Probing the plasmonic near-field of gold nanocrescent antennas.

We present an investigation of the plasmon-induced electromagnetic near-field around gold nanocrescent (NC) antennas which exhibit localized surface plasmon resonances (LSPRs) in the infrared. To probe the near-field behavior, we monitored the LSPR shift of NCs to adsorption of dielectric layers of varying thickness. The experimental results are analyzed using theoretical simulations, and the EM field decay lengths for the NCs are determined. We discuss how the structural properties of NC antennas influence the near-field properties and compare the results with the near-fields of other metal nanostructures. We show that the near-field distribution around NCs depends strongly on the structural parameters of the NC and that its spatial extent can be tuned to large distances (>700 nm) from the nanostructure surface. In addition, we discuss NC antenna structural changes associated with exposure to ethanol and buffer solutions and the impact on LSPR properties.