Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Abstract

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

Plasmonic Enhancement of Local Fields in Ultrafine Metal Nanoparticles

“…The applications alluded to the above have been greatly boosted by the advances in nanofabrication techniques, which have made it possible to control the variation in the shape and size of the particles and their material content . Traditional technologies for the chemical synthesis of nanoparticles based on colloidal systems have been complemented by fabrication based on pulsed laser ablation of bulk materials in liquid media and by the synthesis of self-organizing nanoparticles in gaseous media, which have made it possible to fabricate nanoparticles upon their deposition on a substrate. − Furthermore, technologies have been developed for fabricating nanoparticles and synthesis of periodic arrays by both sputtering onto a substrate from the gas phase through nanomasks and by directional etching of various shapes on the faces of single-crystal samples. − …”