PHYS 235 |
| DNA has emerged as a powerful and versatile tool for nanoscale self-assembly. Several researchers have assembled nanoparticles and colloids into a variety of structures using the sequence specific binding properties of DNA. Colloidal crystallization can be seen as a particularly well-understood prototypical example of self-assembly. Until recently, however, all of the reported colloidal structures assembled using DNA binding were disordered. We detail the experimental approach and surface preparation that we used to form the first DNA-mediated colloidal crystals using polystyrene microspheres. To better understand the kinetics and thermodynamics of self-assembly/crystallization process, we designed a system that forms colloidal ‘solid solution' crystals. The experimental behavior of the solid solutions has been replicated in detailed simulations, and confirms that while growth is reaction limited, colloids are able to equilibrate at the growing interface. We also report the first direct measurements of such DNA-induced interactions between microparticles. The interactions measured with our optical tweezer method can be modeled in detail by well-known statistical physics and chemistry, boding well for their further application to directed self-assembly. The microspheres' reversible adhesion dynamics, however, have an unexpected power-law scaling at high DNA density. Similar experiments in the single molecule limit show DNA hybridization to have stretched exponential kinetics that resemble literature FCS experiments, but on much longer timescales. |
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Emergence of Function in Molecular Assemblies
1:20 PM-5:00 PM, Tuesday, August 21, 2007 BCEC -- 159, Oral
Division of Physical Chemistry |