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The solid-electrolyte interphase (SEI) plays crucial roles for the reversible operation of lithium metal batteries. However, fundamental understanding of the mechanisms of SEI formation and evolution is still limited. Herein, we develop a depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method to enable in-situ and nondestructive characterization of the nanostructure and chemistry of SEI, based on synergistic enhancements of localized surface plasmons from nanostructured Cu, shell-isolated Au nanoparticles and Li deposits at different depths. We monitor the sequential formation of SEI in both ether-based and carbonate-based dual-salt electrolytes on a Cu current collector and then on freshly deposited Li, with dramatic chemical reconstruction. The molecular-level insights from the DS-PERS study unravel the profound influences of Li in modifying SEI formation and in turn the roles of SEI in regulating the Li-ion desolvation and the subsequent Li deposition at SEI-coupled interfaces. Last, we develop a cycling protocol that promotes a favorable direct SEI formation route, which significantly enhances the performance of anode-free Li metal batteries. The solid-electrolyte interphase is crucial for most batteries, but its characterization is challenging. Here, authors develop a depth-sensitive plasmon-enhanced Raman spectroscopy method to enable in-situ and nondestructive resolving of its structure and chemistry as well as formation mechanisms. [ABSTRACT FROM AUTHOR]

CuI N-heterocycle thiolate clusters efficiently catalyze the acceptorless dehydrogenation of alcohols at 70 °C. A variety of secondary/primary benzylic, allylic, and aliphatic alcohols are dehydrogenated to the corresponding ketones and aldehydes in high yields of isolated product upon release of H2. This simple catalytic system is involved in the synthesis of imines through the one-pot reaction of alcohols and amines. [ABSTRACT FROM AUTHOR]

Discharging of aprotic sodium-oxygen (Na-O 2 ) batteries is driven by the cathodic oxygen reduction reaction in the presence of sodium cations (Na + -ORR). However, the mechanism of aprotic Na + -ORR remains ambiguous and is system dependent. In-situ electrochemical Raman spectroscopy has been employed to study the aprotic Na + -ORR processes at three atomically ordered Au( hkl ) single-crystal surfaces for the first time, and the structure-intermediates/mechanism relationship has been identified at a molecular level. Direct spectroscopic evidence of superoxide on Au(110) and peroxide on Au(100) and Au(111) as intermediates/products has been obtained. Combining these experimental results with theoretical simulation has revealed that the surface effect of Au( hkl ) electrodes on aprotic Na + -ORR activity is mainly caused by the different adsorption of Na + and O 2 . This work enhances our understanding of aprotic Na + -ORR on Au( hkl ) surfaces and provides further guidance for the design of improved Na-O 2 batteries.

A measurement method of 85 Kr using an internal gas proportional counter (IGPC) is presented in this study. The operation conditions of the IGPC were determined and optimized, including the operating voltage, pressure, sample volume, interference from other gas components such as nitrogen or air, and mitigation of the memory effect. The IGPC was calibrated using certified standards, and the detection efficiency was approximately 58% for typical samples. A lower limit of detection of approximately 0.11 MBq/m 3 (Kr) was achieved after counting for 5 h with 1 mL pure Kr, corresponding to the atmospheric activity concentration of 0.18 Bq/m 3 (air). It was shown that the IGPC could be used effectively for measuring 85 Kr., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The SiO2 shell with the thickness of 4 nm was attached onto high surface enhanced Raman spectroscopy (SERS) active Au core nanoparticles to obtain Au@SiO2 core shell nanoparticles by the hydrolysis of sodium silicate solution with the boiling water bath. The inert shell of SiO2 isolated the direct interaction of Au nanoparticles and probe molecules. The stable, compact and uniform monolayer nanoparticles film was self assembled at water/oil interface, and one to six monolayers film was transferred to Si wafer as SERS substrates through layer by layer technique. The relationship between the SERS activities and layers of the monolayer nanoparticles film on Si surface was investigated. The SERS mapping was developed to determine the layers of the Au@SiO2 film. The coupling effect among the Au@SiO2 films was explored by changing the adsorption location of the probe on the multilayer films. The result revealed that the monolayer film was a favourable candidate with high-quality performances for the SERS application. The SERS signal was distributed on the surface with high uniformity at the same monolayer film, and it was enhanced in the intensity with the increase in film layers. It reached the maximun intensity as the film was over five layers. It indicated that the SERS signal was contributed mainly by the first five monolayers. The probe molecules were immobilized onto the first monolayer nanoparticles film, and the SERS signal from the probe approached to the maximum as the second monolayer covered the probe modified first nanoparticles film. It was dominated by the coupling effect ("hot spots") of the adjacent layers. The SERS signal decreased in intensity when the third layer was transferred onto the second layer, and it disappeared after the fouth layer was covered, mainly duo to the shield of the nanoparticles film to the incident laser and Raman signal. The preliminary results provided guidance for fabricating optimal SERS substrates.