• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.382-387
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• 2020

Hydrogen (H₂) is considered as a new clean energy resource for replacing petroleum because it produces only H₂O after the combustion process. However, owing to its explosive nature, it is extremely important to detect H₂ gas in the ambient atmosphere. This has triggered the development of H₂ gas sensors. 2-dimensional (2D) graphene has emerged as one of the most promising candidates for chemical sensors in various industries. In particular, graphene exhibits outstanding potential in chemoresistive gas sensors for the detection of diverse harmful gases and the control of indoor air quality. Graphene-based chemoresistive gas sensors have attracted tremendous attention owing to their promising properties such as room temperature operation, effective gas adsorption, and high flexibility and transparency. Pristine graphene exhibits good sensitivity to NO₂ gas at room temperature and relatively low sensitivity to H₂ gas. Thus, research to control the selectivity of graphene gas sensors and improve the sensitivity to H₂ gas has been performed. Noble metal decoration and metal oxide decoration on the surface of graphene are the most favored approaches for effectively controlling the selectivity of graphene gas sensors. Herein, we introduce several strategies that enhance the sensitivity of graphene gas sensors to H₂ gas.

• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.43-44
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• 2006

Characteristics of hydrogen sensors for realization of transformer diagnosis system was studied, sensors used in this work are commercialized for detecting hydrocarbons or hydrogen gases. Based on the experimental results, the sensing characteristics of A company showed the high value even at the lower concentration of 20ppm, and it showed a saturation tendency with increasing it above 500ppm. In the case of B company, it showed the linear characteristics from 20ppm to 7000ppm. In addition, the output acquired from C company was amplified by external circuits due to its low output, and its adequate operation region was above 500ppm. Therefore, it is likely that these sensors are possible to apply for realization of transformer diagnosis system due to the different sensing characteristics of these sensors.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.357-363
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• 2021

We developed a chemiresistive anion sensor using highly conductive carbon nanotube fibers (CNTFs) functionalized with anion receptors. Mechanically robust CNTFs were prepared via wet-spinning utilizing the nematic liquid crystal properties of CNTs in chlorosulfonic acid (CSA). For anion detection, polymeric receptors composed of dual-hydrogen bond donors, including thiourea 1, squaramide 2, and croconamide 3, were prepared and bonded non-covalently on the surface of the CNTFs. The binding affinities of the anion receptors were studied using UV-vis titrations. The results revealed that squaramide 2 exhibited the highest binding affinity toward AcO^-, followed by thiourea 1 and croconamide 3. This trend was consistent with the chemiresistive sensing responses toward AcO^- using functional CNTFs. Selective anion sensing properties were observed that CNTFs functionalized with squaramide 2 exhibited a response of 1.08% toward 33.33 mM AcO^-, while negligible responses (<0.1%) were observed for other anions such as Cl^-, Br^-, and NO₃^-. The improved response was attributed to the internal charge transfer of dual-hydrogen bond donors owing to the deprotonation of the receptor upon the addition of AcO^-.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.23-29
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• 2013

In recent years, development of energy conversion systems using hydrogen as an energy source has been accelerated globally. Even though hydrogen is an environment-friendly energy source, safety and effectiveness issues in storage, transportation, and usage of hydrogen should be clearly resolved in every application. Therefore, sensors for detecting hydrogen leakage, especially for fuel cell electric vehicles, should be designed to have much higher resolution and accuracy in comparison with conventional gas sensors. In this study, we conducted to determine the design parameters for the semiconductor hydrogen sensor with optimized sensing conditions under the thermal distribution characteristic and thermal transfer characteristic. The heat generation study on power supply voltage was studied for correlation analysis of thermal energy according to the power supply voltage variation from 1.0 voltage to 10.0 voltage every 0.5 voltage. And we studied for the temperature coefficient of resistance with hydrogen sensor.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.175-175
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• 2006

Considering the number of chemosensors that have been developed for the sensing of metal ions, only a few chemosensors for fluoride anion have been described in the literature that are based on fluorescent or chromogenic responses. We performed colorimetric anion sensing based on the binding of anion analytes with hydrogen donor group in polymer backbone resulting in naked-eye color change and fluorescent quenching. Our challenges using hydrogen donor moiety was designed effectively are continuing in order for high selectivity and sensitivity for ultimate applications such as fluid solution sensing in biomolecules and gas vapor sensing.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.4
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• pp.145-154
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• 1997

The $H_2$ and $H_2S$ sensing characteristics of Pd and Pd-Rh gate MOS sensor and the effect of Pd deposition condition on the hydrogen sensing performance of Pd gate MOS sensor was investigated. The increase of rf power and deposition temperature led to the decrease in the sensitivity and the initial response rate. The deposition temperature gave more effects on the decrease of the sensitivity and the initial response rate than the rf power. The sensitivity of Pd-Rh sensor gave better performance than pure Pd sensor. As the concentration of Rh in the gate increased, the sensitivity decreased. For Pd-Rh sensor, the sensitivity to $H_2$ was higher than that to $H_2S$. It was demonstrated that rf power, deposition temperature had an important role in the sensor performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.271-274
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• 2000

Gas sensor materials capable of detecting hydrogen gases (H$_2$) or nitrogen oxides (NO$\_$x/, primarily NO and NO$_2$) with high sensitivity have attracted much interest in conjunction with the growing concern to the protection of global environments. Beside conventional sensor materials, such as semiconductors., conducting polymers and solid electrolytes, the potential of sensor materials with a new method for detecting hydrogen gases or nitrogen oxides gas has also been tested. The breakdown voltage of porous varistors shifted to a low electric field upon exposure to H$_2$ gas, whereas it shifted to a reverse direction in an atmosphere containing oxidizing gases such as O$_3$ and NO$_2$ in the temperature range of 300 to 600$^{\circ}C$. Furthermore, it was found that the magnitude of the breakdown voltage shift, i. e. the magnitude of sensitivity, was well correlated with gas concentration, and that the H$_2$ sensitivity was improved by controlling the composition of the Bi$_2$O$_3$ rich grain boundary phase. However, NO$\_$x/ sensing properties of porous varistors have not been studies in detail. The objective of the present study is to investigate the effect of the composition of the Bi$_2$O$_3$ rich grain boundary phase and other additive such as A1$_2$O$_3$ on the hydrogen gases (H$_2$) sensing properties of porous ZnO based varistors.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.447-454
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• 2017

A new amperometric biosensor has been developed for the detection of hydrogen peroxide ($H_2O_2$). The sensor was fabricated through the one-step deposition of a biocomposite layer onto a glassy carbon electrode at neutral pH. The biocomposite, as a $H_2O_2$ sensing element, was prepared by the electrochemical deposition of a homogeneous mixture of graphene oxide, aniline, and horseradish peroxidase. The experimental results clearly demonstrated of that the sensor possessed high electrocatalytic activity and responded to $H_2O_2$ with a stable and rapid manners. Scanning electron microscopy, cyclic voltammetry, and amperometry were performed to optimize the characteristics of the sensor and to evaluate its sensing chemistry. The sensor exhibited a linear response to $H_2O_2$ in the range of 10 to $500{\mu}M$ concentrations, and its detection limit was calculated to be $1.3{\mu}M$. The proposed sensing-chemistry strategy and the sensor format were simple, cost-effective, and feasible for analysis of "food-grade $H_2O_2$" in food samples.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.51.3-51.3
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• 2010

Due to the recent public awareness of global warming and sustainable economic growth, there has been a growing interest in alternative clean energy sources. Hydrogen is considered as a clean fuel for the next generation. One of the technical challenges related to the use of hydrogen is safe monitoring of the hydrogen leak during separation, purification and transportation. For detecting various gases, chemiresistor-type gas sensors have been widely studied and used due to their well-established detection scheme and low cost. However, it is known that many of them have the limited sensitivity and slow response time, when used at low temperature conditions. In our work, a sensor based on Schottky barriers at the electrode/sensing material interface showed promising results that can be utilized for developing fast and highly sensitive gas sensors. Our hydrogen sensor was designed and fabricated based on indium oxide (In2O3)-doped tin oxide (SnO2) semiconductor nanoparticles with platinum (Pt) nanoclusters in combination with interdigitated electrodes. The sensor showed the sensitivity as high as $10^7%$ (Rair/Rgas) and the detection limit as low as 30 ppm. The sensor characteristics could be obtained via optimized materials synthesis route and sensor electrode design. Not only the contribution of electrical resistance from the film itself but also the interfacial effect was identified as an important factor that contribute significantly to the overall sensor characteristics. This promises the applicability of the developed sensor for monitoring hydrogen leak at room temperature.

• Journal of Sensor Science and Technology
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• v.21 no.4
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• pp.283-286
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• 2012

This paper presents the optical hydrogen sensor based on transparent 3C-SiC membrane and photovoltaic effect. Gasochromic materials of Pd and Pd/$WO_3$ were deposited by sputter on 3C-SiC membrane for gas sensing area. Gasochromic materials change to transparency by exposure to hydrogen. The variations of light intensity by hydrogen generate the photovoltaic of P-N junction between N-type 3C-SiC and P-type Si. Single layer of Pd shows higher photovoltaic compared with Pd/$WO_3$. However, phase transition from ${\alpha}$ to ${\beta}$ is shown at 6 %. Pd/$WO_3$ structure show the more linear response to hydrogen range of 2 % ~10 %. Also, almost 2 times fast response and recovery characteristics are shown at Pd/$WO_3$. These fast performances are come from the fact that Pd promoted the chemical reaction between hydrogen and $WO_3$.