In this project we present the first demonstration of large-area crescent-shaped random nanohole arrays in gold film and test their capability for biosensing. Since the discovery of extraordinary transmission of light through subwavelength holes, much attention has been devoted to understanding the role of material properties, film thickness, hole geometry, and relative hole placements in the optical response of hole and hole arrays. Recently, it has been shown that such structures utilize local surface plasmon resonances (LSPR) of the nanohole structures to focus electromagnetic fields into extremely small regions and have the potential to become powerful biomolecular sensors. However, the hole structures have not achieved the sensitivity of nanoparticle-based approaches. This may be largely attributed to limited effort in designing for molecular detection, which is typically focused on creating hot spots near plasmonic surfaces. Specifically, sharp-tip and nanogap geometries are required for high molecular sensitivities.We have used nanosphere lithography to create random arrays of crescent-shaped nanoholes, while reproducibly creating sub-10-nm sharp features to maximize the sensitivity of molecule detection. We demonstrate the biosensing of crescent-shaped nanoholes based on both localized surface plasmon resonance (LSPR) shift and surfaced-enhanced Raman spectroscopy (SERS). Moreover we will demonstrate significant advantages of these hole geometries, including integratability (i.e., integrated optical devices or optical micro/nanofluidics), robustness, and the potential to nanoconfine analyte in hot spot regions.
Project end date: 02/02/10