Stick-slip of the three-phase line in measurements of dynamic contact angles

Contact angles of a series of n-alkanes (i.e., n-heptane to n-hexadecane) are studied on two functionalized maleimide copolymers (i.e., poly(ethene-alt-N-(4-(perfluoroheptylcarbonyl)aminobutyl)maleimide) (ETMF) and poly(octadecene-alt-N-(4-(perfluoroheptylcarbonyl)aminobutyl)maleimide) (ODMF)). On the homogeneous ETMF films, all liquids show a smooth motion of the three-phase line. In contrast, on ODMF surfaces that are found to consist of mainly fluorocarbons and small patches of hydrocarbons, short-chain n-alkanes show a stick-slip pattern. By increasing the chain length of the probe liquids, stick-slip is reduced significantly. The phenomenon is discussed in the framework of the Cassie equation. It is found that the upper limit of contact angles in the stick-slip pattern is given by the advancing angle that would be obtained on the pure fluorocarbon surface, whereas the lower limit of the stick-slip pattern is given by the Cassie angle.     

Conductometric study of complex formation between benzylbisthiosemicarbazone and metal cations in acetonitrile,dimethylformamide, and their binary mixtures

We report on conductometric study of complexation between benzylbisthiosemicarbazone [(2E,2′E)-2,2′-(1,2-diphenylethane-1,2-diylidene)bis(hydrazine-1-carbothioamide)] with Zn²⁺, Cr³⁺, Co²⁺, and Ni²⁺ cations at different temperatures in acetonitrile-dimethylformamide binary solvents of varied composition. The equilibrium constant and standard thermodynamic parameters (Δ_c H ⁰ and Δ_c S ⁰) of the complexes formation have been determined and found to be dependent on the binary solvent composition, the metal ion nature, and temperature.     

Electrochemical study of Cu2O/CuO composite coating produced by annealing and electrochemical methods

The electrochemical behavior of a copper oxide electrode produced by annealing and electrochemical methods was studied in an acetonitrile solvent by means of the cyclic voltammetry method. The presence of different peaks of oxidation and reduction produced by repeating the potential scans, numerous variations in the current, and shifts of peak potentials in consecutive cycles have been justified. Voltammograms proved that various oxidation species can be produced in solid-deposited forms of Cu₂O_s and CuO_s and dissolved forms of Cu(II)_sol and Cu(I)_sol ions. The experimental results indicated that higher amounts of Cu₂O_s than CuO_s can be produced in the process of copper electrode annealing. Also, the nature of copper species is responsible for different peak currents in the cyclic voltammograms, characterized by UV–Vis and XRD spectrometric methods.

     

Effect of the thermal treatment conditions on the formation of zinc ferrite nanocomposite, ZnFe2O4, by sol–gel method

Zinc ferrite nanocomposite was synthesized via thermal decomposition of zinc acetate and iron nitrate at three different temperatures (350, 450, and 550 °C). The influence of the thermal decomposition of precursors on the formation zinc ferrites was studied by differential thermal gravimetry and thermogravimetry (TG). The TG curve shows two steps for the thermal decomposition with mass loss of 17.3 % at 78 °C and 63.3 % at 315 °C. The prepared zinc ferrites nanocomposite was characterized by X-ray diffraction and scanning electron microscopy. The X-ray diffractograms of ZnFe₂O₄ shows that a crystalline phase, spinel system is formed. SEM micrograph of the zinc ferrite nanocomposite indicates the formation of uniformly spherical 48-nm nanograins. The properties of the zinc ferrite phase were strongly dependent on their calcinations temperature and molar ratio of precursors.     

Efficient Multi‐component Synthesis of Highly Substituted Imidazoles Utilizing P2O5/SiO2 as a Reusable Catalyst

Phosphorus pentoxide supported on silica gel (P₂O₅/SiO₂) has been used as an efficient and reusable catalyst for the one‐pot pseudo four‐component synthesis of 2,4,5‐trisubstituted imidazoles from benzil or benzoin, aldehydes, and ammonium acetate. It was also used for four‐component preparation of 1,2,4,5‐tetrasubstituted imidazoles from benzil or benzoin, aldehydes, primary amine, and ammonium acetate under thermal solvent‐free conditions. The remarkable features of this new procedure are high conversions, cleaner reaction, simple experimental and work‐up procedures and also the catalyst can be easily separated from the reaction mixture and reused several times without any loss of its activity.     

Influence of substitution on the strength and nature of CH···N hydrogen bond in XCCH···NH3 complexes

The effect of substitution on the strength and nature of CH···N hydrogen bond in XCCH···NH₃ (X = F, Cl, Br, OH, H, Me) and NCH···NH₃ complexes were investigated by quantum chemical calculations. Ab initio calculations were performed using MP2 method with a wide range of basis sets. With tacking into account the BSSE and ZPVE, the values of BEs decrease. Replacement of the nonparticipatory hydrogen atom of HCCH by the electronegative atoms (F, Cl, and Br), lead to the BEs increases. The BE corresponding to the replacement of the nonparticipatory hydrogen atom of HCCH by the OH and CH₃ groups decreases. A far greater enhancement of the interaction energy arises from replacement of HCCH by the more acidic HCN. The natural bond orbital analysis and the Bader's quantum theory of atoms in molecules were also used to elucidate the interaction characteristics of these complexes. The electrostatic nature of H‐bond interactions is predicted from QTAIM analysis. In addition, the relationship between the isotropic and anisotropic chemical shifts of the bridging hydrogen and binding energy of complexes as well as electron density at N···H BCPs were investigated. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Ab Initio Study of Structures,Metallotropic 1,2-Shifts and Prototropic 1,2-Shifts of Cyclopentadienyl(trimethyl)silane, -germane and -stannane

Molecular structures, metallotropic and prototropic shifts of cyclopentadienyl(trimethyl)silane ( 1 ), cyclopentadienyl(trimethyl)germane ( 2 ), and cyclopentadienyl(trimethyl)stannane ( 3 ) were investigated using ab initio molecular orbital and the Becke, Lee, Yang, and Parr density functional (B3LYP) methods. The results show that the most stable structure of compounds 1-3 has the (CH 3 ) 3 M fragment in the allylic position. The energy barrier of metallotropic shifts in compound 1 is higher than in 2 , and in compound 2 higher than in 3 , in good agreement with experimental data. The cyclopentadienyl rings in compounds 1-3 are found to be planar but this result contradicts the reported experimental data.     

Photoactivated Nitrene Chemistry to Prepare Gold Nanoparticle Hybrids with Carbonaceous Materials

Photolysis of organic solvent soluble aryl azide‐modified gold nanoparticles (N₃‐AuNPs) with a core size of 4.6±1.6 nm results in the generation of interfacial reactive nitrene intermediates. The high reactivity of the nitrenes is utilized to tether the AuNP to the native surface of carbon nanotubes, and reduce graphene oxide and micro‐diamond powder, likely via addition to π‐conjugated carbon skeleton or insertion into the functionalities at the surface, to yield the desired hybrid material without the need for pretreatment of the surface. The AuNP‐covalent hybrid materials are robust in that they survive vigorous washing and sonication. In the absence of photolysis no attachment occurs with the same N₃‐AuNP. The nanohybrid AuNP‐nanohybrid materials are characterized using a combination of TEM, powder XRD, XPS and UV/Vis and IR spectroscopies. All of the characterization studies confirm the uniform incorporation of the AuNP on the irradiated substrates.     

A Study on Transreactions of PET/PEN Reactive Blending in a Twin‐Screw Extruder Using an Axial Dispersion Model

Transreactions of PET and PEN melt‐mixed in a twin‐screw extruder are investigated. The extruder is modeled and characterized in the frame of a tubular system of closed type. The kinetic modeling is based on a modified second‐order reversible reaction equation, which allows the dispersion equation to be solved analytically. The analysis shows a good agreement between the model and experiment. The axial dispersion model is employed to predict the extent of transesterification reactions (X) and degree of randomness (RD). ¹H NMR measurements are performed to estimate X and RD. Theoretical and experimental data are in good agreement. The model can thus be exploited to describe the effects of processing parameters, mixing time, mixing temperature, and blend composition on X and RD.

     

以方沸石负载Ni(Ⅱ)催化剂修饰的电极电氧化甲醇(英文)

There is a high overvoltage in the oxidation of methanol in fuel cells,and so modified electrodes are used to decrease it.A modified electrode that used Ni(II) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed.Analcime zeolite was synthesized by hydrothermal synthesis,and Ni(II) ions were incorporated into the analcime structure,which was then mixed with carbon paste to prepare modified electrode.The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry.The effects of the scan rate of the potential,concentration of methanol,and amount of zeolite were investigated.The rate constant for the catalytic reaction of methanol was 6 × 103 cm3 mol-1 s-1 from measurements using chronoamperometry.The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.