Mo-W-O thin films for CO sensing

2000 ◽  
Vol 638 ◽  
Author(s):  
Elisabetta Comini ◽  
Matteo Ferroni ◽  
Vincenzo Guidi ◽  
Giuliano Martinelli ◽  
Michele Sacerdoti ◽  
...  
Keyword(s):  
Thin Films ◽  
Gas Sensing ◽  
Weight Ratio ◽  
X Ray Diffraction ◽  
Composite Target ◽  
X Ray ◽  
Structural Characterisation ◽  
Gas Sensing Properties ◽  
Recovery Times ◽  
Response And Recovery

AbstractThe Mo-W-O thin films were deposited by RF reactive sputtering from composite target of W and Mo (20:80 weight ratio). Structural characterisation was carried out by X-ray diffraction spectroscopy and the composition of the film was obtained by Rutherford backscattering analysis. The layers were investigated by volt-amperometric technique for electrical and gas-sensing properties. The films were capable of sensing CO. No effect of poisoning of the surface was recorded and recovery of the resistance was complete. A concentration of CO as low as 15 ppm produced a relative variation in the conductance of 390% with response and recovery times of about 2 minutes at a working temperature of 200°C.

A Formaldehyde Gas Sensor Based on Zinc Doped Lanthanum Ferrite

2013 ◽  
Vol 873 ◽  
pp. 304-310 ◽  
Author(s):  
Jin Zhang ◽  
Yu Min Zhang ◽  
Chang Yi Hu ◽  
Zhong Qi Zhu ◽  
Qing Ju Liu
Keyword(s):  
Gas Sensing ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Sensing Properties ◽  
Transmission Electron ◽  
Lanthanum Ferrite ◽  
Gas Sensing Properties ◽  
Recovery Times ◽  
Response And Recovery ◽  
Sensing Characteristics

The gas-sensing properties of zinc doped lanthanum ferrite (Zn-LaFeO3) compounds for formaldehyde were investigated in this paper. Zn-LaFeO3 powders were prepared using sol-gel method combined with microwave chemical synthesis. The powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formaldehyde gas-sensing characteristics for the sample were examined. The experimental results indicate that the sensor based on the sample Zn-LaFeO3 shows excellent gas-sensing properties to formaldehyde gas. At the optimal operating temperature of 250°C, the sensitivity of the sensor based on LaFe0.7Zn0.3O3 to 100ppm formaldehyde is 38, while to other test gases, the sensitivity is all lower than 20. The response and recovery times for the sample to formaldehyde gas are 100s and 100s, respectively.

Au/Pd Bimetallic Nanoparticles Decorated SnSe2 Thin Films for NO2 Detection

2021 ◽  
Vol 21 (9) ◽  
pp. 4916-4920
Author(s):  
Sanju Rani ◽  
Manoj Kumar ◽  
Yogesh Singh ◽  
Vidya Nand Singh
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Ambient Temperature ◽  
Surface Area ◽  
Gas Sensing ◽  
Sensing Properties ◽  
Toxic Gases ◽  
Gas Sensing Properties ◽  
Recovery Times ◽  
Response And Recovery

In order to have a check and balance of the toxic gases in the environment, various kinds of sensors are currently being researched upon. As many of the toxic gases are also inflammable, therefore, there is a constant search for materials which can detect the gases at lower temperatures. Also, it is important that the sensor is selective for a particular gas. To meet such requirements, nanos-tructured materials are extensively being explored for such gas sensing applications, due to their large effective surface area. And, in order to further improve the gas sensing properties, metal catalysts are deposited over such nanomaterials. The smaller sized nanoparticles show better catalytic activity due to its effective larger surface area per unit volume. Depositing bimetallic materials is thus advantageous, since it can reduce the size of nanoparticles produced. In this work, ~7 nm thick Au/Pd thin film was sputter-coated over SnSe2 nanostructured thin films. SnSe2 thin film were deposited by thermally evaporating SnSe2 powder. The materials were characterized for their structural, morphological and gas sensing properties. The ambient temperature response for 5 parts per million (ppm) NO2 gas was measured to be 117%, with the response and recovery times being 10 and 19 seconds, respectively. The performance of the sensor improved with increase in the gas concentration and for 10 ppm gas, the recorded response was 137%, with the corresponding response and recovery times being 9 and 8 seconds, respectively. The limit of detection was 655 parts per billion (ppb). The mechanism of ambient temperature high response and low response/recovery times have been discussed based on physisorption, charge transfer, Au/Pd decoration and SnSe–SnSe2 based p–n junction. In addition, an important aspect of this work worth pointing out is the deposition of a thin film consisting of nanostructured network using an industrially viable thermal evaporation method. Thus, this work opens a new dimension for 2D materials that can be used for selective gas detection at ambient temperature.

scholarly journals Studies on Spray Pyrolised Nanostructured SnO2 Thin Films for H2 Gas Sensing Application

2014 ◽  
Vol 36 ◽  
pp. 125-141 ◽  
Author(s):  
R.H. Bari ◽  
S.B. Patil
Keyword(s):  
Thin Films ◽  
Gas Sensing ◽  
Spray Pyrolysis Technique ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sensing System ◽  
Gas Sensing Properties ◽  
Structural Surface ◽  
Diffraction Peaks ◽  
Gas Response

The objective of this work is to study the influence of pyrolysis temperature on structural, surface morphology and gas sensing properties of the nanostructured SnO2 thin films prepared by spray pyrolysis technique. These films were characterized for the structural, morphological and elemental composition carried by means of X-ray diffraction (XRD), scanning electron mi­croscopy (SEM) and energy dispersive spectrophotometer (EDAX). The information of crystallite size, dislocation density and microstrain is obtained from the full width-at half- maximum (FWHM) of the diffraction peaks. Effect of sprayed deposition temperature on H2 gas sensing performance and electrical properties were studied using static gas sensing system. The sensor (Tpyr. = 350°C) showed high gas response (S = 1200 at 350 °C) on exposure of 500 ppm of H2 and high selectivity against other gases The results are discussed and interpreted.

scholarly journals Preparation, Characterization, and Mechanistic Understanding of Pd-Decorated ZnO Nanowires for Ethanol Sensing

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Xiao Deng ◽  
Shengbo Sang ◽  
Pengwei Li ◽  
Gang Li ◽  
Fanqin Gao ◽  
...  
Keyword(s):  
Gas Sensing ◽  
Operating Temperature ◽  
Zno Nanowires ◽  
X Ray Diffraction ◽  
X Ray ◽  
Recovery Times ◽  
Response And Recovery ◽  
New Perspective ◽  
Ethanol Sensing ◽  
Higher Sensitivity

ZnO nanowires (ZnO-NWs) and Pd-decorated ZnO nanowires (Pd-ZnO-NWs) were prepared by hydrothermal growth and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). When used for gas sensing, both types of nanowires showed a good selectivity to ethanol but a higher sensitivity and lower operating temperature were found with Pd-ZnO-NWs sensors comparing to those of ZnO-NWs sensor. When exposed to 200 ppm ethanol, our ZnO-NWs sensor showed a sensitivity of about 2.69 at 425°C whereas 1.3 at. % Pd-ZnO-NWs sensor provided a 57% more detection sensibility at 325°C. In addition, both response and recovery times of Pd-ZnO-NWs sensors were significantly reduced (9 s) comparing to the ZnO-NWs. Finally, Pd-ZnO-NWs sensor also showed a much lower detection limit of about 1 ppm. The sensing mechanism of Pd-ZnO-NWs sensors has also been clarified, thereby providing a new perspective for further improvement of the sensing performance of ethanol sensors.

Polyaniline/SnO2 Nanocomposite Sensor for NO2 Gas Sensing at Low Operating Temperature

2015 ◽  
Vol 14 (04) ◽  
pp. 1550011 ◽  
Author(s):  
A. Sharma ◽  
M. Tomar ◽  
V. Gupta ◽  
A. Badola ◽  
N. Goswami
Keyword(s):  
Thin Films ◽  
Gas Sensing ◽  
High Sensitivity ◽  
Morphological Properties ◽  
X Ray Diffraction ◽  
Chemical Route ◽  
Sensing Properties ◽  
Response Recovery ◽  
Transmission Electron ◽  
Gas Sensing Properties

In this paper gas sensing properties of 0.5–3% polyaniline (PAni) doped SnO 2 thin films sensors prepared by chemical route have been studied towards the trace level detection of NO 2 gas. The structural, optical and surface morphological properties of the PAni doped SnO 2 thin films were investigated by performing X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Raman spectroscopy measurements. A good correlation has been identified between the microstructural and gas sensing properties of these prepared sensors. Out of these films, 1% PAni doped SnO 2 sensor showed high sensitivity towards NO 2 gas along with a sensitivity of 3.01 × 102 at 40°C for 10 ppm of gas. On exposure to NO 2 gas, resistance of all sensors increased to a large extent, even greater than three orders of magnitude. These changes in resistance upon removal of NO 2 gas are found to be reversible in nature and the prepared composite film sensors showed good sensitivity with relatively faster response/recovery speeds.

scholarly journals Chemically synthesized PbS Nano particulate thin films for a rapid NO2 gas sensor

2016 ◽  
Vol 34 (1) ◽  
pp. 204-211 ◽  
Author(s):  
Vishal V. Burungale ◽  
Rupesh S. Devan ◽  
Sachin A. Pawar ◽  
Namdev S. Harale ◽  
Vithoba L. Patil ◽  
...  
Keyword(s):  
Thin Films ◽  
Gas Sensor ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Morphological Properties ◽  
X Ray Diffraction ◽  
Gas Sensitivity ◽  
Silar Method ◽  
Layer Adsorption ◽  
Gas Sensing Properties

AbstractRapid NO2 gas sensor has been developed based on PbS nanoparticulate thin films synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method at different precursor concentrations. The structural and morphological properties were investigated by means of X-ray diffraction and field emission scanning electron microscope. NO2 gas sensing properties of PbS thin films deposited at different concentrations were tested. PbS film with 0.25 M precursor concentration showed the highest sensitivity. In order to optimize the operating temperature, the sensitivity of the sensor to 50 ppm NO2 gas was measured at different operating temperatures, from 50 to 200 °C. The gas sensitivity increased with an increase in operating temperature and achieved the maximum value at 150 °C, followed by a decrease in sensitivity with further increase of the operating temperature. The sensitivity was about 35 % for 50 ppm NO2 at 150 °C with rapid response time of 6 s. T90 and T10 recovery time was 97 s at this gas concentration.

Preparation and Gas-Sensing Property of Coppertetra-Iso-Propoxyphthalocyanine Spin-Coating Film

2011 ◽  
Vol 197-198 ◽  
pp. 1735-1738
Author(s):  
Qiang Li ◽  
Li Hua Huo ◽  
Shan Gao ◽  
Xiao Juan Qi ◽  
Hui Zhao
Keyword(s):  
Thin Films ◽  
Spin Coating ◽  
Gas Sensing ◽  
High Sensitivity ◽  
Coating Film ◽  
Gas Sensing Properties ◽  
Response And Recovery ◽  
Ft Ir ◽  
Spinning Speed ◽  
Spectroscopy Property

The thin films of copper 2, 9, 16, 23-tetra-iso-propoxy phthalocyanine (i-pro-CuPc) were prepared by spin-coating technique. The surface morphology and spectroscopy property of the thin films were characterized by AFM, UV-Vis and FT-IR spectra. The results show that good films can be obtained under certain spinning speed. The gas-sensing properties of the multilayers to three alcohols gas were measured at room temperature. The spin-coating thin films exhibited high sensitivity and rapid response- recovery characteristics to these gases. The response and recovery time of the thin films to 30*10-6 v/v of C2H5OH vapor is only 28 s and 55 s, respectively.

A Novel Tungsten Trioxide Based Gas Sensor for Indoor Formaldehyde Detection

2021 ◽  
Vol 16 (3) ◽  
pp. 363-367
Author(s):  
Gaoqi Zhang ◽  
Fan Zhang ◽  
Kaifang Wang ◽  
Tao Tian ◽  
Shanyu Liu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Gas Sensor ◽  
Indoor Air ◽  
Gas Sensing ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sensing Material ◽  
Transmission Electron ◽  
Gas Sensing Properties ◽  
Gas Response

Accurate and real-time detection of formaldehyde (HCHO) in indoor air is urgently needed for human health. In this work, a ceramic material (WO3·H2O) with unique structure was successfully prepared using an efficient hydrothermal method. The crystallinity, morphology and microstructure of the as-prepared sensing material were analyzed by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) as well as transmission electron microscope (TEM). The characterization results suggest that the as-prepared sample is composed of square-like nanoplates with uneven surface. Formaldehyde vapor is utilized as the target gas to investigate gas sensing properties of the synthesized novel nanoplates. The testing results indicate that the as-fabricated gas sensor exhibit high gas response and excellent repeatability to HCHO gas. The response value (Ra/Rg) is 24.5 towards 70 ppm HCHO gas at 350 °C. Besides, the gas sensing mechanism was described.

Fabrication of TiO2 sensor using rapid breakdown anodization method to measure pressure, humidity and sense gases at room temperature

2019 ◽  
pp. 1694-1703
Author(s):  
Reem Saadi Khaleel ◽  
Mustafa Shakir Hashim
Keyword(s):  
Room Temperature ◽  
Average Pressure ◽  
Spherical Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Recovery Times ◽  
Sensitivity And Selectivity ◽  
Response And Recovery ◽  
Anodization Method ◽  
Rapid Breakdown Anodization

Rapid breakdown anodization (RBA) process was used to fabricate TiO2 sensor to measure pressure and humidity and sense gases at room temperature. This chemical process transformed Ti to its oxide (TiO2) as a powder with amorphous phase as X ray diffraction (XRD) technique confirmed.  This oxide consisted from semi spherical nanoparticles and titania nanotubes (TNTs) as Scanning electron microscope (SEM) technique showed.  TiO2 powder was deposited on Ti substrates by using electrophoretic deposition (EPD) method.   Average pressure sensitivity was 0.34 MΩ/bar and hysteresis area was 1.4 MΩ .bar. Resistance of TiO2 decreased exponentially with the increasing of relative humidity (RH%). The sensitivity% of TiO2 for RH% was greater than 70% in the range of (50-95). TiO2 was tested as a sensor for Ammonia, Ethanol and Methanol. Its sensitivity and selectivity towards Ammonia were the greatest but the shortest response and recovery times were recorded toward Methanol.

scholarly journals Gas-sensing features of nanostructured tellurium thin films

2020 ◽  
Vol 11 ◽  
pp. 1010-1018
Author(s):  
Dumitru Tsiulyanu
Keyword(s):  
Thin Films ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Active Surface ◽  
Active Surface Area ◽  
Gas Sensitivity ◽  
Nanocrystalline And Amorphous ◽  
Recovery Times ◽  
Order Of Magnitude ◽  
Response And Recovery

Nanocrystalline and amorphous nanostructured tellurium (Te) thin films were grown and their gas-sensing properties were investigated at different operating temperatures with respect to scanning electron microscopy and X-ray diffraction analyses. It was shown that both types of films interacted with nitrogen dioxide, which resulted in a decrease of electrical conductivity. The gas sensitivity, as well as the response and recovery times, differed between these two nanostructured films. It is worth mentioning that these properties also depend on the operating temperature and the applied gas concentration on the films. An increase in the operating temperature decreased not only the response and recovery times but also the gas sensitivity of the nanocrystalline films. This shortcoming could be solved by using the amorphous nanostructured Te films which, even at 22 °C, exhibited higher gas sensitivity and shorter response and recovery times by more than one order of magnitude in comparison to the nanocrystalline Te films. These results were interpreted in terms of an increase in disorder (amorphization), leading to an increase in the surface chemical activity of chalcogenides, as well as an increase in the active surface area due to substrate porosity.

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