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Nat Nanotechnol ; 15(2): 94-98, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31907440


Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3-7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13 and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries.

Antiviral Res ; 174: 104704, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31917237


AIMS: Deguelin, a natural compound derived from Mundulea sericea (Leguminosae) and some other plants exhibits an activity to inhibit autophagy, a cellular machinery required for hepatitis C virus (HCV) replication. This study aimed to illuminate the impact of deguelin on HCV replication and mechanism(s) involved. METHODS: HCV JFH-1-Huh7 infectious system was used for the investigation. Real time RT-PCR, Western blot, fluorescent microscopy assay were used to measure the expression levels of viral or cellular factors. Overexpression and silencing expression techniques were used to determine the role of key cellular factors. RESULTS: Deguelin treatment of Huh7 cells significantly inhibited HCV JFH-1 replication in a dose- and time-dependent manner. Deguelin treatment suppressed autophagy in Huh7 cells, evidenced by the decrease of LC3B-II levels, the conversion of LC3B-I to LC3B-II, and the formation of GFP-LC3 puncta as well as the increase of p62 level in deguelin-treated cells compared with control cells. HCV infection could induce autophagy which was also suppressed by deguelin treatment. Mechanism research reveals that deguelin inhibited expression of Beclin1, which is a key cellular factor for the initiation of the autophagosome formation in autophagy. Overexpression or silencing expression of Beclin1 in deguelin-treated Huh7 cells could weaken or enhance the inhibitory effect on autophagy by deguelin, respectively, and thus partially recover or further inhibit HCV replication correspondingly. CONCLUSIONS: Deguelin may serve as a novel anti-HCV compound via its inhibitory effect on autophagy, which warrants further investigation as a potential therapeutic agent for HCV infection.

Angew Chem Int Ed Engl ; 57(39): 12750-12753, 2018 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-30063281


Lithium metal is an ideal anode for next-generation lithium batteries owing to its very high theoretical specific capacity of 3860 mAh g-1 but very reactive upon exposure to ambient air, rendering it difficult to handle and transport. Air-stable lithium spheres (ASLSs) were produced by electrochemical plating under CO2 atmosphere inside an advanced aberration-corrected environmental transmission electron microscope. The ASLSs exhibit a core-shell structure with a Li core and a Li2 CO3 shell. In ambient air, the ASLSs do not react with moisture and maintain their core-shell structures. Furthermore, the ASLSs can be used as anodes in lithium-ion batteries, and they exhibit similar electrochemical behavior to metallic Li, indicating that the surface Li2 CO3 layer is a good Li+ ion conductor. The air stability of the ASLSs is attributed to the surface Li2 CO3 layer, which is barely soluble in water and does not react with oxygen and nitrogen in air at room temperature, thus passivating the Li core.

Nano Lett ; 18(6): 3723-3730, 2018 06 13.
Artigo em Inglês | MEDLINE | ID: mdl-29742351


We report real time imaging of the oxygen reduction reactions (ORRs) in all solid state sodium oxygen batteries (SOBs) with CuO nanowires (NWs) as the air cathode in an aberration-corrected environmental transmission electron microscope under an oxygen environment. The ORR occurred in a distinct two-step reaction, namely, a first conversion reaction followed by a second multiple ORR. In the former, CuO was first converted to Cu2O and then to Cu; in the latter, NaO2 formed first, followed by its disproportionation to Na2O2 and O2. Concurrent with the two distinct electrochemical reactions, the CuO NWs experienced multiple consecutive large volume expansions. It is evident that the freshly formed ultrafine-grained Cu in the conversion reaction catalyzed the latter one-electron-transfer ORR, leading to the formation of NaO2. Remarkably, no carbonate formation was detected in the oxygen cathode after cycling due to the absence of carbon source in the whole battery setup. These results provide fundamental understanding into the oxygen chemistry in the carbonless air cathode in all solid state Na-O2 batteries.