(216q) Role of Metal Layer Thickness and Surface Chemistry in the Self-Assembly of Metallodielectric Janus Spheres

We study the clustering of colloidal polystyrene spheres with a hemispherical coating of gold and quantify the effects of gold thickness and self-assembled monolayer chemistry on their self-assembly. A gold layer varying from 10nm to 40nm in thickness was deposited on 1-micron diameter carboxylate-stabilized polystyrene spheres.  The metallic surface was functionalized with a self-assembled monolayer of varying chemistry. The kinetics of self-assembly was studied in aqueous suspensions as a function of the concentration of added sodium chloride. The ordered aggregates of these Janus microspheres, formed via gold-gold binding, were studied using confocal laser scanning microscopy. From acquired images we quantify the abundance of each observed cluster size and show how the cluster size distribution changes with increasing gold thickness at a fixed salt concentration. We also investigate cluster formation and equilibration of cluster growth as a function of salt concentration varied from 1mM – 5mM and as a function of self-assembled monolayer chemistry. We discuss the kinetics and equilibrium structures observed in light of the variation in metal layer thickness, self-assembled monolayer chemistry, and Janus particle stability.