Biological Processing of Au Nanorods

Our group's interest in Au nanorods focuses on their use as starting components for the generation of higher ordered assembled materials. Their intrinsic bifurcated plasmon absorbance presents a unique optical handle that can be directly tuned based upon the assembly state of the individual materials such that formation of nanochains shifts the longitudinal plasmon resonance further into the near-IR. We employ biomolecules, such as amino acids, to direct the assembly process; however, we are concerned with the molecular-based interactions that control the assembly. We have already determine the binding effects of cysteine, shown at left, and are in the process of developing new bio-based assembly schemes for added functionality. Additionally, we are also interested in using the interaction between biomacromolecules and Au nanorods for other non-optical based materials applications/integrations. Current publications in this area include:

Sethi, M.; Joung, G.; Knecht, M.R. Linear Assembly of Au Nanorods Using Biomimetic Ligands, Langmuir 2009, 25, 1572-1581.

Sethi, M.; Joung, G.; Knecht, M.R. Stability and Electrostatic Assembly of Au Nanorods for use in Biological Assays, Langmuir 2009, 25, 317-325.

Bio-Inspired Nanocatalysts

The development of green and energy efficient catalytic materials is critically important as the exhaustion of fossil fuels approaches. While standard catalytic designs have demonstrated positive progression towards these goals, new materials must be developed and designed that are fully active under such non-traditional conditions. Bio-inspired nanomaterials have demonstrated some unique abilities under these conditions owing to their peptide surface passivants, which are optimized under ambient and biological-based conditions. We have used such approaches to develop nanocatalysts using a Pd specific peptide that operate in water at room temperature, that emply 0.005 mol% Pd for quantitative yields for Stille coupling. These results position the peptide-based nanocatalysts as unique model systems for understanding the reactive designs for the generation of enhanced catalytic species. Present studies are being conducted to probe these dimensions. A current publication in this area is:

Pacardo, D.B.; Sethi, M.; Jones, S.E.; Naik, R.R.; Knecht, M.R. Biomimetic Synthesis of Pd Nanocatalysts for the Stille Coupling Reaction, ACS Nano 2009, 3, 1288-1296.

Biomolecule Nanomaterial Surface Interactions

In order to employ biomolecules as active surface species for nanomaterials, it is important to understand these interactions at a molecular level. We have begun to study these properties employing citrate-capped Au nanoparticles in solution using simple amino acids to monitor surface changes that may arise. By studying the interactions between these two species, we have observed incomplete surface ligand exchange between citrate and Arg, which results in the self-segregation of the two species to produce an electronic dipole across the surface. As a result, linear assembly of the Au nanoparticles occurs that is dependent upon the Arg concentration. We use this effect to monitor surface exchange rates as well as the binding efficiency of biomolecules. A current publication in this area is:

Sethi, M.; Knecht, M.R. Experimental Studies on the Interactions Between Au Nanoparticles and Amino Acids: Bio-Based Formation of Branced Linear Structures, ACS Appl. Mater. Interfaces 2009, 1, 1270-1278.