Cluster formation and rheology of photoreactive nanoparticle dispersions

Current directions in core-shell nanoparticle design

Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems.

Photochemical gluing of colloidal particles by a simple interparticle polymerization route

We have developed a simple strategy to chemically cross-link polystyrene latex spheres by UV-light-induced polymerization after the particles, which themselves were internally cross-linked with divinylbenzene (DVB), have been carefully swollen in aqueous dispersion with a small amount of the monomer styrene. As a proof of concept, aggregates were preformed by salt-induced aggregation, and successful fixation of the aggregate structure was quantitatively confirmed by dynamic light scattering after the sample was diluted with distilled water and treated with ultrasound. Under this treatment, non-UV-irradiated aggregates dispersed and the single particle size was recovered. This concept was successfully applied also to commercial latex particles. For the future, arranging the colloids in a well-defined way by laser traps before photo-cross-linking opens up a facile method to prepare microscopic devices.