• 센서학회지
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• 제20권5호
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• pp.305-310
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• 2011

This study focuses on the fabrication of $TiO_2$ nanosheets and their gas sensor application. A simple sonochemical method is employed to fabricate the $TiO_2$ nanosheets. The obtained samples were investigated by transmission electron microscope(TEM) and X-ray Diffraction(XRD). The $TiO_2$ nanosheets were coated on substrates by a dropping method followed by heat treatment. The sensor responses to volatile organic compounds(VOCs) such as toluene, benzene, ethanol and acetaldehyde were studied. It was found that the $TiO_2$ nanosheets sensors are able to detect ppb-levels of VOC gases.

• 한국세라믹학회지
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• 제54권4호
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• pp.303-307
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• 2017

Pure $In_2O_3$, 0.5 and 1.0 wt% Mg doped $In_2O_3$ hollow spheres were synthesized by ultrasonic spray pyrolysis of a solution containing In-, Mg-nitrate and sucrose and their gas sensing characteristics to 5 ppm $C_2H_5OH$, p-xylene, toluene, and HCHO were measured at 250, 300 and $350^{\circ}C$. Although the addition of Mg decreases the specific surface area and the volume of meso-pores, the gas response (resistance ratio) of the 0.5 wt% Mg doped $In_2O_3$ hollow spheres to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ (69.4) was significantly higher than that of the pure $In_2O_3$ hollow spheres (24.4). In addition, the Mg doped $In_2O_3$ hollow spheres showed the highest selectivity to $C_2H_5OH$. This was attributed to the dehydrogenation of $C_2H_5OH$ assisted by basic MgO into reactive $CH_3CHO$ and $H_2$.

• 센서학회지
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• 제24권3호
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• pp.151-154
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• 2015

The gas sensing characteristic of $MoS_2-MoO_2$ composite yolk-shell spheres were investigated. $MoO_3$-carbon composite spheres were prepared by ultrasonic spray pyrolysis of aqueous droplets containing Mo-source and sucrose in nitrogen, which were converted into $MoO_3$ yolk-shell spheres by heat treatment at $400^{\circ}C$ in air. Subsequently, $MoS_2-MoO_2$ composite yolk-shell spheres were prepared by the partial sulfidation of $MoO_3$. The $MoS_2-MoO_2$ composite yolk-shell spheres showed relatively low and irreversible gas sensing characteristics at < $200^{\circ}C$. In contrast, the sensor showed high and reversible response (S=resistance ratio) to 5 ppm $NO_2$ (S=14.8) at $250^{\circ}C$ with low cross-responses (S=1.17-2.13) to other interference gases such as ethanol, CO, xylene, toluene, trimethylamine, $NH_3$, $H_2$, and HCHO. The $MoS_2-MoO_2$ composite yolk-shell spheres can be used as reliable sensors to detect $NO_2$ in a selective manner.

• 한국지능시스템학회논문지
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• 제21권1호
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• pp.49-54
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• 2011

본 논문에서는 실내 환경에서 발생 할 수 있는 각종 냄새를 구분하고 농도를 검출하여 냄새 발생지로의 탐색과 이에 관련된 정보를 전송하는 지능 로봇을 구현 하였다. 온도변화에 따라 구동 되는 반도체식 가스센서를 이용하여 에탄올, 암모니아 및 이들의 혼합가스를 신경망 알고리즘을 통해 구분하고, 퍼지 추론방식으로 농도 측정이 가능한 후각 기능을 구현 하여 탑재함과 동시에 비전 시스템을 이용하여 장애물 회피 이동이 가능하게 하였다. 또한 로봇은 센서 네트워크 내에서 동작하며 유해 가스 및 냄새 관련 정보와 이에 따른 경고 메시지를 멀티홉 방식으로 네트워크 내 다른 노드로 전송한다. 비전 시스템과 후각 센서를 이용한 알고리즘으로 냄새의 종류 구분 및 농도 측정, 발생지 탐색이 가능 하였고 센서 네트워크 내 동작으로 이러한 정보전송이 가능한 로봇을 제시 하였다. 실제 실험을 통하여 냄새 인식 및 농도검출, 그리고 냄새 발생지로의 탐색 알고리즘 및 정보전송 성능의 효용성을 입증 하였다.

• 한국전자파학회논문지
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• 제26권1호
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• pp.39-46
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• 2015

본 논문에서는 2.4 GHz에서 동작하는 $90^{\circ}$ 하이브리드 커플러 구조에 전도성 고분자 화합물을 적용한 가스 센서를 제안하였다. 가스 센서에서 전도성 고분자 화합물(Conducting Polymer: CP)는 특정 가스를 검출하는 검출 물질로 사용되며, 특정 가스와 반응할 때 대개 물질의 일함수(work function)와 전도도(conductivity) 및 임피던스가 변하게 된다. 이러한 물성변화 특성의 근거로 마이크로파 대역에서 $90^{\circ}$ 하이브리드 커플러 구조에 전도성 고분자를 적용하여 가변 감쇄기 및 가변 위상 천이기 형태의 센서를 제작하였다. 본 연구에서 제안한 센서는 전도성 고분자 화합물의 높은 전도도를 이용하여 기존 전송선로의 일부를 전도성 고분자 물질로 대체하였다. 실험은 온도 $28^{\circ}$와 상대습도 85 % 환경에서 진행되었으며, 센서에 100 ppm 농도의 에탄올 가스를 노출시켰다. 그 결과, $S_{21}$의 진폭 특성이 최대 0.13 dB 변하였고, ${\angle}S_{21}=360^{\circ}$를 만족하는 주파수가 2.875 MHz 이동한 것을 확인하였다.

• 센서학회지
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• 제23권3호
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• pp.207-210
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• 2014

$TiO_2$ oxide semiconductor is being widely studied in various applications such as photocatalyst and photosensor. Pd/$TiO_2$ gas sensor is mainly used to detect $H_2$, CO and ethanol. This study focus on increasing hydrogen detection ability of Pd/$TiO_2$ in room temperature through Al-doping. Pd/$TiO_2$ was fabricated by the hydrothermal method. Contacting to Aluminum (Al) foil led to Al doping effect in Pd/$TiO_2$ by thermal diffusion and enhanced hydrogen sensing response. $TiO_2$ nanoparticles were sized at ~30 nm of diameter from scanning electron microscope (SEM) and maintained anatase crystal structure after Al doping from X-ray diffraction analysis. Presence of Al in $TiO_2$ was confirmed by X-ray photoelectron spectroscopy at 73 eV. SEM-energy dispersive spectroscopy measurement also confirmed 2 wt% Al in Pd/$TiO_2$ bulk. The gas sensing test was performed with $O_2$, $N_2$ and $H_2$ gas ambient. Pd/Al-doped $TiO_2$ did not response $O_2$ and $N_2$ gas in vacuum except $H_2$. Finally, the normalized resistance ratio ($R_{H2on}/R_{H2off}$) of Pd/Al-doped $TiO_2$ increases about 80% compared to Pd/$TiO_2$.

• The Korean Journal of Ceramics
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• 제2권1호
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• pp.1-10
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• 1996

Transparent conducting $SnO_2$-based thin films have been coated on float substrates such as fused quartz, and ceramic fiber cloths such as the Nexel and E-glass cloth from tin alkoxides by the sol-gel technique. Also, thin films of alternating layers of $SnO_2$ and $SiO_2$ have been fabricated by dip coating. The sheet resistance and average visible transmittance of the films were investigated in the aspect of the applications as transparent electrodes such as liquid crystal displays, photo-detectors and solar cells. The Nextel and E-glass cloths coated with antimony-doped tin oxide (ATO) had sheet resistance of as low as $20 \;ohm/{\Box}$ and $120ohm/\;{\Box}$, respectively. The promotion effects of additives as $La_2O_3$ and Pt on the ethanol gas sensing properties of the films were investigated in the aspects of the applications as an alcohol sensor and a breath alcohol checker. Possible evidence of quantum well effects in the oxide multilayers of $SnO_2$ and $SiO_2$ was investigated.

• Transactions on Electrical and Electronic Materials
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• 제16권2호
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• pp.78-81
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• 2015

Pure ZnO and ZnO nanowires doped with 3 wt.% Ga (‘3GZO’) were grown by pulsed laser deposition in a furnace system. The doping of Ga in ZnO nanowires was analyzed by observing the optical and chemical properties of the doped nanowires. The diameter and length of nanowires were under 200 nm and several ${\mu}m$, respectively. Changes of significant resistance were observed and the sensitivities of ZnO and 3GZO nanowires were compared. The sensitivities of ZnO and 3GZO nanowire sensors measured at 300℃ for 1 ppm of ethanol gas were 97% and 48%, respectively.

• 한국재료학회지
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• 제13권2호
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• pp.106-110
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• 2003

Nano-sized powders of Indium Tin Oxide(ITO) were synthesized by a coprecipitation method. In order to investigate the gas sensing characteristics in the nanocrystalline ITO thick films with various particle sizes, ITO powders with the average particle diameter of 15, 30, and 70 nm respectively were synthesized. And the sensitivity of ITO thick films was measured upon exposure to a target gas($C_2$$H_{5}$ /OH) and some other Volatile Organic Compounds(VOCs), such as, toluene, methanol, benzene, chloroform. As a result, ITO thick films had high sensitivity for ethanol and higher sensitivity with smaller particle size.

• 센서학회지
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• 제29권3호
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• pp.156-161
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• 2020

In this study, hierarchical mesoporous CuO spheres, ZnO flowers, and heterojunction CuO/ZnO nanostructures were fabricated via a facile hydrothermal method. The as-prepared materials were characterized in detail using various analytical methods such as powder X-ray diffraction, micro Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. The obtained results are consistent with each other. The H₂S-sensing characteristics of the sensors fabricated based on the CuO spheres, ZnO flowers, and CuO/ZnO heterojunction were investigated at different temperatures and gas concentrations. The sensor based on ZnO flowers showed a maximum response of ~141 at 225 ℃. The sensor based on CuO spheres exhibited a maximum response of 218 at 175 ℃, whereas the sensor based on the CuO/ZnO nano-heterostructure composite showed a maximum response of 344 at 150 ℃. The detection limit (DL) of the sensor based on the CuO/ZnO heterojunction was ~120 ppb at 150 ℃. The CuO/ZnO sensor showed the maximum response to H₂S compared with other interfering gases such as ethanol, methanol, and CO, indicating its high selectivity.