• Title/Summary/Keyword: Chemical sensing

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Reduced graphene oxide field-effect transistor for biomolecule detection and study of sensing mechanism

  • Kim, D.J.;Sohn, I.Y.;Kim, D.I.;Yoon, O.J.;Yang, C.W.;Lee, N.E.;Park, J.S.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.431-431
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    • 2011
  • Graphene, two dimensional sheet of sp2-hybridized carbon, has attracted an enormous amount of interest due to excellent electrical, chemical and mechanical properties for the application of transparent conducting films, clean energy devices, field-effect transistors, optoelectronic devices and chemical sensors. Especially, graphene is promising candidate to detect the gas molecules and biomolecules due to the large specific surface area and signal-to-noise ratios. Despite of importance to the disease diagnosis, there are a few reports to demonstrate the graphene- and rGO-FET for biological sensors and the sensing mechanism are not fully understood. Here we describe scalable and facile fabrication of rGO-FET with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}1$-antichymotrypsin (PSA-ACT) complex, in which the ultrathin rGO sensing channel was simply formed by a uniform self-assembly of two-dimensional rGO nanosheets on aminated pattern generated by inkjet printing. Sensing characteristics of rGO-FET immunosensor showed the highly precise, reliable, and linear shift in the Dirac point with the analyte concentration of PSA-ACT complex and extremely low detection limit as low as 1 fg/ml. We further analyzed the charge doping mechanism, which is the change in the charge carrier in the rGO channel varying by the concentration of biomolecules. Amenability of solution-based scalable fabrication and extremely high performance may enable rGO-FET device as a versatile multiplexed diagnostic biosensor for disease biomarkers.

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Interaction of Pseudostellaria heterophylla with Quorum Sensing and Quorum Quenching Bacteria Mediated by Root Exudates in a Consecutive Monoculture System

  • Zhang, Liaoyuan;Guo, Zewang;Gao, Huifang;Peng, Xiaoqian;Li, Yongyu;Sun, Shujing;Lee, Jung-Kul;Lin, Wenxiong
    • Journal of Microbiology and Biotechnology
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    • v.26 no.12
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    • pp.2159-2170
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    • 2016
  • Many plant-pathogenic bacteria are dependent on quorum sensing (QS) to evoke disease. In this study, the population of QS and quorum quenching (QQ) bacteria was analyzed in a consecutive monoculture system of Pseudostellaria heterophylla. The isolated QS strains were identified as Serratia marcescens with SwrIR-type QS system and exhibited a significant increase over the years of monoculture. Only one QQ strain was isolated from newly planted soil sample and was identified as Bacillus thuringiensis, which secreted lactonase to degrade QS signal molecules. Inoculation of S. marcescens to P. heterophylla root could rapidly cause wilt disease, which was alleviated by B. thuringiensis. Furthermore, the expression of lactonase encoded by the aiiA gene in S. marcescens resulted in reduction of its pathogenicity, implying that the toxic effect of S. marcescens on the seedlings was QS-regulated. Meanwhile, excess lactonase in S. marcescens led to reduction in antibacterial substances, exoenzymes, and swarming motility, which might contribute to pathogensis on the seedlings. Root exudates and root tuber extracts of P. heterophylla significantly promoted the growth of S. marcescens, whereas a slight increase of B. thuringiensis was observed in both samples. These results demonstrated that QS-regulated behaviors in S. marcescens mediated by root exudates played an important role in replanting diseases of P. heterophylla.

A Study on Selective Metal Ion Sensing Membrane for Bio Environment Measurement (바이오 환경측정용 선택적 금속이온 감지 막의 특성 연구)

  • Park, Hyung-Jun;Jang, Gab-Soo;Kim, In-Su
    • Journal of IKEEE
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    • v.22 no.4
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    • pp.1062-1067
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    • 2018
  • In this study, the research processed with a chemical sensor for measuring trace amount of heavy metal ions which is based on the requirements of the efficient sensing technology as recent equipment is applies molecular system in the chemical sensing section that can precisely recognizing selective target substance and transmit its data to physical signal as a result. In this research is concentrated on realize highly precise by utilizing SPR sensor application of recognition functional sensing membrane. Consequently, according to DTSQ-dye sensing membrane, the resonance angle from low-concentration to the highest concentration $10^{-4}M$ of $Ag^+$ ion is $2.17[^{\circ}]$ and this result indicating 4.3 times larger resonance angle changes compare to the other metal substance. Based on SQ-dye sensing membrane, the difference of resonance angle between low concentration and the highest concentration $10^{-4}M$ of $Cu^{2+}$ ion is $2.3[^{\circ}]$ and this outcome is indicating 4.5 times greater resonance angle change to the other metal substance.

$NO_x$ Sensing Characteristic of $TiO_2$ Thin Film Deposited by R.F Magnetron Sputtering (R.F 마그네트론 스퍼트링으로 작성된 $TiO_2$박막의 $NO_x$ 감지 특성)

  • 고희석;박재윤;박상현
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.51 no.12
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    • pp.567-572
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    • 2002
  • In these days, diesel vehicle or power plant emits $NO_X\; and SO_2$ which cause air pollution like acid-rain, ozone layer destroy and optical smoke, therefore there are many kinds of methods considered for removing them such as SCR, catalyst, plasma process, and plasma-catalyst hybrid process. T$TiO_2$ is commonly used as catalyst to remove $NO_X$ gas because it have very excellent chemical characteristic as photo catalyst. In this paper, $NO_X$ sensing characteristic of $TiO_2$ thin film deposited by R.F Magnetron sputtering is investigated. A finger shaped electrode on $Al_2$O$_3$ substrate is designed and $TiO_2$ is deposited on the electrode by the magnetron sputtering deposition system. Chemical composition of the deposited $TiO_2$ thin film is $TiO_{1.9}$ by RBS analysis. When the UV is irradiated on it with flowing air, capacitance of $TiO_2$ thin film increases, however, when NO gas is put into the system with air, it immediately decreases because of photo chemical reaction. and it monotonously decreases with increasing NO concentration.

A Carbazole Based Bimodal "Turn-On" Fluorescent Probe for Biothiols (Cysteine/Homocysteine) and Fluoride: Sensing, Imaging and its Applications

  • Kaur, Matinder;Yoon, Byungkwon;Kumar, Rajesh;Cho, Min Ju;Kim, Hak Joong;Kim, Jong Seung;Choi, Dong Hoon
    • Bulletin of the Korean Chemical Society
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    • v.35 no.12
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    • pp.3437-3442
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    • 2014
  • A well-known carbazole-based precursor (probe 1) was used for the detection of cysteine/homocysteine and fluoride. Probe 1 shows a "turn-on" response to cysteine/homocysteine and fluoride via enhancement in emission intensity at 442 nm and 462 nm respectively, in solutions and living cells. Furthermore, probe 1 behaves as a fluorescent molecular switch between cysteine/homocysteine and fluoride as the chemical inputs, which have been used for the development of a combinatorial logic circuit and a molecular keypad lock.

Preparation of SnO$_2$ Thin Films by Chemical Vapor Deposition Using Hydrolysis of SnCla$_4$ and Gas-sensing Characterisics of the Film -Effect of Deposition Variables on the Deposition Behavior and the Electrical Resistivity of SnO$_2$ Thin Film- (SnCl$_4$가수분해 반응의 화학증착법에 의한 SnO$_2$박막의 제조 및 가스센서 특징(I) Preparation of SnO2 Thin Films by chemical Vapor Deposition Using Hydrolysis of SnCl4 and gas-sensing characteristics of the Film)

  • 김용일;김광호;박희찬
    • Journal of the Korean institute of surface engineering
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    • v.23 no.2
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    • pp.18-23
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    • 1990
  • Thin films of tin oxide were prepared by chemical vapor deposition (C.V>D) using the hydrolysis reaction of SnCl4, Deposition rate increased with the increase of temperature up to $500^{\circ}C$and then decreased at $700^{\circ}C$, Deposition rate with SnCl4 partial pressure showed RidealEley behavir. It was found that SnO2 thin film deposited at the temperature above $400^{\circ}C$ had(110) and (301) plane preferred orientation with crystallinity of rutite structure. Electrical resisvity of SnO2 thin film decreased with increase increase of deposition temperature and showed minimum value of 10-3 ohm at $500^{\circ}C$and than largely increased increased with further increase of deposition temperture.

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Preparation of Porous Gold for Sensor Applications (센서 응용을 위한 다공성 골드의 제조)

  • Kim, Young-Hun;Kim, He-Ro;Ko, Jae-Wook
    • Journal of the Korean Institute of Gas
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    • v.12 no.2
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    • pp.32-37
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    • 2008
  • For a development of U-safety system, liquid/gas-sensors that are easy to carry and install in any place are needed. Therefore, in this work, we prepared porous gold using a templating method with nanoporous alumina, and it was used as sensing materials and electrode. The resulting materials showed high purity macroporous structure with $200{\sim}300\;nm$ of window-pore and $4.8\;m^2/g$ of surface area. Because porous gold had good electric conductivity, convenience to measure the change of electric resistivity and good reproducibility, it could be used as potential sensing materials. As a proof-of-concept test, the detection test for mercury ion was carried out.

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A Study on the Development of GIS-based Complex Simulation Prototype for Reducing the Damage of Chemical Accidents (화학사고 피해저감을 위한 GIS 연계 복합시뮬레이션 프로토타입 개발에 관한 연구)

  • Kim, Eun-Byul;Oh, Joo-Yeon;Lee, Tae Wook;Oh, Won Kyu;Kim, Hyun-Joo;Lim, Dong-yun
    • Korean Journal of Remote Sensing
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    • v.36 no.5_4
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    • pp.1255-1266
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    • 2020
  • In this study, a complex simulation prototype was developed for rapid and accurate prediction of chemical dispersion range in order to reduce human casualties caused by chemical accidents. Complex simulation considered the leakage momentum during the near-field dispersion to take into account the leakage characteristics of the chemical. In the far-distance dispersion process, the wind distribution of the existing model, which was presented uniformly, was improved using weather and topographical information around the accident site, to realize a wind field similar to the actual one. Finally, the damage range was more precise than the existing model in line with the improved near- and far-distance dispersion process. Based on the results of damage range prediction of the complex simulation, it is expected that it will be highly utilized as a system to support policy decision-making such as evacuation and return of residents after a chemical accident.

Properties and Application of Azo based Dyes for Detecting Hazardous Acids (유해 산 검출용 아조계 색소의 특성 및 응용 연구)

  • Shin, Seung-Rim;Jun, Kun;An, Kyoung-Lyong;Kim, Sang Woong;Kim, Tae-Hwan;Seo, Dong Sung;Lee, Chang Ick
    • Textile Coloration and Finishing
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    • v.33 no.2
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    • pp.49-63
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    • 2021
  • In this study, a convenient approach for sensitive, quick and simple detection of hazardous acids was investigated. A series of azo dyes were synthesized and applied as a chemosensor for the acid detection both on fibers and in solution. Various aniline, benzothiazole or isoxazole derivatives were used as diazo component and coupled with N-benzyl-N-ethylaniline or 2,2'-(phenylimino)bis-ethanol to give azo based dyes. The acid sensing phenomenon was observed by naked-eye and detection was further confirmed by UV-Vis spectrophotometer and hue difference(ΔH*) evaluation. The developed sensors showed a distinct and quick color change from yellow to magenta by addition of trace amounts of the hazardous acids. The absorption maxima was shifted to a longer wavelength by 70 ~ 150nm and hue difference(ΔH*) was 60 ~ 120°. A cotton fiber coated with Dye 1 exhibited excellent storage stability under various temperature(-30 ~ 43℃) and humidity(30 ~ 80%) conditions without discoloration and fading of the fiber sensors. Also the acid sensing properties were maintained.