Detection Of CO Research Articles

Synchronous detection of CO2 and CH4 gas absorption spectroscopy based on TDM and optimized adaptive Whittaker-Henderson filtering algorithm

Synchronous detection of CO2 and CH4 gas absorption spectroscopy based on TDM and optimized adaptive Whittaker-Henderson filtering algorithm

High selectivity and sensitivity through nanoparticle sensors for cleanroom CO2 detection

Clean room facilities are becoming more popular in both academic and industry settings, including low-and middle-income countries. This has led to an increased demand for cost-effective gas sensors to monitor air quality. Here we have developed a gas sensor using CoNiO2 nanoparticles through combustion method. The sensitivity and selectivity of the sensor towards CO2 were influenced by the structure of the nanoparticles, which were affected by the reducing agent (biofuels) used during synthesis. Among all reducing agents, urea found to yield highly crystalline and uniformly distributed CoNiO2 nanoparticles, which when developed into sensors showed high sensitivity and selectivity for the detection of CO2 gas in the presence of common interfering volatile organic compounds observed in cleanroom facilities including ammonia, formaldehyde, acetone, toluene, ethanol, isopropanol and methanol. In addition, the urea-mediated nanoparticle-based sensors exhibited room temperature operation, high stability, prompt response and recovery rates, and excellent reproducibility. Consequently, the synthesis approach to nanoparticle-based, energy efficient and affordable sensors represent a benchmark for CO2 sensing in cleanroom settings.

Waving Hand as Infrared Source for Ubiquitous Gas Sensing

Gases in the environment can significantly affect our health and safety. As mobile devices gain popularity, we consider to explore a human-centered gas detection system that can be integrated into commercial mobile devices to realize ubiquitous gas detection. However, existing gas sensors either have too long response delays or are too cumbersome. This paper shows the feasibility of performing gas sensing by shining infrared (IR) signals emitted from our hands through the gas, allowing the system to rely on a single IR detector. The core opportunity arises from the fact that the human hand can provide stable, broadband, and omnidirectional IR radiation. Considering that IR signals experience distinct attenuation when passing through different gases or gases with different concentrations, we can integrate the human hand into the gas sensing system to enable extremely low-power and sustainable gas sensing. Yet, it is challenging to build up a robust system directly utilizing the hand's IR radiation. Practical issues include low IR radiation from the hand, unstable optical path, impact of environmental factors such as ambient temperature, etc. To tackle these issues, we on one hand modulate the IR radiation from the hand leveraging the controllability of the human hand, which improves the hand's IR radiation. On the other hand, we provide a dual-channel IR detector design to filter out the impact of environmental factors and gases in the environment. Extensive experiments show that our system can realize ethanol, gaseous water, and CO2 detection with 96.7%, 92.1% and 94.2%, respectively.

Wavelength-modulated photoacoustic spectroscopic instrumentation system for multiple greenhouse gas detection and in-field application in the Qinling mountainous region of China

We present a sensitive and compact quantum cascade laser-based photoacoustic greenhouse gas sensor for the detection of CO2, CH4 and CO and discuss its applicability toward on-line real-time trace greenhouse gas analysis. Differential photoacoustic resonators with different dimensions were used and optimized to balance sensitivity with signal saturation. The effects of ambient parameters, gas flow rate, pressure and humidity on the photoacoustic signal and the spectral cross-interference were investigated. Thanks to the combined operation of in-house designed laser control and lock-in amplifier, the gas detection sensitivities achieved were 5.6 ppb for CH4, 0.8 ppb for CO and 17.2 ppb for CO2, signal averaging time 1 s and an excellent dynamic range beyond 6 orders of magnitude. A continuous outdoor five-day test was performed in an observation station in China’s Qinling National Botanical Garden (E longitude 108°29’, N latitude 33°43’) which demonstrated the stability and reliability of the greenhouse gas sensor.

Dual laser based optical feedback cavity enhanced absorption spectroscopy by polarization division multiplexing

This article presents a dual laser-based optical feedback cavity-enhanced absorption spectroscopy technique using polarization division multiplexing. The technique involves two laser beams with orthogonal polarization that enter a V-shaped cavity from two injection directions. This allows for independent control of feedback phase and eliminates the need for an optical component to combine the beams. The two lasers are detected separately at the two ends of the cavity. Additionally, a differential process is proposed to mitigate residual interference between the two lasers. By employing this technique, simultaneous detection of CH4, CO2 and H2O is achieved, resulting in a detection sensitivity of approximately 2 × 10−11 cm−1. Despite using a moderate cavity finesse in our spectrometer, the minimal detectable concentration for the gases is comparable to that of superior gas analyzers using cavity ringdown spectroscopy (CRDS).

Dual-responsive solvatochromic sensor for simultaneous detection and mechanism of Cr(III) and Co(II) cations by a new N2O4-donor tetrabenzodiaza-crown ether Macrocyclic ligand anchored to dipyridine moieties

The present study describes the chemosensing capability of an N2O4-donor tetrabenzodiaza-crown ether macrocyclic ligand derivatized by two pyridine side arms to afford the flexible macrocyclic ligand, 5,20-bis(pyridin-4-ylmethyl)-5,6,12,13,19,20,26,27octahydrotetrabenzo [e,i,o,s][1,4,11,14]tetraoxa[7,18]diazacycloicosine (PMHBOA). A selective colorimetric behavior of PMHBOA for the prompt detection of Cr(ΙΙΙ) and Co(ΙΙ) can be observed with naked eyes. The 1H, 13C{H} NMR, and infrared spectroscopy disclosed the ligand binding capability for selective metal ions, ascribed to a 1:1 complex formation with Cr(III) and Co(II) cations in isopropanol. The limit of detection (LOD) values were calculated as 580 and 850 nM for Cr(ΙΙΙ) and Co(ΙΙ), respectively, accompanied with suitable LOQs as 1.95 µM for Cr(III) and 2.85 µM for Co(II), respectively. The reusability was confirmed in the presence of ethylenediaminetetraacetic acid (EDTA). Moreover, a TLC-based fabricated paper strip successfully applied PMHBOA as a chemosensor for synchronous visible detection of Cr(III) and Co(II) in their alcoholic solution. Meanwhile, the observed color change along with the turn-off fluorescent of PMHBOA guaranteed a felicitous choice of candidate for Cr(III) in the presence of other library metal ions in isopropanol:H2O (9/1 v/v) solution. A fast separation test on the filter paper, impregnated with PMHBOA, was also employed to separate Cr(III) and Co(II) cations from aqueous solutions by recording UV–vis spectra. The 1H NMR spectroscopy supported the macrocycle ring and side arms as the parallel coordination site of PMHBOA with Cr(III) and Co(II).

Enhanced sensitivity of zero‐bias‐operated MXene chemiresistive sensor via lignin hybridization

AbstractAs global urbanization intensifies, there is an increasing need for highly sensitive and accurate environmental monitoring devices that can meet the demands of specific gas sensing applications with low power consumption. This study focuses on enhancing the sensitivity of MXene‐based chemiresistive sensors for detecting CO2(g) and NO2(g) under zero‐bias operation. This study shows that lignin hybridization effectively improves the sensitivity of a Ti3C2Tx MXene‐based chemiresistive sensor; under zero‐bias operation, lignin hybridization increases the sensitivity to 15 ppm NO2(g) and CO2(g) by 157.38% and 297.95%, respectively. When deposited on a flexible substrate, the MXene/lignin flexible sensor shows a similar response and sensitivity to 15 ppm NO2(g) and CO2(g) under 38° curvature compared to the planar sensor. Consequently, the MXene/lignin hybrid sensor is attractive for room temperature and zero‐bias NO2(g) and CO2(g) detection. The MXene/lignin flexible sensor serves as a model system for advanced solid‐state sensory platforms suitable for curved structures.image

A DFT study of natural-based materials kaempferol and apigenin for hazardous CO and CO2 gas detection

In this research, the chemical and structural attributes of two flavonoid compounds, Kaempferol and Apigenin, have been investigated employing DFT. These compounds are considered the most promising options for high-sensitivity gas sensors. Applying DFT computations, the adsorption behaviour of typical gas molecules over Kaempferol and Apigenin was studied. Apigenin (Kaempferol) could respond to physisorption of CO and CO2 molecules sensitively due to their considerable charge transfer (CT). Particularly, notable progress in transport performance is induced by absorption of both CO and CO2, which makes Apigenin (Kaempferol) an appropriate option to detect CO and CO2 molecules sensitively. In order to examine potential application of natural products in sensing toxic gases, we deeply believe that this work supplies guidance for research groups.

A new treatment of telluric and stellar features for medium-resolution spectroscopy and molecular mapping

Molecular mapping is a supervised method exploiting the spectral diversity of integral field spectrographs to detect and characterise resolved exoplanets blurred into the stellar halo. We present an update to the method, aimed at removing the stellar halo and the nuisance of telluric features in the datacubes and accessing a continuum-subtracted spectra of the planets at R ~ 4000. We derived the planet atmosphere properties from a direct analysis of the planet telluric-corrected absorption spectrum. We applied our methods to the SINFONI observation of the planet β Pictoris b. We recovered the CO and H2O detections in the atmosphere of β Pic b by using molecular mapping. We further determined some basic properties of its atmosphere, with Teq=1748−4+3 K, sub-solar [Fe/H]=− 0.235−0.013+0.015 dex, and solar C/O=0.551 ±0.002. These results are in contrast to values measured for the same exoplanet with other infrared instruments. We confirmed a low projected equatorial velocity of 25−6+5 km s−1. We were also able to measure, for the first time and with a medium-resolution spectrograph, the radial velocity of β Pic b relative to the central star at MJD=56910.38 with a km s−1 precision of −11.3±1.1 km s−1. This result is compatible with the ephemerides, based on the current knowledge of the β Pic system.

Dual-Modulation ratiometric fluorescence strategy for cobalt and topotecan detection using Red-Emissive carbon dots

A new ratiometric fluorescence strategy for sensitive and selective detection of cobalt ions (Co2+) and topotecan (TOP) is proposed. The dual-probe system consists of red-emissive nitrogen and sulphur doped carbon dots (R-NS@CDs) and TOP. For Co2+ detection, the fluorescence of R-NS@CDs at 680 nm is enhanced upon addition of Co2+, while complexed TOP emission peak at 545 nm remains constant. This enables ratiometric detection of Co2+ over a range of 5.0–160.0 ng mL−1. The mechanism of R-NS@CDs fluorescence enhancement by Co2+ is elucidated using FTIR, fluorescence spectroscopy, zeta potential measurements, and TEM imaging. For the detection of TOP, a ratiometric probe system comprising R-NS@CDs and Co2+ was utilized. TOP forms a complex with Co2+ bounded to R-NS@CDs, quenching the R-NS@CDs-Co2+ fluorescence and simultaneously the native TOP fluorescence is enhanced. This allows ratiometric quantification of TOP from 1.0-90.0 ng mL−1. The method provides high selectivity and low detection limits of 1.51 ng mL−1 for Co2+ and 0.37 ng mL−1 for TOP. Practical applicability is demonstrated through selective detection of Co2+ in environmental water samples and TOP in real plasma samples. The built-in self-calibration enabled by dual analyte modulation of R-NS@CDs makes this a simple and powerful analytical approach.

Mining Metal‐Biomolecular Framework/PANI Composite CO Sensor: Material Synthesis, Gas Sensing Performance and Mechanism

AbstractIn addressing the issue of poor gas sensitivity in semiconductor CO sensor materials used in mining, such as pure PANI. This study utilized an ice‐water bath in combination with an in‐situ polymerization method to synthesize a new composite material consisting of Cu(II)‐racemic glutamate nanofibers and PANI. The morphology, structure, and chemical bonds of the composite material were analyzed using scanning electron microscopy‐energy dispersive spectroscopy (SEM‐EDS) and spectral analysis. The material's ability to detect CO (100–500 ppm) at room temperature was investigated, revealing a response value of up to 6.8 % for 400 ppm CO detection when the composite material was deposited on a ceramic interdigital electrode. The material exhibited good selectivity and responsiveness to CO detection at room temperature, attributed to the heterojunction formed between Cu(II)‐racemic glutamate nanofibers and PANI, which enhanced carrier migration. Consequently, the Cu(II)‐racemic glutamate nanofiber/PANI composite(Cu(II)‐RGlu/PANI) material shows promise as a high‐performance sensing material for CO detection at room temperature and as a low‐power, integrable sensor material for underground coal mines. This research contributes to the development of a theoretical framework for such applications.

Adsorption behavior of gas molecules on B and Mo co-doped graphitic carbon nitride: A first-principles study

Adsorption mechanism studies of toxic gases (CH2O, SO2, NH3, CO, NO, and NO2) on pristine, one B-atom and Mo-atom (1B/Mo) and two B-atom and Mo-atom (2B/Mo) co-doped g-C3N4 were investigated based on the density functional theory. It is shown that gases adsorbed on the 1B(2B)/Mo-g-C3N4 surface exhibit a variety of bandgap types such as magnetic half-metal, magnetic metal, and magnetic semiconductor, and the magnetic properties change considerably. The partial density of states suggests strong hybridization between gas molecules with Mo-4d (B1-2p and B2-2p) and C-2p (N-2p). NH3 gas adsorbed on the 1B(2B)/Mo-g-C3N4 surface acts as a donor and the remaining five gas molecules act as acceptors. CH2O gas adsorbed on 1B/Mo-g-C3N4 has suitable adsorption energy, large charge transfer, short recovery time, and large conductivity change. Therefore 1B/Mo-g-C3N4 can be used as a good sensor to detect CH2O. Lower sensitivity, long recovery times, or insignificant conductivity changes make 1B/Mo-g-C3N4 unsuitable for the detection of CO, NO, NH3, and SO2 gases. However, 1B/Mo-g-C3N4 can be used as a one-time detection for NO2 gas. The recovery time of gases adsorbed on the surface of 2B/Mo-g-C3N4 ranges from 1.93 × 1020 h to 6.43 × 1068 h. However, the large adsorption energies (−2.12 eV to −4.99 eV), the high sensitivity, and the high electrical conductivity allow the use of 2B/Mo-g-C3N4 as a disposable assay for gas molecules.

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.