Manipulation of the MoO2/MoSe2 Heterointerface Boosting High Rate and Durability for Sodium/Potassium Storage.

The main challenge for sodium/potassium ion storage is to find the suitable host materials to accommodate the larger-sized Na+/K+ and conquer the sluggish chemical kinetics. Herein, by selenation of polyoxometalate in electrospinning fiber, a novel MoO2/MoSe2 heterostructure embedded in one-dimensional (1D) N,P-doped carbon nanofiber (MoO2/MoSe2@NPC) is rationally constructed to show distinct enhancement of rate performance and cycle life for sodium ion batteries (SIBs) and potassium ion batteries (PIBs). The 1D skeleton of MoO2/MoSe2@NPC decreases the diffusion pathway of Na+/K+, and the doping of N/P heteroatoms in carbon fiber creates abundant active sites and provides good reachability for Na+/K+ transportation. MoSe2 nanosheets grow in the bulk phase of MoO2 via in situ local phase transformation to achieve effective and firm heterointerfaces. Especially, the exposure extent of heterointerfaces can be controlled by treatment temperature during the preparation process, and the optimized heterointerfaces result in an ideal synergic effect between MoO2 and MoSe2. DFT calculations confirm that the internal electric field in the heterogeneous interface guides the electron transfer from MoO2 to MoSe2, combined with strong adsorption capacity toward sodium/potassium, facilitating ion/electron transfer kinetics. It is confirmed that the MoO2/MoSe2@NPC anode for SIBs delivers 382 mA h g-1 under 0.1 A g-1 upon 200 cycles; meanwhile, a reversible capacity of 266 mA h g-1 is maintained even under 2 A g-1 after 2000 cycles. For PIBs, it can reach up to 216 mA h g-1 in the 200th cycle and still retain 125 mA h g-1 after 2000 cycles under 1 A g-1. This study opens up a new interface manipulation strategy for the design of anode materials to boost fast Na+/K+ storage kinetics.

Graphene-supported polyoxometalate entrapped in a MIL-88A network with highly efficient conversion of polysulfides in Li-S batteries.

It has been demonstrated that polyoxometalates (POMs) have strong anchoring abilities with efficient catalysis of lithium polysulfides (LiPSs). However, the severe aggregation that buries the effective active sites of POMs along with poor electrical conductivity limits the practical application of POMs in lithium sulfur batteries (LSBs). In our strategy, we utilized reduced graphene oxide (rGO) to support a POM catalyst entrapped in a MIL-88A(FeCo) network with a hollow shell skeleton as the sulfur host material. H4PW11VO40 (PW11V) with optimal vanadium atom implantation ensures the ruggedness and integrity of the hollow structure, which is conducive to achieving high sulfur loading as well as accommodating the volume change of the sulfur cathode during the charging and discharging process. Importantly, PW11V can capture polysulfides through firm chemical adsorption and accelerate redox reactions of LiPS conversion by effective electrochemical catalysis. Furthermore, the satisfactory electrical conductivity of rGO provides access for electrons to reach the interface of PW11V and polysulfides and trigger Li-S conversion reactions. Thus, the constructed PW11V-based sulfur cathode exhibited a superior specific capacity of 905 mA h g-1 after 100 cycles under 0.2 C and long cycling life with a capacity recession rate of 0.046% for each cycle upon 500 cycles under 3 C. This research reveals the effect of vanadium atom substitution of POMs on the cycling performance of a sulfur cathode and affords insight for developing high-performance LSBs.

Effect of dietary γ-aminobutyric acid on laying performance, egg quality, immune activity and endocrine hormone in heat-stressed Roman hens.

This study was conducted to evaluate the effect of γ-aminobutyric acid (GABA) on laying performance, egg quality, digestive enzyme activity, hormone level and immune activities in Roman hens under heat stress. Roman hens (320 days old) were fed with 0, 25, 50, 75 and 100 mg/kg GABA, respectively during a 60-day experiment. Compared with control, supplementation of 50 mg/kg GABA improved the laying performance and egg quality by significantly increasing egg production, average egg weight and shell strength (P < 0.05), while decreasing the feed-egg ratio and cholesterol level. Anti-oxidation activity was improved by significantly increasing the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), but decreasing malondialdehyde level in serum (P < 0.05), while significantly increasing the glucose and total protein (TP) level, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E(2) ), insulin, triiodothyronine (T(3) ) and free triiodothyronine (FT(3) ) levels, and IgG, IgA and complement (C3)activity in serum (P < 0.05). The results indicated that oral GABA improved laying performance and physical condition mainly by modulating hormone secretion, enhancing anti-oxidation and immune activity, and maintaining electrolyte balance. Fifty mg/kg was the optimum level for laying hens under heat stress in the present study.

[Preparative purification and characterization of [Dha7] microcystin RR].

One variant of microcystins was isolated and purified with cyanobacteria natural bloom as the starting material, which was collected in Dianchi Lake, China. The separation protocol involved extraction of cyanobacterial cells by 75% aqueous methanol, isolation by reversed-phase flash chromatography, and purification by reversed-phase semipreparative HPLC. The structure and purity of purified microcystin was identified with electrospray ionization mass spectrometry, UV spectrophotometer, and analytical HPLC. The purified microcystin was assigned as [Dha7]MCRR (purity > 95%), which was a demethylated variant of MCRR. The structure of purified microcystin was identified as cyclo-(Ala-Arg-MeAsp-Arg-Adda-Glu-Dha) with molecular weight of 1023. There was a maximum absorbance at 239 nm in its UV spectrum (200-300 nm). This variant of microcystins occurred frequently, and sometimes could become the main variant in waterbloom from Dianchi Lake.