Controlling Colloidal Interaction Through Assymetric Functionalization
Open Access
- Author:
- Snyder, Charles Eduardo
- Graduate Program:
- Chemical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 07, 2008
- Committee Members:
- Darrell Velegol, Committee Chair/Co-Chair
- Keywords:
- bottom-up assembly
Janus particle
particle lithography
colloid - Abstract:
- The use of colloids and nanoparticles is becoming more and more prevalent across all scientific disciplines. The ability to control how these particles interact may yield new structures with unique and useful properties. This thesis contributes a new method of creating dual functionality on colloids, “particle lithography”. These modified colloids may be used to bottom-up assemble asymmetric colloidal aggregate structures. Particle lithography allows for the site specific functionalization of a colloid at a single site. The technique is not limited to any specific material and is scalable. The ability to control the patch’s size is demonstrated. Characterization of the patch confirms the ability to control the patch size through varying the size of the colloid, the hydrodynamic radius of the coating particles or molecules, and the salt concentration at which the coating is applied. The effects of other experimental conditions on the particle lithography process, such as sonication, are examined. The particle lithography process is extended to functionalize a colloid at two sites. The sites are ninety degrees relative to the center of the colloid. This functionalization is used to form self-assembled trimers. Through this process, the ability to use other particles as masking agents in the particle lithography process is demonstrated. Also demonstrated is the ability to assemble particles composed of differing materials. Modeling aided in understanding how a lithographed and complementary particle might interact. Phase diagrams were constructed to show the critical coagulation concentration of salt needed for a lithographed particle to bind to its complement. This salt concentration is a function of patch size and potential, and particle size and potential. An effective patch size is defined and found to vary little as a function of system parameters. Defining a critical coagulation concentration suggests the ability to store lithographed precursor particles. This ability to create storable particles with controlled reactive sites provides a new tool for bottom up assembly processes. Usefulness is derived from even the most basic of asymmetry in particle assemblies. Application of the particle lithography process may enable the creation of new and elaborate self-assembled structures.