Colloidal Cubes: Preparation, optical properties, & polymer-mediated interactions

Abstract

The shape of colloidal particles affects the properties in colloidal mixtures; mixtures where one of the components has a typica length scale between 1 nm and 1000 nm. In this thesis we explore this influence by studying a system of colloidal cubes. By coating cuprous oxide nanocubes are with silica, core-shell nanocubes with sizes ranging 50–150 nanometre are obtained. These nanocubes can be transformed into cubic silica shells, mesoporous nanoboxes with functional cores, and thermorepsonsive colloidal shape-shifters. The cubic silica shells are characterized by light and X-ray scattering at low concentration, revealing their refractive index and their shape being intermediate a sphere and a cube. Addtionally, concentrated dispersion of cubic silica shells are studied with static light scattering, resulting in the first static structure factors of stable cube fluids, of which the properties can be described by the equation of state of a hard superball fluid. A similar method is employed to determine the stability of silica cubes mixed with non-adsorbing polymers. By measuring apparent structure factors, demixing of cubes and depletants is observed, allowing to construct an experimental phase diagram of cube-polymer mixtures. This phase diagram is in agreement with predictions obtained from free volume theory. Lastly, the hollow silica cubes are demonstrated to manifest anti-reflective properties when coated on a glass surface via “wire wound rod”-coating and Langmuir-Blodget dipcoating. This thesis demonstrates presents methods to obtain model silica nanocubes and explores their shape dependant colloidal properties.