模式识别预报双阳离子共交换Cu,Me-ZSM-5分子筛对NO分解的催化活性

本文采用模式识别方法,分析了用于NO分解反应的分子筛催化剂Cu,Me-ZSM-5中的第二种交换阳离子Me对其活性的影响.根据模式识别二维分类图,很好地预报了不同活性的催化剂.并初步讨论了引入共交换金属离子导致催化剂活性变化的原因.     

模式识别预报双阳离子共交换Cu,Me—ZSM—5分子筛对NO分解的催化…

本文采用模式识别方法，分析了用于ＮＯ分解反应的分子筛催化剂Ｃｕ，Ｍｅ－ＺＳＭ－５中的第二种交换阳离子Ｍｅ对其活性的影响，根据模式识别二维分类图，很好地预报了不同活性的催化剂，并初步讨论了引入共交换金属离子导致催化剂活性变化的原因。     

Pt/Ce0.75Zr0.25O2的催化性能及其氧移动性的 18O 同位素交换表征

 采用浸渍法制备了Pt/Ce0.75Zr0.25O2催化剂,考察了催化剂对乙醇及CO的氧化活性,并采用 18O 同位素交换、乙醇程序升温表面反应(C2H5OH-TPSR)、一氧化碳程序升温脱附(CO-TPD)和程序升温还原(H2-TPR)等技术对催化剂进行了表征. 结果表明, Pt/Ce0.75Zr0.25O2催化剂表现出较高的乙醇和CO氧化活性,其催化活性随着Pt负载量的增加而提高. 当Pt负载量为3%时,活性最高. 继续增加Pt负载量,催化剂活性下降. C2H5OH-TPSR和CO-TPD结果表明,催化剂对乙醇或CO的氧化活性与从催化剂表面脱附出来的CO2量有对应关系, CO2脱附量越大,催化剂活性越高. 18O 同位素交换结果表明,表面氧交换能力与其氧化活性有一定对应关系,催化剂的表面氧交换能力越高,氧化活性越高.     

非均相催化氢化CO_2合成醇Ⅱ．双金属交换顺序及离子交换液pH值的影响

用ＸＰＳ分析由离子交换法制备的Ｒｕ－Ｃｕ双金属非均相催化剂，考察双金属交换顺序对催化剂性能的影响。结果表明，交换顺序对催化剂性能影响较大，先交换铜离子后交换钉离子有助于提高催化剂的活性。低价态金属元素是催化剂在反应状态下的活性组分，此外，高于交换液的ｐＨ值对催化剂性能的影响也较大，ｐＨ值偏碱性时有助于催化剂活性的提高。     

高分子分散钯催化剂催化对硝基苯酚加氢反应的研究

制备了多种商品化的离子交换树脂和螯合树脂分散钯催化剂,考察了它们对对硝基苯酚加氢反应的催化活性。结果表明这些催化剂对对硝基苯酚的加氢反应有较高的活性,其中阴离子交换树脂和H型阳离子交换树脂分散钯催化剂活性最高。催化剂加氢活性与反应进程有关。     

非均相催化氢化CO2合成醇：Ⅱ.双金属交换顺序及离子交换液pH值…

用ＸＰＳ分析由离子交换法制备的Ｒｕ－Ｃｕ双金属非均相催化剂，考察双金属交换顺序对催化剂性能的影响。结果表明，交换顺序对催化剂性能影响较大，先交换铜离子后交换钌离子有助于提高催化剂的活性。低价态金属元素是催化剂在反应状态下的活性组分。此外，离子交换液的ｐＨ值对催化剂性能的影响也较大，ｐＨ值偏碱性时有助于催化剂活性的提高。     

过渡金属氧化物氧还原催化剂的研究进展

过渡金属氧化物（TMOs）是阴离子交换膜燃料电池最有前途的氧还原催化剂之一. 目前,TMOs的氧还原活性同铂基催化剂相比仍然有一定的差距,研究如何合成具有高催化活性的TMOs催化剂非常重要. 导电性和本征活性一直被认为是开发高性能TMOs催化剂的两个关键因素,本文着重总结与评述了近年来有关TMOs氧还原催化剂在导电性和本征活性方面的研究进展,尝试提出了未来提高TMOs氧还原催化活性的努力方向.     

质子交换膜燃料电池阳极抗CO催化剂的研究进展

质子交换膜燃料电池采用重整气或甲醇为燃料时 ,阳极催化剂的CO中毒问题是影响其性能的主要原因 .使用抗CO催化剂是解决该问题的根本方法 .文中对质子交换膜燃料电池的CO问题进行了简介 ,比较详细地介绍了目前抗CO催化剂研究的发展现状 ,包括各种催化剂的活性、制法及抗CO机理 .Mo、W是很有希望改进阳极催化剂抗CO能力的材料 ,多组分催化剂是比较有希望的方向 .     

质子交换膜燃料电池Pd修饰Pt/C催化剂的电催化性能

通过对Pt催化剂表面进行Pd修饰提高质子交换膜燃料电池阴极催化剂的氧还原反应(ORR)活性. 采用乙二醇还原法制备了不同比例的Pd修饰Pt/C催化剂. 透射电镜(TEM)和X射线衍射(XRD)测试结果表明, 制备的催化剂贵金属颗粒粒径主要分布在1.75～2.50 nm之间, 并均匀地分散在碳载体表面. 循环伏安方法(CV)研究表明Pd修饰Pt/C催化剂的电化学活性面积低于传统的Pt/C催化剂. 但通过旋转圆盘电极(RDE)测试研究发现, 制备的催化剂具有比传统Pt/C催化剂高的ORR活性.     

CuCl_2和HY分子筛的表面反应及Cu/Y分子筛的制备及其催化甲醇氧化羰基化（英文）

以CuCl2为前驱物与HY分子筛进行固相离子交换制备了Cu/Y催化剂,采用热重方法研究了CuCl2与HY分子筛的表面固相离子交换反应,结合活性测试表明催化剂中高度分散的CuCl和离子交换形式的Cu+物种是甲醇氧化羰基化合成碳酸二甲酯的催化活性中心.X射线光电子能谱表征和元素分析结果表明,活性金属Cu主要以CuCl形式存在于分子筛外表面,而在分子筛笼内则以交换的Cu+和少量吸附的CuCl形式存在.与以CuCl为交换铜源所制催化剂相比,以CuCl2为铜源制备的催化剂Cu含量低,催化活性更高.     

Theoretical study of Cu(I)Y zeolite: structure and electronic properties

The structural and electronic properties of the accessible Cu(I) site of a faujasite-type zeolite have been studied, by use of large cluster models and a density functional theory-based methodology. We demonstrate that the local ideal C(3) symmetry of the Cu(I) site II is broken. The Cu(I) cation is bonded to the zeolite framework by one bond of about 2.26 A and two shorter ones of 2.07 A. We demonstrate that only one cation position exists at this site. This result is also confirmed by a molecular electrostatic potential analysis. We show that local properties at site II, as well as the global properties of the solid (frontier orbitals), do not depend on the Al and cation distribution and only slightly on the cocation nature. Taking into account the present results and well-known experimental data, we propose that specific catalytic behaviors are correlated with local response properties, such as the local acid strength or, in other reactions, specific local architecture or confinement.     

Fluorescent sensors for the enantioselective recognition of mandelic acid: signal amplification by dendritic branching

Novel chiral bisbinaphthyl compounds have been synthesized for the enantioselective fluorescent recognition of mandelic acid. By introducing dendritic branches to the chiral receptor unit, the fluorescence signals of the receptors are significantly amplified because of the light-harvesting effect of the dendritic structure. This has greatly increased the sensitivity of the sensors in the fluorescent recognition. Study of the three generation sensors demonstrates that the generation zero sensor is the best choice for the recognition of mandelic acid because of its greatly increased fluorescence signal over the core and its high enantioselectivity. This sensor is potentially useful for the high throughput screening of chiral catalysts for the asymmetric synthesis of alpha-hydroxycarboxylic acids.     

Investigation of the origin of selectivity in cavitand-based supramolecular sensors

The sensing properties of functionalized cavitands have been studied by thin-film coating TMSR chemical sensors and by measuring their responses towards model analytes. We studied the relationship between the sensor performance, in terms of sensitivity and selectivity, and the molecular recognition properties of the cavitands. The Langmuir-like shape of the adsorption isotherm, obtained in the case of short-chain alcohols, demonstrated that selective binding can be achieved by the synergistic interactions of the cavity and the bridging PO(in) groups. In the absence of these substituents, the peripheral alkyl chains necessary for the formation of highly permeable thin films attenuate the cavity effect because of nonspecific dispersion interactions. This completely overrides the response originating from molecular recognition. The same effect is observed when the PO groups are oriented outward from the cavity. The use of multivariate chemometrics and the study of the correlations between sensors sensitivity and analyte properties provided further evidence of molecular recognition phenomena, whose intensity is enhanced by the permanent free volume created by the rigid cavity surrounding the PO(in) group.     

NanoSIMS measurements of sub-micrometer particles using the local thresholding technique

NanoSIMS has been the most widely used analytical technique for measuring the elemental and isotopic ratios of micrometer to sub-micrometer particles, e.g., pre-solar grains, soil particles, and fog-helium aerosol particles. Automated sample stage movement combined with particle recognition algorithm is commonly used to improve analytical efficiency. However, due to the effect of sample topography or variation in ion yield rates, the global thresholding method used in previous studies has a low recognition rate. In order to improve the recognition rate, here we have developed a high-efficiency sub-micron particle recognition method. This method searches for the threshold that minimizes the intra-class variance of the local domain (the radius of the local is set to 10 pixels). The central pixel of this circular ROI is then tested against the threshold found for this region. Presolar grains from the Qingzhen (EH3) meteorite and soil organic particles from Oxisol were analyzed. The analytical efficiency was improved by 120-200% compared with the global thresholding algorithms. This method can be widely applied in automated studies of large numbers of micrometer to sub-micrometer particles.     

Development of Enantioselective Fluorescent Sensors for Chiral Recognition

Novel chiral compounds have been synthesized for the enantioselective fluorescent recognition of alpha-hydroxycarboxylic acids and amino acids. By introducing dendritic branches to the chiral receptor units, the fluorescence signals of the receptors are significantly amplified because of the light-harvesting effect of the dendritic structure. This has greatly increased the sensitivity of the sensors in the fluorescent recognition. Highly enantioselective fluorescent responses have also been ac…     

Understanding the recognition mechanism of protein-RNA complexes using energy based approach

Protein-RNA interactions perform diverse functions within the cell. Understanding the recognition mechanism of protein-RNA complexes is a challenging task in molecular and computational biology. In this work, we have developed an energy based approach for identifying the binding sites and important residues for binding in protein-RNA complexes. The new approach considers the repulsive interactions as well as the effect of distance between the atoms in protein and RNA in terms of interaction energy, which are not considered in traditional distance based methods to identify the binding sites. We found that the positively charged, polar and aromatic residues are important for binding. These residues influence to form electrostatic, hydrogen bonding and stacking interactions. Our observation has been verified with the experimental binding specificity of protein-RNA complexes and found good agreement with experiments. Further, the propensities of residues/nucleotides in the binding sites of proteins/RNA and their atomic contributions have been derived. Based on these results we have proposed a novel mechanism for the recognition of protein-RNA complexes: the charged and polar residues in proteins initiate recognition with RNA by making electrostatic and hydrogen bonding interactions between them; the aromatic side chains tend to form aromatic-aromatic interactions and the hydrophobic residues aid to stabilize the complex.     

Radial control of recognition and redox processes with multivalent nanoparticle hosts

Mixed Monolayer Protected Gold Clusters (MMPCs) featuring both hydrogen bonding and aromatic stacking molecular recognition functionalities have been used to create multivalent hosts for flavins. Multitopic binding of these hosts to flavin was shown to have a strong radial dependence: when the recognition site was brought closer to the MMPC surface, recognition was enhanced approximately 3-fold due to increased preorganization. The effect of preorganization is reversed upon reduction of flavin, where the MMPC with longer side chains bind the flavin guest approximately 7-fold stronger than the short chain counterpart due to unfavorable dipolar interactions between the electron-rich aromatic stacking units of the host and the anionic flavin guest. This fine-tuning of recognition and redox processes provides both a model for enzymatic systems and a tool for the fabrication of devices.     

Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective

The recognition of anions in water remains a key challenge in modern supramolecular chemistry, and is essential if proposed applications in biological, medical, and environmental arenas that typically require aqueous conditions are to be achieved. However, synthetic anion receptors that operate in water have, in general, been the exception rather than the norm to date. Nevertheless, a significant step change towards routinely conducting anion recognition in water has been achieved in the past few years, and this Review highlights these approaches, with particular focus on controlling and using the hydrophobic effect, as well as more exotic interactions such as C?H hydrogen bonding and halogen bonding. We also look beyond the field of small‐molecule recognition into the macromolecular domain, covering recent advances in anion recognition based on biomolecules, polymers, and nanoparticles.     

聚合物在荧光检测领域的应用

聚合物是由一种或几种重复单体以共价键连接形成的大分子化合物, 它不仅能够保持单体的性质, 而且由于聚合后单体间的协同作用, 使其表现出独特的性能. 聚合物作为基础材料在荧光检测领域得到广泛应用. 聚合物通过氢键作用、 亲疏水作用及范德华力等分子间相互作用, 实现了对特定目标物的选择性识别; 通过信号转换和放大功能, 可以将分子识别作用转化为荧光信号; 可以作为骨架连接多个识别单元, 通过多价结合作用等提高识别目标物的能力, 或连接不同的功能单元, 构建多功能的分子器件. 本文对聚合物在荧光检测领域的应用进行了概述.     

Investigation of surface interactions in molecular recognition of phosphonate imprinted organosilicates and the role of water

Surface interactions in molecular recognition of phosphonate imprinted organosilicates and the role of water have been studied. NMR and calorimetry studies have shown the changing nature of the surface water structure on silicate surfaces due to template directed molecular imprinting. Results indicate the interaction of an organophosphonate compound with the functionalized silica surfaces to be through surrounding water molecules. However, with nonfunctionalized surfaces, additional higher energy interactions were possible. Further, our results support the possible templating effect of water during the imprint process.