Significant efforts have been made in improving the hydrogen evolution reaction (HER) catalytic activity in transition metal dichalcogenides (TMDs), which are promising nonprecious catalysts. However, previous attempts have exploited possible solutions to activate the inert basal plane, with little improvement. Among them, the most successful modification requires a careful manipulation of vacancy concentration and strain simultaneously. To fully realize the promise of TMD catalysts for HER in an easier and more effective way, a new means in tuning the HER catalytic activity is needed. Herein, we propose exploiting the inherent structural asymmetry in the recently synthesized family of Janus TMDs as a new means to stimulate HER activity. We report a density functional theory (DFT) study of various Janus TMD monolayers as HER catalysts, and identify the WSSe system as a promising candidate, where the basal plane can be activated without large applied tensile strains and in the absence of significant density of vacancies. We predict that it is possible to realize a strain-free Janus TMD-based catalyst that can readily provide promising intrinsic HER catalytic performance. The calculated density of states and electronic structures reveal that the introduction of in-gap states and a shift in the Fermi level in hydrogen adsorbed systems due to Janus asymmetry is the origin of enhanced HER activity. Our results should pave the way to design high-performance and easy-accessible TMD-based HER catalysts.

Here, we reported that sulfur vacancy-rich O-doped 1T-MoS 2 nanosheets (denoted as SV-1T-MoS 2 ) can surpass the activity of Pt as cocatalysts to assist in the photocatalytic nitrogen fixation of CdS nanorods. SV-1T-MoS 2 cocatalysts exhibit sulfur vacancies, O-doping, more metallic 1T phase, and high electronic conductivity, thus leading to the exposure of more active edge sites, high Brunauer−Emmett−Teller surface area, enhanced visible light absorption, and improved electron separation and transfer, which are beneficial for photocatalytic nitrogen fixation. Consequently, the optimized 30 wt % SV-1T-MoS 2 -/CdS composites exhibit an outstanding nitrogen fixation rate of 8220.83 μmol L −1 h −1 g −1 and long-term stability under simulated solar light irradiation, significantly higher than pure CdS nanorods, CdS−Pt (0.1 wt %), and 30 wt % 1T-MoS 2 /CdS composites. The catalytic mechanism of photocatalytic nitrogen fixation on SV-1T-MoS 2 is discussed by density functional theory calculations.

Summary Biogenic amines are formed from precursor amino acids, mainly by the microbial decarboxylation. The presence of these compounds plays a vital role in oenology because high amounts of them can lead to health problems. Thus, the origin, detection, and quantity of biogenic amines in wine are extremely important for winemaking. This study, focusing on the articles of latest 5 years, not only reviews the analytical methods used for the determination of biogenic amines but also describes the source of biogenic amines from the perspective of microbiological and oenological factors and summarises the strategies for the degradation of amines. The information presented in this review is important to alert about the inadequate quality of wine products, and efforts from the entire productive chain and the government are required to attain consumer safety.

ObjectiveThe gastrointestinal tract of sheep contain complex microbial communities that influence numerous aspects of the sheep’s health and development. The objective of this study was to analyze the composition and diversity of the microbiota in the gastrointestinal tract sections (rumen, reticulum, omasum, abomasum, duodenum, jejunum, ileum, cecum, colon, and rectum) of sheep.MethodsThis analysis was performed by 454 pyrosequencing using the V3-V6 region of the 16S rRNA genes. Samples were collected from five healthy, small tailed Han sheep aged 10 months, obtained at market. The bacterial composition of sheep gastrointestinal microbiota was investigated at the phylum, class, order, family, genus, and species levels.ResultsThe dominant bacterial phyla in the entire gastrointestinal sections were Firmicutes, Bacteroidetes, and Proteobacteria. In the stomach, the three most dominant genera in the sheep were Prevotella, unclassified Lachnospiraceae, and Butyrivibrio. In the small intestine, the three most dominant genera in the sheep were Escherichia, unclassified Lachnospiraceae, and Ruminococcus. In the large intestine, the three most dominant genera in the sheep were Ruminococcus, unclassified Ruminococcaceae, and Prevotella. R. flavefaciens, B. fibrisolvens, and S. ruminantium were three most dominant species in the sheep gastrointestinal tract. Principal Coordinates Analysis showed that the microbial communities from each gastrointestinal section could be separated into three groups according to similarity of community composition: stomach (rumen, reticulum, omasum, and abomasum), small intestine (duodenum, jejunum, and ileum), and large intestine (cecum, colon, and rectum).ConclusionThis is the first study to characterize the entire gastrointestinal microbiota in sheep by use of 16S rRNA gene amplicon pyrosequencing, expanding our knowledge of the gastrointestinal bacterial community of sheep.

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