Colloidal assemblies have applications as photonic crystals and templates for functional porous materials. While there has been significant progress in controlling colloidal assemblies into defined structures, their 3D order remains difficult to characterize. Simple, low‐cost techniques are sought that characterize colloidal structures and assist optimization of process parameters. Here, structural color is presented to image the structure and dynamics of colloidal clusters prepared by a confined self‐assembly process in emulsion droplets. It is shown that characteristic anisotropic structural color motifs such as circles, stripes, triangles, or bowties arise from the defined interior grain geometry of such colloidal clusters. The optical detection of these motifs reliably distinguishes icosahedral, decahedral, and face‐centered cubic colloidal clusters and thus enables a simple yet precise characterization of their internal structure. In addition, the rotational motion and dynamics of such micrometer‐scale clusters suspended in a liquid can be followed in real time via their anisotropic coloration. Finally, monitoring the evolution of structural color provides real‐time information about the crystallization pathway within the confining emulsion droplet. Together, this work demonstrates that structural color is a simple and versatile tool to characterize the structure and dynamic properties of colloidal clusters.

Colloidal supraparticles are micron-scale spherical assemblies of uniform primary particles, which exhibit emergent properties of a colloidal crystal, yet exist as a dispersible powder. A prerequisite to utilize these emergent functionalities is that the supraparticles maintain their mechanical integrity upon the mechanical impacts that are likely to occur during processing. Understanding how the internal structure relates to the resultant mechanical properties of a supraparticle is therefore of general interest. Here, we take the example of supraparticles templated from water/fluorinated oil emulsions in droplet-based microfluidics and explore the effect of surfactants on their mechanical properties. Stable emulsions can be generated by nonionic block copolymers consisting of a hydrophilic and fluorophilic block and anionic fluorosurfactants widely available under the brand name Krytox. The supraparticles formed in the presence of both types of surfactants appear structurally similar, but differ greatly in their mechanical properties. While the nonionic surfactant induces superior mechanical stability and ductile fracture behavior, the anionic Krytox surfactant leads to weak supraparticles with brittle fracture. We complement this macroscopic picture with Brillouin light spectroscopy that is very sensitive to the interparticle contacts for subnanometer-thick adsorbed layers atop of the nanoparticle. While the anionic Krytox does not significantly affect the interparticle bonds, the amphiphilic nonionic surfactant drastically strengthens these bonds to the point that individual particle vibrations are not resolved in the experimental spectrum. Our results demonstrate that seemingly subtle changes in the physicochemical properties of supraparticles can drastically impact the resultant mechanical properties.

The preparation of supported catalytically active metal solutions has been investigated using ultrasonication. Sonication conditions and solvents influence the Ga droplet formation and hence the catalytic performance in heptane dehydrogenation.

PPs range in size from nano-to micrometers and can have a variety of compositions. Their assembly into SPs provides synergistic effects giving them additional functionality, [1] which can arise both from the material of PPs themselves, and from the defined arrangement within the SP. The simple colocalization of different PPs within one SP, allows, for example, the combination of multiple properties, to provide, for example, magnetic samples for applications in biotechnology [2] or water purification, [3,4] or reporter particles with the ability to detect environmental changes. [5,6] Emergent properties, caused by the regular arrangement of the PPs give rise to structural coloration from interference effects, [7][8][9][10][11][12][13] or provide defined tailored surface roughness that can increase powder flowability, for example, in additive manufacturing. [14] An important emergent property of SPs is porosity, which naturally arises in such systems if the individual PPs form agglomerates held together only by contact forces or solid bridges. [15,16] In this case, the interstitial structure of the PPs provides a fully interconnected pore system. In an idealized scenario of perfectly packed, monodispersed particles, the A drying droplet containing colloidal particles can consolidate into a spherical assembly called a supraparticle. Such supraparticles are inherently porous due to the spaces between the constituent primary particles. Here, the emergent, hierarchical porosity in spray-dried supraparticles is tailored via three distinct strategies acting at different length scales. First, mesopores (<10 nm) are introduced via the primary particles. Second, the interstitial pores are tuned from the meso-(35 nm) to the macro scale (250 nm) by controlling the primary particle size. Third, defined macropores (>100 nm) are introduced via templating polymer particles, which can be selectively removed by calcination. Combining all three strategies creates hierarchical supraparticles with fully tailored pore size distributions. Moreover, another level of the hierarchy is added by fabricating supra-supraparticles, using the supraparticles themselves as building blocks, which provide additional pores with micrometer dimensions. The interconnectivity of the pore networks within all supraparticle types is investigated via detailed textural and tomographic analysis. This work provides a versatile toolbox for designing porous materials with precisely tunable, hierarchical porosity from the meso-(3 nm) to the macroscale (≈10 µm) that can be utilized for applications in catalysis, chromatography, or adsorption.

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Dye-sensitized photocathodes have the potential to significantly contribute to the efficiency of the solar light-to-current conversion in tandem dyesensitized solar cells (DSSCs). A novel, highly porous nanoarchitecture of NiO is developed in this project. The spongelike material is grown by anodization, shows a virtually crack-free morphology, strongly adheres to the substrate, and can be grown with a controllable thickness of at least up to 6.5 μm. The oxide composition is NiO and the nanosponge exhibits p-type semiconductive behavior. A doubling of the maximum reported p-type DSSC efficiency compared to coumarin C343-sensitized NiO nanoparticle photocathodes can be achieved with the NiO nanosponge. The developed dye-sensitized p-type NiO-based cathodes are promising for application as photocathodes in tandem DSSC devices.

Porous materials are widely used in applications such as adsorption, catalysis and separation. The use of expander molecules is a versatile route to enlarge the mesopore size in micellar templated...

Supraparticle Powders Controlling the structure and porosity in hierarchical materials is a key design feature that can enable their successful application in fields of chromatography, catalysis and adsorption. In article number 2300241, Benjamin Apeleo Zubiri, Alexandra Inayat, Nicolas Vogel, and co‐workers provide a versatile toolbox for designing hierarchical porous materials by tailoring the porosity in spray‐dried supraparticles from the meso‐ (3 nm) to the macroscale (≈10 µm).