RUI: Stabilization of Gold Nanoparticles in Solution by Poly(Vinyl Alcohol) Adsorption

Mount Holyoke College, South Hadley MA

Investigators

Abstract

TECHNICAL SUMMARY Polymer adsorption onto nanoparticles has both technological relevance and scientific significance. Considering the broad range of applications involving gold nanoparticles (AuNPs) and the nontoxicity and water solubility of poly(vinyl alcohol) (PVOH), it is surprising that adsorption studies of PVOH onto AuNPs have not been reported in the literature. An additional rationale for selecting PVOH is that it is commercially available with different molecular weights and extents of hydrolysis, i.e. different amounts of residual poly(vinyl acetate) (PVA) repeat units. The adsorption of PVOH and PVA segments onto AuNPs prepared by the common citrate reduction method is expected to be driven by hydrogen bonding and hydrophobic interactions, respectively. The dominant mode of interaction will depend on the relative energetics of the two processes in a given system. Polymer composition provides an additional control parameter for adsorption and increases the complexity of probing of the adsorption mechanism(s). Understanding the variants of PVOH/PVA adsorption onto AuNPs, such as polymer molecular weight, size of nanoparticles, polymer composition, polymer concentration, and adsorption time, will allow us to propose a robust method to impart the stabilization of AuNPs against variations in solution pH, ionic strength, and temperature. For our long-term interest of preparing self-assembled NPs in polymer thin films, PVOH may be too crystalline to function as an appropriate polymer matrix for particles to form organized arrays and PVA could be important in providing ?softness? to allow particle mobility in self-assembly. The understanding and methodologies developed in the AuNP-PVOH system are potentially extendable to other nanoparticle-hydrophilic polymer conjugates. NON-TECHNICAL SUMMARY Nanoparticles have the tendency to form aggregates in solution, due to their high surface area-to-volume ratio, resulting in the loss of their unique nanoscopic characteristics. Adsorption of a thin polymer layer onto nanoparticles is an effective approach to provide particle stabilization in their applications. In the proposed work, a water-soluble and nontoxic polymer, poly(vinyl alcohol), will be adsorbed onto gold nanoparticle surfaces from aqueous solutions, to prevent nanoparticles from aggregating in response to environmental perturbations in pH, ionic strength, and temperature. The funds requested in this proposal will support the PI?s efforts in research collaborations with undergraduate students at Mount Holyoke College and local female high school students over the next three years. The undergraduate and local female high school students will be involved in all aspects of the work described in this proposal, from design and synthesis to characterization using both routine and sophisticated instrumentation. In the process, researchers will be introduced to the interdisciplinary field of polymer chemistry and be exposed to the vitally important area of nanotechnology. Exposure of undergraduate students to research is important for both education and recruitment purposes. The outreach activities proposed ? having local female high school students involved in frontier research and local middle school students engaged in fun and enlightening polymer workshops ? will inspire and prepare more women to be future scientists and engineers.