Performance degradation study of NiCo2O4-based asymmetric supercapacitors.

The performance of NiCo2O4//GO asymmetric supercapacitors was found to decline after many tests. It was found that the performance of the GO electrode was almost unchanged, while the performance of the NiCo2O4 electrode declined rapidly. Therefore, porous spherical NiCo2O4 nanoparticles were synthesized via a simple hydrothermal method. A NiCo2O4//GO asymmetric supercapacitor was made, which can be charged and discharged 3000 times in the current density of 10 A g-1. The surface morphology, crystal structure and elemental composition were characterized by X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. By comparing the surface morphology, crystal structure and elemental composition of the NiCo2O4 electrode before and after the cycle, it was found that the performance of NiCo2O4 electrode declines rapidly after the cycle due to the formation of new substances and the destruction of the crystal structure of NiCo2O4 electrode. Therefore, maintaining the stability of the crystal structure of the electrode material is an important means to ensure the stability of the performance of the supercapacitor. It provides a meaningful strategy for studying the degradation of supercapacitor electrode materials.

Cycling stability of Fe2O3 nanosheets as supercapacitor sheet electrodes enhanced by MgFe2O4 nanoparticles.

The Fe2O3 material is a common active material for supercapacitor electrodes and has received much attention due to its cheap and easy availability and high initial specific capacitance. In the present study, we prepared adhesive-free Fe2O3 sheet electrodes for supercapacitors by growing Fe2O3 material on nickel foam by hydrothermal method. The sheet electrode exhibited a high initial specific capacitance of 863 F g-1, but we found that the sheet lost its specific capacitance too quickly through cyclic stability tests. To solve this problem, Fe2O3/MgFe2O4 composites were grown on nickel foam (NF). It was found through testing that the cycling stability of the sheet electrode gradually increased as the content of MgFe2O4 material increased. When the molar ratio of Fe2O3 to MgFe2O4 material was 1 : 1, the initial specific capacitance of the sheet electrode was 815 F g-1 and the capacitance remained at 81.25% of the initial specific capacitance after 1000 cycles. The better cycling stability results from the more stable structure of the composite, the synergistic effect leading to better reversibility of the reaction.

Experimental study on the degradation mechanism of LaCoO3-based symmetric supercapacitors.

In this paper, LaCoO3 powders were prepared by the urea combustion method and used as electrode materials for supercapacitors. The effect of the potential window and the current density on the performance degradation of LaCoO3 electrodes during the cycling test was analyzed. The degradation mechanism of LaCoO3-based symmetric supercapacitors was discussed. The results of the cycling test show that: with the increase in potential window and current density, the performance degradation in the cycling test becomes more intense. The results of cyclic voltammetry tests, galvanostatic charge-discharge tests, X-ray photoelectron spectroscopy tests and KOH electrolyte concentration measurements before and after the cycling test show that the degradation of the supercapacitors is mainly caused by the occurrence and accumulation of irreversible redox reactions during the charge and discharge process, which reduces the ratio of Co2+/Co3+ and the number of oxygen vacancies.

Fluorogenic "Photoclick" Labeling and Imaging of DNA with Coumarin-Fused Tetrazole in Vivo.

Photoclickable fluorogenic probes will enable visualization of specific biomolecules with precise spatiotemporal control in their native environment. However, the fluorogenic tagging of DNA with current photocontrolled clickable probes is still challenging. Herein, we demonstrated the fast (19.5 ± 2.5 M-1 s-1) fluorogenic labeling and imaging of DNA in vitro and in vivo with rationally designed coumarin-fused tetrazoles under UV LED photoirradiation. With a water-soluble, nuclear-specific coumarin-fused tetrazole (CTz-SO3), the metabolically synthesized DNA in cultured cells was effectively labeled and visualized, without fixation, via "photoclick" reaction. Moreover, the photoclickable CTz-SO3 enabled real-time, spatially controlled imaging of DNA in live zebrafish.

SnS2/TiO2 nanohybrids chemically bonded on nitrogen-doped graphene for lithium-sulfur batteries: synergy of vacancy defects and heterostructures.

Despite their high-energy density, low cost and environmental friendliness, the commercial application of lithium-sulfur batteries (LSBs) has been plagued by their severe capacity decay during long-term cycling caused by polysulfide shuttling. Herein, we demonstrate a synergetic vacancy and heterostructure engineering strategy using a nitrogen-doped graphene/SnS2/TiO2 (denoted as NG/SnS2/TiO2) nanocomposite to enhance the electrochemical performance of LSBs. It is noted that plentiful sulfur vacancy (Vs) defects and nanosized heterojunctions are created on the NG/SnS2/TiO2 composite as proved using electron paramagnetic resonance, transmission electron microscopy and X-ray photoelectron spectroscopy, which can serve as strong adsorption and activation sites for polar polysulfide intermediates, prevent their dissolution/shuttling, and accelerate their redox reaction. The novel NG/SnS2/TiO2-S cathode delivers a high initial capacity of 1064 mA h g-1 at 0.5 C and a high capacity retention rate of 68% after 500 cycles at 0.5 C.

Ginsenoside Rg3 stereoisomers differentially inhibit vascular smooth muscle cell proliferation and migration in diabetic atherosclerosis.

Ginsenoside 20(R/S)-Rg3, as a natural peroxisome proliferator-activated receptor gamma (PPARγ) ligand, has been reported to exhibit differential biological effects. It is of great interest to understand the stereochemical selectivity of 20(R/S)-Rg3 and explore whether differential PPARγ activation by Rg3 stereoisomers, if it exists, could lead to differential physiological outcome and therapeutic effects in diabetic atherosclerosis. Here, we investigated the binding modes of 20(R/S)-Rg3 stereoisomers in the PPARγ ligand-binding domain (PPARγ-LBD) using molecular modelling and their effects on smooth muscle cell proliferation and migration induced by advanced glycation end products (AGEs). The results revealed that 20(S)-Rg3 exhibited stronger antiproliferative and antimigratory effects due to stronger PPARγ activation. To validate the in vitro results, we used a mice model with diabetic atherosclerosis and obtained that 20(S)-Rg3 markedly reduced the plaque size secondary to reducing the proliferation and migration of VSMCs, while the plaques were more stable due to improvements in other plaque compositions. The results shed light on the structural difference between Rg3 stereoisomers that can lead to significant differential physiological outcome, and the (S)-isomer seems to be the more potent isomer to be developed as a promising drug for diabetic atherosclerosis.

Formation of bicyclic polycyclic aromatic hydrocarbons (PAHs) from the reaction of a phenyl radical with cis-3-penten-1-yne.

The formation of polycyclic aromatic hydrocarbons (PAHs) on the C11H11 potential energy surface involved in the reactions of a phenyl radical (C6H5) with cis-3-penten-1-yne (cis-C1H[triple bond, length as m-dash]C2-C3H[double bond, length as m-dash]C4H-C5H3, referred to as C5H6) and its three radicals (CH[triple bond, length as m-dash]C-C[double bond, length as m-dash]CH-CH3, CH[triple bond, length as m-dash]C-CH[double bond, length as m-dash]C-CH3, and cis-CH[triple bond, length as m-dash]C-CH[double bond, length as m-dash]CH-CH2, referred to as the C3-, C4-, and C5-radicals with the same chemical components, C5H5) assisted by H atoms is investigated by performing combined density functional theory (DFT) and ab initio calculations. Five potential pathways for the formation of PAHs have been explored in detail: Pathways I-II correspond to the reaction of C6H5 with C5H6 at the C1 and C2 position, and Pathways III-V involve the reaction of C6H5 with the C3-, C4-, and C5-radicals with the assistance of H atoms. The initial association of C6H5 with C5H6 or C5H5 is found to be highly exothermic with only minor barriers (1.4-7.1 kcal mol-1), which provides a large driving force for the formation of PAHs. The hydrogen atom is beneficial for the ring enlargement and ring formation processes. The present calculations predict 9 potential PAHs, six (CS6, CS10, CS13, CS26, CS28 and CS29) of which are indicated to be energetically more favorable along Pathways I, III, IV and V at low temperature. The calculated barriers for the formation of these PAHs are around 19.2-38.0 kcal mol-1. All PAHs products could be formed at flame temperature, for the medium barriers are easily overcome in various flame conditions. The theoretical results supplement the PAH formation pathway and provide help to understand PAH growth mechanism.

Genetic polymorphisms associated with heart failure: A literature review.

OBJECTIVE: To review possible associations reported between genetic variants and the risk, therapeutic response and prognosis of heart failure. METHODS: Electronic databases (PubMed, Web of Science and CNKI) were systematically searched for relevant papers, published between January 1995 and February 2015. RESULTS: Eighty-two articles covering 29 genes and 39 polymorphisms were identified. CONCLUSION: Genetic association studies of heart failure have been highly controversial. There may be interaction or synergism of several genetic variants that together result in the ultimate pathological phenotype for heart failure.

Chirality-assisted ring-like aggregation of aß(1-40) at liquid-solid interfaces: a stereoselective two-step assembly process.

Molecular chirality is introduced at liquid-solid interfaces. A ring-like aggregation of amyloid Aß(1-40) on N-isobutyryl-L-cysteine (L-NIBC)-modified gold substrate occurs at low Aß(1-40) concentration, while D-NIBC modification only results in rod-like aggregation. Utilizing atomic force microscope controlled tip-enhanced Raman scattering, we directly observe the secondary structure information for Aß(1-40) assembly in situ at the nanoscale. D- or L-NIBC on the surface can guide parallel or nonparallel alignment of ß-hairpins through a two-step process based on electrostatic-interaction-enhanced adsorption and subsequent stereoselective recognition. Possible electrostatic interaction sites (R5 and K16) and a chiral recognition site (H14) of Aß(1-40) are proposed, which may provide insight into the understanding of this effect.

Stereoisomers ginsenosides-20(S)-Rg3 and -20(R)-Rg3 differentially induce angiogenesis through peroxisome proliferator-activated receptor-gamma.

Ginsenosides are considered the major constituents that are responsible for most of the pharmacological actions of ginseng. However, some ginsenosides exist as stereoisomeric pairs, detailed and molecular exposition based on the structural differences of ginsenoside stereoisomers has not been emphasized in most studies. Here we explore the functional differences of ginsenoside Rg3 stereoisomers on angiogenesis. In this study, we demonstrated the distinctive differential angiogenic activities of 20(S)-Rg3 and 20(R)-Rg3 stereoisomers. 20(S)-Rg3 at micromolar concentration promotes human endothelial cells proliferation, migration and tube formation in vitro, as well as ex vivo endothelial sprouting. The effects induced by 20(S)-Rg3 are significantly more potent than 20(R)-Rg3. These effects are partially mediated through the activation of AKT/ERK-eNOS signaling pathways. Moreover, knockdown of peroxisome proliferator-activated receptor-gamma (PPARγ) by specific small interference RNA abolished the 20(S)-Rg3-induced angiogenesis, indicating that PPARγ is responsible for mediating the angiogenic activity of Rg3. Using reporter gene assay, the PPARγ agonist activity of 20(S)-Rg3 has been found 10-fold higher than that of 20(R)-Rg3. Computer modeling also revealed the differential binding is due to the chiral center of 20(S)-Rg3 can form a critical hydrogen bond with Tyr473 of PPARγ ligand binding domain. The present study elucidated the differential angiogenic effects of Rg3 stereoisomers by acting as agonist of PPARγ. The results shed light on the structural difference between two ginsenoside stereoisomers that can lead to significant differential physiological outcomes which should be carefully considered in the future development of ginsenoside-based therapeutics.

Density functional theory study of geometrical structures and electronic properties of silica nanowires.

Silica nanowires are expected to possess structural diversity like bulk silica. We modeled three silica nanowires based on the side-shared two-membered rings, spiro-united two-membered rings, and three-membered rings, respectively. By performing density functional theory calculations, we studied their geometrical structures and electronic properties with and without the presence of external electric field. It is found that the stability of silica nanowires increases with length and diameter. As indicated by calculated large HOMO-LUMO gaps, silica nanowires are expected to be good insulating materials. The energy gaps, however, gradually decrease with applied electronic field and finally close, resulting in the breakdown of the insulating nanowires. Moreover, it is shown that the breakdown threshold remarkably increases with the nanowire diameter. These significant findings from the present calculations for the simplest silica nanowires will provide relevant insight into the structures and properties of much more complicated real silica nanowires.

New route for stabilizing silicon fullerenes.

Motivated by the recent synthesis of silica-coated silicon nanotubes, we here present the structural models of their counterparts, silica-coated silicon fullerenes, which can be considered as arising from a structurally stable building block, Si3O2. By performing density functional theory calculations we show that the silica-coated silicon fullerenes possess high energetic and thermal stabilities and point group symmetries as well as large energy gaps. The present results indicate that coating silica on silicon clusters would be a new way for stabilizing silicon fullerenes, which is expected to find potential allocations in nanotechnology.