Apex-Enhanced Raman Spectroscopy Using Double-Hole Arrays in a Gold Film

Abstract

Periodic arrays of subwavelength double-hole apertures in a 100 nm gold film were used for surface-enhanced Raman scattering (SERS). The periodicity of the arrays and the double-hole overlap were varied to measure their effect on the Raman enhancement. The experiments were realized in two geometries: forward-scattering (transmission through the holes) and back-scattering. Significant enhancement in the SERS signal was observed in both geometries for the optimized substrates. Electromagnetic calculations verified that the local electromagnetic field intensity was indeed maximized for the arrays that produced the largest SERS effect. The double-hole structure was shown to produce controlled and predictable SERS due to the enhanced field localized at the apexes formed by the overlap between the holes.

Nanohole arrays in metal films as optofluidic elements: progress and potential

“…This enhancement is especially significant considering that the overall excitation laser power was not changed; rather it was focused to an extreme nanoscopic region about the apexes of the holes. Similar increases in the surface-enhanced Raman scattering were observed using the double nanohole arrays (Lesuffleur et al 2007b).…”

Resonant optical transmission through hole‐arrays in metal films: physics and applications

“…The extra enhancement from the localized SP at the apexes can be tuned by changing the double-hole center-to-center distance, which changes the shape of the apexes. The SERS enhancement factor from dyes adsorbed on the double-hole structure was an order of magnitude larger than for circular holes [200]. It should be kept in mind that the field enhancement only occurs over a much smaller area in the double-hole structure, so the enhancement is only "felt" by a small fraction of the molecules covering the surface.…”

“…3.3, the double-hole structure allows for strong local field enhancement when the holes are just touching to produce sharp apexes. The strong field enhancement in this double-hole structure was used to enhance SERS [200], as shown in Fig. 19.…”

Nano-bio-optomechanics: nanoaperture tweezers probe single nanoparticles, proteins, and their interactions

“…In particular, we used the double nanohole (DNH), which we studied since 2004 [12][13][14] because it creates a local hot-spot of around 10 nm in size in the electric field that interacts more strongly with the nanoparticle of interest.…”