Preparation of Reinforced Anisometric Patchy Supraparticles for Self‐Propulsion

Abstract

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 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.

Structure Formation in Supraparticles Composed of Spherical and Elongated Particles

“…Multiple types of materials, ranging from nanometer-sized quantum dots or metal organic frameworks to micrometer-sized polystyrene (PS) particles, with different shapes and chemistries can be used as building blocks to create supraparticles. The supraparticles may have emergent properties that surpass the mere sum of their parts, arising from the interactions between different types of building blocks. , Therefore, supraparticles are versatile materials with potential applications in many fields of science and technology, including catalysis, ,− gas adsorption and sensing, , drug encapsulation and delivery, , photonics, − and energy production and storage. , …”

Confocal micro X-ray fluorescence analysis for the non-destructive investigation of structured and inhomogeneous samples

“…It was stated that the well-defining of the resulting patchy will change the propulsion properties of the particles. CMXRF enabled the 3D investigation of the internal structure and distribution of the nanoparticles with a resolution of about 30 µm [ 64 ].…”

Atomic spectrometry update: review of advances in X-ray fluorescence spectrometry and its special applications

“…Oguzturk et al 22 reported on the preparation of fumed silica-based anisometric supraparticles with catalytically active Pt-covered magnetite (Fe 3 O 4 /Pt) patches, suitable for self-propulsion. Use of confocal μXRF spectrometry made it possible to locate the catalytic Fe 3 O 4 /Pt NPs precisely within the mm-sized supraparticles with a resolution in the μm range and thereby provide detailed internal structural information on various supraparticles.…”