Singly or doubly bonded polynitrogen compounds can decompose to dinitrogen (N) with an extremely large energy release. This makes them attractive as potential explosives or propellants, but also challenging to produce in a stable form. Polynitrogen materials containing nitrogen as the only element exist in the form of high-pressure polymeric phases, but under ambient conditions even metastability is realized only in the presence of other elements that provide stabilization. An early example is the molecule phenylpentazole, with a five-membered all-nitrogen ring, which was first reported in the 1900s and characterized in the 1950s. Salts containing the azide anion (N) or pentazenium cation (N) are also known, with compounds containing the pentazole anion, cyclo-N, a more recent addition. Very recently, a bulk material containing this species was reported and then used to prepare the first example of a solid-state metal-N complex. Here we report the synthesis and characterization of five metal pentazolate hydrate complexes [Na(HO)(N)]·2HO, [M(HO)(N)]·4HO (M = Mn, Fe and Co) and [Mg(HO)(N)]·4HO that, with the exception of the Co complex, exhibit good thermal stability with onset decomposition temperatures greater than 100 °C. For this series we find that the N ion can coordinate to the metal cation through either ionic or covalent interactions, and is stabilized through hydrogen-bonding interactions with water. Given their energetic properties and stability, pentazole-metal complexes might potentially serve as a new class of high-energy density materials or enable the development of such materials containing only nitrogen. We also anticipate that the adaptability of the N ion in terms of its bonding interactions will enable the exploration of inorganic nitrogen analogues of metallocenes and other unusual polynitrogen complexes.

We report epitaxial crystallization of polyethylene (PE) on reduced graphene oxide (RGO) nanosheets via a controlled solution crystallization method. Polarized light microscopy, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy were used to investigate morphology of RGO-induced PE crystals. The PE edge-on crystals formed from randomly distributed rodlike nuclei on the basal plane of RGO nanosheets and further grew into larger lamellae with an average dimension of a few hundreds of nanometers. Selected area electron diffraction (SAED) pattern revealed that the c-axis of polymer chain is parallel to the basal plane of the RGO nanosheets. PE/RGO nanocomposites (PGNs) with different RGO loadings were fabricated through solution crystallization/precipitation using the PE-decorated RGO hybrid as the precursor. Both nonisothermal and isothermal crystallization behaviors of PGNs were studied using differential scanning calorimetry (DSC). Crystallization kinetics of PGNs was substantially accelerated in the presence of 2D RGO nanosheets. Dramatic improvement of thermal stability was found for PE in the presence of a small amount of RGO nanosheets.

Polymer electrolytes have attracted intensive attention due to their potential applications in all-solid-state lithium batteries. Ion conduction in this system is generally considered to be confined in the amorphous polymer/ion phase, where segmental relaxation of the polymer above glass transition temperature facilitates ion transport. In this article, we show quantitatively that the effect of polymer crystallization on ion transport is twofold: structural (tortuosity) and dynamic (tethered chain confinement). We decouple these two effects by designing and fabricating a model polymer single crystal electrolyte system with controlled crystal structure, size, crystallinity, and orientation. Ion conduction is confined within the chain fold region and guided by the crystalline lamellae. We show that, at low content, due to the tortuosity effect, the in-plane conductivity is 2000 times greater than through-plane one. Contradictory to the general view, the dynamic effect is negligible at moderate ion contents. Our results suggest that semicrystalline polymer is a valid system for practical polymer electrolytes design.

BackgroundLactobacillus plantarum is a plant-associated bacterial species but it has also been found in human, mouse and porcine gastrointestinal tracts. It can ferment a broad spectrum of plant carbohydrates; it is tolerant of bile salts and low pH, and it has antagonistic potential against intestinal pathogens. However, experiments reporting the use of L. plantarum as a probiotic are limited. In this study, the effects of L. plantarum ZJ316 isolated from infant fecal samples on pig growth and pork quality were investigated.ResultsOne hundred and fifty newly weaned pigs were selected randomly and divided into five groups. Group 1 was fed a diet supplemented with the antibiotic mequindox; Groups 2, 3 and 4 were fed a diet supplemented with L. plantarum and no antibiotic; and Group 5 was fed a mixture of mequindox and L. plantarum. After a 60 days initial treatment, samples were collected for evaluation. The results showed that, the L. plantarum ZJ316 has probiotic effects on pig growth and that these effects are dose dependent. The effects of a dose of 1 × 109 CFU/d were more pronounced than those of a dose of 5 × 109 CFU/d or 1 × 1010 CFU/d. In Group 2 (1 × 109 CFU/d), the diarrhea (p = 0.000) and mortality rates (p = 0.448) were lower than in antibiotic-treated pigs (Group 1), and the daily weight gain (p = 0.001) and food conversion ratios were better (p = 0.005). Improved pork quality was associated with Lactobacillus treatment. pH (45 min, p = 0.020), hardness (p = 0.000), stickiness (p = 0.044), chewiness (p = 0.000), gumminess (p = 0.000) and restoring force (p = 0.004) were all significantly improved in Lactobacillus-treated pigs (Group 2). Although we found that L. plantarum exerted probiotic effects on pig growth and pork quality, the mechanisms underlying its action require further study. Polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the gut bacterial communities in Lactobacillus- and antibiotic-treated pigs were very similar and the quantity of L. plantarum ZJ316 was below the detection limits of DGGE-band sequencing. The concentration of short-chain fatty acids in Lactobacillus- and antibiotic-treated fecal samples were not significantly different (p = 0.086). However, the villus height of ilea (p = 0.003), jejuna (p = 0.000) and duodena (p = 0.036) were found to be significantly improved by Lactobacillus treatment.ConclusionL. plantarum ZJ316 was found to have probiotic effects, improving pig growth and pork quality. The probiotic mechanism might not involve L. plantarum colonization and alteration of the gut bacterial community. Rather, it might be related to the inhibition of the growth of opportunistic pathogens and promotion of increased villus height.

Adsorption and thermal decomposition of alkanethiols (RSH, R ) CH 3 , C 2 H 5 , and C 4 H 9 ) on a Cu(110) surface have been studied by means of temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy (XPS) with synchrotron radiation. At a small coverage, CH 3 SH and C 2 H 5 SH dissociate to form surface thiolates and hydrogen, whereas C 4 H 9 SH adsorbs molecularly on the surface at 100 K; adsorbed C 4 H 9 SH begins to deprotonate at ∼170 K. All of these alkanethiolates can decompose to evolve hydrocarbon via scission of the C-S bond, resulting in deposition of sulfur on the surface. CH 3 generated from CH 3 S reacts with surface hydrogen to evolve CH 4 , but at a large coverage can also undergo coupling to form C 2 H 6 . The thermal reaction of surface C 2 H 5 formed from C 2 H 5 S produces C 2 H 6 through hydrogenation and C 2 H 4 through β-hydride elimination, the latter with desorption of H 2 ; the ratio of products C 2 H 4 and C 2 H 6 varies with the adsorption site of surface C 2 H 5 S. The C 4 H 9 group of surface C 4 H 9 S undergoes exclusively elimination of β-hydride to form C 4 H 8 . To a small extent the alkyl moiety also undergoes dehydrogenation, resulting in deposition of carbon on the surface. Three CH 4 desorption states are proposed to correspond to CH 3 S intermediates with distinct adsorption sites after decomposition of CH 3 SH, whereas two C 2 H 5 S sites and one C 4 H 9 S site are proposed for cases of C 2 H 5 SH and C 4 H 9 SH, respectively. The distribution of desorption products depends on the nature of the adsorption site of a particular alkanethiolate.