Mackay,Anti-Mackay,Double-Mackay,Pseudo-Mackay,and Related Icosahedral Shell Clusters

Mackay introduced two important crystallographic concepts in a short paper published 40 years ago. One is the icosahedral shell structure (iss) consisting of concentric icosahedra displaying fivefold rotational symmetry. The number of atoms contained within these icosahedral shells and subshells agrees well with the magic numbers in rare gas clusters, (C₆₀) _N molecules, and some metal clusters determined by mass spectroscopy or simulated on energy considerations. The cluster of 55 atoms within the second icosahedral shell occurs frequently and has been called Mackay icosahedron, or simply MI, which occurs not only in various clusters, but also in intermetallic compounds and quasicrystals. The second concept is the hierarchic icosahedral structures caused by the presence of a stacking fault in the fcc packing of the successive triangular faces in the iss. For instance, a fault occurs after the ABC layers resulting an ABCB packing. This is, in fact, a hierarchic icosahedral structure of a core icosahedron connected to 12 outer icosahedra by vertex sharing, or an icosahedron of icosahedra (double MI. Contrary to Mackay's iss, a faulted hierarchic icosahedral shell is, in fact, a twinlike face capping of the underlying triangles; it is, therefore, called an anti-Mackay cluster. The hierarchic icosahedral structure in an Al-Mn-Pd icosahedral quasicrystal has a core of body-centered cube rather than an icosahedron and, therefore, is called a pseudo-Mackay cluster. The hierarchic icosahedral structures have been studied separately in the past in the fields of clusters, nanoparticles, intermetallic compounds, and quasicrystals, but the underlying geometry should be the same. In the following a unified geometrical analysis is presented.     

Green and Efficient Procedure for the Trimethylsilylation of Hydroxy Groups and Their Regeneration Using Sulfamic Acid as Recyclable Catalyst

Structurally diverse alcohols and phenols were efficiently transformed into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of sulfamic acid (SA) at room temperature under both acetonitrile and solvent-free conditions. Deprotection of these trimethylsilyl ethers to their parent alcohols and phenols was also achieved using this catalyst in water at room temperature.     

Rationalizing the Structural Variability of the Exocyclic Amino Groups in Nucleobases and Their Metal Complexes: Cytosine and Adenine

The exocyclic amino groups of cytosine and adenine nucleobases are normally almost flat, with the N atoms essentially sp² hybridized and the lone pair largely delocalized into the heterocyclic rings. However, a change to marked pyramidality of the amino group (N then sp³ hybridized, lone pair essentially localized at N) occurs during i) involvement of an amino proton in strong hydrogen bonding donor conditions or ii) with monofunctional metal coordination following removal of one of the two protons.     

Synthesis of Latex Particles with Surface Functional Groups and Their Applications for the Fabrication of Porous Materials

In this study, monodisperse latex particles with specific surface functional groups were synthesized by emulsifier-free emulsion polymerization. Amidine or carboxylated polystyrene nanospheres with narrow size distribution were prepared by emulsion polymerization using AIBA (α,α′-zodiisobutyramidine dihydrochloride) as amine-containing initiator or acrylic acid as carboxyl-containing comonomer, respectively. Factors affecting the particle size and distribution were systemically studied by changing the amount of initiator or monomer, the polymerization temperature, and the stirring speed of emulsion polymerization reactor. Monodisperse polymethylmethacrylate beads were also synthesized by soapless emulsion polymerization using methacrylic acid or aminoethylmethacrylate hydrogen hydrochloride as comonomer for the surface functionalization of the particles. As applications of the latex beads, the polymeric particles were adopted as templating materials for the fabrication of macroporous titania film and meso-macroporous silica particles by colloidal templating method.     

New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups

Summary. CD exciton chirality methods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of - and -hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids, the direct esterification of sterically hindered carboxyl groups with 2-naphthol also allows the stereochemical assignment via CD spectroscopy.     

含有配位基团的芳基汞化合物的金属转移反应

本文综述了含有配位基团芳基汞化合物与过渡金属和非过渡金属之间的金属转移反应。讨论了底物中的配位基团对于某些金属转移产物形成的影响。     

阴离子-萘四酸双酰亚胺相互作用及其应用

萘四酸双酰亚胺（NDI）具有较大的正四极矩,是探索阴离子-π相互作用的理想π酸性芳香体系。阴离子-NDI相互作用的机制和应用受到了广泛关注,利用阴离子-NDI电子转移导致的NDI体系的颜色变化或光谱学变化实现阴离子识别,已经成为一种有效的离子识别传感器设计策略,尤其在强碱性阴离子识别方面,由于形成易于辨识的自由基阴离子相关UV谱带而展现出了独特的优势。本文综述了近年来阴离子-NDI相互作用的机制、作用模式及其在阴离子识别、对映体识别、有机催化和离子通道构建中的应用研究进展,兼顾基于孤对电子-π相互作用的中性分子-NDI相互作用研究,讨论了NDI结构与阴离子-π相互作用及应用的功能相关性。本文最后展望了阴离子-NDI体系构建及应用研究面临的挑战与未来发展趋势。     

自组装超薄膜及其应用

自组装膜是指以价键或非价键相互作用在一定表面形成的具有某种特定结构、性能的单层或多层超薄膜。在自然界中 ,人们可以看到许多不同的组分通过自组装形成具有层状超分子结构的复杂体系 ,但直到 1 946年 ,人类才在清洁表面制备了单分子层膜[1] 。与分子束外延和化学气相沉积等制备膜的方法相比 ,以自组装方式形成的超薄膜具有有序性高、平整度好、膜的厚度分子水平可控以及不受基底形状限制等优点[2 ] 。近 1 0多年来 ,随着人们对界面化学研究的深入以及对具有特定功能的薄膜材料的需求 ,使自组装超薄膜的研究成为一个热点。本文从分类、…     

酶的固定化及其应用

酶的固定化研究始于1960年代中期,从1970年代初开始酶的固定化技术研究发展很快,至1980年代初,每年约发表1000篇以上的文献和近200篇专利,所报道的固定化方法达100种以上[1].1980年代中以后,酶和细胞固定化研究的发展速度开始减慢,从而有人认为,对酶的固定化技术应予以重新评价     

DNA-modified Surfaces and Their Applications

As is known, DNA biosensors and DNA chips are now of great interest in life sciences, and they are being highlighted by molecular biologists and chemists because of their potential applications in biomedical fields, especially in disease diagnosis1^[1-3]. In addition, with the development of molecular biology there have been increasing demands for new microsample and convenient methods for DNA or gene studies. In most cases of these researches, an extremely important problem is usually to structure DNA-modified surfaces.     

Electro-Deprotection—Electrochemical Removal of Protecting Groups

The reactions of electrochemical splitting may be successfully used for removal of protecting groups. Theoretical and preparative aspects of the method of electro-deprotection are discussed, and examples of its use are given. The removal often requires high potentials. The use of modified protecting groups (“inner activation”) or of catalysts (electron carriers) which facilitate electron transfer against the standard potential gradient (“external activation”), can greatly increase the scope of the electrochemical method.     

Functional Groups on the Surfaces of Solids

Atoms or groups foreign to the structure of a solid are often bonded to its surface. On diamond, graphite, and even silicon dioxide, the foreign atoms are bonded covalently, whereas the bonding of the structural groups to titanium oxide and alumina is predominantly ionic. Oxides are normally covered with a monomolecular hydroxide layer. Changes in the valence of the metal atoms lead to changes in the acidity of the surface; for example, reduction of surface Ti⁴⁺ions gives the surface of TiO₂ an acidic nature.     

Efficient,Optimized Applications of p-Nitrophenyl Active Ester Temporarily Protecting Groups Together with Simultaneous Activation in Synthesis of Special Glu and Lys Peptides

Benzyloxycarbonyl-glutamylpeptide p-nitrophenylesters were prepared from protected amino acids, e.g.: p-nitrophenyl-glutamate as carboxyl component and aminoacid or peptide p-nitrophenylesters as amino components by different kinds of peptide coupling methods. Mixed carbonic anhydride and azide methods gave good results. The p-nitrophenylesters existed as temporary protecting groups, so the peptide couplings proceeded together with simultaneous activation. The conditions and applications of the procedure are discussed. The peptides having one or more active ester groups were used to form amides by their aminolysis with derivatives of ethylamine or were polycondensated (after deprotection) to obtain polypeptides.     

聚合物超强酸催化剂及其应用

本文综述了各种有机聚合物超强酸体系的分类、合成、结构、以及它们在石油化工和有机合成中的催化作用。     

酞青高分子及用途

本文主要介绍酞青高分子目前的研究状况.着重介绍耐热高分子、高分子导体、高分子半导体、高分子光导体及高分子催化剂方面的典型工作及这些材料的可能用途.     

水凝胶的制备及应用

本文回顾了“普通”和“环境敏感”水凝胶的制备方法及其作为生物材料在固定化酶、固定化细胞、免疫测试和药物控制释放等领域的应用。     

晶须及其在高分子材料中的应用

简要介绍了目前高分子材料改性中常用的晶须，如钛酸钾晶须、硼酸铝晶须、氧化锌晶须等，主要对其在橡胶、热塑性弹性体、热塑性树脂以及热固性树脂中的应用作了详尽论述。     

石墨烯的功能化及其相关应用

石墨烯是2004年才被发现的一种新型二维平面纳米材料,其特殊的单原子层结构决定了它具有丰富而新奇的物理性质．过去几年中,石墨烯已经成为了备受瞩目的国际前沿和热点．在石墨烯的研究和应用中,为了充分发挥其优良性质,并改善其成型加工性（如分散性和溶解性等）,必须对石墨烯进行功能化,研究人员也在这方面开展了积极而有效的工作．但是,关于石墨烯的功能化方面的研究还处在探索阶段,对各种功能化的方法和效果还缺乏系统的认识．如何根据实际需求对石墨烯进行预期和可控的功能化是我们所面临的机遇和挑战．本文重点阐述了石墨烯的共价键和非共价键功能化领域的最新进展,并对功能化石墨烯的应用作了介绍,最后对相关领域的发展趋势作了展望．     

生物可降解医用聚氨酯及其应用

生物可降解医用聚氨酯由于其优良的生物相容性、降解性、功能化修饰和力学性能可调控等优点,逐渐引起研究者的关注,尤其在药物传递和组织工程支架等方面可望具有广阔的应用前景。结合本课题组开展的工作,本文综述了生物可降解医用聚氨酯材料在结构、功能化设计及医学应用上的研究进展,并展望了其在医学材料中的发展前景。