Synthesis and analysis of materials at interfaces: From organic soft materials to inorganic hard materials.

摘要

The theme of this dissertation is exploring properties of molecules at the interface between two phases. Under this broad category, work has been done to both develop new methods of material syntheses and characterization at key interfaces. The content of the dissertation is divided into three topics: biomimetics, organic transistors and marine siderophores.; The first topic explores biomimetic strategies for material syntheses, as inspired by biomineralization. Chapter 2 reviews various design principles of biomineralization and biomimetics. Chapter 3 describes the effect on calcite crystallization at air/water interfaces by amphiphilic porphyrin monolayers. Porphyrin templates were found to have a similar function as certain shell proteins have in inducing calcite nucleation at {lcub}00.1{rcub} face. In chapter 4, de novo proteins with alternating polar/nonpolar residues were found to form monolayers having a β-sheet structure, with nonpolar residues facing the air and polar residues facing the water. Such monolayers can be templates for calcium carbonate crystallization. In chapter 5, a template-inhibition strategy was developed to synthesize macroscopic scale calcium carbonate thin films. The films initially deposited onto porphyrin monolayers as amorphous films, followed by a phase transformation to become calcite films. This biomimetic strategy was further applied to the synthesis of calcium phosphate thin films (chapter 6), which were further transformed into dahllite films by heat treatment.; The second topic (chapter 7) focuses on the study of thin film transistors of organic conducting polymers. Thin films of regioregular poly(3-hexylthiophene) were prepared by Langmuir-Blodgett (LB) techniques and characterized by UV-Vis, XRD, and IR; and their field-effect mobility was measured.; The third topic (chapter 8) investigates interfacial properties of a novel amphiphilic marine siderophore, marinobactin. The colligative properties of marinobactin were studied by LB techniques, TEM, NMR and stopped-flow spectroscopy. Both apo and Fe-bound marinobactin were found to form monolayers at air/water interfaces. In addition, ferried marinobactin can form vesicles. Both apo and Fe-bound marinobactin can partition into phospholipid membranes, with the former having a larger partition coefficient than the latter. Apo marinobactin maintained its reactivity towards ferric ions upon attaching to the lipid membranes. Based on the data, an iron acquisition mechanism by marine bacteria was proposed.; In addition to a common theme, the above topics share a common link to LB techniques. LB techniques have essentially initiated and played important roles in all these projects. Thus, an overview of LB techniques (chapter 1) serves as the overall introduction to the dissertation.