• 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 Sensor Science and Technology
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• v.10 no.2
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• pp.101-107
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• 2001

A highly selective, sensitive and reliable ozone sensing $In_2O_3$ thin film was fabricated by a sol-gel method. The fabricated film is operated at a relatively lower temperature than ever developed thin films and saved operating power. $In_2O_3$ films deposited by sol-gel technique has been recently attracted because it is an economical and energy saving method and precisely controlled microstructure. Indium alkoxide precursor was synthesized from the reaction between indium hydroxide and butanol. PVA binder was used to improve adhesion of the films. The $In_2O_3$ thin films were obtained by spin coating from 1 to 5 times followed by drying at $100^{\circ}C$ and calcining at $600^{\circ}C$ for 1h. The film thickness was controlled by the number of coating time. The morphology and the thickness of the $In_2O_3$ films were examined by a SEM and XRD. The $In_2O_3$ thin films show a high sensitive to ozone gas at operating temperature of $250^{\circ}C$. The $In_2O_3$ sensor has very good selectivity to $CH_4$, CO, $C_4H_{10}$ and ethanol.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.704-709
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• 1998

Non-linear optical polymer based on poly (${\alpha}$-methylstyrene-co-maleic anhydride) (MSMA) substrate polymer was prepared by polymer reaction method and its thermal and electro-optic properties were examined. In the polymer reaction between MSMA substrate polymer and 2-[4-(4-nitrophenylazo)-N-ethylphenylamino]ethanol (DR1) chromophore, the degree of substitution of DR1 into MSMA was higher with the 4-dimethylaminopyridine (DMAP) as catalyst and 3-dicyclohexyl carbodiimide (DCC) as dehydrating agent (sample, MSMA-DC) than the one with just 4-dimethylaminopyridine as catalyst (sample, MSMA-D). The synthesized NLO polymer (MSMA-DC) exhibited electro-optic coefficient of 18 pm/V (632.8 nm) and glass transition temperature ($T_g$) of about $175^{\circ}C$.

• Composites Research
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• v.33 no.6
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• pp.365-370
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• 2020

The icing formation at aircraft occur problems such as increasing weight of the body, fuel efficiency reduction, drag reduction, the error of sensor, and etc. The viscosity of polyurethane (PU) topcoat was measured at 60℃ in real time to set the pre-curing time. SiO2 nanoparticles were dispersed in ethanol using ultra-sonication method. The SiO2/ethanol solution was sprayed on PU topcoat that was not cured fully with different pre-curing conditions. Surface roughness of SiO2/PU nanocomposites were measured using surface roughness tester and the surface roughness data was visualized using 3D mapping. The adhesion property between SiO2 and PU topcoat was evaluated using adhesion pull-off test. The static contact angle was measured using distilled water to evaluate the hydrophobicity. Finally, the pre-curing time of PU topcoat was optimized to exhibit the hydrophobicity of SiO2/PU topcoat.

• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.349-361
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• 2010

In this review, the current knowledge of the carbon metabolism and global carbon regulation in Corynebacterium glutamicum are summarized. C. gluamicum has phosphotransferase system (PTS) for the utilization of sucrose, glucose, and fructose. C. glutamicum does not show any preference for glucose when various sugars or organic acids are present with glucose, and thus cometabolizes glucose with other sugars or organic acids. The molecular mechanism of global carbon regulation such as carbon catabolite repression (CCR) in C. glutamicum is quite different to that in Gram-negative or low-GC Gram-positive bacteria. GlxR (glyoxylate bypass regulator) in C. glutamicum is the cyclic AMP receptor protein (CRP) homologue of E. coli. GlxR has been reported to regulate genes involved in not only glyoxylate bypass, but also central carbon metabolism and CCR including glycolysis, gluconeogenesis, and tricarboxylic acid (TCA) cycle. Therefore, GlxR has been suggested as a global transcriptional regulator for the regulation of diverse physiological processes as well as carbon metabolism. Adenylate cyclase of C. glutamicum is a membrane protein belonging to class III adenylate cyclases, thus it could possibly be a sensor for some external signal, thereby modulating cAMP level in response to environmental stimuli. In addition to GlxR, three additional transcriptional regulators like RamB, RamA, and SugR are also involved in regulating the expression of many genes of carbon metabolism. Finally, recent approaches for constructing new pathways for the utilization of new carbon sources, and strategies for enhancing amino acid production through genetic modification of carbon metabolism or regulatory network are described.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.55-61
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• 2002

Ultra-fine particles of $SnO_{2}$ was synthersized by the sol-gel powder processing using tin(II) chloride dihydrate$(SnCl_{2}{\cdot}2H_{2}O)$ and ethanol$(C_{2}H_{5}OH)$ as raw materials. Gel powders can be obtained by drying of sol at $120^{\circ}C$ after aging 72hrs and 168hrs. The amount of $SnO_{2}$ phase was increased with temperature because of the evaporation of volatile components, and the creation of $SnO_{2}$ phase was almost done by the heat treatment at $700^{\circ}C/30min$ The grain sizes after firing are about 20-30nm, and it showed the narrow distribution of grain size. The specimens to measure electrical properties were fabricated by the thick film screen printing technique on the alumina substrates. The conductance of $SnO_{2}$ was increased with temperature up to $380^{\circ}C$ by the typical conduction mechanism of semiconducting ceramics. There was a region of constant conductance between about $200^{\circ}C$ and $380^{\circ}C$ due to the increment of electron concentration with temperature and the annihilation of conduction carriers by the absorption and electron trapped-ionization of oxygen on the surface of $SnO_{2}$, It was finally showed the intrinsic behaviors above $450^{\circ}C$. The sensing properties of response time, recovery, and sensitivity of CO were improved with aging time.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.205-209
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• 2011

Zinc oxide has semi-conductivity and super conductivity characteristics. It can be used optically and is applied on many areas such as gas sensor, solar cell and optical waveguide. In this paper, to improve optical characteristics of ZnO, aluminum was added on zinc oxide. Zinc oxide and aluminum zinc oxide was fabricated as nano fiber form. ZnO solution was created by mixing poly vinyl pyrrolidone, ethyl alcohol, and zinc acetate. An Al doped ZnO was created by adding aluminum solution to ZnO sol. By applying these sols on electro spinning method, nano fibers were fabricated. These fibers are heat treated at 300, 500, and $700^{\circ}C$ degrees and were analyzed with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to examine the nano structures. TGA and DSC measurement was also used to measure the change of mass and calorie upon temperature change. The absorbance of ZnO and Al-doped ZnO was carried out by UV-vis measurement.

• 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 Journal of Materials Research
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• v.12 no.12
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• pp.930-934
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• 2002

Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.218-224
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• 1998

2nO and $Al_{2}O_{3}$ powder were weighed in 1 : 1 mole ratio and ball-milled in ethanol for 3 h. Dried mixture were pressed and then sintered at $900^{\circ}C{\sim}1200^{\circ}C$ for 3 h in vacuum($3{\times}10^{-5}$ Torr). According to XRD, remnant ZnO and $Al_{2}O_{3}$ not converted to $ZnAl_{2}O_{4}$ were observed up to $1100^{\circ}C$, which were completely changed to$ZnAl_{2}O_{4}$ ternary compound at $1200^{\circ}C$. Optical bandgap is calculated at 4.75 eV. With increasing sintering temperature, PL spectrums shifted to shorter wavelengths and are appeared 430nm at $1200^{\circ}C$.