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Near-infrared methane sensor system using off-axis integrated cavity output spectroscopy with novel dual-input dual-output coupling scheme for mode noise suppression
摘要： Mode noise suppression in o?-axis integrated cavity output spectroscopy (OA-ICOS) is a key for improving the signal-to-noise ratio (SNR) of a sensor system, which basically depends on the ability to smooth out the cavity mode structure and to reduce the cavity mode linewidth. We demonstrated a novel dual-input dual-output (DIDO) coupling scheme of OA-ICOS for mode noise suppression. The in?uences of beam splitting ratio and light re?ection number to the output intensity and cavity mode linewidth were theoretically studied. Experimental investigation on the suppression of cavity mode noise was carried out in terms of detection sensitivity and SNR through methane (CH4) measurements. A SNR of 221 and a detection sensitivity of 1.73 × 10-8 cm-1 Hz-1/2 was obtained for the DIDO-based OA-ICOS sensor system. The SNR was improved by a factor of ～ 2.5 and the sensitivity was improved by a factor of ～ 2.2 compared to the regular single-input single-output (R-SISO) approach. Multi-input multi-output (MIMO) con?guration was further numerically studied to verify the noise suppression ability of this detection concept. This work reveals a new laser-to-cavity coupling method and provides a novel way to exploit OA-ICOS sensors with improved SNR and sensitivity.
关键词： Methane detection,O?-axis integrated cavity output spectroscopy,Wavelength modulation spectroscopy,Dual-input dual-output,Chemical gas sensor
更新于2025-09-16 10:30:52
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A Resonant Gas Sensor Based on Multimode Excitation of a Buckled Microbeam
摘要： We report a new gas sensing technique based on the simultaneous tracking of multiple modes of vibration of an electrothermally heated bridge resonator operated near the buckling point. The proposed technique maximizes the sensitivity of the sensor to changes in gases concentrations. We demonstrate a 200% frequency shift in contrast to 0.5% resistance change using the conventional resistive technique. The method also demonstrates selective identification for some gases without the need for surface functionalization of the microstructure. The proposed method is simple in principle and design and is promising for achieving practical low-cost gas sensors.
关键词： buckling point,multimode,Gas sensor,heated microbeam
更新于2025-09-12 10:27:22
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Modeling of 1D Au plasmonic grating as efficient gas sensor
摘要： Gas-sensor reported here consist of a sensingchip of a metallic grating designed on gold (Au) film over a glass substrate which has been modelled using finite element analysis (FEA). The Au is layered in the form of horizontal nano-strips with a periodic nano-sized gap known as slit-width. The transverse magnetic (TM) light illuminates the metallic films from substrate side at normal incidence. The transmission loss spectrums have been extracted for 0th order diffraction for different physical interpretations. The several combinations of periodicity and slit width have been optimized by taking slit width as half of periodicity. The refractive index sensitivity achieved at optimal geometrical parameters is noteworthy and it is reported to be 599 (nm/RIU) at a spatial period of 660 nm. The novel theoretical results has been supported by far field and near field analysis. The design suggested in this report is important becuase of the wavelength range that lie in the visible region where most of the real life spectrometers works. Such sensors can be applicable in industries for detection of toxic gases and harmful metallic pieces in atmosphere.
关键词： Resonance,Gas Sensor,Surface Plasmons resonance,Finite Elemental Analysis (FEA),Sensitivity
更新于2025-09-12 10:27:22
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Flexible and stretchable photodetectors and gas sensors for wearable healthcare based on solution-processable metal chalcogenides
摘要： Wearable smart sensors are considered to be the new generation of personal portable devices for health monitoring. By attaching to the skin surface, these sensors are closely related to body signals (such as heart rate, blood oxygen saturation, breath markers, etc.) and ambient signals (such as ultraviolet radiation, inflammable and explosive, toxic and harmful gases), thus providing new opportunities for human activity monitoring and personal telemedicine care. Here we focus on photodetectors and gas sensors built from metal chalcogenide, which have made great progress in recent years. Firstly, we present an overview of healthcare applications based on photodetectors and gas sensors, and discuss the requirement associated with these applications in detail. We then discuss advantages and properties of solution-processable metal chalcogenides, followed by some recent achievements in health monitoring with photodetectors and gas sensors based on metal chalcogenides. Last we present further research directions and challenges to develop an integrated wearable platform for monitoring human activity and personal healthcare.
关键词： gas sensor,photodetector,solution-processable metal chalcogenides,healthcare
更新于2025-09-12 10:27:22
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Hierarchical heterostructures of nanosheet-assembled NiO-modified ZnO microflowers for high performance acetylene detection
摘要： It is of great signi?cance to monitor internal faults of transformer and ensure its normal and safe operation. Usually, acetylene (C2H2) is considered as the characteristic gas caused by discharge failure in transformer. Using gas sensor technology to analyze dissolved gases in transformer oil is an important strategy. Recently, metal oxide semiconductor (MOS) heterojunctions with tailored microstructures have been developed to fabricate high quality gas sensors for gas detection. In this paper, hierarchical ?ower-like NiO/ZnO heterostructures assembled with 2D nanosheets have been synthesized by a facile hydrothermal method and calcination process. Noticeably, the introduction of di?erent contents of NiO (3.0 at%, 5.0 at% and 10.0 at%) leads to di?erent assembly manners of the building nanosheets into hierarchical ?ower-like structures, thus a?ecting the gas performances. Given this, a variety of microscopic characterization methods were used to observe and compare the di?erences in the structures and morphologies of the composites. Through the gas sensing test, it was found that the 5.0 at% NiO-modi?ed ZnO based sensor exhibited superior sensing performances to C2H2 compared with that of others. The enhanced properties may be attributed to the formation of p-n heterojunctions as well as high porosity of the nanosheets. This promising approach is versatile for the applications of high-quality gas sensors.
关键词： NiO/ZnO composites,Acetylene,Gas sensor,Hierarchical heterostructure
更新于2025-09-12 10:27:22
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Nanoparticles Assembled CdIn2O4 Spheres with High Sensing Properties towards n-Butanol
摘要： Cd/In-glycerate spheres are synthesized through a simple solvothermal method. After thermal treatment, these Cd/In-glycerates can be converted into CdIn2O4 spheres. Many characterization methods were performed to reveal the microstructure and morphology of the CdIn2O4. It was found that pure CdIn2O4 phase was obtained for the Cd/In starting materials at ratios of 1:1.6. The CdIn2O4 spheres are composed by a large number of nanoparticles subunits. The CdIn2O4 sphere-based sensor exhibited a low detection limit (1 ppm), high response (81.20 to 500 ppm n-butanol), fast response (4 s) and recovery (10 s) time, good selectivity, excellent repeatability, and stability at 280 °C. Our findings highlight the possibility to develop a novel gas sensor based on CdIn2O4 for application in n-butanol detection with high performance.
关键词： solvothermal method,spheres,CdIn2O4,gas sensor,n-butnaol
更新于2025-09-12 10:27:22
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Improved formaldehyde gas sensing properties of well-controlled Au nanoparticle-decorated In2O3 nanofibers integrated on low power MEMS platform
摘要： Approaches for the fabrication of a low power-operable formaldehyde (HCHO) gas sensor with high sensitivity and selectivity were performed by the utilization of an effective micro-structured platform with a micro-heater to reach high temperature with low heating power as well as by the integration of indium oxide (In2O3) nanofibers decorated with well-dispersed Au nanoparticles as a sensing material. Homogeneous In2O3 nanofibers with the large specific surface area were prepared by the electrospinning following by calcination process. Au nanoparticles with the well-controlled size as a catalyst were synthesized on the surface of In2O3 nanofibers. The Au-decorated In2O3 nanofibers were reliably integrated as sensing materials on the bridge-type micro-platform including micro-heaters and micro-electrodes. The micro-platform designed to maintain high temperature with low power consumption was fabricated by a microelectromechanical system (MEMS) technique. The micro-platform gas sensor consisting with Au-In2O3 nanofibers were fabricated effectively to detect HCHO gases with high sensitivity and selectivity. The HCHO gas sensing behaviors were schematically studied as a function of the gas concentration, the size of the adsorbed Au nanoparticles, the applied power to raise the temperature of a sensing part and the kind of target gases.
关键词： Formaldehyde,Gold nanoparticle,In2O3 nanofiber,Gas sensor,Micro-platform,Low power
更新于2025-09-12 10:27:22
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Enhanced CH4 sensitivity of porous nanosheets-assembled ZnO microflower by decoration with Zn2SnO4
摘要： In recent years, design and synthesis of heterostructured nanomaterials with high gas-sensing performance for detection of flammable and toxic gases has attracted much research interest. In this paper, pristine and Zn2SnO4-decorated ZnO microflowers with the size about 2?5 μm and assembled by porous nanosheets of about 15 nm in thickness were successfully synthesized via a simple solvothermal method and subsequent calcination process. The methane (CH4) sensing properties of the prepared Zn2SnO4/ZnO were investigated and compared with that of the pure ZnO counterpart. It was found that after decorating with a small amount of Zn2SnO4, the ZnO sensor showed an improved gas sensing properties to CH4. At optimum operating temperature of 250 oC, the sensor based on SZ2 (Zn2SnO4/ZnO composite with the optimal Zn2SnO4 contend) shows a response as high as 27.2 to 1000 ppm CH4, which is about 3.2 times higher than that of SZ0 (pristine ZnO) sensor. Meanwhile, the SZ2 sensor also shows a fast response and recover characteristic, low detection limit (1.48 ppm), good repeatability and long-term stability. The Zn2SnO4/ZnO heterostructures related CH4 sensing mechanism was discussed.
关键词： CH4,Zn2SnO4,Hierarchical structures,Gas sensor,Heterostructures
更新于2025-09-12 10:27:22
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Hydrogen Sensor Based on Tunable Diode Laser Absorption Spectroscopy
摘要： A laser-based hydrogen (H2) sensor using wavelength modulation spectroscopy (WMS) was developed for the contactless measurement of molecular hydrogen. The sensor uses a distributed feedback (DFB) laser to target the H2 quadrupole absorption line at 2121.8 nm. The H2 absorption line exhibited weak collisional broadening and strong collisional narrowing effects. Both effects were investigated by comparing measurements of the absorption linewidth with detailed models using different line profiles including collisional narrowing effects. The collisional broadening and narrowing parameters were determined for pure hydrogen as well as for hydrogen in nitrogen and air. The performance of the sensor was evaluated and the sensor applicability for H2 measurement in a range of 0–10 %v of H2 was demonstrated. A precision of 0.02 %v was achieved with 1 m of absorption pathlength (0.02 %v·m) and 1 s of integration time. For the optimum averaging time of 20 s, precision of 0.005 %v·m was achieved. A good linear relationship between H2 concentration and sensor response was observed. A simple and robust transmitter–receiver configuration of the sensor allows in situ installation in harsh industrial environments.
关键词： laser spectroscopy,WMS,diode laser,TDLAS,absorption spectroscopy,hydrogen sensor,hydrogen,gas sensor
更新于2025-09-11 14:15:04
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Enhanced NO2 gas-sensing properties of Au-Ag bimetal decorated MWCNTs/WO3 composite sensor under UV-LED irradiation
摘要： Novel NO2 gas sensors that were made of Ag, Au and Au-Ag bimetal particles modified composite of multi-walled carbon nanotubes/tungsten oxide (Ag/MWCNTs/WO3, Au/MWCNTs/WO3 and Au-Ag/MWCNTs/WO3) were fabricated for sensing ppb-level NO2 gas under ultraviolet light emitting diode (UV-LED) irradiation. The effects of Ag, Au and Au-Ag bimetal decoration and under UV-LED irradiation on the response of the Ag/MWCNTs/WO3, Au/MWCNTs/WO3 and Au-Ag/MWCNTs/WO3 sensors for sensing NO2 gas were studied. The gas-sensing properties in the detection of a low concentration of NO2 gas of the Au-Ag/MWCNTs/WO3 composite were superior to bare MWCNTs/WO3, Au/MWCNTs/WO3 and Ag/MWCNTs/WO3 under UV-LED irradiation. The Au-Ag/MWCNTs/WO3 composite sensor showed responses of 28–262 % at NO2 concentrations ranging from 100 to 500 ppb under UV-LED irradiation. These responses were 2–5 times higher than that of the bare MWCNTs/WO3 composite sensor at the same NO2 concentration range. The substantial improvement in the response of the bare MWCNTs/WO3 composite to NO2 gas by its decoration with Au-Ag bimetal particles may be attributed to the enhanced catalytically active sites and photocatalytic activity. A reasonable mechanism for enhancing sensitivity was proposed.
关键词： UV irradiation,NO2 gas sensor,Photocatalytic activity,Au-Ag bimetal
更新于2025-09-11 14:15:04