(652a) Tunable Synthesis of Au and Ag Hybrid Asymmetric Nanofingernails with Circular Dichroic Response

Single metal Au or Ag nanostructures are known to exhibit optical activity due to plasmonic effects and have been rationally designed for applications in photonics, sensing, bioimaging and especially surface enhanced Raman scattering (SERS) spectroscopy. Hybrid Au and Ag nanostructures possess additional functionalities due to the presence of both noble metals. However, the current methods used to achieve such hybrid nanostructures are either costly, require many fabrication steps, or are unreliable. Here we introduce a novel hybrid nanostructure composed of Au and Ag whose shape resembles that of a fingernail. The fabrication technique involves sequential thermal evaporation of metals onto track-etched hard templates to produce arrays of nanofingernails reliably, quickly and inexpensively. Moreover, the method is tunable with respect to nanofingernail height and thickness. The optical activity of the fabricated arrays is confirmed via circular dichroism (CD) spectroscopy. The CD spectroscopy demonstrates that the reduced symmetry and hybrid nature of the Au-Ag nanofingernails, which produce localized hot-spots of high intensity that change with incident circular polarization handedness, tailor the CD response. These novel structures have potential utility as platforms in surface-enhanced plasmonic sensing applications where the polarization-dependent hotspots may identify the location of adhered molecules.