We are working on a new class of asymmetric metal particles: nanofabricated pyramids. Because their nanofabrication procedure is extremely versatile, pyramids are ideal for designing multifunctional plasmonic materials that have high potential for creating unexpected applications. For example, pyramids can be generated with variable sizes, thicknesses, and multi-metal compositions. They can also be designed with blunt, ultra-sharp, or no tips, and site-specific chemical and biological functionality on different portions of the pyramids can be achieved. The optical properties of gold pyramids can be tuned across visible and near-infrared wavelengths by changing a variety of parameters. Large (> 250 nm) pyramids support multipolar surface plasmon resonances, which can be used for imaging and spectral identification of their orientation in condensed media.
