基于磁性功能复合材料的新型比色法检测Cu2+

基于新型类过氧化物酶活性的磁性功能化磁珠/金/聚苯胺/MnO2复合物复合材料(MB/Au/PANI/MnO2),联合半胱氨酸的选择性反应机制,构建了一种快速且灵敏的Cu2+比色检测法.采用原位还原法制备MB/Au/PANI/MnO2复合材料,该材料可直接使4,3,3,5,5-四甲基联苯胺(TMB)氧化成阳离子自由基(o...     

Adhesion and friction studies of Au nanoparticle‐textured surfaces with colloidal tips

Surface roughness plays an important role in affecting the adhesive force and friction force in microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS). One effective approach of reducing adhesion and friction of contacting interfaces is to create textured surface, which is especially beneficial for MEMS'/NEMS' production yield and product reliability. In this article, we present a convenient method to fabricate the nano‐textured surfaces by self‐assembling Au nanoparticles (NPs) on the silicon (100) surfaces. The nanoparticle‐textured surfaces (NPTS) with different packing density and texture height were prepared by controlling the assembling time and the size of Au NPs. The morphologies and chemical states of NPTS were characterized by atomic force microscope (AFM), field emission scanning electron microscope, and XPS. The adhesion and friction on the NPTS were studied by AFM with colloidal tip. The results show that the nano‐textured surfaces have effectively reduced adhesive force and friction force compared with the 3‐aminopropyl trimethoxysilane self‐assembled monolayer surfaces. The lowered adhesion and friction were attributed to the reduced real area of contact between NPTS and colloidal tip. The adhesion and friction of the NPTS are varying with the texture packing density and dependent on both the texture height and asperities spacing, which are related to the size and coverage ratio of NPs on surfaces. Copyright © 2011 John Wiley & Sons, Ltd.     

Renewed Insight into the Promoting Mechanism of Magnesium Hydride on Ammonia Borane

Our previous study found that mechanically milling with magnesium hydride (MgH₂) could dramatically improve the dehydrogenation property of ammonia borane (AB). Meanwhile, it appears that the MgH₂ additive maintains its phase stability in the milling and subsequent heating process. In an effort to further the mechanistic understanding of the AB/MgH₂ system, we reinvestigated the property and structure evolution in the hydrogen release process of the AB/0.5MgH₂ sample. Property examination using volumetric method and synchronous thermal analyses showed that the AB/0.5 MgH₂ sample releases ～13.8 wt % hydrogen after being heated at 300 °C. This hydrogen amount is in excess of that available from AB, indicative of the participation of a faction of MgH₂ in the dehydrogenation process of AB. Structural and chemical state analyses using Fourier transformation infrared spectroscopy and solid‐state ¹¹B nuclear magnetic resonance techniques further showed that part of MgH₂ participates in the dehydrogenation process of AB from the first step, resulting in the formation of Mg? B? N? H intermediate species. The incorporation of Mg in AB is believed to be a crucial event leading to dehydrogenation property improvements, particularly for the release of the last equivalent of H₂ in AB at relatively moderate temperature. These findings have provided renewed insight into the promoting mechanism of MgH₂ on the hydrogen release from AB.     

氧化钨对 Pt-RuOxHy 电催化剂甲醇氧化性能的促进作用

 在多壁碳纳米管负载的 Pt-RuOxHy 样品中引入氧化钨 (WOm), 能有效抑制样品中水合氧化钌 (RuOxHy) 在酸性电解质溶液中的溶解. 在扩展电势 (–0.20~0.96 V vs SCE) 的电化学预处理过程中, RuOxHy 的溶解程度从 Pt-RuOxHy 中的 70% 降至 Pt-RuOxHy-WOm 中的 15%. 计时电流曲线测试结果表明, 与窄电势区间 (–0.20~0.46 V vs SCE) 预处理的钌物种没有流失的样品相比, 经扩展电势区间预处理的 Pt-RuOxHy-WOm 样品上甲醇电氧化反应的活性没有下降, 而 Pt-RuOxHy 样品的活性则下降 50%.     

尿样中铀同位素的ICP-MS快速测量技术研究

核事故状态下的应急处理,要求对环境介质中的放射性核素进行快速分析。尿样中铀同位素测量作为内照射剂量评价的主要手段,其分析效率越高,则对核事故中涉铀人员的安全救治越及时、有效。而尿样中其它无机离子是铀含量的106倍,导致ICP-MS测量过程中尿盐堵塞进样毛细管。为降低样品的含盐量并获得较好的检测结果,本文对样品预处理过程进行优化。采用先加热氧化去除有机物,再进行1～10倍稀释后测试样品的铀同位素丰度及浓度。结果表明：将25 mL样品稀释至100 mL后效果最佳,分析方法不确定度为5.4 %,回收率95 %~105 %。     

石墨烯气凝胶吸附剂的制备及其在水处理中的应用

石墨烯气凝胶(GA)是以石墨烯为主体的三维互联的多孔网络结构,因其具有优良的结构可控性、极大的比表面积、独特的空间互联结构、良好的电子传输能力成为水处理中应用的理想材料。至今已经有大量制备GA的方法,其性能和结构因制备方法的不同差异很大,但是尚未有文献系统地报道GA的制备机理和不同方法与GA结构及性能之间的联系。本文系统性地介绍GA吸附剂的制备方法与它在水处理中的应用并进行展望。对GA的结构特性尤其是与吸附有关的特性以及结构和吸附之间的关系进行分析,并通过对GA的制备机理和制备过程中的关键因素进行归纳,基于GA的制备机理将其制备方法进行分类(模板法、垫片支撑法、自支撑法、基面法和凝胶法)并对五种方法进行了详细介绍,对目前GA在水处理技术中(吸附、光催化、去离子电容等)去除重金属和有机污染物相关应用和机理进行综述,最后对目前GA在环境中应用中存在的问题及研究前景进行了总结和展望。     

金属载体强相互作用增强Au/TiO2催化剂在3-硝基苯乙烯选择性加氢反应的活性

自Haruta与Hutchings于上世纪八十年代末发现金纳米催化剂优异的反应活性以来,科研人员对金催化的应用领域进行了广泛而深入地研究.对金催化科学和应用领域的研究一直在进行.大量的研究表明,金催化剂在各种选择性氧化反应中具有优异的催化性能(高活性和高选择性).然而,在催化加氢反应中,尽管金催化剂相比于铂族金属显示出...     

Dynamic analysis for the hyperchaotic system with nonholonomic constraints

Nonlinear Dynamics - This paper first formulates a new hyperchaotic system for particle motion and analyzes the equilibrium stability of the system and the hyperchaotic behaviors in the motion of...     

Synthesis and characterization of Fe3O4@C@Ag nanocomposites and their antibacterial performance

We synthesized Fe₃O₄@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe₃O₄@Ag nanocomposites, the Fe₃O₄@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe₃O₄@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10 μg/mL. Antibacterial activity of the Fe₃O₄@C@Ag nanocomposites was maintained for more than 40 h at 37 °C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe₃O₄@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic-optical materials.     

Maximum likelihood Newton recursive and the Newton iterative estimation algorithms for Hammerstein CARAR systems

This paper discusses the identification problems of Hammerstein controlled autoregressive autoregressive (CARAR) systems using the maximum likelihood principle and Newton optimization method. A Newton recursive algorithm and a Newton iterative algorithm using the maximum likelihood principle are presented. The simulation results show that the proposed algorithms can effectively estimate the parameters of the Hammerstein CARAR systems.