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Copper deposited mesoporous silicon was fabricated by magnesiothermic reduction and electroless deposition and its electrochemical properties as an anode for lithium ion batteries were investigated. The 300–400 nm sized mesoporous Si particles were synthesized by magnesiothermic reduction of SiO2 nanospheres prepared by the Stöber method. The mesopores of Si particles were effectively decorated with Cu using Sn sensitization/Pd activation and subsequent Cu electroless deposition. The homogeneous distribution of Cu inside the mesoporous Si particles was confirmed by high resolution transmission electron microscopy images and energy dispersive spectroscopy mapping on the cross-sectional specimen prepared by a focused ion beam. The mesoporous Si–Cu nanocomposite exhibited high initial Coulombic efficiency, long cycle stability, and high rate capability, delivering a high capacity of 1569 mAh g−1 after 200 cycles at the current density of 1000 mA g−1. The improved electrochemical performance in a mesoporous Si–Cu nanocomposite was attributed to the high electrical conductivity, high Li+ ion mobility, and structural stability to restrict the aggregation and pulverization of active materials. [ABSTRACT FROM AUTHOR]

Purpose: To assess the levels of pesticide residues in commonly used vegetables in Vietnam as a reference for future monitoring. Methods: A total of 180 samples of six different fresh vegetables including watercress, mustard green, choy sum, daikon, okra, and yam were analyzed from Mekong Delta, Vietnam. Ten popular pesticides were evaluated using liquid chromatography-tandem mass spectrometry (LC-MS/MS) after extraction with a multi-residue method (QuEChERS method). Results: The results were assessed according to the maximum residue limit (MRL) provided by Codex for each pesticide in each commodity. Pesticide residues above the MRL were detected in 107 samples (59 %) and 63 samples (47 %) contained residues below the MRL. Multiple residues were present in 38.3% of the samples with two to five pesticides, and 0.6 % of samples were contaminated with more than five pesticide residues. Of the pesticides investigated, eight pesticides were detected, of which abamectin, alpha-cypermethrin, acetamiprid, chlorpyrifos- ethyl, chlorantraniliprole, fenobucarb, fipronil, and trichlorfon exceeded their MRLs. Pesticide residues were detected above MRLs in samples of watercress (14 samples), mustard green (24 samples), choy sum (25 samples), daikon (26 samples), and yam (18 samples). Chlorpyrifos-ethyl, and fipronil were detected in most of the vegetable samples (100% and 89.44%, respectively). Conclusion: The results indicate the occurrence of pesticide residues in commonly consumed vegetables in Vietnam. The need for the regular monitoring of pesticide residues and the sensitization of farmers to better pesticide safety practices, especially the need to adhere to recommended pre-harvest intervals is recommended. [ABSTRACT FROM AUTHOR]

Ni-rich layered LiNixCoyMn1-x-yO2 (LNCM) with Ni content over >90% is considered as a promising lithium ion battery (LIB) cathode, attributed by its low cost and high practical capacity. However, Ni-rich LNCM inevitably suffers rapid capacity fading at a high state of charge due to the mechanochemical breakdown; in particular, the microcrack formation has been regarded as one of the main culprits for Ni-rich layered cathode failure. To address these issues, Ni-rich layered cathodes with a textured microstructure are developed by phosphorous and boron doping. Attributed by the textured morphology, both phosphorous- and boron-doped cathodes suppress microcrack formation and show enhanced cycle stability compared to the undoped cathode. However, there exists a meaningful capacity retention difference between the doped cathodes. By adapting the various analysis techniques, it is shown that the boron-doped Ni-rich layered cathode displays better cycle stability not only by its ability to suppress microcracks during cycling but also by its primary particle morphology that is reluctant to oxygen evolution. The present work reveals that not only restraint of particle cracks but also suppression of oxygen release by developing the oxygen stable facets is important for further improvements in state-of-the-art Li ion battery Ni-rich layered cathode materials. [ABSTRACT FROM AUTHOR]