The Effect of Confinement, Surface Chemistry and Topography on Crystallization

This thesis presents an extensive investigation into the effects of confinement, surface chemistry and topography on the crystallization of various inorganic solids and proteins. Firstly, the crystallization of potassium ferrocyanide trihydrate (KFCT), calcium sulfate and calcium carbonate (CaCO3) was studied in nanopores. Remarkably high stabilization of metastable phases was achieved in the pores due to a significant retardation of the crystallization processes in confinement. Indeed, the retardation effects observed here are far greater than any seen before for inorganic solids. The confinement system presented here, controlled pore glass (CPG) rods, also offered the possibility of imaging and characterizing crystals growing in nanopores using in situ 3D absorption and diffraction tomography with synchrotron radiation. This provided insights into the crystallization pathways of calcium sulfate and CaCO3 and generated a new understanding of the mechanisms that govern crystallization in confinement. Confinement was also used as a tool to reveal information about the crystallization mechanism of model proteins. All of the proteins studied followed a two-step nucleation pathway involving amorphous precursors. The intermediates could be stabilized in confinement for long periods of time but they readily crystallized in larger spaces. Finally, the nucleation of proteins on chemically modified substrates with topographic defects was also investigated. The proteins adsorbed to the topographic features on the substrates, where an increase of the local supersaturation within the cavities promoted their nucleation. Thus, by simply modifying the surface chemistry and topography of a substrate, amazing control of protein crystallization was achieved, such that control over the location of crystal formation could be achieved