Synthesis and applications of cyano‐vinylene‐based polymers containing cyclopentadithiophene and dithienosilole units for photovoltaic cells

Two β‐cyano‐thiophenevinylene‐based polymers containing cyclopentadithiophene ( CPDT‐CN ) and dithienosilole ( DTS‐CN ) units were synthesized via Stille coupling reaction with Pd(PPh₃)₄ as a catalyst. The effects of the bridged atoms (C and Si) and cyano‐vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic properties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about ?5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about ?3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of electron‐donor polymers ( CPDT‐CN and DTS‐CN ) blended with an electron‐acceptor, that is, [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) or [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM), in different weight ratios were explored under 100 mW/cm² of AM 1.5 white‐light illumination. The PSC device based on DTS‐CN: PC₇₁BM (1:2 w/w) exhibited a best power conversion efficiency (PCE) value of 2.25% with V_oc = 0.74 V, J_sc = 8.39 mA/cm², and FF = 0.36. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Preparation and characterization of flame‐retardant lamellar Mg(OH)2 thin films on citric acid‐treated cotton fabrics

Preparation and characterization of lamellar magnesium hydroxide (Mg(OH)₂) thin films on cotton fabrics are reported in this paper. Mercerized cotton fabrics were treated with citric acid, so carboxyl groups were introduced to the surface of the fabrics. Mg(OH)₂ seeds were first adsorbed on the citric acid‐treated cotton fabrics and then Mg(OH)₂ thin films grew on the fabric through secondary growth method. Kinetics and isotherm studies found that the adsorption of Mg(OH)₂ seeds on citric acid‐treated cotton fabrics followed pseudo second‐order kinetic model and Langmuir isotherm. This indicated that Mg(OH)₂ seeds adsorption was monolayer chemical adsorption driven by electric attraction between positively charged Mg(OH)₂ seeds and ? COO^? ions on the cotton fiber surface. The X‐ray diffraction (XRD) and SEM characterizations of the Mg(OH)₂ thin films covered cotton fabrics found that standing flaky Mg(OH)₂ crystals formed a shell of porous but continuous network on cotton fabric surface. Owing to the Mg(OH)₂ thin film covering, the fabric had fireproof property, lower thermal conductivity and higher optical absorbance in the UV, Vis and IR regions. Copyright © 2010 John Wiley & Sons, Ltd.     

Glucose Biosensor Using Glucose Oxidase and Electrospun Mn2O3‐Ag Nanofibers

The highly porous Mn₂O₃‐Ag nanofibers were fabricated by a facile two‐step procedure (electrospinning and calcination). The structure and composition of the Mn₂O₃‐Ag nanofibers were characterized by SEM, TEM, XRD, EDX and SAED. The as‐prepared Mn₂O₃‐Ag nanofibers were then employed as the immobilization matrix for glucose oxidase (GOD) to construct an amperometric glucose biosensor. The biosensor shows fast response to glucose, high sensitivity (40.60 µA mM^?1 cm^?2), low detection limit (1.73 µM at S/N=3), low K_m,app value and excellent selectivity. These results indicate that the novel Mn₂O₃‐Ag nanfibers‐GOD composite has great potential application in oxygen‐reduction based glucose biosensing.     

On-resin peptide ligation via C-terminus benzyl ester

Here, we reported a new approach of on-resin peptide ligation using C-terminal benzyl ester as the stabilized precursor of thioester, which enables both N-terminal elongation and C-terminal peptide ligation on a Rink Amide resin.     

Amine-assisted synthesis of concave polyhedral platinum nanocrystals having {411} high-index facets

High-index surfaces of a face-centered cubic metal (e.g., Pd, Pt) have a high density of low-coordinated surface atoms and therefore possess enhanced catalysis activity in comparison with low-index faces. However, because of their high surface energy, the challenge of chemically preparing metal nanocrystals having high-index facets remains. We demonstrate in this work that introducing amines as the surface controller allows concave Pt nanocrystals having {411} high-index facets to be prepared through a facile wet-chemical route. The as-prepared Pt nanocrystals display a unique octapod morphology with {411} facets. The presence of high-index {411} exposed facets endows the concave Pt nanocrystals with excellent electrocatalytic activity in the oxidation of both formic acid and ethanol.     

Ammonium octahydrotriborate (NH4B3H8): new synthesis, structure, and hydrolytic hydrogen release

A metathesis reaction between unsolvated NaB(3)H(8) and NH(4)Cl provides a simple and high-yield synthesis of NH(4)B(3)H(8). Structure determination through X-ray single crystal diffraction analysis reveals weak N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8) and strong N-H(δ+)---H(δ-)-B interaction in NH(4)B(3)H(8)·18-crown-6·THF adduct. Pyrolysis of NH(4)B(3)H(8) leads to the formation of hydrogen gas with appreciable amounts of other volatile boranes below 160 °C. Hydrolysis experiments show that upon addition of catalysts, NH(4)B(3)H(8) releases up to 7.5 materials wt % hydrogen.     

Quantification of monohydroxy-PAH metabolites in urine by solid-phase extraction with isotope dilution-GC–MS

For measurement of biomarkers from polycyclic aromatic hydrocarbon (PAH) exposure, an analytical method is described quantifying hydroxylated PAH (OH-PAH) in urine samples. This method determined monohydroxy metabolites of naphthalene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[c]phenanthrene, and benz[a]anthracene. The sample preparation consisted of enzymatic hydrolysis, solid-phase extraction and derivatization with a silylating reagent. Five carbon-13 labeled standards were used for isotope dilution. Analytes were separated by gas chromatography (GC) and quantified with high-resolution mass spectrometry (HRMS). This method produced good recoveries (41-70%), linearity, and specificity. Data were corrected for blank levels from the naphthalene, fluorene, and phenanthrene metabolites. Method detection limits ranged from 2 ng L(-1) for 1-hydroxypyrene to 43.5 ng L(-1) for 1-hydroxynaphthalene. Using quality control charts from two urine pools, the method can be readily applied to biomonitoring PAH exposure.     

Determination of cationic surfactants in water samples by their enhanced resonance light scattering with azoviolet

A simple assay of cationic surfactants in water samples was developed based on the measurements of enhanced resonance light scattering (RLS). At pH 6.09 and ionic strength 0.03 M, the interactions of azoviolet (AV) with cationic surfactants, including zephiramine (Zeph) and cetyl trimethyl ammonium bromide (CTMAB), result in enhanced RLS signals characterized by the peaks of 470.0, 485.0 and 495.0 nm. The enhanced RLS intensity is proportional to the concentration of cationic surfactant of Zeph in the range of 0.2~6.0x10(-6) M, and to that of CTMAB in the range of 0.4~4.8x10(-6 )M. The limit of determination (3 sigma) is 2.1x10(-8) M and 3.8x10(-8) M for the two surfactants, respectively. Determinations of cationic surfactants in synthetic and tap water samples were successfully made with a recovery of 90.5~108.6%.     

端羧基芳脂型超支化聚酯自组装性能的研究

利用聚电解质逐层浸渍 ( layer- by- layer dipping)法制备自组装膜是最近发展起来的进行表面改性的新方法[1～ 3] .一方面 ,从理论上来说 ,只要是带电荷的聚合物都可以利用该技术制备具有优异性能的自组装膜 ;另一方面 ,还可以通过调节溶液的 p H值和离子强度等控制阴阳离子的组装过程 ,从而控制自组装膜的内部结构和表面形态 ,为在纳米级范围内设计和控制聚合物聚集态内部结构提供了可能性 .近年来 ,具有高度支化结构的超支化分子由于具有独特的物理和化学性能而受到了广泛的关注 [4 ,5] ,但以聚电解质逐层浸渍法制备超支化分子自组装膜…     

EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE*

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than forunmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flowactivation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque duringsingle screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreasedmarkedly with increasing milling times.