共查询到20条相似文献,搜索用时 15 毫秒
1.
Jin Hyung Junggwon Kyoungah In-Sung Jong-Heun Sangsig 《Sensors and actuators. B, Chemical》2009,140(2):412-417
The NO2 gas sensing characteristics of semiconductor type gas sensors with channels composed of necked ZnO nanoparticles (NPs) were investigated in this study. The heat treatment of the NPs at 400 °C led to their necking and coarsening. The response of the necked-NP-based sensors was as high as 100 when exposed to 0.2 ppm of NO2 at 200 °C. As the concentration of NO2 increased to 5 ppm, their response was enhanced to approximately 400. During the repeated injection of NO2 gas with a concentration of 0.4 ppm, the sensors exhibited stable response characteristics. Furthermore, the 90% response and recovery times of the gas sensor were as fast as 13 and 10 s, respectively. These observations indicate that the non-agglomerated necking of the NPs induced by the heat treatment significantly enhances the gas sensing characteristics of the NP-based gas sensors. 相似文献
2.
R. PearceAuthor Vitae T. IakimovM. AnderssonAuthor Vitae L. HultmanAuthor VitaeA. Lloyd SpetzAuthor Vitae R. YakimovaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):451-455
Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO2. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO2 detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n-p transition upon exposure to increasing concentrations of NO2 indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO2 making holes the majority carriers. 相似文献
3.
Shouli BaiAuthor VitaeXin LiuAuthor Vitae Dianqing LiAuthor Vitae Aifan ChenAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):110-116
One-dimensional (1D) ZnO nanorods with pencil-like shape and high aspect ratio were successfully synthesized using a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal process at 90 °C. The surface morphology and structure of nanocrystals were characterized by FE-SEM, XRD and XPS analysis. Experimental results show that the surfactant and base concentration play important roles in the formation and growth orientation of ZnO nanorods. The ZnO nanorods synthesized exhibits high response and selectivity to NO2, the highest response to 40 ppm NO2 reached 206 and the selectivity with respect to CO and CH4 at same concentration reached 10.3 and 30 times, respectively. The effects of synthesis method, surfactant and calcination condition on sensing properties were systematically investigated. The results indicate that the CTAB-assisted low temperature hydrothermal process is a potentially facile method for synthesis of 1D ZnO nanorods and excellent potential candidates as gas sensing materials. 相似文献
4.
Viruntachar KruefuAuthor VitaeChaikarn LiewhiranAuthor Vitae Anurat WisitsoraatAuthor VitaeSukon PhanichphantAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(1):360-367
Unloaded ZnO and Nb/ZnO nanoparticles containing 0.25, 0.5 and 1 mol.% Nb were produced in a single step by flame-spray pyrolysis (FSP) technique. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The BET surface area (SSABET) of the nanoparticles was measured by nitrogen adsorption. FSP yielded small Nb particles attached to the surface of the supporting ZnO nanoparticles, indicating a high SSABET. The morphology and accurate size of the primary particles were further investigated by TEM. Nb/ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al2O3 substrate interdigitated with gold electrodes to form thick films by spin coating technique. After the sensing tests, the morphology and the cross-section of sensing film were analyzed by SEM and EDS analyses. The influence on a low dynamic range of Nb concentration on NO2 response (0.1-4 ppm) of thick film sensor elements was studied at the operating temperatures ranging from 250 to 350 °C in the presence of dry air. The optimum Nb concentration was found be 0.5 mol.% and 0.5 mol.% Nb exhibited an optimum NO2 response of ∼1640 and a short response time (27 s) for NO2 concentration of 4 ppm at 300 °C. 相似文献
5.
The authors present an ab initio study of NO2 and SO2 chemisorption onto non-polar ZnO and ZnO surfaces with the aim of providing theoretical hints for further developments in gas sensors. From first principles calculations (DFT-GGA approximation), the most relevant surface reduction scenarios are analyzed and, subsequently, considered in the chemisorption study. First, calculations indicate that NO2 adsorbs avidly onto Zn surface atoms. This is compatible with the oxidizing character of NO2. Second, results also explain the sensor poisoning by SO2 adsorption (since this molecule competes with NO2 for the same adsorption sites) and indicate that poisoning can only be reverted at typical operation temperatures (T ≤ 700 °C) in the case of stoichiometric ZnO surfaces. 相似文献
6.
Bai ShouliAuthor VitaeChen LiangyuanAuthor Vitae Hu JingweiAuthor VitaeLi DianqingAuthor Vitae Luo RuixianAuthor VitaeChung Chiun LiuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,159(1):97-102
Quantum size ZnO crystals have been synthesized successfully by a room temperature sol-gel process. Oleic acid (OA) has been used as capping agent to control the particle size of ZnO. The crystal structure and size of the ZnO are characterized by the X-ray diffraction (XRD) and transmission electron microscope (TEM). The XRD results show the as-synthesized ZnO has hexagonal wurtzite structure and the average crystallite size is 5.7 nm which is little less than TEM result. It is testified by photoluminescence (PL) and Raman spectra that the quantum size ZnO keeps the crystal structure of the bulk ZnO and possesses more surface defects. The quantum size ZnO has the highest response of 280 to NO2 and the highest selectivity of 31 and 49 corresponding to CO and CH4 at operating temperature of 290 °C. The effect of calcination temperatures on sensing property and transient response of the ZnO sensor are also investigated. 相似文献
7.
Peng SunAuthor VitaeYanfeng SunAuthor Vitae Jian MaAuthor VitaeLu YouAuthor Vitae Geyu LuAuthor Vitae Wuyou FuAuthor VitaeMinghui LiAuthor Vitae Haibin YangAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):606-611
Large-scale novel core-shell structural SnO2/ZnSnO3 microspheres were successfully synthesized by a simple hydrothermal method with the help of the surfactant poly(vinyl pyrrolidone) PVP. The as-synthesized samples were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results indicate that the shell was formed by single crystalline ZnSnO3 nanorods and the core was formed by aggregated SnO2 nanoparticles. The effects of PVP and hydrothermal time on the morphology of SnO2/ZnSnO3 were investigated. A possible formation mechanism of these hierarchical structures was discussed. Moreover, the sensor performance of the prepared core-shell SnO2/ZnSnO3 nanostructures to ethanol was studied. The results indicate that the as-synthesized samples exhibited high response and quick response-recovery to ethanol. 相似文献
8.
Huijuan Yan Fanhong Shurong Baolin Xianzhi Jun Yanmei Shihua 《Sensors and actuators. B, Chemical》2008,134(1):133-139
Pure and Au-doped WO3 powders for NO2 gas detection were prepared by a colloidal chemical method, and characterized via X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The NO2 sensing properties of the sensors based on pure and Au-doped WO3 powders were investigated by HW-30A gas sensing measurement. The results showed that the gas sensing properties of the doped WO3 sensors were superior to those of the undoped one. Especially, the 1.0 wt% Au-doped WO3 sensor possessed larger response, better selectivity, faster response/recovery and better longer term stability to NO2 than the others at relatively low operating temperature (150 °C). 相似文献
9.
In this work we examine the possibility of using satellite remote sensors for the detection of air traffic emissions produced during the en-route segment of flight in the Upper Troposphere/Lower Stratosphere region (8000-12,000 m). NO2 has been considered as the tracer of aircraft plumes with highest possibility of being successfully detected from space. An analysis of the technical potential of the current orbital sensors capable of measuring NO2 in the proximity of the tropopause has been conducted. In order to estimate an upper bound for the NO2 column related to aircraft emissions, the Canary Islands Corridor has been selected for conducting a simple emission calculation exercise based on real air traffic and operational data, assuming an ideal atmospheric scenario. The results obtained in this approximation have been compared to the actual information retrieved from space sensors. An in-depth inspection of the NO2 column data for two particular areas (Canary Islands Corridor and North Atlantic Flight Corridor) obtained in recent years by SCIAMACHY and OMI has also been carried out.The general conclusions of this viability study are not optimistic. The estimated maximum NO2 column value attributable to aircraft emissions at cruise altitudes were lower than the detection limits associated with SCIAMACHY and OMI for NO2 column measurements. As a result, detecting and quantifying the actual NO2 levels in aircraft corridors by space remote sensing is a very challenging task. 相似文献
10.
In this study, the nitrogen dioxide (NO2) and ozone (O3) sensing properties of a series bis[tetrakis(alkylthio) phthalocyaninato] lutetium(III) complexes [(CnH2n+1S)4Pc]2Lu(III) (n = 6, 10, 16) are investigated as a function of concentration in the temperature range between 25 °C and 150 °C. The concentration ranges were 1–10 ppm for NO2, and 50 ppb–1 ppm for O3. The response time and the sensor response to NO2 are measured for approximately 1 min and 100% ppm−1, respectively, for compound 1 at room temperature. At room temperature, all compounds are in the solid phase. The response time decreases to a few seconds with increasing operation temperature to 150 °C. At this temperature, all compounds are in the liquid crystal phase. The fastest response to oxidizing gases is observed at the liquid crystal phase of the Pcs. It has also been observed that the response time and the sensor response depend on the alkyl chain lengths of the Pcs. The doping effect of oxygen has been determined under high purity nitrogen N2 flow, after exposure to dry air, at a different period of time and after annealing. It has been found that the conductivities of [(CnH2n+1S)4Pc]2Lu(III) thin films increased after exposure to dry air and the conduction mechanism also changed from ohmic behavior to space-charge-limited conduction. 相似文献
11.
Chunbae LimAuthor VitaeWen WangAuthor Vitae Sangsik YangAuthor VitaeKeekeun LeeAuthor Vitae 《Sensors and actuators. B, Chemical》2011,154(1):9-16
A 440 MHz wireless and passive surface acoustic wave (SAW)-based multi-gas sensor integrated with a temperature sensor was developed on a 41° YX LiNbO3 piezoelectric substrate for the simultaneous detection of CO2, NO2, and temperature. The developed sensor was composed of a SAW reflective delay lines structured by an interdigital transducer (IDT), ten reflectors, a CO2 sensitive film (Teflon AF 2400), and a NO2 sensitive film (indium tin oxide). Teflon AF 2400 was used for the CO2 sensitive film because it provides a high CO2 solubility, with good permeability and selectivity. For the NO2 sensitive film, indium tin oxide (ITO) was used. Coupling of mode (COM) modeling was conducted to determine the optimal device parameters prior to fabrication. Using the parameters determined by the simulation results, the device was fabricated and then wirelessly measured using a network analyzer. The measured reflective coefficient S11 in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. The time positions of the reflection peaks were well matched with the predicted values from the simulation. High sensitivity and selectivity were observed at each target gas testing. The obtained sensitivity was 2.12°/ppm for CO2 and 51.5°/ppm for NO2, respectively. With the integrated temperature sensor, temperature compensation was also performed during gas sensitivity evaluation process. 相似文献
12.
Highly sensitive NO2 sensor based on square-like tungsten oxide prepared with hydrothermal treatment
L. YouAuthor VitaeY.F. SunAuthor Vitae J. MaAuthor VitaeY. GuanAuthor Vitae J.M. SunAuthor VitaeY. DuAuthor Vitae G.Y. LuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(2):401-407
The square-like WO3 nanosheets were synthesized by hydrothermal treatment of irregular WO3 nanosheets prepared through acidification of Na2WO4·2H2O. The obtained square-like and irregular WO3 nanosheets were characterized with field emission scanning electron microscopy, X-ray powder diffraction and transmission electron microscopy. The gas sensing properties of sensors based on as-prepared samples were investigated. The results indicated that both samples exhibited high response to NO2. The sensor based on square-like WO3 nanosheets exhibited remarkably enhanced response and faster response/recovery time for NO2 compared with that based on irregular nanosheets. Especially, the sensor based on square-like WO3 nanosheets could detect NO2 down to 40 ppb, which covered environmental standard. A possible reason for the influence of unique structure on the sensing properties of sensors based on square-like WO3 was proposed. 相似文献
13.
Xishuang LiangAuthor VitaeShiqi YangAuthor Vitae Jianguo LiAuthor VitaeHan ZhangAuthor Vitae Quan DiaoAuthor VitaeWan ZhaoAuthor Vitae Geyu LuAuthor Vitae 《Sensors and actuators. B, Chemical》2011,158(1):1-8
This paper focuses on the gas sensing properties of the mixed-potential-type NO2 sensor based on yttria stabilized zirconia (YSZ) and NiO electrode. The sensing performance of the sensor was improved by modifying the three-phase boundary (TPB). Hydrofluoric acid with different concentrations (10%, 20% and 40%) was used to corrode YSZ substrate to obtain large superficial area of TPB. The scanning electron microscope and atomic force microscopic images showed that the 40% HF could form the largest superficial area at the same corroding time (3 h). The sensitivity of the sensor using the YSZ plate corroded with 40% hydrofluoric acid to 20-500 ppm NO2 was 76 mV/decade at 850 °C, which was the largest among the examined HF concentrations. It was also seen that the sensor showed a good selectivity and speedy response kinetics to NO2. On the basis of the measurements of anodic and cathodic polarization curves, as well as the complex impedance of the device, the sensing mechanism was confirmed to involve a mixed potential at the oxide sensing electrode. 相似文献
14.
This paper presents the ability of electrostatic sprayed tin oxide (SnO2) and tin oxide doped with copper oxide (1, 2, and 4 at.% Cu) films to detect different pollutant gases, i.e., H2S, SO2, and NO2. The influence of a copper oxide dopant on the SnO2 morphology is studied using scanning electron microscopy (SEM) technique, which reveals a small decrease in the porosity and particle size when the amount of dopant is increased. The sensing properties of the SnO2 films are greatly improved by doping, i.e., the Cu-doped SnO2 films have large response to low concentration (10 ppm) of H2S at low operating temperature (100 °C). Furthermore, no cross-sensitivity to 1 ppm NO2 and 20 ppm SO2 is observed. Among the studied films, the 1 at.% Cu-doped SnO2 layer is the most sensitive in the detection of all the studied gases. 相似文献
15.
Zeolite A (LTA)-coated micromachined sensors have been prepared and used in the sensing of individual gases (H2, CH4, C2H5OH, C3H8 and CO, in the 10–1000 ppm range) and gas mixtures. Unlike previous works with conventional sensors, a hydrothermal synthesis was not used to prepare a zeolite film. Instead, a zeolite coating was formed on top of the Pd/SnO2 surface by microdropping from a zeolite suspension. In spite of this, the response of the sensor with zeolite is significantly different from that of unmodified sensors, and essentially reproduces the performance of zeolite-coated conventional sensors. By avoiding the use of a hydrothermal synthesis the integrity of the sensor is better preserved, and the resulting non-continuous zeolite film has the added advantage of a strong reduction in response times. 相似文献
16.
Microsphere-templated BaCO3 films with well-defined area were deposited onto quartz crystal microbalances by thermal ink-jet printing, and the devices were characterized with respect to their microstructures and NO2 sensing characteristics. Highly porous three-dimensional BaCO3 frameworks with promising sensor characteristics were obtained. The printed thin films exhibited reversible frequency shifts following exposure to NO2 and subsequent recovery under CO/CO2 at 400 °C. The feasibility of controlled deposition of complex functional films in controlled patterns is discussed in the context of the direct-write features of ink-jet printing. 相似文献
17.
N. BârsanAuthor VitaeM. HübnerAuthor Vitae U. WeimarAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(2):510-517
The conduction mechanism in polycrystalline SnO2 thick sensing films was modeled and experimentally investigated by means of simultaneous DC electrical resistance and work function changes measurements under CO and H2 exposure in different oxygen backgrounds. It was shown that, according to the composition of the ambient atmosphere, the conduction changes from the case in which it is controlled by the surface depletion layers to a situation in which the main contribution comes from free charge transport in the surface accumulation layer. This is significant for the interpretation of work function changes measurements results because the relation between the different measured electrical resistance and surface band bending depends on the conduction model. Furthermore, the CO sensing mechanism dependence on the oxygen amount in the ambient was explained. 相似文献
18.
A. ForleoAuthor Vitae L. FranciosoAuthor VitaeS. CaponeAuthor Vitae F. CasinoAuthor VitaeP. SicilianoAuthor Vitae O.K. TanAuthor VitaeH. HuiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,154(2):283-287
SnO2 nanorods were successfully deposited on 3″ Si/SiO2 wafers by inductively coupled plasma-enhanced chemical vapour deposition (PECVD) and a wafer-level patterning of nanorods layer for miniaturized solid state gas sensor fabrication were performed. Uniform needle-shaped SnO2 nanorods in situ grown were obtained under catalyst- and high temperature treatment-free growth condition. These nanorods have an average diameter between 5 and 15 nm and a length of 160-300 nm. The SnO2-nanorods based gas sensors were tested towards NH3 and CH3OH and gas sensing tests show remarkable response, showing promising and repeatable results compared with the SnO2 thin films gas sensors. 相似文献
19.
N.M. ShaalanAuthor Vitae T. YamazakiAuthor Vitae T. KikutaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):11-16
SnO2 microwires, nanowires and rice-shaped nanoparticles were synthesized by a thermal evaporation method. The diameters of microwire and nanowire were 2 μm and 50-100 nm, respectively, with approximately the same length (∼20 μm). The size of nanoparticles was about 100 nm. It was confirmed that the as-synthesized products have SnO2 crystalline rutile structure. The sensing ability of SnO2 particle and wire-like structure configured as gas sensors was measured. A comparison between the particle and wire-like structure sensors revealed that the latter have numerous advantages in terms of reliability and high sensitivity. Although its high surface-to-volume ratio, the nanoparticle sensor exhibited the lowest sensitivity. The high surface-to-volume ratio and low density of grain boundaries is the best way to improve the sensitivity of SnO2 gas sensors, as in case of nanowire sensor which exhibited a dramatic improvement in sensitivity to NO2 gas. 相似文献
20.
Yu-Jin ChenAuthor Vitae Gang XiaoAuthor VitaeTie-Shi WangAuthor Vitae Fan ZhangAuthor VitaeYang MaAuthor Vitae Peng GaoAuthor VitaeEndi ZhangAuthor Vitae Zhi XuAuthor VitaeQiu-hong LiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):867-874
Crystalline CeO2/TiO2 core/shell nanorods were fabricated by a hydrothermal method and a subsequent annealing process under the hydrogen and air atmosphere. The thickness of the outer shell composed of crystal TiO2 nanoparticles can be tuned in the range of 5-11 nm. The crystal core/shell nanorods exhibited enhanced gas-sensing properties to ethanol vapor in terms of sensor response and selectivity. The calculated sensor response based on the change of the heterojunction barrier formed at the interface between CeO2 and TiO2 is agreed with the experimental results, and thus the change of the heterojunction barrier at different gas atmosphere can be used to explain the enhanced ethanol sensing properties. 相似文献