Preparation of SiO2/TiO2 Janus particles by electrostatic assembly,hydrolysis and calcination

This paper describes a novel chemical method for preparing SiO₂/TiO₂ Janus particles.First,polystyrene（PSt）/SiO₂ particles with a raspberry-like structure are prepared by electrostatic assembly.The influences of the reaction time of sulfonation and the treatment times of polyelectrolyte solutions（PDADMAC,PSS）on PSt and SiO₂ are investigated with respect to the surface charge density of the particles.SiO₂/TiO₂ Janus particles are then obtained by hydrolysis of butyl titanate on the surface of PSt/SiO₂ particles followed by a calcination process.Particle size analyzer,Zeta potential instrument,FTIR,TEM and SEM are used to characterize the particle size,the amount of charge on the surface of PSt and SiO₂ particles and the compositions and morphologies of PSt/SiO₂,SiO₂/TiO₂ and PSt/SiO₂/TiO₂.The diameters of the PSt,SiO₂,PSt/SiO₂ and SiO₂/TiO₂ particles are 2.0 μm,303 nm,2.7 μm and 330nm,respectively.     

H1-superconvergence of finite difference method based on Q1-element on quasi-uniform mesh for the 3D Poisson equation

In this paper, the finite difference (FD) method is considered for the 3D Poisson equation by using the Q₁-element on a quasi-uniform mesh. First, under the regularity assumption of , the H¹-superconvergence of the FD solution u_h based on the Q₁-element to the first-order interpolation function is obtained. Next, the H¹-superconvergence of the second-order interpolation postprocessing function based on the FD solution u_h to u is provided. Finally, numerical tests are presented to show the H¹-superconvergence result of the FD postprocessing function to u if .     

Synthesis, characterization, and crystal structures of two novel high-nuclear nickel-substituted dimeric polyoxometalates

Two novel high-nuclear Ni-substituted polyoxometalates Na9K[Ni7(OH)4(H2O)(CO3)2(HCO3)(A-alpha-SiW9O34)(beta-SiW10O37)].5H3O.18H2O (1) and K6Na4[{Ni6(H2O)4(mu2-H2O)4(mu3-OH)2}(x-SiW9O34)2].17.5H2O (2) have been obtained by reaction of K(8)[gamma-SiW10O36] with NiCl2.2H2O in basic conditions. Compounds 1 and 2 all represent the first polyoxometalates substituted by seven and six Ni centers, respectively. Also, compound 1 exhibits a novel asymmetric dimeric structure, composed of [A-alpha-SiW9O34]10- and [beta-SiW10O37]10- units linked by a Ni7 cluster and three carbonates, which exhibit tri- and bidentate coordination modes in 1.     

2-羟基萘甲醛苯甲酰腙衍生物对Al~(3+)的裸眼识别和荧光传感

设计合成了化合物4-羟基苯甲酰-(2-羟基萘甲醛)腙(L)探针,经金属离子识别研究发现探针L对Al~(3+)具有良好的荧光增强识别效果且不受其它金属离子的干扰,且识别过程中溶液的颜色发生了明显变化,可以实现Al~(3+)的可视法检测,核磁滴定、job-plot、基质辅助激光解吸电离飞行时间质谱(MALDI-TOF)等实验结果显示,探针L与Al~(3+)以摩尔比2∶1的方式进行配位。通过对紫外滴定数据的非线性拟合分析,探针L与Al~(3+)的结合常数为1.3×10~4L/mol,最低检测限为3.71×10~(-6)L/mol。因此,该腙类衍生物作为Al~(3+)的荧光及比色探针,识别体系线性范围较宽,检测限低,在痕量Al~(3+)的检测方面具有潜在的应用价值。     

On solitary waves. Part 2 A unified perturbation theory for higher-order waves

A unified perturbation theory is developed here for calculating solitary waves of all heights by series expansion of base flow variables in powers of a small base parameter to eighteenth order for the one-parameter family of solutions in exact form, with all the coefficients determined in rational numbers. Comparative studies are pursued to investigate the effects due to changes of base parameters on (i) the accuracy of the theoretically predicted wave properties and (ii) the rate of convergence of perturbation expansion. Two important results are found by comparisons between the theoretical predictions based on a set of parameters separately adopted for expansion in turn. First, the accuracy and the convergence of the perturbation expansions, appraised versus the exact solution provided by an earlier paper [1] as the standard reference, are found to depend, quite sensitively, on changes in base parameter. The resulting variations in the solution are physically displayed in various wave properties with differences found dependent on which property (e.g. the wave amplitude, speed, its profile, excess mass, momentum, and energy), on what range in value of the base, and on the rank of the order n in the expansion being addressed. Secondly, regarding convergence, the present perturbation series is found definitely asymptotic in nature, with the relative error δ(n) (the relative mean-square difference between successive orders n of wave elevations) reaching a minimum, δ _m , at a specific order, n=n _m , both depending on the base adopted, e.g. n _{m , α} =11-12 based on parameter α (wave amplitude), n _{m , β} =15 on β (amplitude-speed square ratio), and n _{m , ∈} =17 on ∈ ( wave number squared). The asymptotic range is brought to completion by the highest order of n=18 reached in this work.     

滑移爆轰驱动下飞板运动姿态的连续电阻测试法

飞板运动姿态的测定是爆炸焊接机理研究的基础,针对传统电测方法存在干扰因素多、易产生弯曲波等缺陷,设计了一种适用于野外大当量下爆炸焊接飞板姿态实验的连续电阻测试方法。研制了3种不同结构的梯形支架型连续电阻探针元件,利用有限元程序分析了探针的导通压力和响应时间,在此基础上,对3种探针实施了爆炸焊接实验,实验结果表明:金属丝网型探针元件具有最优的导通效果,各段测试曲线光滑无毛刺。以该探针数据计算获得了待测飞板的运动姿态曲线,并与Richter简化模型下的近似计算公式结果进行了对比,两者基本一致。所述测试方法实现了炸药爆速和飞板变形曲线的连续、可靠和快速测量,为滑移爆轰驱动问题、爆轰产物状态方程等的研究提供了测试方法补充。     

Highly Efficient Photoreduction of Low-Concentration CO2 to Syngas by Using a Polyoxometalates/RuII Composite

At present, the fixation of CO₂ always requires it to be extracted from the atmosphere first, which leads to more energy consumption. Thus, direct photoreduction of low-concentration CO₂ to useful chemicals (e.g., syngas) under sunlight is significant from an energy-saving and environmentally friendly perspective. Here, the design and fabrication of a [Ru(bpy)₃]/[Co₂₀Mo₁₆P₂₄] composite is demonstrated for visible-light-driven syngas production from diluted CO₂ (3–20 %) gas with a high yield of approximately 1000 TONs (turnover number of syngas). This activity is an order of magnitude higher than the reported system with [Ru(bpy)₃]²⁺ participation. With evidence from ultrafast transient absorption, GC-MS, ¹H NMR spectroscopy and in situ transient photovoltage tests, a clear and fundamental understanding of the highly efficient photoreduction of CO₂ by the [Ru(bpy)₃]/[Co₂₀Mo₁₆P₂₄] composite is achieved. Making use of the structure and property designable polyoxometalates towards the photo-fixation of CO₂ is a conceptually distinct and commercially interesting strategy for making useful chemicals and environmental protection.     

Light-induced dielectric transparency in single-walled carbon nanotube films

Light-induced difference THz spectroscopy was used to investigate the dielectric response of free-stand single-walled carbon nanotubes (SWCNTs) films in THz region. We observed an enhanced transmission of the peak-signal of THz wave through SWCNTs films under 800 nm pump. In frequency domain, the transparency came from 0.5 to 2.1 THz and the absorption was in 2.1–3.0 THz region. The pump power dependency of the transmission showed this was a nonlinear effect. The dielectric constant response of the SWCNTs films was analyzed theoretically. The analysis suggests that the nonlinear optical properties stem from two factors, which are Drude and Lorentz term for metallic and semiconducting SWCNTs, respectively.     

Self-assembly of four new extended architectures based on reduced polyoxometalate clusters and cadmium complexes

Four new [P₄Mo₆] cluster-based extended structures containing cadmium complexes, [Cd₃(4,4′-Hbpy)₂(4,4′-bpy)₂(H₂O)₈][Cd(H₂PO₄)₂(HPO₄)₄(PO₄)₂(MoO₂)₁₂(OH)₆]·7H₂O 1, (4,4′-Hbpy)₂[Cd(4,4′-bpy)₃(H₂O)₃][Cd(4,4′-bpy)(H₂O)]₂[Cd(H₂PO₄)₂(HPO₄)₄ (PO₄)₂(MoO₂)₁₂(OH)₆]·H₂O 2, [Cd₄(phen)₂(H₂O)₄][Cd(phen)(H₂O)]₂[Cd(HPO₄)₄ (HPO₄)₄(MoO₂)₁₂(OH)₆]·5H₂O 3 and [Cd₄(2,2′-bpy)₂(H₂O)₄][Cd(2,2′-bpy)(H₂O)]₂ [Cd(HPO₄)₄(HPO₄)₄(MoO₂)₁₂(OH)₆]·3H₂O 4 (4,4′-bpy=4,4′-bpyridine, phen=1,10-phenanthroline, 2,2′-bpy=2,2′-bpyridine), have been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. The structure of compound 1 is constructed from the Cd[P₄Mo₆]₂ dimers linked by [Cd₃(4,4′-Hbpy)₂(4,4′-bpy)₂(H₂O)₈] subunits to generate a plane layer. Compound 2 consists of the positive 2D sheets that constructed from Cd[P₄Mo₆]₂ dimers linked by [Cd(4,4′-bpy)(H₂O)] complexes, then the 2D sheets are further linked up together to form a 3D supramolecular framework via extensive hydrogen-bonding interactions among the [P₄Mo₆] clusters, free 4,4′-bpy molecules, dissociated [Cd(4,4′-bpy)₃(H₂O)₃]²⁺ complexes and water molecules. Compounds 3 and 4 show new 2D layered structure, with Cd[P₄Mo₆]₂ building blocks connected by tetra-nuclear [Cd₄{(phen)₂/(2,2′-bpy)₂}(H₂O)₄] clusters and [Cd(phen/2,2′-bpy)(H₂O)] complexes. The fluorescent activities of compounds 3 and 4 are reported.