A design of MnO-CNT@C3N4 cathodes for high-performance aqueous zinc-ion batteries.

Manganese oxides have been regarded as one of the most promising candidates in rechargeable aqueous zinc ion batteries due to their high specific capacity, high operating voltage, low cost and no-toxicity. Nevertheless, the grievous dissolution of manganese and the sluggish Zn2+ ions diffusion kinetics deteriorate the long cycling stability and the rate performance. Herein, we propose a combination of hydrothermal and thermal treatment strategy to design a MnO-CNT@C3N4 composite cathode material where MnO cubes are coated by carbon nanotubes (CNTs) and C3N4. Owing to the enhanced conductivity by CNTs and the alleviation of the dissolution of Mn2+ from the active material by C3N4, the optimized MnO-CNT@C3N4 exhibits an excellent rate performance (101 mAh g-1 at a large current density of 3 A g-1) and a high capacity (209 mAh g-1 at a current density of 0.8 A g-1), which is much better than its MnO counterpart. The energy storge mechanism of MnO-CNT@C3N4 is confirmed to be the co-insertion of H+/Zn2+. The present work provides a viable strategy for the design of advanced cathodes for high-performance zinc ion batteries.

LiNbO3 dynamic memristors for reservoir computing.

Information in conventional digital computing platforms is encoded in the steady states of transistors and processed in a quasi-static way. Memristors are a class of emerging devices that naturally embody dynamics through their internal electrophyiscal processes, enabling nonconventional computing paradigms with enhanced capability and energy efficiency, such as reservoir computing. Here, we report on a dynamic memristor based on LiNbO3. The device has nonlinear I-V characteristics and exhibits short-term memory, suitable for application in reservoir computing. By time multiplexing, a single device can serve as a reservoir with rich dynamics which used to require a large number of interconnected nodes. The collective states of five memristors after the application of trains of pulses to the respective memristors are unique for each combination of pulse patterns, which is suitable for sequence data classification, as demonstrated in a 5 × 4 digit image recognition task. This work broadens the spectrum of memristive materials for neuromorphic computing.

[Effect of continuous flushing out of root canal on fluid replacement in root canal during mechanical preparation using Ni-Ti instrument].

PURPOSE: To evaluate the effect of continuous flushing out of the canal on fluid exchange in the root canal during mechanical preparation. METHODS: Sixty resin blocks with standardized root canals were divided into 5 experimental groups according to whether continuous flushing was performed during mechanical preparation. Injecting pure black ink into the root canals before each file preparation，the liquid exchange was calculated by measuring the absorbance value of the remaining liquid after performing different preparation and irrigation schemes. Meanwhile, computational fluid dynamics model was established which simulated the flow field in the canal when the file moved up-and-down. SPSS 19.0 software package was used for statistical analysis of the data. RESULTS: The absorbance value of the remaining fluid in the root canal of the three groups in which continuous flushing was performed during mechanical preparation differed significantly from the group without continuous flushing(P<0.05), but no significant difference among the three groups (P>0.05). Computer simulation confirmed that the "efficient regurgitation area" existed in the middle part of the root canal and fluid could be gradually transported to the apical area by the file's up-and-down motion. CONCLUSIONS: Continuous flushing out of the canal during mechanical preparation can replace the original solution in the canal partly, which is beneficial to conventional irrigation for cleaning of the root canal.

Twist-angle-controlled neutral exciton annihilation in WS2 homostructures.

Exciton-exciton annihilation (EEA), as typical nonradiative recombination, plays an unpopular role in semiconductors. The nonradiative process significantly reduces the quantum yield of photoluminescence, which substantially inhibits the maximum efficiency of optoelectronic devices. Recently, laser irradiation, introducing defects and applying strain have become effective means to restrain EEA in two-dimensional (2D) transition metal dichalcogenides (TMDCs). However, these methods destroy the atomic structure of 2D materials and limit their practical applications. Fortunately, twisted structures are expected to validly suppress EEA through excellent interface quality. Here, we develop a non-destructive way to control EEA in WS2 homostructures by changing the interlayer twist angle, and systematically study the effect of interlayer twist angle on EEA, using fluorescence lifetime imaging measurement (FLIM) technology. Due to the large moiré potential at a small interlayer twist angle, the diffusion of excitons is hindered, and the EEA rate decreases from 1.01 × 10-1 cm2 s-1 in a 9° twisted WS2 homostructure to 4.26 × 10-2 cm2 s-1 in a 1° twisted WS2 homostructure. The results reveal the important role of the interlayer twist angle and EEA interaction in high photoluminescence quantum yield optoelectronic devices based on TMDC homostructures.