Both local and far-field optical properties of metallic nanoparticles are determined by plasmon resonances, which depend upon particle geometry. This structural dependence of optical properties across the visible and near-IR spectral regions has enabled their use in a wide range of biomedical applications. Researchers at Rice University’s Laboratory for Nanophotonics (LANP; Houston, TX) have just broadened the possibilities further by adding nanoeggs to their collection of ultrasmall, light-focusing particles that includes nanorods, nanorings, nanocubes, triangular nanoprisms, nanoshells, and branched nanocrystals.
Nanoeggs, like nanoshells, have a spherical dielectric core covered with a thin metal shell. But unlike nanoshells, the metallic casings on nanoeggs are not concentric with respect to the dielectric cores. This offset, according to the researchers, enables optical excitation of all plasmon modes of nanoeggs, broadening the optical spectrum by a factor of five over similarly sized nanoshells, and also sharpening the ability of the egg-shaped nanoparticles to focus light. “The field of nanophotonics is undergoing explosive growth, as researchers gain greater and greater sophistication in the design and manipulation of light-active nanostructures,” said LANP Director Naomi Halas. Contact Naomi Halas at [email protected].