The mechanism of a novel assay technique for nanoparticle-enhanced immunoturbidimetric assays is investigated. In a mixture of latex particles of two different sizes, coated with antibodies of different affinities, the aggregation behavior is monitored, which correlates with the antigen concentration. At low antigen concentrations, only the bigger latex particles coated with the high-reactivity antibody aggregate, whereas at higher antigen concentrations, the smaller latices coated with a lower reactivity antibody follow up in the aggregation process. This is shown for an immunoassay (C-reactive protein) by theoretical considerations based on a diffusion-controlled reaction and by transmission electron microscopy, analytical ultracentrifugation, and static light scattering as complementary qualitative and quantitative analytical techniques.

The mechanism of nitrogen sorption in porous silica was investigated by small-angle neutron scattering (SANS). Two samples of porous silica were studied containing mesopores (pore sizes 5.5 and 9.5 nm, respectively) and additional micropores of irregular shape and statistical distribution. SANS curves were recorded at a temperature of 78 K at various relative pressures pipe during adsorption, The experiment is based on contrast matching between silica and condensed nitrogen with regard to neutron scattering. The sorption process was characterized by the evaluation of the chord-length distributions extracted from SANS data for each pipe. In addition, a general approach was developed to relate the SANS pattern during capillary condensation to the size distribution and the morphology of ordered mesopores. On the basis of these evaluation methods, various uptake mechanisms could be described, which are micropore filling, the formation of nitrogen layers, and capillary condensation. The analysis of the SANS data shows that the mean size of the remaining empty mesopores formally increases, and their size distribution becomes narrower during capillary condensation, which is in agreement with the predictions of the Kelvin equation. Furthermore, our study indicates a significant degree of additional microporosity, the origin of which is discussed. For comparison, the experiment and the data evaluation were also applied to a disordered porous silica with a broad pore size distribution. The combination of SANS and nitrogen sorption turned out to be a powerful technique to investigate both the mechanisms of sorption and the structure of porous silicas in one experiment.

The polymerization of hydrophilic monomers, such as acrylamide, in the nanoscale confinement of lyotropic surfactant phases or microemulsions produces gels with variable pore architecture in the hundreds of nanometers to micrometers size range. The porous gels are characterized by scanning electron microscopy after critical-point drying. The structure of the gels is not a direct copy of the structure and symmetry of the parental surfactant assemblies, but depends on the type of monomer, cross-linking density and both the monomer and surfactant concentration. Nevertheless, a controlled structure set-up is obtained, where different pore morphologies and different pore sizes can be systematically adjusted. In such a way it is possible to build the polymer network structure on a mesoscopic length scale, optimizing different network properties which are otherwise coupled in an opposite fashion, e.g. polymer networks with very large pore size and high mechanical stability can be made. Such porous gels are interesting for modern gel-monolith separation techniques, such as gel electrophoresis for protein and DNA separation where micron sized pores are required. Implementation of a further "nanocasting"-procedure within the pore channel system of these gels allows generation of polymer/inorganic hybrid materials with a similar degree of mesoscale organization and exciting combinations of material properties. The value of such a multiple replica procedure is demonstrated by making superparamagnetic rubbers ("elasde magnets") and highly porous, continuous TiO2-networks for photocatalytic applications.

Two different polyphenylene ethynylene derivatives, one partly hydrophobic and one hydrophilic, were investigated with a combination of X-ray and light scattering techniques and hydrodynamic techniques, as well as scanning force microscopy and transmission electron microscopy to elucidate their molecular structure and aggregation behavior in tetrahydrofuran and water, respectively. It turns out that both polymers possess a rod-like molecular architecture which, however, is the basis of a cascade of aggregation steps. Both, electron microscopy and X-ray analysis support the concept of a primary back-to-back aggregation of polymer chains into cylindrically shaped aggregates with high anisometry. The thickness of these aggregates was between 4.0 and 4.5 nm. The aggregates of the hydrophobic polymer further associate into fibrils and these fibrils form clusters of globular shape, though with high internal anisometry. Copyright 1999 Academic Press.

Angewandte ChemieVolume 111, Issue 21 p. 3347-3349 Highlight Poröse Festkörper aus rigiden Kolloidtemplaten: Morphogenese Christine G. Göltner, Christine G. Göltner goeltner@mpikg-golm.mpg.de Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Forschungscampus Golm, Am Mühlenberg, D-14476 Golm, Fax: (+49) 331-5679502Search for more papers by this author Christine G. Göltner, Christine G. Göltner goeltner@mpikg-golm.mpg.de Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Forschungscampus Golm, Am Mühlenberg, D-14476 Golm, Fax: (+49) 331-5679502Search for more papers by this author First published: 26 October 1999 https://doi.org/10.1002/(SICI)1521-3757(19991102)111:21<3347::AID-ANGE3347>3.0.CO;2-0Citations: 11AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Die moderne Materialwissenschaft strebt danach, bekannten Materialien Struktur auf der Nanometerskala zu verleihen, anstatt chemisch neue Verbindungen zu synthetisieren. Der vorliegende Beitrag beschreibt einen neuartigen Ansatz zur Herstellung poröser Feststoffe aus rigiden Kolloidtemplaten, die in drei Schritten erfolgt (siehe Schema): a) Anordnung kolloidaler Partikel in eine reguläre Packung, b) Tränken des Templats mit Monomer(en) und Polymerisation, c) Entfernen des Templats. Für so hergestellte Materialien gibt es zahlreiche potentielle Anwendungen, von robusten Katalysatoren und Supports über größen- und formselektive Trennmedien bis zu photovoltaischen Geräten. Citing Literature Volume111, Issue21November 2, 1999Pages 3347-3349 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

Lyotropic liquid crystalline phases are exploited as templates for the synthesis of inorganic nanostructures. In this approach the aggregates of non-ionic amphiphiles in water function as confining media, i.e. the polymerisation of a water-soluble precursor takes place in their aqueous domains. This approach to nanostructure design has considerable advantages over previous routes towards mesoporous ceramic oxides. (i) The nanostructure of the solid can be predicted a priori, (ii) this approach allows the use of non-ionic surfactants as templates and (iii) the progress of the formation can be monitored by various analytical techniques. The approach is tolerant to the introduction of metals into the silica framework, as is demonstrated using aluminium silicate as a representative example. The synthesis and a new way of monitoring the temporal evolution of the inorganic nanostructure using deuterium NMR spectroscopy are described. The results show that the lyotropic liquid crystal phase acts as a template. Further, a novel approach to studying sorption properties allows a comparison with other meso- and microporous materials.

Mesoporous silicas with variable pore size and architecture were made by using aqueous solutions of block copolymers with one polyelectrolyte block as templates in a sol-gel process. Pore size and connectivity follow the structure of the block, copolymer micelles or mesophases, i.e., the resulting silica gel network is a precise copy of the original self-assembly structure. In this paper, three cationic polybutadiene-b-poly(vinylpyridinium) block copolymers as well as an anionic poly(ethylethylene)-b-polystyrenesulfonate block are utilized as structure-directing media. Depending on the relative block lengths and the salt content in the reaction mixture, different aggregation structures are obtained, leading to well-defined spherical pores in the size range between 10 nm < xi < 50 nm or more complex architectures, such as "rattles", the casts of multilamellar vesicles. It is proposed that it is possible to use this precise silica casting procedure in order to depict and characterize unknown aggregation structures of block copolymers. Therefore silica casting appears to be a considerable alternative to the more tedious freeze-fracture preparations of similar colloidal systems.

A novel variation of the template route to mesoporous silica is presented, which extends the range of pore sizes that can be achieved to larger sizes. Polymer latex particles in the range from 20 to 400 nm with different surface functionalities are employed as templates. The synthesis of the latices, sol-gel processing, and calcination are described, together with the characterization of the inorganic gels. It is shown that the route of templating polymer dispersions is complementary to the synthesis in lyotropic liquid-crystalline phases, leading to a bimodal size distribution of the pores.

Mesoporose Silicatmonolithe sind jetzt zuganglich: Mit amphiphilen Blockcopolymeren als Template wurden in Sol-Gel-Synthesen biskontinuierliche Materialien erhalten (siehe z. B. die transmissionselektronenmikroskopische Aufnahme rechts), die gestort-hexagonale Symmetrie aufweisen. Die grose Stabilitat der Monolithe und Langperioden von 8–13 nm sind hinsichtlich moglicher Anwendungen dieser Feststoffe vielversprechend.

Die Regeln der Verknüpfung von Atomen und Molekülen zu neuen Funktionseinheiten, die Domänen der molekularen und supramolekularen Chemie, können auch dazu verwendet werden, größere Objekte, deren Dimensionen in Nanometer zu messen sind, zu bilden und zu verbinden. Die Verknüpfung kann dabei nicht mehr statistisch erfolgen, es kommt vielmehr das Prinzip der Selbstorganisation zum Zuge, bei dem lyotrope Strukturbildung oder Wechselwirkungen mit Amphiphilen eine ordnende Rolle spielen. Aufgrund energetischer Gesetzmäßigkeiten sind die so entstehenden Objekte meist wohldefinierte, geschlossene Aggregatstrukturen oder hochsymmetrische Volumenphasen. Im Unterschied zur „molekularen Chemie”︁ geht die Verknüpfung größerer Objekte über die klassischen Grenzen chemischer Fachgebiete hinweg: Durch Verbindung anorganischer Kolloide mit Polymeren sind Hybridmaterialien zugänglich, die die Eigenschaften beider Partner vereinen. Hiermit lassen sich z. B. die katalytischen, optischen und elektronischen Eigenschaften anorganischer Kolloide mit den mechanischen Eigenschaften der Polymere, wie Verfilmbarkeit, Elastizität und Schmelzverarbeitbarkeit, kombinieren.

Hexagonal strukturiertes, mesoporöses Platin (siehe Bild rechts) erhält man durch Reduktion von Platinsalzen in lyotropen Flüssigkristallphasen. Das Templat kann vom nanostrukturierten Metallkolloid entfernt werden, ohne daß dabei dessen Struktur zerstört wird.magnified image

The synthesis of fine polymer latices and ordered polymer gels by polymerization in microemulsions and lyotropic mesophases is described. For this purpose, a new class of surfactants based on the coupling of cetyl trimethylammonium groups with organic counterions was developed. Interface activity, critical micelle concentration as well as lyotropic liquid crystalline phase behavior of these surfactants were investigated, and very high efficiency and high phase stability was found. Systems optimized such do not only allow the synthesis of very small polymer latices ( R h ≥7.5 nm) in reverse systems, but also the generation of gels with lamellar order. Due to the occurrence of phase transitions during polymerization, direct templating of the original lyotropic phase by the polymer gel is prevented, but the final polymer gels are highly ordered and reflect some of the characteristics of the surfactant template.

AbstractChemistry is classically concerned with the connection of atoms and molecules into new functional units. The rules of connection are yet to be extended to the generation and connection of larger objects, whose dimensions are measured in nanometers. However, linking objects of this size through molecules approaching each other randomly is inefficient, instead the principle of self‐assembly is decisive, in which lyotropic structure formation or amphiphilic interaction play a significant role. As a result of the nature of the energetic driving forces, the objects generated in this way are often well‐defined aggregate structures or highly symmetric volume phases. In contrast to “molecular chemistry”, the linking of larger objects also disregards the inherent borders of classical fields of chemistry: for example, the nanoscale association of inorganic colloids with polymers affords hybrid materials that combine the physical properties of both partners. In such a way, catalytic, optical, and electronic features of inorganic colloids might be combined with the mechanical characteristics of polymers such as film formation, elasticity, and melt processibility.

A series of simple deuterium NMR experiments are used to investigate the surfaces of differently structured silicas by studying the sorption of deuteriated solvents. Two mesoporous silicas (MCM-41 and HI-silica), which display hexagonally arranged channels of uniform diameter are studied, as well as amorphous column silica. The deuterium NMR lineshape strongly depends on the anisotropic environment of the adsorbed deuteriated species (D20, benzene-d6, pyridine-d5). This allows differentiation between probe molecules adsorbed to the internal surface (anisotropic) and to the external surface (isotropic, non-ordered surface of particles). Solvents adsorbed within the channels of the silica nanostructure retain a degree of orientational order while moving on the surface, thus producing a Pake pattern. In contrast, solvents adsorbed on the outside of the ordered channels and on domain boundaries retain no orientational order while moving on the surface, therefore giving rise to a singlet in the deuterium NMR spectrum. This phenomenon allows to judge and compare the qualities of hexagonal ceramic nanostructures. The results show that HI-silica exhibits a significantly higher degree of order, due to a larger domain size, than MCM-41.

Liquid crystalline phases, consisting of nonionic surfactant and water, are exploited as templates for the synthesis of inorganic nanostructures. In this approach the aqueous domains of a lyotropic liquid crystal phase function as a confining medium, in which the polymerisation of a water-soluble precursor takes place without destroying the nanostructure. Conducting the prepration of mesoporous silica in a lyotropic liquid crystal phase has considerable advantages over previous routes towards mesoporous ceramic oxides. (i) The nanostructure of the solid can be predicted a priori by knowing the phase structure of the liquid crystal before solidification, (ii) this approach allows the use of nonionic surfactants as templates, (iii) the progress of the reaction can be observed by a variety of methods, such as polarised light optical microscopy, X-ray diffraction, and deuterium NMR spectroscopy, all of which are noninvasive. The synthesis and a new way of monitoring the temporal evolution of the inorganic nanostructure using deuterium NMR spectroscopy are described. The results show unambiguously that the lyotropic liquid crystal phase acts as a template for the nanostructure.

THE synthesis of inorganic mesoporous materials using ionic surfactant template molecules was first reported in 19921,2, and surfactant-mediated synthesis has since been used to form a variety of mesoporous materials3–8. Such materials could find application in catalysis, membrane and separation technology, and molecular engineering. Previous syntheses have used low surfactant concen-trations, and the templating mechanism (which is still controversial) is thought to be a cooperative process involving the interaction of inorganic ions with discrete surfactant aggregates1,2,5,9. Here we report the templating of silica mesostructures from ordered liquid-crystalline mesophases: the resulting silica phase, with pores of ∼3 nm diameter, is a cast of the organic mesophase. As the phase diagram of the surfactant/silica/water system at high surfactant concentration is similar to the (known) phase diagram of surfactant/water alone, this approach should introduce an element of predictability into the synthesis of mesoporous materials.

Two selectively deuterated, liquid-crystalline oligomers of different topology, containing the deep-violet perylene mesogen 1, were prepared by two-fold polymer-analogous reaction of a suitable pre-oligomer or by polycondensation of an ester-functionalized monomer. The materials obtained were investigated by optical microscopy, DSC, X-ray diffraction, and solid-state 2 H NMR spectroscopy. The structural changes in the mesophases formed and the dynamic phase behavior are discussed, and the results are compared with those obtained from low molecular weight model compounds