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[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - Hierarchical MnO<inf>2</inf> Nanoflowers Based Efficient Room Temperature Alcohol Sensor
摘要： In the present work, hierarchical 3-D MnO2 nanoflowers (consisting of 2D nanosheets) were synthesized employing hydrothermal technique and subsequently alcohol sensing performance of the MnO2 NFs was investigated. The morphological (FESEM, Transmission Electron Microscopy), and surface compositional (X-ray Photoelectron Spectroscopy) characterizations were carried out. Lattice fringe of TEM image confirmed that constituents of 3-D nanoflower to be birnessite (i.e. δ-MnO2) 2-D nanosheets. In addition, core level XPS spectra validated the presence of mixed valence state of Mn (i.e. Mn3+ and Mn4+states) in the MnO2 NFs. Further, Electrochemical Impedance Spectroscopy measurement (Mott Schottky analysis) revealed that the n-type conductivity of MnO2 NFs based sensing layer. It is clearly observed from the transient response characteristics that the device offered promising room temperature sensing performance towards alcohols (i.e. methanol, ethanol and 2-propanol). However, the device offered better sensing performance towards methanol than that of ethanol and 2-propanol. The response time and recovery time of the sensor also found to be moderately fast at room temperature. Interestingly, the device resistance was increased in presence of reducing vapor (although MnO2 NFs is a n-type material).
关键词： Birnessite (i.e. δ-MnO2),Room temperature Alcohol sensor,Anomalous gas sensing performance,Hierarchical 3-D MnO2 nanoflowers
更新于2025-09-19 17:15:36
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Enhanced gas-sensing performance of metal@ZnO core–shell nanoparticles towards ppb–ppm level benzene: the role of metal–ZnO hetero-interfaces
摘要： Core–shell metal@ZnO nanoparticles including Au@ZnO, Pd@ZnO and Pt@ZnO were synthesized and utilized for sensing low-concentration benzene. Various techniques were used to characterize the compositional properties of the typical core@shell structure and analyze the relation between the sensing properties and the metal–ZnO hetero-interfaces. When applied as gas-sensing materials, all three core–shell metal@ZnO nanoparticles showed better sensing performance than pure ZnO nanoparticles towards low concentration benzene. In particular, the gas-sensing response of the Pt@ZnO core–shell nanoparticles was 7 times higher than that of pure ZnO towards 0.1 ppm benzene and 63 times higher towards 5 ppm benzene, which was more sensitive than most gas-sensing materials in previous literature. Furthermore, the Pt@ZnO core–shell nanoparticles presented an ultra-low detection limit of no less than 10 ppb, which was lower than those of most gas-sensing materials in previous literature. Besides, the Pt@ZnO core–shell nanoparticles showed high selectivity and long-term response stability with a response value of 2.7 ± 1.6% towards 1 ppm benzene after operating for a month. The enhanced gas-sensing performances of the metal@ZnO core–shell nanoparticles are well correlated to the work function differences between the contacted metal and ZnO within the metal–ZnO hetero-interfaces, which produce high Schottky energy barriers and modulate the electron transfer.
关键词： gas-sensing,Schottky barrier,core–shell nanoparticles,benzene,metal–ZnO hetero-interfaces
更新于2025-09-19 17:15:36
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ZnO Nanosheets Abundant in Oxygen Vacancies Derived from Metal-Organic Frameworks for ppb-Level Gas Sensing
摘要： Surmounting the inhomogeniety issue of gas sensors and realizing their reproducible ppb-level gas sensing are highly desirable for widespread deployments of sensors to build networks in applications of industrial safety and indoor/outdoor air quality monitoring. Herein, a strategy is proposed to substantially improve the surface homogeneity of sensing materials and gas sensing performance via chip-level pyrolysis of as-grown ZIF-L (ZIF stands for zeolitic imidazolate framework) films to porous and hierarchical zinc oxide (ZnO) nanosheets. A novel approach to generate adjustable oxygen vacancies is demonstrated, through which the electronic structure of sensing materials can be fine-tuned. Their presence is thoroughly verified by various techniques. The sensing results demonstrate that the resultant oxygen vacancy-abundant ZnO nanosheets exhibit significantly enhanced sensitivity and shortened response time toward ppb-level carbon monoxide (CO) and volatile organic compounds encompassing 1,3-butadiene, toluene, and tetrachloroethylene, which can be ascribed to several reasons including unpaired electrons, consequent bandgap narrowing, increased specific surface area, and hierarchical micro–mesoporous structures. This facile approach sheds light on the rational design of sensing materials via defect engineering, and can facilitate the mass production, commercialization, and large-scale deployments of sensors with controllable morphology and superior sensing performance targeted for ultratrace gas detection.
关键词： metal-organic frameworks,oxygen vacancies,ppb-level gas sensing,defect engineering,ZnO nanosheets
更新于2025-09-19 17:15:36
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Plasmonic Gas Sensing with Graphene Nanoribbons
摘要： The main challenge to exploiting plasmons for gas vibrational mode sensing is the extremely weak infrared absorption of gas species. In this work, we explore the possibility of trapping free-gas molecules via surface adsorption, optical, or electrostatic fields to enhance gas-plasmon interactions and to increase plasmon-sensing ability. We discuss the relative strengths of these trapping forces and find gas adsorption in a typical nanoribbon array plasmonic setup produces measurable dips in optical extinction of magnitude 0.1% for a gas concentration of about the parts per thousand level.
关键词： Optical extinction,Infrared absorption,Graphene nanoribbons,Gas-plasmon interactions,Plasmonic gas sensing
更新于2025-09-19 17:13:59
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InGaAs Membrane Waveguide: A Promising Platform for Monolithic Integrated Mid-Infrared Optical Gas Sensor
摘要： Mid-infrared (mid-IR) absorption spectroscopy based on integrated photonic circuits has shown great promise in trace-gas sensing applications in which the mid-IR radiation directly interacts with the targeted analyte. In this paper, considering monolithic integrated circuits with quantum cascade lasers (QCLs) and quantum cascade detectors (QCDs), the InGaAs-InP platform is chosen to fabricate passive waveguide gas-sensing devices. Fully suspended InGaAs waveguide devices with holey photonic crystal waveguides (HPCWs) and sub-wavelength grating cladding waveguides (SWWs) are designed and fabricated for mid-infrared sensing at λ=6.15μm in the low index contrast InGaAs-InP platform. We experimentally detect 5 ppm ammonia with a 1 mm long suspended HPCW and separately with a 3 mm long suspended SWW, with propagation losses of 39.1 dB/cm and 4.1 dB/cm, respectively. Furthermore, based on the Beer-Lambert infrared absorption law and the experimental results of discrete components, we estimated the minimum detectable gas concentration of 84 ppb from a QCL/QCD integrated SWW sensor. To the best of our knowledge, this is the first demonstration of suspended InGaAs membrane waveguides in the InGaAs-InP platform at such a long wavelength with gas sensing results. Also, this result emphasizes the advantage of SWWs to reduce the total transmission loss and the size of the fully integrated device’s footprint by virtue of its low propagation loss and TM mode compatibility in comparison to HPCWs. This study enables the possibility of monolithic integration of quantum cascade devices with TM-polarized characteristics and passive waveguide sensing devices for on-chip mid-IR absorption spectroscopy.
关键词： sub-wavelength waveguides,gas sensing,absorption spectroscopy,photonic crystal waveguides,mid-infrared,photonics integrated circuits,quantum cascade devices,parts-per-billion
更新于2025-09-19 17:13:59
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Ultrafast photo-annealed carbon-coated SiO2 sphere electrodes for NO2 gas sensing
摘要： There is great interest in carbon-based printed electronics as a promising technology to achieve lighter, thinner and ?exible electronic devices at low-costs. Despite the surge of enthusiasm in this area, research advances in printed electronics are not yet able to realize diverse carbon structures yet. This is due to the limitations in conventional solution-based printing methods (e.g., inkjet printing, roll-to-roll, screen printing). Processes such as polymer phase-inversion offer one possibility but a much faster and ef?cient method should be devised for reliable production. Here, we demonstrate laser printing combined with intense pulsed-light (IPL) annealing as a novel and ef?cient technique which can form inter-connected carbon spheres electrode on ?exible polymer substrate. Our observations show that the printed patterns from a laser printer consist of a solid-state polymer matrix with inorganic nanoparticles randomly embedded inside. Through ultrafast (5 ms) IPL treatment, core/shell type nanosphere arrays of carbon-coated SiO2 were successfully fabricated, which could be used as a functional platform for highly selective NO2 gas sensing.
关键词： Laser printing,Gas sensing,Intense pulsed-light,SiO2 spheres,Carbon coating
更新于2025-09-19 17:13:59
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Rapid and wide-range detection of NO <sub/>x</sub> gas by N-hyperdoped silicon with the assistance of a photovoltaic self-powered sensing mode
摘要： Wide dynamic range NOx sensors are vital for environment and health purposes, but few sensors could achieve wide range detection with ultralow and ultrahigh concentrations at the same time. In this article, the microstructured and nitrogen-hyperdoped silicon (N-Si) for NOx gas sensing is investigated systematically. Working by the change of surface conductivity, the sensor is ultra-sensitive to low concentration of NOx down to 11 ppb, and shows a rapid response/recovery time of 22/33 s for 80 ppb. When NOx concentration increases and exceeds a threshold value (10–50 ppm), an n–p conduction type transition is observed due to the inversion of the conduction type of major carriers, which limits the sensor’s dynamic range at high concentration. However, when the sensor works in a photovoltaic self-powered mode under the asymmetric light illumination (ALI), the limitation can be successfully overcome. Therefore, with the combination of the two working principles, a wide dynamic range stretching over six orders of magnitude (~0.011–4,000 ppm) can be achieved.
关键词： dynamic range,conduction type transition,asymmetric light illumination,hyperdoped silicon,self-powered gas sensing
更新于2025-09-19 17:13:59
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Fabrication and characterization of PSi/nanometal hybrid structures by laser for CO gas sensor
摘要： Mesoporous silicon (mesoPSi) layers fabricated by the photoelectrochemical etching (PECE) method in hydrofluoric acid (HF) are active as carbon monoxide gas sensors. The modified porous silicon (PSi) can be used with noble metals to manufacture an effective gas sensor. Embedded gold, platinum, and palladium nanoparticles Au, Pt, and Pd-NPs could modify the surface morphology of mesoPSi and form mesoPSi/AuPtPd-NPs hybrid structures through a simple and dipping process in fixed salt concentrations. The morphology of the hybrid structures has been studied using scanning electron microscopy and X-ray diffraction. The prepared gas sensor has measured the electrical characteristics at room temperature. Shape, nanoparticle size, and specific surface area strongly influenced the current–voltage characteristics. The results show that Au, Pd, and Pt-NPs sizes prepared by the dipping process for mesopore-like structures were in the range from 0.64 to 7.53 nm. Besides, considerable improvements in the response, recovery times and sensitivity of gas sensor were noticed when decreasing the incorporated Au, Pd, and Pt-NPs to the mesoPSi matrix.
关键词： SEM,Gas sensing,Photoelectrochemical,AuPtPd-NPs hybrid structures,MesoPSi
更新于2025-09-19 17:13:59
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Multifunctional inorganic nanomaterial aerogel assembled into fSWNT hydrogel platform for ultraselective NO2 sensing
摘要： Facile fabrication of multifunctional porous inorganic aerogels remains an outstanding challenge despite the considerable demand for extensive applications. Here, we present the production of a multifunctional porous inorganic nanomaterial aerogel by controllable surface chemistry of a functionalized SWNT (fSWNT) hydrogel platform for the first time. The versatile functional inorganic nanoparticles can be incorporated uniformly on the porous 3D fSWNT hydrogel platform through a facile dip coating method at ambient conditions. The morphology of the multifunctional inorganic aerogel is manipulated by designing the fSWNT hydrogel platform for different requirements of applications. In particular, Pt-SnO2@fSWNT aerogels exhibit high porosity and uniformly distributed ultrafine Pt and SnO2 on the fSWNT platform with controllable particle size (1.5–3.5 nm), which result in significantly high surface area (393 m2 g-1). The ultrafine Pt-SnO2@fSWNT aerogels exhibit highly sensitive (14.77% at 5 ppm) and selective NO2 sensing performance even at room temperature due to the increased active surface area and controllable porous structure of the ultrafine aerogel, which can provide fast transport and penetration of a target gas into the sensing layers. The newly designed multifunctional inorganic aerogel with ultrahigh surface area and high open porosity is a prospective materials platform of high performance gas sensors, which could be also broadly expanded to widespread applications including catalysis and energy storages.
关键词： fSWNT hydrogel platform,room temperature sensor,ultraselective NO2 gas sensing,Pt-SnO2@fSWNT aerogel,Multifunctional ultrafine inorganic aerogel
更新于2025-09-19 17:13:59
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Analysis of Si3N4 waveguides for on-chip gas sensing by optical absorption within the mid-infrared region between 2.7 and 3.4???μm
摘要： We theoretically investigated the use of a Si3N4 on SiO2 waveguide as an optical interaction part with sensed molecules for multi-gas wideband on-chip spectroscopic sensing. From the analysis, we show that a simple strip Si3N4 waveguide can be employed to achieve acceptable values of performance in term of detection limit, compactness, polarization, and fabrication tolerance for the detection of water vapor (H2O), carbon dioxide (CO2), Nitrous oxide (N2O), Ammonia (NH3), Ethylene (C2H4), and Methane (CH4) gas molecules, with a wideband operation between 2.7 and 3.4 μm optical wavelength. The results show that a simple Si3N4 waveguide structure could attain competitive performance required for generic on-chip spectroscopic sensing for environmental and agricultural usage.
关键词： gas sensing,optical absorption,mid-infrared,on-chip spectroscopic sensing,Si3N4 waveguide
更新于2025-09-16 10:30:52