs. In this study, we propose to use a wide-field imaging system for investigation of CTC cultivation. The imaging system is composed of a LED and CMOS image sensor, called for lens-less imaging. Using this lens-less imaging system, we attempted to observe tumor cell proliferation and distinguish tumor cells from blood cells. This study indicates that the lens-less imaging can be a powerful tool to investigate the CTC proliferation and cultivation.

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32.

Circulating tumor cells (CTCs) are defined as the tumor cells circulating in the peripheral blood of patients with metastatic cancer. Genetic analysis of CTCs at single cell level is believed to provide detailed information of cancer patients. Our research group has developed the size- and deformability-based CTC recovery system using microcavity array (MCA). Recently, we have also developed the single-cell isolation method using photopolymerizable hydrogel encapsulation called “gel-based cell manipulation (GCM)”. GCM allows us to isolate single-cells by tweezers without microscopic observation. However, light irradiation using fluorescent microscopy for each cell is required to hydrogel encapsulation of single-cell, resulting in low throughput. If a number of single-CTCs on MCA are simultaneously encapsulated in hydrogel, high-throughput isolation of CTCs is achieved. In this study, we developed the multiple light irradiation system using two dimensional (2D) complementary metal oxide semiconductor (CMOS) photosensor and digital micromirror device (DMD), and integrated it with the MCA system.

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33.

We have developed all-solid-state K ion-selective electrodes by using a K insertion material placed between metal substrate and ion selective membrane. Three different Prussian blue analogues were employed as insertion materials which are known as candidate materials for positive electrodes of K-ion batteries and allow K⁺ to reversibly be inserted/extracted into/from their crystal structures associated with electrochemical redox reactions. The electrodes of Pt/K insertion material/K⁺-ISM exhibited an ideal Nernstian response in the range of 10^-4.5 – 10^-1 mol dm^-3 with high selectivity for potassium ions and good potential stability. AC impedance analysis of the all-solid-state electrodes revealed that the insertion materials were capable of reducing the electrode impedance at the interface between metal substrate and ion selective membrane, which was responsible for their improved potential stability.

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34.

A field effect transistor (FET) biosensor that can directly detect target molecules is expected to be applied in healthcare and medical fields due to its potential as a diagnosis tool. When the FET sensors are stored in solution environments, a silicon dioxide insulating layer might be damaged, resulting in the degradation of the reproducibility of sensor response. In this study, to stabilize sensor response for long term immersion in solution, graphene oxide (GO) was selected as a coating layer on the gate insulator of FET sensors. The GO sheets were deposited on a self-assembled monolayer, aminopropylsilane (APS), to obtain GO-coated APS-modified FET (GO/APS/SiO₂) sensor. The sensor response, which is observed as a change in the V_g - I_d characteristics, was evaluated before and after storing the sensors in buffer solution environments.

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35.

A fluorine-terminated boron-doped diamond surface is successfully employed as a pH-insensitive solution-gate field-effect transistor for an all-solid-state pH sensor. The fluorinated polycrystalline boron-doped diamond (BDD) channel possesses a pH-insensitivity of less than 3mV/pH. With differential field-effect transistor sensing method, a sensitivity of ca. 0.03 v/pH was obtained in the pH range of 2–10.

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36.

Amorphous RuO₂-Ta₂O₅ catalysts at different Ru:Ta ratios were prepared by thermal decomposition on titanium disk and the electrochemical measurements of HCO₃- in KCl solutions were carried out with the catalysts using rotating disk electrode method. The onset potential for HCO₃- oxidation, the linearity between the HCO₃- concentration and the oxidation current density, the sensitivity, and the linear concentration range were examined by cyclic voltammetry and chronoamperometry, and the results were compared to those obtained with HPO₄²-. The Ru ratio of the catalyst ranging from 20 mol% to 80 mol% examined in this work gave little influence on the onset potential of HCO₃- oxidation as well as that of HPO₄²-, in which the oxidation of HCO₃- occurs at the less novel potential than that of HPO₄²-. The sensitivity to each ion showed a strong dependence on the catalyst’s composition, which was maximum at Ru = 50 mol% for both the ions, suggesting that the catalyst at 50 mol% Ru is favorable to quantify HCO₃- and HPO₄²-.

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37.

The oxidation reactions of HPO₄²- and HCO₃- on amorphous RuO₂-Ta₂O₅ catalytic coatings prepared by thermal decomposition on titanium disk were investigated by electrochemical measurements. Cyclic voltammetry and square wave voltammetry indicated that HPO₄²- and HCO₃- were oxidized and the oxidation wave of HPO₄²- appeared prior to that of HCO₃- . The separation in oxidation potential was about 0.14 V measured in SWV, which suggests that both the ions are quantified separately by changing the detection potential. Chronoamperometry was also performed with the KCl solutions with HPO₄²-, HCO₃-, or both of them to know the diffusion limited current density at different potentials. The results showed that the net current density for the oxidation of both HPO₄²- and HCO₃- is almost the same as the sum of that of HPO₄²- and that of HCO₃-, implying that the quantification of each ion in the solution, where both ions are dissolved, is possible electrochemically with the novel catalyst, amorphous RuO₂-Ta₂O₅ mixed oxide.

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38.

A planar-type sensor using a Li₃Zr₂Si₂PO₁₂ glass-ceramics (Li⁺ ionic conductor : LICGC) as a transducer and metal carbonates as an auxiliary phase was fabricated for monitoring dissolved CO₂ in liquid solution. The electrochemical cell of this sensor element was as follows, （reference electrode） Pt-black, Au / LICGC / Au, Pt-black,　Li₂CO₃+Na₂CO₃ （sensing electrode）. It had no water-proof coating layer on the sensing electrode and the reference electrode. Various mixed solutions were prepared by varying a volume ratio of Li₂CO₃ saturated solution and Na₂CO₃ saturated solution, and Li₂CO₃+Na₂CO₃ layer was formed on Pt-black by dropping and drying one of them. Among the various ratio of Li₂CO₃ and Na₂CO₃ examined, the sensor with a ratio of 1:0.25 was found to show good sensing properties to dissolved CO₂. The EMF response of this sensor was found to vary logarithmically with a change in dissolved CO₂ concentration in the range of 300 to 1300 ppm in a phosphate buffer solution of pH 7.0 at 30℃. The 90% response time to1300 ppm was ca. 2 min.

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39.

Cells control a variety of ion concentrations with ion pumps and channels. The simultaneous monitoring of plural ions is very useful to reveal the behavior of cells and tissues. We have recently developed multi-ion image sensors with ion-sensitive membranes using an ink-jet printing. The Ca²⁺-K⁺ multi-ion image sensor divided with two sensing regions successfully observed dynamic multi-ion images of living cells. In this study, we fabricated a microscale-patterned K⁺-H⁺ multi-ion image sensor that had 64 sensing lines (line width: 70 µm). The half of these lines were coated with K⁺ sensitive membrane, and the sensitivity to K⁺ of each sensing pixel had the average of 50.1 mV/decade. While the other half lines worked as pH sensing pixels. The sensor could compare the local response of K⁺ and H⁺ since K⁺ sensitive lines and H⁺ sensitive lines were alternately aligned on the sensing area. The sensor would be helpful to analyze cell events accompanying with locally changing K⁺ and/or H⁺ concentration.

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40.

We examined the frequency dependence of the resonant length of polyethylene glycol (PEG) on a solid-liquid interface oscillating at MHz area by using a quartz crystal microbalance (QCM). In order to study it in detail, the QCM frequency and a number-average molecular weight of PEG were changed systematically. As results, the study led to the fact that, in all the frequencies used, the series-resonant frequency shift, ΔF, of the QCM against the square root of the density-viscosity product of the PEG solutions was linear and had intercept. Moreover, the analysis made it clear that the ΔF slope was able to be explained by the Debye process and the ΔF intercept became constant above the resonant length. These results revealed that the resonant length of the PEG molecules formed by physisorption was equal to that in the region of the viscous penetration depth and that the frequency dependency of resonant length of physisorption and chemisorption was equal to each other.

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