Self-Assembly of Colloidal Spheres into One, Two, and Three Dimensional Structures

Abstract

The main goal of this thesis is to increase our understanding of colloidal self-assembly processes and develop new strategies to assemble colloidal building blocks into more sophisticated and well-defined super-structures. Self-assembly is a spontaneous process in which a disordered system of pre-existing building blocks forms an ordered structure without human intervention. For example, virus capsid proteins can self-assemble into virus microcapsules. However, direct investigation of the self-assembly process of, for examples, proteins and other molecules in situ, is difficult since those objects are too small and move too fast to be tracked directly by techniques such as electron and optical microscopy. Herein, we employ colloids as models of (macro) molecules to study self-assembly. This thesis divides into two parts. In the first part, we show various methods to tune the properties of the colloids, including shape, charges, morphology, size and surface properties. In the second part, we focus on the self-assembly of spherical colloids into one, two and three-dimensional colloidal aggregates using different principles. We show that the delicate balance of short-range hydrophobic attraction and relatively longer-range electrostatic repulsion can result in the formation of a Bernal spiral-like structure. While the use of a good solvent of colloids during the vertical deposition process allows for the formation of floating colloidal crystal monolayers. We also show that pH reversible encapsulation of oppositely charged colloids with a vast size difference can be achieved in the presence of pH-responsive polyelectrolytes in solution.