• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.44-47
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• 2000

In the recognition of the gases using the quartz crystal microbalance (QCM) coated with the film materials, it is important to obtain the recognition ability of gases, and the stability of film coated above the QCM. Especially, the thickness of film coated above the QCM is decreased according with the using circumstance and time of QCM gas sensor. Therefore, the sensing characteristics of film is changed with these. In this paper, we coated the lipid PC (Phosphatidyl Choline) materials varing with the blended amount of PVC(Poly Vinyl Chloride) and solution (Tetra Hydrofan:THF) above QCM to obtain the sensitive and the stability of lipid PC film. QCM gas sensors coated with film materials were measured the frequency change in the chamber of stationary gas sensing system injected 1-hexane, ethyl acetate, ethanol and benzene of $20{\mu}{\ell}$, respectively. We also measured the degradation characteristics of QCM gas sensor to show the properties of stability.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.361-368
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• 2008

Nanosized $SnO_2$ particles were synthesized by homogeneous precipitation method using tin chloride ($SnCl_4{\cdot}5H_{2}O$) and urea ($CO(NH_2)_2$). The powders were heated at $500^{\circ}C$ and $600^{\circ}C$ for 2h. The crystal structure, microstructure, thermal behavior, specific surface area were analyzed using XRD, FE-SEM, TGA and BET, respectively. The initial resistance and the $H_2$ sensing properties were measured as a function of ${Sb_2}{O_3}$ and Pd doping concentrations. The resistance was decreased with the addition of ${Sb_2}{O_3}$ and the sensitivity for $H_2$ gas was increased with the addition of Pd. Thus, the optimum $H_2$ gas sensing property was obtained in the 0.25.mol% ${Sb_2}{O_3}$ and 1.w% added $SnO_2$ powders.

• Korean Journal of Materials Research
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• v.26 no.9
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• pp.468-471
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• 2016

$SnO_2:CNT$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and were annealed at $300^{\circ}C$ in air. The nano $SnO_2$ powders were prepared by solution reduction method using tin chloride ($SnCl_2.2H_2O$), hydrazine ($N_2H_4$) and NaOH. Nano $SnO_2:CNT$ sensing materials were prepared by ball-milling for 24h. The weight range of CNT addition on the $SnO_2$ surface was from 0 to 10 %. The structural and morphological properties of these sensing material were investigated using X-ray diffraction and scanning electron microscopy and transmission electron microscope. The structural properties of the $SnO_2:CNT$ sensing materials showed a tetragonal phase with (110), (101), and (211) dominant orientations. No XRD peaks corresponding to CNT were observed in the $SnO_2:CNT$ powders. The particle size of the $SnO_2:CNT$ sensing materials was about 5~10 nm. The sensing characteristics of the $SnO_2:CNT$ thick films for 5 ppm $H_2S$ gas were investigated by comparing the electrical resistance in air with that in the target gases of each sensor in a test box. The results showed that the maximum sensitivity of the $SnO_2:CNT$ gas sensors at room temperature was observed when the CNT concentration was 8wt%.

• Polymer(Korea)
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• v.36 no.2
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• pp.169-176
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• 2012

Based on our experience in developing resistive humidity sensor, interdigital gold electrodes with different fingers and gaps have been fabricated on a glass epoxy (GE) substrate using screen printing techniques. The basic structure of the electrode consisted of a 3-, 4- and 5-fingers with gaps of 310 and 460 ${\mu}m$. Gold electrode/GE was prepared by first printing silver nanopaste, followed by consecutive electroless plating of Cu, Ni and then Au. Copolymer of [2-(methacryloyloxy)ethyl] dimethyl benzyl ammonium chloride (MDBAC) and methyl methacrylate (MMA) was used as a humidity-sensing polyelectrolyte, which was fabricated by a screen printing method on the Au electrode/GE substrate. The flexible humidity sensor showed acceptable linearity between logarithmic impedance and relative humidity in the range of 20-95%RH, low hysteresis of 1.5%RH, good response and recovery time of 75 sec at 1 V, 1 kHz, and $25^{\circ}C$. Electrode construction had a significant influence on the humidity-sensing characteristics of polymeric humidity sensors. The activation energy between electrode and ion conducting polyelectrolyte plays an important role in explaining the differences of humidity sensing characteristics such as temperature dependence, sensitivity, linearity and hysteresis.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.345-351
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• 2018

We employed an unprecedented technique to synthesize porous $WO_3@SnO_2$ nanofibers exhibiting core-shell and fiber-in-tube configurations. Firstly, 2-methylimidazole was uniformly incorporated in as-spun nanofibers containing ammonium metatungstate hydrate and the sacrificial polymer (polyacrylonitrile). Secondly, the 2-methylimidazole on the surfaces of nanofibers was complexed with tin(II) chloride ($SnCl_2$) via simple impregnation of the as-spun nanofibers in ethanol containing tin(II) chloride dihydrate ($SnCl_2{\cdot}2H_2O$). The presence of vacant p-orbitals in tin (Sn) and the nucleophilic nitrogen on the imidazole ring allowed for the reaction between $SnCl_2$ and 2-methylimidazole, forming adducts on the surfaces of the as-spun nanofibers. The calcination of these nanofibers resulted in porous $WO_3@SnO_2$ nanofibers with a higher surface area ($55.3m^2{\cdot}g^{-1}$) and a better response to 1-5 ppm of acetone than pristine $SnO_2$ NFs synthesized using a similar method. An improved response to acetone was achieved upon functionalization of the $WO_3@SnO_2$ nanofibers with catalytic palladium nanoparticles. This work demonstrates the potential application of $WO_3@SnO_2$ nanofibers as sensing layers for chemiresistive sensory devices for the detection of acetone in exhaled breath.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.436-442
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• 2014

In this study, we developed an optical-fiber sensor using cobalt chloride solution to monitor temperature in real-time between long distance points unaffected by the electro-magnetic wave and the vibration. Cobalt chloride solutions were made using 10% water and 90% ethanol (v/v) solution. The transmittance of these solutions was analyzed on 655 nm using UV-Visible spectrometer regarding temperature change. Also 30.8 mM cobalt chloride solution was gelled by dissolving polyvinyl butyral and the transmittance of this was analyzed on 655 nm regarding temperature change. The results of transmittance and optical power measurement showed decrease of both transmittance and optical power with increase of temperature from 66.8% and 149.5 nW at $25^{\circ}C$ to 7.1% and 48 nW at $70^{\circ}C$, respectively. These results support the possibility of gelled cobalt chloride/polyvinyl butyral as an optical-fiber sensor to monitor temperature change.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.49-57
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• 2004

The modified polyionene polyelectrolyte inks were newly prepared and applied to the humidity-sensitive membrane of humidity sensor. The films were fabricated on the alumina substrate with comb-type gold electrode using a ink-jet printing technique. The copolymers of methyl methacrylate, acrylic acid, 2-hydroxyethyl methacrylate and [(2-methacryloyloxy)ethyl]trimethylammonium chloride were also prepared for the humidity-sensing material. which was fabricated by dip-coating method. Electrical measurements under various relative humidity were performed. The humidity-sensitive characteristics of sensors obtained by ink-jet printing technique were compared with that of dip-coating method. Humidity sensors showed a decrease in resistance as an increase of relative humidity and their resistance characteristics are in a close agreement each other.

• Journal of the Korean Chemical Society
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• v.35 no.1
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• pp.51-58
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• 1991

A new tubular poly(vinyl chloride) membrane type of nitrate selective electrode was prepared and its characteristics were evaluated. The response slope, detection limit, and response time (t$_{99}$) under the optimum membrane composition (5${\%}$ aliquat-NO$_3$ solution + 32${\%}$ poly(vinyl chloride) + 63${\%}$ dibutyl sebecate) of the electrode were 58.5 ${\pm}$ 0.1 mV/decade, 2.0 ${\times}$ 10$^{-5}$ M, and 25 seconds, respectively. The nitrite ion was determined by the continuous-automated method using the new electrode. 10$^{-2}$ M phosphate buffer solution (pH 7.6) was used as a recipient solution. And also hydrogen peroxide (0.3${\%}$) was added to the recipient as an oxidant. The linear response range and response range and response slope for the standard nitrite solution under the optimum condition of this electrode system were 8.0 ${\times}$ 10$^{-5}$ M ∼ 5.0 ${\times}$ 10$^{-2}$ M and 56.8 ${\pm}$ 0.2 mV/decade, respectively.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1142-1149
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• 2009

Several bioactive metabolites, including pyrrolnitrin, N-acylhomoserine lactones, and polyhydroxyalkanoates were isolated from Burkholderia sp. O33. Effects of various nutrients, including sugars, gluconolactone, glycerol, tryptophan, chloride, and zinc were investigated in relation to the production of these metabolites. Logarithmic increase of pyrrolnitrin was observed between 2-5 days and reached a maximum at 7-10 days. Tryptophan concentration reached the maximum at 3 days, whereas 7-chlorotryptophan was gradually increased throughout the studies. Among various carbon sources, gluconolactone, trehalose, and glycerol enhanced pyrrolnitrin production, whereas strong inhibitory effects were found with glucose. Relative concentrations of pyrrolnitrin and its precursors were in the order of pyrrolnitrin$\gg$dechloroaminopyrrolnitrin or aminopyrrolnitrin throughout the experiments. Among three N-acylhomoserine lactones, the N-octanoyl analog was the most abundant quorum sensing signal, of which the concentrations reached the maximum in 2-3 days, followed by a rapid dissipation to trace level. No significant changes in pyrrolnitrin biosynthesis were observed by external addition of N-acylhomoserine lactones. Polyhydroxyalkanoates accumulated up to 3-4 days and decreased slowly thereafter. According to the kinetic analyses, no strong correlations were found between the levels of pyrrolnitrin, N-acylhomoserine lactones, and polyhydroxyalkanoates.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1234-1240
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• 2015

Heat shock RNA 1 (HSR1) is described as a "eukaryotic heat-sensing noncoding RNA" that regulates heat shock response in human and other eukaryotic cells. Highly conserved HSR1 sequences have been identified from humans, hamsters, Drosophila, Caenorhabditis elegans, and Arabidopsis. In a previous study, however, it was suggested that HSR1 had originated from a bacterial genome. HSR1 showed no detectible nucleotide sequence similarity to any eukaryotic sequences but harbored a protein coding region that showed amino-acid sequence similarity to bacterial voltage-gated chloride channel proteins. The bacterial origin of HSR1 was not convincible because the nucleotide sequence similarity was marginal. In this study, we have found that a genomic contig sequence of Comamonas testosteroni strain JL14 contained a sequence virtually identical to that of HSR1, decisively confirming the bacterial origin of HSR1. Thus, HSR1 is an exogenous RNA, which can ectopically trigger heat shock response in eukaryotes. Therefore, it is no longer appropriate to cite HSR1 as a "eukaryotic functional noncoding RNA."