Effects of nitrogen composition on the resistivity of reactively sputtered TaN thin films

Nanocrystalline tantalum nitride (TaN) thin films have been deposited by reactive direct current magnetron sputtering technique on Si/SiO₂ (100) substrate with nitrogen flow rate ranging from 0, 3, 5, 7, 9 to 11 standard cubic centimeter per minute (sccm). Structural properties, surface morphology, chemical composition and and resistivity of the TaN films were investigated by X‐ray diffraction (XRD), field emission scanning electron microscopy, X‐ray photoemission spectroscopy (XPS) and four‐point probe measurements, respectively. In the XRD spectra, a classical formation sequence of tantalum nitride phases in the order of Ta‐Ta₂N‐TaN‐Ta₄N₅ and decreasing amount of metallic Ta were observed with increasing nitrogen flow. The electrical resistivity of the TaN film was found to increase with increasing N/Ta ratio as a result of the increased electron scattering from interstitial N atoms. In the XPS analysis, two groups of Ta4f doublets relating to different TaN phases were observed in the core level spectra of TaN films. No strong coupling was observed between the Ta4f doublets and the Ta4p and the N1s groups. The appropriate nitrogen flow was believed to be helpful in the bonding and formation of stoichiometric TaN. Copyright © 2014 John Wiley & Sons, Ltd.     

High performance hybrid reinforcement of nitrile rubber using short pineapple leaf fiber and carbon black

Rubber composites with very high moduli at low elongation, high elongation at break and high ultimate breaking strength have been developed. The matrix was acrylonitrile butadiene rubber (NBR) and the hybrid (fibrous and particulate) reinforcements were short, fine pineapple leaf fiber (PALF) and carbon black. The amount of PALF was fixed at 10 parts (by weight) per hundred of rubber (phr) while that of carbon black was varied from 0 to 30 phr. Uniaxial NBR composites were prepared. Tensile strength, elongation at break, modulus and tear strength of the hybrid composites were characterized in both longitudinal (parallel to the fiber axis) and transverse (perpendicular to the fiber axis) directions. The addition of carbon black causes the slope of the early part of the stress–strain curve to increase and also extends breaking to greater strains. At carbon black contents of 20 phr and above, the stress–strain relation displays an upturn at high elongations, providing greater ultimate strength. Comparison with the usual carbon black filled rubber shows that the composite behavior at low strains is determined by the PALF, and at high strains by the carbon black. This high performance PALF-carbon black reinforced NBR shows great promise for engineering applications.     

Application of a multivariate approach for analyte focusing by micelle collapse‐micellar electrokinetic chromatography for analyzing sunscreen agents in cosmetics

The operating parameters that affect the performance of the online preconcentration technique “analyte focusing by micelle collapse‐MEKC (AFMC‐MEKC)” were examined using a multivariate approach involving experimental design to determine the sunscreen agents in cosmetics. Compared to the single‐variable approach, the advantage of the multivariate approach was that many factors could be investigated simultaneously to obtain the best separation condition. A fractional factorial design was used to identify the fewest significant factors in the central composite design (cCD). The cCD was adopted for evaluating the location of the minimum or maximum response in this study. The influences of the experimental variables on the response were investigated by applying a chromatographic exponential function. The optimized condition and the relationship between the experimental variables were acquired using the JMP software. The ANOVA analysis indicated that the Tris pH value, SDS concentration, and ethanol percentage influenced the separation quality and significantly contributed to the model. The optimized condition of the running buffer was 10 mM Tris buffer (pH 9.5) containing 60 mM SDS, 7 mM γ‐CD, and 20% v/v ethanol. The sample was prepared in 100 mM Tris buffer (pH 9.0) containing 7.5 mM SDS and 20% v/v ethanol. The SDS concentration in the sample matrix was slightly greater than the CMC value that makes the micelle be easily collapsed and the analytes be accumulated in the capillary. In addition, sunscreen agents in cosmetics after 1000‐fold dilution were successfully determined by AFMC‐MEKC.     

醚化PBS与CMC液体复合材料的相互作用

采用聚乙二醇(PEG)对聚丁二酸丁二醇酯(PBS)进行醚化改性,得到醚化PBS(PEG/PBS),PEG/PBS与羧甲基纤维素(CMC)共混制备了在水相均匀分散的新型(PEG/PBS)-CMC液体复合材料.结合分子模拟技术对PEG/PBS与CMC复合材料的相互作用机理进行了研究.结果表明,PEG/PBS具有预期的化学结构和优异的水润湿性;含醚链段PEG的引入有效提高了PBS分子链的极性和柔顺性,PEG/PBS与CMC之间存在氢键作用、范德华力作用、疏水作用和吸附作用.红外光谱(FTIR)中官能团(如—OH,—OCO—,—COOH,—C—O—C—等)的吸收峰频率发生偏移;光电子能谱(XPS)中C和O元素的结合能分布转移,表明PBS及PEG/PBS与CMC的官能团之间发生了相互作用;偏光显微镜(POM)和X射线衍射(XRD)结果表明,复合材料之间的相互作用为非共价键的结合;扫描电子显微镜(SEM)结果表明醚化改性后(PEG/PBS)-CMC复合材料间的相互作用增强,表面结合更紧密,相容性得到提高.     

A Spray‐Based Technique for the Production of MnS Thin Films

A spray‐based technique, originally developed for the production of semiconductor nanocrystals, is utilized for the preparation of high‐quality nanocrystalline thin films, as demonstrated with manganese sulfide. The films are formed by the use of pneumatic‐assisted thermospray or pneumatic nebulizers. Our simple, low‐cost, and low‐temperature process results in a dense and phase‐pure grain structure. The concepts and benefits of this technique are described and discussed. The film characteristics show dependence on the experimental parameters, in particular the rate of solvent vaporization. Three alternative film formation mechanisms are suggested for cases with varied experimental conditions.     

Influence of Solution Volume on the Dissolution Rate of Silicon Dioxide in Hydrofluoric Acid

Experimental data and modeling of the dissolution of various Si/SiO₂ thermal coatings in different volumes of hydrofluoric acid (HF) are reported. The rates of SiO₂‐film dissolution, measured by means of various electrochemical techniques, and alteration in HF activity depend on the thickness of the film coating. Despite the small volumes (0.6–1.2 mL) of the HF solution, an effect of SiO₂‐coating thickness on the dissolution rate was detected. To explain alterations detected in HF activity after SiO₂ dissolution, spectroscopic analyses (NMR and FTIR) of the chemical composition of the solutions were conducted. This is associated with a modification in the chemical composition of the HF solution, which results in either the formation of an oxidized species in solution or the precipitation of dissolution products. HF₂^? accumulation in the HF solution, owing to SiO₂ dissolution was identified as the source of the chemical alteration.     

Lithium‐Salt‐Containing High‐Molecular‐Weight Polystyrene‐block‐Polyethylene Oxide Block Copolymer Films

Ionic conductivity in relation to the morphology of lithium‐doped high‐molecular‐weight polystyrene‐block‐polyethylene oxide (PS‐b‐PEO) diblock copolymer films was investigated as solid‐state membranes for lithium‐ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt‐doping level and the temperature. The PEO crystallites completely vanished at a salt‐doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS‐b‐PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded‐like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt‐doping level.     

Rational Design of Selenadiazole Derivatives to Antagonize Hyperglycemia‐Induced Drug Resistance in Cancer Cells

Hyperglycemia is an important factor for chemoresistance of hepatocellular carcinoma patients with diabetes to therapeutics. In the present study, a series of selenadiazole derivatives have been rationally designed, synthesized, and found be able to antagonize drug resistance in HepG2 cells to doxorubicin (DOX) under simulated diabetes conditions. Hyperglycemia could promote the cell proliferation through upregulation of ERK and AKT phosphorylation. However, the synthetic selenadiazole derivatives effectively potentiated the cellular uptake of DOX and enhanced the antiproliferative activity of DOX on HepG2 cells by induction of apoptosis, via regulation of ROS‐mediated AMPK activation, inhibition of mTORC1, and an increase in DNA damage. The selenadiazole derivatives that possess an increased lipophilicity could enhance the cellular uptake and anticancer efficacy of DOX. Taken together, this study provides a rational design strategy of selenadiazole derivatives to overcome hyperglycemia‐induced drug resistance.     

Preparation and Characterization of Chitosan Thin Films on Mixed-Matrix Membranes for Complete Removal of Chromium

Herein we present a new approach for the complete removal of Cr^VI species, through reduction of Cr^VI to Cr^III, followed by adsorption of Cr^III. Reduction of chromium from water is an important challenge, as Cr^IV is one of the most toxic substances emitted from industrial processes. Chitosan (CS) thin films were developed on plain polysulfone (PSf) and PSf/TiO₂ membrane substrates by a temperature-induced technique using polyvinyl alcohol as a binder. Structure property elucidation was carried out by X-ray diffraction, microscopy, spectroscopy, contact angle measurement, and water uptake studies. The increase in hydrophilicity followed the order: PSf < PSf/TiO₂ < PSf/TiO₂/CS membranes. Use of this thin-film composite membrane for chromium removal was investigated with regards to the effects of light and pH. The observations reveal 100 % reduction of Cr^VI to Cr^III through electrons and protons donated from OH and NH₂ groups of the CS layer; the reduced Cr^III species are adsorbed onto the CS layer via complexation to give chromium-free water.     

药物化学课程全英文教学的探索与实践*

药物化学课程是药学类专业的核心课程,在高等院校中开展药物化学课程的全英文教学,对提高药学拔尖人才的综合素质和推动我国制药行业的发展都具有重要的意义。针对药物化学课程全英文教学过程中的难点,在教材选择、教学内容优化、教学方法改进等方面进行了实践与探索,并取得了良好的教学效果,为药物化学课程全英文教学改革提供了参考。