Abstract
AbstractThe preparation of fumed silica‐based anisometric supraparticles with well‐defined catalytically active patches suitable for self‐propulsion is presented here. These sub‐millimeter‐sized particles can self‐propel as they contain Pt‐covered magnetite (Fe3O4) nanoparticles, where the Pt can decompose catalytically a “fuel” like H2O2 and thereby propel the supraparticles. By their magnetic properties, the catalytically active nanoparticles can be concentrated in patches on the supraparticle surface. The goal is to obtain robust supraparticles with well‐defined patchiness and long‐time stability during self‐propulsion through evaporation‐induced self‐assembly (EISA) on a superhydrophobic surface. The latter is a major issue as oxygen evolution can lead to the disintegration of the supraparticles. Therefore, enhanced mechanical stability is sought using a number of different additives, where the best results are obtained by incorporating polystyrene microspheres followed by heat treatment or reinforcement with microfibrillated cellulose (MFC) and sodium trisilicate (Na2SiO3). The detailed internal structure of the different types of particles is investigated by confocal micro‐X‐ray fluorescence spectroscopy (CMXRF), which allows for precisely locating the catalytic Fe3O4@Pt nanoparticles within the supraparticles with a resolution in the µm range. The insights on the supraparticle structure, together with their long‐time stability, allow fabricating optimized patchy supraparticles for potential applications in propulsion‐enhanced catalysis.
Highlights
The hypothesis was that PS may act here as a mechanical strengthening and hydrophobization agent, and to improve the swimming ability of the particles as PS has a lower density (1.05 g cm−3) than the rest of the supraparticles material
We report the formation and characterization of anisometric self-assembled patchy particles that could move by self-propulsion
The particles were based on fumed silica (FS) and prepared by the previously described method[36] of evaporation of mm-sized droplets on a bent superhydrophobic surface
Summary
[+]Present Address: Helmholtz Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin, Germany evaporation-induced self-assembly (EISA) methods.[24,25] For the latter, superhydrophobic surfaces with contact angles > 150° allow for symmetric evaporation from the sessile droplets resulting in spherical particles, typically in the size range of many μm to mm, formed as a result of droplet templating.[3] When the drying droplets contain colloidal particles, these colloids become assembled together This assembly is controlled by the interaction between the colloidal particles, leading to supraparticles with an internal structure formed during the drying process.
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