|WEB seminar: Nanophotonics: from Plasmon Physics to Cancer Therapy |
|Naomi Halas, Rice University|
1:30 PM, Web Connection:
In recent years we have shown that certain metallic nanoparticles possess plasmon resonances that depend very sensitively on the shape of the nanostructure. This interesting observation has led to a fundamentally new understanding of plasmon resonances of metallic nanostructures- “Plasmon Hybridization”- where the collective electronic resonances in a metallic nanostructure is rigorously analogous to the single electron quantum states of simple atoms and
molecules. The Plasmon hybridization picture explains the tunability of nanoshells, a dielectric core, metallic shell nanoparticle which is the simplest nanostructure with tunable plasmon resonances. Moreover, this picture provides a nanoscale “design rule” for understanding the plasmon resonances of an entire new family of plasmonic nanostructures: reduced symmetry nanostructures (nanoeggs and nanorice), multilayer nanoshells (nanomatryushkas), nanoscale dimers, trimers, and Nmers, and a metallic nanosphere adjacent to a thin metallic film (nanoantenna). Since the plasmon resonances give rise to large local field enhancements on the nanostructure surfaces, a variety of surface enhanced spectroscopies such as Surface Enhanced Raman Scattering (SERS) can exploit these types of designed metallic nanostructures as tailored, high-performance SERS substrates. In addition, by tuning plasmon resonances into the near infrared region of the spectrum, the physiological “water window” can be accessed, where blood is essentially transparent and light penetrates maximally through human tissue. With bioengineers, we have developed a suite of applications for nanoshells in the human body, such as a nanoshell-based approach to cancer therapy which will be described.