• Korean Journal of Materials Research
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• v.23 no.4
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• pp.211-214
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• 2013

The effects of a Ni coating on the sensing properties of nano ZnO:Ni based gas sensors were studied for $CH_4$ and $CH_3CH_2CH_3$ gases. Nano ZnO sensing materials were prepared by the hydrothermal reaction method. The Ni coatings on the nano ZnO surface were deposited by the hydrolysis of zinc chloride with $NH_4OH$. The weight % of Ni coating on the ZnO surface ranged from 0 to 10 %. The nano ZnO:Ni gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the nano ZnO : Ni sensing materials were investigated by XRD, EDS, and SEM. The XRD patterns showed that nano ZnO : Ni powders with a wurtzite structure were grown with (1 0 0), (0 0 2), and (1 0 1) dominant peaks. The particle size of nano ZnO powders was about 250 nm. The sensitivity of nano ZnO:Ni based sensors for 5 ppm $CH_4$ gas and $CH_3CH_2CH_3$ gas was measured at room temperature by comparing the resistance in air with that in target gases. The highest sensitivity of the ZnO:Ni sensor to $CH_4$ gas and $CH_3CH_2CH_3$ gas was observed at Ni 4 wt%. The response and recovery times of 4 wt% Ni coated ZnO:Ni gas sensors were 14 s and 15 s, respectively.

• Journal of Sensor Science and Technology
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• v.16 no.1
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• pp.11-16
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• 2007

CuO is an important transition metal oxide with many practical applications such as catalysts, p-type semiconductor, solar cells, magnetic storage media and cathode materials. In this contribution, nanocrystalline CuO powders were prepared by solution reduction method using copper chloride ($CuCl_{2}{\cdot}2H_{2}O$), hydrazine ($N_{2}H_{4}$) and NaOH and subsequent heat treatment. The gas sensor using nanocrystalline CuO powders showed high sensitivities to acetone and ethanol.

• Carbon letters
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• v.11 no.3
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• pp.216-223
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• 2010

Two-types of ionically modified multi-walled carbon nanotube (MWNTs) based sensors were developed by radiationinduced graft polymerization using vinyl monomers such as 3-(butyl imidazol)-2-(hydroxyl)propyl methyl methacrylate and 1-[(4-ethenylphenyl)methyl]-3-buthyl-imidazolium chloride with ionic properties, in aqueous solution at room temperature. Subsequently, the tyrosinase-immobilized biosensor was fabricated by a hand-casting of the ionic property-modified MWNTs, tyrosinase, and chitosan solution as a binder onto ITO glass surface. The sensing ranges of the tyrosinase-biosensor for phenol in phosphate buffer solution was in the range of 0.005~0.2 mM. The total phenolic compounds mainly such as caffeine of the tyrosinase-immobilized biosensor for commercial coffee were also determined.

• YAKHAK HOEJI
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• v.47 no.6
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• pp.356-360
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• 2003

Nitroso-2-naphthol-3,6-disulfonic acid, disodium salt (NRS) was used as an organic ligand to prepare basic drug-selective polymeric membrane electrode. The sensing membrane of the electrode consited of basic drug-meta1(II)-NRS as an ion-exchanger site in a poly(vinyl chloride) matrix plasticized with 2-nitrophenyl octyl ether (NPOE). The metal ions used were Fe$^{2+}$, Co$^{2+}$, Ni$^{2+}$ and Cu$^{2+}$. The electrodes exhibited fast and wide linear response in the basic drug concentration of 10$^{-5}$ ∼10$^{-3}$ mol/l with a response slope of 50∼60 mV/decade in a buffer solution of pH 4∼8. The electrodes exhibited good selectivity for many basic compounds.mpounds.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.79-86
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• 2018

Although the intrinsic characteristics of DNA molecules and carbon nanotubes (CNT) are well known, fabrication methods and physical characteristics of CNT-embedded DNA thin films are rarely investigated. We report the construction and characterization of carboxyl (-COOH) group-modified multi-walled carbon nanotube (MWCNT-COOH)-embedded DNA and cetyltrimethyl-ammonium chloride-modified DNA (DNA-CTMA) composite thin films. Here, we examine the structural, compositional, chemical, spectroscopic, and electrical characteristics of DNA and DNA-CTMA thin films consisting of various concentrations of MWCNT-COOH. The MWCNT-COOH-embedded DNA and DNA-CTMA composite thin films may offer a platform for developing novel optoelectronics, energy harvesting, and sensing applications in physical, chemical, and biological sciences.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.258-259
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• 2019

Corrosion of rebar in RC structures, which results in premature deterioration of reinforced concrete structures, is a very serious problem. Most corrosion monitoring and sensing technologies require some type of wired or wireless connection between the sensor and monitoring electronics. This causes significant problems in their installation and long-term use. In this paper we describe a corrosion monitoring technology of rebar in reinforced concrete structures. Especially, it is emphasize that the development of sensors and monitoring system not only occurrence of rebar corrosion but also penetration of deterioration factor such like chloride ion and carbon dioxite etc..

• 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 Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.589-593
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• 2011

[ $SnO_2$ ]nano powders were prepared by solution reduction method using tin chloride($SnCl_2{\cdot}2H_2O$), hydrazine($N_2H_4$) and NaOH. The $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $300^{\circ}C$ in air, respectively. XRD patterns of the $SnO_2$ nano powders showed the tetragonal structure with (110) dominant orientation. The particle size of $SnO_2$ nano powders at the ratio of $SnCl_2:N_2H_4$+NaOH= 1:6 was about 60 nm. The sensing characteristics were investigated by measuring the electrical resistance of each sensor in a test box. Sensitivity of $SnO_2$ gas sensor to 5 ppm $CH_4$gas and 5 ppm $CH_3CH_2CH_3$ gas was investigated for various $SnCl_2:N_2H_4$+NaOH proportion. The highest sensitivity to $CH_4$ gas and $CH_3CH_2CH_3$ gas of $SnO_2$ sensors was observed at the $SnCl_2:N_2H_4$+NaOH= 1:8 and $SnCl_2:N_2H_4$+NaOH= 1:6, respectively. Response and recovery times of $SnO_2$ gas sensors prepared by $SnCl_2:N_2H_4$+NaOH= 1:6 was about 40 s and 30 s, respectively.

• Journal of the Korean Chemical Society
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• v.65 no.4
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• pp.260-267
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• 2021

Increasing the needs for eco-friendly natural materials, much attention on natural dyes has been attracted. Curcumin, one of abundant natural dyes available in nature, is an eco-friendly molecule found in turmeric. In this study, the colorimetric sensing behavior characteristics of ammonia and hydrogen chloride gases was analyzed using curcumin ink-printed paper and cotton fabric by inkjet printing method. The fabricated paper and fabric were utilized as a colorimetric sensor that can track food spoilage. The color changes of the samples printed on the paper and cotton upon exposure to the toxic gases, the reversibility of the color changes, and the water resistance were investigated. Both samples showed reversible reactions with NH3 and HCl, and small amount of ammonia produced by food spoilage was successfully sensed with naked eyes, confirming its capability to warn food spoilage in our daily life.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.135-135
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• 2003

This paper presents the preparation of SnO$_2$ films by Sol-Gel process and using spin coating method, and their sensing properties in CO gas. Experimental procedure consisted of following steps: (1) Tin chloride(SnCl$_4$) and Ammonium hydrogen carbonate (NH$_4$HCO$_3$) were used as precursors; (2) the Sol solution with concentration of about 10wt% SnO$_2$ was prepared from washed Gel-precipitate for spin coating step; (3) thereafter, the coating solution was dropped onto the alumina (Al$_2$O$_3$) substrate that was then spun, the spin coating was carried out with total 10 times; (4) finally, the films were calcined for 3 hours at 50$0^{\circ}C$ or higher temperature (600, 700, 800 or 90$0^{\circ}C$) in order to obtain various gram sizes. The average grain size was calculated by Scherrer's equation using main peaks in XRD spectra; meanwhile the thickness, microstructure and surface morphology of the films were observed by FE-SEM.