High-sensitivity CO Research Articles

Favorable performance of WSe2 monolayer modified by chromium catalyst for sensing thermal runaway gases H2, CO and C2H4 using first-principles theory

Detections of thermal runaway gases in the Li-ion batteries (LIBs) is a workable method to evaluate its running status. In this work, first-principles theory is adopted to simulate adsorption and sensing performances of Cr-decorated WSe2 (Cr-WSe2) monolayer upon three typical gases, namely H2, CO and C2H4, in the thermal runaway LIBs. Results indicate that Cr-WSe2 monolayer performs physisorption upon H2 with Ead of −0.37 eV and chemisorption upon CO and C2H4 with Ead of −1.62 and −1.41 eV. The Cr adatom causes strong magnetic behavior to Cr-WSe2 monolayer, which impact the magnetic property of the adsorbed gas molecule as well. The analysis of electronic property suggests the strong potential of Cr-WSe2 monolayer as a high-sensitivity CO and C2H4 sensor, and can be applied as a reusable C2H4 sensor after gas desorption for 70.38 s at 398 K. The analysis of work function (WF) reveal its potential as a potential WF-based gas sensor upon H2 and CO as well. The findings in this work uncover the sensing potential of Cr-WSe2 monolayer upon three typical gases of thermal runaway in the LIBs, which can be explored as a nano gas sensor to perform thermal runaway monitoring using the nano-sensing method.

The Cassiopeia Filament: A Blown Spur of the Local Arm

We present wide-field and high-sensitivity CO(1–0) molecular line observations toward the Cassiopeia region, using the 13.7 m millimeter telescope of the Purple Mountain Observatory. The CO observations reveal a large-scale highly filamentary molecular cloud within the Galactic region of 132.°0 ≥ l ≥ 122.°0 and −1.°0 ≤ b ≤ 3.°0 and the velocity range from approximately +1 to +4 km s−1. The measured length of the large-scale filament, referred to as the Cassiopeia Filament, is ∼390 pc. The observed properties of the Cassiopeia Filament, such as length, column density, and velocity gradient, are consistent with those synthetic large-scale filaments in the inter-arm regions. Based on its observed properties and location on the Galactic plane, we suggest that the Cassiopeia Filament is a spur of the Local arm, which is formed due to the galactic shear. The western end of the Cassiopeia Filament shows a giant arc-like molecular gas shell, which extends in the velocity range from roughly −1 to +7 km s−1. Finger-like structures, with systematic velocity gradients, are detected in the shell. The CO kinematics suggest that the large shell is expanding at a velocity of ∼6.5 km s−1. Both the shell and finger-like structures outline a giant bubble with a radius of ∼16 pc, which is likely produced by the stellar wind from the progenitor star of a supernova remnant. The observed spectral line widths suggest that the whole Cassiopeia Filament was quiescent initially until its west part was blown by the stellar wind and became supersonically turbulent.

Tailoring the surface morphology of nanostructured cobalt oxide for high-sensitivity CO sensor

Tailoring the surface morphology of nanostructured cobalt oxide for high-sensitivity CO sensor

High-sensitivity CO electrochemical gas sensor based on a superconductive C-loaded CuO-CeO2 nanocomposite sensing material

The surperconductive C-loaded CuO-CeO2 catalyst was fabricated by a high temperature solid phase reaction. The catalyst was annealed at 500 °C for 4 h then was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), respectively. The results showed that the as-prepared catalyst was consisted of the particles with the size of 20–50 nm. The gas sensing properties of the superconductive C-loaded CuO-CeO2 to CO were investigated at room temperature. In addition, the as-prepared catalyst exhibited superior activity toward CO. The sensor shows characteristics of a practical-use level: range, 0.1–1000 ppm; sensitivity, 192 mV/ppm; response time, 9 s.

A first-principles study of gas molecule adsorption on borophene

Borophene, a new two-dimensional material, was recently synthesized. The unique anisotropic structure and excellent properties of borophene have attracted considerable research interest. This paper presents a first-principles study of the adsorption of gas molecules (CO, CO2, NH3, NO, NO2 and CH4) on borophene. The adsorption configurations, adsorption energies and electronic properties of the gas molecules absorpted on borophene are determined, and the mechanisms of the interactions between the gas molecules and borophene are evaluated. We find that CO, CO2, NH3, NO and NO2 are chemisorbed on borophene, while CH4 is physisorbed on borophene. Furthermore, our calculation also indicate that CO and CO2 are chemisorbed on borophene with moderate adsorption energy and NO, NO2 and NH3 are chemisorbed on borophene via strong covalent bonds. Moreover, CO is found as an electron donor, while CO2 an electron acceptor. The chemisorption of CO and CO2 on borophene increases the electrical conductivity, so It seems that borophene has the potential to be used in high-sensitivity CO and CO2 gas sensors.

Large-field CO (1–0) observations toward the Galactic historical supernova remnants: a large cavity aroundTycho’s supernova remnant

The investigation of the interaction between the supernova remnants (SNRs) and interstellar gas is not only necessary to improve our knowledge of SNRs, but also to understand the nature of the progenitor systems. As a part of the Milky Way Imaging Scroll Painting CO line survey (MWISP), we study the interstellar gas surrounding the Galactic historical SNRs, using the PMO 13.7-meter telescope. In this work, we present large-field (3$^\circ$$\times$2$^\circ$) and high-sensitivity CO(1-0) molecular line observations toward Tycho's SNR. The CO observations reveal, from the outside in, large molecular clouds, stream-like structures, and an inner rim around Tycho's SNR. We derived the basic properties (column density, mass, and kinematics) of these objects based on the CO observations. The large molecular clouds individually show an arc toward the remnant center, outlining a large cavity with radii of $\sim$0.3$^\circ$$\times$0.6$^\circ$ (or 13 pc $\times$27 pc at a distance of 2.5 kpc) around the remnant. The CO line broadenings and asymmetries detected in the surrounding clouds, the observed expansion of the cavity, in concert with enhanced $^{12}$CO(2-1)/(1-0) intensity ratio detected in previous studies, suggest the interaction of the large cavity with a wind in the region. After excluding the scenario of a large bubble produced by bright massive stars, we suggest that the large cavity could be explained by accretion wind from the progenitor system of Tycho's supernova. Nevertheless, the possibility of the random distribution of a large cavity around Tycho's SNR cannot be ruled out thus far. Further observations are needed to confirm the physical association of the large cavity with Tycho's SNR.

AN OUTER ARM IN THE SECOND GALACTIC QUADRANT: STRUCTURE

ABSTRACT The lack of arm tracers, especially remote tracers, is one of the most difficult problems preventing us from studying the structure of the Milky Way. Fortunately, with its high-sensitivity CO survey, the Milky Way Imaging Scroll Painting (MWISP) project offers such an opportunity. Since completing about one-third of its mission, an area of l = [100, 150]°, b = [−3, 5]° has nearly been covered. The Outer arm of the Milky Way first clearly revealed its shape in the second galactic quadrant in the form of molecular gas—this is the first time that the Outer arm has been reported in such a large-scale mapping of molecular gas. Using the 115 GHz 12CO(1–0) data of MWISP at the LSR velocity ≃[−100, −60] km s−1 and in the area mentioned above, we have detected 481 molecular clouds in total, and among them 332 (about 69%) are newly detected and 457 probably belong to the Outer arm. The total mass of the detected Outer arm clouds is ∼3.1 × 106 M ⊙. Assuming that the spiral arm is a logarithmic spiral, the pitch angle is fitted as ∼13.°1. Besides combining both the CO data from MWISP and the 21 cm H i data from the Canadian Galactic Plane Survey (CGPS), the gas distribution, warp, and thickness of the Outer arm are also studied.

Catalyst free vapor–solid deposition of morphologically different β-Ga2O3 nanostructure thin films for selective CO gas sensors at low temperature

As prepared β-Ga2O3 thin films not only possess a unique shape but also influence the morphology dependent high sensitivity CO sensor at 100 °C.

ENHANCEMENT OF CO(3-2)/CO(1-0) RATIOS AND STAR FORMATION EFFICIENCIES IN SUPERGIANT H II REGIONS

We present evidence that super giant HII regions (GHRs) and other disk regions of the nearby spiral galaxy, M33, occupy distinct locations in the correlation between molecular gas, $\Sigma_{\rm H_2}$, and the star formation rate surface density, $\Sigma_{\rm SFR}$. This result is based on wide field and high sensitivity CO(3-2) observations at 100 pc resolution. Star formation efficiencies (SFE), defined as $\Sigma_{\rm SFR}$/$\Sigma_{\rm H_2}$, in GHRs are found to be about 1 dex higher than in other disk regions. The CO(3-2)/CO(1-0) integrated intensity ratio is also higher than the average over the disk. Such high SFE and CO(3-2)/CO(1-0) can reach the values found in starburst galaxies, which suggests that GHRs may be the elements building up a larger scale starburst region. Three possible contributions to high SFEs in GHR are investigated: (1) the $I_{CO}$-$N({\rm H_2})$ conversion factor, (2) the dense gas fraction traced by CO(3-2)/CO(1-0), and (3) the initial mass function (IMF). We conclude that these starburst-like properties in GHRs can be interpreted by a combination of both a top-heavy IMF and a high dense gas fraction, but not by changes in the $I_{CO}$-$N({\rm H_2})$ conversion factor.

GIANT MOLECULAR CLOUD EVOLUTIONS IN THE NEARBY SPIRAL GALAXY M33

We present a Giant Molecular Cloud (GMC) catalog toward M33, containing 71 GMCs in total, based on wide field and high sensitivity CO(J=3-2) observations with a spatial resolution of 100 pc using the ASTE 10 m telescope. Employing archival optical data, we identify 75 young stellar groups (YSGs) from the excess of the surface stellar density, and estimate their ages by comparing with stellar evolution models. A spatial comparison among the GMCs, YSGs, and HII regions enable us to classify GMCs into four categories: Type A showing no sign of massive star formation (SF), Type B being associated only with HII regions, Type C with both HII regions and <10 Myr-old YSGs and Type-D with both HII regions and 10--30 Myr YSGs. Out of 65 GMCs (discarding those at the edges of the observed fields), 1 (1%), 13 (20%), 29 (45%), and 22 (34%) are Types A, B, C, and D, respectively. We interpret these categories as stages in a GMC evolutionary sequence. Assuming that the timescale for each evolutionary stage is proportional to the number of GMCs, the lifetime of a GMC with a mass >10^5 Mo is estimated to be 20--40 Myr. In addition, we find that the dense gas fraction as traced by the CO(J=3-2)/CO(J=1-0) ratio is enhanced around SF regions. This confirms a scenario where dense gas is preferentially formed around previously generated stars, and will be the fuel for the next stellar generation. In this way, massive SF gradually propagates in a GMC until gas is exhausted.

MOLECULAR HYDROGEN DEFICIENCY IN H I-POOR GALAXIES AND ITS IMPLICATIONS FOR STAR FORMATION

We use a sample of 47 homogeneous and high sensitivity CO images taken from the Nobeyama and BIMA surveys to demonstrate that, contrary to common belief, a significant number (~40%) of HI-deficient nearby spiral galaxies are also depleted in molecular hydrogen. While HI-deficiency by itself is not a sufficient condition for molecular gas depletion, we find that H2 reduction is associated with the removal of HI inside the galaxy optical disk. Those HI-deficient galaxies with normal H2 content have lost HI mainly from outside their optical disks, where the H2 content is low in all galaxies. This finding is consistent with theoretical models in which the molecular fraction in a galaxy is determined primarily by its gas column density. Our result is supported by indirect evidence that molecular deficient galaxies form stars at a lower rate or have dimmer far infrared fluxes than gas rich galaxies, as expected if the star formation rate is determined by the molecular hydrogen content. Our result is consistent with a scenario in which, when the atomic gas column density is lowered inside the optical disk below the critical value required to form molecular hydrogen and stars, spirals become quiescent and passive evolving systems. We speculate that this process would act on the time-scale set by the gas depletion rate and might be a first step for the transition between the blue and red sequence observed in the color-magnitude diagram.

Synthesis of La 0.8Sr 0.2Co 0.5Ni 0.5O 3-δ thin films for high sensitivity CO sensing material using the Pechini process

A sol–gel technique including the Pechini process followed by a spin-coating procedure has been employed for the preparation of nano-sized La 0.8Sr 0.2Co 0.5Ni 0.5O 3-δ (LSCN) thin films used as high sensitivity CO sensing materials. In the characterization of the material, X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis–thermogravimetric analysis (DTA–TG) and surface area analyses (BET equation) were used. The results showed that the molar ratio ( R c) of the citrate/metal ions in the gelation process is the critical factor to obtain a thin film with smooth surfaces, low porosity and homogeneous grain sizes. It is found that an R c value of 3.3 can produce the best results compared to other tested values of 4.0, 2.5, and 1.7. Taking this R c value to prepare the precursor powder and calcined at the temperature of 650°C, a thin film of perovskite structure with average grain sizes of ∼60 nm can be obtained.

Molecular Spiral Arms in M31

We describe a high-resolution, high-sensitivity CO(1-0) survey of a large fraction of the south-west star-forming 20 kpc in diameter in M31 made with the 14 m FCRAO telescope and its QUARRY receiver array. At the 45'' angular resolution of the telescope, the ring is resolved into giant complexes of molecular gas with typical sizes of a few hundred parsecs and masses in excess to 106 M☉. Most of these delineate a prominent spiral arm coincident with that traced by atomic hydrogen and dust. This arm appears in all respects quite similar to a prominent spiral arm in our Galaxy at about the same Galactic radius: the Carina arm. Closer to the center, a second fainter molecular spiral arm segment with an H I and dust counterpart is also detected. The main OB associations and the UV light define an arm offset from that traced by the gas by about 500 pc. The H II regions are mainly found either along the edge of the prominent gaseous arm which faces the associations, or aligned with the second fainter gaseous arm. They define Baade's arms S4 and S3, respectively.

Detection of clump and interclump gas in the Rosette Molecular Cloud Complex

view Abstract Citations (127) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of Clump annd Interclump Gas in the Rosette Molecule Cloud Complex Blitz, L. ; Stark, A. A. Abstract High-resolution, high-sensitivity CO and (C-13)O observations have been made of the Rosette Molecular Cloud Complex at one beamwidth resolution. Clumpiness of the (C-13)O is seen everywhere in the complex. The clumps are shown to be easily identified entities with densities 10 times the volume-averaged density of the entire complex. The clumps are shown to be embedded in pervasive molecular 'interclump' gas of low average volume density (2/cu cm) which has not previously been observed. The velocity dispersion of the interclump gas is about 3 times greater than that of the clumps, implying that the gas is not gravitationally bound to the complex. It is shown that no special support of the complex as a whole needs to be postulated to prevent catastrophic collapse. Publication: The Astrophysical Journal Pub Date: January 1986 DOI: 10.1086/184609 Bibcode: 1986ApJ...300L..89B Keywords: Interstellar Gas; Interstellar Matter; Molecular Clouds; Carbon Monoxide; Clumps; Stellar Evolution; Astrophysics; INTERSTELLAR: MATTER; INTERSTELLAR: MOLECULES; STARS: FORMATION full text sources ADS | data products SIMBAD (2)