CO Gas Detection Research Articles

亥姆霍兹光声光谱多气体检测器设计和优化

As one of the most advanced optical detection techniques, photoacoustic spectroscopy has been successfully used in the area of trace gas detection. Realizing a multi-gas photoacoustic spectroscopy sensor while keeping a high detection sensitivity was the design purpose. For the detection application, a multi-gas photoacoustic spectroscopy sensor based on the Helmholtz resonance was designed and optimized. The sensor was modeled by using the finite element method and optimized for its parameters, including the dimensions of excitation cavity, connecting tube and detection cavity. Also the temperature and pressure properties of the sensor were investigated. As a result, the detection sensitivity could be improved by optimizing the parameters and controlling the temperature and pressure. The optimizing result shows that the gas sensor has a best performance with the infrared light source IR-19, and parameters with excitation cavity of 38 mm9 mm, connecting tube of 5.9 mm10.2 mm and detection cavity of 30 mm5.8 mm. Tested by the experiment, the detection limit of 5.08 ppm is achieved for the CO gas detection. The study results also provide the reference for design of photoacoustic sensor in multi-gas detection.

Study on the synthesis of Indium Tinoxide (ITO) nanomaterial using sol gel process and its potential for CO gas detection

This paper described the synthesis of doped and undoped nanomaterial Indium Tinoxide (ITO) using sol-gel process with the base materials from Indium Nitride (In(NO3)) and Tin Chloride (SnCl4). Doping was done using Palladium Chloride (PdCl), with the molar ratio of 90:10 and 70:30, respectively. Physical characteristics of the nanocrystallites were examined using SEM, EDS, XRD, and FTIR, whereas its resistivity was tested agaist CO gas. The result showed that the ITO powders have a crystal size smaller than 100 nm, with a cubic crystal structure (byxbite type), and having strong molecular bonds for In-O-In and Sn-O-Sn. The response to CO gases showed a decreasing resistivity with increasing CO gas concentration, showing its potential for gas sensor application.

Electrospun PEDOT:PSS/PVP Nanofibers for CO Gas Sensing with Quartz Crystal Microbalance Technique

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/polyvinylpyrrolidone (PEDOT:PSS/PVP) composite nanofibers were successfully fabricated via electrospinning and used as a quartz crystal microbalance (QCM) sensor for detecting CO gas. The electrical property of individual PEDOT:PSS/PVP nanofibers was characterized and the room temperature resistivity was at the magnitude of 105 Ω·m. The QCM sensor based on PEDOT:PSS/PVP nanofibers was sensitive to low concentration (5–50 ppm) CO. In the range of 5–50 ppm CO, the relationship between the response of PEDOT:PSS nanofibers and the CO concentration was linear. Nevertheless, when the concentration exceeded 50 ppm, the adsorption of the nanofiber membrane for CO gas reached saturation and the resonant frequency range had no change. Therefore, the results open an approach to create electrospun PEDOT:PSS/PVP for gas sensing applications.

Microwave-assisted hydrolysis preparation of highly crystalline ZnO nanorod array for room temperature photoluminescence-based CO gas sensor

Crystallography plane orientation and surface defect on the nanostructure play an important role in optical gas sensor application due to its peculiar quantum properties. In this paper, we report on a formation of highly oriented (002) plane bounded ZnO nanorods ended with a surface defect hexagonal plane, prepared through microwave assisted hydrolysis within 20s and used as a CO gas detector. A novel photoluminescence-based optical sensor approach was introduced to study the sensor response of the hazardous CO gas as low as 10ppm at room temperature. The effect of ZnO nanorod arrays prepared by microwave-assisted hydrolysis and hydrothermal was studied towards CO gas response. It was found that the ZnO nanorods prepared through a microwave-assisted hydrolysis approach exhibited remarkable response at 81.1% towards 100ppm CO gas exposure and showed an ultrafast recovery time of approximately 2.5min. This provides an excellent sensing approach for operating a low concentration CO gas detection system at room temperature.

The effect of ultraviolet irradiation on the ultra-thin HfO2 based CO gas sensor

In this work, an effort has been made to fabricate ultrathin HfO2/Al2O3 sample by atomic layer deposition method for the fast detection of CO gas at room temperature. The effect of the operating temperature and the UV light on the gas sensing characteristics has been studied. We investigated the optimum operating temperature for the sample by sensing 25 ppm CO and CO2 gases from room temperature to 150 °C for 10 °C steps. The maximum response was obtained at 150 °C for both gases in the measurement temperature range. Also, the photoresponse measurements clearly show the effect of UV light on the sample. At room temperature, sensor showed superior response (14%) for 5 ppm CO gas. The response time of sensor is 6 s to 5 ppm CO gas concentration. The ultrathin HfO2 based sample shows acceptable gas sensitivity for 5 ppm CO gas at room temperature under UV light irradiation.

SnO<sub>2</sub>를 이용한 CO 및 NOx 가스 감지 센서 제작 및 특성 연구

Abstract : In this paper, we fabricated and evaluated the gas sensor for the detection of CO gas and NO x gas among the vehicle exhaust emission gasses. The SnO 2 (tin dioxide) layer is used as the detection material, and the thin-film type and the nano-fiber type layers are deposited with various thicknesses using sputtering method and electro spinning method, respectively. The experiments are performed in the chamber where the gas concentration is controlled with mass flow controller. The fabricated devices are applied to the CO and NO x gas, where the device with the thinner SnO 2 layer shows better sensitivity. The nano-fiber has the larger surface area, and the shorter response time and recovery time are obtained. From the experimental results, both types of gas sensors successfully detect CO and NO x gases, which can be applied to measure those gases from the vehicle emissions. Key words :SnO 2 (산화주석), CO(일산화탄소), NO X (질소산화물), Semiconductor gas sensor(반도체가스센서), MEMS(미세전자기계시스템), Nano fiber(나노섬유), Electro spinning(전기방사)

The interaction of carbon monoxide to Fe(III)(salen)-PEDOT:PSS composite as a gas sensor

PEDOT:PSS/Fe(salen) composite thin films were coated on glass pieces with interdigitated Au electrodes by spin coating method for CO gas sensing application. The metal complex doped PEDOT:PSS film was experienced by some common atmospheric gases to examine its identification ability for CO gas detection. The highest response factor (ΔR/R0×100) and lowest response time were gained −31.32±0.88% and 38s, respectively. An optimum level of doping (0.1wt.% of Fe(salen)) was established for the highest sensitivity. The results showed that the sensor response was reproducible (RD<2%) and fast recovery (5s) in dry atmosphere and room temperature. The Fe(salen)-doped PEDOT:PSS was well characterized by different techniques such as UV–vis and FTIR spectroscopy. In addition, the surface topography of Fe(salen) doped PEDOT:PSS film was investigated using AFM. The results of this study can be helpful in selecting appropriate procedure for utilizing PEDOT:PSS/Fe(salen) composite for effective gas sensing applications.

Gas sensor applications of zinc oxide thin film grown by the polymeric precursor method

Good quality zinc oxide ZnO films were deposited on alumina substrates by the polymeric precursor method (PPM) using zinc acetate as the precursor. X-ray diffraction (XRD) was used to confirm the crystallinity of the zinc oxide films which were free of impurities and SEM study revealed the uniform deposition of fine grains with a thickness of 120nm. ZnO films were used for CO gas detection at different times by recording the change in the film conductance. The faster response of ZnO sensors to CO gas is believed to be due to high porous sensing films which show higher surface-to-volume ratio. The O2′, O″, O′ species concentration emerging from the [ZnO5·VO•]+1/2O2→[ZnO6] chemisorptions reaction affects the ZnO gas sensor response owing to the fact that the oxygen ion acts as a trap for electrons from the bulk of films.

DFT study of CO sensing mechanism on hexagonal WO3 (001) surface: The role of oxygen vacancy

In this work, density functional theory (DFT) calculations have been used to study the adsorption of CO on the oxygen deficient hexagonal WO3 (h-WO3) (0 0 1) surface. Two different situations including the O- and WO-terminated h-WO3 (0 0 1) surfaces are considered. The influence of surface defect density is also concerned. Calculations proposed that the oxygen vacancy exert negative effects on the sensing ability of the h-WO3 material. Under relatively higher defect density, the presence of the oxygen vacancy on both of the O and WO-terminated (0 0 1) surfaces all decreases their sensitivity to CO gas to some extent, while they are still sensitive enough to detect CO gas with the charge transfers of 0.498 and 0.129 e, respectively. Whereas, under lower defect density, calculations indicated that the sensitivity of the material can be lowered largely.

Adsorption of CO on the LaCoO3 (001) surface by density functional theory calculation

Abstract The adsorption of CO molecule on the LaCoO 3 (0 0 1) surface has been investigated using density functional theory calculation. Calculation results show that the most suitable configuration is Co CO structure for the CoO-terminated LaCoO 3 (0 0 1) surface. In the adsorption process electrons transfer from CO molecule to the surface. The Co C bond is mainly from the hybrid between the CO and Co-d orbital. When CO molecule adsorption on the LaO-terminated LaCoO 3 (0 0 1) surface, the most suitable configuration is the O CO structure and the electrons transfer from the surface to the CO molecule in the adsorption process. The bond between the C atom and the surface O atom is mainly from the hybrid between the C-2p and O-2p orbital. The LaCoO 3 could be used as the gas sensing material to detect CO gas.

Star formation in the ultraluminous infrared galaxy F00183-7111

Abstract We report the detection of molecular CO(1–0) gas in F00183-7111, one of the most extreme ultraluminous infrared galaxies (ULIRGs) known, with the Australia Telescope Compact Array. We measure a redshift of 0.3292 for F00183-7111 from the CO(1–0) line and estimate the mass of the molecular gas in 00183 to be 1 × 1010 M⊙. We find that F00183-7111 is predominately powered by the active galactic nucleus (AGN) and only ∼14 per cent of the total luminosity is contributed by star formation (SFR ∼220 M⊙ yr−1). We also present an optical image of F00183-7111, which shows an extension to the east. We searched for star formation in this extension using radio continuum observations but do not detect any. This suggests that the star formation is likely to be predominately nuclear. These observations provide additional support for a model in which the radio emission from ULIRGs is powered by an intense burst of star formation and by a radio-loud AGN embedded in its nucleus, both triggered by a merger of gas-rich galaxies.

Research of Multi-Sensor Information Fusion Fire Detection System

To reduce false fire alarms, combining with the character of fire signal, a kind of intelligent fire detection system of multi-sensor information fusion based on fuzzy neural network is proposed in this paper . This fire detector fuses three sensor data including temperature, smoke and CO air which have obvious character in fire and fire probability can be obtained by intelligent arithmetic of fuzzy neural network. As a result, The accuracy of the fire detection is improved effectively and the feasibility and validity of the system are proved by the simulation effects. 0 Foreword The purpose of fire detection technology is to make accurate judgments of the fire and to predict the fire in the early time, so that people's lives and property can be protected. Based on the monitoring of physical phenomena such as light, smoke, heat, the traditional fire detection usually monitors one kind of physical quantity and establishes a certain threshold value as the criterion for the fire. In practice, it is discovered that fire monitoring, based on a certain physical quantity and threshold value, is often inevitably influenced by a certain similar environmental factors influence which causes false alarm. 1 Multi-sensor Data Fusion Fire Detection System For any kind of detective object, using only one kind of information to reflect its condition is not complete. Only through getting, integrating and using various multi-dimensional information of the same object, it can detect the fire accurately and early. In view of the fact that unit fire detection technology has been unable to meet the needs of real fire alarm, the system uses multiple information fusion fire detection, which is not the simple combination of the fire detectors original single parameter, but the implementation of multiple simultaneous detection, extraction of useful and accurate information. According to different types of fire parameters, it applies intelligent algorithms, fuses the fire parameters of multi-sensor fusion, and determines whether there is a fire hazard. It overcomes the limitations of a single sensor, and effectively improves the ability of identifying real or false fires. Under normal circumstances, CO is extremely low in the air. Only by burning massive CO can be produced, which causes the density of CO in the air to increase sharply. Thus the detection of CO gas will be in large part reflects whether the combustion phenomenon happens or not. The occurring of fire is often accompanied with the elevation of temperature and the enlargement of smoke density, so the system of fire detectors uses 3-layer structure of multi-sensor fusion, selects temperature sensors, smoke sensors, gas sensors, the temperature signal, smoke concentration and the CO concentration as the fire detection signal. 2 Fuzzy Neural Network Applying fuzzy neural network to fire detection information processing can greatly improve the timeliness and accuracy of fire detection, and reduce the rate of false alarm.This system uses fuzzy neural network as shown in Figure 1. Before and after the neural network in the system is in series with the fuzzy system, in order to facilitate the procession of neural network, the smog density signal from the environment examination, the temperature signal as well as the gas signal through the signal pretreatment should be normalized, and sends these three normalized values into the fuzzy system, uses trigonometric functions for transformation, and obtains three degree of membership and the feedback signal of neural network as the neural network input.

Density functional theory study on the mechanism of CO sensing on Cu2O (1 1 1) surface: Influence of the pre-adsorbed oxygen atom

The adsorption of CO molecule on the Cu2O (111) surface with or without pre-adsorbed oxygen atom (Oad) has been investigated using density functional theory calculation. Calculations show that the adsorption of Oad causes obvious changes in the electronic structure and charge distribution of Cu2O with a charge transfer of 0.48e from substrate to Oad. On the perfect Cu2O (111) surface, the one-fold coordinated copper (Cu1c) atom is the most favorable site for the adsorption of CO with a charge transfer of 0.414e from CO molecule to substrate. Moreover, it is found that the adsorption of CO on the O pre-adsorbed Cu2O (111) surface is strengthened. The adsorbed CO molecule tends to interact with Oad atom and release the electrons trapped by the oxygen adatom back to the substrate, resulting in a significant charge variation (0.619e). All these findings indicate that Cu2O would be a good candidate for the detection of CO gas.

CO Gas Detection of Al-Doped ZnO Nanostructures with Various Shapes

Nanostructure of semiconductor type gas sensors that are high sensitivity, fast response time, inexpensive, and easily fabricated, is suggested. One-dimensional (1D) nanostructures, such as nanorods, and hollow spheres, are attracting particularly great interest because of their large specific surface area and their inherent physical properties. This study combined with ZnCl2 (6.95 g, Sigma-Aldrich), Al(NO3)3·9H2O (Junsei), NaOH, ethanol, and deionized water (DI) by hydrothermal synthesis to manufacture, spherical, hollow, hierarchical, and nanorod. The same Al-doped ZnO (AZO) were prepared by a colloidal template on a Si wafer to make a 3D igloo structure as well. Sensitivity to carbon monoxide at 50 ppm was tested at 250 °C the compare the sensing properties. Gas sensitivity of the hierarchical structure showed the highest sensitivity at 31.8, a figure 7 times that of the packed spherical sphere, whereas the igloo structure gave the fastest response speed of 32 s. The results of various shapes of the AZO nanostructures demonstrated high sensitivity and quick response time, which is useful in the detection of harmful gases in automobiles and the atmosphere.

Gold/vanadium–tin oxide nanocomposites prepared by co-precipitation method for carbon monoxide gas sensors

Abstract The gas sensor investigated is constituted by gold/vanadium–tin oxide (Au/V–SnO2) nanocomposite powders, prepared by a co-precipitation method, and evaluated for carbon monoxide detection at low temperature. The Au-loaded sensor exhibited a higher response and shorter response and recovery time than the V–Sn oxide sensor and had good stability. The responses obtained in both air and nitrogen atmospheres increased with increasing sensor temperatures or CO concentrations. X-ray photoelectron spectroscopy (XPS) revealed the presence of gold in the metallic state and vanadium cations with multiple valences on the oxide surface. The gold addition induced an interaction between gold and vanadium and enhanced oxygen adsorption on the sensor surface under electrical field, as indicated by electron paramagnetic resonance (EPR) and electrical analyses. Results demonstrate the viability of the Au/V–SnO2 sensor to detect CO gas in ambient and oxygen-deficient environments. It is postulated that gold and adjacent vanadium or oxygen vacancy sites facilitate oxygen activation for CO oxidation in air or CO chemisorption under nitrogen. Sensing mechanisms that discuss the roles of these active sites and oxygen in the CO detection are proposed.

Low temperature nanocrystalline TiO2–Fe2O3 mixed oxide by a particulate sol–gel route: Physical and sensing characteristics

Nanocrystalline TiO2–Fe2O3 thin films and powders were prepared by a straightforward aqueous particulate sol–gel route at the low temperature of 300°C. Titanium(IV) isopropoxide and iron(III) chloride were used as precursors, and hydroxypropyl cellulose was used as a polymeric fugitive agent in order to increase the specific surface area. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powder crystallised at the low temperature of 300°C, containing anatase-TiO2 and hematite-Fe2O3 phases. Furthermore, it was found that Fe2O3 retarded the anatase-to-rutile transformation up to 500°C. The activation energies for crystallite growth of TiO2 and Fe2O3 components in the binary system were calculated 10.62 and 0.67kJ/mol, respectively. Moreover, one of the smallest crystallite sizes was obtained for TiO2–Fe2O3 binary mixed oxide, being 6nm at 300°C. Field emission scanning electron microscope (FE-SEM) analysis revealed that the deposited thin films had nanostructured morphology. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of CO gas (i.e., 25ppm) at low operating temperature of 150°C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption. Furthermore, TiO2–Fe2O3 sensors follow the power law for the detection of CO gas.

AKARI observations of ice absorption bands towards edge-on young stellar objects

Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts of ice. Such icy material will evolve to become volatile components of planetary systems, such as comets in our solar system. Aims. To investigate the composition and evolution of circumstellar ice around low-mass young stellar objects (YSOs), we observed ice absorption bands in the near infrared (NIR) towards eight YSOs ranging from class 0 to class II, among which seven are associated with edge-on disks. Methods. We performed slit-less spectroscopic observations using the grism mode of the InfraRed Camera (IRC) on board AKARI, which enables us to obtain full NIR spectra from 2.5 μ mt o 5μm, including the CO2 band and the blue wing of the H2O band, which are inaccessible from the ground. We developed procedures to carefully process the spectra of targets with nebulosity. The spectra were fitted with polynomial baselines to derive the absorption spectra. The molecular absorption bands were then fitted with the laboratory database of ice absorption bands, considering the instrumental line profile and the spectral resolution of the grism dispersion element. Results. Towards the class 0-I sources (L1527, IRC-L1041-2, and IRAS 04302), absorption bands of H2O, CO2 ,C O, and XCN are clearly detected. Column density ratios of CO2 ice and CO ice relative to H2O ice are 21−28% and 13−46%, respectively. If XCN is OCN − , its column density is as high as 2−6% relative to H2O ice. The HDO ice feature at 4.1 μm is tentatively detected towards the class 0-I sources and HV Tau. Non-detections of the CH-stretching mode features around 3.5 μm provide upper limits to the CH3OH abundance of 26% (L1527) and 42% (IRAS 04302) relative to H2O. We tentatively detect OCS ice absorption towards IRC-L1041-2. Towards class 0-I sources, the detected features should mostly originate in the cold envelope, while CO gas and OCN − could originate in the region close to the protostar, where there are warm temperatures and UV radiation. We detect H2O ice band towards ASR41 and 2MASSJ1628137-243139, which are edge-on class II disks. We also detect H2O ice and CO2 ice towards HV Tau, HK Tau, and UY Aur, and tentatively detect CO gas features towards HK Tau and UY Aur.

Highly sensitive room-temperature CO gas sensors: Pt and Pd nanoparticle-decorated In2O3 flower-like nanobundles

We discovered a promising room-temperature CO sensing capability of Pt or Pd nanoparticle-functionalized In2O3 flower-like nanobundles (NBs) composed of parallel nanoparticle-chains. The highly branched In2O3 flower-like NBs synthesized through the process of hydrolysis of InCl3 in NaBH4 aqueous solution and the subsequent heat treatment provided an extremely porous matrix required for high-performance gas sensors. The Pt and Pd nanoparticles uniformly deposited on the In2O3 NBs evidently play a key role in enhancing the sensitivity and response, and most importantly lowering the operating temperature to 25 °C for the detection of CO gas. The present innovative hybrid nanostructures offer a potential platform for room-temperature oxide-based gas nanosensors. Moreover, the resulting sensing behaviours lead to a better understanding of using and designing such nanosensors for a number of gas sensory applications.

Free-standing ZnO–CuO composite nanowire array films and their gas sensingproperties

A modified hydrothermal method was developed to synthesize ZnO–CuO compositenanostructures. A free-standing film made of ZnO–CuO nanostructures was assembled onthe surface of the hydrothermal solution with a smooth surface on one side and a sphericalsurface on the other side. The structure, growth mechanism and the optical properties ofthe composite nanostructures were studied. Structural characterizations indicate that thecomposite nanostructure mainly consisted of two single-crystal phases of CuO andZnO. The sensitivity for CO gas detection was significantly improved for thecomposite CuO–ZnO nanostructure film. This method offers a possible route for thefabrication of free-standing nanostructure films of different functional composite oxides.

MOLECULAR CO(1–0) GAS IN THE z ∼ 2 RADIO GALAXY MRC 0152-209

We report the detection of molecular CO(1-0) gas in the high-z radio galaxy MRC 0152-209 (z = 1.92) with the Australia Telescope Compact Array Broadband Backend (ATCA/CABB). This is the third known detection of CO(1-0) in a high-z radio galaxy to date. CO(1-0) is the most robust tracer of the overall molecular gas content (including the wide-spread, low-density and subthermally excited component), hence observations of CO(1-0) are crucial for studying galaxy evolution in the Early Universe. We derive L'(CO) = (6.6 +- 2.0) x 10^10 K km/s pc^2 for MRC 0152-209, which is comparable to that derived from CO(1-0) observations of several high-z submillimetre and starforming BzK galaxies. The CO(1-0) traces a total molecular hydrogen mass of M(H2) = 5 x 10^10 (alpha_x/0.8) Msun. MRC 0152-209 is an infra-red bright radio galaxy, in which a large reservoir of cold molecular gas has not (yet) been depleted by star formation or radio source feedback. Its compact radio source is reliably detected at 40 GHz and has a steep spectral index of alpha = -1.3 between 1.4 and 40 GHz (4-115 GHz in the galaxy's rest-frame). MRC 0152-209 is part of an ongoing systematic ATCA/CABB survey of CO(1-0) in high-z radio galaxies between 1.7 < z < 3.