Detection Of CO Research Articles

ZnO based ultrasensitive CO chemiresistive gas sensor

The detection of hazardous gases in the atmosphere is a topic of interest for public security, environmental pollution and industrial emission. In recent years, semiconductor-based gas sensor attracted wide attention in all over the world. Among various hazardous gases, detection of CO at low temperature with fast response and recovery time is still a challenge. In this work, we have adopted single step synthesis of zinc oxide (ZnO) nanoroads for the fabrication of CO gas sensor. This sensor is found to have ∼8% sensitivity with fast response time of the order of 10 s at 50 °C. Also, selectivity of sensor has been investigated for different gases and observed that ZnO is more active for CO gas at 50 °C. The sensitivity of ZnO based sensor is explained in terms of interaction of CO molecules with adsorbed oxygen vacancies in ZnO which promote better pathway to the charge carrier. The sensing material is characterized by x-ray diffraction (XRD), UV–vis spectroscopy and scanning electron microscopy (SEM). To the best of our knowledge, the detection of 15 ppm CO at 50 ºC with good sensitivity is reported first time.

Gas-Sensitive Performance Study of Metal (Au, Pd, Pt)/ZnO Heterojunction Gas Sensors for Dissolved Gases in Transformer Oil.

An oil-immersed transformer is a critical electrical device for power delivery. Online monitoring of transformer operation is the key to ensuring the regular operation of power systems. This paper proposes Au/ZnO, Pd/ZnO, and Pt/ZnO heterojunctions as new gas-sensitive materials and investigates their gas-sensitive performance to dissolved gases (C2H4, CO, and H2) in transformer oil. Upon theoretical density functional theory (DFT) calculations, the analysis of the total density of states (TDOS), partial density of states (PDOS), molecular orbital theory, and charge deformation density reveals that Au, Pd, and Pt form heterojunctions with ZnO, which enhance the electrical conductivity of the system. Meanwhile, intrinsic ZnO is unsuitable for gas detection and adsorption, while the Au/ZnO heterojunction suits C2H4 detection. In contrast, the Pd/ZnO heterojunction is suitable for H2 detection, and the Pt/ZnO heterojunction is suitable for C2H4 and CO detection. The electrical conductivity of the adsorption models is changed to varying degrees after gas adsorption. The different change rate electrical conductivity just serves as a theoretical foundation for determining the type and concentration of dissolved gases in transformer oil. The research results act as a theoretical foundation for constructing gas sensors with a ZnO-based material.

Nanoscale MOF-74-based QCM gas sensor for CO2 detection at room temperature

CO2 is one of the main components of air, accounting for 0.03–0.04% (300–400 ppm) of the total volume of the atmosphere. CO2 gas is chemically stable and is an inert gas, which makes the means of detecting it extremely limited. To overcome these challenges, in this paper, nanoscale M-MOF-74 (M=Mg, Ni, Zn, Co) was synthesized by a facile method in a two-hour reaction at room temperature, which combined with a quartz crystal microbalance (QCM) sensor-enabled the detection of CO2 gas at room temperature. The CO2 sensing performance of M-MOF-74 coated QCM sensors at room temperature was systematically investigated. The experimental results showed that the Mg-MOF-74 sensor responded to 2000 ppm CO2 at room temperature with 66, and at the same time, had good linearity, high response/recovery (75 s/50 s), and good selectivity to CO2. The electrical parameters and quality factor of the QCM were further verified by impedance analysis. In addition, the potential CO2 adsorption mechanism may be mainly related to the open metal sites in the Mg-MOF-74 material and the synergistic effect of Mg-O bonds. This work confirms that the M-MOF-74 material provides a new avenue for QCM CO2 sensing, and the sensor is expected to be a potential candidate for CO2 detection.

First-Principles Predictions of MoS2-WS2 In-Plane Heterostructures for Sensing Dissolved Gas Species in Oil-Immersed Transformers.

This work from first-principles insight uses a MoS2-WS2 in-plane heterostructure as a potential sensing material for detection of CO and C2H2, two typical dissolved gases in oil-immersed transformers, in order to evaluate the operation status. The adsorption performance of the MoS2-WS2 heterostructure upon two gas species is assessed via three adsorption sites and compared with isolated MoS2 and WS2. Results indicate that MoS2-WS2 performs with a much stronger binding force and charge-transfer for adsorptions of CO and C2H2 in comparison to the isolated counterpart, which gives rise to more obvious deformation in the electronic property of MoS2-WS2 as well as a much larger resistance-based sensing response. The recovery time of MoS2-WS2 for desorption of CO and C2H2 molecules is also appropriate to allow the reusability of such a sensor. The findings in this work uncover the admirable sensing potential of transition metal dichalcogenides (TMDs)-based heterostructures upon oil dissolved gases, which opens up a new way to explore novel 2D nanomaterials as resistive gas sensors for dissolved gas analysis in electrical oil-immersed transformers.

Doppler tomography as a tool for characterising exoplanet atmospheres II: an analysis of HD 179949 b

Abstract High-resolution Doppler spectroscopy provides an avenue to study the atmosphere of both transiting and non-transiting planets. This powerful method has also yielded some of the most robust atmospheric detections to date. Currently, high-resolution Doppler spectroscopy detects atmospheric signals by cross-correlating observed data with a model atmospheric spectrum. This technique has been successful in detecting various molecules such as H2O, CO, HCN and TiO, as well as several atomic species. Here we present an alternative method of performing high-resolution Doppler spectroscopy, using a technique known as Doppler tomography. We present an analysis of HD 179949 b using Doppler tomography and provide Doppler tomograms confirming previous detections of CO at 2.3 μm and H2O at both 2.3 μm and 3.5 μmwithin the atmosphere of HD 179949 b, showing significantly lower background noise levels when compared to cross-correlation methods applied to the same data. We also present a novel detection of H2O at 2.1 μm as well as a tentative detection of CO on the night side of the planet at 2.3 μm. This represents the first observational evidence for molecular absorption in the night-side emission spectrum of an exoplanet using Doppler spectroscopy.

Sol-Gel Multilayered Niobium (Vanadium)-Doped TiO2 for CO Sensing and Photocatalytic Degradation of Methylene Blue.

Multilayered TiO2 films doped either with Niobium or Vanadium (1.2 at. %) were deposited by the sol-gel dip coating method on c-Si and glass substrates. The films on glass substrates were tested for CO sensing and photocatalytic degradation of methylene blue. X-ray diffraction data analysis showed that all the TiO2:Nb(V) films were nanocrystalline in the anatase phase, with a uniform and compact microstructure and a homogeneous superficial structure of small grains with diameters in the range of 13-19 nm. For the electrical characterization, the TiO2:Nb(V) films were incorporated in Metal-Insulator-Semiconductor (MIS) structures. The specific resistivity is of the order of 104 Ωcm and its value decreases with increasing the electrical field, which testifies to the injection of electrons into these layers. From the analysis of the current-voltage curves taken at different temperature- and frequency-dependent capacitance-voltage and conductance-voltage characteristics, the density and parameters of deep levels in these TiO2 films are evaluated and the electron charge transport mechanism is established. It was shown that the current in these TiO2:Nb(V)-Si MIS structures is mainly carried out by inter-trap tunneling via deep levels energetically distributed in the TiO2 bandgap. Testing these sol-gel TiO2:Nb(V) layers for gas sensing and photocatalytic capabilities proved that they could serve such purposes. In particular, the results of the V-doped sol-gel TiO2 film confirm its CO detection capability, which is rarely reported in the literature. For the photodegradation of methylene blue, the Nb-doped TiO2 samples were superior, with nearly double the photocatalytic efficiency of undoped TiO2.

Synthesis of 3-D co(II)-oxonate colorimetric probe for selective detection of isopropanol, Co2+, and MnO4 –

A coordination polymer (CP) based on Co(II), {[Co(Ox)(H2O)3] · 2H2O} n (KA@CP2_ARS), has been synthesized using 1,3,5-tris[(1H-imidazol-1-yl)methyl]benzene (Timb) and potassium oxonate (OxK) at room temperature which was examined by single-crystal X-ray diffraction. KA@CP2_ARS contains a one-dimensional (1-D) helical chain that is extended through hydrogen-bonding interactions to form two-dimensional (2-D) and three-dimensional (3-D) supramolecular networks. KA@CP2_ARS demonstrates highly selective luminescent performance for IPA, Co2+, MnO4 –, and uric acid with detection limits of 0.214, 0.16, 0.076, and 0.65 ppm, respectively, among the screened analytes. KA@CP2_ARS displays strong photocatalytic activities for degrading 88.6% of methyl violet dye under ultraviolet irradiation.

All-fiber-coupled mid-infrared quartz-enhanced photoacoustic sensors

Infrared laser-based gas sensors are mature to take the leap from laboratory prototype to outdoor operation. Considering the demand of high robustness and compactness, the reliability of the optical alignment in a sensor is the top priority. This paper proposes a solution designing an optical system embedded within a sealed metallic cylinder containing an aspheric micro-lens to couple a single-mode interband cascade laser with an indium fluoride glass fiber. The fiber output is plug & play connected to an acoustic detection module of a quartz-enhanced photoacoustic sensor (QEPAS) equipped with a fiber port, avoiding the use of any free-space optics, from the source to the detection module. To demonstrate the operability, three all-fiber-coupled QEPAS sensors were realized for detection of CH4, CO2 and NO reaching sub-ppm ultimate detection limits with a signal integration time of 100 ms.

Chemiresistive Sensor for Enhanced CO2 Gas Monitoring.

Carbon dioxide (CO2) gas sensing and monitoring have gained prominence for applications such as smart food packaging, environmental monitoring of greenhouse gases, and medical diagnostic tests. Although CO2 sensors based on metal oxide semiconductors are readily available, they often suffer from limitations such as high operating temperatures (>250 °C), limited response at elevated humidity levels (>60% RH), bulkiness, and limited selectivity. In this study, we designed a chemiresistive sensor for CO2 detection to overcome these problems. The sensing material of this sensor consists of a CO2 switchable polymer based on N-3-(dimethylamino)propyl methacrylamide (DMAPMAm) and methoxyethyl methacrylate (MEMA) [P(D-co-M)], and diethylamine. The designed sensor has a detection range for CO2 between 103 and 106 ppm even at high humidity levels (>80% RH), and it is capable of differentiating ammonia at low concentrations (0.1-5 ppm) from CO2. The addition of diethylamine improved sensor performance such as selectivity, response/recovery time, and long-term stability. These data demonstrate the potential of using this sensor for the detection of food spoilage.

Xanthan gum-capped Chromia Nanoparticles (XG-CrNPs): A promising nanoprobe for the detection of heavy metal ions

The present study reports on the selective and sensitive detection of metals using xanthan gum-capped chromia nanoparticles (XG-CrNPs). The nanoparticles were synthesized by the chemical reduction method using sodium borohydride and xanthan gum as the reducing and capping agents, respectively. The synthesis of XG-CrNPs was confirmed by the appearance of the two absorption peaks at 272 nm and 371 nm in the UV–visible region. The nanoparticles have been extensively characterized by FTIR, TEM-EDX, XRD, and TGA analyses. The well-dispersed XG-CrNPs exhibited a quasi-spherical structure with an average particle size of 3 nm. A significantly low amount (2 μg/L) of XG-CrNPs was used for selective and sensitive detection of heavy metal ions. It showed excellent metal detecting properties by quenching its band gap signal which was extraordinarily conspicuous for Co(II), Hg(II), and Cd(II) in comparison to other metal ions like Ag(I), Ba(II), Mg(II), Mn(II), Ni(II), and Zn(II). The limit of detection of Co(II), Cd(II), and Hg(II) with this nanoprobe was found to be 2.167 μM, 1.065 μM, and 0.601 μM respectively. The nanoparticles manifested higher shelf-life and can be reused up to three consecutive cycles where most of its activity was conserved even after being used. Thus, it may find use in metal sensor devices for the detection of hazardous metals.

Near-infrared dual-gas sensor for simultaneous detection of CO and CH4 using a double spot-ring plane-concave multipass cell and a digital laser frequency stabilization system

A novel double spot-ring plane-concave multipass cell (DSPC-MPC) gas sensor was proposed for simultaneous detection of trace gases, which has lower cost and higher mirror utilization than the traditional multipass cell with 129 m, 107 m, 85 m, 63 m and 40 m effective optical path lengths adjustable. The performance of the DSPC-MPC gas sensor was evaluated by measuring CO and CH4 using two narrow linewidth distributed feedback lasers with center wavelengths of 1567 nm and 1653 nm, respectively. An adjustable digital PID laser frequency stabilization system based on LabVIEW platform was developed to continuously stabilize the laser frequency within ∼±30.3 MHz. The Allan deviation results showed that the minimum detection limits for CO and CH4 were 0.07 ppmv and 0.008 ppmv at integration times of 711 s and 245 s, respectively. The proposed concept of DSPC-MPC provides more ideas for the realization of gas detection under different absorption path lengths and the development of multi-component gas sensing systems.

Application of ZIF-8/ZIF-67 Multilayer Films for NO2 and CO Detection

Application of ZIF-8/ZIF-67 Multilayer Films for NO2 and CO Detection

Controlling the structure and composition of SnO2-based thin film with reactive sputtering to improve the sensitivity of semiconductor CO2 sensor

The sensitivity of SnO2 thin film-based CO2 gas sensors was enhanced by controlling the surface structure employing reactive sputtering during the deposition process to carefully adjust the oxygen partial pressure to modify the surface structure of the SnO2 films. This process increased the sensitivity, primarily due to larger surface area and improved gas adsorption capabilities. Furthermore, the effect of heterojunctions between p-type SnO and n-type SnO2 on the sensitivity was investigated using a model diagram. Both theoretical analysis and experimental data consistently demonstrated that the number of heterojunction interfaces contributes significantly to the sensitivity of SnO-SnO2 heterojunction gas sensors. These findings highlight the effectiveness of controlling the surface structure and composition ratio of thin films through reactive sputtering to enhance sensitivity. This study offers valuable insights for optimizing SnO2 thin-film-based gas sensors for CO2 detection.

Continuous Detection of Cobalt Ions and Pyrophosphates by NAC-CdTe Quantum Dots Fluorescence Probes.

In this work, a simple and sensitive N-acetyl-L-cysteine (NAC)-covered CdTe quantum dots (NAC-CdTe QDs) fluorescence probe for continuous detection of Co2+ and pyrophosphate ions (PPi, P2O74-) was synthesized. The fluorescence of the quantum dots was significantly quenched by Co2+ through the coordination of Co2+ and the carboxyl groups on the NAC-CdTe quantum dots. Interestingly, the combination of NAC-CdTe quantum dots with Co2+ yields a new fluorescence probe of Co2+-modified NAC-CdTe QDs (Co2+@NAC-CdTe). The addition of PPi restored the fluorescence due to the competition between PPi and carboxyl groups with Co2+ causing Co2+ to detach from the surface of Co2+@NAC-CdTe quantum dots. Thus, a sensitive and reversible detection of Co2+ and PPi had been successfully established. The Co2+@NAC-CdTe quantum dots fluorescence probe exhibits excellent selectivity and high sensitivity toward PPi detection with low detection limit of 0.28μM. In addition, the novel fluorescence probe was successfully applied to detect the concentration of PPi in environmental water samples and in-vitro cells imaging.

In Situ All-Fiber Remote Gas Sensing Strategy Based on Anti-Resonant Hollow-Core Fiber and Middle-Hole Eccentric-Core Fiber

Laser absorption spectroscopy for gas sensing basically employs an air pump located at the gas cell probe to draw in ambient gases, and the on-site gas sample is subsequently delivered for laboratory non-real-time analysis. In this study, an in situ all-fiber remote gas sensing strategy is proposed. The anti-resonant hollow-core fiber (AR-HCF) is used as the sensing fiber, and a 20 m middle-hole eccentric-core fiber (MH-ECF) is used as the conducting fiber. The remote ambient gases can be inhaled into the AR-HCF as a result of the negative pressure transmitted through the MH-ECF when pumping gas at the interface of the MH-ECF. Since the real-time monitoring of greenhouse gas emissions in industrial processes holds immense significance in addressing global climate change, the detection of CO2 is achieved with the TDLAS-WMS method, and the gas sensing performance of an all-fiber remote gas sensing structure (RGS) is experimentally validated. The response time t90 under the pumping condition is about 456 s, which is about 30 times faster than that of free diffusion. Allan deviation results for more than one hour of continuous monitoring indicate that the lowest detection limit for the all-fiber RGS is 0.0373% when the integration time is 184 s. The all-fiber remote gas sensing strategy also possesses the benefits of being applicable to multiplex, hazardous gas environment passive monitoring.

Experimental Characterisation of BGBC OTFT for Indoor CO<sub>2</sub> Gas Sensing

Global warming is a concern nowadays due to excessive release of harmful gasses to the environment, leading to greenhouse effect phenomena worldwide. Based on the data provided by global pollution agencies, the release of greenhouse gasses to the atmosphere is the main cause of pollution and the increase in atmospheric temperature due to warming. Greenhouse gasses (GHGs) contents released to the environment is worrying, with carbon dioxide (CO2) is reported at the highest concentration compared to other gasses. There are many studies conducted to develop and evaluate the performance of harmful gas sensors incorporating inorganic and organic semiconductive materials. Organic semiconductors (OSCs) are environmentally friendly materials, relatively cheaper technology, and comprised of a wide range of materials with good carrier mobility. Therefore, in this work, Organic Thin Film Transistor (OTFT) is developed for gas sensor application. As global warming is becoming more serious, this solution is instead a sustainable solution to the environment, as organic molecules which are held together via Van der Waals bond are easily processed via low-temperature deposition and solution processing as compared to more complicated processes involved in conventional inorganic counterpart. In addition, the developed sensor is generally robust due to the ability to withstand high humidity conditions and can be fabricated on flexible substrates. In this work, suitable materials are identified in basic OTFT construction, which are the electrodes, dielectric and substrate. The scope is mainly focusing on the development of bottom gate OTFT construction, incorporating p-type active material which are Trisisopropylsilylethynyl Pentacene (TIPS Pentacene), Aluminium (Al) as drain and source electrodes, PEDOT: PSS as gate electrode and Polyvinyl alcohol (PVA) as gate dielectric. The materials in bottom gate bottom contact (BGBC) configuration, fabricated via screen printing technique is experimentally tested towards CO2 detection. CO2 is initially detected at 1618 ppm with contact resistance of 15 kΩ, and at 10 ml/minute flow rate, the developed configuration is demonstrated able to achieve sensitivity of 2.069 Ω/ppm. In conclusion, the studied BGBC OTFT has demonstrated suitability and applicability in CO2 gas sensing for sustainable environmental condition monitoring, that could lead to safer environment for the living things on earth. With the proposed dimensions, in the future it is possible to proceed with this work to be fabricated by using more advanced techniques such as photolithography and many others.

The black-legged tick Ixodes scapularis detects CO2 without the Haller's organ.

Both male and female ticks have a strong innate drive to find and blood-feed on hosts. Carbon dioxide (CO2) is considered a critical behavioral activator and attractant for ticks and an essential sensory cue to find hosts. Yet, how CO2 activates and promotes host seeking in ticks is poorly understood. CO2 responses were studied in the black-legged tick Ixodes scapularis, the primary vector for Lyme disease in North America. Adult males and females were exposed to 1%, 2%, 4% or 8% CO2, and changes in walking behavior and foreleg movement were analyzed. CO2 is a potent stimulant for adult I. scapularis, even at lower concentrations (1%). Behavioral reactions depended on the animal's state: walking ticks increased their walking speed, while stationary ticks started to wave their forelegs and began to quest - both behaviors resembling aspects of host seeking. Only in sporadic cases did stationary animals start to walk when exposed to CO2, supporting the hypothesis that CO2 acts as an activator rather than an attractant. Furthermore, I. scapularis did not show a clear concentration preference and was not tuned more robustly to breath-like CO2 concentrations (∼4%) than to the other concentrations tested. Moreover, convincing evidence is provided showing that the foreleg Haller's organ is not necessary for CO2 detection. Even with a disabled or amputated Haller's organ, I. scapularis responded robustly to CO2, signifying that there must be CO2-sensitive structures important for tick host seeking that have not yet been identified.

Ratiometric Fluorescence and Chromogenic Probe for Trace Detection of Selected Transition Metals.

The design and development of a fluorescence sensor aimed at detecting and quantifying trace amounts of toxic transition metal ions within environmental, biological, and aquatic samples has garnered significant attention from diagnostic and testing laboratories, driven by the imperative to mitigate the health risks associated with these contaminants. In this context, we present the utilization of a heterocyclic symmetrical Schiff Base derivative for the purpose of fluorogenic and chromogenic detection of Co2+, Cu2+ and Hg2+ ions. The characterization of the ligand involved a comprehensive array of techniques, including physical assessments, optical analyses, NMR, FT-IR, and mass spectrometric examinations. The mechanism of ligand-metal complexation was elucidated through the utilization of photophysical parameters and FT-IR spectroscopic analysis, both before and after the interaction between the ligand and the metal salt solution. The pronounced alterations observed in absorption and fluorescence spectra, along with the distinctive chromogenic changes, following treatment with Co2+, Cu2+ and Hg2+, affirm the successful formation of complexes between the ligands and the treated metal ions. Notably, the receptor's complexation response exhibited selectivity towards Co(II), Cu(II), and Hg(II), with no observed chromogenic changes, spectral variations, or band shifts for the various tested metal ions, including Na+, Ag+, Ni2+, Mn2+, Pd2+, Pb2+, Cd2+, Zn2+, Sn2+, Fe2+, Fe3+, Cr3+ and Al3+. This absence of interaction between these metal ions and the ligand could be attributed to their compact or inadequately conducive conduction bands for complexation with the ligand's structural composition. To quantify the sensor's efficacy, fluorescence titration spectra were employed to determine the detection limits for Co2+, Cu2+ and Hg2+, yielding values of 2.92 × 10-8, 8.91 × 10-8, and 4.39 × 10-3 M, respectively. The Benesi-Hildebrand plots provided association constant values for the ligand-cobalt, ligand-copper, and ligand-mercury complexes as 0.74, 2.52, and 13.89 M-1, respectively.

N, S co-doped carbon dots for fluorescent and colorimetric dual-mode detection of Co(II) in actual water

This study focuses on the synthesis of nitrogen and sulfur co-doped carbon dots (N, S-CDs) using a hydrothermal method, and its application as a fluorescence and colorimetric dual-mode probe for simple and rapid detection of Co(II). When Co(II) reacts with N, S-CDs, metallic bonds are formed, leading to a static quenching effect (SQE). The electrostatic interaction between positive-charged cobalt complexes and negative-charged N, S-CDs induces the aggregation of metal complexes, increasing the particle size from 5.44 nm to 258.72 nm and resulting in a noticeable visual color change ultimately. N, S-CDs exhibited excellent potential for application in actual water samples, with the low detection limit (LOD) of 2.64 µM and 1.57 µM via fluorescence and colorimetric methods, respectively, and the recovery rate ranged from 94 % to 103 %. As far as we consider, the cross-referenced dual-mode platform proposed here may be an attractive strategy for the construction of high-performance sensors available for metal ion detection in actual aquatic environments.

Development and Testing of NDIR-Based Rapid Greenhouse Gas Detection Device for Dairy Farms

As greenhouse gas emissions from dairy farms are on the rise, effective monitoring of these emissions has emerged as a crucial tool for assessing their environmental impacts and promoting sustainable development. Most of the existing studies on GHGs from dairy farms involve stationary detections with long response times and high costs. In this study, a greenhouse gas detection system was constructed based on NDIR technology using a single broadband light source and a four-channel thermopile detector for the detection of CH4, N2O, and CO2; the detection range of CH4 was 0~100 ppm; that of N2O was 0~500 ppm; and that of CO2 was 0~20%. After the concentration calibration, the cross-interference between the gas measurement channels was studied, and the least-squares method was used to correct the interference between the three gases. The experimental results showed that the full-range deviation of the detection device was lower than 0.81%, the repeatability was lower than 0.39%, the stability was lower than 0.61%, and the response time was lower than 10 s. This study also carried out on-site testing in Luoyang Shengsheng Ranch (Luoyang, China), and the results show that the error between this device and the PTM600 portable gas analyzer is within 9.78%, and the dynamic response time of this device is within 16 s, at which point the content of greenhouse gases in dairy farms can be measured quickly and accurately. The objective of this study is to enhance the precision and effectiveness of greenhouse gas (GHG) emissions monitoring from dairy farms, thereby contributing to environmental protection and sustainable development goals. By achieving this, we aim to facilitate societal progress towards a greener and low-carbon future.