Metal–Organic Frameworks (MOFs) as Multivalent Materials: Size Control and Surface Functionalization by Monovalent Capping Ligands

Control over particle size and composition are pivotal to tune the properties of metal organic frameworks (MOFs), for example, for biomedical applications. Particle‐size control and functionalization of MIL‐88A were achieved by using stoichiometric replacement of a small fraction of the divalent fumarate by monovalent capping ligands. A fluorine‐capping ligand was used to quantify the surface coverage of capping ligand at the surface of MIL‐88A. Size control at the nanoscale was achieved by using a monovalent carboxylic acid‐functionalized poly(ethylene glycol) (PEG‐COOH) ligand at different concentrations. Finally, a biotin–carboxylic acid capping ligand was used to functionalize MIL‐88A to bind fluorescently labeled streptavidin as an example towards bioapplications.     

金属纳米颗粒制备中的还原剂与修饰剂

金属纳米颗粒由于其独特的光学、电学、化学性质以及各种潜在的应用价值,受到不少研究人员的广泛关注。实现金属纳米粒子尺寸、形貌可控,改善粒子分散性和稳定性,提高产率及纯度已成为具有挑战性的研究课题,不断发展和完善金属纳米粒子的合成方法则显得尤为重要。本文总结了目前制备金属纳米材料的几种化学方法：化学试剂还原法、电化学还原法、辐射还原法等,分类介绍了化学试剂还原法中常用的无机、有机还原剂,以及含氮、磷、羧基、巯基小分子有机化合物以及高分子聚合物等修饰剂并重点总结了其还原和修饰机理。     

The Influence of the Capping Agent on the Oxidation of Silver Nanoparticles: Nano‐impacts versus Stripping Voltammetry

The influence of capping agents on the oxidation of silver nanoparticles was studied by using the electrochemical techniques of anodic stripping voltammetry and anodic particle coulometry (“nano‐impacts”). Five spherical silver nanoparticles each with a different capping agent (branched polyethylenimine (BPEI), citrate, lipoic acid, polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP)) were used to perform comparative experiments. In all cases, regardless of the capping agent, complete oxidation of the single nanoparticles was seen in anodic particle coulometry. The successful quantitative detection of the silver nanoparticle size displays the potential application of anodic particle coulometry for nanoparticle characterisation. In contrast, for anodic stripping voltammetry using nanoparticles drop casting, it was observed that the capping agent has a very significant effect on the extent of silver oxidation. All five samples gave a low oxidative charge corresponding to partial oxidation. It is concluded that the use of anodic stripping voltammetry to quantify nanoparticles is unreliable, and this is attributed to nanoparticle aggregation.     

Nanoparticle Capping Agent Controlled Electron‐Transfer Dynamics in Ionic Liquids

Herein, we report a change in the mechanism of the oxidation of silver nanoparticles (Ag NPs) with the molecular weight of a poly(ethylene) glycol (PEG) capping agent. Characterisation of the modified nanoparticles is undertaken using dynamic light scattering and UV/Vis spectroscopy. Electrochemical analyses reveal that the oxidation of 6000 molecular weight (MW) PEG is consistent with a polymer‐gated mechanism, whilst for 2000 MW PEG the polymer does not hinder the oxidation. The 10,000 MW PEG Ag NPs are rendered almost electrochemically inactive. This study demonstrates the ability to alter and better understand the electron‐transfer mechanism in a room temperature ionic liquid (RTIL) by systematically altering the capping agent.     

多效价树枝状糖苷配体的合成

许多生命过程如细胞间的识别、信号传递等通常依赖于细胞表面的多个配体和受体的协同作用.多效价树枝状糖基配体的合成是研究生物体内蛋白质与糖类、糖类与糖类相互作用的重要途径.本文综述了多效价树枝状糖基配体这类合成配体的最新研究进展,包括以树枝状聚合物、环糊精、糖环、芳烃和大环等为框架的多效价树枝状糖基配体的合成.     

Synthesis and Crystal Structures of Gold Nanowires with Gemini Surfactants as Directing Agents

The preparation of crystalline gold nanowires (NWs) by using gemini surfactants as directing agents through a three‐step seed‐mediated method is reported. Unlike the nanorods with relatively low aspect ratios (typically below 20) obtained by using cetyltrimethylammonium bromide as a directing agent, the NWs obtained in this investigation can reach up to 4.4 μm, and the largest aspect ratio is calculated to be 210. For this, each of seven different gemini surfactants are utilized as directing agents, and the length and/or aspect ratio of the NWs can be tuned by varying the hydrocarbon chain lengths of the gemini surfactants. Both single and twinned crystalline structures are elucidated by selected‐area electron diffraction and high‐resolution transmission electron microscopy studies. The use of gemini surfactants not only advances the synthesis of gold nanostructures, but improves the understanding of the growth mechanism for seed‐mediated growth.     

Synthesis of Multivalent Galactosides as Targeting Ligand for Gene Delivery

A series of novel bifunctional glycolipid ligands designed to bind with high affinity and specificity to the asialoglycoprotein receptor (ASGP-R) has been synthesized and assayed in vitro on human hepatoma cells, HepG2, derived from parenchymal liver cells. The compounds bear five β-linked Gal moieties linked to the core scaffold, hexa-antennary alcohol, for interaction with the binding site of the ASGP-R. The liposome/DNA complexes containing the glycolipid ligands are efficiently recognized by ASGP-R and exhibited high affinity and transfection activity.     

混合阳离子-非离子表面活性剂为模板剂合成含沸石次级结构单元的介孔分子筛

利用混合阳离子-非离子表面活性剂为模板剂采用两步晶化法合成了孔壁具有沸石次级结构单元的介孔分子筛，通过XRD、N2吸附-脱附、FT-IR以及异丙苯裂解探针反应等手段对样品进行了表征。结果表明，合成的介孔材料在结构上与相应的M41S材料类似，无微孔沸石相的存在。立方介孔材料具有较高的热稳定性和水热稳定性，在催化异丙苯裂解反应中，六方介孔材料的催化活性明显高于相似条件下用单一表面活性剂为模板剂合成的含沸石次级结构单元的六方介孔材料。     

Gemini表面活性剂合成进展

系统总结了近百种Gemini表面活性剂的合成路线和方法,并且按照其结构特点分门别类地进行比较和归纳,对今后Gemini表面活性剂的合成发展方向提出了一些看法,这对促进此类新颖表面活性剂的工业化进程将具有指导意义。     

Multivalent Pyrrolidine Iminosugars: Synthesis and Biological Relevance

Recently, the strategy of multivalency has been widely employed to design glycosidase inhibitors, as glycomimetic clusters often induce marked enzyme inhibition relative to monovalent analogs. Polyhydroxylated pyrrolidines, one of the most studied classes of iminosugars, are an attractive moiety due to their potent and specific inhibition of glycosidases and glycosyltransferases, which are associated with many crucial biological processes. The development of multivalent pyrrolidine derivatives as glycosidase inhibitors has resulted in several promising compounds that stand out. Herein, we comprehensively summarized the different synthetic approaches to the preparation of multivalent pyrrolidine clusters, from total synthesis of divalent iminosugars to complex architectures bearing twelve pyrrolidine motifs. Enzyme inhibitory properties and multivalent effects of these synthesized iminosugars were further discussed, especially for some less studied therapeutically relevant enzymes. We envision that this comprehensive review will help extend the applications of multivalent pyrrolidine iminosugars in future studies.     

Nonfunctionalized Gold Nanoparticles: Synthetic Routes and Synthesis Condition Dependence

Since Faraday first described gold sol synthesis, synthetic routes to nanoparticles, as well as their applications, have experienced a huge growth. Variations in synthesis conditions such as pH, temperature, reduction, and the stabilizing agent used will determine the morphology, size, monodispersity, and stability of nanoparticles obtained, allowing for modulation of their physical and chemical properties. Although many studies have been made about the synthesis and characterization of individual nanosystems of interest, to our knowledge the common, general traits that all those synthesis share have not been previously compiled. In this review, we aim to offer a global vision of some of the most relevant synthetic procedures reported up to date, with a special focus on nonfunctionalized gold nanoparticle synthetic routes in aqueous media, and to display a broad overview of the influence that synthesis conditions have on the shape, stability, and reactivity of nanoparticle systems.     

Direct Dual‐Template Synthesis of MWW Zeolite Monolayers

A two‐dimensional zeolite with the topology of MWW sheets has been obtained by direct synthesis with a combination of two organic structure‐directing agents. The resultant material consists of approximately 70 % single and double layers and displays a well‐structured external surface area of about 300 m² g^?1. The delaminated zeolite prepared by means of this single‐step synthetic route has a high delamination degree, and the structural integrity of the MWW layers is well preserved. The new zeolite material displayed excellent activity, selectivity, and stability when used as a catalyst for the alkylation of benzene with propylene and found to be superior to the catalysts that are currently used for producing cumene.     

Synthesis and Aqueous Solution Properties of Polyoxyethylene Surfactants with Ultra-Long Unsaturated Hydrophobic Chains

Methoxypolyethylene glycols (M _n = 750, 1000, 2000, and 5000 g/mol) were hydrophobically modified by transestification with mono-unsaturated alkyl chains (UC18, UC22, and UC24), and the obtained ultra-long-chain nonionic surfactants were characterized by ¹H NMR, FTIR and gel permeation chromatographic, respectively. Aqueous solution properties of all these surfactants, including cloud point, surface activities, viscosifying ability, and phase diagrams were examined. It was found that all these ultra-long-chain polyoxyethylene surfactants exhibit good water solubility and typical Newtonian rheological behavior. For the surfactants with the same hydrophobic length, the CP, equilibrium surface tension (γ_cmc), as well as zero-shear viscosity (η₀) increase with increasing their hydrophilic length; for those with same hydrophilic head group, the critical micellar concentration and η₀ increase while the γ_CMC decreases with increasing hydrophobic tail length. Moreover, a decrease in the critical overlap concentration and an increase in the critical temperature were observed in phase diagrams of all these ultra-long-chain polyoxyethylene surfactants. (Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Dispersion Science and Technology to view the free supplemental file.)     

高分子表面活性剂的合成

介绍了高分子表面活性剂的合成方法及其不同于低分子表面活性剂的特点,重点从离子聚合、活性自由基聚合、缩合聚合、开环聚合、高分子化学反应、自由基胶束聚合等角度综述了近几-来高分子表面活性剂的合成研究进展.     

Adaptive Structured Pickering Emulsions and Porous Materials Based on Cellulose Nanocrystal Surfactants

Taking advantage of the formation and assembly of cellulose nanocrystal surfactants (CNCSs) at the water–oil interface, where polar cellulose nanocrystals (CNCs) and end‐functionalized polymer chains interact, the preparation and stability of emulsions prepared with CNCSs were investigated. The packing density of CNCSs at the interface can be adjusted by tuning parameters such as pH, ionic strength, and concentration/molecular weight of the end‐functionalized polymer ligands. Stable non‐spherical emulsions are obtained during homogenization, as a result of the interfacial jamming of CNCSs, with pH‐triggered reconfigurability. Porous materials are prepared by freeze‐drying creamed, CNCS‐stabilized emulsions. The cells of the porous materials have a controlled pore size and shape that are commensurate with the droplets in the emulsion and are responsive to pH. The behavior of the adaptive, reconfigurable supracolloidal system is coupled to its internal and surrounding environment.     

Synthesis of Silicate Zeolite Analogues Using Organic Sulfonium Compounds as Structure‐Directing Agents

A microporous crystalline silica zeolite of the MEL structure type and three other zeolite analogues composed of germanosilicate frameworks were synthesized using tributylsulfonium, triphenylsulfonium, or tri(para‐tolyl)sulfonium as the structure‐directing agent. The germanosilicates thus obtained had ISV, ITT, or a new zeolite structure depending on the synthesis conditions. The structure of the new germanosilicate was solved using X‐ray powder diffraction data with the aid of a charge‐flipping method. The solution indicated a crystal structure belonging to the P63/mmc space group with cell parameters of a=16.2003 Å and c=21.8579 Å. After calcination, the new germanosilicate material exhibited two types of accessible micropores with diameters of 0.61 and 0.78 nm.     

Bola型表面活性剂合成及其应用

介绍了Bola型表面活性剂独特的结构特征与性质,概述了由Bola型两亲分子在气液界面自组装形成的单分子膜及囊泡的特征。重点综述了Bola型表面活性剂的合研究进展,并对其在纳米材料、药物缓释、生物矿化、光化学修饰及抑止金属腐蚀等方面的应用作了介绍。最后对其研究前景作了展望。     

Interaction of Anionic Gemini Surfactants with Other Surfactants

The interaction of anionic gemini surfactants with other surfactants (such as anionic, cationic, nonionic) was systematically overviewed, paying attention to synergism observed in various properties. These mixed systems were found to show remarkable synergism in micelle formation. The critical micelle formation values being lower than the individual gemini surfactants indicate that the mixed micellization is due to attractive interaction between the two components. Almost all combinations were discussed in terms of respective surface tension reduction effectiveness and surface tension reduction efficiency and aggregation number for evaluation of synergism.     

Synthesis and Characterization of Self-Assembling Some Thiol Surfactants on Gold Nanoparticles

The purpose of this work is to study the self-assembling of some synthesized thiol surfactants namely (mercaptopropane-, mercaptohexane-, mercaptooctane-, and mercaptodecane sodium sulfonate) on the fabricated gold nanoparticles. The self-assembling of these surfactants on gold nanoparticles characterized using different techniques such as FTIR spectroscopy, UV spectroscopy, and transmission electron microscopy (TEM). Spectroscopic evidence suggests that the synthesized thiol surfactants have been attached to the gold nanoparticles. The effect of self-assembling of these surfactants on the size of the gold nanoparticles was studied using TEM images. The growth of the gold nanoparticles was investigated with respect to the increase of alkyl chain in the synthesized thiol surfactants. The results show that the stabilization of gold nanoparticles was affected by the increase in alkyl chain length of these surfactants. The effect of gold nanoparticles on the interfacial tension and the emulsion stability of these surfactants with crude oil was studied.