The effect of nanolayer AlF<Subscript>3</Subscript> coating on LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cycle life in high temperature for lithium secondary batteries

The surface of the spinel LiMn₂O₄ was coated with AlF₃ by a chemical process to improve its electrochemical performance at high temperatures. The morphology and structure of the original and AlF₃-coated LiMn₂O₄ samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM). All the samples exhibited a pure cubic spinel structure without any impurities in the XRD patterns. It was found that the surfaces of the original LiMn₂O₄ samples were covered with a nanolayer AlF₃ after the treatment. The charge/discharge of the materials were carried at 220 mA/g in the range of 3.0 and 4.4 V at 55°C. While the original LiMn₂O₄ showed 17.8% capacity loss in 50 cycles at 55°C, the AlF₃-coated LiMn₂O₄ (118.1 mA h/g) showed only 3.4% loss of the initial capacity (122.3 mA h/g) at 55°C. It is obvious that the improvement in cycling performance of the coated-LiMn₂O₄ electrode at 55°C is attributed to the presence of AlF₃ on the surface of LiMn₂O₄. Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 7, pp. 817–819. The article is published in the original     

Fabrication of a high-strength hydrogel with an interpenetrating network structure

Hydrogels have potential applications in many fields, but the poor mechanical strength has limited their further development. In this article, we designed a high-strength hydrogel with an interpenetrating network (IPN) structure from polyacrylamide (PAM) and poly(vinyl alcohol) (PVA). Synthesis parameters, such as PVA/AM mass ratio, crosslinker dosage and elongation time were carried out for high tensile strength and elongation. The results showed that chemical crosslinking, physical entanglement and PVA precipitates were the dominant parameters for the improvement of mechanical properties. The PVA structure transferred from crystal to amorphous due to intermolecular and intramolecular interactions (such as hydrogen bond and self-crosslinking). PVA precipitates scatterred in the brittle PAM matrix homogeneously which dispersed the applied stress and improved the hydrogel toughness. The tensile strength and elongation were extremely high, they were 2.4 MPa and 3100%, respectively. The simple method is versatile in synthesizing high-strength IPN hydrogels using many kinds of polymer species.     

Capping nanoparticles with graphene quantum dots for enhanced thermoelectric performance

Graphene quantum dots (GQDs) are shown to serve as phase transfer agents to transfer various types of nanoparticles (NPs) from non-polar to polar solvents. Thorough characterization of the NPs proves complete native ligand exchange. Pellets of this GQD–NP composite show that the GQDs limit the crystal size during spark plasma sintering, yielding enhanced thermoelectric performance compared with NPs exchanged with inorganic ions. A photoluminescence study of the GQD–NP composite also suggests energy transfer from GQDs to NPs.     

Tetraphenylpyrazine-based AIEgens: facile preparation and tunable light emission

Research on aggregation-induced emission (AIE) has been a hot topic. Due to enthusiastic efforts by many researchers, hundreds of AIE luminogens (AIEgens) have been generated which were mainly based on archetypal silole, tetraphenylethene, distyrylanthracene, triphenylethene, and tetraphenyl-1,4-butadiene, etc. To enlarge the family of AIEgens and to enrich their functions, new AIEgens are in high demand. In this work, we report a new kind of AIEgen based on tetraphenylpyrazine (TPP), which could be readily prepared under mild reaction conditions. Furthermore, we show that the TPP derivatives possess a good thermal stability and their emission could be fine-tuned by varying the substituents on their phenyl rings. It is anticipated that TPP derivatives could serve as a new type of widely utilized AIEgen, based on their facile preparation, good thermo-, photo- and chemostabilities, and efficient emission.     

Aggregation-induced emission of siloles

Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure–property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.     

Cytotoxic triterpenoid saponins from Ardisia pusilla

A new triterpenoid saponin,3-O-{β-D-xylopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)-[β-D-ghcopyranosyl-(1→2)]-α-L-arabinopyranosyl }-3β,16α,28α-trihydroxy-1313,28-epoxy-oleanan-30-al(ardipusilloside Ⅲ,1),together with two known sapo-nins,ardisiacrispins A(2)and B(3),were isolated from the whole plants ofArdisia pusilla A.DC.Their structures were elucidated by extensive spectral analysis and chemical evidences.Saponins 1 and 3 exhibited significant cytotoxicity against human glioblastoma U251MG cells.     

A simple method for fabrication of sole composition nickel hexacyanoferrate modified electrode and its application

Nickel hexacyanoferrate film modified gold electrode was prepared by a simple chemical deposition procedure from a fresh prepared solution containing ferricyanide, Ni²⁺, and sodium nitrate. The resultant films have solo composition and are significantly stable as compared to the electrochemically deposited NiHCF films. For different concentrations of Na⁺ in the solution, the formal potential values of NiHCF shift according to the Nernstian behavior with a slope of 48 mV in the range of 10⁻⁴ to 1.0 M. The NiHCF film was also used for the electrocatalytic oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry increased with the ascorbic acid concentration. At a fixed potential under hydrodynamic conditions, the calibration plot was linear over the ascorbic acid concentration range 0.1-12 mM.     

卟啉－苝酰亚胺分子阵列的合成及应用进展

由于卟啉与苝酰亚胺基元之间存在高效的能量转移或电子转移过程, 卟啉-苝酰亚胺分子阵列表现出优良的光电性能, 在有机分子器件、有机太阳能电池和光收集材料等高新技术领域展示出广阔的应用前景. 综述了近十几年来卟啉-苝酰亚胺分子阵列的合成及应用研究进展, 并展望了其发展前景.     

高效液相色谱法同时测定稻田中苄嘧磺隆和苯噻酰草胺残留

建立了同时测定稻田(稻田土壤、水和植株)中苄嘧磺隆和苯噻酰草胺残留量的高效液相色谱(HPLC)分析方法。稻田水样品用二氯甲烷直接萃取;稻田土壤样品用碱性乙腈-二氯甲烷(1:1, v/v)混合液直接提取;水稻植株样品用碱性二氯甲烷提取后,二氯甲烷提取液经弗罗里硅土柱净化。上述样品溶液采用C18不锈钢色谱柱(150 mm×4.6 mm, 5 μm)分离,流动相为水-甲醇(30:70, v/v),流速为0.5 mL/min,柱温为30 ℃,紫外检测波长为238 nm,外标法定量。苄嘧磺隆和苯噻酰草胺在0.05～5.00 mg/L范围内的线性关系均很好(r＞0.9999)。在稻田水、土壤和水稻植株中添加3个水平(0.05, 0.10, 1.00 mg/kg)的苄嘧磺隆和苯噻酰草胺,两者的回收率均在85.39%～113.33%之间,相对标准偏差为0.91%～10.24%。这表明该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求。     

The skeletal rearrangement of gold- and platinum-catalyzed cycloisomerization of cis-4,6-dien-1-yn-3-ols: pinacol rearrangement and formation of bicyclo[4.1.0]heptenone and reorganized styrene derivatives

With gold and platinum catalysts, cis-4,6-dien-1-yn-3-ols undergo cycloisomerizations that enable structural reorganization of cyclized products chemoselectively. The AuCl3-catalyzed cyclizations of 6-substituted cis-4,6-dien-1-yn-3-ols proceeded via a 6-exo-dig pathway to give allyl cations, which subsequently undergo a pinacol rearrangement to produce reorganized cyclopentenyl aldehyde products. Using chiral alcohol substrates, such cyclizations proceed with reasonable chirality transfer. In the PtCl2-catalyzed cyclization of 7,7-disubstituted cis-4,6-dien-1-yn-3-ols, we obtained exclusively either bicyclo[4.1.0]heptenones or reorganized styrene products with varied substrate structures. On the basis of the chemoselectivity/structure relationship, we propose that bicyclo[4.1.0]heptenone products result from 6-endo-dig cyclization, whereas reorganized styrene products are derived from the 5-exo-dig pathway. This proposed mechanism is supported by theoretic calculations.