CO2 Sensor Research Articles

Vacuum Thermoforming for Packaging Flexible Electronics and Sensors in E-Textiles

Packaging of flexible electronics is essential for e-textile applications to reduce degradation of the performance caused by mechanical stress, environmental effects and to have increased durability. Conformal coatings for packaging have the advantage of reducing rigidity and can be seamlessly integrated into fabrics. Vacuum forming is a technique for packaging electronic devices with thermoplastic films of various thicknesses providing uniform coating. Polyurethane is a widely used thermoplastic material in e-textile and can be easily processed by vacuum forming for packaging. In this paper, a detailed explanation of the working of Formech 450DT vacuum former is discussed for packaging small electronic chip for e-textile application with thermoplastic polyurethane (TPU). Two types of flexible circuits were packaged; a Carbon monoxide gas sensor and a series of resistors on flexible PCB. The packaged CO flexible sensor and series resistors endured 5.3 times and 1.7 times respectively, more bending cycles than unpackaged flexible electronic filament samples. For the washing cycles, the packaged flexible strips with CO sensor and series resistors endured 1.5 times.

Zinc oxide thin films for a room temperature dual carbon dioxide and carbon monoxide sensor

Zinc oxide thin films for a room temperature dual carbon dioxide and carbon monoxide sensor

Research overview of urban carbon emission measurement and future prospect for GHG monitoring network

The majority of anthropogenic carbon dioxide emissions originate from cities, nonetheless, it is common to have inaccuracies and uncertainties in urban carbon emission measurement. Many countries have devoted much effort to improve the accuracy and consistency of urban emission data through improving measurement tools and inversion models. The paper presents achievements of research in the U.S and Europe, as well as discusses their technical impacts and obstacles. The paper provides an overwiew of the technical impacts and research gaps of CO2-USA network and the Carbosense CO2 sensor network in Switzerland, we discuss the spatial and temporal distribution characteristics of greenhouse gas concentrations and explain the principles of carbon emission inversion method. The CO2-USA network applies an interdisciplinary approach to estimate urban carbon emission to simulate the transport process of CO2 molecules in the atmosphere. The Carbosense network employs dense networks to observe the changing process of carbon dioxide emissions via enhancing data quality of low-cost carbon dioxide sensors. The purpose of this paper is to propose a novel framework of GHG observing network which combines carbon emission estimation method and real-time greenhouse gas monitoring network. The framework applies in-situ sites and mobile observations to build high-resolution emissions inventories and gain greenhouse gas concentration mappings in the urban regions. It provides governments with reliable measurement results for planning research directions for carbon emission management in China over the next few years.

Composition of the Gas-Air Mixture in the Containment and Suppression of Forest Fires with Promising Extinguishing Agents

This paper presents experimental research findings on the gas composition of pyrolysis and combustion products of typical forest fuels (leaves, needles, twigs, a mixture of these, and timber). These experiments were performed for the combustion and application of a fire extinguishing agent to a pyrolyzing material. Water, a bischofite solution, a bentonite slurry, and a foaming agent solution were utilized. Two gas analysis systems were used, as follows: an industrial one based on CO2, CO, H2, CH4, and O2 sensors and a scientific one (a gas analyzer with H2, CH4, H2S, SO2, CO, and CO2 sensors). Fires were extinguished by using two common techniques, as follows: continuous liquid supply and cycling spraying. The comparative efficiency of applying a group of fire extinguishing agents to forest fires was estimated, taking account of liquid consumption, suppression time, and environmental pollution. A method was proposed for calculating the relative efficiency factors of fire extinguishing agents when containing and suppressing forest fires, allowing for the consumed time, resources, and anthropogenic emissions.

Kinetics of Chemisorption on the Surface of Nanodispersed SnO2–PdOx and Selective Determination of CO and H2 in Air

In this work, the kinetics and mechanisms of the interaction of carbon monoxide and hydrogen with the surface of a nanosized SnO2-PdOx metal oxide material in air is studied. Non-stationary temperature regimes make it possible to better identify the individual characteristics of target gases and increase the selectivity of the analysis. Recently, chemometric methods (PCA, PLS, ANN, etc.) are often used to interpret multidimensional data obtained in non-stationary temperature regimes, but the analytical solution of kinetic equations can be no less effective. In this regard, we studied the kinetics of the interaction of carbon monoxide and hydrogen with atmospheric oxygen on the surface of SnO2-PdOx using semiconductor metal oxide sensors under conditions as close as possible to classical gas analysis. An analysis of the influence of catalytic surface temperature on the mechanisms of chemisorption processes allowed us to correctly interpret and mathematically describe the electrophysical characteristics of the sensor in the selective determination of carbon monoxide and hydrogen under nonstationary temperature conditions. The reaction mechanism is applied as well to the analysis of the operation scheme of the CO sensor TGS 2442 of Figaro Inc.

Modulation of CO adsorption on 4,12,2-graphyne by Fe atom doping and applied electric field

Adsorption characteristics of CO adsorbed on pristine 4,12,2-graphyne (4,12,2-G) and Fe-doped 4,12,2-graphyne (Fe-4,12,2-G) are studied by first-principles calculations. It is shown that CO is only physically adsorbed on pristine 4,12,2-G. Fe atoms can be doped into 4,12,2-G stably and lead to band gap opening. After doping, the interaction between Fe-4,12,2-G and CO is significantly enhanced and chemisorption occurs. The maximum adsorption energy reaches −1.606 eV. Meanwhile, the charge transfer between them increases from 0.009e to 0.196e. Moreover, the electric field can effectively regulate the adsorption ability of the Fe-4,12,2-G system, which is expected to achieve the capture and release of CO. Our study is helpful to promote applications of two-dimensional carbon materials in gas sensing and to provide new ideas for reversible CO sensor research.

Remote Operation of an Open-Path, Laser-Based Instrument for Atmospheric CO2 and CH4 Monitoring

The technical specifications and the evaluation of the remote operation of the open-path, tunable diode laser absorption spectroscopic (TDLAS) instrument are presented. The instrument is equipped with two low optical power diode lasers in the near-infrared spectral range for the atmospheric detection of carbon dioxide, methane, and water vapors (CO2, CH4, and H2O). Additionally, the instrument eliminates the requirement of retroreflectors since it detects the back reflection of the laser beam from any topographic target. The instrument was operated remotely by measuring background concentrations of CO2 and CH4 in the atmosphere from 24 November 2022 to 4 January 2023. The accuracy of CO2 and CH4 measurement retrievals on a 200 m laser path was estimated at 20 ppm (4.8%) and 60 ppb (3.1%), respectively. The CH4 accuracy is comparable, but the CO2 accuracy is noticeably lower than the accuracy achieved in local operation. The accuracy issues raised are studied and discussed in terms of the laser driver’s cooling performance.

Transition metal (X = Mn, Fe, Co, Ni, Cu, Zn)-doped graphene as gas sensor for CO2 and NO2 detection: a molecular modeling framework by DFT perspective.

In this research, CO2 and NO2 adsorption on doped nanographene (NG) sheets with transition metals (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, have been applied for scavenging of these toxic gases as the environmental pollutants. The values of changes of atomic charge density have illustrated a more significant charge transfer for Ni-doped C-NG through CO2 adsorption and a more remarkable charge transfer for Co-doped C-NG through NO2 adsorption. The data of NMR spectroscopy has depicted several fluctuations around the graph of Zn-doped on the nanographene surface. The thermodynamic results from IR spectroscopy have indicated that [Formula: see text] values are almost similar for doped metal transitions of Mn, Co, and Cu on the C-NG nanosheet, while [Formula: see text] has the largest gap of Gibbs free energy adsorption with dipole moment. The Langmuir adsorption model with a three-layered ONIOM using CAM-B3LYP functional accompanying LANL2DZ, EPR-III and 6-31 + G (d,p) basis sets due to Gaussian 16 revision C.01 program on the complexes of CO2 → (Fe, Ni, Zn) and NO2 → (Mn, Co, Cu) doped on the C-NG has been accomplished. Then, NMR and IR spectroscopy, nuclear quadrupole resonance, and natural bond orbital analysis have been accomplished for evaluating chemical shielding tensors, thermodynamic properties, electric potential, and occupancy fluctuation through bond orbitals, respectively. In addition, frontier orbitals of LUMO, HOMO, and also a series of chemical reactivity parameters have been calculated. Finally, time-dependent-DFT method due to UV-VIS spectrums has been accomplished to discern the low-lying excited states of CO2 and NO2 adsorption on the (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, doped C-NG sheet.

A Tunable Colorimetric Carbon Dioxide Sensor Based on Ion‐Exchanger‐ and Chromoionophore‐Doped Hydrogel

AbstractWe report here a colorimetric carbon dioxide (CO2) optode sensor with a polypropylene microporous membrane on top of a thin layer (30 μm) of polyurethane hydrogel. The diffusion of CO2 across the polypropylene membrane induced pH changes in the hydrogel containing a lipophilic indicator, a cation exchanger, and a cationic amine. The ratio of the indicator and the cation exchanger was successfully utilized to adjust the sensitivity of the CO2 response. Increasing the relative amount of the cation exchanger made the sensor much more sensitive to CO2 in the lower concentration range. Moreover, the carbarmic formation reaction between the primary amine and CO2 was investigated. The results indicated a very small contribution of carbarmic formation to the overall pH change. With a detection limit of 0.014 % for the CO2 partial pressure, the sensor was successful applied to monitor CO2 evolution during yeast catalyzed flour fermentation.

Research on the Seed Respiration CO2 Detection System Based on TDLAS Technology

The traditional detection method of CO2 concentration in seed respiration has defects such as low detection accuracy, low detection efficiency, and inability to monitor in real time. In order to solve these problems, we report a seed respiration CO2 detection system based on wavelength modulation spectroscopy (WMS) techniques in tunable diode laser absorption spectroscopy (TDLAS). This system uses a 2004 nm distributed feedback (DFB) laser as the light source, and a double-layer seed respiration device (about 1.5 L) is designed based on Herriott cell with an effective optical path of about 21 meters. Then, the second harmonic (2f) signal is extracted by the wavelength modulation method for CO2 concentration inversion. When the ambient temperature and pressure changes greatly, the corrected 2f signal is used for CO2 concentration inversion to improve the accuracy. A series of verification and comparison experiments have proved that the seed respiration CO2 detection system has the advantages of strong stability, high sampling frequency, and high detection accuracy. Finally, we used the developed system to measure the respiration intensity and respiration rate of 1 g corn seeds. The respiration intensity curves and respiration rate change details show that the seed respiration CO2 detection system is more suitable for a small amount of seeds than nondispersive infrared (NDIR) CO2 sensor and gas chromatography in real-time monitoring of the breathing process.

Metal-organic framework (MOF)/reduced graphene oxide (rGO) composite for high performance CO sensor

High performance gas sensors are urgently needed for the welfare of modern society. A challenge for sensors to detect analytes is its high response time. Herein, a carbon monoxide sensor has been fabricated using a NiO-based metal–organic framework(MOF)/reduced graphene oxide(rGO) composite. Synthesis of NiO-MOF and NiO-MOF/rGO were carried out by hydrothermal method. All the synthesized materials were multi parametrically tested by X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Raman spectroscopy, UV–visible spectroscopy, Atomic Force Microscopy (AFM), Field emission scanning electron microscopy (Fe-SEM), Current-Voltage characteristics (I-V), Brunauer-Emmett-Teller analysis (BET), etc. for their structural, spectroscopic, morphological, electrical, and surface properties respectively. The NiO-MOF/rGO based chemiresistive sensor fabricated on a glass substrate with a 100 µm gap through a shadow mask using an e-beam evaporator is stable up to 30 days and shows a selective response towards CO with excellent response and recovery, i.e. 30 s and 70 s respectively at 25 ppm.

Computer-aided determination of the effective diffusion coefficient of a gas diffusion layer for polymer electrolyte fuel cells

Accurate measurement of the gas diffusivity in a gas diffusion layer (GDL) for polymer electrolyte fuel cells (PEFCs) is extremely important in order to improve the performance of PEFCs and design fuel cell stacks. In the present study, in order to improve the accuracy in the determination of the gas diffusivity when uisng the simple and inexpensive method newly proposed by Yoshimune (2022), which uses an infrared absorption carbon dioxide sensor, three-dimensional (3D) simulations reproducing the experiments are performed. The results reveal that the gas transport resistance of the measurement apparatus is not small (approximately seven times higher than that of a commercial carbon paper (TGP-H060, Toray)), and the 3D simulation, which considers the resistance, reduces the error in the effective diffusion coefficient of the GDL by 25%. The effective diffusion coefficient for a new sample can be determined using the simulation results already obtained, when the apparatus is unchanged. In addition, a new one-dimensional (1D) model extended from the simple 1D model presented in Yoshimune (2022) is proposed. Since the extended model incorporates the gas transport resistance of the apparatus and dispenses with the generation of computational grids and the use of an expensive computer needed in conducting 3D simulations, this model enables us to obtain the accurate effective diffusion coefficient of a GDL with ease even when using a measurement apparatus with different sizes.

Defect engineering of nanostructured ZnSnO3 for conductometric room temperature CO2 sensors

Slow response/recovery kinetics and high limit of detection (LOD) are crucial challenges for practical room-temperature carbon dioxide (CO2) gas sensor platforms. Herein, visible light-excited ZnSnO3 three-dimensional nanostructures are utilized for highly sensitive and selective detection of CO2. The sensing performance reveals that fine-controlled oxygen vacancy (OV) and highly-active electron transition of defect-rich nanomaterials are obtained via modulating the hydrogen treatment duration, conducive to the prominently enhanced ppm-level CO2 response with low LOD (3.05 ppm), ultrafast response time (16.814 s) and improved stability (14.658 ± 2.339 @ 400 ppm for 14 days) among all the reported ternary metal oxide semiconductor (TMOS) -based gas sensors. The photophysical enhancement mechanism of analyte is discussed in detail by combining experimental and theoretical investigation through the effect of photoexcitation on both adsorbed CO2 molecules and sensing materials, the role of pre-adsorbed oxygen for regulating targeted gas interaction, the changes of electronic transition in the bandgap, the impact of in-plane OV and bridging OV on CO2 sensing, and the function of OV for modifying the coordination sites and geometry of metal cations at the surface. From a broader perspective, the fabricated sensor provides a remarkably facile and effective technique for rapid and repeatable CO2 monitoring.

The ro-vibrational ν2 mode spectrum of methane investigated by ultrabroadband coherent Raman spectroscopy.

We present the first experimental application of coherent Raman spectroscopy (CRS) on the ro-vibrational ν2 mode spectrum of methane (CH4). Ultrabroadband femtosecond/picosecond (fs/ps) CRS is performed in the molecular fingerprint region from 1100 to 2000cm-1, employing fs laser-induced filamentation as the supercontinuum generation mechanism to provide the ultrabroadband excitation pulses. We introduce a time-domain model of the CH4 ν2 CRS spectrum, including all five ro-vibrational branches allowed by the selection rules Δv = 1, ΔJ = 0, ±1, ±2; the model includes collisional linewidths, computed according to a modified exponential gap scaling law and validated experimentally. The use of ultrabroadband CRS for in situ monitoring of the CH4 chemistry is demonstrated in a laboratory CH4/air diffusion flame: CRS measurements in the fingerprint region, performed across the laminar flame front, allow the simultaneous detection of molecular oxygen (O2), carbon dioxide (CO2), and molecular hydrogen (H2), along with CH4. Fundamental physicochemical processes, such as H2 production via CH4 pyrolysis, are observed through the Raman spectra of these chemical species. In addition, we demonstrate ro-vibrational CH4 v2 CRS thermometry, and we validate it against CO2 CRS measurements. The present technique offers an interesting diagnostics approach to in situ measurement of CH4-rich environments, e.g., in plasma reactors for CH4 pyrolysis and H2 production.

A Flexible and Polymer‐Based Chemiresistive CO2 Gas Sensor at Room Temperature

AbstractCO2 sensing is important in many applications ranging from air‐quality monitoring to food packaging. In this study, an amine‐functionalized copolymer, poly(N‐[3‐(dimethylamino)propyl]‐methacrylamide‐co‐2‐N‐morpholinoethyl methacrylate) (p(D‐co‐M)) is synthesized, offering moderate basicity suitable for a wide CO2 detection range. Taking advantage of this characteristic of p(D‐co‐M), this polymer is used for designing a chemiresistive, low‐cost, flexible, and reversible CO2 sensor. The p(D‐co‐M)‐based sensors show a noticeable decrease in their direct current resistance and alternating current impedance upon exposure to a wide range of CO2 concentration (1–100%) at room temperature with a response and a recovery time of 6 and 14 min, respectively. Additionally, the p(D‐co‐M)‐based sensors demonstrate a favorable selectivity to CO2 in the presence of interfering gases including methanol, ethanol, toluene, and acetone. Surface potential measurements show an increase of +6.34 V upon exposure to humidity and CO2, indicating the protonation of the polymer's amine sites, facilitating the detection of CO2 in the wet environment. This sensor is efficient for detecting CO2 concentration released during fermentation of kimchi as a food model.

Study on the Application of Carbon Monoxide Sensors for the Prevention of Unwanted Alarms

This study analyzed the applicability of CO sensors through UL 268 unwanted alarm tests and real-scale unwanted alarm verification tests tailored to the domestic format. A comprehensive literature review indicated that the UL 268 fire test and the cooking nuisance test results revealed the fire-detection concentration and unwanted alarm concentration of CO and suggested that a real fire can be detected if the concentration of CO is above 17 ppm. Accordingly, during the pork belly and mackerel cooking events, which triggers frequent unwanted alarms in domestic multi-unit dwellings, the UL 268 domestic-type and real-scale unwanted alarm tests were conducted. The test results proved that the smoke detector sufficiently generated a fire alarm owing to the cooking by-products, as it measured up to 21.0 ppm, which is the maximum smoke concentration of the analog smoke detector under all conditions. However, as it was confirmed that the CO concentration was not more than 4.9 ppm in all experiments, it was confirmed that it was suitable for the fire and unwanted alarm-detection concentrations suggested in previous studies. Therefore, in the case of fire detectors, to prevent unwanted alarms in the future, it is important to distinguish between fire alarms and unwanted alarms further through crosschecking according to the applications of smoke and CO sensors.

Soil CO2 in organic and no-till agroecosystems

Increased carbon dioxide (CO2) concentrations in soil profiles could increase carbon sequestration via improved residence times of soil organic carbon (SOC), greater nutrient availability and plant growth, and via other pathways, but the effect of agricultural management techniques on soil CO2 is poorly understood. We used nondispersive infrared (NDIR) CO2 sensors to measure gas-phase CO2 concentrations in 1.50 m soil profiles in paired no-till (NT) and organic (ORG) agricultural systems in the Palouse region of eastern Washington State, USA, to investigate the effect of management on soil CO2. CO2 concentrations were significantly greater in ORG than in NT. The CO2 efflux into the atmosphere estimated using Fick's first law was generally greater in ORG due to both greater diffusivity and stronger concentration gradients observed in ORG. Results demonstrate that organic agriculture may facilitate greater soil CO2 concentrations and production rates. Further research is needed to quantify and understand the role of increased CO2 in soil carbon cycling in agroecosystems.

The Berlin-Buch respiration chamber for energy expenditure measurements

PurposeWe present a methodological overview of a respiration chamber at the Experimental and Clinical Research Center in Berlin, Germany. Since 2010, we investigated 750 healthy subjects and patients with various diseases. We routinely measure resting energy expenditure (REE), dietary-induced thermogenesis, and activity energy expenditure.MethodsThe chamber is a pull calorimeter with a total volume of 11,000 L. The majority of measurements is done with a flow rate of 120 L/min, yielding a favorable time constant of 1.53 h. The gas analysis system consists of two paramagnetic O2 sensors and two infrared CO2 sensors, one for incoming and one for outgoing air samples. O2 and CO2 sensors are calibrated simultaneously before each measurement with a 6 min calibration routine. To verify the accuracy of the whole the calorimetric system, it is validated every 2 weeks by 2 h acetone burning tests.ResultsValidation factors (calculated/measured) of 20 representative 2 h acetone burning tests were 1.03 ± 0.03 for dot{V}{text{O}}_{2}, 1.02 ± 0.02 for dot{V}{text{CO}}_{{2}}, 0.99 ± 0.02 for RER, and 1.03 ± 0.03 for EE. Four repeated 60 min REE measurements of a healthy woman showed variabilities of 231.9 ± 4.8 ml/min for dot{V}{text{O}}_{2} (CV 2.1%), 166.0 ± 6.3 ml/min for dot{V}{text{CO}}_{{2}} (CV 3.8%), 0.73 ± 0.03 for RER (CV 4.6%), and 4.55 ± 0.07 kJ/min for EE (CV 1.6%).ConclusionsThe data presented show that our respiration chamber produces precise and valid EE measurements with an exceptionally fast responsiveness.Graphical

Integrated Probe System for Measuring Soil Carbon Dioxide Concentrations.

This article outlines the design and implementation of an internet-of-things (IoT) platform for the monitoring of soil carbon dioxide (CO2) concentrations. As atmospheric CO2 continues to rise, accurate accounting of major carbon sources, such as soil, is essential to inform land management and government policy. Thus, a batch of IoT-connected CO2 sensor probes were developed for soil measurement. These sensors were designed to capture spatial distribution of CO2 concentrations across a site and communicate to a central gateway using LoRa. CO2 concentration and other environmental parameters, including temperature, humidity and volatile organic compound concentration, were logged locally and communicated to the user through a mobile (GSM) connection to a hosted website. Following three field deployments in summer and autumn, we observed clear depth and diurnal variation of soil CO2 concentration within woodland systems. We determined that the unit had the capacity to log data continuously for a maximum of 14 days. These low-cost systems have great potential for better accounting of soil CO2 sources over temporal and spatial gradients and possibly flux estimations. Future testing will focus on divergent landscapes and soil conditions.

Environmental Applications of Zeolites: Hydrophobic Sn-BEA as a Selective Gas Sensor for Exhaust Fumes

Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with tin (Sn-BEA) and dealuminated β (DeAl-BEA) zeolites. The zeolite samples have been extensively investigated by IR, UV-VIS and NMR spectroscopy, XRD, TGA, and N2 adsorption-desorption. The prepared Sn-BEA sample is characterised by the submicron particle size, an almost defect-free structure, and high hydrophobicity. Sensors containing selective microporous layers based on Sn-BEA and DeAl-BEA zeolites have been prepared and extensively tested. Both the Sn-BEA and DeAl-BEA zeolites have been deposited in thin films and evaluated as gas sensors for CO, CO2, NO, and NO2 in the presence of water vapour at room temperature. The Sn-BEA zeolite-based sensor showed high selectivity towards NO2, while the DeAl-BEA is selective towards CO2 and NO2.