scholarly journals Effect of GNWs/NiO-WO3/GNWs Heterostructure for NO2 Gas Sensing at Room Temperature

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 626
Author(s):  
Seokhun Kwon ◽  
Seokwon Lee ◽  
Joouk Kim ◽  
Chulmin Park ◽  
Hosung Jung ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Room Temperature ◽  
Microwave Plasma ◽  
Gas Sensing ◽  
Chemical Vapor ◽  
Gas Concentration ◽  
Negative Change ◽  
Low Concentrations ◽  
Detection Characteristics ◽  
No2 Detection

Recently, as air pollution and particulate matter worsen, the importance of a platform that can monitor the air environment is emerging. Especially, among air pollutants, nitrogen dioxide (NO2) is a toxic gas that can not only generate secondary particulate matter, but can also derive numerous toxic gases. To detect such NO2 gas at low concentration, we fabricated a GNWs/NiO-WO3/GNWs heterostructure-based gas sensor using microwave plasma-enhanced chemical vapor deposition (MPECVD) and sputter, and we confirmed the NO2 detection characteristics between 10 and 50 ppm at room temperature. The morphology and carbon lattice characteristics of the sensing layer were investigated using field emission scanning electron microscopy (FESEM) and Raman spectroscopy. In the gas detection measurement, the resistance negative change according to the NO2 gas concentration was recorded. Moreover, it reacted even at low concentrations such as 5–7 ppm, and showed excellent recovery characteristics of more than 98%. Furthermore, it also showed a change in which the reactivity decreased with respect to humidity of 33% and 66%.

Aerosol-Assisted CVD of SnO2 Thin Films for the Room-Temperature Detection of Hydrogen Sulfide

2013 ◽  
Vol 543 ◽  
pp. 422-425
Author(s):  
Huan Liu ◽  
Min Li ◽  
Jiu Xiao Wan ◽  
Jun Zhao ◽  
Qiu Yun Fu ◽  
...  
Keyword(s):  
Thin Films ◽  
Gas Flow ◽  
Room Temperature ◽  
Gas Sensing ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Temperature Detection ◽  
Low Concentrations ◽  
Initial Resistance ◽  
Deposition Conditions

High-quality SnO2 thin-film materials capable of detecting H2S gas of low concentrations at room temperature was demonstrated in this paper. We employed aerosol-assisted chemical vapor deposition process for the deposition of SnO2 thin films on alumina substrates with pre-patterned electrodes. The gas-sensing performances of the films prepared under different deposition conditions were systematically compared and analyzed. When SnCl2·2H2O was used as the precursor, a response sensitivity of 98.4 toward 50 ppm of H2S at room temperature was achieved. At room temperatures, the resistance upon the H2S gas exposure could recover to 90% of the initial resistance of the sensor when the H2S gas flow was turned off.

Electrical Conductivity as a Function of Temperature of Diamond films Grown by Downstream Microwave Plasma Chemical Vapor Deposition

1992 ◽  
Vol 270 ◽  
Author(s):  
Brian R. Stoner ◽  
Jesko A. von Windheim ◽  
Jeffrey T. Glass
Keyword(s):  
Electrical Conductivity ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Conductivity Measurements ◽  
Plasma Chemical ◽  
Hydrogen Incorporation ◽  
Plasma Chemical Vapor Deposition

ABSTRACTElectrical conductivity measurements were used to study the effects that sample distance from the plasma during growth has on the carrier transport properties of undoped CVD diamond. The films were grown by downstream microwave plasma chemical vapor deposition at distances from 0.5 to 2.0 cm from the edge of plasma glow. Electrical conductivity measurements were performed between room temperature and 1000 °C to gain a better understanding of the CVD growth process and the resulting electrical properties of the diamond film's. Room temperature electrical conductivity was found to vary by over 5 orders of magnitude with increasing growth distance from the plasma, and this is attributed to decreasing hydrogen incorporation efficiencies at further distances from the plasma.

scholarly journals Detection of Emanated Light at the Modified Clad Region (Sno2) of the Optical Fiber for Methanol Gas Sensing

2020 ◽  
Vol 8 (5) ◽  
pp. 3327-3332
Keyword(s):  
Optical Fiber ◽  
Room Temperature ◽  
Gas Sensing ◽  
Output Intensity ◽  
Gas Sensitivity ◽  
Radiation Mode ◽  
Gas Concentration ◽  
Fiber Mode ◽  
Modified Surface ◽  
Different Gases

A leakage detecting sensor (radiation mode (or) double fiber mode) is proposed to monitor the light rays propagates from the surface of the modified clad region (SnO2 ) of the optical fiber. The output intensity increases and decreases for the varying gas concentration (0-500 ppm) with the presence of different gases (methanol, ethanol, acetone and ammonia) at room temperature. The received output intensity from the clad modified surface increases for ammonia and methanol, whereas, it decreases for acetone and ethanol gases for the increase in the gas concentration. However, in the transmitting mode (single fiber mode) the output light intensity decreases for all the gases with varying gas concentration. The output gas sensitivity of the proposed sensor (double fiber mode) is compared with the transmitting mode sensor and the sensor shows superior response for methanol over other gases. The dynamic characteristics of the sensor are reported.

scholarly journals N-doped reduced graphene oxide for room-temperature NO gas sensors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu-Sung Chang ◽  
Feng-Kuan Chen ◽  
Du-Cheng Tsai ◽  
Bing-Hau Kuo ◽  
Fuh-Sheng Shieu
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Room Temperature ◽  
Gas Sensing ◽  
Ambient Conditions ◽  
Gas Sensitivity ◽  
Nitrogen Doped ◽  
Low Concentrations ◽  
Reduced Graphene ◽  
P Type

AbstractIn this study, we use nitrogen-doped to improving the gas-sensing properties of reduced graphene oxide. Graphene oxide was prepared according to a modified Hummers’ method and then nitrogen-doped reduced graphene oxide (N-rGO) was synthesized by a hydrothermal method using graphene oxide and NH4OH as precursors. The rGO is flat and smooth with a sheet-like morphology while the N-rGO exhibits folded morphology. This type of folding of the surface morphology can increase the gas sensitivity. The N-rGO and the rGO sensors showed n-type and p-type semiconducting behaviors in ambient conditions, respectively, and were responsive to low concentrations of NO gases (< 1000 ppb) at room temperature. The gas-sensing results showed that the N-rGO sensors could detect NO gas at concentrations as low as 400 ppb. The sensitivity of the N-rGO sensor to 1000 ppb NO (1.7) is much better than that of the rGO sensor (0.012). Compared with pure rGO, N-rGO exhibited a higher sensitivity and excellent reproducibility.

scholarly journals Highly Sensitive, Selective, Flexible and Scalable Room-Temperature NO2 Gas Sensor Based on Hollow SnO2/ZnO Nanofibers

Molecules ◽  
2021 ◽  
Vol 26 (21) ◽  
pp. 6475
Author(s):  
Jiahui Guo ◽  
Weiwei Li ◽  
Xuanliang Zhao ◽  
Haowen Hu ◽  
Min Wang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Gas Sensing ◽  
Positive Impact ◽  
High Sensitivity ◽  
Detection Sensitivity ◽  
Pure Sno2 ◽  
Flexible Devices ◽  
Low Concentrations ◽  
Highly Sensitive ◽  
Sensitivity And Selectivity

Semiconducting metal oxides can detect low concentrations of NO2 and other toxic gases, which have been widely investigated in the field of gas sensors. However, most studies on the gas sensing properties of these materials are carried out at high temperatures. In this work, Hollow SnO2 nanofibers were successfully synthesized by electrospinning and calcination, followed by surface modification using ZnO to improve the sensitivity of the SnO2 nanofibers sensor to NO2 gas. The gas sensing behavior of SnO2/ZnO sensors was then investigated at room temperature (~20 °C). The results showed that SnO2/ZnO nanocomposites exhibited high sensitivity and selectivity to 0.5 ppm of NO2 gas with a response value of 336%, which was much higher than that of pure SnO2 (13%). In addition to the increase in the specific surface area of SnO2/ZnO-3 compared with pure SnO2, it also had a positive impact on the detection sensitivity. This increase was attributed to the heterojunction effect and the selective NO2 physisorption sensing mechanism of SnO2/ZnO nanocomposites. In addition, patterned electrodes of silver paste were printed on different flexible substrates, such as paper, polyethylene terephthalate and polydimethylsiloxane using a facile screen-printing process. Silver electrodes were integrated with SnO2/ZnO into a flexible wearable sensor array, which could detect 0.1 ppm NO2 gas after 10,000 bending cycles. The findings of this study therefore open a general approach for the fabrication of flexible devices for gas detection applications.

Fabrication of Diamond Based Quartz Crystal Microbalance Gas Sensor

2014 ◽  
Vol 605 ◽  
pp. 589-592 ◽  
Author(s):  
Marián Varga ◽  
Alexandr Laposa ◽  
Pavel Kulha ◽  
Marina Davydova ◽  
Jiri Kroutil ◽  
...  
Keyword(s):  
Gas Sensor ◽  
Quartz Crystal Microbalance ◽  
Room Temperature ◽  
Quartz Crystal ◽  
Microwave Plasma ◽  
Natural Diamond ◽  
Chemical Vapor ◽  
Mass Sensor ◽  
Mass Sensors ◽  
Optical Mirrors

Synthetic diamond has remarkable properties comparable with natural diamond and hence is a very promising material for many various applications (sensors, heat sink, optical mirrors, cold cathode, tissue engineering, etc.). Nowadays, deposition of diamond films is normally employed in chemical vapor deposition (CVD) usually at high temperatures (800900 °C), what limit its application to high melting substrates. Gravimetric (mass) sensors belong to the major categories of chemical sensors and the most common type of mass sensor is the bulk acoustic quartz crystal microbalance (QCM). This contribution deals with a nanocrystalline diamond (NCD) growth from the H2/CH4/CO2gas mixture at low temperature (400 °C) by pulsed linear antenna microwave plasma system on 10 MHz circular AT-cut quartz resonators substrate. Gas sensor based on the NCD-coated QCM was developed for detection of ammonia (NH3) at room temperature. Measurements not only confirmed the functionality of this first published NCD-coated QCM sensor, but in addition its sensitivity was twofold to a virgin QCM sensor with a gold active layer.

Growth of Ternary Silicon Carbon Nitride as a New Wide Band Gap Material

1997 ◽  
Vol 468 ◽  
Author(s):  
L. C. Cheni ◽  
C. K. Chen ◽  
D. M. Bhusari ◽  
K. H. Chen ◽  
S. L. Wei ◽  
...  
Keyword(s):  
Band Gap ◽  
Carbon Nitride ◽  
Room Temperature ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Wide Band ◽  
Hexagonal Structure ◽  
Electron Microscopies ◽  
Compound C ◽  
Si Content

ABSTRACTGrowth of pure crystalline carbon nitride (c-CN) with crystal sizes large enough to enable measurement of its properties has not been achieved so far. We report here that incorporation of silicon in the growth of CN can promote formation of large, well faceted crystallites. Crystalline thin films of SiCN have been grown by microwave plasma-enhanced chemical vapor deposition using CH4, N2, and SiH4 gases. Auger electron spectroscopy, scanning electron microscopies, and X-ray diffraction spectroscopy have been employed to characterize the composition, the morphology and the structure of the films. The new crystalline ternary compound (C; Si)xNy exhibits hexagonal structure and consists of a network wherein the Si and C are believed to be substitutional elements. While the N content of the compound is about 35%, the extent of Si substitution varies from crystal to crystal. In some crystals, the Si content can be as low as 10%. Optical properties of the SiCN compounds have been studied by photoluminescence (PL) and piezoreflectance (PzR) spectroscopies. From the PzR measurement, we determine the band gap of the new crystals to be around 3.8 eV at room temperature. From the PL measurement, it is found that the compounds have a strong subband-gap emission centered around 2.8 eV at room temperature, which can be attributed to the effect of defects containing in the crystals.

The effects of deposition temperature on properties of SiO2 films fabricated by a new electron cyclotron resonance microwave plasma-enhanced chemical-vapor deposition process

1991 ◽  
Vol 69 (3-4) ◽  
pp. 165-169 ◽  
Author(s):  
T. T. Chau ◽  
S. R. Mejia ◽  
K. C. Kao
Keyword(s):  
Chemical Vapor Deposition ◽  
Leakage Current ◽  
Vapor Deposition ◽  
Cyclotron Resonance ◽  
Deposition Temperature ◽  
Room Temperature ◽  
Electron Cyclotron Resonance ◽  
Microwave Plasma ◽  
Chemical Vapor ◽  
Electron Cyclotron

Silicon dioxide (SiO2) films were deposited by a new electron cyclotron resonance (ECR) microwave plasma enhanced chemical vapor deposition (PECVD) process at various deposition temperatures ranging from room temperaure (~25 °C) to 300 °C. The deposition rate increases with increasing deposition temperature and tends to become saturated as the deposition temperature approaches 250 °C, in contrast to the SiO2 films fabricated by the conventional ECR microwave PECVD process. The Fourier transform infrared results provide no evidence of hydrogen incorporation in the SiO2 films even when they were deposited at room temperature. Films deposited at temperatures higher than 270 °C exhibit an excellent electrical integrity that is comparable with high-quality SiO2 films grown thermally at 1000 °C. Films deposited at room temperature have a slightly higher refractive index and also high-leakage current though the films appear as good as those deposited at 300 °C. As the deposition temperature is increased, both the shoulder height of the Si—O stretching band and the leakage current decrease. The correlation between the film properties and the film growth mechanism is also discussed.

scholarly journals Gas sensing with gold-decorated vertically aligned carbon nanotubes

2014 ◽  
Vol 5 ◽  
pp. 910-918 ◽  
Author(s):  
Prasantha R Mudimela ◽  
Mattia Scardamaglia ◽  
Oriol González-León ◽  
Nicolas Reckinger ◽  
Rony Snyders ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Gold Nanoparticles ◽  
Nitrogen Dioxide ◽  
Room Temperature ◽  
Gas Sensing ◽  
Chemical Vapor ◽  
Vertically Aligned Carbon Nanotubes ◽  
Aligned Carbon Nanotubes ◽  
Vertically Aligned ◽  
Carbon Nanotube Forests

Vertically aligned carbon nanotubes of different lengths (150, 300, 500 µm) synthesized by thermal chemical vapor deposition and decorated with gold nanoparticles were investigated as gas sensitive materials for detecting nitrogen dioxide (NO2) at room temperature. Gold nanoparticles of about 6 nm in diameter were sputtered on the top surface of the carbon nanotube forests to enhance the sensitivity to the pollutant gas. We showed that the sensing response to nitrogen dioxide depends on the nanotube length. The optimum was found to be 300 µm for getting the higher response. When the background humidity level was changed from dry to 50% relative humidity, an increase in the response to NO2 was observed for all the sensors, regardless of the nanotube length.

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