Highly Sensing Properties Sensors Based on Ce-doped ZnO and SnO2 Nanoparticles to Ethanol Gas (original) (raw)
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Nanoparticles tin oxide gas sensors having the chemical formula SnO2 + x wt% CeO2 (x = 0, 2, 4 and 6) have been synthesized by chemical precipitation method and sintered at 400, 600 and 800 oC. The composition and the morphology of the prepared samples are investigated and characterized by using XRD, IR, SEM and TEM techniques. XRD and IR results confirmed the formation of SnO2 tetragonal rutile and CeO2 cubic structures. The SEM and TEM investigations revealed that the average particle size of SnO2 increased with increasing the sintering temperature and decreased with CeO2 additions. The electrical conductivity was found to increase with sintering temperature and CeO2 additions. The obtained gas sensing properties data explained that the sensor having 2 wt % CeO2 and sintered at 400◦C has the highest sensitivity, rapid response time and short recovery time to ethanol gas among the prepared sensors. The influence of sintering temperature and CeO2 content on the structure, electrical conductivity and ethanol gas sensing of SnO2 sensors is discussed.
Nanocrystalline sensors having the general formula ZnO + x wt% CeO2, where x = 0, 2, 4 and 6 were prepared by chemical precipitation method and sintered at 400, 600 and 800 oC for 2h in static air atmosphere. The crystal structure and the morphology of the prepared samples were investigated and characterized by using XRD, IR, SEM and TEM techniques. The investigation revealed that the average crystallites size increases with increasing the sintering temperature. The electrical conductivity is found to increase with CeO2 additions and sintering temperature. Gas sensing properties of the prepared samples were also investigated. The effect of CeO2 content and sintering temperature on the structure, electrical conductivity and ethanol gas sensing properties of the prepared samples are discussed.
Nanostructured SnO2–ZnO sensors: Highly sensitive and selective to ethanol
Sensors and Actuators B: Chemical, 2011
Nanostructured SnO 2 -ZnO as selective ethanol gas sensor materials with controlled grain size and morphology were successfully synthesized by a precipitation method. The structure, morphology, and gas sensing performance of calcined SnO 2 -ZnO samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area analyzer (using BET method), and a continuous-flow gas sensing measurement system, respectively. The sensors responses depend on the composition, size and morphology of the samples. The sensor with 0.05:1.0 Zn 2+ :Sn 2+ molar ratio was highly sensitive and selective for the detection of ethanol. The gas-sensing mechanism of the nanostructures was discussed. The different reductive-oxidative and acid-base heterostructures of SnO 2 and ZnO were suggested as the main reasons for the selective detection of ethanol. in 1995. His research interests include catalysis and reaction engineering especially in C1 chemistry, environmental catalysis, chemical gas-sensors and nano-structured materials. Currently he is the chair
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Nanosized ZnO powder was synthesized by using a chemical precipitation method, and loaded with different dopants through impregnation. The as-prepared ZnO powder was characterized by XRD and TEM. The characterization results show that the as-prepared sample is wurtzite polycrystalline ZnO, the mean grain size is 30-40 nm, and there are three types of adsorbed oxygen (O 2 − , O 2 2− , and O 2− ) on the surface of the sample. The as-prepared ZnO powder shows excellent gas responses to alcohol and acetaldehyde, but no response to ethene. The sensing mechanism of ZnO was further studied with the help of gas chromatography (GC) associated with a fixed-bed reactor. The studies show that acetaldehyde, carbon dioxide and water are the only oxidation products of C 2 H 5 OH over ZnO. The gas response to C 2 H 5 OH is strongly dependent on the conversion ratio of C 2 H 5 OH to acetaldehyde. In addition, among all the dopants tested, Ru is the optimal dopant which can increase the response to C 2 H 5 OH, but cannot increase the conversion ratio of C 2 H 5 OH to acetaldehyde. Thus we suggest that the gas sensing mechanism of ZnO to C 2 H 5 OH is the mode controlled by chemisorption of negatively charged oxygen, and the sensitizing role of Ru in the ZnO sensor belongs to the electronic sensitization mechanism.
CeO2 doped ZnO flower-like nanostructure sensor selective to ethanol in presence of CO and CH4
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CeO 2 -doped ZnO nanostructures, with different Ce/Zn ratios, were synthesized via a very fast microwaveassisted method using zinc acetate dihydrate and cerium nitrate as starting materials and water as solvent. The samples were characterized via SEM, EDX, XRD, and BET analyses. Gas sensitivity of the fabricated sensor was studied for selective detection of ethanol in presence of CO and CH 4 and effect of CeO 2 with different concentrations as a dopant was investigated. 5 wt% CeO 2 doped sample was shown to improve the sensor response to 500 ppm ethanol with high selectivity in presence of CO and CH 4 . Furthermore presence of ceria reduced the recovery time of the sensor significantly. The CeO 2 -doped ZnO may be considered a promising sensing material for selective detection of ethanol.
2000
A spray pyrolysis technique was used to obtain ZnO:X films doped with different elements, Xs Al, In, Cu, Fe and Sn. X-Ray diffraction, transmission electron microscopy and scanning electron microscopy were used to study the microstructure and surface morphology of the films. From the microstructural analysis, we can conclude that the amount as well as the type of dopant modifies the microstructure and surface morphology. Since it goes from non-oriented growth, for undoped films, to Ž. Ž. strongly 002 oriented, at intermediate ; 1 at.% doping level; and finally again to non-oriented and poor crystallinity, at high Ž. Ž .) 3 at.% doping level. The sensitivity of the films was studied in two steps: first as a function of their temperature 435᎐675 K Ž. Ž. for a fixed ethanol concentration 40 ppm and secondly as a function of ethanol concentration 4᎐100 ppm for a fixed Ž. temperature 675 K. A better sensitivity can be observed for Sn-and Al-doped films, with a dopantrZn ratio of 0.4 at.
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In this paper, the ZnO target was synthesized by the solid-state reaction method and a nanostructured thin film was deposited by the RF (radio frequency) magnetron sputtering method on a Multi-Sensor-Platform. The obtained ZnO nanostructured film was investigated as the sensing material. Energy-Dispersive X-ray (EDX) analysis indicated the existence of La in the synthesized ZnO material. Scanning Electron Microscope (SEM) images of the film showed the grain sizes in the range of 20–40 nm. Sensor performance characteristics such as a dynamic response, response and recovery times, and ethanol detection range were investigated at 50–300 °C. A sensitivity was observed at extremely low concentrations of ethanol (0.7 ppm). The minimum response and recovery times of the sensor corresponding to 675 ppm ethanol vapor concentration at 250 °C were found to be 14 s and 61 s, respectively. The sensor showed a high response, good selectivity, fast response/recovery behavior, excellent repeatabili...
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Zinc oxide (ZnO) nanostructures were deposited on glass substrates by physical vapor deposition technique. To improve the crystallinity of ZnO, oxidation treatment was conducted at 400 • for 1 h in an atmospheric environment. The films characteristics of the films were examined by X-ray diffraction, ultraviolet-visible spectroscopy, atomic force microscopy, and scanning electron microscopy. The X-ray diffraction results illustrated that the deposited films have a polycrystalline hexagonal structure. The ultraviolet-visible spectrum showed that the transmittance of the ZnO film has an energy gap of about 3.225 eV. The atomic force microscopy images indicated that the films have good homogeneity, and the scanning electron microscopy images reveal that they consist of spherical nanosized grains with a granular surface. The ZnO films revealed good sensing performance to acetone and ethanol gases at an operating temperature of 25 • C with suitable recovery and response times. The sensitivity measured by homemade gas sensor system was approximately 21.
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The present study investigates the electrical and sensing properties of mechanically compacted pellets of nanosized zinc oxide powders synthesized by chemical method at room temperature in alcohol base using Triethanolamine (TEA) as capping agent. Synthesized ZnO particles has been characterized for its optical, structural, morphological properties using UV-VIS spectrophotometer, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ZnO particles have hexagonal wurtzite structure and the particles are of 20-30 nm in size. The electrical properties of the prepared material have been investigated with Impedance Spectroscopy at different temperatures and frequencies and other laboratory setup. Resistivity, I-V curves, AC impedance of ZnO nanoparticles pellets with temperature was investigated and response was compared with commercial ZnO. Piezoelectric and oxygen sensing property of ZnO were also examined. Dynamic hysteresis of sintered ZnO pellet using axis ACCT TF analyzer 2000HS did not show polarization retention by sample. Oxygen sensing of ZnO pellet has been investigated for different concentrations of oxygen for the temperature range of 200-350°C. The decrease of the current flow through the ZnO pellet with increasing oxygen concentration indicates the application of ZnO in oxygen sensing. The prepared ZnO particles were also used for preparing nanofluids of different concentrations and were characterized by measuring thermal conductivity using hot wire method which shows sigmoidal behavior over a temperature range of 10-50°C.