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Abstract: Colloidal molecules, or more general supraparticles, i.e., particles which are themselves assembled of smaller nanoparticles in a defined way, are known to be synthesizable via bottom‐up assembly techniques in colloidal dispersion. The amount of synthesizable particles is mostly limited to milligrams. Herein, a bottom‐up‐programed, triggerable top‐down process is reported to obtain core–satellite supraparticles, i.e., particles composed of a larger core particle surrounded by smaller satellite particles. The key is to prepare a nanostructured, microparticulate powder into which defined burst behavior is preprogramed. Once the system is mechanically triggered, it bursts into well‐defined nanosized core–satellite supraparticles. Scale‐up is easily feasible and several hundred grams per batch can be demonstrated. The product is a ready‐to‐use and flexibly processible powder. Upon simple mixing with a polymer, it disintegrates into the preprogramed core–satellite supraparticles, thus forming a highly sophisticated nanocomposite with the polymer matrix. A pure silica nanoparticle system and a silica–iron oxide nanoparticle hybrid system are presented to demonstrate the versatility of the approach. Enhanced mechanical and unexpected magneto‐optical properties with the particle system are found. The disintegration of the microparticles into individual core–satellite colloidal supraparticles is confirmed via in situ liquid cell transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Janus particles are of great research interest because of their reduced symmetry, which provides them with unique physical and chemical properties. Such particles can be prepared from spherical structures through colloidal assembly. Whilst colloidal assembly has the potential to be a low cost and scalable process, it typically lacks selectivity. As a consequence, it results in a complex mixture of particles of different architectures, which is tedious to purify. Very recently, we reported the colloidal synthesis of Au semishells, making use of polystyrene-polyphenylsiloxane Janus particles as an intermediate product (Chem. Commun. 2017, 53, 3898-3901). Here, we demonstrate that these Janus particles are realized through colloidal assembly of spherical glucose-functionalized polystyrene particles and an emulsion of phenyltrimethoxysilane in aqueous ammonia, followed by interfacial polycondensation to form the polyphenylsiloxane patch. Both the polystyrene spheres and the emulsion of Ph-TMS in aqueous ammonia are stabilized by a surfmer-a reactive surfactant. The colloidal assembly reported in this manuscript proceeds with an unexpected high selectivity, which makes this process exceptionally interesting for the synthesis of Janus particles. Furthermore, we report insights into the details of the mechanism of formation of these Janus particles, and apply those to adapt the synthesis conditions to produce polystyrene particles selectively decorated with multiple polyphenylsiloxane patches, e.g., raspberry particles. [ABSTRACT FROM AUTHOR]

Abstract: The fabrication of heteroaggregates comprising inorganic and organic nanoparticles of different sizes is reported. Control over the assembly of nanoscale functional building units is of great significance to many practical applications. Joining together different spherical nanoparticles in a defined manner allows control over the shape of the composites. If two types of constituents are chosen that differ in size, the surfaces of the composites exhibit two specific radii of curvature, yielding aggregates of dual surface roughness. Moreover, if the constituents consist of different materials, the resulting heteroaggregates feature both compositional and interfacial anisotropy, offering unprecedented perspectives for custom-tailored colloids. This study describes a two-step approach towards such designer particles. At first, amine-modified polystyrene particles with 154nm diameter were assembled into clusters of well-defined configurations. Onto these, oppositely charged inorganic particles with diameters of only a few nanometres were deposited by direct uptake from solution, resulting in numerous functional entities all over the surface of the polymer clusters. Despite the fact that oppositely charged constituents are brought together, charge reversal by uptake of nanoparticles allows for stable suspensions of heterocomposites. Hence, the possibility to assemble particles into nanoscale heterocomposites with full control over shape, composition, and surface roughness is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Pickering emulsions, raspberry particles and other colloidal particle complexes are often characterized using small angle scattering techniques. The present work derives an analytical scattering model that accounts for the self-correlation of a spherical core and surface adsorbed particles as well as the particle–particle and core–particle correlation terms characteristic of Pickering emulsions and raspberry particles. It is shown that contrast matching of the scattering length density is not essential to obtain meaningful information as long as the scattering contrasts of all phases are precisely known. The derived equations are useful for analyzing data and planning experiments for Small Angle Neutron Scattering (SANS) and Small Angle X-ray Scattering (SAXS) involving these colloidal systems. [Copyright &y& Elsevier]

This article describes the preparation of hierarchical microsieves via float-casting using raspberry particles. The raspberry particles consist of a larger spherical particle (the core) and smaller particles (satellites) that are attached on the surface of the core and were connected to the core via a surface reaction of isocyanate and amino groups. The raspberry particles were spread onto a water surface as a monolayer and a mixture of polymethylmethacrylate (PMMA) and toluene was poured over this monolayer. After evaporating the solvent, a composite membrane composed of a continuous polymer film with particles protruding out of at least one of its interfaces is obtained. The raspberry particles were etched away, and the membrane thus converted into a hierarchical microsieve comprising larger and smaller pores caused by the core and satellite particles, respectively. The most promising raspberry particles for this purpose consisted of glass beads of 75 μm diameter as core and Stöber-particles of 316 nm respectively 275 nm diameter. The resulting microsieves were suitable for filtration and permeance tests. The permeance at low Reynold numbers (low liquid flow velocity through the pores) is in accordance with established values for microsieves. The membranes were able to retain particles exceeding the pore size. [Display omitted] • We prepared hierarchical microsieves via float-casting using raspberry particles. • The raspberry particles serve as spreading aids, and structure forming agents. • We obtain a hierarchical structure and sub-micrometric trough pores (Ø=230nm ± 41nm). • The microsieves are sturdy and can be handled manually without further support. • (volumetric flow × viscosity)/(Δpressure × area × pore diametre) ≈ 0.01. [ABSTRACT FROM AUTHOR]