April 24, 2002
FRONTIERS IN MATERIALS SCIENCE
VINSE COLLOQUIUM SERIES
Dr. Naomi Halas
Stanley C. Moore Professor of Electrical and Computer Engineering
Professor of Chemistry
"Metal Nanoshells: Constructing Optics 'From the Dipole Up'"
Abstract. A metal nanoshell is a precisely layered dielectric-metal nanoparticle that is the experimental realization of a spherical 2-D electron gas. This topology supports plasmon resonances whose frequencies are tunable by varying the relative thicknesses of the nanoparticle’s constituent layers. Unlike photonic crystals, which require long-range periodicity to manipulate light, individual metal nanoshells provide precise control over optical fields at subwavelength dimensions and can be considered a fundamental component of nanophotonics. This nanostructure also provides a new way to study the electronic and dynamical properties of mesoscopic metals that is complementary to the low-temperature, transport based methods commonly used.
In our presentation we will discuss the origin of the optical properties of metal nanoshells and their interaction with nearby molecules and structures. We will discuss various ways in which metal nanoshells, embedded in host media, have been used to modify and manipulate optical properties of the host in unusual ways: an example of how nanoshells have been used to develop new materials with a dramatic optomechanical response will be discussed. The role of gold nanoshells as a highly biocompatible substrate that can be used for performing instantaneous medical testing in whole blood and as a promising strategy for cell-specific photothermal cancer therapy will be addressed. We will also show how simple modifications in the core-shell geometry are leading to new functional nanoparticles, as well as a generalization of the tunable plasmon concept to a variety of different geometrical nanostructures.