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

• IEMEK Journal of Embedded Systems and Applications
• /
• v.7 no.6
• /
• pp.301-309
• /
• 2012

In this paper, a real-time monitoring system based on WSN is designed and implemented to monitor livestock growth environment information which includes the temperature, humidity and harmful gases such as $CO_{2},\;CO,\;NH_{3},\;H_{2}S$ and so on. The proposed system consists of the wireless sensor nodes, the monitoring management device, the management server and the user interface program based on PC/Smart phone. To verify the performance of the implemented system, gas measurement experiments are performed in laboratory environment by using the designed wireless sensor nodes. And it is able to estimate the concentration of gases. The implemented system is able to monitor the proposed environmental element information through the developed GUI.

• Korean Journal of Materials Research
• /
• v.13 no.2
• /
• pp.115-119
• /
• 2003

The thick film type sensor having Pt/Na Super Ionic Conductor(NASICON) solid electrolyte/Pt/$Na_2$$SO_4$/Pt catalyst system for $SO_2$gas was fabricated by screen-print method. The phase of Na Super Ionic Conductor solid electrolyte sintered at different temperature of 1050, 1150,$ 1250^{\circ}C$ and for different time of 1.5, 2.5, 3.5 hr were investigated by XRD. The Electromotive Force variation of the sensor with $SO_2$concentrations and operating temperatures were investigated. The major phase of Na Super Ionic Conductor film sintered at 115$0^{\circ}C$ for 3.5 hr was sodium zirconium silicon phosphate($Na_3$Zr$_2$$Si_2$PO$_{12}$). The Nernst's slope of Na Super Ionic Conductor sensor for $SO_2$gas with the variation of concentration from 10 to 100 ppm was 167.14 ㎷/decade at the operating temperature of $500 ^{\circ}C$. The increase of oxygen partial pressure was not affected to the variation of Nernst's slope.e.

• Korean Journal of Materials Research
• /
• v.18 no.11
• /
• pp.628-633
• /
• 2008

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of $C_2H_5OH$, $CH_3COCH_3$, $H_2$, $C_3H_8$, 100 ppm of CO, and 5 ppm of $NO_2$) were measured at $300\;{\sim}\;400^{\circ}C$. The prepared ZnO nanopowders showed high gas responses to $C_2H_5OH$ and $CH_3COCH_3$ at $400^{\circ}C$. The sensing materials prepared at the compositions of [$ZnCl_2$]:[$N_2H_4$]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses ($S\;=\;R_a/R_g,\;R_a$ : resistance in air, $R_g$ : resistance in gas) to 200 ppm of $C_2H_5OH$($S\;=\;102.8{\sim}160.7$) and 200 ppm of $CH_3COCH_3$($S\;= 72.6{\sim}166.2$), while they showed low gas responses to $H_2$, $C_3H_8$, CO, and $NO_2$. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.

• Journal of Sensor Science and Technology
• /
• v.6 no.3
• /
• pp.207-213
• /
• 1997

A field effect transistor(FET) type dissolved carbon dioxide($pCO_{2}$) sensor with a double layer structure of hydrogel membrane and $CO_{2}$ gas permeable membrane was fabricated by utilizing a $H^{+}$ ion selective field effect transistor(pH-ISFET) with Ag/AgCl reference electrode as a base chip. Formation of hydrogel membrane with photo-crosslinkable PVA-SbQ or PVP-PVAc/photosensitizer system was not suitable with the photolithographic process. Furthermore, hydrogel membrane on pH-ISFET base chip could be fabricated by photolithographic method with the aid of N,N,N',N'-tetramethyl othylenediarnine(TED) as $O_{2}$ quencher without using polyester film as a $O_{2}$ blanket during UV irradiation process. Photosensitive urethane acrylate type oligomer was used as gas permeable membrane on top of hydrogel layer. The FET type $pCO_{2}$ sensor fabricated by photolithographic method showed good linearity (linear calibration curve) in the range of $10^{-3}{\sim}10^{0}\;mol/{\ell}$ of dissolved $CO_{2}$ in aqueous solution with high sensitivity.

• Korean Journal of Materials Research
• /
• v.20 no.11
• /
• pp.611-616
• /
• 2010

A cobalt oxide - tin oxide nanocomposite based gas sensor on an $SiO_2$ substrate was fabricated. Granular thin film of tin oxide was formed by a rheotaxial growth and thermal oxidation method using dc magnetron sputtering of Sn. Nano particles of cobalt oxide were spin-coated on the tin oxide. The cobalt oxide nanoparticles were synthesized by polymer-assisted deposition method, which is a simple cost-effective versatile synthesis method for various metal oxides. The thickness of the film can be controlled over a wide range of thicknesses. The composite structures thus formed were characterized in terms of morphology and gas sensing properties for reduction gas of $H_2$. The composites showed a highest response of 240% at $250^{\circ}C$ upon exposure to 4% $H_2$. This response is higher than those observed in pure $SnO_2$ (90%) and $Co_3O_4$ (70%) thin films. The improved response with the composite structure may be related to the additional formation of electrically active defects at the interfaces. The composite sensor shows a very fast response and good reproducibility.

• International Journal of Automotive Technology
• /
• v.7 no.4
• /
• pp.385-390
• /
• 2006

A fast response $CO_2$ analyzer has been developed to study transient characteristics on an SI engine. The analyzer has the delay time of 4.5 ms and time constant of 2.8 ms, which is fast enough to measure $CO_2$ concentration on a transient condition. Wide range of A/F(Air/Fuel) ratio can be estimated using the analyzer with an additional switch type oxygen sensor. The results of measurement of $CO_2$ concentration and A/F ratio on a transient condition including rapid acceleration/deceleration and EGR(Ehxaust Gas Recirculation) on/off are presented and compared with a commercial exhaust gas analyzer and UEGO(Universial Exhaust Gas Oxyzen) sensor.

• Journal of Sensor Science and Technology
• /
• v.23 no.5
• /
• pp.305-309
• /
• 2014

Well-ordered $TiO_2$ nanotubes with Au nanoparticles are a desirable configuration to enhance the gas sensing properties such as response and selectivity due to their high surface area to volume ratio and catalytic effect of Au nanoparticles. We have synthesized the well-ordered $TiO_2$ nanotubes directly on a Pt IDEs patterned $SiO_2/Si$ substrate and then decorated Au nanoparticles on inner and outer surface of $TiO_2$ nanotubes using electrodeposition method. The Au-decorated $TiO_2$ nanotubes shows ultrahigh response to $C2_H_5OH$ and the highest increasing ratio to $H_2$ compared with other gases.

• Proceedings of the KIEE Conference
• /
• 2005.07c
• /
• pp.2369-2371
• /
• 2005

MEMS 기술을 이용하여 마이크로 $H_2$ 가스센서를 제작하고 마이크로 히터의 열적 특성과 $H_2$ 가스 농도 변화에 따를 마이크로 가스센서에 대한 감도를 분석하였다. 마이크로 가스센서의 전압 인가에 따른 히터의 온도는 1.0V에서 $250-280^{\circ}C$의 고온 특성을 보였으며, 동작온도 $250^{\circ}C$에서 $H_2$ 가스는 $SnO_2/V_2O_5/Pd$의 감응물질을 도포한 센서의 반응이 우수한 특성을 확인하였다. 동작 온도 $250^{\circ}C$ $H_2$ 농도 5000ppm의 조건에서 $SnO_2/V_2O_5/Pd$의 감응물질을 도포한 가스센서에서 $H_2$ 흡착 반응 시간은 3sec이 탈착 반응 시간은 8-10sec의 결과를 보였다.

• Journal of Sensor Science and Technology
• /
• v.24 no.6
• /
• pp.419-422
• /
• 2015

Pure and Mo-doped ZnO hollow nanofibers were prepared by single capillary electrospinning and their gas sensing characteristics toward 5 ppm ethanol, trimethylamine (TMA), CO and $H_2$ were investigated. The gas responses and responding kinetics were dependent upon sensing temperature and Mo doping. Mo-doped ZnO hollow nanofibers showed high response to 5 ppm TMA ($R_a/R_g=111.7$, $R_a$: resistance in air, $R_g$: resistance in gas) at $400^{\circ}C$, while the responses of pure ZnO hollow nanofibers was low ($R_a/R_g=47.1$). In addition, the doping of Mo enhanced selectivity toward TMA. The enhancement of gas response and selectivity to TMA by Mo doping to ZnO nanofibers was discussed in relation to the interaction between basic analyte gas and acidic additive materials.