Stimuli-responsive colloidal crystals with reconfigurable structures and properties have garnered significant interest in fields focused on the development of on-demand optics, adaptive catalysts, as well as chemical and biological sensors. A variety of different assembly techniques have been developed to engineer colloidal crystals. However, most reported structures are static as a result of unchangeable interactions between the building blocks. DNA-mediated crystallization offers advantages over other assembly techniques, because the responsive DNA “bonds” allow for dynamic manipulation of programmable structures, post-assembly. Moreover, the identity of the nanoparticle (NP) core “atom” (size, shape, and composition) can be tuned independently of the DNA “bonds” (length, sequence, and density), allowing for generation of an unlimited combination of crystal structures and symmetries. Although colloidal crystals responsive to external stimuli (e.g. DNA strands, enzymes and dielectric media) have been reported recently, a generalizable approach for dynamically manipulating such structures on cue and in a reversible manner does not exist. In this thesis, I investigated how chemical components that respond to stimuli (e.g. pH, light and mechanical force) can be incorporated into colloidal crystals in order to dynamically toggle such structures between different crystal symmetries and lattice constants. I systematically studied the roles of assembly parameters and established a corresponding set of structure design rules. Three different strategies for controllably changing the structures of pre-assembled colloidal crystals with external stimuli have been developed. The location and number of DNA modifications, linker sequence design (length and strength), and NP size are crucial parameters in controlling such structural changes. Chapter 1 introduces the concept of stimuli-responsive colloidal crystals engineered with DNA, and in particular, the idea of utilizing programmable atom equivalents (PAEs) as building blocks to construct colloidal architectures with interchangeable structures and properties. Chapter 2 describes a powerful strategy for creating pH-responsive colloidal crystals by incorporating i-motif DNA into the bonding elements. Rationally designed DNA bonds allow for dynamic changes in either bond length or bond type, resulting in a reversible way to switch lattice parameters or crystal symmetries. Chapter 3 investigates using azobenzene-modified DNA to build light-responsive colloidal crystals and systematically investigates the reversibility of photo-switchable assembly and disassembly. Synthesis and characterization of these colloidal crystals allow for photopatterning hierarchical structures unattainable with other methods. Chapter 4 introduces a new fabrication approach - combining polymer pen printing with DNA-mediated assembly on surfaces to create arbitrarily designed patterns in a massive parallel manner. Chapter 5 introduces three future directions for this thesis work, including developing multi-stimuli-responsive colloidal crystals, building on-demand functional systems, and printing multi-functional nanomaterials. The details for the DNA designs are provided in the appendix. Taken together, this thesis presents a significant advance in colloidal crystal engineering, as well as a systematic route to stimuli-responsive materials with tunable structures and properties.

Creator

• Zhu, Jinghan

DOI

• https://doi.org/10.21985/n2-tqx8-yd04

Subject

• Engineering

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:15066
• etdadmin_upload_739736

Keyword

• DNA
• Colloidal crystals
• Stimuli-responsiveness

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright