Types Of Gas Sensors Research Articles

Brief modeling equation for metal-oxide; TGS type gas sensors

The main aim of this research is to propose a mathematical equation in order to reduce the model parameters based on temperature, humidity and gas density variation in metal-oxide semi-conductive sensors. Also the Arduino based Designed E-nose with the capability to change the temperature and humidity is used to obtain the real sensor?s response in various conditions. The sampling procedure consists of three sectors: fixed temperature and fixed humidity, variable temperature and fixed humidity, fixed temperature and variable humidity, which are stored in Excel software and analyzed with MATLAB. The output response is based on combination of First-Order Plus Dead Time (FOPDT) which has the Minimum Parameters system (MPS) to investigate the behavior of the sensors. Finally, after evaluating the models with the real sensor response and bi-sentence exponentials, it is suggested that the MPS model introduces fewer and simpler parameters, which helps to simulate the sensor?s behavior more accurately and consequently in order to draw a better short response.

In situ Bi2O3-loaded polypyrrole nanocomposites for carbon dioxide gas sensing

In the present work, an attempt has been made to detect carbon dioxide (CO2) using an in situ-loaded Bi2O3–polypyrrole nanocomposite sensor. The polypyrrole (PPy) was prepared by oxidative polymerization method from precursor’s monomer pyrrole and aqueous solution of ammonium persulphate. The prepared nanocomposites were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–Vis), thermogravimetric–differential thermal analysis (TG–DTA) and Raman spectroscopy. Thick films of the synthesized PPy nanocomposites were deposited on glass substrate by screen printing technique. Resistive type gas sensors are extensively used in a number of modern applications such as emission control and energy efficiency. By considering this view, PPy nanocomposite films were prepared for gas sensing application. The XRD analysis revealed amorphous nature. The SEM micrograph showed that nanocomposite particles have irregular morphology and size. The nanocomposites showed a good sensing performance toward CO2 gas. The highest value of CO2 gas sensing response was shown by 25 wt% Bi2O3-loaded PPy nanocomposite sample (S5), which was found to be 0.065 for 50 ppm. Operating temperature for the optimized sample S5 toward CO2 gas was found to be 363 K. Similarly, the optimized sample S5 showed an excellent stability response against CO2 gas and atmospheric change for 30 days.

Performance analysis of gas sensing device and corresponding IoT framework in mines

Gas sensor devices usage have found prominence in fields like artificial olfactory systems and is often used to keep in check pollution and other toxic gas hazards. Graphene mono-layered sensing material along with Gold nano-particles have been previously used to formulate a sensor device. In recent times, internet of things (IoT) capable gas sensing device is a subject of great interest. Previously, it has been implemented through various wired and wireless communications like Zigbee Protocol, IBM Bluemix and sensor nodes but they have their own limitations. In this work nano gas sensor device used for detecting perilous and toxic gas has been fabricated and enhanced to increase its selectivity and sensitivity. Fabrication of Au based TiO2, CuO, ZnO, and WO3 resistive type gas sensor array has been done using sol gel method and analyzed to ensure better conduction. Application of the proposed sensing device can prevent accident in mines by precise and prompt checking of hazardous gases present inside. An IoT frame work has been proposed in this study where Node MCU (ESP8266) is used as a WiFi module along with Message Queuing Telemetry Transport protocol, which resulted in better speed and efficiency. Increased sensitivity and selectivity of the sensor nodes with better efficiency and speed of communication ensures a productive mine hazard management.

Quasi Similar Routes of NO2 and NO Sensing by Nanocrystalline WO3: Evidence by In Situ DRIFT Spectroscopy.

Tungsten oxide is a renowned material for resistive type gas sensors with high sensitivity to nitrogen oxides. Most studies have been focused on sensing applications of WO3 for the detection of NO2 and a sensing mechanism has been established. However, less is known about NO sensing routes. There is disagreement on whether NO is detected as an oxidizing or reducing gas, due to the ambivalent redox behavior of nitric oxide. In this work, nanocrystalline WO3 with different particle size was synthesized by aqueous deposition of tungstic acid and heat treatment. A high sensitivity to NO2 and NO and low cross-sensitivities to interfering gases were established by DC-resistance measurements of WO3 sensors. Both nitrogen oxides were detected as the oxidizing gases. Sensor signals increased with the decrease of WO3 particle size and had similar dependence on temperature and humidity. By means of in situ infrared (DRIFT) spectroscopy similar interaction routes of NO2 and NO with the surface of tungsten oxide were unveiled. Analysis of the effect of reaction conditions on sensor signals and infrared spectra led to the conclusion that the interaction of WO3 surface with NO was independent of gas-phase oxidation to NO2.

In situ exsolution of PdO nanoparticles from non-stoichiometric LaFePd0.05O3+δ electrode for impedancemetric NO2 sensor

Second phase enhanced sensing electrodes have attracted special attention with respect to the effectively improved sensing performance for the solid electrolyte type gas sensors. Herein, we present a facile exsolution process conjunction with non-stoichiometry of oxide host (LaFePd0.05O3+δ) to prepare PdO nanoparticles (NPs) decorated sensing electrode for impedancemetric NO2 sensor. The as-prepared composite electrode was evaluated using various characterization methods and used to detect NO2 with phase angle (Θ) as response signal. The B site excess of the perovskite effectively promoted the NPs exsolution. Well-dispersed PdO NPs were exsolved after treatment in 10% H2/Ar at 700 °C for 30 min and then re-oxidization by switching the Ar to Air atmosphere during the cooling process. The sensor with PdO NPs decorated LaFeO3 sensing electrode exhibited excellent Θ sensing performances toward NO2 at 450–550 °C. Compared with the pristine LaFeO3 and LaFePd0.05O3+δ sensing electrodes, the decoration of PdO NPs further enhanced the response signal (ΔΘ) of the sensor accompanied by the improved sensitivity and detection limit due to the improved electro-catalytic activity of the materials. The concept exemplified here may serve in the design and development of more sensing materials with advanced functionality for gas sensors.

Enhancement of Lewis Acidity of Cr‐Doped Nanocrystalline SnO2: Effect on Surface NH3 Oxidation and Sensory Detection Pattern

Understanding ammonia oxidation over metal oxide surfaces is crucial for improving its detection with resistive type gas sensors. Formation of NOx during this process makes sensor response and calibration unstable. Cr-doping of nanocrystalline metal oxides has been reported to suppress NO2 sensitivity and improve response towards NH3 , however the exact mechanism of such chromium action remained unknown. Herein, by using EPR spectroscopy we demonstrate formation of Cr(VI) lattice defects on the surface of nanocrystalline Cr-doped SnO2 . Enhancement of Cr-doped SnO2 surface acidity and ammonia adsorption as a result has been revealed by using in situ IR spectroscopy. Moreover, a decrease in concentration of free electrons in the conduction band has been shown as a result of substitutional Cr(III) defects formation. Weaker NOx chemisorption during ammonia oxidation over SnO2 surface after Cr doping has been found with the use of mass-spectrometry assisted NH3 thermo-programmed desorption. The given example of surface acidity adjustment and electronic configuration by means of doping may find use in the design of new gas-sensing metal oxide materials.

Solid state electrolyte type gas sensor using stabilized zirconia and MTiO3 (M: Zn, Co and Ni)-SE for detection of low concentration of SO2

This paper deals with solid state electrolyte type gas sensors based on mixed potential mechanism using yttria-stabilized zirconia (YSZ) as solid electrolyte and MTiO3 (M: Zn, Co and Ni) as sensing electrodes (SEs) for monitoring very low concentrations of SO2 in atmospheric environments. Among all the devices attached with different SEs, ZnTiO3-SE brought about the highest response value of −22.5 mV to 1 ppm SO2 at 600 ℃ and even down to 100 ppb SO2 with the response value of −2.5 mV. Meanwhile, the measured ΔV of the sensor was found to vary linearly as a function of the logarithm of SO2 concentration in the range of 100 ppb–2 ppm at 600 ℃ and the sensitivity (slop) was −23 mV/decade. In addition, the sensor coupled with ZnTiO3-SE gave negligible responses to other interfering gases such as C2H2, CH4, CO, NO2, NO, NH3. Furthermore, the present sensor possessed good repeatability, slightly affected by the change of oxygen concentration and relatively stability during 20 days of continuous high-temperature operation. Moreover, the polarization-curve measurements demonstrated that the good agreement between the observed sensitivity and the estimated value, confirming that the sensing mechanism was based on mixed-potential model.

Room-temperature and flexible PEDOT:PSS–WO3 gas sensor for nitrogen dioxide detection

In this paper, a resistance type gas sensor which consists of tungsten oxide (PEDOT:PSS), [Formula: see text] particles and silver finger electrodes was prepared on glass as well as (PET) substrates. The structural and surface morphological properties of the sensors were studied using (XRD), UV-visible, (FTIR), (FE-SEM) and 3D optical microscopy. The influence of fabrication parameters on the sensibility for nitrogen dioxide [Formula: see text] detection is discussed. Experimental results reveal that the sensor with [Formula: see text] content of 2 g/mL shows the highest response rate of 2.31 with increasing concentration up to 80 ppm of nitrogen dioxide gas. The response of the flexible gas sensor reveals improved sensing performance after 500 bending tests.

Improvement of NO2 gas-sensing properties in InGaZnO thin-film transistors by a pre-biasing measurement method

In this work, we investigated the effectiveness of a pre-biasing measurement technique for improving the gas-sensing performance of a metal oxide semiconductor (MOS)-based thin-film transistor (TFT)-type gas sensor for the first time. Various pre-biases voltages were applied to an indium-gallium-zinc oxide (IGZO) TFT gas sensor, and the resulting effects on NO2 detection performances were examined at various NO2 concentrations and temperatures. Our results showed that the NO2 sensing performance of the IGZO TFT sensor could be significantly improved by application of a positive pre-bias voltage to the gate electrode of the IGZO TFT. The impact of pre-bias voltage application was more significant when the pulse amplitude and width were increased, especially at temperatures below 90 °C. Enhancement of IGZO TFT NO2 sensor performance was attributed to an electric-field-induced chemisorption of NO2 on the active back channel of the IGZO TFTs during pre-bias voltage application. Our results demonstrated that the pre-biasing measurement technique is a simple and effective biasing scheme that can enhance the gas-sensing performance of three-terminal TFT-type gas sensors that employ MOS for both the channel and sensing layers.

Operating temperature dependence of sensitivity in Ag-TiO2 Schottky type gas sensors

Noble metal-TiO2 gas sensors have the highest gas sensitivity among all gas sensitive devices at elevated operating temperatures. However, the temperature-dependence of the sensitivity in these devices have remained uninvestigated. Here, we report fabricating Ag-TiO2 structured Schottky type device and utilizing it for methanol vapor detection at different operating temperatures for the purpose of sensitivity versus operating temperature studies. The obtained results revealed for the first time that, unlike metal oxide based chemoresistive gas sensors, the optimum temperature of operation in diode type sensors is gas concentration dependent; as the gas concentration goes up, its maximum sensitivity occurs at a lower operation temperature. The observed effect is described based on the model proposed for the sensing mechanism of device.

Trace Amounts Hydrogen Detection Performance of The Ceria Thick Film Type Gas Sensor in Vacuum Condition.

Trace Amounts Hydrogen Detection Performance of The Ceria Thick Film Type Gas Sensor in Vacuum Condition.

A rapid-response room-temperature planar type gas sensor based on DPA-Ph-DBPzDCN for the sensitive detection of NH3

The rapid-response room-temperature planar type NH3 gas sensor was achieved utilizing the DPA-Ph-DBPzDCN organic material.

Highly selective and stable mixed-potential type gas sensor based on stabilized zirconia and Cd2V2O7 sensing electrode for NH3 detection

In this work, the highly selective and stable mixed potential type stabilized zirconia (YSZ) based gas sensor using Cd2V2O7 sensing electrode (SE) synthesized via simple coprecipitation method was fabricated and developed for effective detection of NH3 at 650 °C. The as-prepared Cd2V2O7 sensing material was characterized by X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS) and Field-emission scanning electron microscopy (FESEM). The results of gas sensing measurement indicated that the sensor attached with Cd2V2O7- SE displayed the response value of −68 mV and rapid response rate of 5 s to 100 ppm NH3 at 650 °C. The present device also exhibited the low detection limit of 1 ppm and the piecewise sensitivities of −6 and −66 mV/decade to NH3 in the concentration ranges of 1–10 ppm and 10–200 ppm, respectively. Moreover, the fabricated sensor showed good reproducibility, excellent selectivity, stability to oxygen concentration, relative humidity and 30 days continuous aging of high temperature at 650 °C. And the complex impedance and polarization curves were performed to explain the selectivity and verify the sensing mechanism involving mixed potential model.

Detection of Wastewater Treatment Process Disturbances in Bioreactors Using the E-Nose Technology

Abstract Wastewater treatment processes are subject to numerous disturbances during biological treatment of wastewater. In order to achieve and sustain suitable conditions of the process, basic wastewater parameters should be frequently monitored. While great improvements have been made in the automatization of treatment process, little is known about automatic measuring systems that can detect unusual process conditions in a bioreactor. Tracking these parameters can be difficult and the time required for the determination might vary from several minutes to few days. The objective of this study is to evaluate the use of an electronic nose in-house device (based on a non-selective gas sensor array) for the detection of process disturbances in a lab-scale sequencing batch reactor (SBR) during biological treatment of wastewater with activated sludge. Measurements were performed during a 12-hours working cycle. Continuous analyses of the headspace were performed using a sensor array based on the resistive Metal Oxide Semiconductor type (MOS) gas sensor. Based on the data obtained and the PCA analysis, this study showed that the e-nose technology can be used to predict or retrieve information about potential disruptions during wastewater processes using the e-nose technology.

Preparation and Gas Sensing Properties of SnO2 Hollow Nanostructures

Gas sensor can be used to detect, monitor, monitor, analyze and alarm. It has very important application value in industry, national defense, food safety and medical examination. Among the gas sensors, the semiconductor resistance type gas sensor has many advantages, such as high sensitivity, fast response, small size, light weight, easy to carry, and so on. As one of the widely used gas sensing materials, SnO2 has been a hot spot in the research and application in 60s, and it has been developing rapidly. SnO2 is one of the most common gas sensitive materials, with physical and chemical properties of gas detection and stability; reversible adsorption and desorption time is short; low cost, energy saving and other advantages, is widely used in the detection of various gas sensitive devices. However, the disadvantages of high working temperature and poor selectivity of SnO2 make it need to be further improved as gas sensitive material. The gas sensing mechanism of semiconductor gas sensitive material is mostly controlled by the surface, which is embodied in: increasing the specific surface area of the material and enhancing the gas sensing performance. At present, the main method of increasing the specific surface area of the material is nano scale. In this paper, the preparation and gas sensing properties of porous and hollow structure SnO2 are mainly discussed on the basis of particle size. Porous structure facilitates the increase of the specific surface area of the material, providing a larger surface area and volume ratio for the material, which is of great benefit to the diffusion and transportation of the gas being measured. Nano hollow structure has a thin shell; the inner and outer surface provides a high surface area and volume ratio, so that the sensor has a faster response and recovery speed, and higher sensitivity. Using carbon micro spheres as hard templates, the structure of SnO2 was successfully prepared by using different raw materials ratio and hydrothermal conditions. The composition and morphology of SnO2 were characterized by XRD, SEM, TEM and so on. The study of gas sensitivity shows that the SnO2 of the hollow classification structure can show good gas sensitivity, which has the advantages of high sensitivity, good selectivity and strong stability.

Dual gas sensing properties of graphene-Pd/SnO2 composites for H2 and ethanol: Role of nanoparticles-graphene interface

In the present work, role of palladium (Pd) and tin oxide (SnO2) nanoparticles (NPs) deposited on graphene has been investigated in terms of dual gas sensing characteristics of ethanol and H2 between two temperatures. The incorporation of nanoparticles into graphene has been observed which results a large change in the sensing response towards these gases. It is investigated that, incorporation of isolated Pd NPs on the graphene facilitates the room temperature sensing of H2 gas with fast response and recovery time whereas, isolated SnO2 NPs on graphene enables the detection of ethanol at 200 °C. However, combination of isolated Pd and SnO2 NPs on graphene shows improved sensitivity and good selectivity towards H2 and ethanol, usually not observed in chemiresistive gas sensors. Catalytic PdH interaction and corresponding change in work function of nanoparticles on hydrogenation resulting in modifications in electronic exchange between Pd, SnO2 and graphene are responsible for the observed behavior. These results are important for developing a new class of chemiresistive type gas sensor based on change in the electronic properties of the graphene and NPs interfaces.

Sulfur dioxide adsorbed on pristine and Au dimer decorated γ-graphyne: A density functional theory study

In this work, we investigated the adsorption behaviour of sulfur dioxide on pristine and Au dimer decorated γ-graphyne (γ-GY). From comparing the adsorption energy, electron transfer and band gap, the most energetically adsorption configurations were gained. Then we made a further discussion of charge density difference, electron localization function (ELF), band structure, density of states (DOS) to evaluate the chemical and physical interactions between the SO2 and the γ-GY. The results indicated that the SO2 adsorption on the pristine γ-GY just exhibited van der Waals force with very weak chemical interactions. But SO2 could be adsorbed on Au dimer decorated γ-GY with relatively stronger chemical interactions due to the larger adsorption energy, larger electron transfer, the obvious change of SO2 molecular orbitals and many hybridizations between the Au and the S atom in DOS. Because of the unchanged band gap of Au dimer decorated γ-GY, it is more suitable for Au2-GY to be applied in QCM gas sensor to detect SO2 rather than resistance type gas sensor.

Ultrafast-response stabilized zirconia-based mixed potential type triethylamine sensor utilizing CoMoO4 sensing electrode

An ultrafast-response yttria stabilized zirconia (YSZ)-based mixed potential type gas sensor utilizing molybdate CoMoO4 sensing electrode was developed to realize the effective detection of triethylamine (TEA) at 600 °C. The gas sensing characteristic of the fabricated sensor was optimized by changing the calcination temperature of CoMoO4 sensing material and results indicated that the device attached with CoMoO4-SE sintered at 1000 °C exhibited the highest response value (−102 mV) to 100 ppm TEA and low detection limit of 100 ppb at 600 °C. Interestingly, the response and recovery times of the present sensor to 100 ppm TEA were 1 s and 10 s, which signified the ultra-fast response rate. The response value of fabricated sensor displayed the piecewise linear function to logarithm of TEA concentrations and the sensitivities were −14 mV/decade (0.1–5 ppm) and −53 mV/decade (5–200 ppm), respectively. More importantly, the present sensor also exhibited good repeatability, selectivity, slight effect of humidity and long-term stability of 20 days, indicating a great candidate for use in detection of TEA. Furthermore, the device based on mixed potential mechanism was proposed and further verified using polarization curve.

CeO2-based mixed potential type acetone sensor using La1-xSrxCoO3 sensing electrode

In this article, CeO2-based mixed potential type gas sensor attached with sensing electrodes (SEs) consisting of perovskite-type La1-xSrxCoO3 (x = 0.1, 0.2, 0.3 and 0.5) composite oxides has been developed for acetone detection. The effect of different Sr2+ doping content in La1-xSrxCoO3 oxide material and calcination temperature on acetone sensing characteristics was investigated. It was seen that the sensor using La0.8Sr0.2CoO3 calcined at 1000 °C as SE gave the largest sensing signal to acetone in the concentration range of 1–50 ppm at 600 °C among these sensors. The response value (ΔV) of the sensor was sectionally linearly changed with the logarithm of acetone concentration within the ranges of 1–5 ppm and 5–50 ppm, and the sensitivities were −26 and −49 mV/decade, respectively. In addition, it is noteworthy that the response of the sensor to 1 ppm acetone was approximately −8.7 mV. The sensor also exhibited consistent response and recovery characteristics in five cycles, indicating the sensing device had good reproducibility. Besides, the sensor exhibited the highest response to 10 and 50 ppm acetone and less effective response to other tested gases, it indicates that the sensor has good selectivity. Furthermore, the long-term stability for the sensor to 20 ppm acetone was good because that only a slight attenuation in the sensing response was observed during 30 days. The sensing characteristics of the sensor attached with La0.8Sr0.2CoO3-SE sintered at 1000 °C to acetone were explained in terms of electrocatalytic activity changes induced by effects of doped Sr divalent cation.

The mixed potential type gas sensor based on stabilized zirconia and molybdate MMoO4 (M: Ni, Co and Zn) sensing electrode aiming at detecting triethylamine

The mixed potential type gas sensors utilizing yttria stabilized zirconia (YSZ) solid electrolyte and molybdates MMoO4 (M: Ni, Co and Zn) sensing electrodes (SEs) were fabricated aiming at detecting triethylamine (TEA) at 600 °C. Results indicated that the device attached with NiMoO4-SE exhibited the highest response value of −71 mV to 50 ppm TEA and low detection limit of 100 ppb at 600 °C. Moreover, the response time of the developed sensor to 50 ppm TEA was 3 s, which signified the fast response rate. The response value of fabricated sensor displayed the piecewise linear relationship to logarithm of TEA concentrations and the sensitivities were −4 mV/decade (0.1–1 ppm) and −37 mV/decade (1–100 ppm), respectively. More importantly, the present sensor also exhibited good repeatability, selectivity, slight effect of humidity and stability of 10 days, indicating a great candidate for use in detection of TEA. Furthermore, the device based on mixed potential mechanism was proposed and further verified using polarization curve.