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Multicomponent Metal Oxide Nanostructures: Fabrication and Study of Core Issues to Improve Gas Sensing Performance
摘要： We have obtained and studied the sensing properties of porous titania-based nanostructures. The materials have been prepared using cost-effective techniques. The morphological and structural analyses of the prepared materials have been performed. The sensing properties of the samples have been studied towards carbon monoxide. The obtained results demonstrate that the prepared structures are promising for the potential applications in the area of chemical sensors for the environmental monitoring.
关键词： metal oxide,nanostructures,chemical gas sensor
更新于2025-09-23 15:22:29
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Gas Sensing with Iridium Oxide Nanoparticle Decorated Carbon Nanotubes
摘要： The properties of multi-wall carbon nanotubes decorated with iridium oxide nanoparticles (IrOx-MWCNTs) are studied to detect harmful gases such as nitrogen dioxide and ammonia. IrOx nanoparticles were synthetized using a two-step method, based on a hydrolysis and acid condensation growth mechanism. The metal oxide nanoparticles obtained were employed for decorating the sidewalls of carbon nanotubes. Iridium-oxide nanoparticle decorated carbon nanotube material showed higher and more stable responses towards NH3 and NO2 than bare carbon nanotubes under different experimental conditions, establishing the optimal operating temperatures and estimating the limits of detection and quantification. Furthermore, the nanomaterials employed were studied using different morphological and compositional characterization techniques and a gas sensing mechanism is proposed.
关键词： carbon nanotubes,relative humidity effect,metal nanoparticles,iridium oxide,chemoresistive gas sensor
更新于2025-09-23 15:22:29
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Zeolitic imidazolate framework-8 (ZIF-8)-coated In2O3 nanofibers as an efficient sensing material for ppb-level NO2 detection
摘要： The development of NO2 gas sensors is of great importance for air quality monitoring and human health. In this work, In2O3 and zeolitic imidazolate framework-8 (ZIF-8) heterostructures were synthesized and designed as efficient sensing materials for NO2 detection. The ZIF-8 nanocrystals were uniformly deposited on In2O3 nanofibers (NFs) by using a self-template strategy, where In2O3/ZnO NFs act as the source of Zn2+ for the formation of ZIF-8 and as the template. By tuning the amount of Zn2+ in the composite NFs, different morphologies from In2O3 NFs with minimal ZIF-8 loading to an In2O3/ZIF-8 core-shell complex were obtained. The optimized In2O3/ZIF-8 NFs show a remarkably high response to 1 ppm NO2 (Rg/Ra=16.4) and enhanced humidity resistance due to the hydrophobicity of ZIF-8 in comparison with those of the pristine In2O3 NF sensor (Rg/Ra=4.9) at 140 °C. The gas sensing mechanism of In2O3/ZIF-8, which is based on electron transduction, surface chemistry, and the functional interface between the loaded ZIF-8 and In2O3 matrix, was proposed. Additionally, the large number of pores, which were formed by the in situ conversion of ZnO grains in the matrix, ensures that all parts of the In2O3 NFs are accessible to gases. This facile strategy paves the way for the design of metal oxide/MOF complex architectures with tunable metal centers for various applications, including gas sensing.
关键词： in situ conversion,electrospinning,In2O3,ZIF-8,gas sensor
更新于2025-09-23 15:22:29
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Design guidelines for high sensitivity ZnO nanowire gas sensors with Schottky contact
摘要： Zinc oxide nanowire (ZnO NW) gas sensor with single Schottky contact is capable of sensitive detection of gas molecules. In this study, we investigate the effect of design factors such as nanowire defect density, diameter, and length on the gas sensitivity using 3-D numerical simulation. The sensor with lower defect density or smaller NW diameter exhibits improved gas sensitivity, while length does not have an impact when not considering the external environment such as background gases and binding probability. Lower defect density causes low electron density within the NW in air environment, and the change in electron density due to gas adsorption is intensified, thus improving gas sensitivity. As the NW diameter decreases, the change in the electrical conductivity due to gas molecules is greatly increased due to an increase in the ratio of the depletion area to the entire NW area. In contrast, the nanowire length does not impact the gas sensitivity because the change in the electron density is independent of the length. These results are helpful to understand the sensing mechanism and provide design guidelines to maximize the sensitivity.
关键词： Zinc oxide,Gas sensitivity,Nanowire,Numerical simulation,Gas sensor
更新于2025-09-23 15:21:21
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Design of Au@WO3 core?shell structured nanospheres for ppb-level NO2 sensing
摘要： As motivated by the driving force of the urgent demand for high-performance nitrogen dioxide (NO2) sensor, in this work, a novel structure of Au@WO3 core?shell nanospheres (CSNSs) was designed and successfully prepared for NO2 detection. The techniques of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller measurement, and elemental mapping analysis were used for the characterizations of the obtained samples. The results demonstrated that Au nanoparticles with 25?50 nm in diameter were successfully encapsulated by WO3 shells with the thickness of 30?50 nm. The NO2 sensing performance of the Au@WO3 CSNSs as well as the pure WO3 nanospheres were systematically investigated. Compared with the pure WO3 nanospheres, Au@WO3 CNNSs exhibited overall enhanced NO2 sensing performances in terms of response, detection limit, and response/recovery times. At the optimal operating temperature of 100 °C, Au@WO3 CSNSs showed excellent NO2 selectivity and long-term stability. Notably, the excellent NO2 sensing performance of Au@WO3 CSNSs was slightly affected by humidity. The possible sensing mechanism of the enhanced NO2 sensing properties of the Au@WO3 CSNSs was discussed.
关键词： Au@WO3,Core?shell structure,Nanosphere,Gas sensor,NO2
更新于2025-09-23 15:21:21
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Double Notched Long-Period Fiber Grating Characterization for CO2 Gas Sensing Applications ?
摘要： In this study, we applied a double-sided inductively coupled plasma (ICP) process to nanostructure long-period fiber grating (LPFG) in order to fabricate a double-notched LPFG (DNLPFG) sensor with a double-sided surface corrugated periodic grating. Using the sol-gel method, we also added thymol blue and ZnO to form a gas sensing layer, thus producing a DNLPFG CO2 gas sensor. The resulting sensor is the first double-sided etching sensor used to measure CO2. The experimental results showed that as the CO2 concentration increased, the transmission loss increased, and that the smaller the fiber diameter, the greater the sensitivity and the greater the change in transmission loss. When the diameter of the fiber was 32 μm (and the period was 570 μm) and the perfusion rate of CO2 gas was 15%, the maximum loss variation of up to 3.881 dB was achieved, while the sensitivity was 0.2146 dB/% and the linearity was 0.992. These results demonstrate that the DNLPG CO2 gas sensor is highly sensitive.
关键词： sol-gel,CO2,gas sensor
更新于2025-09-23 15:21:21
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Optimization of the Pt Nanoparticle Size and Calcination Temperature for Enhanced Sensing Performance of Pt-Decorated In2O3 Nanorods
摘要： The surface-to-volume ratio of one-dimensional (1D) semiconductor metal-oxide sensors is an important factor for achieving good gas sensing properties because it offers a wide response area. To exploit this effect, in this study, we determined the optimal calcination temperature to maximize the specific surface area and thereby the sensitivity of the sensor. The In2O3 nanorods were synthesized by using vapor-liquid-solid growth of In2O3 powders and were decorated with the Pt nanoparticles by using a sol-gel method. Subsequently, the Pt nanoparticle-decorated In2O3 nanorods were calcined at different temperatures to determine the optimal calcination temperature. The NO2 gas sensing properties of five different samples (pristine uncalcined In2O3 nanorods, Pt-decorated uncalcined In2O3 nanorods, and Pt-decorated In2O3 nanorods calcined at 400, 600, and 800 ?C) were determined and compared. The Pt-decorated In2O3 nanorods calcined at 600 ?C showed the highest surface-to-volume ratio and the strongest response to NO2 gas. Moreover, these nanorods showed the shortest response/recovery times toward NO2. These enhanced sensing properties are attributed to a combination of increased surface-to-volume ratio (achieved through the optimal calcination) and increased electrical/chemical sensitization (provided by the noble-metal decoration).
关键词： Calcination,Pt decoration,Gas sensor,In2O3,NO2
更新于2025-09-23 15:21:21
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Orthogonal gas sensor arrays by chemoresistive material design
摘要： Gas sensor arrays often lack discrimination power to different analytes and robustness to interferants, limiting their success outside of research laboratories. This is primarily due to the widely sensitive (thus weakly-selective) nature of the constituent sensors. Here, the effect of orthogonality on array accuracy and precision by selective sensor design is investigated. Therefore, arrays of (2–5) selective and non-selective sensors are formed by systematically altering array size and composition. Their performance is evaluated with 60 random combinations of ammonia, acetone and ethanol at ppb to low ppm concentrations. Best analyte predictions with high coefficients of determination (R2) of 0.96 for ammonia, 0.99 for acetone and 0.88 for ethanol are obtained with an array featuring high degree of orthogonality. This is achieved by using distinctly selective sensors (Si:MoO3 for ammonia and Si:WO3 for acetone together with Si:SnO2) that improve discrimination power and stability of the regression coefficients. On the other hand, arrays with collinear sensors (Pd:SnO2, Pt:SnO2 and Si:SnO2) hardly improve gas predictions having R2 of 0.01, 0.86 and 0.28 for ammonia, acetone and ethanol, respectively. Sometimes they even exhibited lower coefficient of determination than single sensors as a Si:MoO3 sensor alone predicts ammonia better with a R2 of 0.68.
关键词： Ethanol,WO3,SnO2,Electronic nose,Ammonia,Gas sensor,Acetone,Flame spray pyrolysis,MoO3
更新于2025-09-23 15:21:21
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The Enhanced NO2 sensing properties of SnO2 nanoparticles/reduced graphene oxide composite
摘要： Multiple techniques were utilized to characterize the structure and morphology of the SnO2/reduced graphene oxide (rGO) composite, in which the composite was prepared by a facile one-pot microwave-assisted hydrothermal method. As a result, SnO2 nanoparticles with diameters of 3-5 nm were anchored uniformly on both sides of the rGO sheets. Meanwhile, a series of resistive-type gas sensors based on SnO2/rGO composite and pure SnO2 were fabricated and tested for analyzing the effects on introducing rGO. The results revealed that, the composite exhibited obviously enhanced gas sensing properties towards NO2 with high response, fast response and recovery speed, and good selectivity and reproducibility. At 75°C, the response of the composite to 350 ppb NO2 was about 6.6 times of that to pure SnO2. In addition, the response and recovery time of the sensor was greatly reduced from 39.2/54.7 to 6.5/1 minutes, and the detecting limit of the sensor was even as low as 50 ppb. Provided with the enlarged surface area and local p-n heterojunctions, the synergistic effect of SnO2 nanoparticles and rGO contributed to the enhanced gas sensing properties of SnO2/rGO composite.
关键词： SnO2,Graphene,Heterojunctions,Microwave-assisted hydrothermal,Gas sensor
更新于2025-09-23 15:21:21
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Nanocrystalline ZnO Obtained by the Thermal Decomposition of [Zn(H2O)(O2C5H7)2] in 1-Butanol: Synthesis and Testing as a Sensing Material
摘要： The influence of conditions of heat treatment of a solution [Zn(H2O)(O2C5H7)2] in 1-butanol (temperature 125–185°C, treatment times 2, 4, and 6 h) on dispersion and microstructure of the formed nanocrystalline and poorly aggregated zinc oxide, promising component for optoelectronics, including as receptor materials of chemical gas sensors, was investigated. IR spectroscopy showed that the precursor decomposition occurs through the cleavage of the Cβ–Cγ bond of the ligand to form acetone and butyl acetate. It was determined that at the minimum treatment temperature and time (125°C, 2 h) ZnO nanoparticles are nearly spherical, and under hard conditions, rodlike particles are formed. At 125°C (treatment times 4 and 6 h), rodlike particles are organized into dense agglomerates resembling bundles in shape, and at the higher temperatures there is no aggregation of ZnO nanoparticles. The high CO selectivity and sensitivity (4–100 ppm) was revealed for oxide coatings obtained by screen printing using ZnO nanopowders synthesized at 125°C (treatment times 2 and 4 h).
关键词： ZnO,acetylacetonate,zinc oxide,gas sensor,nanoparticles,1-butanol
更新于2025-09-23 15:21:21