钴和铁熔体短程序的分子动力学模拟

通过分子动力学模拟研究了金属钴和铁熔体从普通液态到过冷液态普通微观结构的性质.所计算两体分布函数与可获得的实验结果基本一致,从普通液态到过冷液态的局域结构中的原子配位数为11和12的分布几率随着温度的降低而变小,而原子的配位数大于12的分布几率反而增加,角分布函数位于55.有一个明显的峰,位于110°有一个宽展的峰,位于150°有一个肩膀,表明金属钴和铁熔体的微观局域结构要比规则的二十面体团簇的结构复杂得多.我们的模拟结果表明金属熔体中的二十面体短程序随着温度的降低而增加,并在过冷液态中而占优势.     

Effect of UV anneal on plasma CVD low-k film

Plasma-enhanced chemical vapor deposition (PE-CVD) low-dielectric (low-k) film was irradiated with ultra violet (UV) light of wavelength 172 nm to enhance mechanical strength and reduce dielectric constant (k value). The thickness measurement method for the UV annealed low-k film is discussed. The effects of UV irradiation on dielectric constant, shrinkage, stress, density, pore size, mechanical strength, and structure are clarified and the mechanism is discussed.     

Application of surface‐enhanced Raman scattering in cell analysis

In surface‐enhanced Raman scattering (SERS), the scattered intensity is drastically increased due to a resonant interaction with surface plasmons of coin metals. SERS is a nondestructive spectroscopic method applied also to biomedical samples. It inherits the advantages of normal Raman spectroscopy and at the same time overcomes the inherent low sensitivity problem. These properties endow SERS with exciting opportunities to be a successful analytical tool for cell analysis. SERS can be used to detect only molecules located on or close to the metallic nanostructures which can support surface plasmon resonances for the enhancement of the Raman signals. Therefore, these metallic nanostructures play a key role in the application of SERS in cell analysis. By incorporating the SERS substrates into the biosamples, molecular structural probing and cellular imaging become possible. In the past decade, analysts worldwide have developed many schemes to study the chemical changes and component distribution in cells by using SERS. In this paper, the application of SERS in cell analysis is reviewed. Copyright © 2011 John Wiley & Sons, Ltd.     

Key Role of a-Top CO on Terrace Sites of Metallic Pd Clusters for CO Oxidation

Pd-based catalysts are the most widely used for CO oxidation because of their outstanding catalytic activity and thermal stability. However, fundamental understanding of the detailed catalytic processes occurring on Pd-based catalysts under realistic conditions is still lacking. In this study, we investigated CO oxidation on metallic Pd clusters supported on Al₂O₃ and SiO₂. High-angle annular dark-field scanning transmission electron microscopy revealed the formation of similar-sized Pd clusters on Al₂O₃ and SiO₂. In contrast, CO chemisorption analysis indicated a gradual change in the dispersion of Pd (from 0.79 to 0.2) on Pd/Al₂O₃ and a marginal change in the dispersion (from 0.4 to 0.24) on Pd/SiO₂ as the Pd loading increased from 0.27 to 5.5 wt %; these changes were attributed to differences in the metal-support interactions. Diffuse reflectance infrared Fourier-transform spectroscopy revealed that fewer a-top CO species were present in Pd supported on Al₂O₃ than those in Pd supported on SiO₂, which is related to the morphological differences in the metallic Pd clusters on these two supports. Despite the different dispersion profiles and surface characteristics of Pd, O₂ titration demonstrated that linearly bound CO (with an infrared signal at 2090 cm⁻¹) reacted first with oxygen in the case of CO-saturated Pd on Al₂O₃ and SiO₂, which suggests that a-top CO on the terrace site plays an important role in CO oxidation. The experimental observations were corroborated by periodic density functional calculations, which confirmed that CO oxidation on the (111) terrace sites is most plausible, both kinetically and thermodynamically, compared to that on the edge or corner sites. This study will deepen the fundamental understanding of the effect of Pd clusters on CO oxidation under reaction conditions.     

Synthesis of nanoscale zero‐valent iron modified graphene oxide nanosheets and its application for removing tetracycline antibiotic: Response surface methodology

Nowadays, pharmaceutical antibiotics are known as a serious class of pollutants. Therefore, it is important to develop effective methods for removing these pollutants from aqueous media. Different methods were applied for this purpose, and among these methods, chemical reduction by a cheap and eco‐friendly nanocatalyst is the most efficient and simplest method. In this research, based on graphene oxide supported by zero‐valent iron in mono‐, bi‐, and tri‐metallic systems, various nanocomposites were synthesized and used to degrade tetracycline as a model antibiotic from aqueous media. An investigation was carried out on the synergic effect among graphene oxide and the nano zero‐valent iron‐based tri‐metallic system as well as removal efficiencies. It was found that higher degradation efficiency is yielded by graphene oxide supported by Fe/Cu/Ag tri‐metallic system. The maximum synergic effect occurs at an acidic medium. The Brunauer–Emmett–Teller, Fourier transform spectroscopy, scanning electron microscopy‐energy dispersive X‐ray analysis, transmission electron microscopy, and X‐ray diffraction analysis were used to characterize the synthesized nanocomposites, which has successfully proved the loading of nanoscale Fe/Cu/Ag tri‐metallic on a graphene oxide support. The central composite design was used to model and optimize all involved variables affecting antibiotic removal efficiency. The consequences illustrated the optimum condition regarding the removal of 50 ppm of tetracycline, for the nanocomposites dose of 3.0 mg ml^?1, the contact time of 30 min, and pH of 2, was achieved using the simplex non‐linear optimization method. Moreover, antibiotic adsorption kinetic models were also investigated. Finally, the tetracycline removal from aqueous media at different concentrations, 25, 50, and 75 ppm, was successful by applying the proposed nanocomposite, and the results showed tetracycline removal efficiencies of above 70%.     

Post modification of zinc based coordination polymer to prepare Zn‐Mo‐ICP nanoparticles as efficient self‐supported catalyst for olefin epoxidation

Preparation, characterization, and catalytic properties of bimetallic coordination polymer constructed from 2‐aminoterephthalic acid as linker, zinc cations as node, and cis‐dioxo molybdenum units as catalytic active sites are reported via two pathways. Molybdenum centers were placed in N,O positions created by condensation reaction of 2‐aminoterephthalic acid with salicylaldehyde while zinc cations coordinated via carboxylic acid groups of linker to achieve infinite chains of metalo‐ligand. The obtained coordination polymer was fully characterized and its catalytic properties in the epoxidation of olefins with tert‐butyl hydroperoxide (TBHP) described. In comparison with previously reported heterogenized molybdenum catalysts, this new coordination polymer exhibited good conversion as well as high selectivity in the epoxidation of olefins. The catalyst is stable under ambient conditions and could be reused as active catalyst for at least five times.     

The h-SbxWO3+2x Oxygen Excess Antimony Tungsten Bronze

We describe the previously unreported oxygen excess hexagonal antimony tungsten bronze with composition Sb_0.5W₃O₁₀, in the following denoted as h-Sb_xWO_3+2x with x=0.167, to demonstrate its analogy to classical A_xWO₃ tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 °C<T<620 °C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-Sb_xWO_3+2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a=7.4369(4) Å and c=3.7800(2) Å. The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO₆ octahedra. h-Sb_xWO_3+2x has a resistivity of ρ_{300 K}≈1.28 mΩ cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the Γ point.     

纳米多孔双金属氧化物NiCo2O4的制备及其电化学性能

采用快速凝固与脱合金化相结合的方法制备纳米多孔Ni、Ni-Co合金,分别经腐蚀与退火获得纳米多孔NiO、NiCo_2O_4,采用XRD、SEM、TEM、N_2吸附-脱附等对多孔NiO、NiCo_2O_4电极的物相、形貌结构、孔径分布进行表征,并通过循环伏安、恒电流充放电等方法测试多孔电极的电化学性能。结果表明,得到的纳米多孔NiO具有均匀的"泥裂"式结构,在1A·g~(-1)电流密度下比电容为375 F·g~(-1),当电流密度增加至20 A·g~(-1)时的比容保持率为67.5%,在4 A·g~(-1)电流密度下循环充放电1 000次,比容保持率为81.7%;NiCo_2O_4形成典型的开放式纳米多孔双连续结构,其在1A·g~(-1)电流密度下比电容为674 F·g~(-1),当电流密度增加至20 A·g~(-1),比容保持率达72.0%;在4 A·g~(-1)电流密度下循环充放电1 000次,比容保持率达92.9%,双连续纳米多孔结构及其提供的机械稳定性,使得NiCo_2O_4表现出更为优异的超电容性能。     

Ca12[Mn19N23] and Ca133[Mn216N260]: Structural Complexity by 2D Intergrowth

Two new calcium nitridomanganates, Ca₁₂[Mn₁₉N₂₃] (P3, a=11.81341(3) Å, c=5.58975(2) Å, Z=1) and Ca₁₃₃[Mn₂₁₆N₂₆₀] ( , a=39.477(1) Å, c=5.5974(2) Å, Z=1), were obtained by a gas–solid reaction of Ca₃N₂ and Mn with N₂ at 1273 K and 1223 K, respectively. The crystal structure of Ca₁₂[Mn₁₉N₂₃] was determined from high‐resolution X‐ray synchrotron powder diffraction data, whereas single‐crystal X‐ray diffraction was employed to establish the crystal structure of the Ca₁₃₃[Mn₂₁₆N₂₆₀] phase, which classifies as a complex metallic alloy (CMA). Both crystal structures have 2D nitridomanganate layers containing similar building blocks but of different levels of structural complexity. Bonding analysis as well as magnetic susceptibility and electron spin resonance measurements revealed that only a fraction of the Mn atoms in both structures carries a localized magnetic moment, while for most Mn species the magnetism is quenched as a result of metal–metal bond formation.