Dichlorocarbene‐Functionalized Fluorographene: Synthesis and Reaction Mechanism

Halogen functionalization of graphene is an important branch of graphene research as it provides opportunities to tailor the band gap and catalytic properties of graphene. Monovalent C–X bond obviates pitfalls of functionalization with atoms of groups 13, 15, and 16, which can introduce various poorly defined groups. Here, the preparation of functionalized graphene containing both fluorine and chlorine atoms is shown. The starting material, fluorographite, undergoes a reaction with dichlorocarbene to provide dichlorocarbene‐functionalized fluorographene (DCC‐FG). The material is characterized by X‐ray photoelectron spectroscopy, Raman spectroscopy, and high‐resolution transmission electron microscopy with X‐ray dispersive spectroscopy. It is found that the chlorine atoms in DCC‐FG are distributed homogeneously over the entire area of the fluorographene sheet. Further density functional theory calculations show that the mechanism of dichlorocarbene attack on fluorographene sheet is a two‐step process. Dichlorocarbene detaches fluorine atoms from fluorographene sheet and subsequently adds to the newly formed sp² carbons. Halogenated graphene consisting of two (or eventually three) types of halogen atoms is envisioned to find its way as new graphene materials with tailored properties.     

A New Gas Chromatography Method for Quality Control of Methylsulfonylmethane Content in Multicomponent Dietary Supplements

This paper reports the first gas chromatography method with flame ionization detection (GC–FID) for rapid assay of the quality control of methylsulfonylmethane (MSM) content in multicomponent dietary supplements. The proposed method was completely validated and used for quality control of multicomponent dietary supplements available in the local market. The study showed that the content of MSM varied in different commercial samples (77.7–112.3 % of the declared amount) and was dependent on different qualities of the dietary supplement producer. The developed method was based on the rapid extraction of MSM into acetone using ultrasound bath (5 min) and on the subsequent quantification of the MSM by gas chromatography. The used GC conditions were as follows: fused silica cyanopropylphenylmethylpolysiloxane capillary column Alltech AT^TM-624 (30 m?×?0.32 mm i.d., 1.8-μm film thickness), injection mode split of 1:10, sample volume of 1.0 μL, injector temperature of 190 °C, detector temperature of 190 °C, column temperature held at 190 °C for whole analysis time, and helium carrier gas flow rate of 0.7 mL min^?1. Nitrobenzene was chosen as internal standard for precise and accurate quantification of MSM in dietary supplements. Method precision evaluated as relative standard deviation was 1.7 %, and method accuracy evaluated as recovery was in the range of 102.5–106.2 %. The method required no special sample pretreatment, so it showed to be simple, robust, rapid (short analysis time of less than 4 min), and suitable for routine analysis of MSM in food quality control laboratories.     

Three‐dimensional finite element calculations in acoustic scattering using arbitrarily shaped convex artificial boundaries

We report on a generalization of the Bayliss–Gunzburger–Turkel non‐reflecting boundary conditions to arbitrarily shaped convex artificial boundaries. For elongated scatterers such as submarines, we show that this generalization can improve significantly the computational efficiency of finite element methods applied to the solution of three‐dimensional acoustic scattering problems. Copyright © 2001 John Wiley & Sons, Ltd.     

Formation and behavior of calcium silicate hydrates in a geothermal environment

Research to identify calcium silicate hydrate compositions suitable as cements for geothermal wells is described. Several phases were evaluated in terms of conditions for formation and resistance to thermal and chemical degradation. Truscottite (C₇S₁₂H_～3) and pectolite (NC₄S₆H) were identified as potentially superior binders for use in a geothermal environment.     

Electron‐Deficient Alloxazinium Salts: Efficient Organocatalysts of Mild and Chemoselective Sulfoxidations with Hydrogen Peroxide

A series of substituted alloxazinium perchlorates has been prepared and tested as catalysts for the oxidation of sulfides to sulfoxides with hydrogen peroxide. The logarithms of the observed rate constants of thioanisole oxidation correlate with the Hammett σ constants of the substituents on the alloxazinium catalysts, as well as with their reduction potentials E^0′ and their pK_R+ values, representing the alloxazinium salt/pseudobase equilibrium. The stronger the electron‐withdrawing substituent, the more efficient is the alloxazinium catalyst. The alloxazinium salts with a cyano or trifluoromethyl group in position 8 proved to be the most efficient, operating at room temperature at small loadings, down to 0.1 mol%, achieving turnover number values of up to 640 and acceleration by a factor of 350 relative to the non‐catalyzed oxidation. The 8‐cyanoalloxazinium perchlorate was evaluated as the best catalyst; however, due to its relatively good accessibility, the 8‐(trifluoromethyl)alloxazinium perchlorate seems to be the catalyst of choice for sulfoxidations with hydrogen peroxide. It was successfully tested for the sulfoxidation of a series of aliphatic and aromatic sulfides on a preparative scale. It produced the corresponding sulfoxides in quantitative conversions and with high isolated yields (87–98%). No over‐oxidation to sulfone was ever observed.

     

Experimental Study of Central and Minimum Elastohydrodynamic Film Thickness by Colorimetric Interferometry Technique

Recently developed colorimetric interferometry technique was used for the study of both minimum and central film thicknesses for a wide range of operating parameters. Over 300 film thickness maps were obtained for the combination of four values of the materials parameter G, five values of the load parameter W and many values of the speed parameter U. The use of a spacer layer extended the range of film thickness measurement down to 5 nm. An excellent agreement was found between experimental values and data obtained from numerical solution presented by Venner and ten Napel, especially for thin lubrication films. An increase in a speed exponent with increasing material parameter G was observed for both central and minimum film thicknesses. The minimum film thickness and, thereby, the ratio between central and minimum film thickness was confirmed to be of a stronger dependence on material and load dimensionless parameters than Hamrock and Dowson equations predict.     

Lead and/or Lead Oxide Nanoparticle Generation for Inhalation Experiments

A method of the continual generation of lead or lead oxide nanoparticles for potential subsequent inhalation experiments with laboratory animals was investigated. We examined the thermal decomposition and oxidation of lead bis(2,2,6,6-tetramethyl-3,5-heptanedionate) in an externally heated tube reactor as well as the evaporation and condensation of metallic lead. The particle production dependence on experimental conditions was investigated using a scanning mobility particle sizer (SMPS), and the particle characteristics were studied using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic absorption spectroscopy (AAS), elemental and organic carbon analysis (EC/OC), X-ray photoelectron spectrometry (XPS), and X-ray diffraction (XRD) methods. The evaporation/condensation was evaluated as being the most suitable for inhalation experiments due to its simplicity, high production rate, and the well-defined composition of the nanoparticles.

Copyright 2015 American Association for Aerosol Research     

Ferrate(VI) oxidation of weak-acid dissociable cyanides

Cyanide is commonly found in electroplating, mining, coal gasification, and petroleum refining effluents, which require treatment before being discharged. Cyanide in effluents exists either as free cyanide or as a metal complex. The kinetics of the oxidation of weak-acid dissociable cyanides by an environmentally friendly oxidant, ferrate(VI) (Fe(VI)O4(2-), Fe(VI)), were studied as a function of pH (9.1-10.5) and temperature (15-45 degrees C) using a stopped-flow technique. The weak-acid dissociable cyanides were Cd(CN)4(2-) and Ni(CN)4(2-), and the rate-laws for the oxidation may be -d[Fe(VI)]/dt = k[Fe(VI)][M(CN)4(2-)]n where n = 0.5 and 1 for Cd(CN)4(2-) and Ni(CN)4(2-), respectively. The rates decreased with increasing pH and were mostly related to a decrease in concentration of the reactive protonated Fe(VI) species, HFeO4(-). The stoichiometries with Fe(VI) were determined to be: 4HFeO4(-) + M(CN)4(2-) + 6H2O --> 4Fe(OH)3 + M(2+) + 4NCO(-) + O2 + 4OH(-). Mechanisms are proposed that agree with the observed reaction rate-laws and stoichiometries of the oxidation of weak-acid dissociable cyanides by Fe(VI). Results indicate that Fe(VI) is effective in removing cyanide in coke oven plant effluent, where organics are also present.     

“合成”莫尔道玻陨石和天然莫尔道玻陨石的鉴别（英文）

近期,在宝石市场上出现了大量的合成莫尔道玻陨石。天然莫尔道玻陨石属于玻璃陨石的一种,由撞击地球表面的大陨石而形成。巨大的冲击能量至少可达到8km/s,引起陨石坑基岩(所谓的陨星坑)气化和熔化,并使得一部分物质进入到大气层上层(部分甚至进入到太空),最后在数百公里外落下。最初的莫尔道玻陨石坑位于德国Stuttgart附近的N9rdlingen,然而在捷克共和国South Bohemia的玻陨石散布地区有300~400公里,其南部摩拉维亚很少有发现。与天然莫尔道玻陨石相比,大部分合成莫尔道玻陨石有着异常的高光泽。天然莫尔道玻陨石通常有一个非常尖锐的表面(尤其是来自砂沉积物),与此相反,经过了水流搬运,莫尔道玻陨石表面变得光滑。合成莫尔道玻陨石边缘常常是光滑的,表面的光泽变得更强(通过酸洗)或者更弱。合成莫尔道玻陨石可以由多种方式雕刻,最好的方法之一就是像天然莫尔道玻陨石一样,在氢氟酸中选择性溶解。不同的是在天然莫尔道玻陨石中有焦石英的存在。焦石英常在天然莫尔道玻陨石表面较为突出(用放大镜容易看到),即使切磨好的宝石也可以看到。如果在有争议的情况下,Raman光谱仪或者UVVis光谱能被用以区分天然和合成莫尔道玻陨石。合成莫尔道玻陨石在长波紫外荧光(366nm)特征是具有象征意义的,相反,天然莫尔道玻陨石在此长波紫外下完全惰性。总体上,本文的测试结果显示合成和天然莫尔道玻陨石是完全不同的。