Materials/Surface Chemistry: Particle Synthesis, Bioconjugation, and Assembly

Key challenges in nanoscience today include the synthesis of functional particles, and the controlled assembly of these particles to construct functional architectures. The Keating group is active in nanoparticle synthesis, bioconjugation, and assembly to meet these challenges. We synthesize nanospheres, nanowires, and more complex multiparticle assemblies for a variety of optical, electronic, or structural properties.

A promising route to the assembly of such particles is to employ biomolecules as selective glues. Metal nano- spheres and wires can be derivatized with proteins or nucleic acids to provide selectivity. For example, we have used DNA hybridization to assemble nanowires at surfaces and in suspension. A fundamental question in this work is, “how can the construction of complex, multifunctional assemblies be controlled on the nano- and microscale?” Long-term target structures include electronic and optical devices.

We are also interested in the impact of nonspecific forces such as volume exclusion on biospecific nanoparticle assembly. For example, macromolecular crowding by polymeric solutes can impact the thermodynamics of DNA:Au nanoparticle aggregate formation. Crowded environments are important in biological systems; understanding these forces makes it possible to retain control over assembly selectivity in nonideal solutions.

Representative publications:

• “Batch preparation of linear Au and Ag nanoparticle chains via wet chemistry,” Sioss, J. A.; Keating, C. D. Nano Letters, 2005, 5, 1779-1783

• “Template growth of metal-CdSe-metal nanowires,” Peña, D. J.; Mbindyo, J. K. N.; Carado, A. J.; Mallouk, T. E.; Keating, C. D.; Razavi, B.; Mayer, T. S. Journal of Physical Chemistry B 2002, 106, 7458-7462.

• “Partitioning and assembly of metal nanoparticles and their bioconjugates in aqueous two-phase systems,” Helfrich, M. R.; El-Kouedi, M.; Etherton, M. R.; Keating, C. D. Langmuir 2005, 21, 8478-8486.

• “The effect of macromolecular crowding on DNA:Au nanoparticle bioconjugate assembly,” Goodrich, G. P.; Helfrich, M. R. Overberg, J. J.; Keating, C. D., Langmuir 2004, 20, 10246-10251.

• “Hybridization and extension of Au nanoparticle-bound oligonucleotides,” Nicewarner-Peña, S. R.; Raina, S.; Goodrich, G. P.; Fedoroff, N. V.; Keating, C.D. Journal of the American Chemical Society 2002, 124, 7314-7323.

• “Temperature-programmed assembly of DNA : Au nanoparticle bioconjugates,” Dillenback, L. M.; Goodrich G. P.; Keating, C. D. Nano Letters 2006, 6, 16-23.