Preparation of Reinforced Anisometric Patchy Supraparticles for Self‐Propulsion

The 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 m 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