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High-Performance Photovoltaic Hydrogen Sensing Platform with a Light-Intensity Calibration Module
摘要： Although battery-free gas sensors (e.g., photovoltaic, or triboelectric sensors) have been recently appeared to resolve the power consumption issue of conventional chemiresistors, severe technical barriers remain. Especially, their signals varying with ambient conditions such as light intensity confines the utilization of the sensors. Insufficient sensing performances (low response and slow sensing rate) of the previous battery-free sensors are also an obstacle for practical use. Herein, a photovoltaic hydrogen (H2) sensing platform having constant sensing responses regardless of light condition is demonstrated. The platform consists of two photovoltaic units: (1) a palladium (Pd)-decorated n-IGZO/p-Si photodiode covered with a microporous zeolitic imidazolate framework-8 (ZIF-8) film and (2) the same device configuration without the Pd catalyst as a reference to calibrate the base current of the sensor (1). The platform after calibration yields accurate response values in real-time regardless of unknown irradiance. Besides, the sensing performances (e.g., sensing response of 1.57 × 104% at 1% H2 with a response time < 15 s) of our platform is comparable with those of the conventional resistive H2 sensors, which are unprecedented results in photovoltaic H2 sensors.
关键词： zeolitic imidazolate framework,hydrogen sensor,battery-free gas sensor,light-intensity calibration module,photovoltaic gas sensor
更新于2025-09-23 15:21:01
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Near Infrared Lasera??Annealed IZO Flexible Device as a Sensitive H2S Sensor at Room Temperature
摘要： A metal-oxide material (indium zinc oxide [IZO]) device with near-infrared (NIR) laser annealing was demonstrated on both glass and bendable plastic substrates (polycarbonate, polyethylene, and polyethylene terephthalate). After only 60 s, the sheet resistance of IZO films annealed with a laser was comparable to that of thermal-annealed devices at temperatures in the range of 200°C–300°C (1 hr). XPS, ATR, and AFM were used to investigate the changes in the sheet resistance and correlate them to the composition and morphology of the thin film. Finally, the NIR laser-annealed IZO films were demonstrated to be capable of detecting changes in humidity and serving as a highly sensitive gas sensor of hydrogen sulfide (in parts-per-billion concentration), with room-temperature operation on a bendable substrate.
关键词： IZO,sol-gel,laser annealing,NIR,gas sensor,flexible
更新于2025-09-23 15:21:01
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Evanescent field ratio enhancement of a modified ridge waveguide structure for methane gas sensing application
摘要： We presented a significant improvement of the evanescent field ratio in a ridge waveguide modified into a dual hybrid plasmonic waveguide by tapering the middle section of the waveguide and placing a gold layer on both sides with a sub-wavelength gap. The waveguide geometry is optimized at 3.392 μm which is an absorption line of methane gas. The proposed waveguide scheme provides a large waveguide cross-section which facilitates a light with an enhanced evanescent field in the middle. To validate the study, the evanescent field ratio, propagation loss, confinement factor and electric field distribution of the waveguide is studied via the finite element method. Additionally, the device is also proposed. An elevated evanescent field ratio of 0.74 is obtained with a propagation loss of ~0.7 dB/μm. The sensitivity of 0.0715 (mW/gas conc.) is obtained for the proposed waveguide scheme by calculating the decay in transmission power due to absorption by the gas in the medium.
关键词： Evanescent field absorption gas sensor,3.392 μm,methane,mid-infrared,Lambert-Beer law
更新于2025-09-23 15:21:01
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ZnO Nanosheets Modified with Graphene Quantum Dots and SnO2 Quantum Nanoparticles for Room-Temperature H2S Sensing
摘要： Overcoming the low selectivity issue of semiconductor oxide (SMO)-based gas sensors at room temperature and realizing the accurate detection of trace disease biomarkers are highly desirable for widespread deployments of sensors in exhaled breath. Here, a self-assembly strategy is proposed to create a graphene quantum dot (GQD) functionalized porous and hierarchical SnO2 quantum nanoparticles (SnO2QNP)/ZnO nanostructure. SnO2QNP/ZnO nanosheets self-assembled directly on the digital integrated electrodes with a post-synthetic humidity treatment (psHT), the construction of GQD and SnO2QNP loaded ZnO nanosheet heterostructure is highly controllable and reproducible. The strong synergistic effect and p-n heterojunction between the p-type GQD and n-type SnO2 and ZnO effectively enlarged the resistance variation due to the change in oxygen adsorption. In comparison with pristine ZnO and SnO2/ZnO sensors, the GQD modified hierarchical SnO2QNP/ZnO nanostructure exhibited a remarkably high response (S=15.9 for 0.1 ppm H2S) and rapid response/recovery time (14/13s), and good selectivity towards H2S against other interfering gases. In particular, we applied principal component analysis (PCA) to analyze the sensing performance of GQD-SnO2QNP/ZnO sensor and found that the combined effects of GQD/SnO2QNP/ZnO heterointerfaces contributed to the improvement of selectivity of sensors. The results demonstrate that the GQD modified SMO with the hierarchical structure has a high potential in the non-invasive exhaled diagnosis.
关键词： graphene quantum dot,principal component analysis,exhaled diagnosis,gas sensor,zinc oxide nanosheet,tin dioxide quantum nanoparticle
更新于2025-09-23 15:21:01
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Fabrication cobalt-doped indium oxide/molybdenum disulfide ternary nanocomposite toward carbon monoxide gas sensing
摘要： This paper demonstrated a high-performance carbon monoxide (CO) gas sensor based on cobalt (Co)-doped indium oxide (In2O3) nanoparticles/molybdenum disulfide (MoS2) nanoflowers nanocomposite. Co-In2O3 nanoparticles were synthesized by a co-precipitation method, and flower-like MoS2 was prepared by one-step hydrothermal route. Layer-by-layer self-assembly technique was employed to fabricate Co-In2O3/MoS2 film sensor on an epoxy substrate with interdigital electrodes. Scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were carried out to fully examine the morphology, microstructure, and elementary composition of the as-prepared samples. The CO-sensing characteristics of the Co-In2O3/MoS2 film sensor were systematically investigated under room temperature through exposing the sensor to various concentration of CO gas. The Co-In2O3/MoS2 sensor achieved high sensitivity, fast response/recovery speed, excellent repeatability and stable long-term stability. An approach of combining gas-sensing experiments with density-functional theory (DFT) simulation based on first-principle was used to further explore the CO-sensing mechanism of the Co-In2O3/MoS2 sensor. The Co2+ ion doping, and heterojunctions created at interfaces of Co-In2O3 and MoS2 were attributed to the high-performance CO sensing.
关键词： CO gas sensor,LbL self-assembly,molybdenum disulfide,first-principle theory,Co-doped indium oxide
更新于2025-09-23 15:21:01
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Numerical model for the chemical adsorption of oxygen and reducing gas molecules in presence of humidity on the surface of semiconductor metal oxide for gas sensors applications
摘要： Charge transfer between the interacting gas molecules and the surface of the sensing layer is the main mechanism for the detection of gases in semiconductor metal oxides. In the presented work, the Wolkenstein's theory of adsorption is used instead of the conventional Langmuir isotherm for the numerical modelling of adsorption of oxygen, reducing gas (CO) molecules and water vapours. A numerical model of chemical adsorption of these gas species at the surface of tin oxide (SnO2) semiconductor gas sensor is presented in this paper. Using this model, quantitative calculation of the combined effect of environmental oxygen, reducing gas (CO) and water vapor adsorption on various electronic properties like electrical conductivity, surface potential and the work function of the metal oxide surface has been carried out. The surface coverage of the chemically adsorbed oxygen gas molecules is simulated as a function of oxygen gas pressure, the temperature of the sensor surface and bulk doping level of the n-type SnO2 semiconductor. Along with oxygen, the adsorption of CO gas is simulated as a function of CO gas pressure at constant atmospheric pressure of Oxygen gas. Furthermore, the sensor response is simulated and compared both in presence of dry Carbon Monoxide (CO) gas as well in the humid environment. It is shown that in the presence of water vapor there is an increase in the conductivity due to the decrease in the surface potential barrier at the semiconductor surface.
关键词： Numerical model,Surface potential,Chemical adsorption,Gas sensor
更新于2025-09-23 15:21:01
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A highly sensitive optofluidic-gas sensor using two dimensional photonic crystals
摘要： Photonic crystals (PCs) are optical structures based on periodic arrays of dielectric materials. These structures enable the manipulation of photons as semiconductors do for electrons. Many optical devices with miniature sizes have been designed based on novel properties of PCs. In this paper, we proposed a new refractive index sensor with high sensitivity and high quality factor, which is implemented in a two dimensional PC with a hexagonal lattice structure. The proposed sensor has been constructed using a PC waveguide surrounded by two rows of ring-shaped holes. The emersion of Fabry-Perot interference pattern within the transmission band and its role in the determination of the features of the proposed refractive index sensor has been investigated. The finite-difference time-domain simulation results indicate that in the case of filling the holes of central waveguide and its surrounding ring-shaped holes by different materials with refractive indices from n = 1 to n = 1.5, a high sensitivity of 575 nm/RIU and a high quality factor of 7070 is achieved, which makes the proposed design applicable for liquid and also gas sensing.
关键词： sensing waveguide,quality factor,sensitivity,Fabry-Perot oscillation,gas sensor,photonic crystal
更新于2025-09-23 15:21:01
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A Gas Sensor Based on a Single SnO Micro-Disk
摘要： In this study, individual nanofabricated SnO micro-disks, previously shown to exhibit exceptional sensitivity to NOx, are investigated to further our understanding of gas sensing mechanisms. The SnO disks presenting different areas and thickness were isolated and electrically connected to metallic electrodes aided by a Dual Beam Microscope (SEM/FIB). While single micro-disk devices were found to exhibit short response and recovery times and low power consumption, large interconnected arrays of micro-disks exhibit much higher sensitivity and selectivity. The source of these differences is discussed based on the gas/solid interaction and transport mechanisms, which showed that thickness plays a major role during the gas sensing of single-devices. The calculated Debye length of the SnO disk in presence of NO2 is reported for the first time.
关键词： single-element device,FIB nanofabrication,low power consumption,semiconductor,sensing mechanism,Debye length,gas sensor,SnO
更新于2025-09-23 15:21:01
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Influence of Ag NPs on Silicon Nanocolumns NH <sub/>3</sub> Gas Sensors
摘要： Two NH3 gas sensor devices, Al/Si nanocolumns/n-Si/Al and Al/Ag NPs/Si nanocolumns/n-Si/Al hybrid structures, have been fabricated and tested. A bare silicon nanocolumns layer was synthesized by a laser-assisted electrochemical etching process in HF solutions. The surface morphology of bare Si nanocolumns was modified by incorporating Ag NPs into Si nanocolumns by simple and fast immersions methods in an aqueous solution of AgNO3 to synthesize a hybrid structure. Characteristic features of bare Si nanocolumns and hybrid structure were investigated using scanning electron microscopy, EDS analysis, FTIR spectra, X-ray diffraction, and photoluminescence spectra (PL). The electrical characteristics of sensors with and without NH3 gas were measured at room temperature. The results showed that the nanoparticles grain size, nature, specific surface area (S.S.A) of Ag NPs, and morphological structure of the Si nanocolumns strongly affected the property characteristics. A significant enhancement in sensitivity, response, and recovery times of gas sensor for a hybrid structure was realized after compared with Al/Si nanocolumns/n-Si/Al gas sensor due to the high specific surface area.
关键词： silicon nanocolumns,response time,NH3 gas sensor,sensitivity,Ag NPs,hybrid structure,recovery time
更新于2025-09-23 15:21:01
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Influence of Oxygen Vacancy Behaviors in Cooling Process on Semiconductor Gas Sensors: A Numerical Analysis
摘要： The in?uence of oxygen vacancy behaviors during a cooling process in semiconductor gas sensors is discussed by the numerical analysis method based on the gradient-distributed oxygen vacancy model. A diffusion equation is established to describe the behaviors of oxygen vacancies, which follows the effects of diffusion and exclusion in the cooling process. Numerical analysis is introduced to ?nd the accurate solutions of the diffusion equation. The solutions illustrate the oxygen vacancy distribution pro?les, which are dependent on the cooling rate as well as the temperature interval of the cooling process. The gas-sensing characteristics of reduced resistance and response are calculated. Both of them, together with oxygen vacancy distribution, show the grain size effects and the re-annealing effect. It is found that the properties of gas sensors can be controlled or adjusted by the designed cooling process. The proposed model provides a possibility for sensor characteristics simulations, which may be bene?cial for the design of gas sensors. A quantitative interpretation on the gas-sensing mechanism of semiconductors has been contributed.
关键词： numerical analysis,oxygen vacancy,gas sensor,semiconductor,diffusion equation
更新于2025-09-23 15:21:01