Preparation of submicrometer-sized clusters from polymer spheres using ultrasonication

The fabrication of small assemblies of spherical colloidal particles is presented. Basic principles of the preparation of miniemulsions were combined with the concept originally described by Pine and co-workers for the preparation of clusters from microspheres. The application of ultrasonic emulsification limits the size distribution of the emulsion droplets and thus the statistical distribution of the number of particles per droplet. The small droplet sizes together with the use of building blocks in the submicrometer range leads to large yields of well-defined small clusters with diameters below 300 nm. Such clusters might serve to build novel promising materials that demand high complexity or special symmetries.