Ultrafast temperature relaxation evolution in Au film under femtosecond laser pulses irradiation

Ultrafast temperature relaxation processes in Au film including two temperature relaxation and thermal diffusion relaxation with femtosecond laser pulse excitation were investigated numerically by Finite Element Method (FEM). With the temperature dependent thermal parameters, the full 2D temperature field evolution in picosecond and nanosecond domains were obtained. It is proposed that the heat transfer depth can be alternatively localized or enhanced by the distinct temperature relaxation mechanisms. Moreover, the effect of laser parameters and Au film thickness and surface reflectivity on the two temperature relaxation time were analysed.     

Transformation of methane to synthesis gas over metal oxides without using catalyst

This article reviews a new developing method in the field of metal oxide reduction in chemical and metallurgical processes, which uses methane as a reducing agent. Commonly, coal is used as the reducing agent in the reduction of metal oxide and other inorganic materials; Metal producing factories are among the most intensive and concentrated source of greenhouse gases and other pollutants such as heavy metals, sulfur dioxide and fly ash. Thermodynamically, methane has a great reducing capability and can be activated to produce synthesis gas over a metal oxide as an oxygen donor. Metal oxide reduction and methane activation, two concurrent thermochemical processes, can be combined as an efficient and energy-saving process; nowadays this kind of technologies is of great importance. This new reduction process could improve energy efficiencies and significantly decrease greenhouse gas emission compared to the conventional process; furthermore, the produced gases are synthesis gas that is more valuable than methane. In this paper, thermodynamic studies and advantages of this promising method were discussed. The major aim of this article is to introduce methane as a best and environmentally friendly reducing agent at low temperature.     

Efficient chiral monophosphorus ligands for asymmetric Suzuki-Miyaura coupling reactions

A series of novel P-chiral monophosphorus ligands exhibit efficiency in asymmetric Suzuki-Miyaura coupling reactions, enabling the construction of an array of chiral biaryl products in high yields and excellent enantioselectivities (up to 96% ee) under mild conditions. The carbonyl-benzooxazolidinone moiety in these chiral biaryl products allows facile derivatization for further synthetic applications. A computational study has revealed that a π-π interaction between the two coupling partners can enhance the enantioselectivity of the coupling reaction.     

Iterated fast multiscale Galerkin methods for Fredholm integral equations of second kind with weakly singular kernels

We propose iterated fast multiscale Galerkin methods for the second kind Fredholm integral equations with mildly weakly singular kernel by combining the advantages of fast methods and iteration post-processing methods. To study the super-convergence of these methods, we develop a theoretical framework for iterated fast multiscale schemes, and apply the scheme to integral equations with weakly singular kernels. We show theoretically that even the computational complexity is almost optimal, our schemes improve the accuracy of numerical solutions greatly, and exhibit the global super-convergence. Numerical examples are presented to illustrate the theoretical results and the efficiency of the methods.     

Review: Recent research progress on preparation of silver nanowires by soft solution method and their applications

Owing to the unique and tunable optical, plasmonic and electrical properties of silver nanowires, they are widely used as the templates for the preparation of Au or Pt nanotubes, as substrates for surface‐enhanced Raman scattering (SERS) and detectors for some chemicals. Soft solution method is a facile and effective method for the preparation of silver nanowires with well‐controlled morphology and uniform size. By this approach, silver nanowires can be readily prepared with mild reaction condition, general materials available and facile procedure. This review concentrates on the preparation of silver nanowires via various soft solution methods and their applications in the formation of metallic nanotubes, SERS and detection for some chemicals. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of trace amounts of nitrite by single-sweep polarography

A single-sweep polarographic determination of nitrite in 0.2 M sulphuric acid medium containing nickel(II) sulphate and ammonium thiocyanate is described. The ternary complex (NiSCNNO)⁺ which is formed in the solution is strongly adsorbed on the surface of the mercury electrode and an adsorptive polarographic wave at ?0.57 V (vs. SCE) is related to the concentration of nitrite in the range 2.0 × 10^?8-1.0 × 10^?6 M. The detection limit is 8 × 10^?9 M. The relative standard deviation is 1.5% and the regression coefficient is 0.998. Most common anions and cations do not interfere. The mechanism of the electrode process was studied by several electrochemical methods. The polarographic wave is attributed to the reduction of nitrogen monoxide in the adsorbed (NiSCNNO)⁺ complex to hydroxylamine. The procedure was applied to the determination of trace amounts of nitrite in sausage, water and nitrate.     

Synthesis of TiO2 photocatalysts in supercritical CO2 via a non-hydrolytic route

Nanoscaled TiO2 powders with narrow size dispersion were prepared in supercritical carbon dioxide via non-hydrolytic acylation/deacylation of titanium alkoxide precursors with or without tris-fluorination. The microstructures of these powders were characterized by spectroscopic (FTIR, TGA, and XRD), microscopic (SEM or TEM), and surface area (BET) measurements. Photocatalytic oxidation of 1-octanol on these calcined TiO2 powders and on commercial T805 TiO2 suspended in aerated supercritical carbon dioxide revealed relative reactivity controlled by the powder microstructures. Calcined TiO2 prepared from titanium(IV) isopropoxide and trifluoroacetic anhydride was effectively dispersed in aerated supercritical carbon dioxide under stirring and exhibited high photocatalytic oxidation activity.     

Brillouin power spectrum analysis for partially uniformly strained optical fiber

Due to the restriction of the spatial resolution, about 1 m for current commercially available system, strain distribution measured by Brillouin optical time domain reflectometer (BOTDR) is slightly different from the actual one. In this paper, the equation of the Brillouin power spectrum for partially uniformly strained fiber within the spatial resolution is theoretically derived. Based on the derived results, investigation has been made on the shape characteristics of the superposed Brillouin power spectrum, as well as the dependence of the calculated strain of BOTDR on the actual strain of the fiber. It was found that the difference between the calculated strain and the actual strain depends mainly on the strain value of the fiber and the strained length within the spatial resolution for the given distributed sensing system.     

Eu(TTA)3复合体系荧光性能和FTIR研究

合成Ｅｕ（ＴＴＡ）３复合体系并研究了其荧光性能。     

Holey Graphitic Carbon Derived from Covalent Organic Polymers Impregnated with Nonprecious Metals for CO2 Capture from Natural Gas

Natural gas (NG), as a renewable and clean energy gas, is considered to be one of the most attractive energy carriers owing to its high calorific value, low price, and less pollution. Efficiently capturing CO₂ from NG is a very important issue since CO₂ reduces energy density of natural gas and corrodes equipment in the presence of water. In this study, the authors use holey graphene‐like carbon derived from covalent organic polymers (COP) impregnated with nonprecious metals, i.e., COP graphene, as highly efficient separation materials. The dual‐site Langmuir–Freundlich adsorption model based ideal absorbed solution theory is applied to explore the adsorption selectivity. The experimental results along with first principles calculations show Mn‐impregnated COP graphene exhibits greater CO₂/CH₄ selectivity than Fe and Co impregnated materials. Particularly, the selectivity of C–COP–P–Mn reaches 11.4 at 298 K and 12 bars, which are much higher than those in many reported conventional porous materials and can be compared to the highest separation performance under similar condition. Importantly, all the three COP graphene show remarkably high regenerability (R > 77%), which are much better than many reported promising zeolites, active carbon, and metal organic frameworks. Accordingly, COP graphene are promising cyclic adsorbents with high selectivity for separation and purification of CO₂ from natural gas.