Carbon Dioxide Gas Sensor Research Articles

Electrical Conductivity and Sensitive Characteristics of Ag-Added BaTiO 3-CuO Mixed Oxide for CO 2 Gas Sensing

Carbon dioxide gas sensors based on BaTiO 3-CuO composite with different concentrations of Ag addition (1, 1.5 and 2 wt%) have been prepared by Stander ceramic method and sintered at 500 and 700°C for 5 h. Electrical conductivity and gas sensing properties of the prepared samples were investigated. Electrical conductivity measurement was used to characterize the obtained sintered sensor pellets. It was found that electrical conductivity and the sensitivity to CO 2 were improved with Ag addition and sintering. The correlation between Ag content at different sintering temperature and sensing characteristics towards CO 2 is discussed.

Carbon dioxide gas sensor derived from a 547-hole microstructured polymer optical fiber preform

In this Letter, we report a carbon dioxide gas sensor having 547 pieces of thin-film modified capillaries, which are derived from a microstructured polymer optical fiber preform. Compared with the conventional absorption-based sensor, the monolithic polymer capillary waveguide arrays have better sensitivity, because the huge sensing surfaces, composed of 547 pieces of dye-indicator-doped porous ethyl cellulose layers, interact directly with the gas molecules. As far as we know, a gas sensor based on multichannel capillary waveguide arrays has not been reported before.

A miniaturized carbon dioxide gas sensor based on infrared absorption

A miniaturized sensor for measuring carbon dioxide (CO 2) gas concentration is developed based on infrared absorption. A novel space-double-beam optical probe is designed, which consists of an infrared source, an air chamber, an infrared receiving device, and two sapphire windows. The air chamber is modified by incorporating a parabolic-shaped receiving-light cone to effectively improve the signal-to-noise ratio of the sensor. Four rectangle holes are arranged around the air chamber, and diffusive sampling is adopted to collect gas into the air chamber. The infrared source works between ON and OFF states. The interference of background light is eliminated by subtracting the measured value in the ON state from the OFF state. The measurement model of the sensor is established based on the Lambert–Beer law and the working principle of the sensor. The partial least squares method is applied to calibrate the measurement model. The sensor has a volume of 80 mm ( L)×78 mm ( W)×35 mm ( H), a weight of 200 g, a power consumption of 1.5 W, and a response time of 2.5 s. The experimental results show that the measurement accuracy of the sensor is 0.026% with a measurement range of 0–3% for CO 2 gas concentration.

CO2 Detection in Nanostructured CoSb2O6 Prepared by a Non-aqueous Colloidal Method

Gas sensor materials have played a relevant role in the detection and monitoring of pollutant and toxic gases. Carbon dioxide gas sensors are of particular relevance, because the global warming is mainly caused by emission of CO2 to the atmosphere. In that sense, the research of inorganic materials that can detect small amounts of this gas, have attracted the interest of many laboratories worldwide. On the other hand, it is well known that cobalt oxides have interesting catalytical and gas sensing properties. Therefore, in this work, the synthesis and CO2 gas sensing properties of nanostructured CoSb2O6 were explored.

Advances in Hydrogen, Carbon Dioxide, and Hydrocarbon Gas Sensor Technology Using GaN and ZnO-Based Devices

In this paper, we review our recent results in developing gas sensors for hydrogen using various device structures, including ZnO nanowires and GaN High Electron Mobility Transistors (HEMTs). ZnO nanowires are particularly interesting because they have a large surface area to volume ratio, which will improve sensitivity, and because they operate at low current levels, will have low power requirements in a sensor module. GaN-based devices offer the advantage of the HEMT structure, high temperature operation, and simple integration with existing fabrication technology and sensing systems. Improvements in sensitivity, recoverability, and reliability are presented. Also reported are demonstrations of detection of other gases, including CO2 and C2H4 using functionalized GaN HEMTs. This is critical for the development of lab-on-a-chip type systems and can provide a significant advance towards a market-ready sensor application.

Carbon nanotube-coated surface acoustic wave sensor for carbon dioxide sensing

Carbon dioxide gas sensors have been fabricated by self-assembling single-wall nanotube films on a surface acoustic wave delay line operating at 286 MHz. Polymer functionalization was used to enhance the sensitivity of the carbon nanotubes to carbon dioxide. A pulse radar-type interrogation system was used to monitor the conductivity of the nanotube film by measuring the attenuation of the surface acoustic wave due to film-conductivity changes. The conductivity of the film was found to decrease with carbon dioxide concentration. The effect of varying the sheet conductivity of the nanotube film was examined. Both analytical and experimental results show that controlling the conductivity of the CNT film within a specific range highly enhances the sensitivity to carbon dioxide. Experimental results show that the sensor tracks carbon dioxide concentration changes between 0% and 10%. The final sensor is sensitive, small and wirelessly interrogable, thus making it potentially useful for respiratory monitoring.

Application of chemically synthesized conducting polymer-polypyrrole as a carbon dioxide gas sensor

Abstract A polypyrrole (PPy) has been a subject of many studies because it exhibits relatively high electrical conductivity, good environmental stability and versatility of synthesis. Pyrrole (Py), the monomer of PPy, has been polymerized via chemically oxidative polymerization in the presence of an oxidant (FeCl 3 ). Two samples of PPy in the form of odorless black powder were prepared by taking the weight ratios of Py to FeCl 3 of 0.429 (low) and 4.290 (high). At both ratios, the concentration of oxidant was kept constant. PPy-I sensor using PPy powder of a Py/FeCl 3 weight ratio of 0.429 and PPy-II sensor using PPy powder of a Py/FeCl 3 weight ratio of 4.290 were prepared by screen-printing technique on a glass substrate. For electrical contacts, electrodes of conducting silver paint were printed on adjacent sides of the sensor film. PPy-I and PPy-II sensors were used for CO 2 gas sensing investigation. Sensitivity of sensors at different concentrations of CO 2 gas was measured by a voltage drop method at room temperature (303 K). At certain higher concentration of CO 2 gas, a saturation effect was observed with both sensors. The response and recovery time were found short in PPy-II sensor. XRD, SEM, FTIR and TG/DTA were used to analyze the PPy powder. In the π-orbital overlap of neighboring molecules of the PPy structure, the π-electrons delocalize along the entire chain, which provides semiconducting and conducting properties. CO 2 molecules formed weak bonds with π-electrons of PPy. This causes an increase of resistance of the material in the presence of CO 2 gas.

Synthesis, processing and characterization of nasicon solid electrolytes for CO 2 sensing applications

Precursor powders of nasicon solid electrolytes were synthesized by both the colloidal method (CM) and sol–gel method (SGM) and characterized. The phase evolution of the sensor materials and sintered microstructures was analyzed by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). Zirconia-free nasicon phase was formed at relatively low temperature from the sol–gel precursor powder. Sintered pellets produced from calcined sol–gel powder exhibited single-phase (homogenous) microstructure while a silica-rich glass phase was present at the grain boundaries in the pellets sintered from calcined colloidal powders. Disc-shaped sensor elements were fabricated via uniaxial pressing of the calcined powders and subsequently sintered at 1150 °C for the CM powders and 1200 °C for the SGM powders, respectively. Platinum electrode was applied to the sensor elements to produce potentiometric/electrochemical carbon dioxide gas sensors. The electrical response of the sensors to CO 2 was investigated at various operating temperatures and CO 2 concentrations. Sensors made from sol–gel derived materials displayed better sensing response to CO 2 gas at higher testing temperature as compared to sensors made from the colloidal powders.

A Smart Carbon Dioxide Gas Sensor Based on Solid Electrolytes

A smart carbon dioxide gas sensor was developed by the combination of Al3+ ion conductor [(Al0.2Zr0.8)20/19Nb(PO4)3] and O2− ion conductor [(8 mol%)Y2O3–ZrO2, YSZ] with the refractory Li2CO3-doped La2O2SO4 solid solution as the gas detecting auxiliary electrode. Here, the two layered solid electrolyte pellet was preliminarily fabricated by using the Al3+ ion and the O2− ion conductor powders and then the pellet was pressed and finally sintered. The sensor response was very quick within several seconds, with showing a long term stability over 100 days. The size of the present sensor tip is designed as small as 2 mm×3 mm×1 mm.

Rapid Activated Sludge Respiration Inhibition Test Performed by CO2 Producing Rate Using a Carbon Dioxide Sensor

The rapid activated sludge inhibition test (rapid ASRI) is one of the promising bioassays to evaluate environmental risk to the ecosystem caused by various pollutants. To improve the sensitivity and stability of ASRI, the CO2 producing rate (CPR) using a carbon dioxide gas sensor was employed to examine the respiration activity of activated sludge and to compare it to that by the conventional activated sludge respiration inhibition test using oxygen uptake rate (OUR) by EC50 values derived from dose response curve. Detection of respiratory activity based on CPR has higher reliability and sensitivity than that of OUR. It should be noted that the sensitivity of CPR for evaluating toxicity is sufficiently high in terms of derived dose response curve of some model environmental pollutants and the resultant EC50 values.

Carbon dioxide gas sensor based on trivalent cation and divalent oxide anion conducting solids with rare earth oxycarbonate based auxiliary electrode

A carbon dioxide gas sensor was fabricated by the combination of trivalent Al 3+ cation conducting (Al 0.2Zr 0.8) 20/19Nb(PO 4) 3 and O 2− anion conducting yttria stabilized zirconia (YSZ) with the two phase mixture of 0.5(0.8La 2O 2SO 4–0.2Li 2CO 3) + 0.5(Nd 0.47Ba 0.12Li 0.29) 2O 0.94CO 3 solid as the sensing auxiliary electrode. Since the present sensor shows a quantitative and reproducible response, which exactly obeys the Nernstian theoretical relationship at 500 °C, it is greatly expected that the present sensor would be one of the promising candidates for the practical CO 2 sensing devices applicable at intermediate temperature range around 500 °C.

Cross-sensitivity effects on a new carbon dioxide gas sensor based on solid bielectrolyte

A CO2 gas sensor using Nasicon interfaced Na-β-alumina solid electrolyte pellets with BaCO3–Na2CO3 (weight ratio 44:56) as the auxiliary phase has shown that the measured emf in CO2–air atmosphere is consistent with Nernstian law. In this paper further work has been carried out to investigate cross-sensitivity to humidity, O2, NO2 and SO2. Results have shown that humidity and oxygen have no significant influence on the sensor performance. At a concentration less than 100 ppm, NO2 does not affect the sensor signal. The CO2 sensor can resist any effects from SO2 only up to a concentration of 1.7 ppm. The sensing ability is greatly limited by Na2SO4 formation on the sensing auxiliary electrode and/or the surface of the electrolytes when SO2 gas is present with CO2.

Carbon Dioxide Gas Sensor Suitable for In Situ Monitoring

A type of carbon dioxide gas sensor, which is applicable in various elevated temperatures, has been successfully realized. The primary advantage of this sensor is the ability to apply refractory lanthanum oxysulfate-lithium carbonate solid solution as the detecting auxiliary electrode. The sensor element, including the auxiliary electrode is durable at elevated temperatures and the operating temperature can be varied (from 600 to 450°C). The sensor response becomes <2 min, showing enhanced characteristics compared to similar previously reported CO 2 gas sensors, and follows the Nernst theoretical relationship.

Planar Solid-State Potentiometric Carbon Dioxide Sensors Incorporating Polymer-Gel Electrolyte

A novel, planar, carbon dioxide gas sensor is described, comprising an iridium dioxide working electrode and silver/silver bromide reference electrode in contact with a solid, gas-permeable film of nonaqueous polymer-gel electrolyte. The working and reference electrodes are prepared in an interdigitated thick film format by screen printing sinterable inks onto a low temperature cofired ceramic (LTCC) substrate. After firing, a second printing operation is used to superimpose the polymer-gel electrolyte layer. The completed sensor is shown to exhibit a rapid and reversible near-Nerstian response to changing CO 2 partial pressure in a CO 2 /N 2 gas stream at ambient temperatures. The influence of temperature and relative humidity on sensor response is also described, as is the effect of SO x and NO x interferent gases.

Carbon Dioxide Gas Sensor with Li2TiSiO5 Solid Electrolyte and NiO-Li2CO3 as Sensing Electrode

Sodium ionic conductors such as NASICON (Na3Zr2Si2PO12) have been used as a solid electrolyte for electromotive force (EMF) CO2 sensor. However, it has been difficult to obtain a sufficiently high quality for this type of sensor. In general, when the EMF CO2 senser is left in an atmosphere having a high water concentration, such as a high-humidity atmosphere or condensation atmosphere, the EMF of the sensor greatly decreases. For the purpose of improving the humidity-resistance of the CO2 sensor, Li2TiSiO5 is employed as a solid electrolyte. It is composed of the following electrochemical cell: CO2-Air/Au-Li2CO3/Li2TiSiO5/Au/CO2-Air. The electrochemical reaction is in good agreement with the Nernst equation, and reacted electron is calculated as 2.04. The sensor fabricated with Li2TiSiO5 shows good linearity when it is exposed to an atmosphere of 90% relative humidity at 60°C. However, the EMF of the sensor decreases slightly as compared to its initial value. In order to obtain a high humidity-resistance for the sensor, NiO-Li2CO3 is used as the sensing electrode. In this case, the reaction constant, 2.04, is preserved and the EMF of the sensor does not change after exposure to high humidity atmosphere. Au-NiO-Li2CO3/Li2TiSiO5/Au can be considered to serve as a high humidity-resisting system for solid electrolyte CO2 sensors.

A novel carbon dioxide gas sensor based on solid bielectrolyte

A planar bielectrolyte type of CO 2 gas sensor based on Nasicon and Naβ-alumina solid electrolyte pellets with BaCO 3–Na 2CO 3 (weight ratio 44:56) as the auxiliary phase was fabricated. The sensor had good response to CO 2 over a wide range covering 6 ppm to 100%. The Nasicon/Pt interface was sensitive to oxygen, while auxiliary phase applied at low temperature on the sodium rich Naβ-alumina was stable against decomposition. In this mode, both electrodes are exposed to the same test gas eliminating the need for a separate reference compartment and O 2 concentration does not affect cell EMF. Interface between Nasicon and Naβ-alumina was studied by SEM and EDAX. Diffusion bonding between the two solid electrolytes results in phase change, which affects the electrical properties of electrolyte system.

A carbon dioxide gas sensor by combination of multivalent cation and anion conductors with a water-insoluble oxycarbonate-based auxiliary electrode.

A compact and inexpensive carbon dioxide gas sensor was successfully realized by the combination of a divalent magnesium ionic conductor of Mg0.7(Zr0.85Nb0.15)4P6O24 and a divalent oxide anion conducting ZrO2-Y2O3 solid electrolyte with the water-insoluble Li- and Ba-codoped Nd2O2CO3 solid solution as the auxiliary electrode. The sensor response was continuous and reproducible, and the present sensor also demonstrated a theoretical Nernst response in the atmosphere where water vapor, nitrogen oxides, ammonia, etc., coexist. The exposure of the present sensor to water dew and variation in oxygen concentration does not interfere with the sensor response, which will be a great advantage in applying the in situ practical CO2 detection in combustion exhaust gas atmospheres.

High Performance CO2 Gas Sensing with Combination of Multivalent Ion Conducting Solid Electrolytes with Water-Insoluble Auxiliary Electrode

Abstract A carbon dioxide gas sensor was fabricated by combination of multivalent cation and anion conducting solid electrolytes with a water-insoluble Li and Ba codoped Nd2O2CO3 solid solution as an auxiliary electrode. The present sensor shows such a high durability not only in the atmosphere of gas phase water vapor coexistence but also after the exposure to the liquid phase water dew, in addition to persisting the rapid, reproducible response with a high stability from the operation.

Carbon dioxide gas sensor with multivalent cation conducting solid electrolytes

A compact carbon dioxide gas sensor is fabricated by using the trivalent (M 3+: M=Al, Sc) cation conducting solid electrolyte with an oxide anion conducting stabilized zirconia and lithium carbonate as an auxiliary electrode. The response time which is defined as the time to attain a 90% response is less than several minutes. The sensor output variation with the CO 2 concentration shows a clear 1 to 1 relation and obeys the theoretical Nernst relation. The present sensor can detect the CO 2 gas concentration accurately even in the atmosphere where nitrogen oxides and water vapor coexist. The response is rapid, continuous, and also reproducible and the performance satisfies the need for practical applications.

Novel carbon dioxide gas sensor based on infrared absorption

The feasibility of sensing carbon dioxide with a IR single- beam optical structure is studied, and a novel carbon dioxide gas sensor based on IR absorption is achieved. Applying the Lambert-Beer law and some key techniques such as current stabilization for IR source, using a high-quality IR detector, and data compensation for the influences of ambience temperature and atmosphere total pressure, the sensor can measure carbon dioxide with high precision and efficiency. The math- ematical models for providing temperature and pressure compensation for the sensor are established. Moreover the solutions to the models are proposed. Both the models and the solutions to the models are verified via experiments. The sensor possesses the advantages of small volume, light weight, low power consumption, and high reliability. Therefore it can be used in many associated fields, such as environmental protection, processing control, chemical analysis, medical diagnosis, and space en- vironmental and control systems. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01708-6)