Revealing the CO2 Conversion at Electrode/Electrolyte Interfaces in Li-CO2 Batteries via Nanoscale Visualization Methods.

Lithium-carbon dioxide (Li-CO2 ) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li-CO2 batteries, the complex electrode/electrolyte/CO2 triple-phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy-differential interference contrast microscopy, we directly observed the CO2 conversion processes in Li-CO2 batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li2 CO3 /C, deposits as micron-sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li2 CO3 /C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li2 C2 O4 , which in turn affects growth/decomposition pathways of Li2 CO3 /C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li-CO2 batteries and the laser-tuned CO2 conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.

Design and Research of Chromatic Confocal System for Parallel Non-Coaxial Illumination Based on Optical Fiber Bundle.

Conventional chromatic confocal systems are mostly single-point coaxial illumination systems with a low signal-to-noise ratio, light energy utility and measurement efficiency. To overcome the above shortcomings, we propose a parallel non-coaxial-illumination chromatic-confocal-measurement system based on an optical fiber bundle. Based on the existing single-point non-coaxial-illumination system, the optical fiber bundle is used as the optical beam splitter to achieve parallel measurements. Thus, the system can yield measurements through line scanning, which greatly improves measurement efficiency. To verify the measurement performance of the system, based on the calibration experiment, the system realizes the measurement of the height of the step, the thickness of the transparent specimen and the reconstruction of the three-dimensional topography of the surface of the step and coin. The experimental results show that the measuring range of the system is 200 µm. The measurement accurcy can reach micron level, and the system can realize a good three-dimensional topography reconstruction effect.

In situ visualization of synergistic effects between electrolyte additives and catalytic electrodes in Li-O2 batteries.

By using in situ atomic force microscopy, Li-O2 interfacial reactions promoted synergistically by the electrolyte additive K+ and Pt nanoparticles electrode are visualized. The Pt nanoparticles electrode promotes the formation of the intermediate lithium superoxide (LiO2) and K+ assists its diffusion into the electrolyte, thereby promoting the formation of large-sized discharge products during discharging and increasing the discharge capacity of the Li-O2 battery. These results provide direct evidence for clarifying the interfacial synergy mechanism of electrolyte additives and solid catalysts.

Revealing the Correlations between Morphological Evolution and Surface Reactivity of Catalytic Cathodes in Lithium-Oxygen Batteries.

Lithium-oxygen batteries suffer from the degradation of the catalytic cathode during long-term operation, which limits their practical use. Understanding the direct correlations between the surface morphological evolution of catalytic cathodes at nanoscale and their catalytic activity during cycling has proved challenging. Here, using in situ electrochemical atomic force microscopy, the dynamic evolution of the Pt nanoparticles electrode in a working Li-O2 battery and its effects on the Li-O2 interfacial reactions are visualized. In situ views show that repeated oxidation-reduction cycles (ORCs) trigger the increase in the size of Pt nanoparticles, eventually causing the Pt nanoparticles to fall off the electrode. In 0-80 ORCs, the grown Pt nanoparticles promote the conversion of the Li-O2 reaction route from the surface-mediated pathway to the solution-mediated pathway during discharging and significantly increase the discharge capacity. After 250 ORCs, accompanied by the part of the Pt nanoparticles detaching from the electrode, the nucleation potential of reaction product decreases, and the reaction dynamic slows down, which cause the performance to degrade. Modification of a proper amount of Au nanoparticle on the Pt nanoparticles electrode could improve its stability and maintain the high catalytic activity. These results provide a direct evidence for clarifying the correlations between morphological evolution and surface reactivity of catalytic cathodes during cycling, which is critical for developing high-performance catalysts.

New Gas Tracer Convection-Diffusion Model between Wells in Heavy Oil Reservoirs.

Different from conventional oil and gas, the storage and seepage space of heavy oil reservoirs are extremely complicated, thereby making it difficult to describe reservoirs in detail over the heavy oil production process. Acquiring development results accurately in real time is still a demanding task, and it is also a challenge to predict the average remaining heavy oil saturation during the production process. Tracers are mostly used to monitor steam flooding to obtain the real-time dynamics during heavy oil production in fields. However, the flow pattern of gas tracers in heavy oil is still unclear, with very rare investigations. In this work, a new one-dimensional gas tracer convection-diffusion model that considered the retention and oil phase migration velocity was established using the percolation law of gas tracers. The reservoir description coefficient f was introduced to describe the relationship between the migration velocities of the oil and gas phases in the heavy oil reservoir. Subsequently, a new gas tracer well pattern flow model was also constructed based on the gas tracer linear flow model and verified simultaneously. The results revealed that at a larger partition coefficient, more amounts of gas tracers were distributed in the crude oil, the duration of stagnation was extended, and the start time of tracer production was moved backward. The injection velocity had a very minor effect on the tracer production performance. As the fluid injection rate increased, the duration of gas tracer production was extended; however, after the injection rate reached a certain level, the difference in the arrival time of the peak become minor. The effects of crude oil viscosity on the tracer production were reflected by the breakthrough time, production time, peak concentration, and peak arrival time of the tracer. Compared with the production curve of the crude oil viscosity, the peak of the production curve with high crude oil viscosity has a faster peak time and a large peak value. The reservoir description coefficient mainly affects the peak concentration of tracer production and has very minor effects on the production time and other parameters. The outcomes of this work can be applied in the field of heavy oil development, in particular, for the heavy oil reservoir description and dynamic monitoring.

The Impact of Air Pollution on Outpatient Visits of Children with Asthma in Xi'an, China.

INTRODUCTION: The number of children with asthma has increased significantly in China. In recent years, there has been a steady increase in outpatient visits of children with asthma, attributed to poor air quality and environmental pollution reported regionally and at our institution. This study aimed to assess the association between air pollution and the number of outpatient visits of children with asthma in Xi'an, the largest city in northwest China. METHODS: We searched the database of the largest children's hospital in Xi'an for related information from 2014 to 2018 and then acquired data on air pollution, including the daily average concentrations of fine particles (PM2.5), inhalable particles (PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2) of that same time period. Time-series generalized additive models were used to analyze the relationships. RESULTS: Our results revealed that air pollution was very serious in Xi'an, with elevated average concentrations of PM2.5, PM10, and NO2 from 2015 to 2018. The relative risk of outpatient visits due to asthma associated with PM2.5, PM10, and SO2 pollution rose significantly and reached 1.11 (1.02-1.21), 1.25 (1.01-1.55), and 1.71 (1.31-2.25), respectively, when there was a 10 ug·m-3 increase in concentration, during a lag of 21 d. CONCLUSIONS: A high concentration of particulate matter (PM2.5 and PM10) was the prominent feature of air pollution in Xi'an. Exposure to air pollutant (PM2.5, PM10, SO2) was positively associated with an increased risk of children's outpatient visits for asthma in Xi'an.

Optical-Dielectric Duple Bistable Switches: Photoluminescence of Reversible Phase Transition Molecular Material.

Molecular optical-dielectric duple bistable switches are photoelectric (dielectric and fluorescent) multifunctional materials that can simultaneously convert optical and electrical signals in one device for seamless integration. However, exploring optical-dielectric duple channels of dielectric and photoluminescence is still a bigger challenge than single dielectric or photoluminescence bistable ones, which are hardly reported but probably will be heavily researched owing to the new generation artificial intelligence development needs in the future. Herein, a new optical-dielectric duple bistable switches material, [(CH3 )3 NCH2 CH3 ]2 MnCl4 (I), was obtained by a simple method for volatilization of solvents. Variable temperature single crystal X-ray analysis indicates that material I has a reversible bistable structure (order-disorder structure phase transition) corresponding to switching "ON'' and "OFF''. Unlike the single dielectric bistable structures that were previously reported, material I also own bistable features in terms of fluorescence property. This material enriches the specific examples of photoelectric duple function switch materials and facilitates the development of required devices.

Efficacy and safety of sublingual dust mite drops in children with mono- or polysensitized allergic rhinitis.

OBJECTIVE: To explore the efficacy and safety of sublingual house dust mite (HDM) drops in children with mono- or polysensitized allergic rhinitis. METHODS: We conducted a retrospective cohort study of 65 children with monosensitized AR and 118 children with polysensitized AR who were scheduled for sublingual administration of HDM drops from January 2015 to June 2016. Interleukin (IL)-2, IL-4, and IL-17α, transforming growth factor-ß1 (TGF-ß1), specific immunoglobulin E (IgE), and specific IgG4 were detected by ELISA. The efficacies were assessed using symptoms score and medication score. All the outcomes were measured 1 month before the study and 1 month after the end of the 2-year treatment. RESULTS: The total nasal symptoms score (TNSS) decreased significantly from 11.27 (9.81 ±â€¯12.73) at baseline to 3.48(1.98 ±â€¯4.98) at the end of sublingual treatment for the monosensitized AP group (t = 30.00, P < 0.01), and from 11.54(10.04 ±â€¯13.04) to 3.56 (2.00 ±â€¯5.16) for the polysensitized AR group (t = 40.05, P < 0.01), respectively. IL-2 and TGF-ß1 increased significantly after treatment in contrast with before treatment in both the monosensitized group and the polysensitized group (both P < 0.01). In contrast, IL-4 and IL-17α decreased significantly after treatment compared with the baseline in both groups (both P < 0.01). Sublingual HDM drops were generally safe and well tolerant in both groups. CONCLUSIONS: This study confirmed the efficacy and safety of sublingual AIT in both monosensitized and polysensitized AR patients (Chinese children).

Above room-temperature dielectric and nonlinear optical switching materials based on [(CH3)3S]2[MBr4] (M = Cd, Mn and Zn).

In this paper, three zero-dimensional organic-inorganic hybrid compounds [(CH3)3S]2[CdBr4] (1), [(CH3)3S]2[MnBr4] (2) and [(CH3)3S]2[ZnBr4] (3) were synthesized. The phase transition behavior of 1, 2 and 3 was well characterized by differential scanning calorimetry (DSC) and variable temperature single crystal diffraction measurements. The phase transition temperature of 1, 2 and 3 was at ca. 315 K in the heating process. The vigorous ordered-disordered reorientation and displacement motion of [(Me3)3S]+ and [MBr4]2- of 1, 2 and 3 induce the structural phase transition from the centrosymmetric (CS) space group Pnma to the non-centrosymmetric (NCS) space group P212121. The apparent second-harmonic generation (SHG) switching responses further confirm this CS to NCS symmetry breaking. Moreover, dielectric studies illustrate that 1, 2 and 3 display distinctly switchable dielectric behavior, revealing their potential application in dielectric switches. This finding suggests that sulfonium-based organic-inorganic hybrids can be used to build phase transition materials, broadening the way for exploring dielectric and nonlinear optical (NLO) switching materials.

A Semiconducting Organic-Inorganic Hybrid Perovskite-type Non-ferroelectric Piezoelectric with Excellent Piezoelectricity.

Piezoelectric materials are a class of important functional materials applied in high-voltage sources, sensors, vibration reducers, actuators, motors, and so on. Herein, [(CH3 )3 S]3 [Bi2 Br9 ](1) is a brilliant semiconducting organic-inorganic hybrid perovskite-type non-ferroelectric piezoelectric with excellent piezoelectricity. Strikingly, the value of the piezoelectric coefficient d33 is estimated as ≈18 pC N-1 . Such a large piezoelectric coefficient in non-ferroelectric piezoelectric has been scarcely reported and is comparable with those of typically one-composition non-ferroelectric piezoelectrics such as ZnO (3pC N-1 ) and much greater than those of most known typical materials. In addition, 1 exhibits semiconducting behavior with an optical band gap of ≈2.58 eV that is lower than the reported value of 3.37 eV for ZnO. This discovery opens a new avenue to exploit molecular non-ferroelectric piezoelectric and should stimulate further exploration of non-ferroelectric piezoelectric due to their high stability and low loss characteristics.