P3/O3 Integrated Layered Oxide as High-Power and Long-Life Cathode toward Na-Ion Batteries.

Low-cost and stable sodium-layered oxides (such as P2- and O3-phases) are suggested as highly promising cathode materials for Na-ion batteries (NIBs). Biphasic hybridization, mainly involving P2/O3 and P2/P3 biphases, is typically used to boost their electrochemical performances. Herein, a P3/O3 intergrown layered oxide (Na2/3 Ni1/3 Mn1/3 Ti1/3 O2 ) as high-rate and long-life cathode for NIBs via tuning the amounts of Ti substitution in Na2/3 Ni1/3 Mn2/3- x Tix O2 (x = 0, 1/6, 1/3, 2/3) is demonstrated. The X-ray diffraction (XRD) Rietveld refinement and aberration-corrected scanning transmission electron microscopy show the co-existence of P3 and O3 phases, and density functional theory calculation corroborates the appearance of the anomalous O3 phase at the Ti substitution amount of 1/3. The P3/O3 biphasic cathode delivers an unexpected rate capability (≈88.7% of the initial capacity at a high rate of 5 C) and cycling stability (≈68.7% capacity retention after 2000 cycles at 1 C), superior to those of the sing phases P3-Na2/3 Ni1/3 Mn2/3 O2 , P3-Na2/3 Ni1/3 Mn1/2 Ti1/6 O2 , and O3-Na2/3 Ni1/3 Ti2/3 O2 . The highly reversible structural evolution of the P3/O3 integrated cathode observed by ex situ XRD, ex situ X-ray absorption spectra, and the rapid Na+ diffusion kinetics, underpin the enhancement. These results show the important role of P3/O3 biphasic hybridization in designing and engineering layered oxide cathodes for NIBs.

[Effect of electroacupuncture at different stages on the expression of Fas and FasL in brain tissue of rats with traumatic brain injury].

OBJECTIVE: To investigate the expression of apoptosis-related proteins Fas and FasL in the brain tissue of rats with traumatic brain injury and the effect of electroacupuncture on the expression of Fas and FasL, so as to explore the effective time window of electroacupuncture in the treatment of traumatic brain injury. METHODS: Sprague-Dawley rats were randomly divided into blank group, sham-operation group, model group, and electroacupuncture treatment groups 1, 2, and 3. Traumatic brain injury was induced by the modified Feeney free-fall impact device, and for the rats in the electroacupuncture treatment groups 1, 2, and 3, electroacupuncture started at 4 hours and on days 3 and 7, respectively, after modeling and lasted to day 14. The Morris water maze test was used to evaluate learning and memory ability, and immunofluorescence assay and Western blot were used to observe the changes in the expression of Fas and FasL in traumatic brain tissue. RESULTS: Compared with the blank group and the sham-operation group, the model group had a lower percentage of time spent in the target quadrant from the 3rd day folowing modeling; after electroacupuncture intervention, the electroacupuncture treatment groups showed a gradual increase in the time spent in the target quadrant, and on day 7,10 and 14, electroacupuncture treatment group 1 had a significantly higher percentage than the model group (P<0.05). On day 14, electroacupuncture treatment group 2 had a significantly higher percentage than the model group (P<0.05). After electroacupuncture intervention, all groups except the blank group and the sham-operation group had increases in the expression of Fas and FasL in brain tissue, which reached the highest level on day 7 after modeling and then tended to decrease; compared with electroacupuncture treatment groups 2 and 3 and the model group, electroacupuncture treatment group 1 had significant reductions in the expression of Fas and FasL (P<0.05, P<0.01); compared with electroacupuncture treatment group 3 and the model group, electroacupuncture treatment group 2 had significant decreases in the expression of Fas and FasL (P<0.05) on day 14 after modeling; compared with the model group, electroacupuncture treatment group 3 had significant reductions in the expression of Fas and FasL in brain tissue on day 14 after modeling (P<0.05). CONCLUSION: Early electroacupuncture intervention can regulate the apoptosis receptor pathway by down-regulating Fas and FasL to exert a therapeutic effect on traumatic brain injury and help with the recovery of cognition and memory ability after traumatic brain injury.

Substrate Metabolism-Driven Assembly of High-Quality CdS xSe1- x Quantum Dots in Escherichia coli: Molecular Mechanisms and Bioimaging Application.

Biosynthesis offers opportunities for cost-effective and sustainable production of semiconductor quantum dots (QDs), but is currently restricted by poor controllability on the synthesis process, resulting from limited knowledge on the assembly mechanisms and the lack of effective control strategies. In this work, we provide molecular-level insights into the formation mechanism of biogenic QDs (Bio-QDs) and its connection with the cellular substrate metabolism in Escherichia coli. Strengthening the substrate metabolism for producing more reducing power was found to stimulate the production of several reduced thiol-containing proteins (including glutaredoxin and thioredoxin) that play key roles in Bio-QDs assembly. This effectively diverted the transformation route of the selenium (Se) and cadmium (Cd) metabolic from Cd3(PO4)2 formation to CdS xSe1- x QDs assembly, yielding fine-sized (2.0 ± 0.4 nm), high-quality Bio-QDs with quantum yield (5.2%) and fluorescence lifetime (99.19 ns) far exceeding the existing counterparts. The underlying mechanisms of Bio-QDs crystallization and development were elucidated by density functional theory calculations and molecular dynamics simulation. The resulting Bio-QDs were successfully used for bioimaging of cancer cells and tumor tissue of mice without extra modification. Our work provides fundamental knowledge on the Bio-QDs assembly mechanisms and proposes an effective, facile regulation strategy, which may inspire advances in controlled synthesis and practical applications of Bio-QDs as well as other bionanomaterials.

Manganese deception on graphene and implications in catalysis.

Heteroatom-doped metal-free graphene has been widely studied as the catalyst for the oxygen reduction reaction (ORR). Depending on the preparation method and the dopants, the ORR activity varies ranging from a two-electron to a four-electron pathway. The different literature reports are difficult to correlate due to the large variances. However, due to the potential metal contamination, the origin of the ORR activity from "metal-free" graphene remains confusing and inconclusive. Here we decipher the ORR catalytic activities of diverse architectures on graphene derived from reduced graphene oxide. High angle annular dark field scanning transmission electron microscopy, X-ray absorption near edge structure, extended X-ray absorption fine structure, and trace elemental analysis methods are employed. The mechanistic origin of ORR activity is associated with the trace manganese content and reaches its highest performance at an onset potential of 0.94 V when manganese exists as a mononuclear-centered structure within defective graphene. This study exposes the deceptive role of trace metal in formerly thought to be metal-free graphene materials. It also provides insight into the design of better-performing catalyst for ORR by underscoring the coordination chemistry possible for future single-atom catalyst materials.

Directed Biofabrication of Nanoparticles through Regulating Extracellular Electron Transfer.

Biofabrication of nanomaterials is currently constrained by a low production efficiency and poor controllability on product quality compared to chemical synthetic routes. In this work, we show an attractive new biosynthesis system to break these limitations. A directed production of selenium-containing nanoparticles in Shewanella oneidensis MR-1 cells, with fine-tuned composition and subcellular synthetic location, was achieved by modifying the extracellular electron transfer chain. By taking advantage of its untapped intracellular detoxification and synthetic power, we obtained high-purity, uniform-sized cadmium selenide nanoparticles in the cytoplasm, with the production rates and fluorescent intensities far exceeding the state-of-the-art biosystems. These findings may fundamentally change our perception of nanomaterial biosynthesis process and lead to the development of fine-controllable nanoparticles biosynthesis technologies.