Regioselective layer-by-layer coating of colloidal silica (M.Sc. thesis)

Anisotropic metal nanoparticles show promising features for catalysis, chemical and biological sensors or theranostics. Such anisotropic silver patches on colloidal silica are synthesised, processed and investigated in this current thesis with the goal of introducing a regioselective polyelectrolyte coating to the silica in addition to the silver patch.
The silver patchy particles were synthesised by a modified Tollens process and functionalised with dodecanethiol which acts as a protective layer. The functionalised particles were then coated with PDADMAC using the layer-by-layer technique. The effect of varying coating time, salt type added to the polyelectrolyte solution as well as different salt concentrations was studied. Based on these results, a layer-by-layer coating procedure compatible with silver patchy particles was successfully established. The regioselectivity of the coating was shown by heterocoagulation with oppositely charged magnetite nanoparticles.
The feasibility of a PDADMAC/PSS/PDADMAC multilayer was demonstrated, however, an improvement to a single polyelectrolyte layer was not noticeable. As a preparation for self-organisation studies, the size of regioselectively coated surface has been tuned indirectly by adjusting the silver patch size distribution. Mixing of coated and uncoated particles led to agglomeration, but no ordered self-organisation could be observed in an optical microscopy set-up, partly attributed to the limited magnification.