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Self-assembled highly porous rugby-like hierarchical ZnO thin film formaldehyde gas sensor
摘要： A new rugby-like ZnO thin film was self-assembled via a hydrothermal method and the influences of the hydrothermal temperature on crystal growth and gas sensing properties of ZnO thin films were investigated. The results showed that the highly porous rugby-like ZnO crystals were self-assembled via thin fan-shape sheets with abundant nanopores formed by interconnected the smaller nanoplates when the hydrothermal temperature was 140 (cid:1)C. Its specific surface area value reached 45.0 m2 g(cid:3)1. The sensor exhibited an excellent gas sensing response, a good selectivity towards formaldehyde and quick response characteristics at the optimum working temperature of 250 (cid:1)C.
关键词： self-assemble,zinc oxide,gas sensing property,rugby-like hierarchical nanostructure
更新于2025-09-12 10:27:22
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Excellent ambipolar gas sensing response of Eu[Pc(OC4H9)8]2/acidified multiwalled carbon nanotubes hybrid at room temperature
摘要： A new hybrid material has been developed by mixing a sandwich-type double-decker, Eu[Pc(OC4H9)8]2 = 2,3,9,10,16,17,23,24-octabutoxyphthalocyaninate] with acidified multiwalled carbon nanotubes (aMWCNTs) through non-covalent interactions. The UV-vis spectrum, X-ray diffraction and scanning electron microscope have been employed to reveal the J-aggregate mode and optimized morphology of Eu[Pc(OC4H9)8]2 molecules in the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid material. The gas-sensing devices based on this hybrid material are fabricated by a simple solvent-processing quasi-Langmuir–Sh?fer (QLS) progress. The n-type and p-type response is shown by the Eu[Pc(OC4H9)8]2/aMWCNTs hybrid film at room temperature. The detection limit of the hybrid for ammonia and nitrogen dioxide gas is 0.5 ppm and 0.3 ppm, respectively.
关键词： phthalocyanine,gas sensing,multiwall carbon nanotubes,ambipolar organic semiconductor,europium complex
更新于2025-09-12 10:27:22
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2- <i>μ</i> m band active distributed Bragg reflector laser for CO <sub/>2</sub> gas sensing
摘要： We have developed a 2-μm-band active distributed Bragg reflector (DBR) laser for CO2 gas sensing employing single quantum well (SQW) gain in the tuning sections. The laser covers the double wavelength band with a <3-dB power penalty during tuning compared with our conventional DBR laser having no active SQW. The absorption-line detection of CO2 gas using the laser is also demonstrated. Furthermore, we show that the ～60% tuning efficiency for the tuning current of the active DBR laser compared with our conventional one is explained with an assumed rate equation including the carrier consumption for the active SQW gain.
关键词： 2-μm band,active distributed Bragg reflector laser,single quantum well,tuning efficiency,CO2 gas sensing
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Compact Photoacoustic Spectrometer Based on a Widely Tunable Mid-Infrared Pulsed Optical Parametric Oscillator
摘要： For highly sensitive and selective photoacoustic (PA) trace-gas sensing it is desirable to use high power light sources with large wavelength tunability in the mid-infrared (MIR) region, where most molecules have strong vibrational transitions. The OPO technology is an old technology, but still an excellent choice as light source for PA spectroscopy. The advantages are their molecular specificity due to large wavelength tunability (1.5 to 5μm), high energy output, cost-effectiveness and compactness [1]. The tunability of OPOs together with PA allow for multi-gas detection of several components with common signal processing and data analysis. MIR OPOs can operate in different configurations both pulsed and continuous wave (CW). The pulsed operation results in high peak power, potentially nonlinear absorption effects and a normalized noise equivalent absorption that is not extreme. We demonstrate a novel miniaturized PA trace gas analyzer platform integrated with a MIR OPO targeting the major market opportunity of environmental monitoring and breath analysis [2,3]. We demonstrate that a miniaturized photoacoustic spectroscopic (PAS) cell can be excited resonantly with the MIR OPO by adjusting the laser pulse repetition rate to match the acoustic resonance of the PAS cell. The application of the gas sensor for real time environmental measurements and breath analysis is demonstrated using three samples of gas concentration; 100 ppmV of methane (CH4), 100 ppmV of nitrogen dioxide (NO2), and approximately 1000 ppmV ammonia (NH3) in atmospheric air with a humidity of 40% [3]. A gas flow rate of 300 ml/min through the PAS cell was applied for the three samples. These gases are well-known environmental trace gases and biomarkers in exhaled breath. The gases cause environmental degradation through their effects on soil acidification, eutrophication, and stratospheric ozone depletion. The presence of ammonia in the environment is mainly due to the degradation of animal waste, industrial processes and diesel exhaust. NO2 is a toxic gas and a regulated air pollutant that possess a serious risk for human health. Monitoring them in human breath is also particularly relevant as they are potential cancer biomarkers. We acknowledge the financial support from EUREKA (Eurostars program: E10589 - PIRMAH) and the Danish Agency for Higher Education.
关键词： photoacoustic spectroscopy,optical parametric oscillator,breath analysis,trace-gas sensing,mid-infrared,environmental monitoring
更新于2025-09-11 14:15:04
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Synthesis of orthogonally assembled 3D cross-stacked metal oxide semiconducting nanowires
摘要： Assemblies of metal oxide nanowires in 3D stacks can enable the realization of nanodevices with tailored conductivity, porous structure and a high surface area. Current fabrication methods require complicated multistep procedures that involve the initial preparation of nanowires followed by manual assembly or transfer printing, and thus lack synthesis flexibility and controllability. Here we report a general synthetic orthogonal assembly approach to controllably construct 3D multilayer-crossed metal oxide nanowire arrays. Taking tungsten oxide semiconducting nanowires as an example, we show the spontaneous orthogonal packing of composite nanorods of poly(ethylene oxide)-block-polystyrene and silicotungstic acid; the following calcination gives rise to 3D cross-stacked nanowire arrays of Si-doped metastable ε-phase WO3. This nanowire stack framework was also tested as a gas detector for the selective sensing of acetone. By using other polyoxometallates, this fabrication method for woodpile-like 3D nanostructures can also be generalized to different doped metal oxide nanowires, which provides a way to manipulate their physical properties for various applications.
关键词： gas sensing,metal oxide nanowires,nanodevices,3D stacks,orthogonal assembly
更新于2025-09-11 14:15:04
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Effects of sintering temperature on sensing properties of WO <sub/>3</sub> and Ag-WO <sub/>3</sub> electrode for NO <sub/>2</sub> sensor
摘要： Pure WO3 and Ag-WO3 (mixed solid solutions Ag with WO3) have been successfully synthesized by sol-gel method and the influences of calcination temperature on the particle size, morphology of the WO3 and Ag-WO3 nanoparticles were investigated. Powder X-ray diffraction results show that the hexagonal to monoclinic phase transition occurs at calcination temperature varying from 300°C to 500°C. SEM images show that calcination temperature plays an important role in controlling the particle size and morphology of the as-prepared WO3 and Ag-WO3 nanoparticles. The NO2 gas sensing properties of the sensors based on WO3 and Ag-WO3 nanoparticles calcined at different temperatures were investigated and the experimental results exhibit that the gas sensing properties of the Ag-WO3 sensors were superior to those of the pure WO3. Especially, the sensor based on Ag-WO3 calcined at 500°C 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).
关键词： tungsten trioxide,sintering temperature,low operating temperature,gas sensing properties
更新于2025-09-11 14:15:04
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Gas Sensing Performances of ZnO Hierarchical Structures for Detecting Dissolved Gases in Transformer Oil: A Mini Review
摘要： Power transformer is one of the critical and expensive apparatus in high voltage power system. Hence, using highly efficient gas sensors to real-time monitor the fault characteristic gases dissolved in transformer oil is in pressing need to ensure the smooth functionalization of the power system. Till date, as a semiconductor metal oxide, zinc oxide (ZnO) is considered as the promising resistive-type gas sensing material. However, the elevated operating temperature, slow response, poor selectivity and stability limit its extensive applications in the field of dissolved gases monitoring. In this respect, rigorous efforts have been made to offset the above-mentioned shortcomings by multiple strategies. In this review, we first introduce the various ZnO hierarchical structures which possess high surface areas and less aggregation, as well as their corresponding gas sensing performances. Then, the primary parameters (sensitivity, selectivity and stability) which affect the performances of ZnO hierarchical structures based gas sensors are discussed in detail. Much more attention is particularly paid to the improvement strategies of enhancing these parameters, mainly including surface modification, additive doping and ultraviolet (UV) light activation. We finally review gas sensing mechanism of ZnO hierarchical structure based gas sensor. Such a detailed study may open up an avenue to fabricate sensor which achieve high sensitivity, good selectivity and long-term stability, making it a promising candidate for transformer oil monitor.
关键词： ZnO,sensitivity,gas sensors,hierarchical structures,stability,gas sensing mechanism,selectivity
更新于2025-09-10 09:29:36
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Review of Incoherent Broadband Cavity-Enhanced Absorption Spectroscopy (IBBCEAS) for Gas Sensing
摘要： Incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) is of importance for gas detection in environmental monitoring. This review summarizes the unique properties, development and recent progress of the IBBCEAS technique. Principle of IBBCEAS for gas sensing is described, and the development of IBBCEAS from the perspective of system structure is elaborated, including light source, cavity and detection scheme. Performances of the reported IBBCEAS sensor system in laboratory and field measurements are reported. Potential applications of this technique are discussed.
关键词： supercontinuum light source,incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS),gas sensing,broadband light source,molecular spectroscopy
更新于2025-09-10 09:29:36
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Highly Sensitive Ammonia Sensors Based on Ag-Decorated WO <sub/>3</sub> Nanorods
摘要： In this paper, WO3 nanorods are successfully synthesized via a one-step hydrothermal method, and then, silver nanoparticles are deposited on the WO3 surface by in situ photoreduction method to obtain Ag/WO3 gas sensitive materials. WO3 and Ag/WO3 are characterized by scanning electron microscope techniques, transmission electron microscope, and X-ray diffraction. The experimental results indicated that Ag nanoparticles have an important effect on the gas response of WO3 . The Ag/WO3 sensor greatly improves the selectivity and response compared to the traditional WO3 sensor; the response is 300 for 100 ppm ammonia when the Ag/WO3 sensor operates at the optimum operating temperature. The Ag/WO3 sensor can respond to 50 ppb ammonia.
关键词： nanoparticle,One-step hydrothermal method,gas sensing mechanism,high sensitivity
更新于2025-09-10 09:29:36
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Fabrication of thin films of phosphonated calix[4]arene bearing crown ether and their gas sensing properties
摘要： Calix[4]arenes bearing phosphate and crown ether groups are shown to hold considerable promise as the active layer in volatile organic compound (VOC) vapor sensor. Its chemical sensing selectivity and sensitivity can be altered by different alkyl side chains. These organic architectures were successfully deposited by spin coating method on gold-coated glass surfaces. Surface Plasmon Resonance (SPR) technique was used for VOCs detection to evaluate the chemical-sensing properties of these calix[4]arene derivatives. Spun thin films of calix[4]arene derivatives were exposed to a variety of VOC vapors, and the resonance angles changes of these films were recorded for the specific analyte vapors such as chloroform, carbon tetrachloride, dichloromethane, ethanol, benzene, and toluene. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. The sensing results showed similar response patterns, and our data strongly indicate that response of used thin films of calix[4]arene derivatives to chloroform is much higher than those of any other VOCs used with the values of 0.47×10-3, 1.042×10-3 and 1.952×10-3 (% / ppm) for the compounds 1, 2 and 3 respectively. Furthermore, gas sensing interaction mechanisms of the thin films were evaluated in terms of the molar volumes, dipole moments and refractive indexes of the analyzed gas molecules.
关键词： Calixarene,SPR,thin film,gas sensing
更新于2025-09-10 09:29:36