Self-assembly of stable gold-based catalysts
Similar to atoms in conventional solids, nanoparticles can be used as building blocks to construct larger so-called superstructures. In this project, catalytically active metal nanoparticles (Au-based) are self-assembled with oxide colloids into ordered superstructures. The nanoparticles spontaneously form an ordered colloidal crystal when gradually evaporating the surrounding solvent. Dispersing the nanoparticles in oil droplets rather than a continuous phase results in the formation of spherically shaped superstructures [Figure 1a]. Such well-defined systems can serve as model catalysts of which the composition, size and placement of the components can be tuned with great precision.
The aim of the project is twofold. First, we want to synthesize a set of binary colloidal crystals, identify the different crystal structures and thereby gain a deeper insight in the nucleation of binary crystals, a fundamental issue in soft matter science that is still largely unsolved. Second, we want to study the catalytic properties of these colloidal crystals, in particular the relationship between the crystal structure and the catalytic stability. We expect that the degree of encapsulation of the Au nanoparticles either by neighboring silica nanoparticles or directly with a silica shell [Figure 1b] will prevent particle growth and sintering during catalysis and will thus enhance the catalytic stability. In addition, the melting temperature of gold-based nanoparticles in the colloidal crystal as a function of the crystal structure will be measured.