Zwitterion Intercalated Manganese Dioxide Nanosheets as High-Performance Cathode Materials for Aqueous Zinc Ion Batteries.

In this study, a novel approach is introduced to address the challenges associated with structural instability and sluggish reaction kinetics of δ-MnO2 in aqueous zinc ion batteries. By leveraging zwitterionic betaine (Bet) for intercalation, a departure from traditional cation intercalation methods, Bet-intercalated MnO2 (MnO2-Bet) is synthesized. The positively charged quaternary ammonium groups in Bet form strong electrostatic interactions with the negatively charged oxygen atoms in the δ-MnO2 layers, enhancing structural stability and preventing layer collapse. Concurrently, the negatively charged carboxylate groups in Bet facilitate the rapid diffusion of H+/Zn2+ ions through their interactions, thus improving reaction kinetics. The resulting MnO2-Bet cathode demonstrates high specific capacity, excellent rate capability, fast reaction kinetics, and extended cycle life. This dual-function intercalation strategy significantly optimizes the electrochemical performance of δ-MnO2, establishing it as a promising cathode material for advanced aqueous zinc ion batteries.

MnO2 superstructure cathode with boosted zinc ion intercalation for aqueous zinc ion batteries.

The simultaneous intercalation of protons and Zn2+ ions in aqueous electrolytes presents a significant obstacle to the widespread adoption of aqueous zinc ion batteries (AZIBs) for large-scale use, a challenge that has yet to be overcome. To address this, we have developed a MnO2/tetramethylammonium (TMA) superstructure with an enlarged interlayer spacing, designed specifically to control H+/Zn2+ co-intercalation in AZIBs. Within this superstructure, the pre-intercalated TMA+ ions work as spacers to stabilize the layered structure of MnO2 cathodes and expand the interlayer spacing substantially by 28 % to 0.92 nm. Evidence from in operando pH measurements, in operando synchrotron X-ray diffraction, and X-ray absorption spectroscopy shows that the enlarged interlayer spacing facilitates the diffusion and intercalation of Zn2+ ions (which have a large ionic radius) into the MnO2 cathodes. This spacing also helps suppress the competing H+ intercalation and the formation of detrimental Zn4(OH)6SO4·5H2O, thereby enhancing the structural stability of MnO2. As a result, enhanced Zn2+ storage properties, including excellent capacity and long cycle stability, are achieved.

Asymmetric Transamination of α-Keto Acids Catalyzed by Chiral Pyridoxamines.

A new type of novel chiral pyridoxamines 3a-g containing a side chain has been developed. The pyridoxamines displayed catalytic activity and promising enantioselectivity in biomimetic asymmetric transamination of α-keto acids, to give various α-amino acids in 47-90% yields with up to 87% ee's under very mild conditions. An interesting effect of the side chain on enantioselectivity was observed in the reaction.

Separation and determination of triclosan and bisphenol A in water, beverage, and urine samples by dispersive liquid-liquid microextraction combined with capillary zone electrophoresis-UV detection.

Dispersive liquid-liquid microextraction combined with capillary zone electrophoresis-UV detection was developed for analyzing triclosan (TCS) and bisphenol A (BPA) in water, beverage, and urine samples. The factors influencing microextraction efficiencies, such as the kind and volume of extraction and dispersive solvent, the extraction time, and the salt effect, were optimized. A background electrolyte composed of 8 mM sodium tetraborate at pH 9.8 was used as the running buffer. Detection was performed at 214 nm. Under the optimum conditions (sample volume, 5.0 mL; extraction solvent, tetrachloroethane, 22.0 microL; dispersive solvent, tetrahydrofuran, 1.0 mL; extraction time, fewer than 5 s; and without salt addition), the enrichment factors were 110.2 and 82.0 for TCS and BPA, respectively. The linear range was 0.02-2 microg/mL with correlation coefficients of 0.9966-0.9969. LODs were in the range of 4.0-8.0 ng/mL. The environmental water, beverage, and urine samples (at spiking levels of 0.1 and 0.4 microg/mL) were successfully analyzed by the proposed method; the recoveries compared to previous methods were in the range of 81.2-103.3%. As a result, this method can be successfully applied for the rapid and convenient determination of TCS and BPA in water, beverage, and urine samples.

Effect of BDE-209 on glutathione system in Carassius auratus.

In this study, the oxidative stress induced by deca-polybromodiphenyl ether (BDE-209) was investigated in livers of Carassius auratus. Six groups of fish were exposed to blank and 0, 0.004, 0.04, 0.4, 4 µM BDE-209 (in 0.1% DMSO) for 1, 4, 7, 10, 13 d, respectively. The following oxidative stress markers were analyzed: reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidases (GPx) and glutathione S-transferases (GSTs). No significant difference was observed in the content of GSH over the whole period of exposure (p > 0.05). Increases in hepatic GR and GPx activities were in concomitant with the decrease in GST activity. GR activity was induced after 1 d exposure, while GPx activity reached maximum at 4 d after exposure to 0.04 µM BDE-209 and GST activity was significantly inhibited at 7-13 d in all the treatment groups (0.004-4 µM group).

Dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry determination of polychlorinated biphenyls and polybrominated diphenyl ethers in milk.

An effective multi-residue pretreatment technique, solid-phase extraction (SPE) combined with dispersive liquid-liquid microextraction (DLLME), was proposed for the trace analysis of 14 polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in milk samples using gas chromatography-mass spectrometry (GC-MS). Interesting analytes in milk samples were extracted with hexane after protein precipitation. The hexane extracts were loaded on an LC-Florisil column to isolate analytes from the milk matrix. The elutes were dried and dissolved in acetone, which was used as the disperser solvent in subsequent DLLME procedures. The effects of several important parameters on the extraction efficiency were evaluated. Under the optimized conditions, a linear relationship was obtained in the range of 0.02-10.00 µg/L (PCBs) and 0.5-100.00 µg/L (PBDEs). The LOD (S/N=3) and relative standard deviations (RSDs, n=5) for all analytes were 0.01-0.4 µg/L and 0.6-8.5%, respectively. The recoveries of the standards added to raw bovine milk samples were 74.0-131.8%, and the repeatabilities of the analysis results were 1.12-17.41%. This method has been successfully applied to estimating PCBs and PBDEs in milk samples.