Carbon Monoxide Gas Detection Research Articles

Detection of Dissolved Carbon Monoxide in Transformer Oil Using 1.567 μm Diode Laser-Based Photoacoustic Spectroscopy

Carbon monoxide (CO) is one of the most important fault characteristic gases dissolved in power transformer oil. With the advantages of high sensitivity and accuracy, long-term stability, and short detection time, photoacoustic spectroscopy (PAS) has been proven to be one promising sensing technology for trace gas recognition. In this investigation, a tunable PAS experimental system based on a distributed-feedback (DFB) diode laser was proposed for recognizing dissolved CO in transformer oil. The molecular spectral line of CO gas detection was selected at 1.567 μm in the whole experiment. Relationships between the photoacoustic (PA) signal and gas pressure, temperature, laser power, and CO gas concentration were measured and discussed in detail, respectively. Finally, based on the least square regression theory, a novel quantitative identification method for CO gas detection with the PAS experimental system was proposed. And a comparative research about the gas detection performances performed by the PAS system and gas chromatography (GC) measurement was presented. All results lay a solid foundation for exploring a portable and tunable CO gas PAS detection device for practical application in future.

Carbon monoxide gas detection system based on mid-infrared spectral absorption technique

Based on infrared spectral absorption technique, a carbon monoxide (CO) detection system was developed using the fundamental absorption band at the wavelength of 4.6 μm of CO molecule and adopting pulse-modulated wideband incandescence and dual-channel detector. The detection system consists of pulse-modulated wideband incandescence, open ellipsoid light-collec- tor gas-cell, dual-channel detector, main-control and signal-processing module. By optimizing open ellipsoid light-collector gas- cell, the optical path of the gas absorption reaches 40 cm, and the amplitude of the electrical signal from the detector is 2 to 3 times larger than the original signal. Therefore, by using the ellipsoidal condenser, the signal-to-noise ratio of the system will be to some extent increased to improve performance of the system. With the prepared standard CO gas sample, sensing characteris- tics on CO gas were investigated. Experimental results reveal that, the limit of detection (LOD) is about 10 ppm; the relative er- ror at the LOD point is less than 14%, and that is less than 7. 8% within the low concentration range of 20~180 ppm; the maxi- mum absolute error of 50 min long-term measurement concentration on the 0 ppm gas sample is about 3 ppm, and the standard deviation is as small as 0. 18 ppm. Compared with the CO detection systems utilizing quantum cascaded lasers (QCLs) and dis- tributed feedback lasers (DFBLs), the proposed sensor shows potential applications in CO detection under the circumstances of coal-mine and environmental protection, by virtue of high performance-cost ratio, simple optical-path structure, etc.

On-chip growth of wafer-scale planar-type ZnO nanorod sensors for effective detection of CO gas

The facile engineering of sensing devices is an important technological achievement that will lead to large-scale and cost-effective fabrication of gas nanosensors. This study demonstrates the on-chip and selective growth process of zinc oxide (ZnO) nanorods (NRs) for wafer-scale fabrication of planar-type gas sensors using combined lithography and chemical hydrothermal techniques. This facile route can effectively fabricate ZnO NR gas sensors at low temperatures without the requirement of novel metal catalyst. The gas-sensing characteristics of the ZnO NR sensors to carbon monoxide (CO) and ammonia (NH3) were evaluated as a function of growth time in correlation with operating temperature and target gas concentration. The ZnO NR sensors showed good response and recovery characteristics with a maximum response to CO and NH3 gas at 400°C. The ZnO NR sensors grown at 6h exhibited the highest response to CO and NH3 gases with sensitivities of 0.37 and 0.05%/ppm, respectively. Furthermore, the gas-sensing mechanism of the ZnO NR sensors was also discussed in terms of three types NR/NR junctions, namely, point-junctions, across-junctions, and block-junctions.

Ultra-Rapid CO Gas Detection by a Gas Sensor Based on Flame-Spray-Made Pt/ZnO Nanoparticles

ZnO nanoparticles doped with 0.2-2 at.%Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum (II) acetylacetonate dissolved in xylene. The particle properties were analyzed by XRD, BET and TEM. Depending on FSP conditions, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal particles were found to be ranging from 5 to 20 nm, while ZnO nanorods were seen to be 5-20 nm in width and 20-40 nm in length. ZnO sensing films were prepared using Al2O3 substrate interdigitated with Au electrodes by spin-coating technique. The gas sensing properties toward carbon monoxide (CO) was studied at the operating temperatures ranging from 200 to 350°C. It was found that the 0.2 at.%Pt/ZnO sensing film showed the highest sensitivity and the fastest response time at 350°C.

Optical system for CO and NO gas detection in the exhaust manifold of combustion engines

The experimental characterization of an innovative optical system for detection of carbon monoxide (CO) and nitride oxide (NO) in the exhaust manifold of otto and diesel engines is reported. A photodetector based on gallium nitride (GaN) and an UV light source are integrated in a chamber of analysis and form the detection system. The UV light source, consisting of a spark produced by an arc discharge, induces electronic transitions in the gas molecules flowing between the light source and the GaN photodetector. The transitions modify the fraction of light in the UV spectral region which is detected by the GaN photodetector, as a function of the species concentration. By means of its structural properties, gallium nitride (GaN) allows to operate at high temperature and high speed and to work in situ in the exhaust manifold of combustion engines at temperatures as high as 600 °C, at which the deposited organic residuals on the detector can be oxidized. This assures a clear surface necessary for a real time optical measurement of the species concentration to be used for a closed loop control of the fuel injection process. The system was applied to the detection of CO and NO with concentration between 0% and 2% in a buffer of pure nitrogen gas, showing an increase in the measured photocurrent as a function of the above gases.

GaN optical system for CO and NO gas detection in the exhaust manifold of combustion engines

We report on an optical system for the detection of carbon monoxide (CO) and nitride oxide (NO) concentrations in the exhaust manifolds of internal combustion engines. In this system a detector based on gallium nitride (GaN) and an UV arc discharge lamp are integrated. The arc discharge lamp induces electronic transitions in the gas molecules flowing between the light source and the GaN photodetector. These transitions modify the fraction of light in the UV spectral region which is detected by the GaN photodetector, as a function of the exhaust gas concentration. The system is designed to operate at temperatures as high as 600??C, so that deposited organic residuals on the detector can be oxidized, ensuring the clear surface needed for an optical measurement. The system was tested by measuring the concentrations of CO and NO diluted in pure N2, showing a strong increase in the measured photocurrent as a function of the above gases.

Effect of processing on the properties of tin oxide-based thick-film gas sensors

Semiconducting tin oxide-based powders were synthesized via three different chemical precipitation methods and also obtained from a commercial source. The precursor powders were characterized using X-ray diffraction (XRD), particle size and surface area measurement techniques. Sensor elements were produced from calcined powders using thick-film screen printing technology. The influence of various powder processing methods, sintering conditions, microstructure and moisture on the carbon monoxide gas detection capabilities, and the response and recovery times of the sensors produced from the above four powders are discussed.

Highly Sensitive Metal-Insulator-Semiconductor Field-Effect Transistor Sensors for Detecting Carbon Monoxide Gas Using Porous Platinum and Tungsten Oxide Thin Films

A novel device based on a porous Pt–WO3 metal-insulator-semiconductor field-effect transistor (MISFET) for carbon monoxide (CO) gas sensing has been fabricated. The structure integrates the catalytic properties of porous Pt as a thin catalytic layer, and the spillover effect onto WO3 film as a gas adsorptive oxide layer, with surface-sensitive MISFET. The operation characteristics of the device for the detection of CO gas are presented as a function of CO gas concentration. The drain current increased rapidly with time depending on the CO gas concentration. It was possible to detect 54 ppm of CO gas with a response time of less than 1 min at 75°C. A model was proposed to explain the operation. The sensing mechanism of the device is supported well by experimental data.

Superluminescence in InAsSb circular-ring-mode light-emitting diodes for CO gas detection

We report on the superluminescence of an InAsSb light-emitting diode, operating at 4.6 μm, suitable for carbon monoxide gas detection. The source is based on an optical whispering (or circulating) mode which is generated near the edges of the mesa and which is responsible for the superluminescence. A pulsed optical output power in excess of 2.2 mW at room temperature has been measured, making these emitters suitable for use in cost-effective instruments for the environmental monitoring of carbon monoxide at 4.6 μm.

Highly sensitive MISFET sensors with porous Pt–SnO 2 gate electrode for CO gas sensing applications

Novel devices based on a porous Pt–SnO 2 metal–insulator–semiconductor field-effect transistor (MISFET) for carbon monoxide (CO) gas sensing have been proposed. The structure integrates the catalytic properties of porous Pt, a thin catalytic layer, and the spillover effect onto SnO 2, a gas adsorptive oxide, with surface-sensitive MISFETs. The operation characteristics of the device for the detection of CO gas are presented as a function of CO gas concentration and operating temperature. The threshold voltage decreased rapidly with time when the device was exposed to CO gas depending on the operating temperature. It was possible to detect 54 ppm of CO gas with a response time of less than 1 min at 27°C. A model was proposed to explain the operation. The proposed sensing mechanism of the device is supported well by experimental data.

High power 4.6 µm light emitting diodes for CO detection

We report on a powerful 4.6 µm light emitting diode (LED), operating at room temperature, suitable for carbon monoxide gas detection. The source is based on a InAs0.55Sb0.15P0.30 /InAs0.89Sb0.11/InAs0.55Sb0.15P0.30 symmetrical double heterostructure with large band offsets. To improve performance, the InAs0.89Sb0.11 ternary material in the active region was purified by using rare-earth ion gettering during liquid phase epitaxial growth. A pulsed optical output power in excess of 1 mW at room temperature has been measured, making these emitters suitable for use in cost-effective instruments for the environmental monitoring of carbon monoxide. The Auger coefficient of the InAs0.89Sb0.11 active region material was evaluated by analysis of the temperature quenching of the LED output power measured at constant current. It was found to be C0 = 1.5 × 10-26 cm6 s-1 with an activation energy of E = 31 meV, which is in good agreement with previous findings in the literature.

Urban air pollution monitoring: laser-based procedure for the detection of carbon monoxide gas.

Urban air quality is of considerable importance in many cities throughout Europe and the USA. In particular, current EU legislation has driven an expansion of monitoring of more pollutants at more sites. At present in the UK, real time readings are now available for benzene, buta-1,3-diene and other volatile organic compounds, airborne fine dust (PM10), CO, 03, SO2, and NOX. Carbon monoxide is produced to varying degrees in all combustion processes but more than 90% is caused by emissions from petrol vehicle exhausts. The World Health Ogranisation guidelines for exposure to the gas is < 10 ppm for 8 h and 85 ppm for periods not exceeding 15 min. All the pollutants mentioned above are monitored by different detection techniques and it has been the authors' philosophy to develop instrumentation which can monitor all the different pollutants using a single detector. To this end, a multiphoton laser based procedure, using simple ionization chambers, has been developed to detect the different pollutants with different wavelengths. For CO, a 2 + 1 resonance enhanced multiphoton ionization (REMPI) scheme at 230 nm can be used with detection limits of about 1 ppm.