Search

Herein, La 0.7 Ca 0.3− x K x MnO 3 (LCKMO) films with highly oriented growth were prepared on La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 (00 l) substrates by sol–gel spin coating method. Comprehensive analysis of microstructure, surface morphology, ion valence, and electrical transport properties of LCKMO films indicates that the substitution of K+ ions for Ca2+ ions increased the ratio of Mn4+/(Mn3+ + Mn4+), narrowed the one electron bandwidth, and enhanced double exchange mechanism and electron–lattice coupling. Moreover, the doping of K+ ions induced the dense and uniform conical-structured growth of grains on the surface of the films. Results demonstrated that at x = 0.1, LCKMO film exhibited the maximum TCR of 17.84% K−1 at 253.07 K, which was 31.76% higher than that of previously reported La 1− x−y Ca x K y MnO 3 ceramic with the highest TCR. Further theoretical insights into the effects of Ca/K co-doping on electrical transport properties were supplemented. [ABSTRACT FROM AUTHOR]

Electrical mobility and mass of atmospheric ions are of great importance, since both properties jointly determine their charging states. In this work, different carrier gases of bottle N 2 , bottle air, and particle-free lab air were passed through a TSI® soft X-ray aerosol neutralizer to produce both positive and negative ions. The electrical mobilities and mass-to-charge ratios of these ions were measured with a high-resolution half-mini differential mobility analyzer (DMA) coupled to an atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometer. The effects of carrier gas, sample flowrate, and relative humidity (RH) on the ion mobility and mass-to-charge ratio were evaluated. Most detected ions could be traced back to the impurities in the carrier gases, or the compounds used to manufacture the system components. However, severe fragmentation of DMA-classified clusters was observed, especially under high RH conditions, which likely occurred inside the APi-TOF and complicated the identification of the chemical composition of the DMA-classified clusters. The mobility spectra and ion identities were comparable when using bottle N 2 and bottle air as the carrier gas, whereas different features on ion mobility and mass-to-charge ratio were found in the case of particle-free lab air. Residence time of the carrier gas inside the neutralizer as a function of the sample flowrate, when at the order of a few seconds, exerted a weak impact on the ion mobility spectra. The effect of RH on the electrical mobility was contingent on the polarity and chemical composition of ions. The presence of water vapor would grow the acid radical ions and hydronium ions to larger sizes by forming clusters, whereas the positively charged polydimethylsiloxanes in the case of particle-free lab air were marginally impacted. In addition, the concentration of neutral clusters formed through the ion-ion recombination or radiolysis was measured with a particle size magnifier (PSM). Compared with those in the case of bottle gases, the neutral cluster concentrations were significantly larger when particle-free lab air was used as the carrier gas. Higher concentrations of neutral clusters were observed in the high RH experiments, likely because high RH could either enhance the ion-ion recombination or the detection efficiency of PSM. Our work indicates that RH and the impurities in the carrier gas have a significant effect on the measured electrical mobilities and mass spectra for ions generated by a soft X-ray aerosol neutralizer. • Properties of bipolar ions produced in a soft X-ray neutralizer were measured. • Ion species generated from different carrier gases were compared. • Residence time exerted a weak impact on the ion mobility spectra. • Relative humidity induced-shift in ion mobility was contingent on ion properties. • High concentrations of sub-2 nm neutral clusters were formed and observed. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained a mistake. "Southwest Minzu Nationalities" in affiliation 1 should be "Southwest Minzu University". [ABSTRACT FROM AUTHOR]

Al17 clusters exhibit apparent changes in curvature, which resemble macroscopic metal tips. Here, we show, using the density functional theory method, how surface charges of Al17q (q = −2 to +3) ions affect the adsorption and dissociation behavior of HCl molecules. Geometries, adsorption energies, vibrational frequencies, Mulliken population analysis and transition states of (Al17HCl)q (q = −2 to +3) adsorption complexes were studied. The results revealed that HCl molecules tend to locate on tip sites of the Al17q (q = −2 to +3) ions. Anionic adsorption complexes are prone to H affinity adsorption, whereas cationic adsorption complexes favor Cl-affinity adsorptions. These adsorption behaviors look quite like macroscopic tip effects. H–Cl bonds of the adsorption complexes weaken with an increase in either positive or negative charge. Dissociation barriers of the H–Cl bonds exhibit binding energies that are 2 orders of magnitude smaller than those of an isolated HCl molecule. Considering adsorption energies and dissociation barriers comprehensively, HCl molecules should dissociate spontaneously for all the models considered. Generally, the more negative charges the clusters carry, the more energy the reaction will release. [ABSTRACT FROM AUTHOR]

The newly developed Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-TOF) is able to simultaneously detect hundreds of gaseous compounds including a big fraction of volatile organic compounds (VOCs) with outstanding mass resolution and sensitivity. Here, we present an application of Vocus PTR-TOF to monitor gaseous dimethylamine (DMA). The sensitivity towards DMA was improved by tuning the voltage settings of the segmented quadrupole following the molecular ion reactor to obtain a suitable ion transmission window. With the assistance of a permeation tube calibration method, the sensitivity of Vocus PTR-TOF for DMA detection was 2.68 cps pptv−1 at a TOF extraction frequency of 16 kHz and the detection limit was 1.44 pptv at 3σ of the background signal for a 1 min integration time. Laboratory experiments at a series of controlled relative humidity (RH) show that RH of the sample had little influences on the measurement of DMA. Vocus PTR-TOF with this hardware setup was deployed from December 2018 to January 2019 at Wangdu, Hebei Province, China. The temporal profile of C 2 -amines with a high time resolution was obtained, while the detection of VOCs remained successful. Such simultaneous measurements of these compounds are meaningful as these compounds are all relevant to aerosol nucleation and growth. Our results indicate that Vocus PTR-TOF can be a powerful tool in both field and laboratory studies for new particle formation research. [ABSTRACT FROM AUTHOR]