Tuning Interfacial Interactions in Colloidal Crystal Engineering with DNA

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The rational and deliberate assembly of functional materials from nanoscale building blocks requires a fundamental understanding of interactions between individual components as well as their collective behavior. This thesis investigates the hierarchical organization of nanoparticles using DNA into well-defined three-dimensional materials on the micrometer and millimeter length scales. This assembly strategy utilizes nanoparticle building blocks coated with shells of DNA ligands that direct crystallization through sequence-specific hybridization interactions. This thesis shows how the linkages between particles can be systematically tuned using a variety of stimuli, including small molecule intercalators, changes in salt concentration, and strain energy. The subsequent changes in crystallization at both the local and macroscopic levels are studied, allowing one to increase architectural diversity and draw similarities with atomic systems. Chapter 1 introduces the history and conceptual framework of DNA-mediated crystallization of nanoparticles for materials synthesis. The next two chapters investigate the opportunities that the physical and chemical properties of the DNA shell present for engineering additional functionality and stimuli responsiveness in colloidal crystals. Chapter 2 investigates the response of both the oligonucleotide bonds and macroscopic superlattice structure to small molecule intercalators. The lessons learned are leveraged to synthesize a novel core-shell hierarchical crystal structure. In chapter 3, the properties of DNA as a polyelectrolyte brush, which have been largely ignored, are investigated in the context of a binary DNA-protein and DNA-gold nanoparticle system. In this case, repulsive interactions between non-complementary particles drive the crystallization pathway toward a lattice that is not typically seen in these assemblies. This system exhibits a structural response to salt concentration and lays the groundwork for using repulsive interactions between non-complementary particles to increase structural diversity in colloidal crystals. The next 2 chapters investigate the role of the DNA shell in crystallization behavior at the macroscopic level. Comparisons between colloidal and atomic thin film crystallization are made, elucidating the role of the DNA shell in thin film growth and in the collective response to interfacial strain energy. This work leverages the capabilities of both top down and bottom up processes to assemble colloidal crystal thin films epitaxially from a template. Using this approach, the role of the DNA shell in strain energy dissipation and colloidal thin film growth is determined, and similarities and differences with atomic thin film growth are outlined. Achievements of this work include the assembly of core-shell materials and large-scale single-crystalline thin films of arbitrary shape and size. These advances expand our ability to program the assembly of colloidal crystals across many length scales. Moreover, many of the lessons learned are applicable not only to DNA-mediated assembly, but also other types of polymeric assemblies.

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  • 02/15/2019
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