金属纳米团簇的合成及其光致发光性质的调控

金属纳米团簇是一种既具有出色光物理性质,又具有良好生物相容性的零维材料.利用配体对团簇的热力学稳定产物的选择性和还原剂动力学调控可以合成出结构多样的金属纳米团簇,在光学材料、生物医学和催化材料等领域展示出颇具潜力的应用前景.但金属纳米团簇的稳定性差、发光弱等缺点限制了其实际应用,因此通过聚集诱导发光效应和超分子自组装协同调控金属纳米团簇的稳定性及光学性质,可以构筑出结构与发光可控的金属纳米团簇组装体,有效促进金属纳米团簇的实际可用性.本文简要介绍了不同配体保护的金属纳米团簇的合成,阐述了金属纳米团簇的光致发光性质,总结了聚集诱导发光效应对团簇超分子组装体光致发光性质的影响规律,并分析提出了当前研究仍存在的问题及对未来探究的展望.     

树形大分子的自组装

非共价的分子间作用力或超分子相互作用，可用于树枝直接自组装，或将树枝环绕在以某一中心核作模板的分子周围，最终形成树形大分子。另外，树形大分子自组装，可得到高度有序的液晶聚集体和单层膜，也可增加其它有机物的溶解性。综述了树形大分子的自组装研究进展、研究结果及其应用前景。     

软外延生长法构筑纳米粒子超晶格材料

由纳米粒子自下而上自组装而成、高度有序的纳米粒子超晶格材料是近年来兴起的一类新型材料.本文主要概述了软外延生长法构筑纳米粒子超晶格材料的概念及组装策略,结合近几年本课题组的相关研究工作,主要介绍了几种不同的基底材料,以及通过调控基底与纳米粒子之间的相互作用来构建纳米粒子超晶格材料.具体包括以纳米粒子超晶格、有机分子笼晶体以及超分子组装体等作为基底诱导纳米粒子软外延生长.通过软外延生长法可实现对纳米粒子超晶格维度(包括一维、二维以及三维)的有效调控.同时,阐明了纳米粒子与基底材料的弱键相互作用机制,该机制也成为构筑无机纳米粒子/有机分子有序组装体重要的物理化学基础.     

单分子膜诱导生物矿物晶体生长中的晶格匹配和电荷匹配

有机基质与无机晶体的晶格几何匹配和静电相互作用是导致生物体内矿物有序生长并具有特殊理化性质的重要因素,但有机基质的作用机理至今没有完全弄清.作为模拟生物矿化的重要模板之一,Langmuir单分子膜具有独特的优势.本文综述了单分子膜诱导下生物矿物碳酸钙(文石、方解石和球霰石)、羟磷灰石、硫酸钡和纤铁矿等生长过程中的晶格匹配和电荷匹配,讨论了单分子膜亲水头基、膜的电荷性质、膜聚集态等因素对膜控晶体生长过程中晶格匹配和电荷匹配的影响,指出了该领域所面临的问题和将来的发展方向.     

金属团簇的超原子分子理论

选取合适的金属团簇(超原子)作为结构基元,进而组装形成新的团簇或晶体材料是团簇科学中一个有趣且充满挑战的课题,受到了实验和理论研究者的广泛关注.通过超原子组装这种"自下而上"的组装方式,可以获得具有特定物理化学性质的新材料.但是,长久以来针对如何进行超原子组装并无清晰、统一的理论认识,超原子组装基本等同于超原子的任意堆砌或拼接.那么,超原子能否像原子那样通过特定化学键形成分子或晶体?超原子间如何成键?超原子组装是否有一定模式可循?为了回答这些问题,我们提出了一个唯象理论:超原子分子理论.该理论的核心是构建超原子间的成键规则,将涉及超原子的"超级化学键"概括为3种类型,即超级共价键、超级杂化键和超级非键.超原子可以通过超级化学键结合形成超原子分子或超原子晶体.同时,超原子分子理论指出,超原子具有几何结构不同但电子结构相似的异构体,这些异构体称为"等同超原子".等同超原子同样可以作为组装基元,通过超级化学键进行结合.另外,针对包含复杂成键类型的团簇体系,超原子分子理论概括出了两种超原子组装模式,分别称为超原子网络和杂化超原子网络.综上所述,超原子分子理论包含了对超原子间成键规则的理解,对超原子组装基元的思考以及对超原子组装模式的认识.超原子分子理论的相关内容不仅可以为超原子组装提供系统的理论依据,而且可以对特殊团簇结构的稳定性给出合理解释,还可以为新型团簇的结构设计以及实验合成提供理论指导.     

DNA分子在气液界面的组装相变特性及其LB膜结构研究

对十八胺与DNA在气液界面上组装及其相变过程进行了研究，利用AFM观察了不 同压力下转移的DNA复合LB膜结构。发现在低表面压时，DNA复合单分子膜表现为技 术发散的分形结构；随着压力的升高，DNA复合膜逐渐由紧密的网状排布结构变为 团聚的块状和团簇结构。表明通过调节膜压，可使膜内DNA分子的构象发生大的变 化，从而生成具有特定形态的二维纳米图案。这种具有特殊形态和结构的DNA LB膜 可望为合成新型生物纳米结构有序功能体系提供模板。     

表面印迹交替层状组装薄膜

在简要概述非常规交替层状组装这一进展后,重点总结了如何利用非常规交替层状组装以实现表面印迹膜的制备.模板分子与聚电解质在溶液中组装形成超分子复合物,然后以此超分子复合物为构筑基元,与感光性高分子,如重氮树脂,通过常规交替层状组装形成聚合物多层膜.利用聚合物多层膜之间的光化学反应形成稳定的多层膜,然后去除模板分子得到分子...     

以四肽自组装体为模板制备手性3-氨基苯酚甲醛树脂纳米纤维

采用经典的固相合成法制备了一对烷基取代丙氨酸四肽衍生物对映体,研究了其在不同溶剂中的成胶行为,并以其在甲醇中形成的超分子自组装体为模板,利用溶胶-凝胶法制备了单手螺旋3-氨基苯酚甲醛树脂纳米纤维.利用扫描电子显微镜和透射电子显微镜观察超分子自组装体及3-氨基苯酚甲醛树脂的螺旋形貌,并利用圆二色谱研究其光学性质.研究发现,3-氨基苯酚甲醛树脂纳米纤维既具有纳米尺度的手性,又具有分子尺度的手性.手性从小分子形成的自组装体传递到高分子树脂中.     

LBL自组装技术及自组装生物功能膜结构

主要介绍近几年发展的用于生物大分子自组装功能膜的三种逐层（LBL）自组装技术与制备方法,酰胺化反应自组装技术、生物分子的特异识别自组装技术、分子沉积自组装技术;同时总结了自组装功能膜的结构、特性的表征方法,主要有AFM、TEM、循环伏安法、石英晶体微天平（QCM）技术、UV/VIS、XPS方法等。     

配位化学中的C-H…π非键弱相互作用

随着超分子化学研究的深入和发展,C-H…π非键弱相互作用越来越多地在晶体工程学、分子识别、主客体化学、自组装超分子体系以及生物大分子与配体相互作用等领域中被关注。本文综述了在配位化学中的C-H…π非键弱相互作用,它不仅存在于配合物分子内,亦可在配合物分子间观察到,并对利用配合物体系进行C-H…π非键弱相互作用体系研究提出一些设想。     

Pre‐Incubation of Auric Acid with DNA Is Unnecessary for the Formation of DNA‐Templated Gold Nanoclusters

The rationale for the preparation of DNA‐templated gold nanoclusters (DNA‐Au NCs) has not been well understood, thereby slowing down the advancement of the synthesis and applications of DNA‐Au NCs. The interaction between metal ions and the DNA template seems to be the key factor for the successful preparation of DNA‐templated metal nanoclusters. With the help of circular dichroism in this contribution, we put efforts into interrogating the necessity of pre‐incubation of HAuCl₄ with poly‐adenine template in the formation of Au NCs by citrate reduction. Our results revealed that the pre‐incubation of HAuCl₄ with poly‐adenine is not favorable for the formation of Au NCs, which is distinctly different from the formation process for silver nanoclusters. It is our hope that this study can provide guidance in the preparation of Au NCs with more DNA templates.     

Quick genotyping detection of HBV by giant magnetoresistive biochip combined with PCR and line probe assay

Genotyping of human hepatitis B virus (HBV) can be used to direct clinically effective therapeutic drug-selection. Herein we report that a quick genotyping method for human HBV was established by a specially designed giant magnetoresistive (GMR) biochip combined with magnetic nanoclusters (MNCs), PCR and line probe assay. Magnetic nanoclusters of around 180 nm in diameter were prepared and modified with streptavidin, and resultant streptavidin-modified magnetic nanoclusters were used for capturing biotin-labeled hybrid products on the detection interface of the sensor. The gene fragments of HBV's B and C gene types were obtained by PCR based on a template of B- and C-type plasmids. After gene fragments were hybridized with captured probes, streptavidin-modified magnetic nanoclusters could bind with biotin-conjugated gene fragments, and the resultant hydride products could be quickly detected and distinguished by the GMR sensor, with a detection sensitivity of 200 IU mL(-1) target HBV DNA molecules. The novel method has great potential application in clinical HBV genotyping diagnosis, and can be easily extended to other biomedical applications based on molecular recognition.     

Metal-chelate dye-controlled organization of Cd32S14(SPh)40(4-) nanoclusters into three-dimensional molecular and covalent open architecture

Chalcogenide II-VI nanoclusters are usually prepared as isolated clusters and have defied numerous efforts to join them into covalent open-framework architecture with conventional templating methods such as protonated amines or inorganic cations commonly used to direct the formation of porous frameworks. Herein, we report the first templated synthesis of II-VI covalent superlattices from large II-VI tetrahedral clusters (i.e., [Cd32S14(SPh)38]2-). Our method takes advantage of low charge density of metal-chelate dyes that is a unique match with three-dimensional II-VI semiconductor frameworks in charge density, surface hydrophilicity-hydrophobicity, and spatial organization. In addition, metal-chelate dyes also serve to tune the optical properties of resulting dye semiconductor composite materials.     

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.     

Suppression of background sites in molecularly imprinted polymers via urea-urea monomer aggregation

The molecular imprinting process provides a synthetically efficient route to polymers with tailored recognition properties. However, the binding properties of the templated binding sites are often masked by the more prevalent background binding sites. Therefore, a strategy for reducing the number of background binding sites was developed and evaluated that uses functional monomer aggregation to suppress the formation of background sites. A series of imprinted and non-imprinted polymers was formed using crosslinking urea monomer and were evaluated for their ability to rebind the anionic template, tetrabutylammonium diphenyl phosphate (TBA-DPP). The urea monomer was shown to form linear hydrogen bonded aggregates in solution and in the solid state. Functional monomer aggregation in the polymerization solution was shown to dramatically reduce the numbers of background binding sites by occupying and blocking the urea recognition groups that were not bound to the template molecule. Despite the low aggregation constant of the urea monomer (3.5 M(-1) in chloroform), the number of background sites was reduced by more than 60%. We predict that this strategy of using monomers that aggregate to reduce background binding sites is a general one for MIPs and other types of polymers with tailored recognition properties. The key is to identify self-assembling monomers where the guest binding processes are stronger than the aggregation processes.     

Gap site-specific rapid formation of fluorescent silver nanoclusters for label-free DNA nucleobase recognition

Silver nanoclusters (Ag NCs) templated with DNAs have attracted much attention as novel fluorophores because of their convenient emission tunability by the sequence and length of the template DNAs. However, the precise production of Ag NCs in a site-specific manner still remains a challenge to attain highly selective and label-free DNA recognition. Here we exploited the availability of a gap site in DNA duplexes as a new scaffold for the synthesis of Ag NCs. Compared to the commonly used DNA templates for the creation of Ag NCs, the gap site in DNA duplexes was found to facilitate the rapid formation of the fluorescent Ag NCs without sacrifice of their bright emission and excellent stability. We found that fluorescent Ag NCs were highly selectively formed when cytosine faced toward the gap site in DNA duplexes, and they were in situ utilized as readout by signal-on manner for the DNA mutation assays. This base-selective growth of the fluorescent Ag NCs at the gap site would find promising applications in practical detection of single nucleotide polymorphism (SNP) and construction of DNA-based functional sensors with label-free and cost-effective merits.     

Templated synthesis of silver nanowires based on the layer-by-layer assembly of silver with dithiodipropionic acid molecules as spacers

The layer-by-layer assembly of silver nanoclusters with 3,3'-dithiodipropionic acid (DTDPA) as spacers was prepared through self-assembly on a gold foil and has been characterized by cyclic voltammetric and AFM techniques. The DTDPA molecules acting as spacers between the layers of silver serve as molecular interconnects for the four layers prepared in this work. The organization of layers was found to decrease with an increase in the number of layers. The layer-by-layer assembly of silver clusters motivated us to prepare silver nanowires stabilized by the bifunctional molecules DTDPA through template synthesis using cellulose nitrate membranes. The nanostructures formed by this method were characterized by SEM, TEM, AFM, FTIR, CV, and photoluminescence studies. It is observed that the DTDPA molecules, instead of forming molecular interconnects, protect the structures by self-assembling themselves along the edges of the nanostructures. The concept of self-assembly protecting the nanostructures is demonstrated in this work.     

Site-specific DNA-programmed growth of fluorescent and functional silver nanoclusters

Precise organization of metallic nanoclusters on DNA scaffolds holds great interest for nanopatterned materials that may find uses in electronics, sensors, medicine, and many other fields. Herein, we report the site-specific growth of fluorescent silver nanoclusters by using a mismatched double-stranded DNA template. Few-atom, molecular-scale Ag clusters are found to localize at the mismatched site and the metallized DNA retains its integrity. The DNA-encapsulated nanoclusters can be utilized as functional biological probes to identify single-nucleotide polymorphisms by taking advantage of the very bright fluorescence and excellent photostability of the nanoclusters. This approach offers the possibility of constructing novel DNA-based nanomaterials and nanomechanical devices with more sophisticated functions and will be highly beneficial in future biochemical, pharmaceutical, nanomechanical, and electronic applications.     

Protein-templated organic/inorganic hybrid materials prepared by liquid-phase deposition

Organic/inorganic hybrid thin films for protein recognition have been prepared by the liquid-phase deposition (LPD) coupled with template synthesis, i.e., molecular imprinting, where pepsin (Pep) was used as a model protein and titanium oxide was deposited on gold substrates in the presence of Pep-poly-L-lysine (PL) complexes. The complexes remained in the templated film after the deposition, and the binding sites for Pep were constructured after Pep was removed from the film. Surface plasmon resonance signals on the deposited films were measured to examine the binding behaviors toward proteins. The binding of Pep on the templated film was reversible, and the binding isotherm of Pep depicted a saturation curve with a binding constant of 7.3 x 105 M(-1), which was 10 times higher than that of albumin. In contrast, titanium oxide films prepared without PL did not show any selectivity; therefore, the hybridization of PL as the organic binder with the inorganic material is necessary to obtain selective binding sites for Pep. It was also shown that the hybridization process should proceed without denaturing the template protein, in order to obtain selective binding sites for the template. The procedure for preparation of the films was simple to perform, and the process for hybridization of the thin films with nanometer-order thickness was easily controlled by changing the LPD reaction time period. Consequently, the proposed LPD coupled with template synthesis is among the most appropriate methods to prepare hybrid materials with protein recognition ability, which proceeds under mild conditions in aqueous solution.