A new asymmetric Pseudo‐Voigt function for more efficient fitting of XPS lines

Asymmetric peak profiles for the application in spectroscopy can be obtained in a simple way by substituting the usually constant full width at half maximum parameter in Pseudo‐Voigt functions with an energy‐dependent expression, for instance of sigmoidal shape. While this approach has been successfully applied to vibrational spectra, we find that the resulting curves are less suitable for least‐squares fits of X‐ray photoelectron spectroscopy (XPS) data. However, if one additionally allows a variable displacement of the sigmoidal step relative to the peak, excellent fitting results can be obtained. We demonstrate the applicability of our extended approach on several inherently asymmetric XPS lines, i.e. the C 1s signal of graphite and C₂H₂/Pd(100), the 3d_5/2–3d_3/2 doublet of palladium, and the 4f_7/2–4f_5/2 doublet of platinum. Comparison of the corresponding fit results with the results obtained by the application of more elaborate, theory‐based line profiles (Doniach‐?unji? and Mahan functions) shows that the modified Pseudo‐Voigt function gives practically identical results in terms of peak shape and area, while requiring much less computational effort since no convolution procedures are required for its calculation. Thus, this function is most suitable for application in one of the following situations: (i) the peak shape of a given signal is known but cannot be calculated with ease, and (ii) the theoretical peak shape is not (yet) known, however, one wants to perform a first quantitative screening of the data at issue. Copyright © 2014 John Wiley & Sons, Ltd.     

Influence of surface properties on the interfacial adhesion in carbon fiber/epoxy composites

A polyacrylonitrile‐based carbon fiber was electrochemically oxidized in an aqueous ammonium bicarbonate solution with current density of up to 2.76 A/m² at room temperature. X‐ray photoelectron spectroscopy revealed that the oxygen content increased with increasing current density before approaching saturation. The increase can be divided into two regions, the rapid increase region (0–1.78 A/m²) and a plateau region (1.78–2.76 A/m²). The surface chemistry analysis showed that the interlaminar shear strength (ILSS) value of the carbon fiber/epoxy composite could be improved by 24.7%. The carbon structure was examined using Raman spectroscopy in terms of order/disorder in the graphite structure and the results indicated that the relative percentage of graphite carbon in the form of sp² hybridization increased above a current density of 1.39 A/m². The increasing non‐polar graphite carbon on the carbon fiber surface decreased the surface energy. As a result, both the surface free energy () and its polar component () decreased when current density increased above 1.78 A/m². The ILSS value had no direct relationship with the nature and surface density of the oxygen‐containing functional groups nor with the carbon structure. It is the surface free energy (), especially the polar component (), which played a critical role in affecting the interfacial adhesion of carbon fiber/epoxy composites. The ILSS value changed with increasing current density and could be divided into three distinct regions, as chemical interaction region (I), anchor force region (II) and matrix damage region (III). Copyright © 2013 John Wiley & Sons, Ltd.     

Acceleration of self‐consistent field convergence in ab initio molecular dynamics simulation with multiconfigurational wave function

The Lagrange interpolation of molecular orbital (LIMO) method, which reduces the number of self‐consistent field iterations in ab initio molecular dynamics simulations with the Hartree–Fock method and the Kohn–Sham density functional theories, is extended to the theory of multiconfigurational wave functions. We examine two types of treatments for the active orbitals that are partially occupied. The first treatment, as denoted by LIMO(C), is a simple application of the conventional LIMO method to the union of the inactive core and the active orbitals. The second, as denoted by LIMO(S), separately treats the inactive core and the active orbitals. Numerical tests to compare the two treatments clarify that LIMO(S) is superior to LIMO(C). Further applications of LIMO(S) to various systems demonstrate its effectiveness and robustness. © 2014 Wiley Periodicals, Inc.     

Comprehensive two‐dimensional gas chromatography coupled with static headspace sampling to analyze volatile compounds: Application to almonds

The hyphenation of static headspace sampling with comprehensive 2D GC equipped with a modulator based on capillary flow technology and a flame ionization detector was used to separate and identify 43 representative target volatile compounds (light hydrocarbons, carbonyls, pyrazines, alcohols, furans, and benzenes) frequently detected in the roasting process of nuts. Five column combinations with differing degrees of orthogonality (one conventional and four inverted phase sets) were tested in order to obtain the best conditions for analyzing these volatile compounds. Optimization of the working conditions for each of the different column combinations was performed by means of a central composite design. The best results in terms of separation and differentiation among the different chemical groups were achieved with a combination of inverted phase columns (first dimension: highly polar, INNOWax; second dimension: mid‐polar, ZB‐35). Additionally, a reference template was developed to provide an effective and rapid analysis of the target compounds. Finally, the proposed method was successfully employed to identify volatile compounds in raw and roasted almond samples from the Spanish cultivar Largueta.     

石墨烯/锌铁氧体复合物的制备及抗菌性能

用氧化还原法和化学共沉淀法分别制备了石墨烯(GE)和石墨烯/锌铁氧体(GE/ZnFe2O4)复合物,通过现代测试技术表征了样品的物相结构、组成和微观形貌.以大肠杆菌、金黄色葡萄球菌和白色念珠菌为测试菌种,分别对样品的抗菌性能进行了研究.结果表明,样品的抗菌活性受GE/ZnFe2O4复合物中GE和ZnFe2O4质量比(mG/Z)以及菌种的影响,其中mG/Z=0.4的复合物对三种菌均有较好的抗菌效果,其最小抑菌浓度分别为25、25和12.5μg/mL;复合物对白色念珠菌的抗菌效果最好,这与菌种的结构有关.此外,对样品的抗菌机理进行了详细研究.     

高比能锂硫电池正极材料

锂硫电池被认为是最有发展潜力的新型多电子反应的二次电池体系之一.单质硫与锂反应的理论比容量为1675 mA h g?1,质量比能量达2600 W h kg?1,远远高于现行的传统锂离子二次电池材料.同时硫又具有来源丰富、环境友好等优点.然而,仍然有许多问题制约了锂硫电池的发展与广泛应用.本文综述了近年来锂硫电池正极材料的研究进展.     

Nano-crystalline FeOOH mixed with SWNT matrix as a superior anode material for lithium batteries

Nano-crystalline FeOOH particles(5～10 nm) have been uniformly mixed with electric matrix of single-walled carbon nanotubes(SWNTs)for forming FeOOH/SWNT composite via a facile ultrasonication method. Directly using the FeOOH/SWNT composite(containing 15 wt%SWNTs) as anode material for lithium battery enhances kinetics of the Li+insertion/extraction processes, thereby effectively improving reversible capacity and cycle performance, which delivers a high reversible capacity of 758 mAh g-1under a current density of 400 mA g-1even after 180 cycles, being comparable with previous reports in terms of electrochemical performance for FeOOH anode. The good electrochemical performance should be ascribed to the small particle size and nano-crystalline of FeOOH, as well as the good electronic conductivity of SWNT matrix.     

石榴状凝胶微球固定化漆酶的制备、 表征及降解双酚A

采用铜/锌复合金属磷酸盐晶体和海藻酸钙凝胶双重包覆技术对漆酶进行固定化, 制得石榴状Alg@Cu₃/Zn₃(PO₄)₂@Lac的凝胶微球. SEM, EDX和FTIR表征结果表明, 在凝胶微球内部, 漆酶被成功固定于由海藻酸钙凝胶包覆的铜/锌复合金属磷酸盐晶体内, 铜/锌复合金属磷酸盐晶体镶嵌于海藻酸钙凝胶网格的孔隙中而呈石榴状. 以2,2′-联氮双(3-乙基苯并噻唑啉-6-磺酸)(ABTS)为底物, 经酶学性质研究表明, 在无机盐晶体和海藻酸钙凝胶的双重保护下, Alg@Cu₃/Zn₃(PO₄)₂@Lac的耐热性、 耐酸性以及储存稳定性比游离漆酶均有不同程度增强. 将Alg@Cu₃/Zn₃(PO₄)₂@Lac应用于双酚A(BPA)的降解, 采用孔径约1 mm滤网实现快速回收, 经6次循环利用, 对BPA的降解率下降约14%, 显示出比较稳定的重复利用性和便捷的可操作性, 这主要得益于海藻酸钙和铜/锌无机盐晶体对漆酶蛋白分子的双重保护.     

Experimental design approach for petrochemical waste water treatment using solar assisted photo Fenton process

In this study, the effect of photo-Fenton process on the treatment of petrochemical waste water treatment was investigated. The influence of process conditions were determined by factorial design. Optimization of the process conditions were performed by central composite design. Under, optimized conditions lab scale and solar assisted pilot scale of petrochemical waste water treatment was performed. Three factors namely initial pH, H₂O₂ concentration (mM) and Fe²⁺ concentration (mM) executed the essential role in petrochemical waste water treatment. Central composite design resulted in the prediction of optimized value as 6.5 initial pH, 15.65 mM of H₂O₂ concentration and 2.09 mM of Fe²⁺ concentration. Under these conditions, the reduction in chemical oxygen demand (COD) percentage reached about 68.67 ± 2.8% after 280 min in pilot scale of solar assisted photo Fenton process of petrochemical waste water treatment. Thus, experimental design combined with advanced Fenton process can become a feasible unconventional method for petrochemical waste water treatment.     

Surface and Interface Engineering for Advanced Nanofiltration Membranes

Nanofiltration has been attracting great attention in alleviating the global water crisis because of its high efficiency,mild operation,and strong adaptability.Over decades,it remains a challenge to break the upper limit of performance and establish the formation-structureproperty relationship for nanofiltration membranes.This feature article summarizes our recent progress in the preparation of high-performance thin-film composite(TFC)nanofiltration membranes,focusing on the mussel-inspired deposition method and the optimized interfacial polymerization(IP).By accelerating the oxidation of polydopamine and equilibrating the rate of aggregation and deposition processes,the mussel-inspired deposition method realizes the rapid and uniform formation of selective coatings or nanofilms.Diverse deposition systems endow the selective layer with rich chemical structures and easy post-functionalization,highlighting its potential in water treatment.As for optimizing the conventional IP,the rapid polycondensation of amine and acid chloride groups is slowed down to enable the controllability of IP at the water-organic interface.The homogeneity and integrity of the TFC membranes are improved by constructing a uniform reaction platform and introducing a viscous medium to control the amine diffusion,which facilitates the water permeability and promotes the separation efficiency.We have proposed a series of practical strategies for improving TFC membranes and might provide more inspiration for other nanofiltration techniques.