- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Visible light enhanced black NiO sensors for ppb-level NO2 detection at room temperature
摘要： Although extensive studies have been carried out on n-type semiconductors for room-temperature gas sensor applications, some intrinsic problems remain. Therefore, other interesting attempts should be adopted to solve these issues, like p-type semiconductors. Previous studies have demonstrated that p-type semiconductor gas sensors exhibit better selectivity and less humidity dependence due to the distinctive oxygen adsorption and surface reactivity. Visible light is used as the external activation source to accelerate the sensing kinetics instead of heating. Stoichiometric NiO cannot absorb visible lights. Inspired by the works of black TiO2, we adopted three methods to prepare black NiO. XPS characterizations reveal that the presence of Ni3+ ions leads to the formation of black NiO. However, not all black NiO samples show good responses to NO2 at room temperature. Three main routes: synthesizing specific morphology with large specific surface area and porosity, introduction of Ni3+ ions and oxygen vacancies, are needed to get the enhanced sensing performance. The black NiO samples with large specific surface area and oxygen vacancies and Ni3+ ions show obvious response towards ppb-level NO2 with visible light irradiation at room temperature. Furthermore, light wavelength is found to play a vital role in the sensing characteristics, and blue light is the optimal choice. Different from traditional NiO sensors operated at high temperatures exhibiting superior response to reducing gases, the black NiO show excellent selectivity towards oxidizing gas, ppb-level NO2, at room temperature illuminated by blue light. In contrast with n-type semiconductors, the black NiO samples also exhibit less humidity dependence.
关键词： Room temperature,NO2 sensor,NiO,Visible light irradiation
更新于2025-09-09 09:28:46
-
Core-Shell Electrospun Polycrystalline ZnO Nanofibres for Ultra-Sensitive NO2 Gas Sensing
摘要： This paper discusses the growth of polycrystalline, self-supporting ZnO nanofibres which can detect nitrogen dioxide (NO2) gas down to 1 part per billion (ppb), one of the smallest detection limits reported for NO2 using ZnO. A new and innovative method has been developed for growing polycrystalline ZnO nanofibres. These nanofibres have been created using core-shell electrospinning of inorganic metal precursor zinc neodecanoate, where growth occurs at the core of the nanofibres. This process produces contamination-free, self-supporting, polycrystalline ZnO nanofibres of the average diameter and grain size 50 nm and 8 nm respectively, which are ideal for gas sensing applications. This process opens up an exciting opportunity for creating nanofibres from a variety of metal oxides, facilitating many new applications especially in the areas of sensors and wearable technologies.
关键词： NO2 gas sensing,polycrystalline fibres,ZnO nanofibres,Electrospinning
更新于2025-09-09 09:28:46
-
Effect of NO2 and NO3-/HNO3 adsorption on no photocatalytic conversion
摘要： A study was undertaken of the adsorption and photocatalytic conversion of NO, NO2 and NO3-/HNO3 using two photocatalysts (P25 and HT-ET). The HT-ET is a catalyst synthesized in our laboratory comprised only of anatase phase and with a surface area three times larger than that of the P25. In powder form, the catalyst was introduced into and extended along the length of a tube with no type of compaction on the part of the solid (pressure drops are negligible under these conditions). This tubular photoreactor arrangement operates as a continuous reactor system enabling FTIR analysis of the surface of the catalysts during the conversion process. NO adsorption was negligible, though the FTIR studies revealed the formation of nitrites on the surface after 18 h of reaction. Overall NO conversion efficiency rates were above 68% with both catalysts in that reaction time. However, selectivity to NO2 was very high with both catalysts. It was also found with both catalysts that the number of NOx moles eliminated during NO photocatalytic conversion coincided with the number of adsorbed NO2 moles observed in the adsorption studies performed with this molecule, indicating that the NO2 molecule is not efficiently converted photocatalytically. It was observed that most of the NO2 undergoes disproportionation on the surface of the catalysts, giving rise to nitrates and NO. The FTIR studies showed that a significant proportion of the NO2 interacts with surface nitrates resulting in [(NO3-)-(H2O) n-NO2] complexes which are stable on the catalyst surface in an NO atmosphere.
关键词： NO2,TiO2,NOx,Photocatalysis,Nitrates,FTIR,NO
更新于2025-09-09 09:28:46
-
Effects of daily meteorology on the interpretation of space-based remote sensing of NO<sub>2</sub>
摘要： Retrievals of tropospheric NO2 columns from UV/visible observations of reflected sunlight require a priori vertical profiles to account for the variation in sensitivity of the observations to NO2 at different altitudes. These profiles vary in space and time but are usually approximated using models that do not resolve the full details of this variation. Currently, no operational retrieval simulates these a priori profiles at both high spatial and high temporal resolution. Here we examine the additional benefits of daily variations in a priori profiles for retrievals already simulating a priori NO2 profiles at sufficiently high spatial resolution to identify variations of NO2 within urban and power plant plumes. We show the effects of introducing daily variation into a priori profiles can be as large as 40% and 3×1015 molec. cm?2 for an individual day and lead to corrections as large as 10% for a monthly average in a case study of Atlanta, GA. Comparing an optimized retrieval to a more standard one, we find that NOx emissions estimated from space-based remote sensing can increase by ～100% when daily variations in plume location and shape are accounted for in the retrieval.
关键词： a priori profiles,emissions,satellite remote sensing,NO2,air quality
更新于2025-09-04 15:30:14
-
Tropospheric NO<sub>2</sub>, SO<sub>2</sub>, and HCHO over the East China Sea, using ship-based MAX-DOAS observations and comparison with OMI and OMPS satellites data
摘要： In this study, ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in the Eastern China Sea (ECS) area in June 2017. The tropospheric Slant Column Densities (SCDs) of nitrogen dioxide (NO2), sulfur dioxide (SO2), and formaldehyde (HCHO) were retrieved from the measured spectra by the Differential Optical Absorption Spectroscopy (DOAS) technique. Using the simple geometric approach, the SCDs of different trace gases observed at 15° elevation angle were adopted to convert into tropospheric Vertical Columns Densities (VCDs). During this campaign, the averaged VCDs of NO2, SO2, and HCHO in the marine environment over ECS area are 6.50 × 1015 molec cm-2, 4.28 × 1015 molec cm-2 and 7.39 × 1015 molec cm-2, respectively. In addition, the ship-based MAX-DOAS trace gases VCDs were compared with satellite observations of Ozone Monitoring Instrument (OMI) and Ozone Mapping and Pro?ler Suite (OMPS). The daily OMI NO2 VCDs agree well with ship-based MAX-DOAS measurements showing the correlation coefficient R of 0.83. Besides, the good agreements of SO2 and HCHO VCDs between the OMPS satellite and ship-based MAX-DOAS observations were also found with correlation coefficient R of 0.76 and 0.69. The vertical profiles of these trace gases are achieved from the measured Differential Slant Column Densities (DSCDs) at different elevation angles using optimal estimation method. The retrieved profiles displayed the typical vertical distribution characteristics, which exhibits the low concentrations of < 3, < 3, and < 2 ppbv for NO2, SO2, and HCHO in clean area of the marine boundary layer far from coast of the Yangtze River Delta (YRD) continental region. Interestingly, elevated SO2 concentrations can be observed intermittently along the ship routes, which is mainly attributed to the vicinal ship emissions in the view of the MAX-DOAS measurements. Combined with the on-board ozone lidar measurements, the ozone (O3) formation was discussed with the vertical profile of HCHO/NO2 ratio, which is sensitive to the increases of NO2 concentration. This study provided further understanding of the main air pollutants in the marine boundary layer of the ECS area and also benefited to formulate the policies regulating the shipping emissions in such costal area like YRD region.
关键词： NO2,SO2,OMI,MAX-DOAS,OMPS,ship-based observations,HCHO,East China Sea
更新于2025-09-04 15:30:14
-
Enhanced NO2 gas sensing of a single-layer MoS2 by photogating and piezo-phototronic effects
摘要： NO2 sensors with ultrahigh sensitivity are demanded for future electronic sensing systems. However, traditional sensors are considerably limited by the relative low sensitivity, high cost and complicated process. Here, we report a simply and reliable flexible NO2 sensor based on single-layer MoS2. The flexible sensor exhibits high sensitivity to NO2 gas due to ultra-large specific surface area and the nature of two-dimensional (2D) semiconductor. When the NO2 is 400 ppb (parts per billion), compared with the dark and strain-free conditions, the sensitivity of the single-layer sensor is enhanced to 671% with a 625 nm red light-emitting diode (LED) illumination of 4 mW/cm2 power under 0.67% tensile strain. More important, the response time is dramatically reduced to ～16 s and it only needs ～65 s to complete 90% recovery. A theoretical model is proposed to discuss the microscopic mechanisms. We find that the remarkable sensing characteristics are the result of coupling among piezoelectricity, photoeletricity and adsorption-desorption induced charges transfer in the single-layer MoS2 Schottky junction based device. Our work opens up the way to further enhancements in the sensitivity of gas sensor based on single-layer MoS2 by introducing photogating and piezo-phototronic effects in mesoscopic systems.
关键词： photogating effect,single-layer MoS2,ultrahigh sensitivity,flexible NO2 sensor,piezo-phototronic effect
更新于2025-09-04 15:30:14
-
Synthesis, Characterization and Gas-Sensing Properties of Pristine and SnS2 Functionalized TeO2 Nanowires
摘要： We report the gas-sensing properties of pristine and SnS2 functionalized TeO2 nanowires (NWs). TeO2 NWs were synthesized by a vapor–liquid–solid growth method, and SnS2 functionalization was performed using an atomic layer deposition technique followed by thermal treatment. Structural and morphological analyses verified the formation of pristine and SnS2 functionalized TeO2 NWs with desired composition, phase, and morphology. Interestingly, sensing results showed that the pristine TeO2 NW gas sensor had better sensing properties relative to the SnS2 functionalized TeO2 NW gas sensor. An underlying sensing mechanism is explained in detail, and reasons for the decrease of sensing performance with the SnS2 functionalized TeO2 NW sensor was attributed to the coverage of TeO2 surface by the SnS2 nanoparticles.
关键词： Gas sensor,SnS2,NO2 gas,TeO2,Sensing mechanism
更新于2025-09-04 15:30:14