Younan Xia (NSF Award Number: DMR-0451788) Department of Chemistry, University of Washington

1. Shape-Controlled Nanostructures of Metals Younan Xia (NSF Award Number: DMR-0451788) Department of Chemistry, University of Washington Silver nanostructures are containers for surface plasmons – the collective oscillation of conduction electrons in phase with incident light. By controlling the shape of the container, one can control the ways in which electrons oscillate, and in turn how the nanostructure scatters light, absorbs light, and enhances local electric fields. With a series of discrete dipole approximation calculations, each of a distinctive morphology, we illustrate how shape control can tune the optical properties of silver nanostructures. Calculated predictions are validated by experimental measurements performed on nanocubes with controllable corner truncation, right bipyramids, and pentagonal nanowires. Such a control of nanostructure shape allows one to optimize surface plasmon resonance for improved molecular detection and spectroscopy. Both synthetic and computational studies were recently highlighted as a cover feature article in J. Phys. Chem. B., 2006, 110, 15666. In addition to silver, we have also extended the synthetic methodology to other noble metals including palladium, platinum, and rhodium.

2. Shape-Controlled Nanostructures of Metals Younan Xia (NSF Award Number: DMR-0451788) Department of Chemistry, University of Washington (left) Illustration of the reaction paths leading to well-defined silver nanostructures. Ethylene glycol reduces silver ions to atoms, which form clusters of fluctuating structure. Fluctuation decreases as the cluster grows, until it evolves into a single-crystal, single twinned, or multiple twinned seed. Further growth of seeds can selectively enlarge (100) facets at the expense of (111) facets, resulting in formation of nanocubes, bipyramids, or pentagonal nanowires. (middle) SEM image of Pt nanorods grown on the surfaces of spherical aggregates of Pt nanoparticles that were formed through a surfactant-directed self-assembly process. (right) TEM image of Pt nanorods after they had been released from the surfaces by brief sonication. The inset in (D) gives a typical selected-area electron diffraction pattern of the Pt nanorods, with the four rings indexed to the {111}, {200}, {220}, and {311} diffraction of face-centered cubic Pt, respectively. Note that several nanorods could grown from the same seed of Pt nanoparticle, resulting in a branched morphology.

3. Other Accomplishments • Supervision of 6 undergraduates enrolled for the independent study (with a total of • 21 credits) and 1 REU summer student. Two of them co-authored 3 articles recently • published in Adv. Mater. (2005) Nano Lett. (2005), and Chem. Soc. Rev. (2006) • Supervision of 2 junior students from the Redmond High School in the summer of • 2005 • Giving invited lectures at MRS and ACS national meetings, as well as more than 40 • universities (chemistry, chemical engineering, and materials science & engineering) • around the world • Giving lectures at the Sandia National Laboratories and the 3rd ASME Nano Training • Boot Camp • Serving as a committee member of the Inorganic Nanostructures Facility at the DOE • Molecular Foundry • Serving as the associate editor of Nano Letters • Serving as a member of the advisory board for Nano Today, Langmuir, Chemistry of • Materials, International J. of Nanotechnology, and International J. of Nanoscience. • Serving as symposium co-organizers and session chairs for MRS, ACS, and SPIE • Serving as the guest editor for a special issue on metal nanostructures and surface • plasmon resonance published in Mater. Res. Roc. Bull. (May, 2005) • Preparation of three education articles, which have been accepted for publication in • J. Chem. Educ.