The room temperature gas sensors have always been an important research direction of the gas sensor, and the room temperature gas sensors without the assistance of the light is more valuable. The SnO 2 nanoparticles were synthesized by hydrothermal method, which showed good formaldehyde sensitivity, had the advantages of low test temperature, only [Formula: see text]C, good formaldehyde selectivity, and especially the good response to formaldehyde at room temperature. The nanostructure and gas-sensing properties were characterized by scanning electron microscopy, EDS mapping, nitrogen physical adsorption, and X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and WS-60B gas-sensing measurement system. Compared with the reported research results, we carefully discuss the physical mechanism of the SnO 2 formaldehyde sensor with low operating temperature and good formaldehyde selectivity in this paper.
The configuration, slipping and rotation of self-interstitial atoms cluster along <111> crystal orientation with different sizes in a tungsten are investigated systematically with molecular dynamics. It is found that (I) the SIA clusters with high symmetry are always favoured; (II) the SIA clusters can undergo one-dimensional fast migration along <111> direction, and their migration barriers are no more than 0.07 eV, which is expected due to the strong interaction in the SIA clusters; (III) the rotation energy barriers of the SIA clusters are rather high and they are basically positively correlated with the size of the cluster. For example, the reorientation barrier is 0.66 eV for 1 SIA, 1.2–1.8 eV for SIAn (2 ≤ n ≤ 5) clusters and over 2.7 eV for SIAn (6 ≤ n ≤ 7) clusters. Compared with slipping of SIA clusters, is an infrequent event, especially for larger SIAs cluster, the vast majority SIAs cluster would have already recombination with vacancies or annihilates at surface and grain boundary through slipping before rotation, which explained that there are very low density of SIAs cluster found in the experiment.
ZnO–SnO 2 composite nanorods with rough surfaces were synthesized via a coaxially nested needle electrospinning method. The morphology and nanostructure were characterized by scanning electron microscopy, atomic force microscope, EDS mapping, nitrogen physical adsorption, and X-ray diffraction. The synthesis mechanisms of ZnO–SnO 2 nanorods were discussed, which combined the gas sensitivity advantages of different materials. ZnO–SnO 2 nanorods sensor with good ethanol gas sensitivity achieved accurate measurement of continuous ethanol concentration. The sensor exhibited good selectivity to ethanol in the presence of formaldehyde, methanol, acetone, acetic acid, benzene, and xylene at 290[Formula: see text]C. The response and recovery time to 100 ppm ethanol were about 13 and 35 s, respectively. The energy band, barrier, charge transfer of ZnO–SnO 2 composite material was discussed, and its optimization of gas sensitivity was analyzed in detail.
In this work, oxygen vacancy‐rich C/TiO_{2} (OV‐C/TiO_{2}) samples are prepared by a one‐step calcination approach using Ti_{3}C_{2} MXene as the precursor, and used for the photocatalytic N_{2} reduction. The NH_{3} yields of all the prepared OV‐C/TiO_{2} samples exceed those achieved on commercial anatase TiO_{2} and P25, with both H_{2}O and CH_{3}OH as the proton sources. Among them, the OV‐C/TiO_{2}‐600 offers the remarkable NH3 synthesis rates, which are 41.00 µmol g^{−1} h^{−1} (with CH_{3}OH as the proton source). The photocurrent and fluorescence spectra show that OV‐C/TiO_{2}‐600 exhibit the highest generation/separation rate and longest lifetime of photocarriers among all the prepared samples. ESR and TPD experiments confirm much more efficient chemisoption of N_{2} on the surface of the prepared OV‐C/TiO_{2}‐600 than that on the surface of the commercial anatase TiO_{2}. Moreover, DFT calculations further demonstrate that N2 conversion to NH_{3} through a Gibbs free energy release leading alternating pathway with a low energy barriers, on the oxygen vacancy on TiO_{2} surface.
The behaviors of helium clusters and self-interstitial tungsten atoms at different temperatures are investigated with the molecular dynamics method. The self-interstitial tungsten atoms prefer to form crowdions which can tightly bind the helium cluster at low temperature. The crowdion can change its position around the helium cluster by rotating and slipping at medium temperatures, which leads to formation of combined crowdions or dislocation loop locating at one side of a helium cluster. The combined crowdions or dislocation loop even separates from the helium cluster at high temperature. It is found that a big helium cluster is more stable and its interaction with crowdions or dislocation loop is stronger.
Abstract A new copper phenylacetylide of PhC 2 Cu 2.5 was prepared and compared with PhC 2 Cu, a copper‐based metal–organic coordination polymer we reported previously. Based on the characterizations on the structures of the two prepared samples, they possessed significantly different crystal structures and similar micro and band structures. Interestingly, they also showed different preferences for the photocatalytic degradation of methyl orange (MO) and 2,4‐diclorophenol (2,4‐DCP). The active species trap experimental results show that different active species were required for the degradation of MO and 2,4‐DCP, resulting to different degradation pathways and mechanism. At last, different preferentially production of active species by PhC 2 Cu 2.5 and PhC 2 Cu were studied by electrochemical measurements and fluorescence spectra, as well as the photocatalytic productions of reactive oxygen species by PhC 2 Cu and PhC 2 Cu 2.5 , which further demonstrated the obtained conclusions by active species trap experimental results. This work developed a new copper phenylacetylide of PhC 2 Cu 2.5 as a photocatalyst and demonstrated the different degradation pathways of MO and 2,4‐DCP.
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