CoFe2O4/CdS纳米复合物的制备、表征及其声催化降解有机染料污染物

在低温(200℃)下采用一步水热分解CoFe2O4纳米粒子表面的镉二硫代氨基甲酸酯配合物制备了磁性CoFe2O4/CdS纳米复合物,运用X射线衍射、红外光谱、扫描电镜、X射线能量散射谱、紫外-可见光谱、透射电镜(TEM)、N2吸附-脱附、X射线光电子能谱和振动样品磁强计对所制样品进行了表征.TEM结果表明,CoFe2O4/CdS纳米复合物由几乎均一的约20nm球形纳米粒子组成.光吸收谱显示该样品的带隙为2.24 eV,很适合用于声/光催化降解有机污染物.在紫外光照射下评价了CoFe2O4/CdS纳米复合物的声催化H2O2辅助降解甲基蓝、罗丹明B和甲基橙反应活性.结果表明,该纳米复合物对这3种染料均表现出很好的声催化活性(5-9 min内完全降解).另外,比较实验结果表明,CoFe2O4/CdS纳米复合物是一个比纯CdS更高效的声催化剂.因此,纳米复合是一种非常好的提高CdS声催化活性的手段.该CoFe2O4/CdS纳米复合物表现出的磁性使其很容易从反应混合物中分离出来而重复使用.     

Theoretical investigation of the nature and strength of simultaneous interactions of π–π stacking and halogen bond including NMR,SAPT, AIM and NBO analysis

Ab initio MP2/aug-cc-pVDZ calculations were performed to investigate mutual effect between π–π stacking and halogen bond interactions in X-ben||pyr···Cl–F complexes (X = CN, F, Cl, Br, CH₃, OH and H where || and ··· denote π–π stacking and halogen bonds). The results indicate the cooperativity of π–π stacking and halogen bonds in these complexes. This effect was discussed in terms of the energetic, geometrical parameters and charge-transfer properties of the complexes. To explore on the two-bonded spin–spin coupling constant ^2X J(N–F) across ¹⁵N···³⁵Cl–¹⁹F halogen bond in X-ben||pyr···Cl–F complexes, NMR calculations were performed at PBE0/aug-cc-pVDZ levels of theory. To get more insight into the physical nature of the binding energies, Symmetry Adapted Perturbation Theory calculations were carried out. Energy decomposition indicates that the percentage of the electrostatic term in the halogen bonding system constitutes approximately half of the total attractive binding energies, while the percentage of the dispersion term in the π–π stacking complexes constitutes approximately half of the attractive binding energies. In addition, atoms in molecules, natural bond orbital and molecular electrostatic potential were also used to probe the π–π stacking interactions and halogen bonding strengths.     

Yolk–shell microspheres assembled from Preyssler‐type NaP5W30O11014− polyoxometalate and MIL‐101(Cr) metal–organic framework: A new inorganic–organic nanohybrid for fast and selective removal of cationic organic dyes from aqueous media

Novel inorganic–organic yolk–shell microspheres based on Preyssler‐type NaP₅W₃₀O₁₁₀^14? polyoxometalate and MIL‐101(Cr) metal–organic framework (P₅W₃₀/MIL‐101(Cr)) were synthesized by reaction of K_12.5Na_1.5[NaP₅W₃₀O₁₁₀], Cr(NO₃)₃·9H₂O and terephthalic acid under hydrothermal conditions at 200°C for 24 h. The as‐prepared yolk–shell microspheres were fully characterized using various techniques. All analyses confirmed the incorporation of the Preyssler‐type NaP₅W₃₀O₁₁₀^14? polyoxometalate into the three‐dimensional porous MIL‐101(Cr) metal–organic framework. The results revealed that P₅W₃₀/MIL‐101(Cr) demonstrated rapid adsorption of cationic methylene blue (MB) and rhodamine B (RhB) with ultrahigh efficiency and capacity, as well as achieving rapid and highly selective adsorption of MB from MB/MO (MO = methyl orange), MB/RhB and MB/RhB/MO mixtures. The P₅W₃₀/MIL‐101(Cr) adsorbent not only exhibited a high adsorption capacity of 212 mg g^?1, but also could quickly remove 100% of MB from a dye solution of 50 mg l^?1 within 8 min. The effects of some key parameters such as adsorbent dosage, initial dye concentration and initial pH on dye adsorption were investigated in detail. The equilibrium adsorption data were better fitted by the Langmuir isotherm. The adsorption kinetics was well modelled using a pseudo‐second‐order model. Also, the inorganic–organic hybrid yolk–shell microspheres could be easily separated from the reaction system and reused up to four times without any change in structure or adsorption ability. The stability and robustness of the adsorbent were confirmed using various techniques.     

Kinetic‐Spectrophotometric Determination of Metronidazole Benzoate in Surfactant Medium

A kinetic method for the accurate and sensitive determination of metronidazole benzoate (MB) has been described. The method is based on the oxidation of MB with KMnO₄ in alkaline medium in the presence of sodium dodecyl sulphate (SDS). At a fixed time of 10 min, the formed magnate ion is spectrophotometrically measured at 610 nm. The determination of MB by the fixed‐concentration and rate constant method is feasible with the calibration equation obtained, but the fixed‐time method proves to be more applicable. The proposed method was successfully used for the quantitative determination of MB in suspended oral syrup after the separation of MB with a simple separation method. Beer's law was obeyed from 0.55 mgL^?1 to 33 mgL^?1 and the RSD% value for syrup was 3.44. The results obtained agreed with those obtained by the BP method.     

Ultrasonic-Assisted Dry Creep-Feed Up-Grinding of Superalloy Inconel738LC

Among many machining methods, grinding is the most applicable one for cutting hard-to-cut materials such as superalloys. In this research, effects of longitudinal ultrasonic vibration of workpiece (Inconel738LC) in dry creep-feed up-grinding process were investigated. Mechanism of abrasive grain and workpiece surface interaction and the consequences have been analyzed both analytically and numerically. Then, the results have been compared with experimental findings. Analytical calculations showed that there is a multiple and discontinuous cutting along the contact zone of grinding wheel and the workpiece when longitudinal ultrasonic vibration is used. Two-dimensional finite element modeling in commercial MSC.Superform software, showed the same behavior and results. Grinding forces are one of the major output parameters for evaluations. It was observed that, application of ultrasonic vibration can decrease grinding forces. A practical decrease of up to 27% of vertical grinding forces and up to 22% of horizontal grinding forces has been achieved when using ultrasonic vibration. Finite-Element analysis has shown a reduction of about 40% of grinding forces compared with ordinary grinding. Probable lower risks of thermal damage even for working under dry conditions can be a big advantage of using ultrasonic with grinding.     

Generic tropical initial ideals of Cohen-Macaulay algebras

We study the generic tropical initial ideals of a positively graded Cohen-Macaulay algebra R over an algebraically closed field k. Building on work of Römer and Schmitz, we give a formula for each initial ideal, and we express the associated quasivaluations in terms of certain I-adic filtrations. As a corollary, we show that in the case that R is a domain, every initial ideal coming from the codimension 1 skeleton of the tropical variety is prime, so “generic presentations of Cohen-Macaulay domains are well-poised in codimension 1.”     

Potassium peroxydisulfate as an efficient oxidizing agent for conversion of ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates to their corresponding ethyl pyrimidin-2(1H)-one-5-carboxylates

Various ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates were oxidized to their corresponding ethyl pyrimidin-2(1H)- one-5-carboxylates by potassium peroxydisulfate in refluxing aqueous acetonitrile. The products were obtained in good to excellent yields. The effect of the nature of 4-substituent and also the nature of solvent play an important role on the rate of oxidation.     

Analysis of ethanol and methanol in human body fluids by headspace solid phase microextraction coupled with capillary gas chromatography.

A new method for extraction and analysis of ethanol and methanol in human whole blood, urine and saliva samples based on headspace solid phase microextraction (SPME) using silver sulfide (Ag(2)S) and polyvinyl chloride (PVC) coated on silver wire is described. Unlike commercial fibers, which are coated on fused silica, the proposed fiber has a metallic base to which the coating adheres very strongly. Due to metallic base, this fiber is very durable and is thermally stable up to 250 degrees C. After optimization of coating composition and microextraction conditions, the fiber was used for sampling of methanol and ethanol from human body fluids prior to capillary gas chromatographic analysis. The high recovery (>94%), low detection limits (5.6 mg/L for ethanol and 12.8 mg/L for methanol) and excellent linearity (>0.9900) of calibration graphs made the proposed method suitable for this purpose.