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DOI： 10.18494/sam.2021.3068

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DOI： 10.1021/acsanm.0c01316

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Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.3390/s18103283

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We propose a new simplified fabrication process for poly(N-isopropylacrylamide) (PNIPAM) nanoparticles for a quartz crystal microbalance (QCM)-based HCl gas sensor coating. PNIPAM solution, synthesized via atom transfer radical polymerization (ATRP) below a lower critical solution temperature (LCST), is simply sprayed onto a heated quartz resonator surface at 50 degrees C; nanoparticles with a mean diameter of 100 nm were successfully formed with this method. The PNIPAM nanoparticles produced exhibited a large HCl gas sensor response, and the magnitude of the response increased linearly with PNIPAM loading on the resonator. However, the value of the recovery was unexpectedly less than 90%. The hydrogen-bonding structure of the nanoparticles produced was characterized by water vapor adsorption measurement and FTIR analysis in a humid atmosphere. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2017.05.130

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For the control of asthma symptoms at home via fractional exhaled nitric oxide (FeNO) monitoring, precise, small, and inexpensive measurement systems are necessary. We studied the feasibility of a photochemical NO sensor based on Co tetraphenylporphyrin (Co-TPP) derivatives, the absorption spectra of which are changed when NO is coordinated onto central Co metal. The sensors were fabricated by embedding Co-TPP derivatives into porous nonwoven fabrics. The absorption of the sensors was enhanced by the multiple absorption in the porous fabrics, which led to high sensitivity and low noise. The use of porous fabrics was also effective for reducing the response time to within 1 s. Fast recovery was obtained by optimizing the intensity of illuminated light from the LED to the sensor. A prototype FeNO analyzer was developed using the present Co-TPP-based optochemical sensors. The analyzer was shown to have an accuracy of +/-1 ppb using the test gas based on the compensation of the individual difference of sensors and the drift in sensor response. A comparison of the NO concentration in breath measured with the prototype analyzer and that measured with the chemiluminescence equipment showed substantial agreement between the two. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2016.02.145

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Poly(N-isopropylacrylamide) (PNIPAM) chains were grafted onto a quartz resonator using surface-initiated atom transfer radical polymerization (SI-ATRP). The PNIPAM loading was varied by changing the grafting time and the monomer concentration. AFM analysis revealed that the increase in PNIPAM loading was attributable to increases in the chain length and in the corresponding brush height. The HCl gas adsorption/desorption properties of the resulting PNIPAM brushes were measured by a quartz crystal microbalance (QCM) technique. The PNIPAM brushes adsorbed large amounts of HCl gas, and the adsorption capacity was linearly related to the PNIPAM loading, indicating the homogeneous adsorption of HCl gas inside the PNIPAM brushes. On the other hand, the rate of desorption of the HCl molecules was lower than that of the adsorption process, and slowed with increases in chain length. Reversibility was insufficient, especially at longer chain lengths due to the difficulty of the diffusion of gas molecules from inside the brushes. The reversibility was improved by raising the measuring temperature from 30 degrees C to 50 degrees C, but it was still up to 80%, suggesting the irreversibility of the adsorption. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2014.10.137

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Poly(N-isopropylacrylamide) (PNIPAM) nanoparticles were prepared by precipitation polymerization using atom transfer radical polymerization (ATRP) in aqueous media at 45 degrees C, which is above the lower critical solution temperature (LCST). Nanoparticles were coated on a quartz resonator and their HCl gas-sensing properties were measured by a quartz crystal microbalance (QCM) technique. PNIPAM nanoparticles adsorbed HCl gas reversibly, while PNIPAM thin film showed partly irreversible adsorption. Furthermore, for PNIPAM nanoparticles, the gas adsorption/desorption properties, such as adsorption time and reversibility, were not influenced by the mass loaded on the quartz resonator, which indicated that these properties were derived from the sum of the properties of each individual nanoparticle. The QCM-based PNIPAM nanoparticle sensor showed excellent reproducibility and the sensitivity to 1 ppm of HCl was approximately 3.8 Hz/ppm. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2013.08.095

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An amino-functional copolymer [N,N,-dimethyl-1,3-propanediamine (MCD)] developed in our laboratory was blended with carbon black (CB/MCD composite) and its electrical responses to toluene vapor at low concentrations were measured at 30°C. When exposed to 200 ppm of toluene vapor, the CB/MCD sensor responded at S = 0.04 (S was obtained by dividing the relative change in the resistance of the sensor upon exposure to toluene vapor by the baseline resistance), demonstrating its ability to detect toluene vapor at low concentrations. The response was affected by humidity in the atmosphere due to the hydrophilic nature of MCD film
however, the behavior was reproducible before and after exposure of the sensor to the humid atmosphere. In addition, in 10 consecutive sorbing/desorbing cycles, it was confirmed that the changes in the resistance of the CB/MCD sensor were reproducible. These favorable sensing characteristics were attributed to vapor sorption behavior arising from the glassy and loosely crosslinked nature of MCD and explained by the dual-sorption model. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 Copyright © 2012 Wiley Periodicals, Inc.

DOI： 10.1002/app.37578

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Alumina substrates with interdigitated electrodes were coated with polyaniline (PANI) nanofibers using our newly developed on-substrate method. Uniform HCl-doped PANI nanofibers were reproducibly formed by optimizing the polymerization time. The responsiveness of the HCl-doped PANI nanofiber NH(3) gas sensor was affected by the subsequent heat-treatment time in air, with longer heat treatment resulting in a greater response. Furthermore, redoping with DiOHP instead of HCl was successfully performed without damaging the nanofiber structures. The DiOHP-doped nanofiber sensor demonstrated excellent reproducibility and stability compared with the HCl-doped nanofiber sensor. The DiOHP-doped sensor showed sufficient detection sensitivity for NH(3) at concentrations of 25 ppm or less. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2011.09.017

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SCIENTIFIC PUBLISHERS  

Some of the novel methods to control the chemical structure or morphology of polymers for the gas sensing applications proposed by the author are described. Copolymers whose structures include chloromethyl styrene (CMSt) units are readily modified with amino compounds, and this enables custom-designed materials with large sorption capacity and specific selectivity to target analytes. Some results on the sensor applications for air pollutants in the environment based on these materials are described. Furthermore, in order to fabricate a high-sensitivity polyaniline (PANI) gas sensor, we have developed the on-substrate method for coating the whole surface of the substrate with PANI nanofibers reproducibly. Effects of the polymerization time, the post heat-treatment time in air, and the dopant species on the NH(3) gas-sensing characteristics are also discussed.

DOI： 10.1166/sl.2011.1638

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The sorption properties of toluene vapor were measured for methyl methacrylate (MMA)-co-chloromethyl styrene (CMSt) copolymers chemically modified with N,N-dimethyl-1,3-propanediamine (DMPDA) to develop a novel quartz crystal microbalance toluene-vapor sensor coating. The influence of the structure of the comonomer, the composition of the copolymer, and the film thickness on the toluene sorption properties were investigated. The modified MMA-CMSt copolymers were capable of large, fast, and reversible sorption versus the modified styrene-CMSt copolymers. The largest sorption capacity was obtained for MMA-CMSt-DMPDA with a 96 mol % CMSt concentration. These behaviors were explained by a combination of the plasticization of the copolymers by the introduction of bulky DMPDA at lower CMSt concentrations and the formation of a loosely crosslinked structure at higher CMSt concentrations. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1086-1093, 2009

DOI： 10.1002/app.29142

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Resistive-type humidity sensors using polyaniline blend films were fabricated, and their long-term stability upon application of dc voltage was investigated. The use of blended films of electron-conducting polyaniline (PANI) and polystyrene was effective it) depressing the sensor drift caused by polarization and/or electrolysis, which is a serious problem for polyelectrolyte sensors. However, another kind of drift caused by morphological change in the blend film was observed. To prevent this morphological change, cross-linked polystyrene with divinylbenzene (c-PSt) was used as a matrix polymer. The sensor using blended films of PANI and c-PSt exhibited excellent initial sensing characteristics and improved long-term stability. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3184148] All rights reserved.

DOI： 10.1149/1.3184148

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Styrene-co-chloromethyl styrene copolymers chemically modified with various kinds of monoamines or diamines were synthesized. Their sensing properties based on toluene vapor sorption/desorption behaviors were measured using a quartz crystal microbalance (QCM) technique. Introduction of aliphatic diamine compounds having a proper chain length (e.g., N,N-dimethyl-1,3-propanediamine (DMPDA)) into the structure of the copolymer realized improvements to the toluene vapor sorption capacity, the response time, and reversibility compared to the conventional polymer coatings. FTIR analysis suggests the formation of a loosely cross-linked structure, resulting in the promotion of toluene vapor diffusion into the film. (c) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2007.12.052

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Quartz resonators coated with three kinds of poly(acrylamide) derivatives were studied for simply but accurately detecting HCl gas in air. The exposure of the resonator to HCl gas reversibly decreased the oscillation frequencies. The sensitivity, response time, and reversibility were found to depend on the structure of the amide group. Among the polymers used, poly(NN-dimethylacrylamide) (PDMAA) showed the most relevant data for the HCl sensor. The HCl sensitivity obtained for PDMAA was ca. 250 ppb/Hz. On the other hand, the irreversible response toward NO2 gas was considerably high, and great interference was also produced by changes in the test gas humidity. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2007.10.049

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Quartz resonators coated with various compositions of poly(styrene-co-chloromethyl styrene) reacted with morpholine as adsorption sites were fabricated for simply but accurately monitoring HCl gas in air. The exposure of all resonators to HCl gas irreversibly decreased the oscillation frequencies, indicating that these devices can be used for one-shot detection of HCl gas. The chemical structure and composition of the copolymer affected the sensitivity. The largest sensitivity was obtained for the copolymer having 40.0 mol% CMSt composition cross-linked with 5.0 mol% DVB. The sensitivity was 0.1 ppm/Hz for 10-min sensor operation, demonstrating a ppm level of HCl detection, although great interference was produced by changes in the humidity. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2006.02.039

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The problem of methanol crossover through a Nafion (R) membrane is one of the challenges in the application of direct methanol fuel cells (DMFCs). In order to reduce methanol crossover, a semi-interpenetrating polymer networks (IPNs) membrane composed of Nafion (R) and crosslinked DVB was prepared. This new membrane was found to be effective in reducing methanol permeation compared with unmodified Nafion (R) membrane. Although the conductivity and H-2/O-2 fuel cell performance were still lower than those of unmodified Nafion (R) membrane, the present results demonstrate the potential for using semi-IPN membranes as an electrolyte for DMFC. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.memsci.2006.04.043

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Cross-linked polymers made of methyl methacrylate (MMA) as a monomer and divinylbenzene (DVB) its a cross-linking agent were prepared in the presence of toluene or p-xylene as a solvent. The cross-linked polymer prepared in toluene tended to sorb toluene vapor preferably, while the cross-linked polymer prepared in p-xylene sorbed p-xylene vapor preferably. The observed molecular recognition ability can be explained on the bases of an imprinting effect by solvent molecules. Molecularly imprinted polymer (MIP) powders were blended with PMMA. and the blended films were coated on a piezoelectric quartz crystal with a view to preparing QCM-based VOC sensors. The imprint effect was clearly observed, even in these blended films. The response of the sensor towards toluene or p-xylene vapor was reversible: however, the response time was slow due to the existence of the matrix polymer around the MIP particles, (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2005.02.028

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Piezoelectric devices coated with cross-linked poly(styrene-co-chloromethyl styrene) reacted with morpholine were fabricated to develop a simple system that monitors NO2 gas in air. The introduction of NO2 gas irreversibly decreased the oscillation frequencies of all the devices tested, indicating that these devices can be used for one-shot detection of NO2 concentrations in air. The NO2 sensitivity was defined as hourly changes in frequency. The use of the cross-linked structure clearly increased sensitivity. The largest sensitivity obtained in this study was 1200 Hz/h for 50 ppm, of NO2, which demonstrated a sub-ppm level of NO2 detection. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2004.11.044

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A capacitive-type humidity sensor based on a poly(methyl methacrylate) (PMMA) cross-linked with divinylbenzene (DVB) was fabricated. We examined the influence of introducing a cross-linked structure in the sensing polymer on the long-term stability of the sensor in a hot and humid atmosphere. As the DVB content increased, the irreversible increase in the water sorption ability of the cross-linked PMMA by long-term aging in a 40degreesC and 90% RH atmosphere was depressed. This was because the irreversible increase in volume of the sensing polymer caused by swelling in such atmosphere was prevented due to the rigid cross-linked structure. The depression of the drift of the water sorption ability resulted in the depression of the drift of the sensor capacitance. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.203.12.061

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A novel sensing film for a LiCl dew-point sensor was prepared by incorporating LiCI into the cross-linked porous PVA film. Their impedance characteristics and long-term stability was examined. The porous PVA film cross-linked with formaldehyde exhibited superior stability for more than 50 days, even when the film was stored in 50% RH atmosphere where dewdrops appear on the surface of the film. FTIR analysis, dielectric measurements, and SEM observation suggested that this superior stability may be attributed to the unique layered morphology of the coating, which is composed of a cross-linked PVA exterior layer and a primarily porous PVA interior layer that holds LiCl inside. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2003.07.007

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The effect of humidity on the NH3 detection capability of polyaniline (PANI)-insulating matrix polymer blend films was investigated. Poly(methyl methacrylate) (PMMA) and polystyrene (PSt) were used as the matrix polymers. The presence of water vapor, functioning as the interference gas, led to the lowering of the NH3 response of the sensor in a humid atmosphere. Although PMMA had more hydrophilic character than PSt (PMMA sorbed more than eight times as much water as PSt), the influence of humidity on the sensor response was not as large as expected. This unexpected finding was due to the characteristic morphology of the "PANI-PMMA blend film", that is, the blend film consisted of porous structures which resulted in a composition of the coexistence of the PANI-PMMA blend with the PANI and/or PMMA single species. In such cases, water molecules were able to interact with doped PANI directly, and the water sorbing characteristic of PMMA exerted less influence on the conductivity. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-4005(03)00325-3

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The effect of a sensing film's thickness on the drift phenomenon of capacitive-type humidity sensors in a hot and humid atmosphere was investigated. Poly(methyl methacrylate) (PMMA) was chosen as the model sensing material for this purpose. The electrical capacitance measured at 0% relative humidity (RH, C-0) decreased, while that measured in a wet atmosphere (C-X) increased by aging the sensors in a 40degreesC and 90% RH atmosphere. This aging test showed an increase in the resulting sensitivity (C-X/C-0). The drift of sensitivity can be closely related to the increase of water sorption ability of the sensing polymer. The magnitude of the drift of the water sorption ability was larger for the thicker film. The large increase of film thickness induced by aging was also observed for the thicker film. These results suggest that an irreversible volumetric change in PMMA film caused by the slight swelling that occurs in a hot and humid atmosphere is one of the important contributive factors associated with the drift phenomenon of the water sorption ability of PMMA film. (C) 2003 The Electrochemical Society.

DOI： 10.1149/1.1592522

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Piezoelectric devices coated with amino-functional poly (styrene-co-chloromethyl styrene) derivatives were fabricated to develop a simple system that monitors NO2 gas in air. The introduction of NO2 gas irreversibly decreased the oscillation frequencies of all of the devices tested. The sensitivity estimated from the hourly change in the frequency demonstrated a ppm level of NO2 detection. It was also confirmed that other gases, such as O-2, CO2, and SO2, functioning as an interference gas, showed little response and good selectivity toward NO2. The effect of humidity was also not serious.

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SO2 gas sorption properties were examined for poly(styrene-co-chloromethyl styrene) functionalized with N,N-dimethyl-1,3-propanediamine (DMPDA). The DMPDA-functional copolymers were prepared under various reaction conditions. Two types of SO2 sorption behaviors were observed for these DMPDA-functional copolymers: SO2 sorption capacity was very high irrespective of slow sorption/desorption rates (type I), and the sorption/desorption rates were very fast while SO2 sorption capacity was small (type II). Fourier transform infrared analysis and dielectric loss measurement revealed that the type II sorption behavior was obtained for the highly crosslinked DMPDA-functional copolymers. The degree of cross-linking was affected by both the solvent used to react DMPDA with the copolymer and the percent conversion of the chloromethyl styrene group. It was confirmed that DMPDA-functional copolymers having a highly crosslinked structure are suitable materials in quartz crystal microbalance (QCM)type polymeric SO2 gas sensors. (C) 2003 Wiley Periodicals, Inc.

DOI： 10.1002/app.12135

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The effect of NH3 gas on the electrical conductivity of four kinds of polyaniline-insulating matrix polymer blend films was investigated for the purpose of preparing a practical NH3 gas sensor operable near or at room temperature. The electrical conductivity of all blend films measured in N-2 was enhanced above a 2 wt.% of composition of polyaniline, The electrical conductivity decreased by exposure of the blend films to NH3 gas. It was found that the sensing characteristics depended on the kind of dopant species, measuring temperature, matrix polymers, and the solvent used for film preparation. Among the considered sensors, the polyaniline-poly(methyl methacrylate) blend film prepared with toluene as the solvent showed the fastest response and good reversibility, because the porous film was obtained only by this combination. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(01)00504-5

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The sorption behavior of water vapor and CO2 gas in photocrosslinked poly(vinyl cinnamate) (PVCA) film was examined at 30 degreesC under atmospheric pressure. Both the water sorption isotherm and the CO2 sorption isotherm obtained with quartz crystal microbalance (QCM) method obeyed the simple Langmuir's equation. Water vapor/CO2 mixed-gas sorption isotherms were also obtained. Total amount of sorbed mixed gases was clearly influenced by the partial pressure of water vapor (p(w)) and CO2 gas (p(c)) in the atmosphere. A modified Langmuir's equation based on a dual-site model was employed for predicting the competitive adsorption isotherm, and the isotherm was clearly described by the equation. The theoretically estimated amount of adsorbed water at the constant p(w) decreased slightly with increasing p(c). The effect of this phenomenon on the sensitivity of the capacitive-type relative humidity sensor was examined. As expected, the electrical capacitance of the sensor at the constant relative humidity decreased because of the coexistence of CO2 gas. However, the influence was quite small in the CO2 concentration range in the ordinary environment. (C) 2002 John Wiley & Sons, Inc.

DOI： 10.1002/app.10062

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The QCM-type SO2 gas sensors were fabricated using amino-functional poly(styrene-co-chloromethyl styrene) derivatives. Three kinds of diamine compounds, DMEDA, DMPDA and DPEDA, were comparatively used to introduce amino groups into the copolymer. The response time was the shortest for the sensor using the DPEDA functional copolymer, though the sensitivity was the smallest at the same measuring temperature. Sensing characteristics were affected by the measuring temperature and by the mole fraction of chloromethylstyrene in the copolymers. Further, a small addition of organically modified siloxane oligomer was effective for further reduction of the response time. The sensor using the DPEDA functional copolymer containing 5 wt.% of siloxane oligomer had the fastest response time (t(100) = 11 min) and complete reversibility even at 50 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-4005(01)00735-3

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Poly(2-acrylamido-2-methylpropane sulfonic acid), AMPS, and its alkali salts were prepared. The impedances of these polymers were measured at various humidities and temperatures in the frequency range of 100-1 MHz. The results suggest that in the films of the alkali salts of poly(AMPS) containing 1-2 water molecules per AMPS monomer unit in the low and medium humidity ranges, the majority carrier is the alkali cations. For practical use, a humidity sensor, which is completely water-resistive, was prepared by forming an interpenetrating polymer network composed of a copolymer containing AMPS and hydrophobic poly(ethylene glycol dimethacrylate). (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0013-4686(00)00746-5

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The sorption behavior of CO2 gas in photocrosslinked poly(vinyl cinnamate) film was examined under atmospheric pressure. The sorption isotherm was well described by the Langmuir equation, suggesting that sorption of CO2 is mainly governed by adsorption in the microvoids. The amount of sorbed CO2 was significantly affected by the degree of crosslinking. The CO2 sorption was enhanced at a lower degree of crosslinking but was decreased at a higher degree of crosslinking. The unexpected increase in the amount of adsorbed CO2 correlated with the increase in the number of microvoids that occurred as a result of the crosslinking reaction. However, further crosslinking led to a decrease in the mean size of the microvoids. The smaller microvoids, in comparison to CO2 molecules, did not act as adsorption sites, so that the amount of sorbed CO2 decreased. (C) 2000 John Wiley & Sons, Inc.

DOI： 10.1002/1097-4628(20001205)78:10<1744::AID-APP50>3.0.CO;2-V

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A resistive-type humidity sensor was prepared using a poly(chloromethyl styrene) (PCMS) film which was simultaneously cross-linked and quaternized. The impedance dependence on humidity for samples with various reaction degrees was measured. The sorption isotherm curves of water vapor in the cross-linked films were obtained using the quartz crystal microbalance method for the various samples. It was found that the degree of hysteresis depends on the density of the quaternary ammonium group, which affects the diffusion coefficient of the water molecules in the film. (C) 2000 Elsevier Science S.A. All rights reserved.

DOI： 10.1016/S0925-4005(00)00313-0

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The long-term aging effects on capacitive-type relative humidify sensors in a hot and humid atmosphere were investigated to better understand the mechanism of the drift phenomenon. For this purpose, four kinds of polymers, cellulose acetate (CA), cellulose acetate butyrate (CAB), poly(methyl methacrylate) (PMMA), and cross-linked polyimide (PI) were used as sensing materials. For all sensors, the electrical capacitance increased with aging in a 40 degrees C and 90% relative humidity atmosphere. The QCM measurement showed that the drift of the sensor capacitance was caused by the increase in the water sorption ability of the sensing polymers. From XPS data, the increase in the water sorption ability could be attributed to the introduction of the oxygen-containing group at the surface of the sensing polymers. Morphological changes were also suggested by the film thickness measurement. Furthermore, it was confirmed that the magnitude of the drift was affected not only by the increment but also by the state of the sorbed water. Fourier transform infrared data indicated that the sorbed water in the hydrophobic polymers such as PMMA and PI are close to the isolated state and that the state is hardly affected by aging. Because the change in the isolated water does not significantly affect the electrical capacitance, PMMA and PI sensors show little drift even after 250 days aging. (C) 2000 The Electrochemical Society. S0013-4651(00)01-074-0. All rights reserved.

DOI： 10.1149/1.1393608

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Most of the humidity sensors practically used are based on the change ill electrical properties of polymers or ceramics with humidity. They are either resistive-type or capacitive-type sensors. Various chemical modifications of polymeric materials have been utilized to improve the properties of sensors such as sensitivity, hysteresis, long-term stability, durability in unfavorable atmospheres such as dewdrops or vapors' of volatile organic compounds(VOC), etc. This paper overviews the novel methods of chemical modification which have been proposed by the authors.

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A double layer structure sensor (DLS sensor) consisting of a photocrosslinked PVCA and a PMMA film was prepared. Advantages of the photocrosslinked PVCA sensor and the PMMA sensor were reflected in the initial sensor performance of the DLS sensor. The sensing characteristics were affected by the thickness and the degree of crosslinking of the photocrosslinked PVCA layer. There was an optimum PVCA film thickness (around 0.1 mu m) for reducing the effect of both instantaneous and long-term coexistent acetone vapor.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

In order to fabricate a quartz crystal microbalance sensor to monitor a low percent of CO, gas at room temperature using polymeric materials, four different diamines, that is, athylenediamine, N,N-dimethylethylenediamine, N,N-dimethylpropanediamine, and N,N-dimethyl-p-phenylenediamine, were used to introduce an amino group into the chloromethyl group of poly(styrene-co-chloromethyl styrene). The polymers thus prepared have different branches with amino groups at their ends. The sorption isotherm was measured with quartz crystal oscillators coated with the polymer containing the amino group. The results were analyzed on the basis of the dual sorption model. It was found that the polymer with added ethylenediamine is the most sensitive to CO2, but the response and recovery time is twice as long as those with the other polymers.

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The drift phenomenon of capacitive-type relative humidity sensors in a 40 degrees C and 90 %RH atmosphere was investigated. Four kinds of polymers that have different water sorption abilities were used as the sensing materials. The percent change in the drift was in the order of CA approximate to CAB much greater than PMMA approximate to PI sensor. This order is the same as that of the water sorption ability of these polymers. From the measurement of the water sorption ability, it was confirmed that the drift depended not only on the amount of increased sorbed water but also on the state of the sorbed water. A small change in the clustered water in the hydrophilic polymers caused a large change in the electrical capacitance.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Newly developed crosslinked polyimide and fluorinated polyimide-based humidity sensors were fabricated for office building and factory applications. Both sensors showed good initial sensor performance. The stability and the reliability of these sensors were evaluated by exposing the sensor elements to various test conditions. The crosslinked polyimide sensor was resistant to chemicals and the crosslinked fluorinated polyimide one exhibited long-term stability in harsh environments. By using these sensors properly, their sensor performance is superior to that of most commercially available capacitive-type sensors. (C) 1998 Elsevier Science S.A. All rights reserved.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The water sorption behavior of polymers for a capacitive-type humidity sensor was examined using three different techniques. The sorbed water in hydrophilic polymers with a pyridine or hydroxyl group was highly bound and that in less hydrophilic polymers with a carbonyl or ether group was loosely bound to the polymer as determined from the sorption analysis. Among less hydrophilic polymers, the tendency to form the clustered sorbed water molecules was higher for PEC and EC, which have an ether oxygen as the hydrogen bonding basicity. The results of this study proved that cluster formation of sorbed water of a sensing polymer was closely related to the sensor's characteristics. The polymers with a weak hydrophilic site, which have a low hydrogen bond propensity, are suitable for the capacitive-type humidity sensor. (C) 1998 Elsevier Science S.A. All rights reserved.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Sorption behavior of CO2 in the photocrosslinked poly(vinyl cinnamate) film was examined, The amount of sorbed CO2 was enhanced with the degree of crosslinking, while the amount decreased beyond ca.95 % crosslinking.

DOI： 10.1246/cl.1998.229

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD PUBLISHING CORPORATION  

A resistive-type humidity sensor was prepared using a poly(chloromethyl styrene) film which was simultaneously cross-linked and quaternized. The humidity dependence of impedance for samples with various degrees of reaction was measured. The sorption isotherm curves of water vapor in the cross-linked films were obtained using the quartz crystal microbalance method for the various samples. It was found that the degree of hysteresis depends on the density of the quaternary ammonium group which affects the diffusion coeffecient of the water molecules in the film.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A solvatochromic method was used to characterize the water sorption behavior of polymer films. Four different dyes were dissolved in various solid polymers and the relative water vapor pressure in the atmosphere was changed. Evaluated solvatochromic parameters depended not only on the amount of sorbed water but also on the kind of polymer. A linear correlation between the E(T)(30) value and Taft's multiparameter was confirmed in both the dried and the water sorbed polymers. The correlation equation was almost identical to that obtained by other researchers in liquid solvents. These results suggest that the dissolved dyes behave as indicators of microenvironmental changes in the solid polymer film. (C) 1997 John Wiley & Sons, Inc.

DOI： 10.1002/(SICI)1097-4628(19970321)63:12<1681::AID-APP18>3.0.CO;2-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Studies on humidity sensors fabricated with organic polymers for the last 10 years are reviewed. Several useful methods for improving the characteristics of humidity sensors based on polymers are proposed. In the case of a resistive-type sensor, cross-linking of hydrophilic polymers or formation of interpenetrated polymer networks with a hydrophobic polymer makes the hydrophilic polymers durable at high humidities. Graft polymerization is another method of preparing water-resistive humidity sensors. In the case of capacitive-type sensors, cross-linking is also useful to modify the hydrophobic polymer to produce a sensor with small hysteresis, high selectivity and high sensitivity.

DOI： 10.1016/S0925-4005(96)02019-9

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A cross-linked PVCA film was prepared on a suitable substrate by using a photoirradiation technique and evaluated as a capacitive-type humidity sensor. The sensing characteristics were considerably affected by the degree of cross-linking in the film. The sensitivity was particularly enhanced up to ca. 95% cross-linking, beyond this the sensitivity decreased. This has been explained by the variation in the ability to adsorb water with the degree of cross-linking. Similar behavior was observed for the adsorption of organic vapors and the adsorption of the larger organic vapors was greatly reduced by using the highly cross-linked polymer. This behavior was explained by the molecular sieve effect of the cross-linked film. It was confirmed that the effect of coexistent acetone vapor was considerably smaller for the sensor using highly cross-linked PVCA film.

DOI： 10.1016/S0925-4005(96)01826-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MYU, SCIENTIFIC PUBLISHING DIVISION  

N,N-dimethylaminoethyl methacrylate (DMAEM)-methyl methacrylate (MMA) copolymers with several different compositions were prepared by gamma-ray irradiation. The sorption of carbon dioxide on the copolymer was measured by the frequency change of the 4 MHz quartz oscillators coated with the copolymers. Carbon dioxide sorption on the DMAEM-MMA copolymer was characterized by the dual sorption model (Henry type and Langmuir type). The fraction of Henry-type sorption is the smallest for the copolymer with 0.1 DMAEM mole fraction. A fast-response sensor could be fabricated when a copolymer with 0.1 DMAEM mole fraction was used.

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A cross-linked PVCA film was prepared on the substrate by using photoirradiation technique and it was applied for the capacitive-type humidity sensor. The sensitivity was enhanced until the cross-linking degree became ca. 95%, while further progress of the reaction resulted in the decrement of the sensitivity. This was related to the variation of water adsorption ability with the cross-linking degree. A similar behavior was observed for the adsorption of other organic vapors. These behaviors were explained by the microhole distribution change in the film with the progress of the cross-linking reaction.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

In order to prepare a resistive-type humidity sensor that is durable at high humidities or even in dewing, poly(chloromethyl styrene) is simultaneously crosslinked and quaternized (that is, a quaternary ammonium group is added to the polymer) by the reaction with N,N,N',N'-tetramethyl-1,6-hexanediamine on the surface of an alumina substrate on which a pair or gold electrodes is previously deposited. The sensor is durable even after soaking in water for two hours. The response time is shorter in samples with a higher degree of quaternization. An interpenetrating polymer network (IPN) film is also formed on a similar substrate using the crosslinked quaternized poly(chloromethyl styrene) and ethyleneglycol dimethylacrylate. A sensor based on the IPN film has a shorter response time than a sensor based on the crosslinked quaternized poly(chloromethyl styrene).

DOI： 10.1016/0925-4005(95)85152-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

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A capacitive-type relative-humidity sensor utilizing a thin polysulfone (PSF) sensing material has been fabricated to achieve reproducible relative-humidity measurements with long-term stability even in hot and humid conditions. The sensor showed a good initial performance with 0.5%U(%r.h) hysteresis and 0.1±0.1%U °C-1 temperature coefficient of capacitance along with good stability with less than +3%U shift after 1000 h of exposure to 40 °C, 90%U conditions. © 1995.

DOI： 10.1016/0925-4005(95)85153-4

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A solid film consisting of triethylene glycol, K2CO3-polyethylene glycol of high mol. wt., was prepared on a sintered alumina substrate with a pair of golden electrodes and their electrical conductivity was measured. When CO2 gas was introduced into the air, the conductivity decreased. This change was reversible. The sensitivity to CO2, designated as (change in conductivity caused by CO2)/(conductivity in air), was the highest when a polyethylene glycol of mol. wt. 6000 was used. The sensing mechanism was interpreted in terms of the change in concentration of the charge carrier K+ ion by CO2. © 1995.

DOI： 10.1016/0254-0584(95)80043-3

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Capacitive-type humidity sensors were prepared using four kinds of polymerized vinyl carboxylate, i.e., vinyl benzoate, vinyl methacrylate, vinyl crotonate and vinyl cinnamate. These monomers have different chemical structures and vinyl methacrylate and vinyl crotonate formed a cross-linked film. The sensitivity was enhanced by proceeding the cross-linking reaction. This is due to the increase in the water sorption ability The temperature coefficient of the sensitivity decreased by using the cross-linked polymer. Although the electrical capacitance of all sensors was affected by acetone vapor, the capacitance of the cross-linked sensor recovered to the initial value after removal of the acetone vapor. The cross-linking technique was effective for forming a rigid film which prevents the swelling of the polymer in the acetone. vapor. The present cross-linked humidity sensor is suitable for practical use.

DOI： 10.1149/1.2054779

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Water sorption behavior of four kinds of polymerized vinyl carboxylate, i.e., vinyl benzoate, vinyl methacrylate, vinyl crotonate, and vinyl cinnamate was investigated. The dielectric measurement and quartz crystal microbalance technique were adopted for this purpose. The polymers were hydrophobic and the water sorption ability was enhanced by cross-linking. The dielectric constant of sorbed water was small compared with that of liquid water and the value slightly increased with increasing the amount of sorbed water. The orientation polarization of sorbed water also slightly increased with increasing the amount of sorbed water. It was proved that the cross-linking structure affected the water sorption behavior of the polymer.

DOI： 10.1246/bcsj.67.46

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An interpenetrating polymer network (IPN) film composed of cross-linked 2-hydroxy-3-methacryloxypropyl trimethylammonium chloride (HMPTAC) polymer and cross-linked ethylene glycol dimethacrylate (EGDMA) polymer was formed on a sintered alumina substrate with interdigitated gold electrodes to fabricate a water resistive humidity sensor. The impedance of the sensor decreased from ca. 10(7) OMEGA to ca. 10(2) OMEGA with increasing relative humidity from 0 to 90% (%RH). In spite of cross-linking and interpenetration with the hydrophobic polymer, the sensitivity to humidity is almost the same as that of an HMPTAC homopolymer sensor. Further, little hysteresis was observed. The characteristics of this IPN sensor changed little even after soaking in water for 120 min. It was found that this sensor is more resistant to water than other IPN sensors which were prepared in our laboratory using melamine resin or 2-hydroxyethyl-methacrylate (HEMA) polymer as a second incorporating polymer as previously reported. It appears that this is due to good compatibility between HMPTAC and EGDMA.

DOI： 10.1149/1.2221063

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic Publishers  

The sensing properties and characteristics of a zircon-based sodium ionic conductor as an electrochemical CO2 gas sensor which can be expressed as O2, Pt|Na ion conductor|Pt, Na2CO3, CO2, O2 were examined. The electro motive force (e.m.f.) was found to be a function of the logarithm of CO2 concentration and the 90% response time was less than 2 min at 430°C while the number of electrons for the electrochemical reaction was slightly above than 2. The coexistence of water molecules (≥ 90% RH) induced the response time delay and the lowering of the e.m.f. value. Changes in the response characteristics were mostly recovered after cutting off the water vapour, while the recovery time was prolonged when the working temperature was increased. © 1993 Chapman &amp
Hall.

DOI： 10.1007/BF00367559

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A capacitive type relative humidity sensor utilizing newly developed cross-linked fluorinated polyimide has been fabricated using thin film technology and evaluated for commercial building and factory applications. The sensor showed a good initial performance with less than 1% r.h. hysteresis and a 0 ± 0.1% r.h./°C temperature coefficient of capacitance along with good stability especially under high temperature and high humidity conditions. Also, because of the inherent chemical resistance of the polyimide, good sensor stability when subjected to volatile environments has been demonstrated. © 1993.

DOI： 10.1016/0925-4005(93)85331-4

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A cured acetylene-terminated polyisoimide oligomer was used to prepare a capacitive-type humidity sensor. Sorption behavior of water on the cured film was examinedby measuring the dielectric constant and water content. The amount of sorbed water was small and the sorbed water did not form clusters. This is due to the hydrophobic nature and rigid structure of the film. The sorption behavior reflects its excellent sensor properties, i.e., low hysteresis, low temperature coefficient, durability against acetone vapor, and long-term stability in a high temperature and humid atmosphere. Among the polyimides prepared by curing the oligomers with different chain lengths, the mostsuitable composition for a reliable capacitive-type humidity sensor was API-3-API-1. © 1993, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2056166

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DOI： 10.1016/0925-4005(93)85120-Y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

The sensing characteristics of an NO2 gas sensor using lead phthalocyanine thin film are influenced by heat-pretreatment time and ambient gas. The response behaviour of conductance for the change in ambient gas was characterized using Elovich's equation. The first stage in the adsorption and desorption kinetics reflects surface phenomena and the second stage the film diffusion. Both components were improved by heat treatment in air. The rising time in the NO2 adsorption process was within 2 min, and the recovery time within 5 min at 130-degrees-C for the film annealed in air for 1 h. The heat pretreatment induced the formation of a continuous layer of fine particles, approximately 0.1 mum in size, and larger single crystals isolated from each other, which formed on the continuous layer. The formation of the larger single crystals is not preferable in fabricating a sensor with fast rising and recovery times.

DOI： 10.1007/BF02403819

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Addition of Na2O-Y2O3-SiO2 glass to Na5YSi4O12 during the sintering process induced enhancements in conductivity and decrease in its activation energy. The highest conductivity and activation energy were 1.3 x 10(-1) S cm-1 at 300-degrees-C and 0.21 eV, respectively, for Na5YSi4O12 with about 20 wt % Na2O-Y2O3-SiO2 glass which was sintered at 1 000-degrees-C. This improvement may be caused by the formation of a Na5YSi4O12 phase from the added glass. Such an improvement in the electrical characteristics was not achieved by the addition of 10 wt % or more Na2O-Al2O3-4SiO2 glass or alpha-alumina in which the conductivity decreased monotonically with an increase in the amount of additive.

DOI： 10.1007/BF01105272

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

By using composite films of hydrolysed nafion and dyes having cyanine or triphenyl structures and with a terminal N-phenyl group, an optical humidity sensor has been fabricated. In the reflection mode, the optical intensity of the absorption peaks which depend on the used dyes decreases with relative humidity. The raising and recovery times are less than 1 min. In dry air, the alkyl amine group reacted with SO3H of hydrolysed nafion and formed a proton additive. Sorption of water molecules induces the deprotonation of the quaternized ammonium group.

DOI： 10.1007/BF01105279

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

By using Reichardt's betain dye dispersed in poly(methyl methacrylate) thin film, a bifunctional optical humidity sensor was fabricated. The optical intensity and the wave-length of maximum observed at around 780 nm were sensitive to the humidity. The characteristic of the dye dispersed in polymer was also influenced by the hydrogen bond acidity of the polymer matrix.

DOI： 10.1246/cl.1992.53

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By using composite films of hydrolyzed Nafion and dyes having a terminal N-phenyl group, an optical humidity sensor has been fabricated. In the reflection mode, the optical intensity of the absorption peaks which depend on the dyes used was influenced by relative humidity. In dry air, the alkyl amine group reacted with SO3H of hydrolyzed Nafion and formed a proton additive. Sorption of water molecules induces the deprotonation of the quaternized ammonium group. © 1992.

DOI： 10.1016/0925-4005(92)80340-4

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Language：English   Publishing type：Research paper (international conference proceedings)  

An interpenetrating polymer network (IPN) film composed of cross-linked 2-hydroxy-3-methacryl-oxypropyl trimethylammonium chloride (HMPTAC) polymer and cross-linked ethylene glycol dimethacrylate (EGDMA) polymer was formed on a sintered alumina substrate with interdigitated gold electrodes to fabricate a water-resistive humidity sensor. The impedance of the sensor decreased from ca. 10 7 Ω to ca. 10 2 Ω with increasing humidity from 0% RH to 90% RH. In spite of the cross-linking and interpenetrating with the hydrophobic polymer, the sensitivity is almost the same as that of the HMPTAC homopolymer sensor. Little hysteresis was observed. The characteristics of this IPN sensor changed little even after soaking in water for 120 min. This sensor is more water-resistive than other IPN sensors prepared by using melamine resin or HEMA polymer as a second incorporating polymer. It seems that this is due to the good compatibility of HMPTAC and EGDMA.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

By using Nafion(R) film with crystal violet or pink FGH(R), the optical humidity sensor has been fabricated. In the reflection mode, the optical intensity of the peak at 630 nm for crystal violet and at 540 nm for pink FGH decreases with relative humidity. The raising and recovery times are less than 1 min.

DOI： 10.1246/cl.1991.717

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The conductance of a semiconductor can be expressed by the Meyer-Neldel relation, i.e., σ = σ*exp(E/kT*)exp(-E/kT)
the adsorption of an oxidative molecule induces a decrease in the activation energy, while the pre-exponential factor is almost unchanged. T* for phthalocyanine films is considerably higher than that for whiskers. This difference arises because the interaction between phthalocyanine and an adsorbed molecule is a function of the depth from the phthalocyanine surface. The activation energy for conduction is almostly uninfluenced by the crystal form, i.e., film and whisker. © 1991.

DOI： 10.1016/0925-4005(91)80157-F

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By using Nafion1 film with tri-phenylcarbinol, the optical fiber humidity sensor was fabricated. The optical intensity around 450 nm in the reflection mode increases with the relative humidity. The resolution, i.e., the sensitivity to the relative humidity decreases in the range above 30% relative humidity. In a dry atmosphere, the dye exists in the form of tri-phenylcarbonium ion, and with increasing the relative humidity, the dye structure changes from the carbonium ion to carbinol. © 1991, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2085639

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A capacitive-type humidity sensor was prepared using cross-linked poly(methyl methacrylate) (PMMA). The electrical capacitance changed linearly with the relative humidity over the range of 10-90% RH and the sensitivity (the ratio of capacitance at 90% RH to that at 10% RH) was about 1.13. The amount of sorbed water on PMMA at 90% RH was 25 mg/g which was one-third of that on cellulose acetate butyrate. This low hygroscopicity of PMMA was effective in reducing any hysteresis. The decrement of temperature coefficient and high durability for acetone vapor were achieved using the crosslinked PMMA film with divinyl benzene or ethylene glycol dimethacrylate as the cross-linking agent. © 1991, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2085886

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On polytetrafluoroethylene films (0.05 and 0.5 mm thick), polyvinylpyridine was graft-polymerized by γ-ray irradiation. After quaternization of the pyridyl group of the grafted films, sandwich and surface-type sensors were prepared by vacuum deposition of gold electrodes. Electrical properties of these resistive-type sensors were studied in relation to the grafting ratio as well as the amount of sorbed water. Scanning electron microscopy observations and impedance measurements suggest that for the 0.05 mm film, graft-polymerization proceeds homogeneously into the film, while for the 0.5 mm film, the reaction is limited only near the surface of the film and is inhomogeneous. The prepared sensor is completely resistant to water. © 1991, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2085997

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By using Nafion® film with crystal violet and malachite green, an optical-fibre and quartz oscillator type humidity sensor has been fabricated. The optical intensity, with a minimum at 615 nm in the reflection mode, decreases with relative humidity for a film with malachite green. The rise and recovery times are less than 1 min and the hysteresis is only ± 1%RH at 50%RH. For the film with crystal violet, a similar characteristic is confirmed at 630 nm. Composite films can be used as an optical and quartz oscillator type humidity sensor, since the sorption of water induces colour and oscillating frequency changes. © 1991.

DOI： 10.1016/0924-4247(91)87038-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

DOI： 10.1007/BF00727867

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The interfacial tension between hexane solution of cholesterol and water was measured as a function of temperature and the mole fraction of cholesterol in hexane under atmospheric pressure. The interfacial tension vs. mole fraction of cholesterol curve was observed to have two break points at a certain temperature
the concentration of the break point increases with increasing temperature. The experimental results were analyzed by applying the rigorous thermodynamics of adsorption at interfaces developed previously. The excess number of moles of cholesterol and the thermodynamic quantity changes associated with its adsorption were found to show the discontinuous changes at the break points. It was concluded that the first-order phase transition takes place from the gaseous to the expanded state and from the expanded to the condensed one in the adsorbed film of cholesterol at the hexane/water interface.

DOI： 10.1246/bcsj.63.17

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

For LiLi-form, the decomposition of dilithium zirconium phosphate with a layered structure and formation of lithium dizirconium triphosphate and zirconium pyrophosphate was achieved by firing at 600°C or above. For NaNa- and KK-forms, any distinct variations of the external apperance were not confirmed by heat-treatments, while the crystal growth was detected for RbRb- and CsCs-forms fired at 900°C. For half ion-exchanged forms, monovalent cation dizirconium triphosphate was mainly formed on heating up to 600°C or above. The activation energy in ionic conduction decreases with increasing monovalent cation radius. This dependency can be realized by Anderson and Stuart&#039;s model based on the classical ideas of ionic crystal theory and elasticity theory. The activation energy for the fully exchanged form is slightly higher than that for the half-exchanged form and the pre-exponential factor in σT=σ0 exp (-E/kT) for the former is less than that for the latter. © 1989 Chapman and Hall Ltd.

DOI： 10.1007/BF02385425

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In zirconium bis(monohydrogen phosphate)monohydrate, the stability of water of crystallization and of the crystal form was strongly influenced by its crystal size. The water of crystallization of a smaller crystal was completely released on heating to 200° C while a part of this water was held at 300° C in a larger crystal with a diameter of several micrometres. While a smaller crystal was decomposed by heating to 900° C and cubic zirconium pyrophosphate was formed, for a larger crystal, α-layered zirconium pyrophosphate was formed instead of cubic zirconium pyrophosphate and a layered structure was held. For the Na2-, K2- and Rb2-forms, good layer structure was retained even by heating to 1000° C. For the Li2-form, the layer structure was decomposed on heating at or above 900° C. The thermal stability of the layered structure increased with increasing crystal size and ionic radii of the alkali cation. © 1989 Chapman and Hall Ltd.

DOI： 10.1007/BF01107423

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

An hydrophilic monomer, 2-hydroxy-3-methacryloxypropyl trimethylammonium chloride, was graft-polymerized in a microporous polyethylene film using three different initiation methods, that is, with benzyl peroxide, pre-U.V. irradiation and mutual photo-initiation. Humidity dependence of the impedance was measured for the grafted microporous polyethylene films. Among the three graft polymers, the one prepared by pre photo-irradiation seems to have the most homogeneously grafted layer. The impedance increases as the grafting percentage increases except in the low grafting percentage region. The response time for the abrupt change of humidity becomes longer as the grafting percentage increases. The activation energy for conductivity has a maximum at 40% relative humidity in the plot of activation energy against humidity. © 1989 Chapman and Hall Ltd.

DOI： 10.1007/BF00660939

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Poly(4-vinylpyridine) was simultaneously cross-linked and quaternized with α, ω-dichloroalkane on the surface of an alumina substrate that had a pair of gold electrodes on it. The impedance of this device varied from 107 to 103Ω for the entire humidity range. The effect of preparation conditions such as reaction time or quaternizing reagents on the electrical properties as a humidity sensor was investigated. The resistivity depends on the amount of sorbed water regardless of the degree of quaternization. © 1989, The Electrochemical Society, Inc. All rights reserved.

DOI： 10.1149/1.2096579

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Two types of humidity sensors were prepared from organosilicon compounds having hydrophilic groups such as NH2, N +(CH3)3Cl- and SO3H. The first is a pressed silica gel disk grafted with hydrophilic organosilicon compounds. The second type is a sintered alumina plate on which a cross-linked organopolysiloxane film having a hydrophilic group was formed. The impedance was measured in the humidity range 0 - 100%. The impedance varies with the hydrophilic group in the order SO3H &lt
N +(CH3)3Cl- &lt
NH2 &lt
OH. Also the amount of adsorbed water depends on these groups, according to the order N +(CH3)3Cl- &gt
SO3H &gt
NH2 &gt
OH. The grafted silica gel device is quite resistant to water. The humidity-sensing characteristics of the alumina-plate type sensor do not change even after soaking in water for several hours. © 1989.

DOI： 10.1016/0250-6874(89)85006-1

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Language：English   Publishing type：Research paper (international conference proceedings)  

2-Hydroxy-3-methacryloxypropyl trimethylammonium chloride was grafted on to the pore wall of microporous polyethylene film by a γ-ray pre-irradiation method. A humidity sensor was prepared by depositing gold electrodes on both surfaces of the grafted film. Complex impedance measurements were carried out at various humidities. From the complex impedance analysis, the values of parallel resistance and parallel capacitance were estimated. The parallel resistance decreased as the humidity increased, while the parallel capacitance remained constant. The parallel resistance also decreased as the grafting ratio increased. The value of parallel resistance depends on the amount of sorbed water in the film. The sensor is stable for a long time in ordinary atmospheric conditions. It is even stable in water for more than 2 h. The sensor prepared by γ-ray pre-irradiation at 9.0 × 104 R h-1 for 4 h was heat-resistant up to 130°C.

DOI： 10.1016/0032-3861(89)90081-5

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Language：English   Publishing type：Research paper (scientific journal)  

To improve the electrical conductivity of sodium aluminosilicate glass and Na3Zr2Si2PO12 crystal, crystal-glass composite systems were examined. For the ceramics with a lower content of the glass, the activation energy of ionic conduction was lowered and the conductivity enhanced by adding glass and the pre-exponential factor was lowered. Whilst the activation energy of ionic conduction of Na2O-Al2O3- XSiO2 (X=4, 6) glasses could not be lowered to the limiting value of ca. 0.5 eV, the glass-based sample doped with Na3Zr2Si2PO12 powder indicated that the high ionic conductivity and its activation energy was lowered to ca. 0.3 eV. The composite of Na3Zr2Si2PO12 crystalline powder and sodium aluminosilicate glass is a useful material to the solid electrolyte. © 1989, Chapman and Hall Ltd.. All rights reserved.

DOI： 10.1007/PL00020211

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Humidity dependence of impedance was examined by using the complex impedance analysis for fine crystalline zirconium bis(monohydrogen phosphate) monohydrate and its alkali salts. The value of C0 in Cp(ω)=C0(j ω/ω0)-α was hardly dependent on the relative humidity and monovalent cation species. The resistive component and its activation energy decreased with increase in the relative humidity and the former was expressed as R=R* exp (-E/kT*) exp (E/kT) The pre-exponential factor R*, was hardly influenced by the humidity and decreased when the acidic protons were replaced with monovalent alkali cations. The activation energy of conduction was strongly affected by the degree of orientation and particle size of crystal with layered structure in a whole humidity region and increased by replacing the protons by alkali cations. © 1988 Chapman and Hall Ltd.

DOI： 10.1007/BF00547435

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer-Verlag  

DOI： 10.1007/BF00255390

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

DOI： 10.1007/BF01730591

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Language：Japanese   Publisher：The Surface Science Society of Japan  

Ceramics are useful materials for humidity sensing device because the electric impedance of porous ceramics is strongly affected by the humidity in atmosphere. The sensitivity could be controlled by the pore structure, surface area and/or chemical modification of the pore wall surface. For the sample where the surface occupancy area of acidic protons was larger than ca. 0.1nm<SUP>2</SUP>, the impedance value at 90% r.h. was controlled by the surface area and the morphologies of pores. In the range below 0.1nm<SUP>2</SUP>, the impedance especially for >40% r.h. could be lowered without any increase in the surface area and was reciprocally proportional to the concentration of acidic protons. The introduction of alkali ions to the pore wall surface instead of protons is a preferable method to improve the humidity sensitivity and durability. It is difficult to lower the impedance for <30% r.h. by the introduction of acidic protons and/or alkali cations. To lower the impedance for the lower humidity region, the use of super ionic conductor or ferroelectrics instead of usual insulating metal-oxide was proposed.

DOI： 10.1380/jsssj.9.427

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER VERLAG  

Inside a microporous polyethylene film, 2-acrylamido-2-methylpropane sulfonic acid was graft polymerized by ultraviolet irradiation. A humidity sensor was fabricated by depositing gold electrodes on both sides of the grafted film. The impedance was measured as a function of humidity for the acid and alkali salts of sulfonate. The sensor has long term stability and is resistant to water. © 1987 Springer-Verlag.

DOI： 10.1007/BF00255333

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Humidity sensing devices were prepared by using fine porous (Pb, La)(Zr, Ti)O3 (PLZT) particles with ferroelectricity instead of insulating metal oxides such as alumina and zircon. The impedance of PLZT with 1 wt %. KH2PO4 was 106 Ω and lower than that of zircon with 3.8 wt % KH2PO4 by a factor of 102 in a dry atmosphere. In addition, the impedance in a humid atmosphere was controlled by the adding of potassium dihydrogen phosphate and changed by about four orders of magnitude in the humidity region 0 to 90% relative humidity at 1 kHz for samples burnt at 700° C. The humidity dependence of impedance is mainly governed by the change of coverage of adsorbed water. The hydrophilicity is affected by the burning temperature and lanthanum content of PLZT used as starting particle for porous PLZT ceramics burnt with KH2PO4. From complex impedance analysis it is confirmed that the resistive component inserted in parallel with the capacitive component decreases steeply with an increase in humidity, while the capacitive component is poorly dependent on the humidity. © 1987 Chapman and Hall Ltd.

DOI： 10.1007/BF01161478

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Language：English   Publisher：ELECTROCHEMICAL SOC INC  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHAPMAN HALL LTD  

Humidity-impedance characteristics were examined for amorphous and crystalline zirconium phosphate. The impedance of crystalline zirconium phosphate is lowered with decreasing particle size. While the impedance of amorphous zirconium phosphate increases steeply with an increase in the burning temperature, the impedance is poorly dependent on burning temperature for crystalline zirconium phosphate in a humid atmosphere. Fine-grained crystalline zirconium phosphate is a suitable material for use as a humidity sensing device because of its humidity sensitivity and response to humidity changes. The existence of amorphous phases is responsible for the increase in response time. © 1987 Chapman and Hall Ltd.

DOI： 10.1007/BF01086500

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Language：English   Publisher：ELECTROCHEMICAL SOC INC  

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Language：Japanese   Publisher：化学センサ研究会  

CiNii Books

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：The Society of Polymer Science, Japan  

DOI： 10.1295/kobunshi.52.479

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Effect of NH_3 gas on the electrical conductivity of polyaniline-insulating polymer blend films was investigated for the purpose of preparing a practical NH_3 gas sensor. The sensing characteristics depended on the kind of insulating polymers and dopant species, the solvent used for film preparation, measuring temperature, and heat-treatment temperature. Among the sensors prepared in this study, the polyaniline and rudder-type polysiloxane blend film treated at 120℃ showed the fast response time, large sensitivity, and good reversibility.

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CiNii Books

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