Convective Assembly Of Non-Spherical Colloids

Abstract

Fabricating colloidal based materials from non-spherical particles shows the potential to produce materials having a broader diversity of particle packing arrangements and crystal lattice symmetries than possible for spherical bases. These new materials show enhanced structure-property relations, specifically, in terms of photonic bandgap properties. In order to access these enchance properties, a viable method to assemble non-spherical based ordered structures is required. This dissertation describes the application of the convective self-assembly technique to fabricated regular two- and three-dimensional structures from disc, hemispherical cap, spherocylinder and dumbbell shaped colloids. Aqueous particle suspensions with controlled volume fraction permitted the assembly of large scale crystalline monolayers on substrates vertically immersed in the suspension, as the solvent was evaporated. Systematically tuning the particle volume fraction induced different particle packing arrangements in the monolayer. The monolayer structures were then correlated to the crystallization rate and suspension concentration, the two key convective assembly parameters, establishing process control of film structure in the monolayer regime. Adjusting the parameters for slower film deposition, higher suspension concentrations were used to extend the convective assembly technique three-dimensional structures from spherocylinder and dumbbell shaped particles. Additionally, the photonic band structures of crystals with face-centered cubic (FCC) and base-centered monoclinic lattices and dumbbell shape bases were calculated. The band structures revealed that a range of particle shapes produced complete photonic bandgaps.